JPS62126590A - Exciting structure of microwave oven - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a microwave oven employing a waveguide excitation method, and particularly to improvement of its excitation structure.

[Technical background of the invention and its problems]

This type of microwave oven has conventionally been designed as shown in FIG. 5 or 6. In other words, a is the main body of the device, b is the heating chamber, C is the cooking plate housed in the inner bottom of the heating chamber, d is the excitation port opened on the top wall of the heating chamber, and e is the excitation port d.
A waveguide is connected at one end to f, and f is a magnetron attached to the other end of the waveguide e.

In the structure shown in FIG. 5, a star fan Q is rotatably supported near the excitation port d, and in the structure shown in FIG. It is installed at the outside bottom of the heating chamber.

Due to the oscillation action of the magnetron f, microwaves are guided through the waveguide e to the excitation port d, and are further radiated from the excitation port d into the heating chamber to heat the food to be cooked (not shown) on the cooking plate C. It is ready for cooking.

At this time, the Stara fan Q or the motor h is driven, and the fan Q and cooking plate C are rotated.

The stirrer fan 0 has the effect of stirring the electric field in the heating section 5b, and the rotating cooking plate C has the effect of receiving microwaves from all directions to the food to be cooked. The purpose is to obtain heat.

However, the starvation 7 and 9 only have the effect of stirring the electric field and do not have the function of rotating while radiating microwaves as an antenna, so that the uniform heating effect is not sufficient.

In order to achieve uniform heating with this type of structure, it is necessary to make the star fan shape more complicated or to place it as close as possible to the above-mentioned excitation port d, but even with this, the impedance inside the heating chamber under load will change. becomes large, and range efficiency decreases. That is, as the star fan q rotates, the degree to which the oven impedance deviates from the optimal impedance region for the magnetron f increases.

On the other hand, in the structure in which the cooking device 11C is rotated, there is no substantial effect unless the excitation port d is provided in the center of the upper wall of the heating device VB. The total length of the tube e becomes longer, and the range efficiency decreases due to microwave loss inside the tube e.

Further, due to the shape of the heating chamber, the electric field distribution and strength of the emitted microwaves are significant, and even if the cooking plate C is rotated, subtle heating unevenness is likely to occur.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to prevent uneven heating of food to be cooked and to improve heating efficiency in a waveguide excitation type microwave oven. The purpose of this study is to provide an excitation structure with a specific structure.

[Summary of the invention]

That is, the present invention provides an excitation port on the wall surface of the heating chamber, connects one end of a waveguide to the excitation port, and transmits microwaves oscillated from a magnetron provided at the other end of the waveguide to the excitation port. In the heating chamber, the total length is λ/2N (λ: fundamental wavelength, N: !1
This excitation structure for a microwave oven is characterized in that a secondary radiation antenna (number) is provided, a part of which is spaced apart and opposed to the excitation port.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, reference numeral 1 denotes the main body of the microwave oven. A heating chamber 2 whose front opening is opened and closed by a door (not shown) is provided inside the apparatus body 1. A cooking tray of 1 m3 for placing food to be cooked is attached to the inner bottom of the heating chamber 2.

Further, an excitation port 4 is opened in a part of the upper wall of the heating chamber 2 .

A waveguide 5 is mounted on the upper wall of the heating chamber 2, and an opening at one end thereof communicates with the excitation port 4. The antenna part of the magnetron 6 protrudes from the other end of the waveguide 5, and the antenna part of the magnetron 6 protrudes from the other end of the waveguide 5.
It is now possible to oscillate microwaves inside. A secondary radiation antenna 7 (see below) is provided above the heating chamber 2.

In other words, the total length of this secondary radiation antenna 7 is λ/2N.
(λ: fundamental wavelength, N: integer), and a part thereof faces the excitation port 4 at a distance. One end is
It is rotatably supported on the upper wall of the heating chamber 2 via a pivot pin 8 . A substantially semicircular driven gear 9 is integrally provided at the edge on the side of the pivot bin 8, and the gear portion is close to the side wall of the heating chamber 2. A gear drive motor 10 is attached to the outer surface of the side wall of the heating chamber 2 and is driven to rotate forward and backward intermittently. A drive gear 1 fitted to the rotating shaft of this gear drive motor 10
1 protrudes inward through a small opening provided in the side wall and meshes with the driven gear 9. Therefore, by energizing the gear drive motor 10, the second
As shown in the figure, the drive gear 11 rotates in forward and reverse directions within a predetermined angle range, and the driven gear 9 rotates accordingly, causing the secondary radiation antenna 7 to reciprocate by a predetermined angle. There is. The rotation range of the secondary radiation antenna 7 is set within a range in which only a portion thereof faces the excitation port 4 and does not deviate from the rotation range.

