JP2003229042A - Thermal fuse - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating-resin molded thermosensitive pellet-type thermal fuse having a small number of man-hours and components, and having excellent productivity and heat resistance, as compared with the inletting of the thermal fuse into an insulation tube, or the housing of the thermal fuse in the insulation tube and the embedding of the thermal fuse inside the case by an epoxy resin or the like when executing the coating-resin molding of the thermal fuse. <P>SOLUTION: In this thermosensitive pellet-type thermal fuse, at least a part of a peripheral part of the thermal fuse is coated and applied with the resin molding to insulate the thermal fuse from the outside. As a resin-molding material, a thermoplastic resin is used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fuse used to prevent damage to equipment due to excessive temperature rise,
In particular, the present invention relates to a temperature sensitive pellet type thermal fuse using an insulating chemical substance having a specific melting point as a temperature sensitive material.

[0002]

2. Description of the Related Art As a protective element for protecting electric and electronic devices from overheat damage, a thermal fuse that operates at a specific temperature to interrupt a circuit is used. Thermal fuses of this type include those using a temperature-sensitive pellet made of an insulating chemical substance that melts at a specific temperature as a temperature-sensitive material, and one using a low melting point fusible alloy.

[0003] In particular, a typical one of the former temperature-sensitive pellet type thermal fuse will be described with reference to FIG. In FIG. 6, a lead wire 3 is caulked and fixed to one end of a bottomed cylindrical metal case 1 made of a metal having good electrical conductivity and good thermal conductivity. A columnar thermosensitive pellet 5 made of an insulating chemical substance that melts at a specific temperature in order from the side where the lead wire is crimped and fixed inside the metal case 1, and then a strong compression spring 7.
Of the disk-shaped pressing plate 6 for imparting the elastic force of the above to the temperature-sensitive pellets 5 on average, and the elastic force of the strong compression spring 7 and the strong compression spring 7 for the closed circuit interposed between the pressing plates 6 and 6 in a compressed state. Of the same material as the disk-shaped pressing plate 6 for uniformly giving the movable contact 8 to the movable contact 8, the disk-shaped pressing plate 6 of the same shape, and a metal having good conductivity are pressed against the inner surface of the metal case 1 to make contact therewith. A movable contact 8 having a plurality of tongues therein is accommodated. The open end of the metal case 1 is closed by a ceramic porcelain tube 9 made of insulating ceramics or the like, and the inner end of the trapezoidal portion is engaged with the stepped portion formed on the metal case 1. A portion protruding from the ceramic porcelain tube 9 is bent toward the central axis, and prevents the ceramic porcelain tube 9 from moving inward and outward of the metal case 1. Lead wire 2 is ceramic insulator tube 9
Through the center hole of the lead wire 2, the inward end of the lead wire 2 becomes the fixed contact 10 that contacts the movable contact 8, and the enlarged portion 11 is provided in the portion adjacent to the inside and the outside of the ceramic porcelain tube 9. 2 is prevented from moving inward and outward of the ceramic porcelain tube 9. A weak compression spring 12 is arranged between the movable contact 8 and the ceramic porcelain tube 9, and is in a state of being compressed by the strong compression spring 7 in a steady state. Further, a resin 13 or the like is attached to the outer surface of the ceramic porcelain tube 9 to seal it.

[0004] In the above configuration, the temperature-sensitive pellets 5 at room temperature
Is a solid, and the strong compression spring 7 strongly presses the movable contact 8 against the fixed contact 10 against the elastic force of the weak compression spring 12. Therefore, the lead wire 3-metal case 1-movable contact 8-fixed contact 10-lead wire 2 serves as a current path. When the ambient temperature rises abnormally and reaches the melting point of the temperature sensitive pellets 5, the temperature sensitive pellets 5 are melted, so that the strong compression spring 7 expands and its elastic force decreases, so that the weak compression spring 12 expands. The movable contact 8 is separated from the fixed contact 10 as shown in FIG. 7, and the lead wires 2 and 3 are not electrically connected.

[0005] By the way, since the metal case 1 is used as a conduction path as described above, when the electronic case is installed directly or close to a place where an abnormal temperature rise of an electronic or electric device is to be detected, depending on the conditions of the place, the temperature fuse of the temperature fuse may be used. It may be necessary to insulate the metal case from the outside. To solve this problem, a thermal fuse is fitted into an insulating tube made of silicone or the like so as to insulate the metal case from the outside, a case is made using insulating resin, and the thermal fuse is housed inside the case. It has been carried out by embedding it in a case with an epoxy resin or the like, or by covering and molding the thermal fuse with an epoxy resin or the like so as to be installed directly or close to the relevant place.

