JP3108652B2 - Pilot 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 pilot valve used for controlling the operation of hydraulic equipment such as a directional control valve, a regulator of a variable displacement pump, and a hydraulically operated clutch.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a conventional pilot valve 14. Such a pilot valve 14 is disclosed, for example, in Japanese Utility Model Laid-Open Publication No. 3-39602. The pilot valve 14 has a valve body 1 and a pair of spools 2a and 2b provided on the valve body 1 so as to be displaceable. Since the configuration corresponding to the spool 2b is the same as the configuration corresponding to the spool 2a, the same reference numerals are given and the suffix "a"
And a suffix "b" is appended to the description, and the description is omitted.

The valve body 1 has a spring chamber 15a and a spool hole 3a communicating with the spring chamber 15a. A spool 2a is mounted in the spool hole 3a so as to be movable up and down. The push rod 16a protrudes from the valve body 1 and is provided to be vertically movable. The push rod 16a is elastically pressed upward by the first spring member 5a provided in the spring chamber 15a via the spring receiving member 4a. In the spool 2a, a first spool portion 7a is formed at a lower end portion, and a second spool portion 8a is formed above the first spool portion 7a through a notch groove 9a.
A second spring member 6a is interposed between the spring receiving member 4a and the second spool portion 8a.

An operation lever 13 is provided at an upper portion of the valve main body 1 so as to be tiltable left and right with respect to the plane of FIG. As shown in FIG. 4, when the operation lever 13 is in the neutral position, the first spool portion 7 of each of the spools 2a and 2b
The secondary pressure side flow paths 11a and 11b corresponding to the spools 2a and 2b and the primary pressure side flow path 10 are cut off by the a and 7b, and the cutout grooves 9a and 9a of the spools 2a and 2b are formed.
The secondary pressure side flow passages 11a and 11b communicate with the tank flow passage 12 via 9b, and the control valve 20 is held at the neutral position.

When the operating lever 13 is tilted rightward in FIG.
a, the spool 2a is displaced downward via the spring receiving member 4a and the second spring member 6a, and the primary pressure side flow path 10 and the secondary pressure side flow path 11a communicate with each other to control the control valve 21.
Is moved to the left in FIG. Conversely, when the operation lever 13 is tilted to the left, the control valve 21 is moved to the right by the communication between the secondary pressure side flow path 11b and the primary pressure side flow path.

The pilot valve 14 has spools 2a, 2a
In order to prevent a hunting phenomenon in which b repeatedly slides up and down, pressure receiving pistons 17a and 17b for providing a damping effect to the spools 2a and 2b are provided at the lower ends of the spools 2a and 2b.

The pressure receiving piston 17a is formed in a substantially cylindrical shape with a step, and a stepped concave hole 18a into which the stepped pressure receiving piston 17a is fitted is formed at the lower end of the spool 2a. The lower end of the pressure receiving piston 17a is fixed to the valve body 1 with the lower end facing the tank flow path 12, and the upper part is slidably fitted into the recess 18a of the spool 2a. A damping pressure chamber 19a is formed in the concave hole 18a above the large diameter portion of the pressure receiving piston 17a, and an L-shaped throttle channel 22a is formed from the upper end of the large diameter portion of the pressure receiving piston 17a to the lower end of the pressure receiving piston 17a. And
The damping pressure chamber 19a and the tank channel 12 communicate with each other via the throttle channel 22a. The upper part of the concave hole 18a communicates with the secondary pressure side channel 11a via the communication channel 20a. The structure of the pressure receiving piston 17b of the spool 2b is also the same as the structure of the pressure receiving piston 17a, so that the same reference numerals are given, and the suffix "b" is added instead of the suffix "a", and the description is omitted.

Since the pilot valve 14 is provided with such pressure receiving pistons 17a and 17b, even if a hunting phenomenon occurs, hydraulic oil in the damping pressure chambers 19a and 19b gradually flows through the throttle passages 22a and 22b. Is supplied to the tank flow path 12, or the oil in the tank flow path 12 is supplied to the damping pressure chambers 19a, 1 via the throttle paths 22a, 22b.
The hunting phenomenon of the spools 2a and 2b can be suppressed because the damping effect is obtained by being fed to the spool 9b.

