Microwave irradiation device, microwave irradiation method, and food manufacturing method

Abstract

A microwave irradiation device (1) is provided with: a holder which is arranged so as to hold an object to be irradiated at a holding position; the power supply equipment is configured to be conducted with the oscillator (10); a power supply antenna (40) configured to irradiate microwaves by power supply via conduction of the power supply device, the power supply antenna (40) having directivity in which an irradiation axis is disposed toward the holding position; and a non-power-supply antenna (50) that is disposed so as to face the power supply antenna (40) across the holding position, has directivity such that the irradiation axis is disposed toward the holding position, and is not supplied with power.

Description

Technical Field

[0001] The present invention relates to a microwave irradiation device, a microwave irradiation method and a method for producing food. Background Art

[0002] Generally, a heating device is known that performs induction heating on an irradiated object by irradiating the object with microwaves. For efficient heating, impedance matching is required so that energy is input to the irradiated object. In the case of heating the irradiated object by irradiating microwaves toward the irradiated object using a directional antenna instead of a waveguide, it is necessary to spend time on impedance matching. For example, Patent Document 1 discloses that the heating efficiency in the microwave heating device is improved by repeatedly bringing the irradiated object and the antenna closer or farther away in consideration of such impedance matching. As an example of the moving distance at this time, a range of several mm is shown.

[0003] The impedance matching disclosed in Patent Document 1 can also be said to be fine adjustment. When impedance matching is performed by matching the output frequency of a microwave oscillator that generates microwaves with the resonant frequency of an object to be irradiated, in order to make the output frequency range of a high-output oscillator a wide band, there will be restrictions on the frequency band of the components, reduced efficiency, large size, and high cost, so the frequency range that can be changed is limited. For example, when the type or number of objects to be irradiated is changed, or when the position of the objects to be irradiated changes significantly, another impedance matching mechanism is required.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-3868 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Impedance matching may be achieved by connecting an external matching device to the device. In impedance matching using an external matching device, the resonance frequency is adjusted with the entire device as a load, so matching may be achieved not only with the irradiated object but also with other parts of the device.

[0009] An object of the present invention is to obtain good impedance matching with an object to be irradiated during microwave irradiation.

[0010] Solutions for solving problems

[0011] According to one embodiment of the present invention, a microwave irradiation device comprises: a holding member configured to hold an irradiated object at a holding position; a power supply device configured to be connected to an oscillator; a power supply antenna configured to irradiate microwaves by powering via the power supply device, the power supply antenna having a directivity such that the irradiation axis is configured toward the holding position; and a non-powered antenna configured to be opposite to the power supply antenna across the holding position, the non-powered antenna having a directivity such that the irradiation axis is configured toward the holding position but is not powered.

[0012] Effects of the Invention

[0013] According to the present invention, good impedance matching with an object to be irradiated can be obtained during microwave irradiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram schematically showing an outline of a basic configuration example of the microwave irradiation device according to the first embodiment.

[0015] Figure 2A It is schematically represented in Figure 1 There is no graph of the relationship between reflection loss and frequency for the case of an unpowered antenna.

[0016] Figure 2B This is a diagram schematically showing the relationship between the reflection loss and the frequency when the parasitic antenna is adjusted and installed at an appropriate position.

[0017] Figure 3A This is a diagram schematically showing an example in which one antenna is provided as a feeding antenna and one antenna is provided as a non-feeding antenna.

[0018] Figure 3B This is a diagram schematically showing an example in which two antennas are provided as feeding antennas and one antenna is provided as a non-feeding antenna.

[0019] Figure 3C This is a diagram schematically showing an example in which two antennas are provided as feeding antennas and two antennas are provided as non-feeding antennas.

[0020] Figure 4 1 is a diagram schematically showing the positional relationship between the first feeding loop antenna, the first non-feeding loop antenna, and the irradiated object in Experimental Example 1.

[0021] Figure 5 This is a graph showing the values ​​of the resonance frequency and the reflection loss measured in Experimental Example 1 with respect to the distance from the first feeding loop antenna to the first non-feeding loop antenna.

[0022] Figure 61 is a diagram schematically showing the positional relationship among the first feeding loop antenna, the second feeding loop antenna, the first non-feeding loop antenna, and the irradiated object in Experimental Example 2.

[0023] Figure 7 This is a graph showing the value of the resonant frequency measured in Experimental Example 2 with respect to the distance from the first feeding loop antenna to the first non-feeding loop antenna.

[0024] Figure 8 1 is a diagram schematically showing the positional relationship among the first feeding loop antenna, the second feeding loop antenna, the first non-feeding loop antenna, the second non-feeding loop antenna, and the irradiated object in Experimental Example 3.

[0025] Fig. 9 This is a graph showing the value of the resonant frequency with respect to the distance from the power supply antenna to the non-power supply antenna measured in Experimental Example 3.

[0026] Fig.10 1 is a diagram schematically showing the positional relationship between the first feeding loop antenna, the second feeding loop antenna, and the irradiated object in the comparative experimental example.

[0027] Fig.11 The values ​​of the resonant frequency with respect to the distance between the first feeding loop antenna and the second feeding loop antenna measured in the comparative experiment example are shown.

[0028] Fig.12 1 is a diagram schematically showing the positional relationship between the first power supply antenna, the first non-power supply antenna, and the irradiated object in Experimental Example 4.

[0029] Fig.13 It is a plan view schematically showing a basic structure of a part of an example of a microwave irradiation device according to the second embodiment.

[0030] Fig.14 This is a diagram schematically showing an outline of a basic configuration example of a microwave irradiation device according to a third embodiment.

[0031] Fig.15 This is a diagram schematically showing the arrangement of antennas in Experimental Example 5, etc.

[0032] Fig.16 : is a graph showing the value of the resonant frequency with respect to the distance and length of the two auxiliary antennas.

[0033] Fig.17 The diagrams show simulation results of the temperature distribution of the irradiated object when the irradiated object is heated by the microwave irradiation apparatus having each configuration.

[0034] Fig.18 This is a diagram showing changes in the resonance frequency when one irradiated object is transported.

[0035] Fig.19 This is a diagram showing changes in the resonance frequency when three irradiated objects are transported. DETAILED DESCRIPTION

[0036] [First embodiment]

[0037] The first embodiment is described with reference to the accompanying drawings. The present embodiment relates to a microwave irradiation device. The microwave irradiation device of the present embodiment is configured to irradiate microwaves onto an irradiated object to perform internal heating of the irradiated object. In particular, the microwave irradiation device uses a directional antenna to irradiate microwaves with its directional irradiation axis directed toward the irradiated object. The irradiated object is, for example, food, but is not limited thereto. Therefore, the microwave irradiation device and the microwave irradiation method using the microwave irradiation device can be used, for example, in the manufacture of food including packaged food. The microwave irradiation device of the present embodiment has an excellent impedance matching function. In particular, for various conditions with greatly different types, quantities, positions, etc. of the irradiated objects, appropriate impedance matching can be obtained by the same device, and efficient heating can be achieved by the same device.

[0038] <Basic structure of microwave irradiation device>

[0039] Figure 1 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 is configured to sequentially heat an irradiated object 90 conveyed by a conveying device 85. The conveying device 85 is, for example, a belt conveyor. The conveying device 85 has a conveyor belt 86 that moves along its long dimension direction. The irradiated object 90 is placed at a holding position on the conveyor belt 86 and is conveyed along the long dimension direction of the conveyor belt 86. Thus, in the present embodiment, the conveying device 85 functions as a holder that holds the irradiated object 90 at the holding position.

