JP2887191B2 - Manufacturing method of planar heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sheet heater which has excellent water resistance and can be used in a high humidity atmosphere.

[0002]

2. Description of the Related Art Conventionally, in compression molding using a stampable sheet, which is a thermoplastic resin having a fibrous material such as glass fiber, the stampable sheet is cut in accordance with male and female molds, and the cut stamper is cut. By heating and softening the bull sheet into the male and female molds and compression-molding with the male and female molds, the stampable sheet is
For example, it is typed on a frame of an automobile seat.

When the above-described conventional compression molding method using a stampable sheet is used for manufacturing a sheet heater in which a heating element made of, for example, a positive temperature coefficient thermistor is sealed with a synthetic resin, the compression molding method requires: In the lower female mold, a stampable sheet, a power supply terminal and a metal plate as a heat sink,
A laminated body is formed by laminating a heat-generating body which is a sealed body, a power supply terminal, a metal plate as a heat sink, and a stampable sheet.

Thereafter, the laminate is heated to bring the thermoplastic resin of the stampable sheet into a molten state, and then the laminate is pressed to seal a heating element with the fibrous material and the thermoplastic resin. A method of manufacturing a planar heater is considered.

[0005] This makes it possible for the planar heater to have water resistance and electrical insulation. In addition, since each of the metal plates also has a function as a heat radiating plate, the metal plate has a heat radiating area close to the area of the upper and lower surfaces of the planar heater, so that the heat radiating efficiency of the heating element can be increased.

[0006]

However, in the above-mentioned manufacturing method, in order to electrically insulate between the respective metal plates also functioning as a heat radiating plate, a thermoplastic resin is passed between the ends of the respective metal plates. It is necessary to pour between each metal plate,
Therefore, a mold clamping pressure of about 100 kg / cm ² is required.

For this reason, the metal plate undergoes deformation such as bending due to the mold clamping pressure, thereby deteriorating the dimensional stability of the planar heater. In some cases, a thermoplastic resin may enter between them, making it impossible to conduct electricity and causing heat generation failure. For these reasons, the above-described manufacturing method has a problem that the yield of the obtained planar heater is deteriorated.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a method of manufacturing a sheet heater according to the present invention comprises a method of forming a sheet on a lower sheet, which is a stampable sheet having a fibrous material and a thermoplastic resin. After placing a plate-shaped first metal plate having a plurality of holes penetrating the back surface, the core layer sheet, which is a stampable sheet having a through hole into which a heating element that generates heat when energized is inserted, is placed on the first metal plate. Layer on a metal plate, then
After inserting the heating element into the through hole, a plate-shaped second metal plate having a plurality of holes penetrating the front and back surfaces is placed on the heating element, and then the top sheet made of a stampable sheet is removed. After stacking on the second metal plate to form a laminate so as to match the lower sheet, the laminate is heated so that the thermoplastic resin is melted. Subsequently, the laminate is cooled to 0.8 kg / c.
compression molded at m ² to 10 kg / cm ^2, the heating element and the sealed surface heater and first and second metal plates sandwiching the heating element by said fibrous material and thermoplastic resin It is characterized by obtaining.

Examples of the thermoplastic resin include simple substances or copolymers of polypropylene, polybutylene terephthalate, polyethylene terephthalate, polyphenylene oxide, high-density polyethylene, polyamide, polyphenylene sulfide, polyetherimide, poly (meth) acrylate, and the like. Can be.

As the fibrous material, inorganic fibers such as glass fibers and whiskers, aramid fibers, and boron fibers are used alone or as a mixture. The fibrous material has a fiber length of 6 mm or more and a fiber thickness of 10 μm or more, and is used in a mixture of 15 to 50% by weight with respect to the thermoplastic resin.

The thermoplastic resin of the upper sheet, the core layer sheet and the lower sheet is not necessarily the same component as long as it can be integrated with each other during compression molding.

