JPS62199569A - Rear wheel steering gear for automobile - Google Patents

Abstract

PURPOSE:To continually perform an adequate control of steering rear wheels, by improving both the head-swing characteristic of a car body controlling front and rear wheels as the reverse phase steering, when the car body generates a small roll angle, and the stability of the car body controlling the front and rear wheels as the same phase steering when the car body generates a large roll angle. CONSTITUTION:A control circuit 4 first decides a car to be in stopping or in running by a car speed signal (b) from a car speed sensor 2, and if the car is in running, the control circuit 4 next determines a rear wheel steering direction from a degree of car body roll angle obtained by a roll angle signal (a) from a roll angle sensor 1. For instance, if the car body roll angle is less than a preset value,a turn is decided to be the turn (low-g turn) of small centripetal acceleration, and the control circuit, which controls the rear wheel steering direction in a direction reverse to a front wheel steering direction obtained by a front wheel steering angle signal (c) from a front wheel steering angle sensor 3, improves the head-swing characteristic of a car body. That is, the control circuit 4 drives an electric motor 6 through a driving circuit 5 thus steering rear wheels 12 to right and left through a reduction gear mechanism 7 and transmitting means 8-11.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a rear wheel steering device for an automobile.

Conventional Technology Various types of automobiles have been developed in which the rear wheels are simultaneously steered when the front wheels are steered by turning the steering wheel. This has already been published in publications such as Japanese Patent Laid-Open Publication No. 55-91458.

Problems to be Solved by the Invention Conventionally, when the front wheels are steered, when the front wheels are steered, the rear wheel steering angle of the front wheels is changed. Generally, the rear wheels are steered at a certain steering angle ratio, and the ratio of the rear wheel steering angle to the front wheel steering angle is controlled to vary depending on the vehicle speed.

However, the yaw angle change and the accompanying vehicle body roll that occur when the front wheels are steered by the steering operation of the steering wheel occur with a time delay compared to the front wheels that are steered. In conventional rear wheel steering systems in which rear wheel steering is controlled by angle, the rear wheel steering angle does not match vehicle body behavior such as yaw and roll, and in particular, the temporal phase difference between yaw and roll with respect to steering operation is If it becomes large, the effect of rear wheel steering may have an adverse effect on the behavior of the vehicle body.

The main purpose of the present invention is to address the above-mentioned conventional problems.

Means for Solving the Problems The present invention provides a roll angle sensor that detects the roll angle of a vehicle body and emits a roll angle signal in accordance with the roll angle, a vehicle speed sensor that detects vehicle speed and emits a vehicle speed signal in accordance with it, and a steering wheel operation system. The front wheel steering angle sensor detects the front wheel steering angle controlled by the front wheel steering angle sensor and issues a front wheel steering angle signal, and the roll angle obtained from the roll angle signal of the roll angle sensor is less than the set value or is greater than or equal to the set value. The rear wheel steering direction is determined relative to the front wheel steering direction obtained from the front wheel steering angle signal from the front wheel steering angle sensor, and the ideal rear wheel steering direction is determined from the roll angle and vehicle speed using the roll angle signal and the vehicle speed signal from the vehicle speed sensor. The present invention is characterized in that rear wheel steering control is performed by a control circuit that determines a steering angle, issues an output, and operates a rear wheel steering actuator to perform rear wheel steering.

As described above, when the vehicle body roll angle is small, the front and rear wheels are steered in opposite phases to improve the turning performance of the vehicle body and improve maneuverability.
When the roll angle is large, the front and rear wheels are steered in the same phase to improve stability, and the rear wheel steering angle is controlled by the size of the vehicle roll angle, making it possible to control rear wheel steering that matches the actual vehicle behavior. Become.

Example An embodiment of the present invention will be described below with reference to a face-to-face situation.

In the figure, l is a roll angle sensor that detects the roll angle of the vehicle body and issues a roll angle signal accordingly.For example, in a car that uses an air suspension with a vehicle height adjuster 71, The provided left and right vehicle height sensors for vehicle height adjustment can also be used as the roll angle sensor 1, and in the case of a vehicle that is not equipped with such a vehicle height sensor, it is generally provided in the past to increase roll rigidity. A device that detects the roll angle from the torsion angle of the stabilizer is used.

2 is a vehicle speed sensor that detects the vehicle speed and issues a vehicle speed signal in accordance with the detected vehicle speed.

Reference numeral 3 denotes a front wheel steering angle sensor that detects the steering angle of a front wheel (not shown) that is steered by rotating a steering wheel (not shown) and generates a front wheel steering angle signal.

4 is a control circuit, and the control circuit 4 rotates the rear wheels based on the roll angle signal a from the roll angle sensor 1, the vehicle speed signal from the vehicle speed sensor 2, and the front wheel steering angle signal C from the front wheel steering angle sensor 3. It determines the direction to be steered, calculates the ideal rear wheel steering angle in that state, generates an output e corresponding to that, operates the drive circuit 5, and drives the electric motor 6 in forward or reverse rotation. be.

When the electric motor 6 is driven to rotate, the pinion gear 8 is rotated via the reduction gear mechanism 7 including the cylindrical ohm 7a and the worm wheel 7b, and the rack shaft 9 that fits the pinion gear 8 is moved in the axial direction. Due to the axial movement of tie rod 9. The rear wheel 12 is steered to the left or right via the knuckle arm 11.

