JPH0729678A - Microwave oven - Google Patents

Abstract

PURPOSE:To improve uneven heating by eccentrically mounting a radiating antenna on the antenna of a magnetron. CONSTITUTION:In a microwave oven, the antenna 13 of a magnetron 8 is protruded into a waveguide 7 and mounted on the waveguide 7 provided on a cavity 2. A radiating antenna 15 is fixed to the antenna 13 of the magnetron in the position shifted from the center, whereby the spreading way in the cavity 2 is changed to improve uneven heating.

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, a microwave oven of this kind has been disclosed in Japanese Utility Model No.
No. -50122. In this structure, a magnetron antenna is attached so as to face the inside of a cavity, and a stirrer is attached to its tip.

[0003]

As in the above-mentioned conventional example,
When a magnetron antenna is fixed to the center of the radiating antenna and microwaves are supplied into the cavity, the side surface, the bottom surface, and the top surface of the cavity are all five straight surfaces, and each surface maintains a right angle. If it is an ideal shape like
The heating unevenness in the cavity is small. However, usually, in a microwave oven, although the material forming the cavity is thinned in order to reduce the cost, the strength is reduced by the thinning, so that the shape of the cavity is slightly deformed at the time of manufacturing. When the cavity is deformed, the direction in which the microwave is reflected changes in the cavity, the way the microwave spreads changes, and heating unevenness increases.

Therefore, by changing the shape of the feed port for feeding power from the waveguide into the cavity, inserting a reflecting plate in the waveguide, or changing the position,
Although it is possible to improve the heating unevenness, this work was performed by trial and error, which required a great deal of labor and time.

The present invention solves this problem.

[0006]

Means for solving the problems of the present invention include a cavity for accommodating an object to be heated, a waveguide for propagating and supplying microwaves into the cavity, and a cavity opposed to the cavity. A magnetron fixed to the wall surface of the waveguide and projecting an antenna into the waveguide from the wall surface to radiate microwaves, and the antenna separated from the inside of the waveguide by a distance that does not discharge into the waveguide. A radiating antenna in the form of a plate fixed around the radiating antenna is provided, and the radiating antenna is provided with a through hole penetrating the antenna at a position deviated from the center of the plane.

A cavity for accommodating the object to be heated,
A waveguide for propagating and supplying microwaves into the cavity; a magnetron for projecting and fixing an antenna in the waveguide and on a wall surface facing the cavity and radiating microwaves from the antenna; This is a configuration in which a radiation antenna that is fixed at a position off the center of the plane is provided at the apex of the antenna.

[0008]

Operation: That is, microwaves are radiated between the magnetron antenna and the plate-shaped radiating antenna and between the radiating antenna and the wall of the waveguide, but the antenna is fixed at a position off the center of the radiating antenna. By doing so, a portion where microwaves are easily radiated and a portion where microwaves are not easily emitted are formed to have directivity, and the microwaves are eccentrically radiated to radiate the microwaves to improve uneven heating.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 is an exterior of a microwave oven, 2 is a cavity for accommodating a food 3 to be heated from a front opening (not shown), and 4 is a cavity 3 for accommodating and accommodating the food 3. Is a rotary motor for mounting the above-mentioned plate 4 on the rotary shaft 6 penetrating the bottom surface 2a of the cavity 2 and rotating the plate 4 during cooking.
The plate 4 described above is generally called a turntable because it rotates during cooking.

Reference numeral 7 is a waveguide provided on the side wall 2b of the cavity 2, 8 is a magnetron attached to the wall surface of the waveguide 7 facing the cavity 2, that is, the bottom surface, and 9 is a waveguide opening of the cavity wall surface 2b. It is a protective plate made of a mica plate that closes the wall.

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 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.

An enlarged view of the portion A in FIG. 1 is shown in FIG. 19
Is a vacuum tube container provided with an anode and a cathode, 10 is a radiation fin fixed to the vacuum tube container by press fitting, 11 is a magnet, 1
Reference numeral 2 denotes a yoke that holds the vacuum tube container 19 and the magnet 11 from both sides in the axial direction, 13 denotes an antenna that penetrates the yoke 12 and projects from the vacuum tube container 19, and 14 covers the tip of the antenna. An antenna cap, 15 is a circular flat plate-shaped radiating antenna made of a metal plate such as aluminum arranged around the antenna 13, and 16 is a fixed plate formed by a mica plate having an opening 17 at substantially the center thereof. It is fixed at a position where 15 does not contact the antenna cap 14.

As shown in FIG. 3, the radiating antenna 15 is provided with a through hole 20 at a position displaced from the substantially central portion of the fixed plate 16 to the left side, that is, at a position displaced from the center of the radiating antenna to the right side. The center of the opening 20 and the center of the opening 17 of the fixing plate are fixed at a position in the fixing plate 16 where they coincide with each other, and the radius of the through hole 20 is made larger than the radius of the opening 17.

The distance between the antenna cap 14 and the through hole 20 of the radiating antenna 15 is designed to be approximately 2 mm so that no discharge occurs and the antenna 13 and the radiating antenna 15 can be efficiently coupled. Further, the waveguide 7 and the radiation antenna 15 are provided with a sufficient distance so that no discharge occurs.

