JPS5980511A - Hydraulic servo-valve - Google Patents

Abstract

PURPOSE:To reduce the number of parts and to attain high responsiveness by forming a rotation-translation converting mechanism, a variable orifice portion at the front step port of a hydraulic servo-valve and a main valve displacement feedback mechanism at the same time with an orifice cover and a spool forming a main valve. CONSTITUTION:A plane portion 2a is formed on the upper surface of the central portion of a spool 2 where oil pressure paths 7a, 7b are disposed inside. When an orifice cover 3 is rotated by a motor 12, and the edge of an eccentric boring circle 9 forming a variable orifice with openings 8a, 8b is moved to the right along the axis of the spool 2, the variable orifice closes at the side 8a and opens at the side 8b, so that the pressure in a pressure chamber 4a increases to force the spool 2 to move to the right. With the movement of the spool 2, an opening on the side 8a of the variable orifice is enlarged, and an opening on the side 8b is reduced until both openings are equal to each other and pressures in pressure chambers 4a, 4b are equalized. At that position, the spool 2 is positioned. Therefore, corresponding to the rotation of the motor 12, the spool 2 can switch the oil pressure paths 17a, 17b, so that the thus constructed device functions as a hydraulic servo-valve.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic servo valve that changes the pressure at both ends of a spool-type main valve according to the displacement of a motor, and displaces the main valve in its axial direction in response to the amount of displacement of the motor. be.

Conventionally, the main valve drive mechanism of a hydraulic servo valve consists of a front stage using a nozzle flapper system, an injection pipe system, a guide valve system, etc., and all the output of this front stage is directed to both ends of the main valve to drive the main valve, and a spring balance system is used. In many cases, localization is performed using a method such as , position feedback method, or position feedback method. but,
Both of these methods have their own drawbacks. For example, the nozzle flapper and injection pipe in the front stage are susceptible to oil contamination, and the oil path from the front stage to both ends of the main valve, including the guide valve system, becomes long. Furthermore, since the localization system feeds back the displacement of the main valve via springs, levers, etc., it tends to be mechanically complex and often difficult to adjust.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic servo valve that eliminates the above-mentioned drawbacks of conventional hydraulic servo valves, is mechanically simple, easy to adjust, and has high precision and high responsiveness.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

In the hydraulic servo valve of the embodiment of the present invention shown in FIG.
A spool 2 is housed inside the casing 1 so as to be displaceable in the axial direction. Pressure chambers 4a and 4b provided at both ends of the spool 2 in the casing 1 are connected to the casing l.
f: Penetrating hydraulic passage 5a.

5b and a fixed orifice 6a provided in the middle.

6bf: connected to the front-stage hydraulic power source 18 via
By varying the pressures in both pressure chambers 4a and 4b, the spool 2 is moved in the axial direction. Land 14 on spool 2
a, 14b are provided, and the casing 1 has hydraulic passages 1 corresponding to these lands 14a, 14b.
5a, 16a, 17a and 15b, 16-
b, 17b are provided. Of the above hydraulic passages, 15a and 15b are connected to the hydraulic power source 19 for the rear stage, and 16a and 15b are connected to the rear hydraulic power source 19,
, 16b is the drain 111c, %17a.

17b is connected to a load. Therefore, when the spool 2 moves to the right in FIG.
6a and 17b and 15b are connected, the port of 17a is connected to the drain 11, and the port of 17b is connected to the rear hydraulic power source 19.
connected to. When the spool 2 moves to the left, the hydraulic passage 17a
, 17b are connected in the opposite manner to the above. Therefore, the spool 2 becomes the main valve of the hydraulic servo valve.

As shown in FIGS. 1 and 2, a flat portion 2a is formed on the upper surface of the central portion of the spool 2, one end of which opens into pressure chambers 4a and 4b at both ends of the spool 2, and the other end of which opens into the pressure chambers 4a and 4b at both ends of the spool 2. Hydraulic passages 7a and 7b are provided in the spool 2 and open on the center line of the flat portion 2a at a certain distance from each other in the axial direction of the spool.

On the flat part 2a of the spool 2, the lower surface is
An orifice cover 3 is provided that is in slidable surface contact with the orifice cover 3 and is rotationally driven by a motor 12 via a coupling 13 . This rotating shaft is connected to the spool 2 as shown in Figure 2.
It is located in a vertical plane passing through the axis of , and is provided perpendicularly to the plane portion 2a. The bottom surface of the orifice cover 3 has a
A boring circle 9 eccentric to the rotation axis is provided. The edge of the bored circle 9 is set to a size that allows it to intersect with the openings 8a, 8b in the plane portion 2a of the hydraulic passages 7a, 7b at the same time, and the edge of the bored circle 9 of the orifice cover 3 and the opening 8a , 3b form a variable orifice. variable orifice opening ga,
The downstream side of gb is connected to a drain 11 via a hydraulic passage 10a provided through the spool 2 and a hydraulic passage 10b provided through the casing I. Therefore, between the hydraulic power source 18 and the drain 11, as shown in FIG. 3, there is a fixed orifice 6a and an eb pressure chamber 4a.

