JPH07122351A - Plane heater - Google Patents

Abstract

PURPOSE:To prevent the increase in cost by eliminating individual fixation or preliminary manufacturing of a case. CONSTITUTION:A pair of electrically connected electrode plates 3 are provided on the electrodes 2a of a plate-shape heating element 2 having a positive characteristic thermistor. A resin formation part 1 having electric insulation property is formed so that the electrode plate 3 and the heating element 2 are covered in an integrated manner and fixed. The electrodes 2a of the heating element 2 are formed on one surface of the heating element 2. Since the resin formation part is formed so that the electrode plate 3 and the heating element 2 are thereby covered in an integrated manner and thus are fixed, the heating element 2 can be fixed while electric insulation property between the respective electrode plates 3 and between the outside and the heating element 2 is ensured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet heater using a heating element having a positive temperature coefficient thermistor and having the heating element enclosed in a synthetic resin molded body.

[0002]

2. Description of the Related Art Conventionally, there is known a planar heater using a plate-shaped heating element made of a barium titanate-based ceramic semiconductor which is a positive temperature coefficient thermistor having a self-temperature control function. This planar heater does not require a temperature control circuit for keeping the heat generation temperature constant or an overheat prevention circuit for preventing overheating, and has extremely high safety because there is no risk of overheating. .

Further, in the above-mentioned sheet heater, electrodes are provided on the front surface and the back surface of the heating element, and lead wires are soldered to these electrodes to connect to an external power source to insulate the electrodes from the object to be heated. At the same time, in order to make the surface (heating surface) smooth and to uniformly transfer the heat generated by the heating element to the object to be heated,
A case made of a molded article of ceramics such as alumina having excellent electric insulation, heat resistance, mechanical strength and thermal conductivity,
Alternatively, the heating element is covered with an insulating sheet made of a thermoplastic resin or the like.

In the above-mentioned conventional sheet heater, since the lead wire is directly soldered to the electrodes provided on the front and back surfaces of the heating element, a convex portion is formed at that portion, and
If a space (gap) is formed between the case or the insulating sheet and the heating element, the thermal conductivity between the heating element and the object to be heated is reduced, so the case or the insulating sheet covers the heating element. In this case, a concave portion is provided on the inner surface of the case or the insulating sheet in accordance with the soldering convex portion, and attention is paid to the adhesion between the case or the insulating sheet and the heating element.

[0005]

However, in the above-described conventional planar heater, when the heating element is covered with an insulating sheet, for example, the heating element is fixed to the insulating sheet so that the heating element does not move in the insulating sheet. Therefore, an adhesive or the like must be used for that purpose. Further, when the heating element is covered with a case made of a ceramic molded product, it is necessary to separately manufacture this case.

From the above, in each of the above-mentioned conventional configurations, there are problems that the number of parts and the number of steps for manufacturing the planar heater are increased and the cost is increased.

Further, since the above-mentioned case is formed of a ceramic molded product, it is poor in workability, and since it takes time to form unevenness in its shape, the case where the heating element has a low operating temperature and has heat resistance is not required. In this case, the above problem becomes more serious.

Therefore, an object of the present invention is to ensure the insulation while maintaining the smoothness of the surface (heating surface), efficiently transfer the heat generated by the heating element to the object to be heated, and It is an object of the present invention to provide a planar heater that can fix a heating element to an insulating material that covers and can be reduced in size, weight, and thickness.

[0009]

The planar heater of the present invention comprises:
In order to solve the above problems, a pair of strip-shaped conductive members electrically connected to each electrode of a plate-shaped heating element that is a positive temperature coefficient thermistor And a covering member provided with a synthetic resin having electric insulation is integrally molded so as to cover and fix the conductive member and the heating element, and each electrode of the heating element is the heating element. It is characterized in that it is formed on one side of each.

[0010]

According to the above construction, the heating element can be made to generate heat by energizing each electrode of the heating element through each conductive member, and since the heating element is composed of a positive temperature coefficient thermistor, the heating element is predetermined. It can be maintained at temperature.

Further, in the above structure, since the covering member is integrally formed so as to cover and fix the conductive members and the heating element, the space between the conductive members and the conductive member and the outside are fixed. The heating element can be fixed in the covering member while ensuring electrical insulation with

By the way, conventionally, in order to ensure electric insulation from the outside, the heating element is housed in an insulating sheet or a case made of ceramics. It was necessary to fix it by adhesion or the like, and it was necessary to make the case in advance when storing it in the case.