[0040] The microwave irradiation device 1 includes a power supply antenna 40 configured to irradiate microwaves to the irradiation target 90 conveyed by the conveying device 85. The power supply antenna 40 is a directional antenna such as a loop antenna. Figure 1 In the example shown, the microwave irradiation device 1 includes two loop antennas, ie, a first power feeding loop antenna 41 and a second power feeding loop antenna 42 as the power feeding antenna 40. The number of power feeding loop antennas can be changed appropriately.

[0041] The first power supply loop antenna 41 and the second power supply loop antenna 42 are formed of, for example, a metal component having a length of one wavelength of the microwave to be irradiated, and the metal component has, for example, a circular ring shape. The metal component is not limited to a circular ring, and may also have other circular shapes such as a quadrilateral. Both ends of the metal component serve as power supply points. A coaxial cable 21, for example, is connected to the power supply point as a power supply device. The first power supply loop antenna 41 and the second power supply loop antenna 42 are supplied with high-frequency power from the oscillator 10 via the coaxial cable 21. By supplying power, current flows through the metal component as an element, and the first power supply loop antenna 41 and the second power supply loop antenna 42 radiate radio waves to form an electric field. In the loop antenna, the center of the opening surface formed by the metal component becomes the irradiation source of the radio wave, and the opening surface becomes the irradiation surface, and microwaves are radiated in two directions along the irradiation axis perpendicular to the opening surface.

[0042] The microwave irradiation device 1 is configured to convey the irradiated object 90 through the center of the opening surface that is the irradiation surface of the first power supply loop antenna 41 and the second power supply loop antenna 42. Therefore, the conveyor belt 86 of the conveying device 85 is set to penetrate the opening surface of the first power supply loop antenna 41 and the second power supply loop antenna 42. The irradiation surface of the first power supply loop antenna 41 and the second power supply loop antenna 42 is configured to be perpendicular to the long dimension direction of the conveyor belt 86, and the directional irradiation axis of the first power supply loop antenna 41 and the second power supply loop antenna 42 is configured to be parallel to the long dimension direction of the conveyor belt 86. In this embodiment, the directional irradiation axis of the power supply antenna 40 is referred to as a reference axis.

[0043] The oscillator 10 outputs high-frequency power corresponding to the frequency of the microwave. The frequency is, for example, 450 MHz, 915 MHz, or 2.45 GHz, but is not limited thereto. The output frequency of the oscillator 10 can be adjusted to a certain extent, but its range is limited. In order to efficiently and appropriately heat the irradiated object 90, it is necessary to match the impedance of the oscillation system including the oscillator 10 and the power supply antenna 40 with the impedance of the irradiated object 90. That is, it is necessary to set the resonant frequency with the irradiated object 90 as the load to be within the range of the oscillable frequency of the oscillator 10. The oscillator 10 or its attached device has the function of monitoring the reflected power.

[0044] The microwave irradiation device 1 includes a non-powered antenna 50 for performing the above-mentioned impedance matching. Figure 1 In the example shown, the microwave irradiation device 1 includes one loop antenna, that is, the first parasitic loop antenna 51 as the parasitic antenna 50. The number of parasitic loop antennas can be changed appropriately.

[0045] The first non-powered loop antenna 51 has the same structure as the first powered loop antenna 41, etc., except that it is not connected to the coaxial cable 21 and is not powered. That is, the first non-powered loop antenna 51 is formed of a metal member having a length of one wavelength of microwaves, and the metal member has a circular ring shape, etc. The first non-powered loop antenna 51 is not grounded. The first non-powered loop antenna 51 is set so that the conveyor belt 86 of the conveying device 85 passes through the opening surface of the first non-powered loop antenna 51 in a manner that the irradiated object 90 passes through the center of the opening surface. The first non-powered loop antenna 51 is set to be perpendicular to the long dimension direction of the conveyor belt 86, that is, perpendicular to the above-mentioned reference axis. Therefore, the irradiation axis of the first non-powered loop antenna 51 is set along the reference axis.

[0046] In addition, the non-powered antenna 50 is configured to be movable along the reference axis. As described later, the non-powered antenna 50 is moved along the reference axis, thereby changing the resonant frequency of the object to be irradiated 90 of the microwave irradiation device 1 as a load. In the microwave irradiation device 1, the position of the non-powered antenna 50 is adjusted along the reference axis to perform impedance matching. In this way, the position of the object to be irradiated 90 is changed by the conveying device 85, and the non-powered antenna 50 is moved along the reference axis, but the irradiation axes of the power supply antenna 40 and the non-powered antenna 50 are oriented toward the holding position of the conveying device 85 where the object to be irradiated 90 is held.

[0047] The microwave irradiation device 1 includes a position adjustment mechanism 60 for adjusting the position of the passive antenna 50. Figure 1 In the example shown, the position adjustment mechanism 60 includes: a support portion 62 that supports the non-powered antenna 50; and a track 63 that supports the support portion 62 so as to be movable along the reference axis. In addition, the position adjustment mechanism 60 includes a control portion 61 that controls the position of the support portion 62 on the track 63. The control portion 61 is also connected to the oscillator 10 to obtain information about the reflection loss measured by the oscillator 10.

[0048] The structure of the position adjustment mechanism 60 shown here is an example, and the position adjustment mechanism 60 can be any structure as long as it can change the position of the non-powered antenna 50. For example, the position adjustment mechanism 60 may not be able to continuously change the position of the non-powered antenna 50. The position adjustment mechanism 60 may also be a mechanism such as a user manually adjusting the position of the non-powered antenna 50 and fixing it. In addition, the position adjustment mechanism 60 may also be configured to also change the position of the power supply antenna 40. That is, the position adjustment mechanism 60 may be any mechanism as long as it is configured to change the relative distance between the power supply antenna 40 and the non-powered antenna 50. For example, the position adjustment mechanism 60 may also be a fixing member that can fix the position of the power supply antenna 40 or the non-powered antenna 50 in a changeable manner. However, as the structure of the position adjustment mechanism 60, it is more preferable to fix the position of the power supply antenna 40 and change the position of the non-powered antenna 50.

[0049] The microwave irradiation device 1 includes a metal shell 80 to shield microwaves. That is, the power supply antenna 40 and the non-power supply antenna 50 are covered by the metal shell 80. In addition, the conveyor belt 86 of the conveying device 85 passes through the metal shell 80. In more detail, the metal shell 80 includes a main shell 81. The power supply antenna 40 and the non-power supply antenna 50 are arranged in the main shell 81. Through holes for the conveyor belt 86 to pass through are provided on both side surfaces of the main shell 81. A side shell 82 of a size for the conveyor belt 86 and the irradiated object 90 placed thereon to pass through is connected to each of the through holes.

[0050] Reference Figure 2A and Figure 2B , the impedance matching achieved by the non-powered antenna 50 is described. Figure 2A The schematic diagram shows the case where the unpowered antenna 50 is not provided. Figure 1 The relationship between the reflection loss and the frequency when there is no unpowered antenna 50 is shown in FIG. Figure 2B The relationship between the reflection loss and the frequency when the unpowered antenna 50 is adjusted and set at an appropriate position is schematically shown. Such a relationship can generally be easily obtained by using a network analyzer, etc. It should be noted that the range of 445MHz to 465MHz indicated by shading in these figures is the frequency range that the oscillator 10 can output.

