Hybrid powertrains for vehicles

Abstract

The present invention relates to a hybrid powertrain for a vehicle, which may include: a first input shaft connected to an engine; a second input shaft connected to the engine and mounted coaxially with the first input shaft; a motor input shaft mounted coaxially with the first input shaft and connected to the motor; a first output shaft and a second output shaft mounted parallel to the first input shaft and the second input shaft; a variable drive gear arranged at the motor input shaft to transmit power from the motor input shaft to the first output shaft; a compound synchronizer connecting and disconnecting the first input shaft and the motor input shaft, and connecting and disconnecting the variable drive gear and the motor input shaft; and a plurality of external gear pairs configured to respectively define different gear ratios.

Description

Technical Field

[0001] The present invention relates to a layout of a hybrid powertrain suitable for a vehicle. Background Art

[0002] A transmission mounted electric device (TMED) hybrid powertrain is a hybrid powertrain in which the motor is mounted at the transmission rather than the engine.

[0003] In conventional TMED hybrid powertrains constructed as described above, a structure in which the engine is connected to the motor via an engine clutch is widely used. Because this type of hybrid powertrain is provided with an engine clutch, the installation of the engine clutch increases manufacturing costs. In addition, when the engine clutch is connected, the speed of the engine and the speed of the motor are limited to the same level. In addition, because the speed map is set according to the optimal operating point of the engine, but the main operating range of the motor is concentrated in the low-speed range, it is difficult to achieve the optimal performance of the motor. In addition, because the motor is located on the input side of the transmission, the power transmission path between the drive wheels and the motor becomes complicated during regenerative braking, which reduces the efficiency of regenerative braking.

[0004] The information disclosed in this Background of the invention section is only for enhancement of understanding of the general background of the invention and is not to be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. Summary of the Invention

[0005] Various aspects of the present invention are directed to a hybrid powertrain for a vehicle in which an engine clutch for coupling and decoupling an engine and a motor is omitted, thereby reducing vehicle manufacturing costs and weight. The motor is controlled independently of the engine to achieve optimal operation of the motor and engine, and the power transmission path between the motor and the drive wheels is shortened during regenerative braking, thereby improving the efficiency of both EV mode and regenerative braking.

[0006] According to various aspects of the present invention, the above-mentioned and other objects can be achieved by providing a hybrid powertrain for a vehicle, the hybrid powertrain comprising: a first input shaft selectively connected to an engine via a first clutch; a second input shaft selectively connected to the engine via a second clutch and mounted coaxially with the first input shaft; a motor input shaft mounted coaxially with the first input shaft and connected to the motor; a first output shaft and a second output shaft, each of which is mounted parallel to the first input shaft and the second input shaft; a variable drive gear mounted at the motor input shaft to shift the motor to a higher gear while the rotational speed of the motor input shaft is maintained or increased. Force is transmitted from the motor input shaft to the first output shaft; a compound synchronizer, which is configured to respectively perform coupling and decoupling between the first input shaft and the motor input shaft, and coupling and decoupling between the variable drive gear and the motor input shaft; and a plurality of gear pairs, which are configured to respectively define different gear ratios between the first input shaft and the first output shaft, between the first input shaft and the second output shaft, between the second input shaft and the first output shaft, and between the second input shaft and the second output shaft, wherein the plurality of gear ratios between the plurality of gear pairs and the two gear ratios between the variable drive gear and the first output shaft form a series of gear ratios for driving a vehicle.

[0007] The compound synchronizer may include: a hub mounted on the motor input shaft; and a first sleeve and a second sleeve, each of which is mounted on the hub to be independently slidable in an axial direction of the hub.

[0008] The variable drive gear is integrally arranged with the clutch gear, which is configured to selectively engage with the second sleeve of the compound synchronizer, the first rotating element can be set to be held by a brake, and the second rotating element can be integrally connected to the third rotating element of the planetary gear set, and the third rotating element of the planetary gear set is connected to the motor input shaft.

[0009] The compound synchronizer may form a synchronizer configured to connect the motor input shaft to the first input shaft by a synchronizing action of a synchronizer ring when the first sleeve moves in its axial direction, and wherein the second sleeve forms a dog clutch with the clutch gear of the variable drive gear.

