Planetary gear train of automatic transmission for vehicle

The present application claims priority to Korean Patent Application No. 10-2012-0112464 filed on Oct. 10, 2012, the entire contents of which is incorporated herein for all purposes by this reference.

1. Field of the Invention

The present invention relates to an automatic transmission for a vehicle. More particularly, the present invention relates to a planetary gear train of an automatic transmission for vehicles which improves power delivery performance and reduces fuel consumption.

2. Description of Related Art

Typically, a planetary gear train is realized by combining a plurality of planetary gear sets, and the planetary gear train including the plurality of planetary gear sets receives torque from a torque converter and changes and transmits the torque to an output shaft.

It is well known that when a transmission realizes a greater number of shift speeds, speed ratios of the transmission can be more optimally designed, and therefore a vehicle can have economical fuel mileage and better performance. For that reason, the planetary gear train that is able to realize more shift speeds is under continuous investigation.

Though achieving the same number of speeds, the planetary gear train has a different operating mechanism according to a connection between rotation elements (i.e., sun gear, planet carrier, and ring gear).

In addition, the planetary gear train has different features such a durability, power delivery efficiency, and size depend on the layout thereof. Therefore, designs for a combining structure of a gear train are also under continuous investigation.

Currently, four-speed and five-speed automatic transmissions are most often found on the market. However, six-speed automatic transmissions have also been realized for enhancement of performance of power transmission and for enhanced fuel mileage of a vehicle. In addition, eight-speed automatic transmissions and twelfth-speed automatic transmissions have been developed at a good pace.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Various aspects of the present invention are directed to providing a planetary gear train of an automatic transmission for a vehicle having advantages of achieving eleven forward speeds and one reverse speed by combining a plurality of planetary gear sets and a plurality of friction members and improving power delivery performance and reducing fuel consumption by operating minimum numbers of planetary gear sets.

A planetary gear train of an automatic transmission for vehicles according to one or more exemplary embodiments of the present invention may include an input shaft adapted to receive engine torque, an output shaft adapted to output changed torque, a first compound planetary gear set having five rotation elements by combining first and second planetary gear sets and adapted to primarily change a rotation speed of the input shaft input through one input path and two variable input paths into six rotation speeds and to output the six rotation speeds, a second compound planetary gear set having four rotation elements including a rotation element directly connected to any one rotation element of the first compound planetary gear set by combining third and fourth planetary gear sets and adapted to secondarily change the rotation speeds input from the first compound planetary gear set and the rotation speed of the input shaft input through one variable input path into eleven forward speeds and one reverse speed and to finally output the eleven forward speeds and the one reverse speed, eight rotation paths having two rotation elements connected to each other or one rotation element among the rotation elements of the first and second compound planetary gear sets, and seven friction members including four clutches interposed between the rotation paths or between a selected rotation path and the input shaft, and three brakes variably connecting a selected rotation path to a transmission housing.

The first compound planetary gear set may be formed by combining the first planetary gear set being a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear as rotation elements thereof, and the second planetary gear set being a single pinion planetary gear set including a second sun gear, a second planet carrier, and a second ring gear as rotation elements thereof. The second compound planetary gear set may be formed by combining the third planetary gear set being a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear as rotation elements thereof, and the fourth planetary gear set being a single pinion planetary gear set including a fourth sun gear, a fourth planet carrier, and a fourth ring gear as rotation elements thereof.

The eight rotation paths may include a first rotation path including the first sun gear, and selectively connected to the input shaft or the transmission housing, a second rotation path including the first planet carrier and the second ring gear, and selectively connected to the input shaft or the transmission housing, a third rotation path including the first ring gear and the third and fourth sun gears, a fourth rotation path including the second planet carrier and selectively connected to the third rotation shaft, a fifth rotation path including the second sun gear and directly connected to the input shaft, a sixth rotation path including the third ring gear and selectively connected to the transmission housing, a seventh rotation path including the third planet carrier and the fourth ring gear, and directly connected to the output shaft so as to be operated as a final output element, and an eighth rotation path including the fourth planet carrier and selectively connected to the input shaft.

