CN112092648A - Control method of four-wheel-drive pure electric vehicle power system and vehicle - Google Patents

Abstract

The invention relates to the technical field of control of a four-wheel drive pure electric vehicle power system, and discloses a four-wheel drive pure electric vehicle power system control method and a vehicle; a first motor, a second motor, a transmission and a first two-way clutch are arranged on the vehicle. , the first motor is drivingly connected to the wheels of the vehicle through the first two-way clutch and the transmission, the second motor is drivingly connected to the wheels of the vehicle, and both the first motor and the second motor are used for Driving a vehicle to drive, the control method includes drive control, which includes the following steps: calculating a driving torque required for driving the vehicle; determining whether the driving torque is greater than the maximum torque that can be generated by the first motor to the wheel end; if yes , then the first motor and the second motor drive the vehicle to travel at the same time; if not, the first motor drives the vehicle to travel, and the second motor is in a stationary state.

Description

A kind of control method and vehicle of four-wheel drive pure electric vehicle power system

technical field

The invention relates to the technical field of control of a four-wheel drive pure electric vehicle power system, in particular to a control method and a vehicle of the four-wheel drive pure electric vehicle power system.

Background technique

With the development of pure electric vehicles, in order to pursue better power performance, many models adopt the four-wheel drive scheme, that is, a set of electric drive systems are used in the front and rear. Permanent magnet synchronous motors have been widely used in pure electric vehicles due to their high power density and high efficiency.

However, unlike the asynchronous motor, the permanent magnet synchronous motor has a large anti-drag torque under the rotating condition, and in order to prevent the back EMF from being too high, its field-weakening current in the high-speed section is large and consumes more power, all of which are As a result, the power consumption of four-wheel drive models using permanent magnet synchronous motors is relatively high. As a result, the driving mileage of the whole vehicle is shorter, which affects the competitiveness of the model.

Therefore, there is an urgent need for a control method and a vehicle for a power system of a four-wheel drive pure electric vehicle to solve the above technical problems.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a control method and a vehicle for a power system of a four-wheel drive pure electric vehicle, which have lower power consumption and longer cruising range.

For this purpose, the present invention adopts the following technical solutions:

In one aspect, a method for controlling a power system of a four-wheel drive pure electric vehicle is provided, wherein a first motor, a second motor, a transmission and a first two-way clutch are provided on the vehicle, and the first motor passes through the first two-way clutch and all the The transmission is drivingly connected with the wheels of the vehicle, the second motor is drivingly connected with the wheels of the vehicle, the first motor and the second motor are both used for driving the vehicle, and the control method includes driving driving control, which includes Follow the steps below:

Calculate the driving torque required for the vehicle to run;

determining whether the driving torque is greater than the maximum torque that the first motor can generate to the wheel end;

If yes, the first motor and the second motor drive the vehicle simultaneously;

If not, the first motor drives the vehicle, and the second motor is in a stationary state.

As a preferred technical solution of the control method for the power system of the four-wheel drive pure electric vehicle, the transmission is arranged on the front axle of the vehicle, and the first motor communicates with the other through the first two-way clutch and the transmission. The front wheel of the vehicle is drive-connected, and the second motor is drive-connected to the rear wheel of the vehicle through a second clutch.

As a preferred technical solution of the control method for the power system of the four-wheel drive pure electric vehicle, the transmission is arranged on the rear axle of the vehicle, and the first motor communicates with the other through the first two-way clutch and the transmission. The rear wheel of the vehicle is drive-connected, and the second motor is drive-connected to the front wheel of the vehicle through a second clutch.

As a preferred technical solution of the control method for the power system of the four-wheel drive pure electric vehicle, the second clutch is a two-way clutch, and when the first motor and the second motor drive the vehicle at the same time, the first The second clutch is in an engaged state; when the second motor is in a stationary state, the second clutch is in a disengaged state;

Or, the second clutch is a one-way clutch, and the one-way clutch can only transmit the power of the second motor to the wheel, and cannot transmit the power in the reverse direction.

As a preferred technical solution of the control method for the power system of the four-wheel drive pure electric vehicle, it also includes braking travel control. When the second clutch is a one-way clutch, the braking travel control includes the following steps:

Calculate the braking torque required for vehicle braking;

determining whether the braking torque is greater than the negative torque generated by the first motor;

If not, the negative torque generated by the first motor brakes the vehicle, and at the same time, the negative torque of the first motor is used to generate electricity;

If so, the negative torque generated by the first electric machine provides part of the torque for vehicle braking, and another part of the braking torque is provided by the hydraulic braking system of the vehicle, while the negative torque of the first electric machine is used to generate electricity.

