JPH113642A - Thermal fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal fuse having small internal resistance and reliable operation. SOLUTION: A thermal fuse comprises an elastic contact 1 enclosing a movable contact 2, a temperature sensitive fusible body 8 fusing at a fixed temperature, a widening-toward-the-end shaped coil spring 6 which presses the movable contact 2 against a lead contact 3, and through holes bored in the respective centers of the elastic contact 1 and of the movable contact 2 for leading fusion liquid or generated gas to the side of the lead contact 3. A curvature surface 11 of a through hole end part of the movable contact 2 is caused to fit to a tip end curvature surface of the lead contact 3 so that contact resistance can be reduced. Thus, a thermal fuse is provided having small internal resistance and reliable operation.

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.

[0003]

The automatic insertion of a deformed spring into a small diameter metal case is surprisingly difficult. This is to rotate in the case. Since the movable contact is thin, the resistance value has to be large. The resistance value of the thermal fuse itself is a factor of the internal temperature rise, and causes an upper limit of the allowable current value and unstable operation.

[0004]

Means for Solving the Problems An elastic contact enclosing a movable contact, a temperature-sensitive fusible material that melts when a predetermined temperature is reached, a divergent coil spring that presses the movable contact against a lead contact, A through hole is formed in the elastic contact and the movable contact so as to lead to the lead contact side.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a metal case 9 integral with a lead wire 10, a temperature-sensitive fusible member 8, a ring 7, a divergent coil spring 6, and a through hole are arranged at the center and melted when a predetermined temperature is reached. An elastic contact 1 having a bent portion, a movable contact 2 having a large thickness, an opening spring 4, and an insulating portion 5 integrated with the lead contact 3 are sequentially arranged (first contact).
Figure). The width of the movable contact 2 is much larger than that of the conventional product, and a through-hole curvature surface 11 is provided at the end of the center through-hole. The curvature surface is substantially the same as the curvature surface at the tip of the lead contact 3.
The width reduces the resistance value between the lead contact 3 and the metal case 9 and at the same time increases the heat capacity. Elastic contact 1
Metal case 9 and movable contact 2 into which bent pieces of
Is determined to have a sufficient margin to ensure the operation. In other words, the bent piece rattles in the gap. The present invention employs a system in which the coil spring 6 presses the central bulge of the elastic contact 1 during loading. The expanded bent piece, together with its own elasticity, reduces the contact resistance between the inner wall surface of the metal case and the peripheral surface of the movable contact. By employing the central through hole of the elastic contact 1 and the through hole of the movable contact 2, the gas generated when the temperature-sensitive fusible body 8 is melted can escape to the open spring 4 side, and the movable contact 2 can be easily moved. I do. At the same time, the solution also intervenes between the lead contact 3 and the movable contact 2 through the through hole.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An elastic contact 1 is made of silver plated phosphor bronze.
The movable contact 2 and the ring 7 are formed of copper. Sealing body 5
Is sealed with epoxy resin. Compared with the conventional type in which the movable contact 2 directly contacts the inner wall surface of the metal case 9, the contact resistance of this embodiment is smaller (0.5 to 0.8).
mΩ). The use of the divergent coil spring 6 prevents the coil spring from rotating during loading into the metal case 9. When the temperature-sensitive fusible body 8 is melted, the movable contact 2 moves leftward together with the elastic contact 1 by the elasticity of the release spring 4 (FIG. 3). The bent piece (horizontal part in FIG. 2) of the elastic contact 1 returns to the horizontal state due to the release of the coil spring 6. The movement of the movable contact 2 becomes smoother. Further, the gas generated during melting is vented to the lead contact 3 side through the through hole of the movable contact 2, so that the movement of the movable contact 2 is further smoothed. At the same time, the solution also reaches the lead contact 3 side, intervenes between the lead contact 3 and the movable contact 2 and functions as an insulator. AC50
It does not conduct even at 0V.

[0007]

In short, according to the present invention, the coil spring 6 is compressed between the elastic contact 1 partially enclosing the thick movable contact 2 and the temperature-sensitive fusible material 8 which melts when a predetermined temperature is reached. Since a through hole is formed in the elastic contact 1 and the lead contact 3 is brought into contact with the through-hole curvature surface 11 of the movable contact 2, a thermal fuse with low contact resistance and reliable operation can be provided. Further, since the tip of the coil spring 6 is pressed against the central bulge of the elastic contact 1 to expand the elastic contact 1, contact resistance is reduced and the movable contact 2 can be moved smoothly during operation.

[Brief description of the drawings]

FIG. 1 is a sectional view.

FIG. 2 is an enlarged explanatory view of a main part.

FIG. 3 is a sectional view at the time of operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Elastic contact 2 Movable contact 3 Lead contact 4 Opening spring 5 Sealing body 6 Coil spring 7 Ring 8 Temperature sensitive fusible material 9 Metal case 10 Lead wire

Claims (4)

[Claims] A coil spring (6) is compressed and interposed between an elastic contact (1) partially enclosing a thick movable contact (2) and a temperature-sensitive fusible material (8) that melts when a predetermined temperature is reached. 1 is a thermal fuse in which a through hole is formed in 1 and the lead contact 3 is brought into contact with the through-hole curvature surface 11 of the movable contact 2. 2. A coil spring 6 is compressed and interposed between an elastic contact 1 partially enclosing a movable contact 2 and a temperature-sensitive fusible member 8, and the movable contact 2 is opened by an open spring 4 by this compressive force. The contact of the coil spring 6 is pressed against the central bulge of the elastic contact 1 so that the elastic contact 1
Thermal fuse made by expanding 3. An elastic contact 1 enclosing a movable contact 2, and a temperature-sensitive fusible body 8 that melts when a predetermined temperature is reached.
And a coil spring 6 having a divergent shape for pressing the movable contact 2 against the lead contact 3, and a through hole formed in the elastic contact and the movable contact so as to guide the dissolved liquid or generated gas toward the lead contact 3.
Thermal fuse. 4. A coil spring 6 is compressed and interposed between a ring 7 contacting a temperature-sensitive fusible member 8 and a movable contact 2, and the movable contact 2 is pressed against the opening spring 4 by the compression force. Contact the lead contact 3
A thermal fuse in which a thick movable contact 2 is wrapped by an elastic contact 1, and through holes are formed in both contacts to allow generated gas to escape to the lead contact 3 side.