JPH0424423A - High frequency heating cooking utensil - Google Patents

Abstract

PURPOSE:To obtain prompt heating performance, high temperature radiation, reduce cooking time and scorch food to be cooked more easily by holding a sheet-like heating element with a sustaining device, and allowing the greater part of the heating element to be located into a space. CONSTITUTION:To prevent the penetration of high frequency, it is acceptable to specify the maximum diameter for a through hole for a high frequency shielding board 3 as 5mm and smaller. A sustaining device 5 comprises a rod-shaped member 5a made of heat-resistant glass, and a bonding member 5b which bonds a metal heating element 6 with the rod-shaped member 5a. A sheet-like heating element 4 is a metal heating element made of stainless steel, nickel, chrome, and the like, which is laid out in a zigzag manner. This sheet-like heating element 4 is supported by the sustaining device 5. Moreover, a contact area between the sheet-like heating element 4 and the sustaining device 5 is small, which minimizes thermal diffusion induced by thermal conduction and forces the sheet-like heating element to reach high temperature in a short time by the application of electric power. This high temperature-induced radiation passes through the penetration hole of the high frequency shielding board 3 and directly heats up a heated substance. It is, therefore, possible to reduce cooking time and scorch the heated substance more easily.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high frequency cooking device for general household use, and particularly to a resistance heating mechanism.

Conventional technology The high-temperature planar heating element used in conventional high-frequency heating cookers in microwave ovens and microwave ovens has a structure in which a heating wire is wound around an insulating substrate such as mica and sandwiched between upper and lower mica plates.
It had a structure in which heating wires of a predetermined shape were embedded in a block made of alumina and silica fibers.

Problems to be Solved by the Invention However, the conventional technology has had the following problems.

In other words, with the conventional planar heating method, it was difficult to achieve a radiation temperature of 700 to 800°C, which is the optimum temperature for browning food. It took a long time to cook because it was difficult to raise the temperature to a high temperature.This is because the conventional planar heating element has a structure as described below.

That is, in the case of a mica heating element, the heating wire is embedded in mica, so in order to obtain high-temperature radiation, it is necessary to raise the temperature of the mica plate surface. For this reason, it is necessary to increase the temperature of the heating wire. As such high-temperature heating elements, nickel-chromium heating wires and iron-chromium heating wires are used in general household appliances. Of these, iron-chromium heating wires have a lifespan of about 1000 hours at 1200°C, but in the case of mica heating elements, if the contact between the mica and the heating wire becomes poor, heat conduction decreases, and that part becomes high temperature and generates heat. The wire is more likely to be fused. Therefore, in practical terms, the line temperature is designed to be 1000 to 1100°C. At this time, the surface temperature of the mica plate is only 500 to 600 degrees Celsius, so the temperature as a device is 500 to 600"
It was difficult to utilize the radiation from the heat source of 700 to 800°C, which is necessary for cooking. In addition, radiation is not obtained directly from the heating wire, but from a mica plate or a steel plate provided for mechanical reinforcement, so it takes time for these radiant surfaces to heat up, resulting in rapid heating. I couldn't get it. The same thing happened with the Ninkel chromium heating wire.

In addition, in the case of a heating element in which a part of the heating wire is embedded in a block made of alumina/silica fiber, etc., the mechanical strength of the block is low, and a sudden temperature difference occurs between the heating element and the block when energized. In some cases, cracks appeared in the block, making it difficult to hold the heating wire. In addition, increasing the thickness to increase mechanical strength increases heat capacity, and
Since a considerable part of the heating wire is buried in the block, the heat is taken away by the block and the temperature of the heating wire is raised to a high temperature, e.g.
It took a considerable amount of time to bring it down to °C.

The present invention solves the above problems and has a rapid heating property of 700 to 800
The present invention aims to provide a high-frequency cooker having a planar heating element capable of producing high-temperature radiation of 'C', thereby shortening the cooking time and making it easier to brown the food to be cooked.

Means for Solving the Problems In order to solve the above problems, the present invention provides a high frequency cooking device having the following configuration.

That is, a high frequency shielding plate having a large number of through holes provided on the outer wall of the cooking chamber, a planar heating element arranged in a meandering manner provided on the outside of the high frequency shielding plate, and the surface provided on the outside of the planar heating element. The structure consists of a holding device that supports the shaped heating element.

action The object of the present invention can be achieved by the following configuration.

