Patent Application
20230217559
The present invention relates to a microwave processing apparatus and a microwave processing method that irradiates an object located in a cavity having a cylindrical shape with microwaves.
Conventionally, by irradiating and heating an object (object to be heated) in a predetermined cavity with microwaves, the object is dried or subjected to a reaction, for example (see Patent Document 1). Note that microwave heating can realize selective heating, and thus is characterized by being able to fast heat an object from within and having a high heating efficiency.
[Patent Document 1] JP 2019-125534A
However, there may be a possibility that a region to be heated is partially and locally heated depending on the microwave irradiation direction or the like. Therefore, there is a demand for heating a region to be heated more uniformly.
The present invention was made in view of the above-described circumstances, and it is an object thereof to provide a microwave processing apparatus and a microwave processing method that can realize, when irradiating an object located in a cavity having a cylindrical shape with microwaves, more uniform microwave irradiation of a region to be heated.
To achieve the above-described object, according to an aspect of the present invention, a microwave processing apparatus includes: a cavity that has a cylinder-like shape, and includes an internal space for accommodating a microwave irradiation object, the cavity being provided with a microwave passage area in a partial region in an axial direction; a microwave generator configured to generate microwaves; a rotary member that is provided on an outer circumferential side of the cavity so as to be rotatable, and includes, on an outer circumferential side of the microwave passage area, a cylinder-like member having a cylindrical shape and has a plurality of areas through which microwaves can pass; and a cover member that is provided while covering the entire cylinder-like member in a circumferential direction, and forms, on an outer circumferential side of the cylinder-like member, a wave guidepath for the microwaves introduced from the microwave generator.
With this configuration, it is possible to emit microwaves that propagate in the wave guidepath formed around the cylinder-like member to an object located inside the cavity from the plurality of areas through which microwaves can pass and that are formed in the rotatable cylinder-like member. Therefore, the microwaves are emitted to a region of the object that is to be heated from various positions in the circumferential direction, resulting in realization of more uniform microwave irradiation of a region to be heated.
Also, the microwave processing apparatus according to the aspect of the present invention, the areas of the cylinder-like member through which microwaves can pass may be slit-shaped areas.
With this configuration, similar to microwaves leaking from slots of a leakage waveguide, microwaves can be emitted to the object located inside the cavity more uniformly
Also, the microwave processing apparatus according to the aspect of the present invention, the slit-shaped areas may extend in the circumferential direction of the cylinder-like member.
With this configuration, it is possible to realize more efficient microwave irradiation than in a case where the slit areas extend in the axial direction of the cylinder-like member.
Also, the microwave processing apparatus according to the aspect of the present invention, the microwave passage area may be constituted by a member made of a microwave transmitting material.
With this configuration, even if, for example, water vapor, gas, or the like is generated in response to heating of the object, it is possible to prevent such water vapor, gas, or the like from moving toward the microwave generator. As a result, it is possible to prevent failures of the microwave generator, and the like.
Also, the microwave processing apparatus according to the aspect of the present invention, the microwave passage area may be provided over the entire portion of the cavity in a circumferential direction.
With this configuration, it is possible to irradiate the object with microwaves in all circumferential directions, realizing more uniform irradiation of the entire object with microwaves.
Also, according to an aspect of the present invention, a microwave processing method includes the steps of; rotating, on an outer circumferential side of a microwave passage area provided in a partial region of a cavity in an axial direction, a cylinder-like member that has a cylindrical shape and has a plurality of areas through which microwaves can pass, the cavity having a cylinder-like shape and including an internal space for accommodating a microwave irradiation object; and introducing microwaves into a wave guidepath for microwaves, and irradiating the microwave irradiation object located in the cavity with the microwaves, the wave guidepath for microwaves being formed on an outer circumferential side of the cylinder-like member by a cover member provided while covering the entire cylinder-like member in a circumferential direction.
