JPH061806U - Low leak spool valve - Google Patents

Abstract

(57) [Summary] [Objective] To provide a spool valve capable of maintaining a low leak characteristic for a long period of time. [Structure] A land 16 having a notch 15a formed between the load pressure chamber corresponding groove 13a of the spool 12 and the intermediate pressure chamber corresponding groove 17a.
Provide a. This land 16a is the inner diameter portion 11a of the body 11.
The load pressure chamber 13 and the intermediate pressure chamber 17 are opened and closed. A land 16b having a notch 15b formed on the intermediate pressure chamber side is provided between the intermediate pressure chamber corresponding groove 17a of the spool 12 and the spring mounting portion 22 located on the left end side. This land
16b is slidably fitted into the inner diameter portion 11b of the body 11 to open and close between the intermediate pressure chamber 17 and the discharge pressure chamber 23. The overlap Lsa set by the notch 15a is set equal to or slightly larger than the overlap Lsb set by the notch 15b. The return spring of the spool 12 is composed of a weak coil spring 20a and a strong coil spring 20b mounted via an axial clearance C.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a low-leakage spool valve, and more particularly to a valve structure that has a modulation function in a safety valve directly connected to a cylinder or the like and that minimizes the amount of drift due to internal leakage when holding a load on the cylinder. Is.

[0002]

[Prior art]

 An outline of a conventional spool valve is shown in FIG. In FIG. 5A, the spool 12 is movably fitted inside the body 11, and the load pressure generated in the actuator (cylinder) 10 is supplied to the load pressure chamber 13 formed in the body 11. When the external pilot pressure is not supplied to the pilot pressure inlet 14 to the right end of the spool and the spool 12 is in the normal position (state shown in the figure), the land 16 of the spool having the notch 15 has a short overlap Ls. At the same time, since there is a certain clearance between the body 11 and the spool 12, the load pressure leaks from the load pressure chamber 13 to the intermediate pressure chamber 17 in the figure, and the leak is the line sheet 18 of the body 11 and the spool. It is cut off with the collar part 19 of 12. On the other hand, since the right side of the load pressure chamber 13 has a long overlap Ll, even if there is a certain clearance between the body 11 and the spool 12, there is little leakage. The spool 12 is pressed against the wire sheet 18 by a single return spring 20.

[0003]

[Problems to be solved by the device]

 When this type of spool valve is used for a long time, the spool 12 moves to the left, and the force of the return spring 20 again causes a large impact force when receiving the line seat 18 of the body 11. It can be seen that the normal-shaped line sheet 18 enlarged and displayed in (B) gradually deforms into a face sheet 18a as shown in FIG. 5 (C).

Therefore, as shown in FIG. 5C, the spool 12 cannot be disassembled (cannot be pulled out) due to the occurrence of the flash 18b, and the face sheet 18a forms the pressure receiving area A. Due to the accumulated pressure in the intermediate pressure chamber 17, a thrust to the left that exceeds the preset load of the return spring 20 is generated, and the spool 12 slightly floats above the face sheet 18a, making it difficult to prevent normal leakage at this seat portion. . Therefore, there is a demerit that the intended leak reduction function cannot be obtained stably.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a spool valve capable of stably maintaining a low leak characteristic over a long period of time.

[0006]

[Means for Solving the Problems]

 According to a first aspect of the present invention, there is provided a body in which a load pressure chamber communicating with the load pressure side of the actuator and a discharge pressure chamber communicating with the tank are formed, and a movement amount on the load pressure side of the actuator fitted to the body. In the spool valve provided with a spool communicating with the tank through a notch opened according to the above, and a return spring which is provided for the spool and presses the spool in a direction against the pilot pressure, a load pressure chamber of the body is provided. A low leak leak that has a plurality of lands on the spool that fit axially slidably into the inner diameter of the body with the discharge pressure chamber, and each of these lands has a notch that sets an axial overlap. It is a pool valve.

