Microwave irradiation device and microwave irradiation method

Abstract

To achieve good heating by microwave irradiation.SOLUTION: A microwave irradiation device 1 includes a conveying belt 62 that functions as a holding device configured to hold an object to be irradiated 100 having an opening, a closing belt 72 that is arranged opposing the holding device and functions as an opening-closing device for covering the opening, and a directional antenna 40 configured to emit microwaves along a directional irradiation axis 57 from an irradiation source 56 within an irradiation surface 55 by power supply from an oscillator 10 via conduction through a coaxial cable 12 functioning as a power supply device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a microwave irradiation device and a microwave irradiation method.

Background Art

[0002] Generally, in the production of foods in containers and the like, heat treatment may be performed for cooking or sterilization. There are various heating methods, and as an example, a method of dielectric heating an object to be heated by irradiating the object to be heated with microwaves is known. For example, Patent Document 1 discloses that sterilization of vacuum-packed packaged foods is performed by microwave irradiation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to realize good heating by microwave irradiation.

Means for Solving the Problems

[0005] According to one aspect of the present invention, a microwave irradiation device includes a holder configured to hold an object to be irradiated having an opening, an opening closing member disposed to face the holder and covering the opening, and a directional antenna configured to irradiate microwaves along a directional irradiation axis from an irradiation source in an irradiation plane by power supply from an oscillator through electrical conduction of a power supply device.

Effects of the Invention

[0006] According to the present invention, good heating by microwave irradiation can be realized.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

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Figure 7

[0008] [Embodiment] An embodiment will be described with reference to the drawings. This embodiment relates to a microwave irradiation device and a microwave irradiation method using the same. The microwave irradiation device of this embodiment is configured to irradiate an object to be irradiated with microwaves to internally heat the object to be irradiated. That is, the microwave irradiation device of this embodiment functions as a heating device.

[0009] Generally, for example, a method is widely used in which microwaves radiated from a microwave oscillator such as a magnetron are guided into an applicator such as a metal housing using a waveguide, and the object to be irradiated disposed in the applicator is irradiated with microwaves to heat the object to be irradiated. However, in such a method, standing waves are generated due to reflection of microwaves in the applicator, the electric field in the applicator becomes non-uniform, and as a result, the heating of the object to be irradiated tends to be non-uniform. In contrast, in the microwave irradiation device of the present embodiment, a directional antenna is used. In the microwave irradiation device of the present embodiment, by irradiating microwaves from the directional antenna toward the object to be irradiated, generation of standing waves can be suppressed to form a uniform electric field, and the object to be irradiated can be heated uniformly.

[0010] The object to be irradiated is not limited to this, but is, for example, food contained in a container. Therefore, this microwave irradiation device and the microwave irradiation method using the same can be used, for example, in the production of foods including packaged foods.

[0011] In the present embodiment, the container containing food is not covered with a lid. For this reason, for example, the upper part of the container is open. The microwave irradiation device of the present embodiment is configured such that during the irradiation of microwaves, the conveyor belt as an opening / closing device covers this opening.

[0012] <Configuration of the Microwave Irradiation Device> FIG. 1 is a diagram schematically showing an outline of a basic configuration example of a microwave irradiation device 1 according to the present embodiment. The microwave irradiation device 1 functioning as a heating device is configured to successively heat an object 100 to be irradiated, which is conveyed by a conveying device 60. The conveying device 60 is, for example, a belt conveyor. The conveying device 60 has a conveying belt 62 that moves in its longitudinal direction. The conveying belt 62 is made of, for example, a synthetic resin and has microwave permeability. The object 100 to be irradiated is placed at a holding position on the conveying belt 62 and is conveyed in the longitudinal direction of the conveying belt 62. Thus, in the present embodiment, the conveying device 60 having the conveying belt 62 functions as a holder configured to hold the object 100 having an opening at the bottom of the object 100 on the side opposite to the opening.

