JPH0792158B2 - Overload safety valve - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload safety valve for an operating device such as a press machine that generates an overload pressure.

[Prior art]

In a press machine, an overload safety valve is installed in the hydraulic circuit that operates the machine, protects the hydraulic circuit from overload pressure when the press machine is overloaded, stops the machine, and presses the machine and the work material pressure plate. It has already been proposed to prevent mold damage.

In a conventional overload safety valve, for example, as shown in Japanese Patent Laid-Open No. 60-234800, a sensor piston is arranged separately from a main valve body and a pilot valve body, and functional elements are arranged in two rows.

The main valve body that opens and closes the main valve seat formed between the pressure chamber that is connected to the flow passage that generates the overload pressure and the discharge chamber that is connected to the discharge passage is internally provided with the pressure chamber and the orifice. Has an internal pressure chamber that communicates with each other, and a pilot valve seat that is opened and closed by a pilot valve body in the flow path that connects the internal pressure chamber and the discharge chamber, and a hole passage and sensor that guides the pressure fluid from the pilot valve seat to the sensor piston. The opening portion opened and closed by the piston is sequentially arranged independently of each other.

In the conventional overload safety valve, when the actuator generates overload pressure, the internal pressure chamber of the main valve body rises to press the pilot valve body, open the pilot valve seat, and discharge the pressure fluid from the internal pressure chamber to release the pressure chamber. When the pressure difference between the internal pressure chamber and the internal pressure chamber becomes larger than the spring force that presses the main valve body and the main valve seat, the main valve body is moved to open the main valve seat and prevent overload. On the other hand, the pressure fluid discharged from the pilot valve seat passes through the hole passage and acts on the sensor piston arranged on the upper side, and the sensor piston is pushed to the position where the switch is turned off. The sensor piston passes through the pilot valve seat and the pressure receiving surface that produces the force to move the sensor piston to the switch ON position against the spring force when the fluid pressure in the pressure chamber acts in the direction opposing the spring force. And a counter pressure receiving surface having a larger area than the pressure receiving surface that receives the fluid pressure and generates a force in the same direction as the spring force.

[Problems to be solved by the invention]

In the above-mentioned conventional overload safety valve, the main valve body is configured so that the force acting on the main valve body and the main valve body due to the pressure difference between the internal pressure chamber and the pressure chamber communicating with the main valve body are communicated with each other. Since the main valve body is moved according to the difference in spring force pressing against the main valve seat, there is a problem that the responsiveness of the main valve body to overload is not so fast. Further, there is a problem that it is not possible to meet the demand for releasing the overload pressure early when the shock overload pressure occurs.

Secondly, if the pressure fluid in the flow path that supplies fluid to the operating machine through the overload safety valve, that is, the flow path where the overload occurs and the portion that communicates with the flow path expands in volume due to the temperature rise, the overload pressure is generated in the flow path. To occur. In this case, the pressure will return to normal if only the volume expansion fluid is discharged, but in such a case as well, in the conventional case it is necessary to open the main valve seat and discharge the fluid, and at the same time turn off the switch to temporarily stop the machine. However, there was a problem that work efficiency was poor.

Thirdly, in the conventional overload safety valve, the pressure fluid discharged by opening the pilot valve seat is guided through the hole passage and acts on the sensor piston arranged on the upper side. There is a problem that the operating pressure of the piston does not act immediately after the pilot valve seat is opened, and the operating response of the sensor piston is not good.

Fourth, with the conventional switch-off prevention mechanism, the switch is turned off.
N ・ OFF fluid pressure was constant and could not be adjusted. The relationship between switch ON / OFF pressure, pump generated pressure and overload set pressure is switch ON / OFF pressure <pump generated pressure <overload set pressure.

Since the pump generated pressure can be adjusted by the discharge capacity of the pump, it may be adjusted to a discharge pressure close to the switch ON / OFF pressure and be loaded on the overload safety valve, at which time the pump operates like a single-acting piston type pump. There is a problem that the discharge pressure pulsates during the operation, or the predetermined pressure pulsates while the actuator is driving, and if it fluctuates below the switch ON / OFF pressure, the sensor piston swings and the switch repeats ON / OFF. .

