JPS6336094B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD This invention relates to an improvement in a non-returnable temperature fuse using a temperature-sensitive pellet made of an insulating chemical substance that melts at a specific temperature.

BACKGROUND TECHNOLOGY Overtemperature prevention devices have come into use from the standpoint of safety in electrical equipment, but recently non-returnable devices have been developed that use temperature-sensitive pellets made of insulating chemicals that melt at a specific temperature. Temperature fuses are used. A typical temperature fuse of this type has the structure shown in FIG. In the figure,
Reference numeral 1 denotes a cylindrical metal case made of a highly conductive and thermally conductive metal such as copper or brass, and a lead wire 2 made of copper is caulked and fixed to one end of the case. 3 is a cylindrical temperature-sensitive pellet made of an insulating chemical substance that melts at a specific temperature, and 4 and 5 are for applying the elasticity of a strong compression spring 6, which will be described later, to the temperature-sensitive pellet 3 and a movable contact 7, which will be described later. 6 is a strong compression spring for closing the circuit which is interposed in a compressed state between the pressing plates 4 and 5, and 7 is made of a silver alloy or the like having good conductivity and appropriate elasticity. The movable contact has a plurality of tongues 7a around the movable contact, and each tongue 7a is in pressure contact with the inner surface of the metal case 1. The temperature-sensitive pellet 3 or the movable contact 7
are housed in the metal case 1 in the order mentioned above. Reference numeral 8 denotes an insulating bushing made of ceramic or the like that closes the open end of the metal case 1. The inner end of the large diameter part 8a is engaged with the stepped part 1a formed in the metal case 1. A portion 1b at the opening end of the insulating bushing 8 that protrudes beyond the insulating bushing 8 is bent toward the central axis to prevent the insulating bushing 8 from moving inwardly and outwardly. Reference numeral 9 denotes a lead wire passing through the center hole of the insulating bushing 8, and the movable contact 7 is connected to the inner end of the lead wire.
It has a fixed contact 10 that comes into contact with the insulating bushing 8, and has enlarged portions 9a and 9b in the vicinity of the fixed contact 10 and adjacent to the outside of the insulating bushing 8,
Lead wire 9 is prevented from moving outward and inward. Reference numeral 11 designates a weak compression spring for opening the circuit which is interposed in a compressed state between the movable contact 7 and the insulating bushing 8, and 12 designates a sealing resin made of epoxy resin or the like that is adhered to the outer surface of the insulating bushing 8. . Reference numeral 13 denotes an insulating cylindrical body made of ceramic or the like, which is adhesively fixed to the outer surface of the insulating bushing 8 via a sealing resin 12, if necessary.

In the above configuration, at room temperature, the temperature-sensitive pellet 3
is solid, and the strong compression spring 6 resists the elastic force of the weak compression spring 11 to force the movable contact 7 into strong pressing contact with the fixed contact 10. Therefore, lead wire 2
- Metal case 1 - Movable contact 7 - Fixed contact 10 - Lead wire 9 is maintained in a conductive state between lead wires 2 and 9 along the route.

When the ambient temperature rises abnormally and reaches the melting point of the temperature-sensitive pellet 3, the temperature-sensitive pellet 3 melts, and the strong compression spring 6 expands and its elastic force decreases, resulting in the elasticity of the weak compression spring 11 decreasing. The force exceeds the elastic force of the strong compression spring 6 and the weak compression spring 11 expands, so that the movable contact 7 moves to the fixed contact 1 as shown in FIG.
0, and the lead wires 2 and 9 become non-conductive.

The above-mentioned temperature fuse not only provides highly accurate operation by utilizing the stable melting point of the temperature-sensitive pellet 3 made of an insulating chemical substance, but also allows the temperature-sensitive pellet 3 to have a desired melting point. There is an advantage that a temperature fuse of any operating temperature can be obtained with the same structure.

By the way, when the metal case 1 itself is used as a part of the conductive path as described above, and the metal case 1 and the movable contact 7 are brought into contact and electrically connected,
In order to reduce the contact resistance between the metal case 1 and the movable contact 7, a silver plating layer 15 with a thickness of about 5 μm is formed on the entire surface of the metal case body 14, as shown in FIG. However, depending on the operating temperature, this type of temperature fuse may not be suitable for evaluation tests or usage conditions.
It may be exposed to high temperatures of 100°C or higher, and copper, which is the constituent material of the metal case body 14 made of copper-based materials such as copper and brass, diffuses into the silver plating layer 15 and oozes out onto the surface of the silver plating layer 15. This oxidation causes an increase in contact resistance with the movable contact 7 on the inner surface of the metal case 1, and discoloration on the outer surface reduces commercial value and makes the stamp display unclear. In order to solve such problems,
For example, the thickness of the silver plating layer 15 may be made sufficiently thick, but if the silver plating layer 15 is made thicker, not only will the cost increase significantly, but the sliding property of the movable contact 7 on the inner surface of the metal case 1 will deteriorate. The dot was hot.

