JPH02193775A - Four-wheel steering device - Google Patents

Abstract

PURPOSE:To obtain a device high in reliability and unconstrained in layout by providing a rear wheel solenoid control valve with a negative-phase mode change-over position and an in-phase mode change-over position maintained in relation to the actuation of a metering cylinder. CONSTITUTION:When a steering wheel 11 is turned largely, a metering cylinder MC is put in action to actuate a pilot cylinder CM feeding it with delivered fluid pressure so as to change a rear wheel solenoid control valve RV over to the negative-phase mode. If the turning angle of the steering wheel 11 is small, fluid is not delivered as the metering cylinder MC maintains the deadband, and when the speed exceeds the fixed speed, a controller C excites solenoids 43, 44 so as to change the rear wheel solenoid control valve RV over to the in-phase mode. When the steering wheel is turned largely, the steering directions of front and rear wheels 14, 50 are reversed in the case of low speed running, and in small turning, the steering directions of the front and rear wheels 14, 15 are made the same in the case of high speed running.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a four-wheel steering device that steers rear wheels in conjunction with steering front wheels.

(Prior Art) As a device of this type, one disclosed in Japanese Unexamined Patent Publication No. 178787/1987 has been known for some time, and FIG. 3 shows this conventional device.

According to the conventional device shown in FIG. 3, the front wheels 2 are steered by turning the steering wheel l, and the steering shaft 3 rotates in conjunction with the steering of the front wheels.

When the steering shaft 3 rotates, the bevel gear 4 rotates, and the valve rod 5 linked to the bevel gear 4 swings. If the swing shaft 6 is tilted at this time, the valve rod 5 will be pulled or pushed depending on the tilt. When the valve rod 5 moves in the axial direction in this way, the rear wheel electromagnetic control valve 7 is switched accordingly, and pressure fluid is supplied to the rear wheel cylinder 8 according to the switching position.

(Problems to be Solved by the Present Invention) The conventional device as described above has a problem in that the rear wheel steering mechanism is quite complicated.

Moreover, since the front wheel steering device and the rear wheel steering device are linked via the steering shaft 3, there is a problem in that the steering shaft 3 becomes a constraint and the layout is restricted.

An object of the present invention is to provide a device that has a simple structure and is free from layout constraints.

(Means for Solving Problems) This invention provides a metering cylinder that is linked to front wheel steering and has a dead zone that does not discharge fluid when the front wheel steering angle is small, and a metering cylinder for steering the rear wheels. a rear wheel cylinder, a rear wheel pump that supplies pressurized fluid to the rear wheel cylinder, a rear wheel solenoid control valve connected between the rear wheel pump and the rear wheel cylinder, and a rear wheel solenoid control valve connected between the rear wheel pump and the rear wheel cylinder; The rear wheel solenoid control valve includes a pilot cylinder that operates the rear wheel solenoid control valve, a controller connected to a solenoid of the rear wheel solenoid control valve, and a vehicle speed sensor that transmits a vehicle speed signal to the controller. It is characterized by the fact that it maintains a negative phase mode switching position where the rear wheels are switched to the opposite phase to the front wheels in relation to the operation of the metering cylinder, and an in-phase mode switching position where the rear wheels are switched to the same phase as the front wheels using the excitation force of the solenoid. have

(Operation of the present invention) According to the present invention, when the steering wheel is turned significantly, the metering cylinder operates to discharge a predetermined amount of fluid.

The fluid pressure discharged in this manner is supplied to the pilot cylinder and operates the pilot cylinder. This operation of the pilot cylinder switches the rear wheel electromagnetic control valve to reverse phase mode.

Furthermore, when the rotation angle of the steering wheel is small, the metering cylinder maintains a dead zone, so fluid is not discharged from the metering cylinder.
In such a case, when the vehicle speed of the vehicle reaches a certain level, the controller operates to excite the solenoid and switch the rear wheel electromagnetic control valve to the in-phase mode using the excitation force of the solenoid.

When the steering wheel is turned significantly as described above, the vehicle is running at low speed, so the steering directions of the front and rear wheels are reversed at this time.

Furthermore, when the steering wheel is turned slightly, such as when driving at high speeds, the rear wheel electromagnetic control valve is switched by a solenoid, so that the front and rear wheels are steered in the same direction.

(Effects of the present invention) According to the four-wheel steering device of the present invention, when turning the steering wheel significantly to reversely steer the front wheels and rear wheels,
Since the rear wheel electromagnetic control valve is switched to reverse phase mode using fluid pressure, its reliability is extremely high.

