JP5102792B2 - Microwave heating device - Google Patents

Description

  The present invention relates to a microwave heating apparatus that irradiates an object to be heated with microwave power, and more particularly to a microwave heating apparatus that performs heating processing, sterilization, and the like of individual foods stored in a food pack or the like.

  Conventionally, a microwave oven or the like is widely known as an applicator for heating an object to be heated such as food using microwave power. It is also widely practiced to reheat individual foods stored in food packs using such a microwave oven. In this case, it is general that the shape of the microwave oven serving as the microwave irradiation chamber is a cube, and the volume of the microwave oven is considerably larger than that of the individual food. For this reason, the individual foods to be irradiated are not uniformly irradiated with microwaves, and so-called heating unevenness occurs. Therefore, in the microwave oven, the microwave irradiation is made uniform by a stirrer (metal rotating blade) that disturbs microwaves, a turntable that rotates a tray (a tray: a table), or the like.

  In addition, the microwave loss on the inner wall of the microwave oven increases due to the larger size of the microwave oven. As a result, the heating efficiency (the ratio of the microwave power absorbed by the food to the microwave power supplied into the microwave oven) is increased. ) Will be bad. Therefore, the microwave oven is uniformly irradiated using a plurality of microwave generators to reduce the uneven heating of the object to be heated and improve the heating efficiency.

  In addition, a technique for concentrating microwaves in the vicinity of an object to be heated using a rectangular waveguide and a circular waveguide to improve heating efficiency is also disclosed (for example, see Patent Document 1). According to this technology, a magnetron is attached to a rectangular waveguide, and microwave power is transmitted to the object to be heated contained in the circular waveguide by the microwave power transmitted from the rectangular waveguide to the circular waveguide. Since it concentrates, the to-be-heated material can be heated efficiently.

JP-A 63-299084

  However, when heating and sterilizing a single food for industrial use, it is natural to irradiate microwave power uniformly, but it is possible to irradiate the object to be heated with the maximum improvement in heating efficiency. There is a growing demand for microwave heating devices dedicated to individual foods. In addition, from the viewpoint of the reliability of the microwave heating apparatus, there is a demand for a microwave heating apparatus that does not require a stirrer or a turntable rotation mechanism in the applicator that is a microwave irradiation chamber. In the technique disclosed in Patent Document 1, the heating efficiency can be increased without using a rotation mechanism of a stirrer or a turntable, but if the object to be heated is not similar in shape to a circular waveguide, In some cases, microwaves cannot be concentrated on the object to be heated. In such a case, the heating efficiency cannot be improved. This problem is the same in microwave heaters (microwave ovens) for home use and business use.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a microwave heating apparatus that can uniformly and efficiently irradiate an object to be heated without using a rotating mechanism. And

In order to achieve the above object, a microwave heating apparatus of the present invention includes a waveguide that transmits microwave power , and a bottom surface that uniformly distributes the microwave power transmitted from the waveguide to an object to be heated. And a dielectric plate that is a fluororesin spacer having a relative dielectric constant greater than 1 , and a mounting table on which an object to be heated is placed. And the structure provided with the cylindrical applicator which irradiates the said to- be-heated material with the microwave electric power irradiated from the waveguide via a dielectric material board is taken.

  According to the present invention, by optimizing the shape of a dielectric plate (for example, a fluororesin plate such as Teflon (registered trademark)) having a relative dielectric constant greater than 1 and a low dielectric loss, The microwave can be refracted by the wavelength shortening effect when passing through, and the object to be heated can be uniformly irradiated with the microwave. As a result, the object to be heated can be efficiently and uniformly irradiated with microwaves without providing a stirrer that scatters microwaves or a turntable that rotates the object to be heated in the applicator.

