JPH11238440A - Alloy type thermal fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alloy type thermal fuse of high reliability whereby mechanical damage by thermal stresses can be prevented even if it is exposed to severe temp. cycles. SOLUTION: An alloy type thermal fuse 10 is structured so that a thermo- sensitive soluble material 14 consisting of a low-melting point alloy is accommodated in a cylindrical insulation case 12 and the opening of this case 12 is sealed with a resin molding 11, wherein the resin molding 11 holds the edge 12a of the case opening pinchedly by the inside surface 12ai and outside surface 12ao and is attached fast to the opening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fuse, and more particularly to an alloy-type thermal fuse in which a heat-sensitive fusible body made of a low melting point alloy is housed in a cylindrical insulating case.

[0002]

2. Description of the Related Art A thermal fuse has a small and robust structure capable of detecting a temperature abnormality and interrupting a circuit.
Detects an abnormal rise in the heat of household or industrial electrical equipment and immediately shuts off the circuit to prevent damage to equipment and fire. There are two types of thermosensitive elements: one using a thermosensitive pellet and the other using a low melting point alloy. The general operating temperature range is 70 ° C. to 24 using thermosensitive pellets.
About 0 ° C, 70 ° C to 180 ° C using low melting point alloy
To about 190 ° C., and the rated current corresponds to a wide current range of about 0.5 to about 15 amps. The characteristics of thermal fuses are that they are compact and have excellent temperature sensitivity to ambient temperature, that they have high operating accuracy due to their airtight structure, so that their characteristics do not change over time. However, there is no recovery even after the above operation, and the application can be optimized by selecting two types of thermal fuses according to the application.

[0003] In particular, recently, the safety of so-called devices and the like has been enhanced, and this kind of thermal fuse has been widely and generally used in the industrial world. Specifically, electric kotatsu, electric stove, electric carpet,
Iron and trouser press, hair dryer, air conditioner and ventilation fan, gas bath and gas water heater, pencil sharpener, sewing machine,
LCD TVs and game consoles, color TVs and stereos, videos, refrigerators, electric rice cookers, microwave ovens, fluorescent lamps, desk lamps, transformers and power supplies, inverters, chargers and rechargeable batteries, pack batteries, copiers and printers Used in products.

[0004] A conventional thermal fuse will be briefly described below with reference to the drawings. First, the type using the thermosensitive pellet is a thermal fuse 9 as shown in FIG.
However, the movable electrode 92, the spring 93, and the 94 thermosensitive pellet 95 are sealed in the metal case 91, and the spring B94 shown in FIG. The movable electrode 92 via the disk 96
Is kept in contact with the lead wire A97. The normal current is the lead wire A97, the movable electrode 92, the metal case 91,
It flows along the path of the lead wire B98. When the ambient temperature rises and exceeds the operating temperature as shown in FIG. 3B, the thermosensitive pellet is melted by the heat transmitted from the wall surface of the metal case 91, becomes a liquid 95m, and the springs A93 and B94 expand. The movable electrode 92 is pushed toward the spring B94 by the extension force of the spring A93, and the lead wire A
97 is broken. In this way, the circuit is interrupted. However, this type has a large number of parts and is expensive.

FIG. 10 shows a low-melting point alloy type thermal fuse 100 shown in FIG. This type of thermal fuse includes lead wire A107 and lead wire B1 in ceramic case 101.
A fusible body 105 typified by a low melting point alloy is connected between the parts 08 by welding or the like. Therefore, the current is
5, flowing through the low melting point alloy body, the fusible body 105 is covered with a special flux 104. As shown in FIG. 3B, when the ambient temperature rises, the low-melting alloy body, which is the fusible body 105, also rises in temperature depending on the ambient temperature and eventually melts. At this time, the low melting point alloy as the fusible body 105 is instantaneously formed in the ceramic case 101 in the ceramic case 101 by the action of the special flux 104 surrounding the fusible body and the surface tension of the low melting point alloy as the fusible body 105 (b). Are agglomerated at the ends of the lead wires 107 and 108 shown in FIG.