[0013] The microwave irradiation device 1 includes an antenna 40 configured to irradiate the object 100 to be irradiated, which is conveyed by the conveying device 60, with microwaves. The antenna 40 is a directional antenna. In the example shown in FIG. 1, the microwave irradiation device 1 has, as the antenna 40, two loop antennas, that is, a first loop antenna 41 and a second loop antenna 42. The number of loop antennas can be appropriately changed. The oscillator 10 outputs high-frequency power corresponding to the frequency of microwaves. The frequency is not limited to this, but is, for example, 200 MHz to 500 MHz, 915 MHz, or 2.45 GHz. Microwave power is supplied from the oscillator 10 to the first loop antenna 41 and the second loop antenna 42 via a coaxial cable 12. For example, by supplying power to the first loop antenna 41 and the second loop antenna 42 in parallel and in phase via a coaxial cable 12 branched from one oscillator 10, the output from one antenna is not misrecognized as the reflection of microwaves output from the other antenna by the other antenna, and simultaneous irradiation is possible.

[0014] The antenna 40 will be described. The first loop antenna 41 includes, for example, a conductor 52 that has a length corresponding to one wavelength of the microwave to be irradiated and is formed in an annular shape. Both ends of the conductor 52 serve as feeding points 53. For example, a coaxial cable 12 as a feeding device is connected to the feeding point 53. The coaxial cable 12 connects and electrically conducts the oscillator 10 and the first loop antenna 41. The oscillator 10 supplies microwave power to the first loop antenna 41 via the coaxial cable 12. When powered, an electric current is generated in the conductor 52 as an element, and the first loop antenna 41 radiates radio waves to form an electric field.

[0015] In the annular first loop antenna 41, the opening surface 54 formed by the conductor 52 becomes the irradiation surface 55 of the microwave, and the center of the opening surface 54 becomes the irradiation source 56 of the microwave. A directivity irradiation axis 57 is formed in a direction perpendicular to the opening surface 54 passing through the irradiation source 56, and microwaves are radiated in both directions along the directivity irradiation axis 57. The second loop antenna 42 also has the same configuration as the first loop antenna 41.

[0016] Note that the shape formed by the conductor 52 is not limited to an annulus, and other annular shapes such as a quadrilateral, a triangle, or an asymmetric shape may be used. The position of the irradiation source and the direction of the directivity irradiation axis of the loop antenna can vary depending on the shape and the position of the feeding point. However, in any case, for a loop antenna, the concept that the irradiation source as the source from which radio waves are radiated when powered is formed on the opening surface can be obtained. Also, the concept that the directivity irradiation axis indicating the direction in which radio waves are mainly radiated from the irradiation source when powered is formed can be obtained.

[0017] The microwave irradiation device 1 is configured such that the object 100 to be irradiated is conveyed through the opening surface 54 which is the irradiation surface 55 of the first loop antenna 41 and the second loop antenna 42. For this reason, the conveyor belt 62 of the conveying device 60 is provided so as to penetrate the opening surface 54 of the first loop antenna 41 and the second loop antenna 42. The irradiation surfaces 55 of the first loop antenna 41 and the second loop antenna 42 are arranged perpendicular to the longitudinal direction of the conveyor belt 62. That is, the directivity irradiation axes 57 of the first loop antenna 41 and the second loop antenna 42 are arranged parallel to the longitudinal direction of the conveyor belt 62. Also, the first loop antenna 41 and the second loop antenna 42 are arranged such that their directivity irradiation axes 57 coincide.

[0018] In the microwave irradiation device 1 of the present embodiment, the object 100 to be irradiated is heated by irradiating the microwave radiated from the antenna 40 to the object 100 to be irradiated. The object 100 to be irradiated has, for example, a structure in which an object to be heated such as food is placed in a container. For cooling required after heating, the object 100 to be irradiated is carried into the microwave irradiation device 1 with the lid of the container not closed. That is, for example, the upper side of the container is open. On the other hand, for the sake of heating uniformity and efficiency, the opening of the container is preferably covered and closed during heating. For this reason, the microwave irradiation device 1 of the present embodiment includes an opening closing device 70.

