JP2003059629A - Flat heater element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat heater element enabled to highly control the electric resistant with few temperature variations at a low cost. SOLUTION: The flat heater element is formed by (1) impregnating a carbon fiber woven body or a carbon fiber felt with conductive paint, and by (2) forming a plurality of openings for adjusting the electric resistance to a prescribed value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet heating element having an electric resistance value adjusted to a predetermined value, a heating toilet seat device having the heating element as a heating element, and a soil heating sheet having the heating element as a heating element.

[0002]

2. Description of the Related Art Conventionally, as a planar heating element, a nichrome wire meanderingly arranged on the surface of an insulator, a resin sheet in which conductive material particles such as carbon powder are dispersed, and electrodes are attached, carbon There is known one in which an electrode is formed on the surface of a fiber sheet. These sheet heating elements require complicated steps when they are used as heating elements by being mounted on the surface of a three-dimensional or three-dimensional object, for example, a curved surface. Moreover, it is difficult to provide a uniform temperature distribution as a heating element, and it is difficult to maintain a given object to be heated or heated at a steady temperature.

More specifically, for example, in a conventional heated toilet seat, generally, a sheet heating element having nichrome wires arranged in a meandering state on the surface of an insulator is used as a heating element. In this type of heated toilet seat, since the amount of heat generated by the nichrome wire needs to be increased considerably in order to maintain the prescribed toilet seat surface temperature, the toilet seat device part in contact with the nichrome wire is exposed to a higher temperature than other parts. Therefore, there is a drawback that it is easily damaged by heat and that the nichrome wire used may be broken within a relatively short time.

In order to eliminate the drawbacks of the planar heating element using a nichrome wire as a heating element, a planar heating element in which conductive fibers such as carbon fibers are combined has been proposed. However,
When this planar heating element is also processed into a complicated shape such as a curved surface, a large variation occurs in the temperature distribution, so it is difficult to maintain the entire heating element at a constant temperature. Also in the agricultural field, heating and heat insulation in so-called vinyl greenhouses, growth of seedlings by heating the seedbed, early shipment by promoting growth of bamboo shoots, etc. are easy to use and inexpensive agricultural soil heating and heat insulation materials. Is eagerly awaited. However, the conventional heat insulation sheet is
The main purpose is to prevent the temperature of the soil from decreasing due to cooling, and it is not possible to raise the temperature by heating the soil in winter or in cold regions, for example. In addition, although attempts have been made to heat the soil by using the electric resistance of the conductive wire, the cost is high, so that it is practically used only in part.

[0005]

SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to provide an inexpensive sheet heating element which can control the electric resistance to a high degree and which has a small temperature variation.

[0006]

Means for Solving the Problems The present inventor has conducted earnest research in view of the current state of the art as described above, and as a result, the carbon fiber paper body was provided with a conductive paint and a plurality of openings were provided. The inventors have found that a conductive sheet can achieve the above object, and completed the present invention.

That is, the present invention provides the following sheet heating element and its application. 1. (1) made of carbon fiber paper impregnated with a conductive paint,
(2) A planar heating element having a plurality of openings for adjusting the electric resistance value to a predetermined value. 2. The sheet heating element according to item 1 above, wherein the area of one opening is in the range of 3 to 2000 mm ² , and the total area of all the openings is in the range of 30 to 70% of the area of the sheet heating element. 3. A heating toilet seat device including the sheet heating element according to the above item 1 as a heating element. 4. A soil heating sheet comprising the sheet heating element according to the above 1 as a heating element.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a carbon fiber paper body or a carbon fiber felt is used as a base material for a sheet heating element.

In the present specification, "carbon fiber papermaking body"
Includes a carbon fiber papermaking body and a graphitized carbon fiber papermaking body. Such carbon fiber papermaking body is not particularly limited, and for example, commercially available products such as "Kureka Paper" (Kureha Chemical Industry Co., Ltd.) can be used. The carbon fiber papermaking body is sold in the form of a roll or a sheet, and can be used by cutting it into a predetermined size if necessary. It is preferable to use a carbon fiber paper body having a porosity of about 96 to 99.4 vol.%.

In the present specification, the "carbon fiber felt" includes carbon fiber felt and graphitized carbon fiber felt. Such a carbon fiber felt is not particularly limited, and commercially available products such as "Donnacarbo Felt" (Donac Co., Ltd.) can be used. The carbon fiber felt is sold in a roll form, and can be cut into a predetermined size and used as necessary. Carbon fiber felt has a porosity of 86-99.5
It is preferable to use the one of about vol.%.

