Planetary gear train of automatic transmission for vehicle

This application claims priority to and the benefit of Korean Patent Application No. 10-2017-0090831, filed on Jul. 18, 2017, which is incorporated herein by reference in its entirety.

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

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Recently, increase of oil price leads to more competition to enhance fuel efficiency in automotive industry.

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

In order to achieve more shift stages for an automatic transmission, the number of parts is typically increased. This negatively affects installability, production cost, weight and/or power flow efficiency.

Therefore, in order to maximally enhance fuel efficiency and to lower manufacturing cost of an automatic transmission via multi shift stages, it is important to reduce number of parts of the transmission.

In this background, an eight-speed automatic transmission has been introduced recently to perform more shift stages via planetary gear trains for an automatic transmission.

However, we have discovered that disclosed automatic transmissions of eight or more shift-stages typically include many components and thus may easily become lengthy.

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

The present disclosure provides a planetary gear train of an automatic transmission for a vehicle having advantages of realizing at least eight forward speeds and at least one reverse speed by a combination of four planetary gear sets, two external gears and five control elements, thereby providing improvement of power delivery performance and fuel consumption and improving installability by reducing the length of the transmission.

In addition, a wide available range of varying gear teeth of transfer gears enables easily obtaining desired gear ratios for respective vehicles, thereby improving power delivery performance and fuel consumption.

In one form of the present disclosure, a planetary gear train includes: a first planetary gear set having first, second, and third rotational elements, a second planetary gear set having fourth, fifth, and sixth rotational elements, a third planetary gear set having seventh, eighth, and ninth rotational elements, a fourth planetary gear set having 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. An exemplary planetary gear train may further include a first shaft fixedly connected with the first rotational element and the fourth rotational element, a second shaft fixedly connected with the second rotational element and fixedly connected with the input shaft, a third shaft fixedly connected with the third rotational element, a fourth shaft fixedly connected with the fifth rotational element and the eighth rotational element, a fifth shaft fixedly connected with the sixth rotational element, a sixth shaft fixedly connected with the seventh rotational element, a seventh shaft fixedly connected with the ninth rotational element, an eighth shaft fixedly connected with the tenth rotational element and externally gear-meshed with the sixth shaft, a ninth shaft fixedly connected with the eleventh rotational element and connected with the output shaft, a tenth shaft fixedly connected with the twelfth rotational element and externally gear-meshed with the fourth shaft, and first and second transfer gears configured to form external gear-engagement with the corresponding shafts selected from the first to tenth shafts.

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

An exemplary planetary gear grain may further include a first clutch arranged between the second shaft and the sixth shaft, a second clutch arranged between the third shaft and the sixth shaft, a third clutch arranged between the third shaft and the seventh shaft, a first brake arranged between the first shaft and the transmission housing, and a second brake arranged between the fifth shaft and the transmission housing.

The first transfer gear is arranged between the fourth shaft and the tenth shaft, and the second transfer gear is arranged between the sixth shaft and the eighth shaft.

The first planetary gear set may include a first sun gear, a first planet carrier, and a first ring gear as the first, second, and third rotational elements. The second planetary gear set may include a second sun gear, a second planet carrier, and a second ring gear as the fourth, fifth, and sixth rotational elements. The third planetary gear set may include a third sun gear, a third ring gear, and a third planet carrier as the seventh, eighth, and ninth rotational elements. The fourth planetary gear set may include a fourth sun gear, a fourth planet carrier, and a fourth ring gear as the tenth, eleventh, and twelfth rotational elements.

The first planetary gear set may include a first sun gear, a first planet carrier, and a first ring gear as the first, second, and third rotational elements. The second planetary gear set may include a second sun gear, a second planet carrier, and a second ring gear as the fourth, fifth, and sixth rotational elements. The third planetary gear set may include a third planet carrier, a third ring gear, and a third sun gear as the seventh, eighth, and ninth rotational elements. The fourth planetary gear set may include a fourth sun gear, a fourth planet carrier, and a fourth ring gear as the tenth, eleventh, and twelfth rotational elements.

