阅读说明：本技术 车辆的双离合器变速器 (Double clutch transmission for vehicle ) 是由 鱼顺基 黄圣旭 赵源珉 蔡民浩 权纯星 金千玉 于 2019-08-06 设计创作，主要内容包括：本发明提供一种车辆的双离合器变速器。该双离合器变速器(DCT)可以包括：第一输入轴和第二输入轴布置为分别从相同的动力源接收动力；第一输出轴和第二输出轴的每个与第一输入轴平行布置；第一驱动齿轮布置于第一输入轴并且与第一输入轴一起旋转；第二驱动齿轮布置于第二输入轴并且与第二输入轴一起旋转；第一从动齿轮与第一驱动齿轮啮合并且可旋转地布置于选择输出轴,所述选择输出轴是第一输出轴与第二输出轴中的一个；第二从动齿轮与第二驱动齿轮啮合并且可旋转地布置于所述选择输出轴；套筒同步器在第一从动齿轮与第二从动齿轮之间选择性地连接。(The invention provides a dual clutch transmission for a vehicle. The Dual Clutch Transmission (DCT) may include: the first input shaft and the second input shaft are arranged to receive power from the same power source, respectively; each of the first output shaft and the second output shaft is arranged in parallel with the first input shaft; a first drive gear is disposed on the first input shaft and rotates with the first input shaft; a second drive gear is arranged on the second input shaft and rotates together with the second input shaft; a first driven gear meshed with the first drive gear and rotatably disposed at a selection output shaft which is one of the first output shaft and the second output shaft; a second driven gear meshed with the second drive gear and rotatably disposed at the selection output shaft; the sleeve synchronizer is selectively connected between the first driven gear and the second driven gear.)

1. A dual clutch transmission of a vehicle, the dual clutch transmission comprising:

a first input shaft and a second input shaft configured to respectively change states of power received from the same power source;

a first output shaft and a second output shaft each mounted parallel to the first input shaft;

a first drive gear mounted to the first input shaft and rotating with the first input shaft;

a second drive gear mounted to the second input shaft and rotating with the second input shaft;

a first driven gear that meshes with the first drive gear and is rotatably mounted to a selection output shaft that is one of a first output shaft and a second output shaft;

a second driven gear that meshes with the second drive gear and is rotatably mounted to the selection output shaft;

a sleeve synchronizer configured to selectively connect between the first driven gear and the second driven gear.

2. The dual clutch transmission of a vehicle according to claim 1, wherein the selection output shaft to which the first and second driven gears are mounted includes:

a first synchronizer selectively connecting or disconnecting the first driven gear to the selection output shaft;

a second synchronizer selectively connecting or disconnecting the second driven gear to the select output shaft.

3. The dual clutch transmission of a vehicle according to claim 2,

the first input shaft and the second input shaft are respectively provided with at least one driving gear for shifting gears;

at least one of the first output shaft and the second output shaft is provided with a plurality of driven gears for gear shifting stages, which are meshed with at least one driving gear for gear shifting stages to form respective gear shifting stages.

4. The dual clutch transmission of a vehicle according to claim 3,

the at least one drive gear for the gear shift is mounted to and rotates with the first or second input shaft;

the plurality of driven gears are rotatably mounted on the first output shaft or the second output shaft;

the first output shaft or the second output shaft is provided with a synchronizer for a shift gear, the synchronizer being configured to selectively connect a plurality of driven gears to the first output shaft or the second output shaft for the shift gear.

5. The dual clutch transmission of a vehicle according to claim 4,

the at least one drive gear and the plurality of driven gears are arranged to form the remaining shift stages of all shift stages realized by the dual clutch transmission, except for the lowest shift stage and the highest shift stage;

in a state where the first driven gear is connected to the second driven gear by the sleeve synchronizer, a lowest shift range and a highest shift range are achieved by the at least one driving gear and the plurality of driven gears.

6. The dual clutch transmission of a vehicle according to claim 5,

the selection output shaft is a second output shaft;

when the lowest shift range is achieved, power transmitted from the first input shaft is transmitted to the second input shaft through the first and second driven gears, and then transmitted to the first output shaft through one of the at least one driving gear installed at the second input shaft and the plurality of driven gears engaged with the at least one driving gear.