The seven friction members may include a first clutch variably connecting the third rotation path with the fourth rotation shaft, a second clutch variably connecting the input shaft with the second rotation shaft, a third clutch variably connecting the input shaft with the eighth rotation shaft, a fourth clutch variably connecting the input shaft with the first rotation shaft, a first brake variably connecting the second rotation path with the transmission housing, a second brake variably connecting the first rotation path with the transmission housing, and a third brake variably connecting the sixth rotation path with the transmission housing.

A first forward speed may be achieved by operating the first clutch and the first and third brakes, a second forward speed may be achieved by operating the first clutch and the second and third brakes, a third forward speed may be achieved by operating the first and second clutches and the third brake, a fourth forward speed may be achieved by operating the second clutch and the second and third brakes, a fifth forward speed may be achieved by operating the second and third clutches and the third brake, a sixth forward speed may be achieved by operating the second and third clutches and the second brake, a seventh forward speed may be achieved by operating the first, second, and third clutches, an eighth forward speed may be achieved by operating the first and third clutches and the second brake, a ninth forward speed may be achieved by operating the first and third clutches and the first brake, a tenth forward speed may be achieved by operating the third clutch and the first and second brakes, an eleventh forward speed may be achieved by operating the third and fourth clutches and the first brake, and a reverse speed may be achieved by operating the fourth clutch and the first and third brakes.

A planetary gear train of an automatic transmission for a vehicle according to another exemplary embodiment of the present invention may include an input shaft adapted to receive engine torque, an output shaft adapted to output changed torque, a first compound planetary gear set formed by combining first and second planetary gear sets, each of which is a single pinion planetary gear set, a second compound planetary gear set formed by combining third and fourth planetary gear sets, each of which is a single pinion planetary gear set, and friction members, wherein the first and second compound planetary gear sets may include a first rotation path including a first sun gear, and selectively connected to the input shaft or a transmission housing, a second rotation path including a first planet carrier and a second ring gear, and selectively connected to the input shaft or the transmission housing, a third rotation path including a first ring gear and third and fourth sun gears, a fourth rotation path including a second planet carrier and selectively connected to the third rotation shaft, a fifth rotation path including a second sun gear and directly connected to the input shaft, a sixth rotation path including a third ring gear and selectively connected to the transmission housing, a seventh rotation path including a third planet carrier and a fourth ring gear, and directly connected to the output shaft so as to be operated as a final output element, and an eighth rotation path including a fourth planet carrier and selectively connected to the input shaft, and wherein the friction members may include a first clutch variably connecting the third rotation path with the fourth rotation shaft, a second clutch variably connecting the input shaft with the second rotation shaft, a third clutch variably connecting the input shaft with the eighth rotation shaft, a fourth clutch variably connecting the input shaft with the first rotation shaft, a first brake variably connecting the second rotation path with the transmission housing, a second brake variably connecting the first rotation path with the transmission housing, and a third brake variably connecting the sixth rotation path with the transmission housing.

A first forward speed may be achieved by operating the first clutch and the first and third brakes, a second forward speed may be achieved by operating the first clutch and the second and third brakes, a third forward speed may be achieved by operating the first and second clutches and the third brake, a fourth forward speed may be achieved by operating the second clutch and the second and third brakes, a fifth forward speed may be achieved by operating the second and third clutches and the third brake, a sixth forward speed may be achieved by operating the second and third clutches and the second brake, a seventh forward speed may be achieved by operating the first, second, and third clutches, an eighth forward speed may be achieved by operating the first and third clutches and the second brake, a ninth forward speed may be achieved by operating the first and third clutches and the first brake, a tenth forward speed may be achieved by operating the third clutch and the first and second brakes, an eleventh forward speed may be achieved by operating the third and fourth clutches and the first brake, and a reverse speed may be achieved by operating the fourth clutch and the first and third brakes.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

FIG. 1 is a schematic diagram of a planetary gear train according to an exemplary embodiment of the present invention.

FIG. 2 is an operational chart of friction members at each shift-speed applied to a planetary gear train according to an exemplary embodiment of the present invention.

FIG. 3 is a lever diagram for a planetary gear train according to an exemplary embodiment of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Description of components that are not necessary for explaining the present exemplary embodiment will be omitted, and the same constituent elements are denoted by the same reference numerals in this specification.

