Planetary gear train of automatic transmission for vehicles

The present application claims priority to Korean Patent Application No. 10-2011-0050584 filed in the Korean Intellectual Property Office on May 27, 2011, 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 vehicles. 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.

In addition, the planetary gear train realizes a plurality of shift-speeds. However, another friction member must be operated after one friction member is released so as to shift to a neighboring shift-speed from a view of shift control.

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 tenth-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 vehicles having advantages of achieving nine forward speeds and a reverse speed by combining a plurality of planetary gear sets with a plurality of friction members and reducing drag loss by reducing the number of friction members which are not operated at each shift-speed.

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 gear adapted to output a shifted torque, a first compound planetary gear set having four rotation elements by combining first and second planetary gear sets and adapted to primarily shift torque input through two input paths into five speed ratios and to output the primarily shifted torque, a second compound planetary gear set having four rotation elements by combining third and fourth planetary gear sets and adapted to secondarily shift the torque input from the first compound planetary gear set and the torque input from the input shaft through one path into nine forward speeds and one reverse speed and to output nine forward speeds and one reverse speed, eight rotation shafts including 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 six friction members including three clutches interposed between a selected rotational shaft among the rotational shafts and the input shaft and adapted to selectively transmit the torque and three brakes interposed between a selected rotational shaft among the rotational shafts and a transmission housing.

In addition, the first compound planetary gear set may include the first planetary gear set being a single pinion planetary gear set having a first sun gear, a first planet carrier, and a first ring gear, the second planetary gear set being a single pinion planetary gear set having a second sun gear, a second planet carrier, and a second ring gear, a first rotation shaft including the first sun gear and adapted to be selectively connected to the transmission housing, a second rotation shaft including the first planet carrier and the second ring gear, a third rotation shaft including the first ring gear and the second planet carrier, and adapted to be selectively connected to the input shaft or to the transmission housing, a fourth rotation shaft including the second sun gear and adapted to be selectively connected to the input shaft, a first clutch interposed between the input shaft and the fourth rotation shaft, a second clutch interposed between the input shaft and the third rotation shaft, a first brake interposed between the third rotation shaft and the transmission housing, and a second brake interposed between the first rotation shaft and the transmission housing.

The second compound planetary gear set may include the third planetary gear set being a single pinion planetary gear set having a third sun gear, a third planet carrier, and a third ring gear, the fourth planetary gear set being a single pinion planetary gear set having a fourth sun gear, a fourth planet carrier, and a fourth ring gear, a fifth rotation shaft including the fourth sun gear and adapted to be directly connected to the second rotation shaft of the first compound planetary gear set, a sixth rotation shaft including the third ring gear and the fourth planet carrier, and adapted to be selectively connected to the input shaft, a seventh rotation shaft including the third planet carrier and the fourth ring gear, and adapted to be directly connected to the output gear, an eighth rotation shaft including the third sun gear and adapted to be selectively connected to the transmission housing, a third clutch interposed between the input shaft and the sixth rotation shaft, and a third brake interposed between the eighth rotation shaft and the transmission housing.

A first forward speed is achieved by operating the first clutch, the second brake, and the third brake, a second forward speed is achieved by operating the second clutch, the second brake, and the third brake, a third forward speed is achieved by operating the first clutch, the second clutch, and the third brake, a fourth forward speed is achieved by operating the first clutch, the third clutch, and the third brake, a fifth forward speed is achieved by operating the first clutch, the second clutch, and the third clutch, a sixth forward speed is achieved by operating the second clutch, the third clutch, and the second brake, a seventh forward speed is achieved by operating the first clutch, the third clutch, and the second brake, an eighth forward speed is achieved by operating the third clutch, the first brake, and the second brake, a ninth forward speed is achieved by operating the first clutch, the third clutch, and the first brake, and a reverse speed is achieved by operating the first clutch, the first brake, and the third brake.

According to another exemplary embodiment of the present invention, the first compound planetary gear set is a compound planetary gear set formed by combining the first planetary gear set being a double pinion planetary gear set and the second planetary gear set being a single pinion planetary gear set by sharing a ring gear and a planet carrier in common, and may include a first sun gear engaged with a short pinion, a second sun gear engaged with a long pinion, a common planet carrier, and a common ring gear. The first compound planetary gear set may include a first rotation shaft including the first sun gear and adapted to be selectively connected to the transmission housing, a second rotation shaft including the common ring gear, a third rotation shaft including the common planet carrier, and adapted to be selectively connected to the input shaft or to the transmission housing, a fourth rotation shaft including the second sun gear and adapted to be selectively connected to the input shaft, a first clutch interposed between the input shaft and the fourth rotation shaft, a second clutch interposed between the input shaft and the third rotation shaft, a first brake interposed between the third rotation shaft and the transmission housing, and a second brake interposed between the first rotation shaft and the transmission housing.