However, in the above structure, since the cover member is integrally molded, it is possible to save the time and labor required for fixing the insulating sheet to the insulating sheet by adhesion or preliminarily manufacturing the case.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS. In the planar heater, as shown in FIG. 1, a plurality of, for example, five heating elements 2 are provided in a resin molding portion (covering member) 1 molded in a flat plate shape.
And an electrode plate (conductive member) 3 for supplying electric power to the heating elements 2 ...

The heating element 2 has a positive temperature coefficient (Positive T).
It has a low resistance from room temperature to the Curie temperature Tc (rapid change temperature), but has a steep resistance value when it exceeds the Curie temperature Tc. It is a positive temperature coefficient thermistor as a heat-sensitive element having a characteristic that increases rapidly.

Due to the above characteristics, when a voltage is applied to the heat generating element 2, the resistance value is small at first and a large current flows, so that the temperature rises rapidly. Further, when the temperature exceeds the Curie temperature Tc, the resistance value sharply increases, so that the temperature does not rise above a certain Curie temperature Tc and the temperature is kept stable. That is, the heating element 2 has a self-temperature control function.

Therefore, in the configuration of the above embodiment, the temperature control circuit and the overheat prevention circuit can be omitted, the power consumption is small, and the size can be reduced. Further, there is no fear of ignition due to local overheating. The Curie temperature Tc of the heating element 2 can be arbitrarily set within the range of about 30 to 250 ° C. depending on the material composition. Therefore, in the heating element 2 of this embodiment, the resin molding portion effective for heating the object to be heated is used. The Curie temperature Tc may be set in consideration of safety and power saving while achieving a surface temperature of 1.

The heating element 2 is formed into a flat, substantially rectangular parallelepiped shape, and is provided with a pair of strip-shaped electrodes 2a, 2a which are parallel to each other at predetermined intervals at both ends of one surface thereof. The electrode 2a is formed by applying a silver paste or the like and then baking it, as described later.

On the other hand, the above-mentioned electrode plates 3 and 3 are made of a metal mesh or a perforated metal plate having excellent thermal conductivity (however, in FIG. 1, the electrode plates 3 and 3 are shown as a metal mesh) in a strip shape. Has been formed. It is also possible to use a simple metal plate as the electrode plates 3, 3.

Moreover, in order to supply electric power to the plurality of heating elements 2, ..., Each of the electrode plates 3 and 3 has two feeding electrode plates extending from mutually parallel base electrode plates so as to face each other.
Have a set. Therefore, the electrode plates 3 and 3 are formed in a comb shape.

As a result, the respective electrode plates 3 and 3 have a function as an electric wire for energizing the heating elements 2 by combining their tips in parallel and equidistantly on the same plane. It also has a function as a heat transfer plate that efficiently and uniformly transfers the heat generated by the bodies 2 to the entire surface of the resin molding portion 1.

The electrode plate 3 is made of, for example, iron, copper, stainless steel or the like, and the mesh of the metal mesh of the electrode plate 3, that is, the size of the mesh is, for example, if the opening (opening) is several tens of microns or more. Good. Also, on the periphery of the wire mesh,
A frame may be provided with, for example, the same material as the wire mesh so that the lead wire (not shown) can be easily soldered. Furthermore, the thickness of the wire mesh is set to be thin so that the resin molding portion 1 can be made lighter and thinner. The size of the mesh, the thickness of the wire mesh, the forming method, and the like are not particularly limited.

When a perforated metal plate is used in place of the above-mentioned wire net, the perforated metal plate is, for example, a copper plate, a phosphor bronze plate, an aluminum plate, a stainless plate, etc. punched out by a die or the like to open a large number of holes. It is formed by The diameter of the holes of the perforated metal plate may be smaller than the diameter of the heating elements 2 ..., For example, it may be about several mm. Moreover, the thickness of the perforated metal plate is set to be thin so that the planar heater can be made lighter and thinner. The thickness of the perforated metal plate, the diameter of the hole, the forming method, the forming position, and the like are not particularly limited.

For each electrode plate 3, for example, a wire net, a perforated metal plate, or a simple metal plate may be properly used depending on the use, size, shape, etc. of the resin molding portion 1. Of course, one electrode plate 3 is a wire net. The other electrode plate 3 may be a perforated metal plate or a simple metal plate.