Fifthly, the overload safety valve has a main valve, a pilot valve, and a sensor piston, which are functional elements, arranged in two rows.
The holes for accommodating each member and the flow path connecting each member cannot be processed holes in one direction, and it is necessary to form a cross hole crossing the diagonal hole or one main direction hole. Therefore, there has been a problem that machining and assembling of parts are complicated, workability is poor, quality is unstable, and manufacturing cost is increased. In addition, burrs and burrs are generated in the holes in the main direction in a cross hole, etc., and secondary processing is required to remove the burrs and burrs, which not only increases the product cost but also affects the quality.

[Means and Actions for Solving Problems]

The present invention has solved the above-mentioned problems by the characteristic structure described in claim 1. That is, at a predetermined pressure, with the main valve body seated on the main valve seat and the pilot valve seat seated on the closing valve part, respectively, the pressure piston, the sensor piston engaged with the pressure piston, and the pilot valve body are moved from the stop position by hydraulic thrust. When the valve moves to the operating position and overload pressure occurs, the overload pressure fluid rapidly flows into the pilot chamber when the closing valve section separates from the pilot valve seat due to the difference in pressure receiving area between the closing valve section and the pressure receiving wall section. The first urging force based on the pressure difference between the pressure chamber and the internal pressure chamber, and the second urging force based on the pressure received by the end portion of the main valve piston by the overload pressure fluid flowing into the pilot chamber. The main valve body is configured to open from the main valve seat, and when an overload pressure occurs, the differential pressure between the pressure chamber and the internal pressure chamber and the overload pressure acting on the main valve piston are simultaneously generated in the main valve seat. It was solved by the overload relief valve for use.

Further, it is achieved by providing the pilot valve body with a closing valve portion which is in close contact with the pilot valve seat, and a pressure receiving wall portion which carries the closing valve portion and has a larger pressure receiving area than the pilot valve seat. With this configuration, when the pilot valve seat is slightly opened and the overpressure fluid flows out, the fluid acts on the pressure receiving wall with a large pressure receiving area, the pilot valve body is rapidly opened, and the overload pressure fluid immediately flows into the main valve. It acts on the piston. This makes the main valve sensitive to overload.

The second problem is solved by forming a temperature compensating orifice in the pressure receiving wall portion of the pilot valve body and allowing a part of the fluid in the pilot chamber to be discharged to the discharge passage through the temperature compensating orifice of the pressure receiving wall portion. did. With this configuration, when overload pressure is generated by thermal expansion and the pilot valve is opened, the fluid that has flowed into the pilot chamber is discharged through the temperature compensating orifice to the extent of thermal expansion, and the main valve piston receives the overload pressure as the main valve pressure. The force to open the body does not act, and the pressure difference enough to open the main valve seat by the main valve body does not occur in the pressure chamber and the internal pressure chamber. As a result, overload pressure due to thermal expansion can be compensated without opening and closing the main valve seat.

The third problem is that the sensor piston having the sensor part for turning the switch on and off contains the pilot valve body, and is discharged when the pilot valve seat is opened in the pilot chamber formed between the pilot valve body and the main valve piston. The internal pressure of the main valve body is formed by forming a pressure receiving surface facing the pressure receiving wall of the pilot valve body where the pressure fluid acts immediately, and the pilot valve seat on which the pilot valve body is seated is movable with respect to the main valve body. When a predetermined fluid pressure acts on the chamber, the pilot valve seat can be moved while being closed by the pilot valve body, and the movement of the pilot valve seat is transmitted to the sensor piston, for example, via the pressure receiving surface portion, and the sensor piston switches the sensor piston. Moves against the pressing member that presses toward the OFF position and turns on the switch
The pilot valve seat opens when an overload pressure of a predetermined pressure or more acts, and the fluid flowing into the pilot chamber immediately acts on the pressure receiving surface of the sensor piston, and the pressure receiving surface of the sensor piston and the inside of the pilot valve seat. The problem was solved by making it possible to move the sensor piston to the switch OFF position due to the difference in pressure receiving area on the end surface on the pressure chamber side. The pressure change in the internal pressure chamber of the main valve disc moves the pilot valve seat and the pressure that flows into the pilot chamber immediately opens the pilot valve seat, and the sensor piston moves directly, causing the sensor piston to overload. The switch can be turned off with high sensitivity.

