JPS6136062A - Rear-wheel steering controller - Google Patents

Abstract

PURPOSE:To secure the always stable traveling by installing a fluid control valve for controlling the fluid flow-rate on the basis of the lateral acceleration speed of a car into a fluid feeding passage to a rear-wheel control valve, thus certainly preventing the delay in following rear wheels, in a 4-wheel steering apparatus. CONSTITUTION:A 4-wheel steering apparatus is equipped with power cylinders 3 and 4 for generating each steering assisting power for front and rear wheels 1 and 2, and hydraulic pumps 7 and 8 for feeding the pressurized oil into the power cylinders through control valves 5 and 6. A flow-rate control valve 9 is installed into a pressurized-oil feeding passage 21 to the control valve 6 for rear wheels. A direction selector valve 11 is installed into a pressurized-oil return passage 10 to the power cylinder 4 for rear wheels. The lateral acceleration speed of the chassis is estimated on the basis of the signal supplied from a car- speed sensor 17, load sensor 18, or a pressure sensor 20, and the flow-rate control valve 9 is properly controlled by a controller 12. The direction selector valve 11 is switched to the pressurized-oil return direction in the medium or high speed revolution, and front and rear wheels 1 and 2 are steered in the same direction.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a four-wheel steering system for a vehicle in which both the front wheels and the rear wheels are controlled by a hydraulic power steering system. The present invention relates to a steering control device for improving.

[Conventional technology]

Conventionally, in order to improve the vehicle's ability to turn around quickly, or to make it easier to change lanes or run slalom, a front and rear wheel steering system has been adopted in which the rear wheels are steered along with the front wheels, and power cylinders have also been used to steer the front and rear wheels. It has become.

However, since rear wheel steering is controlled by conditions such as vehicle speed,
There was a problem in that the rear wheels inevitably had a follow-up delay, and the operation feeling did not necessarily match the driver's preference.

[Problem that the invention seeks to solve]

The above problem is caused by the fact that the greater the lateral acceleration g generated on the vehicle body by centrifugal force when the vehicle is turning, the more the steering of the rear wheels is delayed and the deviation from the predetermined turning radius is greater. therefore,
The present invention attempts to effectively solve the above problems by controlling rear wheel steering using lateral acceleration.

[Means for resolving the gap and illumination point]

The relationship between front wheel power steering output or front wheel power steering pressure, front wheel steering torque, speed, and lateral acceleration of the vehicle is shown in FIG. As shown in FIG. 1, by detecting the front wheel power steering output or the front wheel power steering pressure and the vehicle speed, the lateral acceleration of the vehicle can be predicted, and the rear wheel power steering characteristics can be changed based on the lateral acceleration of the vehicle.

[For production]

By using the above means, the rear wheels can be steered to a desired amount of rear wheel steering relative to the amount of front wheel steering, and the followability of rear wheel steering can be optimally maintained to ensure stable running without causing slippage of the rear wheels. I can do it.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. The four-wheel steering device includes a front wheel power cylinder 3 and a rear wheel power cylinder 4 that generate steering assist force for the front wheels 1 and rear wheels 2, and a front wheel power cylinder that controls the direction of pressure oil supply to both power cylinders 3 and 4, respectively. control valve 5
, an oil pump 7.8 that supplies pressure oil to both power cylinders via the rear wheel control valve 6, a flow control valve 9 provided in the pressure oil supply path 21 to the rear wheel control valve 6, and a rear wheel control valve 6. Pressure oil return path 10 to wheel power cylinder 4
It is comprised of a directional switching valve 11 provided midway, and a controller 12 that sends control signals for operating the flow rate control valve 9 and the directional switching valve 11. Pistons are inserted into the power cylinder 3 for the front wheels and the power cylinder 4 for the rear wheels, respectively, and both ends of both pistons are connected to the quirods 13 and 14 of the front and rear wheels, respectively, to prevent pressure oil from flowing into the cylinders. The supply causes the pistons to slide, and the wheels 1 and 2 are steered, respectively. The handle 15 is adapted to steer the front wheels 1. In addition, 16
indicates an oil tank. The controller 12 includes a vehicle speed sensor 1
7 indicates the vehicle speed while driving, the front wheel power steering output is detected from the load sensor 18 installed on the tie rod 13, or the front wheel power is detected from the pressure sensor 20 installed in the middle of the pressure oil supply path 19 of the front wheel control valve 5. The working pressure of the steering wheel is constantly sent to each of them.

