JP2001297904A - Temperature fuse built-in varistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature fuse built-in varistor which is never deteriorated in varistor function when an excessive surge voltage is applied from a power supply, high in safety, and excellent in reliability. SOLUTION: A temperature fuse built-in varistor is composed of a varistor element 9, a pair of conductive plates 12 and 13 provided and electrically connected to both surfaces of the element 9, a first terminal 26 connected to the conductive plate 12 out of the pair of the electrodes, a second terminal 27 connected to the other conductive plate 13, a temperature fuse 31 connected to the conductive plates 13 coming into contact with it, and a third terminal 25 connected to the temperature fuse 31 all housed in an insulating case 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a varistor with a built-in thermal fuse for protecting various electronic devices and electrical equipment to which varistors are applied from noise such as lightning surges and switching surges.

[0002]

2. Description of the Related Art FIG. 9 is an external perspective view of a conventional varistor, FIG. 10 is a sectional view of the varistor, and FIG. 11 is an electric circuit diagram of the varistor.

9 through 11, reference numeral 51 denotes a through hole 52.
And a varistor element 53 having electrodes 54 and 55 formed on both sides thereof.
Are connected to a pair of conductive plates 56 and 57, and this conductive plate 5
Projecting pieces 58, 59 protruding from the outer shapes of terminals 6, 57 and terminals 6
0 and 61 are stored. Further, one end face of the through hole 52 is shielded by a shield plate 62, and the terminals of the terminals 60 and 61 are drawn out of the insulating case 51 through the through holes formed in the shield plate 62. Things.

A method of manufacturing a conventional varistor having the above-described configuration will be described below.

First, an electrode paste such as Ag is printed and baked on both surfaces of the varistor element 53 to form a pair of electrodes 54.
55, and then the electrodes 54, 55 and the conductive plate 5
6 and 57 are brought into close contact with each other, and this contact surface is joined with a conductive paste or an adhesive. Next, the terminals 60 and 61 are inserted into the through holes formed in the shielding plate 62, the terminals of the terminals 60 and 61 projecting from the shielding plate 62, and the protruding pieces 58 and 59 projecting from the outer shape of the conductive plates 56 and 57. Soldering is performed, and a varistor element 53 is inserted into the through hole 52 of the insulating case 51.
Then, a pair of conductive plates 56 and 57 are housed, and one end of the through hole 52 is shielded and joined by the shielding plate 62 to complete a varistor. The varistor completed as described above has a circuit configuration shown in FIG. 11, in which the varistor element 53 is connected between the electronic device side and the power supply side to absorb surge voltage generated on the power supply side and This protects the circuit.

[0006]

In this conventional varistor, when an excessive surge voltage exceeding the rating of the electronic device invades from the power supply circuit side, the electrode 5 of the varistor element 53 is closed.
A current that absorbs the surge voltage flows between 4 and 55 to protect the signal circuit of the electronic device. At this time, however, the varistor element 53 abnormally generates heat due to an excessive surge current and impairs the varistor function. Had.

The present invention solves the above-mentioned conventional problems, and provides a varistor with a built-in thermal fuse that can prevent abnormal heat generation of the varistor element 53 when an excessive surge voltage is applied from the power supply circuit side. The purpose is to do so.

[0008]

To achieve the above object, a varistor with a built-in thermal fuse of the present invention has the following configuration.

According to a first aspect of the present invention, there is provided an insulating case, a varistor element having a pair of electrodes housed in the insulating case, a pair of conductive plates connected to each of the pair of electrodes, A first terminal connected to one conductive plate of a pair of conductive plates, a second terminal connected to the other conductive plate, and one end of the other conductive plate in close contact with the other conductive plate. A thermal fuse connected to the conductive plate, and a third terminal connected to the other end of the thermal fuse, the first terminal, the second terminal, a part of the third terminal of the insulating case. This is a varistor with a built-in thermal fuse drawn out to the outside, whereby the third terminal and the first terminal are connected to a power supply circuit of an electronic device, and the second terminal and the first terminal are connected to an electronic device. Connect to the signal circuit of the device and set the electronic device from the power circuit. When an abnormal surge voltage exceeding the threshold voltage is applied, the abnormal surge voltage is absorbed to protect the signal circuit of the electronic device, and when an excessive surge current flowing through the varistor element causes abnormal heat generation, The circuit is cut off by the thermal fuse, so that the varistor element can be prevented from being abnormally heated, and the surge absorbing function of the varistor element can be protected.

