KR101338423B1 - Power train of automatic transmission - Google Patents

Abstract

A first planetary gear set including a first operating member fixedly connected to the input shaft, a second operating member, and a third operating member fixedly connected to the output shaft; A second operating member selectively connected to the input shaft and selectively connected to a transmission case, a fifth operating member selectively connected to the input shaft, and a second operating member fixedly connected to the second operating member. Planetary gear sets; A seventh operating member fixedly connected to the transmission case, an eighth operating member selectively connected to the fourth operating member and selectively connected to the output shaft, and a ninth operating member fixedly connected to the fifth operating member; A third planetary gear set comprising; And a plurality of friction members selectively connecting the operation members of the first, second and third planetary gear sets, the input shaft, the output shaft, and the transmission case.

Automatic transmission, power train, planetary gear set

Description

POWER TRAIN OF AUTOMATIC TRANSMISSION}

The present invention relates to a power train of an automatic transmission, and more particularly, to a power train of an automatic transmission that implements eight forward speeds and one reverse speed by using four clutches and one brake in three simple planetary gear sets. will be.

In general, a multi-stage shifting mechanism of an automatic transmission is implemented by combining a plurality of planetary gearsets, and a power train in which the plurality of planetary gearsets is combined receives a torque from a torque converter included in the automatic transmission and shifts it. It will function to transfer to the output shaft.

However, the more transmission stages that can be implemented, the more appropriate transmission ratios can be designed, and the vehicle can be realized in terms of power performance and fuel efficiency. Therefore, automatic transmissions that implement more transmission stages are of interest for continuous research. have.

In addition, even if the same number of gear stages are implemented, the durability, power transmission efficiency, and size of the power train vary according to the combination method of the planetary gear set. Efforts are always underway to invent.

In particular, unlike manual transmissions in which the driver has to shift frequently if the shift stage is too large, the automatic transmission performs shifting by controlling the operation of the power train by the control unit according to the driving condition. Efforts to find the configuration of the power train that implements the stage become more important for automatic transmissions.

Therefore, the present invention is devised to meet the development of the automatic transmission as described above, the object of the present invention is to use 8 clutches forward and 1 reverse speed by using four clutches and one brake in three simple planetary gear sets. It is to provide a power train of automatic transmission to implement.

The power train of the automatic transmission according to the embodiment of the present invention for achieving this object comprises a first operating member fixedly connected to the input shaft, a second operating member, a third operating member fixedly connected to the output shaft 1 planetary gear set; A second operating member selectively connected to the input shaft and selectively connected to a transmission case, a fifth operating member selectively connected to the input shaft, and a second operating member fixedly connected to the second operating member. Planetary gear sets; A seventh operating member fixedly connected to the transmission case, an eighth operating member selectively connected to the fourth operating member and selectively connected to the output shaft, and a ninth operating member fixedly connected to the fifth operating member; A third planetary gear set comprising; And a plurality of friction members selectively connecting the operation members of the first, second and third planetary gear sets, the input shaft, the output shaft, and the transmission case.

The plurality of friction members may include: a first clutch selectively connecting the fifth operation member to the input shaft; A second clutch selectively connecting the fourth operating member to the input shaft; A third clutch selectively connecting the eighth operating member to the output shaft; A fourth clutch for selectively connecting the fourth operating member to the eighth operating member; And a first brake for selectively connecting the fourth operating member to the transmission case.

The first, second and fourth clutches may be disposed between the first planetary gear set and the third planetary gear set.

The first, second, third, fourth clutch and the first brake may be disposed outside the first, second and third planetary gear sets.

The first planetary gear set is a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear as its operating member, wherein the first sun gear acts as a first actuating member. The first planetary carrier acts as the second actuating member, and the first ring gear can act as the third actuating member.

The second planetary gear set is a single pinion planetary gear set including a second sun gear, a second planet carrier, and a second ring gear as its operating member, wherein the second sun gear acts as a fourth operating member. The two planetary carriers may act as the fifth actuating member, and the second ring gear may act as the sixth actuating member.

The third planetary gear set is a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear as its operating member, wherein the third sun gear acts as a seventh operating member. The third planetary carrier acts as the eighth actuating member, and the third ring gear can act as the ninth actuating member.

