JPH0327902Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an improvement of a device that controls the rear wheels of a vehicle by following the steering of the front wheels.

(Conventional technology) In order to improve the running stability and maneuverability of vehicles,
Front and rear wheel steering devices that steer the rear wheels at the same time as the front wheels are increasingly being adopted.

In this case, there are various methods for detecting the steering of the front wheels and steering the rear wheels, but one that is structurally simple is one that detects the steering hydraulic pressure generated during steering in the front wheel power cylinder. One example is a system that controls the hydraulic pressure sent to the power cylinder on the rear wheel side.

Such a device will be specifically explained with reference to FIG. 1 is a power cylinder on the front wheel side, and by supplying hydraulic oil to oil chambers 2 and 3 on the left and right sides of the cylinder, a piston 4 moves in either direction, displacing a steering linkage 5 linked to this, The direction of the front wheels 10 is changed. Control is performed in response to the rotation of the handle 7 in order to selectively supply pressure oil from the hydraulic source, that is, the hydraulic pump 6, to the oil chambers 2 and 3 of the power cylinder 1 according to the rotation direction of the handle 7. The valve 8 is adapted to perform a switching operation. Therefore, when the control valve 8 is switched by rotating the handle 7 and pressure oil is supplied to one oil chamber 3, the other oil chamber 2 is simultaneously released to the tank 9 side, and the piston 4 is thereby moved. and handle 7
The direction of the front wheel 10 is changed in accordance with the direction of rotation of the front wheel 10.

In this way, the front wheels are steered while receiving power assistance from the hydraulic pressure, and at the same time, in order to turn the rear wheels 20, the oil chambers 14 and 15 of the rear wheel power cylinder 11 are also provided in the front and rear sides. Remote control valve 1 that switches by sensing the generated steering oil pressure
Pressure oil from a hydraulic pump 13 is selectively fed through 2. The remote control valve 12 has pressure chambers 17 and 18 formed at both ends of the spool 16, and passages 21a and 2 that branch from passages 21 and 22 that communicate the control valve 8 and the oil chambers 2 and 3 of the front wheel power cylinder 1.
Steering oil pressure is conducted as pilot pressure via 2a. The spool 16 is displaced depending on the balance between this pilot pressure and the springs 23 and 24, and is maintained in a neutral state when the pilot pressures in both pressure chambers 17 and 18 are equal, but as the front wheel side is steered, the spool 16 is displaced depending on the balance between the pilot pressure and the springs 23 and 24. When a pressure difference occurs across 22, the spool 16 is displaced in either direction, causing the remote control valve 12 to switch. As a result, the rear wheel side power cylinder 1
Pressure oil from the hydraulic pump 13 is fed into one oil chamber 14 of the engine 1, and the other oil chamber 15 is released to the tank 25, and the piston 26 moves to align the direction of the rear wheel 20 with the direction of the front wheel 10. Change it. The steering hydraulic pressure generated in the oil chambers 2 and 3 of the front wheel power cylinder 1 corresponds to the direction of rotation of the steering wheel 7, and when one side is high pressure, the other side is always low pressure, and when the rotation of the steering wheel 7 is stopped, Only the left and right sides will have the same pressure.

Therefore, the remote control valve 12, which selectively sends pressure oil to the oil chambers 14 and 15 of the power cylinder 11 on the rear wheel side, responds to the steering direction of the front wheels by sensing the steering hydraulic pressure on the front wheels. It is possible to switch to either one without fail. However, the steering direction of the rear wheels may be the same as that of the front wheels or may be opposite. For example, if the emphasis is on improving cornering stability when driving at high speeds, the front wheels 10 and the rear wheels 20 may be aligned in the same direction, or when it is important to reduce the turning radius when driving at low speeds, The direction of the front wheels 10 and the rear wheels 20 may be reversed, and these can be appropriately selected by changing the connection of the pressure circuit depending on the intended use of the vehicle.

(Problem to be Solved by the Invention) However, in such a conventional device, the front wheel side steering hydraulic pressure is directly transmitted to the pressure chambers 17 and 18 of the remote control valve 12, and this and the spring 23,
The displacement characteristics of the spool 16 are uniquely determined by the balance with the load of the spool 16. When the steering wheel 7 is switched quickly, the flow rate of pressure oil sent to the front wheel side power cylinder 6 increases, and the turning speed of the front wheels 10 becomes faster. As long as the oil pressure does not increase, the displacement speed of the spool 16 of the remote control valve 12 will not change, and therefore the turning speed of the rear wheels will be slower than that of the front wheels. In other words, there was a tendency for the steering operation of the rear wheels to follow the front wheels and be delayed.

In order to reduce this response delay, the capacity of the hydraulic pump 13 on the rear wheel side is increased, and the remote control valve 12
One idea is to be able to supply a large flow rate even with the slightest switching action, but this would increase the driving horsepower of the rear hydraulic pump and consume extra engine output to drive the pump. , resulting in deterioration of vehicle fuel efficiency.

This invention solves this delay in control response on the rear wheel side.
The purpose of the present invention is to provide a device that can easily prevent the problem without increasing the size of the pump.

