JPH1173868A - Thermal fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further reduce the cost, to facilitate the assembling work and to improve reliability by simplifying a structure and reduce the number of part items. SOLUTION: This thermal fuse is provided with an insulating base plate 1, two contacts 2, 3 provided at separate positions on the base plate 1, a cap 4 covering one side face of the base plate 1, an insulating melt body 5 fused when temperature rises to a rated temperature, an electrode plate 6 fitted to one contact 2 of the contacts 2, 3 and pressed by the insulating melt body 5 into contact with the other contact 3, and an elastic arm 7 fitted to one contact 2 and separating the electrode plate 6 from the other contact 3 when the insulating melt body 5 is fused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fuse. More specifically, the present invention relates to a thermal fuse that opens a circuit by melting an insulating melt by a rise in temperature.

[0002]

2. Description of the Related Art A temperature-sensitive pellet that melts at a rated temperature as a fuse that cuts off current when the ambient temperature reaches a temperature (referred to as a rated temperature in this specification) previously determined by various standards or design conditions. Conventionally, there is a thermal fuse that uses a thermal fuse.

A thermal fuse using this thermosensitive pellet cuts a part of an electric passage by releasing the spring force of a spring compressed by the presence of the thermosensitive pellet by melting of the thermosensitive pellet, thereby cutting a current. Is to shut off.

[0004]

However, the conventional thermal fuse using a thermosensitive pellet has a large number of components, and it is difficult to sufficiently meet the demand for cost reduction and facilitation of assembling work. Was.

An object of the present invention is to provide a thermal fuse capable of simplifying the structure, reducing the number of parts, further reducing costs, facilitating assembly work and improving reliability. .

[0006]

According to one aspect of the present invention, there is provided a thermal fuse, comprising: an insulating base plate; two terminals provided at positions separated from the base plate; and a cap for covering the base plate. And an insulating melt provided on the inner surface of the cap facing the base plate and melting when the temperature rises to the rated temperature, and attached to one of the terminals and pressed by the insulating melt. An electrode plate that is in contact with the other terminal, one end of which is attached to one terminal and constantly urges the electrode plate away from the other terminal, and when the insulating melt is melted, the electrode plate is connected to the other terminal It is configured to have an elastic arm separated from the arm.

Therefore, when the ambient temperature is lower than the set temperature, the insulating melt is solidified, and the electrode plate is brought into contact with the other terminal by the spring force of the electrode plate itself against the spring force of the elastic arm, and the base plate Are conducted between the two terminals. When the ambient temperature rises above the set temperature, the heat mainly transmitted through the cap melts the insulating melt, the support for the electrode plate disappears, and the electrode plate separates from the base plate by the biasing force of the elastic arm. The terminal is pushed away from the other terminal and the conduction between both terminals is released.

According to a second aspect of the present invention, there is provided a thermal fuse, comprising: an insulating base plate; two terminals provided at positions separated from the base plate; a cap covering the base plate; and a base plate inside the cap. A pair of insulating melts that are provided on the surface and melt when the temperature rises to the rated temperature, and a base end is attached to each terminal, and the tip ends contact each other when pressed by the insulating melt and elastically deformed. The pair of leaf spring electrodes are configured to separate their tips by their own elastic force when the insulating melt melts and the pressing force disappears.

Therefore, when the ambient temperature is lower than the rated temperature, the insulating melt is solidified, the tips of the pair of leaf spring electrodes are kept in contact with each other, and the terminals of the base plate are conducted. Then, when the ambient temperature rises above the rated temperature, the insulating melt is melted mainly by the heat transmitted through the cap, the support for each leaf spring electrode disappears, and each leaf spring electrode loses its own elastic force. It returns to its original shape and separates the tips. That is,
The conduction between the contacts is released.

Further, the thermal fuse according to claim 3 is
An insulating base plate, two terminals provided at positions apart from the base plate, a cap covering the base plate, and an insulating member provided on a surface of the cap opposite to the base plate and melting when the temperature rises to a rated temperature. And a leaf spring electrode attached to one of the terminals of each of the terminals and contacting the other terminal when pressed by the insulating melt and elastically deformed. When the melt is melted, it is separated from the other terminal by its own elastic force.

