JPH11283517A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress noise by forming asymmetrically with respect to a tube axis, a small diameter flat surface of at least one pole piece, arranged at each end of an anode cylinder, for guiding magnetic face into the acting space between a cathode and a vein. SOLUTION: A pole piece 21, arranged in an opening part at each end of an anode cylinder 1, has a large diameter flat part 22, a slanting part 23 projecting toward a vane 2 as approaching the center, and a small diameter flat part 24 in the central part of the slanting part 23. A circular through-hole 25 is formed in the eccentric position to the tube axis of the small diameter flat part 24. The eccentric positions of the through-holes 25 are arranged, so as to be about 180 degrees symmetric with respect to the tube axis in the pole pieces 21 on the upper side and the lower side. Magnetic field strength and the direction of a magnetic flux become asymmetric with respect to the tube axis, electron orbitaling motion on the end side in the tube axial direction of an acting space 5 becomes discontinuous, so that oscillation in this part is suppressed to prevent multiple oscillations, and only the main oscillation in the central part is generated.

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]

2. Description of the Related Art A conventional magnetron used in a microwave oven for home use will be described with reference to a sectional view of a main part shown in FIG. 10. Reference numeral 1 denotes an anode cylinder, and a plurality of anode cylinders are arranged radially on the inner peripheral surface thereof. It has a plurality of vanes 2 and forms a plurality of resonance cavities surrounded by adjacent vanes 2 and the inner peripheral wall of the anode cylinder 1. Reference numeral 3 denotes a strap ring for connecting the vanes 2 alternately.

Reference numeral 4 denotes a cathode disposed in a space surrounded by the vane 2, and a working space 5 is formed between the cathode 4 and the vane 2. Reference numeral 6 denotes a stem structure for supporting and fixing the cathode 4 via a lead terminal 7. Reference numeral 8 denotes a pole piece disposed at both open ends of the anode cylinder 1, a large-diameter flat portion 9 and an inclined portion 10.
And a small-diameter flat portion 11 formed at the center of the inclined portion 10.
And a through-hole 12 formed at the center of the small-diameter flat portion 11 so as to form an orthogonal electrostatic magnetic field in the working space 5 together with a DC voltage applied between the vane 2 and the cathode 4. The magnetic force of a magnet (not shown) is guided to the working space 5.

In the magnetron having the above structure, the cathode 4
The electrons radiated from are rotated in the circumferential direction by the orthogonal electrostatic magnetic field, approach the vane 2, and are converted into energy in the form of an electron cloud into a resonant cavity. As a result, the weak microwave in the resonance cavity is amplified and radiated from the antenna lead 13 electrically connected to one of the vanes 2 into a storage such as a microwave oven.

However, in the magnetron having the above-described configuration, the magnetic field intensity in the working space 5 is not uniform in the axial direction of the vane 2. That is, since the magnetic lines of force between the pole pieces 6 are drawn in an arc from one pole piece 6 to the other pole piece 6, the magnetic lines of force are located at the center of the interval between the pole pieces 6 from the action space 5 to the vane 2 side. Deviate to the cathode 4 side. As a result, the intensity of the magnetic field in the working space 5 was such that, as shown in FIG. 11, the distribution at the axial end of the vane 2 was about 16% stronger than that at the center.

[0006] The value of the ratio E / B of the electric field strength E and the magnetic field strength B in the orthogonal electrostatic magnetic field determines the rotational speed of the electrons.
Since the magnetic field strength B is unevenly distributed in the tube axis direction, the rotational speed of the electrons is also uneven, which causes multiple oscillations. The frequency deviation at the time of the multiple oscillation becomes noise leaking from the cathode side terminal of the magnetron to the outside, and there is a problem that the reception of a radio or a television is disturbed, and the frequency of the multiple oscillation itself disturbs the communication. . FIG. 12 shows the frequency characteristics of a conventional magnetron, in which a side lobe B indicating multiple oscillation is confirmed around a main lobe A which is a fundamental wave.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a low-noise magnetron.

