JP2955517B2 - Relief valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a miniaturized relief valve capable of exhausting a large volume of air.

[0002]

2. Description of the Related Art Conventionally, when the pressure of air flowing in a pneumatic circuit exceeds a set value, a relief valve that exhausts air to adjust the pressure in the circuit has been used. For example, a flow type shown in FIG. 11 is employed. Hereinafter, this relief valve will be briefly described. In the body 61, a pressure chamber 63 is formed in a communication hole 62 connected to a pneumatic circuit (not shown).
Has a flow valve 6 urged by a spring 64 from above.
5 is fitted. On the upper wall surface of the pressure chamber 63, a conical inclined surface 63a is formed.
5 is formed with an inclined surface 65a whose cylindrical upper portion follows the inclined surface 63a of the pressure chamber 63. The pressure chamber 6
An orifice 67 communicating with the exhaust hole 66 is formed on the ceiling of the third. A pressing rod 68 inserted into the orifice 67 is slidably fitted into the body 61.

[0003] The relief valve having such a configuration is urged downward by the spring 64 when the compressor is stopped, so that the inclined surface 65 a of the flow valve 65 and the pressure chamber 63.
Is in a valve-open state separated from the inclined surface 63a. On the other hand, when the compressor starts, while the air pressure in the pressure chamber 63 does not reach the set pressure, the inclined surface 65a of the flow valve 65 and the inclined surface 63a of the pressure chamber 63 are not in contact with each other by the urging force of the spring 64. In state. Therefore, the air flowing into the communication hole 62 is exhausted from the pressure chamber 63 through the orifice 67 and the exhaust hole 66.

However, the discharge flow rate from the compressor is proportional to the pressure in the piping, and the air pressure in the circuit gradually increases as the air is discharged. Then, the set pressure of 1.2 k
When the flow rate reaches g / cm ² , the flow valve 65 rises against the urging force of the spring 64, and the inclined surface 65 a of the flow valve 65 and the inclined surface 63 a of the pressure chamber 63 come into contact with each other to be closed. . When the pressure in the circuit reaches the set value following the discharge from the compressor, the pressing rod 68 is pressed down,
The inclined surface 65a of the flow valve 65 and the inclined surface 63 of the pressure chamber 63
The air in the pressure chamber 63 is exhausted from the exhaust hole 66 by separating the air pressure a from the pressure chamber a to adjust the pressure in the circuit.

[0005] In addition to the above-mentioned flow type, a solenoid valve type shown in FIG. 12 is used as the relief valve. In this solenoid valve type relief valve, a fixed iron core 72 is fitted and fixed above a coil 71 wound in a cylindrical shape to a solenoid portion constituting the solenoid valve, and a lower end thereof is fixed to a lower end thereof. The movable core 73 is the spring 7
4 so as to be vertically movable. The body 75 has a communication hole 77 from an input port 76 connected to the primary pipe.
Are formed so as to communicate with the exhaust hole 78. An orifice 79 having a reduced diameter is formed from the communication hole 77 to the exhaust hole 78. Orifice 79
A lower end of the valve seat 80 has a valve seat 80 projecting downward, and a valve body 81 corresponding to the valve seat 80 is slidably fitted in the communication hole 77. The valve body 81 has a groove through which air is formed on the outer periphery, and is urged toward the valve seat 80 by a spring 83 engaged between the valve body 81 and a cylindrical stopper 82 fixed to the communication hole 77. A valve rod 84 inserted into the orifice 79 is slidably fitted in the body 75.

In the relief valve having such a configuration, when the power to the relief valve is turned off, the movable iron core 73 urged by the spring 74 presses the valve rod 84,
The valve element 81 is separated from the valve seat 80, and the orifice 79 is opened. Therefore, the air in the circuit is exhausted from the communication passage 77 through the orifice 79 and the exhaust hole 78. On the other hand, when the coil 71 is energized, the movable iron core 73 is attracted to the excited fixed iron core 72 and rises against the urging force of the spring 74. Therefore, the valve body 81 urged downward via the valve rod 84 is opened, and conversely, the valve body 81
Is urged upward by a spring 83 to abut against the valve seat 80, the orifice 79 is shut off, and the air pressure in the circuit is increased.

[0007]

However, in the above-mentioned flow type relief valve, the flow valve 65 is operated and closed by the air pressure in the pressure chamber 63. To some extent, the orifice 67 is structurally small. Therefore, there is a problem that it is not suitable for a large pneumatic circuit using a compressor having a large discharge amount.

