JPH07248073A - Pilot switching valve - Google Patents

Abstract

PURPOSE:To reduce the collision force of a spool to the inner end surface of a valve box by fitting, to the spool end surface, a block body for blocking the most part of a pilot passage when the spool approaches the stroke terminal end. CONSTITUTION:When a pilot fluid pressure is introduced mainly through a pilot fluid outlet and inlet port PL having a large diameter to press a spool 2, the spool 2 is quickly moved to the right since the pilot fluid in the space on the right end surface outside of the spool 2 flows out at a high flow rate mainly from a pilot fluid outlet and inlet port PR having a large diameter. When the right end surface of the spool 2 approaches the right inner end surface of a valve box 1, a block body 4 makes contact with the pilot fluid outlet and inlet port PR on the right to block it, and the pilot fluid situated in the space on the right end surface outside of the spool 2 thus must flow out thereafter only through a small pilot fluid outlet and inlet port PRs. Since the small pilot fluid outlet and inlet port PRs has a small diameter, its flow rate is low, and the moving speed of the spool 2 is lowered. Thus, the collision force is minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pilot switching valve for switching a flow path of a target fluid by moving a position of a spool by pilot fluid pressure, and more particularly to a means for reducing an impact sound generated at the time of switching. is there.

[0002]

2. Description of the Related Art FIG. 5A shows a conventional pilot switching valve. A spool 2 is inserted in a valve housing 1 finished in a cylindrical shape so as to be freely movable in the axial direction. Collar-shaped portions 2c, 2a, 2b that are slidable in contact with the inner surface of the valve casing 1 without a gap are formed at the center and both ends of the spool 2. Target fluid inlets / outlets (ports) 1c, 1a, 1b are opened in the central portion of the valve housing 1 and slightly left and right, and pilot fluid inlets / outlets PL, PR are opened at both ends of the valve housing 1, and pipe lines are respectively formed. It is connected. As shown, when the spool 2 is at the left position, the target fluid inlet / outlet port 1c communicates with 1b,
The target fluid inlet / outlet port 1a is closed. When the pilot fluid pressure enters from the left pilot fluid inlet / outlet PL and flows out from the right pilot fluid inlet / outlet PR, the spool 2 moves from the left position to the right position, and the target fluid inlet / outlet 1c is 1a.
And the target fluid inlet / outlet port 1b is closed. 5B is a diagram showing the cross-sectional area of the narrowest part of the pilot flow path while the spool 2 is moving, and the cross-sectional area of the flow path is constant and does not change.

[0003]

The conventional pilot switching valve is as described above, but when the spool 2 is driven by the pilot fluid pressure and reaches the end, the end surface of the spool 2 becomes the inner end surface of the valve casing 1. Collision produces impact noise. Also,
When the pilot fluid is a liquid, there is a problem that a water hammer phenomenon may occur due to sudden stop of collision.

The present invention has been made to solve the above problems, and when the spool 2 moves in the valve casing 1 and collides with the inner end surface of the valve casing 1 at the end, the collision force is reduced,
Therefore, it is an object of the present invention to obtain a pilot switching valve that reduces impact noise and prevents the occurrence of a water hammer phenomenon when the pilot fluid is liquid.

[0005]

In the pilot switching valve according to the present invention, a closing member is attached to the spool for closing most of the pilot passage when the spool approaches the end of the stroke.

[0006]

In the obstruction body attached to the spool of the pilot switching valve according to the present invention, when the spool approaches the stroke end,
Block most of the pilot channel. Therefore, the pilot fluid must flow through a small portion of the pilot flow path, reducing the flow rate. Therefore, the moving speed of the spool decreases and the end of the stroke is collided at the decreased speed, so the collision energy decreases, the impact noise decreases, and when the pilot fluid is liquid, the water hammer phenomenon is also prevented. It

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1 (A), 1 is a valve casing which is a main body of an outer shell of a valve, and an inner surface of the valve casing 1 is smoothly and precisely finished in a cylindrical shape. Reference numeral 2 is a spool, and the spool 2 is provided inside the valve casing 1 so as to be freely movable in the axial direction. Collar-shaped portions 2c, 2a and 2b are provided at the center and both ends of the spool 2.
Are formed. The outer peripheral surfaces of the collar-shaped portions 2c, 2a, 2b are formed so as to slide in contact with the inner peripheral surface of the valve casing 1 without a gap, and the space inside the valve casing 1 is formed on the right side of the collar-shaped portion 2b and the collar-shaped portion 2
It is divided into four spaces, that is, between b and the collar-shaped portion 2c, between the collar-shaped portion 2c and the collar-shaped portion 2a, and on the left side of the collar-shaped portion 2a. A target fluid inlet / outlet (port) 1c is opened in the central portion of the valve casing 1, target fluid inlet / outlet ports 1a and 1b are opened slightly left and right from the center, and pilot fluid inlet / outlet ports are provided on both end faces of the valve casing 1. PL and PR are opened, and pipes are connected to each.