[0019] The opening / closing device 70 includes a closing belt 72 that functions as an opening / closing tool for closing the opening of the object to be irradiated 100. The closing belt 72 is made of, for example, synthetic resin and has microwave permeability. The closing belt 72 is provided to face the conveyor belt 62 of the conveying device 60 from the upstream side to the downstream side of the antenna 40. The conveyor belt 62 and the closing belt 72 are configured to sandwich the object to be irradiated 100 from above and below. By the closing belt 72 advancing in synchronization with the advancement of the conveyor belt 62, with the closing belt 72 closing the upper opening of the object to be irradiated 100, the object to be irradiated 100 passes through the opening surface 54, which is the irradiation surface 55 of the first loop antenna 41 and the second loop antenna 42. That is, with the closing belt 72 closing the upper opening of the object to be irradiated 100, the object to be irradiated 100 is heated. As means for bringing the closing belt 72 into close contact with the upper opening of the object to be irradiated 100, the deflection of the closing belt 72 due to its own weight may be utilized, or means for pressing the closing belt 72 from above may be provided.

[0020] In the microwave irradiation device 1 of the present embodiment, the conveyor belt 62 and the closing belt 72 move along the directivity irradiation axis of the microwave radiated from the antenna 40 to convey the object to be irradiated 100 along the directivity irradiation axis. As a result, the object to be irradiated 100 passes through the uniform electric field formed by the microwave radiated from the antenna 40. As a result, the object to be irradiated 100 is uniformly heated.

[0021] The closing belt 72 is provided to circulate in a loop. Since the closing belt 72 may be soiled, for example, by the object to be heated of the object to be irradiated 100, the opening / closing device 70 includes a cleaning device 73 for cleaning the closing belt 72 and the like. The cleaning device 73 cleans and sterilizes the closing belt 72. By the cleaning device 73, the closing belt 72 is always kept clean.

[0022] The microwave irradiation device 1 includes a metal housing 80 for shielding microwaves. That is, the antenna 40 is covered by the metal housing 80. The conveyor belt 62 of the conveyor device 60 and the closing belt 72 of the opening / closing device 70 pass through the metal housing 80. More specifically, the metal housing 80 includes a main housing 81. The antenna 40 is disposed within the main housing 81. Through holes through which the conveyor belt 62 and the closing belt 72 pass are provided on both side surfaces of the main housing 81. Side housings 82 sized to allow the conveyor belt 62, the irradiated object 100 placed thereon, and the closing belt 72 to pass are connected to each of these through holes.

[0023] In order to form microwaves by the antenna 40, which is a loop antenna, within the metal housing 80, the width of the main housing 81 of the metal housing 80 in the electric field amplitude direction of the microwaves is configured to satisfy the following conditions. Here, the electric field amplitude direction of the microwaves radiated from the annular loop antenna is the direction on the plane perpendicular to the straight line passing through the power feeding point 53 and the irradiation source 56 among the directions passing through the directivity irradiation axis 57 and perpendicular to it. That is, in the example shown in FIG. 1, the electric field amplitude direction of the microwaves is the horizontal direction perpendicular to the longitudinal direction of the conveyor belt 62.

[0024] First, the wavelength of the microwaves radiated from the loop antenna when microwave power of a predetermined frequency is fed to the loop antenna is defined as the feeding wavelength λ. The feeding wavelength λ is the free space wavelength. As described above, the length of the annular conductor 52 constituting the loop antenna is an integer multiple or more of the feeding wavelength λ, and using the integer value at that time, it is defined as, for example, a one-wavelength loop antenna, a two-wavelength loop antenna, and the like.

[0025] Since the loop antenna is disposed within the main housing 81, the effective space within the main housing 81 is reduced by the width of the loop antenna. The apparent width L' of the housing in the direction of the microwave electric field amplitude of the main housing 81 is such that when the width of the main housing 81 in this direction is L and the width of the loop antenna in this direction is t, L' = L - 2t. Based on this apparent housing width L', the cutoff wavelength λc of the main housing 81 is defined as λc = 2L' = 2(L - 2t). Further, when the length of the conductor 52 of the loop antenna described above is n times the feeding wavelength λ (n is an integer, and n is the integer closest to the value obtained by dividing the length of the conductor 52 of the loop antenna by the feeding wavelength λ), the cutoff wavelength λc' in terms of one wavelength of the antenna is defined as λc' = λc / n.