[0010] The external gear pair between the first input shaft and the first output shaft can be configured to define a fourth speed transmission ratio, the external gear pair between the first input shaft and the second output shaft can be configured to define a sixth speed transmission ratio, the external gear pair between the second input shaft and the first output shaft can be configured to define a fifth speed transmission ratio, the external gear pair between the second input shaft and the second output shaft can be configured to define a third speed transmission ratio, and the variable drive gear can transmit power to the first output shaft at the first speed transmission ratio and the second speed transmission ratio.

[0011] The first input shaft may be provided with a first drive gear, which is commonly used to achieve the fourth speed transmission ratio and the sixth speed transmission ratio, the second input shaft may be provided with a second drive gear, which is commonly used to achieve the third speed transmission ratio and the fifth speed transmission ratio, the first output shaft may be provided with a fourth driven wheel engaged with the first drive wheel and a fifth driven wheel engaged with the second drive wheel, and the second output shaft may be provided with a sixth driven gear engaged with the first drive gear and a third driven gear engaged with the second drive gear.

[0012] The first drive gear can be installed on the first input shaft so that its rotation is restricted, the second drive gear can be installed on the second input shaft so that its rotation is restricted, the first output shaft can be provided with a fourth-fifth synchronizer, the fourth-fifth synchronizer is configured to selectively hold the fourth driven gear or the fifth driven gear to restrict its rotation relative to the first output shaft, and the second output shaft can be provided with a third-sixth synchronizer, the third-sixth synchronizer is configured to selectively connect the third driven gear or the sixth driven gear to the second output shaft to restrict its rotation relative to the second output shaft.

[0013] The first drive gear may be integrally provided with a clutch gear selectively engaged with a first sleeve of the compound synchronizer.

[0014] The first output shaft may be provided with a first output gear, the second output shaft may be provided with a second output gear, and the first output gear and the second output gear may be engaged with a ring gear of the differential.

[0015] The first clutch and the second clutch may form a dual clutch formed at a single clutch housing, and the second input shaft may include a hollow shaft surrounding the first input shaft.

[0016] The methods and apparatus of the present invention will be apparent from or set forth in greater 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A diagram exemplarily illustrating a configuration of a hybrid powertrain for a vehicle according to an exemplary embodiment of the present invention;

[0018] FIG. 2A , FIG. 2B and FIG. 2C are diagrams showing exemplary Figure 1 A diagram illustrating a process of shifting gears from a first gear to a second gear in a hybrid powertrain;

[0019] FIG3A, FIG3B, FIG3C and FIG3D are exemplary diagrams showing Figure 1A diagram illustrating the process of shifting from second gear to third gear in a hybrid powertrain;

[0020] FIG. 4A , FIG. 4B , FIG. 4C and FIG. 4D are diagrams showing exemplary Figure 1 A view showing the process of shifting from third gear to fourth gear in a hybrid powertrain;

[0021] FIG5A, FIG5B, FIG5C, FIG5D and FIG5E are exemplary diagrams showing Figure 1 A view showing the process of shifting from fourth gear to fifth gear in a hybrid powertrain;

[0022] FIG6A, FIG6B, FIG6C and FIG6D are exemplary diagrams showing Figure 1 A view showing the process of shifting from fifth gear to sixth gear in a hybrid powertrain;

[0023] Figure 7 For example, Figure 1 A diagram showing a state in which an EV first gear is established in a hybrid powertrain; and

[0024] Figure 8 For example, Figure 1 A diagram illustrating a state in which an EV second gear is established in a hybrid powertrain is shown.

[0025] It should be understood that the accompanying drawings are not necessarily drawn to scale, presenting a somewhat simplified representation of various features illustrating the basic principles of the invention. The specific design features of the present invention as incorporated herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

[0026] In the drawings, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. DETAILED DESCRIPTION

[0027] Reference will now be made in detail to various embodiments of the present invention, examples of which are shown in the accompanying drawings and described below. Although the present invention will be described in conjunction with exemplary embodiments thereof, it should 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 the exemplary embodiments of the present invention, but also various alternatives, modifications, equivalents and other embodiments that may be included within the spirit and scope of the present invention as defined by the appended claims.

