JPH0765947A - Microwave oven - Google Patents

Abstract

PURPOSE:To improve the uniformity in heating by adjusting a radiation antenna secured on the antenna of a magnetron. CONSTITUTION:To the antenna cap 14a of a magnetron 8, a radiation antenna 22 is secured inclining relative to the side wall 2b of a cavity 2. Thus the transmission unevenness in the cavity 2 is improved by changing the transmission direction of microwaves to be radiated from the radiation antenna 22, and unevenness in the heating is improved.

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 Publication 55.
No. -50122. This one is equipped with a magnetron attached so that an antenna is projected in the heating chamber, and a flat plate electrode serving as a radiation antenna attached to the antenna of the magnetron with screws or the like. It is installed in parallel.

However, since a discharge may occur between the antenna and the plate electrode depending on how the screws are attached, a radiation antenna as described below has been considered.

This is shown in FIGS. 1, 5 and 6. Reference numeral 1 is an exterior of a microwave oven, 2 is a cavity for accommodating food 3 to be heated from a front opening (not shown), 4 is a placing plate for arranging the accommodated food 3 in the cavity 2, Reference numeral 5 is a motor that attaches the plate 4 to the rotary shaft 6 that penetrates the bottom surface 2a of the cavity 2 and rotates 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 wall surface of the waveguide 7 facing the cavity 2, that is, a magnetron attached to the bottom surface 7a, and 9 is a waveguide of the cavity side wall 2b. It is a protective plate made of a mica plate that closes the opening.

The waveguide 7 has a substantially trapezoidal cross section with a large opening area on the cavity 2 side and a smaller opening area.
For example, it has a substantially truncated cone shape, and the wall surface facing the cavity 2, that is, the bottom surface 7a is designed to have a diameter of 80 mm or more.

The magnetron 8 includes a vacuum tube container 19 having an anode and a cathode, a radiation fin 10 fixed to the outer circumference of the vacuum tube container 19 by press fitting or the like, a magnet 11, and the vacuum tube container 19 and the magnet 11 both in the axial direction. It is composed of a yoke 12 which is sandwiched and held from the inside, and an antenna portion 13 which penetrates the yoke 12 and projects from the vacuum tube container 19.

The antenna portion 13 has an antenna cap 14a covered at its tip and the antenna cap 14a.
And an insulating tubular body 14b made of ceramic interposed between the vacuum tube container 19 and the vacuum tube container 19.

Reference numeral 15 denotes a radiation antenna which is arranged around the antenna cap 14a and has a substantially donut shape in a front view and which is made of a circular flat plate metal material such as aluminum so as not to come into contact with the antenna cap 14a.

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

Reference numeral 16 is a fixing plate which is provided with a through hole 17 having a diameter smaller than the inner circumference of the radiation antenna 15 at a substantially central portion and is formed of a mica plate for fixing the radiation antenna 15.

The diameter of the through hole 17 of the fixed plate 16 is made substantially equal to the diameter of the antenna cap 14a of the magnetron 8, and the fixed plate 16 is attached so as to be pushed into the antenna cap 14a.

This is a radiation antenna 1 for repairing.
If the diameter of the through hole 17 is larger than the diameter of the antenna 13 when the 5 is removed and then reattached, the attachment is easy, but the distance between the radiation antenna 15 and the antenna cap 14a is changed, and the radio wave mode in the cavity 2 is changed. This is because there is a risk that heating unevenness may occur or discharge may occur between the radiation antenna 15 and the side wall of the waveguide 7.

Reference numerals 15a, 15b and 15c are radiation antennas 1.
5, ribs 16c, 16 provided at intervals of about 120 °
Reference numerals d and 16e are mounting holes provided in the fixed plate 16, and the ribs 15a, 15b, and 15c are formed by bending the radiation antenna 15.
Through the mounting holes 16c, d, and e to fix the radiation antenna 15.

Reference numerals 16a and 16b denote ribs provided around the fixed plate 16. The ribs 16a and 16b are penetrated through slits (not shown) provided at appropriate places on the side wall of the waveguide 7 to fix the fixed plate 16 in the waveguide. The radiation antenna 15 is arranged in the waveguide 7.

Reference numeral 18 denotes a plurality of vent holes provided on the side wall of the waveguide 7, which is for 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 14a of the magnetron 8 and the ventilation hole 18 is seen from the outside of the waveguide 7, the radiation antenna 1 is at a predetermined position.
If 5 is attached, it will not be visible, and if it is attached at a shifted position, it will be visible, so that the attachment state can be easily confirmed.

In this structure, the antenna cap 14a and the radiation antenna 15 of the magnetron 8 are heated during the heating operation.
An electric field is generated between the two, 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.

The radiating antenna 15 floats in the space without touching anything, whereas the wall surface of the waveguide 7 is grounded, so that the radiating antenna 15 is formed by the electric field between the antenna cap 14a and the radiating antenna 15. Since the electric field between the wall surface of the waveguide 7 and the wall surface of the waveguide 7 becomes very strong, the microwave is more often radiated from between the radiation antenna 15 and the wall surface of the waveguide 7.

Therefore, the microwave is radiated only from the space between the antenna cap 14a and the wall surface of the waveguide 7 in the related art. The space between the antenna cap 14a and the radiation antenna 15 is between the radiation antenna 15 and the wall surface of the waveguide 7. Since the microwaves are radiated, the radiation area for radiating the microwaves becomes very large, and the microwaves can be radiated in the shape of a shower in the cavity 2, and the uneven heating can be improved by that amount.

