JPH0578159B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heating device such as a so-called microwave oven.

Conventional technology In general, oven microwave ovens use a heating method using a heater; a top-bottom heater type that uses heat radiation and natural convection, and has sheathed heaters on the top and bottom of the heating chamber; and a top-bottom heater type that uses a heater outside the heating chamber. It can be roughly divided into hot air circulation type, which heats the food by forcing the generated heat into the heating chamber using a fan.
The former generally performs well as an electric oven;
It has become mainstream because it has a simple configuration and can be made at low cost.

As shown in FIG. 8, the top surface 2 and bottom surface 3 of the heating chamber 1
Sheathed heaters 4 and 5 are disposed in each of the two. The sheathed heaters 4 and 5 pass through the rear wall 6 of the heating chamber and are supplied with power within the microwave oven main body 7. When high frequency energy is irradiated into the heating chamber 1 in this state,
Current flows through the heaters 4 and 5, and energy leaks to the outside of the heating chamber. To prevent this, high frequency attenuation grooves, so-called chiyokes 8 and 9, are provided on the wall surface. In particular, the sheathed heater 5 on the bottom surface 3 has a removable structure in order to facilitate cleaning of the bottom surface 3 when food or boiled liquid is spilled, so the connections of the sheathed heater 5 are complicated. Since the upper side is difficult to clean and easily gets dirty, it is recommended to use a sheathed heater 4.
Although it cannot be removed, it has a so-called self-cleaning layer that can decompose adhering oil stains into water and carbon dioxide when the temperature exceeds a certain level.

Problems to be Solved by the Invention However, even during grilling, when the sheathed heater 4 reaches its highest temperature, the temperature of the self-cleaning layer directly above the sheathed heater 4 rarely exceeds 300°C. However, the temperature range in which it could be used to its full potential had not yet been reached. In fact, more people use ovens to make bread and cakes than grill them to brown them at home.
In this case, since a large amount of power is also supplied to the sheathed heater 5 on the bottom surface 3, the temperature of the self-cleaning layer on the top surface is kept lower, and the purification ability is further reduced. In terms of cooking performance, in the case of a sheathed heater, since the outer skin is made of pipe-shaped metal, the minimum bending radius is limited, and the shape must be relatively simple. During heating, the surface temperature of the heaters 4 and 5 rises to about 600 to 800°C, and even within each plane including the sheathed heaters 4 and 5, the ambient temperature outside the sheathed heater portion is relatively low, making uniform heating difficult. As a result, it was necessary to maintain a large distance between the sheathed heaters 4 and 5 and the food. To solve this problem, there are methods of embedding the sheathed heater in cast metal or sandwiching it between metal plates, and methods of embedding a metal heating element in the enamel layer to form a planar heating element, but none of them work quickly. It does not fully satisfy thermal properties and uniformity. Due to the difference in thermal expansion coefficient between the metal heating element and the enamel layer at high temperatures, the enamel sheet heating element
It cannot be said that the reliability is sufficient as cracks and peeling occur in the enamel layer. Furthermore, the dimensions of the cheese yokes 8 and 9, which are provided to prevent the high frequency energy inside the heating chamber from leaking to the outside from the sheathed heaters 4 and 5 during high frequency heating, are limited depending on the wavelength to be handled. When installed on a wall, the overall dimension A in the depth direction has to be increased.
Furthermore, although the lower heater 5 is designed to be removable, it is more time-consuming than expected, and the heater 5 itself is likely to be washed, which is not desirable from the standpoint of insulation and durability, and above all, the heater protrudes into the heating chamber. The problem was that it was not only difficult to clean, but also aesthetically undesirable.

The present invention solves these conventional problems, and since the heater does not protrude into the heating chamber, it is easy to clean and looks good, the effective dimensions of the heating chamber can be increased, and the characteristics of the planar heater are utilized. Even if oil stains are severe due to cooking methods, the self-cleaning layer can be used at a temperature suitable for purification, which not only makes the most of its features, but also ensures the heat resistance and durability of the self-cleaning layer. Moreover, the present invention provides a high-frequency heating device that is excellent in rapid heating, uniformity, and durability, since it can reduce adverse thermal effects on the parts constituting the planar heater.

Means for Solving the Problems The high-frequency heating device of the present invention includes a planar heater composed of a heating wire made of metal or ceramic and an insulating material such as mica for insulating the heating wire, so that the upper surface of the heating chamber is heated. installed in close contact with the outer surface of the heating chamber on the wall surface formed by the heating chamber,
A layer having a self-purifying effect is applied to the upper surface of the heating chamber, and the upper surface has a shape that makes the heating chamber space a convex surface.

