Abstract:
The present disclosure provides a planetary gear train of an automatic transmission for a vehicle having advantages of improving power transfer performance and fuel efficiency by implementing ten forward speeds and one reverse speed. The planetary gear train includes: first, second, third, and fourth planetary gear sets; an input shaft; an output shaft; eight shafts connected to the respective rotation elements of the first, second, third, and fourth planetary gear sets; four clutches and two brakes which are control elements; and a transmission housing H. With this arrangement, rotation power from an engine which is input from the input shaft is shifted by a mutual complementing operation between the first, second, third, and fourth planetary gear sets, and is then output through the output shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2016-0117355, filed on Sep. 12, 2016, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The present disclosure relates to an automatic transmission for a vehicle that can improve power delivery performance and reduce fuel consumption. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     In the field of an automatic transmission, more multiple shift-stages are used to enhance fuel efficiency and drivability of a vehicle. Recently increased oil price leads to a more competition in enhancing fuel efficiency of a vehicle. 
     In this sense, research for the engine-downsizing has been conducted to reduce weight while enhancing fuel efficiency. Similarly, research on an automatic transmission has been performed to simultaneously provide better drivability and fuel efficiency through more shift stages with reduced the number of parts. 
     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. 
     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 thus may be easily lengthy transmission, thereby undermining installability. 
     We have discovered that 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. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. 
     SUMMARY 
     The present disclosure provides a planetary gear train of an automatic transmission for a vehicle, which improves power delivery performance and fuel efficiency by providing ten forward speed stages and one reverse speed stage using a driving point positioned at a low engine speed. 
     A planetary gear train of an automatic transmission for a vehicle in one exemplary form of the present disclosure may include: an input shaft configured to receive torque from an engine; an output shaft configured to output a 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 connected to the first rotation element, the fifth rotation element, and the input shaft; a second shaft connected to the second rotation element, and configured to selectively connected to the first shaft; a third shaft connected to the third rotation element; a fourth shaft connected to the fourth rotation element; a fifth shaft connected to the sixth rotation element and the tenth rotation element, and configured to selectively connected to the second shaft; a sixth shaft connected to the seventh rotation element and the twelfth rotation element, and configured to be selectively connected to the second shaft; a seventh shaft connected to the eighth rotation element, the eleventh rotation element, and the output shaft; and an eighth shaft connected to the ninth rotation element, and configured to be selectively connected to the third shaft. 
     The fourth shaft and the sixth shaft may be selectively connected to a transmission housing, respectively. 
     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, and 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. 
     The planetary gear train may further include: a first clutch configured to selectively connect the first shaft and the second shaft; a second clutch configured to selectively connect the second shaft and the fifth shaft; a third clutch configured to selectively connect the second shaft and the sixth shaft; a fourth clutch configured to selectively connect the third shaft and the eighth shaft; a first brake configured to selectively connect the fourth shaft and the transmission housing; and a second brake configured to selectively connect the sixth shaft and the transmission housing. 
     The planetary gear train according to the exemplary form of the present disclosure may achieve ten forward speed stages and one reverse speed stage by combining four planetary gear sets with six control elements. The four planetary gear sets may be in the form of a simple planetary gear set. 
     In addition, the planetary gear train in the exemplary form of the present disclosure may achieve speed stages suitable to a rotational speed of the engine due to multiple-speed stages of the automatic transmission. Particularly, silent driving of the vehicle may be improved by using operation point positioned at a low rotational speed region of an engine. 
     In addition, the planetary gear train may increase driving efficiency of the engine and may improve power delivery performance and fuel efficiency. 
     Other effects obtainable or predictable from the exemplary forms of the present disclosure will be explicitly or implicitly described in a DETAILED DESCRIPTION section. That is, various effects predictable from the exemplary forms of the present disclosure will be described in the DETAILED DESCRIPTION section. 
     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. 
    
    
     
       DRAWINGS 
       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 in one exemplary form of the present disclosure; and 
         FIG. 2  is an operational chart for respective control elements at respective shift stages in a planetary gear train in one form of the present disclosure. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     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. 
     Hereinafter, an exemplary form 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 forms of the present disclosure. 
     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 in one exemplary form of the present disclosure. 
     Referring to  FIG. 1 , a planetary gear train 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 (i.e., PG 1 , PG 2 , PG 3 , and PG 4 ); four clutches (i.e., C 1 , C 2 , C 3  and C 4 ) and two brakes (i.e., B 1  and B 2 ) 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 (i.e., PG 1 , PG 2 , PG 3 , and PG 4 ), and then the shifted torque is 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. The torque from a crankshaft of an engine is converted through a torque converter and then delivered to the input shaft IS. 
     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. 
