JPH0620574A - Temperature fuse - Google Patents

Abstract

PURPOSE:To prevent a rush current normally used from being cut off while surely cutting off currents in abnormalities. CONSTITUTION:One end portion of a conductive, columnar fuse main body 2 having a lead wire 4b connected thereto is held on a socket portion 1 having a lead wire 4a connected thereto. The socket portion 1 comprises two conductors of different coefficients of thermal expansion stacked one atop the other along the radial direction of the fuse main body 2 in such a manner that the outside conductor is greater in coefficient of thermal expansion than the inside one. A plate spring 3 for constantly pressing the fuse main body 2 so that the main body 2 is pulled out of the socket portion 1 is provided at the other end face of the fuse main body 2. When an excess current flows between the lead wires 4a, 4b, the socket portion 1 is heated and expanded because of the difference in coefficient of thermal expansion between the conductors. Therefore, the fuse main body 2 is pulled out of the socket main body 1 by the plate spring 3 so that the current is cut off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fuse for preventing smoking and ignition of electric parts due to overcurrent in electric circuits of office machines and home electric appliances.

[0002]

2. Description of the Related Art Conventionally, as fuses used in office machines, home appliances, etc., a tubular fuse in which a fuse element is sealed in a glass tube or a metal film having a spiral groove is formed on the fuse body. A fuse resistor or the like is known in which an electric current is caused to flow along a spiral groove and a fuse function is provided by fusing a metal film due to an overcurrent. Moreover, an IC protector is used as a fuse for protecting a semiconductor element.

[0003]

However, among the above-mentioned conventional fuses, the tubular fuse and the fuse resistor interrupt the current by melting the thermoplastic metal, and therefore transiently occur when the power is turned on. There is a problem in that the current is also cut off by the inrush current. Further, in the IC protector, there is a problem that the current may not be easily interrupted even when an abnormality occurs.

An object of the present invention is to provide a thermal fuse which is not interrupted by a rush current during normal use, and which is capable of reliably interrupting current in the event of an abnormality.

[0005]

In order to achieve the above object, the present invention provides a conductive columnar fuse main body provided with one wiring, and holding the fuse main body and providing the one wiring. A socket portion provided with other wiring that makes a pair with, and an elastic member that constantly urges the fuse body so as to be removed from the socket portion, and the socket portions each have a plurality of different thermal expansion coefficients. Is laminated so that the thermal expansion coefficient of the inner conductor is larger than the thermal expansion coefficient of the outer conductor in the radial direction of the fuse body.

[0006] In addition, a conductive fuse body having a constricted portion in an intermediate portion, and an axis line of the fuse body projecting from both ends of the fuse body for connecting the fuse body to an electric circuit. A conductor having a high thermal expansion coefficient and extending in opposite directions in the vertical direction, and an elastic member for constantly urging each conductor toward the axis of the fuse body. May be

[0007]

In the invention according to claim 1 configured as described above, the fuse main body is normally held in the socket portion, and a current flows through the fuse main body through the wiring.
At this time, if an overcurrent flows through the temperature fuse, the socket portion is heated by the overcurrent. The conductor of the socket is
Since the inside has a higher coefficient of thermal expansion than the outside,
The socket portion expands outward due to the difference in their thermal expansion coefficients, and the holding of the fuse body is released. On the other hand, the fuse body is provided with an elastic member that constantly urges the fuse body to be removed from the socket portion. , The current flowing through the electric circuit is cut off.

According to the second aspect of the invention, when an overcurrent flows through the thermal fuse, the conductors fixed to both ends of the fuse body are heated and thermally expanded. Due to the thermal expansion of the conductors, a shear load is applied to the fuse body in the opposite directions and in the axial direction of the fuse body. When a shear load is applied to the fuse body, the fuse body breaks at the constricted portion where the strength is weakest, and the current is cut off. Since each conductor is constantly urged by the elastic member in the direction in which the shear load acts, even if each conductor cools and contracts, the blown fuse bodies are displaced relative to each other. Therefore, it does not become conductive.

[0009]

Embodiments of the present invention will now be described with reference to the drawings.

(First Embodiment) FIG. 1 is a perspective view of a first embodiment of the thermal fuse of the present invention, and FIG. 2 is a side view of the thermal fuse shown in FIG.