The heating elements 2 are electrically connected to the electrode plates 3, 3 by pressing the electrodes 2a of the heating element 2 and the electrode plate 3 against each other. The electrical connection between the electrode plates 3 and 3 and the lead wires is made by, for example, soldering corresponding lead wires to the end faces of the electrode plates 3 and 3. Note that the heating elements 2, ... And the electrode plates 3, 3 may be electrically connected to each other by, for example, adhering them with a conductive adhesive of epoxy resin / silver mixture.

The resin molding portion 1 is integrally formed of a synthetic resin mixed with a filler and covers the heating elements 2 ... And the electrode plates 3 and 3 to hermetically seal, that is, maintain a waterproof state. It is sealed like this. Further, although not shown, the resin molded portion 1 also covers the end portion of the lead wire on the electrode plate 3 side so that a mechanical load is not applied to the soldered portion between the lead wire and the electrode plate 3 to prevent disconnection or the like. It is like this.

The synthetic resin used for the resin molding part 1 has a small heat shrinkage ratio, is excellent in thermal conductivity, electric insulation, and mechanical strength, and has heat resistance capable of withstanding the heat generation temperature of the heating elements 2, ... It is necessary to have waterproofness that does not allow moisture to pass inside, airtightness that does not allow air to pass inside, and good adhesion to the coating material of the lead wire. For example, unsaturated polyester Thermosetting resin such as resin, vinyl ester resin, epoxy resin, phenol resin, polypropylene resin, polyamide resin,
A thermoplastic resin such as polyethylene terephthalate resin is used.

The above synthetic resin is, for example,
Affinity with the filler used, molding method of the resin molding part 1,
It may be appropriately selected depending on the application and size of the sheet heater, the shape, the required strength, various physical properties, and the like. Further, the synthetic resin may contain a curing agent, a release agent, a low-shrinking agent, a coloring agent, a thickening agent and the like.

The above-mentioned filler (hereinafter referred to as "filler")
Must have excellent thermal conductivity and electrical insulation properties, must have heat resistance to withstand the heat generation temperature of the heating elements 2, and have a good affinity with synthetic resins. , Organic fiber, inorganic fiber, organic powder, inorganic powder and the like are used. However, considering the formability, the above fibers are preferably used.

Examples of the organic fiber include cotton, wool,
Natural fibers such as hemp, chemical fibers such as rayon,
Synthetic fibers made of polyvinyl chloride resin, polyamide resin, wholly aromatic polyamide resin, saturated polyester resin or the like are used. As the inorganic fiber, for example, glass fiber, potassium titanate, boron, silicon carbide, alumina, polytitanocarbosilane and the like are used.

The fiber length is preferably about 3 times or more the size of the hole of the electrode plate 3 so that the resin molding portion 1 can be molded by compression molding which will be described later. In addition,
The aspect ratio of the glass fiber, the organic fiber and the inorganic fiber is not particularly limited. Further, the form of each of the above fibers is not particularly limited.

Further, as the organic powder, for example, rubber such as styrene-butadiene rubber is used. As the inorganic powder, for example, calcium carbonate, kaolin, clay, alumina, aluminum hydroxide, barium sulfate, lithopone, glass powder in the form of cut fibers or milled fibers, glass flakes, glass beads, glass microballoons, aluminosilicate microballoons. , Silica microballoons, wollastonite, boron nitride, fine particle silicon, ultra fine particle anhydrous silica,
Quartz powder, talc, mica, antimony trioxide, etc. are used.

The particle diameters of the above-mentioned organic powder and inorganic powder are not particularly limited. The forms of the organic powder and the inorganic powder are not particularly limited.

The above-mentioned fillers are, for example, price, affinity with synthetic resin to be used, molding method of resin molding portion 1, use and size as planar heater, shape, strength required for planar heater, and the like. It may be appropriately selected according to various physical properties and the like.
Moreover, the compounding amount of the filler with respect to the synthetic resin is not particularly limited. Each of the above fillers may be blended in the synthetic resin alone, or two or more kinds may be mixed in the synthetic resin if necessary.
Furthermore, the method of mixing the synthetic resin and the filler is not particularly limited.

