Patent Publication Number: US-10330180-B2

Title: Planetary gear train of automatic transmission for vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2017-0140014 filed on Oct. 26, 2017, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a planetary gear train of an automatic transmission for a vehicle. 
     Description of Related Art 
     Research on realizing more shift-stages of an automatic transmission are undertaken to achieve enhancement of fuel consumption and better drivability, and 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 research on an automatic transmission has been performed to simultaneously provide better drivability and fuel consumption by achieving more shift stages. 
     To achieve more shift stages for an automatic transmission, the number of parts is typically increased, which may deteriorate installability, production cost, weight and/or power flow efficiency. 
     Therefore, to maximally enhance fuel consumption of an automatic transmission having more shift stages, it is important for better efficiency to be derived by fewer number of parts. 
     In this respect, an eight-speed automatic transmission has been recently introduced, and a planetary gear train for an automatic transmission facilitating more shift stages is under investigation. 
     An automatic transmission of eight or more shift-stages typically may include three to four planetary gear sets and five to seven engagement elements (frictional elements), and may easily become lengthy, deteriorating installability. 
     In this regard, disposing planetary gear sets in parallel or employing dog clutches instead of wet-type control elements is attempted. However, such an arrangement may not be widely applicable, and using dog clutches may easily deteriorate shift-feel. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY 
     Various aspects of the present invention are directed to providing a planetary gear train of an automatic transmission for a vehicle facilitating at least ten forward speeds, providing better performance and fuel efficiency of a vehicle. 
     A planetary gear train according to an exemplary embodiment of the present invention may include an input shaft receiving an engine torque, an output shaft outputting a shifted torque, a first planetary gear set having first, second and third rotation elements, a second planetary gear set having fourth, fifth, and sixth rotation elements, a third planetary gear set having seventh, eighth, and ninth rotation elements, and a fourth planetary gear set having tenth, eleventh, twelfth, and thirteenth rotation elements. An exemplary planetary gear train may further include a first shaft fixedly connected to the second rotation element and the input shaft, a second shaft fixedly connected to the eleventh rotation element and the output shaft, a third shaft fixedly connected to the first rotation element and the seventh rotation element, a fourth shaft fixedly connected to the fifth rotation element and the twelfth rotation element, a fifth shaft fixedly connected to the eighth rotation element and the tenth rotation element, a sixth shaft fixedly connected to the thirteenth rotation element, and a plurality of shafts each selectively connecting a corresponding element to the transmission housing, the corresponding element being a rotation element of the first, second and third planetary gear sets which is not fixedly interconnected. 
     The plurality of shafts may include a seventh shaft fixedly connected to the third rotation element and selectively connectable to the transmission housing, an eighth shaft fixedly connected to the fourth rotation element and the ninth rotation element and selectively connectable to the transmission housing, and a ninth shaft fixedly connected to the sixth rotation element, and selectively connectable to the transmission housing. The first shaft and the fifth shaft, the third shaft and the sixth shaft, and the fifth shaft and the seventh shaft may be selectively interconnected respectively. 
     The exemplary planetary gear train may further include three clutches each selectively connecting a corresponding pair among the input shaft, the output shaft, and the first to ninth shafts, and three brakes selectively connecting the seventh shaft, the eighth shaft, and the ninth shaft to the transmission housing respectively. 
     The three clutches may include a first clutch disposed between the first shaft and the fifth shaft, a second clutch disposed between the third shaft and the sixth shaft, and a third clutch disposed between the fifth shaft and the seventh shaft. The three brakes may include a first brake disposed between the seventh shaft and the transmission housing, a second brake disposed between the eighth shaft and the transmission housing, and a third brake disposed between the ninth shaft and the transmission housing. 
     The first planetary gear set may be a single pinion planetary gear set having a first sun gear, a first planet carrier, and a first ring gear as the first, second and third rotation elements. The second planetary gear set may be a single pinion planetary gear set having a second sun gear, a second planet carrier, and a second ring gear as the fourth, fifth, and sixth rotation elements. The third planetary gear set may be a single pinion planetary gear set having a third sun gear, a third planet carrier, and a third ring gear as the seventh, eighth, and ninth rotation elements. The fourth planetary gear set may be a compound planetary gear set having a common sun gear, a common planet carrier, a fourth ring gear, and a fifth ring gear as the tenth, eleventh, twelfth, and thirteenth rotation elements. 
