A dual-motor central drive system

Abstract

This utility model relates to the field of electric drive system technology and discloses a dual-motor central drive system, including a gearbox, a four-speed transmission mechanism, and a shifting mechanism. The four-speed transmission mechanism includes two sets of drive motors, a main transmission assembly, a first transmission assembly, and a second transmission assembly disposed within the gearbox. The shifting mechanism includes a main shift sleeve, a first shift sleeve, and a second shift sleeve. Controlling the sliding of the main shift sleeve, the first shift sleeve, and the second shift sleeve changes the transmission route of the four-speed transmission mechanism, enabling uninterrupted gear shifting. This system can solve the problem of power interruption during gear shifting, improving driving safety and comfort. Furthermore, the system adopts a dual-motor parallel arrangement structure, with the two motors having identical structures. The gearbox uses a dual intermediate shaft structure, which can achieve force balance on the main shaft during high torque output, and reduces the number of parts, improving reliability and reducing costs.

Description

Technical Field

[0001] This utility model belongs to the field of electric drive system technology, specifically relating to a dual-motor central drive system. Background Technology

[0002] Currently, most new energy heavy-duty trucks use a central drive system, which typically consists of a motor and a matching automated manual transmission (AMT). Because the AMT experiences power interruptions during gear shifts, existing drive systems are unsuitable for operating conditions requiring uninterrupted power, such as steep inclines, poor road conditions, and scenarios demanding high reliability and comfort in gear shifting. Therefore, there is an urgent need for a drive system that can achieve uninterrupted power during gear shifts.

[0003] Existing dual-motor transmission systems and their layouts mainly include coaxial dual-motor structures and parallel dual-motor structures. Coaxial dual-motor structures result in different shaft structures for the two motors, often with hollow shafts, increasing manufacturing difficulty and cost. Parallel dual-motor structures currently suffer from problems such as an excessive number of intermediate shafts leading to increased bearing counts, structural complexity, and unbalanced forces on the output spindle under low-gear, high-torque conditions, also increasing costs. Summary of the Invention

[0004] The purpose of this invention is to provide a simple and reasonably designed dual-motor central drive system to solve the above problems.

[0005] This utility model achieves the above objectives through the following technical solutions:

[0006] This utility model provides a dual-motor central drive system, including a gearbox, a four-speed transmission mechanism and a shifting mechanism. The four-speed transmission mechanism includes two sets of drive motors, a main transmission assembly, a first transmission assembly and a second transmission assembly disposed in the gearbox.

[0007] The shifting mechanism includes a main shifting sleeve, a first shifting sleeve, and a second shifting sleeve. Controlling the sliding of the main shifting sleeve, the first shifting sleeve, and the second shifting sleeve changes the transmission path of the four-speed transmission mechanism, enabling the four-speed transmission mechanism to shift gears without interruption.

[0008] The first transmission component and the second transmission component are respectively connected to the drive ends of the two sets of drive motors. The two sets of drive motors transmit power to the main transmission component through the first transmission component and the second transmission component, respectively, and the main transmission component outputs power. The main shift sleeve is configured to control the power transmission direction of the main transmission component. The first shift sleeve controls the power transmission direction of the first transmission component, and the second shift sleeve controls the power transmission direction of the second transmission component.

[0009] As a further optimization of this utility model, the gearbox includes a front auxiliary gearbox and a main gearbox;

[0010] The first transmission assembly includes a first input shaft, on which a first gear and a third gear are loosely fitted. The second transmission assembly includes a second input shaft, on which a second gear and a fourth gear are loosely fitted. Both the first and second input shafts are rotatably connected inside the front auxiliary housing. One end of both the first and second input shafts extends outside the front auxiliary housing and is respectively connected to the drive ends of two sets of drive motors. The first and second shift sleeves are respectively connected to the first and second input shafts. The first and second shift sleeves are respectively disposed between the first and third gears and between the second and fourth gears.

[0011] The main drive assembly includes an output spindle that passes through the front auxiliary gearbox and the main gearbox. A fifth gear and a sixth gear are loosely fitted at one end of the output spindle located in the main gearbox. A main shift sleeve is connected to the output spindle and is positioned between the fifth gear and the sixth gear.

[0012] As a further optimization of this utility model, the first transmission assembly further includes a first transmission shaft rotatably connected inside the main housing, and a seventh gear and a ninth gear are fixedly connected to the first transmission shaft.

