WO2016047322A1

WO2016047322A1 - Switching valve

Info

Publication number: WO2016047322A1
Application number: PCT/JP2015/073387
Authority: WO
Inventors: 中村　雅之
Original assignee: Ｋｙｂ株式会社
Priority date: 2014-09-22
Filing date: 2015-08-20
Publication date: 2016-03-31
Also published as: JP2016061427A

Abstract

A switching valve is provided with: a valve body (B); a spool (S) mounted in the valve body (B) in a slidable manner; and two pilot chambers (1, 2) toward which the ends of the spool (S) face. The position of the spool (S) is changed by the pressure of operating fluid conducted to the two pilot chambers (1, 2). The spool (S) has a communication hole (14) formed extending in the axial direction. The communication hole (14) is provided with a single orifice (15), and the two pilot chambers (1, 2) are in communication with each other through the communication hole (14).

Description

Switching valve

This invention relates to a switching valve having both ends of a spool facing a pilot chamber.

This type of switching valve may accumulate air in the pilot chamber or pilot piping during the assembly process. If the air in the pilot chamber or the pilot piping is left unattended, the responsiveness at the time of switching the spool is deteriorated, or the operator's operation is uncomfortable. Therefore, as disclosed in JP 2004-293735A, a structure for removing air from the pilot chamber has been proposed.

In the switching valve described in JP2004-293735A, an air vent passage that connects the pilot chamber and the reflux passage is formed on the surface of the spool between the reflux passage and the pilot chamber. Therefore, for example, as in the switching valve described in JP2005-127467A, even if an attempt is made to form a signal passage on the inner surface of the spool hole between the recirculation passage and the pilot chamber, the air vent passage is obstructed. I can't. Thus, the conventional switching valve also has a problem that the degree of freedom in design is limited.

This invention is intended to provide a switching valve in which the degree of freedom of design is not limited.

According to an aspect of the present invention, there is provided a switching valve in which the position of the spool is switched by the pressure of the working fluid guided to the pilot chamber, the valve body, a spool slidably incorporated in the valve body, Two pilot chambers facing the end surfaces, the spool has a communication hole formed through one axial orifice and penetrating in the axial direction, and the two pilot chambers have a switching valve communicating through the communication hole. Provided.

FIG. 1 is a cross-sectional view of a switching valve according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a switching valve of a comparative example.

Hereinafter, a switching valve according to an embodiment of the present invention will be described with reference to the drawings.

In the switching valve according to the embodiment of the present invention shown in FIG. 1, the spool S is slidably incorporated in the valve body B, and both ends of the spool S face the pilot chambers 1 and 2.

The pilot chambers 1 and 2 are connected to the pilot valve 16, and by operating the lever of the pilot valve 16, one pilot chamber 1 is connected to the pilot pump 17, and the other pilot chamber 2 is connected to the tank 19 through the drain passage 18. Communicate.

When operating oil from the pilot pump 17 is introduced into one pilot chamber 1 by operating the pilot valve 16, the spool S is switched to the right in the drawing by the pressure of the operating oil. At this time, the other pilot chamber 2 is connected to the drain passage 18 through the pilot valve 16.

When the spool S is switched to the right in the drawing, a pressure fluid from a main pump (not shown) flows into the supply passage 7 and the pressure fluid guided to the supply passage 7 is supplied to the load check valve 8, the relay passage 9, and the spool S. Then, it is guided to one actuator port 11 via the first annular groove 10 formed in.

At this time, the return fluid flowing into the other actuator port 12 is returned to the reflux passage 6 via the second annular groove 13 formed in the spool S. On the other hand, when the spool S is switched in the opposite direction, that is, the left direction in the drawing, the pressure fluid guided to the supply passage 7 is guided to the actuator port 12 through the load check valve 8, the relay passage 9, and the second annular groove 13, The return fluid flowing into the actuator port 11 is returned to the reflux passage 5 via the first annular groove 10.

Further, the spool S is formed with a communication hole 14 penetrating in the axial direction. The communication hole 14 is provided with one orifice 15, and the pilot chambers 1 and 2 communicate with each other through the communication hole 14. For this reason, the hydraulic oil guided from the pilot pump 17 to one pilot chamber flows into the other pilot chamber via the communication hole 14 and the orifice 15.

In the switching valve having the above-described configuration, when the air in the pilot chambers 1 and 2 is extracted, the hydraulic oil is guided from the pilot pump 17 to one pilot chamber 1. The hydraulic fluid guided to the pilot chamber 1 flows into the other pilot chamber 2 through the communication hole 14 and the orifice 15, and is discharged to the tank 19 through the other pilot chamber 2, the pilot valve 16 and the drain passage 18. .

