JPH01146235A - Cathode composition of x-ray tube and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an excellent welding strength and to make it possible to assemble at a high accuracy by pressing with a unitary type tablet striding to both legs, and welding to fix. CONSTITUTION:In a focus electrode 21 which has large and small sizes of focus grooves 22 and 23, cathode filaments 15 and 18 are furnished responding to the focus grooves 22 and 23 respectively. Legs 16 and 17 are fixed to a pair of filament supporting rods 24 and 25, and near the tips 31, a cutting 33 to be a flat part and a slope 32 following the cutting 33 are formed. And the cuttings 33 are lined up on the same plane, and recessed grooves 34 are furnished along the axes of supporting rods 24 and 25 respectively, over which a ruthenium coating is applied. After that, to the coated recessed grooves 34, the legs 16 and 17 of the cathode filament 15 are engaged, and moreover, they are pressed from the outside by a unitary type tablet 35 striding the legs 16 and 17. A cathode composition with an excellent welding property, an easy assembling property, and a high accuracy can be obtained consequently.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method of manufacturing a cathode assembly for an X-ray tube.

(Prior Art) Generally, X-ray tubes are used for medical purposes such as X-ray diagnosis, but fixed anode X-ray tubes have an anode structure and a cathode structure facing each other in a vacuum envelope. It is arranged.

Conventionally, in the cathode structure, a spiral cathode filament 15 made of tungsten as shown in FIG. 4 is provided in a cup-shaped focusing electrode having a substantially rectangular focusing groove. 17 are respectively fixed to filament support rods 11 and 12 made of molybdenum or iron.

By the way, since the relative position of the cathode filament 15 and the focusing groove has a strong influence on the focusing characteristics of the electron beam, it is necessary to assemble the cathode filament 15 with high precision.

On the other hand, the cathode filament 15 and the filament support rod 11
．． When welding with 12, since both are metal materials that are difficult to weld to each other, the accuracy is likely to be lost during welding.

Therefore, conventionally, the filament support rod 11.
A split groove 13.14 along the axial direction is formed at the tip of the cathode filament 12, and both end legs 16.17 of the cathode filament 15 are inserted into the split groove 13.14, and the welding electrode (Fig. (not shown), and spot welding is performed at several locations while applying pressure to connect electrically and mechanically.

(Problems to be solved by the invention) However, in the conventional structure and manufacturing method as described above,
During welding, the centers of the legs 16 and 17 at both ends of the cathode filament 15 are not always located on the line connecting the contact points of the pair of welding electrodes. For this reason, stress such as torsional force acts on the leg portions 16 and 17, and the helical portion of the cathode filament 15, particularly the portion A, tends to bend. Also, the filament support rod 11.1
2 and the center of the legs 16.17 may be misaligned, or there may be local differences in contact resistance within the grooves 13.14, resulting in disturbances in the welding strength, and in extreme cases, the welding may become brittle and break. It will happen.

As described above, the conventional structure has disadvantages in that it is difficult to assemble and it is difficult to obtain a highly accurate cathode structure.

This invention facilitates welding and has excellent welding strength.
An object of the present invention is to provide a cathode structure for an X-ray tube that can assemble a cathode structure with high precision, and a method for manufacturing the same.

[Structure of the Invention (Means for Solving Problems)] This invention provides a focusing electrode having a focusing groove, in which a spiral cathode filament made of tungsten is provided corresponding to the focusing groove, and both ends of the cathode filament are In an X-ray tube cathode structure in which the legs are fixed to a pair of filament support rods made of molybdenum, the pair of filament support rods have a flat portion, and a plated concave groove is provided in the flat portion. This is a cathode structure for an X-ray tube, in which the legs of the cathode filament are fitted into the concave grooves, and are pressed by a tablet and fixed by welding. The plating is ruthenium, platinum, or rhodium, and the tablet is made of stainless steel (5us304L is particularly good).

The present invention also provides a method for manufacturing a cathode assembly for an X-ray tube in which both end legs of a spiral cathode filament made of tungsten are fixed to a pair of filament support rods made of molybdenum.
A flat portion is formed on the pair of filament support rods, and a concave groove is provided in the flat portion and plated. This is a method of manufacturing a cathode structure for an X-ray tube, in which unnecessary parts of the integrated tablet are removed after the integrated tablet is pressed and fixed by welding.

(Function) According to the present invention, it is possible to obtain a highly accurate cathode structure in which deformation such as bending of the cathode filament is difficult to occur, excellent weldability is achieved, and assembly is easy.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The cathode structure of the X-ray tube according to the present invention is constructed as shown in FIGS. 1 to 3, and the same parts as in the conventional example (FIG. 4) are given the same reference numerals.

That is, FIG. 3 is a plan view showing the entire cathode structure, in which cathode filaments 15 are provided in the focusing electrode 21 having large and small focusing grooves 22,23 corresponding to the focusing grooves 22,23.
．． 18 are provided.

As shown in FIG. 1(a), this cathode filament 15.18 is made of tungsten and made into a spiral shape, and both ends are bent to form leg portions 16.17. Only the case of cathode filament 15 is shown). The legs 16, 17 are each fixed to a pair of fixture support rods 24, 25 made of molybdenum, as shown in FIG.
As shown in b), in the present invention, a notch 33 serving as a flat portion and a slope 32 continuing thereto are formed near the tip portions 31 of the pair of filament support rods 24 and 25, respectively. The notches 33 of both filament support rods 24.25 are arranged on the same plane, and the notches 33 include the following along the axis of the filament support rods 24.25.
For example, concave grooves 34 each having an arcuate cross section are provided, and the concave grooves 34 are plated with ruthenium.

