KR20110027072A - Gear train of automatic transmission for vehicles - Google Patents

Abstract

PURPOSE: A vehicle automatic transmission gear train is provided to reduce the capacity of oil pump and increase the oil pressure control efficiency by comprising first through third planetary gear sets arranged on the same axis. CONSTITUTION: A first planetary carrier(PC1) comprises a first rotation element(N1). A first ring gear(R1) comprises a second rotation element(N2). Second and third planetary gear sets(PG2, PG3) directly connects the second and third sun gears. The second and third planetary carriers comprise a sixth rotation element(N6). A second ring gear(R2) comprises a seventh rotation element.

Description

GEAR TRAIN OF AUTOMATIC TRANSMISSION FOR VEHICLES}

The present invention relates to a gear train of an automatic transmission for a vehicle so that three simple planetary gear sets may be combined with four clutches and two brakes to realize an eighth speed shift stage.

In general, a multi-stage shifting mechanism of an automatic transmission is implemented by combining a plurality of planetary gear sets, and a gear train in which the plurality of planetary gear sets is combined receives a rotational power from a torque converter and shifts it to the output shaft. Will be

In such automatic transmissions, the more transmission stages that can be implemented, the more appropriate the transmission ratio can be designed and the vehicle can be realized in terms of power performance and fuel efficiency. Therefore, there is a demand for an automatic transmission that implements more transmission stages.

And even if the same shift stage is implemented, the durability, power transmission efficiency, size and weight are greatly changed depending on the combination method of the planetary gear set. Therefore, it is possible to develop a gear train that can be more robust and compact while minimizing power loss. Efforts are underway.

In particular, unlike the manual transmission in which the shifting step is more inconvenient for the driver to shift frequently, the automatic transmission is shifted by the transmission control unit (TCU) controls the operation of the gear train according to the driving state, Efforts are being made to find a gear train configuration that can implement more gears.

From this point of view, four-speed and five-speed automatic transmissions are the mainstream automatic transmissions currently in use, but recently, six-speed automatic transmissions have been developed and applied to vehicles, while the development of automatic transmissions of eight or more speeds is active. It's going on.

Accordingly, the present inventors have proposed the present invention in order to meet the development of the automatic transmission as described above, and the object of the present invention is to combine three simple planetary gear sets with four clutches and two brakes for eight forward speeds and backwards. By providing two speeds, the present invention provides a gear train of an automatic transmission for a vehicle to improve power transmission performance, reduce fuel consumption, and improve reverse shift performance.

In order to realize the above object, the present invention provides a first planetary gear set PG1 consisting of a double pinion planetary gear set having three operating elements S1 (PC1) R1, and three operating elements S2. 2nd planetary gear set PG2 consisting of a single pinion planetary gearset having (PC2) (R2) and a double pinion planetary gearset having three operating elements S3 (PC3) (R3). The third planetary gear set PG3 formed is combined by applying four clutches C1, C2, C3 and C4 and two brakes B1 and B2,

The first planetary gear set PG1 is directly connected to the input shaft IS to operate at least two of the first rotating element N1 and the operating element of the second planetary gear set PG2. And a second rotating element N2 selectively connected to and a third rotating element N3 directly connected to the transmission housing.

The second and third planetary gear sets PG2 and PG3 may be combined in the form of a composite planetary gear set having four rotating elements N4 to N7, respectively, in which two operating elements are directly and independently connected to each other. Fourth rotating element N4 selectively connected to the rotational element N2 and the input shaft IS to which the rotational power of the engine is input, and optionally connected to the transmission housing H, and an input shaft to which the rotational power of the engine is input. A fifth rotating element N5 selectively connected to the IS and optionally connected to the transmission housing H, a sixth rotating element N6 connected to the output gear OG, and the second rotating element. It provides a gear train of an automatic transmission for a vehicle, characterized in that it has a seventh rotating element (N7) that is selectively connected with (N2).

