JP2811690B2 - Rear wheel steering mechanism - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering mechanism that feeds back an operation of a rear wheel steering actuator driven by a hydraulic control device to a hydraulic control device via a feedback cable. Things.

2. Description of the Related Art In a four-wheel steering vehicle disclosed in Japanese Utility Model Laid-Open Publication No. Sho 62-38781, control valves of a front wheel steering mechanism and a rear wheel steering mechanism are connected to each other by a remote cable. In the above-described four-wheel steering vehicle, when the remote cable is elongated, play occurs between the front wheel steering mechanism and the rear wheel steering mechanism, and the control accuracy of the rear wheel steering mechanism is reduced. Accordingly, a control valve for the rear wheel steering mechanism is disposed adjacent to the front wheel steering mechanism such that the control valve is directly driven in connection with steering wheel control and is connected by a pipe to the control valve. Preferably, the amount of operation of the rear wheel steering actuator is fed back to the output of the control valve via a feed back cable. In this case as well, the load acting on the feedback cable is small, but if the feedback cable extends, the control accuracy of the actuator is reduced. Also, if the feedback cable is broken, the actuator may be riot.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, an object of the present invention is to make a tension spring absorb timely expansion of a feedback cable,
It is an object of the present invention to provide a rear wheel steering mechanism in which, when a tension spring or a feedback cable is broken, a hydraulic circuit is immediately opened to return a servo control valve to a neutral position.

Means for Solving the Problems In order to achieve the above object, the configuration of the present invention drives a servo control valve in connection with operation of a steering wheel, and controls the hydraulic circuit of the rear wheel steering actuator by the servo control valve. In the rear wheel steering mechanism described above, the servo control valve is a valve having an input port connected to a discharge port of a hydraulic pump, a drain port connected to an oil tank, and a pair of output ports respectively connected to both end chambers of the rear wheel steering actuator. The relative movement between the input shaft, which is engaged with the steering wheel, and the output shaft, which is associated with the piston rod of the rear-wheel steering actuator, is fitted into the housing, so that the input port has a pair of output ports. On the other hand, a drain port is a four-port neutral position open type directional control valve connected to the other of the pair of output ports, and the output shaft is connected to the output port through a clutch. A lever is connected to the connected shaft, the lever and the piston rod are connected by a field back cable, and a tension spring for tensioning the field back cable is provided between the lever and the bell crank abutting on the stopper. And a spring weaker than the tension spring that urges the bell crank in a direction away from the stopper, between the bell crank and the fixed portion, and turns the bell crank in a direction away from the stopper. A normally-closed on-off valve arranged in a passage connecting the discharge port of the hydraulic pump and the oil tank is opened in conjunction with the movement.

[Operation] When the tension spring or the feedback cable is cut, a bell crank as a detecting member is pushed by the force of the weak spring, and the normally closed on-off valve is opened by the bell crank.
The discharge port of the hydraulic pump communicates with the oil tank. The servo control valve returns to the neutral position, and the rear wheel steering actuator is returned to the neutral position by the force of the return spring.

[Embodiment of the Invention] The present invention will be described in the case of a rear wheel steering mechanism of a four-wheel steering vehicle. However, the present invention is not limited to this, and is applied to a mechanism for feeding back the operation of a hydraulic actuator remotely controlled by a hydraulic pressure via a servo control valve to the servo control valve using a feedback cable.

As shown in FIG. 1, when the relay shaft 19 rotated in association with the operation of the front wheel steering mechanism 30 is transmitted to the input shaft 24 of the servo control valve B via the steering angle ratio control mechanism A, the steering is started. The actuator D is driven and the rear wheel 60 is steered. The steering amount of the rear wheel 60 is fed back to the servo control valve B via the feedback cable 50.

When the steering shaft 37 is driven by the handle 41, the output shaft 29 of the hydraulic front wheel steering mechanism 30 is rotated, and the drag link 33 is moved forward and backward by the steering original arm 32 projecting downward from the output shaft 29, and the front wheels are moved. Steered. At the same time, the arm 31 of the output shaft 29 and the arm 36 of the relay shaft 19 supported by the bracket 16 of the housing of the front wheel steering mechanism 30 are connected by the link 35, and the rotation of the output shaft 29 is transmitted to the relay shaft 19. A projecting piece 22 extending in the radial direction from the control member 20 spline-fitted to the relay shaft 19 is
V formed on the peripheral surface of the cup-shaped notch member 21 connected to 24
It can be engaged with the cutout 21a.

The gap between the notch 21a and the projection 22 is adjusted by the axial movement of the control member 20. Therefore, the fork-shaped lower end of the lever 18 supported on the vehicle body side by the support shaft 17 is engaged with the annular groove of the control member 20, while the upper end is connected to the piston rod of the actuator 15. The stroke of the actuator 15 is controlled against the force of the spring 13 in relation to the vehicle speed.
Accordingly, when the handle 41 is turned at a certain angle from the neutral position, the rotation of the relay shaft 19 is transmitted to the input shaft 24.

