JP2005050644A - Microwave heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved microwave heating device with a broad width and thin wall thickness, uniformly and effectively heating an object to be heated having a large microwave loss. <P>SOLUTION: The microwave heating device is constructed so as to excite a microwave in resonance mode generating a constant electric field in one direction in a resonance cavity 1, and to make the object to be heated W absorb a leaked power by generating leakage power having uniform electric field generated at the inside of the cavity 1, by forming a leakage hole 7 on a part of a side wall 6 of the resonance cavity 1 from which, a part of microwave leaks. By the above, a uniform microwave heating with high efficiency can be applied even to the object to be heated having a relatively large microwave loss. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a microwave heating apparatus that can uniformly and efficiently heat a sheet-like object to be heated.

Since microwaves can be heated by directly raising the temperature of an object to be heated, rapid and efficient heating is possible. However, it is generally difficult to heat the object to be heated uniformly. For example, Patent Document 1 discloses a technique for drying a ceramic green sheet with a microwave heating and drying apparatus. In this method, the ceramic green sheet before drying is dried by being irradiated with microwaves while being transported on a belt in a microwave heating and drying apparatus. However, in general, when the heated object is a thin sheet, the thickness of the sheet is thin, so that the microwave power absorbed by the sheet is reduced, so that it is more difficult to heat efficiently. The same applies to the microwave heating and drying apparatus described in Patent Document 1, and sufficient uniform and efficient heating cannot be expected. For this reason, there is a strong demand for high-efficiency and uniform heating using microwaves.
JP 7-294122 A

  The present invention solves the disadvantages in the prior art as described above, and is improved in that uniform and efficient heating can be performed even on an object to be heated that is wide, thin, and has a large microwave loss. Another object is to provide a microwave heating apparatus.

  By exciting a resonance mode microwave that generates a constant electric field in one direction in the resonance cavity 1, and providing a leak hole 7 through which a microwave leaks in a part of the side wall 6 of the resonance cavity 1, The apparatus is configured to generate a uniform electric field leakage from inside the cavity 1 and to absorb the leakage power in the heated object W. By this method, uniform and highly efficient microwave heating can be performed even on an object to be heated W with relatively large loss.

  In the present invention, the object to be heated W is irradiated with microwaves leaking from the leak hole 7 outside the cavity 1 without directly inserting the object to be heated W into the cavity 1. The side wall 6 having the leak hole 7 hardly affects the resonance mode of the microwave excited in the cavity 1, for example, TM 110. For this reason, uniform high-efficiency heating is possible in the width direction of the article W to be heated. Moreover, since microwave power is averaged also about a moving direction by moving the to-be-heated object W, it can heat uniformly over the to-be-heated object W. Since the object to be heated W is not directly inserted into the resonant cavity 1, even when the microwave loss due to the object to be heated W is large, stable and uniform heating can be realized.

  Embodiments of the present invention will be described with reference to the drawings. In FIG. 1, the heating device includes a metal resonant cavity 1 having a rectangular parallelepiped shape, a waveguide 2 that couples microwaves to the resonant cavity 1, and a microwave shield that is disposed below the resonant cavity 1. A member 3 and a transfer unit 4 that moves the sheet-like object W so as to pass through the shielding member 3 are provided. Although not shown, a tuner for matching microwaves, a circulator for preventing microwaves reflected from the cavity from returning further upstream, and a microwave for generating microwave power are not shown. A wave oscillator or the like is connected.

  A waveguide 2 is coupled to the center of a first side wall (upper side wall in the figure) 5 of the resonant cavity 1 to generate, for example, a TM110 mode electromagnetic field in the cavity. If the central axis x of the resonant cavity 1 parallel to the side wall 5 of the resonant cavity 1 is defined as the major axis, the electric field in this mode is constant in the major axis x direction toward the major axis x direction. It changes in a sine half-wave shape in a direction y perpendicular to. A second side wall (lower side wall in the figure) 6 that faces the side wall 5 in parallel is provided with a plurality of slot-like leak holes 7 substantially parallel to the long axis x. The microwave leaks toward the sheet-like object to be heated W. A box-shaped shielding member 3 is provided at the lower portion of the side wall 6 so as to cover the inside and form a heating space 8 inside. A slot-like carry-in port 11 and a carry-out port 12 along the long axis of the resonance cavity 1 are provided at opposing positions of the side walls 9, 10 facing each other parallel to the long axis x of the shielding member 3.

  The microwave excited in the resonance cavity 1 leaks a constant electric field in the major axis x direction from the leakage hole 7 provided in the side wall 6 into the heating space 8 and heats the sheet-like object W to be heated. The distance between the side wall 6 and the article to be heated W is set to an appropriate distance so that the heating does not become uneven due to the strength of the microwave power due to the leakage hole 7. Here, the reason why the object to be heated is not allowed to pass through the resonant cavity 1 is that if an object with a large loss is inserted into the cavity, the electric field of the TM110 mode is considerably disturbed. When receiving the leakage electric field outside the cavity, the electric field of TM110 mode is hardly disturbed.