[0051] exist Figure 2A In the figure, several peaks can be observed. These peaks are resonant frequencies. Among these peaks, the peak shown in (a) is the resonant frequency of the irradiated object 90. Figure 2A In FIG. 1 , the resonance frequency of the irradiated object 90 shown in (a) is outside the output frequency range of the oscillator 10 shown in the shaded area.

[0052] On the other hand, in the case where the unpowered antenna 50 is provided Figure 2B In the figure, the resonant frequency of the irradiated object 90 shown in (a) is within the output frequency range of the oscillator 10 shown in the shaded area. If the resonant frequency of the irradiated object 90 as a load is within the output frequency range of the oscillator 10, the output frequency can be made consistent with the resonant frequency by adjusting the oscillator 10. In this case, the irradiated object 90 can be efficiently heated.

[0053] <Operation of the microwave irradiation device>

[0054] The operation of the microwave irradiation device 1 of the present embodiment will be described. The high frequency power output from the oscillator 10 is supplied to the power supply antenna 40 via the coaxial cable 21. The power supply antenna 40 radiates microwaves based on the power supply.

[0055] When the irradiated object 90 is changed, the position of the passive antenna 50 is adjusted to perform impedance matching with the irradiated object 90. At this time, microwave irradiation is performed while the irradiated object 90 is arranged between the power antenna 40 and the passive antenna 50, and the reflection loss is monitored. The control unit 61 obtains the value of the reflection loss measured by the oscillator 10, etc., and the position adjustment mechanism 60 adjusts the position of the passive antenna 50 so that the resonance frequency of the irradiated object 90 is within the range of the output frequency of the oscillator 10.

[0056] After impedance matching is performed, the microwave irradiation device 1 is used. That is, heating of the irradiated object 90 using the microwave irradiation device 1 is performed. The irradiated object 90 is sequentially transported to the heating position between the power supply antenna 40 and the non-power supply antenna 50 by the transport device 85, and the irradiated object 90 is sequentially inductively heated by the irradiation of the microwave from the power supply antenna 40. The transport device 85 may be moved intermittently so that the irradiated object 90 stops at the heating position, or may be moved continuously so that the irradiated object 90 passes through the heating position after a sufficient period of time.

[0057] Here, an example in which the operation related to impedance matching is performed before the microwave irradiation device 1 is used is shown, but the present invention is not limited thereto. The operation related to impedance matching may be performed during the use of the microwave irradiation device 1 .

[0058] <Configuration Example of Microwave Irradiation Device>

[0059] For the microwave irradiation device 1 described above, several modes with different numbers of the power supply antenna 40 and the non-power supply antenna 50 are considered. FIG. 3A to FIG. 3C Three examples are shown, but not limited to these.

[0060] Figure 3AThe example shown is an example in which one antenna, namely, a first feeding loop antenna 41, is provided as the feeding antenna 40, and one non-feeding antenna, namely, a first non-feeding loop antenna 51, is provided as the non-feeding antenna 50. The first non-feeding loop antenna 51 is configured to be movable along the reference axis.

[0061] Figure 3B The example shown is an example in which two antennas, namely, a first power supply loop antenna 41 and a second power supply loop antenna 42, are provided as the power supply antenna 40, and one non-power supply antenna, namely, a first non-power supply loop antenna 51, is provided as the non-power supply antenna 50. The first non-power supply loop antenna 51 is arranged between the first power supply loop antenna 41 and the second power supply loop antenna 42. The first non-power supply loop antenna 51 is arranged to be movable between the first power supply loop antenna 41 and the second power supply loop antenna 42 along the reference axis.

[0062] Figure 3C The example shown is an example in which two antennas, namely, a first power supply loop antenna 41 and a second power supply loop antenna 42, are provided as the power supply antenna 40, and two non-power supply antennas, namely, a first non-power supply loop antenna 51 and a second non-power supply loop antenna 52, are provided as the non-power supply antenna 50. The first non-power supply loop antenna 51 and the second non-power supply loop antenna 52 are arranged between the first power supply loop antenna 41 and the second power supply loop antenna 42. The first non-power supply loop antenna 51 and the second non-power supply loop antenna 52 are arranged to be movable between the first power supply loop antenna 41 and the second power supply loop antenna 42 along the reference axis, respectively.

[0063] As described later, in this example, the first power supply loop antenna 41 and the first non-power supply loop antenna 51 form a pair, and the second power supply loop antenna 42 and the second non-power supply loop antenna 52 form a pair. The first non-power supply loop antenna 51 is arranged between the second power supply loop antenna 42 and the second non-power supply loop antenna 52, and the second non-power supply loop antenna 52 is arranged between the first power supply loop antenna 41 and the first non-power supply loop antenna 51.

[0064] <Experimental Example 1>

[0065] use Figure 3A The microwave irradiation device 1 of the structure shown, that is, the microwave irradiation device 1 having one first feeding loop antenna 41 and one first non-feeding loop antenna 51, was used to measure the resonant frequency and reflection loss with the irradiated object 90 as a load when the position of the first non-feeding loop antenna 51 was changed. In addition, the temperature of the irradiated object 90 when heated by using the device was measured.

[0066] (method)

[0067] In the microwave irradiation device 1 of the test device, the main housing 81 is formed of aluminum material, and its dimensions are set to 440 mm in length along the conveying direction, 350 mm in width perpendicular to the conveying direction, and 400 mm in height. The side housings 82 are each formed of aluminum material, and their dimensions are set to 250 mm in length, 220 mm in width, and 80 mm in height. The resin conveyor belt 86 of the conveying device 85 is provided so as to pass through the metal housing 80, and its width is set to 150 mm.

[0068] A circular first power supply loop antenna 41 is provided in the main housing 81 so that the conveyor belt 86 passes through. The first power supply loop antenna 41 is formed of aluminum material, and its inner diameter is set to 232 mm, its outer diameter is set to 258 mm, and its thickness is set to 2 mm. The oscillator 10 is connected to the first power supply loop antenna 41 via a coaxial cable 21. The frequency of the output power of the oscillator 10 is set to 450 MHz (output wavelength λ = 666 mm).

[0069] Similar to the first feeding loop antenna 41, a circular first passive feeding loop antenna 51 is provided in the main housing 81 so that the conveyor belt 86 passes therethrough. The first passive feeding loop antenna 51 is made of aluminum and has an inner diameter of 232 mm, an outer diameter of 258 mm, and a thickness of 2 mm.

[0070] The irradiated object 90 is a cup made of polypropylene (PP) with a diameter of 85 mm filled with 140 g of potato salad. The irradiated object 90 is arranged on the conveyor 86 at a distance of 167 mm (λ / 4) from the first feeding loop antenna 41 .

[0071] The resonant frequency and reflection loss were measured using a network analyzer. Here, the reflection loss RL is defined as follows.

[0072] RL=20log 10 (b1 / a1)

[0073] Here, a1 is the square root of the input power, and b1 is the square root of the reflected power.