Therefore, when the ambient temperature is lower than the set temperature, the insulating melt is solidified, the leaf spring electrode is elastically deformed and is kept in contact with the other contact, and conduction is established between both terminals of the base plate. . Then, when the ambient temperature rises above the rated temperature, the insulating melt is melted mainly by the heat transmitted through the cap, the support for the leaf spring electrode disappears, and the leaf spring electrode loses its original strength by its own elastic force. It returns to its shape and moves away from the other contact. That is, conduction between the contacts is released.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on the best mode shown in the drawings.

FIG. 1 shows a first embodiment of a thermal fuse to which the present invention is applied. The thermal fuse includes an insulating base plate 1, two terminals 8 and 9 provided at positions separated from the base plate 1, a cap 4 covering the base plate 1, and an inner surface of the cap 4 and opposed to the base plate 1. An insulating melt 5 that is solidified on the surface to be melted and melts when the temperature rises to the rated temperature, and is attached to one of the terminals 8 and 9 and supported by the insulating melt 5 and the other terminal 9 An electrode plate 6 that contacts the
One end is attached to one terminal 8 to constantly bias the electrode plate 6 away from the other terminal 9, and the elastic arm 7 separates the electrode plate 6 from the other terminal 9 when the insulating melt 5 is melted. And

The base plate 1 is formed of an insulating material, for example, ceramic in the case of the present embodiment. However, the base plate 1 is not limited to ceramic, but may be made of any material having excellent insulating properties and excellent heat resistance. Things can be used. In addition, the cap 4 is preferably made of a material having excellent heat conductivity, for example, a metal material such as brass which is easy to process in the case of the present embodiment, but is coated with an insulating material such as polytetrafluoroethylene. Preferably. It is not necessarily limited to this, and may be glass or plastic, for example.
When glass is used as the material of the cap 4, the state of the inside can be visually checked from the outside,
It is convenient for quality inspection. Also, the base plate 1
Two lead wires (terminals) 8 and 9 are attached.
The base ends of the lead wires 8 and 9 are swaged through the base plate 1 to form the contacts 2 and 3 projecting into a space S formed by the cap 4 and the base plate 1.

This thermal fuse has, for example, a cylindrical shape. That is, the base plate 1 has a disk shape, and the cap 4 has a cylindrical shape with one end opened. The opening of the cap 4 is fixed to the peripheral surface of the base plate 1 by, for example, caulking.

The insulating melt 5 is a temperature-sensitive pellet that rapidly melts at a rated temperature. The insulating melt (hereinafter referred to as a thermosensitive pellet) 5 is made of the same material as a conventional thermal fuse made of an insulating chemical substance, and detailed description thereof is omitted here. It is suitable to use one that melts with a temperature error within ± 1.5 degrees from the rated temperature.

The electrode plate 6 is manufactured by applying silver plating to a molded product made of, for example, zirconium copper. When the electrode plate 6 is made of zirconium copper, a material having high elasticity and low electric resistance can be obtained. However, it goes without saying that the material of the electrode plate 6 is not limited to zirconium copper.

The electrode plate 6 has its free end bent at an acute angle upward at a position 6a near the head / contact 3 of the other terminal 9 and further at a substantially central position 6b of the folded portion.
, And has a spring structure in which a curved portion abuts against the thermosensitive pellet 5. In the case of this structure, when the curved portion is supported by the temperature-sensitive pellet 5, the electrode plate 6 is elastically deformed as shown by a solid line in the drawing, and the vicinity of the folded position is opposed to the other side against the spring force of the elastic arm 7. A force is generated to make the contact point 3 come into close contact, and the contact state is maintained.