7. The dual clutch transmission of a vehicle according to claim 5,

the selection output shaft is a second output shaft;

when the highest shift range is achieved, power transmitted from the second input shaft is transmitted to the first input shaft through the second driven gear and the first driven gear, and then transmitted to the first output shaft through one of the at least one driving gear installed at the first input shaft and the plurality of driven gears engaged with the at least one driving gear.

8. The dual clutch transmission of a vehicle according to claim 5,

the first drive gear and the first driven gear, the second drive gear and the second driven gear are each configured to form one of the remaining shift gears other than the lowest shift gear and the highest shift gear.

9. The dual clutch transmission of a vehicle according to claim 2,

the first input shaft or the second input shaft is provided with at least one driving gear for shifting gears;

at least one of the first output shaft and the second output shaft is provided with a plurality of driven gears for a shift range, which are meshed with at least one driving gear for a shift range to form a predetermined shift range.

10. The dual clutch transmission of a vehicle according to claim 9,

the at least one drive gear is mounted to and rotates with the first input shaft or the second input shaft;

the plurality of driven gears are rotatably mounted on the first output shaft or the second output shaft;

the first output shaft or the second output shaft is provided with a synchronizer for shifting gears for selectively connecting the plurality of driven gears.

11. The dual clutch transmission of a vehicle according to claim 10,

the at least one drive gear and the plurality of driven gears are arranged to form the remaining shift stages of all shift stages realized by the dual clutch transmission, except for the lowest shift stage and the highest shift stage;

in a state where the first driven gear is connected to the second driven gear by the sleeve synchronizer, a lowest shift range and a highest shift range are achieved by the at least one driving gear and the plurality of driven gears.

Technical Field

The present invention relates to a Dual Clutch Transmission (DCT) for a vehicle, and more particularly, to a technology related to a DCT structure capable of relatively reducing an overall length while implementing a plurality of shift stages.

Background

In many cases, in front engine front drive (FF) vehicles, the engine and transmission combination form a component in the transverse direction of the vehicle. In this case, since the overall length of the assembly of the engine and the transmission may be accommodated within the width in the lateral direction of the engine room of the vehicle, reducing the overall length of the assembly of the engine and the transmission is one of the most important objectives of the power train design.

On the other hand, since the output and fuel efficiency characteristics vary greatly depending on the operating region of the engine, it is desirable to operate the engine in the optimum operating region as much as possible. To this end, the transmission connecting the engine and the drive wheels may be configured to provide as many shift positions as possible.

Generally, as the number of shift ranges that can be provided by the transmission increases, the overall length of the transmission is longer. Therefore, the shift range increase of the transmission and the vehicle mountability have a trade-off relationship incompatible with each other.

The information included in this background section of the invention is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information constitutes prior art already known to a person skilled in the art.

Disclosure of Invention

Various aspects of the present invention are directed to provide a Dual Clutch Transmission (DCT) of a vehicle configured to provide a plurality of shift stages and having a relatively short overall length to improve fuel efficiency of the vehicle and ensure mountability of the vehicle.

In order to achieve the above object, the DCT for a vehicle of the present invention may include: first and second input shafts configured to respectively change states of power received from the same power source, first and second output shafts, a first driving gear, a second driving gear, a first driven gear, a second driven gear, and a sleeve synchronizer; each of the first and second output shafts is arranged in parallel with the first input shaft; the first drive gear is arranged to the first input shaft and rotates with the first input shaft; the second drive gear is arranged on the second input shaft and rotates together with the second input shaft; the first driven gear is meshed with the first drive gear and is rotatably arranged on a selection output shaft, and the selection output shaft is one of a first output shaft and a second output shaft; a second driven gear meshed with the second drive gear and rotatably disposed at the selection output shaft; the sleeve synchronizer is configured to selectively connect between the first driven gear and the second driven gear.

The selection output shaft, in which the first and second driven gears are arranged, may be provided with a first synchronizer and a second synchronizer, which may connect or disconnect the first driven gear to or from the selection output shaft; the second synchronizer may connect the second driven gear to the selection output shaft or disconnect the second synchronizer from the selection output shaft.

The first input shaft and the second input shaft may be provided with at least one drive gear for shifting gears, respectively; at least one of the first output shaft and the second output shaft is provided with a plurality of driven gears for shift stages, which mesh with a drive gear for shift stages to form the respective shift stages.