The second compound planetary gear set may include the third planetary gear set being a single pinion planetary gear set having a third sun gear, a third planet carrier, and a third ring gear, the fourth planetary gear set being a single pinion planetary gear set having a fourth sun gear, a fourth planet carrier, and a fourth ring gear, a fifth rotation shaft including the third ring gear and adapted to be directly connected to the second rotation shaft of the first compound planetary gear set, a sixth rotation shaft including the third planet carrier and the fourth ring gear, and adapted to be selectively connected to the input shaft, a seventh rotation shaft including the fourth planet carrier and adapted to be directly connected to the output gear, an eighth rotation shaft including the third sun gear and the fourth sun gear, and adapted to be selectively connected to the transmission housing, a third clutch interposed between the input shaft and the sixth rotation shaft, and a third brake interposed between the eighth rotation shaft and the transmission housing.

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 the various exemplary embodiments 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 the various exemplary embodiments of the present invention.

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

FIG. 4 is a schematic diagram of a planetary gear train according to the various exemplary embodiments 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 the first exemplary embodiment of the present invention.

Referring to FIG. 1 , a planetary gear train according to the first 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 gear OG, eight rotation shafts TM 1 -TM 8 directly or selectively connecting rotation elements of the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , six friction members C 1 -C 3 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 gear OG.

In addition, the 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 gear OG 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 engaged with the first sun gear S 1 , and a first ring gear R 1 internally engaged 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 engaged with the second sun gear S 2 , and a second ring gear R 2 internally engaged 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 engaged with the third sun gear S 3 , and a third ring gear R 3 internally engaged 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 engaged with the fourth sun gear S 4 , and a fourth ring gear R 4 internally engaged 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 nine forward speeds, and output the nine 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 .

That is, the first compound planetary gear set CPG 1 is operated by four rotation elements by directly connecting the first planet carrier PC 1 with the second ring gear R 2 and directly connecting the first ring gear R 1 with the second planet carrier PC 2 , and includes first, second, third, and fourth rotation shafts TM 1 , TM 2 , TM 3 , and TM 4 .

In addition, the second compound planetary gear set CPG 2 is operated by four rotation elements by directly connecting the third planet carrier PC 3 with the fourth ring gear R 4 and directly connecting the third ring gear R 3 with the fourth planet carrier PC 4 , and includes fifth, sixth, seventh, and eighth rotation shafts TM 5 , TM 6 , TM 7 , and TM 8 .

Accordingly, the planetary gear train according to the present exemplary embodiment includes eight rotation shafts TM 1 -TM 8 .

The first rotation shaft TM 1 includes the first sun gear S 1 and is selectively connected to the transmission housing H.

The second rotation shaft TM 2 includes the first planet carrier PC 1 and the second ring gear R 2 .

The third rotation shaft TM 3 includes the first ring gear R 1 and the second planet carrier PC 2 , and is selectively connected to the input shaft IS or to the transmission housing H.

The fourth rotation shaft TM 4 includes the second sun gear S 2 and is selectively connected to the input shaft IS.

The fifth rotation shaft TM 5 includes the fourth sun gear S 4 and is directly connected to the second rotation shaft TM 2 .

The sixth rotation shaft TM 6 includes the third ring gear R 3 and the fourth planet carrier PC 4 , and is selectively connected to the input shaft IS.

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

The eighth rotation shaft TM 8 includes the third sun gear S 3 and is selectively connected to the transmission housing H.

In addition, the third, fourth, and sixth rotation shafts TM 3 , TM 4 , and TM 6 among the rotation shafts TM 1 -TM 8 selectively connected to the input shaft IS and operated as a selective input element are connected to the input shaft IS respectively through clutches C 2 , C 1 , and C 3 .

In addition, the first, third, and eighth rotation shafts TM 1 , TM 3 , and TM 8 among the rotation shafts TM 1 -TM 8 selectively connected to the transmission housing H and operated as a selective fixed element are connected to the transmission housing H respectively through brakes B 2 , B 1 , and B 3 .