The elastic arm 7 applies an upward spring force to the electrode plate 6, that is, a force for urging the electrode plate 6 toward the temperature-sensitive pellet 5, so that the vicinity of the folded position 6a of the electrode plate 6 closes the other contact 3 (the caulking of the terminal 9). Away from the head). For example, as shown in FIG. 2A, a distal end portion 7b extends from a base end portion 7a formed into a ring shape into an arm shape. The elastic arm 7 is slightly bent upward near the base end 7a. Also,
The distal end portion 7b extending in the shape of an arm is bent substantially horizontally at a right angle on the way, and then rises substantially vertically. Therefore, the elastic arm 7 is connected to the base plate 1.
When the elastic arm 7 is disposed between the electrode plate 6 and the electrode plate 6 and is caulked to one contact 2 together with the electrode plate 6, the elastic arm 7 holds the electrode plate 6 at the tip 7b and lifts it. The elastic arm 7 is not particularly limited to the one shown in (A), but may be, for example, a leaf spring 7 'as shown in (B). The leaf spring 7 'has a spring structure in which the free end 7b' side is bent with respect to the fixing portion 7a ', and is fixed by crimping the terminal 8 through the hole 7c'.

In the thermal fuse having such a structure, an elastic arm 7 and an electrode plate 6 are fixed to one terminal 8 by caulking, and a thermosensitive pellet 5 is adhered to the inner surface of the cap 4. 4 can be assembled. When the cap 4 is attached to the base plate 1, the thermosensitive pellet 5
Is pressed, and the electrode plate 6 is brought into surface contact with the contact 3 of the other terminal 9 which is formed by swaging the head against the spring force of the elastic arm 7. When the cap 4 is fixed to the base plate 1 by caulking or the like in this state, the assembling of the thermal fuse is completed. That is, by attaching the cap 4 to the base plate 1, the electrode plate 6 attached by caulking to the head of one of the terminals 8 comes into contact with the other contact 3, so that the electrode plate 6 can be easily assembled. It is easy to automate.
The crimped head of the terminal 8 constitutes the contact 2.

In this thermal fuse, the current is cut off when the ambient temperature rises above the rated temperature as follows. That is, when the temperature is lower than the rated (set) temperature, the thermosensitive pellet 5 is solidified, and the electrode plate 6 attached to one contact 2 is in contact with the other contact 3. Then, when the ambient temperature becomes abnormally high and becomes equal to or higher than the set temperature, the heat-sensitive pellet 5 is melted mainly by heat transmitted through the cap 4. As a result, the force supporting the electrode plate 6 disappears, and the electrode plate 6 is separated from the contact 3 of the other terminal 9 by the spring force of the elastic arm 7 as shown by a two-dot chain line in FIG.
The conduction between the contacts 2 and 3 of the terminals 8 and 9 is released. That is, the current is cut off.

Since the terminals (lead wires) 8 and 9 of the thermal fuse extend in parallel from the other side surface of the base plate 1, the terminals 8 and 9 are bent when mounted on a printed wiring board such as an electric product. There is no necessity, it can be mounted as it is, and mounting work is easy. Further, when the current is cut off, the electrode plate 6 attached to one contact 2 is separated from the other contact 3 by the elastic force of the elastic arm 7, so that the number of parts is small and the structure is simple, and the productivity is low. The cost is low and the reliability is excellent. Further, when the cap 4 is coated with Teflon, short-circuiting with an electronic component or the like on the printed board can be prevented.

Next, a description will be given of a second embodiment of a thermal fuse to which the present invention is applied. The thermal fuse of FIG. 3 includes an insulating base plate 1 and the base plate 1.
Two terminals (lead wires) provided at distant positions from each other,
9, a cap 4 covering the base plate 1, a temperature-sensitive pellet 5 fixed on a surface inside the cap 4 facing the base plate 1, and a temperature-sensitive pellet having base terminals attached to the terminals 8, 9, respectively. 5 is provided with a pair of leaf spring electrodes 10 and 11 for bringing the tip portions into contact with each other when they are elastically deformed by being pressed by 5. A pair of leaf spring electrodes 10, 1
Numeral 1 is configured such that when the thermosensitive pellet 5 is melted and loses its support, the distal ends 10b and 11b are separated from each other by its own elastic force.