[0026] The width L of the main housing 81 is set such that the cutoff wavelength λc' in terms of one wavelength of the antenna and the feeding wavelength λ satisfy λc' > λ That is, L' = L - 2t > nλ / 2 The width L of the main housing 81 is set to satisfy this condition. In principle, it must satisfy this condition to form microwaves with the loop antenna within the main housing 81, which has also been confirmed by numerical simulation. If this condition is not satisfied, the reproducibility of the electric field formation decreases.

[0027] Also, the apparent width L' of the main housing 81 must be greater than nλ / 2. However, if it further increases by nλ / 2 each time, multiple peak waveforms are formed inside the main housing 81, and multiple reflections of microwaves can occur within the main housing 81. When multiple reflections occur, multiple resonance frequencies are generated, making it difficult to detect the resonance frequencies for impedance matching. Therefore, L' = L - 2t < nλ / 2 + nλ / 2 = nλ The width L of the main housing 81 is designed to satisfy this condition.

[0028] As described above, the width L of the main housing 81 in the direction of the microwave electric field amplitude is designed such that the apparent housing width L' = L - 2t satisfies nλ / 2 < L' < nλ That is, it is designed to satisfy this condition.

[0029] On the downstream side in the conveying direction by the conveying device 60 outside the metal housing 80, the closing belt 72 separates from the conveying belt 62. That is, for the irradiated object 100 conveyed by the conveying device 60, downstream of the metal housing 80, the opening is reopened when the closing belt 72 separates from the opening.

[0030] A cooling device 90 is provided further downstream of the conveying device 60. The cooling device 90 is configured to cool the heated object of the irradiated object 100, such as by blowing cold air onto the opening of the irradiated object 100. By the cooling device 90, the irradiated object 100 after heating can be quickly cooled, and deterioration of the heated object such as food can be suppressed.

[0031] <Outline of the operation of the microwave irradiation device> The operation of the microwave irradiation device 1 of this embodiment will be described. The microwave power output from the oscillator 10 is supplied to the first loop antenna 41 and the second loop antenna 42 via the coaxial cable 12. The first loop antenna 41 and the second loop antenna 42 radiate microwaves based on this power supply.

[0032] The irradiated object 100 is supplied to the upstream side of the conveying device 60 of the microwave irradiation device 1. The irradiated object 100 is carried into the metal housing 80 by the conveying device 60. Before being carried into the metal housing 80, the opening of the irradiated object 100 is closed by the closing belt 72 of the opening / closing device 70. The irradiated object 100 is successively conveyed to the heating position irradiated with the microwaves radiated from the first loop antenna 41 and the second loop antenna 42 while being sandwiched from above and below by the conveying belt 62 and the closing belt 72. By this irradiation with microwaves, the irradiated object 100 is successively dielectrically heated. The conveying belt 62 and the closing belt 72 may be intermittently moved so that the irradiated object 100 stops at the heating position, or the conveying belt 62 and the closing belt 72 may be continuously moved so that the irradiated object 100 passes through the heating position over a sufficient period of time.

[0033] The microwave radiated from the antenna 40 within the metal housing 80 irradiates the object to be irradiated 100 sufficiently, so that the object to be irradiated 100 is heated sufficiently. The object to be irradiated 100 after heating is carried out of the metal housing 80 by the conveyor belt 62 and the closing belt 72. Subsequently, the closing belt 72 separates from the object to be irradiated 100. As a result, the opening of the object to be irradiated 100 is opened. The object to be irradiated 100 continues to be conveyed by the conveyor belt 62 with the opening being open. The object to be irradiated 100 conveyed by the conveyor belt 62 reaches the cooling device 90, and the object to be irradiated 100 is cooled by the cooling device 90. Thereafter, the object to be irradiated 100 is carried out of the microwave irradiation device 1.

[0034] 〈Regarding the microwave irradiation device〉 The microwave irradiation device 1 according to the present embodiment can be used, for example, in a food manufacturing factory when heating for cooking, sterilization, etc. after putting food in a container. According to the microwave irradiation device 1 according to the present embodiment, since the steam generated during heating circulates within the container covered by the closing belt 72, the temperature of the food within the container becomes uniform and the heating efficiency is also good.