In the detailed description, ordinal numbers are used for distinguishing constituent elements having the same terms, and have no specific meanings.

FIG. 1 is a schematic diagram of a planetary gear train according to an exemplary embodiment of the present invention.

Referring to FIG. 1 , a planetary gear train according to an exemplary embodiment of the present invention includes first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 disposed on the same axis, an input shaft IS, an output shaft OS, eight rotation paths TM 1 -TM 8 connecting rotation elements of the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , seven friction members C 1 -C 4 and B 1 -B 3 , and a transmission housing H.

A rotation speed input from the input shaft IS is changed by the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 and is output through the output shaft OS.

In addition, the simple planetary gear sets are disposed in a sequence of the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 from the rear to an engine.

The input shaft IS is an input member, and torque from a crankshaft of the engine is changed through a torque converter and is input to the input shaft IS.

The output shaft OS is an output member and delivers driving torque so as to run driving wheels through a differential apparatus.

The first planetary gear set PG 1 is a single pinion planetary gear set, and includes a first sun gear S 1 , a first planet carrier PC 1 rotatably supporting a first pinion P 1 externally meshed with the first sun gear S 1 , a first ring gear R 1 internally meshed with the first pinion P 1 as rotation elements thereof.

The second planetary gear set PG 2 is a single pinion planetary gear set, and includes a second sun gear S 2 , a second planet carrier PC 2 rotatably supporting a second pinion P 2 externally meshed with the second sun gear S 2 , a second ring gear R 2 internally meshed with the second pinion P 2 as rotation elements thereof.

The third planetary gear set PG 3 is a single pinion planetary gear set, and includes a third sun gear S 3 , a third planet carrier PC 3 rotatably supporting a third pinion P 3 externally meshed with the third sun gear S 3 , a third ring gear R 3 internally meshed with the third pinion P 3 as rotation elements thereof.

The fourth planetary gear set PG 4 is a single pinion planetary gear set, and includes a fourth sun gear S 4 , a fourth planet carrier PC 4 rotatably supporting a fourth pinion P 4 externally meshed with the fourth sun gear S 4 , a fourth ring gear R 4 internally meshed with the fourth pinion P 4 as rotation elements thereof.

In addition, the first, second, third, and fourth simple planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 form two compound planetary gear sets CPG 1 and CPG 2 , change the torque transmitted from the input shaft into eleven forward speeds, and output the eleventh forward speeds.

The first compound planetary gear set CPG 1 includes the first and second planetary gear sets PG 1 and PG 2 , and the second compound planetary gear set CPG 2 includes the third and fourth planetary gear sets PG 3 and PG 4 .

The first compound planetary gear set CPG 1 is operated by five rotation elements by directly connecting the first planet carrier PC 1 with the second ring gear R 2 .

The second compound planetary gear set CPG 2 is operated by four rotation elements by directly connecting the third sun gear S 3 with the fourth sun gear S 4 and directly connecting the third planet carrier PC 3 with the fourth ring gear R 4 .

In addition, any one rotation element of the first compound planetary gear set CPG 1 is directly connected to any one rotation element of the second compound planetary gear set CPG 2 such that the eight rotation paths TM 1 -TM 8 are formed.

A first rotation path TM 1 includes the first sun gear S 1 , and is selectively connected to the input shaft IS or the transmission housing H.

A second rotation path TM 2 includes the first planet carrier PC 1 and the second ring gear R 2 , and is selectively connected to the input shaft IS or the transmission housing H.

A third rotation path TM 3 includes the first ring gear R 1 and the third and fourth sun gears S 3 and S 4 .

A fourth rotation path TM 4 includes the second planet carrier PC 2 and is selectively connected to the third rotation path TM 3 .

A fifth rotation path TM 5 includes the second sun gear S 2 and is directly connected to the input shaft IS.

A sixth rotation path TM 6 includes the third ring gear R 3 and is selectively connected to the transmission housing H.

A seventh rotation path TM 7 includes the third planet carrier PC 3 and the fourth ring gear R 4 , and is directly connected to the output shaft OS.

An eighth rotation path TM 8 includes the fourth planet carrier PC 4 and is selectively connected to the input shaft IS.