At least one drive gear for shifting gears may be arranged on the first input shaft or the second input shaft and rotate together with the first input shaft or the second input shaft; a plurality of driven gears for shifting gears may be arranged rotatably on the first output shaft or the second output shaft; and the first output shaft or the second output shaft may be provided with a synchronizer for shifting gears, which may or may not be connected with a driven gear for shifting gears.

The driving gear for the shift stages and the driven gear for the shift stages may be arranged to form remaining shift stages except for the lowest shift stage and the highest shift stage among all shift stages implemented by the DCT; in a state where the first driven gear is connected to the second driven gear by the sleeve synchronizer, a lowest shift range and a highest shift range are achieved by the driving gear for the shift range and the driven gear for the shift range.

The selection output shaft may be a second output shaft; when the lowest shift stage is achieved, the power transmitted from the first input shaft is transmitted to the second input shaft through the first and second driven gears, and then transmitted to the first output shaft through any one of the driving gears for shift stage disposed at the second input shaft and the driven gear for shift stage meshed with the driving gear for shift stage.

The selection output shaft may be a second output shaft; when the highest shift range is achieved, the power transmitted from the second input shaft is transmitted to the first input shaft through the second driven gear and the first driven gear, and then transmitted to the first output shaft through any one of the driving gears for shift range disposed at the first input shaft and the driven gear for shift range meshed with the driving gear for shift range.

The first drive gear and the first driven gear, the second drive gear and the second driven gear may be respectively configured to form any one of the remaining shift stages other than the lowest shift stage and the highest shift stage.

The first input shaft or the second input shaft may be provided with at least one driving gear for shifting gears; and at least one of the first output shaft and the second output shaft may be provided with a driven gear for a shift range, which is meshed with a driving gear for shifting to form the shift range.

A drive gear for shifting gears may be arranged on the first input shaft or the second input shaft and rotate together with the first input shaft or the second input shaft; the driven gear for shifting gears may be arranged rotatable on the first output shaft or the second output shaft; and the first output shaft or the second output shaft may be provided with a synchronizer for a shift gear for selectively connecting a driven gear for the shift gear.

The driving gear for the shift stages and the driven gear for the shift stages may be arranged to form the remaining shift stages except for the lowest shift stage and the highest shift stage among all the shift stages that may be realized by the DCT; and in a state where the first driven gear is connected to the second driven gear through the sleeve synchronizer, the lowest shift stage and the highest shift stage can be achieved by the driving gear for the shift stage and the driven gear for the shift stage.

The DCT for a vehicle of the invention can provide a plurality of shift stages and is configured such that the overall length of the transmission is relatively short, thereby improving the vehicle mountability of the transmission, and ultimately contributing to improving the fuel efficiency of the vehicle by providing a plurality of shift stages.

The method and apparatus of the present invention have other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.

Drawings

Fig. 1 is a schematic view illustrating various exemplary embodiments of a DCT of a vehicle according to an exemplary embodiment of the present invention;

fig. 2 is a schematic diagram explaining the implementation of the first gear shift by means of the respective exemplary embodiment of fig. 1;

fig. 3 is a schematic diagram explaining the implementation of the second gear shift by means of the respective exemplary embodiment of fig. 1;

fig. 4 is a schematic diagram explaining the implementation of the third gear shift by the various exemplary embodiments of fig. 1;

fig. 5 is a schematic diagram explaining the implementation of the fourth gear shift by the various exemplary embodiments of fig. 1;

fig. 6 is a schematic diagram explaining the implementation of the fifth gear shift by the respective exemplary embodiment of fig. 1;

fig. 7 is a schematic diagram explaining the implementation of the sixth shifting gear by means of the respective exemplary embodiment of fig. 1;

FIG. 8 is a schematic diagram explaining the implementation of the R range by the various exemplary embodiments of FIG. 1;

fig. 9 is a schematic view illustrating various exemplary embodiments of a DCT of a vehicle according to an exemplary embodiment of the present invention; and

fig. 10 is a schematic diagram illustrating various exemplary embodiments of a DCT of a vehicle according to an exemplary embodiment of the present invention.

It should be understood that the drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the invention as embodied herein, including, for example, specific dimensions, orientations, locations, and shapes, will be determined in part by the particular intended application and environment of use.