The resin molding part 1 is, for example, SMC (She
et Molding Compound), BMC (Bulk Molding Compoun)
When a thermosetting resin such as d) is used, it is molded and manufactured by a heat compression molding method or the like. When FRTP (Fiber Reinforced ThermoPlastics), which is a thermoplastic resin such as polypropylene resin or polyamide resin reinforced with long fibers, is used, it is molded and manufactured by a compression molding method of compressing a heated resin.

Next, the molding and manufacturing of the planar heater by the above SMC will be described. First, a synthetic resin containing a filler (hereinafter referred to as a composite) is formed into three sheets having a predetermined shape and size. A perforated sheet is formed by forming two of these sheets into an upper surface sheet and a lower surface sheet, and opening a hole of a size that can accommodate the heating elements 2 at a predetermined position of the remaining one sheet. And The thickness and forming method of these sheets are not particularly limited.

Next, the comb-shaped electrode plates 3 are formed on the lower surface sheet.
Place the perforated sheet in which the heating elements 2 are fitted in the holes and the top sheet in this order at predetermined positions. After that, this laminate is placed in a press molding machine (not shown) and pressed under predetermined conditions, that is, predetermined temperature, pressure, time, etc., to heat-cure the composite and integrate the three sheets. The resin molding part 1 is formed. As a result, the heat generating elements 2 ...

Further, the molding and manufacturing of the above-mentioned planar heater by BMC is performed by the following procedure. That is, first, the composite is made into a paste and then the paste-like composite is expanded by a predetermined amount. Next, each electrode plate 3, 3, the heating element 2, ... And the paste-like composite are arranged on the paste-like composite at a predetermined position in this order,
Further spread a predetermined amount of the paste composite. After that, by pressing this laminate under predetermined conditions,
The composite is heat-cured to form the resin molding portion 1 to form a planar heater.

Further, the above-mentioned FRTP sheet heater is molded and manufactured by the following procedure. That is, first, the composite is formed into three sheets having a predetermined shape and size, and two of these sheets are used as an upper surface sheet and a lower surface sheet, while the remaining one sheet has each heating element 2 ...
A perforated sheet is prepared by opening holes according to the size and position. The thickness and forming method of these sheets are not particularly limited.

Next, on the bottom sheet, each electrode plate 3, 3,
The perforated sheet having the heating elements 2 fitted in the holes is placed, and the upper surface sheet is placed thereon. After that, this laminate is heated to a predetermined temperature to melt the synthetic resin, and then placed in a press molding machine, and pressed under predetermined conditions to cool and press the composite, and the three sheets are integrated to form a resin. Part 1
To form a planar heater.

The procedure for molding / manufacturing the planar heater by SMC, BMC, and FRTP is not limited to the above-described procedure, but the resin molding part 1 is used to heat the heating element 2.
... and the procedure for forming and manufacturing the planar heater by covering and sealing the electrode plates 3.3.

Further, in the above electrode plate 3.3, the lead wires coated on the end face side of the electrode plate 3.3 are connected and integrally formed, so that the outer surface side of the electrode plate 3.3 is formed. Does not cause irregularities due to the connection of the covered lead wires.

Therefore, it is not necessary to provide the resin molding portion 1 with a thickness for absorbing the unevenness, and the resin molding portion 1,
That is, the planar heater can be formed thin. Further, since the composite containing the filler is used, the resin molding portion 1 can be thinly formed while ensuring the electric insulation between the electrode plates 3 and 3 and the outside.

As a result, the planar heater can be made smaller, lighter and thinner, and the heat generated by the heating elements 2 can be efficiently transferred to the object to be heated. Furthermore, since the surface of the resin molded portion 1 is smooth and can be brought into close contact with the object to be heated, the heat transfer efficiency can be further improved.

Moreover, since the electrode plates 3 and 3 are made of metal, the conductivity of heat is high, and the heat is quickly transferred through the electrode plates 3 and 3. The surface on the side of each of the electrode plates 3 and 3 can be efficiently heated.

The lead wire is connected to a power cord (not shown), and is electrically connected to an external power source through the power cord. The heating elements 2 are connected in parallel with each other. The lengths of the lead wire and the power cord are not particularly limited.

Since the sheet heater having the above-mentioned structure uses the heating elements 2 made of positive temperature coefficient thermistors as the heating means, the temperature rises rapidly after energization, and when the temperature reaches a predetermined temperature, the temperature is maintained. Further, since the respective electrode plates 3 and 3 are formed in a comb shape and are installed so as to be alternately assembled at a predetermined interval, heat from the respective heating elements 2 ... Is transferred to the resin through the respective electrode plates 3 and 3. Since it is transmitted to the entire molding unit 1, the surface of the resin molding unit 1 is quickly raised to a predetermined temperature, and the object to be heated can be quickly heated.