The servo control valve B is, for example, a known rotary type 4-port neutral position open type directional control valve. That is, the servo control valve B is connected to the input port connected to the discharge port of the hydraulic pump 25 and the oil tank.
26 and a pair of output ports respectively connected to both end chambers 46, 48 of the rear wheel steering actuator D, and a cutting angle of a handle 41 fitted to the valve housing. Input shaft 24 and the piston rod or tie rod 51 of the rear wheel steering actuator D
And an output shaft 6 that operates in conjunction with the
The input port is connected to one of the pair of input ports and the drain port is connected to the other of the pair of output ports by the relative movement of the output shaft 6 and the output shaft 6. That is, when the input shaft 24 is rotated, the pressure oil of the hydraulic pump 25 is supplied to the pipe 27, the servo control valve B, and the pipe 4
The oil in the other end chamber is supplied to one of the end chambers 46, 48 of the steering actuator D via one of the pipes 2, 43, and returned to the oil tank 26 through the other of the pipes 42, 43, the servo control valve B, and the pipe 28. . Accordingly, the piston 47 fitted to the cylinder 44 of the rear wheel steering actuator D is pushed rightward or leftward against the force of the return spring 45, and the rear wheel is 60 is deflected about a pivot 58.

At the same time when the servo control valve B is operated, the switching valve 38 is operated, and the actuator is switched from the hydraulic pump 25 through the switching valve 38.
Pressure oil is supplied to the end chamber 53 of the cylinder 54 of the piston 55 and the piston 57
Is pushed up against the force of the spring 56, and the locking member 52 is disengaged from the receiving member 49 of the tie rod 51.

According to the present invention, in order to feed back the operation amount of the rear wheel steering actuator D to the servo control valve B, one end of the feedback cable 50 is connected to the tie rod 51, and the other end is connected to the lever 9a of the output shaft 6 at the output end. Connected to the end. In practice, the feedback cable 50 is guided through an outer tube having one end fixed to the cylinder 44 of the rear wheel steering actuator D and the other end fixed to the housing of the servo control valve B, for example.

An electromagnetic clutch C is constituted by the friction plate 9 connected to the lever 9a, the friction plate 7 connected to the output shaft 6, and the electromagnetic coil 8. The friction plate 9 is supported on another shaft coaxially arranged with the output shaft 6. When the electromagnetic coil 8 is excited, the friction plate 9 and the friction plate 7 are frictionally engaged, and the rotation of the lever 9a is transmitted to the output shaft 6. The amount of rotation in the same direction corresponding to the amount of rotation of the input shaft 24 is given to the output shaft 6, at which position the piston 47 of the rear wheel steering actuator D stops.

According to the present invention, the tension spring 5 is provided between the lever 9a and the bell crank 10 as a detection member which is abutted against the stopper 11.
And a spring 12 that is weaker than the tension spring 5 is bridged between the bell crank 10 and the fixed portion 14, and the force of the spring 12 urges the bell crank 10 to rotate away from the stopper 11. A normally closed on-off valve 39 connected between the hydraulic pump 25 and the oil tank 26 and the bell crank 10 are linked by a link 3.

Next, the operation of the rear wheel steering configuration according to the present invention will be described. When the servo control valve B is in the neutral position, the electromagnetic clutch C is shut off. The feedback cable 50 is tensioned by the force of the tension spring 5, and the slack is removed. At the same time as the servo control valve B is operated from the neutral position during steering, the electromagnetic clutch C is connected, and the operation of the rear wheel steering actuator D is transmitted to the output shaft 6 via the feedback cable 50 and the lever 9a.

When the feedback cable 50 is broken or the tension spring 5 is broken, the bell crank 10 as a detecting member is rotated clockwise about the support shaft 4 by the force of the spring 12. Specifically, the normally closed on-off valve 39 is opened, the hydraulic pressure supplied to the rear wheel steering actuator D via the servo control valve B is released, and the rear wheel steering actuator D is returned to the return spring 45.
To return to the neutral position. At the same time, the hydraulic pressure of the actuator 55 is released, so that the piston 57 is pushed down by the force of the spring 56, the locking member 52 is engaged with the receiving member 49, and the rear wheel 60 is locked to the straight traveling position.

In the embodiment shown in FIGS. 2 and 3, the tension spring 5 is wound around the output shaft 6. One end 5b of the tension spring 5 is engaged with a lever 9a that locks the feedback cable 50, while the other end 5b is engaged with the lever 9a.
5a is locked to a lever 10a as a detection member which is supported at the output end 6 so as to be freely rotatable independently of the lever 9a. The end of the lever 10a abuts a stepped rod 68 of the switch device 70.

