JPH1032074A - Heat switch - Google Patents

Abstract

(57) [Problem] To provide a thermal switch which reliably performs an opening operation, has high reliability, and can be easily miniaturized. SOLUTION: When a high voltage surge is applied for a relatively long time, fitting holes 65d of movable members 65, 75 are provided.
75d, an overcurrent flows through the operating shafts 63 and 73, the low melts 61 and 71, the varistors 53 and 54, the gas arresters 51 and 52, and the ground terminal 55, and the varistors 53 and 54 and the gas arresters 51 and 52 are overheated. . Then, the low-melting bodies 61 and 71 are melted, and the operating shafts 63 and 73 are pressed by the elastic bodies 64 and 74 toward the varistor, and the fitting holes 65 are formed.
d, 75d, the movable members 65, 75 are moved upward by the elastic bodies 67, 77. This allows
The varistors 53 and 54 are cut off from the electric circuit to prevent further overheating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating an electric component (for example, a surge protection element such as a gas-filled discharge tube or a varistor for protecting electric equipment from lightning surge or the like) which has been abnormally overheated by an overcurrent from an electric circuit. It relates to a thermal switch.

[0002]

2. Description of the Related Art Electrical components that frequently flow excessive current are:
Deterioration progresses quickly. From the viewpoint of safety, electrical components that may be thermally destroyed or thermally destroyed due to the progress of this deterioration,
It is desirable to disconnect from the electrical circuit as soon as possible.
As a technology related to a heat switch for separating such an electric component (for example, a surge protection element for protecting an electric device from a lightning surge or the like) from an electric circuit, for example, the technology described in the following document is described. is there. Reference 1: Japanese Utility Model Application Laid-Open No. 63-7937 Reference 2: Japanese Utility Model Application Laid-Open No. 3-130186 FIG. 2 is a schematic circuit diagram of a conventional surge protection device described in the above-mentioned reference 1.

[0003] This surge protection device is a device for protecting a device to be protected 3, which is an electric device connected to electric lines 1 and 2 constituting an electric circuit, from a high voltage surge or the like by a surge protection element 10. The configuration of the surge protection element 10 is 3
Polar gas-filled discharge tube (hereinafter referred to as gas arrester) 11
The varistors 12 and 13 are connected in series on both sides with the center as the center, and the whole thereof is coated with an insulating material. An earth terminal 11a is drawn out from the gas arrester 11, and further, varistors 12 and 13 are provided with electrode portions 12a and 13a. In order to prevent thermal destruction of the surge protection element 10 due to overcurrent, thermal switches 20 and 30 are connected between the electrode portions 12a and 13a and the electric lines 1 and 2, respectively.

FIGS. 3 (a) and 3 (b) are structural views of the surge protector 10 and the thermal switches 20, 30 which are the main parts of FIG. 2, and FIG. 3 (a) is a longitudinal sectional view and FIG. FIG. 2B is an exploded perspective view. The insulated surge protection element 10 has a plate-shaped ground terminal 11a drawn out from an internal gas arrester 11, and further has round bar-shaped electrode portions 12a, 13a protruding from the internal varistors 12, 13. The thermal switches 20, 30 for separating the surge protection element 10 from the electric lines 1, 2 are plate-shaped conductive metal pieces 21 having spring properties.
31. The conductive metal pieces 21, 31 are attached to a case or the like, and are connected to the electric wires 1, 2.
1a, 31a, operating springs 21b, 31b extended from the terminals 21a, 31a and urged upward, and arc-shaped tips 21c formed at the tips of the operating springs 21b, 31b. 31c.

The tip portions 21c, 3 of the conductive metal pieces 21, 31
1c is pressed in the direction of the lower electrode portions 12a and 13a, and is joined to the electrode portions 12a and 13a by a manual soldering operation using the solder 32. Conductive metal piece 2
The front end portions 21c, 31c are provided on the front end portions 21c, 31c.
Insulating display pieces 23 and 33 which move upward by the upward spring force of c and 31c are provided. The display pieces 23 and 33 are provided at the tip portions 21 of the conductive metal pieces 21 and 31.
This is for displaying outside that the joined state between the electrodes c and 31c and the electrode portions 12a and 13a has been released. next,
2 and 3 will be described. Tip portions 21c, 31c of conductive metal pieces 21, 31 constituting thermal switches 20, 30
Are always connected to the electrode portions 12a and 13a of the surge protection element 10 by the solder 32. Therefore, the surge protection element 10 includes the electrode portions 12a and 13a and the heat switch 2
0 and 30 are connected to the electric lines 1 and 2. In this state, for example, when a high-voltage surge such as lightning enters the electric lines 1 and 2 for a relatively short time, the thermal switches 20 and 30
, The surge protection element 10 operates, and the overcurrent caused by the invading high-voltage surge is released to the ground through the ground terminal 11a. As a result, the protected device 3 connected to the electric lines 1 and 2 is protected from the high-voltage surge.

