JP2023003097A - Heating device and heating method - Google Patents

Abstract

To simplify other heat sources, in heating using microwave heating.SOLUTION: A heating device includes: a heating compartment forming a heating chamber, in which an object to be heated is stored, therein; an antenna for radiating a microwave for microwave heating for the object to be heated; and a heat source for externally heating the object to be heated. The heat source includes a conductor heated by the microwave radiated from the antenna.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to a heating device and a heating method.

Patent Literature 1 discloses a microwave oven that includes a high-frequency oscillator and a radiant electric heater, and uses both of them to heat and cook.

JP 2004-100987 A

In a heating apparatus that uses microwave heating, such as a microwave oven, it is advantageous to use a heating source other than microwave heating, because heating can be performed more effectively.

However, if the other heating source is an electric heater as in Patent Document 1, a circuit or the like for heating the electric heater is required.

Therefore, in heating using microwave heating, it is desired to simplify other heating sources.

One aspect of the present disclosure is a heating device. The disclosed heating device includes a heating chamber that internally forms a heating chamber in which an object to be heated is stored, an antenna that emits microwaves for microwave heating of the object to be heated, and an external heating of the object to be heated. a heating source, said heating source comprising an electrical conductor heated by said microwaves radiated by said antenna.

Another aspect of the present disclosure is a heating method. The disclosed heating method includes microwave heating of an object to be heated by microwaves radiated from an antenna, and external heating of the object to be heated by a conductor heated by the microwave heating.

Further details are described as embodiments below.

FIG. 1 is a schematic diagram of a heating device. FIG. 2 is a perspective view of the heating device. FIG. 3 is a schematic diagram showing a helical antenna. FIG. 4 is a schematic diagram showing a loop antenna. FIG. 5 is a schematic diagram showing a dipole antenna. FIG. 6 is a plan view of a conductor and a shield according to a modification. FIG. 7 is a cross-sectional view taken along line AA of FIG. 6, showing the arrangement of shields and conductors in the first mode. FIG. 8 is a schematic diagram showing the placement of shields and conductors in the second mode. FIG. 9 is a schematic diagram of a heating device according to another modification. FIG. 10 is a graph showing the results of the first experiment. FIG. 11 is a graph showing the results of the second experiment.

<1. Overview of heating device and heating method>

(1) A heating apparatus according to an embodiment includes a heating chamber that internally forms a heating chamber in which an object to be heated is stored, an antenna that emits microwaves for microwave heating of the object to be heated, and the object to be heated. and a heating source for externally heating the object to be heated. The heating source comprises an electrical conductor heated by the microwaves radiated by the antenna. In this case, since the conductor included in the heat source is heated by microwaves, a dedicated circuit or the like for heating the heat source is not required.

(2) Preferably, the conductor has a portion located in the near field of the antenna.

(3) It is preferable that the conductor has a portion arranged at a distance of 1/2 or less of one wavelength of the microwave from the antenna.

(4) In (1) above, the conductor is preferably a magnetic material.

(5) In (2) or (3) above, the conductor is preferably a magnetic material.

(6) Preferably, the antenna is a helical antenna, a loop antenna, or a dipole antenna. Preferably, the antenna has a looped portion. An antenna having a looped portion is, for example, a helical antenna or a loop antenna.

(7) It is preferable that the conductor is arranged on the side opposite to the object to be heated as viewed from the antenna.

(8) The frequency of the microwave is preferably in the range of 500MHz to 3GHz.

(9) The heating device may further include an adjuster for adjusting heating of the conductor by the microwaves radiated from the antenna. The regulator has a first mode in which the microwave radiated from the antenna reaches the conductor and heats the conductor, and a first mode in which the microwave reaches the conductor. Preferably, it is arranged to switch to a second mode which is more suppressed than the second mode.

(10) The adjuster preferably includes a microwave shield disposed between the antenna and the conductor in the second mode to suppress the microwave from reaching the conductor. .

(11) A heating method according to an embodiment includes microwave heating of an object to be heated by microwaves radiated from an antenna, and external heating of the object to be heated by a conductor heated by the microwave heating. .

<2. Example of heating device and heating method>

Hereinafter, the heating device 10 and the heating method according to the embodiment will be described in more detail with reference to the drawings. 1 and 2 show a heating device 10 according to an embodiment. The heating device 10 heats the object 60 to be heated. The object 60 to be heated is, for example, food or medical or inspection substances. Medical or diagnostic substances are, for example, drugs, reagents or specimens. The object to be heated 60 may be a frozen product. The heating device 10 is suitable for thawing frozen products. The heating device 10 is suitable for thawing frozen products and then heating them. The heating device 10 may be used for heating refrigerated goods or room temperature goods.