With the microwave processing apparatus according to the aspect of the present invention, it is possible to realize more uniform microwave irradiation to a region to be heated of an object in a cavity.
Hereinafter, the microwave processing apparatus and the microwave processing method according to the present invention will be described with reference to an embodiment. Note that in the following embodiment, constituent components denoted by the same reference numerals are identical or correspond to each other, and thus redundant descriptions may be omitted. In the microwave processing apparatus according to the present embodiment, a microwave passage area is provided in a part of a cavity having a cylindrical shape in an axial direction thereof, and a wave guidepath for microwaves is formed over the entire outer circumference of the passage region in a circumferential direction. An object located in the cavity is irradiated with microwaves propagating in the wave guidepath via a cylindrical member that rotates on the outer circumferential side of the microwave passage area in the circumferential direction, and has a plurality of regions through which microwaves can pass.
The microwave processing apparatus 1 according to the present embodiment includes the cavity 11, the rotary member 12, the cover member 13, the microwave generator 14, and a rotary drive unit 15. Any type of object 5 may be irradiated with and heated by microwaves. The object 5 may be, for example, an elongated solid object, an elongated hollow object, or another type of elongated object. Note that, for example, one elongated object 5 or two or more elongated objects 5 may be put into the cavity 11. The object 5 may also be an object other than an elongated one, such as a granular solid, powder, or fluid, for example. The object 5 such as a granular solid, powder, or fluid may flow in a pipe or the like laid inside the cavity 11, for example. The pipe or the like may be made of a microwave transmitting material. Examples of the microwave transmitting material will be given later. In a case where the object 5 is an elongated object, a configuration for supporting the object 5 may also be provided inside or outside the cavity 11. Preferably, the object 5 is arranged near the central axis of an internal space 11c of the cavity 11.
While being irradiated with microwaves, the object 5 arranged in the internal space 11c of the cavity 11 may or may not move. That is to say, processing performed by irradiating the object 5 with microwaves may be continuous processing or batch processing. When continuous processing is performed on the object 5, the object 5 may continuously move, or may repeat moving and stopping, for example. When continuous processing is performed on the object 5, a mechanism for transporting the object 5 may be provided inside or outside the cavity 11, for example.
The irradiation of the object 5 with microwaves may be performed, for example, to dry the object 5, or may be performed to melt, sublimate, or evaporate the object 5. The irradiation of the object 5 with microwaves may also be performed to subject the object 5 to a reaction, to sterilize the object, or for other usages. The reaction of the object may be a chemical reaction, for example.
The cavity 11 is a cavity that has a cylindrical shape and includes the internal space 11c for accommodating the object 5 to be irradiated with microwaves. In the internal space 11c of the cavity 11, the object 5 is irradiated with microwaves. The mode of microwaves in the space 11c is typically a multimode. As shown in
The cavity main body 11a is preferably a component through which no microwave pass. The cavity main body 11a may be made of a microwave reflective material. The microwave reflective material may be a metal, for example. The metal is not particularly limited, and may be, for example, a stainless steel, a carbon steel, nickel, a nickel alloy, copper, a copper alloy, or the like. As shown in
When continuous processing is performed on an object 5, an entrance and an exit through which the object 5 is passed may be provided at end portions of the cavity 11 in the axial direction. Also, to prevent microwaves inside the cavity 11 from leaking to the outside, the entrance and the exit may also be provided with a mechanism for preventing leakage of microwaves such as a choke structure. Also, when irradiation with microwaves is performed in batch processing, the end portions of the cavity 11 in the axial direction may be closed. Note that, for example, the end portions may also be openable and closable, in order for an operator to bring the object 5 into and out of the cavity 11.