In addition, four clutches C 1 , C 2 , C 3 , and C 4 of the friction members are disposed at positions where the rotation paths TM 1 -TM 8 are selectively connected to the input shaft IS or another rotation shaft.

In addition, three brakes B 1 , B 2 , and B 3 of the friction members are disposed at positions where the rotation paths TM 1 -TM 8 are selectively connected to the transmission housing H.

A first clutch C 1 is interposed between the third rotation path TM 3 and the fourth rotation path TM 4 and selectively connects the third and fourth rotation paths TM 3 and TM 4 .

A second clutch C 2 is interposed between the input shaft IS and the second rotation path TM 2 such that the second rotation path TM 2 is operated as a selective input element.

A third clutch C 3 is interposed between the input shaft IS and the eighth rotation path TM 8 such that the eighth rotation path TM 8 is operated as a selective input element.

A fourth clutch C 4 is interposed between the input shaft IS and the first rotation path TM 1 such that the first rotation path TM 1 is operated as a selective input element.

A first brake B 1 is interposed between the second rotation path TM 2 and the transmission housing H such that the second rotation path TM 2 is operated as a selective fixed element.

A second brake B 2 is interposed between the first rotation path TM 1 and the transmission housing H such that the first rotation path TM 1 is operated as a selective fixed element.

A third brake B 3 is interposed between the sixth rotation path TM 6 and the transmission housing H such that the sixth rotation path TM 6 is operated as a selective fixed element.

In addition, a one-way clutch F 1 , in parallel with the first brake B 1 , may be disposed between the second rotation path TM 2 and the transmission housing H.

The first, second, and fourth clutch C 1 , C 2 , and C 4 and the first and second brake B 1 and B 2 are applied to the first compound planetary gear set CPG 1 .

Therefore, the first compound planetary gear set CPG 1 changes the rotation speed of the input shaft IS input through one input path IP and first and second variable input paths VIP 1 and VIP 2 into six rotation speeds by operation of the first and second brakes B 1 and B 2 and the first clutch C 1 , and transmits the six rotation speeds to the second compound planetary gear set CPG 2 through one intermediate output path MOP.

At this time, the six rotation speeds include two reduced rotation speeds, one fixed rotation speed (rotation speed is 0), one unchanged rotation speed (the same rotation speed as the input shaft IS), one increased rotation speed, and one inverse rotation speed.

In addition, the third clutch C 3 and the third brake B 3 are applied to the second compound planetary gear set CPG 2 .

Therefore, the second compound planetary gear set CPG 2 changes the rotation speeds input through an intermediate input path MIP and a third variable input path VIP 3 into eleven forward speeds and one reverse speed by operation of the third brake B 3 , and outputs the eleven forward speeds and the one reverse speed through a final output path OP.

Friction member including the first, second, third, and fourth clutches C 1 , C 2 , C 3 , and C 4 and the first, second, and third brakes B 1 , B 2 , and B 3 are conventional multi-plate friction elements of wet type that are operated by hydraulic pressure.

FIG. 2 is an operational chart of friction members at each shift-speed applied to a planetary gear train according to an exemplary embodiment of the present invention.

As shown in FIG. 2 , three friction members are operated at each shift-speed according to an exemplary embodiment of the present invention.

A first forward speed D 1 is achieved by operating the first clutch C 1 , the first brake B 1 , and the third brake B 3 .

A second forward speed D 2 is achieved by operating the first clutch C 1 , the second brake B 2 , and the third brake B 3 .

A third forward speed D 3 is achieved by operating the first clutch C 1 , the second clutch C 2 , and the third brake B 3 .

A fourth forward speed D 4 is achieved by operating the second clutch C 2 , the second brake B 2 , and the third brake B 3 .

A fifth forward speed D 5 is achieved by operating the second clutch C 2 , the third clutch C 3 , and the third brake B 3 .

A sixth forward speed D 6 is achieved by operating the second clutch C 2 , the third clutch C 3 , and the second brake B 2 .

A seventh forward speed D 7 is achieved by operating the first clutch C 1 , the second clutch C 2 , and the third clutch C 3 .

