Planetary gear train of automatic transmission for vehicle

The present application claims priority to Korean Patent Application No. 10-2016-0013650, filed Feb. 3, 2016, the entire contents of which is incorporated herein for all purposes by this reference.

The present invention relates to an automatic transmission for a vehicle.

Recent increases in oil prices are triggering stiff competition in enhancing fuel consumption of a vehicle.

In this sense, research on an automatic transmission has been performed to simultaneously provide better drivability and fuel consumption by achieving more shift stages.

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

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.

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

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

In addition, a recent eight-speed automatic transmission typically shows a gear ratio span in a level of 6.5 to 7.5, which may require improvement for better fuel consumption.

Thus, shortening a length of an automatic transmission without deteriorating performance will be beneficial.

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

Various aspects of the present invention are directed to providing a planetary gear train of an automatic transmission for a vehicle having advantages of realizing at least nine forward speeds and at least one reverse speed by a combination of four planetary gear sets, two external gears and six control elements, thereby providing improvement of power delivery performance and fuel consumption and improving installability by reducing a length.

In addition, various aspects of the present invention are directed to providing a wide available range of varying gear teeth of transfer gears enabling easy obtaining of optimum gear ratios for respective vehicles, thereby improving power delivery performance and fuel consumption.

According to various aspects of the present invention, a planetary gear train of an automatic transmission for a vehicle may include 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, an input shaft mounted with the first, second, and third planetary gear sets at an external circumference of the input shaft, an output shaft disposed in parallel with the input shaft and mounted with the fourth planetary gear set on external circumference of the output shaft, a first shaft interconnecting the first rotational element and the fourth rotational element, a second shaft connected with the second rotational element and directly connected with the input shaft, a third shaft interconnecting the third rotational element and the eighth rotational element, a fourth shaft connected with the fifth rotational element and gear-meshed with the output shaft, a fifth shaft connected with the sixth rotational element, a sixth shaft connected with the seventh rotational element, a seventh shaft connected with the ninth rotational element, an eighth shaft connected with the tenth rotational element, a ninth shaft connected with the eleventh rotational element and directly connected with the output shaft, a tenth shaft connected with the twelfth rotational element, and transfer gears, each gear-meshed with at least one of the shafts, in which one shaft among the eighth and tenth shafts may be selectively connected with a transmission housing and another shaft among the eighth and tenth shafts may be gear-meshed with the third shaft.

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.

A pinion supported by the second planet carrier acting as the fifth rotational element may be a 2-stage pinion including a smaller diameter portion and a larger diameter portion, and the smaller diameter portion may be gear-meshed with the second sun gear acting as the fourth rotational element, and the larger diameter portion may be gear-meshed with the second ring gear acting as the sixth rotational element.

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

The eighth shaft may be gear-meshed with the third shaft, and the tenth shaft may be selectively connected with the transmission housing.

The transfer gears may include a first transfer gear disposed between the fourth shaft and the output shaft, and a second transfer gear disposed between the third shaft and the eighth shaft.

The planetary gear train may further include a first clutch disposed between the second shaft and the sixth shaft, a second clutch disposed between the first shaft and the sixth shaft, a third clutch disposed between the fifth shaft and the sixth shaft, a first brake disposed between the fifth shaft and the transmission housing, a second brake disposed between the seventh shaft and the transmission housing, and a third brake disposed between the tenth shaft and the transmission housing.

The eighth shaft may be selectively connected with the transmission housing, and the tenth shaft may be gear-meshed with the third shaft.

The transfer gears may include a first transfer gear disposed between the fourth shaft and the output shaft, and a second transfer gear disposed between the third shaft and the tenth shaft.

The planetary gear train may further include a first clutch disposed between the second shaft and the sixth shaft, a second clutch disposed between the first shaft and the sixth shaft, a third clutch disposed between the fifth shaft and the sixth shaft, a first brake disposed between the fifth shaft and the transmission housing, a second brake disposed between the seventh shaft and the transmission housing, and a third brake disposed between the eighth shaft and the transmission housing.

