Hybrid power system of four-wheel-drive vehicle, hybrid electric vehicle and power control strategy

Abstract

The invention discloses a hybrid power system of a four-wheel-drive vehicle, the vehicle and a control strategy, the hybrid power system of the four-wheel-drive vehicle comprises an engine, a first motor, a second motor, a front axle transmission part and a rear axle transmission part, the engine is provided with a first input shaft, and the power output is connected to the first input shaft; the front axle transmission part comprises a first clutch, a first speed reducer, a hydraulic torque converter, a planetary gear mechanism, a second speed reducer, a third clutch and a differential mechanism; according to the power system of the hybrid power vehicle, only two motors and one engine are used for achieving all functions needed by the four-wheel-drive hybrid power vehicle, and a power assembly is more simplified.

Description

Technical Field

[0001] This invention relates to the field of hybrid electric vehicles, and more particularly to a hybrid power system, vehicle, and control strategy for a four-wheel drive vehicle. Background Technology

[0002] my country's new energy vehicle technology has developed rapidly in recent years. How to further improve the technical level of new energy vehicle powertrains and lay the foundation for the sustainable, healthy and rapid development of new energy vehicles has become a key issue that needs to be addressed in the automotive industry.

[0003] Currently, BYD is a typical example of a successful plug-in hybrid electric vehicle (PHEV) in the Chinese market. Patent document CN117885515A discloses a four-wheel drive hybrid system, control method, and vehicle. This four-wheel drive hybrid system includes an engine, a first motor, a second motor, a third motor, and further includes: a first transmission unit; a second transmission unit, which includes a second drive shaft and a first transmission gear mounted on the second drive shaft; a third transmission unit, located on the side of the second transmission unit away from the first transmission unit; and a fourth transmission unit. The engine, first motor, second motor, first transmission unit, second transmission unit, and third transmission unit constitute the front axle drive system, while the third motor and fourth transmission unit constitute the rear axle drive system. By dividing the four-wheel drive hybrid system into a front axle drive system and a rear axle drive system, when the vehicle only requires two-wheel drive, the front axle hybrid system provides the driving force, while the rear axle pure electric drive system is decoupled from the rear wheel end. This ensures both vehicle power and off-road capability while also maintaining vehicle economy.

[0004] The main shortcomings of this hybrid drive system are as follows: First, the internal combustion engine drive mode is only used at higher speeds, and the engine cannot drive directly at low speeds and during start-up; Second, the structure is complex, using a total of three motors, with two motors used in the front axle, one of which is mainly used for driving and the other for generating electricity. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology, which is that the internal combustion engine drive mode can only be used for high-speed driving conditions, cannot be directly driven by the engine at low speeds and when starting, and has a complex structure. The present invention provides a hybrid power system, vehicle and control strategy for a four-wheel drive vehicle.

[0006] The technical solution adopted by the present invention to solve its technical problem is a hybrid power system for a four-wheel drive vehicle, including an engine, a first motor, a second motor, a front axle drive unit and a rear axle drive unit. The engine has a first input shaft and the power output is connected to the first input shaft. The front axle drive unit includes a first clutch, a first reducer, a hydraulic torque converter, a planetary gear mechanism, a second reducer, a third clutch and a differential. The rear axle drive unit includes a third reducer.

[0007] Furthermore, the first reducer includes a first drive shaft, a first drive gear, a second drive gear, and a second input shaft. The first drive gear meshes with the second drive gear, and the power of the first motor is transmitted to the first drive gear through the second input shaft. The first clutch can engage or disengage the engine's power, which is transmitted to the first drive shaft through the first input shaft.

[0008] Furthermore, the hydraulic torque converter includes a pump wheel shaft, a pump wheel, a turbine, a hydraulic torque converter lock-up clutch, and a turbine bushing. The pump wheel shaft is coaxially connected to the first drive shaft, and the hydraulic torque converter lock-up clutch selectively engages the pump wheel and the turbine together. The planetary gear mechanism includes a sun gear, planetary gears, a planet carrier, and a large ring gear. The sun gear is coaxially connected to the pump wheel shaft and the first drive shaft of the hydraulic torque converter, and the large ring gear is connected to the turbine bushing of the hydraulic torque converter. The second reducer includes an intermediate shaft, a third drive gear, and a fourth drive gear. The intermediate shaft is connected to the planet carrier, and the intermediate shaft and the third drive gear rotate coaxially. The third and fourth drive gears mesh with each other. The third clutch selectively engages the fourth drive gear with the differential. Power is output from the intermediate shaft to the wheels via the second reducer, the third clutch, and the differential.

[0009] Furthermore, the third reducer includes a fifth transmission gear, a sixth transmission gear, a seventh transmission gear, a rear axle differential, and a third input shaft. The rotor shaft of the second motor is coaxially connected to the third input shaft. The fifth transmission gear is coaxially connected to the third input shaft. The fifth transmission gear meshes with the sixth transmission gear, and the seventh transmission gear rotates coaxially with the sixth transmission gear. The seventh transmission gear is connected to the rear axle differential, which transmits power to the wheels.

[0010] Furthermore, when the hydraulic torque converter lock-up clutch is locked, the pump wheel and turbine are locked together, simultaneously connecting the sun gear, large ring gear, and planetary carrier. At this time, the front axle drive unit operates in a direct drive state, and the torque input to the first drive shaft is directly output to the planetary carrier. When the hydraulic torque converter lock-up clutch is released, the input speed and torque from the first drive shaft are continuously changed and then output to the planetary carrier.