The heating device 10 includes a heating chamber 20 in which a heating chamber 30 in which an object 60 to be heated is heated is formed. The illustrated heating chamber 30 includes a bottom surface 31, a top surface 32, a right side surface 33, a left side surface 34, and a back surface 35 (back side). An object to be heated 60 such as food is stored in the heating chamber 30 for heating. The front surface of the heating chamber 30 is opened and closed by a door portion (not shown).

The heating device 10 has an antenna 40 . Antenna 40 radiates into heating chamber 30 microwaves M for microwave heating object to be heated 60 housed in heating chamber 30 . In the microwave heating, the microwaves M vibrate molecules (in particular, water molecules) of the object 60 to be heated, which is a dielectric, thereby heating the object 60 to be heated. Microwave heating is dielectric heating by microwaves. Microwave heating is internal heating. In internal heating, heat is generated from inside the object 60 to be heated.

Antenna 40 may be disposed within heating chamber 30 . Moreover, a partition member that does not interfere with the microwave M and, if necessary, heat conduction, which will be described later, may be provided between the antenna 40 and the heating chamber 30 .

The antenna 40 installed in the heating chamber 30 is preferably covered with a protector (not shown). The protector for the antenna 40 is also called a radome. The protector is preferably made of a material having high microwave transmittance and excellent heat resistance. A material having high microwave transmittance and excellent heat resistance is, for example, fluororesin.

For example, the microwave M is preferably an electromagnetic wave with a frequency (center frequency, hereinafter the same) of 300 MHz to 300 GHz, more preferably an electromagnetic wave with a frequency of 300 MHz to 30 GHz, and an electromagnetic wave with a frequency of 500 MHz to 3 GHz. is more preferable.

If the frequency is 300 MHz, the wavelength λ is approximately 1 m. If the frequency is 300 GHz, the wavelength λ is approximately 1 mm. If the frequency is 30 GHz, the wavelength λ is approximately 10 mm. If the frequency is 500 MHz, the wavelength λ is approximately 600 mm. If the frequency is 3 GHz, the wavelength λ is approximately 100 mm.

The frequency of the microwave M is preferably a frequency included in the ISM (Industrial Scientific and Medical) band, for example 433.92 MHz, 915 MHz, 2.45 GHz, 5.8 GHz, 24.125 GHz, 61.25 GHz, 122 .5 GHz and 245 GHz.

As an example, the frequency of microwave M is more preferably 915 MHz or 2.45 GHz. If the frequency is 915 MHz, the wavelength λ is approximately 328 mm. If the frequency is 2.45 GHz, the wavelength λ is approximately 122 mm.

The heating device 10 comprises a microwave circuit 90 for generating microwaves M emitted from the antenna 40 . The microwave circuit 90 includes, for example, a microwave generator 70 and an amplifier 80 for amplifying microwaves. The microwave amplified by amplifier 80 is connected to antenna 40 via feed line 50 . The feed line 50 is, for example, a coaxial cable or two parallel wires. A connection point between the feed line 50 and the antenna 40 is called a feed point 40A.

The heating chamber 20 includes a circuit housing portion 37 in which the microwave circuit 90 and the like are arranged. In FIG. 1 , the circuit housing portion 37 is formed above the top surface 32 . However, the position of the circuit housing portion 37 is not particularly limited. A feeder line 50 extending from a microwave circuit 90 arranged in the circuit housing portion 37 is connected to a feeding point 40A of an antenna 40 arranged outside the circuit housing portion 37 .

In FIG. 1, the antenna 40 is arranged near the top surface 32 . However, the position of the antenna 40 is not particularly limited. The antenna 40 is arranged at one or more positions near the bottom surface 31, near the top surface 32, near the right side surface 33, near the left side surface 34, and near the rear surface (inner side surface) 35. may have been Since the heating device 10 includes a plurality of antennas 40, the object 60 to be heated can be efficiently internally heated.

The heating device 10 has a heating source 100 separate from the antenna 40 . The heating source 100 externally heats the object 60 to be heated. Heating by the heat source 100 is external heating. That is, the heat source 100 itself is heated, and the heat R is transferred to the object 60 to be heated. The transferred heat R heats the object 60 to be heated from its surface. Therefore, the heating device 10 of the embodiment can heat the object 60 to be heated internally and externally.

