JP2538365Y2 - Front and rear wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a front and rear wheel steering device that also steers a rear wheel in response to steering of a front wheel, and particularly, front and rear wheel steering that steers rear wheels by hydraulic pressure. Related to the device.

[Related Art] Conventionally, as such a front and rear wheel steering device, for example, a device described in Japanese Patent Application Laid-Open No. 61-81869 is known.

This is provided in the fluid supply path from the oil pump to the rear wheel steering power cylinder and the oil pump to the rear wheel steering power cylinder, and controls the pressure of the fluid in accordance with the vehicle lateral acceleration. And a pressure direction control valve for switching the fluid return direction based on the pressure. And
The pressure directional control valve has a one-handed proportional solenoid disposed at both ends of a valve spool, drains the fluid supplied from the oil pump when in the neutral state, or either of the proportional solenoids when steering the rear wheel. By energizing one, the valve spool is slid in one direction to define the supply direction of the pressure oil and supply it to one pressure chamber of the rear wheel steering power cylinder.

[Problems to be Solved by the Invention] However, in such a conventional front and rear wheel steering device, even when the pressure directional control valve in which the rear wheel is not steered is in a neutral state, the fluid is always supplied from the oil pump. Therefore, there is a problem that the drive horsepower of the oil pump is unnecessarily wasted.

In particular, in a vehicle in which an oil pump is driven by an engine, constantly driving the oil pump wastes fuel, and in view of the fact that the engine is often arranged in front of the vehicle. However, the piping distance from the engine driven oil pump to the rear wheel steering power cylinder cannot be neglected, and there is a problem that the cost increases as a measure against leakage of the working fluid.

SUMMARY OF THE INVENTION An object of the present invention is to provide a front and rear wheel steering device that can solve such a conventional problem and can save energy and reduce costs.

Means for Solving the Problems To achieve the above object, the present invention provides a pump connected to a motor driven at a predetermined time, an accumulator for accumulating a discharge fluid of the pump at a predetermined pressure, and a rear wheel. A power cylinder for steering, and a pressure control valve provided in the middle of a fluid supply path from the pump and the pressure accumulator to the rear wheel steering power cylinder, and for switching a supply pressure and a return direction of the fluid in accordance with steering of the front wheels. In the front and rear wheel steering device provided with, when the pressure control valve is in its neutral state, a supply port from the pump and the pressure accumulator is closed, and a supply port to the rear wheel steering power cylinder is a drain port. A pilot check valve is interposed in the drain port, and the pilot check valve is closed when the pressure control valve is in a neutral state. It is characterized by being opened when activated.

According to the present invention, in the neutral state of the pressure control valve in which the rear wheel steering is not performed, the supply ports from the pump and the accumulator are closed, and the drain port is closed by the pilot check valve. It will be in the state that was done. If the pressure of the accumulator becomes equal to or lower than the predetermined value in this state, the pump is driven by the motor, and the accumulator accumulates the discharge fluid at the predetermined pressure. Further, leakage of fluid from the supply port of the pressure control valve to the drain port is prevented by the pilot check valve.

On the other hand, when the pressure control valve is switched in either direction, the supply port is opened and the pilot check valve is opened, the working fluid in the accumulator is supplied to the pressure chamber of the rear wheel steering power cylinder, and The wheels are steered.
Further, at this time, as described above, when the pressure of the accumulator becomes equal to or less than the predetermined value, the pump is driven again by the motor, and stops when the pressure exceeds the predetermined value.

 Therefore, the pump is driven only at a predetermined time.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

 FIG. 1 shows an embodiment of the present invention.

In the figure, reference numeral 10 denotes a rear-wheel steering power cylinder, and reference numeral 20 denotes a pressure control valve that controls the pressure of the pressure oil to the rear-wheel steering power cylinder 10 and switches the return direction. The rear wheel steering power cylinder 10 has a piston 11 defined in left and right pressure chambers 10L, 10R, left and right piston rods 12L, 12R fixed to both ends thereof, and left and right centering for holding the piston 11 in a neutral position. It has springs 13L and 13R, and the outer ends of the piston rods 12L and 12R are respectively connected to tie rods (not shown) to steer the rear wheels.

