Heating device and heating method

Abstract

To realize heating of an object to be heated in a short period of time with respect to a heating element capable of various configurations and forms in a heating device.SOLUTION: In a heating device 10 in which a microwave irradiation space MS is formed by arranging a heating element unit 130 in an opening 20A of a reflecting container 20 that reflects microwaves, an antenna 60 is arranged in the microwave irradiation space MS, and the axis is rotated.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heating apparatus that heats an object to be heated using a heating element that generates heat by absorbing microwaves.

Background Art

[0002] As a heating apparatus for firing organic substances, ceramics and the like, a heating apparatus utilizing microwaves is known (see Patent Document 1). In such an apparatus, a heating element in which a heating material made of carbon is filled in a tube is housed in a microwave reflecting container, and an object to be heated is arranged adjacent to the heating element. The carbon heating material absorbs microwaves oscillated by a microwave oscillator, whereby the heating element is heated, and the object to be heated can be heated, fired, dried, or the like.

Prior Art Literature

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The shape, form and the like of the heating element can be appropriately determined according to the configuration of the heating apparatus, the installation location of the heating element, the type of the object to be heated, the intended use, and the like. For example, the shape of the heating element can be not only tubular but also annular. On the other hand, since the heating element is characterized by generating heat at an early stage due to microwave absorption, it is desirable to heat the object to be heated in as short a time as possible.

[0005] Accordingly, there is a demand to enable heating of an object to be heated in a short time for heating elements that can have various configurations and forms.

Means for Solving the Problems

[0006] A heating device according to one aspect of the present invention comprises a container that reflects microwaves, a heating element arranged in the microwave irradiation space within the container and having a heating material that absorbs microwaves and generates heat, and an antenna.

[0007] The antenna of the present invention is configured as an antenna that is placed in a microwave irradiation space and capable of scattering microwaves radiated into the microwave irradiation space. The term "antenna" here does not include an antenna that acts as a primary radiator.

[0008] The antenna can be configured to bring the electric field strength distribution within the microwave irradiation space closer to an electric field strength distribution that equalizes the heating of the heating material. For example, by configuring the antenna to equalize, or approximate, the electric field strength distribution within the microwave irradiation space, the heating of the heating material can be made more uniform.

[0009] The antenna can be positioned in various configurations within the microwave irradiation space, and can be placed along the vertical direction of the container, closer to the center of the microwave irradiation space than the heating element, and above the bottom of the microwave irradiation space.

[0010] For example, the antenna can be positioned at least partially opposite the heating element. Furthermore, the waveguide that guides microwaves into the container, the antenna, and the heating element can be arranged side-by-side so that their positions at least partially overlap each other.

[0011] The antenna can be constructed in various shapes, and can include a plate section that extends across the microwave irradiation space. For example, it can be made in a propeller shape.

[0012] The antenna can be configured to change position within the microwave irradiation space. For example, the antenna can be configured to rotate on an axis at a constant rotational speed or while changing the rotational speed.

[0013] One aspect of the present invention is a heating method in which a heating element having a heating material that absorbs microwaves and generates heat is placed in a microwave irradiation space inside a container that reflects microwaves, and an antenna capable of scattering microwaves radiated into the microwave irradiation space is placed in the microwave irradiation space.

[0014] Another embodiment of the present invention is a heating device comprising a container that reflects microwaves, a heating element having a heating material that absorbs microwaves and generates heat, and an antenna positioned in the microwave irradiation space within the container. The antenna is configured to bring the electric field strength distribution in the microwave irradiation space closer to an electric field strength distribution that uniformly heats the heating material. [Effects of the Invention]

