JPH06122100A - Relief valve - Google Patents

Abstract

PURPOSE:To provide a relief valve, the responsibility of which has been enhanced. CONSTITUTION:In a relief valve interposing sealing members 14, 25 between a valve chest 2 surface and valve stems 4, 5 inserted freely advancing and retiring inside the valve chest 2, the constitution is made so that sleeves 10, 24 slidable against the valve stems 4, 5 and the valve chest 2 surface are provided between the valve stems 4, 5 and the valve chest 2 surface, the sealing members 14, 15 are interposed between the sleeves 10, 24 and either one side of the valve stems 4, 5 and the valve chest 2 surface, and auxiliary valve seats 11, 26 receiving the sleeves 10, 24 in sealing-like from a valve closing direction are provided on the other side, and pressing springs 12, 27 pressing the sleeves 10, 24 to the auxiliary valve seats 11, 26 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relief valve, and more particularly to a relief valve which can improve responsiveness.

[0002]

2. Description of the Related Art Conventionally, in a hydraulic circuit, an overload safety device is provided in order to prevent damage to circuit parts due to overload and damage to mechanical parts driven by a hydraulic device. The overload safety device of this type will be described below by taking the press overload safety device as an example.

As shown in FIG. 6, pressurizing means of a press machine.
A booster cylinder 103 for detecting overload is interposed between 101 and the slide (or ram) 102, and a relief valve 106 is interposed in a pressure oil passage 105 connecting the hydraulic pump (booster pump) 104 and this booster cylinder 103. When the internal pressure of the pressure oil passage 105 rises to a predetermined value or more, the relief valve 106 is opened to let the pressure oil of the pressure oil passage 105 flow out to the drain oil passage 107.
The internal pressure of 105 does not exceed a specified value.

By the way, as a relief valve of this kind, as shown in FIGS. 7 to 9, for example, a pilot valve 203 and a main valve 204 are opposed to each other in a valve chamber 202 formed in a valve box 201. There are things that fit inside to move forward and backward. The pilot valve element 203 is urged to advance toward the main valve element 204 by the pressure setting spring 205, and the main valve element 204 is urged to advance toward the pilot valve element 203 by the pressing spring 206, and is moved into the valve chamber 202. The maximum advancing position is limited by the formed limiting surface 207.

A sealing member 208 composed of an O-ring is externally fitted to the outer peripheral portion of the main valve element 204, and the sealing member 208 is slidably brought into contact with the inner surface of the valve chamber 202, whereby the valve chamber 202 is compressed into a pressure oil passage. It is divided into a pressure oil chamber 209 communicating with 105 and a drain chamber 210 to which the drain oil passage 107 is connected. A main pressure transmission path 211 is formed in a central portion of the main valve 204 in a penetrating manner, and an annular pilot valve seat 212 surrounding the main pressure transmission path 211 is projectingly provided on an end surface of the pilot valve 203 side. It Further, the main valve element 204 includes a sleeve 213 that is in sliding contact with the peripheral surface of the drain chamber 210, and the interior of the drain chamber 210 is partitioned into an external communication chamber 214 and a back pressure holding chamber 215 by the sleeve 213.

The back pressure holding chamber 215 is communicated with the pressure oil chamber 209 via the main pressure transmission path 211 when the main valve 204 is separated from the pilot valve 203, and the main valve 204 is connected to the pilot valve 203.
Is shut off from the pressure oil chamber 209 and the main pressure transmission path 211. The back pressure holding chamber 215 communicates with the external communication chamber 214 via the main valve hole 216 formed in the sleeve 213 only when the main valve 204 is separated from the restriction surface 207 by a certain amount or more.

A pilot valve face 217 is provided on the end face of the pilot valve 203 on the side of the main valve 204, and a temperature of the pilot valve face 217 inserted between the pilot valve 203 and the pressure setting spring 205 is provided on the opposite end face. Temperature compensating valve seat 219 for receiving compensating valve 218
Is formed. Further, a temperature compensation pressure receiving chamber 220 is formed between the pilot valve 203 and the temperature compensation valve 218, and a temperature compensation for communicating the temperature compensation pressure receiving chamber 220 to the main pressure transmission path 211 is formed in the central portion of the pilot valve 203. The pressure transmission path 221 is formed.

A sealing member 222 formed of an O-ring is fitted around the outside of the temperature compensating valve element 218, and the sealing member 222 is slidably brought into contact with the peripheral surface of the valve chamber 202, whereby the inside of the valve chamber 202 is closed. The pressure setting chamber 223 that houses the pressure setting spring 205 is the drain chamber 210.
Partitioned from. A booster pump 104 is integrally attached to the relief valve. Reference numeral 104a in FIGS. 6 to 8 denotes a pump chamber thereof, 104b denotes an inlet check valve, 104c denotes an outlet check valve, and 104d denotes a plunger. Show and inlet check valve
104b and the outlet check valve 104c are biased in the valve closing direction by a valve closing spring (not shown).

