JP3434978B2 - Hydraulic servo valve - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic servo valve having a sleeve and a spool built therein, a member for forming a working fluid switching port by these members, and using water or a viscous liquid close to water as the working fluid. Is.

[0002]

2. Description of the Related Art FIG. 9 shows the structure of a conventional hydraulic servo valve of this type. In the figure, reference numeral 1 denotes a valve main body, and a torque motor 22 is fixedly installed on an upper portion of the valve main body 1, and a flapper 23 of the torque motor 22 projects into the central chamber 8. A pair of nozzles 5L and 5L are provided on the same horizontal line on both sides of the flapper 23.
R and the nozzle back pressure chambers 6L and 6R are provided to face each other,
A small gap is formed between the nozzles 5L and 5R and the flapper 23.

Reference numeral 2 is a sleeve, and a sleeve port 3 and sleeve ports 4L and 4R are formed in the sleeve 2. The sleeve port 3 is connected to the pump port P, the sleeve ports 4L and 4R are connected to tank ports R1 and R2, respectively, and the tank ports R1 and R2 are connected to tanks (not shown). The sleeve ports 4L and 4R are connected to the central chamber 8 via the passages 7L and 7R.

A spool 13 is housed in the sleeve 2, and a gap C is formed between the inner wall surface of the sleeve 2 and the outer peripheral surface of the spool 13. That spool 1
3, small diameter portions 14L and 14R are formed, and chambers 9L and 9R formed by the outer peripheral surfaces of these small diameter portions 14L and 14R and the inner peripheral surface of the sleeve 2 are respectively cylinder ports C1 and C1.
It is connected to C2. Further, the pilot chambers 10L, 1 surrounded by both end surfaces of the spool 13 and the inner wall surface of the sleeve 2
Springs 0RL and 11R are provided at 0R, and pilot chambers 10L and 10R are connected to nozzle back pressure chambers 6L and 6R by passages 12L and 12R, respectively. In addition, 15
L and 15R are hydrostatic bearings, and 17L and 17R are orifices.

The operation of the hydraulic servo valve having the above structure will be described by taking the right side of the spool 13 as an example. The hydraulic pressure is from the pump port P to the sleeve port 3, the passage 19R, the orifice 17R, the pocket 16R, the gap C and the pilot 10.
R, the passage 12R, the nozzle back pressure chamber 6R, the nozzle 5R, the central chamber 8 through the gap between the nozzle 5R and the flapper 23, and the passage 7R, the sleeve port 4R, and the tank port R2 to return to the tank.

In operation, when the flapper 23 is moved to the left, for example, by an electric input signal to the torque motor 22, the pressure in the nozzle back pressure chamber 6L rises, and the nozzle back pressure chamber 6
The pressure in R drops, the pressure in pilot chamber 10L rises, and the pressure in pilot chamber 10R falls. As a result, the spool 13 is displaced rightward against the spring 11R. Therefore, the working fluid from the pump port P is guided to the load through the sleeve port 3, the chamber 9L, and the cylinder port C1, and the returning working fluid from the load is the cylinder port C2, the chamber 9R, the sleeve port 4R, and the tank port. It is returned to a tank (not shown) via R2. Flapper 2
When 3 moves to the right, the spool 13 is displaced to the left and operates in the opposite manner.

[0007]

In the hydraulic servo valve having the above structure, when water or a liquid having a viscosity close to that of water is used as the working fluid, the occurrence of cavitation erosion becomes a problem. This cavitation erosion
It is expected to occur in the portions A to D of FIG. That is, it is expected that the high pressure fluid will be generated at the edges of the sleeve 2 and the spool 13 of the guide valve portion where the high pressure fluid is switched, or at the portions where the high pressure fluid abuts.

Conventionally, the sleeve 2 and the spool 13 are made of plastic or ceramic material in order to cope with the above-mentioned cavitation erosion. However, when plastics or ceramics are used as the material, there are problems that the workability and processing accuracy are low and the material itself is expensive.

The present invention has been made in view of the above points, and an object thereof is to provide a hydraulic servo valve which is excellent in cavitation erosion resistance and can maintain the linearity of the spool valve flow rate characteristic.

[0010]

In order to solve the above-mentioned problems, the invention according to a first aspect of the present invention is to provide a sleeve in which a working fluid channel is formed and which is fixed in a valve body, and a working fluid which moves in the sleeve. Equipped with a spool that switches the flow direction of
In a hydraulic servo valve that uses water or a viscous liquid close to water as a working fluid, the sleeve and spool base materials are
Tsu to form a rounded shaped portion, at least one of the liquid contact portion of the sleeve and the spool is coated with the hard material matrix, further edge portions of the sleeve and spool are mutually
The structure is such that the sleeve and spool are overlapped.
Working fluid due to overlapping of the cage parts
Compensation means for linearly compensating for the non-linear characteristic of the flow rate is provided .

