JP2001060440A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an influence to a rsonance frequency even when component dimensions are disperesed, so as to restrain fluctuation of the resonance requency. SOLUTION: An intermediate portion of a face 27 facing to an upper pole piece 9 and lower pole piece 10 of a vane 2 is remained and its both faces 29 are cut out, as a feature of the vane 2. A thickness of the face 27 of the vane 2 approached most to the pole pieces 9, 10 is made thin thereby to halving an increase of a conductance and to restrain an influence to a resonance requency. The efficient thickness of the face 27 approached most to the pole pieces 9, 10 of the vane 2 is preferably a half or more of thickness of other portion in the vane 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron used for a microwave heating device such as a microwave oven, a radar, and the like.

[0002]

FIG. 3 is a half sectional view of a conventional magnetron. Reference numeral 1 denotes an anode shell made of oxygen-free steel or the like and forming a part of a vacuum wall (a wall surface of a vacuum vessel, the same applies hereinafter). A plurality of vanes 2 are radially provided on the inner periphery of the anode shell toward the center. Are connected by alternately small and large diameter strap rings 7 and 8 to stabilize π mode oscillation. At both ends of the anode shell 1, pole pieces 9, 10 for concentrating a magnetic field in a working space between the tip of the vane 2 and the filament 3 installed in the axial direction at the center of the anode shell 1 are provided, respectively. These form an anode part.

[0003] The filament 3 is made of, for example, a thorium-tungsten wire wound in a coil shape, and is provided at the center of the anode shell 1 in a space surrounded by the tip of each vane 2. End hats are fixed to both ends thereof, and the end hats are connected to cathode leads 4 and 5, respectively. Reference numeral 6 denotes an antenna conductor connected to one of the vanes 2, and the pole piece 9 is provided with a hole through which the antenna conductor 6 passes.

[0004] Reference numeral 11 denotes a top shell which is a sealing metal fixed to the anode shell 1 with the pole piece 9 interposed therebetween.
Is a stem metal which is a sealing metal fixed to the anode shell 1 with the pole piece 10 interposed therebetween, and 13 is the top shell 1
An output-portion-supporting antenna ceramic fixed to 1 by brazing, 14 is an output pipe fixed to the antenna ceramic 13 and joined to the antenna conductor 6, 15 is an antenna cap press-fitted into the output pipe 14, and 16 is stem metal. 12 is a stem ceramic fixed to the support 12 and supporting the cathode leads 4 and 5.

[0005] A vacuum tube is constituted by the above, and
Reference numeral 8 denotes an annular magnet disposed above and below the anode shell 1, respectively, 19 denotes cooling fins fitted on the outer peripheral surface of the anode shell 1, and 20 denotes an anode shell 1 and the magnet 1
A yoke surrounding the cooling fins 19 and 18. Reference numeral 21 denotes a shield case that surrounds the stem ceramic 16 protruding from the yoke 20 and includes a choke 22 and a feedthrough capacitor 23 that constitute a filter circuit.

Reference numeral 24 denotes a gasket which is in close contact with the joint of the microwave oven, and reference numeral 25 denotes a gasket ring which holds the gasket 24 and is press-fitted into the top shell 11. In the above structure, the microwave generated at the anode portion transmits through the antenna conductor 6 in a state where the microwave (fundamental wave) of the original oscillation frequency and a harmonic of an integral multiple are mixed, and the microwave from the surface of the antenna cap 15 Radiated to the outside.

In the above structure, the space between the filament 3 and the vane 2 is referred to as a working space. In this space, a magnetic field is applied perpendicularly to the traveling direction of the electrons, and the electrons circulate to generate high-frequency energy. The microwave generated at the anode portion is transmitted through the antenna conductor 6 and radiated to the outside from the surface of the antenna cap 15.

Since the efficiency of conversion from the input energy to the high-frequency energy is directly proportional to the applied magnetic flux density, it is desirable to shorten the facing distance between the pole pieces 9 and 10. However, Bain 2 and pole pieces 9, 10
When the distance is short, the conductance increases, which affects the resonance frequency. That is, the resonance frequency greatly fluctuates due to variations in component dimensions, but the resonance frequency is restricted by international regulations, and it is necessary to obtain a resonance frequency as designed.

[0009]

However, as shown in FIG. 2, the conventional vane has a surface 27 facing the upper pole piece 9 and the lower pole piece 10 of the vane 2 in a rectangular plane, and has a rectangular flat surface. The thickness is the same and the thickness of the vane is uniform. The shorter the distance between the surface 27 and the pole pieces 9 and 10 is, the more convenient the passage of magnetic flux is. However, if the opposing distance of the pole pieces is shortened by such a vane thickness, the conductance increases. As a measure against this,
It is easy to reduce the height of the vane,
Since the working space formed by the surface 28 of the vane 2 facing the filament 3 is reduced, an unstable oscillation state is likely to occur. Therefore, it is necessary to suppress an increase in conductance without changing the size of the working space.

