JP4527594B2 - Thermal fuse built-in resistor - Google Patents

Description

  The present invention relates to a resistor with a built-in thermal fuse.

The fuse resistor is used to prevent the occurrence of an accident such as a fire by interrupting energization when the resistance element is heated to a predetermined allowable temperature due to overcurrent. Thermal resistors with built-in thermal fuses as shown in (a) to (d) (for example, see Patent Document 1) are widely used.
2 (a) is a longitudinal sectional view of a resistor with a built-in thermal fuse, FIG. 2 (b) is a cross-sectional view of FIG. 2 (a), and FIG. 2 (c) is FIG. FIG. 2D is a front view of the resistor with a built-in temperature fuse.
Japanese Utility Model Publication No. 48-105038

In FIG. 2, 1 ′ is a ceramic case having an opening. A ′ is a series connection body of the wire-wound resistance element 2 ′ and the cylindrical thermal fuse 3 ′, which is accommodated in the case 1 ′, and the lead conductor 21 ′ of the resistance element 2 ′ and the lead conductor 31 of the thermal fuse 3 ′. 'Is pulled out from the slits 12' and 13 'on the front side wall of the case. 4 ′ is a heat-resistant sealing material filled in the case 1 ′.
When an overcurrent flows through this temperature fuse built-in resistor, the resistance element 2 'generates heat, and the generated heat is released from the resistance element 2' to the outside of the case 1 ', with a time constant determined by the thermal resistance and heat capacity. The temperature rises.
During this time, the connecting element 211 ′, 311 ′ between the resistance element 2 ′ and the thermal fuse 3 ′ and the sealing material portion between the resistance element 2 ′ and the thermal fuse 3 ′ are connected to the thermal fuse 3 ′. A part of the generated heat is propagated, and the temperature fuse 3 'is also heated.
When the temperature of the fuse element of the temperature fuse reaches the melting point, the fusing of the temperature fuse is started, and when the fusing is completed, the energization is cut off. From the start of fusing to the completion of fusing, the resistance element continues to generate heat and the temperature continues to rise.However, the heat generation of the resistance element is stopped when the fusing is completed, and the amount of heat that has been charged according to the heat capacity is released. The whole is cooled to room temperature with a predetermined time constant.

FIG. 3 shows the temperature increase / decrease process.
The heating-cooling course of (i) the resistance element in FIG. 3, in FIG. 3 (b) shows a heating-cooling course of temperature fuse, respectively, the operation starting point of time t ₀ is a temperature fuse, t ₁ is an operation completion time of the temperature fuse, respectively until the operation completion time t ₁ of the thermal fuse was raised at a predetermined time constant, the time t ₁ later, are respectively lowered at a predetermined time constant.
As shown in (c) of FIG. 3, a sealing material was heated even to time t _1, time t ₁ and later gradually lowering the temperature.
The temperature of temperature rise / fall of the encapsulant differs depending on the location, but unlike the thermal fuse, there is no heat transfer from the resistance element through the metal conductor, so the operation complete temperature T ₁ which is the maximum temperature of the thermal fuse Can be kept at a low temperature.
The temperature fuse of the resistor with a built-in temperature fuse is a cylindrical temperature fuse whose operating temperature (temperature when the current is cut off in oil that rises 1 ° C per minute at a current of 0.1 A or less) is approximately 135 ° C. Because the sealant is made of quartz powder as the main component and silicone resin as the binder, the quartz powder is not carbonized, and a material with excellent heat resistance is selected for the binder. There is no problem of heat resistance on the carbonized surface of the sealing material.

However, during the operation of the thermal fuse, the sealing material is heated to 100 ° C. or higher, and this heating evaporates easily vaporizable substances such as moisture in the sealing material, and the evaporated gas condenses depending on the ambient temperature. As a result, it becomes a mist, and there is a fear that it is illusioned with the white smoke of a fire.
In particular, the silicone resin as the binder is produced by mixing and dispersing an uncrosslinked reactive silicone emulsion in an inorganic powder, and dehydrating and condensing between silanol groups of the reactive silicone. The generation of the white smoke is remarkable.

  An object of the present invention is to accommodate a series connection body of a resistance element and a thermal fuse in a heat-resistant case having an opening, pull out a lead conductor of the series connection body from a slit of the case, and heat resistance is mainly composed of inorganic powder. In a fuse resistor that is filled with a sealing material with an effect resin as a binder and operates a thermal fuse with abnormal energization heat generation of the resistance element, even under high load application, from the sealing material It is intended to reduce or substantially reduce the generation of white smoke by suppressing evaporation of easily vaporized components.

