JPS59113378A - Counterbalance valve - Google Patents

Abstract

PURPOSE:To prevent hunting, by placing both the ends of a spool on damper chambers, making the pressure-receiving areas of the spool's ends different from each other, and providing damper orifices in the inlet and outlet ports of the damper chambers. CONSTITUTION:Both the ends of a spool 25 are placed on damper chambers 26, 27. The pressure-receiving areas of the spool 25 on the damper chambers 26, 27 are made different from each other. Damper orifices 31, 32 are provided in the inlet and outlet ports of the damper chambers. The damper chambers 26, 27 are connected to each other through a fluid passage 33. The thrust on the spool 25 is made so small, by decreasing the difference between the pressure-receiving areas of both the ends of the spool 25, that hunting is prevented even if the cross- sectional areas of the damper orifices 31, 32 are made large.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a counterbalance valve that reduces the acting force that moves the spool during counterflow and prevents hunting.

(Conventional Counterbalance Valve) The conventional counterbalance valve shown in Fig. 1 has a configuration in which the pilot pressure is introduced into the pilot chamber 1 at the time of counterflow, and acts on the pilot piston 2 provided in the pilot chamber 1. I have to.

When pilot pressure acts on the pilot piston 2 as described above, the spool 3 provided integrally with the pilot piston 2 moves to open the control orifice 4. When the control orifice 4 is opened, the return oil from the first port 5 returns to a tank (not shown) via the control orifice 4 and the second port 6.

The counter pressure at this time is introduced into the pressure chambers 9 and IO formed on both sides of the spool 3 via the 1.2 damper orifice 7.8. Therefore, when the spool 3 moves as described above, the second damper orifice 8 functions to exert a damper effect.

On the other hand, during free flow, the pressure oil flowing from the second port 6 pushes open the check valve 13 via the communication hole 11 and the communication chamber 12, and flows out from the first port 5.

The conventional counterbalance valve as described above requires the pilot piston 2 in order to reduce the pressure receiving area of the pilot pressure. Providing this pilot piston 2 inevitably increases the overall length of the spool 3, which has the drawback of increasing the size of the valve itself.

Moreover, since the pilot piston 2 must ensure concentricity with other parts, particularly the spool 3, it requires highly accurate machining. This has resulted in poor workability in the manufacturing process and increased costs.

Furthermore, a seal 14 must be provided to separate the pilot chamber 1 and the pressure chamber 9. However, the provision of this seal 14 had the disadvantage that the friction increased and the operability of the spool 3 deteriorated.

(Objective of the Invention) An object of the present invention is to provide a counterbalance valve that eliminates the need for the conventional pilot piston and eliminates the drawbacks of the conventional pilot piston.

Embodiment of the Invention In the embodiment of the invention shown in FIG. 2, a bore 16 is formed in the longitudinal direction of the valve body 15, and both ends of this bore are closed with covers 17, 18. And this valve body 1
5 is formed with a first boat 19 and a second port 20, the first port 19 is directly connected to the bottom side chamber 22 of the cylinder 21, and the second port 20 is connected to the directional control valve 23.
is connected to.

Note that the rod side chamber 24 of the cylinder 21 is connected to the directional switching valve 23.

A spool 25 is slidably housed in the bore 16 as described above, and both ends of the spool 25 are exposed to damper chambers 26 and 27. The pressure receiving areas of the spools in the damper chamber are slightly different.

That is, for the pressure receiving area D1 of one damper chamber 28,
The pressure receiving surface 1XLD2 of the other damper chamber 27 is made slightly smaller. Furthermore, a spring 28 is interposed in the other damper chamber 27, and a stopper 29, which is usually an annular protrusion formed on the spool 25, contacts the seat portion 30 of the valve body 15, so that the spool 25 is We have a relationship that maintains the status.

Damper orifices 31 and 32 are provided at the inlet and outlet of the damper chambers 28 and 27 as described above, and both damper chambers are communicated with each other via a flow path 33. This flow passage 33 is connected via a pilot passage 34 to
It is connected to a passage that supplies pressure oil to the rod side chamber 24.

Further, inside the spool 25, the damper chamber 26.
27 and a through hole 35 is formed. Furthermore, this spool 25 is formed with a first communication boat 36 and a second communication boat 37, and each of these communication ports 36.
37 communicates with the through hole 35. A check valve is provided in the passage hole 35 to permit flow only from the second communication port 37 to the first communication port 38.

When the spool 25 configured as described above is in the illustrated state, the control aperture 39 formed on its outer periphery is closed, and when the spool 25 moves against the spring 28, the control aperture 39 changes depending on the amount of movement. It is made to open.

When the directional control valve 23 is switched from the illustrated neutral position to the left position, the oil discharged from the pump 40 pushes the check valve 38 open via the second port 20 → second communication port 37 → through hole 35. , flows into the bottom side chamber 22 of the cylinder 21 through the first communication port 36 and the first port I.18.

