JPH0145081Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to a rotating anode X-ray tube, and more particularly to improvements in its rotation mechanism.

BACKGROUND TECHNOLOGY AND PROBLEMS A rotating anode X-ray tube has a rotating anode target disk (hereinafter simply referred to as a target) mounted on a shaft of a rotor that is rotatably supported by at least one ball bearing provided at predetermined intervals. ) is fixed, and the target is rotated at a high speed of, for example, 9000 revolutions per minute. The ball bearing enables this high-speed rotation and also functions as a path for the anode current. For this reason, conventional ball bearings generally consist of a metal inner ring, outer ring, and a large number of balls.In order to suppress wear between these balls, conductive solids such as lead or gold are coated on the surface of the balls. Lubricant is attached. When the X-ray tube is in operation, the bearings reach a high temperature of several hundred degrees Celsius due to conduction heat from the target, and since this is in a vacuum, the lubricant in the bearings evaporates in a relatively short period of time, reducing rotational performance. There is a risk of causing Of a pair of ball bearings, the one that is closer to the target in terms of thermal path tends to be about 100 degrees hotter than the one that is farther away. When a bearing reaches a high temperature of 500℃ or higher, the hardness of the balls decreases, and they may become deformed due to thermal expansion, and proper contact with the inner and outer rings may be impaired, and in extreme cases, it may become impossible to rotate. . Generally, in order to prevent such inconveniences from occurring, measures are taken such as minimizing the input to the target to suppress the rise in bearing temperature.

Purpose of the invention The present invention provides a rotating anode type X-ray tube having a rotation mechanism in which ball bearings exhibit almost no deterioration in high-speed rotation performance even at high temperatures.

Summary of the invention This invention has at least one ball bearing interposed between a rotating support and a fixed support that support the target, and the balls of this ball bearing include balls made of ceramic with excellent wear resistance and balls made of metal. It is a mixture of

Embodiment of the invention An X-ray tube according to an embodiment of the invention has a structure shown in FIG. In the figure, 1 is a vacuum envelope, 2 is a cathode assembly, 3 is an electron emitting part thereof, 4 is a rotating target, 5 is a shaft for supporting the target, 6 is a rotor, 7 is a stator, 8 is a rotating shaft, and 9 is a fixed anode,
10 is a fixed shaft cylinder integrated therein; 11;
12 is a sealing ring; 13 and 14 are a pair of ball bearings to be described later; 15 is a rotating shaft sleeve for keeping the distance between the inner rings of each bearing constant;
Reference numeral 6 denotes a sleeve for the fixed shaft cylinder to press and fix the outer ring of the target bearing 13 to the fixed shaft cylinder 10, 17 a movable sleeve, and 18 a pressure that pushes the sleeves 16 and 17 apart in opposite directions. The springs are used to apply preload to the outer rings of both bearings.

Next, the configuration of the ball bearing will be explained.

The ball bearing of this invention has an angular contact type as shown in FIGS. 2 and 3. The outer ring 21 and inner ring 22 are made of metal such as high speed steel. Therefore, among the many balls interposed between the inner and outer rings, balls 23 made of wear-resistant ceramic and balls 26 made of metal are alternately arranged and mixed. Ceramic balls are made of, for example, alumina (Al ₂ O ₃ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ),
Alternatively, it may be made of cermet or the like and formed into a spherical shape. In this case, it is better to form the metal ball 26 to have a slightly smaller diameter than the ceramic ball 23, thereby preventing premature wear of the metal ball.
Electrical contact through the balls of the inner and outer rings is achieved by the weight of the metal balls when the rotation is stopped, and by the centrifugal force during rotation, which causes some of the many metal balls to come into contact with the inner and outer rings. shape the current path.
Further, a preload F is applied to the outer ring 21 via the sleeve 16.

Such bearings can be used near or far from the target, or both. It is also possible to use this bearing closer to the target, while the bearing farther away in terms of thermal path is made up of only metal balls.

In addition, a solid lubricant is attached to a part or all of the surfaces of the ball or the inner and outer rings that are in contact with the ball.

An X-ray tube having such a configuration can maintain high-speed rotation performance in extremely stable operation for a long period of time. In other words, the ball 23 made of ceramic is 800
There is no decrease in strength even at high temperatures of ~1000°C, and the coefficient of friction and heat of abrasion with the metal inner and outer rings are small, and the rotatability does not deteriorate in any way. On the other hand, since the ceramic ball has a large electrical resistance, the path of the X-ray tube current is mainly formed through the metal ball 26. In this manner, the X-ray tube of the present invention maintains stable operation even during long-term high-speed rotation and relatively large input power.

It has been found that ceramic balls can be fully used in rotating anode X-ray tube bearings as long as the surface roughness is 1.2S or less, the sphericity is 5μm or less, and the ball diameter is 5μm or less. Such precision can be achieved with today's ceramic processing technology. Moreover, even if there are variations in diameter, for example, by using a structure in which the angular contact type is used while applying preload as in the above embodiment, as the larger diameter balls gradually wear out, the sizes will become uniform overall. This ensures stable operation for long periods of time.

Effects of the invention As described above, the invention is a rotating anode type X-ray tube that uses a mixture of highly wear-resistant ceramic balls and metal balls as ball bearing balls. High-speed rotation performance is maintained for a long time even when the bearing part becomes hot due to relatively high input. Therefore, it has a practical advantage of extending the life of a large-capacity X-ray tube. Since the anode current path is formed through the metal balls, there are no special restrictions on combinations when using multiple bearings, and the bearing is highly versatile.

In the above embodiments, the rotary support supporting the target is the rotary shaft 8 on the tube axis, and the fixed support is the rotary support 10, but the present invention is not limited to this. Needless to say, the present invention can also be applied to a rotating mechanism in which the fixed support is fixed integrally with the outer ring of the bearing, and the fixed support is located inside the fixed support and is fixed integrally with the inner ring of the bearing.

Further, there is at least one ball bearing, and the other ball bearings may be different bearings.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing an embodiment of the present invention;
The figure is a plan view of the main part, and FIG. 3 is a sectional view taken along line 3-3 in FIG. 4... Target, 8... Rotating shaft, 6... Rotor, 10... Fixed shaft cylinder, 13 , 14 ... Ball bearing, 21... Outer ring, 22... Inner ring, 23...
...ceramic ball, 26...metal ball.

Claims (1)

[Claims for Utility Model Registration] (1) A rotating support that supports a rotating anode target and is provided integrally with the rotor, a fixed support that is coaxially provided with this rotating support, and both supports. In a rotating anode X-ray tube, the tube is equipped with an inner ring, an outer ring, and a ball bearing having a large number of balls, which are interposed between the bodies. A rotating anode type X-ray tube characterized in that it is made of a mixture of balls and balls. (2) The rotating anode X-ray tube according to claim 1, wherein the ball bearing is of an angular contact type, and a preload in the thrust direction is applied to the inner or outer ring.