JPH04363844A - Rotary anode type x-ray tube - Google Patents

Abstract

PURPOSE:To provide a rotary anode type X-ray tube excellent in wettability between a bearing surface and a liquid metal lubricating agent and capable of keeping the stable operation of a dynamic pressure type sliding bearing. CONSTITUTION:The bearing surface of at least one sliding bearing 19 of a rotating body 2 rotatably supporting an anode target 11 and forming a dynamic pressure type sliding bearing part and a fixed body 15 is formed of a metal base material, nitride ceramics, carbide ceramics, or carbo-nitride ceramics. On the surface part of the base material, reacting layers 31, 32, 34 containing the element forming this base material and at least one metal element selected from gallium, indium, bismuth and tin are thinly formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating anode type X-ray tube, and more particularly to an improvement in a bearing structure.

0002

[Prior Art] As is well known, a rotating anode X-ray tube supports a disk-shaped anode target with a rotating body having a bearing and a fixed body, and energizes an electromagnetic coil of a stator placed outside the vacuum vessel. A rotating magnetic field is generated, and while the anode target is rotating at high speed, the electron beam emitted from the cathode is applied to the anode target to emit 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 gallium-indium-
It consists of a hydrodynamic sliding bearing that uses a liquid metal such as a tin (Ga-In-Sn) alloy as a lubricant. An example using the latter sliding bearing is, for example, published in Japanese Patent Publication No. 60-2146.
No. 3, JP-A-60-97536, JP-A-60-11
It is disclosed in various publications such as JP-A No. 7531, JP-A No. 62-287555, and JP-A No. 2-227947.

0003

[Problems to be Solved by the Invention] In the rotating anode X-ray tubes disclosed in the above-mentioned publications, molybdenum (Mo), Mo alloy, or tungsten (W) is used as the rotating body and fixed body constituting the sliding bearing. ) or W alloy is used. However, bearing surfaces made of such metals are easily oxidized during the assembly process in air.
This oxide film deteriorates the wettability between the bearing surface and the liquid metal lubricant of the Ga alloy. Therefore, a special treatment is required to remove the oxide film formed on the bearing surface, the assembly process is complicated, and the performance of a highly reliable hydrodynamic sliding bearing may not be obtained.

The present invention provides a rotating anode type X-ray tube that eliminates the above-mentioned disadvantages, has excellent wettability between the bearing surface and a liquid metal lubricant, and is capable of maintaining stable operation of a hydrodynamic sliding bearing. The purpose is to provide

[0005]

[Means for Solving the Problems] The present invention is characterized in that the sliding bearing surface of at least one of the rotating body and the fixed body that rotatably supports an anode target and constitutes a hydrodynamic sliding bearing section is made of a metal base material or a nitride ceramic. , carbide ceramics, or carbonitride ceramics, the elements constituting the base material and at least one metal element selected from gallium, indium, bismuth, and tin are added to the surface of the base material made of carbide ceramics or carbonitride ceramics. This is a rotating anode type X-ray tube that includes a thin reaction layer.

[0006]

According to the present invention, the wettability between the bearing surface and the liquid metal lubricant is excellent, and stable operation of the hydrodynamic sliding bearing can be maintained. Additionally, this bearing is easy to assemble and provides highly reliable bearing operation.

[0007]

Embodiments The embodiments will be described below with reference to the drawings. Note that the same parts are represented by the same symbols. The embodiment shown in FIGS. 1 to 6 has a disk-shaped anode target 11 made of heavy metal.
However, a rotating shaft portion 13 protruding from one end of the cylindrical rotating body 12
is fixed with a nut 14. 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 fitting portion between the cylindrical rotating body 12 and the fixed body 15 constitutes a dynamic pressure type radial bearing and thrust bearing portion 19 as shown in the above-mentioned publications. Therefore, spiral grooves 20 and 21 in a herringbone pattern as described in the above-mentioned publications are formed on the outer circumferential wall and both end walls of the fixed body 15, 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 or other groove formed therein as required. A ferromagnetic cylinder 12a such as iron is fitted to the outer periphery of the Mo base material of the rotating body 12, and a rotor cylinder 12b made of a low electrical resistance material such as copper is fitted and fixed to the outer periphery of the ferromagnetic cylinder 12a.

