Planetary gear train of automatic transmission for vehicle

This application claims the benefit of Korean Patent Application No. 10-2015-0129855, filed on Sep. 14, 2015, the contents of which are incorporated herein by reference in its entirety.

The present disclosure relates to a planetary gear train of 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.

In recent years, a rise in oil price causes dashing into unlimited competition for enhancing fuel efficiency.

As a result, research into reduction of weight and the enhancement of fuel efficiency through downsizing is conducted in the case of an engine and research for simultaneously securing operability and fuel efficiency competitiveness through multiple speed stages are conducted in the case of an automatic transmission.

However, in the automatic transmission, as the number of speed stages increases, the number of internal components increase, and as a result, mountability, cost, weight, transmission efficiency, and the like may still deteriorate.

Accordingly, development of a planetary gear train which may bring about improved efficiency with a small number of components may further increase fuel efficiency through the multiple speed stages.

In this aspect, in recent years, 8-speed automatic transmission tends to be implemented and the research and development of a planetary gear train capable of implementing more speed stages has also been actively conducted.

Since a span of gear ratios of the recent 8-speed automatic transmission is 6.5 to 7.5, the 8-speed automatic transmission has no great effect for improving fuel efficiency.

In addition, since step ratios between speed stages may not be increased or decreased linearly in a case in which a span of gear ratios of the 8-speed automatic transmission, driving efficiency of an engine and drivability of a vehicle may be deteriorated.

The present disclosure has been made in an effort to provide a planetary gear train of an automatic transmission for a vehicle that improves power delivery performance and fuel efficiency by achieving nine forward speed stages and one reverse speed stage using a minimum number of constituent elements, by enlarging a span of gear ratios, and by linearly increasing or decreasing step ratios between speed stages.

One form of the present disclosure provides a planetary gear train of an automatic transmission for a vehicle that may include an input shaft receiving torque of an engine; an output shaft outputting changed torque; a first planetary gear set including first, second, and third rotation elements; a second planetary gear set including fourth, fifth, and sixth rotation elements; a third planetary gear set including seventh, eighth, and ninth rotation elements; a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements; and six friction elements disposed between at least one rotation element among the twelve rotation elements and another rotation element or a transmission housing, wherein the input shaft is continuously connected to the second rotation element and selectively connected to the twelfth rotation element, the output shaft is continuously connected to the eleventh rotation element, the first rotation element is continuously connected to the fourth rotation element, the fifth rotation element is continuously connected to the eighth rotation element, the sixth rotation element is continuously connected to the tenth rotation element, the ninth rotation element is continuously connected to the eleventh rotation element, three friction elements among the six friction elements are operated at each speed stage.

The second rotation element may be is selectively connected to the seventh rotation element, the fourth rotation element may be selectively connected to the seventh rotation element, the third rotation element may be selectively connected to the eighth rotation element, the first rotation element may be selectively connected to the transmission housing, the sixth rotation element may be selectively connected to the transmission housing.

A sun gear, a planet carrier, and a ring gear of the first planetary gear set may be set as the first, second, and third rotation elements, a sun gear, a planet carrier, and a ring gear of the second planetary gear set may be set as the fourth, fifth, and sixth rotation elements, a sun gear, a planet carrier, and a ring gear of the third planetary gear set may be set as the seventh, eighth, and ninth rotation elements, and a sun gear, a planet carrier, and a ring gear of the fourth planetary gear set may be set as the tenth, eleventh, and twelfth rotation elements.