[0015] According to the present invention, in a heating device, it is possible to achieve rapid heating of the object to be heated using a heating element that can have various configurations and forms. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic internal diagram of a heating device, which is an embodiment of the present invention. [Figure 2] This is a schematic plan view of a heating element unit in which multiple heating elements are arranged adjacent to each other. [Figure 3] This figure shows the antenna in this embodiment. [Figure 4] This graph shows the rotational speed (angular velocity) when the antenna is rotated. [Figure 5A] This figure illustrates the electric field strength distribution when the antenna is positioned at a rotation angle of Φ0° to 50°. [Figure 5B] This figure illustrates the electric field strength distribution when the antenna is positioned at a rotation angle of Φ60° to 90°. [Figure 6] This figure shows the electric field strength distribution based on the simulation results. [Figure 7] This figure shows the sheet resistance measurement distribution of a silicon substrate. [Figure 8] This is a diagram showing the activation rate distribution of a silicon substrate. [Mode for Carrying Out the Invention]

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0018] Figure 1 is a schematic configuration diagram of a heating apparatus that is an embodiment of the present invention. Figure 2 is a schematic plan view of a heating element unit in which a plurality of heating elements are arranged adjacent to each other.

[0019] The heating apparatus 10 is an apparatus capable of heating, firing, or drying a heated object K using microwaves, and is configured herein as a microwave multiple reflection type heating apparatus. The heating apparatus 10 includes a heat-resistant cylindrical reflection container (cavity) 20 and a heating element 30, and further includes one or a plurality of microwave oscillators (not shown) and a power supply circuit (not shown) capable of controlling the microwave oscillators.

[0020] The reflection container 20 has a reflection surface (inner wall) 20R that reflects microwaves, and by installing the heating element 30 so as to close the opening 20A of the reflection container 20, an internal space (hereinafter referred to as a microwave irradiation space) MS is formed.

[0021] The support member 90 on which the heating element 30 is mounted can be detachably installed on the reflection container 20, and can be inserted from an insertion port (not shown) of the reflection container 20. A part of the bottom surface 20B of the reflection container 20 is connected to waveguides 50A and 50B that guide microwaves oscillated from the microwave oscillator to the reflection container 20.

[0022] The waveguides 50A and 50B herein have end portions 51A and 51B formed with horn portions (also referred to as flares) whose opening regions expand toward the vertical direction of the container (hereinafter also referred to as the longitudinal direction), and the end portions 51A and 51B respectively protrude from the bottom surface 20B of the reflection container 20. The microwaves oscillated from the microwave oscillator are radiated toward the reflection container 20 via the waveguides 50A and 50B.

[0023] In this case, the heating element 30 is configured as a heating element unit 130 in which multiple rod-shaped heating elements are arranged adjacent to each other (perpendicular to the plane of the paper), and is supported by a frame-shaped support member 90. The heating element 30 is a tubular member in which granular carbon CF, which absorbs microwaves and generates heat, is sealed and filled into an elongated heating tube 133, and the heating tube 133 is formed from a microwave-transmitting material (in this case, quartz glass).

[0024] The heating element 30 consists of a portion filled with carbon CF (heating portion) 131 and portions not filled with carbon CF (non-heating portions) 132A and 132B. Here, a unit is constructed by arranging 55 heating elements 30 of 24 different lengths, with the heating portions 131 of the heating elements 30 located at both ends having the shortest heating portions 131, and the heating elements 30 located in the middle having the longest heating portions 131.

[0025] In other words, as shown in Figure 2, when the heating element unit 130 is viewed from above, the heating element 30 is arranged in a circular shape in the area of ​​the heating portion 131, and the heating portion 131 fits within the area of ​​the opening 20A of the cylindrical reflective container 20. On the other hand, the non-heating portions 132A and 132B, which are supported by the support member 90, are outside the area of ​​the opening 20A.

[0026] The particle size and packing density of carbon CF in the heating tube 133, the type of noble gas sealed in the heating tube 133, and the gas pressure (sealing pressure) can be arbitrarily adjusted. For example, a packing density of 0.12, a particle size of 5 μm, Ar gas, and a gas pressure of 14 kPa can be set. The length and diameter of the heating tube 133 can also be appropriately determined depending on the size and arrangement of the reflecting container 20.

