JPH0714121Y2 - Safety device for vehicle four-wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a four-wheel steering system for a vehicle, and more particularly to a safety device for a four-wheel steering system including a front wheel steering mechanism and a rear wheel steering mechanism.

(Prior Art) Generally, there are two types of vehicle four-wheel steering systems, one in which a front wheel steering mechanism and a rear wheel steering mechanism are mechanically connected and the other in which they are not connected. The output shaft of the rear wheel steering mechanism is configured to be able to move almost freely in the axial direction, except for those that mechanically connect both mechanisms. Due to the control being applied, the rear wheel steering mechanism is operating normally.

Furthermore, in case the hydraulic control or electric control becomes abnormal while the vehicle is running and the output shaft becomes free,
A centering spring etc. is built into the rear wheel steering mechanism to hold the output shaft at the neutral position of the rear wheel steering mechanism.

Similarly, measures such as locking the output shaft in the axial direction with pressure oil accumulated in an accumulator provided in the hydraulic control means are taken.

(Problems to be Solved by the Invention) The safety device of the conventional four-wheel steering system described above includes the centering spring, the accumulator, and the power cylinder of the rear wheel steering mechanism in relation to the axial direction of the output shaft. In many cases, they are arranged in series with each other, so that they become large in the axial direction, and as a result, the entire rear wheel steering mechanism becomes large, and the device cannot be designed compact. As a result, the space required for installation becomes large, which may hinder the vehicle design.

In addition, in order to hold down the length in the axial direction, there is one provided with a member that locks the output shaft in the radial direction of the output shaft, but even in this case, in terms of compact design of the device, it is not always necessary.
I'm not satisfied.

Therefore, an object of the present invention is to provide a safety device for a four-wheel steering system for a vehicle, which has a compact structure, can lock the output shaft of the rear wheels in the event of an abnormality in hydraulic pressure or an electrical system, and has improved design freedom. is there.

(Means for Solving the Problems) In order to achieve the above-mentioned object, a safety device for a four-wheel steering system according to the present invention includes a front wheel steering mechanism for steering front wheels, a cylinder portion, and a cylinder portion. An output shaft and a fixing member fixed to the output shaft, and a rear-wheel steering mechanism that is interlocked with the front-wheel steering mechanism and is controlled by hydraulic pressure supplied into the cylinder. In a four-wheel steering device for a vehicle that steers the rear wheels by axially displacing the output shaft to which the rear wheels are coupled according to the turning of the front wheels, the four-wheel steering device is provided in the cylinder portion, A piston member axially slidably mounted on the output shaft, and an accumulator for holding a predetermined hydraulic pressure, and hydraulic means for applying hydraulic pressure to the cylinder portion and hydraulically controlling the piston member, Monitoring means for monitoring the hydraulic pressure of the hydraulic means, Detection means for detecting an abnormality in the electric system of the rear wheel steering mechanism, the monitoring means detects that the hydraulic pressure of the hydraulic means has dropped below a predetermined value, and / or the detection means is electrically When a system abnormality is detected, the piston member moves in the axial direction by the hydraulic pressure from the accumulator, and the fixing means is locked at the neutral position of the rear wheel steering mechanism.

(Operation) With the above-described structure, the safety device for a four-wheel steering system according to the present invention can lock the output shaft of the rear wheels with a simple structure, which ensures reliable operation even when the vehicle is abnormal. To ensure safety.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same parts are designated by the same reference numerals.

First, a four-wheel steering system incorporating the safety device of the present invention will be described. FIG. 3 is a schematic system diagram showing the entire four-wheel steering system.

In FIG. 3, the front wheel steering mechanism A is configured such that the turning amount of the handlebar 1, that is, the turning amount is transmitted to the rear wheel steering mechanism B via a mechanical or electrical mechanism (not shown). Has been done.

The details of the configuration and operation of the front wheel steering mechanism will be described below.
When the handle 1 is operated, that is, rotated, the steering shaft 6 that integrally supports the handle 1 rotates, and the pinion 2 fixed to the steering shaft 6 also rotates. Pinion 2
The rotation amount of is taken out as an axial movement amount of the rack shaft 3 via rack teeth (not shown) formed on the outer periphery of the rack shaft 3 of the front wheel meshing with the pinion 2.

When the rack shaft 3 moves in the axial direction, the front wheels 5 that are rotatably connected to the rack shaft 3 via the tie rods 4 are steered. A power cylinder member 7 that assists the steering of the front wheels is provided so as to penetrate the rack shaft 3 so as to be axially displaceable.

The power cylinder member 7 is pumped from an oil supply source 10 via a flow control valve 9 and a control valve 8 which works in conjunction with the pinion 2.
Oil having a predetermined hydraulic pressure for control is supplied by 11.

Further, the steering shaft 6 is provided with a steering angle sensor 36 for detecting the steering angle of the front wheels, and the steering angle signal from the steering angle sensor 36 controls the electric system of the four-wheel steering system as described later. It is sent to the controller 34.