As a preferred technical solution of the control method for the power system of the four-wheel drive pure electric vehicle, it also includes braking travel control. When the second clutch is a two-way clutch, the braking travel control includes the following steps:

Calculate the braking torque required for vehicle braking;

determining whether the braking torque is greater than the negative torque generated by the first motor;

If not, the negative torque generated by the first motor brakes the vehicle, and at the same time, the negative torque of the first motor is used to generate electricity;

If so, determine whether the braking torque is greater than the sum of the negative torques generated by the first motor and the second motor;

If not, the negative torque generated by the first electric machine and the second electric machine brakes the vehicle, and the negative torque of the first electric machine and the second electric machine is used to generate electricity at the same time;

If so, braking torque is provided by the vehicle's hydraulic braking system.

As a preferred technical solution of the control method for the four-wheel drive pure electric vehicle power system, the transmission is a two-speed transmission, the first two-way clutch is provided between the first motor and the transmission, and the transmission is When connecting the first motor and the transmission; the control method further includes shifting control, which includes the following steps:

Shifting is performed by adjusting the state of the first two-way clutch.

As a preferred technical solution of the control method of the four-wheel drive pure electric vehicle power system, the transmission is a two-speed transmission, and the first two-way clutch is provided at the output end of the transmission; the control method further Including shift control, which includes first gear up to second gear, which includes:

The first motor reduces the torque to 0;

Shift actuator to remove gear;

Reduce the first motor speed to the second gear target speed;

The shift actuator performs the shift to the second gear.

As a preferred technical solution of the control method for the power system of the four-wheel drive pure electric vehicle, the shift control further includes a second gear downshift and a first gear, which includes:

The first motor reduces the torque to 0;

Shift actuator to remove gear;

Reduce the speed of the first motor to the target speed of the first gear;

The shift actuator performs the shift to first gear.

On the other hand, a vehicle is provided, characterized in that it adopts the control method for the power system of a four-wheel drive pure electric vehicle as described above.

The beneficial effects of the present invention: when the vehicle is in two-wheel drive, only the first motor drives the vehicle, and the second motor is in a stationary state, which can reduce the loss of the motor with the rotation, the resistance when the vehicle is driven is smaller, and the power consumption of the vehicle is reduced. low, making the vehicle's cruising range longer.

In addition, through the shifting of the transmission, the working point of the motor is adjusted, so that the motor works in a more efficient area, the power consumption of the vehicle is lower, and the driving mileage is longer.

Description of drawings

Fig. 1 is the structural representation of combination 1 provided by the present invention;

Fig. 2 is the structural representation of combination 2 provided by the present invention;

Fig. 3 is the structural representation of combination 3 provided by the present invention;

Fig. 4 is the structural representation of combination 4 provided by the present invention;

Fig. 5 is the structural representation of combination 5 provided by the present invention;

Fig. 6 is the structural representation of combination 6 provided by the present invention;

Fig. 7 is the structural representation of combination 7 provided by the present invention;

Fig. 8 is the structural representation of the combination 8 provided by the present invention;

9 is a schematic diagram of a driving method provided by the present invention when a first motor-driven vehicle is traveling;

10 is a schematic diagram of vehicle braking provided by the present invention;

11 is a schematic diagram of the formulation of a shifting strategy provided by the present invention;

FIG. 12 is a schematic diagram of the shifting strategy provided by the present invention.

In the figure: 1, the first motor; 2, the second motor; 3, the transmission; 4, the first two-way clutch; 5, the second clutch; 6, the transmission mechanism; 7, the front wheel main reducer; 8, the rear wheel main reducer reducer.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

Thus, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further definition and explanation in subsequent figures.

In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate the orientation or The positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of the invention is usually placed when it is used. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying the device referred to. Or elements must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first", "second", "third", etc. are only used to differentiate the description and should not be construed as indicating or implying relative importance. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of the present invention, it should also be noted that, unless otherwise expressly specified and limited, the terms "arrangement" and "connection" should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection, or Integrally connected; either mechanical or electrical. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

In the present invention, unless otherwise expressly specified and limited, a first feature "on" or "under" a second feature may include the first and second features in direct contact, or may include the first and second features Not directly but through additional features between them. Also, the first feature being "above", "over" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is level higher than the second feature. The first feature is "below", "below" and "below" the second feature includes the first feature being directly below and diagonally below the second feature, or simply means that the first feature has a lower level than the second feature.

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present invention, and should not be construed as a limitation of the present invention.

