JPH0195227A - Heat generating element for microwave oven - Google Patents

Abstract

PURPOSE:To increase a heating efficiency and to prevent a heat generating material from deteriorating, cracking or the like by a method wherein a ceramic-molded material containing therein, as a main ingredient, porous silicon carbide having specific porosity is formed into a heat generating element. CONSTITUTION:In a plane-shaped heater 1 for a microwave oven, when embeds a heat generating element 11, exposing its one surface only, into an adiabatic material 10 comprising such a material as, for example, a ceramic fiber board or the like, which easily transmits a microwave radiated from a magnetron and has adiabatic properties, the heat generating element 11 has silicon carbide particles 11a bonded by a binder 11b. Also, air pores 11c exist among the respective particles. Their porosity is set to 15-50%. A microwave reflecting damper 6 is disposed rotatably in an intermediate portion between a microwave radiating port 5 and the heater 1, and when the damper 6 is moved upwardly, the microwave is led to the heater 1, which is thereby red-heated. Since such a ceramic-molded material itself is formed into the heat generating element, all of them aid in the conversion action of the microwave into heat, so that a heating efficiency is markedly increased.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a heating element for a microwave oven that generates heat by irradiation with microwaves emitted from a magnetron of a microwave oven and browns the food to be cooked. be.

<Prior Art> Generally, a microwave oven is a cooking device that guides microwaves emitted from a magnetron into an oven chamber and irradiates the food to be cooked to generate heat in the food to cook the food. Therefore, there is a drawback that the food to be cooked is not browned and does not stimulate the appetite. Therefore, there is a microwave oven that has a built-in sheathed heater so that the heat generated by the heater is directly applied to the food to be cooked in parallel with the heating of the food by microwaves.

However, since two types of heating means are used as described above,
This requires a magnetron and a heater as a heat source, which increases costs, complicates the configuration, and increases the size of the entire device. Recently, with the aim of improving these problems, the heating element that generates heat when irradiated with microwaves can be dielectrically heated by microwaves alone using a plate with a double structure made by polymerizing an insulating base material as a heating element. A proposal has been made by the same applicant to provide the same effect of heating by thermal radiation. (Jitsugan Sho 61-149372
Issue) <Problem to be solved by the invention> However, this proposal does not specify a specific material for the exothermic substance, and it is not possible to put it into practical use by coating a generally known ferrite type or silicon carbide powder on a base material such as ceramic. When attempting to do so, the following problems occurred.

1. The heat generation efficiency is poor, and the browning effect is poor. 2. The heat generation rate is low, and it takes a long time to brown. 3. The tendency to generate heat in extreme areas is significant, and the heat generating layer may partially change in quality, or the base material may deteriorate. Purpose of the Invention The present invention has been devised in view of the above-mentioned problems, and has been developed to improve heat generation efficiency, eliminate deterioration and cracking of the heat generating material during heat generation, and create a practical microwave oven. The purpose is to provide a heating element.

<Means for solving the problems> A ceramic molded body mainly composed of porous silicon carbide having a porosity of 15 to 50 is used as a heating element.

Function> Unlike when coating other materials (ceramic molded bodies of other types), the ceramic molded body itself, which is mainly composed of porous silicon carbide with a porosity of 15 to 50 cm, is used as a heating element. The entire heating element itself contributes to the heat conversion effect of microwaves, and the heat generation efficiency increases significantly.Since it has a moderate amount of pores, the structural strength of the heating element itself can be maintained while reducing thermal shock during heating. In addition, the heat capacity of the heat generating material itself is reduced compared to a dense body, so the overall heat generation efficiency is further improved. In addition, since silicon carbide itself has good heat resistance, it can be used for a long time without causing deterioration reactions at high temperatures.

<Example> Two examples of the present invention will be described below based on the drawings.

■ When a heat generating material is built into the microwave oven body.

FIG. 1 shows a heat generating element 11 of the great invention exposed only on one side (lower side) on a heat insulating material 10 made of a material such as a ceramic fiberboard that is easily permeable to microwaves emitted from a magnetron of a microwave oven and has heat insulating properties. FIG. 2 is a cross-sectional view of a planar heater l for a microwave oven installed in the microwave oven.