The first clutch C 1 is interposed between the input shaft IS and the fourth rotation shaft TM 4 , and operates the fourth rotation shaft TM 4 as the selective input element.

The second clutch C 2 is interposed between the input shaft IS and the third rotation shaft TM 3 , and operates the third rotation shaft TM 3 as the selective input element.

The third clutch C 3 is interposed between the input shaft IS and the sixth rotation shaft TM 6 , and operates the sixth rotation shaft TM 6 as the selective input element.

The first brake B 1 is interposed between the third rotation shaft TM 3 and the transmission housing H, and operates the third rotation shaft TM 3 as the selective fixed element.

The second brake B 2 is interposed between the first rotation shaft TM 1 and the transmission housing H, and operates the first rotation shaft TM 1 as the selective fixed element.

The third brake B 3 is interposed between the eighth rotation shaft TM 8 and the transmission housing H, and operates the eighth rotation shaft TM 8 as the selective fixed element.

In addition, a one-way clutch F 1 is further included between the eighth rotation shaft TM 8 and the transmission housing H. The one-way clutch F 1 is disposed in parallel with the first brake B 1 .

The first and second clutches C 1 and C 2 and the first and second brakes B 1 and B 2 are applied to the first compound planetary gear set CPG 1 , and torque input through the first and second clutches C 1 and C 2 is changed into five speed ratios according to operations of the first and second brakes B 1 and B 2 .

In addition, the third clutch C 3 and the third brake B 3 are applied to the second compound planetary gear set CPG 2 , and the torque directly input from the input shaft IS through the third clutch C 3 and the torque changed into the five speed ratios and input from the first compound planetary gear set CPG 2 are changed into the nine forward speeds and one reverse speed by operation of the third brake B 3 .

Friction members including the first, second, and third clutches C 1 , C 2 , and C 3 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 the first exemplary embodiment of the present invention.

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

The first clutch C 1 , the second brake B 2 , and the third brake B 3 are operated at a first forward speed D 1 .

The second clutch C 2 , the second brake B 2 , and the third brake B 3 are operated at a second forward speed D 2 .

The first clutch C 1 , the second clutch C 2 , and the third brake B 3 are operated at a third forward speed D 3 .

The first clutch C 1 , the third clutch C 3 , and the third brake B 3 are operated at a fourth forward speed D 4 .

The first clutch C 1 , the second clutch C 2 , and the third clutch C 3 are operated at a fifth forward speed D 5 .

The second clutch C 2 , the third clutch C 3 , and the second brake B 2 are operated at a sixth forward speed D 6 .

The first clutch C 1 , the third clutch C 3 , and the second brake B 2 are operated at a seventh forward speed D 7 .

The third clutch C 3 , the first brake B 1 , and the second brake B 2 are operated at an eighth forward speed D 8 .

The first clutch C 1 , the third clutch C 3 , and the first brake B 1 are operated at a ninth forward speed D 9 .

The first clutch C 1 , the first brake B 1 , and the third brake B 3 are operated at a reverse speed REV.

It is described in this specification that the first clutch C 1 and the second and third brakes B 2 and B 3 are operated at the first forward speed D 1 , but the one-way clutch F 1 instead of the third brake B 3 can be operated at a normal driving.

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

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, second, third, and fourth rotation shafts TM 1 , TM 2 , TM 3 , and TM 4 from the left to the right.

Herein, distances between the first, second, third, and fourth rotation shafts TM 1 , TM 2 , TM 3 , and TM 4 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 .

Four vertical lines of the second compound planetary gear set CPG 2 sequentially represent the fifth, sixth, seventh, and eighth rotation shafts TM 5 , TM 6 , TM 7 , and TM 8 from the left to the right.

Herein, distances between the fifth, sixth, seventh, and eighth rotation shafts TM 5 , TM 6 , TM 7 , and TM 8 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 .

Referring to FIG. 2 and FIG. 3 , shifting processes for each shift-speed in the planetary gear train according to the first exemplary embodiment will be described.

[First Forward Speed]

Referring to FIG. 2 , the first clutch C 1 and the second and third brakes B 2 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 fourth rotation shaft TM 4 by operation of the first clutch C 1 , the first rotation shaft TM 1 is operated as the fixed element by operation of the second brake B 2 in the first compound planetary gear set CPG 1 .