[0035] Instead of the closing belt 72, for example, it is also conceivable to seal the container with a lid material. However, for example, when sealing with a lid material, isobaric control is difficult when rapidly raising the temperature, and there is a risk that the container may be damaged by the internal pressure during heating. Also, when putting a lid on the container, the efficiency of cooling the food required after heating decreases. Further, it is also conceivable to arrange a temporary lid material on each container. However, in this case, for example, positioning of the container and the temporary lid is required, and the device becomes complicated. Also, when the container shape changes, a mold change is required.

[0036] In contrast, in the microwave irradiation device 1 according to the present embodiment, a temporary lid is formed by the closing belt 72. By adjusting the height of the closing belt 72, the upper surface that is open can appropriately close the opening of any container as long as the upper surface is flat. Further, since it does not seal, when the pressure rises, a gap is formed and the pressure is released. After heating, the opening of the container is opened again, so that cooling can be efficiently performed.

[0037] [Experimental Example] The effect on uniform heating by closing the opening using the closing belt 72 of the above-described embodiment was evaluated by experiments.

[0038] The object to be irradiated 100 was a synthetic resin tray-shaped container with an open upper surface filled with a combination of boiled foods at room temperature or bracken tempura. As shown in the device configuration of FIG. 1, experiments were conducted when the opening on the upper surface of the container was closed with a closing belt 72, which is a conveyor belt, to form a temporary lid, and when the opening on the upper surface of the container was left open without providing the opening closing device 70. The first loop antenna 41 and the second loop antenna 42 provided in the metal housing 80 were fed in parallel and in phase from the oscillator 10 via the coaxial cable 12. The frequency of the output power of the oscillator 10 was 450 MHz, the output power was 300 W, and the heating time was 4 minutes. The temperature immediately after heating was evaluated by thermography.

[0039] The experimental results are shown in FIG. 2. When heating was performed without providing the opening closing device 70 and without covering the opening of the container, i.e., in a state without a lid, unevenness in the surface temperature and insufficient heating occurred in any of the samples. It is presumed that these temperature non-uniformities occur because the way the electric field enters varies depending on the shape of the food ingredients, there are differences in the electrical properties depending on the food ingredients, and there are differences in the heat dissipation state depending on the uneven shape of the food ingredients.

[0040] On the other hand, when heating in a state where the opening of the container is covered with the closing belt 72 to form a temporary lid, the temperature uniformity improved in any of the samples. This is presumably because the steam generated by heating circulates inside the covered container, resulting in a uniform temperature inside the container.

[0041] [Modification Examples Regarding the Conveyor Device and the Opening / Closing Device] A modification example regarding the conveyor device 60 and the opening / closing device 70 of the above-described embodiment will be described. Here, the differences from the above-described embodiment will be explained, and the same parts will be denoted by the same reference numerals and their description will be omitted.

[0042] FIG. 3 is a schematic diagram showing an outline of a configuration example of a microwave irradiation device 1a according to a first modification example, and is a schematic diagram of the microwave irradiation device 1a viewed from the side. In the above-described embodiment, the opening / closing device 70 had a closing belt 72 which is a conveyor belt for closing the opening of the object to be irradiated 100. In contrast, the opening / closing device 70a according to the first modification example has a stationary plate-like member. The opening / closing device 70a is, for example, a plate made of synthetic resin, and the lower surface facing the conveyor belt 62 is configured to be slippery.

[0043] The object to be irradiated 100 conveyed by the conveyor belt 62 of the conveyor device 60 passes between the conveyor belt 62 and the opening / closing device 70a such that the upper surface having the opening thereof slides on the lower surface of the opening / closing device 70a. The microwave irradiation device 1a according to the first modification example also provides the same effects as the microwave irradiation device 1 according to the above-described embodiment.

[0044] FIG. 4 is a schematic diagram showing an outline of a configuration example of a microwave irradiation device 1b according to a second modification example, and is a schematic diagram of the microwave irradiation device 1b viewed from the side. In the above-described embodiment, the object to be irradiated 100 was placed on the conveyor device 60 and conveyed by the conveyor device 60. In contrast, in the microwave irradiation device 1b according to the second modification example, the object to be irradiated 100 is conveyed inside the metal housing 80 by the closing belt 72 of the opening / closing device 70.