The third clutch and the first brake operate at the forward 1 speed, the third clutch and the fourth clutch operate at the forward 2 speed, the third clutch and the second clutch operate at the forward 3 speed, and the third clutch and the third clutch at the forward 4 speed. 1st clutch operates, 1st clutch and 2nd clutch operate at 5th forward speed, 1st clutch and 4th clutch operate at 6th forward speed, 1st clutch and 1st brake operate at 7th forward speed, 8th forward The second clutch and the fourth clutch operate in the inside, and the fourth clutch and the first brake operate in the reverse speed 1.

As described above, according to the power train of the automatic transmission according to the present invention, three forward planetary gear sets can be implemented using eight clutches and one brake using four clutches and one brake.

In addition, by providing a large number of gear stages it is possible to effectively use the power of the engine to improve the power transmission performance and reduce fuel economy.

In addition, upshifts and downshifts to all adjacent shifts and skipshifts can be implemented by releasing and engaging only one clutch.

In addition, since all the shift stages are implemented by operating only two friction members, the shift between any shift stage and the shift stage can be implemented by releasing and engaging only two clutches.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, a power train of an automatic transmission according to an exemplary embodiment of the present invention includes an input shaft 10, an output shaft 20, a transmission case 30, and first, second, and third planetary gear sets PG1, PG2, PG3).

The input shaft 100 receives power from an engine (not shown) through a torque converter (not shown).

The output shaft 20 outputs power from the power train.

The first planetary gear set PG1 is a single pinion planetary gear set including a first sun gear S1, a first planet carrier PC1, and a first ring gear R1 as its operating member. The first planetary gear PC1 rotates by connecting the first sun gear S1 and the first pinion gear P1 gear-coupled to the first ring gear R1.

The second planetary gear set PG2 is a single pinion planetary gear set including a second sun gear S2, a second planet carrier PC2, and a second ring gear R2 as its operating member. A second pinion gear P2 gear-coupled to the second sun gear S2 and the second ring gear R2 is connected to the second planet carrier PC2 to rotate.

The third planetary gear set PG3 is a single pinion planetary gear set including a third sun gear S3, a third planet carrier PC3, and a third ring gear R3 as its operating member. The third planet carrier PC3 is connected to and rotates with a third pinion gear P3 gear-coupled with the third sun gear S3 and the third ring gear R3.

The first sun gear S1 is fixedly connected to the input shaft 10 and functions as an input member at all times. The first planet carrier PC1 is fixedly connected to the second ring gear R2. The first ring gear R1 is fixedly connected to the output shaft 20 to act as an output member at all times.

The second planet carrier PC2 is fixedly connected to the third ring gear R3.

The third sun gear S3 is fixedly connected to the transmission case 30 and functions as a stop member at all times.

The power train of the automatic transmission according to the embodiment of the present invention uses four clutches and one brake.

The first clutch C1 selectively connects the second planet carrier PC2 to the input shaft 10. The second clutch C2 selectively connects the second sun gear S2 to the input shaft 10. The third clutch C3 selectively connects the third planet carrier PC3 to the output shaft 20. The fourth clutch C4 selectively connects the second sun gear S2 to the third planet carrier PC3. The first brake B1 selectively connects the second sun gear S2 to the transmission case 30.

As shown in FIG. 2, the automatic transmission according to the embodiment of the present invention implements 8 forward speeds and 1 reverse speed, and two friction members operate at each shift stage.

That is, the third clutch C3 and the first brake B1 operate at the first forward speed. At the second forward speed, the third clutch C3 and the fourth clutch C4 operate. At the third forward speed, the third clutch C3 and the second clutch C2 operate. At the fourth forward speed, the third clutch C3 and the first clutch C1 operate. At the 5th forward speed, the first clutch C1 and the second clutch C2 operate. At the sixth forward speed, the first clutch C1 and the fourth clutch C4 operate. At 7th forward speed, the first clutch C1 and the first brake B1 operate. At 8th forward speed, the second clutch C2 and the fourth clutch C4 operate. In the reverse first speed R1, the fourth clutch C4 and the first brake B1 operate.

Hereinafter, the formation of eight forward speeds and one reverse speed in the power train of the automatic transmission according to an embodiment of the present invention will be described in detail.

