Patent Publication Number: US-9897169-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. 10-2015-0176079, filed Dec. 10, 2015, 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 an automatic transmission for a vehicle. 
     Description of Related Art 
     Recent increases in oil prices are triggering hard competition in enhancing fuel consumption of a vehicle. 
     In this sense, research is being conducted on engines in terms of reducing weight and improving fuel efficiency by down-sizing, and research is also being conducted to ensure both drivability and competitiveness for maximizing fuel efficiency by implementing an automatic transmission with multiple speed stages. 
     In order 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, in order to maximally enhance fuel consumption of an automatic transmission having more shift stages, it is important for better efficiency to be derived by a smaller number of parts. 
     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. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY 
     Various aspects of the present invention are directed to providing a planetary gear train of an automatic transmission for a vehicle having advantages of, by minimal complexity, realizing at least forward tenth speeds and at least one reverse speed, thereby improving power delivery performance and fuel consumption due to multi-stages, and improving driving stability of a vehicle by utilizing a low rotation speed of an engine. 
     According to various aspects of the present invention, a planetary gear set of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft for outputting a shifted torque of the engine, a first planetary gear set including first, second, and third rotational elements, a second planetary gear set including fourth, fifth, and sixth rotational elements, a third planetary gear set including seventh, eighth, and ninth rotational elements, a fourth planetary gear set including tenth, eleventh, and twelfth rotational elements, six control elements for selectively interconnecting the rotational elements and a transmission housing, a first connecting member connected with the first rotational element and the fourth rotational element and directly connected with the input shaft, a second connecting member connected with the second rotational element and directly connected with the transmission housing, a third connecting member connected with the third rotational element, a fourth connecting member connected with the fifth rotational element and the seventh rotational element, selectively connected with the third connecting member, a fifth connecting member connected with the sixth rotational element, selectively connected with the third connecting member, and selectively connected with the transmission housing, a sixth connecting member connected with the eighth rotational element and the twelfth rotational element, and selectively connected with the transmission housing, a seventh connecting member connected with the ninth rotational element and the tenth rotational element, and selectively connected with the input shaft, and an eighth connecting member connected with the eleventh rotational element, and directly connected with the output shaft. 
     The first planetary gear set may be a single pinion planetary gear set, where the first rotational element may be a first sun gear, the second rotational element may be a first planet carrier, and the third rotational element may be a first ring gear; 
     the second planetary gear set may be a single pinion planetary gear set, where the fourth rotational element may be a second sun gear, the fifth rotational element may be a second planet carrier, and the sixth rotational element may be a second ring gear; 
     the third planetary gear set may be a single pinion planetary gear set, where the seventh rotational element may be a third sun gear, the eighth rotational element may be a third planet carrier, and the ninth rotational element may be a third ring gear; and 
     the fourth planetary gear set may be a single pinion planetary gear set, where the tenth rotational element may be a fourth sun gear, the eleventh rotational element may be a fourth planet carrier, and the twelfth rotational element may be a fourth ring gear. 
     The six control elements may include a first clutch selectively connecting the input shaft and the sixth connecting member, a second clutch selectively connecting the input shaft and the seventh connecting member, a third clutch selectively connecting the third connecting member and the fourth connecting member, a fourth clutch selectively connecting the third connecting member and the fifth connecting member, a first brake selectively connecting the fifth connecting member and the transmission housing, and a second brake selectively connecting the sixth connecting member and the transmission housing. 
     Shift stages realized by selective operation of the six control elements may include a forward first speed formed by simultaneous operation of the fourth clutch and the second brake, a forward second speed formed by simultaneous operation of the third clutch and the second brake, a forward third speed formed by simultaneous operation of the second clutch and the second brake, a forward fourth speed formed by simultaneous operation of the second and third clutches, a forward fifth speed formed by simultaneous operation of the second and fourth clutches, a forward sixth speed formed by simultaneous operation of the second clutch and the first brake, a forward seventh speed formed by simultaneous operation of the first and second clutches, a forward eighth speed formed by simultaneous operation of the first clutch and the first brake, a forward ninth speed formed by simultaneous operation of the first and fourth clutches, a forward tenth speed formed by simultaneous operation of the first and third clutches, and a reverse speed formed by simultaneous operation of the first and second brakes. 