[0045] The conveying device 60b includes a plate-shaped member 64b on which the object to be irradiated 100 is placed, instead of the conveying belt 62, at a portion facing the closing belt 72. The plate-shaped member 64b is, for example, a plate made of synthetic resin, and the upper surface facing the closing belt 72 is configured to be slippery. Further, the conveying device 60b includes a loading belt 63b that conveys the object to be irradiated 100 to the plate-shaped member 64b and an unloading belt 65b that unloads the object to be irradiated 100 from the plate-shaped member 64b.

[0046] The object to be irradiated 100 is carried by the loading belt 63b to the plate-shaped member 64b and placed thereon. Thereafter, the object to be irradiated 100 is conveyed while sliding on the plate-shaped member 64b by the closing belt 72 that contacts the upper surface of the object to be irradiated 100. The object to be irradiated 100 is heated while being conveyed by the opening / closing device 70, and after heating, it is passed to the unloading belt 65b and unloaded by the unloading belt 65b. The microwave irradiation device 1b according to the second modification also provides the same effects as the microwave irradiation device 1 according to the above-described embodiment.

[0047] Thus, in the microwave irradiation device, the object to be irradiated 100 may be conveyed by moving at least one of the lower holder and the upper opening / closing tool.

[0048] [Modification Example Regarding Antenna] A modification example regarding the antenna 40 of the above-described embodiment will be described. Here, the differences from the above-described embodiment will be described, and the same parts will be denoted by the same reference numerals and their description will be omitted.

[0049] FIG. 5 is a schematic diagram showing a configuration example of the microwave irradiation device 1c according to the third modification, and is a schematic diagram of the microwave irradiation device 1c viewed from above. In the above-described embodiment, a loop antenna was used for the antenna 40, and the conveyor belt 62 and the closing belt 72 passed through the opening surface of the loop antenna. On the other hand, in the microwave irradiation device 1c according to the third modification, a plurality of antennas 40c are arranged beside the conveyor belt 62 and the closing belt 72 with the microwave irradiation direction directed toward the conveyor belt 62 and the closing belt 72. The antenna 40c may be a loop antenna or may be another type of antenna such as, for example, a microstrip antenna. For example, a microstrip antenna is also a directional antenna that radiates microwaves from an irradiation source in its irradiation plane along a directional irradiation axis.

[0050] The object to be irradiated 100 is irradiated with microwaves while being conveyed in the conveying direction by the conveyor belt 62 and the closing belt 72. In the third modification, the directional irradiation axis along which the antenna 40c radiates microwaves and the conveying direction intersect, rather than being parallel. The microwave irradiation device 1c according to the third modification can obtain the same effects as the microwave irradiation device 1 according to the above-described embodiment.

[0051] [Modification Example Regarding the Object to be Irradiated] A fourth modification example regarding the object to be irradiated 100 will be described. Here, the differences from the above-described embodiment will be described, and the same parts will be denoted by the same reference numerals and their description will be omitted. In the above-described embodiment, the object to be irradiated 100 heated by the microwave irradiation device 1 has an opening at its upper part, and the opening is open. On the other hand, in the fourth modification, a lid material partially sealed to the opening of the object to be irradiated is provided.

[0052] FIG. 6 is a diagram showing an outline of a configuration example of an object 110 to be irradiated according to the fourth modification. The container 111 of the object 110 to be irradiated is, for example, a tray-shaped synthetic resin container with an open top surface. An object 118 to be heated, such as food, is placed inside the container 111. A lid member 112 made of, for example, a synthetic resin film is provided at the opening of the container 111. The lid member 112 is a film that is sealed to the upper surface portion of the container 111 to seal the upper opening surface in the completed food in the container. In a state before being heated by the microwave irradiation device 1, the lid member 112 is adhered to the container 111 at a sealing portion 115 corresponding to, for example, half of the upper surface of the container 111, and is not adhered to the container 111 at an unsealed portion 116 corresponding to, for example, the remaining half of the upper surface of the container 111.

