Planetary gear train of automatic transmission for vehicle

This application claims priority to and the benefit of Korean Patent Application No. 10-2016-0007779, filed on Jan. 21, 2016, which is incorporated herein by reference in its entirety.

The present disclosure relates to an automatic transmission for a vehicle. More particularly, the present disclosure relates to a planetary gear train of an automatic transmission for a vehicle.

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Generally, an automatic transmission achieving more speed stages has been developed to enhance fuel economy and improve drivability.

Such an automatic transmission achieving more speed stages is necessary to improve power performance and driving efficiency according to downsizing of an engine. Particularly, it is desired to develop high efficiency multiple-speeds transmissions having excellent linearity of step ratios that can be used as an index closely related to drivability such as acceleration before and after shift and rhythmical engine speed.

However, in the automatic transmission, as the number of speed stages increase, the number of internal components increase, and as a result, mountability, cost, weight, transmission efficiency, and the like may still deteriorate.

Accordingly, development of a planetary gear train which may achieve maximum efficiency with a small number of components is desired in order to increase a fuel efficiency enhancement effect through the multiple-speeds.

In this aspect, in recent years, 8-speed automatic transmissions tend to be implemented and the research and development of a planetary gear train capable of implementing more speed stages has also been actively conducted.

However, since a conventional 8-speed automatic transmission has gear ratio span of 6.5-7.5 (gear ratio span is an important factor for securing linearity of step ratios), improvement of power performance and fuel economy may not be great.

In addition, if a 8-speed automatic transmission has gear ratio span larger than 9.0, it is hard to secure linearity of step ratios. Therefore, driving efficiency of an engine and drivability of a vehicle may be deteriorated, and thus, development of high efficiency automatic transmissions which achieve at least nine forward speed stages is desired.

The present disclosure provides a planetary gear train of an automatic transmission for a vehicle having advantages of improving power delivery performance and fuel economy by achieving ten forward speed stages and one reverse speed stage, and widening gear ratio span and of securing linearity of step ratios.

Another embodiment of the present disclosure provides a planetary gear train of an automatic transmission for a vehicle having advantages of maintaining durability of pinion shafts by avoiding applying load to planet carriers at stopped states when the vehicle runs at a high speed stage.

A planetary gear train of an automatic transmission for a vehicle according to an exemplary embodiment of the present disclosure may include: an input shaft receiving torque of an engine; an output shaft outputting changed torque; a first planetary gear set including first, second, and third rotation elements; a second planetary gear set including fourth, fifth, and sixth rotation elements; a third planetary gear set including seventh, eighth, and ninth rotation elements; a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements; a first shaft connecting the first rotation element to the fourth rotation element; a second shaft connected to the second rotation element and directly connected to the input shaft; a third shaft connecting the third rotation element to the tenth rotation element; a fourth shaft connected to the fifth rotation element and selectively connected to the second shaft; a fifth shaft connecting the sixth rotation element to the ninth rotation element and selectively connected to the second shaft; and a sixth shaft connecting the seventh rotation element to the twelfth rotation element.

The first shaft, fourth shaft and sixth shaft may be selectively connected to a transmission housing.

The planetary gear train may further include: a seventh shaft connected to the eighth rotation element and selectively connected to the third shaft; and an eighth shaft connected to the eleventh rotation element, selectively connected to the seventh shaft, and directly connected to the output shaft.

The first, second, and third rotation elements of the first planetary gear set may be a first sun gear, a first planet carrier, and a first ring gear, the fourth, fifth, and sixth rotation elements of the second planetary gear set may be a second sun gear, a second planet carrier, and a second ring gear, the seventh, eighth, and ninth rotation elements of the third planetary gear set may be a third sun gear, a third planet carrier, and a third ring gear, and a tenth, eleventh, and twelfth rotation elements of the fourth planetary gear set may be a fourth sun gear, a fourth planet carrier, and a fourth ring gear, respectively.

