JP2014067615A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a magnetron of a 915-MHz band to have substantially the same external dimension and substantially the same output as a magnetron of a 2450-MHz band having a smaller size, to reduce costs of a power supply, and to enhance the reliability of a coaxial waveguide connection structure and apply it to a high output application.SOLUTION: A magnetron comprises: a cathode part 78 including a cathode filament 51 that is a thermoelectron emission source; an anode part 79 configured by arranging a plurality of anode vanes 52 at a constant interval in an annular ring shape in an anode cylinder part 53, and having a cavity resonator by cavity between the anode vanes 52; an output part 69 for transmitting a microwave stored in the cavity resonator to the exterior; and a magnetic circuit part 70 in which magnets are arranged at upper and lower ends in an axial direction, of a vacuum pipe main body interior-sealing a part of the cathode part 78, the anode part 79, and the output part 69. The number of the cavity resonators is 10. A ratio of an outer diameter of the cathode part 78 and an inner diameter at a front end of the anode vanes 52 is 0.36-0.59. An outer diameter of the anode cylinder part 53 is 80-100 mm. An oscillation frequency of the vacuum pipe main body is 800 to 1000 MHz.

Description

  The present invention relates to a magnetron that is an electron tube that generates a microwave.

  In general, a magnetron has a vacuum tube portion disposed at the center thereof, a cooling portion on the outer periphery of the vacuum tube portion, a pair of annular magnets arranged coaxially with the vacuum tube portion, and a yoke that magnetically connects the annular magnets. And a filter circuit unit.

  A conventional magnetron of this type is described in Patent Document 1 and shown in FIG. 9 in this specification. FIG. 9 is a cross-sectional view for explaining an example of the structure of a conventional magnetron. In the figure, 1 is a filament serving as a thermionic emission source, 2 is a plurality of anode vanes, 3 is an anode cylinder (anode cylinder), 4 and 4a are annular permanent magnets, 5 and 5a are magnetic poles, and 6a Is a yoke, 7 is an antenna lead, 8 is an antenna, 9 is an exhaust pipe, 10 is an antenna cover, 11 is an insulator, 12 is an exhaust pipe support, 13 is a working space, 14 and 15 are inner and outer straps, 16 and 17 Is a bar-shaped upper and lower sealing metal, 18 is a metal gasket, and 19 is an output portion. The output unit 19 includes the antenna lead 7, the antenna 8, the exhaust pipe 9, and the antenna cover 10. A magnetic circuit unit 20 includes the permanent magnets 4 and 4a, magnetic poles 5 and 5a, and yokes 6 and 6a as magnetic generation sources.

  21 is an upper end shield, 22 is a lower end shield, 23 and 24 are cathode leads, 23 is a center lead, and 24 is a side lead. Reference numeral 25 denotes an input side ceramic, 26 denotes a cathode terminal, 27 denotes an external lead, 28 denotes a cathode portion, the cathode portion 28 is a cathode filament 1 serving as a thermionic emission source, upper and lower end shields 21 and 22, and Includes cathode leads 23, 24 and the like. Reference numeral 29 denotes an anode portion. The anode portion 29 includes a plurality of anode vanes 2, an anode portion cylinder 3, inner and outer straps 14, 15, and the like. 31 is a choke coil, 32 is a feedthrough capacitor, 33 is a filter case, and 34 is a cooling fin. Reference numeral 35 denotes a cooling fin installed on the outer periphery of the anode cylinder 3.

  In FIG. 9, a plurality of anode vanes 2 are fixed to the anode cylinder 3 by brazing or the like around the spiral cathode filament 1 or integrally formed with the anode cylinder 3 by extrusion molding. Magnetic poles 5 and 5a made of a ferromagnetic material such as soft iron and cylindrical permanent magnets 4 and 4a are arranged above and below the anode cylinder 3, respectively. The magnetic flux generated from the permanent magnets 4 and 4a enters the working space 13 formed between the cathode filament 1 and the anode vane 2 through the magnetic poles 5 and 5a, and gives a necessary DC magnetic field in the axial direction.

  The yokes 6 and 6a constitute a magnetic circuit through which the magnetic fluxes of the permanent magnets 4 and 4a pass. The magnetic circuit is composed of the yokes 6 and 6a, the permanent magnets 4 and 4a, and the magnetic poles 5 and 5a. Electrons emitted from the cathode filament 1 having a negative high voltage form a high-frequency electric field in each anode vane 2 while circularly moving under the action of the electric field and magnetic field.

  The formed high frequency electric field reaches the antenna 8 through the antenna lead 7 and is output from the antenna cover 10 to an external device. The cathode filament 1 is generally made of tungsten wire containing about 1% thorium oxide (ThO 2) in consideration of electron emission characteristics and workability. The upper end shield 21, the lower end shield 22, and the cathode leads 23, 24 are used. It is supported by.