     According to various aspects of the present invention, a planetary gear set of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft for outputting a shifted torque, a first planetary gear set as a single pinion planetary gear set including first, second, and third rotational elements, a second planetary gear set as a single pinion planetary gear set including fourth, fifth, and sixth rotational elements, a third planetary gear set as a single pinion planetary gear set including seventh, eighth, and ninth rotational elements, a fourth planetary gear set as a single pinion planetary gear set including tenth, eleventh, and twelfth rotational elements, a first connecting member connected to the first rotational element and the fourth rotational element and directly connected to the input shaft, a second connecting member connected to the second rotational element and directly connected with the transmission housing, a third connecting member connected to the third rotational element, a fourth connecting member connected to the fifth rotational element and the seventh rotational element, selectively connected to the third connecting member, a fifth connecting member connected to the sixth rotational element, selectively connected to the third connecting member, and selectively connected to the transmission housing, a sixth connecting member connected to the eighth rotational element and the twelfth rotational element, and selectively connected to the transmission housing, a seventh connecting member connected to the ninth rotational element and the tenth rotational element, and selectively connected to the input shaft, an eighth connecting member connected to the eleventh rotational element, and directly connected to the output shaft, a first clutch selectively connecting the input shaft and the sixth connecting member, a second clutch selectively connecting the input shaft and the seventh connecting member, a third clutch selectively connecting the third connecting member and the fourth connecting member, a fourth clutch selectively connecting the third connecting member and the fifth connecting member, a first brake selectively connecting the fifth connecting member and the transmission housing, and a second brake selectively connecting the sixth connecting member and the transmission housing. 
     The first planetary gear set may include a first sun gear as the first rotational element, a first planet carrier as the second rotational element, and a first ring gear as the third rotational element, the second planetary gear set may include a second sun gear as the fourth rotational element, a second planet carrier as the fifth rotational element, and a second ring gear as the sixth rotational element, the third planetary gear set may include a third sun gear as the seventh rotational element, a third planet carrier as the eighth rotational element, and a third ring gear as the ninth rotational element, and the fourth planetary gear set may include a fourth sun gear as the tenth rotational element, a fourth planet carrier as the eleventh rotational element, and a fourth ring gear as the twelfth rotational element. 
     According to various aspects of the present invention, a planetary gear set of an automatic transmission for a vehicle may include an input shaft for receiving an engine torque, an output shaft for outputting a shifted torque, a first planetary gear set as a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear, a second planetary gear set as a single pinion planetary gear set including a second sun gear, a second planet carrier, and a second ring gear, a third planetary gear set as a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear, a fourth planetary gear set as a single pinion planetary gear set including a fourth sun gear, a fourth planet carrier, and a fourth ring gear, a first connecting member connected to the first sun gear and the second sun gear, and directly connected to the input shaft, a second connecting member connected to the first planet carrier, and directly connected to the transmission housing, a third connecting member connected to the first ring gear, a fourth connecting member connected to the second planet carrier and the third sun gear, and selectively connected to the third connecting member, a fifth connecting member connected to the second ring gear, selectively connected to the third connecting member, and selectively connected to the transmission housing, a sixth connecting member connected to the third planet carrier and the fourth ring gear, and selectively connected to the transmission housing, a seventh connecting member connected to the third ring gear and the fourth sun gear, and selectively connected to the input shaft, an eighth connecting member connected to the fourth planet carrier, and directly connected to the output shaft, and six control elements selectively connecting the connecting members and the transmission housing. 
     A planetary gear train according to various embodiments of the present invention may realize at least forward tenth speeds and at least one reverse speed formed by operating the four planetary gear sets as simple planetary gear sets by controlling six control elements. 
     In addition, a planetary gear train according to various embodiments of the present invention may substantially improve driving stability by realizing shift stages appropriate for rotation speed of an engine due to multi-stages of an automatic transmission. 
     In addition, a planetary gear train according to various embodiments 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. 
     It is understood that the term “vehicle” or “vehicular” or other similar terms as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuel derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example, both gasoline-powered and electric-powered vehicles. 
     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 an exemplary planetary gear train according to the present invention. 
         FIG. 2  is an operational chart for respective control elements at respective shift stages in the exemplary planetary gear train according to the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     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. 