[0008] Therefore, the base material of the rotating body 12 and the fixed body 15 is made of Mo or a Mo alloy (hereinafter simply referred to as Mo). Then, a thin reaction layer (hereinafter simply referred to as Mo-Ga reaction layer) containing Mo, which is a metal element of the bearing base material, and at least Ga, is formed on the surface of the rotating body, which becomes the bearing surface, and the outer surface of the fixed body. , 32 are each formed thinly. The Mo--Ga reaction layers 31 and 32 are previously formed on the surface of the base material to a thickness in the range of 1 to 100 micrometers. An example of its formation will be described later.

[0009] The bearing surfaces of both the rotating body and the fixed body on which the Mo-Ga reaction layers 31 and 32 are formed are approximately 2
The bearings are assembled close to each other with a bearing gap g of 0 micrometers. The fixed body 15 is provided with a lubricant storage chamber 22 whose center portion is a through hole hollowed out in the axial direction. This lubricant storage chamber 22 also serves as a passage for circulating lubricant, and its upper end 22a in the drawing opens at the bearing surface of the tip of the fixed body and communicates with a bearing gap having spiral grooves 21 and 20. Further, a slightly tapered small-diameter portion 23 is formed on the outer circumferential wall of the intermediate portion of the fixed body 15, and three radial passages 24 are connected to the small-diameter portion 23 from the lubricant storage chamber 22. They are formed axially symmetrically at 120 degree intervals. Furthermore, the illustrated lower end opening 22 of the central lubricant storage chamber 22
b is closed by a plug 25 made of Mo, which is the same as that of the fixed body 15, and a circumferential groove 26 with a small diameter is formed near the plug 25. Then, from this circumferential groove 26 to the central lubricant storage chamber 2
Similarly, three radial passages 27 leading to the radial passages 2 are formed axially symmetrically at intervals of 120 degrees. As a result, the lower end portion 22b of the lubricant storage chamber 22 passes through the radial holes 27 and the circumferential groove 26, and the helical grooves 21, 20 of the lower portion in the figure.
and communicates with the bearing gap g. The helical grooves 20 and 21 of the bearing portion 19, the bearing gap g, and the lubricant storage chamber 22 and passageway 24 communicating therewith are filled and accommodated with an amount of liquid metal lubricant (not shown) to fill these spaces. Due to the presence of the lubricant storage chamber 22, a necessary and sufficient amount of liquid metal lubricant is supplied into each bearing gap g and spiral groove even during long-time operation, and the required operation of the hydrodynamic sliding bearing is maintained. .

An anode support portion 17 made of iron is integrally fixed to the lower end of the fixed body 15 in the drawing by soldering. The anode support portion 17 is hermetically sealed to the vacuum container 18 . Then, outside the vacuum container at a position corresponding to the rotating body 12,
A stator having an electromagnetic coil (not shown) is arranged to generate a rotating magnetic field, and the rotating anode is rotated at high speed as indicated by arrow P. An electron beam emitted from a cathode (not shown) collides with the surface of the anode target 11 to generate X-rays. Most of the heat generated in the target is dissipated by radiation, and a portion of it is dissipated from the rotating body through the liquid metal lubricant in the bearing section, through the fixed body, and to the outside. The Mo-Ga reaction layers 31 and 32 that constitute the bearing surface have sufficient electrical conductivity and thermal conductivity for a rotating anode X-ray tube, so they can function as anode current and heat paths without any problem. Function. Furthermore, a rotating anode X-ray tube with sufficiently high mechanical strength at high temperatures and stable bearing performance can be obtained.

Now, Mo- is applied to the bearing surfaces of the rotating body and the fixed body.
An example of forming the Ga reaction layers 31 and 32 will be described. One example is first the Mo rotating body 12 and the fixed body 15.
Spiral grooves 20 and 21 in a herringbone pattern were formed at predetermined locations that would become the bearing surfaces of the base material. Next, this Mo base material was heated to approximately 700° C. in a vacuum to clean the bearing surface. Next, in the same vacuum, increase the temperature to about 450-550
℃ range, for example, 500℃ and placed in the same room.
(However, this includes an alloy mainly composed of Ga, such as a Ga-In-Sn alloy).The base material was immersed in a bath, held for a predetermined time, and then cooled. As a result, Mo, Ga, and In with a total thickness of about 14 micrometers are generated from the original surface of the Mo base material with a thickness of about 5 micrometers inside and about 9 micrometers outside.
, Mo-Ga consisting of an intermetallic compound (alloy) containing Sn
A bearing surface was obtained in which reaction layers 31 and 32 were formed on the surface of the base material.