In an embodiment, heating source 100 is heated by microwaves M emitted from antenna 40 . Therefore, the heating device 10 does not need to have an electric circuit dedicated to heating the heat source 100 . The heating source 100 of the embodiment comprises a conductor 110 heated by microwaves M radiated by the antenna 40 . The shape of the conductor 110 is, for example, plate-like or box-like. The shape of the conductor 110 is not particularly limited. The conductor 110 absorbs the microwaves M emitted from the antenna 40 and generates heat.

Conductor 110 is preferably a magnetic material such as a magnetic metal. A magnetic body absorbs microwaves M more easily than a non-magnetic body. The magnetic material is, for example, a magnetic material such as stainless steel (SUS), iron oxide, chromium oxide, cobalt, ferrite, or a non-oxidized metal magnetic material (oxide). Stainless steel (SUS), which is a magnetic material, is, for example, ferritic stainless steel or martensitic stainless steel.

Although the conductor 110 may be a non-magnetic material, it is preferable that the conductor 110 be a magnetic material from the viewpoint of the heating efficiency of the microwave because the reflection of the microwaves M increases. Conversely, if it is desired to suppress the temperature rise of the conductor 110, a non-magnetic material is preferable. In addition, the non-magnetic material is a portion required to reflect the microwave M, for example, the inner surface of the heating chamber 30 (bottom surface 31, top surface 32, right side surface 33, left side surface 34, and rear surface 35) or It can be suitably used for the shield 120 . The non-magnetic material is, for example, copper, aluminum, or stainless steel which is non-magnetic material. Non-magnetic stainless steel is, for example, austenitic stainless steel.

The conductor 110 is attached to the top surface 32 via a support 115, for example. That is, the conductor 110 is arranged near the top surface 32 . However, the position of the conductor 110 is not particularly limited. The conductor 110 is positioned near the bottom surface 31, near the top surface 32, near the right side surface 33, near the left side surface 34, and near the back surface (inner side surface) 35, or at a plurality of positions. may be placed. Since the heating device 10 includes a plurality of conductors 110, the object 60 to be heated can be externally heated efficiently.

In FIG. 1 , the conductor 110 is arranged on the side opposite to the object 60 to be heated as viewed from the antenna 40 . That is, assuming that the heated object 60 side is the front side and the opposite side is the back side when viewed from the antenna 40 , the conductor 110 is arranged on the back side of the antenna 40 . By arranging the conductor 110 on the back side of the antenna 40, it is possible to obtain an arrangement in which the conductor 110 does not interfere with the microwaves M radiated to the object 60 to be heated, which is preferable.

In FIG. 1, the feeder 50 extending from the microwave circuit 90 passes through a through hole 111 formed in the conductor 110 and extends from the rear surface 110B side of the conductor 110 to the front surface 110A side. A feeder line 50 passing through the through hole 111 is connected to the antenna 40 arranged on the front surface 110A side of the conductor 110 .

At least a portion of conductor 110 is preferably located in close proximity to antenna 40 . The inventors have experimentally found that the conductor 110 to be heated is surprisingly very efficiently heated by arranging the conductor 110 in close proximity to the antenna 40 . In general, a conductor such as a metal reflects most of the microwaves it radiates, even if the material is a magnetic material, and the energy absorbed for heating is not so large. Therefore, when heating the conductor 110 with microwaves, it is desired to increase the heating efficiency.

The inventors have found that by arranging at least part of the conductor 110 in the near field N (near field) of the antenna 40, the conductor 110 can be efficiently heated by microwaves. In particular, it has been found that by arranging the conductor 110, which is a magnetic material, in the near field N, it is possible to heat very efficiently.

The near field N is a region near the antenna 40, which is the radiation source of the microwave M, and is a region having electromagnetic field characteristics different from those of the far field. According to experiments conducted by the present inventor, the conductor 110 shown in FIG. 1 is arranged near the antenna 40 as shown in FIG. When the conductor 110 is arranged in the vicinity of the antenna 40 as shown in FIG. 1, the heating efficiency is higher.

Therefore, it is considered that the microwaves M are less likely to be reflected in the near field N than in the far field, and that the microwaves M are more likely to be absorbed by the conductor 110 such as metal.

Also, in embodiments, heating of the conductor 110 by microwaves M is considered to include electromagnetic induction heating. Electromagnetic induction heating is heating that utilizes the fact that electromagnetic induction occurs when a magnetic field penetrating a conductor changes, current flows through the conductor, and Joule heat is generated. A larger magnetic field can be expected in the near field N than in the far field. Therefore, in the conductor 110 placed in the near field N, electromagnetic induction can be efficiently generated.

