JPH1089315A - Hydraulic pilot switching valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic pilot switching valve in which air vent within a valve element can be easily attained. SOLUTION: A hydraulic pilot switching valve 10 is constituted to be provided with an entrance port 12 in which hydraulic operating fluid for driving an actuator 40 flows, an exit port 18 connected with a tank 36, a return passage 16 which is connected with this port 18 and in which return oil from the actuator 110 flows and upper pilot port 22 and lower pilot port 24 making pilot pressure oil of a switching spool 20 act and to perpendicularly move the switching spool 20 in the vertical direction between both of the pilot ports. In this case, a pilot oil path is provided within a valve element 11 so that the pilot oil chamber 22b of the upper pilot port 22 may be communicated and connected with the return passage 16. The pilot oil path is communicated and opened when pilot pressure oil acts on a lower pilot chamber 24b and the switching spool 20 is moved toward an upper pilot chamber 22b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic pilot type switching valve mounted on a construction machine such as a hydraulic excavator.
In particular, the present invention relates to a hydraulic pilot type switching valve improved so as to improve the responsiveness of the switching valve arranged such that the spool operation of the switching valve is in the vertical direction.

[0002]

2. Description of the Related Art In general, in a construction machine such as a hydraulic excavator, a hydraulic pilot type switching valve is used to control various actuators. As this type of hydraulic pilot switching valve, there is known a hydraulic pilot switching valve having the configuration shown in FIG.

[0003] That is, in FIG. 3, this type of switching valve 10 comprises a valve element 11 provided on a vehicle body frame 13, and supplies the valve element 11 from a main pump 30 to an actuator (cylinder) 40. An inlet port 12, a center bypass passage 14, a return passage 16, and an outlet port 18 for allowing hydraulic oil to flow in the lateral direction are provided. Pilot pressure oil from the remote control valve 50 to the switching spool 20 is supplied from above or below. An upper pilot port 22 and a lower pilot port 24 are provided. And the two pilot ports 22,
Between 24, the switching spool 20 is disposed so as to vertically stroke in the vertical direction.

As described above, the reason why the switching spool 20 is arranged to operate vertically in the vertical direction is that a large number of other devices are installed around the switching valve, so that there is little space, and the switching spool 20 is located above the switching valve. This is because there is sufficient space, and when the maintenance and replacement of the switching spool 20 are performed, the operation is simplified. Therefore, according to this type of switching valve (referred to as a vertical spool type switching valve), the switching spool 20 is connected to the cover 2 of the upper pilot port 22.
It can be easily pulled out simply by removing 2a.
That is, while the members such as the cap 20a, the guide 20b, the stopper 20c, and the spring 20d for controlling the position of the switching spool 20 are still attached, the switching spool 20 is removed from the valve body 11 of the switching valve 10. It can be easily pulled out.

In FIG. 3, the switching valve 10 is composed of a composite control valve having three switching spools. The connection configuration of the actuator and the remote control valve corresponding to the other two switching spools is described above. This is the same as the switching spool 20 described above, and is not shown for simplification.

[0006] However, the vertical spool type switching valve 10
The operation of will be briefly described. First, the remote control valve 50
However, as shown in FIG. 3, when in the neutral state, the switching valve 10 is also in the neutral state as shown, so that the hydraulic oil from the main pump 30 flows from the pump line 32 to the inlet port 12 and the center bypass passage 14. Through the return passage 16, the outlet port 18 and the tank line 34,
And is returned to the tank 36 via the filter 34b.

Next, the operation lever 50a of the remote control valve 50
Is operated, for example, to the left by a predetermined amount, pilot pressure oil having a pressure proportional to the operation angle of the operation lever 50a acts on the pilot oil chamber 22a of the upper pilot port 22 from one of the pilot lines 54a. The switching spool 20 is moved downward in the figure to a position where the force generated by the spring 20d balances the elastic force of the spring 20d.