In the first planetary gear set PG1, the first planetary carrier PC1 includes the first rotating element N1, the first ring gear R1 the second rotating element N2, and the first sun gear S3. It consists of a third rotating element (N3),

The second and third planetary gear sets PG2 and PG3 are directly connected to the second and third sun gears S2 and S3, and the second and third planetary carriers PC2 and PC3 are directly connected to the second and third planetary gear sets PG2 and PG3. The sun gear S2 and S3 are the fourth rotating element N4, the third ring gear R3 is the fifth rotating element N5, and the second and third planet carriers PC2 and PC3 are the sixth rotating element N6), the second ring gear R2 is composed of a seventh rotating element N7.

In the above description, the first, second, and third planetary gear sets PG1, PG2, and PG3 include the first, second, third, and fourth clutches C1, C2, C3, C4, and the first and second brakes B1. ) (B2),

The first clutch C1 connects the input shaft IS and the fourth rotating element N4,

The second clutch C2 connects the input shaft IS and the fifth rotating element N5.

The third clutch C3 connects the second rotating element N2 and the fourth rotating element N4,

The fourth clutch C4 connects the second rotating element N2 and the seventh rotating element N7,

The first brake B1 connects the fifth rotating element N5 and the transmission housing H,

The second brake B2 may be arranged to connect the fourth rotating element N4.

In the first forward speed, the fourth clutch C4 and the first brake B1 are operated.

At the second forward speed, the fourth clutch C4 and the second brake B2 are operated.

At the third forward speed, the fourth clutch C4 and the third clutch C3 are operated.

At fourth forward speed, the fourth clutch C4 and the first clutch C1 are operated.

At the fifth forward speed, the fourth clutch C4 and the second clutch C2 are operated.

At the sixth forward speed, the second clutch C2 and the first clutch C1 are operated.

At seventh forward speed, the second clutch C2 and the third clutch C3 are operated.

At the 8th forward speed, the second clutch C2 and the second brake B2 are operated.

At the first reverse speed, the third clutch C3 and the first brake B1 are operated.

In the second reverse speed, the first clutch C1 and the first brake B1 are operated to shift.

In the first planetary gear set PG1, the first planetary carrier PC1 includes the first rotating element N1, the first ring gear R1 the second rotating element N2, and the first sun gear S3. It consists of a third rotating element (N3),

The second and third planetary gear sets PG2 and PG3 are directly connected to the second and third sun gears S2 and S3, and are directly connected to the third planet carrier PC3 and the second ring gear R2. The second and third sun gears S2 and S3 are the fourth rotating element N4, the third ring gear R3 is the fifth rotating element N5, and the second planet carrier PC2 is the sixth rotating element N6. The second ring gear R2 and the third planet carrier PC3 may be configured by the seventh rotation element N7.

As described above, the first, second and third planetary gear sets PG1, PG2 and PG3, which consist of three simple planetary gear sets, have four clutches C1, C2, C3, C4 and 2 as friction elements. Combination of the two brakes (B1) and (B2) to implement the shift stage of the eight forward speed and two reverse speed it is possible to improve the power transmission performance and fuel economy.

In addition, by shifting the two friction elements in each shift stage while operating, it is possible to reduce the capacity of the oil pump and increase the hydraulic control efficiency.

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

 1 shows a first embodiment of a gear train according to the present invention, wherein the gear train of the present invention includes first, second and third planetary gear sets PG1 (PG2) and PG3 disposed on the same axis. And clutch means composed of four clutches C1, C2, C3 and C4, and brake means composed of two brakes B1 and B2.

Accordingly, the rotation input from the input shaft IS is shifted by the complementary operation of the first, second, and third planetary gear sets PG1, PG2, and PG3, and is output through the output gear OG connected to the output element. The first, second, and third planetary gear sets PG1, PG2, and PG3 are sequentially disposed from the rear side toward the engine side on the input shaft IS.