Incidentally, the sealing structure of such an alloy type thermal fuse has a configuration shown in FIG. FIG. 11 is an enlarged view of a resin molded portion 111 of a conventional alloy-type thermal fuse 110. The heat-sensitive fusible material 114 is disposed at the center of the cylindrical insulating case 112 and the end is connected to the lead 1.
13 and its lead 113 is a cylindrical insulating case 1
Twelve opening portions 112a are fixed and disposed by a resin molding material. As can be seen from this figure, the resin molding portion 111 of the conventional resin molding material is formed at the end of the cylindrical insulating case 112 to have an outer diameter substantially the same as the outer diameter of the cylindrical insulating case 112. ing. One of the reasons for this is that the resin molded part does not protrude outside the cylindrical insulating case in view of the recent miniaturization of electronic component materials, etc. This is because the length is reduced.

[0007]

As described above, at present, high performance, high reliability and miniaturization are the most important factors required for this type of thermal fuse. However, when adopting the same manufacturing process and the same configuration as the conventional one in order to meet these needs, increase in cost cannot be avoided and the function may be insufficient. The problems to be solved for the above-described conventional alloy-type thermal fuse and the like are described below in order.

First, there is shown a thermal fuse 90 of a thermal sensitive pellet type shown in FIG. 9. This thermal fuse 90 is of a type in which a contact is separated by a spring and the current is interrupted. However, since many parts are used, the manufacturing process is complicated and the manufacturing cost is high. Therefore, there is an alloy type thermal fuse 100 having a simple configuration. However, in this type, the selection of the sealing resin and the sealing step are complicated, and the gas generated from the sealing resin or the crack generated in the sealing resin or the deformation of the sealing resin is required. Is also a problem.

That is, a specific diagram showing such a problem is shown in FIG. FIG. 12 shows the stress of the resin molding material 111 shown in FIG. In general, the thermal fuse is made of an insulating material in order to ensure insulation after the thermal fuse operates.However, as an insulating material, for example, a material such as glass or ceramics has a small coefficient of thermal expansion. The resin molding material molded at the end of the case is made of an organic material,
It has the characteristic of having a very large coefficient of thermal expansion.

Therefore, for example, when the temperature of the entire insulating case rises, the resin molding material greatly expands despite the fact that the insulating case having a relatively small coefficient of thermal expansion does not expand. As a result, as shown in FIG. Since the resin molding material 121 expands more outward than the case 122, a large stress is applied between the connection portions. On the other hand, when the temperature decreases as shown in FIG. 3B, the insulating case 122 having a small coefficient of thermal expansion has a relatively small shrinkage, but the resin molding material 121 having a large coefficient of thermal expansion has a large shrinkage. A large stress acts between the edge of the insulating case 122 and the resin molding material.

In this case, the lead 123 and the resin molding material 12
Although both have a contact interface, this contact interface has a relatively large area and the volume of the lead 123 is small, so that the problem of stress due to the difference in the coefficient of thermal expansion when raising or lowering the temperature is relatively unlikely to occur. Therefore, in this type of alloy type thermal fuse 120, the opening 122 of the insulating case 122 is formed.
(a) Resin molding material 121 and insulating case 122
Is a problem due to the thermal stress generated between the end of the opening 122a and the interface with which the resin molding material is in contact.

FIG. 13 shows this more specifically. FIG. 13 specifically shows a problem caused by such thermal stress. FIG. 13A shows the interface between the insulating case 132 and the resin molding material near the edge of the opening 132 a of the insulating case 132. This is the case where peeling has occurred. Since a large thermal stress is applied to this portion, peeling is apt to occur, and in the case where peeling occurs, in particular, since the contact surface area between the insulating case 132 of the insulating case 132 and the resin molding material is small or the fixing force at the contact interface is small, such a problem is caused. Phenomenon occurs.

