A Hybrid System for a Tractor Driven by Three Motors and a Power Coupling Control Method

Abstract

The present invention provides a hybrid system for a tractor driven by three motors and a power coupling control method, including an engine, an alternator, a motor assembly, a battery pack, wheels, a power take-off device and a vehicle controller. The engine is connected to the motor assembly through a power coupling mechanism to the wheels and the power take-off device. The engine is respectively connected to the power coupling mechanism and the alternator through a first clutch and a second clutch. By setting the engine and three motors to drive the whole vehicle to work, two motors respectively drive the wheels and the power take-off device separately during operation, and the other motor selects to perform power compensation according to the current working condition, so that the tractor can have sufficient power for driving and operation under various working conditions. When the state of the vehicle battery pack is poor, starting the engine for power compensation can also charge the battery pack, greatly improving the operation duration of the tractor, and at the same time ensuring sufficient power under various working conditions to meet the operation requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of hybrid tractors, and particularly relates to a tractor hybrid system driven by three motors and a power coupling control method. Background Art

[0002] A tractor is a self-propelled power machine that completes various mobile operations by towing or driving mechanical equipment, and can also be used as a power source for fixed operations. Common tractors usually consist of devices such as an engine, a transmission system, a running system, a steering system, a hydraulic suspension system, a power output system, electrical instruments, a driving and operating system, and a towing system. The power of the engine is transmitted to the driving wheels through the transmission system to drive the tractor to run. In real life, a rubber belt is commonly used as the medium for power transmission. According to functions and uses, tractors can be divided into agricultural, industrial, and special-purpose tractors; according to structural types, they can be divided into wheeled, crawler-type, boat-shaped tractors, and self-propelled chassis, etc.

[0003] Wheeled tractors are usually used for flatland operations, and crawler tractors are often used for forestry operations. This type of tractor has excellent off-road performance and strong climbing ability; among many types of tractors, the tillage boat, also known as the boat-shaped tractor, is an original paddy field power machine in the mechanized operation of paddy fields in China. The tillage machine is suitable for farmers with small fields, narrow ridges, "interspersed" crops, and "interspersed" fields.

[0004] Tractors equipped with agricultural implements such as plows, harrows, and rotary tillers mostly operate in the fields, consuming a large amount of fuel and having poor emissions. The existing hybrid power systems of hybrid tractors often use hybrid systems in which the engine and the motor are connected in series or in parallel. Although the overall driving ability of the tractor can be improved, due to the narrow type of power sources, the power adjustment range is small, which easily leads to power waste. In order to make the engine work in a better range and meet the driving requirements under different working conditions, the present invention proposes a tractor hybrid system driven by three motors and a power coupling control method to solve the above problems. Summary of the Invention

[0005] Object of the Invention: Aiming at the deficiencies in the prior art, the present invention provides a tractor hybrid system driven by three motors. By setting three driving motors and corresponding coupling devices, when the tractor performs different operations, the power coupling method corresponding to the current working condition is automatically selected through preset working condition parameters, meeting various working conditions of the tractor, making the work more stable, improving the utilization rate of the motor at the same time, and avoiding power waste.

[0006] Technical solution: A hybrid system for a tractor driven by three motors, comprising an engine, an alternator, a motor assembly, a battery pack, wheels, a power take-off device and a vehicle controller. The engine and the motor assembly are connected to the wheels and the power take-off device through a power coupling mechanism. The engine is connected to the power coupling mechanism and the alternator through a first clutch and a second clutch respectively. The power coupling mechanism is connected to the wheels through a gearbox, a reducer and an axle in sequence. The alternator is connected to the battery pack through an inverter. The battery pack is connected to the motor assembly through an inverter. The power coupling mechanism includes a first input shaft, a second input shaft and a third input shaft. The first input shaft and the second input shaft are connected by a first transmission gear pair. The second input shaft and the third input shaft are connected by a second transmission gear pair. The motor assembly includes a first motor, a second motor and a third motor. The output ends of the first motor, the second motor and the third motor are connected to the first input shaft, the second input shaft and the third input shaft through a third clutch, a fourth clutch and a fifth clutch respectively. The second input shaft is connected to the first transmission gear pair and the second transmission gear pair through a first synchronizer and a second synchronizer respectively. The third input shaft is connected to the input shaft of the power take-off device through a third synchronizer and a gear pair for gears.