The microwave passage area 11b may be an open area without any substance for example, or may be constituted by a member made of a microwave transmitting material. The present embodiment will mainly describe the latter case, that is, a case where the microwave passage area 11b is constituted by a member that has a cylindrical shape and is made of a microwave transmitting material. As a result of the microwave passage area 11b being closed in this manner, it is possible to prevent water vapor, gas, and the like generated by heating the object 5 arranged in the internal space 11c of the cavity 11 from flowing toward the microwave generator 14 via the microwave passage area 11b, making it possible to prevent failures of the microwave generator 14, or the like. Accordingly, it is preferable that no gap be formed between the microwave passage area 11b, which is a member that has a cylindrical shape and is made of a microwave transmitting material, and the cavity main body 11a. The cavity main body 11a and the microwave passage area 11b, which is a member having a cylindrical shape, may also be connected to each other by screw fastening, bonding, or the like, for example.
A microwave transmitting material is a material having a small relative dielectric loss, and may be, without being specifically limited to, a fluoroethylene resin such as polytetrafluoroethylene, quartz, glass, or the like, for example. The relative dielectric loss of the microwave transmitting material is preferably less than 1, more preferably less than 0.1, and further preferably less than 0.01, under, for example, the frequency and the temperature of microwaves during operation of the microwave processing apparatus 1.
Within the cavity 11, air may be blown in the axial direction. If, for example, the object 5 is dried by microwave irradiation, the air blow may discharge humid air. Also, the object 5 may be preliminarily heated by a heating means other than microwaves before being irradiated with microwaves. A heating means other than microwaves may be, for example, an electric heater, a gas heater, or the like.
The rotary member 12 is a member that has a cylindrical shape and is provided on the outer circumferential side of the cavity 11 so as to be rotatable, and includes, as shown in
The cylindrical member 12a is a member having a cylindrical shape, and is arranged on the outer circumferential side of the microwave passage area 11b. Note that the length of the cylindrical member 12a in the axial direction, and the length of the microwave passage area 11b in the axial direction are preferably the same. Also, the position of the cylindrical member 12a in the axial direction and the position of the microwave passage area 11b in the axial direction are preferably the same. As shown in
Note that, in order for microwaves to efficiently pass through the areas 12c from a wave guidepath 13b formed by the cover member 13 and enter into the cylindrical member 12a, the slit-shaped areas 12c preferably extend in the circumferential direction of the cylindrical shape. It is also preferable that the distances, in the circumferential direction and the axial direction, between the slit-shaped areas 12c extending in the circumferential direction be set so as to allow microwaves to easily enter the inside of the cylindrical member 12a. The distances may be, for example, the same distances as those in well-known leakage waveguides, which are square-shaped waveguides provided with, in a surface thereof, a plurality of slit-shaped slots extending in the longitudinal direction.
The rotating support members 12b support the cylindrical member 12a, and as a result of the rotating support members 12b rotating on the outer circumferential side of the cavity 11, the cylindrical member 12a is rotated together. Accordingly, the rotating support members 12b support the cylindrical member 12a so that the cylindrical member 12a is rotatable on the outer circumferential side of the microwave passage area 11b.
The cylindrical member 12a excluding the plurality of areas 12c, and the rotating support member 12b are preferably made of a material that does not allow passage of microwaves. The cylindrical member 12a excluding the plurality of areas 12c, and the rotating support members 12b may be made of a microwave reflective material. The microwave reflective material may be a metal, for example. Examples of the metal are as described above.
The cover member 13 is provided while covering the entire cylindrical member 12a in the circumferential direction. The cover member 13 does not rotate with respect to the cavity 11. Therefore, the rotary member 12 rotates in the circumferential direction between the cavity 11 and the cover member 13. As shown in
The wave guidepath 13b has an opening 13c for introducing microwaves generated by the microwave generator 14. The cover member 13 may have a waveguide 13a connected to the opening 13c. Also, by the waveguide 13a, the microwaves from the microwave generator 14 are guided to the wave guidepath 13b. As shown in
The cross section taken along a plane perpendicular to the circumferential direction of the wave guidepath 13b preferably has the same size as the cross section of a square waveguide suitable for the frequency of microwaves that propagate in the wave guidepath 13b. For example, if microwaves of 2.45 GHz propagate in the wave guidepath 13b, the length of the wave guidepath 13b in the axial direction may be 109.2 (mm), and the length of the wave guidepath 13b in the radial direction may be 54.6 (mm).