At this time, the supply passage 26a connected to the inlet port 12 of the switching valve 10 communicates with the cylinder port 42a, the cylinder port 42b communicates with the return passage 16, and the center bypass passage 14 and the return passage 16 communicate with each other. Is reduced by the center groove 43 provided on the switching spool 20, the flow rate from the center bypass passage 14 to the return passage 16 is reduced, and the reduced amount of hydraulic oil is supplied from the supply passage 26a to the cylinder It is supplied to the actuator 40 via the port 42a and the actuator line 44a. The return oil from the actuator 40 is returned from the actuator line 44b to the tank 36 via the cylinder port 42b, the return passage 16, the outlet port 18, and the tank line 34, further passes through the cooler 34a and the filter 34b.

Therefore, according to the vertical spool type switching valve configured as described above, the speed control of the actuator in the construction machine can be controlled in many cases by the switching spool 20.
Is adjusted by adjusting the opening area of the center groove 43 on the switching spool 20 controlled by the position, that is, by controlling the flow rate of the hydraulic oil that bleeds off from the center bypass passage 14 to the return passage 16 (bleed-off flow rate control). be able to.

The operation when the operation lever 50a is operated to the right is the same as that described above, and the description is omitted.

[0011]

However, this kind of conventional vertical spool type switching valve still has the following disadvantages.

As described above, this type of vertical spool type switching valve is intended to improve the workability of maintenance and replacement of the spool by configuring the spool to operate vertically. On the other hand, there is an essential difficulty that the responsiveness of the switching valve is reduced. That is, gas mixed in the pilot pressure oil gradually accumulates in the pilot oil chamber 22b in the cover 22a of the upper pilot port 22 via the pilot line 54a, and the accumulated air is more compressible than the oil. (Volume reduction rate with respect to pressure) is large, so that after operating the operation lever 50a of the remote control valve 50, the pilot oil chamber 22
It takes a considerable time for the pressure of b to reach the specified pressure,
The response of the switching valve 10 to the operation of the remote control valve 50 is deteriorated.

For this reason, in this type of conventional vertical spool type switching valve, the gas is manually discharged, or a special automatic air release device or the like is provided (for example, Japanese Utility Model 3). No. 49286) has been proposed. However, in the above configuration, it is obvious that the former case is extremely complicated. Further, in the latter case, not only the manufacturing cost is increased because an additional drain pipe is required in the pilot oil chamber, but also in the case of a combined control system having a plurality of spools,
In order to use only one drain pipe, a cover to be provided for each spool is integrated with the spool for maintenance. Also need to be attached and detached, which increases the time required for maintenance and replacement of the spool, and also increases maintenance costs.

Further, in an emergency, the spool must be operated even when the engine of the construction machine is stopped. Therefore, an accumulator 58 for accumulating the pressure oil of the pilot pump 52 is provided. In this case, if the flow rate of the pilot pressure oil leaking from the drain passage is large, the pressure oil accumulated in the accumulator 58 immediately decreases, and the spool cannot be operated. Therefore, an expensive accumulator having a large capacity is required. There are difficulties.

The air remaining in the pilot oil chamber 24b in the cover 24a of the lower pilot port 24 of the switching valve 10 collects in the upper part of the pilot oil chamber 24b. 11 and easily returns to the return passage 16 from the gap between the spool 20 and the pilot oil chamber 24b. In the pilot oil chamber 24b, a position control member (cap 20a, guide 20b, stopper 20c,
Since there is no need to provide a spring 20d), the capacity of the pilot oil chamber 24b is limited to the upper pilot port 22.
Of the pilot oil chamber 22b, and even if air stays there, there is no effect that the response of the switching valve 10 becomes a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to easily and reliably achieve air bleeding in a valve body of a hydraulic pilot type switching valve provided to operate a spool in a vertical direction without requiring additional piping. An object of the present invention is to provide a hydraulic pilot type switching valve which can be manufactured at a low cost with a simple structure.

