Power assembly having differential gear protection function, method, and electric vehicle

Abstract

Provided are a power assembly (30) having a differential gear protection function, a control method for the power assembly (30), and an electric vehicle (10), relating to the field of new energy vehicles, and applicable to pure electric vehicles and hybrid vehicles. The power assembly (30) comprises a driving motor (60), a motor controller (50) and a differential gear (70), wherein the driving motor (60) is transmittingly connected to the differential gear (70); the differential gear (70) is transmittingly connected to two wheels (12) of an electric vehicle respectively, and the two wheels (12) are two front wheels or two rear wheels; and the motor controller (50) is configured to control a torque value output by the driving motor (60) to be less than or equal to a torque limit value, the torque limit value being reduced along with the increase of a wheel speed difference between the two wheels. The motor controller (50) protects the differential gear (70) according to the hardware capability and working boundary of the differential gear (70), thereby improving the reliability of the power assembly (30) and the safety of the entire vehicle.

Description

Powertrain, method and electric vehicle with differential protection function

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on November 3, 2023, with application number 202311464444.6 and invention name “A powertrain, method and electric vehicle with differential protection function”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of electric vehicles, and more particularly, to a powertrain with a differential protection function, a control method, and an electric vehicle. Background Art

[0003] A split road refers to a road surface with different adhesion coefficients on both sides of the wheels. The driving performance of a car on split roads / slopes can reflect the vehicle's ability to escape from difficulties. This performance places higher technical demands on pure electric vehicles. Compared with traditional power vehicles, pure electric vehicles tend to be heavier and have faster power response. The lack of a clutch further increases the impact. These factors will cause the entire vehicle to produce a larger speed difference and torque under split road / slope conditions, placing higher demands on the differential's load-bearing capacity. The body stability system will adjust the vehicle's torque when the vehicle slips to improve the vehicle's stability and handling, but the body stability system's calibration does not take into account the differential's load-bearing capacity. The current differential hardware in the industry cannot withstand the differential load requirements caused by medium and large pure electric vehicles under such conditions.

[0004] Therefore, how to protect the differential under extreme differential conditions is an urgent problem that needs to be solved.

[0005] Summary of the Invention

[0006] The present application provides a motor controller, a control method, a powertrain, and an electric vehicle. The motor controller implements intelligent protection of the differential based on the capabilities and working boundaries of the differential hardware, limits the output torque of the drive motor under extreme wheel speed difference conditions, reduces the risk of differential failure, improves the reliability of the powertrain, and enhances the safety of the entire vehicle.

[0007] In the first aspect, the present application provides a powertrain for an electric vehicle, which includes a drive motor, a motor controller and a differential. The drive motor is used to transmit power to the differential, and the differential is used to transmit power to two wheels of the electric vehicle, respectively. The two wheels are two front wheels or two rear wheels. The motor controller is used to reduce the torque limit output by the drive motor as the wheel speed difference between the two wheels increases; and control the torque value output by the drive motor to be less than or equal to the torque limit.

[0008] According to the solution of the present application, the motor controller controls the working condition of the differential according to the capability and working boundary of the differential hardware, and limits the torque output by the drive motor under extreme differential conditions, thereby protecting the differential from hardware failure due to excessive differential coupling torque, which is beneficial for the powertrain to achieve intelligent protection of the differential. The motor controller can especially provide protection for the operation of performance vehicles, large vehicles and off-road vehicles.

[0009] In addition, setting the differential protection in the motor controller can reduce the signal interaction between the vehicle controller and the motor controller, increase the speed of determining the final output torque, and reduce delays. The motor controller can enhance the intelligent characteristics of the powertrain.

[0010] In combination with the first aspect, in certain implementations of the first aspect, the motor controller responds to the wheel speed difference between the two wheels being a first wheel speed difference, and the motor controller is used to control the torque value output by the drive motor to be less than or equal to a first limit value, and the first limit value corresponds to the first wheel speed difference; the motor controller responds to the wheel speed difference between the two wheels being a second wheel speed difference, and the motor controller is used to control the torque value output by the drive motor to be less than or equal to a second limit value, and the second limit value corresponds to the second wheel speed difference; wherein, the first wheel speed difference is less than the second wheel speed difference, and the first limit value is greater than the second limit value.

[0011] In conjunction with the first aspect, in certain implementations of the first aspect, in response to the torque indicated by the torque signal being less than or equal to a torque limit, the motor controller is configured to control the drive motor to output the torque indicated by the torque signal. In response to the torque indicated by the torque signal being greater than the torque limit, the motor controller is configured to control the drive motor to output a torque value equal to the torque limit.

[0012] When the torque value indicated by the torque signal is less than the torque limit corresponding to the current wheel speed difference, the differential is operating safely, so the motor controller can directly output torque according to the torque value indicated by the torque signal. However, when the torque value indicated by the torque signal is greater than the torque limit corresponding to the current wheel speed difference, if the motor controller directly outputs torque according to the torque value indicated by the torque signal, the torque value output by the drive motor will be greater than the torque limit corresponding to the current wheel speed difference, which will damage the differential. Therefore, the motor controller is used to control the torque value output by the drive motor to be equal to the torque limit. In other words, at this time, the torque value actually output by the motor controller is less than the torque value indicated by the torque signal.

[0013] In conjunction with the first aspect, in certain implementations of the first aspect, the motor controller is configured to receive a torque signal and output a torque value indicated by the torque signal. In response to the torque value output by the drive motor being greater than a torque limit, the motor controller is configured to control the drive motor to reduce the output torque value to less than or equal to the torque limit.

[0014] In combination with the first aspect, in certain implementations of the first aspect, when the motor controller is used to control the drive motor to reduce the output torque value, the torque value indicated by the torque signal is greater than the torque value output by the drive motor.