When the overload safety device is not in operation, as shown in FIG. 6, the temperature compensating valve element 2 is operated by the pressure setting spring 212.
18 and the pilot valve 203 are pushed out to the maximum advance position, and the main valve 204 is pushed out by the pressing spring 208 and received by the pilot valve 203. As a result, the pilot valve element 203 closes the main pressure transmission path 211 and the pilot valve 203 is closed, and the main valve hole 216 is closed in the valve chamber 20.
2, the main valve is closed by being closed on the peripheral surface.

By operating the booster pump 104, the pressure oil passage 105
When the internal pressure of the booster cylinder 103 is raised to a predetermined value, the pressure oil chamber 209 of the relief valve, the main pressure transmission passage 211, the pilot pressure transmission passage 221, and the temperature compensation pressure receiving chamber 220 are also raised to the same pressure, as shown in FIG. As described above, the main valve 204, the pilot valve 203 and the temperature compensating valve 218 move toward the pressure setting spring 205 while the main valve 204 and the pilot valve 203 are closed, and the main valve 204 is restricted. Received by face 207.

When an overload is applied to the press machine,
The internal pressures of the booster cylinder 103, the pressure oil passage 105, the pressure oil chamber 210, and the main pressure transmission passage 211 suddenly rise, and as shown in FIG. 8, the pilot valve 203 and the temperature compensating valve 218 have the pressure setting spring 205 side. The pilot valve 203 is opened and the internal pressure of the back pressure holding chamber 215 is rapidly increased. As a result, the main valve element 204 is pushed back to the pressure oil chamber 209 side and the main valve hole 216
Is opened, and the pressure oil chamber 209 opens the main pressure transmission path 211 and the back pressure holding chamber 21.
5 to the external communication chamber 214 through the main valve hole 216,
The pressure oil chamber 209, the pressure oil passage 105, and the booster cylinder 103 are depressurized, the gap between the pressurizing means 101 and the slide (or ram) 102 is shortened, and the overload state is eliminated.

[0012]

In the conventional example, when an overload occurs, the pilot valve 203 opens, the main pressure transmission path 211 communicates with the back pressure holding chamber 215, and further through the main valve hole 216. The pressure oil in the pressure oil chamber 209 is communicated with the drain chamber 210 and is relieved from the external communication chamber 214, in which the main valve pressure transmission path 2
When 11 communicates with the back pressure holding chamber 215, the passage area increases rapidly at a right angle, resulting in a large pressure loss due to turbulent flow. Also, from the main pressure transmission passage 211 through the back pressure holding chamber 215 to the main valve hole.
Since the flow from 216 to the drain chamber 210 is jetted in a U-shape in the opposite direction, there is a problem that the pressure loss becomes large.
Further, a sealing member 208 is provided between the main valve 204 and the peripheral surface of the valve chamber 202.
However, since the sealing member 208 is strongly pressed against the peripheral surface of the valve chamber 202 by the internal pressure of the pressure oil chamber 209, a large frictional resistance is generated when the main valve element 204 moves in the valve opening direction. However, there is also a problem that the valve opening speed of the main valve 204 becomes slow.

Further, when pressure is received on the entire surfaces of the pilot valve surface 217 and the temperature compensating valve seat 219, the pressing force by the hydraulic pressure becomes large, and the pressure setting spring 205 requires a large spring for generating a strong spring load. There is also a problem that the accommodation space becomes large and a large force is required for adjusting the load of the pressure setting spring, which is inconvenient. Further, a temperature compensating valve 218 is provided for temperature compensation to form a temperature compensating valve face, and the temperature compensating valve seat 21
There is also a problem that the formation of 9 and the development of new parts and the addition of functional parts are inferior in terms of simplicity and reliability is inferior accordingly.

In view of the above circumstances, the present invention reduces the pressure loss at the time of opening the valve, enhances the responsiveness, increases the convenience of setting the relief pressure, reduces the size and the number of functional parts, and improves the reliability. The purpose of the present invention is to provide a relief valve having a high temperature.

[0015]

[Means for Solving the Problems] In order to reduce the pressure loss when the valve is opened, the following means are taken. In other words, the main valve is arranged on the high pressure side and the pilot valve is arranged on the low pressure side (atmosphere side), and a circular pipe passage whose cross-sectional passage area expands conically is formed inside the main valve, increasing the passage area. A pilot valve seat is formed on the convex corner of the main valve, and has a pilot valve surface that abuts on this valve seat and closes the passage. A part of the main valve element is fitted internally by sliding so that the main valve hole has a main valve hole that opens and closes according to the peripheral surface of the pilot valve. It is characterized in that it is arranged at a position where it is opened when it is separated from the child by a predetermined size or more.

