JPH0660948U - Thermal fuse - Google Patents

Abstract

(57) [Abstract] [Purpose] The structure is simple, the operating speed is fast, large current can be cut off, and the operating temperature from low temperature to high temperature is realized by one system configuration without using the temperature sensitive material of chemical substance. It is a thermal fuse. [Structure] The lead wires 1 and 1'are inserted and fixed in a case 7 made of an insulating material by fixing members 6 and 6 ', and adhered and sealed by an adhesive agent 8 and 8'. The end portion of the lead wire 1 is joined by the low melting point alloy 3 while being in contact with the movable contact 2 whose one end is closed, and the end portion of the other lead wire 1 ′ is separated by a predetermined distance and the other end is opened. It is fitted to the cylindrical movable contact 2,
The joint ends are joined by the low melting point alloys 3 and 3 '. A biasing means 4 formed of a coil spring is provided between the collar 2a of the movable contact 2 and the insulating cylinder 5 provided on the outer periphery of the movable contact 2.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a thermal fuse for protecting various electric devices such as a low voltage switchboard, a small electric motor or an electric kotatsu.

[0002]

[Prior art]

 Thermal fuses are used in various electric devices driven by electric circuit systems, and when these devices are exposed to a dangerous temperature environment, they open the electric circuit and stop the operation of the device. There are roughly two types of thermal fuses in the past, and the first type is, for example, the type shown in FIG. 1 of JP-A-54-39844.

The thermal fuse disclosed in this publication has a metal cylindrical case 11 whose one end is open, and a lead wire 12 is caulked to the other end of the metal case 11. The temperature fuse is in the form of a solid pellet that melts at a predetermined temperature. A disk-shaped movable contact 17 that is movable by sandwiching the temperature-sensitive material 13 and a biasing means 16 that is compressed and abutted against the temperature-sensitive material 13 and abutted on the inner peripheral surface of the case and the end of the lead wire on the case opening side, and insulated. An end portion of the lead wire 19 inserted from the case opening side fixed by the plug 18 is provided.

In this thermal fuse, since the temperature sensitive material 13 remains solid when the temperature is lower than a predetermined temperature, the movable contact 17 is overcome by the biasing means 16 to overcome the biasing force to separate it from the end of the lead wire 19 to generate electricity. However, when the temperature reaches a predetermined temperature, the temperature sensitive material 13 is melted and the contact is dissociated from the end of the lead wire 19 by the urging force to cut off the electrical conduction.

The second method is, for example, the method disclosed in Japanese Patent Laid-Open No. 56-114238. In the thermal fuse according to this publication, the ends of the lead wires 23 and 23 'are inserted into the cylindrical case 21 whose both ends are closed by insulating materials 22 and 22', and the left and right equal lengths are inserted, so that the end portions of the lead wires are linear low. The low melting point alloy 24 is connected and the surface of the low melting point alloy 24 is covered with a rosin-based flux 25 or the like. 26 is air.

In this thermal fuse, when the temperature reaches a predetermined temperature, the low melting point alloy 24 and the flux 25 are melted, and as a result of the action of the flux 25, dirt and an oxide film on the surface of the low melting point alloy are removed. The surface tension of the low melting point alloy 24 is exerted and the end portions of the lead wire are aggregated into a spherical shape, so that the electrical conduction is cut off.

[0007]

[Problems to be solved by the device]

 By the way, in the thermal fuse according to the above-mentioned first publication, electrical conduction is made between the contact that contacts the metal case and the end of the lead wire, and the contact is simply mechanically connected to the inner surface of the case and the end of the lead wire. Is only in contact with. For this reason, when an impact or vibration is applied to the thermal fuse, the attitude and position of the contact point will change to some extent and the contact will become unstable, and the electrical contact resistance tends to increase.

Further, since both ends of the case are caulked, the wall thickness of the end of the case cannot be increased. When a force is applied, the case is deformed and the movement of the contacts is obstructed, and the function as a thermal fuse is achieved. It may disappear. Since the thermal fuse is usually attached in close contact with the heating element in order to improve the thermal sensitivity, it has to be fixed in some way, and therefore excessive force may be applied to the case. Moreover, since the case is generally made of metal and is usually electrically insulated by covering it with a resin tube, it is difficult to check it beforehand even if the case is deformed. To be done.

