JPH05144380A - Magnetron - Google Patents

Abstract

PURPOSE:To reduce a harmful influence due to through holes by constituting in such a way that microwave output is taken out via the through holes formed on the inclined surface of conical magnetic pole pieces. CONSTITUTION:A large number of vanes 2 arranged on the inner peripheral surface of a cylindrical anode 1 are arranged in the radial direction with the pipe axis as its enter. Respective central holes of a pair of magnetic pole pieces 22 and 23 arranged in both opening edge parts of the anode 1 are formed in a polygon having the same square numbers with the vanes 2. A stable microwave oscillating operation can be obtained. The occurrence of noise due to unnecessary radiation can be reduced.

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 high frequency heating equipment such as a microwave oven.

[0002]

2. Description of the Related Art Usually, such a magnetron is constructed as shown in FIG. 4, and 12 or 10 vanes 2 provided on the inner peripheral surface of a cylindrical anode 1 form a cavity resonator. They are arranged in a radial direction around the tube axis.
The cathode 3 is coaxially arranged on the tube axis. At both ends of the vane 2 in the axial direction, equalizing rings 4 and 5 of small diameter for commonly connecting every other vane, and the remaining There are provided pressure equalizing rings 6 and 7 having a large diameter for commonly connecting the pressure equalizing rings. The anode 1, the vane 2 and the pressure equalizing rings 4, 5, 6, 7 are all made of copper.

First and second magnetic pole pieces 8 and 9 are provided at both open ends of the cylindrical anode 1 so as to face each other. Both pole pieces 8 and 9 are made of a magnetic metal such as iron, are formed in a mortar shape for focusing a magnetic field, and have circular center holes 10 and 11, respectively. First pole piece 8
A ceramic stem 13 that is sealed to the inside of the metal cylinder 12 has a pair of cathode terminals 14, and the cathode terminals 14 are connected to a pair of lead wires 15 extending from both ends of the cathode 3. ing. Further, the metal exhaust pipe 1 sealed to the second magnetic pole piece 9 via the metal cylinder body 16 and the ceramic ring 17.
A tip portion of an elongated microwave output lead-out conductor 19 extending from the vane 2 is pressure-bonded to the vane 8. A metal cap 20 serving as an electromagnetic wave emitting antenna is attached to the exhaust pipe 18, and the pole piece 9 is a conductor 19 for deriving a microwave output.
Has a through hole 21 on the inclined surface.

An external magnetic circuit for such a magnetron includes an annular permanent magnet and the same permanent magnet stacked on the outer end faces of both pole pieces 8 and 9, as disclosed in Japanese Patent Laid-Open No. 2-30037. It is composed of a frame-shaped yoke for connecting in series, and a focusing magnetic field is applied to the working space between both pole pieces 8 and 9.

[0005]

By the way, the diametrical magnetic field strength distribution in the cylindrical anode 1 is as shown in FIG. 5, and shows a low value in the central region around the tube axis a. This is because the central holes 10 and 11 are present, and since the cathode 3 is only present in the central region, there is no significant adverse effect. However, the magnetic flux density difference A caused by the effect of the through holes 21 disturbs the circumferential uniformity of the magnetic field strength in the working space, and the orbital motion of the thermoelectrons emitted from the cathode 3 to the working space becomes uneven. Therefore, not only the microwave oscillating operation becomes unstable, but also a considerable amount of unnecessary radiation occurs, which adversely affects communication radio waves.

[0006]

The present invention has been made to solve the above-mentioned conventional problems. A large number of vanes provided on the inner peripheral surface of a cylindrical anode form a cavity resonator. Therefore, a pair of magnetic pole pieces arranged in the radial direction around the tube axis and provided at both open end portions of the anode and facing each other each have a central hole, and at least one of the magnetic pole pieces is inclined. In a magnetron having through holes on its surface, the planar shape of the central hole is made polygonal having the same number of angles as the vanes.

[0007]

In the magnetron thus constructed, since the magnetic pole pieces have polygonal central holes having the same number of angles as the vanes, the magnetic flux concentration points by the magnetic pole pieces are generated corresponding to the vane number, and the action space As a result of substantially flattening the magnetic field distribution in the circumferential direction inside, stable microwave oscillation operation can be obtained, and generation of noise due to unnecessary radiation can be reduced.

[0008]

The present invention will be described below with reference to the embodiments shown in the drawings.

As shown in FIGS. 1 and 2, the first and second magnetic pole pieces 22 and 23 provided at both open ends of the cylindrical anode 1 made of copper and facing each other are made of magnetic metal such as iron. ,
It is formed like a mortar, and the central hole 24 is the vane 2.
It is formed into a polygon with the same number of angles as. Further, the through hole 2 for inserting the microwave output lead-out conductor 19
5 on the inclined surface. The corner of the polygonal central hole 24 occupies the position facing the vane 2, and this positional relationship is the same for the polygonal central hole of the second magnetic pole piece 23.

In the embodiment shown in FIG. 3, the corners of the polygonal central hole 24 of the first magnetic pole piece 22 are made to correspond to the mutual gaps of the vanes 2, and this positional relationship is the second magnetic pole piece 23. The same applies to the polygonal central hole.

In any of the embodiments, since the central hole of the pole piece is a polygon having the same number of angles as the vanes, the magnetic flux concentration point by the pole piece corresponds to the vane number, and within the working space. The magnetic field distribution in the circumferential direction is substantially flattened, stable microwave oscillation operation can be obtained, and noise generation due to unnecessary radiation can be reduced.

[0012]

As described above, according to the present invention, stable microwave oscillating operation can be obtained by only changing the center hole of the magnetic pole piece for magnetic flux focusing from the conventional circular shape to a polygonal shape. Generation of noise due to unnecessary radiation can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a magnetron embodying the present invention.

FIG. 2 is a partially cutaway plan view of the same main part.

FIG. 3 is a partially cutaway plan view of an essential part of another embodiment of the present invention.

FIG. 4 is a side sectional view of a conventional magnetron.

[Fig. 5] Magnetic field strength distribution map of the same magnetron

[Explanation of symbols]

 1 Cylindrical Anode 2 Vane 3 Cathode 22 First Pole Piece 23 Second Pole Piece 24 Central Hole 25 Through Hole

Claims (1)

[Claims] 1. A large number of vanes provided on the inner peripheral surface of a cylindrical anode are arranged in a radial direction around a tube axis to form a cavity resonator, and are provided at both open ends of the anode. In a magnetron in which each of a pair of magnetic pole pieces facing each other has a central hole, and at least one of the magnetic pole pieces has a through hole in its inclined surface, the planar shape of the central hole is the same as that of the vanes. A magnetron characterized by being formed into a polygonal shape having a number of angles.