JP2823484B2 - microwave - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven.

[0002]

2. Description of the Related Art Conventionally, this kind of microwave oven is disclosed in
No. 295386. According to this method, a waveguide wall facing a cavity of a waveguide for transmitting microwaves from a magnetron to a cavity is projected in a substantially truncated conical shape toward the inside of the waveguide. And a substantially cylindrical radiation antenna made of a conductor penetrating through the hole and held on the waveguide wall or cavity wall by a dielectric.

A microwave oven having a flat radiation antenna fixed to a magnetron antenna with a screw is disclosed in Japanese Utility Model Publication No. 53-50122.

[0004]

In the above conventional example,
Microwaves are radiated into the cavity by the electric field generated between the cylindrical radiation antenna and the waveguide wall, but are radiated only in a direction perpendicular to the electric field, that is, in only one direction. Also, since the cross-sectional area of the cavity is larger than the cross-sectional area of the waveguide, even if microwaves are supplied into the cavity and spread, the blind spots are formed or concentrated in one part, so that they do not spread sufficiently and become uneven. Therefore, radio wave unevenness occurs in the cavity, which causes heating unevenness.

[0005] Also, as a method of fixing the radiating antenna to the magnetron antenna, using a screw,
If the screws are loosened due to vibration during use or not tightened after being removed after repair, a gap may be formed between the antenna and the radiating antenna, and a discharge may occur between them.

[0006] The present invention solves such a problem.

[0007]

The object of the present invention is to provide a cavity for accommodating an object to be heated and a cross section having a large opening area on the cavity side for transmitting and supplying microwaves into the cavity. A trapezoidal waveguide, a magnetron having an antenna protruding into the waveguide from the bottom surface of the waveguide facing the cavity, and a distance that does not discharge to the waveguide in the waveguide. In this configuration, a flat radiating antenna fixed around the antenna is provided.

A through hole for penetrating the antenna is provided substantially at the center, and a fixing plate of a dielectric material fixed to the waveguide is provided at a distance which does not discharge the antenna and the waveguide and around the through hole. And the radiation antenna attached to the fixed plate.

Further, the diameter of the through hole of the fixing plate is substantially equal to the diameter of the antenna.

[0010]

The microwave is radiated by the electric field generated between the magnetron antenna and the radiation antenna, and the microwave is also radiated by the electric field generated between the radiation antenna and the waveguide wall. And the radiation area to be radiated is larger than when the radiation is performed only from between the waveguide walls. Therefore, the spread of the microwave supplied into the cavity is increased, so that the radio wave unevenness in the cavity is reduced, and the uneven heating is suppressed.

The radiating antenna is fixed at a position separated from the magnetron antenna and the waveguide by a fixing plate made of a dielectric material, and the diameter of the through hole of the fixing plate is substantially equal to the diameter of the magnetron antenna. Because we are equal,
Even if the radiation antenna is removed and re-mounted at the time of repair, the distance between the radiation antenna and the magnetron antenna or waveguide is kept constant, and no discharge occurs between them.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes an exterior of a microwave oven, 2 denotes a cavity for accommodating a food 3 to be heated from a front opening (not shown), and 4 denotes a food 3 disposed in the cavity 2 and accommodated. And a rotary motor 5 for mounting the mounting plate 4 on the rotating shaft 6 penetrating the bottom surface 2a of the cavity 2 and rotating the mounting plate 4 during cooking.
In addition, since the placing plate 4 rotates during cooking, it is generally called a turntable.

7 is a waveguide provided on the side wall 2b of the cavity 2, 8 is a wall facing the cavity 2 of the waveguide 7, that is, a magnetron mounted on the bottom surface, and 9 is a waveguide opening on the cavity wall 2b. Is a protective plate made of a mica plate that closes off.

The waveguide 7 has a substantially trapezoidal cross section in which the opening area on the side of the cavity 2 is large and becomes smaller as the distance from the cavity 2 increases.
For example, it has a substantially truncated cone shape, and the diameter of the surface facing the cavity 2 is designed to be 80 mm or more.