[0021]

However, since the above-mentioned radiation antenna 15 is fixed parallel to the side wall 2b of the cavity 2, the radiation antenna 15 is radiated from the entire circumference of the radiation antenna 15 in the waveguide 7. The waves are similarly reflected in the waveguide and diffused into the cavity 2.

Therefore, the heating unevenness in the vertical direction may not be improved only by moving the mounting position of the radiation antenna forward and backward, because the position where the heating unevenness occurs is changed.

In particular, when the amount of food to be heated is large, the microwaves absorbed in the food are large, so it is not noticeable. However, when heating a small amount of food, for example, when heating sake or milk, the cavity is not absorbed by the food. Since there are many microwaves propagating in 2, heating unevenness becomes conspicuous.

The present invention solves this problem.

[0025]

A means for solving the problems 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 propagating and supplying microwaves into the cavity. A trapezoidal waveguide, a magnetron having an antenna projecting from the bottom surface of the waveguide facing the cavity into the waveguide, and a discharge that does not discharge around the antenna and to the antenna and the waveguide. A radiating antenna in the form of a flat plate attached at a position spaced apart from each other, wherein the radiating antenna is fixed to the wall surface of the cavity while being inclined.

[0026]

That is, the microwave radiated from the radiating antenna into the cavity is mounted so as to be inclined with respect to the wall surface of the cavity, and the direction of the microwave radiated from the cavity is radiated from other portions. Since the direction of the microwave is different from the direction of the thing, the direction of the microwave incident from the waveguide into the cavity is also different, and the microwave is diffused substantially uniformly in the cavity.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. However, the parts having the same numbers as those already described have the same functions, and the description thereof will be omitted.

Reference numeral 20 denotes a fixed plate formed of a mica plate having a through hole 21 at a substantially central portion thereof, which is inclined by approximately 30 ° with respect to the side wall 2b of the cavity 2 toward the cavity 2 side (see FIG. 2).
(Inclined to the inside x direction) and fixed to the waveguide 7,
The surface 20a faces the cavity 2 and the surface 20b faces the magnetron 8 side.

Reference numeral 22 denotes a flat plate-shaped radiation antenna fixed to the surface 20b of the fixed plate 20 on the magnetron 8 side,
A substantially elliptical opening 23 larger than the through hole 21 in the center
Is provided.

The shape of the opening 23 is the same as the shape of the radiating antenna 15 of the above-mentioned conventional example, that is, the shape of the inner circle corresponding to the opening 23, when it is attached to the antenna portion 13 of the magnetron 8 together with the fixed plate 20 with an inclination. If it is a circle, the distance between the antenna unit 13 and the radiation antenna 15 is not uniform,
For example, if the distance between the antenna unit 13 and the radiating antenna 15 is set to 2 mm so that the most distant part can be efficiently coupled, there is a risk that other parts will come too close and discharge will occur. 13 and radiation antenna 1
If the closest distance to 5 is 2 mm, the other portions will be too far apart and efficient radio wave coupling will not be possible this time, so make it approximately oval and keep the distance between the antenna unit 13 and the radiation antenna 22 constant. This is because

In such a structure, the microwave is applied to the antenna cap 14a of the magnetron 8 and the radiation antenna 22.
, And the radiating antenna 22 and the waveguide 7 generate an electric field and are radiated in the direction of the cavity 2. However, since the radiating antenna 22 is inclined and fixed, the side wall 2b of the cavity 2 and The distance to the outer circumference of the radiation antenna 22 is different over the entire circumference.

Therefore, when the portion of the radiating antenna 22 near the cavity 2 is radiated, it propagates into the cavity 2 as it is, but at the portion away from the cavity 2, it is reflected on the wall surface of the waveguide 7 and the above-mentioned microwave is transmitted. Then, the direction of propagation changes and it propagates into the cavity 2.

Therefore, in the cavity 2, the microwaves propagate in a complicated manner and the unevenness of propagation is eliminated, and the unevenness of heating is improved.

FIG. 4 shows another embodiment. The shape of the waveguide 7 and the mounting method of the radiation antenna 22 are different from the embodiment of FIG.

First, the waveguide 7 has the same cross-sectional area as the side wall approaches the cavity 2 from the bottom surface 7a, that is, it is formed in a truncated cone shape, but the bottom surface 7a is formed on the side wall 2b of the cavity 2. Is inclined by about 30 °.

The radiating antenna 22 is fixed so that the antenna cap 14a and the radiating antenna 22 are at a right angle, as in the prior art described above.

Therefore, as in the embodiment of FIG. 2, the radiation antenna 22 is inclined with respect to the side wall 2b of the cavity 2, and uneven heating can be improved by the same action.

[0038]

According to the present invention, the radiation antenna is tilted and fixed to change the microwave radiation direction from the radiation antenna to improve the microwave propagation unevenness in the cavity and improve the heating unevenness. To do.

[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.

FIG. 4 is a diagram showing another embodiment.

5 is an enlarged cross-sectional view showing a conventional structure of a portion A in FIG.

FIG. 6 is a front view of a conventional radiation antenna.

[Explanation of symbols]

 2 Cavity 7 Waveguide 8 Magnetron 13 Antenna 14a Antenna Cap 20 Fixing Plate 22 Radiating Antenna

Claims (1)

[Claims] 1. A cavity for 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 cavity facing the cavity. A magnetron having an antenna protruding from the bottom surface of the waveguide into the waveguide, and a flat radiating antenna mounted around the antenna and at a position separated from the antenna and the waveguide by a distance that does not cause discharge. And a radiation antenna fixed to the wall surface of the cavity in a tilted manner.