JPH06337080A - Solenoid valve - Google Patents

Abstract

PURPOSE:To ensure the proper open/close operation of a valve, even when the valve is used in close state over a long time, and improve the reliability thereof by preventing the occurrence of seizure between a valve seat and the valve. CONSTITUTION:A solenoid valve has a valve seat 3 laid in a flow passage 2 formed in a valve box 1, a valve 4 formed out of an elastic body for blocking the seat 3 and the flow of fluid, and a valve driving section for actuating the valve 4 with a core 11, a coil 8 and a coil spring 12. In this case, the solenoid valve is fitted with a voltage regulator 20 for adjusting a voltage value applied to a coil 10 with the coil 8 excited, to such voltage as generating a magnetic force slightly larger than the spring force of the spring 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solenoid valve used for shutting off a fluid when necessary on a pipe through which the fluid flows.

[0002]

2. Description of the Related Art Generally, a valve is composed of a valve seat formed in a flow path inside a valve box and a valve body operated by a valve body drive section. The fluid is shut off by bringing this valve element into close contact with the valve seat. The valve is roughly classified into a manual valve, an air operated valve, a solenoid valve, etc. The present invention relates to a solenoid valve of this type, and the structure of a conventional solenoid valve will be described below.

FIG. 16 is a vertical sectional view showing the basic structure of a solenoid valve. As shown in FIG. 16, a flow path 2 through which a fluid flows is formed inside the valve box 1, and a valve seat 3 made of metal is disposed in the middle of the flow path 2 and is in close contact with the valve seat 3. The valve body 4 for shutting off the fluid is fixed to the valve body holding portion 5. As the material of the valve body 4, a fluorine-based rubber having good heat resistance and good weather resistance is used.

A casing 7 is fixed above the neck portion 6 formed in the upper portion of the valve box 1, a coil 8 is installed in the casing 7, and the neck portion is provided on the inner peripheral side of the coil 8. A closed box 9 is fixed to the upper surface of 6.

Further, the valve body holding portion 5 is connected to the core 11 via the stem 10, and the core 11 is moved upward by the excitation of the coil 8 provided on the outer periphery of the closed box 9, while the coil 8 is The non-excitation makes the core 11 move downward by the spring force of the spring 12 provided between the core 11 and the closed box 9.

Here, the coil 8 is connected to an AC power supply 15 via a cable 13 and a switch 14. As the material of the core 11, SUS430F, which is a kind of electromagnetic steel sheet and has a relatively small eddy current loss, is used.

With the above structure, the fluid enters the flow path 2 in the valve box 1 from the fluid inlet 16, and when the valve seat 3 and the valve body 4 are in close contact with each other, the fluid is shut off while the valve is closed. When the seat 3 and the valve body 4 are separated, the fluid flows out from the fluid outlet 17.

FIGS. 17 and 18 show the operating principle of the above solenoid valve. When the switch 14 is off and the coil 8 is not excited, the spring force of the spring 12 located at the upper portion of the spring 18 located at the lower portion of the spring 18 is reduced. Greater than force, stem 10
The valve body holding portion 5 is pushed down as shown in FIG. 17, and the valve is open with the valve seat 3 and the valve body 4 separated from each other.

On the other hand, when the switch 14 is turned on and the coil 8 is in the excited state, the electromagnetic force of the coil 8 reduces the force from above and the spring 18 extends, so that FIG.
As shown in FIG. 8, the valve element 4 is seated on the valve seat 3 and the valve is closed. The conditions at this time are: attraction force of coil 8 + spring force of spring 18-weight of valve body component-spring 12
Only when the spring force of> is 0, the valve is fully opened.

[0010]

By the way, if the solenoid valve is shut off for a long time or at a high temperature, a phenomenon in which the valve seat 3 made of metal and the valve body 4 made of fluororubber stick to each other occurs. There is. In this case, there is a problem in that the valve body 4 and the valve seat 3 cannot be separated from each other even when the coil 8 is de-energized, the valve becomes inoperable, and the flow rate cannot be controlled.

The cause of sticking between the valve seat 3 and the valve body 4 is that the core 1
The heat generated in the core 11 and the coil 8 caused by the iron loss (eddy current loss + hysteresis loss) of No. 1 causes the temperature of the valve body 4 and the valve body drive portion of the valve seat 3 to rise, which deteriorates the material of the valve body 4. Then, sticking occurs.