The base plate 1, the cap 4, the temperature-sensitive pellet 5 and the like have the same material structure as that of the embodiment shown in FIG. 1, but are not particularly limited thereto.

This thermal fuse has, for example, a cylindrical shape. That is, the base plate 1 has a disk shape, and the cap 4 has a cylindrical shape with one end opened. The opening of the cap 4 is caulked on the peripheral surface of the base plate 1. Of course, on the peripheral surface of the base plate 1,
For example, it may be fixed by an adhesive.

The base plate 1 is provided with lead wires 8 and 9 as two terminals. The base ends of the respective lead wires 8 and 9 penetrate the base plate 1 and protrude into a closed space formed by the base plate 1 and the cap 4. The protruding portions of these lead wires 8, 9 are contact points 2,
It is 3.

The pair of leaf spring electrodes 10 and 11 are manufactured by applying silver plating to a molded product made of, for example, zirconium copper.
The electric resistance is small and the elasticity is high. That is, by making each of the leaf spring electrodes 10 and 11 made of zirconium copper, it is possible to obtain a material having high elasticity and low electric resistance.
However, the material of each of the leaf spring electrodes 10 and 11 is not limited to zirconium copper.

The base ends 10a of the leaf spring electrodes 10, 11
11a is bent at a substantially right angle, and is caulked to the corresponding contacts 2 and 3, respectively. The portions other than the base end of each of the leaf spring electrodes 10 and 11 extend so as to bring the front ends closer to each other while being curved in an arc shape. One leaf spring electrode 10 is supported in a state of being urged toward the base plate 1 by the temperature-sensitive pellet 5, and is elastically deformed so that its tip 10 b overlaps with the tip 11 b of the other leaf spring electrode 11. I'm matching. That is, as shown by the solid line in the figure, the tip 10b of one leaf spring electrode 10 is in surface contact with the tip 11b while pressing the tip 11b of the other leaf spring electrode 11 toward the base plate 1. . In a so-called free state in which one of the leaf spring electrodes 10 is not supported by the temperature-sensitive pellet 5, the shape of each spring electrode returns to its original shape and the tips of the spring electrodes are sufficiently separated from each other, as shown by a two-dot chain line in the figure. Let me.

On one leaf spring electrode 10, a reinforcing leaf spring 13 is overlapped and fixed. Leaf spring 13 for reinforcement
Is formed of a material such as stainless steel that is less likely to deteriorate due to heat. However, the reinforcing leaf spring 13 is not necessarily required, and may be omitted.

The thermal fuse having such a structure includes the terminals 8,
After caulking the leaf spring electrodes 10 and 11 on 9 and attaching the thermosensitive pellet 5 to the inner surface of the cap 4, the cap 4 is put on the base plate 1 and caulked, or assembled by bonding or the like. When the cap 4 is attached to the base plate 1, the temperature-sensitive pellet 5 presses the vicinity of the center of one leaf spring electrode 10 toward the base plate 1, and the tip 10 b is pushed from the outside to the tip 11 b of the other leaf spring electrode 11. Make surface contact. When the cap 4 is fixed to the base plate 1 in this state, the assembly of the thermal fuse is completed. That is, when the cap 4 is attached to the base plate 1, the tip 1 of each of the leaf spring electrodes 10, 11 is provided.
Since the surfaces 0b and 11b are in surface contact with each other, the assembling work is simple and the automation thereof is easy.

In this thermal fuse, the current is cut off when the ambient temperature rises above the rated temperature as follows. That is, at a normal use temperature, the thermosensitive pellet 5 is solidified, and the respective leaf spring electrodes 10 and 11 are kept in contact with each other and the terminals 8 and 9 are electrically connected. When the ambient temperature becomes abnormally high and becomes higher than the rated temperature, mainly the cap 4
The thermo-sensitive pellet 5 is melted by the heat transmitted through the thermo-sensitive pellet. For this reason, the force supporting one leaf spring electrode 10 disappears, and each leaf spring electrode 10 and 11 returns its shape by its own elastic force. Therefore, each leaf spring electrode 10, 11
Are separated from each other, and the conduction state between both terminals 8, 9 is released.

