JP2003272537A - Magnetron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetron not required to use a costly, high melting point metal not only in its cathode but also in the peripheral components. <P>SOLUTION: Using a lathe, etc., flange-shaped or needle-shaped projections 11 are coarsely processed at a certain spacing on the peripheral surface of the cathode body 10 in the form of hollow cylinder made of nickel, etc. Each projection 11 is subjected to polishing by an electric field polishing method or discharge machining method, wherein the radius of curvature at the tip of each projection 11 is formed within 1 μm, and with this cathode body 10 produced, the intended magnetron is accomplished. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a cathode part of a magnetron used in a high frequency heating device such as a microwave oven or a pulse generator such as a radar.

[0002]

2. Description of the Related Art In the currently used magnetron, a hot cathode is used as an electron source. The hot cathode supplies electrons by thermionic emission. Thermionic emission is a mechanism in which, by heating these hot cathodes to 1500 to 2700K, free electrons in the conduction band in the cathode metal get thermal energy, get over the potential barrier on the cathode metal surface, and are emitted to the space. Is.

Next, a conventional magnetron will be described with reference to the drawings. FIG. 4 is a cross-sectional view of an essential part showing an embodiment of a conventional hot cathode magnetron, and FIG. 5 is an enlarged view of the essential part of FIG. In the figure, there is a DC magnetic field T due to the external magnet 1 in the axial direction. For example, the cathode 2 made of thorium-tungsten filament is arranged substantially at the center of the anode 3. Apply a direct current of over a dozen A to the cathode 2 and
Heat to 1800 ° C. Several kV between anode 3 and cathode 2
When a voltage of 2 is applied to generate a direct current electric field in the radial direction, thermoelectrons 4 are emitted from the cathode 2. The anode 3 is the anode body 5
Is a split anode in which a cavity resonator (not shown) is formed by a plurality of anode vanes 6 provided on the inner surface of the above so as to project toward the central axis. The space between the cathode 2 and the anode 3 is called the working space 7. Electrodes called end hats 8 are arranged on both upper and lower sides of the cathode 2 in the axial direction. By setting the end hat 8 to have the same potential as the cathode 2 or a negative potential, it is possible to confine the thermoelectrons in the working space 7. In the working space 7, the electrons are bent by the DC magnetic field T and make a cycloidal motion. The anode 3 has a vibration circuit based on a cavity resonator,
The velocity of the electron flow is modulated by the high-frequency electric field (not shown) generated in the division gap of the. Eventually, the electron flow becomes a sparse part and a dense part to form a rotating electron pole in synchronization with the adjacent different polarities between the vanes, and an induction current flows in the cavity resonator of the anode 3 to generate high frequency power. The high frequency power generated in the anode 3 is taken out from the external output terminal 9.

In the case of a magnetron, the electrons emitted from the cathode are cycloidally moved by the magnetic field and re-enter the cathode. At that time, if the secondary electron emission gain on the cathode surface is large, secondary electrons are emitted. This conventional example is a thorium-tungsten filament cathode, but oxide cathodes such as barium oxide and strontium oxide have a very large secondary electron emission gain when heated, and the thermal emission current itself emits a large current by at least secondary electron emission. It is possible.

[0005]

However, in the conventional magnetron, since the hot cathode is used as described above, heat is generated from the hot cathode itself in addition to the heat loss during the oscillation of the magnetron, and the magnetron itself is usually present. Had to be cooled.

Further, since the hot cathode has a high temperature of 1500 to 1800 ° C., it is necessary to use expensive refractory metal such as tungsten or molybdenum not only in the cathode itself but also in the peripheral parts.

The present invention has been made for the purpose of solving the above problems, and provides a magnetron which solves these problems.

[0008]

The magnetron of the present invention is a magnetron composed of a hollow cylindrical cathode body, wherein at least one electric field is formed on the outer peripheral surface of the hollow cylinder by electrolytic polishing or electric discharge machining. It has a structure in which an electron emission electrode is formed to project.

With this structure, electrons can be emitted without heating the cathode.

Further, it is preferable that the field electron emission electrode is formed in a brim shape, a needle shape, or an oxide film is formed on at least the outer peripheral surface of the hollow cylinder. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the magnetron of the present invention will be described below with reference to the drawings. The same components as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a sectional view of a main part of a cathode body according to the present invention, and FIG. 2 is an enlarged sectional view of the main part.

