JP3783272B2 - Manufacturing method of thermal fuse - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a thermal fuse that is attached to an electronic circuit of various electric devices and used as overheat protection.
[0002]
[Prior art]
As this type of conventional thermal fuse, one described in the microfilm of Japanese Utility Model Application No. 1-65151 (Japanese Utility Model Application Publication No. 3-4635) is known.
[0003]
FIG. 6 is a cross-sectional view of a conventional thermal fuse. In the figure, reference numeral 1 denotes a fusible alloy made of a low melting point metal body. Reference numeral 2 denotes a flux applied to the surface of the soluble alloy 1. Reference numeral 3 denotes a lead wire electrically connected to both ends of the fusible alloy 1. Reference numeral 4 denotes a case that houses at least the fusible alloy 1 and has an opening 5 through which the lead wire 3 is drawn. Reference numeral 6 denotes a sealing member made of epoxy that seals the opening 5 of the case 4. Reference numeral 7 denotes an insulating member made of polyethylene vinyl chloride, nylon, or the like provided so as to cover the lead wire 3 in a portion drawn from the case 4 and the sealing member 6.
[0004]
The operation of the conventional thermal fuse configured as described above will be described below.
[0005]
FIG. 7 is a sectional view showing an example of use of a conventional thermal fuse. In the figure, the same components as those in FIG. In the figure, 8 is a transformer for attaching the thermal fuse 9 to the upper surface. Reference numeral 10 denotes a substrate on which the transformer 8 and the thermal fuse 9 are mounted. Reference numeral 11 denotes a hole provided in the substrate 10 for mounting the thermal fuse 9. The thermal fuse 9 is directly attached to the upper surface of the transformer 8 and is mounted on the substrate 10 by fitting the end of the lead wire 3 into the hole 11 provided in the substrate 10. Are used in series. When the transformer 8 becomes abnormal and generates heat, the heat is transferred to the fusible alloy 1 of the thermal fuse 9. When the fusible alloy 1 reaches a high temperature equal to or higher than the melting point, melting starts from the central portion and is attracted spherically to both ends of the lead wire 3 due to surface tension, and the thermal fuse 9 is disconnected to interrupt the electric circuit.
[0006]
[Problems to be solved by the invention]
However, in the above conventional configuration, as shown in FIG. 7, when the thermal fuse 9 is attached to a component such as a transformer 8 by bending the lead wire 3 into a U-shape, it is insulated from the sealing member 6 covering the lead wire 3 corresponding to the bent portion. It had the subject that the clearance gap 11 by bending stress was easy to be made in the boundary with the member 7. FIG.
[0007]
In order to solve the above-described problems, an object of the present invention is to provide a method for manufacturing a thermal fuse in which a gap is hardly generated at the boundary between a sealing member and an insulating member.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention forms a fuse unit by welding the first and second lead wires to a fusible alloy, and then stores at least the fusible alloy of the fuse unit and the first. , A case having an opening for drawing the second lead wire is inserted, a sealing member for sealing the opening of the case is then formed, and then the first and second lead wires drawn from the case The first insulating member is inserted so as to cover the first insulating member and the first insulating member covering the first and second lead wires is brought into contact with the heater plate, and the case containing the soluble alloy is interposed between the heater plates. The first insulating member is heated and shrunk on the heater plate by rotating the thermal fuse while being heated on the heater plate, and the first insulating member is moved to the first and second lead wires. Adhering to , In which finally forming at least the sealing member and the first insulating member and the second insulating member and dried by applying a second insulating member covering the boundary.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
According to the first aspect of the present invention, the first and second lead wires are welded to a fusible alloy to form a fuse unit, and then at least the fusible alloy of the fuse unit is accommodated and the first 1. Insert a case having an opening for pulling out the second lead wire, then form a sealing member for sealing the opening of the case, and then the first and second leads drawn from the case A first insulating member is inserted so as to cover the wire, and the first insulating member covering the first and second lead wires is brought into contact with the heater plate, and the case containing the soluble alloy is heated. The first insulating member is heated and shrunk on the heater plate by rotating the thermal fuse on the heater plate while being positioned between the plates, and the first insulating member is moved to the first and second leads. Adhere to the wire Finally, a second insulating member is formed by applying and drying a second insulating member that covers at least the boundary between the sealing member and the first insulating member. Since the second insulating member is formed by applying and drying a second insulating member that covers the boundary between the sealing member that seals the opening of the case containing the alloy and the first insulating member, bending is performed. It becomes difficult to form a gap at the boundary between the first insulating member and the sealing member covering the first and second lead wires corresponding to the portion, and the second and second lead wires are not exposed. Since it is covered with the insulating member, it has an effect that the insulating property is maintained even when the first and second lead wires are bent.