Further, the following measures are taken in order to increase the valve opening speed of the main valve and improve the responsiveness. That is,
A main valve element and a sleeve slidable with respect to the main valve chamber surface are provided between the main valve element and the main valve chamber surface, and between either one of the main valve element and the main valve chamber surface and the sleeve. A sub-valve seat for sealingly receiving the sleeve from the valve closing direction is provided on the other side with a sealing member interposed, and a pressing spring for pressing the sleeve against the sub-valve seat is provided. In addition, the following measures are taken to increase the convenience of setting the relief pressure, reduce the size of the relief pressure, and solve the resulting problems.

That is, the pilot valve element is formed in a cylindrical shape, slidably inscribes on its inner peripheral surface, engages with the pilot valve element and operates, and abuts against the valve box due to the pressure received during pressure increase and stands still. However, after depressurizing or adding excessive pressure after the valve opening of the pilot valve, a pressure receiving column that separates from the contact with the valve box and is released to the pilot valve face side together with the pilot valve is formed inside the pilot valve cylinder. It is characterized by

In addition to this, a sleeve slidable with respect to the pressure receiving column and the inner surface of the pilot valve is provided between the outer surface of the pressure receiving column and the inner surface of the pilot valve inner, so that the pressure receiving column and the inner surface of the pilot valve can be slid. A sub-valve seat, in which a sealing member is interposed between any one of the cylindrical surface and the sleeve, and which receives the sleeve in a sealing manner from the valve closing direction, the sub-valve surface that abuts on the sub-valve seat And a pressing member that presses the sub valve surface of the sleeve against the sub valve seat.

Further, in order to reduce the size, reduce the number of functional parts, and improve the reliability, the following measures are taken. In other words, the temperature compensating valve is eliminated, and it is formed on a circular pipe passage whose cross-sectional passage area expands conically inside the main valve between the main valve hole and the pilot valve seat. A temperature compensating orifice that connects the pilot chamber whose opening pressure receiving area rapidly expands to the drain passage formed downstream of the main valve hole is provided in the main valve or pilot valve in the part that forms the pilot chamber. Is characterized by.

[0020]

[Function] A circular pipe passage having a conical cross-sectional passage area is formed inside the main valve, and a pilot valve seat is formed at a convex corner of the main valve having a larger passage area. A part of the tip outer shape or a conical pilot valve that has a pilot valve surface that abuts and closes the passage is slidable on the enlarged passage in the main valve by fitting internally in the main valve, A main valve hole that opens and closes on the peripheral surface of the pilot valve is formed in the main valve, and the main valve hole is located at a position opened when the pilot valve seat is separated from the pilot valve by more than a predetermined size. , When the pilot valve is opened, the pressure oil in the pressure oil chamber passes through the circular pipe passage whose cross-sectional passage area in the main valve expands in a conical shape.
Since the outer shape of the tip of the pilot valve is guided by the conical portion, there is little turbulent flow, and it smoothly flows into the main valve hole and is relieved to the tank port, so that the pressure loss is reduced during this period.

Further, the sealing member causes a frictional resistance which prevents the relative movement of the sleeve with respect to either the main valve element or the main valve chamber surface due to the pressure of the pressure fluid, but the sleeve has the frictional resistance against the other. Since the main valve element can move without being affected by the resistance, the main valve element can freely move in the circumferential valve direction with respect to the main valve chamber surface without being affected by the frictional resistance caused by the sealing member. That is, when the sealing member is interposed between the main valve element and the sleeve, the main valve element and the sleeve are difficult to move relative to each other due to the frictional resistance caused by the sealing member, but the sleeve has an effect of the frictional resistance. Since the main valve element can move relative to the main valve chamber surface without receiving the friction, the main valve element and the sleeve can move relative to the main valve chamber surface without being affected by the frictional resistance caused by the sealing member. Further, when the sealing member is interposed between the main valve chamber surface and the sleeve, the sleeve is difficult to move with respect to the main valve chamber surface due to the frictional resistance generated by the sealing member, but Since the main valve element can move without being affected by its frictional resistance, the main valve element can move relative to the sleeve and the main valve chamber surface without being affected by its frictional resistance. Furthermore, a sub-valve seat that receives the sleeve in a sealing manner from the valve closing direction is provided,
By pressing the sleeve against the sub valve seat with a spring,
When the main valve is closed, it is possible to prevent the pressure fluid from leaking between the sleeve and the main valve or the main valve chamber surface that can move without being affected by frictional resistance against the sleeve.

As a result, the valve opening speed of the main valve element can be increased and the responsiveness can be improved with the pressure fluid sealed when necessary. In addition, the pilot valve is formed in a cylindrical shape, slidably inscribes on its inner peripheral surface, engages also with the pilot valve, and operates, and due to the pressure received at the time of pressure increase, it abuts against the valve box and stands still. When the pilot valve is opened during pressure or overload, the pressure receiving column that separates from the contact with the valve box and is released to the pilot valve face side together with the pilot valve is formed inside the pilot valve cylindrical The pressure force generated by the hydraulic pressure generated by the valve on the pilot valve surface is reduced, the load on the pressure setting spring can be reduced, and the pressure setting spring is made smaller and more convenient.

