Heating device and heating method

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

[0001] The present disclosure relates to a heating device and a heating method.

Background Art

[0002] Patent Document 1 discloses a microwave oven that includes a high-frequency oscillator and a radiant electric heater, and performs cooking using both of them.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] In a heating device that uses microwave heating such as a microwave oven, it is advantageous to be able to perform more effective heating by using a heating source other than microwave heating.

[0005] 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.

[0006] Therefore, in heating using microwave heating, it is desirable to simplify the other heating source.

[0007] One aspect of the present disclosure is a heating device. The disclosed heating device includes a heating chamber in which an object to be heated is housed, an antenna that radiates microwaves for microwave heating of the object to be heated, and a heating source that externally heats the object to be heated. The heating source includes a conductor that is heated by the microwaves radiated by the antenna.

[0008] Another aspect of the present disclosure is a heating method. The disclosed heating method includes 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.

[0009] Further details will be described as embodiments below.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0011] <1. Overview of the Heating Device and the Heating Method>

[0012] (1) The heating device according to the embodiment includes a heating chamber in which an object to be heated is housed, an antenna that emits microwaves for microwave heating of the object to be heated, and a heating source that externally heats the object to be heated. The heating source includes a conductor that is heated by the microwaves emitted by the antenna. In this case, since the conductor included in the heating source is heated by microwaves, a dedicated circuit or the like for heating the heating source is unnecessary.

[0013] (2) It is preferable that the conductor has a portion disposed in the near field of the antenna.

[0014] (3) It is preferable that the conductor has a portion disposed at a distance of 1 / 2 or less of one wavelength of the microwaves from the antenna.

[0015] (4) In the above (1), it is preferable that the conductor is a magnetic material.

[0016] (5) In the above (2) or (3), it is preferable that the conductor is a magnetic material.

[0017] (6) The antenna is preferably a helical antenna, a loop antenna, or a dipole antenna. The antenna preferably has a portion formed in a loop shape. An antenna having a portion formed in a loop shape is, for example, a helical antenna or a loop antenna.

[0018] (7) It is preferable that the conductor is disposed on the side opposite to the object to be heated as viewed from the antenna.

[0019] (8) The frequency of the microwaves is preferably in the range of 500 MHz to 3 GHz.

[0020] (9) The heating device may further include an adjuster that adjusts the heating of the conductor by the microwave radiated from the antenna. The adjuster is preferably configured to switch between a first mode in which the microwave radiated from the antenna reaches the conductor and the conductor is heated, and a second mode in which the reaching of the microwave to the conductor is suppressed more than in the first mode.

[0021] (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.

[0022] (11) The heating method according to the embodiment includes microwave-heating an object to be heated with microwaves radiated from an antenna, and externally heating the object to be heated with a conductor heated by the microwave heating.

[0023] <2. Examples of Heating Device and Heating Method>

[0024] Hereinafter, with reference to the drawings, the heating device 10 and the heating method according to the embodiment will be described in more detail. FIGS. 1 and 2 show the heating device 10 according to the embodiment. The heating device 10 heats an object to be heated 60. The object to be heated 60 is, for example, a food or a medical or inspection substance. The medical or inspection substance is, for example, a medicine, a reagent, or a specimen. The object to be heated 60 may be a frozen product. The heating device 10 is suitable for use in thawing frozen products. The heating device 10 is suitable for use in thawing and further heating frozen products. The heating device 10 may be used for heating refrigerated or room-temperature products.

[0025] The heating device 10 includes a heating cabinet 20 in which a heating chamber 30 where the heat treatment of the object to be heated 60 is performed 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 (rear side surface). An object to be heated 60 such as food is stored in the heating chamber 30 for heating. Note that the front of the heating chamber 30 is opened and closed by a door portion (not shown).

[0026] The heating device 10 includes an antenna 40. The antenna 40 radiates microwaves M for microwave heating of the object to be heated 60 housed in the heating chamber 30 into the heating chamber 30. Microwave heating heats the object to be heated 60 by vibrating the molecules (especially water molecules) of the object to be heated 60, which is a dielectric, by the microwaves M. Microwave heating is dielectric heating by microwaves. Microwave heating is internal heating. Internal heating generates heat from the inside of the object to be heated 60.

