Planetary gear train of automatic transmission for vehicles

This application claims priority to and the benefit of Korean Patent Application No. 10-2017-0077691, filed on Jun. 20, 2017, which is incorporated herein by reference in its entirety.

The present disclosure relates to an automatic transmission for a vehicle. More particularly, the present disclosure relates to a planetary gear train of an automatic transmission of a vehicle that improves power delivery performance, reduces fuel consumption, and improves installability.

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 a 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 respect, an eight-speed automatic transmission has been recently introduced to perform more shift stages via planetary gear trains.

However, we have discovered that disclosed automatic transmissions of eight or more shift-stages includes a lot of 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 eight forward speeds and 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 a length.

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

A planetary gear train according to an exemplary form of the present disclosure may include 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, wherein the first rotational element is fixedly connected with the sixth rotational element, the second rotational element is fixedly connected with the input shaft, the third rotational element is fixedly connected with the seventh rotational element, the tenth rotational element is externally gear-meshed with the fifth rotational element, the eleventh rotational element is externally gear-meshed with the eighth rotational element and is fixedly connected with the output shaft, and first and second transfer gear units.

The first transfer gear unit is externally gear-meshed with the fifth rotational element and the tenth rotational element, and the second transfer gear unit is externally gear-meshed with the eighth rotational element and eleventh rotational element.

The fourth rotational element may be selectively connected with the second rotational element, the seventh rotational element, and the ninth rotational element respectively, and the sixth rotational element and the twelfth rotational element may be selectively connected with a transmission housing respectively.

An exemplary gear train may further include a first clutch arranged between the second rotational element and the fourth rotational element; a second clutch arranged between the third rotational element and the fourth rotational element; a third clutch arranged between the fourth rotational element and the ninth rotational element; a first brake arranged between the sixth rotational element and the transmission housing; and a second brake arranged between the twelfth rotational element and the transmission housing.

The first transfer gear unit is arranged between the fifth rotational element and the tenth rotational element; and the second transfer gear unit is arranged between the eighth rotational element and the eleventh rotational element.

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. 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 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 ratios 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 greater than 8.6 may be achieved while realizing eight forward speeds and 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 gear shift, an engine speed rhythmic sense, and the like.

In addition, the material cost can be reduced by applying the five control elements, and the drag loss can be reduced and the transmission efficiency (fuel economy) can be increased by reducing the non-operating control element at each gear range.

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 an exemplary form of the present disclosure; and

FIG. 2 is an operational chart for respective control elements at respective shift-stages in a planetary gear train according to an 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 following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

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 an 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 control elements including 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, so as to output 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, and are arranged in the order of first, third, and second planetary gear sets PG 1 , PG 3 , 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 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 double pinion planetary gear set, and includes a fourth sun gear S 4 , a fourth ring gear R 4 that is internally gear-meshed with a fourth pinion P 4 externally gear-meshed with the fourth sun gear S 4 , and a fourth planet carrier PC 4 that supports the fourth pinion P 4 . The fourth sun gear S 4 acts as a tenth rotational element N 10 , the fourth ring gear R 4 acts as an eleventh rotational element N 11 , and the fourth planet carrier PC 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 fixedly connected with the sixth rotational element N 6 , the third rotational element N 3 is fixedly connected with the seventh rotational element N 7 , by corresponding shaft selected from 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 is fixedly connected with the first rotational element N 1 (first sun gear S 1 ) and the sixth rotational element N 6 (second ring gear R 2 ), and is selectively connected with a transmission housing H, thereby selectively acting as a fixed element.

The second shaft TM 2 is fixedly connected with the second rotational element N 2 (first planet carrier PC 1 ) and is 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 ) and the seventh rotational element S 3 .

The fourth TM 4 is fixedly connected with the fourth rotational element N 4 (second sun gear S 2 ), and is selectively connected with the second and third shafts TM 2 and TM 3 respectively.

The fifth shaft TM 5 is fixedly connected with the fifth rotational element N 5 (second planet carrier PC 2 ).

The sixth shaft TM 6 is fixedly connected with the eighth rotational element N 8 (third planet carrier PC 3 ).

The seventh shaft TM 7 is fixedly connected with ninth rotational element N 9 (third ring gear R 3 ), is selectively connected with the fourth shaft TM 4 .

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 fifth shaft TM 5 .

The ninth shaft TM 9 is fixedly connected with the eleventh rotational element N 11 (fourth ring gear R 4 ), externally gear-meshed with the sixth shaft TM 6 , and is 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 planet carrier PC 4 ), and is selectively connected with the transmission housing H thereby selectively acting as a fixed element.

The two transfer gears TF 1 and TF 2 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 , in a reverse rotation.

The first transfer gear TF 1 includes a first transfer drive gear TF 1 a fixedly connected with the fifth shaft TM 5 and a first transfer driven gear TF 1 b connected with the eighth shaft TM 8 , and externally gear-meshes the fifth shaft TM 5 and the eighth shaft TM 8 .

