JP2646005B2 - Control method of rear wheel turning amount - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling a rear wheel turning amount in a four-wheel steering system.

[Conventional technology]

A conventional control method of this type is disclosed in Japanese Patent Application Laid-Open No. 62-146779. The control method of the rear wheel turning angle described in the publication is to reduce the steering angle ratio at an extremely low speed.

[Problems to be solved by the invention]

However, when the above-described control method is applied to an electric power steering device, when the rear wheels are steered, parked, and the engine is running, the rear wheels are continuously assisted, and eventually the battery is overcharged. There was a risk of discharge.

The present invention has been made in view of such a point,
It is an object of the present invention to provide a method of controlling the amount of rear wheel turning in which the battery is not over-discharged.

[Means for solving the problem]

In order to solve such a problem, the method of controlling the amount of rear wheel turning according to the present invention provides a method of energizing the assist motor when the vehicle is stopped and the front wheel turning angle (front steering angle) does not change. Is gradually reduced to stop the assist in a certain time.

[Action]

In the method of controlling the rear wheel turning amount according to the present invention, overdischarge of the battery is prevented.

〔Example〕

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

In FIG. 2, a controller 3 receives a vehicle speed signal a and a front steering angle signal b, and determines whether the vehicle is stopped and a change in a front steering angle (a steering wheel angle) as a front wheel turning angle.

FIG. 3 shows an H-bridge circuit for driving the rear wheel steering motor 2a. In the figure, 11 to 14 are transistors, T1 is a power supply terminal to which a power supply voltage from a battery is supplied, RL is a relay, and E is a ground. First, the arrow AR1 shown by a solid line
The operation when a current is supplied in the direction of will be described.
The power supply voltage is supplied from the terminal T to the H bridge circuit via the “closed” relay RL. In order to flow a current in the direction of the arrow AR1, as shown in FIG. 4, the transistor 11 is turned on and off at a certain duty ratio, the transistor 14 is turned on, and the transistors 12 and 13 are turned off. As a result, current flows as indicated by arrow AR1, and electric motor 2a rotates in one direction.

When a current flows in the direction of arrow AR2, as shown in FIG. 5, transistor 12 is turned on / off at a certain duty ratio, transistor 13 is turned on, and transistors 11 and 14 are turned off. As a result, a current flows as shown by a dashed arrow AR2 in FIG. 3, and the electric motor 2a rotates in a direction opposite to that in the case of the arrow AR1.

Next, an embodiment of a method for controlling the amount of rear wheel turning according to the present invention will be described with reference to the flowchart of FIG. After the main control A ends (step 21), it is determined whether or not the vehicle speed is zero (step 22). If the vehicle speed is zero, the process proceeds to step 23; That is, when the vehicle speed is not zero, or when there is a change in the front steering angle even when the vehicle speed is zero, the duty ratio corresponding to 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 rudder angle, a predetermined value m
The value obtained by subtracting is used as the new duty ratio (steps 25 to 2
7). When the duty ratio is calculated in step 24 or steps 25 to 27, the on / off control of the transistor 11 or 12 is performed at this duty ratio (step 28, see FIGS. 4 and 5). Next, in step 29, the process of the main control B is performed, and the process returns to the first process of the main control A.

By repeating the processing 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, steps 25 to 27 are performed.
The new duty ratio calculated by the above becomes zero, the power supply to the rear wheel steering motor 2a is stopped, and the assist is stopped.

Further, in this embodiment, the assist is stopped based on the vehicle speed and the front rudder angle. However, it is also possible to prevent the overdischarge by determining the stop based on the parking brake signal, the gear shift signal, and the like, and generating a change in the assist amount. It is.

〔The invention's effect〕

As described above, in the method of controlling the amount of rear wheel turning according to the present invention, when the vehicle is stopped and the front steering angle does not change, the power supply to the assist motor is gradually reduced, and By stopping the vehicle, even when the rear wheel is steered and parked to start the engine, the rear wheel is not continuously assisted, so that there is an effect that overdischarge of the battery can be prevented. .

[Brief description of the drawings]

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

Claims (1)

(57) [Claims] 1. A front wheel steering mechanism for steering a front wheel, a rear wheel steering mechanism for steering a rear wheel, and a steering angle ratio calculating mechanism for calculating a steering angle ratio corresponding to a front wheel steering angle or a 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 stopped and the front wheel steering angle does not change, the energization of the electric motor is gradually performed. A method of controlling the amount of rear wheel turning to decrease and stop assist in a certain time.