[0011] The technical solution adopted by the present invention to further solve its technical problem is a four-wheel drive hybrid vehicle, including the hybrid power system of the four-wheel drive vehicle described above, wherein any one of the engine, the first motor, and the second motor can drive the vehicle alone, any two of them can drive the vehicle together, or all three of them can drive the vehicle together.

[0012] The technical solution adopted by the present invention to further solve its technical problem is a power control strategy for a hybrid electric vehicle with a four-wheel drive vehicle hybrid power system. When the power battery has sufficient power, the electric motor drives the vehicle. There are five electric drive modes: pure electric rear-wheel drive mode, pure electric front-wheel drive mode without torque, pure electric front-wheel drive mode with torque change, first pure electric four-wheel drive mode and second pure electric four-wheel drive mode.

[0013] Furthermore, when the power battery charge is low, the engine is started, and the vehicle enters the engine-dominated drive mode. After the engine starts, there are six vehicle operating modes: pure engine drive mode, driving power generation mode, front-wheel drive hybrid mode, first hybrid four-wheel drive mode, second hybrid four-wheel drive mode, and third hybrid four-wheel drive mode.

[0014] Furthermore, when the power battery charge is low, the engine can be started by the first motor while the vehicle is parked. After the engine starts, it outputs torque to drive the first motor to generate electricity, and the vehicle enters the parking power generation mode.

[0015] In summary, the present invention has the following beneficial technical effects:

[0016] First, the power system of the hybrid vehicle of the present invention uses only two electric motors and one engine to achieve all the functions required for a four-wheel drive hybrid vehicle, thus simplifying the powertrain. For example, the existing BYD Tang four-wheel drive hybrid solution requires one engine and three electric motors, while the present invention can use one less electric motor.

[0017] Secondly, this invention can also directly drive the vehicle using the engine during start-up and low-speed driving. Currently, most hybrid power solutions cannot directly drive the vehicle during start-up and low-speed driving when the battery is low and the engine needs to participate in driving. For example, in BYD, the engine is only used to drive a generator to produce electricity during start-up and low-speed driving, which then powers the electric motor to drive the vehicle. This invention utilizes a hydraulic-mechanical torque converter to enable direct engine driving during start-up and low-speed driving. The power output from the engine does not need to undergo a secondary conversion between electricity generation and electric power generation, thus improving efficiency.

[0018] Third, in this invention, both the engine and the two electric motors can participate in driving at any time. The power of the engine and the electric motors can be matched to a lower value, especially the electric motors. For example, the output power can be selected based on the engine's lowest fuel consumption operating point. The rated power of the first and second electric motors can be selected to be around 30kW to 40kW, which is significantly lower than the electric motor power matched in existing four-wheel drive plug-in hybrid electric vehicles. Lower electric motor power can increase the electric motor load rate and also help improve electric motor efficiency, thereby reducing the overall energy consumption of the vehicle.

[0019] Fourth, by reducing the motor power in the power system design of this invention, the discharge rate of the power battery can be lowered, resulting in better battery system safety. Existing hybrid vehicles use relatively high-power motors for driving requirements, leading to frequent high-rate discharges of the power battery during operation. This is detrimental to the battery's lifespan and safety. Using a lower-power motor can reduce these high-rate discharges, thus extending battery life and improving battery safety. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a hybrid power system embodiment 1 for a four-wheel drive vehicle according to the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of a hybrid power system for a four-wheel drive vehicle of the present invention, in which the first clutch is not engaged, the hydraulic torque converter lock-up clutch is engaged, and the third clutch is engaged (pure electric, constant torque four-wheel drive).

[0022] Figure 3 This is a schematic diagram of the structure of a hybrid power system for a four-wheel drive vehicle of the present invention, in which the first clutch is not engaged, the hydraulic torque converter lock-up clutch is disengaged, and the third clutch is engaged (pure electric torque converter four-wheel drive).

[0023] Figure 4 This is a schematic diagram of the structure of a hybrid power system for a four-wheel drive vehicle of the present invention, showing the engagement of the first clutch, the disengagement of the hydraulic torque converter lock-up clutch, and the engagement of the third clutch (hybrid four-wheel drive torque converter).

[0024] Figure 5 This is a schematic diagram of the first clutch engagement, the hydraulic torque converter lock-up clutch engagement, and the third clutch engagement of a hybrid power system for a four-wheel drive vehicle according to the present invention (hybrid four-wheel drive without torque conversion).

[0025] Figure 6 This is a schematic diagram of the structure of a hybrid power system for a four-wheel drive vehicle of the present invention, showing the engagement of the first clutch, the disengagement of the torque converter lock-up clutch, and the disengagement of the third clutch (engine start mode, parking power generation mode 1).

[0026] Figure 7 This is a schematic diagram of the structure of a hybrid power system for a four-wheel drive vehicle of the present invention, showing the engagement of the first clutch, the engagement of the hydraulic torque converter lock-up clutch, and the disengagement of the third clutch (parking power generation mode two).

[0027] Figure 8 This is a schematic diagram of a hybrid power system embodiment 2 for a four-wheel drive vehicle according to the present invention.

