Hybrid power system of off-road vehicle

Abstract

The invention provides a hybrid power system of an off-road vehicle. The hybrid power system comprises an engine, a front motor, a front clutch, a motor controller, a front axle, a pair of front wheels arranged at the two ends of the front axle, a rear axle and a pair of rear wheels arranged at the two ends of the rear axle. The engine is in transmission connection with the rear axle and used for transmitting power to the rear wheels, and the front motor is in transmission connection with the front axle and used for transmitting power to the front wheels. The front clutch is arranged between the front motor and the front axle, and the motor controller is electrically connected with the front motor and the front clutch and used for controlling output of the front motor and controlling the connection state of the front motor and the front axle through the front clutch. When the vehicle speed is smaller than the maximum safe rotating speed of the front motor, the front motor is connected with the front axle; and when the speed is greater than the maximum safe rotating speed of the front motor, the front motor is disconnected from the front axle.

Description

Technical Field

[0001] This invention relates to the field of vehicle technology, specifically to a hybrid power system for off-road vehicles. Background Technology

[0002] Off-road vehicles have three different drive systems: rear-wheel drive, four-wheel drive, and hybrid, each with its own characteristics and applicable scenarios.

[0003] Among them, the power of a rear-wheel drive off-road vehicle (rear-mounted engine two-wheel drive) is only transmitted to the rear wheels, while the front wheels are responsible for steering; this layout makes the front and rear weight distribution of the vehicle more balanced, with a low center of gravity, high reliability, and good handling and stability, making it suitable for high-speed off-roading and jumping, but it is easy to get stuck, and it is difficult to get out of trouble once stuck.

[0004] Four-wheel drive off-road vehicles distribute power to all four wheels, giving them high off-road mobility. However, traditional rear-engine four-wheel drive vehicles require the power to be transmitted from rear to front. The central driveshaft, transfer case, and differential force the engine, transmission, chassis, and suspension geometry to be raised, resulting in a higher center of gravity and relatively lower reliability. Furthermore, the increased number of transmission components in four-wheel drive off-road vehicles leads to relatively lower transmission efficiency.

[0005] Hybrid off-road vehicles combine a fuel engine and an electric motor to provide superior off-road performance. However, when driving at high speeds, the electric motor may exceed its maximum safe speed. To avoid this, the peak power of the electric motor needs to be increased accordingly, resulting in a heavier electric motor. This leads to a corresponding increase in the weight of the hybrid off-road vehicle, which in turn affects the vehicle's reliability and makes it unsuitable for high-speed off-roading. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a hybrid power system for off-road vehicles with low overall weight, high transmission efficiency, and strong off-road mobility and traction.

[0007] The technical solution of the present invention is to provide an off-road vehicle hybrid power system having the following structure: including an engine, a front motor, a front clutch, a motor controller, a front axle, a pair of front wheels disposed at both ends of the front axle, a rear axle, and a pair of rear wheels disposed at both ends of the rear axle; the engine is driven to the rear axle for transmitting power to the rear wheels, and the front motor is driven to the front axle for transmitting power to the front wheels; The front clutch is located between the front motor and the front axle. The motor controller is electrically connected to the front motor and the front clutch, and is used to control the output of the front motor and control the connection state between the front motor and the front axle through the front clutch. When the vehicle speed is less than the maximum safe speed of the front motor, the front motor is connected to the front axle; when the vehicle speed is greater than the maximum safe speed of the front motor, the front motor is disconnected from the front axle.

[0008] As a preferred option, it includes four hybrid driving modes: asphalt mode, gravel mode, desert mode, and snow mode, to adapt to different road conditions; When the vehicle is in motion, the engine serves as the power source. At low speeds, the front clutch is normally closed, and the front motor gradually engages when the rear wheels slip or when the open-loop prediction conditions are met. At high speeds, the front clutch disengages, and the vehicle is fully rear-wheel drive.

[0009] Preferably, the main logic allows the rear wheels to have a certain slip rate. When the slip rate exceeds this slip rate, the front motor is activated and maintained within the slip rate.

