JP2001296027A - Heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform highly-efficient grill cooking through optimum heater mounting constitution, in a microwave oven with a heater function. SOLUTION: A heating device is constituted that the modulus of infrared radiation of the surface, commonly using a ceiling surface 22 of a heating chamber 18, of wall surfaces of which a partition chamber 33 consists is maximized. This constitution improves a heating efficiency by absorbing heat rays, reflected in the partition chamber 33, by the ceiling surface 22 of the heating chamber 18 and reduces heat carried out from the partition chamber 33, resulting in suppression of the increase of the temperature of the armor of the heating device. Thereby, each cooking is practicable with high efficiency at an optimum heating condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating apparatus, and more particularly to a microwave oven having a heater function.

[0002]

2. Description of the Related Art Conventionally, as a heater function of a microwave oven of this kind, there are a grill function for burning food with strong radiant heat and an oven function for increasing the food temperature with ambient temperature and far infrared rays. Most of the products called "high frequency heating" have both of these functions.

A conventional example of a microwave oven with a grill function (Japanese Patent Publication No. 3-43538) will be described below with reference to the drawings.

[0004] In FIG.
Is stored. The heater 3 is mounted near the ceiling surface of the heating chamber 1. A waveguide 4 for introducing a high frequency wave is coupled to the ceiling surface, and a reflector 5 is buried with the waveguide 4 interposed therebetween, and the reflector 5 is welded to the ceiling surface of the heating chamber 1 at both right and left ends thereof. Are combined. Therefore, even if a high frequency is introduced into the heating chamber 1, there is no possibility that the reflection plate 5 is charged and sparks. In the case of grill cooking, simply heating with the heater 3 makes the surface of the food 2 scorch due to the near-infrared rays emitted by the heater, but the temperature inside the food 2 hardly rises. Therefore, in this example, high-frequency heating is performed in advance to raise the internal temperature of the food 2, and then the heater 3 is burnt by near-infrared rays.

In grill cooking that does not use high-frequency heating, many heaters are devised as shown in the following conventional example (Japanese Patent Publication No. 1-51865) shown in FIG.

In FIG. 7, a coil-shaped heating wire 7 is inserted inside a transparent crystallized glass tube 6. A coating 8 is formed on the surface of the glass tube 6 for selectively absorbing heat rays having wavelengths from visible light to near infrared rays emitted from the heating wire 7, and the wavelength of radiant heat finally reaching the object to be heated is increased. It is converted to the infrared region. If this heater is mounted on, for example, the conventional example of FIG. 6 described above to cook the food, the food temperature can be raised by the effect of far-infrared rays without burning only the food surface.

[0007] A particularly desired capability of the tubular heater used in such a configuration is the speed at which the temperature of the heating element rises. This is because the wavelength of infrared light that foods can easily absorb is approximately 3 μm, and considering the relationship between the temperature and the wavelength of a heating element generally expressed by Wien's law, the heating efficiency is 700-900 ° C. if the temperature of the heating element is 700-900 ° C. Is good. However, with a heater of about 1.2 kW and a coil-shaped heating element, the cross-sectional area is 0.3 mm2 in terms of mechanical strength.
The above is necessary, and it takes about 40 seconds from energization to have a large heat capacity and exceed 700 ° C.

FIG. 8 shows a conventional example (Japanese Patent Publication No. 4-541).
38) is a planar heater mainly used for oven cooking. Oven cooking, unlike grill cooking, raises the ambient temperature of the food by convection and slowly heats up with far-infrared rays from each wall of the heating chamber. For this reason, strong radiation emitted from the grill heater is rather detrimental, and a heater dedicated to oven cooking is required. The planar heater is obtained by further insulating a mica winding core 10 around which a heating wire 9 is wound, between two mica plates 11 from above and below. Due to the structure in which the heating wire 9 is wound on the flat core 10, the surface shape formed by the heating wire 9 is relatively flexible, and the object to be heated is heated via the sheet metal 12. The entire sheet metal 12 is heated, including the part away from the heating chamber, and uniform heating of the inside of the heating chamber becomes possible.

FIG. 9 shows a conventional example equipped with the above-described grill heater and oven heater. The grill heater 13 is located at a position for heating the vicinity of the center of the heating chamber 15, and an oven heater 14 is fixed so as to surround it. The heating chamber ceiling 16 of the grill heater 13 has been removed, and the reflection plate 17 and the ceiling 1 have been removed so that high frequency does not leak therefrom or sparks are generated near the reflection plate 17.
Reference numeral 6 denotes a welding process. Therefore, as an assembling process at the time of manufacturing, the grill heater 13 and the oven heater 1 are attached to the reflecting plate 17 fixed as a part of the heating chamber 15.
4 are inserted, fixed, and wired.

