JPH09139279A - Surface heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface heater in which temperature distribution on a cooking surface is uniform, and the temperature on the cooking surface is hardly decreased even when a food material is placed on the cooking surface. SOLUTION: A heat resistant insulating plate 2 has a cooking surface 2a for cooking a food material, and a heating film 3 is formed on the surface of the heat resistant insulating plate 2. The heating film 3 has a positive electric resistance-temperature characteristic which changes the resistance value in the same direction as the change of the temperature, forms 25 heating blocks each covers the area of 21cm<2> or less on the surface of the heat resistant insulating plate 2, and these heating blocks 5 are electrically connected in parallel.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a planar heating element. More specifically, the present invention relates to a planar heating element for heating and cooking used in a cooking device for heating (for example, a hot plate used for domestic cooking).

[0002]

2. Description of the Related Art In a hot plate generally known in the past, the upper surface of an iron or aluminum plate is used as a cooking surface. Therefore, the cooking surface is heated by the sheathed heater installed below the plate or the heater embedded in the lower surface of the plate. In addition, recently, a planar heating element has been proposed in which a heating film for heating the plate is formed on the surface of the plate having heat resistance and insulation properties, aiming to reduce the thickness and make the temperature uniform (Japanese Patent Laid-Open Publication No. Sho. 57-107583).

[0003]

In the above hot plate in which the cooking surface is heated by the sheathed heater installed below the plate or the heater embedded in the lower surface of the plate, the heater has a turn shape in which the heater is folded back about two times. Therefore, the temperature distribution on the cooking surface is not uniform. For this reason,
Depending on the food material (for example, meat to be roasted, food to be cooked such as vegetables), uneven roasting may occur.

Further, in the above-mentioned sheet heating element in which the heat-generating film for heating the plate is formed on the surface of the plate having heat resistance and insulation, the variation in temperature distribution is improved as compared with the above-mentioned hot plate, When foodstuffs are placed on the cooked surface that has generated heat, it is not possible to quickly raise the temperature of only the cooking surface portion whose temperature has been lowered by the foodstuffs and to make the temperature distribution on the cooking surface uniform. Since the partially lowered temperature of the cooking surface continues for a long time, the cooking time becomes longer and the cookability becomes worse.

The present invention has been made in view of the above problems, and has a uniform surface temperature distribution on a cooking surface, and moreover, even if food is placed on the cooking surface, the surface temperature of the cooking surface is unlikely to drop. The purpose is to provide a heating element.

[0006]

In order to achieve the above object, the sheet heating element of the first invention is a heat-resistant insulating plate having a cooking surface for heating and cooking food, and a heat-resistant insulating plate of the heat-resistant insulating plate. A heat generating film formed on the surface, wherein the heat generating film has a positive electric resistance-temperature characteristic that changes a resistance value in the same direction as a temperature change, and the heat resistant insulation. A plurality of heat generating blocks each covering an area of 21 cm ² or less are formed on the surface of the heat-resistant plate, and the heat generating blocks are electrically connected in parallel.

The heating film having a positive electric resistance-temperature characteristic changes its resistance value in the same direction as the temperature change. Therefore, when the temperature of the heat-resistant insulating plate decreases, the temperature of the heat-generating film formed on the surface of the heat-resistant insulating plate also decreases, so the resistance value of the heat-generating film decreases and the current flowing through the heat-generating film increases. The heating value of the heating film increases. Conversely, when the temperature of the heat-resistant insulating plate rises, the temperature of the heat-generating film formed on the surface of the heat-resistant insulating plate also increases, so the resistance value of the heat-generating film increases and the current flowing through the heat-generating film decreases. As a result, the amount of heat generated by the heating film is reduced. Since a plurality of heat generating blocks made of this heat generating film are electrically connected in parallel, the current flows through the heat generating films constituting each heat generating block so that all the heat generating blocks have the same temperature. Become.

On the other hand, the heat-generating film forms a plurality of heat-generating blocks each covering an area of 21 cm ² or less on the surface of the heat-resistant insulating plate, and therefore heat-insulates foods currently generally used in Japan. When placed on the sex plate, there are at least two heat generating blocks below the food due to the size of the food.

