Planetary gear train of automatic transmission for vehicles

A planetary gear train of an automatic transmission 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 shaft connecting the first rotation element and the fourth rotation element; a second shaft connected with the second rotation element and connected with the input shaft; a third shaft connecting the third rotation element and the fifth rotation element; a fourth shaft connecting the sixth rotation element and the ninth rotation element; a fifth shaft connecting the eighth rotation element and the twelfth rotation element; and a sixth shaft connected with the tenth rotation element.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2016-0088622 filed on Jul. 13, 2016, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an automatic transmission for the vehicle. More particularly, the present invention relates to a planetary gear train of an automatic transmission for a vehicle that improves power delivery performance and fuel efficiency by achieving at least ten forward speeds and widening speed ratio with a minimum number of constituent elements being used, and secures linearity of step ratios.

Description of Related Art

In the field of an automatic transmission, more multiplicity of shift-stages is useful technology for enhancement of fuel consumption and drivability of a vehicle. Recently increase of oil price is triggering a hard competition in enhancing fuel consumption of a vehicle.

In this sense, research on an engine has been undertaken to achieve weight reduction and to enhance fuel consumption by so-called downsizing and 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, especially the number of planetary gear sets, is typically increased, which may deteriorate installability, production cost, weight and/or power flow efficiency.

Therefore, development of a planetary gear train capable of achieving maximum efficiency by minimum number of parts is substantially beneficial for maximizing improvement of fuel consumption by multiple shift-stages of an automatic transmission.

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 seven 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, since a conventional 8-speed automatic transmission has gear ratio span of 6.5-7.5 (gear ratio span is an important factor for securing linearity of step ratios), improvement of power performance and fuel economy may not be great. In addition, if 8-speed automatic transmission has gear ratio span larger than 9.0, it is hard to secure linearity of step ratios. Therefore, driving efficiency of an engine and drivability of a vehicle may be deteriorated, and thus, development of high efficiency automatic transmissions which achieve at least nine forward speed stages is necessary.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a planetary gear train of an automatic transmission for the vehicle that improves power delivery performance and fuel efficiency by achieving ten forward speeds and one reverse speed using a minimum number of constituent elements, by enlarging a span of gear ratios, and by almost linearly increasing or decreasing step ratios between transmission steps.

A planetary gear train of an automatic transmission for the vehicle according to an exemplary embodiment of the present invention may include, an input shaft receiving torque of an engine; an output shaft outputting changed torque; a first planetary gear set including a first rotation element, a second rotation element, and a third rotation element, a second planetary gear set including a fourth rotation element, a fifth rotation element, and a sixth rotation element, a third planetary gear set including a seventh rotation element, an eighth rotation element, and a ninth rotation element, a fourth planetary gear set including a tenth rotation element, an eleventh rotation element, and a twelfth rotation element, a first shaft connecting the first rotation element and the fourth rotation element, a second shaft connected with the second rotation element and connected with the input shaft; a third shaft connecting the third rotation element and the fifth rotation element, a fourth shaft connecting the sixth rotation element and the ninth rotation element, a fifth shaft connecting the eighth rotation element and the twelfth rotation element, and a sixth shaft connected with the tenth rotation element.

The planetary gear train may further include, a seventh shaft connected with the seventh rotation element, and selectively connectable with the third shaft and the sixth shaft respectively, and an eighth shaft connected with the eleventh rotation element, and connected with the output shaft, wherein the first, third, and fourth shafts are selectively connectable with a transmission housing respectively, the second shaft is selectively connectable with the sixth shaft, and the third shaft is selectively connectable with the fifth shaft.

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

The first, second, third, and fourth planetary gear sets may be disposed in a sequence of the first, second, third, and fourth planetary gear sets from an engine side.

The planetary gear train may further include, a first clutch selectively connecting the second shaft and the sixth shaft, a second clutch selectively connecting the third shaft and fifth shaft, a third clutch selectively connecting the third shaft and the seventh shaft, a fourth clutch selectively connecting the sixth shaft and the seventh shaft; a first brake selectively connecting the first shaft and the transmission housing; a second brake selectively connecting the third shaft and the transmission housing; and a third brake selectively connecting the fourth shaft and the transmission housing.

An exemplary embodiment of the present invention may achieve at least ten forward speeds and one reverse speed by combining four planetary gear sets being simple planetary gear sets with seven control elements.

In addition, a planetary gear train according to an exemplary embodiment of the present invention may realize a gear ratio span of more than 9.0, thereby maximizing efficiency of driving an engine.

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.

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

DETAILED DESCRIPTION

Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to drawings.