The second type thermal fuse has a merit that it has a simple structure because it is a type in which the end portion of the lead wire in the case is connected to the end portion with a low melting point metal. Some melting point alloys are hard and brittle, which makes them difficult to process into a linear shape, and limits the achievable operating temperature to some extent. An expensive metal such as indium is used to make the low-melting point alloy soft and good in workability, which eventually increases the cost.

On the other hand, considering the rated current of the second type thermal fuse, there are the following problems. When the rated current becomes large, the amount of Jule heat generated by the electric resistance of the self becomes large and the operating temperature of the thermal fuse is lowered. Therefore, in order to alleviate this, it is necessary to increase the cross-sectional area of the lead wire and the cross-sectional area of the low melting point alloy.

However, when the cross-sectional area of the low melting point alloy portion is increased, the operation speed is often slowed, that is, the so-called sharpness tends to be deteriorated. In addition, the number of arcs generated during fusing increases, the arc generation time increases, and a large amount of metal vapor is generated, which adheres to the inner surface of the container together with the carbide of the flux, resulting in a significant decrease in electrical insulation performance after operation. To do.

Therefore, in order to secure the insulation performance, the case must be made sufficiently larger than the thermal fuse element, and the overall thermal fuse becomes large, which is uneconomical and impractical. Also, the rosin-based flux used in this thermal fuse is an organic substance, and if exposed to a temperature environment of approximately 200 ° C for a long time, decomposition of the active ingredient contained in this flux is promoted, and it is low. The surface of the melting point alloy is not clean, and the agglomeration on the lead wire described above does not occur. In other words, it is difficult to realize a thermal fuse having an operating temperature of over 200 ° C. with the thermal fuse of this system.

In consideration of various problems of the above-mentioned conventional thermal fuse, the present invention has a simple structure without using a temperature sensitive material made of a chemical substance as in the conventional one, has a high operating speed, and interrupts a large current. It is an object of the present invention to provide an economical and inexpensive thermal fuse that can be realized and can be operated in a single operating temperature range from low temperature to high temperature.

[0014]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention has a cup-shaped movable contact in which one end is opened and the other end is closed by inserting and fixing the lead wire end portions at a predetermined distance from both ends of the insulating material case. Insert one end of the lead wire into the open end and braze it with a low melting point alloy, and contact the other end with the other end of the lead wire and braze it with a low melting point alloy to form a movable contact. The temperature fuse was constructed with means for urging it away from one of the lead wires.

In this case, in order to fix the lead wire in the case, there is provided a caulking-fixed fixing member which is fitted over the lead wire, and the fixing member holds the biasing means, and the movable contact and the biasing means are provided in the case. It is preferable that the lead wire and the case are easily housed in the center and can also serve as means for firmly sealing, adhering, and fixing the lead wire and the case.

In any case, the low melting point alloy may be interposed in the inner space formed by inserting and fixing the lead wire of the movable contact.

[0017]

[Action]

 In the thermal fuses of the first and second inventions configured as described above, the low melting point alloy does not melt below a preset temperature, and the movable contact does not move with the biasing means compressed. Therefore, an electric path is formed from one lead wire to the other lead wire via the movable contact. When the temperature exceeds the set temperature, the low melting point alloy melts, and at that moment, the movable contact is separated from one of the lead wires by the biasing means and moves. Therefore, the electric circuit is cut off. At this time, since the lead wire is not inserted in the movable contact on the side where the lead wire end of the movable contact is fixed, the low melting point alloy is immediately separated at the moment of melting, The shutoff operation is extremely quick.

This thermal fuse does not use a chemical substance as a temperature sensitive material as in the past, but operates by melting a low melting point alloy. Therefore, it can be applied to a wide temperature range by selecting an alloy that melts at a desired temperature from low temperature to high temperature as the low melting point alloy. Further, since the movable contact is moved by the urging means, the moving speed is high, so that the arc is less likely to occur and the movable contact can be used for interrupting a large current.

Further, in the third aspect of the invention, another low melting point alloy is enclosed in the internal space of the movable contact, and the low melting point alloy is the same as or different from the low melting point alloy at both ends of the movable contact. You can In the case of a different alloy, for example, if the melting temperature is higher than that at both ends of the movable contact, the alloy on both ends of the movable contact will first melt when the ambient temperature rises, and when the temperature further rises, the alloy inside will melt. The movable contact moves and the electrical connection is cut off. This greatly expands the range of set operating temperature.

[0020]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a main longitudinal sectional view of the thermal fuse of the first embodiment. 1, 1'is a lead wire, 2 is a movable contact, 3'is a low melting point alloy, 4 is an urging means consisting of a coil spring, 5 is an insulating cylinder, 6 and 6'is a fixed member, and 7 is a cylindrical shape. Cases 8, 8'are adhesives.

