JPS5978427A - Magnetron - Google Patents

Abstract

PURPOSE:To economically obtain a magnetron with high mass-productivity and reliability by forming the third electrode which provides spiral protrusion and is disposed at the area near the cathode as a half-completed products divided into plural segments through the sintering of a high melting point metal. CONSTITUTION:A third electrode 60 is provided at the area near the cathode 25, this electrode 60 is provided with a conductive cylindrical base material 61 which is smaller than the spiral internal diameter of cathode 25 at the internal side of cathode 25, and a spiral protrusion 62 which is protruded at the circumference of the base material 61 and between each spiral parts of cathode 25 is also integrally provided. Moreover, this third electrode 60 is formed with a single material selected from infusible metals such as W, Mo, Ta, Ti etc. or alloy of them in such surface condition which shows bad primary and secondary electron emitting characteristic and is located in such a position as is near the cathode and is not interfering the flow of electrons from the cathode to anode. Thereby, a magnetron ensuring mass-productivity and high reliability can be obtained economically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetron, and particularly to improvements in its cathode structure.

[Technical background and problems of the invention]

In general, magnetrons that apply a magnetic field perpendicular to an electric field are now widely used in electronic equipment such as electronic lenses, but as a result, regulations on noise leakage are becoming stricter. Regarding this noise regulation, the International Special Committee on Radio Interference (CRSPA)
Based on the recommendations, each country is implementing or considering it. Therefore, measures to reduce the noise generated from the magnetron itself have become even more desirable.

By the way, there is a first-order theory as a cause of low frequency noise (for example, 1' 00 Mllz or less) generated from a magnetron. That is, FIG. 1 shows the anode pane 2 constituting the coaxially arranged anode of the magnetron.
6 and the cathode 25. In the figure, a high voltage of several thousand V is applied between the cathode and the anode, with the cathode 25 being negative and the anode pane 26 being positive, and thermoelectrons are emitted from the cathode 25. In the electron action space 39, due to the space charge near the cathode, υ creates a potential distribution with a concave portion that is more negative than the cathode potential, as shown by the dotted curve a in the figure. Become.

On the other hand, as shown by arrow B, l is added to this electron action space 39.
d11) Since a DC magnetic field of OO~2000 #us is applied in the cathode axial direction, the electrons leaving the cathode 25 orbit around the bite of the cathode 25 due to the action of the electric field and the magnetic field. In particular, due to the orthogonal electromagnetic field, the traveling distance of the electrons is long, so there is a high probability that the electrons will collide with residual gas, and significantly more glass ions (2) are generated than in other straight tubes. The positive ions generated by N are shown by curve a.The valley of the potential distribution is J? It flows into the tensile minimum (indicated by the symbol m in the figure), and the electrons in the space charge gradually become neutralized with the glass ions, and as a result, the potential near this valley rises, as indicated by the symbol n. It is raised to a potential equal to or slightly higher than that of the cathode 25. In this state, the potential distribution between the working walls becomes as shown by a solid curve #b. Positive ions flow into the cathode. In the next step, a valley m at the stain level is again formed by the space charge. This series of processes is repeated periodically. As a result, a complicated pulsation phenomenon occurs in the current between the cathode and the anode, that is, the anode current, and it can be assumed that this leaks into the external circuit as noise. Such noise mainly appears as so-called line noise that leaks along the input line, causing various radio interference.

Therefore, as one of the measures to reduce such Korean style, a third electrode is provided near the cathode, and a negative potential of several tens to several 1 oov is applied to the third electrode with respect to the cathode, thereby reducing the valleys of the potential distribution. one! It is considered that the third electrode captures the glass ions that gather at the point m, thereby reducing the noise caused by the glass ions.

This example is constructed as shown in FIG. 2. That is,
An end knot 51h and an end tip 52 are fixed to one end of a rod-shaped cathode support 32 arranged on the tube axis. (not shown). The sleeve-shaped cathode support 33 has one end insulated and coaxially arranged with a Hiramix shield 55 and joined to an end node 51b, and the other end is connected to another cathode terminal (not shown). is joined to. A spirally wound thorium-tungsten directly heated cathode 25 is bonded between the end tip 52 and the end tip 51b. Thereby, the cathode 25 is heated by the heating power supplied to the cathode terminal.