According to various aspects of the present invention, a planetary gear train of an automatic transmission for a vehicle may include 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, an input shaft mounted with the first, second, and third planetary gear sets at an external circumference of the input shaft, and an output shaft disposed in parallel with the input shaft and mounted with the fourth planetary gear set on external circumference of the output shaft, in which the first rotational element may be directly connected with the fourth rotational element, the second rotational element may be directly connected with the input shaft, the third rotational element may be directly connected with the eighth rotational element and gear-meshed with one rotational element among the tenth and twelfth rotational elements, the fifth rotational element may be gear-meshed with the output shaft through a first transfer gear, the sixth rotational element may be selectively connected with a transmission housing, the ninth rotational element may be selectively connected with the transmission housing, the eleventh rotational element may be directly connected with the output shaft, and a remaining rotational element, among the tenth and twelfth rotational elements, excluding a rotational element gear-meshed with the third rotational element may be selectively connected with the transmission housing.

The second rotational element may be selectively connected with the seventh rotational element, the first rotational element may be selectively connected with the seventh rotational element, and the sixth rotational element may be selectively connected with the seventh rotational element.

The third rotational element may be gear-meshed with the tenth rotational element through a second transfer gear, and the twelfth rotational element may be selectively connected with the transmission housing.

The planetary gear train may further include a first clutch selectively connecting the second rotational element and the seventh rotational element, a second clutch selectively connecting the first rotational element and the seventh rotational element, a third clutch selectively connecting the sixth rotational element and the seventh rotational element, a first brake selectively connecting the sixth rotational element with the transmission housing, a second brake selectively connecting the ninth rotational element with the transmission housing, and a third brake selectively connecting the twelfth rotational element with the transmission housing.

The third rotational element may be gear-meshed with the twelfth rotational element through a second transfer gear, and the tenth rotational element may be selectively connected with the transmission housing.

The planetary gear train may further include a first clutch selectively connecting the second rotational element and the seventh rotational element, a second clutch selectively connecting the first rotational element and the seventh rotational element, a third clutch selectively connecting the sixth rotational element and the seventh rotational element, a first brake selectively connecting the sixth rotational element with the transmission housing, a second brake selectively connecting the ninth rotational element with the transmission housing, and a third brake selectively connecting the tenth rotational element with the transmission housing.

According to a planetary gear train of various embodiments of the present invention, planetary gear sets are dividedly arranged on input and output shafts disposed in parallel, thereby reducing a length and improving installability.

According to a planetary gear train of various embodiments of the present invention, at least eight forward speeds and at least one reverse speed are realized by employing two transfer gears in addition to a combination of planetary gear sets, thereby providing a wide range of varying gear teeth so as to easily achieve optimum gear ratio and to easily comply with required performance for respective vehicles.

In addition, according to a planetary gear train of various embodiments of the present invention, a gear ratio span of more than 9.8 may be achieved while realizing at least nine forward speeds and at least one reverse speed, thereby maximizing an engine driving efficiency.

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

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.

FIG. 1 is a schematic diagram of a planetary gear train according to various embodiments of the present invention.

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.

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

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 an input shaft IS, an output shaft OS, first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , two transfer gears TF 1 and TF 2 , and control elements of three clutch C 1 , C 2 , and C 3 and three brakes B 1 , B 2 , and B 3 .

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

The output shaft OS is an output member, and, arranged in parallel with the input shaft IS, outputs a shifted driving torque to a drive shaft through a differential apparatus.

The first, second, and third planetary gear sets PG 1 , PG 2 , and PG 3 are arranged at external circumference of the input shaft IS and form a main shifting portion. With respect to the third planetary gear set PG 3 , the first planetary gear set PG 1 is arranged toward an engine side, and the second planetary gear set PG 2 is arranged toward an opposite side of the engine.

The fourth planetary gear set PG 4 is arranged at external circumference of the output shaft OS disposed in parallel with the input shaft IS and forms an auxiliary shifting portion.

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 first pinion P 1 externally engaged with the first sun gear S 1 , and a first ring gear R 1 that is 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 second pinion P 2 externally engaged with the second sun gear S 2 , and a second ring gear R 2 that is 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 second pinion P 2 is a 2-stage pinion having a smaller diameter portion P 21 and a larger diameter portion P 22 . The smaller diameter portion P 21 is externally gear-meshed the second sun gear S 2 , and the larger diameter portion P 22 is internally gear-meshed with the second ring gear R 2 .