The heating element 11 is made of silicon carbide particles 11a as shown in FIG.
A binder 11b (for example, made of clay or other raw material and made of mullite ceramic after firing) binds the members. Moreover, pores 11c exist between each particle. If the porosity is more than 50 inches, it becomes difficult to manufacture and the strength of the heating element itself becomes extremely weak.
If it is less than 5%, the heat capacity of the exothermic material itself becomes too high, so it takes too long to raise the temperature, and the temperature is difficult to lower even after the microwave irradiation is finished, which poses a practical problem.

Figure 3 shows the average surface temperature as a function of microwave (500W output) irradiation time for an 80-square silicon carbide ceramic molded plate with a thickness of 3IEs and a porosity of 45%, an initial 15% porosity, and a dense body. FIG. 3 is a relationship diagram showing the relationship between the average surface temperature (when the temperature is rising) and the relationship between the average surface temperature and the elapsed time after the end of microwave irradiation (when the temperature is falling).

FIG. 4 is a front sectional view of a microwave oven employing the heater l shown in FIG.
and an oven chamber 3 are connected by a waveguide 4. A microwave radiation port 5 is provided at the tip of the waveguide 4, and the heater 1 is placed along the top surface of the oven 3 in the middle thereof. Also, the microwave radiation port 5
A microwave reflection damper 6 is rotatably disposed between the heater 1 and the heater 1, and when the damper 6 is moved downward, it is blocked and the microwave is guided to the radiation port 5. Microwaves M are radiated inside, and cooking is performed using normal microwave heating.

Moreover, when the damper 6 is moved upward, the microwave is guided to the heater 1, and the heater 1 absorbs the microwave, becomes red hot through thermal conversion, and emits infrared rays (heat rays) R into the oven chamber 3. Then, infrared radiant heating is performed.

■ When the heating element and the microwave oven are made removable.

FIG. 5 is a structural diagram of the heating device 7 that can be taken in and out of the oven chamber 3. A heating element 7b made of a silicon carbide-based ceramic molded plate having a porosity of 15 to 50 cm, on which a porous saucer 7a having microwave permeability and heat insulation properties is coated with a heat-resistant fluororesin coating 7c, forms an air insulation layer 7d. It is installed through. When the object 8 to be cooked is placed on the heating element 7b and placed in the oven compartment 3 of the microwave oven and irradiated with microwaves, the microwave is absorbed by the object 8 and heats it. At the same time, microwaves from the sides or bottom that are not transmitted through the food to be cooked 8 or irradiated to the food to be cooked 8 are absorbed by the heating element 7b and converted into heat, so that the heating element 7b itself rapidly heats up and comes into contact with the food. The heat is transferred to the bottom of the food 8 that is being cooked, and it is completely browned. When cooking does not require browning, the heating device 7 is removed from the oven chamber 3 of the microwave oven.

<Effects of the Invention> As mentioned above, the heating element of the present invention has high heat generation efficiency due to microwave absorption in microwave ovens, and there is no deterioration or cracking of the heating material even after repeated use, making it suitable for use in microwave ovens. Ideal as a sheet heating element.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a heater incorporating the heating element of the present invention, Fig. 2 is an enlarged sectional view of the heating element of the invention, and Fig. 3 is a sectional view of a microwave oven incorporating the heating element of the invention. , Figure 4 shows the relationship between the average surface temperature and the microwave irradiation time of the heating element of the present invention (when the temperature is rising), and the relationship between the average surface temperature and the elapsed time after the end of the microwave irradiation (when the temperature is falling) f
Figure 5 is a structural diagram of a heating device incorporating an uninvented heating element. Code 11: Heating element, 11a: Silicon carbide particles, 11b: Binder, 11C: Pores / Agent Patent attorney Takeshi Sugiyama (and 1 other person) No. 1! 11 Figure 2 No. 3! ! 1 4th chart 5th diagram

Claims (1)

[Scope of Claims] 1. A heating element for a microwave oven that generates heat by microwave irradiation and is made of a ceramic molded body mainly composed of porous silicon carbide having a porosity of 15 to 50%. body.