It is a block diagram of the T-type waveguide which synthesize | combines the microwave power of 2.45 GHz, (a) is sectional drawing of the T-type waveguide 1, (b) shows the A surface of (a), (c ) Shows the B side of (a). It is a figure which shows the electric field direction of the C surface in the T-type waveguide 1 shown in FIG. It is a composition sectional view of the applicator concerning the embodiment of the present invention. It is the temperature distribution figure which measured the effect of the microwave heating device of the embodiment by the present invention compared with the comparative example, (a) is the actual measurement result of the comparative example, and (b) is the actual measurement result of the embodiment by the present invention. Show.

  Hereinafter, embodiments of a microwave heating apparatus according to the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  As an example, the microwave heating apparatus of this embodiment irradiates microwave power to the article to be heated 12 (see FIG. 3) using the T-type waveguide 1. The configuration will be described. FIG. 1 is a configuration diagram of a T-type waveguide 1 that synthesizes microwave power of 2.45 GHz. FIG. 1A shows a cross-sectional view of the T-type waveguide 1, and FIG. FIG. 1 (a) shows the A surface, and FIG. 1 (c) shows the B surface of FIG. 1 (a). As shown in FIG. 1A, the T-type waveguide 1 is configured such that a main waveguide 1a and a sub-waveguide 1b are orthogonal to each other.

  That is, the T-type waveguide 1 shown in FIG. 1A includes a main waveguide 1a having an A-side opening dimension of 80 mm × 80 mm as shown in FIG. As shown in the figure, the size of the opening on the B surface is orthogonal to the sub-waveguide 1b having a size of 80 mm × 40 mm. With such a configuration, the microwave power supplied from the A surface side of the main waveguide 1a and the microwave power supplied from the B surface side of the sub-waveguide 1b are converted into the inside of the T-type waveguide 1. Is synthesized. The synthesized microwave power is transmitted to the C-plane side of the main waveguide 1a and supplied to the applicator 10 (see FIG. 3).

  FIG. 2 is a diagram showing the electric field direction of the C plane in the T-type waveguide 1 of FIG. That is, the electric field direction contributing to the heating of the microwave power synthesized on the C plane of the T-shaped waveguide 1 (that is, the electric field direction of the C plane in FIG. 1A) is the A plane as shown in FIG. Electric field direction formed by microwave power supplied from the side (hereinafter referred to as main microwave electric field direction 1ae) and electric field direction formed by microwave power supplied from the B-side (hereinafter referred to as sub-microwave electric field) Direction 1be) has a direction difference of 90 degrees and is supplied to the applicator 10 (see FIG. 3) from the C-plane side.

  In this way, both microwave electric fields (that is, the electric field direction 1ae of the main microwave and the electric field direction 1be of the sub microwave) having a direction difference of 90 degrees are shown in FIG. 3 from the C-plane side of the main waveguide 1a. It is fed into an applicator (microwave irradiation chamber) 10 shown. Therefore, the power supplied to the applicator 10 is the sum of the microwave power transmitted through the main waveguide 1a and the microwave power transmitted through the sub waveguide 1b. In this way, high-power microwave power obtained by combining two microwave powers can be supplied to the applicator 10.

  FIG. 3 is a sectional view of the configuration of the applicator 10 according to the embodiment of the present invention. As shown in FIG. 3, the applicator 10 has a cylindrical shape and is configured with a minimum volume from the viewpoint of maximizing heating efficiency. The inner diameter of the volume is Φ150 mm, and the height is 75 mm. In such a volume, a heated object 12 such as a food is placed on the upper surface of the metal table 11.

  In addition, a fluororesin spacer 13 cut out in a conical shape is disposed on the top of the article 12 to be heated. The fluororesin spacer 13 has an outer diameter of 150 mm and a thickness of 30 mm, and a conical cutout is formed on the surface facing the object to be heated 12. The shape of this notch is a conical shape with a bottom diameter of 150 mm and a top diameter of 20 mm. The microwave power synthesized by the T-shaped waveguide 1 is irradiated to the object to be heated 12 through the fluororesin spacer 13 cut out in a conical shape.