This embodiment discloses a four-wheel drive pure electric vehicle power system, which includes a first motor 1 , a second motor 2 , a transmission 3 , a first two-way clutch 4 , a second clutch 5 and a transmission mechanism 6 . The first motor 1 , the second motor 2 , a transmission 3 , the first two-way clutch 4 , the second clutch 5 and the transmission mechanism 6 are all provided on the vehicle. The transmission 3 is a two-speed transmission.

Specifically, the first electric motor 1 is drive-connected with one of the front wheel and the rear wheel of the vehicle, and the second electric machine 2 is drive-connected with the other.

The transmission 3 is arranged on the front axle of the vehicle, the first motor 1 is drivingly connected to the front wheel of the vehicle through the first two-way clutch 4 and the transmission 3 , and the second motor 2 is drivingly connected to the rear wheel of the vehicle through the second clutch 5 . Or the transmission 3 is arranged on the rear axle of the vehicle, the first motor 1 is drivingly connected to the rear wheel of the vehicle through the first two-way clutch 4 and the transmission 3 , and the second motor 2 is drivingly connected to the front wheel of the vehicle through the second clutch 5 .

The first motor 1 , the second motor 2 , a transmission 3 , the first two-way clutch 4 , the second clutch 5 and the transmission mechanism 6 have eight combinations.

As shown in the combination 1 shown in FIG. 1 , the transmission 3 is arranged on the front axle of the vehicle, the first motor 1 is drivingly connected with the transmission 3 through the first two-way clutch 4 , and the first two-way clutch 4 is arranged between the first motor 1 and the transmission 3 The output end of the transmission 3 is connected to the front wheel of the vehicle through the front wheel final reducer 7. The second motor 2 is drive-connected with the transmission mechanism 6 through the second clutch 5 , the second clutch 5 is arranged between the second motor 2 and the transmission mechanism 6 , and the transmission mechanism 6 is drive-connected with the rear wheel of the vehicle through the rear wheel final reducer 8 . The vehicle can be switched between four-wheel drive and front-wheel drive.

As shown in the combination 2 in FIG. 2 , the transmission 3 is arranged on the front axle of the vehicle, the first motor 1 is drivingly connected with the first two-way clutch 4 through the transmission 3 , and the transmission 3 is arranged between the first motor 1 and the first two-way clutch 4 In between, that is, the first two-way clutch 4 is connected to the output end of the transmission 3 , and the output end of the first two-way clutch 4 is connected to the front wheel drive of the vehicle through the front wheel final reducer 7 . The second motor 2 is drive-connected with the transmission mechanism 6 through the second clutch 5 , the second clutch 5 is arranged between the second motor 2 and the transmission mechanism 6 , and the transmission mechanism 6 is drive-connected with the rear wheel of the vehicle through the rear wheel final reducer 8 . The vehicle can be switched between four-wheel drive and front-wheel drive.

As shown in the combination 3 shown in FIG. 3 , the transmission 3 is arranged on the front axle of the vehicle, the first motor 1 is drivingly connected with the transmission 3 through the first two-way clutch 4 , and the first two-way clutch 4 is arranged between the first motor 1 and the transmission 3 The output end of the transmission 3 is connected to the front wheel of the vehicle through the front wheel final reducer 7. The second motor 2 is connected to the second clutch 5 through a transmission mechanism 6, the transmission mechanism 6 is arranged between the second motor 2 and the second clutch 5, and the second clutch 5 and the rear wheels of the vehicle are driven through the rear wheel main reducer 8 connect. The vehicle can be switched between four-wheel drive and front-wheel drive.

As shown in the combination 4 in FIG. 4 , the transmission 3 is arranged on the front axle of the vehicle, the first motor 1 is drivingly connected with the first two-way clutch 4 through the transmission 3 , and the transmission 3 is arranged between the first motor 1 and the first two-way clutch 4 The first two-way clutch 4 is connected to the output end of the transmission 3; the output end of the first two-way clutch 4 is connected to the front wheel of the vehicle through the front wheel final reducer 7. The second motor 2 is connected to the second clutch 5 through a transmission mechanism 6, the transmission mechanism 6 is arranged between the second motor 2 and the second clutch 5, and the second clutch 5 and the rear wheels of the vehicle are driven through the rear wheel main reducer 8 connect. The vehicle can be switched between four-wheel drive and front-wheel drive.

As shown in combination 5 in FIG. 5 , the transmission 3 is arranged on the rear axle of the vehicle, the first motor 1 is drive-connected with the transmission 3 through the first two-way clutch 4 , and the first two-way clutch 4 is arranged between the first motor 1 and the transmission 3 The output end of the transmission 3 is connected to the rear wheel drive of the vehicle through the rear wheel final reducer 8. The second motor 2 is drive-connected to the second clutch 5 through a transmission mechanism 6, the transmission mechanism 6 is arranged between the second motor 2 and the second clutch 5, and the second clutch 5 is driven to the front wheel of the vehicle through the front wheel main reducer 7 connect. The vehicle can be switched between four-wheel drive and rear-wheel drive.

