JPH01145405A - Hydraulic servo valve - Google Patents

Abstract

PURPOSE:To improve the responsiveness of a flapper mechanism by providing a pair of spools, nozzles and nozzle back pressure chambers on the coaxial line of a valve unit in both sides of a flapper and forming a static pressure bearing in both ends of the pair of spools. CONSTITUTION:A valve unit 1 forms on its horizontal coaxial line sleeves 2L, 2R, nozzle back pressure chambers 3L, 3R and nozzles 4L, 4R being opposed facing. Spools 15L, 15R are housed in these sleeves 2L, 2R, forming static pressure bearings 18R, 21R, in the both ends. These static pressure bearings 18R, 21R are connected to a pump port P through a passage 26 and chambers 24, 25. In this way, the spools 15L, 15R, spreading their displacement range, increase a flow quantity, further the valve main unit 1, eliminating its through clearance with the spools 15L, 15R, eliminates leakage, and a flapper mechanism enables its responsiveness to 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 40R of the torque motor 39 is excited by an electric input signal and the movable shaft 41 moves to the right and the flapper 32R is displaced to the left, the back pressure in the nozzle back pressure chamber 33R increases and the pressure in the pilot chamber 34R increases. do. As a result, the spool 35 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 guided from the cylinder boat C2 to the passage 36 and the tank boat R. Then return to the tank (not shown). On the other hand, oil flowing out from between the nozzle 37R and the flapper 32R returns from the tank boat R to the tank via a passage 38.

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 control used to be hydraulic machines.
Water was used 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 11ffiS (Fig. 3) in the sliding part, which is poor efficiency, and there is a lot of wear in the sliding part. Machines made of metal materials (particularly iron) have problems such as 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 the machine that come into contact with the working fluid with new materials. It 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. Further, since the gaps between the nozzles 37L, 37R and the flappers 32L, 32R are small, the stroke of the spool 35 cannot be made large, and therefore the flow rate cannot be made large. Further, leakage from the gap S1 still exists, causing a problem in the responsiveness of the flapper mechanism. Furthermore, since the flapper mechanisms are arranged on the left and right sides, adjustment is difficult.

[Object of the Invention] The present invention was proposed in view of the problems of the prior art described above.
The object of the present invention is to provide a hydraulic servo valve that solves problems such as rust and leakage, increases the flow rate, improves the responsiveness of the flapper mechanism, and is easy to adjust.

[Structure of the Invention] According to the hydraulic servo valve of the present invention, a spool that is displaced within the valve body to switch the direction of the working fluid and change the flow rate, and a nozzle back pressure to which pilot pressure that displaces the spool is applied. In this servo valve, a pair of spools, a nozzle, and a nozzle back pressure chamber are provided on the same axis of the valve body on both sides of the flapper, and both ends of each of the pair of spools are provided. A hydrostatic bearing is formed in the nozzle, and a working fluid passage is formed from the pump port to the nozzle back pressure chamber via the hydrostatic bearing.

[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. Furthermore, when water is used as the working fluid, the working fluid is nonflammable and easy to handle. Furthermore, even if the working fluid is disposed of, it will not cause environmental pollution, and some of the working fluid will not be used in IW for hydrostatic bearings.
By making full use of it, the problem of leakage can also be solved. Furthermore, the spool and flapper mechanism are separated, that is, the nozzle of the flapper mechanism is formed separately from the spool, expanding the range of displacement of the spool, increasing the flow rate, and eliminating leakage from the spool's passage through the valve body. Therefore, the responsiveness of the flapper mechanism can be improved accordingly. Furthermore, in the present invention, the spool in the conventional servo valve is divided into two parts, and the flappers, which were two in the conventional servo valve, are combined into one, making it easy to adjust the flapper and the nozzle.

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

In FIG. 1, sleeves 2L, 2R, nozzle back pressure chambers 3L, 3R, and nozzles 4L, 4R are formed facing each other on the same horizontal axis of a valve body 1 made of a rust-resistant material such as a plastic material. The sleeves 2L and 2R have spools 15L and 15 made of rust-resistant material such as plastic material.
Contains R. The nozzles 4L and 4R protrude into the central chamber 5 formed in the valve body 1.
, 4R is the flapper 28 of the torque motor 27.
is inserted through the valve body 1, and its torque motor 27 is fixed to the valve body 1. Sleeve boats 6L, 6R and sleeve ports 7L, 7R are formed in the sleeves 2L, 2R, and the sleeve boats 6L, 6R are connected to the pump port P via a passage 8,
is tank port R1 communicating with a water tank (not shown)
, R2.

At the ends of the sleeves 2L, 2R opposite to the nozzles 4L, 4R, the casing of the valve body 1 and the spools 15L, 1
5R, spring chambers 10L and 10R are formed with springs 29L and 29R interposed therebetween. These spring chambers 10
L and IOR are connected to tank ports R1 and IOR by passages 11L and 11R with orifices 30L and 30R, respectively.
R2 and the central chamber 5.