  The cathode leads 23 and 24 are generally made of molybdenum (Mo) from the viewpoint of heat resistance and workability, and the choke coil 31 is made of a terminal plate 26 brazed to the upper surface of the input side ceramic 25 with silver brazing or the like. Are connected to external lead-out leads 27, 27 connected to. A filter structure including a filter case 33 that supports the choke coil 31 and the feedthrough capacitor 32 and a lid 34 that closes the filter case 33 is attached to the lower part of the magnetron.

  The choke coil 31 connected to the external lead leads 27 and 27 forms an L-C filter with the feedthrough capacitor 32 and suppresses low frequency components transmitted from the cathode leads 23 and 24. The high frequency component is shielded by the filter case 33 and its lid 34. And the cooling fin 35 installed in the outer periphery of the anode cylinder 3 diffuses the heat accompanying the operation of the magnetron.

  In the conventional magnetron having such a configuration, two types of oscillation frequency of 915 MHz and 2.45 GHz (or 2450 MHz) which is an ISM (Industry Science Medical) band have been put into practical use. In the market, a magnetron having an oscillation frequency in the 2450 MHz or 915 MHz band is the mainstream, and in particular, the former 1450 MHz one is frequently used. The 2450 MHz magnetron has features that can reduce the size of the processing chamber and the object to be heated, the size of the waveguide, etc., so that it can be used not only for heating devices such as microwave ovens for business use and home use, but also for semiconductor manufacturing equipment. As a thin film dry etching apparatus and a microwave plasma CVD (Chemical Vapor Deposition) apparatus.

JP 2002-124196 A

  However, when a 2450 MHz magnetron is used for a heating device, for example, heating unevenness is likely to occur in a heated object such as a large heating object, a thick heating object, or a thawed object. That is, uniform heating is difficult in a short time from the outer surface to the center of the object to be heated. Also, when used in semiconductor manufacturing equipment such as thin film dry etching equipment and microwave plasma CVD equipment, fluctuations in the output supplied to the processing chamber are likely to occur, and precise control with a feedback circuit is performed. However, uniform processing is difficult, and there is a risk of damaging the semiconductor wafer.

  On the other hand, in recent years, the demand for 900 MHz band microwaves is increasing. For example, a 915 MHz magnetron is a large electromagnet type magnetron, and is used in industrial heating devices having a large output of several tens of kW or more. It is also conceivable to mount a 915 MHz magnetron in the heating device described above. However, the 915 MHz magnetron itself is large, and the heating device itself must be enlarged to be mounted on the heating device, which is difficult to use in practice.

  Moreover, since the rectangular waveguide to transmit becomes large, so that the frequency of a microwave is low, the rectangular waveguide for 915 MHz becomes large compared with 2450 MHz use. Further, in the semiconductor manufacturing apparatus described above, it is also considered to use a semiconductor as a transmission source, but the output is as low as several tens of W / piece, and it is difficult to cope with a desired high output, and to drive the device. Power supply costs are high, and these are problems to be solved.

  There is a coaxial waveguide coupling method as a method for miniaturizing the microwave transmission path, but the structure of the output part of a general 915 MHz magnetron is covered with ceramic, so that it can be attached to the coaxial waveguide. It was not possible to attach to the rectangular waveguide. As shown in Patent Document 1 (shown in FIG. 10 in this specification), an antenna 309f is passed through an exhaust pipe 301 for evacuating the inside of the pipe, pressed together, and a cover 302 is provided to protect the pressed part, A method for coupling the inner conductor 309a of the coaxial waveguide to the protective cover 302 is described. However, the fitting portion and the pressure contact portion of the protective cover 302 are mechanically and thermally unreliable as a coaxial waveguide connection structure, and sufficient attention is required for replacement of the coaxial waveguide portion. Therefore, it is considered difficult to adopt it for high output applications.

  As described above, only a large electromagnet type of the 915 MHz band magnetron has been commercialized, so that it becomes heavier and larger than the 2450 MHz band magnetron in which the permanent magnet type is generalized. Moreover, the dimension of the rectangular waveguide which transmits a microwave will become larger than the dimension of 2450 MHz. In addition, an electromagnet excitation power source is required, which complicates the power source and increases the cost. The reliability of the coaxial waveguide connection structure is low, making it difficult to apply to high power applications.

  The present invention has been made in view of such circumstances, and a 915 MHz band magnetron can have substantially the same external dimensions and substantially the same output as a smaller 2450 MHz band magnetron. An object of the present invention is to provide a magnetron that is low in reliability and can be applied to high-power applications by increasing the reliability of the coaxial waveguide connection structure.