When the molding pressure is less than 0.8 kg / cm ² , the thermoplastic resin spreads on the surface of the obtained sheet heater due to insufficient molding pressure, and the fibrous material is exposed on the surface. By doing so, water easily penetrates through the space between the fibrous materials, and thus the water resistance of the planar heater is deteriorated.

On the other hand, if the molding pressure exceeds 10 kg / cm ² , the dimensional stability of the obtained sheet heater is deteriorated such that the second metal plate of the sheet heater is deformed or the position of the heating element is deviated. Improper energization of the body increased significantly. The poor current supply is caused by poor contact between the second metal plate and the heating element due to the intrusion of the thermoplastic resin between the second metal plate curved by the molding pressure and the heating element, Deformed first
And those caused by contact between the second metal plates.

[0014]

According to the above-mentioned method, when the laminate is compression-molded, since the thermoplastic resin of the core layer sheet is molten, the heating element is first sandwiched between the first and second metal plates, Thus, the thermoplastic resin containing the fibrous material is integrated through each hole of the first and second metal plates and between the ends of the first and second metal plates.

Therefore, in the above-described method, it is not necessary to fill the thermoplastic resin containing the fibrous material between the metal plates with high pressure from between the ends of each metal plate as in the conventional method. It can be performed at a low pressure of / cm ^{2 to} 10 kg / cm ² .

Thus, the first and second metal plates are prevented from being deformed by the low molding pressure as described above, and a thermoplastic material is provided between the heating element and the first and second metal plates. Intrusion of resin can also be prevented.

Further, the fibrous material and the thermoplastic resin of each of the upper and lower sheets are formed between the first and second metal plates during compression molding by the first and second metal plates having holes. Since each remains, a space is always formed between the first and second metal plates and the mold. Thus, the heating element and the first and second metal plates sandwiching the heating element are always covered and sealed with the fibrous material and the thermoplastic resin.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. First, a description will be given of a compression molding die used in a method of manufacturing a planar heater. As shown in FIGS. 1 and 2, a polypropylene resin containing glass fiber (fibrous material) is used in the compression molding die. A receiving plate 2, on which a laminate 1 having a heater as an object to be sealed placed and movable, is provided detachably with respect to a lower mold 3 between stampable sheets made of a plastic resin). ing. Therefore, the receiving plate 2 includes
A mounting surface 2a having the same shape as the bottom surface of the laminate 1 is formed.

Then, when inserted into the substantially U-shaped edge portion 3a of the lower mold 3 on the receiving plate 2,
The rising part 2b which becomes one side part of the shear edge of the lower female die 3e in the lower die 3 is erected along one side of the mounting surface 2a.

Thus, the edge portion 3a and the rising portion 2
Since the lower female mold 3e is formed by the b and the mounting surface 2a, the laminate 1 is formed into a plate shape by clamping the upper male mold 4 and the lower female mold 3e. Has become.

The receiving plate 2 is provided with two fixing holes 2c for fixing the receiving plate 2 at predetermined positions of the lower mold 3, so that fixing pins (not shown) are inserted therethrough. ing. Therefore, the lower mold 3 is provided with fixing holes 3b into which the fixing pins are fitted.

Further, the lower mold 3 is provided with lower heaters 3c for heating so as to maintain a predetermined temperature, and heat from each of the lower heaters 3c is efficiently transmitted to the lower mold 3. The upper male mold 4 is provided with an upper heater 4a for heating to maintain a predetermined temperature, and heat from the upper heaters 4a. An upper heat insulating layer 4b for efficiently transmitting the upper male mold 4 is incorporated.

Next, a method of manufacturing a sheet heater using the compression mold and the stampable sheet will be described. First, in the manufacturing method, a stampable sheet having a thickness of 0.85 mm (manufactured by Cape Rasheet Co., Ltd.) Product name: C8010
-N, composition: polypropylene resin 60wt%, glass fiber 40
wt%) was cut into 15 cm squares to form two sheets, a lower sheet 5 and an upper sheet 6.

