Microwave irradiation device

Abstract

To properly control heating in a microwave irradiation device.SOLUTION: A microwave irradiation device 1 includes a power supply device 20 configured to be in electrical communication with an oscillator 10, a directional antenna group 34 including at least one directional antenna 40 configured to radiate microwaves by being fed by conduction through the power supply device 20, and a secondary radiating antenna group 35 including at least one secondary radiating antenna 50 configured to secondary radiate microwaves.SELECTED DRAWING: Figure 1A

Description

Technical Field

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

Background Art

[0002] Generally, a heating device that dielectrically heats an object to be irradiated by irradiating the object with microwaves is known. In dielectric heating, the object to be irradiated may not be heated evenly for various reasons. Therefore, various measures have been taken for uniform heating.

[0003] For example, Patent Document 1 discloses the following microwave heating device. In this microwave heating device, microwaves are supplied from a power supply port to a heating chamber through a waveguide. The heating chamber is partitioned into an upper space and a lower space by a mounting shelf. The peripheral edge of the mounting shelf is disposed at the vertical center of the power supply port. The mounting surface has a plurality of parallel lines with a length that is an integral multiple of half the wavelength and having openings, and is configured such that microwaves are secondarily radiated from these parallel lines. Equal amounts of objects to be heated are disposed in the upper space and the lower space, and while the objects to be heated and the mounting shelf rotate, the objects to be heated are simultaneously heated by microwaves. The microwaves supplied from the power supply port at the peripheral edge of the mounting surface are evenly dispersed in the upper space and the lower space, and by secondarily radiating microwaves vertically from the parallel lines, the objects to be heated are heated evenly and efficiently.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above microwave heating device, although there is an effect of evenly dispersing microwaves into the upper space and the lower space, the heating uniformity of the objects to be heated placed in each space cannot be controlled, and there is a possibility of non-uniform heating depending on the shape and type of the objects to be heated. The present invention aims to appropriately control heating in a microwave irradiation device.

Means for Solving the Problem

[0006] According to one aspect of the present invention, a microwave irradiation device includes a power supply appliance configured to conduct with an oscillator, and a directional antenna group including at least one directional antenna configured to irradiate microwaves by power supply through conduction via the power supply appliance, and a secondary radiation antenna group including at least one secondary radiation antenna configured to secondarily radiate microwaves.

Effect of the Invention

[0007] According to the present invention, heating can be appropriately controlled in a microwave irradiation device.

Brief Description of the Drawings

[0008]

Figure 1A

Figure 1B

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MODE FOR CARRYING OUT THE INVENTION

[0009] [First Embodiment] A first embodiment will be described with reference to the drawings. This embodiment relates to a microwave irradiation device. 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. The object to be irradiated is, but not limited to, for example, food.

[0010] <Configuration> FIGS. 1A and 1B are diagrams schematically showing an outline of a configuration example of a microwave irradiation device 1 according to this embodiment. FIG. 1A is a front view of the microwave irradiation device 1, and schematically shows a state in which the plate of the front portion of a metal housing 82 described later is removed so that the inside can be seen. FIG. 1B is a right side view of the microwave irradiation device 1, and schematically shows a state in which the plate of the right side portion of a metal housing 82 described later is removed so that the inside can be seen.

[0011] As shown in these figures, the microwave irradiation device 1 includes a holder 60. The holder 60 holds an object 90 to be heated, which is an object to be irradiated with microwaves. The holder 60 can be, for example, a table on which the object 90 to be irradiated is placed. The holder 60 is configured to hold the object 90 at an irradiation position where microwaves can be appropriately irradiated.

[0012] The microwave irradiation device 1 includes a directional antenna group 34 including two directional antennas 40 configured to irradiate microwaves to the object 90 to be irradiated held by the holder 60. Each directional antenna 40 is, for example, an antenna such as a loop antenna or a patch antenna. The two directional antennas 40 are arranged to face each other with the object 90 interposed therebetween so that the directional irradiation axes thereof are directed toward the object 90. The two directional antennas 40 are arranged along the irradiation axes of these directional antennas 40.

[0013] In the example shown in FIGS. 1A and 1B, the two directional antennas 40 are loop antennas 41. The holder 60 is provided so as to penetrate through the loops of the two loop antennas 41. In the present embodiment, the irradiation position where the microwave is appropriately irradiated is the intermediate position between the two opposing loop antennas 41. That is, the two loop antennas 41 are symmetrically arranged with the object to be irradiated 90 interposed therebetween.

[0014] The loop antenna 41 includes, for example, a conductor 42 having a length equal to one wavelength of the microwave to be irradiated and formed in an annular shape. Both ends of the conductor 42 serve as power supply points 43. For example, a coaxial cable 21 as a power supply device 20 is connected to the power supply point 43. The coaxial cable 21 connects the oscillator 10 and the loop antenna 41 to make them conductive. The oscillator 10 supplies high-frequency power to the loop antenna 41 via the coaxial cable 21. When powered, a current is generated in the conductor 42 as an element, and the loop antenna 41 radiates radio waves to form an electric field.

[0015] In the loop antenna 41, the surface formed by the conductor 42 becomes the irradiation surface of the radio wave, and a directional microwave is radiated from the irradiation source at the center of the irradiation surface toward the irradiation axis perpendicular to the irradiation surface. The loop antenna 41 is provided so as to be perpendicular to the mounting surface of the holder 60, and the irradiation axis is along the mounting surface of the holder 60.