(Means for solving the problem) Therefore, the present invention selectively supplies pressure oil from a hydraulic source to the left and right oil chambers of the power cylinder linked to the front wheels via a control valve that switches according to the operation of the steering wheel. In a vehicle equipped with a power steering device that supplies power to a rear wheel, a remote control valve is provided to selectively supply pressure oil from a hydraulic source to a control actuator on the rear wheel side,
In order to switch the remote control valve, a passage branched from a passage leading pressure oil from the front wheel side control valve to the power cylinder is connected to pressure chambers formed at both ends of the spool, and this branch point and the power cylinder are connected. A diaphragm was inserted between each.

(Function) The switching amount of the control valve increases in accordance with the rotational operation speed of the handle, and the flow rate of pressure oil increases accordingly. The front wheel steering hydraulic pressure generated by steering wheel operation increases in accordance with the flow rate upstream of the throttle. Since the hydraulic pressure upstream of this throttle becomes the pilot pressure for the remote control valve, the switching amount of the remote control valve spool will eventually increase in response to the rotational speed of the handle, and the flow rate of pressure oil supplied to the rear wheels will also increase. It increases responsively according to the operating speed of the steering wheel, and the followability of the rear wheels relative to the front wheels also increases.

(Embodiment) An embodiment in which the present invention is applied to a device for steering both front wheels and rear wheels will be described below with reference to FIG.

As shown in the figure, pilot pressure is applied to pressure chambers 17 and 18 of a remote control valve 12 that controls the steering angle of the rear wheels 20 in passages 21 and 22 that lead pressure oil from the control valve 7 to the front wheel side power cylinder 1. Restrictions 30 and 31 are interposed in the passages 21 and 22, respectively, located downstream of the point where the guiding passages 21a and 22a diverge. In other words, the remote control valve 12 has each throttle 3
The upstream passage pressure of 0.31 is guided as the pilot pressure.

The structure is as described above, and the other parts that are the same as those in FIG. 2 are given the same reference numerals, and the operation will be explained next.

As the rotational speed of operating the handle 7 increases,
Correspondingly, the switching amount of the control valve 8 increases,
The flow rate supplied to the oil chambers 2 and 3 of the power cylinder 1 increases, and the front wheel 10 can be turned quickly. Since throttles 30 and 31 are interposed in the middle of the passages 21 and 22 from the control valve 8 to the power cylinder 1, the passages 21 and 2
The more the flow rate flowing through 2 increases, the more the pressure upstream of the throttle increases. Therefore, the spool 16 of the remote control valve 12 operates using this upstream pressure as the pilot pressure.
is displaced more quickly and switched more greatly as the flow rate increases. When the remote control valve 12 is switched significantly, the flow rate of pressure oil sent from the hydraulic pump 13 to the power cylinder 11 as a rear wheel actuator also increases, and the rear wheels 20 are also switched in response to the front wheels 10.

In this way, the steering speed of the rear wheels increases in accordance with the steering speed of the front wheels, and control of the rear wheels with excellent followability is realized. Note that the aperture 30,
Reference numeral 31 is a variable diaphragm that changes the diaphragm opening depending on the driving conditions of the vehicle, for example, the vehicle speed, so that the follow-up response of the rear wheels can be changed in accordance with the driving conditions in this way.

In this embodiment, the rear wheels are steered in accordance with the front wheels, but even if the direction of the rear wheels is not changed, in order to prevent the vehicle from rolling toward the rear wheels, When the vehicle is equipped with a known hydroneumatic shock absorber, pressure oil supplied via the remote control valve 12 is introduced into the shock absorber on the outside of the turn when the vehicle turns,
The inclination of the vehicle body can also be corrected by extending the shock absorber on the outside of the turn from the neutral position.

(Effects of the invention) As described above, according to the invention, the steering hydraulic pressure for the front wheels is guided from upstream of the throttle to the remote control valve for the rear wheels. The rear wheels can be controlled in response to the steering speed, resulting in improved running stability and handling stability of the vehicle.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional example. 1...Power cylinder, 2, 3...Oil chamber, 5...
...Steering linkage, 6...Hydraulic pump,
7... Handle, 8... Front wheel side control valve, 10...
Front wheel, 11...Power cylinder, 12...Remote control valve, 13...Hydraulic pump, 16...Spool,
17, 18...pressure chamber, 20...rear wheel, 21,2
2... passage, 21a, 22a... branch passage, 3
0,31...Aperture.

Claims (1)

[Scope of utility model registration request] In a vehicle equipped with a power steering device that selectively supplies pressurized oil from a hydraulic source to the left and right oil chambers of a power cylinder linked to the front wheels through a control valve that switches according to the operation of the steering wheel, the rear wheel side A remote control valve is provided to selectively supply pressure oil from a hydraulic source to a control actuator of the front wheel side control valve and a pressure chamber formed at both ends of the spool is provided with a remote control valve that selectively supplies pressure oil from a hydraulic source to a control actuator of the power cylinder. A rear wheel control device for a vehicle, characterized in that a passage branching from a passage leading to pressure oil is connected to a passageway, and a throttle is interposed between each branching point and a power cylinder.