Therefore, in order to solve such problems,
As shown in FIG. 4, the present applicant previously formed an electroless or electric nickel plating layer 17 with a thickness of 1 μ or more on the surface of a metal case body 14 made of a copper-based material, that is, copper or brass, etc. It has been proposed to use a metal case 16 in which a silver plating layer 18 with a thickness of about 1 to 2 microns is formed on the nickel plating layer 17.

According to the above configuration, the copper-based metal case body 1
Since the silver plating layer 18 is formed on the entire surface of the metal case body 14 via the nickel plating layer 17, when exposed to high temperatures of 100°C or higher during evaluation tests or in use, the copper of the metal case body 14 will not bond to the silver plating layer 18. Even if it tries to diffuse into the air, it is blocked by the nickel layer 17.
Copper does not ooze out onto the surface of the silver plating layer 18, and therefore, the contact resistance with the movable contact 7 increases due to oxidation of the copper, the appearance becomes poor, and the display stamp becomes unclear. Then everything that happened will be gone. Further, since the silver plating layer 18 can be made much thinner than the conventional silver plating layer 15, the cost can be reduced.

However, as the nickel plating layer 17,
When an electroless nickel plating layer is formed, it is difficult to activate the surface and the adhesion with the silver plating layer 18 is poor, resulting in peeling and blistering during high temperature storage, which only reduces the product value. However, a new problem was encountered in that the smooth operation of the movable contact 7 became difficult, especially when the temperature-sensitive pellet 3 melted, and the reliability of the temperature fuse decreased.

On the other hand, there is also known a temperature fuse using a metal case in which an electric nickel plating layer is formed on the surface of the metal case body 14, and a silver plating layer is formed on the electric nickel plating layer. In this way, when a silver plating layer is formed through an electric nickel plating layer, the adhesion with the silver plating layer is good, and there is no peeling or blistering during high temperature storage, and when the thermosensitive pellets are melted, This has the advantage that the movable contact can operate smoothly.

However, it is extremely difficult to form an electric nickel plating layer on the inner surface of the metal case body, and the minimum thickness required to achieve the desired purpose is extremely difficult.
It takes 1 hour of plating time to form 1μ,
It was found that in order to obtain the desired thickness of 4μ, it actually required 4 hours of plating time, which significantly increased the cost.

DISCLOSURE OF THE INVENTION [Purpose] This invention prevents copper from leaching out and oxidizing on the surface of the silver plating layer of a metal case, and furthermore, it is possible to form a nickel plating layer of uniform thickness on the inner surface of a bottomed cylindrical metal case. To provide a temperature fuse that can be easily and in a significantly short time, has good adhesion between a nickel plating layer and a silver plating layer, and does not cause peeling or blistering of the silver plating layer.

〔composition〕

This invention uses a metal case in which an electroless nickel plating layer is formed on a metal case body made of a copper-based material, an electric nickel plating layer is formed on the electroless nickel plating layer, and a silver plating layer is further formed. This is a characteristic feature.

〔effect〕

According to this invention, since an electroless nickel plating layer is first formed on the metal case body made of a copper-based material, one end is closed compared to the conventional case in which an electrolytic nickel plating layer is directly formed on the metal case body. An electroless nickel plating layer with a uniform thickness can be easily and extremely quickly formed not only on the outer surface but also on the inner surface of a bottomed cylindrical metal case.

In addition, since the silver plating layer is formed by forming an electroless nickel plating layer on the electroless nickel plating layer, the electroless nickel plating layer Since both the electrolytic nickel plating layer and the electrolytic nickel plating layer are nickel plating layers, the adhesion is good.Furthermore, the surface of the electrolytic nickel plating layer is more active than that of the electroless nickel plating layer, so the adhesion between the electrolytic nickel plating layer and the silver plating layer is good. Since the adhesion between the nickel plating layer and the silver plating layer is greatly increased, the silver plating layer does not peel off or blister due to high temperature storage. Furthermore, even if copper in the metal case body made of a copper-based material attempts to diffuse into the silver plating layer during high-temperature storage, the presence of the nickel plating layer prevents the copper from diffusing to the surface of the silver plating layer and preventing oxidation. However, in this invention, the electroless nickel plating layer and the electric nickel plating layer prevent copper from diffusing and oxidizing to the surface of the silver plating layer more reliably, thereby reducing the internal resistance. There is no reduction in product value due to growth or discoloration. Therefore, it is possible to provide a temperature fuse of higher quality than before at a lower price than before.

