KR100269479B1 - Magnetron cathode structure - Google Patents

Abstract

The present invention relates to a cathode structure of a magnetron, comprising: a magnetron having a filament for emitting hot electrons, a filament electrode for supplying power to the filament, and a choke ring bonded to the filament electrode to form a choke structure, When the filament electrode and the choke ring are bonded, the choke ring is positioned in the upper direction of the filament electrode so as to effectively attenuate the fifth harmonic and noise leaking through the cathode part, thereby simplifying the bonding process. Attenuated fifth harmonics and noise can be effectively attenuated.

Description

Magnetron cathode structure

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron used in microwave heating equipment such as a microwave oven, and more particularly to a magnetron structure of a magnetron that effectively attenuates harmonic components and noise leaked through a cathode part.

In general, as shown in Fig. 1, the magnetron has a plurality of (even) vanes 15 that form a plurality of resonators such that high frequency is generated inside the anode cylinder 13 formed in a cylindrical shape by a copper pipe or the like. These anodes 13 and vanes 15 are disposed at equal intervals in a direction, and positive voltages are applied to these anode cylinders 13 and vanes 15 so that hot electrons generated from cathode filaments receive an electric field and reach the cathode cylinders 13 and vanes 15. It is authorized.

The space between the vanes 15 is an inductance in a circuit composed of a capacitance component that is a capacitance acting between vanes 15 adjacent to each other, and an anode cylinder 13 connecting the vanes 15 and the vanes 15 facing each other. The components form a resonator.

In addition, the inner and outer straps 15a and 15b flowing through the high frequency current are formed to have the same potential between the vanes 15 near the tip side of the vanes 15 to obtain a constant resonance frequency. Each of them is arranged and connected, and between the vanes 15 and the filaments 17, a working space 12 in which magnetic flux forms a magnetic field is formed, and in the working space 12, tungsten ( A filament 17 wound in a spiral shape by mixing and sintering W) and thorium oxide (ThO ₂ ) is arranged coaxially with the anode body 13.

Upper and lower shield hats 20 and 21 are fixed to both ends of the filament 17 so as to prevent radiation of hot electrons, which do not contribute to oscillation, from being radiated in the central axis direction. The first filament electrode 23, which is a central support made of molybdenum, is welded to the lower end of the upper shield hat 20 through a through hole formed in the center portion, and molybdenum is formed on the bottom surface of the lower shield hat 21 at the center portion. The second second filament electrode 25 is welded and fixed.

Here, the first filament electrode 23 supports the upper shield hat 20 while penetrating the central axis of the filament 17, and the first and second filament electrodes 23 and 25 are cathodes of the magnetron. Is electrically connected to the first and second external connection terminals 29 and 31, which are connected to the power supply terminals 30b and 32b, through a through hole formed in the insulating ceramic 27 supporting and fixing the current to the filament 17. It is a cathode support to supply.

One end of the choke coils 30 and 32 is electrically connected to the first and second external connection terminals 29 and 31, and the other end of the choke coils 30 and 32 is a side wall portion of the box filter. And ferrites 30a and 32a, which absorb noise, are inserted and fixed in the choke coils 30 and 32 in the choke coils 30 and 32, respectively. have.

In addition, the top and bottom of the funnel shape, which is a magnetic body that forms a magnetic flux on both side openings of the anode cylinder 13 to form a magnetic flux uniformly in the working space 12 formed by the filaments 17 and the vanes 15. The pole pieces 33 and 35 are welded together.

Upper and lower shield cups 37 and 39 are hermetically welded to upper and lower portions of the upper and lower pole pieces 33 and 35, respectively, and the anode body is upper and lower portions of the upper and lower shield cups 37 and 39, respectively. The antenna ceramic 45 and the insulating ceramic 27 are hermetically welded to seal the inside of the vacuum chamber 13 with a vacuum.

In addition, on the outer surface of the upper and lower shield cups 37 and 39, annular upper and lower magnets 41 and 43 are disposed in the anode cylinder 13 so as to maintain a constant magnetic field distribution. A cylindrical antenna ceramic 45 is insulated from the upper opening end of the upper shield cup 37 to be insulated.

Further, in the drawing, an exhaust pipe 47 made of copper is joined to the upper end of the antenna ceramic 45, and the vane (near the inner center of the exhaust pipe 47) outputs the high frequency oscillated in the resonance cavity. An antenna 49 derived from 15 extends axially through the through hole 33b of the upper pole piece 33, and the end of the antenna 49 is fixed in the exhaust pipe 47.

In addition, the outer surface of the exhaust pipe 47 protects the welded and fixed portion of the exhaust pipe 47 as well as prevents sparking due to electric field concentration and acts as a high frequency antenna, and simultaneously emits a high frequency output to the outside. The antenna ceramic 45 and the antenna cap 51 are placed on it.