Therefore, according to the present invention, by making the thickness of the vane closest to the pole piece thinner than the thickness of the other portions, the increase in conductance can be halved without largely changing other characteristics, and the resonance frequency can be reduced. It is an object of the present invention to provide a magnetron capable of reducing fluctuation.

[0011]

According to a first aspect of the present invention, there is provided a magnetron having a filament for emitting thermoelectrons and vanes arranged radially, wherein the filament has an inner diameter, In a magnetron having pole pieces disposed above and below a working space having an outer diameter of the vane tip, the thickness of a portion of the vane closest to the pole piece is made thinner than the thickness of other portions of the vane. It was configured as follows.

By making the thickness of the vane closest to the pole piece thinner than the thickness of the other portions in this manner, the area facing the pole piece can be reduced, the conductance is reduced, and the component dimensions are varied. Can also suppress the influence on the resonance frequency.

[0013] The magnetron according to claim 2 of the present invention comprises:
In a magnetron having a filament for emitting thermoelectrons and a vane radially disposed, and a pole piece disposed above and below a working space having an inner diameter of a filament and an outer diameter of a tip of the vane and opposed pole pieces, The thickness of the part closest to the pole piece was configured to be at least half the thickness of the other parts of the vane.

In this way, by making the thickness of the vane at the portion closest to the pole piece at least half the thickness of the other portions, the facing area can be reduced,
The dimensions of the parts are reduced while the conductance is reduced and the electrons to be confined in the working space do not diverge much from the gaps. Even if it varies, the influence on the resonance frequency can be suppressed.

[0015]

Embodiments of the present invention will be described below. Although the basic configuration of the magnetron of the present invention is the same as that shown in FIG. 3, there is a feature in the configuration of the vane, and since this vane is incorporated in the magnetron of FIG.
Since the basic configuration of FIG. 3 has already been described, the description is omitted here.

FIG. 1 shows an embodiment of the vane of the present invention.
The same parts as those in FIG. 2 are denoted by the same reference numerals. The difference between the features of the vane of the present invention and the vane of FIG. 2 is that both sides 29 of the vane 2 remain at an intermediate portion of each surface 27 facing the upper pole piece 9 and the lower pole piece 10.
Is cut off.

In this manner, by making the thickness of the surface 27 of the vane 2 closest to the pole pieces 9 and 10 smaller than the thickness of the other portions, the increase in conductance can be reduced to half without greatly changing other characteristics, and the resonance can be reduced. The influence on the frequency can be suppressed.

As another means, the surface 2 of the vane 2 which comes closest.
It is conceivable that not only the side portions 29 of the 7 but also the thickness of the other portions may be reduced. However, the thermal resistance of the vane 2 increases, and the thermal stress of the strap rings 7 and 8 fixed to the vane 2 increases. . As a result, the strap rings 7, 8
Is not preferred because the time required to reach thermal fatigue fracture becomes short.

In the vane of FIG. 1, both sides 29 of the surface 27 closest to the pole pieces 9 and 10 may be cut off to further reduce the thickness. A lot of electrons to be confined in the working space formed opposite to the filament 3 diverge from the gap of the surface 27. If the electrons converge too much on a small area of the working space, an unstable oscillation state is likely to occur. Is not preferred. Therefore, experience has shown that it is more efficient to make the thickness of the surface 27 of the vane 2 closest to the pole pieces 9 and 10 at least half the thickness of the other portions of the vane.

[0020]

As described above, according to the present invention, the area facing the pole piece can be reduced by making the thickness of the vane closest to the pole piece smaller than the thickness of the other parts. Without greatly changing the characteristics of the magnetron, the effect on the resonance frequency can be suppressed even when the conductance is reduced and the component dimensions are varied, so that it is possible to provide a magnetron in which the fluctuation of the resonance frequency is suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram of a vane shape according to the present invention.

FIG. 2 is a conventional vane shape diagram.

FIG. 3 is a half sectional view of a conventional magnetron.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode shell 2 Bain 3 Filament 4,5 Cathode lead 6 Antenna conductor 7,8 Strap ring 9,10 Pole piece 11 Top shell 12 Stem metal 13 Antenna ceramic 14 Output pipe 15 Antenna cap 16 Stem ceramic 17,18 Ring magnet 19 Cooling Fin 20 Yoke 21 Shield case 22 Choke 23 Feedthrough capacitor 24 Gasket 25 Gasket ring 26 Disc-shaped metal plate 27 Vane surface facing pole piece 28 Vane working space forming surface 29 Cut-off portion

Claims (2)

[Claims] 1. A pole piece having a filament for emitting thermoelectrons and a vane radially arranged, and disposed above and below a working space having an inner diameter of the filament and an outer diameter of a tip of the vane, and opposing pole pieces. A magnetron, wherein a thickness of a portion of a vane closest to a pole piece is smaller than a thickness of another portion of the vane. 2. The magnetron according to claim 1, wherein the thickness of the portion of the vane closest to the pole piece is at least half the thickness of the other portion of the vane.