Next, a method for manufacturing the planar heater having the above-mentioned structure will be described in detail with reference to specific examples, but the present invention is not limited to these. In the following specific examples, the shape of the planar heater is a flat rectangular parallelepiped shape.

Concrete Example: A planar heater was molded and manufactured by SMC. First, SMC (manufactured by Showa Polymer Co., Ltd., product number: H8D6H, composition: 33 wt% polyester resin, 1 wt. Long glass fiber 32 wt% as filler, other filler 35 wt%, density: 1.8 g / cm ³ ) is 15 cm square It is cut into 3 sheets (one weight is about 80g), 2 of which are used as the top sheet and the bottom sheet, while the remaining 1 sheet has a hole of 23 x 23mm at a predetermined position. Portions were opened to form a perforated sheet.

The Curie temperature Tc is 63 ° C. and the resistance value is
Using a heating element of 150 Ω, size 22 × 22 mm, thickness 2.7 mm,
A wire mesh having a mesh size of 2 mm and soldered with a lead wire was used as an electrode plate.

Next, a lower surface sheet is set, each electrode plate and the perforated sheet are placed on the lower surface sheet in this order, and a heating element is fitted into the holes of the perforated sheet, and then further on top. The top sheet was placed in this order. Then, this laminate is pressed at a temperature of 160 ° C. and a pressure of 100 kg / cm ^{2 for} 4 minutes to heat-cure the polyester resin and integrate the three sheets into a 15 cm × 15 cm × 6.0 mm electrically insulating coating member. That is, a planar heater was obtained. The electric insulation of the obtained sheet heater was good.

When the polyester resin was thermoset by pressing under the same conditions except that the pressure was changed to 80 kg / cm ² , a planar heater of 15 cm × 15 cm × 5.5 mm was obtained.

Concrete Example: A planar heater of FRTP was molded and manufactured. First, the FRTP stumpable sheet (made by Cape La Sheet Co., Ltd., product number: C8010-N
, Composition: Polypropylene resin 60wt%, Glass fiber 40wt
%, Thickness: 0.85 mm) was cut into 15 cm squares to obtain two sheets, an upper sheet and a lower sheet. Also, a stamp sheet made by the same company (product number: C8040-N, composition: same as above, thickness: 3.3 mm) was cut into 15 cm squares, and then 5 holes with dimensions 23 × 23 mm were opened at predetermined positions to form a perforated sheet. And Further, a heating element having a size of 22 × 22 mm and a thickness of 2.7 mm was used, and a wire mesh with a mesh size of 2 mm to which a lead wire was soldered was used as an electrode plate.

Next, the above-mentioned top sheet and bottom sheet were heated for 2 minutes and 30 seconds using an infrared heater, while the perforated sheet was heated for 4 minutes and 30 seconds to about 200 ° C., respectively, and then the bottom sheet was heated. Place the electrode plate and perforated sheet on this bottom sheet in this order, fit the heating element into the holes of the perforated sheet, and then place the top sheet on it in that order. did.

Thereafter, the laminate is heated at a temperature of 50 ° C. and a pressure of 100.
Press at 40 kg / cm ^{2 for} 40 seconds, melt the polypropylene resin, then cool and integrate the 3 sheets into 15 cm x 15 cm x
A 5.0 mm electrically insulating coating member, that is, a planar heater was obtained. The electric insulation of the obtained sheet heater was good.

As described above, the planar heater having the above structure is
Flat rectangular parallelepiped heating element 2 consisting of positive temperature coefficient thermistor
A pair of comb-shaped electrode plates 3 and 3 are electrically connected to the electrodes 2a and 2a provided on one side of ..., and a pair of lead wires are electrically connected to these electrode plates 3 and 3, respectively. Further, the entire resin molded portion 1 is covered and electrically insulated from the outside.

Therefore, the surface temperature of the resin molding portion 1 rapidly rises to a predetermined temperature after the heating elements 2 are energized, and when the temperature reaches the predetermined temperature, the temperature is kept stable.
It is possible to efficiently transfer the heat generated by the heating elements 2 to the object to be heated via the electrode plates 3 and 3 and the resin molding portion 1.

