JPH0231644Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) This invention relates to a counterbalance valve that applies back pressure to an actuator when the load on the actuator suddenly decreases, for example.

(Prior Art) As this type of device, the one shown in FIG. 2 has been known in the past.

In the apparatus shown in FIG. 2, one end of a spool 2 housed in a main body 1 faces a pilot chamber 3, and the other end faces a damping chamber 4.

When the discharge oil of the pump 5 is supplied to the supply port 6, the pressure at that time acts on the pilot chamber 3 via the orifice 7, so the spool 2
moves against the spring 8 in the damping chamber 4.

With the spool 2 moved in this way, the discharge oil that has flowed into the supply port 6 is supplied to the actuator 10 via one actuator port 9, and the return oil of this actuator 10 is transferred to the other actuator port 9. Returns to tank 14 via Yueta port 11 → annular recess 12 formed in spool 2 → return port 13.

In addition, the reference numeral 15 in the figure is a damping orifice, and the hydraulic oil in the damping chamber 4 is returned to the return port 13.
It provides resistance when flowing, creating a damping effect.

(Problems to be Solved by the Present Invention) In this counterbalance valve, the smaller the gap between the opening/closing portion 16, the smaller the amount of leakage therefrom, and therefore the greater the load holding power. However, in reality, there is a limit to how small the gap between the opening and closing portion 16 can be made due to processing accuracy, thermal expansion of the material, and other factors.

Therefore, in order to increase the load holding force, as shown in Fig. 2, the overlap amount L must be increased. 2, a delay in operation occurs.

Furthermore, in order to prevent a delay in the operation of the spool 2, it is also conceivable to set the spring 8 in the damping chamber 4 in two stages. In this case, the spring force is set to be weak at the beginning of the movement of the spool 2, so that the first stage spring acts at the beginning of the movement of the spool 2, and then both springs act.

Therefore, in this case, one spring acts at the beginning of the movement of the spool, and then the other spring acts, so the spool moves quickly to the predetermined position, and the two springs act together. When the spring acts, the spool will move slowly.

However, in this case, there was a problem that not only the space of the damping chamber had to be enlarged, but also that it was difficult to set the spring force of these two springs.

This design has a structure in which pilot pressure is applied to the spool in two stages, maintaining a large pressure receiving area of the spool during the initial movement of the spool, and reducing the pressure receiving area after the initial movement of the spool. Thus, it is an object of the present invention to provide a counterbalance valve that improves the responsiveness of the spool while sufficiently maintaining the amount of wrap.

(Means for Solving the Problems) In order to achieve the above object, this device moves the spool under the action of the pilot pressure in the pilot chamber, and the return passage of the actuator is moved in accordance with the amount of movement of the spool. In the counterbalance valve that controls the opening degree of the spool, the spool end facing into the pilot chamber forms a small diameter part, and a cap-shaped guide member is slidably covered with this small diameter part. While the engagement gap with the small diameter portion is made small, the oil that has passed through this engagement gap is guided to the tank.

(Operation of the present invention) Since the present invention is constructed as described above, the pressure receiving area of the small diameter part of the spool in the pilot chamber is set as _S2 , and the pressure receiving area of the other part is _S1.
Then, at the beginning of the movement of the spool,
Its effective pressure receiving area becomes _S1 , and after moving by a predetermined amount, the effective pressure receiving area becomes ( _S1 - _S2 ).

Therefore, at the beginning of the spool's movement, the spool is pushed by a large force, so the spool moves faster. Further, after the spool has moved by a predetermined amount, the effective pressure receiving area becomes smaller, so the moving speed of the spool becomes slower.

(Effects of the present invention) By simply providing a guide member at one end of the spool as described above, the speed of movement of the spool at the beginning of its movement and at other times can be changed, so the amount of overlap described above can be made sufficiently large. Even though
The responsiveness of the spool is not impaired.

Furthermore, since the amount of overlap can be made sufficiently large in this way, a large load holding force can be maintained.

(Embodiment of the present invention) The embodiment of the present invention shown in FIG.
A cap-shaped guide member 18 is slidably engaged with this small diameter portion 17, and a stopper 19 is provided protruding from the inside of this guide member 18.

Then, the engagement gap 20 between the guide member 18 and the small diameter portion 17 is kept sufficiently small, and this gap 20 is connected to the drain passage formed in the spool 2.
The stopper 19 is connected to the return port 13 through the stopper 19, and a through hole 22 is formed in the stopper 19.

Further, the guide member 18 strokes until the stopper 19 comes into contact with the end surface of the pilot chamber 3, but this stroke amount is equal to the above-mentioned overlap amount L.
It is made to be L±Δl with respect to the distance.

The other configurations are the same as those of the prior art described above.

When the pilot pressure from the pump 5 is guided to the pilot chamber 3 with the spool 2 in the position shown in the figure, the pressure receiving area of this pilot pressure becomes _S1 , and the spool 2 is integrated with the guide member 18. The overlap distance L is reduced to almost zero.

When the spool 2 and the guide member 18 move to this position, the stopper 19 of the guide member 18 comes into contact with the wall surface of the pilot chamber 3, and the guide member 18
stops.

As mentioned above, the stopper 19 is connected to the pilot chamber 3.
When it comes into contact with the wall surface, the pilot pressure in the pilot chamber 3 is transferred to the spool 2 through the through hole 22.
It acts on the pressure-receiving area (S ₁ − S ₂ ) of .

In this way, the effective pressure receiving area of the spool 2 is reduced to 2
Since the moving speed of the spool 2 is controlled in stages, the spool 2 can be moved quickly until the overlap amount L is reached. Therefore, even if the overlap amount L is made large, the responsiveness will not be impaired.

Furthermore, since the above-mentioned wrap amount L can be made sufficiently large, the load holding force is also increased.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an embodiment of this invention;
FIG. 2 is a sectional view of a conventional device. 2...Spool, 3...Pilot chamber, 10...
...actuator, 17...small diameter portion, 18... guide member, 20... mating gap.

Claims (1)

[Scope of utility model registration request] The spool moves under the action of the pilot pressure in the pilot chamber, and the counterbalance valve controls the opening of the actuator's return passage according to the amount of movement of the spool. A cap-shaped guide member is slidably covered over this small diameter part, and the engagement gap between this guide member and the small diameter part is made small, and the oil that has passed through this engagement gap is sent to the tank. Counterbalance valve designed to guide.