As shown in detail in FIG. 2, the pressure control valve 20 includes a valve spool 22 having three lands 22L, 22C, and 22R slidably fitted in a valve body 21. Proportional solenoids 23L and 23R as pressing means for the valve spool 22 are arranged. Then, in the illustrated neutral state, annular grooves 24L, 24C and 24R are formed at positions of the valve body 21 corresponding to the lands of the valve spool 22, and the width of the central annular groove 24C is equal to the width of the central land 22C. The width of the left and right annular grooves 24L and 24R is set smaller than the width of the left and right lands 22L and 22R. Further, a pump port P as a supply port from a pump and an accumulator described later is opened in the left and right annular grooves 24L and 24R, and a tank port T as a drain port communicating with a tank described later is opened in the central annular groove 24C. Is open. Also, the left and center annular grooves 24L and 2L
4C, and between the right and center annular grooves 24R and 24C, a left cylinder port CL as a supply port communicating with the left pressure chamber 10L and the right pressure chamber 10R of the above-described rear wheel steering power cylinder 10, respectively. And the right cylinder port CR is open.

Incidentally, 25L and 25R are left and right centering springs for holding the valve spool 22 in a neutral state, and 26L and 26R are reaction force pistons opposing the suction force of the proportional solenoid 23 for stabilizing the operating pressure to the power cylinder 10. is there.

When the pressure control valve 20 is in the neutral state shown in the figure, the pump port P is closed by the left and right lands 22L and 22R of the valve spool 22, and the left and right cylinder ports CL are closed.
And CR are in communication with the tank port T.

Next, the working fluid supply device 30 will be described again with reference to FIG.

Reference numeral 31 denotes a pump driven by a motor 32, which draws a working fluid from a tank 33 and discharges the working fluid toward the pump port P. A check valve 34 is provided in the discharge passage, and a pressure accumulator 35 is further connected downstream via a branch passage. Reference numeral 36 denotes a pressure switch that responds to the pressure downstream of the check valve 34, and reference numeral 37 denotes a relief valve that releases excess pressure.

It should be noted that a plunger pump can be used as the pump 31 described above, and thus the pressure control valve 20 and the working fluid supply device 30 can be configured in a unit that does not require piping.

In the middle of the drain passage from the tank port T of the pressure control valve 20 to the tank 33, a pilot check valve 38 is interposed, and a branch of the branch passage from the pilot port of the pilot check valve 38 to the accumulator 35 is provided. The point is connected via a three-port type electromagnetic directional control valve 39. The electromagnetic directional control valve 39 is switch-controlled by a control signal of the controller 40.When the pressure control valve 20 is in a neutral state, the pilot port of the pilot check valve 38 is communicated with the tank 33, and when the pressure control valve 20 is operated. In this case, the pilot port is communicated with the accumulator 35.

Reference numeral 40 denotes a controller constituted by a microcomputer or the like, which includes a steering angle sensor 41 for detecting a steering angle, a steering direction and a steering speed of a steering wheel (not shown), a vehicle speed sensor 42 for detecting a vehicle speed of the vehicle, and a rear wheel Based on a signal input from a rear wheel steering angle sensor 43 for detecting a steering angle and a signal input from the above-described pressure switch 36, a predetermined operation is performed, and a predetermined control signal is output to the left and right proportional solenoids 23L and 23R and the motor 32.

In the present embodiment having the above configuration, the steering angle sensor 41
When it is determined that the steering wheel is not being steered, that is, the vehicle is in a straight running state,
The controller 40 does not output a control signal to the left and right proportional solenoids 23L and 23R, and the pressure control valve 20 is maintained in a neutral state.

At this time, if the pressure of the accumulator 35 is lower than the predetermined value, the pressure switch 36 is activated, and the controller 40 outputs a signal for driving the motor 32. The pump 31 rotates with the rotation of the motor 32, and discharges the working fluid from the tank 33 via the check valve 31. As described above, when the pressure control valve 20 is in the neutral state, the pump port P is closed.
The discharge pressure from the pump 31 is used only for accumulating the pressure in the accumulator 35. When the pressure in the accumulator 35 reaches a predetermined value, the pressure switch
36 operates, and the rotation of the pump 31 by the motor 32 is stopped. Even if the pump 31 stops, the pressure in the accumulator 35 is prevented from backflow by the check valve 34, and is maintained at a predetermined value.

Further, the pilot check valve 38 functions as a check valve and prevents discharge of the working fluid leaking from the tank port T of the pressure control valve 20 to the tank 33. This means that leakage of the working fluid from the pump port P to the tank port T due to the use of the valve spool 22 by the pressure control valve 20 is prevented.
A pressure drop of 35 is prevented.