Now, in the vicinity of the cathode 25, a third electrode is provided. This third electrode is provided with a conductive cylindrical base 6 which is smaller than the spiral inner diameter of the cathode 25 inside the cathode 25, and which is located on the outer periphery of the base 6 and the cathode 2.
A helical protruding piece 62 protruding between each of the spirals 5 is integrally provided. The lower end 61h of the base body 61 is tied together as a free end without intervening an insulator or the like, and is connected to the inner rod-shaped cathode support 32 by a ceramic insulator 63 at a position farther upward in the figure than the end node 51b. is held in
Further, the other end is tightly fitted into the center hole of a third electrode terminal (not shown) and is mechanically held. In this way, the third electrode is held on the cathode support via the insulator at a position that is optically separated from the cathode 25, and its tip remains free. Moreover, this third electrode gong has its protruding piece 6
2 is located between the spirals of the cathode 25 and is formed to protrude to a position equivalent to the outer periphery of the cathode 25. In addition, this third electrode is made of a single substance or an alloy selected from 4-9 of refractory gold such as W, Mo, Ta, and Ti, and -
Next, JL formed in a surface state with poor secondary electron emissivity,
As shown in the figure, it is placed in the vicinity of the cathode and in a position that does not impede the flow of electrons from the cup 12 to the anode. - For example, a magnetron with an output of about 800 W in the 2.45G)+2 band, the cathode coil wire diameter is 1t1 diameter and 0.58m+n, and the depression between each pip of the curated and :3 electrode protruding pieces is 2. ．． (l wn , spiral outer diameter is 5.0 m, anode pane tip y; M inner diameter is 10
I can cum with nrm. Therefore, the outer circumferential surfaces of the cathode spiral, the third electrode spiral, and Q can be alternately arranged on the same 1+r at intervals of one. Note that the anode-1 pane 26 and the anode cylinder (not shown) contain multiple cavity resonators in one.
14, and the whole forms an anode.

2B is a stratono 0 ring.

Next, the operation will be explained. When the capacitor 1°25 is heated, it emits thermoelectrons. This cathode 25 and anode vane 2
6, a high voltage of several 1 oOO'V is applied, and a DC magnetic field of approximately 1500 Gauss of magnetic flux parallel to the tube axis is applied to the electron action space 39, causing oscillation.

The microwave energy generated in the cavity resonator is transmitted from the output to the external load through the antenna conductor. Now, when the cathode 25 is heated, a potential valley m is formed near the front surface of the cathode 25 from about several 10 μll Tl to several 100 Ytrn as shown in FIG.
(if there is no electrode), the third electrode is placed at a distance of, for example, -several 10 to -several 10. When the potential is set to a negative potential of about tl V, the positive ions that gather toward the valley m of the potential are immediately captured by the third electrode μJ, since the potential is even more negative than this. . That is, the glass ions flow into the third electrode without being frozen near the cathode, and unstable electron-ion neutralization f-51 near the cathode does not occur. As a result, 100 Ml
Noise below 1z is greatly reduced.

In addition, in FIG. 3, the drain operation is improved by providing a slit (gap) SO, which becomes a path for charged particles to move in the direction of the magnetic field B, on the protruding piece 75, and this is particularly effective in reducing noise in the medium wave band. In the figure, 73 is a third electrode, and 74 is a base 75 that is a spiral protruding piece.

Now, the third electrode μ0,7 as shown in FIGS. 2 and 3
30 The usual manufacturing procedure is as follows.

That is, first, a spiral groove is created using a lathe, and complicated parts that cannot be processed using a lathe are processed using a milling cutter. And slit 8o
is formed by electric discharge machining. However, cutting methods such as lathes and milling machines inevitably leave blade marks and edges, resulting in uneven surfaces. Therefore, there are parts that are easily overheated locally due to electron reverse impact during oscillation, which may cause gas to be released or thermionic emission to occur.

Generally speaking, the third electrode in terms of heat resistance! □, Mo is suitable as the material for the magnet, but electric discharge machining is used for machining minute parts due to the difficulty of cutting. but,
In electric discharge machining, metal particles adhere to the third electrode (H) during machining and are difficult to remove completely, so there is a probability that similar problems will occur.

[Purpose of the invention]

An object of the present invention is to provide a magnet 1.1 which is inexpensive, has high productivity and reliability.

[Comparison of inventions]

In this invention, the third electrode, which has a spiral projecting piece and is placed near the cathode, is formed by sintering a high-melting point metal as a product in the shape of a plurality of parts, which are then integrally joined. It is a magnetron that can be easily manufactured despite its complicated shape.