  In order to solve the above problems, the present invention is a structure in which a cathode part including a thermionic emission source and a plurality of anode vanes are arranged in a ring shape inside the anode cylindrical part, and the anode vanes are arranged in an annular shape. An anode part having a cavity resonator formed by a cavity, an output part for sending microwaves stored in the cavity resonator to the outside, and a vacuum tube for enclosing a part of the cathode part, anode part and output part And a magnetic circuit part having magnets disposed at upper and lower ends in the axial direction of the main body, the number of cavity resonators is 10, and the ratio of the outer diameter of the cathode part to the inner diameter of the tip of the anode vane is 0.36 to 0.59. The outer diameter of the anode cylindrical portion was 80 to 100 mm, and the oscillation frequency of the vacuum tube body was set to 800 to 1000 MHz.

  According to the present invention, a magnetron in the 915 MHz band can have substantially the same output with substantially the same external dimensions as a smaller 2450 MHz band magnetron, the power supply cost is low, and the coaxial waveguide connection structure is reliable. Therefore, it is possible to provide a magnetron that can be applied to high power applications with high performance.

It is sectional drawing which shows the structure of the permanent magnet type | mold 900 MHz band magnetron which concerns on embodiment of this invention. It is a principal part top view of the part containing the anode part and cathode part in the magnetron of this embodiment. It is AA sectional drawing of FIG. The structural example of one anode vane in the magnetron of this embodiment is shown, (a) is a top view, (b) is a front view, (c) is a bottom view. It is a figure which shows an example of the oscillation spectrum of the magnetron of this embodiment. It is a figure which shows the relationship between the oscillation frequency (horizontal axis) of a magnetron, and the weight ratio (vertical axis) of a magnetron. It is principal part sectional drawing which shows the structure at the time of connecting the 39D standard coaxial waveguide to the output part of the magnetron of this embodiment. It is principal part sectional drawing which shows the structure at the time of connecting the 77D standard coaxial waveguide to the output part of the magnetron of this embodiment. It is principal part sectional drawing explaining the structural example of the conventional magnetron. It is principal part sectional drawing explaining the structural example of the coaxial waveguide coupling part of the conventional magnetron.

Embodiments of the present invention will be described below with reference to the drawings.
<Configuration of Embodiment>
FIG. 1 is a cross-sectional view showing a configuration of a permanent magnet type 900 MHz band magnetron 100 according to an embodiment of the present invention.
In the magnetron 100, 51 is a cathode filament (directly heated spiral cathode) serving as a thermionic emission source, 52 is a plurality of anode vanes (also simply referred to as vanes), and 53 is an anode cylinder (anode cylinder). The dimensions and arrangement of the anode cylindrical portion 53, the anode vane 52, and the cathode filament 51 have a specific relationship described later.

  54 and 54a are annular permanent magnets, 55 and 55a are magnetic poles, and 56 and 56a are yokes. 57 is an antenna lead, 58 is a cylindrical antenna block, 61 is an insulator, 63 is a working space, 64 is a strap, 66 and 67 are bar-shaped upper and lower sealing metals, 68 and 68a are upper and lower anode plates, and 69 is an output section. It is. The output unit 69 includes an antenna lead 57 and an antenna block 58. The antenna lead 57 and the antenna block 58 are joined by a method such as silver brazing or arc welding.

Reference numeral 70 denotes a magnetic circuit unit. The magnetic circuit unit 70 includes permanent magnets 54 and 54a, magnetic poles 55 and 55a, and yokes 56 and 56a, which are magnetic generation sources. 71 is an upper end shield (also referred to as an output side end shield), 72 is a lower end shield (also referred to as an input side end shield), 73 is a center lead of a cathode lead, and 74 is a side lead of a cathode lead.
75 is an input side ceramic, and 78 is a cathode part. The cathode portion 78 includes a cathode filament 51 serving as a thermionic emission source, upper and lower end shields 71 and 72, cathode leads 73 and 74, and the like. Reference numeral 79 denotes an anode portion. The anode portion 79 is fixed to the plurality of anode vanes 52 and the anode cylindrical portion 53 by brazing or the like, or integrally formed with the anode cylindrical portion 53 by extrusion molding. 76 is a terminal plate, and 80 is an exhaust pipe.

  In the magnetron 100 having such components, the yokes 56 and 56a constitute the magnetic circuit unit 70, but contain the permanent magnets 54 and 54a, the magnetic poles 55 and 55a, the antenna lead 57, the cathode unit 78, and the anode unit 79. It is also a housing that is disposed on the microwave output side, and is also used as a coupling member with an external mechanism (not shown). The casing is formed in a box shape in which one yoke 56 is open on the lower surface, and the other yoke 56a is formed in a lid shape that closes the opening. Further, the yoke 56 and the yoke 56a are screwed together with a screw 205, and the yoke 56 is further screwed to the cooling mechanism 77 with a screw 205a.