[0009]

In such a conventional pilot valve 14, since the damping pressure chambers 19a and 19b are provided above the tank flow path 12, the hydraulic oil mixed with air due to cavitation or the like is subjected to the damping pressure. When the air is supplied into the chambers 19a and 19b, the air mixed with the hydraulic oil is accumulated above the damping pressure chamber 19a, and is less likely to be discharged to the tank channel 12 through the throttle channels 19a and 19b. When the air accumulates in the damping pressure chambers 19a and 19b in this manner, there is a problem that the damping effect is reduced and the hunting phenomenon is likely to occur.

An object of the present invention is to provide a pilot valve capable of reliably discharging air from a damping pressure chamber and reliably obtaining a damping effect.

[0011]

SUMMARY OF THE INVENTION The present invention provides a valve body having a spring chamber and a spool hole communicating therewith, a push rod movably mounted on the valve body, and a movably mounted in the spool hole. The push rod is interposed between the valve body and the spring receiving member, and is disposed between the valve body and the spring receiving member in the spring chamber. A first spring member that resiliently presses the spring toward a protruding position protruding from the valve body; and a spring interposed between the spring receiving member and the spool, and resiliently pushes the spool away from the push rod. A second spring member which presses the push rod in a direction in which the push rod is buried in the valve body from the protruding position, and wherein the spool has a small pressure receiving area of the pressure receiving portion. It has a pool portion, a second spool portion having a large pressure receiving area of the pressure receiving portion, and a notch groove provided between the first and second spool portions, and when the push rod is at the projecting position, the first spool portion is A cut-off groove communicates between the primary pressure side flow path and the secondary pressure side flow path, and a second chamber connected to the secondary pressure side flow path and the drain flow path. When pressed in the direction of being buried in the main body, the spool is moved by the second spring member in the direction of being buried, and the notch groove communicates with the primary pressure side flow path and the secondary pressure side flow path. A tank flow path communicating with the drain flow path is provided below the second chamber, and a damping pressure chamber is provided below the tank flow path, facing the lower end surface of the spool, and the damping pressure chamber has a single surface. Have A first hole formed in the lower end surface of the pool and a hole provided in the valve body and having an inner diameter substantially equal to the outer diameter of the lower end portion of the spool, the first hole extending upward in the axial direction from the lower end surface of the spool. And a throttle channel extending radially from the vicinity of the tip of the first hole to the outer peripheral surface, having a smaller inner diameter than the first hole, and having a second hole communicating with the tank channel. A pilot valve, wherein the damping chamber communicates with a tank channel via a throttle channel.

According to the present invention, the spool has first and second spool portions, and the pressure receiving area of the second spool portion is the first spool portion.
It is larger than the pressure receiving area of the spool part. When the push rod is pressed by the operating lever from the projecting position in the direction of being buried in the valve body, the primary pressure side flow path and the secondary pressure side flow path communicate with each other. At this time, even if a hunting phenomenon occurs in the spool, the fluid in the damping pressure chamber facing the lower end surface of the spool is gradually fed to the tank flow path through the throttle flow path having the throttle portion, or Since the fluid is gradually fed into the damping pressure chamber, a damping effect is obtained on the spool, and the hunting phenomenon is suppressed.
At this time, since the damping pressure chamber is provided below the tank flow path, even if air is mixed in the fluid,
Since the air is easily discharged from the damping pressure chamber via the throttle flow path connected to the upper tank flow path, the air is prevented from being accumulated in the damping pressure chamber, and the damping effect is reduced by mixing of the air. The problem that the hunting phenomenon occurs is prevented. Further, since the throttle channel is formed at the lower end of the spool, processing is easy, and further, since the tank channel is provided at a position close to the damping pressure chamber, the configuration becomes easy, and the throttle channel is formed. It will be easier.

