JPH0535761B2 - - Google Patents

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, change the direction of working fluid, and change its flow rate, and are used for numerical control of machine tools, remote control, etc. Widely used for operations, etc. An example of the prior art of such a hydraulic servo valve is illustrated in 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 an electric input signal and the movable shaft 24 moves to the right, and the lower end 20Ra of the flapper 20R is displaced to the left, the nozzle back pressure chamber 3
The back pressure of 0R increases and the pressure of the pilot chamber 31R increases. As a result, the spool 32 is displaced to the left, and the pressure oil is guided from the pump port P to the hydraulic cylinder (not shown) via the cylinder port C1.
Return oil from the hydraulic cylinder is at cylinder port C2
From there, it returns to a tank (not shown) via passage 33 and tank port R. On the other hand, oil flowing out from between the nozzle 34R and the flapper 20R returns to the tank from the tank port R via the passage 35.

Here, the oil used as the working fluid is highly flammable, so care must be taken when handling it. 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) of the sliding part, resulting in 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 unattended.

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 using water as a working fluid, can be solved by forming at least the parts of machines that come into contact with the working fluid with new materials. This can be solved by 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.

[Object of the Invention] The present invention was proposed in view of the problems of the prior art described above, and provides a hydraulic servo valve that can use water as a working fluid and solves problems such as wear, rust, and leakage. is intended to provide.

[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 is applied to displace the spool. , a servo valve equipped with a nozzle and a flapper mechanism consisting of a flapper, wherein static pressure bearings are formed at both ends of the spool, and a passage for working fluid from a pump port to the nozzle back pressure chamber via the static pressure bearings. has been established.

[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. This makes it possible to manufacture valve bodies using new materials that are difficult to precisely process (such as plastic).
As a result, even if the working fluid is water, it is possible to prevent rust from forming. Furthermore, in the prior art, the fluid that is led from the main flow path to the nozzle back pressure chamber and then returned to the tank for use in controlling the nozzle back pressure is not used for purposes other than controlling the nozzle back pressure. In the present invention, such a working fluid is used as a working fluid for a hydrostatic bearing before being used for nozzle backpressure technology. By doing so, part of the leakage of the working fluid can be used effectively.

Furthermore, if water is used as the working fluid in the present invention, the working fluid will not be flammable and will be easier to handle. And even if the working fluid is exhausted, it will not cause environmental damage.

[Preferred Embodiment] When carrying out the present invention, it is preferable to use a rust-proof material such as plastic for the portion that comes into contact with the working fluid. In this way, rust caused by water can be prevented as described above.

[Examples] Examples of the present invention will be described below with reference to the drawings.

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

A sleeve port 3 is formed in the sleeve 2,
Sleeve ports 4L and 4R are formed on both sides of the sleeve port 3. The sleeve port 3 is connected to a pump port P, and the sleeve port 4L is a tank port R of a water tank (not shown).
The sleeve port 4R is communicated with the tank port R via the passage 5. And sleeve port 3 and sleeve port 4L of sleeve 2
An intermediate location between the sleeve port 3 and the sleeve port 4R communicates with the cylinder port C1, and an intermediate location between the sleeve port 3 and the sleeve port 4R communicates with the cylinder port C2. In addition, the sleeve ports 4L and 4R are connected to the passage 6.
Through the chamber 7 formed on both sides of the sleeve 2
It is connected to L and 7R. Those rooms 7L, 7
R is connected to chamber 8. Here, the chamber 8 is defined in the upper part of the valve body 1 by a cover 1a. In addition, the chambers 7L and 7R have a double tubular gap 9.
It is communicated with gap C via L and 9R.

