JPH04287102A - Pilot valve - Google Patents

Abstract

PURPOSE:To prevent the mismatched output of the pilot valve caused by rapidly operating a pedal or the like and to present the pilot valve which can be produced in a compact size at low cost. CONSTITUTION:High-pressure fluid supplied to a high pressure port 32 and low-pressure fluid supplied to a low pressure port 30 is controlled by a spool 14 which is freely movably fitted into a cylinder 12 and oscillated according to balance between energizing force generated by an energizing member 19 and pressure on the side of an output port 34, the fluid having desired pressure is outputted from the output port 34. At such a pilot valve, a pressing member 24 to be pressed from the outside to the inside of the cylinder 12, a return spring 18 to be energized oppositely to the pressing direction of the pressing member 24, a piston 22 to be slid between the pressing member 24 in the cylinder 12 and the return spring 18, and a communicating hole 23 having a small diameter provided at the piston 22 so as to communicate fluid chambers before and behind the piston are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pilot valve that adjusts high-pressure fluid supplied to a high-pressure port and low-pressure fluid supplied to a low-pressure port, and outputs fluid at a desired pressure from an output port.

0002

2. Description of the Related Art Conventionally, pilot valves have been used to control control valves, which are switching valves of hydraulic motors of hydraulic excavators. The structure and operation of such a conventional pilot valve will be explained with reference to FIG. The cam 40 is moved to the shaft 4 by an operating member such as a pedal.
1, the rod 24, which comes into contact with the cam 40 and slides into the insertion hole at the end of the cylinder 12, moves inward into the cylinder 12. At this time, the rod 24 acts as a pressing member that applies a pressing force from the outside to the inside of the side end of the cylinder 12, and presses the return spring 18 via the spring guide 20, which is a guide member. 14 is a spool, which is movably inserted into the cylinder 12;
Communication portion 13 that communicates from the cylinder 12 to the output port 34
It is slidably connected to the Further, the spring guide 20 biases the spool 14 toward the output port via a spring 19, which is a biasing member, and guides the spool 14 so as to be movable within a predetermined movement range. Therefore, when the spring 19 moves along with the spring guide 20 due to the pressing force of the rod 24, the spool 14 moves toward the output port 34 side. At this time, the recess 3 provided on the outer peripheral surface of the spool 14 from the high pressure port 32
5 and the inner wall surface of the communication portion 13, pressure oil flows to the output port 34 side, and the pressure on the output port 34 side increases. Next, when the pressure on the output port 34 side increases to a predetermined level or more, the spool 14 is pushed back against the urging force of the spring 19 in the opposite direction to the pressing direction of the rod 24, and the cylinder connected to the low pressure oil source is pushed back. 12 and the output port 34 are provided in the spool 14 through a communication hole 15.
communicated by. Then, when the pressure on the output port 34 side decreases, the spool 14 is again urged toward the output port 34 side by the spring 19, and high pressure oil flows from the high pressure port 32 toward the output port 34 side. Through the above series of operations, pressure oil at a predetermined pressure can be output from the output port 34.

[0003] A conventional pilot valve having a pressure reducing valve configured as described above is operated by a pedal or a lever, but the user may accidentally release the pedal or lever suddenly. If such a sudden pedal operation is performed, the pedal or the like may vibrate due to the damping movement of the return spring 18, or the control by the pilot valve may be abruptly performed due to the sudden pedal operation. There was a problem that hydraulic excavators etc. could not run smoothly. For this reason, conventionally, as shown in FIG. 4, a shock absorber 64 is disposed between the base 10 of the pilot valve and the main body of the hydraulic excavator to dampen the movements of the pedal 62 and lever 63. be. As a result, even if the pedal 62 or the lever 63 is suddenly operated, vibration of the pedal 62, etc. can be prevented, so irregular output of the pilot valve can be prevented, and the running of the hydraulic excavator etc. can be made smooth. Can be done.

0004

As described above, by using the shock absorber disposed outside the pilot valve, the operation of the pedal and lever can be damped. However, when the shock absorber is attached to the outside of the pilot valve, there are problems in that the device becomes larger and the cost for attaching it increases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pilot valve that can prevent irregular output of the pilot valve caused by sudden operation of a pedal or lever, and that can be manufactured in a small size and at low cost.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present inventor has provided a pressure reduction valve of a pilot valve with a structure that buffers movements such as vibrations of a return spring caused by sudden operation of a pedal or the like. The present invention was arrived at as a result of thinking that providing a mechanism would be effective.