A fourth problem is that the operating pressure applying means for pressing the pilot valve body against the pilot valve seat is used as a pressing member for pressing the sensor piston to the switch OFF position, and the set pressure of the operating pressure applying means is adjustable. This has been solved by configuring so that the fluid pressure that activates the sensor piston and turns the switch on and off is proportional to the overload set pressure. With this configuration, the sensor piston operates the switch not at a constant pressure but at a fluid pressure proportional to the operation set pressure.

The fifth problem was solved by arranging the main valve body, the pilot valve body, and the sensor piston in the same axial core. With this configuration, it is possible to connect between the chambers or between the flow passages, etc., with almost no need to process diagonal holes or cross holes.

〔Example〕

 The details of the present invention will be described based on the embodiments shown in the drawings.

In FIG. 1, the overload safety valve can be used, for example, as an overload protection device for a mechanical drive type press machine. In the casing 2 of the overload safety valve 1, an inlet port 3 connected to a fluid pressure source 50 such as a pump via a supply path 54,
The output port 4 and the discharge port 5 are formed.

The output port 4 is connected via a channel 55 to a cylinder chamber 52 in a slide 51 which presses the material against an actuating device, for example a die of a press machine. In the example of the press machine, the pressure fluid, such as pressure oil, flowing from the inlet port 3 is supplied from the output port 4 through the flow passage 55 to the cylinder chamber 52 of the slide 51.
The cylinder chamber 52 is filled with oil. The pressing force P obtained by the crank mechanism of the pressing machine is transmitted to the material via the oil in the cylinder chamber 52. When the load acting on the slide 51 exceeds a predetermined value, the hydraulic pressure in the cylinder chamber 52 rises. This increase in oil pressure immediately increases the pressure in the output port 4 of the overload safety valve 1, and when the pressure exceeds a predetermined pressure, the pilot valve body 25 and the main valve body 10 are activated and oil is discharged to the discharge port 5 of the overload safety valve 1. Through the discharge path 56 to the tank 53, the crank mechanism of the press machine, other motion mechanisms, and the work material pressing die are prevented from being overloaded and the safety of the pressing machine and the protection of the pressing die are ensured.

A pressure fluid chamber 6 communicating with the inlet port 3 and the output port 4 and a discharge chamber 7 communicating with the discharge port 5 are formed in the casing 2, and an outlet 8 communicating between the pressure fluid chamber 6 and the discharge chamber 7 is a main valve. It is formed as a hole surrounded by a seat 9.

A main valve body 10 is slidably arranged in the pressure fluid chamber 6, and a first spring 11 stretched between the casing 2 and the main valve body 10 causes the main valve body 10 to move against the main valve seat 9. Pressed.

The pressure fluid chamber 6 is divided by the main valve body 10 into a pressure chamber 6a on the valve seat 9 side and an internal pressure chamber 6b containing a spring 11. Pressure chamber
6a is always linked with the inlet port 3 by the supply path 12 and is always in communication with the output port 4 at the same time. On the other hand, the internal pressure chamber 6b communicates with the inlet port 3 through the orifice 13 and the supply passage 12.

A cylindrical first piston chamber 14 opening to the discharge chamber 7 and a cylindrical second piston chamber 15 having a diameter larger than that of the first piston chamber 14 concentrically with the main valve seat 9 follow the first piston chamber 14. It is formed.

A two-step sensor piston 16 slidably formed in the first piston chamber 14 and the second piston chamber 15 is slidably guided in the first piston chamber 14 and the second piston chamber 15. A tip portion of the sensor piston 16 protruding into the discharge chamber 7 is formed as a cylinder portion 17, and a main valve piston 18 formed so as to protrude into the discharge chamber 7 of the main valve body 10 slides inside the cylinder portion 17. You will be notified.

A through hole 19 that is substantially concentric with the valve seat 9 is formed in the main valve body 10 and the main valve piston 18, and a pressure piston 20 is slidably guided in the through hole 19. A pilot valve seat 26 is formed on the end face of the pressure piston 20 on the discharge chamber 7 side, and the piston portion 20a is slidably guided inside the cylinder portion 17 at the tip of the sensor piston 16. A second spring 21 is provided between the piston portion 20a and the main valve piston 18, and the piston portion 20a abuts on a flange portion 22a formed on the cylinder portion 17 and its movement is restricted.