  Magnetic poles 55 and 55a made of a ferromagnetic material such as soft iron and cylindrical permanent magnets 54 and 54a are arranged above and below the anode cylindrical portion 53. Magnetic flux generated from the permanent magnets 54 and 54a enters the working space 63 formed between the cathode filament 51 and the anode vane 52 through the magnetic poles 55 and 55a, and is necessary in the axial direction which is the vertical direction of the magnetron 100. A direct magnetic field.

  This DC magnetic field has the following effects. That is, in a state where the main axis of the magnetron 100 is installed perpendicular to the horizontal plane, the magnetic flux is perpendicular to the electrons flying in the horizontal direction from the cathode filament 51 toward the anode vane 52 (axial direction). When applied, Lorentz force is applied to the electrons. Due to this Lorentz force, electrons fly while spirally turning in the horizontal direction, and a high frequency electric field is formed in the anode vane 52.

  The cathode filament 51 emits electrons when a negative high voltage of 4 kV to 8 kV of direct current is applied, and the electrons are subjected to high frequency to each anode vane 52 while being spirally moved under the action of an electric field and a magnetic field as described above. Create an electric field. The formed high frequency electric field is output from the antenna block 58 to an external device (not shown) through the antenna lead 57. However, the negative high voltage of 4 kV to 8 kV of direct current is not realistic because the magnetic force of the permanent magnets 54 and 54a is insufficient when the negative high voltage is less than 8 kV. When the negative high voltage exceeds 4 kV, it is difficult to obtain a sufficient output, which is not practical.

  The cathode filament 51 is generally made of tungsten wire containing about 1% thorium oxide (ThO 2) in consideration of electron emission characteristics, workability, and the like. The upper end shield 71, the lower end shield 72, Supported by cathode leads 73 and 74. The cathode leads 73 and 74 are generally made of molybdenum (Mo) from the viewpoint of heat resistance and workability, and the choke coil is connected via a terminal plate 76 brazed to the upper surface of the input-side ceramic 75 with silver brazing or the like. 81.

  A filter structure 85 including a filter case 83 that supports the choke coil 81 and the feedthrough capacitor 82 and a lid 84 that closes the filter case 83 is attached to the lower portion of the magnetron 100. The choke coil 81 connected to the terminal plate 76 forms an L-C filter with the feedthrough capacitor 82 and suppresses low frequency components transmitted from the cathode leads 73 and 74. However, the high frequency component is shielded by the filter case 83 and its lid 84. Further, the cooling mechanism 77 installed on the outer periphery of the anode cylindrical portion 53 is provided with a cooling water passage 77a through which the cold water passes around, and diffuses heat accompanying the operation of the magnetron 100 with the cold water passing therethrough. Let

The exhaust pipe 80 is for venting the gas inside the magnetron vacuum tube body in which the cathode part 78, the anode 79 and the like, a part of the output part 69 and the like are enclosed. After venting the gas and creating a vacuum state, the tip of the exhaust pipe 80 is sealed.
2 is a plan view of the main part of the portion including the cathode part 78 and the anode part 79 shown in FIG. 1, FIG. 3 is a sectional view taken along the line AA in FIG. 2, and FIG. 4 is one anode vane in the magnetron 100 of this embodiment. 52 shows a configuration example of (52), (a) is a plan view, (b) is a front view, and (c) is a bottom view.

  As shown in FIG. 2, the ends of ten anode vanes 52 having a rectangular planar shape are arranged and fixed uniformly on the inner peripheral side of the anode cylindrical portion 53. Further, the tip of each anode vane 52 protrudes from the fixed position toward the center of the cathode filament 51 in a reverse radial shape and is arranged in a circular shape, and an action space 63 is provided between each tip of the circular array and the cathode filament 51. Is formed.

  Furthermore, as shown in FIG. 4B, a strap storage groove 52a having a depth H3 is formed on the tip side of each anode vane 52, and a depth H2 is formed at a position opposite to the strap storage groove 52a in the vertical direction. A cut 52b is formed. As shown in FIG. 3, the strap storage grooves 52a and the cuts 52b are formed alternately at each anode vane 52, that is, alternately, and an annular strap 64 is formed in the strap storage grooves 52a and the cuts 52b. It is fitted and assembled.

  However, the strap 64 is fitted to the strap housing groove 52a without a gap, and the notch 52b is fitted so that a gap (gap) is formed between both sides and the bottom surface side. That is, the width and depth H3, H2 of the strap storage groove 52a and the notch 52b are formed in such dimensions. The gap between the strap 64 and the notch 52b has a correlation with the size of the capacitance C as described later.