4b, and variable orifices 8a and 8b are connected as shown in the figure to form a hydraulic bridge.

As shown in Fig. 4, the spool 2 is provided with a detent 2o on the casing l to prevent it from rotating around its axis.
As a result, a uniform gap is always maintained between the flat part 2a of the spool 2 and the lower surface of the orifice cover 3, so that they can slide smoothly through a uniform oil film. It has become.

The operation of the apparatus constructed as above will be explained below.

The boring circle 9 is eccentrically formed with respect to the rotation axis of the orifice cover 3 which is on the center line of the spool 2, so when the orifice cover 3 is rotated by the motor 12, as shown in FIGS. The edge of the bore circle 9, which together with the openings 8a, 8b forms the variable orifice, will move in the axial direction of the spool 2. If the edge of the boring circle 9 now moves to the right in Figures 1 and 2,
The 8a side of the variable orifice is closed, and the 8b side is open. Therefore, among the pressure chambers at both ends of the spool 2, the pressure in the left pressure chamber 4a becomes high, and the pressure in the right pressure chamber 4b becomes low.

Therefore, the spool 2 moves to the right.As the spool 2 moves, the opening degree on the variable orifice 8a side gradually increases, and the opening degree on the 8b side gradually decreases, and the opening degree of both variable orifices 8a and 8b gradually increases. are the same and pressure chamber 4
The spool 2 is positioned at a position where the pressures of a and 4b are equal. Conversely, when the edge portion of the boring circle 9 moves to the left in FIGS. 1 and 2, the spool 2 also moves to the left due to the aforementioned reverse operation. That is, the position of the spool 2 is determined in accordance with the position of the edge portion of the boring circle 9 with proper positioning. The position of the edge of the bored circle 3 corresponds to the rotational displacement of the orifice cover 3, so the spool 2
is the rotational change of the orifice cover 3 and therefore the motor 12.
The position will be determined according to the position.

Therefore, in response to the rotation of the motor 12, the spool 2F
i Hydraulic passages 17a and 17b can be switched,
This device operates as a hydraulic servo valve.

The operation of the orifice cover 3 and the variable orifice sections 8a, 8b will be considered in more detail with reference to FIGS. 5 to 1O.

As shown in FIG. 5, the centers of the variable orifices 3a and 3b and the rotation center 01 of the orifice cover 3 are
The center 02 of the bored circle 9 is eccentric from the center 01 of the orifice cover 3 by a length a, and when the rotation angle θ of the orifice cover 3 is θ=08, the center 02 of the bored circle 9 is placed on the center line 9 has a variable orifice 8a,
It is located at a position equidistant from 8b and offset by a from the axis X, and the edge of the bored circle 9 forms the variable orifice 8a, 8
Let it cross the center point of b.

The solid line in FIG. 6 shows the state in which the orifice cover 3 has been rotated by θ-90° clockwise in FIG. In this case, it is moved to the right from its original position to the intersection between the edge of the bored circle 9 and the center line X of the spool 2. therefore,
As described above, the spool 2 follows this and moves to the right, and is positioned at a position where the opening degrees of the variable orifices 8a and 8b are equal. Since Qi in FIG. 6, the amount of displacement of the spool 2 is a.

Rotation angle θ of orifice cover 3 and displacement amount 2 of spool 2
The relationship becomes a sine curve as shown in Figure 7, and θ=9
At 0°, the amount of displacement of the spool 2 is equal to the amount of eccentricity a of the bored circle 9. Therefore, by changing the eccentricity of the boring circle 9, the stroke of the spool 2 can be changed. Furthermore, by making the shape of the bored circle 9 into a shape other than the one with the opening, the relationship between the rotation angle of the orifice cover and the displacement of the spool can be changed arbitrarily.

In FIGS. 5 and 6, variable orifice ~.

If the distance between the centers of 8b is 11 and the radius of the bored circle is r, then from the Pythagorean theorem, 2-a2 + (k)2,', L1= 2〆? At y θ-90° (Fig. 6), if the distance between the two intersections of the edge of the bored circle 9 and the axis The edge of the bored circle 9 is shifted outward from the center of the variable orifices ga, 8b by (L2-Ll)
=00.