That is, the present invention provides a pilot valve that adjusts the high pressure fluid supplied to the high pressure port and the low pressure fluid supplied to the low pressure port and outputs fluid at a desired pressure from the output port. A cylinder that is open and has an output port and a pressing member insertion hole opened in the wall surfaces facing each other, and a cylinder that is slidable in the pressing member insertion hole of the cylinder and can be moved inward by being pressed by an external operating member. a pressing member, a spool that is movably inserted into the cylinder, has one end facing the output port side, and partitions the inside of the cylinder into a high pressure side where the output port is located and a low pressure side where the low pressure port is connected; A piston that movably slides into the cylinder on the low pressure side by being pressed by the pressing member and defines fluid chambers at the front and rear; a communicating hole, a guide member interposed between the other end of the spool and the piston and movably guiding the spool within a predetermined movement range; a biasing member that biases the guide member in a protruding direction, and a piston and a spool that are elastically mounted between the inner wall surface of the cylinder and the guide member and bias the guide member in a direction opposite to the pressing direction of the pressing member. The return spring is normally closed, and communicates between the high pressure port and the high pressure side of the cylinder when the pressing member is pushed in by the operating member and the spool is moved via the piston, the guide member, and the biasing member. and a passage that communicates the high pressure side and the low pressure side of the cylinder and releases fluid when the spool is pushed a predetermined distance against the biasing force of the biasing member due to pressure fluctuations on the high pressure side of the cylinder. The pilot valve is characterized by:

[0008] In the pilot valve having such a configuration,
In order to improve the response and operability of the pilot valve, at least two communication holes are bored in the piston to communicate the fluid chambers before and after the piston, and in one of the communication holes, pressure is applied from the fluid chamber on the guide member side. A check valve may be provided that allows fluid to flow into the fluid chamber on the member side and prevents fluid from flowing from the fluid chamber on the pressing member side to the fluid chamber on the guide member side.

[0009]

According to the present invention, a piston is disposed within the cylinder of the pilot valve, and the piston is provided with a small diameter communication hole. In order for this piston to slide within the cylinder, the fluid filled in the cylinder must flow between the fluid chambers before and after the piston, but the flow rate is limited to the flow rate that passes through the small diameter communication hole. The fluid filled in the cylinder acts as a resistor,
Piston operates slowly. Therefore, even if the pressing force on the piston is suddenly released and the piston return spring is suddenly urged in the opposite direction to the pressing force, the piston will operate slowly due to the resistance of the fluid in the cylinder. . That is, the damping movement and sudden movement of the return spring can be suppressed by the action of the piston and the small diameter communication hole provided in the piston. As a result, even if the pedal or the like is suddenly operated, the spool that is linked to the piston operates slowly, and the pressure of the output fluid changes slowly, making it possible to prevent irregular output from the pilot valve. Further, the piston includes a non-return check that allows fluid to flow from the fluid chamber on the guide member side to the fluid chamber on the pressing member side, and prevents fluid from flowing from the fluid chamber on the pressing member side to the fluid chamber on the guide member side. When a communication hole having a valve is provided, the pilot valve can be operated quickly using a pedal or the like, thereby preventing vibrations of the pedal or the like and improving the responsiveness of the operation.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a partial cross-sectional view showing one embodiment of the present invention, and shows the internal structure of one pressure reducing valve of a pilot valve having two pressure reducing valves. In addition,
The two pressure reducing valves have the same structure and are arranged symmetrically on the base 10 of the pilot valve, and the control valve (switching valve) of the hydraulic motor is controlled by the pressure balance of the pressure oil output from these two pressure reducing valves. ) etc. This pressure reducing valve is operated by the action of a spool 14 which swings in a cylinder 12 provided in a base 10 of the pilot valve due to the balance between the biasing force of a spring 19 which is a biasing member and the pressure on the output port 34 side. Pressure oil having been arbitrarily adjusted can be output from the output port 34, and its configuration will be described next. Reference numeral 12 denotes a cylinder, in which a low pressure port 30 and a high pressure port 32 are opened, and an output port 34 and a pressing member insertion hole are opened at mutually opposing side ends. 40 is a cam;
A pedal and a lever, which are operating members, are connected to the upper surface thereof, and are rotated about a shaft 41 by being operated by the operating members. A rod 24 is a pressing member that slides into a pressing member insertion hole provided at one side end of the cylinder 12 and is movable inwardly of the cylinder 12 when pressed by the cam 40 . Note that the cam 40 is designed so that the rotational motion of the cam 40 is smoothly converted into the reciprocating motion of the rod 24.
A sphere is provided at the tip of the rod 24 that comes into contact with the rod 24 . Further, the oil filled in the cylinder 12 is kept liquid-tight by an O-ring 26 disposed between the rod 24 and a fitting hole for the rod 24 formed in the cylinder 12. A spool 14 is movably inserted into the cylinder 12, with one end facing the output port 34 side, and a spool that connects the inside of the cylinder 12 to a high pressure side where the output port 34 is located and a low pressure side where the low pressure port 30 is connected. It's in charge. 2
A piston 2 is movably slid into the cylinder 12 on the low pressure side by being pressed by a rod 24, and defines a fluid chamber at the front and rear. This piston 22 is provided with a small diameter communication hole that communicates the fluid chambers before and after the piston 22. A spring guide 20 acts as a guide member, and is interposed between the other end of the spool 14 and the piston 22, and guides the spool 14 movably within a predetermined movement range. That is, the end of the spool 14 is fitted into the spring guide 20, and the spool 14 is connected to the end surface of the piston 22 and the spring guide 2.
It is possible to swing within a predetermined range regulated by the inner edge of 0. Note that this spring guide 20 is
Since it moves together with the piston 22, it may be molded integrally with the piston 22. A spring 19 acts as a biasing member, and is elastically loaded between the spool 14 and the spring guide 20 with one end in contact with the middle part of the spool via a ring and the other end in contact with the spring guide 20. The spool 14 is urged in the projecting direction relative to the guide member. Reference numeral 18 denotes a return spring for the piston 22 and the spool 14, which is elastically mounted between the inner wall surface of the cylinder 12 and the spring guide 20, and urges the spring guide 20 in a direction opposite to the pressing direction of the pressing member. Reference numeral 13 denotes a communication portion that communicates from the high pressure port 32 to the output port 34, which is normally closed by the spool 14 and is connected to the rod 24 by the operating member.
are pushed in, and the piston 22, spring guide 20,
When the spool 14 is moved via the spring 19, a passage is formed between the recess 35 provided on the outer circumferential surface of the end of the spool 14 and the inner wall of the communication portion 13, and the passage is formed between the high pressure port 32 and the output port 34. communicate. In addition, high pressure port 3
2 is a connection port for connecting to a high pressure oil source. Reference numeral 15 denotes a passage provided inside the spool 14 for releasing fluid, and due to pressure fluctuations on the high pressure side of the cylinder 12, the spool 1
4 is pushed a predetermined distance against the biasing force of the spring guide 20, the output port 34 and the low pressure side of the cylinder 12 are communicated with each other. Note that the low pressure side of the cylinder 12 communicates with a low pressure port 30, and the low pressure port 30 is a connection port for connecting to a low pressure oil source such as an oil tank. Also, 42
is a cover made of synthetic rubber or the like that covers and protects the contact portion between the cam 40 and the rod 24.