[0008]

A first means of the present invention is as follows.
An anode cylinder, and a cathode disposed on a tube axis of the anode cylinder,
A stem structure fixed to one end of the anode cylinder and supporting and fixing the cathode, a plurality of vanes radially arranged on an inner peripheral surface of the anode cylinder, and an antenna lead connected to the vane; An output portion fixed to the other end of the anode cylinder and surrounding the antenna lead, and a pole piece having a small-diameter flat surface disposed at both ends of the anode cylinder and guiding a magnetic force to a working space between the cathode and the vane. Wherein the small-diameter flat surface of at least one of the pole pieces is formed in an asymmetric shape with respect to the tube axis.

A second means of the present invention comprises an anode cylinder, a cathode disposed on a tube axis of the anode cylinder, and a stem assembly fixed to one end of the anode cylinder for supporting and fixing the cathode. A plurality of vanes radially arranged on the inner peripheral surface of the anode cylinder, an antenna lead connected to the vane, and an output unit fixed to the other end of the anode cylinder and surrounding the antenna lead And a pair of pole pieces of the same shape having a small-diameter flat surface disposed at both ends of the anode cylinder and guiding a magnetic force to a working space between the cathode and the vane. While being formed asymmetrical with respect to the axis,
One pole piece is arranged at a position rotated by about 180 degrees with respect to the tube axis with respect to the other pole piece.

A third means of the present invention comprises an anode cylinder, a cathode disposed on a tube axis of the anode cylinder, and a stem assembly fixed to one end of the anode cylinder for supporting and fixing the cathode. A plurality of vanes radially arranged on the inner peripheral surface of the anode cylinder, an antenna lead connected to the vane, and an output unit fixed to the other end of the anode cylinder and surrounding the antenna lead And a pole piece for guiding a magnetic force to the working space between the cathode and the vane, wherein a through hole formed substantially at the center of the pole piece is formed by being displaced with respect to a tube axis. .

According to a fourth aspect of the present invention, there is provided an anode cylinder, a cathode disposed on a tube axis of the anode cylinder, and a stem structure fixed to one end of the anode cylinder for supporting and fixing the cathode. A plurality of vanes radially arranged on the inner peripheral surface of the anode cylinder, an antenna lead connected to the vane, and an output unit fixed to a multi-end side of the anode cylinder and surrounding the antenna lead. A pair of pole pieces that are disposed at both ends of the anode cylinder and guide magnetic force to the working space between the cathode and the vane, and a through hole formed substantially at the center of the pole piece is formed with respect to the tube axis. It is characterized by being displaced in opposite directions.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. The same components as those in the above-described conventional technology are denoted by the same reference numerals, and description thereof will be omitted.

Reference numeral 21 denotes a pole piece disposed at the opening at both ends of the anode cylinder 1, a large-diameter flat portion 22, an inclined portion 23 protruding toward the vane 2 toward the center, and a center of the inclined portion 23. The small-diameter flat portion 24 is formed with a circular through hole 25 at a position eccentric with respect to the tube axis. The eccentric position of the through hole 25 is about 18
The anode cylinder 1 is disposed at both ends of the opening so as to be symmetric with respect to 0 degrees.

FIG. 4 shows the difference in magnetic field strength in the tube axis direction at the vane end face of the magnetron using this embodiment. still,
The magnetron used in the experiment uses a pole piece 21 having a material thickness of 1.6 mm, the diameter of the through hole 25 is 9.2 mm, the eccentricity a of the through hole 25 with respect to the pipe axis is 0.3 mm, and the diameter of the inscribed circle of the vane 2 D is 9.0 mm, the outer diameter d of the cathode 4 is 4.0 mm, and the height h of the vane 2 is 9.0 mm.

As shown in FIG. 4, in the magnetron using this embodiment, the magnetic field strength at the end of the working space in the tube axis direction is about 16 times higher than that at the center, like the conventional magnetron shown in FIG. % Distribution is strong. However, in the conventional magnetron, the magnetic field strength and the direction of the magnetic flux at the end of the working space 5 in the tube axis direction are all axially symmetric with respect to the tube axis. In the magnetron, since the magnetic field strength and the direction of the magnetic flux are asymmetric with respect to the tube axis, the electron circulating motion at the end portion of the working space 5 in the tube axis direction also becomes discontinuous, and oscillation in this portion is suppressed. Multiple oscillations are prevented.

That is, the magnetron of the present invention suppresses the electron orbital movement at the end of the working space 5 in the tube axis direction and generates only the main oscillation at the central portion of the working space 5 so that the multiple oscillation is achieved. It is to prevent.