Preferably, the cover member 13 is a member through which no microwave pass. The cover member 13 may be made of a microwave reflective material. The microwave reflective material may be a metal, for example. Examples of the metal are as described above.
Note that the present embodiment shows a case where the outer shape of the cover member 13 is a cylindrical shape, but the cover member 13 does not need to have such a shape. The outer shape of the cover member 13 may also be a cuboid shape or the like. Even in this case, the inner circumferential surface of the cover member has a cylindrical shape since the inner circumferential surface of the cover member forms the wave guidepath 13b or allows the rotary member 12 to rotate.
As shown in
Also, choke structures 31, 32 shown in
Also, the cavity 11, the cylindrical member 12a, the rotating support members 12b, the inner circumferential surface of the wave guidepath 13b of the cover member 13, and the inner circumferential surface of the portion of the cover member 13 that faces the outer circumferential surface of the rotary member 12 are preferably concentric. Also, the rotation axis of the rotary member 12 preferably matches the central axes of the cavity 11 and the like.
The microwave generator 14 generates microwaves. The microwave generator 14 may use, for example, magnetron, klystron, gyrotron, or the like to generate microwaves, or may use a semiconductor element to generate microwaves. Microwaves may have a frequency of, for example, 915 MHz, 2.45 GHz, 5.8 GHz, or 24 GHz, or may have another frequency in a range from 300 MHz to 300 GHz. Also, the intensity of microwaves may be controlled as appropriate by a not-shown control unit. The control may be feedback control that uses sensing results such as, for example, the temperature in the cavity 11, the temperature of the object 5, and the amount of moisture of the object 5.
The rotary drive unit 15 rotates the rotary member 12 with respect to the cavity 11. The rotary drive unit 15 may be, for example, a motor or the like. The rotary drive unit 15 may be fixed, for example, to the cover member 13 as shown in
The rotary drive unit 15 may or may not rotate the rotary member 12 at a constant rotation speed. Also, if the rotary member 12 is rotated in one direction and continuous processing is performed, the rotary drive unit 15 may rotate the rotary member 12 at a rotation speed at which, for example, the rotary member 12 is rotated by 360 degrees or more while the object 5 moves for the length of the wave guidepath 13b in the axial direction. Also, if the rotary member 12 is rotated in one direction, continuous processing is performed, and the areas 12c of the cylindrical member 12a are M-fold symmetric (that is, the positions of the areas 12c match each other when the cylindrical member 12a is rotated by (360/M) degrees), the rotary drive unit 15 may rotate the rotary member 12 at a rotation speed at which, for example, the rotary member 12 is rotated by (360/M) degrees or more while the object 5 moves for the length of the wave guidepath 13b in the axial direction. Here, M is an integer number of 2 or more.
The following will briefly describe a method in which the microwave processing apparatus 1 according to the present embodiment irradiates the object 5 with microwaves. In a case of batch processing, the object 5 is arranged in the cavity 11 so as to be in a resting state, and in a case of continuous processing, the object 5 is moved in the axial direction in the cavity 11. Then, microwaves are generated by the microwave generator 14, and the rotary member 12 is rotated by the rotary drive unit 15. As a result, the microwaves guided from the microwave generator 14 to the wave guidepath 13b are emitted to the object 5 via the areas 12c of the rotating cylindrical member 12a and the microwave passage area 11b. Here, since the cylindrical member 12a rotates on the outer circumferential side of the cavity 11, the microwaves are emitted to the object 5 from various positions in the circumferential direction. As a result, it is possible to realize uniform irradiation of the object 5 with the microwaves.
