JPH1186743A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the development of gaps at the joint of a shield case with a shield case cover and thereby prevent wanted radiation from leaking to the outside. SOLUTION: In a magnetron provided with a magnetron body, a filter connected to the input side of the magnetron body, a shield case 5 receiving the filter and a shield case cover on which a bent part having a U-shaped cross section is crimped around the opening of the shield case 5, multiple bent pieces 11 are formed around the opening 6 by bending them outward, and the dimension of each gap A for forming the bent pieces 11 is set at not more than one fourth the wavelength of the desired harmonics of the fundamental frequency. Thereby, the leakage of the desired harmonics of the fundamental frequency can be prevented, even if the bent part is deformed by a spring back or the like after crimping.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron used for a microwave heater such as a microwave oven.

[0002]

2. Description of the Related Art A magnetron used in a microwave heater or the like for a microwave oven generates unnecessary radiation in a large frequency band from a low frequency to a high frequency in addition to a fundamental oscillation frequency.

Therefore, a conventional magnetron is disclosed in Japanese Utility Model Laid-Open No. 4-4.
As disclosed in Japanese Patent No. 3958 (H01J 23/12), a filter including an inductor and a feedthrough capacitor is provided on the cathode input side of the magnetron, and unnecessary radiation leaking to the cathode input terminal side is removed by this filter.

Further, a circuit such as an inductor is housed in a shield case, an opening of the shield case is inserted into a U-shaped bent portion of the shield case cover, and the bent portion is swaged to form the shield case and the shield case cover. By preventing a gap from being formed at the joint, unnecessary radiation leaking from the magnetron body into the shield case is prevented from leaking outside the shield case.

[0005]

However, the caulking portion of the shield case and the cover of the shield case have dimensional variations and deformation of each component and the elasticity of the material itself. Some gaps may occur. Further, even when caulking is performed without a gap, deformation may occur due to external pressure or the like applied after manufacturing, and a gap may be generated in the caulked portion.

[0006] Also, no oil is required for drawing.
In some cases, a shield case or a metal plate coated with an insulating coating is used on the shield case lid because it does not rust because it does not directly touch the metal surface even if touched by hand. Even when squeezed, there may be a gap where the insulating film is interposed on the connection surface and the metal plate is not in contact.

Accordingly, an object of the present invention is to provide a magnetron that prevents a gap from being formed at a joint between a shield case and a shield case lid and prevents unnecessary radiation from leaking to the outside.

[0008]

Means for solving the problems include a magnetron body, a filter connected to the input side of the magnetron body, a shield case for housing the filter, and an opening of the shield case. And a shield case lid on which a bent portion having a U-shaped cross section is crimped,
A plurality of bent pieces are formed on the outer periphery of the opening, and the bent pieces are bent outward. Thus, each bent piece is swaged in a state of being elastically contacted with the bent portion by the restoring force of the bent piece.

In the above structure, the bent piece may be bent inward.

[0010] The bent piece may be alternately bent inward and outward.

It is desirable that the interval at which the bent pieces are formed is set to a quarter wavelength or less of a desired harmonic of the fundamental frequency. This prevents the desired harmonic from leaking.

Further, it is desirable that the shield case and / or the cover of the shield case be formed of a metal plate having an insulating coating.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

Reference numeral 1 denotes a magnetron body in which a cathode, a vane, a magnetic pole piece (not shown), and the like are disposed, and generate a microwave when the magnetron operates. Reference numeral 2 denotes a pair of permanent magnets disposed on both sides in the axial direction of the magnetron main body 1, and reference numeral 3 denotes a yoke surrounding the magnetron main body 1 and the permanent magnet 2. Reference numeral 4 denotes a plurality of heat sinks mounted on the outer periphery of the magnetron main body 1 for cooling the magnetron main body 1.

Reference numeral 5 denotes a shield case provided on the input side of the magnetron body 1, which is formed of a metal plate having an insulating coating. The shield case 5 has a box shape with an opening 6 on the entire lower surface, and has a hole 7 in the center of the surface that contacts the magnetron body 1. A cathode input terminal (not shown) of the magnetron body 1 penetrates the hole 7. Further, on the side surface of the shield case 5, a through hole 8 through which a through capacitor 12 described later is passed, and a mounting hole 9
Are formed.

A plurality of bent pieces 11 are formed in the opening 6 by V-shaped cuts 10, and the bent pieces 11 are bent outward. The interval A at which the bent pieces 11 are formed is formed to be equal to or less than 分 の mm of the wavelength of a harmonic wave whose leakage of the fundamental frequency is to be prevented.

For example, when it is desired to prevent the leakage of the fifth harmonic of the fundamental frequency, the fifth harmonic is 12.25 GHz, so its wavelength is about 24 mm, and the length of a quarter of the wavelength is 6 mm. . Therefore, the interval at which the bent pieces 11 are formed is set to 6 mm or less.

An inductor (not shown) is housed in the shield case 5 and is connected to a cathode input terminal of the magnetron main body 1. The inductor is an electric wire wound around a fillite core and a ferrite core. (Both are not shown).

