JP2622550B2 - 4-wheel steering system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a four-wheel steering device that drives a power cylinder and a rear wheel cylinder with separate pumps.

(Prior Art) The conventional device shown in FIG.
Front-wheel control valve V ₁ is switched in accordance with the rotational direction, the front wheel pump P _1, communicates either one of the pressure chambers of the pressure chamber 2 of the power cylinder S _1, and the other of the pressure chambers To the tank T.

For example, turn off the handle H to the left and right, the pressure chamber 1 is communicated with the tank T, the pressure chamber 2 is communicated with the pump P _1. Thus, the piston 3 of the power cylinder S ₁ is moved to the left together with the tie rod 4, which steers the front wheels 5 in the right direction.

When the handle H is turned to the left, the pressure oil is supplied to the pressure chamber 1 and the hydraulic oil in the pressure chamber 2 is returned to the tank T. Therefore, the piston 3 moves rightward together with the tie rod 4, and steers the front wheel 5 leftward.

While the vehicle is traveling, traveling conditions such as the vehicle speed and the steering angle are detected by a sensor (not shown), and an output signal of the sensor is input to the controller C. The controller C is electrically connected to the solenoid 6 and 7 the rear wheel control valve V _2.

The rear-wheel control valve V ₂ has a supply port 8 on its upstream side,
9 and a tank port 10, and downstream ports 11 and 12 are formed on the downstream side.

The said feed ports 8 and 9 connected to the pump P ₂ for the rear wheels, the tank port 10 is communicated with the tank T. Further, the downstream ports 11 and 12, the rear wheel cylinder S ₂ pressure chambers 13, 14
Is in communication with

When the rear wheel control valve V ₂ is in the neutral position shown, because both the pump port 8,9 and downstream ports 11 and 12 communicated with the tank port 10, the rear wheel piston 15 of cylinder S ₂ is spring The neutral position shown is maintained by the action of 16 and 17, and the rear wheel 18 is kept straight.

From the above state, for example, exciting the solenoid 6, moving the spool 19 of the rear wheel control valve V ₂ in the right direction of the drawing, with the supply port 9 and the downstream port 12 is communicated with the tank port 10 is downstream Connect to port 11. Therefore, oil discharged from the rear wheel pump P ₂ is supplied to the pressure chamber 14 of the rear wheel cylinder S ₂ via the supply port 9 and the downstream port 12. The hydraulic oil in the pressure chamber 13 at this time is returned from the downstream port 11 to the tank T via the tank port 10, so that the piston 15 of the rear wheel cylinder S ₂
Together with the vehicle, and steers the rear wheel 20 to the right.

If moving the spool 19 by exciting the solenoid 7 in the opposite direction, communicates with the supply port 8 and the downstream port 11, since the tank port 10 and the downstream port 12 is communicated, the rear wheel cylinder S ₂ The piston 15 moves rightward and steers the rear wheel 18 to the left.

Then, either switch the rear wheel control valve V ₂ in either direction, one in which the controller C is controlled according to the vehicle speed. That is, when the vehicle is traveling at a low speed, the turning directions of the front wheels 5 and the rear wheels 18 are reversed.
And a rear wheel 18 so as to steer in the same direction, controls the rear wheel control valve V _2.

In the conventional apparatus as described above (problems present invention is to solve), since in the switch the rear wheel control valve V ₂ using the controller C, as a control circuit becomes complicated problem was there.

Further, the controller C sometimes malfunctions due to the action of an electromagnetic disturbance, a strong magnetic field, or the like. Thus, the controller C
Malfunctions, for example, when the vehicle is running at high speed, the front and rear wheels should be turned in the opposite phase where they should be. However, if the front and rear wheels are turned in opposite phases during high-speed running, the vehicle body shakes greatly, and there is a danger of causing an accident.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device which has a simple structure and does not malfunction.

(Means for Solving the Problems) The present invention relates to a front-wheel control valve that switches with the rotation of a steering wheel, a front-wheel pump and a tank that communicate with a power cylinder via the control valve, a rear-wheel pump,
It is premised on a four-wheel steering system including a rear wheel cylinder for steering the rear wheel, and a rear wheel control valve provided between the rear wheel pump and the rear wheel cylinder.

On the premise of the above device, the present invention provides a phase mode switching valve between a rear wheel control valve and a rear wheel cylinder, the phase mode switching valve having a spool in a main body, One end faces the spring chamber, and the other end faces the pilot chamber, and the pilot chamber guides the discharge pressure of the front wheel pump upstream of the front wheel control valve. It is characterized in that, when the discharge pressure of the front wheel pump is equal to or higher than the set pressure, the mode is switched to the reverse phase mode position while the pressure is maintained.

(Operation of the present invention) When the steering wheel is turned during low-speed running, the turning resistance is large, so that the load pressure of the power cylinder increases. Since the increased load pressure acts on the phase mode switching valve as pilot pressure, the phase mode switching valve is switched to the reverse phase mode position.

When the steering wheel is turned during high-speed running, the turning resistance is small at that time, so that the load pressure on the power cylinder decreases. Therefore, the phase mode switching valve maintains the common mode position.