Another form of the present disclosure provides a planetary gear train of an automatic transmission for a vehicle that may include an input shaft receiving torque of an engine; an output shaft outputting changed torque; a first planetary gear set including first, second, and third rotation elements; a second planetary gear set including fourth, fifth, and sixth rotation elements; a third planetary gear set including seventh, eighth, and ninth rotation elements; a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements; a first rotation shaft engaging the first rotation element and the fourth rotation element and selectively connected to the transmission housing; a second rotation shaft engaging the second rotation element and directly connected to the input shaft; a third rotation shaft engaging the third rotation element; a fourth rotation shaft engaging the fifth rotation element and the eighth rotation element and selectively connected to the third rotation shaft; a fifth rotation shaft engaging the sixth rotation element and the tenth rotation element and selectively connected to the transmission housing; a sixth rotation shaft engaging the seventh rotation element and selectively connected to the first rotation shaft and the second rotation shaft; a seventh rotation shaft engaging the ninth rotation element and the eleventh rotation element and directly connected to the output shaft; and an eighth rotation shaft engaging the twelfth rotation element and selectively connected to the second rotation shaft and the input shaft.

The first planetary gear set may be a single pinion planetary gear set and may include a first sun gear that is the first rotation element, a first planet carrier that is the second rotation element, and a first ring gear that is the third rotation element, the second planetary gear set may be a single pinion planetary gear set and may include a second sun gear that is the fourth rotation element, a second planet carrier that is the fifth rotation element, and a second ring gear that is the sixth rotation element, the third planetary gear set may be a single pinion planetary gear set and may include a third sun gear that is the seventh rotation element, a third planet carrier that is the eighth rotation element, and a third ring gear that is the ninth rotation element, and the fourth planetary gear set may be a single pinion planetary gear set and may include a fourth sun gear that is the tenth rotation element, a fourth planet carrier that is the eleventh rotation element, and a fourth ring gear that is the twelfth rotation element.

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

A first forward speed stage may be achieved by operation of the second and third clutches and the second brake, a second forward speed stage may be achieved by operation of the third and fourth clutches and the second brake, a third forward speed stage may be achieved by operation of the second and fourth clutches and the second brake, a fourth forward speed stage may be achieved by operation of the first and second clutches and the second brake, a fifth forward speed stage may be achieved by operation of the first, second and third clutches, a sixth forward speed stage may be achieved by operation of the first and second clutches and the first brake, a seventh forward speed stage may be achieved by operation of the first and fourth clutches and the first brake, an eighth forward speed stage may be achieved by operation of the second and fourth clutches and the first brake, a ninth forward speed stage may be achieved by operation of the third and fourth clutches and the first brake, a reverse speed stage may be achieved by operation of the second clutch and the first and second brakes.

Still another form of the present disclosure provides a planetary gear train of an automatic transmission for a vehicle that may include an input shaft receiving torque of an engine; an output shaft outputting changed torque; a first planetary gear set including a first sun gear, a first planet carrier, and a first ring gear; a second planetary gear set including a second sun gear, a second planet carrier, and a second ring gear; a third planetary gear set including a third sun gear, a third planet carrier, and a third ring gear; a fourth planetary gear set including a fourth sun gear, a fourth planet carrier, and a fourth ring gear; a first rotation shaft engaging the first sun gear and the second sun gear and selectively connected to a transmission housing; a second rotation shaft engaging the first planet carrier and directly connected to the input shaft; a third rotation shaft engaging the first ring gear; a fourth rotation shaft engaging the second planet carrier and the third planet carrier and selectively connected to the third rotation shaft; a fifth rotation shaft engaging the second ring gear and the fourth sun gear and selectively connected to the transmission housing; a sixth rotation shaft engaging the third sun gear and selectively connected to the first rotation shaft and the second rotation shaft; a seventh rotation shaft engaging the third ring gear and the fourth planet carrier directly connected to the output shaft; an eighth rotation shaft engaging the fourth ring gear and selectively connected to the second rotation shaft and the input shaft; and six friction elements disposed between at least one rotation shaft among the eight rotation shafts and another rotation shaft or the transmission housing.

Each of the first, second, third, and fourth planetary gear sets may be a single pinion planetary gear set.

The six friction elements may include a first clutch disposed between the input shaft and the eighth rotation shaft; a second clutch disposed between the second rotation shaft and the sixth rotation shaft; a third clutch disposed between the first rotation shaft and the sixth rotation shaft; a fourth clutch disposed between the third rotation shaft and the fourth rotation shaft; a first brake disposed between the first rotation shaft and the transmission housing; and a second brake disposed between the fifth rotation shaft and the transmission housing.