According to a second aspect of the present invention, a bent portion is formed in a part of the other conductive plate so as to be bent into an outer shape of a thermal fuse, and a thermal fuse is inserted into the bent portion to form the bent portion. The varistor with a built-in thermal fuse according to claim 1, wherein the thermal fuse is fixed by closely contacting the inner surface of the thermal fuse with the outer peripheral surface of the thermal fuse, whereby the heat generated by the varistor element is accurately transmitted to the thermal fuse. In addition, the operation and effect of having a highly reliable thermal fuse operation with excellent thermal responsiveness can be obtained.

According to a third aspect of the present invention, a tongue-shaped bent portion is formed on the other conductive plate, and a thermal fuse is sandwiched between the tongue-shaped bent portion and the varistor element surface. The varistor with a built-in thermal fuse according to claim 1, wherein the thermal fuse is tightly fixed to the tongue piece and the varistor element surface of the other conductive plate, whereby the thermal fuse is held down by the conductive plate. The varistor element can be fixed in close contact with the varistor element surface, so the thermal fuse has an even higher accuracy and better thermal response to the heat generated by the varistor element. can get.

According to a fourth aspect of the present invention, there is provided the varistor with a built-in thermal fuse according to the first aspect, wherein the thermal fuse and the other conductive plate are bonded and fixed with a first resin. Thus, there is obtained an operational effect that the thermal fuse and the conductive plate are fixed to each other, and deterioration of characteristics can be prevented even by a mechanical shock and the operation of the thermal fuse with high reliability can be configured.

According to a fifth aspect of the present invention, there is provided a varistor with a built-in thermal fuse according to the fourth aspect, wherein the first resin is a heat conductive resin having elasticity. The heat generated by the varistor element can be accurately transmitted to the thermal fuse via the conductive resin, and even when a mechanical shock is applied, the elasticity of the thermal conductive resin reduces the impact of the adhesive between the thermal fuse and the conductive plate. As a result, it is possible to reduce the damage such as cracks, and to obtain the effect of having a highly reliable operation of the thermal fuse.

According to a sixth aspect of the present invention, there is provided a varistor with a built-in thermal fuse according to the fifth aspect, wherein a second resin having lower thermal conductivity than the first resin is filled in the insulating case. Because of this, it is possible to suppress the heat radiation of the thermal fuse, so that the varistor element has a more accurate and excellent thermal response to the heat generated by the varistor element, and has a highly reliable operation of the thermal fuse. The effect is obtained.

According to a seventh aspect of the present invention, the current fuse is connected between the other conductive plate and the thermal fuse or between the thermal fuse and the third terminal. This is a varistor configuration, which has the effect of cutting off the current fuse due to an excessive surge current, the circuit self-interrupting and protecting the signal circuit of the equipment, and also preventing the varistor from overheating. can get.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is an external perspective view of the first embodiment of the present invention, FIG. 2 is an exploded perspective view of the first embodiment, FIG. 3 is an assembly view of a main part of the first embodiment, and FIG. FIG. 4 is an electric circuit diagram of the first embodiment.

1 to 3, reference numeral 1 denotes an insulating case formed of a synthetic resin such as polycarbonate.
Through holes 4 extending from the lower surface 3 to the lower surface 3 are formed, and mounting flanges 5 and 6 formed with holes 7 and 8 are formed on the side wall of the lower surface 3 so that the holes 7 and 8 can be mounted on the housing of the electronic device.

Reference numeral 9 denotes a varistor element, which has a pair of electrodes 10 and 11 formed by baking silver on both surfaces. 13 are adhered and fixed with a conductive adhesive so as to adhere to each other (hereinafter, these conductive plates 12 and 13 are fixed).
Among them, 12 is called one conductive plate, and 13 is called the other conductive plate. ).

A bent portion 15 is formed at the tip of a protruding piece 14 formed on the outer shape of the one conductive plate 12, and a bent portion 16 cut and bent is formed on the other conductive plate 13. The inside diameter of the bent portion 16 is formed to be slightly smaller than the outside diameter of the body 32 of the thermal fuse 31, and the body 32 of the thermal fuse 31 is inserted into the bent portion 16 to bend the other conductive plate 13. The element 32 of the thermal fuse 31 is held in close contact with the other conductive plate 13 by the spring pressure of the portion 16, and sufficiently withstands vibration and impact. Heat transfer is not impaired.

The thermal fuse 31 is formed of a body 32 having excellent heat conductivity, and lead wires 33 and 34 are provided at both ends thereof.
And one lead wire 33 and the other conductive plate 1 are attached.
The third protruding piece 17 is fixed by soldering to the surface of the bent portion 18 at the tip end.

Reference numeral 19 denotes a shielding plate made of a synthetic resin such as polycarbonate, which has thick portions 20 and 21 protruding from the upper surface and the lower surface, and extends from the upper surface of the thick portion 20 to the lower surface of the thick portion 21. Through holes 22, 23, 24 are formed.

Reference numerals 25, 26 and 27 denote terminals, and the small width portion 2
8, 29, 30 are formed to form holes 22, 2,
3 and 24, and protrudes from the lower surface of the shielding plate 19 to form an end (hereinafter, these terminals 25, 2
6, 27, the third terminal, 26 the first terminal, 2
7 is called a second terminal. ).

The small width portion 29 of the first terminal 26
And the bent portion 15 of the one conductive plate 12 are soldered and joined, and the small width portion 30 of the second terminal 27 and the bent portion 18 of the other conductive plate 13 are soldered and joined, The small width portion 28 of the third terminal 25 and the lead wire 34 of the thermal fuse 31 are joined by soldering.

As described above, the varistor element 9, the one conductive plate 12, the other conductive plate 13, the temperature fuse 31, and the shielding plate 1
9, first terminal 26, second terminal 27, third terminal 25
Then, the shielding plate 19 is housed in the through hole 4 of the insulating case 1 and the shielding plate 19 is overlapped on the upper surface 2 of the insulating case 1 and bonded with an adhesive. Then, a liquid resin such as epoxy or butadiene is injected into the through hole 4 by changing the direction so that the lower surface 3 of the insulating case 1 is directed upward, and then dried and cured to complete a varistor with a built-in thermal fuse. I do.

As shown in the electric circuit diagram of FIG. 4, the varistor with a built-in thermal fuse constructed as described above is provided with the second terminal 27 and the third terminal 25 on the power supply side, the first terminal 26 and the second terminal 26 on the second side. By connecting the terminal 27 to the electronic device side and inserting the thermal fuse 31 and the varistor element 9 into this circuit, if an abnormal surge exceeding the rating of the electronic device enters from the power supply side, the abnormal surge Before the varistor element generates abnormal heat due to the current and the varistor function is destroyed, the generated heat is transmitted to the thermal fuse 31 and the thermal fuse 31 is operated, so that the current on the power supply side, the varistor element 9 and the electronic device side are automatically controlled. Thus, it is possible to provide a highly reliable varistor that is excellent in safety, that is, it cuts off the entire circuit and protects the entire circuit.

(Embodiment 2) Hereinafter, the second embodiment of the present invention will be described with reference to Embodiment 2. FIG. 5 is a sectional view showing a main part according to the second embodiment of the present invention.

The varistor with a built-in thermal fuse according to the second embodiment shown in FIG. 5 has basically the same configuration as the varistor with a built-in thermal fuse shown in FIGS. 1 to 3. The same reference numerals are given and the detailed description is omitted, and the characteristic portions will be described here.

In FIG. 5, reference numeral 35 denotes a tongue-shaped bent portion of a part of the other conductive plate 36. The bent portion 35 is formed by bending in a semicircular shape along the outer shape of the thermal fuse 31. Then, the thermal fuse 31 is inserted between the bent portion 35 and the varistor element 9 and is sandwiched and fixed.

In the varistor with a built-in thermal fuse configured as described above, the element body 32 of the thermal fuse 31 is connected to the inner surface of the tongue-shaped bent portion 35 of the other conductive plate 36 and the varistor element 9.
The thermal fuse 31 has good thermal conductivity with the varistor element 9 and the thermal responsiveness of the thermal fuse 31 is excellent. Further, the thermal fuse 31 can be securely held by the tongue-shaped bent portion 35, and can withstand vibration and shock sufficiently.
The heat transfer between the tongue-shaped bent portion 35 of the other conductive plate 36 and the varistor element 9 is not impaired.

(Embodiment 3) Hereinafter, a third embodiment of the present invention will be described with reference to a third embodiment. FIG. 6 is a sectional view of a varistor with a built-in thermal fuse according to Embodiment 3 of the present invention.

The varistor with a built-in thermal fuse of the third embodiment shown in FIG. 6 has basically the same configuration as the varistor with a built-in thermal fuse shown in FIGS. 1 to 3. The same reference numerals are given and the detailed description is omitted, and the characteristic portions will be described here.

In FIG. 6, reference numeral 37 denotes the other conductive plate. The element 32 of the thermal fuse 31 is provided on the other conductive plate 37 and adhered and fixed with a first resin 38. The first resin 38 is made of a thermally conductive silicone rubber having good conductivity and elasticity. The elasticity absorbs vibrations and shocks and does not cause cracks in the bonded portion.
It will be excellent in reliability.

Further, the second resin 39 is filled in the through hole 4 of the insulating case 1 so as to cover the conductive plate 37, the thermal fuse 31, and the varistor element 9. The second resin 39 is selected from silicone rubber or butadiene resin having a lower thermal conductivity than the first resin 38. Thus, the heat radiation of the thermal fuse 31 can be suppressed, so that the thermal effect of the thermal fuse, which has higher accuracy and excellent thermal response to the temperature rise of the varistor element 9 and has high reliability, can be obtained.

(Embodiment 4) Hereinafter, the fourth embodiment of the present invention will be described with reference to Embodiment 4. FIG. 7 is an assembly view of a main part of a varistor with a built-in thermal fuse according to a fourth embodiment of the present invention, and FIG. 8 is an electric circuit diagram of the fourth embodiment.

The varistor with a built-in thermal fuse of the fourth embodiment shown in FIGS. 7 and 8 has basically the same configuration as the varistor with a built-in thermal fuse shown in FIGS. Portions are assigned the same reference numerals, and detailed description is omitted. Here, characteristic portions will be described.

7 and 8, reference numeral 40 denotes a current fuse. One of the lead wires 41 attached to the current fuse 40 is joined to the lead wire 34 of the temperature fuse 31 by soldering or welding. The other lead wire 42 attached to the fuse 40 is joined to the third terminal 25 by soldering or welding. Here, the current fuse 40 is connected between the thermal fuse 31 and the third terminal.
1 may be connected.

In the varistor with a built-in thermal fuse according to the fourth embodiment of the present invention, the varistor element 9 is protected by the thermal fuse 31 and when an excessive surge current flows, the current fuse 40 is switched off. The circuit is cut off by fusing, and the varistor element 9 and the circuit of the electronic device are double protected, so that the reliability is improved.