[0028] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Throughout the drawings, the same reference numerals will be used wherever possible to refer to the same or like parts.

[0029] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

[0030] refer to Figure 1 , a hybrid powertrain for a vehicle according to an exemplary embodiment of the present invention includes: a first input shaft IN1, which is selectively connected to an engine E via a first clutch CL1; a second input shaft IN2, which is selectively connected to the engine E via a second clutch CL2 and is coaxially installed with the first input shaft IN1; a motor input shaft MI, which is coaxially installed with the first input shaft IN1 and connected to the motor M; a first output shaft OUT1 and a second output shaft OUT2, which are installed parallel to the first input shaft IN1 and the second input shaft IN2; a variable drive gear VD, which is provided at the motor input shaft MI to rotate the motor input shaft MI. a composite synchronizer CS configured to individually perform coupling and decoupling between the first input shaft IN1 and the motor input shaft, and coupling and decoupling between the first drive gear DG1 and the motor input shaft MI; and a plurality of external gear pairs configured to respectively define different gear ratios between the first input shaft IN1 and the first output shaft OUT1, between the first input shaft IN1 and the second output shaft OUT2, between the second input shaft IN2 and the first output shaft OUT1, and between the second input shaft IN2 and the second output shaft OUT2.

[0031] The plurality of gear ratios between the plurality of external gear pairs and the gear ratio between the variable drive gear VD and the first output shaft OUT1 form a series of gear ratios for driving the vehicle.

[0032] According to an exemplary embodiment of the present invention, a plurality of external gear pairs are configured to limit a third speed transmission ratio to a sixth speed transmission ratio, and the variable drive gear VD is configured to limit a first speed transmission ratio when power is transmitted from the motor input shaft MI while maintaining its rotational speed, and to limit a second speed transmission ratio when power is transmitted from the motor input shaft MI while its rotational speed is increased, resulting in the vehicle being configured to achieve a series of transmission ratios from the first speed transmission ratio to the sixth speed transmission ratio.

[0033] The first clutch CL1 and the second clutch CL2 form a dual clutch DCL within a single clutch housing CH. The second input shaft IN2 comprises a hollow shaft surrounding the first input shaft IN1, and the first output shaft OUT1 is provided with a first output gear OG1. The second output shaft OUT2 is provided with a second output gear OG2, and both the first and second output gears OG1 and OG2 engage with the ring gear RG of the differential DF.

[0034] The powertrain according to an exemplary embodiment of the present invention is configured so that the power transmitted from the engine E to the first input shaft IN1 and the second input shaft IN2 via the first clutch CL1 and the second clutch CL2 of the dual clutch DCL, respectively, is transmitted to the differential DF via the variable drive gear VD, thereby establishing the first forward gear to the sixth forward gear, and performing smooth gear shifting through the gear shifting action (which will be described later) without generating torque interruption during gear shifting.

[0035] Since the motor M is not coupled to the engine E via an engine clutch, the need for an engine clutch is eliminated, thereby reducing vehicle manufacturing costs and vehicle weight. Furthermore, since the motor M is controlled independently of the engine E, a high degree of control freedom is ensured for the motor M. Furthermore, since power can be transmitted between the motor M and the drive wheels via a relatively short power transmission path, high power transmission efficiency can be ensured.

[0036] The compound synchronizer CS includes a hub HB mounted on the motor input shaft MI and a first sleeve SB1 and a second sleeve SB2 mounted on the hub HB so as to be independently slidable.

[0037] As used herein, the term "axial" refers to the longitudinal direction of the motor input shaft MI.

[0038] The variable drive gear VD is integrally provided with the clutch gear CG, which is configured to engage with the second sleeve SB2 of the compound synchronizer CS. The first rotation element is configured to be retained by the brake BK fixed to the transmission housing H, and the second rotation element is integrally connected to the third rotation element of the planetary gear set PG, which is connected to the motor input shaft MI.

[0039] Here, the first rotation element of the planetary gear set PG includes a sun gear S, the second rotation element includes a planet carrier C, and the third rotation element includes a ring gear R.