A through passage 23 is formed in the pressure piston 20.
One end of 23 is opened to the internal pressure chamber 6b, and the other end is opened to the pilot valve chamber 24 inside the sensor piston 16.

A pilot valve body 25 is slidably guided in the sensor piston 16, and the pilot valve body 25 is seated on a pilot valve seat 26 for the through passage 23 of the pressure piston 20. A pilot chamber 24 is formed between the sensor piston 16 and the main valve piston 18. A space 35 communicating with the discharge chamber 7 separated from the pilot chamber 24 is formed between the pilot valve body 25 and a spring seat 27 movably arranged in the casing 2, and a third spring 28 is provided in this space 35. The pilot valve body 25 acts as a working pressure applying means for pressing the pilot valve body 25 against the pilot valve seat 26.
The position of the spring seat 27 is finely adjusted by adjusting the screwing amount of the adjusting screw 29 screwed into the casing 2, and the force of the third spring 28 acting on the pilot valve body 25 is adjusted. The adjusting screw 29 can be locked in the adjusting position by the nut 30.

Instead of the third spring, a pressure adjustable pneumatic piston can be used as the working pressure applying means. Further, the pressure receiving wall portion 25c of the pilot valve body 25 is provided with a temperature compensating orifice 36 which communicates with the pilot chamber 24.
The fluid having a volume expansion amount due to the temperature rise that has flowed into the chamber is discharged from the space 35 to the discharge chamber 7.

The pilot valve body 25 is a valve body portion that sits on the pilot valve seat 26.
Cylinder 25b in which 25a and its valve body are fixed or integrally formed
The cylinder portion 25b slides in the pilot chamber 24 of the sensor piston 16. The pressure receiving wall portion 25c of the cylinder portion 25b facing the piston portion 20a of the pressure piston 20 is formed as a pressure receiving portion having an area larger than the pressure receiving area of the valve body portion 25a. The third spring 28 is adjusted and set so that the working pressure of the fluid on the pressure receiving surface of the valve body 25a becomes a predetermined pressure.

A switch 31, for example, an approach switch is attached to the casing 2, and a portion of the sensor piston 16 that is slidably guided in the second piston chamber 15, that is, the main valve piston 18 is used as a sensor portion for turning the switch 31 on and off. The skirt portion 32 formed at the opposite end portion acts. The skirt portion 32 is formed as a large-diameter piston portion that is slidably guided in the second piston chamber 15. The sensor piston 16 can be directly pressed to a position where the switch 31 is turned off by a pressing member, for example, a spring, but it is also possible to use the working pressure applying means also as a pressing member and press it via the pilot valve body 16.

When the sensor piston 16 is located at a position where the switch 31 is turned off, and the pilot valve body 25 closes the pilot valve seat 26, the pilot chamber 24 is placed in the pilot chamber 24 at a position spaced from the pressure receiving wall portion 25c of the pilot valve body 25. The flange portion 22a is formed so as to project.

The operation of the overload safety valve will be described.

Before starting, as shown in FIG. 1, the main valve body 10 is pressed against the main valve seat 9 and seated by the force of the first spring 11. On the other hand, the pilot valve body 25 receives a force toward the main valve piston 18 by the third spring 28, and the protrusion 25d formed on the pilot valve body 25 abuts on the stepped portion 16a of the sensor piston 16 so that the sensor piston 16 is moved. Press to the left in the figure. As a result, the sensor piston 16 is held at the standby position where the skirt portion 32 of the sensor piston 16, that is, the sensor portion contacts the left end of the second piston chamber 15, and the sensor 32 turns off the proximity switch 31.

The pressure piston 20 is pressed by the spring 21 toward the pilot valve body 16 held by the sensor piston 16 and the third spring 28 at the standby position due to the engagement of the protrusion 25d and the step 16a, and the pilot valve seat 26 The valve body portion 25a of the pilot valve body 25 is seated.

Even if the operating device such as the press machine is started without fluid in the pipeline to which the overload safety valve is connected, the proximity switch 31
The press machine cannot be started because it is OFF. Therefore, it is possible to prevent the press machine and the whole mold from being damaged by operating without pressure oil in the cylinder chamber 52 of the slide 51 of the press machine.