Such a 2-stage pinion planetary gear set may contribute to achieving a speed ratio of 1 to 1.5 that might not obtained by a single pinion planetary gear set, thereby increasing a gear ratio span and enhancing a step ratio linearity. Such a 2-stage pinion planetary gear set typically shows higher gear efficiency in comparison with a double pinion planetary gear set that shows poor gear efficiency.

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 third pinion P 3 externally engaged with the third sun gear S 3 , and a third ring gear R 3 that is 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 fourth pinion P 4 externally engaged with the fourth sun gear S 4 , and a fourth ring gear R 4 that is 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 a eleventh rotational element N 11 , and the fourth ring gear R 4 acts as a twelfth rotational element N 12 .

In the arrangement of the first, second, and third planetary gear sets PG 1 , PG 2 , and PG 3 , the first rotational element N 1 is directly connected with the fourth rotational element N 4 , the third rotational element N 3 is directly connected with the eighth rotational element N 8 , by seven shafts TM 1 to TM 7 .

Three shafts TM 8 to TM 10 are connected to the fourth planetary gear set PG 4 .

The ten shafts TM 1 to TM 10 are hereinafter described in detail.

The first shaft TM 1 interconnects the first rotational element N 1 (first sun gear S 1 ) and the fourth rotational element N 4 (second sun gear S 2 ).

The second shaft TM 2 is connected with the second rotational element N 2 (first planet carrier PC 1 ), and directly connected with the input shaft IS, thereby always acting as an input element.

The third shaft TM 3 interconnects the third rotational element N 3 (first ring gear R 1 ) and the eighth rotational element N 8 (third planet carrier PC 3 ).

The fourth shaft TM 4 is connected with the fifth rotational element N 5 (second planet carrier PC 2 ), and externally gear-meshed with the output shaft OS.

The fifth shaft TM 5 is connected with the sixth rotational element N 6 (second ring gear R 2 ), and is selectively connected with the transmission housing H, thereby selectively acting as a fixed element.

The sixth shaft TM 6 is connected with the seventh rotational element N 7 (third sun gear S 3 ), and selectively connected with the first, second, fifth shaft TM 1 , TM 2 , and TM 5 .

The seventh shaft TM 7 is connected with the ninth rotational element N 9 (third ring gear R 3 ), and selectively connected with the transmission housing H, thereby selectively acting as a fixed element.

The eighth shaft TM 8 is connected with the tenth rotational element N 10 (fourth sun gear S 4 ), and externally gear-meshed with the third shaft TM 3 .

The ninth shaft TM 9 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.

The tenth shaft TM 10 is connected with the twelfth rotational element N 12 (fourth ring gear R 4 ), and selectively connected with the transmission housing H, thereby selectively acting as a fixed element.

The two transfer gear TF 1 and TF 2 delivers a shifted torque of the main shifting portion having the first, second, and third planetary gear sets PG 1 , PG 2 , and PG 3 to the auxiliary shifting portion having the fourth planetary gear set PG 4 , in a reverse rotation.

The first transfer gear TF 1 includes a first transfer drive gear TF 1 a directly connected with the fourth shaft TM 4 and a first transfer driven gear TF 1 b directly connected with the output shaft OS, and externally gear-meshes the fourth shaft TM 4 and the output shaft OS.

The second transfer gear TF 2 includes a second transfer drive gear TF 2 a directly connected with the third shaft TM 3 and a second transfer driven gear TF 2 b directly connected with the eighth shaft TM 8 , and externally gear-meshes the third shaft TM 3 and the eighth shaft TM 8 .

Respective shafts connected by the first and second transfer gears TF 1 and TF 2 rotate in opposite directions, and the gear ratios of the first and second transfer gears TF 1 and TF 2 may be preset in consideration of required speed ratio of the transmission.

The control elements include three clutches C 1 , C 2 , and C 3 and three brakes B 1 , B 2 , and B 3 , and are arranged as follows.

The first clutch C 1 is arranged between the second shaft TM 2 and the sixth shaft TM 6 , such that the second shaft TM 2 and the sixth shaft TM 6 may selectively become integral.

The second clutch C 2 is arranged between the first shaft TM 1 and the sixth shaft TM 6 , such that the first shaft TM 1 and the sixth shaft TM 6 may selectively become integral.

The third clutch C 3 is arranged between the fifth shaft TM 5 and the sixth shaft TM 6 , such that the fifth shaft TM 5 and the sixth shaft TM 6 may selectively become integral.

