JPH0340915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a high-frequency heating device commonly called a microwave oven, which applies high-frequency dielectric heating mainly to heating foods.

Prior art (1) As seen in Japanese Unexamined Patent Publication No. 15594/1983,
The solution is to adjust the length of the horizontal part of the rotating strip antenna.

(2) A configuration in which a gutter-shaped rotating waveguide is rotated by a method of propagating electromagnetic waves in the horizontal direction from the center of rotation, as in Japanese Patent Publication No. 48-2144.

(3) A method of coupling an antenna and a waveguide as shown in Japanese Utility Model Publication No. 47-35741.

Problems to be Solved by the Invention However, method (1) suppresses excessive heating of the center of rotation by adjusting the impedance matching of the horizontal rotating strip antenna and the object to be heated. The shape and size of the load change depending on the method. Therefore, it was uniform for a certain limited load, but less effective for different loads. In other words, it seems difficult to use a strip antenna to reduce the radiation of electromagnetic waves from the center of rotation and propagate in the horizontal direction for any load.

In method (2), it is difficult to connect the feed port and the gutter-shaped rotating waveguide. In other words, since the direction of the electric field at the feed port is constant, when the direction of the electric field becomes the same as that of the rotating waveguide, the radio waves will propagate inside the trough-shaped rotating waveguide.
When the two are at right angles, there is almost no propagation. In other words, no matter which direction the rotating waveguide faces, radio waves will not propagate inside the rotating waveguide.
Therefore, the heating distribution will also be different between the front and rear and the left and right sides. In addition, in method (3), the antenna and waveguide are coupled, so even if the rotation direction changes, the amount of radio wave propagation in the waveguide remains constant, but the antenna and waveguide are electrically connected. Since the antenna is not in contact with the waveguide, it is difficult for all the radio waves from the antenna to be transmitted to the waveguide, so a maze of radio waves is required around the outer circumference of the waveguide, making the waveguide complicated. As described above, the conventional method has the above-mentioned problems.

The present invention solves the conventional problems and provides a structure that greatly improves the uniformity of distribution and reduces variations in the uniformity of distribution using a simple construction method.

Means for Solving the Problems The present invention has a configuration in which radio waves are supplied from below the heating chamber, and a substantially fan-shaped antenna for magnetic field coupling is rotated.
Moreover, a low impedance portion is provided in addition to the fan-shaped circular arc portion and the opposite portion of the circular arc portion.

Effect The high-frequency heating device of the present invention rotates a magnetically coupled substantially fan-shaped antenna, and the antenna has radio waves radiated from a low impedance portion, a circular arc portion, and a portion opposite the circular arc portion, so that the central bottom portion is overheated. It is possible to uniformly heat food to avoid overheating, and it is also possible to uniformly heat both the bottom and top surfaces of food even if the food is of a certain height.

Embodiment Hereinafter, a high frequency heating device according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, high-frequency electromagnetic waves from a magnetron 1, which is a high-frequency oscillator, pass through a waveguide 2, enter the heating chamber 3 from below, and heat food (not shown), etc. . At the bottom of the heating chamber 3, there is provided a tray pedestal 4 on which food made of a low-loss dielectric is placed.
Antenna A6 and antenna B7, which are rotated by a motor 5, are arranged under the dish holder 4.

