JP5859264B2 - Magnetron - Google Patents

Description

  The present invention relates to a magnetron.

  The magnetron has an oscillation unit, an input unit, and an output unit. The oscillating unit includes an anode unit, a cathode unit, and a pair of pole pieces. The anode part has an anode cylinder and a plurality of vanes arranged inside the anode cylinder. The cathode portion has a filament disposed on the axis of the anode cylinder. The pair of pole pieces are disposed at both ends of the anode cylinder in the axial direction.

  The input unit has a stem that supports a cathode lead extending through one pole piece of the oscillation unit. The output unit has an antenna extending through the other pole piece. The pole piece is arranged so as to be sandwiched between permanent magnets, and concentrates the magnetic flux in the working space between the anode part and the cathode part.

  When a filament current is supplied from the input section to the cathode and a voltage is applied between the anode section and the cathode section, the magnetron oscillates in the microwave and outputs a microwave from the output section. In a general microwave magnetron, the oscillation frequency is 2450 MHz. Since a part of the oscillation output leaks from the input unit and becomes an obstacle to the external device, the input unit is shielded by a filter box, and radio wave leakage is suppressed. The oscillation output oscillates not only the fundamental wave of 2450 MHz but also a radio wave having a wide frequency band due to electronic disturbance or the like, and the filter box suppresses leakage of these radio waves.

  The filter box has a pair of feedthrough capacitors that are connected to an external power source and also serve as external input terminals. In the filter box, a pair of choke coils that connect the pair of cathode input stem terminals and the feedthrough capacitors in series are arranged. Each choke coil is composed of a coiled core type inductor having a ferrite core and an air core type inductor of an air core coil connected in series.

  The choke coil constituting the filter circuit consumes the microwave leaking from the cathode part as heat. For this reason, if the leak output becomes large, the choke coil may be burned out. If the choke coil burns out and the enamel insulation coating on the surface disappears, it may not function as an inductor.

  Moreover, when the magnetic permeability of ferrite decreases due to overheating, inductance decreases and microwave leakage increases. In addition, the air core type inductor is positioned within the inductor to attenuate the maximum amplitude portion of the 2450 MHz fundamental wave, which is the maximum component of the leakage wave, so as not to reach the core type inductor. The burden is reduced.

Japanese Patent Laid-Open No. 2005-38806

  Generally, a coil wire used for a choke coil of a magnetron filter box is covered with an enamel insulating coating. For this reason, the inductance is maintained even when the coil is tightly wound. However, when the temperature of the choke coil rises and the enamel insulation coating burns out, the inductance decreases, and this increases the filament current and shortens the life of the filament.

  In the manufacture of the magnetron, the choke coil, the feedthrough capacitor, and the stem terminal of the magnetron main body are joined by TIG welding. If welding is performed with the enamel insulation coating on the coil wire of the choke coil, poor welding is likely to occur. For this reason, the peeling process which peels off the enamel insulation coating of the both ends of the choke coil which is a welding location is needed. Also, the blade for peeling needs to be replaced periodically, and the equipment operation rate in this process is lowered. Furthermore, in this peeling process, enamel insulation coating dust is generated, which has an environmental impact.

  As a coil material of the choke coil, a copper wire is generally used because of its good electrical conductivity and good machinability. However, in recent years, since the price of copper has soared, it has been studied to use an aluminum wire or a copper clad aluminum wire having a relatively low electrical resistance. However, when TIG welding is performed on aluminum wire and the center conductor of the feedthrough capacitor and iron, which is the material of the stem terminal of the magnetron, a fragile layer is formed between the iron and aluminum, resulting in low welding strength and practical application. difficult.

  Therefore, an object of the present invention is to reduce the number of work steps in manufacturing a choke coil.

In order to solve the above-mentioned problems, the present invention provides a magnetron main body having a cathode terminal, a filter box covering the cathode terminal, a choke coil connected to the cathode terminal and accommodated in the filter box, And a capacitor connected to the choke coil, the choke coil having an air core type inductor connected to the cathode terminal and a magnetic core and having a core type inductor connected in series to the air core type inductor. In addition, it is formed by winding a bare conducting wire having a specific resistance higher than that of a copper wire, the conducting wire is made of an alloy mainly composed of copper and zinc, and an oxide film is formed on the surface of the conducting wire. It is characterized by.

  According to the present invention, the number of work steps in manufacturing a choke coil can be reduced.

It is a top view of the filter box vicinity in one Embodiment of the magnetron based on this invention. It is sectional drawing of one Embodiment of the magnetron based on this invention. It is a table | surface which shows the test result of the temperature of the choke coil in one Embodiment of the magnetron based on this invention.