  The structure shown in FIG. 2 is called a multi-segment structure anode structure and is a cavity resonator divided by ten anode vanes 52. The resonance frequency, that is, the oscillation frequency of the magnetron 100 is determined by the capacitance C and the inductance L that each cavity resonator constitutes.

  The inductance L is determined by the size of a triangular cavity between the anode vanes 52 located between the inner peripheral side of the anode cylindrical portion 53 and the outer peripheral side of the annular strap 64. The inductance L increases as the cavity increases. That is, as the inner diameter of the anode cylindrical portion 53 is increased, the triangular cavity is increased, so that the inductance L is increased.

The capacitance C is determined by the gap between the tip portions of the anode vanes 52 that are attached to the inner peripheral side of the strap 64. The capacitance C increases as the gap decreases. In addition, the capacitance C increases as the area of the opposing portions of the tip ends increases. That is, as the height H1 of the tip portion of the anode vane 52 shown in FIG. 4B increases, the tip portion area increases and the capacitance C also increases.
Furthermore, as shown in FIG. 3, the electrostatic capacitance C also changes depending on the size of the gap between the strap 64 and both sides and the bottom surface side of the cut 52b. The capacitance C increases as the gap decreases.

  The upper end of the cathode filament 51 disposed at the center of the circumference of the anode cylindrical portion 53 is fixed to the output side end shield 71, and the lower end is fixed to the input side end shield 72. The output side end shield 71 is supported by a rod-shaped cathode lead 73, and the input side end shield 72 is supported by a rod-shaped cathode lead 74.

Here, the dimensions of each part of the magnetron 100 having ten anode vanes 52 are determined as follows, for example, in order to obtain an oscillation frequency of 800 to 1000 MHz.
F (filament outer diameter) = 9.2 mm (see FIG. 3)
G (anode vane tip inner diameter) = 20 mm (see FIG. 3)
D1 (inner cylindrical part inner diameter) = 85 mm (see FIG. 3)
D2 (anode cylindrical outer diameter) = 95 mm (see FIG. 3)
F / G [(cathode filament outer diameter) / (anode vane tip inner diameter)] = 0.46 (see FIG. 3)
L1 (total length of anode vane) = 32.5 mm {see FIG. 4B}
L2 (length of anode vane tip tapered portion) = 4.6 mm {see FIG. 4A}
H1 (anode vane height) = 24 mm {see FIG. 4B}
H2 (the height of the strap storage groove passage) = 6.8 mm {see FIG. 4B}
H3 (Strap storage groove brazing section height) = 5.8 mm {see FIG. 4B}
T1 (anode vane thickness) = 8.0 mm {see FIG. 4A}
T2 (anode vane tip portion thickness) = 5.0 mm {see FIG. 4A}
R1 (curvature of strap storage groove wall) = 14.9 mm {see FIG. 4 (a)}
R2 (curvature of strap storage groove wall surface) = 20.5 mm {see FIG. 4 (a)}
R3 (Surface of groove storing groove wall) = 15.9 mm {see FIG. 4 (c)}
R4 (Surface of groove storing groove wall) = 19.8 mm {see FIG. 4 (c)}
Strap outer diameter: 39.3 mm (see Fig. 3)
Strap inner diameter: 31.7 mm (see Fig. 3)

  FIG. 5 shows the oscillation frequency spectrum of the magnetron 100 having the anode structure having the above dimensions. As is apparent from the oscillation frequency spectrum shown in FIG. 5, the oscillation frequency has a peak of 914 MHz in this anode structure, which satisfies the conditions of the oscillation frequency of 800 to 1000 MHz according to the present invention. Moreover, the microwave output at this time is 6 kW.

  FIG. 6 is a diagram showing the relationship between the oscillation frequency (horizontal axis) of the magnetron 100 and the weight ratio (vertical axis) of the magnetron 100. In FIG. 6, the weight of a magnetron with an oscillation frequency of 2450 MHz is assumed to be 100% by weight, and the relationship between each oscillation frequency of 2450 MHz or less and the weight ratio of the magnetron is represented by a curve ML.

  When a conventional magnetron, for example, the number of anode vanes is 14, the oscillation frequency is 2450 MHz, and the microwave output is 6 kW (6 kW class), the mass of the magnetron is about 2.7 kg. The relative position between the mass of the conventional magnetron and the oscillation frequency is indicated by a point a in FIG. In order to realize a magnetron with an oscillation frequency of 915 MHz based on this, it is necessary to make the length of the anode vane 7 times or more, and its weight is located at a point b in FIG.