The input shaft IS refers to the turbine shaft of the torque converter as an input member, which means that the rotational power from the engine crankshaft is input as the torque is converted through the torque converter, and the output gear OG is not shown as the output member. One known differential is used to drive the drive wheels.

The first planetary gear set PG1 is a double-pinion planetary gear set, and has three operating elements consisting of a sun gear, a planet carrier, and a ring gear, as is well known.For convenience of description, the first gear is a first sun gear S1, The planet carrier is referred to as a first planet carrier PC1 and the ring gear is referred to as a first ring gear R1.

In the first planetary gear set PG1, the first planet carrier PC1 is connected to the input shaft IS as the first rotary element N1 to operate as an input element at all times, and the first ring gear R1 is operated. The reduced rotational power as the second rotating element N2 is selectively transmitted to two rotations selected among the operating elements of the second planetary gear set PG2, and the first sun gear S1 is the third rotating element N3. As is fixedly connected to the transmission housing (H) to operate as a fixed element at all times.

Accordingly, the first planetary gear set PG1 decelerates the rotational power input to the first rotating element N1 and outputs the reduced speed through the second rotating element N2.

The second planetary gear set PG2 is a single-pinion planetary gear set, and has three operating elements consisting of a sun gear, a planet carrier, and a ring gear, as is well known. For convenience of description, the sun gear is referred to as a second sun gear S2, The planet carrier is referred to as the second planet carrier PC2 and the ring gear is referred to as the second ring gear R2.

The third planetary gear set is a double pinion planetary gear set, and has three operating elements consisting of a sun gear, a planet carrier, and a ring gear, as known, and the sun gear is referred to as a third sun gear S3 and a planet carrier. Is referred to as the third planet carrier PC3 and the ring gear is referred to as a third ring gear R3.

The second and third planetary gear sets (PG2) (PG3) is a composite planetary gear set having two rotary elements (N4 ~ N7) is fixed to each other two operating elements are fixedly connected, of the present invention In the first embodiment, the second sun gear S2 and the third sun gear S3 are directly connected, and the second planet carrier PC2 and the third planet carrier PC3 are directly connected.

Accordingly, the second and third sun gears S2 and S3 are selectively operated as the input element and the fixed element as the fourth rotary element N4, and the third ring gear R3 is the fifth rotary element N5. It is selectively operated as an input element and a fixed element, and the second and third planet carriers PC2 and PC3 are connected to the output gear OG as the sixth rotating element N6 and always operate as the final output element. The second ring gear R2 acts as an optional input element as the seventh rotating element N7.

For the above operation, the third sun gear S3, which is the fourth rotating element N4, is connected to the input shaft IS via the first clutch C1 to selectively input rotational power of the input shaft IS. At the same time it is connected to the transmission housing (H) via the second brake (B2) to operate as an optional fixing element, the first planetary carrier (PC1), the first rotating element (N1) is the second clutch (C2). It is connected to the third ring gear (R3) that is the fifth rotating element (N5) via the selectively transmit the rotational power of the input shaft (IS) to the third ring gear (R3).

The first ring gear R1 of the second rotating element N2 is connected to the second and third sun gears S2 and S3 of the fourth rotating element N4 via the third clutch C3. The decelerating output of the second rotating element N2 is selectively connected to the second ring gear R2, which is the seventh rotating element N7, via the fourth clutch C4 to selectively select the fourth rotating element N4 and the seventh. The third ring gear R3, which is transmitted to the rotating element N7 and is the fifth rotating element N5, is connected to the transmission housing H through the first brake B1 in which the one-way clutch F1 is disposed in parallel. Connected to act as an optional fixing element.

 The rotational power of the engine transmitted from the input shaft IS by the above configuration is always input to the first rotating element N1 of the first planetary gear set PG1 and at the same time the fourth rotating element N4 and the fifth rotation. Selective input is made to the element (N5) and complementary operation is shifted to 8 forward speed and 2 reverse speed, and the output is made through the output gear (OG) which is the final output path.

