JPH0828882A - High frequency heater - Google Patents

Abstract

PURPOSE:To make the propagation of microwave complicated and to improve unevenness in heating by forming a pan provided on the bottom part of a heating chamber with a metal net made with the combination of grates of rectangles of specific forms and grates of squares of specific size. CONSTITUTION:A pan 10 provided on the bottom part of a heating chamber comprises an outer peripheral part 18 and an inner circular part 19 inside it. The inner circular part 19 comprises grate parts 24a, 24b, 24c and 24d arranged about the center of an engaging part 23 serving as the center of rotation of the pan 10, which engages with the rotation axis of a rotating motor at its center. The grate part 24a made of a metal net comprises a rectangular grate 26 having long sides with length not less than 1/2 times the wavelength of magnetron microwave and short sides with length not more than 1/4 times its wavelength, a substantial rectangle 27 with one corner cut arranged in parallel with the rectangular grate 26 and square grates 28 and 29 arranged in parallel in the side of the short sides of the rectangular grates 26 and 27 and having, as one side, length not more than 1/4 times its wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency heating device.

[0002]

2. Description of the Related Art A high-frequency heating device of this type is disclosed in Japanese Patent Laid-Open No. 4-2.
No. 33189 and Japanese Patent Laid-Open No. 1-296589.

First, in Japanese Patent Laid-Open No. 4-233189, a magnetron for supplying microwaves to a heating chamber, heaters arranged on the ceiling and the bottom of the heating chamber, and a heater provided on the bottom of the heating chamber, one side Has an opening with a length of 1/4 or less of the wavelength of the microwave, and has a mesh-shaped saucer (rotary table) for placing bread on it for baking (hereinafter referred to as toast cooking), and to the saucer. A metal turntable (mounting table) that is placed and has a diameter larger than that of the pan that serves as an oven plate for cooking in order to reduce costs.
It is provided with.

Further, Japanese Patent Laid-Open No. 1-296589 discloses a magnetron for supplying microwaves into a heating chamber,
A heater for heating an object to be heated arranged in the upper and lower parts of the heating chamber, a net-shaped saucer (rotary mounting table) made of metal and arranged in the bottom of the heating chamber for performing toast cooking,
A glass turntable (borosilicate glass tray) mounted on the tray is provided.

[0005]

In the above-mentioned conventional example,
First, in Japanese Unexamined Patent Publication No. 4-233189, since a metal turntable is placed on a saucer used during toast cooking and microwave heating is performed, microwaves enter between the saucer and the turntable to cause discharge. There is a fear. Therefore, the length of one side of the mesh opening of the saucer is set to 1/4 or less of the wavelength of the microwave, and the microwave reflected from the bottom wall of the heating chamber and reaching the saucer is reflected again toward the bottom wall of the heating chamber, The discharge between the saucer and the turntable is prevented.

However, in such a microwave oven, when an object to be heated placed on a turntable, for example, sake bottle containing sake, is heated, the top portion of the bottle becomes hot but the bottom portion becomes luke, that is, uneven heating occurs at the top and bottom. .

This is because when the sake bottle is placed on the metal turntable, the vicinity of the sake bottle upper portion is caused by the microwave radiated from the waveguide or the microwave reflected on the ceiling wall, the side wall and the bottom wall of the heating chamber. Although it is heated, the lower part of the bottle is reflected by the bottom wall of the heating chamber and hits the bottle, and the microwave that is about to hit the bottle is again reflected by the turntable and the saucer toward the bottom wall. Since the amount is reduced, heating unevenness occurs.

In order to eliminate such heating unevenness, a glass turntable made of a microwave permeable material is used instead of the metal turntable as described in JP-A-1-296589, and the saucer It is conceivable to enlarge the opening of the mesh.

[0009] However, although the microwave can be easily transmitted by simply increasing the size of the mesh opening, it is possible to improve the inherent heating unevenness determined by the size and shape of the heating chamber. However, the uneven heating will still remain.

If the large and small openings of the mesh are solidified and arranged on the saucer, the food is better heated on the side on which the large openings are arranged than on the side on which the small openings are arranged. When placing food,
The heating state changes depending on the place of placement.