[0017]

In order to achieve the above object, a hydraulic pilot type switching valve according to the present invention comprises an inlet port through which hydraulic oil for driving an actuator flows, an outlet port connected to a tank, A return passage connected to the outlet port and through which return oil from the actuator flows, an upper pilot port and a lower pilot port for allowing pilot pressure oil of the switching spool to act from above or below; In a hydraulic pilot switching valve having a switching spool arranged to move vertically in a vertical direction, a pilot oil passage is connected to a pilot oil chamber of an upper pilot port so as to connect the pilot oil chamber to the return passage. Is installed in the valve body. Acts when moving toward the switching spool to the upper pilot chamber, characterized by being configured to communicate opened to.

In this case, the pilot oil passage connecting the pilot oil chamber of the upper pilot port to the return passage connected to the outlet port is provided with a switching spool located between the pilot oil chamber and the return passage. An orifice can be formed by the spool hole and the groove formed on the circumference of the spool land inserted into the spool hole.

It is preferable that the pilot oil passage connecting the pilot oil chamber of the upper pilot port to the return passage connected to the outlet port has a communication opening near the stroke end of the switching spool. .

In the hydraulic pilot type switching valve according to the present invention, the pilot oil chamber of the upper pilot port and the return passage connected to the outlet port are communicatively connected.
By forming the pilot oil passage in the spool, the oil remaining in the pilot oil chamber together with the oil flowing in the pilot oil passage from the return passage toward the pilot oil chamber can be provided without providing additional piping equipment. Can flow out smoothly.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a hydraulic pilot switching valve according to an embodiment of the present invention. For convenience of description, the same components as those of the conventional configuration shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

First, the configuration of the hydraulic pilot type switching valve in this embodiment is basically the same as the conventional configuration shown in FIG. Therefore, the description will be briefly repeated once again. Referring to FIG. 1, the hydraulic pilot type switching valve 10 of the present embodiment basically includes a valve body 11 provided on a body frame 13. In contrast, an inlet port 12, a center bypass passage 14, a return passage 16, and an outlet port 18 through which hydraulic oil supplied from the main pump 30 to the actuator 40 flows in the lateral direction are provided. An upper pilot port 22 and a lower pilot port 24 are provided for applying pilot pressure oil to the spool 20 from above or below. And the two pilot ports 22,
Between 24, the switching spool 20 is arranged to move vertically in the vertical direction.

Therefore, the operation lever 50 of the remote control valve 50
is operated, for example, to the left, the operation lever 50a
Pilot pressure oil having a pressure proportional to the operation angle of the above acts on the pilot oil chamber 22a of the upper pilot port 22 from one of the pilot lines 54a to a position where the generated force balances with the resilient force of the spring 20d. Then, the switching spool 20 is moved downward in the figure.

At this time, the supply passage 26a connected to the inlet port 12 of the switching valve 10 communicates with the cylinder port 42a, the cylinder port 42b communicates with the return passage 16, and the center bypass passage 14 and the return passage 16 communicate with each other. Is reduced by the center groove 43 provided on the switching spool 20, the flow rate from the center bypass passage 14 to the return passage 16 is reduced, and the reduced amount of hydraulic oil is supplied from the supply passage 26a to the cylinder It is supplied to the actuator 40 via the port 42a and the actuator line 44a. The return oil from the actuator 40 is returned from the actuator line 44b to the tank 36 via the cylinder port 42b, the return passage 16, the outlet port 18, and the tank line 34, further passes through the cooler 34a and the filter 34b.

In this embodiment, however, in the above configuration, as shown in an enlarged view in FIG. 2, it is located between the pilot oil chamber 22b of the upper pilot port 22 and the return passage 16 connected to the outlet port 18. , The switching spool 20 inserted into the spool hole 62b formed in the valve body 11
A groove 62 a is provided on the circumference of the spool land 60.
When the operation lever 50a of the remote control valve 50 is operated rightward to press the pilot oil chamber 24b of the lower pilot port 24 and the switching spool 20 moves upward, this groove 62a Pilot oil chamber 22b of lower pilot port 22 and return passage 16
Is formed so as to form a pilot oil passage 62 that connects the Therefore, the groove 62 a forming the pilot oil passage 62 is provided with the spool hole 62 b provided in the valve body 11.
Are formed as orifices with a small opening area.