[0028] Explanation of reference numerals in the attached figures:

[0029] 10. Engine; 11. First input shaft

[0030] 20. First motor;

[0031] 30. First reducer; 31. First clutch; 32. First drive shaft; 33. First transmission gear; 34. Second transmission gear; 35. Second input shaft

[0032] 40. Hydraulic torque converter; 41. Pump impeller shaft; 42. Pump impeller; 43. Turbine; 44. Hydraulic torque converter lock-up clutch; 45. Turbine bushing;

[0033] 50. Planetary gear mechanism; 51. Sun gear; 52. Planetary gear; 53. Planet carrier; 54. Large gear ring;

[0034] 60. Second reducer; 61. Second drive shaft; 63. Third drive gear; 64. Fourth drive gear; 65. Front axle differential; 66. Third clutch;

[0035] 70. Second motor;

[0036] 81. Fifth transmission gear; 82. Sixth transmission gear; 83. Seventh transmission gear; 84. Rear axle differential; 85. Third input shaft;

[0037] 91. Front wheel; 92. Rear wheel. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0039] Reference Figure 1 The hybrid power system of the four-wheel drive vehicle in this embodiment includes a front axle drive system and a rear axle drive system. The front axle drive system includes an engine 10, a first motor 20, and a front axle transmission unit; the rear axle drive system includes a second motor and a rear axle transmission unit. The front axle drive system drives the front wheels, and the rear axle drive system drives the rear wheels.

[0040] The crankshaft output end of engine 10 is connected to the input end of the front axle drive unit, enabling the output power of engine 10 to be transmitted to the front axle drive unit, which then performs speed and torque changes and transmission of the engine 10's output power. The rotor shaft output end of first motor 20 is connected to the other input end of the front axle drive unit, enabling the output power of first motor 20 to be transmitted to the front axle drive unit, which then performs speed changes and transmission of the first motor 20's output power.

[0041] The front axle drivetrain includes a first clutch 31, a first reducer 30, a hydraulic torque converter 40, a planetary gear mechanism 50, a second reducer 60, a third clutch 66, and a differential 65. Specifically, the engine 10 has a first input shaft 11. The first reducer 30 includes a first drive shaft 32, a first drive gear 33, a second drive gear 34, and a second input shaft 35. The first drive gear 33 and the second drive gear 34 mesh and transmit power. The first clutch 31 can transmit the output torque of the engine 10 to the first drive shaft 32 via the first input shaft 11. Disengaging the first clutch 31 can cut off the transmission path of the output torque of the engine 10. Controlling the engagement or disengagement of the first clutch 31 can realize the switching between the vehicle's electric mode and engine drive mode. The output torque of the first motor 20 is transmitted to the first drive gear 33 via the second input shaft 35, and then transmitted to the second drive gear 34 through gear meshing. The gear shaft of the drive gear 34 is coaxially connected to the first drive shaft 32. The output torque of the first motor 20 is reduced and increased in torque by the first reducer 30 before being transmitted to the first drive shaft 32, which better meets the requirements of vehicle driving. At the same time, the output torque of the engine 10 and the output torque of the first motor 20 are coupled together on the first drive shaft 32.

[0042] The hydraulic torque converter 40 includes a pump wheel shaft 41, a pump wheel 42, a turbine 43, a hydraulic torque converter lock-up clutch 44, and a turbine bushing 45. The hydraulic torque converter lock-up clutch 44 selectively engages the pump wheel 42 and the turbine 43 together. The planetary gear mechanism 50 includes a sun gear 51, planetary gears 52, a planet carrier 53, and a large ring gear 54. The pump wheel shaft 41 is coaxially connected to the first drive shaft 32, and the other end of the pump wheel shaft 41 is connected to the sun gear 51 of the planetary gear mechanism. The turbine 43 is connected to the large ring gear 54 of the planetary gear mechanism 50 through the turbine bushing 45. The second reducer 60 includes an intermediate shaft 61, a third drive gear 63, and a fourth drive gear 64. The intermediate shaft 61 is connected to the planet carrier 53, and the intermediate shaft 61 and the third drive gear 63 rotate coaxially. The third drive gear 63 and the fourth drive gear 64 mesh with each other. The third clutch 66 selectively engages the fourth drive gear 64 with the differential 65.

[0043] When the lock-up clutch 44 of the torque converter 40 is engaged, the pump wheel 42 and the turbine 43 are locked together. Since the pump wheel 42 is connected to the sun gear 51 of the planetary gear mechanism via the pump wheel shaft 41, and the turbine 43 is connected to the large ring gear 54 of the planetary gear mechanism via the turbine bushing 45, locking the pump wheel 42 and the turbine 43 simultaneously also locks the sun gear 51 and the large ring gear 54 of the planetary gear mechanism together. Therefore, the sun gear 51, the large ring gear 54, and the planetary carrier 53 of the planetary gear mechanism 50 are locked together and rotate at the same speed. The torque transmitted to the first drive shaft 32 is directly transmitted to the planetary carrier 53, and then through the second drive shaft 61 to the third drive gear 63 of the second reducer 60. The third drive gear 63 meshes with the fourth drive gear 64, and the torque transmitted to the third drive gear 63 is reduced and increased in torque before being transmitted from the fourth drive gear 64 to the third clutch 66. After the third clutch is engaged, the torque of the fourth drive gear 64 can be transmitted to the differential 65 to drive the vehicle.

