JP2002317802A - Bleeder structure for pilot operation control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly and positively carry out bleeding in a bleeding structure for a pilot fluid operating a pilot operation control valve by discharging the pilot fluid along with air by generating a sufficient flow to a drain and stopping a flow of the pilot fluid to the drain or other liquid chambers when bleeding is not carried out by randomly intermitting discharging. SOLUTION: The bleeder structure is provided with a selector valve selectively connecting a plurality of liquid chambers of the pilot operation control valve supplied with the pilot fluid and discharging it with a tank or a pressure fluid source, and a check valve provided in a passage connecting the liquid chambers and the selector valve and allowing a flow only in a direction of the selector valve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air release structure for a pilot operation control valve, and more particularly to an air release structure for releasing air mixed in a pilot fluid for operating a pilot operation control valve.

[0002]

2. Description of the Related Art A known pilot operation control valve supplies a pilot fluid having a pressure corresponding to an operation amount from a pilot valve operated by an operator to a liquid chamber facing a control spool of the control valve. Is switched from the position held by the spring to a position corresponding to the magnitude of the pressure against the spring force. When the pressure of the pilot fluid is released, the control spool is returned to the original position by the force of the spring. As described above, the pilot operation control valve switches the control spool to an arbitrary position by supplying and discharging the pilot fluid.

[0003] Construction machines such as hydraulic excavators are provided with a plurality of pilot operation control valves for operating hydraulic actuators. As a pilot fluid for operating the pilot operation control valve, hydraulic oil of a hydraulic device is used. In this hydraulic device, if air is mixed in the pilot oil, the pilot oil, which is a liquid chamber to which the pilot oil is supplied / discharged, has a dead end. The pilot oil that switches the control spool against the force becomes a sponge state, and causes problems such as a delay in switching response of the pilot operation control valve and a deterioration in switching operation feeling. Further, the working performance of the construction machine is also deteriorated.

[0004] The mixing of air into the pilot oil may be caused when hydraulic oil is filled with hydraulic oil, when hydraulic equipment such as a control valve is additionally constructed to change the specifications of the hydraulic equipment, or when the hydraulic oil tank is filled. It is easy to occur when the oil level is wavy. Part of the air discharged with the hydraulic oil by the hydraulic pump returns to the tank and is released to the atmosphere.
Some will remain in the pilot room described above. Therefore, this air bleeding is important.

A typical conventional air vent structure for discharging air mixed in pilot oil will be described.

(1) One of them will be described with reference to FIG. The control spool 52 of the pilot operation control valve 50 has a notch 52a for air release. Notch 5
2a, when pilot oil is supplied to the pilot chamber 54 as indicated by an arrow Y and the control spool 52 is pushed to approach the end of the sliding stroke, the pilot chamber 54 opens to the drain flow path 51a of the valve body 51 (2). Indicated by a dashed line). When the notch 52a opens into the drain flow path 51a, a part of the pilot oil supplied to the pilot chamber 54 is discharged to the drain flow path 51a through the notch 52a together with the mixed air as shown by an arrow D.

(2) Another structure will be described with reference to FIG. In this structure, an air vent channel 66 is formed in a connector 64 for connecting a pipe (not shown) for supplying and discharging pilot oil to and from a pilot chamber 62 of a pilot operation control valve 60. The air vent channel 66 is provided between the through channel 64 a of the connector 64 and the drain space 6 of the valve body 61.
1b is formed by reducing the outer diameter of a part of the hole 64c connecting the through flow path 64a and the external thread 64b on the outer circumference and the external thread 64a. The connector 64 has a female screw 61 connected to a pilot chamber 62 facing a spool 63 of the valve body 61.
A male screw 64b is screwed into and attached to a. Therefore, when the pilot oil is supplied to the pilot chamber 62 as shown by the arrow Y, a part of the pilot oil
Is discharged to the drain channel 61b together with the mixed air as shown by.

When a plurality of pilot operation control valves are provided, the above-described air bleeding structure is provided for each pilot operation control valve.

[0009]

The conventional venting structure of the pilot operation control valve having the above-described configuration has the following problems to be solved.

(1) Forming an air bleed notch on the spool (FIG. 4): In the structure in which the air bleed notch 52a is formed on the control spool 52, the exhaust of air in the pilot oil is performed by fully operating the pilot valve, that is, This is only when the control spool 52 is fully moved. Therefore, in order to release the air, it is necessary to switch the pilot valve fully and hold it for a certain period of time, or to repeatedly switch the pilot valve to full.

