JP3018586B2 - Positive resistance temperature coefficient heating element and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element having a positive temperature coefficient of resistance used for heating appliances and general heating appliances, and a method for producing the same.

[0002]

2. Description of the Related Art A conventional technique of this kind is disclosed in
As shown in JP-A-3-102193 and FIG. 3, a pair of electrodes 2 and 3 are formed on the front and back surfaces of a positive resistance temperature coefficient resistor 1 in which conductive fine powder is dispersed in a crystalline polymer. In some cases, the electrically insulating layers 4 and 5 to be coated are formed via hot-melt hot-melt layers 6 and 7. Such a positive resistance temperature coefficient heating element can make the distance between a pair of electrodes close to the voltage breakdown limit of the resistor, so that the heat transfer performance between the electrodes is greatly improved, and due to thermal imbalance, The constraint on output was virtually eliminated.

[0003]

However, although the above-described conventional positive resistance temperature coefficient heating element has a very high output performance, it has a particularly short distance between the electrodes. Local carbonization occurred due to a high electric field in the extreme part, air and humidity, and shape factors such as unevenness, and there was a danger of breakdown from breakdown voltage to ignition and smoke. Further, in order to prevent the occurrence of such a phenomenon at the electrode end, an exposed portion of the resistor is formed at the electrode end to secure a creepage distance, and a sealing configuration using an electric insulating layer is achieved. . However, since the resistor at the position exposed from the electrode is electrically and thermally unstable, the current path and the voltage gradient are not determined, and a discontinuous point in the conduction path is easily generated. Here, if air or humidity is present, microcracks are likely to occur due to a synergistic effect with thermal stress strain concentrated on the exposed portion, and this will trigger discontinuous points in the conduction path. Since the voltage is concentrated at the discontinuous point, the discontinuous point grows, and eventually spreads inside the resistor, damaging the entire heating element and impairing the normal heating function. In particular, the positive resistance temperature coefficient heating element as described above has a slight gap layer at the electrode end, no matter how strong the exterior structure is applied, and the deterioration gradually progresses through the tunnel of this gap layer. Could not be avoided.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a configuration of a positive resistance temperature coefficient heating element that can withstand long-term use and that is highly safe and a method of manufacturing the same.

[0005]

Means for Solving the Problems In order to achieve the above object, a positive resistance temperature coefficient heating element according to the present invention is a resistor having a positive resistance temperature coefficient obtained by adding a conductive fine powder to a crystalline polymer. Layers, a pair of opposed electrodes formed on the front and back surfaces of the resistor layer, a pair of hot-melt layers and a pair of electrical insulating layers that cover the entire resistor layer and the electrodes from the front and back surfaces And a power supply terminal connected to the pair of electrodes , and protrudes from at least one of the pair of electrodes.
The resistor formed so as to intervene in the current path between the electrodes
In the positive resistance temperature coefficient heating element in which the creepage distance of the side end of the antibody layer is larger than the thickness of the resistor layer, the side end of the resistor layer has a slope that is thinned in the outer edge direction. Along with the hot melt layer and the electrical insulating layer.

[0006]

The operation of this technical means is as follows.
That is, the surface resistance at the side end of the resistor layer, which tends to have lower withstand voltage characteristics than inside the resistor layer, is increased by the creepage distance, thereby improving the withstand voltage characteristics. In addition, the slope at which the side end of the resistor layer is thinned eliminates the step when the pair of hot melt layers and the pair of electric insulating layers are stacked, so that the flow path of air or humidity to the end of the electrode is reduced. It is cut off and the main cause of deterioration of the exposed portion of the resistor at the electrode end is cut off.

[0007]

Embodiments of the present invention will be described below.