     The first, second, third and fourth planetary gear sets may be disposed in the order of the first, third, second, and fourth planetary gear sets from an engine side. 
     A planetary gear train according to an exemplary embodiment of the present invention may realize at least ten forward speeds one reverse speed by combination of three simple planetary gear sets and one compound planetary gear set together with six engagement elements. 
     Furthermore, a planetary gear train according to an exemplary embodiment of the present invention may improve driving stability by realizing shift-stages appropriate for rotation speed of an engine due to multi-stages of an automatic transmission. 
     Furthermore, a planetary gear train according to an exemplary embodiment of the present invention may maximize engine driving efficiency by multi-stages of an automatic transmission, and may improve power delivery performance and fuel consumption. 
     Furthermore, effects that can be obtained or expected from exemplary embodiments of the present invention are directly or suggestively described in the following detailed description. That is, various effects expected from exemplary embodiments of the present invention will be described in the following detailed description. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a planetary gear train according to an exemplary embodiment of the present invention. 
         FIG. 2  is an operational chart for respective control elements at respective shift-stages applicable to a planetary gear train according to an exemplary embodiment that realizes ten forward speeds and one reverse speeds. 
         FIG. 3  is an operational chart for respective control elements at respective shift-stages applicable to a planetary gear train according to an exemplary embodiment that realizes fourteen forward speeds and one reverse speeds. 
     
    
    
     It may be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particularly intended application and use environment. 
     In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     Hereinafter, an exemplary embodiment of the present invention will be described more specifically with reference to drawings. 
     The drawings and description are to be regarded as illustrative in nature and not restrictive, and like reference numerals designate like 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 an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , a planetary gear train according to an exemplary embodiment of the present invention may include first, second, third and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4  disposed on a same axis, an input shaft IS, an output shaft OS, nine shafts TM 1  to TM 9  interconnecting rotation elements of the first, second, third and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , engagement elements of three clutches C 1  to C 3  and three brakes B 1  to B 3 , 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 disposed in the order of first, third, second, and fourth planetary gear sets PG 1 , PG 3 , PG 2 , and PG 4 , from an engine side. 
     The input shaft IS is an input member and may receive a torque from a crankshaft of an engine through a torque converter. 
     The output shaft OS is an output element disposed on a same axis with the input shaft IS, and outputs a shifted driving torque to a driveshaft through a differential apparatus. 
     The first planetary gear set PG 1  is a single pinion planetary gear set, and may include a first sun gear S 1 , a first planet carrier PC 1  rotatably supporting a plurality of first pinion gears P 1  externally gear-meshed with the first sun gear S 1 , and a first ring gear R 1  internally gear-meshed with the plurality of first pinion gears P 1  engaged with the first sun gear S 1 . The first sun gear S 1  acts as a first rotation element N 1 , the first planet carrier PC 1  acts as a second rotation element N 2 , and the first ring gear R 1  acts as a third rotation element N 3 . 
     The second planetary gear set PG 2  is a single pinion planetary gear set, and may include a second sun gear S 2 , a second planet carrier PC 2  rotatably supporting a plurality of second pinion gears P 2  externally gear-meshed with the second sun gear S 2 , and a second ring gear R 2  internally gear-meshed with the plurality of second pinion gears P 2  engaged with the second sun gear S 2 . The second sun gear S 2  acts as a fourth rotation element N 4 , the second planet carrier PC 2  acts as a fifth rotation element N 5 , and the second ring gear R 2  acts as a sixth rotation element N 6 . 