In the above, the friction elements composed of the first, second, third and fourth clutches C1, C2, C3 and C4 and the first and second brakes B1 and B2 are multi-plate hydraulic friction frictionally coupled by hydraulic pressure. It is customary to consist of a coupling unit.

In this way, the output gear OG is arranged on the engine side of the third planetary gear set PG3.

Figure 2 is an operating table showing the friction elements applied to the present invention, that is, the clutch and the brake at each shift stage, the gear train of the present invention is known that the shift is made while the two friction members at each shift stage operating. Can be.

That is, the fourth clutch C4 and the first brake B1 are operated at the first forward speed,

At the second forward speed, the fourth clutch C4 and the second brake B2 are operated.

The fourth and third clutches C4 and C3 are operated at three forward speeds,

The fourth and first clutches C4 and C1 are operated at four forward speeds,

The fourth and second clutches C4 and C2 are operated at five forward speeds,

At the sixth forward speed, the second and first clutches C2 and C1 are operated.

The second and third clutches C2 and C3 are operated at seven forward speeds,

At the 8th forward speed, the second clutch C2 and the second brake B2 are operated.

At the first reverse speed, the first brake B1 and the third clutch C3 are operated.

In the second reverse speed, the first brake B1 and the first clutch C1 are operated to shift.

Although the third clutch C3 and the first brake B1 are operated at the forward 1 speed, in the case where the first brake B1 is disposed in parallel with the one-way clutch F1 as in the present invention, The one-way clutch F1 is operated without the operation control of the first brake B1 in the normal D range 1 speed, thereby improving the shifting feeling when shifting to the second speed.

FIG. 3 shows a shift diagram of the gear train according to the present invention, in which the horizontal line on the lower side represents the rotational speed "0", and the horizontal line on the upper side represents the rotational speed "1.0", that is, the same rotational speed as the input shaft IS. .

The three vertical lines of the first planetary gear set PG1 have a first planetary carrier PC1, which is a first rotating element N1, and a first ring gear R1, which is a second rotating element N2, and a third, in turn from the left. It is set as the 1st sun gear S1 which is the rotating element N3, and these space | intervals are determined according to the gear ratio (number of teeth of a sun gear / number of ring gears) of the 1st planetary gear set PG1.

Four vertical lines of the second and third planetary gear sets PG2 and PC3 are second and third sun gears S2 and S3, which are fourth rotation elements N4, in turn from the left, and fifth rotation elements N5. The third ring gear R3, the second and third planet carriers PC2 and PC3 as the sixth rotating element N6 and the second ring gear R2 as the seventh rotating element N7 are set. The gear ratio (number of teeth of the sun gear / number of teeth of the ring gear) of the second and third planetary gear sets PG2 and PC3 is determined.

Since the positioning of each rotating element in the above-described shift diagram is well known to those skilled in the art of a gear train, a detailed description thereof will be omitted.

[1st speed forward]

In the forward 1 speed, as shown in FIG. 2, the fourth clutch C4 and the first brake B1 are operated and controlled.

Accordingly, the seventh rotating element N7 is operated by the operation of the fourth clutch C4 while the rotational power of the input shaft IS is input to the first rotating element N1 and the deceleration output is performed to the second rotating element N2. Deceleration input is made.

Then, while the input is made to the seventh rotation element N7, the fifth rotation element N5 operates as the fixed element by the operation of the first brake B1 and forms the first transmission line SP1 while the output element is formed. Through the sixth rotating element (N6) is output as much as D1 is to be made the first forward speed of about 4.333 as the maximum speed ratio.

Although the first brake B1 is operated in the forward 1 speed shift process, the first brake B1 is disposed in parallel with the one-way clutch F1. As the clutch F1 is operated, it is common to make the first forward speed change and to operate and control the first brake B1 at the first forward speed in the "L" range.

