# Patent

## Title
Solenoid valve

## Abstract

A solenoid valve has: a valve body; a moving core with a valve body on one end; a guide tube slidably enclosing the moving core; a stationary core disposed in an inner circumference of an opposite end portion of the guide tube so as to face an opposite end of the moving core; a valve spring to urge the moving core in a direction away from the stationary core; an electromagnetic coil disposed to enclose the guide tube; and a magnetic plate disposed on an opposite end of the guide tube having a caulked portion. The guide tube has a caulked portion formed to fix in position the stationary core by engagement of the caulked portion with a recessed groove formed on an outer periphery of the stationary core. When the stationary core is fixed in position by the caulked portion, that surface of the stationary core which faces the magnetic plate is either flush with, or is protruding beyond, the opposite end of the guide tube.

## Background
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a solenoid valve for use mainly in a combustion apparatus.
2. Background Art
This kind of solenoid valve is conventionally provided with: a valve body; a moving core having connected to one end thereof the valve body; a guide tube having slidably inserted thereinto the moving core; a stationary core disposed in an inner periphery of an opposite end portion of the guide tube so as to face an opposite end of the moving core; a valve spring to urge (press or force) the moving core in a direction away from the stationary core; an electromagnetic coil disposed to enclose the guide tube; and a magnetic plate disposed on the opposite end of the guide tube, whereby the moving core is sucked to the stationary core by a magnetic force transmitted through the magnetic plate to the stationary core due to electric charging to the electromagnetic coil.
In order to enable to efficiently transmit the magnetic force from the magnetic plate to the stationary core, it is necessary to bring the surface of the stationary core, said surface lying opposite to (or facing) the magnetic plate, into contact with the magnetic plate. The surface in question is hereinafter also called “that surface of the stationary core which faces the magnetic plate.” This expression of “that . . . which” will make it clear that it is the “surface” (not the “stationary core”) that faces or lies opposite to the magnetic plate. As a solution, conventionally there is formed, in a part of that surface of the stationary core which faces the magnetic plate, a projection to penetrate through a perforation (through hole) that is formed in the magnetic plate. Such a tip portion of the projection as is protruding through the perforation is thereafter caulked so as to bring that surface of the stationary core which faces the magnetic plate into contact with the magnetic plate (see, for example, JP-A-2010-164104).
In this conventional example, however, the magnetic plate is pushed toward the electromagnetic coil when the tip portion of the projection is caulked. As a consequence, in case the caulking force is excessive, an undue compression load will be applied to the electromagnetic coil. There is therefore a possibility that a bobbin of the electromagnetic coil gives rise to deformation.
SUMMARY
Problems that the Invention is to Solve
In view of the above points, this invention has a problem of providing a solenoid valve which is capable of bringing that surface of the stationary core which faces the magnetic plate into abutment with the magnetic plate without causing an undue compression load to operate on the electromagnetic coil.
Means for Solving the Problems
In order to solve the above-described problems, there is provided a solenoid valve comprising: a valve body; a moving core having connected to one end thereof the valve body; a guide tube having slidably inserted thereinto the moving core; a stationary core disposed in an inner circumference of an opposite end portion of the guide tube so as to face an opposite end of the moving core; a valve spring to urge the moving core in a direction away from the stationary core; an electromagnetic coil disposed to enclose the guide tube; and a magnetic plate disposed on the opposite end of the guide tube, whereby the moving core is sucked to the stationary core by a magnetic force transmitted through the magnetic plate to the stationary core due to electric charging to the electromagnetic coil. The guide tube has a caulked portion formed to fix in position the stationary core by engaging the caulked portion with a recessed groove formed on an outer periphery of the stationary core such that, in a state in which the stationary core is fixed in position by the caulked portion, that surface of the stationary core which faces the magnetic plate is either flush with, or is protruding beyond, the opposite end of the guide tube, whereby, by thus disposing the magnetic plate on the opposite end of the guide tube, that surface of the stationary core which faces the magnetic plate is in contact with the magnetic plate.
According to this invention, the stationary core is fixed in position to the guide tube. As a result, by disposing the magnetic plate on the opposite end of the guide tube, that surface of the stationary core which faces the magnetic plate and which is either flush with, or is protruding beyond, the opposite end of the guide tube is in contact with the magnetic plate. Therefore, unlike an example in which caulking is made to force the magnetic plate toward the electromagnetic coil, that surface of the stationary core which faces the magnetic plate can be contacted with the magnetic plate without causing an undue compression load on the electromagnetic coil.
Further, in this invention, the solenoid valve preferably comprises: a projection disposed in a protruding manner so as to be inserted into a through hole formed in the magnetic plate, the projection being formed in a part of that surface of the stationary core which faces the magnetic plate; and a spring interposed between a spring stopper formed at a tip portion of the projection that protrudes beyond the through hole, and the magnetic plate, such that an urging force of the spring maintains that surface of the stationary core which faces the magnetic plate in a state of being in contact with the magnetic plate. According to this arrangement, even if a force is applied to the guide tube to bring that surface of the stationary core which faces the magnetic plate away from the magnetic plate at the time of assembling the solenoid valve, that surface of the stationary core which faces the magnetic plate will not be leaving away from the magnetic plate as long as the urging force of the spring is stronger than the above-described force applied to the guide tube. This brings about an improvement in reliability.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a zero-governor in which is built a solenoid valve according to a first embodiment of this invention.
FIG. 2 is an enlarged sectional view of the solenoid valve shown in FIG. 1.
FIG. 3 is a sectional view of a solenoid valve according to a second embodiment of this invention.



DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to FIG. 1, reference numeral 1 denotes a dual plunger solenoid valve which is a solenoid valve according to this invention. The dual plunger solenoid valve is built into a zero governor 100 which is interposed in a gas supply passage to a burner. The zero governor 100 is provided with an inlet chamber 101; an intermediate chamber 103 which is partitioned by a first valve seat 102 from the inlet chamber 101; a first pressure chamber 105 which is partitioned by a second valve seat 104 from the intermediate chamber 103; an outlet chamber 107 which is partitioned by a third valve seat 106 from the intermediate chamber 103; a second pressure chamber 110 which is partitioned by a first diaphragm 108 from the outlet chamber 107 and which comes into communication with the first pressure chamber 105 through a flow communication path 109; a third pressure chamber 114 which is partitioned by a fourth valve seat 112 from a flow communication path 111 which is in communication with the second pressure chamber 110, and which comes into communication with the outlet chamber 107 through a flow communication path 113 and also which comes into communication with the first pressure chamber 105 through a flow communication path (not illustrated); an atmospheric-pressure chamber 118 which is partitioned by a second diaphragm 115 from the third pressure chamber 114; a first valve body 21 of the dual plunger solenoid valve 1 which opens or closes a first valve hole 102a which is formed in the first valve seat 102; a second valve body 22 of the dual plunger solenoid valve 1 which opens or closes a second valve hole 104a which is formed in the second valve seat 104; a first diaphragm valve 117 which is connected to the first diaphragm 108 to open or close a third valve hole 108a which is formed in a third valve seat 106; a second diaphragm valve 118 which is connected to the second diaphragm 115 to open or close a fourth valve hole 112a which is formed in a fourth valve seat 112; a first spring 119 which urges (or presses) the first diaphragm valve 117 toward a downward closing side; and a second spring 120 which urges the second diaphragm valve 118 toward a downward closing side. Then, when the first and the second valve bodies 21, 22 are both made to be the valve-open states, gas flows, as in the conventional manner, from the inlet chamber 101 to the outlet chamber 107. Even if the gas pressure (primary pressure) in the inlet chamber 101 varies, the gas pressure (secondary pressure) in the outlet chamber 107 can be maintained at the atmospheric pressure.
With reference also to FIG. 2, the dual plunger solenoid valve 1 is provided with: the first and the second valve bodies 21, 22; first and second moving cores 31, 32 each having connected to one end (lower end) thereof the first and the second valve bodies 21, 22; first and second tubes 41, 42 which have slidably inserted thereinto the first and the second moving cores 31, 32, respectively; first and second stationary cores 51, 52 which are disposed on an inner circumference at an upper end of the first and the second guide tube tubes 41, 42 in a manner to lie opposite to the other end (upper end) of the first and the second moving cores 31, 32, respectively; and first and second valve springs 61, 62 which respectively push the first and the second moving cores 31, 32 in a direction away from the stationary cores 5, 52. The first and the second valve bodies 21, 22 are of a normally-closed type in which the first and the second valve bodies 21, 22 are urged by the first and the second valve springs 61, 62, respectively, toward a closing position to close the first and the second valve holes 102a, 104a. 
The dual plunger solenoid valve 1 is further provided with: first and second electromagnetic coils 71, 72 which are disposed so as to enclose the first and the second guide tubes 41, 42, respectively; a first magnetic plate 81 which is disposed on the upper end of the first and the second guide tubes 41, 42 so as to bridge over the first and the second guide tubes 41, 42; and a second magnetic plate 82 which is disposed on the lower end of the first and the second guide tubes 41, 42 so as to bridge over the guide tubes 41, 42. Ordinarily, it is normal practice to provide a magnetic side plate which connects together the first and the second magnetic plates 81, 82. In this embodiment, however, the magnetic side plate is omitted and an arrangement has been made that a common magnetic path is formed from the first moving core 31 through the first stationary core 51, the first magnetic plate 81 the second stationary core 52, the second moving core 32, and the second magnetic plate 82 back to the first moving core 31. When electric currents that are opposite to each other in flow direction are caused to flow through the first electromagnetic coil 71 and the second electromagnetic coil 72, the first and the second moving cores 31, 32 are caused to be sucked to the first and the second stationary cores 51, 52 by means of the magnetic forces to be transmitted through the fit magnetic plate 81 to the first and the second stationary cores 51, 52. Thereafter, only by causing the electric current to flow only through one of the first electromagnetic coil 71 and the second electromagnetic coil 72, e.g., only through the first electromagnetic coil 71, there can be maintained a state in which the first and the second moving cores 31, 32 get sucked to the first and the second stationary cores 51, 52, i.e., there can be maintained a state in which the first and the second valve bodies 21, 22 are kept open. Energy saving can thus be attained.
In addition, the second magnetic plate 82 is disposed on a cover plate 121 that, is mounted on an upper surface of the zero governor 100. The lower end portions of the first and the second guide tubes 41, 42 are arranged to be penetrated through the second magnetic plate 82 and the cover plate 121. Flange portion 4a is formed at the lower end of the first and the second guide tubes 41, 42, respectively. A packing 122 on the bottom surface of the cover plate 121 is then brought into close contact with the upper surface of the flange portion 4a, thereby securing good sealing property. The above-described first valve spring 61 is interposed between the flange portion 4a at the lower end of the first guide tube 41 and the first valve body 21. The second valve spring 62 is interposed between the second stationary core 52 and the second moving core 22. Further, between a bobbin 7a of the first and the second. electromagnetic coils 71, 72 and the first and the second guide tubes 41, 42, a pair of upper and lower collars 7c, 7c are inserted.