[0027] Alternatively, instead of constructing the heating element using a unit composed of multiple rod-shaped heating elements, the reflector container 20 may be miniaturized and constructed with a single rod-shaped heating element. Furthermore, the heating element may be constructed using a heating material other than powder or granular material. In addition, various configurations and forms are possible, such as a semi-circular heating element or a flat, integrated heating element.

[0028] A microwave irradiation space MS is formed below the heating element 30 (towards the center of the container), while a heating chamber (heating space) HS is formed above the heating element 30 in the reflecting container 20. The object to be heated K is placed in the heating chamber HS by a support member (not shown), and a reflector MR is formed on the ceiling surface 20T of the heating chamber HS. A window 120 for measuring the temperature with a radiation thermometer 110 is provided on the ceiling surface 20T.

[0029] When microwaves are emitted by the microwave oscillator, the heating element 30 facing the microwave irradiation space MS absorbs the microwaves and generates heat. The object to be heated K, placed in the heating space HS, is then heated by the heat generated by the heating element 30.

[0030] An antenna 60 is positioned in the microwave irradiation space MS formed by the reflective container 20 and the heating element 30. The antenna 60 is capable of re-radiating or reflecting microwaves guided into the microwave irradiation space MS, and is also capable of re-radiating (reflecting) microwaves reflected by the reflective container 20, and has the function of scattering and / or diffusing microwaves in the microwave irradiation space MS.

[0031] Figure 3 shows the antenna 60 in this embodiment. Here, the antenna 60 is configured as a propeller shape with the left-right direction (hereinafter also referred to as the lateral direction) of the reflecting container 20 as its longitudinal direction, and extends to traverse the microwave irradiation space MS along the left-right direction.

[0032] The antenna 60 comprises two rectangular plate sections 80A and 80B, with a shaft 65 connected between them. The plate sections 80A and 80B are identical in size and shape, and are symmetrically arranged with respect to the z-direction (shaft 65). Furthermore, the plate sections 80A and 80B are tilted at predetermined angles θL and θR with respect to the z-direction, and are mounted so that they face the same direction. For example, angles θL and θR can be set to 45° each.

[0033] An insulating shaft 65, such as one made of ceramic, is attached to the antenna 60 along a center line, with the midpoint of the length L, including both plate sections along the longitudinal direction, being the center line. Therefore, the antenna 60 is symmetrical with respect to the shaft 65, and since the above line coincides with the central axis C along the vertical direction of the reflecting container 20, it is also coaxially positioned with respect to the reflecting container 20.

[0034] The antenna 60 is rotatable and is insulated from the reflecting container 20 by being positioned above the bottom surface 20B of the reflecting container 20. The shaft 65 is connected to a servo motor (not shown), and a controller (not shown) controls the servo motor. This allows the position (angle), rotation speed, acceleration and deceleration, and operating time of the antenna 60 to be set and adjusted. The rotation of the antenna 60 may also be controlled by means other than the servo motor. Because of the need to withstand such rotational control and heating, the antenna 60 is preferably made of a lightweight, heat-resistant metal, such as titanium or stainless steel.

[0035] The length L of the antenna 60 along the left-right direction of the container is determined so that both ends are located near the inner wall 20R of the reflective container 20, and may be determined to match the length of the heating element 30. The height H along the vertical direction up to the antenna 60 (the connection point between the plate center line and the shaft) is determined so that both ends of the antenna 60 in the shorter direction are located near the heating element 30. The width W of the antenna 60 can be, for example, a width that allows the shaft 65 to be attached.

[0036] The antenna 60 is positioned so that at least a portion of it faces the heating element unit 130 along the vertical direction of the container. Furthermore, a portion of the antenna 60 is also positioned so that it faces the waveguides 50A and 50B (waveguide ends 51A and 51B). Therefore, when viewed from the vertical direction of the container, the antennas 60 are aligned so that their positions overlap each other.