As shown in the combination 6 in FIG. 6 , the transmission 3 is arranged on the rear axle of the vehicle, the first motor 1 is drivingly connected with the transmission 3 through the first two-way clutch 4 , and the first two-way clutch 4 is arranged between the first motor 1 and the transmission 3 The output end of the transmission 3 is connected to the rear wheel drive of the vehicle through the rear wheel final reducer 8. The second motor 2 is in driving connection with the transmission mechanism 6 through the second clutch 5 , the second clutch 5 is arranged between the second motor 2 and the transmission mechanism 6 , and the transmission mechanism 6 is in transmission connection with the front wheel of the vehicle through the front wheel main reducer 7 . The vehicle can be switched between four-wheel drive and rear-wheel drive.

As shown in the combination 7 in FIG. 7 , the transmission 3 is arranged on the rear axle of the vehicle, the first motor 1 is drivingly connected with the first two-way clutch 4 through the transmission 3 , and the transmission 3 is arranged between the first motor 1 and the first two-way clutch 4 In other words, the first two-way clutch 4 is connected to the output end of the transmission 3; the output end of the first two-way clutch 4 is connected to the rear wheel drive of the vehicle through the rear wheel final reducer 8. The second motor 2 is in driving connection with the transmission mechanism 6 through the second clutch 5 , the second clutch 5 is arranged between the second motor 2 and the transmission mechanism 6 , and the transmission mechanism 6 is in transmission connection with the front wheel of the vehicle through the front wheel main reducer 7 . The vehicle can be switched between four-wheel drive and rear-wheel drive.

As shown in the combination 8 in FIG. 8 , the transmission 3 is arranged on the rear axle of the vehicle, the first motor 1 is drive-connected with the first two-way clutch 4 through the transmission 3 , and the transmission 3 is arranged between the first motor 1 and the first two-way clutch 4 . In other words, the first two-way clutch 4 is connected to the output end of the transmission 3; the output end of the first two-way clutch 4 is connected to the rear wheel drive of the vehicle through the rear wheel final reducer 8. The second motor 2 is drivingly connected to the second clutch 5 through a transmission mechanism 6, the transmission mechanism 6 is arranged between the second motor 2 and the second clutch 5, and the second clutch 5 is drivingly connected to the front wheel of the vehicle through the front road final reducer . The vehicle can be switched between four-wheel drive and rear-wheel drive.

The power system also includes vehicle controller (VCU), ESP, first motor 1 controller (MCU1), second motor 2 controller (MCU2), battery, battery management system (BMS), shift controller (TCU) . The ESP, the first motor 1 controller, the second motor 2 controller, the battery management system and the shift controller are all electrically connected to the vehicle controller. The battery management system is electrically connected to the battery, and can detect the battery SOC, the temperature of the battery, the fault state of the charging and discharging power meter, etc., and can transmit it to the vehicle controller. The controller of the first motor 1 is electrically connected to the first motor 1 , and can detect the torque, rotation speed, power, temperature and fault status of the first motor 1 and transmit it to the vehicle controller. The second motor 2 controller is electrically connected to the second motor 2, and can detect the torque, rotation speed, power, temperature and fault status of the second motor 2, and can transmit it to the vehicle controller. The shift controller is electrically connected to the first two-way clutch 4 and the second clutch 5 , and can detect the states of the first two-way clutch 4 and the second clutch 5 and transmit them to the vehicle controller.

The vehicle controller sends the first two-way clutch 4 and the second clutch 5 control commands to the shift controller, the vehicle controller controls the actuators of the two clutches to execute the above control commands, and the vehicle controller sends the motor torque and speed control commands To the first motor 1 controller and the second motor 2 controller, the first motor 1 controller and the second motor 2 controller execute control instructions, and control the first motor 1 and the second motor 2 to operate according to the instructions.

The first two-way clutch 4 has three states: separation, engagement and slipping. These three states can be controlled by the vehicle controller. When the state is in the disengaged state, the parts at both ends of the clutch cannot transmit power; when the state is in the combined state, the parts at both ends of the clutch can transmit power normally; when the state is in the slipping state, the clutch can transmit part of the power. An example is as follows: in the state of combination 1, when the first two-way clutch 4 is engaged, the first motor 1 can transmit the driving force to the transmission 3, so as to transmit the driving force to the front wheel final reducer 7 to drive the vehicle. During the vehicle braking process In the middle, the first motor 1 can also be controlled to generate electricity to generate a negative torque to brake the vehicle, so as to realize the function of braking energy recovery. When the first two-way clutch 4 is disengaged, the first motor 1 cannot drive the vehicle, nor can the brake recovery be performed, and the first motor 1 will not generate a resistance to the vehicle.

