JP5984720B2 - Unload valve device - Google Patents

Description

  The present invention relates to an unload valve device that opens when a circuit pressure reaches a predetermined pressure.

As this type of unloading valve device, the one described in Patent Document 1 has been conventionally known. A circuit diagram of this conventional device is shown in FIG. 3 of this application, and a cross-sectional view of a device substantially identical to the conventional device is shown in FIG.
The circuit diagram shown in FIG. 3 shows a load sensing control device, and the variable displacement pump P is provided with a regulator 1 for controlling the tilt angle. An unload valve device A connected to the discharge side of the variable displacement pump P is provided.

The unloading valve device A includes a valve body 2, one pilot chamber 3 facing one end face of the valve body 2, the other pilot chamber 4 facing the other end face of the valve body 2, And a spring 5 provided in the other pilot chamber 4.
The one pilot chamber 3 communicates with the discharge side of the variable displacement pump P via the passage 6, and the other pilot chamber 4 communicates with the introduction passage through which the loads of the cylinders 8 and 9 are introduced via the pilot passage 7. 10, a point where the pilot passage 7 and the introduction passage 10 meet is a joining point 11.

  Further, an orifice 12 is provided on the downstream side with respect to the flow of the pressure fluid flowing toward the pilot chamber 1a of the regulator 1, and an orifice 13 is provided on the upstream side. By providing the orifices 12 and 13 in this way, pressure is prevented from acting on the pilot chamber 1a of the regulator 1 abruptly.

  The unload valve device A communicates the passage 6 communicating with the discharge side of the variable displacement pump P with the tank T or shuts off the communication. The illustrated closed position (a) is maintained. When the total pressure of the pressure of the other pilot chamber 4 and the spring force of the spring 5 overcomes the pressure of the one pilot chamber 3, it switches to the open position (b), and the variable displacement pump P and the tank Communicate with T.

  For example, when the switching valves 14 and 15 are switched and the pressure fluid from the variable displacement pump P is supplied to the cylinders 8 and 9, the maximum load pressure at that time is selected by the shuttle valve 16 and introduced into the introduction passage 10. It is written. The pressure guided to the introduction passage 10 acts on the pilot chamber 1a of the regulator 1 and the other pilot chamber 4 of the unload valve device A.

At this time, the unload valve device A keeps the closed position (a) by the pressure of the other pilot chamber 4 and the spring force of the spring 5 and shuts off the communication between the variable displacement pump P and the tank T.
If the switching valves 14 and 15 are closed and the load on the cylinders 8 and 9 is made zero, the pressure in the other pilot chamber 4 is also zero. At this time, the valve body 2 is connected to the variable displacement pump P. It switches to the open position (b) by the action of the discharge pressure required to discharge the standby flow rate, and the discharge fluid of the variable displacement pump P is guided to the tank T.

FIG. 4 shows a specific configuration of the unload valve device A. The valve body B of this conventional unloading valve device A is formed with a circuit pressure introduction port 17 connected to the discharge side of the variable displacement pump P through the passage 6 and a tank port 18 communicating with the tank. ing.
Further, a valve body 2 made of a spool is incorporated in the valve body B, and one end face of the valve body 2 faces one pilot chamber 3 and the other end face faces the other pilot chamber 4.

The other pilot chamber 4 is closed with a plug 19, and a spring 5 is interposed between the plug 19 and the valve body 2.
In addition, a passage 20 is formed in the plug 19, and the downstream orifice 12 is provided in the passage 20. Therefore, the other pilot chamber 4 communicates with the pilot chamber 1 a of the regulator 1 via the passage 20 and the orifice 12 provided in the passage 20.

Further, a passage 21 communicating with the introduction passage 10 is formed in the valve body B, and the passage 21 is communicated with the other pilot chamber 4. The upstream orifice 13 is provided in the passage 21.
When the valve body 2 is in the illustrated position, that is, the closed position (a), the communication between the circuit pressure introduction port 17 and the tank port 18 is blocked.