  A resistor having a built-in temperature fuse according to claim 1 accommodates a series connection body of a resistance element and a temperature fuse in a heat-resistant case having an opening, and draws out a lead conductor of the series connection body from a slit of the case. In a fuse resistor in which a case is filled with a sealing material containing powder as a main component and a heat-resistant resin as a binder, and a thermal fuse is operated by abnormally energizing heat generation of the resistance element, the filling and sealing at the case opening An airtight shielding plate is embedded on the surface of the stop material.

  The resistor with a built-in thermal fuse according to claim 2 is the resistor with a built-in thermal fuse according to claim 2, wherein the binder of the sealing material is a silicone resin.

A resistor with a built-in thermal fuse according to a third aspect is characterized in that, in the resistor with a built-in thermal fuse according to the first or second aspect, the shielding plate has better thermal conductivity than the sealing material.
A resistor with a built-in thermal fuse according to claim 4 is the resistor with a built-in thermal fuse according to claim 3, wherein the shielding plate is a ceramic plate.

  A temperature fuse built-in resistor according to claim 5 is the temperature fuse built-in resistor according to any one of claims 1 to 4, wherein the temperature fuse is a cylindrical temperature fuse having an operating temperature of 110 ° C to 160 ° C. And

  A temperature fuse built-in resistor according to claim 6 is the temperature fuse built-in resistor according to any one of claims 1 to 5, wherein the case is made of ceramics having a bottom wall and a four-side wall, and the lead conductor of the temperature fuse It has a lead slit and a lead conductor lead slit of the resistance element on the front side wall.

Even if a high load is applied to the fuse resistor and the encapsulant is heated, the encapsulant has heat resistance that is not carbonized by the heating, but there is no problem with heat resistance. When readily vaporizable components such as water are evaporated, depending on the ambient temperature, water vapor may condense and atomize, resulting in the illusion of white smoke from fire.
However, (b) the evaporation of moisture is blocked by the shielding plate. (B) By making the shielding plate have good thermal conductivity, the surface temperature of the sealing material can be lowered by increasing the heat dissipation to the outside air. Since the amount of evaporation can be suppressed, the generation of white smoke is reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A is a longitudinal cross-sectional view of an embodiment of a resistor with a built-in thermal fuse according to the present invention, FIG. 1B is a cross-sectional view of FIG. 1A, and FIG. ) Is a cross-sectional view of FIG. 1 (a), and FIG. 1 (d) is a front view of the same embodiment.
In FIG. 1, is a heat-resistant upper open case made of ceramics, for example, having a low wall and a four-sided side wall, and provided with lead conductor insertion slits 12 and 13 on the front side wall.
Reference numeral 2 denotes a resistance element. Cap electrodes with lead conductors are attached to both ends of a heat-resistant core such as ceramics, resistance wires are wound on the core, and both ends thereof are connected to each cap electrode by welding or the like.
Reference numeral 3 denotes a thermal fuse, for example, a cylindrical thermal fuse, in which a lead conductor is welded to both ends of a fuse element made of a fusible alloy piece, a flux is applied to the fuse element, and a heat resistant cylinder, for example, ceramic The tube is inserted, and the space between both ends and each lead conductor is sealed with a heat-resistant sealing material, for example, an epoxy resin containing an inorganic filler.
The resistance element 2 and the thermal fuse 3 are connected in series at the other lead conductors 211 and 311 so that the distance between the one lead conductors 21 and 31 is a predetermined distance. This connection can be made by welding, and in order to prevent thermal damage to the fuse element of the thermal fuse, the other lead conductor 311 of the thermal fuse 3 is made sufficiently long and short-time welding, for example, spot welding. Resistance welding, laser welding, etc. are used. A caulking connection or a torsional connection can also be used.
The resistance element / thermal fuse connector A is accommodated in the case 1, and the lead conductor 21 of the resistance element 2 and the lead conductor 31 of the thermal fuse 3 are drawn out from the slits 12 and 13, respectively.
Reference numeral 4 denotes a sealing material filled in the case 1, in which a binder of a curable resin is blended with an inorganic powder. As the inorganic powder, powdered quartz, alumina, mica, zirconia, titanium dioxide or the like can be used, and a silicone resin can be used as the binder. The amount of inorganic powder is 80% by weight or more, and the amount of silicone resin is 1 to 4% by weight.
In order to fill the case 1 with the sealing material 4, an inorganic powder, a silicone emulsion, and a catalyst (salts such as tin, zinc, iron, lead, and organic amine acid) are mixed and injected into the case. The silicone emulsion is cured at room temperature or under heating. This curing is based on cross-linking by dehydration condensation reaction of silanol groups, and water is generated.
In FIG. 1, reference numeral 5 denotes a shielding plate embedded on the surface of the filling sealing material 4, which is placed on the upper surface of the injection sealing material at the end of the injection of the sealing material, and with the hardening of the sealing material. It is fixed. The outer outline of the shielding plate 5 is the same as or slightly smaller than the opening outline of the case 1.
As the material of the shielding plate 5, it is preferable to use a material having higher thermal conductivity than the sealing material, for example, a ceramic plate, an aluminum plate, or a copper plate.