[0006]

However, when performing insulation or coating resin molding of the temperature sensitive pellet type thermal fuse as described above, when processing or mounting using an insulating tube or when housing in a case or the like. However, there is a problem in that it takes a lot of man-hours and the number of parts is large, and further that the resin curing time is long in the case of molding with room temperature curing type epoxy resin or the like.

[0007] Further, when the insulating tube is used, there is a problem that an air layer or the like is formed between the temperature sensitive pellet type thermal fuse and the insulator, and heat transfer efficiency is deteriorated.

[0008] Further, in the case of a thermosetting epoxy resin or the like that cures the resin by heating, there is a problem that the thermal fuse is broken due to the temperature required for curing. Also, depending on the resin used, thermal decomposition may occur below the temperature fuse operating temperature, causing a problem with the heat resistance of the molded body.Therefore, the operating temperature of the temperature fuse used is limited to those in the low temperature range. It may end up.

[0009] From the above, an object of the present invention is to provide a temperature-sensitive pellet type thermal fuse which has a small number of steps and a small number of parts in coating and molding the temperature-sensitive pellet type thermal fuse, is excellent in productivity, and is excellent in heat resistance. is there.

[0010]

The present invention is characterized in that at least a part of the outer peripheral portion of a thermal fuse is covered and resin-molded to be insulated from the outside, and a thermoplastic resin is used as a material used for resin molding. It is a temperature sensitive pellet type thermal fuse.

[0011] Further, the present invention is characterized in that a metal plate is connected to the metal case of the thermal fuse formed by the resin coating, and is used by being thermally coupled to a place where it is desired to detect an abnormal temperature rise of electronic and electric devices. It is a temperature sensitive pellet type thermal fuse.

[0012] The temperature-sensitive pellet type thermal fuse according to the present invention,
The thermal fuse according to claim 1, wherein at least a part of an outer peripheral portion of the thermal fuse is formed by coating resin using a thermoplastic resin. By molding the thermal fuse with the resin in this manner, the thermal fuse can be insulated from the outside and directly installed at a location where it is desired to detect an abnormal temperature rise of electronic or electric equipment. Further, by molding the thermal fuse with the resin coating, an air layer is not formed between the thermal fuse and the insulator, and the heat transfer efficiency is improved.

The temperature-sensitive pellet type thermal fuse according to the present invention is the thermal fuse according to claim 2, characterized in that a crystalline resin is used as the thermoplastic resin used for coating and molding the thermal fuse. According to this configuration, the curing time of the crystalline resin is shorter than that of other coating molding resins,
It is possible to perform coating molding without causing erroneous disconnection of the thermal fuse due to melting of the temperature-sensitive pellets at the time of coating molding of the thermal fuse.

The temperature-sensitive pellet type thermal fuse according to the present invention,
As the thermoplastic resin used when forming the coating,
The thermal fuse according to claim 3, wherein a liquid crystal polymer is used. According to this configuration, since the curing time of the liquid crystal polymer is shorter than that of other coating molding resin like the above-mentioned crystalline resin, the temperature fuse is erroneously disconnected due to the melting of the temperature sensitive pellet during the molding molding of the temperature fuse. It can be coated and molded without any treatment. In addition, since the liquid crystal polymer has an orientation, a thin molded product can be molded.

The temperature-sensitive pellet type thermal fuse according to the present invention is the thermal fuse according to claim 4, wherein the thermoplastic resin has a melting point or a melting temperature higher than the melting point of the temperature-sensitive material. . Here, the melting temperature is
Indicates the temperature at which a thermoplastic resin having no melting point can be molded. According to this configuration, when the thermal fuse is used, the molding resin has a melting point or a melting temperature higher than the thermal fuse operating temperature.
That is, even if the melting point of the temperature-sensitive material is reached, the temperature-sensitive material is melted, and the thermal fuse is in a non-conducting state, the resin does not melt and a resin-molded thermal fuse having excellent heat resistance is obtained.

[0016] The temperature-sensitive pellet type thermal fuse according to the present invention,
The thermal fuse according to claim 5, wherein the lead wire is provided with a connecting terminal. According to this configuration, when connecting a temperature fuse to a place where the abnormal temperature rise of the electronic or electric equipment is desired to be detected or in the vicinity thereof, the connection to the electronic or electric equipment is simplified, and the lead wire connection work can be speeded up. Is.

