JPH05250982A - Manufacture of magnetron - Google Patents

Abstract

PURPOSE:To stabilize characteristics while restraining dispersion in the pipe axial directional length by brazing both ends of a spiral filament after a side lead, a lower end shield, a monitor lead and an upper end shield are welded together. CONSTITUTION:A place, where a molybdenum center lead 4 is inserted into the center hole of a molybdenum upper end shield 2, is welded/fixed. A molybdenum lower end shield and the upper end of a molybdenum side shield are also welded/fixed together. Next, a solder material 7 of ruthenium-molybdenum eutectic alloy is arranged between a thorium tungsten filament 1 and a filament support part of the upper/lower end shields, and is heated in a reducing atmosphere such as hydrogen, and is brazed/fixed. In this way, a brazing work is carried out at a temperature lower than a melting point of molybdenum, so that dispersion in the pipe axial directional length between the upper/lower shields can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetron, which is capable of performing stable microwave oscillation operation and obtaining a product with a small reactive current from the cathode.

[0002]

2. Description of the Related Art FIGS. 3 and 4 are side sectional views of a cathode assembly of a magnetron manufactured by a conventional manufacturing method. In the figure,
1 is a spiral filament that is generally made of thorium-containing tungsten wire that emits thermoelectrons, 2 is an upper end shield, 3 is a lower end shield, 4 is a center lead,
Reference numeral 5 is a side lead, 6 is a paste-like brazing material, and 7 is a plate-like brazing material. As shown in the drawing, a hole is provided at the center of the upper end shield 2, and the center lead 4 is engaged with this hole, and the upper end shield is slid on the center lead, and the spiral filament 1 The length in the center lead direction (pipe axis direction in use) is adjusted to a predetermined value so that fixed connection can be made. Further, the cathode heating power is supplied to the spiral filament from the center lead and the side lead connected to the power electrode via the upper end shield and the lower end shield, respectively.

Normally, when the magnetron is operated, the temperature at the center of the filament 1 is about 1,800 ° C., and the temperature at the fixed connection with the end shields 2, 3 is about 1,200 ° C. 2, the lower end shield 3, the center lead 4, and the side lead 5 are each made of a high melting point metal such as molybdenum or tungsten. In addition, platinum was used as the material of the brazing material 6 or 7 used for mechanical fixing and electrical connection of each fixing connection part in the past, but since it is expensive, in recent years, a eutectic alloy of ruthenium and molybdenum or The ruthenium and molybdenum disclosed in JP-A-58-204436 are used, to which nickel is further added. In the conventional example shown in FIG. 3, a brazing material 6 formed by mixing the above-mentioned brazing material powder with a viscous volatile liquid to form a paste is provided inside the lower end shield 3 welded and fixed to the upper ends of the side leads in advance. The filament supporting portion is coated and the lower end of the filament 1 is inserted therein, and then the paste-like brazing material 6 is previously applied to the filament supporting portion on the lower surface of the upper end shield 2, and the upper end of the filament 1 is supported by the above-mentioned filament supporting portion. When the center lead 4 is inserted into the spiral of the spiral filament 1 at the same time as inserting it into the spiral part, and the upper end of the center lead 4 is engaged with the center hole of the upper end shield 2 and inserted, the upper end of the center lead 4 is further inserted. The paste brazing material 6 is also applied to the engaging and inserting portion with the shield 2 to assemble the cathode assembly. After that, the paste-like brazing material 6 is dried, and the entire cathode assembly is heated in a reducing atmosphere to perform brazing all at once. Further, in the conventional example shown in FIG. 4, a brazing material 7 formed in a plate shape is used instead of the paste-shaped brazing material, and the brazing material is assembled in the same procedure as in the conventional example shown in FIG. Brazing is performed by heating in a sex atmosphere. When the paste-like brazing filler metal is used, the amount of the brazing filler metal used tends to vary slightly. On the other hand, when the plate-shaped brazing filler metal is used, there is no variation, but the brazing material molding cost is somewhat high.