In the drawings, like numerals refer to like or equivalent parts throughout the several views of the drawings.

Detailed Description

Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with the exemplary embodiments of the invention, it will be understood that this description is not intended to limit the invention to those exemplary embodiments. On the other hand, the present invention is intended to cover not only exemplary embodiments of the present invention, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the present invention as defined by the appended claims.

Exemplary embodiments of the present invention will be described in detail below with reference to the following drawings.

Referring to fig. 1 to 8, each exemplary embodiment of a Dual Clutch Transmission (DCT) of a vehicle according to an exemplary embodiment of the present invention is configured to include: first and second input shafts IN1 and IN2, first and second output shafts OUT1 and OUT2, first and second drive gears D1 and D2, first and second driven gears P1 and P2, and sleeve synchronizer ST; the first and second input shafts IN1 and IN2 are configured to change the state of power received from the same power source, respectively; the first output shaft OUT1 and the second output shaft OUT2 are arranged IN parallel with the first input shaft IN 1; the first drive gear D1 is disposed on the first input shaft IN1 and rotates together with the first input shaft IN 1; the second drive gear D2 is disposed on the second input shaft IN2 and rotates together with the second input shaft IN 2; the first driven gear P1 meshing with the first drive gear D1 and rotatably arranged at a selection output shaft which is one of the first output shaft OUT1 and the second output shaft OUT 2; the second driven gear P2 is meshed with a second drive gear D2 and is rotatably disposed at the select output shaft; the sleeve synchronizer ST is selectively connected between the first driven gear P1 and the second driven gear P2.

The first input shaft IN1 and the second input shaft IN2 may have a connection state of sequentially providing or receiving power between the first input shaft IN1 and the second input shaft IN2 through the first driving gear D1, the first driven gear P1, the sleeve synchronizer ST, the second driven gear P2, and the second driving gear D2, and the connection state of the first input shaft IN1 and the second input shaft IN2 may be released through the sleeve synchronizer ST.

The first input shaft IN1 is configured to receive power from the power source through the first clutch CL1, and the second input shaft IN2 is configured to receive power from the power source through the second clutch CL 2.

The first input shaft IN1 may be formed as a hollow shaft, the second input shaft IN2 is inserted into the first input shaft IN1, the first output shaft OUT1 may be provided with a first output gear OG1 for outputting power, and the second output shaft OUT2 may be provided with a second output gear OG2 for outputting power.

The first output gear OG1 and the second output gear OG2 are configured to mesh with a ring gear of a differential, respectively, to output power to running wheels.

The first and second input shafts IN1 and IN2 may be provided with at least one driving gear for a shift range, respectively, and at least one of the first and second output shafts OUT1 and OUT2 may be provided with a plurality of driven gears for the shift range that mesh with the driving gear for the shift range to form the respective shift ranges.

A driving gear for the shift position may be disposed at the first input shaft IN1 or the second input shaft IN2 and rotated together with the first input shaft IN1 or the second input shaft IN2, a driven gear for the shift position may be disposed rotatably on the first output shaft OUT1 or the second output shaft OUT2, and the first output shaft OUT1 or the second output shaft OUT2 may be provided with a synchronizer for the shift position for selectively connecting the driven gear for the shift position.

That is, IN an exemplary embodiment of the present invention, the first input shaft IN1 may be provided with a drive gear 5SD for the fifth gear, the second input shaft IN2 may be provided with a drive gear 2SD for the second gear, the first output shaft OUT1 may be provided with a driven gear 5SP for the fifth gear (which meshes with the drive gear 5SD for the fifth gear) and a driven gear 2SP for the second gear (which meshes with the drive gear 2SD for the second gear), and the first output shaft OUT1 may be provided with a synchronizer 5SS for the fifth gear which connects the driven gear 5SP for the fifth gear to the first output shaft OUT1 to realize the fifth gear, and a synchronizer 2SS for the second gear; the synchronizer 2SS for second gear connects the driven gear 2SP for second gear to the first output shaft OUT1 to realize the second gear.

Of course, the drive gear 2SD for the second gear and the drive gear for the fifth gear 5SD belong to the drive gears for the shift gears, the driven gear 2SP for the second gear and the driven gear 5SP for the fifth gear belong to the driven gears for the shift gears, and the synchronizer 2SS for the second gear and the synchronizer 5SS for the fifth gear belong to the synchronizers for the gears.