In some aspects, the first, second, third, and fourth planetary gear sets may be disposed in a sequence of the second planetary gear set, the first planetary gear set, the third planetary gear set, and the fourth planetary gear set from the engine.

In some aspects, the first, second, third, and fourth planetary gear sets may be disposed in a sequence of the first planetary gear set, the second planetary gear set, the third planetary gear set, and the fourth planetary gear set from the engine.

In some aspects, the first, second, third, and fourth planetary gear sets may be disposed in a sequence of the first planetary gear set, the second planetary gear set, the fourth planetary gear set, and the third planetary gear set from the engine.

The planetary gear train may further include: a first clutch selectively connecting the seventh shaft to the eighth shaft; a second clutch selectively connecting the second shaft to the fifth shaft; a third clutch selectively connecting the second shaft to the fourth shaft; a fourth clutch selectively connecting the third shaft to the seventh shaft; a first brake selectively connecting the first shaft to the transmission housing; a second brake selectively connecting the sixth shaft to the transmission housing; and a third brake selectively connecting the fourth shaft to the transmission housing.

A planetary gear train of an automatic transmission for a vehicle according to another exemplary embodiment of the present disclosure may include: an input shaft receiving torque of an engine; an output shaft outputting changed torque; a first planetary gear set including first, second, and third rotation elements; a second planetary gear set including fourth, fifth, and sixth rotation elements; a third planetary gear set including seventh, eighth, and ninth rotation elements; and a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements, wherein the input shaft is directly connected to the second rotation element, the output shaft is directly connected to the eleventh rotation element, the first rotation element is directly connected to the fourth rotation element and is selectively connected to a transmission housing, the third rotation element is directly connected to the tenth rotation element, the sixth rotation element is directly connected to the ninth rotation element, the seventh rotation element is directly connected to the twelfth rotation element and is selectively connected to the transmission housing, and the fifth rotation element is selectively connected to the transmission housing.

The eleventh rotation element may be selectively connected to the eighth rotation element, the second rotation element may be selectively connected to the sixth rotation element, the second rotation element may be selectively connected to the fifth rotation element, and the third rotation element may be selectively connected to the eighth rotation element.

The first, second, and third rotation elements of the first planetary gear set may be a first sun gear, a first planet carrier, and a first ring gear, the fourth, fifth, and sixth rotation elements of the second planetary gear set may be a second sun gear, a second planet carrier, and a second ring gear, the seventh, eighth, and ninth rotation elements of the third planetary gear set may be a third sun gear, a third planet carrier, and a third ring gear, and a tenth, eleventh, and twelfth rotation elements of the fourth planetary gear set may be a fourth sun gear, a fourth planet carrier, and a fourth ring gear, respectively.

In some aspects, the first, second, third, and fourth planetary gear sets may be disposed in a sequence of the second planetary gear set, the first planetary gear set, the third planetary gear set, and the fourth planetary gear set from the engine.

In some aspects, the first, second, third, and fourth planetary gear sets may be disposed in a sequence of the first planetary gear set, the second planetary gear set, the third planetary gear set, and the fourth planetary gear set from the engine.

In some aspects, the first, second, third, and fourth planetary gear sets may be disposed in a sequence of the first planetary gear set, the second planetary gear set, the fourth planetary gear set, and the third planetary gear set from the engine.

The planetary gear train may further include: a first clutch selectively connecting the eleventh rotation element to the eighth rotation element; a second clutch selectively connecting the second rotation element to the sixth rotation element; a third clutch selectively connecting the second rotation element to the fifth rotation element; a fourth clutch selectively connecting the third rotation element to the eighth rotation element; a first brake selectively connecting the first rotation element and the fourth rotation element to the transmission housing; a second brake selectively connecting the seventh rotation element and the twelfth rotation element to the transmission housing; and a third brake selectively connecting the fifth rotation element to the transmission housing.

An exemplary embodiment of the present disclosure may achieve at least ten forward speed stages and one reverse speed stage by combining four planetary gear sets being simple planetary gear sets with seven control elements.