[0007] In the present invention, the engine and three motors are provided to drive the whole vehicle. When the state of the vehicle battery pack is good, pure electric drive is selected to save fuel consumption and reduce exhaust emissions. When the three motors work, two motors drive the wheels and the power take-off device separately, and the other motor selects to perform power compensation according to the current working conditions, so that the tractor can have sufficient power for driving and operation under various working conditions. When the state of the vehicle battery pack is poor, the engine is started to perform power compensation and can also charge the battery pack at the same time, greatly improving the operation duration of the tractor and ensuring sufficient power under various working conditions to meet the operation requirements.

[0008] The vehicle controller controls the start and stop of the motor assembly and the alternator through a motor controller. The vehicle controller controls the power coupling mechanism through a coupling mechanism controller. The vehicle controller controls the start and stop of the engine through an engine controller. The vehicle controller monitors the remaining power of the battery pack through a battery management system.

[0009] By setting multiple controllers, accurate control can be achieved while the current vehicle state can be monitored in real time and fed back to the vehicle controller, so as to realize timely and rapid switching to the power required for the current working condition and improve the working efficiency of the vehicle.

[0010] The gear pair for gears is a two-speed gear pair, including a first-speed gear pair and a second-speed gear pair installed on the input shaft of the power take-off device.

[0011] The vehicle controller is signal-connected to a vehicle speed sensor.

[0012] Through the vehicle speed sensor, the current vehicle speed is monitored and fed back to the vehicle controller in real time. The collected vehicle speed data is matched with the system to improve the operation accuracy of the tractor during driving, and the power switch is more timely and accurate.

[0013] According to the operating state of the equipment, it is divided into two states: non-operation driving and operation driving, which are specifically as follows:

[0014] Non-operation driving includes: low-speed driving, medium-speed driving, high-speed driving, heavy load, and deceleration braking regeneration;

[0015] Operation driving includes: seeding operation, plowing operation, and rotary tillage operation.

[0016] The non-operation driving is specifically as follows:

[0017] Low-speed driving, where the vehicle speed V ≤ V1 and the battery pack capacity SOC ≥ SOC min , the third clutch engages, the battery pack drives the first motor to work, and the first motor drives the wheels alone;

[0018] Medium-speed driving, where V1 < V ≤ V2 or the battery pack capacity SOC < SOC min , the first clutch engages, and the engine drives the wheels alone;

[0019] High-speed driving, V > V2 and the battery pack capacity SOC ≥ SOC min , the first clutch and the third clutch engage, and the engine and the first motor are power-coupled to jointly drive the wheels;

[0020] Load, that is, hauling goods. In actual work, tractors are often used for hauling goods, which is also a common working condition, P req >P max , and the battery pack capacity SOC ≤ SOC target , the first clutch, the second clutch, and the third clutch engage, the engine charges the battery pack and supplies power to the first motor at the same time, and the engine and the first motor jointly drive the wheels. At this time, the first motor is the main power source for the wheels;

[0021] Deceleration braking regeneration, P req <0 and the battery pack capacity SOC ≤ SOC max , the third clutch engages, the rotational force of the wheels drives the motor to operate, and the first motor acts as a generator to convert mechanical energy into electrical energy and store it in the battery pack;

[0022] Among them, V is the current vehicle speed, V1 is the demarcation point between low speed and medium speed, which is 15 km / h, V2 is the demarcation point between medium speed and high speed, which is 35 km / h, SOC is the current state of charge of the battery pack, SOC minThe minimum state of charge of the battery pack is 20%, SOC target The target state of charge of the battery is 60%, SOC max The maximum state of charge of the battery is 90%, P req Is the wheel demand power, P max Is the maximum output power of the first motor.

[0023] The specific operation of driving is as follows:

[0024] For seeding operation, the state of charge of the battery pack SOC≥SOC min , the third clutch and the fifth clutch are engaged, the third synchronizer is engaged to the left and engaged with the first gear pair, the first motor drives the wheels, and the third motor drives the power output device;

[0025] The plowing operation includes:

[0026] Light plowing load, where 0 < P req ≤P a , and the state of charge of the battery pack SOC≥SOC min , the third clutch, the fourth clutch and the first synchronizer are engaged, and the first motor and the second motor are power-coupled to jointly drive the wheels;