The invention according to claim 2 is, as the return spring according to claim 1, a strong spring provided on the spool end through an axial clearance substantially equal to the overlap, and a weak spring constantly acting on the spool end. The springs are arranged concentrically.

[0008]

[Action]

 According to the first aspect of the present invention, since the spool is provided with a plurality of lands that are slidably fitted into the inner diameter portion of the body, the spool does not have the conventional collar portion, and the problem of sag of the wire sheet occurs. It cannot happen. Further, the leak can be suppressed low by the plurality of overlaps provided between the load pressure chamber and the discharge pressure chamber.

According to the second aspect of the present invention, a wide metering range can be secured even with a large overlap due to the non-linear characteristic of the combination of the strong spring having the clearance and the weak spring.

[0010]

【Example】

 Hereinafter, the present invention will be described in detail with reference to the embodiment shown in FIGS. 1 to 3 and the characteristic diagram shown in FIG. The same parts as those of the conventional example shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows a structural diagram in a normal position in which the spool 12 is locked by the stopper 21 of the body 11 because the pilot pressure introduced to the right end of the spool is 0 or very low.

In FIG. 1, a land 16a having a notch 15a is provided between the load pressure chamber corresponding groove 13a and the intermediate pressure chamber corresponding groove 17a of the spool 12. The land 16a is slidably fitted into the inner diameter portion 11a of the body 11, and opens and closes between the load pressure chamber 13 and the intermediate pressure chamber 17 which are in communication with the actuator (cylinder) 10.

Further, a land 16b having a notch 15b formed on the intermediate pressure chamber side is provided between the intermediate pressure chamber corresponding groove 17a of the spool 12 and the spring mounting portion 22 located on the left end side. The land 16b is slidably fitted into the inner diameter portion 11b of the body 11, and opens and closes between the intermediate pressure chamber 17 and the discharge pressure chamber 23 communicating with the tank.

Both the notch 15a and the notch 15b have a shape having a modulation function (V notch, drill hole, etc.), and the overlap Lsa set by the notch 15a is the overlap Lsb set by the notch 15b. Set the same as or slightly larger.

As described above, the spool 12 does not have the conventional collar portion 19 and is provided with the slightly longer overlap Lsb instead of the conventional wire sheet 18.

As the return spring of the spool 12, a large-diameter coil spring 20a and a small-diameter coil spring 20b are doubly provided in the spring mounting portion 22.

The large-diameter coil spring 20a presses the spool 12 via the spacer 24, and brings the spool 12 into contact with the right stopper 21 when pilot pressure is not supplied to the pilot pressure inlet 14. It has a weak spring constant and a preset load.

The small-diameter coil spring 20b is a spring having a strong spring constant for metering, and an axial clearance C is provided between the coil spring 20b and the spacer 24. The clearance C is set to be equal to or slightly smaller than the slightly longer overlap Lsa.

The large-diameter coil spring has a strong spring constant for metering and has an axial clearance with the spacer 24, and the small-diameter coil spring has a weak spring constant and a preset load and is constantly operated. It may be configured to contact the spacer 24.

In the above-described configuration, during the transition start period of the modulation, the spool 12 moves leftward against the spool 20a by the pilot pressure acting on the right end surface of the spool 12 from the pilot pressure inlet 14. , Axial clearance C is reduced. Then, as shown in FIG. 2, when the clearance C becomes 0, the notch 15b between the intermediate pressure chamber 17 and the discharge pressure chamber 23 is slightly opened, but the load pressure chamber 13 and the intermediate pressure chamber 17 are opened. The notch 15a between and is in a closed state just before opening.

FIG. 3 shows the spool 12 in a full shift state. After the axial clearance C becomes 0, the spool pressure is applied from the pilot pressure introducing port 14 to the right end surface of the spool 12 to cause the spool 12 to move. Moves to the left while compressing the springs 20a and 20b, and enters this full shift state. At this time, the load pressure oil of the actuator (cylinder) 10 passes through the load pressure chamber 13, the load pressure chamber corresponding groove 13a, the notch 15a, the intermediate pressure chamber 17, the intermediate pressure chamber corresponding groove 17a, and the discharge pressure chamber 23 to the tank. Is discharged.