(2) Forming an air vent channel in the connector (FIG. 5): In a structure in which an air vent channel 66 is formed in the connector 64, when the pilot operation switching valve is switched, air flows through the air vent channel 66. Although the pilot oil is discharged together with a part of the pilot oil, a part of the pilot oil is always released to the drain.
The operability etc. deteriorate. Further, it is necessary to form a drain passage 61b on the valve body 61 outside the pilot oil chamber 62.

(3) In any of the above-described air bleeding structures, the notch 52a or the throttle flow path formed by the air bleed flow path 66 is used to minimize the switching response and operability of the pilot operation control valve. It is desired to be as small as possible. However, there is a contradictory problem that the throttle passage must be enlarged to generate a flow in order to sufficiently release air.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a technical problem thereof is that in a pilot fluid air vent structure for operating a pilot operation control valve, a sufficient flow of the pilot fluid to a drain can be generated and discharged. In addition, the discharge can be arbitrarily interrupted so that when the air is not vented, the outflow of the pilot fluid to the drain is stopped, so that the air can be vented appropriately and reliably. Further, it is possible to easily release air from a plurality of pilot operation control valves.

[0014]

According to the first aspect of the present invention, each of a plurality of liquid chambers of one or more pilot operation control valves for supplying and discharging a pilot fluid is connected to a drain or a pressure fluid source. A switching valve that is selectively connected, and a check valve that is provided in each of the flow paths connecting each of the liquid chambers and the switching valve and that allows flow only in the direction of the switching valve. An air vent structure for a pilot operation control valve.

A plurality of liquid chambers for supplying and discharging the pilot fluid are connected to a drain via a check valve and a switching valve when air is released, so that a sufficient flow is generated and air can be reliably released. For example, during normal operation of the pilot operation control valve which does not perform air bleeding, the switching fluid supplies the pressure fluid of the pressure fluid source to each of the check valves, and the check valves are securely closed to allow the pilot fluid to flow out of the liquid chamber. Don't do it.

According to a second aspect of the present invention, there is provided a switching valve for intermittently connecting each of a plurality of liquid chambers of one or more pilot operation control valves to which a pilot fluid is supplied and discharged to a drain, A check valve provided in each of the flow paths connecting each of the liquid chambers and the switching valve, the check valve being configured to permit flow only in the direction of the switching valve, It is a punching structure.

A plurality of liquid chambers to which the pilot fluid is supplied and discharged are connected to a drain via a check valve and a switching valve at the time of air bleeding so that a sufficient flow is generated so that air bleeding can be performed reliably. For example, during normal operation of the pilot operation control valve which does not perform air bleeding, the switching valve is closed to prevent the pilot fluid in the liquid chamber from flowing out to the drain, and the pilot operation control valve operated by the check valve Of the pilot fluid does not flow into another liquid chamber.

According to a third aspect of the present invention, in the air vent structure of the pilot operation control valve according to the first or second aspect, a throttle is provided between the liquid chamber and the check valve to narrow a flow path. It is what is being done.

When the air is bleeded, the flow of the fluid in the initial movement is prevented, and the bleeding can be performed more efficiently.

According to a fourth aspect of the present invention, the switching valve according to the first or second aspect is an air release structure of a pilot operation control valve including an electromagnetic switching valve.

Then, the switching valve is operated by operating the electric switch so that air can be vented freely.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a pilot control valve of a hydraulic system according to a preferred embodiment of the present invention; Will be described.

The first embodiment will be described first with reference to FIG. This air bleeding structure is provided by the pilot operation control valve 2.
a switching valve 8 for selectively connecting each of the pilot chambers 3a, 3b, and 3c, which are liquid chambers for supplying and discharging the pilot fluids a, 2b, and 2c, to a tank 4 that is a drain or a hydraulic source 6 that is a pressure fluid source; Check valve 1 provided in each of flow paths 10a, 10b, 10c connecting pilot chambers 3a, 3b, 3c to switching valve 8, and allowing only flow in the direction of switching valve 8
2a, 12b, and 12c. Further, the pilot chambers 3a, 3b, 3c and the check valves 12a, 12b, 1
Apertures 28a, 28b, 28c are provided between the apertures 2a and 2c.

The structure of the air vent structure in each of the pilot operation control valves 2a, 2b and 2c is the same. Therefore, the details will be described with reference to the pilot operation control valve 2a and the outline of the hydraulic device will be described with reference to FIG.

The hydraulic device includes a hydraulic oil tank 4, a variable displacement hydraulic pump 14 for discharging the hydraulic oil from the tank 4,
A hydraulic cylinder 16 as an actuator is provided, and the discharge oil of the hydraulic pump 14 is switched and supplied to the rod-side oil chamber 16a or the head-side oil chamber 16b of the hydraulic cylinder 16 by the pilot operation control valve 2a. The hydraulic device includes a pilot valve 18 that supplies and discharges pilot oil as a pilot fluid for a switching operation to the pilot operation control valve 2a. The pilot valve 18 is operated by an operator.