[0074] Figure 4 The schematic diagram shows the positional relationship between the first power supply loop antenna 41, the first non-power supply loop antenna 51, and the irradiated object 90. Measurements were performed under the conditions where the distance between the first non-power supply loop antenna 51 and the first power supply loop antenna 41 was 42 mm, 83 mm, 125 mm, 167 mm, 208 mm, 250 mm, 292 mm, and 333 mm. That is, the first non-power supply loop antenna 51 was arranged at Figure 4 The measurement was performed at each position (a) to (h) indicated by the dotted lines.

[0075] In the temperature measurement experiment of the irradiated object 90, the initial temperature of the irradiated object 90 was set to 10°C, the output was set to 150W, and the temperature after heating for 5 minutes was measured.

[0076] (result)

[0077] Figure 5 Indicates the values ​​of the resonant frequency and the reflection loss relative to the distance from the first powered loop antenna 41 to the first non-powered loop antenna 51. When the distance from the first non-powered loop antenna 51 to the first powered loop antenna 41 is 167 mm and 208 mm, the resonant frequency is as low as 451 MHz. As the distance from the first non-powered loop antenna 51 to the first powered loop antenna 41 decreases from 167 mm to 42 mm, the resonant frequency increases. As the distance from the first non-powered loop antenna 51 to the first powered loop antenna 41 increases from 208 mm to 333 mm, the resonant frequency increases. The reflection loss is approximately constant when the distance from the first non-powered loop antenna 51 to the first powered loop antenna 41 is less than 167 mm, and when the distance is from 167 mm to 333 mm, the reflection loss decreases as the distance increases.

[0078] It should be noted that the irradiated object 90 is arranged at a position where the distance from the first powered loop antenna 41 to the first non-powered loop antenna 51 is 167 mm, so when the distance from the first powered loop antenna 41 to the first non-powered loop antenna 51 is less than 167 mm, the irradiated object 90 is arranged outside the first powered loop antenna 41 and the first non-powered loop antenna 51. When the distance from the first powered loop antenna 41 to the first non-powered loop antenna 51 is greater than 167 mm, the irradiated object 90 is arranged inside the first powered loop antenna 41 and the first non-powered loop antenna 51.

[0079] The temperature of the heated object 90 was measured for the case where the resonant frequency was 455 MHz, which is the central value of the output frequency range of 445 MHz to 465 MHz of the oscillator 10. That is, the temperature of the heated object 90 was measured for the case where the distance between the first power supply loop antenna 41 and the first non-power supply loop antenna 51 was 125 mm and 241 mm. When the distance between the antennas was 125 mm, the reflection loss was -8 dB, and when the distance between the antennas was 241 mm, the reflection loss was -12 dB. The temperature of the object 90 with an initial temperature of 10° C. after being heated at 150 W for 5 minutes was 32° C. when the distance between the antennas was 125 mm, and 74° C. when the distance between the antennas was 241 mm. It is believed that when the object 90 is arranged between the power supply antenna 40 and the non-power supply antenna 50 and the resonant frequencies are matched to achieve impedance matching, the reflection loss is small and the heating efficiency is good.

[0080] <Experimental Example 2>

[0081] use Figure 3B The microwave irradiation device 1 of the structure shown, that is, the microwave irradiation device 1 using two power supply antennas 40 including a first power supply loop antenna 41 and a second power supply loop antenna 42 and a first non-power supply loop antenna 51, measures the resonant frequency with the irradiated object 90 as a load when the position of the first non-power supply loop antenna 51 is changed.

[0082] (method)

[0083] The experiment was conducted under the same conditions as those of Experimental Example 1 except for the configuration of the power supply antenna 40. That is, the configurations of the metal housing 80 and the conveyor belt 86 were the same as those of Experimental Example 1. The first power supply loop antenna 41 and the second power supply loop antenna 42 were configured the same as the first power supply loop antenna 41 of Experimental Example 1. The first non-power supply loop antenna 51 was configured the same as the first non-power supply loop antenna 51 of Experimental Example 1.

[0084] The interval between the first feeding loop antenna 41 and the second feeding loop antenna 42 was set to 333 mm. The first feeding loop antenna 41 and the second feeding loop antenna 42 were connected to the oscillator 10 via the coaxial cable 21. The frequency of the output power of the oscillator 10 was set to 450 MHz, and the first feeding loop antenna 41 and the second feeding loop antenna 42 were fed in phase.

[0085] The irradiated object 90 is an 85 mm polypropylene (PP) cup filled with 140 g of potato salad, similar to Experimental Example 1. The irradiated object 90 is arranged at a middle position between the first power supply loop antenna 41 and the second power supply loop antenna 42, that is, the irradiated object 90 is arranged on the conveyor belt 86 at a distance of 167 mm from the first power supply loop antenna 41 and the second power supply loop antenna 42.

[0086] The resonance frequency was measured under the conditions where the distance between the first parasitic loop antenna 51 and the first feeding loop antenna 41 was 167 mm, 208 mm, 250 mm, and 292 mm. The resonance frequency was measured under the same conditions except that the first parasitic loop antenna 51 was not provided.

[0087] Figure 6The positional relationship between the first power supply loop antenna 41, the second power supply loop antenna 42, the first non-power supply loop antenna 51 and the irradiated object 90 is schematically illustrated. The first non-power supply loop antenna 51 is arranged at each position (a) to (d) shown by the dotted line. In Experimental Example 1, it was found that it is meaningful to consider the case where the irradiated object 90 is arranged between the power supply antenna 40 and the non-power supply antenna 50. Therefore, the distance between the first non-power supply loop antenna 51 and the power supply antenna 40 is defined as the distance between the first power supply loop antenna 41 and the first non-power supply loop antenna 51 instead of the distance between the second power supply loop antenna 42 and the first non-power supply loop antenna 51, so that the irradiated object 90 is arranged between the power supply antenna 40 and the non-power supply antenna 50.

[0088] (result)

[0089] Figure 7 represents the value of the resonant frequency relative to the distance from the first feeding loop antenna 41 to the first non-feeding loop antenna 51. In addition, when the first non-feeding loop antenna 51 is not configured, the resonant frequency is 513 MHz, so this value is set to Figure 7 In the case where the first parasitic loop antenna 51 is provided, the resonance frequency is lowered in any case compared to the case where the first parasitic loop antenna 51 is not provided.

[0090] When the distance from the first non-powered loop antenna 51 to the first powered loop antenna 41 is 167 mm, the resonance frequency is at least 460 MHz. The greater the distance from the first non-powered loop antenna 51 to the first powered loop antenna 41, the higher the resonance frequency. This is the same tendency as the result of Experimental Example 1.

[0091] It can be seen that if the first parasitic loop antenna 51 is not configured, the resonant frequency will greatly deviate from the oscillable frequency of 445 MHz to 465 MHz of the oscillator 10 . However, by configuring the first parasitic loop antenna 51 , the resonant frequency can be within the oscillable frequency range of the oscillator 10 .

[0092] <Experimental Example 3>

[0093] use Figure 3C The microwave irradiation device 1 of the structure shown, that is, the microwave irradiation device 1 using two powered antennas 40 including a first powered loop antenna 41 and a second powered loop antenna 42 and two unpowered antennas 50 including a first unpowered loop antenna 51 and a second unpowered loop antenna 52, measures the resonant frequency with the irradiated object 90 as a load when the position of the unpowered antenna 50 is changed.