In the figure, a collar-shaped projection or a needle-shaped projection 11 is roughly processed at a predetermined interval on the outer peripheral surface of a hollow cylindrical cathode body 10 made of nickel, for example, by lathing. After that, each protrusion is polished by using an electrolytic polishing method or an electric discharge machining method to finish the tip of the protrusion.

Here, the present inventors have made the collar-shaped protrusions almost 2
Rough machining was performed at 5 points at intervals of mm. After that, each of the five flange-shaped projections 11 was polished by electric discharge machining to finish the tip portion of the flange-shaped projections 11 so that the radius of curvature was within 1 micrometer. FIG. 2 is an enlarged cross-sectional view of the main part of the collar-shaped projection 11 that has been subjected to the polishing process, and shows the width W of the collar-shaped projection.
Were processed to have a height H of about 0.1 mm and a height H of about 0.1 mm, whereby a hollow cylindrical cathode body 10 provided with a field electron emission electrode by a collar-shaped projection could be formed.

Next, in the second embodiment, as shown in FIG. 3, an oxide film 12 of several micrometers is formed on the surface of the cathode body 10. The oxide film 12 is formed by heating the cathode body 10 at a high temperature (about 800 ° C.) in a vacuum evacuation process at the time of manufacturing a magnetron, and thermally decomposing barium carbonate into barium oxide by a vacuum vapor deposition film forming method in vacuum to deposit barium carbonate. A film is formed.

When the magnetron is oscillated using the cathode on which the oxide film is formed, the oxide film 12 serves as a secondary electron emission source and electron emission is repeated one after another, and more electrons can be emitted. .

Therefore, the present inventors have made a prototype of a magnetron using the above-mentioned cathode and confirmed the operation. As the anode at that time, an existing magnetron (10 divided anodes, anode inner diameter 8 mm, resonance frequency 2.45 GHz) was used. Then, the distance between the cathode body 10 and the anode vane 6 is set to 1.8 mm, and a DC voltage of -6.0 is applied to the cathode body 10.
When a direct current magnetic field T of 0.35 Tesla was applied in the axial direction of kV, a field electron emission current (primary electron) was emitted from the flange-shaped projection 11 arranged on the surface of the cathode body 10, and the primary electron was cycloidized by the direct current magnetic field. The secondary electrons move and collide with the oxide film 12 on the surface of the cathode body 10. The colliding secondary electrons serve as new secondary electron emission sources, and secondary electron emission is repeated one after another. Then, a maximum current of 50 mA in both flowed between the anode and the cathode.

As a result of the above, it was confirmed that the microwave output was 200 W in the frequency band of 2.45 GHz.

The oxide film 12 of the present invention does not affect the emission of the field electron emission current (primary electron) even if it is formed on the surface of the flange-shaped projection 11 as shown by the phantom line 13 in FIG. Absent.

[0020]

As described above, according to the magnetron of the present invention, since at least one field electron emission electrode is formed to project on the outer peripheral surface of the hollow cylinder by the electrolytic polishing method, a cathode assembly that operates stably can be obtained. It is possible to obtain the equipped magnetron.

Since the operating temperature of the cathode is lower than that of the conventional hot cathode, it is possible to use an inexpensive metal without using an expensive refractory metal for parts around the cathode.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a magnetron according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the magnetron according to the first embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view of a main part of a magnetron according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of essential parts showing an embodiment of a conventional hot cathode magnetron.

5 is an enlarged view of a main part of FIG.

[Explanation of symbols]

10 Cathode body 11 Field electron emission electrode (collar-shaped protrusion or needle-shaped protrusion) 12 Oxide film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayuki Aiga             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Toshiyuki Tsukada             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5C029 CC01 CC07

Claims (5)

[Claims] 1. A magnetron comprising a hollow cylindrical cathode body, characterized in that at least one field electron emission electrode is formed so as to project on the outer peripheral surface of said hollow cylinder by electrolytic polishing. . 2. A magnetron comprising a hollow cylindrical cathode body, characterized in that at least one field electron emission electrode is projectingly formed on an outer peripheral surface of said hollow cylinder by an electric discharge machining method. . 3. The magnetron according to claim 1, wherein the field electron emission electrode is formed in a brim shape. 4. The magnetron according to claim 1 or 2, wherein the field electron emission electrode is formed in a needle shape. 5. The magnetron according to claim 1, wherein an oxide film is formed on at least an outer peripheral surface of the hollow cylinder.