Next, the rear wheel steering mechanism B and the safety device C will be described.

First, the rear wheel steering mechanism B will be described. Cylinder member 30
Has its both ends closed by end members 29 fixed to its both ends to define an isolated chamber to which hydraulic pressure is supplied. The rear wheel rack shaft 24 is
Penetrates 29. Since the center piston 31 is fixed to substantially the center of the rack shaft 24, the center piston 31 can move in accordance with the axial movement of the rack shaft 24.
It moves in the axial direction together with.

The rear wheel steering mechanism B will be described in more detail with reference to FIG. Two piston members 32 are slidably fitted on the outer circumference of the cylindrical portion of the end member 29 relative to the cylindrical portion of the cylinder member 30. At one axial end of the piston member 32, cylindrical projecting portions 32a extending in the axial direction are provided so as to face each other, and at the other axial end, radially outward. Flange portions 32b protruding inward are respectively provided. The flange portion 32b comes into contact with the step portion 30c provided on the cylinder member 30 when the piston member 32 moves in the axial direction toward the center piston 31, so that the amount of movement in the axial direction is limited. this is,
This is to prevent one of the piston members 32 from penetrating too much into the side of the center piston 31 and thus hindering the centering function of the rack shaft 24. The piston members 32 are usually held by springs 41 on the outer sides of both ends.

Hydraulic pressure is supplied to the cylinder member 30 by the center piston 31, the piston member 32, and the end member 29.
Two hydraulic chambers, the first hydraulic chambers 30a and 30b, are defined.

Further, the space provided between the piston member 32 and the end member 29 so that the flange portion 32b of the piston member 32 moves is the third and fourth hydraulic chambers 37 and 38. There is.

Further, on a part of the outer peripheral surface of the rack shaft 24, a rack tooth portion 24a in which rack teeth are engraved is provided. A pinion 26 that rotates integrally with the shaft 25 is meshed with the rack tooth portion 24a. When the pinion 26 is rotated by driving the electric motor 22, the rack shaft 24 moves in the axial direction depending on the rotation direction of the motor 22. Displace, that is, move in either direction. The electric motor 22 is controlled by the controller 34. In addition, the control valve 40 interlocking with the shaft 25 controls the hydraulic pressure to power-assist the rack shaft 24.

In this embodiment, the rear wheel steering mechanism B is electrically controlled, but it goes without saying that it may be mechanically controlled.

Now, returning to FIG. 3, the rear wheel rack shaft 24 has
A rear wheel 28 is rotatably connected via a tie rod 27. Further, in order to detect the amount of axial displacement of the rack shaft 24, a detector 33 that detects the amount of axial displacement of the rack shaft (in other words, the amount of steering of the rear wheels) is provided near the rack shaft 24. The detection signal from the detector is provided to the controller 34.

Next, the safety device C will be described with reference to FIG. still,
FIG. 1 is a system diagram when the hydraulic and electrical systems of the four-wheel steering system of the present invention are functioning in a normal state.
The oil from the hydraulic power supply source 10 for power steering of the front wheels is controlled by the pump 12 via the oil passages by the control valve 13 and the diversion valve 14 for controlling the rear wheel steering mechanism B.
Of the power cylinder member 30. A relief valve 15 is provided in the oil passage extending from the control valve 13 and releases the oil pressure when an excessive oil pressure is applied to the oil passage.

The oil passage from the flow dividing valve 14 branches into an oil passage L ₁ and an oil passage L ₂ . The oil passage L ₁ is provided with a check valve 17 for backflow prevention, and a control valve 18 for rack shaft locking controlled by a solenoid.
It is connected to the. An accumulator 16 for holding and accumulating a predetermined oil pressure is provided in an oil passage between the check valve 17 and the control valve 18.

The control valve 18 is further connected to a closing valve 19 which is also controlled by a solenoid, and the closing valve 19 is connected to an oil recovery pan 20.

The oil passages from the control valve 18 and the shutoff valve 19 merge on the way to form an oil passage L ₃ . This oil passage L ₃ has two oil passages from the middle.
Branched to L ₆ and L ₇ , respectively the 3rd and 4th hydraulic chambers
Connected to 37 and 38.

On the other hand, the other oil passage L ₂ branched from the diversion valve 14 is connected to the cylinder member 30 via a control valve 21 controlled by a solenoid.
Supply hydraulic pressure to. Two oil passages L ₄ and L ₅ are branched from the control valve 21 and are connected to the first and second hydraulic chambers, respectively.
Connected to 30a and 30b. The oil passage L ₂ is provided with a pressure sensor 23 for constantly monitoring the oil pressure supplied to the cylinder member. The magnitude of the hydraulic pressure detected by the pressure sensor 23 is applied to the controller 34 in the form of an electric signal (see FIG. 3). Therefore, when the hydraulic pressure becomes equal to or lower than the predetermined hydraulic pressure value, the controller 34 functions based on the information from the pressure sensor 23 to lock the rack shaft 24 at the center position as described below.