  The side wall 6 is a thin metal plate, and the wall surface current due to the electric field generated in the cavity 1 flows in the long axis x direction of the cavity 1, so that the wall surface current is almost disturbed by cutting the slot-like leakage hole 7. Absent. Therefore, the electromagnetic field of TM110 mode is hardly affected. By setting the thickness of the side wall 6 to an appropriate value, a part of the microwave power excited in the cavity 1 leaks into the heating space 8, and this heats the article to be heated W. The amount of leakage is adjusted by appropriately setting the width of the leakage hole 7 and the thickness of the side wall 6.

  In another embodiment shown in FIG. 6, a large number of leak holes 7 made of relatively small round holes are arranged almost uniformly on the side wall 6. Although the wall current is slightly disturbed, the resonance mode of the cavity 1 is not greatly affected. The microwave leaks from the leakage hole 7 and heats the article to be heated W. The amount of leakage is adjusted by appropriately setting the arrangement and diameter of the leakage holes 7 and the thickness of the side wall 6.

  The power for heating the article to be heated W can be adjusted not only by the leakage hole 7 but also by the microwave power applied from the waveguide 2. The speed of moving the article to be heated W is an important parameter that determines the amount of heat treatment per hour, and the value of the microwave power, the size of the leakage hole 7 and the like are determined according to this value.

  Although the rectangular parallelepiped cavity 1 has been described above, the shape when the cavity 1 is cut in the direction perpendicular to the major axis x is not necessarily rectangular, and may be circular or elliptical. Further, in the illustrated embodiment, the side wall 6 of the cavity 1 is planar, but can be deformed into an appropriate shape in accordance with the cross-sectional shape of the cavity 1.

  The electric field in the cavity 1 changes in a sinusoidal half-wave shape with respect to the moving direction of the object to be heated W, but by moving the object to be heated W, the micro as viewed from a specific position of the object to be heated W is shown. Since the wave electric field is averaged, uniform heating is performed in the moving direction z of the article to be heated W.

  Although not shown, when the temperature of the object to be heated W is monitored, the signal is fed back and the microwave power is controlled by the control device, the object to be heated W can be stably heated without overheating.

  The present invention heats, for example, a sheet-like object to be heated that is impregnated with water or the like, which has a large microwave loss and greatly disturbs the electric field in the cavity when directly inserted into the resonant cavity. And can be used as an apparatus for drying.

It is the schematic perspective view which notched a part of microwave heating device. It is a schematic perspective view of a resonance cavity. It is a front view of a resonance cavity. It is a longitudinal cross-sectional view of a resonance cavity. It is a cross-sectional view of a resonant cavity. It is a cross-sectional view showing another embodiment of a resonant cavity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microwave resonance cavity 2 Microwave waveguide 3 Microwave shielding member 4 Transfer means 5 First side wall of resonance cavity 6 Second side wall of resonance cavity 7 Microwave leakage hole 8 Heating space 9 Side wall of shielding member DESCRIPTION OF SYMBOLS 10 Opposite side wall 11 of shielding member Carry-in entrance 12 Carry-out exit W Sheet-like to-be-heated object

Claims (7)

A sheet-like covering with a microwave resonant cavity through which microwaves are introduced into the cavity from a waveguide coupled to one side wall of the cavity so as to produce a constant electric field in a certain direction within the cavity. In the microwave heating device for heated objects,
The opposite side wall facing one side wall of the resonant cavity includes an electromagnetic wave leakage hole,
A microwave heating apparatus, further comprising: a transfer unit configured to move the sheet-like object to be heated in a direction perpendicular to the fixed direction so as to face the electromagnetic wave leakage hole outside the resonance cavity.   The microwave heating apparatus according to claim 1, wherein the resonant cavity has a rectangular parallelepiped shape.   The microwave heating device according to claim 1, wherein the electromagnetic wave leakage hole is configured by a plurality of holes arranged uniformly.   The microwave heating apparatus according to any one of claims 1 to 3, wherein the leakage hole is constituted by a plurality of strip-shaped slots.   5. The resonance cavity according to claim 1, wherein a plurality of the resonance cavities are arranged side by side in the moving direction of the sheet-like object to be heated, and the sheet-like object to be heated is sequentially heated by each resonance cavity. A microwave heating apparatus according to claim 1.   The microwave heating apparatus according to any one of claims 1 to 5, further comprising shielding means for preventing leakage of leaked microwaves that have not been absorbed by the sheet-like object to be heated. .   The microwave heating device according to any one of claims 1 to 6, further comprising a control device that monitors the temperature of the heated sheet and feeds back a signal to control the microwave power.

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