As shown in the drawing, the lead wires 1 and 1 ′ are inserted into the case 7 from the left and right sides, and the ends thereof are separated by a predetermined distance, and electrically insulated by metallic donut-shaped fixing members 6 and 6 ′, respectively. The case 7 having the property is caulked. Both ends of the case are sealed and adhered with adhesives 8 and 8 '.

The movable contact 2 is interposed between both ends of the lead wires 1 and 1 ′, and is made of a cup-shaped body in which a metal tubular body is opened at one end and closed at the other end, and a brim 2 a is provided at the open end. Have. A lead wire 1'is inserted into the open end of the movable contact 2, and the closed end is in contact with the terminal head 1a of the lead wire 1. The fitting part on the open end side is brazed for a certain length with a low melting point alloy 3 ′ that melts at a predetermined temperature, and the closed end side is simply abutted and brazed with the low melting point alloy 3 between them. As a result, electrical continuity is maintained through the paths of the lead wire 1, the movable contact 2, and the lead wire 1 '.

An urging means 4 and an insulating cylinder 5 having electrical insulation are externally fitted to the outer periphery of the movable contact 2, and the urging force of the coil spring compressed between the flange 2 a of the movable contact 2 and the insulating cylinder 5. The movable contact is constantly pressed in the axial direction, and the urging means 4 and the insulating cylinder 5 are dimensioned so as to move smoothly with respect to the movable contact.

The thermal fuse of the embodiment configured as described above operates as follows. FIG. 1 shows the internal structure of the thermal fuse in a normal state below the operating temperature. In the illustrated state, an electric path is formed from the lead wire 1 to the lead wire 1 ′ through the low melting point alloys 3 and 3 ′ and the movable contact 2.

In this state, the biasing means 4 is constrained in a state where the coil spring is compressed and has a biasing force that separates the movable contact point 2 from the lead wire 1, but the biasing means 4 rises to a predetermined temperature. Until then, the movable contact 2 is fixed to the lead wires 1 and 1'by the low melting point alloys 3 and 3 ', so that the movable contact 2 is not dissociated from the lead wire 1. When the temperature exceeds a predetermined temperature, the low melting point alloys 3 and 3 ′ are melted and lose the fixing force to the lead wires 1 and 1 ′. Therefore, as shown in FIG. As a result, it is dissociated from the lead wire 1 and the electric circuit is cut off.

At this time, since the movable contact 2 is only in contact with the end of the lead wire 1 at the end head 1a, if the low melting point alloy 3 between them is melted, it is immediately separated from the lead wire 1. Since the end of the lead wire 1 is not inserted and fixed inside like the lead wire 1 ′ on the opposite side to the movable contact 2, the movable contact 2 pulls the thread when the movable contact 2 separates from the lead wire 1. So it is easily separated without hindering its migration.

In the thermal fuse of the above-described embodiment, since the movable contact 2 is simply brazed to the lead wires 1 and 1 ′ by the low melting point alloys 3 and 3 ′, it is resistant to shock and vibration, and its position and attitude are It does not change and the electric resistance value is low and stable. The movable contact 2 is brought into contact with the end head 1a of the lead wire 1 and can be moved by the length of the space 2X in the movable contact 2, so that the entire length of the thermal fuse becomes extremely short. Therefore, since the amount of deflection of the coil spring of the biasing means 4 can be reduced, thermal deterioration of the coil spring at high temperature, so-called settling, can be reduced, and the operation is stable for a long period of time. Therefore, the time required for the coil spring of the biasing means 4 to restore its original shape from the compressed state is extremely short. Therefore, when the low melting point alloy melts, the movable contact 2 is immediately dissociated from the lead wire 1. Therefore, the occurrence of arc during operation is extremely small, and a thermal fuse with good insulation performance can be realized.

Further, since the operating mechanism does not use chemical substances such as flux and resin pellets as in the conventional example, it can be applied as a thermal fuse which operates at a relatively high temperature exceeding 200 ° C. Further, the fixing member 6 not only restrains the urging means 4, but also fits the other fixing member 6'in the center of the case by appropriately determining these dimensions and the dimensions of the case 7. This is extremely easy and the assembly is easy.