  Further, when the cylinders 8 and 9 are operating, the pressure fluid led to the introduction passage 10 reaches the other pilot chamber 4 from the passage 21 through the upstream orifice 13 and further, the other pilot. The chamber 4 is introduced into the pilot chamber 1 a of the regulator 1 through the passage 20 and the downstream orifice 12 provided in the passage 20. In other words, in the configuration of FIG. 4, the passage 21, the other pilot chamber 4, and the passage 20 are combined to bear a part of the introduction passage 10.

The reason why the two orifices 12 and 13 are provided as described above is as follows.
For example, if the fluctuation of the load pressure of the cylinders 8 and 9 is directly transmitted to the pilot chamber 1a of the regulator 1, shock and hunting will occur when the cylinders 8 and 9 are started. Therefore, the orifices 12 and 13 are provided to positively delay the response of the variable displacement pump P at the start-up, thereby preventing the occurrence of shock and hunting.

However, the reason why the two orifices 12 and 13 are provided as described above is to make the openings of these orifices 12 and 13 large. That is, since the flow rate flowing through the introduction passage 10 is extremely small, if only the downstream orifice 12 is used, the desired effect cannot be exhibited unless the opening of the orifice 12 is made extremely small. However, if the opening of the orifice 12 is made as small as possible, this time, there arises a problem that foreign matter is easily clogged in the orifice 12. Moreover, if the opening of the orifice 12 is made small, the problem that the responsiveness becomes too bad at a low temperature when the viscosity of the hydraulic oil is large also occurs.
Therefore, the downstream orifice 12 and the upstream orifice 13 are provided as described above, and these orifices 12 and 13 are combined to function as one orifice.

  Under the above configuration, when the switching valves 14 and 15 are in the closed position and the actuators 8 and 9 are not operating, the pressure guided to the introduction passage 10 and the pilot chamber 1a becomes zero or Become close. When the pilot pressure guided to the pilot chamber 1a is zero or close to it, the regulator 1 keeps the discharge amount of the variable displacement pump P at the standby flow rate. If the pressure in the introduction passage 10 is zero as described above, the pressure action of the other pilot chamber 4 in the unload valve device A is also zero or close thereto.

  At this time, a pressure necessary for discharging the standby flow rate acts on one pilot chamber 3 of the unload valve device A. Therefore, in the unload valve device A, the valve element 2 moves to the left in FIG. 4 against the spring 5 by the pressure action of one pilot chamber 3, and switches to the open position (b) side. In the open position (b), the circuit pressure introduction port 17 and the tank port 18 communicate with each other through the notch 2a of the valve body 2, so that the standby flow rate is unloaded to the tank T. Therefore, the standby flow rate continues to be discharged from the variable displacement pump P.

  When the switching valves 14 and 15 are switched from the above state, the fluid discharged from the variable displacement pump P is supplied to the cylinders 8 and 9. When the fluid is supplied to the cylinders 8 and 9 in this way, the load pressure is guided to the pilot chamber 1a of the regulator 1 as a pilot pressure. Therefore, the regulator 1 increases the discharge capacity of the variable displacement pump P according to the pilot pressure, which is controlled so that the pump discharge pressure is always higher than the maximum load pressure derived as the pilot pressure. . At this time, the unload valve device A is switched from the open position (b) to the closed position (a).

That is, the valve body 2 moves rightward in FIG. 4 and the notch 2a returns to the position shown in FIG. 4 to block the communication between the circuit pressure introduction port 17 and the tank port 18. At this time, the volume of the pilot chamber 4 is substantially increased by the amount the valve body 2 is removed from the other pilot chamber 4. The pilot flow rate via the upstream orifice 13 flows into the pilot chamber 4 whose volume has increased. Thus, since the flow rate corresponding to the increase in the volume of the other pilot chamber 4 becomes relatively large, a sufficient pressure drop can be caused without making the opening of the upstream orifice 13 so small. .
In the figure, reference numerals 22 and 23 are pressure compensation flow control valves provided downstream of the switching valves 14 and 15, respectively.