A gap C is formed between the spool 10 and the sleeve 2, and the sleeve ports 3 and 4L of the sleeve 2 are located in the middle of the spool 10 at the illustrated position.
Small diameter portions 11L, 11R having a longitudinal dimension slightly shorter than the distance between the sleeve ports 3 and 4L are formed, and small diameter portions 12L, 12R are formed at both ends of the sleeve 2 to fit into the double tubular gaps 9L, 9R. is formed. At both ends of the spool 10, the pilot chamber 13 is formed by the sleeve 2, the end surface of the spool 10, and the small diameter portions 12L, 12R.
L, 13R are formed. Furthermore, spool 1
Known hydrostatic bearings 14L and 14R are formed at both ends of the bearing 0. To explain the hydrostatic bearing 14R, the hydrostatic bearing consists of a pocket 15 and a plurality of (four in the illustrated example) orifices 16 arranged at equal intervals in the circumferential direction.
It communicates with the sleeve port 3 via 7.
Also, to explain the small diameter portion 12R, the small diameter portion 12R
has a through hole 1 perpendicular to the axis of the spool 10.
8a and a nozzle back pressure chamber 1 communicating with the through hole 18a.
8 and a nozzle 19 communicating with the nozzle back pressure chamber 18
and is provided. Therefore, pump port P
is in communication with the nozzle back pressure chamber 18 via the passage 17, the hydrostatic bearing 14R, the gap C and the through hole 18a, and further communicates with the chamber 8 via the nozzle 19.

The lower end portion 20Ra of the flapper 20R (the member on the right side in FIG. 1: the member on the left side is the flapper 20L) is arranged to face the nozzle 19 with a gap D formed between the flapper 20R and the flapper 20R. Main body 1
is supported by.

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 has coils 22L, 22R, amateur 2
3 and a movable shaft 24, both ends of the movable shaft 24 are connected to the upper ends of the flappers 20L, 20R. A return spring 25,
25 is installed.

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 out from the orifice 16 and pocket 15 of the right hydrostatic bearing 14R into the gap C, 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,
The distribution of the pressure fluid can be determined by the size and length of the gap C and the size of the pocket 15. 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 machining accuracy of the spool 10 and slube 2 made of plastic material can be lowered, and since they are made of plastic material, rust can be prevented.

The pressure liquid that has flowed to the right in the axial direction through the space C passes through the nozzle back pressure chamber 18 and the nozzle 19 from the pilot chamber 13R, and flows out from the space D. The water that flowed out was in room 7.
R, passage 6, sleeve port 4R, passage 5 and tank port R to be returned to the tank.

During 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 20 of the flapper 20R is energized.
Ra is displaced to the left, and the back pressure in the nozzle back pressure chamber 18 increases. As a result, the pressure in the pilot chamber 13R increases and the spool 10 is displaced to the left. Therefore, the hydraulic fluid is guided from the hydraulic pump port P to a hydraulic cylinder (not shown) via the sleeve port 3 and the cylinder port C2. The return pressure liquid from the hydraulic (hydraulic) cylinder is from the cylinder port C1 to the sleeve port 4L,
It is returned to the tank via tank port R. In the case where coil 22L is illustrated, it operates in the opposite manner to that described above.

[Summary] As explained above, according to the present invention, a hydrostatic bearing is formed by actively utilizing the leakage flow rate, and the spool and sleeve are maintained in a non-contact state to prevent wear between them. By appropriately designing the bearing characteristics, the size of the sleeve can be set arbitrarily, so that machining accuracy can be lowered. Therefore, the spool and sleeve can be manufactured using a rust-resistant material such as plastic, and rust can be prevented. Therefore, water can be used as the working fluid.

[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...
Passage, 10...Spool, 13L, 13R...Pilot chamber, 14L, 14R...Static pressure bearing, 16
... Orifice, 18 ... Nozzle back pressure chamber, 19 ...
...Nozzle, 20L, 20R...Flappa, 21...
...Torque motor.

Claims (1)

[Claims] 1 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. A hydraulic servo valve, characterized in that static pressure bearings are formed at both ends of the spool, and a working fluid passage is provided from the pump port to the nozzle back pressure chamber via the static pressure bearings.