When food is placed on the heat-resistant insulating plate which is generating heat as described above, the temperature of the heat-resistant insulating plate portion on which the food is placed is lowered, and the temperature of the heat generating block located below it is also lowered. Since the heat generating blocks are electrically connected in parallel, the resistance value of the heat generating film forming the heat generating block whose temperature has dropped becomes smaller than the resistance value of the heat generating film forming the other heat generating blocks. . As a result, the current flowing through the heat-generating film forming the heat-generating block whose temperature has decreased increases and the amount of heat generated by the heat-generating film increases, so the temperature rise of the heat-resistant insulating plate in the temperature-decreased portion is accelerated, The temperature recovers quickly.

In the sheet heating element of the second invention, in the structure of the first invention, the heating block has a film thickness of 15 to 20.
It is characterized by being composed of parallel and meandering heat-generating films having a thickness of μm, a film width of 0.5 to 2.0 mm and a film pitch of 1.0 to 4.0 mm. Even if the heat-generating coating is formed to have a parallel meandering shape, abnormal heat generation does not occur at the folded portion of the meandering as long as the thickness, coating width and coating pitch are satisfied.

In the sheet heating element of the third invention, in the structure of the first invention, a heating block located in an intermediate portion of the plurality of heating blocks is located in an intermediate portion of a resistance value of a heating block located in an outer peripheral portion. Is higher, and the resistance value of the heat generating block located in the central portion is higher than the resistance value of the heat generating block located in the middle portion. Also,
In the sheet heating element of the fourth aspect of the invention, in the configuration of the third aspect of the invention, the resistance value of the heat generating block located in the middle portion is set to 5 relative to the resistance value of the heat generating block located in the outer peripheral portion.
% Higher than the resistance value of the heating block located in the central part
It is characterized by being set 10% higher.

The conventional sheet heating element described above (Japanese Patent Laid-Open No. 57-1075)
(No. 83, etc.) has a better heat radiation balance and a stable heat generation state than the above-mentioned hot plate, but regarding the temperature distribution on the cooking surface, the temperature of the central part of the cooking surface due to heat radiation and convection, etc. The temperature tends to be higher than the temperature of the outer peripheral portion of the cooking surface. Therefore, it cannot be said that the temperature distribution on the cooking surface is sufficiently uniform. According to the configurations of the third and fourth aspects, the resistance value is set to be higher in the heat generating block closer to the center of the cooking surface, so that the current value flowing in the heat generating block closer to the center of the cooking surface is suppressed. , Fever is suppressed.

In the sheet heating element of the fifth invention, in the structure of the first invention, the structure in which the heat generating blocks are electrically connected in parallel is electrically separated for each heat generating block and independently. It is characterized in that the pattern of the formed heat generating film and the pattern of the electrode film are formed to overlap each other. Since the heat generating film is electrically separated and independently formed for each heat generating block, the resistance value can be measured for each heat generating block before the electrode film is formed.

In the sheet heating element of the sixth invention, in the structure of the first invention, the structure in which the heating blocks are electrically connected in parallel is electrically separated for each heating block and independently. The pattern of the heating film formed, 180
It is characterized by being formed by overlapping with an electrode film pattern having a power supply electrode pair having rotational symmetry.

The electrode film requires a power supply electrode pair for supplying power to the heat generating film. When the sheet heating element is provided so as to be removable from the cooking appliance body, when the sheet heating element is attached to the cooking appliance body, the power supply terminal provided on the cooking appliance body becomes the sheet heating element. It is necessary to perform the alignment while confirming the positions of the power supply terminal and the electrode pair so as to be in contact with the provided power supply electrode pair. If this work is not performed properly, it may be necessary to reattach the sheet heating element. For example,
If the planar heating element has a rectangular shape, the rectangle
Since there is 180 ° rotational symmetry, there are two mounting directions, but if there is only one power feeding point, one of them will be an unsuitable mounting direction. Therefore, if the confirmation of the left-right alignment is not performed, the planar heating element may have to be re-mounted after being rotated 180 ° further from the improperly mounted state. According to the sixth aspect of the invention, since the electrode coating has the pair of electrodes for power supply with 180 ° rotational symmetry, when the planar heating element is attached to the cooking appliance body, the positions of the terminal for power supply and the position of the electrode pair are set. Alignment can be performed without confirmation.