[0016] The microwave irradiation device 1 includes a secondary radiation antenna group 35 including two secondary radiation antennas 50. The two secondary radiation antennas 50 are arranged between the two loop antennas 41. In the example shown in FIGS. 1A and 1B, the two thin plate-like secondary radiation antennas 50 are provided so as to extend in parallel along the irradiation axis of the loop antenna 41 and penetrate both loop antennas 41, and to sandwich the object to be irradiated 90 from the horizontal direction. The loop antenna 41, which is a directional antenna 40, and the secondary radiation antenna 50 are not electrically connected and are insulated. In the present embodiment, the two secondary radiation antennas 50 are arranged symmetrically with respect to the irradiation position where the object to be irradiated 90 is held. Although not limited to this, since the electric field strength becomes strong and the heating efficiency is good in the middle of the two loop antennas 41, the object to be irradiated 90 is preferably arranged in the middle of the two loop antennas 41, and the secondary radiation antenna 50 is also preferably arranged in the middle of the two loop antennas 41.

[0017] The above-described configuration is covered with metal for shielding microwaves. That is, the holder 60, the directional antenna 40, the secondary radiation antenna 50, etc. are arranged in the metal housing 82.

[0018] <Operation> The operation of the microwave irradiation device 1 of the present embodiment will be described. The oscillator 10 outputs high-frequency power corresponding to the frequency of the microwave. The frequency is not limited to this, and is, for example, 2.45 GHz or 915 MHz, or 450 MHz. The high-frequency power output from the oscillator 10 is supplied to the directional antenna 40 via the power supply device 20. The directional antenna 40 radiates microwaves based on this power supply.

[0019] The secondary radiation antenna 50 is electromagnetically induced by the microwaves radiated from the directional antenna 40. As a result, an electric field is generated by the secondary radiation antenna 50.

[0020] The object 90 placed on the holder 60 is irradiated with microwaves from the directional antenna 40 and the secondary radiation antenna 50. By these microwaves, the object 90 is dielectrically heated.

[0021] 〈Regarding the generated electric field, etc.〉 In the microwave irradiation device 1 of the present embodiment, as described above, since the directional antenna 40 and the secondary radiation antenna 50 are provided, the object 90 is heated more uniformly. This will be described with reference to FIGS. 2A to 2E. Here, as shown in FIG. 2A, the placement surface of the horizontal holder 60 is defined as the xy plane, and the vertical direction is defined as the z axis. The loop antenna 41 as the directional antenna 40 is provided in the yz plane, and its irradiation axis is along the x axis.

[0022] FIG. 2A is a diagram showing the direction and magnitude of the current at a certain moment when high-frequency power is supplied from the oscillator 10 to the loop antenna 41 by the directions and magnitudes of a number of small vectors. A current flows through the loop antenna 41 in the direction indicated by the large white arrow. At this time, a magnetic field in the direction indicated by the large arrow with diagonal lines is generated around the loop antenna 41.

[0023] FIG. 2B is a diagram showing the direction and intensity of the magnetic field in the xz cross section including the irradiation axis of the loop antenna 41 at this time by the directions and magnitudes of a number of small vectors. Generally, a magnetic field in the direction indicated by the large arrow with diagonal lines is generated in FIG. 2B.

[0024] FIG. 2C is a diagram showing the direction and magnitude of the current by the directions and magnitudes of a number of small vectors, as also shown in FIG. 2A. When a magnetic field as shown in FIG. 2B penetrates the secondary radiation antenna 50, eddy currents are generated, and as a result of their synthesis, a current is induced in the secondary radiation antenna 50. The direction of the current in the secondary radiation antenna 50 is indicated by a large white arrow in FIG. 2C. That is, in one secondary radiation antenna 50, a current directed toward its center is generated, and in the other secondary radiation antenna 50, a current directed outward from its center is generated. As shown in FIG. 2C, positive and negative charges accumulate at the portions where the induced currents face each other, that is, at the central portion of the secondary radiation antenna 50.

[0025] FIGS. 2D and 2E are diagrams showing the direction and intensity of the electric field generated at this time by the directions and magnitudes of a number of small vectors. FIG. 2D shows an xy cross section passing through the secondary radiation antenna 50, and FIG. 2E shows a yz cross section passing through the irradiated object 90. As indicated by large shaded arrows in FIGS. 2C to 2E, an electric field is generated across the irradiated object 90 between the two secondary radiation antennas 50.

[0026] As described above, by providing the two secondary radiation antennas 50 between the two opposing loop antennas 41, the irradiated object 90 is efficiently dielectrically heated.