Therefore, the first compound planetary gear set CPG 1 forms a first reduced speed line T 1 and outputs a first reduced speed through the second rotation shaft TM 2 .

In a state that the first reduced speed is input through the fifth rotation shaft TM 5 directly connected to the second rotation shaft TM 2 , the eighth rotation shaft TM 8 is operated as the fixed element by operation of the third brake B 3 . Therefore, the second compound planetary gear set CPG 2 forms a first shift line SP 1 .

The first shift line SP 1 crosses a vertical line of the seventh rotation shaft TM 7 that is the output element such that the first forward speed D 1 is output.

[Second Forward Speed]

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

In a state that the rotation speed of the input shaft IS is input to the third rotation shaft TM 3 by operation of the second clutch C 2 , the first rotation shaft TM 1 is operated as the fixed element by operation of the second brake B 2 in the first compound planetary gear set CPG 1 .

Accordingly, the first compound planetary gear set CPG 1 forms a second reduced speed line T 2 and outputs a second reduced speed through the second rotation shaft TM 2 .

In a state that the second reduced speed is input through the fifth rotation shaft TM 5 directly connected to the second rotation shaft TM 2 , the eighth rotation shaft TM 8 is operated as the fixed element by operation of the third brake B 3 . Therefore, the second compound planetary gear set CPG 2 forms a second shift line SP 2 .

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

[Third Forward Speed]

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

The first and second clutch C 1 and C 2 are operated simultaneously such that the rotation speed of the input shaft IS is input simultaneously to the third and fourth rotation shafts TM 3 and TM 4 . Therefore, the first compound planetary gear set CPG 1 becomes a direct-coupling state. Therefore, the first compound planetary gear set CPG 1 forms a direct-coupling speed line T 3 and outputs the rotation speed of the input shaft IS through the second rotation shaft TM 2 .

In a state that the rotation speed of the input shaft IS is input through the fifth rotation shaft TM 5 directly connected to the second rotation shaft TM 2 , the eighth rotation shaft TM 8 is operated as the fixed element by operation of the third brake B 3 . Therefore, the second compound planetary gear set CPG 2 forms a third shift line SP 3 .

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

[Fourth Forward Speed]

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

The rotation speed of the input shaft IS is input to the fourth rotation shaft TM 4 by operation of the first clutch C 1 , but 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 sixth rotation shaft TM 6 by operation of the third clutch C 3 , the eighth rotation shaft TM 8 is operated as the fixed element by operation of the third brake B 3 . Therefore, the second compound planetary gear set CPG 2 forms a fourth shift line SP 4 .

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

[Fifth Forward Speed]

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

The first and second clutch C 1 and C 2 are operated simultaneously such that the rotation speed of the input shaft IS is input simultaneously to the third and fourth rotation shafts TM 3 and TM 4 . Therefore, the first compound planetary gear set CPG 1 becomes the direct-coupling state. Therefore, the first compound planetary gear set CPG 1 forms the direct-coupling speed line T 3 and outputs the rotation speed of the input shaft IS through the second rotation shaft TM 2 .

In a state that the rotation speed of the input shaft IS is input to the fifth rotation shaft TM 5 directly connected to the second rotation shaft TM 2 , the rotation speed of the input shaft IS is input to the sixth rotation shaft TM 6 . Therefore, the second compound planetary gear set CPG 2 becomes a direct-coupling state and forms a fifth shift line SP 5 .

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

That is, a rotation speed that is the same as the rotation speed of the input shaft IS is output.

[Sixth Forward Speed]

The first clutch C 1 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 .

The rotation speed of the input shaft IS is input to the third rotation shaft TM 3 by operation of the second clutch C 2 , the first rotation shaft TM 1 is operated at the fixed element by operation of the second brake B 2 in the first compound planetary gear set CPG 1 .

Therefore, the first compound planetary gear set CPG 1 forms the second reduced speed line T 2 and outputs the second reduced speed through the second rotation shaft TM 2 .

In a state that the second reduced speed is input to the fifth rotation shaft TM 5 directly connected to the second rotation shaft TM 2 , the rotation speed of the input shaft IS is input to the sixth rotation shaft TM 6 by operation of the third clutch C 3 . Therefore, the second compound planetary gear set CPG 2 forms a sixth shift line SP 6 .