[0040] The second sleeve SB2 engages the clutch gear CG of the variable drive gear VD, and the compound synchronizer CS connects the variable drive gear VD to the motor input shaft MI. When the brake BK is not engaged, the variable drive gear VD transmits power from the motor input shaft MI to the first output shaft OUT1 without any change. At this time, since the ring gear R and the planetary carrier C of the planetary gear set PG are considered to be connected to each other, all rotating elements rotate with the variable drive gear VD at the same speed as the motor input shaft MI.

[0041] When the second sleeve SB2 is disengaged from the clutch gear CG of the variable drive gear VD and the brake BK is engaged, power from the motor input shaft MI is input to the planetary gear carrier C of the planetary gear set PG, and its speed increases. Therefore, the variable drive gear VD, which is directly connected to the ring gear R, transmits power from the motor input shaft MI to the first output shaft OUT1 in a state in which its speed increases.

[0042] The compound synchronizer CS forms a synchronizer configured to be connected to the first input shaft IN1 by a synchronizing action of a synchronizer ring when the first sleeve SB1 moves in its axial direction, and the second sleeve SB2 forms a dog clutch together with the clutch gear CG of the variable drive gear VD.

[0043] According to an exemplary embodiment of the present invention, the first drive gear DG1 to be described later is integrally arranged with the clutch gear CG, which forms a part of the compound synchronizer CS, so that the first input shaft IN1 is directly connected to the motor input shaft MI through the engagement between the clutch gear CG and the first sleeve SB1, as described above.

[0044] Since the synchronizer ring is provided between the clutch gear CG of the first drive gear DG1 and the first sleeve SB1 , the first sleeve SB1 is engaged with the clutch gear CG of the first drive gear DG1 by a synchronizing action of a synchromesh type synchronizer.

[0045] For reference, the synchronizer ring may be embodied by the same synchronizer ring as that used in a conventional synchromesh type synchronizer, and thus illustration of the synchronizer ring is omitted in the drawings.

[0046] As described above, the second sleeve SB2 of the compound synchronizer CS forms a dog clutch together with the clutch gear CG of the variable drive gear VD, so that a synchronizing action can be actively performed by the motor M and the brake BK.

[0047] The external gear pair between the first input shaft IN1 and the first output shaft OUT1 is configured to define a fourth speed gear ratio, and the external gear pair between the first input shaft IN1 and the second output shaft OUT2 is configured to define a sixth speed gear ratio. The external gear pair between the second input shaft IN2 and the first output shaft OUT1 is configured to define a fifth speed gear ratio, and the external gear pair between the second input shaft IN2 and the second output shaft OUT2 is configured to define a third speed gear ratio. The variable drive gear VD is configured to transmit power to the first output shaft OUT1 at the first speed gear ratio and the second speed gear ratio.

[0048] In other words, the first input shaft IN1 is provided with a first drive gear DG1, which is used in common to achieve the fourth speed gear ratio and the sixth speed gear ratio, and the second input shaft IN2 is provided with a second drive gear DG2, which is used in common to achieve the third speed gear ratio and the fifth speed gear ratio. The first output shaft OUT1 is provided with a fourth driven gear P4 engaged with the first drive gear DG1 and a fifth driven gear P5 engaged with the second drive gear DG2, and the second output shaft OUT2 is provided with a sixth driven gear P6 engaged with the first drive gear DG1 and a third driven gear P3 engaged with the second drive gear DG2.

[0049] The first drive gear DG1 is mounted on the first input shaft IN1 so that its rotation is restricted, and the second drive gear DG2 is mounted on the second input shaft IN2 so that its rotation is restricted. The first output shaft OUT1 is provided with fourth and fifth synchronizers 4 & 5S, which are configured to selectively hold the fourth driven gear P4 or the fifth driven gear P5 to restrict their rotation relative to the first output shaft OUT1, and the second output shaft OUT2 is provided with third and sixth synchronizers 3 & 6S, which are configured to selectively hold the third driven gear P3 or the sixth driven gear P6 to restrict their rotation relative to the second output shaft OUT2.

[0050] The first output shaft OUT1 is provided with a variable driven gear VP that meshes with the variable drive gear VD in a state where the rotation of the variable driven gear VD is restricted. Therefore, power can be transmitted from the variable drive gear VD to the first output shaft OUT1.

[0051] Hereinafter, a sequential shifting process from the first gear to the sixth gear will be described with reference to FIG. 2 to FIG. 6 .