[0044] When the lock-up clutch 44 of the torque converter 40 is disengaged, the torque transmitted to the first drive shaft 32 is split into two parts. One part of the torque is transmitted to the pump wheel 42, and after hydraulic torque conversion, it is output from the turbine 43 and transmitted to the large ring gear 54 of the planetary gear mechanism; the other part of the torque is transmitted from the pump wheel shaft 41 to the sun gear 51 of the planetary gear mechanism 50. The two parts of the torque converge in the planetary gear mechanism 50 and are output from the planet carrier 53. They are transmitted through the second drive shaft 61 to the third drive gear 63 of the second reducer 60. The third drive gear 63 meshes with the fourth drive gear 64, and the torque transmitted to the third drive gear 63 is reduced and increased in torque before being transmitted from the fourth drive gear 64 to the third clutch 66. After the third clutch 66 is engaged, the torque of the fourth drive gear 64 can be transmitted to the differential 65 to drive the vehicle.

[0045] The third reducer includes a fifth transmission gear 81, a sixth transmission gear 82, a seventh transmission gear 83, a rear axle differential 84, and a third input shaft 85. The rotor shaft of the second motor 70 is coaxially connected to the third input shaft 85. The fifth transmission gear 81 is coaxially connected to the third input shaft 85. The fifth transmission gear 81 meshes with the sixth transmission gear 82. The seventh transmission gear 83 rotates coaxially with the sixth transmission gear 82. The seventh transmission gear 83 is connected to the rear axle differential 84, which transmits power to the wheels.

[0046] Table 1 describes the power control strategy, power transmission, and applicable vehicle operating conditions of the hybrid power system under different operating modes in this invention.

[0047] Table 1 Power control strategies of hybrid power systems under different operating modes

[0048]

[0049]

[0050]

[0051] Reference Figure 1 When the vehicle's battery has a high remaining charge and the required torque to drive the vehicle is low, the powertrain operates in pure electric rear-drive mode. Engine 10 is not operating, the first motor 20 is not operating, the second motor 70 is driving, the first clutch 31 is disengaged, the torque converter lock-up clutch 44 is disengaged, and the third clutch 66 is disengaged. The output torque of the second motor 70 is transmitted through the third input shaft 85 to the fifth transmission gear 81, and then through meshing transmission to the sixth transmission gear 82 and the seventh transmission gear 83 coaxial with the sixth transmission gear 82, before being output to the rear axle differential 84, thus driving the rear wheels 92 of the vehicle. This operating mode is preferred for most low-power pure electric applications.

[0052] Reference Figure 2 As shown, when the vehicle's battery has a high remaining charge and the required torque to drive the vehicle is low, the powertrain operates in a pure electric, constant-torque front-wheel-drive mode. Engine 10 is not operating, the first motor 20 is driven, the second motor 70 is not operating, the first clutch 31 is disengaged, the torque converter lock-up clutch 44 is engaged, and the third clutch 66 is engaged. The output torque of the first motor 20 is reduced and increased in torque by the first reducer 30 before being transmitted to the first drive shaft 32, and also to the pump wheel shaft 41. Without changing speed or torque, it is directly transmitted to the planetary carrier 53 of the planetary gear mechanism 50, and then output to the second reducer 60 for further reduction and torque increase before being transmitted to the third clutch 66, which then drives the front wheels 91 of the vehicle. This is the front-wheel-drive scheme for low-power pure electric operation.

[0053] Reference Figure 3As shown, when the vehicle's battery has a high remaining charge, the vehicle speed is low, and the torque required to drive the vehicle is high, the power system operates in pure electric torque converter front drive mode. Engine 10 is not operating, the first motor 20 is driving, the second motor 70 is not operating, the first clutch 31 is disengaged, the hydraulic torque converter lock-up clutch 44 is disengaged, and the third clutch 66 is engaged. The output torque of the first motor 20 is reduced and increased in torque by the first reducer 30 and then transmitted to the first drive shaft 32, and also to the pump wheel shaft 41. After speed and torque conversion, it is transmitted to the planetary gear carrier 53, and then output to the second reducer 60 for further reduction and torque conversion before being transmitted to the third clutch 66, which then drives the front wheels 91 to move the vehicle. The torque required to drive the vehicle is high. When the torque required during pure electric driving exceeds the maximum torque that the motor can directly output, this mode is used to change the speed and torque of the motor to meet the required driving torque. Typical applications include climbing hills in pure electric mode or when there is a high acceleration demand during pure electric driving.

[0054] Reference Figure 2 As shown, when the vehicle's power battery has a high remaining charge, the vehicle speed is high, and the torque required to drive the vehicle is high, the power system operates in a pure electric, constant-torque four-wheel drive mode. Engine 10 is not operating; the first motor 20 and the second motor 70 drive the vehicle. The first clutch 31 is disengaged, the torque converter lock-up clutch 44 is engaged, and the third clutch 66 is engaged. The output torque of the first motor 20 is reduced and increased in torque by the first reducer 30 before being transmitted to the first drive shaft 32 and also to the pump wheel shaft 41. Without changing speed or torque, it is directly transmitted to the planetary carrier 53 of the planetary gear mechanism 50, and then output to the second reducer 60 for further reduction and torque increase before being transmitted to the third clutch 66, thus driving the front wheels 91. The output torque of the second motor 70 is transmitted through the third input shaft to the fifth transmission gear 81, and then through meshing transmission to the sixth transmission gear 82 and the seventh transmission gear 83, which is coaxial with the sixth transmission gear 82. Finally, it is output to the rear axle differential 84, driving the rear wheels 92. The torque obtained from the front wheels 91 and the rear wheels 92 together propel the vehicle. Typical applications include climbing steep hills in pure electric mode, or when there is a high demand for acceleration while driving in pure electric mode and when the ground adhesion is low.