On the other hand, a stampable sheet having a thickness of 2.5 mm (made by Cape La Sheet Co., Ltd., trade name: C8030-N, composition: 60% by weight of polypropylene resin, 40% by weight of glass fiber) is cut into 15 cm square, and the center of the sheet is cut. Then, a through-hole 7a having a diameter of 15 mm penetrating the front and back surfaces was formed in one place to obtain a core layer sheet 7.

A heating element 8 made of a barium titanate-based ceramic semiconductor having PTC characteristics (positive temperature thermistors)
Is used. The heating element 8 has a diameter of, for example, 15 m.
It is formed in a disk shape having a thickness of 2.5 mm and a thickness of 2.5 mm.

On the other hand, a metal plate (first and second metal plates) 9 for supplying power to the heating element 8 and efficiently radiating heat from the heating element 8 to the outside is used. The metal plate 9 is made of, for example, a 140 mm square aluminum plate having a thickness of 1 mm, and has a 5 mm-diameter hole (not shown) penetrating the front and back surfaces thereof in a grid pattern. Although not shown, lead wires are soldered to each of the metal plates 9, 9 on one side facing each other as described later.

Next, as shown in FIG. 3, the lower surface sheet 5, the metal plate 9, and the core layer sheet 7 are formed coaxially on the mounting surface 2a of the receiving plate 2 on which a 150 mm square molded product is mounted. The heating element 8 was fitted into the through hole 7a of the core layer sheet 7, and then the metal plate 9 and the top sheet 6 were laminated in this order to form the laminate 1.

The term "coaxially overlapping" means that the lower surface sheet 5, the metal plate 9, and the core layer sheet 7 are overlapped so that their respective axes of symmetry extending vertically to the upper and lower surfaces are coaxial. It is to match.

Thereafter, the receiving plate 2 on which the above-mentioned laminate 1 is placed
As shown in FIG. 4, the laminate 1 is heated by, for example, being put in a heater so that each of the sheets 5, 6.
7 was heated to 220 ° C. for 7 minutes.

At this time, since the laminated body 1 expands by heating, as shown in FIG. 4, the distance h between the heater 10 for preheating the laminated body 1 and the laminated body 1 is maintained at a predetermined distance, for example, 2 mm. As described above, the heater 10 is raised according to the expansion caused by the temperature rise of the laminate 1. Thereby, the laminated body 1 is efficiently heated while preventing shape collapse due to contact with the heater 10.

The top sheet 6 thus heated is
Although the core layer sheet 7 and the lower sheet 5 have their polypropylene resins melted, they do not flow out due to the glass fibers filled in the sheets 5, 6 and 7. When the sheets 5, 6, 7 are formed into a sheet, the glass fibers contained therein are disposed substantially along the surface direction. It expands mainly in the layer direction. As a result, the sheets 5, 6, 7 heated on the receiving plate 2 are held on the receiving plate 2 while maintaining their substantially rectangular plate shapes.

Next, as shown in FIGS. 1 and 5, the receiving plate 2 is attached to a lower mold 3, and
And the lower metal mold 3 by the edge 3a of the lower mold 3.
After forming e, the upper male mold 4 and the female mold 3e
At a temperature of 100 ° C. and a molding pressure of 1 kg / cm ² ,
Cold pressed for minutes.

As described above, in the cooling press, first, since the polypropylene resin of the core layer sheet 7 is molten, the heating element 8 is sandwiched by the metal plates 9.
Subsequently, the polypropylene resin of each of the sheets 5, 6, 7 is connected to each hole (not shown) of the metal plate 9 and each of the metal plates 9
The sheets 5, 6, and 7 were integrated through the end portions of No. 9 to obtain a sheet heater of 15 cm × 15 cm × about 5 mm.

At this time, since the upper and lower sheets 5 and 6 hardly move through the holes (not shown) of the metal plate 9, much of the upper and lower sheets 5 and 6 remain on the front side of the sheet heater. From this, a gap was always formed between the male and female molds 3, 4 and each metal plate 9, 9 by the interposition of glass fibers.