[0027] The antenna 40 may be disposed in the heating chamber 30. Also, a partition member that does not interfere with the microwaves M and, if necessary, heat conduction described later may be provided between the antenna 40 and the heating chamber 30.

[0028] The antenna 40 installed in the heating chamber 30 is preferably covered by a protective body (not shown). The protective body of the antenna 40 is also called a radome. The protective body is preferably made of a material with high microwave transmittance and excellent heat resistance. A material with high microwave transmittance and excellent heat resistance is, for example, a fluororesin.

[0029] As an example, the microwave M is preferably an electromagnetic wave with a frequency (center frequency, the same hereinafter) of 300 MHz to 300 GHz, more preferably an electromagnetic wave with a frequency of 300 MHz to 30 GHz, and even more preferably an electromagnetic wave with a frequency of 500 MHz to 3 GHz.

[0030] When the frequency is 300 MHz, the wavelength λ is about 1 m. When the frequency is 300 GHz, the wavelength λ is about 1 mm. When the frequency is 30 GHz, the wavelength λ is about 10 mm. When the frequency is 500 MHz, the wavelength λ is about 600 mm. When the frequency is 3 GHz, the wavelength λ is about 100 mm.

[0031] The frequency of the microwave M is preferably a frequency included in the ISM (Industrial Scientific and Medical) band, for example, any one selected from the group consisting of 433.92 MHz, 915 MHz, 2.45 GHz, 5.8 GHz, 24.125 GHz, 61.25 GHz, 122.5 GHz, and 245 GHz.

[0032] As an example, the frequency of the microwave M is more preferably 915 MHz or 2.45 GHz. When the frequency is 915 MHz, the wavelength λ is about 328 mm. When the frequency is 2.45 GHz, the wavelength λ is about 122 mm.

[0033] The heating device 10 includes a microwave circuit 90 that generates the microwave M radiated from the antenna 40. The microwave circuit 90 includes, for example, a microwave generator 70 and an amplifier 80 that amplifies the microwave. The microwave amplified by the amplifier 80 is connected to the antenna 40 via a power supply line 50. The power supply line 50 is, for example, a coaxial cable or a twin lead. The connection point between the power supply line 50 and the antenna 40 is referred to as a power supply point 40A.

[0034] 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. The power supply line 50 extending from the microwave circuit 90 arranged in the circuit housing portion 37 is connected to the power supply point 40A of the antenna 40 arranged outside the circuit housing portion 37.

[0035] 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 may be arranged at any one position or a plurality of positions among the vicinity of the bottom surface 31, the vicinity of the top surface 32, the vicinity of the right side surface 33, the vicinity of the left side surface 34, and the vicinity of the back surface (rear side surface) 35. By providing the heating device 10 with a plurality of antennas 40, the object to be heated 60 can be efficiently heated internally.

[0036] The heating device 10 includes a heating source 100 that is separate from the antenna 40. The heating source 100 externally heats the object to be heated 60. The heating by the heating source 100 is external heating. That is, the heating source 100 itself is heated, and its heat R is transmitted to the object to be heated 60. The transmitted heat R heats the object to be heated 60 from its surface. Therefore, the heating device 10 of the embodiment can internally heat and externally heat the object to be heated 60.

[0037] In the embodiment, the heating source 100 is heated by the microwave M radiated from the antenna 40. Therefore, the heating device 10 does not need to include a dedicated electric circuit for heating the heating source 100. The heating source 100 of the embodiment includes a conductor 110 that is heated by the microwave 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 microwave M radiated from the antenna 40 and generates heat.

[0038] The conductor 110 is preferably a magnetic material such as a magnetic metal. A magnetic material is more likely to absorb the microwave M than a non-magnetic material. Examples of the magnetic material include stainless steel (SUS) which is a magnetic material, iron oxide, chromium oxide, cobalt, ferrite, or a non-oxidized metal magnetic material (oxide). The stainless steel (SUS) which is a magnetic material is, for example, ferritic stainless steel or martensitic stainless steel.