In addition to this, a sleeve slidable with respect to the pressure receiving column and the inner surface of the pilot valve inner cylinder is provided between the outer peripheral surface of the pressure receiving column and the inner surface of the pilot valve inner cylinder. A sealing member is interposed between any one of the surfaces and the sleeve, a sub-valve seat that receives the sleeve in a sealing manner from the valve closing direction is provided, and the sub-valve surface that abuts the sub-valve seat is provided on the sleeve. A state in which a pressing member for pressing the sub-valve surface of the sleeve against the sub-valve seat is provided and the pressure fluid is sealed when necessary without being affected by the frictional resistance generated by the sealing member when increasing the pressure. As a result, the pilot valve can be moved with respect to the pressure receiving column, the valve opening speed of the pilot valve can be increased, and the responsiveness can be improved. Further, the responsiveness of the valve closing speed is also enhanced.

Further, inside the main valve between the main valve hole and the pilot valve seat, the opening pressure receiving area of the main valve and the pilot valve formed on the circular pipe passage whose cross-sectional passage area expands conically is sharp. The temperature-compensating orifice that connects the expanding pilot chamber to the drain passage formed downstream of the main valve hole is provided in the main valve or pilot valve in the part that forms the pilot chamber, and the number of functional parts is reduced. However, the size was reduced, and the temperature compensation function was easily added to improve reliability.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A relief valve according to the present invention will be specifically described below with reference to FIGS. 1 to 4 by taking an example in which the relief valve is applied to an overload safety device of a press machine.
Each cross section of this booster pump of this overload safety device
31 shows a cross section of a part where a booster pump 33 and a relief valve are incorporated in a unit part in which 31, a reciprocating drive device 39 for driving this, and a relief valve are integrally assembled.

In the valve box 1 of the relief valve, there are formed a valve chamber 2 and a pressure setting chamber 3 which are vertically coaxial and continuous with each other.
And a pilot valve 4 slidably inserted into the pressure setting chamber 3 and a main valve 5 slidably inserted into the valve chamber 2. The pilot valve element 4 is formed in a cylindrical shape, and the sealing member 6 supported by the valve box 1 is slidably contacted with the outer peripheral surface thereof to separate the valve chamber 2 and the pressure setting chamber 3 from the outer periphery of the pilot valve element 4. It is partitioned. Further, the main valve element 5 is formed in a cylindrical shape with a different diameter, and the large diameter portion 7 is slidably fitted on the upper portion of the pilot valve element 4.

A pressure oil chamber 8 communicating with a booster cylinder formed between a pressurizing means (not shown) and a slide is formed in the upper portion of the valve chamber 2 and has a cylindrical shape having a labyrinth groove 9 on its outer peripheral surface. The sleeve 10 is slidably fitted inside. A sub-valve seat 11 for receiving the sleeve 10 in an oil-tight manner from below is formed at an intermediate height portion of the valve chamber 2, and a pressing spring 12 for pressing the sleeve 10 against the sub-valve seat 11 is formed.
Is inserted. Then, the small-diameter portion 13 of the main valve element 5 is slidably fitted into the sleeve 10, and the sealing member 14 composed of an O-ring supported by the main valve element 5 is oil-tightly formed on the inner peripheral surface of the sleeve 10. By slidingly contacting each other, the auxiliary valve seat 11, the sleeve 10, the sealing member 14, the main valve element 5 and the pilot valve element 4 allow the valve chamber 2 to move.
Drain chamber 15 connected to the drain oil passage (not shown) at the bottom of
Is partitioned.

As shown in FIG. 1, on the inner peripheral surface of the different diameter portion 16 of the main valve element 5, an annular pilot valve is sealingly abutted on a pilot valve surface 17 formed at the upper end of the pilot valve element 4. A seat 18 is provided so as to project, and an annular temperature compensating oil chamber 19 defined by the pilot valve 4 and the main valve 5 is formed around the pilot valve seat 18. This temperature compensating oil chamber 19 has a main valve 5
Is constantly communicated with the drain chamber 15 through the temperature compensating orifice 20 that penetrates the different diameter portion 16 of the pilot valve face.
When the pilot valve seat 18 is separated from the valve seat 17 by a certain amount or more, the pilot valve seat 18 is communicated with the drain chamber 15 through the main valve hole 21 which is formed in the large diameter portion 7 of the main valve element 5 and which is opened and closed around the pilot valve element 4. .

Inside the pressure setting chamber 3, a pressure receiving column 22 standing upright from the bottom to the hollow portion of the pilot valve 4 is erected, and a pressure setting spring 23, which is a compression coil spring and surrounds the pressure receiving column 22, is provided. Another sleeve 24 is provided between the upper portion of the pressure receiving column 22 and the upper portion of the pilot valve 4 so as to be slidable with respect to the pressure receiving column 22 and the pilot valve 4, and
The sealing member 25 composed of an O-ring supported on the pressure receiving column 22
Another auxiliary valve seat 26 that receives the sleeve 24 in an oil-tight manner from below on the inner peripheral surface of the pilot valve 4 while slidingly contacting the peripheral surface of
And a pressure spring 27 that presses the sleeve 24 against the auxiliary valve seat 26, the valve chamber 2 and the pressure setting chamber 3 are partitioned inside the pilot valve 4.