[0055] Reference Figure 3As shown, when the vehicle's battery has a high remaining charge, the vehicle speed is low, and the torque required to drive the vehicle is high, the power system operates in pure electric torque converter four-wheel drive mode. Engine 10 is not operating; the first motor 20 and the second motor 70 drive the vehicle. The first clutch 31 is disengaged, the torque converter lock-up clutch 44 is disengaged, and the third clutch 66 is engaged. The output torque of the first motor 20 is reduced and increased by the first reducer 30 before being transmitted to the first drive shaft 32 and also to the pump wheel shaft 41. After speed and torque conversion, it is transmitted to the planetary carrier 53 of the planetary gear mechanism 50, and then output to the second reducer 60 for further reduction and torque increase before being transmitted to the third clutch 66, thus driving the front wheels 91. The output torque of the second motor 70 is transmitted through the third input shaft to the fifth transmission gear 81, and then through meshing transmission to the sixth transmission gear 82 and the seventh transmission gear 83 coaxial with the sixth transmission gear 82, before being output to the rear axle differential 84, thus driving the rear wheels 92. The torque obtained from the front wheels 91 and the rear wheels 92 together propel the vehicle. When the required torque during pure electric constant torque four-wheel drive exceeds the maximum torque that the motor can directly output, this mode is used to change the motor torque to meet the required drive torque. Typical applications include climbing steep inclines in pure electric mode, situations requiring significant acceleration during pure electric driving, and when ground traction is low.

[0056] In pure electric driving conditions, if the required torque is low, the rear-wheel drive pure electric mode is used. If the torque requirement is high, the front axle drive motor also participates in driving, using the four-wheel drive pure electric mode. The four-wheel drive pure electric mode preferentially uses the constant torque four-wheel drive mode, and only when the required torque is very high and the vehicle speed is low will the four-wheel drive variable torque pure electric mode be used. Another necessity for the application of four-wheel drive mode is that if the coefficient of friction of the ground is low, it can enhance driving stability, improve power performance and climbing ability.

[0057] Reference Figure 4 As shown, when the vehicle's power battery has a low remaining charge and the vehicle speed is low, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 disengages, and the engine outputs torque at its operating point with the lowest fuel consumption rate. If the engine's output torque equals the torque required to drive the vehicle, the first motor 20 operates in an idling state. The torque of the engine 10 is transmitted to the first input shaft 32, then to the pump wheel shaft 41, and then, after speed and torque conversion, is transmitted to the planetary gear carrier 53 of the planetary gear mechanism. It is then output to the second reducer 60 for speed reduction and torque increase, and then transmitted to the third clutch 66, which in turn drives the front wheels 91 of the vehicle to propel it. At this time, the power system operates in engine torque conversion drive mode.

[0058] Reference Figure 4As shown, when the vehicle's power battery has a low remaining charge and the vehicle speed is low, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 disengages, and the engine outputs torque at its optimized operating point. If the engine's output torque is greater than the torque required to drive the vehicle, the excess torque is used for power generation, and the first motor 20 operates in power generation mode. The torque remaining after subtracting the power generation torque from the engine 10's output torque is transmitted to the first input shaft 32, then to the pump wheel shaft 41, then through a speed change and torque conversion, and finally to the planetary gear carrier 53 of the planetary gear mechanism. It is then output to the second reducer 60 for speed reduction and torque increase, and finally transmitted to the third clutch 66, which then drives the vehicle's front wheels 91 to propel the vehicle. At this time, the power system operates in a low-speed front-wheel-drive driving power generation mode.

[0059] Reference Figure 4 As shown, when the vehicle's battery has a low remaining charge but still allows for power output, and the vehicle speed is low, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 disengages, and the engine outputs torque at its optimized operating point. If the engine's output torque is less than the torque required to drive the vehicle, the insufficient torque is supplemented by the first motor 20, which operates in drive mode. The output torque of the engine 10 and the drive torque of the first motor 20 are transmitted to the first input shaft 32, then to the pump wheel shaft 41, and then, after speed and torque conversion, to the planetary gear carrier 53 of the planetary gear mechanism. The torque is then output to the second reducer 60 for reduction and torque increase, and then transmitted to the third clutch 66, which drives the front wheels 91 of the vehicle to propel it. At this time, the power system operates in hybrid front-wheel drive torque converter mode.

[0060] Reference Figure 5 As shown, when the vehicle's battery has a low remaining charge and the vehicle speed is high, the engine 10 operates, the first clutch 31 engages, and the torque converter lock-up clutch 44 engages. The engine outputs torque at its operating point with the lowest fuel consumption. If the engine's output torque equals the torque required to drive the vehicle, the first motor 20 operates in an idling state. The torque of the engine 10 is transmitted to the first input shaft 32, then to the pump wheel shaft 41, and then transmitted at constant speed and torque to the planetary gear carrier 53. It is then output to the second reducer 60 for speed reduction and torque increase before being transmitted to the third clutch 66, which then drives the front wheels 91 to propel the vehicle. At this time, the power system operates in engine torque-constant drive mode.

[0061] Reference Figure 5As shown, when the vehicle's power battery has a low remaining charge and the vehicle speed is high, the engine 10 operates, the first clutch 31 engages, and the torque converter lock-up clutch 44 engages. The engine outputs torque at its operating point with the lowest fuel consumption rate. If the engine's output torque is greater than the torque required to drive the vehicle, the first motor 20 operates in generator mode. The remaining torque after subtracting the generator torque from the engine 10's output torque is transmitted to the first input shaft 32, then to the pump wheel shaft 41, and then transmitted at constant speed and torque to the planetary carrier 53 of the planetary gear mechanism 50. It is then output to the second reducer 60 for speed reduction and torque increase before being transmitted to the third clutch 66, which then drives the vehicle's front wheels 91 to propel the vehicle. At this time, the power system operates in a high-speed front-wheel-drive generator mode.

