Planetary gear train of automatic transmission for vehicles

This application claims priority to and the benefit of Korean Patent Application No. 10-2016-0127463 filed in the Korean Intellectual Property Office on Oct. 4, 2016, the entire contents of which are incorporated herein by reference.

(a) Field

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 that improves power delivery performance and fuel efficiency by achieving at least ten forward speed stages and widening speed ratio with a minimum number of constituent elements being used, and secures linearity of step ratios.

(b) Description of the Related Art

In the field of an automatic transmission, more multiplicity of shift-stages is useful technology for enhancement of fuel consumption and drivability of a vehicle. Recently increase of oil price is triggering a hard competition in enhancing fuel consumption of a vehicle.

In this sense, research on an engine has been undertaken to achieve weight reduction and to enhance fuel consumption by so-called downsizing and research on an automatic transmission has been performed to simultaneously provide better drivability and fuel consumption by achieving more shift stages.

In order to achieve more shift stages for an automatic transmission, the number of parts, especially the number of planetary gear sets, is typically increased, which may deteriorate installability, production cost, weight and/or power flow efficiency.

Therefore, development of a planetary gear train capable of achieving maximum efficiency by minimum number of parts is substantially beneficial for maximizing improvement of fuel consumption by multiple shift-stages of an automatic transmission.

In this respect, an eight-speed automatic transmission has been recently introduced, and a planetary gear train for an automatic transmission enabling more shift stages is under investigation.

An automatic transmission of eight or more shift-stages typically includes three to four planetary gear sets and five to seven control elements (frictional elements), and may easily become lengthy, thereby deteriorating installability.

In this regard, disposing planetary gear sets in parallel or employing dog clutches instead of wet-type control elements is sometimes attempted. However, such an arrangement may not be widely applicable, and using dog clutches may easily deteriorate shift-feel.

In addition, since an 8-speed automatic transmission generally 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 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 desirable.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

The disclosure of this section is to provide background of the invention. Applicant notes that this section may contain information available before this application. However, by providing this section, Applicant does not admit that any information contained in this section constitutes prior art.

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 second rotation element and the fourth rotation element and connected with the input shaft; a second shaft connecting the third rotation element and the tenth rotation element; a third shaft connecting the fifth rotation element and the ninth rotation element; a fourth shaft connected with the sixth rotation element; a fifth shaft connecting the seventh rotation element and the twelfth rotation element; a sixth shaft connected with the eighth rotation element; a seventh shaft connected with the eleventh rotation element and connected with the output shaft; and an eighth shaft connected with the first rotation element.

The fifth, sixth, and eighth shafts may be selectively connected with a transmission housing respectively, the first shaft may be selectively connected with the fourth shaft, the second shaft may be selectively connected with the fourth shaft and the sixth shaft respectively, and the sixth shaft may be selectively connected with the seventh shaft.

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

The fifth, sixth, and eighth shafts may be selectively connected with a transmission housing respectively, the first shaft may be selectively connected with the third shaft, the second shaft may be selectively connected with the fourth shaft and the sixth shaft respectively, and the sixth shaft may be selectively connected with the seventh shaft.

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

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

The first, second, third, and fourth planetary gear sets may be disposed in a sequence of the first, second, third, and fourth planetary gear sets from an engine side.

Further, effects that can be obtained or expected from exemplary embodiments of the present disclosure are directly or suggestively described in the following detailed description. That is, various effects expected from exemplary embodiments of the present disclosure will be described in the following detailed description.

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

FIG. 2 is an operational chart for respective friction elements at respective shift-stages in a planetary gear train according to a first exemplary embodiment of the present disclosure.

FIG. 3 is a schematic diagram of a planetary gear train according to a second 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

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

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.

The planetary gear train according to the exemplary embodiment of the present disclosure may achieve 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, a planetary gear train according to an exemplary embodiment of the present disclosure may realize a gear ratio span of more than 10.0, thereby maximizing efficiency of driving an engine.

In addition, the linearity of step ratios of shift stages is secured while multi-staging the shift stage with high efficiency, thereby making it possible to improve drivability such as acceleration before and after a shift, an engine speed rhythmic sense, and the like.

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

Referring to FIG. 1 , a planetary gear train according to a first exemplary embodiment of the present disclosure includes first, second, third, and four planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 arranged on a same axis, an input shaft IS, an output shaft OS, eight shafts TM 1 to TM 8 interconnecting rotation elements of the first, second, third, and four 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 as control elements, and a transmission housing H.