The first brake B 1 is arranged between the fifth shaft TM 5 and the transmission housing H, such that the fifth shaft TM 5 may selectively act as a fixed element.

The second brake B 2 is arranged between the seventh shaft TM 7 and the transmission housing H, such that the seventh shaft TM 7 may selectively act as a fixed element.

The third brake B 3 is arranged between the tenth shaft TM 10 and the transmission housing H, such that the tenth shaft TM 10 may selectively act as a fixed element.

The control elements of the first, second, and third clutch C 1 , C 2 , and C 3 and the first, second, third brake B 1 , B 2 , and B 3 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.

Referring to FIG. 2 , a planetary gear train according to various embodiments of the present invention realizes shifting by operating three control elements among the three clutches C 1 , C 2 , and C 3 and the three brakes B 1 , B 2 , and B 3 .

The Forward First Speed

In the forward first speed shift-stage D 1 , the first clutch C 1 and the second and third brakes B 2 and B 3 are operated.

As a result, the second shaft TM 2 is connected with the sixth shaft TM 6 by the operation of the first clutch C 1 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , and the seventh shaft TM 7 and the tenth shaft TM 10 act as fixed elements by the operation of the second brake B 2 and the third brake B 3 , thereby realizing the forward first speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

The Forward Second Speed

In the forward second speed shift-stage D 2 , the second clutch C 2 and the second and third brakes B 2 and B 3 are operated.

As a result, the first shaft TM 1 is connected with the sixth shaft TM 6 by the operation of the second clutch C 2 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , and the seventh shaft TM 7 and the tenth shaft TM 10 act as fixed elements by the operation of the second brake B 2 and the third brake B 3 , thereby realizing the forward second speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

The Forward Third Speed

In the forward third speed shift-stage D 3 , the second clutch C 2 and the first and third brakes B 1 and B 3 are operated.

As a result, in the main shifting portion, the first shaft TM 1 is connected with the sixth shaft TM 6 by the operation of the second clutch C 2 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , and the fifth shaft TM 5 and the tenth shaft TM 10 act as fixed elements by the operation of the first brake B 1 and the third brake B 3 , thereby realizing the forward third speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

The Forward Fourth Speed

In the forward fourth speed shift-stage D 4 , the first and second clutch C 1 and C 2 and the third brake B 3 are operated.

As a result, the second shaft TM 2 is connected with the sixth shaft TM 6 by the operation of the first clutch C 1 , and the first shaft TM 1 is connected with the sixth shaft TM 6 by the operation of the second clutch C 2 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , and the tenth shaft TM 10 acts as a fixed element by the operation of the third brake B 3 , thereby realizing the forward fourth speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

The Forward Fifth Speed

In the forward fifth speed shift-stage D 5 , the second and third clutches C 2 and C 3 and the third brake B 3 are operated.

As a result, the first shaft TM 1 is connected with the sixth shaft TM 6 by the operation of the second clutch C 2 , and the fifth shaft TM 5 is connected with the sixth shaft TM 6 by the operation of the third clutch C 3 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , and the tenth shaft TM 10 acts as a fixed element by the operation of the third brake B 3 , thereby realizing the forward fifth speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

The Forward Sixth Speed

In the forward sixth speed shift-stage D 6 , the first and third clutches C 1 and C 3 and the third brake B 3 are operated.

As a result, the second shaft TM 2 is connected with the sixth shaft TM 6 by the operation of the first clutch C 1 , and the fifth shaft TM 5 is connected with the sixth shaft TM 6 by the operation of the third clutch C 3 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , and the tenth shaft TM 10 acts as a fixed element by the operation of the third brake B 3 , thereby realizing the forward sixth speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

The Forward Seventh Speed

In the forward seventh speed shift-stage D 7 , the first, second, and third clutches C 1 , C 2 , and C 3 are operated.

As a result, the second shaft TM 2 is connected with the sixth shaft TM 6 by the operation of the first clutch C 1 , the first shaft TM 1 is connected with the sixth shaft TM 6 by the operation of the second clutch C 2 , and the fifth shaft TM 5 is connected with the sixth shaft TM 6 by the operation of the third clutch C 3 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , thereby realizing the forward seventh speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

The Forward Eighth Speed

In the forward eighth speed shift-stage D 8 , the first and third clutches C 1 and C 3 and the second brake B 2 are operated.