On the other hand, according to the above-mentioned solenoid valve type relief valve, the valve can be opened and closed by operating the solenoid valve to adjust the exhaust of air.
9 can be formed, and the capacity of the air flow can be increased. However, if the diameter of the orifice 79 is increased, the air pressure applied to the valve body 81 increases accordingly, and a spring 74 having a strong spring force to open the valve against the air pressure is required. Therefore, the greater the spring force of the spring, the more the movable iron core 7 closes the valve.
A large solenoid that generates an exciting force enough to attract the 3 is required, and there is a disadvantage that the relief valve is correspondingly enlarged.

Accordingly, an object of the present invention is to provide a small-sized relief valve capable of increasing the air flow rate.

[0010]

The present invention is provided on a primary pipe side connected to an air compressor, and exhausts air discharged into the primary pipe at a predetermined timing to reduce the pressure in a pneumatic circuit. An electromagnetic valve type relief valve for adjusting, comprising: a first valve formed on a flow path communicating with the primary pipe.
A non-contact portion that forms a flow channel between the valve seat and the inner wall surface of the flow passage and a sliding contact portion that is slidable on the inner wall surface of the flow passage are formed on the outer periphery. A first valve body with respect to the first valve seat having the through hole formed therein, a second valve seat formed at an opening of the through hole at a downstream end surface of the first valve body, and the through hole. A second valve body for the second valve seat fixed to the lower end of the valve stem which is loosely fitted therethrough, wherein the valve stem is disposed coaxially below the movable core, and extends downward from the movable core. The transmission piece for transmitting the movement of the first valve body to the first valve body is fixed.

Further, in the relief valve of the present invention, it is preferable that a through-hole formed in the first valve body has a through-hole formed in an opening portion where the transmission piece contacts. Further, it is preferable that the relief valve of the present invention delays closing of the first valve body and the second valve body for a predetermined time after the start of the air compressor.

The relief valve of the present invention having such a structure operates as follows. That is, the relief valve of the present invention opens when the air pressure in the pneumatic circuit reaches a predetermined value by the air discharged from the air compressor to the primary pipe to exhaust the air. At this time, the solenoid is de-energized and the movable iron core is lowered to open the valve. However, at first, the second valve having a small pressure receiving area with the first valve body abutting on the first valve seat and the orifice being shut off. The valve body is separated from the second valve seat by the lowering of the valve stem, whereby the through hole communicates with the orifice, and the air in the primary pipe is exhausted through the narrow through hole. Then, when the air in the primary pipe is released to some extent and the pressure is lowered, the first valve body having a large pressure receiving area is pressed by the transmitting piece of the descending valve rod to be pressed by the first valve body.
By separating from the valve body, the orifice is fully opened, and the air in the primary pipe flows through the flow path between the inner wall surface of the flow path and the outer periphery of the first valve body.

Therefore, when the air in the primary pipe with the increased pressure is exhausted, the air is exhausted by opening only the second valve body having a small pressure receiving area, thereby reducing the pressure in the primary pipe. Subsequently, since the first valve body having a large pressure receiving area was subsequently opened, the load applied to the movable core via the valve rod was small, and the spring for urging the movable core could be small. In order to reduce the size of the spring, the exciting force for attracting the movable iron core against the elastic expansion force of the spring may be small.As a result, the capacity of the orifice with a large flow rate can be increased, while the size of the solenoid is reduced. This makes it possible to reduce the size of the relief valve itself. In the relief valve of the present invention, the closing of the first valve body and the second valve body is delayed for a predetermined time after the start of the air compressor. It is possible to prevent a load from being applied to the motor to be driven, and to supply a stable air.

[0014]

Next, an embodiment of a relief valve according to the present invention will be described with reference to the drawings. FIG. 1 shows a pressure switch with a relief mechanism provided with a relief valve according to the present embodiment (hereinafter, referred to as “pressure switch”).
FIG. 3 is a diagram showing an air supply device having the pressure switch. In the air supply device according to the present embodiment, a pressure switch 1 connects a compressor 2 that discharges compressed air and an air tank 3 that stores the compressed air, thereby forming a pneumatic circuit. Hereinafter, the configuration of the air supply device including the relief valve according to the present invention will be described.