Hereinafter, the specific operation of the safety device of this embodiment will be described in detail.

In the system diagram of FIG. 1 showing the state where the rear wheel steering mechanism B of the four-wheel steering device is operating normally, that is, the state where the safety device C is not operating, the control valve 18 closes the hydraulic circuit. In the OFF state, the stop valve 19 and the control valve 21 are in the ON state, which releases the hydraulic circuit, and the control valve 21 controls the first and second hydraulic pressures via the oil passages L ₄ and L ₅ , respectively. Chamber 30
The specified hydraulic pressure is supplied to a and 30b.

In the state of FIG. 1, when the abnormality of the electric system of the rear wheel steering mechanism B is detected or the pressure sensor 23 detects the decrease of the hydraulic pressure,
Or, if both are detected, the controller 34
Switches the control valve 21 to the OFF state and stops the supply of hydraulic pressure to the first and second hydraulic chambers 30a and 30b. On the other hand, in parallel with this, the control valve 18 is switched from the OFF state to the ON state based on the signal from the controller 34, and at the same time, the closing valve 19 is switched from the ON state to the OFF state. A current for control and a current for abnormality detection are constantly supplied to the controller 34.

As described above, the high-pressure oil accumulated in the accumulator 16 immediately after the valves 18, 19 and 21 are switched to the _third valve via the control valve 18 and the oil passages L ₃ , L ₆ and L ₇ . And to the fourth hydraulic chambers 37 and 38. Therefore, the two piston members 32 move toward each other in the axial direction so as to sandwich the center piston 31 by the hydraulic pressure.
Finally, the protruding portion 32a of the piston member 32 comes into contact with the end surface of the center piston 31 and sandwiches it, so that it cannot move in the axial direction. This position is set to the neutral position of the rack shaft 24 of the rear wheel as described above. The piston member 32
With the center piston 31 sandwiched and locked,
Since the flange portion 32b contacts the stepped portion 30c of the cylinder member 30, the piston member 32 is prevented from being displaced and the neutral position described above can be accurately maintained.

The locking operation of the center piston 31 by the piston member 32 is not performed instantaneously. This is because when the safety device is activated, the control valve 21 is turned off so that the rear wheel is temporarily blocked at that position, and at the same time, the high pressure oil from the accumulator 16 presses the piston member 32. Then, the center piston 31 is gradually fixed to the center position due to the leakage of the control valve 21. Therefore, it is possible to prevent the impact due to this locking operation from being immediately transmitted to the vehicle.

(Effects of the Invention) According to the safety device of the present invention described above, the following effects can be obtained.

Since only the cylinder member of the conventional rear wheel steering mechanism is simply improved, the safety device has a compact structure.

In addition, the axial length of the output shaft of the rear wheel and the space in the radial direction can be reduced, so that the degree of freedom in designing the vehicle is improved.

[Brief description of drawings]

FIG. 1 is an overall system diagram of a four-wheel steering system showing one embodiment of the present invention, and FIG. 2 is a system diagram showing an outline of a safety system of this embodiment when the rear wheel steering mechanism is normally operating. FIG. 3 is a schematic system diagram showing a state in which an abnormality of the vehicle is detected and the safety device is activated in FIG. [Description of symbols of main parts] 18, 21 ...... Control valve 23 ...... Pressure sensor 19 ...... Closed valve 30 ...... Cylinder member 31 ...... Center piston 32 ...... Piston member 34 ...... Controller B ...... Rear wheel steering Mechanism C ... Safety device

Claims (1)

[Scope of utility model registration request] 1. A front wheel steering mechanism for steering front wheels, a cylinder portion, an output shaft housed in the cylinder portion, and a fixing member fixed to the output shaft, the front wheel steering mechanism being interlocked with the front wheel steering mechanism. ,
A rear wheel steering mechanism that is controlled by hydraulic pressure supplied to the cylinder, both front and rear wheels can be steered, and the output shaft, to which the rear wheels are connected according to the steering of the front wheels, is axially displaced. In a four-wheel steering device for a vehicle that steers the rear wheels, a piston member provided inside the cylinder portion and axially slidably mounted on the output shaft, and an accumulator holding a predetermined hydraulic pressure. And hydraulic means for hydraulically controlling the piston member while applying hydraulic pressure to the cylinder part, monitoring means for monitoring the hydraulic pressure of the hydraulic means, and detecting an abnormality in the electrical system of the rear wheel steering mechanism. A detection means, and when the monitoring means detects that the hydraulic pressure of the hydraulic means has dropped below a predetermined value and / or the detection means detects an abnormality in the electric system, the accumulator Due to the oil pressure, Tons member safety device, characterized in that to lock the said fixing means to move in the axial direction to the neutral position of the rear wheel steering mechanism.