FIG. 1B shows a case where a crack occurs. As described above, a stress concentration portion occurs at the end 132a of the insulating case 132, and the stress concentration portion is a square portion of the insulating case opening 132a. Since stress concentrates on such a square portion, a crack is generated from this portion, and a crack leading to the inside of the resin molding material may be generated from this portion as a base point. This phenomenon is also caused by material damage due to thermal stress, as shown in FIG.

[0014]

According to the present invention, in order to solve the above-mentioned problems, a heat-sensitive fusible body made of a low melting point alloy is housed in a cylindrical insulating case, and the opening of the insulating case is made of a resin molding material. A sealed alloy type thermal fuse, wherein the resin molding material sandwiches an opening edge of the insulating case from an inner surface and an outer surface and is fixed to the opening. .

Further, the present invention provides an alloy type thermal fuse, wherein the resin molding material is an epoxy resin molding material. Also,
The insulating case provides an alloy type thermal fuse made of a ceramic material. Further, the resin molding material provides an alloy-type thermal fuse containing 60% or more and 70% or less by weight of silica powder as a filler. Further, the present invention provides an alloy-type thermal fuse in which a side surface of an opening edge of the insulating case in contact with the resin molding material has a surface roughness of 5 μm or more and 50 μm or less.

Further, the present invention provides an alloy-type thermal fuse in which a cutout is formed on a side surface of an opening edge of the insulating case which is in contact with the resin molding material. Further, the thickness of the resin molding material formed on the outer surface of the insulating case,
When the outer diameter of the insulating case is 1.3 mm or more and 2.6 mm or less, an alloy type thermal fuse of 0.06 mm or more and 0.24 mm or less is provided. The surface area of the resin molding material formed on the outer surface of the insulating case is 0.26 mm square or more and 0.8 mm square or less when the outer diameter of the insulating case is 1.3 mm or more and 2.6 mm or less. An alloy type thermal fuse is provided.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. First, the invention according to claim 1 is an alloy-type thermal fuse in which a heat-sensitive fusible body made of a low melting point alloy is housed in a cylindrical insulating case, and an opening of the insulating case is sealed with a resin molding material. The resin molding material is an alloy-type thermal fuse in which an opening edge of the insulating case is sandwiched between an inner surface and an outer surface and is fixed to the opening. This is shown in FIG. FIG.
The hatched portion shown in FIG. 3A is the resin molding material 11, and the resin molding material 11 sandwiches the opening edge 12a of the insulating case 12 from the inner side surface 12ai and the outer side surface 12ao, as is apparent from FIG. It is fixed to the opening in such a form. A lead 13 for holding a low-melting-point alloy, which is a heat-sensitive fusible member 14, is inserted through the center of the resin molding material 11.

In the case shown in FIG. 1A, the cylindrical insulating case 12 is a cylindrical one having openings at both ends, but is not necessarily limited to this form due to the characteristics of this kind of the invention. The cross section may be not only circular but also rectangular or any other shape. Needless to say, one of the cylinders may have a shape having a bottom without opening. The characteristic part of the present invention is that, if repeated, the opening edge 12a of the insulating case 12 is sandwiched between the inner side surface 12ai and the outer side surface 12ao by the resin molding material 11, and the resin molding material 11 is fixed to the insulating case 12. Figure 1
FIG. 2B shows the main part of FIG. By sandwiching the opening edge 12a of the insulating case 12 from both sides of the inner side surface 12ai and the outer side surface 12ao, the contact area between the insulating case 12 and the resin molding material 11 is almost doubled, and the fixing strength is increased. Since it becomes larger, the mechanical strength is improved with respect to the thermal stress, and the problems such as the occurrence of cracks and peeling as described above can be solved.

Although the present invention claims only the alloy type thermal fuse, the invention is not necessarily limited to this type. The insulating case and the opening edge of the insulating case are sealed with a resin molding material. Needless to say, it can be applied to various electronic components. In particular, in the present application, limited to the alloy type thermal fuse, this kind of electronic component is generally exposed to a thermal cycle, and when exposed to a thermal cycle, thermal stress due to a difference in thermal expansion coefficient is reduced. This is a very problematic electronic component that is most suitable for adopting such a structure.