[0027] Medium plowing load, where P a <P req ≤P b , and the state of charge of the battery pack SOC≥SOC min , the first clutch, the third clutch, the fourth clutch and the first synchronizer are engaged, and the engine, the first motor and the second motor are power-coupled to jointly drive the wheels;

[0028] Heavy plowing load, where P b <P req ≤P c , when the state of charge of the battery pack SOC≥SOC min , the first clutch, the third clutch, the fourth clutch and the first synchronizer are engaged, and the engine, the first motor and the second motor are power-coupled to jointly drive the wheels;

[0029] When the state of charge of the battery pack SOC < SOC min , the first clutch, the second clutch, the third clutch, the fourth clutch and the first synchronizer are engaged, and the engine, the first motor and the second motor are power-coupled to jointly drive the wheels, and at the same time the engine charges the battery pack through the alternator;

[0030] The rotary tillage operation includes:

[0031] Light rotary tillage load, where 0 < P req +P pto ≤P d, and the battery pack capacity SOC ≥ SOC min , the third clutch, the fourth clutch, the fifth clutch, and the second synchronizer are engaged. The third synchronizer engages to the left and engages with the first gear pair. The second motor and the third motor are power-coupled to drive the power output device in the first gear, and the first motor drives the wheels to rotate;

[0032] Heavy-duty rotary tillage, where P d <P req +P pto ≤P e , and the battery pack capacity SOC ≥ SOC min , the third clutch, the fourth clutch, the fifth clutch, and the second synchronizer are engaged. The third synchronizer engages to the right and engages with the second gear pair. The second motor and the third motor are power-coupled to drive the power output device in the second gear, and the first motor drives the wheels to rotate;

[0033] Among them, SOC is the current state of charge of the battery pack, SOC min is the minimum state of charge of the battery pack at 20%, SOC target is the target state of charge of the battery at 60%, SOC max is the maximum state of charge of the battery at 90%, P req is the power demand of the wheels, P pto is the power demand of the power output device, P max is the maximum output power of the first motor, P a is the proportion of the current total output power in the plowing operation at 30%, P b is the proportion of the current total output power in the plowing operation at 60%, P c is the proportion of the current total output power in the plowing operation at 90%, P d is the proportion of the current total output power in the rotary tillage operation at 50%, P e is the proportion of the current total output power in the rotary tillage operation at 100%.

[0034] Beneficial effects: By setting the combined use of the engine and three motors, according to the battery state and the current power demand, and according to the preset working condition power selection strategy, when the current vehicle state reaches the preset interval, the corresponding power coupling method is selected. The hybrid series-parallel mode makes the device and the control method more applicable; when the battery state is poor, by the operation of the engine, it can not only provide power for the vehicle operation, but also charge the battery pack at the same time, enhancing the endurance of the tractor; it can also convert mechanical energy into electrical energy through the braking of the vehicle and store it in the battery pack, further improving the endurance of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0036] Figure 1 This is the overall structure diagram of the tractor of the present invention.

[0037] Figure 2 This is the structure diagram of the power coupling device of the present invention.

[0038] Figure 3 This is the power flow diagram for low-speed driving during non-operation.

[0039] Figure 4 This is the power flow diagram for medium-speed driving during non-operation.

[0040] Figure 5 This is the power flow diagram for high-speed driving during non-operation.

[0041] Figure 6 This is the power flow diagram for loaded driving during non-operation.

[0042] Figure 7 This is the power flow diagram for decelerating braking and regenerating power during non-operation.

[0043] Figure 8 This is the power flow diagram for seeding operation during operation.

[0044] Figure 9 This is the power flow diagram for light-load plowing operation during operation.

[0045] Figure 10 This is the power flow diagram for medium-load plowing operation during operation.

[0046] Figure 11 This is the power flow diagram for heavy-load plowing operation during operation.

[0047] Figure 12 This is the power flow diagram for light-load rotary tillage operation during operation.

[0048] Figure 13 This is the power flow diagram for heavy-load rotary tillage operation during operation. Detailed implementation manners

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0051] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the indirect contact between the first and second features through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature.