A first forward speed stage may be achieved by operation of the second and third clutches and the second brake, a second forward speed stage may be achieved by operation of the third and fourth clutches and the second brake, a third forward speed stage may be achieved by operation of the second and fourth clutches and the second brake, a fourth forward speed stage may be achieved by operation of the first and second clutches and the second brake, a fifth forward speed stage may be achieved by operation of the first, second and third clutches, a sixth forward speed stage may be achieved by operation of the first and second clutches and the first brake, a seventh forward speed stage may be achieved by operation of the first and fourth clutches and the first brake, an eighth forward speed stage may be achieved by operation of the second and fourth clutches and the first brake, a ninth forward speed stage may be achieved by operation of the third and fourth clutches and the first brake, a reverse speed stage may be achieved by operation of the second clutch and the first and second brakes.

One form of the present disclosure may achieve nine forward speed stages and one reverse speed stage by combining four planetary gear sets that are simple planetary gear sets with six friction elements.

In addition, engine driving efficiency may be increased by achieving a span of gear ratios to be greater than or equal to 9.0.

In addition, drivability such as acceleration before and after the shift and timing of engine speed may be improved by linearly increasing or decreasing step ratios between speed stages.

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 one form of the present disclosure; and

FIG. 2 is an operation chart of friction elements at each speed stage in the planetary gear train according to one 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.

In the following description, dividing names of components into first, second, and the like is to divide the names because the names of the components are the same as each other and an order thereof is not particularly limited.

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

Referring to FIG. 1 , a planetary gear train according to one form of the present disclosure includes first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 disposed on the same axis, an input shaft IS, an output shaft OS, eight rotations shafts TM 1 to TM 8 engaging at least one rotation elements of the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , six friction elements C 1 to C 4 and B 1 to B 2 , and a transmission housing H.

As a result, torque input from the input shaft IS is changed by cooperation of the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 , and the changed torque is output through the output shaft OS.

The planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 are disposed sequentially from an engine side.

The input shaft IS is an input member and power from a crankshaft of an engine is converted through a torque converter to be an input into the input shaft IS.

The output shaft OS is an output member, is disposed in parallel with the input shaft IS, and transmits driving torque to a driving wheel through a differential apparatus.

The first planetary gear set PG 1 is a single pinion planetary gear set and includes a first sun gear S 1 of a first rotation element N 1 , a first planet carrier PC 1 of a second rotation element N 2 rotatably supporting a first pinion P 1 externally engaged the first sun gear S 1 , and a first ring gear R 1 of a third rotation element N 3 internally engaged with the first pinion P 1 .

The second planetary gear set PG 2 is a single pinion planetary gear set and includes a second sun gear S 2 of a fourth rotation element N 4 , a second planet carrier PC 2 of a fifth rotation element N 5 rotatably supporting a second pinion P 2 externally engaged the second sun gear S 2 , and a second ring gear of a sixth rotation element N 6 internally engaged with the second pinion P 2 .

The third planetary gear set PG 3 is a single pinion planetary gear set and includes a third sun gear S 3 of a seventh rotation element N 7 , a third planet carrier PC 3 of an eighth rotation element N 8 rotatably supporting a third pinion P 3 externally engaged with the third sun gear S 3 , and a third ring gear R 3 of a ninth rotation element N 9 internally engaged with the third pinion P 3 .

The fourth planetary gear set PG 4 is a single pinion planetary gear set and includes a fourth sun gear S 4 of a tenth rotation element N 10 , a fourth planet carrier PC 4 of an eleventh rotation element N 11 rotatably supporting a fourth pinion P 4 externally engaged with the fourth sungear S 4 , and a fourth ring gear R 4 of a twelfth rotation element N 12 internally engaged with the fourth pinion P 4 .

