JPH01112005A - Hydraulic servo valve - Google Patents

Abstract

PURPOSE:To improve the responsiveness of a flapper mechanism by forming static-pressure bearings at both ends of a spool and also forming a passage, which is led from a pump port to a nozzle-back-pressure-chamber via the static- pressure bearings. CONSTITUTION:Static-pressure bearings 14L and 14R are formed at both ends of a spool 10, while nozzle back-pressure-chambers 18L and 18R and nozzles 19L and 19R are formed in a valve main body 1. At this time, the nozzles 19L and 19R are formed, being separated from the spool 10. In addition, a pump port P is connected to the back-pressure-chambers 18L and 18R via a passage 17, the static-pressure bearings 14L and 14R, a gap C and pilot chambers 13L and 13R. With this contrivance, both spool 10 and sleeve 2 can be manufactured by using corrosion resisting material such as plastics. Therefore, water can be used as the working fluid. In addition, since the moving range of the spool 10 can be enlarged, the responsiveness of the flapper mechanism can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic servo valve suitable for using water as a working fluid.

[Prior art] Electro-hydraulic servo valves (hereinafter referred to as hydraulic servo valves) convert weak electrical input signals into hydraulic pressure, switch the direction of working fluid, and change its flow rate. Widely used for operations, etc. An example of the prior art of such a hydraulic servo valve will be described with reference to FIGS. 2 and 3.

In FIGS. 2 and 3, pressure oil is supplied from pump port P. When, for example, the coil 22R of the torque motor 21 is excited by the electric input signal and the movable shaft 24 moves to the right, and the lower end 20Ra of the flapper 2OR is displaced to the left, the back pressure in the nozzle back pressure chamber 30R increases and the pilot The pressure in the chamber 31R increases. As a result, the spool 32 is displaced to the left, pressure oil is guided from the pump port P to a hydraulic cylinder (not shown) via the cylinder boat C1, and return oil from the hydraulic cylinder is passed from the cylinder boat C2 to the passage 33.
and returns to the tank (not shown) via tank boat R.

On the other hand, oil flowing out between the nozzle 34R and the flapper 20R returns from the tank boat R to the tank via a passage 35.The oil used as the working fluid is highly flammable, so be careful when handling it. is necessary. There is also the problem of environmental pollution due to waste oil.

By the way, hydraulic drive and its control used to be hydraulic machines, which used water as the working fluid. However, when the working fluid is water, the viscosity of the working fluid is low, so there is a lot of leakage from the gap S (Fig. 3) in the sliding part, which is poor efficiency, and there is a lot of wear in the sliding part. Furthermore, machines made of metal materials (particularly iron) have the problem of rusting if left unused.

Recently, advances in new materials such as plastics have been remarkable, and the problem of rust mentioned above, which is one of the problems when water is used as a working fluid, can be solved by using new materials for at least the parts of machines that come into contact with the working fluid. This can be solved by forming However, the problem of wear due to the low viscosity of the working fluid still exists, and it is difficult with new materials to machine the sliding parts with high precision to suppress leakage. Furthermore, since the gaps between the nozzles 34L, 34R and the flappers 2OL, 20R are small, it is not possible to take a large stroke of the spool 32, and therefore the flow rate cannot be increased, and leakage from the gap S1 is prevented. Because of this, there was also a problem with the responsiveness of the flapper mechanism.

[Object of the Invention] The present invention was proposed in view of the problems of the prior art described above, and it is capable of using water as a working fluid, and also solves problems such as mold wear, rust, and leakage. It is an object of the present invention to provide a hydraulic servo valve that has a large flow rate and improved response of flapper Ia rating.

