JPH0435264Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a four-wheel steering device that power-assists the steering force of front wheels and rear wheels.

(Prior Art) FIG. 4 shows a rear wheel steering device among conventional devices, particularly a control mechanism for the cylinder S thereof.
That is, this conventional device has four on/off valves 1
- 4 are provided, and these on/off valves 1 - 4 are connected in series via communication passages 5 - 7 , and the on/off valves 1 and 4 located at the outermost side are communicated with the tank T. A main passage 8 connected to the pump P is connected to the communication passage 6, and the communication passages 5 and 7 are connected to pressure chambers 9 and 10 of the cylinder S.

Thus, while the solenoids of on-off valves 2 and 4 are energized to turn them on, the solenoids of on-off valves 1 and 4 are energized and turned on.
3 is kept off, the oil discharged from pump P is
It is supplied to one pressure chamber 9 of the cylinder S via the main passage 8 → on/off valve 2 → communication passage 5. Further, the return oil in the other pressure chamber 10 at this time is returned to the tank T via the communication path 7 → the on-off valve 4.

Therefore, the piston 11 of the cylinder S moves in the direction of the arrow 12 to move the rod 13. Since both ends of this rod 13 are connected to the knuckle arms on the wheel side, the piston 11
As the rear wheel moves, the rear wheel is steered in a predetermined direction.

Moreover, contrary to the above, if the on-off valves 1 and 3 are turned on while the on-off valves 2 and 4 are kept in the off state, the discharge oil of the pump P is supplied to the other pressure chamber 10, and one The hydraulic oil in the pressure chamber 9 is returned to the tank T.

Furthermore, when all of the above-mentioned on-off valves 1 to 4 are turned on, the state is similar to the center open state of a four-way switching valve.

Note that the reason why four on/off valves are used instead of a four-way switching valve is to make the control mechanism inexpensive.

(Problem to be solved by the present invention) In the conventional device as described above, the cylinder S
In order to unload the pump P by blocking the pressure chambers 9 and 10 of the main passage 8, an on-off valve for unloading must be separately connected to the main passage 8. In particular, it is necessary to connect the front wheel steering device and the cylinder concerned separately. In the case of a mechanism in which the main passages are connected through a pair of main passages, an on/off valve for unloading must be connected to each main passage. However, the reason why on-off valves were used instead of four-way switching valves as described above was to reduce costs, but if an on-off valve was required for each main passage, this would defeat the purpose of reducing costs. There was a problem that it was impossible to achieve.

The purpose of this invention is to enable it to be applied to a mechanism provided with a pair of main passages by simply adding one on/off valve in addition to the four on/off valves for directional switching.

(Means for solving the problem) This invention is equipped with a front wheel steering device and a rear wheel steering device. The present invention is based on a four-wheel steering system in which one of the pressure chambers of the cylinders communicates with the high-pressure side and the other pressure chamber communicates with the low-pressure side in connection with driving the device.

Based on the above-mentioned device, this invention provides two sets of on-off valves, one set of on-off valves, and one set of on-off valves that connect one main passage and one pressure chamber to each other. The other on-off valve of this one set is provided between the passage that communicates the other main passage and one pressure chamber, and the one on-off valve of the other set is provided between the passage that communicates the other main passage and the other pressure chamber. The other on-off valve of the other set is provided between the passage communicating between the other main passage and the other pressure chamber, and the on-off valve of the other set is provided between the passages communicating between the other main passage and the other pressure chamber. It is characterized by communication via an on-off valve for unloading that is separate from the valve.

(Operation of the present invention) Since the present invention is constructed as described above, the pair of main passages can be short-circuited by opening the on-off valve for unloading. In other words, since the main passage on the high pressure side and the main passage on the low pressure side can be connected, the result is the same as if the high pressure side was unloaded.

(Effects of the present invention) Even in a device in which the front wheel steering device and the rear wheel steering device are communicated through a pair of main passages, the pressure chamber of the cylinder can be locked by providing only one on/off valve for unloading. The pump can be unloaded at the same time.

(Embodiment of the present invention) Front wheel steering device The front wheel steering device a in the embodiment shown in FIGS. 1 and 2 is of an integral type. When the handle 14 is turned, the input shaft 15 rotates while twisting the torsion bar 16, The rotary valve 17 is switched depending on the rotation direction of the input shaft 15.
Further, chambers 19 and 20 partitioned by the piston 18
communicates with either the pump P or the tank T, depending on the switching position of the rotary valve 17, and controls the moving direction of the piston 18.
The piston 18 thus constructed has a rack portion 18a.
A sector gear 21 is engaged with this rack portion 18a.

Therefore, when one chamber 19 communicates with the pump P and the other chamber 20 communicates with the tank T, the piston 18 moves to the right in FIG. Rotate clockwise. Further, when one chamber 19 communicates with the tank T and the other chamber 20 communicates with the pump P, the piston 18 moves to the left in the drawing and rotates the sector gear 21 counterclockwise. When the sector gear 21 rotates in this manner, the pitman arm 22 rotates and power assists the steering force of the front wheels.