As shown in FIG. 1 (A), in addition to the pilot fluid inlets / outlets PL and PR, small pilot fluid inlets / outlets PLs and PRs having a small diameter are opened on both end surfaces of the valve casing 1.
Each is connected to the left and right pilot lines. A recess is formed in each end face of the spool 2 facing the pilot fluid inlets / outlets PL and PR, the base end of the compression spring 3 is attached to the bottom of the recess, and the closing body 4 is attached to the tip of the compression spring 3. Has been. The closing body 4 is in the shape of a thick disk, and the periphery thereof is cut obliquely toward the front. The inner end portions of the pilot fluid inlets / outlets PL and PR are formed in a shape in which the closing body 4 can be fitted and inscribed.

Next, the operation of the embodiment shown in FIG. 1 will be described. As shown in FIG. 1A, when the spool 2 is at the left position, the target fluid inlets / outlets 1c and 1b communicate with each other, and the target fluid inlet / outlet 1a is a dead end and is closed inside the valve housing 1. The pilot fluid pressure enters from the left pilot fluid inlets PL and PLs and pushes the left end surface of the spool 2 to the right, and the pilot fluid in the space outside the right end surface of the spool 2 flows out from the right pilot fluid inlets PR and PRs. Then, the spool 2 moves to the right position, and the target fluid inlet / outlet port 1
c and 1a communicate with each other, and the target fluid inlet / outlet port 1b is closed.

In FIG. 1A, as described above, the pilot fluid pressure is mainly large.
When the spool 2 is pushed to the right after entering from above, the pilot fluid in the space outside the right end surface of the spool 2 mainly flows out from the large-diameter pilot fluid inlet / outlet PR at a large flow rate, so that the spool 2 relatively quickly. Move to the right. However, when the right end surface of the spool 2 approaches the right inner end surface of the valve casing 1, the closing body 4 contacts and closes the right pilot fluid inlet / outlet PR, and thereafter, in the space outside the right end surface of the spool 2. Pilot fluid in the small pilot fluid inlet / outlet PRs
You will have to pass through and out only. Since the small pilot fluid inlet / outlet PRs has a small diameter, the flow rate is small and the moving speed of the spool 2 is low. At the reduced moving speed, the right end surface of the spool 2 comes into contact with the right inner end surface of the valve housing 1, and the energy of collision, impact force, and impact noise are reduced. Further, when the pilot fluid is a liquid, the water hammer phenomenon is prevented from occurring.

The solid line shown in FIG. 1 (B) shows the change in the cross-sectional area or flow rate of the narrowest part of the pilot flow passage when the spool 2 moves to the right as described above. In the left part, a large amount of pilot fluid flows through the large-diameter pilot fluid inlet / outlet PR. Therefore, the moving speed of the spool 2 is fast. In the right portion, since the closing body 4 abuts and closes the pilot fluid inlet / outlet PR, only a small amount of pilot fluid can flow through only the small pilot fluid inlet / outlet PRs. Therefore, the moving speed of the spool 2 also decreases. In the initial stage of the movement of the spool 2, the closing body 4 which is in contact with the left pilot fluid inlet / outlet PL is pushed by the pressure of the inflowing pilot fluid and immediately separates from the pilot fluid inlet / outlet PL.

Contrary to the above, the broken line shown in FIG. 1 (B) shows the change in the flow passage cross-sectional area or flow rate when the spool 2 moves from right to left. Since the pilot switching valve shown in FIG. 1 (A) is symmetrically configured, even when the spool 2 moves from right to left, the same operation as above causes the initial movement to quickly approach the end. Since the left closed body 4 closes the pilot fluid inlet / outlet PL, the speed becomes low at the time of collision.