Next, based on the detection signals from the steering angle sensor 41 and the vehicle speed sensor 42, when a control signal is output to one of the left and right proportional solenoids 23L, 23R of the pressure control valve 20 to steer the rear wheels, For example, if the vehicle is in a high-speed running state and the front wheels are steered to the right, the rear wheels are also steered in phase, for example, when a control signal is output to the right proportional solenoid 23R,
The valve spool 22 moves to the left in FIG. Then, the pump port P of the pressure control valve 20 is in communication with the left cylinder port CL, and conversely, the right cylinder port CR is in communication with the tank port T. Accordingly, the pressure fluid is supplied from the pressure accumulator 35 to the left pressure chamber 10L of the rear wheel steering power cylinder 10, and the piston 11
Stroke right while compressing R. Accordingly, the fluid in the right pressure chamber 10R is discharged to the tank 33 via the tank port T in a communicating state.

That is, the left and right proportional solenoids 23L, 23 of the pressure control valve 20
R is supplied with a proportional current, that is, when the pressure control valve 20 is activated,
A control signal is output from 40 to the electromagnetic direction switching valve 39, and pressure is applied to the pilot port of the pilot check valve 38. Then, the pilot check valve 38 is opened and the tank port T and the tank 33 are communicated with each other.
(Or 10R), the working fluid extruded from the tank through the tank port T and the pilot check valve 38
Discharged to 33.

As a result, the rear wheels are steered to the right similarly to the front wheels, and the steered angle is detected by the rear wheel steering angle sensor 43. Then, the feedback control of the proportional solenoid 23R is performed with the target steering angle set based on the front wheel steering angle and the vehicle speed.

Here, when the pressure of the pressure accumulator 35 decreases to the lower limit value of the pressure switch 36, the controller 40 outputs a control signal for rotating the motor 32, and the pressure accumulation operation by the pump 31 is performed.

According to the present embodiment, in the neutral state of the pressure control valve 20, the left and right pressure chambers 10L and 10R of the rear wheel steering power cylinder 10 are communicated with the tank 33, so that a differential pressure is generated between the left and right pressure chambers 10L and 10R. Does not occur, left and right lands 22L, 22R of valve spool 22
A stable straight running can be performed even if there is a variation in processing. Further, in the neutral state of the pressure control valve 20, the working fluid leaking to the tank 33 through the gap of the valve spool 22 is shut off, so that the pressure drop of the pressure accumulator 35 is prevented, and the frequent driving of the pump 31 and, consequently, the motor 32 is performed. Energy saving without the need for

[Effects of the Invention] As is apparent from the above description, according to the present invention, the supply ports from the pump and the accumulator are closed when the pressure control valve is in the neutral state, and the supply port to the power cylinder for rear wheel steering is provided. Is connected to the drain port, and the motor connected to the pump is driven when the pressure of the accumulator drops, so that the pump operates only when necessary and energy can be saved. Further, since the pump can be arranged near the rear wheel, long piping is not required, and cost can be reduced. In addition, in the neutral state of the pressure control valve, the working fluid leaking into the tank through the gap between the valve spools is blocked by the pilot check valve, so that the pressure drop of the pressure accumulator is prevented, and the frequent drive of the pump and, consequently, the motor. It is possible to save energy without the need for

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a sectional view showing an example of a pressure control valve. 10 ... Power cylinder for rear wheel steering, 20 ... Pressure control valve,
22: Valve spool, 23: Proportional solenoid, P:
Pump port, T …… Tank port, CL, CR …… Cylinder port, 30 …… Working fluid supply device, 31 …… Pump, 32
…… Motor, 33 …… Tank, 34 …… Check valve, 35
... pressure accumulator, 36 ... pressure switch, 38 ... pilot check valve, 39 ... electromagnetic directional control valve, 40 ... controller.

Claims (1)

(57) [Scope of request for utility model registration] A pump connected to a motor driven at a predetermined time; a pressure accumulator for accumulating a discharge fluid of the pump at a predetermined pressure; a power cylinder for rear wheel steering; A pressure control valve provided in the middle of a fluid supply path to a wheel steering power cylinder, for switching a supply pressure and a return direction of the fluid in accordance with steering of a front wheel. In its neutral state, the supply ports from the pump and the pressure accumulator are closed, the supply port to the rear wheel steering power cylinder is connected to the drain port, and a pilot check valve is connected to the drain port. The pilot check valve is closed when the pressure control valve is neutral, and is opened when the pressure control valve is operated. .