[0027] <Simulation of Temperature Distribution by Dielectric Heating> FIG. 3 shows the simulation results of the temperature distribution of the irradiated object 90 when heated by the above-described microwave irradiation device 1, and each result when the length of the secondary radiation antenna 50 is different. The diameter of the irradiated object 90 was set to 80 mm, the frequency of power supply to the loop antenna 41 was set to 450 MHz, and the distance between the two loop antennas 41 was set to 333 mm corresponding to 1 / 2 wavelength for analysis. In FIG. 3, the upper part shows the model used for the simulation and indicates the arrangement of the secondary radiation antenna 50. In any case, the width of the secondary radiation antenna 50 was set to 20 mm and the distance between them was set to 95 mm. The secondary radiation antenna 50 was arranged at the central position in the height direction of the irradiated object 90. Analysis was performed for the case where (a) the secondary radiation antenna 50 was not provided and for the cases where the length of the secondary radiation antenna 50 was set to lengths corresponding to (b) 1 / 32 wavelength, (c) 1 / 16 wavelength, (d) 1 / 8 wavelength, and (e) 1 / 4 wavelength, respectively. In the analysis, the electromagnetic field generated for each condition was calculated, and the temperature distribution based on this electromagnetic field was calculated. The lower part of FIG. 3 shows the analysis results of the temperature distribution of the xy cross-section including the center of the irradiated object 90 where the secondary radiation antenna 50 was arranged after uniformly heating the irradiated object 90 at an output of 150 W for 5 minutes.

[0028] In any case, the central part of the irradiated object 90 is the hottest, and the temperature decreases as the distance from the center increases. In the case of (a) where the secondary radiation antenna 50 is not provided, radio waves are radiated along the irradiation axis 45 connecting the centers of the two loop antennas 41 by the loop antenna 41, so a high-temperature region is formed along this irradiation axis 45, and the temperature difference due to position becomes large in the direction orthogonal to the irradiation axis. On the other hand, when the secondary radiation antenna 50 is provided and its length increases, the temperature difference due to position in the direction orthogonal to the irradiation axis 45 becomes smaller. In particular, in the cases of (d) and (e) where the length of the secondary radiation antenna 50 is 1 / 8 wavelength or more, it was found that the temperature difference due to position is small in both the direction along the irradiation axis 45 and the direction orthogonal to the irradiation axis 45, and the entire irradiated object 90 is heated more uniformly. It was considered that the secondary radiation antenna 50 preferably has a certain length.

[0029] In addition, as shown in FIG. 4A, analysis was similarly performed for the case where the secondary radiation antenna 50 was arranged so as to penetrate the loop antenna 41. FIGS. 4B and 4C show the analysis results and the temperature distribution. FIG. 4C shows the temperature distribution of the 4C-4C cross section shown in FIG. 4A. As shown in this result, it was confirmed that high uniformity was obtained with respect to the heating of the object 90 to be irradiated.

[0030] 〈Experimental Results〉 The heating uniformity by the above-described microwave irradiation device 1 was evaluated with the object to be heated being potato salad packed in a container.

[0031] The oscillation frequency of the oscillator 10 was set to 450 MHz. As the loop antenna 140, a square loop antenna 41 made of aluminum and having a perimeter corresponding to one wavelength (λ = 666 mm) was used. The distance between the two loop antennas 41 was set to λ / 2 = 333 mm. The power supply to the two loop antennas 41 was in-phase power supply. As the holder 60, a plate made of polyethylene (PE) with a thickness of 5 mm was used for the holding table. The food holding table 166 was arranged so as to penetrate the two loop antennas 140. A plate-shaped secondary radiation antenna 50 having a length penetrating the two loop antennas 41 and a width of 40 mm was arranged with a 95-mm interval so as to sandwich the object 90 to be irradiated.

[0032] The object 90 to be irradiated was a potato salad filled in a polypropylene (PP) container with a diameter of 80 mm. Temperature measurement was performed by attaching a plurality of thermolabels (registered trademark) to the surface of the potato salad. The temperature measurement was performed after heating at an output of 150 W for 5 minutes.

[0033] The irradiated object 90 after heating is shown in Fig. 5. As shown in this figure, the temperature reached 70°C at any location along the irradiation axis 45. Also, regarding the direction orthogonal to the irradiation axis 45, the central part was 70°C and both sides thereof were 80°C. Thus, it was confirmed that the microwave irradiation device 1 can perform uniform heating. Incidentally, as a comparative example, when the secondary radiation antenna 50 was not provided, the temperatures on both sides in the direction orthogonal to the irradiation axis 45 were lower than that of the central part. That is, measurement results similar to the simulation results in Fig. 3(a) were obtained.

[0034] As a heating device by dielectric heating, for example, a multi-mode heating device that reflects microwaves in a metal housing to heat an object to be heated is known. Also, a single-mode heating device that arranges an object to be heated in a waveguide that conveys microwaves is known. In a multi-mode heating device, heating unevenness is likely to occur. Also, in a heating device using a waveguide, the device is likely to be enlarged, such as the waveguide becoming large especially when the frequency is low. Further, when combining multiple types of heating devices for uniform heating, the entire device is likely to be enlarged. In contrast, the microwave irradiation device 1 of the present embodiment does not use a waveguide and does not require combining multiple types of devices, so it is easy to miniaturize the device. Also, since it does not use a waveguide, it is easy to use microwaves of a relatively low frequency. By lowering the frequency, the power half-value depth can also be increased.