[Structure of the Invention] The hydraulic servo valve of the present invention includes a spool that is displaced within the valve body to switch the direction of working fluid and change the flow rate, and a nozzle back pressure chamber to which pilot pressure for displacing the spool is applied. , a servo valve equipped with a flapper mechanism consisting of a nozzle and a flapper, in which static pressure bearings are formed at both ends of the spool, the nozzle back pressure chamber and the nozzle are formed in the valve body, and the static pressure is discharged from the pump port. A working fluid passage is formed that reaches the nozzle back pressure chamber via a bearing, and the nozzle of the flapper mechanism is provided separately from the spool.

[Operations and Effects of the Invention] According to the hydraulic servo valve of the present invention, the static pressure bearings formed at both ends of the spool can keep the spool and the valve body in a non-contact state and eliminate wear between them. Machining accuracy at the sliding portion with the valve body can be lowered. As a result, the valve body can be manufactured from a new material (for example, plastic) that is difficult to precisely process, and as a result, rust can be prevented even if the working fluid is water. Further, the problem of leakage can be solved by positively utilizing the leakage of the working fluid to increase the static pressure of the hydrostatic bearing. Furthermore, the spool and flapper am are separated, that is, the nozzle of the flapper mechanism is formed separately from the spool, thereby expanding the range of displacement of the spool, increasing the flow rate, and eliminating leakage from the valve body passage part of the spool. Therefore, the responsiveness of the flapper mechanism can be improved accordingly.

Furthermore, if water is used as the working fluid in the present invention, the working fluid is nonflammable and easy to handle.

And even if the working fluid is disposed of, it will not cause environmental damage.

[Preferred Embodiment] When carrying out the present invention, it is preferable to use a non-rusting material such as plastic in the portion that comes into contact with the working fluid. By doing so, rust caused by water can be prevented as described above.

[Example] The present invention will be described in detail below with reference to the drawings.

In FIG. 1, a sleeve 2 is formed on a valve body 1;
A spool 10 is built into the sleeve 2, and both of them are made of rust-resistant material such as plastic material.

A sleeve boat 3 is formed on the sleeve 2, and sleeve boats 4L and 4R are formed on both sides of the sleeve boat 3. The sleeve boat 3 is the pump port P
The sleeve boat 4L is communicated with a tank boat R of a water tank (not shown), and the sleeve boat 4R is communicated with the tank boat R via a passage 5. A portion of the sleeve 2 between the sleeve boat 3 and the sleeve boat 4L communicates with the cylinder boat C1, and a portion between the sleeve boat 3 and the sleeve boat 4R communicates with the cylinder boat C2. Further, the sleeve boats 4L and 4R communicate with chambers 7L and 7R formed on both sides of the sleeve 2 via a passage 6. those rooms 7
L and 7R communicate with a chamber 9 (defined by a cover 1a on the upper part of the valve body 1). Also rooms 7L and 7R
is a nozzle 1 formed on the axis of the sleeve 2 of the valve body 1
It communicates with the sleeve 2 via 9L, 19R and nozzle back pressure chambers 18L, 18R.

A gap C is formed between the spool 10 and the sleeve 2, and in the middle of the spool 10, sleeve boats 3 and 4L of the sleeve 2, sleeve boats 3 and 4
Small diameter portions 11L and IIR having a longitudinal dimension slightly shorter than the distance between the sleeve 2 and the sleeve 2 are formed at both ends of the sleeve 2.
Pilot chambers 13L and 13R are formed by the sleeve 2 and the end surface of the spool 10. And spool 1
Known static pressure bearings 14L and 14R are formed at both ends of the angle. To explain the hydrostatic bearing 14R, the hydrostatic bearing has a pocket 15R and a plurality of pockets (
In the illustrated example, the orifice 16R is composed of four orifices 16R, and the orifice 16R is communicated with the sleeve boat 3 via a passage 17. Therefore, the pump port P is the passage 17
, the nozzle back pressure chambers 18L, 18R via the static pressure bearings 14L, 14R1 and the pilot chambers 13L, 13R.

Lower end portions 20Ra and 20La of the flapper 2OR120L are arranged to face each other with a gap formed between the nozzles 19L and 19R, and the flapper 20R is pivotally supported on the valve body 1.