[0010]
Further, according to this manufacturing method, the first insulating member covering the first and second lead wires is brought into contact with the heater plate, the case containing the fusible alloy is positioned between the heater plates, and the temperature is further increased. By rotating the fuse while heating it on the heater plate, the first insulating member is heated and shrunk on the heater plate so that the first insulating member is attached to the first and second lead wires. Therefore, the shrinkage of the first insulating member becomes uniform, so that the first insulating member can be uniformly applied to the first and second lead wires, Since the accommodated case is located between the heater plates, the fusible alloy is not exposed to high temperature and melts, and only the first insulating member can be heated.
[0011]
Hereinafter, a method for manufacturing a thermal fuse in an embodiment of the present invention will be described with reference to the drawings.
[0012]
FIG. 1 is a cross-sectional view of a thermal fuse in an embodiment of the present invention. In FIG. 1, 13 is a fusible alloy composed of at least one of low melting point metals such as tin, lead, bismuth and indium. Reference numeral 14 denotes a rosin flux applied to the surface of the soluble alloy 13 as necessary. Reference numerals 15 and 16 denote first and second lead wires electrically connected via the fusible alloy 13, and the fuse unit is constituted by the first and second lead wires 15 and 16 and the fusible alloy 13. It is composed. Reference numeral 17 denotes a case made of ceramic or the like that houses at least the fusible alloy 13 and has an opening 18 through which the first and second lead wires 15 and 16 are drawn. Reference numeral 19 denotes a sealing member made of a thermosetting resin such as an epoxy resin or a urethane resin that seals the opening 18 of the case 17, and is provided so as to taper away from the case 17. Reference numeral 20 denotes a first insulating member made of vinyl chloride, polyolefin, polyethylene or the like provided so as to cover the first and second lead wires 15 and 16. Reference numeral 21 denotes a second insulating member made of a thermosetting resin such as an epoxy resin that covers at least the boundary between the sealing member 19 and the first insulating member 20.
[0013]
A method for manufacturing the thermal fuse according to the embodiment of the present invention configured as described above will be described below.
[0014]
FIGS. 2A to 2H are process diagrams showing a method for manufacturing a thermal fuse in one embodiment of the present invention.
[0015]
First, as shown in FIG. 2 (a), first and second lead wires obtained by plating a copper wire on a fusible alloy 22 made of at least one low melting point metal such as tin, lead, bismuth or the like. 23 and 24 are welded at about 300 ° C. to form a fuse unit.
[0016]
Next, as shown in FIG. 2B, a rosin flux 25 is applied to the entire surface of the fusible alloy 22. This flux 25 has the effect of promoting the function of surface tension when the fusible alloy 22 is melted and shortening the disconnection time.
[0017]
Next, as shown in FIG. 2 (c), from an insulating material such as ceramic that houses at least the fusible alloy 22 of the fuse unit and has an opening 27 through which the first and second lead wires 23 and 24 are drawn. A case 26 is inserted.
[0018]
Next, as shown in FIG. 2 (d), a thermosetting resin such as an epoxy resin or a urethane resin is applied with a dispenser 28 so as to seal the opening 27 of the case 26, and then about 1 at about 80 ° C. The sealing member 29 is formed by drying for a period of time. At this time, the sealing member 29 is formed so as to be tapered and conical as the distance from the case 26 increases.
[0019]
Next, as shown in FIG. 2E, a first heat-shrinkable material such as vinyl chloride, polyolefin, polyethylene, or the like is provided so as to cover the first and second lead wires 23, 24 drawn from the case 26. The insulating member 30 is inserted into the first and second lead wires 23 and 24. At this time, in order to securely attach the first insulating member 30 in a later step, the first insulating member 30 is pushed into a position where the conical sealing member 29 can be inserted.
[0020]
Next, as shown in FIG. 2 (f), the first and second lead wires 23, 24 are placed on a heater plate 31 that is installed at substantially the same interval as the combined width of the case 26 and the sealing member 29. The first insulating member 30 inserted in the contact is in contact, the case 26 is located between the heater plates 31, and the first and second lead wires 23 and 24 are arranged in contact with the transport belt 32. The belt 32 is moved to rotate the thermal fuse formed in the previous process so that it is uniformly shrunk while being heated in the direction from A to B at about 130 ° C., as shown in FIG. 30 is uniformly applied to the first and second lead wires 23 and 24. At this time, the surface temperature of the case 26 when the first insulating member 30 is heated by the heater plate 31 is about 60 to 70 ° C., and does not rise to a temperature at which the fusible alloy 22 melts. Only the member 30 can be heated. Further, when the melting point of the fusible alloy 22 is as low as about 70 ° C., for example, the fusible alloy 22 may be cooled to the case 26 using a spot cooler or the like.
[0021]
Finally, as shown in FIG. 2 (h), a thermosetting resin such as an epoxy resin or a urethane resin is applied so as to cover at least the boundary between the sealing member 29 and the first insulating member 30, and about 80 ° C. The second insulating member 33 is formed by drying for about 1 hour, and the thermal fuse of the present invention is manufactured.
[0022]
The operation of the thermal fuse according to the embodiment of the present invention constructed and manufactured as described above will be described below.