[0052] A hybrid system for a tractor driven by three motors, comprising an engine 1, an alternator 2, a motor assembly 3, a battery pack 4, wheels 5, a power take-off device 6 and a vehicle controller 7. The engine 1 and the motor assembly 3 are connected to the wheels 5 and the power take-off device 6 through a power coupling mechanism 8. The engine 1 is connected to the power coupling mechanism 8 and the alternator 2 through a first clutch 9 and a second clutch 10 respectively. The power coupling mechanism 8 is sequentially connected to the wheels 5 through a gearbox 11, a reducer 12 and an axle 13. The alternator 2 is connected to the battery pack 4 through an inverter 14. The battery pack 4 is connected to the motor assembly 3 through the inverter 14. The power coupling mechanism 8 includes a first input shaft 81, a second input shaft 82 and a third input shaft 83. The first input shaft 81 and the second input shaft 82 are drivingly connected through a first transmission gear pair 84. The second input shaft 82 and the third input shaft 83 are connected through a second transmission gear pair 85. The motor assembly 3 includes a first motor 31, a second motor 32 and a third motor 33. The output ends of the first motor 31, the second motor 32 and the third motor 33 are connected to the first input shaft 81, the second input shaft 82 and the third input shaft 83 through a third clutch 15, a fourth clutch 16 and a fifth clutch 17 respectively. The second input shaft 82 is connected to the first transmission gear pair 84 and the second transmission gear pair 85 through a first synchronizer 86 and a second synchronizer 87 respectively. The third input shaft 83 is sequentially connected to the input shaft of the power take-off device 6 through a third synchronizer 88 and a gear pair for shifting gears.

[0053] In the present invention, the engine and three motors are provided to drive the whole vehicle. When the battery pack of the vehicle is in good condition, pure electric drive is selected to save fuel consumption and reduce exhaust emissions. When the three motors are working, two motors respectively drive the wheels and the power take-off device alone, and the other motor selects to perform power compensation according to the current working condition, so that the tractor can have sufficient power for driving and operation under various working conditions. When the battery pack of the vehicle is in poor condition, the engine is started to perform power compensation and can also charge the battery pack at the same time, greatly improving the operation duration of the tractor, and at the same time ensuring sufficient power under various working conditions to meet the operation requirements.

[0054] The vehicle controller 7 controls the start and stop of the motor assembly 3 and the alternator 2 through a motor controller 71. The vehicle controller 7 controls the power coupling mechanism 8 through a coupling mechanism controller 72. The vehicle controller 7 controls the start and stop of the engine 1 through an engine controller 73. The vehicle controller 7 monitors the remaining power of the battery pack 4 through a battery management system 75.

[0055] By setting multiple controllers, accurate control can be achieved while the current vehicle state can be monitored in real time and fed back to the vehicle controller, so as to realize timely and rapid switching to the power required by the current working condition and improve the working efficiency of the vehicle.

[0056] The gear pair is a two-speed gear pair, including a first-speed gear pair 89 and a second-speed gear pair 90 mounted on the input shaft of the power output device 6.

[0057] The vehicle controller 7 is signal-connected to the vehicle speed sensor 74.

[0058] Through the vehicle speed sensor, the current vehicle speed is monitored and fed back to the vehicle controller in real time. The collected vehicle speed data is matched with the system to improve the operation accuracy of the tractor during driving, and the power switch is more timely and accurate.

[0059] At the same time, a tire roughness detector is also equipped to measure the friction force between the tire and the ground, which is used to calculate the force condition of the tractor during operation more accurately.

[0060] According to the operating state of the equipment, it is divided into two states: non-operation driving and operation driving. Light load, medium load, and heavy load are determined according to the rated load of the current tractor. Light load means the rated load is less than 1 / 3, medium load means it is less than 2 / 3 of the rated load and higher than 1 / 3 of the rated load, and heavy load means it is greater than 2 / 3 of the rated load. Specifically as follows:

[0061] Non-operation driving includes: low-speed driving, medium-speed driving, high-speed driving, large load, and deceleration braking regeneration;

[0062] Operation driving includes: seeding operation, plowing operation, and rotary tillage operation.