[0062] Reference Figure 5 As shown, when the vehicle's power battery has a low remaining charge but still allows for power output, and the vehicle speed is high, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 engages, and the engine outputs torque at its operating point with the lowest fuel consumption rate. If the engine's output torque is less than the torque required to drive the vehicle, the first motor 20 operates in drive mode. The output torque of the engine 10 plus the drive torque of the first motor 20 is transmitted to the first input shaft 32, then to the pump wheel shaft 41, and then transmitted to the planetary gear carrier 53 of the planetary gear mechanism without changing speed or torque. It is then output to the second reducer 60 for speed reduction and torque increase before being transmitted to the third clutch 66, which then drives the front wheels 91 of the vehicle to propel it. At this time, the power system operates in a hybrid front-wheel drive constant torque drive mode.

[0063] Reference Figure 5 As shown, when the vehicle's battery has a low remaining charge but still allows for power output, and the vehicle speed is high, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 engages, and the engine outputs torque at its point of minimum fuel consumption. The first motor 20 does not operate. The output torque of the engine 10 is transmitted to the first input shaft 32, then to the pump wheel shaft 41, and then, without changing speed or torque, to the planetary carrier 53 of the planetary gear mechanism 50. It is then output to the second reducer 60 for speed reduction and torque increase, and then transmitted to the third clutch 66, driving the front wheels 91 of the vehicle. Simultaneously, the second motor 70 operates in drive mode. The output torque of the second motor 70 is transmitted through the third input shaft 85 to the fifth transmission gear 81, and then, through meshing transmission, to the sixth transmission gear 82 and the seventh transmission gear 83 coaxial with the sixth transmission gear 82. Finally, it is output to the rear axle differential 84, driving the rear wheels 92 of the vehicle. The front axle drive force and the rear axle drive force jointly drive the vehicle. At this time, the power system operates in hybrid dual-power constant torque four-wheel drive mode.

[0064] Reference Figure 4As shown, when the vehicle's battery has a low remaining charge but still allows for power output, and the vehicle speed is low, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 disengages, and the engine outputs torque at its lowest fuel consumption point. The first motor 20 does not operate. The output torque of the engine 10 is transmitted to the first input shaft 32, then to the pump wheel shaft 41, and after speed and torque conversion, it is transmitted to the planetary carrier 53 of the planetary gear mechanism 50. It is then output to the second reducer 60 for speed reduction and torque increase, and then transmitted to the third clutch 66, driving the front wheels 91 of the vehicle. Simultaneously, the second motor 70 operates in drive mode. The output torque of the second motor 70 is transmitted through the third input shaft 85 to the fifth transmission gear 81, and then through meshing transmission to the sixth transmission gear 82 and the seventh transmission gear 83 coaxial with the sixth transmission gear 82. It is then output to the rear axle differential 84, driving the rear wheels 92 of the vehicle. The front axle drive force and the rear axle drive force jointly drive the vehicle. At this time, the power system operates in hybrid dual-power torque-converting four-wheel drive mode.

[0065] Reference Figure 4 As shown, when the vehicle's power battery has a low remaining charge and the vehicle speed is low, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 disengages, and the engine outputs torque at its operating point with the lowest fuel consumption rate. The first motor 20 operates in generator mode. The torque remaining after subtracting the generator torque from the output torque of the engine 10 is transmitted to the first input shaft 32, then to the pump wheel shaft 41, and after speed and torque conversion, it is transmitted to the planetary carrier 53 of the planetary gear mechanism 50. It is then output to the second reducer 60 for speed reduction and torque increase, and then transmitted to the third clutch 66, which drives the front wheels 91 of the vehicle. Simultaneously, the second motor 70 operates in drive mode. The output torque of the second motor 70 is transmitted through the third input shaft 85 to the fifth transmission gear 81, and then through meshing transmission to the sixth transmission gear 82 and the seventh transmission gear 83 coaxial with the sixth transmission gear 82. Finally, it is output to the rear axle differential 84, which drives the rear wheels 92 of the vehicle. The front axle drive force and the rear axle drive force work together to drive the vehicle. At this time, the power system is operating in low-speed four-wheel drive driving and power generation mode.

[0066] Reference Figure 5As shown, when the vehicle's power battery has a low remaining charge and the vehicle speed is high, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 engages, and the engine outputs torque at its point of minimum fuel consumption. The first motor 20 operates in generator mode. The torque remaining after subtracting the generator torque from the output torque of the engine 10 is transmitted to the first input shaft 32, then to the pump wheel shaft 41, and then through a speed change and torque conversion to the planetary carrier 53 of the planetary gear mechanism 50. It is then output to the second reducer 60 for speed reduction and torque increase, and then transmitted to the third clutch 66, driving the front wheels 91 of the vehicle. Simultaneously, the second motor 70 operates in drive mode. The output torque of the second motor 70 is transmitted through the third input shaft 85 to the fifth transmission gear 81, and then through meshing transmission to the sixth transmission gear 82 and the seventh transmission gear 83 coaxial with the sixth transmission gear 82. Finally, it is output to the rear axle differential 84, driving the rear wheels 92 of the vehicle. The front axle drive force and the rear axle drive force jointly drive the vehicle. At this time, the power system is operating in a high-speed four-wheel drive power generation mode.