The compressor 2 is connected to an air tank 3 via a primary pipe 4, and the primary pipe 4 is connected to an input port 6 communicating with a relief valve 5 provided in the pressure switch 1. A check valve 7 is formed at a connection portion of the air tank 3 connected to the primary pipe 4 so that air once entering the air tank 3 does not flow back to the primary pipe 4 side. The check valve 7 is urged by a spring at 0.3 kgf / cm ² . Air tank 3
Is connected to an input port 9 formed in the pressure switch 1 and also communicates with an output port 10 formed in the pressure switch 1.
Connected through. The communication path 11 branches off and is also connected to the pressure switch 12.

Next, the configuration of the pressure switch 1 will be specifically described. The pressure switch 1 is roughly composed of a relief valve 5 and a switch unit 12. 2 to 4 are cross-sectional views showing the relief valve according to the present embodiment, and show changes in the operation from the valve-closed state in FIG. 2 to the valve-opened state in FIGS. 3 and 4. . The relief valve 5 of the present embodiment employs an electromagnetic valve system. The solenoid part of the solenoid valve has a fixed iron core 22 fitted and fixed above the inside of the coil 21 wound on a cylindrical coil 21, and a movable iron core 23 at the lower end thereof via a spring 24. It is movably fitted. On the other hand, the body 13 constituting the pressure switch 1
A communication hole 14 extends coaxially with the movable iron core 23, and the communication hole 14 is formed so as to communicate with the exhaust hole 15 in the input port 6 formed at the bottom. And this communication hole 1
A valve portion of an electromagnetic valve that constitutes the relief valve 5 is formed in 4.

An orifice 20 having a reduced diameter is formed from the communication hole 14 to the exhaust hole 15, and a first valve seat 25 projects downward from the lower end of the orifice 20. In the communication hole 14, the first valve seat 25
The valve body 26 is slidably fitted. A cylindrical stopper 27 is further fixed in the communication hole 14, a spring 28 is engaged between the stopper 27 and the first valve body 26, and the first valve body 26 is moved toward the first valve seat 25. Being energized. Next, FIG. 5 is a cross-sectional view showing the first valve body 26, and FIG. 6 is a plan view showing the first valve body 26. First
The valve body 26 forms a cylindrical body having a smaller diameter than the communication hole 14, and sliding protrusions 26a, 26a,.
Are formed. Then, the first valve body 26 is connected to the communication hole 14.
When fitted inside, the sliding protrusions 26a, 26a,.
Slidably contacts the inner wall of the communication hole 14 so that the first valve body 2
6 is coaxially positioned with respect to the communication hole 14.

The first valve body 26 has a through hole 29 formed through the center thereof and having a step on the inner periphery, and a second valve seat 30 projecting downward is formed at the lower end opening. Then, as shown in FIG. 2, the second valve body 31 that comes into contact with and separates from the second valve seat 30 is fitted to the valve stem 3 loosely fitted in the through hole 29.
2 Fixed to the tip. Further, the through hole 29 of the first valve body 26 is formed such that the upper end portion has an enlarged diameter, and the transmission piece 33 that contacts the step portion is fixed in the middle of the valve rod 32. The stepped portion has four through holes 29a, 29a so that the flow of air in the through-hole 29 is not interrupted by the transmission piece 33 abutting on the stepped portion having an increased diameter in the through-hole 29.
... are formed. By the way, the valve stem 32 is not fixed at its upper end to the movable iron core 23,
9 so that it can be freely moved up and down freely.

Next, as shown in FIG. 1, one of the communication paths 11 communicating with the air tank 3 is attached to a switch section 12 constituting the pressure switch 1 and a diaphragm 41 is attached to an opening on the upper surface of the body 13. It is configured to communicate with the pressure chamber 42. On the upper surface of the diaphragm 41, an operation panel 43 whose center is projected is fitted so as to be able to move up and down. The projection of the operation panel 43 is in contact with a passive lever 45 supported by a support shaft 44. FIG. 7 is a side view of the pressure switch 1 with the cover 16 removed. As shown in the drawing, the tip of the lever 47 for operating the contact point of the limit switch 46 is disposed on the tip of the passive lever 45 in an overlapping manner.

In this embodiment, a single-phase motor 50 having a small output but a low cost is used. The motor 50 is connected to a power source via a limit switch 46 as shown in FIG. 8, and at the same time, the relief valve 5 is connected to the limit switch 46 via a delay circuit 59. Here, FIG. 8 is a block diagram showing a configuration of the pressure switch 1, and FIG. 9 is a block diagram showing a delay circuit. The delay circuit 59 has output terminals 54 and 56 connected to the solenoid of the relief valve 5, respectively, and input terminals 51 and 52 connected to an AC power supply. And
A circuit M for reducing the load on the motor 50 is configured as described later. On the other hand, the pressure switch 1 is provided with a manual switch 17 on the cover 16 so that the limit switch 46 can be switched manually, and a switch operation plate disposed on the tip end of the lever 47 similarly to the passive lever 45. 18 is supported on the support shaft 44.

Next, the operation of the relief valve of the present embodiment will be described for an air supply device. Here, FIG.
5 is a graph showing the passage of time of the air pressure in a graph. FIG. 6A is a diagram showing the air pressure in the air tank 3, and FIG. First, when the motor 50 is started to drive the compressor 2, compressed air is supplied from the compressor 2 into the primary pipe 4. One of the air supplied into the primary pipe 4 is a check valve 7.
Is supplied to the air tank 3 through the other port, and the other flows into the relief valve 5 from the input port 6. When air is supplied into the primary pipe 4 in this manner, 250 mm in diameter of 4 mm
The pressure in the primary pipe at a distance of instantaneously rises to 1 kgf / cm ² (0.3 seconds between 0 and A shown in FIG. 10B).

By the way, when the motor 50 is started, the supply voltage to the motor 50 drops and drops extremely, and the starting force is remarkably reduced. Therefore, a load is applied to the motor 50 in order to stably supply the supply voltage. Need not be. For this purpose, it is conceivable to provide a constant voltage device. However, in order to increase the cost, in this embodiment, the valve closing operation of the relief valve 5 having the above configuration is delayed by the delay circuit 59. That is, as shown in FIG.
Is opened, and the supplied air is exhausted so as not to increase the pressure in the primary pipe 4 so as not to apply a load to the motor 50.

Specifically, when an AC voltage is applied to the input terminals 51 and 52, the diodes D1, D2, D3 and D3 (indicated by the symbol "D") in the delay circuit 59 shown in FIG.
DC current is obtained by a rectifier circuit in which D4 is connected in a bridge shape. At this time, no current flows to the solenoid portion of the relief valve 5 because the output terminal 56 is not conducting.
This is because a time difference is generated between the output terminal 56 and the circuit M forming the delay circuit 59. That is, the resistor R3 and the capacitor (symbol "C")
C2 is charged with a time constant determined by C2). Therefore, the potential of C2 becomes the Zener diode ZD1.
, The capacitor C2 causes a discharge current to flow through the gate of the thyristor T. Then, the thyristor T is turned on, and a current flows through the terminal 56. Since the time constant at this time is approximately 3.5 seconds, the current flows to the terminal 56 with a delay of about 3.5 seconds, so that the relief valve closes with a corresponding delay.

Therefore, for 3.5 seconds after starting the motor 50,
Since the movable iron core 23 is kept lowered by the urging force of the spring 24, the first valve seat 25 and the first valve body 26 and the second valve seat 30 and the second valve body 31 are separated from each other, and the communication passage 11
The air that has flowed into the inside is divided into two directions, flows into the exhaust hole 15, and is exhausted. That is, one passes through the through hole 29 of the first valve body 26 when the valve rod 32 is loosely fitted, and the other
Slide protrusions 26a formed on the outer periphery of the valve body 26,.
Pass through the gap between. Therefore, the air pressure in the primary pipe 4 instantaneously increases to 1 kgf / cm ² until a predetermined time (3.5 seconds) at which the supply voltage to the motor 50 is stabilized (point A). Since the relief valve 5 is open, a constant value is maintained as it is (between AB).

Then, 3.5 seconds after the supply voltage to the motor is stabilized, a current flows to the terminal 56 by the delay circuit 59, so that the movable iron core 23 is attracted to the fixed iron core 22, which is energized when the coil 21 is energized and excited. It will rise against the urging force of the spring 24. When the movable iron core 23 rises, the first valve body 26 released from the regulation of the transmission piece 33
Is raised by the urging force of the spring 28 and comes into contact with the first valve seat 25. Further, since the valve stem 32 is loosely fitted in the through hole 29 of the first valve body 26, the second valve body 31 rises by the pressure of the air and comes into contact with the second valve seat 30. Therefore, the orifice 20 is shut off and the exhaust of air is stopped.