According to a second aspect of the present invention, in the hydraulic servo valve according to the first aspect, the hard material is ceramic or cemented carbide.

The invention described in claim 3 is the same as that of claim 2
In the hydraulic servo valve described in the paragraph 1, the cemented carbide is an alloy steel containing titanium.

[0013]

[0014]

[0015]

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing the structure of a hydraulic servo valve according to the present invention. In FIG. 1, the same reference numerals as those in FIG. 9 denote the same parts. The structure of the hydraulic servo valve of the present invention is the same as that of the conventional hydraulic servo valve, and the operation thereof is also the same, and therefore the description thereof is omitted.

The difference between the hydraulic servo valve of the present invention and the conventional hydraulic servo valve is that, as shown in FIGS. 1 and 2A, portions A to D where cavitation erosion is predicted to occur. That is, the edges of the sleeve 2 and the spool 13 of the guide valve portion where the high-pressure fluid is switched are rounded, and the wetted portions of the sleeve 2 and the spool 13 that come into contact with the working fluid are as shown in FIG. It is that hard material coatings 2A and 13A such as ceramics and cemented carbide are applied. As a result, even if cavitation occurs near the edges of the sleeve 2 and the spool 13 of the guide valve portion where the high-pressure fluid is switched, damage to the sleeve 2 and the spool 13, that is, cavitation erosion is suppressed.

Conventionally, the edge portion of the sleeve 2 and the spool 13 of the guide valve portion where the high pressure fluid is switched is shown in FIG.
It has a sharp edge at a right angle as shown in. Conventionally, the reason why the structure has a sharp edge is that the flow rate through the metering orifice (control flow rate) is linear with respect to the displacement (valve opening) of the spool. Further, since the hardening is performed while maintaining the structure of the sharp edge, the treatment method such as nitriding or induction hardening is limited. As shown in FIG. 3B, it is difficult to apply the hard material coatings 2A and 13A made of ceramics or cemented carbide to such sharp edge portions, and at the same time, the hard material coatings 2A and 13A can be applied. Even if it does, there is a problem that the hard material coatings 2A and 13A at that portion are easily peeled off and the durability of the coating is lacking. Therefore, in the present embodiment, as shown in FIG. 2, the edges of the sleeve 2 and the spool 13 of the guide valve portion for switching the high-pressure fluid are rounded. As a result, the hard material coatings 2A and 13A are facilitated, peeling is less likely to occur at the edge portions, and durability is also improved.

When the metering orifice portion of the hydraulic servo valve, that is, the sleeve 2 and the edge portion of the spool 13 are rounded, the leakage flow rate at the neutral position of the hydraulic servo valve (the neutral position of the spool 13) is reduced. May increase. Therefore, in order to deal with this, the leakage flow rate at the neutral position is reduced by overlapping between the spool 13 and the sleeve 2.

FIG. 4 is a diagram showing a leak flow rate characteristic of the hydraulic servo valve. In the same figure, as shown in FIG. 5 (a), the curve B shows the case where the amount of wrap between the spool 13 and the sleeve 2 is zero (zero lap), and the curve A shows the spool as shown in FIG. 5 (b). A case where the lap amount between the sleeve 13 and the sleeve 2 is a predetermined amount ΔR is shown. Spool 1 as shown
By providing a predetermined amount of wrap between the sleeve 3 and the sleeve 2, the leakage flow rate at the spool neutral position can be reduced.

FIG. 6 is a diagram showing the flow rate characteristics of the hydraulic servo valve when the metering orifices of the hydraulic servo valve are overlapped. As shown in the figure, when the metering orifices are overlapped, the gradient near the neutral position of the spool becomes small and the flow rate characteristic becomes non-linear. When the flow rate characteristic becomes non-linear in this way, it becomes difficult to control the actuator such as the cylinder or the motor by the hydraulic servo valve.

FIG. 7 is a block diagram showing a system configuration in the case of controlling an actuator using the hydraulic servo valve. As shown, the command signal is sent to the servo amplifier 30.
Through the torque servo motor 22 of the hydraulic servo valve, the nozzle flapper 23, and the guide valve 31 composed of the spool 13 and the sleeve 2, the metering orifice portion is overlapped as described above. By doing so, the flow rate characteristic of the guide valve 31 becomes non-linear, so it is necessary to input a command signal in consideration of the non-linear element D of this flow rate characteristic.