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the present invention will be described below with reference to the drawings.

FIG. 5 shows a sectional view of the temperature fuse, and FIG. 6 shows an enlarged sectional view of the main part of the metal case 19.

5 is the same as FIG. 1 except for the following points, and the same parts are given the same reference numerals. The difference from FIG. 1 is that a metal case 19 is used instead of the metal case 1. As shown in FIG. 6, the metal case 19 has a metal case body 14 made of a copper-based material such as copper or brass with a thickness of 1 μm or more on both the inside and outside surfaces using a hypophosphite reduction reaction. An electroless nickel plating layer 20 is formed, and an electric nickel plating layer 21 with a thickness of 0.05μ or more is formed on this electroless nickel plating layer 20 using a nickel chloride bath. A silver plating layer 22 of about 2 μm is formed. The electroless nickel plating layer 20 can be formed almost evenly on both the inner and outer surfaces of the metal case body 14, and in only about 4 minutes per 1μ, so even if it is formed to the preferred thickness of 4μ, it only takes about 16 minutes. It takes only 1/15th of the time required to form an electric nickel plating layer. Further, the electrical nickel plating layer 2
1 is for activating the surface of the electroless nickel plating layer 20, so it does not need to be too thick, but if it is less than 0.05 μm, it cannot be formed over the entire surface due to pinholes and unevenness. However, even if 0.1μ is formed, it can be plated in about 6 minutes.

According to the above configuration, the copper-based metal case body 1
4, a silver plating layer 22 is formed with an electroless nickel plating layer 20 and an electric nickel plating layer 21 interposed therebetween. 14 is prevented from diffusing and oozing out to the surface of the silver plating layer 22, and therefore, due to the oxidation of the copper, the movable contact 7 on the inner surface side of the metal case 19 is prevented.
An increase in internal resistance due to an increase in contact resistance with the silver plating layer 22 is prevented, and on the outside side, there will be no appearance defects or unclear markings due to discoloration of the surface of the silver plating layer 22.

Furthermore, since the silver plating layer 22 is formed by activating the surface of the electroless nickel plating layer 20 with the electric nickel plating layer 21, the adhesion of the silver plating layer 22 is good and no peeling or blistering occurs during high temperature storage. , a highly reliable temperature fuse in which the movable contact 7 moves smoothly when the temperature-sensitive pellet 3 is melted can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional temperature fuse.
FIG. 2 is a sectional view showing the temperature fuse of FIG. 1 after operation. FIG. 3 is an enlarged sectional view of the main part of the metal case in the temperature fuse shown in FIG. 1.
FIG. 4 is an enlarged sectional view of a main part of a metal case in a temperature fuse, which is the background of this invention. FIG. 5 is a sectional view of a temperature fuse according to an embodiment of the present invention. FIG. 6 is an enlarged sectional view of a main part of a metal case used in the temperature fuse shown in FIG. 3... Temperature-sensitive pellet, 6... Strong compression spring, 7...
...Movable contact, 8...Insulating bushing, 9...Lead wire, 10...Fixed contact, 11...Weak compression spring,
14...Metal case body, 19...Metal case,
20... Electroless nickel plating layer, 21... Electric nickel plating layer, 22... Silver plating layer.

Claims (1)

[Scope of Claims] 1. A metal case, a temperature-sensitive pellet housed in the metal case, a strong compression spring, and a movable contact, an insulating bushing that closes the open end of the metal case, and an insulating bushing that penetrates the insulating bushing and extends inward. A temperature fuse having a lead wire having a fixed contact at an end that contacts the movable contact, and a weak compression spring interposed between the insulating bushing and the movable contact, wherein the metal case is made of a copper-based material. An electroless nickel plating layer with a thickness of 1μ or more is formed on the surface of the metal case body, an electric nickel plating layer with a thickness of 0.05μ or more is formed on this electroless nickel plating layer, and a silver plating layer is further formed. A temperature fuse characterized by: 2. The temperature fuse according to claim 1, wherein the silver plating layer has a thickness of 1 to 2 microns.