JPH01120741A - X-ray tube device - Google Patents

Abstract

PURPOSE:To reduce the thermal load on insulators and maintain the insulation property for a long time by brazing the insulators to outer peripheries of a filament supporter and a focusing electrode respectively to integrate them via the insulators. CONSTITUTION:A directly heated filament 14 is fitted to a pair of stanchions 21 and 21, which are supported by a filament supporter 19 directly or via an insulator 20. Insulators 17 and 25 are brazed to outer peripheries of the filament supporter 19 and a focusing electrode 15 to be integrated via the insulators 17 and 25. In this case, the insulators 17 and 25 are brazed to outer peripheries of the filament supporter 19 and the focusing electrode 15 via metal members 16 and 18 with nearly the same thermal expansion coefficient as that of the insulators 17 and 25 respectively. The breakage of the insulators 17 and 25 caused by the heating of the filament is thereby prevented, and the insulation property can be maintained for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an X-ray tube device, and particularly to an improvement of its cathode structure.

(Prior Art) Generally, X-ray tube devices are used for medical purposes by being attached to, for example, an X-ray diagnostic device. equipment is used.

This X-ray tube device is of the so-called rotating anode type, with a vacuum envelope 1
Inside, a cathode structure 2 and an umbrella-shaped anode target 3 are arranged opposite to each other and eccentric from the tube axis. The anode target 3 is rotated by a rotor 5 which is rotated by electromagnetic induction by a stator 4.
It is designed to rotate.

Now, the cathode structure 2 of the conventionally used X-ray tube device
is constructed as shown in FIGS. 3(a) and 3(b), and a spiral cathode filament 6 is disposed in a focusing electrode 7 having a focusing groove 7a in correspondence with the focusing groove 7a. Both ends of this cathode filament 6 are fixed to pillars 11.11,
This column 11.11 is supported directly or via an insulator 10 on the filament support 9. This filament support 9 is insulated from the focusing electrode 7 via an insulator 8. In addition, 12 in the figure is a stopper, and 13 is a bias terminal.

(Problems to be Solved by the Invention) In the conventional cathode assembly 2 described above, the focusing electrode 7 applies a negative voltage to the cathode filament 6 for the purpose of controlling thermionic emission, and the focusing electrode 7 There are two methods in which a positive voltage is applied to the tube to draw out thermionic electrons, causing efficient thermionic emission, and aiming at a high tube current. In the former case, the heating element is only the cathode filament 6, and most of the heat can be absorbed by the filament support 9 through thermal conduction, and the heat is radiated, so that no thermal load is applied to the insulator 8.

However, in the latter case, the cathode filament 6 is
A current equal to or greater than the tube current flows between the cathode filament 6 and the focusing electrode 7, and the focusing electrode 7 is heated by the electrons flying from the cathode filament 6.

Therefore, the focusing electrode 7 becomes heated and a thermal load is directly applied to the insulator 8, causing the joint between the focusing electrode 7 and the insulator 8 to peel off or break the insulator 8. .

In particular, if a planar cathode filament with a large electron-emitting surface area is used to increase thermionic emission in order to obtain a considerably large tube current, the load on the insulator 8 will be extremely large, and the Bonding materials, such as brazing materials, often melt, peeling of bonded parts, and damage to insulators, resulting in extremely dangerous conditions.

Furthermore, if the insulator 8 is provided inside the focusing electrode 7 and exposed from the cathode filament 6, the focusing electrode 7 will be insulated from the cathode filament 6 as the frequency of use increases regardless of whether the voltage is positive or negative. Tungsten or the like, which is the material of the cathode filament 6, is deposited on the exposed surface of the body 8, deteriorating the insulation.
The problem arises that it cannot withstand long-term use.

Furthermore, since the insulator 8 is sandwiched between the focusing electrode 7 and the filament support 9, the positional accuracy of the focusing electrode 7 in front and behind with respect to the cathode filament 6 is determined by the insulator 8.
The accuracy tends to decrease depending on the accuracy of the joint and the thickness of the joining material, such as solder material, at the joint, making highly accurate positioning difficult.

This invention was made in view of the above circumstances, and by improving the placement position and shape of the insulator, the thermal load on the insulator is reduced and insulation properties are maintained for a long time. The purpose is to provide an X-ray tube device that can perform

[Configuration of the Invention (Means for Solving Problems) This invention provides a method in which a cathode structure and an anode target are disposed facing each other in a vacuum envelope, and the cathode structure is supported by at least a filament support. In an X-ray tube device comprising a flat cathode filament and a focusing electrode provided in front of the cathode filament, an insulator is soldered to each outer periphery of the filament support and the focusing electrode, and the filament support and the focusing electrode are integrated via the insulator. It is an X-ray tube device consisting of
Aluminum nitride-based or alumina-based ceramic insulators are used.

(Function) According to the present invention, since the insulator that insulates the filament support and the focusing electrode is provided on the outer surface of the cathode assembly, it is possible to increase the cross-sectional area and surface area of the insulator. As a result, it can be expected that the radiation cooling effect and heat conduction effect of the insulator itself will be improved. Furthermore, since the insulator is not directly exposed from the cathode filament, there is no vapor deposition of tungsten, etc., and it maintains insulation properties for a long time. It is possible to increase the distance and increase the creeping resistance.

Further, according to the present invention, the distance between the cathode filament and the focusing electrode, which requires precision control, can be controlled with an accuracy of 10 μm or less.