3 to 11, the first sun gear S1 is set to the first operating member N1, the first planet carrier PC1 is set to the second operating member N2, and the first ring gear R1. ) Is set as the third operating member N3, the second sun gear S2 is set as the fourth operating member N4, the second planetary carrier PC2 is set as the fifth operating member N5, The second ring gear R2 is set to the sixth operating member N6, the third sun gear S3 is set to the seventh operating member N7, and the third planetary carrier PC3 is set to the eighth operating member ( N8), and the third ring gear R3 is set to the ninth operating member N9.

3 to 11, the first sun gear S1, which is always the first operating member N1 serving as the input member, rotates at the rotational speed of the input shaft 10 at all times. Further, since the first planet carrier PC1, which is the second operating member N2, and the second ring gear R2, which is the sixth operating member N6, are fixedly connected, they always rotate at the same speed. Further, since the second planetary carrier PC2, which is the fifth actuation member N5, and the third ring gear R3, which is the ninth actuation member N9, are fixedly connected, they are always rotated at the same speed. In addition, since the third sun gear S3, which is the seventh operation member N7, is fixedly connected to the transmission case 30, it is always stopped.

In this state, the first to eighth speeds and the first and second speeds are realized by the selective operation of the first clutch C1 to the fourth clutch C4 and the first brake B1. Explain.

[1st speed forward]

In the first forward speed D1, the third clutch C3 and the first brake B1 operate.

By the operation of the third clutch C3, the third operating member N3, which is an output member, has the same speed as the eighth operating member N8.

Then, the second sun gear S2, which is the fourth operating member N4, is stopped by the operation of the first brake B1.

Therefore, the speed diagram as shown in FIG. 3 is formed, and the first forward speed D1 is output through the third operating member N3 as the output member.

[2 speed forward]

At the second forward speed D2, the third clutch C3 and the fourth clutch C4 operate.

By the operation of the third clutch C3, the third operating member N3, which is an output member, has the same speed as the eighth operating member N8.

By the operation of the fourth clutch C4, the fourth operating member N4 has the same speed as the eighth operating member N8. Accordingly, the third, fourth and eighth operating members N3, N4 and N8 all rotate at the same speed as the output speed.

Therefore, the speed diagram as shown in FIG. 4 is formed, and the second forward speed D2 is output through the third operating member N3 as the output member.

[3 speed forward]

In the third forward speed D3, the third clutch C3 and the second clutch C2 operate.

By the operation of the third clutch C3, the third operating member N3, which is an output member, has the same speed as the eighth operating member N8.

By the operation of the second clutch C2, the fourth operating member N4 rotates at the same speed as the input shaft 10.

Accordingly, the speed diagram as shown in FIG. 5 is formed, and the third forward speed D3 is output through the third operating member N3 as the output member.

[4 forward speed]

In the fourth forward speed D4, the third clutch C3 and the first clutch C1 operate.

By the operation of the third clutch C3, the third operating member N3, which is an output member, has the same speed as the eighth operating member N8.

By the operation of the first clutch C1, the fifth operating member N5 and the ninth operating member N9 fixedly connected thereto rotate at the same speed as the input shaft 10. Accordingly, the speed diagram of the third planetary gear set PG3 in which the third sun gear S3, which is the fourth operating member N4, is stopped is formed as shown in FIG.

Therefore, the speed diagram as shown in FIG. 6 is formed, and the fourth forward speed D4 is output through the third operating member N3 as the output member.

[5th forward]

In the fifth forward speed D5, the first clutch C1 and the second clutch C2 operate.

By the operation of the first clutch C1, the fifth operating member N5 and the ninth operating member N9 fixedly connected thereto rotate at the same speed as the input shaft 10. Accordingly, the speed diagram of the third planetary gear set PG3 in which the third sun gear S3, which is the fourth operating member N4, is stopped is formed as shown in FIG.

By the operation of the second clutch C2, the fourth operating member N4 rotates at the same speed as the input shaft 10. Accordingly, the second planetary gear set PG2 is integrally rotated at the same speed as the input shaft 10.

Therefore, since the second operating member N2 fixedly connected to the sixth operating member N6 also rotates at the same speed as the input shaft, the first planetary gear set PG1 rotates integrally.

