A dual-motor hybrid power transmission system for medium and large-sized tractors

Abstract

The application discloses a double-motor hybrid power transmission system for medium and large tractors, which comprises an engine, an intermediate shaft, a main motor, an auxiliary motor, a power coupling device, a variable speed transmission mechanism and a PTO output shaft; the double-input ends of the power coupling device are connected with the auxiliary motor and the main motor respectively, the power of the main motor can be directly input into the power coupling device, the power of the auxiliary motor is input into the power coupling device through the intermediate shaft and a second clutch, the total power is output to the PTO output shaft through the intermediate shaft and to the variable speed transmission mechanism through a second planetary gear, the speed coupling of the engine and the double motor can be realized through the power coupling device, different driving modes are realized, the system is compact and efficient, the stepless speed regulation characteristics of the efficient cooperation of multiple power sources are fully utilized, the gear requirement of the system is reduced, the space cost is optimized, the chassis specific power is significantly improved, and the efficient transmission purpose is achieved; the utilization rate of the double motor is high, and the power output is balanced under the cooperation of the engine in the high load working condition.

Description

Technical Field

[0001] This invention relates to the field of transmission system technology, and more specifically to a dual-motor hybrid power transmission system for medium and large tractors. Background Technology

[0002] The development of agricultural modernization technology is closely linked to the development of the automotive industry. In recent years, with the rapid advancement of new energy vehicle technology, pure electric and hybrid technologies have become increasingly mature, and major agricultural machinery companies have launched pure electric and hybrid tractors. However, considering the range and complex working conditions of tractors during long-term field operations, hybrid technology is more favored by developers, including series hybrid, parallel hybrid, and series-parallel hybrid systems.

[0003] In existing hybrid tractor drive systems, most dual-motor hybrid structures operate with two motors working independently. The PTO motor outputs torque to independently drive the power take-off shaft, while the travel motor drives the tractor. While this drive method reduces fuel consumption to some extent and aligns with the call for green development, it doesn't fully utilize the speed regulation capabilities of the motors, and power loss can easily occur when the two motors operate incompatiblely. To address these issues, existing technologies utilize planetary gear sets to achieve coupled transmission between the two motors.

[0004] For example, patent application CN111016642A discloses a multi-mode coupling transmission device and its control system for an electric tractor. It uses a combination of two planetary gear assemblies and two synchronizer shifting mechanisms as the power coupling device between the main motor and the auxiliary motor, enabling multiple operating modes including single drive of the main motor, torque coupling of the two motors, and speed coupling of the two motors. While the aforementioned multi-mode power coupling transmission device and its control system for an electric tractor can couple the power of the two motors through the two planetary gear assemblies, thereby achieving multiple drive modes and improving motor utilization, the device still has the following shortcomings:

[0005] 1. The combination of multiple planetary gear assemblies and synchronizers results in a complex structure, increasing the difficulty and cost of system maintenance.

[0006] 2. The power distribution problem under high load conditions has not been effectively solved, which may lead to unbalanced power output.

[0007] 3. Energy loss during the power coupling process reduces overall efficiency, and complex control systems may cause response delays, thus affecting operational flexibility; while hybrid tractor transmission systems based on dual planetary gear sets have failed to effectively solve the problem of insufficient power of dual motors at full load output, which may lead to unbalanced power output. Summary of the Invention

[0008] The purpose of this invention is to overcome the above-mentioned problems and provide a dual-motor hybrid power transmission system for medium and large tractors. This transmission system has a compact and efficient structure, high utilization of the dual motors, and, in conjunction with the engine, provides balanced power output under high load conditions.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A dual-motor hybrid power transmission system for medium and large tractors includes an engine, an intermediate shaft, a main motor, an auxiliary motor, a power coupling device, a transmission mechanism, and a PTO output shaft. The engine has an engine output shaft. The auxiliary motor is mounted on the intermediate shaft. One end of the intermediate shaft is connected to the engine output shaft via a first clutch, and the other end of the intermediate shaft is connected to one end of the PTO output shaft via a third clutch. The power coupling device is connected to the intermediate shaft via a second clutch.

[0011] The power coupling device includes a brake, a first planetary gear mechanism and a second planetary gear mechanism arranged in parallel; the first planetary gear mechanism includes a first sun gear, a first set of planetary gears, a first ring gear, and a first planet carrier; the second planetary gear mechanism includes a second sun gear, a second set of planetary gears, a second ring gear, and a second planet carrier; wherein, the first sun gear is connected to the intermediate shaft via a second clutch; the first planet carrier is connected to the second ring gear; the second planet carrier is connected to the transmission mechanism; the main shaft of the main motor is connected to the second sun gear; the brake is used to simultaneously lock the first planet carrier and the second ring gear.

[0012] The working principle of the dual-motor hybrid power transmission system used in medium and large tractors described above is as follows:

[0013] The dual input ends of the power coupling device are connected to the auxiliary motor and the main motor respectively. The power of the main motor can be directly input into the power coupling device, and the power of the auxiliary motor is input into the power coupling device through the intermediate shaft and the second clutch. The total power is output to the PTO output shaft through the intermediate shaft and to the transmission mechanism through the second set of planetary gears. The power coupling device can couple the speed of the engine and the dual motors (main motor and auxiliary motor) to achieve different driving modes. Specifically, the engine's power is transmitted to the intermediate shaft via the engine output shaft and the first clutch, through the auxiliary motor. When the second clutch engages, it drives the first sun gear, which in turn drives the first set of planetary gears. This, in turn, drives the second ring gear via the first planetary carrier, which in turn drives the second set of planetary gears, and finally the second planetary carrier, thus transmitting power to the transmission mechanism. With the third clutch engaged, the rotation of the intermediate shaft also drives the PTO output shaft. The auxiliary motor drives the intermediate shaft, enabling the PTO output shaft to rotate. With the second clutch engaged, this drives the first planetary gear mechanism, which in turn drives the second planetary gear mechanism, thus driving the transmission mechanism. The main motor's power drives the second sun gear, which in turn drives the second set of planetary gears, which in turn drives the second planetary carrier, thus driving the transmission mechanism. It also drives the second ring gear, which in turn drives the first planetary gear mechanism, thus driving the PTO output shaft. Different driving modes can be achieved through the engagement and disengagement of the first, second, and third clutches, as well as the locking and disengagement of the brakes.

[0014] In a preferred embodiment of the present invention, the engine, the first clutch, the auxiliary motor, the second clutch, the intermediate shaft, the main motor, the first sun gear, the second sun gear, the third clutch, and the PTO output shaft are arranged coaxially; the main motor is arranged between the first sun gear and the second sun gear, and the auxiliary motor is arranged between the first clutch and the first sun gear.