[0013]

[0014]

[0015]

FIG. 1 shows a pilot valve 3 according to the present invention.
FIG. 2 is a cross-sectional view illustrating an embodiment of the present invention. In FIG.
The pilot valve 30 has a valve body 31. Valve body 3
1, a pair of spring chambers 32, 33 are provided at an interval in the left-right direction of FIG.
33, spool holes 34 and 35 are provided. Although the lower ends of the spool holes 34 and 35 are closed,
Their upper ends communicate with the spring chambers 32 and 33, and their inner diameters are set smaller than the inner diameters of the spring chambers 32 and 33. The spool holes 34 and 35 have spools 36a and 36
b is mounted movably in the vertical direction in FIG. The spools 36a and 36b have substantially the same configuration, and the configuration corresponding to the spool 36a will be described. The configuration corresponding to the spool 36b is denoted by the same reference numeral, and the suffix "b" is used instead of the suffix "a". And the description is omitted.

A first spool portion 37a is provided at a lower end of the spool 36a, and a second spool portion 38a is provided at an intermediate portion thereof. A first spool portion 37a is provided between the first spool portion 37a and the second spool portion 38a. An annular notch 39a is formed. As will be described later, the annular surface of the first spool portion 37a formed by the cutout groove 39a (the upper surface in FIG. 1).
40a and the annular surface (the lower surface in FIG. 1) 41a of the second spool portion 38a function as a pressure receiving portion on which a pressure fluid acts. In the present embodiment, the outer diameter of the second spool portion 38a is a stepped spool set to be larger than the outer diameter of the first spool portion 37a. Therefore, the second spool portion 38a
The pressure receiving area of the pressure receiving portion is larger than the pressure receiving area of the pressure receiving portion of the first spool portion 37a. The spool hole 34 has a first inner diameter corresponding to the outer diameter of the first spool portion 37a.
A hole 42a and a second hole 43a having an inner diameter corresponding to the outer diameter of the second spool 38a are provided, and the inner diameter of the second hole 43a is set to be larger than the inner diameter of the first hole 42a. The first spool portion 37a of the spool 36a is slidably inserted into the first hole portion 42a of the spool hole 34, whereby the spool 36a is guided in the first hole portion 42a and moved vertically. The second spool portion 38a is slidably inserted into the second hole portion 43a of the spool hole 34 by the vertical movement of the spool 36a.
It is guided to the hole 43a.

A first chamber 46 as a pressure port is provided below the valve body 31. The first chamber extends in the lateral direction in FIG. 1 and the first holes 42 of the spool holes 34 and 35 are provided.
a. The first chamber 46 is provided in the valve main body 31 and connected to a hydraulic supply source 48 such as a hydraulic pump via a primary pressure side flow path 47. Pressure oil as a working fluid from the hydraulic supply source 48 is The first through the primary pressure side channel 47
Is supplied to the chamber 46. At the lower end of the valve body 31, secondary pressure side flow paths 49, 50 that are controlled to be switched by spools 36a, 36b are provided. One secondary pressure side flow path 49 is provided in association with the spool hole 34, and is connected between the first hole 42 a and the second hole 43 a of the spool hole 34. The secondary pressure side flow path 49 is connected to a spool control pilot port 52 of the control valve 51 via a flow path 53a. Also, the other secondary pressure side flow path 5
0 is provided in connection with the spool hole 35 and is connected between the first hole portion 42b and the second hole portion 43b of the spool hole 35. This secondary pressure side flow path 50 is connected to a spool control reverse pilot port 81 of the control valve 51 via a flow path 53b.

At the top of the valve body 31, a second chamber 54 is provided as a tank port. The second chamber 54 extends in the left-right direction in FIG. 1 and communicates with the spring chambers 32 and 33. The second chamber 54 communicates with an oil tank 56 via a drain flow path 55 formed at a lower portion of the valve body 31, and the oil in the second chamber 54 passes through the drain flow path 55 to the oil tank 56. Will be returned. A tank flow path 76 communicating with the drain flow path 55 is provided below the second chamber 54. The tank flow path 76 extends in the left-right direction in FIG. 42a, 42b
Communicate with

At the upper ends of the spring chambers 32 and 33, cylindrical plug members 57a and 57b are provided. Each plug member 57a, 57b is provided with a stepped portion 58a, 58b. The upper cover 80 is brought into contact with the stepped portion 58a, 58b, and is fixed to the valve body 31 with a fixing screw (not shown). And the plug members 57a and 57b are
2, 33. Plug members 57a, 57b
Are formed with rod holes 59a and 59b, and push rods 60a and 60b are mounted in these rod holes 59a and 59b so as to be vertically movable in FIG.

