JPH0785376B2 - Temperature fuse - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal fuse that cuts off an electric circuit when a device temperature reaches a certain temperature or higher in order to prevent an accident of overheating of an electric device.

[Conventional technology]

The thermal fuse is used for the purpose of detecting the overheat of the device, melting the fusible substance, and breaking the current circuit. The heat can be sensed by detecting the heat generated by the equipment by convective heat transfer due to the temperature rise of the surrounding air, by sensing the radiant heat generated by the heat generated by the equipment, or by conducting the heat of the equipment itself to a thermal fuse. There are three methods of sensing.

Among them, the method of detecting by convection or radiant heat can be applied to a slight difference in environmental conditions completely different from the characteristics unique to the thermal fuse, such as the mounting position of the thermal fuse on the heating surface, the direction, the distance, and the degree of the surrounding air flow. It is difficult to set the temperature because it is greatly affected. Also, the sensed temperature itself does not match the temperature of the device, and the heat followability is poor, so it is necessary to set the temperature considerably lower than the temperature of the device. Therefore, the temperature cannot be set without special technical consideration such as accurately investigating the correlation between the temperature of the heat generating part and the temperature actually reached by the thermal fuse. This correlation is also greatly affected by the magnitude of the rate of temperature change. Therefore, the method of sensing by convection or radiant heat is generally accurate in sensing the temperature of the equipment itself unless it is used in an environment where the temperature of each part is uniform and the rate of temperature change is small, such as in a constant temperature bath. Is difficult to do. This indicates that the nominal operating temperature and its accuracy, which indicate the performance of thermal fuses, do not make much sense in general practical use.

On the other hand, the method of directly contacting the heat-generating part of the equipment with the thermal fuse and sensing the temperature by conduction heat transfer is far more sensitive than the method of sensing by convection or radiation, and it is also less sensitive to ambient conditions. The temperature of the device can be sensed without being affected.

Therefore, the method of using the thermal fuse in close contact with the device is preferable for ensuring the accuracy of the operating temperature.

For this reason, conventionally, it has been practiced to bring the thermal fuse into contact with the heat generating portion of the device so that the heat is transferred and conducted as much as possible, and the thermal fuse itself is intended to be directly attached to the heat generating portion of the device. Are also known.

[Problems to be solved by the invention]

However, in the case of a conventional thermal fuse in which the fuse is used in close contact with the equipment, it has one or more of the following drawbacks, and it is difficult to mount the fuse in close contact, or it is sensitive to temperature. There is a problem that it does not work or is poor in reliability.

That is, in the case of a thermal fuse of a type that senses the ambient temperature and operates, when it is used in close contact with the equipment, special parts for attachment to the equipment must be prepared.

Since the contact surface of the thermal fuse heat receiving surface is a curved surface or has irregularities, the contact area is small and not flat, so the heat conduction is small. Further, since the distance between the device and the fusible body is long, the heat transfer resistance is large and the heat conduction is small.

Even if the material of the heat receiving surface of the thermal fuse is a heat non-conductive material such as plastic, or even if it is a metal, it is an electric charger, so it is still necessary to make contact with the device via an electrical insulating material. . As described above, with the structure in which the device is brought into contact with the insulating material, the heat cannot be transferred sharply due to the close contact between the metals. Some electrical insulators have been devised for heat conduction, but they are not far from metals, and there is a limit to the thickness from the viewpoint of electrical insulation, so only heat conduction can be considered. In addition, the harder ones have drawbacks such as poor compatibility with the contact surface.

As the temperature-sensitive substance, there are a substance using a metal alloy having excellent thermal conductivity and a non-conducting organic substance, but the organic substance has a drawback that thermal conductivity is also poor. In addition, the organic temperature sensitive material is weaker in strength than metal, and if left near the melting point for a long time, it may dry and cannot keep external force, and the contacts may open.

Even if a metal-fusible body is used, the metal-fusible body serves as a charging part, such as a contact member for an electric contact portion. Therefore, when the fusible metal is made of a low melting point metal such as Sn, Pb or Bi, the resistance value is higher than that of a low resistance metal such as copper and the operating temperature is significantly affected by the heat generated by Joule heat. Received, or deteriorated over time due to long-term energization or repeated energization, etc., resulting in low reliability.

Even if a fusible metal is used, the movement of the fusible material after the melting operation is not completely regulated, such as scattering or flowing in the air or in a container when the fusible metal is dissolved. For this reason, there may occur a trouble of leakage between the opened contacts and between the metal to be insulated from the charging part, or deterioration of insulation, and reliability during and after operation is poor.

The present invention has been made in view of the above problems (1) to (3), and an object thereof is to simultaneously solve the above six conditions.