[0015] For example, if an electric vehicle starts traveling on a normal road, the speed difference between the two wheels is small, and the drive motor outputs a large torque. Then, the electric vehicle suddenly crosses a road on the other side. Although the torque value indicated by the torque signal is still large, the motor controller will actively reduce the torque value output by the drive motor to less than or equal to the torque limit to protect the safety of the differential. During this process, the torque value indicated by the torque signal is greater than the torque value output by the drive motor.

[0016] In combination with the first aspect, in certain implementations of the first aspect, if the torque value indicated by the torque signal is less than the torque limit, the motor controller is configured to receive the torque signal and control the drive motor to output the torque value indicated by the torque signal.

[0017] If the torque value indicated by the torque signal is less than the torque limit, it means that the drive motor outputs the torque value indicated by the current torque signal, which can put the differential in a safe state. Therefore, the motor controller can directly output the torque value according to the instruction of the torque signal.

[0018] In combination with the first aspect, in certain implementations of the first aspect, the motor controller is configured to control the drive motor to output a torque value indicated by the torque signal in response to the wheel speed difference between the two wheels being less than a preset third wheel speed difference.

[0019] The third wheel speed differential is a smaller wheel speed differential. That is, when the wheel speed difference between the two wheels is less than the preset third wheel speed differential, the differential is considered to be in a safe state. Specifically, at the current wheel speed differential, the differential can withstand any torque output by the drive motor. In this case, the motor controller can control the torque value indicated by the drive motor output torque signal without considering the torque limit. For example, the third wheel speed differential can be 50 rpm.

[0020] In combination with the first aspect, in certain implementations of the first aspect, the motor controller includes an inverter circuit and a control device, the control device includes a storage unit, and the storage unit is used to store multiple wheel speed differences and multiple torque limits, each wheel speed difference and each torque limit having a one-to-one correspondence.

[0021] The wheel speed differences and torque limits in the storage unit are used to calibrate the operating limits of the differential. That is, the differential is tested and calibrated, and the torque limits that the differential can withstand under different speed differences are calibrated to obtain the corresponding relationship between the wheel speed differences and the torque limits. Then, multiple wheel speed differences and corresponding multiple torque limits are stored in the storage device.

[0022] In conjunction with the first aspect, in certain implementations of the first aspect, the motor controller is configured to control the output torque of the drive motor based on a torque signal from a vehicle controller in response to a wheel speed difference between the two wheels being less than or equal to a fourth wheel speed difference. In response to the wheel speed difference between the two wheels being greater than the fourth wheel speed difference, the motor controller is configured to control the output torque of the drive motor based on a torque signal from a traction control system. The fourth wheel speed difference is less than the first wheel speed difference and greater than the third wheel speed difference.

[0023] The fourth wheel speed differential can be the threshold that triggers the vehicle stability system's control. That is, when the wheel speed differential between the two wheels is less than or equal to the preset fourth wheel speed differential, the electric vehicle operates stably, the vehicle controller performs torque control, and the motor controller controls the drive motor's output torque based on the vehicle controller's instructions. However, when the wheel speed differential between the two wheels exceeds the preset fourth wheel speed differential, indicating unstable operation, the vehicle stability system performs torque control. The motor controller controls the drive motor's output torque based on the instructions of the traction control system within the vehicle stability system, thereby controlling the differential speed between the two wheels and improving the vehicle's handling characteristics.

[0024] In combination with the first aspect, in certain implementations of the first aspect, the torque signal is determined by a vehicle controller based on the travel of a drive pedal or a brake pedal, or the torque signal is determined by a traction control system based on the motion state of the electric vehicle.

[0025] In combination with the first aspect, in certain implementations of the first aspect, the two wheels are respectively provided with wheel speed sensors, and the motor controller is used to receive speed signals sent by the wheel speed sensors, and the speed signals are used to indicate the speed difference between the two wheels.

[0026] In a second aspect, the present application provides a control method for a powertrain, the powertrain including a drive motor, a motor controller and a differential, the drive motor being used to drive and connect the differential, the differential being used to drive and connect the two wheels of the electric vehicle respectively, the two wheels being two front wheels or two rear wheels, and during the driving of the electric vehicle, the control method including: in response to the wheel speed difference between the two wheels being a first wheel speed difference, controlling the output torque of the drive motor to be less than or equal to a first limit value, the first limit value corresponding to the first wheel speed difference; in response to the wheel speed difference between the two wheels increasing from the first wheel speed difference to the second wheel speed difference, controlling the torque output by the drive motor to be reduced to less than or equal to a second limit value, the second limit value corresponding to the second wheel speed difference; wherein, the first wheel speed difference is less than the second wheel speed difference, and the first limit value is greater than the second limit value.

[0027] In combination with the second aspect, in certain implementations of the second aspect, the torque value output by the drive motor is controlled to be less than or equal to a torque limit, wherein the torque limit decreases as the speed difference between the two wheels increases.

[0028] In a third aspect, an electric vehicle is provided, comprising a wheel, a wheel speed sensor, a traction control system, a vehicle controller, and the powertrain described in the first aspect. The wheel speed sensor is configured to detect the rotational speed of the wheel, wherein the motor controller is configured to receive a rotational speed signal transmitted by the wheel speed sensor; the vehicle controller is configured to receive an accelerator pedal travel signal and output a torque signal to the motor controller based on a torque value indicated by the travel signal; and the traction control system is configured to output the torque signal to the motor controller.