The upper ends of the push rods 60a, 60b protrude upward from the plug members 57a, 57b, and each protruding end is formed in a hemispherical shape. Also, push rod 6
The lower ends of Oa and 60b protrude from the plug members 57a and 57b into the spring chambers 32 and 33, and the protruding ends are provided with flanges 61a and 61b that protrude outward in the radial direction, and the outer diameters of the flanges 61a and 61b. Are rod holes 59a and 59b
Is set to be larger than the inner diameter of. Therefore, the push rods 60a and 60b are not moved upward beyond the protruding position shown in FIG. 1 by the flanges 61a and 61b abutting on the bottom surfaces of the plug members 57a and 57b.

Each of the spring chambers 32 and 33 has a spring receiving member 6.
2a and 62b are accommodated in FIG. 1 so as to be vertically movable. The spring receiving members 62a and 62b are cylindrical, and first receiving portions 63a and 63b are formed by first concave portions provided at lower ends thereof, and the first receiving portions 63a and 63b are formed.
b and a part of the valve body 31 (in the embodiment, the spring chambers 32, 33).
Between the first spring member 64 and the wall defining the lower end surface of the first spring member 64
a, 64b are interposed. The first spring member 64a,
64b is composed of a coil spring,
a and 62b are pushed upward in FIG.
a, 60b resiliently presses toward a projecting position where the push rods 60a, 60b project from the valve body.
b is elastically held at the projecting position.

The spring receiving members 62a and 62b are provided with a second concave portion inside the first concave portion, and the second concave portions form second receiving portions 65a and 65b.
a, 36b, between the second spool portions 38a, 38b and the second receiving portions 65a, 65b.
b is interposed. Second spring members 66a, 66b
Are constituted by coil springs, and the first spring members 64a,
64b. Spools 36a, 36b are provided at the lower ends of the push rods 60a, 60b.
Accommodating recesses 67a and 67b are formed corresponding to.
The accommodation recesses 67a, 67b are provided with the push rods 60a, 6b.
0b extends upward from the lower end surface in the axial direction. As shown in FIG. 1, the upper ends of the spools 36a, 36b are passed upward through holes formed in the spring receiving members 62a, 62b, and the accommodation recesses 67a, 6b of the push rods 60a, 60b are raised.
7b, which are provided with somewhat larger diameter heads 68a, 68b at their protruding ends.
8a and 68b are accommodated in the accommodation recesses 67a and 67b so as to be vertically movable.

With this construction, the second spring members 66a and 66b act on the spools 36a and 36b to move downward in FIG.
The spools 31a, 31b are resiliently pressed in the direction away from the spring receiving members 62a, 62b so that the heads 68a, 68b abut against the upper surfaces of the spring receiving members 62a, 62b. Will be retained. Spool 3
When the first and second spools 6a and 36b are in the non-operating position, the first spool 37a is in the first hole 42 of the spool holes 34 and 35.
a, 42b and the first chamber 46 and the secondary pressure side flow path 4
The communication with the first and second chambers 9 and 50 is interrupted, and the pressure oil in the first chamber 46 does not flow into the second-pressure side channels 49 and 50. At this time, the second spool portions 38a, 38b of the spools 36a, 36b are located in the spring chambers 32, 33, and the second chamber 54 and the secondary pressure side flow path 49, via the cutout grooves 39a, 39b of the spools 36a, 36b. And 50. In this embodiment,
Although the spring receiving members 62a and 62b are movably mounted on the spring chambers 32 and 33, they may be movably mounted on the lower ends of the spools 36a and 36b.