As shown in FIGS. 2 to 4, an adjusting screw 29 is screwed into the bottom wall 28 of the valve box 1, and the adjusting screw 29 is used.
It is possible to adjust the pressure of the pressure setting spring 23 by screwing back and forth to move the spring seat 31 up and down via the pin 30. The adjusting screw 28 is fixed by adjusting the pressure of the pressure setting spring 23 and then screwing a fixing nut 32 from below the bottom wall 27.

The booster pump 33 includes a pump chamber 34 arranged coaxially with the valve chamber 2 above the valve chamber 2, an inlet check valve 35 for opening and closing the inlet of the pump chamber 34, and an inlet reverse valve 35. Stop valve
A valve closing spring 36 for closing 35, an outlet check valve 38 interposed in a portion of the pressure oil passage 37 from the pump chamber 34 to the valve chamber 2, and a closing valve for urging the outlet check valve 38 to close. A spring 39 and a plunger 40 that moves back and forth in the pump chamber 34 are provided, and the working oil is sucked into the pump chamber 34 from the suction oil passage 42 by reciprocating the plunger 40 by, for example, an air-driven reciprocating drive device 41. ,
The pressure oil is discharged to the pressure oil passage 37 in which the pressure oil chamber 8 is interposed.

In this overload safety device, when not in operation, as shown in the right half of FIG. 1 and FIG. 2, the pilot valve 4 is pressed against the main valve 5 by the pressure setting spring 23, and the pilot valve face 5 is pressed. 17 is sealingly contacted with the pilot valve seat 18 to close the pilot valve, the main valve hole 21 is closed by the peripheral surface of the pilot valve element 5 to close the main valve, and the sleeve 10 is It is received by the sub valve seat 11. This prevents the pressure oil from flowing out from the pressure oil chamber 8 to the drain chamber 15.

When the reciprocating drive device 41 is operated to drive the booster pump 33 and pressure oil is supplied to the pressure oil passage 37 and the pressure oil chamber 8, the pressure oil chamber 8 is provided to the main valve 5 and the pilot valve 5. Hydraulic pressure of. In this embodiment, the pilot valve element 5 is formed in a tubular shape, and the pressure receiving column 22 having a diameter smaller than the shape (inner diameter) of the pilot valve seat 18 is provided inside the pilot valve element 5, so that the pilot valve element 5 can be moved up and down. The pressure difference in both directions acts downward in the plane projection of the pilot valve seat 18 and in the area outside the plane projection of the pressure receiving column 22. Therefore, the pressure setting spring 23
Since the pressure of the pressure setting spring 23 can be made smaller than the hydraulic pressure acting on the entire area of the pilot valve seat 18 in the plane projection, the pressure setting spring 23 can be downsized, and the elastic coefficient of the pressure setting spring 23 can be made small to respond. You can improve your sex.

When the hydraulic pressure of the pressure oil chamber 8 acts on the main valve 5 and the pilot valve 5, the main valve 5 and the pilot valve 4 are lowered against the pressure setting spring 23. And the pressure oil passage
When the internal pressure of 37 and the pressure oil chamber 8 becomes equal to or higher than a predetermined preload pressure, the lower end of the large-diameter portion 7 of the main valve element 5 is received by the sealing member 6 and enters the standby state. If the load condition of the press machine becomes overloaded in this state, if the internal pressure of the pressure oil passage 37 and the pressure oil chamber 8 rises above the set pressure higher than the preload pressure, the differential pressure acting on the pilot valve 4 will be a constant value. More than ever,
The pressure setting spring 23 is bent down and lowered, and the pilot valve seat 18
The pilot valve face 17 separates from and the pilot valve opens.

Here, the sleeve 24 is interposed between the pilot valve 4 and the pressure receiving column 22, and the sealing member 25 supported on the inner peripheral portion of the sleeve 24 is slidably contacted with the outer peripheral surface of the pressure receiving column 22. Therefore, the sealing member 25 is strongly pressed against the outer peripheral surface of the pressure receiving column 22 by the hydraulic pressure received from above. As a result, a large frictional resistance is generated with respect to the hydraulic pressure that attempts to move the sleeve 24 downward, and the sleeve 24 becomes difficult to descend with respect to the pressure receiving column 22, but the sleeve 24, the pilot valve 4, and the sleeve 24 are Since there is no sealing member between them, the pilot valve 4 is a sleeve.
It is possible to move easily without being affected by the frictional resistance of the sealing member 25 with respect to the pressure receiving column 24 and the pressure receiving column 22, and high responsiveness is obtained.