Therefore, as is clear from the hydraulic circuit diagram shown in Figure 3,
Pressure chambers 4a and 4b at both ends of spool 2 and drain 11
The resistance between them decreases, and the pressure in pressure chambers 4m and 4b becomes
This results in a disadvantage that the dynamic characteristics change depending on the spool position.

An effective method for minimizing changes in the opening area of the variable orifices 8a and 8b will be described with reference to FIGS. 8 to 1θ.

As shown in FIG. 8, consider a case where the positions of the variable orifices 3a and 3b are shifted from the center line X of the spool 2 by a length b. Figure 8 shows that the rotational position of the orifice cover 3 is θ.
-0°, and FIG. 9 shows the case of θ=90° as a solid line. θ=
In the case of 0° (shown by the dashed line in Fig. 9), the edge of the bored circle 9 crosses the center of the variable orifice 88° 8b,
Let Ls be the distance between the centers of a and 8b. Also, θ=90°
The edge of the boring circle 9 and the variable orifice 8a when ゛
, the distance between the two intersections with the straight line passing through the center of 8b is L
4, then L3=2〆r''-(a-b)''L4''2p'r-V, and if b=odd, then L3=L,
Even when θ=90°, the edge of the bored circle 9 can be made to pass through the center of the variable orifices 8a, 3b.

In Figure 1O, the value of b/a when a = 0.2r is used as a parameter, the vertical axis represents the deviation Δ between the center of the variable orifice and the edge of the bored circle, and the horizontal axis represents the amount of deviation Δ of the orifice cover. This is a curve representing the relationship between Δ and θ, which is shown by taking the rotation angle θ. When θ=90°, '=(L3-L+) urine.

As is clear from Figure 1θ, Δ
Although it is not possible to reduce Δ to zero, by shifting the position of the variable orifice from the spool center line, Δ can be significantly reduced to 0. In other words, the spool generated by the rotation of the orifice cover 3 without changing the spool stroke. Pressure fluctuations in the pressure chambers 4a and 4b at both ends of the pressure chamber 2 can be suppressed to a minimum.

As explained above, according to the present invention, the orifice cover that is directly connected to the rotating shaft of the drive motor and is rotationally displaced and the spool that forms the main valve are used to control the rotational/linear conversion mechanism and the front stage of the hydraulic servo valve. The orifice portion and the main valve displacement feedback mechanism can be configured simultaneously, the number of parts is reduced, and the structure is simplified. In addition, since the hydraulic passages from the front stage to the pressure chambers at both ends of the spool are provided only within the spool, high responsiveness can be expected, and the variable orifice section is a small orifice type, so it requires less oil pressure than a nozzle flapper type. Various effects can be obtained, such as having almost no problem with contamination.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a view taken along the line ■-■ in Fig. 1, Fig. 3 is a circuit diagram of the hydraulic bridge in this embodiment, and Fig. 4 is A sectional view taken along the line ■-■ in FIG. 1, FIGS. 5 to 7 are diagrams explaining the relationship between the displacement of the variable orifice cover and the displacement of the spool,
10 to 10 are diagrams for explaining the effect when the variable orifice portion is provided offset from the spool centerline. l...Casing 2...Spool (main valve) 2
a...Flat part 3...Variable orifice cover 4a, 4b...Spool both ends pressure chamber 7a,
7b... Hydraulic passage in the spool 8a, 3b...
Hydraulic passage opening (variable orifice part) 9...bore circle
II...Drain 12...Motor

Claims (2)

[Claims] (1) It has a spool-type main valve that is displaceable in the axial direction within the caking chamber, and a motor, and the displacement of the motor changes the pressure in the pressure chambers at both ends of the main valve to match the amount of displacement of the motor. Correspondingly, in a hydraulic servo valve that displaces the main valve, a flat part is provided on a part of the peripheral surface of the main valve, one end opens to the pressure chambers at both ends of the main valve, and the other end opens to the pressure chambers at both ends of the main valve, and the other end is connected to the flat part. Two hydraulic passages are provided in the main valve that open at a distance in the axial direction of the valve, and the lower surface slides into contact with the flat part, and the motor drives the axis that passes through the axis of the main valve and is perpendicular to the flat part. A cover is provided that rotates around the cover, and a generally circular boring portion is provided on the surface of the cover that slides in contact with the flat surface, which is eccentric to the axis of rotation and whose peripheral edge can intersect at the same time as the opening of the two hydraulic passages. A hydraulic servo valve characterized in that the hollow space is connected to a drain. (2) The opening position in the flat part of the hydraulic passage leading from the pressure chambers at both ends of the main valve to the flat part of the peripheral surface of the main valve,
2. The hydraulic servo valve according to claim 1, wherein the boring portion is offset from the center line of the main valve by approximately % of the eccentricity of the boring portion.