Since the leads 8 and 9 of the thermal fuse protrude in parallel from the base plate 1, the leads 8 and 9 are mounted when mounted on a printed wiring board such as an electric product.
There is no need to bend, and mounting can be performed as it is and mounting work is easy. Further, when the current is interrupted, the distal ends are separated by the elastic force of the leaf spring electrodes 10 and 11 themselves, so that there are few movable parts and the number of components is small, so that there is little malfunction and the reliability is excellent. At the same time, the productivity is excellent and the cost can be reduced.

The tips of the leaf spring electrodes 10 and 11 are
As shown in detail in FIG. 4, the contact surface may be bent to the opposite side. By bending the tips of the leaf spring electrodes 10 and 11, the tips of the leaf spring electrodes 10 and 11 can be guided in the direction in which they come into correct surface contact when assembling the thermal fuse. Even if there is, the contact between the leaf spring electrodes 10 and 11 can be further ensured.

Next, a description will be given of a third embodiment of the thermal fuse according to the present invention. Note that the same members as those of the thermal fuse of FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

The thermal fuse shown in FIG. 5 comprises an insulating base plate 1, two terminals 8 and 9 provided at positions separated from the base plate 1, a cap 4 covering the base plate 1, and an inside of the cap 4. Base plate 1
And the temperature-sensitive pellet 5 fixed to the surface opposite to the first terminal 8, and is attached to one of the terminals 8 and 9 and is supported by the temperature-sensitive pellet 5 and contacts the other terminal 9 when elastically deformed. A leaf spring electrode 12 is provided. The leaf spring electrode 12 is configured to be separated from the other terminal 9 by its own elastic force when the thermosensitive pellet 5 is melted. That is, in the thermal fuse of FIG.
While the terminals 8 and 9 are electrically connected at 0 and 11, the two terminals 8 and 9 are electrically connected by one leaf spring electrode 12 in the thermal fuse of FIG.

The distal end portion 12b of the leaf spring electrode 12 whose base end portion 12a is crimped to one contact 2 is bent substantially at a right angle to form a flat plate, and can be brought into surface contact with the other contact 3. ing. Therefore, when the cap 4 is attached to the base plate 1, the temperature-sensitive pellet 5
2 is pressed in the vicinity of its center, and its tip 12b is brought into contact with the other contact 3. In this state, when the cap 4 is fixed to the base plate 1 by bonding, caulking, or the like, each contact 2,
The state between the three is kept electrically connected by one leaf spring electrode 12, and the assembling of the thermal fuse is completed.

When the temperature reaches the set temperature due to an increase in the ambient temperature, the thermosensitive pellet 5 melts, the force supporting the leaf spring electrode 12 disappears, and the leaf spring electrode 12 returns to its shape by its own elastic force. . Therefore, the distal end portion 12b of the leaf spring electrode 12 is separated from the other terminal 9, and the conduction between the two terminals 8, 9 is released.

The above embodiments are examples of preferred embodiments of the present invention, but are not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in each of the thermal fuses shown in FIGS. 3 and 5, both terminals 8 and 9 project from the base plate 1 into the space S inside the cap. However, as shown in FIG.

In each of the thermal fuses shown in FIGS. 1, 3, and 5, the leaf spring electrodes 10, 11, 12, the electrode plate 6, and the elastic arm 7 are attached to the corresponding terminals 8, 9 by caulking. However, the present invention is not limited to this, and may be attached by spot welding or the like, for example, as shown in FIG.

In each of the thermal fuses shown in FIGS. 1, 3 and 5, the surface of the thermosensitive pellet 5 is formed flat while the electrode plate 6 or each of the leaf spring electrodes 10, 11, and 12 is formed.
Bends to support the contact between the contacts 2 and 3.
Although the configuration for obtaining the pressing force is described above, the configuration for obtaining the pressing force is not limited to this. For example, a convex portion may be formed on the thermosensitive pellet 5 and the flat portion may be used as the flat electrode plate 6 or the plate spring electrode 10. , 11, 12 may be pressed. FIG. 8 shows an example of this case.

