JPH01198201A - Controller for braking of electric automobile - Google Patents

Abstract

PURPOSE:To keep the ratio of car deceleration to the quantity of pedalling or the magnitude of force of pedalling at the time of the braking of a car constant by applying the sum of mechanical braking force and the regenerative braking force of a motor when the brake pedal is operated. CONSTITUTION:When a brake pedal 14 is operated, the quantity of pedalling or magnitude of pedalling force of the brake pedal 14 is detected as the quantity of braking in a braking-quantity detecting section 20. A master cylinder 30 is worked in response to the magnitude of the quantity of braking by the brake pedal 14 at that time, and pressure oil is fed to brake mechanisms for each wheel 18 through a brake piping 32. On the other hand, a control section 28 arithmetically operates torque required for a motor 16 in response to the state of the travelling of a car in this case on the basis of a signal from the braking- quantity detecting section 20 and a signal from a revolution detecting section 22 for the motor, and outputs a motor drive signal to a power converter 26 on the basis of the result of the arithmetic operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brake control device for an electric vehicle, and particularly to a brake control device that can improve brake feeling when braking the vehicle.

[Prior Art] In conventional electric vehicles, in addition to mechanical braking force, regenerative braking force of a motor equivalent to the engine brake of an engine vehicle is used, or this regenerative braking force is applied depending on the amount or force of the brake pedal. By changing the braking force,
Efforts are being made to improve vehicle braking characteristics and increase the mileage per charge of the battery using regenerated energy. Conventionally, means have been used to increase the regenerative braking force of the motor in proportion to the amount or force of the brake pedal (for example, Utility Model Application No. 62-15 filed by the present applicant).
1901).

[Problems to be Solved by the Invention] Conventional Problems However, when obtaining braking force by adding mechanical braking force and regenerative braking force of a motor that is proportional to the amount of depression or force of the brake pedal, the amount of depression of the brake pedal or The lock point of the wheels relative to the pedal force may be excessively lower than when only mechanical braking force is used, and even if the amount of brake pedal depression or pedal force is constant, the vehicle speed may decrease due to differences in vehicle speed at that time. There was a problem in that the speed changed, which worsened the brake feeling.

On the other hand, mechanical brakes have a problem in that their braking characteristics change depending on temperature and humidity, making them difficult to control.

Purpose of the Invention This invention was made to solve the problem,
An object of the present invention is to provide a braking control device for an electric vehicle that can improve brake feeling by making constant the ratio of vehicle deceleration to the amount of depression or force of the brake pedal when braking the vehicle.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a brake control device for an electric vehicle that generates mechanical braking force and regenerative braking force of a motor by operating a brake pedal. A braking control device for an electric vehicle that generates mechanical braking force and regenerative braking force of a motor by operating the brake pedal includes a brake amount detection section that detects the amount of braking based on the operation of the brake pedal, and a brake amount detection section that detects the amount of braking based on the operation of the brake pedal. A mechanical braking means that includes a fluid pressure control actuator and applies braking force to the wheels using fluid pressure that changes due to the operation of the fluid pressure control actuator, a rotation speed detection section that detects the rotation speed of the motor, and an interconnection between the battery and the motor. regenerative braking means comprising: a power converter that performs energy conversion; and a control unit that calculates an output torque required for the motor and outputs a motor drive signal to the power converter based on the calculation result.

The control unit calculates the mechanical braking force when the brake pedal is operated and the regenerative braking force of the motor, and controls the regenerative braking force of the motor so that the sum of these braking forces matches the target deceleration characteristic. It is characterized by being made to do.

[Operation] With the above configuration, in the present invention, when the brake pedal is depressed while the electric vehicle is running, the amount of depression or the force of depression at this time is detected by the brake amount detection section. A fluid pressure control actuator is operated according to the amount of depression of the brake pedal at this time, and mechanical braking force is applied to the wheels by this fluid pressure.

In addition, the output torque required for the motor is calculated by the control unit, and the motor is driven by receiving power from the battery based on the drive signal, but since the motor is controlled to decelerate when the brake pedal is depressed, the motor has regenerative braking. Torque is generated, and the regenerated energy at this time is used to charge the battery via the power converter.

In this way, braking action is applied to the electric vehicle by the sum of the mechanical braking force and the regenerative braking force of the motor when the brake pedal is operated.

