JPH0766729B2 - Thermal fuse - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an alloy type thermal fuse.

<Prior Art> An alloy type thermal fuse has a structure in which a low melting point alloy piece as a fuse element is bridged between lead wires, a flux is applied on the low melting point alloy piece, and an insulating layer is coated on these. Then, when the electrical equipment to be protected generates heat due to overcurrent, the thermal fuse is heated by the generated heat, the fuse element is melted, and the molten metal is leaked to each lead wire due to the leakage property based on the material of the lead wire. It is pulled toward and divided, and at the same time an arc is generated,
Due to the surface tension, the divided molten metal becomes spherical with each lead wire as a core, and the dividing interval increases, so that the arc disappears and the electric power to the electric device is cut off.

Therefore, the interval between the lead wires is closely related to the interval at which the fused fuse element is divided, and it is essential that the interval be a certain interval or longer to extinguish the arc. However, if the interval is made too wide, the size of the thermal fuse increases, which is disadvantageous for downsizing. Therefore, it is necessary to strictly set the interval between the lead wires to a predetermined constant value.

Therefore, FIG. 8A and FIG. 8B (b in FIG. 8A)
As shown in (b) cross-sectional view), a conductor is extended from one end of a flat type insulation covered wire having two parallel conductors 1'and 1 ', and a low melting point is provided between these conductors 10' and 10 '. In the alloy type thermal fuse in which the alloy wire 3'is bridged, the flux 4'is applied on the low melting point alloy wire, and the insulating layer 5'containing the lead conductor wire and the low melting point alloy wire is provided, between the lead conductor wires. The distance is constant and no special jig or the like is required to keep the distance between the lead conductors constant when the low melting alloy wire is bridged (welding), and welding can be performed easily.

In addition to such manufacturing advantages, if the insulating layer 5'can be formed by a dip coating method, the manufacturing method can be significantly simplified.

<Problems to be Solved> However, in the corner portion of the insulating coated body, when the coating film is not cured during the dip coating, the surface tension f ′ significantly reduces the thickness of the coating film. It is hard to avoid becoming a weak point in terms of mechanical strength.
Therefore, in the alloy type thermal fuse shown in FIG. 8A and FIG. 8B, it is difficult to form the insulating layer by the dip coating method.
Achieving a simplified manufacturing method is extremely difficult.

An object of the present invention is to make it possible to use a dip coating method for forming an insulating layer in the alloy type thermal fuse, thereby facilitating the manufacture of the thermal fuse.

<Means for Solving the Problems> In the thermal fuse according to the present invention, the insulating coating layer is cut and removed from one end of the flat type insulating coated wire having two conducting wires to expose the conductor, and the insulating coating layer is cut and removed. Leaves protruding parts on both sides of the cut end of the insulation coating layer, bridges the low melting point soluble metal piece to the lead wire, and insulates between the lead wires, the low melting point soluble metal piece, and the end of the insulation coating layer. This is a structure characterized by being coated.

<Description of Embodiments> Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1A is a partially cutaway top view showing an embodiment of the present invention, and FIG. 1B is a sectional view taken along line bb in FIG. 1A.

In FIG. 1A and FIG. 1B, W is a flat type insulation covered wire, and two parallel conductive wires 1.1 (copper wire,
Aluminum wire), and the insulating coating layer 2 has both side portions 21 and 21,
It is composed of the conductor wire surrounding portions 22 and 22 and the intermediate portion 23.
For this flat type insulation covered wire, two parallel conductive wires sandwiched between plastic films and the films are bonded by heat fusion or an adhesive can be used. Reference numeral 10 denotes a lead wire which is projected by cutting and removing one end of the insulating coating layer. 20 and 20 are protrusions left on both sides of the cut end of the insulating coating layer. 3 is a low melting point fusible metal piece bridged between the lead wires. For example, Sn-Pb based alloy wire can be used, and the low melting point fusible metal piece and the lead wire are joined by welding or the like. There is. 4 is a flux that can be applied on the low melting point soluble metal wire. Reference numeral 5 is an insulating layer coated by a dip coating method.

For this dip coating method, for example, a room temperature curable epoxy resin liquid containing an amine-based curing agent (the content of the curing agent is 10 to 30 parts by weight with respect to 100 parts by weight of epoxy), and the viscosity at 25 ° C is 30000. You can use ~ 70000 CPS.