Reference numeral 13 denotes a rear wheel steering angle sensor that detects the actual steering angle of the rear wheels 12 and generates a rear wheel steering angle signal d corresponding to the detected actual steering angle. Feedback control is performed so that the angle substantially matches the ideal rear wheel steering angle.

The control circuit 4 first determines whether the vehicle is stopped or running based on the vehicle speed signal from the vehicle speed sensor 2. If the vehicle is stopped, the rear wheels are not steered, but if the vehicle is running, the roll angle is determined. The rear wheel steering direction is determined from the magnitude of the vehicle body roll angle obtained from the roll angle signal a of the sensor l. In other words, if the vehicle body roll angle is less than a set value (for example, around 1 degree), it is determined that the centripetal acceleration is in a turning state (hereinafter referred to as a low-g turning), and the rear wheel steering direction is determined by the front wheel steering angle signal. The steering direction of the vehicle body is measured in the opposite direction to the front wheel steering direction obtained by C, that is, the front and rear wheels are reversely steered, and if the vehicle body roll angle is greater than the above setting value, the turning direction with a large centripetal acceleration (hereinafter referred to as high It is determined that the steering wheel is in the same state as the front wheel steering direction obtained from the front wheel steering angle signal C, that is, the front and rear wheels, giving priority to stability over turning performance of the vehicle body. In-phase steering.

Based on a setting function that determines the relationship between the roll angle and the rear wheel steering angle using the vehicle speed as a parameter, the vehicle speed signal of the vehicle speed sensor 2 and the roll angle signal a of the roll angle sensor l are The control circuit 4 calculates the ideal steering angle of the wheels, generates an output e to obtain the rear wheel steering direction and the ideal rear wheel steering angle determined as described above, and drives the electric motor 6 to rotate.

The setting function for the control circuit 4 to find the ideal rear wheel steering angle is, for example, in the front and rear wheel reverse phase steering range where the roll angle is less than the set value, the rear wheel steering angle gradually increases as the roll angle increases from zero. After that, the function gradually decreases to the rear wheel steering angle zea, and in the range of front and rear wheel in-phase steering where the roll angle is greater than the set value, the rear wheel steering angle increases as the roll angle increases. In addition, it is conceivable to use an increasing function in which the ratio of the increase in the rear wheel steering angle to the increase in the roll angle increases as the vehicle speed increases. Any function that should yield a result can be employed.

In the illustrated embodiment, an electric motor is used as a seven-wheel drive unit for steering the rear wheels, and the rotation of the electric motor causes the rear wheels to be steered through a reduction gear mechanism, a pinion gear, a rack shaft, etc. However, the rear wheel steering actuator and the mechanism for transmitting the steering force from the rear wheel steering actuator to the rear wheels are other than those of the above-described embodiment, and for example, the rear wheels are steered by the hydraulic pressure of a hydraulic actuator. Any configuration such as a mechanism may be adopted.

Effects of the Invention As described above, according to the present invention, it is determined whether the vehicle is in a low-g turning state or a high-g turning state based on the size of the roll angle of the vehicle body, and priority is given to turning performance in the low-g turning state. In order to improve stability, the front and rear wheels are steered in opposite phases, and in the case of high-g turning conditions, the front and rear wheels are steered in the same phase, and the rear wheel steering angle is controlled by the size of the vehicle roll angle and the vehicle speed. Compared to conventional rear wheel steering systems that control rear wheel steering using the front wheel steering angle and vehicle speed, it is now possible to set rear wheel steering characteristics that match the actual vehicle behavior, making it possible to set the rear wheel steering characteristics accurately to match various driving conditions. This enables rear wheel steering control to be performed, which can bring about great practical effects.

[Brief explanation of drawings]

The right figure is an explanatory plan view showing one embodiment of the present invention. ■...Roll angle sensor, 2...Vehicle speed sensor, 3...
- Front wheel steering angle sensor, 4... Control circuit, 5... Drive circuit, 6... Electric motor, 12... Rear wheel, 13...
Rear wheel steering angle sensor. that's all

Claims (2)

[Claims] (1) A roll angle sensor that detects the roll angle of the vehicle body and issues a roll angle signal accordingly, a vehicle speed sensor that detects vehicle speed and issues a vehicle speed signal accordingly, and a front wheel steering angle that is controlled by steering wheel operation. The front wheel steering angle sensor detects and issues a front wheel steering angle signal, and the front wheel steering angle signal of the front wheel steering angle sensor is determined depending on whether the roll angle obtained from the roll angle signal of the roll angle sensor is less than a set value or greater than the set value. The system determines the rear wheel steering direction relative to the front wheel steering direction obtained by , and also determines the ideal rear wheel steering angle based on the roll angle and vehicle speed using the roll angle signal and the vehicle speed signal from the vehicle speed sensor, and outputs it. A rear wheel steering device for an automobile, characterized in that rear wheel steering control is performed by a control circuit that operates a wheel steering actuator to perform rear wheel steering. (2) A patent characterized in that the rear wheel steering direction is set in the opposite direction to the front wheel steering direction when the roll angle is less than a set value, and in the same direction as the front wheel steering direction when the roll angle is greater than the set value. A rear wheel steering device for an automobile according to claim 1.