[0029] Specifically, the beneficial effects of other aspects can refer to the beneficial effects described in the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a schematic diagram of a differential provided by an embodiment of the present application;

[0031] FIG2 is a schematic diagram of an electric vehicle provided in an embodiment of the present application;

[0032] FIG3 is a schematic diagram of a motor controller provided in an embodiment of the present application;

[0033] FIG4 is a schematic diagram of a control flow of a motor controller provided in an embodiment of the present application;

[0034] FIG5 is a schematic diagram of a differential torque limit curve provided by an embodiment of the present application;

[0035] FIG6 is a schematic diagram of an operation situation in a possible scenario provided by an embodiment of the present application;

[0036] FIG7 is a schematic diagram of an operation situation in another possible scenario provided by an embodiment of the present application;

[0037] FIG8 is a schematic diagram of a motor control method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0038] The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0039] With the widespread adoption of electric vehicles, vehicle handling and safety have drawn increasing attention. Compared to conventional vehicles, pure electric vehicles are often heavier, have faster power response, and experience greater impact. These factors result in greater speed differentials and torque on split-road and sloped roads, placing higher demands on the differential's load-bearing capacity.

[0040] The differential is a differential transmission mechanism that enables the left and right (or front and rear) drive wheels to rotate at different speeds. This ensures power transmission to each drive wheel under various driving conditions and prevents slip between the tires and the ground. The differential primarily consists of left and right axle gears, two planetary gears, and a gear carrier. The differential's characteristic is "speed differential, not torque differential." This means that although the left and right drive wheels rotate at different speeds, the driving torque transmitted to both is equal.

[0041] FIG1 is a schematic diagram of a differential provided by an embodiment of the present application. As shown in FIG1 , an electric vehicle 10 may include wheels 12 and wheel drive axles 13 mounted on the vehicle body. A differential 70 is drivingly connected to the wheel drive axles 13, and the wheels 12 are drivingly connected to the wheel drive axles 13. Power generated by the powertrain 30 is sequentially transmitted to the wheel drive axles 13 and the wheels 12, thereby enabling the vehicle to move. The differential 70 enables the left and right (or front and rear) wheel drive axles 13 to rotate at different speeds, thereby rotating the left and right (or front and rear) wheels 12 at different speeds. When the electric vehicle 10 is turning or driving on a divided road, the left and right (or front and rear) wheels 12 roll at different speeds, ensuring pure rolling motion of the wheels 12. The powertrain 30 includes a drive motor 60, a main reduction gear 14, and a differential 70. The main reduction gear 14 is fixedly connected to the housing of the differential 70. The drive motor 60 is drivingly connected to the main reduction gear 14 to provide power to the main reduction gear 14. The powertrain 30 further includes a speed reducer 80 . The gear assembly 15 in the speed reducer 80 receives power transmitted by the drive motor 60 and delivers the power to the final reduction gear 14 .

[0042] When the electric vehicle 10 turns right, the rotation speed of the left side gear 200a is greater than the rotation speed of the right side gear 200b. The resistance difference between the left wheel 12a and the right wheel 12b causes the planetary gear 300a to rotate clockwise, the planetary gear 300b to rotate counterclockwise, and the planetary gear 300c to rotate counterclockwise. This allows the left side gear 200a and the right side gear 200b to rotate differentially. The left wheel 12a rotates faster than the right wheel 12b, allowing the electric vehicle 10 to turn smoothly.

[0043] Most electric vehicles have single-speed reducers and no clutch to attenuate the torque impact in the powertrain. In the case of a double-slope operation, the speed difference of the differential will increase. At the same time, due to the need to climb, a certain torque needs to be maintained in the transmission system, which further increases the load-bearing demand of the differential compared to traditional models. Under this condition, the fundamental reason for the failure of the differential is that the friction pair between the planetary gear and the planetary shaft inside the differential cannot withstand the PV demand brought by the heavy and large pure electric vehicles under the extreme double-slope operation. This leads to the breakdown of the oil film during operation, direct metal contact friction, and the melting and adhesion of the planetary gear and the axle, resulting in bonding failure. However, the current differential hardware in the industry is unable to withstand the differential load requirements caused by medium and large pure electric vehicles under this condition. If it is not effectively controlled, it will lead to a series of serious consequences such as differential ablation, insulation failure, and power loss.

[0044] The Electronic Stability Program (ESP) is an active safety system that intervenes in emergency situations to prevent the vehicle from skidding, leading to loss of control, rollover, oversteer, or understeer, thereby improving vehicle handling and driving safety. ESP typically consists of a central control unit, steering sensors, wheel speed sensors, lateral acceleration sensors, side slip sensors, and actuators. These sensors sense the vehicle's state and transmit data to the control unit. If the vehicle approaches a loss of control, the control unit immediately activates the actuators to stabilize the vehicle. ESP includes a traction control system (TCS) for controlling pure electric vehicles and managing vehicle handling stability. The ESP (TCS) sends signals to the vehicle control unit (VCU). Upon receiving these signals, the motor control unit (MCU) coordinates the output torque of the engine or drive motor and the wheel cylinder pressure to reduce torque. It also signals braking requirements to the braking system, thereby controlling the differential speed between the two wheels and improving vehicle handling stability.

[0045] It should be understood that during the chassis TCS calibration process, more attention is often paid to the performance of the entire vehicle. In scenarios such as double-sided roads and double-sided ramps that have high requirements for the differential load, the TCS calibration process often only considers the handling stability requirements. When controlling the output torque of the drive motor, the differential load is not considered, which can easily cause the differential to ablate and fail.

[0046] Based on the above problems, the present application provides a motor controller, a motor control method, a powertrain and an electric vehicle. The motor controller realizes intelligent protection of the differential according to the capabilities of the differential hardware and the actual working boundary conditions, thereby improving the reliability of the powertrain and ensuring the safety of the entire vehicle.

[0047] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "set", "install", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances. The term "including" used in this application should not be interpreted as being limited to the contents listed thereafter; it does not exclude other elements or steps. Therefore, it should be interpreted as specifying the existence of the mentioned features, wholes, steps or parts, but does not exclude the existence or addition of one or more other features, wholes, steps or parts and groups thereof. Therefore, the expression "a device comprising means A and B" should not be limited to a device consisting only of parts A and B.

