JPH065211A - Magnetron - Google Patents

Abstract

(57) [Abstract] [Purpose] A pressure equalizing ring is installed only on one end face of the vane, and the frequency spectrum of the oscillated fundamental wave has well suppressed side lobes and spurious noise, making it easy to take noise countermeasures.
It is to provide a magnetron with a good performance price ratio. [Structure] An equalizer ring is installed only on one end face of the vane, and an anode with a bulge at the tip of the vane is used as a frequency countermeasure, and the magnetic poles closest to the vane end face on the microwave output extraction side are used. The peripheral surface was flattened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the number of steps by arranging a pressure equalizing ring only on the end face of the vane on the side of the microwave output extraction portion, facilitating adjustment to a desired resonance frequency, and further, incorporating a cavity resonance. The present invention relates to a magnetron suitable for a microwave oven or the like, in which the frequency spectrum of the fundamental wave of the microwave excited in the vessel group is improved to a side lobe or spurious that is sufficiently suppressed, and which has a small amount of noise radiated to the outside.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view taken along a plane passing through a tube axis of an example of a conventional magnetron. The tip of a vane 3 radially protruding from the inner wall of the anode cylinder 2 surrounds the cathode 1 with a cylindrical working space. The anode cylinder and the vane may be integrally molded by hobbing, or may be separately manufactured and brazed. An annular permanent magnet 6 which is short in the tube axis direction is arranged above and below the anode cylinder 2, and this magnet serves as a magnetomotive force source that contacts the outer surface of the permanent magnet 6 and surrounds the outside of the tubular body to form an external magnetic circuit. And a magnetic pole 4 having an outer peripheral edge portion sandwiched between the end portion of the anode cylinder 2 and the inner side surface of the permanent magnet 6 and an inner peripheral edge portion extending near the end portion of the working space. A static magnetic field is formed in the working space in the tube axis direction. Anode cylinder 2
For safety reasons, the portion that serves as a vacuum envelope is grounded, and a high DC negative potential is applied to the cathode 1. Electrons are attracted from the cathode 1 toward the tip of the vane 3 at the ground potential, but since a static magnetic field is formed in the working space in the tube axis direction, the electrons have a force perpendicular to the magnetic field and the movement direction. Acts,
Electrons that cross the tip of the vane in the circumferential direction and try to return to the cathode side also appear, and a part with a high electron density and a sparse part are generated in the action space, and an electron cloud with a high electron density orbits in the action space at a high speed. The microwave electric vibration is excited in the cavity resonator group formed by the anode cylinder and the adjacent vane. Among the electric vibrations in the cavity resonator group, what is oscillated most strongly and stably is so-called π-mode vibration having an opposite phase between the adjacent cavities. In order to further stabilize this vibration by connecting points having the same potential (same phase) by this π-mode vibration, every other one of the vanes is alternately connected to the inner pressure equalizing ring 10 and the outer pressure equalizing ring 11.
And are housed and installed inside the groove provided on the end surface of the vane in the tube axial direction. The microwave electric vibration is guided to the microwave output extraction portion 8 by the antenna 5 attached to the end surface of the vane, and is used outside, for example, for heating food in a microwave oven. The cathode 1 is supported by the cathode stem 9 via the heating power supply line.

At present, the largest quantity of magnetrons are used for microwave ovens, but for household electric appliances,
As important as performance is price. Therefore, in the case of a magnetron for a microwave oven, various measures are taken to reduce the price. In the above-mentioned conventional magnetron, pressure equalizing rings were installed on both the microwave output extraction side end surface and the cathode stem side end surface of the vane, but if this is installed on one side end surface, man-hours and parts cost can be reduced. .

However, if the pressure equalizing ring is installed only on one end face of the vane and the other part is left as it is, the resonance frequency of the cavity becomes too high. This is because the capacitance between the inner and outer pressure equalizing rings or between the pressure equalizing ring and the vane (which passes over the bottom surface of the storage groove without connecting the pressure equalizing ring) affects the resonance frequency. This is because the capacitance will be almost halved. In order to suppress this increase in frequency, Japanese Patent Application No. 2-405641 discloses that each vane is provided with a single vane inside by engraving grooves equidistant from the tube axis only on the end face on the microwave output extraction side. Alternately electrically connected every other, accommodating the outer pressure equalizing ring, provided at the tip of each vane symmetrically projecting to the tip side of both adjacent vanes, and providing an overhanging portion facing the adjacent vane side in a parallel plane, Compensating for the lack of electrostatic capacity, further, at the cathode stem side end surface of the vane, a step is provided at the boundary between the overhanging portion and the portion farther from the tube axis to narrow the width of the vane at the portion far from the tube axis, A technique for increasing the inductance of the vane in the portion far from the tube axis is described. According to this technique, the capacitance of the cavity resonator increases and the amount of inductance also increases. Therefore, even if the pressure equalizing ring is provided only on one end face of the vane, the frequency can be made similar to the conventional frequency. FIG. 3A is a plan view of the anode cylinder of the magnetron according to the above technique, and FIG. 3B is a sectional view thereof. In the figure, 31 is a protruding portion of the tip of the vane 3,
Reference numeral 3a denotes a pressure equalizing ring storage groove, and 3b denotes a step on the boundary between the overhanging portion and the portion further away from the pipe axis. The one shown in the figure is integrally formed by hobbing, and the groove for attaching the antenna end part without reference numeral is actually required for only one vane, but since it is formed by lathe, the end faces of all vanes are formed. Is formed in. Note that integrally forming such a magnetron anode by hobbing makes the shape of the hob somewhat complicated, but the amount of material extruded in the central portion of the material blank decreases, so the resistance to the hob decreases. However, the hob will have a longer life.

