Automatic transmission of motor vehicle

The disclosures of Japanese Patent Applications No. 2002-144616 filed on May 20, 2002, No. 2002-153088 filed on May 27, 2002, and No. 2002-162118 filed on Jun. 3, 2002, each including the specification, drawings and abstract, are incorporated herein by reference in their entireties.

1. Field of the Invention

The invention generally relates to automatic transmissions of motor vehicles, and in particular to an automatic transmission which includes a plurality of planetary gear sets and provides seven or more forward gear stages, and which has a relatively small size and operates with a reduced loss.

2. Description of Related Art

Automatic transmissions of motor vehicles each having a plurality of planetary gear sets, clutches and brakes have been widely used. One example of such automatic transmissions as disclosed in Japanese Laid-open Patent Publication No. 2000-266138 is able to provide seven forward gear stages by using four planetary gear sets.

However, the use of the four planetary gear sets in the known automatic transmission causes an increase in the axial length of the transmission and an increased difficulty in installing the transmission on the vehicle, and also results in increases in the weight and cost of the transmission. Furthermore, the known automatic transmission includes seven friction devices which are selectively engaged and released for establishing seven gear stages. Thus, the known transmission requires an increased number of components, which results in an increased cost, and suffers from relatively large drag resistance, which causes deterioration in the fuel economy.

It is therefore an object of the invention to provide an automatic transmission of a motor vehicle which is able to provide seven or more forward gear stages or speeds by using three or four planetary gear sets and a reduced number of friction devices.

To accomplish the above object, there is provided according to a first aspect of the invention an automatic transmission, which comprises (a) an input member, (b) an output member, (c) an auxiliary power transmitting portion including a planetary gear set having three rotating elements, wherein when one of the three rotating elements is coupled to and rotated with the input member and another one of the rotating elements is fixed to be inhibited from rotating, the remaining rotating element serving as an intermediate rotating element is rotated at a reduced speed as compared with that of the input member, the auxiliary power transmitting portion further including an intermediate rotation output friction device that is operable, when engaged, to permit the intermediate rotating element to output rotary power at the reduced speed, and (d) a main power transmitting portion including a plurality of planetary gear sets including sun gears, carriers and ring gears, parts of which are coupled to each other to provide a first rotating element, a second rotating element, a third rotating element, a fourth rotating element and a fifth rotating element, which are arranged in the order of description from one end to the other end in a nomogram in which speeds of rotation of the first, second, third, fourth and fifth rotating elements are represented by straight lines, the main power transmitting portion further including a first brake, a second brake, a first clutch and a second clutch, wherein the first rotating element is coupled to the intermediate rotating member and is selectively inhibited from rotating by the second brake, the second rotating element is selectively inhibited from rotating by the first brake, the third rotating element is selectively coupled to the input member via the second clutch, the fifth rotating element is selectively coupled to the input member via the first clutch, and the fourth rotating element is coupled to the output member so as to output rotary power from the main power transmitting portion. In this automatic transmission, a first-speed gear stage having the largest gear ratio is established when the first clutch and the first brake are engaged, a second-speed gear stage having a smaller gear ratio than that of the first-speed gear stage is established when the first clutch and the second brake are engaged, a third-speed gear stage having a smaller gear ratio than that of the second-speed gear stage is established when the first clutch and the intermediate rotation output friction device are engaged, a fourth-speed gear stage having a smaller gear ratio than that of the third-speed gear stage is established when the first clutch and the second clutch are engaged, a fifth-speed gear stage having a smaller gear ratio than that of the fourth-speed gear stage is established when the second clutch and the intermediate rotation output friction device are engaged, a sixth-speed gear stage having a smaller gear ratio than that of the fifth-speed gear stage is established when the second clutch and the second brake are engaged, and a seventh-speed gear stage having a smaller gear ratio than that of the sixth-speed gear stage is established when the second clutch and the first brake are engaged.

The automatic transmission constructed as described above is able to establish seven forward gear stages by using three planetary gear sets and a total of five friction devices. Thus, the weight and size of the transmission can be reduced as compared with the case where four planetary gear sets are used. At the same time, the number of friction devices required for shifting the transmission is reduced, resulting in a reduced number of components and reduced cost. Furthermore, the drag resistance is reduced, and the fuel economy can be further improved.

According to a second aspect of the invention, there is provided an automatic transmission, which comprises (a) an input member, (b) an output member, (c) an auxiliary power transmitting portion including a planetary gear set having three rotating elements, wherein when one of the three rotating elements is coupled to and rotated with the input member, and another one of the rotating elements is fixed to be inhibited from rotating, the remaining rotating element serving as an intermediate rotating element is rotated at a reduced speed as compared with that of the input member, the auxiliary power transmitting portion further including an intermediate rotation output friction device that is operable, when engaged, to permit the intermediate rotating element to output rotary power at the reduced speed, and (d) a main power transmitting portion including a plurality of planetary gear sets including sun gears, carriers and ring gears, parts of which are coupled to each other to provide a first rotating element, a second rotating element, a third rotating element, a fourth rotating element and a fifth rotating element, which are arranged in the order of description from one end to the other end in a nomogram in which speeds of rotation of the first, second, third, fourth and fifth rotating elements are represented by straight lines, the main power transmitting portion further including a first brake, a second brake, a first clutch and a second clutch, wherein the first rotating element is selectively coupled to the input member via the second clutch and is selectively inhibited from rotating by the second brake, the second rotating element is selectively inhibited from rotating by the first brake, the third rotating element is selectively coupled to the input member via the first clutch, the fifth rotating element is coupled to or selectively coupled to the intermediate output member, and the fourth rotating element is coupled to the output member so as to output rotary power from the main power transmitting portion. In this automatic transmission, a first-speed gear stage having the largest gear ratio is established when the intermediate rotation output friction device and the first brake are engaged, a second-speed gear stage having a smaller gear ratio than that of the first-speed gear stage is established when the intermediate rotation output friction device and the second brake are engaged, a third-speed gear stage having a smaller gear ratio than that of the second-speed gear stage is established when the second clutch and the intermediate rotation output friction device are engaged, a fourth-speed gear stage having a smaller gear ratio than that of the third-speed gear stage is established when the first clutch and the intermediate rotation output friction device are engaged, a fifth-speed gear stage having a smaller gear ratio than that of the fourth-speed gear stage is established when the first clutch and the second clutch are engaged, a sixth-speed gear stage having a smaller gear ratio than that of the fifth-speed gear stage is established when the first clutch and the second brake are engaged, and a seventh-speed gear stage having a smaller gear ratio than that of the sixth-speed gear stage is established when the first clutch and the first brake are engaged.

The automatic transmission constructed as described above is able to establish seven forward gear stages by using three or four planetary gear sets and a total of five friction devices. Thus, the weight and size of the transmission can be reduced as compared with the case where four planetary gear sets and a total of seven friction devices are used. At the same time, the number of friction devices required for shifting the transmission is reduced, resulting in a reduced number of components and reduced cost. Furthermore, the drag resistance is reduced, and the fuel economy can be further improved.

According to a third aspect of the invention, there is provided an automatic transmission, which comprises (a) an input member, (b) an output member, (c) an auxiliary power transmitting portion including a planetary gear set having three rotating elements, wherein when one of the rotating elements is coupled to and rotated with the input member, and another one of the rotating element is fixed to be inhibited from rotating, the remaining rotating element serving as an intermediate rotating element is rotated at a reduced speed as compared with that of the input member, the auxiliary power transmitting portion further including an intermediate rotation output friction device that is operable, when engaged, to permit the intermediate rotating element to output rotary power at the reduced speed, and (d) a main power transmitting portion including a plurality of planetary gear sets including sun gears, carriers and ring gears, parts of which are coupled to each other to provide a first rotating element, a second rotating element, a third rotating element, a fourth rotating element and a fifth rotating element, which are arranged in the order of description from one end to the other end in a nomogram in which speeds of rotation of the first, second, third, fourth and fifth rotating elements are represented by straight lines, the main power transmitting portion further including a first brake, a second brake, a first clutch, a second clutch and a third clutch, wherein the first rotating element is selectively inhibited from rotating by the second brake and is selectively coupled to the intermediate rotating member via the third clutch, the second rotating element is selectively inhibited from rotating by the first brake, the third rotating element is selectively coupled to the input member via the second clutch, the fifth rotating element is selectively coupled to the intermediate rotating member via the first clutch, and the fourth rotating element is coupled to the output member so as to output rotary power from the main power transmitting portion. In this automatic transmission, a first-speed gear stage having the largest gear ratio is established when the first clutch and the first brake are engaged, a second-speed gear stage having a smaller gear ratio than that of the first-speed gear stage is established when the first clutch and the second brake are engaged, a third-speed gear stage having a smaller gear ratio than that of the second-speed gear stage is established when the first clutch and the third clutch are engaged, a fourth-speed gear stage having a smaller gear ratio than that of the third-speed gear stage is established when the first clutch and the second clutch are engaged, a fifth-speed gear stage having a smaller gear ratio than that of the fourth-speed gear stage is established when the second clutch and the third clutch are engaged, a sixth-speed gear stage having a smaller gear ratio than that of the fifth-speed gear stage is established when the second clutch and the second brake are engaged, and a seventh-speed gear stage having a smaller gear ratio than that of the sixth-speed gear stage is established when the second clutch and the first brake are engaged.

The automatic transmission constructed as described above is able to establish seven or more forward gear stages by using three planetary gear sets and a total of five friction devices, i.e., three clutches and two brakes. Thus, the weight and size of the transmission can be reduced as compared with the case where four planetary gear sets are used. At the same time, the number of friction devices required for shifting the transmission is reduced, resulting in a reduced number of components and reduced cost. Furthermore, the drag resistance is reduced, and the fuel economy can be further improved.

The foregoing and further objects, features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a schematic view showing an automatic transmission of a motor vehicle according to a first embodiment of the invention;

FIG. 2 is an operation table indicating a plurality of gear stages of the automatic transmission of FIG. 1, and selected ones of a plurality of friction devices for establishing each of the gear stages;

FIG. 3 is a nomogram plotted with respect to the automatic transmission of FIG. 1;

FIG. 4 is a schematic view showing an automatic transmission of a motor vehicle according to a second embodiment of the invention, as a modified example of the automatic transmission of FIG. 1;

FIG. 5 is a schematic view showing an automatic transmission of a motor vehicle according to a third embodiment of the invention;

FIG. 6 is an operation table indicating a plurality of gear stages of the automatic transmission of FIG. 5, and selected ones of a plurality of friction devices for establishing each of the gear stages;

FIG. 7 is a nomogram plotted with respect to the automatic transmission of FIG. 5;

FIG. 8 is a schematic view showing an automatic transmission of a motor vehicle according to a fourth embodiment of the invention, as a modified example of the automatic transmission of FIG. 5;

FIG. 9 is a schematic view showing an automatic transmission of a motor vehicle according to a fifth embodiment of the invention;

FIG. 10 is a nomogram plotted with respect to the automatic transmission of FIG. 9;

FIG. 11 is a schematic view showing an automatic transmission of a motor vehicle according to a sixth embodiment of the invention, as a modified example of the automatic transmission of FIG. 9;

FIG. 12 is a schematic view showing an automatic transmission of a motor vehicle according to a seventh embodiment of the invention;

FIG. 13 is a nomogram plotted with respect to the automatic transmission of FIG. 12;

FIG. 14 is a schematic view showing an automatic transmission of a motor vehicle according to an eighth embodiment of the invention, as a modified example of the automatic transmission of FIG. 12;

FIG. 15 is a schematic view showing an automatic transmission of a motor vehicle according to a ninth embodiment of the invention;

FIG. 16 is an operation table indicating a plurality of gear stages of the automatic transmission of FIG. 15, and selected ones of a plurality of friction devices for establishing each of the gear stages; and

FIG. 17 is a nomogram plotted with respect to the automatic transmission of FIG. 15 .

Some exemplary embodiments of the invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows a planetary gear type automatic transmission (hereinafter simply referred to as “transmission”) 10 of a motor vehicle according to a first embodiment of the invention. FIG. 2 is an operation table indicating engaging elements and the gear ratio (or speed ratio) with respect to each of a plurality of gear stages or speeds to be established by the transmission. FIG. 3 is a nomogram plotted with respect to the transmission of FIG. 1 .

Referring first to FIG. 1, the transmission 10 receives rotary power transmitted from an engine (not shown) to an input shaft 16 thereof, changes the speed of rotation at a given gear ratio, and transmits the power from an output gear 24 to right and left driving wheels, via a propeller shaft (not shown), a differential gear unit (not shown), and other members. The transmission 10 includes a torque converter (not shown) provided with a lockup clutch, the input shaft 16 coupled to the torque converter, a third planetary gear set 22 , a first planetary gear set 18 , and a second planetary gear set 20 , which are arranged on the common axis of rotation within a transmission case (non-rotating member) 12 attached to the vehicle body. The transmission 10 further includes the output gear 24 that is disposed at one side of the second planetary gear set 20 remote from the input shaft 16 , to be located between the second planetary gear set 20 and a second clutch C 2 . The above-indicated torque converter is coupled to a crankshaft (not shown) of the engine. In this embodiment, the input shaft 16 and the output gear 24 correspond to an input rotating member and an output rotating member, respectively, and the transmission case 12 corresponds to a non-rotating or stationary member. It is to be noted that the transmission 10 is constructed symmetrically with respect to the rotational axis thereof, and that the lower half of the transmission 10 is not shown in FIG. 1 (i.e., only the upper half of the transmission 10 is illustrated in FIG. 1 ).

The automatic transmission 10 is transversely or laterally installed on, for example, a front engine front drive (FF) vehicle, such that the axis of the transmission 10 extends in the width direction of the vehicle. The transmission 10 includes an auxiliary power transmitting portion 26 that mainly consists of the third planetary gear set 22 of a double pinion type, and a main power transmitting portion 28 that mainly consists of the first planetary gear set 18 of a double pinion type and the second planetary gear set 20 of a double pinion type. The transmission 10 is adapted to establish a selected one of seven forward gear stages having seven different gear ratios γ n and one reverse gear stage, by engaging selected ones of five friction devices. With the selected gear stage thus established, the transmission 10 changes the speed of rotation of the input shaft 16 at a gear ratio corresponding to the gear stage, and transmits the resulting rotary power to the output gear 24 .