When the high-voltage surge enters for a relatively short time as described above, the surge protection element 10 operates to protect the device 3 to be protected. In addition, when a high-voltage surge enters for a short time, the surge protection element 10 is not overheated, and the high-voltage surge can be safely processed. However, if the high-voltage surge continues to intrude for a relatively long time, the surge protection element 10 becomes overloaded in terms of current capacity. Therefore, in order to prevent this, the thermal switches 20, 30 are provided. When the high voltage surge enters for a relatively long time, the surge protection element 10 generates heat due to the overcurrent of the high voltage surge. This heat is guided to the electrode portions 12a and 13a protruding from the surge protection element 10, and the solder 32 is melted. When the solder 32 is melted, the conductive metal pieces 21, 3
As shown by the broken line in FIG. 3A, the front end portions 21c and 31c of the first heat switch 20 and 30 are opened upward from the electrode portions 12a and 13a by the spring force, and the heat switches 20, 30 are turned off, thereby preventing surge protection. The element 10 is disconnected from the electric lines 1 and 2. Thereby, abnormal overheating, burnout, etc. of the surge protection element 10 can be prevented.

However, in this surge protection device, the electrode portions 12a, 13a and the tip portions 21 of the conductive metal pieces 21, 31 are provided.
Since c and 31c are joined by a manual soldering operation, there is a problem that the soldering operation requires time and effort. Therefore, a technique as described in Document 2 has been proposed. 4 (a) and 4 (b) are structural views of a main part (surge protection element and thermal switch) of another conventional surge protection device described in Document 2 and FIG. 4 (a) is a longitudinal section. FIG. 2B and FIG. 2B are exploded perspective views, in which components common to those in FIGS. 2 and 3 are denoted by common reference numerals. The broken line in FIG. 4A indicates the operating state.

In the surge protection device shown in FIG.
1, 31 and tip portions 21c, 31c and electrode portions 12a, 13
a are joined manually by solder 32.
On the other hand, in the surge protection device of FIG. 4, the mounting holes 21d, 31d are formed at the tips of the plate-shaped conductive metal pieces 21, 31.
Are formed, and solder forming members 24 and 34 formed in a predetermined shape in advance are inserted into the mounting holes 21d and 31d. That is, fitting holes 24a, 34a are formed in the solder forming members 24, 34, and these fitting holes 24a, 3a are formed.
By fitting the round bar-shaped electrode portions 12a and 13a into 4a, the tip portions of the conductive metal pieces 21 and 31 and the electrode portions 12a and 13a are fitted.
13a. In this way, if the tip portions of the conductive metal pieces 21 and 31 are joined to the electrode portions 12a and 13a using the solder molding members 24 and 34, the manual soldering operation as shown in FIG. 3 is omitted. The tip portions of the conductive metal pieces 21, 31 and the electrode portions 12a,
This has the effect of simplifying the joining operation with 13a.

[0009]

However, the conventional thermal switch shown in FIGS. 3 and 4 has the following problems (1) and (2), which are difficult to solve. . (1) In the thermal switches 20 and 30 shown in FIG. 3, the tip portions 21c and 31c of the conductive metal pieces 21 and 31 which are important as the switching mechanism.
Since the opening / closing portions between the electrodes and the electrode portions 12a and 13a are manually soldered using the solder 32, the degree of attachment and the amount of the solder 32 vary, resulting in a lack of reliability in quality and a smooth opening operation. Inconvenience occurs in openness and stability. In addition, if the conductive metal pieces 21 and 31 having the operating spring portions 21b and 31b are given a predetermined spring force,
The conductive metal pieces 21 and 31 have to be lengthened, which has the disadvantage that the entire thermal switch becomes large.

