JPH01145403A - Hydraulic servo valve - Google Patents

Abstract

PURPOSE:To enable the characteristics to be changed of a flapper mechanism by forming static pressure bearings in both ends of a spool while providing a displacement meter in a pair of spools and controlling, in accordance with the displacement of the one spool, the displacement of the other spool. CONSTITUTION:Forming static pressure bearings 18R, 21R in both end parts of spools 15L, 15R and providing displacement bars 15La, 15Ra in outer end parts of the spools 15L, 15R to be inserted into coils 13La, 13Ra of displacement meters 13L, 13R, they are connected to a microcomputer. Thus contactlessly supporting the spools 15L, 15R, sleeves 2L, 2R and the spools 15L, 15R are prevented from wearing, while machining accuracy can be decreased. Further changing the characteristic of both flapper mechanisms by the microcomputer, the motion of one side rod cylinder can be accurately controlled.

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 i 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, the pressure oil is guided from the pump port P to the hydraulic cylinder (not shown) via the cylinder boat C1, and the return oil from the hydraulic cylinder is transferred from the cylinder boat C2 to the passage 36 and the passage (not shown). The tank boat R returns to a link (not shown) via the tank boat R. 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 its control used to be a hydraulic mechanism, using 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, resulting in poor efficiency.
Furthermore, there is a problem that there is a lot of wear on the sliding parts, and if the machine is made of metal material (particularly iron), it will rust 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 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. However, the problem of wear due to the low viscosity of the working fluid still exists, and it is difficult with new materials to process the sliding parts with high precision to prevent leakage. . Furthermore, 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 increased, and leakage still exists from the gap S1. However, there is a problem with the responsiveness of the flapper AM. Furthermore, since the characteristics of the left and right flapper mechanisms of conventional servo valves are the same, it is inconvenient to control the cylinder at two speeds or to precisely control the movement of the cylinder on one side of the valve.

[Object of the Invention] The present invention was proposed in view of the problems of the prior art described above.
It is an object of the present invention to provide a hydraulic servo valve that can solve problems such as rust and leakage, increase the flow rate, improve the responsiveness of the flapper mechanism A, and change the characteristics of both flapper mechanisms.

[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 a servo valve equipped with a flapper chamber and a flapper mechanism consisting of a nozzle and a flapper, a pair of spools, a nozzle, and a nozzle back pressure chamber are provided on the same axis of the valve body outside the pair of flappers, and each of the pair of spools is A static pressure bearing is formed at both ends of the spool, and a working fluid passage is formed from the pump port to the nozzle back pressure chamber via the static pressure bearing, and a displacement gauge is provided on each of the pair of spools, and the displacement gauge Control means is provided for controlling the displacement of one spool in accordance with the displacement of the other spool based on the detection signal from the spool.

[Operations and Effects of the Invention] According to the hydraulic servo valve of the present invention, the spool and the valve body can be kept in a non-contact state and wear can be eliminated by the static pressure bearings formed at both ends of the spool. 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. And even if the working fluid is disposed of, it will not cause environmental pollution. Further, by actively utilizing a portion of the working fluid for the hydrostatic bearing, 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. Because
The responsiveness of the flapper mechanism can be improved accordingly. In addition, according to the hydraulic servo valve of the present invention, the control means can control the displacement of one spool in accordance with the displacement of the other spool, thereby changing the characteristics of both spool mechanisms. When controlling a single-sided rod cylinder with a conventional valve,
The problem is that the area of the cylinder is different, so naturally there are differences in the characteristics of left-right motion, and the time constants etc. are also different.On the other hand, manufacturing a double-sided rod cylinder is generally more difficult in terms of accuracy than a single-sided rod cylinder. was there. According to the present invention, even in a single-sided rod cylinder, if this servo valve is used, movement in both directions can be controlled with the same characteristics or accuracy.

[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 15 made of rust-resistant material such as plastic! -11
Contains 5R. The nozzles 4L and 4R protrude into the central chamber 5 formed in the valve body 1.
A gap A is formed between , 4R, and a flapper 2 of a torque motor (not shown) fixed to the valve body 1 is installed in the gap A.
8L and 28R are inserted through the nozzles 4L and 4R, respectively, with a slight gap B between them.

Sleeve boats 6L, 6R and sleeve boats 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, and the sleeve boats 7L, 7R are tank boats). R
1, connected to 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, a spring chamber 10L and IOR are formed with springs 29L and 29R interposed therebetween. These spring chambers 10
L, IOR are connected to tank boat R1,
R2 and the central chamber 5.

A gap C is formed between the spools 15L, 15R and the sleeves 2L, 2R, and a gap C is formed in the middle of the spools 15L, 15R. Small diameter portions 16L and 16R are formed which have a slightly shorter width in the direction dimension.