Therefore, a speed diagram as shown in FIG. 7 is formed, and the fifth forward speed D5 is output through the third operating member N3 as the output member.

[6th forward]

At the sixth forward speed D6, the first clutch C1 and the fourth clutch C4 operate.

By the operation of the first clutch C1, the fifth operating member N5 and the ninth operating member N9 fixedly connected thereto rotate at the same speed as the input shaft 10. Accordingly, the speed diagram of the third planetary gear set PG3 in which the third sun gear S3, which is the fourth operating member N4, is stopped is formed as shown in FIG.

By the operation of the fourth clutch C4, the fourth operating member N4 has the same speed as the eighth operating member N8.

At the fifth forward speed D5 at which the second clutch C2 operates, the fourth operating member N4, which is the second sun gear S2, rotates at the speed of the input shaft 10, while the fourth clutch C4 operates. At the sixth forward speed D6, the fourth operating member N4 rotates at the speed of the eighth operating member N8 lower than the speed of the input shaft.

Therefore, the velocity diagram of the second planetary gear set PG2 at the sixth forward speed D6 rotates counterclockwise as compared to the fifth forward speed D5, and the sixth operating member N6 at the sixth forward speed D6. ) Rotates faster than the forward five speeds.

Therefore, since the rotational speed of the second operating member N2 is increased in the first planetary gear set PG1, the speed diagram of the first planetary gear set PG1 is counterclockwise as compared to the fifth forward speed D5. Will rotate.

Therefore, the speed diagram as shown in FIG. 8 is formed, and the sixth forward speed D6 is output through the third operating member N3 as the output member.

[7th forward]

In the seventh forward speed D7, the first clutch C1 and the first brake B1 operate.

By the operation of the first clutch C1, the fifth operating member N5 and the ninth operating member N9 fixedly connected thereto rotate at the same speed as the input shaft 10. Accordingly, the speed diagram of the third planetary gear set PG3 in which the third sun gear S3, which is the fourth operating member N4, is stopped is formed as shown in FIG.

The fourth operating member N4 is stopped by the operation of the first brake B1. That is, the fourth operating member N4 of the second planetary gear set PG2 rotates at the speed of the eighth operating member N8 at the sixth forward speed D6 at which the fourth clutch C4 operates. The fourth operating member N4 is stopped at the seventh forward speed at which the brake B1 operates.

Therefore, the velocity diagram of the second planetary gear set PG2 at the seventh forward speed D7 rotates counterclockwise as compared to the sixth forward speed D6, and the sixth operating member N6 at the seventh forward speed D7. ) Rotates faster than the forward 6 speed.

Therefore, since the rotational speed of the second operating member N2 is increased in the first planetary gear set PG1, the speed diagram of the first planetary gear set PG1 is counterclockwise compared to the sixth forward speed D6. Will rotate.

Therefore, the speed diagram as shown in FIG. 9 is formed, and the seventh forward speed D7 is output through the third operating member N3 as the output member.

[8th forward]

At the eighth forward speed D8, the second clutch C2 and the fourth clutch C4 operate.

By the operation of the second clutch C2, the fourth operating member N4 rotates at the same speed as the input shaft 10.

By the operation of the fourth clutch C4, the fourth operating member N4 has the same speed as the eighth operating member N8.

Accordingly, the third planetary gear set is set at the eighth forward speed at which the eighth operating member N8 rotates at the speed of the input shaft 10 as compared to the seventh forward speed at which the ninth operating member N9 rotates at the speed of the input shaft 10. The velocity diagram of PG3 is rotated counterclockwise.

Accordingly, the ninth operating member N9 and the fifth operating member N5 fixed thereto are rotated at a faster speed than the input shaft 10.

Therefore, the speed diagram as shown in FIG. 10 is formed, and the eighth forward speed D8 is output through the third operating member N3 as the output member.

[1 speed reverse]

In the reverse first speed R1, the fourth clutch C4 and the first brake B1 operate.

The fourth operating member N4 is stopped by the operation of the first brake B1. In addition, the eighth operating member N8 is also stopped by the operation of the fourth clutch C4. Therefore, since the seventh operating member N7 and the eighth operating member N8 stop, the third planetary gear set PG3 stops integrally.