In the sheet heating element of the seventh invention, in the constitution of the fifth or sixth invention, a portion of the heating film which overlaps with the electrode film is largely formed along the pattern shape of the electrode film. It is characterized by Since the portion of the heating film that overlaps with the electrode film is formed large along the pattern shape of the electrode film, the area of the portion where the heating film and the electrode film overlap and contact each other is large.
Therefore, the contact between the heat generating film and the electrode film is ensured.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a planar heating element embodying the present invention will be described with reference to the drawings. The same parts or corresponding parts in the embodiments will be assigned the same reference numerals and overlapping description will be omitted.

<< First Embodiment >> FIG. 1 is a bottom view showing a planar heating element 1 of the first embodiment, and FIG. 2 is a detailed view showing one heating block 5 constituting the sheet heating element 1. FIG. 3 is a bottom view showing a state where a food material (eg, meat to be cooked, meat to be cooked such as vegetables) 6 is placed on the cooking surface 2a. 1 and 3, the number of coating turns of the heating coating 3 is omitted. That is, the number of coating turns of the heating coating 3 used for the planar heating element 1 is 37 as shown in FIG. The number of film turns is the number of straight portions of the pattern of the heating film 3 (that is, one reciprocation is counted as two).

The sheet heating element 1 shown in FIG. 1 comprises a heat resistant insulating plate 2, a heating film 3 and an electrode film 4.
The heat resistant insulating plate 2 has a cooking surface 2a for heating and cooking the food 6. Examples of the material for the heat resistant insulating plate 2 include crystallized glass, lithia ceramics, cordierite ceramics and the like.
Since these materials have high heat resistance, the heat resistance of the sheet heating element 1 itself is improved by using the heat resistant insulating plate 2 made of these materials. In addition, 4a in FIG.
It is a pair of power supply electrodes composed of the electrode film 4.

The heating film 3 is formed on the rear surface of the cooking surface 2a of the heat resistant insulating plate 2 (that is, the bottom surface of the sheet heating element 1). The heating film 3 is formed by screen-printing a conductor paste on the surface of the heat-resistant insulating plate 2, drying and baking. The surface on which the heat generating film 3 is formed may be coated with heat resistant insulation, and the coated surface may be used as a cooking surface.

Further, the heat generating film 3 has a positive electric resistance-temperature characteristic in which the resistance value changes in the same direction as the change in temperature, and the heat generating film 3 having this characteristic is used to form the heat generating film 3. A conductor paste for forming the is used. Heating film 3
For example, the resistance-temperature characteristic TCR (that is, the rate of change in resistance with temperature) is 0.65% / ° C, nickel-based coating or 0.35% /
An example is a silver-based film at ℃.

Further, the heat generating film 3 covers an area of 21 cm ² or less on the surface of the heat resistant insulating plate 25.
Each heat generating block 5 is formed. The area 21 (cm ² ) of the heating block 5 adopted here covers the size of the foodstuff that is generally used for roasted meat, etc. in Japan at present, by the heating block unit. It is a size that can be efficiently backed up. When the area of the heat generating block 5 exceeds 21 cm ² , it becomes difficult to obtain a resistance value suitable for a cooking device. Desirably, the area of the heat generating block 5 is 8 to 21 cm ² . This is because if the area of the heat generating block 5 becomes extremely small, the specifications of the heat generating film 3 that constitutes it will be limited.

As shown in FIG. 2, the heat generating film 3 which constitutes the heat generating block 5 has a parallel meandering shape. Therefore, this parallel meandering pattern is applied to the heating block 5
The resistance value can be adjusted in units of heat generation blocks by changing the value inside. Here, changing the parallel serpentine pattern means, for example, changing the number of film turns and the film pitch (that is, the interval between the straight portions of the patterns of the adjacent heating films 3 in the center).