Since the strong spring 20b for metering has an axial clearance C substantially equal to the overlap Lsa, the pilot pressure-spool stroke characteristic due to the combination with the weak spring 20a is as shown in FIG. 4 (A). Become. 4A shows the case where the clearance C is equal to the overlap Lsa, while FIG. 4B shows the case where the clearance C is equal to the overlap Lsb.

As is apparent from FIGS. 4 (A) and 4 (B), in the case of the two return springs of the present invention, the axial clearance C becomes zero after the return clearance of the present invention is two, as compared with the case of the conventional one return spring. Since the slope of the pilot pressure-spool stroke characteristic straight line of can be made gentle, a constant spool stroke can be controlled with a wider pilot pressure than before after both notches 15a and 15b open.

That is, even if the overlaps Lsa and Lsb are set to be larger than in the case of the conventional single return spring, it has a wide metering (modulation) range and the operability is not impaired.

The lands 16a and 16b for providing the overlaps Lsa and Lsb are not limited to the two positions shown in the figure, and a plurality of intermediate pressure chambers may be provided and three lands may be provided if necessary. The number of overlap lands may be increased, and the total number of overlap lands is increased, so that the leak can be further reduced.

If the clearance C does not exceed the overlap Lsa, it is not necessary to match it with Lsb, and the clearance C may be set to be substantially equal to or slightly smaller.

[0027]

[Effect of device]

 According to the first aspect of the present invention, since the spool does not have the flange portion as in the conventional case and the problem of the settling of the wire sheet does not occur, it is possible to prevent the leakage amount from changing over time, and to improve stability. A leak spool valve can be provided. Further, since a plurality of overwraps are provided in the spool moving direction, the leak can be remarkably reduced as compared with an ordinary spool valve that uses only a single land to reduce the leak.

According to the invention as set forth in claim 2, since the strong spring for metering has a clearance almost equal to that of the overlap, the conventional non-linear characteristic due to the combination of the strong spring and the weak spring is used. Compared to a single return spring, a large metering range can be secured even if the overlap is large.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a low leak spool valve of the present invention.

FIG. 2 is a sectional view showing a modulation start transition period of the spool valve of the same.

FIG. 3 is a cross-sectional view showing a full shift state of the same spool valve.

FIG. 4 is a graph showing pilot pressure-spool stroke characteristics of the same spool valve, FIG. 4A shows the case where the axial clearance C is equal to the overlap Lsa,
(B) is the case where the axial clearance C is equal to the overlap Lsb.

FIG. 5A is a sectional view showing a conventional spool valve,
(B) is an enlarged cross-sectional view of the line sheet portion, and (C) is a cross-sectional view showing a sagging state of the line sheet.

[Explanation of symbols]

 10 Actuator 11 Body 11a, 11b Inner diameter 12 Spool 13 Load pressure chamber 15a, 15b Notch 16a, 16b Land 20a, 20b Return spring 23 Discharge pressure chamber Lsa, Lsb Overlap C Axial clearance

Claims (2)

[Scope of utility model registration request] 1. A body in which a load pressure chamber communicating with the load pressure side of the actuator and a discharge pressure chamber communicating with the tank are formed, and the load pressure side of the actuator fitted into this body is opened according to the amount of movement. A spool valve having a spool communicating with a tank through a notch and a return spring provided for the spool to press the spool in a direction against a pilot pressure, the spool valve between the load pressure chamber and the discharge pressure chamber of the body. A low-leakage spool characterized in that the spool is provided with a plurality of lands that are slidably fitted in the inner diameter portion of the body in the axial direction, and the plurality of lands are each provided with a notch that sets an axial overlap. valve. 2. As the return spring, a strong spring provided at the spool end with an axial clearance substantially equal to the overlap and a weak spring constantly acting on the spool end are concentrically arranged. The low leak spool valve according to claim 1.