[0039] Note that the conductor 110 may be a non-magnetic material, but from the viewpoint of the heating efficiency by microwaves, it is preferably a magnetic material because the reflection of the microwave M becomes large. Conversely, when it is desired to suppress the temperature rise of the conductor 110, a non-magnetic material is preferable. The non-magnetic material can be suitably used for a part where reflection of the microwave M is required, for example, the inner surface (bottom surface 31, top surface 32, right side surface 33, left side surface 34, and back surface 35) of the heating chamber 30 or the shield 120 described later. Examples of the non-magnetic material include copper, aluminum, or stainless steel which is a non-magnetic material. The stainless steel which is a non-magnetic material is, for example, austenitic stainless steel.

[0040] The conductor 110 is attached to the top surface 32 via, for example, a support 115. That is, the conductor 110 is disposed in the vicinity of the top surface 32. However, the position of the conductor 110 is not particularly limited. The conductor 110 may be disposed at any one or a plurality of positions among the vicinity of the bottom surface 31, the vicinity of the top surface 32, the vicinity of the right side surface 33, the vicinity of the left side surface 34, and the vicinity of the back surface (rear side surface) 35. By providing the heating device 10 with a plurality of conductors 110, the object to be heated 60 can be efficiently externally heated.

[0041] In FIG. 1, the conductor 110 is disposed on the side opposite to the object to be heated 60 when viewed from the antenna 40. That is, when the side of the object to be heated 60 is regarded as the front and the opposite side is regarded as the back when viewed from the antenna 40, the conductor 110 is disposed on the back side of the antenna 40. By disposing the conductor 110 on the back side of the antenna 40, an arrangement in which the conductor 110 does not obstruct the microwave M radiated to the object to be heated 60 is obtained, which is preferable.

[0042] In FIG. 1, the power supply line 50 extending from the microwave circuit 90 extends from the back surface 110B side to the front surface 110A side of the conductor 110 through the through hole 111 formed in the conductor 110. The power supply line 50 that has passed through the through hole 111 is connected to the antenna 40 disposed on the front surface 110A side of the conductor 110.

[0043] It is preferable that at least a part of the conductor 110 is disposed in the very vicinity of the antenna 40. The inventor has experimentally found that, surprisingly, the conductor 110 is heated very efficiently when the conductor 110 to be heated is disposed in the very vicinity of the antenna 40. Generally, a conductor such as metal reflects most of the received microwaves even if its material is a magnetic material, and the energy absorbed for heating is not so large. Therefore, when heating the conductor 110 by microwaves, it is desired to increase the heating efficiency.

[0044] The inventor has found that by arranging at least a part of the conductor 110 in the near field N of the antenna 40, the conductor 110 can be efficiently heated by microwaves. In particular, it has been found that the conductor 110, which is a magnetic material, can be heated very efficiently by arranging it in the near field N.

[0045] The near field N is a region near the antenna 40, which is the radiation source of the microwave M, and is a region where the characteristics of the electromagnetic field are different from those of the far field. According to the experiment of the inventor, when the conductor 110 in FIG. 1 is arranged near the antenna 40 as shown in FIG. 1 and when it is arranged near the bottom surface 31, which is a position far from the antenna 40 and in the far field, are compared, the heating efficiency is higher when the conductor 110 is arranged near the antenna 40 as shown in FIG. 1.

[0046] Therefore, in the near field N, it is considered that the microwave M is less likely to be reflected than in the far field, and the microwave M is easily absorbed by the conductor 110 such as metal.

[0047] Also, in the embodiment, the heating of the conductor 110 by the microwave M is considered to include electromagnetic induction heating. Electromagnetic induction heating is heating that utilizes the fact that electromagnetic induction occurs when the magnetic field passing through the conductor changes, an electric current flows through the conductor, and Joule heat is generated. In the near field N, a larger magnetic field can be expected than in the far field. Therefore, in the conductor 110 arranged in the near field N, electromagnetic induction can be efficiently generated.

[0048] From the viewpoint of more effectively causing electromagnetic induction heating, the antenna 40 preferably generates a larger magnetic field in its near field N. In order to generate a larger magnetic field, the antenna 40 preferably has a portion formed in a loop shape. By having a portion formed in a loop shape, the antenna 40 can generate a magnetic field passing through the portion formed in a loop shape in the near field N. Therefore, in the near field N, the magnetic field becomes more dominant and electromagnetic induction is more likely to occur. The antenna 40 having a portion formed in a loop shape is, for example, a loop antenna or a helical antenna.