A screw hole is provided in an upper middle portion of the valve body 31, that is, a portion between the spring chambers 32 and 33, and a screw portion 70 of a mounting member 69 is screwed into the screw hole. A pin 71 is attached to an upper end of the mounting member 69, and a lower end of the operation lever 72 is connected to the lower end of the operation lever 72 via the pin 71 so as to be tiltable in the left-right direction in FIG. Operation lever 7
A pressing member 73 is screwed to the lower end of the second member 2, and the pressing member 73 has operating portions 74 and 75 corresponding to the push rods 60a and 60b. In a state where the operation lever 72 is not operated, as shown in FIG. 1, the push rods 60a and 60b are in the protruding positions, and the upper ends of the push rods 60a and 60b are actuated portions 74 and 7 of the pressing member 73.
5 or comes into contact with a relatively weak force, whereby the operating lever 72 is held in the neutral position. When the operation lever 96 is tilted from this neutral position to the arrow A (to the right in FIG. 1), the action portion 74 of the pressing member 73 presses the push rod 60a from the protruding position in the direction in which it is buried in the valve body 31, and This causes the spool 36a to move downward as described later. Contrary to this, arrow B (left side in FIG. 1)
When the operating lever 72 is tilted to
The spool 36b moves downward via b.

Below the spools 36a, 36b, damping pressure chambers 45a, 45b are provided facing the lower end surfaces 44a, 44b of the spools 36a, 36b. The damping pressure chambers 45a, 45b are connected to the spools 36a, 3
6b and a hole provided on the valve body 31 and having an inner diameter substantially equal to the outer diameter of the lower end of the spool 36a, 36b.
The damping pressure chambers 45a, 45b are provided with spools 36a,
The damping pressure chambers 45a, 77b are formed through flow paths 77a, 77b formed in the first spool portions 37a, 37b of the 36b.
It communicates with the tank flow path 76 above 45b.
The throttle channels 77a, 77b are formed with first holes 78a, 78b extending upward in the axial direction from the lower end surfaces 44a, 44b of the spools 36a, 36b, and radially outer peripheral surfaces near the tips of the first holes 78a, 78b. Second hole 79 extending to
a, 79b. Second holes 79a, 7
9b has an inner diameter smaller than that of the first holes 78a and 78b, and the second holes 79a and 79b function as aperture portions. A shallow groove 82 facing the second holes 79a and 79b.
a, 82b are formed over the entire circumference of the first spool portions 37a, 37b of the spools 36a, 36b. Therefore, even if each of the spools 36a, 36b moves up and down, the throttle channels 77a, 77b are formed through the grooves 82a, 82b.
7b can always communicate with the tank flow path 76. Such throttle paths 77a and 77b are provided in each spool 36.
Since they are formed at the lower ends of the a and 36b, processing is easy, and the tank flow path 76 and the damping pressure chambers 45a and 4b are formed.
5b is provided in close proximity to the throttle channels 77a, 77b.
The formation of 7b is further facilitated. Further, the throttle portion is not limited to the second holes 79a and 79b, and may be formed in the middle of the throttle channels 77a and 77b, for example, in the first holes 78a and 78b.

The operation and effect of the above-described pilot valve 31 will be described with reference to FIG. 2 together with FIG. When the operation lever 72 is in the neutral position, as described above, the push rods 60a and 60b are connected to the first spring members 64a and 64a.
64b, the spool 36a, 36b is held at the above-mentioned projecting position, and the spools 36a, 36b
In the inoperative position. Therefore, the communication between the first chamber 46 and the secondary pressure side flow paths 49 and 50 is cut off by the first spool portions 37a and 37b of the spools 36a and 36b, but the cutout grooves 39 of the spools 36a and 36b.
a, 39b, and the second chamber 54 and the secondary pressure side flow path 49,
50 and the spool control pilot ports 52 and 81 of the control valve 51 are connected to the secondary pressure side flow path 4.
The control valve 51 is held at a neutral position by being communicated with the oil tank 56 through the second and third chambers 50, 50, and the drain passage 55.