An eighth forward speed D 8 is achieved by operating the first clutch C 1 , the third clutch C 3 , and the second brake B 2 .

A ninth forward speed D 9 is achieved by operating the first clutch C 1 , the third clutch C 3 , and the first brake B 1 .

A tenth forward speed D 10 is achieved by operating the third clutch C 3 , the first brake B 1 , and the second brake B 2 .

An eleventh forward speed D 11 is achieved by operating the third clutch C 3 , the fourth clutch C 4 , and the first brake B 1 .

A reverse speed REV is achieved by operating the fourth clutch C 4 , the first brake B 1 , and the third brake B 3 .

Although it is explained that the first clutch C 1 and the first and third brakes B 1 and B 3 are operated at the first forward speed D 1 , the one-way clutch F 1 instead of the first brake B 1 may be operated at a normal driving condition.

FIG. 3 is a lever diagram for a planetary gear train according to an exemplary embodiment of the present invention. In FIG. 3 , shifting processes of the planetary gear train according to an exemplary embodiment of the present invention are illustrated through lever analysis method.

Referring to FIG. 3 , a lower horizontal line represents a rotation speed is “0”, and an upper horizontal line represents a rotation speed is “1.0”, that is the rotation speed thereof is the same as that of the input shaft IS.

Four vertical lines of the first compound planetary gear set CPG 1 sequentially represent the first rotation path TM 1 , the second rotation path TM 2 , the third rotation path TM 3 or the fourth rotation path TM 4 , and the fifth rotation path TM 5 from the left to the right.

Herein, distances between the first rotation path TM 1 , the second rotation path TM 2 , the third rotation path TM 3 or the fourth rotation path TM 4 , and the fifth rotation path TM 5 are set according to gear ratios (teeth number of the sun gear/teeth number of the ring gear) of the first and second planetary gear sets PG 1 and PG 2 .

Since the third rotation path TM 3 and the fourth rotation path TM 4 are operated as one rotation path when the first clutch C 1 is operated, the third rotation path TM 3 and the fourth rotation path TM 4 are disposed on one vertical line.

Four vertical lines of the second compound planetary gear set CPG 2 sequentially represent the sixth rotation path TM 6 , the seventh rotation path TM 7 , the eighth rotation path TM 8 , and the third rotation path TM 3 from the left to the right.

Herein, distances between the sixth, seventh, eighth, and third rotation paths TM 6 , TM 7 , TM 8 , and TM 3 are set according to gear ratios (teeth number of the sun gear/teeth number of the ring gear) of the third and fourth planetary gear sets PG 3 and PG 4 .

Hereinafter, referring to FIG. 2 and FIG. 3 , shifting processes for each shift-speed in the planetary gear train according to an exemplary embodiment of the present invention will be described.

[First Forward Speed]

Referring to FIG. 2 , the first clutch C 1 and the first and third brakes B 1 and B 3 are operated at the first forward speed D 1 .

As shown in FIG. 3 , in a state that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the second rotation path TM 2 is operated as a fixed element by operation of the first brake B 1 .

Therefore, the rotation paths of the first compound planetary gear set CPG 1 form a first reduced speed line T 1 , and output a first reduced rotation speed through the third rotation path TM 3 .

In a state that the first reduced rotation speed of the third rotation path TM 3 is input to the second compound planetary gear set CPG 2 , the sixth rotation path TM 6 is operated as a fixed element by operation of the third brake B 3 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form a first shift line SP 1 .

Therefore, the first shift line SP 1 crosses the vertical line of the seventh rotation path TM 7 that is an output element such that the first forward speed D 1 is output.

In addition, the first forward speed D 1 is output by operation of the second and third planetary gear sets PG 2 and PG 3 .

[Second Forward Speed]

The first brake B 1 that was operated at the first forward speed D 1 is released and the second brake B 2 is operated at the second forward speed D 2 .

As shown in FIG. 3 , in a state that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the first rotation path TM 1 is operated as a fixed element by operation of the second brake B 2 .

Therefore, the rotation paths of the first compound planetary gear set CPG 1 form a second reduced speed line T 2 and output a second reduced rotation speed through the third rotation path TM 3 .