[0023]
FIG. 3 is a cross-sectional view showing an example of a method of using the thermal fuse in one embodiment of the present invention. In the figure, the same components as those in FIG. Reference numeral 34 denotes a transformer for attaching the thermal fuse to the upper surface. Reference numeral 35 denotes a substrate on which the transformer 34 and the thermal fuse 36 are mounted. Reference numeral 37 denotes a hole provided in the substrate 35 for mounting the thermal fuse 36. The thermal fuse 36 is mounted directly on the upper surface of the transformer 34 and mounted on the substrate 35 by fitting the end portions of the first and second lead wires 15 and 16 into holes 37 provided in the substrate 35. Used in series with 35 electrical circuits. When the transformer 34 becomes abnormal and generates heat, the heat is transmitted to the fusible alloy 13 of the temperature fuse 36. When the fusible alloy 13 is heated to a temperature higher than the melting point, the melting starts from the central portion, and is attracted spherically to both ends of the first and second lead wires 15 and 16 by the surface tension, and the thermal fuse 36 is disconnected, and the electric circuit Is to shut off. As shown in FIG. 3, when the thermal fuse 36 is attached to the transformer 34 by bending the first and second lead wires 15 and 16 into a U shape, the first and second lead wires 15 and 16 corresponding to the bent portions are attached. Since the boundary between the sealing member 19 that covers the first insulating member 20 and the first insulating member 20 is covered with the second insulating member 21, even if bending stress acts on the boundary, the resin that forms the second insulating member 21 is subjected to the stress. , The gap generated at the boundary is suppressed, and the exposed portion can be prevented from coming into direct contact with the transformer 34 without the first and second lead wires 15 and 16 being exposed.
[0024]
The above-described method for manufacturing a thermal fuse has been described by taking as an example a thermal fuse in which the first and second lead wires 15 and 16 are arranged in a straight line with the fusible alloy 13 being shown in FIG. As described above, even when the first and second lead wires 39 and 40 are drawn in parallel from below through the fusible alloy 38, the boundary between the sealing member 41 and the first insulating member 42 is covered. Even if the second insulating member 43 is provided, the insulation is enhanced and the same effect can be obtained.
[0025]
In addition, when the first insulating member 42 is attached to the thermal fuse in which the first and second lead wires 39 and 40 are formed in parallel, as shown in FIG. Except for the case 45, only the first insulating member 46 is heated using a member provided with a groove 49 for installing the first and second lead wires 47 and 48 into which the first insulating member 46 is inserted. Thus, the same effect can be obtained even if the first insulating member 46 is applied while being heated and contracted. At this time, in order to deposit the first insulating member 46 more uniformly, the heater plate 44 may be moved up and down.
[0026]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent the second insulating member from forming a gap at the boundary between the first insulating member and the sealing member covering the first and second lead wires corresponding to the bent portions . Therefore, since the first and second lead wires are not exposed and are covered with the second insulating member, the insulating property is maintained even when the first and second lead wires are bent. A first insulating member covering the first and second lead wires is brought into contact with the heater plate, a case containing a fusible alloy is positioned between the heater plates, and a thermal fuse is disposed on the heater plate. by rotating with heating, since the so deposited on the first insulating member first insulating member the first by heat shrinking over the heater plate, the second lead, the first The insulation member shrinks evenly Thus, the first insulating member can be uniformly attached to the first and second lead wires, and the case containing the fusible alloy is located between the heater plates. It is possible to provide a method for manufacturing a thermal fuse in which only the first insulating member can be heated without the alloy being exposed to a high temperature and melting .
[Brief description of the drawings]
FIG. 1 is a sectional view of a thermal fuse in an embodiment of the present invention. FIGS. 2A to 2H are process diagrams showing a manufacturing method of the thermal fuse . FIG. 4 is a cross-sectional view of a thermal fuse in another embodiment of the present invention. FIG. 5 is a perspective view showing a part of the manufacturing process of the thermal fuse. FIG. 6 is a cross-sectional view of a conventional thermal fuse. 7] Cross sectional view showing usage example of the same temperature fuse 【Explanation of symbols】
13 fusible alloy 15 first lead wire 16 second lead wire 17 case 18 opening 19 sealing member 20 first insulating member 21 second insulating member

Claims (1)

A fuse unit is formed by welding the first and second lead wires to a fusible alloy, and then an opening for accommodating at least the fusible alloy of the fuse unit and drawing out the first and second lead wires is provided. the case having inserted, then forming a sealing member for sealing the opening portion of the case, the first drawn from the case then, so as to cover the second lead wire insertion first insulating member And the first insulating members covering the first and second lead wires are brought into contact with the heater plate, the case containing the fusible alloy is positioned between the heater plates, and a thermal fuse is disposed on the heater plate. The first insulating member is heated and shrunk on the heater plate by being rotated while being heated in order to adhere the first insulating member to the first and second lead wires, and finally at least the sealing member. When Thermal fuse fabrication method of forming the second insulating member and dried by applying a second insulating member which covers the boundary between the first insulating member.

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