Fig. 2 shows the film formation state during this dip coating. Since there are protrusions 20 on both sides of the cut end of the insulating coating layer, the joint a between the lead wire and the low melting point fusible metal piece a The corner angle due to the surface tension f / f of the coating film can be made dull compared to the case where there is no protruding portion (shown by the dotted line), and therefore the resultant force of the surface tension f / f can be reduced, and the thickness of the coating film can be reduced accordingly it can.

In the above, it is desirable that the distance b between the low melting point soluble metal piece and the cut end of the insulating coating layer and the distance C between the lead wire and the protrusion be as small as possible. Further, the protrusion length d of the lead wire for the low melting point soluble metal piece and the protrusion length e of the low melting point metal piece for the lead wire are made as small as possible within a range that does not impair the welding strength. Is desirable.

It is desirable that the tip end 24 of the protruding portion of the insulating coating layer be as close as possible to the connection point a between the low melting point fusible metal piece and the lead wire.

The protrusion 20 may be thicker than the insulating coating layer 2 (for example, folded back to be doubled).

FIG. 3 is a partially cutaway upper surface showing another embodiment of the present invention. In this other embodiment, both side projecting portions 20, 20 at the cut end of the insulating coating layer are projected more than the lead wire 10. Thus, since a coating film with a sufficient amount of resin can be formed between these protrusions 10 and 10, the connecting portion a between the lead wire and the low melting point soluble metal piece is covered with a coating film with a sufficient amount of resin. it can. Third
In the figure, h is preferably 1 to 5 times the thickness of the insulating coating. In the above-mentioned other embodiment, as shown in FIG. 4, the protrusions 20 may be curved outward. Further, as shown in FIG. 5, both protrusions 20 may be formed in a hook shape to enhance the fixing strength of the insulating coating resin body. Further, as shown in FIG. 6 or 7, it is also possible to remove the intermediate portion of the insulating coating layer at the other portion of the flat type insulating coating wire W excluding one end portion.

In FIGS. 3 to 7, the same reference numerals as those in FIGS. 1A and 1B indicate the same components as those in FIGS. 1A and 1B.

<Effects of the Invention> As described above, in the alloy type thermal fuse according to the present invention, the flat type insulation coated wire is used as the lead wire,
When the lead wire and the low melting point soluble metal piece bridged between the lead wires are covered with a coating film by the dip coating method, the corner of the coating film on the joint between the lead wire and the low melting point metal piece The protrusions are left on both sides of the cut end of the coating layer of the coated wire so as not to make the corners blunt or to make a corner angle, and it is possible to reduce the thinning of the above-mentioned bonding upper coating film. Therefore,
According to the thermal fuse of the present invention, the insulation treatment can be easily performed by the dip coating method, and the lead wire interval is stable and constant, and the low melting point fusible metal piece can be easily welded, and The spacing between the lead wires can be strictly guaranteed to the insulation distance when the thermal fuse is activated and the specified value that is regulated from the miniaturization of the thermal fuse, so it is easy to manufacture and is a small alloy type with excellent withstand voltage. A thermal fuse can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is an explanatory view showing an embodiment of the present invention, FIG. 1B is a sectional view taken along line bb in FIG. 1A, and FIG. 2 shows a thermal fuse according to the present invention. Explanatory drawing showing the state of dip coating, 3rd
FIG. 4, FIG. 5, FIG. 5, FIG. 6 and FIG. 7 are explanatory views showing another embodiment of the present invention, FIG. 8A is an explanatory view showing a conventional example, and FIG. 8B is FIG. It is bb sectional drawing in A. FIG. W: Flat type insulation layer wire, 1 ... Lead wire, 10
...... Lead wire, 2 ... Insulating coating layer, 20 ... Projection part, 3 ...
… Low melting point soluble metal pieces, 5… Insulating coating.

Claims (2)

[Claims] 1. A flat type insulating coated wire having two conducting wires, the insulating coating layer is cut and removed from one end to expose a conductor, and when the insulating coating layer is cut and removed, the conductor is projected on both sides of the cut end of the insulating coating layer. Part, the low melting point fusible metal piece is bridged between the lead wires, and the insulating coating is applied between the lead wires, the low melting point metal piece, and the end of the insulating coating layer. fuse. 2. The thermal fuse according to claim 1, wherein the protruding portion is made to protrude beyond the tip of the lead conductor.