However, parts which are not related with the description are omitted for clearly describing the exemplary embodiments of the present invention and like reference numerals refer to like or similar elements throughout the specification.

FIG. 1is a schematic diagram of a planetary gear train according to an exemplary embodiment of the present invention.

Referring toFIG. 1, a planetary gear train according to various exemplary embodiments of the present invention includes first, second, third, and four planetary gear sets PG1, PG2, PG3, and PG4arranged on a same axis, an input shaft IS, an output shaft OS, eight shafts TM1to TM8interconnecting rotation elements of the first, second, third, and four planetary gear sets PG1, PG2, PG3, and PG4, four clutches C1to C4and three brakes B1to B3as control elements, and a transmission housing H.

Torque input from the input shaft IS is shifted by cooperative operation of the first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, and then output through the output shaft OS.

The planetary gear sets are arranged in the order of first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, from an engine side.

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, 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 PG1is a single pinion planetary gear set and includes a first sun gear S1, a first planet carrier PC1rotatably supporting a first pinion P1that is externally meshed with the first sun gear S1, and a first ring gear R1that is internally meshed with the first pinion P1respectively as first, second, and third rotation elements N1, N2, and N3.

The second planetary gear set PG2is a single pinion planetary gear set and includes a second sun gear S2, a second planet carrier PC2rotatably supporting a second pinion P2that is externally meshed with the second sun gear S2, and a second ring gear R2that is internally meshed with the second pinion P2respectively as fourth, fifth, and sixth rotation elements N4, N5, and N6.

The third planetary gear set PG3is a single pinion planetary gear set and includes a third sun gear S3, a third planet carrier PC3rotatably supporting a third pinion P3that is externally meshed with the third sun gear S3, and a third ring gear R3that is internally meshed with the third pinion P3respectively as seventh, eighth, and ninth rotation elements N7, N8, and N9.

The fourth planetary gear set PG4is a single pinion planetary gear set and includes a fourth sun gear S4, a fourth planet carrier PC4rotatably supporting a fourth pinion P4that is externally meshed with the fourth sun gear S4, and a fourth ring gear R4that is internally meshed with the fourth pinion P4respectively as tenth, eleventh, and twelfth rotation elements N10, N11, and N12.

In the first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4, the first rotation element N1is directly connected to the fourth rotation element N4, the third rotation element N3is directly connected to the fifth rotation element N5, the sixth rotation element N6is directly connected to the ninth rotation element N9, and the eighth rotation element N8is directly connected to the twelfth rotation element N12, such that the first, second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4are operated while having a total of eight shafts TM1to TM8.

The eight shafts TM1to TM8will be described in further detail.

The eight shafts TM1to TM8directly connects a plurality of rotation elements among the rotation elements of the planetary gear sets PG1, PG2, PG3, and PG4, are rotation members that are directly connected to any one rotation element of the planetary gear sets PG1, PG2, PG3, and PG4and rotate with the any one rotation element to transmit torque, or are rotation members that selectively connect any one rotation element of the planetary gear sets PG1, PG2, PG3, and PG4to the transmission housing H to fix the any one rotation element.

The first shaft TM1connects the first rotation element N1(first sun gear S1) and the fourth rotation element N4(second sun gear S2), and is selectively connectable with the transmission housing H.

The second shaft TM2is connected with the second rotation element N2(first planet carrier PC1) and is directly connected with the input shaft IS so as to always be operated as an input element.

The third shaft TM3connects the third rotation element N3(first ring gear R1) and the fifth rotation element N5(second planet carrier PC2), and is selectively connectable with the transmission housing H.

The fourth shaft TM4connects the sixth rotation element N6(second ring gear R2) and the ninth rotation element N9(third ring gear R3), and is selectively connectable with the transmission housing H.

The fifth shaft TM5connects the eighth rotation element N8(third planet carrier PC3) and the twelfth rotation element N12(fourth ring gear R4), and is selectively connectable with the third shaft TM3.

The sixth shaft TM6is connected with the tenth rotation element N10(fourth sun gear S4), and is selectively connectable with the second shaft TM2.

The seventh shaft TM7is connected with the seventh rotation element N7(third sun gear S3), and is selectively connectable with the third shaft TM3and the sixth shaft TM6respectively.

The eighth shaft TM8is connected with the eleventh rotation element N11(fourth planet carrier PC4), and is directly connected with the output shaft OS so as to always be operated as an output element.

In addition, four clutches C1, C2, C3, and C4are disposed at portions at which any two shafts among the eight shafts TM1to TM8including the input shaft IS and the output shaft OS are selectively connected to each other.