[0035] <Modification Example> FIG. 6 shows the simulation results of the temperature distribution of the object 90 to be irradiated when heated by the microwave irradiation device 1 according to the modified example. In this modified example, the major axis of the secondary radiation antenna 50 is provided so as to be orthogonal to the irradiation axis 45. Each of FIGS. 6(a) to (d) shows, as the model thereof in the upper part, (a) the case where the secondary radiation antenna 50 is not provided, and the analysis when the length of the secondary radiation antenna 50 is set to lengths corresponding to (b) 1 / 32 wavelength, (c) 1 / 16 wavelength, and (d) 1 / 8 wavelength, respectively. In any case, the width of the secondary radiation antenna 50 is 10 mm, and the distance between them is 95 mm. The secondary radiation antenna 50 is arranged at the central position in the height direction of the object 90 to be irradiated. The frequency of power supply to the loop antenna 41 is 450 MHz, and the analysis was performed with the distance between the two loop antennas 41 being 333 mm corresponding to 1 / 2 wavelength.

[0036] The lower part of FIG. 6 shows the analysis results of the temperature distribution of the xy cross section including the center of the object 90 to which the secondary radiation antenna 50 is arranged after heating a uniform object 90 with a diameter of 80 mm at an output of 150 W for 5 minutes. In any case, the central part of the object 90 is the hottest, and the temperature decreases as the distance from the center increases. In the case of (a) where the secondary radiation antenna 50 is not provided, as described above, a high-temperature region is formed along the irradiation axis 45, and the temperature difference depending on the position becomes large in the direction orthogonal to the irradiation axis. On the other hand, when the secondary radiation antenna 50 is provided and it becomes longer, a high-temperature region is formed in the direction orthogonal to the irradiation axis. In the case of (c) where the length of the secondary radiation antenna 50 is 1 / 16 wavelength, it was found that the temperature difference depending on the position is relatively small in both the direction along the irradiation axis and the direction orthogonal to the irradiation axis, and the entire object 90 to be irradiated is heated relatively uniformly.

[0037] In addition, in the above-described embodiments and modified examples, an example in which the thin-plate secondary radiation antenna 50 is arranged so that the main surface is horizontal is shown, but it is not limited to this. The secondary radiation antenna 50 may be arranged so that its main surface is vertical.

[0038] The dimensions of the secondary radiation antenna 50 can be appropriately determined so as to achieve impedance matching, taking into account the output frequency of the oscillator 10 and the like. Also, since the electric field formed in the region of the object to be irradiated 90 becomes weaker as the distance from the object to be irradiated 90 increases, the secondary radiation antenna 50 is preferably arranged at a position moderately close to the object to be irradiated 90.

[0039] [Second Embodiment] <Configuration> The second embodiment will be described. Here, the differences from the first embodiment will be described, and for the same parts, the same reference numerals will be given and the description thereof will be omitted. The microwave irradiation device 2 of the present embodiment further includes an additional secondary radiation antenna as a secondary radiation antenna 52 for heating control, as compared with the microwave irradiation device 1 according to the first embodiment. That is, in the present embodiment, the secondary radiation antenna group 35 includes the secondary radiation antenna 52 for heating control in addition to the two secondary radiation antennas 50 on both sides of the object to be irradiated 90.

[0040] FIGS. 7A and 7B are diagrams schematically showing the outline of a configuration example of the microwave irradiation device 2 according to the present embodiment. FIG. 7A is a front view of the microwave irradiation device 2, and schematically shows a state in which the plate of the front part of the metal housing 82 is removed so that the inside can be seen. FIG. 7B is a right side view of the microwave irradiation device 2, and schematically shows a state in which the plate of the right side part of the metal housing 82 is removed so that the inside can be seen.

[0041] As shown in this figure, the microwave irradiation device 2 is provided with a secondary radiation antenna 52 for heating control under the holder 60. The secondary radiation antenna 52 for heating control extends parallel to the irradiation axis 45, but its position is not through directly below the center of the object to be irradiated 90 to be arranged, and is arranged biased to the left side in FIG. 7B. That is, in the present embodiment, the plurality of secondary radiation antennas included in the secondary radiation antenna group 35 are arranged asymmetrically with respect to the irradiation position where the object to be irradiated 90 is arranged. The configuration of the other microwave irradiation device 2 is the same as that in the case of the first embodiment.

[0042] <Regarding the Electric Field Generated, etc.> In the microwave irradiation device 2 of the present embodiment, as described above, since the directional antenna 40, the secondary radiation antenna 50, and the secondary radiation antenna 52 for heating control are provided, the object to be irradiated 90 is unevenly heated. This will be described with reference to FIGS. 8A to 8E. Here, similar to the description of the first embodiment, as shown in FIG. 8A, the placement surface of the horizontal holder 60 is defined as the xy plane, and the vertical direction is defined as the z axis. The loop antenna 41 is provided in the yz plane, and its irradiation axis is along the x axis.

[0043] FIG. 8A is a diagram showing the direction and magnitude of current at a certain moment when high-frequency power is supplied from the oscillator 10 to the loop antenna 41 by the directions and magnitudes of a number of small vectors. A current flows through the loop antenna 41 in the direction indicated by the large white arrow. At this time, a magnetic field in the direction indicated by the large arrow with slashes is generated around the loop antenna 41.

[0044] FIG. 8B is a diagram showing the direction and intensity of the magnetic field in the xz cross section including the irradiation axis of the loop antenna 41 at this time by the directions and magnitudes of a number of small vectors. Generally, a magnetic field in the direction indicated by the large arrow with slashes is generated in FIG. 8B.