Torque input from the input shaft IS is shifted by cooperative operation of the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , and then output through the output shaft OS.

The planetary gear sets are arranged in the order of first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , from an engine side.

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

The output shaft OS is an output member, is disposed in parallel with the input shaft IS, and transmits driving torque to a driving wheel 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 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 is directly connected with the fourth rotation element N 4 , the third rotation element N 3 is directly connected with the tenth rotation element N 10 , the fifth rotation element N 5 is directly connected with the ninth rotation element N 9 , and the seventh rotation element N 7 is directly connected with the twelfth rotation element N 12 such that the first, the second, the third, and the fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 include 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 may be rotation members that directly connect a plurality of rotation elements among the rotation elements of the planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 with each other or 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 may be fixed members that selectively or 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 connects the second rotation element N 2 (first planet carrier PC 1 ) and the fourth rotation element N 4 (second sun gear S 2 ), and is directly connected with the input shaft IS.

The second shaft TM 2 connects the third rotation element N 3 (first ring gear R 3 ) and the tenth rotation element N 10 (fourth sun gear S 4 ).

The third shaft TM 3 connects the fifth rotation element N 5 (second planet carrier PC 2 ) and the ninth rotation element N 9 (third ring gear R 3 ).

The fourth shaft TM 4 is connected with the sixth rotation element N 6 (second ring gear R 2 ), and is selectively connected with the first shaft TM 1 and the second shaft TM 2 .

The fifth shaft TM 5 connects the seventh rotation element N 7 (third sun gear S 3 ) and the twelfth rotation element N 12 (fourth ring gear R 4 ), and is selectively connected with the transmission housing H to be operated as a selective fixed element.

The sixth shaft TM 6 is connected with the eighth rotation element N 8 (third planet carrier PC 3 ), is selectively connected with the second shaft TM 2 , and is selectively connected with the transmission housing H to be operated as a selective fixed element.

The seventh shaft TM 7 is connected with the eleventh rotation element N 11 (fourth planet carrier PC 4 ), is selectively connected with the sixth shaft TM 6 , and is directly connected with the output shaft OS.

The eighth shaft TM 8 is connected with the first rotation element N 1 (first sun gear S 1 ), and is selectively connected with the transmission housing H to be operated as a selective fixed element.

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 including the input shaft IS and the output shaft OS 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 sixth shaft TM 6 and the seventh shaft TM 7 , and selectively connects the sixth shaft TM 6 and the seventh shaft TM 7 .

The second clutch C 2 is disposed between the first shaft TM 1 and the fourth shaft TM 4 , and selectively connects the first shaft TM 1 and the fourth shaft TM 4 .

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 and the fourth shaft TM 4 .

The fourth clutch C 4 is disposed between the second shaft TM 2 and the sixth shaft TM 6 , and selectively connects the second shaft TM 2 and the sixth shaft TM 6 .

The first brake B 1 is disposed between the fifth shaft TM 5 and the transmission housing H, and selectively connects the fifth shaft TM 5 to the transmission housing H.

The second brake B 2 is disposed between the eighth shaft TM 8 and the transmission housing H, and selectively connects the eighth shaft TM 8 to the transmission housing H.

the third brake B 3 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 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 operational chart for respective friction elements at respective shift-stages in a planetary gear train according to a first exemplary embodiment of the present disclosure.

Referring to 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 of the present disclosure can achieve one reverse speed stage and ten forward speed stages.

The second and fourth clutches C 2 and C 4 and the first brake B 1 are simultaneously operated at a first forward speed stage D 1 .

In a state that the first shaft TM 1 is connected to the fourth shaft TM 4 by operation of the second clutch C 2 and the second shaft TM 2 is connected to the sixth shaft TM 6 by operation of the fourth clutch C 4 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the fifth shaft TM 5 is operated as a fixed element by the operation of the first brake B 1 . Therefore, the torque of the input shaft IS is shifted into the first forward speed stage D 1 , and the first forward speed stage D 1 is output through the output shaft OS connected to the seventh shaft TM 7 . That is, the operating of the second clutch C 2 results in the ninth rotation element N 9 of the planetary gear set PG 3 being driven by torque from the fifth rotation element N 5 (i.e., equal to the torque of the input shaft IS). The seventh rotation element N 7 is braked by the brake B 1 . The operating of clutch C 4 connects the eighth rotation element N 8 to the tenth rotation element N 10 . Accordingly, the planetary gear sets PG 1 , PG 3 , PG 4 operate in compound and torque is outputted from with the eleventh rotation element N 11 to the seventh shaft TM 7 and the output shaft OS at a ratio of 4.804:1. The second and third clutches C 2 and C 3 and the first brake B 1 are simultaneously operated at a second forward speed stage D 2 .