By the way, in order to make the magnetic forces to be efficiently transmitted between the first magnetic plate 81 and the first and the second stationary cores 51, 52, the surface 5a that is on the upper. end of the stationary cores 51, 52, respectively, and that faces (or lies opposite to) the first magnetic plate 81 (i.e., that surface of the stationary core which faces the magnetic plate) must be brought into contact with the first magnetic plate 81. In case that surface 5a of the respective stationary cores 51, 52 which faces the magnetic plate 81 is brought into contact with the first magnetic plate 81 by caulking a projection that is formed in the stationary core 51, 52 in a projecting manner like in the conventional way, the first magnetic plate 81 will be pushed or forced, at the time of calking, toward each of the first and the second electromagnetic coils 71, 72. When caulking is excessive, an undue compression load will be applied to the electromagnetic coils 71, 72. There is, therefore, a possibility that the bobbins 7a of the electromagnetic coils 71, 72 are deformed.
As a solution, the following arrangement has been employed in this embodiment. In other words, a caulked portion 4b is formed in the first and the second guide tubes 41, 42, respectively, so as to be in engagement with a recessed groove 5b that is formed on an outer periphery of the first and the second stationary cores 51, 52, respectively, thereby fixing in position the stationary cores 51, 52. It is thus so arranged that, in a state in which the stationary cores 51, 52 are fixed in position by the caulked portion 4b, that surface, of the stationary core 51, 52 which faces the magnetic plate 81, respectively, becomes flush (or on the same line) with the upper end of the guide tubes 41, 42. By disposing the first magnetic plate 81 on the upper end of the guide tubes 41, 42, that surface 5a of the stationary core 51, 52 which faces the magnetic plate 81 is, respectively, brought into contact with the first magnetic plate 81. Alternatively, it may also be so arranged that, in a state in which the stationary cores 51, 52 are fixed in position by the caulked portion 4b, that surface 5a of the stationary core 51, 52 which faces the magnetic plate 81, respectively, projects or protrudes beyond the upper ends of the guide tubes 41, 42 to a certain degree. The first magnetic plate 81 is pushed downward from an upper side by means of an inverse U-shaped push plate 123 to be mounted on the cover plate 121.
According to this arrangement, the first and the second stationary cores 51, 52 is fixed to the guide tubes 41, 42, respectively. Therefore, as long as the first magnetic plate 81 is disposed on the upper end of the guide tube 41, 42, that surface 5a of the stationary core 51, 52 which faces the magnetic plate 81 and which is flush with the upper end of the guide tube 41, 42 or is protruding therefrom, is brought into contact with the first magnetic plate 81. Therefore, unlike a caulking practice in which the first magnetic plate 81 is pushed toward the electromagnetic coils 71, 72, that surface 5a of the of the stationary cores 51, 52 which faces the magnetic plate 81 can be brought into contact with the first magnetic plate 81 without applying an undue compression load to the electromagnetic coils 71, 72.
However, in case the flange portion 4a of the first and the second guide tubes 41, 42 is deflected downward due to compression reaction force of the packing 122, the guide tubes 41, 42 will be deviated downward. As a result, that surface 5a of the stationary core 51, 52 which faces the magnetic plate 81 of the stationary cores 51, 52 will be away from the first magnetic plate 81.
Description will now be made of a second embodiment, as shown in FIG. 3, in which the above-mentioned disadvantage has been eliminated. Since the basic construction of the second embodiment is not particularly different from that of the first embodiment, the same reference numerals are assigned to the similar parts or members. The difference of the second embodiment from the first embodiment is as follows.
In other words, according to the second embodiment, a projection 5c which is inserted into a perforation 8a formed in the first magnetic plate 81 is formed on a part of that surface 5a of the first and the second stationary core 51, 52 which faces the magnetic plate 81 in a projecting manner. A spring stopper (spring receiving portion) 5d is disposed at a tip portion (upper end portion) of the projection 5c that protrudes beyond the perforation 8a. A spring 9 is then interposed between the spring stopper 5d and the first magnetic plate 81 so that the stationary cores 51, 52 are pushed upward against the first magnetic plate 81. In the example as shown in FIG. 3, a plate spring is used as the spring 9, but a coil spring may be used. Further, a spring stopper 5d is formed by a flange portion that is integrally formed in the projection 5c, but the spring stopper 5d may alternatively be formed by a snap ring which is attached to the tip portion of the projection 5c. 
According to the second embodiment, by adjusting the urging force of the spring 9 to a strength enough to prevent, the flange portion 4a from deflecting downward due to the compression reaction force of the packing 122, the guide tubes 41, 42 can be prevented from deviating downward. Therefore, that surface 5a of the first and the second stationary core 51, 52 which faces the magnetic plate 81, can be maintained by the urging force of the spring 9 to the state of being in contact with the first magnetic plate 81.
Descriptions have so far been made of the embodiments of this invention, but this invention shall not be limited to the above. For example, although the solenoid valve according to the above-described embodiments is a dual guide solenoid valve 1 for use in a zero-governor 100, this invention can also be applied to a dual plunger solenoid valve for other uses, or to a solenoid valve having a single valve body. Further, in the above-described embodiments, side plates for connecting the first magnetic plate 81 and the second magnetic plate 82 are omitted. This invention can also be applied to a solenoid valve having magnetic side plates.
EXPLANATION OF REFERENCE MARKS