[2 speed forward]

At the 2nd forward speed, the operation of the 1st brake B1 is canceled in the state of 1st forward speed, and the 2nd brake B2 is operationally controlled.

Then, the fixed element is converted from the fifth rotary element N5 to the fourth rotary element N4 by the operation of the second brake B2 in the shifting state of the first forward speed as described above to form the second transmission line SP2. Through the sixth rotating element (N6) as the output element is output as much as D2 is to be a two-speed forward speed shift of about 2.333.

[3 speed forward]

At the third forward speed, as shown in FIG. 2, the operation of the second brake B2 operated in the second forward speed is released, and the third clutch C3 is operated and controlled.

Then, the fixing of the fourth rotating element N4, which has been operated as the fixing element in the shifting state of the second forward speed, is released and at the same time, the rotational power of the second rotating element N2 is controlled by the operation of the third clutch C3. The bar is input to the rotating element N4, and simultaneously inputs to the fourth and seventh rotating elements N4 and N7 to form a third transmission line SP3.

Accordingly, as much as D3 is output through the sixth rotating element N6, which is an output element, and thus the forward three-speed shift of about 1.667 is performed.

[4 forward speed]

In the fourth forward speed, as shown in FIG. 2, the operation of the third clutch C3 operated in the third forward speed is released, and the first clutch C1 is operated and controlled.

Then, the deceleration input of the second rotating element N2 input to the fourth rotating element N4 is blocked in the third forward speed, and the rotational power of the input shaft IS is activated by the operation of the first clutch C1. This input bar, while forming the fourth transmission line (SP4) is output as much as D4 through the sixth rotation element (N6) as the output element is to perform a forward four-speed shift of the speed ratio "1.400". .

[5th forward]

At the 5th forward speed, as shown in FIG. 2, the operation of the first clutch C1 operated in the state of the 4th forward speed is released, and the second clutch C2 is operated and controlled.

Then, the rotational power of the input shaft IS inputted to the fourth rotating element N4 in the shifting state of the fourth forward speed is cut off, and the rotational power of the input shaft IS is driven by the operation of the second clutch C2. The bar is inputted to the rotating element N5, and the fifth shifting line SP5 is formed to output as much as D5 through the sixth rotating element N6, which is an output element. This will be done.

[6th forward]

At the sixth forward speed, as shown in FIG. 2, the fourth clutch C4 operated from the first forward speed to the fifth forward speed is released while the first clutch C1 is operated, and the first clutch C1 is released. Operation is controlled.

Then, when the rotational power of the input shaft IS is input to the fifth rotating element N5 by the operation of the second clutch C2, the input shaft (4) is driven to the fourth rotating element N4 by the operation of the first clutch C1. When the rotational power of IS is input, the second and third planetary gear sets PG2 and PG3 are directly connected to form the sixth shift line SP6.

Accordingly, the rotational power input from the input shaft IS is output as much as D5 through the sixth rotation element N6, which is an output element, so that the sixth forward speed of the transmission ratio “1.000” as it is is achieved.

[7th forward]

In the seventh forward speed, as shown in FIG. 2, the operation of the first clutch C1 operated in the sixth forward speed is released, and the third clutch C3 is operated and controlled.

Then, when the rotational power of the input shaft IS is input to the fifth rotary element N5 by the operation of the second clutch C2, the second clutch is driven to the fourth rotary element N4 by the operation of the third clutch C3. As the deceleration output of the rotating element N2 is input, as much as D7 is output through the sixth rotating element N6 which is an output element while forming the seventh shift line SP7, the forward ratio of about 0.882 is advanced. 7-speed shift will be achieved.

[8th forward]

In the eighth forward speed, as shown in FIG. 2, the operation of the third clutch C3 operated in the seventh forward speed is released, and the second brake B2 is operated and controlled.

