Bearing and rotary anode X-ray tube employing the bearing

DETAILED DESCRIPTION To solve the problems, an object of the present invention is to provide a bearing that can maintain stable lubrication under the conditions of high temperature and vacuum, and a rotary anode X-ray tube that can maintain stable lubrication even with an increased output.
In order to accomplish the object, the present invention provides a bearing coated with a lubricant that achieves low vapor pressure at high temperatures.
The present invention also provides a rotary anode X-ray tube comprising a cathode for emitting electrons in a vacuum vessel, an anode target with which the electrons emitted from the cathode collide to generate X-rays, a rotor fixed integrally with the anode target, and a plurality of bearings for rotatably supporting the anode target.
Frictional surfaces of at least one of the bearings that is located in the vicinity of the anode target are coated with a lubricant that demonstrates low vapor pressure at high temperatures.
The frictional surfaces of the bearings may be coated with a lubricant whose main component is at least one of tin, aluminum and indium.
Mother material of at least one of the bearings may be ceramics.
As described in the above, the frictional surfaces of the bearings of the invention employed for the rotary anode X-ray tube are coated with a lubricant that achieves low vapor pressure at high temperatures.
The lubricant may be tin (Sn), aluminum (Al) or indium (In).
As shown in FIG.
3, these materials demonstrate low vapor pressure compared to lead (Pb) that is conventionally used as a lubricant, so that they can maintain stable lubrication even at high temperatures exceeding 350 degrees centigrade and in vacuum without deteriorating the degree of vacuum.
Since the tin (Sn) and indium (In) have lower melting points than the lead (Pb), they are easily liquidized according to an increase of temperature to reduce friction under the conditions of high temperature and vacuum and maintain stable lubrication.
Although the aluminum (Al) has a relatively high melting point and is hardly liquidized, it is sufficiently soft compared to silver (Ag) that is also conventionally used a lubricant