JPH073554Y2 - Pellet type thermal fuse - Google Patents

Description

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

<Prior Art> The basic structure of a pellet type thermal fuse is as shown in FIG. 3. One end of a cylindrical metal case 1'is provided with a first lead conductor 21 ', and the cylindrical metal case 1'can be sequentially inserted from one end. The molten insulating pellet 3 '(cold compression molded powder), the first spring 51', the pressing plate 6 ', the movable electrode 7'for sliding contact with the inner surface of the case, and the second lead conductor 22' penetrating therethrough. A bushing 8'for attaching the bushing 8'is attached to the other end of the case, and a second spring 52 'is provided between the movable electrode 7'and the bushing 8'.
Thus, in normal times, when the current flows through the route of the first lead conductor 21 '→ the metal case 1' → the movable electrode 7 '→ the second lead conductor 22', and the ambient temperature rises, the fusible insulator 3 ′
Is melted, the first spring 51 'is released from the compressed state, the compressive stress is reduced, and as shown in FIG.
The spring 52 'expands, the movable electrode 7'is separated from the second lead conductor 22', and the energization is cut off. In this case, if the frictional force between the movable electrode 7'and the case 1'is f ₀ ,
Due to the compressive stress f ₂ of the second spring 52 ′, the movable electrode 7 ′
In order to disengage from the second lead conductor 22 ', it is necessary to make the compressive stress f ₂ larger than the frictional force f ₀ by a predetermined value (a constant value k for obtaining a predetermined disengagement speed), and f ₂ = It can be expressed by f ₀ + k, and k can be regarded as an acceleration force at the moment of separation of the movable electrode. Further, in the normal state shown in FIG. 3, in order to sufficiently reduce the contact resistance between the movable electrode 7'and the second lead conductor 22 ', it is necessary to apply a predetermined pressure K between them. In FIG.
The compressive stress of the first spring 51 'is f ₁ , and the second spring 5'
If f ₂ as described above compressive stress of 2 ', f ₁ = f ₂ + K can be represented by ... and more this second equation with the first _{formula, f 1 = f 0 + k} + K ...... Becomes

<Problems to be Solved> By the way, conventionally, the movable electrode is formed by bending the outer peripheral portion of an elastic metal plate on a skirt having a notch, but it is considerably thick to reduce resistance. Because of this thick wall, the bending reaction force of the skirt caused by pressure contact with the inner surface of the case is large, and the pressure contact force is correspondingly large, so between the movable electrode and the case. Has a large frictional force f _{0 and} it is necessary to set the compressive stress f ₁ of the first spring to be large, as is apparent from the third equation. Therefore, a large pressure is applied to the fusible insulator. Normally, the fusible insulator uses a multi-gap body capable of cold compression forming organic powder. There is a possibility that the movable electrode may be degenerated by a large pressure, and the movable electrode may be separated from the second lead conductor in a normal state to cause a malfunction.

An object of the present invention is to provide a pellet type thermal fuse that can prevent such malfunctions well.

<Means for Solving the Problems> In a pellet type thermal fuse according to the present invention, a first lead conductor is provided at one end of a cylindrical metal case, and a fusible insulator, a first spring, A thermal fuse is provided in which a movable electrode that makes sliding contact with the inner surface of the case is provided, a bushing that penetrates the second lead conductor is attached to the other end of the case, and a second spring is provided between the movable electrode and the bushing. A disk for bending the outer peripheral portion of the elastic metal disk into a skirt having a notch and thinning the bent portion is used with the skirt facing the other end side of the case. .

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

FIG. 1 is a vertical sectional view showing an embodiment of the present invention. In FIG. 1, reference numeral 1 is a metal case having a first lead conductor 21 bonded to one end thereof. 3 is a soluble insulating pellet housed in the case, 4 is a pressure equalizing plate, 51 is a first spring, and 6 is a pressing plate. Numeral 7 is a movable electrode, and as shown in FIG. 2, a large number of flower pieces 71,
...... is formed, the root of each flower piece is thinned, each flower piece is bent into a skirt, and as shown in FIG. 1, the skirt 71 ,. Inside,
The skirt tip is in contact with the inner surface of the case. 8 is a bushing, 22 is a second lead conductor provided through the bushing, 52
Is a second spring provided between the bushing and the movable electrode. The bushing 8 is attached to the case 1 by crimping the other end of the case. 9 is a sealing resin (for example, epoxy resin).

In the above pellet type thermal fuse, the contact pressure of the movable electrode 7 to the second lead conductor 22 during normal times is K,
If the acceleration force at the moment when the movable electrode 7 is disengaged is k, and the frictional force between the movable electrode and the inner surface of the case is f ₀ , the compressive stress f ₁ of the first spring 51 in the normal state is expressed by the third formula. You can

Therefore, in the pellet type thermal fuse according to the present invention, the base 70 of the skirt portion 71 of the movable electrode 7 is thinned, and even if the electrode 7 is thickened, the contact pressure of the skirt portion 71 on the inner surface of the case is reduced. Since it can be made sufficiently small, the frictional force f ₀ of the movable electrode 7 can be made small and the compressive stress f ₁ of the first spring 51 can be made small. Therefore, it is possible to prevent the fusible insulating pellet 3 from shrinking, and to eliminate the separation of the movable electrode 7 from the second lead conductor 22 in normal times. Of course, since the thickness of the movable electrode can be increased, the resistance of the electrode can be made sufficiently low. Moreover, since the mechanical strength of the movable electrode can be improved by increasing the thickness,
The push plate 6 can be omitted.

In the above, if a soluble insulating material having a high compression deformation resistance is used and the compressive stress f ₁ of the first spring is increased,
As is clear from the above third formula, the acceleration force k at the moment when the movable electrode is disengaged can be increased (compressive stress f _{2 of} the second spring f ₂
Since the detachment speed of the movable electrode can be increased, re-ignition can be well prevented even when used for high voltage.

<Advantages of the Invention> The pellet-type thermal fuse according to the present invention has the above-described configuration, can well prevent the degeneration of pellets, and can eliminate malfunctions caused by this. Alternatively, it is possible to provide a pellet type thermal fuse advantageous for high voltage because the movable electrode can be released at a high speed at the time of operating the fuse.

[Brief description of drawings]

1 is an explanatory view showing an embodiment of the present invention, FIG. 2 is an explanatory view showing a movable electrode used in the present invention, FIG. 3, FIG.
The drawings are explanatory views showing a normal state and an operating state of a conventional example, respectively. 1 ... Case, 21 ... First lead conductor, 22 ... Second lead conductor, 3 ... Soluble pellet, 51 ... First spring,
52: second spring, 7: movable electrode, 71: skirt, 70: thin portion, 8: bushing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiro Kawanishi 1-1-11 Shimanouchi, Chuo-ku, Osaka-shi, Osaka Uchihashi STEC Co., Ltd. (72) Inventor Kazumi Toyoda 1-11, Shimanouchi, Chuo-ku, Osaka-shi, Osaka No. 28 Uchihashi STEC Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A first lead conductor is provided at one end of a cylindrical metal case, and a fusible insulator and a first lead conductor are sequentially provided in the case from one end.
In a thermal fuse, a spring and a movable electrode that slides in contact with the inner surface of the case are provided, a bushing that penetrates the second lead conductor is attached to the other end of the case, and a second spring is provided between the movable electrode and the bushing. Pellet characterized by using, as an electrode, a disk for bending the outer peripheral portion of an elastic metal disk into a skirt shape having a notch and thinning the bent portion with the skirt facing the other end side of the case Mold thermal fuse.