[0010] As a preferred option, the predictive open-loop program is based only on gear, vehicle speed, and throttle. If the vehicle is launching, an engine clutch sensor is also required.

[0011] Preferably, the front motor has a drag compensation function: when the vehicle speed is less than the maximum safe speed of the front motor, even if the conditions for the front motor to be turned on are not met, a little torque will be applied to counteract the drag caused by the front wheels, making the driving experience more natural.

[0012] Preferably, the front motor provides drag compensation when the vehicle is cruising, accelerating, or coasting; drag compensation is canceled when the vehicle is braking.

[0013] Preferably, the front motor has a cornering traction function: when the vehicle speed is less than the maximum safe speed of the front motor and the vehicle is exiting a corner, the front motor intervenes to increase the cornering speed and stabilize the vehicle body.

[0014] Preferably, the intervention torque of the front motor is adjusted according to the steering wheel angle, driving speed, throttle opening degree, and rear wheel slippage rate. Depending on the situation, motor preload speed and torque can also be added to reduce system response time. Specifically, the output torque of the front motor gradually decreases as the vehicle speed increases. This is not only to smoothly transition to the motor disconnection point at the maximum safe speed of the front motor, but also conforms to the basic principles of vehicle dynamics: the lower the vehicle speed, the easier it is for the rear wheels to slip when accelerating out of a curve. Rear wheel slippage causes the vehicle to fishtail, and the intervention of the front motor can help correct this fishtailing; the more severe the rear wheel slippage, the greater the intervention of the front motor is required.

[0015] Preferably, a rear motor is also included, which is connected to the engine drive, continuously generates electricity during cruising, and disconnects from the engine during full throttle acceleration.

[0016] Preferably, the front motor and the rear motor have kinetic energy recovery functions; when the vehicle speed is less than the maximum safe speed of the front motor, the front motor participates in mild kinetic energy recovery; when the ABS is activated, the kinetic energy recovery of the front motor and the rear motor is automatically cut off; when braking, the rear motor's participation in kinetic energy recovery needs to be based on the front wheel recovery torque and gear to ensure that it does not affect braking.

[0017] By adopting the above structure, the off-road vehicle hybrid power system of the present invention has the following advantages compared with the prior art: In this invention, the engine driving the rear axle is the same as that of a rear-mounted two-wheel-drive vehicle, offering advantages such as high reliability and a low center of gravity. The front drive is powered by a front motor, eliminating the need for a driveshaft below the engine and further lowering the vehicle's center of gravity. The front motor, driven by a reduction gear, requires only a relatively small peak power to provide strong torque output and low-speed off-road capability, allowing it to deliver all its power up to 100 kph. However, this configuration causes the front motor to exceed its maximum safe speed above 100 kph. To address this, this invention incorporates a front clutch between the front motor and the front axle to control engagement and disengagement. Above 100 kph, the front clutch completely disengages from the front motor and axle to prevent over-revving. The front clutch can be equipped with a locking mechanism for extended disengagement without requiring additional energy. Practical experience shows that the advantages of four-wheel drive are negligible above 100 kph for off-road vehicles; therefore, disengaging the front motor from the front axle does not affect the vehicle's high-speed performance. In addition, because the front motor has relatively low power, its weight can be greatly reduced. At the same time, the weight of the matching battery, motor controller, gearbox, generator, etc. can also be significantly reduced, thus avoiding the shortcomings of existing hybrid off-road vehicles.

[0018] This invention combines a novel hybrid architecture, enabling off-road vehicles to have advantages such as low overall weight, low center of gravity, high transmission efficiency, high reliability, strong off-road mobility and traction, and can recover some braking energy. In addition, the front motor can also be used to enhance acceleration when cornering and on straight lines, as well as provide dynamic traction assistance. Furthermore, the output power of the front motor can be adjusted in real time to modify the driving characteristics of the vehicle when accelerating out of a corner. Detailed Implementation

[0019] The present invention will now be described in further detail.