(Effect of the Present Invention) According to the four-wheel steering system of the present invention, one phase mode switching valve can switch between the in-phase mode and the opposite-phase mode. No need to provide. Since one phase mode switching valve is sufficient as described above, the overall configuration is simplified.

In addition, since the pilot pressure for switching the phase mode switching valve depends on the load pressure of the front wheels, a malfunction such as turning the front and rear wheels in opposite phases during high-speed running can be reliably prevented.

Embodiment shown in (Example of the present invention) first and second figure characterized in that connecting the phase mode switching valve V _D between the rear wheel control valve V ₂ and the rear wheel cylinder S ₂ Have.

The specific configuration of the phase mode switching valve V _D is
As shown in FIG.

That is, the phase mode switching valve V _D, as well as the spool 22 slidably furnished to the body 21, to face the one end of the spool 22 to the pilot chamber 23, and to face the other end to the spring chamber 24 . Since the spring 25 is provided in the pilot chamber 23, unless the pressure acts on the pilot chamber 23, the spool 22
The position shown in FIG.

Further, the pilot chamber 23 is connected to the upstream side of the front-wheel control valve V _1, the load pressure of the power cylinder S ₁ to the pilot chamber 23 is to act.

The body 21 of the phase mode switching valve V _D were as described above,
While forming the upstream port 26, to connect the upstream port 26 in the one to one downstream port 11 of the rear wheel control valve V _2, the control for the rear wheels to the other upstream ports 27 It is connected to the other downstream port 12 of the valve V _2.

Moreover, this forms a cylinder port 28, 29 to the body 21, the pressure chamber of the rear wheel cylinder S ₂ these cylinder port
It communicates with 13 and 14.

When the spool 22 of the phase mode switching valve V _D are in the normal position shown, the upstream port 26 and cylinder port 28
And the communication between the upstream port 27 and the cylinder port 29 to maintain the in-phase mode position.

When the spool 22 moves against the spring 25, the upstream port 26 and the cylinder port 29 communicate with each other, and the upstream port 27 and the cylinder port 28 communicate with each other via the flow path 30 formed in the spool 22. Communicate.

Incidentally, the front-wheel control valve V ₁ and the rear wheel control valve V ₂ configuration,
It is the same as the conventional case.

A steering angle sensor 32 is provided on the input shaft 31 of the steering wheel H, and the steering angle sensor 32 is connected to the controller C. Then, in accordance with the output signal of the steering angle sensor 32, the controller C is operated, and to switch the rear wheel control valve V ₂ in response to the switching replacement amount H of the handle H.

When the steering wheel H is turned, the steering angle sensor 32
In addition to detecting, switching the rear wheel control valve V ₂ in accordance with the rotational direction and the steering angle of the steering wheel H.

If this time the vehicle is traveling at low speed, because the換向resistance increases, the load pressure of the power cylinder S ₁ is increased. This load pressure acts on the pilot chamber 23 of the phase mode switching valve V _D as a pilot pressure, the spool 22 moves against the spring 25, the phase mode switching valve V _D
To the reverse phase mode position.

Therefore, the front wheels 5 and the rear wheels 18 are switched in opposite directions, and the turning radius of the vehicle is reduced.

Also, cutting the handle H in a high speed running of the vehicle, so that time is not so large換向resistance to, not higher load pressure of the power cylinder S _1. Since the pilot pressure is low which acts on the pilot chamber 23 of the phase mode switching valve V _D Therefore, the spool 22 is in the action of the spring 25, to retain the common mode position shown.

Therefore, the front wheels 5 and the rear wheels 18 are steered in the same direction, and the rear wheels do not skid when changing lanes during high-speed running.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention.
FIG. 2 is a circuit diagram, FIG. 2 is a sectional view of a phase mode switching valve, FIG.
The figure is a circuit diagram of a conventional device. H… Handle, V ₁ … Front wheel control valve, P ₁ … Front wheel pump, T …… Tank, V ₂ … Rear wheel control valve, P ₂ … Rear wheel pump, S ₂ … Rear wheel cylinder, V _D …… Phase mode switching valve, 23 …… Pilot room.

Claims (1)

(57) [Claims] 1. A control valve for a front wheel, which is switched with a rotation of a steering wheel, a pump and a tank for a front wheel, a pump for a rear wheel, and a pump for a rear wheel, which are connected to a power cylinder through the control valve. In a four-wheel steering system including a rear wheel cylinder and a rear wheel control component provided between the rear wheel pump and the rear wheel cylinder, the rear wheel control valve and the rear wheel cylinder In between, a phase mode switching valve is provided, the phase mode switching valve is provided with a spool in the main body, and one end of the spool faces the spring chamber, and the other end faces the pilot chamber. The discharge pressure of the front-wheel pump upstream of the front-wheel control valve is derived. Normally, the in-phase mode position is maintained, while the discharge pressure of the front-wheel pump becomes equal to or higher than the set pressure. To switch to Four-wheel steering system.