     In one form, the first planetary gear set PG 1  may be a single pinion planetary gear set and include: 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 . The first sun gear, the first planet carrier, and the first ring gear correspond to first, second, and third rotation elements (i.e., N 1 , N 2 , and N 3 ), respectively. 
     The second planetary gear set PG 2  may be a single pinion planetary gear set and include: 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 . The second sun gear, the second planet carrier, and the second ring gear correspond to fourth, fifth, and sixth rotation elements (i.e., N 4 , N 5 , and N 6 ), respectively. 
     The third planetary gear set PG 3  may be a single pinion planetary gear set and include: 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 . The third sun gear, the third planet carrier, and the third ring gear correspond to seventh, eighth, and ninth rotation elements (i.e., N 7 , N 8 , and N 9 ), respectively. 
     The fourth planetary gear set PG 4  may be a single pinion planetary gear set and include: 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 . The fourth sun gear, the fourth planet carrier, and the fourth ring gear correspond to tenth, eleventh, and twelfth rotation elements (i.e., N 10 , N 11 , and N 12 ), respectively. 
     Referring to  FIG. 1 , the first rotation element N 1  is directly connected to the fifth rotation element N 5 , the sixth rotation element N 6  is directly connected to the tenth rotation element N 10 , the seventh rotation element N 7  is directly connected to the twelfth rotation element N 12 , and the eighth rotation element N 8  is directly connected to the eleventh rotation element N 11  such that the first, the second, the third, and the fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4  are operated through 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 rotation elements to each other among the rotation elements of the planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4  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 rotation element to transmit torque. The eight shafts TM 1  to TM 8  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 rotation element. 
     The first shaft TM 1  is directly connected to the first rotation element N 1  (first sun gear S 1 ) and the fifth rotation element N 5  (second planet carrier PC 2 ), and is directly connected to the input shaft IS to be continuously operated as an input element. 
     The second shaft TM 2  is directly connected to the second rotation element N 2  (first planet carrier PC 1 ) and is selectively connected to the first shaft TM 1 . 
     The third shaft TM 3  is directly connected to the third rotation element N 3  (first ring gear R 1 ). 
     The fourth shaft TM 4  is directly connected to the fourth rotation element N 4  (second sun gear S 2 ) and is selectively connected to the transmission housing H to be operated as a selective fixed element. 
     The fifth shaft TM 5  is directly connected to the sixth rotation element N 6  (second ring gear R 2 ) and the tenth rotation element N 10  (fourth sun gear S 4 ), and is selectively connected to the second shaft TM 2 . 
     The sixth shaft TM 6  is directly connected to 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 to the second shaft TM 2  and the transmission housing H to be operated as a selective fixed element. 
     The seventh shaft TM 7  is directly connected to the eighth rotation element N 8  (third planet carrier PC 3 ), the eleventh rotation element N 11  (fourth planet carrier PC 4 ), and the output shaft OS. 
     The eighth shaft TM 8  is directly connected to the ninth rotation element N 9  (third ring gear R 3 ) and is selectively connected to the third shaft TM 3 . 
     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, two brakes B 1  and B 2  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 two brakes B 1  and B 2  are described in detail. 
     The first clutch C 1  is disposed between the first shaft TM 1  and the second shaft TM 2 , and selectively connects the first shaft TM 1  and the second shaft TM 2 . 
     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  and the fifth shaft TM 5 . 
     The third clutch C 3  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 fourth clutch C 4  is disposed between the third shaft TM 3  and the eighth shaft TM 8 , and selectively connects the third shaft TM 3  and the eighth shaft TM 8 . 
     The first brake B 1  is disposed between the fourth shaft TM 4  and the transmission housing H, and selectively connects the fourth shaft TM 4  and 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  and the transmission housing H. 
     The control elements including the first, the second, the third, and the fourth clutches C 1 , C 2 , C 3 , and C 4  and the first and second brakes B 1  and B 2  may be frictionally engaging units that are operated by hydraulic pressure. Particularly, the control elements may be, but not limited to, multi-plates friction elements of wet type. However, the control elements may be engaging units that are operated by electrical signal, such as dog clutches, electric clutches, magnetic particle clutches, etc. 
       FIG. 2  is an operational chart for respective friction elements at respective shift-stages in a planetary gear train according to a first exemplary form of the present disclosure. 
     Referring to  FIG. 2 , three control elements among the six control elements (i.e., the first, second, third, and fourth clutches C 1 , C 2 , C 3  and C 4  and the first and second brakes B 1  and B 2 ) are operated at each speed stage in the planetary gear train. The exemplary form 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 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 eighth shaft TM 8  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 sixth shaft TM 6  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 first forward speed stage by cooperative operation of respective shafts, and the first forward speed stage is output through the output shaft OS connected to the seventh shaft TM 7 . 