Then, the fourth rotating element N4 is fixed by the operation of the second brake B2 while the rotational power of the input shaft IS is input to the fifth rotating element N5 by the operation of the second clutch C2. As the eighth shift line SP7 is formed, the D8 is output as much as D8 through the sixth rotation element N6, which is an output element, and thus the eighth speed shift of about 0.750 is achieved. will be.

[1 speed reverse]

In the reverse 1 speed shift stage, as shown in FIG. 2, the first brake B1 and the third clutch C3 are operated and controlled.

Then, when the deceleration output of the second rotary element N2 is input to the fourth rotary element N4 by the operation of the third clutch C3, the fifth rotary element N5 is operated by the operation of the first brake B1. Is operated as a fixed element, and as much as REV1 is output through the sixth rotating element N6, which is an output element, forming the reverse first shift line SR1, and thus, the reverse 1 speed of the speed ratio “-5.000” is achieved. The shift will be made.

[2 speed reverse]

In the reverse 2-speed shift stage, as shown in FIG. 2, the operation of the third clutch C3 operated at the reverse 1 speed is released, and the first clutch C1 is operated and controlled.

Then, the fourth rotary element N4 is operated as an input element by the operation of the first clutch C1 while the fifth rotary element N5 is operated as a fixed element by the operation of the first brake B1. In addition, as much as REV2 is output through the sixth rotating element N6 as the output element while forming the reverse second shift line SR2, the reverse two-speed shift of about -3.000 is achieved.

In addition to the above shifts, skip down shifts such as 8 → 6, 7 → 5, 6 → 4, 5 → 3, 4 → 2, 3 → 1, 8 → 4, 7 → 3, 6 → 2, 5 → 1 Control can be carried out. Skip except 8 → 4, 6 → 2 Skip Down Shift. It is achieved by releasing one friction element and combining one friction element in another shift. Will be.

The shift ratios presented at the respective gear stages are set to 30 and 60 teeth of the first sun gear S1 and the first ring gear R1 of the first planetary gear set PG1 and the second planetary gear set PG2. The number of teeth of the second sun gear (S2) and the second ring gear (R2) is 30. 60, and the number of teeth of the third sun gear (S3) and the third ring gear (R2) of the third planetary gear set (PG3). 30. Based on 51.

4 shows a gear train of a second embodiment according to the present invention, in which the second and third planetary gear sets PG2 and PG3 are combined, but in the first embodiment of the present invention, the second and third sun gears S2. (S3) is directly connected, and the second and third planet carriers (PC2) (PC3) are directly connected, but in the second embodiment, the second and third sun gears (S2) and S3 are directly connected and the second planet carriers are directly connected. (PC2) and the third ring gear (R3) is an integrated connection.

Accordingly, the fourth rotary element N4 is the second and third sun gears S2 and S3, the fifth rotary element N5 is the third ring gear R3, and the sixth rotary element N6 is the second planet carrier. (PC2), the seventh rotating element N7 is set to the second ring gear R2 and the third planet carrier PC3.

In addition, in the shifting process of the gear train according to the second embodiment as described above, only the components of the sixth and seventh rotation elements N6 and N7 are different from the first embodiment, as shown in FIGS. 2 and 3. Since the operation and the shifting process of the friction element are the same, a detailed description of the shifting process will be omitted.

In the second embodiment as described above, the output gear OG should be directly connected to the second planetary carrier PC2, which is the sixth rotating element N6, on the engine side. Unlike the first embodiment in which the three planetary gear sets PG1, PG2, and PG3 are sequentially arranged, the arrangement positions of the second and third planetary gear sets PG2 and PG3 are changed. 2 planetary gear sets PG1, PG3, and PG2 are arranged in this order.

Although a preferred embodiment of the gear train of the present invention has been described above, the present invention is not limited to the above embodiment, and those skilled in the art can easily invent the present invention from the embodiment of the present invention. It includes all changes to the extent considered equivalent.

1 is a configuration diagram of a gear train according to a first embodiment of the present invention.

Figure 2 is a shift-specific operation of the friction element applied to the gear train according to the present invention.

