JPS63312269A - Method of controlling rear wheel steering operation for automobile - Google Patents

Abstract

PURPOSE:To facilitate the roll-in and -out of a vehicle to and from a garage by variably controlling the steering angle of the rear wheels of the vehicle in such a range that the vehicle body does no make contact with an obstruct, in accordance with the distance between the vehicle body and the obstacle. CONSTITUTION:There are provided and obstacle detector 13 and a forward and backward movement detector 14 for detecting whether a vehicle body is moved forward or backward. A control unit 2 receives signals from these detectors, and determines the direction of steering of rear wheels R in accordance with the vehicle speed V from a vehicle speed detector 11 and a front wheel steering angle thetaf so as to steer the rear wheels R in a direction reverse to a steering direction of front wheels F in the case of, for example, a low speed running, but to steer the rear wheels R in the same direction as the steering direction of the front wheels F in the case of high speed running. Further, the control unit determines a rear wheel steering angle in accordance with the ratio between the front wheel steering angle and the rear wheel steering angle, that is, the front and rear wheel steering ratio, and the thus determined value is delivered to a rear wheel steering mechanism 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for controlling rear wheel steering of an automobile.

Conventional technology In automobiles, when the front wheels are steered by steering the steering wheel, for example, at low i1j speeds, the rear wheels are steered in the opposite direction to the direction in which the front wheels are steered to improve maneuverability. Various rear wheel steering devices have been developed in the past that aim to improve stability by steering the rear wheels in the same direction as the front wheels at high vehicle speeds.

In a vehicle equipped with a rear wheel steering device as described above, when steering in a place where there is not much room on either side, such as when entering or leaving a garage, the rear wheels may shift as the front wheels are steered. The problem is that the steering is performed in the opposite direction to that of the front wheels, and the rear of the vehicle body moves left and right, making it extremely difficult to drive.

Therefore, a lateral distance detector is installed to detect the distance between the side of the vehicle body and an obstacle on the side, and when the distance to the obstacle on the side is less than a set value, the rear wheel steering angle is maintained at zero, that is, in a straight-ahead state. A device for this purpose has been developed and published in Japanese Unexamined Patent Publication No. 1986-1
It is published in Publication No. 81778.

Problem to be Solved by the Invention As stated in Problem 1-1 above, it is difficult to set the rear wheel steering angle to zero when the distance to a side obstacle is less than a set value. For example, when driving on a narrow road, the various advantages of the rear wheel steering system are not utilized at all when steering the vehicle into a garage or out of a small distance, which is extremely inconvenient.

The present invention aims to address the above-mentioned problems.

Means for Solving the Problems In the rear wheel steering device as described above, the present invention provides an obstacle detector for detecting obstacles around the vehicle body, and when the obstacle detector detects an obstacle during steering, The present invention is characterized in that a rear wheel steering angle is determined to obtain a vehicle turning trajectory that does not cause the vehicle body to come into contact with an obstacle, and the rear wheel steering angle is variably controlled in accordance with the distance between the vehicle body and the obstacle.

As a result of the above, when maneuvering in narrow spaces such as entering or exiting the garage, maximum maneuverability can be ensured without the vehicle body coming into contact with obstacles, improving steering performance in narrow spaces. obtain.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

In Fig. 1, B is the vehicle body, and the rear wheel R is a rear wheel consisting of an actuator such as an electric motor or a hydraulic cylinder operated by a command from a control unit, and a mechanism that transmits the operation of the actuator to the rear wheels. It is designed to be steered by a steering mechanism.

As shown in FIG. 2, the control unit 2 generally uses the heavy speed signal V of the vehicle speed detector 11 and the front wheel steering angle signal Of of the front wheel F steering angle detector 12. For example, in the case of a low vehicle speed, The rear wheel R is steered in the opposite direction to the steering direction of the front wheels F (reverse phase steering), and at high vehicle speeds, the rear wheel R is steered in the same direction as the front wheel steering direction (in-phase steering). In addition to determining the wheel steering direction, the rear wheel steering angle to be steered is determined based on the preset ratio of the rear wheel steering angle to the front wheel steering angle, that is, the front and rear wheel steering angle ratio. In order to perform wheel steering, an output is issued to the rear wheel steering mechanism 3, and the rear wheel steering mechanism 3 operates to steer the rear wheels R.

