JP2636086B2 - Hydraulic circuit for all hydraulic power steering - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for a fully hydraulic power steering in a tractor or the like.

[0002]

2. Description of the Related Art All-hydraulic power steering (hereinafter abbreviated as PS) devices are used in vehicles such as tractors. This all-hydraulic PS device includes a hydraulic pump,
A control valve and a hydraulic cylinder form a single circuit, and a load sensing valve is provided to supply hydraulic oil unnecessary for steering operation to another hydraulic system, for example, a hydraulic cylinder of a working machine. is there.

[0003] However, in the former PS device, although a large capacity hydraulic pump is generally required, hydraulic oil from the hydraulic pump is not used at all except during the steering operation. . Further, the latter PS device has a disadvantage that the whole device is very complicated and expensive.

Therefore, when the steering operation is not being performed, the hydraulic oil from the hydraulic pump flows into the fifth excess flow port, and the hydraulic oil is supplied to another hydraulic system through the excess flow port. (See, for example, Japanese Patent Publication No. 63-58144).

[0005]

However, in the conventional five-line type all-hydraulic PS device, both the hydraulic cylinder side and the excess flow side are limited to the maximum working pressure of the hydraulic cylinder side , and the high working pressure is higher than the maximum working pressure. Hydraulic oil cannot be taken out to another hydraulic system. In view of the above, it is an object of the present invention to be able to take out hydraulic oil having a pressure higher than the maximum working pressure during steering to another hydraulic system.

[0006]

SUMMARY OF THE INVENTION The present invention provides a hydraulic pump.
(1) Control valve linked to steering operation
In the hydraulic circuit for all-hydraulic power steering which is supplied to the hydraulic cylinder (2) via (9) to perform the steering operation, the excess flow side of the control valve (9) is connected to the check valve (14).
And other hydraulic systems (12)
When (12) is lower than the maximum working pressure during steering, the hydraulic oil of the hydraulic pump (1) flows to the control valve (9) side, and the other hydraulic system
When (12) is higher than the maximum working pressure, the pressure of the control valve (9) is reduced to the maximum working pressure, and the hydraulic oil of the hydraulic pump (1) is changed to another hydraulic pressure without passing through the control valve (9). A pressure reducing valve (16) for flowing into the system (12) is interposed between the hydraulic pump (1), the control valve (9), and another hydraulic system (12).

[0007]

When the other hydraulic system (12) is smaller than the maximum operating pressure during steering, the hydraulic oil from the hydraulic pump (1) flows to the control valve (9) through the pressure reducing valve (16). Therefore, the control valve
If (9) is in operation, the hydraulic oil is supplied to the hydraulic cylinder (2) via the control valve (9), and if it is neutral, the other hydraulic fluid is supplied from the excess flow side via the check valve (14). It is supplied to the system (12).

When the other hydraulic system (12) is higher than the maximum operating pressure, the pressure reducing valve (16) operates to reduce the pressure on the control valve (9) side to the maximum operating pressure while the control valve (9) is operated. Pressure reducing valve (1
Supply hydraulic oil from 6) to another hydraulic system (12). Therefore, hydraulic oil having a pressure higher than the maximum working pressure can be taken out to another hydraulic system (12).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. Fig. 1 shows the hydraulic circuit of a fully hydraulic PS device for a tractor, (1) is a hydraulic pump for PS, (2) is a hydraulic cylinder for PS, and both ends of a piston rod (3) are tie rods.
It is connected to the knuckle arm (5) via (4), and the left and right wheels (7) are steered around the kingpin (6). (8) is a control valve device that is interlocked with the operation of the handle, and is a control valve that switches the oil passage of the hydraulic cylinder (2).
(9) and a metering pump (10).

(11) is a working hydraulic pump, and (12) is a working hydraulic system, which is composed of a hydraulic actuator such as a cylinder and a motor and a control valve for controlling the same. The excess flow circuit (13) of the control valve (9) is connected to the hydraulic system via a check valve (14).
Connected to (12). (15) is a check valve. A pressure reducing valve (16) is interposed between the hydraulic pump (1), the control valve (9), and the hydraulic system (12). When the hydraulic pressure is too small, the hydraulic oil of the hydraulic pump (1) flows to the control valve (9) side, and when the hydraulic system (12) is higher than the maximum operating pressure, the pressure in the control valve (9) is reduced to the maximum operating pressure. In addition, the hydraulic oil of the hydraulic pump (1) flows directly to the hydraulic system (12) without passing through the control valve (9).