[0017] Furthermore, the temperature-sensitive pellet type thermal fuse according to the present invention is the thermal fuse according to claim 6, wherein the shape of the resin molded body has a mounting shape. According to this configuration, when the resin molded body is directly installed at or near a location where an abnormal temperature rise of electronic or electric equipment is to be detected, the resin molded body can be mounted to the installation location by using the mounting shape of the resin molded body. It is possible to strengthen and improve the adhesion.

The temperature-sensitive pellet type thermal fuse according to the present invention,
8. The thermal fuse according to claim 7, wherein a metal plate is connected to the metal case and at least one end is led out to the outside of the resin molded body. According to this structure, the thermal fuse is installed at a location where an abnormal temperature rise of electronic or electric equipment is to be detected, and the metal plate is brought into direct contact with and thermally connected to the location to improve heat transfer efficiency. It is to detect the abnormal temperature rise at a location promptly and activate the thermal fuse.

[0019] Next, the temperature-sensitive pellet type thermal fuse according to the present invention is characterized in that at least one end connected to the metal case has a mounting portion on a metal plate led out of the resin molded body. 8 is a thermal fuse. According to this configuration, when the metal plate is mounted and directly contacted with a place where an abnormal temperature rise of electronic or electric equipment is to be detected, it is securely fixed by using the mounting portion, and the metal plate and the place are closely attached. As a result, the heat transfer efficiency is improved due to the improved efficiency, and the mounting work is simplified.

Embodiments according to the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 is a partially cutaway side view showing a first embodiment of a temperature-sensitive pellet type thermal fuse according to the present invention. In FIG. 1, reference numeral A denotes a temperature-sensitive pellet type thermal fuse, which is housed in the metal case 1 and includes a temperature-sensitive pellet using an insulating chemical substance as a temperature-sensitive material, a strong compression spring and a movable contact, and a metal case 1. A lead wire 2 provided with an insulating porcelain tube closing the opening, a fixed contact penetrating the insulating porcelain tube and contacting the movable contact at an inward end, and a weak compression interposed between the insulating porcelain tube and the movable contact. It is composed of a spring and a lead wire 3 which is caulked and fixed to the metal case 1 and is led out. Reference numeral 4 denotes a thermoplastic resin which is insulation-coated by injection molding on at least a part of the outer peripheral portion of the metal case 1 of the temperature-sensitive pellet type thermal fuse A.

[0021] The thermoplastic resin 4 has a melting point or melting temperature higher than that of the temperature-sensitive material of the temperature-sensitive pellet type temperature fuse, but the temperature-sensitive pellet type temperature fuse is insert-molded by injection molding. Insulation coating can be performed without accidentally disconnecting the temperature-sensitive pellet type temperature fuse due to melting of the temperature-sensitive material. In addition, by performing insulation coating molding by injection molding, insert a temperature-sensitive pellet type temperature fuse into the insulating tube to insulate the metal case from the outside, and store the temperature-sensitive pellet type temperature fuse in the insulating case with resin. The number of parts and the number of assembly steps can be reduced as compared with embedding.

A crystalline resin can be used as the thermoplastic resin 4. By using the crystalline resin, the resin curing time during coating molding can be shortened, and the heat resistance of the coated molding can be improved.

As the crystalline resin, a material having a benzene ring can be used. As an example, polyphenylene sulfide (hereinafter referred to as PPS) is suitable. Further, polyether ether ketone or the like can be used as the material of the same system.

Aromatic polyester can also be used as the crystalline resin. Polyethylene naphthalate is suitable as an example of the aromatic polyester. Further, polyethylene terephthalate or the like can be used as the material of the same system.

[0025] An aliphatic polyamide can also be used as the crystalline resin. Polyamide 66 as an example of aliphatic polyamide
Is preferred. In addition, polyamide 6 as a material of the same system
Etc. can be used.

[0026] Further, as the crystalline resin, a polymer material having an ether bond in the main chain can be used. Polyoxymethylene and the like are suitable as an example of the polymer material having an ether bond in the main chain.

Next, a liquid crystal polymer may be used as the thermoplastic resin. By using the liquid crystal polymer, it is possible to shorten the resin curing time at the time of molding the coated resin and improve the heat resistance of the coated molded body, as in the case of using the crystalline resin. Further, since it has better fluidity than the crystalline resin, a thin molded product can be obtained. As an example of the liquid crystal polymer, polyparaphenylene terephthalamide classified into aromatic polyamide is suitable.