[0020] In the description of this invention, it should be understood that the terms "front" and "rear" and other terms indicating orientation or positional relationship are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Example

[0021] This invention discloses a hybrid power system for off-road vehicles, comprising a rear-end mechanical power mechanism, a front-end mechanical power mechanism, a front-end control mechanism, a central battery and energy mechanism, a cooling system, and a sensing and communication mechanism. Specifically, the rear mechanical power mechanism includes an engine, a generator, an engine control unit, a rear axle, and a pair of rear wheels located at both ends of the rear axle. The engine is connected to the rear axle for transmitting power to the rear wheels, and the rear motor is connected to the rear axle for generating electricity.

[0022] The front-end mechanical power mechanism includes a front motor, a motor reduction gearbox, a differential assembly, a clutch assembly (i.e., the front clutch, located between the motor and the differential, integrated within the housing), a power unit housing / box (integrating the motor, gearbox, differential, and clutch), a front axle, and a pair of front wheels located at both ends of the front axle; the front motor is connected to the front axle for transmitting power to the front wheels.

[0023] The front-end control mechanism includes a motor controller (MCU / inverter), a clutch control unit, a front-end motor high-voltage / medium-voltage wiring harness, a front-end low-voltage control wiring harness (including CAN communication), a motor position / speed sensor (Hall sensor / encoder), a motor temperature sensor, and a clutch operating status sensor. The front-end control mechanism is used to control the drive status of the front-end mechanical power mechanism.

[0024] The central battery and energy system includes a central battery pack (serving as the main power source for the front-end motor and the entire vehicle), a battery management system (BMS), a main high-voltage / medium-voltage power distribution module (containing fuses and relays), and a DC / DC converter (which converts the battery voltage to 12V / vehicle low-voltage system).

[0025] The cooling system includes a front-end motor unit cooling circuit, a motor gearbox cooling channel, a motor controller cooling plate / cooling channel, a radiator (arranged at the front or rear, depending on the vehicle design), a cooling fan, and control relays, used for heat dissipation and cooling of the off-road vehicle's hybrid power system.

[0026] The sensing and communication mechanisms include vehicle speed-related sensors (which can read front / rear wheel speed information), driving mode switches (off-road / high-speed mode signals), brake signal and brake pressure sensors (used for energy recovery logic), vehicle control unit (VCU), and CAN bus (used for communication between engine ECU, VCU, motor MCU, and clutch control unit).

[0027] The front clutch is located between the front motor and the front axle. The motor controller is electrically connected to the front motor and the front clutch to control the output of the front motor and to control the connection status between the front motor and the front axle through the front clutch. When the vehicle speed is less than the maximum safe speed of the front motor, the front motor is connected to the front axle; when the vehicle speed is greater than the maximum safe speed of the front motor, the front motor is disconnected from the front axle.

[0028] The off-road vehicle hybrid system of this invention includes four hybrid driving modes: asphalt mode, gravel mode, desert mode, and snow mode, to adapt to different road conditions. When the vehicle is in motion, the engine serves as the power source. At low speeds (e.g., 0–100 km / h), the front clutch is normally closed, and the front motor gradually engages when the rear wheels slip or when the open-loop prediction conditions are met. At high speeds (e.g., ≥100 km / h), the front clutch disengages, and the vehicle is fully rear-wheel drive.

[0029] The main logic allows for a certain degree of rear wheel slippage (the slippage rate can be adjusted according to different road conditions and driving habits; for example, the slippage rate is 5%-30% in tarmac mode, 30%-50% in snow mode, and 50%-80% in desert mode). When the slippage rate exceeds this set range, the front motor is activated and keeps the slippage rate within that range, which helps maintain the vehicle's posture. In other words, if the vehicle has a certain degree of oversteer when cornering, the motor will intervene to maintain this driving posture.

[0030] The predictive open-loop program is based only on gear, vehicle speed, and throttle (opening angle and opening rate). If the vehicle is launching, an engine clutch sensor is also required.

[0031] For example, when the vehicle speed is significantly lower than the matched engine speed (i.e., low vehicle speed, high engine speed, such as engine speed of 4500 rpm and vehicle speed below 5 kph), the clutch is depressed. At this time, although the front motor does not turn, the computer has already set the expected speed and torque. Once the clutch is released, or the rear wheels start to turn, the front wheels will immediately exert force. Then, the second step is to increase the torque and speed of the front wheels based on the rear wheel slippage rate.