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

This invention can be used, for example, for mammography with an anode voltage of 30 KV.
, a case where the present invention is applied to an X-ray tube device with a maximum anode current of 300 mA will be shown as an example, but the cathode structure is improved to solve the above-mentioned conventional problems, and only the cathode structure will be described.

That is, the cathode structure in this invention is shown in FIGS. 1(a) and 1(b).
), the directly heated cathode filament 14
is attached to a pair of columns 21.21, and this column 21.
21 is supported by the filament support 19 directly or via the insulator 20. In this case, the cathode filament 14 is made into a band-like and flat-like shape, as is clear from the figure.
For example, it is made of a thin tungsten plate with a uniform width of about 3 mm throughout and a thickness of about 0.03 mm.

The central portion is formed flat so as to serve as an electron emitting portion, and both sides thereof are curved to form leg portions, and these leg portions are attached to the support columns 21 and 21. A shield 24 is provided to surround the cathode filament 14 and is fixed to a filament support 19.

Furthermore, a focusing electrode 15 is disposed in front of the cathode filament 14 for applying a high voltage to the cathode filament 14 to extract electrons and focusing them in a desired shape on the anode target.

Further, an insulator 17.25 is soldered to each outer periphery of the filament support 19 and the focusing electrode 15.
They are integrated via 25.

In this case, an insulator 17.25 is connected to the outer periphery of each of the filament support 19 and the focusing electrode 15 via a metal member 16.18 whose coefficient of thermal expansion is approximately equal to that of the insulator 17.25.
are soldered.

This insulator 17.25 has a total cross-sectional area of 0. Set in the range of 5cm2 to 2cm2, and the total surface area is 50m2
The area is set within a range of 200m2 to 200m2. In this embodiment, the insulator 17.25 is made of, for example, an insulator made of fired aluminum nitride ceramic having a total cross-sectional area of ICm2 and a total surface area of about 100 m2. In addition to aluminum nitride ceramics, an insulator made of a fired product of alumina ceramics with relatively high thermal conductivity may be used to increase the total cross-sectional area and total surface area.

In addition, 22 in the figure is a bias terminal, which penetrates the filament support 19 and the shield 24 and is fixed to the focusing electrode 15. 23 is an insulator.

Further, since the configuration other than the above is the same as that of the conventional X-ray tube device (FIG. 2), detailed explanation will be omitted.

Now, in this invention, an insulator 17.2 for insulating the focusing electrode 15 from the filament support 19 and the shield 24
5 is placed far from the outer surface of the cathode structure, that is, from the heat generating part, so that the total surface area is large, and as a result, the insulator 17.25 itself has a radiation cooling effect, and the focusing electrode 1
The load on the insulator 17.25 due to the heat generated in step 5 is reduced.

In addition, by increasing the total cross-sectional area and using a material with high thermal conductivity, heat conduction is improved, and the filament support 19 and the shield 2 are
4. Heat can be released and the thermal load can be further reduced.

Furthermore, since the insulators 17 and 25 are provided on the outer surface of the cathode structure, they are not directly exposed from the cathode filament 14, which prevents evaporation of tungsten, which is the filament material, due to long-term use, and prevents deterioration of insulation properties. There is no heat radiation from the cathode filament 14, and there is no fear of radiation heating.

In addition, the accuracy control of the focusing electrode 15 with respect to the cathode filament 14 and the shielding body 24 is not performed in the front-to-back direction, but in the side direction, so that the insulator 17, 25, the joining member, etc. Does not include accuracy errors due to
Can be managed with high precision.

(Modification) In the above embodiment, the insulator 17.25 was plate-shaped, but
It may have a cylindrical shape, a rectangular tube shape, a cross-sectional shape, or a shape similar to these.

[Effect of the invention] According to this invention, the following excellent effects can be obtained.

(2) Breakage of the insulator due to heat generated by the cathode filament can be eliminated, and a sufficiently reliable X-ray tube device can be provided.

- Prevents insulation deterioration due to vapor deposition of tungsten, etc. on the insulator, and can maintain insulation properties for a long time.

■Since the focusing electrode and filament support are connected on the outer surface of the cathode structure, the dimensional accuracy of the focusing electrode, shield, and cathode filament can be ensured.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are cross-sectional views showing the main part (cathode structure) of an X-ray tube device according to an embodiment of the present invention, and FIG.
A sectional view taken along line A-A' in a) and viewed in the direction of the arrow; FIG. 2 is a schematic configuration diagram showing the entire conventional X-ray tube device;
FIGS. 3(a) and 3(b) are cross-sectional views showing the main parts (cathode structure) of a conventional X-ray tube device, and FIG. 3(b) is a cross-sectional view taken along the line BB' in FIG. FIG. 1... Vacuum envelope, 3... Anode target, 14.
...Cathode filament, 15...Focusing electrode, 17.2
5... Insulator, 19... Filament support. Applicant's agent Patent attorney Takehiko Suzue 12 Figure 12 (b) B. (a) Kano 3 (b) Agony

Claims (2)

[Claims] (1) A cathode assembly and an anode target are disposed facing each other in a vacuum envelope, and the cathode assembly consists of at least a flat cathode filament supported by a filament support and a focusing electrode provided in front of the cathode filament. An X-ray tube device, characterized in that an insulator is soldered to the outer periphery of each of the filament support and the focusing electrode, and the filament support and the focusing electrode are integrated via the insulator. (2) The X-ray tube device according to claim 1, wherein the insulator is an aluminum nitride-based or alumina-based ceramic insulator.