The operation lever 96 is moved from the neutral position to the arrow A.
When the pilot valve 31 is tilted rightward as shown in FIG. That is, when the operation lever 72 is operated, the action portion 74 of the pressing member 73 is pushed.
And the push rod 60a and the spring receiving member 62a are moved downward against the elastic force of the first spring member 64a, and the spool is moved by the second spring member 66a with the movement of the spring receiving member 62a. 36a is moved downward. At this time, the oil in the spring chamber 32 is supplied to the spring receiving member 6.
It flows above the spring receiving member 62a through the hole 2a.

When the spool 36a moves downward in this manner, the notch 39a of the spool 36a
6 and the secondary pressure side flow path 49. Therefore, the pressure oil from the hydraulic pressure supply 48 is supplied to the primary pressure side flow path 47 and the first chamber 4.
6 and one of the pilot ports 52 for controlling the spool of the control valve 51 via the secondary pressure side flow path 49, and the spool of the control valve 51 is moved from the neutral position by the pressure oil from the pressure oil supply source 48 in FIG. Is moved to the left. In this pilot valve 30,
As described above, the damping pressure chamber 45a is
It communicates with the tank flow path 76 via 7a. The spool 36a is a stepped spool in which the outer diameter of the first spool portion 37a is set smaller than the outer diameter of the second spool portion 38a, and the pressure receiving area of the first spool portion 37a is the second spool portion.
It is smaller than the pressure receiving area of the spool portion 38a.
Therefore, the pressure oil supplied to the secondary pressure side flow path 49 acts in a direction to push up the spool 36a by the force generated by the pressure receiving area difference. Therefore spool 3
6a is the operating force of the operating lever 72, in other words, the second
Of the pressing force of the spring member 66a and the secondary pressure side flow path 49
Is held at a position where the above-mentioned pushing force by the pressure oil is suspended.

In such a pilot valve 31, when the spool 36a moves downward and pressure oil is supplied from the primary pressure side flow path 47 to the secondary pressure side flow path 49, the pressure of the secondary pressure side flow path 49 is reduced. When the spool 36a moves upward and moves in this way, and the secondary pressure side flow path 49 and the spring chamber 32 communicate with each other, the pressure oil from the secondary pressure side flow path 49 flows into the spring chamber 32, When the pressure in the pressure side flow path 49 decreases, the secondary pressure side flow path 4
9, the excessive pressure rise is suppressed, and the spool 36a moves downward again.

In this control state, the spool 36a may vibrate vertically, that is, hunting may occur.
5a and the throttle channel 77a operate as follows. That is, when the pressure in the secondary pressure side flow path 49 decreases and the spool 36a moves downward by the action of the second spring member 66a, the oil in the damping pressure chamber 45a
And a part of the oil is discharged to the tank channel 76 through the throttle channel 77a. At this time, the amount of oil discharged to the tank flow path 76 is
Since the damping pressure chamber 45a and the throttle passage 77a are restricted by the throttle portion 7a (the second hole 79a in the present embodiment), the damping pressure chamber 45a and the throttle channel 77a function as damping means for suppressing rapid movement of the spool 36a. Similarly, when the spool 36a moves up and down, the oil in the tank flow path 76 is supplied to the damping pressure chamber 45a via the throttle flow path 77a, so that rapid movement of the spool 36a is suppressed and the damping effect is obtained. Is obtained. In this way, the hunting phenomenon is prevented.

At this time, the damping pressure chamber 45a is provided below the tank flow passage 76a, and the throttle flow passage 77a extends upward from the damping pressure chamber 45a.
Through the tank flow path 76a, the oil flows into the damping pressure chamber 45a even if the oil mixed with the air by cavitation or the like flows into the damping pressure chamber 45a.
Through the upper tank flow path 76 to prevent accumulation of air in the damping pressure chamber 45a. Therefore, the undesirable effect that the damping effect is reduced due to the remaining air and the hunting phenomenon cannot be suppressed can be prevented.

Since the oil in the damping pressure chamber 45a acts on the entire bottom surface 44a of the spool 36a, a sufficient damping effect can be exerted on the spool 36a.