The second clutch 5 is a one-way clutch or a two-way clutch. The one-way clutch has only one default state. There is no separation or combination of two states, and no controller is required to control it. The one-way clutch can only transmit power from one direction to another direction, and cannot transmit power in the reverse direction. An example is as follows, if the second clutch 5 in the combination 1 is a one-way clutch, the driving force of the second motor 2 can be transmitted to the transmission mechanism 6 through the second clutch 5, that is, the second motor 2 can drive the vehicle forward. , but can not drive the vehicle backwards, and when the vehicle is driving forward, when the vehicle is decelerating under braking conditions, due to the one-way nature of the transmission force of the one-way clutch, the second motor 2 will not produce a block that hinders the vehicle from moving forward. The resistance of the second motor 2 is also unable to realize the braking energy recovery function: that is, by controlling the second motor 2 to generate a negative torque to generate a negative torque to brake the vehicle, and at the same time, the feedback energy is stored in the power battery.

The transmission 3 is a two-speed transmission 3 having two speed ratios. The transmission 3 includes an input shaft of the transmission 3, an output shaft of the transmission 3, a first-speed gear pair of the transmission 3, a second-speed gear pair of the transmission 3, a shifting mechanism and other components.

The first motor 1 and the second motor 2 are the same type of motor, both of which are permanent magnet synchronous motors. The transmission mechanism 6 is a gear transmission mechanism 6, a chain transmission mechanism 6, etc., and has a speed ratio.

Embodiment 2

This embodiment discloses a control method for a 4WD pure electric vehicle power system, which adopts the 4WD pure electric vehicle power system in the first embodiment, and the control method includes driving driving control, braking driving control and shifting control.

The driving form control includes the following steps:

Calculate the driving torque required for the vehicle to run;

Determine whether the driving torque is greater than the maximum torque that can be generated by the first motor 1 to the wheel end;

If not, the first motor 1 drives the vehicle, and the second motor 2 is in a stationary state. Specifically, when the running torque is not greater than the maximum torque generated by the first motor 1 to the wheel ends, the vehicle is running under low load conditions, such as vehicle starting, smooth acceleration, stable high-speed running, and the like. When the second clutch 5 is a two-way clutch, the first two-way clutch 4 is in an engaged state, the second clutch 5 is in a disengaged state, the first motor 1 is running, and the second motor 2 is in a stationary state, so that the first motor 1 drives the vehicle to run, The second motor 2 does not provide driving force. When the second clutch 5 is a one-way clutch, the first two-way clutch 4 is in a combined state, the first motor 1 is running, and the second motor 2 is in a static state; so that the first motor 1 drives the vehicle, and the second motor 2 does not provide power .

If yes, then the first motor 1 and the second motor 2 drive the vehicle simultaneously; specifically, the driving torque is greater than the maximum torque that can be generated by the first motor 1 to the wheel end, and the vehicle is running under a heavy load condition, such as a vehicle Rapid acceleration, uphill slope, high-speed overtaking, etc., at this time, both the first motor 1 and the second motor 2 are required to provide power to drive the vehicle. When the second clutch 5 is a two-way clutch, both the first two-way clutch 4 and the second clutch 5 are in a combined state, the first motor 1 and the second motor 2 are both running, and both drive the vehicle to run simultaneously. When the second clutch 5 is a one-way clutch, the first two-way clutch 4 is in a combined state, the first motor 1 and the second motor 2 are both running, and both drive the vehicle to run at the same time.

Take the transmission 3 arranged on the front axle as an example to illustrate: when the vehicle is driving, the vehicle controller calculates the driving torque T_driver required by the wheel end according to the accelerator pedal opening, the brake pedal state and the vehicle speed signal. The calculation method is as follows: A common technology in the industry, at this time, the controller of the first motor 1 reports the maximum available torque T1 of the first motor 1 according to the state of the first motor 1. The maximum torque that can be generated by the first motor 1 to the wheel end is T1*i11, and i11 is The product of the first gear ratio of the transmission 3 and the speed ratio of the front wheel main reducer 7. At this time, the second motor 2 controller reports the maximum available torque T2 of the second motor 2 according to the state of the second motor 2. The maximum torque that can be generated at the wheel end is T2*i21, where i21 is the product of the first gear ratio and the speed ratio of the rear wheel final reducer 8.