The heating block 5 has a film thickness of 15 to 20 μm.
It is preferable that the heat-generating coating 3 has a meandering shape and has a width of 0.5 to 2.0 mm and a coating pitch of 1.0 to 4.0 mm. If the film width is less than 0.5 mm, the screen will be easily clogged during screen printing.
The pattern is likely to be cut. When the film width exceeds 2.0 mm, an electric current flows inside the pattern of the heating film 3 which is in a meandering shape in parallel, and heat unevenness is likely to occur between the inside and the outside of the pattern. Therefore, if the above-mentioned specifications are satisfied, the manufacturing becomes easy, and a uniform and stable heat generation state of the entire heat generation film 3 can be obtained. In addition, when the heating film 3 has a parallel meandering shape, the meandering folded portion (that is,
Although abnormal heat generation is likely to occur in the portion where the direction is changed), if the above specifications are satisfied, abnormal heat generation is less likely to occur in the meandering folded portion, so that a uniform and stable heat generation state of the entire heat generation film 3 can be obtained. Therefore, there is an effect that the life of the coating is extended.

The heating film 3 has a structure in which 25 heating blocks 5 are electrically connected in parallel. This connection structure has a pattern of the heating film 3 which is electrically separated and independently formed for each heating block, and an electrode film 4.
It is configured by overlapping and forming the pattern. That is, the electrode coating 4 is formed on the heat resistant insulating plate 2 on which the heat generating coating 3 is formed. The formation of the electrode film 4 will be described in detail later.

As described above, the heating film 3 having a positive electric resistance-temperature characteristic changes its resistance value in the same direction as the temperature change. Therefore, when the temperature of the heat-resistant insulating plate 2 becomes low, the temperature of the heat-generating film 3 formed on the surface of the heat-resistant insulating plate 2 also becomes low, so that the resistance value of the heat-generating film 3 becomes small and flows into the heat-generating film 3. The current increases and the amount of heat generated by the heat generating film 3 increases. On the contrary, when the temperature of the heat-resistant insulating plate 2 rises, the temperature of the heat-generating film 3 formed on the surface of the heat-resistant insulating plate 2 also rises, so that the resistance value of the heat-generating film 3 increases and The flowing current decreases and the amount of heat generated by the heat generating film 3 decreases. The twenty-five heat generating blocks 5 made of the heat generating film 3 are electrically connected in parallel by the electrode film 4, so that the heat generating films 3 forming each heat generating block 5 have no heat generating block 5 at all. An electric current flows so that the temperature becomes the same, and the temperature distribution on the cooking surface 2a is made uniform. In addition, since the temperature of the exothermic film 3 is low immediately after the power is supplied, the rising speed of the rising temperature of the cooking surface 1a is increased, and the cooking time is shortened to that extent, which facilitates cooking.

On the other hand, since the heat-generating film 3 comprises a plurality of heat-generating blocks 5 covering the area of 21 cm ² or less on the surface of the heat-resistant insulating plate 2 as described above, it is generally used in Japan at present. When the known foodstuff 6 is placed on the heat-resistant insulating plate 2, the size of the foodstuff 6 causes
For example, as shown in FIG. 3, there are three heating blocks 5A, 5B, 5C below the food material 6. Therefore, as described below, it is possible to efficiently back up the heat of the food material 6.

The food 6 is placed on the heat-resistant insulating plate 2 which is generating heat.
On the heat-resistant insulating plate 2 on which the food 6 is placed
The temperature of the part decreases, and the temperature of the heat generating blocks 5A, 5B, 5C located below the part also decreases. All heating block 5
Are electrically connected in parallel, so that the heating film 3 forming the heating blocks 5A, 5B, 5C whose temperature has dropped
Has a smaller resistance value than the resistance value of the heating film 3 forming the other heating block 5. As a result, the current flowing through the heat generating film 3 forming the heat generating blocks 5A, 5B, 5C increases and the amount of heat generated by the heat generating film 3 increases, so that the temperature rise of the heat resistant insulating plate 2 is accelerated. Even when the food 6 is placed and the temperature of the cooking surface 1a is lowered in this way, the heat of the food 6 is efficiently backed up and the temperature is quickly recovered. Therefore, even if the food material 6 is placed on the cooking surface 2a, the temperature of the cooking surface 2a does not easily decrease.