When pressure fluid, for example pressure oil, is supplied by the pump 50, the pressure oil is supplied from the inlet port 3 through the supply passage 12 and the pressure chamber 6a to the cylinder chamber 52 of the slide 51 of the press machine from the output port 4. At the same time, the pressure oil enters the internal pressure chamber 6b through the orifice 13, and acts on the main valve body 19, while a part of the pressure oil acts on the pilot valve body 25 through the through passage 23. The hydraulic pressure in the pressure chamber 6a rises. When the hydraulic pressure in the internal pressure chamber 6b reaches a predetermined pressure, the pressure piston 20 moves to the end surface 20 on the internal pressure chamber 6b side.
The force of the third spring 28 is overcome by the pressure received by c and the pilot valve seat 25 and the sensor piston 16 move to the right in the drawing while maintaining the closed state of the pilot valve seat 26. When the piston portion 20a of the pressure piston 20 comes into contact with the flange portion 22a formed on the cylinder portion 17 of the sensor piston 16, the sensor piston 16 is also moved to the right in the figure, and the second
As shown in the figure, the skirt portion 32 of the sensor piston 16 comes into contact with the right end of the second piston chamber 15, and the pressure piston 20, the pilot valve body 25, and the sensor piston 16 stop. At this time, the skirt portion 32, that is, the sensor portion turns on the switch 31, for example, the proximity switch.

Only when the hydraulic pressure supplied from the output port 4 reaches a predetermined pressure, the switch 31 is turned on as described above and the operating machine, for example, the press machine can be driven.

Since both end portions of the second piston chamber 15 are communicated with the discharge port 5 by the escape passages 33, the fluid is not trapped in the second piston chamber 15 when the skirt portion 32 moves.

When the load of the operating machine, for example, the load acting on the cylinder chamber 52 of the press machine becomes larger than a predetermined value and becomes overloaded, the pressure of the output port 4, that is, the pressure chamber 6a increases. As the pressure in the pressure chamber 6a increases, the pressure in the internal pressure chamber 6b increases, and this increased pressure acts on the valve body portion 25a of the pilot valve body 25 via the through passage 23, and as shown in FIG. The body 25 is moved against the force of the third spring 28 to open the pilot valve seat 26.

The pressure receiving wall portion 25c having a pressure receiving area larger than the pressure receiving area of the valve body portion 25a is acted on by the fluid of the overload pressure flowing into the pilot chamber 24 through the open pilot valve seat 26, thereby causing the pilot valve body 25 Quickly opens the pilot valve seat 26. The pilot valve body 25 rapidly opens the pilot valve seat 26 by a slight increase in pressure below a predetermined pressure, so that it can respond sensitively to the increase in pressure.

When the pilot valve seat 26 is opened, the fluid flowing into the pilot chamber 24 acts on the main valve piston 18 through the cutout portion 20b provided in the piston portion 20a of the pressure piston 20. The pilot valve seat 26 opens, and the overload pressure that causes the main valve piston 18 to generate the opening force of the main valve element acts at the same time.
Since the fluid in the internal pressure chamber 6b flows into the pilot chamber 24, the pressure in the internal pressure chamber 6b decreases due to the effect of the orifice 13. Therefore, the overload pressure acts on the main valve piston 18 as a force for opening the main valve seat 9 against the first spring 11 for closing the main valve seat 9 and the hydraulic pressure on the main valve body 10. Moreover, the pressure suddenly acts, while the pressure in the internal pressure chamber 6b decreases because the inflow of the fluid in the pressure chamber 6b is suppressed by the orifice 13 during overload, and the pressure difference between the pressure chamber 6a and the internal pressure chamber 6b is reduced. Occurs, the main valve body 10 is released from the main valve seat 9. As a result, the fluid in the pressure chamber 6a is discharged to the tank 53 through the discharge port 5 through the main valve seat 9 formed as a large opening. Thus, when the load exceeds a predetermined amount, the fluid acting on the working machine can be discharged from the discharge port 5 via the output port 4, the pressure chamber 6a, and the main valve seat 9. At that time, the pilot valve seat 26 is opened and the pilot chamber
When the overload pressure fluid flows into 24, the main valve body 10 opens the main valve seat 9 to the left in the figure, and the sensor piston 16 is also fluid pressure so that the skirt portion 32 has the second piston chamber as shown in FIG. It is moved until it contacts the left end in the figure of 15, and the sensor unit turns off the proximity switch 31. As a result, the operating device such as the press machine is stopped. At this position, the sensor orifice 34 formed on the sensor piston 16 causes the pilot chamber 24 to communicate with the discharge chamber 7, and the fluid in the pilot chamber 24 is discharged from the discharge port 5 to the tank through the discharge chamber 7.