Since the eighth operating member N8 is stopped, the fifth operating member N5 fixed thereto is also stopped. Therefore, since the fourth operating member N4 and the fifth operating member N5 stop, the second planetary gear set PG2 stops integrally.

Accordingly, with respect to the first planetary gear set PG1, the first operating member N1 rotates at the speed of the input shaft 10 while the second operating member N2 fixedly connected to the sixth operating member N6 is stopped. Will be done.

Accordingly, the speed diagram as shown in FIG. 11 is formed, and the reverse first speed R1 is output through the third operating member N3 as the output member.

In FIG. 2, an example of the speed ratio which is possible with respect to 8 forward speeds and 1 reverse speed is described. For example, the number of sun gear / ring gear teeth of the first planetary gear set PG1 is 10 and 25, the number of sun gear / ring gear teeth of the second planetary gear set PG2 is 10 and 23, respectively, and the third planetary gear The number of sun gear / ring gear teeth of the set PG3 is 10 and 30, respectively.

However, the protection scope of the present invention should not be construed as being limited thereto. By controlling the number of sun gear / ring gear teeth of the first, second and third planetary gear sets PG1, PG2 and PG3, various other speed ratios can be obtained.

In the powertrain of the automatic transmission according to the first embodiment of the present invention described above, as shown in FIG. 1, the first, second and fourth clutches C1, C2 and C4 are the first planetary gear sets PG1. ) And the third planetary gear set PG3.

However, the protection scope of the present invention should not be understood to be limited thereto. Variations are possible regarding the arrangement of the clutches. Hereinafter, the powertrain of the automatic transmission according to the second embodiment of the present invention in which the arrangement of the clutches is modified in comparison with the first embodiment will be described with reference to FIG.

As shown in FIG. 12, in the powertrain of the automatic transmission according to the second embodiment of the present invention, the first, second, third and fourth clutches C1, C2, C3, C4 and the first brake B1 are The first, second and third planetary gear sets PG1, PG2 and PG3 are disposed outside.

The configuration of the first, second and third planetary gear sets PG1, PG2, and PG3 and the fixed and variable connection relationships of the first, second and third planetary gear sets PG1, PG2, and PG3 are the same as those of the first embodiment of the present invention.

Therefore, the powertrain of the automatic transmission according to the second embodiment of the present invention can be shifted by the operation table as shown in Fig. 2, and accordingly, the speed line diagram as shown in Figs. 3 to 11 To form the forward 8-speed and the reverse 1-speed.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And all changes to the scope that are deemed to be valid.

1 is a configuration diagram of a powertrain of an automatic transmission according to an embodiment of the present invention.

2 is an operation table of a powertrain of an automatic transmission according to an embodiment of the present invention.

3 is a speed diagram showing rotational speeds of the respective operating members in the first forward speed of the power train of the automatic transmission according to the embodiment of the present invention.

Figure 4 is a speed diagram showing the rotational speed of each operating member at the second forward speed of the power train of the automatic transmission according to an embodiment of the present invention.

Figure 5 is a speed diagram showing the rotational speed of each operating member at the third forward speed of the power train of the automatic transmission according to an embodiment of the present invention.

Figure 6 is a speed diagram showing the rotational speed of each operating member at the fourth forward speed of the power train of the automatic transmission according to an embodiment of the present invention.

Figure 7 is a speed diagram showing the rotational speed of each operating member at 5 forward speeds of the power train of the automatic transmission according to the embodiment of the present invention.

8 is a speed diagram showing the rotational speed of each operating member at sixth forward speed of the power train of the automatic transmission according to the embodiment of the present invention.

Figure 9 is a speed diagram showing the rotational speed of each operating member at seven forward speeds of the power train of the automatic transmission according to the embodiment of the present invention.

10 is a speed diagram showing rotational speeds of respective operating members in eight forward speeds of a power train of an automatic transmission according to an embodiment of the present invention.

11 is a speed diagram showing the rotational speeds of the respective operating members in the reverse rotation of the power train of the automatic transmission according to the embodiment of the present invention.

12 is a block diagram of a power train of an automatic transmission according to another embodiment of the present invention.