From the viewpoint of generating electromagnetic induction heating more effectively, it is preferable that the antenna 40 generates a larger magnetic field in the near field N thereof. In order to generate a stronger magnetic field, the antenna 40 preferably has a looped portion. Since the antenna 40 has the loop-shaped portion, it is possible to generate a magnetic field in the near field N that penetrates the loop-shaped portion. Therefore, in the near field N, the magnetic field becomes more dominant, and electromagnetic induction is more likely to occur. Antenna 40 having a portion formed in a loop shape is, for example, a loop antenna or a helical antenna.

Assuming that the wavelength of the microwave M emitted from the antenna 40 is λ, the near field N is preferably a region where the distance D from the antenna 40 is λ/2 or less, and the distance D is λ/(2π) ( ≈λ/6.28) or less, and more preferably the distance D is λ/16 or less. The distance D from the antenna 40 may be a distance with the feeding point 40A of the antenna 40 as a starting point, or may be a distance with an arbitrary position of the antenna 40 as a starting point.

If the frequency of microwave M is 915 MHz, its wavelength λ is approximately 328 mm. In this case, at least a part of the conductor 110 preferably exists in a region where the distance D from the antenna 40 is 164 mm or less (≈λ/2 or less), and the distance D is 52 mm or less (≈λ/2 or less). (2π) or less), and more preferably, the distance D is 20 mm or less (≈λ/16 or less).

If the microwave M has a frequency of 2.45 GHz, its wavelength λ is approximately 122 mm. In this case, at least part of the conductor 110 preferably exists within a region where the distance D from the antenna 40 is 61 mm or less (≈λ/2 or less), and the distance D is 19 mm or less (≈λ/2). (2π) or less), and more preferably within a region where the distance D is 8 mm or less (≈λ/16 or less).

Moreover, the conductor 110 is preferably arranged so that the shortest distance between the conductor 110 and the antenna 40 is λ/(2π) (≈λ/6.28) or less, and λ/16 or less. More preferably, they are arranged as such. The shortest distance between conductor 110 and antenna 40 is the shortest distance between an arbitrary position on conductor 110 and an arbitrary position on antenna 40 .

Moreover, the conductor 110 is preferably arranged so that the shortest distance between the conductor 110 and the feeding point 40A of the antenna 40 is λ/(2π) (≈λ/6.28) or less. /16 or less is more preferable. The shortest distance between the conductor 110 and the feeding point 40 A of the antenna 40 is the shortest distance from the feeding point A of the antenna 40 to the conductor 110 .

When microwaves generated by a magnetron placed outside the heating chamber are transmitted to the heating chamber through a waveguide as in a general microwave oven, the heating chamber becomes a far field. Therefore, even if the conductor 110 is arranged in or near the heating chamber, there is a possibility that efficient heating of the conductor 110 cannot be expected. In particular, difficulties arise when the distance D between the conductor and the antenna is desired to be λ/16 or less. On the other hand, as in the present embodiment, the antenna 40 itself is arranged in the heating chamber 30 or in the vicinity of the heating chamber 30, and at least part of the conductor 110 is arranged in the near field N of the antenna 40. , the conductor 110 can be easily and efficiently heated.

When it is desired to make the distance between the antenna 40 and the conductor 110 sufficiently small, for example, when it is desired to be λ/16 or less from the wavelength λ of the microwave M, the larger the frequency of the microwave M, the better the distance between the antenna 40 and the conductor 110. Advantageously, the physical length of the interval with 110 can be increased. The larger the physical length of the space between the antenna 40 and the conductor 110, the higher the degree of freedom in design and arrangement, which is advantageous. As an example, the wavelength of the microwave M is preferably 915 MHz. If the frequency is 915 MHz, the wavelength λ is approximately 328 mm and λ/16 is approximately 20 mm. Therefore, even if the distance between the antenna 40 and the conductor 110 is sufficiently small, the physical length of the gap between the antenna 40 and the conductor 110 can be secured to some extent from the wavelength λ of the microwave M.

The heating chamber 30 may be wholly or mostly in the near field N of the antenna 40 . Conversely, the heating chamber 30 may include regions that are far-field. In this case, the microwave M emitted from the antenna 40 can heat the conductor 110 in the near field N and heat the object 60 in the far field.

When the heating device 10 is used for an application that requires heating at a relatively low temperature, the conductor 110 is preferably heated to 100° C. or higher, preferably 120° C. or higher, at the highest temperature portion. is more preferred, heating to 130° C. or higher is more preferred, heating to 150° C. or higher is even more preferred, and heating to 200° C. or higher is even more preferred.