[0015] Preferably, the dual-motor hybrid power transmission system further includes a battery system and a reducer; the battery system is connected to the main motor and the auxiliary motor respectively, and the reducer is connected between the PTO output shaft and the third clutch.

[0016] Preferably, the transmission mechanism includes a first gear, a second gear, and a gearbox; the first gear is connected to and coaxially arranged with the second planetary carrier, the second gear meshes with the first gear, and the gearbox input shaft of the gearbox is connected to the second gear.

[0017] Preferably, the driving modes of the dual-motor hybrid power transmission system include a parking driving mode, a first driving and working driving mode, a second driving and working driving mode, a third driving and working driving mode, and a regenerative braking mode.

[0018] Preferably, the parking driving mode includes an auxiliary motor single-drive PTO mode and a parking charging mode; wherein,

[0019] When in auxiliary motor single-drive PTO mode, the brake is disengaged, the first clutch and the second clutch are disengaged, and the third clutch is engaged; the engine does not start, the battery system discharges, the main motor does not work, and the auxiliary motor works; at this time, the power transmission between the engine and the intermediate shaft is interrupted, the battery system supplies power to the auxiliary motor, and the auxiliary motor outputs power to the PTO output shaft through the intermediate shaft.

[0020] When in parking charging mode, the brake is disengaged, the first and third clutches are engaged, the second clutch is disengaged, the engine starts, the auxiliary motor acts as a generator, a portion of the engine's power drives the auxiliary motor to generate electricity, and the remaining power output by the engine is transmitted to the PTO output shaft through the intermediate shaft.

[0021] Preferably, the first driving and operating condition driving mode includes a main motor single-drive driving mode; the first driving and operating condition driving mode is a pure electric mode with only the main motor as the power source; wherein, when in the main motor single-drive driving mode, the brake is locked, the first clutch, the second clutch and the third clutch are disengaged, the engine does not start, the battery system discharges, the main motor works, the auxiliary motor does not work, and the battery system supplies power to the main motor.

[0022] Preferably, the second driving and operating condition driving mode includes a dual-motor independent driving mode and an engine and dual-motor independent driving mode; wherein,

[0023] When in the dual-motor independent drive mode, the brake is in the disengaged or locked state, the first clutch and the second clutch are in the disengaged state, the third clutch is in the engaged state, the engine does not start, the battery system discharges, the main motor works, and the auxiliary motor works; the battery system simultaneously supplies power to the auxiliary motor and the main motor.

[0024] When in the engine and dual-motor independent drive mode, the brake is disengaged or locked, the first and third clutches are engaged, the second clutch is disengaged, the engine starts, the battery system discharges, and the main motor works; the battery system only supplies power to the main motor, and the auxiliary motor acts as a generator; the battery system discharges to supply power to the main motor, the auxiliary motor acts as a generator, and the electricity generated by the auxiliary motor is used to supply power to the main motor.

[0025] Preferably, the third driving and operating condition drive mode includes an engine and main motor speed coupling mode, a dual-motor speed coupling mode, a first engine and dual-motor speed coupling mode, and a second engine and dual-motor speed coupling mode; wherein,

[0026] When in the engine and main motor speed coupling mode, the brake is disengaged, the first clutch, the second clutch and the third clutch are engaged, the engine starts, the battery system discharges, the main motor works, the auxiliary motor does not work, and the battery system supplies power to the main motor.

[0027] When in dual-motor speed coupling mode, the brake is disengaged, the first clutch is disengaged, and the second and third clutches are engaged. The engine does not start, the battery system discharges, the main motor works, and the auxiliary motor works; the battery system supplies power to both the auxiliary motor and the main motor simultaneously.

[0028] When the dual-motor hybrid powertrain is in the speed coupling mode of the first engine and the dual motors, the brakes are disengaged, the first clutch, the second clutch and the third clutch are engaged, the engine starts, the battery system discharges, the main motor works, and the auxiliary motor works; the battery system simultaneously supplies power to the main motor and the auxiliary motor for driving.

[0029] When the dual-motor hybrid powertrain is in the speed coupling mode of the second engine and the dual motors, the brakes are disengaged, and the first, second, and third clutches are engaged. The engine starts, the battery system discharges, the main motor works, and the auxiliary motor acts as a generator. The battery system only supplies power to the main motor for driving. A portion of the engine's power is output to the auxiliary motor via the intermediate shaft to generate electricity, and the electricity generated by the auxiliary motor is transmitted to the main motor.

[0030] Preferably, the regenerative braking mode includes an independent drive regenerative braking mode and a coupled drive regenerative braking mode; wherein,

[0031] When the tractor is in motion and is in single-drive mode of the main motor, independent drive mode of the dual motors, or independent drive mode of the engine and dual motors, the driver presses the brake pedal, and the dual-motor hybrid power transmission system enters the independent drive regenerative braking mode. When in the independent drive regenerative braking mode, the brake is locked, the second clutch is disengaged, and the main motor acts as a generator. All the recovered braking force is absorbed by the main motor, which then converts into a generator to charge the battery system.

[0032] When the tractor is in motion and is in the engine-main motor speed coupling mode, dual-motor speed coupling mode, first engine-dual-motor speed coupling mode, or second engine-dual-motor speed coupling mode, the driver presses the brake pedal, and the dual-motor hybrid power transmission system enters the coupled drive regenerative braking mode. When in the coupled drive regenerative braking mode, the brake is disengaged, the second clutch is engaged, the third clutch is engaged, and the main motor acts as a generator. Part of the recovered braking force is absorbed by the main motor, which always remains in a power generation state to charge the battery system. The remaining recovered braking force is transmitted to the intermediate shaft through the power coupling device.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1. The dual-motor hybrid power transmission system of this invention uses a first planetary gear mechanism and a second planetary gear mechanism arranged in parallel for speed coupling between the main motor and the auxiliary motor. This results in a compact and efficient structure. The dual-input, single-output characteristics of the first and second planetary gear mechanisms enable hybrid power output in both high-speed and high-power modes. The auxiliary motor connects to the engine via a first clutch and to the PTO output shaft via a third clutch, serving as an independent drive motor for both the range extender generator and the PTO output shaft. The main motor is the primary source of power for the tractor wheels. This structure fully utilizes the excellent high-efficiency speed range of the motors, reducing the speed regulation requirements of the transmission system and significantly simplifying the number of gears in the gearbox. This avoids the problems of complex transmission structures, poor coordination performance under different working conditions, and high fuel consumption and low efficiency of existing tractor transmissions. Furthermore, it fully utilizes the stepless speed regulation characteristics of efficient multi-power source coordination, reducing the gear requirements of the transmission system, optimizing space costs, and significantly improving the chassis power-to-weight ratio, achieving efficient transmission. The dual-motor system of this invention has high utilization and, under high-load conditions, works in conjunction with the engine to provide balanced power output.