Further, if the pan is smaller than that of the turntable, the area of the bottom of the heating chamber for reflecting and diffusing the microwave is small and the effect of complicating the propagation of the microwave is small.
In other words, the part of the turntable where the saucer exists reflects and diffuses the microwaves, complicating the propagation.
In the portion where the saucer does not exist, the microwave reflected by the portion of the saucer and the microwave propagating in the heating chamber are crowded, and since the saucer is metal, the electric field in the outer peripheral portion of the saucer is concentrated and the microwave Since the surroundings are gathered together, the surroundings are heated better than the central portion of the turntable, and uneven heating occurs depending on the place where the turntable is placed. Also,
When the saucer is made larger than that of the turntable, there is a disproportion that the placing portion of the turntable can be made large and it is small, and the heating chamber cannot be effectively used.

Incidentally, in Japanese Patent Application Laid-Open No. 1-296589,
Although there is a description that several projections are provided around the saucer and the outer circumference of the turntable is brought into contact with the saucer, this description does not indicate that the outer dimensions of the saucer and the turntable are substantially equal. This is because it can be considered that the place where the projection of the tray is provided is made substantially the same as the outer dimension of the turntable in order to contact the outer periphery of the turntable, and the outer dimensions of the other portions are small.

The present invention solves this problem.

[0014]

A first means for solving the problems of the present invention is to provide a heating chamber for containing food, a microwave supply device for supplying microwaves to the heating chamber, and a heating chamber provided for the heating chamber. A heater, and a saucer arranged at the bottom of the heating chamber,
It is composed of a turntable made of a microwave permeable material placed on the pan and a motor for rotating the pan, and the pan has a long side of ½ of the wavelength of the microwave.
It is configured by a metal net which is a combination of a rectangular lattice having the above length and a square lattice having a side length of ¼ or less of the wavelength of the microwave.

In the second means, the rectangular grid and the square grid of the saucer are combined to form a grid portion, and the grid portion is rotationally moved about the rotation center of the saucer at a predetermined angle. It is the structure arrange | positioned in the said position in the said saucer.

[0016] In the third means, a heating chamber for storing food, a microwave supply device for supplying microwaves to the heating chamber, a tray made of metal net arranged at the bottom of the heating chamber, and the tray It is composed of a turntable of a microwave permeable material placed on it and a motor for rotating the pan, and the pan has an outer dimension substantially equal to the outer dimension of the turntable.

In the fourth means, the saucer has a rectangular lattice whose long side is at least ½ of the wavelength of the microwave, and one side is 1 at the wavelength of the microwave. It is composed of a metal net in which square lattices having a length of / 4 or less are combined.

Further, in a fifth means, the rectangular grid and the square grid of the saucer are combined to form a grid portion, and the grid portion is rotationally moved about a rotation center of the saucer at a predetermined angle. It is the structure arrange | positioned in the said position in the said saucer.

[0019]

In other words, the first means is that the wavelength of the microwave is 1
The rectangular grid of the saucer with a length of / 2 or more as the long side passes most of the microwave, and the square grid with a length of ¼ or less of the wavelength of the microwave passes the microwave. Do not let it reflect. By combining these grids, the microwaves that enter under the saucer pass through the rectangular grid and hit food from the bottom, and the square grid further reflects the microwaves toward the bottom wall of the heating chamber. Since the direction of the radio wave is changed, the propagation of microwaves becomes more complicated and heating unevenness is improved.

In the second means, since the grid portion formed by combining the rectangular grid and the square grid of the first means is arranged at the position inside the pan rotated by a predetermined angle, the pan is rotated. Rectangular and square lattices can be evenly arranged around the center, and the heating state does not change no matter where the food is placed on the turntable.

In the third means, since the outer dimensions of the tray and the turntable are substantially equal to each other, the entire lower portion of the tray can be agitated, and uneven heating can be eliminated.

In the fourth means, since the saucer of the third means is made of a metal net which is a combination of a rectangular lattice and a square lattice, the action of the first means and the action of the third means are combined, Further, the propagation of microwaves becomes complicated and uneven heating is improved.

In the fifth means, since the rectangular grid and the square grid of the saucer can be arranged substantially evenly, the propagation of microwaves on the turntable can be made substantially equal, so that the food is the same no matter where it is placed. It will be in a heated state.

[0024]

1 and 2, 1 is a metal outer casing,
Reference numeral 2 is a metal heating chamber arranged in the exterior 1; 3 is a magnetron for generating microwaves; 4 is a truncated cone-shaped metal guide provided on a side wall 2a of the heating chamber 2 for supplying microwaves of the magnetron 3. A wave tube, 5 is a protective plate made of a mica plate that closes the opening of the waveguide 4, 6 is an upper heater provided outside the ceiling wall 2b of the heating chamber 2, and 7 is outside the bottom wall 2c of the heating chamber 2. It is a lower heater provided.