The oscillation frequency f of the anode structure having a multi-cavity such as a magnetron (divided cavities at each anode vane 52 in FIG. 2 described above) depends on the inductance L and the capacitance C formed by one cavity. It is determined as the following formula (1).
f = 1 / 2π√ (LC) (1)
From this equation (1), it can be seen that the cavity needs to be enlarged to some extent in order to obtain a stable oscillation frequency f. For this reason, the enlargement of the anode structure is inevitable conventionally.

  Generally, the inductance L is corrected by reducing the thickness of the anode vane, and the correction of the thermal margin due to the thinner anode vane is dealt with by increasing the number of anode vanes. For example, in the 14 anode vane magnetrons, since the number of vanes is large, the triangular cavity between the vanes becomes small. In order to increase this, it is necessary to increase the diameter of the anode cylindrical portion 53. In other words, the 14 anode vane magnetrons have a larger anode structure than the 12 anode vane magnetrons.

On the other hand, even if it is attempted to increase the capacitance C with 12 anode vanes, there is a structural limit because the size between the vane tips is 0.5 mm or less. For this reason, as a result, even if a magnetron that oscillates at 915 MHz is realized, it becomes about three times as large as point a as shown by point b in FIG.
However, when the distance between the tip portions of the anode vane 52 is made as small as possible, the capacitance C increases, and the high-frequency electric field between the tip portions of the anode vane 52 can be relatively strengthened, and the load stability is improved. Will be.

As in this embodiment, if the number of vanes is less than that of the prior art, that is, the anode vane 52 is ten, the inter-vane cavity is increased and the inductance L is increased without changing the capacitance C. Accordingly, the diameter of the anode cylindrical portion 53 can be reduced. Further, when the inductance L increases, the oscillation frequency decreases and becomes a low frequency. That is, if the number of anode vanes 52 is ten, a small, low frequency (oscillation frequency 800 to 1000 MHz) magnetron 100 can be realized.
Practical size ranges of each part that are satisfied as the magnetron 100 are as follows. Each of the above dimensions is an example, but as a result of various studies, the practical range of dimensions of each part that can be satisfied as a magnetron 100 having an oscillation frequency of 800 to 1000 MHz is as follows.

F (filament outer diameter) = 8.0 to 10.0 mm (see FIG. 3)
G (anode vane tip inner diameter) = 17 to 22 mm (see FIG. 3)
D1 (inner cylinder inner diameter) = 70 to 90 mm (see FIG. 3)
D2 (outer diameter of anode cylindrical portion) = 80 to 100 mm (see FIG. 3)
F / G [(cathode filament outer diameter) / (anode vane tip inner diameter)] = 0.36 to 0.59 (see FIG. 3)
L1 (the total length of the anode vane) = 30 to 35 mm {see FIG. 4B}
H1 (anode vane height) = 23 to 25 mm {see FIG. 4B}
T1 (anode vane thickness) = 7.5 to 8.5 mm {see FIG. 4A}
When the value of F / G is less than 0.36, the oscillation efficiency is deteriorated and is not practical. A value exceeding 0.59 is not practical because the magnetic flux density is insufficient and the anode voltage is difficult to increase. The value of the result of (D2-D1) / 2 is the thickness of the anode cylindrical portion 53. If the thickness is less than 5 mm, the anode cylindrical portion 53 is easily distorted and the quality is deteriorated. Although oscillation is possible even if the thickness exceeds 5 mm, not only the cooling efficiency of the anode cylindrical portion 53 is deteriorated, but also problems such as an increase in the price of the anode cylindrical portion 53 and an increase in weight occur. Therefore, D1 = 70 to 90 mm and D2 = 80 to 100 mm. Here, it is preferable that at least D2 = 80 to 100 mm.

  On the other hand, the ratio (D1 / G) between the anode cylinder inner diameter D1 and the anode vane tip inner diameter G shown in FIG. 3 for maintaining a stable oscillation operation and reducing the diameter of the anode cylinder portion 53 is shown in FIG. As a result, about 4.2 times is appropriate. The anode cylindrical portion outer diameter D2 is determined to be 80 to 100 mm in consideration of the mechanical strength of the anode cylinder, the heat radiation efficiency, and the like.

  The magnetron 100 has a multi-cavity resonance structure as described above. For this reason, when the number of vanes is increased to 14 as in the prior art, the rate at which the cavity formation error is reflected in the entire cavity shape increases as one cavity becomes smaller. For this reason, since the shape variation of each cavity resonator becomes large, the oscillation frequency becomes unstable.