[0037] In Figure 1, the antenna 60 is positioned at a predetermined angle. Here, the xyz coordinate system is defined with the origin near the radial center of the reflecting container 20 (along the central axis C line), and the x direction is defined as the direction in which the heating element 30 extends.

[0038] The antenna 60 installed inside the reflecting container 20 can change the electric field strength distribution by rotating on its axis (see arrow in Figure 1), scattering microwaves that are primarily radiated to the microwave irradiation space MS through waveguides 50A and 50B, as well as microwaves reflected by the reflecting container 20.

[0039] Here, the antenna 60 is configured to equalize the electric field strength distribution by rotating its axis. Specifically, the antenna 60 functions to equalize, or approximate, the two-dimensional electric field strength distribution when viewed in the xy coordinate system.

[0040] As the electric field strength distribution becomes more or nearly equal, the microwaves in the microwave irradiation space MS are absorbed evenly by the heating element 30 which traverses the container horizontally. Because the heating element 30 heats up evenly throughout, uniform heating can be achieved for the object K being heated.

[0041] In particular, because the antenna 60 is positioned opposite the heating element 30 and is placed between the waveguides 50A and 50B, they are aligned along the same line, which effectively enables microwave absorption by the heating element 30.

[0042] Furthermore, the reflective container 20 is divided into a heating chamber HS and a microwave irradiation space MS by a heating element 30. Therefore, without considering the placement of the object to be heated K, the antenna 60 can be placed in the center of the reflective container 20 and set to have a shape with a transverse length, and the size and placement position of the antenna 60 can be easily set.

[0043] Thus, according to this embodiment, in a heating device 10 in which a microwave irradiation space MS is formed by arranging a heating element unit 130 in the opening 20A of a reflective container 20 that reflects microwaves, the antenna 60 is positioned in the microwave irradiation space MS and rotates on an axis.

[0044] The antenna 60, which is configured in the propeller shape described above, is just one example of how to equalize the electric field strength distribution, and it is also possible to configure the antenna 60 in other shapes. For example, it is possible to use a rectangular plate and attach a shaft 65 to its short side to allow it to rotate on an axis, or to arrange a rectangular plate along the side of the container and attach it to the upper end of the shaft 65, or to configure the antenna 60 with an L-shaped plate.

[0045] Furthermore, it is also possible to make the antenna 60 a triangular plate and attach the shaft 65 near the center of the base of the plate. On the other hand, it is also possible to apply any plate shape with a surface as appropriate, and depending on the antenna shape, the antenna may not rotate (no rotation) or may rotate on the horizontal axis.

[0046] Antenna 60 can rotate around its axis while changing its rotational speed. Therefore, the rotational speed can be modulated so that the electric field strength distribution becomes equal or approaches equal. Specifically, the electric field strength distribution when antenna 60 completes one rotation (0° to 360°) while changing the rotation angle Φ can be calculated or measured using simulations, and the rotational speed at a position where the electric field strength distribution is relatively equalized can be reduced compared to the rotational speed at a position where the electric field strength distribution is relatively biased.

[0047] Furthermore, in addition to a configuration that equalizes the electric field strength distribution by axially rotating such an antenna 60, a configuration that equalizes the electric field strength distribution by changing the position of the antenna through movements other than axial rotation, such as rotation or reciprocating motion, is also possible. In this case, an actuator and control mechanism should be provided that are appropriate to the position change and movement of the antenna. Moreover, it is also possible to equalize the electric field strength distribution while fixing the antenna position by making the shape of the antenna a shape with multiple plate shapes or other complex curved surfaces.

[0048] The above explanation describes a configuration aimed at equalizing the electric field strength distribution. However, depending on the shape and configuration of the heating element 30, it may be more effective to create localized biases in the electric field strength to achieve uniform heating of the heating element 30. For example, if a spherical heating element is configured, the antenna arrangement and position fluctuation control should be performed to create biases in the electric field strength distribution so that the heating of such a spherical heating element becomes uniform. It is also possible to achieve this by fixing the position of the antenna. The object to be heated K can be heated in a short time without being limited by the configuration or shape of the heating element 30. In other words, it is sufficient to provide an antenna equipped with a function to achieve uniform heating.