  That is, the T-shaped waveguide 1 is positioned on the upper surface side of the cylindrical applicator 10, and a fluororesin spacer 13 having a shape cut out in a conical shape is attached to the inner surface of the cylindrical applicator 10 immediately below it. It has been.

  Therefore, the synthesized microwave power transmitted from the T-shaped waveguide 1 and having an electric field direction difference of 90 degrees is irradiated to the food that is the object to be heated 12 through the fluororesin spacer 13. Fluororesin generally has a relative dielectric constant ε of about 2 (at 2.45 GHz) and has a low microwave loss (tan δ). Therefore, it is generally used as a microwave transmitting material for the purpose of partition plates and the like. Yes. That is, the fluororesin is used as a thin partition plate so that water vapor or oil vapor generated from the object to be heated 12 does not flow into the waveguide.

  The speed of the microwave passing through the fluororesin is 1 / √ε in vacuum, and the wavelength is also 1 / √ε times the wavelength λo in vacuum. In other words, while the microwave passes through the fluororesin spacer 13, the wavelength of the microwave is shortened. Therefore, by optimizing the fluororesin spacer 13 by cutting it into a conical shape, the microwave is refracted. Since the object to be heated 12 can be dispersed and uniformly irradiated, the object to be heated 12 can be efficiently irradiated with microwaves.

  More specifically, the fluororesin spacer 13 cut into a conical shape exhibits the same refracting action as that of the concave lens of the optical system. Therefore, the synthetic micro-fiber introduced into the applicator 10 from the T-type waveguide 1. Waves are refracted by the fluororesin spacer 13 and can be radiated in a concentrated manner on the area of the object to be heated 12 while being dispersed throughout the object to be heated 12. Therefore, even if the volume of the applicator 10 is larger than that of the object to be heated 12, if the shape of the fluororesin spacer 13 is optimized according to the shape of the object to be heated 12, the microwaves are concentrated on the object to be heated 12. And since the to-be-heated material 12 can be irradiated uniformly, the to-be-heated material 12 can be heated efficiently.

  Note that a drain receiving tray 14 for receiving a drain and a drain pit 15 for discharging the drain are provided at a lower portion of a metal stand 11 made of a metal plate or a punching metal. If the cradle is made of a microwave permeable material instead of the metal cradle 11 and the drain tray 14 is made of a metal material, the microwave irradiated from above is reflected by the drain pan 14 to be heated. 12 can be irradiated. Thereby, the article to be heated 12 can be heated more efficiently.

  As described above, according to the microwave heating apparatus of the present invention, by optimizing the shape of the fluororesin plate such as Teflon (registered trademark), the microwave is refracted when entering and exiting the fluororesin plate. Thus, the object 12 to be heated can be uniformly irradiated with microwaves. As a result, even if there is no stirrer that scatters microwaves in the applicator 10 or a turntable that rotates the irradiated object, the object to be heated 12 can be irradiated with microwaves uniformly. Supplementally, the object to be heated 12 can be selectively irradiated with microwaves, and the object to be heated 12 selectively irradiated with microwaves can be heated uniformly.

  FIG. 4 is a temperature distribution diagram in which the effect of the microwave heating apparatus according to the embodiment of the present invention is measured in comparison with the comparative example. FIG. 4 (a) is the actual measurement result of the comparative example, and FIG. The actual measurement result of embodiment is shown. That is, in this figure, the temperature distribution when the food stored in the round pack is microwave-heated with an infrared radiation thermometer is measured by the presence or absence of the fluororesin spacer 13 notched in a conical shape shown in FIG. 4A shows the temperature distribution when the fluororesin spacer 13 is not provided, and FIG. 4B shows the temperature distribution when the fluororesin spacer 13 is provided.

  As is apparent from FIG. 4, when the fluororesin spacer 13 is present, it can be seen that in FIG. 4B, the object to be heated 12 is evenly irradiated with microwaves and the heating temperature is higher. That is, by using the microwave heating apparatus according to the present invention, the heating efficiency of the object to be heated 12 is increased, and the object to be heated 12 can be uniformly irradiated.