When the heating device 10 is used for an application that requires heating at a relatively high temperature, the temperature of the conductor 110 is preferably less than 100° C. at the highest temperature portion, and preferably 40° C. or more and less than 100° C. is more preferably 40°C or higher and lower than 80°C, and even more preferably 40°C or higher and lower than 60°C.

Note that the conductor 110 is preferably insulated from the ground of the antenna 40 in order to improve the efficiency of microwave heating. The ground GND of the antenna 40 is, for example, equipotential to the ground GND in the microwave circuit 90 . A ground GND of the microwave circuit 90 is connected to, for example, the heating chamber 20 of the heating device 10 for grounding. In this case, if the conductor 110 is insulated from the heating chamber 20 , it is insulated from the ground of the antenna 40 . In order to provide the conductor 110 insulated from the heating chamber 20, for example, the support 115 may be made of an insulating material.

FIG. 3 shows a helical antenna 41 as an example of the antenna 40. As shown in FIG. The helical antenna 41 is, for example, a normal mode helical antenna. A normal mode helical antenna is obtained by forming the antenna element of a monopole antenna into a spiral shape. In the helical antenna 41, the helical portion has a three-dimensional loop shape and can generate a magnetic field penetrating the helical portion.

Helical antenna 41 is connected to feed line 50 at feed point 40A. The microwaves M radiated from the helical antenna 41 microwave-heat the object 60 to be heated and heat the conductor 110 .

FIG. 4 shows a loop antenna 42 as another example of the antenna 40. As shown in FIG. The loop antenna 42 is formed by forming an antenna element in a loop shape. The loop may be one turn or multiple turns. The loop antenna 42 has a loop-shaped portion and can generate a magnetic field that penetrates the loop-shaped portion.

The loop antenna 42 is connected to the feeding line 50 at its feeding point 40A. The microwaves M radiated from the loop antenna 42 microwave-heat the object 60 to be heated and heat the conductor 110 .

FIG. 5 shows a dipole antenna 43 as another example of the antenna 40. As shown in FIG. Dipole antenna 43 has two linear antenna elements and is connected to feeder 50 at feed point 40A. The microwaves M emitted from the dipole antenna 43 microwave-heat the object 60 to be heated and heat the conductor 110 .

FIGS. 6-8 illustrate variations in configuration associated with the heating source 100. FIG. The heating device 10 according to the modification includes an adjuster 160 that adjusts the heating of the conductor 110 by the microwaves M. As shown in FIG. The adjuster 160 has a first mode in which the microwave M radiated from the antenna 40 reaches the conductor 110 and heats the conductor 110, and a first mode in which the microwave M reaches the conductor 110. and a second mode in which the power is also suppressed.

Adjuster 160 includes, as an example, microwave shield 120 and driver 130 that moves conductor 110 . Conductor 110 and drive unit 130 are connected via rod 140 . The conductor 110 is made of a material that absorbs the microwaves M more easily than the shield 120, such as a magnetic material, so that it can be easily heated. The shield 120 is made of a material that reflects the microwaves M more easily than the conductor 110, such as a non-magnetic material.

Shield 120 is positioned between conductor 110 and antenna 40 in the second mode to block microwaves M emitted from antenna 40 from reaching conductor 110 . Therefore, in the second mode, heating of the conductor 110 is suppressed, and the object to be heated 60 is exclusively heated by microwave heating. In addition, it is preferable that the intervals between the comb teeth of the comb-shaped shield 120 are sufficiently small so that the microwaves M cannot pass through the gaps between the comb teeth. The interval through which the microwaves M cannot pass is appropriately set according to the wavelength of the microwaves M. As shown in FIG.

On the other hand, in the first mode, the shield 120 does not block the microwave M radiated from the antenna 40 from reaching the conductor 110, or blocks it to a lesser degree. Therefore, in the first mode, the conductor 110 is easily heated, and the object 60 to be heated is heated by the internal heating by microwave heating and the external heating by the conductor 110 .

As shown in FIG. 6, the shield 120 and the conductor 110 are formed in a comb-tooth shape that meshes with each other. As an example, the shield 120 is attached to the top surface 32 via the support 115 described above, and is provided in a fixed position within the heating chamber 20 . On the other hand, the conductor 110 is provided movably with respect to the shield 120 . More specifically, the conductor 110 is in a position meshing with the shield 120 (the position in FIG. 7) in the first mode, and in the second mode the conductor 110 is in the upper position (the position in FIG. 8). ) and position the shield 120 between the conductor 110 and the antenna 40 .

Feeder line 50 extends to antenna 40 through a through hole formed in conductor 110 and shield 120 . A through-hole through which the power supply line 50 can be inserted is constituted by a cutout 110C formed in the conductor 110 and a cutout 120C formed in the shield 120 .