     The third planetary gear set PG 3  is a single pinion planetary gear set, and may include a third sun gear S 3 , a third planet carrier PC 3  rotatably supporting a plurality of third pinion gears P 3  externally gear-meshed with the third sun gear S 3 , and a third ring gear R 3  internally gear-meshed with the plurality of third pinion gears P 3  engaged with the third sun gear S 3 . The third sun gear S 3  acts as a seventh rotation element N 7 , the third planet carrier PC 3  acts as an eighth rotation element N 8 , and the third ring gear R 3  acts as a ninth rotation element N 9 . 
     The fourth planetary gear set PG 4  is a compound planetary gear set as a combination of two single pinion planetary gear sets having a common sun gear and a common planet carrier. 
     As a result, the fourth planetary gear set PG 4  forms four rotation elements of a sun gear, a planet carrier, and two ring gears. In more detail, the fourth planetary gear set PG 4  may include a common sun gear S 45 , a common planet carrier PC 45  rotatably supporting a plurality of fourth pinion gears P 4  and fifth pinion gears P 5  each externally gear-meshed with the common sun gear S 45 , a fourth ring gear R 4  internally gear-meshed with a plurality of fourth pinion gears P 4 , and a fifth ring gear R 5  internally gear-meshed with a plurality of fifth pinion gears P 5 . The common sun gear S 45  acts as a tenth rotation element N 10 . The common planet carrier PC 45  acts as an eleventh rotation element N 11 . The fourth ring gear R 4  acts as a twelfth rotation element N 12 . The fifth ring gear R 5  acts as a thirteenth rotation element N 13 . 
     In the first, second, third and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , the first rotation element N 1  and the seventh rotation element N 7  are fixedly connected, the fourth rotation element N 4  and the ninth rotation element N 9  are fixedly connected, the fifth rotation element N 5  and the twelfth rotation element N 12  are fixedly connected, the eighth rotation element N 8  and the tenth rotation element N 10  are fixedly connected, and nine shafts TM 1  to TM 9  are formed. 
     In the fourth planetary gear set PG 4 , the common planet carrier PC 45  may support separate pinion gears P 4  and P 5  as describe above, the, however, the present invention is not limited thereto. It may be understood that a common pinion gear may be formed between the ring gears R 4  and R 5  and the common sun gear S 45  and the common planet carrier PC 45  may support the common pinion gears. 
     It is merely for convenience&#39;s sake and a mere exemplification that the common planet carrier PC 45  supports separate pinion gears of the fourth pinion gears P 4  and the fifth pinion gear P 5 . 
     The nine shafts TM 1  to TM 9  are hereinafter described more specifically. 
     The first shaft TM 1  is fixedly connected to the second rotation element N 2  (first planet carrier PC 1 ), and fixedly connected to the input shaft IS, always acting as an input element. 
     The second shaft TM 2  is fixedly connected to the eleventh rotation element N 11  (common planet carrier PC 45 ), and fixedly connected to the output shaft OS always acting as an output element. 
     The third shaft TM 3  is fixedly connected to a first rotation element N 1  (first sun gear S 1 ) and seventh rotation element N 7  (third sun gear S 3 ). 
     The fourth shaft TM 4  is fixedly connected to fifth rotation element N 5  (second planet carrier PC 2 ) and twelfth rotation element N 12  (fourth ring gear R 4 ). 
     The fifth shaft TM 5  is fixedly connected to the eighth rotation element N 8  (third planet carrier PC 3 ) and the tenth rotation element N 10  (common sun gear S 45 ). 
     The sixth shaft TM 6  is fixedly connected to the thirteenth rotation element N 13  (fifth ring gear R 5 ). 
     The seventh shaft TM 7  is fixedly connected to the third rotation element N 3  (first ring gear R 1 ). 
     The eighth shaft TM 8  is fixedly connected to fourth rotation element N 4  (second sun gear S 2 ) and ninth rotation element N 9  (third ring gear R 3 ). 
     The ninth shaft TM 8  is fixedly connected to the sixth rotation element N 6  (second ring gear R 2 ). 
     Each of the nine shafts TM 1  to TM 9  may be a rotation member that fixedly interconnects the input and output shafts and rotation elements of the planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , or may be a rotation member that selectively interconnects a rotation element to the transmission housing H, or may be a fixed member fixed to the transmission housing H. 