[0049] In this embodiment, the heating device is configured with a container that separates the heating chamber from the microwave irradiation space. However, an inner cylinder may be provided inside the reflective container, and the microwave irradiation space MS may be formed by the inner cylinder and the heating element. Furthermore, it is also possible to configure the device so that the microwave irradiation space MS serves as the heating chamber without providing a separate heating chamber HS.

[0050] On the other hand, it is also possible to configure a heating device in which the inside of the container is formed as a microwave irradiation space that also serves as a heating space. Alternatively, instead of radiating microwaves into the microwave irradiation space through a waveguide, a primary radiator (antenna) that radiates microwaves emitted from a microwave oscillator into the microwave irradiation space (MS) may be provided near the microwave irradiation space.

[0051] The following describes the antenna rotation speed (angular velocity) and electric field strength distribution obtained from simulations for the given examples. [Examples]

[0052] Example 1 is a heating device corresponding to this embodiment, and a model of a heating device equipped with a propeller-type antenna was constructed. In this model, the diameter of the reflecting container 20 is 330 mm, the height to the heating element 30 is 198 mm, the longitudinal length of both plates of the antenna is 280 mm, the transverse length is 30 mm, the angle θL of plate 80A is 45°, the angle θR of plate 80B is -45°, and the height H to the antenna (connection between the plate center line and the shaft) is 105 mm.

[0053] Figure 4 is a graph showing the rotational speed (angular velocity) when the antenna 60 is rotated. As shown in Figure 4, there is no significant change in rotational speed between 0° and 70°, but the rotational speed decreases from 70° to 90°. The rotational speed is similarly modulated between 90° and 180°, 180° and 270°, and 270° and 360°. However, the position of the antenna 60 in Figure 3 is defined as 0°. [Examples]

[0054] Next, we will describe the electric field strength distribution obtained by simulation for Example 2.

[0055] The heating device in Example 2 was modeled the same as in Example 1, except that the angles θL and θR of the plate portion of the propeller-shaped antenna were set to 45° each, and the height H to the antenna was 100mm. The electric field strength distribution was measured using a heat generation analysis simulator software when the input power during microwave oscillation was 3000W.

[0056] Figure 5 is an illustrative diagram showing the electric field strength distribution when the antenna 60 is positioned at a rotation angle of Φ0° to 90°. As shown in Figures 5A(A) and 5B(J), when the antenna 60 is positioned at 90°, the bias in the strength distribution is less compared to when it is positioned at 0°. Therefore, by controlling the rotation speed as shown in Figure 4, the equalization of the electric field strength distribution can be further achieved during the axial rotation of the antenna 60.

[0057] Figure 6 shows the electric field strength distribution obtained from the simulation. Figure 6(A) shows the average electric field strength distribution in the xy coordinate system when the antenna is rotated axially by the optimal speed modulation shown in Figure 4. Figure 6(B) shows the electric field strength distribution when the antenna is rotated axially at a constant rotational speed. Figure 6(C) shows the electric field strength distribution when no antenna is provided. It was confirmed that when an antenna is provided and rotated axially, the electric field strength distribution is more uniform compared to when no antenna is provided. Furthermore, it was confirmed that modulating the rotational speed results in a more uniform electric field strength distribution than when the antenna is rotated at a constant speed. [Examples]

[0058] Next, we will describe the results of a heating experiment on a phosphorus-doped silicon substrate using Example 3.

[0059] Example 3 differs from the heating device models shown in Examples 1 and 2 in that it is configured as an actual prototype heating device. Except for adjusting the height H to the antenna to 100 mm, the configuration is the same as the heating device model in Example 1. A 300 mm diameter silicon substrate with phosphorus added was heated at 800°C for 170 seconds. The sheet resistance of the heated silicon substrate was then measured to obtain the sheet resistance distribution.