Since the fluid pressure in the pressure chamber 6a is reduced and the fluid pressure in the pilot chamber 24 is reduced, the force of the first spring 11 acts on the main valve body 10 largely, and the main valve body 10 closes the main valve seat 9. To the second spring 21 and the third spring 28 at the same time.
When the pilot valve seat of the pressure piston 20 is closed by the action of, the fluid pressure of the pressure chamber 6a and the internal pressure chamber 6b is increased by the fluid supplied from the fluid pressure source 50 such as a pump,
When the specified pressure is reached, the internal pressure chamber of the pressure piston 20
The pressure of the end face 20c on the 6b side keeps the pilot valve seat 26 closed, and the pressure piston 20 moves to the right in the figure.
And the pilot valve body 25 and the sensor piston 16 move together,
It returns to the state of FIG. When the state returns to the state shown in FIG. 2, the proximity switch 31 is turned on and the state where the operating device can be operated is restored.

In the illustrated embodiment, the pump is shown separately, but the overload safety valve and the pump may be integrally formed.

〔effect〕

According to the present invention, when an overload pressure of a certain pressure or more is generated in the flow path connecting the overload safety valves in communication, the closing valve portion of the pilot valve body is pressed by this fluid pressure, the pilot valve seat is opened, and the main valve body The fluid in the internal pressure chamber flows into the pilot chamber through the pilot valve seat, creating a pressure difference between the pressure chamber and the internal pressure chamber due to the orifice effect provided in the main valve body. Since the piston is pressurized, the main valve element is moved in the direction to open the main valve seat by both the differential pressure and the fluid pressure acting on the main valve piston.
As a result, the main valve body becomes sensitive to overload pressure, and even if a shocking overload pressure occurs, the main valve body responds very sensitively to the operation of the pilot valve body and responds instantaneously to a large flow rate. It was possible to discharge the pressure fluid of, and an overload safety valve with excellent responsiveness was obtained.

Further, according to the present invention, by making the pressure receiving area of the pressure receiving wall portion that carries the closing valve portion of the pilot valve body larger than the pilot valve seat, when the closing valve portion is separated from the pilot valve seat by the action of the overload pressure, the pilot valve Since the fluid flowing through the seat into the pilot chamber immediately exerts pressure on the pressure receiving wall, the pilot valve body receives a force larger than the closing force when the pilot valve seat is closed at the moment of opening the pilot valve seat, and The body moved instantly greatly, and the pilot valve body responded extremely sensitively to the shocked overload pressure generation, and the operating accuracy was extremely high and the responsiveness was excellent.

According to the present invention, the temperature compensating orifice is provided on the pressure receiving wall portion of the pilot valve body, and the pilot chamber and the exhaust chamber are communicated with each other, so that the fluid temperature in the flow path communicating with the pressure chamber is formed. When the pressure rises and causes volume expansion to reach an overload pressure condition, the closing valve part of the pilot valve body slightly opens the pilot valve seat and causes slight leakage, and the volume expansion fluid flows through the temperature compensation orifice and is discharged to the discharge chamber. Is discharged to
The fluid pressure in the pilot chamber does not rise to a pressure enough to move the main valve body, and the sensor piston does not move. Therefore, the valve opening / closing function of the overload safety valve does not operate, and the operating machine can continue to operate without stopping. The simple structure of forming an orifice in the pilot valve body can absorb the overload pressure due to temperature rise, and it is possible to remove the overload pressure without stopping the operating machine, thus improving work efficiency. became.