Function The high-frequency heating device of the present invention has a planar heating element, which is a heat source during electric heating, in close contact with the outer surface of the upper surface of the heating chamber, so that a self-purifying effect is applied to the entire inner surface of the heating chamber. The temperature of the motsu layer rises to 400 to 450 degrees Celsius during so-called grill heating, and 300 to 400 degrees Celsius even when heated in the oven, so compared to the conventional upper and lower heater type, the average temperature is about 100 degrees Celsius when grilling.
There is a difference of about 100-200℃ between ~150℃ and oven, and the self-cleaning effect is significantly improved. In addition, the self-purifying layer is made of a material such as glass or ceramic, and has high heat absorption and heat diffusion ability, so it has the ability to quickly and efficiently absorb heat from the heater, which is the heat source, and dissipate it within the heating chamber. Motsu. This not only eliminates the abnormal heating of the heater wire itself, but also eliminates the negative effects on the insulating mica, etc., and greatly contributes to speeding up cooking and improving cooking performance.

In addition, by making the wall surface on which the self-purifying layer is formed into a concave shape, when the self-purifying layer itself repeatedly expands and contracts due to changes in heat from the heater, it is possible to eliminate The heating chamber has a self-purifying layer that is extremely strong against thermal stress because the tensile stress applied to the self-purifying layer, which is a component, is kept to a minimum and stress is mainly applied in the compressive direction. realizable. This shape can also be used as a high frequency heating chamber.
Since food is very often placed near the center of the refrigerator, it also serves as a heat reflection box, so high frequency energy,
It is easy to imagine that this is the configuration that provides the most efficient thermal energy. In addition, since it is a surface heater, it has excellent uniform heating properties, so food can be brought close to it.Furthermore, since it is a black body, it has good heat dissipation and self-purification ability can be maximized, so it will not get dirty even if food is brought close. Due to these features, it has excellent heating properties, is easy to clean, has a good appearance, and is durable.
It has the effect of having good performance in both high frequency cooking and electric heating cooking.

Embodiment An embodiment of the present invention will be described below based on the drawings.

As shown in FIG. 1, reference numeral 1 denotes a microwave oven main body case, which together with the bottom of the main body 2 constitutes an outer frame. 3 is a heating chamber for heating food; a magnetron 5 for high-frequency oscillation is mounted on the heating chamber side wall 4; planar mica heaters 6 and 7 for electric heating are mounted on the heating chamber upper plate 8; The top heat insulating material 11 and the bottom heat insulating material 12 are sandwiched between the top heat insulating material 11 and the bottom heat insulating material 12, respectively, and are press-fixed to the room bottom plate 10 by a top metal pressure band 13 and a bottom metal pressure band 14. In addition, 2
Reference numerals 1 and 22 are lead wires for power supply to the heater. 1
Numerals 5 and 16 are convex fixing parts provided on the metal pressure welding bands 13 and 14, and each of the heaters 6, 7, and 9 is pressed against the heating chamber 3 at a plurality of locations. 1
7 is a motor for driving the turntable 18. Reference numeral 19 denotes shelves for oven plates 20 provided on both sides of the heating chamber side wall 4, on which food 21 (gratin is shown in this figure) is placed. The distance L between the food 21 and the top surface 8 of the heating chamber can be made extremely small since the planar heaters 6 and 7 are provided over almost the entire top surface 8 of the heating chamber, so the surface has a uniform surface distribution. becomes. The space can be used more efficiently than the space that was previously used as a dead space for the sheathed heater. oven plate 20
By heating in a narrow space V partitioned by the upper surface 8 of the heating chamber and the side walls 4 of the heating chamber, it has become possible to efficiently cook a larger amount than ever before in an extremely short time. At this time, the distance L dimension from the food 21 to the top surface 8 of the heating chamber is small and the temperature of the food rises quickly, so that the food can be browned quickly and the umami flavor is not lost. Since a self-cleaning hollow layer 8a is provided on the heating chamber side of the heating chamber upper surface 8, heat dissipation is also good. In other words, the temperature of the food tends to rise easily, causing more oil and water to splatter, but since the enamel layer has reached the appropriate temperature to maximize its purifying ability, some oil stains that remain with the conventional method can also be removed. , the effect was so improved that it could not be seen at all.