Next, the operating state of the pilot valve according to the present invention will be explained with reference to FIG. By operating a pedal or the like connected to the cam 40, the cam 40 is rotated about the shaft 41, and the rod 24 is pressed. This rod 24 presses a piston 22 that is slidably engaged with the cylinder 12. As a result, the piston 22 moves together with the spring guide 20 toward the output port 34 against the repulsive force of the return spring 18. Spring guide 2
0 presses the middle part of the spool 14 via the spring 19, and as the spring guide 20 moves, the spool 14 also moves toward the output port 34 side. As a result, the high pressure port 32 and the output port 34 communicate with each other through the recess 35 provided on the outer peripheral surface of the spool 14.
High pressure oil flows into the output port 34 side. Next, when the pressure on the output port 34 side increases beyond a predetermined level, the spool 14 is pushed back toward the inside of the cylinder 12 by the pressure. When the spool 14 is pushed back, the end of the spool 14 closes the communication passage between the high pressure port 32 and the output port 34, the output port 34 and the low pressure side of the cylinder 12 are communicated through the passage 15, and the Pressure decreases. When the pressure on the output port 34 side decreases,
Again, due to the biasing force of the spring 19, the spool 14
moves to the output port 34 side. By operating the spool 14 as described above, pressure oil adjusted to an arbitrary pressure can be output from the output port 34.

Next, when the operator releases the pressing force on the pedal etc., the spring guide 20, piston 22, rod 24 and cam 40 are pushed back by the repulsive force of the return spring 18, and the pedal returns to its initial position. . At this time, as the spring guide 20 moves, the spool 14 also moves in the opposite direction to the pressing direction of the rod, and the communication portion 13 that communicates the high pressure port 32 and the output port 34 is closed. Also,
Since the output port 34 and the low pressure side of the cylinder 12 communicate with each other through the passage 15, the pressure on the output port 34 side decreases and the output of pressure oil stops. When the pressing force on the pedal etc. is suddenly released, the piston 22 returns to the spring 18.
tries to be pushed back rapidly by the repulsive force of However, the cylinder 12 is filled with oil, and this oil must pass through the small diameter communication hole 23 provided in the piston 22 and flow from the rod 24 side in the cylinder 12 to the spring guide 20 side. Piston 22 cannot be moved. At this time, since the amount of flowing oil is limited to the amount that passes through the small-diameter communication hole 23, the oil filled in the cylinder 12 acts as a resistance, causing the piston 22 to return to the spring 18.
The repulsive force slows down the sliding motion. As a result, even if a pedal or the like is suddenly operated, the spool that is linked to the piston 22 through the spring guide 20 operates slowly, and the pressure of the output pressure oil changes slowly. Therefore, with this pilot valve pressure reducing valve, even if the pedal or lever connected to the cam 40 is suddenly operated, the return spring 18 will not attenuate or operate suddenly, resulting in irregularities in the pilot valve. It is possible to prevent unnecessary output.