[0049] Assuming that the wavelength of the microwave M radiated 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, more preferably a region where the distance D is λ / (2π) (≈λ / 6.28) or less, and even more preferably a region where the distance D is λ / 16 or less. The distance D from the antenna 40 may be the distance starting from the power supply point 40A of the antenna 40, or may be the distance starting from an arbitrary position of the antenna 40.

[0050] When the frequency of the 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), more preferably exists in a region where the distance D is 52 mm or less (≈λ / (2π) or less), and even more preferably exists in a region where the distance D is 20 mm or less (≈λ / 16 or less).

[0051] When the frequency of the microwave M is 2.45 GHz, its wavelength λ is approximately 122 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 61 mm or less (≈λ / 2 or less), more preferably exists in a region where the distance D is 19 mm or less (≈λ / (2π) or less), and even more preferably exists in a region where the distance D is 8 mm or less (≈λ / 16 or less).

[0052] Further, the conductor 110 is preferably arranged such that the shortest distance between the conductor 110 and the antenna 40 is λ / (2π) (≈λ / 6.28) or less, and more preferably λ / 16 or less. The shortest distance between the conductor 110 and the antenna 40 is the distance between an arbitrary position on the conductor 110 and an arbitrary position on the antenna 40, and is the shortest distance.

[0053] Further, the conductor 110 is preferably arranged such 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, and more preferably λ / 16 or less. The shortest distance between the conductor 110 and the feeding point 40A of the antenna 40 is the shortest distance from the feeding point A of the antenna 40 to the conductor 110.

[0054] In addition, when microwaves generated by a magnetron arranged outside the heating chamber are transmitted to the heating chamber through a waveguide, like in a general microwave oven, the heating chamber becomes a far-field region. Therefore, even if the conductor 110 is arranged inside the heating chamber or in its vicinity, there may be a risk that efficient heating of the conductor 110 cannot be expected. In particular, when it is desired to make the distance D between the conductor and the antenna λ / 16 or less, particular difficulties arise. In contrast, as in this embodiment, by arranging the antenna 40 itself inside the heating chamber 30 or in the vicinity of the heating chamber 30, and arranging at least a part of the conductor 110 in the near-field region N of the antenna 40, the conductor 110 can be easily and efficiently heated.

[0055] When it is desired to make the distance between the antenna 40 and the conductor 110 sufficiently small in terms of the wavelength λ of the microwave M, for example, when it is desired to make it λ / 16 or less, it is advantageous for the frequency of the microwave M to be higher, as this can increase the physical length of the distance between the antenna 40 and the conductor 110. It is advantageous for the physical length of the distance between the antenna 40 and the conductor 110 to be greater, as this provides a higher degree of freedom in design and arrangement. As an example, a wavelength of 915 MHz for the microwave M is suitable. When 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 made sufficiently small in terms of the wavelength λ of the microwave M, a certain physical length of the distance between the antenna 40 and the conductor 110 can be ensured.

[0056] The heating chamber 30 may be entirely or mostly within the near field N of the antenna 40. Conversely, the heating chamber 30 may include a region that is the far field. In this case, the microwave M radiated from the antenna 40 can heat the conductor 110 in the near field N and heat the object to be heated 60 in the far field.

[0057] When the heating device 10 is used for applications that require heating at a relatively low temperature, the conductor 110 is preferably heated to 100 °C or higher, more preferably 120 °C or higher, even more preferably 130 °C or higher, even more preferably 150 °C or higher, and even more preferably 200 °C or higher at the hottest part.

[0058] When the heating device 10 is used for applications that require heating at a relatively high temperature, the conductor 110 is preferably less than 100 °C, more preferably 40 °C or higher and less than 100 °C, even more preferably 40 °C or higher and less than 80 °C, and even more preferably 40 °C or higher and less than 60 °C at the hottest part.

[0059] 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, at the same electric potential as the ground GND in the microwave circuit 90. The 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 provided in an insulated state with respect to the heating chamber 20, it will be insulated from the ground of the antenna 40. To provide the conductor 110 in an insulated state with respect to the heating chamber 20, for example, the support 115 may be formed of an insulating material.