[0045] FIG. 8C is a diagram showing the direction and magnitude of the current, also shown in FIG. 8A, by the directions and magnitudes of a number of small vectors. When the magnetic field as shown in FIG. 8B penetrates the secondary radiation antenna 50 and the secondary radiation antenna 52 for heating control, eddy currents are generated, and as a result, currents are induced in the secondary radiation antenna 50 and the secondary radiation antenna 52 for heating control. The directions of the currents in the secondary radiation antenna 50 and the secondary radiation antenna 52 for heating control are indicated by large white arrows. Charges accumulate at the portions where the induced currents face each other.

[0046] Figures 8D and 8E are diagrams showing the direction and intensity of the electric field generated at this time by the directions and magnitudes of a number of small vectors. Figure 8D shows the xy cross-section passing through the secondary radiation antenna 50, and Figure 8E shows the yz cross-section passing through the irradiated object 90. As indicated by the large shaded arrows in Figures 8D and 8E, an electric field crossing the irradiated object 90 between the opposing secondary radiation antennas 50 and an electric field crossing the irradiated object 90 from the secondary radiation antenna 50 on the far side of the secondary radiation antenna 52 for heating control are generated. As a result, on the side of the secondary radiation antenna 50 far from the secondary radiation antenna 52 for heating control, the intensity of the electric field becomes stronger than on the side of the opposing secondary radiation antenna 50. Therefore, on the side of the secondary radiation antenna 50 far from the secondary radiation antenna 52 for heating control where the electric field intensity is strong, the irradiated object 90 is more strongly dielectrically heated.

[0047] 〈Simulation of Temperature Distribution by Dielectric Heating〉 Figures 9A and 9B are the simulation results of the temperature distribution of the irradiated object 90 when the irradiated object 90 is heated by the microwave irradiation device 2 of the present embodiment. Similar to the case of the first embodiment, the diameter of the irradiated object 90 was set to 80 mm, the frequency of power supply to the loop antenna 41 was set to 450 MHz, and the distance between the two loop antennas 41 was set to 333 mm corresponding to half a wavelength for analysis. The width of the secondary radiation antenna 50 was set to 40 mm, and the distance between them was set to 95 mm. The secondary radiation antennas 50 were arranged at the central position in the height direction of the irradiated object 90. The width of the secondary radiation antenna 52 for heating control was set to 30 mm, and it was arranged under the holder 60 so that the end in the width direction of the secondary radiation antenna 52 for heating control was located at the central position of the irradiated object 90. Figure 9B shows the temperature distribution of the cross-section 9B-9B shown in Figure 9A. As a result, it was clarified that the irradiated object 90 is more strongly heated on the side of the secondary radiation antenna 50 far from the secondary radiation antenna 52 for heating control.

[0048] 〈Experimental Results〉 Regarding the heating by the microwave irradiation device 2 of the present embodiment, the object to be heated was evaluated as potato salad packed in a container. The experimental conditions were the same as those in the case of the first embodiment, except that the microwave irradiation device 2 was provided with the secondary radiation antenna 52 for heating control.

[0049] The irradiated object 90 after heating is shown in FIG. 10. As shown in this figure, the temperature after heating on the side where the secondary radiation antenna 52 for heating control was arranged was 70°C, whereas the temperature after heating on the side opposite to the side where the secondary radiation antenna 52 for heating control was arranged was 90°C. Thus, it was confirmed that the microwave irradiation device 2 can perform uneven heating. It became clear that the heating distribution can be controlled by adjusting the arrangement of the secondary radiation antenna 52 for heating control.

[0050] In the heating of the irradiated object 90, it is not always preferable to be heated uniformly. For example, when there are regions in the irradiated object 90 that are easily heated and regions that are difficult to heat, more power is input to the regions that are difficult to heat, so that the entire irradiated object 90 is heated uniformly. Also, one irradiated object 90 may include something that is desired to be heated and something that is not desired to be overheated. In such a case, it is required that power be input to the region of the object to be heated.

[0051] According to the present embodiment, by adjusting the position, size, etc. of the secondary radiation antenna 52 for heating control according to the electric field strength required at each part of the irradiated object 90, the microwave irradiation device 2 can perform appropriate heating.

[0052] Note that the microwave irradiation device 2 may be configured such that the position of the secondary radiation antenna 52 for heating control can be changed. In this way, by changing the position of the secondary radiation antenna 52 for heating control according to the irradiated object 90, heating according to the irradiated object 90 becomes possible.

[0053] Here, an example was shown in which the secondary radiation antenna 52 for heating control is provided in addition to the secondary radiation antenna 50 of the microwave irradiation device 1 of the first embodiment, but the present invention is not limited to this. Without distinguishing between the secondary radiation antenna 50 and the secondary radiation antenna 52 for heating control, by appropriately adjusting the position, size, etc. of one or more secondary radiation antennas 50 included in the secondary radiation antenna group 35, the microwave irradiation device can adjust the electric field strength and control the heating of the irradiated object 90. For example, in the first embodiment, by providing the secondary radiation antennas symmetrically with respect to the irradiated object 90, power is uniformly supplied to the irradiated object. In the second embodiment, by providing the secondary radiation antennas asymmetrically with respect to the irradiated object 90, power is non-uniformly supplied to the irradiated object. Particularly when the secondary radiation antennas are arranged asymmetrically, the distribution of the electric field strength can vary in various ways depending on various conditions.