[0035] 2. The dual-motor hybrid power transmission system of this invention can achieve engine-main motor speed coupling, dual-motor speed coupling, and engine-dual-motor speed coupling by controlling the first clutch, second clutch, third clutch, and brake. The power distribution problem under high load conditions can be effectively solved. The coupling mode can be selected according to the actual situation, making the power output more balanced. Moreover, the structure of this application is compact and efficient, with less energy loss in the power coupling process and simple control. When the power output of the main motor and auxiliary motor is insufficient at full load, the power output is improved by coupling the engine and dual motor speeds, making the power output more balanced.

[0036] 3. The dual-motor hybrid power transmission system of this invention achieves four different driving modes—hybrid drive mode, pure electric drive mode, range-extended drive mode, and regenerative braking mode—through the parallel arrangement of a first planetary gear mechanism and a second planetary gear mechanism for engine-dual-motor speed coupling. Combining the transmission principle of the planetary gear mechanism and the regenerative braking principle, it achieves 11 different gear modes. Specifically, the four gear modes in the hybrid drive mode are: engine and dual-motor independent drive mode, engine and main motor speed coupling mode, first engine and dual-motor speed coupling mode, and second engine and dual-motor speed coupling mode. The four gear modes in the pure electric drive mode are: auxiliary motor single-drive PTO mode, main motor single-drive mode, dual-motor independent drive mode, and dual-motor speed coupling mode. The range-extended drive mode includes parking charging mode, engine and dual-motor independent drive mode, and second engine and dual-motor speed coupling mode. The regenerative braking mode includes independent drive regenerative braking mode and coupled drive regenerative braking mode. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a dual-motor hybrid power transmission system for medium and large tractors according to the present invention.

[0038] Figure 2 This is an integrated diagram of the power flow direction in the parking driving mode of this invention.

[0039] Figure 3 This is an integrated diagram of the power flow direction for the first driving and operating conditions in this invention.

[0040] Figure 4 This is an integrated diagram of the power flow direction for the second driving and operating conditions in this invention.

[0041] Figure 5 This is an integrated diagram of the power flow direction for another implementation of the second driving and operating condition drive mode in this invention.

[0042] Figure 6 This is an integrated diagram of the power flow direction for the third driving and operating conditions in this invention.

[0043] Figure 7 This is an integrated diagram of the braking force flow direction in the independent drive regenerative braking mode of this invention.

[0044] Figure 8 This is an integrated diagram of the braking force flow direction in the coupled-drive regenerative braking mode of this invention. Detailed Implementation

[0045] To enable those skilled in the art to fully understand the technical solutions of the present invention, the present invention will be further described below in conjunction with embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0046] See Figure 1 This embodiment discloses a dual-motor hybrid power transmission system for medium and large tractors, including an engine 1, an intermediate shaft 16, a main motor 9, an auxiliary motor 4, a power coupling device 11, a transmission mechanism 27, and a PTO output shaft 19; the engine 1 is provided with an engine output shaft 2; the auxiliary motor 4 is provided on the intermediate shaft 16 and can be used to drive the intermediate shaft 16 to rotate; one end of the intermediate shaft 16 is connected to the engine output shaft 2 through a first clutch 3, and the other end of the intermediate shaft 16 is connected to one end of the PTO output shaft 19 through a third clutch 17; the power coupling device 11 is connected to the intermediate shaft 16 through a second clutch 5.

[0047] See Figure 1The power coupling device 11 includes a brake 13, a first planetary gear mechanism and a second planetary gear mechanism (i.e., the first planetary gear mechanism and the second planetary gear mechanism are arranged in parallel); the first planetary gear mechanism includes a first sun gear 8, a first set of planetary gears 6, a first ring gear 7, and a first planet carrier 12; the first sun gear 8 meshes with the first set of planetary gears 6, the first set of planetary gears 6 meshes with the first ring gear 7, and the first planet carrier 12 is connected to the first set of planetary gears 6; the second planetary gear mechanism includes a second sun gear 20, a second set of planetary gears 15, a second ring gear 14, and a second planet carrier 22; the second sun gear 20 meshes with the second set of planetary gears 15, the second set of planetary gears 15 meshes with the second ring gear 7, and the second planet carrier 12 is connected to the first set of planetary gears 6; the second planetary gear mechanism includes a second sun gear 20, a second set of planetary gears 15, a second ring gear 14, and a second planet carrier 22; the second sun gear 20 meshes with the second set of planetary gears 15, and the second set of planetary gears 15 meshes with the second ring gear 7. 14. The second planetary carrier 22 is connected to the second row of planetary gears 15. The first sun gear 8 is connected to the intermediate shaft 16 via a second clutch 5. The first planetary carrier 12 is connected to the second ring gear 14. The second planetary carrier 22 is connected to the transmission mechanism 27. The main shaft of the main motor 9 is connected to the second sun gear 20. The first ring gear 7 is fixed to the housing of the power coupling device 11. The brake 13 is used to simultaneously lock the first planetary carrier 12 and the second ring gear 14, thereby interrupting the power transmission between the first and second planetary gear mechanisms. When the brake 13 is disengaged, power can be transmitted between the first and second planetary gear mechanisms. Both the first row of planetary gears 6 and the second row of planetary gears 15 include multiple planetary gears.

