JPH0453105A - Surge absorber with safety function - Google Patents

Abstract

PURPOSE:To avoid ignition of a varistor element and a circuit to be protected by a method wherein a low melting point metal element is melted by heat from the varistor element and separated by the shrinkage of a heat-shrinkable insulating tube and the heat shrinkable insulating tube which is an insulator isolates the separated parts of the low melting point metal element from each other. CONSTITUTION:A surge absorber is composed of a plate-shaped varistor element which has electrodes on its surface and rear, at least a pair of parallel sides and an insulating coating on its whole surface or on a part of its surface, a low melting point metal element and a heat-shrinkable insulating tube which is made to shrink by heat so as to have its diameter smaller than the diameter of the varistor element 21 and has an aperture at a part of it. If a continuous overvoltage is applied, the varistor element 21 gradually generates heat and the heat is transmitted to the low melting point metal element 25 through the heat-conducting insulating coating 24 to melt the element 25. At the same time, the heat-shrinkable insulating tube 28 are made to shrink and separate the melted low melting temperature metal element 25. That is, the insulating tube isolate the separated parts of the low melting point metal element 25 from each other to break an overcurrent perfectly without an arc discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a surge absorber with a security function for protecting equipment from surge voltages caused by lightning, etc. The present invention relates to a surge absorber with a security function that includes a surge absorbing element and an element that cuts off overcurrent to prevent a protected circuit from igniting.

2. Description of the Related Art Conventionally, this type of surge absorber has had a configuration as shown in FIG. 6 (for example, there is a surge absorber as shown in Japanese Patent Laid-Open No. 60-76551). In FIG. 6, 1 is a disk-shaped surge absorption element, 2a and 2b are electrodes provided on both sides of the element, and an elastic lead wire 3.4 is connected to the electrode 2a with a low melting point solder 5. The lead wire 6 is connected to the electrode 2b with high melting point solder (not shown). Further, the lead wires 3.4゜6 are connected and fixed to the connection terminals 8, 9.10 of the support 7, respectively, and are configured in the form of four or more J]-1p 4f->2 absorber j). , the following is the key to its operation. (:,
(7:) Use the surge absorber as shown in Figure 7.3
, connect the connection terminals 8 and 9 to the power supply 11, and
, connect the connecting terminal 9°1° to the protected circuit 12. Ij
,, -t, usually between connecting terminals 8 and 10, connecting terminal 1
Between '8.9 and 7.9, the resistance is high and the power is close to an open circuit. When a surge voltage occurs at the input terminal 5, the resistance of the voltage absorbing circuit 1 becomes low, and the connection terminals 8 and 9 are in a smooth state, and the surge current flows through the protected circuit 12. t1
It flows between the connection terminals 8 and 9 without any damage, absorbing the current.

In this circuit, when a continuous overvoltage is applied to the power supply no.in, a continuous overcurrent flows through the surge absorption element f1, and the surge absorption element 1 generates heat l,5, which melts the low melting point solder 5. , the lead wire 3.4 shown in FIG. It will be blocked.

Since the burden that the invention seeks to solve, the configuration ゛r' is continuous b, vortex T 5
P: ,,6:→;・-di absorption t'lr, ;1
If the low melting point is 1, the wire is connected, and the wire is 7L away from the electrode, but due to the large current, theノ、Leave me、"ToA11...
1-1 discharge occurs between the 1-1, Is it a problem that the engine absorbs Ie and ignites?) ノ: 1゜This invention! -:f, What is the solution to these problems? What is the aim of eliminating the above surge absorbing element from the flow due to continuous overload? In order to solve this problem, the present invention proposes a plate-like structure having electrodes on the front and back sides and having sides opposite to one row of at least one set of XF. , a low melting point metal element electrically connected in series with the varistor body, ], = 'ae
'F' of the ballista body One side of the side facing the ladle and 15"
The low melting point metal elements are covered so as to be in close contact with each other; -2
Part of contact surface (7) with low melting point metal element<)1. ,,
< is composed of a heat-shrinkable insulating tube with holes in several places.

Effect: With this configuration, when continuous overvoltage is applied to the surge absorber with safety function of the present invention, continuous overcurrent flows to the varistor body, the varistor body generates heat, and the heat causes low The melting point metal element melts, and then the heat shrinkable insulating tube contracts, thereby causing the low melting point metal element to melt, and the heat shrinkable insulation tube as an insulator 7 intervenes in the low melting point metal element to prevent an overcurrent. It is possible to completely shut off and prevent the varistor body and the protected circuit from igniting.

EXAMPLES Below, examples of the present invention will be explained with reference to the drawings.

FIG. 1 is a front view showing the structure of a surge absorber with a security function according to a first embodiment of the present invention, and FIG. 2 is a side view showing the structure of the same surge absorber with a security function. In FIGS. 1 and 2, 21 (, -1) is a plate-shaped varistor body in the form of a long force, each side of which is cut out. 22 and 22a.

(・”Electrodes numbered on the front and back of the varimetal element body 21, 2
3 and 23& are connecting ground wires, and the varistor element body 21
The picture electrodes 22 and 22aK are directly connected. 24 is an insulator made of an inorganic nonmetallic material such as glass,
The entire (or part) surface of the varistor body 21 is coated. 26 is a low melting point metal element such as lead eutectic solder wire, and this low melting point metal element 2
One end of the low melting point metal element 25 and the connecting lead wire 26 are connected, for example, by a caulking 27, and the other end of the low melting point metal element 25 and the connecting lead wire 23a are connected, for example, by a caulking 27a. 28 is a heat-shrinkable insulating tube having an opening 29 at one location so that its diameter shrinks to a smaller diameter than the diameter of the varistor body 21 due to heat; The surface and the low melting point metal element 25 are in close contact j2, and the divided parts 282L and 28b, which are divided into two by the opening 29, cover and fix the low melting point metal element 26 so that they are in contact with them. Furthermore, in order to prevent the low melting point metal element 26 from scattering during melting and to prevent moisture, the product of the present invention leaves the tips of the connection lead wires 23, 232L and 26, and at least has a cavity around the low melting point metal element 25. Although it is often used with a casing made of insulating resin or the like, these are not shown in FIGS. 1 and 2.

The operation of the surge absorber with security function configured as described above will be explained below. Here, this surge absorber with safety function is used as shown in FIG. That is, in FIG. 3, 30 is a surge absorber with a safety function. Reference numeral 31 denotes a power supply or signal source, which is connected to the connection lead wire 23.26 of the surge absorber with safety function 30, and 32, a circuit to be protected, which is connected to the connection lead wire 23.23&. And usually the connection lead wire 231L
There is a short circuit between the connecting lead wire 260 and the connecting lead wire 23! The resistance between L is high and it is almost open. Now, if a surge voltage occurs in the power supply line or signal line, the varistor element 21 forming the surge absorber 30 will have a low resistance, and the connection lead wire 23 and the connection lead wire 23a will be in a state close to a short circuit. , the surge current does not flow through the protected circuit 31 but flows between the connection lead wire 23 and the connection lead wire 26, and the surge is absorbed.

In this circuit, when a continuous overvoltage is applied to the power supply line or signal line due to contact with high voltage lines, a continuous overcurrent flows to the varistor body 21, and the varistor body 21
gradually generates heat, and this heat is transferred to the low melting point metal element 26 by the insulator 24, such as glass, which has good thermal conductivity.
The low melting point metal element 25 melts. At the same time, either or both of the divided portions 28a and 28b of the heat-shrinkable insulating tube 28 shrinks in the radial direction, and the molten low-melting metal element 25 is transferred to the divided portion 28 of the heat-shrinkable insulating tube 28.
The low melting point metal element 25 is pushed out by the contraction force in the radial direction of either or both of the heat-shrinkable insulating tube 28, and the low melting point metal element 25 is inserted between the divided portions 28L and 28b or both of the heat-shrinkable insulating tube 28. separated into That is, the overcurrent flowing through the lister element body 21 is transferred to the divided portion 28L of the heat-shrinkable insulating tube 28, which is an insulator.
By intervening with one or both of the low melting point metal elements 28b, the arc is completely cut off without any arc discharge occurring after the low melting point metal elements 26 are separated. Therefore, the varistor body 21 stops generating heat, and ignition can be prevented.

As described above, the surge absorber with security function of this embodiment has the effect of preventing the varistor element body 21 and the protected circuit 32 from igniting due to continuous overvoltage.

Next, a second embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a front view showing the structure of a surge absorber with a security function according to a second embodiment of the present invention, and FIG. 6 is a side view showing the structure of the surge absorber with a security function.

The difference from the first embodiment is that the heat-shrinkable insulating tube has two openings instead of one. In FIG. 4 and FIG. 5, 33 is a varistor element body, 34
and 341L are electrodes, and 35 and 361L are connection lead wires, which are directly connected to the picture electrodes 34, 34& of the varistor element body 33.

Reference numeral 36 is an insulator made of an inorganic non-metallic material such as glass, and coats the entire (or part) of the surface of the varistor body 33. 37 is a low melting point metal element such as a eutectic solder wire of tin or lead, and one end of this low melting point metal element 37 and a connecting lead wire 38 are connected to each other by caulking 3, for example.
9 or the like, and the other end of the low melting point metal element 37 and the connecting lead wire 36& are connected by, for example, caulking 391L or the like. Reference numeral 40 denotes a heat-shrinkable insulating tube having two openings 41 and 41a so that its diameter shrinks to be smaller than the diameter of the varistor body 33 due to heat, and an insulating material coating the surface of the varistor body 33. The surface of 36 and the low melting point metal element 37 are in close contact with each other, and the divided portions 401L and 4 are divided into three by the openings 41 and 41a.
0b and 40C cover and fix the low melting point metal element 37 so that they are in contact with it.