[Means for solving problems]

In order to achieve this object, a metal container having a bottom surface as a heat receiving surface is slidably fitted to the metal container having a bottom surface as a heat receiving surface in an insulating case having a pair of fixed electrodes fixed, and the top portion is fixed to the pair of fixing members. A movable cylindrical body including an insulating cap that is an abutting portion for a movable contact that abuts on the base end of the electrode to bring the fixed electrodes into contact is housed, and the movable contact is separated from the fixed electrodes in the insulating case. A spring for
An elastic member that gives an elastic force for pressing the movable contact against the fixed electrodes against the urging force of the spring, and a meltable member that melts when it is overheated to cancel the elastic force of the elastic member. A metal cover, which is housed in the movable cylinder and is in direct contact with the bottom surface of the metal container or is integral with the bottom surface of the metal container and is attached in close contact with an electric device to be overheat-protected, is provided in the insulating case. It is characterized by being attached to the opening.

If the fusible metal is made into pellets and housed in a metal container, the manufacturing process of the thermal fuse is simplified, and even if the thermal fuses with different operating temperatures are manufactured, only the type of pellet is changed. Can be dealt with.

[Action]

In the present invention, the fusible metal is housed in a metal container made of a heat conductive metal such as copper. This metal container accommodates a resilient member such as a spring, and is covered with a cap made of plastic or ceramic, which is excellent in electrical and thermal insulation, with a small gap that can move during operation over the outer circumference. To form. Further, the bottom surface of the metal container containing the fusible metal is brought into contact with the device via the metal cover or directly, and the heat transfer from the device of the temperature sensing part is conducted mainly between the metals. That is, in the thermal fuse case, the tip of the insulating cap is brought into pressure contact with the movable contact biased in the direction of separating from the fixed electrode, and with respect to the metal cover on the bottom of the thermal fuse case, or The movable cylindrical body is arranged so that the bottom surface of the metal container comes into close contact with the mounting surface.

In addition, the heat receiving part and the equipment enhance heat conduction by conduction and heat transfer between metals, and increase the heat transfer area by making the contact surface parallel to the equipment parallel, and further, it is always stable by the force of the elastic member. So that it closely contacts the heat receiving surface. In this way, there is no intervening space or non-metal electrical insulator or the like having poor heat conduction between the device mounting surface and the fuse heat receiving surface and between the fuse heat receiving surface and the fusible body. Also,
Since the heat transfer distance between the mounting surface and the fusible body is extremely short, the heat transfer resistance can be reduced.

The metal fusible body and the current-carrying part are completely electrically insulated by the insulating cap, and there is no electric current to the metal fusible body.
There is no deterioration of the fusible material due to the electric current. Also, since the electrical contact and the fusible metal are thermally and electrically insulated,
The electrical contact can be made of a resistor such as copper, and Joule heat is reduced. In addition, the heat generated in the current-carrying part has a very small effect on the fusible body. Since the movable cylinder has a nearly sealed structure, the fusible body melted by overheating of the equipment cannot flow out of the movable cylinder due to its viscosity and surface tension, regardless of posture, vibration, or shock. Absent.

It should be noted that the metal fusible body, which is a temperature-sensing body, is formed into a metal pellet, and various pellets are prepared according to the operating temperature to provide a thermal fuse having the same structure and the same manufacturing process but different operating temperatures. can do.

〔Example〕

Hereinafter, the present invention will be specifically described based on the embodiments shown in the drawings.

1 is a vertical sectional front view of an embodiment of the present invention, FIG. 2 is a partial vertical sectional plan view thereof, FIG. 3 is a plan view thereof, and FIG. 4 is I of FIG.
It is sectional drawing in the -I line.

In these figures, in the insulating case 3 having a pair of fixed electrodes 1 and 2 at one end opening,
An electric circuit is formed between the movable contact 4 made of a good electric conductor and a set of movable cylinders 5 so that the movable contact 4 is always in pressure contact with the fixed electrodes 1, 2. This movable cylinder 5
Has a chamber 8 inside, both ends of which are closed by an electrically insulating cap 6 and a metal container 7 having good heat conductivity.
Inside the chamber 8, in order from the bottom, a resilient member 10 made of a metal-fusible body 9, a compression coil spring, a leaf spring or the like is housed (see FIG. 5). Therefore, the movable tubular body 5 is a component that can expand and contract in the longitudinal direction.

When assembling the thermal fuse, the movable cylindrical body 5 is compressed by the insulating case 3 in which the fixed electrodes 1 and 2, the movable contact and the compression coil spring 12 are incorporated.
Attach the metal cover 11. In FIG. 2 and FIG. 3, 11a is a fixed piece integrally formed with the metal cover 11, and is fixed to the insulating case 3 by folding it. The metal cover 11 substantially closes the opening of the insulating case 3. In this way, the metal meltable body 9, the metal container 7, and the metal cover 11 are constantly pressed by the elastic force of the elastic member 10 and come into close contact with each other. By making the tip of the insulating cap 6 spherical, the contact pressure of the movable contact 4 on the fixed electrodes 1 and 2 can be made uniform.

The compression coil spring 12 is for separating the contact member 4 from the fixed electrodes 1 and 2, and is housed with a bending amount larger than the bending amount of the elastic member 10, but the elastic force is the elastic member 10. Since it is much weaker, the movable contact 4 is not normally separated. When attaching to the device, through the mounting hole 13 in the metal cover 11 or the mounting holder,
Tighten with screws, bolts, etc. to fix it tightly to the device.