The upper heater 6 is composed of a radiant heater such as a halogen heater or an infrared heater, and is heated through a plurality of punching holes 8 provided in the ceiling wall 2a of the heating chamber 2. Further, although the lower heater 7 uses a plane heater, a radiation heater such as a halogen heater may be used as in the upper heater 6.

Reference numeral 9 is a turntable made of a microwave permeable material such as glass for placing food on it, 10 is a metal tray on which the turntable is placed, and 11 is a tray for rotating the tray via a rotary shaft 12. Rotation motor, 13 is upper heater 6
Is an upper heater cover that covers and supports the above and reflects the heat rays radiated by the upper heater 6 into the heating chamber 2.

A buzzer 14 notifies the end of the cooking operation,
Reference numeral 15 denotes a key input unit having a numeric key for setting temperature and cooking time, a start button 16 for starting cooking, and the like.
Reference numeral 17 is a control unit composed of a microcomputer.

As shown in FIG. 3, the tray 10 is composed of an outer peripheral portion 18 and an inner circular portion 19 on the inner surface thereof.

First, the outer peripheral portion 18 radiates from the magnetron 3 and an outer peripheral rail 20 curled to prevent discharge, an inner circular rail 21 concentrically arranged with the outer peripheral rail 20 inside the outer peripheral rail 20. 1/4 of the microwave wavelength (hereinafter 1
/ 4 wavelength) and the outer peripheral rail 20 at intervals of the following length
And a connecting bar 22 for connecting the inner circular bar 21.

Further, the inner circle portion 18 engages with the rotating shaft 12 of the rotary motor 11 at its center portion, and the engaging portion 23 serving as the rotation center of the tray 10 and the engaging portion 23 as the center, It is composed of lattice portions 24a, 24b, 24c, 24d arranged at positions rotated by 90 ° each having a predetermined angle, and a connecting portion 25 connecting each lattice portion and the engaging portion.

In this embodiment, the predetermined angle is 90 ° and the lattice portions are provided at four places.
The grid portions may be provided at eight locations by setting the angle to 180 degrees, or the grid portions may be provided at two locations by setting the angle at 180 degrees. That is, if the predetermined angle is kept substantially constant and the lattice portions are arranged substantially evenly on the saucer centering on the center of rotation of the saucer, the microwave propagation on the turntable becomes substantially equal, and at any position on the turntable. The same heating condition can be obtained by placing food on the.

The lattice portions 24a, 24b, 24c, 24
Since d is only rotated by 90 ° and the lattices arranged are the same, the lattice portion 24a will be described as a representative.

The grating portion 24a has a long side having a length of ½ (hereinafter, referred to as ½ wavelength) of the microwave wavelength of the magnetron 3 and a short side having a length of ¼ wavelength or less. A rectangular lattice 26 and the rectangular lattice 26 are arranged side by side,
Compared to the rectangular grating 26, a substantially rectangular grating 27 with one corner missing, and a square grating 28 having one side of a length of ¼ wavelength or less arranged side by side on the shorter sides of the rectangular gratings 26, 27. , 29 and.

Since the microwave oven uses a radio wave of 2450 MHz, the wavelength of the radio wave has a light propagation speed of 3 ×.
If it is 10 ¹¹ mm · s, it will be about 122 mm. Therefore,
Half wavelength is about 61 mm, quarter wavelength is about 30.5 mm
Becomes

Therefore, in this embodiment, the long side of the rectangular lattice is 72 mm, the short side is 22 mm, and one side of the rectangular lattice is 2.
2 mm, the connecting bar 21 has a length of 15 mm, and the connecting bar 21 has an interval of 22 mm.

The operation of this configuration will be described. First, when microwave heating is performed, the turntable 9 is placed on the saucer 10, the food to be heated is further placed on the turntable 9, and then the start button 16 is operated. Based on this operation, the control unit 17 starts counting the cooking time, energizes the magnetron 3 to generate microwaves, and also rotationally drives the rotary motor 11 to rotate the turntable 9.