When T_driver≤T1*i11, that is, in the region A, B or C in FIG. 9 , the first motor 1 drives the vehicle alone, the first motor 1 outputs power according to the driving torque requirement, and the first two-way clutch 4 is engaged , the second motor 2 is in a static state and does not output torque, the second clutch 5 is disengaged if it is a double clutch, and the one-way clutch does not need to be controlled. As shown in Figures 1 and 2, due to the disengagement of the second clutch 5 (if it is a dual clutch, the one-way clutch does not need to be controlled), the second motor 2 is disconnected from the wheels and does not transmit power. The mechanical frictional resistance of the second motor 2 itself will not hinder the vehicle from moving forward. As shown in Figures 3 and 4, due to the separation of the second clutch 5, the second motor 2 and the transmission mechanism 6 are separated from the wheels at this time. The mechanical frictional resistance of the motor 2 and the transmission mechanism 6 itself will not hinder the vehicle from moving forward. The second motor 2 is stationary, and the permanent magnet synchronous motor does not generate field weakening current to consume battery power. Compared with the prior art (without clutch), the vehicle resistance is lower, and the use efficiency of a motor-driven vehicle in the present invention is higher, the power consumption of the whole vehicle is lower, and the driving mileage is longer.

When T1*i11<T_driver, both the first motor 1 and the second motor 2 are involved in driving the vehicle, both clutches are engaged, and the output torques of the front and rear axles are both T_driver/2.

The braking demand torque during braking is defined as a negative value. Similarly, the allowable braking feedback torque of the first motor 1 and the second motor 2 is also a negative value. In order to avoid ambiguity, the following describes the process, and the torque values are both Its absolute value size, without negative sign.

When the second clutch 5 is a one-way clutch, the braking travel control includes the following steps:

Calculate the braking torque required for vehicle braking;

Determine whether the braking torque is greater than the negative torque generated by the first motor 1;

If no, at this time the driver lightly steps on the brake pedal, and the braking demand is small; then the first two-way clutch 4 is in the engaged state, the negative torque generated by the first motor 1 brakes the vehicle, and at the same time, the first motor 1 is used to brake the vehicle. Negative torque generates electricity; the second electric machine 2 is at rest and does not generate torque.

If it is, it is emergency braking at this time, the driver depresses the brake pedal hard, and the braking demand is very large, then the first two-way clutch 4 is in the engaged state, and the negative torque generated by the first motor 1 provides part of the torque for vehicle braking, Another part of the braking torque is provided by the hydraulic braking system of the vehicle, while the negative torque of the first electric machine 1 is used to generate electricity. The second electric machine 2 is in a stationary state and does not generate torque.

Taking the structure of combination 5 in Fig. 5 as an example, the specific example is described as follows: the vehicle controller calculates the braking torque T_brake required by the wheel end according to the pressure of the driver's brake master cylinder and the state of the accelerator pedal, and the first motor 1 The size of its own allowable braking torque is T1, and i11 is the product of the speed ratio of the transmission 3 and the first final reducer.

As shown in Figure 10, when T_brake≤T1*i11, that is, in the A1, B1 or C1 area, the vehicle controller sends a control command according to the braking demand torque, the first motor 1 generates electricity, and the generated negative torque brakes the vehicle. At the same time, the generated electric energy is stored in the power battery, and the first two-way clutch 4 is engaged. The second motor 2 does not work, does not rotate with it, and is in a static state. At this time, one motor is braked and recovered, and its efficiency is higher than that of the two motors, which recovers more electric energy and is more conducive to the overall power consumption of the vehicle. decrease; when T1*i11<T_brake, the vehicle controller sends a control command according to the braking demand torque, the first motor 1 generates a negative torque T2 to meet part of the braking demand (the satisfied part is T2*i21,), not satisfying part is provided by a conventional hydraulic braking system.

When the second clutch 5 is a two-way clutch, the braking travel control includes the following steps:

Calculate the braking torque required for vehicle braking;

Determine whether the braking torque is greater than the negative torque generated by the first motor 1;

If no, at this time the driver lightly steps on the brake pedal, and the braking demand is small; then the first two-way clutch 4 is in the engaged state, the negative torque generated by the first motor 1 brakes the vehicle, and at the same time, the first motor 1 is used to brake the vehicle. Negative torque generates electricity; the second clutch 5 is in a disengaged state, and the second motor 2 is in a static state, and no torque is generated.

If so, determine whether the braking torque is greater than the sum of the negative torques generated by the first motor 1 and the second motor 2;

If no, the driver may be stepping on the brake pedal in the middle at this time, and the braking demand is large, then the first two-way clutch 4 and the second clutch 5 are both in the engaged state, and the negative torque generated by the first motor 1 and the second motor 2 is generated. Brake the vehicle and use the negative torque of the first motor 1 and the second motor 2 to generate electricity;

If it is, emergency braking at this time, the driver depresses the brake pedal hard, and the braking demand is very large, the braking torque is provided by the hydraulic braking system of the vehicle.