In addition, in order to regulate the position of the movable cylindrical body 5 in the insulating case 3, both walls of the insulating case 3 are recessed as shown in FIG.

In the thermal fuse configured as described above, when heat is transferred through the metal cover 11 and the temperature of the fusible metal 9 reaches a predetermined temperature and melts, the elastic member 10 expands as shown in FIG. Elasticity disappears. When the elastic member 10 loses its elastic force, the movable contact 4 is separated from the fixed electrodes 1 and 2 by the elastic force of the compression coil spring 12, and the current circuit is cut off. At this time, even if the entire meltable metal body 9 is dissolved, it is designed to be sufficiently accommodated in the metal container 7. Therefore, the meltable metal body melted into a liquid never flows out of the movable cylindrical body 5. Absent.

FIGS. 7 and 8 show another embodiment of the present invention, which is applied to a cylindrical thermal fuse. In this example, the mounting holder 12 is separate from the metal cover 11, and both are rotatably coupled. This is so that the mounting position for the device and the terminal direction can be freely changed.

FIG. 9 shows an example in which the fitting of the insulating cap 6 and the metal container 7 is reversed.

FIG. 10 shows a disk 14 interposed between the metal meltable body 9 and the elastic member 10 so that the elastic force of the elastic member 10 is evenly distributed over the entire surface of the metal meltable body 9. is there.

FIG. 11 shows an example in which the metal cover 11 and the metal container 7 are integrated to further enhance heat conduction.

FIG. 12 shows an example in which the mounting hole 13 is provided in the insulating case 3.

Further, FIG. 13 shows an example in which the bottom surface of the metal container 7 is brought into direct contact with the device, and the elastic force of the elastic member 10 acts to enhance the close contact with the surface of the device. .

〔The invention's effect〕

As described above, in the present invention, a metal meltable body having excellent heat transfer is used, the heat transfer area between planes is widened, and the heat transfer distance is extremely small, and the metal has excellent heat conductivity. They are completely in close contact with each other. Therefore,
The heat of the equipment can be sensed sensitively and is hardly affected by the environmental conditions or the rate of change of the temperature of the equipment. When the thermal fuse of the present invention is attached to a device, it is possible to easily perform close contact with the device without separately preparing a mounting bracket or the like. Moreover, since it can be considered that the temperature of the device and the heat sensing temperature of the thermal fuse are almost the same, the temperature can be easily set without requiring preliminary experiments.

Further, since the heat receiving portion and the fixed electrode are electrically insulated, it is not necessary to electrically insulate the device. In addition, the current-carrying part and the fusible metal are thermally insulated through the insulating material, so they are not affected by Joule heat due to the current flow.
Deterioration of the fusible body due to long-term use and error in the sensed temperature hardly occur.

Further, since the metal-fusible body is sealed in the movable cylinder and does not flow out of the movable cylinder even after the metal-soluble body is melted, troubles such as grounding of the fixed electrode or grounding of the charging part and the equipment may occur. Highly reliable with no occurrence.

[Brief description of drawings]

1 is a vertical sectional front view of an embodiment of the present invention, FIG. 2 is a partial vertical sectional plan view thereof, FIG. 3 is a plan view thereof, and FIG. 4 is I of FIG.
Fig. 5 is a sectional view taken along line -I, Fig. 5 is an exploded perspective view of the movable cylindrical body, Fig. 6 is a vertical sectional front view after operation, and Figs. 7 to 13 are vertical sectional views showing other examples of the movable cylindrical body. It is a front view. 1,2: Fixed electrode, 3: Insulation case 4: Movable contact, 5: Movable cylinder 6: Insulation cap, 7: Metal container 8: Chamber, 9: Metal fusible body 10: Resilient member, 11: Metal cover 12 : Compression coil spring 13: Mounting hole

Claims (2)

[Claims] 1. A metal container having a bottom surface as a heat receiving surface, and a metal container slidably fitted in the metal container having a bottom surface as a heat receiving surface, and an apex of the pair of fixed electrodes. In order to separate the movable contact from the fixed electrodes in the insulating case, the movable cylindrical body including an insulating cap that is an abutting portion for the movable contact that abuts on the base end to bring the fixed electrodes into contact with each other is housed. Is provided, and an elastic member that gives an elastic force for pressing the movable contact to both the fixed electrodes against the biasing force of the spring and an elastic member that melts when overheated to increase the elastic force of the elastic member. A metal cover that accommodates a deliquescent soluble metal body in the movable cylinder and is in direct contact with the bottom surface of the metal container or is integrally attached to the bottom surface of the metal container and is attached in close contact with an electric device to be overheat-protected. In the opening of the insulating case Temperature fuse, characterized in that the Attach. 2. The thermal fuse according to claim 1, wherein the fusible metal body is formed into a pellet shape and housed in a metal container.