(2) In the thermal switch of FIG. 4, solder forming members 24 and 3 are used instead of the manual soldering process of FIG.
Since the molded parts are formed using the components 4, the variation in the amount of solder and the variation in the quality of the operation due to the soldering operation as shown in FIG. 3 are eliminated. However, the electrode portions 12a, 13a are fitted into the fitting holes 24a, 34a of the solder molding members 24, 34, and the solder molding members 24, 34 are urged upward by the distal end portions of the conductive metal pieces 21, 31. The solder molding members 24, 3
The spring pressure concentrates in the vicinity of the fitting holes 24a and 34a. Therefore, due to various stresses, the fitting holes 24a, 34a
The vicinity is extended, and finally that part is cut off to form the electrode part 12.
a, 13a. Further, similarly to FIG. 3, the conductive metal pieces 21, 31 are released from the electrode portions 12a, 13a by the spring force of the conductive metal pieces 21, 31, so that a sufficient spring force is required. In addition, there is a disadvantage that the conductive metal pieces 21 and 31 are lengthened, thereby increasing the size of the entire heat switch. SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems of the prior art and to provide a heat switch that can reliably perform an opening operation, has high reliability, and can be easily miniaturized.

[0011]

According to a first aspect of the present invention, an electric component overheated to a temperature higher than an allowable overheating temperature by receiving an overcurrent is separated from an electric circuit. In the thermal switch, a conductive movable member having a fitting hole connected to the electric circuit and supported movably along a first direction of a first direction and a second direction orthogonal to each other. A conductive operating shaft having a member, one end and the other end, movably supported along the second direction, one end of which is removably inserted into the fitting hole; A first elastic body biasing the movable member in a direction in which the fitting hole of the movable member moves away from one end of the operating shaft along the direction of
A second elastic body for urging the operating shaft in a direction in which one end of the operating shaft is separated from the fitting hole along the second direction; and a conductive low-melting material. The conductive low melt has a predetermined thickness in the second direction according to a distance required when one end of the operating shaft is detached from the fitting hole, and the electric component and the operating shaft And is pressed at the other end of the operating shaft to make surface contact with the electric component, absorbs conduction heat from the electric component and melts at a temperature corresponding to the allowable overheating temperature. Things.

According to a second aspect of the present invention, in the thermal switch according to the first aspect, the electric component, the low melting material, and the operating shaft are provided in an insulating case having a guide portion on an outer surface and a bearing portion on a side wall. And the second elastic body. Further, the movable member is slidably supported by a guide portion of the case, the operating shaft is movably supported by a bearing portion of the case, and the first elastic body is formed of a spring. The movable member is provided between the outer surface of the case and the movable member. The second elastic body is formed of a spring having a spring pressure equal to or higher than the spring pressure of the first elastic body, and is provided between an inner surface of the case and the low melt, and Is made of any one of a low melting metal, a shape memory metal, and a conductive shape memory resin. According to a third aspect of the present invention, in the thermal switch according to the first or second aspect, a conductive layer for reducing a contact resistance value is formed at a contact portion between the fitting hole of the movable member and one end of the operating shaft. .

According to the fourth aspect of the present invention, the first, second or third aspect of the present invention is provided.
In the thermal switch of (1), the electric component is constituted by a surge protection element. According to the present invention, since the thermal switch is configured as described above, for example, a high voltage surge such as lightning is applied for a relatively long time, and an electric component such as a surge protection element is generated by an excessive current of the high voltage surge. When the current exceeds the current capacity, the overheating occurs. When the electric component is overheated, the heat is efficiently absorbed by the low melt in surface contact with the electric component, and the low melt melts. When the low melt is melted, the operating shaft pressed by the second elastic body moves toward the electric component along the second direction. When the operating shaft moves toward the electric component, one end of the operating shaft is pulled out of the fitting hole of the movable member. Then, the movable member moves in the direction away from one end of the operating shaft along the first direction by the first elastic body. As described above, when the operating shaft is detached from the fitting hole of the movable member, the electric component pressed at the other end of the operating shaft is separated from the electric circuit, and further overheating of the electric component is prevented.

[0014]

FIG. 5 shows an embodiment of the present invention and is a schematic circuit diagram of a surge protection device having a thermal switch. This surge protection device protects a protected device 43, which is an electric device, connected to electric lines 41, 42 constituting an electric circuit from a high voltage surge such as lightning by a surge protection element 50, which is an electric component. is there. Thermal switches 60 and 70 are connected to both ends of the surge protection element 50 for disconnecting the surge protection element 50 from the electric lines 41 and 42 when the surge protection element 50 is overheated by an overcurrent. The surge protection element 50 includes two two-pole gas arresters 51 and 5.
2 and two varistors 53 and 54, which are connected in series. An earth terminal 55 is connected between the two gas arresters 51 and 52. One of the two heat switches 60 and 70 is a low-melting material 61 that is connected between the varistor 53 and the electric line 41 and melts at a temperature according to a preset allowable superheat temperature. , And an opening / closing section 6 for interrupting a circuit by melting of the low melt 61
2 and so on. The other heat switch 70 is connected between the varistor 54 and the electric wire 42 and melts at a temperature corresponding to a preset allowable overheating temperature, and a circuit is formed by melting the low melt 71. And an opening / closing section 72 for shutting off. The low melting bodies 61 and 71 are made of a low melting metal such as solder, a shape memory metal, or a conductive shape memory resin.