Next, the switching valve of the comparative example shown in FIG. 2 will be described.

The switching valve of the comparative example shown in FIG. 2 has the same basic configuration as the switching valve according to the present embodiment shown in FIG. That is, the spool S is slidably incorporated in the valve body B, and both ends of the spool S face the pilot chambers 1 and 2.

The switching valve of the comparative example is different from the switching valve according to the present embodiment in the following points.

The air vent passages 3 and 4 are provided at both ends of the spool S of the switching valve of the comparative example. One opening 3a, 4a of the air vent passages 3, 4 is always open to the pilot chambers 1, 2, and the other opening 3b, 4b is a tank when the spool S is stroked to some extent from the illustrated neutral position. Open to the

reflux passages

5 and 6 communicating with each other. In addition, orifices 3c and 4c are provided in the passages connecting the openings 3a and 4a and the

openings

3b and 4b, respectively.

In the switching valve of the comparative example, when the air in the pilot chambers 1 and 2 is extracted, the working fluid is guided to the pilot chambers 1 and 2 and the spool S is stroked to some extent from the neutral position to Are opened to the

reflux passages

5 and 6. When the

other openings

3b and 4b of the air vent passages 3 and 4 open to the

reflux passages

5 and 6 in this way, the working fluid guided to the pilot chambers 1 and 2 passes through the orifices 3c and 4c. Flows out to 5 and 6. By such a flow of the working fluid, the air in the pilot chamber is discharged to the tank through the

return passages

5 and 6.

In the switching valve of the comparative example, air vent passages 3 and 4 are formed for the pilot chambers 1 and 2, respectively, and orifices 3c and 4c are provided in the air vent passages 3 and 4, respectively. Therefore, the opening diameters of both the orifices 3c and 4c must be made equal. If the opening diameters of both the orifices 3c and 4c are different, the flow rate of the working fluid flowing out for air bleeding is different, and therefore the amount of movement of the spool may be different even if the lever of the pilot valve 16 is operated by the same amount. There is. For this reason, when an operator performs operation, there exists a possibility of feeling uncomfortable.

In order to prevent such a phenomenon from occurring, the opening diameters of both the orifices 3c and 4c must be completely matched, and high machining accuracy is required. However, in order to increase the processing accuracy of the fine opening diameter, there is a problem that the processing takes time and productivity is inferior. As a solution to this problem, there is a switching valve described in JP2004-293735A shown as a conventional switching valve.

This conventional switching valve connects the pilot chamber and the return passage when the spool is fully stroked. In the configuration in which the pilot chamber and the return passage are communicated with each other when the spool is fully stroked, even if the opening diameters of the orifices provided in the communication passage are slightly different, the operator is hardly discomforted. This is because when the spool is fully stroked, the pilot flow rate is large, so even if there is a slight difference in the flow rate flowing between the pilot chamber and the return passage, the amount of movement of the spool is not significantly affected.

However, the following problems occur when a warm-up operation is performed on a system that employs a switching valve of a comparative example or a conventional switching valve. For example, in the warm-up operation, pilot pressure is guided to the pilot chamber to switch the spool, and the hydraulic oil is circulated while operating the actuator, and the hydraulic oil is warmed in the circulation process. In a situation where warm-up operation is required, the outside air temperature is low, the temperature of the hydraulic oil is lowered, and the viscosity of the hydraulic oil is increased. In addition, since the return passage provided in the valve body of the switching valve communicates with the tank via the return passage of the valve body of the other switching valve, the flow path becomes complicated and the length to the tank is increased. As a result, the pressure of the hydraulic oil flowing through the reflux passage during the warming-up operation increases.

When the pressure in the reflux passage is high and the viscosity of the hydraulic fluid is high, the hydraulic fluid guided to the pilot chamber is difficult to flow into the reflux passage. As a result, the hydraulic oil guided to the pilot chamber only moves back and forth between the tank and the pilot chamber by the amount corresponding to the volume change of the pilot chamber, and the air venting of the pilot chamber becomes incomplete, The hydraulic oil having a low temperature remains in the pilot chamber, and the warming property of the hydraulic oil also decreases.

Further, in the switching valve of the comparative example shown in FIG. 2, the pressure in the pilot chambers 1 and 2 connected to the drain passage 18 of the pilot valve 16 is lower than the pressure in the

reflux passages

5 and 6, and the working oil is recirculated. There is a risk of backflow from the

passages

5 and 6 to the pilot chambers 1 and 2. The reason is as follows. The

reflux passages

5 and 6 formed in the valve body B communicate with the tank 19 via the reflux passages in the valve bodies of other switching valves. For this reason, the pressure loss in the entire recirculation passage increases, and the pressure in the recirculation passage increases.