(Embodiment 1) As shown in FIG. 1, a heating element having a temperature coefficient of positive resistance according to this embodiment has an electrode 8 having a width of 10 mm and a width of 20 mm.
While extruding a positive resistance temperature coefficient resistor material between the electrodes 9 of mm, the electrodes are welded by a hot roll to form a resistor layer 10 having a thickness of 0.5 mm, a width of 15 mm, and a resistor side end of 2.5 mm. Formed. Next, this was cut into a length of 200 mm, and a part of the electrode was also removed in order to form a side end having a width of 2.5 mm in the cut portion. Further, the power supply terminals 11 and 12 made of nickel-plated copper wires having a diameter of 2.0 mm were welded to the terminals of the electrodes 8 and 9 and the side ends of the resistor layer 10 were heated at ± 30 ° C. of the melting point of the crystalline polymer. Then, the thickness thereof was processed into a gradient thinned in the outer edge direction. Next, the hot melt layer 13 and the electrical insulating layer 14 made of a polyester film were used to sandwich the resistor layer 10, and pressure-bonded with a 180 ° C. rubber roll. As a result, as shown in FIG. 1, a positive resistance temperature coefficient heating element was completed in which the resistor layer 10 was hermetically sealed by the hot melt layer 13 and the electric insulating layer 14 with no room for an air layer to intervene. In FIG. 1, the upper hot melt layer 13 and the electric insulating layer 14 are omitted.

The electrodes 8 and 9 are made of copper foil having a thickness of 35 μm, and the resistor layer 10 having a positive resistance temperature coefficient is made of a high-density polyethylene resin which is a crystalline polymer and 28% of a furnace-based conductive carbon black. A polyester resin having a melting point of 140 ° C. was used for the hot melt layer 13. The electrodes, crystalline polymer, carbon black, hot melt layer, electric insulating layer, and power supply terminal are shown here. The materials are not limited to those described above, and all materials having the same effect can be used.

[0010] As a result of conducting an energization test by applying AC 100 V to the heating element of this embodiment, after 14,000 hours, all 50 samples maintain a normal heating function.

(Embodiment 2) As shown in FIG. 2, a heating element having a temperature coefficient of positive resistance according to this embodiment has an electrode 8 having a width of 10 mm and a width of 20 mm.
While extruding a positive resistance temperature coefficient resistor material between the electrodes 9 of mm, the electrodes are welded by a hot roll to form a resistor layer 10 having a thickness of 0.5 mm, a width of 15 mm, and a resistor side end of 2.5 mm. Formed. Next, this was cut into a length of 200 mm, and a part of the electrode was also removed in order to form a side end having a width of 2.5 mm in the cut portion. Further, the power supply terminals 15 and 16 made of nickel-plated copper plates having a thickness of 0.3 mm and a width of 2.5 mm whose side ends are thinned are welded to the terminals of the electrodes 8 and 9, and the side ends of the resistance layer 10 are made of crystalline. ± 30 of the melting point of the polymer
It heated at ℃, and processed the thickness into the gradient thinned in the outer edge direction. Next, after passing through a preheating device at 120 ° C., the hot melt layer 13 and the electric insulating layer 14 of a polyester film are used to sandwich
Pressure bonding was performed with a rubber roll at 0 ° C. As a result, FIG.
As shown in (1), a positive-resistance temperature coefficient heating element whose side ends of the resistor layer and the power supply terminal are hermetically sealed by the hot melt layer 13 and the electric insulating layer 14 in a state where there is no room for an air layer to intervene is obtained. Was. In FIG. 2, the upper hot melt layer 13 and the electrical insulating layer 14 are omitted.

In this case, the pressure and heat bonding temperature is very important, and the preheating of the crystalline polymer constituting the resistor to near the melting point, the instantaneous pressurization by the roll exceeding the melting point, and the instantaneous roll A hot-melt adhesive layer that can be thermally bonded by pressure is indispensable. A material having a melting point of the hot melt layer slightly lower than the melting point of the crystalline polymer gives good results in workability. In the present embodiment, a copper foil having a thickness of 35 μm is used for the electrodes 15 and 16, and the resistor layer 10 is made of a high-density polyethylene resin which is a crystalline polymer to which 28% of furnace conductive carbon black is added. A low-density polyethylene having a melting point of 110 ° C. was used for the hot melt layer 13. The electrodes, the crystalline polymer, the carbon black, the hot melt layer, the electrical insulating layer, and the power supply terminal are not limited to those shown here, and all materials having the same effect can be used. It is.

When a heating test was performed on the positive resistance temperature coefficient heating element of the present embodiment under the same conditions as in the first embodiment, after 12,000 hours, all 86 samples maintained a normal heating function. Has been confirmed. As a comparative example, an energization test was performed under the same conditions on 120 samples having a square power supply terminal without thinning the side end of the power supply terminal. As a result, 65 samples were obtained from 4,000 to 14,000 hours. However, the phenomenon that the exothermic temperature was lowered was observed.