In such a surge protection device, for example,
When a high voltage surge due to lightning or the like enters the electric lines 41 and 42, a surge protection element 50 composed of gas arresters 51 and 52 and varistors 53 and 54 operates, and an overcurrent due to the high voltage surge is transmitted to the ground through a ground terminal 55. Escaped to Thereby, the protected device 43 is protected from the invading high voltage surge. On the other hand, when the high voltage surge extends for a relatively long time, the surge protection element 50 is overheated by an overcurrent passing therethrough. When the overheating becomes equal to or higher than a preset allowable overheating temperature, the low melting bodies 61 and 71 joined to the varistors 53 and 54 are melted, and the melting opens the opening / closing portions 62 and 72. As a result, the surge protection element 50 is disconnected from the electric lines 41 and 42, and the surge protection element 50 is prevented from being overheated. Hereinafter, FIG.
The structure of each part of the surge protection device will be described with reference to (a) and (b) and FIG.

FIGS. 1A and 1B are structural views of the surge protector of FIG. 5 showing an embodiment of the present invention. FIG. 1A is a longitudinal sectional view, and FIG. It is a side view. Note that the left movable member 65 and the display member 6 in FIG.
Reference numeral 6 denotes an operating state, and the upper broken line in FIG. 1B indicates the operating state. FIG. 6 is an exploded perspective view of the surge protection device of FIG. The opening / closing portions 62 and 72 in FIG.
As shown in FIG. 7, operating shafts 63 and 73 movable along a second direction (for example, a horizontal direction) X, and the operating shafts 63 and 7
A second elastic body 64, 74 made of a coil spring for urging the third member 3 in the horizontal direction X, and a movable member slidable in a first direction (eg, vertical direction) Z orthogonal to the horizontal direction X. The members 65 and 75, the display members 66 and 76 for externally displaying that the thermal switches 60 and 70 are in the open state, and the movable members 65 and 75 and the display members 66 and 76 are urged in the vertical direction Z. And first elastic bodies 67 and 77 formed of coil springs. The operating shafts 63 and 73 and the elastic bodies 64 and 74 are housed together with the low melting bodies 61 and 71 and the surge protection element 50 in a case main body 81 constituting an insulating case 80. A case lid 82 is detachably attached to the upper end opening of the case body 81. The movable members 65 and 75, the display members 66 and 76, and the elastic bodies 67 and 77 are mounted on the case lid 82.

First, the surge protection element 50 and the thermal switch 6
The structure of the case 80 for housing 0, 70 will be described in detail with reference to FIG. The case 80 includes a case body 81 having an open upper end and a case lid 82 for closing the opening.
These are formed of insulating members such as synthetic resin and ceramics. At the approximate center of the inside of the case body 81, there are provided two
A set of convex housing portions 81a and 81b is formed, and a cutout 81c for fixing the ground terminal 55 and pulling it out to the outside is formed between the two sets of housing portions 81a and 81b. The varistors 53 and 54 and the low melting material 6 are provided between the convex housing portions 81 a and 81 b and both side surfaces in the case body 81.
1, 71 and recessed accommodation portions 81d and 81e for accommodating the operation shafts 63 and 73 are formed. On both side walls of the case body 81, groove-shaped bearing portions 81f and 81g that support one ends of the operating shafts 63 and 73 are formed. Further, inside the bearing portions 81f and 81g, one ends of the elastic bodies 64 and 74 are attached. Steps 81h and 81i for locking are formed. Of the four corners of the upper end opening of the case body 81, screw holes 81j and 81k are formed on one diagonal, and mounting holes 81l and 81m are formed on the other diagonal.

At the four corners of the case cover 82 for closing the upper end opening of the case body 81, screw holes 81 on the case body 81 side are provided.
Screw holes 82a and 82b corresponding to j and 81k are formed, and mounting holes 81l and 81m on the case body 81 side.
Protrusions 82c and 82d for fitting into are projected downward. On both sides of the case lid 82, a case body 81
Closing portions 82e and 82f for closing the upper portions of the bearing portions 81f and 81g on the side are protruded downward. Concave guides 82g, 82h, 82i, 82j for sliding the movable members 65, 75 along the vertical direction Z are formed near both ends of the front surface and both ends of the rear surface of the case lid 82. . Elastic bodies 67 and 7 are provided on the upper surface of case lid 82.
The recesses 82k and 82l for locking one end of the connector 7 are formed. Next, the structure of each member housed in the case 80 will be described in detail. Of the surge protection elements 50, 2
The two gas arresters 51 and 52 have a columnar shape and are housed in housing portions 81a and 81b of the case body 81, respectively. A plate-like ground terminal 55 is disposed between the two gas arresters 51 and 52 so as to come into contact with the gas arresters 51 and 52. The varistors 53, 54 located on both sides of the gas arresters 51, 52 have a disk shape, are housed in the housing portions 81 d, 81 e of the case body 81, and are in contact with the gas arresters 51, 52. The low-melting bodies 61 and 71 located on both sides of the varistors 53 and 54 have a disk shape and are accommodated in the accommodating portions 81d and 81e of the case main body 81. In order to increase heat absorption from the varistors 53 and 54, the varistors 53 and 54 are provided. 53 and 54 are in surface contact.

The operating shaft 6 constituting the thermal switches 60 and 70
Each of the ends 3a, 3b has a round bar shape at one end 63a, 73a side, and flange portions 63b, 73b are provided at the other end side, and are formed of a conductive member. It is preferable to use a material having a small electric resistance such as copper as the conductive member. Alternatively, the electric resistance value may be reduced by forming a conductive film such as silver, gold, or an alloy thereof on the surfaces of the operating shafts 63 and 73. Further, one end 63 of the operating shafts 63, 73
Since a and 73a are in electrical contact with the movable members 65 and 75, it is preferable to perform a surface treatment to reduce the contact resistance value. As the surface treatment, for example, tin, which has a low melting point, or a metal such as solder containing 60% or more of tin is used, and plating, soldering, or bonding of a metal plate is performed. It is preferable to reduce the value. The thickness of the plating process or the soldering process may be appropriately selected depending on the material to be used (for example, it is preferably 5 μm or more, although it depends on the surge current to be processed). When the operating shafts 63 and 73 are formed of, for example, a brass member, it is preferable to perform a tin plating process or a soldering process with a high tin content as the surface treatment of the one ends 63a and 73a.

The operating shafts 63 and 73 are accommodated in accommodating portions 81d and 81e of the case main body 81, and one ends 63a and 73a of the operating shafts 63 and 73 are connected to the bearings 81 of the case main body 81.
f, 81g, and flange portions 63b, 7 on the other end side.
3b is in electrical contact with the low melts 61,71. The flanges 63b, 73b are provided on the outer circumference of the operating shafts 63, 73.
Elastic bodies 64 and 74 made of a coil spring in a compressed state are mounted between the case 81 and the steps 81 h and 81 i of the case body 81. The elastic bodies 64 and 74 press the flange portions 63b and 73b of the operating shafts 63 and 73 along the horizontal direction X toward the center ground terminal 55 side by the spring pressure.
The flange portions 63b and 73b, the low melts 61 and 71, the varistors 53 and 54, the gas arresters 51 and 52, and the ground terminal 55 have a function of mutually pressing. The spring pressure of the elastic bodies 64 and 74 is preferably equal to or greater than the spring pressure of the elastic bodies 67 and 77 on the movable members 65 and 75 side.

At the time of assembly, these ground terminals 55, gas arresters 51 and 52, varistors 53 and 54,
Low melting materials 61, 71, operating shafts 63, 73, and elastic body 6
4 and 74 are accommodated in the case body 81, the case cover 82 is placed on the opening of the case body 81, and the case cover 8 is
The two projections 82c and 82d are fitted into the mounting holes 81l and 81m on the case body 81 side, and the screw holes 82a and 82b on the case lid 82 side and the screw holes 81 on the case body 81 side.
j and 81k are fixed by screws 83 and 84. On a case lid 82 fixed to the case body 81, movable members 65 and 75 are slidably mounted in the vertical direction Z. The movable members 65 and 75 include plate-shaped horizontal portions 65a and 75a, mounting holes 65b and 75b formed substantially in the center of the horizontal portions 65a and 75a, and downward from sides of the horizontal portions 65a and 75a. Extended hanging part 6
5c, 75c, fitting holes 65d, 75d formed at the lower ends of the hanging portions 65c, 75c, and the horizontal portions 65a, 75c.
a terminals 65e, 65f, extending downward from both ends of
75e and 75f, and are integrally formed of a conductive member. Like the operating shafts 63 and 73, the conductive member is made of a material having a small electric resistance such as copper, or is subjected to a surface treatment with silver, gold, an alloy thereof, or the like so as to reduce the electric resistance. Is preferred. In particular, since the inner surfaces of the fitting holes 65d and 75d make electrical contact with the one ends 63a and 73a of the operating shafts 63 and 73, the operating shaft 6
Similar to the ends 63a and 73a of the base members 3 and 73, it is preferable to perform a surface treatment such as plating treatment with tin or the like, soldering treatment, or bonding a metal plate for reducing the contact resistance value.

Of the two movable members 65, 75, one of the movable members 65 has terminals 65e, 65f inserted into concave guide portions 82g, 82h on the case lid 82 side, and
Is slidably mounted on. A fitting hole 65d formed in the hanging portion 65c of the movable member 65 is fitted with one end 63a of the operating shaft 63. The other movable member 75 also has terminals 75e and 75f with concave guide portions 82 on the case lid 82 side.
i, 82 j slidably inserted therein, and a fitting hole 75 d formed in the hanging portion 75 c is fitted to one end 73 a of the operating shaft 73. The terminals 65f, 75f of the movable members 65, 75
They are connected to the electric wires 41 and 42 of FIG. 5, respectively. Insulating display members 66 and 76 are inserted into the mounting holes 65b and 75b of the movable members 65 and 75 from below.
The display members 66 and 76 have round bar-shaped protrusions 66a and 76a.
And flanges 66b and 76b formed on the lower side. The protrusions 66a and 76a are
5 is inserted into the mounting holes 65b and 75b, and the flange 66
b and 76b are horizontal portions 65a and 75 of the movable members 65 and 75, respectively.
a. Recesses 66c, 76c are formed on the bottom surfaces of the flanges 66b, 76b.
Elastic bodies 67 and 77 made of a coil spring are mounted in a compressed state between 76c and the recesses 82k and 82l on the case lid 82 side. The elastic members 67 and 77 are provided on the display member 6.
It has a function of urging the movable members 65 and 75 upward through the members 6 and 76.

The operation of the surge protection device having the above-described structure shown in FIGS. 1 and 6 will be described below. For example, when a high-voltage surge enters the electric wire lines 41 and 42 in FIG. 5 due to lightning or the like, the high-voltage surge is applied to the terminals 65 of the movable members 65 and 75.
f, 75f, fitting holes 65d, 75d, operating shafts 63, 7
3. Flow through the low melt 61, 71, varistors 53, 54, gas arresters 51, 52, and ground terminal 55 to the ground. Then, the varistors 53 and 54 or the gas arresters 51 and 52 operate, and the overcurrent flowing therethrough is released to the ground through the ground terminal 55. Thereby, the protected device 43 of FIG. 5 is protected from the high voltage surge. On the other hand, when the intrusion of the high-voltage surge takes a relatively long time, the current capacity of the varistors 53 and 54 and the gas arresters 51 and 52 exceeds due to the overcurrent, and the overheating occurs. When the varistors 53 and 54 and the gas arresters 51 and 52 are overheated to a preset allowable overheating temperature, the varistor 5
The low melts 61 and 71 which are in surface contact with 3, 54 are melted. When the low melts 61, 71 are melted, the elastic bodies 64, 7
The operating shafts 63 and 73 are pressed in the horizontal direction X toward the varistors 53 and 54 by the spring force of
One end 63a, 73a of 3, 73 moves toward varistor 53, 54 along horizontal direction X.

When the one ends 63a, 73a of the operating shafts 63, 73 move, the fitting holes 65d, 75 of the movable members 65, 75 move.
Pulled out of d. When the one ends 63a, 73a of the operating shafts 63, 73 are pulled out from the fitting holes 65d, 75d, the movable members 65, 75 together with the display members 66, 76 are guided by the spring force of the elastic members 67, 77 to the guide portions of the case lid 82. 82
It moves upward along g, 82h, 82i, and 82j. Thereby, one ends 63a, 73 of the operating shafts 63, 73
a is disengaged from the fitting holes 65d, 75d of the movable members 65, 75, the varistors 53, 54 are separated from the terminals 65f, 75f of the movable members 65, 75, and the varistors 53, 5 are separated.
4 and the gas arresters 51 and 52 are prevented from being overheated.

As described above, this embodiment has the following effects (a) to (f). (A) In the conventional thermal switch, heat generated by the surge protection element 10 due to an overcurrent is transmitted to the solder 32 or the solder molding members 24 and 34 via the electrode portions 12a and 13a, and the solder 32 or the solder molding members 24 and 34 are transmitted. 34 are molten.
On the other hand, in the present embodiment, the low melts 61 and 71 are brought into surface contact directly with the varistors 53 and 54. Therefore, the low-melting bodies 61 and 71 have good heat-absorbing properties, and the low-melting bodies 61 and 71 can be reliably melted. (B) In the conventional thermal switch, since heat detection and separation are integrated, a large spring tension is applied to the solder 32 or the solder molded members 24 and 34 which are the molten metal, so that a large spring force is applied to the joint of the molten metal. And it was not in a favorable state. On the other hand, in the present embodiment, since the heat detection and the separation are provided as separate mechanisms, the low melting materials 61 and 71 are used.
Spring tension to the minimum. Therefore, no extra spring force is applied to the low melts 61 and 71, so that the conventional inconvenience can be solved.

(C) Low melting materials 61 and 71 and operating shaft 6
3, 73 and the open portions of the movable members 65 and 75 are separately provided, so that each operation is an independent operation, and a reliable shut-off operation is performed. (D) When the spring pressure of the elastic members 64 and 74 on the side of the operating shafts 63 and 73 is equal to or greater than the spring pressure of the elastic members 67 and 77 on the movable members 65 and 75,
The movement of the operating shafts 63 and 73 is restricted and the movable member 6 is moved.
The inconvenience that the fitting holes 65d and 75d do not come out of the fitting holes 65d and 75d can be accurately prevented. (E) Conventionally, solder 32 or solder molded member 2
After the electrodes 4 and 34 are melted, the conductive metal pieces 21 and 31 are released from the electrode portions 12a and 13a. On the other hand, in the present embodiment, the low melts 61 and 71 and the
2 and 72 are separately formed, and the low melts 61 and 71 are directly connected to the varistors 53 and 5 in order to increase heat absorption.
4, the spring pressure of the elastic bodies 64, 74 on the operating shafts 63, 73 side can be further reduced by the action of both. As a result, the entire thermal switch does not need to be increased in size to increase the spring pressure as in the related art, and the overall thermal switch can be further reduced in size.

(F) Operating shafts 63 and 73 and movable member 6
5 and 75 are made of a member having a small electric resistance such as copper, or are subjected to a surface treatment for reducing the contact resistance, so that they can be properly prevented from welding by a high voltage surge. In particular, one ends 63a, 7 of the operating shafts 63, 73
A surface treatment such as metal plating or soldering to reduce the contact resistance value on both or one of the contact portions between the 3a and the fitting holes 65d and 75d of the movable members 65 and 75;
Alternatively, when a bonding process of a metal plate or the like is performed, even if a surge or the like of a high voltage and a large current flows for a short time, welding between them can be more accurately prevented. Note that the present invention is not limited to the above embodiment, and various modifications are possible. For example, there are the following modifications (i) to (iv). (I) Gas arresters 51 and 5 in surge protection element 50
Although the two-pole type has been described as 2, the present invention is not limited to the two-pole type, and for example, can be configured using one three-pole type. The varistors 53 and 54 may be composed of resistors. Further, in the above-described embodiment, the surge protection element 50 has been described as an example of the electric component.
The thermal switches 60 and 70 of the above embodiment can be applied to disconnection of other electric components.

(Ii) Although the operating shafts 63 and 73 are arranged in the horizontal direction X, they may be arranged in other directions according to the mounting position of the surge protection element 50. The operating shafts 63, 73
The movable members 65 and 75 perpendicular to the vertical direction may be slidably mounted in directions other than the vertical direction Z. Further, the structures of the low-melting material 61 and the opening / closing portion 62 can be changed to shapes other than those illustrated. (iii) The elastic bodies 67 and 77 that press the movable members 65 and 75 upward are located at approximately the center of the horizontal portions 65a and 75a.
The movable members 65, 7 can be provided by providing two each slightly shifted from the center of each of the horizontal portions 65a, 75a.
5 can be pushed up more smoothly while maintaining the horizontal state. (Iv) The elastic bodies 64, 74, 67, and 77 are constituted by coil springs, but may be constituted by other elastic members such as leaf springs.

[0029]

As described above in detail, according to the first aspect of the present invention, since the low melting material is brought into direct surface contact with the electric component which generates heat due to the overcurrent, the heat of the low melting material is reduced as compared with the prior art. The absorbability is improved, and the low melt can be melted quickly and reliably. Thus, the electric component can be quickly and reliably separated from the electric circuit. In addition, the fitting hole of the movable member and one end of the operating shaft are fitted to each other to make electrical contact, and the low melting material is melted so that the two are separated from each other. Tension is not applied, so that deterioration of the low melt during use can be prevented. In addition, the melting point of the low melt,
Since the movable member and the separation point of the operating shaft are separately provided separately, these operations are independent operations, and a reliable shut-off operation is possible. In addition, since the movable member is biased by the first elastic body and the operating shaft is biased by the second elastic body, an appropriate spring pressure can be obtained without increasing the size of the elastic body. In addition, the size of the entire heat switch can be reduced.