[0048] FIG2 is a schematic diagram of an electric vehicle provided in an embodiment of the present application. As shown in FIG2 , the electric vehicle 10 includes a power battery 20, a powertrain 30, and a vehicle controller 40. The vehicle controller 40 can send instructions to the powertrain 30 to control the operation of the vehicle or perform operations such as heating. The powertrain 30 is used to drive the electric vehicle 10. The powertrain 30 includes a motor controller 50, a drive motor 60, and a differential 70. The motor controller 50 includes a control device 51 and an inverter circuit 52. The inverter circuit 52 can be a control circuit composed of an insulated gate bipolar transistor (IGBT), and the on-off control signal of the IGBT in the control circuit is provided by the above-mentioned control device 51. Taking the control of a three-phase motor as an example, by using 6 IGBTs to form an inverter control circuit, the DC current at the battery end is converted into a three-phase AC current, which is respectively provided to the three-phase windings of the three-phase motor to control the speed or torque output of the three-phase motor. The differential 70 is connected to the drive motor 60 in a driving manner. The differential 70 is also connected to the left wheel and the right wheel of the electric vehicle 10 in a driving manner. The differential 70 receives the torque output by the drive motor 60 and transmits the torque to the left wheel and the right wheel respectively.

[0049] The power battery in the embodiment of the present application can be a lithium-ion battery, a lithium metal battery, a lead-acid battery, a nickel-cadmium battery, a nickel-metal hydride battery, a lithium-sulfur battery, a lithium-air battery or a sodium-ion battery, etc., which are not limited here. In terms of scale, the power battery 20 in the embodiment of the present application can be a single cell, or a battery module or a battery pack, which are not limited here. In terms of application scenarios, the power battery 20 can be used in power devices such as automobiles and ships. For example, it can be applied to power vehicles to power the motors of power vehicles and serve as a power source for electric vehicles. The power battery 20 can also power other electrical devices in electric vehicles, such as in-car air conditioners, car players, etc.

[0050] This application is mainly used for electric vehicles operating in extreme scenarios. The electric vehicle 10 can be any of different types of vehicles such as cars, trucks, and passenger buses. It can also be a three-wheeled vehicle, a two-wheeled vehicle, a train, and other transportation devices for carrying people or goods, or other types of vehicles driven by power batteries. The electric vehicle 10 includes but is not limited to pure electric vehicles (pure electric vehicles / battery electric vehicles, pure EV / battery EV), hybrid electric vehicles (hybrid electric vehicles, HEV), range extended electric vehicles (REEV), plug-in hybrid electric vehicles (PHEV), new energy vehicles (NEV), etc.

[0051] Extreme scenarios refer to situations where the speed difference between the left and right wheels is too large, and the required torque is too high, on a split road / ramp or in an escape scenario. For example, a split ramp can have a low-adhesion surface (e.g., icy, wet tiled, etc.) on one side and a high-adhesion surface (e.g., regular asphalt or asphalt) on the other, and the vehicle needs to negotiate the ramp. Another example is a scenario where the vehicle is in trouble and the wheels are slipping, resulting in large speed differences between the left and right wheels and requiring a high torque to escape.

[0052] The motor controller 50 of the present embodiment includes an inverter circuit 52 and a control device 51. The inverter circuit 52 is composed of IGBTs, and the on / off control signals for the IGBTs in the inverter circuit 52 are provided by the control device 51. Taking the control of a three-phase motor as an example, by using six IGBTs to form the inverter circuit 52, current from the power battery 20 is passed to the drive motor 60, providing current to the three-phase windings of the three-phase motor to control the speed or torque output of the three-phase motor.

[0053] An embodiment of the present application provides a powertrain 30 .

[0054] The powertrain 30 includes a drive motor 60 , a motor controller 50 , a speed reducer 80 , and a differential 70 .

[0055] The drive motor 60 is used to transmit the connection to the differential 70, and the differential is used to transmit the connection to the two wheels of the electric vehicle respectively. The two wheels are two front wheels or two rear wheels. For example, the differential is used to transmit the connection to the left wheel and the right wheel of the electric vehicle 10 respectively. The differential 70 is used to receive the torque output by the drive motor 60 and transmit the torque to the left wheel and the right wheel of the two wheels respectively.

[0056] The motor controller 50 is used to control the drive motor 60 to output torque, and the torque is transmitted to the left wheel and the right wheel respectively through the differential 70.

[0057] As shown in Figure 3, the motor controller 50 includes a control device 51 and an inverter circuit 52. The inverter circuit 52 includes three parallel-connected bridge arms. One end of each bridge arm is connected to the positive electrode of the power battery 20, and the other end of each bridge arm is connected to the negative electrode of the power battery 20. The midpoint of each bridge arm is connected to one of the three-phase stator windings of the drive motor 60. The inverter circuit 52 is used to output a drive current to the drive motor 60, thereby driving the drive motor 60 to output torque, which is transmitted to the wheels through the differential.

[0058] The control device 51 is used to control the inverter circuit 52 to output a driving current, and the driving current is used to control the driving motor 60 to output a torque.

[0059] Power from the drive motor 60 enters the differential, directly driving the differential housing, which in turn drives the planetary gear shafts. The planetary gears then mesh with the side gears, distributing the power to the left and right side gears to drive the vehicle's left and right drive wheels. The input torque is evenly distributed to the left and right side gears through this system, and the sum of their rotational speeds equals the speed at the differential housing. Therefore, when the vehicle is traveling straight, the left and right side gears and the differential housing are in relative equilibrium, and the entire differential transmits power as a single unit. When the vehicle turns or skids, the outer wheels increase in speed / slip, while the inner wheels decrease in speed.

[0060] When the vehicle starts on a separated road surface, the driving wheel on the low-adhesion road surface reaches the adhesion limit first, so that the driving force of the entire drive shaft is affected by the low-adhesion road surface. The driving force of the high-adhesion side is equal to the driving torque of the low-adhesion side road surface, resulting in the driving torque transmitted to the high-adhesion side being limited, and the vehicle cannot start due to insufficient driving force.