In a state that the first shaft TM 1 is connected to the fourth shaft TM 4 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 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the fifth shaft TM 5 is operated as a fixed element by the operation of the first brake B 1 . Therefore, the torque of the input shaft IS is shifted into the second forward speed stage D 2 , and the second forward speed stage D 2 is output through the output shaft OS connected to the seventh shaft TM 7 . That is, the operating of the second and third clutches C 2 and C 3 results in the torque of the input shaft IS being transferred to the tenth rotation element N 10 (fourth sun gear S 4 ) via the second shaft TM 2 . The twelfth rotation element N 12 is braked. The torque is outputted from the second rotation element N 2 to the tenth rotation element N 10 (fourth sun gear S 4 ) via the second and third clutches C 2 and C 3 connecting first, second and fourth shafts TM 1 , TM 2 , TM 4 . Accordingly, the planetary gear set PG 4 is driven by torque from second rotation element N 2 which drives tenth rotation element N 10 while the twelfth rotation element N 12 is braked by the brake B 2 . As such, torque is outputted from with the eleventh rotation element N 11 to the seventh shaft TM 7 and the output shaft OS at a ratio of 3.13:1.

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 first shaft TM 1 is connected to the fourth shaft TM 4 by operation of the second clutch C 2 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the fifth shaft TM 5 and the eighth shaft TM 8 are operated as a fixed element by the operation of the first brake B 1 and the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the third forward speed stage D 3 , and the third forward speed stage D 3 is output through the output shaft OS connected to the seventh shaft TM 7 . That is, the torque of the input shaft IS is inputted into the second rotation element N 2 with the first rotation element N 1 braked by the second brake B 2 . The torque is outputted from the third rotation element N 3 (first ring gear R 3 ) to the tenth rotation element N 10 (fourth sun gear S 4 ) via the second shaft TM 2 . Accordingly, the planetary gear set PG 4 is driven by torque from the third rotation element N 3 which drives tenth rotation element N 10 while the twelfth rotation element N 12 is braked by the brake B 2 . As such, torque is outputted from with the eleventh rotation element N 11 to the seventh shaft TM 7 and the output shaft OS at a ratio of 2.12:1.

The first and second clutches C 1 and C 2 and the first brake B 1 are simultaneously operated at a fourth forward speed stage D 4 .

In a state that the sixth shaft TM 6 is connected to the seventh shaft TM 7 by operation of the first clutch C 1 and the first shaft TM 1 is connected to the fourth shaft TM 4 by operation of the second clutch C 2 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the fifth shaft TM 5 is operated as a fixed element by the operation of the first brake B 1 . Therefore, the torque of the input shaft IS is shifted into the fourth forward speed stage D 4 , and the fourth forward speed stage D 4 is output through the output shaft OS connected to the seventh shaft TM 7 . That is, the operating of the first and second clutches C 1 and C 2 results in the torque of the input shaft IS being transferred to the ninth rotation element N 9 (third ring gear R 3 ) via third shaft TM 3 . The seventh rotation element N 7 is braked by the brake B 1 . Accordingly, planetary gear set PG 3 is driven by torque from fifth rotation element N 5 (i.e., equal to the torque of the input shaft IS) which drives ninth rotation element N 9 . The seventh rotation element N 7 and the twelfth rotation element N 12 are connected by fifth shaft TM 5 . The seventh rotation element is braked by the brake B 2 . Clutch C 1 connects seventh rotation element N 7 with the twelfth rotation element N 12 . Accordingly, the eighth rotation element N 8 drives eleventh rotation element N 11 which drives the seventh shaft TM 7 and the output shaft OS at a ratio of 1.535:1.

The first and second clutches C 1 and C 2 and the second brake B 2 are simultaneously operated at a fifth forward speed stage D 5 .