Each spool 36 of the above-described pilot valve 30
The spools a and 36b are not limited to stepped spools, and may be non-stepped spools in which the outer diameters of the first spool portion 37a and the second spool portion 38a are equal. Even if the damping pressure chambers 45a and 45b and the throttle passages 77a and 77b are formed in such a non-stepped spool, the rapid movement of the spool can be suppressed and the damping effect can be exerted as described above.

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

As described above, according to the present invention, the damping pressure chamber configured to exert a damping effect on the spool is provided below the tank flow path. Since the air is reliably discharged to the upper tank flow path through the passage, it is possible to prevent the accumulation of air in the damping pressure chamber, and to reliably obtain the damping effect. Further, since the tank flow path and the damping pressure chamber are provided close to each other, it is easy to form a throttle flow path. In particular, according to the present invention, the damping pressure chamber is formed at a lower end portion of the spool, and a throttle flow path having a throttle portion is formed on the spool above the lower end portion. Therefore, since it is connected to the tank flow path through the throttle flow path formed in the spool, it is possible to sufficiently discharge the air in the damping pressure chamber, and thus to reliably perform the damping action and prevent the occurrence of hunting. it can. Further, according to the present invention, the spool has a first hole extending axially upward from the lower end of the spool, and a radially outer peripheral surface extending from the vicinity of the tip of the first hole to the radially outer surface. A throttle channel is formed by the second hole having a small inner diameter. Therefore, the configuration is simple, the processing is easy, no additional parts are required for drawing, and the configuration is inexpensive.

[0041]

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a pilot valve 30 of the present invention.

FIG. 2 is a cross-sectional view of the pilot valve 30 showing a state where an operation lever 72 is operated.

FIG. 3 is a sectional view showing a conventional pilot valve 14;

[Explanation of symbols]

 30, 90 Pilot valve 31 Valve body 32, 33 Spring chamber 34, 35 Spool hole 36a, 36b; 89a, 89b Spool 37a, 37b First spool portion 38a, 38b Second spool portion 39a, 39b Notched groove 45a, 45b Damping pressure Chamber 47 Primary pressure side flow path 49, 50 Secondary pressure side flow path 62a, 62b Spring receiving member 60a, 60b Push rod 64a, 64b First spring member 66a, 66b Second spring member 72 Operating lever 76 Tank flow path 77a, 77b throttle channel

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F15B 13/042

Claims (1)

(57) [Claims] A valve body having a spring chamber and a spool hole communicating with the spring chamber, a push rod movably mounted on the valve body, a spool movably mounted on the spool hole, and the spring chamber. A spring receiving member movably disposed with respect to the valve body, a projecting position interposed between the valve body and the spring receiving member, and projecting the push rod from the valve body via the spring receiving member. A first spring member that resiliently presses the spool, and a second spring that is interposed between the spring receiving member and the spool and that resiliently presses the spool in a direction away from the push rod. A member, and an operation lever for pressing the push rod from the projecting position in a direction to be buried in the valve body, wherein the spool has a first spool portion having a small pressure receiving area of the pressure receiving portion, and a pressure receiving portion of the pressure receiving portion. A second spool portion having a large area; and a notch groove provided between the first and second spool portions. When the push rod is at the protruding position, the first spool portion is connected to the primary pressure side flow path and the secondary pressure side. A cut-off groove connects the secondary pressure side flow path and the second chamber connected to the drain flow path, and the push rod is pressed by the operation lever in a direction in which the push rod is buried in the valve body. Then, the spool moves in the direction in which the spool is buried by the second spring member, and the cutout groove communicates with the primary pressure side flow path and the secondary pressure side flow path. A damping pressure chamber is provided below the tank flow path, facing the lower end face of the spool, and the damping pressure chamber has a spool lower end face having a single surface and a valve body. To The spool is formed with a hole having an inner diameter substantially equal to the outer diameter of the lower end of the spool. The spool has a first hole extending upward in the axial direction from a lower end surface of the spool, and a first hole formed in the first hole. Extending from the vicinity of the tip to the outer peripheral surface in the radial direction, the inner diameter is smaller than the first hole,
A pilot valve, wherein a throttle flow path having a second hole communicating with the tank flow path is formed, and the damping chamber is connected to the tank flow path via the throttle flow path.