On the other hand, when the number of vanes is 10 as in the magnetron 100 of the present embodiment, since one cavity is large, the ratio that the formation error of the cavity is reflected in the entire cavity shape is small. For this reason, since the shape variation of each cavity resonator is small, the oscillation frequency is stabilized. In other words, since the capacitance C is constant and the inductance L is large, the variation of individual cavity resonators is reduced, and thus the oscillation frequency is stabilized.
Therefore, the magnetron 100 using the ten anode vanes 52 and having a smaller number of cavities has better oscillation frequency characteristics than the conventional magnetron. When the number of vanes is 8, which is smaller, the cavity becomes larger, but the input / output efficiency is deteriorated and cannot be used.

<39D coaxial waveguide structure>
FIG. 7 is a cross-sectional view of the main part showing the structure when a 39D standard coaxial waveguide is connected to the output part 69 of the magnetron 100.
The 39D inner conductor 91 which is a cylindrical block having an outer diameter Di1 is in direct contact with the antenna block 58, and the 39D outer conductor 93 which is a cylindrical block having an inner diameter Do1 is fixed to a yoke 56 (see FIG. 1). . The 39D inner conductor 91 is electrically connected to the 39D inner 92, and the 39D outer conductor 93 is fixed to the 39D flange 94 by bolts 201 and nuts 202.

  The 39D inner conductor 91 and the 39D outer conductor 93 are fixed by a fluororesin spacer 95 so as to maintain the same axis. The 39D outer conductor 93 is attached to the inner wall surface of the 39D flange 94, and the 39D inner conductor 91 is attached to the outer wall surface of the 39D inner 92. A portion surrounded by a broken line frame 98 is an airtight sealing mechanism in which the antenna block 58 and the ceramic cylindrical portion 60 are in close contact with each other.

<Use of 77D coaxial waveguide>
FIG. 8 is a cross-sectional view of the main part showing the structure when a 77D standard coaxial waveguide is connected to the output unit 69.
The 77D inner conductor 103, which is a cylindrical block having an outer diameter Di2, is provided with a slit, and is coupled to the antenna block 58 via a coupling portion 101 having a spring property. The 77D outer conductor fixing plate 106 fixes the 77D outer conductor 104, which is a cylindrical block having an inner diameter Do2, to the yoke 56. The 77D inner conductor 103 is electrically connected to the 77D inner conductor 102, and the 77D outer conductor 104 is screwed 203 to the 77D outer conductor 105.

The 77D inner conductor 104 and the 77D outer conductor 105 are fixed by a fluororesin spacer 107. A 77D flange is attached to the outer wall surface of the 77D outer conductor 105, and a 77D inner is attached to the inner wall surface of the 77D inner conductor 102.
However, in the above embodiment, the permanent magnets 54 and 54a are used as the magnets, but electromagnets may be used.

<Effect of embodiment>
As described above, the magnetron 100 of the present embodiment has an annular shape in which the cathode portion 78 including the cathode filament 51 that is a thermionic emission source and the plurality of anode vanes 52 are separated from each other inside the anode cylindrical portion 53 by a certain distance. An anode part 79 having a cavity resonator with a cavity formed between the anode vanes 52, an output part 69 for sending the microwave stored in the cavity resonator to the outside, a cathode part 78, And a magnetic circuit unit 70 having magnets disposed at the upper and lower ends in the axial direction of the vacuum tube main body enclosing part of the anode unit 79 and the output unit 69. The number of cavity resonators was 10, the ratio of the outer diameter of the cathode portion 78 to the inner diameter of the tip of the anode vane 52 was 0.36 to 0.59, and the outer diameter of the anode cylindrical portion 53 was 80 to 100 mm. Further, the oscillation frequency of the vacuum tube main body is 800 to 1000 MHz.

  According to this configuration, the number of anode vanes 52 is set to ten, which is smaller than the conventional twelve. When the number of vanes is 10 in this way, the cavity resonator between the vanes is increased and the inductance L is increased without changing the electrostatic capacitance C. Therefore, the diameter of the anode cylindrical portion 53 is reduced accordingly. be able to. Therefore, since the circular diameter of the anode part 79 can be reduced, the entire magnetron can be reduced in size.

Further, when the number of vanes is 10, since one cavity is large, the rate at which the cavity formation error is reflected in the entire cavity shape is small. For this reason, since the shape variation of each cavity resonator is small, the oscillation frequency is stabilized. In other words, since the capacitance C is constant and the inductance L is large, the variation of individual cavity resonators is reduced, and thus the oscillation frequency is stabilized. Further, when the inductance L is increased, the oscillation frequency is lowered and becomes a low frequency. That is, if the number of anode vanes 52 is ten, a small, low frequency (oscillation frequency 800 to 1000 MHz) magnetron 100 can be realized.
Therefore, a 900 MHz band magnetron can be provided with substantially the same outer diameter and substantially the same output as a conventional 2450 MHz band magnetron.