When a high load is applied to the temperature fuse built-in resistor according to the present invention, the resistance element generates heat, and the generated heat heats the temperature fuse and heats the sealing material.
In this case, the temperature change of the resistance element, a thermal fuse and sealing material, there are following relationships as explained by FIG. 3, the number to a maximum temperature T _R is operating completed at a temperature T ₁ of the temperature fuse resistor element The temperature is 10 degrees higher, and the operating temperature (temperature when the current is cut off in oil that rises 1 ° C per minute at a current of 0.1 A or less) of 110 ° C to 160 ° C is used for the thermal fuse. Therefore, it can be understood that substantially all of the sealing material is exposed to a temperature higher than 100 ° C.
The time during which the encapsulant is heated to over 100 ° C. varies depending on the load power applied to the resistance element. However, even if the load power is small, the temperature rise rate becomes slow, so the encapsulant exceeds 100 ° C. Therefore, the time until the final temperature (temperature when the operation of the thermal fuse is completed) is long, and the problem of white smoke cannot be neglected even when the load power is relatively small.
As the load power increases, the rate of temperature rise increases, so the time until the encapsulant exceeds 100 ° C and reaches the final temperature (the temperature at the completion of the thermal fuse operation) is shortened, but the white smoke concentration Become stronger.
Thus, in the temperature fuse built-in resistor according to the present invention, since the surface of the filling sealing material is covered with an airtight shielding plate, it is possible to prevent evaporation of moisture well, regardless of overloading. White smoke generation can be sufficiently reduced.

The opening case is made of ceramic with a length of 25 mm, the width of 14 mm, and the height of 9.0 mm, the resistance element is a 10 Ω winding type resistor with an outer diameter of 4.6 mmφ, and the thermal fuse has an outer diameter of 2 ° A cylindrical thermal fuse of 0.5 mmφ was used. The lead conductor diameter of the thermal fuse was 0.6 mmφ, the lead conductor diameter of the resistance element was 0.8 mmφ, and the distance between the lead conductors was 5.5 mm.
The sealing material is 96.0 wt% quartz powder and 4.0 wt% silicone resin. The shielding plate is a 96% alumina ceramic plate with a length of 18.5mm, a width of 10.2mm and a thickness of 0.8mm. used.
This thermal fuse built-in resistor has a rating of 1.6 W.
When a load of 250 W was applied at room temperature of 25 ° C. (number of samples: 20), generation of smoke weaker than the rising smoke of incense was only observed for 3.0 to 5.0 seconds.
On the other hand, in the case of omitting the shielding plate, generation of smoke more than cigarette smoke continued for 13.9 seconds to 14.6 seconds, and there was a high probability that it would be an illusion of fire.

1 is a diagram illustrating an embodiment of a resistor with a built-in thermal fuse according to the present invention. 2 is a diagram illustrating a conventional resistor with a built-in thermal fuse. It is drawing which shows the temperature change of a resistive element, a thermal fuse, and a sealing material at the time of the overload of the resistor with a built-in thermal fuse.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 12 Slit 13 Slit 2 Resistive element 21 Resistive element lead conductor 3 Thermal fuse 31 Thermal fuse lead conductor 4 Sealing material 5 Shielding plate

Claims (6)

A series connection body of a resistance element and a thermal fuse is accommodated in a heat-resistant case having an opening, a lead conductor of the series connection body is drawn out from a slit of the case, and inorganic powder is a main component and a heat-resistant resin is used as a binder. In a fuse resistor in which a sealing material is filled in a case and a thermal fuse is operated by abnormally energizing heat generation of a resistance element, an airtight shielding plate is embedded on the surface of the filling sealing material in the case opening. Features a built-in thermal fuse resistor. 2. The thermal fuse built-in resistor according to claim 1, wherein the binder of the sealing material is a silicone resin. 3. The temperature fuse built-in resistor according to claim 1, wherein the shielding plate has better thermal conductivity than the sealing material. 4. The temperature fuse built-in resistor according to claim 3, wherein the shielding plate is a ceramic plate. The temperature fuse built-in type resistor according to any one of claims 1 to 4, wherein the temperature fuse is a cylindrical temperature fuse having an operating temperature of 110 ° C to 160 ° C. 6. The case according to claim 1, wherein the case is made of ceramics having a bottom wall and a four-side wall, and has a lead conductor lead slit for a thermal fuse and a lead conductor lead slit for a resistance element on a front side wall. Temperature fuse built-in resistor.

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