In addition, three brakes B1, B2, and B3are disposed at portions at which any one shaft among the eight shafts TM1to TM8is selectively connectable to a transmission housing H.

Arrangements of the four clutches C1to C4and the three brakes B1to B3are described in detail.

The first clutch C1is disposed between the second shaft TM2and the sixth shaft TM6, and selectively connects the second shaft TM2and the sixth shaft TM6.

The second clutch C2is disposed between the third shaft TM3and the fifth shaft TM5, and selectively connects the third shaft TM3and the fifth shaft TM5.

The third clutch C3is disposed between the third shaft TM3and the seventh shaft TM7, and selectively connects the third shaft TM3and the seventh shaft TM7.

The fourth clutch C4is disposed between the sixth shaft TM6and the seventh shaft TM7, and selectively connects the sixth shaft TM6and the seventh shaft TM7.

The first brake B1is disposed between the first shaft TM1and a transmission housing H, and selectively connects the first shaft TM1with a transmission housing H.

The second brake B2is disposed between the third shaft TM3and a transmission housing H, and selectively connects the third shaft TM3with a transmission housing H.

The third brake B3is disposed between the fourth shaft TM4and a transmission housing H, and selectively connects the fourth shaft TM4with a transmission housing H.

The control elements including the first, second, third, and fourth clutches C1, C2, C3, and C4and the first, second, third, and three brakes B1, B2, and B3may be multi-plates friction elements of wet type that are operated by hydraulic pressure.

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

Referring toFIG. 2, three control elements among the first, second, third, and fourth clutches C1, C2, C3, and C4and the first, second, and third brakes B1, B2, and B3that are control elements are operated at each speed stage in the planetary gear train according to the exemplary embodiment of the present invention. The exemplary embodiment of the present invention can achieve one reverse speed and ten forward speeds.

The third and fourth clutches C3and C4and the third brake B3are simultaneously operated at a first forward speed D1.

In a state that the third shaft TM3is connected to the seventh shaft TM7by the operation of the third clutch C3and the sixth shaft TM6is connected to the seventh shaft TM7by the operation of the fourth clutch C4, the torque of the input shaft IS is input to the second shaft TM2.

In addition, the fourth shaft TM4is operated as the fixed elements by the operation of the third brake B3. Therefore, the torque of the input shaft IS is shifted into the first forward speed, and the first forward speed is output to the output shaft OS connected to the eighth shaft TM8.

The first and third clutches C1and C3and the third brake B3are simultaneously operated at a second forward speed D2.

In a state that the second shaft TM2is connected to the sixth shaft TM6by the operation of the first clutch C1and the third shaft TM3is connected to the seventh shaft TM7by the operation of the third clutch C3, the torque of the input shaft IS is input to the second shaft TM2and the sixth shaft TM6.

In addition, the fourth shaft TM4is operated as the fixed elements by the operation of the third brake B3. Therefore, the torque of the input shaft IS is shifted into the second forward speed, and the second forward speed is output to the output shaft OS connected to the eighth shaft TM8.

The first and fourth clutches C1and C4and the third brake B3are simultaneously operated at a third forward speed D3.

In a state that the second shaft TM2is connected to the sixth shaft TM6by the operation of the first clutch C1and the sixth shaft TM6is connected to the seventh shaft TM7by the operation of the fourth clutch C4, the torque of an input shaft IS is input to the second shaft TM2and the sixth shaft TM6.

In addition, the fourth shaft TM4is operated as the fixed elements by the operation of the third brake B3. Therefore, the torque of an input shaft IS is shifted into the third forward speed, and the third forward speed is output to the output shaft OS connected to the eighth shaft TM8.

The first clutch and the second clutch C1and C2and the third brake B3are simultaneously operated at a fourth forward speed D4.

In a state that the second shaft TM2is connected to the sixth shaft TM6by the operation of the first clutch C1and the third shaft TM3is connected to the fifth shaft TM5by the operation of the second clutch C2, the torque of an input shaft IS is input to the second shaft TM2and the sixth shaft TM6.

In addition, the fourth shaft TM4is operated as the fixed elements by the operation of the third brake B3. Therefore, the torque of an input shaft IS is shifted into the fourth forward speed, and the fourth forward speed is output to the output shaft OS connected to the eighth shaft TM8.

The second and fourth clutches C2and C4and the third brake B3are simultaneously operated at a fifth forward speed D5.

In a state that the third shaft TM3is connected to the fifth shaft TM5by the operation of the second clutch C2and the sixth shaft TM6is connected to the seventh shaft TM7by the operation of the fourth clutch C4, the torque of an input shaft IS is input to the second shaft TM2.