The present invention has been made in consideration of the above-mentioned circumstances, and prevents the valve seat and the valve body from sticking to each other and can reliably open and close the valve body even when used in a closed state for a long time. , And to provide a solenoid valve with improved reliability.

[0013]

In order to solve the above-mentioned problems, a solenoid valve according to claim 1 of the present invention comprises a valve seat provided in a flow passage formed inside a valve box, and this valve. In a solenoid valve having a valve body formed of an elastic body that closes a seat to shut off a fluid and is driven by a core, a coil, and a spring, the solenoid valve has the above-mentioned structure with the coil being excited. A voltage regulator for adjusting the voltage value applied to the coil to a voltage value that generates a magnetic force slightly larger than the spring force of the spring is provided.

According to another aspect of the solenoid valve of the present invention, there is provided a valve seat formed in the flow path formed inside the valve box, and a valve body formed of an elastic body that closes the valve seat to shut off fluid. And a casing provided with a core and a coil for driving the valve element, a neck portion formed between the valve box and the casing is provided with at least one of a heat insulating unit and a heat radiating unit. It is a thing.

Further, the solenoid valve according to a third aspect of the present invention includes a valve seat formed in the flow path formed inside the valve box, and a valve body formed of an elastic body that closes the valve seat to shut off fluid. And a solenoid valve having a valve body driving section for driving the valve body,
An adjusting mechanism for adjusting the movement stroke of the valve element with respect to the valve seat to a predetermined value is provided.

According to another aspect of the solenoid valve of the present invention, there is provided a valve seat formed in the flow path formed inside the valve box, and a valve body formed of an elastic body that closes the valve seat to shut off fluid. In a solenoid valve having a valve body driving section for driving the valve body with a core and a coil, the core is made of a low iron loss material.

[0017]

In the first aspect of the present invention having the above-mentioned structure, the voltage value applied to the coil is adjusted to a voltage value for generating a magnetic force slightly larger than the spring force of the spring with the coil being excited. As a result, the Joule heat generated in the coil is reduced after the excitation. as a result,
A rise in temperature inside the coil is suppressed, and sticking between the valve seat and the valve body is prevented.

Further, in the present invention, the neck portion formed between the valve box and the casing is provided with at least one of the heat insulating means and the heat radiating means, so that the heat generated from the coil and the core is applied to the valve seat. And it becomes difficult to transmit to the valve body, and the temperature of the valve body can be suppressed low. As a result, sticking between the valve seat and the valve body does not occur.

Further, according to the third aspect of the present invention, the movement stroke of the valve body with respect to the valve seat is adjusted by a mechanism.
The valve body does not come into close contact with the valve seat more than necessary and is kept in the minimum necessary condition for sealing the fluid, preventing deterioration of the valve body even during long-term use, and preventing the valve seat and valve body from being deteriorated. Is prevented from sticking.

Further, according to the present invention, since the core is made of the low iron loss material, the eddy current loss of the core is reduced, and the heat transfer amount to the contact portion between the valve seat and the valve body can be reduced. it can. As a result, it is possible to prevent the valve seat and the valve body from becoming hot, and the valve seat and the valve body do not stick to each other.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show a first embodiment of a solenoid valve according to the present invention. Note that the same or corresponding portions as those of the conventional configuration will be described using the same reference numerals as those in FIGS.

As shown in FIG. 1, a flow path 2 through which a fluid flows is formed inside a valve box 1. A valve seat 2 is arranged in the middle of this flow path 2 and is in close contact with the valve seat 2. The valve body 4 for shutting off the fluid is fixed to the valve body holding portion 5. As the material of the valve element 4, a fluorine-based rubber having good heat resistance and good weather resistance is used.

A neck portion 6 is formed on the upper portion of the valve box 1, a casing 7 is fixed above the neck portion 6, and a coil 8 is installed in the casing 7.
A closed box 9 is fixed to the upper surface of the neck portion 6 on the inner peripheral side of the coil 8. Then, the coil 8, the core 11 and the spring 12 constitute a valve body drive unit for driving the valve body 4.