According to the second aspect of the present invention, since the electric component, the low melting material, the operating shaft and the second elastic body are housed in the case, the manufacture and assembly of the thermal switch become simple.
Moreover, it becomes easy to incorporate this thermal switch into various devices. Further, since the spring pressure of the second elastic body is set to be equal to or greater than the spring pressure of the first elastic body, it is possible to prevent one end of the operating shaft from falling out of the fitting hole of the movable member at the time of interruption. In addition to the fact that the low-melting material is brought into direct surface contact with the electric component, the melting point of the low-melting material and the cut-off portion of the movable member and the operating shaft are configured separately and independently. When it is done, it can be more smoothly separated from the electric circuit. Thereby, the spring pressure of the second elastic body can be further reduced, and as a result, the overall size of the thermal switch can be more easily reduced.

According to the third aspect of the present invention, since the conductive layer for reducing the contact resistance is formed at the contact portion between the fitting hole of the movable member and one end of the operating shaft, a surge of a high voltage and a large current can be obtained. , The welding between these fitting holes and one end of the working shaft can be more accurately prevented. According to the fourth aspect of the present invention, since the electric component is constituted by the surge protection element, even if the surge protection element is overheated by an overcurrent, it can be more reliably separated from the electric circuit by the heat switch of the present invention. .

[Brief description of the drawings]

FIG. 1 is a structural diagram of a surge protection device showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional surge protection device.

FIG. 3 is a structural view of a main part of FIG. 2;

FIG. 4 is a structural view of a main part of another conventional surge protection device.

FIG. 5 is a circuit diagram of a surge protection device showing an embodiment of the present invention.

FIG. 6 is an exploded perspective view of FIG.

[Explanation of symbols]

 41, 42 Electric wire path 43 Protected equipment 50 Surge protection element 51, 52 Gas arrestor 53, 54 Varistor 55 Ground terminal 60, 70 Thermal switch 61, 71 Low melting material 62, 72 Opening / closing part 63, 73 Operating shaft 64, 74 Second elastic body 65, 75 Movable member 65d, 75d Fitting hole 65e, 65f, 75e, 75f Terminal 66, 76 Display member 67, 77 First elastic body 80 Case 81 Case main body 81f, 81g Bearing part 82 Case lid 82e, 82f, 82g, 82h Guide

Claims (4)

[Claims] 1. A thermal switch for separating an electric component heated to a temperature equal to or higher than an allowable overheating temperature by receiving an overcurrent from an electric circuit, comprising: a first hole having a fitting hole connected to the electric circuit; A conductive movable member movably supported along a first direction of the second direction and a second direction; and a movable member having one end and the other end supported movably along the second direction. A conductive operating shaft whose one end is removably inserted into the fitting hole; and a movable operating member in the direction in which the fitting hole of the movable member moves away from one end of the operating shaft along the first direction. A first elastic body that urges the member, a second elastic body that urges the operating shaft in a direction in which one end of the operating shaft is separated from the fitting hole along the second direction, A predetermined direction in the second direction corresponding to a distance required when one end of the operating shaft is detached from the fitting hole. Having only one, and interposed between the electric component and the other end of the operating shaft, pressed by the other end of the operating shaft to make surface contact with the electric component, and absorbing conduction heat from the electric component. And a conductive low melting material that melts at a temperature corresponding to the allowable overheating temperature. 2. The thermal switch according to claim 1, wherein the electric component, the low-melting material, the operating shaft, and the second housing are provided in an insulating case having a guide portion on an outer surface and a bearing portion on a side wall. The movable member is slidably supported by a guide portion of the case, the operating shaft is movably supported by a bearing portion of the case, and the first elastic member is The second elastic body is provided between the outer surface of the case and the movable member, and is configured by a spring having a spring pressure equal to or higher than the spring pressure of the first elastic body. A thermal switch provided between an inner surface of the case and the low-melting material, wherein the low-melting material is made of one of a low-melting metal, a shape memory metal, and a conductive shape memory resin. 3. The heat switch according to claim 1, wherein a conductive layer for reducing a contact resistance value is formed at a contact portion between the fitting hole of the movable member and one end of the operating shaft. Switch. 4. The thermal switch according to claim 1, 2 or 3, wherein the electric component is a surge protection element.