In addition, the fourth shaft TM4is operated as the fixed elements by the operation of the third brake B3. Therefore, the torque of an input shaft IS is shifted into the fifth forward speed, and the fifth forward speed is output to the output shaft OS connected to the eighth shaft TM8.

The first, second, and fourth clutches C1, C2, and C4are simultaneously operated at a sixth forward speed D6.

In a state that the second shaft TM2is connected to the sixth shaft TM6by the operation of the first clutch C1, the third shaft TM3is connected to the fifth shaft TM5by the operation of the second clutch C2, and the sixth shaft TM6is connected to the seventh shaft TM7by the operation of the fourth clutch C4, the torque of an input shaft IS is input to the second shaft TM2and the sixth shaft TM6.

In this case, entire planetary gear sets PG1, PG2, PG3, and PG4integrally rotate, thereby forming the sixth forward speed and outputting the inputted torque to the output shaft OS connected with the eighth shaft TM8.

The second and fourth clutches C2and C4and the first brake B1are simultaneously operated at a seventh forward speed D7.

In a state that the third shaft TM3is connected to the fifth shaft TM5by the operation of the second clutch C2and the sixth shaft TM6is connected to the seventh shaft TM7by the operation of the fourth clutch C4, the torque of an input shaft IS is input to the second shaft TM2.

In addition, the first shaft TM1is operated as the fixed elements by the operation of the first brake B1. Therefore, the torque of an input shaft IS is shifted into the seventh forward speed, and the seventh forward speed is output to the output shaft OS connected to the eighth shaft TM8.

The first clutch and the second clutch C1and C2and the first brake B1are operated at an eighth forward speed D8.

In a state that the second shaft TM2is connected to the sixth shaft TM6by the operation of the first clutch C1and the third shaft TM3is connected to the fifth shaft TM5by the operation of the second clutch C2, the torque of an input shaft IS is input to the second shaft TM2and the sixth shaft TM6.

In addition, the first shaft TM1is operated as the fixed elements by the operation of the first brake B1. Therefore, the torque of an input shaft IS is shifted into the eighth forward speed, and the eighth forward speed is output to the output shaft OS connected to the eighth shaft TM8.

The first and fourth clutches C1and C4and the first brake B1are simultaneously operated at a ninth forward speed D9.

In a state that the second shaft TM2is connected to the sixth shaft TM6by the operation of the first clutch C1and the sixth shaft TM6is connected to the seventh shaft TM7by the operation of the fourth clutch C4, the torque of an input shaft IS is input to the second shaft TM2and the sixth shaft TM6.

In addition, the first shaft TM1is operated as the fixed elements by the operation of the first brake B1. Therefore, the torque of an input shaft IS is shifted into the ninth forward speed, and the ninth forward speed is output to the output shaft OS connected to the eighth shaft TM8.

The third and fourth clutches C3and C4and the first brake B1are simultaneously operated at a tenth forward speed D10.

In a state that the third shaft TM3is connected to the seventh shaft TM7by the operation of the third clutch C3and the sixth shaft TM6is connected to the seventh shaft TM7by the operation of the fourth clutch C4, the torque of an input shaft IS is input to the second shaft TM2.

In addition, the first shaft TM1is operated as the fixed elements by the operation of the first brake B1. Therefore, the torque of an input shaft IS is shifted into the tenth forward speed, and the tenth forward speed is output to the output shaft OS connected to the eighth shaft TM8.

The first and third clutches C1and C3and the second brake B2are simultaneously operated at a reverse speed REV.

In a state that the second shaft TM2is connected to the sixth shaft TM6by the operation of the first clutch C1and the third shaft TM3is connected to the seventh shaft TM7by the operation of the third clutch C3, the torque of an input shaft IS is input to the second shaft TM2and sixth shaft TM6.

In addition, the third shaft TM3is operated as the fixed elements by the operation of the second brake B2. Therefore, the torque of an input shaft IS is shifted into the reverse speed by cooperative operation of respective shafts, and the reverse speed is output to the output shaft OS connected to the eighth shaft TM8.

The planetary gear train according to the exemplary embodiment of the present invention may achieve at least ten forward speeds and one reverse speed by combining four planetary gear sets PG1, PG2, PG3, and PG4with the four clutches C1, C2, C3, and C4and the three brakes B1, B2, and B3.

In addition, a planetary gear train according to an exemplary embodiment of the present invention may realize a gear ratio span of more than 9.0, thereby maximizing efficiency of driving the engine.

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.