JPH11149879A - Magnetron for microwave oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetron for a microwave oven with a simple structure that suppresses a higher harmonics output. SOLUTION: This magnetron for a microwave oven is provided with a cylindrical anode 12, a cathode 13 positioned at the center of the anode 12, a plurality of vanes 14 arranged radially in all directions between the anode 12 and the cathode 13. In this case, a groove 14c is provided on top end or bottom end of at least one of a plurality of the vanes 14. A depth L of the groove 14c is in a range of 0 mm<L<6 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetron for a microwave oven with reduced harmonic output.

[0002]

2. Description of the Related Art Magnetrons for microwave ovens are used as microwave sources for microwave ovens and the like, and are used for cooking and thawing foods. There is a demand from the market for a microwave oven using a magnetron for a microwave oven, and suppression of harmonics is required. For this reason, it is necessary to suppress harmonics also in a magnetron for a microwave oven used as a microwave generation source.

[0003]

A conventional magnetron for a microwave oven has, for example, a quarter-wave choke having a coaxial structure in an output section or the like in order to suppress harmonics.
Quarter-wave chokes are usually used for suppressing the third to fifth harmonics. However, recently, suppression is required for higher order harmonics. In order to suppress higher-order harmonics than these, it is conceivable to provide a quarter-wave choke in the output unit.

However, the size of a magnetron for a microwave oven has been reduced, and the space left in an output unit has been reduced.
Therefore, in order to suppress higher order harmonics, 1/4
It is difficult to provide a new wavelength choke at the output section. In addition, in order to add a quarter-wave choke, the output portion of the magnetron for a microwave oven must be increased accordingly, which increases the size of the microwave oven and increases the cost.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and to provide a magnetron for a microwave oven which can suppress harmonic output with a simple structure.

[0006]

SUMMARY OF THE INVENTION The present invention provides a cylindrical anode, a cathode located at the center of the anode, and a plurality of vanes radially arranged between the anode and the cathode. In the magnetron for a microwave oven, a groove is provided on at least one of an upper side and a lower side of the plurality of vanes, and a depth L of the groove is set to 0 mm <L <6 m.
m.

[0007]

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a sectional view showing a main part of a magnetron for a microwave oven.

Reference numeral 11 denotes a magnetron oscillating section main body for generating a high-frequency signal. The oscillating section main body 11 includes a cylindrical anode 12 and the like. Cylindrical anode 1
A cathode 13 that emits electrons is provided at the center of 2.
A plurality of plate-like vanes 14 are radially arranged between the cylindrical anode 12 and the cathode 13. Pole pieces 15 are provided at openings at both upper and lower ends of the cylindrical anode 12. An envelope 16 connected to the cylindrical anode 12 is provided outside the pole piece 15. The envelope 16 includes a flange portion 16a and a cylindrical portion 16b, and forms a part of a vacuum vessel integrally with the cylindrical anode 12. Cylindrical portion 16b
For example, the upper end is folded inward to form a 1/4 wavelength choke 17a having a coaxial structure. It should be noted that the inside of the quarter-wave choke 17a is also coaxially formed with 1 / of the other coaxial structure.
A four-wavelength choke 17b is formed.

The plurality of plate-shaped vanes 14 located between the cylindrical anode 12 and the cathode 13 are provided with an antenna mounting groove 14a, a strap ring mounting groove 14b, a harmonic suppression groove 14c, and the like. Plural plate vanes 14
Is generally of the same structure, and is fixed, for example, with its top and bottom reversed in the arrangement direction.

Therefore, the antenna mounting groove 14a is located on the upper side of the output side in one plate-like vane 14, and is located on the lower side of the input side in the adjacent plate-like vane 14. An output antenna 18 is fixed to one plate-shaped vane 14 in an antenna mounting groove 14a. In this case, the antenna mounting groove 1 where the output antenna is not fixed
4a is left as a groove.

The output antenna 18 extends upward through the through hole of the pole piece 15 and further has an insulating cylindrical portion 19.
And an upper end portion thereof constitutes an output unit 20 for extracting microwaves to the outside.

The strap ring mounting grooves 14b are provided on the upper side and the lower side of each plate-like vane 14, and the strap ring 21 is fixed to the strap ring mounting grooves 14b. The strap ring 21 connects every other plate-shaped vane 14 so that the polarity is inverted between adjacent ones.

A radiator 22 is press-fitted around the cylindrical anode 12. The radiator 22 is composed of a plurality of cooling fins 22a extending perpendicular to the tube axis. In addition, annular permanent magnets 23 are arranged above and below the oscillating portion main body 11, respectively.

A gasket contact ring 24 is arranged outside the insulating cylindrical portion 19, and a gasket 25 is annularly arranged in contact with the gasket contact ring 24. A first magnetic yoke 26 is provided in contact with the gasket 25 in a direction perpendicular to the tube axis. Gasket 25
Are press-fitted and sandwiched between the gasket contact ring 24 and the first magnetic yoke 26. Further, a second magnetic yoke 27 is arranged so as to surround the radiator 22 and the permanent magnet 23 at the lower end of the oscillation section main body 11. The second magnetic yoke 27 is
The magnetic circuit is magnetically connected to the magnetic yoke 26 and connects the permanent magnets 23 positioned above and below.

Here, the structure of each part of the cylindrical anode 12 and the plate-like vane 14 of the magnetron for a microwave oven having the above-described structure will be described with reference to FIG. FIG.
Then, the same reference numerals are given to the portions corresponding to FIG. 1, and the overlapping description is partially omitted. The axis of the magnetron for a microwave oven is indicated by a line MM.