[0012] In the bearing member manufactured in this manner, the metal component content at each position in the depth direction of the surface portion had a distribution as shown in FIG. This is a rough estimate of the molar ratio by determining the component amounts from EPMA analysis. The position of the dashed-dotted line A in the figure corresponds to the original surface of the Mo base material. A region from this position A to the dotted line B position, which is mainly composed of an intermetallic compound of Ga and base material Mo, can be confirmed in the inner direction of the base material. The thickness from A to B is approximately 5 micrometers. It can be seen that near position B, the ratio of Ga and Mo is rapidly reversed, and from there onwards there is a metal region consisting only of Mo. That is, up to the depth B position, Ga in the bathtub diffuses into the Mo base material to generate a Ga-Mo reaction layer. In the region from surface A to surface C of the original Mo base material, a layer of an intermetallic compound consisting of Ga, In, Sn, and Mo is observed. Note that the surface position C is a surface where the outermost surface, which has become rough after the above-mentioned reaction treatment, is removed by polishing to a thickness of about 2 micrometers to make it flat. It was confirmed that this reaction layer on the surface had a high enough hardness for practical use as a sliding bearing surface. In this way, surface C
The Mo--Ga reaction layer 31 (or 32) extends from the point B to a predetermined depth position B. Note that the bearing gap size of the rotating body or fixed body before the reaction layer is formed is made larger by the thickness of the reaction layer, so that the bearing gap size becomes a predetermined bearing gap size when completed. Note that the low melting point metal in the bath that forms a reaction layer with the base metal may be Ga alone or G
It may also be an alloy of a and another relatively low melting point metal.

[0013] The bearing surface having this reaction layer experiences a maximum temperature of approximately 400°C during operation of the X-ray tube;
Due to its short duration, this reaction layer hardly changes and a highly hard bearing surface is maintained. Furthermore, even if an oxide film is formed on the surface during the assembly process, this reaction layer is extremely easy to remove, and after assembling a sliding bearing, Ga or If a liquid lubricant made of Ga alloy is injected and filled, the heat treatment in vacuum during the subsequent X-ray tube finishing process will
Stable direct contact with good wettability between the bearing surface made of the Mo--Ga reaction layer and the liquid metal lubricant can be obtained. therefore,
It is easy to assemble and provides sufficient functionality as a hydrodynamic sliding bearing.

In the embodiment shown in FIG. 8, a relatively thick Mo--Ga reaction layer 31 (about 50 micrometers, for example) is preliminarily formed on the surface of the base material of the rotating body or stationary body that does not have a spiral groove.
or 32) is formed by the method described above, the surface of this reaction layer is cut to have a predetermined diameter dimension as a bearing surface, and a spiral groove 20 (or 21) is formed in this reaction layer.
It is formed by mechanical processing or chemical etching. According to this manufacturing method, it is possible to finally obtain an X-ray tube having a hydrodynamic sliding bearing having a desired high-precision helical groove and bearing gap size.

Furthermore, after forming the Mo-Ga reaction layer, the area from the surface portion C to at least the original base material surface portion A is polished away to form a compound layer in which Ga is diffused into Mo (Fig. 7
(corresponding to the region A to B shown in FIG. 1) may be exposed on the surface, and a spiral groove may be formed in this layer to use this as a bearing surface. Thereby, an X-ray tube is obtained that has higher hardness at high temperatures and has a stable bearing surface that is compatible with liquid metal lubricant.

In the embodiments described above, the surface reaction layer is formed independently on each part of the rotary body or the fixed body, but the present invention is not limited thereto, and the following method can also be used. That is, the rotating body and the fixed body are manufactured in advance so that the bearing gap size is larger than the bearing gap when completed, and these are combined, and Ga or Ga alloy is injected into the bearing gap, the spiral groove, and the lubricant storage chamber. Inject and fill with lubricant. Then, these are heated to about 500° C. in vacuum, held for a predetermined time, and then cooled. As a result, a Mo-Ga reaction layer of a predetermined thickness is formed on each bearing surface of the rotating body and the fixed body, and the remaining Ga or Ga alloy lubricant remains between the bearing surfaces at a predetermined interval. . Then, if necessary, Ga or Ga alloy lubricant is replenished into the bearing gap and the lubricant storage chamber to complete the X-ray tube. According to this manufacturing method, the Mo-
By precisely controlling the amount of Ga reaction layer generated, heat treatment temperature and holding time, the assembled structure of the rotating body and fixed body can be finished into a product without disassembling it, and no extra assembly process is required. become. Therefore, it is highly suitable for mass production.