Further, in FIG. 2, another communication hole is formed in the piston 22 to communicate the fluid chambers before and after the piston 22, and the spring guide 2 of the cylinder 12 is inserted into this communication hole.
Open to allow oil to flow from the fluid chamber on the rod 24 side to the fluid chamber on the rod 24 side, and closed to prevent oil from flowing from the fluid chamber on the rod 24 side to the fluid chamber on the spring guide 20 side. Another embodiment is shown in which a check valve 50 is provided. In this case, the operation of depressing the pilot valve pedal or operating the lever can be done quickly, but when the pedal or the like is suddenly released, the piston 22 and the piston 22
Vibration of the pedal or lever can be prevented by the action of the small-diameter communication hole 23 provided in the pilot valve, thereby improving the responsiveness and operability of the pilot valve.

Although the above embodiments have been explained using hydraulic pressure, the same effect can be obtained by using other liquids such as water or gases such as air.

[0015]

According to the present invention, by disposing a piston having a small diameter communication hole in the cylinder of the pressure reducing valve of the pilot valve, even if the pedal or lever for operating the pilot valve is suddenly operated, A damping movement or sudden movement of the return spring can be prevented. Therefore, it is possible to prevent irregular output of the pilot valve caused by sudden operation.Furthermore, since only a piston with a small diameter communication hole is installed in the cylinder, the device can be made smaller and manufacturing costs can be reduced. This has the effect of keeping it low.

[Brief explanation of the drawing]

[Fig. 1] Partial sectional view showing one embodiment of the present invention.

FIG. 2 is a partial sectional view showing another embodiment of the present invention.

[Figure 3] Partial cross-sectional view showing conventional technology

[Figure 4] Front view showing conventional technology

[Explanation of symbols]

10 Pilot valve base 12 Cylinder 13 Communication part 14 Spool 15 Passage 18 Return spring 19 Spring 20 Spring guide 22 Piston 23 Communication hole 24 Rod 30 Low pressure port 32 High pressure port 34 Output port 40 Cam 50 Check valve

Claims (2)

[Claims] Claim 1: A pilot valve that adjusts high-pressure fluid supplied to a high-pressure port and low-pressure fluid supplied to a low-pressure port and outputs fluid at a desired pressure from an output port, the low-pressure port and the high-pressure port being opened, and a cylinder in which an output port and a pressing member insertion hole are opened in mutually opposing wall surfaces; a pressing member that is slidable in the pressing member insertion hole of the cylinder and can be moved inward of the cylinder by being pressed by an external operating member; a spool that is movably inserted into the cylinder, has one end facing the output port side, and partitions the inside of the cylinder into a high pressure side where the output port is located and a low pressure side where the low pressure port is connected; a piston that slides movably into a cylinder by being pressed by the pressing member and defines fluid chambers at the front and rear; a small-diameter communication hole provided in the piston that communicates the fluid chambers at the front and rear of the piston; a guide member interposed between the other end of the spool and the piston and movably guides the spool within a predetermined movement range; and a guide member provided elastically between the spool and the guide member to guide the spool to the guide member. and a return spring for the piston and spool, which is elastically loaded between the cylinder inner wall surface and the guide member and urges the guide member in a direction opposite to the pressing direction of the pressing member. , a passage that is normally closed and communicates the high pressure port with the high pressure side of the cylinder when the pressing member is pushed in by the operating member and the spool is moved via the piston, the guide member, and the biasing member; The cylinder is characterized by having a passage that communicates the high pressure side and the low pressure side of the cylinder and allows fluid to escape when the spool is pushed a predetermined distance against the biasing force of the biasing member due to pressure fluctuations on the high pressure side. pilot valve. 2. At least two communication holes are formed in the piston to communicate fluid chambers before and after the piston, and one of the communication holes allows fluid to flow from the fluid chamber on the guide member side to the fluid chamber on the pressing member side. 2. The pilot valve according to claim 1, further comprising a check valve that allows the flow of fluid and blocks the flow of fluid from the fluid chamber on the pressing member side to the fluid chamber on the guide member side.