JP4815146B2 - Magnetron - Google Patents

Description

  The present invention relates to a magnetron whose oscillation frequency is in the 5.8 GHz band.

  In general, a magnetron includes a vacuum tube portion disposed in the center thereof, a plurality of heat radiation fins disposed on the outer periphery of the vacuum tube portion, a pair of annular magnets disposed coaxially with the vacuum tube portion, and an annular magnet It is comprised by the frame-shaped yoke which connects the magnetically, and the filter circuit part.

  As shown in FIG. 5, the vacuum tube portion includes a cylindrical anode cylinder 26, a cathode 27 arranged coaxially with the anode cylinder, and a plurality of radially arranged around the central axis of the anode cylinder. A configuration having a plate-shaped vane 28, four equalizing rings 29 for electrically connecting every other one of them, an antenna 30 having one end connected to any one of the plate-shaped vanes 28, and a magnetic pole 31 It has become.

  Until now, the magnetron having an oscillation frequency in the 2.45 GHz or 915 MHz band which is an ISM band has been the mainstream in the market.

  Conventionally, for the purpose of mainly suppressing relatively low frequency noise, for example, a vane width La is 9.5 mm, a flat portion facing distance Lp between both magnetic poles 31 is 12.7 mm, and a magnetic pole height h is 7.0 mm. A magnetron that operates at a fundamental frequency of 2.45 GHz designed as is proposed (Patent Document 1).

  On the other hand, in recent years, in the field of equipment using magnetrons, there is a demand for downsizing of equipment in order to develop new applied equipment and expand the market.

  When miniaturizing equipment, it must be constructed so that its minimum dimensions do not block the magnetron oscillation frequency.

  For example, in general, a microwave oven, which is a representative example of an electric device using a magnetron, includes a waveguide portion that propagates microwaves and a cavity portion that resonates microwaves, and the dimensions thereof are below a certain value. Then, the fundamental frequency is cut off.

  Thus, since the structure of peripheral devices such as waveguides and cavities is limited by the oscillation frequency of the magnetron, the dimensions cannot be changed greatly.

  Therefore, development of a magnetron having an oscillation frequency of 5.8 GHz, which is allocated next to 2.45 GHz as a frequency (ISM band) that can be used for industrial use, has been demanded.

The reason for this is that, with a magnetron with an oscillation frequency of 5.8 GHz, the wavelength of the oscillation frequency is about half that of a conventional 2.45 GHz magnetron. This is because the device can be greatly downsized.
JP-A-63-91932

  However, in developing a magnetron with an oscillation frequency of 5.8 GHz, when the design concept of the 2.45 GHz magnetron described in Patent Document 1 is applied to a magnetron with an oscillation frequency of 5.8 GHz, It has been found that a stable oscillation frequency cannot be obtained because high-frequency coupling due to a capacitive component or an inductive component occurs between the resonant cavity and the surrounding conductor (such as a magnetic pole) and the resonant frequency fluctuates.

  An object of the present invention is to provide a magnetron that has a stable oscillation frequency even at 5.8 GHz and is suitable for downsizing of applied equipment.

  The magnetron of the present invention has a cylindrical anode cylinder and one end fixed to the inner wall surface of the anode cylinder, and a tip opposite to the one end radially toward the center of the anode cylinder. A plurality of extended anode vanes, a plurality of pressure equalizing rings electrically connecting every other anode vane, a cathode provided at the center of the anode cylinder, and an axial direction of the anode cylinder 4. A magnetron having a pair of funnel-shaped magnetic poles disposed at both opening ends of the first and second resonance frequencies of microwaves generated in a resonance cavity composed of the anode cylinder, the anode vane, and the pressure equalizing ring. It is an 8 GHz band, and the minimum proximity distance between the side edge of the anode vane and the magnetic pole is set in a range of 2.2 mm or more and 5.0 mm or less.

  According to this configuration, the minimum proximity distance between the side edge of the anode vane and the magnetic pole is ensured to be at least 2.2 mm, so that a high frequency due to a capacitive component or an inductive component is generated between the resonant cavity and the surrounding conductor (magnetic pole, etc.). The coupling can be prevented and the resonance frequency can be stabilized.

  Moreover, the microwave application apparatus of this invention is provided with the said magnetron.

  With this configuration, the wavelength of the oscillation frequency is about half that of the conventional 2.45 GHz magnetron, so the size of peripheral devices such as waveguides can be reduced to about half, and the microwave application equipment can be downsized. it can.