In addition, the radiation antenna 15 is surrounded by approximately 120
The ribs 15a, 15b, 15c are provided at the intervals and the fixing plate 1
The radiating antenna 15 is curved in the mounting holes 16c, 16d, 16e provided in 6, and the ribs 15a, 15b, 15c are penetrated and fixed.

Further, a rib 16 is provided around the fixed plate 16.
The radiating antenna 15 is provided by providing a and 16b, and similarly penetrating through a slit (not shown) provided at an appropriate position on the side wall of the waveguide 7 and fixing the same inside the waveguide.

The diameter of the opening 17 of the fixed plate 16 is substantially equal to the diameter of the antenna cap 14 of the magnetron 8. This is because when the radiating antenna 15 is removed for repair and then reattached, the opening 17
If the diameter is larger than the diameter of the antenna 13, it is easy to mount, but the distance between the radiating antenna 15 and the antenna cap 14 changes, the radio wave mode in the cavity 2 changes, and uneven heating occurs, and This is because there is a risk that discharge will occur between the waveguide 7 and the side wall thereof, and in order to prevent these factors, it is possible to firmly press the antenna 13 into the antenna 13.

Reference numeral 18 designates a plurality of vent holes provided in the side wall of the waveguide 7 for the purpose of dissipating this heat because the temperature inside the waveguide becomes high during the heating operation. The ventilation hole 18 is provided so as to be parallel to the radiation antenna 15, and the ventilation hole 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 the ventilation port 18 is seen from the outside of the waveguide 7, it cannot be seen if the radiation antenna 15 is attached at a predetermined position. Also, since it can be seen if it is mounted at a displaced position, the mounting state can be easily confirmed.

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

It should be noted that the radiation antenna 15 floats in the space without making contact with anything, while the wall surface of the waveguide 7 is grounded, so that the radiation antenna 15 is separated from the electric field between the antenna 13 and the radiation antenna 15. Since the electric field between the wall surfaces of the waveguide 7 becomes much stronger, the microwave is emitted by the radiating antenna 1.
5 is more radiated from between the wall surface of the waveguide 5 and the wall surface of the waveguide 7.

Further, the distances between the antenna 13 and the radiation antenna 15 of the magnetron 8 and between the radiation antenna 13 and the wall surface of the waveguide 7 are too long due to the matching relationship with the wavelength of the generated microwave. If it is too short, the output will decrease.

As can be seen from the experimental results of FIG. 4, this is the distance x from the end of the antenna cap 14 on the magnetron 8 side to the radiating antenna 15 and the distance from the center of the antenna 13 to the outer periphery of the radiating antenna 15. That is, the distance (x + y) obtained by adding the radius y of the outer circumference of the radiation antenna 15
However, it can be seen that the output is high when it is 35 mm to 40 mm, and the output decreases when it is out of this range.

The experimental method shown in FIG. 4 is one in which one cavity and a magnetron are used as an experimental table, the distances x and y are changed, and the outputs at that time are measured and plotted.

Therefore, the microwave is emitted from the radiation antenna 13
Since the radiation is not radiated from the entire circumference of the cavity with the same output, one part is radiated in a biased state where the output is high and the other is low, so the micro can change the diffusion method of it can.

Therefore, even if the cavity 2 is deformed, the unevenness of heating can be improved and the time can be shortened only by adjusting the deviation of the center of the radiation antenna 15 from the center of the antenna 13 of the magnetron 8, that is, the degree of eccentricity. .

In order to exert the function of the radiation antenna 15, the outer diameter of the radiation antenna 15 is designed to be 1/2 or more of the wavelength of the microwave used.

In the above-described embodiment, the radiation antenna 15 is fixed to the fixed plate 16, and the fixed plate 16 is fixed by inserting the antenna 13 of the magnetron 8 into the opening 17, but the present invention is not limited to this. However, as shown in FIG. 5, the opening 17 of the fixing plate 16 to which the radiation antenna 15 is fixed is closed, and the center of the opening 17 and the apex portion 13 of the antenna 13 are closed.
A screw hole may be provided in a, and the fixing plate 16 may be fixed to the antenna 13 by inserting the screw 21 into this screw hole.

[0029]

According to the present invention, heating unevenness can be easily improved and the time required therefor can be shortened.

[Brief description of drawings]

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

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

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

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

FIG. 5 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

 2 Cavity 7 Waveguide 8 Magnetron 13 Antenna 14 Antenna cap 15 Radiating antenna 16 Fixing plate 17 Opening 20 Through hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Zenji Takada 2-18 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A cavity for accommodating an object to be heated, a waveguide for propagating and supplying microwaves into the cavity, and a wall surface of the waveguide opposed to the cavity, the antenna being fixed to the wall surface. A magnetron for projecting microwaves by projecting from the waveguide into the waveguide, and a plate-like radiation antenna fixed in the waveguide and around the antenna at a distance that does not discharge to the waveguide, The microwave oven, wherein the antenna is provided with a through hole penetrating the antenna at a position deviated from the center of the plane. 2. A cavity for accommodating an object to be heated, a waveguide for propagating and supplying a microwave into the cavity, and an antenna protruding and fixed in the waveguide and on a wall surface facing the cavity. A microwave oven, comprising: a magnetron that radiates microwaves from the antenna; and a radiating antenna that is fixed to a vertex of the antenna at a position deviated from the center of the plane.