The magnets described above are permanent magnets 54 and 54a.
According to this configuration, since no electromagnet is used, an electromagnet excitation power source is not necessary, and the cost of the power source is reduced accordingly. Further, when an electromagnet is used, three power sources for the cathode portion 78, the anode portion 79, and the electromagnet are required, and it is necessary to control and operate each power source while considering the operation of each power supply target. However, if there is no electromagnet, only two power sources, ie, the cathode portion 78 and the anode portion 79 are provided, so that there is an effect that the operation control of the power source is simplified correspondingly.

Further, the cathode portion 78 emits electrons to the anode portion 79 in a state where a negative high voltage of 4 kV to 8 kV of direct current is applied, and the anode portion 79 forms a high-frequency electric field in response to the electron emission, thereby generating a microwave. Output it.
According to this configuration, it is easier to increase the output than in the case where a semiconductor device is used as a transmission source as in the prior art, and there is an effect that the cost can be reduced as compared with a high-cost power source for driving the semiconductor device. is there.

Further, the output unit 69 is an inner conductor 91 of a coaxial waveguide (39D coaxial waveguide or 77D coaxial waveguide) through which the microwave propagates to an antenna block 58 as an antenna tip that outputs the microwave to the outside. , 103 are fitted in an airtight manner, and the microwave propagating through the coaxial waveguide is transmitted from the tip of the antenna to the outside.
According to the configuration of the output unit 69, compared with the conventional press-contact structure, since it is a combined structure by fitting or the like, mechanical reliability is increased. For this reason, the coupling with the inner conductors 91 and 103 (see FIGS. 7 and 8) of the coaxial waveguide (39D coaxial waveguide or 77D coaxial waveguide) is facilitated, and breakage occurs even when the coaxial waveguide is replaced. The risk of occurrence of such problems is reduced.

Moreover, since it is a fitting structure, it is possible to raise the heat conductivity of the coupling | bond part 101 (refer FIG. 8), and an electrical conductivity, and the loss of the part can also be reduced.
Furthermore, since the reliability is improved mechanically and thermally, it is advantageous for a specification in which the antenna portion including the antenna block 58 is at a high temperature, such as a high-power magnetron.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

51 Cathode filament 52 Anode vane 52a Strap receiving groove 52b Notch 53 Anode cylindrical portion 54, 54a Permanent magnet 55, 55a Magnetic pole 56, 56a Yoke 57 Antenna lead 58 Antenna block 60 Ceramic cylindrical portion 61 Output side ceramic 63 Working space 64 Strap 66, 67 Upper / lower sealing metal 68, 68a Upper / lower anode plate 69 Output section 70 Magnetic circuit section 71 Upper end shield 72 Lower end shield 73 Cathode lead (center lead)
74 Cathode lead (side lead)
75 Input side ceramic 76 Terminal plate 77 Cooling mechanism 77a Cooling water passage 78 Cathode part 79 Anode part 80 Exhaust pipe 81 Choke coil 82 Through-pass capacitor 83 Filter case 84 Cover body 85 Filter structure 91 39D inner conductor 93 39D outer conductor 98 Airtight Stop mechanism 100 Magnetron 103 77D inner conductor 104 77D outer conductor

Claims (4)

A cathode portion including a thermionic emission source;
A structure in which a plurality of anode vanes are arranged in an annular shape inside the anode cylindrical portion and spaced apart from each other, and an anode portion having a cavity resonator formed by a cavity formed between the anode vanes,
An output unit for sending microwaves stored in the cavity resonator to the outside;
A magnetic circuit unit having magnets disposed at upper and lower ends in the axial direction of a vacuum tube body enclosing a part of the cathode unit, the anode unit, and the output unit,
The number of the cavity resonators is 10, the ratio of the outer diameter of the cathode part to the inner diameter of the tip of the anode vane is 0.36 to 0.59, the outer diameter of the anode cylindrical part is 80 to 100 mm, A magnetron characterized in that the oscillation frequency of the vacuum tube body is 800 to 1000 MHz. The magnetron according to claim 1, wherein
The magnetron is a permanent magnet. The magnetron according to claim 1 or 2, wherein
The cathode part emits electrons to the anode part in a state where a negative high voltage of 4 kV to 8 kV of direct current is applied, and the anode part forms a high-frequency electric field according to the electron emission and outputs the microwave. Magnetron characterized by that. The magnetron according to claim 1 or 2, wherein
The output section is fitted with an inner conductor of a coaxial waveguide through which the microwave propagates in an airtight manner at an antenna tip that transmits the microwave to the outside, and the microwave that propagates through the coaxial waveguide is transmitted. The magnetron is sent out from the front end of the antenna.

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