The first, second, and third planetary gear sets may be arranged in the order of the third, first, and second planetary gear sets from an engine side.

According to a planetary gear train according to an exemplary form of the present disclosure, 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 according to an exemplary form of the present disclosure, at least eight forward speeds and at least one reverse speed may be 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 desired performance for respective vehicles.

In addition, according to a planetary gear train according to an exemplary form of the present disclosure, a gear ratio span of more than 8.0 may be achieved while realizing at least eight forward speeds and at least one reverse speed, thereby increasing 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.

In addition, a planetary gear train according to an exemplary form of the present disclosure utilizes five engagement elements thereby reducing the number of parts employed to achieve the shift stages, and reduces the number of non-engaged elements thereby reducing a drag loss and enhancing efficiency and fuel economy.

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

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

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

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

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

FIG. 4 is an operational chart for respective control elements at respective shift-stages in a planetary gear train according to a second exemplary form of the present disclosure.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

The present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary forms of the present disclosure are shown. As those skilled in the art would realize, the described forms may be modified in various different ways, all without departing from the spirit or scope of the present disclosure.

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.

Here, the term “fixedly connected” or the like means at least two members are connected to each other to always rotate together. Therefore, it is to be understood by a person of an ordinary skill in the art that the term “fixedly connected” or the like differs from the term “operably connected” or the like.

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

Referring to FIG. 1 , a planetary gear train 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 engagement elements of three clutches C 1 , C 2 , and C 3 and two brakes B 1 and B 2 .

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

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 third planetary gear set PG 3 is a double pinion planetary gear set, and includes a third sun gear S 3 , a third ring gear R 3 that is internally gear-meshed with a third pinion P 3 externally gear-meshed with the third sun gear S 3 , and a third planet carrier PC 3 that supports the third pinion P 3 . The third sun gear S 3 acts as a seventh rotational element N 7 , the third ring gear R 3 acts as an eighth rotational element N 8 , and the third planet carrier PC 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 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, and third planetary gear sets PG 1 , PG 2 , and PG 3 , the first rotational element N 1 is fixedly connected with the fourth rotational element N 4 , the fifth rotational element N 5 is fixedly connected with the eighth rotational element N 8 , and seven shafts TM 1 to TM 7 are formed.

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 is fixedly connected with first rotational element N 1 (first sun gear S 1 ) and fourth rotational element N 4 (second sun gear S 2 ), and selectively connected with the transmission housing H.

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

The third shaft TM 3 is fixedly connected with the third rotational element N 3 (first ring gear R 1 ).

The fourth shaft TM 4 is fixedly connected with fifth rotational element N 5 (second planet carrier PC 2 ) and eighth rotational element N 8 (third ring gear R 3 ).

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

The sixth shaft TM 6 is fixedly connected with the seventh rotational element N 7 (third sun gear S 3 ), and selectively connected with each of the second shaft TM 2 (input shaft IS) and the third shaft TM 3 .

The seventh shaft TM 7 is fixedly connected with the ninth rotational element N 8 (third planet carrier PC 3 ), and selectively connected with the third shaft TM 3 .

The eighth shaft TM 8 is fixedly connected with the tenth rotational element N 10 (fourth sun gear S 4 ), and externally gear-meshed with the sixth shaft TM 6 .

The ninth shaft TM 9 is fixedly connected with the eleventh rotational element N 11 (fourth planet carrier PC 4 ), and fixedly connected with the output shaft OS, thereby always acting as an output element.

The tenth shaft TM 10 is fixedly connected with the twelfth rotational element N 12 (fourth ring gear R 4 ), and externally gear-meshed with the fourth shaft TM 4 .

The first and second transfer gears TF 1 and TF 2 of externally gear-meshed gear sets deliver 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 .