In the above, a target braking characteristic is set in advance in the control section, and the difference between this target braking force and the mechanical braking force due to the fluid pressure is calculated in the control section, and this difference is used to control the motor's regeneration. Ideal vehicle deceleration characteristics can be obtained by supplementing with power.

[Example code] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a schematic configuration of a braking control device for an electric vehicle according to the present invention.

In the figure, the device of this embodiment includes a mechanical braking means 10 and a regenerative braking means 12 of a motor, and a brake pedal 1.
4 is depressed, the mechanical braking means 10 causes the wheels 18 to
A mechanical braking force by hydraulic pressure is applied to the motor 16 , and a regenerative braking force is generated in the motor 16 by the motor regenerative braking means 12 .

Characteristic features of the present invention include a brake ffi detection unit that detects the amount of braking based on the operation of the brake pedal, a fluid pressure control actuator that is actuated by the operation of the brake pedal, and a fluid pressure control actuator that changes depending on the operation of the fluid pressure control actuator. The vehicle is equipped with mechanical braking means that applies braking force to the wheels using fluid pressure.

In this embodiment, the mechanical braking means 10 includes a wheel 18 and a brake mechanism (not shown) that provides a braking action to the wheel 18.
This brake mechanism is hydraulically driven by a brake pipe 32. Then, when the brake pedal 14 is operated, the brake amount detection section 20 detects that the brake pedal 14
The amount of depression or the magnitude of the depression force is detected as the amount of braking, and the mask cylinder 30 detects the magnitude of the amount of depression on the brake pedal 14 at this time.
It is operated according to the magnitude of the brake amount.

This mask cylinder 30 is, for example, a brake pedal 14
When the amount of depression is large, the brake pedal operates to a large extent and causes a large change in the oil pressure in the brake pipe 32, and on the other hand, when the amount of depression is small, it moves a minute amount and causes a small change in the oil pressure.

By operating the mask cylinder 30, pressure oil is supplied to the brake mechanism of each wheel 18 via the brake pipe 32, and mechanical braking force is applied to each wheel 18.

In addition, in the present invention, a rotation speed detection section that detects the rotation speed of the motor, a power converter that performs mutual energy conversion between the battery and the motor, and a power converter that calculates the output torque necessary for the motor and drives the motor based on the calculation result. The present invention is characterized in that it includes a regenerative braking means for the motor, including a control section that outputs a signal to the power converter.

The control section 28 includes an output torque calculation section 28-1 and a motor control section 28-2, and the control section 28 receives a signal from the brake amount detection section 20 and a signal from the motor rotation speed detection section 22. . Then, based on these signals, the vehicle running state at that time is determined. The motor 16 is driven by a battery 24 mounted on the electric vehicle, and during braking, energy generated by regenerative braking of the motor 16 is used to charge the battery 24. That is, the rotation speed of this motor 16 is detected by the rotation speed detection section 22, but when the vehicle is normally running, the DC power from the battery 24 is converted into three-phase AC power by the power converter 26 and then supplied to the motor 16. Ru.

Furthermore, during braking, the battery 24 is charged by the regenerative braking force of the motor 16.

As described above, the control unit 28 calculates the torque required for the motor 16 according to the vehicle condition, and outputs a motor drive signal to the power converter 26 based on the calculation result.

FIG. 2 shows the relationship between "brake amount and vehicle deceleration characteristics" applied to this embodiment.

Vehicle deceleration generally linearly follows brake pedal force, brake oil pressure, etc., and a vehicle with no play in the brake pedal is considered to have good drivability. Therefore, for example, in this embodiment, C is set as the ideal brake characteristic, and the vehicle deceleration characteristic at this time is set by a map or a calculation formula.

In the above, when the mechanical braking characteristic is shown by the straight line a, it is necessary to obtain the braking force corresponding to the line C minus the straight line a by regenerative braking (horizontal line in FIG. 2). Here, the brake temperature or l! When the mechanical braking characteristics change in a straight line due to temperature and humidity, according to the conventional open control method, the regenerative braking force of the portion corresponding to the horizontal line is directly added to the deceleration characteristic shown by the straight line. Therefore, the braking force applied to the vehicle becomes a straight line d.

However, as in this embodiment, if deceleration feedback control is performed, the regenerative braking force of the motor is controlled.
A braking force corresponding to part # in FIG. 2 is applied, and the vehicle deceleration coincides with the ideal straight line C.