As shown in FIGS. 1 and 2, the socket portion 1 is electrically connected to the substrate 5 via a lead wire 4a as another wiring soldered to the substrate 5. The socket portion 1 has a shape in which a part of a ring is cut and the cut portion is curved outward. Further, the socket portion 1 is formed by laminating two conductors having different thermal expansion coefficients in the radial direction of the socket portion 1, and laminating the inner conductors more than the outer conductors. Is a big one. The number of conductors forming the socket portion 1 is not limited to two, and may be three or more. Even in this case, the thermal expansion coefficient of each conductor is from the outside to the inside of the socket portion 1. , Are arranged so that they become larger in sequence.

On the other hand, the columnar fuse body 2 made of a conductor is electrically connected to the substrate 5 at one end portion (right end portion in the drawing) of the fuse body 2 via the lead wire 4b as one wiring which is soldered to the substrate 5. Fuse body 2
The other end of is firmly fitted and held in the socket 1. As a result, the fuse body 2 and the socket portion 1 are electrically connected. Further, one end of a leaf spring 3 made of a non-conductive material and serving as an elastic member is fixed to the other end surface of the fuse body 2, and the other end of the leaf spring 3 is fixed to the substrate 5. The leaf spring 3 is curved into an acute angle as shown in the side view of FIG. 3 showing the state after the operation when no load is applied to the leaf spring 3.
The curved portion of the leaf spring 3 is stretched in a state in which is held by the socket portion 1. Therefore, the fuse body 2 is always urged by the leaf spring 3 to the right in the figure, that is, in the direction in which the fuse body 2 is disengaged from the socket portion 1.

Next, the operation of this embodiment will be described.

First, the fuse body 2 is inserted from the open end portion (upper end portion in the drawing) of the socket portion 1 and held by the socket portion 1. In this state, a current flows between the lead wires 4a and 4b.

Here, if an abnormality occurs in the electric circuit of the substrate 5 and an overcurrent flows between the lead wires 4a and 4b, the socket 1 portion generates heat due to the overcurrent. When the socket portion 1 generates heat, the diameter of the socket portion 1 expands due to the difference in thermal expansion coefficient between the two conductors forming the socket portion 1, and the fitting of the socket portion 1 loosens. On the other hand, since the fuse body 2 is biased to the right in the figure by the leaf spring 3, the loosened fitting of the socket portion 1 causes the fuse body 2 to move as shown in FIG.
It is pulled to the right in the figure by the urging force of the leaf spring 3. As a result, the fuse body 2 is detached from the socket portion 1 and the current between the lead wires 4a and 4b is cut off.

Since the current is cut off by utilizing the thermal expansion of the socket portion 1 in this way, the current is not cut off by the rush current transiently generated when the power is turned on. Further, when the socket portion 1 thermally expands, the fuse body 2
When the overcurrent occurs, the current can be cut off without fail, and the fuse body 2 can be used again by re-inserting it in the socket 1. Can be omitted.

In this embodiment, the leaf spring 3 is used as the elastic member, but the elastic member is not limited to this, and a tension coil spring or the like for urging the fuse body 2 to the right in the drawing may be used. Further, the fixing position of the elastic member to the fuse body 2 is not limited to the one end surface of the fuse body 2,
It may be provided on the lower surface of the fuse body 2 to urge the fuse body 2 upward in the drawing. In this case, the loose fitting of the socket portion 1 causes the fuse body 2 to be disengaged from the open end portion of the socket portion 1. Further, since the elastic member is a conductor electrically connected to the substrate 5, the fuse body 2 and the substrate 5 can be electrically connected by the elastic member, and thus the fuse body 2 is connected. The lead wire 4b is unnecessary and the number of parts can be reduced.

(Second Embodiment) FIG. 4 is a side view in which a part of the thermal fuse of the present invention is cut away, and FIG. 5 is a side view showing a state after the thermal fuse shown in FIG. 4 is activated. is there.

As shown in FIG. 4, two conductor wirings 14 as elastic members are soldered and electrically connected to the substrate 15, respectively.

On the other hand, the fuse body 12 made of a brittle material having conductivity has a constricted portion 12a at the center thereof, and conductors 11 made of a member having a large coefficient of thermal expansion are fixed to both ends thereof. There is. Each conductor 11
One end of each is perpendicular to the axis of the fuse body 12,
Moreover, they extend in directions opposite to each other and are fixed to the conductor wirings 14. As a result, each conductor wiring 1
A current flows between the four via the conductors 11 and the fuse body 12. Also, on the surface of the fuse body 12,
Non-conductive paint is applied.