The valve body holding portion 5 is provided with the core 1 via the stem 10.
1, the core 11 is excited by the coil 8 through the closed box 9 and is movable upward by the spring force of the spring 18, while the core 11 and the closed box 9 are connected to each other.
It is configured so as to be movable downward by the spring force of the spring 12 interposed between and.

The coil 8 is connected to a voltage regulator 20 via a cable 13, and this voltage regulator 20 is connected to a switch 14
And is connected to the AC power supply 15. Therefore, the solenoid valve is turned on and off by the switch 14, and the coil 10
The voltage value applied to is adjusted by the voltage adjuster 20.

Next, the operation of this embodiment will be described.

When the switch 14 is off, the fluid is discharged from the fluid inlet 16 to the outside through the flow passage 2 in the valve box 1 and the fluid outlet 17. Next, when shutting off the fluid for a long time, when the switch 14 is turned on as shown in FIG. 2, the coil 8 is excited and the core 11 moves upward, so that the valve body 4 comes into close contact with the valve seat 2. To do.

Subsequently, the exciting force of the coil 8 is significantly larger than the spring force of the spring 12 in the closed state as shown in FIG. 3, and it is prevented that a useless voltage is continuously applied to the coil 8 for a long time. Therefore, the voltage regulator 2 is immediately adjusted so that an exciting force slightly larger than the spring force of the spring 12 is generated.
When 0, the voltage value applied to the coil 8 is adjusted.

Specifically, as shown in FIG. 3, the spring force of the spring 12 at the moment when the coil 8 is excited is 1.8 kgf, and this spring force is 1.6 kg of the spring force when the solenoid valve is open.
Although it is larger than f, it is much smaller than the excitation force of 4.8 kgf at the moment when the coil 8 is excited, so after the solenoid valve is closed, the voltage value applied to the coil 8 by the voltage regulator 20 is gradually changed. Lower the spring force of the spring 12 to 1.8 kgf
Lower to generate a slightly larger excitation force of 2.3 kgf. This state is maintained until the solenoid valve opens.

As described above, according to this embodiment, the voltage value applied to the coil 8 is adjusted by the voltage adjuster 15 to a voltage value that generates a magnetic force slightly larger than the spring force of the spring 12 while the coil 8 is excited. The coil 8
The Joule heat generated at 1 is reduced after excitation. As a result, the temperature rise inside the coil 8 is suppressed, so that the heat transferred to the seal portion between the valve seat 3 and the valve body 4 through the neck portion 6 is reduced, and the valve seat 3 and the valve body 4 are fixed to each other. Is prevented.

That is, in the present embodiment, even when the solenoid valve is kept in the excited state for a long time, the rise of the ambient temperature of the contact surface between the valve seat 3 and the valve body 4 due to the heat generated by the coil 8 (Joule heat) is suppressed. Therefore, the occurrence of sticking between the valve seat 3 and the valve body 4 can be significantly reduced.

4 and 5 show a second embodiment of the solenoid valve according to the present invention. The same parts as those of the first embodiment described above will be designated by the same reference numerals. The same applies to the following embodiments and modifications. Further, the solenoid valve of the second embodiment has the valve seat 3, the mounting position of the valve body 4, the stem 10
Although the number and the presence / absence of the spring 18 are different from those of the first embodiment, the basic structure and operating principle are the same as those of the first embodiment.

In the second embodiment, a hollow portion 21 as a heat insulating means is formed in the axial direction in the neck portion 6 which structurally connects the valve box 1 and the casing 7.

Next, the operation of this embodiment will be described.

If the electromagnetic valve is kept closed for a long time, a current will continuously flow through the coil 8. For this reason,
The coil 8 itself and the core 11 generate heat. This heat is divided into one that is convectively transmitted to the surrounding air and one that is thermally transmitted through the neck portion 6.

In this embodiment, since the hollow portion 21 is formed in the neck portion 6, the area through which the heat of the coil 8 itself and the core 11 passes is significantly narrower than that of the solid structure. Therefore, since the amount of heat passing is approximately proportional to the cross-sectional area, the hollow portion 21 is formed in the neck portion 6 as in the present embodiment.
If the cross-sectional area is made smaller by forming the, the amount of heat transfer to the valve box 1 can be significantly reduced.