       FIG. 1  is a schematic diagram of a planetary gear train according to various embodiments of the present invention. 
     Referring to  FIG. 1 , a planetary gear train according to various embodiments of the present invention includes first, second, third, and fourth 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 connecting members TM 1  to TM 8  for interconnecting rotational elements of the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , six control elements C 1  to C 4  and B 1  to B 2 , 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 simple planetary gear sets are arranged in the order of first, 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, after being torque-converted through a torque converter, is input into the input shaft IS. 
     The output shaft OS is an output member, and being arranged on a same axis with the input shaft IS, delivers a shifted torque to a drive shaft 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  that supports a first pinion P 1  externally engaged with the first sun gear S 1 , and a first ring gear R 1  internally engaged with the first pinion P 1 . The first sun gear S 1  acts as a first rotational element N 1 , the first planet carrier PC 1  acts as a second rotational element N 2 , and the first ring gear R 1  acts as a third rotational element 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  that supports a second pinion P 2  externally engaged with the second sun gear S 2 , and a second ring gear R 2  internally engaged with the second pinion P 2 . The second sun gear S 2  acts as a fourth rotational element N 4 , the second planet carrier PC 2  acts as a fifth rotational element N 5 , and the second ring gear R 2  acts as a sixth rotational element 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  that supports a third pinion P 3  externally engaged with the third sun gear S 3 , and a third ring gear R 3  internally engaged with the third pinion P 3 . The third sun gear S 3  acts as a seventh rotational element N 7 , the third planet carrier PC 3  acts as an eighth rotational element N 8 , and the third ring gear R 3  acts as a ninth rotational element 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  that supports a fourth pinion P 4  externally engaged with the fourth sun gear S 4 , and a fourth ring gear R 4  internally engaged with the fourth pinion P 4 . The fourth sun gear S 4  acts as a tenth rotational element N 10 , the fourth planet carrier PC 4  acts as an eleventh rotational element N 11 , and the fourth ring gear R 4  acts as a twelfth rotational element N 12 . 
     In the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , the first rotational element N 1  is directly connected with the fourth rotational element N 4 , the fifth rotational element N 5  is directly connected with the seventh rotational element N 7 , the eighth rotational element N 8  is directly connected with the twelfth rotational element N 12 , and the ninth rotational element N 9  is directly connected with tenth rotational element N 10 , by eight connecting members TM 1  to TM 8 . 
     The eight connecting members TM 1  to TM 8  are arranged as follows. 
     The first connecting member TM 1  is connected with the first rotational element N 1  (first sun gear S 1 ) and the fourth rotational element N 4  (second sun gear S 2 ), and directly connected with the input shaft IS, thereby always acting as an input element. 
     The second connecting member TM 2  is connected with second rotational element N 2  (first planet carrier PC 1 ), and directly connected with the transmission housing H, thereby always acting as a fixed element. 
     The third connecting member TM 3  is connected with third rotational element N 3  (first ring gear R 1 ). 
     The fourth connecting member TM 4  is connected with the fifth rotational element N 5  (second planet carrier PC 2 ) and the seventh rotational element N 7  (third sun gear S 3 ), and selectively connected with the third connecting member TM 3 . 
     The fifth connecting member TM 5  is connected with the sixth rotational element N 6  (second ring gear R 2 ), selectively connected with the third connecting member TM 3 , and selectively connected with the transmission housing H. 
     The sixth connecting member TM 6  is connected with the eighth rotational element N 8  (third planet carrier PC 3 ) and the twelfth rotational element N 12  (fourth ring gear R 4 ), selectively connected with the input shaft IS, and selectively connected with the transmission housing H. 
     The seventh connecting member TM 7  is connected with the ninth rotational element N 9  (third ring gear R 3 ) and the tenth rotational element N 10  (fourth sun gear S 4 ), and selectively connected with the input shaft IS. 
     The eighth connecting member TM 8  is connected with the eleventh rotational element N 11  (fourth planet carrier PC 4 ), and directly connected with the output shaft OS thereby always acting as an output element. 
     It has been described above that the sixth connecting member TM 6  and the seventh connecting member TM 7  are selectively connected with the input shaft IS. It is notable that a selective connection with the first connecting member TM 1  also implies selective connection with the input shaft since the first connecting member TM 1  is directly connected with the input shaft IS. 