[0094] (method)

[0095] The experiment was conducted under the same conditions as those of Experimental Example 2 except for the configuration of the parasitic antenna 50. That is, the configurations of the metal housing 80 and the conveyor belt 86 were the same as those of Experimental Example 2. The first power supply loop antenna 41 and the second power supply loop antenna 42 were configured the same as those of the first power supply loop antenna 41 and the second power supply loop antenna 42 of Experimental Example 2. The interval between the first power supply loop antenna 41 and the second power supply loop antenna 42 was set to 333 mm. The first parasitic loop antenna 51 and the second parasitic loop antenna 52 were configured the same as those of the first parasitic loop antenna 51 of Experimental Example 2.

[0096] The irradiated object 90 was an 85 mm polypropylene (PP) cup filled with 140 g of potato salad, similar to Experimental Example 2. The irradiated object 90 was arranged at a middle position between the first power supply loop antenna 41 and the second power supply loop antenna 42, that is, the irradiated object 90 was arranged on the conveyor belt 86 at a distance of 167 mm from the first power supply loop antenna 41 and the second power supply loop antenna 42.

[0097] In Experimental Example 1, it was found that it is meaningful to consider the case where the irradiated object 90 is arranged between the power supply antenna 40 and the non-power supply antenna 50. Therefore, the first power supply loop antenna 41 and the first non-power supply loop antenna 51 arranged across the irradiated object 90 are considered as a pair, and the second power supply loop antenna 42 and the second non-power supply loop antenna 52 arranged across the irradiated object 90 are considered as a pair. That is, the positional relationship is as follows: the first non-power supply loop antenna 51 is arranged between the second power supply loop antenna 42 and the second non-power supply loop antenna 52, and the second non-power supply loop antenna 52 is arranged between the first power supply loop antenna 41 and the first non-power supply loop antenna 51.

[0098] The resonance frequency was measured under the conditions that the distance between the first parasitic loop antenna 51 and the first feeding loop antenna 41 and the distance between the second parasitic loop antenna 52 and the second feeding loop antenna 42 were 208 mm, 250 mm, and 292 mm. Figure 8 The positional relationship between the first power supply loop antenna 41, the second power supply loop antenna 42, the first non-power supply loop antenna 51, the second non-power supply loop antenna 52, and the irradiated object 90 is schematically illustrated. The first non-power supply loop antenna 51 and the second non-power supply loop antenna 52 are arranged at the positions (a) to (c) shown by the dotted lines. As described above, the distance between the non-power supply antenna 50 and the power supply antenna 40 is defined in a state where the irradiated object 90 is arranged between the power supply antenna 40 and the non-power supply antenna 50.

[0099] (result)

[0100] Fig. 9represents the value of the resonant frequency relative to the distance from the power supply antenna 40 to the non-power supply antenna 50. In addition, when the non-power supply antenna 50 is not configured, the resonant frequency is 513 MHz, so this value is set to Fig. 9 Indicated by a dotted line. In the case where the unpowered antenna 50 is configured, the resonant frequency is lowered in any case compared to the case where the unpowered antenna 50 is not configured. For the resonant frequency, the greater the distance from the powered antenna 40 to the unpowered antenna 50, the higher the resonant frequency. This is the same tendency as the results of Experimental Examples 1 and 2. However, even if the distance from the powered antenna 40 to the unpowered antenna 50 is the same, the resonant frequency of Experimental Example 3 in which two unpowered loop antennas are configured is lower than that of Experimental Example 2 in which one unpowered loop antenna is configured. That is, the adjustment of the resonant frequency can also be achieved by configuring the number of unpowered antennas.

[0101] It can be seen that if the first unpowered loop antenna 51 is not configured, the resonant frequency will deviate significantly from the oscillating frequency of 445MHz~465MHz of the oscillator 10. However, by configuring the first unpowered loop antenna 51 and the second unpowered loop antenna 52, the resonant frequency can be within the oscillating frequency range of the oscillator 10.

[0102] <Comparative Experimental Example>

[0103] The resonant frequency with the irradiated object 90 as a load was measured when the parasitic antenna 50 was not provided and the interval between the two feeding antennas 40 was changed.

[0104] (method)

[0105] The experiment was conducted under the same conditions as those of Experimental Example 2 except that the parasitic antenna 50 was not provided and the interval between the first power feeding loop antenna 41 and the second power feeding loop antenna 42 was changed. That is, the configurations of the metal housing 80 and the conveyor belt 86 were the same as those of Experimental Example 2. The first power feeding loop antenna 41 and the second power feeding loop antenna 42 were configured the same as those of the first power feeding loop antenna 41 and the second power feeding loop antenna 42 of Experimental Example 2.

[0106] The irradiated object 90 is an 85 mm polypropylene (PP) cup filled with 140 g of potato salad, similar to Experimental Example 2. The irradiated object 90 is disposed on the conveyor 86 so as to be located between the first feeding loop antenna 41 and the second feeding loop antenna 42 .

[0107] The resonance frequency was measured under the conditions where the distance between the first power feeding loop antenna 41 and the second power feeding loop antenna 42 was 167 mm, 250 mm, 333 mm, and 417 mm. Fig.10The diagram schematically shows the positional relationship between the first power feeding loop antenna 41, the second power feeding loop antenna 42, and the irradiated object 90. The first power feeding loop antenna 41 and the second power feeding loop antenna 42 are arranged at positions (a) to (d) indicated by dotted lines.

[0108] (result)

[0109] Fig.11 The resonance frequency is expressed as a value of the distance between the first feeding loop antenna 41 and the second feeding loop antenna 42. As the distance between the antennas increases, the resonance frequency decreases. It can be seen that the resonance frequency can be adjusted even if the distance between the first feeding loop antenna 41 and the second feeding loop antenna 42 is changed.

[0110] It is believed that the resonant frequency decreases when the distance between the antennas is increased because the coupling between the antennas becomes weaker. Taking this into consideration, in the present embodiment, it is believed that the resonant frequency is lowered by providing the unpowered antenna 50 for the following reasons. That is, a current in the opposite direction to the power supply antenna 40 is induced in the unpowered antenna 50. It is believed that this reverse induced current plays a role in weakening the coupling between the power supply antennas 40 and the coupling between the power supply antenna 40 and other elements. In addition, it is believed that the closer the unpowered antenna 50 is to the power supply antenna 40, the stronger this effect is, so the results are as in Experimental Examples 1 to 3 described above.

[0111] Even if the distance between the first power supply loop antenna 41 and the second power supply loop antenna 42 is changed without using the non-powered antenna 50, the resonant frequency can be adjusted, but for this purpose, a large metal shell 80 needs to be used to significantly change the position of the antenna. In addition, compared with adjusting the position of the non-powered antenna 50 not connected to the coaxial cable 21, adjusting the position of the first power supply loop antenna 41 and the second power supply loop antenna 42 connected to the coaxial cable 21 is accompanied by greater difficulty. Therefore, it is considered that the present embodiment, which can adjust the resonant frequency by fixing the position of the power supply antenna 40 and adjusting the position of the non-powered antenna 50, is excellent in terms of the size of the device and the simplicity of the device structure.

[0112] <Experimental Example 4>

[0113] use Figure 3A The microwave irradiation device 1 having the structure shown, that is, the microwave irradiation device 1 including a first power feeding loop antenna 41 and a first non-power feeding loop antenna 51, was used to study the relationship between the position of the irradiated object 90 during impedance matching and the reflection loss during heating of the irradiated object 90.