[0013] The second transmission assembly also includes a second transmission shaft rotatably connected inside the main housing, on which the eighth gear, the fourteenth gear and the tenth gear are fixedly connected in sequence;

[0014] The main drive assembly also includes a gear shaft, which is loosely fitted onto the surface of the output main shaft. An eleventh gear is fixedly connected to one end of the gear shaft located in the front auxiliary housing, and a twelfth gear is fixedly connected to one end of the gear shaft located in the main housing. A thirteenth gear is fixedly connected to the surface of the output main shaft located in the front auxiliary housing. The eleventh gear meshes with the third and fourth gears, the twelfth gear meshes with the seventh and eighth gears, the thirteenth gear meshes with the first and second gears, the sixth gear meshes with the ninth and tenth gears, and the fourteenth gear meshes with the fifth gear.

[0015] As a further optimization of this utility model, when the four-speed transmission mechanism is switched to the first gear, the first shift sleeve slides to the side of the third gear and connects with the engagement teeth of the third gear, the second shift sleeve slides to the side of the fourth gear and connects with the engagement teeth of the fourth gear, and the main shift sleeve slides to the side of the sixth gear and connects with the engagement teeth of the sixth gear.

[0016] As a further optimization of this utility model, when the four-speed transmission mechanism is switched to the second gear, the first shift sleeve slides to one side of the first gear and connects with the engagement teeth of the first gear, the second shift sleeve slides to one side of the fourth gear and connects with the engagement teeth of the fourth gear, and the main shift sleeve slides to one side of the sixth gear and connects with the engagement teeth of the sixth gear.

[0017] As a further optimization of this utility model, when the four-speed transmission mechanism is switched to the third gear, the first shift sleeve slides to one side of the first gear and connects with the engagement teeth of the first gear, the second shift sleeve slides to one side of the fourth gear and connects with the engagement teeth of the fourth gear, and the main shift sleeve slides to one side of the fifth gear and connects with the engagement teeth of the fifth gear.

[0018] As a further optimization of this utility model, when the four-speed transmission mechanism is switched to the fourth gear, the first shift sleeve slides to one side of the first gear and connects with the engagement teeth of the first gear, the second shift sleeve slides to one side of the second gear and connects with the engagement teeth of the second gear, and the main shift sleeve does not connect with the engagement teeth of the fifth gear and the sixth gear.

[0019] As a further optimization of this utility model, when the four-speed transmission mechanism switches to any of the four gears, both sets of drive motors start simultaneously or either one set of motors starts.

[0020] The beneficial effects of this utility model are as follows: The system provided by this utility model can solve the problem of power interruption caused by gear shifting, improve driving safety and comfort, and the system adopts a dual-motor parallel arrangement structure with the two motors having the same structure. The gearbox adopts a dual intermediate shaft structure, which can achieve the balance of the main shaft force when the large torque output is achieved, and the number of parts is reduced, improving reliability and reducing costs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of this utility model;

[0022] Figure 2 This is the power transmission route diagram for the first gear of this utility model;

[0023] Figure 3 This is the power transmission route diagram for the second gear of this utility model;

[0024] Figure 4 This is the power transmission route diagram for the third gear of this utility model;

[0025] Figure 5 This is the power transmission route diagram for the fourth gear of this utility model.

[0026] In the diagram: 1. First input shaft; 2. First gear; 3. First shift sleeve; 4. Third gear; 5. Seventh gear; 6. First drive shaft; 7. Ninth gear; 8. Sixth gear; 9. Main shift sleeve; 10. Fifth gear; 11. Twelfth gear; 12. Gear shaft; 13. Eleventh gear; 14. Thirteenth gear; 15. Second input shaft; 16. Second gear; 17. Second shift sleeve; 18. Fourth gear; 19. Eighth gear; 20. Fourteenth gear; 21. Tenth gear; 22. Second drive shaft; 23. Output main shaft; 24. Front auxiliary gearbox; 25. Main gearbox; 26. First motor; 27. Second motor. Detailed Implementation

[0027] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0028] like Figure 1 As shown, a dual-motor central drive system includes a front auxiliary gearbox 24, a main gearbox 25, a four-speed transmission mechanism and a shifting mechanism. The four-speed transmission mechanism includes a main transmission assembly, a first transmission assembly, a second transmission assembly and two sets of drive motors. The first transmission assembly and the second transmission assembly are connected by transmission through the main transmission assembly.