That is, in the present invention, since the planar heating element is held by the holding device, most of the heating element is in space. Therefore, the planar heating element becomes high in temperature in a short time when energized. Therefore, the object to be heated is easily heated and cooked by high temperature radiation through the high frequency shielding plate having a large number of through holes.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

In FIG. 1, a high-frequency heating cooking device 1 includes a high-frequency shielding plate 3 having a large number of through holes provided on the outer wall of a cooking chamber 2, a planar heating element 4 provided on the outer wall thereof, and a heating element 4 provided on the outside thereof. It is composed of a holding device 5 that holds a planar heating element 4. The other configurations of the high-frequency heating cooker 1 are omitted because they are not directly related to the present invention.

The high frequency shielding plate 3 is made of a heat-resistant metal plate or wire mesh having a large number of through holes. The higher the aperture ratio of this through hole, the higher the transmittance of radiation from the planar heating element 3, and the higher the efficiency of heating the object to be heated in the cooking chamber 2. Increasing the aperture ratio generally means increasing the size of the through hole. However, as the through-hole becomes larger, high frequencies also become more easily transmitted. When high frequency waves pass through and some of them are absorbed by the heating element, the potential becomes high locally, causing external discharge, which may damage the heating element. Therefore, the size of the through hole must be an appropriate size or less.

The wavelength of the high-frequency heating cooker used in general households is 2.4.
5GHz, and to prevent the intrusion of this high frequency, approximately 511
It needs to be 11φ or less. Since through-holes are not necessarily circular, the maximum diameter is 5mm for through-holes of various shapes.
It is sufficient if it is not more than mm. The planar heating element 4 is a metal heating element made of stainless steel, nickel, chromium, etc. arranged in a meandering pattern. This sheet heating element 4 is held by a holding device 5 which will be described later, and since the contact area between the sheet heating element 4 and the holding device 5 is small, there is little heat dissipation due to thermal conduction, and therefore the sheet heating element 4 is energized. It reaches high temperature in a short time. In addition, various substances scattered from the food during cooking adhere to the sheet heating element 4. If substances containing salt among these scattered objects, especially water droplets, adhere to the metal heating element 6, the metal heating element 6 may corrode. In order to prevent this, it is effective to provide a heat-resistant coating layer 7 on the metal heating element 6 as shown in FIG. This heat-resistant coating N7 uses an inorganic powder as a binder and at least one resin having a non-carbon skeleton, such as polyborosiloxane, polytitanocarbosilane, polysilastyrene, polysilazane, polycarbosilane, and polysiloxane, and uses a metal heating element. 6 and then ceramicized. The coating film having the above composition prevents the flying salt from directly adhering to the metal heating element 6, and also has an effect as an insulating coating or a high radiation coating.

In a temperature increase test using the planar heating element 4, the surface temperature of the metal heating element 60 was set at 800°C, and the time required to reach 700'C was within 1 minute and 30 seconds.

Further, in the repeated fish frying test, almost no damage was observed even after 500 cycles regardless of the presence or absence of the heat-resistant coating layer 7. However, when the metal heating element 6 is energized,
In an accelerated deterioration test in which salt water was repeatedly dropped once every 2 minutes at 0°C, a sample without the heat-resistant coating layer 7 on the metal heating element 6 broke after about 10 cycles, but the heat-resistant coating layer 7 It took more than 20 cycles to break the sample with . From this, it is considered that the sample having the heat-resistant coating layer 7 has better corrosion resistance. Therefore, it is preferable to use the planar heating element 4 made of the metal heating element 6 having the heat-resistant coating layer 7 for the i-type high-frequency cooking device 1 in which there are many substances scattered from the heated object. However, when the thickness of the coating layer becomes thinner than 2 μm, a complete coating layer cannot be obtained and pinholes are likely to occur. When the metal heating element 6 having such a heat-resistant coating layer 7 was subjected to the accelerated deterioration test, it broke at approximately the same IO cycles as the sample without the heat-resistant coating layer 7. Further, as the thickness of the coating layer increases, cracks are more likely to occur between the metal heating element 6 and the heat-resistant coating layer 7 due to the difference in coefficient of thermal expansion. When a crack occurs, the metal heating element breaks after about 12 to 15 cycles in the accelerated test. These cracks tend to occur when the film thickness exceeds 40 μm. Therefore, the heat-resistant coating layer 7 is effective at 2 to 40 am. As described above, the holding device 5 is provided on the outside of the sheet heating element 4, and holds the metal heating element 6 so that the metal heating element 6 constituting the sheet heating element 4 does not come into contact with the high frequency shielding plate and electrically short circuit. It was retained. Therefore, the holding device has a skeleton made of ceramic or glass having excellent heat resistance, corrosion resistance, and electrical insulation, and is composed of wires or bands for fixing the planar heating element 4 to the skeleton. FIG. 3 shows the relative relationship between the planar heating element 4 and the holding device 5. In the case of FIG. 3, the holding device 5
consists of a rod-shaped body 5a made of heat-resistant glass with a diameter of 3 am, and a bonding body 5b that connects the metal heating element 6 and the rod-shaped body 5a. In this example, a stainless steel wire is used as the bonding body 5b. Also, as shown in Figure 4, a hook-shaped object is provided that is integrated with the rod-shaped body, and a metal heating element is placed on top of this, or alternatively, as shown in Figure 5, the hook-shaped object is fixed by passing it alternately above and below. Other means may also be used. Further, if necessary, a spacer may be inserted between the high frequency shielding plate and the planar heating element to perform part of the function of the holding device. Hereinafter, specific examples of the present invention will be described.