Due to the increase in the amount of heat generated, the temperature of the heat resistant insulating plate 2 on which the food material 6 is placed rises, and the temperature distribution of the entire heat resistant insulating plate 2 becomes uniform, so that the heat generating blocks 5A, 5B. , 5C, the resistance value of the heat generating film 3 becomes large. As a result, the current flowing through the heat generating film 3 decreases and the amount of heat generated by the heat generating film 3 decreases, so that the temperature rise of the heat resistant insulating plate 2 is suppressed. When the temperature distribution on the cooking surface 2a becomes uniform, the resistance values of the heat-generating films 3 forming all the heat-generating blocks 5 become equal, and the respective heat generation amounts become equal.

As described above, according to the planar heating element 1, the temperature of the cooking surface 1a whose temperature has dropped can be quickly returned without a control circuit, so that the cooking time is greatly shortened and the cooking time is improved. It will be easier. Moreover, since the temperature suitable for the foodstuff 6 is always maintained, the cookability of the foodstuff 6 is improved. Not only when the food material 6 is placed on the heat-resistant insulating plate 2 that is generating heat, but when the temperature of some of the heat generating blocks 5 changes, the temperature of all the heat generating blocks 5 becomes the same as above. Thus, the heat generation amount is self-controlled in each heat generation block unit.

As shown in FIG. 2, the heat generating block 5 has a vertical length (Y) equal to a horizontal length (X) (X =
Y). The shape of the heat generating block 5 is preferably as close to a square as possible. This is because a shape close to a square is advantageous in efficiently backing up heat for the food 6 in view of the size and shape of the food currently generally used for roasted meat in Japan.

<< Second Embodiment >> FIG. 4A shows the first embodiment.
4B shows the temperature distribution of the cooking surface 2a of the sheet heating element 1 according to the embodiment, and FIG. 4B shows the arrangement of the heating blocks 5 formed on the bottom surface of the sheet heating element 1. , Fig. 4
(C) shows the pattern of the heat-generating film 3 which constitutes the heat-generating block 5. Further, FIG. 5 (A) shows the temperature distribution of the cooking surface 2a of the sheet heating element 1 of the second embodiment,
FIG. 5B shows the arrangement of the heat generating blocks P1, P2, P3 formed on the bottom surface of the sheet heating element 1.
(C) shows the pattern of the heat-generating film 3 which constitutes the heat-generating blocks P1, P2, P3.

While the first embodiment has 25 heating blocks 5 having the same structure, the second embodiment has three types of heating blocks (ie, 16 heating blocks). P1 has eight heat generating blocks P2 and one heat generating block P3). In addition, in the second embodiment, of the 25 heat generating blocks P1 to P3, the resistance value of the heat generating block P2 located in the middle part is 5 with respect to the resistance value of the heat generating block P1 located in the outer peripheral part. %
High, the resistance value of the heating block P3 located in the center is 10
The feature is that it is set high. Table 1 shows the number of film turns, the resistance value, and the resistance ratio of each heating block P1 to P3.

[0034]

[Table 1]

The heat-generating film 3 forming the heat-generating block 5 has 37 film turns in all the heat-generating blocks, whereas the heat-generating film 3 forming the heat-generating block P1 has 37 film turns. The number of film turns of the heat generating film 3 constituting the heat generating block P2 is 39, and the number of film turns of the heat generating film 3 constituting the heat generating block P3 is 41.
It is a book. By changing the number of film turns and changing the film pitch accordingly, the resistance value of the heat generating film 3 is adjusted in units of three types of heat generating blocks P1 to P3.

The above-mentioned conventional sheet heating element (Japanese Patent Laid-Open No. 57-1075)
According to (No. 83 etc.), compared to the above-mentioned hot plate that heats the cooking surface with a sheathed heater installed below the plate, the heat dissipation is well balanced and a stable heat generation state is obtained, but the temperature distribution of the cooking surface Regarding the above, due to heat radiation and convection, the temperature of the central portion of the cooking surface tends to be higher than the temperature of the outer peripheral portion of the cooking surface. Therefore, it cannot be said that the temperature distribution on the cooking surface is sufficiently uniform.