[0054] For example, in the second embodiment, when the secondary radiation antenna 50 on the side far from the secondary radiation antenna 52 for heating control is not provided, that is, when only the two secondary radiation antennas, the left secondary radiation antenna 50 and the secondary radiation antenna 52 for heating control, are provided without providing the right secondary radiation antenna 50 in FIG. 8E, a strong electric field is formed between these two secondary radiation antennas. As a result, unlike the case of the second embodiment, the left side of the irradiated object 90 in FIG. 8E is strongly heated.

[0055] [Third Embodiment] The third embodiment will be described. Here, the differences from the first embodiment will be described, and the same parts will be denoted by the same reference numerals and their descriptions will be omitted. In the third embodiment, the position of the secondary radiation antenna 50 of the microwave irradiation device 1 according to the first embodiment is considered.

[0056] Fig. 11 shows the simulation results of the temperature distribution of the irradiated object 90 when the content 91 in a cup with a taper of 80 mm to 85 mm in diameter is heated by the microwave irradiation device 1. (a) shows the case where the secondary radiation antenna 50 is not provided, (b) shows the case where the secondary radiation antenna 50 is arranged at the central position of the height of the content 91, and (c) shows the case where the secondary radiation antenna 50 is arranged at the same height as the holder 60.

[0057] In Fig. 11, the upper and middle sections respectively show the models used in the simulation. The upper section shows a perspective view, and the middle section shows the yz cross-section passing through the center of the irradiated object 90. In the cases shown in (b) and (c), the width of the secondary radiation antenna 50 was set to 20 mm. In the case (b) where the secondary radiation antenna 50 is arranged at the central position of the height of the content 91, the interval between the secondary radiation antennas 50 was set to 95 mm. In the case (c) where the secondary radiation antenna 50 is arranged at the same height as the holder 60, the interval between the secondary radiation antennas 50 was set to 140 mm. The frequency of the power supply to the loop antenna 41 was set to 450 MHz, and the distance between the two loop antennas 41 was set to 333 mm corresponding to half a wavelength for the analysis. In the analysis, the electromagnetic field generated for each condition was calculated, and the temperature distribution based on this electromagnetic field was calculated.

[0058] The lower section of Fig. 11 shows the analysis results of the temperature distribution of the yz cross-section including the center of the irradiated object 90 after the irradiated object 90 is heated at an output of 150 W for 5 minutes. When there is no secondary radiation antenna in (a) or when the secondary radiation antenna 50 is arranged at the central position of the height of the content 91 in (b), the upper edge of the content 91 generates strong heat and the temperature is high. In contrast, when the secondary radiation antenna 50 is arranged at the same height as the holder 60 in (c), the heat generation at the upper edge of the content 91 is suppressed.

[0059] Similar to the case of the first embodiment, an experiment was conducted with the irradiated object 90 being potato salad packed in a container. The irradiated object 90 was potato salad packed in a polypropylene (PP) container with a taper having a diameter of 80 mm to 85 mm. Except for the position of the secondary radiation antenna 50, other experimental conditions were the same as those shown in the first embodiment.

[0060] Similar to Fig. 11(b), when the secondary radiation antenna 50 was arranged at the central position of the height of the potato salad, burning occurred on a part of the upper surface edge of the potato salad. On the other hand, similar to Fig. 11(c), when the secondary radiation antenna 50 was arranged at the same height as the holder 60, no burning occurred on the upper surface edge of the potato salad. Thus, also in the experiment, results similar to the simulation results shown in Fig. 11 were obtained.

[0061] As described above, by controlling the temperature distribution by adjusting the position of the secondary radiation antenna, it is possible to suppress problems that may occur depending on the shape of the packaging container of the irradiated object and the type of the contents, such as burning of the upper surface edge of the contents.

[0062] [Fourth Embodiment] The fourth embodiment will be described. Here, differences from the first embodiment will be described, and the same parts will be denoted by the same reference numerals and their description will be omitted. Fig. 12 is a front view schematically showing an outline of a configuration example of the microwave irradiation device 3 according to the fourth embodiment. The microwave irradiation device 3 according to the present embodiment is configured to irradiate an irradiated object 90, such as food, with microwaves to internally heat the irradiated object 90. The microwave irradiation device 3 is configured such that a plurality of irradiated objects are conveyed one after another and heated one after another.

[0063] The microwave irradiation device 3 includes a conveying device 61 as a holder 60 that conveys an irradiated object 90 which is an object to be heated and irradiated with microwaves. The conveying device 61 includes, for example, a belt 62 and rollers 63. The belt 62 is looped around the rollers 63. The rollers 63 are rotated by a motor (not shown) to move the belt 62 in the longitudinal axis direction. The irradiated object 90 is placed on the belt 62 and conveyed in the conveying direction 89 by the movement of the belt 62. On the upstream side in the conveying direction 89 of the conveying device 61, a supply device 84 is provided for successively supplying the irradiated objects 90 onto the belt 62. On the downstream side in the conveying direction 89 of the conveying device 61, a discharging device 86 is provided for discharging the conveyed irradiated objects 90 from the belt 62.