As shown in this figure, the upper side of each plate-like vane 14, that is, the output side, is provided with the harmonic suppression groove 1.
4c is provided. Depth L of harmonic suppression groove 14c
Is set shorter than 6 mm in consideration of the wavelength of the harmonic to be suppressed or in consideration of the mechanical strength of the plate-like vane 14.

Next, as shown in FIG. 2, the intensity of the electric field radiated from the output side to the outside is measured for the magnetron for the microwave oven in which the harmonic suppression grooves 14c are provided on the upper side of each of the plurality of plate-shaped vanes 14. An example of the result is described with reference to FIG. The horizontal axis in FIG. 3 is the frequency (GHz), and the vertical axis is the electric field strength (dBm). The mark x indicates the case where there is no harmonic suppression groove, and the mark ◆, the mark Δ and the mark ▲ indicate the case where the depth of the harmonic suppression groove is 2.7 mm, 3.0 mm and 3.3 mm, respectively. From this figure, it can be seen that, when the harmonic suppression grooves are provided, for example, the fifth and sixth harmonics are suppressed as indicated by symbols P and Q. In particular, the sixth harmonic is suppressed.

It is considered that this is because the microwave current proceeds along the surface of the plate-like vane, and the harmonics resonate by the harmonic suppression grooves. Note that a quarter-wave choke having a coaxial structure that has been provided so far in an output section of a magnetron for a microwave oven or the like is usually configured to suppress the third to fifth harmonics. Therefore, the depth of the harmonic suppression groove is longer than 1 mm and shorter than 6 mm, for example, so as to suppress the fifth or higher order harmonic.

As described above, according to the present invention, since the harmonic suppression groove is formed in the plate-like vane, the overall structure is not enlarged. In addition, harmonics can be suppressed with a simple structure.

Next, another embodiment of the present invention will be described with reference to FIGS. 4 to 6, parts corresponding to those in FIG. 2 are denoted by the same reference numerals, and redundant description is partially omitted.

FIG. 4 shows that a plurality of plate-like vanes 14 are each provided with a harmonic suppression groove 14c on the side opposite to the output side, that is, on the lower side which is the input side. FIG. 5 shows that a plurality of plate-like vanes 14 are provided with a harmonic suppression groove 14c at every other upper and lower sides. FIG. 6 shows that one of the plurality of plate-like vanes 14, for example, only the plate-like vane 14 to which the output antenna 18 is attached is provided with the harmonic suppression groove 14c.

In the above embodiment, the harmonic suppression groove is provided between the output antenna mounting groove and the cylindrical anode. However, in the case of a magnetron for a microwave oven, electrons are generated from a cathode, converted into microwaves by a resonance circuit including a cylindrical anode and a plate-like vane, and output from an output antenna. Therefore, by providing a harmonic suppression groove inside the output antenna mounting groove, for example, between the output antenna mounting groove and the strap ring mounting groove, a magnetron for a microwave oven that can further suppress harmonics is provided. realizable.

[0023]

According to the present invention, a magnetron for a microwave oven which can suppress harmonics with a simple structure can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining an embodiment of the present invention, in which main parts are extracted and shown.

FIG. 2 is a structural view showing each part of a cylindrical anode and a plate-like vane used in the present invention.

FIG. 3 is a characteristic diagram for explaining characteristics of the present invention.

FIG. 4 is a structural view showing another example of each part of a cylindrical anode and a plate-like vane used in the present invention.

FIG. 5 is a structural view showing another example of each part of a cylindrical anode or a plate-like vane used in the present invention.

FIG. 6 is a structural view showing another example of each part of a cylindrical anode and a plate-like vane used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Oscillation part main body 12 ... Cylindrical anode 13 ... Cathode 14 ... Plate-like vein 14a ... Antenna mounting groove 14b ... Strap ring mounting groove 14c ... Harmonic suppression groove 15 ... Pole piece 16 ... Envelope 17a, 17b ... 1 / 4 wavelength choke 18 ... output antenna 19 ... insulating cylindrical part 20 ... output part 21 ... strap ring 22 ... radiator 23 ... permanent magnet 24 ... gasket contact ring 25 ... gasket 26 ... first magnetic yoke 27 ... second magnetic yoke

Claims (4)

[Claims] 1. A magnetron for a microwave oven comprising: a cylindrical anode; a cathode located at the center of the anode; and a plurality of vanes radially arranged between the anode and the cathode. 3. The magnetron according to claim 1, wherein a groove is provided in at least one of an upper side and a lower side of the plurality of vanes, and a depth L of the groove is in a range of 0 mm <L <6 mm. 2. The magnetron according to claim 1, wherein all of the plurality of vanes have grooves. 3. The magnetron for a microwave oven according to claim 1, wherein a part of the plurality of vanes is provided with a groove on an upper side on an output side, and at least a part is provided with a groove on a lower side on an input side. 4. A cylindrical anode, a cathode located at the center of the anode, and radially arranged between the anode and the cathode to form a groove for mounting an antenna and a groove for mounting a strap ring. In a magnetron for a microwave oven comprising a plurality of vanes provided with grooves, a groove is provided on at least one of an upper side and a lower side of the plurality of vanes, and a depth L of the groove is set to 0 mm <L <6 mm. A magnetron for a microwave oven, wherein the magnetron has a range.