JPH04144047A - Rotating anode type x-ray tube - Google Patents

Abstract

PURPOSE:To restrain erosion due to a lubricant with the high temperature strength of a bearing surface maintained by interposing a liquid metal lubricant between the bearing parts of a rotation body and a fixed body to which an anode target is fixed, and forming a tungsten thin film on the surface of the bearing surface. CONSTITUTION:A liquid metal lubricant is packed in a gap between both the bearing surfaces of a rotation body 12 and a fixed body 15 and in spiral grooves 20 and 21. An electromagnetic coil is arranged outside a vacuum vessel at a position corresponding to the rotation body 12 to rotate a rotation anode in a high speed, and electron beams emitted from a cathode collides with an anode target to generate a X-ray. A W thin film forming the bearing surfaces has sufficient electricity conductivity and heat conductivity, allowing smooth functioning as the passage of an anode current and heat. Also the W thin film is not eroded with the liquid metal lubricant such as Ga or a Ga alloy, and is difficult to be oxidized.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. OBJECTS OF THE INVENTION (Industrial Application Field) The present invention relates to a rotating anode X-ray tube, and particularly relates to an improvement of a bearing structure.

(Prior art) As is well known, a rotating anode X-ray tube supports a disk-shaped anode target between a rotating body and a fixed body that have bearings between them, and is equipped with an electromagnetic coil placed outside a vacuum vessel. While rotating at high speed, an electron beam is emitted from the cathode and hits the anode target, emitting X-rays. The bearing part is a rolling bearing such as a ball bearing, a spiral groove is formed on the bearing surface, and the bearing part is made of gallium (Ga) or an alloy selected from Ga, indium (In), tin (Sn), or other metals. It consists of a hydrodynamic sliding bearing that uses liquid metal as a lubricant. Examples using the latter sliding bearing are, for example, Japanese Patent Publication No. 60-21463 and Japanese Patent Application Laid-open No. 60-975.
No. 36, JP-A-60-117531, and JP-A-62-287555.

(Problems to be Solved by the Invention) In the rotating anode X-ray tubes disclosed in the above publications, molybdenum (Mo), an MO alloy, or tungsten (W) is used as the rotating body and fixed body that constitute the sliding bearing. ) and rhenium (Re) are used. However, if the bearing surface is made of such a metal and a liquid metal lubricant of Ga or Ga alloy is interposed between the bearing surfaces, especially if the bearing surface is made of Mo, heat treatment at high temperatures or operation of an X-ray tube may cause problems. At the high temperatures reached, these bearing surfaces and Ga
Alternatively, interpenetration with the Ga alloy may occur, which may easily cause roughness on the bearing surface. As a result, the high-temperature strength of the bearing surface may deteriorate, and stable bearing operation may not be maintained.

In addition, the surface is easily oxidized during the assembly process in air, and it is difficult to obtain direct contact with a liquid metal lubricant with good wettability. Furthermore, if it is made of W-Re alloy, there are disadvantages in that the material is expensive and it is difficult to process it into a complicated shape.

The present invention eliminates the above-mentioned disadvantages, maintains sufficient high-temperature strength of the bearing surface, has excellent wettability with a liquid metal lubricant, and suppresses corrosion caused by this lubricant.
It is an object of the present invention to provide a relatively low-cost rotating anode type X-ray tube that can maintain stable bearing operation.

[Structure of the Invention] (Means for Solving the Problems) In the present invention, at least one of a rotating body and a fixed body that rotatably supports an anode target and constitutes a part of a sliding bearing portion is configured such that at least one of the rotating body and the fixed body that rotatably supports an anode target and that the sliding bearing surface thereof This is a rotating anode type X-ray tube with a thin tungsten film attached to its surface.

(Function) According to the present invention, since a thin tungsten film is attached to the surface that becomes the sliding bearing surface, the mechanical strength of the bearing surface at high temperatures is high and the wettability of the liquid metal lubricant is excellent. At the same time, this lubricant hardly causes corrosion and can maintain stable bearing operation for long periods of time at high temperatures. Moreover, a relatively inexpensive material can be used as the base material of the bearing, and this base material can also be easily processed, making it possible to obtain a rotary anode type X-ray tube that is inexpensive and easy to manufacture.

(Example) The example will be described below with reference to the drawings. Identical parts are designated by the same reference numerals.

In the embodiment shown in FIGS. 1 and 2, a disc-shaped anode target 11 made of heavy metal is integrally fixed to a rotating shaft portion 13 protruding from one end of a cylindrical rotating body 12 with a fixing screw 14. There is. A fixed body 15 is fitted inside the cylindrical rotating body 12, and a disk-shaped flange 16 is fixed to the lower end opening of the rotating body. The anode support portion 17 at the lower end of the fixed body 15 is hermetically sealed to a vacuum container 18 made of glass. The fixed body 15 also has a cooling medium passage 22 with a hollowed out center portion, into which a pipe 23 is inserted, so that the cooling medium can be circulated as shown by arrow C. Cylindrical rotating body 12 and fixed body 15
The fitting portion thereof constitutes a dynamic pressure slide bearing portion 19 as shown in each of the above-mentioned publications. Therefore, the fixed body 15
Spiral grooves 20 and 21, as described in the above-mentioned publications, are formed in the outer circumferential wall and both end walls, which serve as sliding bearing surfaces. The sliding bearing surface of the rotating body 12 facing this may be a simple smooth surface, or may have a helical groove formed thereon as required.