According to the present invention, it is configured as described in claim 3, the sensor piston is formed with a flange portion that projects into the pilot chamber, the pilot valve seat is movably formed, and the movement of the pilot valve seat can be transmitted to the sensor piston. As a result, when a predetermined fluid acts on the internal pressure chamber of the main valve body, the pilot valve seat moves with the pilot valve seat closed, and the movement causes the sensor piston to resist the force of the pressing member and actuate the switch.
When moving to the ON position, when the overload pressure occurs, the pilot valve seat opens and the fluid pressure flowing into the pilot chamber immediately acts on the pressure receiving surface of the sensor piston, and the pressure receiving surface of the sensor piston and the internal pressure chamber side of the pressure piston. The sensor piston is moved to the switch OFF position due to the difference in area from the pressure receiving end face, and the fluid in the pilot chamber is discharged to the discharge chamber through the communication hole formed in the sensor piston at the switch OFF position.
With this configuration, changes in fluid pressure sensitively act on the sensor piston, turning the switch on and off. When overload pressure occurs, the switching response from ON to OFF of the switch can be performed extremely sensitively, and an overload safety valve with good responsiveness was obtained.

According to the present invention, as described in claim 4, by using the operating pressure applying means capable of adjusting the set pressure for pressing the pilot valve body against the pilot valve seat as the pressing member for pressing the sensor piston to the switch OFF position, ON / OF
The F pressure can be easily adjusted to prevent it from approaching the pump set pressure.

As a result, if the discharge pressure pulsates while the pump is operating, or if the operating device pulsates the specified pressure while driving, and the specified pressure applied to the overload safety valve falls below the switch ON / OFF pressure, an overload occurs. By adjusting the set pressure, the switch ON / OFF pressure is proportionally changed, and it is possible to easily adjust and change to a safe pressure below the pulsation fluctuation range.Therefore, the sensor piston oscillates due to pulsation fluctuation of the specified pressure. The problem that the switch repeatedly turns on and off has been resolved.

According to the present invention, as described in claim 5, by arranging the functional elements such as the main valve body, the pilot valve body, and the sensor piston on the same axis, the parts can be easily processed and assembled, and the quality is further improved. It became stable and the product cost became cheaper. In addition, diagonal processing and cross hole processing can be extremely reduced, the occurrence of burrs and burrs can be prevented, and the internal cause of the contamination overload safety valve that causes malfunctions has been removed, so quality is improved and stable, Since the secondary processing for removing burrs and burrs is no longer necessary, the product cost is further reduced.

[Brief description of drawings]

1 to 4 are cross-sectional views of the relief valve device according to the present invention, which sequentially show the progress of operation. 1 ... Relief valve device, 2 ... Casing 4 ... Output port, 5 ... Discharge port 6 ... Pressure fluid chamber, 6a ... Pressure chamber 6b ... Internal pressure chamber, 7 ... Discharge chamber 9 ... Main Valve seat, 10 ... Main valve body 13 ... Olifis, 16 ... Sensor piston 17 ... Cylinder part, 18 ... Main valve piston 22 ... Pressure receiving surface, 22a ... Flange part 23 ... Through passage, 24 ... … Pilot chamber 25 …… Pilot valve body 25a …… Closed valve section, 25c …… Pressure receiving wall section 26 …… Pilot valve seat 28 …… Spring (pressing member, operating pressure applying means) 31 …… Proximity switch, 32 …… Sensor section 34 …… Communication hole, 35 …… Space 36 …… Temperature compensation orifice 55 …… Flow path, 56 …… Discharge path

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-49-828 (JP, A) JP-A-53-10133 (JP, A) JP-A-53-48226 (JP, A)

Claims (5)

