JPS6059692B2 - temperature fuse resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in thermal fuse resistors.

A thermal fuse resistor is an assembly of a wire-wound resistor and a thermal fuse. When the wire-wound resistor generates heat due to abnormal overcurrent or long-term energization, the thermal fuse is activated by the heat generated. , which protects the circuit from abnormal conditions.

Figure 3A shows a known thermal fuse resistor (Special Publication No. 57-
46197), in which a pellet type thermal fuse 2' is housed in a wire-wound resistor 1' in which a resistance wire 12' is wound around a ceramic bobbin 11'.

FIG. 3B shows this pellet type thermal fuse, in which the lead wire 21' is encapsulated in a sealing compound 23' fixed to one end of the conductive case 22', and the lead wire 24' is disposed at the opposite end. A pellet 25' of a non-conductive material, which is electrically conductively fixed to the case 22' and changes from a solid state to a liquid state at a predetermined temperature, is attached to the disc member 26.
The metal star-shaped contact member 28' is arranged in contact with the disk member 29' and the inner wall of the conductive case 22', and the lead wire 21'. The trip spring 27 is in contact with the inner end.
'' forces the contact member 28' in the opposite direction, causing the lead wire 2
1' is maintained in position by a magnetic bushing 231' extending therethrough. In the thermal fuse resistor shown in FIG. 3A, the wire-wound resistor 1' and the thermal fuse 2' each have a specific thermal resistance and heat capacity, and the wire-wound resistor 1' and the thermal fuse 2' are connected to each other. has a gap resistance and a heat capacity.

The thermal resistance and thermal capacity of the wire-wound resistor 1' are R and C, respectively, and the thermal resistance and thermal capacity of the thermal fuse 2' are R, respectively. , Co, and the gap thermal resistance and heat capacity between the wire-wound resistor 1' and the thermal fuse 2' are R, respectively. , C6, the heat transfer circuit from the wire-wound resistor of the resistor to the temperature-sensitive pellet of the thermal fuse is shown in FIG. 3C. In this heat transfer circuit, the thermal time constant T indicating the degree of delay in heat transfer is T=C, R, +C.

R. +C. R, 1, and the heat transfer delay based on the resistor and the gap (the gap between the resistor and the thermal fuse) is added to the normal activation delay of the thermal fuse (C3Ra), so the activation delay is significant and does not work properly. Circuit protection becomes difficult.

In view of the above, it is an object of the present invention to provide a thermal fuse resistor that can guarantee operating characteristics almost equivalent to that of a thermal fuse.

That is, in the thermal fuse resistor according to the present invention, a low melting point alloy is provided between both lead conductors, the low melting point alloy is covered with an insulating tube, an insulating coating is provided on one lead conductor, and the above-mentioned insulation This structure is characterized in that a resistance wire is wound over the tube and the insulation-covered sorting conductor, and the tip of the resistance wire is connected to the insulation-covered lead conductor.

The present invention will be explained below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an insulating tube having good heat resistance and good thermal conductivity, such as a glass tube, in which a low melting point alloy 2 is sealed.

31 and 32 are lead conductors (copper wires) inserted into both ends of the insulated tube 1, and the space between each of these lead conductors and the end of the insulated tube is sealed with a sealant 4 such as epoxy resin or glass. .

Reference numeral 5 denotes a resistance wire, such as a resistance wire such as Fe-Ni or Fe-Cr, which is wound around the insulating tube 1, and one end 51 of which is soldered (indicated by 6) to one end 31 of the lead conductor. ing. 310 is an insulator such as a varnish film coated on the lead conductor 31.

In the above, the other end 52 of the resistance wire 5 and the other sorting conductor 3 are used as both terminals of the resistor.

The thermal fuse according to the present invention is used by being housed in a protective container. In this case, as shown in FIG. 2, it is also possible to house an auxiliary wire-wound resistor 8 in the protective container 7 made of ceramic or the like. be.

In FIG. 2, A is a thermal fuse resistor according to the present invention, and 9 is a filler such as glass or epoxy resin. In the above, the heat-resistant and good thermal conductivity insulating tube 1, the low melting point alloy 2, the lead conductors 31, 32, and the sealants 4, 4 are equivalent in thermal characteristics to a general-purpose alloy type thermal fuse. Then,
Temperature view of insulation tube. Therefore, if the thermal fuse resistor according to the present invention is compared with the thermal fuse resistor shown in FIG. 3A, the thermal fuse resistor according to the present invention has the resistor shown in FIG. 3A. 1" ceramic bobbin 1" does not exist, therefore, the thermal resistance and heat capacity of the resistor are very small, and RlC3 in the first equation can be ignored.Furthermore, the resistor 1" in FIG. The gap thermal characteristic C2R2 between the thermal fuses 2'' is also very small due to the direct contact between the resistance wire and the thermal fuse, and C2R2 in the first equation can also be ignored. An insulating coating 310 is provided, and a part of the resistance wire 5 is wound on this coating 310, and the thickness of this coating 310 can be made significantly thinner than the thickness of the insulating tube 1 (in the insulating tube 1, the alloy 2 is melted). However, in the coating 310, the wound resistance wire 5 and the lead conductor 31 are at the same potential. , the insulation thickness of the coating 310 can be made extremely thin), so that the heat generated in the resistance wire portion wound around the lead conductor 31 is transmitted to the low melting point alloy 2 via the thin insulation layer 310 and the lead conductor 310 with good conductivity. It can be transmitted through thermal resistance.

Further, since the resistance wire 5 and the lead conductor 31 are connected, the heat generated by the resistance wire can be transmitted to the low melting point alloy 2 with low thermal resistance through this connection point and the lead conductor. As described above, in the thermal fuse resistor according to the present invention, the heat generated by the resistance wire is transferred to the low melting point alloy through the heat transfer path passing through the insulating tube 1, the heat transfer path passing through the insulation coating 310 and the lead conductor 31,
Further, since heat can be transferred with low thermal resistance via the heat transfer path passing through the connection point 6 between the resistance wire and the lead conductor and the lead conductor 31, a thermal fuse resistor with excellent heat transfer characteristics can be provided.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing embodiments of the present invention, FIG. 3A is an explanatory diagram showing a conventional thermal fuse resistor, and FIG. 3B shows details of the thermal fuse in FIG. 3A. FIG. 3C is an explanatory diagram showing a thermal equivalent circuit of the thermal fuse resistor shown in FIG. 3A. In the figure, 1 is an insulating tube, 2 is a low melting point alloy, 31, 32
is a lead conductor, and 5 is a resistance wire.

Claims (1)

[Claims] 1 A low melting point alloy is provided between both lead conductors, the low melting point alloy is covered with an insulated tube, one lead conductor is provided with an insulating coating, and a resistance is applied over the above insulated tube and the insulated lead conductor. A thermal fuse resistor characterized in that a wire is wound around the resistor wire, and the tip of the resistance wire is connected to the insulated lead conductor.