Therefore, since the glass fiber and the polypropylene resin are always present at the above-mentioned interval, each of the metal plates 9.
A sheet heater in which 9 and the heating element 8 were sealed with the glass fiber and the polypropylene resin was obtained.

Thus, the entire surface of the planar heater was covered with the glass fiber-containing polypropylene resin, and thus had good electric insulation. Further, in the above-mentioned sheet heater, the heating element 8 made of PTC quickly generates heat by energizing the metal plates 9 via lead wires (not shown), and the heat of the heating element 8 is
・ The surface of the planar heater is quickly reached via 9. Thus, the temperature of the planar heater rises quickly.

Next, in place of the molding pressure of 1 kg / cm ² at the time of compression molding in the method of the above embodiment, sheet heaters were produced using various other molding pressures. The results shown were obtained. From these results, assuming that the defective rate of the molded product is 1% or less as a preferable yield, in the above method, a molding pressure in a range of 0.8 kg / cm ² or more and 10 kg / cm ² or less is desirable, and further, 1.0 kg / cm ² or more. It was found that a molding pressure in the range of 5 kg / cm ² or less was preferable.

That is, if the molding pressure is less than 0.8 kg / cm ² , the dimensional stability of the obtained sheet heater is deteriorated, and the shortage of the molding pressure reduces the spread of the polypropylene resin on the surface of the sheet heater. However, when the glass fibers are exposed on the surface, water easily penetrates between the glass fibers, and thus the water resistance of the planar heater is deteriorated.

On the other hand, if the molding pressure exceeds 10 kg / cm ² , the metal plate 9 of the obtained planar heater will be deformed and the position of the heating element 8 will be degraded, resulting in deterioration of dimensional stability and heat generation. The energization failure of the body 8 increased remarkably. It should be noted that the above-mentioned electric conduction failure is caused by the fact that each of the metal plates 9 and 9 curved by the molding pressure and the heating element 8
The lead caused by the poor contact between the metal plates 9 and the heating element 8 due to the infiltration of the polypropylene resin between them, the one caused by the contact between the deformed metal plates 9 and 9, the lead The occurrence of disconnection of the wire (not shown) was considered.

As described above, according to the method of the above embodiment, when the laminated body 1 is compression-molded, the polypropylene resin of each of the sheets 5, 6, 7 is converted into the holes of each of the metal plates 9, 9, and Since the metal plates 9 are integrated through the end portions thereof, it is necessary to fill a thermoplastic resin containing a fibrous material between the metal plates from the end portions of each metal plate by a high pressure as in the related art. Whilst the compression molding can be performed with low pressure of ^{0.8kg / cm 2 ~10kg / cm 2} .

Accordingly, the metal plates 9 are prevented from being deformed by the low molding pressure as described above, and the polypropylene resin is interposed between the heating element 8 and the metal plates 9. Since the intrusion can be prevented, deterioration of the yield of the planar heater caused by contact between the metal plates 9 and poor contact between the heating element 8 and the metal plate 9 can be avoided.

Further, at the time of compression molding, the upper and lower sheets 5.
Since the glass fiber and polypropylene resin of No. 6 remain between the male and female molds 3.4 and the respective metal plates 9.9 at the time of compression molding, the respective metal plates 9.9 and the male and female metal members respectively facing them A space is always formed between the molds 3 and 4. Thus, the metal plates 9 sandwiching the heating element 8 are always covered and sealed by the glass fiber and the polypropylene resin.

Thus, in the above method, each metal plate 9.
Since 9 is always covered with glass fiber and polypropylene resin, the electrical insulation of each metal plate 9 can be maintained, and the water resistance of each metal plate 9 can be ensured. Therefore, the electrical insulation can be maintained and the water resistance can be ensured even for the heating element 8 sandwiched between the metal plates 9.

As a result, according to the above method, a sheet heater excellent in water resistance and moisture resistance and suitable for use in a bathroom or a high humidity atmosphere can be stably manufactured with high yield.