In the auxiliary power transmitting portion 26 , the third planetary gear set 22 includes a third sun gear S 3 , a third ring gear R 3 , a fifth pinion P 5 , a sixth pinion P 6 , and a third carrier CA 3 . The third ring gear R 3 is disposed coaxially with and radially outwardly of the third sun gear S 3 , and the fifth pinion P 5 meshes with the third sun gear S 3 , while the sixth pinion P 6 meshes with the third ring gear R 3 . The third carrier CA 3 supports the fifth pinion P 5 and the sixth pinion P 6 that mesh with each other, such that the fifth and sixth pinions P 5 , P 6 are able to rotate about themselves and rotate about the axis of the third planetary gear set 22 (i.e., input shaft 16 ). The third sun gear S 3 is coupled to the input shaft 16 , such that the sun gear S 3 and the input shaft 16 are rotated or driven together. The third carrier CA 3 is selectively coupled to the transmission case 12 as the non-rotating member, via a third brake B 3 . The above-indicated third ring gear R 3 is selectively coupled to the transmission case 12 as the non-rotating member, via a second brake B 2 , and is coupled to the first sun gear S 1 of the first planetary gear set 18 . The ring gear R 3 functions as an intermediate rotating member that outputs driving power to the main power transmitting portion 28 at an intermediate rotational speed to which the speed of rotation of the input shaft 16 is reduced by the third planetary gear set 22 . The third brake B 3 serves as an intermediate rotation output friction device which operates, when engaged, to output rotary power from the third ring gear R 3 at the intermediate rotational speed.

In the main power transmitting portion 28 , the first planetary gear set 18 includes the first sun gear S 1 , a first ring gear R 1 , a first pinion P 1 , a second pinion P 2 and a first carrier CA 1 . The first sun gear S 1 is selectively coupled to the transmission case 12 via the second brake B 2 , and is also coupled to the third ring gear R 3 of the third planetary gear set 22 . The first ring gear R 1 is selectively coupled to the transmission case 12 via a first brake B 1 . The first pinion P 1 meshes with the first sun gear S 1 and the second pinion P 2 meshes with the first ring gear R 1 . The first carrier CA 1 supports the first pinion P 1 and the second pinion P 2 that mesh with each other, such that the first and second pinions P 1 , P 2 are able to rotate about themselves and rotate about the axis of the first planetary gear set 18 . The second planetary gear set 20 includes a second sun gear S 2 , a second ring gear R 2 , a third pinion P 3 , a fourth pinion P 4 , and a second carrier CA 2 . The second sun gear S 2 is selectively coupled to the input shaft 16 via a first clutch C 1 , and the second ring gear R 2 is coupled to the output gear 24 . The third pinion P 3 meshes with the second sun gear S 2 , and has a larger diameter than the second pinion P 2 . The third pinion P 3 is coaxially coupled to the second pinion P 2 such that the third and second pinions P 3 , P 2 rotate as a unit. The fourth pinion P 4 meshes with the second ring gear R 2 and the third pinion P 3 . The second carrier CA 2 supports the third pinion P 3 and the fourth pinion P 4 such that the third and fourth pinions P 3 , P 4 are able to rotate about themselves and rotate about the axis of the second planetary gear set 20 . Furthermore, the second carrier CA 2 is coupled to the first carrier CA 1 such that the first and second carriers CA 1 , CA 2 rotate as a unit, and is also selectively coupled to the input shaft 16 via the second clutch C 2 . A one-way clutch F 1 is disposed in parallel with the first brake B 1 , between the first ring gear R 1 and the transmission case 12 . The first brake B 1 and the one-way clutch F 1 may be replaced by only one of the first brake B 1 and the one-way clutch F 1 .

Each of the first clutch C 1 , second clutch C 2 , first brake B 1 , second brake B 2 and the third brake B 3 is a hydraulically operated friction device, which may be generally used in conventional planetary gear type automatic transmissions. The friction device serves to selectively couple two members between which the device is interposed, to each other. For example, the friction device may be of a wet multiple disc type in which a plurality of friction plates that are superposed on each other are pressed by a hydraulic actuator, or may be in the form of a band brake in which one end of one or two band(s) wound around the outer circumferential surface of a rotating drum is strained or drawn in by a hydraulic actuator. The one-way clutch F 1 disposed in parallel with the first brake B 1 also functions as an engaging device equivalent to the first brake, and only one of the one-way clutch F 1 and the first brake B 1 may be provided.

In the transmission 10 constructed as described above, a selected one of the forward 1 st -speed gear stage through 7 th -speed gear stage and reverse gear stage is established by engaging two friction devices selected from the first clutch C 1 , second clutch C 2 , first brake B 1 , second brake B 2 and the third brake B 3 at the same time, as indicated in the operation table of FIG. 2 . As described later, the gear ratios γ (=input shaft rotational speed Nin/output shaft rotational speed Nout) of the forward gear stages differ successively at substantially equal ratios (namely, the ratio of the gear ratio γ of one of the forward gear stages to that of the next gear stage is substantially constant.)

More specifically described referring to FIG. 2, the 1 st -speed gear stage having the largest gear ratio γ 1 , which is, for example, equal to 2.52, is established by engaging the first clutch C 1 and the first brake B 1 so that the input shaft 16 and the second sun gear S 2 are coupled to each other and the first ring gear R 1 and the transmission case 12 are coupled to each other. The 2 nd -speed gear stage having a gear ratio γ 2 , which is smaller than the gear ratio γ 1 and is, for example, equal to 1.88, is established by engaging the first clutch C 1 and the second brake B 2 so that the input shaft 16 and the second sun gear S 2 are coupled to each other and the first sun gear S 1 , third ring gear R 3 and the transmission case 12 are coupled to each other. The 3 rd -speed gear stage having a gear ratio γ 3 , which is smaller than the gear ratio γ 2 and is, for example, equal to 1.35, is established by engaging the first clutch C 1 and the third brake B 3 so that the input shaft 16 and the second sun gear S 2 are coupled to each other, and the third carrier CA 3 and the transmission case 12 are coupled to each other. The 4 th -speed gear stage having a gear ratio γ 4 , which is smaller than the gear ratio γ 3 and is, for example, equal to 1.00, is established by engaging the first clutch C 1 and the second clutch C 2 so that the input shaft 16 and the second sun gear S 2 are coupled to each other, and the input shaft 16 , the second carrier CA 2 and the first carrier CA 1 are coupled to each other. The 5 th -speed gear stage having a gear ratio γ 5 , which is smaller than the gear ratio γ 4 and is, for example, equal to 0.83, is established by engaging the second clutch C 2 and the third brake B 3 so that the input shaft 16 , the second carrier CA 2 and the first carrier CA 1 are coupled to each other, and the third carrier CA 3 and the transmission case 12 are coupled to each other. The 6 th -speed gear stage having a gear ratio γ 6 , which is smaller than the gear ratio γ 5 and is, for example, equal to 0.74, is established by engaging the second clutch C 2 and the second brake B 2 so that the input shaft 16 , the second carrier CA 2 and the first carrier CA 1 are coupled to each other, and the first sun gear S 1 , the third ring gear R 3 and the transmission case 12 are coupled to each other. The 7 th -speed gear stage having a gear ratio γ 7 , which is smaller than the gear ratio γ 6 and is, for example, equal to 0.55, is established by engaging the second clutch C 2 and the first brake B 1 so that the input shaft 16 , the second carrier CA 2 and the first carrier CA 1 are coupled to each other, and the first ring gear R 1 and the transmission case 12 are coupled to each other. The reverse gear stage having a gear ratio γ R , which is between the gear ratio γ 2 and the gear ratio γ 3 and is, for example, equal to 1.65, is established by engaging the first brake B 1 and the third brake B 3 so that the first ring gear R 1 and the transmission case 12 are coupled to each other, and the third carrier CA 3 and the transmission case 12 are coupled to each other. The gear ratio (=the number of teeth of the sun gear/the number of teeth of the ring gear) ρ 1 of the first planetary gear set 18 , the gear ratio ρ 2 of the second planetary gear set 20 , and the gear ratio ρ 3 of the third planetary gear set 22 are determined so as to provide the gear ratios γ 1 -γ 7 and γ R as indicated above. For example, ρ 1 is equal to 0.43, ρ 2 is equal to 0.23, and ρ 3 is equal to 0.44.

In the transmission 10 as described above, the rate of change of the gear ratio (i.e., ratio of the gear ratios of the adjacent gear stages=γ n /γ n+1 ) may be determined as follows: the ratio (=γ 1 /γ 2 ) of the gear ratio γ 1 of the 1 st -speed gear stage to the gear ratio γ 2 of the 2 nd -speed gear stage is 1.34, the ratio (=γ 2 /γ 3 ) of the gear ratio γ 2 of the 2 nd -speed gear stage to the gear ratio γ 3 of the 3 rd -speed gear stage is 1.39, the ratio (=γ 3 /γ 4 ) of the gear ratio γ 3 of the 3 rd -speed gear stage to the gear ratio γ 4 of the 4 th -speed gear stage is 1.35, the ratio (=γ 4 /γ 5 ) of the gear ratio γ 4 of the 4 th -speed gear stage to the gear ratio γ 5 of the 5 th -speed gear stage is 1.20, the ratio (=γ 5 /γ 6 ) of the gear ratio γ 5 of the 5 th -speed gear stage to the gear ratio γ 6 of the 6 th -speed gear stage is 1.12, and the ratio (=γ 6 /γ 7 ) of the gear ratio γ 6 of the 6 th -speed gear stage to the gear ratio γ 7 of the 7 th -speed gear stage is 1.35. Thus, the gear ratios γ change at substantially equal ratios or rates. Also, in the transmission 10 , the total width of the gear ratios (γ 1 /γ 7 ), namely, the ratio of the gear ratio γ 1 of the 1 st -speed gear stage to the gear ratio γ 7 of the 7 th -speed gear stage, is a sufficiently large value, which is, for example, 4.61. Also, the gear ratio of the reverse gear stage “Rev” is an appropriate value. Thus, the transmission 10 provides appropriate gear-ratio (speed-change) characteristics over the entire range of operation.

FIG. 3 is a nomogram in which straight lines represent the relationships of the speeds of rotation of rotating elements (as described later) which are in different coupling states for respective gear stages. The nomogram of FIG. 3 is a two-dimensional coordinate system in which the horizontal axis indicates the relationship among the gear ratios ρ of the respective planetary gear sets 18 , 20 , 22 , and the vertical axis indicates relative rotational speeds. In the nomogram of FIG. 3 showing three horizontal lines, the lower horizontal line X 1 indicates rotational speed “0”, the middle horizontal line X 3 indicates a rotational speed that is lower than the speed of rotation of the input shaft 16 , and the upper horizontal line X 2 indicates rotational speed “1.0”, which is equal to the speed of rotation of the input shaft 16 . Five vertical lines Y 1 through Y 5 in the section of the main power transmitting portion 28 respectively represent the first sun gear S 1 corresponding to a first rotating element RE 1 , the first ring gear R 1 corresponding to a second rotating element RE 2 , the first carrier CA 1 and the second carrier CA 2 that are coupled to each other and correspond to a third rotating element RE 3 , the second ring gear R 2 corresponding to a fourth rotating element RE 4 , and the second sun gear S 2 corresponding to a fifth rotating element RE 5 . The intervals of these vertical lines are determined in accordance with the gear ratio ρ 1 of the first planetary gear set 18 and the gear ratio ρ 2 of the second planetary gear set 20 . More specifically, the interval between the vertical lines corresponding to the sun gear and the carrier is set as “1”, and the interval between the vertical lines corresponding to the carrier and the ring gear is set as “ρ”. In FIG. 3, the interval between the vertical line Y 5 corresponding to the second sun gear S 2 of the second planetary gear set 20 and the vertical line Y 4 corresponding to the second ring gear R 2 is set as “1”.

The main power transmitting portion 28 will be described by utilizing the nomogram of FIG. 3 . Parts of the first sun gear S 1 , first carrier CA 1 and the first ring gear R 1 of the first planetary gear set 18 and the second sun gear S 2 , second carrier CA 2 and the second ring gear R 2 of the second planetary gear set 20 are coupled to each other so as to provide five rotating elements RE 1 through RE 5 . In the monogram of FIG. 3, the speeds of rotation of the five rotating elements RE 1 through RE 5 are represented by straight lines, and the first rotating element RE 1 , second rotating element RE 2 , third rotating element RE 3 , fourth rotating element RE 4 and the fifth rotating element RE 5 are arranged in this order from one end (i.e., left end in FIG. 3) to the other end (i.e., right end in FIG. 3 ). In the transmission 10 of this embodiment, the first rotating element RE 1 (S 1 ) is coupled to the third ring gear R 3 serving as an intermediate rotating member so as to be rotated at an intermediate rotational speed, and is also selectively inhibited from rotating by the second brake B 2 . The second rotating element RE 2 (R 1 ) is selectively inhibited from rotating by the first brake B 1 , and the third rotating element RE 3 (CA 1 , CA 2 ) is selectively coupled to the input shaft 16 (input member) via the second clutch C 2 . The fifth rotating element RE 5 (S 2 ) is selectively coupled to the input shaft 16 via the first clutch C 1 , and the fourth rotating element RE 4 (R 2 ) is coupled to the output gear 24 (output member).