[0067] Reference Figure 5 As shown, when the driving power demand is very high, the remaining power of the power battery still allows for power output, and the vehicle speed is high, the engine 10 operates, the first clutch 31 engages, the hydraulic torque converter lock-up clutch 44 engages, the engine outputs torque at its maximum power operating point, and the first motor 20 operates in drive mode. The output torque of the engine 10 is transmitted to the first input shaft 32, and the drive torque of the first motor 20 is also transmitted to the first input shaft 32 after being reduced and increased in torque by the first reducer. The two torques are superimposed on the first input shaft 32 and then transmitted to the pump wheel shaft 41, and then transmitted to the planet carrier 53 of the planetary gear mechanism 50 without changing speed or torque. Then it is output to the second reducer 60 for reduction and increased torque and then transmitted to the third clutch 66, which then drives the front wheels 91 of the vehicle. Simultaneously, the second motor 70 operates in drive mode. The output torque of the second motor 70 is transmitted to the fifth transmission gear 81 via the third input shaft 85, and then through meshing transmission to the sixth transmission gear 82 and the seventh transmission gear 83, which is coaxial with the sixth transmission gear 82. The torque is then output to the rear axle differential 84, driving the rear wheels 92 of the vehicle. The front axle drive force and the rear axle drive force jointly propel the vehicle. At this time, the powertrain operates in a hybrid three-power four-wheel drive constant torque drive mode. Typical application scenarios include highway overtaking and high-speed hill climbing.

[0068] Reference Figure 4As shown, when the driving power demand is very high, the remaining power of the power battery still allows for power output, and the vehicle speed is low, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 disengages, the engine outputs torque at its maximum power operating point, and the first motor 20 operates in drive mode. The output torque of the engine 10 is transmitted to the first input shaft 32, and the drive torque of the first motor 20 is also transmitted to the first input shaft 32 after being reduced and increased in torque by the first reducer. The two torques are superimposed on the first input shaft 32 and then transmitted to the pump wheel shaft 41. Then, the speed and torque are changed and transmitted to the planetary carrier 53 of the planetary gear mechanism 50, and then output to the second reducer 60 for further reduction and torque increase before being transmitted to the third clutch 66, which then drives the front wheels 91 of the vehicle. Simultaneously, the second motor 70 operates in drive mode. The output torque of the second motor 70 is transmitted to the fifth transmission gear 81 via the third input shaft 85, and then through meshing transmission to the sixth transmission gear 82 and the seventh transmission gear 83, which is coaxial with the sixth transmission gear 82. The torque is then output to the rear axle differential 84, driving the rear wheels 92 of the vehicle. The front axle drive force and the rear axle drive force jointly propel the vehicle. At this time, the powertrain operates in a hybrid three-power four-wheel drive torque converter mode. Typical application scenarios include low-speed rapid acceleration and low-speed steep hill climbing.

[0069] Reference Figure 6 As shown, when the vehicle's power battery has very low remaining charge and the vehicle speed is zero, and the engine 10 needs to be started, the first clutch 31 engages, the torque converter lock-up clutch 44 disengages, the first motor 20 drives the first input shaft to rotate, and transmits torque to the engine through the first input shaft, completing the starting process. At this time, the power system operates in engine start mode.

[0070] Reference Figure 6 As shown, when the vehicle's battery has very low remaining charge and the vehicle speed is zero, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 disengages, the engine outputs torque at its optimized operating point, and the first motor 20 operates in generator mode. All the torque output by the engine 10 supplies power to the first motor 20. At this time, the power system operates in a parking generator mode.

[0071] Reference Figure 7 As shown, when the vehicle's power battery has a very low remaining charge and the vehicle speed is zero, the engine 10 operates, the first clutch 31 engages, the torque converter lock-up clutch 44 engages, the engine outputs torque at its optimized operating point, and the first motor 20 operates in generator mode. All the torque output by the engine 10 supplies power to the first motor 20. At this time, the power system operates in a parking generator mode.

[0072] Reference Figure 1As shown, when the power demand for driving the vehicle is negative, engine 10 does not work, first motor 20 does not work, first clutch is disengaged, torque converter lock-up clutch 44 is disengaged, third clutch is disengaged, and second motor 70 operates in generator mode. At this time, the power system operates in rear axle brake energy recovery mode.

[0073] Reference Figure 2 As shown, when the power demand for driving the vehicle is negative, engine 10 does not work, first motor 20 operates in generator mode, first clutch is disengaged, torque converter lock-up clutch 44 is engaged, third clutch is engaged, and second motor 70 does not work. At this time, the power system operates in front axle regenerative braking mode.

[0074] Reference Figure 2 As shown, when the power demand for driving the vehicle is negative, engine 10 does not work, first motor 20 operates in generator mode, first clutch is disengaged, torque converter lock-up clutch 44 is engaged, third clutch is engaged, and second motor 70 operates in generator mode. At this time, the power system operates in dual-axle regenerative braking mode.

[0075] The choice of which mode to use among the various regenerative braking modes depends on the braking intensity. For low braking intensity, the rear axle regenerative braking mode is used; for high braking intensity, the dual-axle regenerative braking mode is used.