[0063] The specific non-operation driving is as follows:

[0064] Low-speed driving, where the vehicle speed V ≤ V1 and the battery pack 4 capacity SOC ≥ SOC min , the third clutch 15 is engaged, the battery pack 4 drives the first motor 31 to work, and the first motor 31 drives the wheels 5 alone;

[0065] Medium-speed driving, where V1 < V ≤ V2 or the battery pack 4 capacity SOC < SOC min , the first clutch 9 is engaged, and the engine 1 drives the wheels 5 alone;

[0066] High-speed driving, V > V2 and the battery pack 4 capacity SOC ≥ SOC min , the first clutch 9 and the third clutch 15 are engaged, and the engine 1 and the first motor 31 are power-coupled to jointly drive the wheels 5;

[0067] Load, P req >P max and the battery pack 4 capacity SOC ≤ SOC target, the first clutch 9, the second clutch 10, and the third clutch 15 are engaged. The engine 1 charges the battery pack 4 while supplying power to the first motor 31. The engine 1 and the first motor 31 jointly drive the wheels 5. At this time, the first motor 31 is the main power source for the wheels 5;

[0068] Regenerative braking during deceleration, P req <0 and the battery pack 4 capacity SOC ≤ SOC max , the third clutch 15 is engaged. The rotational force of the wheels 5 drives the motor to operate. The first motor 31 acts as a generator and converts mechanical energy into electrical energy to be stored in the battery pack 4;

[0069] Among them, V is the current vehicle speed, V1 is the low-speed and medium-speed demarcation point at 15 km / h, V2 is the medium-speed and high-speed demarcation point at 35 km / h, SOC is the current state of charge of the battery pack 4, SOC min is the minimum state of charge of the battery pack 4 at 20%, SOC target is the target state of charge of the battery at 60%, SOC max is the maximum state of charge of the battery at 90%, P req is the power demand of the wheels 5, P max is the maximum output power of the first motor 31.

[0070] The specific operation during work driving is as follows:

[0071] During seeding operation, the battery pack 4 capacity SOC ≥ SOC min , the third clutch 15 and the fifth clutch 17 are engaged. The third synchronizer 88 engages to the left and engages with the first gear pair. The first motor 31 drives the wheels 5, and the third motor 33 drives the power output device 6;

[0072] The plowing operation includes:

[0073] Light plowing load, where 0 < P req ≤ P a , and the battery pack 4 capacity SOC ≥ SOC min , the third clutch 15, the fourth clutch 16, and the first synchronizer 86 are engaged. The first motor 31 and the second motor 32 are power-coupled to jointly drive the wheels 5;

[0074] Medium plowing load, where P a < P req ≤ P b , and the battery pack 4 capacity SOC ≥ SOC min , the first clutch 9, the third clutch 15, the fourth clutch 16, and the first synchronizer 86 are engaged. The engine 1, the first motor 31, and the second motor 32 are power-coupled to jointly drive the wheels 5;

[0075] Heavy plowing load, where Pb <P req ≤P c When the state of charge (SOC) of the battery pack 4 ≥ SOC min , the first clutch 9, the third clutch 15, the fourth clutch 16, and the first synchronizer 86 are engaged, and the engine 1, the first motor 31, and the second motor 32 are power-coupled to jointly drive the wheels 5;

[0076] When the state of charge (SOC) of the battery pack 4 < SOC min , the first clutch 9, the second clutch 10, the third clutch 15, the fourth clutch 16, and the first synchronizer 86 are engaged, and the engine 1, the first motor 31, and the second motor 32 are power-coupled to jointly drive the wheels 5. At the same time, the engine 1 charges the battery pack 4 through the alternator 2;

[0077] The rotary tillage operation includes:

[0078] Light load rotary tillage, where 0 < P req +P pto ≤P d , and the state of charge (SOC) of the battery pack 4 ≥ SOC min , the third clutch 15, the fourth clutch 16, the fifth clutch 17, and the second synchronizer 87 are engaged, the third synchronizer 88 is engaged to the left and meshes with the first gear pair, the second motor 32 and the third motor 33 are power-coupled to drive the power output device 6 in the first gear, and the first motor 31 drives the wheels 5 to rotate;

[0079] Heavy load rotary tillage, where P d <P req +P pto ≤P e , and the state of charge (SOC) of the battery pack 4 ≥ SOC min , the third clutch 15, the fourth clutch 16, the fifth clutch 17, and the second synchronizer 87 are engaged, the third synchronizer 88 is engaged to the right and meshes with the second gear pair, the second motor 32 and the third motor 33 are power-coupled to drive the power output device 6 in the second gear, and the first motor 31 drives the wheels 5 to rotate;

[0080] Among them, SOC is the current state of charge of the battery pack 4, SOC min is the minimum state of charge of the battery pack 4 at 20%, SOC target is the target state of charge of the battery at 60%, SOC max is the maximum state of charge of the battery at 90%, P req is the required power of the wheels 5, P pto is the required power of the power output device 6, P max is the maximum output power of the first motor 31, P a is the proportion of the current total output power in the plowing operation condition at 30%, Pb is 60% of the current total output power in the plowing operation, P c is 90% of the current total output power in the plowing operation, P d is 50% of the current total output power in the rotary tillage operation, P e is 100% of the current total output power in the rotary tillage operation.