Then, an object to be cooked (not shown) is placed on the cooking plate 3, and the magnetron 6 is oscillated to heat and cook the object. That is,
Microwaves oscillated by the magnetron 6 are guided into the waveguide 5 and excited into the heating chamber 2 through the excitation port 4 . A strong electric field exists approximately at the longitudinal center of the excitation port 4, and microwaves are efficiently transmitted to the secondary radiation antenna 7 facing away from the electric field. Further, as the magnetron 6 oscillates, the gear drive motor 10 rotates the secondary radiation antenna 7 via the drive gear 11 and the driven gear 9. The antenna 7 reciprocates like a wiper and sends the received microwaves to the heating chamber 2.
radiate widely within. There is a uniformly strong electric field in the vicinity of the pivot pin 8, and even if the secondary radiation antenna 7 is rotated, the excitation electric field to the antenna 7 can always be maintained substantially constant. For this reason, impedance changes within the heating chamber 2 can be suppressed to a minimum, and the microwave oven is efficient and there is no uneven heating of the food to be cooked. In addition, the above-mentioned N (integer), which is a requirement for setting the total length of the secondary radiation antenna 7, can be changed and adjusted as appropriate to match the dimensions of the heating chamber 2, so that the electric field distribution within the heating chamber 2 can be changed and adjusted. Needless to say.

In the above embodiment, the secondary radiation antenna 7 is reciprocated in a wiper-like manner, but the present invention is not limited to this, and may be as shown in FIGS. 3 and 4. In other words, in the case of the m-built one in which a motor 12 is connected to the cooking plate 3 and is driven to rotate, a part of the secondary radiation antenna 70 is placed approximately at the center of the excitation port 4 in a spaced manner facing each other, and both ends of the secondary radiation antenna 70 are heated. Attach and fix to the upper wall of chamber 2. The total length of this secondary radiation antenna 70 is λ/2N as in the above embodiment.
(λ: fundamental wavelength Oka: N: an integer, and the distance H from the top wall of the heating chamber 2 is from λ/8 to λ/4. (In addition,
Parts similar to those in the above embodiment are given the same numbers and new explanations will be omitted. ) Accordingly, the motor 12 rotates the cooking plate 3 as the magnetron 6 oscillates. The excitation port 4 has a strong electric field, and the distance between this and the secondary radiation antenna 70 is λ.
/8 to λ/4, the microwave is efficiently transmitted to the antenna 70. Since the total length of the secondary radiation antenna 70 is λ/2N, the microwave is radiated into the heating chamber 2 over a wide range, and there is no strength or weakness in electric field distribution. Moreover, since the cooking plate 3 is rotating during the heating operation, the food placed on the cooking plate 3 is evenly heated and cooked.

In this case, since the position and overall length of the secondary radiation antenna 70 are defined, the position of the excitation port 4 does not necessarily need to be provided in the center of the upper wall of the heating chamber 2, and the length of the waveguide 5 can be set short. There is no internal microwave loss. Furthermore, since the secondary radiation antenna 70 is fixed, the structure is simple, and by changing the above N (integer) according to the dimensions of the heating chamber 2, the electric field distribution within the heating v2 can be changed and adjusted. , similar to the above embodiment.

(Effects of the Invention) As explained above, according to the present invention, the provision of the secondary radiation antenna facilitates the design and layout of the waveguide and the excitation port (as well as eliminates uneven heating and improves heating efficiency). This has the effect of helping you improve your skills.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention, FIG. 1 is a schematic longitudinal sectional front view of a microwave oven, FIG. 2 is a top view of the main part showing its excitation structure, and FIGS. The figures show other embodiments of the present invention, Fig. 3 is a schematic longitudinal sectional front view of a microwave oven, Fig. 4 is a top view of the main part showing its excitation structure, and Fig. 5 shows a conventional example of the present invention. FIG. 6 is a schematic longitudinal sectional front view of a microwave oven having a further different structure. 2... Heating chamber, 4... Excitation port, 5... Waveguide, 6
...Magnetron, 7.70...Secondary radiation antenna. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (3)

[Claims] (1) An excitation port is provided on the wall of the heating chamber, one end of the waveguide is connected to this excitation port, and the microwaves oscillated from the magnetron provided at the other end of the waveguide are transmitted through the excitation port. The apparatus is provided in the heating chamber, a part of which faces the excitation port at a distance, and has a total length of λ.
An excitation structure for a microwave oven, characterized in that it is equipped with a secondary radiation antenna of /2N (λ: fundamental wavelength, N: integer). (2) The excitation structure for a microwave oven according to claim 1, wherein the secondary radiation antenna always has a portion facing the excitation port and is rotatably supported. (3) The distance between the secondary radiation antenna and the excitation port is 1/1.
An excitation structure for a microwave oven according to claim 1 or 2, characterized in that the excitation structure is provided at a distance of 8λ to 1/4λ.