FIG. 2 is an enlarged view of a portion A in FIG. 19
Is a vacuum tube container having an anode and a cathode, 10 is a radiation fin fixed to the vacuum tube container by brazing or the like, 11 is a magnet, 12 is a yoke holding the vacuum tube container 19 and the magnet 11 in both axial directions, Reference numeral 13 denotes an antenna that penetrates the yoke 12 and protrudes from the vacuum tube container 19, 14 denotes an antenna cap that covers the tip of the antenna, 15
Numeral denotes a circular flat radiating antenna arranged around the antenna 13 so as not to contact the antenna cap 14.

The antenna cap 14 and the radiation antenna 1
5 and the distance are designed to be approximately 2 mm so that no discharge occurs and the antenna 13 and the radiation antenna 15 can be efficiently coupled. In addition, a sufficient distance is provided between the waveguide 7 and the radiation antenna 15 so that no discharge occurs.

As shown in FIG. 3, the radiating antenna 15 is fixed to a fixing plate 16 formed of a mica plate having a through hole 17 at a substantially central portion, has a substantially donut shape in a front view, and has an inner diameter. It is made of a metal plate made of a material such as aluminum which is larger than the through hole 17 and has an outer periphery smaller than the outer periphery of the fixed plate 16.

The diameter of the through hole 17 of the fixing plate 16 is substantially equal to the diameter of the antenna cap 14 of the magnetron 8. This is because the radiating antenna 15
If the diameter of the through-hole 17 is larger than the diameter of the antenna 13 when the antenna is removed, it is easy to install the antenna, but the distance between the radiating antenna 15 and the antenna cap 14 changes and the radio wave mode in the cavity 2 changes. Uneven heating may occur, and the radiation antenna 15 and the waveguide 7
This is because a discharge may occur between the side wall of the antenna 13 and the antenna 13 can be firmly pushed into the antenna 13 without any gap in order to prevent such factors.

In addition, approximately 120 around the radiation antenna 15.
The ribs 15a, 15b, 15c are provided at intervals of
The radiation antenna 15 is curved into the mounting holes 16c, 16d, and 16e provided in 6 and penetrates and fixes the ribs 15a, 15b, and 15c.

Further, a rib 16 is provided around the fixing plate 16.
a and 16 b are provided, similarly penetrated through slits (not shown) provided at appropriate positions on the side wall of the waveguide 7, and fixed in the waveguide, and the radiation antenna 15 is disposed.

Numeral 18 denotes a plurality of vents provided on the side wall of the waveguide 7 for dissipating the heat because the temperature inside the waveguide becomes high during the heating operation. The vent 18 is provided so as to be parallel to the radiation antenna 15, and the vent 18 is not provided on the side wall of the waveguide 7 facing the radiation antenna 15.

That is, when the radiation antenna 15 is attached to the antenna cap 14 of the magnetron 8, and when the ventilation port 18 is viewed from outside the waveguide 7, the radiation antenna 15 cannot be seen if the radiation antenna 15 is mounted at a predetermined position. In addition, since it becomes visible if it is mounted at a shifted position, the mounted state can be easily checked.

In this configuration, during the heating operation, an electric field is generated between the antenna 13 of the magnetron 8 and the radiation antenna 15, and microwaves are emitted in a direction perpendicular to the electric field. Also, an electric field is generated between the radiation antenna 15 and the wall surface of the waveguide 7, and the microwave is radiated similarly.

The radiation antenna 15 floats in space without touching anywhere, whereas the wall surface of the waveguide 7 is grounded. Since the electric field between the walls of the waveguide 7 is much stronger, the microwave
5 and the radiation from the wall of the waveguide 7 increases.