    1 dual plunger solenoid valve (solenoid valve)
    21, 22 valve body
    31, 32 moving core
    41, 42 guide tube
    4b caulked portion
    51, 52 stationary core
    5a that surface of the stationary core which faces the magnetic plate (i.e., the surface of the stationary core, said surface lying opposite to, or facing, the magnetic plate)
    5b recessed groove,
    5c projection
    5d spring stopper (spring receiving portion)
    61, 62 valve spring
    71, 72 electromagnetic coil
    81 first magnetic plate (magnetic plate)
    9 spring

## Claims

1. A solenoid valve comprising:
a valve body;
a moving core having connected to one end thereof the valve body;
a guide tube having slidably inserted thereinto the moving core;
a stationary core disposed in an inner circumference of an opposite end portion of the guide tube so as to face an opposite end of the moving core;
a valve spring to urge the moving core in a direction away from the stationary core;
an electromagnetic coil disposed to enclose the guide tube; and
a magnetic plate disposed on the opposite end of the guide tube, whereby the moving core is sucked to the stationary core by a magnetic force transmitted through the magnetic plate to the stationary core due to electric charging to the electromagnetic coil,
wherein the guide tube has a caulked portion formed to fix in position the stationary core by engaging the caulked portion with a recessed groove formed on an outer periphery of the stationary core such that, in a state in which the stationary core is fixed in position by the caulked portion, that surface of the stationary core which faces the magnetic plate is either flush with, or is protruding beyond, the opposite end of the guide tube,
whereby, by thus disposing the magnetic plate on the opposite end of the guide tube, that surface of the stationary core which faces the magnetic plate is in contact with the magnetic plate.

2. The solenoid valve according to claim 1, further comprising:
a projection disposed in a protruding manner so as to be inserted into a through hole formed in the magnetic plate, the projection being formed in a part of that surface of the stationary core which faces the magnetic plate; and
a spring interposed between a spring stopper formed at a tip portion of the projection that protrudes beyond the through hole, and the magnetic plate, such that an urging force of the spring maintains that surface of the stationary core which faces the magnetic plate in a state of being in contact with the magnetic plate.