3 is a shift diagram of a gear train according to a first embodiment of the present invention;

4 is a configuration diagram of a gear train according to a second embodiment of the present invention.

Claims (10)

A first planetary gear set PG1 consisting of a double pinion planetary gearset having three operating elements S1 (PC1) R1 and a single holding three operating elements S2 (PC2) R2. The second planetary gear set PG2 composed of a pinion planetary gear set and the third planetary gear set PG3 composed of a double pinion planetary gear set having three operating elements S3, PC3 and R3 are provided. Clutch C1 (C2) (C3) (C4) and two brakes (B1) (B2) by applying a combination, The first planetary gear set PG1 is directly connected to the input shaft IS to operate at least two of the first rotating element N1 and the operating element of the second planetary gear set PG2. And a second rotating element N2 selectively connected to and a third rotating element N3 directly connected to the transmission housing. The second and third planetary gear sets PG2 and PG3 may be combined in the form of a composite planetary gear set having four rotating elements N4 to N7, respectively, in which two operating elements are directly and independently connected to each other. Fourth rotating element N4 selectively connected to the rotational element N2 and the input shaft IS to which the rotational power of the engine is input, and optionally connected to the transmission housing H, and an input shaft to which the rotational power of the engine is input. A fifth rotating element N5 selectively connected to the IS and optionally connected to the transmission housing H, a sixth rotating element N6 connected to the output gear OG, and the second rotating element. And a seventh rotating element (N7) selectively connected with (N2). 2. The first planetary gear set PG1 has a first planetary carrier PC1 having a first rotating element N1, a first ring gear R1 having a second rotating element N2, and a first sun gear. (S3) is composed of a third rotating element (N3), The second and third planetary gear sets PG2 and PG3 are directly connected to the second and third sun gears S2 and S3, and the second and third planetary carriers PC2 and PC3 are directly connected to the second and third planetary gear sets PG2 and PG3. The sun gear S2 and S3 are the fourth rotating element N4, the third ring gear R3 is the fifth rotating element N5, and the second and third planet carriers PC2 and PC3 are the sixth rotating element N6), the gear train of the automatic transmission for a vehicle, characterized in that the second ring gear (R2) consists of a seventh rotating element (N7). 3. The gear train of an automatic transmission for a vehicle according to claim 2, wherein the first, second, and third planetary gear sets (PG1) (PG2) (PG3) are sequentially arranged from the rear side to the engine side on the same axis. 3. The first, second and third planetary gear sets PG1, PG2 and PG3 have a first, second, third and fourth clutch C1, C2, C3 and C4. And the first and second brakes B1 and B2, The first clutch C1 connects the input shaft IS and the fourth rotating element N4, The second clutch C2 connects the input shaft IS and the fifth rotating element N5. The third clutch C3 connects the second rotating element N2 and the fourth rotating element N4, The fourth clutch C4 connects the second rotating element N2 and the seventh rotating element N7, The first brake B1 connects the fifth rotating element N5 and the transmission housing H, The second brake (B2) is a gear train of the automatic transmission for a vehicle, characterized in that arranged to connect the fourth rotating element (N4). 5. The gear train of claim 4, wherein the first clutch C1 is arranged in parallel with the one-way clutch F1. The method of claim 4, wherein the fourth clutch (C4) and the first brake (B1) is operated at the first forward speed, At the second forward speed, the fourth clutch C4 and the second brake B2 are operated. At the third forward speed, the fourth clutch C4 and the third clutch C3 are operated. At fourth forward speed, the fourth clutch C4 and the first clutch C1 are operated. At the fifth forward speed, the fourth clutch C4 and the second clutch C2 are operated. At the sixth forward speed, the second clutch C2 and the first clutch C1 are operated. At seventh forward speed, the second clutch C2 and the third clutch C3 are operated. At the 8th forward speed, the second clutch C2 and the second brake B2 are operated. At the first reverse speed, the third clutch C3 and the first brake B1 are operated. The gear train of the automatic transmission for a vehicle, characterized in that shifting is performed while the first clutch (C1) and the first brake (B1) are operated at the reverse second speed. 