As is apparent from the nomogram of FIG. 3, when the first clutch C 1 and the first brake B 1 are engaged, and the fifth rotating element RE 5 (S 2 ) is rotated as a unit with the input shaft 16 while the second rotating element RE 2 (R 1 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “1 st ” in FIG. 3, so that the 1 st -speed gear stage having the largest gear ratio is established. When the first clutch C 1 and the second brake B 2 are engaged, and the fifth rotating element RE 5 (S 2 ) is rotated as a unit with the input shaft 16 while the first rotating element RE 1 (S 1 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “2 nd ” in FIG. 3, so that the 2 nd -speed gear stage having a smaller gear ratio than that of the 1 st -speed gear stage is established. When the first clutch C 1 and the third brake B 3 are engaged, and the fifth rotating element RE 5 (S 2 ) is rotated as a unit with the input shaft 16 while the first rotating element RE 1 (S 1 ) is rotated with the third ring gear R 3 at the intermediate rotational speed, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “3 rd ” in FIG. 3, so that the 3 rd -speed gear stage having a smaller gear ratio than that of the 2 nd -speed gear stage is established. When the first clutch C 1 and the second clutch C 2 are engaged, and the third rotating element RE 3 (CA 1 , CA 2 ) and the fifth rotating element RE 5 (S 2 ) are rotated at the same speed as the input shaft 16 , the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “4 th ” in FIG. 3, namely, at the same speed as the input shaft 16 , so that the 4 th -speed gear stage having a smaller gear ratio than that of the 3 rd -speed gear stage is established. The gear ratio of the 4 th -speed gear stage is equal to 1. When the second clutch C 2 and the third brake B 3 are engaged, and the third rotating element RE 3 (CA 1 , CA 2 ) are rotated as a unit with the input shaft 16 while the first rotating element RE 1 (S 1 ) is rotated along with the third ring gear R 3 at the intermediate rotational speed, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “5 th ” in FIG. 3, so that the 5 th -speed gear stage having a smaller gear ratio than that of the 4 th -speed gear stage is established. When the second clutch C 2 and the second brake B 2 are engaged, and the third rotating element RE 3 (CA 1 , CA 2 ) is rotated along with the input shaft 16 while the first rotating element RE 1 (S 1 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “6 th ” in FIG. 3, so that the 6 th -speed gear stage having a smaller gear ratio than that of the 5 th -speed gear stage is established. When the second clutch C 2 and the first brake B 1 are engaged, and the third rotating element RE 3 (CA 1 , CA 2 ) is rotated along with the input shaft 16 while the second rotating element RE 2 (R 1 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “7 th ” in FIG. 3, so that the 7 th -speed gear stage having a smaller gear ratio than that of the 6 th -speed gear stage is established.

When the first brake B 1 and the third brake B 3 are engaged, and the first rotating element RE 1 (S 1 ) is rotated along with the third ring gear R 3 at the intermediate rotational speed while the second rotating element RE 2 (R 1 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated in the reverse direction at a speed denoted by “REV” in FIG. 3, so that the reverse gear stage “Rev” is established.

As described above, the automatic transmission 10 of the present embodiment is able to establish seven forward gear stages by using three gear sets, i.e., the first planetary gear set 18 , second planetary gear set 20 , and the third planetary gear set 22 , and a total of five friction devices, i.e., two clutches C 1 and C 2 and three brakes B 1 , B 2 and B 3 . Thus, the weight and size of the transmission 10 can be reduced as compared with the case where four planetary gear sets are used, thus making it easier to install the transmission 10 on the vehicle. At the same time, the number of friction devices required for shifting the transmission 10 is reduced, resulting in a reduced number of components and reduced cost. Furthermore, the drag resistance is reduced, and the fuel economy can be further improved.

In the first embodiment as described above, the second pinion P 2 of the double-pinion type first planetary gear set 18 and the third pinion P 3 of the double-pinion type second planetary gear set 20 are coupled to each other on the same axis so that these pinions P 2 , P 3 are rotated as a unit. Like Ravigneaux type planetary gear trains, this arrangement requires a further reduced number of components and further reduced axial length, which result in further reduction in the size and cost of the transmission 10 .

In the first embodiment as described above, the main power transmitting portion 28 includes the first planetary gear set 18 and the second planetary gear set 20 , and the first rotating element RE 1 is the first sun gear S 1 , the second rotating element RE 2 is the first ring gear R 1 , the third rotating element RE 3 consists of the first carrier CA 1 and the second carrier CA 2 , the fourth rotating element RE 4 is the second ring gear R 2 , and the fifth rotating element RE 5 is the second sun gear S 2 . With this arrangement, the automatic transmission 10 having seven forward gear stages can be made compact.

Next, a second embodiment of the invention will be described with reference to FIG. 4 . In the following description, the same reference numerals as used in the first embodiment are used for identifying corresponding elements or portions, of which no detailed description is provided. FIG. 4 schematically shows the construction of an automatic transmission 30 that provides seven forward gear stages by using five friction devices, like the transmission 10 of the first embodiment.

The transmission 30 is different from the transmission 10 in that the third carrier CA 3 of the auxiliary power transmitting portion 26 is directly coupled to the transmission case 12 such that the carrier CA 3 is always inhibited from rotating, and that a third clutch C 3 is provided between the third ring gear R 3 and the first sun gear S 1 , such that the third ring gear R 3 and the first sun gear S 1 are selectively coupled to each other. The transmission 30 is similar to the transmission 10 in the other aspects. In the second embodiment, the third sun gear S 3 as one of three rotating elements of the third planetary gear set 22 is rotated along with the input shaft 16 , and rotation of the third ring gear R 3 corresponding to an intermediate rotating member that is rotated at a lower speed than the input shaft 16 is transmitted to the main power transmitting portion 28 via the third clutch C 3 . The third clutch C 3 of this embodiment functions as an intermediate rotation output friction device in a similar manner to the third brake B 3 of the transmission 10 . Thus, the transmission 30 is able to establish seven forward gear stages based on an operation table similar to that of FIG. 2 and a nomogram similar to that of FIG. 3, in which the third brake B 3 is replaced by the third clutch C 3 . The rotating elements RE 1 , RE 2 , RE 3 , RE 4 and RE 5 of this embodiment are identical with those of the first embodiment. With this arrangement, the transmission 30 of the second embodiment yields similar advantageous effects to those provided by the transmission 10 of the first embodiment.

While the first and second embodiments of the invention have been described in detail with reference to FIG. 1 through FIG. 4, the invention may be otherwise embodied.

While the third planetary gear set 22 that constitutes the auxiliary power transmitting portion 26 is of a double pinion type in the illustrated embodiments, the third planetary gear set 22 may be of a single pinion type. Also, any one of the third sun gear S 3 , third carrier CA 3 and the third ring gear R 3 corresponding to three rotating elements of the third planetary gear set 22 may be fixed, or may serve as an intermediate rotating member, or may be directly or indirectly coupled to the input member. In sum, the auxiliary power transmitting portion 26 is constructed such that when one of the three rotating elements of the planetary gear set that is coupled to the input member is rotated with the input member, and another one of the rotating elements is fixed to be inhibited from rotating, while the remaining one of the rotating elements serving as an intermediate rotating member is rotated at a reduced speed as compared with that of the input member. When the intermediate rotation output friction device is engaged, the reduced-speed rotation of the intermediate rotating member is selectively transmitted to the main power transmitting portion 28 .

While the automatic transmissions 10 , 30 of the illustrated embodiments are suitably installed in the lateral direction on front engine front drive (FF) vehicles in which the axis of the transmission 10 , 30 extends in the width direction of the vehicle, the automatic transmissions 10 , 30 may be installed in the vertical direction on front engine rear drive (FR) vehicles in which the axis of the transmission 10 , 30 extends in the longitudinal or running direction of the vehicle.

While the automatic transmission 10 , 30 may automatically change its gear ratio or gear stage depending upon vehicle operating conditions, such as an accelerator pedal position and a vehicle speed, the transmission 10 , 30 may change its gear ratio in response to switching operations (e.g., upshifting and downshifting operations) performed by the vehicle operator or driver.

In the automatic transmission 10 , 30 as described above, hydraulically operated friction devices of multiple-disc type, single-disc type or belt type, which are frictionally engaged by use of hydraulic actuators, are suitably used as the first clutch C 1 , second clutch C 2 , third clutch C 3 , first brake B 1 , second brake B 2 and the third brake B 3 . However, other types of engaging devices, such as those of electromagnetic type, may also be used as the clutches and brakes. To make shift control easy, one-way clutches may be provided in parallel with the brakes or clutches. If an engine brake need not be applied, one-way clutches may be used in place of the brakes or clutches. Here, one-way clutches function, like brakes, to stop rotation of corresponding rotating members. Other than the above arrangements, the automatic transmission 10 , 30 may be constructed in various ways. For example, a brake and a one-way clutch, which are connected in series, may be provided in parallel with the first brake B 1 .

In the automatic transmission 10 , 30 , for example, the positional relationship between the main power transmitting portion 28 and the auxiliary power transmitting portion 26 and the positional relationship between the first planetary gear set 18 and the second planetary gear set 20 of the main power transmitting portion 58 are not particularly limited, but may be changed in various ways. In addition, the clutches and brakes may be located to be concentrated in one end portion of the transmission 10 , 30 , or may be otherwise positioned. Furthermore, the first planetary gear set 18 , second planetary gear set 20 and the third planetary gear set 22 are not necessarily disposed on the same axis.

While the vertical lines Y 1 , Y 2 , Y 3 , Y 4 , Y 5 respectively corresponding to the rotating elements RE 1 , RE 2 , RE 3 , RE 4 , RE 5 are arranged in this order from the left to the right in the nomogram of FIG. 3 in the illustrated embodiments, these vertical lines, Y 1 , Y 2 , Y 3 , Y 4 , Y 5 may be arranged in this order from the right to the left. While the horizontal line X 2 corresponding to the rotational speed “1” is located above the horizontal line X 1 corresponding to the rotational speed “0” in the nomogram of FIG. 3, the horizontal line X 2 may be located below the horizontal line X 1 .

In the illustrated embodiments, the second pinion P 2 of the double-pinion type first planetary gear set 18 and the third pinion P 3 of the double-pinion type second planetary gear set 20 are coupled to each other on the same axis such that the pinions P 2 , P 3 are rotated as a unit. While the second pinion P 2 and the third pinion P 3 have different diameters in the illustrated embodiments, these pinions P 2 , P 3 may have the same diameter. It is also to be understood that the diameter (or the number of teeth) of each of the first pinion P 1 , second pinion P 2 , third pinion P 3 and the fourth pinion P 4 may be changed as needed.

While the main power transmitting portion 28 is constituted by two planetary gear sets in the embodiments of FIG. 1 and FIG. 4, the number of the planetary gear sets is not limited to two.

In the main power transmitting portion 28 of the illustrated embodiments, the first rotating element RE 1 , second rotating element RE 2 , third rotating element RE 3 , fourth rotating element RE 4 , and the fifth rotating element RE 5 may be suitably selected from the sun gears, ring gears and carriers of the first planetary gear set 18 and second planetary gear set 20 , and those of other planetary gear sets.

Next, a third embodiment of the invention will be described in detail with reference to FIG. 5, FIG. 6 and FIG. 7 . FIG. 5 schematically shows a planetary gear type automatic transmission (hereinafter simply referred to as “transmission”) 40 of a motor vehicle according to the third embodiment of the invention. FIG. 6 is an operation table indicating engaging elements and the gear ratio (or speed ratio) with respect to each of a plurality of gear stages or speeds to be established by the transmission 40 . FIG. 7 is a nomogram plotted with respect to the transmission of FIG. 5 .

Referring first to FIG. 5, the transmission 40 receives rotary power transmitted from an engine (not shown) to an input shaft 16 thereof, changes the speed of rotation at a given gear ratio, and transmits the power from an output gear 24 to right and left driving wheels, via a propeller shaft (not shown), a differential gear unit (not shown), and other members. The transmission 40 includes a torque converter (not shown) provided with a lockup clutch, the input shaft 16 coupled to the torque converter, a third planetary gear set 52 , a first planetary gear set 48 , and a second planetary gear set 50 , which are arranged on the common axis of rotation within a transmission case (non-rotating member) 12 attached to the vehicle body. The transmission 40 further includes the output gear 24 that is disposed at one side of the second planetary gear set 50 remote from the input shaft 16 , to be located between the second planetary gear set 50 and a first brake B 1 . The above-indicated torque converter is coupled to a crankshaft (not shown) of the engine. In this embodiment, the input shaft 16 and the output gear 24 correspond to an input rotating member and an output rotating member, respectively, and the transmission case 12 corresponds to a non-rotating or stationary member. It is to be noted that the transmission 40 is constructed symmetrically with respect to the rotational axis thereof, and that the lower half of the transmission 40 is not shown in FIG. 5 (i.e., only the upper half of the transmission 40 is illustrated in FIG. 5 ).

The automatic transmission 40 is transversely or laterally installed on, for example, a front engine front drive (FF) vehicle, such that the axis of the transmission 40 extends in the width direction of the vehicle. The transmission 40 includes an auxiliary power transmitting portion 56 that mainly consists of the third planetary gear set 52 of a double pinion type, and a main power transmitting portion 58 that mainly consists of the first planetary gear set 48 of a double pinion type and the second planetary gear set 50 of a single pinion type. The transmission 40 is adapted to establish a selected one of seven forward gear stages having seven different gear ratios γ n and one reverse gear stage, by engaging selected ones of five friction devices. With the selected gear stage thus established, the transmission 40 changes the speed of rotation of the input shaft 16 at a gear ratio corresponding to the gear stage, and transmits the resulting rotary power to the output gear 24 .

In the auxiliary power transmitting portion 56 , the third planetary gear set 52 includes a third sun gear S 3 , a third ring gear R 3 , a fourth pinion P 4 , a fifth pinion P 5 , and a third carrier CA 3 . The third ring gear R 3 is disposed coaxially with and radially outwardly of the third sun gear S 3 , and the fourth pinion P 4 meshes with the third sun gear S 3 , while the fifth pinion P 5 meshes with the third ring gear R 3 . The third carrier CA 3 supports the fourth pinion P 4 and the fifth pinion P 5 that mesh with each other, such that the fourth and fifth pinions P 4 , P 5 are able to rotate about themselves and rotate about the axis of the third planetary gear set 52 (i.e., input shaft 16 ). The third sun gear S 3 is selectively coupled to the transmission case 12 via a third brake B 3 , such that the sun gear S 3 is selectively inhibited from rotating. The third carrier CA 3 of the third planetary gear set 52 is coupled to the input shaft 16 such that the carrier CA 3 and the input shaft 16 are rotated as a unit. The third carrier CA 3 is also selectively coupled to a first ring gear R 1 of the first planetary gear set 48 via a first clutch C 1 , and is coupled to a second sun gear S 2 of the second planetary gear set 50 via a second clutch C 2 , such that power is transmitted directly from the input shaft 16 to the main power transmitting portion 58 . The third ring gear R 3 of the third planetary gear set 52 functions as an intermediate rotating member which is coupled to a first sun gear S 1 of the first planetary gear set 48 so as to output driving power to the main power transmitting portion 58 at an intermediate rotational speed to which the speed of rotation of the input shaft 16 is reduced by the third planetary gear set 52 . The third brake B 3 serves as an intermediate rotation output friction device which operates, when engaged, to transmit rotary power from the third ring gear R 3 to the first sun gear S 1 of the main power transmitting portion 58 such that the speed of rotation is reduced as compared with the speed of the input shaft 16 .