Therefore, the temperature of the casing 7 is as shown in FIG.
As shown in FIG. 5, the temperature of the valve box 1 can be remarkably reduced, although it is slightly higher than that of the conventional structure. As a result, the temperature of the valve body 4 can be kept low, so that the valve seat 2 and the valve body 4 can be prevented from sticking to each other.

As described above, according to this embodiment, since the valve seat 2 and the valve body 4 can be prevented from sticking to each other, even when the solenoid valve is used in a closed state for a long time in a high temperature state. , The reliability of the solenoid valve is not impaired. The rest of the configuration and operation are the same as in the first embodiment, so a description thereof will be omitted.

FIG. 6 shows a first modification of the second embodiment of the solenoid valve according to the present invention. In this modification, the hollow portion 21 is eliminated and a fin 22 as a heat radiation means is attached to the outer peripheral surface of the neck portion 6. It is fixed.

Therefore, in this modification, the fins 22 are attached, so that part of the heat passing through the neck portion 20 is dissipated by the fins 22 into the surrounding air, and the amount of heat reaching the valve box 1 is reduced. The same effect as the second embodiment can be obtained.

FIG. 7 shows a second modification of the second embodiment of the solenoid valve according to the present invention. In this modification, the neck portion 6a is made of a material having a low thermal conductivity, such as a sintered metal, to constitute the heat insulating means. ing. Also in this modification, the same effect as that of the second embodiment can be obtained.

In this embodiment, the neck portion 6 is provided with the hollow portion 21 and the like as the heat insulating means and the fins 22 are attached as the heat radiating means. The heat transfer amount can be further reduced.

FIG. 8 shows a third embodiment of the solenoid valve according to the present invention. In this embodiment, the threaded portion 1 is provided on one lower part of the stem 10.
0a is provided, and a stopper nut 25 as an adjusting mechanism is screwed into the screw portion 10a. By changing the screwing position of the stopper nut 25 to the screw portion 10a,
The movement stroke of the valve body 4 and the valve body support 3 with respect to the valve seat 2 can be adjusted appropriately.

Next, the operation of this embodiment will be described.

In the excited state of the coil 8, the valve body 4 is pressed against the valve seat 3 by the spring force of the spring 18, but the stopper nut 25 is attached to the lower portion of the stem 10 so that the stopper nut 25 can be inserted into the valve box. By making contact with the inner surface of 1, the movement stroke of the valve body 4 and the valve body support 3 with respect to the valve seat 2 is adjusted to a predetermined value, and the bite of the valve body 3 into the valve seat 2 is optimized. Therefore, the valve body 3
Does not come into pressure contact with the valve seat 2 more than necessary, and the adherence to the valve seat 2 is significantly reduced.

Further, by changing the position of the stopper nut 25 at the time of long-term use or when the setting is changed, the setting can be changed appropriately and easily.

FIG. 9 shows a first modified example of the third embodiment of the solenoid valve according to the present invention. In this modified example, the adjusting mechanism is replaced by a stopper nut 25 and a double nut 26 having a detent function. There is. Thus, once the movement strokes of the valve body 4 and the valve body support 3 with respect to the valve seat 2 are set, they do not easily change due to the operation of the solenoid valve. FIG. 10 shows a second modified example of the third embodiment of the solenoid valve according to the present invention. In this modified example, the outer diameter of the stem 5 is the inner diameter of the inner surface of the valve box 1 connected to the valve seat 2. The stopper 27 is fixed. By fixing the stopper 27 to the valve box 1, it is possible to prevent the metal portion of the valve body support 3 from coming into contact with the stopper 27 in the excited state and preventing the valve body 4 from being caught in the valve seat 3 more than necessary. Become.

If the stopper 27 is made of a material having a large coefficient of thermal expansion, the stopper 27 linearly expands from the stem 10 as the temperature of the valve box 1 rises. Automatically lowers slightly,
It is possible to prevent the valve body 4 from sticking to the valve seat 2.

Although the stopper nut 25 and the stopper 27 shown in FIGS. 9 and 10 are of a bolt shape and a pipe shape, respectively, the present invention is not limited to this and other shapes can be used as long as they have a position adjusting function. It may be one.

