JPH0448528A - Circuit breaking element - Google Patents

Abstract

PURPOSE:To eliminate degradation of mechanical strength due to wire narrowing of a current fuse part by enabling the use of a common low melting point fusible alloy piece of the same diameter for both a temperature fuse part and a current fuse part. CONSTITUTION:An interval I1 between an electrode 21 and an electrode 22 is larger than an interval I2 between the electrode 22 and an electrode 23. A part 31 between the electrode 21 and the electrode 22 forms a current fuse part and a part 32 between the electrode 22 and the electrode 23 forms a temperature fuse part, in a low melting point fusible alloy piece 3 having the same diameter and the same quality, spanning from the electrode 21 to the electrode 23. In this circuit breaking element, when the low melting point fusible alloy piece 3 receives the machine generated heat and heated to its melting point, the low melting point fusible alloy piece is melted to function as a temperature fuse. A relationship as S1/I1<S2/I2 is given, where S1 is the sum of the volume of the electrode 21 and the half volume of the electrode 22, I1 is the length of the low melting point fusible alloy piece between the electrode 21 and the electrode 22, S2 is the sum of the half volume of the electrode 22 and the volume of the electrode 23, and I2 is the length of the low melting point fusible alloy piece between the electrode 22 and the electrode 23.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a current interrupting element having a current fuse function and a temperature fuse function.

(Prior Art) Temperature fuses and current fuses are known as current interrupting elements that protect electrical equipment from overcurrent.

Among these elements, temperature fuses are used by being attached to a predetermined location on a device, and when the device generates heat due to overcurrent, the generated heat heats the temperature fuse, and this heating causes the temperature fuse element (low melting point (molten alloy) melts, cutting off power to the equipment. In this case, the temperature of the temperature fuse increases with a certain time lag in response to the heat generated by the equipment, and when the equipment generates heat quickly, even if the equipment reaches a dangerous temperature due to its heat resistance, the temperature fuse will not rise. The temperature may not be raised, and therefore the temperature fuse may not operate, resulting in one piece of equipment suffering thermal damage.

In order to eliminate such unreasonableness, it is possible to add a current fuse element in series with the temperature fuse, and in the event of a sudden overcurrent, the current fuse element is fused by its Joule heat, cutting off the power to the equipment. It is publicly known.

Such a temperature fuse with a current fuse element includes a temperature fuse part made of a low melting point fusible alloy piece and the same material as the low melting point fusible alloy piece of the temperature fuse part.

In addition, a current fuse part made of a low melting point fusible alloy piece having a diameter smaller than that of the low melting point fusible alloy piece is known.

According to this temperature fuse with a current fuse element, when an overcurrent suddenly flows, the heat generated by one device is received and the temperature of the entire fuse rises, and the current fuse part melts due to Joule heat and is transferred to the device. Not only can the current flow be cut off, but also the structure can be simplified because a common low melting point fusible alloy piece can be used for the temperature fuse section and the current fuse section.

(Problem to be solved) However, alloys such as PB and Sn are used for low melting point fusible alloy pieces, which are mechanically fragile. Therefore, the mechanical strength is weak, and there is a concern that the current fuse portion may be damaged due to impact during fuse transportation.

An object of the present invention is to make it possible to use a common low-melting point fusible alloy piece having the same diameter for the temperature fuse part and the current fuse part in a temperature fuse with a current fuse element, thereby reducing wire thinning in the current fuse part. The objective is to eliminate the decrease in mechanical strength due to

(Means for Solving the Problems) A current interrupting element according to the present invention has a first electrode, a second electrode, and a third electrode arranged on a forest base, and has wires of the same diameter and the same width across these electrodes. A low melting point fusible alloy piece of material is installed as a bridge,
The total volume of half of the first electrode and the second electrode is 81, the length of the low melting point fusible alloy piece between the first electrode and the second electrode is 1,
The total volume of half of the second electrode and the third electrode is 81, and the length of the low melting point fusible alloy piece between the second and third electrodes is S/I<S2 This configuration is characterized by the following relationship: /2.

(Explanation of Examples) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a heat-resistant insulating substrate, for example, a ceramic plate can be used. 21.22 and 23
are a first electrode, a second electrode, and a third electrode made of metal foil fixed on the insulating substrate 1, and the spacing between the first electrode 21 and the second electrode 22 is the second electrode 22 and the third electrode. The distance from the electrode 23 is wider than the distance I2. 3 is the first electrode 21
This is a low melting point fusible alloy piece of the same diameter and the same material, which is bridged over the third electrode 23.