[0029] The shifting mechanism includes a main shifting sleeve 9, a first shifting sleeve 3, and a second shifting sleeve 17. The first transmission assembly includes a first input shaft 1, on which a first gear 2 and a third gear 4 are loosely fitted. The second transmission assembly includes a second input shaft 15, on which a second gear 16 and a fourth gear 18 are loosely fitted. Both the first input shaft 1 and the second input shaft 15 are rotatably connected inside the front auxiliary housing 24. One end of both the first input shaft 1 and the second input shaft 15 extends outside the front auxiliary housing 24 and is connected to the drive ends of two sets of drive motors, respectively. The first shifting sleeve 3 and the second shifting sleeve 17 are respectively connected to the first input shaft 1 and the second input shaft 15. The first shifting sleeve 3 and the second shifting sleeve 17 are respectively disposed between the first gear 2 and the third gear 4 and between the second gear 16 and the fourth gear 18.

[0030] The main drive assembly includes an output spindle 23, which passes through the front auxiliary housing 24 and the main housing 25. The output spindle 23 is located at one end of the main housing 25 and is loosely fitted with the fifth gear 10 and the sixth gear 8. The main shifting sleeve 9 is connected to the output spindle 23 and is located between the fifth gear 10 and the sixth gear 8.

[0031] The sliding main shift sleeve 9, the first shift sleeve 3, and the second shift sleeve 17 control the four-speed transmission mechanism to perform uninterrupted gear shifting.

[0032] Specifically, the two sets of drive motors include a first motor 26 and a second motor 27. The first input shaft 1 is fixedly connected to the drive end of the first motor 26, and the second input shaft 15 is fixedly connected to the drive end of the second motor 27.

[0033] It should be noted that this system is a dual intermediate shaft gear transmission structure, which has fewer shafts, a simple structure and small size, and a total of four gears with a wide range of speed ratios.

[0034] Furthermore, the first transmission assembly also includes a first transmission shaft 6 rotatably connected inside the main housing 25, and a seventh gear 5 and a ninth gear 7 are fixedly connected to the first transmission shaft 6.

[0035] The second transmission assembly also includes a second transmission shaft 22 rotatably connected inside the main housing 25, and an eighth gear 19, a fourteenth gear 20 and a tenth gear 21 are sequentially fixedly connected to the second transmission shaft 22.

[0036] The main drive assembly also includes a gear shaft 12, which is loosely fitted on the surface of the output main shaft 23. The eleventh gear 13 is fixedly connected to one end of the gear shaft 12 located in the front auxiliary housing 24, and the twelfth gear 11 is fixedly connected to one end of the gear shaft 12 located in the main housing 25. The thirteenth gear 14 is fixedly connected to the surface of the output main shaft 23 located in the front auxiliary housing 24. The eleventh gear 13 meshes with the third gear 4 and the fourth gear 18. The twelfth gear 11 meshes with the seventh gear 5 and the eighth gear 19. The thirteenth gear 14 meshes with the first gear 2 and the second gear 16. The sixth gear 8 meshes with the ninth gear 7 and the tenth gear 21. The fourteenth gear 20 meshes with the fifth gear 10.

[0037] It should be noted that the main shift sleeve 9 can be connected to one set of engagement teeth of the fifth gear 10 and the sixth gear 8 by sliding the main shift sleeve 9, the first shift sleeve 3 can be connected to one set of engagement teeth of the first gear 2 and the third gear 4 by sliding the first shift sleeve 3, and the second shift sleeve 17 can be connected to one set of engagement teeth of the second gear 16 and the fourth gear 18 by sliding the second shift sleeve 17.

[0038] Furthermore, when the four-speed transmission mechanism switches to the first gear, the first shift sleeve 3 slides to one side of the third gear 4 and connects with the engagement teeth of the third gear 4, the second shift sleeve 17 slides to one side of the fourth gear 18 and connects with the engagement teeth of the fourth gear 18, and the main shift sleeve 9 slides to one side of the sixth gear 8 and connects with the engagement teeth of the sixth gear 8.