     The first and second clutches C 1  and C 2  and the second brake B 2  are simultaneously operated at a second forward speed stage D 2 . 
     In a state that the first shaft TM 1  is connected to the second shaft TM 2  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 , torque of the input shaft IS is input to the first shaft TM 1 . 
     In addition, the sixth shaft TM 6  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 second forward speed stage, and the second forward speed stage is output through the output shaft OS connected to the seventh shaft TM 7 . 
     The first clutch C 1  and 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 second shaft TM 2  by operation of the first clutch C 1 , torque of the input shaft IS is input to the first shaft TM 1 . 
     In addition, the fourth shaft TM 4  and the sixth shaft TM 6  are operated as a fixed element by the 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 by cooperative operation of respective shafts, and the third forward speed stage is output through the output shaft OS connected to the seventh shaft TM 7 . 
     The first and fourth clutches C 1  and C 4  and the second brake B 2  are simultaneously operated at a fourth forward speed stage D 4 . 
     In a state that the first shaft TM 1  is connected to the second shaft TM 2  by operation of the first clutch C 1  and the third shaft TM 3  is connected to the eighth shaft TM 8  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 sixth shaft TM 6  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 fourth forward speed stage, and the fourth forward speed stage is output through the output shaft OS connected to the seventh shaft TM 7 . 
     The first and fourth clutches C 1  and C 4  and the first brake B 1  are simultaneously operated at a fifth forward speed stage D 5 . 
     In a state that the first shaft TM 1  is connected to the second shaft TM 2  by operation of the first clutch C 1  and the third shaft TM 3  is connected to the eighth shaft TM 8  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 fourth shaft TM 4  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 fifth forward speed stage, and the fifth forward speed stage is output through the output shaft OS connected to the seventh shaft TM 7 . 
     The first, third, and fourth clutches C 1 , C 3 , and C 4  are simultaneously operated at a sixth forward speed stage D 6 . 
     In a state that the first shaft TM 1  is connected to the second shaft TM 2  by operation of the first clutch C 1 , the second shaft TM 2  is connected to the sixth shaft TM 6  by operation of the third clutch C 3 , and the third shaft TM 3  is connected to the eighth shaft TM 8  by operation of the fourth clutch C 4 , 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 is output through the output shaft OS connected to the seventh shaft TM 7 . At the sixth forward speed stage, rotation speed which is the same as rotation speed of the input shaft IS is output through the output shaft OS. 
     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 first shaft TM 1  is connected to the second shaft TM 2  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 third clutch C 3 , torque of the input shaft IS is input to the first shaft TM 1 . 
     In addition, the fourth shaft TM 4  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 seventh forward speed stage, and the seventh forward speed stage is output through the output shaft OS connected to the seventh shaft TM 7 . 
     The third and fourth clutches C 3  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 second shaft TM 2  is connected to the sixth shaft TM 6  by operation of the third clutch C 3  and the third shaft TM 3  is connected to the eighth shaft TM 8  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 fourth shaft TM 4  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 eighth forward speed stage, and the eighth forward speed stage is output through the output shaft OS connected to the seventh shaft TM 7 . 
     The second and third clutches C 2  and C 3  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 fifth shaft TM 5  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 third clutch C 3 , torque of the input shaft IS is input to the first shaft TM 1 . 
     In addition, the fourth shaft TM 4  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 ninth forward speed stage, and the ninth forward speed stage is output through the output shaft OS connected to the seventh shaft TM 7 . 
     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 eighth shaft TM 8  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 fourth shaft TM 4  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 tenth forward speed stage, and the tenth forward speed stage is output through the output shaft OS connected to the seventh shaft TM 7 . 
     The third and fourth clutches C 3  and C 4  and the second brake B 2  are simultaneously operated at a reverse speed stage REV. 
     In a state that the second shaft TM 2  is connected to the sixth shaft TM 6  by operation of the third clutch C 3  and the third shaft TM 3  is connected to the eighth shaft TM 8  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 sixth shaft TM 6  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 reverse speed stage, and the reverse speed stage is output through the output shaft OS connected to the seventh shaft TM 7  as inverse rotation speed. 
     The planetary gear trains according to the exemplary form 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 two brakes B 1  and B 2 . 
     In addition, the planetary gear train according to the exemplary form of the present disclosure may achieve suitable speed stages according to rotation speed of the engine. Particularly, silent driving of the vehicle may be improved by using operation point positioned at a low rotational speed region of the engine. 
     In addition, the planetary gear train may increase driving efficiency of the engine and may improve power delivery performance and fuel consumption. 
     While this present disclosure has been described in connection with what is presently considered to be practical exemplary forms, it is to be understood that the present disclosure is not limited to the disclosed forms, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     DESCRIPTION OF SYMBOLS 
     
         
         
           
             B 1 , B 2 : first and second 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