In the above embodiment, an example was described in which holes were formed in the metal plate 9 in a grid pattern. However, the shape of the metal plate 9 is not limited to the above unless deformed by pressure during molding. It does not have to be, for example, it may be a wire mesh.

[0046]

As described above, the method of manufacturing a planar heater according to the present invention generates heat when electricity is supplied between the first and second metal plates having a plurality of holes formed through the front and back surfaces. A heating element, and a core layer sheet which is a stampable sheet in which the heating element is inserted into a through-hole; and the first and second upper and lower sheets which are a stampable sheet having a fibrous material and a thermoplastic resin. And after preparing a laminate sandwiching the second metal plate from the outside, the laminate is heated so that the thermoplastic resin is melted, and then the laminate is 0.8 kg / cm ^{2 to} 10 kg / cm. ² is a method of obtaining a planar heater in which the heating element and the first and second metal plates sandwiching the heating element are sealed with the fibrous material and thermoplastic resin.

Therefore, in the above method, when the laminate is compression-molded, the thermoplastic resin of the upper and lower sheets and the core layer sheet is formed by the holes of the first and second metal plates and the first and second metal sheets. Since it is integrated through the ends of the plate, the compression molding is 0.8 kg / This can be performed at a low pressure of cm ^{2 to} 10 kg / cm ² .

Thus, the first and second metal plates are prevented from being deformed by the molding pressure, and the thermoplastic resin enters between the heating element and the first and second metal plates during molding. Can also be prevented.

Further, the fibrous material and the thermoplastic resin of each upper and lower sheet are formed by the first and second metal plates having the holes, so that the fibrous material and the thermoplastic resin are compressed between the mold and the first and second metal plates at the time of compression molding. Therefore, a gap is always formed between the first and second metal plates and the mold.

From this, the heating element and the first and second metal plates sandwiching the heating element are always covered with the fibrous material and the thermoplastic resin. Electrical insulation can be maintained and water resistance can be secured. Therefore, even for the heating element sandwiched between the first and second metal plates, electrical insulation can be maintained and water resistance can be ensured.

As a result, the above-mentioned method has an effect that a sheet heater excellent in water resistance and moisture resistance and suitable for use in a high humidity atmosphere such as a bathroom can be stably manufactured with good yield.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a laminate and a compression mold showing one step of a method for manufacturing a planar heater according to the present invention.

FIG. 2 is a perspective view of a receiving plate forming a part of a lower female mold of the compression molding mold.

FIG. 3 is a front view of a receiving plate on which the laminate is placed.

FIG. 4 is a front view when the receiving plate is heated.

FIG. 5 is a plan view when the receiving plate is mounted on a lower mold.

FIG. 6 is a graph showing a change in a product defect rate with respect to a change in compression pressure in the manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laminated body 5 Lower sheet 6 Upper sheet 7 Core layer sheet 7a Through hole 8 Heating element 9 Metal plate (1st and 2nd metal plate)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B 3/02-3/82

Claims (1)

(57) [Claims] 1. After a first metal plate having a plurality of holes penetrating the front and back surfaces is placed on a lower sheet which is a stampable sheet having a fibrous material and a thermoplastic resin, heat is generated when electricity is supplied. A core layer sheet which is a stampable sheet having a through hole into which a heating element to be inserted is inserted is overlaid on the first metal plate, and then, after the heating element is inserted into the through hole,
After placing a second metal plate having a plurality of holes penetrating the front and back surfaces on the heating element, an upper sheet made of a stampable sheet is overlaid on the second metal plate so as to match the lower sheet. after producing the laminate Te, and heated so that the thermoplastic resin of the above laminate melts, subsequently, by compression molding the laminate at ^{0.8kg / cm 2 ~10kg / cm 2} , the heating A method for manufacturing a planar heater, comprising: obtaining a planar heater in which a body and first and second metal plates sandwiching the heating element are sealed with the fibrous material and a thermoplastic resin.