Next, the second aspect of the present invention will be described. As described above, the invention according to claim 2 is the invention according to claim 1, wherein the resin molding material is an epoxy resin molding material. As described above, a characteristic part of the present invention is that the alloy type thermal fuse has an opening edge of the insulating case which is sandwiched and fixed from the inner surface and the outer surface by a resin molding material. By doing so, the most important part of the alloy type thermal fuse is to protect the heat-sensitive fusible body from the outside air and to prevent this part from being deteriorated by the atmosphere.

Since the heat-sensitive fusible portion is easily deteriorated by an external atmosphere, it is very important to seal this portion. However, it is not only necessary to simply seal the portion, but it is also necessary to consider various gases generated from the sealing material of this portion or gases that pass through the sealed portion. Therefore, the epoxy resin which is the most suitable for such a material and can secure sufficient mechanical strength against thermal stress, which is an important subject of the present invention, is a feature of the invention according to claim 2. This is the alloy type thermal fuse used.

Here, the manufacturing process of the epoxy resin material will be briefly described. As shown in FIG. 2, raw materials are first prepared, dry-blended, kneaded, quenched, pulverized,
It is sieved to obtain a molding material. The kneading is carried out by a roll mill or an extruder, and in the steps of pulverization and sieving, a recycle step of re-grinding those coarse by sieving is used. The epoxy resin molding material is a composite obtained by blending a reaction product such as an epoxy resin, a curing agent or a curing accelerator, a silane coupling agent, and a non-reactive component such as an inorganic filler, a reinforcing material, an internal mold release agent, and a pigment. Material.

Various epoxy compounds can be used as the epoxy resin, but recently, ortho-cresol novolak epoxy resin is widely used to improve the moisture resistance, heat resistance, moldability, etc. of the cured resin. For the curing agent,
Phenol novolak or cresol novolak has been used. Tertiary amines or imidazoles are often used as curing accelerators, and when a catalyst that promotes the reaction between phenolic hydroxyl groups and epoxy groups and suppresses the reaction between secondary alcohols and epoxy groups is used, the physical properties of the cured resin will increase. Is improved.

When the sealing is performed using the epoxy resin molding material as described above, it is possible to sufficiently assure the moisture resistance of the heat-sensitive fusible material, which is a particularly important component, as described above, and to obtain the ionic impurities contained in the epoxy resin. Is small and the adhesive strength between the epoxy resin material and the ceramic is high, so it can be said that the material is extremely suitable as a sealing material for the alloy type thermal fuse. Further, by selecting a filler optimized for the alloy-type thermal fuse as will be claimed later, a higher-performance alloy-type thermal fuse can be realized.

Next, the third aspect of the present invention will be described. The invention according to claim 3 is the alloy type thermal fuse according to any one of claims 1 and 2, wherein the insulating case is made of a ceramic material. As described above, the thermal fuse is a functional element whose purpose is to cut off the current when certain conditions are satisfied and to ensure the safety of the equipment, so that it is important to ensure insulation. From this point of view, an insulating case should be adopted, and glass and ceramic materials can be used as the material, but if it is made of ceramic material, ensure sufficient mechanical strength against problems such as thermal stress. It is an excellent material in that physical properties required for alloy type thermal fuses such as adjustment of thermal conductivity and adjustment of surface roughness can be easily controlled.

FIG. 3 briefly summarizes alumina-based ceramic materials which are considered particularly suitable for the present invention. The dielectric constant, the bending strength, the thermal conductivity, the surface roughness, and the like are summarized for those having an alumina content of about 96% to 99.7%. The flexural strength is about 3000 to 6500 kg / cm 2, and if the mechanical strength is at this level, there is no need to worry about damage due to thermal stress. In addition, if the thermal conductivity is relatively high and has this level of thermal conductivity, the solder heat when mounting the alloy type thermal fuse on a printed circuit board etc. should be effectively released to the outside, causing thermal damage to the heat-sensitive fusible material. Can be prevented. Further, the surface roughness can be adjusted in various ways, and the surface roughness can be extremely increased as described in the following claims. Further, the coefficient of thermal expansion can be made relatively large. From such a viewpoint, by controlling the coefficient of thermal expansion of the ceramic material, the difference in thermal expansion from the resin molding material can be reduced.