     The connecting members TM 1  to TM 8  may be selectively interconnected with one another by control elements of four clutches C 1 , C 2 , C 3 , and C 4 . 
     The connecting members TM 1  to TM 8  may be selectively connected with the transmission housing H, by control elements of two brakes B 1  and B 2 . 
     The six control elements C 1  to C 4  and B 1  to B 2  are arranged as follows. 
     The first clutch C 1  is arranged between the input shaft IS (or first connecting member TM 1 ) and the sixth connecting member TM 6 , such that the input shaft IS (or first connecting member TM 1 ) and the sixth connecting member TM 6  may selectively become integral. 
     The second clutch C 2  is arranged between the input shaft IS (or first connecting member TM 1 ) and the seventh connecting member TM 7 , such that the input shaft IS (or first connecting member TM 1 ) and the seventh connecting member TM 7  may selectively become integral. 
     The third clutch C 3  is arranged between the third connecting member TM 3  and the fourth connecting member TM 4 , such that the third connecting member TM 3  and the fourth connecting member TM 4  may selectively become integral. 
     The fourth clutch C 4  is arranged between the third connecting member TM 3  and the fifth connecting member TM 5 , such that the third connecting member TM 3  and the fifth connecting member TM 5  may selectively become integral. 
     The first brake B 1  is arranged between the fifth connecting member TM 5  and the transmission housing H, such that the fifth connecting member TM 5  may selectively act as a fixed element. 
     The second brake B 2  is arranged between the sixth connecting member TM 6  and the transmission housing H, such that the sixth connecting member TM 6  may selectively act as a fixed element. 
     The control elements of 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  may be realized as multi-plate hydraulic pressure friction devices that are frictionally engaged by hydraulic pressure. 
       FIG. 2  is an operational chart for respective control elements at respective shift stages in a planetary gear train according to various embodiments of the present invention. 
     As shown in  FIG. 2 , a planetary gear train according to various embodiments of the present invention performs shifting by operating two control elements at respective shift stages. 
     In the forward first speed shift stage D 1 , the fourth clutch C 4  and the second brake B 2  are simultaneously operated. As a result, the third connecting member TM 3  is connected with the fifth connecting member TM 5  by the operation of the fourth clutch C 4 . In this state, torque of the input shaft IS is input to the first connecting member TM 1 . In addition, the second connecting member TM 2  acts as a fixed element and the sixth connecting member TM 6  simultaneously acts as a fixed element by the operation of second brake B 2 , thereby realizing the forward first speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the forward second speed shift stage D 2 , the third clutch C 3  and the second brake B 2  are simultaneously operated. As a result, the third connecting member TM 3  is connected with the fourth connecting member TM 4  by the operation of the third clutch C 3 . In this state, torque of the input shaft IS is input to the first connecting member TM 1 . In addition, the second connecting member TM 2  acts as a fixed element and the sixth connecting member TM 6  simultaneously acts as a fixed element by the operation of second brake B 2 , thereby realizing the forward second speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the forward third speed shift stage D 3 , the second clutch C 2  and the second brake B 2  are simultaneously operated. As a result, the input shaft IS is connected with the seventh connecting member TM 7  by the operation of the second clutch C 2 , and the torque of the input shaft IS is simultaneously input to the first connecting member TM 1  and the seventh connecting member TM 7 . In addition, the second connecting member TM 2  acts as a fixed element and the sixth connecting member TM 6  simultaneously acts as a fixed element by the operation of second brake B 2 , thereby realizing the forward third speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the forward fourth speed shift stage D 4 , the second clutch C 2  and the third clutch C 3  are simultaneously operated. As a result, the input shaft IS is connected with the seventh connecting member TM 7  by the operation of the second clutch C 2 , the third connecting member TM 3  is connected with the fourth connecting member TM 4  by the operation of the third clutch C 3 , and the torque of the input shaft IS is simultaneously input to the first connecting member TM 1  and the seventh connecting member TM 7 . In addition, the second connecting member TM 2  acts as a fixed element, thereby realizing the forward fourth speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the forward fifth speed shift stage D 5 , the second clutch C 2  and the fourth clutch C 4  are simultaneously operated. As a result, the input shaft IS is connected with the seventh connecting member TM 7  by the operation of the second