The first transfer gear TF 1 includes a first transfer gear TF 1 a fixedly connected with the fourth shaft TM 4 and a first transfer gear TF 1 b fixedly connected with the tenth shaft TM 10 , and externally gear-meshes the fourth shaft TM 4 and the tenth shaft TM 10 .

The second transfer gear TF 2 includes a second transfer gear TF 2 a fixedly connected with the sixth shaft TM 6 and a second transfer gear TF 2 b fixedly connected with the eighth shaft TM 8 , and externally gear-meshes the sixth shaft TM 6 and the eighth shaft TM 8 .

As a result, 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 desired speed ratio of the transmission.

Each of the ten shafts TM 1 to TM 10 may be a rotational member that fixedly interconnects the input and output shafts and rotational elements of the planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , or may be a rotational member that selectively interconnects a rotational 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 rotational member, and a transmission housing, the fixedly connected members always rotate together such that they may rotate at a same speed and/or in a same direction.

When two or more members are described to be “selectively connected” by an engagement element, it means that the selectively connected members rotates separately when the engagement element is not engaged, and rotates at a same speed when the engagement element is engaged.

The engagement elements include three clutches C 1 , C 2 , and C 3 and two brakes B 1 and B 2 , 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 third shaft TM 3 and the sixth shaft TM 6 , such that the third shaft TM 3 and the sixth shaft TM 6 may selectively become integral.

The third clutch C 3 is arranged between the third shaft TM 3 and the seventh shaft TM 7 , such that the third shaft TM 3 and the seventh shaft TM 7 may selectively become integral.

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

The second brake B 2 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 engagement elements of the first, second, and third clutches C 1 , C 2 , and C 3 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, however, it should 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 in a planetary gear train according to a first exemplary form of the present disclosure.

Referring to FIG. 2 , a planetary gear train according to a first exemplary form of the present disclosure realizes shifting by operating three elements among the three clutches C 1 , C 2 , and C 3 and the two brakes B 1 and B 2 .

[The Forward First Speed]

In the forward first speed D 1 , the first clutch C 1 and the first and second brakes B 1 and B 2 are simultaneously 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 torque of the input shaft IS is input to the second shaft TM 2 , and the first, fifth shaft TM 1 and TM 5 acts as a fixed element by the operation of the first and second brakes B 1 and B 2 , 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 D 2 , 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 with the sixth shaft TM 6 by the operation of the second clutch C 2 , the torque of the input shaft IS is input to the second shaft TM 2 , and the first, fifth shaft TM 1 and TM 5 acts as a fixed element by the operation of the first and second brakes B 1 and B 2 , 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 D 3 , the first and second clutch C 1 and C 2 and the second brake B 2 are simultaneously 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 third shaft TM 3 is connected with the sixth shaft TM 6 by the operation of the second clutch C 2 , the torque of the input shaft IS is input to the second shaft TM 2 , and the fifth shaft TM 5 acts as a fixed element by the operation of the second brake B 2 , 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 D 4 , 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 with the sixth shaft TM 6 by the operation of the second clutch C 2 , the third shaft TM 3 is connected with the seventh shaft TM 7 by the operation of the third clutch C 3 , the torque of the input shaft IS is input to the second shaft TM 2 , and the fifth shaft TM 5 acts as a fixed element by the operation of the second brake B 2 , 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 D 5 , the first and third clutches C 1 and C 3 and the second brake B 2 are simultaneously 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 third shaft TM 3 is connected with the seventh shaft TM 7 by the operation of the third clutch C 3 , the torque of the input shaft IS is input to the second shaft TM 2 , and the fifth shaft TM 5 acts as a fixed element by the operation of the second brake B 2 , 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 D 6 , the first, second, and third clutches C 1 , C 2 , and C 3 are simultaneously 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 third shaft TM 3 is connected with the sixth shaft TM 6 by the operation of the second clutch C 2 , the third shaft TM 3 is connected with the seventh shaft TM 7 by the operation of the third clutch C 3 , and the torque of the input shaft IS is input to the second shaft TM 2 , 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 D 7 , the first and third clutches C 1 and C 3 and the first brake B 1 are simultaneously 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 third shaft TM 3 is connected with the seventh shaft TM 7 by the operation of the third clutch C 3 , the torque of the input shaft IS is input to the second shaft TM 2 , and the first shaft TM 1 acts as a fixed element by the operation of the first brake B 1 , 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 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 with the sixth shaft TM 6 by the operation of the second clutch C 2 , the third shaft TM 3 is connected with the seventh shaft TM 7 by the operation of the third clutch C 3 , the torque of the input shaft IS is input to the second shaft TM 2 , and the first shaft TM 1 acts as a fixed element by the operation of the first brake B 1 , 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 Reverse Speed]