Therefore, as shown in FIG. 8, the compensating element 33 inserted in the preceding stage of the servo amplifier is capable of arbitrarily adjusting (adjusting) the non-linear characteristic according to the desired characteristic. By providing a compensating element (circuit) 33 having a compensating characteristic E for compensating the non-linear element D of the flow rate characteristic in the preceding stage of the servo amplifier 30, if the flow rate characteristic is linearized F, the metering orifice portion is overlapped. It is possible to simplify the control of the actuator by the hydraulic servo valve.

The structure of the hydraulic servo valve in the above-described embodiment of the present invention is an example, and the structure of the hydraulic servo valve to which the present invention is applied is not limited to this. That is, it is provided with a sleeve fixed in the valve body and in which a working fluid flow path is formed, and a spool that moves in the sleeve and switches the flow direction of the working fluid, and the working fluid is water or a viscous liquid close to water. A hydraulic servo valve having any structure may be used as long as it is a hydraulic servo valve using the above, and at least one liquid contact portion of the sleeve and the spool may have a structure in which a base material is coated with a hard material.

[0025]

As described above , according to the present invention,
The following excellent effects can be obtained. In the hydraulic servo valve the viscosity of the liquid near the water or water and the working fluid, Sri
If a rounded edge is formed on the base material of the sleeve and spool
At the same time, the liquid contact portion of at least one of the sleeve and the spool has a base material coated with a hard material, and
With the structure that the edge parts of the spool overlap each other
Since the, improved resistance to cavitation erosion resistance, coating is easily the improved peeling resistance of the coating at the same time, it is possible to suppress an increase in leakage flow rate in the spool neutral position. In addition, the sleeve and
Because the edges of the pool overlap each other
Compensator for linearly compensating the nonlinear characteristics of the flow rate of the working fluid
Since there are steps, the flow rate characteristic of the hydraulic servo valve is made linear.
be able to.

[0026]

[0027]

[0028]

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a hydraulic servo valve of the present invention.

FIG. 2 is an enlarged view of an edge portion of a sleeve and a spool of the hydraulic servo valve according to the present invention.

FIG. 3 is an enlarged view of an edge portion of a sleeve and a spool of a conventional hydraulic servo valve.

FIG. 4 is a diagram showing a leak flow rate characteristic of a hydraulic servo valve.

FIG. 5A is a diagram showing a case where the amount of lap between the spool and the sleeve is zero, and FIG. 5B is a diagram showing a case where a predetermined amount of lap is provided.

FIG. 6 is a diagram showing flow rate characteristics of the hydraulic servo valve when the metering orifices are overlapped.

FIG. 7 is a block diagram showing a system configuration for controlling an actuator using a hydraulic servo valve.

FIG. 8 is a block diagram showing a system configuration for controlling an actuator using a hydraulic servo valve.

FIG. 9 is a diagram showing a structure of a conventional hydraulic servo valve.

FIG. 10 is an enlarged view of a portion predicted to cause cavitation erosion in the hydraulic servo valve.

[Explanation of symbols]

1 valve body 2 sleeve 3 sleeve port 4L, 4R Sleeve port 5L, 5R nozzle 6L, 6R nozzle back pressure chamber 7L, 7R passage 8 Central room 9L, 9R room 10L, 10R pilot room 11L, 11R spring 12L, 12R passage 13 spools 14L, 14R Small diameter part 15L, 15R hydrostatic bearing 16L, 16R pocket 17L, 17R Orifice 19L, 19R passage 22 Torque motor 23 flapper

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keizo Takahashi 4-2-1 Honfujisawa, Fujisawa-shi, Kanagawa Inside EBARA Research Institute Co., Ltd. No. 18 (56) Reference JP-A-5-44865 (JP, A) JP-A-5-60250 (JP, A) Actual development Sho-56-79702 (JP, U) (58) Fields investigated (Int.Cl . ^7, DB name) F16K 31/12 - 31/165 F16K 3/00 - 3/36 F16K 11/00 - 11/24 F16K 31/36 - 31/42

Claims (3)

(57) [Claims] 1. A flow path for a working fluid fixed in a valve body is formed.
The formed sleeve and the working fluid that moves in the sleeve
And a working fluid.
Hydraulic servo valve that uses water or a viscous liquid close to water
AtRound the edges of the base material of the sleeve and spool.
Together with At least one of sleeve and spool
The wetted part of one is coated with a hard material on the base material,Furthermore,
Leaves and spool edges overlap each other
Configuration, The edges of the sleeve and spool overlap each other.
The nonlinear characteristic of the flow rate of the working fluid
Compensation means to compensate The hydraulic sir characterized by
Bo valve. 2. The hydraulic servo valve according to claim 1, wherein the hard material is ceramic or cemented carbide. 3. The hydraulic servo valve according to claim 2 , wherein the cemented carbide is an alloy steel containing titanium.