Next, a second embodiment shown in FIG. 2 will be described. As shown in FIG. 2A, the closing body 4 is a spool 2.
It is formed so as to be fixed to the spool 2 so as to project from both end surfaces in a cylindrical shape. The outer diameter of the closing body 4 is formed to be slightly smaller than the inner diameters of the pilot fluid inlets and outlets PR and PL. A change in the cross-sectional area or flow rate of the pilot flow channel narrowest part when the spool 2 moves becomes as shown in FIG. 2B, and at the end of the movement, the pilot fluid passes through a narrow gap around the closing body 4. Therefore, as in the case of the above description, the moving speed of the spool 2 decreases near the moving end point, and the impact noise at the time of a collision decreases.

Next, a third embodiment shown in FIG. 3 will be described. As shown in FIG. 3A, the closing body 4 is a spool 2
It is formed so as to be fixed so as to project in a conical shape from both end faces. The outer diameter of the base of the closing body 4 is formed to be slightly smaller than the inner diameters of the pilot fluid inlets and outlets PR and PL.
The change in the cross-sectional area or flow rate of the narrowest part of the pilot flow passage when the spool 2 moves is as shown in FIG. 3B, and at the end of the movement, the pilot fluid passes through the narrow gap around the closing body 4. I have to do so, like above,
Near the end point of the movement of the spool 2, the movement speed decreases and the impact decreases.

Next, a fourth embodiment shown in FIG. 4 will be described. As shown in FIG. 4A, the closing body 4 is in the shape of a thick disc and is attached to the recesses on both end surfaces of the spool 2 via the compression spring 3. Notch or small hole 4 in the closing body 4
c is open. Notch or small hole 4c of the closing body 4
Since the pilot fluid passes therethrough, the change in the cross-sectional area of the narrowest part of the pilot flow passage when the spool 2 moves is as shown in FIG. 4 (B), and the operation is described with reference to the embodiment shown in FIG. It will be the same as what you did.

Although the above embodiment has been described with respect to the pilot switching valve of the double pilot type without 3-port 2-position spring return, the pilot switching valve of other types is also appropriately modified and applied. can do. Further, when the impact sound of only one side is a problem, the closing body 4 may be provided on only one side. Further, it is also possible to provide different shapes of the closing bodies on the left and right sides. Further, the compression spring 3 is not limited to the spiral spring as shown in the drawing, but other types of spring or rubber may be used. Further, the shape and the like of the closing body 4 can be appropriately changed in design.

[0017]

As described above, according to the present invention, when the spool approaches the end of the stroke, the closing member closes most of the pilot flow path, so that the moving speed of the spool decreases and the end impact force. Becomes smaller and the impact sound is reduced. Further, when the pilot fluid is a liquid, water hammer is prevented from occurring.

[Brief description of drawings]

FIG. 1A is a vertical sectional view of a pilot switching valve according to a first embodiment of the present invention, and FIG. 1B is a diagram showing a change in sectional area or flow rate of a pilot flow channel narrowest portion.

FIG. 2A is a vertical cross-sectional view of a pilot switching valve according to a second embodiment of the present invention, and FIG. 2B is a view showing a change in cross-sectional area or flow rate of a pilot flow channel narrowest part.

FIG. 3A is a vertical cross-sectional view of a pilot switching valve according to a third embodiment of the present invention, and FIG. 3B is a view showing a change in cross-sectional area or flow rate of a pilot flow channel narrowest part.

FIG. 4A is a vertical cross-sectional view of a pilot switching valve according to a fourth embodiment of the present invention, and FIG. 4B is a view showing a change in cross-sectional area or flow rate of a pilot flow channel narrowest part.

FIG. 5 (A) is a longitudinal sectional view of a conventional pilot switching valve,
(B) is a diagram showing a change in cross-sectional area or flow rate of the narrowest part of the pilot channel.

[Explanation of reference numerals] 1: Valve casing, 1a, 1b, 1c: Target fluid inlet / outlet port, 2:
Spools, 2a, 2b, 2c: collar-shaped part, 3: compression spring, 4: closed body, 4c: notch or small hole, PL, P
R: pilot fluid inlet / outlet, PLs, PRs: small pilot fluid inlet / outlet.

Claims (2)

[Claims] 1. A pilot switching valve for driving a spool by pilot fluid pressure to switch a flow path of a target fluid, wherein a closing member that closes most of the pilot flow path when the spool approaches a stroke end of the spool. A pilot switching valve characterized by being attached to the end face. 2. A pilot switching valve that drives a spool in both reciprocating directions by pilot fluid pressure to switch the flow path of a target fluid, and a closing member that closes most of the pilot flow path when the spool approaches the stroke end. A pilot switching valve mounted on both end faces of the spool.