The corner piece of the security function tt"j-di absorber configured in this way is the same as that in the first embodiment, but compared to the first embodiment, holes are provided at two locations in the heat-shrinkable insulating tube 40. Part 41
．． ．． 41a, the number of fusing points of the low melting point metal element 37 is three, and the insulation distance is long, so that continuous overcurrent can be cut off more reliably. In addition, the variation in time until melting can be reduced.

In the above embodiment, glass, which is one of the inorganic and nonmetallic materials, was used as the insulator coating the surface of the varistor body, but the insulator is not limited to this. Furthermore, although a tin-lead eutectic wire was used as the low-melting point metal element 7, the low-melting point metal element is not limited to this. Although openings are provided at certain locations, it goes without saying that the number of openings should also be limited. In addition, the heat-shrinkable insulating tubes having such openings may be provided at two or more locations at a predetermined interval, and in this case, the function can be more reliably performed3. In the embodiment of the present invention, a case was explained in which a rectangular plate with two sets of parallel opposing sides of 4'-J was used as the plate-shaped varistor element. Any varistor element body may be used as long as it has at least one set of parallel opposing sides: a side on which the element is provided and a side opposite thereto. In the example, the entire surface (or part of the surface) of the varistor body was coated with an insulator, and the surface of the insulator was in close contact with the low melting point metal element. 2, it is also possible to omit the above structure and adopt a structure in which one of the parallel opposing sides of the varistor body and the low melting point metal element are in close contact with each other. However, in this case, in the case of a structure in which an insulator is interposed between the electrodes provided on the front and back of the varistor body (the electrode 22 on the front surface when applied to the structure shown in FIG. 1) and the low melting point metal element, It is necessary to make the electrode area relatively wider, which forces the electrode area to be smaller.
Care must be taken to ensure that characteristics such as surge resistance are low. Also, whether there is an insulator intervening or not.
Although it differs slightly, if the distance between the parallel opposing side of the lister element and the front and back electrodes is too close, the low melting point metal elements will be in close contact with each other. Due to the insufficient creepage distance between the metal element and the melting point metal element, electric discharge will occur, making it impossible to perform its original function.

Furthermore, in the above embodiment, the case where each side of the varistor element is chamfered is explained, but the varistor element in which the low melting point metal element is closely attached (7) directly or with an insulator interposed If l'l'11 on the side facing parallel to Chi, -) becomes the first Yazu,
Juru-1, which performs its original function, has the potential to cause some problems, so you need to be careful.

According to the present invention, electrodes are placed on the front and back sides,
a plate-shaped varistor element body having at least one set of parallel opposing sides; a low melting point metal element electrically connected to the upper varistor element body in series; The low melting point metal element is covered so as to be in close contact with one side of the varistor element 1', and is contracted by the heat generated by the varistor element 1' to melt and cut the low melting point metal element. The varistor body and the protected circuit can be prevented from catching fire due to continuous overvoltage by being composed of a heat-shrinkable insulation tube with openings in a portion or several places of the contact surface with the tf. This effect can be obtained.

4. Explanation of drawings Fig. 1 is a front view showing the structure of the first embodiment of the surge absorber with security function of the present invention, and Fig. 2 is a side view showing the structure of the same embodiment. 3 is a circuit diagram showing an example of use according to the same embodiment, FIG. 4 is a front view showing a structure according to a second embodiment of the present invention, and FIG. 5 is a side view showing a structure according to the same embodiment. Fig. 6 is a close-up view of the structure of a conventional large absorber, Fig. 7 is a circuit diagram showing an example of the use of the same surge absorber, and Fig. 8 is a front view showing the operating state of the same surge absorber. It is a diagram.

21.33...Ballista body, 22.22a.

34.34a... Electrode, 24.36...
Insulator, 2537...Low melting point metal element, 28.40
...Heat-shrinkable insulating tube, 29.41.41&...
...Open hole.

Claims (3)

[Claims] (1) A plate-shaped varistor body having electrodes on the front and back sides and at least one set of parallel opposing sides, a low melting point metal element electrically connected in series with the varistor body, and the varistor body. The low melting point metal element covers one parallel opposing side of the element body so as to be in close contact with the low melting point metal element, and contracts due to heat generation of the varistor element body, melting the low melting point metal element, and the low melting point metal element. A surge absorber with a security function that consists of a heat-shrinkable insulating tube with holes in a portion or several locations of the contact surface with the element. (2) The surge absorber with a security function according to claim 1, wherein the varistor body has a part or all of its surface coated with an insulating material. (3) The surge absorber with a security function according to claim 1, wherein two or more heat-shrinkable insulating tubes are provided at a predetermined interval.