If the material of the case 7 is an electrically insulating material such as ceramics or glass that is not easily deformed, even if the movable contact 2 has a brim 2 a at the end, the case 7 will not be separated from the inner surface of the case 7. Since the gap is provided, the movement of the movable contact 2 is not obstructed by the external force. Further, since the adhesives 8 and 8'enter the fixing members 6 and 6'and the inner surface of the case 7 to increase the adhesion area, they are firmly fixed and a robust product can be manufactured.

FIG. 3 shows a vertical cross section of a thermal fuse of another embodiment. This embodiment has substantially the same structure as the first embodiment, except that the same or another kind of low melting point alloy 9 is enclosed in the space 2X in the movable contact 2. The other same functional members are designated by the same reference numerals.

The low melting point alloy 9 may have a poor brazing property (soldering property) with respect to a copper alloy used for a lead wire or a movable contact such as bismuth.

In this embodiment, assuming that bismuth is used as the low melting point alloy 9 and lead-tin alloy is used as the low melting point alloys 3 and 3'as described above, the melting point of bismuth is 271 ° C. It becomes a thermal fuse of about 273 ° C.

When the ambient temperature rises with respect to the thermal fuse and reaches a temperature at which the low melting point alloys 3 and 3 ′ are melted, the low melting point alloys 3 and 3 ′ are melted, but the low melting point alloy 9 is not yet melted, Therefore, the biasing force of the coil spring of the biasing means 4 is overcome, and the electrical connection is maintained. When the ambient temperature further rises and the low melting point alloy 9 melts, the movable contact 2 is dissociated from the lead wire 1 and the electrical connection is cut off.

As described above, since alloys having poor brazing properties can be used as temperature sensitive materials, a wide range of operating temperatures can be realized, and when alloys having good brazing properties are included, thermal fuses with extremely various types of temperature characteristics can be obtained. To be

[0035]

【effect】

 As described in detail above, in the thermal fuses of the first and second inventions, the ends of the lead wires inserted and fixed in the insulating material case are separated by a predetermined distance and joined to the movable contact. It is brazed with a low melting point alloy and urging means is provided on the outer periphery of the movable contact.

Therefore, the structure is simple and robust, and the operation speed is fast, so that a relatively large current exceeding 10 A can be cut off, and since no chemical substance is used as a temperature sensitive material, a design of a desired operation temperature from low temperature to high temperature can be achieved. The contact point is stable and the electrical resistance is low because the movable contact does not change its position or posture, and it is resistant to vibration and shock.

Further, since high temperature to low temperature can be realized by one method, standardization of parts can be achieved, and total cost reduction including process control and quality control can be achieved, so that an inexpensive temperature fuse can be provided. The advantages of

In the third invention, since another low melting point alloy is enclosed in the movable contact internal space, if another low melting point alloy other than the low melting point alloys at both ends of the movable contact is selected as the other low melting point alloy, It is possible to allow other low melting point alloys to be melted after they are melted, so that there is an advantage that the setting range of the temperature condition of the thermal fuse can be easily expanded.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a thermal fuse of a first embodiment.

FIG. 2 is an operation explanatory diagram of the same as above.

FIG. 3 is a vertical sectional view of a thermal fuse of a second embodiment.

FIG. 4 is an operation explanatory diagram of the same as above.

FIG. 5 is a vertical sectional view of a conventional thermal fuse.

FIG. 6 is an operation explanatory diagram of the above.

[Explanation of symbols]

 1, 1'lead wire 1a end head 2 movable contact 3, 3'low melting point alloy 4 urging means 5 insulating cylinder 6, 6'fixing member 7 case 9 low melting point alloy

Claims (3)

[Scope of utility model registration request] 1. A lead wire end portion is inserted and fixed at a predetermined distance from both ends of an insulating material case, and a cup-shaped movable contact having one end open and the other end closed is interposed between the lead wire ends, and the open end is provided at the open end. Inserts one end of the lead wire and brazes it with a low melting point alloy, and abuts the other end with the end of the other lead wire and brazes it with a low melting point alloy to separate the movable contact from one lead wire. A thermal fuse comprising means for biasing in a direction. 2. A fixing member fixed to the lead wire by caulking for fixing the lead wire in a case,
This fixing member holds the biasing means, easily accommodates the movable contact and the biasing means in the center of the case, and also serves as means for firmly sealing, bonding and fixing the lead wire and the case. The thermal fuse according to claim 1, which is characterized in that 3. The thermal fuse according to claim 1, wherein a low melting point alloy is interposed in an internal space formed by inserting and fixing the lead wire of the movable contact.