JPS62131878A - Four wheel steering device for vehicle provided with safety device - Google Patents

Abstract

PURPOSE:To prevent a vehicle from fluctuating when a failure occurs, by providing a means for blocking the communication between a hydraulic actuator and a control valve therefor when a fluid pressure system for a rear wheel steering mechanism fails. CONSTITUTION:When a hydraulic system fails, no oil flows through pipe lines 31, 17, and therefore, the pressures of pipe lines 33, 32 are made to be equal to each other. Accordingly, no axial force due to the pressure differential is effected across a spool 26a in a block valve 26, and therefore, the spool 26a may be moved by a spring 42. At this position the passages between pipe lines 28, 24 and between pipe lines 27, 25 are blocked, and hydraulic oil in a hydraulic actuator 23 is confined so that a piston 23d is made to be stationary. With this arrangement, even if the system is failed, the chambers in the hydraulic actuator 23 resist against the external force, sufficiently, and therefore, it is possible to restrain the vehicle from being fluctuated.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a four-wheel steering device for steering both the front and rear wheels of a vehicle, a fluid pressure actuator in the rear wheel steering mechanism, and this fluid pressure actuator. The present invention relates to a four-wheel steering system equipped with a safety device that ensures safety when a failure occurs in a fluid pressure system for a control valve means for controlling a vehicle.

(Prior Art) Conventionally, various configurations of four-wheel steering devices have been proposed, including one that uses a fluid pressure actuator for a rear wheel steering mechanism. (For example, see Japanese Patent Laid-Open No. 59-128054).

The problem with these devices is that when a failure occurs in the fluid pressure system, the fluid pressure actuator loses force and is moved by external force from the rear wheels, etc., resulting in the vehicle shaking. There is.

(Object of the Invention) Therefore, an object of the present invention is to provide a four-wheel steering system with a safety device that prevents the vehicle from shaking when a failure occurs in the fluid pressure system.

(Structure of the Invention) In order to achieve this object, in the four-wheel steering device according to the invention, when the control valve means for the fluid pressure actuator of the rear wheel steering mechanism normally operates, the control valve means controls the fluid pressure to 7.
The two are normally connected so that the actuator is controlled normally, and if a failure occurs in the fluid pressure system that supplies fluid pressure to both, the connection between the two is cut off and the fluid pressure actuator fails. Safety devices are in place to keep the situation nearly as it was when it occurred.

(Example) Examples will be described below.

In Fig. 1, IR is the right front wheel, 1L is the left front wheel, 2R is the right rear wheel, and 2L is the left rear wheel.The left and right front wheels IR and IL are linked by a front wheel steering mechanism A, and the left and right rear wheels are 2R,
2L is linked by rear wheel steering mechanism B.

In the embodiment, the front wheel steering mechanism includes a pair of left and right knuckle arms 3R, 3L and tie rods 4R, 4L, a relay rod 5 that connects the pair of left and right tie rods 4R, 4L, and a power steering mechanism C. It is configured. A steering mechanism is linked to this front wheel steering mechanism A, and this steering mechanism is of a power assist type in this embodiment. In other words, it is as follows. A rack 6 is formed on the relay rod 5, and a pinion 7 that meshes with the rack 6 is connected to a handle 9 via a shaft 8. Furthermore, a hydraulic actuator 10 is attached to the relay rod 5,
A piston 10d that divides the inside of the cylinder 10a into two chambers 10b and 10e is integrated into the relay rod 5. The two chambers 10b110e in the cylinder 10a are connected to the piping 11.1.
Control valve 13 provided on shaft 8 via 2
It is connected to the. This control valve 13 has
A pipe 16 extends from a branch valve 15 connected to the discharge side of an oil pump 14 driven by an engine (not shown), and a nine pipe 18 is connected to the pipe 17 branching off from the pipe 17. With such a power steering mechanism C, the steering wheel 9
The operating force of is boosted (boosted by supplying oil to chamber 10b or 10eK of hydraulic actuator 1o)
and is transmitted to the relay rod 5. As a result, when the handlebar 9 is turned to the right, the relay rod 5 is power-assisted and displaced to the left in FIG.
The vehicle is steered clockwise in the figure by an amount corresponding to the amount of operational displacement of the handle 9, that is, the steering angle of the handle 9, with L' as the center. Similarly, when the steering wheel S is operated to the left, the left and right front wheels IB and IL are steered to the left in accordance with the amount of displacement of this operation.