As shown in FIG. 6, the shield 120 and the conductor 110 are generally formed in a rectangular shape when they are engaged with each other. In the first mode, the shield 120 and the conductor 110 are meshed with each other, that is, the shield 120 and the conductor 110 are vertically in the same position. In this case, the conductor 110 can be irradiated with the microwave M emitted from the antenna 40 without being blocked by the shield 120 (see FIG. 7). Therefore, the conductor 110 is heated and can radiate heat R to the object 60 to be heated. Moreover, the heat of the conductor 110 is conducted to the shield 120, and the shield 120 is also heated. The heated shield 120 radiates heat to the object 60 to be heated.

In the second mode, the conductor 110 is moved upward by the driving section 130 . The microwaves M emitted from the antenna 40 are reflected by the shield 120 and do not or hardly reach the conductor 110 . Therefore, heating of the conductor 110 is suppressed.

Alternatively, the conductor 110 may be fixed and the shield 120 may be moved by the drive unit 130 . Also, both conductor 110 and shield 120 may move to change their relative positions.

The driving unit 130 has, for example, a motor or a solenoid, and has a mechanism necessary for movement. As shown in FIG. 7 , the operation of the drive unit 130 is controlled by a controller 150 . The controller 150 is configured by, for example, a microcontroller. The controller 150 switches between the first mode and the second mode according to an input from the outside or by internal control. The controller 150 controls the drive section 130 so that the conductor 110 is positioned at the same height as the shield 120 when in the first mode, and the conductor 110 is positioned above the shield 120 when in the second mode. The driving unit 130 is controlled to position.

FIG. 9 shows another modification of the heating device 10. As shown in FIG. In the heating device 10 shown in FIG. 9, the surface forming the heating chamber 30 (for example, the top surface 32) itself constitutes a conductor heated by the microwaves M. As shown in FIG. That is, the surface forming the heating chamber 30 (for example, the top surface 32) itself constitutes a heat source for externally heating the object 60 to be heated. In the case of the heating device 10 shown in FIG. 9, the conductor 110 shown in FIG. 1 can be omitted, which is advantageous in that the structure can be made simpler.

The surfaces heated by the microwaves M may be surfaces other than the top surface 32 , such as the bottom surface 31 , the right side surface 33 , the left side surface 34 , or the back surface 35 . Two or more surfaces may be heated by the microwaves M. At least part of the surface heated by the microwaves M lies within the near field N of the antenna 40 . One or more antennas 40 are placed near the surface to be heated by the microwaves M. FIG.

When the top surface 32 and the like positioned within the near field N are heated by the microwaves M, the heat R is radiated to the object 60 to be heated, and the object 60 to be heated is externally heated. Therefore, the object 60 to be heated is heated by internal heating by microwave heating and external heating. Even if only the top surface 32 is heated by the microwaves M, the other surfaces 31, 33, 34, and 35 can also be heated by heat conduction. Therefore, other surfaces 31 , 33 , 34 , 35 can also radiate heat R for external heating of the object 60 to be heated.

It is expected that the portions outside the near field N among the surfaces 31, 32, 33, 34, and 35 forming the heating chamber 30 will reflect the microwave M more easily than inside the near field N. be done.

It is preferable that the member forming the surface (for example, the top surface 32) forming the heating chamber 30 is a magnetic material so that it can be efficiently heated by the microwaves M. As shown in FIG. A member forming a surface (for example, the top surface 32) forming the heating chamber 30 may be configured by a combination of a magnetic material and a non-magnetic material. In this case, part or all of the surface (for example, the top surface 32) located in the near field N may be formed of a magnetic material, and the other surfaces 31, 33, 34, and 35 may be formed of a non-magnetic material. good. In this case, the surface formed of a non-magnetic material can efficiently reflect the microwaves M, and is suitable from the viewpoint of irradiating the object 60 to be heated with the microwaves M.

It is preferable that the member forming the surface (for example, the top surface 32) forming the heating chamber 30 is insulated from the ground of the antenna 40 in order to improve the efficiency of microwave heating. The ground GND of the microwave circuit 90 is preferably connected to a member other than the member constituting the surface forming the heating chamber 30 in the heating chamber 20 for grounding. By insulating the members forming the surfaces forming the heating chamber 30 from other members, the members forming the surfaces forming the heating chamber 30 can be insulated from the ground of the antenna 40. .