JP 2007-092774 A

  In the conventional unloading valve apparatus as described above, the other pilot chamber 4 serves as a part of the introduction passage 10, so that a relatively high-pressure fluid flows through the other pilot chamber 4. For this reason, the spring 5 provided in the other pilot chamber 4 is exposed to the flow of the high-pressure fluid, so that the spring 5 is affected by the pressure and flow of the high-pressure fluid and is distorted or bent. . When the spring 5 is distorted or bent, the initial spring force is not exerted, and there arises a problem that the opening / closing characteristics of the valve body 2 are adversely affected.

  An object of the present invention is to provide an unload valve device in which the spring of the other pilot chamber is not exposed to the flow of high-pressure fluid and can always exert a stable spring force.

  The first invention includes the following components. That is, the valve body, the circuit pressure introduction port formed in the valve body, the tank port formed in the valve body, and the valve body are incorporated into the valve body to communicate the circuit pressure introduction port and the tank port. Or a valve body that cuts off the communication thereof, one pilot chamber that is formed in the valve body, faces one side of the valve body, and is guided by the pressure of the circuit pressure introduction port, and the valve The other pilot chamber that is provided in the main body and faces the other surface of the valve body, and is interposed in the other pilot chamber, and a spring force is applied to the valve body so that the circuit pressure introduction port and the tank A spring that holds the valve element at a position where communication with the port is blocked, and one end is opened in the other pilot chamber, and the other end is provided separately from the valve body. The pilot passage connected to the control means, the first orifice provided between the pilot passage and the load pressure introduction passage for introducing the load pressure, and the flow from the load pressure introduction passage to the control means And a second orifice provided at a position downstream of the first orifice.

  According to a second aspect of the present invention, the pilot passage is provided with a third orifice in parallel with the second orifice with respect to the first orifice, and the third orifice serves to change the pressure in the other pilot chamber. On the other hand, it is configured to exhibit a damping effect.

  In a third aspect of the invention, the pilot passage and the first and second orifices are provided in a cartridge, and the cartridge is assembled to the valve body.

  According to a fourth aspect of the invention, the cartridge is provided with a third orifice in addition to the first and second orifices.

  According to a fifth aspect of the present invention, the spring pilot is provided in the other pilot chamber, the spring is interposed between the spring guide and the valve body, and an adjuster for moving the spring guide in the axial direction of the valve body is provided. The configuration is provided.

  According to the first invention, the high-pressure fluid guided to the pilot passage can be guided to the control means without passing through the other pilot chamber. Is not exposed to the flow of Therefore, a stable spring force can always be exhibited, and the opening characteristics of the valve body are also stable.

  Further, when the valve body moves to the closed position with respect to the other pilot chamber, the substantial volume of the other pilot chamber expands, but since the flow rate corresponding to the expanded volume flows to the other pilot chamber, As in the prior art, the orifice opening need not be so small.

  According to the second invention, since the third orifice is provided in addition to the first and second orifices, a damping effect on the other pilot chamber can be expected by the third orifice, and the valve body can be stabilized. Can be operated.

  According to the third and fourth aspects of the present invention, the pilot passage and the first and second orifices or the first to third orifices are provided in the cartridge. Or the first to third orifices can be easily provided.

  According to the fifth aspect of the invention, since the adjuster for adjusting the spring force of the spring is provided, the standby flow rate of the variable displacement pump can be adjusted by adjusting the spring force of the spring.

It is sectional drawing of 1st Embodiment. It is sectional drawing of 2nd Embodiment. It is the figure which showed the load sensing circuit incorporating the conventional unloading valve apparatus. It is sectional drawing of the conventional unloading valve apparatus.

  FIG. 1 shows an unload valve device A according to the first embodiment, and the positioning in the load sensing circuit is the same as in the prior art. Therefore, the following description will be made on the assumption that the unload valve device A is used in the load sensing circuit shown in FIG. 3, and the same components as in FIG. I will explain.

The valve body B is formed with a circuit pressure introduction port 24 that communicates with the variable displacement pump P through the passage 6 and a tank port 25 that communicates with the tank T.
Then, the valve body B is assembled with a spool 26 which is a valve body of the present invention. One end face of the spool 26 faces one pilot chamber 27 and the other end face faces the other pilot chamber 28. Yes.