[0053] FIG. 7 is a schematic diagram showing an outline of a configuration example of the microwave irradiation device 1d according to the fourth modification, and is a schematic diagram of the microwave irradiation device 1d viewed from the side. In the microwave irradiation device 1d, a lid closing device 96 is provided upstream of the metal housing 80 in which the antenna 40 is arranged. The lid closing device 96 closes the lid member 112 on the unsealed portion 116 side of the object 110 to be irradiated, which is conveyed from upstream, so as to cover the container 111. The lid closing device 96 may have any mechanism. The object 110 with the lid member 112 closed is conveyed to the portion of the opening closing device 70.

[0054] In the opening closing device 70, the closing belt 72 covers the opening of the object 110 to be irradiated from above the closed lid member 112. At this time, the lid member 112 functions as a partition member disposed between the opening of the object 110 to be irradiated and the closing belt 72, and the closing belt 72 covers the opening of the object 110 to be irradiated through this partition member. In a state where the lid is covered by the lid member 112 pressed by the closing belt 72 covering the opening, the object 118 to be irradiated of the object 110 to be irradiated is heated by the microwave radiated from the antenna 40.

[0055] Downstream of the metal housing 80 where the antenna 40 is disposed, a lid-opening device 97 is provided. The lid-opening device 97 peels off the lid material 112 on the unsealed portion 116 side of the irradiated object 110 conveyed from upstream from above the container 111. The irradiated object 110 with the lid material 112 peeled off and the unsealed portion 116 side opened is conveyed to the portion of the cooling device 90. The cooling device 90 cools the irradiated object 110, for example, by blowing cold air onto the irradiated object 110 with the lid material 112 peeled off and a part of its upper surface opened. The lid-opening device 97 may have any mechanism. Also, for example, when the lid material 112 is not pressed by the closing belt 72 or the like and is configured to open, the lid-opening device 97 may not be provided.

[0056] According to the fourth modification, since the closing belt 72 of the opening / closing device 70 covers the opening of the irradiated object 110 via the lid material 112, contamination of the closing belt 72 is prevented as compared with the case where the closing belt 72 directly covers the opening of the irradiated object 100. Therefore, in the microwave irradiation device 1d according to the fourth modification, the cleaning device 73 may not be provided in the opening / closing device 70. Also, covering the container 111 with the lid material 112 results in a relatively high sealing degree, and since a part of the moisture evaporated by heating becomes water droplets and adheres to the lid material 112 and remains in the irradiated object 110 even after heating, a decrease in the moisture content of the object to be heated 118 is suppressed. Note that if the lid material 112 such as a film closed by the lid closing device 96 is not pressed from above by the closing belt 72, it will turn up during heating and uniform heating cannot be achieved.

[0057] Also, according to the fourth modification, since a part of the lid material 112 is peeled off from the container 111 after heating, high cooling efficiency by the cooling device 90 can be obtained. Also, after heating the irradiated object 110, it becomes possible to add food that is not heated into the container 111.

[0058] Note that the partition member disposed between the opening of the container 111 and the closing belt 72 is not limited to the lid member 112 which is a film for sealing the opening surface of the container 111 in the completed food in the container. For example, any member may be used as long as it is interposed between the opening of the container 111 and the closing belt 72 so as to prevent contamination of the closing belt 72. The lid member of the completed food in the container is to be sealed separately, and when heated by the microwave irradiation device 1d, another member may be disposed between the opening of the container 111 and the closing belt 72.

[0059] [Modification Example Regarding Heating Method] A fifth modification example regarding the heating method will be described. The above-described embodiment relates to a heating device that heats an object to be irradiated by microwave irradiation. The heating method is not limited to microwave irradiation. For example, a heater may be provided at a position corresponding to the metal housing 80 which is a portion for heating the object to be heated, and the object to be heated may be heated by the heat generated by this heater. Further, a device for blowing hot air into a position corresponding to the metal housing 80 may be provided, and the object to be heated may be heated by this hot air. Further, a coil or the like may be provided at a position corresponding to the metal housing 80, and by using a container of the object to be heated made of metal or a conveyor belt 62 made of metal, the object to be heated may be heated by induction heating. Further, not limited to the microwave irradiation using the above-described directional antenna, the object to be heated may be heated by various dielectric heating methods.

[0060] As in the fifth modification example, even when a heating tool based on any heating principle is used, like the opening / closing device 70 having the closing belt 72, by covering the opening of the object to be heated having an opening with an opening / closing tool having a conveyor belt, the object to be heated can be heated uniformly and efficiently. Further, by the conveying device 60 and the opening / closing device 70 successively conveying the objects to be heated, heating of a large number of objects to be heated can be sequentially performed.