In the main power transmitting portion 58 , the first planetary gear set 48 includes the first sun gear S 1 , the first ring gear R 1 , a first pinion P 1 , a second pinion P 2 and a first carrier CA 1 . The first sun gear S 1 is coupled to the third ring gear R 3 . The first ring gear R 1 is selectively coupled to the third carrier CA 3 via the first clutch C 1 . The first pinion P 1 meshes with the first sun gear S 1 and the second pinion P 2 meshes with the first ring gear R 1 . The first carrier CA 1 supports the first pinion P 1 and the second pinion P 2 that mesh with each other, such that the first and second pinions P 1 , P 2 are able to rotate about themselves and rotate about the axis of the first planetary gear set 48 . The second planetary gear set 50 includes the second sun gear S 2 , a second ring gear R 2 , a third pinion P 3 , and a second carrier CA 2 . The second sun gear S 2 is selectively coupled to the transmission case 12 via the second brake B 2 , and is also selectively coupled to the input shaft 16 via the second clutch C 2 . The second ring gear R 2 is coupled to the output gear 24 . The third pinion P 3 meshes with the second sun gear S 2 and the second ring gear R 2 , and has a larger diameter than the second pinion P 2 . The third pinion P 3 is coaxially coupled to the second pinion P 2 such that the third and second pinions P 3 , P 2 rotate as a unit. The second carrier CA 2 supports the third pinion P 3 such that the third pinion P 3 is able to rotate about itself and rotate about the axis of the second planetary gear set 50 . Furthermore, the second carrier CA 2 is coupled to the first carrier CA 1 such that the first and second carriers CA 1 , CA 2 rotate as a unit, and is also selectively coupled to the transmission case 12 via a first brake B 1 . A one-way clutch F 1 is disposed in parallel with the first brake B 1 , between the second carrier CA 2 and the transmission case 12 . The first brake B 1 and the one-way clutch F 1 may be replaced by only one of the first brake B 1 and the one-way clutch F 1 .

The first clutch C 1 , second clutch C 2 , first brake B 1 , second brake B 2 and the third brake B 3 are hydraulically operated friction devices, which may be generally used in conventional planetary gear type automatic transmissions. Each of the friction devices serves to selectively couple two members between which the device is interposed, to each other. For example, the friction device may be of a wet multiple disc type in which a plurality of friction discs or plates that are superposed on each other are pressed by a hydraulic actuator, or may be in the form of a band brake in which one end of one or two band(s) wound around the outer periphery of a rotating drum is strained or drawn in by a hydraulic actuator. The one-way clutch F 1 disposed in parallel with the first brake B 1 also functions as an engaging device equivalent to the first brake, and only one of the one-way clutch F 1 and the first brake B 1 may be provided.

In the transmission 40 constructed as described above, a selected one of the forward 1 st -speed gear stage through 7 th -speed gear stage and the reverse gear stage is established by engaging two friction devices selected from the first clutch C 1 , second clutch C 2 , first brake B 1 , second brake B 2 and the third brake B 3 at the same time, as indicated in the operation table of FIG. 6 . As described later, the gear ratios γ (=input shaft rotational speed Nin/output shaft rotational speed Nout) of the forward gear stages differ successively at substantially equal ratios (namely, the ratio of the gear ratio γ of one of the forward gear stages to that of the next gear stage is substantially constant.)

More specifically described referring to FIG. 6, the 1 st -speed gear stage having the largest gear ratio γ 1 , which is, for example, equal to about 3.90, is established by engaging the third brake B 3 and the first brake B 1 so that the third sun gear S 3 and the transmission case 12 are coupled to each other and the second carrier CA 2 and the transmission case 12 are coupled to each other. The 2 nd -speed gear stage having a gear ratio γ 2 , which is smaller than the gear ratio γ 1 and is, for example, equal to about 2.64, is established by engaging the third brake B 3 and the second brake B 2 so that the third sun gear S 3 and the transmission case 12 are coupled to each other and the second sun gear S 2 and the transmission case 12 are coupled to each other. The 3 rd -speed gear stage having a gear ratio γ 3 , which is smaller than the gear ratio γ 2 and is, for example, equal to about 1.81, is established by engaging the second clutch C 2 and the third brake B 3 so that the input shaft 16 and the second sun gear S 2 are coupled to each other, and the third sun gear S 3 and the transmission case 12 are coupled to each other. The 4 th -speed gear stage having a gear ratio γ 4 , which is smaller than the gear ratio γ 3 and is, for example, equal to about 1.20, is established by engaging the first clutch C 1 and the third brake B 3 so that the input shaft 16 and the first ring gear R 1 are coupled to each other, and the third sun gear S 3 and the transmission case 12 are coupled to each other. The 5 th -speed gear stage having a gear ratio γ 5 , which is smaller than the gear ratio γ 4 and is, for example, equal to about 1.00, is established by engaging the first clutch C 1 and the second clutch C 2 so that the input shaft 16 and the first ring gear R 1 are coupled to each other, and the input shaft 16 and the second sun gear S 2 are coupled to each other. The 6 th -speed gear stage having a gear ratio γ 6 , which is smaller than the gear ratio γ 5 and is, for example, equal to about 0.91, is established by engaging the first clutch C 1 and the second brake B 2 so that the input shaft 16 and the first ring gear R 1 are coupled to each other and the second sun gear S 2 and the transmission case 12 are coupled to each other. The 7 th -speed gear stage having a gear ratio γ 7 , which is smaller than the gear ratio γ 6 and is, for example, equal to about 0.65, is established by engaging the first clutch C 1 and the first brake B 1 so that the input shaft 16 and the first ring gear R 1 are coupled to each other and the second carrier CA 2 and the transmission case 12 are coupled to each other. The reverse gear stage having a gear ratio γ R , which is between the gear ratio γ 1 and the gear ratio γ 2 and is, for example, equal to about 2.79, is established by engaging the second clutch C 2 and the first brake B 1 so that the input shaft 16 and the second sun gear S 2 are coupled to each other and the second carrier CA 2 and the transmission case 12 are coupled to each other. The gear ratio (=the number of teeth of the sun gear/the number of teeth of the ring gear) ρ 1 of the first planetary gear set 48 , the gear ratio ρ 2 of the second planetary gear set 50 , and the gear ratio ρ 3 of the third planetary gear set 52 are determined so as to provide the gear ratios γ 1 -γ 7 and γ R as indicated above. For example, ρ 1 is equal to 0.36, ρ 2 is equal to 0.36, and ρ 3 is equal to 0.54.

In the transmission 40 as described above, the rate of change of the gear ratio (i.e., ratio of the gear ratios of the adjacent gear stages=γ n /γ n+1 ) may be determined as follows: the ratio (=γ 1 /γ 2 ) of the gear ratio γ 1 of the 1 st -speed gear stage to the gear ratio γ 2 of the 2 nd -speed gear stage is 1.48, the ratio (=γ 2 /γ 3 ) of the gear ratio γ 2 of the 2 nd -speed gear stage to the gear ratio γ 3 of the 3 rd -speed gear stage is 1.46, the ratio (=γ 3 /γ 4 ) of the gear ratio γ 3 of the 3 rd -speed gear stage to the gear ratio γ 4 of the 4 th -speed gear stage is 1.51, the ratio (=γ 4 /γ 5 ) of the gear ratio γ 4 of the 4 th -speed gear stage to the gear ratio γ 5 of the 5 th -speed gear stage is 1.20, the ratio (=γ 5 /γ 6 ) of the gear ratio γ 5 of the 5 th -speed gear stage to the gear ratio γ 6 of the 6 th -speed gear stage is 1.10, and the ratio (=γ 6 /γ 7 ) of the gear ratio γ 6 of the 6 th -speed gear stage to the gear ratio γ 7 of the 7 th -speed gear stage is 1.40. Thus, the gear ratios γ change at substantially equal ratios or rates. Also, in the transmission 40 , the total width of the gear ratios (γ 1 /γ 7 ), namely, the ratio of the gear ratio γ 1 of the 1 st -speed gear stage to the gear ratio γ 7 of the 7 th -speed gear stage, is a sufficiently large value, which is, for example, 6.00. Also, the gear ratio of the reverse gear stage “Rev” is an appropriate value. Thus, the transmission 40 provides appropriate gear-ratio (speed-change) characteristics over the entire range of operation.

FIG. 7 is a nomogram in which straight lines represent the relationships of the speeds of rotation of rotating elements (as described later) which are in different coupling states for respective gear stages. The nomogram of FIG. 7 is a two-dimensional coordinate system in which the horizontal axis indicates the relationship among the gear ratios ρ of the respective planetary gear sets 48 , 50 , 52 , and the vertical axis indicates relative rotational speeds. In the nomogram of FIG. 7, the lower horizontal line X 1 , out of three horizontal lines, indicates rotational speed “0”, and the middle horizontal line X 3 indicates a rotation speed lower than the speed of rotation of the input shaft 16 , while the upper horizontal line X 2 indicates rotational speed “1.0”, which is equal to the speed of rotation of the input shaft 16 . Five vertical lines Y 1 through Y 5 arranged from the left to the right in the section of the main power transmitting portion 58 respectively represent the second sun gear S 2 corresponding to the first rotating element RE 1 , the first carrier CA 1 and the second carrier CA 2 that are coupled to each other and correspond to the second rotating element RE 2 , the first ring gear R 1 corresponding to the third rotating element RE 3 , the second ring gear R 2 corresponding to the fourth rotating element RE 4 , and the first sun gear S 1 corresponding to the fifth rotating element RE 5 . The intervals of these vertical lines are determined in accordance with the gear ratio ρ 1 of the first planetary gear set 48 and the gear ratio ρ 2 of the second planetary gear set 50 . More specifically, the interval between the vertical lines corresponding to the sun gear and the carrier is set as “1”, and the interval between the vertical lines corresponding to the carrier and the ring gear is set as “ρ”.

The main power transmitting portion 58 will be described by utilizing the nomogram of FIG. 7 . Parts of the first sun gear S 1 , first carrier CA 1 and the first ring gear R 1 of the first planetary gear set 48 and the second sun gear S 2 , second carrier CA 2 and the second ring gear R 2 of the second planetary gear set 50 are coupled to each other so as to provide five rotating elements RE 1 through RE 5 . In the monogram of FIG. 7, the speeds of rotation of the five rotating elements RE 1 through RE 5 are represented by straight lines, and the first rotating element RE 1 , second rotating element RE 2 , third rotating element RE 3 , fourth rotating element RE 4 and the fifth rotating element RE 5 are arranged in this order from one end (i.e., the left end in FIG. 7) to the other end (i.e., the right end in FIG. 7 ). In the transmission 40 of this embodiment, the first rotating element RE 1 (S 2 ) is selectively inhibited from rotating by the second brake B 2 , and is selectively coupled to the input shaft 16 (input member) via the second clutch C 2 . The second rotating element RE 2 (CA 1 , CA 2 ) is selectively inhibited from rotating by the first brake B 1 , and the third rotating element RE 3 (R 1 ) is selectively coupled to the input shaft 16 (input member) via the first clutch C 1 . The fifth rotating element RE 5 (S 1 ) is coupled to the third ring gear R 3 (intermediate rotating member), and the fourth rotating element RE 4 (R 2 ) is coupled to the output gear 24 (output member).

As is apparent from the nomogram of FIG. 7, when the third brake B 3 and the first brake B 1 are engaged, and the third sun gear S 3 is inhibited from rotating while the second rotating element RE 2 (CA 1 , CA 2 ) is also inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “1 st ” in FIG. 7, so that the 1 st -speed gear stage having the largest gear ratio is established. When the third brake B 3 and the second brake B 2 are engaged, and the third sun gear S 3 is inhibited from rotating while the first rotating element RE 1 (S 2 ) is also inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “2 nd ” in FIG. 7, so that the 2 nd -speed gear stage having a smaller gear ratio than that of the 1 st -speed gear stage is established. When the second clutch C 2 and the third brake B 3 are engaged, and the first rotating element RE 1 (S 2 ) is rotated at the same speed as the input shaft 16 while the third sun gear S 3 is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “3 rd ” in FIG. 7, so that the 3 rd -speed gear stage having a smaller gear ratio than that of the 2 nd -speed gear stage is established. When the first clutch C 1 and the third brake B 3 are engaged, and the third rotating element RE 3 (R 1 ) is rotated at the same speed as the input shaft 16 while the third sun gear S 3 is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “4 th ” in FIG. 7, so that the 4 th -speed gear stage having a smaller gear ratio than that of the 3 rd -speed gear stage is established. When the first clutch C 1 and the second clutch C 2 are engaged, and the third rotating element RE 3 (R 1 ) is rotated along with the input shaft 16 while the first rotating element RE 1 (S 2 ) is also rotated along with the input shaft 16 , the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “5 th ” in FIG. 7, namely, at the same speed as the input shaft 16 , so that the 5 th -speed gear stage having a smaller gear ratio than that of the 4 th -speed gear stage is established. The gear ratio of the 5 th -speed gear stage is equal to 1. When the first clutch C 1 and the second brake B 2 are engaged, and the third rotating element RE 3 (R 1 ) is rotated along with the input shaft 16 while the first rotating element RE 1 (S 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “6 th ” in FIG. 7, so that the 6 th -speed gear stage having a smaller gear ratio than that of the 5 th -speed gear stage is established. When the first clutch C 1 and the first brake B 1 are engaged, and the third rotating element RE 3 (R 1 ) is rotated along with the input shaft 16 while the second rotating element RE 2 (CA 1 , CA 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “7 th ” in FIG. 7, so that the 7 th -speed gear stage having a smaller gear ratio than that of the 6 th -speed gear stage is established.

When the second clutch C 2 and the first brake B 1 are engaged, and the first rotating element RE 1 (S 2 ) is rotated along with the input shaft 16 while the second rotating element RE 2 (CA 1 , CA 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated in the reverse direction at a speed denoted by “REV” in FIG. 7, so that the reverse gear stage “Rev” is established.