Therefore, microwaves are radiated only between the antenna 13 and the wall surface of the waveguide 7 in the related art because the microwave is radiated between the antenna 13 and the radiation antenna 15 and between the radiation antenna 15 and the wall surface of the waveguide 7. Because it becomes radiated, the radiated area from which microwaves are radiated becomes very large, for example, in water supply, it is easier to discharge water through a shower with a large discharge area than to discharge water directly from a faucet, Using the radiation antenna 15, microwaves can be radiated into the cavity 2 like a shower, and the heating unevenness can be reduced accordingly.

In FIG. 2, the antenna cap 14
From the end on the magnetron 8 side to the radiation antenna 15 and the distance from the center of the antenna 13 to the outer periphery of the radiation antenna 15, that is, the radius y of the outer periphery of the radiation antenna 15.
Is added to the distance from 35 mm to 40 mm.

This is obtained based on the experimental results shown in FIGS. First, FIG. 4 shows the relationship between the output and the distance of (x + y). It can be seen that there is a vertex between 35 mm and 40 mm, and the output decreases when it deviates therefrom.

In FIG. 5, the uneven heating and (x +
y) represents the relationship between the distances. Similarly, the distance between 35 mm and 40 mm is the smallest, and from 35 mm to 40 mm as described above.
It turns out that a distance of mm is appropriate.

The experimental method shown in FIG. 4 uses one cavity and a magnetron as an experimental table, changes the distances x and y, measures the output at that time, and graphs the results.

In the experimental method of FIG. 5, first, beakers are placed at the four corners and the center of the bottom of the cavity and heated for a predetermined time.
Measure the temperature rise of each beaker at that time. Next, the average value of the temperature rise value of each beaker is obtained, and the difference between the maximum value and the minimum value of the temperature rise value is divided by the average value. This is expressed as a percentage, obtained for each distance of (x + y), and is graphed.

Further, in order to exhibit the function of the radiation antenna 15, the outer diameter of the radiation antenna 15 is designed to be at least half the wavelength of the microwave used.

[0032]

According to the present invention, the radiation area of the microwave from the magnetron is increased, it is easy to spread in the cavity, and the uneven heating can be improved.

Further, by mounting the radiation antenna so as not to contact the magnetron, and by further mounting the radiation antenna to the magnetron antenna without any gap, the distance between the radiation antenna and the antenna does not change at the time of re-attachment, and there is a danger of discharge. Is lost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a microwave oven according to the present invention.

FIG. 2 is a partially enlarged view of a portion A in FIG.

FIG. 3 is a front view of a radiation antenna according to the present invention.

FIG. 4 is a diagram showing a relationship between a magnetron output and a distance (x + y) in FIG. 2;

FIG. 5 is a diagram showing a relationship between heating unevenness and a distance (x + y) in FIG. 2;

[Explanation of symbols]

 2 Cavity 7 Waveguide 8 Magnetron 13 Antenna 14 Antenna Cap 15 Radiation Antenna 16 Fixing Plate 17 Through Hole

Continued on the front page (72) Inventor Yoshiharu Omori 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Shinyasu Kubo 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric (56) References JP-A-62-295386 (JP, A) JP-A-58-8897 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 6/72 F24C 7/02 H05B 6/70

Claims (3)

(57) [Claims] 1. A cavity accommodating an object to be heated, a waveguide having a substantially trapezoidal cross section having a large opening area on the cavity side for propagating and supplying microwaves into the cavity, and the waveguide facing the cavity. A magnetron having an antenna projecting from the bottom surface of the waveguide into the waveguide, and a flat radiation antenna fixed around the antenna at a distance within the waveguide and at a distance that does not discharge the waveguide. A microwave oven characterized in that: 2. A through hole through which the antenna penetrates is provided substantially at the center, and a fixing plate made of a dielectric material fixed to the waveguide, and a distance that does not discharge the antenna and the waveguide and around the through hole. 2. The microwave oven according to claim 1, further comprising: the radiation antenna attached to the fixing plate. 3. The microwave oven according to claim 2, wherein the diameter of the through hole of the fixing plate is substantially equal to the diameter of the antenna.