The pilot operation control valve 2a is
And a control spool 2 slidably inserted into the valve body 20.
The pilot chamber 3a, which is a liquid chamber for supplying and discharging pilot oil, faces one end (right end) of the control spool 22, and the pilot chamber 3d faces the other end (left end) of the control spool 22. Have been. Control spool 2
Numeral 2 is held at a neutral position in the figure by the urging force of a double compression coil spring 24 disposed in the pilot chamber 3a. When the pilot oil is supplied to any of the pilot chambers 3a and 3b, the control spool 22 is pushed and moved against the urging force of the spring 24.

Flow path 10a leading to pilot chamber 3a
Is formed through a housing 21 forming the pilot chamber 3a and the valve body 20 of the pilot operation control valve 2a.

The switching valve 8 is constituted by an electromagnetic switching valve.
It is a two-position valve that is switched by a well-known electromagnetic solenoid. In a non-excited state (illustrated state) in which the solenoid is not energized, the hydraulic pressure source 6 is connected to the flow path 10a. Is connected to the tank 4. An electric switch 26 for operating the electromagnetic switching valve 8
Is provided near the pilot valve 18.

The check valve 12a is provided at a portion of the housing 21 where the flow path 10a is connected to the pilot chamber 3a. The throttle 28a is formed between the check valve 12a and the pilot chamber 3a with a small diameter of the flow path 10a.

The pressure fluid source 6 includes a pilot valve 18
Such as the discharge oil of the pilot pump 19 that discharges pressure oil to
An appropriate hydraulic source can be used.

The operation of the hydraulic device having the pilot operation switching valve 2a will be described. When the pilot valve 18 is operated and one of the pilot chambers, for example, the pilot chamber 3 a is supplied with pilot oil having a pressure corresponding to the operation, the spool 22 moves inside the valve body 20 against the urging force of the spring 24. (To the left in FIG. 2) and the pump 14
Flows through the load check valve 30, flows into the flow path 32, flows into the port 34, flows into the head-side oil chamber 16b of the hydraulic cylinder 16, and the hydraulic cylinder 16 extends.
At this time, the hydraulic oil in the rod-side oil chamber 16a of the hydraulic cylinder 16 flows through the port 36 of the valve body 20, the flow path 38, the drain flow path 40, and the tank 4. The other pilot chamber 3 d is opened to the tank 4 via the pilot valve 18.

When the pilot oil is supplied to the other pilot chamber 3d by operating the pilot valve 18, the spool 22 is pushed in the opposite direction (rightward) to the above, and the discharge oil of the pump 14 Flows into the oil chamber 16a,
The hydraulic cylinder 16 contracts and the hydraulic oil in the head-side oil chamber 16b flows to the tank 4. The pilot chamber 3a is opened to the tank 4 via the pilot valve 18.

Referring to FIGS. 1 and 2, mainly referring to FIG.
The air bleeding operation and operation of the air bleeding structure of the pilot operation control valve will be described.

(1) Air release operation: To release air mixed in the pilot oil, the electromagnetic switching valve 8 must be turned on by the electric switch 26.
To connect the flow path 10a to the tank 4. In this state, the pilot valve 18 is operated to operate the pilot chamber 3a.
When the pilot oil is supplied to the tank 4, the pilot oil passes through the orifice 28a and the check valve 12a together with the mixed air, and is discharged to the tank 4 via the flow passage 10a and the electromagnetic switching valve 8. Therefore, a sufficient flow of the pilot fluid to the tank 4, which is a drain, can be generated and discharged. Also, by operating the electric switch 26 of the electromagnetic switching valve 8,
Discharge can be easily interrupted arbitrarily.

(2) Normal operation of pilot operation control valve:
When air bleeding is completed or when air bleeding is not performed, the electromagnetic switch valve 8 is operated by the electric switch 26 so that the flow path 10a is connected to the hydraulic power source 6 (the state illustrated). In this state, the check valve 12a is closed by the pressure oil of the hydraulic pressure source 6. Therefore, the pilot room 3a
Of the pilot oil into the tank 4 through the check valve 12a,
Alternatively, it is used for operating the spool 22 without flowing to another pilot chamber. Further, deterioration of the switching response and operability of the pilot operation control valve is also prevented.

(3) Restrictor: Further, by providing a restrictor 28a between the check valve 12a and the pilot chamber 3a,
Since the initial flow of oil during air bleeding is hindered, air bleeding can be performed more efficiently. Also, the diaphragm 28
In the case of a, the pilot oil is extruded from the pilot chamber 3a with a certain level of pressure, so that the air can be reliably extruded.