In the reverse speed REV, the third clutch C 3 and the first and second brakes B 1 and B 2 are simultaneously operated.

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

FIG. 3 is a schematic diagram of a planetary gear train according to a second exemplary form of the present disclosure. FIG. 4 is an operational chart for respective control elements at respective shift-stages in a planetary gear train according to a second exemplary form of the present disclosure.

In a planetary gear train according to a first exemplary form of the present disclosure shown in FIG. 1 , the third sun gear S 3 acts as the seventh rotational element N 7 and the third planet carrier PC 3 acts as the ninth rotational element N 9 . However, referring to FIG. 3 , the third planet carrier PC 3 acts as the seventh rotational element N 7 and the third sun gear S 3 acts as the ninth rotational element N 9 in a planetary gear train according to a second exemplary form.

That is, a planetary gear train according to the first and second exemplary form show that the seventh and ninth rotational element N 7 and N 9 are oppositely set and other cooperative relationship of other elements remains the same.

Referring to FIG. 2 and FIG. 4 , a planetary gear train according to first and second exemplary form realizes respective shift-stages in the same way by operation of the same engagements, which is therefore not described in further detail.

It may be understood that gear ratios or step ratios may have different values since the seventh and ninth rotational elements N 7 and N 9 are replaced with each other.

As described above, according to a planetary gear train according to an exemplary form of the present disclosure, at least eight forward speeds and at least one reverse speed may be realized by a combination of four planetary gear sets, two transfer gears, and control elements of three clutches and two brakes, 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 according to an exemplary form of the present disclosure, 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 desired gear ratio and to easily comply with desired performance for respective vehicles.

In addition, according to a planetary gear train according to an exemplary form of the present disclosure, a gear ratio span of more than 8.0 may be achieved while realizing at least eight forward speeds and at least one reverse speed, thereby increasing 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.

In addition, a planetary gear train according to an exemplary form of the present disclosure utilizes five engagement elements thereby reducing the number of parts employed to achieve the shift stages, and reduces the number of non-engaged elements thereby reducing a drag loss and enhancing efficiency and fuel economy.

While this present disclosure has been described in connection with what is presently considered to be practical exemplary forms, it is to be understood that the present disclosure is not limited to the disclosed forms, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

PG 1 , PG 2 , PG 3 , PG 4 : first, second, third, and fourth planetary gear sets

S 1 , S 2 , S 3 , S 4 : first, second, third, and fourth sun gears

PC 1 , PC 2 , PC 3 , PC 4 : first, second, third, and fourth planet carriers

R 1 , R 2 , R 3 , R 4 : first, second, third, and fourth ring gears

IS: input shaft

OS: output shaft

B 1 , B 2 : first and second brakes

C 1 , C 2 , C 3 : first, second, and third clutches

TF 1 , TF 2 : first and second transfer gears

TM 1 , TM 2 , TM 3 , TM 4 , TM 5 , TM 6 , TM 7 , TM 8 , TM 9 , TM 10 : first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, and tenth shafts