Similarly to the front wheel steering mechanism, the rear wheel steering mechanism B also includes a pair of left and right knuckle arms 20R120L and tie rods 21R, 21L, a relay rod 22 that connects the tie rods 21B, 21L, and a hydraulic power steering mechanism. It is said to be configured with E. To explain this power steering mechanism E, a hydraulic actuator 23 is attached to the relay rod 22, and a piston 23d defining two chambers 23b and 23eK in the cylinder 231 is integrated with the relay rod 22.

The two chambers 23b123a in this cylinder 23a are arranged W2
4.25 to a block valve or switching valve 26 constituting a safety device, and this block valve 26
is connected via pipes 27, 28 to a control valve 29 constituting control valve means.

The above-mentioned pipe 17 extending from the reservoir tank 30 and the pipe 31 extending from the diversion valve 15 are connected to the valve 2S. Piping 17.31 is branched midway and becomes pipe 3.
2.33 to the block valve 26.

The pipe 17 is provided with a throttle 34 before entering the control valve 29. The above control valve 29
has an input shaft 291 serving as an input member of the power steering mechanism E, and an output shaft 29b serving as an output member connected to the human power shaft 29m.

In such a power steering mechanism EK, when the input shaft 29& is moved in one predetermined direction, the output shaft 29b is correspondingly moved in a predetermined direction, and the relay rod 22 is moved, for example, to the left in FIG. From this point K, the knuckles 7-m 20R, 20L are at their rotation centers 20R',
The rear wheels 2R and 2L are turned to the right by rotating clockwise in FIG. 1 about 20L'. And during this turning,
Oil is supplied into the chamber 23e of the cylinder device 23 according to the momentum of the input shaft 29m, and the relay rod 2
2 (boosting effect). Similarly, when the input shaft 29m is moved in the opposite direction, the rear wheels 2R and 2L are rotated to the left while receiving the boosting action of the cylinder device 230 (oil is supplied to the chamber 23b) according to this momentum. It will be steered.

In FIG. 1, reference numerals 23 and 23f are return springs that bias the relay rod 22 toward the neutral position.

The steering mechanism and the rear wheel steering mechanism B are linked via the front wheel steering mechanism A and the steering ratio changing device F.

An intermediate rod 35 extends forward from the steering ratio changing device F, and a pinion 36 attached to the front end of the intermediate rod 35 meshes with a rack 37 formed on the relay rod 5 of the front wheel steering mechanism A. Furthermore, the steering ratio changing device F and the control valve 29 are coupled via the input shaft 29m.

In the case of this embodiment, the steering ratio changing device F changes the steering ratio according to the vehicle speed. For example, at low speed, rear wheel 2R,
The 2L is steered in the opposite direction to the front wheels IR and IL, and is steered in the same direction when the vehicle speed exceeds a predetermined value.

To describe the configuration of this part, a vehicle speed signal from a vehicle speed sensor 39 and a steering ratio signal from a steering ratio detection sensor 40 are input to the control circuit 38, and a signal from the control circuit 38 is input based on a comparison result of both signals. A control signal is output to the steering ratio changing device F. In this way, the steering ratio is set in the steering ratio changing device F according to the vehicle speed while performing feedback control. In FIG. 1, 4.1 is a battery.

The control valve 29, block valve 26, and hydraulic actuator 230 will now be described in detail with reference to FIGS. 2 to 4. As shown in FIG. 2, the control valve 29 is a four-way open type.
Controlled by the steering ratio changing device F, the connection between the piping 17.31 and the piping 27.28 is switched in three stages. The block valve 26 is a 4-way closed type.
The spool 26a is biased to the left in FIG. 82 and to the right in FIG. 3 by a coil spring 42. Therefore, only when the oil pressure in the pipe 33 becomes higher than the oil pressure in the pipe 32 and the oil in the pipe 33 flows into the space 26d through the circumference $26b and the hole 26e (during normal operation), The spool 26m overcomes the force of the coil spring 42 and moves to the left in Figure 3, resulting in the state shown in Figure 4. Similarly, the space 26d is sealed by an O-ring 43 and a screwed plug 44.

In the position shown in FIG. 4, the pipe 28 is communicated with the pipe 24 through the circumferential groove 26, and the pipe 27 is communicated with the pipe 25 through the circumferential groove 26f, so that the fi 23b of the hydraulic actuator 23.