In a state that the second reduced rotation speed of the third rotation path TM 3 is input to the second compound planetary gear set CPG 2 , the sixth rotation path TM 6 is operated as a fixed element by operation of the third brake B 3 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form a second shift line SP 2 .

Therefore, the second shift line SP 2 crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the second forward speed D 2 is output.

In addition, the second forward speed D 2 is output by operation of the second, third, and fourth planetary gear sets PG 2 , PG 3 , and PG 4 .

[Third Forward Speed]

The second brake B 2 that was operated at the second forward speed D 2 is released and the second clutch C 2 is operated at the third forward speed D 3 .

In a state that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the rotation speed of the input shaft IS is also input to the second rotation path TM 2 by operation of the second clutch C 2 . Therefore, the first compound planetary gear set CPG 1 becomes a direct-coupling state, and the rotation paths of the first compound planetary gear set CPG 1 form a direct-coupling speed line T 3 so as to output the same rotation speed as the input shaft IS through the third rotation path TM 3 .

In a state that the same rotation speed as the input shaft IS is input to the second compound planetary gear set CPG 2 through the third rotation path TM 3 , the sixth rotation path TM 6 is operated as a fixed element by operation of the third brake B 3 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form a third shift line SP 3 .

Therefore, the third shift line SP 3 crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the third forward speed D 3 is output.

In addition, the third forward speed D 3 is output by operation of the third planetary gear set PG 3 .

[Fourth Forward Speed]

The first clutch C 1 that was operated at the third forward speed D 3 is released and the second brake B 2 is operated at the fourth forward speed D 4 .

In a state that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the rotation speed of the input shaft IS is input to the second rotation path TM 2 by operation of the second clutch C 2 .

However, the rotation speed of the input shaft IS is input to the second rotation path TM 2 in a state that the first clutch C 1 is released and the first rotation path TM 1 is operated as a fixed element by operation of the second brake B 2 . Therefore, the rotation paths of the first compound planetary gear set CPG 1 form an increased speed line T 4 an output an increased rotation speed through the third rotation path TM 3 .

In a state that the increased rotation speed is input to the second compound planetary gear set CPG 2 through the third rotation path TM 3 , the sixth rotation path TM 6 is operated as a fixed element by operation of the third brake B 3 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form a fourth shift line SP 4 .

Therefore, the fourth shift line SP 4 crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the fourth forward speed D 4 is output.

In addition, the fourth forward speed D 4 is output by operation of the first and third planetary gear sets PG 1 and PG 3 .

[Fifth Forward Speed]

The second brake B 2 that was operated at the fourth forward speed D 4 is released and the third clutch C 3 is operated at the fifth forward speed D 5 .

In a state that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the rotation speed of the input shaft IS is also input to the second rotation path TM 2 by operation of the second clutch C 2 .

However, since related friction members such as the first and second brakes B 1 and B 2 are not operated, the first compound planetary gear set CPG 1 does not have any effect on shifting.

In a state that the rotation speed of the input shaft IS is input to the eighth rotation path TM 8 by operation of the third clutch C 3 , the sixth rotation path TM 6 is operated as a fixed element by operation of the third brake B 3 in the second compound planetary gear set CPG 2 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form a fifth shift line SP 5 .

Therefore, the fifth shift line SP 5 crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the fifth forward speed D 5 is output.

In addition, the fifth forward speed D 5 is output by operation of the third and fourth planetary gear sets PG 3 and PG 4 .

[Sixth Forward Speed]

The third brake B 3 that was operated at the fifth forward speed D 5 is released and the second brake B 2 is operated at the sixth forward speed D 6 .

In a state that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the rotation speed of the input shaft IS is also input to the second rotation path TM 2 by operation of the second clutch C 2 .

Since the rotation speed of the input shaft IS is input to the second rotation path TM 2 and the first rotation path TM 1 is operated as a fixed element by operation of the second brake B 2 in a state that the first clutch C 1 is released, the rotation paths of the first compound planetary gear set CPG 1 form the increased speed line T 4 and output the increased rotation speed through the third rotation path TM 3 .

In a state that the increased rotation speed is input to the second compound planetary gear set CPG 2 through the third rotation path TM 3 , the rotation speed of the input shaft IS is input to the eighth rotation path TM 8 by operation of the third clutch C 3 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form a sixth shift line SP 6 .