  That is, if a spacer having a relative permittivity larger than 1 and a dielectric loss (tan δ) with a notch optimized for a dielectric is used, the same effect as the above embodiment can be obtained. In this way, if microwaves are evenly irradiated to the object 12 to be heated, there is no need to use a metal rotating blade (stirrer) for microwave disturbance or a turntable for rotating the object to be irradiated, so a rotating mechanism is unnecessary. Thus, the reliability of the microwave heating apparatus can be further improved.

  Although the present invention has been specifically described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, it is not limited to Teflon (registered trademark) or the like (fluororesin), and the object to be heated 12 can be uniformly irradiated with microwaves even if a silicone resin spacer notched in a conical shape is interposed.

In addition, in the case of food with an outer ring shape that is ring-shaped or food that is depressed in the center while being placed on a tray, the surrounding area is irradiated with microwaves rather than intensively irradiating the center with microwaves. Better heating (reduction of time required for heating) can be achieved. In such a case, the shape of the spacer is appropriately changed so that the microwave is irradiated more to the periphery than the center of the article to be heated 12.
Or about the food in which the center part rose, heating of the center part is overdue. In such a case, the shape of the spacer is revised as appropriate so that a large amount of microwaves is irradiated on the central portion of the article to be heated 12.

  Further, by allowing the inside of the applicator 10 to be hermetically pressurized using a spacer 13 or the like, moisture loss from food can be prevented, and uniform heating of the article to be heated 12 by steam filled in the applicator 10 is possible. You can.

In addition, by making the spacer 13 replaceable, the heating characteristics of the microwave heating device can be completely changed by simply replacing the spacer 13.
By such measures, heating according to the shape and purpose of the food can be performed.

  According to the present invention, since the heating efficiency of the object to be heated is high, and the object to be heated can be uniformly irradiated, it can be effectively used for a microwave heating apparatus that performs heating processing and sterilization of individual foods. Can do.

1 T-type waveguide 1a Main waveguide 1b Sub-waveguide 1ae Electric field direction of main microwave 1be Electric field direction of sub-microwave 10 Applicator (microwave irradiation chamber)
11 Stand 12 Object to be heated (food)
13 Fluorine resin spacer

Claims (6)

A waveguide for transmitting microwave power;
A dielectric that is a fluororesin spacer having a disc shape with a lower surface cut out in a conical shape so as to uniformly disperse the microwave power transmitted from the waveguide to an object to be heated. body plate, and is formed of a metallic material, having a stand for placing the object to be heated, the microwave power radiated from the waveguide, through a dielectric body plate to the object to be heated A cylindrical applicator to be irradiated;
A microwave heating apparatus comprising: A waveguide for transmitting microwave power;
A dielectric plate which is a fluororesin spacer having a shape in which a lower surface is cut out in a conical shape so as to uniformly disperse microwave power transmitted from the waveguide to an object to be heated. The microwave power irradiated from the waveguide has a placing base on which the object to be heated is placed, and a drain pan made of a metal material. an applicator for irradiating the said object to be heated via a dielectric plate,
A microwave heating apparatus comprising: The microwave heating apparatus according to claim 1 or 2, wherein the applicator is configured to be able to replace the dielectric plate according to the object to be heated. The microwave applicator according to any one of claims 1 to 3, wherein the applicator is configured to be capable of being sealed and pressurized by the dielectric plate. The waveguide is connected to a main waveguide that transmits the first microwave power and a sub-waveguide that transmits the second microwave power so that directions of electric fields generated by the respective microwaves are orthogonal to each other. The microwave heating device according to any one of claims 1 to 4 , wherein the microwave heating device is a T-shaped waveguide. Wherein T Katashirubehakan are dimensions 80 mm × 80 mm of the opening of the main waveguide, according to claim 5, the dimension of the opening of the sub-wave tube is characterized by a 80 mm × 40 mm Microwave heating device.