The pressure in the primary pipe 4 from which the exhaust of the air has been stopped rapidly increases, and the pressure in the air tank 3 similarly increases. The air that has flowed into the air tank 3 flows from the secondary pipe 8 to the input port 9, flows through the communication path 11, and is discharged from the output port 10. On the other hand, the air in the air tank 3 also flows from the communication passage 11 into the pressure chamber 42, so that the same pressure as the discharged air is applied to the diaphragm 41.
In the present embodiment, the air pressure of the air discharged from the output port 10 is set to 5 to 7 kg / cm ² . Therefore, the air pressure applied to the diaphragm 41 becomes the upper limit set pressure 7 kg / c.
When m ² is exceeded, diaphragm 41 expands and operation panel 4
3 is set. Diaphragm 41
Acts on the operation panel 43, the passive lever 45 is lifted, the lever 47 rotates, and the contact of the limit switch 46 is cut off.

When the limit switch 46 is turned off, the power supply to the motor 50 and the solenoid is cut off, the supply of air from the compressor 2 is stopped, and the relief valve 5 is opened. Therefore, as shown in FIG.
Between -C, the air pressure in the primary pipe 4 sharply rises from the point B where the relief valve 5 is closed, but the air supply is stopped at the point C exceeding the upper limit set pressure of 7 kg / cm ^2. Since the relief valve 5 is opened, the air pressure in the primary pipe 4 drops rapidly in a short time between C and D. On the other hand, since the backflow of the air supplied into the air tank 3 is stopped by the check valve 7, the air in the air tank 3 is consumed only by discharging from the output port 10, and FIG. It gradually decreases as shown in the middle.

Here, when the energization of the coil 21 is interrupted, the relief valve 5 opens as follows. First, the movable iron core 23 released from the suction of the fixed iron core 22,
It is lowered by the urging force of the spring 24. for that reason,
As shown in FIG. 3, the spring 2
The urging force of 4 pushes down the valve rod 32 against the air pressure in the primary pipe 4 applied to the second valve body 31. Therefore, the second valve element 31 and the second valve seat 30 are separated from each other, and the air in the primary pipe 4 passes through the through hole 29 of the first valve element 26 to the exhaust hole 15.

Then, since the air in the primary pipe 4 is exhausted to reduce the pressure, the valve rod 32 is pushed down by the movable iron core 23 which is continuously lowered as shown in FIG. The transmission piece 33 pushes down the first valve body 26 against the urging force of the spring 28. Therefore, the first valve body 26 and the first valve seat 25 are separated from each other, and the sliding protrusions 26a, 2
The air in the primary pipe 4 also flows out to the exhaust hole 15 from the gap between 6a. When the air pressure in the air tank 3 that is reduced by the opening of the relief valve 5 falls below the lower limit set pressure of 5 kg / cm ² , the diaphragm 41 is restored and the passive lever 45 is lowered, and the limit switch is turned on. Forty-six contacts are connected.

When power is again supplied to the motor 50, air is discharged from the compressor 2 and the relief valve 5 operates with a delay. As in the above case, the air pressure in the primary pipe 4 is instantaneous (see FIG. 1).
0 kg (0.3 seconds between EF shown in (b))
^It rises to ² , but keeps a constant value (between FG). At the point G 3.5 seconds after the point E, the relief valve 5 is closed, and thus rises sharply. Since the air pressure in the primary pipe 4 exceeds 5 kg / cm ² between G and H, the air pressure in the air tank 3 that changes at the lower limit set value of 5 kg / cm ² starts to rise again from the point d. Then, the air pressure in the air tank 3 is again set to the upper limit set value of 7
At a point e exceeding kg / cm ² , the limit switch 46 is turned off, and the air pressure similarly decreases. In the air supply device of the present embodiment, the air pressure in the air tank 3 is thus maintained at the set pressure of 5 to 7 kg / cm ² .

By the way, the pressure switch 1 of the present embodiment
Is provided with a manual switch 17, and when the manual switch 17 is turned, the cam plate 17 a
Rotates to rotate the upper end of the switch operation plate 18 rightward in FIG. Therefore, the other end of the switch operation plate 18 is lifted and acts on the lever 47 to cut off the contact of the limit switch 46. Therefore, the power supply to the motor 50 and the coil 21 is shut off, and the motor 50 and the coil 21 can be stopped at an arbitrary air pressure position.