In an exemplary embodiment of the invention, the selection output shaft may include a second output shaft OUT 2. However, the first output shaft OUT1 may also be configured as the selection output shaft.

The driving gear for the shift stages and the driven gear for the shift stages may be provided to form the remaining shift stages except for the lowest shift stage and the highest shift stage among all the shift stages that may be realized by the DCT.

For reference, the DCT according to the exemplary embodiment of the present invention is configured to realize a total of six forward gears and an R gear as a reverse shift gear, and the lowest shift gear is a first shift gear and the highest shift gear is a sixth shift gear. As described above, the drive gear for the shift range and the driven gear for the shift range realize the second shift range and the fifth shift range, and as described later, the third shift range may be realized by the first drive gear D1, the first driven gear P1, the first synchronizer 1SH, and the fourth shift range may be realized by the second drive gear D2, the second driven gear P2, and the second synchronizer 2 SH.

The lowest shift stage and the highest shift stage are configured to be achieved by the driving gear for the shift stage and the driven gear for the shift stage in a state where the first driven gear P1 and the second driven gear P2 are connected through the sleeve synchronizer ST.

That is, IN implementing the lowest shift stage, the power configured to be transmitted from the first input shaft IN1 may be transmitted to the first output shaft OUT1 through any one of the driving gears for shift stage disposed at the second input shaft IN2 and the driven gear for shift stage meshed with the driving gear for shift stage after being transmitted to the second input shaft IN2 through the first driven gear P1 and the second driven gear P2.

Fig. 2 shows a state in which the first gear is achieved in the exemplary embodiment of the present invention. The sleeve synchronizer ST connects the first driven gear P1 and the second driven gear P2 to each other, and the synchronizer 2SS for the second gear connects the driven gear 2SP for the second gear to the first output shaft OUT1, so that the power input from the power source to the first input shaft IN1 through the first clutch CL1 sequentially passes through the first drive gear D1, the first driven gear P1, the sleeve synchronizer ST, the second driven gear P2, the second drive gear D2, the second input shaft IN2, the drive gear 2SD for the second gear, the driven gear 2SP for the second gear, the synchronizer 2SS for the second gear, and the first output shaft OUT1 to be shifted to the first gear.

That is, the present invention realizes the first gear as the lowest shift gear by combining the transmission gear ratios of the other shift gears without preparing separate driving gears, driven gears, and synchronizers for realizing the first gear, thereby reducing the number of parts to reduce the overall length and weight of the transmission.

Further, when the highest shift position is achieved, the power configured to be transmitted from the second input shaft IN2 may be transmitted to the first input shaft IN1 through the second driven gear P2 and the first driven gear P1, and then transmitted to the first output shaft OUT1 through any one of the driving gears for shift position disposed at the first input shaft IN1 and the driven gear for shift position engaged with the driving gear for shift position.

Fig. 7 shows a state where the sixth gear is achieved in the exemplary embodiment of the present invention. IN a state where the sleeve synchronizer ST connects the first driven gear P1 with the second driven gear P2 and the synchronizer 5SS for the fifth gear connects the driven gear 5SP for the fifth gear to the first output shaft OUT1, power input from the power source to the second input shaft IN2 through the second clutch CL2 is sequentially shifted to the sixth gear through the second drive gear D2, the second driven gear P2, the sleeve synchronizer ST, the first driven gear P1, the first drive gear D1, the first input shaft IN1, the drive gear 5SD for the fifth gear, the driven gear 5SP for the fifth gear, the synchronizer for the fifth gear 5SS and the first output shaft OUT 1.

That is, the present invention realizes the sixth gear, which is the highest shift gear, by combining gears and synchronizers for realizing other shift gears without preparing a separate gear or synchronizer for the sixth gear, which is used only for realizing the sixth gear, reduces the overall length of the transmission by reducing the number of parts and improves fuel efficiency by reducing the weight of the transmission.

On the other hand, the second output shaft OUT2 is provided with a first driven gear P1 and a second driven gear P2 as the selection output shaft, the second output shaft OUT2 may be provided with a first synchronizer 1SH and a second synchronizer 2SH, the first synchronizer 1SH may connect the first driven gear P1 to the selection output shaft or disconnect the first driven gear P1 from the selection output shaft; the second synchronizer 2SH may connect the second driven gear P2 to the select output shaft or disconnect the second driven gear P2 from the select output shaft.