The second transfer gear TF 2 includes a second transfer drive gear TF 2 a fixedly connected with the sixth shaft TM 6 and a second transfer driven gear TF 2 b fixedly connected with the ninth shaft TM 9 , and externally gear-meshes the sixth shaft TM 6 and the ninth shaft TM 9 .

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.

Here, each of the ten shafts TM 1 to TM 10 may be a rotational member that fixedly connects 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 rotated members that selectively connect the rotational elements to the transmission housing H, or may be a fixed members that fix the rotational elements to the transmission housing H.

In addition, in the above description, the term “fixedly connected” or similar term means that a plurality of rotational elements including the input and output shafts, which are connected through the corresponding shafts, and the corresponding shaft are connected so as to always rotate together such that a plurality of fixedly connected rotational elements and corresponding shafts may rotate in the same rotation direction and/or same number of revolutions.

In addition, in the above description, the term “selectively connected” or similar terms means that a plurality of shafts, including an input and output shafts, are connected to each other through coupling elements, or the corresponding shaft is fixedly connected to the transmission housing via a coupling element. Once connected, the connected shafts and/or rotational elements may rotate in the same rotation direction and/or same number of revolution (i.e., rotation speed).

For example, when the coupling element operates to selectively connect two shafts to each other, the two shafts may rotate in the same rotation direction with same number of revolutions. Conversely, when the coupling element is released, the connection of the two shafts is released.

Further, when the coupling element operates to selectively connect the corresponding shaft and the transmission housing, the corresponding shaft is fixedly connected to the transmission housing. Conversely, when the coupling element is released, the corresponding shaft is in a rotatable state.

The control 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 fourth shaft TM 4 , such that the second shaft TM 2 and the fourth shaft TM 4 may selectively become integral.

The second clutch C 2 is arranged between the third shaft TM 3 and the fourth shaft TM 4 , such that the third shaft TM 3 and the fourth shaft TM 4 may selectively become integral.

The third clutch C 3 is arranged between the fourth shaft TM 4 and the seventh shaft TM 7 , such that the fourth shaft TM 4 and the seventh shaft TM 7 may selectively 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 tenth shaft TM 10 and the transmission housing H, such that the tenth shaft TM 10 may selectively act as a fixed element.

The respective control 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. Meanwhile, the control element is any of a dog clutch, an electric clutch, and a magnetic particle clutch, the like which may be automatically controlled, and may be adopted.

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

Referring to FIG. 2 , a planetary gear train according to an exemplary form of the present disclosure realizes shifting by operating three control 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 shift-stage 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 fourth shaft TM 4 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 first and tenth shafts TM 1 and TM 10 act as fixed elements 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 shift-stage 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 fourth shaft TM 4 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 first and tenth shafts TM 1 and TM 10 act as fixed elements 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 shift-stage D 3 , the first and second clutches 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 fourth shaft TM 4 by the operation of the first clutch C 1 , and the third shaft TM 3 is connected with the fourth shaft TM 4 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 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 shift-stage D 4 , the second and third first clutch 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 fourth shaft TM 4 by the operation of the second clutch C 2 , and the fourth shaft TM 4 is connected with the seventh shaft TM 7 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 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 shift-stage 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 fourth shaft TM 4 by the operation of the first clutch C 1 , and the fourth shaft TM 4 is connected with the seventh shaft TM 7 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 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 shift-stage 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 fourth shaft TM 4 by the operation of the first clutch C 1 , the third shaft TM 3 is connected with the fourth shaft TM 4 by the operation of the second clutch C 2 , and the fourth shaft TM 4 is connected with the seventh shaft TM 7 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 sixth speed that outputs a torque as inputted, 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 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 fourth shaft TM 4 by the operation of the first clutch C 1 , and the fourth shaft TM 4 is connected with the seventh shaft TM 7 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 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 shift-stage 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 fourth shaft TM 4 by the operation of the second clutch C 2 , and the fourth shaft TM 4 is connected with the seventh shaft TM 7 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 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, the third clutch C 3 and first and second brakes B 1 and B 2 are simultaneously operated.

As a result, the fourth shaft TM 4 is connected with the seventh shaft TM 7 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 first and tenth shafts TM 1 and TM 10 act 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 shifted torque to the output shaft OS connected with the ninth shaft TM 9 .

As described above, according to a planetary gear train according to an exemplary form of the present disclosure, eight forward speeds and one reverse speed may be realized by a combination of four planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , two transfer gears TF 1 and TF 2 , 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 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 greater than 8.6 may be achieved while realizing eight forward speeds and 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 gear shift, an engine speed rhythmic sense, and the like.

In addition, the material cost can be reduced by applying the five control elements, and the drag loss can be reduced and the transmission efficiency (fuel economy) can be increased by reducing the non-operating control element at each gear range.

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 present disclosure.

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

61 , 62 . . . 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