[0060] Figure 7 shows the sheet resistance measurement distribution. Figure 7(A) shows the sheet resistance measurement distribution in the xy coordinate system when the antenna is rotated on the axis by modulating the rotational speed in the same manner as in this embodiment. Figure 7(B) shows the sheet resistance measurement distribution when no antenna is provided. It was confirmed that when the antenna is provided and rotated on the axis, the sheet resistance decreases over a wider area compared to when no antenna is provided.

[0061] Figure 8 shows the electron mobility of the silicon substrate used in Example 4 at 120 cm². 2 This figure shows the activation rate distribution when / Vs is used. Figure 8(A) shows the activation rate distribution in the xy coordinate system when the antenna is rotated on the axis by modulating the rotational speed in the same way as in this embodiment. Figure 8(B) shows the activation rate distribution when no antenna is provided. It was confirmed that when an antenna is provided and rotated on the axis, the activation rate is higher over a wider area compared to when no antenna is provided.

[0062] Thus, the effect of more uniformizing the microwave field strength distribution was revealed, and this uniformity of field strength was achieved by introducing a suitable rotating antenna. Furthermore, it was shown that rotational speed modulation enables more uniform heating of the object being heated. [Explanation of Symbols]

[0063] 10 Heating device 20 Reflecting container (cavity) 30 Heating element 60 Antennas MS microwave irradiation space K Heated object

Claims

1. A container that reflects microwaves, A heating element is provided, which is placed in the microwave irradiation space within the container and contains a heating material that absorbs microwaves and generates heat, filled into a microwave-transmitting tube. The system includes an antenna positioned in the microwave irradiation space and capable of scattering microwaves radiated into the microwave irradiation space, The heating element is positioned inside the container such that the container is divided into a microwave irradiation space and a heating space where the object to be heated is located. The heating device is characterized in that the object to be heated is placed in the heating space by a support member at a distance from the heating element so that the heat generated by the heating element is transferred to the object to be heated through the space between the object to be heated and the heating element.

2. The heating apparatus according to claim 1, characterized in that the antenna brings the electric field strength distribution in the microwave irradiation space closer to an electric field strength distribution that uniformly heats the heating material.

3. The heating apparatus according to claim 1 or 2, characterized in that the antenna equalizes or approximates the electric field strength distribution in the microwave irradiation space.

4. The heating device according to any one of claims 1 to 3, characterized in that the antenna is positioned at least partially opposite the heating element.

5. The container further comprises a waveguide for guiding microwaves into the container. The heating device according to any one of claims 1 to 4, characterized in that the waveguide, the antenna, and the heating element are arranged side by side such that their positions overlap at least partially.

6. The heating device according to any one of claims 1 to 5, characterized in that the antenna is positioned along the vertical direction of the container, on the central side of the microwave irradiation space relative to the heating element, and above the bottom of the microwave irradiation space.

7. The heating apparatus according to any one of claims 1 to 6, characterized in that the antenna has a plate portion that extends across the microwave irradiation space.

8. The heating device according to any one of claims 1 to 7, characterized in that the antenna is capable of changing position.

9. The heating device according to any one of claims 1 to 8, characterized in that the antenna is capable of axial rotation at a constant rotational speed or while changing the rotational speed.

10. A heating element is placed inside a microwave-reflecting container, with a microwave-transmitting tube filled with a heating material that absorbs microwaves and generates heat. This divides the inside of the container into a microwave irradiation space and a heating space where the object to be heated is located. The object to be heated is placed in the heating space by a support member at a distance from the heating element, such that the heat generated by the heating element is transferred to the object to be heated through the space between the object to be heated and the heating element. An antenna capable of scattering microwaves radiated into the microwave irradiation space is placed in the microwave irradiation space. A heating method characterized by the following features.

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