JPH03238736A - Magnetron - Google Patents

Abstract

PURPOSE:To obtain sufficient effect of suppressing higher harmonics of short wavelength easily and surely be setting a higher harmonics suppressing choke structure electrically connected with a cylindrical metal container between an insulating cylinder in the output side and an antenna conductor. CONSTITUTION:To add higher harmonics suppressing choke, a choke structure 13 having circular grooves with a depth of 1/4 wavelength of any higher harmonics is set toward the inside space of an insulating cylinder 8 in the output side while its end part to be connected air-tightly with the insulating cylinder 8 in the output side of the metal container 7 being electrically connected. The insulating cylinder 8 having length (l) in the output side is thus covered with a metallic choke structure 13 to the extent of over 1/2 of the length (l), so that the length (l) of the insulating cylinder 8 in the output side which is regard as a space for high frequency is shortened to (l). As a result, sufficient effect of suppressing higher harmonics of short wavelength is obtained simply and surely.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a magnetron used in microwave ovens and the like.

(b) Conventional technology The basic oscillation frequency of magnetrons generally used in household microwave ovens is determined by the International Telecommunication Union (ITU) to be in the range of 2450±50MHz. The second,
Many harmonics such as the third harmonic are included, and the fundamental wave also includes components outside the above range. For example, when this harmonic wave is propagated into the cavity of a microwave oven, the shorter the wavelength of this harmonic wave, the more difficult it is to shield it, and the more likely it is to leak to the outside. Even if these leaked radio waves are quite weak, they may cause radio interference. Particularly recently, unnecessary radiation corresponding to the fifth harmonic has been viewed as a problem because it overlaps with the 12 GHz band of SHF band satellite broadcasting.

Incidentally, it is already known that a wavelength choke is provided at the output section of the magnetron itself as a technique for suppressing unnecessary radiation. For example, Tokuko Sho 54-6862
This method is disclosed in Japanese Patent Application Laid-Open No. 61-288347, etc. Such a magnetron has a structure approximately as shown in FIG. In the figure, (7) is a metal container, (8
) is the output side insulating tube, and (9) is the antenna conductor. Then, the depth d of the groove of the choke structure (12) provided in the metal container (7) surrounding the antenna conductor (9) is set to approximately % of the harmonic wavelength, and the choke structure for the harmonics is constructed. Further, by varying the depth d, arbitrary harmonics can be suppressed.

However, although this conventional technology is effective in suppressing relatively long wavelength harmonics such as second and third harmonics, SHF
A sufficient effect cannot be obtained in suppressing harmonics of short wavelengths, such as the fifth harmonic of microwave ovens, which is a problem because it almost coincides with 12GH2, which is the frequency band of satellite broadcasting. The reason for this is that the length l of the output side insulating cylinder shown in Figure 5 is generally required to be about 10 mm due to its high frequency insulation properties, so for short wavelength harmonics, it is considered as space and radiated to the outside. It is presumed that this is because the

(c) Problems to be Solved by the Invention Therefore, an object of the present invention is to provide a magnetron having a choke structure that can easily and reliably obtain a sufficient effect to suppress harmonics of short wavelengths. .

(d) Means for Solving the Problems The present invention is characterized in that a harmonic suppression choke structure electrically coupled to the cylindrical metal container is disposed between the output-side insulating cylinder and the antenna conductor.

(E) Function According to the present invention, since the harmonic suppression choke is provided in the inner space of the insulating cylinder, which was conventionally considered as a space, the length l of the output side insulating cylinder, which was considered as a space, is shortened. Therefore, leakage from this part can be suppressed and the choke effect can be improved.

(f) Example FIG. 1 shows a magnetron according to an embodiment of the present invention.

(1) is a cylindrical anode body, (5) is a cathode structure installed on the central axis of the cylindrical anode body, and (2) is fixed to the inner surface of the cylindrical anode body (1), and is attached to the cathode (5). A plurality of anode vanes (6) are arranged radially around the anode body, and a pole piece (6) is fixed to one open end of the cylindrical anode body (1). (7) is a cylindrical metal container, (8) is an output side insulating cylinder, (10) is an exhaust pipe,
They are sequentially stacked and fixed to form an airtight space communicating within the cylindrical anode body (1). (9) is fixed at one end to the anode vane (2), extends inside the airtight space, and then the other end is attached to the exhaust pipe (
10) is an antenna conductor fixedly attached, and (11) is an antenna cap capped on the exhaust pipe (10).

In the above configuration, in order to add a harmonic suppression choke, the output side insulating tube (8) is electrically coupled to the end of the metal container (7) on the side that is hermetically sealed to the output side insulating tube (8).
A choke structure (13) having an annular groove having a depth of % wavelength of an arbitrary harmonic is disposed toward the inner space of the harmonic. This wavelength choke structure has the same principle as a door seal or the like which is generally used as a countermeasure against radio wave leakage in microwave ovens, and the choke structure (13) acts as a cavity resonator. The choke structure (13) is formed integrally with the metal container (7) by deep drawing using a press. The dimensions of the choke structure (13) at this time are: If the purpose is to suppress the fifth harmonic of a microwave oven magnetron whose fundamental wave is 2450 MHz, the depth d shown in FIG.
Approximately 4.5 strokes equals 6.01111.

In this embodiment, the dimension D1 within the choke structure shown in FIG. g, dimension D2 outside the choke structure, D1=11.0ml, g”t, omnD2, respectively.
=8.01+11. Note that a sufficient distance is maintained between the choke structure (13) and the antenna conductor (9) so that no discharge occurs due to the high frequency electric field generated between them.

An experiment between this embodiment and the conventional one revealed that in this embodiment, the output-side insulating tube (8), which generally has a length of 1, has a choke structure (8) made of strong metal, whose length is l. 13〉, the length l of the output side insulating tube (8), which is regarded as space in terms of high frequency, is shortened to 1′, and even for high-order harmonics with short wavelengths, As shown, a better suppression effect than the conventional choke configuration can be obtained.

In this embodiment, when l is constant, the shorter the wavelength to be suppressed, the shorter d becomes and the more l' increases. In this case, it is not expected to suppress the leakage from the output-side insulating tube (8) to a great extent, so the %λ choke structure is constructed without changing 1', as in the configuration of the second embodiment shown in FIG. It is desirable to form a

(g) Effects of the invention The present invention has sufficient effects for suppressing short wavelength harmonics.
Furthermore, by arranging the reliable choke structure inside the output side insulating cylinder, it is possible to suppress radio wave leakage to a greater extent, and it is possible to suppress radio wave interference to SHF band satellite broadcasting, etc. play.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a magnetron according to an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the main part of the same embodiment, Fig. 3 is an enlarged sectional view of the main part of another embodiment, and Fig. 4 is a conventional one. FIG. 5 is a sectional view of a main part of a conventional harmonic suppressing magnetron. (1)...Cylindrical anode body, (5)...Cathode structure, (7
)...Cylindrical metal container, (8)...Output side insulating tube, na conductor, (12) (13)...Choke structure. (9)...Anti

Claims (1)

[Claims] (1) A cathode assembly, a cylindrical anode body having a plurality of vanes arranged around the cathode assembly, a cylindrical metal container forming an airtight space at one end of the cylindrical anode body, and the cylindrical metal container. In the magnetron, the magnetron has an output-side insulating tube hermetically sealed to the vane, and an antenna conductor having one end electrically coupled to the vane and extending through the inner space of the cylindrical metal container and the insulating tube. A magnetron characterized in that a harmonic suppressing choke structure electrically coupled to a metal container and surrounding the antenna conductor is disposed in an inner space of the output side insulating tube.