As described above, the automatic transmission 40 of the present embodiment is able to establish seven forward gear stages by using three gear sets, i.e., the first planetary gear set 48 , second planetary gear set 50 , and the third planetary gear set 52 , and a total of five friction devices, i.e., two clutches C 1 and C 2 and three brakes B 1 , B 2 and B 3 . Thus, the weight and size of the transmission 40 can be reduced as compared with the case where four planetary gear sets are used, thus making it easier to install the transmission 40 on the vehicle. At the same time, the number of friction devices required for shifting the transmission 40 is reduced, resulting in a reduced number of components and reduced cost. Furthermore, the drag resistance is reduced, and the fuel economy can be further improved.

In the third embodiment as described above, the second pinion P 2 of the double-pinion type first planetary gear set 48 and the third pinion P 3 of the single-pinion type second planetary gear set 50 are coupled to each other on the same axis so that these pinions P 2 , P 3 are rotated as a unit. Like Ravigneaux type planetary gear trains, this arrangement requires a further reduced number of components and further reduced axial length, which result in further reduction in the size and cost of the transmission 40 .

In the third embodiment as described above, the main power transmitting portion 58 includes the first planetary gear set 48 and the second planetary gear set 50 , and the first rotating element RE 1 is the second sun gear S 2 , the second rotating element RE 2 consists of the first carrier CA 1 and the second carrier CA 2 , the third rotating element RE 3 is the first ring gear R 1 , the fourth rotating element RE 4 is the second ring gear R 2 , and the fifth rotating element RE 5 is the first sun gear S 1 . With this arrangement, the automatic transmission 40 having seven forward gear stages can be made compact.

Next, a fourth embodiment of the invention will be described. In the following description, the same reference numerals as used in the third embodiment will be used for identifying corresponding elements or portions, of which no detailed description is provided.

FIG. 8 schematically shows the construction of an automatic transmission 60 that provides seven forward gear stages by using five friction devices, like the transmission 40 of the third embodiment. The transmission 60 is different from the transmission 40 in that the third sun gear S 3 of the auxiliary power transmitting portion 56 is coupled to the transmission case 12 such that the sun gear S 3 is inhibited from rotating, and that a third clutch C 3 is provided between the third ring gear R 3 and the first sun gear S 1 , such that the third ring gear R 3 and the first sun gear S 1 are selectively coupled to each other. The transmission 60 is similar to the transmission 40 in the other aspects. In the fourth embodiment, the third clutch C 3 similar to the third brake B 3 of the transmission 40 functions as an intermediate rotation output friction device, which operates, when engaged, to transmit rotary power from the third ring gear R 3 serving as an intermediate rotating member to the first sun gear S 1 of the main power transmitting portion 58 at a lower speed than that of the input shaft 16 . Thus, the transmission 60 is able to establish seven forward gear stages based on an operation table similar to that of FIG. 6 and a nomogram similar to that of FIG. 7, in which the third brake B 3 is replaced by the third clutch C 3 . The rotating elements RE 1 , RE 2 , RE 3 , RE 4 and RE 5 of this embodiment are identical with those of the third embodiment.

Next, a fifth embodiment of the invention will be described. FIG. 9 schematically shows the construction of an automatic transmission 70 that provides seven forward gear stages by using three planetary gear sets, like the transmission 40 and the transmission 60 of the third and fourth embodiments. FIG. 10 is a monogram plotted with respect to the transmission of FIG. 9 . An operation table indicating the combination of friction devices used for establishing each of a plurality of gear stages is similar to that of FIG. 6, and is therefore omitted. The transmission 70 of this embodiment includes an auxiliary power transmitting portion 66 that mainly consists of a third planetary gear set 80 of a double pinion type, and a main power transmitting portion 68 that mainly consists of a first planetary gear set 76 of a double pinion type and a second planetary gear set 78 of a double pinion type. The transmission 70 is adapted to establish a selected one of seven forward gear stages having seven different gear ratios γ n and one reverse gear stage, by engaging selected ones of five friction devices. With the selected gear stage thus established, the transmission 70 changes the speed of rotation of the input shaft 16 at a gear ratio corresponding to the gear stage, and transmits the resulting rotary power to the output gear 24 . As shown in FIG. 9, the third planetary gear set 80 , first planetary gear set 76 and the second planetary gear set 78 are arranged in this order from the side of the input shaft 16 along the axis of rotation thereof.

In the auxiliary power transmitting portion 66 , the third planetary gear set 80 includes a third sun gear S 3 , a third ring gear R 3 , a fifth pinion P 5 , a sixth pinion P 6 , and a third carrier CA 3 . The third sun gear S 3 is coupled to the input shaft 16 , and the third ring gear R 3 is disposed coaxially with and radially outwardly of the third sun gear S 3 . The fifth pinion P 5 meshes with the third sun gear S 3 , and the sixth pinion P 6 meshes with the third ring gear R 3 . The third carrier CA 3 supports the fifth pinion P 5 and the sixth pinion P 6 that mesh with each other, such that the fifth and sixth pinions P 5 , P 6 are able to rotate about themselves and rotate about the axis of the third planetary gear set 80 (i.e., input shaft 16 ). The third carrier CA 3 is also selectively coupled to the transmission case 12 via a third brake B 3 . In the third planetary gear set 80 , when the third carrier CA 3 is inhibited from rotating by engagement of the third brake B 3 , the third ring gear R 3 reduces the speed of rotation of the third sun gear S 3 coupled to the input shaft 16 , and transmits the reduced-speed rotation to the first carrier CA 1 and the second carrier CA 2 of the main power transmitting portion 68 . Thus, the third ring gear R 3 functions as an intermediate rotating member which is adapted to rotate at a lower speed than the input shaft 16 when the third brake B 3 serving as an intermediate rotation output friction device is engaged, so as to transmit rotary power to the main power transmitting portion 68 at a lower rotational speed than that of the input shaft 16 .

In the main power transmitting portion 68 , the first planetary gear set 76 includes a first sun gear S 1 , a first ring gear R 1 , a first pinion P 1 , a second pinion P 2 and a first carrier CA 1 . The first sun gear S 1 is selectively coupled to the transmission case 12 via a second brake B 2 , and is also selectively coupled to the input shaft 16 via a second clutch C 2 . The first ring gear R 1 is selectively coupled to the input shaft 16 via a first clutch C 1 . The first pinion P 1 meshes with the first sun gear S 1 and the second pinion P 2 meshes with the first ring gear R 1 . The first carrier CA 1 supports the first pinion P 1 and the second pinion P 2 that mesh with each other, such that the first and second pinions P 1 , P 2 are able to rotate about themselves and rotate about the axis of the first planetary gear set 76 . The second planetary gear set 78 includes a second sun gear S 2 , a second ring gear R 2 , a third pinion P 3 , a fourth pinion P 4 , and a second carrier CA 2 . The second sun gear S 2 is selectively coupled to the transmission case 12 via a first brake B 1 , and the second ring gear R 2 is coupled to the output gear 24 . The third pinion P 3 meshes with the second sun gear S 2 , and has a smaller diameter than the first pinion P 1 . The third pinion P 3 is coaxially coupled to the first pinion P 1 such that the first and third pinions P 1 , P 3 rotate as a unit. The fourth pinion P 4 meshes with the second ring gear R 2 . The second carrier CA 2 supports the third pinion P 3 and the fourth carrier P 4 that mesh with each other such that the third and fourth pinions P 3 , P 4 are able to rotate about themselves and rotate about the axis of the second planetary gear set 78 . Furthermore, the second carrier CA 2 is coupled to the first carrier CA 1 such that the first and second carriers CA 1 , CA 2 rotate as a unit, and is also coupled to the third ring gear R 3 .

The first pinion P 1 and the third pinion P 3 may be formed by gear cutting from the same member, or may be formed from different members and fixed integrally with each other. While the first pinion P 1 has a larger diameter than the third pinion P 3 , the diameter of the first pinion P 1 may be made equal to or smaller than that of the third pinion P 3 so as to provide appropriate gear ratios γ. In this embodiment, a one-way clutch F 1 is provided in parallel with the first brake B 1 disposed between the second sun gear S 2 and the transmission case 12 . The first brake B 1 and the one-way clutch F 1 may be replaced by either of the first brake B 1 and the one-way clutch F 1 .

In the transmission 70 constructed as described above, a selected one of the forward 1 st -speed gear stage through 7 th -speed gear stage and the reverse gear stage is established by engaging two friction devices selected from five friction devices, i.e., the first clutch C 1 , second clutch C 2 , first brake B 1 , second brake B 2 and the third brake B 3 at the same time, as indicated in the operation table of FIG. 6 . As described later, the gear ratios γ of the forward gear stages change at substantially equal ratios (namely, the ratio of the gear ratio γ of one of the forward gear stages to that of the next gear stage is substantially constant.)

In the main power transmitting portion 68 of the transmission 70 of the fifth embodiment, parts of the first sun gear S 1 , first carrier CA 1 and the first ring gear R 1 of the first planetary gear set 76 and the second sun gear S 2 , second carrier CA 2 and the second ring gear R 2 of the second planetary gear set 78 are coupled to each other so as to provide five rotating elements RE 1 through RE 5 , as shown in the monogram of FIG. 10 . In the monogram of FIG. 10, the speeds of rotation of the five rotating elements RE 1 through RE 5 are represented by straight lines, and the first rotating element RE 1 , second rotating element RE 2 , third rotating element RE 3 , fourth rotating element RE 4 and the fifth rotating element RE 5 are arranged in this order from one end (i.e., the left end in FIG. 10) to the other end (i.e., the right end in FIG. 10 ). In the transmission 70 of this embodiment, the first rotating element RE 1 (S 1 ) is selectively inhibited from rotating by the second brake B 2 , and is selectively coupled to the input shaft 16 (input member) via the second clutch C 2 . The second rotating element RE 2 (S 2 ) is selectively inhibited from rotating by the first brake B 1 , and the third rotating element RE 3 (R 1 ) is selectively coupled to the input shaft 16 (input member) via the first clutch C 1 . The fifth rotating element RE 5 (CA 1 , CA 2 ) is coupled to the third ring gear R 3 (intermediate rotating member), and the fourth rotating element RE 4 (R 2 ) is coupled to the output gear 24 (output member).

As is apparent from the nomogram of FIG. 10, when the third brake B 3 and the first brake B 1 are engaged, and the third carrier CA 3 is inhibited from rotating while the second rotating element RE 2 (S 2 ) is also inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “1 st ” in FIG. 10, so that the 1 st -speed gear stage having the largest gear ratio is established. When the third brake B 3 and the second brake B 2 are engaged, and the third carrier CA 3 is inhibited from rotating while the first rotating element RE 1 (S 1 ) is also inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “2 nd ” in FIG. 10, so that the 2 nd -speed gear stage having a smaller gear ratio than that of the 1 st -speed gear stage is established. When the second clutch C 2 and the third brake B 3 are engaged, and the first rotating element RE 1 (S 1 ) is rotated at the same speed as the input shaft 16 while the third carrier CA 3 is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “3 rd ” in FIG. 10, so that the 3 rd -speed gear stage having a smaller gear ratio than that of the 2 nd -speed gear stage is established. When the first clutch C 1 and the third brake B 3 are engaged, and the third rotating element RE 3 (R 1 ) is rotated at the same speed as the input shaft 16 while the third carrier CA 3 is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “4 th ” in FIG. 10, so that the 4 th -speed gear stage having a smaller gear ratio than that of the 3 rd -speed gear stage is established. When the first clutch C 1 and the second clutch C 2 are engaged, and the third rotating element RE 3 (R 1 ) is rotated along with the input shaft 16 while the first rotating element RE 1 (S 1 ) is also rotated along with the input shaft 16 , the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “5 th ” in FIG. 10, namely, at the same speed as the input shaft 16 , so that the 5 th -speed gear stage having a smaller gear ratio than that of the 4 th -speed gear stage is established. The gear ratio of the 5 th -speed gear stage is equal to 1. When the first clutch C 1 and the second brake B 2 are engaged, and the third rotating element RE 3 (R 1 ) is rotated along with the input shaft 16 while the first rotating element RE 1 (S 1 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “6 th ” in FIG. 10, so that the 6 th -speed gear stage having a smaller gear ratio than that of the 5 th -speed gear stage is established. When the first clutch C 1 and the first brake B 1 are engaged, and the third rotating element RE 3 (R 1 ) is rotated along with the input shaft 16 while the second rotating element RE 2 (S 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated at a speed denoted by “7 th ” in FIG. 10, so that the 7 th -speed gear stage having a smaller gear ratio than that of the 6 th -speed gear stage is established.

When the second clutch C 2 and the first brake B 1 are engaged, and the first rotating element RE 1 (S 1 ) is rotated along with the input shaft 16 while the second rotating element RE 2 (S 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 2 ) is rotated in the reverse direction at a speed denoted by “REV” in FIG. 10, so that the reverse gear stage “Rev” is established.

As described above, the automatic transmission 70 of the present embodiment is able to establish seven forward gear stages by using five friction devices, i.e., two clutches C 1 , C 2 and three brakes B 1 , B 2 and B 3 , in a similar manner to the transmission 40 of FIG. 5 . Thus, the number of friction devices required for shifting the transmission 70 is reduced, resulting in a reduced number of components and reduced cost. Furthermore, the drag resistance is reduced, and the fuel economy can be further improved.

Next, a sixth embodiment of the invention will be described. FIG. 11 schematically shows the construction of an automatic transmission 90 that provides seven forward gear stages by using five friction devices, like the transmission 70 of the fifth embodiment. The transmission 90 is different from the transmission 70 in that the third carrier CA 3 of the auxiliary power transmitting portion 66 is directly coupled to the transmission case 12 so as to be inhibited from rotating, and that a third clutch C 3 is provided between the third ring gear R 3 and the first and second carriers CA 1 , CA 2 , such that the third ring gear R 3 and the first and second carriers CA 1 , CA 2 are selectively coupled to each other. The transmission 90 is similar to the transmission 70 in the other aspects. In the sixth embodiment, the third clutch C 3 similar to the third brake B 3 of the transmission 70 functions as an intermediate rotation output friction device, which operates, when engaged, to transmit rotary power from the third ring gear R 3 serving as an intermediate rotating member to the first and second carriers CA 1 , CA 2 of the main power transmitting portion 68 at a lower speed than that of the input shaft 16 . Thus, the transmission 90 is able to establish seven forward gear stages based on an operation table similar to that of FIG. 6 and a nomogram similar to that of FIG. 10, in which the third brake B 3 is replaced by the third clutch C 3 . The rotating elements RE 1 , RE 2 , RE 3 , RE 4 and RE 5 of this embodiment are identical with those of the transmission 70 of the fifth embodiment.