FIG. 5 shows the frequency characteristics around the fundamental wave of the magnetron using the above-described embodiment. Compared with the frequency characteristics of the conventional magnetron shown in FIG. 12, it can be seen that side lobes around the main lobe A due to multiple oscillation are suppressed.

In the above-described embodiment, the circular through hole 25 is configured to be eccentric with respect to the center line. However, as shown in FIGS. 6 and 7, the through hole 25 may be formed in an elliptical shape. As shown in FIGS. 8 and 9, the small diameter flat portion 24 may be configured to be eccentric with respect to the tube axis.

The through holes 2 of both pole pieces 21
5 is eccentric, but one pole piece 21
Only the through hole 25 may be eccentric. Furthermore, a configuration in which a part of the edge of the through hole 25 of the pole piece 21 is chamfered,
Alternatively, the configuration may be such that the thickness of the edge of the through hole 25 is changed. In short, any configuration may be used as long as it can change the gradient of the magnetic field at the end of the working space 5 in the tube axis direction.

[0020]

According to the structure of the present invention, with a simple structure,
It is possible to reduce multiplex oscillation and to reduce noise generation.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of the pole piece.

FIG. 3 is a plan view of the pole piece.

FIG. 4 is a diagram showing the same magnetic field intensity distribution.

FIG. 5 is a diagram showing the same frequency waveform.

FIG. 6 is a sectional view of a pole piece according to another embodiment.

FIG. 7 is a plan view of the pole piece.

FIG. 8 is a sectional view of a pole piece according to another embodiment.

FIG. 9 is a plan view of the pole piece.

FIG. 10 is a sectional view showing a conventional magnetron.

FIG. 11 is a diagram showing the same magnetic field intensity distribution.

FIG. 12 is a diagram showing the same frequency waveform.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode cylinder 2 Bain 4 Cathode 5 Working space 21 Pole piece 24 Small diameter flat part 25 Through hole

Claims (4)

[Claims] 1. An anode cylinder, a cathode disposed on a tube axis of the anode cylinder, a stem assembly fixed to one end of the anode cylinder to support and fix the cathode, and A plurality of vanes radially arranged on the peripheral surface, an antenna lead connected to the vane, an output portion fixed to the other end of the anode cylinder and surrounding the antenna lead, A pole piece disposed at both ends and having a small-diameter flat surface that guides magnetic force to the working space between the cathode and the vane, wherein the small-diameter flat surface of at least one of the pole pieces is formed asymmetrically with respect to the tube axis. A magnetron, characterized in that: 2. An anode cylinder, a cathode disposed on a tube axis of the anode cylinder, a stem assembly fixed to one end of the anode cylinder to support and fix the cathode, and A plurality of vanes radially arranged on the peripheral surface, an antenna lead connected to the vane, an output portion fixed to the other end of the anode cylinder and surrounding the antenna lead, A pair of pole pieces of the same shape having a small-diameter flat surface that is disposed at both ends and guides magnetic force to the working space between the cathode and the vane, wherein the small-diameter flat surface of the pole piece is asymmetric with respect to the tube axis. And forming one pole piece relative to the other pole piece at approximately 180
A magnetron characterized by being disposed at a position rotated by degrees. 3. An anode cylinder, a cathode disposed on a tube axis of the anode cylinder, a stem assembly fixed to one end of the anode cylinder to support and fix the cathode, and A plurality of vanes radially arranged on the peripheral surface, an antenna lead connected to the vane, an output unit fixed to the other end of the anode cylinder and surrounding the antenna lead, the cathode and the vane And a pole piece for guiding a magnetic force to a working space between the pole pieces, wherein a through hole formed substantially at the center of the pole piece is formed displaced with respect to a tube axis. 4. An anode cylinder, a cathode disposed on a tube axis of the anode cylinder, a stem assembly fixed to one end of the anode cylinder to support and fix the cathode, and A plurality of vanes radially arranged on a peripheral surface, an antenna lead connected to the vane, an output portion fixed to a multi-end side of the anode cylinder and surrounding the antenna lead, and both ends of the anode cylinder And a pair of pole pieces for guiding a magnetic force to the working space between the cathode and the vane, and the through holes formed substantially in the center of the pole pieces are displaced in directions opposite to each other with respect to the tube axis. A magnetron, characterized in that: