JPS6240403Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improved structure of a voltage nonlinear resistor comprising a columnar element body.

In general, a voltage nonlinear resistor consisting of a columnar element is made by molding a powder mixture of several types of metal oxides into a cylinder shape, for example, and sintering it at high temperature, as shown in Figure 1.Silver paste is applied to both ends of the element 1. Apply and bake electrode 2
Form a and 2b. However, the electrodes 2a, 2b
The lead wires 3a and 3b are attached with solder 4 and coated with synthetic resin to provide an exterior 5. However, a varistor with such a configuration uses silver and solder 4 constituting the electrodes 2a and 2b.
Since the coefficient of thermal expansion is different between the electrodes 2a and 2b and the element body 1, tensile stress is applied to the contact interface between the electrodes 2a and 2b and the element body 1 due to temperature changes during use, causing the electrodes 2a and 2b to separate, resulting in partial contact between the electrodes 2a and 2b and the element body 1. resistance increases. However, when surge energy is applied, the current is concentrated at the lowest contact resistance portions of the electrodes 2a and 2b, and the energy is absorbed at the extreme portions, promoting deterioration of the element body 1. Therefore, there was a natural limit to its use in places subject to rapid temperature changes, such as in automobiles. Therefore, as shown in FIG. 2, silver paste is continuously applied and baked on the side surfaces near both ends and both end surfaces of the element body 6 to form electrodes 7a and 7b, and lead wires 8a and 8b are integrally connected to the electrodes 7a and 7b. metal caps 9a, 9
A structure in which the lead wires 11 are press-fitted or the lead wires 11 are connected directly to both ends of the element body 10 as shown in FIG.
Metal cap 12a, 1 that integrates a, 11b
A structure in which 2b is press-fitted and no soldering has been proposed has been proposed, but in both cases, the opposing electrodes are not parallel in a plane, so the surface layer between the electrodes is the closest to the distance between the electrodes, that is, between A and B. It had the disadvantage that energy was concentrated and high surge resistance could not be obtained. Furthermore, the structure shown in FIG. 3 also has the disadvantage that the contact resistance is large, and the surge energy is concentrated in extreme areas, resulting in severe deterioration of characteristics. Note 1
3 and 14 are exteriors.

The present invention was developed in view of the above points, and involves forming an insulating layer on the circumferential side of a columnar element body, closely adhering conductive rubber electrodes to both end surfaces, and press-fitting a metal cap in close contact with the electrodes. The object of the present invention is to provide a voltage nonlinear resistor with excellent anti-surge characteristics. An embodiment of the present invention will be described below with reference to the drawings. That is, as shown in Fig. 4, a powder made mainly of zinc oxide, titanium oxide, tin oxide, barium titanate, etc., mixed with several other metal oxides, is formed into a columnar shape with a circular or square cross section. Element 2 sintered at a high temperature of ~1500℃
The entire circumferential surface of 1 is coated with an organic insulating material such as epoxy, phenol, or silicone, or an inorganic insulating material such as enamel or low-melting glass.
The insulating layer 22 is formed by coating with a thickness of 10 μm to 1000 μm. Then, elastic conductive rubber electrodes 23a and 23b made of, for example, synthetic rubber mixed with carbon or fine metal powder such as silver, nickel, or zinc are closely attached to both end surfaces of the element body 21.
As shown in FIG. 5, metal caps 24 made of brass, iron, copper, etc., for example, are press-fitted to both ends, and the element body 21, the conductive rubber electrodes 23a, 23b, and the metal caps 24 are tightly fixed. The lead wires 25a and 25b are attached to the metal cap 24, and then covered with a synthetic resin to form an exterior 26. The voltage nonlinear resistor constructed as described above uses elastic conductive rubber electrodes 23a and 23b as electrodes, and does not use solder to connect to the metal cap 24, so that tensile stress is reduced due to temperature changes. Even if it were to work, there would be no peeling phenomenon between the element body 21 and the conductive rubber electrodes 23a, 23b, and there would be no change in the contact resistance at that part. Therefore, even if surge energy is applied during use, the current will be absorbed by the entire contact surface between the element body 21 and the conductive rubber electrodes 23a, 23b, so that deterioration of the element body 21 will not be accelerated.
It exhibits stable performance over a wide temperature range from ℃ to +150℃, and its characteristics do not deteriorate even when used in places where temperature changes are severe, such as in automobiles. Furthermore, element body 21
Since an insulating layer 22 is formed between the inner peripheral surface of the metal cap 24 which is press-fitted with the element body 21, surge absorption is uniformly performed between the conductive rubber electrodes 23a and 23b serving as opposing electrodes. It has the advantage of being able to eliminate deterioration of surge characteristics like the voltage non-linear resistors shown in FIGS. Next, we will discuss in detail the effects of the present invention based on experimental results.
First, as a sample, ZnO 96 mol%, MgO 1 mol%
Others Bi ₂ O ₃ , Sb ₂ O ₃ , CoO, MnO, Cr ₂ O ₃ ,
Powder made by mixing 0.5 mol% of each composition of SiO ₂ was formed into a cylinder shape with a diameter of 3.5 mm and a length of 10 mm, and sintered at 1200°C to make 40 element bodies, 10 of which are shown in Figure 4. The remaining 30 pieces are 10
The conventional example B shown in FIG. 1, the conventional example C shown in FIG. 2, and the conventional example D shown in FIG. 3 are divided into A to D.
A heat cycle test was conducted and the results are shown in FIG. The conductive rubber electrode in this invention A was 3 mm in diameter and 0.25 mm in thickness, and the insulating layer was made of low melting point glass with a thickness of 30 μm. Further, the metal caps of the present invention A and conventional examples C and D were made of brass. In other words, in Figure 5, one cycle is -50℃ 30 minutes + 150℃ 30 minutes, and 8
The figure shows the rate of change in the rising voltage (ΔV0.1 mA) with respect to the number of cycles when sec10A was applied 10 times in forward and reverse directions. As is clear from Fig. 6, conventional example C,
D shows a rate of change of almost 100% at the 10th cycle, indicating rapid characteristic deterioration, and conventional example B shows that the rate of change and variation increase as the number of cycles increases, indicating deterioration of characteristics due to temperature changes. On the other hand, present invention A demonstrated the excellent effects of the present invention with almost no change even after 50 cycles.

