JPH01285463A - Control method for rear-wheel steered variable - Google Patents

Abstract

PURPOSE:To prevent the over-discharge of a battery from occurring by decreasing the extent of current-energization to an assist motor by degrees, and making it so as to come to an assist stop at a specified time in the case where a vehicle is in a stopped state and there is no variation in a steering angle. CONSTITUTION:A four-wheel steering system is provided with a front-wheel steering mechanism 1, a rear-wheel steering mechanism 2, and a steering angle ratio operational mechanism 3 operating a steering angle ratio corresponding to a front-wheel steering angle or car speed. The steering angle ratio operational mechanism 3 inputs a car speed signal and a front steering angle signal and judges on whether there are stoppage of a vehicle and any variation in a front steering angle as a front-wheel steering angle or not. In the case where a car speed is zero and there is no variation in the front steering angle, a duty ratio, turning a transistor to drive an electric motor to ON or OFF, is made so as to be gradually decreased, and after the elapse of the specified time, this duty ratio is made so as to become zero and thereby the transistor is turned to OFF, thus current-energization to a rear-wheel steering motor 2a is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the amount of rear wheel turning in a four-wheel steering system.

[Conventional technology]

A conventional control method of this type is disclosed in Japanese Patent Application Laid-Open No. 1467-1986.
There is one described in Publication No. 79.

The method for controlling the rear wheel steering angle described in the publication is to reduce the steering angle ratio at extremely low speeds.

[Problem to be solved by the invention]

However, when the above-mentioned control method is applied to an electric power steering system, when the rear wheels are steered and parked and the engine is running, the rear wheels are continuously assisted, which ultimately leads to battery overload. There was a risk of electrical discharge.

The present invention has been made in view of these points, and an object of the present invention is to provide a method for controlling the amount of rear wheel turning that prevents the battery from becoming over-discharged.

[Means to solve the problem]

In order to solve these problems, the method of controlling the amount of rear wheel turning according to the present invention gradually decreases the power supply to the assist motor when the vehicle is stopped and there is no change in the steering angle. The assist is stopped depending on the time.

[Effect]

In the method for controlling the amount of rear wheel turning according to the present invention, over-discharge of the battery is prevented.

〔Example〕

FIG. 2 is a configuration diagram showing a general four-wheel steering system.
In the figure, 1 is a front wheel steering device having a front wheel steering mechanism, la is a steering angle sensor, 2 is a rear wheel steering device having a rear wheel steering mechanism, 2a is a rear wheel steering electric motor, 2b is a reduction gear,
2c is a steering angle sensor, 2d is a centering spring,
3 is a controller to which vehicle speed signal a, front steering angle signal etc. are input, 4 is a safety relay as a relay for supplying power to the electric motor 2a, 5 is a fuse, 6 is an ignition switch, and T is supplied with power from the battery. This is the power supply terminal.

In FIG. 2, the controller 3 manually inputs the vehicle speed signal a and the front steering angle signal A, and determines whether the vehicle has stopped or whether the front steering angle (steering wheel angle) has changed as the front wheel turning angle.

FIG. 3 shows an H-bridge circuit that drives the rear wheel steering electric motor 2a. In the figure, 11 to 14 are transistors;
T1 is a power terminal to which power voltage from the battery is supplied, RL is a relay, and E is a ground. First, the operation when a current is caused to flow in the direction of the arrow ARI shown by the solid line will be described. Power supply voltage is supplied to the H bridge circuit from terminal T via relay RL which is in the "closed" state. To flow a current in the direction of the arrow API, as shown in FIG. 4, the transistor 11 is turned on and off at a duty ratio, the transistor 14 is turned on, and the transistors 12 and 13 are turned off. As a result, a current flows as shown by the arrow API, and the electric motor 2a rotates in one direction.

When flowing current in the direction of arrow AR2, as shown in FIG. 5, the transistor 12 is turned on and off at a duty ratio of
Turn off transistor 13, turn on transistor 11.
14 is turned off. As a result, the dashed arrow A in FIG.
A current flows as shown by R2, and the motor 2a
rotates in the opposite direction.

Next, an embodiment of the method for controlling the amount of rear wheel turning according to the present invention will be described with reference to the flowchart shown in FIG.

The main side? After the IA is completed (step 21), it is determined whether the vehicle speed is zero or not (step 22). If it is zero, the process proceeds to step 23; if it is not zero, the process proceeds to step 24. That is, if the vehicle speed is not zero, or if there is a change in the front steering angle even if the vehicle speed is zero, the duty ratio for the target value of the rear wheel turning amount is calculated (step 24).
. If the vehicle speed is zero and there is no change in the front steering angle, the value obtained by subtracting the predetermined value m from the previous duty ratio is set as the new duty ratio (steps 25 to 27). When the duty ratio is calculated in step 24 or steps 25 to 27, the transistor 11 or 12 is controlled to be on/off based on this duty ratio (step 28, see FIGS. 4 and 5).

Next, in step 29, main control B processing is performed, and the process returns to the first main control A processing.

By repeating the process of the flowchart shown in FIG. 1, the duty ratio gradually decreases when the vehicle speed is zero and there is no change in the front steering angle, and after a predetermined time, step 25
The new duty ratio calculated in steps 27 to 27 becomes zero, power supply to the rear wheel steering electric motor 2a is stopped, and the assist is stopped.

In addition, in this example, the assist is stopped based on the vehicle speed and front wheel steering angle, but it is also possible to determine whether the vehicle has stopped based on the parking brake signal, gear shift signal, etc. and change the amount of assist to prevent overdischarge. It is.

〔Effect of the invention〕

As explained above, in the method for controlling the amount of rear wheel turning according to the present invention, when the vehicle is stopped and there is no change in the steering angle, the power supply to the assist electric motor is gradually reduced, and the assist stops after a certain period of time. By doing so, even when the rear wheels are steered, the vehicle is parked, and the engine is running, the rear wheels are not continuously assisted, which has the effect of preventing over-discharge of the battery.

[Brief explanation of the drawing]

FIG. 1 is a flow chart for explaining one embodiment of the method for controlling the amount of rear wheel turning according to the present invention, and FIG.
A configuration diagram showing the wheel steering system, FIG. 3 is a circuit diagram showing an H-bridge circuit that drives the rear wheel steering electric motor, and FIGS. 4 and 5 are time charts for explaining the operation of the circuit in FIG. 3. It is. DESCRIPTION OF SYMBOLS 1... Front wheel steering device, la, 2c... Steering angle sensor, 2... Rear wheel steering device, 2a... Rear wheel steering electric motor, 2b... Reduction gear, 2d... Centering spring , 3...Controller, 4...Safety relay, 5...Fuse, 6...Ignition switch, T, T1...Power terminal, 11-14...Transistor, RL...Relay, E...Earth.

Claims (1)

[Claims] The vehicle has a front wheel steering mechanism that steers the front wheels, a rear wheel steering mechanism that steers the rear wheels, and a steering angle ratio calculation mechanism that calculates a steering angle ratio corresponding to the front wheel steering angle or the vehicle speed, In an all-electric four-wheel steering system in which the rear wheel steering mechanism is directly controlled by an electric motor, when the vehicle is at a standstill and there is no change in the steering angle, the power to the electric motor is gradually reduced to provide assistance for a certain period of time. A method of controlling the amount of rear wheel turning required for stopping.