[0114] (method)

[0115] The length of the main housing 81 of the microwave irradiation device 1 along the conveying direction is set to 660 mm. The configurations of the side housing 82 and the conveyor belt 86 are the same as those in Experimental Example 1. The distance between the first power supply loop antenna 41 and the first non-power supply loop antenna 51 is set to 333 mm. The other configurations of the microwave irradiation device 1 are the same as those in Experimental Example 1.

[0116] The irradiated object 90 was obtained by filling 140 g of potato salad in an 85 mm polypropylene (PP) cup, similarly to Experimental Example 1. Three irradiated objects 90 were arranged on the conveyor 86 at intervals of 120 mm.

[0117] Fig.12 The positional relationship between the first power feeding loop antenna 41, the first non-powered loop antenna 51, and the irradiated object 90 is schematically shown. When impedance matching is performed with the irradiated object 90 disposed between the first power feeding loop antenna 41 and the first non-powered loop antenna 51, Fig.12 The resonant frequency and the reflection loss at that time were measured in the state shown in the upper left column of . That is, in the state where one of the three irradiated objects 90 is arranged between the first power supply loop antenna 41 and the first non-power supply loop antenna 51, the resonant frequency is determined, and the reflection loss when the output frequency is set to the resonant frequency is measured. In the state where the output frequency is fixed to the resonant frequency, as shown in FIG. Fig.12 As shown in the lower left column of , a state was set in which three irradiated objects 90 were arranged between the first feeding loop antenna 41 and the first parasitic loop antenna 51, and the reflection loss at this time was measured.

[0118] When impedance matching is performed without placing the irradiated object 90 between the first power feeding loop antenna 41 and the first non-power feeding loop antenna 51, Fig.12 In the state shown in the upper right column of , the resonant frequency and the reflection loss at that time were measured. That is, when the irradiated object 90 was arranged outside the first power supply loop antenna 41 and the first non-power supply loop antenna 51, that is, at a position 60 mm away from the first non-power supply loop antenna 51, the resonant frequency was determined, and the reflection loss when the output frequency was set to the resonant frequency was measured. When the output frequency was fixed to the resonant frequency, as shown in FIG. Fig.12 As shown in the lower right column of , a state was set where three irradiated objects 90 were arranged between the first feeding loop antenna 41 and the first parasitic loop antenna 51, and the reflection loss at this time was measured.

[0119] (result)

[0120] like Fig.12As shown in the upper left column of , when impedance matching is performed with an irradiated object 90 disposed between the first powered loop antenna 41 and the first unpowered loop antenna 51, the resonant frequency is 427 MHz, and the reflection loss at this time is -12 dB. When the output frequency is fixed at 427 MHz, the irradiated object 90 is transmitted, as shown in FIG. Fig.12 As shown in the lower left column of , it is assumed that three irradiated objects 90 are arranged between the first feeding loop antenna 41 and the first non-feeding loop antenna 51. At this time, the reflection loss is -18 dB, and a sufficiently small reflection loss is maintained.

[0121] like Fig.12 As shown in the upper right column of , when impedance matching is performed without irradiated object 90 between the first powered loop antenna 41 and the first unpowered loop antenna 51, the resonant frequency is 432MHz, and the reflection loss at this time is -12dB. When the output frequency is fixed at 432MHz, the irradiated object 90 is transmitted, as shown in FIG. Fig.12 As shown in the lower right column of , it is assumed that three irradiated objects 90 are arranged between the first feeding loop antenna 41 and the first non-feeding loop antenna 51. At this time, the reflection loss is -4.4 dB, which is a state in which the reflection loss is large and the efficiency is poor.

[0122] This result shows that, particularly when the microwave output frequency is fixed and the irradiated object 90 is transmitted to heat it, impedance matching is performed with the irradiated object 90 arranged between the first power feeding loop antenna 41 and the first non-power feeding loop antenna 51, thereby achieving efficient heating with little reflection loss.

[0123] [Second embodiment]

[0124] As a second embodiment, various embodiments are described. Here, the differences from the first embodiment are described, and the same parts are marked with the same reference numerals and their descriptions are omitted. In the first embodiment, the conveyor belt 86 of the conveying device 85 is set to penetrate the power supply antenna 40 and the non-power supply antenna 50, but it is not limited to this.

[0125] For example, the reference axis and the longitudinal direction of the conveyor belt 86 may be orthogonal. Fig.13 86 is a top view schematically showing this example. In this example, the first power supply loop antenna 41 and the second power supply loop antenna 42 are arranged to sandwich the conveyor belt 86, and the first non-power supply loop antenna 51 and the second non-power supply loop antenna 52 are arranged between the first power supply loop antenna 41 and the second power supply loop antenna 42 in a manner of sandwiching the conveyor belt 86. The first non-power supply loop antenna 51 and the second non-power supply loop antenna 52 are arranged to be movable to change the interval between them.

[0126] Alternatively, only one of the first parasitic loop antenna 51 and the second parasitic loop antenna 52 may be provided. Alternatively, only the first parasitic loop antenna 41 and the first parasitic loop antenna 51 may be provided.

[0127] Alternatively, the configuration including the first feeding loop antenna 41 , the second feeding loop antenna 42 , the first parasitic loop antenna 51 , and the second parasitic loop antenna 52 may be used as one set, and a plurality of sets of these may be arranged along the conveyor belt 86 .

[0128] In these examples, the power supply antenna 40 is not limited to the loop antenna, and various directional antennas such as microstrip antennas can be used. In addition, similarly, the non-power supply antenna 50 is not limited to the loop antenna, and other antennas or various conductors that function as antennas can be used. In these examples, the position of the irradiated object 90 is changed by the conveying device 85, so the irradiation axes of the power supply antenna 40 and the non-power supply antenna 50 are not always but at least temporarily directed to the holding position of the conveying device 85 where the irradiated object 90 is held.

[0129] In addition, in the first embodiment and the second embodiment, an example in which the irradiated object 90 is transported by the transport device 85 is shown, but the present invention is not limited thereto. Instead of the transport device 85, a table configured to place the irradiated object 90 on the reference axis may be provided. Thus, in these embodiments, various holders configured to hold the irradiated object 90 on the reference axis between the power supply antenna 40 and the non-power supply antenna 50, such as the conveyor belt 86 and the table of the transport device 85, are used. That is, the irradiation axes of the power supply antenna 40 and the non-power supply antenna 50 are at least temporarily oriented toward the holding position where the irradiated object 90 is held.

[0130] [Third Embodiment]

[0131] The third embodiment will be described. Here, the differences from the first embodiment will be described, and the same parts will be given the same reference numerals and their description will be omitted. In addition to the configuration of the first embodiment, another non-powered antenna may be further provided.

[0132] Fig.14 1 is a diagram schematically showing an example of the configuration of the microwave irradiation device 1 of the present embodiment. In this example, an elongated plate-shaped unpowered auxiliary antenna 56 is provided on both sides of the conveyor belt 86 in parallel with the conveyor belt 86. The auxiliary antenna 56 is not grounded.