Therefore, in this case, in a general construction machine, the discharge oil of the main pump 30 or the actuator 4 returning from the outlet port 18 of the switching valve 10 to the tank 36 is used.
The flow rate of the return oil from 0 is a relatively large flow rate, and is usually about 0 in the outlet port 18 and the return passage 16 connected thereto due to the flow path resistance of the tank line 34, the cooler 34a, the filter 34b and the like. A back pressure of 0.5 MPa has developed. On the other hand, unless the pressure in the upper pilot port 22 and the lower pilot port 24 is increased by the remote control valve 50, no oil flows from the pilot ports 22 and 24 to the remote control valve 50. That is, it is equal to the atmospheric pressure.

Next, a description will be given of the air bleeding operation and the operation of the switching valve of this embodiment having the above-described configuration.

Cover 22a of upper pilot port 22
And / or when air accumulates (accumulates) in the pilot oil chamber 22b,
0a is tilted rightward from the state shown in FIG. As a result, the pilot pressure oil from the pilot pump 52 flows from the pilot line 54b below in the figure.
Acting in the pilot oil chamber 24b of the lower pilot port 24, the switching spool 20 is moved upward in the figure.

As shown in FIG. 2, when the switching spool 20 rises to the vicinity of its stroke end, the pilot oil passage 62 opens as described above, and
2a and the pilot oil chamber 2 through the spool hole 62b.
2b communicates with the return passage 16. At this time, since the pressure in the return passage 16 is about 0.5 MPa and the pressure in the pilot oil chamber 22b is atmospheric pressure, a part of the discharge oil of the main pump 30 or the return oil from the actuator 40 (ΔQ) represents the return passage 16 from the spool hole 62b and the groove 62a (the pilot oil passage 62), the pilot oil chamber 22b, the gap between the cover 22a and the guide 20b, the upper pilot port 22, the pilot line 54.
After that, the air is returned to the tank 36 via the tank line 56 of the remote control valve 50 shown in FIG. Therefore, along with this oil, the upper pilot port 22
The air 64 staying in the cover 22a and / or the pilot oil chamber 22b can flow out to the tank 36.

The opening area of the orifice formed by the groove 62a and the spool hole 62b forming the pilot oil passage 62 is set to be small so that a small flow of oil through which air can flow out can flow. Therefore, the back pressure generated in the pilot oil chamber 22b due to the flow path resistance of the pilot line 54a and the remote control valve 50 and the like becomes negligibly low. In addition, since the switching valve 10 controls the bleed-off flow rate in many cases as described above, after the center groove 43 of the switching spool 20 blocks the center bypass passage 14 and the return passage 16, Until the end of the stroke of the spool 20,
The flow control performance does not depend on the position of the spool 20.
Therefore, the timing at which the groove 62a of the pilot oil passage 62 is opened to the pilot oil chamber 22b is determined by the switching spool 2
If it is set near the stroke end of 0, even if a slight back pressure occurs in the pilot oil chamber 22b, the flow control performance does not deteriorate in practical use.

On the contrary, when the operation lever 50a of the remote control valve 50 is tilted leftward, the pilot pressure oil from the pilot pump 52 is supplied from the pilot line 54a to the pilot oil chamber 22b of the upper pilot port 22. To move the switching spool 20 downward in the figure (see FIG. 1). In this case, since the space between the pilot oil chamber 22b and the return passage 16 is blocked by the spool land 60 of the spool 20, the discharge oil of the pilot pump 52 or the accumulated oil of the accumulator 58 returns from the pilot oil chamber 22b. The amount of oil leaking into the passage 16 is extremely small. Therefore, according to the present embodiment,
It is not necessary to increase the capacity of the accumulator 58.