The resin molding portion 1 is made of synthetic resin mixed with a filler and is integrally formed by compression molding. Therefore, the surface, that is, the heating surface can be made smooth, and the electrode plate 3 formed by the resin molding portion 1 ...
The filler allows the filler to be thin while maintaining electrical insulation.

Thus, in the configuration of the above embodiment,
Since the heat from the heating elements 2 is transferred to the electrode plates 3 more largely, the surface of the resin molding portion 1 on the side of the electrode plates 3 can be more efficiently heated.

Further, since the electrode plates 3 and 3 are made of a metal net, a perforated metal plate or a simple metal plate, when the resin molding portion 1 is integrally formed by compression molding, the heating element 2 ...
The space is filled not only with the synthetic resin from the opposite side of the electrodes 2a, but also with the synthetic resin that has passed through the holes of the electrode plates 3 and 3 to fix the respective heating elements 2.

By the way, in the past, it was necessary to separately fix the heating element when it was housed in the insulating sheet, and in the case of housing it in a ceramic case, it was necessary to make the case in advance.

However, in the structure of the above-mentioned embodiment, since it is integrally molded, it is possible to reduce the number of parts and the number of steps because it is not necessary to separately fix it or to prepare a case in advance. The cost can be reduced, and the size, weight and thickness can be reduced.
Further, so-called unitization is possible and mass production is possible. The thickness of the planar heater may be, for example, about 3.0 mm, though it depends on the thickness of the heating elements 2.

By the way, when electrodes are formed on both surfaces of the heating element and electrode plates having holes are respectively connected to the electrodes, when the synthetic resin portion containing the filler is integrally molded, the synthetic resin portion The entry of the synthetic resin into the periphery of the heating element may be hindered by the clogging of the electrode plate by the filler.

However, in the above structure, since the electrodes 2a, 2a are formed on one surface of the heating element 2, the heating element 2
It is not necessary to provide the electrode plate 3 on the other surface, and the above inhibition can be reduced.

As a result, the heating element 2 is connected to the synthetic resin portion 1
Since it can be more completely covered and abutted tightly, it is possible to suppress a decrease in thermal conductivity due to the formation of a gap between the heating element 2 and the resin molding portion 1. Further, the strength of the resin molded portion 1 is reduced due to the formation of voids, and the creep fatigue due to the repeated expansion pressure during heating of the air in the voids and the reduced pressure during cooling is prevented, and the strength of the resin molded portion 1 is reduced. Can be avoided.

The positions where the heating elements 2 are disposed are of course not limited to the above-mentioned positions, and for example, the optimum positions according to the Curie temperature Tc of the heating elements 2 and the surface temperature of the sheet heater. It may be appropriately arranged so as to be at the position.

In the above embodiment, the planar heater has been described by taking the case where the five heating elements 2 are used as an example, but the number of the heating elements 2 is of course limited to the above five. The size and shape of the sheet heater, the application,
Alternatively, it may be appropriately changed according to the size of the heating element 2 and the Curie temperature Tc.

The shape of the heating element 2 is not limited to the above-mentioned flat rectangular parallelepiped shape, and a flat disk shape or a substantially disk-shaped heating element 2'as shown in FIG. 2 is used. Good. At this time, a pair of arcuate electrodes 2c, 2c whose opposite sides are parallel to each other are formed. The heating element 2 '
Alternatively, the through hole 2b may be formed coaxially.

Further, as shown in FIG. 3, comb-shaped electrodes 2d and 2d may be formed on one surface of the heating element 2 or, as shown in FIG. The comb-shaped electrodes 2e and 2e may be formed. Thereby, each electrode 2d
Since the length of the opposing sides of 2d and each of the electrodes 2e and 2e can be increased and the distance between the two can be reduced, the effective heat generation area can be increased and heat generation efficiency can be improved.

Further, the shape, size, and thickness of the resin molding portion 1, that is, the planar heater, are not limited to the above-mentioned flat and substantially disc shape, and are optimal depending on the size and shape of the object to be heated. The shape, size, and thickness can be variously changed, and various shapes such as a flat rectangular parallelepiped shape, a triangular prism shape, and an ellipse shape may be used.

In the configuration of the above embodiment, an example in which the resin molding portion 1 is molded by compression molding has been described, but the invention is not particularly limited to the above. For example, the resin molding portion 1 is molded by injection molding. Good.