[0039] For details, please refer to Figure 2The route shown in bold black indicates that when the four-speed transmission mechanism switches to the first gear, the specific power transmission route is as follows: the first shift sleeve 3 and the second shift sleeve 17 both move to the right side and connect with the engagement teeth of the third gear 4 and the fourth gear 18, respectively. The first motor 26 transmits power to the third gear 4 through the first input shaft 1, and the second motor 27 transmits power to the fourth gear 18 through the second input shaft 15. Since the third gear 4 and the fourth gear 18 mesh with the eleventh gear 13, the power flow converges at the eleventh gear 13 and is transmitted to the twelfth gear 11 through the gear shaft 12. The twelfth gear 11 meshes with the seventh gear 5 and the eighth gear 19. The twelfth gear 11 splits the power flow to the seventh gear 5 and the eighth gear 19. The seventh gear 5 transmits power to the ninth gear 7 through the first drive shaft 6, and the eighth gear 19 transmits power to the tenth gear 21 through the second drive shaft 22. The sixth gear 8 meshes with the ninth gear 7 and the tenth gear 21 simultaneously, while the main shift sleeve 9 slides to the right and connects with the engagement teeth on the sixth gear 8. Power is transmitted to the output main shaft 23 through the main shift sleeve 9 to complete the power output. This mode is a dual-motor simultaneous operation mode. If single-motor operation is required, only one of the first shift sleeve 3 and the second shift sleeve 17 needs to be slid according to the power requirements of the whole vehicle.

[0040] It should be noted that the transmission route of the first gear of this system is a three-stage reduction double intermediate shaft gear transmission structure. When switching to the first gear mode, the output main shaft 23 is under balanced force, has a long bearing life, a large speed ratio and strong power, a compact structure, and high vehicle space matching, and can be compatible with multiple heavy commercial vehicle models and application scenarios.

[0041] Furthermore, when the four-speed transmission mechanism switches to the second gear, the first shift sleeve 3 slides to one side of the first gear 2 and connects with the engagement teeth of the first gear 2, the second shift sleeve 17 slides to one side of the fourth gear 18 and connects with the engagement teeth of the fourth gear 18, and the main shift sleeve 9 slides to one side of the sixth gear 8 and connects with the engagement teeth of the sixth gear 8.

[0042] For details, please refer to Figure 3The route shown in bold black indicates the power transmission path when the four-speed transmission shifts to the second gear: the first shift sleeve 3 moves to the left and engages with the gear teeth of the first gear 2; the second shift sleeve 17 remains stationary on the right and engages with the gear teeth of the fourth gear 18; the first motor 26 transmits power to the first gear 2 via the first input shaft 1; the first gear 2 meshes with the thirteenth gear 14; the thirteenth gear 14 transmits power to the output main shaft 23; the second motor 27 transmits power to the fourth gear 18 via the second input shaft 15; the fourth gear 18 meshes with the eleventh gear 13; the eleventh gear 13 transmits power to the twelfth gear 11 via the gear shaft 12; and the twelfth gear 11 engages with the seventh gear 5 and the eighth gear... When gear 19 meshes, the twelfth gear 11 splits the power flow to the seventh gear 5 and the eighth gear 19. The seventh gear 5 transmits power to the ninth gear 7 through the first drive shaft 6, and the eighth gear 19 transmits power to the tenth gear 21 through the second drive shaft 22. The sixth gear 8 meshes with the ninth gear 7 and the tenth gear 21 simultaneously. The main shift sleeve 9 slides to the right and connects with the engagement teeth on the sixth gear 8. Power is transmitted to the output main shaft 23 through the main shift sleeve 9. After merging with the power transmitted by the thirteenth gear 14, the power is output through the output main shaft 23. This mode is a dual-motor simultaneous operation mode. If single-motor operation is required, only one of the first shift sleeve 3 and the second shift sleeve 17 needs to be slid, depending on the power requirements of the vehicle.

[0043] Furthermore, when the four-speed transmission mechanism switches to the third gear, the first shift sleeve 3 slides to one side of the first gear 2 and connects with the engagement teeth of the first gear 2, the second shift sleeve 17 slides to one side of the fourth gear 18 and connects with the engagement teeth of the fourth gear 18, and the main shift sleeve 9 slides to one side of the fifth gear 10 and connects with the engagement teeth of the fifth gear 10.