FIG. 2 shows the structure of the planar mica heater of this embodiment. Reference numeral 23 denotes a heater wire, which is a heating element, and is made of nickel chrome or iron chrome wire, and is wound around the mica plate 24, leaving pull-out portions 25 at both ends. Details are shown in Figure 3. heater wire 2
3 is wound in accordance with the guide groove 31 provided in the winding mica 24, so that it has a predetermined length, and
Care has been taken to prevent sparks and disconnections from coming into contact with neighboring wires during expansion and contraction during heating and cooling. In FIG. 2a, 26 is an upper insulating mica plate, and 27 is a lower insulating mica plate. Reference numeral 28 denotes a holding plate for holding mica plates 24, 26, and 27 together, and a plurality of holding bending claws 29 are arranged on the outer and inner circumferential parts. 30 is heater wire 2
This is the hole for drawing out No.5. Figure 2b shows how these were assembled as a heater unit, taken along the plane A-A'. The respective mica plates are fixed in close contact with each other while sandwiching the heater wires 23.

FIG. 4 is an example showing the arrangement of the planar mica heater in the heating chamber 3. An outer heater 32 and an inner heater 33 are disposed on the top plate 8, and a bottom mica heater 34 is disposed on the bottom plate 10 so as to cover almost the entire area.

FIG. 5 is a partial view of the upper part of the main body of this embodiment cut in the front-rear direction. A door 36 and a handle 37 are provided on the heating chamber front plate 35 so as to be openable and closable. There is a sash 38 at the top of the door 36, which serves as a radio wave seal. Heating chamber front plate 35
The metal band 1 for pressure welding the heater passes through the hole 39 of
3 is hooked, and the heaters 6 and 7 are pressed against the heating chamber upper plate 8. A self-cleaning enamel layer is applied to the heating chamber inner side surface 8a of the heating chamber upper plate 8 to cover the difficulty of cleaning the upper surface. Further, the upper plate 8 has a slightly concave shape as shown in the O part, and as shown in FIG.
expands due to heat from a heater (not shown). At this time, the upper plate 8 is fixed around the entire circumference as shown at 41 and 42, so the circumference cannot be extended, and due to its shape, it extends as shown at 8'. At this time, a force as shown in FIG. 7a is acting on the self-cleaning layer 8a of the upper plate 8 at point P. A compressive force f _i acts on the inner part of the thickness t of the upper plate 8, and a tensile force acts on the outer part.
f _p works. On the contrary, if the shape of the upper plate 8 is
If it has a convex shape toward the heating chamber 3 as shown in Figure b, P
At the point, there is a tensile force f _p on the inside of the heating chamber (enamel layer side)
However, a compressive force f _i will act on the outside of the heating chamber.
That is, in the example of the present invention, a self-cleaning layer is applied, but since the enamel layer is mainly composed of glassy and inorganic materials, it has characteristics that are quite strong against compressive stress but extremely weak against tensile stress. This is especially noticeable when the thickness is about 300 microns or more. This was clearly confirmed through experiments. That is, when the upper plate 8 was made of aluminized steel plate treated with a self-cleaning enamel for aluminum and mounted on the main body, and continuous and intermittent dry-firing tests were conducted assuming grilled food, the upper plate with the shape shown in Fig. 7b was All of the plate thickness of 8, 0.60.81.0mm
While cracks occurred in the enamel layer after 80 to 120 hours, the shape of the enamel layer shown in Figure 7a remained free of cracks even after 500 hours.
It can be said that the theory has been proven through experiment.

In FIG. 6, 5 is a magnetron for high frequency oscillation. In the case of radio-wave cooking, the food is placed on a turntable, so if the food is flat, the electric field in the center will weaken and it will be difficult to cook because the food will be close to the plate. With the shape of the top plate 8, reflected radio waves tend to gather in the center, and the radio wave cooking performance can also be improved. When the upper plate 8 is drawn as in this example, processing distortion etc. are easily removed and a stable shape can be obtained. When power is supplied from the side as shown in FIG. 6, even a small change of about 1 to 2 mm due to unevenness on each wall surface can have an extreme effect on the results depending on the cooking menu. The meaning of obtaining a stable shape of the upper plate 8 is also a great effect.

In addition, in FIG. 5, in order to effectively transfer the heat of the heaters 6 and 7 to the heating chamber upper plate 8, a metal pressure band 13 having both ends 40 fixed to a part of the heating chamber 3 is used to hold down a part of the heating chamber 3, but in this case, When the heater is supplied with electricity and generates heat, the upper plate 8 thermally expands and causes the change shown in FIG. In fact, it will improve. In the case of FIG. 7b, the adhesion deteriorates and the performance and efficiency of the oven deteriorate.

In this example, a type in which the planar heater is installed directly in close contact with the top plate and the bottom plate of the heating chamber is used. There is no need to explain that the same thing can be considered when installing.

Effects of the Invention As described above, according to the high frequency heating device of the present invention, the following effects can be obtained.