In addition, since gear ratio span greater than 10.0 is secured, driving efficiency of the engine may be maximized.

In addition, since linearity of step ratios can be secured due to multiple speed stages, drivability such as acceleration before and after shift, rhythmical engine speed, and so on may be improved.

In addition, durability of pinion shafts connected to pinion gears may be maintained due to smooth lubrication by avoiding applying load to planet carriers at stopped states when the vehicle runs at a high forward speed stage.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a planetary gear train according to the first exemplary embodiment of the present disclosure;

FIG. 2 is an operation chart of control elements at each speed stage in the planetary gear train according to the first exemplary embodiment of the present disclosure;

FIG. 3 is another operation chart of control elements at each speed stage in the planetary gear train according to the first exemplary embodiment of the present disclosure;

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

FIG. 5 is a schematic diagram of a planetary gear train according to the third exemplary embodiment of the present disclosure;

FIG. 6 is a schematic diagram of a planetary gear train according to the fourth exemplary embodiment of the present disclosure; and

FIG. 7 is a schematic diagram of a planetary gear train according to the fifth exemplary embodiment of the present disclosure.

B 1 , B 2 , B 3 : first, second, and third brakes

C 1 , C 2 , C 3 , C 4 : first, second, third, and fourth clutches

PG 1 , PG 2 , PG 3 , PG 4 : first, second, third, and fourth planetary gear sets

S 1 , S 2 , S 3 , S 4 : first, second, third, and fourth sun gears

PC 1 , PC 2 , PC 3 , PC 4 : first, second, third, and fourth planet carriers

R 1 , R 2 , R 3 , R 4 : first, second, third, and fourth ring gears

IS: input shaft OS: output shaft

TM 1 , TM 2 , TM 3 , TM 4 , TM 5 , TM 6 , TM 7 , TM 8 : first, second, third, fourth, fifth, sixth, seventh, and eighth shafts

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

However, parts which are not related with the description are omitted for clearly describing the exemplary embodiments of the present disclosure and like reference numerals refer to like or similar elements throughout the specification.

In the following description, dividing names of components into first, second, and the like is to divide the names because the names of the components are the same as each other and an order thereof is not particularly limited.

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

Referring to FIG. 1 , a planetary gear train 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 shafts TM 1 to TM 8 connected to at least one of rotation elements of the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , four clutches C 1 to C 4 and three brakes B 1 to B 3 that are control elements, and a transmission housing H.

Torque input from the input shaft IS is changed by cooperation of the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , and the changed torque is output through the output shaft OS.

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

The input shaft IS is an input member and torque from a crankshaft of the engine is torque-converted through a torque converter to be input into the input shaft IS.

The output shaft OS is an output member, which is disposed in parallel with the input shaft IS, and transmits driving torque to a driving wheel through a differential apparatus (e.g., a differential gear).

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 that is externally meshed with the first sun gear S 1 , and a first ring gear R 1 that is internally meshed with the first pinion P 1 respectively as first, second, and third rotation elements N 1 , N 2 , and N 3 .

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 that is externally meshed with the second sun gear S 2 , and a second ring gear R 2 that is internally meshed with the second pinion P 2 respectively as fourth, fifth, and sixth rotation elements N 4 , N 5 , and N 6 .

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 that is externally meshed with the third sun gear S 3 , and a third ring gear R 3 that is internally meshed with the third pinion P 3 respectively as seventh, eighth, and ninth rotation elements N 7 , N 8 , and N 9 .

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 that is externally meshed with the fourth sun gear S 4 , and a fourth ring gear R 4 that is internally meshed with the fourth pinion P 4 respectively as tenth, eleventh, and twelfth rotation elements N 10 , N 11 , and N 12 .

The first rotation element N 1 and the fourth rotation element N 4 are directly connected to each other, the third rotation element N 3 and the tenth rotation element N 10 are directly connected to each other, the sixth rotation element N 6 and the ninth rotation element N 9 are directly connected to each other, and the seventh rotation element N 7 and the twelfth rotation element N 12 are directly connected to each other through four shafts among the eight shafts TM 1 to TM 8 .