[Claims] 1. An overload safety valve communicatively connected to a flow path of a fluid for generating an overload pressure of an actuator, comprising: a pressure chamber (6a) and a discharge path (56) communicatively connected to the flow path (55). A main valve body (10) which is seated from the pressure chamber (6a) side on a main valve seat (9) formed between a discharge chamber (7) connected to the main valve seat (9) and opens and closes the main valve seat (9). An internal pressure chamber (6b) which is communicated with the pressure chamber (6a) through an orifice (13) and is provided at an end portion of the main valve body (10) on the main valve seat opening direction side, A main valve piston (18) fixed to the main valve seat closing direction side of the valve body (10) and the main valve piston (18) slidably fitted in the cylinder part (17) of the sensor piston (16). And a sensor piston (16) slidable between the stop position and the operating position with respect to the casing (2), and a method of closing the main valve seat of the main valve piston (18). The pilot chamber (24) provided on the opposite end side, and penetrates the main valve body (10) and the main valve piston (18),
A pressure piston (20) slidably fitted in a through hole (19) reaching the pilot chamber (24) from the internal pressure chamber (6b), and the internal pressure formed in the pressure piston (20). A through passage (23) reaching the pilot chamber (24) from the chamber (6b), a pilot valve seat (26) provided at an end of the through passage (23) on the pilot chamber (24) side, and the pilot Valve seat (2
(6) A pilot valve body (25a) having a closing valve portion (25a) that can be seated from the pilot chamber (24) side and a pressure receiving wall portion (25c) having a pressure receiving area larger than the pressure receiving area of the closing valve portion (25a). 25) and at a predetermined pressure, the main valve body (10) is seated on the main valve seat (9) and the pilot valve seat (26) is seated on the shutoff valve part (25a). Pressure piston (20)
And the sensor piston (16) and pilot valve body (25) engaged with this move from the stop position to the operating position, and when the overload pressure occurs, the shut-off valve part (25a) and the pressure receiving wall part (25c) Due to the difference in pressure receiving area between the pilot valve seat (26) and the closing valve part (25a), the overload pressure fluid rapidly flows into the pilot chamber (24) and the orifice (13)
The first urging force based on the pressure difference between the pressure chamber (6a) and the internal pressure chamber (6b), and the main valve piston (18) due to the overload pressure fluid flowing into the pilot chamber (24). ) An overload safety valve, characterized in that the main valve body (10) is opened from the main valve seat (9) by a second urging force due to the pressure applied based on the pressure received at the end. 2. A pressure receiving wall portion (25) of the pilot valve body (25).
The space (3) separated from the pilot room (24) by c)
5) is formed, the space (35) communicates with the discharge chamber (7), and the pressure receiving wall portion (25c) communicates the space (35) with the pilot chamber (24) for temperature compensation. An orifice (36) is provided, the pressure fluid volume expands due to temperature rise, and overload pressure is generated, and the pilot valve body (25) minutely opens the pilot valve seat (26) to cause the pilot chamber (24). The volume expansion fluid due to the temperature rise flowing into the space passes through the temperature compensating orifice (36) and the space (35).
2. The overload safety valve according to claim 1, wherein the main valve seat (9) is discharged to a discharge chamber (7) and the main valve seat (9) is not opened. 3. The sensor piston (16) has a pressure receiving surface (22) facing the pressure receiving wall portion (25c) of the pilot valve body (25) in the pilot chamber (24), and a casing of an overload safety valve. The sensor part (32) formed at one end for turning on and off the switch (31) fixed to the pilot chamber (24) and the discharge chamber only at the stop position where the switch (31) is turned off. And a communication hole (34) formed so as to communicate with the sensor piston (1).
6) is pressed directly or indirectly by the pressing member (28) toward the stop position where the switch (31) is turned off, and the pilot valve seat (26) can move with respect to the main valve body (10). When the end surface (20c) of the pilot valve seat (26) on the internal pressure chamber (6b) side receives a pressure smaller than a predetermined fluid pressure, the force of the pressing member (28) causes the switch (31). When the sensor piston (16) moves to a stop position where the switch is turned off, and the end surface (20c) of the pilot valve seat (26) receives a predetermined fluid pressure, the pressing member (2
The sensor piston (16) moves to an operating position in which the switch (31) is turned on against the force of (8), and the pilot valve body (25) causes the pilot valve seat ( The fluid flowing into the pilot chamber (24) after opening the valve (26) is the pressure receiving surface (2) of the sensor piston (16).
2) is pressurized to move the sensor piston (16) to a stop position where the switch (31) is turned off. At the stop position where the switch is turned off, the fluid in the pilot chamber (24) is passed through the communication hole (34). The overload safety valve according to claim 1 or 2, characterized in that it is discharged into a discharge chamber (7). 4. The pilot member (25) for the pressing member.
Is formed as an operating pressure applying means (28) for pressing the valve to the pilot valve seat (26), and the operating set pressure as an overload safety valve by the operating pressure applying means and the switch (31).
The overload safety valve according to claim 3, wherein the fluid pressure for turning ON and OFF can be adjusted in proportion to each other. 5. The main valve body (10), the pilot valve body (25), and the sensor piston (16) are arranged on the same axis. The overload safety valve according to any one of 1.