As a result, the second shaft TM 2 is connected with the sixth shaft TM 6 by the operation of the first clutch C 1 , and the fifth shaft TM 5 is connected with the sixth shaft TM 6 by the operation of the third clutch C 3 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , and the seventh shaft TM 7 acts as a fixed element by the operation of the second brake B 2 , thereby realizing the forward eighth speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

The Forward Ninth Speed

In the forward ninth speed shift-stage D 9 , the second and third clutches C 2 and C 3 and the second brake B 2 are operated.

As a result, the first shaft TM 1 is connected with the sixth shaft TM 6 by the operation of the second clutch C 2 , and the fifth shaft TM 5 is connected with the sixth shaft TM 6 by the operation of the third clutch C 3 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , and the seventh shaft TM 7 acts as a fixed element by the operation of the second brake B 2 , thereby realizing the forward ninth speed by cooperative operation of respective shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

The Reverse Speed

In the reverse speed REV, the third clutch C 3 and the second and third brakes B 2 and B 3 are operated.

As a result, the fifth shaft TM 5 is connected with the sixth shaft TM 6 by the operation of the third clutch C 3 . In this state, the torque of the input shaft IS is input to the second shaft TM 2 , and the seventh shaft TM 7 and the tenth shaft TM 10 act as fixed elements by the operation of the second brake B 2 and the third brake B 3 , thereby realizing the reverse speed by cooperative operation of shafts and outputting a shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

FIG. 2 shows gear ratios calculated under the condition that the gear ratio of the first ring gear R 1 /the first sun gear S 1 is 1.20, the gear ratio of the second ring gear R 2 /the second sun gear S 2 is 2.69, the gear ratio of the third ring gear R 3 /the third sun gear S 3 is 1.84, the gear ratio of the fourth ring gear R 4 /the fourth sun gear S 4 is 1.86, the gear ratio of the first transfer driven gear TF 1 b/ the first transfer drive gear TF 1 a is 1.00, and the gear ratio of the second transfer driven gear TF 2 b /the second transfer drive gear TF 2 a is 0.78.

FIG. 3 is a schematic diagram of a planetary gear train according to various embodiments of the present invention.

In a planetary gear train according to various embodiments of FIG. 1 , the third shaft TM 3 is externally gear-meshed with the eighth shaft TM 8 through the second transfer gear TF 2 , and the tenth shaft TM 10 is selectively connected with the transmission housing H thereby selectively acting as a fixed element, as shown in FIG. 1 . However, referring to FIG. 3 , the third shaft TM 3 is externally gear-meshed with the tenth shaft TM 10 through the second transfer gear TF 2 , and the eighth shaft TM 8 is selectively connected with the transmission housing H thereby selective acting as a fixed element, according to the various embodiments of FIG. 3 .

As a result, the various embodiments of FIG. 3 differ from the various embodiments of FIG. 1 in that the shaft of the auxiliary shifting portion externally gear-meshed with the third shaft TM 3 and the shaft of the auxiliary shifting portion selectively connected with the transmission housing are interchanged. However, a function and shift pattern of the gear train remains the same as will be obvious to a person of an ordinary skill in the art, which is therefore not described in further detail.

As described above, according to a planetary gear train of various embodiments of the present invention, at least nine forward speeds and at least one reverse speed are realized by a combination of four planetary gear sets, two transfer gears, and five control elements, thereby providing improvement of power delivery performance and fuel consumption and improving installability by shortening the length of an automatic transmission.

In addition, according to a planetary gear train of various embodiments of the present invention, two transfer gears of external gears arranged on the output shaft OS are employed in addition to three planetary gear sets, and thus, gear teeth may be widely varied so as to easily achieve optimum gear ratio and to easily comply with required performance for respective vehicles.

Furthermore, according to a planetary gear train of various embodiments of the present invention, a gear ratio span of more than 9.8 may be achieved while realizing at least nine forward speeds and at least one reverse speed, thereby maximizing an engine driving efficiency.

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

For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner” and “outer”, “up,” “down,” “upper”, “lower,” “upwards,” “downwards”, “front”, “rear”, “back”, “inside”, “outside”, “inwardly,” “outwardly,” “interior”, “exterior”, “inner,” “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 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.