[0004]

However, in the cathode assembly formed by the above-mentioned conventional technique, the weight of the upper end shield is increased by the length of the filament (in the center lead direction) in the spiral filament during the heating and melting operation of the brazing material. It acts to compress the sag. Since some variations in the actual heating temperature and the filament material during the work are unavoidable, the shrinkage amount of the filaments caused by the above-mentioned action varies. That is, even if the brazing operation is performed in consideration of the shrinkage of the filament, it is inevitable that the interval between the upper end shield and the lower end shield of the cathode assembly in the tube axis direction (that is, the length of the filament) changes. Such variations in the cathode structure may cause problems such as when the magnetron is assembled into the magnetron, the reactive current from the cathode increases when the interval is too large, or when it is too small, stable oscillation operation is disturbed. Becomes

The present invention solves the above-mentioned conventional problems, does not cause a variation in the gap between the upper end shield and the lower end shield of the cathode assembly in the tube axis direction, and has high operation efficiency and stable operation. It is an object of the present invention to provide a method of manufacturing a magnetron.

[0006]

In order to solve the above problems, in the present invention, a spiral filament for emitting thermoelectrons arranged concentrically with the tube axis and its upper end are supported via an upper end shield. A cathode assembly including a center lead and a side lead that supports the lower end of the center lead via a lower end shield is an even number of vane groups that protrude from the inner circumference of the anode cylinder toward the tube axis with a working space. In the manufacturing method of the magnetron surrounded by the individual cavity resonators,
First, insert the lower end of the filament together with the brazing material made of ruthenium-molybdenum alloy into the filament support part of the lower end shield that is welded and fixed to the upper end of the side lead in advance.
Next, at the same time as inserting the upper end of the filament into the filament supporting portion of the upper end shield together with the alloy brazing material,
Insert the center lead into the spiral of the spiral filament, insert the center lead upper end into the center hole of the upper end shield, and then insert it so that the length of the spiral filament in the center lead direction will be the correct value. The position of the upper end shield on the center lead is determined, and after the center lead and the upper end shield are welded and fixed at the engaging and inserting points, the alloy brazing material is heated and melted, and both ends of the filament are respectively attached to the upper end shield. I decided to braze to the lower end shield to form the cathode assembly.

[0007]

When the center lead is inserted through the center hole of the upper end shield and the two are fixed by welding, both the center lead and the upper end shield are made of a refractory metal such as molybdenum. At the welding point where the refractory metals of both of these are once melted and fixed, even if the brazing material made of the ruthenium-molybdenum eutectic alloy is heated to the brazing temperature, the melting of the material at the welding point Does not occur (this is also the case because the lower end shield is fixed to the upper ends of the side leads by welding), and therefore the length of the filament along the tube axis does not fluctuate due to sliding of the welded relative positions of both members.

[0008]

1 is a side sectional view of a cathode assembly according to one embodiment of the present invention, and FIG. 2 is a side sectional view of the entire magnetron of the same embodiment.

First, FIG. 2 will be described. In the figure, 1 is a filament, 2 is an upper end shield, 3 is a lower end shield, 4 is a center lead, 5 is a side lead, 7 is a brazing filler metal, 8 is an anode cylinder, 8a is a vane, 9 is a magnetic pole, 10 is a permanent wire. Magnet, 11 is an external yoke, 12 is a microwave power extraction part, 13 is a filter case, 14 is an antenna, 15
Is a cooling fin. The cathode (filament 1) and the vane 8 are made by the magnetic pole 9, the permanent magnet 10, and the external yoke 11.
A static magnetic field in the tube axis direction is formed in the working space sandwiched at the end of a. The electrons emitted from the filament are attracted to the anode side to which a high positive voltage is applied to the filament 1 and gradually accelerated in the working space, but in the working space, the tube axis direction, that is, the direction perpendicular to the electron orbit. Since the above static magnetic field exists, the electron cloud forms an electron cloud in the working space by the Lorentz force acting in the direction orthogonal to the electron orbit and the magnetic field moves at a high speed. Therefore, if various conditions are adjusted, microwave oscillation having a phase difference of π between adjacent resonators is generated in the cavity resonator group formed by the anode cylinder and the vane and surrounding the cathode with the working space therebetween. The electric power of the microwave generated in the cavity resonator is commonly referred to by the antenna 14 to the microwave electric power extraction unit 12, and is applied to the load through a waveguide (not shown) and used. If microwave power is leaked by being placed on a power supply line that supplies heating power to the cathode structure, it becomes a problem as a noise source. Therefore, when the center lead 4 and the side lead 5 are outside the vacuum envelope, A filter including a series choke coil and a so-called feedthrough capacitor is installed to trap microwaves, and the outside of the filter is further covered and sealed with a filter case 13 to prevent microwave leakage. The electrons emitted from the filament are effectively used for microwave oscillation in the working space, but the electrons that stray outside the working space are only absorbed by the member at the same potential as the surrounding anode and oscillate. Does not get involved.
The upper and lower end shields suppress such unnecessary loss of electrons. That is, if the distance between the upper and lower end shields in the tube axis direction is too long, the reactive current will increase due to the electrons wandering out of the working space. If it is too short, the electron density in the working space becomes high, and it may be difficult to satisfy the microwave oscillation conditions, and the microwave oscillation state may become unstable.