Next, the invention according to claim 4 will be described. The invention according to claim 4 is the alloy-type thermal fuse according to any one of claims 1 to 3, wherein the resin molding material contains 60% or more and 70% or less by weight of silica powder as a filler. As described above, the problem in the present invention is that a part of the structure is damaged by thermal stress generated between the resin molding material and the insulating case of the alloy type thermal fuse. This can be solved by means of reducing the difference in the coefficient of thermal expansion between the case and the case. One method for that purpose is to include a filler in the resin molding material.

As the filler, crystalline silica fused silica synthetic silica or the like is preferably used. FIG. 4 shows these characteristics.
It is. Fused silica has a very low coefficient of thermal expansion, so that the thermal expansion coefficient of the resin molding material as a whole can be reduced, and the thermal expansion difference between the resin and the insulating case can be reduced to reduce the thermal stress generated. In addition, since crystalline silica has excellent thermal conductivity, the rise in temperature of the resin molded portion can be suppressed relatively low as a whole, and as a result, generation of thermal stress can be reduced. Although not particularly important in the present invention, synthetic silica is excellent in that the generation of α-particles is small and the malfunction can be reduced if the insulating case contains a semiconductor element or the like. Filler.

Generally, in order to reduce the thermal expansion coefficient of the resin molding material, it is preferable to add a large amount of this kind of inorganic filler, but if it is less than 60%, the thermal expansion coefficient can be reduced sufficiently and effectively. On the other hand, if it is more than 70%, there is a problem that the content of the epoxy resin becomes small and the mechanical strength is reduced as a whole. Therefore, it is preferable that the silica powder be contained in an amount of about 60% to 70% by weight. That is, the present invention is an alloy type thermal fuse characterized in that the resin molding material contains 60% or more and 70% or less by weight of silica powder as a filler.

Next, the invention according to claim 5 will be described. The invention according to claim 5 is as described in any one of claims 1 to 4, wherein the side surface of the opening edge of the insulating case that is in contact with the resin molding material has a surface roughness of 5 μm or more and 50 μm or less. It is an alloy type thermal fuse of the above description. The present invention is proposed to further increase the fixing strength between the opening edge of the insulating case and the resin molding material, and the means is as shown in FIG.
Is made rough so that the resin molding material 51 is firmly fixed to the portion so that peeling and cracking do not occur even when thermal stress increases.

Specifically, the surface roughness is 5 μm or more and 50 μm or more.
It is desirable that it is not more than μm. If the thickness is 5 μm or less, sufficient fixation strength cannot be expected, while if it is 50 μm or more, stress concentration or the like is generated from that portion as a starting point, which rather induces structural destruction. Further, when the present invention is applied to a ceramic material according to the third aspect of the present invention and is applied to a material containing alumina as a main component, it is relatively easy to control the surface roughness. Therefore, the present invention can be easily realized.

Next, the invention according to claim 6, which is based on the same idea, will be described. The invention according to claim 6 is, as described above, according to any one of claims 1 to 4, wherein a notch is formed on a surface of a contact side surface of the opening edge of the insulating case with the resin molding material. This is an alloy type thermal fuse. If the surface roughness is increased as described above, the bonding strength between the insulating case and the resin molding material is increased at that portion. The described method can increase the fixing strength.