Therefore, the sixth shift line SP 6 crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the sixth forward speed D 6 is output.

In addition, the sixth forward speed D 6 is output by operation of the first and fourth planetary gear sets PG 1 and PG 4 .

[Seventh Forward Speed]

The second brake B that was operated at the sixth forward speed D 6 is released and the first clutch C 1 is operated at the seventh forward speed D 7 .

In a state that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the rotation speed of the input shaft IS is input to the second rotation path TM 2 by operation of the second clutch C 2 . Therefore, the first compound planetary gear set CPG 1 becomes the direct-coupling state and the rotation paths of the first compound planetary gear set CPG 1 form the direct-coupling speed line T 3 so as to output the same rotation speed as the input shaft IS through the third rotation path TM 3 .

In a state that the same rotation speed as the input shaft IS is input to the second compound planetary gear set CPG 2 through the third rotation path TM 3 , the rotation speed of the input shaft IS is input to the eighth rotation path TM 8 by operation of the third clutch C 3 . Therefore, the second compound planetary gear set CPG 2 becomes the direct-coupling state and the rotation paths of the second compound planetary gear set CPG 2 form a seventh shift line SP 7 such that the seventh forward speed D 7 that is the same rotation speed as the input shaft IS is output.

In addition, the first and second compound planetary gear sets CPG 1 and CPG 2 transmits a rotation speed of the engine to the output shaft OS at the seventh forward speed D 7 .

[Eighth Forward Speed]

The second clutch C 2 that was operated at the seventh forward speed D 7 is released and the second brake B 2 is operated at the eighth forward speed D 8 .

As shown in FIG. 3 , in a state that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the first rotation path TM 1 is operated as a fixed element by operation of the second brake B 2 .

Therefore, the rotation paths of the first compound planetary gear set CPG 1 form the second reduced speed line T 2 and output the second reduced rotation speed through the third rotation path TM 3 .

In a state that the second reduced rotation speed is input through the third rotation path TM 3 , the rotation speed of the input shaft IS is input to the eighth rotation path TM 8 by operation of the third clutch C 3 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form an eighth shift line SP 8 .

Therefore, the eighth shift line SP 8 crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the eighth forward speed D 8 is output.

In addition, the eighth forward speed D 8 is output by operation of the first, second, and fourth planetary gear sets PG 1 , PG 2 , and PG 4 .

[Ninth Forward Speed]

The second brake B 2 that was operated at the eighth forward speed D 8 is released and the first brake B 1 is operated at the ninth forward speed D 9 .

As shown in FIG. 3 , in a state that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the second rotation path TM 2 is operated as a fixed element by operation of the first brake B 1 .

Therefore, the rotation paths of the first compound planetary gear set CPG 1 form the first reduced speed line T 1 and output the first reduced rotation speed through the third rotation path TM 3 .

In a state that the first reduced rotation speed is input through the third rotation path TM 3 , the rotation speed of the input shaft IS is input to the eighth rotation path TM 8 by operation of the third clutch C 3 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form a ninth shift line SP 9 .

Therefore, the ninth shift line SP 9 crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the ninth forward speed D 9 is output.

In addition, the ninth forward speed D 9 is output by operation of the second and fourth planetary gear sets PG 2 and PG 4 .

[Tenth Forward Speed]

The first clutch C 1 that was operated at the ninth forward speed D 9 is released and the second brake B 2 is operated at the tenth forward speed D 10 .

In a case that the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , the third rotation path TM 3 is fixed by operation of the first and second brakes B 1 and B 2 .

In a state that the rotation speed of the input shaft IS is input to the eighth rotation path TM 8 , the third rotation path TM 3 is fixed. Therefore, the rotation paths of the second compound planetary gear set CPG 2 form a tenth shift line SP 10 .

Therefore, the tenth shift line SP 10 crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the tenth forward speed D 10 is output.

In addition, the tenth forward speed D 10 is output by operation of the fourth planetary gear set PG 4 .

[Eleventh Forward Speed]

The second brake B 2 that was operated at the tenth forward speed D 10 is released and the fourth clutch C 4 is operated at the eleventh forward speed D 11 .