As described above, according to the microwave processing apparatus 1 of the present embodiment, by irradiating the object 5 inside the cavity 11 with microwaves that propagates in the wave guidepath 13b provided on the outer circumferential side of the cavity 11, via the plurality of areas 12c of the cylindrical member 12a rotating on the inner circumferential side of the wave guidepath 13b, it is possible to realize more uniform heating of the object 5. As a result, it is possible to realize more uniform drying of the object 5, and more uniform reaction of the object 5, for example. Note that, as described above, the microwave passage area 11b may be provided in a partial portion of the cavity 11 in the circumferential direction. Specifically, the microwave passage area 11b may only be provided in a lower portion of the cavity 11. In this case, the object 5 is irradiated with microwaves only from below, but this irradiation is made via the plurality of areas 12c, through which microwaves can pass, of the rotating cylindrical member 12a, and thus it is possible to realize more uniform heating of a region of the object 5 (in this case, the lower region, for example) that is to be subjected to microwave irradiation.
Note that the present embodiment has described a case where irradiation with microwaves is performed at one position of the cavity 11 in the axial direction, but irradiation with microwaves may also be performed at two or more positions of the cavity 11 in the axial direction. In this case, microwave passage areas 11b and the cylindrical member 12a may be provided at two or more positions of the cavity 11 in the axial direction, and wave guidepaths 13b for microwaves may be formed at the two or more positions. Note that, for example, one rotary member 12, one cover member 13, and one rotary drive unit 15 may be provided for each wave guidepath 13b for microwaves, or may be provided for a plurality of wave guidepaths 13b for microwaves. In the latter case, the rotary member 12 includes a plurality of cylindrical members 12a, and the cover member 13 forms a plurality of wave guidepaths 13b. Also, when irradiation with microwaves is performed at two or more positions of the cavity 11 in the axial direction, the microwave processing apparatus 1 may include one microwave generator 14, or may include a plurality of microwave generators 14. In the former case, microwaves generated by one microwave generator 14 may be branched and emitted. Also, when a plurality of microwave generators 14 are used, microwaves generated by the microwave generators 14 may have the same frequency, or may have different frequencies.
Also, the present embodiment has described a case where microwaves generated by the microwave generator 14 are introduced into the wave guidepath 13b by the waveguide 13a, but microwaves generated by the microwave generator 14 may be introduced into the wave guidepath 13b by another transmission means such as a coaxial cable. When microwaves are transmitted by a coaxial cable, an antenna for radiating microwaves that is connected to the coaxial cable may be provided in the wave guidepath 13b.
Also, the present embodiment has described a case where the length of the rotary member 12 in the axial direction is larger than that of the cover member 13, but another configuration is also possible. The length of the cover member 13 in the axial direction may be larger than that of the rotary member 12 as long as a mechanism for rotating the rotary member 12 can be installed.
Also, the present embodiment has been described on the assumption that the cavity 11 is cylindrical, that is to say, the cross section of the cavity 11 that is perpendicular to the axial direction thereof has the shape of a precise circle, but the cavity 11 may have a cross section having a shape slightly deviated from a precise circle, for example, an ellipsoidal shape or a regular polygonal shape, and the shape of the cavity 11 may be sometimes referred to as a “cylinder-like shape”. In the latter case, also the rotary member 12 may have a cylinder-like shape whose cross section perpendicular to the axial direction is slightly deviated from a precise circle, and the rotary member 12 may be rotatable on the outer circumferential side of the cavity 11.
It will be appreciated that the present invention is not limited to the above-described embodiments, and various modifications are possible which are intended to be encompassed within the scope of the present invention.
As described above, the microwave processing apparatus and the microwave processing method according to the aspects of the present invention can achieve effects of enabling more uniform irradiation of an object in a cavity with microwaves. The present invention is useful for a microwave processing apparatus and a microwave processing method that irradiates an object with microwaves.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP 2020-020275 | Feb 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/004921 | 2/10/2021 | WO |