[0017] In addition to Mo, the base material of the bearing part may be W (this includes alloys mainly composed of W), niobium (Nb, which includes alloys mainly composed of Nb), or tantalum (Ta, which includes alloys mainly composed of Nb). (including Ta-based alloys) or an alloy thereof. Alternatively, the bearing base material may be made of other metals such as iron or stainless steel, or ceramics, and the portion that becomes the bearing surface is thinly coated with the above-mentioned high melting point metal. . When these high melting point metals are used as the base material of the bearing, the thickness of the reaction layer between these base metals and Ga formed on the surface must be 1 micrometer or more in order to easily control the formation. There is.

The base material of the bearing portion may also be a ceramic such as titanium nitride, molybdenum nitride, or niobium nitride, or a ceramic such as vanadium carbide, titanium carbide, or niobium carbide. Alternatively, carbonitride ceramics such as vanadium carbonitride or titanium carbonitride may be used.

Further, the bearing surface base material may be formed by forming a coating of nitride, carbide, or carbonitride ceramics on the surface of another metal. These nitrides, carbides,
Or, in the case of a carbonitride ceramic bearing base material, the thickness of the reaction layer between the bearing base material and Ga should be 1 micrometer or less (not including 0, of course) for ease of controlling adhesion. This is desirable. That is, as shown in FIG.
A titanium nitride ceramic layer 33 with a thickness of several micrometers is deposited by CVD on the bearing surface of the stainless steel fixed body 15 in which spiral grooves 20 and 21 have been formed in advance, and titanium nitride is further applied to the surface. A reaction layer 34 of material and Ga may be deposited to a thickness of about 0.5 micrometers to form the bearing surface.

[0020] The reaction layer that becomes the bearing surface is composed of elements constituting the base material and Ga, bismuth (Bi), In, or S.
Any reaction layer may be used as long as it contains at least one element selected from n. When the base material is metal, it is desirable that the thickness of the reaction layer be 1 micrometer or more. Furthermore, since the reaction layer when the base material is metal has conductivity, it can also be used as a part of the path for the X-ray tube anode current. On the other hand, when the base material is a nitride, carbide, or carbonitride ceramic, the thickness of the reaction layer is desirably 1 micrometer or less for ease of manufacture.

Furthermore, the lubricant is not limited to those mainly composed of Ga, such as Ga, Ga-In alloys, or Ga-In-Sn alloys; for example, lubricants containing a relatively large amount of bismuth (Bi) In-Pb-Sn alloy, In-Bi alloy containing a relatively large amount of In, or In-Bi-Sn
Alloys may be used. Since these have melting points above room temperature, it is desirable to preheat the lubricant to a temperature above the melting point before rotating the anode target.

[0022]

[Effects of the Invention] As explained above, according to the present invention,
A thin reaction layer containing the elements constituting the base material and at least one selected from gallium, indium, bismuth, and tin is formed on the surface of the bearing base material, which becomes the sliding bearing surface. Therefore, the wettability of the liquid metal lubricant to the bearing surface is excellent, and stable operation of the hydrodynamic sliding bearing can be maintained. In addition, this bearing is easy to assemble and has a rotating anode type X with highly reliable bearing performance.
You can get wire tube.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a main part showing an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG. 1;

FIG. 3 is a half-longitudinal cross-sectional view of a part of FIG. 1;

FIG. 4 is an enlarged vertical cross-sectional view showing the main part of FIG. 1;

FIG. 5 is a cross-sectional view taken at 5-5 in FIG. 4;

FIG. 6 is a cross-sectional view taken at 6-6 in FIG. 4;

FIG. 7 is a characteristic diagram showing the distribution of metal components near the bearing surface of the invention.

FIG. 8 is an enlarged vertical sectional view of a main part showing another embodiment of the present invention.

FIG. 9 is an enlarged vertical sectional view of a main part showing still another embodiment of the present invention.

[Explanation of symbols]

11...Anode target, 12...Rotating body, 18...vacuum container, 15...Fixed body, 19...Sliding bearing part, 20, 21... spiral groove, g...Bearing clearance, 31, 32, 34...reaction layer.

Claims (1)

[Claims] 1. A sliding member having a rotating body to which an anode target is fixed to a part, a fixed body rotatably holding the rotating body, and a spiral groove provided in a fitting portion of the rotating body and the fixed body. In a rotating anode X-ray tube comprising a bearing portion and a liquid metal lubricant filled in the bearing gap of the sliding bearing portion, at least one bearing surface of the sliding bearing portion is made of a metal base material or a nitride. The elements constituting the base material, gallium,
1. A rotating anode type X-ray tube comprising a thin reaction layer containing at least one metal element selected from indium, bismuth, and tin.