2. The first planetary gear set PG1 has a first planetary carrier PC1 having a first rotating element N1, a first ring gear R1 having a second rotating element N2, and a first sun gear. (S3) is composed of a third rotating element (N3), The second and third planetary gear sets PG2 and PG3 are directly connected to the second and third sun gears S2 and S3, and are directly connected to the third planet carrier PC3 and the second ring gear R2. The second and third sun gears S2 and S3 are the fourth rotating element N4, the third ring gear R3 is the fifth rotating element N5, and the second planet carrier PC2 is the sixth rotating element N6. The gear train of the automatic transmission for a vehicle, characterized in that the second ring gear (R2) and the third planet carrier (PC3) are composed of a seventh rotating element (N7). 8. The first, second and third planetary gear sets PG1, PG2 and PG3 are arranged on the same axis from the rear side toward the engine side. Gear train of the automatic transmission for a vehicle, characterized in that arranged in the order of PG1) (PG2) (PG3). The first planetary gear set PG1 consisting of a double pinion planetary gear set having a first sun gear S1, a first planet carrier PC1, and a first ring gear R1. A second planetary gear set PG2 composed of a single pinion planetary gear set having a second sun gear S2, a second planet carrier PC2, and a second ring gear R2; Four clutches C1 (C2) comprising a third planetary gear set PG3 including a double pinion planetary gear set including a third sun gear S3, a third planet carrier PC3, and a third ring gear R3. (C3) (C4) and two brakes (B1) (B2), The input shaft IS is directly connected to the first planet carrier PC1, the second and third sun gears S2 and S3 are directly connected to each other, and the second and third planet carriers PC2 and PC3 are directly connected. In a state in which the third planet carrier PC3 is connected to the output gear OG and the first sun gear S1 is directly connected to the transmission housing H, The first clutch C1 connects the input shaft IS and the third sun gear S3. The second clutch C2 connects the first planet carrier PC1 and the third ring gear R3. The third clutch C3 connects the first ring gear R1 and the second sun gear S2, The fourth clutch C4 connects the first ring gear R1 and the second ring gear R2. The first brake B1 connects the third ring gear R3 and the transmission housing H together with the one-way clutch F1, The second brake (B2) is a gear train of the automatic transmission for a vehicle, characterized in that made by connecting the third sun gear (S3) and the transmission housing (H). The first planetary gear set PG1 consisting of a double pinion planetary gear set having a first sun gear S1, a first planet carrier PC1, and a first ring gear R1. A second planetary gear set PG2 composed of a single pinion planetary gear set having a second sun gear S2, a second planet carrier PC2, and a second ring gear R2; Four clutches C1 (C2) comprising a third planetary gear set PG3 including a double pinion planetary gear set including a third sun gear S3, a third planet carrier PC3, and a third ring gear R3. (C3) (C4) and two brakes (B1) (B2), The input shaft IS is directly connected to the first planet carrier PC1, the second and third sun gears S2 and S3 are directly connected, and the third planet carrier PC3 and the second ring gear R2 are connected. Directly connected, the second planetary carrier (PC2) is connected to the output gear (OG), and the first sun gear (S1) is directly connected to the transmission housing (H), The first clutch C1 connects the input shaft IS and the second sun gear S2, The second clutch C2 connects the first planet carrier PC1 and the third ring gear R3. The third clutch C3 connects the first ring gear R1 and the third sun gear S3, The fourth clutch C4 connects the first ring gear R1 and the third planet carrier PC3. The first brake B1 connects the third ring gear R3 and the transmission housing H together with the one-way clutch F1, The second brake (B2) is a gear train of the automatic transmission for a vehicle, characterized in that made by connecting the second sun gear (S2) and the transmission housing (H).

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