Taking the structure in combination 5 as an example, the specific example is described as follows: the vehicle controller calculates the required braking torque T_brake at the wheel end according to the pressure of the driver's brake master cylinder and the state of the accelerator pedal, the first motor 1 and the second motor 2 Report their allowable braking torque T1, T2 respectively, i11, i21 are the product of the speed ratio of the transmission 3, the first main reducer, and the speed ratio of the second main reducer, respectively.

As shown in Figure 10, when T_brake≤T1*i11, that is, in the A1, B1 or C1 area, the vehicle controller sends a control command according to the braking demand torque, the first motor 1 generates electricity, and the generated negative torque brakes the vehicle. At the same time, the generated electric energy is stored in the power battery, and the first two-way clutch 4 is engaged. The second motor 2 does not work and does not rotate with it. At this time, one motor is braked and recovered, and its efficiency is higher than that of the two motors recovered separately, and the recovered electric energy is more, which is more conducive to the reduction of the overall power consumption of the vehicle; when When T1*i11＜T_brake≤T2*i21+T1*i11, the vehicle controller sends a control command according to the braking demand torque, the first motor 1 and the second motor 2 both generate negative torque, and the output braking torque is T_brake /2; When T_brake>T2*i21+T1*i11, neither the first motor 1 nor the second motor 2 works, even the clutches are maintained in the default engagement state, and the braking requirement is met by the traditional hydraulic braking system.

According to the current vehicle speed, the torque allocated to the front or rear axle, combined with the torque, speed, efficiency and other factors of the motor, a shifting strategy is formulated to determine whether the current gear is the first gear or the second gear. An example of the structure in combination 1 is described below, taking the front axis as an example.

As shown in Figure 9, V11 is the highest speed that can be achieved in first gear, and V12 is the highest speed that can be achieved in second gear. When the torque and vehicle speed allocated to the front axle motor are in the B region, the transmission 3 is in second gear at this time. When the torque and vehicle speed allocated to the front axle motor are in the C area, the transmission 3 is in the first gear at this time. When it is in the A area, the gear shift is carried out according to the shifting rule. The specific shifting rule formulation method is shown in Figure 11. According to Motor efficiency map, if the motor works in the first gear at the current moment, its operating point is as shown in point B in Figure 11. If the motor works in the second gear at the current moment, its operating point is as shown in point A in Figure 11, if the motor efficiency of point A is shown in Figure 11. If the motor efficiency is higher than that corresponding to point B, the transmission 3 is in the second gear at this time, otherwise, it is in the first gear. According to the above method, the shift rule curve is formulated as shown in Figure 12. The boundary line between the A area and the B area in FIG. 12 is the downshift line, and the boundary line between the B area and the C area is the upshift line. Based on these two lines, it is determined whether to perform an upshift or a downshift.

When the first two-way clutch 4 is provided between the first motor 1 and the transmission 3, the first motor 1 and the transmission 3 are drive-connected; The shifting control includes the following steps: shifting by adjusting the state of the first two-way clutch 4 .

When the first two-way clutch 4 is arranged at the output end of the transmission 3, that is, in the state of the combination 2, the combination 4, the combination 6 and the combination 8, the shift control includes the first gear up to the second gear and the second gear down to the first gear,

The first and second gears include:

The first motor 1 reduces the torque to 0;

Shift actuator to remove gear;

Reduce the speed of the first motor 1 to the target speed of the second gear;

The shift actuator performs the shift to the second gear. Among them, the target speed of the second gear = the current motor speed * the speed ratio of the second gear / the speed ratio of the first gear.

Among them, the second gear and the first gear include:

The first motor 1 reduces the torque to 0;

Shift actuator to remove gear;

Reduce the speed of the first motor 1 to the target speed of the first gear;

The shift actuator performs the shift to first gear. Among them, the target speed of the first gear = the current motor speed of the change * the speed ratio of the first gear/the speed ratio of the second gear.

This embodiment also discloses a vehicle, which is characterized in that it adopts the above-mentioned control method for a power system of a four-wheel drive pure electric vehicle.

Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. A control method of a four-wheel-drive pure electric vehicle power system is characterized in that a first motor (1), a second motor (2), a transmission (3) and a first two-way clutch (4) are arranged on a vehicle, the first motor (1) is in transmission connection with wheels of the vehicle through the first two-way clutch (4) and the transmission (3), the second motor (2) is in transmission connection with the wheels of the vehicle, and the first motor (1) and the second motor (2) are used for driving the vehicle to run, and the control method comprises a driving running control and comprises the following steps:

calculating a driving torque required by the driving of the vehicle;

determining whether the running torque is larger than a maximum torque that can be generated from the first motor (1) to a wheel end;

if yes, the first motor (1) and the second motor (2) drive the vehicle to run simultaneously;

if not, the first motor (1) drives the vehicle to run, and the second motor (2) is in a static state.

2. The control method of a four-wheel drive electric-only vehicle powertrain according to claim 1, characterized in that the transmission (3) is arranged on a front axle of a vehicle, the first electric machine (1) is drivingly connected to front wheels of the vehicle via the first bi-directional clutch (4) and the transmission (3), and the second electric machine (2) is drivingly connected to rear wheels of the vehicle via a second clutch (5).

3. A control method of a four-wheel drive electric-only vehicle powertrain according to claim 1, characterized in that the transmission (3) is arranged on a rear axle of a vehicle, the first electric machine (1) is drivingly connected to rear wheels of the vehicle via the first bi-directional clutch (4) and the transmission (3), and the second electric machine (2) is drivingly connected to front wheels of the vehicle via a second clutch (5).

4. The control method of the four-wheel drive pure electric vehicle power system according to claim 2 or 3, characterized in that the second clutch (5) is a two-way clutch, and when the first electric machine (1) and the second electric machine (2) drive the vehicle to run simultaneously, the second clutch (5) is in a combined state; when the second motor (2) is in a static state, the second clutch (5) is in a separation state;

or the second clutch (5) is a one-way clutch which can only transmit the power of the second motor (2) to wheels and can not transmit the power reversely.

5. The control method of the four-wheel drive pure electric vehicle power system according to claim 4, characterized by further comprising a braking driving control, wherein when the second clutch (5) is a one-way clutch, the braking driving control comprises the following steps:

calculating the braking torque required by vehicle braking;

-determining whether the braking torque is greater than a negative torque generated by the first electric machine (1);

if not, the negative torque generated by the first motor (1) brakes the vehicle, and meanwhile, the negative torque of the first motor (1) is used for generating power;

if yes, the negative torque generated by the first motor (1) provides partial torque for vehicle braking, and the other part of braking torque is provided by a hydraulic braking system of the vehicle, and meanwhile, the negative torque of the first motor (1) is used for generating power.

6. The control method of the four-wheel drive pure electric vehicle power system according to claim 4, characterized by further comprising a braking driving control, wherein when the second clutch (5) is a bidirectional clutch, the braking driving control comprises the following steps:

calculating the braking torque required by vehicle braking;

-determining whether the braking torque is greater than a negative torque generated by the first electric machine (1);

if not, the negative torque generated by the first motor (1) brakes the vehicle, and meanwhile, the negative torque of the first motor (1) is used for generating power;

if yes, determining whether the braking torque is larger than the sum of negative torques generated by the first motor (1) and the second motor (2);

if not, braking the vehicle by using the negative torque generated by the first motor (1) and the second motor (2), and simultaneously generating power by using the negative torque of the first motor (1) and the second motor (2);

if so, braking torque is provided by the hydraulic braking system of the vehicle.

7. The control method of the four-wheel drive pure electric vehicle power system according to claim 1, characterized in that the transmission (3) is a two-gear transmission, the first bidirectional clutch (4) is arranged between the first electric machine (1) and the transmission (3), and when the first electric machine (1) and the transmission (3) are in transmission connection; the control method further includes shift control including the steps of:

shifting is performed by adjusting the state of the first bidirectional clutch (4).

8. The control method of the four-wheel drive electric vehicle powertrain according to claim 1, characterized in that the transmission (3) is a two-gear transmission, and the first bidirectional clutch (4) is provided at the output of the transmission (3); the control method further includes a shift control including one gear up and two gears, including:

the first motor (1) reduces the torque to 0;

the gear shifting actuating mechanism is used for gear shifting;

reducing the rotating speed of the first motor (1) to a second target rotating speed;

and the gear shifting actuating mechanism shifts gears to the second gear.

9. The method of controlling a four-wheel-drive electric-only vehicle powertrain of claim 8, wherein the shift control further includes a second gear down shift by a first gear comprising:

the first motor (1) reduces the torque to 0;

the gear shifting actuating mechanism is used for gear shifting;

reducing the rotating speed of the first motor (1) to a first gear target rotating speed;

and the gear shifting actuating mechanism shifts gears to shift to the first gear.

10. A vehicle, characterized in that it employs the control method of the four-wheel-drive pure electric vehicle powertrain according to any one of claims 1 to 9.

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