[0081] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0082] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-motor driven tractor hybrid system, comprising an engine (1), an alternator (2), a motor assembly (3), a battery pack (4), wheels (5), a power output device (6) and a vehicle controller (7), wherein the engine (1) and the motor assembly (3) are connected to the wheels (5) and the power output device (6) via a power coupling mechanism (8), the engine (1) is connected to the power coupling mechanism (8) and the alternator (2) via a first clutch (9) and a second clutch (10), the power coupling mechanism (8) is connected to the wheels (5) via a gearbox (11), a speed reducer (12) and an axle (13), the alternator (2) is connected to the battery pack (4) via a frequency converter (14), the battery pack (4) is connected to the motor assembly (3) via the frequency converter (14), It is characterized in that The power coupling mechanism (8) comprises a first input shaft (81), a second input shaft (82) and a third input shaft (83); the first input shaft (81) and the second input shaft (82) are connected to each other via a first transmission gear pair (84); the second input shaft (82) and the third input shaft (83) are connected via a second transmission gear pair (85); the motor assembly (3) comprises a first motor (31), a second motor (32) and a third motor (33); the first motor (31), the second motor (32) and the third motor The output end of (33) is connected to the first input shaft (81), the second input shaft (82) and the third input shaft (83) through the third clutch (15), the fourth clutch (16) and the fifth clutch (17), respectively; the second input shaft (82) is connected to the first transmission gear pair (84) and the second transmission gear pair (85) through the first synchronizer (86) and the second synchronizer (87), respectively; the third input shaft (83) is connected to the input shaft of the power output device (6) through the third synchronizer (88) and the gear gear pair.

2. The three-motor driven tractor hybrid system according to claim 1, It is characterized in that The vehicle controller (7) controls the start and stop of the motor assembly (3) and the alternator (2) via a motor controller (71), the vehicle controller (7) controls the power coupling mechanism (8) via a coupling mechanism controller (72), the vehicle controller (7) controls the start and stop of the engine (1) via an engine controller (73), and the vehicle controller (7) monitors the remaining power of the battery pack (4) via a battery management system (75).

3. The three-motor driven tractor hybrid system according to claim 1, It is characterized in that The gear pair is a two-speed gear pair, comprising a first-speed gear pair (89) and a second-speed gear pair (90) mounted on the input shaft of the power output device (6).

4. The three-motor driven tractor hybrid system according to claim 1, It is characterized in that The vehicle controller (7) is signal-connected to the vehicle speed sensor (74).

5. The power coupling control method of a three-motor driven tractor hybrid system according to claim 1, It is characterized in that According to the operating state of the equipment, it is divided into two states: driving without operation and driving with operation, which are specifically as follows: Driving without operation includes: low-speed driving, medium-speed driving, high-speed driving, large load, and deceleration braking regeneration; Driving with operation includes: seeding operation, ploughing operation, and rotary tillage operation.

6. The power coupling control method of the three-motor-driven tractor hybrid system according to claim 5, It is characterized in that The driving without operation is specifically as follows: Low-speed driving, where the vehicle speed V ≤ V1 and the capacity SOC of the battery pack (4) ≥ SOC min , the third clutch (15) is engaged, the battery pack (4) drives the first motor (31) to work, and the first motor (31) drives the wheels (5) alone; Travel at medium speed, where V1 < V ≤ V2 or the battery pack (4) capacity SOC < SOC min , the first clutch (9) is engaged, and the engine (1) drives the wheels (5) alone; High-speed driving, V > V2, and the capacity SOC of the battery pack (4) ≥ SOC min , the first clutch (9) and the third clutch (15) are engaged, and the engine (1) and the first motor (31) are power-coupled to jointly drive the wheels (5); Load, P req > P max , and the capacity SOC of the battery pack (4) ≤ SOC target , the first clutch (9), the second clutch (10) and the third clutch (15) are engaged, the engine (1) charges the battery pack (4) and supplies power to the first motor (31) at the same time, the engine (1) and the first motor (31) jointly drive the wheels (5), and at this time the first motor (31) is the main power source for the wheels (5); Decelerating braking regeneration, P req <0 and the battery pack (4) capacity SOC ≤ SOC max , the third clutch (15) engages, the rotational force of the wheel (5) drives the motor to operate, the first motor (31) acts as a generator, and converts mechanical energy into electrical energy to be stored in the battery pack (4); Wherein, V is the current vehicle speed, V1 is the speed dividing point between low speed and medium speed, which is 15 km / h, V2 is the speed dividing point between medium speed and high speed, which is 35 km / h, SOC is the state of charge of the current battery pack (4), SOC min is the minimum state of charge of the battery pack (4), which is 20%, SOC target is the target state of charge of the battery, which is 60%, SOC max is the maximum state of charge of the battery, which is 90%, P req is the required power of the wheel (5), P max is the maximum output power of the first motor (31).