The eight shafts TM 1 to TM 8 will be described in further detail.

The eight shafts TM 1 to TM 8 directly connects a plurality of rotation elements among the rotation elements of the planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , are rotation members that are directly connected to any one rotation element of the planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 and rotate with the any one rotation element to transmit torque, or are fixed members that directly connect any one rotation element of the planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 to the transmission housing H to fix the any one rotation element.

The first shaft TM 1 directly connects the first rotation element N 1 (first sun gear S 1 ) to the fourth rotation element N 4 (second sun gear S 2 ) and is selectively connected to the transmission housing H.

The second shaft TM 2 is connected to the second rotation element N 2 (first planet carrier PC 1 ) and is directly connected to the input shaft IS.

The third shaft TM 3 directly connects the third rotation element N 3 (first ring gear R 1 ) to the tenth rotation element N 10 (fourth sun gear S 4 ).

The fourth shaft TM 4 is connected to the fifth rotation element N 5 (second planet carrier PC 2 ) and is selectively connected to the second shaft TM 2 or the transmission housing H.

The fifth shaft TM 5 directly connects the sixth rotation element N 6 (second ring gear R 2 ) to the ninth rotation element N 9 (third ring gear R 3 ) and is selectively connected to the second shaft TM 2 .

The sixth shaft TM 6 directly connects the seventh rotation element N 7 (third sun gear S 3 ) to the twelfth rotation element N 12 (fourth ring gear R 4 ) and is selectively connected to the transmission housing H.

The seventh shaft TM 7 is connected to the eighth rotation element N 8 (third planet carrier PC 3 ) and is selectively connected to the third shaft TM 3 .

The eighth shaft TM 8 is connected to the eleventh rotation element N 11 (fourth planet carrier PC 4 ), is selectively connected to the seventh shaft TM 7 , and is directly connected to the output shaft OS.

In addition, four clutches C 1 , C 2 , C 3 , and C 4 are disposed at portions at which any two shafts among the eight shafts TM 1 to TM 8 are selectively connected to each other.

In addition, three brakes B 1 , B 2 , and B 3 are disposed at portions at which any one shaft among the eight shafts TM 1 to TM 8 is selectively connected to the transmission housing H.

Arrangements of the four clutches C 1 to C 4 and the three brakes B 1 to B 3 are described in detail.

The first clutch C 1 is disposed between the seventh shaft TM 7 and the eighth shaft TM 8 and selectively connects the seventh shaft TM 7 to the eighth shaft TM 8 .

The second clutch C 2 is disposed between the second shaft TM 2 and the fifth shaft TM 5 and selectively connects the second shaft TM 2 to the fifth shaft TM 5 .

The third clutch C 3 is disposed between the second shaft TM 2 and the fourth shaft TM 4 and selectively connects the second shaft TM 2 to the fourth shaft TM 4 .

The fourth clutch C 4 is disposed between the third shaft TM 3 and the seventh shaft TM 7 and selectively connects the third shaft TM 3 to the seventh shaft TM 7 .

The first brake B 1 is disposed between the first shaft TM 1 and the transmission housing H and selectively connects the first shaft TM 1 to the transmission housing H.

The second brake B 2 is disposed between the sixth shaft TM 6 and the transmission housing H and selectively connects the sixth shaft TM 6 to the transmission housing H.

The third brake B 3 is disposed between the fourth shaft TM 4 and the transmission housing H and selectively connects the fourth shaft TM 4 to the transmission housing H.

The control elements 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 may be multi-plates friction elements of wet type that are operated by hydraulic pressure.

FIG. 2 is an operation chart of control elements at each speed stage in the planetary gear train according to the first exemplary embodiment of the present disclosure.

As shown in FIG. 2 , three control elements among 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 that are control elements are operated at each speed stage in the planetary gear train according to the first exemplary embodiment of the present disclosure. The first exemplary embodiment can achieve one reverse speed stage and ten forward speed stages and shifting processes will be described in detail.