The sector gear 21 has a gear portion 21a.
This gear portion 21a is located on the opposite side of the engaging portion with the rack portion 18a, and the gear portion 21a is connected to the rack portion 2 of the rack piston 23 of the metering cylinder m.
It engages with 3a.

Further, this meter ring cylinder m has oil chambers 24 and 25 partitioned by the rack piston 23.
The main passages 26 and 27 are connected to the cylinder S of the rear wheel steering system b via a control valve mechanism v, as shown in FIG.

Note that the reference numeral 28 in the figure is a suction solenoid valve that is opened when the hydraulic oil from the tank T is sucked into the main passage 26.

The specific configuration of the control valve mechanism v is as shown in FIG. 3.

That is, the control valve v includes one set of on-off valves 29 and 30, and another set of on-off valves 31,
32 is provided, and these on/off valves are connected via communication passages 33 to 35. Of the on-off valves 29 and 30 of one set, one of the on-off valves 29 is provided between the passages communicating the other main passage 27 and one pressure chamber 9 of the cylinder. Further, the other on/off valve 30 of this one set has one main passage 26 and one pressure chamber 9.
It is provided between the passages that communicate with the Further, among the on-off valves 31 and 32 of the other set, one on-off valve 31 is provided between the passages communicating between the main passage 26 on one side and the pressure chamber 10 on the other side of the cylinder.
Moreover, the other on-off valve 32 of this one set is
It is provided between the passages that communicate the main passage 26 on one side and the pressure chamber 10 on the other side.

An on-off valve 36 for unloading is provided between the main passages 26 and 27 as described above, and when the on-off valve 36 is open, both main passages 26 and 27
6 and 27 are short-circuited.

When the front wheel steering device a is driven, the sector gear 21 rotates as the piston 18 moves, and the rack piston 23 of the metering cylinder m also moves. for example,
If the rack piston 23 moves to the left in the drawing,
One oil chamber 24 becomes high pressure, the other oil chamber 25 becomes low pressure, and accordingly, one main passage 26 becomes high pressure and the other main passage 27 becomes low pressure.

At this time, the on-off valve 3 of the control valve mechanism v
When the valves 0 and 32 are opened and the on-off valves 29 and 31 are kept closed, the hydraulic oil in one of the main passages 26 flows through the communication passage 34 → on-off valve 30 → actuator passage 37 to the other main passage 26. It is supplied to the pressure chamber 9. In addition, the other pressure chamber 10 of the cylinder S
The hydraulic oil is from the actuator passage 38 to the communication passage 3.
5 → is returned to the other main passage 27 via the on/off valve 32.

Further, if the on-off valves 29 and 31 are opened in the above state and the on-off valves 30 and 32 are kept closed, the flow path becomes opposite to that described above.

Therefore, among the on-off valves 29 to 32,
By appropriately selecting the valve that opens and the valve that closes, the moving direction of the piston 11 of the cylinder S, in other words, the steering direction of the rear wheels can be controlled, and moreover, the steering direction between the front wheels and the rear wheels can be controlled. The rudder directions can be in the same phase or in opposite phases.

Furthermore, when each of the on-off valves 29 to 32 is closed and the on-off valve 36 for unloading is opened, the pressure chambers 9 and 10 of the cylinder S are locked and the main passages 26 and 27 are short-circuited. , it is essentially in an unloaded state.

Note that reference numerals 39 and 40 in the figure are centering springs provided in the cylinder S.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of this invention, with Figure 1 being a circuit diagram, Figure 2 being a sectional view of the front wheel steering device, and Figure 3 being a circuit diagram showing details of the control valve mechanism. FIG. 4 is a conventional circuit diagram. S...Cylinder, 9, 10...Pressure chamber, 13...
... Rod, a... Front wheel steering device, b... Rear wheel steering device, 26, 27... Main passage, 29-32...
...On-off valve, 36...On-off valve for unloading.

Claims (1)

[Scope of utility model registration request] The rear wheel steering device includes a front wheel steering device and a rear wheel steering device. In a four-wheel steering device configured such that one pressure chamber communicates with a high pressure side and the other pressure chamber communicates with a low pressure side, two sets of on-off valves each having two sets are provided,
One on-off valve of one set is provided between a passage that communicates one main passage and one pressure chamber, and the other on-off valve of this one set communicates the other main passage and one pressure chamber. one on-off valve of the other set is provided between the passages communicating one main passage and the other pressure chamber,
The other on-off valve of the other set is provided between the passage communicating the other main passage and the other pressure chamber, and an on-off valve for unloading separate from the on-off valve is provided between the two main passages. A four-wheel steering device communicated through the.