In a state that the sixth shaft TM 6 is connected to the seventh shaft TM 7 by operation of the first clutch C 1 and the first shaft TM 1 is connected to the fourth shaft TM 4 by operation of the second clutch C 2 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the eighth shaft TM 8 is operated as a fixed element by the operation of the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the fifth forward speed stage D 5 , and the fifth forward speed stage D 5 is output through the output shaft OS connected to the seventh shaft TM 7 . That is, the braking of the first rotation element N 1 by the brake B 2 and the operating of the first and second clutches C 1 and C 2 results in the torque of the input shaft IS being transferred to the ninth rotation element N 9 (third ring gear R 3 ) via third shaft TM 3 . The first rotation element N 1 is braked by the brake B 2 . Accordingly, the planetary gear set PG 3 is driven by torque from the fifth rotation element N 5 (i.e., equal to the torque of the input shaft) which drives the ninth rotation element N 9 . The third rotation element N 3 is connected to the tenth rotation element N 10 by the second shaft TM 2 , The seventh rotation element N 7 and the twelfth rotation element N 12 are connected by the fifth shaft TMS. Accordingly, the planetary gear sets PG 1 , PG 3 , PG 4 operate in compound and torque is outputted by the eleventh rotation element N 11 to the seventh shaft TM 7 and the output shaft OS at a ratio of 1.19:1.

The first, second, and third clutches C 1 , C 2 , and C 3 are simultaneously operated at a sixth forward speed stage D 6 .

In a state that the sixth shaft TM 6 is connected to the seventh shaft TM 7 by operation of the first clutch C 1 , the first shaft TM 1 is connected to the fourth shaft TM 4 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 , torque of the input shaft IS is input to the first shaft TM 1 .

In this case, the first, the third, and the fourth planetary gear sets PG 1 , PG 3 , and PG 4 become lock-up states. Therefore, the torque of the input shaft IS input to the first shaft TM 1 is shifted into the sixth forward speed stage, and the sixth forward speed stage D 6 is output through the output shaft OS connected to the seventh shaft TM 7 . At the sixth forward speed stage D 6 , rotation speed which is the same as rotation speed of the input shaft IS is output. That is, the operating of the first, second and third clutches C 1 , C 2 , C 3 results in the torque of the input shaft IS being transferred to the tenth rotation element N 10 via the second shaft TM 2 . Accordingly, the planetary gear set PG 3 is driven by torque from fifth rotation element N 5 (i.e., equal to the torque of the input shaft IS) which drives the ninth rotation element N 9 . The seventh rotation element N 7 and the twelfth rotation element N 12 are connected by fifth shaft TMS. The torque is outputted from the second rotation element N 2 to the tenth rotation element N 10 (fourth sun gear S 4 ) via the second and third clutches C 2 and C 3 connecting the first, second and fourth shafts TM 1 , TM 2 , TM 4 . Accordingly, the planetary gear sets PG 3 and PG 4 operate in compound and torque is outputted by the eleventh rotation element N 11 to the seventh shaft TM 7 and the output shaft OS at a ratio of 1:1.

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

In a state that the sixth shaft TM 6 is connected to the seventh shaft TM 7 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 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the eighth shaft TM 8 is operated as a fixed element by the operation of the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the seventh forward speed stage D 7 , and the seventh forward speed stage D 7 is output through the output shaft OS connected to the seventh shaft TM 7 . That is, the braking of the first rotation element N 1 by the brake the B 2 and the operating of the first and third clutches C 1 and C 3 results in the torque from the third rotation element N 3 being transferred to the tenth rotation element N 10 via the second shaft TM 2 . The planetary gear set PG 2 is driven by torque from the second rotation element N 2 which drives the fourth rotation element N 4 and torque from the third rotation element N 3 which drives the sixth rotation element N 6 . Also, the fifth rotation element N 5 and the ninth rotation element N 9 are connected by the third shaft TM 3 . Accordingly, the planetary gear set PG 3 is driven by torque from the fifth rotation element N 5 which drives the ninth rotation element N 9 . The seventh rotation element N 7 and the twelfth rotation element N 12 are connected by the fifth shaft TMS. Accordingly, the planetary gear sets PG 1 , PG 2 , PG 3 , PG 4 operate in compound and torque is outputted by the eleventh rotation element N 11 to the seventh shaft TM 7 and the output shaft OS at a ratio of 0.811:1.