In addition, an outer and outer yoke 53 and 55 for determining the amount of magnetic flux in the anode cylinder 13 are provided outside the anode cylinder 13 to connect the returned magnetic flux. And a plurality of aluminum cooling fins 57 are disposed between the anode yoke 55 and the lower yoke 55 by the clamp member 55a fixed to the anode cylinder 13 and the lower yoke 55. 43) is covered by the upper and lower yoke (53, 55) for forming a magnetic path, the upper opening of the upper yoke (53) is formed of a metal mesh or the like to prevent radio frequency leakage of high-frequency (59) ) Is arranged.

In the magnetron configured as described above, first, when power is applied through the first and second external connection terminals 29 and 31, the first external connection terminal 29 → the first filament electrode 23 → the upper shield. The hat 20 is formed by the filament 17, the lower shield hat 21, the second filament electrode 25, the second external connection terminal 31, and a closed circuit is supplied to the filament 17. Heated.

When the filament 17 is heated to a high temperature of 1800 ° C. or more, the electrons inside the filament 17 absorb heat and increase thermal energy, and the electrons with increased thermal energy reach energy above a predetermined value. At the surface, hot electrons begin to be released into the working space 12.

At this time, a strong electric field is formed in the working space 12 between the outer surface of the filament 17 and the vane 15 by the high voltage applied to the second filament electrode 25 and the vane 15. Starts at vane 15 and leads to filament 17.

On the other hand, the magnetic flux generated from the two upper and lower magnets (41, 43) is guided toward the working space 12 along the lower pole piece 35, the guided magnetic flux through the working space 12, the upper pole piece (33) In the working space 12 is distributed in the magnetic circuit consisting of the upper yoke 53, the lower yoke 55, the upper pole piece 33, the lower pole piece 35 and the working space 12 It forms a high magnetic flux density.

Accordingly, the hot electrons emitted from the surface of the hot filament 17 into the working space 12 travel to the vane 15 in the horizontal direction by the strong electric field present in the working space 12 and simultaneously in the working space 12. The force is perpendicular to the direction of travel by the existing strong magnetic field, and the electrons spirally circle to reach the vanes 15.

The electron group formed by the movement of the electrons causes the vane 15 to interfere with the vane 15 at a period equivalent to a reciprocal of the multiple of the periodic microwave oscillation frequency, and by this action, the vane 15 and the vane 15 In the resonator space, ie the capacitance component which acts between the vanes 15 facing each other, and the inductance component on the circuit composed of the opposing vanes 15 and the anode cylinder 13 connecting them are A resonant frequency according to the structure of the vane 15 is composed of a parallel resonance circuit and f = To generate 2450MHz band (fundamental wave) microwaves.

Therefore, the microwave energy generated in the vane 15 is conducted through the antenna 49 connected to the vane 15 and radiated to the output of the magnetron and into the cavity of the microwave oven through the antenna cap 51 connected to the outside. Delivered.

On the other hand, even if oscillation is ideally performed in the anode body 13, microwave energy of 2450 MHz band (fundamental wave) is generated due to temperature increase, reflected wave, or impedance defect of microwave and magnetron, and corresponds to integer multiple of the fundamental wave. Harmonic components are also generated.

At this time, the energy of the fundamental wave and harmonic components generated in the anode cylinder 13 is transmitted to the output of the magnetron while most of the energy is conducted through the antenna 49 is transferred to the cavity of the microwave oven through the waveguide, the anode cylinder 13 Part of the microwave energy (3-4%) generated in the inside is induced into the filament 17 of the cathode portion is leaked to the outside through the filament electrodes (23, 25).

As described above, the microwave energy leaked to the outside not only causes wireless communication disturbance, but also harms the human body, and the limit of leakage is regulated by law in some regions.

Currently, in the case of the microwave magnetron, harmonics ranging from the second harmonic (4900 MHz) to the seventh harmonic WH wave (7350 MHz) and frequencies from 30 KHz to 2 GHz are regulated or recommended standards, but the fundamental wave (2450 MHz) and its The harmonic content of the fundamental wave is mostly leaked to the output of the magnetron, and part of the microwave energy is leaked to the cathode part of about 3 to 4% of the fundamental wave, so the fundamental wave and the fifth harmonic of the fundamental wave and the noise of the 15KHz to 2GHz band Saving measures are needed.

Thus, in order to attenuate the microwave energy leaked through the cathode, in the conventional magnetron, the choke ring 24 is bonded to the first filament electrode 23 to form a choke structure, as shown in FIG. 2.

However, in the conventional magnetron, since the choke ring 24 is positioned in the lower direction of the first filament electrode 23, the choke ring 24 when the choke ring 24 is bonded to the first filament electrode 23 is formed. There was a problem that the joining process was difficult because it overlapped with the insulating ceramic 27 supporting and fixing the cathode of the magnetron.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and by changing the direction of the choke ring bonded to the filament electrode to the upper portion, the joining process is simple and effectively attenuates the fifth harmonic and noise leaking through the cathode part. The purpose is to provide a cathode structure of the magnetron that can be made.