[0028] As the thermoplastic resin, it is possible to use a mixture of the above-mentioned crystalline resin or one kind of liquid crystal polymer as a main component and at least one other kind of crystalline resin or liquid crystal polymer.

[0029] It is also possible to use the thermoplastic resin 4 containing, as a main component, one of the above-mentioned crystalline resins or liquid crystal polymers, and one or more additives such as fibers, fillers and pigments added thereto. In particular, those to which glass fiber or an inorganic filler is added can improve heat resistance and heat transfer properties. Also,
For coloring with pigments, for example, by changing the color according to the operating temperature of the temperature sensitive pellet type thermal fuse, it is possible to distinguish the operating temperature at a glance. Can be prevented from being mistakenly incorporated.

[0030] By connecting the lead wires 2 and 3 of the thermosensitive pellet type thermal fuse A, which is insulated and coated with the thermoplastic resin 4, to terminals of electronic and electric devices by screwing, soldering, welding, etc., electronic and electrical If connected to equipment in series and installed directly or in the vicinity of a place where you want to detect abnormal temperature rise of electronic or electrical equipment, you can energize electronic or electrical equipment via temperature sensitive pellet type thermal fuse A. You can In addition, if the temperature at the point where you want to detect an abnormal temperature rise rises to the operating temperature of the temperature-sensitive pellet type thermal fuse due to the occurrence of an abnormality caused by a short circuit of electronic or electrical equipment, the temperature-sensitive pellet melts and the compression spring By extension, the movable contact is separated from the fixed contact, and the lead wires 2 and 3 are brought into a non-conductive state, and the circuit is opened. As a result, the power supply to the electronic and electric devices is stopped, the temperature rise of the electronic and electric devices is prevented from further increasing, and the heat damage to the electronic and electric devices or the occurrence of a fire due to the damage is prevented in advance.

[0031] Since the temperature-sensitive pellet type thermal fuse A is insulation-coated with the thermoplastic resin 4, it can be placed in direct contact with a place where an abnormal temperature rise is desired to be detected,
As a result, the heat transfer efficiency is improved, and the accuracy of detecting an abnormal temperature rise is improved.

Since the thermoplastic resin 4 is insulation-coated and molded, the resin has a higher heat resistance temperature as compared with a conventional insulation-coated epoxy resin or the like, and thus reaches the operating temperature of the temperature-sensitive pellet type thermal fuse. There is no thermal deterioration of the resin that was insulation coated before, so the temperature at the point where you want to detect an abnormal temperature rise reaches the operating temperature of the temperature-sensitive pellet type thermal fuse, and the thermal pellet melts and becomes non-conductive inside the thermal fuse. Even if it happens, there is no possibility that the metal case and the outside are short-circuited due to the heat deterioration of the resin molded by the insulation coating, and it becomes impossible to stop the energization of electronic and electric devices.

[0033]

Second Exemplary Embodiment Next, a second exemplary embodiment of the present invention will be described with reference to FIG. 2a and 3a in FIG.
Is a connection mounting terminal connected to the lead wires 2 and 3 of the temperature-sensitive pellet type thermal fuse A by crimping, welding, etc., and the thermoplastic resin 4 is injected onto the temperature-sensitive pellet type thermal fuse A by insulation molding. It is molded.

[0034] According to the above configuration, the temperature-sensitive pellet type thermal fuse A can be electrically and mechanically connected to an electronic or electric device by screwing or the like, and the connection is facilitated by soldering or the like. The number of man-hours to be worked can be shortened.

[0035] When the temperature sensitive pellet type temperature fuse A is injection-molded using the thermoplastic resin 4 for the connecting portions 2a and 3a attached to the lead wires 2 and 3 as described above, the temperature sensitive pellet type temperature is By using it for positioning the fuse, it is possible to improve the positional accuracy of the temperature sensitive pellet type thermal fuse in the insulating coating molded body.

[0036]

Third Embodiment of the Invention Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those in FIG. 1 are designated by the same reference numerals. In FIG.
4a and 4b are for forming an insulating coating on the temperature-sensitive pellet type thermal fuse A by injection molding of the thermoplastic resin 4.
The mounting portion is formed in the molded shape.