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

[Seventh Forward Speed]

The second clutch C 2 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 fourth rotation shaft TM 4 by operation of the first clutch C 1 , the first rotation shaft TM 1 is operated as the fixed element by operation of the second brake B 2 in the first compound planetary gear set CPG 1 .

Therefore, the first compound planetary gear set CPG 1 forms the first reduced speed line T 1 and outputs the first reduced speed through the second rotation shaft TM 2 .

In a state that the first reduced speed is input to the fifth rotation shaft TM 5 directly connected to the second rotation shaft TM 2 , the rotation speed of the input shaft IS is input to the sixth rotation shaft TM 6 by operation of the third clutch C 3 . Therefore, the second compound planetary gear set CPG 2 forms a seventh shift line SP 7 .

The seventh shift line SP 7 crosses the vertical line of the seventh rotation shaft TM 7 that is the output element such that the seventh forward speed D 7 is output.

[Eighth Forward Speed]

The first clutch C 1 that was operated at the seventh forward speed D 7 is released and the first brake B 1 is operated at the eighth forward speed D 8 .

The first compound planetary gear set CPG 1 does not rotate by operations of the first and second brakes B 1 and B 2 , and forms a stopped speed line T 4 .

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

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

[Ninth Forward Speed]

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

In a state that the rotation speed of the input shaft IS is input to the fourth rotation shaft TM 4 by operation of the first clutch C 1 , the third rotation shaft TM 3 is operated as the fixed element by operation of the first brake B 1 in the first compound planetary gear set CPG 1 .

Therefore, the first compound planetary gear set CPG 1 forms an inverse speed line T 5 and outputs an inverse speed through the second rotation shaft TM 2 .

In a state that the inverse speed is input to the fifth rotation shaft TM 5 directly connected to the second rotation shaft TM 2 , the rotation speed of the input shaft IS is input to the sixth rotation shaft TM 6 by operation of the third clutch C 3 . Therefore, the second compound planetary gear set CPG 2 forms a ninth shift line SP 9 .

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

[Reverse Speed]

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

In a state that the rotation speed of the input shaft IS is input to the fourth rotation shaft TM 4 by operation of the first clutch C 1 , the third rotation shaft TM 3 is operated as the fixed element by operation of the first brake B 1 in the first compound planetary gear set CPG 1 .

Therefore, the first compound planetary gear set CPG 1 forms the inverse speed line T 5 and outputs the inverse speed through the second rotation shaft TM 2 .

In a state that the inverse speed is input to the fifth rotation shaft TM 5 directly connected to the second rotation shaft TM 2 , the eighth rotation shaft TM 8 is operated as the fixed element by operation of the third brake B 3 . Therefore, the second compound planetary gear set CPG 2 forms a reverse shift line SR.

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

Four planetary gear sets PG 1 , PG 2 , P 03 , and PG 4 is combined to form two compound planetary gear sets CPG 1 and CPG 2 such that the nine forward speeds and one reverse speed is achieved by operation of three clutches C 1 , C 2 , and C 3 and three brakes B 1 , B 2 , and B 3 according to the first exemplary embodiment of the present invention.

That is, the rotation speed of the input shaft IS is changed into the speed ratios and the speed ratios are output from the first compound planetary gear set CPG 1 . In addition, the second compound planetary gear set CPG 2 receives the speed ratios from the first compound planetary gear set CPG 1 and secondarily shifts the five speed ratios into the nine forward speeds and one reverse speed.

Therefore, power delivery performance and fuel economy may be improved since the planetary gear train according to the first exemplary embodiment of the present invention can achieve multiple shift-speeds.

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

FIG. 4 is a schematic diagram of a planetary gear train according to the second exemplary embodiment of the present invention.

Referring to FIG. 4 , the first compound planetary gear set CPG 1 according to the second exemplary embodiment is formed by combining the first planetary gear set PG 1 being a double pinion planetary gear set and the second planetary gear set PG 2 being a single pinion planetary gear set.

That is, the first compound planetary gear set CPG 1 is formed by combining the first planetary gear set PG 1 being the double pinion planetary gear set and the second planetary gear set PG 2 being the single pinion planetary gear set so as to be a compound planetary gear set of Ravingneaux type having a ring gear and a planet carrier in common.

Therefore, the compound planetary gear set CPG is operated by four rotation elements including a ring gear, a planet carrier, and two sun gears. For convenience of explanation, the ring gear is called a common ring gear R, the planet carrier is called a common planet carrier PC, the sun gear engaged with a short pinion P 1 is called a first sun gear S 1 , and the sun gear engaged with a long pinion P 2 is called a second sun gear S 2 .