Therefore, the relief valve 5 of the present embodiment having the above-described configuration uses an electromagnetic valve as its configuration and further has a double valve structure as its valve portion. The capacity was reduced and the size was reduced. That is, since the relief valve is configured to open and close the valve by operating the solenoid valve without using the flow valve as in the related art, the diameter of the orifice 20 can be increased, and the flow rate can be increased. did it. Further, in the present embodiment, first, the second valve element 31 having a small pressure receiving area is opened, whereby the air on the primary pipe 4 side is evacuated to reduce the pressure, and then the pressure receiving area is large. Since the first valve body 26 is opened, the load on the spring 24 is reduced. Therefore, the solenoid itself was reduced in size together with the spring 24, and the relief valve itself could be reduced in size.

In the pressure switch 1 according to the present embodiment, the manual switch 17 is provided so that the limit switch 46 can be turned off. Therefore, even if the air pressure rises excessively due to a sudden failure or the like, it is manually adjusted. can do. Further, by energizing the coil 21 by the delay circuit 59 and exhausting air at the time of starting the motor 50 to restrict the rise in pressure, the motor 50 whose starting force is reduced by a voltage drop at the time of starting is reduced. It was possible to avoid the load.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes can be made without changing the gist of the present invention. For example, in the above-described embodiment, the relief valve is provided integrally with the pressure switch, but may be configured as a single relief valve.

[0035]

According to the present invention, a first valve seat formed in a flow passage extending from a primary pipe and a first valve body slidable on the inner wall surface of the flow passage are provided. A second valve seat is formed at the opening of the through hole of the first valve body, and a second valve body is fixed to the lower end of the valve rod that is loosely fitted through the through hole. The second valve has a double structure. The first valve body has a non-contact portion with the inner wall of the flow passage and a flow passage formed by a through hole into which the valve rod is loosely fitted. Therefore, a small relief valve capable of increasing the air flow rate can be provided.

In the relief valve of the present invention, the closing of the first valve body and the second valve body is delayed for a predetermined time after the start of the air compressor. A load can be prevented from being applied to the motor whose power is reduced, and a stable supply of air has become possible.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of an air supply device having a pressure switch with a relief valve according to the present invention.

FIG. 2 is a cross-sectional view illustrating the relief valve according to the embodiment when the valve is closed.

FIG. 3 is a cross-sectional view showing a relief valve according to one embodiment.

FIG. 4 is a sectional view showing a relief valve according to one embodiment.

FIG. 5 is a sectional view showing a first valve body.

FIG. 6 is a plan view showing a first valve body.

FIG. 7 is an internal side view of the pressure switch.

FIG. 8 is a block diagram showing a configuration of a pressure switch.

FIG. 9 is a block diagram showing a delay circuit.

FIG. 10 is a graph showing a time course of air pressure.

FIG. 11 is a sectional view showing a conventional flow type relief valve.

FIG. 12 is a sectional view showing a conventional electromagnetic relief valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure switch 2 Compressor 3 Air tank 4 Primary piping 5 Relief valve 14 Communication hole 15 Exhaust hole 21 Coil 23 Moving iron core 25 First valve seat 26 First valve body 30 Second valve seat 31 Second valve body 32 Valve rod

Claims (3)

(57) [Claims] An electromagnetic valve-type relief valve provided on a primary pipe side connected to an air compressor, for discharging air discharged into the primary pipe at a predetermined timing and adjusting a pressure in a pneumatic circuit. A first valve seat formed on a flow path communicating with the primary pipe; and a non-contact portion forming a flow channel between the flow path inner wall surface and an outer peripheral surface and a flow path inner wall surface slidable. A first valve body with respect to the first valve seat, wherein a through hole penetrating vertically is formed at the center, and a downstream end surface of the first valve body, A second valve seat formed at an opening; and a second valve body fixed to a lower end of a valve stem loosely fitted through the through-hole and corresponding to the second valve seat, wherein the valve stem is movable. A transmission piece disposed coaxially below the iron core and transmitting the downward movement of the movable iron core to the first valve body is fixed. Relief valve, characterized in that those that are. 2. The relief valve according to claim 1, wherein a through-groove is formed in an opening of the first valve body with which the transmission piece abuts. Relief valve. 3. The relief valve according to claim 1, wherein the closing of the first valve body and the second valve body is delayed for a predetermined time after the start of the air compressor. Relief valve.