JPS62113378A - Surface heating unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sheet heating element used in various heating devices and cooking devices using electrical energy as a heat source.

BACKGROUND OF THE INVENTION Conventionally, planar heating elements in which a metal heating element element is sandwiched between resin films have been widely used, but because the resin film has low heat resistance, it cannot be used at temperatures above 200°C.

Therefore, as shown in Japanese Patent Application Laid-Open No. 57-109419, an insulating hollow layer is formed on a metal substrate for hollow holes, and then a foil-shaped electric heating element is further embedded in the hollow layer. is proposed.

The structure of this heating element is shown in FIGS. 7 and 8. Reference numeral 1 denotes a metal substrate, the surface of which is coated with an insulating hollow layer 2. 3
is a planar heating element (a typical example of a heating element is shown in Figure 6).
This element 3 is placed on the surface of the hollow layer 2, and a slip for forming the hollow layer 4 is applied thereon and fired to form the hollow layer 4. Thus, the element 3 is covered with the hollow layer 4, and is bonded to the substrate. An integrally connected heating element is obtained. This heating element has relatively good electrical insulation, so 150
It is suitable for use in the medium to high temperature range of ~400°C, and has characteristics such as being thin and expected to have a long life.

Problems to be Solved by the Invention The electrical appliance standards stipulate that the insulation resistance is 1 MΩ or more during use, and the dielectric strength is 1 kV or more. The most important point of this sheet heating element is stabilization of the above characteristics.

The insulation resistance of the sheet heating element is expressed by the following formula.

R = ρt
indicates the thickness of the hollow layer.

The thickness of the hollow layer is determined from the viewpoint of hollow adhesion, and is approximately 100 to 300 μm at most. Therefore, in order to improve and stabilize the insulation resistance of the planar heating element, it is necessary to increase the volume resistivity. An insulating hollow layer may be formed using a high-quality glass frit. The volume resistivity of glass frit is determined by the amount of alkaline components in the glass (Na2O, K2O,
(Li2O, etc.), so if you choose a glass frit with a low alkali content,
Stabilization of insulation resistance can be achieved.

However, with regard to dielectric strength, there is no clear relationship between the above-mentioned insulation resistance and its properties vary significantly depending on the type of glass frit used, film thickness, firing conditions, etc. As shown in Japanese Patent Application No. 58-181029, the inventors of the present invention have found that dielectric strength can be improved by using a titanium opalescent frit in the hollow layer shown in FIG. 8. However, this method alone still has problems in terms of stabilization of dielectric strength, large variations in characteristics, and problems in terms of mass production yield.

Means to Solve the Problem In a planar heating element in which a foil-shaped electric heating element is covered and bonded with a titanium milky white hollow layer on a metal substrate on which an insulating hollow layer is formed, the titanium milky white hollow layer is bonded. Precipitation strength TA of anatase type TiO□ and rutile type TiO
The precipitation strength of □ is 8 and 2TR/ (TA +TR)
<O-6.

Effect: With the above-described configuration, it is possible to stabilize dielectric strength, increase product yield, and provide a heating element with excellent longevity.

Embodiment The configuration of the present invention is essentially the same as the conventional configuration. Figures 1 (a), (b), (c), and (c) show examples of the configuration of the planar heating element of the present invention. Reference numeral 1 denotes a metal substrate, on both sides of which a hollow layer 2 having insulation properties is formed.

The heating element 3 is installed on the surface of the hollow layer 2 and covered with a titanium milky white hollow layer 4, so that the heating element 3 is sandwiched between the hollow layers.

Note that, as shown in (b), (c), and (b), it is also possible to provide an intermediate hollow layer 6 in order to match the expansion coefficient of the hollow layer. Further, it is also possible to overcoat each hollow layer on the side opposite to the side on which the heating element is provided, in order to prevent thermal deformation during firing.

Each component will be explained below.

(1) Metal base material The metal base material of the hollow substrate constituting the planar heating element of the present invention is aluminum or aluminum die-cast.

Cast iron, aluminized steel, low carbon steel, hollow steel plate, and stainless steel plate are used, and their selection is determined by usage conditions, usage temperature, base material shape, and workability, and pretreatment is performed as necessary. .

The following explanation will focus on steel plates for hollow holes.

(2) Heating element The electric heating element used in the present invention is basically in the shape of a thin strip or lath steel, and its thickness is 10 to 16 mm.
0 μm is suitable, preferably 30 to ioo μm.

In addition to the usual methods of cold rolling and hot rolling, there is also a method of forming a metal into a thin ribbon using an ultra-quenching method. A method of forming a thin strip of metal into a desired pattern, a sheet metal etching method, a press punching method, and an expand band method are suitable.

FIG. 6 shows an example of a patterned heating element. The material of the heating element is Fe-Ni, Fe-Ni-0
r.

Various electrical heating materials can be used, such as stainless steel.

(3) Hollow layer with electrical insulation properties As mentioned above, in order to make the electrical insulation properties of the planar heating element comply with electrical appliance standards, it is recommended to use a glass lift as shown in Table 1. preferable.