When the pilot valve element 24 descends with respect to the sleeve 24, the sleeve 24 separates from the sub-valve seat 26, so that the pressure difference between the upper side and the lower side of the sleeve 24 is eliminated within a very short time, and sealing is performed. The member 25 is a pressure receiving column only by its elastic restoring force.
Since it is pressed against 22, the frictional resistance to the outer peripheral surface of the pressure receiving column 22 is remarkably reduced, the sleeve 24 is pushed down by the force of the weak pressing spring 27, catches up on the sub valve seat 26, and is received by the sub valve seat 26.

As described above, when the pilot valve is opened due to the occurrence of overload, the internal pressure of the temperature compensating oil chamber 19 rapidly increases. As a result, the area where the main valve element 5 receives the upward pressure is rapidly expanded, and the main valve element 5 is rapidly raised. At this time, the main valve element 5 becomes difficult to move with respect to the sleeve 10 due to the frictional force of the sealing member 14 supported by the main valve element 5, but the sleeve 10 is urged downward by the weak pressing spring 12. Therefore, the main valve element 5 can be easily lifted with the sleeve 10, and the main valve element 5 moves in the valve opening direction without being affected by the frictional resistance generated by the sealing member 14.

Therefore, the responsiveness of the main valve 5 can be greatly improved as compared with the conventional example in which the sealing member 208 is directly interposed between the main valve 204 and the peripheral surface of the valve chamber 202. Figure 1
4, the main valve is opened by opening the main valve hole 21 formed in the large diameter portion 7 of the main valve 5 from the peripheral surface of the pilot valve 4, as shown in the solid line in the left half of FIG. The pressure oil in the pressure oil passage 37 and the pressure oil chamber 8 flows out to the drain chamber 15 through the temperature compensating oil chamber 19 and the main valve hole 21, and the pressure oil passage 37 and the pressure oil chamber 8 are depressurized.

When the main valve is opened, the differential pressure for moving the main valve element 5 in the vertical direction is canceled, and the differential pressure for moving the sleeve 10 in the vertical direction is also canceled. It is pushed back to the sub valve seat 11, entangled with the main valve element 5 and moves in the valve closing direction. In addition, the pressure oil passage
When the internal pressure (exhaust pressure) of 37 and the pressure oil chamber 8 decreases, the pressure setting spring 23 raises the pilot valve 4.

As a result, the opening degree of the main valve hole 21 is narrowed, the pressure reducing rate of the internal pressure of the pressure oil passage 37 and the pressure oil chamber 8 is gradually reduced, and when the exhaust pressure becomes equal to or lower than a predetermined pressure, the main valve hole 21 is opened. The pilot valve 4 is closed by the peripheral surface and the main valve is closed. This prevents the internal pressure of the pressure oil passage 37 and the pressure oil chamber 8 from dropping below a predetermined exhaust pressure higher than the preload pressure, and prevents the press force required by the press machine from being lost. It can be prevented.

Pilot valve face when main valve hole 21 is closed
17 is far from pilot valve seat 18, but orifice 20
By gradually depressurizing the internal pressure of the pressure oil passage 37 and the pressure oil chamber 8 to the preload pressure, the pilot valve 4 slightly rises and the phantom line of the left half of FIG. 1 and FIG.
Return to the standby state shown in. If the overload state occurs again before returning to the standby state, the overload safety operation is performed again to depressurize the pressure oil passage 37 and the pressure oil chamber 8 and then wait as described above. Return to the state.

When the press machine is operated in the standby state to heat the working oil and the internal pressure in the pressure oil chamber 8 increases, the pilot valve 4 is slightly lowered to lower the pilot valve surface.
17 is separated from the pilot valve seat 18. As a result, the internal pressure of the temperature compensating oil chamber 19 rises, but since this pressure rise is slow, the speed at which the pilot valve face 17 separates from the pilot valve seat 18 becomes very slow.

For this reason, the increase in the internal pressure of the temperature compensating oil chamber 19 becomes very slow due to the throttling action between the pilot valve surface 17 and the pilot valve seat 18. Further, the orifice 20 depressurizes the temperature compensating oil chamber 19 to the drain chamber 15. Therefore, the pressure acting on the main valve 5 from the temperature compensating oil chamber 19 is small, and the main valve 4 does not rise to the extent that the main valve hole 21 is opened.
A small amount of pressure oil is discharged from the pressure oil chamber 8 through the temperature compensating oil chamber 19 and the orifice 20 and the internal pressure of the pressure oil chamber 8 gradually exceeds the preload pressure with almost no decrease in the internal pressure of the pressure oil chamber 8. Can be prevented.

A sleeve 24 is inserted between the pilot valve 4 and the pressure receiving column 22, and a sealing member 25 supported by the sleeve 24 is slidably brought into contact with the peripheral surface of the pressure receiving column 22.
Since the sleeve 24 and the pressure receiving column 22 are sealed, the sleeve 24 is less likely to move with respect to the pressure receiving column 22 due to the frictional resistance generated by the sealing member 25. However, between the pilot valve 4 and the pilot valve 4, a weak pressing spring 27 is used.
The pilot valve 4 is not affected by the frictional resistance generated by the sealing member 25.
And it can move downward with respect to the pressure receiving column 22. Therefore, the pilot valve 4 can be smoothly lowered even when the hydraulic pressure rises slowly such as the hydraulic pressure rises due to the temperature rise of the pressure oil, and the temperature can be smoothly compensated.