Further, each soldering portion of each conductor wiring 14 with the board 15 is elastically deformed so as to increase the distance therebetween and fixed to the board 15, and the upper half portion of each conductor wiring 14 is fixed. Is applied to the upper half portions of the conductor wirings 14 with respect to each other. This force acts on the fuse body 12 via each conductor 11, and in the state shown in FIG. 4, a shearing force acts on the fuse body 12 by each conductor wiring 14. Next, the operation of this embodiment will be described.

In the normal case, as shown in FIG. 4, the conductor 11 and the fuse body 1 are provided between the conductor wirings 14.
Current is flowing through 2.

Here, when an abnormality occurs in the circuit of the substrate 15 and an overcurrent flows between the conductor wirings 14, each conductor 11 generates heat due to the overcurrent. When each conductor 11 generates heat, each conductor 11 greatly expands in a direction perpendicular to the axis of the fuse body 12, and a stronger shearing force acts on the fuse body 12. This shearing force is applied to the fuse body 12
When the shear strength of the fuse body 12 is exceeded, the fuse body 12 is broken at the constricted portion 12a, and the current between the conductor wirings 14 is cut off. After the fuse body 12 is broken, even if each conductor 11 cools and contracts, the upper half of each conductor wiring 14 inclines inward and the surface of the fuse body 12 is coated with the non-conductive paint 13. By being applied,
The blown fuse bodies 12 do not come into contact with each other again to be conductive, and the current is surely cut off.

As described above, the current is interrupted by utilizing the thermal expansion of each conductor 11, so that the current is not interrupted by the rush current transiently generated when the power is turned on. Further, when each conductor 11 thermally expands, the fuse body 1
Since the current is interrupted by the breakage of 2, the current can be reliably interrupted when an overcurrent occurs.

In this embodiment, each conductor wiring 14
Although a shearing force is applied to the fuse body 12, a shearing force may be applied to the fuse body 12 by tensioning a tension coil spring between the conductor wirings 14.
In this case, each conductor wiring 14 does not need to have elasticity.

[0026]

Since the present invention is configured as described above, it has the following effects.

In the thermal fuse according to the first aspect, a socket portion in which conductors having different thermal expansion coefficients are laminated, a fuse main body held by the socket portion, and a biasing force for removing the fuse main body from the socket portion. Since the fuse main body comes off from the socket portion due to thermal expansion of the socket portion due to the overcurrent, the current can be surely interrupted when the overcurrent occurs, and the current is interrupted by the inrush current. There is no such thing. Further, even if the fuse body is disengaged from the socket portion due to an overcurrent, the fuse body can be held again in the socket portion, so that the labor of fuse replacement can be saved.

A thermal fuse according to a second aspect of the present invention has a fuse body having conductors fixed to both ends thereof, and elastic members for biasing the conductors toward the axis of the fuse body. Since the fuse body is broken by the thermal expansion of each conductor due to the overcurrent, the current can be reliably cut off when the overcurrent occurs, and the current is not cut off by the inrush current. After the fuse body is broken, the relative position of the blown fuse body is displaced by the biasing force of the elastic member, so that the blown fuse bodies do not come into contact with each other and the fuse body does not become inadvertently brought into conduction. .

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of a thermal fuse of the present invention.

2 is a side view of the thermal fuse shown in FIG. 1. FIG.

FIG. 3 is a side view showing a state after the thermal fuse shown in FIG. 1 is activated.

FIG. 4 is a partially cutaway side view of a second embodiment of the thermal fuse of the present invention.

5 is a side view showing a state after the thermal fuse shown in FIG. 4 is activated.

[Explanation of symbols]

 1 Socket Part 2, 12 Fuse Main Body 3 Leaf Springs 4a, 4b Lead Wires 5, 15 Board 11 Conductor 12a Constricted Part 13 Non-Conductive Paint 14 Conductor Wiring

Claims (2)

[Claims] 1. A conductive columnar fuse main body provided with one wiring, and a socket portion holding the fuse main body and provided with another wiring paired with the one wiring. An elastic member that constantly urges the fuse body to be detached from the socket portion, wherein the socket portion has a plurality of conductors each having a different thermal expansion coefficient from the outside in the radial direction of the fuse body. 2. The thermal fuse, wherein the thermal conductors are laminated so that the thermal expansion coefficient of the inner conductor is larger than the thermal expansion coefficient of the electrical conductor. 2. An electrically conductive fuse body having a constriction in an intermediate portion, and an axis line of the fuse body projecting from both ends of the fuse body for connecting the fuse body to an electric circuit. A temperature characterized by having conductors having a high coefficient of thermal expansion that extend in opposite directions in the vertical direction and elastic members that constantly urge each conductor toward the axis of the fuse body. fuse.