[0005]

However, when the magnetron anode as described above is used, the frequency spectrum of the fundamental wave of the microwave vibration actually excited is such that the side lobe is suppressed as shown in FIG. Not enough, spurious was also noticeable, and when the magnetron was attached to a device such as a microwave oven for use, a large amount of noise was emitted to the outside.

Microwave ovens are supposed to use microwaves of 2450 MHz, but if the fifth harmonic leaks to the outside, the frequency of satellite broadcasting has become very widespread in recent years. It appears as noise in the band and becomes a problem. Some countries are already legally regulated. Therefore, it is a problem to suppress and reduce noise in the magnetron in which the pressure equalizing ring is formed only on one end surface of the vane.

The present invention solves the above-mentioned problems of the prior art and provides a magnetron with a good performance-price ratio which can sufficiently suppress noise, especially that appearing in the 12 GHz band, while installing the pressure equalizing ring only on one side of the end face of the vane. The purpose is to provide.

[0008]

In order to solve the above-mentioned problems, according to the present invention, a vane storage groove is provided only on the end face of the vane on the microwave output extraction side, and the tip of each vane is extended to the tip side of both adjacent vanes. Protruding symmetrically, providing an overhanging portion facing the adjacent vane side in a parallel plane, and providing a step at the boundary between the overhanging portion and the portion farther from the tube axis on the end surface of the vane on the cathode stem side, and the vane of the portion far from the tube axis In the magnetron with a narrow width, the surface of the inner peripheral edge of the magnetic pole closest to the end surface of the vane on the microwave output extraction side was flattened.

[0009]

The present inventor repeated trial manufacture and experimentation in the case of changing the distribution state of the magnetic field and electric field near the end of the working space in order to reduce the noise of the magnetron having the above-mentioned anode structure. As described above, by flattening the surface of the inner peripheral edge of the magnetic pole that is closest to the end face of the vane on the microwave output extraction side, the frequency spectrum of the fundamental wave generated by the magnetron is one in which side lobes and spurs are suppressed. We have found that the noise radiated to the outside is reduced.

[0010]

1 is a side sectional view of a portion including an anode cylinder and a magnetic pole, which is a main part of one embodiment of the present invention. In the figure, 1 is a cathode,
2 is an anode cylinder, 3 is a vane, 4 is a conventional magnetic pole attached to the cathode stem side of the anode cylinder, 4a is a magnetic pole according to the present invention attached to the microwave output extraction side of the anode cylinder, and 5 is an antenna, Whereas the conventional magnetic pole 4 has a protrusion on the surface of the portion closest to the end face of the vane, the magnetic pole 4 according to the present invention.
The surface of the portion of a closest to the vane end surface is flat as shown. As a result, the magnetron of the present invention 2
The frequency spectrum of the fundamental wave of 450 MHz is as shown in FIG. 5, and in the case of the conventional magnetron, the spectrum of the fundamental wave is the width of the ISM band of 2450 MHz assigned to the microwave application device as shown in FIG. In contrast, in the magnetron of the present invention, side lobes and spurs of the oscillation frequency spectrum are significantly reduced. Therefore, when the magnetron of the present invention is used in a microwave application device such as a microwave oven, it is easy to take measures against noise radio wave leakage.

[0011]

As described above, according to the present invention, the manufacturing work is easy, and the measures against the leakage of noise radio waves are easy.
A magnetron with a good performance price ratio can be obtained.

[Brief description of drawings]

FIG. 1 is a side sectional view of a part including an anode cylinder and a magnetic pole, which is a main part of one embodiment of the present invention.

FIG. 2 is a sectional view taken along a plane passing through a tube axis of an example of a conventional magnetron.

FIG. 3 (a) is a view showing that the pressure equalizing ring is installed only on the end surface of the vane on the side where the microwave output is taken out, and the end of the vane is provided with an overhanging portion protruding toward the end of the adjacent vane. FIG. 3 (b) is a plan view of the magnetron anode in which a step is provided at the boundary between the overhanging portion and the portion further away from the tube axis to narrow the width of the vane at the portion farther from the tube axis, and FIG.

FIG. 4 is a diagram showing a fundamental wave spectrum in a 2450 MHz band of a magnetron in which a pressure equalizing ring is installed only on one end surface of a conventional vane.

FIG. 5 is a diagram showing a fundamental wave spectrum in a 2450 MHz band of a magnetron according to an embodiment of the present invention.

[Explanation of symbols]

2 ... Anode cylinder, 3 ... Vane, 31 ... Vane tip overhanging portion, 4 ... Conventional magnetic pole, 4a ... Magnetic pole according to the present invention.

Claims (1)

[Claims] 1. A cathode resonator arranged concentrically with a tube axis is surrounded by an anode cylinder and a cavity resonator group consisting of an even number of vanes radially projecting from an inner wall of the anode cylinder, with a cylindrical operating space being separated from each other. In order to form a static magnetic field in the tube axis direction, each has an inner peripheral edge portion extending near the end portion in the tube axial direction of the working space, and an outer peripheral edge portion sandwiched between the anode cylindrical end portion and the annular permanent magnet. Each pole is provided with a pole-shaped magnetic pole, and grooves are formed equidistantly from the tube axis only on the end surface of each vane on the microwave output extraction side to alternately electrically connect every other vane inside. , The outer pressure equalizing ring is housed, and a protruding portion is provided at the tip of each vane symmetrically projecting toward the tip side of both adjacent vanes and facing the adjacent vane side in a plane parallel to the vane. A portion further away from the pipe axis by providing a step on the boundary with the portion further away from In narrowed magnetron width of the vane, the magnetron, characterized in that the flat surface of the inner peripheral edge portion of the magnetic pole closest to the microwave output extraction portion side vane end face.