The switch device 70 slidably supports a stepped rod 68 on both end walls of a stepped housing 67, and interposes a spring 12a between a spring seat 65 connected to the stepped rod 68 and an end wall of the housing 67. It becomes. A pair of fixed contact pieces 61 and 62 are supported on the end wall of the housing 67. A spring 64 is interposed between a movable contact 66 slidably supported by a stepped rod 68 within a predetermined range and a spring seat 65.

Normally, the lever 10 shown in FIG.
a is pressed against the stepped rod 68, and the spring seat 65 is pressed against the step of the housing 67. At the same time, tension spring 5
With this force, the lever 9a is rotated clockwise about the output shaft 6, and the feedback cable 50 is tensioned.

If the feed back cable 50 breaks or the tension spring 5
Is broken, the force for urging the lever 10a to rotate counterclockwise is released, and the force of the spring 12a of the switch device 70 causes
The step rod 68 is returned to the right along with the spring seat 65. Accordingly, the movable contact piece 66 is separated from the fixed contact pieces 61 and 62, the switch is opened, and the energizing circuit of the normally closed solenoid on-off valve is opened to open the solenoid on-off valve.

In the above embodiment, the case of the hydraulic actuator has been described, but the present invention can also be applied to a pneumatic actuator.

[Effects of the Invention] As described above, the present invention relates to a rear wheel steering mechanism that drives a servo control valve in association with operation of a steering wheel and controls a hydraulic circuit of a rear wheel steering actuator by the servo control valve. The control valve has a handle housing fitted with a valve housing having an input port connected to the discharge port of the hydraulic pump, a drain port connected to the oil tank, and a pair of output ports respectively connected to both end chambers of the rear wheel steering actuator. Due to the relative movement between the input shaft operating in relation to the turning angle and the output shaft operating in relation to the piston rod of the rear wheel steering actuator, the input port becomes one of a pair of output ports,
A 4-port neutral position open type directional control valve having a drain port connected to the other of the pair of output ports, and a lever connected to a shaft connected to the output shaft via a clutch;
The lever and the piston rod are connected by a feedback cable, and a tension spring for tensioning the feedback cable is bridged between the bell crank abutting against the stopper and the lever. A spring, which is weaker than the tension spring that urges the bell crank away from the stopper, is suspended between the fixed portion and the bell crank, and the hydraulic pressure is interlocked with the rotation of the bell crank away from the stopper. Because the normally closed on-off valve arranged in the passage connecting the discharge port of the pump and the oil tank was opened,
If the feedback cable breaks or the tension spring that tensions the feedback cable breaks, the bell crank that has been pressed against the stopper by the tension spring is pulled back by the force of the weak spring, and interlocks with the bell crank. The normally closed on-off valve disposed in the passage connecting the discharge port of the hydraulic pump and the oil tank opens, and the hydraulic circuit of the servo control valve that controls the rear wheel steering actuator is opened. Operation is prevented.

A rear-wheel steering actuator remotely controlled by a servo control valve adjacent to a hydraulic power source is controlled with high accuracy by a simple and inexpensive feedback cable.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a rear wheel steering mechanism applied to a case of a four-wheel steering vehicle, FIG. 2 is a side view of a main part of a rear wheel steering mechanism according to a second embodiment of the present invention, and FIG. It is the same front view. B: servo control valve, C: clutch, D: rear wheel steering actuator, 5: tension spring, 6: output shaft, 12, 12a: spring, 9a: lever,
10, 10a: Bell crank, 11: Stopper, 24: Input shaft, 25: Hydraulic pump, 26: Oil tank, 41: Handle, 39: Normally closed on-off valve, 5
0: Feed back cable, 51: Piston rod

Claims (1)

(57) [Claims] In a rear wheel steering mechanism for driving a servo control valve in association with operation of a steering wheel and controlling a hydraulic circuit of a rear wheel steering actuator by the servo control valve, the servo control valve is a discharge port of a hydraulic pump. And a drain port connected to the oil tank and a pair of output ports respectively connected to both end chambers of the rear-wheel steering actuator. Due to the relative movement between the input shaft and the output shaft that operates in relation to the piston rod of the rear wheel steering actuator,
An input port is one of a pair of output ports, and a drain port is a four-port neutral position open type directional control valve connected to the other of the pair of output ports, and is connected to a shaft connected to the output shaft via a clutch. A lever is connected, the lever and the piston rod are connected by a field back cable, and a tension spring for tensioning the feed back cable is bridged between the bell crank abutting on the stopper and the lever; A spring that is weaker than the tension spring that urges the bell crank in a direction away from the stopper is applied between the bell crank and the fixed portion, and is interlocked with the rotation of the bell crank in a direction away from the stopper. Then, a normally-closed on-off valve disposed in a passage connecting the discharge port of the hydraulic pump and the oil tank is opened.