A spring guide 29 is slidably incorporated in the other pilot chamber 28, and a spring 30 is interposed between the spring guide 29 and the spool 26. The spring guide 29 thus configured includes a piston portion 29a slidable with respect to the other pilot chamber 28, and a rod-shaped guide portion 29b protruding from the piston portion 29a toward the spool 26 side. The guide portion 29b is protruded into the spring 30.
In the figure, reference numeral 31 denotes a seal member provided around the piston portion 29a.

In addition, an adjuster 32 is provided outside the piston portion 29a opposite to the spool 26, and the adjuster 32 is rotated to move the piston portion 29a in the axial direction so that the spring force of the spring 30 can be adjusted. ing.
Further, the valve body B is provided with a plug 33 constituting the cartridge of the present invention. The plug 33 is formed with a pilot passage 34 having one end opened in the other pilot chamber 28. The other end of the pilot passage 34 is connected to the pilot chamber 1a of the regulator 1 of the variable displacement pump P.

  A first orifice 35 corresponding to the upstream orifice 13 in the circuit diagram of FIG. The pilot passage 34 and the load pressure introduction passage 36 are communicated with each other through the first orifice 35 thus configured. The load pressure introduction passage 36 communicates with the introduction passage 10 connected to the shuttle valve 16. Therefore, the load pressure of the cylinders 8 and 9 is guided to the pilot passage 34 via the first orifice 35.

  Further, the plug 33 is provided with a second orifice 37 corresponding to the downstream orifice 12 in the circuit diagram of FIG. The second orifice 37 is provided downstream of the first orifice 35 with respect to the flow flowing from the load pressure introduction passage 36 toward the pilot chamber 1 a of the regulator 1.

Next, the operation of the first embodiment will be described.
In a state where the pressure action of the other pilot chamber 28 and the action force of the spring 30 are overcome with respect to the pressure action of the one pilot chamber 27, the spool 26 maintains the illustrated closed position and the circuit pressure introduction port The communication between the tank 24 and the tank port 25 is blocked.

  When the switching valves 14 and 15 in the circuit diagram of FIG. 3 are switched and pressure fluid is supplied to the cylinders 8 and 9 as actuators, the discharge pressure of the variable displacement pump P at that time is supplied from the passage 6 to the circuit pressure introduction port 24 To the one pilot chamber 27. Accordingly, a force against the spring 30 acts on one end surface of the spool 26.

  On the other hand, the fluid flowing into the load pressure introduction passage 36 via the shuttle valve 16 is guided to the pilot chamber 1a of the regulator 1 through the first orifice 35, the pilot passage 34, and the second orifice 37, and the cylinder 8 , 9 is applied to the pilot chamber 1a, and the variable displacement pump P is tilted so that the discharge pressure of the variable displacement pump P is higher than the load pressure of the cylinders 8, 9. Control the corners.

  However, when the cylinders 8 and 9 are operated as described above, since the load pressure is guided to the other pilot chamber 28, the total acting force of this load pressure and the spring force of the spring 30 is the above one. The state in which the acting force of the pump discharge pressure in the pilot chamber 27 is overcome is maintained. Therefore, when the cylinders 8 and 9 are operated as described above, the spool 26 maintains the illustrated closed position.

On the other hand, in the state where the switching valves 14 and 15 are kept in the closed position, the load pressure of the cylinders 8 and 9 is zero or close thereto, so that the pressure in the other pilot chamber 28 is also substantially zero or close thereto. Thus, the spring force of the spring 30 acts on the spool 26, and the pressure of the other pilot chamber 28 has little influence.
Since the variable displacement pump P continues to rotate in the above state, the discharge pressure at that time is guided to one pilot chamber 27, and the pressure acts on the spool 26.

Therefore, the acting force on the spool 26 due to the pressure of the one pilot chamber 27 overcomes the acting force of the spring 30 provided in the other pilot chamber 28, and the spool 26 resists the spring force of the spring 30, and FIG. Move left.
When the spool 26 moves to the left as described above, the circuit pressure introduction port 24 and the tank port 25 communicate with each other through the notch 26a formed in the spool 26, and the discharge fluid of the variable displacement pump P is unloaded. The

However, at this time, the spring force of the spring 30 is set in advance so that the variable displacement pump P can secure a predetermined standby flow rate.
Since the adjuster 32 can be turned to adjust the spring force of the spring 30,
The standby flow rate of the variable displacement pump P can be adjusted by adjusting the spring force.