FIG. 10 shows the results of a first experiment in which the conductor 110 was heated by the heating device 10 shown in FIG. In the first experiment, the antenna 40 was the helical antenna 41 .
The frequency of the microwave M was adjusted to 915 MHz (wavelength λ: about 328 mm), and the power of the microwave M was adjusted to about 300 W in terms of effective value. The helical antenna 41 is configured by spirally forming an antenna element with a length of 248 mm, which is close to the element length of 5/8λ where the gain of a linear antenna can be obtained. (The same applies to the following antenna structures). The conductor 110 was arranged so that the shortest distance to the helical antenna 41 was less than 1 cm. Therefore, at least part of the conductor 110 is within the near field N of the helical antenna 41 .

In the first experiment, the heating temperature of the conductor 110 was measured when the conductor 110 was made of magnetic stainless steel and when it was made of non-magnetic stainless steel. As for the temperature, the surface temperature of the conductor 110 was measured by stopping the output of the microwave M every 5 minutes after the start of heating. Note that the first experiment was conducted without the object 60 to be heated. The measured temperature is the temperature at the hottest location on the conductor 110 .

As shown in FIG. 10, when the conductor 110 was non-magnetic, the temperature of the conductor 110 increased to 50° C. in 5 minutes, and then increased to about 60° C. When the conductor is magnetic, the temperature of conductor 110 rises to 180° C. in 5 minutes. After that, although the temperature dropped, it was possible to heat up to 140°C.

According to the results shown in FIG. 10, in the case of the non-magnetic conductor 110, the temperature rise of the conductor 110 can be suppressed. Therefore, the non-magnetic conductor 110 is suitable for applications requiring heating at a relatively low temperature, eg, less than 100.degree. Applications requiring heating at relatively low temperatures are, for example, low temperature cooking or thawing. Thawing may be, for example, thawing of frozen food, or thawing of frozen medical or diagnostic material.

Also, the magnetic conductor 110 is heated more efficiently than the non-magnetic conductor 110 . Therefore, the magnetic conductor 110 is suitable for applications requiring heating at a relatively high temperature, for example, 100° C. or higher. Applications that require heating at relatively high temperatures are, for example, cooking or other food processing that requires the surface to be browned.

When the object 60 to be heated is present and the conductor 110 is heated by the microwaves M, the energy of the microwaves M is absorbed by the object 60 to be heated. temperature rise can be suppressed.

FIG. 11 shows the results of a second experiment in which the type of antenna 40 was changed in the heating device 10 shown in FIG. In the second experiment, a loop antenna 42 and a dipole antenna 43 were used as the antenna 40 . Also in the second experiment, the frequency of the microwave M was adjusted to 915 MHz (wavelength λ: about 328 mm), and the power of the microwave M was adjusted to about 300 W in terms of effective value. The conductor 110 was arranged so that the shortest distance to the antenna 40 was less than 1 cm. Therefore, at least part of the conductor 110 is within the near field N of the helical antenna 41 . The conductor 110 was magnetic stainless steel.

The loop antenna 42 has a loop length shorter than 1λ. The dipole antenna 43 was configured so that the element length was 1/2 of 248 mm.

In the second experiment, the material of the conductor 110 was magnetic stainless steel, and the heating temperature of the conductor 110 was measured. As for the temperature, the surface temperature of the conductor 110 was measured by stopping the output of the microwave M every 5 minutes after the start of heating. The second experiment was conducted without the object 60 to be heated. The measured temperature is the temperature at the hottest location on the conductor 110 .

FIG. 11 shows temperature changes when the antenna 40 is the loop antenna 42 and when the antenna 40 is the dipole antenna 43 . FIG. 11 also shows the temperature change of the conductor 110 when the material of the conductor 110 is magnetic stainless steel in the first experiment in which the antenna 40 is the helical antenna 41 .

According to the results shown in FIG. 11, when comparing the maximum temperatures, the temperature of the loop antenna 42 was the highest, and the temperature of the helical antenna 41 and the dipole antenna 43 became lower in that order. In the case of the helical antenna 41, the temperature of the conductor 110 increased to 175°C in 5 minutes, and then increased to 230°C. In the case of the dipole antenna 43, the temperature was raised to 105°C in 5 minutes and then to 125°C.

Since the loop antenna 42 and the helical antenna 41 are antennas having loop-shaped portions, the magnetic field can be more dominant in the near field N than the dipole antenna 43 . As a result, in the loop antenna 42 and the helical antenna 41, it is considered that the electromagnetic induction heating effectively occurred and the maximum temperature increased. Therefore, the loop antenna 42 and the helical antenna 41 are suitable for applications that require heating at relatively high temperatures. Moreover, the maximum temperature of the loop antenna 42 exceeds 200° C., which is preferable.