In order to prevent the stopper nut 25 and the stopper 27 from hitting each other, it is effective to install at least three stopper nuts 25 and 27, respectively. With respect to the fine adjustment function of the position adjustment of the stopper nut 25 and the automatic adjustment function with the temperature change of the stopper 27, the same effect can be obtained even with other shapes, and these may be used at the same time. .

FIG. 11A shows a fourth embodiment of the solenoid valve according to the present invention.
An example is shown. In this embodiment, the core 11 is made of SUS430.
The eddy current loss is about twice as large as that of F, but the eddy current loss is 1/2 to 1/3 smaller than that of silicon, and a laminated structure as shown in FIG. The current loss is further reduced.

As described above, in this embodiment, since the core 11 is made of the silicon steel plate, the transmission from the core 11 and the coil 8 to the seal portion composed of the valve seat 2 made of metal and the valve body 4 made of rubber. The amount of heat can be reduced, and the temperature rise of the valve seat 2 and the valve body 4 can be prevented.

Although the silicon steel sheets have a laminated structure in the fourth embodiment, the core 11 may be formed by dividing the silicon steel sheets in the circumferential direction as shown in FIG. Also, the core 11
In addition to the above-mentioned silicon steel sheet, ferrite may be used as a material of which the eddy current loss is substantially zero and the iron loss is small, and the iron loss (eddy current loss + hysteresis loss) is 1/3 or less of that of the silicon steel sheet. The same effect can be obtained by using a magnetic alloy.

FIG. 13 shows a fifth embodiment of the solenoid valve according to the present invention. In this embodiment, a large number of fins 30 are formed on the outer peripheral surface of the casing 7, and the heat generated by the core 11 and the coil 8 is radiated by the casing 7.

Therefore, according to this embodiment, the heat of the casing 7 is dissipated to the ambient air by the fins 30,
The amount of heat reaching the valve box 1 is reduced, and the same effect as the second embodiment can be obtained.

FIG. 14 shows a first modification of the fifth embodiment of the solenoid valve according to the present invention. In this modification, the cooling line valve is applied to the bottom surface of the valve body holding portion 5 when the fluid is air. Body 3
1 is attached and this cooling line valve body 31
A cooling line valve seat 32 is installed in the flow path 2 immediately below the.

Further, one end of the cooling line 33 is opened in the cooling line valve seat 32, and the other end of the cooling line 33 is arranged so as to extend to the vicinity of the fin 30 formed in the casing 7. As a result, the air guided from the flow path 2 through the cooling line 33 can be jetted to the fins 30 to forcibly cool the heat generated in the core 11 and the coil 8. As a result, as compared with the fifth embodiment. A higher heat dissipation effect can be obtained.

FIG. 15 shows a second modification of the fifth embodiment of the solenoid valve according to the present invention. In this modification, an air supply source 35 is used.
Is separately provided, and the air from the air supply source 35 is jetted to the fins 30 through the cooling line 33 to cool the casing 7. Therefore, also in this modification, the same effect as that of the first modification of the fifth embodiment can be obtained.

It should be noted that the present invention is not limited to the above-mentioned respective embodiments, and if a plurality of the above-mentioned embodiments and respective modified examples are combined and constructed, the heat generated from the coil 8 and the core 11 is generated by the valve seat 3.
And, it becomes more difficult to transmit to the valve body 4.

[0061]

As described above, according to the first aspect of the present invention.
According to this, the Joule heat generated in the coil is reduced after the excitation by adjusting the applied voltage with the voltage regulator to a voltage value that causes the coil to generate a magnetic force slightly larger than the spring force of the spring when the coil is excited. . As a result, the temperature rise inside the coil is suppressed, the valve seat and the valve body are prevented from sticking to each other, the opening / closing operation of the solenoid valve is ensured, and the reliability can be improved.

According to the second aspect of the present invention, since the neck portion formed between the valve box and the casing is provided with at least one of the heat insulating means and the heat radiating means, it is generated from the coil and the core. It becomes difficult for heat to be transferred to the valve seat and the valve body, and the temperature of the valve body can be kept low. As a result, sticking between the valve seat and the valve body does not occur.

Further, according to claim 3 of the present invention, by adjusting the movement stroke of the valve body with respect to the valve seat to a predetermined value by the adjusting mechanism, the valve body does not contact the valve seat more than necessary, and the fluid Will be held in the minimum necessary state for sealing the valve, and deterioration of the valve element is prevented even during long-term use, and sticking between the valve seat and the valve element is prevented.