Claims (11)

A first planetary gear set including a first operating member fixedly connected to the input shaft, a second operating member, and a third operating member fixedly connected to the output shaft; A second operating member selectively connected to the input shaft and selectively connected to a transmission case, a fifth operating member selectively connected to the input shaft, and a second operating member fixedly connected to the second operating member. Planetary gear sets; A seventh operating member fixedly connected to the transmission case, an eighth operating member selectively connected to the fourth operating member and selectively connected to the output shaft, and a ninth operating member fixedly connected to the fifth operating member; A third planetary gear set comprising; And A plurality of friction members for selectively connecting the operation members of the first, second and third planetary gear sets, the input shaft, the output shaft, and the transmission case; A power train of an automatic transmission comprising a. The method according to claim 1, The plurality of friction members, A first clutch selectively connecting the fifth operating member to the input shaft; A second clutch selectively connecting the fourth operating member to the input shaft; A third clutch selectively connecting the eighth operating member to the output shaft; A fourth clutch for selectively connecting the fourth operating member to the eighth operating member; And A first brake for selectively connecting the fourth operating member to the transmission case; A power train of an automatic transmission comprising a. 3. The method of claim 2, And the first, second and fourth clutches are disposed between the first planetary gear set and the third planetary gear set. 3. The method of claim 2, And the first, second, third, fourth clutch and first brake are disposed outside the first, second and third planetary gear sets. The method according to claim 1, The first planetary gear set is a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear as its operating member, The first sun gear acts as a first actuating member, the first planet carrier acts as a second actuating member, and the first ring gear acts as a third actuating member. . The method according to claim 1, The second planetary gear set is a single pinion planetary gear set including a second sun gear, a second planet carrier, and a second ring gear as its operating member, The second sun gear acts as a fourth actuating member, the second planet carrier acts as a fifth actuating member, and the second ring gear acts as a sixth actuating member. . The method according to claim 1, The third planetary gear set is a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear as its operating member, The third sun gear acts as a seventh actuating member, the third planet carrier acts as an eighth actuating member, and the third ring gear acts as a ninth actuating member. . 3. The method of claim 2, In the forward 1 speed, the third clutch and the first brake are operated, At the 2nd forward speed, the third clutch and the fourth clutch operate. At the 3rd forward speed, the third clutch and the second clutch operate At the 4th forward speed, the third clutch and the first clutch operate At the 5th forward, the first clutch and the second clutch operate At the 6th forward speed, the first clutch and the fourth clutch operate. At the 7th forward, the first clutch and the first brake operate At 8th forward, the second clutch and the fourth clutch operate, A power train of the automatic transmission, characterized in that the fourth clutch and the first brake operate in reverse 1 speed. The method according to claim 1, The first planetary gear set is a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear as its operating member, wherein the first sun gear acts as a first actuating member. One planetary carrier acts as a second actuating member, and the first ring gear acts as a third actuating member, Wherein the second planetary gear set is a single pinion planetary gear set including a second sun gear, a second planetary carrier, and a second ring gear as its operating members, the second sun gear serving as a fourth operating member, 2 planetary carrier acts as a fifth operating member, and the second ring gear acts as a sixth operating member, The third planetary gear set is a single pinion planetary gear set including a third sun gear, a third planet carrier, and a third ring gear as its operating member, wherein the third sun gear acts as a seventh operating member. 3. The planetary carrier acts as an eighth actuating member, and the third ring gear acts as a ninth actuating member. 10. The method of claim 9, The plurality of friction members, A first clutch selectively connecting the second planet carrier to the input shaft; A second clutch for selectively connecting the second sun gear to the input shaft; A third clutch selectively connecting the third planetary carrier to the output shaft; A fourth clutch selectively connecting the second sun gear to the third planet carrier; And A first brake selectively connecting the second sun gear to the transmission case; A power train of an automatic transmission comprising a. The method of claim 10, In the forward 1 speed, the third clutch and the first brake are operated, At the 2nd forward speed, the third clutch and the fourth clutch operate. At the 3rd forward speed, the third clutch and the second clutch operate At the 4th forward speed, the third clutch and the first clutch operate At the 5th forward, the first clutch and the second clutch operate At the 6th forward speed, the first clutch and the fourth clutch operate. At the 7th forward, the first clutch and the first brake operate At 8th forward, the second clutch and the fourth clutch operate, A power train of the automatic transmission, characterized in that the fourth clutch and the first brake operate in reverse 1 speed.

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