In the structure of the above embodiment, each electrode plate 3
Although the example in which 3 is formed in a straight line parallel to each other has been described, the present invention is not particularly limited to the above, and may be formed in a double spiral shape as shown in FIG. 7, for example. As a result, the electrodes 3, 3 can be formed in a large area without crossing each other, and more heat generating elements 2 ... Can be formed in the electrode plates 3, 3.
It is possible to place it on top.

Next, an example in which the above configuration is applied to a heat insulation container will be described by showing the manufacturing process thereof. As shown in FIG. 5, in the heat insulation container, first, in a heat insulation container, a synthetic resin molded in a substantially box shape is used. Two pairs of electrode plates 3 and 3 are attached to the outer periphery of the base material 4 in parallel with each other. After that, a predetermined number of heating elements 2 ... Are provided on each of the electrode plates 3, 3.
... are attached with a conductive adhesive or the like so that they come into contact with each other. On the other hand, lead wires 5 are connected to the electrode plates 3 and 3, respectively.

Subsequently, as shown in FIG. 6, each heating element 2 ...
A bottomed box with a synthetic resin exterior material 6 having electrical insulation so as to cover the heating elements 2 ... And the electrode plates 3 ... To obtain a heat-retaining container.

In such a heat retaining container, the exterior material 6 is filled between the heating elements 2 and the heating elements 2 are sealed in a space between the base material 4 and the exterior material 6. Because
Each heating element 2 can be maintained in an electrically insulated state from the outside, and damage due to poor insulation can be avoided even when the heating elements 2 are used in places with high humidity or flooding, for example.

Moreover, in the heat insulating container, more heat from the heating elements 2 is transferred to the inner surface of the heat insulating container via the electrode plates 3, so that the internal space of the heat insulating container is efficiently heated. It can be heated and kept warm.

[0077]

As described above, the planar heater of the present invention has the following features.
A pair of strip-shaped conductive members electrically connected to each electrode of a plate-shaped heating element consisting of a positive temperature coefficient thermistor, which generates heat when energized and whose resistance value rises sharply when the temperature exceeds a predetermined value, is provided. A covering member including a synthetic resin having an insulating property is integrally molded so as to cover and fix the conductive member and the heating element, and each electrode of the heating element is formed on one surface of the heating element. It has a structure.

Therefore, in the above structure, since the covering member is integrally formed so as to cover and fix the conductive members and the heating element, the electric insulation between the conductive members and the outside is ensured. The above heating element can be fixed while securing.

By the way, in the past, it was necessary to separately fix the heating element when storing it in the insulating sheet, and in the case of storing it in a ceramic case, it was necessary to make the case in advance.

However, in the above-mentioned structure, since the cover member is integrally molded, it is possible to save the costs of separately fixing and previously manufacturing the case, and thus it is possible to avoid the cost increase.

[Brief description of drawings]

FIG. 1 shows a planar heater of the present invention,
(A) is a plan view of an essential part, and (b) is I-of the above (a).
It is a sectional view taken along the line I.

FIG. 2 is a plan view of a modified example of a heating element used for the planar heater.

FIG. 3 is a plan view of another modification of the heating element used for the planar heater.

FIG. 4 is a plan view of still another modification of the heating element used for the planar heater.

5A and 5B are explanatory views showing a part of a manufacturing process of a heat retaining container as an application example of the planar heater, wherein FIG. 5A is a perspective view of the heat retaining container in the process of manufacturing, and FIG. II of (a)
It is a sectional view taken along the line II.

6A and 6B are explanatory views showing a completed heat insulating container, FIG. 6A is a perspective view of the heat insulating container, and FIG. 6B is a sectional view taken along line III-III of FIG. is there.

FIG. 7 is a front view of a modification of the electrode plate of the planar heater.

[Explanation of symbols]

 1 Resin Molding Part (Coating Member) 2 Heating Element 2a Electrode 3 Electrode Plate (Conductive Member)

Claims (1)

[Claims] 1. A pair of strip-shaped conductive members electrically connected to the respective electrodes of a plate-shaped heating element composed of a positive temperature coefficient thermistor which generates heat when energized and whose resistance value rises when a predetermined temperature is exceeded. And a covering member provided with an electrically insulating synthetic resin is integrally molded so as to cover and fix the conductive member and the heating element, and each electrode of the heating element is provided on one side of the heating element. A planar heater characterized by being formed.