[0133] When power is supplied to the power supply antenna 40, a current is also induced in the auxiliary antenna 56. This induced current also affects the electric field around the irradiated object 90. The length, width, shape, number, and configuration of the auxiliary antenna 56 can be appropriately changed. In addition, the auxiliary antenna 56 can be fixed in position or movable. By using the auxiliary antenna 56, the state of the electric field around the irradiated object 90 can be adjusted. Of course, this embodiment can also be applied in combination with the second embodiment.

[0134] <Experimental Example 5>

[0135] The resonant frequency with the irradiated object 90 as a load was measured when two auxiliary antennas 56 were provided without providing the parasitic antenna 50 and the interval between the auxiliary antennas 56 was changed.

[0136] (method)

[0137] The length of the main housing 81 of the microwave irradiation device 1 along the conveying direction was set to 660 mm. The configuration of the side housing 82 and the conveyor belt 86 was the same as that of Experimental Example 2. The experiment was conducted under the same conditions as Experimental Example 2 except that the non-powered antenna 50 was not configured and two auxiliary antennas 56 were configured and the interval between the auxiliary antennas 56 was changed.

[0138] Fig.15 : is a diagram schematically showing the arrangement of antennas, etc. The distance between the first power supply loop antenna 41 and the second power supply loop antenna 42 is set to 333 mm. The irradiated object 90 is the same as in Experimental Example 2, and is an 85 mm polypropylene (PP) cup filled with 140 g of potato salad. The irradiated object 90 is arranged on the conveyor 86 so as to be located in the middle of the first power supply loop antenna 41 and the second power supply loop antenna 42.

[0139] The auxiliary antenna 56 has a width W of 20 mm and a length L of 320 mm, 400 mm, and 480 mm. The long axes of the two auxiliary antennas 56 are parallel to the irradiation axes of the first power supply loop antenna 41 and the second power supply loop antenna 42, and the two auxiliary antennas 56 are arranged on both sides of the irradiated object 90. The resonant frequency of each auxiliary antenna 56 having different lengths was measured under various conditions in which the interval D between the auxiliary antennas 56 was changed from 90 mm to 150 mm.

[0140] (result)

[0141] Fig.16 represents the value of the resonant frequency relative to the distance and length of the two auxiliary antennas 56. When the auxiliary antenna 56 is not configured, the resonant frequency is 489 MHz. Fig.16In any case where the auxiliary antenna 56 is provided, the resonance frequency is lower than that in the case where the auxiliary antenna 56 is not provided. As the interval between the auxiliary antennas 56 increases, the resonance frequency increases. As the length of the auxiliary antenna increases, the resonance frequency decreases.

[0142] It can be confirmed that the resonant frequency can be adjusted even if the interval or length of the auxiliary antenna 56 is changed without using the parasitic antenna 50. However, the adjustment range of the interval of the auxiliary antenna 56 is limited by the size of the irradiated object, and the change of the length is complicated and discontinuous adjustment due to the replacement of parts.

[0143] Fig.17 The simulation result of the temperature distribution of the irradiated object 90 when the irradiated object 90 is heated by the microwave irradiation device is shown. Fig.17 In the figure, the upper part shows the model used in the analysis, and the lower part shows the temperature distribution as the analysis result. (a) is a case where the non-powered antenna 50 and the auxiliary antenna 56 are not provided and only the power supply antenna 40 is provided. (b) is a case where the non-powered antenna 50 is not provided and the auxiliary antenna 56 is provided. (c) and (d) are cases where the non-powered antenna 50 is provided without the auxiliary antenna 56. Here, (c) is a case where the non-powered antenna 50 is configured in a manner that the gaps 54 provided in the two non-powered antennas 50 are both on the upper side, and (d) is a case where the non-powered antenna 50 is configured in a manner that one of the gaps 54 provided in the non-powered antenna 50 is on the upper side and the other is on the lower side.

[0144] In the case of using the auxiliary antenna 56 shown in (b), the temperature distribution changes significantly compared to the case of only the power supply antenna 40 shown in (a). This indicates that if the auxiliary antenna 56 is provided to adjust the resonant frequency, the temperature distribution will be affected. In the case of using the non-power supply antenna 50 shown in (c) and (d), a temperature distribution similar to the case of only the power supply antenna 40 shown in (a) is obtained. Therefore, it can be confirmed that by using the non-power supply antenna 50, the resonant frequency can be adjusted while suppressing the influence on the temperature distribution.

[0145] Comparison between (c) and (d) shows that the temperature distribution in the case of using multiple parasitic antennas 50 is affected by the position of the gap 54 provided in the parasitic antenna 50. When multiple parasitic antennas 50 are used, by arranging the parasitic antennas 50 so that the gaps 54 are on opposite sides, a temperature distribution close to that in the case of only the power supply antenna 40 can be obtained compared to the case of arranging the parasitic antennas 50 so that the gaps 54 are on the same side. It can be confirmed that by arranging the parasitic antennas 50 so that the gaps 54 are on opposite sides, the resonant frequency can be adjusted without affecting the temperature distribution.

[0146] From the above, it is considered that the method of adjusting the resonance frequency by adjusting the position of the parasitic antenna 50 is superior in terms of simplicity of device configuration and little influence on temperature distribution.

[0147] <Experimental Example 6>

[0148] In each device in which only the power supply antenna 40 is arranged and in which the auxiliary antenna 56 is arranged in addition to the power supply antenna 40 or in which no power supply antenna 50 is arranged, changes in the resonance frequency when the irradiated object 90 is transported are measured.

[0149] (method)

[0150] The length of the main housing 81 of the microwave irradiation device 1 along the conveying direction is set to 660 mm. The configuration of the side housing 82 and the conveyor belt 86 is the same as that of Experimental Example 2. The distance between the first power supply loop antenna 41 and the second power supply loop antenna 42 is set to 333 mm. When the power supply antenna 40 and the auxiliary antenna 56 are combined, the length of the auxiliary antenna is set to 480 mm, and the interval between the two auxiliary antennas is set to 150 mm. When the power supply antenna 40 and the non-power supply antenna 50 are combined, a non-power supply antenna 50 is arranged in the center at an equal distance from the two power supply antennas 40.

[0151] The irradiated object 90 is the same as in Experimental Example 2, and is an 85 mm polypropylene (PP) cup filled with 140 g of potato salad. One irradiated object 90 is arranged on the conveyor belt 86. Alternatively, three irradiated objects 90 are arranged on the conveyor belt 86 at intervals of 120 mm. In the case of one irradiated object 90, its center is set as the position of the irradiated object 90. In the case of three irradiated objects 90, the center of the central one is set as the position of the irradiated object 90. The irradiated object 90 is transported, and the resonant frequency is measured at each position at intervals of 82.5 mm from the end position of the main shell 81.

[0152] (result)

[0153] Fig.18The figure shows the change of the resonance frequency when one irradiated object 90 is transported. In any of the three-mode antenna configurations, the resonance frequency of the irradiated object 90 is the lowest at the center of the main shell 81, and the highest at the end of the main shell 81. When only the power supply antenna 40 is used, the maximum value of the resonance frequency is 496MHz, the minimum value is 489MHz, and the fluctuation range is 7MHz. When the auxiliary antenna 56 is used, the maximum value of the resonance frequency is 488MHz, the minimum value is 469MHz, and the fluctuation range is 19MHz. When the non-power supply antenna 50 is used, the maximum value of the resonance frequency is 457MHz, the minimum value is 454MHz, and the fluctuation range is 3MHz. That is, when the auxiliary antenna 56 is used, the fluctuation range of the resonance frequency accompanying the transport becomes larger than when only the power supply antenna 40 is used. On the other hand, when the non-power supply antenna 50 is used, the fluctuation range of the resonance frequency accompanying the transport becomes smaller than when only the power supply antenna 40 is used.