In the sheet heating element 1 shown in FIG. 4 (B), the temperature distribution on the cooking surface 2a is fairly uniformized (FIG. 4 (A)).
However, in the planar heating element 1 shown in FIG. 5 (B), the temperature distribution on the cooking surface 2a is more uniform than that (FIG. 5 (A)).
According to the configuration of the sheet heating element 1 shown in FIG.
Since the heat generating block closer to the center of a has a higher resistance value, the heat generating block closer to the center of the cooking surface 2a suppresses the flowing current value and suppresses heat generation.
Therefore, the closer to the center of the cooking surface 2a, the less the amount of heat generation, so that the temperature distribution on the cooking surface 2a becomes uniform as shown in FIG. 5 (A).

<< Third Embodiment >> FIG. 6 is a bottom view showing a planar heating element 1 according to a third embodiment. Electrode film 4
Requires a power supply electrode pair for supplying power to the heat generating film 3, and the planar heating element 1 shown in FIG. 1 has a power supply electrode pair 4a formed at one location. On the other hand, in the planar heating element 1 shown in FIG. 6, the pattern of the electrode coating 4 having the power supply electrode pair 4b having 180 ° rotational symmetry is the heating coating 3
Is formed so as to overlap the pattern. That is, the pattern of the electrode coating 4 is formed in a comb shape with respect to the pattern of the heat generating coating 3, and the pattern of the electrode coating 4 is diagonally formed in the same shape so as to have the same shape. Two
A pair of power supply electrode pairs 4b is formed.

When the sheet heating element 1 is detachably provided to the cooking appliance main body (not shown), when the sheet heating element 1 is attached to the cooking appliance main body, the power supply provided in the cooking appliance body is provided. It is necessary to perform the alignment while checking the positions of the power supply terminal and the electrode pair so that the power supply terminal is in contact with the power supply electrode pair provided on the planar heating element. When the heat-generating film 3 is provided on the bottom surface of the heat-resistant insulating plate 2 as in the planar heating element 1 shown in FIG. 1, the confirmation of the above position is a particularly troublesome work. If this work is not performed properly, the sheet heating element 1 may have to be reattached.

For example, when the sheet heating element 1 has a rectangular shape, the rectangle has 180 ° rotational symmetry, so the mounting direction is two. However, the sheet heating element 1 shown in FIG. As described above, if there is only one power feeding point (power feeding electrode pair 4a), one of the directions is an inappropriate mounting direction.
Therefore, if the alignment of the left and right sides is not confirmed, it may be necessary to rotate the sheet heating element 1 further from the improperly mounted state by 180 ° and then mount it again.

In the third embodiment, the electrode film 4 has 180
Since it has a pair of power supply electrodes 4b that are rotationally symmetrical,
When the planar heating element 1 is attached to the cooking appliance main body, the above-mentioned alignment can be reliably performed without checking the positions of the power feeding terminal and the power feeding electrode pair 4b. Therefore, as described above, it is not necessary to confirm the left and right alignment, and the planar heating element 1 can be easily attached to the cooking appliance body.

<< Formation of Electrode Coating 3 in First to Third Embodiments >> FIGS. 7 and 8 both show patterns of the heating coating 3 before formation of the electrode coating 4 in the first to third embodiments. Is shown. The electrode coating 4 is formed on the electrode printing portion 4c indicated by a chain double-dashed line with the marks formed by the heat generating coatings 3 above and below the center in FIGS. However, FIG.
When the electrode coating 4 is formed on the electrode printed portion 4c shown in (1), the area of the overlapping portion of the electrode coating 4 and the heating coating 3 becomes extremely small, so that the heating coating 3 and the electrode coating 4 are in point contact with each other. Therefore, contact failure may occur.