[0052] Figures 2A to 2C illustrate the shifting process from first gear to second gear. In the state shown in Figure 2A , the first clutch CL1 is engaged, and the first sleeve SB1 of the compound synchronizer CS connects the variable drive gear VD to the motor input shaft MI. Subsequently, the second sleeve SB2 connects the variable drive gear VD to the motor input shaft MI, transmitting power from the engine E to the variable drive gear VD via the motor input shaft MI, thereby driving the variable drive gear VD and achieving a first speed ratio between the variable drive gear VD and the variable driven gear VP.

[0053] In the state shown in FIG. 2B , the second sleeve SB2 of the compound synchronizer CS is released to the neutral state by applying force, and the brake BK starts to be engaged.

[0054] When brake BK is engaged, the speed of the variable drive gear VD begins to increase compared to the speed of the motor input shaft MI. At this point, the direction of the torque acting between the hub HB of the compound synchronizer CS, the second sleeve SB2, and the clutch gear CG of the variable drive gear VD changes. When the second sleeve SB2 is released to neutral after the torque direction changes, the state shown in Figure 2C is established. Since the planetary gear set PG increases the speed of the power from the motor input shaft MI, the power output via the variable drive gear VD and the variable driven gear VP becomes the output at the second gear.

[0055] 3A to 3D illustrate the process of shifting from the second gear to the third gear. When a command for shifting to the third gear is generated in the second gear driving state shown in FIG3A , the third to sixth synchronizers 3 & 6S connect the third driven gear P3 to the second output shaft OUT2 (as shown in FIG3B ), and the second clutch CL2 begins to slip (as shown in FIG3C ).

[0056] With the second clutch CL2 engaged and the first clutch CL1 released, a third-gear driving state is achieved, as shown in FIG3D .

[0057] 4A to 4D illustrate the process of shifting from third gear to fourth gear. When a command to shift to fourth gear is generated while the vehicle is in third gear as shown in FIG. 4A , the fourth-fifth synchronizer 4 & 5S connects the fourth driven gear P4 to the first output shaft OUT1 (as shown in FIG. 4B ), and the first clutch CL1 begins to slip (as shown in FIG. 4C ).

[0058] With the first clutch CL1 engaged and the second clutch CL2 released, a fourth-gear driving state is achieved, as shown in FIG. 4D .

[0059] 5A to 5E illustrate a process for shifting from fourth gear to fifth gear. When a command for shifting to fifth gear is generated in the fourth gear driving state shown in FIG. 5A , the motor M is driven with the brake BK engaged, and the first output shaft OUT1 is driven to the fourth gear driving state via the variable drive gear VD and the variable driven gear VP.

[0060] 5C , the first clutch CL1 is released, and the fourth-fifth synchronizer 4 & 5S is released from the fourth driven gear P4 while maintaining the driving state at the fourth gear position only by the driving force from the motor M, thereby connecting the fifth driven gear P5 to the first output shaft OUT1 .

[0061] 5D , the second clutch CL2 is connected, and the running state at the fifth gear is established. When the connection with the motor M is released, the running state at the fifth gear is established only by the power from the engine E.

[0062] According to an exemplary embodiment of the present invention, when shifting from fourth gear to fifth gear, the fourth-fifth synchronizer 4 & 5S, which connects the fourth driven gear P4 to the first output shaft OUT1, is released to a neutral state. Subsequently, when the fifth driven gear P5 is connected to the first output shaft OUT1, a torque interruption may occur, where the power from the engine E is blocked and not transmitted to the drive wheels. However, since the exemplary embodiment of the present invention is configured so that power is continuously transmitted from the motor M to the first output shaft OUT1, a smooth gear shift can be ensured without torque interruption.

[0063] 6A to 6D illustrate a process for shifting from fifth gear to sixth gear. When a command for shifting to sixth gear is generated in the fifth gear driving state shown in FIG. 6A , the third-sixth synchronizer 3 & 6S connects the sixth driven gear P6 to the second output shaft OUT2 (as shown in FIG. 6B ), and the first clutch CL1 begins to slip (as shown in FIG. 6C ).

[0064] When the first clutch CL1 is coupled and the second clutch CL2 is released, a driving state at the sixth gear position is established, as shown in FIG. 6D .