[0060] FIG. 3 shows a helical antenna 41 which is an example of the antenna 40. The helical antenna 41 is, for example, a normal mode type helical antenna. The normal mode type helical antenna is formed by forming the antenna element of a monopole antenna in a spiral shape. In the helical antenna 41, the portion formed in a spiral shape is a three-dimensional loop shape, and a magnetic field penetrating the spiral portion can be generated.

[0061] The helical antenna 41 is connected to the feeding line 50 at its feeding point 40A. The microwave M radiated from the helical antenna 41 microwave-heats the object to be heated 60 and also heats the conductor 110.

[0062] FIG. 4 shows a loop antenna 42 which is another example of the antenna 40. The loop antenna 42 is formed by forming the antenna element in a loop shape. The loop may be wound once or multiple times. The loop antenna 42 has a portion formed in a loop shape, and a magnetic field penetrating the loop-shaped portion can be generated.

[0063] The loop antenna 42 is connected to the feeding line 50 at its feeding point 40A. The microwave M radiated from the loop antenna 42 microwave-heats the object to be heated 60 and also heats the conductor 110.

[0064] FIG. 5 shows a dipole antenna 43, which is another example of the antenna 40. The dipole antenna 43 has two linear antenna elements, and is connected to a feeding line 50 at its feeding point 40A. The microwave M radiated from the dipole antenna 43 heats the object to be heated 60 and also heats the conductor 110.

[0065] FIGS. 6 to 8 show modified examples of the configuration related to the heating source 100. The heating device 10 according to the modified example includes a regulator 160 that adjusts the heating of the conductor 110 by the microwave M. The regulator 160 is configured to switch between a first mode in which the microwave M radiated from the antenna 40 reaches the conductor 110 and the conductor 110 is heated, and a second mode in which the microwave M reaching the conductor 110 is suppressed more than in the first mode.

[0066] The regulator 160 includes, as an example, a microwave shield 120 and a drive unit 130 that moves the conductor 110. The conductor 110 and the drive unit 130 are connected via a rod 140. The conductor 110 is formed of a material that absorbs the microwave M more easily than the shield 120, for example, a magnetic material, so as to be easily heated. The shield 120 is formed of a material that reflects the microwave M more easily than the conductor 110, for example, a non-magnetic material.

[0067] The shield 120 is positioned between the conductor 110 and the antenna 40 in the second mode to inhibit the microwave M radiated from the antenna 40 from reaching the conductor 110. Therefore, in the second mode, the heating of the conductor 110 is suppressed, and the object to be heated 60 is heated solely by microwave heating. Note that the interval between the teeth of the comb-shaped shield 120 is preferably made sufficiently small so that the microwave M cannot pass through the gap between the teeth. The interval at which the microwave M cannot pass through is appropriately set according to the wavelength of the microwave M.

[0068] On the one hand, in the first mode, the shield 120 does not inhibit or only slightly inhibits the microwave M radiated from the antenna 40 from reaching the conductor 110. Therefore, in the first mode, the conductor 110 is easily heated, and the object 60 to be heated is heated by both internal heating by microwave heating and external heating by the conductor 110.

[0069] As shown in FIG. 6, the shield 120 and the conductor 110 are formed in a comb shape that meshes with each other. The shield 120 is attached to the top surface 32 via the support 115 as an example and is fixedly provided in the heating chamber 20. On the other hand, the conductor 110 is provided so as to be movable relative to the shield 120. More specifically, in the first mode, the conductor 110 is in a position meshed with the shield 120 (the position in FIG. 7), and in the second mode, the conductor 110 moves to an upper position (the position in FIG. 8), and the shield 120 is positioned between the conductor 110 and the antenna 40.

[0070] The power supply line 50 extends to the antenna 40 through through holes formed in the conductor 110 and the shield 120. The through hole through which the power supply line 50 can be inserted is constituted by a notch 110C formed in the conductor 110 and a notch 120C formed in the shield 120.

[0071] As shown in FIG. 6, the shield 120 and the conductor 110 are formed in a rectangular shape as a whole in a meshed state with each other. In the first mode, the shield 120 and the conductor 110 are in a meshed state, that is, the shield 120 and the conductor 110 are in the same position in the vertical direction. In this case, the conductor 110 can receive the irradiation of the microwave M radiated from the antenna 40 without being inhibited 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. Further, 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.