[0076] In summary, the internal combustion engine in this hybrid system can engage to drive the vehicle across the entire speed range, reducing the load on the electric drive. The engine and two electric motors can drive the vehicle individually, or both can drive it together, or all three can drive it together, across the entire speed range. This lays the foundation for reducing the power of the engine and electric motors, provides the conditions for reducing battery capacity, and enables powertrain optimization.

[0077] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Identical components are represented by the same reference numerals. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, while the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component. Therefore, all equivalent changes made to the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A hybrid power system for a four-wheel drive vehicle, characterized in that, It includes an engine (10), a first motor (20), a second motor (70), a front axle drive unit and a rear axle drive unit. The engine (10) has a first input shaft (11) and the power output is connected to the first input shaft (11). The front axle drive unit includes a first clutch (31), a first reducer (30), a hydraulic torque converter (40), a planetary gear mechanism (50), a second reducer (60), a third clutch (66), and a differential (65). The rear axle drive unit includes a third reducer (80).

2. The hybrid power system for a four-wheel drive vehicle according to claim 1, characterized in that, The first reducer (30) includes a first drive shaft (32), a first drive gear (33), a second drive gear (34), and a second input shaft (35). The first drive gear (33) meshes with the second drive gear (34) for transmission. The power of the first motor (20) is transmitted to the first drive gear (33) through the second input shaft (35), and the first clutch (31) can engage or disengage the power of the engine (10) to be transmitted to the first drive shaft (32) through the first input shaft (11).

3. The hybrid power system for a four-wheel drive vehicle according to claim 2, characterized in that, The hydraulic torque converter (40) includes a pump wheel shaft (41), a pump wheel (42), a turbine (43), a hydraulic torque converter lock-up clutch (44), and a turbine bushing (45). The pump wheel shaft (41) is coaxially connected to the first drive shaft (32), and the hydraulic torque converter lock-up clutch (44) selectively engages the pump wheel (42) and the turbine (43). The planetary gear mechanism (50) includes a sun gear (51), planetary gears (52), a planet carrier (53), and a large gear ring (54). The sun gear (51) is coaxially connected to the pump wheel shaft (41) and the first drive shaft (32) of the hydraulic torque converter, and the large gear ring (54) is coaxially connected to the pump wheel shaft (41) and the first drive shaft (32) of the hydraulic torque converter. The turbine bushings (45) of the hydraulic torque converter are connected together; the second reducer (60) includes an intermediate shaft (61), a third transmission gear (63), and a fourth transmission gear (64). The intermediate shaft (61) is connected to the planetary carrier (53), and the intermediate shaft (61) and the third transmission gear (63) rotate coaxially. The third transmission gear (63) and the fourth transmission gear (64) mesh with each other. The third clutch (66) selectively engages the fourth transmission gear (64) with the differential (65). Power is output from the intermediate shaft (61) to the wheels via the second reducer (60), the third clutch (66), and the differential (65).

4. The hybrid power system for a four-wheel drive vehicle according to claim 1, characterized in that, The third reducer includes a fifth transmission gear (81), a sixth transmission gear (82), a seventh transmission gear (83), a rear axle differential (84), and a third input shaft (85). The rotor shaft of the second motor (70) is coaxially connected to the third input shaft (85). The fifth transmission gear (81) is coaxially connected to the third input shaft (85). The fifth transmission gear (81) meshes with the sixth transmission gear (82). The seventh transmission gear (83) rotates coaxially with the sixth transmission gear (82). The seventh transmission gear (83) is connected to the rear axle differential (84). The rear axle differential (84) transmits power to the wheels.

5. A hybrid power system for a four-wheel drive vehicle according to claim 3, characterized in that, When the hydraulic torque converter lock-up clutch (44) is locked, the pump wheel (41) and the turbine (43) are locked together, and the sun gear (51) is connected to the large ring gear (54) and the planetary carrier (53). At this time, the front axle drive unit works in direct drive mode, and the torque input to the first drive shaft (32) is directly output to the planetary carrier (53). When the hydraulic torque converter lock-up clutch (44) is unlocked, the input speed and torque of the first drive shaft (32) are continuously changed and then output to the planetary carrier (53).

6. A four-wheel drive hybrid vehicle, comprising the hybrid power system of the four-wheel drive vehicle according to any one of claims 1-5, characterized in that, The engine (10), the first motor (20), and the second motor (70) can drive the vehicle individually, any two of them can drive the vehicle together, or all three of them can drive the vehicle together.

7. A power control strategy based on the four-wheel drive hybrid vehicle of claim 6, characterized in that, When the power battery has sufficient charge, the electric motor drives the vehicle. There are five electric drive modes: pure electric rear-wheel drive mode, pure electric front-wheel drive mode without torque, pure electric front-wheel drive mode with torque change, first pure electric four-wheel drive mode, and second pure electric four-wheel drive mode.

8. The power control strategy for a four-wheel drive hybrid vehicle according to claim 7, characterized in that, When the power battery charge is low, the engine (10) is started and the vehicle enters the engine-driven mode. There are six vehicle working modes after the engine (10) starts working: pure engine drive mode, driving power generation mode, front-wheel drive hybrid mode, first hybrid four-wheel drive mode, second hybrid four-wheel drive mode, and third hybrid four-wheel drive mode.

9. The power control strategy for a four-wheel drive hybrid vehicle according to claim 7, characterized in that, When the power battery charge is low, the engine (10) can be started by the first motor (20) while the vehicle is parked. After the engine (10) starts, it outputs torque to drive the first motor (20) to generate electricity, and the vehicle enters the parking power generation mode.

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