  An embodiment of a magnetron according to the present invention will be described with reference to the drawings. The following embodiments are merely examples, and the present invention is not limited thereto.

  FIG. 1 is a cross-sectional view of an embodiment of a magnetron according to the present invention.

  This magnetron is used for a microwave oven, for example. The magnetron includes a magnetron main body and a filter box 31.

  The magnetron main body has an anode part and a cathode part. The anode part has an anode cylinder 12 and a plurality of vanes 13 protruding from the inner peripheral surface of the anode cylinder 12 toward the tube axis. The cathode portion has a filament 15, a pair of end hats 16, 17, a cathode center lead 18, and a cathode side lead 19. The filament 15 is disposed on the tube axis of the magnetron. The end hats 16 and 17 are provided at both ends of the filament 15 in the tube axis direction. The cathode center lead 18 and the cathode side lead 19 extend toward the input portion of the magnetron body. The cathode center lead 18 and the cathode side lead 19 are connected to both ends of the filament 15 via end hats 16 and 17, respectively.

  Between the free end of the vane 13 opposite to the anode cylinder 12 and the filament 15, the vane 13 is disposed so as to have a predetermined interval. The annular space having the predetermined interval becomes an action space 23.

  At both ends of the anode cylinder 12 in the tube axis direction, a pair of funnel-shaped (mortar-shaped) pole pieces 20 and 21 are provided to face each other so as to sandwich the working space. On the outer side in the tube axis direction of each of the pole pieces 20 and 21, an input unit for supplying a current for applying a filament and a high voltage for driving a magnetron, and an output unit including an antenna lead 41 for transmitting and radiating microwaves, Is provided. One end of the antenna lead 41 is connected to one vane 13. The other of the antenna leads 41 extends toward the output unit along the tube axis.

  A pair of annular permanent magnets 50 and 51 made of ferrite are provided on both outer sides in the tube axis direction of the pair of pole pieces 20 and 21. In addition, frame-shaped yokes 52 and 53 are provided so as to surround the outer sides and the side surfaces of the annular permanent magnets 50 and 51 in the tube axis direction. The frame-like yokes 52 and 53 are made of a ferromagnetic material. The annular permanent magnets 50, 51 are magnetically coupled to the pole pieces 20, 21 on the surface facing the pole pieces 20, 21 and to the frame-shaped yokes 52, 53 on the opposite surface of the pole pieces 20, 21, respectively. A magnetic field is supplied to the working space 23 between the vane 13 and the filament 15 by the constructed magnetic circuit.

  FIG. 1 is a bottom view of the inside of the filter box in the present embodiment.

  The filter box 31 covers the input part of the magnetron. The input unit includes a ceramic stem 32 that holds the cathode center lead 18 and the cathode side lead 19, and a pair of cathode terminals 33 connected to the cathode center lead 18 and the cathode side lead 19, respectively.

  A two-terminal feedthrough capacitor 34 that passes through the side wall of the filter box 31 is attached. A choke coil 35 is connected in series between each of a pair of cathode terminals 33 located substantially in the center of the filter box and a terminal 81 inside the filter box 31 of the feedthrough capacitor 34. The feedthrough capacitor 34 and the choke coil 35 form a filter circuit.

  Each choke coil 35 is formed by connecting a core type inductor 36 and an air core type inductor 37 in series. The core type inductor 36 has a columnar magnetic core 91. The air core type inductor 37 side is connected to the cathode terminal 33 through a bent wire 38 having a predetermined length. The core type inductor 36 side is connected to the terminal 81 of the feedthrough capacitor.

  Of the microwaves leaking through the cathode terminal 33, the fundamental wave component of 2450 MHz is the largest, and the position corresponding to a quarter wavelength of the fundamental wave, that is, the position where the amplitude of the leaked microwave is maximized is the air-core type. The length of the choke coil including the bent wiring 38 is set so as to be within the inductor 37. In this case, most of the leaking microwave is absorbed by the air-core type inductor 37. Since the air core type inductor 37 can be cooled using ambient air or the like, the temperature rise of the core type inductor 36 is suppressed by separating the maximum heat generating portion of the loosely wound air core type inductor 37 from the core type inductor 36. A decrease in inductance of the choke coil 35 can be suppressed.