     In the disclosure, when two or more members are described to be “fixedly connected”, where the member may be any of a shaft, an input shaft, an output shaft, a rotation member, and a transmission housing, it means that the fixedly connected members always rotate at a same speed. 
     When two or more members are described to be “selectively connectable” by an engagement element, it means that the selectively connectable members rotates separately when the engagement element is not engaged, and rotates at a same speed when the engagement element is engaged. It may be understood that in the case that a member is “selectively connectable” with a transmission housing by an engagement element, the member may be stationary when the engagement element is engaged. 
     The first shaft TM 1  is selectively connectable to the fifth shaft TM 5 , the third shaft TM 3  is selectively connectable to the sixth shaft TM 6 , and the fifth shaft TM 5  is selectively connectable to the seventh shaft TM 7 . 
     Furthermore, the seventh shaft TM 7 , the eighth shaft TM 8 , and ninth shaft TM 9  are selectively connectable to the transmission housing H, selectively acting as fixed elements respectively. 
     Engagement elements of three clutches C 1 , C 2 , and C 3  are disposed for selectively connecting elements of the input shaft IS, the output shaft OS, and the nine shafts TM 1  to TM 9 . 
     Engagement elements of three brakes B 1 , B 2 , and B 3  are disposed for selectively connecting corresponding shafts among the nine shafts TM 1  to TM 9  to the transmission housing H. 
     The first clutch C 1  is disposed between the first shaft TM 1  and the fifth shaft TM 5 , and selectively connects the first shaft TM 1  and the fifth shaft TM 5 , controlling power delivery therebetween. 
     The second clutch C 2  is disposed between the third shaft TM 3  and the sixth shaft TM 6 , and selectively connects the third shaft TM 3  and the sixth shaft TM 6 , controlling power delivery therebetween. 
     The third clutch C 3  is disposed between the fifth shaft TM 5  and the seventh shaft TM 7 , and selectively connects the fifth shaft TM 5  and the seventh shaft TM 7 , controlling power delivery therebetween. 
     The first brake B 1  is disposed between the seventh shaft TM 7  and the transmission housing H, and selectively connects the seventh shaft TM 7  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 ninth shaft TM 9  and the transmission housing H, and selectively connects the ninth shaft TM 9  to the transmission housing H. 
     The engagement elements of the first, second and third clutches C 1 , C 2 , and C 3  and the first, second and third brakes B 1 , B 2 , and B 3  may be realized as multi-plate hydraulic pressure friction devices that are frictionally engaged by hydraulic pressure, however, it may not be understood to be limited thereto, since various other configuration that are electrically controllable may be available. 
       FIG. 2  is an operational chart for respective control elements at respective shift-stages applicable to a planetary gear train according to an exemplary embodiment that realizes ten forward speeds and one reverse speeds. 
     Referring to  FIG. 2 , a planetary gear train according to an exemplary embodiment of the present invention realizes shifting between ten forward speeds and one reverse speed by operating three elements among the engagement elements of the first, second and third clutches C 1 , C 2 , and C 3  and the first, second and third brakes B 1 , B 2 , and B 3 . 
     In the first forward speed D 1 , the third clutch C 3  and the second and third brakes B 2  and B 3  are simultaneously operated. 
     As a result, the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the eighth shaft TM 8  and the ninth shaft TM 9  act as fixed elements by the operation of the second and third brakes B 2  and B 3 , realizing the first forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the second forward speed D 2 , the first and second, third brakes B 1 , B 2 , and B 3  are simultaneously operated. 
     As a result, the torque of the input shaft IS is input to the first shaft TM 1 , and the seventh shaft TM 7 , the eighth shaft TM 8 , and the ninth shaft TM 9  act as fixed elements by the operation of the first, second and third brakes B 1 , B 2 , and B 3 , realizing the second forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the third forward speed D 3 , the first clutch C 1  and the first and third brakes B 1  and B 3  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh shaft TM 7  and the ninth shaft TM 9  act as fixed elements by the operation of the first and third brakes B 1  and B 3 , realizing the third forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the fourth forward speed D 4 , the first and second clutch C 1  and C 2  and the third brake B 3  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 , and the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the ninth shaft TM 9  acts as a fixed element by the operation of the third brake B 3 , realizing the fourth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the fifth forward speed D 5 , the second and third clutches C 2  and C 3  and the third brake B 3  are simultaneously operated. 
