JP3776744B2 - Air bleeding structure of pilot operated control valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air bleeding structure for a pilot operation control valve, and more particularly to an air bleeding structure for bleeding air mixed in a pilot fluid that operates a pilot operation control valve.
[0002]
[Prior art]
A known pilot operation control valve, for example, 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, so that the control spool is held by a spring. The selected position is switched to a position corresponding to the magnitude of 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. In this way, the pilot operation control valve is operated to switch its control spool to an arbitrary position by supplying and discharging pilot fluid.
[0003]
Construction machines such as hydraulic excavators are provided with a plurality of pilot operation control valves for operating hydraulic actuators. As the pilot fluid for operating the pilot operation control valve, hydraulic fluid of the 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 and discharged, has a dead end, so that the air is trapped and is not easily discharged. The pilot oil that switches the control spool against force is in a sponge state, causing problems such as a delay in switching response of the pilot operation control valve and deterioration of the switching operation feeling. Furthermore, the work performance of the construction machine is also deteriorated.
[0004]
Air contamination in the pilot oil may occur when the hydraulic system is filled with hydraulic fluid, or when hydraulic equipment such as a control valve is added to change the specifications of the hydraulic system, or when the hydraulic oil level of the hydraulic oil tank It is likely to occur when the wave is inclined. A part of the air discharged together with the hydraulic oil by the hydraulic pump returns to the tank and is released to the atmosphere, but a part remains in the pilot chamber. Therefore, this air bleeding is important.
[0005]
A typical conventional air venting structure for discharging air mixed in pilot oil will be described.
[0006]
(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 bleeding air. When the pilot oil is supplied to the pilot chamber 54 as indicated by an arrow Y and the control spool 52 is pushed and approaches the end of the sliding stroke, the notch 52a opens to the drain passage 51a of the valve body 51 ( Indicated by a two-dot chain line). When the notch 52a is opened to the drain passage 51a, part of the pilot oil supplied to the pilot chamber 54 is discharged to the drain passage 51a through the notch 52a and indicated by arrow D together with the mixed air.
[0007]
(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 the pilot chamber 62 of the pilot operation control valve 60. The air vent channel 66 reduces the outer diameter of a part of the hole 64c and the male screw 64a that connect the through channel 64a of the connector 64 and the drain space 61b of the valve body 61 to the through channel 64a and the outer male screw 64b. Is formed. The connector 64 has a male screw 64 b screwed to a female screw 61 a connected to a pilot chamber 62 facing the spool 63 of the valve body 61. Therefore, when the pilot oil is supplied to the pilot chamber 62 as indicated by the arrow Y, a part of the pilot oil is always discharged to the drain passage 61b together with the mixed air as indicated by the arrow D.
[0008]
When a plurality of pilot operation control valves are installed, the above-described air vent structure is provided for each pilot operation control valve.
[0009]
[Problems to be solved by the invention]
The conventional air bleed structure of the pilot operation control valve as described above has the following problems to be solved.
[0010]
(1) Air vent notch is formed in the spool (Fig. 4):
In the structure in which the air vent notch 52a is formed in the control spool 52, the air in the pilot oil is discharged only when the pilot valve is fully operated, that is, when the control spool 52 is fully moved. Therefore, in order to bleed air, it is necessary to switch the pilot valve fully and hold it for a certain period of time, or to repeatedly switch it to full.
[0011]
(2) Form an air vent channel in the connector (Fig. 5):
In the structure in which the air vent channel 66 is formed in the connector 64, when the pilot operation switching valve is switched, the air is discharged together with part of the pilot oil through the air vent channel 66, but part of the pilot oil is always drained. Therefore, the switching response and operability of the pilot operation switching valve are deteriorated. Further, it is necessary to form a drain passage 61 b in the valve body 61 on the outer side of the pilot oil chamber 62.
[0012]
(3) In any of the above air vent structures, in order to reduce the switching response and operability of the pilot operation control valve as much as possible, the throttle passage by the notch 52a or the air vent passage 66 is made as much as possible. It is desirable to make it smaller. However, there is a conflicting problem that the flow must be generated by enlarging the throttle channel for sufficient air bleeding.