  According to the magnetron of the present invention, a stable oscillation frequency can be obtained even at 5.8 GHz, and the applied equipment can be downsized.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a magnetron according to the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view of the main part in the longitudinal direction of the magnetron of the first embodiment. FIG. 2 is an enlarged view of a portion A in FIG. FIG. 3 is a graph showing the relationship between the minimum proximity distance D and the resonance frequency.

  Although not shown, the magnetron of the first embodiment is disposed coaxially with the vacuum tube portion disposed at the center thereof, the plurality of heat radiation fins disposed on the outer periphery of the vacuum tube portion, and the vacuum tube portion. A pair of annular magnets, a frame yoke that magnetically connects the annular magnets, and a filter circuit unit.

  As shown in FIG. 1, the vacuum tube portion is arranged radially around a cylindrical anode cylinder 6, a cathode portion 7 arranged coaxially with the anode cylinder 6, and a central axis of the anode cylinder 6. A plate-shaped vane 8, four equalizing rings 9 for electrically connecting every other plate-shaped vane 8, an antenna 10 having one end connected to any one of the plate-shaped vanes 8, and a mortar shape The magnetic pole 11 is provided.

  The antenna 10 serves to radiate microwaves to the outside of the magnetron. The magnetism 11 has a mortar shape in order to effectively induce magnetism by forming a magnetic circuit at the opening end of the anode cylinder 6.

  In the vacuum tube portion 1, a resonance cavity is formed by the general envelope of the anode cylinder 6, the plate-shaped vane 8, and the pressure equalizing ring 9. A gap between the resonance cavity and the magnetic pole 11 is referred to as an end space 14.

  Here, D is the minimum height of the end space 14, that is, the minimum proximity distance between the plate-shaped vane 8 and the magnetic pole 11. FIG. 2 shows an enlarged view of the vicinity of the plate-shaped vane 8 and the magnetic pole 11.

  The magnetron of the first embodiment has a dimension of Lp + h1 + h2 with a vane width La of 8.5 mm, a flat portion facing distance Lp between both magnetic poles 11 of 13.5 mm, a magnetic pole height h1 of 6.6 mm, and h2 of 6.6 mm. However, the minimum proximity distance D is set to 2.5 mm, which is 1.8 mm.

  Next, the operation of the magnetron according to the first embodiment will be described.

  First, the magnetron according to the first embodiment is formed by the magnetic pole 11 when a DC electric field is applied between the anode portion composed of the anode cylinder 6, the plate-shaped vane 8, and the pressure equalizing ring 9, and the cathode portion 7. Under the influence of the magnetic field, electrons emitted from the cathode part 7 circulate around the cathode part 7 while performing a cycloid motion.

  On the other hand, the anode part is a cavity resonance circuit, and a high-frequency electric field is generated between the plate-like vanes 8 due to the natural vibration of the resonator. When the high-frequency electric field and the electron circular motion around the cathode portion 7 are synchronized, the electrons are subjected to the action of the high-frequency electric field to form a rotating electron electrode, whereby an induced current flows and oscillates in the cavity resonance circuit.

  By the way, as described in the problem, in developing a magnetron having an oscillation frequency of 5.8 GHz, a stable oscillation frequency could not be obtained when the design concept of the 2.45 GHz magnetron was applied.

  As described above, the present inventor explained that the wavelength of 5.8 GHz is about 52 mm, which is half or less than the wavelength of about 122 mm of 2.45 GHz. It has been found that a component and an inductive component are generated and high-frequency coupling is likely to occur, so that the resonance frequency changes.

  Therefore, the relationship between the minimum proximity distance D between the plate-shaped vane and the magnetic pole and the resonance frequency was examined. Further, from the viewpoint of the output of the magnetron and the magnetic circuit efficiency, the relationship between the minimum proximity distance D and the magnetic field strength was similarly examined. These relationships are shown in FIG.

  Referring to the graph shown in FIG. 3, it can be seen that the resonance frequency fluctuates drastically when the minimum proximity distance D is smaller than 2.2 mm. This is because the resonant cavity and the magnetic pole 11 are high-frequency coupled by a capacitive component or an inductive component.

  Therefore, from this graph, in a magnetron having an oscillation frequency of 5.8 GHz, if the minimum proximity distance D between the plate-shaped vane 8 and the magnetic pole 11 is at least 2.2 mm, it is generated between the resonant cavity and the magnetic pole 11. It was confirmed that the influence of the capacitive component was sufficiently negligible.