Example 1 A large number of holes of 3 am diameter were drilled in a heat-resistant stainless steel plate having a thickness of 0.4 mm, and the aperture ratio was set to 60% or more. This was used as the high frequency shielding plate 3. The planar heating element 4 was obtained by punching a 0.05- iron/chromium/aluminum steel plate into a serpentine shape. This planar metal heating element 4 has a total length of 2 m, a width of 7 cylinders, and a voltage of 100 V.
It has an output of 1.2KH.

This planar heating element 4 was attached to a holding device 5. The positional relationship between this planar heating element and the holding device is shown in FIG. In this embodiment, a heat-resistant glass pipe was used as the rod-shaped body 5a, and a soft stainless steel wire was used as the bonded body 5b. These were attached to a high frequency cooker as shown in Figure 1. When a rated voltage of 100 cm is applied, the surface temperature of the metal heating element 6 is approximately 1
It reached 700°C in minutes and 30 seconds, and 800°C in 3 minutes. When I put fish (the object to be heated) in cooking chamber 2 and grilled it,
The fish could be grilled in about 11 minutes using the high temperature radiation of 700 to 800°C. In other words, the surface could be browned almost uniformly, and the heat had sufficiently reached the inside. It took about 25 minutes to achieve almost the same degree of doneness with conventional mica heat. Furthermore, when high-frequency cooking such as heating was performed, the high-frequency waves did not leak and damage the planar heating element 3.

Example 2 The configuration was the same as in Example 1, except that only the planar heating element was changed. That is, a metal heating element 6 was obtained by punching a 0.05 mm steel plate made of iron, chromium, and aluminum. This metal heating element 6 has a total length of 2 m.
The convergence is 6IIl111. This metal heating element 6 was provided with a heat-resistant coating layer of 8 μm as described above to form a planar heating element 4. When fish was grilled in the same manner as in Example 1 using this planar heating element 3, almost the same results were obtained.

Effects of the Invention As described above, the high frequency cooking device of the present invention provides the following effects.

That is, in the present invention, since there is a high frequency shielding plate between the food to be cooked and the planar heating element, there is no leakage of high frequencies and the planar heating element absorbs the high frequency and is not damaged. Further, since the planar heating element is held by a heat-resistant holding device and has a small contact area with the holding material, there is little heat loss due to thermal conduction, and since it is a metal heating element, the specific heat of the heating element itself is also small. Therefore, the temperature rises quickly due to energization.
Temperatures of ~800°C are reached in a short time. Since this high-temperature radiation passes through the through-hole of the high-frequency shielding plate and directly heats the object to be heated, the cooking time can be shortened and the object to be heated can be easily browned. As described above, according to the configuration of the present invention, it is possible to provide a high frequency cooking device that can easily perform high frequency cooking and resistance heating cooking.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the main parts of a high-frequency cooker according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a part of a sheet heating element of the high-frequency cooker, and FIG. FIG. 4 is a cross-sectional view of the holding device of the same embodiment, and FIG. 5 shows support of the planar heating element by the holding device of another embodiment. FIG. 1... High frequency cooker, 2... Cooking room,
3...High frequency shielding plate, 4... Planar heating element, 5... Holding device, 6... Metal heating element. Figure I-・-Breath M 澹 Nozomi Rikonmen 3 Heat Suspension Resistance P Hinoki +14 Figure Figure

Claims (1)

[Claims] A high frequency shielding plate having a large number of through holes provided on the outer wall of the cooking chamber, a planar heating element provided outside the high frequency shielding plate, and the planar heating element provided outside the planar heating element. A high-frequency heating cooker equipped with a holding device that holds the.