Magnetron

Abstract

The magnetron of the present invention includes an anode cylinder, a plurality of vanes, a cathode filament, an input-side magnetic pole, an output-side magnetic pole, and a choke structure portion. The anode cylinder has an input-side opening portion and an output-side opening portion, and has a cylindrical shape. The plurality of vanes are radially arranged from the central axis of the anode cylinder to the inner wall surface of the anode cylinder. The cathode filament is arranged along the central axis of the anode cylinder. The input-side magnetic pole and the output-side magnetic pole are respectively arranged at the input-side opening portion and the output-side opening portion. The choke structure portion is arranged inside an opening formed in the input-side magnetic pole. The choke structure portion is formed without a seam and is arranged so as to cover the peripheral portion of the opening of the input-side magnetic pole with respect to the central axis of the anode cylinder.

Description

Technical Field

[0001] The present invention relates to a magnetron. Background Art

[0002] Patent Document 1 discloses a magnetron for a microwave oven that prevents an electrical short circuit between vanes and a cathode filament and deterioration of the vacuum degree inside the tube. The magnetron described in Patent Document 1 has, inside an anode cylinder, a plurality of vanes radially arranged from a central axis and a cathode filament arranged along the central axis of the anode cylinder.

[0003] Both ends of the cathode filament are fixed to respective end caps. Pole pieces (magnetic poles) are fixed to two openings of the anode cylinder, respectively. The axial interval between the end cap and the vane is set as dimension A, and the axial interval between the inner peripheral end of the pole piece and the vane is set as dimension B, and dimension A and dimension B are set to satisfy a specified relational expression.

[0004] Regarding a high-output industrial magnetron, Patent Document 2 has, at both end openings of an anode cylinder, a substantially funnel-shaped output-side magnetic pole, an input-side magnetic pole, and a side tube fixed thereto. A heat dissipation plate and a choke structure portion are fixed to the input-side magnetic pole. The heat dissipation plate releases heat generated in the input-side magnetic pole. The choke structure portion attenuates microwaves leaking toward the cathode side.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Laid-Open No. 6-290712

[0008] Patent Document 2: Japanese Patent Laid-Open No. 2018-56078 Summary of the Invention

[0009] Conventionally, in a high-output industrial magnetron of 2 kW or more, a heat dissipation plate and a cylindrical choke structure portion are fixed to an input-side magnetic pole inside a core tube. Generally, the magnetic pole and the cylindrical choke structure portion are formed, for example, by punching a plate of a ferromagnetic material such as cold-rolled steel sheet.

[0010] However, in the case of manufacturing a magnetic pole having a complex shape such as deep drawing or providing a step difference, it is very difficult even if a material for deep drawing is used. In the case of manufacturing such a complex-shaped magnetic pole, burrs or edge collapse may occur.

[0011] Therefore, due to the influence of burrs or edge collapse generated during stamping or deviation caused by component tolerances, coaxial deviation or solder retention may occur when the magnetic pole and the cylindrical choke structure portion are fixed. Therefore, it is difficult to manufacture to the designed dimensions, which becomes a cause of adverse effects on characteristics, unstable operation, or short life.

[0012] An object of the present invention is to provide a magnetron that can suppress the generation of unnecessary protrusions and prevent tube internal discharge and deterioration of the internal vacuum degree of the tube.

[0013] The magnetron of the present invention includes an anode cylinder, a plurality of vanes, a cathode filament, an input-side magnetic pole, an output-side magnetic pole, and a choke structure portion.

[0014] The anode cylinder has an input-side opening and an output-side opening and is in a cylindrical shape. The plurality of vanes are radially arranged from the central axis of the anode cylinder to the inner wall surface of the anode cylinder. The cathode filament is arranged along the central axis of the anode cylinder. The input-side magnetic pole and the output-side magnetic pole are respectively arranged at the input-side opening and the output-side opening.

[0015] The choke structure portion is arranged inside the opening provided in the input-side magnetic pole. The choke structure portion is formed without seams and is arranged so as to cover the peripheral portion of the opening of the input-side magnetic pole with respect to the central axis of the anode cylinder.

[0016] The magnetron of the present invention can prevent tube internal discharge and deterioration of the internal vacuum degree of the tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a cross-sectional view of the magnetron according to an embodiment of the present disclosure.

[0018] Figure 2 is a partial cross-sectional perspective view of the magnetron according to the embodiment.

[0019] Figure 3 is a partial cross-sectional view of the magnetron according to the first modification of the embodiment.