[0037] According to the above configuration, when the temperature sensitive pellet type thermal fuse, in which the thermoplastic resin is insulation-molded by the injection molding, is installed by directly contacting with the place where it is desired to detect the abnormal temperature rise of the electronic or electric equipment, the molding resin is used. It is possible to make close contact with and fix it to the relevant part by utilizing the attachment site of, so that the abnormal temperature rise of the relevant part can be detected efficiently.

[0038]

Fourth Embodiment FIG. 4 is a perspective view showing a fourth embodiment of the present invention. In FIG. 4, 15 is a metal case 1.
A heat-sensitive pellet type thermal fuse B, which is a metal plate having good thermal conductivity and is connected by welding or the like, and which is manufactured using the metal case 1 to which the metal plate 15 is connected, by injection molding using the thermoplastic resin 4. The temperature sensitive pellet type thermal fuse B is formed by coating resin molding, and a mounting portion 15a is provided on a portion of the metal plate 15 which is led out from the resin molded body.

[0039] According to the above configuration, the temperature-sensitive pellet type thermal fuse is installed at a location where an abnormal temperature rise of electronic or electrical equipment is desired to be detected, and the metal plate 15 is screwed and soldered at the location by the mounting portion 15a of the metal plate 15. By connecting by welding, etc., the fixing can be surely fixed, and since it is thermally connected to the relevant place, the abnormal temperature rise of the relevant place can be detected promptly.

[0040] Further, the temperature-sensitive pellet type temperature fuse is installed at a place where it is desired to detect an abnormal temperature rise of electronic or electric equipment, and when the metal plate 15 is connected to the place, the metal plate 15 is insulated from the place. In the case of connection, an insulating screw, an insulating washer, or the like is used between the mounting portion 15a of the metal plate 15 and the relevant portion to connect to the relevant portion.

[0041] Next, the same effect can be obtained when the metal plate 15 is mechanically wound around the metal case 1 and at least one end of the metal plate 15 is led out to the outside of the molded body and the resin is molded.

[0042]

First Embodiment Next, a first embodiment according to the present invention will be described with reference to FIG. In FIG. 2, the temperature-sensitive pellet type temperature fuse has an insulating property as a temperature-sensing material in a metal case 1 made of brass having a diameter of 1.0 mm and a lead wire 3 made of brass and caulked and fixed at one end thereof. Temperature sensitive pellets using chemical substances, strong compression springs and movable contacts, an insulating porcelain tube made of alumina ceramics that closes the opening of the metal case 1, and a fixing that penetrates the insulating porcelain tube and contacts the movable contact at the inward end. Wire diameter 1.0 mm made of copper with contacts
Of the lead wire 2 and a weak compression spring interposed between the insulating porcelain tube and the movable contact have an operating temperature of 70.
Of about 240 ° C. PPS, which is a crystalline resin, is used as the thermoplastic resin 4 used for insulating-molding the metal case 1 of the temperature-sensitive pellet type thermal fuse A by injection molding. PPS is a polymer compound having physical properties with a melting point of about 290 ° C and a vitrification temperature of about 92 ° C.

[0043] The thermoplastic resin PPS is melted and injection-molded to form a resin molding of a temperature-sensitive pellet type thermal fuse arranged in an injection-molding die. The resin melted by the injection molding die is molded into a shape having the mounting portion 4a. By making in this way, for the one in which the temperature sensitive pellet type thermal fuse is housed in the insulating tube or the insulating case and embedded and hardened with the epoxy resin or the like,
The number of parts and man-hours can be reduced, and the curing time can be shortened. Also, since a thermoplastic resin having a melting point or melting temperature higher than that of the temperature sensitive material of the temperature sensitive pellet type thermal fuse can be used, the heat resistance can be improved. Even if an overshoot that exceeds the operating temperature occurs, the coated resin molded body can sufficiently maintain insulation. Then, by using the mounting shape 4a of the coated resin molded body, by screwing and fixing it to a place where it is desired to detect an abnormal temperature rise of an electronic or electric device, and closely adhering the heat, the heat transfer efficiency is improved. The abnormal temperature rise is rapidly detected, and the activation of the temperature fuse thereby stops the energization of the electronic and electric devices to prevent the electronic and electric devices from being damaged by heating.

