JPH04133245A - Cathode structure for magnetron - Google Patents

Abstract

PURPOSE:To enhance the accuracy or assembly by furnishing a pair of plane- form side wall portions parallel with a stem insulation, stretching one of them toward the two side of the other, and providing there a metallized layer for sealing of a pair of leads to secure projecting tabs of a metal ring for choke. CONSTITUTION:A plurality of projecting tabs 24c, 24d of a metal ring 24 for choke are brazed fast to the extension parts 21a, 21b of No.1 metallized layer 21, and thereby the ring 24 is supported stably relative to stem insulation 19. Plane-form side wall portions 24a, 24b of this ring 24 are fitted to a pair of plane-form side wall portions 19b, 19c of the stem insulation 19, and thereby assembling the ring 24 can be performed with high precision. Because the two tabs 24c, 24d first intrude a little upward from the bottom of the ring 24 and then stretch out in horizontal direction, the bottom edge of the ring 24 interferes between a cathode and the metallized layer held at the anode potential, and thus spark generation is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a cathode structure of a magnetron used in a microwave oven or the like.

Conventional technology The cathode structure of a magnetron used in microwave ovens, etc.
For example, a spiral directly heated cathode 1 made of a thorium-tungsten alloy is configured as shown in FIG.
It is fixed to each inner end of a pair of internal lead wires 4.5 via a pair of end hats 2, 3 provided at both ends thereof. However, in this example, each internal lead wire 4,
5 forms a lead wire for leading out a cathode terminal together with external lead wires 6 and 7 that are spliced to each other.

The metal tube 8 coaxially protrudes from one opening edge of an anode cylinder (not shown), and a ceramic stem insulator 9 that closes the outer end opening is a pair of ceramic stem insulators 9 as shown in FIG. A pair of through holes 10.1 for passing the external lead wires 6, 7 of the
1. On the inner end surface of the stem insulator 9, annular first and second metallized layers 12 and 13 surrounding the pair of through holes 10 and 11 are provided. The butt portions of the lead wires 4 and 6 are brazed to the ring-shaped metal plate 14 for sealing, which is brazed to the ring-shaped metal plate 14 for sealing, which is brazed to the ring-shaped metal plate 15 for sealing, which is brazed to the second metallized layer 13. The abutting portions of the lead wires 5 and 7 are brazed.

The choke metal ring 16, which is coaxially arranged in the metal tube 8 and held at a cathode potential, has an electrical length in the axial direction corresponding to about 1/4 of the arbitrary harmonic wavelength of the magnetron, The tab 16a provided at the bottom and brazed to the second metallized layer 12 has a hole 16b through which the lead wire 4 is inserted. Note that a ring-shaped metallized layer 17 is provided on the inner surface of the stem insulator 9 along the outer periphery.
This is to enable the outer end surface of the metal tube 8 to be brazed to the stem insulator 9. Further, a metal plate 18 is provided to prevent sparks from occurring between the metallized layer 12.13 held at the cathode potential and the metallized layer 17 held at the anode potential.

In such a conventional cathode structure, the cathode terminal lead wires are divided into internal lead wires 4 and 5 and external lead wires 6.7, so even if an expensive high-melting point metal such as molybdenum is used for the former, the latter is has the advantage of using relatively inexpensive metals such as iron. Further, since such a composite lead wire is fixed on the inner surface of the stem insulator 9, there is an advantage that the cathode 1 can be supported seismically. Furthermore, there is an advantage that the choke metal ring 16 can be fixed at the same time at the abutting portion of the composite lead wire.

Note that brazing is performed in a high-temperature hydrogen furnace with each component set in a jig.

Problems to be Solved by the Invention By the way, in order to fix the choke metal ring 9 with the sealing part of the composite lead wire, the prongs 1 of the choke metal ring 9 must be fixed.
6a has a hole 16b, and the lead wire 4 is inserted into this hole 16b.
must be inserted. In addition, in order to determine the rotational position of the choke metal ring 9, a jig having an outer diameter slightly smaller than the inner diameter of the metal ring 9 is required when assembling the electrode. to 0
．． A clearance of 2-0.3 m is required. Moreover,
Since the metal ring 9 is fixed in one place, it is not possible to assemble it with high precision, and there is a risk that the electromagnetic wave leakage prevention effect of the metal ring 9 may vary, or the metal ring 9 may come close to or come into contact with the metal tube 8. Ta.

Means for Solving the Problems According to the present invention, a pair of cathode terminals are attached to a ceramic stem insulator that closes the outer end opening of a metal tube coaxially protruding from one opening edge of an anode cylinder. A pair of through holes are provided through which the lead wires are inserted, and first and second metallized layers are provided on the inner end surface to hermetically seal the pair of lead wires to the stem insulator, respectively. In this case, the first metallized layer has extensions extending toward the second metallization layer on both sides thereof, and the choke metal ring coaxially disposed within the metal tube has extensions extending to the second metallization layer. It has a pair of prongs that are brazed to the section.

Function: With this structure, the choke metal ring is stably fixed to the stem insulator at two locations, and the metal ring has a hole in the prong, or a lead wire can be inserted through the hole in the prong. It is no longer necessary to do so. Further, the choke metal ring has a pair of parallel planar side wall portions, and these side wall portions are connected to the mutually parallel one side wall portion of the stem insulator.
By mating with a pair of planar side wall sections,
This enables assembly with higher precision.

Embodiments Next, the present invention will be explained along with embodiments shown in the drawings.

The configuration shown in FIG. 1 is different from the configuration shown in FIG. The point having portions 19b and 19c, and the convex portion 19a
A metallized layer 21 provided above and surrounding the first through hole 20 is provided on the convex portion 19a and surrounds the first through hole 20.
The second metallized layer 23 surrounding the second metallized layer 23 has an approximately crescent-shaped point on both sides with extensions 21a and 21b extending downwardly, and is coaxially arranged within the metal tube 8 held at an anode potential. As shown in FIG.
, 24b, and these side wall portions 24a, 24b are a pair of planar side wall portions 19b of the convex portion 19a of the stem insulator 19.
, 19C, and a pair of prongs 24 formed by cutting and raising the metal ring 24.
c, 24d, and both protrusions 24c, 24d are brazed to the pair of extensions 21a, 21b of the first metallized layer 21, respectively. There is no difference. However, both protruding ears 24c, 24
d does not immediately protrude horizontally from the bottom of the metal ring 24, but enters slightly upward and then protrudes horizontally. Therefore, the lower edge of the metal ring 24 cuts between the metallized layers 21 and 23 held at the cathode potential and the metallized layer held at the anode potential, and serves to prevent the generation of sparks.

In the magnetron cathode structure configured in this way, the pair of prongs 24c and 24d of the choke metal ring 24 are connected to the pair of extensions 21a and 21b of the first metallized layer 21.
Since the metal ring 24 is brazed to the stem insulator 19, it is not only stably supported by the stem insulator 19, but there is no need to provide a hole in the protrusion or to insert a lead wire into such a hole. . In this example, the l pair of planar g4 wall portions 24a, 241) of the choke metal ring 24 are connected to the pair of planar side wall portions 19b of the stem insulator 19.

19c, the precision in assembling the metal ring 24 can be improved.

Effects of the Invention As described above, according to the present invention, the choke metal ring held at the cathode potential can be supported accurately (stablely) against the stem insulator, and changes in characteristics due to variations in the choke ring and sparks can be prevented. It is possible to prevent the occurrence of
It would be better to reduce the number of assembly steps by replacing the pair of planar side walls of the choke metal ring with one of the stem insulators.
By mating with a pair of planar side wall sections,
The accuracy of assembling the metal ring can be further improved.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a magnetron cathode assembly according to the present invention, FIG. 2 is a perspective view of a stem insulator of the cathode assembly, and FIG. 3 is a perspective view of a choke metal ring of the cathode assembly. 4 is a partially cutaway perspective view of a conventional cathode assembly for a magnetron, and FIG. 5 is a perspective view of a stem insulator of the cathode assembly. 1...Cathode, 4-7...Lead wire, 8
...Metal tube, 19...Stem insulator,
21・Old...First metallized layer, 23...Metallized layer of inner cylinder 2, 21a, 21b...Extension part, 2
4. Metal ring for choke. Name of agent: Patent attorney Haruaki Koebi (2 persons) Figure 1 Figure 1

Claims (2)

[Claims] (1) A ceramic stem insulator that closes the outer end opening of a metal tube that protrudes coaxially from one opening edge of the anode cylinder, and a pair of ceramic stem insulators for inserting a pair of cathode terminal lead wires. and has first and second metallized layers on the inner end surface for hermetically sealing the pair of lead wires to the stem insulator, and the first metallized layer has a through hole in the stem insulator. A choke metal ring, which has extensions on both sides projecting toward the second metallized layer and is coaxially disposed within the metal tube, has a pair of prongs brazed to the extensions. A cathode structure for a magnetron that is characterized by: (2) The choke metal ring has a pair of parallel planar sidewall portions, and the sidewall portions are engaged with a pair of parallel planar sidewall portions of the stem insulator. The cathode assembly for a magnetron according to claim 1.