[0065] Figure 7 and Figure 8 Shown in Figure 1 The hybrid powertrain is shown in a state where the EV first gear and the EV second gear are established.

[0066] exist Figure 7 In the EV first gear shown, the motor M is driven in a state where the second sleeve SB2 of the compound synchronizer CS connects the variable drive gear VD to the motor input shaft MI, and thus the variable drive gear VD rotates at the same speed as the motor input shaft MI. Figure 8 In the EV second gear shown, the brake BK is engaged and the motor M is driven in a state where the second sleeve SB2 is released to a neutral state, and thus the speed of the variable drive gear VD is increased compared to the speed of the motor input shaft MI.

[0067] Figure 7 EV first gear and Figure 8 The EV second gear in the vehicle can be converted into a reverse speed by the reverse rotation of the motor M.

[0068] Needless to say, the hybrid powertrain according to an exemplary embodiment of the present invention is configured to achieve a hybrid mode in which the motor M is driven to supplement the power from the engine E in a state in which the variable drive gear VD is connected to the motor input shaft MI at all first to sixth gears via the second sleeve SB2 of the compound synchronizer CS, wherein the power from the engine E is output via the first output shaft OUT1 or the second output shaft OUT2.

[0069] As apparent from the foregoing description, according to the exemplary embodiments of the present invention, the omission of the engine clutch for coupling and decoupling the engine and motor reduces wheel manufacturing costs and vehicle weight. Furthermore, since the motor is controlled independently of the engine, optimal operation of the motor and engine is possible. Furthermore, since the power transmission path between the motor and the drive wheels is shortened during regenerative braking, the efficiency of both EV mode and regenerative braking can be improved.

[0070] To facilitate interpretation and accurate definition in the appended claims, the terms "upper," "lower," "inner," "outer," "up," "lower," "upward," "downward," "front," "rear," "back," "inner," "outer," "inwardly," "outwardly," "inner," "external," "forward," and "rearward" are used to describe features of the exemplary embodiments with reference to the positions of features as shown in the accompanying drawings. It will be further understood that the term "connect" or its derivatives refers to both direct and indirect connections.

[0071] Furthermore, the term “fixedly connected” means that the fixedly connected members always rotate at the same speed. Furthermore, the term “selectively connected” means that the selectively connected members rotate individually when the selectively connected members are not engaged with each other, rotate at the same speed when the selectively connected members are engaged with each other, and remain stationary when at least one of the selectively connected members is a fixed member and the remaining selectively connected members are engaged with the fixed member.

[0072] The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously, many modifications and variations are possible in light of the above teachings. The exemplary embodiments are chosen and described to explain certain principles of the present invention and their practical application, thereby enabling others skilled in the art to make and utilize various exemplary embodiments of the present invention and various alternatives and modifications thereof. The scope of the present invention is intended to be defined by the appended claims and their equivalents.

Claims

1. A powertrain for a vehicle, comprising: a first input shaft selectively connected to the engine via a first clutch; a second input shaft selectively connected to the engine via a second clutch and mounted coaxially with the first input shaft; a motor input shaft mounted coaxially with the first input shaft and connected to the motor; a first output shaft and a second output shaft, each of the first output shaft and the second output shaft being mounted parallel to the first input shaft and the second input shaft; a variable drive gear mounted at the motor input shaft for transmitting power from the motor input shaft to the first output shaft while the rotational speed of the motor input shaft is maintained or increased; a compound synchronizer configured to respectively perform coupling and decoupling between the first input shaft and the motor input shaft, and coupling and decoupling between the variable drive gear and the motor input shaft; as well as a plurality of gear pairs configured to define different gear ratios between the first input shaft and the first output shaft, between the first input shaft and the second output shaft, between the second input shaft and the first output shaft, and between the second input shaft and the second output shaft, respectively; The plurality of gear ratios between the plurality of gear pairs and the two gear ratios between the variable drive gear and the first output shaft form a series of gear ratios for driving the vehicle.

2. The powertrain for a vehicle according to claim 1, wherein: The variable drive gear is rotatably mounted at the motor input shaft.