As described above, according to the present invention, it is possible to easily and reliably achieve air bleeding in the valve body 11 only by forming the pilot oil passage 62 by drilling it in the valve body 11. it can. In addition, in this case, since the configuration is simple, there is no need for additional equipment as in the prior art, and the workability of maintenance and replacement by pulling out the switching spool 20 is not impaired.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and many design changes can be made without departing from the spirit of the present invention.

[0034]

As described above, the hydraulic pilot type switching valve according to the present invention has an inlet port into which hydraulic oil for driving an actuator flows, an outlet port connected to a tank, and a port connected to the outlet port. A return passage through which return oil from the actuator flows, an upper pilot port and a lower pilot port for allowing pilot pressure oil of the switching spool to act from above or below, and the switching spool is vertically moved between the two pilot ports. In a hydraulic pilot switching valve arranged to move vertically in the direction, a pilot oil passage is provided in the valve body so as to connect the pilot oil chamber and the return passage to the pilot oil chamber of the upper pilot port. This pilot oil passage is switched by the pilot pressure oil acting on the lower pilot chamber. When the valve is moved toward the upper pilot chamber, the opening of the communication port is opened, so that air in the valve body can be easily and reliably achieved with a simple configuration just by drilling a pilot oil passage. And without the need for additional equipment as before.
Enables smooth air release.

Therefore, according to the switching valve of the present invention, air can be easily and reliably achieved with a simple structure without losing the workability of maintenance and replacement of the switching spool. The responsiveness of this type of switching valve can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part and a control system diagram showing an embodiment of a hydraulic pilot type switching valve according to the present invention.

FIG. 2 is an enlarged sectional view showing a state near a rising stroke end of a switching spool of an upper pilot port shown in FIG. 1;

FIG. 3 is a sectional view of a main part showing a conventional hydraulic pilot type switching valve and a control system diagram thereof.

[Explanation of symbols]

 Reference Signs List 10 switching valve 11 valve body 12 inlet port 13 body frame 14 center bypass passage 16 return passage 18 exit port 20 switching spool 20a cap 20b guide 20c stopper 20d spring 22 upper pilot port 22a cover 22b upper pilot oil chamber 24 lower pilot port 24a cover 24b Lower pilot oil chamber 30 Main pump 32 Pump line 34 Tank line 34a Cooler 34b Filter 36 Tank 40 Actuator 42a, 42b Cylinder port 43 Center groove 44a, 44b Actuator line 50 Remote control valve 50a Operating lever 52 Pilot pump 54a, 54b Pilot line 56 Tank line 58 Accumulator 60 Spool land 62 Pilot oil passage 62 Grooves 62b spool hole 64 air

Claims (3)

[Claims] 1. An inlet port through which hydraulic oil for driving an actuator flows, an outlet port connected to a tank, a return passage connected to the outlet port and through which return oil from the actuator flows, and a switching spool. An upper pilot port and a lower pilot port for applying pilot pressure oil from above or below,
In a hydraulic pilot type switching valve having a switching spool arranged vertically to move vertically between the two pilot ports, a pilot oil chamber of an upper pilot port is connected to the pilot oil chamber and the return passage. The pilot oil passage is provided in the valve body so that the pilot oil passage opens when the pilot pressure oil acts on the lower pilot chamber to move the switching spool toward the upper pilot chamber. A hydraulic pilot type switching valve characterized by the above-mentioned. 2. A pilot oil passage which connects a pilot oil chamber of an upper pilot port to a return passage connected to an outlet port, a spool hole of a switching spool located between the pilot oil chamber and the return passage. 2. The hydraulic pilot-operated switching valve according to claim 1, wherein an orifice is constituted by a groove formed on a circumference of a spool land inserted into the spool hole. 3. The pilot oil passage connecting the pilot oil chamber of the upper pilot port to the return passage connected to the outlet port is configured to open in the vicinity of the stroke end of the switching spool. The described hydraulic pilot type switching valve.