[0064] The microwave irradiation device 3 has the same configuration as the microwave irradiation device 1 according to the first embodiment as a device for heating the irradiated object 90. The microwave irradiation device 3 includes a pair of loop antennas 41 configured to irradiate the irradiated object 90 conveyed by the conveying device 61 with microwaves. The loop antennas 41 are powered from an oscillator 10 electrically connected via a power feeding device 20 such as a coaxial cable, for example.

[0065] In the microwave irradiation device 3 of the present embodiment, the belt 62 of the conveying device 61 is provided so as to penetrate the irradiation surfaces which are the opening surfaces of the two loop antennas 41. That is, the irradiated object 90 is conveyed in the conveying direction 89 so as to pass through the loop antennas 41. Further, the microwave irradiation device 3 includes a pair of secondary radiation antennas 50 so as to sandwich the irradiated object 90 conveyed in the conveying direction 89.

[0066] The surroundings of the loop antennas 41 and the secondary radiation antennas 50 are covered with metal for shielding microwaves. That is, the conveying device 61 is provided so as to pass through a metal housing 82, and the loop antennas 41 and the secondary radiation antennas 50 are arranged inside the metal housing 82.

[0067] In the microwave irradiation device 3 of the present embodiment, the object 90 to be irradiated passes through the loop antenna 41 and passes between the secondary radiation antennas 50, thereby realizing efficient and uniform heating of the object 90 to be irradiated.

[0068] The operation of the microwave irradiation device 3 of the present embodiment will be described. The oscillator 10 outputs high-frequency power corresponding to the frequency of the microwave. The frequency is not limited to this, but for example, it is 2.45 GHz, 915 MHz, 450 MHz, or the like. The high-frequency power output from the oscillator 10 is supplied to the loop antenna 41 via the power feeding device 20. The loop antenna 41 radiates microwaves in the direction of the irradiation axis 45 based on this power supply. In this way, an electric field is formed by the loop antenna 41 and the secondary radiation antennas 50.

[0069] The conveying device 61 rotates the belt 62 by the rotation of the roller 63. The supply device 84 supplies the object 90 to be irradiated onto the belt 62 of the conveying device 61, for example, at regular intervals. The conveying device 61 conveys the supplied object 90 to be irradiated in the conveying direction 89 and passes it through the opening surface of the loop antenna 41 in the metal housing 82. The conveying device 61 further passes the object 90 to be irradiated between the pair of secondary radiation antennas 50 and through the opening surface of the other loop antenna 41. The object 90 to be irradiated is irradiated with microwaves from the loop antenna 41 and the secondary radiation antennas 50. By this microwave, the object 90 to be irradiated is dielectrically heated. The heated object 90 to be irradiated is conveyed to the outside of the metal housing 82 by the conveying device 61. The unloading device 86 unloads the heated object 90 to be irradiated from the conveying device 61.

[0070] The conveying device 61 may continuously move the object 90 to be irradiated, or may intermittently move the object 90 to be irradiated, for example, to stop it at the midpoint between the pair of loop antennas 41. By passing between the loop antenna 41 that radiates microwaves and the secondary radiation antennas 50, the object 90 to be irradiated is uniformly heated.

[0071] The microwave irradiation device 3 according to this embodiment can be incorporated into processing devices for various applications or configured in an appropriate manner. For example, when used for heat sterilization of sealed-packaged foods, the microwave irradiation device 1 is incorporated into a device configured such that the irradiated object 90, which is the sealed-packaged food, is pressurized or kept warm for the time required for sterilization. Alternatively, for use in reaction processing of materials and the like, the irradiated object 90, which is the object to be processed, may be housed in an appropriate reaction vessel, or the conveying device 61 may be configured as a pipe or the like through which the object to be processed flows.

[0072] Also, in the microwave irradiation device 3 of this embodiment, an example is shown in which two loop antennas 41 are arranged along the radiation axis, but it is not limited to this. For example, three loop antennas 41, such as the first, second, and third loop antennas 41, may be arranged along the radiation axis, a secondary radiation antenna 50 may be provided between the first and second loop antennas 41, and a secondary radiation antenna 50 may also be provided between the second and third loop antennas 41, and the device may be configured such that appropriate heating is performed at two locations. The number of loop antennas 41 may be one or any number.

[0073] In addition, in the microwave irradiation device 3 of this embodiment, although an example is shown in which the device configuration for heating the irradiated object 90 is the same as that of the microwave irradiation device 1 of the first embodiment, it is not limited to this. For example, the microwave irradiation device 3 may have the same device configuration as the microwave irradiation device 2 of the second embodiment. By having such a configuration, the microwave irradiation device 3 of this embodiment can also perform uneven heating.

[0074] In this embodiment, an example in which the conveying device 61 changes the position of the irradiated object 90 with respect to the loop antenna 41 and the secondary radiation antenna 50 has been shown. However, the present invention is not limited to this, and it is also conceivable that the position of the loop antenna 41 or the secondary radiation antenna 50 with respect to the irradiated object 90 is changed. That is, the holder 60 may fix the position of the irradiated object 90 and the loop antenna 41 or the secondary radiation antenna 50 may move. Thus, the same effect can be obtained if the relative positional relationship between the loop antenna 41 and the holder 60 or the relative positional relationship between the secondary radiation antenna 50 and the holder 60 is changed.