7. The power coupling control method of the three-motor-driven tractor hybrid system according to claim 5, It is characterized in that The driving with operation is specifically as follows: Seeding operation, battery pack (4) capacity SOC ≥ SOC min , the third clutch (15) and the fifth clutch (17) are engaged, the third synchronizer (88) engages to the left and engages with the first gear pair, the first motor (31) drives the wheels (5), and the third motor (33) drives the power take-off device (6); The ploughing operation includes: Light plowing load, where 0 < P req ≤ P a , and the battery pack (4) capacity SOC ≥ SOC min . The third clutch (15), the fourth clutch (16), and the first synchronizer (86) are engaged, and the first motor (31) and the second motor (32) are power-coupled to jointly drive the wheels (5); Plowing medium load, where P a <P req ≤P b , and the capacity SOC of the battery pack (4) ≥ SOC min , the first clutch (9), the third clutch (15), the fourth clutch (16) and the first synchronizer (86) are engaged, and the engine (1), the first motor (31) and the second motor (32) are power-coupled to jointly drive the wheels (5); Heavy plowing load, where P b <P req ≤P c , when the capacity SOC of the battery pack (4) ≥ SOC min , the first clutch (9), the third clutch (15), the fourth clutch (16) and the first synchronizer (86) are engaged, and the engine (1), the first motor (31) and the second motor (32) are power-coupled to jointly drive the wheels (5); When the capacity SOC of the battery pack (4) < SOC min the first clutch (9), the second clutch (10), the third clutch (15), the fourth clutch (16), and the first synchronizer (86) are engaged, and the engine (1), the first motor (31), and the second motor (32) are power-coupled to jointly drive the wheels (5). At the same time, the engine (1) charges the battery pack (4) through the alternator (2); The rotary tillage operation includes: Rotary tillage under light load, where 0 < P req +P pto ≤P d , and the capacity SOC of the battery pack (4) ≥ SOC min , the third clutch (15), the fourth clutch (16), the fifth clutch (17), and the second synchronizer (87) are engaged. The third synchronizer (88) engages to the left and engages with the first gear pair. The second motor (32) and the third motor (33) are power-coupled to the first-gear driving power output device (6), and the first motor (31) drives the wheels (5) to rotate; Heavy rotary tillage, where P d <P req +P pto ≤P e , and the capacity SOC of the battery pack (4) ≥ SOC min , the third clutch (15), the fourth clutch (16), the fifth clutch (17), and the second synchronizer (87) are engaged, the third synchronizer (88) is engaged and engaged with the second gear pair, the second motor (32) and the third motor (33) are power-coupled to the second gear drive power output device (6), and the first motor (31) drives the wheels (5) to rotate; Among them, SOC is the state of charge of the current battery pack (4), and SOC min is the minimum state of charge of the battery pack (4) at 20%, and SOC target is the target state of charge of the battery at 60%, and SOC max is the maximum state of charge of the battery at 90%, and P req is the required power of the wheel (5), and P pto is the required power of the power output device (6), and P max is the maximum output power of the first motor (31), and P a is the proportion of the current total output power in the plowing operation at 30%, and P b is the proportion of the current total output power in the plowing operation at 60%, and P c is the proportion of the current total output power in the plowing operation at 90%, and P d is the proportion of the current total output power in the rotary tillage operation at 50%, and P e is the proportion of the current total output power in the rotary tillage operation at 100%.

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