The leg portion 16 of the cathode filament 15 is fitted into the plated concave groove 34, and is pressed by an integrated tablet 35 made of stainless steel and fixed by, for example, resistance welding. The X marks in FIG. 1(a) indicate welding locations.

The above description and FIGS. 2(a) and 2(b) refer to one leg 16 of the cathode filament 15 and one filament support rod 24, but the other leg 17 and filament support rod 25 are also It's exactly the same. Further, the case of the cathode filament 18 is also exactly the same as the case of the cathode filament 15, and the explanation thereof will be omitted. Reference numeral 26 in FIG.
27 indicates a filament support rod to which the cathode filament 18 is fixed.

Now, to describe the method for manufacturing such a cathode structure, especially the method for fixing the cathode filament 15 to the filament support V%24.25, first, the pair of filament support rods 24.25 are placed on the same plane near the tips 31 of each of them. A notch 33 and a slope 32 following the notch 33 are formed.

A concave groove 34 having a diameter approximately equal to the diameter of the leg 16.17 and having, for example, an arcuate cross section, is provided in this cutout 33 along the axis of the filament support rod 24.25. This concave groove 34
Laser machining is suitable for forming the concave grooves, which can fit snugly into the leg portions 16 and 17 of the cathode filament 15 as thin as 0.2 mm in diameter. 34 types of processing are possible.

Next, such concave grooves 34 are plated with ruthenium. Thereafter, the leg portions 16.17 of the cathode filament 15 are fitted into the plated concave groove 34, and the thickness of the cathode filament 15 is then extended from above to the leg portions 16.17 as shown in FIG. 2(C). Press with an integrated tablet 35 of about 50 μm.

Then, as shown by the arrow in FIG. 1(b), the integrated tablet 35 and the filament support rod 24 are sandwiched between a pair of welding electrodes (not shown) and fixed by resistance welding. The X mark in FIG. 1(a) is the welding location.

Finally, the constricted portion B1C of the integrated tablet 35 is cut to remove the unnecessary portion.

Incidentally, the case of the cathode filament 18 is also exactly the same as the case of the cathode filament 15, and the explanation thereof will be omitted.

(Modification) In the above embodiment, the concave groove 34 had an arcuate cross section;
It may have a V-shaped cross section, a U-shaped cross section, or a polygonal cross section. Further, the welding is not limited to resistance welding, but may also be laser welding.

Also, in the above example, the plating was ruthenium, but
The plating may be platinum or rhodium.

[Effects of the Invention] According to the present invention, a concave groove is provided in the notch, which is the flat part of the filament support rod, and plating is applied, one leg of the cathode filament is fitted into this concave groove, and both legs are fitted. Since the integrated tablet is pressed and welded together, the use of the integrated tablet avoids the generation of local stress during welding of the legs of the cathode filament.

Furthermore, since the number of welding points is small, accidents such as the cathode filament coming off can be prevented. As a result, there is less risk of deformation such as undesired bending of the cathode filament, allowing for highly accurate assembly.

Furthermore, in order to improve the weldability between the integrated tablet and the filament support rod, the filament support rod is plated. It also works well and is very useful for improving weldability.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) show essential parts of a cathode structure of an X-ray tube according to an embodiment of the present invention, and FIG. 1(a) is a front view;
(b) is a side view, (C) is a sectional view taken along line AA' in (b) and seen in the direction of the arrow, Figures 2 (a), (b),
(C) is an exploded perspective view and a plan view, FIG. 3 is a plan view showing a cathode structure of an X-ray tube according to an embodiment of the present invention, and FIG. 4 is a cathode structure of a conventional X-ray tube. FIG. 15.18... Cathode filament, 21... Focusing electrode, 22.23... Focusing groove, 24.25.26.27
... filament support rod, 33 ... notch, 34.
...concave groove, 35...tablet. Applicant's agent Patent attorney Takehiko Suzue (a) (b) Figure 1 Figure 2 (translated) Figure 3 Figure 4

Claims (3)

[Claims] (1) A spiral cathode filament made of tungsten is provided in a focusing electrode having a focusing groove in correspondence with the focusing groove, and both end legs of this cathode filament are fixed to a pair of filament support rods made of molybdenum. In the cathode structure of the X-ray tube, the pair of filament support rods have a flat part, a plated concave groove is provided in the flat part, and the leg part of the cathode filament is fitted into the concave groove. What is claimed is: 1. A cathode assembly for an X-ray tube, characterized in that the cathode assembly is pressed by a tablet and fixed by welding. (2) The cathode assembly for an X-ray tube according to claim 1, wherein the plating is ruthenium, platinum, or rhodium, and the tablet is made of stainless steel. (3) A method for manufacturing an X-ray tube cathode assembly in which both end legs of a spiral cathode filament made of tungsten are fixed to a pair of filament support rods made of molybdenum, wherein a flat portion is formed on the pair of filament support rods, Further, a concave groove is provided in this flat part and plating is applied, and the leg part of the cathode filament is fitted into this concave groove, and after being pressed by an integrated tablet that spans both legs and fixed by welding, A method for manufacturing a cathode assembly for an X-ray tube, comprising removing unnecessary parts of the integrated tablet.