[0048] The working principle of the dual-motor hybrid power transmission system used in medium and large tractors described above is as follows:

[0049] The dual input terminals of the power coupling device 11 are connected to the auxiliary motor 4 and the main motor 9, respectively. The power of the main motor 9 can be directly input into the power coupling device 11, and the power of the auxiliary motor 4 is input into the power coupling device 11 through the intermediate shaft 16 and the second clutch 5. The total power is output to the PTO output shaft 19 through the intermediate shaft 16 and to the transmission mechanism 27 through the second row of planetary gears 15. The power coupling device 11 can couple the speeds of the engine 1 and the two motors (main motor 9 and auxiliary motor 4) to achieve different driving modes. Specifically, the power of engine 1 is transmitted to intermediate shaft 16 via engine output shaft 2 and first clutch 3, through auxiliary motor 4. After second clutch 5 is engaged, it drives first sun gear 8 to move, then drives first planetary gear 6 to move, then drives second ring gear 14 via first planetary carrier 12 to move, thereby driving second planetary gear 15 to move, and then driving second planetary carrier 22 to move, transmitting power to transmission mechanism 27. With third clutch 17 engaged, the rotation of intermediate shaft 16 can also drive PTO output shaft 19 to rotate. Auxiliary motor 4 can drive intermediate shaft 16 to move, realizing the rotation of PTO output shaft 19. With second clutch 5 engaged, it drives first planetary gear mechanism to move, and then drives second planetary gear mechanism to move, realizing the drive of transmission mechanism 27. The power of main motor 9 can drive second sun gear 20 to move, driving second planetary gear 15 to move, and then driving second planetary carrier 22 to move, realizing the drive of transmission mechanism 27. It can also drive second ring gear 14 to move, thereby driving first planetary gear mechanism to move, realizing the drive of PTO output shaft 19. Different driving modes can be achieved by engaging and disengaging the first clutch 3, the second clutch 5, and the third clutch 17, as well as locking and disengaging the brake 13.

[0050] See Figure 1 The engine 1, first clutch 3, auxiliary motor 4, second clutch 5, intermediate shaft 16, main motor 9, first sun gear 8, second sun gear 20, and third clutch 17 are coaxially arranged with the PTO output shaft 19. The main motor 9 is arranged between the first sun gear 8 and the second sun gear 20, and the auxiliary motor 4 is arranged between the first clutch 3 and the first sun gear 8. In the above structure, the entire transmission system layout is very compact, occupies little space, and has a very reasonable layout.

[0051] See Figure 1The dual-motor hybrid power transmission system also includes a battery system 10 and a reducer 18; the reducer 18 is represented by "i". The battery system 10 is connected to both the main motor 9 and the auxiliary motor 4, and the reducer 18 is connected between the PTO output shaft 19 and the third clutch 17. In the above structure, by setting the battery system 10, the main motor 9 and the auxiliary motor 4 can be driven, and energy recovery can also be achieved; the reducer 18 can reduce the output speed of the PTO output shaft 19, increase torque, and improve load capacity. Through the PTO output shaft 19, field operations such as tilling, sowing, fertilizing, or harvesting can be realized.

[0052] See Figure 1 The transmission mechanism 27 includes a first gear 22, a second gear 23, and a gearbox 25. The first gear 22 is connected to and coaxially arranged with the second planetary carrier 22, and the second gear 23 meshes with the first gear 22. The gearbox input shaft 24 of the gearbox 25 is connected to the second gear 23. In this structure, the second planetary carrier 22 drives the first gear 22 to rotate, thereby driving the second gear 23 to rotate. Power is then transmitted to the gearbox 25 through the gearbox input shaft 24, and the gearbox 25 outputs power to the wheels through the gearbox output shaft 26, thus driving the tractor.

[0053] See Figure 1 See Figure 1 The first planetary carrier 12 and the second gear ring 14 are mounted on the same shaft and fixedly connected as a whole.

[0054] See Figure 1 The dual-motor hybrid powertrain system includes a parking driving mode, a first driving and working driving mode, a second driving and working driving mode, a third driving and working driving mode, and a regenerative braking mode. The parking driving mode is the driving mode under parking conditions. The first driving and working driving mode, the second driving and working driving mode, and the third driving and working driving mode are all driving modes under driving and working conditions. The regenerative braking mode is the driving mode during braking.

[0055] See Figure 1 In the table below, "A" represents brake 13, "C1" represents first clutch 3, "C2" represents second clutch 5, "C3" represents third clutch 17, "E1" represents auxiliary motor 4, and "E2" represents main motor 9. The operating states of each component are as follows:

[0056] “◆” indicates that brake 13 is locked, “◇” indicates that brake 13 is disengaged; “▲” indicates that clutch (first clutch 3 or second clutch 5 or third clutch 17) is engaged, “△” indicates that clutch is disengaged; “●” indicates that motor (main motor 9 or auxiliary motor 4) is working, that is, the motor is driving; “○” indicates that motor is not working, that is, the motor is not driving; “■” indicates that engine 1 is started, “□” indicates that engine 1 is not started.

[0057] Table 1. Operating status of each component in parking driving mode.

[0058]

[0059] See Figure 1 and Figure 2 The parking driving modes include an auxiliary motor single-drive PTO mode and a parking charging mode. In the auxiliary motor single-drive PTO mode, the power source is the auxiliary motor 4, and the battery system 10 supplies power to the auxiliary motor 4 along the power transmission route ①. In the parking charging mode, the power source is the engine 1, and the auxiliary motor 4 acts as a generator to charge the battery system 10 along the power transmission route ②.

[0060] See Figure 1 and Figure 2 When the battery system 10 is fully charged, the dual-motor hybrid power transmission system selects the auxiliary motor single-drive PTO mode. In this mode, brake 13 is disengaged, the first clutch 3 and the second clutch 5 are disengaged, and the third clutch 17 is engaged. Engine 1 does not start, battery system 10 discharges, main motor 9 does not operate, and auxiliary motor 4 operates. At this time, power transmission between engine 1 and intermediate shaft 16 is interrupted. Battery system 10 supplies power to auxiliary motor 4, and auxiliary motor 4 outputs power through intermediate shaft 16 to PTO output shaft 19, driving the PTO to perform field operations such as hole digging and fertilization.

[0061] See Figure 1 and Figure 2 When the battery system 10 charge is lower than the minimum preset value, the dual-motor hybrid power transmission system selects the parking charging mode. When in the parking charging mode, the brake 13 is disengaged, the first clutch 3 and the third clutch 17 are engaged, the second clutch 5 is disengaged, the engine 1 starts, and the auxiliary motor 4 acts as a generator. At this time, the tractor is in a parking charging state. Part of the power of the engine 1 drives the auxiliary motor 4 to generate electricity. At the same time, part of the power output by the engine 1 is transmitted to the PTO output shaft 19 through the intermediate shaft 16 to drive the PTO to perform field operations such as digging holes and applying fertilizer.

[0062] Table 2. Operating status of each component in the first driving and working condition driving mode.

[0063]

[0064] See Figure 1 and Figure 3 The first driving and operating conditions include a main motor single-drive driving mode. In the main motor single-drive driving mode, the power source is the main motor 9. When the brake 13 is locked, the power of the main motor 9 can only be transmitted to the wheels through the second planetary gear mechanism and the transmission mechanism 27.