[0014]

As described above, according to the positive temperature coefficient heating element of the present invention and the method of manufacturing the same, the following effects can be obtained.

(1) By reducing the thickness of the side end portion of the resistor layer in the outer edge direction, the sealing performance is improved, and a positive resistance temperature coefficient heating element that can be used for a long time even in a high humidity environment can be obtained.

(2) By heating the side end portions of the resistor layer at ± 30 ° C. of the melting point of the crystalline polymer, the thickness can be processed into a gradient whose thickness is reduced in the outer edge direction.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional perspective view of a positive resistance temperature coefficient heating element according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional perspective view of a positive resistance temperature coefficient heating element of another embodiment.

FIG. 3 is a partial cross-sectional perspective view of a conventional positive resistance temperature coefficient heating element.

[Explanation of symbols]

 8, 9 electrode 10 resistor layer 11, 12 power supply terminal 13 hot melt layer 14 electric insulating layer 15, 16 power supply terminal

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-102193 (JP, A) JP-A-55-25499 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01C 7/02-7/22

Claims (4)

(57) [Claims] 1. A resistor layer having a positive resistance temperature coefficient obtained by adding a conductive fine powder to a crystalline polymer, and a pair of opposed electrodes formed on the front and back surfaces of the resistor layer, It consists of a pair of hot-melt layers and a pair of electrical insulating layers that cover the entirety of the resistor layer and the electrodes from the front and back surfaces, and a power supply terminal connected to the pair of electrodes , and at least the pair of electrodes .
Protrudes from one side and intervenes in the current path between the electrodes
Creepage distance of the side end of the resistor layer formed as
In the heating element having a positive resistance temperature coefficient larger than the thickness of the resistor layer, a side edge of the resistor layer has a slope whose thickness is reduced in an outer edge direction, and the hot melt layer and the electrical insulating layer are along the slope. A positive resistance temperature coefficient heating element characterized by being sealed with: 2. A resistor layer having a positive resistance temperature coefficient obtained by adding a conductive fine powder to a crystalline polymer, and a pair of opposed electrodes formed on the front and back surfaces of the resistor layer, It consists of a pair of hot-melt layers and a pair of electrical insulating layers that cover the entirety of the resistor layer and the electrodes from the front and back surfaces, and a power supply terminal connected to the pair of electrodes , and at least the pair of electrodes .
Protrudes from one side and intervenes in the current path between the electrodes
Creepage distance of the side end of the resistor layer formed as
In the heating element having a positive resistance temperature coefficient larger than the thickness of the resistor layer, a side end of the resistor layer and a side end of the power supply terminal have a slope whose thickness is reduced in an outer edge direction. A heating element having a positive resistance temperature coefficient, which is sealed by a hot melt layer and the electric insulating layer. 3. A pair of electrodes facing each other on the front and back surfaces of a positive resistance temperature coefficient resistor layer obtained by adding conductive fine powder to a crystalline polymer , and at least one of the electrodes is welded.
And formed so as to intervene in the current path between the electrodes.
The creepage distance of the side edge of the resistor layer is larger than the thickness of the resistor layer, a power supply terminal is welded to the electrode, and the side edge of the resistor layer is ± 10% of the melting point of the crystalline polymer. 30 ° C
The thickness of the side end portion of the resistor is reduced so as to be thinner in the outer edge direction, and the whole of the electrode is sealed from the front and back surfaces with a pair of hot melt layers and a pair of electrical insulating layers. The method for producing a positive resistance temperature coefficient heating element according to the item. 4. A front surface and a back surface of a resistor layer having a positive resistance temperature coefficient obtained by adding a conductive fine powder to a crystalline polymer and having a slope power supply terminal whose side end is thinned toward an outer edge. Welded a pair of electrodes facing each other, from at least one of the electrodes
Extruded, formed so as to intervene in the current path between the above electrodes
The creepage distance of the side edge portion of the resistor layer to be formed is larger than the thickness of the resistor layer, and the side edge portion of the resistor layer is heated to ± 30 ° C. of the melting point of the crystalline polymer to form the resistor. 3. The temperature coefficient of positive resistance according to claim 2, wherein the thickness of the side end portion is a gradient reduced in the outer edge direction, and the whole of the electrode is sealed from the front and back surfaces with a pair of hot melt layers and a pair of electric insulating layers. Heating element manufacturing method.