In the present invention, the present invention includes, for example, an ultrasonic transmitter/receiver and a distance calculation section (the distance calculation section may be incorporated in the control unit 2), etc., for detecting the presence or absence of obstacles around the vehicle body and the distance to the obstacles. An obstacle detector 13 and a forward/backward detector 14 for detecting whether the vehicle body is in the forward state IE are provided, and signals from these detectors 13 and 14 are input to the control unit 2 to perform control as described below. This is how it was done.

That is, when the front wheels are steered by operating the steering wheel while a forward signal is input from the forward/reverse detector 14, the control unit 2 performs steering based on the vehicle speed signal V and the front wheel steering angle signal of, as described above. The rear wheel steering angle (including the direction in which the rear wheels are steered) to be steered is determined, and an output signal is issued to the rear wheel steering mechanism 3 to perform rear wheel steering. When a signal indicating that an obstacle exists on the side of the vehicle body in the direction opposite to the front wheel steering direction is input from the control unit 2, the control unit 2 adjusts the wheelbase and front and rear body overhangs.

Based on the vehicle body dimensions stored in advance, such as the vehicle width, the distance between the left and right front wheels, and the distance between the left and right front wheels, and the front wheel steering angle information, the trajectory that the rear end of the vehicle near the obstacle will take is determined. Find the maximum value a of the amount of lateral displacement, compare this value a with the estimated distance to the obstacle, and if a > 1-α, a is set to a predetermined value α (for example, about ioam). This system calculates the rear wheel steering angle that can take a trajectory that is smaller than the specified value (set), issues an output signal, and steers the rear wheels according to the calculated rear wheel steering angle. .

The control mode of the control unit 2 as described above is the third
This is as shown in the flowchart of the figure, and the target value of the steering angle 11 of the rear wheels with respect to the distance 2 to the obstacle is as shown by the solid line in FIG.

By controlling the rear wheel steering angle as described above, ・Even when steering in a place where there is not much margin between the 11th vehicle and an obstacle, 4-wheel steering can be performed within the range where the vehicle body does not come into contact with the obstacle. It is possible to maximize the ability to maneuver, which is one of its characteristics.

Effects of the Invention As described in 1-1, according to the present invention, in a low vehicle speed range, the rear wheels are steered in a direction opposite to the direction in which the front wheels are steered to improve maneuverability, and in a high vehicle speed range, the rear wheels are steered in a direction opposite to the direction in which the front wheels are steered. In a vehicle that performs rear wheel steering control to improve stability by steering in the same direction as the wheel steering direction, an obstacle detector that detects obstacles around a heavy object is installed, and the obstacle detector is located near the vehicle body. When steering when an obstacle is detected, the rear wheel steering angle is variably controlled according to the distance between the vehicle and the obstacle within a range where the vehicle does not come into contact with the obstacle. When steering in narrow spaces, such as when steering into or out of the garage, the vehicle maximizes the maneuverability unique to 4-wheel steering without making contact with obstacles, making it easy to enter or exit the garage. This can be done in a number of ways, and can bring about great practical effects.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the present invention, and FIG. 1 is an explanatory plan view during steering when an obstacle is near the side of the vehicle;
FIG. 2 is a block diagram showing an example of a rear wheel steering control device, FIG. 3 is a flow chart showing an example of a rear wheel steering control mode,
FIG. 4 is a diagram showing an example of rear wheel turning angle target values with respect to the distance from the vehicle body to an obstacle. 2... Control unit, 3... Rear wheel steering mechanism, 11... Vehicle speed detector, 12... Front wheel steering angle detector, 13... Obstacle detector, 14... Forward/reverse Detector. that's all

Claims (1)

[Claims] The control unit uses the vehicle speed signal and the front wheel steering angle signal to control the rear wheels to steer in the opposite direction to the front wheel steering direction in low vehicle speed ranges and in the same direction as the front wheel steering direction in high vehicle speed ranges. The wheel steering system is equipped with an obstacle detector that detects obstacles around the vehicle body, and when the obstacle detector detects an obstacle during steering, the control unit compares the vehicle turning trajectory and the distance to the obstacle. The vehicle is characterized in that the rear wheel steering angle is calculated to obtain a turning trajectory in which the vehicle body does not come into contact with obstacles, and the rear wheel steering angle is variably controlled according to the distance to the obstacle. Wheel steering control method.