FIG. 3 shows a control flowchart of this embodiment. ' First, in step 100, the magnitude of vehicle deceleration is calculated. That is, vehicle deceleration (acc-r e
a l ) is obtained by multiplying the difference between the motor rotation speed (n mot) and the previous motor rotation speed (lb mot) by a coefficient of -. In step 110, it is determined whether the brake pedal is depressed.

In this embodiment, the stop lamp switch (stop-SW
) is ON, it is assumed that the brake pedal is depressed and the process proceeds to regenerative braking control from step 120 onwards.
When the brake pedal is F, it is determined that the brake pedal is not depressed, and other control is performed.

In step 120, a target deceleration (acc ref) is set, and the target deceleration (acc-ref) at this time is based on the brake depression force, brake depression, brake oil pressure (brk), etc., and motor rotation speed (n
mot) is set from a map or calculation formula. In this embodiment, for example, the characteristic of the straight line C in FIG. 2 mentioned above is set as the In +fi deceleration characteristic. Note that this target deceleration can be arbitrarily changed depending on the vehicle speed at that time even if the brake pedal depression force is the same. Furthermore, the difference in vehicle deceleration (Δacc) is calculated from the target deceleration 1 (acc ref) to the vehicle deceleration (Bc
c real).

Next, in step 130, the motor output torque (t
ref) is determined, and this output torque is the so-called P
This is done by ID control. That is, this PID control uses a proportional constant (KpXΔacc...Kp is a proportional constant), an integral control (KiXΣ(Δacc×Δt)...Ki is the command multiplication, and Δt is the calculation time), and a differential control (KdXΔac
c/Δt...K (d is a proportionality constant). In addition, in some cases, for stable control, the target output torque (t ref) may be added to the motor output torque (t ref).
'refl) is added.

In step 140, it is determined whether the motor output torque (t ref) obtained in step 130 is greater than or equal to the maximum output torque (t max) of the motor;
If the motor maximum output torque is greater than or equal to the motor maximum output torque, step 150
is limited to the maximum output torque of the motor. Also,
In step 160, it is similarly determined whether the calculated motor output torque is less than the minimum torque (t-min) of the motor, and if it is less than the minimum torque, control is performed to the minimum torque of the motor in step 170. be done.

As explained above, according to the embodiment of the present invention, the motor rotation speed is fed back when the vehicle is braked, and the deceleration of the vehicle is determined from the changes in the motor rotation speed, so that when the brake pedal is depressed, the ideal The vehicle deceleration is controlled to achieve a Furthermore, even if the deceleration characteristics of the vehicle based on mechanical braking force change due to temperature, humidity, etc.
This has the advantage that the brake feeling is improved because the rate of vehicle deceleration is constant with respect to the amount and force of the brake pedal depression.

[Effects of the Invention] As explained above, the present invention combines mechanical braking means and motor regenerative braking means, and feedback-controls the regenerative braking force of the motor by operating the brake pedal.
It is possible to make the vehicle deceleration characteristic with respect to the brake amount constant and improve the brake feeling.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a braking control device for an electric vehicle according to the present invention, FIG. 2 is a diagram showing heavy vehicle deceleration characteristics with respect to brake amount,
. FIG. 3 is a diagram showing a control flowchart used in this embodiment. 10... Mechanical braking means 12... Motor regenerative braking means 14... Brake pedal 16... Motor 20... Brake amount detection section 22... Rotation speed detection section 24... Battery 26 ... Power converter 28 ... Control Department Applicant: Toyota Motor Corporation 11 Agent: Patent Attorney Yoshi 1) Kenji [No. 8-561! Figure 2 Fluky 1 Figure 3

Claims (1)

[Scope of Claims] A brake control device for an electric vehicle that generates mechanical braking force and regenerative braking force of a motor by operating a brake pedal, comprising: a brake amount detection section that detects a brake amount based on the operation of the brake pedal; Mechanical braking means includes a fluid pressure control actuator actuated by operating the brake pedal, and applies braking force to the wheels using fluid pressure that changes due to the operation of the fluid pressure control actuator; and a rotation speed detection device that detects the rotation speed of the motor. a power converter that performs mutual energy conversion between the battery and the motor; and a control unit that calculates the output torque required for the motor and outputs a motor drive signal to the power converter based on the calculation result. regenerative braking means; the control unit calculates the mechanical braking force when the brake pedal is operated and the regenerative braking force of the motor, and regenerates the motor so that the sum of these braking forces matches the target deceleration characteristic. A brake control device for an electric vehicle, characterized in that it controls braking force.