[0013]
The present invention has been made in view of the above-described facts, and a technical problem thereof is that a pilot fluid can be discharged to a sufficient flow through a drain in a pilot fluid air vent structure for operating a pilot operation control valve. At the same time, the discharge can be arbitrarily interrupted so that when the air is not vented, the pilot fluid is prevented from flowing out to the drain so that the air can be vented appropriately and reliably. Further, it is possible to easily bleed a plurality of pilot operation control valves.
[0014]
[Means for Solving the Problems]
The invention described in claim 1 is a switching valve for selectively connecting each of a plurality of liquid chambers of one or more pilot operation control valves to which pilot fluid is supplied and discharged to a drain or a pressure fluid source, A pilot operated control valve comprising: a check valve provided in each of the flow paths connecting each of the liquid chambers and the switching valve and allowing only a flow in the direction of the switching valve. Air bleeding structure.
[0015]
A plurality of fluid chambers to which pilot fluid is supplied and discharged are connected to a drain via a check valve and a switching valve when air is released, so that a sufficient flow can be generated and air can be surely released. For example, during normal operation of the pilot operation control valve, the switching valve is used to apply pressure fluid from the pressure fluid source to each check valve so that the check valve is securely closed so that the pilot fluid does not flow out of the liquid chamber. To do.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a pilot operation control valve bleed structure constructed according to the present invention will be described in more detail with reference to the accompanying drawings illustrating a preferred embodiment of a pilot operation control valve of a hydraulic device.
[0023]
A first embodiment will be described first with reference to FIG. In this air venting structure, each of the pilot chambers 3a, 3b, 3c, which is a liquid chamber into which pilot fluids of the pilot operation control valves 2a, 2b, 2c are supplied and discharged, is supplied to the tank 4 which is a drain or a hydraulic power source 6 which is a pressure fluid source. And a switching valve 8 that is selectively connected to each other and a flow path 10a, 10b, and 10c that connects each of the pilot chambers 3a, 3b, and 3c to the switching valve 8 and that allows only a flow in the direction of the switching valve 8 Stop valves 12a, 12b, and 12c are provided. Further, throttles 28a, 28b, 28c are respectively provided between the pilot chambers 3a, 3b, 3c and the check valves 12a, 12b, 12c.
[0024]
The configuration of the air bleeding structure in each part of the pilot operation control valves 2a, 2b, 2c is the same. Therefore, the details will be described with reference to FIG. 2, which is represented by the pilot operation control valve 2 a and includes the outline of the hydraulic device.
[0025]
The hydraulic apparatus includes a hydraulic oil tank 4, a variable displacement hydraulic pump 14 that discharges the hydraulic oil in the tank 4, and a hydraulic cylinder 16 as an actuator. The hydraulic oil discharged from the hydraulic pump 14 is a pilot operation control valve 2 a. As a result, the rod-side oil chamber 16a or the head-side oil chamber 16b of the hydraulic cylinder 16 is switched and supplied. The hydraulic apparatus includes a pilot valve 18 for supplying and discharging pilot oil as a pilot fluid for switching operation to the pilot operation control valve 2a. The pilot valve 18 is operated by an operator.
[0026]
The pilot operation control valve 2 a includes a valve main body 20 and a control spool 22 that is slidably inserted into the valve main body 20, and a pilot chamber 3 a that is a liquid chamber through which pilot oil is supplied and discharged is one end of the control spool 22. The pilot chambers 3d are respectively provided facing the other end (left end) of the control spool 22 facing the (right end). The control spool 22 is held at the neutral position shown in the figure by the urging force of a double compression coil spring 24 disposed in the pilot chamber 3a. When pilot oil is supplied to one of the pilot chambers 3a and 3b, the control spool 22 is pushed and moved against the urging force of the spring 24.