[0020] Figure 4 is a partial cross-sectional view of the magnetron according to the second modification of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] (Insights etc. that form the basis of the present disclosure)

[0022] When the inventors came up with the present disclosure, the above problems were known. Therefore, generally, those skilled in the art design the axial interval between the end cap and the vane and the radial interval between the end cap and the inner peripheral end portion of the input-side magnetic pole within a specified range. Thereby, discharge generated between the end cap at the cathode portion and the input-side magnetic pole is prevented.

[0023] Under this condition, the inventors obtained the idea of preventing tube internal discharge at the inner peripheral end portion of the input-side magnetic pole by being inspired by preventing electrons (stray electrons) released from the cathode filament from flowing excessively into the magnetic pole.

[0024] In order to implement this concept, it is necessary to suppress the coaxial offset when the input-side magnetic pole is joined to the cylindrical choke structure portion, and suppress the generation of unevenness and protrusions caused by solder retention. To solve this problem, the inventor came up with the subject matter of the present disclosure.

[0025] The present invention provides a magnetron that can prevent the occurrence of internal tube discharge and the accompanying deterioration of the internal tube vacuum degree.

[0026] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments, descriptions of known matters and repeated descriptions of the same or substantially the same structures may sometimes be omitted.

[0027] Use Figure 1 and Figure 2 to describe this embodiment. Figure 1 and Figure 2 are a cross-sectional view and a partially cutaway perspective view of the main part of the magnetron 100 of this embodiment, respectively.

[0028] [Structure]

[0029] The magnetron 100 of this embodiment has an operating frequency in the 2450 MHz band and an output of 2 kW or more. The operating frequency is not limited to the 2450 MHz band and may also be other operating frequencies, such as the 5.8 GHz band.

[0030] As Figure 1 and Figure 2 shown, the magnetron 100 has a magnetic circuit 10, a cooling circuit 20, an LC filter circuit 30, and a core tube 40.

[0031] The magnetic circuit 10 has a magnetic yoke 11, an input-side permanent magnet 12, and an output-side permanent magnet 13. The input-side permanent magnet 12, the output-side permanent magnet 13, and the cooling circuit 20 are arranged inside the magnetic yoke 11. The LC filter circuit 30 is arranged inside a filter housing 31 and has a choke coil 32 and a capacitor 33.

[0032] The core tube 40 has an output portion 41, an anode portion 42, and a cathode portion 43. The anode portion 42 has 14 copper blades 45 arranged on the inner wall surface of an anode cylinder 44. The blades 45 are arranged at equal intervals and radially from the central axis of the anode cylinder 44 to the inner wall surface of the anode cylinder 44.

[0033] The blades 45 form an LC circuit. Two coupling rings 46 are electrically connected to a total of 7 blades 45 at intervals of one blade each. The anode cylinder 44 has an input-side opening and an output-side opening. The input-side opening and the output-side opening respectively have a substantially funnel-shaped input-side magnetic pole 47 and an output-side magnetic pole 48. Thus, a cavity resonator is formed.

[0034] The input-side magnetic pole 47 and the output-side magnetic pole 48 effectively guide the magnetic field into the action space that is the space between the inner surface of the vane 45 and the cathode filament 49 described later. The input-side magnetic pole 47 and the output-side magnetic pole 48 each have an opening formed in the central portion. The central axis of the anode cylinder 44 passes through the openings of the input-side magnetic pole 47 and the output-side magnetic pole 48.

[0035] At the peripheral portion 471 of the opening of the input-side magnetic pole 47, a heat dissipation plate 56 for heat dissipation and a choke structure portion 57 are joined by brazing. The choke structure portion 57 is a cylindrical choke structure portion for attenuating microwaves leaking to the cathode side. The input-side magnetic pole 47 is electrically connected to the heat dissipation plate 56 and the choke structure portion 57.

[0036] The choke structure portion 57 has a cylindrical portion 571 and a flange portion 572. The flange portion 572 is bent so as to extend in the radial direction of the opening of the input-side magnetic pole 47. The cylindrical portion 571 and the flange portion 572 are arranged at the side end portion of the input-side magnetic pole 47 so as to cover the peripheral portion 471 of the opening of the input-side magnetic pole 47 with respect to the central axis of the anode cylinder 44. The cylindrical portion 571 and the flange portion 572 are formed without a seam.

[0037] In the present embodiment, the flange portion 572 of the choke structure portion 57 is formed by bending. However, the flange portion 572 may be formed without a seam with the cylindrical portion 571, and for example, it may also be formed by cutting.

[0038] Brazing is carried out using a jig for joining. Therefore, due to the influence of the positional relationship of each component and the component tolerance, the input-side magnetic pole 47, the heat dissipation plate 56, and the choke structure portion 57 may sometimes be joined at positions deviating from the positions that should be coaxial in the design. This displacement and the solder retention at the joint portion may have an adverse effect on the characteristics of the magnetron 100. For example, in-tube discharge may occur at the inner peripheral end portion of the input-side magnetic pole 47.

[0039] Therefore, the choke structure portion 57 covers the input-side magnetic pole 47 without a seam, thereby suppressing the coaxial offset during joining and the solder retention at the joint portion. The input-side magnetic pole 47, the heat dissipation plate 56, and the choke structure portion 57 of the joint portion are arranged opposite to each other. Since the gaps between the input-side magnetic pole 47, the heat dissipation plate 56, and the choke structure portion 57 communicate with each other, the amount of brazing material required for joining can be reduced.

[0040] In the present embodiment, the number of vanes 45 is set to 14. However, it is not limited to this. For example, 10 copper vanes may be arranged radially at equal intervals from the central axis of the anode cylinder 44.

[0041] In the cathode section 43 of the electron action space surrounded by the inner side of the vane 45, a helical cathode filament 49 is arranged along the central axis of the anode cylinder 44. The output side end cap 50 and the input side end cap 51 are respectively fixed to both ends of the cathode filament 49. The output side end cap 50 and the input side end cap 51 are respectively supported by the central lead 52 and a side lead (not shown) and fixed to the cathode tube socket 53 of the input section.

[0042] The side tubes 54 and 55 are respectively fixed to the output side magnetic pole 48 and the input side magnetic pole 47. The output section 41 and the cathode tube socket 53 are respectively provided on the side tubes 54 and 55 so as to protrude from the side tubes 54 and 55.

[0043] The input side permanent magnet 12 and the output side permanent magnet 13 are coaxially arranged so as to surround the side tubes 54 and 55. Usually, a cooling block 21 as a cooling circuit 20 is provided on the outer periphery of the anode cylinder 44. The yoke 11 is arranged so as to surround the cooling block 21, the input side permanent magnet 12 and the output side permanent magnet 13. One of the vanes 45 is electrically connected to one end of the antenna 58. The antenna 58 penetrates the output side magnetic pole 48 and extends along the tube axis of the core tube 40 to constitute the output section 41.

[0044] [Operation]

[0045] Refer to Figure 1 , the operation of the magnetron 100 configured as above will be described.

[0046] The thermoelectrons released from the cathode filament 49 perform circular motion in the action space of the cavity formed between the vane 45 and the cathode filament 49. Thus, the magnetron 100 oscillates microwaves.

[0047] This microwave is transmitted to one vane 45, and after being transmitted to the antenna 58 joined to this one vane 45, it is released into the external space. However, the conversion efficiency is not 100%. Heat is generated due to the electrons that cannot contribute to the oscillation of the microwave. As a result, the temperature near the action space rises, and unstable oscillation may occur.

[0048] The microwave that is not released into the external space leaks to the cathode side. Therefore, disadvantages such as unstable oscillation or adverse effects on the drive power source occur. The larger the output, the more significant such adverse conditions become.

[0049] As a countermeasure against these problems, in a magnetron of 2 kW or more, the temperature rise caused by the electrons that cannot contribute to the oscillation of the microwave is suppressed through the heat dissipation plate 56 arranged on the input side magnetic pole 47, via the anode cylinder 44 and the cooling block 21.

[0050] By arranging the choke structure portion 57 disposed on the input side magnetic pole 47 coaxially with the center lead 52, the attenuation of the microwave leaking to the cathode side is achieved.

[0051] In the structure of the magnetron 100, due to the coaxial arrangement of the cathode portion 43, the input side magnetic pole 47, and the choke structure portion 57, electrons (stray electrons) released from the cathode filament 49 excessively flow into the input side magnetic pole 47. As a result, an internal tube discharge is generated at the inner peripheral end portion of the input side magnetic pole 47. Consequently, the internal vacuum degree of the tube deteriorates, which has an adverse effect on the characteristics.

[0052] In the present embodiment, the inner peripheral end portion of the input side magnetic pole 47 is covered by the choke structure portion 57. Thus, even if burrs or collapses are generated in the input side magnetic pole 47 and the choke structure portion 57 during stamping, the coaxial deviation when the input side magnetic pole 47 and the choke structure portion 57 are joined can be suppressed. The generation of unevenness and protrusions caused by solder retention can also be suppressed.

[0053] [Effect]

[0054] In the present embodiment, the inner peripheral end portion of the input side magnetic pole 47 is covered by the choke structure portion 57 integrally formed with the input side magnetic pole 47. Thus, the coaxial deviation when the input side magnetic pole 47 and the choke structure portion 57 are joined can be suppressed, and the generation of unevenness and protrusions caused by solder retention can be suppressed. As a result, internal tube discharge and deterioration of the internal vacuum degree of the tube can be prevented.

[0055] [First Modification Example]

[0056] Figure 3 is a main part cross-sectional view of the first modification example of the present embodiment. As Figure 3 shown, this modification example has an input side magnetic pole 47A, a heat dissipation plate 56A, and a choke structure portion 57A instead of the input side magnetic pole 47, the heat dissipation plate 56, and the choke structure portion 57 in the above-described embodiment.

[0057] In this modification example, the input side magnetic pole 47A and the choke structure portion 57A are integrally formed. Thus, the coaxial deviation when the input side magnetic pole 47A and the choke structure portion 57A are joined can be suppressed, and the generation of unevenness and protrusions caused by solder retention can be suppressed. As a result, internal tube discharge and deterioration of the internal vacuum degree of the tube can be prevented.

[0058] [Second Modification Example]

[0059] Figure 4 is a main part cross-sectional view of the second modification example of the present embodiment. As Figure 4 shown, this modification example has an input side magnetic pole 47B, a heat dissipation plate 56B, and a choke structure portion 57B instead of the input side magnetic pole 47, the heat dissipation plate 56, and the choke structure portion 57 in the above-described embodiment.

[0060] In this modification example, the input-side magnetic pole 47B is integrally formed with the choke structure portion 57B and the heat dissipation plate 56B without seams. Thereby, coaxial deviation when the input-side magnetic pole 47B is joined to the choke structure portion 57B can be suppressed, and generation of unevenness and protrusions caused by solder retention can be suppressed. As a result, in-tube discharge and deterioration of the in-tube vacuum degree can be prevented.

[0061] Industrial applicability

[0062] The present disclosure can be applied to magnetrons and microwave application devices using magnetrons. The microwave application devices include a device for generating artificial diamond, a radar device, a medical device, a cooker such as a microwave oven, a semiconductor manufacturing device, and the like.

[0063] Explanation of reference numerals

[0064] 100: Magnetron; 10: Magnetic circuit; 11: Yoke; 12: Input-side permanent magnet; 13: Output-side permanent magnet; 20: Cooling circuit; 21: Cooling block; 30: LC filter circuit; 31: Filter housing; 32: Choke coil; 33: Capacitor; 40: Core tube; 41: Output portion; 42: Anode portion; 43: Cathode portion; 44: Anode cylinder; 45: Vane; 46: Coupling ring; 47, 47A, 47B: Input-side magnetic poles; 471: Peripheral portion of the opening; 48: Output-side magnetic pole; 49: Cathode filament; 50: Output-side end cap; 51: Input-side end cap; 52: Center lead; 53: Cathode tube base; 54, 55: Side tubes; 56, 56A, 56B: Heat dissipation plates; 57, 57A, 57B: Choke structure portions; 571: Cylindrical portion; 572: Flange portion; 58: Antenna.

Claims

1. A magnetron, wherein, The magnetron includes: An anode cylinder body, which has an input-side opening portion and an output-side opening portion and is in a cylindrical shape; A plurality of vanes, which are radially arranged from the central axis of the anode cylinder body to the inner wall surface of the anode cylinder body; A cathode filament, which is arranged along the central axis of the anode cylinder body; An input-side magnetic pole and an output-side magnetic pole, which are respectively arranged at the input-side opening portion and the output-side opening portion; And A choke structure portion, which is arranged inside an opening provided on the input-side magnetic pole, The choke structure portion is formed seamlessly with the input-side magnetic pole and is arranged in a manner of covering the peripheral portion of the opening of the input-side magnetic pole with respect to the central axis of the anode cylinder body.

2. The magnetron according to claim 1, wherein The magnetron further includes a heat dissipation plate, which is joined to the input-side magnetic pole, The input-side magnetic pole, the heat dissipation plate, and the choke structure portion are arranged opposite to each other, and the gaps between the input-side magnetic pole, the heat dissipation plate, and the choke structure portion communicate with each other.

3. The magnetron according to claim 1, wherein The magnetron further includes a heat dissipation plate, which is joined to the input-side magnetic pole, The input-side magnetic pole, the heat dissipation plate, and the choke structure portion are arranged opposite to each other, and the input-side magnetic pole is formed seamlessly with the choke structure portion and the heat dissipation plate.

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