[0061] In one possible scenario, when a vehicle is driving normally, it suddenly enters a road / slope with high and low adhesion surface from a normal road surface, and the wheels on the low adhesion surface side begin to slip.

[0062] In this scenario, the actual torque output by the drive motor may be the result of the combined effects of the vehicle stability system and the differential protection module of the motor controller 50. The motor controller 50 limits the torque output capacity of the drive motor 60 based on the differential's operating state and capacity. The actual torque output by the drive motor 60 is the smaller of the torque demanded by the TCS (i.e., the torque value indicated by the torque signal) and the torque limit set by the motor controller 50.

[0063] In one possible implementation, the motor controller 50 receives the torque signal output from the vehicle controller 40 in response to the wheel speed difference between the two wheels being less than or equal to a preset fourth wheel speed difference.

[0064] In a possible implementation, in response to a wheel speed difference between two wheels being greater than a preset fourth wheel speed difference, the motor controller 50 receives a torque signal output from a traction control system TCS.

[0065] The fourth wheel speed difference can be the threshold for triggering the control of the vehicle stability system TCS. The TCS sends a signal to the vehicle controller 40. After receiving the signal, the VCU controls the drive motor to reduce the torque and outputs the braking demand to the braking system, thereby controlling the differential state of the wheels on both sides and improving the handling stability of the vehicle. This application does not limit the specific setting of the fourth wheel speed difference.

[0066] The motor controller 50 is configured to obtain a torque signal from the vehicle controller 40 or the traction control system (TCS). The torque signal is determined by the vehicle controller based on the travel of the drive pedal or brake pedal, or by the traction control system (TCS) based on the vehicle's motion state. The torque signal indicates the torque value determined by the vehicle controller or the TCS.

[0067] The motor controller 50 is configured to obtain a rotational speed signal, which includes the rotational speeds of the left and right wheels, or the speed difference between the left and right wheels. The rotational speeds of the left and right wheels can be obtained by sensors, and this application does not limit the method for obtaining the wheel speeds.

[0068] In a possible implementation, the two wheels are respectively provided with wheel speed sensors, and the motor controller 50 is used to receive rotation speed signals sent by the wheel speed sensors, where the rotation speed signals are used to indicate the rotation speed difference between the two wheels.

[0069] As shown in Figure 4, each wheel speed sensor transmits the collected signal to the vehicle controller 40. After processing by the vehicle controller 40, the speed and acceleration of each drive wheel are obtained. The wheel speed signal and steering wheel angle signal are then sent to the motor controller 50 through the vehicle controller 40. When the wheel speed difference reaches a threshold, the TCS in the ESP system is required to control the vehicle. The TCS sends a signal to the vehicle controller 40. After receiving the signal, the motor controller 50 controls the drive motor 60 to reduce torque or outputs a braking request to the braking system, thereby controlling the differential speed of the two wheels and improving the vehicle's handling characteristics.

[0070] In one possible implementation, in response to the wheel speed difference between the two wheels being less than a preset third wheel speed difference, the motor controller 50 is configured to control the drive motor to output a torque value indicated by the torque signal.

[0071] When the wheel speed difference between the two wheels is very small or even no wheel speed difference exists, there is no need to protect the differential, and the third wheel speed difference can be a small value.

[0072] In one possible implementation, in response to the torque indicated by the torque signal being less than or equal to the torque limit, the motor controller 50 is configured to control the drive motor to output the torque indicated by the torque signal.

[0073] When the torque indicated by the torque signal determined by the TCS is less than or equal to the torque that the differential can withstand, the differential protection module of the motor controller 50 can be in a permanent closed state, and the torque output by the drive motor 60 is the TCS required torque.

[0074] It should be understood that the TCS calibration process often only considers the handling stability requirements. When determining the torque output by the drive motor 60, the differential load is not considered. That is, the torque indicated by the torque signal determined by the TCS may exceed the load-bearing capacity of the differential, thereby easily causing the differential to ablate and fail, affecting driving safety.

[0075] When the torque determined by the TCS is greater than the torque that the differential can withstand, the differential protection module of the motor controller 50 is triggered, and the motor controller 50 obtains the working boundary of the differential 70. The working boundary can be the limit boundary obtained from the differential test. The motor controller 50 judges the torque indicated by the torque signal and the torque that the differential can bear.

[0076] The motor controller 50 is used to control the torque value output by the driving motor to be less than or equal to the torque limit value, wherein the torque limit value decreases as the speed difference between the two wheels increases.

[0077] In one possible implementation, in response to the torque value output by the drive motor 60 being greater than the torque limit, the motor controller 50 is configured to control the drive motor to reduce the output torque value to less than or equal to the torque limit.

[0078] In one possible implementation, the motor controller 50 is used to control the torque value output by the drive motor 60 to be less than or equal to a first limit value in response to the wheel speed difference between the two wheels being a first wheel speed difference; and to control the torque value output by the drive motor 60 to be less than or equal to a second limit value in response to the wheel speed difference between the two wheels being a second wheel speed difference; wherein the first wheel speed difference is less than the second wheel speed difference, and the first limit value is greater than the second limit value.

[0079] Exemplarily, when the wheel speed difference between the left wheel and the right wheel of the electric vehicle 10 is a first wheel speed difference, in response to the torque value indicated by the torque signal being greater than a first limit value, the first limit value corresponds to the first wheel speed difference, and the control device 51 controls the inverter circuit 52 to output current, and the current controls the torque value output by the drive motor 60 to be less than or equal to the torque limit value, and at this time the torque limit value is lower than the torque value indicated by the torque signal.

[0080] In one possible implementation, the motor controller 50 is configured to control the torque value output by the drive motor to be equal to the torque limit in response to the torque indicated by the torque signal being greater than the torque limit.