[0032] When a vehicle is turning in a curve and the throttle is opened rapidly (i.e., rapid acceleration in a curve, for example, when the vehicle is turning at 50 kph and the throttle opening is 20%, the throttle opening rate is higher than 60% / s), we immediately apply a preload speed and torque to the front motor, because slippage is inevitable in this situation, and we do not need to wait for the rear wheels to reach a certain slippage rate before calculating.

[0033] Considering that the rear wheels are more prone to slipping during steering, but due to the complexity of off-road conditions, this invention does not intend to use a steering sensor. The prediction program of this invention predicts the steering conditions. This program may cause the prediction value under straight driving conditions to be lower, but this delay is acceptable.

[0034] The front motor has a drag compensation function: when the vehicle speed is less than the maximum safe speed of the front motor (i.e., the vehicle speed is within 100kph), even if the conditions for the front motor to be turned on are not met, a little torque will be applied to counteract the drag from the front wheels, making the driving experience more natural.

[0035] When the vehicle is cruising, accelerating, or coasting, the front motor provides drag compensation; drag compensation is canceled when the vehicle brakes. The optimal compensation value is just right when the motor is neither charging (too little compensation) nor discharging (too much compensation) (this value may need to be fine-tuned according to speed).

[0036] The front motor has cornering traction: In addition to the aforementioned situations where the front motor will intervene, it will also intervene when the vehicle speed is less than the maximum safe speed of the front motor (within 100kph) and when exiting a corner, in order to increase the exit speed and stabilize the vehicle.

[0037] During this phase, the intervention torque of the front motor will be adjusted according to the steering wheel angle, driving speed, throttle opening degree, and rear wheel slippage rate. Depending on the situation, motor preload speed and torque can also be added to reduce system response time. Specifically, the output torque of the front motor will gradually decrease as the vehicle speed increases. This is not only to smoothly transition to the 100kph motor disconnection point, but also in accordance with the basic principles of vehicle dynamics. That is, the lower the vehicle speed, the easier it is for the rear wheels to slip when accelerating out of a corner. Rear wheel slippage will cause the vehicle to fishtail, and the intervention of the front motor drive can help correct the fishtailing. The more severe the rear wheel slippage, the more intervention the front motor needs to provide.

[0038] The invention also includes a rear motor, which is connected to the rear axle drive, continuously generating 5–10 kW of power during cruising, and disconnecting from the rear axle during full throttle acceleration.

[0039] Both the front and rear motors have energy recovery functions. At low vehicle speeds (e.g., ≤100 km / h), the front motor participates in mild energy recovery (e.g., 0.05–0.1g equivalent braking). When ABS is activated, the energy recovery of the front motor is automatically cut off. During braking, the rear motor participates in energy recovery, which needs to be determined based on the recovery torque and gear of the front wheels to ensure that it does not affect braking.

[0040] In this invention, the engine driving the rear axle is the same as that of a rear-mounted two-wheel-drive vehicle, offering advantages such as high reliability and a low center of gravity. The front drive is powered by a front motor, eliminating the need for a driveshaft below the engine and further lowering the vehicle's center of gravity. The front motor, driven by a reduction gear, requires only a relatively small peak power to provide strong torque output and low-speed off-road capability. This configuration allows the front motor to unleash its full power up to 100 kph (i.e., at low speeds). However, with this configuration, the front motor will exceed its maximum safe speed when the vehicle speed exceeds 100 kph (i.e., at high speeds). To address this issue, this invention incorporates a front clutch between the front motor and the front axle to control engagement and disengagement. Above 100 kph, the front clutch completely disengages the front motor and front axle to prevent over-revving. The front clutch can be equipped with a locking mechanism, allowing for prolonged disengagement without requiring additional energy. Practical experience shows that the advantages of four-wheel drive are largely negligible for off-road vehicles above 100 kph; therefore, disengaging the front motor from the front axle does not affect the vehicle's high-speed performance. In addition, because the front motor has relatively low power, its weight can be greatly reduced. At the same time, the weight of the matching battery, motor controller, gearbox, generator, etc. can also be significantly reduced, thus avoiding the shortcomings of existing hybrid off-road vehicles.