The first and fourth clutches C 1 and C 4 and the second brake B 2 are simultaneously operated at an eighth forward speed stage D 8 .

In a state that the sixth shaft TM 6 is connected to the seventh shaft TM 7 by operation of the first clutch C 1 , and the second shaft TM 2 is connected to the sixth shaft TM 6 by operation of the fourth clutch C 4 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the eighth shaft TM 8 is operated as a fixed element by the operation of the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the eighth forward speed stage D 8 , and the eighth forward speed stage D 8 is output through the output shaft OS connected to the seventh shaft TM 7 . That is, the braking of the first rotation element N 1 by the brake B 2 and the operating of the first and fourth clutches C 1 and C 4 results in the torque from the third rotation element N 3 being transferred to the tenth rotation element N 10 and the eleventh rotation element N 11 . Accordingly, the planetary gear set PG 4 is driven by torque from third rotation element N 3 which drives tenth rotation element N 10 and the eleventh rotation element N 11 . As such, torque is outputted by the eleventh rotation element N 11 to the seventh shaft TM 7 and the output shaft OS at a ratio of 0.677:1.

The third and fourth clutches C 3 and C 4 and the second brake B 2 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 second shaft TM 2 is connected to the sixth shaft TM 6 by operation of the fourth clutch C 4 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the eighth shaft TM 8 is operated as a fixed element by the operation of the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the ninth forward speed stage D 9 , and the ninth forward speed stage D 9 is output through the output shaft OS connected to the seventh shaft TM 7 . That is, the braking of the first rotation element N 1 by the brake B 2 and the operating of the third and fourth clutches C 3 and C 4 results in the torque from the third rotation element N 3 being transferred to the eight rotation element N 8 and the tenth rotation element N 10 via the second shaft TM 2 . The planetary gear set PG 2 is driven by torque from the second rotation element N 2 which drives the fourth rotation element N 4 and torque from the third rotation element N 3 which drives the sixth rotation element N 6 . Also, the fifth rotation element N 5 and the ninth rotation element N 9 are connected by the third shaft TM 3 . Accordingly, the planetary gear set PG 3 is driven by torque from fifth rotation element N 5 which drives the ninth rotation element N 9 and torque from the third rotation element N 3 which drives the eighth rotation element N 8 . The seventh rotation element N 7 and the twelfth rotation element N 12 are connected by fifth shaft TMS. Accordingly, the planetary gear sets PG 1 , PG 2 , PG 3 PG 4 operate in compound and torque is outputted by the eleventh rotation element N 11 to the seventh shaft TM 7 and the output shaft OS at a ratio of 0.585:1.

The second and fourth clutches C 2 and C 4 and the second brake B 2 are simultaneously operated at a tenth forward speed stage D 10 .

In a state that the first shaft TM 1 is connected to the fourth shaft TM 4 by operation of the second clutch C 2 , and the second shaft TM 2 is connected to the sixth shaft TM 6 by operation of the fourth clutch C 4 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the eighth shaft TM 8 is operated as a fixed element by the operation of the second brake B 2 . Therefore, the torque of the input shaft IS is shifted into the tenth forward speed stage D 10 , and the tenth forward speed stage D 10 is output through the output shaft OS connected to the seventh shaft TM 7 . That is, the braking of the first rotation element N 1 by the brake B 2 and the operating of the second and fourth clutches C 2 and C 4 results in the torque from the third rotation element N 3 being transferred to the eight rotation element N 8 and the tenth rotation element N 10 via the second shaft TM 2 . The planetary gear set PG 3 is driven by torque from the second rotation element N 2 which drives the ninth rotation element N 9 and torque from the third rotation element N 3 which drives the eighth rotation element N 8 . The seventh rotation element N 7 and the twelfth rotation element N 12 are connected by the fifth shaft TM 5 . Accordingly, the planetary gear sets PG 1 , PG 3 and PG 4 are operated in compound and torque is outputted by the eleventh rotation element N 11 to the seventh shaft TM 7 and the output shaft OS at a ratio of 0.48:1.

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

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 , torque of the input shaft IS is input to the first shaft TM 1 .