[0081] In response to the torque value indicated by the torque signal being greater than the torque limit, the motor controller 50 controls the control device 51 to control the inverter circuit 52 to output current, so that the motor controller 50 controls the drive motor 60 to output the torque limit.

[0082] The torque limit is determined by the differential design, the working state of the differential in the assembly and other conditions.

[0083] In a possible implementation, the control device 51 includes a storage unit, which is used to store a plurality of wheel speed differences and a plurality of torque limits, where each wheel speed difference corresponds to each torque limit.

[0084] In one possible implementation, the motor controller 50 controls the drive motor 60 to reduce the output torque value to less than or equal to the torque limit in response to the torque value output by the drive motor 60 being greater than the torque limit; in the process of controlling the drive motor 60 to reduce the output torque value, the torque value indicated by the torque signal is greater than the torque value output by the drive motor.

[0085] When the wheel speed difference of the electric vehicle increases, causing the torque value output by the drive motor to be greater than the torque limit corresponding to the wheel speed difference, the motor controller 50 is used to control the torque value output by the drive motor to be reduced to a range less than or equal to the torque limit. During the control process, the output torque does not exceed the torque value indicated by the torque signal.

[0086] As shown in Figure 5, the corresponding relationship between wheel speed difference and torque limit is shown in the curve in the figure. The torque limit that the differential can bear at different differential speed values ​​can be obtained through calculation or calibration. Within the torque value range of the calibrated value, the differential protection module of MCU 50 can be in a closed state or not triggered.

[0087] It should be understood that the calibration curve in FIG5 is only a schematic diagram, and the specific values ​​may vary depending on the capacity of the differential, the state of the vehicle, etc. The value in FIG5 is only a possible situation provided in the embodiment of the present application.

[0088] For example, as shown in FIG6 , the electric vehicle initially drives normally, with a small or zero left and right wheel speed difference. The torque indicated by the torque signal is consistent with the actual output torque, maintaining stability. At time t1, when the vehicle enters a road / ramp from a normal road surface and encounters a high-low-grid surface, the wheels on the low-grid surface begin to slip, increasing the speed difference between the left and right wheels. The wheel sensors transmit the signals they collect to the vehicle controller 40. The TCS determines torque reduction based on the vehicle's wheel operating conditions and transmits the torque signal after torque reduction to the motor controller 50. The motor controller 50 obtains the left and right wheel speeds or left and right wheel speed difference signals from the vehicle controller 40. The motor controller 50 determines that the left and right wheel speed difference at this time is a first wheel speed difference. The MCU 50 determines, based on the differential's operating boundaries, a first limit value for the differential's calibrated torque capacity under the first wheel speed difference. The motor controller 50 then makes a determination based on the torque indicated by the torque signal determined by the TCS and the torque limit that the differential can handle.

[0089] For example, when the wheel speed difference between the left and right wheels is 600 rpm, i.e., the first wheel speed difference is 600 rpm, as shown in FIG5 , the torque limit calibrated based on the differential capacity at the first wheel speed difference is 2000 N·m, i.e., the first limit corresponding to the first wheel speed difference is 2000 N·m. When the torque indicated by the torque signal received by the motor controller 50 is less than or equal to 2000 N·m, there is no need to protect the differential, i.e., the differential protection module of the motor controller 50 is not triggered. However, when the torque indicated by the torque signal is greater than 2000 N·m, in response to the torque value indicated by the torque signal being greater than the torque limit, the inverter circuit 52 is controlled to output current to the drive motor 60 so that the drive motor 60 outputs the first limit of 2000 N·m corresponding to the first wheel speed difference at this time; thereby, the differential still operates within its load capacity.

[0090] At this time, the wheel speed difference of the vehicle may remain unchanged, may decrease, or may increase. The wheel speed difference actually exists and is affected by the vehicle's driving conditions and road conditions. This application does not limit the changes in the wheel speed difference under this extreme condition.

[0091] The drive motor 60 outputs a torque limit under the control of the MCU50 to drive the vehicle, and the vehicle can travel normally. When the vehicle returns to the normal road surface at time t2, the wheels no longer slip, the differential protection module of the MCU50 is turned off, and the vehicle continues to operate normally. In response to the wheel speed difference between the two wheels being less than the preset third wheel speed difference, the torque output by the drive motor 60 is equal to the torque indicated by the torque signal.

[0092] The torque limit is a torque calibrated based on the differential's capacity. This torque limit is less than or equal to the maximum torque the differential can handle at that wheel speed differential. The torque limit decreases as the wheel speed differential increases.

[0093] In another possible scenario, when the vehicle is in trouble, such as the vehicle wheels are stuck in mud, sand, etc., the wheels may slip.

[0094] In this state, the vehicle switches the driving mode to the escape mode, which can be started by the vehicle controller 40 based on the vehicle wheel operating status, or it can be an operating mode preset by the vehicle itself and started by the driver through a button or the like.

[0095] For example, as shown in FIG7 , when a vehicle is in trouble or in the process of escaping a situation, the wheels slip and are unable to move forward. The wheel speed difference between the left and right wheels is the first wheel speed difference. As one would expect, the driver would want to extricate the vehicle from the situation and would therefore depress the drive pedal or brake pedal. Upon receiving the drive pedal or brake pedal signal, the VCU 40 would determine the driver's current required torque signal based on the travel of the drive pedal or brake pedal. The vehicle controller 40 would then transmit this demand to the motor controller 50 via a torque signal. After obtaining the wheel speed or wheel speed difference signals of the left and right wheels, the motor controller 50 would compare the stored differential operating state with the differential limit boundary test case. Based on the differential limit boundary test case, the MCU 50 would determine the torque limit corresponding to the first wheel speed difference. This torque limit is also the current maximum torque capacity of the powertrain 30. The motor controller 50 would then make a determination based on the torque indicated by the torque signal determined by the vehicle controller 40 and the differential load torque (i.e., the torque limit).