In the production of the sheet heating element, first, a plurality of holes (hereinafter referred to as "openings") are opened in the carbon fiber paper body as a base material. The total area of these openings defines the effective area of the planar heating element (= area of planar heating element-total area of holes). Therefore, by selecting the electrical characteristics of the carbon fiber paper itself, the size and number of openings, etc., selection of the electrical characteristics of the carbon fiber paper (surface resistance, etc.), the selection of the characteristics of the conductive paint described below. In addition to adjusting the coating amount and the like, it is possible to easily control the conductivity or heat generation amount of the planar heating element.

The number, shape, area, etc. of the openings may be appropriately selected depending on the electrical / mechanical characteristics of the base material, the application of the sheet heating element, and the like. The area of one opening is usually 3 to 2000 mm ²
Within the range of about (more preferably within the range of about ²⁰ to 1200 mm ² ), and the total area of all openings is 3 of the planar heating element area.
It is within the range of 0 to 70% (more preferably within the range of 40 to 60%).

Next, the base material having the openings as described above is dipped in the conductive paint to impregnate it. As the conductive paint, known materials can be used. The conductive substance is not particularly limited, but usually has an average particle size.
Carbon particles having an average particle diameter of about 0.2 to 100 μm, more preferably about 1 to 50 μm, are suitable. Examples of such carbon fine particles include milled carbon fiber fine particles obtained by chopping graphite-based carbon fibers. As the conductive paint, either a water-based paint or an organic paint may be used, but the water-based paint is more preferable from the viewpoint of environmental load, cost and the like.

The conductive coating material has the function of improving the conductivity and the function of reinforcing the base material of the carbon fiber paper body (base material) provided with the openings. The two functions tend to conflict with each other. Therefore, the content of carbon particles in the conductive coating material may be appropriately selected according to the application of the sheet heating element, but is generally 10 to 70.
It is in the range of about wt%, and more preferably in the range of about 30 to 50 wt.

The base material coated with the conductive paint is dried and then coated or attached to form an insulating layer such as a resin film film or rubber on both surfaces.

In order to use the sheet heating element according to the present invention as a heating element in a predetermined application, an electrode, a temperature sensor, a temperature controller, a current adjusting device, etc. are attached as needed. Is a well-known electric element and is not shown.

Some specific examples of use of the sheet heating element according to the present invention will be described below, but the present invention is not limited to these applications. Further, in the drawings showing the outline of the embodiments described below, the size of the opening and the planar heating element does not indicate the actual relative size. Further, the size and shape of the opening are merely examples and do not limit the present invention.

FIG. 1 shows an outline of an example in which the heating element of the present invention is used as a heating element in a toilet seat heating device.
In this case, in order to make the temperature distribution as uniform as possible, increase the total area of the openings (the number of holes is large) in the wide part when viewed from above, and increase the total opening area in the narrow part. It is preferable to reduce the area. Practically, the shape of the opening is preferably a circle having a diameter up to 1/3 of the width of the planar heating element or an elliptical shape having a major axis. The minimum diameter of the opening is
It is about 2 mm. As an example, in a part with a width of 50 mm or more, the opening is usually circular or elliptical (major axis) with a diameter of about 2 to 20 mm, and if workability is considered, about 3 to 10 mm is preferable, and about 5 to 7 mm. Is more preferable.

FIG. 2 shows an outline of an example of using the heating element of the present invention as a heating element in a soil heating sheet. In the case of a soil heating sheet, if a high degree of drainage or air permeability is required, the diameter of one opening is preferably 10 mm or more, and considering strength, the sheet width direction It is preferable that the total length of the opening diameters (including single opening and multiple openings) does not exceed about 2/3 of the sheet width. For example. When a planar heating element having a width of 300 mm is used, a circular opening having a maximum total length of about 200 mm can be provided, but it is usually about 50 to 150 mm, more preferably 100 to 130 mm.

In the soil heating sheet according to the present invention,
Opening characteristics different from the above depending on when the heat retention effect after heat generation is emphasized more and the mechanical strength is emphasized more.
It goes without saying that (opening shape, opening area, etc.) can be adopted.

After use, the soil heating sheet according to the present invention can be wound into a roll and stored until the next use time.