Next, another embodiment of the present invention will be explained with reference to FIG. That is, FIG. 7 shows a structure in which a lead wire is not attached to the metal cap 24 and the exterior 26 is provided except for the metal cap 24.
4 can be directly attached to a printed circuit board (not shown) or the like and used as a chip structure.
Note that other parts that are the same as those in the embodiment shown in FIG. 4 are designated by the same reference numerals, and explanations thereof are omitted. In the above embodiment, the structure in which the insulating layer is formed on the entire circumferential side of the element body was explained as an example, but a structure in which the insulating layer is formed only on the circumferential side surfaces at both ends of the element body into which the metal cap is fitted may also have the same effect. be.

As described above, according to the present invention, a powder made of zinc oxide, titanium oxide, tin oxide, barium titanate, etc. as the main ingredients and a mixture of several other metal oxides is molded into a columnar shape and sintered. By forming an insulating layer on the entire circumferential side surface, adhering conductive rubber electrodes to both end faces, and press-fitting metal caps to both ends, we have created a voltage nonlinear resistor with excellent characteristics that do not deteriorate in characteristics. can be provided.

[Brief explanation of the drawing]

FIGS. 1 to 3 are cross-sectional views showing conventional voltage non-linear resistors, and FIGS. 4 and 5 are cross-sectional views showing an embodiment of the present invention, and FIG. 4 is a cross-sectional view showing a voltage non-linear resistor. , FIG. 5 is a perspective view of the metal cap, FIG. 6 is a characteristic curve diagram showing the rate of change in rising voltage corresponding to the number of heat cycles, and FIG. 7 is a voltage nonlinear resistor according to another embodiment of the present invention. FIG. 21...Element body, 22...Insulating layer, 23a, 23
b... Conductive rubber electrode, 24... Metal cap, 25a, 25b... Lead wire.

Claims (1)

[Claims for Utility Model Registration] (1) A columnar element formed by molding and sintering a metal oxide, an insulating layer formed on the peripheral side of the element, and conductive rubber electrodes in close contact with both end surfaces of the element. A voltage nonlinear resistor comprising: a metal cap that is in close contact with the electrode and fitted to both ends of the element body. (2) The voltage nonlinear resistor according to claim (1) of the utility model registration, characterized in that a lead wire is attached to the metal cap.