[0065] See Figure 1 and Figure 3 When in main motor single-drive mode, brake 13 is locked, first clutch 3, second clutch 5, and third clutch 17 are disengaged, engine 1 does not start, battery system 10 discharges, main motor 9 operates, and auxiliary motor 4 does not operate. In dual-motor hybrid transmission system mode, when in main motor single-drive mode, the tractor only performs driving operations. Battery system 10 supplies power to main motor 9. The power from main motor 9 passes sequentially through second sun gear 20, second set of planetary gears 15, second planetary carrier 22, first gear 22, second gear 23, gearbox input shaft 24, and gearbox 25, and is output from gearbox output shaft 26 to drive the tractor.

[0066] Table 3. Operating status of each component in the second driving and work conditions.

[0067]

[0068] See Figure 1 and Figure 4 The second driving and operating conditions include a dual-motor independent drive mode and an engine and dual-motor independent drive mode. In the dual-motor independent drive mode, the power source is the main motor 9 and the auxiliary motor 4. The battery system 10 simultaneously supplies power to the auxiliary motor 4 and the main motor 9 along power transmission routes ⑤ and ⑥, respectively. In the engine and dual-motor independent drive mode, the power source is the engine 1 and the main motor 9. In this mode, the auxiliary motor 4 acts as a generator, generating electricity under the action of the engine 1 and supplying power to the main motor 9 along power transmission route ⑦. Simultaneously, the battery system 10 supplies power to the main motor 9 along power transmission route ⑥.

[0069] See Figure 1 and Figure 4When in the dual-motor independent drive mode, brake 13 is disengaged, first clutch 3 and second clutch 5 are disengaged, third clutch 17 is engaged, engine 1 is not started, battery system 10 discharges, main motor 9 operates, and auxiliary motor 4 operates. When the dual-motor hybrid power transmission system is in the dual-motor independent drive mode, the tractor performs driving and field operations. Battery system 10 simultaneously supplies power to auxiliary motor 4 and main motor 9. Power from auxiliary motor 4 is sequentially transmitted through intermediate shaft 16 and reducer 18, and output to PTO output shaft 19 via reducer 18 to drive the tractor in field operations. Power from main motor 9 is sequentially transmitted through second sun gear 20, second planetary gear set 15, second planetary carrier 22, first gear 22, second gear 23, gearbox input shaft 24, and gearbox 25, and output to gearbox output shaft 26 to drive the tractor. See also Figure 5 In another embodiment, when in the dual-motor independent drive mode, the brake 13 is in a locked state.

[0070] See Figure 1 and Figure 4 When in the engine and dual-motor independent drive mode, the brake 13 is disengaged, the first clutch 3 and the third clutch 17 are engaged, the second clutch 5 is disengaged, the engine 1 starts, the battery system 10 discharges, and the main motor 9 works; the battery system 10 only supplies power to the main motor 9, and the auxiliary motor 4 acts as a generator. In the dual-motor hybrid powertrain system, when the engine and dual motors are in independent drive mode, the battery system 10 discharges to power the main motor 9. The auxiliary motor 4 acts as a generator, driven by the engine 1, causing the intermediate shaft 16 to rotate, which in turn causes the auxiliary motor 4 to generate electricity, which is then used to power the main motor 9. A portion of the power from the engine 1 is used to generate electricity for the auxiliary motor 4. The remaining power from the engine 1 is sequentially transmitted through the intermediate shaft 16 and the reducer 18, and then output to the PTO output shaft 19 through the reducer 18 to drive the tractor in field operations. The power from the main motor 9 is sequentially transmitted through the second sun gear 20, the second set of planetary gears 15, the second planetary carrier 22, the first gear 22, the second gear 23, the gearbox input shaft 24, and the gearbox 25, and then output to the gearbox output shaft 26 to drive the tractor. See also Figure 5 In another implementation, when in the engine and dual-motor independent drive mode, the brake 13 is locked.

[0071] Table 4. Operating status of each component in the third driving and work conditions.

[0072]

[0073] See Figure 1 and Figure 6The third driving and operating mode includes an engine and main motor speed coupling mode, a dual motor speed coupling mode, a first engine and dual motor speed coupling mode, and a second engine and dual motor speed coupling mode. In the engine-main motor speed coupling mode, the power source is engine 1 and main motor 9, and battery system 10 supplies power to main motor 9 along power transmission route ⑥. In the dual-motor speed coupling mode, the power source is main motor 9 and auxiliary motor 4, and battery system 10 supplies power to auxiliary motor 4 and main motor 9 simultaneously along power transmission routes ⑤ and ⑥. In the first engine-dual-motor speed coupling mode, the power source is engine 1, main motor 9, and auxiliary motor 4. In this mode, battery system 10 supplies power to auxiliary motor 4 and main motor 9 simultaneously along power transmission routes ⑤ and ⑥, and the power from engine 1 and auxiliary motor 4 is output coaxially. In the second engine-dual-motor speed coupling mode, the power source is engine 1 and main motor 9. In this mode, auxiliary motor 4 acts as a generator, generating electricity under the action of engine 1 and supplying power to main motor 9 along power transmission route ⑦. At the same time, battery system 10 supplies power to main motor 9 along power transmission route ⑥.

[0074] See Figure 1 and Figure 6 When in the engine and main motor speed coupling mode, the brake 13 is in the disengaged state, the first clutch 3, the second clutch 5 and the third clutch 17 are in the engaged state, the engine 1 starts, the battery system 10 discharges, the main motor 9 works, and the auxiliary motor 4 does not work. When the dual-motor hybrid power transmission system is in the engine and main motor speed coupling mode, the tractor drives and performs field operations. Part of the power from engine 1 passes sequentially through engine output shaft 2, intermediate shaft 16, and reducer 18, and is output from reducer 18 to PTO output shaft 19 to drive the tractor in field operations. At the same time, the remaining power from engine 1 passes sequentially through engine output shaft 2, intermediate shaft 16, first sun gear 8, first row of planetary gears 6, first planetary carrier 12, second ring gear 14, and second row of planetary gears 15, while battery system 10 discharges and supplies power to main motor 9. The power from main motor 9 passes sequentially through second sun gear 20 and second row of planetary gears 15. After the power from engine 1 and main motor 9 is speed-coupled in the second planetary gear mechanism (second row of planetary gears 15), it passes sequentially through second planetary carrier 22, first gear 22, second gear 23, gearbox input shaft 24, and gearbox 25, and is output from gearbox output shaft 26 to drive the tractor.

[0075] See Figure 1 and Figure 6When in dual-motor speed coupling mode, brake 13 is disengaged, first clutch 3 is disengaged, and second clutch 5 and third clutch 17 are engaged. Engine 1 is not started, battery system 10 is discharging, main motor 9 is operating, and auxiliary motor 4 is operating. In dual-motor hybrid power transmission mode, the tractor travels and performs field operations. Battery system 10 discharges, simultaneously supplying power to auxiliary motor 4 and main motor 9. A portion of the power from auxiliary motor 4 is transmitted sequentially through intermediate shaft 16 and reducer 18, and then output from reducer 18 to PTO output shaft 19 to drive rotary tillage operations. The power of the main motor 9 is output to the second row of planetary gears 15 via the second sun gear 20; the remaining power of the auxiliary motor 4 is sequentially transmitted through the intermediate shaft 16, the first sun gear 8, the first row of planetary gears 6, the first planetary carrier 12, the second ring gear 14, and the second row of planetary gears 15. After the auxiliary motor 4 and the main motor 9 are coupled in speed in the second planetary gear mechanism (second row of planetary gears 15), the power is sequentially transmitted through the second planetary carrier 22, the first gear 22, the second gear 23, the gearbox input shaft 24, and the gearbox 25, and the power is output by the gearbox output shaft 26 to drive the tractor.

[0076] See Figure 1 and Figure 6 When the dual-motor hybrid power transmission system is in the speed coupling mode of the first engine and the dual motors, the brake 13 is in the disengaged state, the first clutch 3, the second clutch 5 and the third clutch 17 are in the engaged state, the engine 1 starts, the battery system 10 discharges, the main motor 9 works, and the auxiliary motor 4 works. When the dual-motor hybrid power transmission system is in the speed coupling mode of the first engine and the dual motors, the tractor is driving and performing field operations. The battery system 10 discharges, and the battery system 10 simultaneously supplies power to the main motor 9 and the auxiliary motor 4 for driving. The power provided by the engine 1 and the power provided by the auxiliary motor 4 are coupled on the intermediate shaft 16. Part of the coupled power passes through the intermediate shaft 16 and the reducer 18 in sequence, and is output by the reducer 18 to the PTO output shaft 19, driving the PTO output shaft 19 to perform field operations such as tilling, fertilizing, sowing, or harvesting. The remaining coupled power passes through the first sun gear 8, the first row of planetary gears 6, the first planetary carrier 12, and the second ring gear 14 in sequence to the second row of planetary gears 15. The power of the main motor 9 is output to the second row of planetary gears 15 through the second sun gear 20. The remaining coupled power and the power of the main motor 9 are coupled in speed at the second planetary gear mechanism (second row of planetary gears 15) in sequence, and then pass through the second planetary carrier 22, the first gear 22, the second gear 23, the gearbox input shaft 24, and the gearbox 25, and is output by the gearbox output shaft 26 to drive the tractor.

[0077] See Figure 1 and Figure 6When the dual-motor hybrid powertrain is in the second engine and dual-motor speed coupling mode, brake 13 is disengaged, and the first clutch 3, second clutch 5, and third clutch 17 are engaged. Engine 1 starts, battery system 10 discharges, main motor 9 operates, and auxiliary motor 4 acts as a generator. When the dual-motor hybrid powertrain is in the second engine and dual-motor speed coupling mode, the tractor travels and performs field operations. Battery system 10 discharges, supplying power only to the main motor 9 for drive. A portion of the power from engine 1 is output to auxiliary motor 4 via intermediate shaft 16 to generate electricity, which is then transmitted to the main motor 9. The remaining power from engine 1 is output via intermediate shaft 16 to drive PTO output shaft 19 and the first sun gear 8. The power generated by the first sun gear 8 passes sequentially through the first set of planetary gears 6 and the first planet carrier. 12. The second gear ring 14 transmits power to the second row of planetary gears 15. The power of the main motor 9 is output to the second row of planetary gears 15 via the second sun gear 20. Part of the power of the engine 1 and the power of the main motor 9 are coupled at the second planetary gear mechanism (second row of planetary gears 15) and then sequentially pass through the second planetary carrier 22, the first gear 22, the second gear 23, the gearbox input shaft 24 and the gearbox 25. The power is output by the gearbox output shaft 26 to drive the tractor. The rotation of the PTO output shaft 19 is used for field operations such as tilling, fertilizing, sowing or harvesting.

[0078] Table 5. Operating status of each component in regenerative braking mode.

[0079]

[0080] See Figure 1 and Figure 7 The regenerative braking modes include independent drive regenerative braking mode and coupled drive regenerative braking mode. The main difference between independent drive regenerative braking mode and coupled drive regenerative braking mode is the disengagement or engagement of the second clutch 5.

[0081] See Figure 7 The independent drive regenerative braking mode corresponds to the main motor single drive driving mode, the dual motor independent drive mode, and the engine and dual motor independent drive mode. In this independent drive regenerative braking mode, the brake 13 is locked and the second clutch 5 is disengaged. All the recovered braking force is absorbed by the main motor 9, which is converted into a generator to charge the battery system 10. Specifically, the battery system 10 is powered through the power transmission route (2). The engine 1 and the auxiliary motor 4 maintain the working state of the original drive mode. The battery system 10 can be powered through the power transmission route (8). The auxiliary motor 4 can also act as a generator to charge the battery system 10 through the power transmission route (4).

[0082] See Figure 1 and Figure 8 The driving modes corresponding to the coupled drive regenerative braking mode are engine and main motor speed coupling mode, dual motor speed coupling mode, first engine and dual motor speed coupling mode, and second engine and dual motor speed coupling mode. At this time, the brake 13 in the coupled drive regenerative braking mode is in a disengaged state, the second clutch 5 is in an engaged state, most of the recovered braking force is absorbed by the main motor 9, and the main motor 9 always maintains the power generation state to charge the battery system 10. Specifically, it transmits power to the battery system 10 through the power transmission route (2), and part of the braking force is transmitted to the intermediate shaft 16 through the power coupling device 11. Compared with the driving mode before the tractor brakes and decelerates, the torque of the PTO output shaft 19 increases after braking and deceleration. At this time, in order to obtain a stable output of the PTO output shaft 19 before and after braking and deceleration, it is necessary to adjust the distribution ratio of the output power of the auxiliary motor 4 or convert the auxiliary motor 4 into a generator to charge the battery system 10. The engine 1 maintains the working state of the driving mode before the tractor brakes and decelerates.

[0083] See Figure 1 and Figure 7 In the aforementioned regenerative braking mode, when the driver depresses the brake pedal, the main motor 9 converts into a generator. The tractor's braking energy is transmitted to the power coupling device 11 via the transmission mechanism 27. Part of the kinetic energy is absorbed by the main motor 9 and used to generate electricity by reverse-drafting the main motor 9. This regenerative braking mode enables energy recovery. During braking and deceleration, regenerative braking can compensate for the insufficient mechanical braking capacity and also feed excess electrical energy back to the battery system 10, thereby improving overall energy utilization.

[0084] See Figure 1 and Figure 7During tractor operation, when the driver depresses the brake pedal, the dual-motor hybrid powertrain enters either an independent drive regenerative braking mode or a coupled drive regenerative braking mode. Specifically, when the tractor is in main motor single-drive mode, dual-motor independent drive mode, or engine and dual-motor independent drive mode, depressing the brake pedal activates the dual-motor hybrid powertrain into independent drive regenerative braking mode. In independent drive regenerative braking mode, brake 13 is locked, first clutch 3 is engaged / disengaged, second clutch 5 is disengaged, third clutch 17 is engaged / disengaged, engine 1 starts / stops, battery system 10 charges / discharges, main motor 9 acts as a generator, and auxiliary motor 4 operates / does not operate / acts as a generator. All recovered braking force is absorbed by main motor 9, which then converts into a generator to charge battery system 10. When the engine and dual-motor independent drive mode enters independent drive regenerative braking mode, auxiliary motor 4 switches from generating electricity to charging battery system 10. In other drive modes, engine 1 and auxiliary motor 4 maintain their original drive mode operation.

[0085] See Figure 1 and Figure 8 When the tractor is in motion and is in the engine and main motor speed coupling mode, or the dual motor speed coupling mode, or the first engine and dual motor speed coupling mode, or the second engine and dual motor speed coupling mode, the driver presses the brake pedal, and the dual motor hybrid power transmission system enters the coupling drive regenerative braking mode. When in the coupling drive regenerative braking mode, the brake 13 is in the disengaged state, the first clutch 3 is in the engaged / disengaged state, the second clutch 5 is in the engaged state, the third clutch 17 is in the engaged state, the engine 1 is started / not started, the battery system 10 is charged / discharged, the main motor 9 acts as a generator, and the auxiliary motor 4 works / does not work / acts as a generator. Most of the recovered braking force is absorbed by the main motor 9, and the main motor 9 always maintains the power generation state to charge the battery system 10. The remaining part of the recovered braking force is transmitted to the intermediate shaft 16 through the power coupling device 11. The movement of the intermediate shaft 16 can also drive the auxiliary motor 4 to generate electricity. The auxiliary motor 4 transmits power to the battery system 10 through the power transmission line (4). When the second engine and dual motor speed coupling mode enter the coupled drive regenerative braking mode, the auxiliary motor 4 switches to charge the battery system 10; in other drive modes, the engine 1 and auxiliary motor 4 maintain the original drive mode operation.

[0086] See Figures 1-8In this embodiment, the dual-motor hybrid power transmission system achieves four different driving modes—hybrid drive mode, pure electric drive mode, range-extended drive mode, and regenerative braking mode—through the parallel arrangement of the first and second planetary gear mechanisms to couple the speeds of the engine and dual motors. Combining the transmission principle of the planetary gear mechanism and the regenerative braking principle, it realizes 11 different gear modes, namely, auxiliary motor single-drive PTO mode, parking and charging mode, main motor single-drive driving mode, dual-motor independent drive mode, engine and dual-motor independent drive mode, engine and main motor speed coupling mode, dual-motor speed coupling mode, first engine and dual-motor speed coupling mode, second engine and dual-motor speed coupling mode, independent drive regenerative braking mode, and coupled drive regenerative braking mode. The engine and dual motor independent drive mode, the engine and main motor speed coupling mode, the first engine and dual motor speed coupling mode, and the second engine and dual motor speed coupling mode constitute a hybrid electric drive mode; the auxiliary motor single-drive PTO mode, the main motor single-drive driving mode, the dual motor independent drive mode, and the dual motor speed coupling mode constitute a pure electric drive mode; the parking charging mode, the engine and dual motor independent drive mode, and the second engine and dual motor speed coupling mode constitute a range-extended drive mode; by locking and disengaging the brake 13 and engaging and disengaging the first clutch 3 and the second clutch 5, the tractor can switch between the hybrid electric drive mode, the pure electric drive mode, and the range-extended drive mode according to different cyclic driving conditions; by engaging the third clutch 17, PTO can be used for field operations such as tillage, sowing, fertilization, or harvesting.

[0087] Most existing tractors are driven coaxially with the PTO output shaft 19 and the engine 1. Due to the fixed speed ratio, the working condition coordination performance is poor, and the engine 1 is often forced to operate in a high fuel consumption range. In this embodiment, the dual-motor hybrid power transmission system uses the two motors to achieve speed coupling through the first planetary gear mechanism and the second planetary gear mechanism set in parallel. The dual-input single-output characteristic of the planetary gear set realizes the power hybrid output of high-speed gear / high-power mode. The auxiliary motor 4 is connected to the engine 1 through the first clutch 3 and to the PTO output shaft 19 through the third clutch 17. It can be used as an independent drive motor for the range extender generator and the PTO output shaft 19. The main motor 9 is the main source of power for the tractor wheels. This structure can make full use of the excellent high-efficiency speed range of the motor, reduce the speed adjustment requirements of the transmission system, and thus greatly simplify the number of gears in the gearbox 25. Considering the relatively poor mechanical braking capability of the tractor, this embodiment sets up an energy recovery mechanism. During braking and deceleration, regenerative braking can be used to make up for the lack of mechanical braking capability, and excess electrical energy can be fed back to the battery system 10, thereby improving the overall energy utilization rate.