The first rotation element N 1 is directly connected to the fourth rotation element N 4 , the fifth rotation element N 5 is directly connected to the eighth rotation element N 8 , the sixth rotation element N 6 is directly connected to the tenth rotation element N 10 , the ninth rotation element N 9 is directly connected to the eleventh rotation element N 11 , and the first, second, third, and fourth planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 are operated with eight rotation shafts TM 1 to TM 8 .

The eight rotation shafts TM 1 to TM 8 will be described in further detail.

The first rotation shaft TM 1 engages the first rotation element N 1 , and the fourth rotation element N 4 .

The second rotation shaft TM 2 engages the second rotation element N 2 , and is directly connected to the input shaft IS so as to be always operated as an input element.

The third rotation shaft TM 3 engages the third rotation element N 3 .

The fourth rotation shaft TM 4 engages the fifth rotation element N 5 and the eighth rotation element N 8 , and is selectively connected to the third rotation shaft TM 3 .

The fifth rotation shaft TM 5 engages the sixth rotation element N 6 and the tenth rotation element N 10 , and is selectively connected to the transmission housing H.

The sixth rotation shaft TM 6 engages the seventh rotation element N 7 , is selectively connected to the first rotation shaft TM 1 and the second first rotation shaft TM 2 .

The seventh rotation shaft TM 7 engages the ninth rotation element N 9 and the eleventh rotation element N 11 , and is directly connected to the output shaft OS so as to be always operated as an output element.

The eighth rotation shaft TM 8 engages the twelfth rotation element N 12 , and is selectively connected to the input shaft IS.

In addition, four clutches C 1 , C 2 , C 3 , and C 4 which are friction elements are disposed at connection portions between any two rotation shafts.

In addition, two brakes B 1 and B 2 which are friction elements are disposed at connection portions between any one rotation shaft and the transmission housing H.

The six friction elements C 1 to C 4 and B 1 to B 2 will be described in further detail.

The first clutch C 1 is disposed between the input shaft IS and the eighth rotation shaft TM 8 and selectively connects the input shaft IS and the eighth rotation shaft TM 8 .

The second clutch C 2 is disposed between the second rotation shaft TM 2 and the sixth rotation shaft TM 6 and selectively connects the second rotation shaft TM 2 and the sixth rotation shaft TM 6 .

The third clutch C 3 is disposed between the first rotation shaft TM 1 and the sixth rotation shaft TM 6 and selectively connects the first rotation shaft TM 1 and the sixth rotation shaft TM 6 .

The fourth clutch C 4 is disposed between the third rotation shaft TM 3 and the fourth rotation shaft TM 4 and selectively connects the third rotation shaft TM 3 and the fourth rotation shaft TM 4 .

The first brake B 1 is disposed between the first rotation shaft TM 1 and the transmission housing H and causes the first rotation shaft TM 1 to be operated as a selective fixed element.

The second brake B 2 is disposed between the fifth rotation shaft TM 5 and the transmission housing H and causes the fifth rotation shaft TM 5 to be operated as a selective fixed element.

The friction elements including the first, second, third, and fourth clutches C 1 , C 2 , C 3 , and C 4 and the first and second brakes B 1 and B 2 may be multi-plates friction elements of wet type that are operated by hydraulic pressure.

FIG. 2 is an operation chart of friction elements at each speed stage in the planetary gear train according to one form of the present disclosure.

As shown in FIG. 2 , three friction elements are operated at each speed stage in the planetary gear train according to a form of the present disclosure. Shifting processes in one form of the present disclosure will be described in further detail.

If the second and third clutches C 2 and C 3 and the second brake B 2 are operated at a first forward speed stage D 1 , the sixth rotation shaft TM 6 is connected to the second rotation shaft TM 2 and the first rotation shaft TM 1 , rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , and the fifth rotation shaft TM 5 is operated as the fixed element. Therefore, the first forward speed stage is achieved.

If the third and fourth clutches C 3 and C 4 and the second brake B 2 are operated at a second forward speed stage D 2 , the first rotation shaft TM 1 is connected to the sixth rotation shaft TM 6 , the third rotation shaft TM 3 is connected to the fourth rotation shaft TM 4 , rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , and the fifth rotation shaft TM 5 is operated as the fixed element. Therefore, the second forward speed stage is achieved.