(1) Since the electric heating device is a planar heater, for example, if it is installed on the upper surface of the heating chamber, the self-purifying layer applied to the upper heating chamber side will be heated to a temperature of 300 to 450°C that allows for efficient catalytic action. By using a planar heater to improve uniformity, even if food is brought close to the wall (heat source), the top surface, which is relatively difficult to clean, can be kept cleaner than before, making it possible to improve the uniformity of the planar heater. The main feature is that the effective size of the heating chamber can be increased, there are no protrusions, and the inside of the refrigerator can be kept clean, making it possible to create a heating chamber that is both visually and practically clean.

(2) The self-purifying layer provided on the top surface is made of glass or ceramic, like a self-cleaning hollow layer, and has excellent heat absorption and heat dissipation. Therefore, it becomes possible to effectively absorb the heat of the planar mica heater, which has excellent insulation properties up to high temperatures, and efficiently transmit it to the food. While preventing the heating wire and mica, which is an insulator, from rising abnormally in temperature and losing its function or shortening the life of the heating wire, it quickly burns the area around the food, allowing cooking without losing the flavor inside. It works to make it possible to improve efficiency,
This greatly contributes to improving safety, grilling performance, and speed.

(3) Since the surface forming the heating chamber provided with the self-purifying layer has a concave shape, even if the surface expands thermally due to a heater or high frequency, compressive stress mainly acts on the self-purifying layer. Because it is less prone to cracking or peeling, it is possible to maximize the temperature of the wall surface on which the self-purifying layer is applied, and when applied to the upper surface, it has good grill performance and a long life with stable purifying ability. A heating room can be provided.

(4) When pressing a sheet heater against a wall, even if the wall expands thermally, if the heating chamber has a convex shape, the adhesion will not be weakened even if it is pressed with a metal band, etc. This makes it possible to transfer heat from the planar heater stably and efficiently, and also prevents abnormal heat generation caused by floating heater wires and the adverse effects of this on the mica.

(5) If the heating chamber wall surface is uneven, either uneven or convex, it will greatly affect the radio wave cooking performance. Especially in the case of side power supply, the cooking tendency may change drastically. For these reasons, it is necessary to stabilize the wall surface, and this requirement is satisfied. Since it also works to concentrate radio waves to the center, it can be said that it contributes to improving cooking performance.

(6) According to the present invention, the electric heating device, which is highly reliable, durable, and safe, has uniform heating properties and quick heating properties, which are the major features of sheet heaters, and expands the effective dimensions of the inside and main body. This can be achieved while satisfying these requirements, such as having a beautiful interior and being easy to clean.

This simple configuration produces many effects.

[Brief explanation of drawings]

Fig. 1 is an overall sectional view of a high-frequency heating device that is an embodiment of the present invention, Fig. 2 is an exploded perspective view of a coplanar mica heater and a partial sectional view after assembly, and Fig. 3 is a coplanar mica heater. Fig. 4 is an exploded perspective view showing the arrangement of the same-planar mica heater in the heating chamber, Fig. 5 is a partial sectional view including the heater of the same high-frequency heating device, and Fig. 6 is the top surface of the heating chamber. Figure 7 is a diagram showing the stress applied to point P on the upper surface of the heating chamber, and Figure 8 is a cross-sectional view showing a conventional heating device of the upper and lower sheathed heater type. . 1... Heating chamber, 5... High frequency generator, 6,
7, 9... Electric heating device, 8... Top surface of heating chamber, 8
H...Self-purifying layer, 23...Heating element, 24,
26, 27... Mica plate, O... Concavity on top surface, 1
0...Bottom surface of the heating chamber.

Claims (1)

[Scope of Claims] 1. Of the walls constituting the heating chamber in which food is stored and heated within the main body, at least the upper heating chamber side is coated with a layer having a self-purifying action and infrared radiation action, thereby forming the first heating chamber. A high-frequency heating device having a structure in which a heating element and a planar heating element made of an insulator are closely provided on the outer surface of the heating chamber on at least the upper surface of the wall surface. 2. The high-frequency heating device according to claim 1, wherein the wall surface of the heating chamber provided with a layer having a self-purifying action and an infrared ray radiation action is configured such that the surface of the self-purifying action layer is concave. 3. The high-frequency heating device according to claim 1, wherein the wall surface of the heating chamber provided with the layer having a self-purifying action is made of an aluminized steel plate, and the layer having a self-purifying action is an aluminum self-purifying action layer. 4. The high-frequency heating device according to claim 1, wherein a planar heating element made of a heating element and an insulator is provided in close contact with substantially the entire outer bottom surface of the bottom plate of the heating chamber. 5. The high-frequency heating device according to any one of claims 1 to 4, wherein the planar heating element comprises a heating element and a multilayer insulator.