As the hollow forming method, hollow slip spray method, dipping method, powder electrostatic method, electrophoresis method, etc. are used.
It is fired at a predetermined firing temperature.

(4) Titanium milky white hollow layer The crystal system of precipitated TiO2 in the titanium milky white hollow layer differs depending on the firing conditions, milling conditions, type of glass fribut, etc. An example of the results is shown in the X-ray pattern of FIG. The precipitated crystals of TiO□ are anatase type and rutile type. In FIG. 2, (&) is an amorphous state in which no TiO□ crystals are precipitated, (11) is a state in which anatase type TiO2 is slightly precipitated, and (Q) is a state in which anatase type TiO□ is precipitated. (d) shows a state in which rutile-type TiO□ is precipitated.

As shown in Fig. 3, the type and amount of precipitated crystals in a typical titanium milky hollow layer vary markedly depending on the firing temperature, for example, and as the firing temperature increases, it changes from anatase type Ti02 to rutile type Ti02. Shift to TiO2. Here, the X-ray intensity is a plot of the intensity of the 101 plane where the intensity is the strongest. The present inventors have discovered that there is a close relationship between the state of crystal precipitation and dielectric strength.

The results are shown in Figure 4. Here, TA and TR are 1 of anatase TiO□ and rutile TiO2, respectively.
The X-ray intensity on the 01 plane is shown. From now on, T
As the value of R/(TA +TIl) increases, that is, as the amount of rutile TiO□ increases, the dielectric strength decreases significantly, and the dielectric strength decreases to 1 kV as specified in the electrical appliance standards.
It becomes impossible to clear the O value.

That is, from these results, the titanium milky white hollow layer of the planar heating element of the present invention satisfies TR/(T□10TR)<0.
．． It is necessary to keep it in the range of 6.

As long as these values are satisfied, it can be formed by spraying tita 7 extract, transfer paper method, dipping, powder electrostatic method, etc.

Next, a specific example will be described.

Using the configuration shown in FIG. 1(a), 60 samples were each produced in order to compare the product of the present invention and the conventional product.

The metal substrate has a size of 20CHIM x 200MM and a thickness of 0.
After pickling and nickel treatment using an 8MM hollow steel plate, an insulating hollow layer was formed. The glass frit used for this hollow layer is a low-alkali borosilicate glass as shown in Table 1, which has a mill composition as shown in Table 2, and is wet-pulverized and mixed in a ball mill for 3 hours to obtain the desired slip. I got it.

Table 2 This slip was spray coated onto the above-mentioned substrate to a thickness of about 160 μm, dried, and fired at about 860° C. to form a hollow layer having insulating properties.

In addition, as a heating element, 5US43o (
A pattern made of 60 μm thick was used. This was installed on the above-mentioned hollow layer, and from above, 15s3c manufactured by Ferro Co.
A slip of the composition shown in Table 2 was spray coated using a titanium opalescent frit, dried, and fired to form a sample of 6.
0 prototypes were produced.

Here, the product of the present invention has a value of TR/CT□+TR) of 0.
．． The firing conditions, milling conditions, etc. were strictly controlled so that the result was 4. For comparison, the current product was prototyped without taking any of the above values into account.

The dielectric strength of each of these 60 samples was measured and the degree of variation was compared. The results are shown in FIG.

As is clear from these results, the present invention shows that a stable product with high dielectric strength can be obtained.

As described above, the present invention has excellent electrical characteristics,
Moreover, it is possible to provide a planar heating element that can be stably produced and has an increased product yield.

[Brief explanation of drawings]

Figures 1 (A), (B), (C), and 2) are longitudinal sectional views showing an example of the configuration of a heating element according to the present invention, and Figure 2 is an X-ray pattern 7 showing the state of precipitation of TlO2 particles in a titanium milky white hollow. , Figure 3 is a diagram showing the relationship between the TlO2 particle precipitation state and firing temperature of a typical titanium milky white hollow layer, and Figure 4 is a diagram showing the relationship between the dielectric strength and TR
/(TA +TR), Figure 5 is a diagram comparing the degree of variation in dielectric strength between the product of the present invention and a conventional example, and Figure 6 is a plan view showing an example of an electric heating element. , 7th
The figure is a cutaway perspective view of main parts showing a conventional example, and Fig. 8 is Fig. 7A-
It is an X-ray cross-sectional view. DESCRIPTION OF SYMBOLS 1...Metal substrate, 2...Hollow layer having insulation properties, 3...Electric heating element, 4...
...Titanium milky white hollow layer, 6...Intermediate hollow layer. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
14th Figure 2 × 4th Figure ``A TA Shiding Rn 5th Figure

Claims (1)

[Claims] In a planar heating element in which a foil-like electric heating element is covered and bonded with a titanium milky white hollow layer on a metal substrate on which an insulating hollow layer is formed, the anatase type TiO_2 precipitation strength T_A of the titanium milky white hollow layer and rutile Type Ti
The precipitation strength T_R of O_2 is expressed by the formula T_R/(T_A+T_
A planar heating element characterized by a relationship satisfying R)<0.6.