Further, in each of the thermal fuses shown in FIGS. 1, 3 and 5, the surrounding heat is indirectly transmitted to the thermosensitive pellet 5 mainly through the cap 4, but an air hole is formed in the cap 4. Then, the surrounding heat may be directly transmitted to the thermosensitive pellet 5 by introducing hot air from the air hole.

[0042]

As described above, in the thermal fuse according to the first aspect, when the insulating melt is melted, the electrode plate attached to one contact is moved from the contact of the other terminal by the elastic force of the elastic arm. Since they are separated, the current can be reliably shut off with a simple structure having few movable parts. For this reason, the number of components is reduced, productivity is improved, production costs can be reduced, and reliability as a thermal fuse is improved. Also, when the cap is attached to the base plate during assembly, the insulating melt makes the electrode plate contact the other contact against the spring force of the elastic arm, which simplifies assembly work, improves productivity and improves assembly work. Automation becomes easier.

In each of the thermal fuses according to the second and third aspects, when the insulating melt is melted, the conductive state between the respective contacts is released by the elastic force of the leaf spring electrode itself. Like a fuse, the current can be reliably cut off with a simple structure. For this reason, the number of components is reduced, productivity is improved, production costs can be reduced, and reliability as a thermal fuse is improved. In addition, when a cap is attached to the base plate during assembly, the insulating melt deforms the leaf spring electrode elastically and conducts between the contacts, simplifying the assembly work, improving productivity and facilitating the automation of the assembly work. become.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a thermal fuse according to the present invention.

FIG. 2 shows an elastic arm of the thermal fuse of FIG. 1,
(A) is a perspective view of a linear elastic arm, (B) is a perspective view of a leaf spring-like elastic arm.

FIG. 3 is a sectional view showing a second embodiment of the thermal fuse according to the present invention.

FIG. 4 is an enlarged view showing a main part of a modification of the thermal fuse of FIG. 3;

FIG. 5 is a sectional view showing a third embodiment of the thermal fuse according to the present invention.

FIG. 6 is a sectional view showing a modification of the contact point of the thermal fuse according to the present invention.

FIG. 7 is a sectional view showing another modified example of the contact point of the thermal fuse according to the present invention.

FIG. 8 is a sectional view showing a modified example of the insulating melt of the thermal fuse according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base plate 2, 3 Contact 4 Cap 5 Thermosensitive pellet (insulating melt) 6 Electrode plate 7 Elastic arm 10, 11, 12 Leaf spring electrode

Claims (3)

[Claims] 1. An insulating base plate, two terminals provided at positions separated from the base plate, a cap covering the base plate, and a rated temperature provided on a surface inside the cap facing the base plate and facing the rated temperature. An insulating melt that melts when the temperature rises, an electrode plate attached to one of the terminals and pressed by the insulating melt to contact the other terminal,
One end is attached to the one terminal to constantly urge the electrode plate away from the other terminal, and an elastic arm that separates the electrode plate from the other terminal when the insulating melt is melted. A thermal fuse, comprising: 2. An insulating base plate, two terminals provided at positions apart from the base plate, a cap covering the base plate, and a rated temperature provided on a surface inside the cap facing the base plate and facing the base plate. An insulating melt that melts when the temperature rises, and a pair of leaf spring electrodes each having a base end attached to each of the terminals and contacting the distal ends when elastically deformed by being pressed by the insulating melt. The thermal fuse, wherein the pair of leaf spring electrodes separates the distal ends of the pair of leaf spring electrodes by their own elasticity when the insulating melt melts and the pressing force disappears. 3. An insulating base plate, two terminals provided at positions apart from the base plate, a cap covering the base plate, and a rated temperature provided on a surface inside the cap facing the base plate and facing the rated temperature. An insulating melt that melts when the temperature rises, and a leaf spring electrode that is attached to one of the terminals and that contacts the other terminal when pressed by the insulating melt and elastically deformed, The thermal fuse, wherein the leaf spring electrode is separated from the other terminal by its own elastic force when the insulating melt is melted.