The second and fourth clutches C 2 and C 4 and the second brake B 2 are simultaneously operated at a first forward speed stage D 1 . In a state that the second shaft TM 2 is connected to the fifth shaft TM 5 by operation of the second clutch C 2 and the third shaft TM 3 is connected to the seventh shaft TM 7 by operation of the fourth clutch C 4 , torque of the input shaft IS is inputted to the second shaft TM 2 and the sixth shaft TM 6 is operated as a fixed element by operation of the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the first forward speed stage, and the first forward speed stage is output through the eighth shaft TM 8 .

The second and third clutches C 2 and C 3 and the second brake B 2 are simultaneously operated at a second forward speed stage D 2 . In a state that the second shaft TM 2 is connected to the fifth shaft TM 5 by operation of the second clutch C 2 and the second shaft TM 2 is connected to the fourth shaft TM 4 by operation of the third clutch C 3 , the torque of the input shaft IS is inputted to the second shaft TM 2 and the sixth shaft TM 6 is operated as a fixed element by operation of the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the second forward speed stage, and the second forward speed stage is output through the eighth shaft TM 8 .

The second clutch C 2 and the first and second brakes B 1 and B 2 are simultaneously operated at a third forward speed stage D 3 . In a state that the second shaft TM 2 is connected to the fifth shaft TM 5 by operation of the second clutch C 2 , the torque of the input shaft IS is inputted to the second shaft TM 2 , and the first shaft TM 1 and the sixth shaft TM 6 are operated as fixed elements by operation of the first and second brakes B 1 and B 2 . Therefore, the torque of the input shaft IS is shifted into the third forward speed stage, and the third forward speed stage is output through the eighth shaft TM 8 .

The first and second clutches C 1 and C 2 and the second brake B 2 are simultaneously operated at a fourth forward speed stage D 4 . In a state that the seventh shaft TM 7 is connected to the eighth shaft TM 8 by operation of the first clutch C 1 and the second shaft TM 2 is connected to the fifth shaft TM 5 by operation of the second clutch C 2 , the torque of the input shaft IS is inputted to the second shaft TM 2 and the sixth shaft TM 6 is operated as a fixed element by operation of the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the fourth forward speed stage, and the fourth forward speed stage is output through the eighth shaft TM 8 .

The first and second clutches C 1 and C 2 and the first brake B 1 are simultaneously operated at a fifth forward speed stage D 5 . In a state that the seventh shaft TM 7 is connected to the eighth shaft TM 8 by operation of the first clutch C 1 and the second shaft TM 2 is connected to the fifth shaft TM 5 by operation of the second clutch C 2 , the torque of the input shaft IS is inputted to the second input shaft TM 2 and the first shaft TM 1 is operated as a fixed element by operation of the first brake B 1 . Therefore, the torque of the input shaft IS is shifted into the fifth forward speed stage, and the fifth forward speed stage is output through the eighth shaft TM 8 .

The first, second, and third clutches C 1 , C 2 , and C 3 are simultaneously operated at a sixth forward speed stage D 6 . The seventh shaft TM 7 is connected to the eighth shaft TM 8 by operation of the first clutch C 1 , the second shaft TM 2 is connected to the fifth shaft TM 5 by operation of the second clutch C 2 , and the second shaft TM 2 is connected to the fourth shaft TM 4 by operation of the third clutch C 3 such that all the planetary gear sets can rotate as one body. Therefore, the sixth forward speed stage where the torque of the input shaft IS is inputted through the second input shaft TM 2 is output without speed change is output through the eighth shaft TM 8 .