Next, the operation of one embodiment of the present invention will be explained.

A flow control valve 9 consisting of an electromagnetic valve with a variable throttle passage is installed in the middle of the pressure oil supply path 21 to the rear wheel control valve 6, and a solenoid 22 is actuated by a signal from the controller 12. The aperture amount is adjusted,
Power cylinder 4 via rear wheel control valve 6
The flow rate supplied to the pump is adjusted. The controller 12 predicts the lateral acceleration of the vehicle body based on input signals indicating the vehicle speed, the output of the front wheel power steering, or the working pressure of the front wheel power steering sent from the vehicle speed sensor 17, the load sensor 18, or the pressure sensor 20. The flow rate control valve 9 is controlled by outputting a valve opening signal that provides a desired rear wheel turning amount (desired flow rate supplied to the power cylinder 4). In this manner, in this embodiment, the rear wheels 2 can be steered by the flow control valve 9 according to the driver's intention and to a desired amount of rear wheel turning relative to the amount of front wheel turning. Therefore, the followability of the rear wheel steering can be optimally maintained, and the rear wheels 2 can travel stably without slipping. Further, a direction switching valve 11 is provided in the middle of the pressure oil return path 10 between the control valve 6 and the rear TLTl Hower cylinder 4, so that the front and rear wheels 1 and 2 are steered in opposite directions to each other at low speeds. However, at medium to high speeds, the controller 12 sends a valve switching signal to the direction switching valve 11 in response to a signal from the vehicle speed sensor 17, which activates the solenoid 23 to switch the pressure oil supply direction, thereby switching between the front and rear wheels 1, 2. are designed to steer in the same direction. In this way, when the vehicle is running at low speeds, the front and rear wheels are steered in opposite directions, which improves the turning radius by reducing the turning radius.At medium and high speeds, the front and rear wheels are steered in the same direction, which improves the turning direction of the front and rear wheels in the opposite direction. Since the tracking ability of the wheels can be predictively matched to the steering direction, lane changes and slalom driving can be performed smoothly.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, there is no follow-up delay of the rear wheels in any driving situation, and stable driving can be realized.

[Brief explanation of drawings]

Figure 1 shows a correlation diagram between front wheel power steering output or front wheel power steering pressure, speed, and lateral acceleration.
FIG. 2 shows the entire front and rear wheel steering power steering system, and FIG. 3 is a detailed view of the directional control valve portion of the rear wheel steering control device. 3...Power cylinder for front wheels, 4...Power cylinder for rear wheels, 5...Control valve for front wheels, 6...
・Rear wheel control valve, 9...Flow rate control valve, 1
1... Directional switching valve, 12... Controller, 17.
...Vehicle speed sensor, 18...Load sensor, 20...Pressure sensor, 22.23...Solenoid.

Claims (2)

[Claims] (1) Each power cylinder for front wheel steering and rear wheel steering, a control valve that switches the working fluid supply direction to both power cylinders, and a fluid supply path to the rear wheel control valve are installed to reduce vehicle lateral acceleration. This includes a fluid control valve that controls the fluid flow rate, and a direction control valve that is installed in the fluid return path to the rear wheel steering power cylinder and switches the pressure oil return direction based on a signal from the vehicle speed sensor. Features a rear wheel steering control device. (2) The vehicle lateral acceleration is predicted by a controller using the vehicle speed from a vehicle speed sensor and the front wheel power steering output from a load sensor or the front wheel power steering working pressure from a pressure sensor. Rear wheel steering control device according to item 1.