Reference numeral 12 denotes a feedthrough capacitor connected to the inductor, which is fixed through the shield case 5. A filter is formed by the inductor and the feedthrough capacitor 12, and removes unnecessary radiation leaking from the cathode input terminal.

Reference numeral 13 denotes a shield case cover which is caulked to the shield case 5, and is formed of a metal plate having an insulating coating. The shield case lid 13 has a box shape with an open top, and has a bent portion 14 having a U-shaped cross section that is crimped to hold the opening 6 of the shield case 5 at the open end.

In the magnetron having the above configuration, first, the opening 6 in which the plurality of bent pieces 11 are formed has the shield case lid 1.
3 is inserted into the bent portion 14. In this state, the bent portion is swaged so as to sandwich the shield case 5, and the shield lid 13 is fixed to the shield case 5.

Thus, even if the bent portion 14 is deformed by the restoring force of the bent portion 14, the bent piece 11 is similarly bent.
The bent portion 14 is deformed in the direction in which the bent portion 14 is deformed by the restoring force, and the bent piece 11 and the bent portion 14 are maintained in a state of being pressed against each other. Therefore, no gap is generated between the bent piece 11 and the bent portion 14. Further, even if the bent portion 14 is deformed due to external pressure applied after manufacturing, the bent piece 11 is similarly deformed in a direction in which the bent portion 14 is deformed by the restoring force of the bent piece 11,
1 and the bent portion 14 are maintained in a pressed state. Therefore, no gap is generated between the bent piece 11 and the bent portion 14.

Therefore, there is no gap longer than the interval A at which the bent pieces 11 are formed, and the interval A at which the bent pieces 11 are formed is set to a quarter of the wavelength of the desired harmonic of the fundamental frequency. By doing so, leakage of desired harmonics can be prevented.

Further, as described above, since the bent piece 11 is bent outward, the coating of the bent portion 14 is formed at the tip of the bent piece 11 when the shield case lid 13 is swaged to the shield case 5. Since the strips are separated from each other, the bent portion 11 and the bent portion 14 are directly in contact with the metal portion, so that leakage of a desired harmonic can be reliably prevented.

Therefore, even if a metal plate covered with an insulating film is used for the shield case 5 and the shield case lid 13, the interval A at which the bent piece 11 is formed is set to the desired harmonic wavelength of the fundamental frequency. By setting the length to 分 の mm or less, leakage of desired harmonics can be prevented.

Although the bent piece 11 is bent outward, the bent piece 11a may be bent alternately inward and outward as shown in FIG. 6, or may be bent only inward. Is also good. It is desirable to use a metal plate having an insulating coating for both the shield case 5 and the shield case lid 13 as in the above embodiment, but using either one of them is effective.

[0027]

According to the present invention, a plurality of bent pieces are caulked by the restoring force of the bent pieces in a state of being elastically contacted with the bent portions, respectively, so that the caulked portions are deformed by external pressure applied after manufacturing. However, no gap is generated.

Also, by setting the interval between the formation of the bent pieces to be equal to or less than a quarter wavelength of the harmonic to be suppressed, leakage of the desired harmonic can be prevented.

Further, since the insulating film is peeled off at the end of the bent piece during the swaging, leakage of harmonics can be prevented even if a metal plate covered with the insulating film is used for the shield case and / or the shield case lid. .

[Brief description of the drawings]

FIG. 1 is a side view of a magnetron showing an embodiment of the present invention.

FIG. 2 is a bottom view of the shield case.

FIG. 3 is a side view of the shield case.

FIG. 4 is a cross-sectional view of a main part before the shield case lid is caulked to the shield case.

FIG. 5 is a cross-sectional view of a main part after the shield case lid is swaged to the shield case.

FIG. 6 is a cross-sectional view of a main part before the shield case lid is crimped on the shield case when the bent pieces are alternately bent inward or outward.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetron main body 5 Shield case 6 Opening 11 Folding piece 13 Shield case lid 14 Bend

Claims (5)

[Claims] 1. A magnetron body, a filter connected to an input side of the magnetron body, a shield case for accommodating the filter, and a shield case in which a bent portion having a U-shaped cross section is swaged in an opening of the shield case. A magnetron comprising: a lid; a plurality of bent pieces formed on an outer periphery of the opening; and the bent pieces are bent outward. 2. A magnetron main body, a filter connected to an input side of the magnetron main body, a shield case for accommodating the filter, and a U-shaped hole in an opening of the shield case.
A magnetron, comprising: a shield case lid in which a bent portion having a character-shaped cross section is swaged; a plurality of bent pieces formed on the outer periphery of the opening; and the bent pieces are bent inward. 3. A magnetron main body, a filter connected to an input side of the magnetron main body, a shield case for accommodating the filter, and a U-shaped hole in an opening of the shield case.
And a shield case lid in which a bent portion having a U-shaped cross section is crimped, a plurality of bent pieces are formed on the outer periphery of the opening, and the bent pieces are alternately bent inward and outward. Magnetron. 4. The magnetron according to claim 1, wherein an interval at which the bent pieces are formed is set to a quarter wavelength or less of a desired harmonic of a fundamental frequency. 5. The magnetron according to claim 1, wherein the shield case and / or the shield case lid are formed of a metal plate having an insulating coating.