[0044]

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 shows the connection between the lead wires 2 and 3 of the temperature-sensitive pellet type thermal fuse A to which the connection terminals 2b and 3b are connected by spot welding or the like, and the connection terminals 2b and 3b connected to the lead wires 2 and 3. The thermosensitive pellet type thermal fuse, the lead wires 2 and 3, and the connection terminal 2 are installed in an injection molding die that can be positioned by utilizing them, and injection molded using PPS which is a crystalline resin as the thermoplastic resin 4.
The temperature-sensitive pellet-type thermal fuse is manufactured by forming a resin-molded body of b and 3b and having a mounting portion 4a on the resin-molded body. At this time, injection molding is performed so that the connection portions of the connection terminals 2b and 3b are led out of the resin molded body.

With such a configuration, the leads 2 and 3 can be easily connected to the electronic and electric devices by using the connection terminals 2b and 3b, and the electronic and electric devices are abnormal. By mounting the resin molded body at a location where it is desired to detect a temperature rise by using the mounting portion 4a, fixing and adhesion can be easily performed, and an abnormal temperature rise at the location can be promptly detected, thereby operating the temperature fuse. As a result, the energization of the electronic and electric devices is stopped and the electronic and electric devices are prevented from being damaged by heating.

[0046]

As described above, according to the temperature-sensitive pellet type thermal fuse of the present invention, when the metal case is insulated from the outside, a thermoplastic resin is used to cover the whole or at least a part of the outer peripheral portion of the metal case. By coating and resin molding, the number of parts and man-hours can be reduced compared to the method using an insulating tube, and the resin curing time can be shortened compared to the method of molding a thermal fuse in an insulating case with epoxy resin or the like. The number of parts can be reduced. Further, according to the temperature-sensitive pellet type thermal fuse of the present invention, the one having excellent heat resistance can be obtained by using the thermoplastic resin having the melting point or the melting point higher than the operating temperature of the temperature-sensitive pellet type thermal fuse. It is a thing.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a thermal fuse showing a first embodiment of the present invention.

FIG. 2 is a perspective view of a thermal fuse showing a second embodiment of the present invention.

FIG. 3 is a perspective view of a thermal fuse showing a third embodiment of the present invention.

FIG. 4 is a perspective view of a thermal fuse showing a fourth embodiment of the present invention.

FIG. 5 is a perspective view of a thermal fuse showing a second embodiment of the present invention.

FIG. 6 is a vertical cross-sectional view showing a conventional temperature-sensitive pellet type thermal fuse.

FIG. 7 is a vertical cross-sectional view showing a state after operation of a conventional temperature-sensitive pellet type thermal fuse.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Metal case 2, 3 Lead wire 4 Thermoplastic resin 5 Temperature sensitive pellet 6 Disk 7 Strong compression spring 8 Moving contact 9 Ceramic porcelain tube 10 Fixed contact 11 Enlarged part 12 Weak compression spring 13 Resin 14 Insulator porcelain tube 15 Metal plate 2a, 3a, 2b, 3b Connection terminals 4a, 15a Mounting area A Temperature-sensitive pellet type temperature fuse B Temperature-sensitive pellet type temperature fuse attached to a metal plate

Claims (8)

[Claims] 1. A metal case, a temperature-sensitive pellet, a strong compression spring and a movable contact housed in the metal case, an insulating porcelain tube for closing an opening of the metal case, and an inward end penetrating the insulating porcelain tube. In a thermal fuse having a lead wire having a fixed contact in contact with the movable contact, and a weak compression spring interposed between the insulating porcelain tube and the movable contact, at least a part of an outer peripheral portion of the thermal fuse is provided. A thermal fuse characterized by being molded with a covering resin using a thermoplastic resin. 2. The thermal fuse according to claim 1, wherein a crystalline resin is used as the thermoplastic resin in the resin molding of the thermal fuse. 3. The thermal fuse according to claim 1, wherein a liquid crystal polymer is used as a thermoplastic resin in the resin molding of the thermal fuse. 4. The thermal fuse according to claim 1, wherein the melting point or melting temperature of the thermoplastic resin is higher than the operating temperature of the thermal fuse. 5. The thermal fuse according to claim 1, wherein the lead wire of the thermal fuse is provided with a terminal for connection. 6. The thermal fuse according to claim 1, wherein the thermal fuse has a mounting shape in a resin molding shape when molding the thermal fuse with the resin. 7. The thermal fuse according to claim 1, wherein a metal piece is connected to the surface of the metal case, and at least one end of the metal piece is led out from a resin molded body. 8. The metal piece, which is connected to the surface of the metal case and has at least one end led out from the resin molded body, wherein the metal piece has a mounting shape at the led-out portion. Thermal fuse.