FIGS. 6A and 6B show this.
FIG. 6A shows an opening edge 62 of the insulating case 62.
cutouts 62 in the inner side surface 62ai and the outer side surface 62ai
b, and the resin molding material 61 is also disposed at the point, and the resin molding material 61 is consequently wedge-shaped.
The fixing strength is increased by being fixed to the second opening edge 62a. The notch 62b need not be provided on both the inner side surface 62ai and the outer side surface 62ao, and may be provided only on the inner side surface 62ai or only on the outer side surface 62ao. Also, the number of cutouts is not necessarily limited to one or two, and it goes without saying that a plurality of cutouts may be provided. However, care must be taken in this case that if the notches are provided too deeply, the mechanical strength of the insulating case at the edge of the opening is reduced.

FIG. 1B has been proposed in view of this point. FIG. 7B shows a substantially similar effect to that shown in FIG. 7A by cutting out a part of the leading end of the opening edge 62 a of the insulating case 62. As a result, the contact area between the opening edge 62a and the resin molding material 61 can be increased, and the fixing strength can be increased. Note that this notch is not necessarily provided only on the outer surface, but only on the inner surface 62ai or the inner surface 62ai.
ai It may be provided on both outer side surfaces 62ao. Further, the means for providing the notches 62b can be realized by a method in which a plurality of insulating cases 62 before the notches are provided are placed in a basket or the like and agitated to reduce the corners by mutual contact. .

Next, the invention according to claim 7 will be described. The thickness of the resin molding material formed on the outer surface of the insulating case is, as described above, when the outer diameter of the insulating case is 1.3 mm or more and 2.6 mm or less. The alloy-type thermal fuse according to any one of claims 1 to 7, which has a thickness of 0.06 mm or more and 0.24 mm or less. The invention according to the present invention specifically shows the result of finding the optimum value of the molding thickness of the resin molding material at the opening edge portion of the insulating case.

In general, even if the coefficient of thermal expansion is constant, the problem due to thermal stress becomes more pronounced as the contact interface between two materials having different thermal expansions becomes larger. When the diameter is 1.3 mm or more and 2.6 mm or less, as shown in FIG. 7, the thickness of the resin molding material 71 formed on the outer surface 72ao of the insulating case 72 is 0.06 m.
m or more and 0.24 mm or less is appropriate. Within this range, the resin molding material 71 and the opening edge 72a of the insulating case 72
Therefore, it is possible to sufficiently secure the bonding strength with the above.
Of course, it can be ensured sufficiently that the temperature cycle ranges from room temperature to the operating temperature of the alloy type thermal fuse.

Here, the insulating case 72 of the resin molding material 71
When the thickness formed on the outer side surface 72ao is smaller than 0.06 mm, the mechanical strength of the resin forming material 71 formed on the outer side surface 72ao becomes weak. unacceptable. On the other hand, this thickness is 0.24m
When it is larger than m, the mechanical strength is sufficient, but there is a problem in that it is not possible to reduce the size of electronic components, which are becoming lighter and thinner.

Next, the invention according to claim 8 will be described. As described above, the surface area of the resin molding material formed on the outer surface of the insulating case is such that the outer diameter of the insulating case is 1.3 mm or more and 2.6 mm.
The alloy-type thermal fuse according to any one of claims 1 to 7, which has a square of not less than 0.26 mm and not more than 0.8 mm in the following cases. As described above, the fixing strength between the opening edge portion of the insulating case and the resin molding material depends on the thickness of the resin molding material formed on the outer surface of the insulating case. And the contact surface area of the resin-forming material formed on the inner side surface with the outer side surface of the insulating case.

The magnitude of the contact surface area naturally depends on the size of the insulating case and the like. However, when the outer diameter of the insulating case is 1.3 mm or more and 2.6 mm or less, As shown in FIG. 8, the present inventors have found that it is desirable that the area be 0.26 mm square or more and 0.8 mm square or less. If it is less than 0.26 mm square, sufficient fixing strength cannot be realized,
On the other hand, if it is 0.8 mm square or more, the resin molding material 8
This causes a problem that the surface area of the component 1 distributed on the outer surface 82ao of the insulating case 82 becomes too large and the outer diameter of the electronic component cannot be reduced.