The microwave generated by the magnetron 3 is
The heating chamber 2 propagates through the waveguide 4 and passes through the power supply port cover 5.
Irradiate inside. The microwave radiated in the heating chamber 2 is
Irradiation is directed toward the ceiling wall 2b and the bottom wall 2c of the heating chamber. Then, the microwave that has reached the ceiling wall 2b of the heating chamber 2 is reflected and radiated toward the bottom wall 2b. The microwave radiated to the bottom wall reaches the turntable 9, but since the turntable 9 is made of glass, the microwave penetrates the microwave and reaches the saucer 10 therebelow. In the saucer 10, the microwaves hitting the rectangular gratings 26 and 27 pass through the saucer 10 as they are and reach the bottom wall 2c. Then, it is reflected by the bottom wall 2c and reaches the saucer 10 again. At this time, the microwaves that have reached the rectangular gratings 26 and 27 pass through the saucer 10 and the turntable 9 and are reflected toward the ceiling wall. The microwaves that have reached the gratings 28 and 29 are reflected again toward the bottom wall. By repeating this action, the degree of reflection of the microwave is changed, the propagation of the microwave is complicated, and uneven heating is improved.

Irradiation from the ceiling wall 2b and the waveguide 4
The microwaves that have reached the square gratings 28 and 29 are not transmitted and are reflected in the ceiling wall direction.

When the cooking time counted by the control unit 17 reaches the end time, the magnetron 3 is de-energized and the cooking is ended. At this time, the control unit controls the rotary motor 11
Does not stop immediately but continues rotating to the position where the cooking started and stops at that position and then sounds the buzzer 14 to notify the end. That is, the time for the turntable 9 to make one turn is stored, and at the end of heating, the rotary motor 11 is continuously rotated until the time for which the heating time is a multiple of one turn of the turntable 9 has elapsed. .

Next, when performing toast cooking, the turntable 9 is removed and only the saucer 10 is left. And
When the bread is placed on the tray 10, for example, two breads are placed side by side, the toast cooking is selected by the key input unit 15 and the start button 16 is operated, the control unit 17 starts the cooking. At this time, the control unit starts energizing the upper heater 6 and the lower heater 7, but does not rotate the turntable 9.

When the cooking time counted by the control unit 17 reaches the cooking end time, the energization of the upper heater 6 and the lower heater 7 is stopped and the cooking is ended.

[0042]

According to the present invention, since microwaves can be reflected and diffused even by a metal net tray on which a turntable is placed, microwave propagation becomes more complicated and uneven heating can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a microwave oven of the present invention.

FIG. 2 is a control block diagram of the present invention.

FIG. 3 is a plan view of a saucer.

[Explanation of symbols]

 3 magnetron 9 turntable 10 saucer 11 rotary motor 26, 27 rectangular grid 28, 29 square grid

Claims (5)

[Claims] 1. A heating chamber for storing food, a microwave supply device for supplying microwaves to the heating chamber, a saucer arranged at the bottom of the heating chamber, and a microwave permeable material placed on the saucer. Of the turntable and a motor for rotating the saucer, the saucer having a rectangular lattice whose long side is at least ½ of the wavelength of the microwave, and 1
A high-frequency heating device, characterized in that it is constituted by a metal net in which square lattices each having a side length of ¼ or less of the wavelength of the microwave are combined. 2. The inside of the saucer in which the grating portion is formed by combining the rectangular lattice and the square lattice of the tray, and the lattice portion is rotationally moved at a predetermined angle around a rotation center of the saucer. The high frequency heating apparatus according to claim 1, wherein the high frequency heating apparatus is arranged at a position. 3. A heating chamber for accommodating food, a microwave supply device for supplying microwaves to the heating chamber, a tray made of metal net arranged at the bottom of the heating chamber, and a microwave placed on the tray. A high-frequency heating device comprising a turntable made of a wave-transmissive material and a motor for rotating the pan, the pan having an outer dimension substantially equal to that of the turntable. 4. The saucer has a rectangular lattice whose long side is ½ or more of the wavelength of the microwave, and one side is ¼ or less of the wavelength of the microwave. The high-frequency heating device according to claim 3, wherein the high-frequency heating device is configured by a metal net which is a combination of square lattices. 5. The inside of the saucer in which the rectangular grid and the square grid of the saucer are combined to form a grid portion, and the grid portion is rotationally moved at a predetermined angle around a rotation center of the saucer. The high frequency heating apparatus according to claim 4, wherein the high frequency heating apparatus is arranged at a position.