The first and third clutches C 1 and C 3 and the first brake B 1 are simultaneously operated at a seventh forward speed stage D 7 . In a state that the seventh shaft TM 7 is connected to the eighth shaft TM 8 by operation of the first clutch C 1 and the second shaft TM 2 is connected to the fourth shaft TM 4 by operation of the third clutch C 3 , the torque of the input shaft IS is inputted to the second input shaft TM 2 and the first shaft TM 1 is operated as a fixed element by operation of the first brake B 1 . Therefore, the torque of the input shaft IS is shifted into the seventh forward speed stage, and the seventh forward speed stage is output through the eighth shaft TM 8 .

The first and fourth clutches C 1 and C 4 and the first brake B 1 are simultaneously operated at an eighth forward speed stage D 8 . In a state that the seventh shaft TM 7 is connected to the eighth shaft TM 8 by operation of the first clutch C 1 and the third shaft TM 3 is connected to the seventh shaft TM 7 by operation of the fourth clutch C 4 , the torque of the input shaft IS is inputted to the second input shaft TM 2 and the first shaft TM 1 is operated as a fixed element by operation of the first brake B 1 . Therefore, the torque of the input shaft IS is shifted into the eighth forward speed stage, and the eighth forward speed stage is output through the eighth shaft TM 8 .

The third and fourth clutches C 3 and C 4 and the first brake B 1 are simultaneously operated at a ninth forward speed stage D 9 . In a state that the second shaft TM 2 is connected to the fourth shaft TM 4 by operation of the third clutch C 3 and the third shaft TM 3 is connected to the seventh shaft TM 7 by operation of the fourth clutch C 4 , the torque of the input shaft IS is inputted to the second input shaft TM 2 and the first shaft TM 1 is operated as a fixed element by operation of the first brake B 1 . Therefore, the torque of the input shaft IS is shifted into the ninth forward speed stage, and the ninth forward speed stage is output through the eighth shaft TM 8 .

The second and fourth clutches C 2 and C 4 and the first brake B 1 are simultaneously operated at a tenth forward speed stage D 10 . In a state that the second shaft TM 2 is connected to the fifth shaft TM 5 by operation of the second clutch C 2 and the third shaft TM 3 is connected to the seventh shaft TM 7 by operation of the fourth clutch C 4 , the torque of the input shaft IS is inputted to the second input shaft TM 2 and the first shaft TM 1 is operated as a fixed element by operation of the first brake B 1 . Therefore, the torque of the input shaft IS is shifted into the tenth forward speed stage, and the tenth forward speed stage is output through the eighth shaft TM 8 .

The fourth clutch C 4 and the second and third brakes B 2 and B 3 are simultaneously operated at a reverse speed stage REV. In a state that the third shaft TM 3 is connected to the seventh shaft TM 7 by operation of the fourth clutch C 4 , the torque of the input shaft IS is inputted to the second input shaft TM 2 and the sixth shaft TM 6 and the fourth shaft TM 4 are operated as fixed elements by operation of the second and third brakes B 2 and B 3 . Therefore, the torque of the input shaft IS is shifted into the reverse speed stage, and the reverse speed stage is output through the eighth shaft TM 8 .

FIG. 3 is another operation chart of control elements at each speed stage in the planetary gear train according to the first exemplary embodiment of the present disclosure.

Referring to FIG. 3 , the planetary gear train according to the first exemplary embodiment of the present disclosure can achieve one reverse speed stage and eleven forward speed stages.

That is, a speed stage that is achieved by operating the third and fourth clutches C 3 and C 4 and the second brake B 2 is set as a new first forward speed stage D 1 , and the first forward speed stage to the tenth forward speed stage D 1 to D 10 illustrated in FIG. 2 are set as a new second forward speed stage to a new eleventh forward speed stage D 2 to D 11 . Since shifting processes from the second forward speed stage to the eleventh forward speed stage D 2 to D 11 are described above, shifting process of the first forward speed stage D 1 will be described.

The third and fourth clutches C 3 and C 4 and the second brake B 2 are simultaneously operated at the first forward speed stage D 1 in FIG. 3 . In a state that the second shaft TM 2 is connected to the fourth shaft TM 4 by operation of the third clutch C 3 and the third shaft TM 3 is connected to the seventh shaft TM 7 by operation of the fourth clutch C 4 , the torque of the input shaft IS is inputted to the second shaft TM 2 and the sixth shaft TM 6 is operated as a fixed element by operation of the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the first forward speed stage, and the first forward speed stage is output through the eighth shaft TM 8 .