clutch C 2 , the third connecting member TM 3  is connected with the fifth connecting member TM 5  by the operation of the fourth clutch C 4 , and the torque of the input shaft IS is simultaneously input to the first connecting member TM 1  and the seventh connecting member TM 7 . In addition, the second connecting member TM 2  acts as a fixed element, thereby realizing the forward fifth speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the forward sixth speed shift stage D 6 , the second clutch C 2  and the first brake B 1  are simultaneously operated. As a result, the input shaft IS is connected with the seventh connecting member TM 7  by the operation of the second clutch C 2 , and the torque of the input shaft IS is simultaneously input to the first connecting member TM 1  and the seventh connecting member TM 7 . In addition, the second connecting member TM 2  acts as a fixed element and the fifth connecting member TM 5  simultaneously acts as a fixed element by the operation of first brake B 1 , thereby realizing the forward sixth speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the forward seventh speed shift stage D 7 , the first clutch C 1  and the second clutch C 2  are simultaneously operated. As a result, the input shaft IS is connected with the sixth connecting member TM 6  and the seventh connecting member TM 7  by the operation of the first and second clutches C 1  and C 2 , and the torque of the input shaft IS is simultaneously input to the first, sixth, and seventh connecting members TM 1 , TM 6 , and TM 7 . Then, the third and fourth planetary gear sets PG 3  and PG 4  becomes integral to output torque as input, thereby realizing the forward seventh speed and outputting an input torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the forward eighth speed shift stage D 8 , the first clutch C 1  and the first brake B 1  are simultaneously operated. As a result, the input shaft IS is connected with the sixth connecting member TM 6  by the operation of the first clutch C 1 , and the torque of the input shaft IS is simultaneously input to the first connecting member TM 1  and the sixth connecting member TM 6 . In addition, the second connecting member TM 2  acts as a fixed element, and the fifth connecting member TM 5  simultaneously acts as a fixed element by the operation of first brake B 1 , thereby realizing the forward eighth speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the forward ninth speed shift stage D 9 , the first clutch C 1  and the fourth clutch C 4  are simultaneously operated. As a result, the input shaft IS is connected with the sixth connecting member TM 6  by the operation of the first clutch C 1 , the third connecting member TM 3  is connected with the fifth connecting member TM 5  by the operation of the fourth clutch C 4 , and the torque of the input shaft IS is simultaneously input to the first connecting member TM 1  and the sixth connecting member TM 6 . In addition, the second connecting member TM 2  acts as a fixed element, thereby realizing the forward ninth speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the forward tenth speed shift stage D 10 , the first clutch C 1  and the third clutch C 3  are simultaneously operated. As a result, the input shaft IS is connected with the sixth connecting member TM 6  by the operation of the first clutch C 1 , the third connecting member TM 3  is connected with the fourth connecting member TM 4  by the operation of the third clutch C 3 , and the torque of the input shaft IS is simultaneously input to the first connecting member TM 1  and the sixth connecting member TM 6 . In addition, the second connecting member TM 2  acts as a fixed element, thereby realizing the forward tenth speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     In the reverse speed REV, the first and second brakes B 1  and B 2  are simultaneously operated. As a result, torque of the input shaft IS is input to the first connecting member IS, the second connecting member TM 2  acts as a fixed element, and the fifth and sixth connecting members TM 5  and TM 6  simultaneously act as fixed elements by the operation of the first and second brakes B 1  and B 2 , thereby realizing the reverse speed and outputting a shifted torque through the output shaft OS connected with the eighth connecting member TM 8 . 
     As described above, a planetary gear train according various embodiments of the present invention may realize the forward tenth speed and one reverse speed formed by operating four planetary gear set PG 1 , PG 2 , PG 3 , and PG 4  by controlling four clutches C 1 , C 2 , C 3 , and C 4  and two brake B 1  and B 2 . 
     In addition, a planetary gear train according to various embodiments of the present invention may substantially improve driving stability by realizing shift stages appropriate for rotation speed of an engine due to multiple speed stages of an automatic transmission. 
     In addition, a planetary gear train according to various embodiments of the present invention may maximize engine driving efficiency by multiple speed stages of an automatic transmission, and may improve power delivery performance and fuel consumption. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.