On the other hand, when the switching amount of the switching valve is small, that is, when the pressure in the pilot chambers 1 and 2 is small, the pressure in the pilot chambers 1 and 2 is lower than the pressure in the

reflux passages

5 and 6.

When hydraulic fluid flows backward from the

return passages

5 and 6 to the pilot chambers 1 and 2 due to the pressure difference between the pilot chambers 1 and 2 and the

return passages

5 and 6, the pressure in the

return passages

5 and 6 acts on one end of the spool S. . If the pressure in the

reflux passages

5 and 6 acts on one end of the spool S when the switching valve is in the neutral position, the spool may be displaced by the pressure and the actuator may malfunction.

The above-described problems occur in the switching valve of the comparative example, whereas these problems can be solved in the switching valve according to the present embodiment.

In the switching valve according to the present embodiment, as described above, the hydraulic oil flows between the pilot chambers 1, 2 and the tank 19, so that the air remaining in the pilot chambers 1, 2 is Open to the atmosphere. Further, since the drain passage 18 is used as the passage from the pilot valve 16 to the tank 19, the pressure loss during the passage can be kept small. Therefore, a flow easily occurs in the communication hole 14 and the orifice 15, and the air remaining in the pilot chambers 1 and 2 can be reliably discharged.

Further, the orifice 15 equally applies resistance to the hydraulic fluid flowing between the pilot chambers 1 and 2, so that when the hydraulic fluid is guided to the pilot chambers 1 and 2 to switch the spool S to the left and right, the operator 15 Does not give a sense of incongruity.

Further, since only one orifice 15 is required, it is not necessary to provide an orifice for each pilot chamber 1 and 2 like the switching valve of the comparative example shown in FIG. Therefore, the manufacturing cost of the switching valve can be reduced. Further, unlike the switching valve of the comparative example, the problem of processing that the opening diameters of the respective orifices have to be matched does not occur.

Furthermore, in the switching valve according to the present embodiment, the communication hole 14 for communicating the pilot chambers 1 and 2 is formed so as to penetrate in the axial direction of the spool S, and the orifice 15 is provided in the communication hole 14. For this reason, it is not necessary to perform special processing for air bleeding on the outer peripheral surface of the spool S and the inner peripheral surface of the spool hole of the valve body B. Therefore, for example, a signal passage can be formed on the outer peripheral surface of the spool S and the inner peripheral surface of the spool hole of the valve body B, and the degree of freedom in design can be improved.

Further, since the working fluid flowing from one pilot chamber to the other pilot chamber flows out to the tank 19 through the drain passage 18, the pressure is higher than when returning to the tank 19 through the

reflux passages

5 and 6 provided in the valve body B, for example. Loss is kept small and hydraulic oil flows easily. Therefore, during the warming-up operation, the working fluid guided to one pilot chamber flows to the tank 19 through the other pilot chamber, and therefore, it is possible to suppress the operation oil having a low temperature between the pilot valve and the pilot chamber.

Furthermore, since air can be vented through the communication hole 14 that communicates both the pilot chambers 1 and 2, it is not necessary to connect the pilot chambers 1 and 2 to the

reflux passages

5 and 6 for air venting. Since the pilot chambers 1 and 2 and the

return passages

5 and 6 do not communicate with each other in this way, the pressure in the

return passages

5 and 6 does not act on the spool S. Therefore, it is possible to prevent the actuator from malfunctioning due to the pressure of the

reflux passages

5 and 6 acting on the spool S.

It should be noted that the position where the orifice 15 is provided is not limited to the center of the spool S, and may be any position in the communication hole 14. Further, the configuration of the switching valve is not limited to the above configuration, and the present invention can be applied as long as the switching valve has a type in which both ends of the spool face the pilot chamber.

The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

This application claims priority based on Japanese Patent Application No. 2014-192423 filed with the Japan Patent Office on September 22, 2014, the entire contents of which are incorporated herein by reference.

Claims

A switching valve whose position is changed by the pressure of the working fluid guided to the pilot chamber,
A valve body;
The spool slidably incorporated in the valve body;
Two pilot chambers facing each end face of the spool, and
The spool has a communication hole provided with one orifice and penetrating in the axial direction.
The two pilot chambers are switching valves that communicate with each other through the communication hole.
The switching valve according to claim 1,
In response to switching of the pilot valves connected to the two pilot chambers, one of the two pilot chambers is connected to a pilot pump, and the other pilot chamber communicates with a tank. A switching valve connected to the drain passage.