JPH0817077B2 - Cathode structure for magnetron - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cathode assembly of a magnetron used in a microwave oven or the like.

2. Description of the Related Art A cathode assembly of a magnetron used in a microwave oven is constructed as shown in FIG. 4, for example, and is a spiral direct heating cathode 1 made of thorium-tungsten alloy.
Are fixed to the inner ends of the pair of inner lead wires 4 and 5 via a pair of end hats 2 and 3 provided at both ends thereof. However, in the case of this example, each internal lead wire 4,5
Together with the external lead wires 6 and 7 added to each, form a lead wire for leading the cathode terminal.

The metal tube 8 is coaxially projected from one opening edge of the anode cylinder (not shown), and the ceramic stem insulator 9 that closes the outer opening is a pair as shown in FIG. It has a pair of through holes 10 and 11 for inserting the external lead wires 6 and 7. A pair of through holes are formed on the inner end surface of the stem insulator 9.
Circular first and second metallized layers 12 and 13 surrounding the respective metallized layers 10 and 11 are provided, and a ring-shaped metal plate 14 for brazing is brazed on the first metallized layer 12,
The abutting portions of the lead wires 4 and 6 are brazed, and the abutting portions of the lead wires 5 and 7 are brazed to the ring-shaped metal plate 15 for sealing which is brazed on the second metallization layer 13.

The metal ring 16 for chocks, which is coaxially arranged in the metal tube 8 and is held at the cathode potential, has an electric length corresponding to about 1/4 of the arbitrary harmonic wavelength of the magnetron in the axial direction,
The ear 16a provided on the bottom and brazed to the second metallized layer 12 has a hole 16b for inserting the lead wire 4 therethrough.
have. The ring-shaped metallization layer 17 provided on the inner surface of the stem insulator 9 along the outer circumference is a metal tube 8
The outer end face of the above is capable of being brazed to the stem insulator 9. In addition, the metallized layer that is held at the cathode potential
A metal plate 18 is provided to prevent sparks from occurring between 12, 13 and the metallized layer 17 held at the anode potential.

In such a conventional cathode assembly, the lead wire for leading out the cathode terminal is divided into the inner lead wires 4,5 and the outer lead wires 6 and 7, so that even if an expensive refractory metal such as molybdenum is used for the former, Has the advantage that relatively inexpensive metals such as iron can be used. Further, since the 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 in a seismic resistant manner. Further, there is an advantage that the choke metal ring 16 can be simultaneously fixed at the butting portions of the composite lead wires. Brazing is performed in a high temperature hydrogen furnace with each part set in a jig.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By the way, in order to fix the metal ring 9 for chokes by the sealing portion of the composite lead wire, the ear of the metal ring 9 for choke is to be fixed.
The hole 16b must be provided in 16a, and the lead wire 4 must be inserted into this hole 16b. Further, 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 at the time of assembling the electrode. 0.2mm ~
0.3mm clearance is required. In addition, since the metal ring 9 is fixed at one place, it is not possible to assemble it with high precision, which may cause variations in the electromagnetic wave leakage prevention effect of the metal ring 9 or the metal ring 9 may approach or contact the metal tube 8. was there.

Means for Solving the Problems According to the present invention, a pair of cathode terminals for leading out a pair of cathode terminals is provided on a ceramic stem insulator that closes an outer end opening of a metal tube that coaxially protrudes from one opening edge of an anode cylinder. In addition to having a pair of through holes for inserting lead wires,
First and second metallization layers for hermetically sealing the pair of lead wires to the stem insulator are provided on the inner end face, and the second metallization layers are provided on both sides of the first metallization layer. The metal ring for chokes coaxially arranged in the metal tube has a pair of lugs brazed to the extension.

Function With this structure, the metal ring for choke is stably fixed to the stem insulator at two places, and moreover, the ear of this metal ring has a hole or the lead wire is inserted into the hole of the ear. It becomes unnecessary to do. Further, the choke metal ring is provided with a pair of flat side wall portions parallel to each other, and the side wall portions are engaged with the pair of flat side wall portions parallel to each other of the stem insulator. It is possible to assemble in.