[0072] In the second mode, the conductor 110 moves upward by the driving unit 130. The microwave M radiated from the antenna 40 is reflected by the shield 120 and hardly reaches the conductor 110 or does not reach it at all. Therefore, heating of the conductor 110 is suppressed.

[0073] Note that the conductor 110 may be provided with a fixed position, and the shield 120 may be provided to move by the driving unit 130. Also, both the conductor 110 and the shield 120 may move so that the relative position changes.

[0074] The driving unit 130 has, for example, a motor or a solenoid, and includes a mechanism necessary for movement. As shown in FIG. 7, the operation of the driving unit 130 is controlled by the controller 150. The controller 150 is constituted by, for example, a microcontroller. The controller 150 switches between the first mode and the second mode according to an external input or by internal control. When in the first mode, the controller 150 controls the driving unit 130 so that the conductor 110 is positioned at the same height as the shield 120, and when in the second mode, the controller 150 controls the driving unit 130 so that the conductor 110 is positioned above the shield 120.

[0075] FIG. 9 shows another modification of the heating device 10. 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 microwave M. That is, the surface forming the heating chamber 30 (for example, the top surface 32) itself constitutes a heating source for externally heating the object to be heated 60. In the case of the heating device 10 shown in FIG. 9, the conductor 110 shown in FIG. 1 can be omitted, and the structure can be made simpler, which is advantageous.

[0076] The surface heated by the microwave M may be a surface other than the top surface 32, for example, 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 microwave M. At least a part of the surface heated by the microwave M is located within the vicinity N of the antenna 40. One or a plurality of antennas 40 are arranged in the vicinity of the surface to be heated by the microwave M.

[0077] When a surface such as the top surface 32 located within the vicinity N is heated by the microwave M, the heat R is radiated to the object to be heated 60, and the object to be heated 60 is externally heated. Therefore, the object to be heated 60 is heated by both internal heating by microwave heating and external heating. Even when only the top surface 32 is heated by the microwave M, the other surfaces 31, 33, 34, 35 can also be heated by heat conduction. Therefore, the other surfaces 31, 33, 34, 35 can also radiate the heat R for externally heating the object to be heated 60.

[0078] Note that, among the surfaces 31, 32, 33, 34, 35 forming the heating chamber 30, the portion outside the vicinity N is expected to be more likely to reflect the microwave M than within the vicinity N.

[0079] The member constituting the surface (for example, the top surface 32) forming the heating chamber 30 is preferably a magnetic material so as to be efficiently heated by the microwave M. The member constituting the surface (for example, the top surface 32) forming the heating chamber 30 may be constituted by a combination of a magnetic material and a non-magnetic material. In this case, a part or all of the surface (for example, the top surface 32) located within the vicinity N may be formed of a magnetic material, and the other surfaces 31, 33, 34, 35 may be formed of a non-magnetic material. In this case, the surface formed of the non-magnetic material can efficiently reflect the microwave M and is suitable from the viewpoint of irradiating the object to be heated 60 with the microwave M.

[0080] The member constituting the surface forming the heating chamber 30 (for example, the top surface 32) is preferably insulated from the ground of the antenna 40 for improving 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 cabinet 20 for grounding. By insulating the member constituting the surface forming the heating chamber 30 from other members, the member constituting the surface forming the heating chamber 30 can be insulated from the ground of the antenna 40.

[0081] FIG. 10 shows the results of the first experiment in which the conductor 110 was heated by the heating device 10 shown in FIG. 1. In the first experiment, the antenna 40 was a helical antenna 41. The frequency of the microwave M was 915 MHz (wavelength λ: approximately 328 mm), and the power of the microwave M was adjusted to be approximately 300 W in the effective value. The helical antenna 41 was configured by forming a helically shaped antenna element with a length of 248 mm, which is close to the element length of 5 / 8λ where the gain of the linear antenna is maximized (since it is not antenna radiation in free space, the target microwave radiation cannot be achieved with the element length according to antenna theory, so it was optimized by adjustment. The same applies to the following antenna structures). The conductor 110 was arranged such that the shortest distance from the helical antenna 41 was less than 1 cm. Therefore, at least a part of the conductor 110 is within the near field N of the helical antenna 41.