[0044] For details, please refer to Figure 4The route shown in bold black indicates the power transmission path when the four-speed transmission shifts to the third gear: the first shift sleeve 3 moves to the left and engages with the first gear 2; the second shift sleeve 17 remains stationary on the right and engages with the fourth gear 18; the first motor 26 transmits power to the first gear 2 via the first input shaft 1; the first gear 2 meshes with the thirteenth gear 14; the thirteenth gear 14 transmits power to the output main shaft 23; the second motor 27 transmits power to the fourth gear 18 via the second input shaft 15; the fourth gear 18 meshes with the eleventh gear 13; and the eleventh gear 13 transmits power through the gear shaft 12... Power is transmitted to the twelfth gear 11, which meshes with the eighth gear 19. The twelfth gear 11 then transmits power to the eighth gear 19, which in turn transmits power to the fourteenth gear 20 via the second drive shaft 22. The main shift sleeve 9 slides to the left and connects with the engagement teeth on the fifth gear 10. Power is then transmitted to the output main shaft 23 via the main shift sleeve 9. After merging with the power transmitted by the thirteenth gear 14, the power is output via the output main shaft 23. This mode is a dual-motor simultaneous operation mode. If single-motor operation is required, only one of the first shift sleeve 3 and the second shift sleeve 17 needs to be slid, depending on the overall vehicle power requirements.

[0045] Furthermore, when the four-speed transmission mechanism is switched to the fourth gear, the first shift sleeve 3 slides to one side of the first gear 2 and connects with the engagement teeth of the first gear 2, the second shift sleeve 17 slides to one side of the second gear 16 and connects with the engagement teeth of the second gear 16, and the main shift sleeve 9 does not connect with the engagement teeth of the fifth gear 10 and the sixth gear 8.

[0046] For details, please refer to Figure 5 The route shown in bold black indicates that when the four-speed transmission mechanism switches to the fourth gear, the specific power transmission route is as follows: the first shift sleeve 3 and the second shift sleeve 17 both move to the left side and connect with the engagement teeth of the first gear 2 and the second gear 16 respectively. The main shift sleeve 9 is placed in the neutral position (i.e., it does not connect with the engagement teeth of the fifth gear 10 or the sixth gear 8). The first motor 26 transmits power to the first gear 2 through the first input shaft 1, and the second motor 27 transmits power to the second gear 16 through the second input shaft 15. The first gear 2 and the second gear 16 simultaneously mesh with the thirteenth gear 14. The thirteenth gear 14 combines the power and transmits it to the output main shaft 23 to complete the power output. This mode is a dual-motor simultaneous operation mode. If single-motor operation is required, only one of the first shift sleeve 3 and the second shift sleeve 17 needs to be slid, depending on the power requirements of the vehicle.

[0047] It should be noted that the transmission route of the fourth gear in this system is a single-stage reduction parallel shaft gear transmission structure. In this mode, there are fewer gear transmission paths, higher transmission efficiency, and the energy consumption of the whole vehicle can be reduced.

[0048] Furthermore, when the four-speed transmission mechanism switches to any of the four gears, it can simultaneously start two sets of drive motors or start any one set of motors.

[0049] It should be noted that this dual-motor central drive system can be matched with a power take-off unit, taking into account both driving and parking power take-off, making the whole vehicle flexible in matching.

[0050] It should be further explained that this system can solve the problem of power interruption caused by gear shifting, improve driving safety and comfort. In addition, the system adopts a dual-motor parallel arrangement structure, with the two motors having the same structure. The gearbox adopts a dual intermediate shaft structure (the gearbox includes a front auxiliary gearbox and a main gearbox), which can achieve force balance on the main shaft when high torque output is achieved. Furthermore, the number of parts is reduced, improving reliability and reducing costs.

[0051] The embodiments described above are merely examples of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these modifications and improvements all fall within the protection scope of this utility model.