EXAMPLES Next, the present invention will be described with reference to the examples shown in the drawings.

The structure shown in FIG. 1 is different from the structure shown in FIG. 4 in that the ceramic stem insulator 19 has a pair of planar side walls parallel to each other on the convex portion 19a at the center of the upper surface as shown in FIG. A point having the portions 19b and 19c and a first metallization layer 21 provided on the convex portion 19a and surrounding the first through hole 20 are provided on the convex portion 19a and the first through hole is formed. A point of a substantially crescent shape having extension portions 21a, 21b projecting to the side of the second metallized layer 23 surrounding 22 and a coaxial arrangement in the metal tube 8 held at the anode potential. The choked metal ring 24 has a pair of flat side wall portions 24a and 24b which are parallel to each other as shown in FIG. 3, and these side wall portions 24a and 24b are one of the convex portions 19a of the stem insulator 19. A pair of flat sidewalls 19b, 1
It is configured to mate with 9c and metal ring 24
Has a pair of ears 24c, 24d formed by cutting and raising, and both ears 24c, 24d are brazed to the pair of extensions 21a, 21b of the first metallized layer 21 respectively. There is no difference in other configurations. However, the protruding ears 24c, 24d do not immediately project horizontally from the bottom of the metal ring 24, but slightly protrude upward and then project horizontally. Therefore, the lower edge of the metal ring 24, the metallization layers 21 and 23 held at the cathode potential,
It breaks in between the metallization layer held at the anode potential and plays a role of preventing sparks.

In the magnetron cathode assembly configured in this way,
Since the pair of prongs 24c, 24d of the choke metal ring 24 are brazed to the pair of extensions 21a, 21b of the first metallization layer 21, the metal ring 24 is stably supported on the stem insulator 19. In addition, it is not necessary to provide the ear with a hole or insert a lead wire into the hole. Further, in this example, since the pair of flat side wall portions 24a, 24b of the choke metal ring 24 are fitted to the pair of flat side wall portions 19b, 19c of the stem insulator 19, the assembly accuracy of the metal ring 24 is improved. Can be increased.

As described above, according to the present invention, it is possible to accurately and stably support the choke metal ring held at the cathode potential with respect to the stem insulator, and it is possible to prevent characteristic changes and sparks from occurring due to variations. Can be prevented. Further, the number of assembling steps can be reduced, and by assembling the pair of planar side wall portions of the choke metal ring with the pair of planar side wall portions of the stem insulator, the metal ring assembly accuracy can be improved. It can be further enhanced.

[Brief description of drawings]

FIG. 1 is a partially broken perspective view of a cathode assembly for a magnetron embodying the present invention, FIG. 2 is a perspective view of a stem insulator of the same cathode assembly, and FIG. 3 is a perspective view of a choke metal ring of the same cathode assembly. FIG. 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 …… first metallization layer, 23 …… second metallization layer, 21a, 21b …… extension part, 24 …… metal ring for choke.

Claims (2)

[Claims] 1. A ceramic stem insulator for closing an outer end opening of a metal tube coaxially protruding from one opening end edge of an anode cylinder for inserting a pair of lead wires for leading out a cathode terminal. The first metallization layer has a pair of through holes, and first and second metallization layers on the inner end surface for airtightly attaching the pair of lead wires to the stem insulator, respectively. Is a pair of ear tabs having extension portions projecting toward the second metallization layer on both sides, and choke metal rings coaxially arranged in the metal tube, which are brazed to the extension portions. A cathode assembly for a magnetron, comprising: 2. The choke metal ring has a pair of planar sidewall portions parallel to each other, the sidewall portions mating with a pair of planar sidewall portions parallel to each other of the stem insulator. The cathode assembly for a magnetron according to claim 1, which is characterized in that.