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

The planetary gear sets are disposed in a sequence of the second planetary gear set PG 2 , the first planetary gear set PG 1 , the third planetary gear set PG 3 , and the fourth planetary gear set PG 4 from the engine in the planetary gear train according to the first exemplary embodiment of the present disclosure, but, as shown in FIG. 4 , the planetary gear sets are disposed in a sequence of the first planetary gear set PG 1 , the second planetary gear set PG 2 , the third planetary gear set PG 3 , and the fourth planetary gear set PG 4 from the engine in the planetary gear train according to the second exemplary embodiment.

Since connections between the rotation elements of the planetary gear sets and operation of the control elements according to the second exemplary embodiment are the same as those according to the first exemplary embodiment, however, the planetary gear train according to the second exemplary embodiment achieves the same speed stages and shifting processes as those according to the first exemplary embodiment.

FIG. 5 is a schematic diagram of a planetary gear train according to the third exemplary embodiment of the present disclosure.

The planetary gear sets are disposed in a sequence of the second planetary gear set PG 2 , the first planetary gear set PG 1 , the third planetary gear set PG 3 , and the fourth planetary gear set PG 4 from the engine in the planetary gear train according to the first exemplary embodiment of the present disclosure, but, as shown in FIG. 5 , the planetary gear sets are disposed in a sequence of the first planetary gear set PG 1 , the second planetary gear set PG 2 , the fourth planetary gear set PG 4 , and the third planetary gear set PG 3 in the planetary gear train according to the third exemplary embodiment.

Since connections between the rotation elements of the planetary gear sets and operation of the control elements according to the third exemplary embodiment are the same as those according to the first exemplary embodiment, however, the planetary gear train according to the third exemplary embodiment achieves the same speed stages and shifting processes as those according to the first exemplary embodiment.

FIG. 6 is a schematic diagram of a planetary gear train according to the fourth exemplary embodiment of the present disclosure, and FIG. 7 is a schematic diagram of a planetary gear train according to the fifth exemplary embodiment of the present disclosure.

The planetary gear sets are disposed in a sequence of the second planetary gear set PG 2 , the first planetary gear set PG 1 , the third planetary gear set PG 3 , and the fourth planetary gear set PG 4 from the engine in the planetary gear train according to the first exemplary embodiment of the present disclosure, but, as shown in FIG. 6 and FIG. 7 , the planetary gear sets are disposed in a sequence of the first planetary gear set PG 1 , the second planetary gear set PG 2 , the third planetary gear set PG 3 , and the fourth planetary gear set PG 4 in the planetary gear trains according to the fourth and fifth exemplary embodiments.

Since connections between the rotation elements of the planetary gear sets and operation of the control elements according to the fourth and fifth exemplary embodiments are the same as those according to the first exemplary embodiment, however, the planetary gear trains according to the fourth and fifth exemplary embodiments achieve the same speed stages and shifting processes as those according to the first exemplary embodiment.

The planetary gear trains according to the first to the fifth exemplary embodiments of the present disclosure may achieve at least ten forward speed stages and one reverse speed stage by combining four planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 with the four clutches C 1 , C 2 , C 3 , and C 4 and the three brakes B 1 , B 2 , and B 3 .

In addition, since gear ratio span greater than 10.0 is secured, driving efficiency of the engine may be improved.

In addition, since linearity of step ratios can be secured due to multiple speed stages, drivability such as acceleration before and after shift, rhythmical engine speed, and so on may be improved.

In addition, durability of pinion shafts connected to pinion gears may be maintained due to smooth lubrication by avoiding applying load to planet carriers at stopped states when the vehicle runs at a high forward speed stage (higher than or equal to the seventh forward speed stage).

While this present disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the present disclosure.