FIG. 2 is an enlarged view of the bottom of the heating chamber in FIG. 1. FIG. 3 is a view taken along arrow G in FIG. A coupling hole 9 is provided approximately at the center of the heating chamber wall 8 of the heating chamber 3 . The heating chamber wall 8 around the coupling hole 9 is slightly raised, so that even if food juice spills, it does not easily flow into the motor 5. The rotating shaft 10 of the motor 5 is made of a low-loss dielectric material,
High frequency electromagnetic waves in the waveguide 2 are prevented from leaking to the motor 5 side, and heat in the heating chamber 3 is made difficult to be transmitted to the motor 5. Antenna A6 is attached to the rotating shaft, and the antenna A6 is rotated. Antenna A6 guides the high frequency electromagnetic waves of waveguide 2 into heating chamber 3. An antenna B7 is caulked to the tip of the antenna A6 in the heating chamber 3, and is fixed electrically and mechanically. Therefore, the high frequency electromagnetic waves propagate between the antenna B7 and the heating chamber wall 8. The antenna B7 is provided with a low impedance section 11, and most of the radio waves within the antenna B7 are reflected by the low impedance section 11, so the radio waves of the antenna B7 are propagated in the A direction and the B direction. The antenna B7 has a substantially fan shape as shown in FIG. 3, and the arcuate portion 7 of the antenna B7
(a) A low impedance portion 11 is provided in a portion other than the arc-shaped opposite portion 7b and reflects radio waves, so that radio waves are radiated from the tips 7a and 7b of the antenna B7. Therefore, radio wave emission port 1
2a, 12b rotate, and the radiation ports 12a, 1
The direction of the electric field 2b is vertical and excites the inside of the heating chamber. Therefore, the bottom of the load such as food is heated by the leakage radio waves from the low impedance section 11, the radio waves from the radiation port 12a heat the food from the periphery toward the center, and the food is heated by the radio waves from the radiation port 12b. It is possible to heat the vicinity of the center. radiation port 12a,
Since the electric field direction of the radio waves from 12b is vertical, a vertical electric field direction is generated in the heating chamber 3, so that the uniformity is stable for so-called planar foods with many horizontal components. Further, since radio waves are emitted from the radiation port 12b, the uniformity is stable even for irregularly shaped foods with a certain height. Antenna B7 and heating chamber wall 8
In order to stabilize dimension C in FIG. 2, an antenna spacer 13 made of a low-loss dielectric material is provided in an arc shape between the two antennas.

Effects of the Invention As described above, the high frequency heating device of the present invention has the following effects.

(1) Since the radio waves from antenna A are reliably propagated to the surrounding area, the rotation effect is good, and therefore the heating distribution is good.

(2) The degree of heating at the bottom of the food can be freely adjusted by the length of the low impedance section, the distance F, and the position of the antenna A, so the heating at the bottom of the food will not be too strong or too weak.

(3) Since the heating chamber is excited by vertical radio waves, stable uniformity is maintained even if the shape of flat food changes.

(4) The radio waves emitted from the center side radiation port provide stable uniformity even for irregularly shaped foods of a certain height.

(5) The low impedance part of antenna B can be made by simply bending a sheet metal, so the cost does not increase.

(6) Since high frequency electromagnetic waves are emitted from the bottom,
Since heating is mainly caused by radio wave radiation, the uniformity of the distribution does not change depending on the size of the heating chamber. Therefore, it can accommodate heating chambers of various sizes.

(7) Since there are no protrusions inside the heating chamber, it is easy to use and clean.

[Brief explanation of drawings]

FIG. 1 is a front sectional view of a high-frequency heating device showing an embodiment of the present invention, FIG. It is an H arrow view. 6...Antenna A, 7...Antenna B, 8...
Heating chamber wall, 9... coupling hole, 11... low impedance section, 13... antenna spacer.

Claims (1)

[Claims] 1 A high-frequency oscillator that oscillates high-frequency electromagnetic waves within a main body, a heating chamber for heating an object to be heated, a waveguide that guides the high-frequency electromagnetic waves of the high-frequency oscillator to the heating chamber, and the waveguide and the heating chamber. a first antenna penetrating through a coupling hole; and a second antenna that is substantially perpendicular to the first antenna and fixed to the tip of the first antenna on the heating chamber side, the second antenna is formed into a substantially fan shape, and the second antenna has a fan-shaped arc portion and a portion opposite to the fan-shaped arc portion.
A line with low characteristic impedance is formed at other locations, and the low impedance portion of the second antenna is formed by bending the second antenna and has a distance less than half the distance between the second antenna and the heating chamber wall. The length of the line is approximately one-fourth of the wavelength of the high-frequency electromagnetic wave, and the coupling between the first antenna and the second antenna is performed by narrowing the vicinity of the coupling hole of the first antenna upward. A high-frequency heating device having a configuration in which a hole is provided in a lower part of the heating chamber, and the second antenna is rotated about the first antenna as a rotation axis.