     As a result, the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 , and the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the ninth shaft TM 9  acts as a fixed element by the operation of the third brake B 3 , realizing the fifth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the sixth forward speed D 6 , the first, second and third clutches C 1 , C 2 , and C 3  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 , the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 , and the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     As such, the first, second, third and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4  integrally rotate, realizing the sixth forward speed where a torque is output as inputted, and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the seventh forward speed D 7 , the second and third clutches C 2  and C 3  and the second brake B 2  are simultaneously operated. 
     As a result, the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 , and the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the eighth shaft TM 8  acts as a fixed element by the operation of the second brake B 2 , realizing the seventh forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the eighth forward speed D 8 , the second and third clutches C 2  and C 3  and the first brake B 1  are simultaneously operated. 
     As a result, the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 , and the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh shaft TM 7  acts as a fixed element by the operation of the first brake B 1 , realizing the eighth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the ninth forward speed D 9 , the second clutch C 2  and the first and second brakes B 1  and B 2  are simultaneously operated. 
     As a result, the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh and eighth shafts TM 7  and TM 8  act as fixed elements by the operation of the first and second brakes B 1  and B 2 , realizing the ninth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the tenth forward speed D 10 , the first and second clutch C 1  and C 2  and the second brake B 2  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 , and the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the eighth shaft TM 8  acts as a fixed element by the operation of the second brake B 2 , realizing the tenth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the reverse speed REV, the third clutch C 3  and the first and third brakes B 1  and B 3  are simultaneously operated. 
     As a result, the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh shaft TM 7  and the ninth shaft TM 9  act as fixed elements by the operation of the first and third brakes B 1  and B 3 , realizing the reverse speed by cooperative operation of respective shafts, and outputting a reverse torque through the output shaft OS connected to the second shaft TM 2 . 
       FIG. 3  is an operational chart for respective control elements at respective shift-stages applicable to a planetary gear train according to an exemplary embodiment that realizes fourteen forward speeds and one reverse speeds. 
     Referring to  FIG. 3 , a planetary gear train according to an exemplary embodiment of the present invention realizes shifting between fourteen forward speeds and one reverse speed by operating three elements among the engagement elements of the first, second and third clutches C 1 , C 2 , and C 3  and the first, second and third brakes B 1 , B 2 , and B 3 . 
     In the first forward speed D 1 , the third clutch C 3  and the second and third brakes B 2  and B 3  are simultaneously operated. 
     As a result, the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the eighth shaft TM 8  and the ninth shaft TM 9  act as fixed elements by the operation of the second and third brakes B 2  and B 3 , realizing the first forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the second forward speed D 2 , the first and second, third brakes B 1 , B 2 , and B 3  are simultaneously operated. 
     As a result, the torque of the input shaft IS is input to the first shaft TM 1 , and the seventh shaft TM 7 , the eighth shaft TM 8 , and the ninth shaft TM 9  act as fixed elements by the operation of the first, second and third brakes B 1 , B 2 , and B 3 , realizing the second forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the third forward speed D 3 , the first clutch C 1  and the second and third brakes B 2  and B 3  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the eighth shaft TM 8  and the ninth shaft TM 9  act as fixed elements by the operation of the second and third brakes B 2  and B 3 , realizing the third forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the fourth forward speed D 4 , the first clutch C 1  and the first and third brakes B 1  and B 3  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh shaft TM 7  and the ninth shaft TM 9  act as fixed elements by the operation of the first and third brakes B 1  and B 3 , realizing the fourth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the fifth forward speed D 5 , the first and third clutches C 1  and C 3  and the third brake B 3  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 , and the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the ninth shaft TM 9  acts as a fixed element by the operation of the third brake B 3 , realizing the fifth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the sixth forward speed D 6 , the first and second clutch C 1  and C 2  and the third brake B 3  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 , and the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the ninth shaft TM 9  acts as a fixed element by the operation of the third brake B 3 , realizing the sixth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the seventh forward speed D 7 , the second and third clutches C 2  and C 3  and the third brake B 3  are simultaneously operated. 