[0041] This invention combines a novel hybrid architecture, enabling off-road vehicles to have advantages such as low overall weight, low center of gravity, high transmission efficiency, high reliability, strong off-road mobility and traction, and can recover some braking energy. In addition, the front motor can also be used to enhance acceleration when cornering and on straight lines, as well as provide dynamic traction assistance. Furthermore, the output power of the front motor can be adjusted in real time to modify the driving characteristics of the vehicle when accelerating out of a corner.

[0042] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A hybrid power system for off-road vehicles, characterized in that: It includes an engine, a front motor, a front clutch, a motor controller, a front axle, a pair of front wheels mounted at both ends of the front axle, a rear axle, and a pair of rear wheels mounted at both ends of the rear axle; the engine is driven to the rear axle to transmit power to the rear wheels, and the front motor is driven to the front axle to transmit power to the front wheels. The front clutch is located between the front motor and the front axle. The motor controller is electrically connected to the front motor and the front clutch, and is used to control the output of the front motor and control the connection state between the front motor and the front axle through the front clutch. When the vehicle speed is less than the maximum safe speed of the front motor, the front motor is connected to the front axle; when the vehicle speed is greater than the maximum safe speed of the front motor, the front motor is disconnected from the front axle.

2. The off-road vehicle hybrid power system according to claim 1, characterized in that: It includes four hybrid driving modes: Asphalt, Gravel, Desert, and Snow, to adapt to different road conditions; When the vehicle is in motion, the engine serves as the power source. At low speeds, the front clutch is normally closed, and the front motor gradually engages when the rear wheels slip or when the open-loop prediction conditions are met. At high speeds, the front clutch disengages, and the vehicle is fully rear-wheel drive.

3. The off-road vehicle hybrid power system according to claim 2, characterized in that: The main logic allows the rear wheels to have a certain slip rate. When the slip rate is exceeded, the front motor is activated and maintained within that slip rate.

4. The off-road vehicle hybrid power system according to claim 3, characterized in that: The predictive open-loop program is based only on gear, vehicle speed, and throttle. If the vehicle is launching, an engine clutch sensor is also required.

5. The off-road vehicle hybrid power system according to claim 2, characterized in that: The front motor has a drag compensation function: when the vehicle speed is less than the maximum safe speed of the front motor, even if the conditions for the front motor to be turned on are not met, a little torque will be applied to counteract the drag from the front wheels, making the driving experience more natural.

6. The off-road vehicle hybrid power system according to claim 5, characterized in that: When the vehicle is cruising, accelerating, or coasting, the front motor provides drag compensation; drag compensation is canceled when the vehicle brakes.

7. The off-road vehicle hybrid power system according to claim 2, characterized in that: The front motor has a cornering traction function: when the vehicle speed is less than the maximum safe speed of the front motor and the vehicle is exiting a corner, the front motor intervenes to increase the exit speed and stabilize the vehicle body.

8. The off-road vehicle hybrid power system according to claim 7, characterized in that: The intervention torque of the front motor will be adjusted according to the steering wheel angle, driving speed, throttle opening degree and rear wheel slip rate.

9. The off-road vehicle hybrid power system according to claim 2, characterized in that: It also includes a rear motor, which is connected to the engine drive, continuously generates electricity during cruising, and disconnects from the engine during full throttle acceleration.

10. The off-road vehicle hybrid power system according to claim 9, characterized in that: The front and rear motors have kinetic energy recovery functions. When the vehicle speed is less than the maximum safe speed of the front motor, the front motor participates in mild kinetic energy recovery. When the ABS is activated, the kinetic energy recovery of the front and rear motors is automatically cut off. When braking, the rear motor's participation in kinetic energy recovery needs to be based on the front wheel recovery torque and gear to ensure that it does not affect braking.