[0027]
The flow path 10a connected to the pilot chamber 3a is formed through the housing 21 forming the pilot chamber 3a and the inside of the valve body 20 of the pilot operation control valve 2a.
[0028]
The switching valve 8 is a two-position valve configured by an electromagnetic switching valve and switched by a known electromagnetic solenoid. In the non-excited state (shown) where the solenoid is not energized, the hydraulic source 6 is connected to the flow path 10a. In the excited state where the solenoid is energized, the connection between the hydraulic source 6 and the flow path 10a is cut off, and the flow path 10a. Is connected to the tank 4. An electric switch 26 for operating the electromagnetic switching valve 8 is provided in the vicinity of the pilot valve 18.
[0029]
The check valve 12a is provided in 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 passage 10a.
[0030]
As the pressure fluid source 6, an appropriate hydraulic source such as a discharge oil of a pilot pump 19 that discharges pressure oil to the pilot valve 18 can be used.
[0031]
The operation of the hydraulic device provided with the pilot operation switching valve 2a will be described. When the pilot valve 18 is operated and pilot oil having a pressure corresponding to the operation is supplied to one of the pilot chambers, for example, the pilot chamber 3 a, the spool 22 resists the urging force of the spring 24 and the inside of the valve body 20. The oil discharged from the pump 14 flows into the flow path 32 via the load check valve 30, flows into the port 34, and flows into the head side oil chamber 16b of the hydraulic cylinder 16, The hydraulic cylinder 16 is extended. At this time, the hydraulic oil in the rod side oil chamber 16 a of the hydraulic cylinder 16 flows through the port 36 and the flow path 38 of the valve body 20, flows through the drain flow path 40, and flows into the tank 4. The other pilot chamber 3 d is opened to the tank 4 via a pilot valve 18.
[0032]
When the pilot valve 18 is operated and the pilot oil is supplied to the other pilot chamber 3d, the spool 22 is pushed in the opposite direction (to the right), and the pump 14 discharges the oil on the rod side oil chamber 16a of the hydraulic cylinder 16. The hydraulic cylinder 16 contracts and the hydraulic oil in the head side oil chamber 16 b flows into the tank 4. The pilot chamber 3 a is opened to the tank 4 through a pilot valve 18.
[0033]
With reference to FIG.1 and FIG.2, mainly FIG. 2, the air bleeding operation and effect | action of the air bleeding structure of the above-mentioned pilot operation control valve are demonstrated.
[0034]
(1) Air bleeding operation:
In order to remove air mixed in the pilot oil, the electromagnetic switching valve 8 is operated by the electric switch 26 and the flow path 10 a is connected to the tank 4. In this state, when the pilot valve 18 is operated and the pilot oil is supplied to the pilot chamber 3a, the pilot oil is mixed with air, passes through the orifice 28a and the check valve 12a, and passes through the passage 10a and the electromagnetic switching valve 8 to the tank 4. To be discharged. Accordingly, the pilot fluid can be discharged by generating a sufficient flow to the tank 4 as a drain. Further, the discharge can be arbitrarily interrupted easily by operating the electric switch 26 of the electromagnetic switching valve 8.
[0035]
(2) Normal operation of pilot operated control valve:
When the air venting is completed, or when the air venting is not performed, the electromagnetic switching valve 8 is operated by operating the electric switch 26 so that the flow path 10a is connected to the hydraulic pressure source 6 (the state shown in the drawing). In this state, the check valve 12 a is closed by the pressure oil from the hydraulic source 6. Accordingly, the pilot oil in the pilot chamber 3a is used for the operation of the spool 22 without flowing into the tank 4 or the other pilot chamber through the check valve 12a. And deterioration of the switching responsiveness and operability of the pilot operation control valve is also prevented.
[0036]
(3) Aperture:
Furthermore, by providing the throttle 28a between the check valve 12a and the pilot chamber 3a, the initial flow of oil during air bleeding is hindered, so that air can be vented more efficiently. Further, the throttle 28a pushes out the pilot oil from the pilot chamber 3a with a certain pressure, so that the air can be pushed out reliably.