A portion 31 between the first electrode 21 and the second electrode 22 constitutes a current fuse section, and the second W1. A portion 32 between the pole 22 and the third electrode 23 constitutes a temperature fuse. 4 is a flux applied on the temperature fuse portion; 51 is a lead wire connected to the first electrode 21; 52 is a lead wire connected to the third electrode 23; and 6 is an insulating layer coated on the insulating substrate 1.

In the current interrupting element, when the low melting point fusible alloy piece receives heat generated by the equipment and is heated to its melting point, the low melting point fusible alloy piece melts and functions as a temperature fuse.

On the other hand, even if a sudden overcurrent flows through a device and the device is heated to a dangerous temperature, the heat generated by the device may not yet begin to rise due to the delay in heat transfer to the current interrupting element. Considering the state in which the low melting point fusible alloy pieces are heated at each fuse part, the generation of Joule heat is instantaneous, so the Joule heat of the low melting point fusible alloy pieces at each fuse part is Based on the assumption that the time is spent raising the temperature of the melting point fusible alloy piece and the electrodes on both sides, it is possible to grasp the instantaneous temperature rise state of each fuse part.

Compared to the temperature fuse part, the current fuse part has a higher Joule heat generation amount (which is proportional to the length of the low melting point fusible alloy piece, k18 in the current fuse part and kI2 in the temperature fuse part). The ratio of volumes (in the central second electrode 22, half belongs to the temperature fuse side and the other half belongs to the current fuse side, the volume is 1.58, where S is the volume of each electrode) (1.5 at the current fuse part
1.58/kL) is small in the temperature fuse section, so the temperature increase due to Joule heat at the current fuse section occurs more rapidly than the temperature increase due to Joule heat at the temperature fuse section. However, melting due to Joule heat occurs in the current fuse section.

FIG. 2 shows another embodiment of the present invention, in which the first electrode 21° and the second
The spacing between the electrodes 22 and the third electrode 23 is made equal, and the plane area of each electrode 21, 22, 23 is made equal, and the same wire diameter and the same material are used for the low melting point fusible alloy pieces 3. However, by making the thickness of the first electrode 21 thicker than the thickness of the third electrode 23, the volume ratio of both electrodes to the low melting point fusible alloy piece 3 in the current fuse part is made lower than that in the temperature fuse part. This is smaller than the volume ratio of both side electrodes to the melting point fusible alloy piece 3.

FIG. 3 shows another embodiment of the present invention, in which the first electrode 21,
The spacing between the second electrode 22 and the third electrode 23, and the thickness of each electrode are made equal, and the low melting point fusible alloy piece 3 is made of the same wire diameter and material. The planar area of the first electrode 21 is made larger than the planar area of the third electrode 23, and the volume ratio of the electrodes on both sides to the low melting point fusible alloy piece 3 in the current fuse part is made to be the same as that of the low melting point fusible alloy in the temperature fuse part. This is smaller than the volume ratio of the electrodes on both sides to the piece 3.

In FIGS. 2 and 3 above, 1 indicates an insulating substrate, 4
51 and 52 indicate the flux, 51 and 52 the lead wires, and 6 the insulating layer, respectively.

Although each of the above embodiments of the present invention belongs to the substrate type, the implementation of the present invention is not limited to this type.6For example, the first electrode, the second ffi electrode, and the third electrode are fixed on an insulating bar. However, the present invention can also be applied to a type in which a low melting point fusible alloy wire of the same wire diameter and the same material is wound across these electrodes, flux is applied to the temperature fuse part, and the whole is covered with an insulating layer. Applicable.

(Effects of the Invention) As described above, the current interrupting element according to the present invention can function as a temperature fuse and a current fuse by using low melting point fusible alloy pieces of the same diameter and the same material, and the current fuse part also has a temperature It can provide mechanical strength equivalent to that of the fuse section. Furthermore, since a single piece of low melting point fusible alloy can be used, manufacturing is easy.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are explanatory views showing different embodiments of the present invention, respectively. 1... Insulating base, 21.22.23... Electrode, 3... Low melting point fusible alloy piece.

Claims (2)

[Claims] (1) A first electrode, a second electrode, and a third electrode are arranged on an insulating substrate, and a low melting point fusible alloy piece of the same wire diameter and the same material is bridged over these electrodes, and the first electrode and the total volume of half of the second electrode is S_1, the length of the low melting point fusible alloy piece part between the first electrode and the second electrode is I_1, the half of the second electrode and the third
Between the total volume of the electrodes S_2 and the length I_2 of the low melting point fusible alloy piece between the second and third electrodes, S_1/
A current interrupting element characterized by having a relationship of I_1<S_2/I_2. (2) The current interrupting element according to claim (1), characterized in that the planar area and thickness of each electrode are equal, and I_1>I_2.