On the other hand, the dipole antenna 43 can maintain the conductor 110 at a relatively low temperature and is suitable for applications requiring heating at a relatively low temperature.

As a third experiment, heating was performed using frozen beef as the object 60 to be heated. The experimental conditions of the third experiment are the same as those of the first experiment. However, the conductor 110 is a magnetic material. The weight of the frozen beef was 150g. Frozen beef frozen in a food freezer was immediately cooked by a heating device 10 for 30 minutes after being taken out from the food freezer. By this cooking, the frozen beef was thawed and heated to the inside, and the surface was browned. In other words, it was possible to make roast beef from frozen beef.

When a frozen product is heated only by microwave heating, the heating may not be sufficiently performed or uneven heating may occur. This is because in frozen products, since water is solid, microwave heating due to the vibration of water molecules cannot be sufficiently performed, and when partially thawed, heating progresses locally in that part. is. In contrast, in the heating device 10 of the present embodiment, even if the object 60 to be heated is a frozen product, the object 60 to be heated can be thawed by external heating by the conductor 110 . In other words, at the initial stage of heating, the energy of the microwave radiated from the antenna 40 is mainly used for heating the conductor 110 rather than being absorbed by the object 60 to be heated for microwave heating of the object 60 to be heated. Used. As a result, at the initial stage of heating, the conductor 110 is heated more efficiently, and the entire surface of the object 60 to be heated can be externally heated.

When the surface of the object 60 to be heated is thawed by external heating, the microwave heating becomes effective, and the object 60 to be heated can be heated to the inside along with the external heating. In addition, since the object to be heated 60 is entirely heated by the external heating, it is difficult for the microwave heating to concentrate and uneven heating is unlikely to occur. As a result, the frozen product can be cooked satisfactorily.

As described above, the heating device 10 of the embodiment can be used as a food processing machine for cooking or processing a frozen product when the object to be heated 60 is food. The heating device 10 can, for example, defrost a frozen product, heat it to cooking temperature, and give it brown marks. As a result, everything from thawing to cooking can be performed at once.

The present invention is not limited to the above embodiments, and various modifications are possible.

10 : Heating device 20 : Heating chamber 30 : Heating chamber 31 : Bottom surface 32 : Top surface 33 : Right surface 34 : Left surface 35 : Rear surface 37 : Circuit storage unit 40 : Antenna 40A : Feeding point 41 : Helical antenna 42 : Loop antenna 43: Dipole antenna 50: Feeder line 60: Object to be heated 70: Microwave generator 80: Amplifier 90: Microwave circuit 100: Heat source 110: Conductor 110A: Front surface 110B: Rear surface 110C: Notch 111: Through hole 115: Support 120 : Microwave shield 120C : Notch 130 : Actuator 140 : Rod 150 : Controller 160 : Regulator A : Feeding point D : Distance GND : Ground M : Microwave N : Near field R : Heat

Claims (11)

a heating chamber internally forming a heating chamber in which an object to be heated is stored;
An antenna that radiates microwaves for microwave heating of the object to be heated;
a heating source that externally heats the object to be heated;
with
The heating device, wherein the heating source comprises a conductor heated by the microwaves radiated by the antenna. The heating device according to claim 1, wherein the conductor has a portion located in the near field of the antenna. 3. The heating device according to claim 1, wherein the conductor has a portion arranged at a distance of 1/2 or less of one wavelength of the microwave from the antenna. The conductor is a magnetic material,
The heating device according to claim 1. The heating device according to claim 2 or 3, wherein the conductor is a magnetic material. The heating device according to any one of claims 1 to 4, wherein the antenna is a helical antenna, a loop antenna, or a dipole antenna. The heating device according to any one of claims 1 to 6, wherein the conductor is arranged on the side opposite to the object to be heated when viewed from the antenna. 8. The heating device according to any one of claims 1 to 7, wherein the microwave frequency is in the range of 500 MHz to 3 GHz. further comprising a regulator for regulating heating of the conductor by the microwaves radiated from the antenna;
The regulator has a first mode in which the microwave radiated from the antenna reaches the conductor and heats the conductor, and a first mode in which the microwave reaches the conductor. 9. A heating device according to any one of the preceding claims, wherein the heating device is configured to switch between a second mode which is more constrained than the 10. The regulator of claim 9, wherein in the second mode, the regulator comprises a microwave shield disposed between the antenna and the conductor to suppress the microwaves from reaching the conductor. heating device. A heating method comprising microwave heating an object to be heated by microwaves radiated from an antenna, and externally heating the object to be heated by a conductor heated by the microwave heating.

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