[0096] For example, when the wheel speed difference between the left and right wheels is 800 rpm, i.e., the second wheel speed difference is 800 rpm, as shown in FIG5 , the torque calibrated according to the differential capacity at the second wheel speed difference is 1500 N·m, i.e., the second limit corresponding to the first wheel speed difference is 1500 N·m. When the torque indicated by the torque indication signal received by the motor controller 50 is less than or equal to 1500 N·m, there is no need to protect the differential, i.e., the differential protection module of the motor controller 50 is not triggered, and the current driver's requested torque is directly output. When the torque indicated by the torque signal is greater than 1500 N·m, in response to the torque value indicated by the torque signal being greater than the torque limit, the inverter circuit 52 is controlled to output current to the drive motor 60 so that the drive motor 60 outputs the second limit of 1500 N·m corresponding to the first wheel speed difference, thereby maintaining the differential operating within its load capacity.

[0097] Under the control of the motor controller 50, the drive motor 60 outputs a torque limit corresponding to the first wheel speed differential to propel the vehicle. This torque is transmitted to the wheels through the differential, allowing the vehicle to escape at time t3. When the vehicle returns to normal road surface at time t3, the wheels no longer slip, the differential protection module of the motor controller 50 disengages, and the vehicle resumes normal operation at the torque requested by the driver.

[0098] It should be understood that the curves of wheel speed difference and torque in FIG. 6 and FIG. 7 are merely schematic, indicating possible changing trends, and the present application does not limit the actual possible values.

[0099] As can be seen above, the motor controller 50's differential protection control takes precedence over the torque signal control determined by the TCS system and the vehicle controller 40. As will be readily understood, in the aforementioned operating scenario, there's no need to disable the vehicle's differential in order to escape; there are also options for escaping the vehicle, such as waiting for rescue. Therefore, the torque limit corresponding to the wheel speed difference determined by the motor controller 50 for differential protection is the maximum limit of the actual output torque of the drive motor 60.

[0100] According to the solution of the present application, the motor controller 50 controls the limit boundary of the differential, thereby protecting the differential from hardware failure due to excessive differential and excessive coupling torque, which is beneficial to the intelligent protection of the differential by the powertrain 30. The motor controller 50 can especially provide protection for the operation of performance vehicles, large vehicles and off-road vehicles.

[0101] Furthermore, placing the differential protection module within the motor controller 50 reduces signal interaction between the vehicle controller 40 and the motor controller 50, enabling a fast closed-loop torque determination within the motor controller without requiring it to pass through other systems such as the vehicle controller. This reduces signal transmission latency and speeds up the determination of final output torque. This motor controller 50 enhances the intelligent features of the powertrain 30 and decouples powertrain 30 hardware protection from vehicle performance calibration. This eliminates the need to delegate differential capabilities to vehicle system developers for system software recalibration, allowing hardware providers to directly implement protection at the hardware level.

[0102] FIG8 is a schematic diagram of a control method for a motor controller provided in the present application.

[0103] The control method is applied to an electric vehicle 10 , which includes a power battery 20 and the powertrain 30 described above.

[0104] As shown in FIG8 , the method may include the following steps:

[0105] S120, controlling the drive motor output to be less than or equal to the torque limit.

[0106] The driving current is used to control the output torque of the driving motor 60, and the torque is transmitted to the left and right wheels of the electric vehicle through the differential 70.

[0107] In response to the wheel speed difference between the two wheels being the first wheel speed difference, the output torque of the drive motor 60 is controlled to be less than or equal to a first limit value, and the first limit value corresponds to the first wheel speed difference; in response to the wheel speed difference between the two wheels increasing from the first wheel speed difference to the second wheel speed difference, the output torque of the drive motor 60 is controlled to be reduced to less than or equal to a second limit value, and the second limit value corresponds to the second wheel speed difference; wherein, the first wheel speed difference is less than the second wheel speed difference, and the first limit value is greater than the second limit value.

[0108] In one possible implementation, when the wheel speed difference between the left wheel and the right wheel of the electric vehicle 10 is a first wheel speed difference, in response to the torque value indicated by the torque signal being greater than a first limit value, the first limit value corresponds to the first wheel speed difference, and the control device 51 controls the inverter circuit 52 to output a current, and the current controls the torque value output by the drive motor 60 to be less than the first limit value.

[0109] The torque limit decreases as the wheel speed difference increases.

[0110] The description of the method execution process can be found above and will not be repeated here.

[0111] Optionally, the method may further include the following steps:

[0112] S110 , obtaining wheel speed signals and torque signals.

[0113] The wheel signal includes the left wheel speed and the right wheel speed, or the wheel speed difference between the left and right wheels. The torque signal comes from the vehicle controller or the body stability system.

[0114] Optionally, the motor controller 50 may also obtain other vehicle information such as steering wheel signals, wheel speeds, wheel accelerations, and wheel sideslip rates.

[0115] In a possible implementation, the torque signal may be determined by the vehicle controller 40 according to the travel of the driving pedal; or the torque signal may be determined by the traction control system TCS according to the vehicle operating state.

[0116] According to the solution of the present application, the motor controller 50 controls the limit boundary of the differential, thereby protecting the differential from hardware failure due to excessive differential and excessive coupling torque, which is beneficial to the protection of the differential by the powertrain 30. The motor controller 50 can especially provide protection for the operation of performance vehicles, large vehicles and off-road vehicles.

[0117] The present application also provides an electric vehicle 10 .

[0118] The electric vehicle 10 includes a vehicle controller 40 and the powertrain as described above.

[0119] The vehicle controller is used to output a torque signal to the powertrain in response to the wheel speed difference between the two wheels being less than or equal to a preset fourth wheel speed difference, where the torque signal is determined according to the travel of the drive pedal and / or brake pedal.