The pipes 23a are connected to the pipes 2B and 27, respectively, and oil flows therein to achieve a normal operating state. That is, the control valve 29 and the hydraulic actuator 23 are in a normal connection state in which the hydraulic actuator 23 is normally controlled. For example, if the control valve 29 is switched to the state shown on the right side in FIG. 2 under the control of the steering ratio changing device F, oil will flow into the left chamber 23b of the hydraulic actuator 23 via the pipes 31, 28, and 24. Push the piston 23d to the right, move the relay rod 22 to the right, and move the rear wheel 2R.
, 2L to the left in Figure 1.

When the control valve 29 is switched to the state shown in the center of FIG. 2, the left and right chambers 23b and 2311 of the hydraulic actuator 23 have the same pressure, and the rear wheels 2R and 2L are operated by the action of the return springs 23e and 23f and the self-alignment action of the rear wheels.
attempts to return to neutral position. Further, when the control valve 29 is switched to the state shown on the left side in FIG. 2, oil flows into the right chamber 23e of the hydraulic actuator 23, steering the rear wheels 2R, 2L to the right in FIG.

Next, whether a failure occurs in the hydraulic system and a hydraulic failure occurs;
When the engine stops and the oil pressure is turned off, pipe 31.1
Since oil is not flowing to 7, the control valve 29
There is no pressure drop caused by the orifice 34, and the piping 31.1
T, that is, the pipes 33 and 32 have the same pressure.

Therefore, the pressure in the spaces 26d and 28g is the same, and the pressure difference of 8CL in the spool 2BaK of the block valve 26 is not generated, and the spool 26m, which is extended to the right in FIG. 3 by the coil spring 42, moves in the same direction. The state shown in Figure 3 will be reached. In this position, the flow paths are blocked between the pipes 28 and 24 and between the pipes 27 and 25, so the oil in the left and right chambers 23b and zae of the hydraulic actuator 23 is trapped, respectively, and the piston 2
3d is fixed. In this way, the hydraulic actuator 23 is maintained almost in the state at the time of failure or when the hydraulic pressure is turned off. In this case, if the rear wheels 2R, 2L are cut in either direction and an external force is applied to the relay rod 22 from the rear wheel side, oil will leak little by little and the return springs 23, 23f
Due to this action, the rear wheels 2R and 2L gradually try to return to the neutral position.

(Effects of the Invention) As described above, according to the present invention, even if the fluid pressure actuator' is used in the rear wheel steering mechanism, a safety device such as the switching valve as described above is provided between the control valve means and the fluid pressure actuator. Because of this, even if a failure occurs in the fluid pressure system, each chamber of the fluid pressure actuator is sealed and is sufficiently resistant to external forces, and the vehicle is prevented from shaking.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view of a vehicle equipped with an embodiment of the present invention, FIG. 2 is an enlarged view of the main parts of FIG. 1, and FIGS.
The figure is a diagram for explaining the operation of the block valve. [Explanation of symbols of main parts] A...Front wheel steering mechanism D...Steering mechanism 23...
・Fluid pressure actuator 29, F...control valve means 14.15.17, 24, 25.27.2B, 30°3
1...Fluid pressure system 26.32.33...Safety devices 23b, 23c
......Fluid pressure actuator chamber 26...Switching valve Fig. 1

Claims (1)

[Claims] 1. A front wheel steering mechanism; A steering mechanism linked to the front wheel steering mechanism; A rear wheel steering mechanism including a fluid pressure actuator that generates a rear wheel steering force; At least according to the steering angle of the steering wheel. A control valve means for controlling the fluid pressure actuator; A fluid pressure system for supplying fluid pressure to the fluid pressure actuator and the control valve means; When the control valve means is in normal operation, the control valve means normally operates the fluid pressure actuator. A safety device is provided to maintain the fluid pressure actuator in a normal state of connection so as to be controlled, and to cut off the connection between the two when a failure occurs in the fluid pressure system to maintain the fluid pressure actuator almost in the state at the time the failure occurred. Four-wheel steering system for vehicles. 2. The safety device detects a fluid pressure difference between a pair of pipes of the fluid pressure system entering the control valve means, and when there is a fluid pressure difference, directs a pair of pipes exiting from the control valve means to the pair of pipes of the fluid pressure actuator. take an open state communicating with the respective chambers,
4. The vehicle according to claim 1, further comprising a switching valve that takes a closed state to close communication to the chamber when there is no fluid pressure difference.
Wheel steering device.