[0010]

However, in the above configuration, in grill cooking, the surface is scorched by near infrared rays emitted by the heater before the temperature inside the food rises sufficiently, so that high-frequency heating is performed in advance. Or the surface of the heater glass tube had to be painted to emit far-infrared rays. In addition, since the ceiling surface of the heating chamber in the grill heater section is removed, heat conduction from the surrounding oven heater to the section is cut off, so that the inside of the heating chamber cannot be uniformly heated during oven cooking. In addition, in order to prevent high-frequency leakage and sparks, the reflector must be welded to the ceiling surface, and there is a problem in that there is no freedom in the order of assembling the heaters during manufacturing. Further, in such a heating device, the power consumption of the heater is limited, and it is necessary to improve the efficiency of heating the food.

An object of the present invention is to solve such a conventional problem and to improve the efficiency of heating the inside of a heating chamber.

[0012]

In order to solve the above-mentioned object, a heating apparatus according to the present invention comprises a heating chamber, a compartment located outside the heating chamber and connected to the heating chamber with a ceiling surface shared by the heating chamber. A first heater which has a heating wire inside the insulating protective tube made of quartz or crystallized glass and which is located in the room and which heats the heating chamber through the ceiling of the heating chamber; And a magnetron for supplying high frequency to the inside of the heating chamber,
In the ceiling surface of the heating chamber, a large number of through-holes having a hole diameter such that high frequency does not leak and an opening ratio exceeding 50% are arranged only in a range where the first heater radiates heat rays to the inside of the heating chamber. The emissivity of the surface sharing the ceiling of the heating chamber among the walls constituting the room is set to be higher than the emissivity of the other walls.

[0013]

According to the present invention, the above structure maximizes the emissivity of the surfaces sharing the ceiling of the heating chamber among the respective walls constituting the compartment, so that the heat rays reflected in the compartment can be removed from the ceiling of the heating chamber. And the heating efficiency is improved, and the heat taken out of the compartment is reduced, so that the temperature rise of the heating device exterior can be suppressed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, a door 19 which can be freely opened and closed is provided on the front surface of the heating chamber 18. Food is placed on the bottom of the heating chamber 18. A magnetron 20 is connected to the heating chamber 18 and a high frequency is supplied thereto. A grill heater 21 as a first heater is fixed to the outer upper portion of the heating chamber 18, and is located substantially at the center of the ceiling surface 22 of the heating chamber. The heating member of the grill heater 21 is a coil-shaped heating wire 23 made of Ni, Cr, or the like, and is housed in a transparent quartz tube 24 that is both insulated and protected. The grill heater 21 heats the heating chamber 18 through the ceiling surface 22, and a large number of through holes 25 are formed in the ceiling surface 22 in a range where the radiant heat is radiated from the grill heater 21 to the inside of the heating chamber 18. The through-hole 25 has a diameter of 4 mm and an opening ratio of 62%, and a majority of heat rays containing a large amount of near-infrared rays emitted from the grill heater 21 are supplied to the heating chamber 18. Further, the heat rays blocked by the ceiling surface 22 once heat the ceiling surface 22, and far infrared rays are supplied as secondary radiation from the heated ceiling surface 22 to the inside of the heating chamber 18. The inside of the food is heated by the far infrared rays, and the surface is scorched by the near infrared rays directly received from the grill heater 21. In this manner, efficient grill cooking can be performed by the function of the far and near infrared rays.

On the other hand, in oven cooking, an oven heater 26 is provided as a second heater provided around the ceiling surface 22.
Is performed by alternately and intermittently heating the lower heater 27 provided at the lower portion of the heating chamber. Heat rays from the oven heater 26 are completely blocked by the ceiling surface 22 and far infrared rays are given to the food as secondary radiation from the heated ceiling surface 22.
In this example, a planar heater was used as the oven heater 26. In addition, the ceiling surface 2 including the area below the grill heater 21
Since 2 is made of one sheet metal, the entire ceiling surface 22 is heated by heat conduction, and uniform heating inside the heating chamber 18 is realized.

Further, since the ceiling surface 22 is formed of a single sheet metal, high-frequency leakage from the heating
There is no spark at around 8. Therefore, the reflection plate 28 does not need to be welded to the ceiling surface 22 and can be simply fixed with screws. In addition, since the attachment of the reflection plate 28 is simple, the order of assembling the heater portion is free. In this example, an assembling method was adopted in which the heater part and the reflector part were completed as one unit as shown in FIG. 2 and fixed on the heating chamber with screws. In this case, the volume of parts handled during assembly is reduced, and advantages in assembly and transportation, such as continuous automatic production of the unit, are also produced.