That is, the pressure reducing valve (16) is, as shown in FIG.
Consists of a valve body (17), a spool (18) slidably assembled in the valve body (17) in the axial direction, and a coil spring (19) for urging the spool (18) in one direction. Have been. Valve body
(17) is an input port (20) connected to the hydraulic pump (1),
A first outlet port (21) connected to the control valve (9), and a hydraulic system
(12) connected to the pressure-sensitive surface (24) of the spool (18) via a small-diameter pressure-sensitive port (23). Are in communication. Spool (18)
Is formed with a circumferential groove so as to simultaneously or selectively connect the inlet port (20) to the outlet ports (21) and (22). The spring (19) balances the force acting on the pressure-sensitive surface (24) of the spool (18) when the hydraulic system (12) side is smaller than the maximum operating pressure during steering, and moves the spool (18) to the position shown in FIG. And when the hydraulic system (12) side is higher than the maximum working pressure, the pressure-sensitive surface (24)
The spool (18) is slid to the position shown in FIG. (25) is the spool (1
8) The safety valve formed in 8), comprising a ball (26), a spring (27) and the like.

Next, the operation will be described. When the hydraulic system (12) including the non-operating state of the hydraulic system (12) is lower than the maximum operating pressure during steering, the pressure at the first outlet port (21) is low, and the spool of the pressure reducing valve (16) is reduced. (18) is Fig. 2 by spring (19)
Is held in the position. Therefore, hydraulic oil from the hydraulic pump (1) is supplied to the inlet port (20) of the pressure reducing valve (16) and the spool (1).
It is supplied to the control valve (9) through the circumferential groove of 8) and the first outlet port (21). Therefore, the control valve is linked with the operation of the steering wheel.
When (9) works, hydraulic oil is fed into one chamber of the hydraulic cylinder (2), and the operating shaft of the other chamber is controlled by the control valve (9), the excess flow side circuit (13), and the check valve (14). ) And is sent to the hydraulic system (12).

If the steering oil is not being operated, the hydraulic oil flows from the first outlet port (21) of the pressure reducing valve (16) through the control valve (9), the excess flow side circuit (13), and the check valve (14). It is supplied to the system (12). Therefore, there is no loss. During the steering operation, hydraulic oil can be preferentially supplied to the hydraulic cylinder (2) through the control valve (9). When the hydraulic system (12) is heavy load and is larger than the maximum operating pressure of the steering, the first outlet port (16) of the pressure reducing valve (16) through the port in the control valve (9) and the excess flow side circuit (13). 21) is connected to the second outlet port (22). However, since the check valve (14) shuts off the two,
The pressure at the outlet port (21) rises to the maximum working pressure, and that pressure acts on the pressure-sensitive surface (24) of the spool (18). As a result, the spool (18) slides in the direction of the arrow a as shown in FIG. 3 against the spring (19), the first outlet port (21) is throttled, and the control valve is moved.
(9) Reduce the side pressure to the maximum working pressure. At the same time, the spool (18) opens the second outlet port (22) and connects the inlet port (20) and the second outlet port (22) through the circumferential groove. Hydraulic oil at a pressure higher than the working pressure can be taken out.

The pressure reducing valve (16) is not limited to the structure of the embodiment.

[0015]

According to the present invention, the excess flow side of the control valve (9) is connected to another hydraulic system (12) via the check valve (14), and the other hydraulic system (12) is When the hydraulic pressure of the hydraulic pump (1) is smaller than the maximum operating pressure during steering, the hydraulic oil of the hydraulic pump (1) flows to the control valve (9) side, and when the other hydraulic system (12) is higher than the maximum operating pressure,
The pressure on the control valve (9) side is reduced to the maximum working pressure, and the hydraulic oil of the hydraulic pump (1) is supplied to the other hydraulic system (1) without passing through the control valve (9).
The pressure reducing valve (16) for flowing to 2) is connected to the hydraulic pump (1) and the control valve.
Since it is interposed between (9) and another hydraulic system (12), it is possible to take out hydraulic oil higher than the maximum working pressure to the other hydraulic system (12).

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of an all-hydraulic power steering hydraulic circuit.

FIG. 2 is a sectional view of a pressure reducing valve.

FIG. 3 is a diagram illustrating the operation of a pressure reducing valve.

[Explanation of symbols]

 1 Hydraulic pump 2 Hydraulic cylinder 9 Control valve 12 Hydraulic system 13 Excess flow circuit 14 Check valve 16 Pressure reducing valve

Claims (1)

(57) [Claims] A hydraulic cylinder (2) is supplied with hydraulic oil from a hydraulic pump (1) via a control valve (9) interlocked with handle operation.
In the hydraulic circuit for all-hydraulic power steering which is supplied to the hydraulic system for steering operation, the excess flow side of the control valve (9) is connected to another hydraulic system (12) via a check valve (14). At the same time, when the other hydraulic system (12) is smaller than the maximum operating pressure during steering, the hydraulic oil of the hydraulic pump (1) is controlled by the control valve (9).
When the other hydraulic system (12) is higher than the maximum working pressure, the pressure of the control valve (9) is reduced to the maximum working pressure, and the hydraulic oil of the hydraulic pump (1) is controlled by the control valve (9). ), A pressure reducing valve (16) for flowing to the other hydraulic system (12) without intervention is interposed between the hydraulic pump (1), the control valve (9), and the other hydraulic system (12). A hydraulic circuit for an all-hydraulic power steering, characterized by the following.