[0040]

As described above, in the present invention, in the alloy type thermal fuse in which the heat-sensitive fusible body made of the low melting point alloy is housed in the cylindrical insulating case and sealed with the resin molding material, the resin molding material is The opening edge of the insulating case is sandwiched between the inner surface and the outer surface and fixed to the opening, and the material of the insulating case is optimized, the resin molding material is optimized, or the forming range of the resin molding material is optimized. To provide a reliable alloy type thermal fuse that can prevent mechanical damage due to thermal stress even if it is an alloy type thermal fuse exposed to severe temperature cycling You can do it.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an alloy type thermal fuse of the present invention.

[Figure 2] Epoxy material manufacturing process diagram

FIG. 3 is a diagram summarizing the physical properties of an alumina-based ceramic material used in the present invention.

FIG. 4 is a diagram showing characteristics of silica used in the present invention.

FIG. 5 is a diagram in which the surface roughness of the opening edge of the insulating case of the present invention is roughened.

FIG. 6 is a diagram in which cutouts are provided on the inner side surface and the outer side surface of the opening edge of the insulating case of the present invention.

FIG. 7: The outer diameter of the insulating case is 1.3 mm or more and 2.6 m.
Figure showing the thickness of the resin molding material when it is less than m

FIG. 8: The outer diameter of the insulating case is 1.3 mm or more and 2.6 m.
The figure which shows the desirable contact surface area of the resin forming material with the outer surface of the opening edge of the insulating case when it is less than m.

FIG. 9 is a diagram showing the operation of a conventional thermosensitive pellet type thermal fuse.

FIG. 10 is a diagram showing the operation of a conventional low melting point alloy type thermal fuse.

FIG. 11 is an enlarged view of a resin molding material of a conventional alloy-type thermal fuse.

12 is a diagram showing the stress of the resin molding material shown in FIG. 11 by arrows.

FIG. 13 is a diagram specifically showing a defect of the thermal fuse caused by thermal stress.

[Explanation of symbols]

10, 50, 60, 70 Alloy type thermal fuse 11, 51, 61, 71 Resin molding material 12, 52, 62, 72 Insulating case 12a, 52a, 62a, 72a Opening edge 12ai Inner side surface 12ao, 52ao, 62ao, 72ao , 82ao
Outer surface 14, 54, 64, 74 Thermosensitive fusible material

Claims (8)

[Claims] 1. An alloy type thermal fuse in which a heat-sensitive fusible body made of a low melting point alloy is housed in a cylindrical insulating case, and an opening of the insulating case is sealed with a resin molding material. An alloy-type thermal fuse in which an opening edge of the insulating case is sandwiched between an inner surface and an outer surface and fixed to the opening. 2. The alloy type thermal fuse according to claim 1, wherein said resin molding material is an epoxy resin molding material. 3. The alloy type thermal fuse according to claim 1, wherein said insulating case is made of a ceramic material. 4. The alloy type thermal fuse according to claim 1, wherein said resin molding material contains silica powder as a filler in an amount of 60% or more and 70% or less by weight. 5. A side surface of an opening edge of the insulating case which is in contact with the resin molding material has a surface roughness of 5 μm or more and 50 μm or more.
The alloy type thermal fuse according to any one of claims 1 to 4, wherein: 6. The alloy type thermal fuse according to claim 1, wherein a notch is formed on a surface of a side surface of said insulating case that contacts an opening edge of said insulating case with said resin molding material. 7. The thickness of the resin molding material formed on the outer surface of the insulating case is such that the outer diameter of the insulating case is 1.
The alloy type thermal fuse according to any one of claims 1 to 7, wherein the thickness is 0.06 mm or more and 0.24 mm or less when 3 mm or more and 2.6 mm or less. 8. The surface area of the resin molding material formed on the outer surface of the insulating case is 0.26 mm when the outer diameter of the insulating case is 1.3 mm or more and 2.6 mm or less.
The alloy-type thermal fuse according to any one of claims 1 to 7, which is not less than square and not more than 0.8 mm square.