[0039]

As described above, the varistor with a built-in thermal fuse of the present invention having a built-in thermal fuse does not deteriorate the varistor function due to heat generation of the varistor element even if an excessive surge voltage is generated in the power supply. It has high safety and high reliability.

[Brief description of the drawings]

FIG. 1 is an external perspective view showing a first embodiment of a varistor with a built-in thermal fuse of the present invention.

FIG. 2 is an exploded perspective view showing the first embodiment.

FIG. 3 is an assembly view showing a main part of the first embodiment;

FIG. 4 is an electric circuit diagram using the varistor with a built-in thermal fuse according to the first embodiment.

FIG. 5 is an assembly view of a main part of a varistor with a built-in thermal fuse according to a second embodiment of the present invention;

FIG. 6 is an assembled view of a main part of a varistor with a built-in thermal fuse according to a third embodiment of the present invention;

FIG. 7 is a sectional view showing a main part of a varistor with a built-in thermal fuse according to a fourth embodiment of the present invention;

FIG. 8 is an electric circuit diagram using the varistor with a built-in thermal fuse of the fourth embodiment.

FIG. 9 is an external perspective view of a conventional varistor.

FIG. 10 is a sectional view of the varistor.

FIG. 11 is an electric circuit diagram using the varistor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating case 2 Upper surface 3 Lower surface 4 Through hole 5, 6 Flange 7, 8 hole 9 Varistor element 10, 11 Electrode 12 One conductive plate 13, 36, 37 The other conductive plate 14, 17 Projection piece 15, 18 Bending part 16 Bending part 19 Shielding plate 20, 21 Thick part 22, 23, 24 Hole 25 Third terminal 26 First terminal 27 Second terminal 28, 29, 30 Small width part 31 Thermal fuse 32 Element body 33, 34, 41, 42 Lead wire 35 Bent portion bent in a tongue shape 38 First resin 39 Second resin 40 Current fuse

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kei Ishibashi 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (72) Inventor Masaaki Sato 1006 Odakadoma Kadoma, Osaka Pref. Terms (reference) 5E034 DA03 DB05 DB06 DB09 DC02 DC05 FA02

Claims (7)

[Claims] 1. A varistor element having an insulating case, a pair of electrodes housed in the insulating case, a pair of conductive plates connected to each of the pair of electrodes, and one of the pair of conductive plates. A first terminal connected and provided;
A second terminal connected to the other conductive plate, a thermal fuse having one end connected to the other conductive plate in close contact with the other conductive plate, and a third terminal connected to the other end of the thermal fuse And a varistor with a built-in thermal fuse, wherein a part of the first terminal, the second terminal, and the third terminal are drawn out of the insulating case. 2. A bent portion which is bent into an outer shape of a thermal fuse is formed on a part of the other conductive plate, and a thermal fuse is inserted into the bent portion so that an inner surface of the bent portion and an outer peripheral surface of the thermal fuse are brought into close contact with each other. 2. The varistor with a built-in thermal fuse according to claim 1, wherein the thermal fuse is fixed. 3. A tongue-shaped bent portion is formed on the other conductive plate, and a thermal fuse is sandwiched between the bent portion and the varistor element surface, and the thermal fuse is connected to the tongue-shaped portion of the other conductive plate. 2. The varistor with a built-in thermal fuse according to claim 1, wherein the varistor is closely fixed to a bent portion of the varistor and a varistor element surface. 4. The varistor with a built-in thermal fuse according to claim 1, wherein the thermal fuse and the other conductive plate are bonded and fixed with a first resin. 5. The varistor with a built-in thermal fuse according to claim 4, wherein the first resin is a heat conductive resin having elasticity. 6. The varistor with a built-in thermal fuse according to claim 5, wherein a second resin having lower thermal conductivity than the first resin is filled in the inside of the insulating case. 7. The varistor with a built-in thermal fuse according to claim 1, wherein the current fuse is connected between the other conductive plate and the thermal fuse or between the thermal fuse and the third terminal.