[0082] In the first experiment, the heating temperature of the conductor 110 was measured when the material of the conductor 110 was magnetic stainless steel and when it was non-magnetic stainless steel, respectively. The temperature was measured by stopping the output of the microwave M every 5 minutes after the start of heating and measuring the surface temperature of the conductor 110. Note that the first experiment was conducted without the object to be heated 60. The measured temperature is the temperature at the position where the temperature of the conductor 110 is the highest.

[0083] As shown in FIG. 10, when the conductor 110 is a non-magnetic material, the temperature of the conductor 110 rises to 50° C. in 5 minutes and then rises to about 60° C. When the conductor is a magnetic material, the temperature of the conductor 110 rises to 180° C. in 5 minutes. Then, although the temperature decreased, it was possible to heat up to 140° C.

[0084] 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 that require heating at a relatively low temperature, for example, less than 100° C. Applications that require heating at a relatively low temperature are, for example, low-temperature cooking or thawing. Thawing may be, for example, thawing of frozen foods or thawing of frozen medical or test substances.

[0085] Also, in the case of the magnetic conductor 110, it is heated more efficiently than the non-magnetic conductor 110. Therefore, the magnetic conductor 110 is suitable for applications that require heating at a relatively high temperature, for example, 100° C. or higher. Applications that require heating at a relatively high temperature are, for example, cooking or other food processing that requires charring on the surface.

[0086] When heating the conductor 110 with the microwave M in the presence of the object to be heated 60, since the energy of the microwave M is absorbed by the object to be heated 60, the temperature rise of the conductor 110 can be suppressed compared to the results of the first experiment.

[0087] Figure 11 shows the results of the second experiment conducted by changing the type of the antenna 40 in the heating device 10 shown in FIG. 1. 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 915 MHz (wavelength λ: approximately 328 mm), and the power of the microwave M was adjusted to be approximately 300 W in terms of the effective value. The conductor 110 was arranged such that the shortest distance from the antenna 40 was less than 1 cm. Therefore, at least a part of the conductor 110 is within the near field N of the helical antenna 41. The conductor 110 was made of magnetic stainless steel.

[0088] The loop antenna 42 was configured to have a loop length shorter than 1λ. The dipole antenna 43 was configured such that the element length was half of 248 mm.

[0089] In the second experiment, the material of the conductor 110 was magnetic stainless steel, and the heating temperature of the conductor 110 was measured. The temperature was measured by stopping the output of the microwave M every 5 minutes after the start of heating and measuring the surface temperature of the conductor 110. Note that the second experiment was conducted without the object to be heated 60. The measured temperature is the temperature at the position where the temperature of the conductor 110 is the highest.

[0090] FIG. 11 shows the temperature changes when the antenna 40 is the loop antenna 42 and when the antenna 40 is the dipole antenna 43, respectively. In FIG. 11, the temperature change of the conductor 110 when the material of the conductor 110 is magnetic stainless steel in the first experiment where the antenna 40 is the helical antenna 41 is also shown.

[0091] 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 temperatures decreased in the order of the helical antenna 41 and the dipole antenna 43. In the case of the helical antenna 41, the temperature of the conductor 110 rose to 175° C. in 5 minutes and then rose to 230° C. In the case of the dipole antenna 43, it rose to 105° C. in 5 minutes and then rose to 125° C.

[0092] Since the loop antenna 42 and the helical antenna 41 are antennas having a loop-shaped portion, they can more prominently generate a magnetic field in the near field N than the dipole antenna 43. As a result, it is considered that electromagnetic induction heating effectively occurs in the loop antenna 42 and the helical antenna 41, and the maximum temperature becomes high. Therefore, the loop antenna 42 and the helical antenna 41 are suitable for applications that require heating at a relatively high temperature. Moreover, the maximum temperature of the loop antenna 42 exceeds 200° C., which is suitable.

[0093] On the other hand, the dipole antenna 43 can maintain the conductor 110 at a relatively low temperature and is suitable for applications that require heating at a relatively low temperature.

[0094] As a third experiment, the object to be heated 60 was frozen beef, and heating was performed. The experimental conditions of the third experiment were the same as those of the first experiment. However, the conductor 110 was made of a magnetic material. The weight of the frozen beef was 150 g. The frozen beef frozen in a food freezer was taken out of the food freezer and immediately cooked by heating in the heating device 10 for 30 minutes without leaving it for a while. By this cooking, the frozen beef was thawed and heated to the inside, and a grilled mark was formed on the surface. That is, roast beef could be made from the frozen beef.

[0095] When heating frozen foods using only microwave heating, the heating may not be sufficient or uneven heating may occur. This is because in frozen foods, since water is in a solid state, microwave heating due to the vibration of water molecules may not be sufficient, or when partially thawed, local heating may progress in that part. On the other hand, in the heating device 10 of this embodiment, even if the object to be heated 60 is a frozen food, the object to be heated 60 can be thawed by external heating by the conductor 110. That is, in 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 to be heated 60 for microwave heating of the object to be heated 60. As a result, in the initial stage of heating, the conductor 110 is heated more efficiently, and the surface of the object to be heated 60 can be externally heated as a whole.

[0096] When the surface of the object to be heated 60 is thawed by external heating, microwave heating becomes effective, and the object to be heated 60 can be heated to the inside together with external heating. Also, because of the overall heating of the object to be heated 60 by external heating, concentration of microwave heating is less likely to occur, and uneven heating is also less likely to occur. As a result, frozen foods can be cooked well.

[0097] As described above, when the object to be heated 60 is food, the heating device 10 of the embodiment can be used as a food processing machine for cooking or processing frozen foods. The heating device 10 can, for example, thaw frozen foods and heat them to a cooking temperature to give them a grilled appearance. Thereby, it is possible to perform the process from thawing to cooking in one go.

[0098] The present invention is not limited to the above embodiment, and various modifications are possible.

Explanation of Reference Numerals

[0099] 10: Heating device 20: Heating chamber 30: Heating room 31: Bottom surface 32: Ceiling surface 33: Right side surface 34: Left side surface 35: Back side 37: Circuit housing part 40: Antenna 40A: Power supply 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 side 110B: Back side 110C: Notch 111: Through hole 115: Support 120: Microwave shield 120C: Notch 130: Driving part 140: Rod 150: Controller 160: Regulator A: Power supply point D: Distance GND: Ground M: Microwave N: Near field R: Heat

Claims

1. A heating cabinet that forms inside thereof a heating chamber having an inner surface of the heating chamber for accommodating an object to be heated and reflecting microwaves; An antenna that radiates microwaves for microwave heating of the object to be heated; A heat source for externally heating the object to be heated; Comprising: The heat source includes a conductor that is heated by the microwaves radiated by the antenna; The conductor: Is a conductive magnetic body that absorbs the microwaves and is disposed between the inner surface of the heating chamber that reflects the microwaves and the antenna in the heating chamber so as to be located on the side opposite to the object to be heated as viewed from the antenna; Has a portion that is attached with a space therebetween from the inner surface of the heating chamber via a support of an insulating material and is disposed in the vicinity of the antenna with respect to the inner surface of the heating chamber. Heating device.

2. The antenna is a helical antenna, a loop antenna, or a dipole antenna. The heating device according to Claim 1.

3. The frequency of the microwaves is in the range of 500 MHz to 3 GHz. The heating device according to Claim 1 or Claim 2.

4. The heating device further includes an adjuster for adjusting the heating of the conductor by the microwaves radiated from the antenna; The adjuster is configured to switch between a first mode in which the microwaves radiated from the antenna reach the conductor and the conductor is heated, and a second mode in which the reaching of the microwaves to the conductor is suppressed more than in the first mode. The heating device according to any one of Claims 1 to 3.

5. The adjuster includes a microwave shield disposed between the antenna and the conductor in the second mode to suppress the reaching of the microwaves to the conductor. The heating device according to Claim 4.

6. In a heating chamber having an inner surface of the heating chamber for accommodating an object to be heated and reflecting microwaves, the object to be heated is microwave-heated by microwaves radiated from an antenna, and the object to be heated is externally heated by a conductor heated by microwave heating. Comprising: The conductor: Is a conductive magnetic body that absorbs the microwaves and is disposed between the inner surface of the heating chamber that reflects the microwaves and the antenna in the heating chamber so as to be located on the side opposite to the object to be heated as viewed from the antenna; A heating method, comprising a portion which is arranged in the near field of the antenna and is attached with a space therebetween to the inner surface of the heating chamber via a support of an insulating material with respect to the inner surface of the heating chamber. Heating method.

Images