FIG. 3 shows an embodiment in which an oven heater is devised to obtain the same effect with a simpler structure than the above-described embodiment. FIG. 3 is a view of the inside of the main body viewed from above. A grill heater 21 is disposed near the center. A large number of through holes 25 are formed in the ceiling surface 22 of the grill heater 21. The oven heater 30 can be seen in an arrangement for heating outside. The members constituting the oven heater 30 are the same as the grill heater, in which the heating wire 31 is housed in a transparent quartz tube 32. Since the radiant heat generated by the heating element is radially dispersed, if the heat is uniformly generated from one end of the straight tubular heater to the other, the radiant heat overlaps and the heat is excessively concentrated at the central portion. In order to prevent this, the heating wire 31 near the center in the longitudinal direction represented by B in the figure was formed in a straight line shape, and the calorific value in the same volume was reduced as compared with the end portion of the coil shape. The radiant heat received by the ceiling surface 22 when the ratio of the portion B near the center is changed to 0%, 21%, and 39% with respect to the total length A of the quartz tube 32 is shown as a five-step intensity distribution in FIG.
Are shown by contour lines. At 0%, especially the center 2 of each heater
Strong radiation is concentrated in several places. At 21%, the distribution is considerably dispersed, and at 39%, the distribution has vertices at locations corresponding to the four corners of the ceiling surface 22. By providing the top of the distribution around and at the corners of the ceiling surface 22 where heat can easily escape as described above, and by conducting heat from there to the center of the ceiling surface 22, uniform heating of the inside of the heating chamber becomes possible.

In FIG. 1, the emissivity of each wall surface of the compartment 33 surrounded by the reflector 28 and the ceiling surface 22 is devised in order to further promote the heater performance. The emissivity is used as a measure for generating radiant heat from an object. The emissivity is also equal to the rate of absorbing radiation, and the lower the emissivity, the more easily radiant heat is reflected. Radiated heat from each heater is in compartment 3
The reflection and absorption are repeated on the three wall surfaces, but the original purpose is to heat the ceiling surface 22 of the heating chamber. The heating room ceiling surface 22 was easily coated with a double-sided ceramic coating in order to easily receive radiation and to easily emit secondary radiation inside the heating room 18. The emissivity of the ceramic painted surface is 0.9 or more. On the other hand, an aluminum-plated steel plate having an emissivity of 0.5 was used for the reflection plate 28 in order to make it difficult to absorb radiant heat. With this configuration, the heat generated by the heater is efficiently supplied to the inside of the heating chamber 18 and is not easily transmitted to the exterior.

FIG. 5 shows a reference example of the tubular heater used in these configurations, in which the temperature of the heating element rises quickly to enhance the heating effect. The components of the heating element 34 are Fe, Cr, A
1, its thickness is 50 μm, its width is 4 mm, and its cross-sectional area is 0.2 mm 2. When the belt-shaped heating element 34 was continuously bent into a corrugated shape and inserted into the quartz tube 35, it took less than 5 seconds to raise the temperature of the heating element 34 to 700 ° C. The reason is that first, the heat capacity of the heating element 34 is small, that there is no portion in contact with the quartz tube 35 except for the corners of the bent portion, and that the quartz tube 35 is not easily deprived of heat. This is because they have created an environment where they can interact with each other. Therefore, the most efficient wavelength can be emitted in a very short time. In addition, since it is a band-shaped corrugation, directivity can be given to radiation, and the most efficient heating can be achieved by directing the projected area of the heating element 34 to the food in the largest direction.

[0021]

As described above, according to the heating device of the present invention,
It has the following effects:

(1) By maximizing the emissivity of the surfaces sharing the ceiling of the heating chamber among the walls constituting the compartment, heat rays reflected in the compartment are absorbed by the ceiling of the heating chamber for heating. Efficiency can be improved, and a rise in the temperature of the exterior of the heating device can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a heating device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the heater unit shown in FIG. 1;

FIG. 3 is a plan view of a main part of a heating device according to another embodiment of the present invention.

FIG. 4 is a distribution diagram of radiant heat in FIG.

FIG. 5 is a sectional perspective view of a heater according to a reference example of the present invention.

FIG. 6 is a sectional view of a main part of a conventional heating device.

FIG. 7 is a sectional view of a main part of a conventional heater.

FIG. 8 is an exploded perspective view of a conventional heater.

FIG. 9 is a sectional view of a main part of a conventional heating device.

[Explanation of symbols]

 Reference Signs List 18 heating chamber 20 magnetron 21 first heater (grill heater) 22 ceiling surface 23, 31 heating wire 24, 32, 35 insulating protective tube (quartz tube) 25 through hole 26 second heater (oven heater) 33 isolated room 34 Heating element

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F24C 15/24 F24C 15/24 B

Claims (1)

[Claims] 1. A heating chamber, a compartment located outside the heating chamber and connected to the heating chamber with a ceiling surface shared by the heating chamber, and a heating wire inserted into an insulating protection tube located in the compartment to form a heating chamber. A first heater that heats the heating chamber through the ceiling surface, a second heater that is located in the compartment and heats the heating chamber through the ceiling surface, and a magnetron that supplies high frequency to the inside of the heating chamber. In the ceiling surface of the heating chamber, a large number of holes having a hole diameter such that high frequency does not leak and an aperture ratio exceeding 50% are arranged only in a range where the first heater radiates heat rays into the inside of the heating chamber. In addition, a heating device configured so that the infrared emissivity of the surface sharing the ceiling of the heating chamber among the wall surfaces constituting the compartment is maximized.