[0075] As described above, the present invention has been described by showing preferred embodiments. However, it goes without saying that the present invention is not limited only to the above-described embodiments, and various modifications can be made within the scope of the present invention.

Explanation of reference numerals

[0076] 1, 2, 3 Microwave irradiation device 10 Oscillator 20 Power supply device 21 Coaxial cable 34 Directive antenna group 35 Secondary radiation antenna group 40 Directive antenna 41 Loop antenna 42 Conductive wire 43 Feeding point 45 Irradiation axis 50 Secondary radiation antenna 52 Secondary radiation antenna for heating control 60 Holder 61 Conveying device 62 Belt 63 Roller 82 Metal housing 84 Supply device 86 Unloading device 89 Conveying direction 90 Irradiated object

Claims

1. A power supply device configured to conduct with an oscillator, A directional antenna group including at least one directional antenna configured to irradiate microwaves by power supply through conduction via the power supply device, A secondary radiation antenna group including at least one secondary radiation antenna configured to secondarily radiate microwaves are provided, The directional antenna group includes a plurality of directional antennas, The plurality of directional antennas are arranged along the irradiation axes of the plurality of directional antennas, The secondary radiation antenna is arranged between the directional antennas constituting the directional antenna group, A microwave irradiation device.

2. A power supply device configured to conduct with an oscillator, A directional antenna group including at least one directional antenna configured to irradiate microwaves by power supply through conduction via the power supply device, A secondary radiation antenna group including at least one secondary radiation antenna configured to secondarily radiate microwaves are provided, The directional antenna group includes a plurality of directional antennas, The plurality of directional antennas are arranged along the irradiation axes of the plurality of directional antennas, The plurality of directional antennas are arranged symmetrically with respect to the irradiation position where the object to be irradiated is held, A microwave irradiation device.

3. A power supply device configured to conduct with an oscillator, A directional antenna group including at least one directional antenna configured to irradiate microwaves by power supply through conduction via the power supply device, A secondary radiation antenna group including at least one secondary radiation antenna configured to secondarily radiate microwaves are provided, The secondary radiation antenna has a shape extending along the irradiation axis of the directional antenna, A microwave irradiation device.

4. A power supply device configured to conduct with an oscillator, A directional antenna group including at least one directional antenna configured to irradiate microwaves by power supply through conduction via the power supply device, A secondary radiation antenna group including at least one secondary radiation antenna configured to secondarily radiate microwaves are provided, The secondary radiation antenna group includes a plurality of secondary radiation antennas, The plurality of secondary radiation antennas are arranged symmetrically with respect to the irradiation position where the object to be irradiated is held, A microwave irradiation device.

5. A power supply device configured to conduct with an oscillator, A directional antenna group including at least one directional antenna configured to irradiate microwaves by power supply through conduction via the power supply device, A secondary radiation antenna group including at least one secondary radiation antenna configured to secondarily radiate microwaves, A holder for holding an object to be irradiated and comprising At least one of the directional antenna and the holder is configured to move along the irradiation axis of the directional antenna and change the relative positional relationship between the directional antenna and the holder. A microwave irradiation device.

6. The microwave irradiation device according to any one of claims 1 to 5, wherein the secondary radiation antenna is insulated from the directional antenna.

7. The directional antenna group includes a plurality of directional antennas, The plurality of directional antennas are arranged along the irradiation axes of the plurality of directional antennas. The microwave irradiation device according to claim 3, 4 or 5.

8. The plurality of directional antennas are arranged symmetrically with respect to the irradiation position where the object to be irradiated is held. The microwave irradiation device according to claim 7.

9. The secondary radiation antenna is arranged between the directional antennas constituting the directional antenna group. The microwave irradiation device according to claim 7 or 8.

10. The secondary radiation antenna has a shape extending along the irradiation axis of the directional antenna. The microwave irradiation device according to claim 1, 2, 4 or 5.

11. The secondary radiation antenna group includes a plurality of secondary radiation antennas. The microwave irradiation device according to claim 1, 2, 3 or 5.

12. The plurality of secondary radiation antennas are arranged symmetrically with respect to the irradiation position where the object to be irradiated is held. The microwave irradiation device according to claim 11.

13. The plurality of secondary radiation antennas are arranged asymmetrically with respect to the irradiation position where the object to be irradiated is held. The microwave irradiation device according to claim 11.

14. The secondary radiation antenna is configured to be able to change its position with respect to the directional antenna. The microwave irradiation device according to any one of claims 1 to 13.

15. The microwave irradiation device according to claim 2 or 4, further comprising a holder configured to be able to hold the object to be irradiated at least at the irradiation position.

16. Further comprising a holder for holding the object to be irradiated, At least one of the directional antenna and the holder is configured to move along the irradiation axis of the directional antenna and change the relative positional relationship between the directional antenna and the holder. The microwave irradiation device according to any one of claims 1 to 4.

17. Further comprising a holder for holding the object to be irradiated, At least one of the secondary radiation antenna and the holder is configured to move and change the relative positional relationship between the secondary radiation antenna and the holder. The microwave irradiation device according to any one of claims 1 to 4.

18. The microwave irradiation device according to any one of claims 1 to 17, wherein the directional antenna is a loop antenna.

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