According to the fourth aspect of the present invention, since the core is made of the low iron loss material, the eddy current loss of the core is reduced, and the heat transfer amount to the seal portion between the valve seat and the valve body is reduced. It can be reduced. As a result, it is possible to prevent the valve seat and the valve body from becoming hot, and the valve seat and the valve body do not stick to each other.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a first embodiment of a solenoid valve according to the present invention.

FIG. 2 is a vertical cross-sectional view showing an excited state of a coil in the solenoid valve according to the first embodiment.

FIG. 3 is a graph showing the relationship between the spring force and the exciting force in the stroke of the core in the first embodiment.

FIG. 4 is a vertical cross-sectional view showing a second embodiment of the solenoid valve according to the present invention.

FIG. 5 is a temperature distribution chart showing the effect of the second embodiment.

FIG. 6 is a vertical cross-sectional view showing a first modification of the second embodiment.

FIG. 7 is a vertical sectional view showing a second modification of the second embodiment.

FIG. 8 is a vertical cross-sectional view showing the main parts of a third embodiment of a solenoid valve according to the present invention.

FIG. 9 is a vertical cross-sectional view showing the main parts of a first modification of the third embodiment.

FIG. 10 is a vertical cross-sectional view showing the main parts of a second modification of the third embodiment.

11A is a longitudinal sectional view showing a fourth embodiment of the solenoid valve according to the present invention, and FIG. 11B is a perspective view showing the core of FIG.

FIG. 12 is a perspective view showing a modification of the core of the fourth embodiment.

FIG. 13 is a longitudinal sectional view showing a fifth embodiment of the solenoid valve according to the present invention.

FIG. 14 is a vertical sectional view showing a first modification of the fifth embodiment.

FIG. 15 is a vertical sectional view showing a second modification of the fifth embodiment.

FIG. 16 is a vertical sectional view showing a conventional solenoid valve.

FIG. 17 is a longitudinal sectional view of a main part showing a non-excited state of a coil in a conventional solenoid valve.

FIG. 18 is a longitudinal cross-sectional view of a main portion showing a coil excitation state in a conventional solenoid valve.

[Explanation of symbols]

 1 valve box 2 flow path 3 valve seat 4 valve body 5 valve body holding part 6 neck part 7 casing 8 coil 9 closed box 10 stem 11 core 12 spring 15 AC power supply 20 voltage regulator 21 hollow part (heat insulating means) 22 fin ( Heat dissipation means) 25 Stopper nut (adjustment mechanism) 26 Double nut (adjustment mechanism) 27 Stopper (adjustment mechanism)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuzo Yamamoto 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside the Corporate Research and Development Center, Toshiba Corporation (72) Inventor Koji Mizuguchi 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Address Stock Company Toshiba Yokohama Office

Claims (4)

[Claims] 1. A valve seat provided in a flow path formed inside a valve box, a valve body formed of an elastic body for closing the valve seat to shut off a fluid, and a core of the valve body, In a solenoid valve having a coil and a valve body driving unit driven by a spring, a voltage for adjusting a voltage value applied to the coil in a state where the coil is excited to a voltage value for generating a magnetic force slightly larger than the spring force of the spring. A solenoid valve that is equipped with a regulator. 2. A valve seat provided in a flow passage formed inside a valve box, a valve body formed of an elastic body for closing fluid by blocking the valve seat, and driving the valve body. A solenoid valve having a casing provided with a core and a coil, wherein a neck portion formed between the valve box and the casing is provided with at least one of a heat insulating unit and a heat radiating unit. 3. A valve seat provided in a flow passage formed inside a valve box, a valve body formed of an elastic body for closing the valve seat to shut off a fluid, and driving the valve body. A solenoid valve having a valve body drive part, wherein the solenoid valve is provided with an adjusting mechanism for adjusting a movement stroke of the valve body with respect to the valve seat to a predetermined value. 4. A valve seat provided in a flow passage formed inside a valve box, a valve body formed of an elastic body for closing the valve seat to shut off a fluid, and the valve body as a core and A solenoid valve having a valve body drive section driven by a coil, wherein the core is made of a low iron loss material.