  Further, when the switching valves 14 and 15 are switched from the state in which the variable displacement pump P secures the standby flow rate, that is, the state in which the spool 26 moves against the spring force of the spring 30, the cylinders 8 and 9 are switched. Since the load pressure is guided to the other pilot chamber 28, the spool 26 returns to the closed position shown in FIG.

In the process of returning the spool 26 in this way, the substantial volume of the other pilot chamber 28 is increased by the volume of movement of the spool 26 from the other pilot chamber 28 to the closed position.
Therefore, since the fluid whose volume has been expanded flows into the other pilot chamber 28, the openings of the orifices 35 and 37 do not have to be so small as in the conventional case.

  In the process of operating the unload valve device A, the pressure is guided to the other pilot chamber 28 or the pressure becomes zero, but the other pilot chamber 28 has a fluid flow path. The spring 30 is not affected by the flow of the pressure fluid, and is not distorted or bent.

  Further, since the pilot passage 34 and the first and second orifices 35 and 37 are provided in the plug 33 and these are formed into a cartridge, the pilot passage 34 and the first and second orifices 35 and 37 with respect to the valve body B are provided. It becomes easy to provide.

Further, if the unload valve device A of the first embodiment is provided in the load sensing circuit, the regulator 1 can be stably controlled.
Note that the position of the unload valve device A of the first embodiment in the load sensing circuit is the same as that of the conventional art as described above.

  In the second embodiment shown in FIG. 2, the third orifice 38 is provided at a position downstream of the first orifice 35 in the pilot passage 34 with respect to the flow guided to the other pilot chamber 28. The other configurations are the same as those of the first embodiment.

  As described above, according to the second embodiment, since the third orifice 38 is provided, the third orifice 38 can exert a damping effect on the other pilot chamber. Therefore, a sudden pressure change in the other pilot chamber 28 can be prevented, and the spool 26 can be stably operated correspondingly.

  Ideal for use in load sensing circuits.

P Variable displacement pump 1 Regulator 1a Pilot chamber B Valve body 24 Circuit pressure introduction port 25 Tank port 26 Valve spool 27 One pilot chamber 28 Other pilot chamber 30 Spring 33 Cartridge plug 34 Pilot passage 35 First Orifice 37 Second orifice 38 Third orifice

Claims (5)

A valve body;
A circuit pressure introduction port formed in the valve body;
A tank port formed in the valve body;
A valve body incorporated in the valve body, for communicating the circuit pressure introduction port and the tank port, or for blocking the communication;
One pilot chamber formed on the valve body, facing one side of the valve body, and leading to the pressure of the circuit pressure introduction port;
The other pilot chamber provided on the valve body and facing the other surface of the valve body;
A spring for holding the valve body in a position to interrupt the communication between the circuit pressure introduction port and the tank port by interposing in the other pilot chamber and applying a spring force to the valve body;
A pilot passage having one end opened in the other pilot chamber and the other end connected to a control means provided separately from the valve body;
A first orifice provided between the pilot passage and a load pressure introduction passage for introducing load pressure;
An unload valve device comprising: a second orifice provided at a position downstream of the first orifice with respect to a flow flowing from the load pressure introduction passage to the control means.   The pilot passage is provided with a third orifice in parallel with the second orifice with respect to the first orifice, and the third orifice exhibits a damping effect against the pressure change in the other pilot chamber. The unloading valve device according to claim 1.   The unload valve device according to claim 1, wherein the pilot passage and the first and second orifices are provided in a cartridge, and the cartridge is assembled to the valve body.   4. The unload valve device according to claim 3, wherein the cartridge is provided with a third orifice together with the first and second orifices.   A spring guide is provided in the other pilot chamber, and an adjuster is provided for moving the spring guide in the axial direction of the valve body while interposing the spring between the spring guide and the valve body. 4. The unload valve device according to any one of 4 above.

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