3. The powertrain for a vehicle according to claim 1, wherein: The compound synchronizer comprises: a hub mounted on the motor input shaft; and A first sleeve and a second sleeve, each of the first sleeve and the second sleeve is mounted on the hub to be independently slidable in an axial direction of the hub.

4. The powertrain for a vehicle according to claim 2, further comprising: a planetary gear set connected to the motor input shaft, Wherein, the planetary gear set includes: a first rotating element rotatably mounted on the motor input shaft and selectively connected to the transmission case via a brake; a second rotating element engaged with the first rotating element and fixedly connected to the motor input shaft; and A third rotating element is engaged with the second rotating element and is fixedly connected to the variable drive gear.

5. The powertrain for a vehicle according to claim 4, wherein: The first rotation element is a sun gear, the second rotation element is a planetary carrier, and the third rotation element is a ring gear.

6. The powertrain for a vehicle according to claim 3, in, The variable drive gear includes a clutch gear configured to selectively engage with the second sleeve of the compound synchronizer.

7. The powertrain for a vehicle according to claim 6, in, The compound synchronizer forms a synchronizer configured to connect the motor input shaft to the first input shaft by a synchronizing action of a synchronizer ring when the first sleeve moves in the axial direction, and Wherein, the second sleeve forms a dog clutch with the clutch gear of the variable drive gear.

8. The powertrain for a vehicle according to claim 3, in, The series of gear ratios includes a first speed gear ratio, a second speed gear ratio, a third speed gear ratio, a fourth speed gear ratio, a fifth speed gear ratio and a sixth speed gear ratio, The plurality of gear pairs include a first gear pair, a second gear pair, a third gear pair and a fourth gear pair. wherein the first gear pair between the first input shaft and the first output shaft is configured to define the fourth speed gear ratio, wherein the second gear pair between the first input shaft and the second output shaft is configured to define the sixth speed gear ratio, wherein the third gear pair between the second input shaft and the first output shaft is configured to define the fifth speed gear ratio, wherein the fourth gear pair between the second input shaft and the second output shaft is configured to define the third speed gear ratio, and The variable drive gear transmits power to the first output shaft at the first speed transmission ratio and the second speed transmission ratio.

9. The powertrain for a vehicle according to claim 8, in, The first gear pair and the second gear pair include a first drive gear mounted on the first input shaft, the first drive gear being used together to achieve the fourth speed gear ratio and the sixth speed gear ratio. The third gear pair and the fourth gear pair include a second drive gear mounted on the second input shaft, and the second drive gear is used together to achieve the third speed transmission ratio and the fifth speed transmission ratio. Wherein, the first output shaft is fixedly mounted with a first output gear, Wherein, the second output shaft is fixedly mounted with a second output gear, wherein the first output gear and the second output gear are engaged with the ring gear of the differential, The first gear pair further comprises a fourth driven gear rotatably mounted on the first output shaft, the fourth driven gear being engaged with the first driving gear, and the third gear pair further comprises a fifth driven gear rotatably mounted on the first output gear and engaged with the second driving gear, and The second gear pair further includes a sixth driven gear rotatably mounted on the second output shaft, the sixth driven gear being engaged with the first drive gear, and the fourth gear pair further includes a third driven gear rotatably mounted on the second output gear and engaged with the second drive gear.

10. The powertrain for a vehicle according to claim 9, in, The first drive gear is fixedly mounted on the first input shaft, and Wherein, the second driving gear is fixedly mounted on the second input shaft.

11. The powertrain for a vehicle according to claim 9, in, The first output shaft is installed with a fourth-fifth synchronizer configured to selectively connect the fourth driven gear or the fifth driven gear to the first output shaft to restrict its rotation relative to the first output shaft, and The second output shaft is installed with a third-sixth synchronizer, and the third-sixth synchronizer is configured to selectively connect the third driven gear or the sixth driven gear to the second output shaft to restrict its rotation relative to the second output shaft.

12. The powertrain for a vehicle according to claim 9, wherein: The first drive gear is integrally mounted with a clutch gear that selectively engages with the first sleeve of the compound synchronizer.

13. The powertrain for a vehicle according to claim 1, in, The first clutch and the second clutch form a double clutch formed at a single clutch housing, and The second input shaft includes a hollow shaft surrounding the first input shaft.

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