In the above-mentioned embodiment, the sleeves 10 and 24 are respectively provided between the pilot valve 4 and the outer peripheral surface of the pressure receiving column 22 and between the main valve 5 and the inner peripheral surface of the pressure oil chamber 8. Although the sealing members 14 and 25, the presser springs 12 and 27, and the auxiliary valve seats 11 and 26 are interposed, the space between the pilot valve 4 and the pressure receiving column 22 or between the main valve 5 and the pressure oil chamber 8 is increased. There is no obstacle to adopting the conventional sealing structure in which the sleeve, the pressing spring and the sub valve seat are omitted for either one of the inner peripheral surface and the inner peripheral surface.

Further, in the above-mentioned embodiment, the end face of the pilot valve 4 on the side of the main valve 5 is formed into a tapered surface, and the inner peripheral surface of the different diameter portion 16 of the main valve 5 facing the tapered surface is formed. To form a taper surface parallel to the above end surface of the pilot valve element 4 so as to reduce the flow resistance of the pressure oil flowing from the pressure oil chamber 8 to the main valve hole 21 through the small diameter portion 13 of the main valve element 5. However, forming the end face of the pilot valve 4 on the side of the main valve 5 or, together with this, the face of the main valve 4 facing this end face to a flat surface is not hindered.

FIG. 5 shows a sectional view of another embodiment of the overload safety device according to the present invention. Parts having the same functions as those in the above-described embodiment are designated by the same reference numerals.

[0048]

EFFECTS OF THE INVENTION A circular pipe passage having a conical cross-sectional passage area is formed inside the main valve, and a pilot valve seat is formed at a convex corner of the main valve having a larger passage area. A pilot valve with a conical outer tip that has a pilot valve surface that abuts against the seat and closes the passage is slidable on the enlarged passage in the main valve. The main valve hole is formed in the main valve element so as to be opened and closed by the peripheral surface of the pilot valve element, and the main valve hole is arranged at a position opened when the pilot valve seat is separated from the pilot valve element by a predetermined dimension or more. Therefore, when the pilot valve is opened, the pressure oil in the pressure oil chamber passes through the circular pipe passage in which the cross-sectional passage area in the main valve expands conically, and the tip outer shape of the pilot valve has a conical shape. Since it is guided by, there is little turbulent flow, it flows smoothly into the main valve hole, and is returned to the tank port. Since the-safe, during which the pressure loss is reduced, and improved relief function.

Furthermore, a pressure difference can be provided between the pilot valve opening pressure at which the pilot valve element can be separated from the pilot valve seat and the valve pressure for the main valve at which the main valve hole is opened, and the valve opening at the time of overload occurs. When the exhaust pressure decreases, the valve can be closed when the main valve opening pressure, which is higher than the preload pressure and the pilot valve opening pressure, can be closed, so that the exhaust pressure can be rapidly reduced to the preload pressure or less. It is possible to prevent the output of load equipment such as a press machine from decreasing due to a decrease in discharge of the overload safety device.

Further, in the present invention, the main valve element and the sleeve slidable with respect to the main valve chamber surface are provided between the pilot valve element or the main valve element driven by the differential pressure and the main valve chamber surface, A sealing member is interposed between one of the main valve element and the main valve chamber surface and the sleeve, and the other side is provided with a sub-valve seat that receives the sleeve in a sealing manner from the valve closing direction,
By pressing the sleeve against the auxiliary valve seat with the pressing spring, it is possible to obtain an oil-tight state of hardness when the valve is closed.
During valve opening operation, the main valve element can be moved with respect to the main valve chamber surface without being affected by the frictional resistance generated by the sealing member, and the responsiveness can be improved.

Further, in the present invention, in particular, the pilot valve is formed in a tubular shape, the pressure receiving column is inserted into the inner peripheral surface thereof, and the pressure receiving column slides and abuts against the valve box when pressure is received. The pressure receiving area can be reduced, the pressure setting spring can be miniaturized, the elastic coefficient of the pressure setting spring can be reduced, and sliding between the cylindrical inner surface of the pilot valve and the pressure receiving column formed inside it can be achieved. The sleeve provided so that the pilot valve can move with respect to the pressure receiving column without being affected by the frictional resistance generated by the sealing member between the pilot valve and the pressure receiving column, further improving the responsiveness of the pilot valve. The convenience has increased.

In addition, in the present invention, the main valve forming the pilot chamber between the main valve hole and the pilot valve seat, and the main valve or the pilot valve at a part of the pilot valve,
Since a temperature compensating orifice that communicates with the drain passage formed downstream of the main valve hole is formed, only the pilot valve will be opened to compensate for the temperature increase due to the temperature increase caused by the load equipment operation. The pressure oil chamber can be depressurized through the use orifice, and a smooth and suitable temperature compensation function can be obtained with a highly reliable and simple structure.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of the present invention.