Furthermore, there is no longer any inconvenience that the layout is restricted due to the steering shaft being a constraint as in the past.

(Embodiment of the present invention) In the first embodiment shown in 1rA, a binion 13 is provided at the tip of the shaft 12 of the steering wheel 11, and this binion 13 is connected to the rack shaft of the front wheel 14.
It is engaged with a rack 16 formed at 5. The rack shaft 15 is integrated with the piston rod of the front wheel power cylinder FP. Further, the shaft 12 is provided with a switching valve 17, and the steering wheel 11
By turning the shaft 12, the shaft 12 is swung.
This is a known device in which the switching valve 17 is switched in relation to the swinging.

Then, if the switching valve 17 is switched as described above,
One of the pressure chambers 18 or 19 of the front wheel power cylinder is connected to a pump (not shown),
The other pressure chamber is the one that connects to the tank.

When pressure fluid is supplied to the front wheel power cylinder FP in this way, the rack shirt 15 moves in the axial direction, but
When the rack shaft 15 moves to the right in the drawing, the front wheels are steered to the left, and when the rack shaft 15 moves to the left, the front wheels are steered to the right.

The front wheel power cylinder FP is integrally provided with a metering cylinder MC, and the operating rod 20 of the metering cylinder MC is connected to the rack shirt) 1.
5, so that the operating rod 20 and the rack shaft 15 move together in the same direction.

The metering cylinder MC configured as described above has a pair of pistons 21 and 22 slidably installed therein, and
These pistons 21, 22 are normally held in the position shown by the action of springs 23, 24. In this illustrated position, both pistons 21, 22 are at the step 2.
5.26 and maintain a constant distance between them.

A stopper 27 is formed at the center of the actuating rod 20. This stopper 27 is positioned midway between the opposed distances between the pistons 21 and 22 when the steering wheel 11 is held in a neutral position and the front wheels 14 are maintained in a straight-ahead state.

The metering cylinder MC constructed as described above is located adjacent to the piston in the normal position shown in 1 and at the tank port 2.
8.29 and actuator ports 30.31 are formed on the opposite side.

Now, if you turn the steering wheel 11 by a small amount, the amount of movement of the rack shirt 15 will also become smaller, so the amount of axial movement of the second actuating rod 20 will also become smaller. 21
．． The pistons 21, 22 do not move at all since they only move within the opposing spacing of the pistons 21, 22. This piston 21.
The range in which 22 does not move is the dead zone of this invention.

If the steering wheel 11 is turned a large amount, the amount of movement of the rack shirt 15 and the operating rod 20 will also increase accordingly, so during the movement process, the stopper 27 hits the piston 21 or 22 and moves it against the spring 23. .

When the piston moves as described above, the fluid in the metering chamber 32, 33 of the cylinder MC is forced out of the actuator boat 30 or 31.

Metering cylinder MC 7-cut unit boat 30
．． 31 is connected to the pilot cylinder P via passages 55 and 56.
C. This pilot cylinder PC has its cylinder body 34 fixed to a cylinder body 35 of a rear wheel cylinder RC. The cylinder body 34 constructed in this manner
A support piece 36 is formed on the support piece 36 . A valve drive lever 38 provided at the tip of the piston rod 37 of the pilot cylinder PC is rotatably supported around the tip of the support piece 36.

The other end of the valve drive lever 38 configured as described above is connected to a spool 39 of a rear wheel electromagnetic control valve RV. Therefore, when the fluid from the passage 55 is supplied to one pilot chamber 40 of the pilot cylinder PC and the piston 42 moves to the left in the drawing, the valve drive lever 38 rotates clockwise in the drawing to move the spool 39 to the right in the drawing. Switch to .

Conversely, when fluid is supplied to the pilot chamber 41, the piston 42 moves to the left and rotates the valve drive lever 38 counterclockwise. When the valve drive lever 38 rotates counterclockwise in this manner, the spool 39 switches to the left.

Further, the rear wheel electromagnetic control valve RV is provided with solenoids 43.44 at both ends thereof, and this solenoid 43.4
4 is electrically connected to controller C. A vehicle speed sensor and a steering angle sensor are connected to this controller C, and when the vehicle is in a medium to high speed range, either solenoid 43 or 44 is energized to switch the spool 39. The rear wheel electromagnetic control valve RV configured as described above communicates the pressure chambers 45, 46 of the rear wheel cylinder RC with the rear wheel pump P or the tank T depending on its switching position.

The rear wheel electromagnetic control valve RV has its main body 47 fixed to a rear wheel shaft 49 that is integrated with a piston 48 of a rear wheel cylinder RC.

If the steering wheel 11 is turned significantly to the left, the rack shaft 15 and the operating rod 20 will move significantly to the right. When the actuating rod 20 moves to the right in this way, the stopper 27 hits the piston 22 and pushes it, so fluid is discharged from the actuator bow 31 of the metering cylinder MC.

The fluid discharged from the metering cylinder in this way flows into one pilot chamber 40 of the pilot cylinder PC via the passage 56, and the fluid in the other pilot chamber 41 flows from the passage 55 to the actuator boat 3.
Since the piston rod 37 of the pilot cylinder PC moves to the right in the drawing, the piston rod 37 of the pilot cylinder PC moves to the right in the drawing. If the piston rod 37 moves to the right in this way, the valve drive lever 3
8 rotates counterclockwise to switch the spool 39 of the rear wheel electromagnetic control valve RV to the left.

When the rear wheel electromagnetic control valve RV is switched to the left, the fluid discharged from the rear wheel pump P flows into the pressure chamber 46 of the rear wheel cylinder RC.
At the same time, the fluid in the pressure chamber 45 is supplied to the tank T.
Therefore, the piston 48 of the rear wheel cylinder RC moves to the left and steers the rear wheel 50 to the right, which is the opposite direction to the front wheel 14.

When the rear wheel 50 is steered in this manner, the main body 47 of the rear wheel electromagnetic control valve RV fixed to the rear wheel shaft 49 also moves following the spool 39, and position feedback functions.

Note that when the steering wheel 11 is turned to the right, the rear wheels 50 are steered to the left, which is the opposite direction to the front wheels 14, based on the same principle as described above.

When the steering angle of the steering wheel 11 is small and in the dead zone of the metering cylinder MC, the stop bar 27 of the metering cylinder MC moves toward the piston 21.2.
Since neither of the above conditions applies, no fluid is discharged from this cylinder MC.

At this time, the solenoids 43 and 44 are energized by the output signal of the controller C, but the controller C controls the rear wheels 50 and the front wheels 14 and 44 according to the vehicle speed and steering direction.
The control is performed so that the steering is steered in the same direction as the steering wheel.

As described above, according to the first embodiment, when the front and rear wheels are steered in the reverse phase mode, the rear wheel electromagnetic control valve RV is switched by the fluid pressure, so that its reliability is increased. Since the reliability in the reverse phase mode in which the steering wheel 11 is turned significantly is increased, the danger is reduced accordingly.

Further, since the conventional steering shaft 3 is not required, there are no restrictions on the layout.

The second embodiment shown in FIG.
1.52 are provided, and the upstream sides of these throttles 51 and 52 are communicated through a short-circuit passage 53, and a throttle 54 is also formed in this short-circuit passage 53.The other configuration is exactly the same as that of the first embodiment. It is.

In the second embodiment as described above, the flow rate from the metering cylinder MC is adjusted by a throttle, and the steering angle of the rear wheels 50 can be specified according to the flow rate controlled by the throttle. This is what I did.

[Brief explanation of the drawing]

FIG. 1 is a mechanical diagram showing a first embodiment of the present invention, FIG. 2 is a mechanical diagram of a second embodiment, and FIG. 3 is a mechanical diagram of a conventional device. 14...Front wheel, MC...Metering cylinder, R
■...Solenoid control valve for rear wheels, PC...Pilot cylinder, C...Controller, 43.44...Solenoid, RC...Cylinder for rear wheels, P...Pump for rear wheels, 50... Rear wheel.

Claims (1)

[Claims] A metering cylinder that is linked to the steering of the front wheels and has a dead zone that does not discharge fluid when the steering angle of the front wheels is small, a rear wheel cylinder for steering the rear wheels, and this rear wheel cylinder. a rear wheel pump that supplies pressure fluid; a rear wheel solenoid control valve connected between the rear wheel pump and the rear wheel cylinder; and a pilot cylinder that operates the rear wheel solenoid control valve. The rear wheel solenoid control valve includes a controller connected to the solenoid of the rear wheel solenoid control valve, and a vehicle speed sensor that transmits a vehicle speed signal to the controller. A four-wheel steering device that maintains a reverse-phase mode switching position where the front wheels are switched to the opposite phase, and an in-phase mode switching position where the rear wheels are switched to the same phase as the front wheels using the excitation force of a solenoid.