JP2000331582A - Thermal fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal fuse low in internal resistance and reliable in function. SOLUTION: A press spring 6, a temperature-sensitive fusible element 4, a movable contact 3, an elastic contact 2, an opening spring 5, a sealing body 7 with lead wires 8, 9, are in order inserted into a metallic sleeve 1. The temperature-sensitive fuse element 4 abuts on the movable contact 3. The elastic contact 2 and the movable contact 3 are each provided with a through hole in their middle for inserting therein an end of the lead wire 8. This construction allows a press spring 6 stronger than before to be used, and therefore contact resistance is lowered between the temperature-sensitive fuse element and the movable contact, abutting on each other, and thus internal temperature rise can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fuse that cuts off a circuit when a predetermined temperature is reached.

[0002]

2. Description of the Related Art An expensive silver plate is used for a movable contact (movable contact) to reduce contact resistance. The deformed spring that presses the movable contact against the lead contact adopts a Tyco type with a bulged central part so that it can roll quickly when the temperature-sensitive fusible material melts. Automatic insertion of a deformed spring into a small diameter metal case is surprisingly difficult. This is to rotate in the case. The present inventor has developed Japanese Patent Application No. 9-169559 which employs a Suehiro spring in place of a deformed spring.

[0003]

The spring force between the movable contact and the temperature-sensitive fusible element cannot be increased so much as to ensure the operation at the time of fusing. The contact resistance cannot be reduced below 1 mΩ. Further, in a mass production system in which the sealing body is sealed with a metal sleeve opening portion caulking, the spring force cannot be increased more than necessary in order to improve the yield.

[0004]

A pressing spring, a temperature-sensitive fusible material, a movable contact having a through hole, and an elastic contact having a bent outer peripheral portion and a through hole are provided in a metal sleeve having a lead wire attached to a bottom portion. , An opening spring, and a sealing body having a lead wire at the center are sequentially arranged.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a metal sleeve 1 integral with a lead wire 9, a pressing spring 6 of 3 to 4 turns, a metal plate, a temperature-sensitive fusible material 4 which melts at a predetermined temperature, and a through hole are provided. As shown in FIG. 2, a movable contact 3, a resilient contact 2 formed by punching and molding 0.1 mm thick pure copper, an opening spring 5, and a sealing body 7 having a lead wire 9 at the center are sequentially inserted. The part is fixed by caulking and sealed with epoxy resin or the like. The elastic contact 2 has a bent outer peripheral portion and a through hole, and is plated with silver. The conventional elastic contact 2 is an expensive silver plate. Conventional pressing spring 6
Is disposed between the movable contact 3 and the elastic contact 2, and moves together with the movable contact 3 when the temperature-sensitive fusible substance 4 is melted. The spring force (pressing force at the time of setting) of the pressing spring 6 could not be increased so much.
However, the pressing spring 6 of the present invention has the
, The spring force can be increased, and the contact resistance between the lead wire 9 and the elastic contact 2 can be reduced. When using a 1.5 mm diameter lead wire, the resistance is
Fits in 0.5 mΩ. An internal heat generating portion when the thermal fuse is energized is a contact surface between the end of the lead wire 8 and the elastic contact 2. The temperature rise due to this internal heat generation was 7 ° C. for the conventional product (internal resistance 1 mΩ, 10 amps), but was 4 ° C. for the present invention (internal resistance 1 mΩ, 10 amps).
The temperature-sensitive fusible body 4 in contact with the movable contact 3 diffuses internal heat generation and prevents a local temperature rise. The through hole of the movable contact 3 allows surface contact with the tip of the lead wire 8 and also functions as positioning of the lead wire 8 during automatic insertion.

Next, the operation will be described. When the temperature fuse reaches a predetermined temperature, the temperature-sensitive fusible substance 4 melts (gasifies). The generated liquid or gas enters the opening spring 5 side through the through holes of the movable contact 3 and the elastic contact 2, and the elastic contact 2
And the lead wire 8 are promoted. The movable contact 3 separated from the lead wire 8 moves in a free state. The pressing spring 6, which is opened at the same time, does not affect the movement of the movable contact 3 at all.

[0007]

According to the present invention, a pressing spring 6, a temperature-sensitive fusible member 4, a movable contact 3 having a through hole, a bent outer peripheral portion, and a pressing member 6 are provided in a metal sleeve 1 having a lead wire 9 attached to a bottom portion. Elastic contact 2 having a hole, and opening spring 5
And the sealing body 7 having the lead wire 8 at the center are sequentially arranged, so that the pressing spring 6 can be made stronger than before, and the contact resistance between the lead wire 8 and the elastic contact 2 can be reduced.
Further, since the temperature-sensitive fusible member 8 comes into contact with the movable contact 3, internal heat generation can be diffused, and a local temperature rise can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view.

FIG. 2 is a perspective view of main components.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal sleeve 2 Elastic contact 3 Movable contact 4 Temperature sensitive fusible material 5 Opening spring 6 Pressing spring 7 Sealing body 8 Lead wire 9 Lead wire

Claims (2)

[Claims] 1. In a metal sleeve 1 having a lead wire 9 attached to a bottom portion, a pressing spring 6, a temperature-sensitive fusible member 4, a movable contact 3 having a through hole, an elastic member having a bent outer peripheral portion and a through hole. A thermal fuse in which a contact 2, an opening spring 5, and a sealing body 7 having a lead wire 8 at the center are sequentially arranged. 2. The thermal fuse according to claim 1, wherein the temperature-sensitive fusible member is always in contact with the movable contact by the pressing spring.