     As a result, the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 , and the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the ninth shaft TM 9  acts as a fixed element by the operation of the third brake B 3 , realizing the seventh forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the eighth forward speed D 8 , the first, second and third clutches C 1 , C 2 , and C 3  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 , the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 , and the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     As such, the first, second, third and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4  integrally rotate, realizing the eighth forward speed where a torque is output as inputted and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the ninth forward speed D 9 , the second and third clutches C 2  and C 3  and the second brake B 2  are simultaneously operated. 
     As a result, the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 , and the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the eighth shaft TM 8  acts as a fixed element by the operation of the second brake B 2 , realizing the ninth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the tenth forward speed D 10 , the second and third clutches C 2  and C 3  and the first brake B 1  are simultaneously operated. 
     As a result, the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 , and the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh shaft TM 7  acts as a fixed element by the operation of the first brake B 1 , realizing the tenth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the eleventh forward speed D 11 , the second clutch C 2  and the first and second brakes B 1  and B 2  are simultaneously operated. 
     As a result, the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh shaft TM 7  and the eighth shaft TM 8  act as fixed elements by the operation of the first and second brakes B 1  and B 2 , realizing the eleventh forward speed, which is an overdrve speed, by the cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the twelfth forward speed D 10 , the first and second clutch C 1  and C 2  and the first brake B 1  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 , and the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh shaft TM 7  acts as a fixed element by the operation of the first brake B 1 , realizing the twelfth forward speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the forward thirteenth speed D 10 , the first and second clutch C 1  and C 2  and the second brake B 2  are simultaneously operated. 
     As a result, the first shaft TM 1  is connected to the fifth shaft TM 5  by the operation of the first clutch C 1 , and the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the eighth shaft TM 8  acts as a fixed element by the operation of the second brake B 2 , realizing the forward thirteenth speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the forward fourteenth speed D 14 , the second clutch C 2  and the first and third brakes B 1  and B 3  are simultaneously operated. 
     As a result, the third shaft TM 3  is connected to the sixth shaft TM 6  by the operation of the second clutch C 2 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh shaft TM 7  and the ninth shaft TM 9  act as fixed elements by the operation of the first and third brakes B 1  and B 3 , realizing the forward fourteenth speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected to the second shaft TM 2 . 
     In the reverse speed REV, the third clutch C 3  and the first and third brakes B 1  and B 3  are simultaneously operated. 
     As a result, the fifth shaft TM 5  is connected to the seventh shaft TM 7  by the operation of the third clutch C 3 . In the present state, the torque of the input shaft IS is input to the first shaft TM 1 . 
     Furthermore, the seventh shaft TM 7  and the ninth shaft TM 9  act as fixed elements by the operation of the first and third brakes B 1  and B 3 , realizing the reverse speed by cooperative operation of respective shafts, and outputting a reverse torque through the output shaft OS connected to the second shaft TM 2 . 
     A planetary gear train according to an exemplary embodiment of the present invention may realize at least ten forward speeds one reverse speed by controlling four planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4  by three clutches C 1 , C 2 , and C 3  and three brakes B 1 , B 2 , and B 3 . 
     Furthermore, a planetary gear train according to an exemplary embodiment of the present invention may improve driving stability by realizing shift-stages appropriate for rotation speed of an engine due to multi-stages of an automatic transmission. 
     Furthermore, a planetary gear train according to an exemplary embodiment of the present invention may maximize engine driving efficiency by multi-stages of an automatic transmission, and may improve power delivery performance and fuel consumption. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “internal”, “outer”, “up”, “down”, “upper”, “lower”, “upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”, “inwardly”, “outwardly”, “internal”, “external”, “internal”, “outer”, “forwards”, and “backwards” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described to explain certain principles of the invention and their practical application, to enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.