Therefore, the base material of the rotating body 12 and the fixed body 15 is made of a material such as Kovar (trade name) whose coefficient of thermal expansion is equal to or close to that of tungsten (W). and,
On the surface that will become the bearing surface, a thin film 26,27 of W is coated, for example, with C.
It is attached to a thickness of 5 to 500 μm using the VD method.

In addition, if the helical groove 20.2+ is formed in the fixed body 15 in advance, sufficient bearing surface strength can be obtained by coating the thin film 26.27 of W to a thickness of 5 to 15 μm, and the helical groove is formed by CVD. It can be coated on the inner surface of the body with almost uniform thickness. This W thin film has high adhesion strength to the base material, excellent high-temperature strength and abrasion resistance, and also has excellent wettability with liquid metal lubricants.

Now, the bearing surfaces of both the rotating body and the fixed body are approximately 20 μm.
They face each other with a gap g, and a liquid metal lubricant (not shown) that becomes liquid during operation is filled and interposed in this gap g and the spiral groove. And rotating body 1
A stator (not shown), ie, an electromagnetic coil, is placed outside the vacuum vessel at a position corresponding to 2 to generate a rotating magnetic field, causing the rotating anode to rotate at high speed as indicated by arrow P. An electron beam emitted from a cathode (not shown) impinges on an anode target 11 to generate X-rays, and most of the heat generated in this target is dissipated by radiation, and some of it is emitted from the rotating body. The liquid metal lubricant in the bearing is radiated to the outside through the fixed body directly or via a cooling medium. The W thin film constituting the bearing surface has electrical conductivity and thermal conductivity necessary and sufficient for a rotating anode type X-ray tube, so it functions without any problem as a path for anode current and heat.

Moreover, it has high mechanical strength at high temperatures, and Ga or Ga
Will not be attacked by liquid metal lubricants such as alloys.

Furthermore, since the bearing surface is resistant to oxidation, it is easy to assemble and handle, and has the advantage that no extra steps are required to obtain sufficient wettability with the liquid metal lubricant. In this way, a rotating anode type X-ray tube with stable bearing performance can be easily obtained.

In the embodiment shown in FIG. 3, the base material 15b of the bearing is kept flat in advance, and a W thin film 27 is coated on the surface with a thickness of, for example, 50 to 500.
A spiral groove 20.21 having a depth of 10 to 20 .mu.m is formed by depositing a relatively thick W film 27 of 10 to 20 .mu.m in depth and then etching the W thin film 27. According to this embodiment, the spiral groove can be formed with high precision.

In the embodiment shown in FIGS. 4 to 6, the rotating body 12 is prepared in advance as parts divided into a flat plate part 12m at the top of the cylindrical part 12m1, a rotating shaft part 13, and a flange 16, and the bearing surface of each part is prepared. Individually W thin film 26.26...
* is attached by, for example, the CVD method. A W thin film 27 is also attached to the bearing surface of the fixed body 15.

Note that a copper cylinder 12c is provided on the outer periphery of the cylindrical portion 12m of the rotating body 12.
It is fixed by fitting into the honey.

According to this embodiment, since the W thin film can be attached to the cylindrical rotating body in the form of a simple cylinder and disk, it can be easily manufactured to have a uniform thickness over the entire body.

Note that the base material of the bearing surface is preferably a material whose coefficient of thermal expansion is close to W as described above. Moreover, it is particularly preferable to use a ferromagnetic material such as an alloy mainly composed of iron and nickel because the efficiency of magnetic coupling with the rotating magnetic field is high. Furthermore,
The liquid metal lubricant used is Ga5Ga-InN or G
Not limited to those mainly composed of Ga such as a-In-3n, but also B1-, which contains a relatively large amount of bismuth (Bi).
An In-Pb-8n alloy, an In-B1 alloy containing a relatively large amount of In, or an In-B1-3n alloy can be used. Since these have melting points above room temperature, it is desirable to preheat the lubricant to above this temperature before rotating the anode target.

[Effects of the Invention] As explained above, according to the present invention, the bearing surface of the sliding bearing portion is constructed by attaching a thin film of W to the surface of the base material, so it has high mechanical strength at high temperatures; Furthermore, it is possible to obtain a rotating anode type X-ray tube that has excellent wettability with a liquid metal lubricant, is hardly corroded by this lubricant, and has stable bearing operation performance for long periods of time at high temperatures.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a main part showing an embodiment of the present invention, FIG. 2 is a partially enlarged view thereof, and FIG. 3 is a longitudinal cross-sectional view of a main part showing another embodiment of the invention. Further, J is a vertical cross-sectional view of a main part showing another embodiment of the present invention, and FIGS. 5 and 6 are exploded half-sectional views thereof, respectively. DESCRIPTION OF SYMBOLS 11...Anode target, 12...Rotating body, 18...Vacuum container, 15...Fixed body, 19...Slip bearing part, 20, 21...Spiral groove, g...Gap, 26 .27... Tungsten thin film.

Claims (1)

[Claims] A rotating body to which an anode target is fixed, a fixed body that rotatably holds this rotating body, and a bearing surface provided on a part of the rotating body and the fixed body. In a rotating anode X-ray tube equipped with a sliding bearing portion having a liquid metal lubricant interposed therebetween, at least one of the rotating body and the fixed body has a thin tungsten film on the surface that becomes the sliding bearing surface. A rotating anode type X-ray tube characterized in that: