Dual-motor hybrid power transmission system for medium and large tractors

Abstract

The invention discloses a dual-motor hybrid power transmission system for medium and large tractors. The dual-motor hybrid power transmission system 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, power of the main motor can be directly input into the power coupling device, and power of the auxiliary motor is input into the power coupling device through the intermediate shaft and the second clutch. Total power is output to a PTO output shaft through an intermediate shaft and output to a variable speed transmission mechanism through a second row of planetary wheels, rotating speed coupling of the engine and the double motors can be carried out through a power coupling device, different driving modes are achieved, the system is compact and efficient in structure, the efficient and cooperative stepless speed regulation characteristic of multiple power sources is fully utilized, and the power efficiency is improved. The gear requirement of the system is reduced, the space cost is optimized, the chassis specific power is remarkably improved, and the efficient transmission purpose is achieved; and under the high-load working condition, the engine is matched, and power output is balanced.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission systems, and in particular to a dual-motor hybrid power transmission system for medium and large tractors. Background Art

[0002] The development of agricultural modernization technology is closely linked to the development of the automobile industry. In recent years, with the rapid development of new energy vehicle technology, the development of pure electric technology and hybrid technology has become more mature, and major agricultural machinery companies have also launched pure electric and hybrid tractors. However, considering the endurance and complex working conditions of tractors in the field for a long time, hybrid technology is more favored by developers, including series hybrid, parallel hybrid and hybrid-parallel hybrid.

[0003] In the existing hybrid tractor transmission system, most of the dual-motor hybrid structures have two motors working independently. The PTO motor output torque is used to independently drive the power output shaft, and the travel motor is used to drive the tractor. Although this driving method reduces the fuel consumption of the whole machine to a certain extent and responds to the call for green development, it does not fully utilize the speed regulation performance of the motor, and it is easy to cause power loss when the two motors do not work in coordination. In order to solve the above problems, the prior art realizes the coupling transmission of dual motors through the combination of planetary gear sets.

[0004] For example, the invention patent application with application publication number CN111016642A discloses a multi-mode coupling transmission device and control system for an electric tractor, which uses a combination of two planetary gear assemblies and two synchronizer shift mechanisms as a power coupling device for the main motor and the auxiliary motor, realizing multiple working modes including main motor single drive, dual motor torque coupling, and dual motor speed coupling. Although the above-mentioned multi-mode power coupling transmission device and control system for an electric tractor can couple the power of the dual motors through two planetary gear assemblies, thereby realizing multiple driving modes and improving the utilization rate of the motors, the above-mentioned device still has the following deficiencies:

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

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

[0007] 3. The energy loss in the power coupling process reduces the overall efficiency. The complex control system may cause response delays and thus affect the flexibility of operation. The hybrid tractor transmission system based on the double planetary gear design fails to effectively solve the problem of insufficient power of the dual motors at full load output, which may lead to unbalanced power output. Summary of the invention

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

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A dual-motor hybrid power transmission system for medium and large tractors, comprising an engine, an intermediate shaft, a main motor, an auxiliary motor, a power coupling device, a speed transmission mechanism and a PTO output shaft; the engine is provided with an engine output shaft; the auxiliary motor is provided on the intermediate shaft; one end of the intermediate shaft is connected to the engine output shaft through a first clutch, and the other end of the intermediate shaft is connected to one end of the PTO output shaft through a third clutch; the power coupling device is connected to the intermediate shaft through a second clutch; wherein,

[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 row of planetary gears, a first ring gear and a first planet carrier; the second planetary gear mechanism includes a second sun gear, a second row of planetary gears, a second ring gear and a second planet carrier; wherein the first sun gear is connected to the intermediate shaft through a second clutch; the first planet carrier is connected to the second ring gear; the second planet carrier is connected to the speed transmission mechanism; the main shaft of the main motor is connected to the second sun gear; and the brake is used to lock the first planet carrier and the second ring gear at the same time.

[0012] The working principle of the above dual-motor hybrid powertrain for medium and large tractors is:

[0013] The dual input ends of the power coupling device are respectively connected to the auxiliary motor and the main motor. 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 speed transmission mechanism through the second row of planetary gears. The speed coupling of the engine and the dual motors (main motor, auxiliary motor) can be carried out through the power coupling device to realize different driving modes. Specifically, the power of the engine is transmitted to the intermediate shaft through the engine output shaft and the first clutch through the auxiliary motor. After the second clutch is engaged, the first sun gear is driven to move, and then the first row of planetary gears are driven to move, and then the second ring gear is driven to move through the first planetary carrier, thereby driving the second row of planetary gears to move, and then driving the second planetary carrier to move, and the power is transmitted to the speed transmission mechanism; when the third clutch is engaged, the rotation of the intermediate shaft can also drive the PTO output shaft to rotate; the auxiliary motor can drive the intermediate shaft to move, realize the rotation of the PTO output shaft, and when the second clutch is engaged, drive the first planetary gear mechanism to move, and then drive the second planetary gear mechanism to move, and realize the driving of the speed transmission mechanism; the power of the main motor can drive the second sun gear to move, drive the second row of planetary gears to move, and then drive the second planetary carrier to move, and realize the driving of the speed transmission mechanism, and can also drive the second ring gear to move, thereby driving the first planetary gear mechanism to move, and realize the driving of the PTO output shaft. Different driving modes can be achieved by the engagement and disengagement of the first clutch, the second clutch and the third clutch, and the locking and disengagement of the brake.

[0014] A preferred embodiment of the present invention is that 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 coaxially arranged; 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 powertrain 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 speed transmission mechanism includes a first gear, a second gear and a gearbox; the first gear is connected to the second planetary carrier and is coaxially arranged, the second gear is meshed 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 powertrain system include a parking condition driving mode, a first driving and working condition driving mode, a second driving and working condition driving mode, a third driving and working condition driving mode and a regenerative braking mode.

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

[0019] When in the auxiliary motor single-drive PTO mode, the brake is in a disengaged state, the first clutch and the second clutch are in a disengaged state, and the third clutch is in an engaged state; the engine is not started, the battery system is discharged, the main motor is not working, and the auxiliary motor is working; 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 output power is transmitted to the PTO output shaft through the intermediate shaft;

[0020] When in parking charging mode, the brake is in a disengaged state, the first clutch and the third clutch are in an engaged state, the second clutch is in a disengaged state, the engine is started, the auxiliary motor acts as a generator, and part of the engine power drives the auxiliary motor to generate electricity. At the same time, the remaining power output by the engine is transmitted to the PTO output shaft through the intermediate shaft.

[0021] Preferably, the first driving and working condition driving mode includes a main motor single-drive driving mode; the first driving and working condition driving mode is a pure electric mode in which the power source is only the main motor; wherein, when in the main motor single-drive driving mode, the brake is in a locked state, the first clutch, the second clutch and the third clutch are in a disengaged state, 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.

[0022] Preferably, the second driving and working 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 a disengaged or locked state, the first clutch and the second clutch are in a disengaged state, the third clutch is in an engaged state, the engine is not started, the battery system is discharged, the main motor is working, and the auxiliary motor is working; the battery system supplies power to the auxiliary motor and the main motor at the same time;

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

[0025] Preferably, the third driving mode for traveling and working conditions 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 in a disengaged state, the first clutch, the second clutch and the third clutch are in an engaged state, the engine is 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;

[0027] When in dual-motor speed coupling mode, the brake is in a disengaged state, the first clutch is in a disengaged state, the second clutch and the third clutch are in an engaged state, the engine is not started, the battery system is discharged, the main motor is working, and the auxiliary motor is working; the battery system supplies power to the auxiliary motor and the main motor at the same time;

[0028] When the dual-motor hybrid powertrain system is in the first engine and dual-motor speed coupling mode, the brake is in a disengaged state, the first clutch, the second clutch and the third clutch are in an engaged state, the engine is started, the battery system is discharged, the main motor is working, and the auxiliary motor is working; 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 second engine and dual-motor speed coupling mode, the brake is in a disengaged state, the first clutch, the second clutch and the third clutch are in an engaged state, the engine is started, the battery system is discharged, the main motor is working, and the auxiliary motor acts as a generator; the battery system only supplies power to the main motor for driving, and part of the engine power is output to the auxiliary motor through 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 the main motor single-drive mode or the dual-motor independent drive mode or the engine and dual-motor independent drive mode, the driver steps on the brake pedal and the dual-motor hybrid drive system enters the independent drive regenerative braking mode; when in the independent drive regenerative braking mode, the brake is in a locked state, the second clutch is in a disengaged state, and the main motor acts as a generator; all the recovered braking force is absorbed by the main motor, and the main motor is converted into a generator to charge the battery system;

[0032] When the tractor is driving and 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 steps on 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 in a disengaged state, the second clutch is in an engaged state, the third clutch is in an engaged state, and the main motor acts as a generator; part of the recovered braking force is absorbed by the main motor, and the main motor always maintains a power generation state to charge the battery system, and the remaining part of the 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 beneficial effects:

[0034] 1. In the dual-motor hybrid power transmission system of the present invention, the main motor and the auxiliary motor are speed-coupled through the first planetary gear mechanism and the second planetary gear mechanism arranged in parallel, and the structure is compact and efficient. The dual-input single-output characteristics of the first planetary gear mechanism and the second planetary gear mechanism realize the power hybrid output of the high-speed gear / high-power mode. The auxiliary motor is connected to the engine through the first clutch and connected to the PTO output shaft through the third clutch. It can be used as an independent drive motor for the range-extending generator and the PTO output shaft. The main motor is the main source of power on the tractor wheel. This structure can make full use of the excellent high-efficiency speed range of the motor and reduce the speed regulation requirements of the transmission system, thereby greatly simplifying the number of gears of the gearbox, avoiding the problems of complex transmission structure, poor coordination performance under different working conditions, high fuel consumption and low efficiency of the engine in the existing tractor, and making full use of the stepless speed regulation characteristics of efficient coordination of multiple power sources, reducing the gear requirements of the transmission system, optimizing space costs, and significantly improving the chassis specific power, so as to achieve the purpose of efficient transmission. The dual motors of the present invention have high utilization rate, and under high load conditions, they cooperate with the engine to achieve balanced power output.

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

[0036] 3. The dual-motor hybrid power transmission system of the present invention realizes four different driving modes of hybrid driving mode, pure electric driving mode, extended-range driving mode and regenerative braking mode by coupling the engine-dual motor speed through the first planetary gear mechanism and the second planetary gear mechanism arranged in parallel. Combining the speed change principle and regenerative braking principle of the planetary gear mechanism, 11 different gear modes are realized; among them, the working modes of the four gears realized by the hybrid driving mode are the engine and dual motor independent driving 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; the working modes of the four gears realized by the pure electric driving mode are the auxiliary motor single-drive PTO mode, the main motor single-drive driving mode, the dual motor independent driving mode and the dual motor speed coupling mode; the extended-range driving mode includes the parking charging mode, the engine and dual motor independent driving mode and the second engine and dual motor speed coupling mode, and the regenerative braking mode includes the independent drive regenerative braking mode and the coupled drive regenerative braking mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The figure is a schematic structural diagram of a dual-motor hybrid power transmission system for medium and large tractors in the present invention.

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

[0039] Figure 3 This is a power flow integration diagram of the first driving mode of travel and working condition in the present invention.

[0040] Figure 4 This is a power flow integration diagram of the second driving mode of the driving mode of the working condition in the present invention.

[0041] Figure 5 This is a power flow integration diagram of another implementation of the second driving mode for traveling and working conditions in the present invention.

[0042] Figure 6 This is a power flow integration diagram of the third driving mode of the driving mode of the working condition in the present invention.

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

[0044] Figure 8 This is an integrated diagram of the braking force flow in the coupled drive regenerative braking mode of the present invention. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0046] See also Figure 1 The present embodiment discloses a dual-motor hybrid power transmission system for medium and large tractors, comprising an engine 1, an intermediate shaft 16, a main motor 9, an auxiliary motor 4, a power coupling device 11, a speed 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 the auxiliary motor 4 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 also Figure 1The power coupling device 11 includes a brake 13, a first planetary gear mechanism and a second planetary gear mechanism arranged in parallel (that is, 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 row of planetary gears 6, a first ring gear 7 and a first planet carrier 12; the first sun gear 8 is meshed with the first row of planetary gears 6, the first row of planetary gears 6 is meshed with the first ring gear 7, and the first planet carrier 12 is connected to the first row of planetary gears 6; the second planetary gear mechanism includes a second sun gear 20, a second row of planetary gears 15, a second ring gear 14 and a second planet carrier 22; the second sun gear 20 is meshed with the second row of planetary gears 15, the second row of planetary gears 15 is meshed with the second ring gear 14 is meshed, the second planet carrier 22 is connected to the second row of planetary gears 15; wherein, the first sun gear 8 is connected to the intermediate shaft 16 via the second clutch 5; the first planet carrier 12 is connected to the second ring gear 14; the second planet carrier 22 is connected to the speed 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, and the brake 13 is used to lock the first planet carrier 12 and the second ring gear 14 at the same time, thereby interrupting the power transmission between the first planetary gear mechanism and the second planetary gear mechanism. When the brake 13 is in a disengaged state, the power between the first planetary gear mechanism and the second planetary gear mechanism can be transmitted. The first row of planetary gears 6 and the second row of planetary gears 15 both include a plurality of planetary gears.

[0048] The working principle of the above dual-motor hybrid powertrain for medium and large tractors is:

[0049] The dual input ends of the power coupling device 11 are respectively connected to the auxiliary motor 4 and the main motor 9. The power of the main motor 9 can be directly input into the power coupling device 11. 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 speed transmission mechanism 27 through the second row of planetary gears 15. The speed coupling of the engine 1 and the dual motors (main motor 9, auxiliary motor 4) can be performed through the power coupling device 11 to realize different driving modes. Specifically, the power of the engine 1 is transmitted to the intermediate shaft 16 through the engine output shaft 2 and the first clutch 3 through the auxiliary motor 4. After the second clutch 5 is engaged, the first sun gear 8 is driven to move, and then the first row of planetary gears 6 are driven to move, and then the second ring gear 14 is driven to move through the first planetary carrier 12, thereby driving the second row of planetary gears 15 to move, and then driving the second planetary carrier 22 to move, and the power is transmitted to the speed transmission mechanism 27; when the third clutch 17 is engaged, the rotation of the intermediate shaft 16 can also drive the PTO output shaft 19 to rotate; the auxiliary motor 4 can drive the intermediate shaft 16 to move, realize the rotation of the PTO output shaft 19, and when the second clutch 5 is engaged, drive the first planetary gear mechanism to move, and then drive the second planetary gear mechanism to move, and realize the driving of the speed transmission mechanism 27; the power of the main motor 9 can drive the second sun gear 20 to move, drive the second row of planetary gears 15 to move, and then drive the second planetary carrier 22 to move, and realize the driving of the speed transmission mechanism 27, and can also drive the second ring gear 14 to move, thereby driving the first planetary gear mechanism to move, and realize the driving of the 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 , and locking and disengaging the brake 13 .

[0050] See also Figure 1 The engine 1, the first clutch 3, the auxiliary motor 4, the second clutch 5, the intermediate shaft 16, the main motor 9, the first sun gear 8, the second sun gear 20, the third clutch 17 and the PTO output shaft 19 are arranged coaxially; 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 is very compact, occupies a small space, and has a very reasonable layout.

[0051] See also Figure 1, the 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 the main motor 9 and the auxiliary motor 4 respectively, 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 driving of the main motor 9 and the auxiliary motor 4 can be realized, and the electric energy recovery can also be realized; the reducer 18 can reduce the output speed of the PTO output shaft 19, increase the torque, and improve the load capacity. Through the PTO output shaft 19, field operations such as tillage, sowing, fertilizing or harvesting can be realized.

[0052] See also Figure 1 The speed transmission mechanism 27 includes a first gear 22, a second gear 23 and a gearbox 25; the first gear 22 is connected to the second planetary carrier 22 and is coaxially arranged, the second gear 23 is meshed with the first gear 22, and the gearbox input shaft 24 of the gearbox 25 is connected to the second gear 23. In the above structure, the first gear 22 is driven to rotate by the second planetary carrier 22, thereby driving the second gear 23 to rotate, and then the power is transmitted to the gearbox 25 through the gearbox input shaft 24, and the gearbox 25 then outputs the power to the wheels through the gearbox output shaft 26 to drive the tractor.

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

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

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

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

[0057] Table 1 Working status of each component in parking condition driving mode

[0058]

[0059] See also Figure 1 and Figure 2 The parking condition driving mode includes an auxiliary motor single drive PTO mode and a parking charging mode. The power source of the auxiliary motor single drive PTO mode is the auxiliary motor 4, and the battery system 10 transmits power to the auxiliary motor 4 along the power transmission route ①; the power source of the parking charging mode 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 also 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. When in the auxiliary motor single-drive PTO mode, the brake 13 is in a disengaged state, the first clutch 3 and the second clutch 5 are in a disengaged state, and the third clutch 17 is in an engaged state; the engine 1 is not started, the battery system 10 is discharged, the main motor 9 is not working, and the auxiliary motor 4 is working. At this time, the power transmission between the engine 1 and the intermediate shaft 16 is interrupted, the battery system 10 supplies power to the auxiliary motor 4, and the output power of the auxiliary motor 4 is transmitted to the PTO output shaft 19 through the intermediate shaft 16, driving the PTO to perform field operations such as digging holes and fertilizing.

[0061] See also Figure 1 and Figure 2 When the battery system 10 power 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 in a disengaged state, the first clutch 3 and the third clutch 17 are in an engaged state, the second clutch 5 is in a disengaged state, the engine 1 is started, and the auxiliary motor 4 acts as a generator. At this time, the tractor is in a parking charging state, and 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 fertilizing.

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

[0063]

[0064] See also Figure 1 and Figure 3 The first driving and working condition driving mode includes 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 in a locked state, the power of the main motor 9 can only be transmitted to the wheels along the second planetary gear mechanism and the speed transmission mechanism 27.

[0065] See also Figure 1 and Figure 3 When in the main motor single-drive driving mode, the brake 13 is in a locked state, the first clutch 3, the second clutch 5 and the third clutch 17 are in a disengaged state, the engine 1 is not started, the battery system 10 is discharged, the main motor 9 is working, and the auxiliary motor 4 is not working. When the dual-motor hybrid power transmission system is in the main motor single-drive driving mode, the tractor only performs driving operations, the battery system 10 supplies power to the main motor 9, and the power of the main motor 9 passes through the second sun gear 20, the second row 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 in sequence, and the gearbox output shaft 26 outputs power to drive the tractor to drive.

[0066] Table 3 Working status of each component in the second driving mode of driving and working condition

[0067]

[0068] See also Figure 1 and Figure 4 , the second driving and working condition driving mode includes a dual-motor independent driving mode and an engine and dual-motor independent driving mode. The power source of the dual-motor independent driving mode is the main motor 9 and the auxiliary motor 4, and the battery system 10 transmits power to the auxiliary motor 4 and the main motor 9 respectively along the power transmission route ⑤ and the power transmission route ⑥; the power source of the engine and dual-motor independent driving mode is the engine 1 and the main motor 9. At this time, the auxiliary motor 4 acts as a generator to generate electricity under the action of the engine 1, and transmits power to the main motor 9 along the power transmission route ⑦. At the same time, the battery system 10 transmits power to the main motor 9 along the power transmission route ⑥.

[0069] See also Figure 1 and Figure 4When in the dual-motor independent drive mode, the brake 13 is in a disengaged state, the first clutch 3 and the second clutch 5 are in a disengaged state, the third clutch 17 is in an engaged state, the engine 1 is not started, the battery system 10 is discharged, the main motor 9 is working, and the auxiliary motor 4 is working. When the dual-motor hybrid power transmission system is in the dual-motor independent drive mode, the tractor is driving and performing field operations. The battery system 10 supplies power to the auxiliary motor 4 and the main motor 9 at the same time. The power of the auxiliary motor 4 is sequentially transmitted through the intermediate shaft 16 and the reducer 18, and is output to the PTO output shaft 19 through the reducer 18 to drive the tractor to perform field agricultural machinery operations; the power of the main motor 9 is sequentially transmitted through the second sun gear 20, the second row 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 the gearbox output shaft 26 outputs power to drive the tractor to travel. See Figure 5 In another embodiment, when in the dual-motor independent driving mode, the brake 13 is in a locked state.

[0070] See also Figure 1 and Figure 4 When in the engine and dual-motor independent driving mode, the brake 13 is in a disengaged state, the first clutch 3 and the third clutch 17 are in an engaged state, the second clutch 5 is in a disengaged state, the engine 1 is started, the battery system 10 is discharged, and the main motor 9 is working; the battery system 10 only supplies power to the main motor 9, and the auxiliary motor 4 acts as a generator. When the dual-motor hybrid powertrain is in the engine and dual-motor independent drive mode, the battery system 10 discharges to power the main motor 9, and the auxiliary motor 4 acts as a generator. Driven by the engine 1, the intermediate shaft 16 rotates, thereby enabling the auxiliary motor 4 to generate electricity. The electricity generated by the auxiliary motor 4 is used to power the main motor 9; part of the power of the engine 1 is used to generate electricity for the auxiliary motor 4, and the remaining power of the engine 1 is sequentially output to the PTO output shaft 19 through the intermediate shaft 16 and the reducer 18 through the reducer 18 to drive the tractor to perform field agricultural machinery operations; the power of the main motor 9 is sequentially output through the second sun gear 20, the second row 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 the gearbox output shaft 26 outputs power to drive the tractor to travel. See Figure 5 In another embodiment, when the engine and dual motors are in independent driving mode, the brake 13 is in a locked state.

[0071] Table 4 Working status of each component in the third driving mode of driving and working condition

[0072]

[0073] See also Figure 1 and Figure 6The third driving mode for traveling and working conditions 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. The power sources of the engine and main motor speed coupling mode are the engine 1 and the main motor 9, and the battery system 10 transmits power to the main motor 9 along the power transmission route ⑥; the power sources of the dual motor speed coupling mode are the main motor 9 and the auxiliary motor 4, and the battery system 10 transmits power to the auxiliary motor 4 and the main motor 9 respectively along the power transmission route ⑤ and the power transmission route ⑥; the power sources of the first engine and dual motor speed coupling mode are the engine 1, the main motor 9 and the auxiliary motor 4. At this time, the battery system 10 transmits power to the auxiliary motor 4 and the main motor 9 respectively along the power transmission route ⑤ and the power transmission route ⑥, and the power of the engine 1 and the power of the auxiliary motor 4 are coaxially output; the power sources of the second engine and dual motor speed coupling mode are the engine 1 and the main motor 9. At this time, the auxiliary motor 4 acts as a generator, generates electricity under the action of the engine 1, and transmits power to the main motor 9 along the power transmission route ⑦. At the same time, the battery system 10 transmits power to the main motor 9 along the power transmission route ⑥.

[0074] See also Figure 1 and Figure 6 When in the engine and main motor speed coupling mode, the brake 13 is in a disengaged state, the first clutch 3, the second clutch 5 and the third clutch 17 are in an engaged state, the engine 1 is started, the battery system 10 is discharged, the main motor 9 is working, and the auxiliary motor 4 is not working. When the dual-motor hybrid power transmission system is in the engine and main motor speed coupling mode, the tractor is driving and working in the field, and part of the power of the engine 1 is sequentially transmitted through the engine output shaft 2, the intermediate shaft 16 and the reducer 18, and is output from the reducer 18 to the PTO output shaft 19 to drive the tractor to perform field agricultural machinery operations; at the same time, the remaining power of the engine 1 is sequentially transmitted through the engine output shaft 2, 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, and the battery system 10 discharges, and the battery system 10 supplies power to the main motor 9. The power of the main motor 9 is sequentially transmitted through the second sun gear 20 and the second row of planetary gears 15. After the power of the engine 1 and the power of the main motor 9 are speed-coupled in the second planetary gear mechanism (the second row of planetary gears 15), they are 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 gearbox output shaft 26 outputs power to drive the tractor to travel.

[0075] See also Figure 1 and Figure 6When in the dual motor speed coupling mode, the brake 13 is in a disengaged state, the first clutch 3 is in a disengaged state, the second clutch 5 and the third clutch 17 are in an engaged state, the engine 1 is not started, the battery system 10 is discharged, the main motor 9 is working, and the auxiliary motor 4 is working. When the dual motor hybrid power transmission system is in the dual motor speed coupling mode, the tractor is driving and working in the field, the battery system 10 is discharged, and the battery system 10 supplies power to the auxiliary motor 4 and the main motor 9 at the same time. A part of the power of the auxiliary motor 4 is sequentially outputted from the reducer 18 to the PTO output shaft 19 through the intermediate shaft 16 and the reducer 18, and the tractor performs rotary tillage operation. 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 power of the auxiliary motor 4 and the main motor 9 is speed-coupled in the second planetary gear mechanism (the second row of planetary gears 15), it 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 to move.

[0076] See also Figure 1 and Figure 6 When the dual-motor hybrid powertrain system is in the first engine and dual-motor speed coupling mode, the brake 13 is in a disengaged state, the first clutch 3, the second clutch 5 and the third clutch 17 are in an engaged state, the engine 1 is started, the battery system 10 is discharged, the main motor 9 is working, and the auxiliary motor 4 is working. When the dual-motor hybrid power transmission system is in the first engine and dual-motor speed coupling mode, the tractor is traveling and performing field operations, the battery system 10 is discharged, and the battery system 10 simultaneously supplies power to the main motor 9 and the auxiliary motor 4 for driving. After 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 is sequentially transmitted through the intermediate shaft 16 and the reducer 18, and is output to the PTO output shaft 19 by the reducer 18, driving the PTO output shaft 19 to perform field operations such as tillage, fertilization, sowing or harvesting; the remaining coupled power is sequentially transmitted to the second row of planetary gears 15 through the first sun gear 8, the first row of planetary gears 6, the first planetary carrier 12, and the second ring gear 14, and the power of the main motor 9 is output to the second row of planetary gears 15 through the second sun gear 20. After the remaining coupled power and the power of the main motor 9 are speed-coupled in the second planetary gear mechanism (the second row of planetary gears 15), they are 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 gearbox output shaft 26 outputs power to drive the tractor to travel.

[0077] See also Figure 1 and Figure 6When the dual-motor hybrid powertrain is in the second engine and dual-motor speed coupling mode, the brake 13 is in a disengaged state, the first clutch 3, the second clutch 5 and the third clutch 17 are in an engaged state, the engine 1 is started, the battery system 10 is discharged, the main motor 9 is working, and the 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 is driving and working in the field, the battery system 10 is discharged, and the battery system 10 only supplies power to the main motor 9 for driving. A part of the power of the engine 1 is output to the auxiliary motor 4 through the intermediate shaft 16 to generate electricity, and the electricity generated by the auxiliary motor 4 is transmitted to the main motor 9; the remaining part of the power of the engine 1 is output through the intermediate shaft 16 to drive the PTO output shaft 19 and to drive the first sun gear 8. The power generated by the first sun gear 8 is sequentially transmitted through the first row of planetary gears 6, the first planetary carrier 12. The second ring gear 14 is transmitted to the second row of planetary gears 15, and the power of the main motor 9 is output to the second row of planetary gears 15 through the second sun gear 20. After the speed coupling of part of the power of the engine 1 and the power of the main motor 9 is carried out in the second planetary gear mechanism (the second row of planetary gears 15), the power is output by the gearbox output shaft 26 through the second planetary carrier 22, the first gear 22, the second gear 23, the gearbox input shaft 24 and the gearbox 25 in sequence, and the power is output by the gearbox output shaft 26 to drive the tractor to travel; the rotation of the PTO output shaft 19 is used for field operations such as tillage, fertilization, sowing or harvesting.

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

[0079]

[0080] See also Figure 1 and Figure 7 The regenerative braking mode includes an independent drive regenerative braking mode and a coupled drive regenerative braking mode. The independent drive regenerative braking mode and the coupled drive regenerative braking mode are mainly different in the separation or engagement of the second clutch 5 .

[0081] See also Figure 7 The driving modes corresponding to the independent drive regenerative braking mode are the main motor single drive mode, the dual motor independent drive mode and the engine and dual motor independent drive mode. The brake 13 in the independent drive regenerative braking mode is in a locked state, the second clutch 5 is in a disengaged state, and the recovered braking force is completely absorbed by the main motor 9. The main motor 9 is converted into a generator to charge the battery system 10. Specifically, the battery system 10 is powered by the power transmission route (2). The engine 1 and the auxiliary motor 4 maintain the working state of the original driving mode. The battery system 10 can power the auxiliary motor 4 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 also Figure 1 and Figure 8 , the driving modes corresponding to the coupled drive regenerative braking mode are the engine and main motor speed coupling mode, the dual motor speed coupling mode, the first engine and dual motor speed coupling mode, and the 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, and most of the recovered braking force is absorbed by the main motor 9. The main motor 9 always maintains the power generation state to charge the battery system 10, specifically through the power transmission route (2) to transmit power to the battery system 10, 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 brake deceleration, the torque of the PTO output shaft 19 increases after the brake deceleration. At this time, in order to obtain a stable output of the PTO output shaft 19 power before and after the brake 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, and the engine 1 maintains the working state of the tractor's driving mode before the brake deceleration.

[0083] See also Figure 1 and Figure 7 In the above regenerative braking mode, when the driver steps on the brake pedal, the main motor 9 is converted into a generator, and the braking energy of the tractor is transmitted to the power coupling device 11 through the speed transmission mechanism 27, wherein part of the kinetic energy is absorbed by the main motor 9 for reverse pulling the main motor 9 to generate electricity. The above regenerative braking mode can realize energy recovery. During braking deceleration, regenerative braking can be used to make up for the lack of mechanical braking capacity and the excess electric energy can be fed back to the battery system 10, thereby improving the overall energy utilization rate.

[0084] See also Figure 1 and Figure 7, when the driver steps on the brake pedal during the driving of the tractor, the dual-motor hybrid powertrain enters the independent drive regenerative braking mode or the coupled drive regenerative braking mode; specifically, when the tractor is in the main motor single drive mode or the dual motor independent drive mode or the engine and dual motor independent drive mode, the driver steps on the brake pedal, and the dual-motor hybrid powertrain enters the independent drive regenerative braking mode; when in the independent drive regenerative braking mode, the brake 13 is in a locked state, the first clutch 3 is in an engaged / disengaged state, the second clutch 5 is in a disengaged state, the third clutch 17 is in an engaged / disengaged 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. The recovered braking force is all absorbed by the main motor 9, and the main motor 9 is converted into a generator to charge the battery system 10; when the engine and dual motor independent drive mode enter the independent drive regenerative braking mode, the auxiliary motor 4 switches to power generation to charge the battery system 10, and in other drive modes, the engine 1 and the auxiliary motor 4 maintain the working state of the original drive mode.

[0085] See also Figure 1 and Figure 8 When the tractor 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 steps on 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 a disengaged state, the first clutch 3 is in an engaged / disengaged state, the second clutch 5 is in an engaged state, the third clutch 17 is in an 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 / not works / 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, and the auxiliary motor 4 transmits power to the battery system 10 through the power transmission route (4). When the second engine and dual motor speed coupling mode enters the coupled drive regenerative braking mode, the auxiliary motor 4 switches power generation to charge the battery system 10; in other driving modes, the engine 1 and the auxiliary motor 4 maintain the working state of the original driving mode.

[0086] See also Figure 1-Figure 8The dual-motor hybrid power transmission system in this embodiment realizes four different driving modes, namely, oil-electric hybrid driving mode, pure electric driving mode, extended-range driving mode and regenerative braking mode, by coupling the engine-dual motor speed through the first planetary gear mechanism and the second planetary gear mechanism arranged in parallel. Combining the speed change principle and regenerative braking principle of the planetary gear mechanism, 11 different gear modes are realized, namely, auxiliary motor single-drive PTO mode, parking charging mode, main motor single-drive driving mode, dual-motor independent driving mode, engine and dual-motor independent driving 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 driving 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 driving mode; the auxiliary motor single-drive PTO mode, the main motor single-drive driving mode, the dual motor independent driving mode and the dual motor speed coupling mode constitute a pure electric driving mode; the parking charging mode, the engine and dual motor independent driving mode and the second engine and dual motor speed coupling mode constitute an extended-range driving mode; through the locking and release of the brake 13 and the engagement and release of the first clutch 3 and the second clutch 5, the tractor can realize the engine-dual motor hybrid structure according to different cyclic driving conditions. Switching between the hybrid driving mode, the pure electric driving mode and the extended-range driving mode; the engagement of the third clutch 17 is used to realize PTO field operations such as tilling, sowing, fertilizing or harvesting.

[0087] Most of the existing tractors have a PTO output shaft 19 coaxially driven with the engine 1. Due to the fixed speed ratio, the working condition coordination performance is poor, and the engine 1 is often forced to run in a high fuel consumption working range. In the dual-motor hybrid power transmission system in this embodiment, the dual motors are speed-coupled through the first planetary gear mechanism and the second planetary gear mechanism arranged in parallel, and the dual-input single-output characteristics of the planetary gear set are used to achieve a high-speed gear / high-power mode power hybrid output; the auxiliary motor 4 is connected to the engine 1 through the first clutch 3 and the PTO output shaft 19 through the third clutch 17, and can be used as an extended-range generator and an independent drive motor of the PTO output shaft 19; and the main motor 9 is the main source of power on the tractor wheels. This structure can make full use of the excellent high-efficiency speed range of the motor, reduce the speed regulation requirements of the transmission system, and thus greatly simplify the number of gears of the gearbox 25; considering the problem that the mechanical braking ability of the tractor is relatively poor, this embodiment is provided with an energy recovery mechanism, which can not only use regenerative braking to make up for the lack of mechanical braking ability during braking and deceleration, but also feed back excess electrical energy to the battery system 10, thereby improving the overall energy utilization rate.

[0088] The above is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited to the above content. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be equivalent replacement methods and are included in 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 speed transmission mechanism and a PTO output shaft; the engine is provided with an engine output shaft; the auxiliary motor is provided on the intermediate shaft; one end of the intermediate shaft is connected to the engine output shaft through a first clutch, and the other end of the intermediate shaft is connected to one end of the PTO output shaft through a third clutch; the power coupling device is connected to the intermediate shaft through a second 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 row of planetary gears, a first ring gear and a first planet carrier; the second planetary gear mechanism includes a second sun gear, a second row of planetary gears, a second ring gear and a second planet carrier; wherein the first sun gear is connected to the intermediate shaft through a second clutch; the first planet carrier is connected to the second ring gear; the second planet carrier is connected to the speed transmission mechanism; the main shaft of the main motor is connected to the second sun gear; and the brake is used to lock the first planet carrier and the second ring gear at the same time.

2. A dual-motor hybrid power transmission system for medium and large tractors according to claim 1, characterized in that: 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.

3. A dual-motor hybrid power transmission system for medium and large tractors according to claim 1, characterized in that: 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.

4. A dual-motor hybrid power transmission system for medium and large tractors according to claim 3, characterized in that: The speed transmission mechanism includes a first gear, a second gear and a gearbox; the first gear is connected to the second planet carrier and is coaxially arranged, the second gear is meshed with the first gear, and the gearbox input shaft of the gearbox is connected to the second gear.

5. A dual-motor hybrid power transmission system for medium and large tractors according to claim 3 or 4, characterized in that: The driving modes of the dual-motor hybrid powertrain system include a parking condition driving mode, a first driving and working condition driving mode, a second driving and working condition driving mode, a third driving and working condition driving mode, and a regenerative braking mode.

6. A dual-motor hybrid power transmission system for medium and large tractors according to claim 5, characterized in that: The parking condition driving mode includes an auxiliary motor single drive PTO mode and a parking charging mode; wherein, When in the auxiliary motor single-drive PTO mode, the brake is in a disengaged state, the first clutch and the second clutch are in a disengaged state, and the third clutch is in an engaged state; the engine is not started, the battery system is discharged, the main motor is not working, and the auxiliary motor is working; 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 output power is transmitted to the PTO output shaft through the intermediate shaft; When in parking charging mode, the brake is in a disengaged state, the first clutch and the third clutch are in an engaged state, the second clutch is in a disengaged state, the engine is started, the auxiliary motor acts as a generator, and part of the engine power drives the auxiliary motor to generate electricity. At the same time, the remaining power output by the engine is transmitted to the PTO output shaft through the intermediate shaft.

7. A dual-motor hybrid power transmission system for medium and large tractors according to claim 6, characterized in that: The first driving and working condition driving mode includes a main motor single-drive driving mode; wherein, when in the main motor single-drive driving mode, the brake is in a locked state, the first clutch, the second clutch and the third clutch are in a disengaged state, 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.

8. A dual-motor hybrid power transmission system for medium and large tractors according to claim 6, characterized in that: The second driving and working condition driving mode includes a dual-motor independent driving mode and an engine and dual-motor independent driving mode; wherein, When in the dual-motor independent drive mode, the brake is in a disengaged or locked state, the first clutch and the second clutch are in a disengaged state, the third clutch is in an engaged state, the engine is not started, the battery system is discharged, the main motor is working, and the auxiliary motor is working; the battery system supplies power to the auxiliary motor and the main motor at the same time; When in the engine and dual-motor independent drive mode, the brake is in a disengaged or locked state, the first clutch and the third clutch are in an engaged state, the second clutch is in a disengaged state, the engine is started, the battery system is discharged, and the main motor is working; 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 power the main motor.

9. A dual-motor hybrid power transmission system for medium and large tractors according to claim 6, characterized in that: The third driving mode for traveling and working conditions 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 in a disengaged state, the first clutch, the second clutch and the third clutch are in an engaged state, the engine is 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; When in dual-motor speed coupling mode, the brake is in a disengaged state, the first clutch is in a disengaged state, the second clutch and the third clutch are in an engaged state, the engine is not started, the battery system is discharged, the main motor is working, and the auxiliary motor is working; the battery system supplies power to the auxiliary motor and the main motor at the same time; When the dual-motor hybrid powertrain system is in the first engine and dual-motor speed coupling mode, the brake is in a disengaged state, the first clutch, the second clutch and the third clutch are in an engaged state, the engine is started, the battery system is discharged, the main motor is working, and the auxiliary motor is working; the battery system simultaneously supplies power to the main motor and the auxiliary motor for driving; When the dual-motor hybrid powertrain is in the second engine and dual-motor speed coupling mode, the brake is in a disengaged state, the first clutch, the second clutch and the third clutch are in an engaged state, the engine is started, the battery system is discharged, the main motor is working, and the auxiliary motor acts as a generator; the battery system only supplies power to the main motor for driving, and part of the engine power is output to the auxiliary motor through the intermediate shaft to generate electricity, and the electricity generated by the auxiliary motor is transmitted to the main motor.

10. A dual-motor hybrid power transmission system for medium and large tractors according to claim 6, characterized in that: The regenerative braking mode includes an independent drive regenerative braking mode and a coupled drive regenerative braking mode; wherein, When the tractor is in the main motor single-drive mode or the dual-motor independent drive mode or the engine and dual-motor independent drive mode, the driver steps on the brake pedal and the dual-motor hybrid drive system enters the independent drive regenerative braking mode; when in the independent drive regenerative braking mode, the brake is in a locked state, the second clutch is in a disengaged state, and the main motor acts as a generator; all the recovered braking force is absorbed by the main motor, and the main motor is converted into a generator to charge the battery system; When the tractor is driving and 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 steps on 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 in a disengaged state, the second clutch is in an engaged state, the third clutch is in an engaged state, and the main motor acts as a generator; part of the recovered braking force is absorbed by the main motor, and the main motor always maintains a power generation state to charge the battery system, and the remaining part of the recovered braking force is transmitted to the intermediate shaft through the power coupling device.

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