A second embodiment will be described with reference to FIG. This air release structure is different from the first embodiment shown in FIG. 1 in that an electromagnetic switching valve 8 for selectively connecting the pilot chambers 3a, 3b, and 3c to the tank 4 or the hydraulic pressure source 6 is provided in the pilot chambers 3a, 3b, It is the same except that 3c is replaced by an electromagnetic switching valve 42 that is connected to the tank 4 in an intermittent manner.

In the first embodiment, the check valve 12
While a, 12b, and 12c are forcibly closed by the pressure oil of the hydraulic pressure source 6, in this embodiment, they are closed by the pilot pressure oil of the operated pilot operation control valve.

As described above, the present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above-described embodiments. It can be changed or modified.

(1) Number of pilot operation control valves: In this embodiment, three pilot operation control valves (2
a, 2b, 2c), the air vent structure according to the present invention can be applied to one or more appropriate number of pilot operated control valves.

(2) Liquid chamber: In the present embodiment, one pilot chamber 3a of the pair of liquid chambers 3a and 3d is provided with an air vent structure. Normally, this type of pilot operation control valve is mounted with one of the liquid chambers facing upward, and since the air is lighter than oil, it is easy to collect in one of the liquid chambers. Good.
However, if necessary, depending on the mounting form of the pilot operation control valve, the air vent structure may be provided in both pilot chambers.

(3) Pilot operation control valve: In this embodiment, the pilot operation control valve 2a is a directional control valve for controlling the direction of the flow of hydraulic oil to the hydraulic cylinder 16, and is provided at both ends of the spool 22. Pilot room 3a, 3
b), the pilot operation control valve may be any valve that is operated by a pilot fluid, and may be an appropriate valve such as a pressure control valve, a flow control valve, and the number of pilot chambers is limited to two. It is not something to be done.

(4) Switching valve: In this embodiment,
Although an electromagnetic switching valve is used as the switching valve, any switching valve may be used as long as it can switch the connection of the flow path. For example, a manual switching valve having a lever with a detent, a rotary switching valve, or the like may be used. Is also good.

[0044]

According to the air bleeding structure of the pilot operation control valve constructed in accordance with the present invention, a sufficient flow of the pilot fluid containing air can be generated and discharged to the drain.
In addition, this discharge can be interrupted arbitrarily, and when the air is not vented, the flow of the pilot fluid to the drain and other liquid chambers is stopped, so that the switching response and operability of the pilot operation control valve are deteriorated. Air can be properly and reliably removed. Further, air can be easily removed from the plurality of pilot operation control valves.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an outline of a first embodiment of an air release structure of a pilot operation control valve configured according to the present invention.

FIG. 2 is a detailed circuit diagram of a hydraulic device having the air release structure shown in FIG.

FIG. 3 is a circuit diagram showing an outline of a second embodiment of an air release structure of a pilot operation control valve configured according to the present invention.

FIG. 4 is a cross-sectional view showing a typical example of a conventional air vent structure.

FIG. 5 is a sectional view showing another typical example of the conventional air vent structure.

[Explanation of symbols]

 2a: Pilot control valve 2b: Pilot control valve 2c: Pilot control valve 3a: Pilot chamber (liquid chamber) 3b: Pilot chamber (liquid chamber) 3c: Pilot chamber (liquid chamber) 4: Tank (drain) 6: Hydraulic source (pressure fluid source) 8: Electromagnetic switching valve (switching valve) 10a: Flow path 10b: Flow path 10c: Flow path 12a: Check valve 12b: Check valve 12c: Check valve 28a: Restrictor 28b: Restrictor 28c : Throttle 42: Electromagnetic switching valve (switching valve)

Claims (4)

[Claims] A switching valve for selectively connecting each of a plurality of liquid chambers of one or more pilot operation control valves to which a pilot fluid is supplied and discharged to a drain or a pressure fluid source, and each of the liquid chambers And a check valve provided in each of the flow paths connecting the switching valve and the switching valve to allow flow only in the direction of the switching valve. 2. A switching valve for intermittently connecting each of a plurality of liquid chambers of one or more pilot operation control valves to which a pilot fluid is supplied and discharged with a drain, and each of the liquid chambers and the switching valve And a check valve provided in each of the flow paths connecting the two valves to allow the flow only in the direction of the switching valve. 3. The air vent structure for a pilot operation control valve according to claim 1, wherein a throttle for narrowing a flow path is provided between the liquid chamber and the check valve. 4. The switching valve includes an electromagnetic switching valve.
An air vent structure for a pilot operation control valve according to claim 1 or 2.