On the other hand, in the pattern of the heat generating film 3 shown in FIG. 8, the overlapping portion 3a of the pattern of the heat generating film 3 and the pattern of the electrode film 4 is formed largely along the pattern shape of the electrode film 4. . FIG. 9 is an enlarged view of the overlapping portion 3a formed of the pattern of the heat generating film 3. As shown in FIG. 9, in the overlapping portion 3a, a space d (= 0.5 mm) is provided between the heat generating films 3 of the adjacent heat generating blocks,
The width is formed to be the same as the width of the electrode print portion 4c. Therefore, as compared with the case where the pattern of the heat generating film 3 in FIG. 7 is adopted, the area in which the heat generating film 3 and the electrode film 4 are in contact with each other becomes large, and even if the formation position of the electrode film 4 is slightly displaced, the contact is made. Will be certain. As a result, contact failure can be prevented and reliable power supply can be performed.

By providing the spacing d as shown in FIG. 9, the pattern of the heat generating film 3 can be electrically separated and independently formed for each heat generating block. Therefore, the above-described structure in which the heating blocks 5 are electrically connected in parallel is formed by superposing the pattern of the electrode coating 4 on the pattern of the heating coating 3 which is electrically separated and independently formed for each heating block. It is configured by The interval d may be formed when designing a screen plate used for forming the heat generating film 3.

As described above, since the heat generating film 3 is electrically separated and independently formed for each heat generating block by the interval d, the resistance value should be measured for each heat generating block before the electrode film 4 is formed. You can Therefore, the resistance distribution (for example, the variation of the resistance value) of the entire heating film 3 can be confirmed in units of heating blocks. By confirming the resistance distribution, it is possible to know whether the adjustment of the heater pattern of the firing furnace used for baking the heat generating film 3 or the printing conditions for screen printing the heat generating film 3 are appropriate. Therefore, these manufacturing conditions can be fed back to the formation of the heating film 3 to be performed next, and the non-defective products can be selected before the electrode film 4 is formed, so that the manufacturing process can be improved. You can

[0046]

The following is a description of the sheet heating element embodying the present invention.
A more specific description will be given with reference to Examples and Comparative Examples. The same parts as those in the above-described embodiment and corresponding parts will be described using the same reference numerals.

Table 2 shows the constitution of the exothermic coatings 3 of Examples 1 to 4, and Table 3 shows the constitution of the exothermic coatings of Comparative Examples 1 to 4. In addition, Example 1 is the heating film 3 shown in FIGS.
The initial resistance (combined resistance) is 8 (Ω) and the rated power is 1,250 (W). As described above, the first embodiment is suitable for a domestic hot plate.

The heat generating film 3 is formed under the following conditions. The area of the heat-resistant insulating plate 2 on which the heat-generating coating 3 is printed is 230 × 230 mm. Surface resistance: 70 (mΩ / □), electric resistance-temperature characteristics: 0.35 (%
/ ° C.) is used for the conductor paste that produces the exothermic film 3. The conductor paste is baked by air baking. The heating block 5 is connected in parallel with the electrode film 4.

The data in Tables 2 and 3 are defined below. (1) Number of blocks: The number of heat generating blocks 5 formed on the surface of the heat resistant insulating plate 2. (2) Block area: The area where the heat generating block 5 covers the surface of the heat resistant insulating plate 2. (3) X × Y size: horizontal size (X) and vertical size (Y) of the heat generating block 5 shown in FIG. (4) Block resistance value: The resistance value of the heating film 3 that constitutes one heating block 5. (5) Block magnification: [length of heat-generating film 3 that constitutes one heat-generating block 5] / [film width], film width,
Calculated from the film pitch, film turn number, film turn width, and sheet resistance. Then, the resistance value of the block is calculated from the magnification of the block and the sheet resistance. (6) Coating width: Heating coating 3 that constitutes the heating block 5
Width of. (7) Film turn width: The distance between the folded portions (corresponding to the vertical size Y in FIG. 2). (8) Coating pitch, number of coating turns: As described above.

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

As described above, according to the first to seventh inventions, the heat generating block is composed of a heat generating film having a positive electric resistance-temperature characteristic, and is electrically connected in parallel. , The temperature distribution on the cooking surface is kept uniform. Furthermore, the heat-generating film is formed on the surface of the heat-resistant insulating plate.
Since it consists of multiple heating blocks that cover an area of 21 cm ² or less, the temperature of the cooking surface does not easily drop even if food is placed on the cooking surface. Therefore, the cooking time can be shortened and the cookability of the food material can be improved.