[Embodiments of the invention]

In order to eliminate the above-mentioned drawbacks, this φ-generated magnetron has an improved third electrode, and only the third electrode will be explained in terms of its manufacturing method. That is, the third electrode (corresponding to the third electrode in FIG. 2) used in the present invention is made of a high melting point metal such as Mo as shown in FIGS. 4 and 5 (a) to (c).
The powder is put into a mold with a spiral protrusion on the surface of the cylinder and divided into two in parallel in the axial direction, and then press-molded and sintered at high temperature to form a parts reel for the third electrode. 60h, 6
Create 0b. The arrow in FIG. 5(a) indicates the pressing direction. Next, if the third electrodes 60h and 60b are joined together to form a cylindrical shape as shown in FIG.
A shape close to that of the electrode μJ can be obtained. In this case, considering the movement of the press die, the protruding piece 62 does not have a perfect spiral shape but a pseudo spiral shape.

Incidentally, FIG. 7 corresponds to FIG. 3, and shows a case in which a slit 80 is formed in the protruding piece 75, and is manufactured in the same manner as the above embodiment, and the figure shows a single unit 7, ? a.7. ? b.

〔Effect of the invention〕

According to this invention, it is possible to obtain a magnetron that is inexpensive and has high productivity and reliability. That is, in this invention, since the third electrode is formed by sintering Mo, localized overheating due to electron reverse impact can be prevented, and the third electrode with a complicated shape can be prevented.
The electrodes can also be manufactured easily and mass production becomes possible.

Note that in order to suppress thermionic emission from the third electrode, the third electrode may be plated with PT or the like.

Furthermore, when manufacturing the third electrode by sintering, the cathode support and the electrode may also be manufactured integrally.

Furthermore, the third electrode of the above embodiment is required! , L was cylindrical, but as shown in FIG. 8, in the case of the third electrode U having a cylindrical base 91 and a spiral protruding piece 92, it is divided into two in the axial direction as in the above embodiment. Multiple individual parts 90n, 90b
It is sufficient to form multiple layers by sintering MO and then join them together. In this modified example, as shown in the figure, the third electrode is fixedly supported by a rod-shaped cathode support 32 and also serves as a path for cathode current, and is used in zero bias operation.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the noise generation mechanism in a magnetron, Figure 2 is a cross-sectional view of an example of a magnetron equipped with a third electrode to reduce noise, and Figure 3 is another example. A sectional view, FIG. 4 is a perspective view showing a single unit constituting the third electrode of a magnetron according to an embodiment of the present invention,
Figures 5 (a), (b), and (C) are the same left side IZ, top view, and right side view. Figure 6 is a perspective view of the single body joined to form the third electrode. Figure 7 is the single body. A plan view showing another example of
The figure is a sectional view showing a modification of the invention. 25... Cathode, 26... Anode pane, 32
... Rod-shaped cathode support, 3,9... Cylindrical cathode support, 39... Electron action space, 51h, 51b...
End hat, 5. ? ...End tip, 60...
Third electrode, 60a, 60b...Single body, 6th...Base, 62...Protruding piece, -ζF...Third electrode, 73h
, 73b...Single body, 74...Base body, 75...Protruding piece, 80...Slit (gap), Darg=...Third electrode, 90IL, 90b...Single body, 91... Base, 9
2...Protruding piece. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 (a) (b) (C) Figure 6
Figure 7 Figure 8

Claims (4)

[Claims] (1) In a magnetron that has an electron-emitting cathode and an anode containing a cavity resonator that are arranged coaxially with each other, and a magnetic field parallel to the six-sode axis is applied to the electron action space between the cathode and the anode. , A third electrode made of a conductor is provided near the cathode and is electrically conductively connected to or electrically insulated from the cathode, and the third electrode is formed by press-molding and sintering high-melting point metal powder. A magnetron is characterized by being formed. (2) The magnetron according to claim 1, wherein the third electrode is formed into a cylindrical shape by integrally joining parts that are divided into a plurality of parts parallel to the axis and molded. . (3),] - the cathode has a spiral shape, and the third cathode has a spiral shape, and
3. The magnetron according to claim 1, wherein the electrode has a protruding piece spirally provided between the spirals of the cathode. (4) The magnetro 7° according to claim 3, wherein a slit is formed in the protruding piece.