FIG. 1 is a side sectional view of a cathode assembly according to an embodiment of the present invention immediately before brazing. As shown in the drawing, a molybdenum center lead 4 is inserted into a central hole of a molybdenum upper end shield 2. The two parts are welded together and fixed in place. Between the filament 1 made of thorium-tungsten and the filament supporting portions of the upper and lower end shields, a brazing material 7 processed into a plate shape of a ruthenium-molybdenum eutectic alloy is arranged, and the cathode assembly is filled with a reducing atmosphere such as hydrogen. When heated by passing through the furnace, both ends of the filament are melted and brazed to the filament supporting portions of the upper and lower end shields. As described above, the molybdenum lower end shield and the molybdenum side lead upper ends are also fixed by welding. Therefore, in the brazing work performed at a temperature considerably lower than the melting point of molybdenum, there is no fear that the length of the upper and lower end shields in the axial direction of the pipe will change.

[0011]

As described above, according to the present invention, since the variation in the length in the tube axis direction between the upper end shield and the lower end shield of the cathode assembly at the time of manufacturing is suppressed, the operation efficiency is high. Moreover, it is possible to manufacture a magnetron capable of obtaining stable operation.

[Brief description of drawings]

FIG. 1 is a side sectional view of a cathode assembly according to an embodiment of the present invention immediately before brazing.

FIG. 2 is a side sectional view of the entire magnetron of the same embodiment.

FIG. 3 is a side sectional view of a cathode assembly of a magnetron manufactured by using a pasty brazing material by a conventional manufacturing method.

FIG. 4 is a side sectional view of a cathode assembly of a magnetron manufactured by using a brazing filler metal processed into a plate shape by a conventional manufacturing method.

[Explanation of symbols]

1 ... Filament, 2 ... Upper end shield, 3 ... Lower end shield, 4 ... Center lead, 5 ... Side lead, 7 ... Brazing material.

Claims (1)

[Claims] 1. A spiral filament which is arranged concentrically with a tube axis and which emits thermoelectrons, a center lead which supports its upper end through an upper end shield, and its lower end which supports through a lower end shield. In the method of manufacturing a magnetron, in which a cathode assembly having side leads is surrounded by an even number of cavity resonator groups consisting of an anode cylinder and a vane group protruding toward the tube axis from the inner circumference of the cathode cylinder, with a working space in between, Insert the lower end of the filament together with the brazing material made of ruthenium molybdenum alloy into the filament supporting part of the lower end shield welded and fixed to the upper ends of the side leads, and then insert the upper end of the filament into the filament supporting part of the upper end shield together with the alloy brazing material. At the same time as inserting, insert the center lead inside the spiral of the spiral filament,
Insert the upper end of the center lead into the center hole of the upper end shield by inserting it, and then position the upper end shield on the center lead so that the length of the spiral filament in the center lead direction will be the correct value. After the center lead and the upper end shield are welded and fixed at the engaging and inserting points, the brazing alloy material is heated and melted, and both ends of the filament are brazed to the upper end shield and the lower end shield, respectively, to form the cathode assembly. A method for manufacturing a magnetron, which is characterized by being formed.