[0061] Note that the above-described modification examples can be applied in appropriate combinations.

[0062] As described above, the present invention has been described with reference to preferred embodiments. However, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the present invention.

Explanation of Reference Numerals

[0063] 1, 1a, 1b, 1c, 1d: Microwave irradiation device 10: Oscillator, 12: Coaxial cable 40, 40c: Antenna, 41: First loop antenna, 42: Second loop antenna, 52: Conductive wire, 53: Feeding point, 54: Aperture surface, 55: Irradiation surface, 56: Irradiation source, 57: Directional irradiation axis 60, 60b: Conveyor, 62: Conveyor belt, 63b: Loading belt, 64b: Plate-like member, 65b: Unloading belt 70, 70a: Aperture closing device, 72: Closing belt, 73: Cleaning device 80: Metal housing, 81: Main housing, 82: Side housing 90: Cooling device, 96: Lid closing device, 97: Lid opening device 100, 110: Object to be irradiated, 111: Container, 112: Lid material, 118: Object to be heated, 115: Sealed portion, 116: Unsealed portion

Claims

1. A holder configured to hold an object to be irradiated having an opening, An opening closing device disposed opposite to the holder and covering the opening, A directional antenna configured to irradiate microwaves along a directional irradiation axis from an irradiation source within an irradiation plane by power supply from an oscillator through conduction via a power supply device A microwave irradiation device comprising.

2. The microwave irradiation device according to claim 1, wherein at least one of the holder and the opening closing device is configured to convey the object to be irradiated along the directional irradiation axis by moving along the directional irradiation axis.

3. At least a part of at least one of the holder and the opening closing device is constituted by a part of a conveyor belt, The microwave irradiation device according to claim 1.

4. The microwave irradiation device according to claim 3, wherein the conveyor belt has microwave permeability.

5. The opening closing device is constituted by a conveyor belt, The microwave irradiation device according to claim 1, further comprising a cleaning device for cleaning the conveyor belt. The microwave irradiation device according to claim 1.

6. The opening closing device is configured to open the opening after the object to be irradiated is irradiated with microwaves, The microwave irradiation device according to claim 1, further comprising a cooling device configured to cool the object to be irradiated with the opening opened after being irradiated with microwaves. The microwave irradiation device according to claim 1.

7. The microwave irradiation device according to claim 1, wherein the antenna is a loop antenna having an opening plane as the irradiation plane.

8. The microwave irradiation device according to claim 7, wherein the holder or the opening closing device is provided through the opening plane.

9. Covering the opening of the object to be irradiated having an opening with an opening closing device, Irradiating microwaves along a directional irradiation axis from an irradiation source within an irradiation plane from a directional antenna to the object to be irradiated in a state where the opening is covered with the opening closing device by power supply from an oscillator through conduction via a power supply device, After irradiating the object to be irradiated with microwaves, opening the opening covered with the opening closing device, A microwave irradiation method including.

10. Further comprising conveying the object to be irradiated in a state where the opening is covered with the opening closing device, The irradiating of the microwaves is performed while conveying the object to be irradiated. The microwave irradiation method according to claim 9.

11. The microwave irradiation method according to claim 9, wherein the opening closing device covers the opening through a partition member.

12. The microwave irradiation method according to claim 11, wherein a part of the partition member is adhered to the object to be irradiated.

13. The microwave irradiation method according to claim 12, wherein opening the opening is to open the opening by separating the non - adhered part of the partition member from the object to be irradiated.

14. The microwave irradiation method according to claim 11, wherein the partition member is a lid member that closes the opening.

15. The microwave irradiation method according to claim 9, further comprising cooling the object to be irradiated with the opening opened.

16. A heating method, comprising irradiating the object to be irradiated with the microwave by the microwave irradiation method according to claim 9 to heat a heated object contained in the object to be irradiated.

17. A food manufacturing method, comprising heating the heated object including food by the heating method according to claim 16.

18. The food manufacturing method according to claim 17, further comprising adding food to the heated object after heating the heated object.

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