  In addition, by setting the minimum proximity distance D to at least 2.2 mm or more, even if the dimension between the resonant cavity and the magnetic pole 11 changes due to thermal expansion or assembly error, the effect can be sufficiently ignored. I understood.

  Therefore, in the first embodiment, the minimum proximity distance D is set to 2.5 mm in consideration of the stability of the resonance frequency and the magnetic circuit efficiency.

  In the oscillation operation as described above, the magnetron of the first embodiment has a minimum proximity distance D of 2.5 mm between the plate-shaped vane 8 and the magnetic pole 11, so that the gap between the resonance cavity and the magnetic pole 11 is secured. The effect of the generated capacitance component can be sufficiently ignored, and the resonance frequency can be kept stable.

  In the magnetron of the first embodiment, the basic resonance frequency is 5.85 GHz ± 0.075 GHz.

  Next, an application example in which the magnetron of the first embodiment is applied to an electronic device will be described. FIG. 4A shows an application example using a conventional 2.45 GHz magnetron. FIG. 4B shows an application example using a 5.8 GHz magnetron.

  In general, there is a cutoff wavelength in a waveguide. An electromagnetic wave having a wavelength longer than that length cannot propagate. For example, to propagate a 2.45 GHz microwave, that is, a microwave having a wavelength of about 122 mm, the long side of the waveguide needs to be at least 61 mm.

  Actually, if the cutoff wavelength of the waveguide is close to the wavelength of the propagating electromagnetic wave, the propagation loss of the waveguide is large, so that the waveguide is designed with a slight margin. As shown in FIG. 4A, for example, the dimensions of the 2.45 GHz waveguide 15 are such that the width a1 is about 95.3 mm and the length b1 is about 54.6 mm.

  On the other hand, since the wavelength of the microwave of 5.8 GHz is about 52 mm, if the horizontal width of the waveguide is 26 mm or more, the microwave of 5.8 GHz can be propagated. As shown in FIG. 4B, for example, the waveguide 5.8 for 5.8 GHz can have a width a2 of 40 mm and a length b2 of 20 mm.

  As described above, when the frequency at which the magnetron oscillates is changed from 2.45 GHz to 5.8 GHz, the wavelength is shortened. Therefore, peripheral devices such as a waveguide or a cavity whose structure is limited by the wavelength are greatly reduced in size. be able to. Therefore, it is possible to reduce the size of magnetron application devices such as a microwave oven, a microwave ceramic kiln, and a power transmission antenna.

  The magnetron of the present invention can obtain a stable oscillation frequency even at 5.8 GHz, and is suitable for downsizing application equipment.

Sectional drawing of the principal part of the magnetron of this Embodiment 1 in the vertical direction Enlarged view of part A in Fig. 1 Graph showing the relationship between minimum proximity distance and resonance frequency (A) The figure which shows an example of the electronic device which uses a 2.45 GHz magnetron (b) The figure which shows an example of the electronic device which uses a 5.8 GHz magnetron Sectional view of the main part of a conventional magnetron in the vertical direction

Explanation of symbols

6 Anode cylinder 7 Cathode part 8 Plate-shaped vane 9 Pressure equalizing ring 10 Antenna 11 Magnetic pole 14 End space 15, 16 Waveguide D Minimum proximity distance between plate-shaped vane and magnetic pole

Claims (2)

A vacuum tube portion disposed in the center portion, a plurality of radiating fins disposed on the outer periphery of the vacuum tube portion, a pair of annular magnets disposed coaxially with the vacuum tube portion, and the annular magnet magnetically In a magnetron having an oscillation frequency of 5.8 GHz band including a frame-shaped yoke to be joined and a filter circuit unit ,
The vacuum tube section includes the anode cylinder body , a cathode section coaxially arranged with the anode cylinder body, and a plurality of plates arranged radially in the anode cylinder body and around the central axis of the anode cylinder body A plate-shaped vane, a plurality of pressure equalizing rings that electrically connect every other plate-shaped vane, an antenna that has one end connected to any one of the plate-shaped vanes and radiates microwaves to the outside, and the anode A magnetic pole whose cross section parallel to the axial direction of the cylindrical body is a mortar shape,
Before SL and side edges of the plate-like vanes the pole and minimum proximity distance is 2.2mm or more, the magnetron, characterized in that set in the range 5.0 mm.   A microwave application apparatus comprising the magnetron according to claim 1.

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