As shown in FIG. 3 , although the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , it does not any effect on shifting.

In a state that the rotation speed of the input shaft IS is input to the first rotation path TM 1 by operation of the fourth clutch C 4 , the rotation paths of the first compound planetary gear set CPG 1 form an inverse speed line T 5 by operation of the first brake B 1 . Therefore, an inverse rotation speed is output through the third rotation path TM 3 .

In a state that, the inverse rotation speed is input through the third rotation path TM 3 , the rotation speed of the input shaft IS is input to the eighth rotation path TM 8 by operation of the third clutch C 3 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form an eleventh shift line SP 11 .

Therefore, the eleventh shift line SP 11 crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the eleventh forward speed D 11 is output.

In addition, the eleventh forward speed D 11 is output by operation of the first and fourth planetary gear sets PG 1 and PG 4 .

[Reverse Speed]

The fourth clutch C 4 and the first and third brakes B 1 and B 3 are operated at the reverse speed REV.

As shown in FIG. 3 , although the rotation speed of the input shaft IS is input to the fifth rotation path TM 5 of the first compound planetary gear set CPG 1 , it does not have any effect on shifting.

In a state that the rotation speed of the input shaft IS is input to the first rotation path TM 1 by operation of the fourth clutch C 4 , the rotation paths of the first compound planetary gear set CPG 1 form the inverse speed line T 5 by operation of the first brake B 1 . Therefore, the inverse rotation speed is output through the third rotation path TM 3 .

In a state that the inverse rotation speed is input through the third rotation path TM 3 , the sixth rotation path TM 6 is operated as a fixed element by operation of the third brake B 3 . Therefore, the rotation paths of the second compound planetary gear set CPG 2 form a reverse shift line SR.

Therefore, the reverse shift line SR crosses the vertical line of the seventh rotation path TM 7 that is the output element such that the reverse speed REV is output.

In addition, the reverse speed REV is output by operation of the first and third planetary gear sets PG 1 and PG 3 .

According to an exemplary embodiment of the present invention, since four planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 are combined to two compound planetary gear sets CPG 1 and CPG 2 and are controlled by four clutches C 1 , C 2 , C 3 , and C 4 and three brakes B 1 , B 2 , and B 3 , eleven forward speeds and one reverse speed may be achieved.

Therefore, the planetary gear train according to an exemplary embodiment of the present invention may improve power delivery efficiency and reduce fuel consumption by achieving multi shift-speeds of the automatic transmission.

Since three friction members are operated at each shift-speed, the number of the friction members that are not operated can be minimized and friction drag loss may be reduced. Therefore, power delivery efficiency and fuel economy may be further improved.

In addition, the number of planetary gear sets that are operated differ at each shift-speed in the planetary gear train according to an exemplary embodiment of the present invention.

That is, the first forward speed D 1 is achieved by operating the second and third planetary gear sets PG 2 and PG 3 , the second forward speed D 2 is achieved by operating the first, second, and third planetary gear sets PG 1 , PG 2 , and PG 3 , the third forward speed D 3 is achieved by operating the third planetary gear set PG 3 , the fourth forward speed D 4 is achieved by operating the first and third planetary gear sets PG 1 and PG 3 , the fifth forward speed D 5 is achieved by operating the third and fourth planetary gear sets PG 3 and PG 4 , the sixth forward speed D 6 is achieved by operating the first and fourth planetary gear sets PG 1 and PG 4 , the seventh forward speed D 7 is achieved by operating the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , the eighth forward speed D 8 is achieved by operating the first, second, and fourth planetary gear sets PG 1 , PG 2 , and PG 4 , the ninth forward speed D 9 is achieved by operating the second and fourth planetary gear sets PG 2 and PG 4 , the tenth forward speed D 10 is achieved by operating the fourth planetary gear set PG 4 , the eleventh forward speed D 11 is achieved by operating the first and fourth planetary gear sets PG 1 and PG 4 , and the reverse speed REV is achieved by operating the first and third planetary gear sets PG 1 and PG 3 .

That is, the number of planetary gear sets that are operated at each shift-speed is minimized and power loss may be minimized.

For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.