Claims

1. A dual-motor central drive system, characterized in that, It includes a gearbox, a four-speed transmission mechanism, and a shifting mechanism. The four-speed transmission mechanism includes two sets of drive motors, a main transmission assembly, a first transmission assembly, and a second transmission assembly disposed in the gearbox. The shifting mechanism includes a main shifting sleeve, a first shifting sleeve, and a second shifting sleeve. Controlling the sliding of the main shifting sleeve, the first shifting sleeve, and the second shifting sleeve changes the transmission path of the four-speed transmission mechanism, enabling the four-speed transmission mechanism to shift gears without interruption. The first transmission component and the second transmission component are respectively connected to the drive ends of the two sets of drive motors. The two sets of drive motors transmit power to the main transmission component through the first transmission component and the second transmission component, respectively, and the main transmission component outputs power. The main shift sleeve is configured to control the power transmission direction of the main transmission component. The first shift sleeve controls the power transmission direction of the first transmission component, and the second shift sleeve controls the power transmission direction of the second transmission component.

2. The dual-motor central drive system according to claim 1, characterized in that: The gearbox includes a front auxiliary gearbox and a main gearbox; The first transmission assembly includes a first input shaft, on which a first gear and a third gear are loosely fitted. The second transmission assembly includes a second input shaft, on which a second gear and a fourth gear are loosely fitted. Both the first and second input shafts are rotatably connected inside the front auxiliary housing. One end of both the first and second input shafts extends outside the front auxiliary housing and is respectively connected to the drive ends of two sets of drive motors. The first and second shift sleeves are respectively connected to the first and second input shafts. The first and second shift sleeves are respectively disposed between the first and third gears and between the second and fourth gears. The main drive assembly includes an output spindle that passes through the front auxiliary gearbox and the main gearbox. A fifth gear and a sixth gear are loosely fitted at one end of the output spindle located in the main gearbox. A main shift sleeve is connected to the output spindle and is positioned between the fifth gear and the sixth gear.

3. The dual-motor central drive system according to claim 2, characterized in that: The first transmission assembly further includes a first transmission shaft rotatably connected inside the main housing, and a seventh gear and a ninth gear are fixedly connected to the first transmission shaft; The second transmission assembly also includes a second transmission shaft rotatably connected inside the main housing, on which the eighth gear, the fourteenth gear and the tenth gear are fixedly connected in sequence; The main drive assembly also includes a gear shaft, which is loosely fitted onto the surface of the output main shaft. An eleventh gear is fixedly connected to one end of the gear shaft located in the front auxiliary housing, and a twelfth gear is fixedly connected to one end of the gear shaft located in the main housing. A thirteenth gear is fixedly connected to the surface of the output main shaft located in the front auxiliary housing. The eleventh gear meshes with the third and fourth gears, the twelfth gear meshes with the seventh and eighth gears, the thirteenth gear meshes with the first and second gears, the sixth gear meshes with the ninth and tenth gears, and the fourteenth gear meshes with the fifth gear.

4. The dual-motor central drive system according to claim 3, characterized in that: When the four-speed transmission mechanism is switched to the first gear, the first shift sleeve slides to the side of the third gear and connects with the engagement teeth of the third gear, the second shift sleeve slides to the side of the fourth gear and connects with the engagement teeth of the fourth gear, and the main shift sleeve slides to the side of the sixth gear and connects with the engagement teeth of the sixth gear.

5. A dual-motor central drive system according to claim 3, characterized in that: When the four-speed transmission mechanism is switched to the second gear, the first shift sleeve slides to one side of the first gear and connects with the engagement teeth of the first gear, the second shift sleeve slides to one side of the fourth gear and connects with the engagement teeth of the fourth gear, and the main shift sleeve slides to one side of the sixth gear and connects with the engagement teeth of the sixth gear.

6. A dual-motor central drive system according to claim 3, characterized in that: When the four-speed transmission mechanism is switched to the third gear, the first shift sleeve slides to one side of the first gear and connects with the engagement teeth of the first gear, the second shift sleeve slides to one side of the fourth gear and connects with the engagement teeth of the fourth gear, and the main shift sleeve slides to one side of the fifth gear and connects with the engagement teeth of the fifth gear.

7. A dual-motor central drive system according to claim 3, characterized in that: When the four-speed transmission mechanism is switched to the fourth gear, the first shift sleeve slides to one side of the first gear and connects with the engagement teeth of the first gear, the second shift sleeve slides to one side of the second gear and connects with the engagement teeth of the second gear, and the main shift sleeve does not connect with the engagement teeth of the fifth and sixth gears.

8. A dual-motor central drive system according to any one of claims 4-7, characterized in that: When the four-speed transmission mechanism switches to any of the four gears, both sets of drive motors start simultaneously or either one set of motors starts.

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