[0037]
A second embodiment will be described with reference to FIG. This air vent structure is the same as that of the first embodiment shown in FIG. 1, and the electromagnetic switching valve 8 for selectively connecting the pilot chambers 3a, 3b, 3c to the tank 4 or the hydraulic source 6 is connected to the pilot chambers 3a, 3b, 3C is the same except that the electromagnetic switching valve 42 is connected to the tank 4 in an intermittent manner.
[0038]
In the first embodiment, the check valves 12a, 12b, and 12c are forcibly closed by the pressure oil of the hydraulic source 6, whereas in this embodiment, the pilot of the operated pilot operation control valve Closed with pressure oil.
[0039]
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, and various modifications or corrections may be made within the scope of the present invention, for example, as described below. It is something that can be done.
[0040]
(1) Number of pilot operated control valves:
Although three pilot operation control valves (2a, 2b, 2c) are shown in the present embodiment, the air vent structure according to the present invention can be applied to one or more appropriate numbers of pilot operation control valves. Is.
[0041]
(2) Liquid chamber:
In this embodiment, one pilot chamber 3a of the pair of liquid chambers 3a and 3d is provided with an air vent structure. Normally, this kind of pilot operation control valve is mounted with one liquid chamber facing up, and since air is lighter than oil, it is easy to gather in one liquid chamber, so it is only necessary to provide an air vent structure in one pilot chamber 3a. Good. However, if necessary, an air vent structure may be provided in both pilot chambers depending on the mounting mode of the pilot operation control valve.
[0042]
(3) Pilot operated control valve:
In the present embodiment, the pilot operation control valve 2a is a directional control valve that controls the flow direction of hydraulic oil to the hydraulic cylinder 16, and includes pilot chambers 3a and 3b at both ends of the spool 22, Since the pilot operation control valve may be a valve operated by a pilot fluid, an appropriate valve such as a pressure control valve or a flow rate control valve may be used, and the number of pilot chambers is not limited to two.
[0043]
(4) Switching valve:
In this embodiment, an electromagnetic switching valve is used as the switching valve. However, since the switching valve only needs to switch the connection of the flow path, for example, a manual switching valve provided with a lever with a detent, a rotary valve It may be a type switching valve.
[0044]
【The invention's effect】
According to the air bleeding structure of the pilot operation control valve configured in accordance with the present invention, the pilot fluid containing air can be discharged while generating a sufficient flow to the drain. Also, this discharge can be interrupted arbitrarily, and when the air is not vented, the pilot fluid drain and the outflow to other liquid chambers are stopped, so the switching response and operability of the pilot operation control valve are deteriorated. Air can be removed properly and reliably. Further, the plurality of pilot operation control valves can be easily vented.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an outline of a first embodiment of an air bleeding structure of a pilot operation control valve constructed according to the present invention.
FIG. 2 is a detailed circuit diagram of a hydraulic apparatus having an air vent structure shown in FIG.
FIG. 3 is a circuit diagram showing an outline of a second embodiment of an air bleeding structure of a pilot operation control valve constructed according to the present invention.
FIG. 4 is a cross-sectional view showing one typical example of a conventional air vent structure.
FIG. 5 is a cross-sectional view showing another typical example of a conventional air vent structure.
[Explanation of symbols]
2a: Pilot operation control valve 2b: Pilot operation control valve 2c: Pilot operation 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: channel 10b: channel 10c: channel 12a: check valve 12b: check valve 12c: check valve 28a: throttle 28b: throttle 28c: throttle 42: electromagnetic switching valve (switching valve)

Claims (1)

  A switching valve for selectively connecting each of the plurality of liquid chambers of the one or more pilot operation control valves to which the pilot fluid is supplied and discharged to a drain or a pressure fluid source, each of the liquid chambers and the switching valve; An air vent structure for a pilot operation control valve, comprising: a check valve provided in each of the flow paths connecting the two, and allowing only a flow in the direction of the switching valve.

Images