Next, a seventh embodiment of the invention will be described. FIG. 12 schematically shows the construction of an automatic transmission 100 that provides seven forward gear stages by using five friction devices, like the transmission 40 and the transmission 70 of the third and fifth embodiments. FIG. 13 is a monogram plotted with respect to the transmission of FIG. 10 . An operation table indicating the combination of engaging devices used for establishing each of a plurality of gear stages is similar to that of FIG. 6, and is therefore omitted. The transmission 100 of this embodiment includes an auxiliary power transmitting portion 86 that mainly consists of a fourth planetary gear set 112 of a double pinion type, and a main power transmitting portion 88 that mainly consists of a first planetary gear set 106 , a second planetary gear set 108 , and a third planetary gear set 110 , all of which are of a single pinion type. The transmission 100 is adapted to establish a selected one of seven forward gear stages having seven different gear ratios γ n and one reverse gear stage, by engaging selected ones of five friction devices. With the selected gear stage thus established, the transmission 100 changes the speed of rotation of the input shaft 16 at a gear ratio corresponding to the selected gear stage, and transmits the resulting rotary power to the output gear 24 . As shown in FIG. 12, the first planetary gear set 106 , second planetary gear set 108 , third planetary gear set 110 and the fourth planetary gear set 112 are coaxially arranged in this order from the side of the input shaft 16 along the axis of rotation thereof.

In the auxiliary power transmitting portion 86 , the fourth planetary gear set 112 includes a fourth sun gear S 4 , a fourth ring gear R 4 , a fourth pinion P 4 , a fifth pinion P 5 and a fourth carrier CA 4 . The fourth sun gear S 4 is coupled to the input shaft 16 , and the fourth ring gear R 4 is disposed coaxially with and radially outwardly of the fourth sun gear S 4 , and is coupled to a second sun gear S 2 and a third sun gear S 3 . The fourth pinion P 4 meshes with the fourth sun gear S 4 , and the fifth pinion P 5 meshes with the fourth ring gear R 4 . The fourth carrier CA 4 supports the fourth pinion P 4 and the fifth pinion P 5 that mesh with each other, such that the fourth and fifth pinions P 4 , P 5 are able to rotate about themselves and rotate about the axis of the fourth planetary gear set 112 (i.e., input shaft 16 ). The fourth carrier CA 4 is also selectively coupled to the transmission case 12 via a third brake B 3 . In the fourth planetary gear set 112 , when the fourth carrier CA 4 is inhibited from rotating by engagement of the third brake B 3 , the fourth ring gear R 4 reduces the speed of rotation of the fourth sun gear S 4 coupled to the input shaft 16 , and transmits the reduced-speed rotation to the second sun gear S 2 and the third sun gear S 3 of the main power transmitting portion 88 . Thus, the fourth ring gear R 4 functions as an intermediate rotating member which is adapted to rotate at a lower speed than the input shaft 16 so as to transmit rotary power to the main power transmitting portion 88 at a lower rotational speed than that of the input shaft 16 . Also, the third brake B 3 functions as an intermediate rotation output friction device which operates, when engaged, to transmit rotary power from the fourth ring gear R 4 to the second sun gear S 2 and the third sun gear S 3 of the main power transmitting portion 88 at a speed lower than that of the input shaft 16 .

In the main power transmitting portion 88 , the first planetary gear set 106 includes the first sun gear S 1 , a first ring gear R 1 , a first pinion P 1 and a first carrier CA 1 . The first sun gear S 1 is selectively coupled to the input shaft 16 via a second clutch C 2 , and the first ring gear R 1 is coupled to the output gear 24 . The first pinion P 1 meshes with the first sun gear S 1 and the first ring gear R 1 . The first carrier CA 1 supports the first pinion P 1 such that the first pinion P 1 is able to rotate about itself and rotate about the axis of the first planetary gear set 106 . The first carrier CA 1 is also selectively coupled to the transmission case 12 via a first brake B 1 . The second planetary gear set 108 includes the second sun gear S 2 , a second ring gear R 2 , a second pinion P 2 and a second carrier CA 2 . The second sun gear S 2 is coupled to the fourth ring gear R 4 serving as an intermediate rotating member. The second ring gear R 2 is coupled to the first carrier CA 1 , and is also selectively coupled to the transmission case 12 via the first brake B 1 . The second pinion P 2 meshes with the second sun gear S 2 and the second ring gear R 2 . The second carrier CA 2 supports the second pinion P 2 such that the second pinion P 2 is able to rotate about itself and rotate about the axis of the second planetary gear set 108 . The second carrier CA 2 is also selectively coupled to the input shaft 16 via a first clutch C 1 . The third planetary gear set 110 includes a third sun gear S 3 , a third ring gear R 3 . a third pinion P 3 and a third carrier CA 3 . The third sun gear S 3 is coupled to the fourth ring gear R 4 and the second sun gear S 2 . The third ring gear R 3 is coupled to the second carrier CA 2 , and is also selectively coupled to the input shaft 16 via the first clutch C 1 . The third pinion P 3 meshes with the third sun gear S 3 and the third ring gear R 3 . The third carrier CA 3 supports the third pinion P 3 such that the third pinion P 3 is able to rotate about itself and rotate about the axis of the third planetary gear set 110 . The third carrier CA 3 is also coupled to the first ring gear R 1 and the output gear 24 .

In the seventh embodiment, a one-way clutch F 1 is provided in parallel with the first brake B 1 disposed between the first carrier CA 1 and the transmission case 12 . The first brake B 1 and the one-way clutch F 1 may be replaced by either of the first brake B 1 and the one-way clutch F 1 .

In the transmission 100 constructed as described above, a selected one of the forward 1 st -speed gear stage through 7 th -speed gear stage and the reverse gear stage is established by engaging two friction devices selected from five friction devices, i.e., the first clutch C 1 , second clutch C 2 , first brake B 1 , second brake B 2 and the third brake B 3 at the same time, as indicated in the operation table of FIG. 6 . Similarly to the transmission 40 of FIG. 5, the gear ratios γ of the forward gear stages differ successively at substantially equal ratios (namely, the ratio of the gear ratio γ of one of the forward gear stages to that of the next gear stage is substantially constant.)

In the main power transmitting portion 88 of the transmission 100 of the seventh embodiment, parts of the first sun gear S 1 , first carrier CA 1 and the first ring gear R 1 of the first planetary gear set 106 , the second sun gear S 2 , second carrier CA 2 and the second ring gear R 2 of the second planetary gear set 108 , and the third sun gear S 3 , third carrier CA 3 and the third ring gear R 3 of the third planetary gear set 110 are coupled to each other so as to provide five rotating elements RE 1 through RE 5 , as shown in the monogram of FIG. 13 . In the monogram of FIG. 13, the speeds of rotation of the five rotating elements RE 1 through RE 5 are represented by straight lines, and the first rotating element RE 1 , second rotating element RE 2 , third rotating element RE 3 , fourth rotating element RE 4 and the fifth rotating element RE 5 are arranged in this order from one end (the left end in FIG. 13) to the other end (the right end in FIG. 13 ). In the transmission 100 of this embodiment, the first rotating element RE 1 (S 1 ) is selectively inhibited from rotating by the second brake B 2 , and is selectively coupled to the input shaft 16 (input member) via the second clutch C 2 . The second rotating element RE 2 (R 2 , CA 1 ) is selectively inhibited from rotating by the first brake B 1 , and the third rotating element RE 3 (R 3 , CA 2 ) is selectively coupled to the input shaft 16 (input member) via the first clutch C 1 . The fifth rotating element RE 5 (S 2 , S 3 ) is coupled to the fourth ring gear R 4 (intermediate rotating member), and the fourth rotating element RE 4 (R 1 , CA 3 ) is coupled to the output gear 24 (output member).

As is apparent from the nomogram of FIG. 13, when the third brake B 3 and the first brake B 1 are engaged, and the fourth carrier CA 4 is inhibited from rotating while the second rotating element RE 2 (CA 1 , R 2 ) is also inhibited from rotating, the fourth rotating element RE 4 (R 1 , CA 3 ) is rotated at a speed denoted by “1 st ” in FIG. 13, so that the 1 st -speed gear stage having the largest gear ratio is established. When the third brake B 3 and the second brake B 2 are engaged, and the fourth carrier CA 4 is inhibited from rotating while the first rotating element RE 1 (S 1 ) is also inhibited from rotating, the fourth rotating element RE 4 (R 1 , CA 3 ) is rotated at a speed denoted by “2 nd ” in FIG. 13, so that the 2 nd -speed gear stage having a smaller gear ratio than that of the 1 st -speed gear stage is established. When the second clutch C 2 and the third brake B 3 are engaged, and the first rotating element RE 1 (S 1 ) is rotated at the same speed as the input shaft 16 while the fourth carrier CA 4 is inhibited from rotating, the fourth rotating element RE 4 (R 1 , CA 3 ) is rotated at a speed denoted by “3 rd ” in FIG. 13, so that the 3 rd -speed gear stage having a smaller gear ratio than that of the 2 nd -speed gear stage is established. When the first clutch C 1 and the third brake B 3 are engaged, and the third rotating element RE 3 (CA 2 , R 3 ) is rotated at the same speed as the input shaft 16 while the fourth carrier CA 4 is inhibited from rotating, the fourth rotating element RE 4 (R 1 , CA 3 ) is rotated at a speed denoted by “4 th ” in FIG. 13, so that the 4 th -speed gear stage having a smaller gear ratio than that of the 3 rd -speed gear stage is established. When the first clutch C 1 and the second clutch C 2 are engaged, and the third rotating element RE 3 (CA 2 , R 3 ) is rotated along with the input shaft 16 while the first rotating element RE 1 (S 1 ) is also rotated along with the input shaft 16 , the fourth rotating element RE 4 (R 1 , CA 3 ) is rotated at a speed denoted by “5 th ” in FIG. 13, namely, at the same speed as the input shaft 16 , so that the 5 th -speed gear stage having a smaller gear ratio than that of the 4 th -speed gear stage is established. The gear ratio γ 5 of the 5 th -speed gear stage is equal to 1. When the first clutch C 1 and the second brake B 2 are engaged, and the third rotating element RE 3 (CA 2 , R 3 ) is rotated along with the input shaft 16 while the first rotating element RE 1 (S 1 ) is inhibited from rotating, the fourth rotating element RE 4 (R 1 , CA 3 ) is rotated at a speed denoted by “6 th ” in FIG. 13, so that the 6 th -speed gear stage having a smaller gear ratio than that of the 5 th -speed gear stage is established. When the first clutch C 1 and the first brake B 1 are engaged, and the third rotating element RE 3 (CA 2 , R 3 ) is rotated along with the input shaft 16 while the second rotating element RE 2 (CA 1 , R 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 1 , CA 3 ) is rotated at a speed denoted by “7 th ” in FIG. 13, so that the 7 th -speed gear stage having a smaller gear ratio than that of the 6 th -speed gear stage is established.

When the second clutch C 2 and the first brake B 1 are engaged, and the first rotating element RE 1 (S 1 ) is rotated along with the input shaft 16 while the second rotating element RE 2 (CA 1 , R 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 1 , CA 3 ) is rotated in the reverse direction at a speed denoted by “REV” in FIG. 13, so that the reverse gear stage “Rev” is established.

As described above, the automatic transmission 100 of the present embodiment is able to establish seven forward gear stages by using five friction devices, i.e., two clutches C 1 , C 2 and three brakes B 1 , B 2 and B 3 , in a similar manner to the transmission 40 of FIG. 5 . Thus, the number of friction devices required for shifting the transmission 100 is reduced, resulting in a reduced number of components and reduced cost. Furthermore, the drag resistance is reduced, and the fuel economy can be further improved.

Next, an eighth embodiment of the invention will be described. FIG. 14 schematically shows the construction of an automatic transmission 114 that provides seven forward gear stages by using five friction devices, like the transmission 100 of the seventh embodiment. The transmission 114 is different from the transmission 110 in that the fourth carrier CA 4 of the auxiliary power transmitting portion 86 is directly coupled to the transmission case 12 so as to be inhibited from rotating, and that a third clutch C 3 is provided between the fourth ring gear R 4 and the second and third sun gears S 2 , S 3 , such that the fourth ring gear R 4 and the second and third sun gears S 2 , S 3 are selectively coupled to each other. The transmission 114 is similar to the transmission 100 in the other aspects. In the eighth embodiment, the third clutch C 3 similar to the third brake B 3 of the transmission 100 functions as an intermediate rotation output friction device, and is thus able to establish seven forward gear stages based on an operation table similar to that of FIG. 6 and a nomogram similar to that of FIG. 13, in which the third brake B 3 is replaced by the third clutch C 3 . The rotating elements RE 1 , RE 2 , RE 3 , RE 4 and RE 5 of this embodiment are identical with those of the transmission 100 of the seventh embodiment.

While the third through eighth embodiments of the invention have been described in detail with reference to FIG. 5 through FIG. 14, the invention may be otherwise embodied.

While the third planetary gear set 52 , 80 or the fourth planetary gear set 112 that constitutes the auxiliary power transmitting portion 56 , 66 , 86 is of a double pinion type in the illustrated embodiments, the third or fourth planetary gear set 52 , 80 , 112 may be of a single pinion type. Also, any of the third sun gear S 3 or the fourth sun gear S 4 , the third carrier CA 3 or the fourth carrier CA 4 , and the third ring gear R 3 or the fourth ring gear R 4 corresponding to three rotating elements of the third or fourth planetary gear set 52 , 80 , 112 may be fixed, or may serve as an intermediate rotating member, or may be directly or indirectly coupled to the input member.

While the automatic transmissions 40 , 60 , 70 , 90 , 100 , 114 of the illustrated embodiments are suitably installed in the lateral direction on front engine front drive (FF) vehicles in which the axis of the transmission extends in the width direction of the vehicle, the transmissions 40 , 60 , 70 , 90 , 100 , 114 may be installed in the vertical direction on front engine rear drive (FR) vehicles in which the axis of the transmission extends in the longitudinal or running direction of the vehicle.