[0154] Fig.19 The figure shows the change of the resonance frequency when three irradiated objects 90 are transported. In any of the three-mode antenna configurations, the resonance frequency of the irradiated object 90 is the lowest at the center of the main shell 81, and the highest at the end of the main shell 81. When only the power supply antenna 40 is used, the maximum value of the resonance frequency is 494MHz, the minimum value is 477MHz, and the fluctuation range is 17MHz. When the auxiliary antenna 56 is used, the maximum value of the resonance frequency is 487MHz, the minimum value is 461MHz, and the fluctuation range is 26MHz. When the non-power supply antenna 50 is used, the maximum value of the resonance frequency is 455MHz, the minimum value is 448MHz, and the fluctuation range is 7MHz. That is, even when there are three irradiated objects 90, as in the case of one irradiated object 90, when the auxiliary antenna 56 is used, the fluctuation range of the resonance frequency accompanying the transport becomes larger than when only the power supply antenna 40 is used. On the other hand, when the non-power supply antenna 50 is used, the fluctuation range of the resonance frequency accompanying the transport becomes smaller than when only the power supply antenna 40 is used.

[0155] It can be confirmed that the resonance frequency can be adjusted and the fluctuation of the resonance frequency accompanying the transmission can be suppressed by using the parasitic antenna 50. Therefore, it can be known that the adjustment range of the output frequency of the microwave oscillator 10 can be narrowed by using the parasitic antenna 50, or the output frequency can be fixed for irradiation.

[0156] [Application of microwave irradiation device]

[0157] The microwave irradiation device 1 of each embodiment described above can be installed in a processing device for various purposes, or can be configured in an appropriate scheme. For example, in the case of heating and sterilizing sealed packaged food, the microwave irradiation device 1 is installed in a device configured to pressurize the irradiated object 90 as the sealed packaged food, or to keep it warm for the time required for sterilization. In addition, the microwave irradiation device 1 can be used for the manufacture of food, and the manufacture of the food includes: accommodating the food in a packaging container and sealing the packaging container, thereby becoming a packaging container food; and heating the packaging container food using the microwave irradiation device 1.

[0158] As mentioned above, although the present invention was described by showing the preferred embodiment, the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0159] In the above-mentioned embodiment, the shape and size of the non-powered antenna 50 are the same as those of the power feeding antenna 40, but the present invention is not limited thereto. For example, if the diameter of the non-powered loop antenna is increased, the resonant frequency is reduced, and if the diameter is reduced, the resonant frequency is increased, so the size of the non-powered antenna 50 may be changed so as to meet the required frequency band.

[0160] The above-mentioned embodiments show an example in which the reference axis as the directional irradiation axis of the power supply antenna 40 is horizontal, but the invention is not limited thereto. The reference axis may be set vertically or inclined relative to the horizontal, for example. For example, the power supply antenna 40 and the non-power supply antenna 50 may be set in a manner that the irradiated object 90 horizontally transported by the conveying device 85 is separated from the top and the bottom, and the power supply antenna 40 is used to irradiate the irradiated object 90 with microwaves from the top, the bottom or both. In addition, the conveying device 85 may also transport the irradiated object 90 in the vertical direction. For example, the microwave irradiation device 1 may also be configured such that the reference axis is vertical and the opening surface is horizontally provided with loop antennas as the power supply antenna 40 and the non-power supply antenna 50, and the irradiated object 90 transported by the conveying device 85 passes through these loop antennas in the vertical direction. In addition, the microwave irradiation device 1 may also be configured such that the irradiated object 90 is transported in the vertical direction by the conveying device 85 and passes between the antennas with the reference axis horizontally arranged. In this way, the reference axis, the conveying direction, etc. may be set arbitrarily.

[0161] Description of Reference Numerals

[0162] 1: Microwave irradiation device;

[0163] 10: Oscillator;

[0164] 21: coaxial cable;

[0165] 40: power supply antenna;

[0166] 41: first power supply loop antenna;

[0167] 42: second power supply loop antenna;

[0168] 50: No powered antenna;

[0169] 51: a first unpowered loop antenna;

[0170] 52: second unpowered loop antenna;

[0171] 56: Auxiliary antenna;

[0172] 60: Position adjustment mechanism;

[0173] 61: Control unit;

[0174] 62: supporting part;

[0175] 63: track;

[0176] 80: Metal shell;

[0177] 81: Main shell;

[0178] 82: side housing;

[0179] 85: conveying device;

[0180] 86: conveyor belt;

[0181] 90: Irradiated object.

Claims

1. A microwave irradiation device, comprising: a holding member configured to hold the irradiated object at a holding position; A power supply device configured to be in conduction with the oscillator; a power supply antenna configured to irradiate microwaves by powering via conduction of the power supply device, the power supply antenna having directivity such that an irradiation axis is arranged toward the holding position; and The non-powered antenna is disposed opposite to the power-supplying antenna across the holding position, has directivity such that an irradiation axis is disposed toward the holding position, but is not powered.

2. The microwave irradiation device according to claim 1, further comprising: The position adjustment mechanism is configured to change the relative distance between the non-powered antenna and the power supplied antenna.

3. The microwave irradiation device according to claim 2, wherein: The position adjustment mechanism is configured to change the position of the non-powered antenna.

4. The microwave irradiation device according to any one of claims 1 to 3, further comprising: The other power supply antenna is configured to irradiate microwaves by power supplying through conduction via the power supply device, and the other power supply antenna has directivity arranged with an irradiation axis toward the holding position.

5. The microwave irradiation device according to claim 4, further comprising: Another non-powered antenna is disposed opposite to the other powered antenna across the holding position, and has directivity with its irradiation axis directed toward the holding position but is not powered.

6. The microwave irradiation device according to claim 5, comprising: The position adjustment mechanism is configured to change the position of the other non-powered antenna.

7. The microwave irradiation device according to any one of claims 1 to 6, wherein: The powered antenna or the unpowered antenna is a loop antenna.

8. The microwave irradiation device according to claim 7, wherein: The holding member is provided so as to penetrate the loop antenna.

9. The microwave irradiation device according to any one of claims 1 to 8, wherein The holder has a conveying device configured to convey the irradiated object.

10. A microwave irradiation method, comprising: In the directional antennas arranged to face each other with the irradiation axis directed toward the irradiated object across the irradiated object, power is supplied to one antenna and not to the other antenna, so that the irradiated object is irradiated with microwaves.

11. The microwave irradiation method according to claim 10, further comprising: The impedance is adjusted by changing the distance between the directional antennas arranged opposite to each other.

12. The microwave irradiation method according to claim 11, wherein: The adjusting of the impedance includes: among the directional antennas arranged opposite to each other, the antenna supplying power does not move and the antenna not supplying power moves.

13. A method for producing a food, comprising heating the food using the microwave irradiation method according to any one of claims 10 to 12.

14. The method for producing a food according to claim 13, wherein: The food is a packaged container food.

15. The method for producing a food according to claim 14, further comprising: The food is placed in a packaging container and the packaging container is sealed to obtain the packaging container food.

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