In addition, the fifth shaft TM 5 and the sixth shaft TM 6 are operated as a fixed element by the operation of the first brake B 1 and the third brake B 3 . Therefore, the torque of the input shaft IS is shifted into the reverse speed stage R, and the reverse speed stage R is output through the output shaft OS connected to the seventh shaft TM 7 as inverse rotation speed. That is, the operating of the brakes B 1 , B 3 and the clutch C 3 results in torque of the input shaft IS being transferred to the fourth rotation element N 4 and the fifth rotation element N 5 and twelfth rotation element N 12 being braked. Accordingly, the sixth rotation element N 6 drives the tenth rotation element N 10 and torque is outputted from with the eleventh rotation element N 11 to the output shaft OS at a ratio of −5.039:1.

FIG. 3 is a schematic diagram of a planetary gear train according to a second exemplary embodiment of the present disclosure.

Referring to FIG. 3 , a planetary gear train according to a second exemplary embodiment of the present disclosure includes first, second, third, and four planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , eight shafts TM 1 to TM 8 , and seven control elements C 1 to C 4 and B 1 to B 3 .

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

The first shaft TM 1 connects the second rotation element N 2 (first planet carrier PC 1 ) and the fourth rotation element N 4 (second sun gear S 2 , and is directly connected with the input shaft IS.

The second shaft TM 2 connects the third rotation element N 3 (first ring gear R 3 ) and the tenth rotation element N 10 (fourth sun gear S 4 ).

The third shaft TM 3 connects the fifth rotation element N 5 (second planet carrier PC 2 ) and the ninth rotation element N 9 (third ring gear R 3 , and is selectively connected with the first shaft TM 1 .

The fourth shaft TM 4 is connected with the sixth rotation element N 6 (second ring gear R 2 ), and is selectively connected with the second shaft TM 2 .

The fifth shaft TM 5 is connects the seventh rotation element N 7 (third sun gear S 3 ) and the twelfth rotation element N 12 (fourth ring gear R 4 ), and is selectively connected with the transmission housing H to be operated as a selective fixed element.

The sixth shaft TM 6 is connected with the eighth rotation element N 8 (third planet carrier PC 3 ), is selectively connected with the second shaft TM 2 , and is selectively connected with the transmission housing H to be operated as a selective fixed element.

The seventh shaft TM 7 is connected with the eleventh rotation element N 11 (fourth planet carrier PC 4 ), is selectively connected with the sixth shaft TM 6 , and is directly connected with the output shaft OS.

The eighth shaft TM 8 is connected with the first rotation element N 1 (first sun gear 51 , and is selectively connected with the transmission housing H to be operated as a selective fixed element.

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 including the input shaft IS and the output shaft OS 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 and B 3 are described in detail.

The first clutch C 1 is disposed between the sixth shaft TM 6 and the seventh shaft TM 7 , and selectively connects the sixth shaft TM 6 and the seventh shaft TM 7 .

The second clutch C 2 is disposed between the first shaft TM 1 and the third shaft TM 3 , and selectively connects the first shaft TM 1 and the third shaft TM 3 .

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 and the fourth shaft TM 4 .

The fourth clutch C 4 is disposed between the second shaft TM 2 and the sixth shaft TM 6 , and selectively connects the second shaft TM 2 and the sixth shaft TM 6 .

The first brake B 1 is disposed between the fifth shaft TM 5 and the transmission housing H, and selectively connects the fifth shaft TM 5 to the transmission housing H.

The second brake B 2 is disposed between the eighth shaft TM 8 and the transmission housing H, and selectively connects the eighth shaft TM 8 to the transmission housing H.

The third brake B 3 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.

As a result, the planetary gear train according to the second exemplary embodiment merely differs from the planetary gear train according to a first exemplary embodiment only in a location of the second clutch C 2 but other elements are the same the planetary gear train according to a first exemplary embodiment.

The shifting operations of the planetary gear train according to the second exemplary embodiment is the same the shifting operations of the planetary gear train according to the first embodiment, as shown in FIG. 2 , which is therefore not described in further detail.

The planetary gear trains according to the 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 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, a planetary gear train according to an exemplary embodiment of the present disclosure may realize a gear ratio span of more than 10.0, thereby maximizing efficiency of driving an engine.

In addition, the linearity of step ratios of shift stages is secured while multi-staging the shift stage with high efficiency, thereby making it possible to improve drivability such as acceleration before and after a shift, an engine speed rhythmic sense, and the like.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention 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 appended claims.