While the automatic transmission 40 , 60 , 70 , 90 , 100 , 114 may automatically change its gear ratio or gear stage depending upon vehicle operating conditions, such as an accelerator pedal position and a vehicle speed, the transmission may change its gear ratio in response to switching operations (e.g., upshifting and downshifting operations) performed by the vehicle operator or driver.

In the automatic transmission 40 , 60 , 70 , 90 , 100 , 114 as described above, hydraulically operated friction devices of multiple-disc type, single-disc type or belt type, which are frictionally engaged by use of hydraulic actuators, are suitably used as the first clutch C 1 , second clutch C 2 , third clutch C 3 , first brake B 1 , second brake B 2 and the third brake B 3 . However, other types of engaging devices, such as those of electromagnetic type, may also be used as the clutches and brakes. To make shift control easy, one-way clutches may be provided in parallel with the brakes or clutches. If an engine brake need not be applied, one-way clutches may be used in place of the brakes or clutches. Here, one-way clutches function, like brakes, to stop rotation of corresponding rotating members. Other than the above arrangements, the automatic transmission 40 , 60 , 70 , 90 , 100 , 114 may be constructed in various ways. For example, a brake and a one-way clutch, which are connected in series, may be provided in parallel with the first brake B 1 .

In the automatic transmission 40 , for example, the positional relationship between the main power transmitting portion 58 and the auxiliary power transmitting portion 56 and the positional relationship between the first planetary gear set 48 and the second planetary gear set 50 of the main power transmitting portion 58 are not particularly limited, but may be changed in various ways. In addition, the clutches and brakes may be located to be concentrated in one end portion of the transmission 40 , or may be otherwise positioned. Furthermore, the first planetary gear set 48 , second planetary gear set 50 and the third planetary gear set 52 are not necessarily disposed on the same axis.

While the vertical lines Y 1 , Y 2 , Y 3 , Y 4 , Y 5 respectively corresponding to the rotating elements RE 1 , RE 2 , RE 3 , RE 4 , RE 5 are arranged in this order from the left to the right in the nomogram of each of the illustrated embodiments, these vertical lines, Y 1 , Y 2 , Y 3 , Y 4 , Y 5 may be arranged in this order from the right to the left. While the horizontal line X 2 corresponding to the rotational speed “1” is located above the horizontal line X 1 corresponding to the rotational speed “0” in the nomogram, the horizontal line X 2 may be located below the horizontal line X 1 .

In the third embodiment of FIG. 5, the second pinion P 2 of the double-pinion type first planetary gear set 48 and the third pinion P 3 of the double-pinion type second planetary gear set 50 are coupled to each other on the same axis such that the pinions P 2 , P 3 are rotated as a unit. While the second pinion P 2 and the third pinion P 3 have different diameters in the illustrated embodiments, these pinions P 2 , P 3 may have the same diameter. It is also to be understood that the diameter (or the number of teeth) of each of the first pinion P 1 , second pinion P 2 , third pinion P 3 and the fourth pinion P 4 may be changed as needed.

While each of the main power transmitting portions 58 , 68 of the third through sixth embodiments of FIG. 5, FIG. 8, FIG. 9 and FIG. 11 is constituted by two planetary gear sets, and the main power transmitting portion 88 of the seventh and eighth embodiments of FIG. 12 and FIG. 14 is constituted by three planetary gear sets, the number of the planetary gear sets is not limited to two or three.

In the main power transmitting portions 58 of the illustrated embodiment, for example, the first rotating element RE 1 , second rotating element RE 2 , third rotating element RE 3 , fourth rotating element RE 4 , and the fifth rotating element RE 5 may be selected from the sun gears, ring gears and carriers of the first planetary gear set 48 and second planetary gear set 50 , and those of other planetary gear sets.

Next, a ninth embodiment of the invention will be described in detail with reference to FIG. 15, FIG. 16 and FIG. 17 . FIG. 15 schematically shows a planetary gear type automatic transmission (hereinafter simply referred to as “transmission”) 130 of a motor vehicle according to the ninth embodiment of the invention. FIG. 16 is an operation table indicating engaging devices for establishing each of a plurality of gear stages and the gear ratio of each gear stage. FIG. 17 is a nomogram plotted with respect to the transmission 130 of FIG. 15 .

Referring first to FIG. 15, the transmission 130 receives rotary power transmitted from an engine (not shown) to the input shaft 16 thereof, changes the speed of rotation at a given gear ratio, and transmits the resulting power from the output gear 24 to right and left driving wheels, via a propeller shaft (not shown), a differential gear unit (not shown), and other members. The transmission 130 includes a torque converter (not shown) provided with a lockup clutch, the input shaft 16 coupled to the torque converter, a third planetary gear set 122 , a first planetary gear set 118 , and a second planetary gear set 120 , which are arranged on the common axis of rotation within a transmission case (non-rotating member) 12 attached to the vehicle body. The transmission 130 further includes the output gear 24 that is disposed between the third planetary gear set 122 and the first planetary gear set 118 . The above-indicated torque converter is coupled to a crankshaft (not shown) of the engine. In this embodiment, the input shaft 16 and the output gear 24 correspond to an input rotating member and an output rotating member, respectively, and the transmission case 12 corresponds to a non-rotating or stationary member. It is to be noted that the transmission 130 is constructed symmetrically with respect to the rotational axis thereof, and that the lower half of the transmission 130 is not shown in FIG. 15 (i.e., only the upper half of the transmission 130 is illustrated in FIG. 15)

The automatic transmission 130 is transversely or laterally installed on, for example, a front engine front drive (FF) vehicle, such that the axis of the transmission 130 extends in the width direction of the vehicle. The transmission 130 includes an auxiliary power transmitting portion 126 that mainly consists of the third planetary gear set 122 of a double pinion type, and a main power transmitting portion 128 that mainly consists of the first planetary gear set 118 of a double pinion type and the second planetary gear set 120 of a double pinion type. The transmission 130 is adapted to establish a selected one of seven forward gear stages having seven different gear ratios γ n and one reverse gear stage, by engaging selected ones of five friction devices. With the selected gear stage thus established, the transmission 130 changes the speed of rotation of the input shaft 16 at a gear ratio corresponding to the gear stage, and transmits the resulting rotary power to the output gear 24 .

In the auxiliary power transmitting portion 126 , the third planetary gear set 122 includes a third sun gear S 3 , a third ring gear R 3 , a fifth pinion P 5 , a sixth pinion P 6 and a third carrier CA 3 . The third ring gear R 3 is disposed coaxially with and radially outwardly of the third sun gear S 3 . The fifth pinion P 5 meshes with the third sun gear S 3 , and the sixth pinion P 6 meshes with the third ring gear R 3 . The third carrier CA 3 supports the fifth pinion P 5 and the sixth pinion P 6 that mesh with each other, such that the fifth and sixth pinions P 5 , P 6 are able to rotate about themselves and rotate about the axis of the third planetary gear set 122 . The third sun gear S 3 is coupled to the transmission case 12 so as to be inhibited from rotating. The third carrier CA 3 of the third planetary gear set 122 is coupled to the input shaft 16 , and is also selectively coupled to a first carrier CA 1 of the first planetary gear set 118 via a second clutch C 2 , so as to transmit rotary power from the input shaft 16 to the main power transmitting portion 128 without changing its speed. The third ring gear R 3 of the third planetary gear set 122 is selectively coupled to a first sun gear S 1 of the first planetary gear set 118 via a first clutch C 1 , and is also selectively coupled to a second sun gear S 2 of the second planetary gear set 120 via a third clutch C 3 . Thus, the third ring gear R 3 functions as an intermediate rotating member that is rotated at a lower speed than that of the input shaft 16 so as to transmit rotary power to the main power transmitting portion 128 at the reduced speed.

In the main power transmitting portion 128 , the first planetary gear set 118 includes the first sun gear S 1 , a first ring gear R 1 , a first pinion P 1 , a second pinion P 2 and the first carrier CA 1 . The first sun gear S 1 is selectively coupled to the third ring gear R 3 via the first clutch C 1 . The first ring gear R 1 is coupled to the output gear 24 , and functions as an output member. The first pinion P 1 meshes with the first sun gear S 1 and the second pinion P 2 meshes with the first ring gear R 1 . The first carrier CA 1 supports the first pinion P 1 and the second pinion P 2 that mesh with each other, such that the first and second pinions P 1 , P 2 are able to rotate about themselves and rotate about the axis of the first planetary gear set 118 . The first carrier CA 1 is also selectively coupled to the input shaft 16 via a second clutch C 2 . The second planetary gear set 120 includes the second sun gear S 2 , a second ring gear R 2 , a third pinion P 3 , a fourth pinion P 4 and a second carrier CA 2 . The second sun gear S 2 is selectively coupled to the third ring gear R 3 (intermediate rotating member) via the third clutch C 3 , and is also selectively coupled to the transmission case 12 via a second brake B 2 . The second ring gear R 2 is selectively coupled to the transmission case 12 via a first brake B 1 and a one-way clutch F 1 that are arranged in parallel with each other. The third pinion P 3 meshes with the second sun gear S 2 , and the fourth pinion P 4 meshes with the second ring gear R 2 . The fourth pinion P 4 is coaxially coupled to the first pinion P 1 such that the first and fourth pinions P 1 , P 4 rotate as a unit. The second carrier CA 2 supports the third pinion P 3 and the fourth pinion P 4 that mesh with each other, such that the third and fourth pinions P 3 , P 4 are able to rotate about themselves and rotate about the axis of the second planetary gear set 120 . Also, the second carrier CA 2 is coupled to the first carrier CA 1 such that the first and second carriers CA 1 , CA 2 rotate as a unit.

The first clutch C 1 , second clutch C 2 , third clutch C 3 , first brake B 1 , and the second brake B 2 are hydraulically operated friction devices, which may be generally used in conventional planetary gear type automatic transmissions. Each of the friction devices serves to selectively couple two members between which the device is interposed, to each other. For example, the friction device may be of a wet multiple disc type in which a plurality of friction discs or plates that are superposed on each other are pressed by a hydraulic actuator, or may be in the form of a band brake in which one end of one or two band(s) wound around the outer periphery of a rotating drum is strained or drawn in by a hydraulic actuator. The one-way clutch F 1 disposed in parallel with the first brake B 1 also functions as an engaging device equivalent to the first brake, and only one of the one-way clutch F 1 and the first brake B 1 may be provided.

In the transmission 130 constructed as described above, a selected one of the forward 1 st -speed gear stage through 7 th -speed gear stage and the reverse gear stage is established by engaging two friction devices selected from the first clutch C 1 , second clutch C 2 , third clutch C 3 , first brake B 1 , and the second brake B 2 at the same time, as indicated in the operation table of FIG. 16 by way of example. As described later, the gear ratios γ (=input shaft rotational speed Nin/output shaft rotational speed Nout) of the forward gear stages differ successively at substantially equal ratios (namely, the ratio of the gear ratio γ of one of the forward gear stages to that of the next gear stage is substantially constant.)

More specifically described referring to FIG. 16, the 1 st -speed gear stage having the largest gear ratio γ 1 , which is, for example, equal to about 3.77, is established by engaging the first clutch C 1 and the first brake B 1 so that the third ring gear R 3 and the first sun gear S 1 are coupled to each other and the second ring gear R 2 and the transmission case 12 are coupled to each other. The 2 nd -speed gear stage having a gear ratio γ 2 , which is smaller than the gear ratio γ 1 and is, for example, equal to about 2.67, is established by engaging the first clutch C 1 and the second brake B 2 so that the third ring gear R 3 and the first sun gear S 1 are coupled to each other and the second sun gear S 2 and the transmission case 12 are coupled to each other. The 3 rd -speed gear stage having a gear ratio γ 3 , which is smaller than the gear ratio γ 2 and is, for example, equal to about 1.82, is established by engaging the first clutch C 1 and the third clutch C 3 so that the third ring gear R 3 and the first sun gear S 1 are coupled to each other and the third ring gear R 3 and the second sun gear S 2 are coupled to each other. The 4 th -speed gear stage having a gear ratio γ 4 , which is smaller than the gear ratio γ 3 and is, for example, equal to about 1.14, is established by engaging the first clutch C 1 and the second clutch C 2 so that the third ring gear R 3 and the first sun gear S 1 are coupled to each other and the third carrier CA 3 and the first carrier CA 1 are coupled to each other. The 5 th -speed gear stage having a gear ratio γ 5 , which is smaller than the gear ratio γ 4 and is, for example, equal to about 0.91, is established by engaging the second clutch C 2 and the third clutch C 3 so that the third carrier CA 3 and the first carrier CA 1 are coupled to each other and the third ring gear R 3 and the second sun gear S 2 are coupled to each other. The 6 th -speed gear stage having a gear ratio γ 6 , which is smaller than the gear ratio γ 5 and is, for example, equal to about 0.82, is established by engaging the second clutch C 2 and the second brake B 2 so that the third carrier CA 3 and the first carrier CA 1 are coupled to each other and the second sun gear S 2 and the transmission case 12 are coupled to each other. The 7 th -speed gear stage having a gear ratio γ 7 , which is smaller than the gear ratio γ 6 and is, for example, equal to about 0.59, is established by engaging the second clutch C 2 and the first brake B 1 so that the third carrier CA 3 and the first carrier CA 1 are coupled to each other and the second ring gear R 2 and the transmission case 12 are coupled to each other. The reverse gear stage having a gear ratio γ R , which is between the gear ratio γ 2 and the gear ratio γ 3 and is, for example, equal to about 2.35, is established by engaging the third clutch C 3 and the first brake B 1 so that the third ring gear R 3 and the second sun gear S 2 are coupled to each other and the second ring gear R 2 and the transmission case 12 are coupled to each other. The gear ratio (=the number of teeth of the sun gear/the number of teeth of the ring gear) ρ 1 of the first planetary gear set 118 , the gear ratio ρ 2 of the second planetary gear set 120 , and the gear ratio ρ 3 of the third planetary gear set 122 are determined so as to provide the gear ratios γ 1 -γ 7 and γ R as indicated above. For example, ρ 1 is equal to 0.28, ρ 2 is equal to 0.31, and ρ 3 is equal to 0.45.