  In the present embodiment, these choke coils 35 are formed by winding a bare conducting wire. Here, “bare” means that there is no resin-made insulating coating unlike an enameled copper wire or the like. An oxide film may be provided for insulation between the lines. In the case of using a bare conductor provided with an oxide film, the coil can be formed at a pitch of about 0.3 to 0.5 mm in consideration of the withstand voltage of the oxide film. These choke coils 35 are made of a material having a specific resistance higher than that of the copper wire. As the magnetic core 91 of the core type inductor 36, a material having a Curie point higher than that in the case where an enameled copper wire is used is used.

  As described above, in the present embodiment, since the choke coil 35 does not have a resin insulating film, the manufacturing process of the choke coil 35 does not require an insulating film peeling process, and the manufacturing cost is reduced. Moreover, the merit that the dust of an insulating film is not discharged | emitted is acquired.

  Further, since the choke coil 35 does not have a resin insulating film, a material that increases the temperature of the choke coil 35 can be used for the choke coil 35. Even when the temperature of the choke coil 35 is higher than when the enameled copper wire is used, there is no fear of insulation failure due to burning of the insulating coating. That is, the choke coil 35 can be formed of a material having a higher electric resistance than the enameled copper wire that has been used as a material of the choke coil in the past. However, if the choke coil 35 is formed using a material having an excessively high electrical resistance, heat is generated by the resistance of the coil wire, the temperature of the magnetic core 91 exceeds the Curie point, and the inductance is reduced. Are preferred.

  The choke coil 35 may be formed of a brass (copper / zinc alloy) wire having a relatively small electrical resistance, or an alloy containing copper and zinc as main components and containing Sn, Fe, Au, Ag, or the like. These materials have the advantage of being easy to weld.

  A test was conducted to examine how much the temperature rises as the material of the choke coil 35 is changed.

  FIG. 3 is a table showing the test results of the temperature of the choke coil in the present embodiment.

  In this test, the temperatures of three types of choke coils 35 using brass wires having a wire diameter of φ1.2 mm were measured. These three types of choke coils 35 have the same air core portion in 3 turns, but the core portion has 10 turns, 8 turns or 6 turns. For comparison, the temperature of a choke coil using enameled copper wire with a wire diameter of φ1.2 mm was measured.

  The core part temperature of the test body 1 having the same number of turns as that of the comparative example is about 50 ° C. higher than that of the comparative example. Therefore, as the material of the magnetic core 91, it is necessary to select a material having a Curie point higher by 50 ° C. or more than that used in a magnetron using an enameled copper wire having a wire diameter of φ1.2 mm. In a magnetron, inexpensive ferrite is often used as the magnetic core 91. Therefore, in such a case, the choke coil 35 is made of brass or brass by forming the magnetic core 91 with a material having a Curie point higher by 50 ° C. or more than ferrite without changing the design of other parts. It can be manufactured using a bare coil wire made of a material having a low electrical resistance.

  In addition, from the test result of the core part of the test body 2 or the test body 3 having a small number of turns in the core part, the temperature of the core part decreases to some extent as the number of turns decreases, but is higher than in the case of enameled copper wire. I understand that. However, if the number of turns is too small, the inductance becomes too small. Further, if the wire diameter is increased in order to reduce the electric resistance, there is a problem in terms of manufacturability. Therefore, it is necessary to determine the wire diameter and wire length of the choke coil 35 in consideration of these points.

12 ... anode cylinder, 13 ... vane, 15 ... filament, 16 ... end hat, 17 ... end hat, 18 ... cathode center lead, 19 ... cathode side lead, 20 ... pole piece, 21 ... pole piece, 23 ... working space, DESCRIPTION OF SYMBOLS 31 ... Filter box, 32 ... Ceramic stem, 33 ... Cathode terminal, 34 ... Feed-through capacitor, 35 ... Choke coil, 36 ... Core type inductor, 37 ... Air core type inductor, 38 ... Bending wiring, 41 ... Antenna lead, 50 ... Ring Permanent magnet, 51 ... annular permanent magnet, 52 ... frame-shaped yoke, 53 ... frame-shaped yoke, 81 ... terminal, 91 ... magnetic core

Claims (1)

A magnetron body having a cathode terminal, a filter box covering the cathode terminal, a choke coil connected to the cathode terminal and housed in the filter box, and a capacitor connected to the choke coil,
The choke coil is
An air-core type inductor connected to the cathode terminal and a core-type inductor connected in series to the air-core type inductor with a magnetic core;
It is formed by winding a bare conductor whose specific resistance is higher than copper wire ,
The magnetron is characterized in that the conducting wire is made of an alloy mainly composed of copper and zinc, and an oxide film is formed on the surface of the conducting wire .

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