On the other hand, the return oil in the rod side chamber 24 returns directly to the tank 41 via the directional switching valve 23.

Therefore, when the directional control valve 23 is switched to the left position, the cylinder 21 expands and enters a free flow state in which the load W is increased A.

Furthermore, when the directional control valve 23 is switched to the right position in the figure, the oil discharged from the pump 40 flows directly into the rod side chamber 24 and passes through the pilot passage 34 to the flow passage 33.
It also flows into

The pilot pressure flowing into the IAε passage 33 passes through the damper orifice 31.32 to the damper chamber 26.27.
The damper chambers 26 and 27 are maintained at the same pressure.

When both damper chambers become the same pressure, the pressure receiving area of the spool 25 in the damper chamber becomes Dl>Dl as described above.
Therefore, the spool 25 is connected to the spring 28.
move against.

When the spool 25 moves as described above, the control throttle 39 opens in accordance with the amount of movement, in other words, in proportion to the pilot I pressure. Since the control throttle 39 is opened in this manner, the return oil from the bottom side chamber 22 is transferred to the first port 111 → the control throttle 39 → the opening between the stopper 29 and the seat portion 30 → the second boat 20 → the directional control valve 23 via tank 4
Return to 1.

Therefore, when the directional control valve 23 is switched to the right position shown in the figure, the cylinder 21 contracts to lower the load W, but a counterflow state is created in which the control throttle 39 functions.

The most important feature of the counterbalance valve as described above is that the pressure receiving areas of the spools 25 in the damper chambers 26 and 27 are different, so that the relationship DI>Dl is established.

In other words, since the pressure-receiving area is set to the relationship DI>Dl as shown in "-," the Ilu force that moves the spool 25 against the spring 2 is caused by the difference in the pressure-receiving area.
It will be done.

Therefore, if the pressure receiving area difference =L is made sufficiently small, the thrust of the spool 25 can be made small.

111 of spool 25. Since the force can be reduced, a sufficient damping effect can be exerted without reducing the opening area of the damper orifices 31, 32.

This embodiment also has the advantage that the damper orifices 31 and 32 can be easily replaced compared to the conventional one shown in FIG.

That is, in the above conventional configuration, both damper orifices 7.
8 directly on the spool 3, the spool itself must be removed in order to replace this damper orifice 7.8.

In contrast, in the embodiment described above, the cover 17, ! Since the damper orifices 31 and 32 are provided at 8, the damper orifices can be easily replaced by removing the cover.

(Configuration of the present invention) The configuration of the present invention is such that a spool moves according to the pilot pressure, the opening area of the control diaphragm is determined in proportion to the amount of movement of the spool, and the counterflow is temporarily controlled by the control diaphragm. In the counterbalance valve, both ends of the spool are made to face the damper chamber, and the two damper chambers are communicated with each other, so that the pressure receiving area of the spool in the damper chamber is different, and the thrust of the spool is controlled by the difference in the pressure receiving area. The present invention is characterized in that a damper orifice is provided at the outflow inlet of the damper chamber.

As mentioned above, since the two gunpa chambers facing both ends of the spool are communicated with each other, the pressure in these two chambers is always the same. Moreover, since the pressure-receiving areas of the spools in the damper chamber are different, the thrust of the spools is obtained by the difference in the pressure-receiving areas.

Therefore, the thrust of the spool can be made sufficiently small, and the damper effect can be increased accordingly. .

(Effects of the Present Invention) In the present invention, the thrust of the spool can be made sufficiently small as shown in "-2", so even if the opening area of the damper orifice is made thicker, hunting can be prevented from occurring. Since the opening area of the damper orifice can be increased, problems such as clogging of the orifice with dirt can be solved.

In addition, in this invention, 1. In order to reduce the pressure receiving area of the pilot pressure, a pilot piston as in the prior art is not required, so the total length of the counterbalance valve can be known accordingly. Moreover, since there is no need to consider the concentricity of the pyro-nt piston and the spool, manufacturing becomes easier.

Furthermore, since the pilot piston is not required, there is no need to provide a seal around it, and the system is not affected by the friction of the seal.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional device, and FIG. 2 is a sectional view showing an embodiment of the present invention. 2511...Spool, 26.27...Damper chamber, 3
8. Conflict/control. Attorney ± l++8 Nobuyuki

Claims (1)

[Claims] In a counterbalance valve, a spool moves according to pilot pressure, and the opening area of a control orifice is determined in proportion to the amount of movement of the spool, and the counterflow is temporarily controlled by the control orifice. Both ends of the spool are connected to a damper chamber. At the same time, these two damper chambers are made to communicate with each other, and the pressure receiving areas of the spools in the damper chambers are made different, so that the thrust of the spools is obtained by the difference in the pressure receiving areas. A counterbalance valve with an orifice.