In the transmission 130 as described above, the rate of change of the gear ratio (i.e., ratio of the gear ratios of the adjacent gear stages=γ n /γ n+1 ) may be determined as follows: the ratio (=γ 1 /γ 2 ) of the gear ratio γ 1 of the 1 st -speed gear stage to the gear ratio γ 2 of the 2 nd -speed gear stage is 1.41, the ratio (=γ 2 /γ 3 ) of the gear ratio γ 2 of the 2 nd -speed gear stage to the gear ratio γ 3 of the 3 rd -speed gear stage is 1.47, the ratio (=γ 3 /γ 4 ) of the gear ratio γ 3 of the 3 rd -speed gear stage to the gear ratio γ 4 of the 4 th -speed gear stage is 1.59, the ratio (=γ 4 /γ 5 ) of the gear ratio γ 4 of the 4 th -speed gear stage to the gear ratio γ 5 of the 5 th -speed gear stage is 1.25, the ratio (=γ 5 /γ 6 ) of the gear ratio γ 5 of the 5 th -speed gear stage to the gear ratio γ 6 of the 6 th -speed gear stage is 1.11, and the ratio (=γ 6 /γ 7 ) of the gear ratio γ 6 of the 6 th -speed gear stage to the gear ratio γ 7 of the 7 th -speed gear stage is 1.39. Thus, the gear ratios γ change at substantially equal ratios or rates. Also, in the transmission 130 , the total width of the gear ratios (γ 1 /γ 7 ), namely, the ratio of the gear ratio γ 1 of the 1 st -speed gear stage to the gear ratio γ 7 of the 7 th -speed gear stage, is a sufficiently large value, which is, for example, 6.38. Also, the gear ratio of the reverse gear stage “Rev” is an appropriate value. Thus, the transmission 130 provides appropriate gear-ratio (speed-change) characteristics over the entire range of operation.

FIG. 17 is a nomogram in which straight lines represent the relationships of the speeds of rotation of rotating elements (as described later) which are in different coupling states for respective gear stages. The nomogram of FIG. 17 is a two-dimensional coordinate system in which the horizontal axis indicates the relationship among the gear ratios ρ of the respective planetary gear sets 118 , 120 , 122 , and the vertical axis indicates relative rotational speeds. In the nomogram of FIG. 17, the lower horizontal line X 1 , out of three horizontal lines, indicates rotational speed “0”, and the middle horizontal line X 3 indicates a rotational speed lower than the speed of rotation of the input shaft 16 , while the upper horizontal line X 2 indicates rotational speed “1.0”, which is equal to the speed of rotation of the input shaft 16 . Five vertical lines Y 1 through Y 5 arranged from the left to the right in the section of the main power transmitting portion 128 respectively represent the second sun gear S 2 corresponding to the first rotating element RE 1 , the second ring gear R 2 corresponding to the second rotating element RE 2 , the first carrier CA 1 and the second carrier CA 2 that are coupled to each other and correspond to the third rotating element RE 3 , the first ring gear R 1 corresponding to the fourth rotating element RE 4 , and the first sun gear S 1 corresponding to the fifth rotating element RE 5 . The intervals of these vertical lines are determined in accordance with the gear ratio ρ 1 of the first planetary gear set 118 and the gear ratio ρ 2 of the second planetary gear set 120 . More specifically, the interval between the vertical lines corresponding to the sun gear and the carrier is set as “1”, and the interval between the vertical lines corresponding to the carrier and the ring gear is set as “ρ”.

The main power transmitting portion 128 will be described by utilizing the nomogram of FIG. 17 . Parts of the first sun gear S 1 , first carrier CA 1 and the first ring gear R 1 of the first planetary gear set 118 and the second sun gear S 2 , second carrier CA 2 and the second ring gear R 2 of the second planetary gear set 120 are coupled to each other so as to provide five rotating elements RE 1 through RE 5 . In the monogram of FIG. 17, the speeds of rotation of the five rotating elements RE 1 through RE 5 are represented by straight lines, and the first rotating element RE 1 , second rotating element RE 2 , third rotating element RE 3 , fourth rotating element RE 4 and the fifth rotating element RE 5 are arranged in this order from one end (i.e., the left end in FIG. 17) to the other end (i.e., the right end in FIG. 17 ). In the transmission 130 of this embodiment, the first rotating element RE 1 (S 2 ) is selectively inhibited from rotating by the second brake B 2 , and the second rotating element RE 2 (R 2 ) is selectively inhibited from rotating by the first brake B 1 . The first rotating element RE 1 (S 2 ) is selectively coupled to the third ring gear R 3 (intermediate rotating member) via the third clutch C 3 . The third rotating element RE 3 (CA 1 , CA 2 ) is selectively coupled to the input shaft 16 (input member) via the second clutch C 2 and the third carrier CA 3 . The fifth rotating element RE 5 (S 1 ) is selectively coupled to the third ring gear R 3 (intermediate rotating member) via the first clutch C 1 , and the fourth rotating element RE 4 (R 1 ) is coupled to the output gear 24 (output member).

As is apparent from the nomogram of FIG. 17, when the first clutch C 1 and the first brake B 1 are engaged, and the fifth rotating element RE 5 (S 1 ) is coupled to the third ring gear R 3 so as to be rotated at a lower speed than the input shaft 16 via the auxiliary power transmitting portion 126 while the second rotating element RE 2 (R 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 1 ) is rotated at a speed denoted by “1 st ” in FIG. 17, so that the 1 st -speed gear stage having the largest gear ratio is established. When the first clutch C 1 and the second brake B 2 are engaged, and the fifth rotating element RE 5 (S 1 ) is coupled to the third ring gear R 3 so as to be rotated at a lower speed than the input shaft 16 while the first rotating element RE 1 (S 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 1 ) is rotated at a speed denoted by “2 nd ” in FIG. 17, so that the 2 nd -speed gear stage having a smaller gear ratio than that of the 1 st -speed gear stage is established. When the first clutch C 1 and the third clutch C 3 are engaged, and the main power transmitting portion 128 as a whole is rotated at a reduced speed along with the third ring gear R 3 of the auxiliary power transmitting portion 126 , the fourth rotating element RE 4 (R 1 ) is rotated at a speed denoted by “3 rd ” in FIG. 17, namely, at the same speed as the third ring gear R 3 of the auxiliary power transmitting portion 126 , so that the 3 rd -speed gear stage having a smaller gear ratio than that of the 2 nd -speed gear stage is established. When the first clutch C 1 and the second clutch C 2 are engaged, and the fifth rotating element RE 5 (S 1 ) is coupled to the third ring gear R 3 so as to be rotated at a lower speed than the input shaft 16 via the auxiliary power transmitting portion 126 while the third rotating element RE 3 (CA 1 , CA 2 ) is rotated along with the input shaft 16 , the fourth rotating element RE 4 (R 1 ) is rotated at a speed denoted by “4 th ” in FIG. 17, so that the 4 th -speed gear stage having a smaller gear ratio than that of the 3 rd -speed gear stage is established. When the second clutch C 2 and the third clutch C 3 are engaged, and the third rotating element RE 3 (CA 1 , CA 2 ) is rotated along with the input shaft 16 while the first rotating element RE 1 (S 2 ) is rotated at a reduced speed, the fourth rotating element RE 4 (R 1 ) is rotated at a speed denoted by “5 th ” in FIG. 17, so that the 5 th -speed gear stage having a smaller gear ratio than that of the 4 th -speed gear stage is established. When the second clutch C 2 and the second brake B 2 are engaged, and the third rotating element RE 3 (CA 1 , CA 2 ) is rotated along with the input shaft 16 while the first rotating element RE 1 (S 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 1 ) is rotated at a speed denoted by “6 th ” in FIG. 17, so that the 6 th -speed gear stage having a smaller gear ratio than that of the 5 th -speed gear stage is established. When the second clutch C 2 and the first brake B 1 are engaged, and the third rotating element RE 3 (CA 1 , CA 2 ) is rotated along with the input shaft 16 while the second rotating element RE 2 (R 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 1 ) is rotated at a speed denoted by “7 th ” in FIG. 17, so that the 7 th -speed gear stage having a smaller gear ratio than that of the 6 th -speed gear stage is established.

When the third clutch C 3 and the first brake B 1 are engaged, and the first rotating element RE 1 (S 2 ) is rotated at a lower speed than the input shaft 16 while the second rotating element RE 2 (R 2 ) is inhibited from rotating, the fourth rotating element RE 4 (R 1 ) is rotated in the reverse direction at a speed denoted by “REV” in FIG. 17, so that the reverse gear stage “Rev” is established.

As described above, the automatic transmission 130 of the present embodiment is able to establish seven forward gear stages by using three gear sets, i.e., the first planetary gear set 118 , second planetary gear set 120 , and the third planetary gear set 122 , and a total of five friction devices, i.e., three clutches C 1 , C 2 and C 3 and two brakes B 1 and B 2 . Thus, the weight and size of the transmission 130 can be reduced as compared with the case where four planetary gear sets are used, thus making it easier to install the transmission 130 on the vehicle. At the same time, the number of friction devices required for shifting the transmission 130 is reduced, resulting in a reduced number of components and reduced cost. Furthermore, the drag resistance is reduced, and the fuel economy can be further improved.

In the ninth embodiment as described above, the first pinion P 1 of the double-pinion type first planetary gear set 118 and the fourth pinion P 4 of the double-pinion type second planetary gear set 120 are coupled to each other on the same axis so that these pinions P 1 , P 4 are rotated as a unit. Like Ravigneaux type planetary gear trains, this arrangement requires a further reduced number of components and further reduced axial length, which result in further reduction in the size and cost of the transmission 130 .

Also, the gear ratios ρ 1 , ρ 2 and ρ 3 of the first planetary gear set 118 , second planetary gear set 120 and the third planetary gear set 122 are set within the range of about 0.3 to 0.6. Thus, the transmission 130 is able to provide appropriate speed-change characteristics as a whole as shown in FIG. 16, while permitting the planetary gear sets 118 , 120 and 122 to be relatively small sized or have relatively small diameters.

While the ninth embodiment of the invention has been described referring to FIG. 15 -FIG. 17, the invention may be otherwise embodied.

While the third planetary gear set 122 is of a double pinion type in the ninth embodiment, the third planetary gear set 122 may be of a single pinion type. Also, any of the third sun gear S 3 , third carrier CA 3 and the third ring gear R 3 corresponding to three rotating elements of the third planetary gear set 122 may be fixed, or may serve as an intermediate rotating member, or may be directly or indirectly coupled to the input member.

While the automatic transmission 130 of the ninth embodiment is suitably installed in the lateral direction on the front engine front drive (FF) vehicle in which the axis of the transmission 130 extends in the width direction of the vehicle, the transmissions 130 may be installed in the vertical direction on a front engine rear drive (FR) vehicle in which the axis of the transmission 130 extends in the longitudinal or running direction of the vehicle.

While the automatic transmission 130 may automatically change its gear ratio or gear stage depending upon vehicle operating conditions, such as an accelerator pedal position and a vehicle speed, the transmission 130 may change its gear ratio in response to switching operations (e.g., upshifting and downshifting operations) performed by the vehicle operator or driver.

In the automatic transmission 130 as described above, hydraulically operated friction devices of multiple-disc type, single-disc type or belt type, which are frictionally engaged by use of hydraulic actuators, are suitably used as the first clutch C 1 , second clutch C 2 , third clutch C 3 , first brake B 1 and the second brake B 2 . However, other types of engaging devices, such as those of electromagnetic type, may also be used as the clutches and brakes. To make shift control easy, one-way clutches may be provided in parallel with the brakes or clutches. If an engine brake need not be applied, one-way clutches may be used in place of the brakes or clutches. Here, one-way clutches function, like brakes, to stop rotation of corresponding rotating members. Other than the above arrangements, the automatic transmission 130 may be constructed in various ways. For example, a brake and a one-way clutch, which are connected in series, may be provided in parallel with the first brake B 1 .

In the automatic transmission 130 , the positional relationship between the main power transmitting portion 128 and the auxiliary power transmitting portion 126 and the positional relationship between the first planetary gear set 118 and the second planetary gear set 120 of the main power transmitting portion 128 are not particularly limited, but may be changed in various ways. In addition, the clutches and brakes may be located to be concentrated in one end portion of the transmission 130 , or may be otherwise positioned. Furthermore, the first planetary gear set 118 , second planetary gear set 120 and the third planetary gear set 122 are not necessarily disposed on the same axis.

While the vertical lines Y 1 , Y 2 , Y 3 , Y 4 , Y 5 respectively corresponding to the rotating elements RE 1 , RE 2 , RE 3 , RE 4 , RE 5 are arranged in this order from the left to the right in the nomogram of FIG. 17 in the ninth embodiment, these vertical lines, Y 1 , Y 2 , Y 3 , Y 4 , Y 5 may be arranged in this order from the right to the left. While the horizontal line X 2 corresponding to the rotational speed “1” is located above the horizontal line X 1 corresponding to the rotational speed “0” in the nomogram of FIG. 17, the horizontal line X 2 may be located below the horizontal line X 1 .

In the illustrated embodiment, the first pinion P 1 of the double-pinion type first planetary gear set 118 and the fourth pinion P 4 of the double-pinion type second planetary gear set 120 are coupled to each other on the same axis such that the pinions P 1 , P 4 are rotated as a unit. While the first pinion P 1 and the fourth pinion P 4 have different diameters in the illustrated embodiment, these pinions P 1 , P 4 may have the same diameter. It is also to be understood that the diameter (or the number of teeth) of each of the first pinion P 1 , second pinion P 2 , third pinion P 3 and the fourth pinion P 4 may be changed as needed.

While the main power transmitting portion 128 is constituted by two planetary gear sets, i.e., the first planetary gear set 118 and the second planetary gear set 120 , in the ninth embodiment, the number of the planetary gear sets is not limited to two, but may be three or greater.

In the main power transmitting portion 128 of the illustrated embodiment, the first rotating element RE 1 , second rotating element RE 2 , third rotating element RE 3 , fourth rotating element RE 4 , and the fifth rotating element RE 5 may be selected from the sun gears, ring gears and carriers of the first planetary gear set 118 and second planetary gear set 120 , and those of other planetary gear sets.

While the invention has been described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the exemplary embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the exemplary embodiments are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.