A gap C is formed between the spools 15L, 15R and the sleeves 2L, 2R, and the longitudinal dimension is larger than the gap between the spools 15L, 15R and the sleeve boats 6L, 7L and the gap between the sleeve boats 6R and 17R. Slightly narrow small diameter portions 16L and 16R are formed. The chambers 12L, 12R formed between the small diameter portions 16L, 16R and the sleeves 2L, 2R are filled with liquid (not shown), respectively.
The cylinder ports C1 and C2 to the water pressure cylinders are connected to the cylinder ports C1 and C2. Also, known static pressure bearings 18L, 18R and static pressure bearings 21L, 21 are provided at both ends of the spools 15L, 15H.
R is formed. In addition, in FIG. 1, only the static pressure bearing 18R521R of the spool 15R is shown. Taking the spool 15R side as an example, the static pressure bearing 18R
is equipped with a pocket 19, an orifice 20, and a hydrostatic bearing 21.
R is provided with a pocket 22 and an orifice 23, which are connected to the sleeve boat 6R via chambers 24, 25 and passages 26, respectively. That is, the pump port P is communicated with the nozzle back pressure chamber 3R via the passage 8, the sleeve boat 6R1 passage 826, the chamber 24, the static pressure bearing 18R1 gap C, and the pilot chamber 9R, It communicates with the spring chamber 10R via the bearing 21''R and the gap C.

Next, the effect will be explained.

Taking the right spool 15R as an example, the pressure liquid flows from the pump port P through passage 8 and sleeve boat 6R to passage 2.
It branches left and right at 6. The pressure liquid flowing to the left passes through the chamber 24, the orifice 20, the pocket 19, the gap C, the pilot chamber 9R, the nozzle back pressure chamber 3R, and the nozzle 4R, and flows from between the nozzle 4R and the flapper 28 to the central chamber 5, Passage 11
R, flows to tank port R2, and returns to a tank (not shown). The liquid from chamber 25 flows through orifice 23 and pocket 2.
2. Pass through gap C, from spring chamber 10R to orifice 30R
It flows through the first passage 11R to the tank port R2 and returns to the tank. Here, the amount of pressure liquid that returns directly to the tank via the orifice 30R is lost, but the ratio of left and right distribution of the pressure liquid in the passage B26 is determined by the throttling effect of the orifice 20.23 of the hydrostatic bearing 18R121R, the pocket 19. Area of 22,
It can be adjusted by changing the size of the gap C.

In this way, the spool 1 is
It is possible to support the sleeve 2R in a non-contact manner to eliminate wear between the sleeves 2R and 2R, thereby preventing various problems caused by the wear. Furthermore, the spool 15R is made of plastic material.
, there is no need to increase the machining accuracy of sleeve 2R,
Moreover, since the servo valve is made of plastic material, water rust can be prevented.

During operation, when the flapper 28 is moved, for example, to the left by an electrical input signal to the torque motor 27, the pressure in the nozzle back pressure chamber 3L increases, while the pressure in the nozzle back pressure chamber 3R decreases.
As a result, the pressure in the pilot chamber 9L increases and the pressure in the pilot chamber 9R decreases. Then, the spool 15L is displaced to the left against the spring 29L, and the spool 15R is displaced to the left by the spring 29R. Therefore, pump port P
Pressure fluid from through R8, sleeve port 6R1 chamber 12R,
The liquid is guided to a hydraulic cylinder (not shown) via the cylinder boat C2, and the liquid returned from the hydraulic cylinder is returned to the cylinder boat C2.
1. Chamber 12L, sleeve boat 7L, tank port R1
is returned to a tank (not shown) via the When the flapper 28 moves to the right, it operates in the opposite manner to that described above. and,
These operations can be performed by simply moving a single flapper 28 to the left or right, making adjustment of the hydraulic cylinder extremely simple.

[Summary] As explained above, according to the hydraulic servo valve of the present invention, a part of the working fluid and leakage flow rate is actively used to form a static pressure bearing, and the spool is supported in a non-contact manner to form a sleeve. This prevents mold wear of the spool and lowers machining accuracy. The spool and sleeve can be manufactured using non-cast materials such as plastic materials, and water rust can be prevented even if water is used as the working fluid. In addition, the spool and flapper mechanism are separated, the spool's displacement range is expanded to increase the flow rate, and the gap between the spool and the valve body is eliminated to eliminate leakage, thereby improving the responsiveness of the flapper mechanism. can. Furthermore, since there is only one flapper, the adjustment of the hydraulic mechanism equipped with the hydraulic servo valve can be made easier.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of the present invention, FIG. 2 is a side sectional view showing a conventional hydraulic servo valve, and FIG. 3 is an enlarged view of the main part of FIG. 2. 1... Valve body 2L, 2R... Sleeve 3L, 3
R...Nozzle back pressure chamber 4L, 4R...Nozzle
8.26...Aisle 9L, 9R...Pilot room 15L, 15R...Spool 18L, 18
R121L, 21R...Static pressure bearing 27...Torque motor 28...Flapper patent applicant Ura 1) Mizo Eki

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, a pair of spools, a nozzle and a nozzle back pressure chamber are provided on the same axis of the valve body on both sides of the flapper, hydrostatic pressure bearings are formed at both ends of each of the pair of spools, and the hydrostatic pressure bearing is connected from the pump port. A hydraulic servo valve characterized in that a working fluid passage is formed to reach the nozzle back pressure chamber through the nozzle.