According to the second aspect of the present invention, the heating film uniformly generates heat, so that the cooking surface can be brought into a uniform and stable heat generation state. According to the third and fourth inventions, the heat generation amount decreases as the heat generating block is closer to the central portion of the cooking surface, so that the temperature distribution on the cooking surface becomes more uniform. According to the fifth and sixth aspects, it is possible to confirm the resistance distribution (for example, the variation in the resistance value) of the entire heating film in units of heating blocks.
According to the sixth aspect, even when the sheet heating element is provided so as to be removable from the cooking appliance body, it can be easily attached to the cooking appliance body. According to the seventh aspect of the present invention, it is possible to prevent contact failure and perform reliable power supply.

[Brief description of the drawings]

FIG. 1 is a bottom view showing a planar heating element according to a first embodiment.

FIG. 2 is a detailed view showing one heating block forming the planar heating element shown in FIG.

FIG. 3 is a bottom view showing a state where food is placed on the cooking surface of the sheet heating element shown in FIG.

FIG. 4 is a diagram showing the temperature distribution on the cooking surface of the sheet heating element shown in FIG. 1 in association with the configuration and arrangement of heating blocks.

FIG. 5 is a diagram showing a temperature distribution on a cooking surface of the planar heating element according to the second embodiment in association with the configuration and arrangement of heating blocks.

FIG. 6 is a bottom view showing the planar heating element according to the third embodiment.

FIG. 7 is a diagram showing a pattern of a heat generating film before forming an electrode film in the first to third embodiments.

FIG. 8 is a diagram showing another heating film pattern before electrode film formation in the first to third embodiments.

9 is an enlarged view showing an overlapping portion of the patterns of the heat generating film shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Planar heating element 2 Heat-resistant insulating plate 2a Cooking surface 3 Exothermic film 3a Overlapping part 4 Electrode film 4a Power supply electrode pair 4b Power supply electrode pair 4c Electrode printing part 5 Heat generation block 6 Food material P1 Heat generation block P2 located on the outer periphery Heat generating block located in the middle part P3 Heat generating block located in the central part

Claims (7)

[Claims] 1. A planar heating element having a heat-resistant insulating plate having a cooking surface for cooking food, and a heat-generating film formed on the surface of the heat-resistant insulating plate, wherein the heat-generating film. Has a positive electric resistance-temperature characteristic that changes the resistance value in the same direction as the temperature change, and forms a plurality of heating blocks each covering a width of 21 cm ² or less on the surface of the heat-resistant insulating plate. A sheet heating element having a structure in which these heating blocks are electrically connected in parallel. 2. The heating block has a film thickness of 15 to 20 μm.
The planar heating element according to claim 1, wherein the heating element has a parallel meandering shape and has a film thickness of m, a film width of 0.5 to 2.0 mm, and a film pitch of 1.0 to 4.0 mm. 3. The resistance value of the heat generating block located in the middle part of the plurality of heat generating blocks is higher than the resistance value of the heat generating block located in the outer peripheral part, and the resistance value of the heat generating block located in the middle part is higher. The sheet heating element according to claim 1, wherein a resistance value of the heating block located in the central portion is higher than that of the heating block. 4. The resistance value of the heat generating block located in the middle part is 5% higher than the resistance value of the heat generating block located in the outer peripheral part, and the resistance value of the heat generating block located in the central part is 10% higher. The sheet heating element according to claim 3, wherein the sheet heating element is set high. 5. The structure in which the heat generating blocks are electrically connected in parallel has a structure in which the pattern of the heat generating film and the pattern of the electrode film, which are electrically separated and independently formed for each heat generating block, are overlapped. The sheet heating element according to claim 1, wherein the sheet heating element is configured by being formed. 6. The structure in which the heat generating blocks are electrically connected in parallel has a pattern for the heat generating film that is electrically separated and independently formed for each heat generating block and is 180 ° rotationally symmetrical for power supply. The sheet heating element according to claim 1, wherein the sheet heating element is formed by forming a pattern of an electrode film having an electrode pair on top of each other. 7. The sheet heating element according to claim 5, wherein a portion of the heating film that overlaps the electrode film is formed to be large along the pattern shape of the electrode film. .