[0022]

EXAMPLES The present invention will be described in more detail below with reference to examples. Examples 1 and 2 The carbon fiber paper bodies used as the base material are made of carbon fibers having a true specific gravity of 1.63, an apparent specific gravity of 0.0996, and an apparent resistivity of 7.51 Ω · cm (resistivity of carbon fiber 0.015 Ω · cm). , Porosity 99.4%, tensile strength 16.0kgf / 5cm.

This carbon fiber papermaking body was impregnated with a conductive paint prepared by adding 10 parts by weight of carbon black and 20 parts by weight of graphite powder to 100 parts by weight of a water-soluble urethane paint, squeezing with a roller and drying. The obtained material was used as a basic material for the sheet heating element according to the present invention.

The carbon fiber paper body after the above-mentioned impregnation treatment had an impregnation rate of 141% (weight increased to 1.41 times by impregnation), an apparent specific gravity of 0.171, an apparent resistivity of 1.28 Ω · cm, and a porosity of 89.6%.
The tensile strength was 40.0 kgf / 5 cm. After cutting this impregnated carbon fiber papermaking body to 32 × 30 × 0.075 cm ³ , aluminum foil electrodes with a width of 1 cm were attached to both ends on the long side, and an intermediate material with a resistor portion of 30 × 30 × 0.075 cm ³ was attached. Obtained. In this intermediate material, the apparent resistance value between the electrodes was 17Ω. 172 circular openings with a diameter of 1 cm were punched out at equal intervals in this intermediate material to make the total area of the openings 15%. The apparent resistance value of the sheet heating element A (Example 1) having this opening was 20Ω.

After preparing the basic material by the same method as described above, an intermediate material having the same size as the above was prepared. Then
Seven circular openings with a diameter of 1 cm were punched out at equal intervals in this intermediate material to make the total area of the openings 15%. The apparent resistance value of the planar heating element B (Example 2) having this opening was 20Ω.

A thickness of 100 μm is provided on the upper surfaces of the heating elements A and B.
I put the PET film of and put it on the infrared radiation thermometer and the controller with the built-in microcomputer so that the surface temperature would be 50 ℃. In such a state, the maximum temperature and the minimum temperature 5 minutes after the power was turned on were observed with a thermoviewer. The temperature of the sheet heating element A was 50 ± 1 ° C., whereas that of the sheet heating element B was 50 ± 7 ° C. Comparative Example 1 A 0.1 mm nichrome wire was meandered on a mica plate of 30 × 30 × 0.1 cm ³ and fixed with polyimide tape so that the apparent resistance value became 20Ω, and then the same as Example. Then, the maximum temperature and the minimum temperature were evaluated, and it was 50 ± 17 ° C. It was found that the temperature on the Nichrome wire was high, but the other part was affected by the thermal conductivity of the PET film.

[0027]

According to the present invention, since the electric resistance can be controlled to a high degree, it is possible to obtain an inexpensive planar heating element with little temperature variation as a whole.

Further, the sheet heating element according to the present invention has little thermal damage due to the temperature distribution, and the impregnated conductive paint improves the mechanical strength. Therefore, the durability is improved, and it becomes possible to repeatedly use the soil heating sheet for a long period of time.

[Brief description of drawings]

FIG. 1 is a plan view showing an outline of an example of a planar heating element according to the present invention used as a heating element in a heating toilet seat device.

FIG. 2 is a plan view showing an outline of an example of using the heating element of the present invention as a heating element in a soil heating sheet.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yukio Matsui             2101 Koshinohara, Yasu-machi, Yasu-gun, Shiga Prefecture             2 Within E-Tech Co., Ltd. F-term (reference) 2D037 AD03                 3K034 AA05 AA15 AA28 BB10 HA04                 3K092 PP20 QA05 QB16 QB17 QB30                       QB73 RF02 RF06 RF13 RF17                       VV22

Claims (4)

[Claims] 1. A carbon fiber papermaking body or a carbon fiber felt is impregnated with a conductive paint, and (2) a plurality of openings for adjusting an electric resistance value to a predetermined value are provided. Sheet heating element to be. 2. The area of one opening is in the range of 3 to 2000 mm ² , and the total area of all openings is 30 to 70% of the area of the planar heating element.
The planar heating element according to claim 1, which is within the range. 3. A heating toilet seat device comprising the sheet heating element according to claim 1 as a heating element. 4. A soil heating sheet provided with the sheet heating element according to claim 1 as a heating element.