The first compound planetary gear set CPG 1 includes the first, second, third, and fourth rotational shafts TM 1 , TM 2 , TM 3 , and TM 4 .

The second compound planetary gear set CPG 2 , the same as the first exemplary embodiment, is formed by combining the third planetary gear set PG 3 being the single pinion planetary gear set and the fourth planetary gear set PG 4 being the single pinion planetary gear set.

The second compound planetary gear set CPG 2 includes the fifth, sixth, seventh, and eighth rotational shafts TM 5 , TM 6 , TM 7 , and TM 8 by connecting the third planet carrier PC 3 with the fourth ring gear R 4 and connecting the third sun gear S 3 with the fourth sun gear S 4 .

Accordingly, the second exemplary embodiment includes eight rotation shafts TM 1 -TM 8 .

The first rotation shaft TM 1 includes the first sun gear S 1 and is selectively connected to the transmission housing H.

The second rotation shall TM 2 includes the common ring gear R.

The third rotation shaft TM 3 includes the common planet carrier PC, and is selectively connected to the input shaft IS or to the transmission housing H.

The fourth rotation shaft TM 4 includes the second sun gear S 2 and is selectively connected to the input shaft IS.

The fifth rotation shaft TM 5 includes the third ring gear R 3 and is directly connected to the second rotation shaft TM 2 .

The sixth rotation shaft TM 6 includes the third planet carrier PC 3 and the fourth ring gear R 4 , and is selectively connected to the input shaft IS.

The seventh rotation shaft TM 7 includes the fourth planet carrier PC 4 and is connected to the output gear OG.

The eighth rotation shaft TM 8 includes the third sun gear S 3 and the fourth sun gear S 4 , and is selectively connected to the transmission housing H.

In addition, the third, fourth, and sixth rotation shafts TM 3 , TM 4 , and TM 6 among the rotation shafts TM 1 -TM 8 selectively connected to the input shaft IS and operated as a selective input element are connected to the input shaft IS respectively through clutches C 2 , C 1 , and C 3 .

In addition, the first, third, and eighth rotation shafts TM 1 , TM 3 , and TM 8 among the rotation shafts TM 1 -TM 8 selectively connected to the transmission housing H and operated as a selective fixed element are connected to the transmission housing H respectively through brakes B 2 , B 1 , and B 3 .

The first clutch C 1 is interposed between the input shaft IS and the fourth rotation shaft TM 4 , and operates the fourth rotation shaft TM 4 as the selective input element.

The second clutch C 2 is interposed between the input shaft IS and the third rotation shaft TM 3 , and operates the third rotation shaft TM 3 as the selective input element.

The third clutch C 3 is interposed between the input shaft IS and the sixth rotation shaft TM 6 , and operates the sixth rotation shaft TM 6 as the selective input element.

The first brake B 1 is interposed between the third rotation shaft TM 3 and the transmission housing H, and operates the third rotation shaft TM 3 as the selective fixed element.

The second brake B 2 is interposed between the first rotation shaft TM 1 and the transmission housing H, and operates the first rotation shaft TM 1 as the selective fixed element.

The third brake B 3 is interposed between the eighth rotation shaft TM 8 and the transmission housing H, and operates the eighth rotation shaft TM 8 as the selective fixed element.

In addition, the one-way clutch F 1 is further included between the eighth rotation shaft TM 8 and the transmission housing H. The one-way clutch F 1 is disposed in parallel with the first brake B 1 .

The first compound planetary gear set CPG 1 according to the second exemplary embodiment of the present invention is different from that of the first exemplary embodiment. In addition, the connections between the first compound planetary gear set CPG 1 and the second compound planetary gear set CPG 2 according to the second exemplary embodiment are different from those according to the first exemplary embodiment.

Therefore, eight rotational shafts of the second exemplary embodiment, as shown in FIG. 3 and FIG. 4 , are different from those of the first exemplary embodiment. However, operation of the friction members at each shift-speed and shifting processes of the second exemplary embodiment are the same as those of the first exemplary embodiment. Therefore, detailed description will be omitted.

Since nine forward speeds are achieved by combining four planetary gear sets being simple planetary gear sets with six friction members, power delivery performance and fuel consumption may be improved according to exemplary embodiments of the present invention.

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

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.