FIG. 2 is a cross-sectional view of a main part of the overload safety device according to the present invention when not operating.

FIG. 3 is a sectional view of a main part of the overload safety device according to the present invention in a standby state.

FIG. 4 is a cross-sectional view of a main part of the overload safety device according to the present invention when an overload occurs.

FIG. 5 is a sectional view of another embodiment of the overload safety device according to the present invention.

FIG. 6 is a schematic configuration diagram of an overload safety device for a press machine.

FIG. 7 is a cross-sectional view of a main part of an overload safety device according to a conventional example when not operating.

FIG. 8 is a sectional view of a main part of an overload safety device according to a conventional example in a standby state.

FIG. 9 is a cross-sectional view of a main part of an overload safety device according to a conventional example when an overload occurs.

[Explanation of symbols] 2 ... Valve chamber 4 ... Pilot valve 5 ... Main valve 8 ... Pressure oil chamber 10 ... Sleeve 11 ... Sub valve seat 12 ... Pressing spring 13 ... Small diameter part 14 ... Sealing member 15 ... Drain chamber 17 … Pilot valve face 18… Pilot valve seat 19… Temperature compensation oil chamber 20… Orifice 21… Main valve hole 22… Pressure receiving column 24… Sleeve 25… Seal member 26… Sub valve seat 27… Pressing spring

Claims (5)

[Claims] 1. A main valve element is arranged on the high-pressure side and a pilot valve element is arranged on the low-pressure side (atmosphere side), and a circular pipe passage whose cross-sectional passage area expands conically is formed inside the main valve element. A pilot valve seat is formed on the convex corner of the main valve that expands, and a pilot valve with a conical tip outer diameter that has a pilot valve surface that abuts this valve seat and closes the passage A part of the main valve is fitted internally to be slidable on the enlarged passage, and the main valve has a main valve hole that opens and closes according to the peripheral surface of the pilot valve. The seat is arranged in a position that is opened when the seat is separated from the pilot valve by a predetermined dimension or more, and when the hydraulic pressure in the pressure oil chamber rises above a certain level, the pilot valve opens the low pressure side against the pressing member, The pilot valve surface is opened from the pilot valve seat of the main valve, and the pressure oil expands the passage of the main valve. When the pilot valve is fitted into the stacking part and the partly built-in main valve and the pilot valve flow into the pilot chamber where the pressure receiving area rapidly expands and the main valve moves in the opposite direction, A relief valve that relieves pressure oil through the main valve hole formed in the valve. 2. A sealing member is interposed between a main valve chamber surface and a main valve element inserted in the main valve chamber so as to be able to move back and forth, and a main valve element and a main valve element are provided between the main valve element and the main valve chamber surface. A sleeve slidable with respect to the main valve chamber surface is provided, and a sealing member is interposed between one of the main valve element and the main valve chamber surface and the sleeve, and the sleeve is sealed from the valve closing direction. A sub-valve seat that receives the sub-valve seat is provided, a sub-valve surface that contacts the sub-valve seat is formed in the sleeve, and a pressing member that presses the sub-valve surface of the sleeve against the sub-valve seat is provided. Relief valve. 3. The pilot valve element is formed in a cylindrical shape, slidably inscribes on the inner peripheral surface thereof, engages with the pilot valve element and operates, and abuts against the valve box by pressure reception at the time of pressure increase and stands still. After the valve opening of the pilot valve during depressurization or overload, the pressure receiving column that separates from the contact with the valve box and is released to the pilot valve face side together with the pilot valve is formed inside the pilot valve cylinder. The relief valve according to claim 1 or 2. 4. A sealing member is interposed between the pilot valve inner cylinder surface and the pressure receiving column inserted into the pilot valve inner cylinder so as to be able to move back and forth, and the pressure receiving column outer peripheral surface and the pilot valve inner cylindrical surface are formed. A sleeve slidable with respect to the pressure receiving column and the pilot valve inner cylinder surface is provided between the pressure receiving column and the pilot valve inner cylinder surface, and a sealing member is interposed between the sleeve and the sleeve. A sub-valve seat for sealingly receiving the sleeve from the valve closing direction is provided, a sub-valve surface that contacts the sub-valve seat is formed on the sleeve, and a pressing member that presses the sub-valve surface of the sleeve against the sub-valve seat is provided. The relief valve according to claim 3, which is provided. 5. The opening pressure receiving area of the main valve and the pilot valve is sharply formed on a circular pipe passage whose cross-sectional passage area expands conically inside the main valve between the main valve hole and the pilot valve seat. 2. A temperature compensating orifice for communicating a pilot chamber expanding to a drain passage formed downstream of the main valve hole with a temperature compensating orifice provided in the main valve or pilot valve in the portion forming the pilot chamber. The relief valve according to claim 2, claim 3, or claim 4.