Then, the small diameter portions 16L, 16R and the sleeves 2L, 2
The chambers 12L and 12R formed between the cylinder boats C1 and R are respectively connected to a liquid (water) pressure cylinder (not shown).
Connected to C2. Also, spools 15L, 15H
Known static pressure bearings 18L, 18R and static pressure bearings 19L, 19R are formed at both ends of the shaft. In addition, in FIG. 1, only the static pressure bearing 18R121R of the spool 15R is shown. Taking the spool 15R side as an example, the hydrostatic bearing 18R includes a pocket 19, an orifice 20,
The hydrostatic bearing 21R is provided with a pocket 22, an orifice 23 and is connected to the sleeve boat 6R via a chamber 24, 25 and a passage 26, respectively. That is, the pump port P is connected to the passage 8 and the sleeve boat 6R1 passage 26.
, communicates with the nozzle back pressure chamber 3R via the chamber 24, the static pressure bearing 18R1 gap C and the pilot chamber 9R, and communicates with the spring chamber 10R via the passage 26, the chamber 25, the static pressure bearing 21R and the gap C. ing.

In addition, displacement rods 15 are provided at the outer ends of the spools 15L and 15R.
La, 15Ra are provided, and these displacement rods 15L
a, 15Ra are displacement meters 13L, 1 provided in the valve body 1;
It is inserted through the 3R coils 13La and 13Ra. The displacement gauges 13L and 13R and the torque motor are connected to a microcomputer (not shown). This makes it possible to control movement in both directions with the same characteristics or accuracy, even in a one-sided rod cylinder.

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
It flows through R to tank boat 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 26 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 28R moves to the left due to an electrical input signal to the torque motor, the nozzle back pressure chamber 3
The pressure at R decreases. As a result, the pressure in the pilot chamber 9R decreases and the spool 15R is moved to the left by the spring 29R. The leftward displacement of spool 15R is caused by displacement rod 1.
5Ra, it is detected by the displacement meter 13R, and input to the microcomputer. When the spool 15R is displaced to the left, the pressure fluid from the pump port P is guided to the hydraulic cylinder via the passage 8, the sleeve bow) 6R1 chamber 12R, and the cylinder port C2. On the other hand, the current position of the spool 15L is detected by the displacement meter 13L and input to the microcomputer. The microcomputer compares the detected value of the displacement meter 13L with the detected value of the displacement meter 13R, and outputs a signal to the torque motor so that, for example, the difference between the detected values of the displacement meters 13L and 13R becomes zero, and the torque motor Based on the signal, the flapper 28L is moved to the left. As a result, the pressure in the nozzle back pressure chamber 3L and the pilot chamber 9L increases,
The spool 15L is displaced to the left against the spring 29L.

When the spool 15L is displaced to the left, the liquid returned from the hydraulic cylinder is returned to the tank via the cylinder boat C1, the chamber 12L, the sleeve port 7L, and the tank boat R1. When the flapper 28L moves to the right, the hydraulic servo valve operates in the opposite manner to the above-described mode, and the spool 15L moves to the right by the spring 29L.

In this way, the microcomputer is connected to the displacement meter 13L and 1.
3R is input, and the computer outputs a signal based on the difference between the detected values to change the characteristics of both flappers l11rR.

- [Summary] As explained above, according to the hydraulic servo valve of the present invention, the leakage flow rate and a part of the working fluid are actively used to form a hydrostatic bearing, and the spool is supported without contact. This prevents wear on the sleeve and spool, and also reduces machining accuracy. Therefore, the spool and sleeve can be manufactured using a rust-resistant material such as a plastic material, and water rust can be prevented even if water is used as the working fluid. In addition, the spool and flapper am are separated, the spool's displacement range is expanded to increase the flow rate, and the through gap between the spool and the valve body is eliminated to eliminate leakage, thereby improving the responsiveness of the flapper mechanism. can. Furthermore, the characteristics of both flapper mechanisms can be changed by a microcomputer, the cylinders, etc. can be controlled at two speeds, and the movement of the cylinder of one rod can be precisely controlled.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing one 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... Passage 9L, 9R... Pilot room 13L, 13R... Displacement meter 15L, 15R.
...Spools 18L, 18R121L, 21R...Static pressure bearings 28L, 28R...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 outside the pair of flappers, and static pressure bearings are formed at both ends of each of the pair of spools. A passage for working fluid leading to the nozzle back pressure chamber via a pressure bearing is provided, and a displacement gauge is provided on each of the pair of spools, and based on detection signals from the displacement gauges, the displacement of one spool is determined according to the displacement of the other spool. A water pressure servo valve characterized in that it is provided with a control means for controlling the displacement of a spool.