If the second and fourth clutches C 2 and C 4 and C 4 and the second brake B 2 are operated at a third forward speed stage D 3 , the second rotation shaft TM 2 is connected to the sixth rotation shaft TM 6 , rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , and the fifth rotation shaft TM 5 is operated as the fixed element. Therefore, the third forward speed stage is achieved.

If the first and second clutches C 1 and C 2 and the second brake B 2 are operated at a fourth forward speed stage D 4 , the input shaft IS is connected to the eighth rotation shaft TM 8 , the second rotation shaft TM 2 is connected to the sixth rotation shaft TM 6 , rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , and the fifth rotation shaft TM 5 is operated as the fixed element. Therefore, the fourth forward speed stage is achieved.

If the first, second and third clutches C 1 , C 2 , and C 3 are operated at a fifth forward speed stage D 5 , the input shaft IS is connected to the eighth rotation shaft TM 8 , the sixth rotation shaft TM 6 is connected to the second rotation shaft TM 2 and the first rotation shaft TM 1 . Therefore, all the planetary gear sets become direct-coupling states. At this state, if rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , the fifth forward speed stage is achieved. At the fifth forward speed stage, rotation speed that is the same as that of the input shaft IS is output.

If the first and second clutches C 1 and C 2 and the first brake B 1 are operated at a sixth forward speed stage D 6 , the input shaft IS is connected to the eighth rotation shaft TM 8 , the second rotation shaft TM 2 is connected to the sixth rotation shaft TM 6 , rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , and the first rotation shaft TM 1 is operated as the fixed element. Therefore, the sixth forward speed stage is achieved.

If the first and fourth clutches C 1 and C 4 and the first brake B 1 are operated at a seventh forward speed stage D 7 , the input shaft IS is connected to the eighth rotation shaft TM 8 , the third rotation shaft TM 3 is connected to the fourth rotation shaft TM 4 , rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , and the first rotation shaft TM 1 is operated as the fixed element. Therefore, the seventh forward speed stage is achieved.

If the second and fourth clutches C 2 and C 4 and the first brake B 1 are operated at an eighth forward speed stage D 8 , the second rotation shaft TM 2 is connected to the sixth rotation shaft TM 6 , the third rotation shaft TM 3 is connected to the fourth rotation shaft TM 4 , rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , and the first rotation shaft TM 1 is operated as the fixed element. Therefore, the eighth forward speed stage is achieved.

If the third and fourth clutches C 3 and C 4 and the first brake B 1 B 2 are operated at a ninth forward speed stage D 9 , the first rotation shaft TM 1 is connected to the sixth rotation shaft TM 6 , the third rotation shaft TM 3 is connected to the fourth rotation shaft TM 4 , rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , and the first rotation shaft TM 1 is operated as the fixed element. Therefore, the ninth forward speed stage is achieved.

If the second clutch C 2 and first and second brakes B 1 and B 2 are operated at a reverse speed stage REV, the second rotation shaft TM 2 is connected to the sixth rotation shaft TM 6 , rotation speed of the input shaft IS is input to the second rotation shaft TM 2 , and the first rotation shaft TM 1 and the fifth rotation shaft TM 5 are operated as the fixed elements. Therefore, the reverse speed stage is achieved.

The planetary gear train according to one form of the present disclosure may achieve nine forward speed stages and one reverse speed stage by controlling four planetary gear sets PG 1 , PG 2 , PG 3 , and PG 4 with four clutches C 1 , C 2 , C 3 , and C 4 and two brakes B 1 and B 2 .

In addition, step ratios between speed stages are 1.2 or more except for between the sixth and seventh forward speed stages and between the eighth and ninth forward speed stages and linearity of step ratios between speed stages can be secured. Thus, drivability such as acceleration before and after the shift and timing of engine speed may be improved.

In addition, engine driving efficiency may be maximized by achieving a span of gear ratios to be greater than or equal to 9.0.

The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.