[0120] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0121] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0122] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0123] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0124] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A powertrain with differential protection function, characterized in that: The powertrain includes a drive motor, a motor controller and a differential, wherein the drive motor is used to drive and connect the differential, and the differential is used to drive and connect two wheels of the electric vehicle respectively, wherein the two wheels are two front wheels or two rear wheels, and the motor controller is used to: reducing the torque limit value output by the drive motor as the wheel speed difference between the two wheels increases; The torque value output by the driving motor is controlled to be less than or equal to the torque limit value.

2. The powertrain according to claim 1, characterized in that: The motor controller is used to: In response to the torque indicated by the torque signal being less than or equal to the torque limit, controlling the drive motor to output the torque indicated by the torque signal; In response to the torque indicated by the torque signal being greater than the torque limit, the drive motor is controlled to output a torque value equal to the torque limit.

3. The powertrain according to claim 1 or 2, characterized in that: The motor controller is used to: In response to the torque value output by the drive motor being greater than the torque limit value, the drive motor is controlled to reduce the output torque value to be less than or equal to the torque limit value.

4. The powertrain according to any one of claims 1 to 3, characterized in that: The motor controller is used to control the drive motor to reduce the output torque value, and the motor controller is used to: In response to an increase in the wheel speed difference between the two wheels, the drive motor is controlled to reduce an output torque value.

5. The powertrain according to any one of claims 1 to 4, characterized in that: The motor controller is used to: In response to the wheel speed difference between the two wheels being a first wheel speed difference, controlling the torque value output by the drive motor to be less than or equal to a first limit value, where the first limit value corresponds to the first wheel speed difference; In response to the wheel speed difference between the two wheels being a second wheel speed difference, controlling the torque value output by the drive motor to be less than or equal to a second limit value, where the second limit value corresponds to the second wheel speed difference; The first wheel speed difference is smaller than the second wheel speed difference, and the first limit value is larger than the second limit value.

6. The powertrain according to claim 5, characterized in that: The motor controller is used to: In response to the wheel speed difference between the two wheels being less than a preset third wheel speed difference, the drive motor is controlled to output the torque value indicated by the torque signal, and the third wheel speed difference is less than the first wheel speed difference.

7. The powertrain according to claim 6, characterized in that: The motor controller is used to: In response to the wheel speed difference between the two wheels being less than or equal to a fourth wheel speed difference, the drive motor output torque is controlled according to a torque signal from a vehicle controller, and the fourth wheel speed difference is less than the first wheel speed difference and greater than the third wheel speed difference.

8. The powertrain according to claim 7, characterized in that: The motor controller is used to: In response to the wheel speed difference between the two wheels being greater than the fourth wheel speed difference, the drive motor is controlled to output torque according to a torque signal from a traction control system.

9. A control method for a powertrain, characterized in that: The powertrain includes a drive motor, a motor controller and a differential, the drive motor is used to drive and connect the differential, the differential is used to drive and connect two wheels of the electric vehicle respectively, the two wheels are two front wheels or two rear wheels, and during the driving of the electric vehicle, the control method includes: reducing the torque limit value output by the drive motor as the wheel speed difference between the two wheels increases; The torque value output by the driving motor is controlled to be less than or equal to the torque limit value.

10. The control method according to claim 9, characterized in that: The control method comprises: In response to the torque indicated by the torque signal being less than or equal to the torque limit, controlling the drive motor to output the torque indicated by the torque signal; In response to the torque indicated by the torque signal being greater than the torque limit, the drive motor is controlled to output a torque value equal to the torque limit.

11. The control method according to claim 9 or 10, characterized in that: The control method comprises: In response to the torque value output by the drive motor being greater than the torque limit value, controlling the drive motor to reduce the output torque value to be less than or equal to the torque limit value; In the process of controlling the drive motor to reduce the output torque value, in response to the increase in the wheel speed difference between the two wheels, the drive motor is controlled to reduce the output torque value. The drive motor reduces the output torque value.

12. The control method according to any one of claims 9 to 11, characterized in that: The control method comprises: In response to the wheel speed difference between the two wheels being a first wheel speed difference, controlling the output torque of the drive motor to be less than or equal to a first limit value, wherein the first limit value corresponds to the first wheel speed difference; In response to the wheel speed difference between the two wheels increasing from the first wheel speed difference to a second wheel speed difference, controlling the torque output by the drive motor to decrease to less than or equal to a second limit value, the second limit value corresponding to the second wheel speed difference; The first wheel speed difference is smaller than the second wheel speed difference, and the first limit value is larger than the second limit value.

13. The control method according to claim 12, characterized in that: The control method comprises: In response to the wheel speed difference between the two wheels being less than a preset third wheel speed difference, the drive motor is controlled to output the torque value indicated by the torque signal, and the third wheel speed difference is less than the first wheel speed difference.

14. The control method according to claim 13, characterized in that: The control method comprises: In response to the wheel speed difference between the two wheels being less than or equal to a fourth wheel speed difference, controlling the drive motor to output torque according to a torque signal from a vehicle controller; In response to the wheel speed difference between the two wheels being greater than the fourth wheel speed difference, the drive motor is controlled to output torque according to a torque signal from a traction control system, and the fourth wheel speed difference is less than the first wheel speed difference and greater than the third wheel speed difference.

15. An electric vehicle, characterized in that: The electric vehicle comprises a wheel, a wheel speed sensor, a traction control system, a vehicle controller and a powertrain according to any one of claims 1 to 8, wherein the wheel speed sensor is used to detect the rotation speed of the wheel, wherein: The motor controller is used to receive the rotation speed signal sent by the wheel speed sensor; The vehicle controller is used to receive a travel signal of an accelerator pedal and output a torque signal to the motor controller according to a torque value indicated by the travel signal; The traction control system is used to output a torque signal to the motor controller.

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