At the center of the chamber 8 described above, a torque motor, generally designated by the reference numeral 21, is provided. The torque motor 21 includes coils 22L, 22R, an armature 23, and a movable shaft 24, and both ends of the movable shaft 24 are connected to the upper ends of the flappers 2OL, 2OR. And flapper 2OL, 2
A return spring 25.25 is stretched between the upper end of the OR and the valve body 1.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

Pressure liquid (water) passes through the passage 17 from the pump port P, and leaks into the gap C from, for example, the orifice 16R and pocket 15R of the right hydrostatic bearing 14R, thereby supporting the spool 10 in a non-contact manner. The pressure liquid is distributed from the pocket 15 to both sides in the longitudinal direction, and the distribution of the pressure liquid can be determined by the size and length of the gap C and the size of the pocket 15R. The spool 10 is supported without contacting the sleeve 2 by the pressure fluid leaking from the gap C, thereby eliminating wear on both. Therefore, the processing accuracy of the spool 10 and sleeve 2 made of plastic material can be lowered, and since they are made of plastic material,
Rust can be prevented.

The pressure liquid flowing to the right in the axial direction through the gap C flows into the pilot chamber 13.
From R, it passes through the nozzle back pressure chamber 18R and the nozzle 19R, and flows out from the gap. The leaked pressure liquid (water) is transferred to chamber 7L1 passage 6, sleeve boat 4R1 passage 5 and tank boat R.
is returned to the tank via

In operation, when, for example, the coil 22R of the torque motor 21 is excited by an electric input signal, the movable shaft 24 moves to the right, and the end 2°Ra of the flapper 2OR is displaced to the left.
The back pressure in the nozzle back pressure chamber 18R increases. As a result, the pressure in the pilot chamber 13R increases and the spool 10 is displaced to the left. Therefore, the pressure liquid is guided from the pump port P to a hydraulic cylinder (not shown) via the sleeve boat 3 and the cylinder boat C2. The return pressure liquid from the hydraulic (hydraulic) cylinder is returned to the tank via the cylinder boat C1, sleeve boat 4L, and tank boat R.

When the coil 22L is energized, it operates in the opposite manner to that described above.

[Summary] As explained above, according to the present invention, the leakage flow is actively used to form a static pressure bearing, the spool and sleeve are maintained in a non-contact state to prevent wear of both, and , machining accuracy can be lowered.

Therefore, the spool and sleeve can be manufactured using a rust-resistant material such as a plastic material, and rust can be prevented. Therefore, no problem arises even when water is used as the working fluid. Furthermore, by separating the spool and flapper mechanism, the range of movement of the spool and the flow rate can be increased.

Further, by eliminating the penetrating portion of the spool with the valve body, leakage can be eliminated, and the responsiveness of the flapper mechanism can be improved accordingly.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are configuration diagrams each showing a prior art. 1...Valve body 2...Sleeve 6.17...
・Aisle 10...Spool 13L, 13R...
・Pilot chamber 14L, 14R...Static pressure bearing
16L, 16R... Orifice 18L, 18R...
...Nozzle back pressure chamber 19L, 19R...Nozzle 2O
L, 20R...Flapper 21...Torque motor patent applicant Ura 1) Emi San

Claims (1)

[Claims] A servo equipped with a spool that is displaced within the valve body to switch the direction of working fluid and change the flow rate, a nozzle back pressure chamber to which pilot pressure is applied to displace the spool, and a flapper mechanism consisting of a nozzle and a flapper. In the valve, hydrostatic pressure bearings are formed at both ends of the spool, and the nozzle back pressure chamber and the nozzle are formed in the valve body, and the working fluid flows from the pump port to the nozzle back pressure chamber through the hydrostatic pressure bearings. A hydraulic servo valve, characterized in that a passage is formed, and a nozzle of a flapper mechanism is provided separately from a spool.