The first drive gear D1 and the first driven gear P1, the second drive gear D2 and the second driven gear P2 are respectively configured to form any one of the remaining shift stages except the lowest shift stage and the highest shift stage.

That is, the first driving gear D1 and the first driven gear P1 are configured to realize the third shift stage through the first synchronizer 1SH, and the second driving gear D2 and the second driven gear P2 are configured to realize the fourth shift stage through the second synchronizer 2 SH.

In other words, the first driving gear D1 and the first driven gear P1, the second driving gear D2 and the second driven gear P2 may form a third shift stage and a fourth shift stage, respectively, and may also be used to realize the first stage as the lowest shift stage and the sixth stage as the highest shift stage.

Of course, the exemplary embodiment of the present invention assumes that the highest shift stage is the sixth stage, but the present invention is not limited thereto. When the shift gears between the lowest shift gear and the highest shift gear are configured as, for example, seven gears, the lowest shift gear may be the first gear, and the highest shift gear may be the ninth gear, while the lowest shift gear and the highest shift gear are realized by combining the transmission gear ratios of the shift gears connected by the sleeve synchronizer ST as described above, and when the shift gears between the lowest shift gear and the highest shift gear are configured as, for example, eight gears, the highest shift gear may be the tenth gear.

For reference, the transmission gear ratio of the first gear in the exemplary embodiment of the present invention may be achieved by multiplying the gear ratio between the first driving gear D1 and the first driven gear P1, the gear ratio between the second driven gear P2 and the second driving gear D2, and the gear ratio between the driving gear 2SD for the second gear and the driven gear 2SP for the second gear, and the transmission gear ratio of the sixth gear may be achieved by multiplying the gear ratio between the second driving gear D2 and the second driven gear P2, the gear ratio between the driven gear for the first gear and the driving gear for the first gear, and the gear ratio between the driving gear 5SD for the fifth gear and the driven gear 5SP for the fifth gear.

For reference, fig. 8 shows a state in which the R range, which is a reverse shift range, is implemented in the exemplary embodiment of the present invention. To achieve the R range, the first driven gear P1 may be integrally provided with a reverse drive gear RD, which is meshed with the reverse drive gear RD and is arranged rotatably on the first output shaft OUT 1. When the reverse driven gear RP is connected to the first output shaft OUT1 by using the synchronizer 2SS for the second gear, the power transmitted to the first input shaft IN1 is output to the first output shaft OUT1 while the R gear is formed by the first drive gear D1, the first driven gear P1, the reverse drive gear RD, the reverse driven gear RP, and the synchronizer 2SS for the second gear.

Fig. 9 illustrates various exemplary embodiments of the present invention. Corresponding to the case of using the motor as a power source, a simpler DCT is configured by removing components for realizing the R range in each exemplary embodiment.

In this case, the synchronizer 5SS for the fifth gear is also removed, the synchronizer 2SS for the second gear has a function of connecting the driven gear 2SP for the second gear to the first output shaft OUT1 and a function of connecting the driven gear 5SP for the fifth gear to the first output shaft OUT1, and reverse travel can be achieved by rotating the motor in reverse while achieving the first gear.

Fig. 10 illustrates various exemplary embodiments of the present invention. In contrast to the respective exemplary embodiments of the present invention in which the driven gear 2SP for the second gear, which is disposed on the first output shaft OUT1, is disposed on the second output shaft OUT2, the second synchronizer 2SH may have an additional function of selectively connecting the driven gear 2SP for the second gear to the second output shaft OUT2, making it a structure that can be utilized in the case where the overall length of the portion where the first output shaft OUT1 is located is at an unfavorable position.

For convenience in explanation and accurate definition in the appended claims, the terms "upper", "lower", "inner", "outer", "upper", "lower", "upward", "downward", "front", "rear", "back", "inner", "outer", "inward", "outward", "inner", "outer", "inboard", "outboard", "forward", "rearward" are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. It will be further understood that the term "connected," or derivatives thereof, refers to both direct and indirect connections.

The foregoing description of specific exemplary embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable others skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the following claims and their equivalents.