[0088] The above are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above content. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A dual-motor hybrid power transmission system for medium and large tractors, characterized in that, It includes an engine, an intermediate shaft, a main motor, an auxiliary motor, a power coupling device, a transmission mechanism, and a PTO output shaft; the engine is equipped with an engine output shaft; the auxiliary motor is mounted on the intermediate shaft; one end of the intermediate shaft is connected to the engine output shaft via a first clutch, and the other end of the intermediate shaft is connected to one end of the PTO output shaft via a third clutch; the power coupling device is connected to the intermediate shaft via a second clutch; the power coupling device is positioned between the auxiliary motor and the third clutch; wherein... The power coupling device includes a brake, a first planetary gear mechanism and a second planetary gear mechanism arranged in parallel; the first planetary gear mechanism includes a first sun gear, a first set of planetary gears, a first ring gear, and a first planet carrier; the first sun gear meshes with the first set of planetary gears, the first set of planetary gears meshes with the first ring gear, and the first planet carrier is connected to the first set of planetary gears; the second planetary gear mechanism includes a second sun gear, a second set of planetary gears, a second ring gear, and a second planet carrier; the second sun gear meshes with the second set of planetary gears, the second set of planetary gears meshes with the second ring gear, and the second planet carrier is connected to the second set of planetary gears; wherein, the first sun gear is connected to the intermediate shaft via a second clutch; the first planet carrier is connected to the second ring gear; the second planet carrier is connected to the transmission mechanism; the main shaft of the main motor is connected to the second sun gear; the first ring gear is fixed to the housing of the power coupling device; the brake is used to simultaneously lock the first planet carrier and the second ring gear; The engine, first clutch, auxiliary motor, second clutch, intermediate shaft, main motor, first sun gear, second sun gear, and third clutch are coaxially arranged with the PTO output shaft; the main motor is arranged between the first sun gear and the second sun gear, and the auxiliary motor is arranged between the first clutch and the first sun gear. The dual-motor hybrid power transmission system also includes a battery system and a reducer; the battery system is connected to the main motor and the auxiliary motor respectively, and the reducer is connected between the PTO output shaft and the third clutch; The transmission mechanism includes a first gear, a second gear, and a gearbox; the first gear is connected to and coaxially arranged with the second planetary carrier, the second gear meshes with the first gear, and the gearbox input shaft is connected to the second gear.

2. The dual-motor hybrid power transmission system for medium and large tractors according to claim 1, characterized in that, The driving modes of the dual-motor hybrid power transmission system include a parking driving mode, a first driving and working driving mode, a second driving and working driving mode, a third driving and working driving mode, and a regenerative braking mode.

3. A dual-motor hybrid power transmission system for medium and large tractors according to claim 2, characterized in that, The parking driving modes include auxiliary motor single-drive PTO mode and parking charging mode; wherein... When in auxiliary motor single-drive PTO mode, the brake is disengaged, the first clutch and the second clutch are disengaged, and the third clutch is engaged; the engine does not start, the battery system discharges, the main motor does not work, and the auxiliary motor works; at this time, the power transmission between the engine and the intermediate shaft is interrupted, the battery system supplies power to the auxiliary motor, and the auxiliary motor outputs power to the PTO output shaft through the intermediate shaft. When in parking charging mode, the brakes are disengaged, the first and third clutches are engaged, the second clutch is disengaged, the engine starts, the auxiliary motor acts as a generator, a portion of the engine's power drives the auxiliary motor to generate electricity, and the remaining power output from the engine is transmitted to the PTO output shaft through the intermediate shaft.

4. A dual-motor hybrid power transmission system for medium and large tractors according to claim 2, characterized in that, The first driving and operating conditions include a main motor single-drive driving mode; wherein, when in the main motor single-drive driving mode, the brake is locked, the first clutch, the second clutch and the third clutch are disengaged, the engine is not started, the battery system is discharged, the main motor is working, the auxiliary motor is not working, and the battery system supplies power to the main motor.

5. A dual-motor hybrid power transmission system for medium and large tractors according to claim 2, characterized in that, The second driving and operating condition drive modes include a dual-motor independent drive mode and an engine and dual-motor independent drive mode; wherein, When in the dual-motor independent drive mode, the brake is in the disengaged or locked state, the first clutch and the second clutch are in the disengaged state, the third clutch is in the engaged state, the engine does not start, the battery system discharges, the main motor works, and the auxiliary motor works; the battery system simultaneously supplies power to the auxiliary motor and the main motor. When in the engine and dual-motor independent drive mode, the brake is in the disengaged or locked state, the first and third clutches are in the engaged state, the second clutch is in the disengaged state, the engine starts, the battery system discharges, and the main motor works; the battery system only supplies power to the main motor, and the auxiliary motor acts as a generator; the electricity generated by the auxiliary motor is used to supply power to the main motor.

6. A dual-motor hybrid power transmission system for medium and large tractors according to claim 2, characterized in that, The third driving and operating mode includes an engine and main motor speed coupling mode, a dual-motor speed coupling mode, a first engine and dual-motor speed coupling mode, and a second engine and dual-motor speed coupling mode; wherein... When in the engine and main motor speed coupling mode, the brake is disengaged, the first clutch, the second clutch and the third clutch are engaged, the engine starts, the battery system discharges, the main motor works, the auxiliary motor does not work, and the battery system supplies power to the main motor. In the dual-motor speed coupling mode, the brakes are disengaged, the first clutch is disengaged, and the second and third clutches are engaged. The engine does not start, the battery system discharges, and the main motor and auxiliary motor operate. The battery system simultaneously supplies power to both the auxiliary and main motors. In the dual-motor hybrid powertrain mode, when the engine and dual-motor speed coupling mode is in the first mode, the brakes are disengaged, and the first, second, and third clutches are engaged. The engine starts, the battery system discharges, and the main and auxiliary motors operate. The battery system simultaneously supplies power to both the main and auxiliary motors for drive. When the dual-motor hybrid powertrain is in the speed coupling mode of the second engine and the dual motors, the brakes are disengaged, and the first, second, and third clutches are engaged. The engine starts, the battery system discharges, the main motor works, and the auxiliary motor acts as a generator. The battery system only supplies power to the main motor for driving. A portion of the engine's power is output to the auxiliary motor via the intermediate shaft to generate electricity, and the electricity generated by the auxiliary motor is transmitted to the main motor.

7. A dual-motor hybrid power transmission system for medium and large tractors according to claim 2, characterized in that, The regenerative braking modes include an independent drive regenerative braking mode and a coupled drive regenerative braking mode; wherein... When the tractor is in motion and is in single-drive mode of the main motor, independent drive mode of the dual motors, or independent drive mode of the engine and dual motors, the driver presses the brake pedal, and the dual-motor hybrid power transmission system enters the independent drive regenerative braking mode. When in the independent drive regenerative braking mode, the brake is locked, the second clutch is disengaged, and the main motor acts as a generator. All the recovered braking force is absorbed by the main motor, which then converts into a generator to charge the battery system. When the tractor is in motion and is in the engine-main motor speed coupling mode, dual-motor speed coupling mode, first engine-dual-motor speed coupling mode, or second engine-dual-motor speed coupling mode, the driver presses the brake pedal, and the dual-motor hybrid power transmission system enters the coupled drive regenerative braking mode. When in the coupled drive regenerative braking mode, the brake is disengaged, the second clutch is engaged, the third clutch is engaged, and the main motor acts as a generator. Part of the recovered braking force is absorbed by the main motor, which always remains in a power generation state to charge the battery system. The remaining recovered braking force is transmitted to the intermediate shaft through the power coupling device.

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