JPH02266801A - Brake controller for electric vehicle - Google Patents

Abstract

PURPOSE:To prevent slip of drive wheel upon braking of vehicle and to shorten brake distance by setting the current command value low when an advancing command is produced and electrical braking is carried out during backward powering operation. CONSTITUTION:When a reverse switch 16 is opened and a drive switch 15 is closed under reversely rotating condition of a motor 2, a drive contactor 4 is opened as shown by an arrow 4a and a drive contactor 3 closes as shown by an arrow 3a. When a chopper is operated under this condition, current flows through a field coil 20 in reverse direction from the rotary direction of the motor 2. Since voltage induced in the motor 2 is shortcircuited through a plugging diode 7, a large current flows through the motor 2 even if the duty of a transistor 6 is low. Electrical brake condition is judged based on the duty, and the current flowing through the motor 2 can be lowered by setting the current command low upon closure of the drive switch 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electric vehicle braking control device, and particularly to an electric vehicle control device suitable for electric braking of battery forklifts and the like.

[Conventional technology]

Conventional devices are disclosed in Japanese Patent Application Laid-Open Nos. 56-41701 and 1983.
As described in No. 101302, the prevention of slippage of the drive wheels when the vehicle starts and accelerates is described, but the prevention of slippage when the vehicle is braked is not described.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into account prevention of drive shaft slippage during vehicle braking. In other words, in electric vehicles such as battery forklifts, the front wheels are the driving wheels for loading cargo, and the rear wheels are the steering shafts. Therefore, when applying electric braking to the vehicle from the forward state,
Load is placed on the front wheels, making it extremely difficult to slip. However, when electric braking is applied to a vehicle while it is in reverse, the load on the front wheels is extremely light despite the same braking current, which causes the vehicle to slip easily and reduce braking distance. .

An object of the present invention is to prevent a drive shaft from slipping when braking a vehicle and to shorten the braking distance.

[Means to solve the problem]

The above object can be achieved by setting the braking current command value, that is, the armature current command value of the motor, to a low value when the command is switched from the forward state to the reverse state of the vehicle.

[Effect]

The first current command generating means operates to cause the chopper control device to generate a command value for an armature current of the electric motor. The second current detection means operates to detect an armature current of the motor and feed it back to the chopper control device. The third forward/backward command means operates to detect the direction of travel of the vehicle intended by the operator and transmit it to the first means. The fourth determining means operates to transmit to the first means whether the vehicle is in a moving state or a braking state. As described above, if the current command value is set low when a command is generated in the forward direction and electric braking is performed while the vehicle is moving backward, slippage of the drive shaft can be prevented and the braking distance can be shortened. be able to.

[Example] An example of the present invention will be described below with reference to FIG. 1(a).

1 is a battery, current detector 5.1 motive 2. Forward contactor 3. Reverse contactor 4. It is connected to the field coil 20 and the chopper transistor 6. 7 is a plugging diode, and 8 is a flywheel diode. The control circuit is composed of a microcomputer 10 and a ROM II in which a program is stored. The signal from the forward switch 15 is connected to the microcomputer via the detection circuit 12, and the signal from the reverse switch 16 is connected to the microcomputer via the detection circuit 13. 17 and 18 are excitation coils for driving the forward and reverse contactors 3 and 4, and the amplifier circuit 1 is activated by a signal from the microcomputer.
4, the transistor 19 is driven to energize the coil. Similarly, the transistor 6 is chopper driven via the amplifier circuit 9 to control the speed of the motor. A key switch 21 is connected to a power supply circuit 22.

FIG. 1(b) is a diagram showing the general appearance of a forklift truck, in which a forward/reverse selector switch is located at hand, and the front wheels, which are the drive shaft, are also located as shown in the diagram.

Next, the operation will be explained. When the key switch 21 is closed, the power supply circuit 22 starts operating, power supply voltage is supplied to the microcomputer and ROM, and the microcomputer starts operating. Microcomputer is ROMI
It is designed to operate according to a program that is stored in advance in the I. A flowchart of the program is shown in FIG. The program operates in the order of P1 to P4. As shown in FIG. 3, Pl determines the presence or absence of a signal from the forward switch 15 or reverse switch 16, and turns the transistor 19 on or off. FIG. 1 shows a state in which the reverse switch is closed and the reverse contactor 4 is closed. P
2, as shown in FIG. 4, if the chopper duty given to the transistor 6 is 10 (%) or less, the vehicle is determined to be in a braking state, and if it is 10 (%) or more, the vehicle is determined to be in a running state. I have to. As shown in FIG. 5, P3 further determines the presence or absence of input signals to the forward switch and reverse switch based on the determination obtained in P2.
The current command S is selected from SL, 82, and S3. P4 performs a duty calculation having the control system shown in FIG. 7 based on the determined current command S and the motor current value i obtained by the current detector 5, determines the duty, and drives the transistor 6. That's what I do.

When the transistor 6 is operated as a chopper in the state shown in FIG. 1, the motor 2 rotates in the backward direction.

From this state, when the reverse switch 16 is opened and the forward switch 15 is closed, the forward contactor 4 opens as shown by the arrow 4a, and then the forward contactor 3 closes as shown by the arrow 3a. If the transistor 6 is operated as a chopper in this state, the current direction of the field coil 2o will be opposite to the rotational direction of the motor 2, resulting in plugging braking. In this state, the induced voltage generated in the motor is short-circuited by the plugging diode 7, so the dut given by the transistor 6
Even if y is small, a large current flows through the motor.

Therefore, electric braking can be determined based on this duty. By determining the braking state in this way and setting the current command S to a low value such as 83 when the forward switch 15 indicates, the motor current flowing to the electric motor 2 can be reduced, and the braking torque will also be reduced. This prevents the drive shaft from slipping and shortens the braking distance.

〔Effect of the invention〕

Advantageous Effects of Invention According to the present invention, it is possible to prevent slippage during braking of a vehicle and shorten the braking distance.

[Brief explanation of drawings]

FIG. 1(a) is a circuit diagram showing an embodiment of the present invention, FIG. 1(b) is a diagram showing a forklift, and FIG. 3, 4, 5, and 6 are program flowcharts showing one embodiment of the present invention, and FIG. 7 is a calculation block diagram showing one embodiment of the present invention. 2...Electric motor, 3...Forward contactor, 4...
Reverse contactor, 6...transistor, 10...
Microcomputer, 11...ROM, 15...
Forward switch figure 4 (g)

Claims (1)

[Claims] 1. A first means for generating an armature current command of a motor;
A chopper control device comprising a second means for detecting the armature current, a third means for detecting a forward or reverse command, and a fourth means for determining whether the vehicle is in a running state or a braking state, An electric vehicle brake characterized in that a braking current command value when electrical control is performed when the vehicle is in a reverse moving state is set lower than a braking current command value when electrical braking is performed when the vehicle is in a forward moving state. Control device.