JPS6151375B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in rotating anode type X-ray tubes. Generally, X-ray tubes are used for medical purposes, such as X-ray diagnosis, but in cases such as stomach examinations,
Conventionally, an X-ray tube as shown in FIG. 1 has been used. This X-ray tube is of a so-called rotating anode type, and a cathode 2 and an anode 3 are disposed facing each other in a vacuum envelope 1 made of glass. In this case, the end of the vacuum envelope 1 on the side of the cathode 2 becomes a sealing part 1a having a substantially H-shaped cross section, and a support ring 4 is positioned and fixed inside the tube at the tip of this sealing part 1a. A disk 6 is attached to 4 via a fixture 5. A cup 7 containing a cathode filament and a focusing electrode is provided on the disk 6 eccentrically from the tube axis. The cathode filament in the cup 7 is connected via lead wires 8, 9 to terminal pins 10, 11.
11 is implanted through the sealing portion 1a.
In addition, 12 in the figure is a target of the anode 3, and this target 12 is connected to the rotor 14 via the support column 13.
It is attached to the rotor 14 and rotates with the rotation of the rotor 14 during operation. By the way, in the conventional X-ray tube as mentioned above,
During use, the target 12 is housed in a tube container filled with insulating oil, and most of the heat generated in the target 12 is transmitted through the glass vacuum envelope 1 by radiation heat transfer and released into the surrounding insulating oil. However, in recent years, as the capacity of the target 12 has increased and usage conditions have become stricter, an increase in heat release has become noticeable. In particular, in order to improve heat dissipation of the target 12, TiO ₂ is applied to the surface.
etc., and the emissivity ε is reduced to 0.3 compared to the conventional
In the case where the heat radiation was improved from about 0.6 to about
It has started to exceed 70kjoule/min. On the other hand, in order to improve the voltage resistance between the cathode and the anode, it is effective to make the surface of the disk 6 facing the target flat and large, and to make the surface smooth, so the surface of the disk 6 facing the target is considerably large. , currently 1/2 to the target area
1 is often used. With such a large area, about 20% of the total radiant heat from the target 12 hits the disk 6, so if left as it is, the temperature of the disk 6 will become too high, causing adverse effects such as gas release. Therefore, the surface facing the target is made to have a metallic luster, and the heat absorption rate is set to about 0.1 compared to a black body to prevent temperature rise. however,
In such a method, thermal radiation from the target 12 is reflected off the disk surface and returned to the target 12, and is prevented from being properly radiated through the vacuum envelope 1. As a result, the cooling performance deteriorated by about 15% compared to the case without a disk, which resulted in a reduction in performance when the X-ray tube was used repeatedly. In addition, since the target 12 is shaped like a reflector provided on the top, the target 12
The heat dissipated from the target 12 is concentrated around the target 12 and at the bottom, increasing the possibility that the vacuum envelope 1 will be damaged by thermal strain due to an excessive rise in the temperature of the glass in the vicinity. The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a rotating anode type X-ray tube that significantly improves heat dissipation from a target. Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. The rotating anode type X-ray tube of the present invention is constructed as shown in FIGS. 2 and 3, and a cathode 16 and an anode 17 are disposed facing each other in a vacuum envelope 15 made of glass. In this case, the vacuum envelope 15
The end of the cathode 16 side is an opening, unlike the conventional sealing part having a substantially H-shaped cross section. A substantially cylindrical disk support 19 having a stepped portion 19a is fixed to the open end 18.
A cathode disk 20 is hermetically fixed and supported by silver brazing so as to cover the opening. Therefore, the disk 20 substantially forms a part of the vacuum envelope 15, and when the X-ray tube is stored in the tube container during use, the tube container is filled with insulating oil, but this insulating oil Since it has penetrated into the inside of the support body 19,
The back side of the disk 20 is designed to come into direct contact with oil. The disk 20 is made of Ni with a thickness of 2 mm, and a black layer made of black chrome plating or metal oxide is deposited on the surface facing the target (described later), and the absorption rate of radiant heat from the target is 0.9 compared to the black body. It's getting to the point. Furthermore, the size of the surface of the disk 20 facing the target is set to be at least 1/2 of the target area. In such a disk 20, a cup 21 containing a cathode filament and a focusing electrode is provided eccentrically from the tube axis. The cathode filament in the cup 21 is connected to the terminal pin 23 via the lead wire 22.
This terminal pin 23 is connected to the support body 19.
It penetrates through the stepped portion 19a and is fixed by a ceramic body 24. Note that 25 in the figure is the target of the anode 17 , and this target 25 is connected to the support column 26.
It is attached to the rotor 27 via the rotor 27, and rotates as the rotor 27 rotates during operation. Since the rotating anode type X-ray tube of the present invention is constructed as described above and shown in the drawings, the target 25
The resulting heat was radiated to the outside of the tube through the cathode 16 with almost no reflection. Since the temperature at the part in contact with oil is determined approximately by the oil temperature, the cathode 16
The overall temperature was determined by the heat conduction of the disk 20, and as a result, the temperature was kept below 300°C, except for the electron gun. Considering that conventional cathodes had poor thermal conductivity, reaching temperatures of nearly 500 degrees Celsius in the high-temperature section, this results in better results in terms of gas release. The temperature of target 25 was 1200 when the average maximum input was applied, but it dropped by 50 degrees to 1150. A 50 degree difference in these high temperatures greatly improves tube life. Also, when used up to the same temperature, the rating can be improved by about 15%. In this way, the rotating anode type X-ray tube of the present invention
Since heat dissipation from the target 25 can be improved, when used with the same load as before, the life can be improved by lowering the target temperature, and
When used at the same temperature, the load capacity can be improved, which is particularly effective when a large capacity X-ray tube is used repeatedly. As explained above, according to the present invention, it is possible to provide a rotating anode type X-ray tube with great practical value.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional rotating anode type X-ray tube, FIG. 2 is a sectional view showing a rotating anode type X-ray tube according to an embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view taken along line A' and viewed in the direction of the arrow. 15... Vacuum envelope, 16 ... Cathode, 17 ...
Anode, 19... disk support, 20... disk, 21... cup, 25... target.

Claims (1)

[Scope of Claims] 1. In a rotating anode X-ray tube in which a cathode disk, in which a cup containing a cathode filament and a focusing electrode is attached eccentrically to the tube axis, and an anode target are disposed facing each other in a vacuum envelope. . A rotating anode X-ray tube, wherein the cathode disk is a part of the vacuum envelope. 2. The rotating anode X-ray tube according to claim 1, wherein the size of the surface of the cathode disk facing the target is set to be 1/2 or more of the target area. 3. The rotating anode X-ray tube according to claim 1, wherein a black layer is deposited on the surface of the cathode disk facing the target.