In order to achieve the above object, the magnetron structure of the magnetron according to the present invention includes a filament for emitting hot electrons, a filament electrode for supplying power to the filament, and a choke ring joined to the filament electrode to form a choke structure. The magnetron is characterized in that the choke ring is positioned in the upper direction of the filament electrode so as to effectively attenuate the fifth harmonic and noise leaking through the cathode by simplifying the bonding process when the filament electrode and the choke ring are joined. do.

1 is a longitudinal cross-sectional view of a typical magnetron,

2 is an enlarged cross-sectional view of a conventional cathode portion structure;

Figure 3 is an enlarged cross-sectional view of the cathode portion structure according to the present invention.

<Description of the code | symbol about the principal part of drawing>

17 filament 23 first filament electrode

25: second filament electrode 26: choke ring

27: insulating ceramic

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

About the same part as a conventional structure, the description which overlaps by specifying the same name and the same code | symbol is abbreviate | omitted.

As shown in FIG. 3, the first filament electrode is used to simplify the joining process when the first filament electrode 23 and the choke ring 26 are bonded to effectively attenuate the fifth harmonic and noise leaking through the cathode part. The choke ring 26 joined to the (23) is positioned in an upward direction.

Hereinafter, the effect of the cathode portion structure of the magnetron configured as described above will be described.

First, when power is applied through the first and second external connection terminals 29 and 31, the first external connection terminal 29 → the first filament electrode 23 → the upper shield hat 20 → the filament 17 The closed circuit is formed by the lower shield hat 21, the second filament electrode 25, and the second external connection terminal 31, and an operating current is supplied to the filament 17 to be heated.

When the filament 17 is heated to a high temperature of 1800 ° C. or more, the electrons inside the filament 17 absorb heat and increase thermal energy, and the electrons with increased thermal energy reach energy above a predetermined value. At the surface, hot electrons begin to be released into the working space 12.

At this time, a strong electric field is formed in the working space 12 between the outer surface of the filament 17 and the vane 15 by the high voltage applied to the second filament electrode 25 and the vane 15. Starts at vane 15 and leads to filament 17.

On the other hand, the magnetic flux generated from the two upper and lower magnets (41, 43) is guided toward the working space 12 along the lower pole piece 35, the guided magnetic flux through the working space 12, the upper pole piece (33) In the working space 12 is distributed in the magnetic circuit consisting of the upper yoke 53, the lower yoke 55, the upper pole piece 33, the lower pole piece 35 and the working space 12 It forms a high magnetic flux density.

Accordingly, the hot electrons emitted from the surface of the hot filament 17 into the working space 12 travel to the vane 15 in the horizontal direction by the strong electric field present in the working space 12 and simultaneously in the working space 12. The force is perpendicular to the direction of travel by the existing strong magnetic field, and the electrons spirally circle to reach the vanes 15.

The electron group formed by the movement of the electrons causes the vane 15 to interfere with the vane 15 at a period equivalent to a reciprocal of the multiple of the periodic microwave oscillation frequency, and by this action, the vane 15 and the vane 15 In the resonator space, ie the capacitance component which acts between the vanes 15 facing each other, and the inductance component on the circuit composed of the opposing vanes 15 and the anode cylinder 13 connecting them are A resonant frequency according to the structure of the vane 15 is composed of a parallel resonance circuit and f = It is determined by and generates microwaves in the 2450MHz band (fundamental wave).

Therefore, the microwave energy generated in the vane 15 is conducted through the antenna 49 connected to the vane 15 and radiated to the output of the magnetron and into the cavity of the microwave oven through the antenna cap 51 connected to the outside. Delivered.

However, even when oscillation is ideally performed in the anode body 13, microwave energy of 2450 MHz band (fundamental wave) is generated due to temperature increase, reflected wave, or impedance defect of microwave and magnetron, and corresponds to integer multiple of the fundamental wave. Harmonic components are also generated and induced into the filament 17 of the cathode part, and leak out to the outside through the first and second filament electrodes 23 and 25.

Accordingly, in the present invention, as shown in FIG. 3, the direction of the choke ring 26 bonded to the first filament electrode 23 is changed to the upper side, thereby changing the first filament electrode 23 and the choke ring 26. By forming the choke structure by bonding, it is possible to effectively attenuate the fifth harmonic and noise leaking to the outside through the cathode while reducing the defect rate of the bonding process.

According to the cathode portion structure of the magnetron according to the present invention as described above, by changing the direction of the choke ring bonded to the filament electrode to the upper portion, the bonding process is simple but effectively attenuates the fifth harmonic and noise leaking through the cathode portion. The effect is that you can.

Claims (2)

In a magnetron having a filament for emitting hot electrons, a filament electrode for supplying power to the filament, and a choke ring bonded to the filament electrode to form a choke structure, The cathode portion of the magnetron, characterized in that the choke ring is located in the upper direction of the filament electrode to effectively attenuate the fifth harmonics and noise leaked through the cathode by simplifying the bonding process when the filament electrode and the choke ring is bonded. rescue. The method of claim 1, The choke ring is a cathode portion structure of the magnetron, characterized in that located on the inner peripheral surface of the lower shield cup through which the filament electrode.