JPH05144395A - Rotary anode type x-ray tube - Google Patents

Abstract

PURPOSE:To provide a rotary anode type X-ray tube in which high temperature strength of the bearing surfaces can be maintained sufficiently and wettability with liquid metal lubricant is excellent and a stable bearing operation can be maintained by restraining errosion caused by this lubricant. CONSTITUTION:In a rotary anode type X-ray tube, the bearing surfaces 22 and 25 of a slide bearing part 21 to support an anode target 11 so as to be rotatable freely are composed of metal nitride being ceramics, for example, the ceramics selected from vanadium nitride, hafnium nitride, titanium nitride, tungsten nitride, molybdenum nitride, zirconium nitride, tantalum nitride, niobium nitride, chromium nitride and iron nitride.

Description

Detailed Description of the Invention

 [Object of the Invention]

[0001]

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

[0002]

2. Description of the Related Art As is well known, a rotary anode type X-ray tube supports a disk-shaped anode target with a rotating body and a fixed body having a bearing part, and energizes an electromagnetic coil arranged outside a vacuum container. Then, while rotating at a high speed, an electron beam is emitted from the cathode and applied to the anode target to emit X-rays. The bearing portion is a rolling bearing such as a ball bearing, or a gallium (Ga) or Ga
It is composed of a dynamic pressure type sliding bearing using a liquid metal such as an alloy of indium (In) and tin (Sn) as a lubricant. An example of using the latter slide bearing is, for example, Japanese Patent Publication No. 60.
-21463, JP-A-60-97536, JP-A-60-113817, JP-A-60-117531, JP-A-61-2914, or JP-A-61-2914.
It is disclosed in various publications such as 62-287555.

[0003]

In the rotary anode type X-ray tubes disclosed in the above publications, molybdenum (Mo) or Mo alloy, or tungsten (W) or W alloy is used as the bearing surface of the sliding bearing. It is used. However, if the bearing surfaces are made of, for example, Mo, and a liquid metal lubricant of Ga or Ga alloy is interposed between them, the bearing surfaces will be exposed to the heat treatment at high temperatures or at high temperatures reached by the operation of the X-ray tube. Mutual permeation with Ga or a Ga alloy is likely to occur, and the bearing surface is likely to be roughened or dimensionally changed. As a result, the distance between the bearing surfaces may change, and stable bearing operation may not be maintained. Further, if the bearing surface is made of these metals, the material is expensive and it is difficult to process it into a complicated shape, resulting in a very expensive X-ray tube as a whole.

The present invention eliminates the above inconveniences, can sufficiently maintain the high temperature strength of the bearing surface, has excellent wettability with the liquid metal lubricant, and suppresses erosion by the lubricant to stabilize the stability. An object of the present invention is to provide a relatively inexpensive rotary anode type X-ray tube capable of maintaining various bearing operations. [Constitution of Invention]

[0005]

SUMMARY OF THE INVENTION According to the present invention, at least one bearing surface of a sliding bearing portion that rotatably supports an anode target is a metal nitride, such as vanadium nitride, hafnium nitride, or titanium nitride, which is ceramics. , Tungsten nitride, molybdenum nitride, zirconium nitride, tantalum nitride, niobium nitride, chromium nitride,
A rotating anode X-ray tube made of at least one ceramic selected from iron nitrides.

[0006]

According to the present invention, since the bearing surface of the slide bearing portion is made of metal nitride, which is a ceramic having excellent electrical conductivity and thermal conductivity, it has high mechanical strength at high temperature and liquid metal. The lubricant has excellent wettability and is hardly corroded by this lubricant, and stable bearing operation at high temperature for a long time can be maintained.

[0007]

Embodiments will be described below with reference to the drawings.
The same parts are denoted by the same reference numerals.

In the embodiment shown in FIGS. 1 and 2, a disk-shaped anode target 11 made of heavy metal is integrally fixed by a fixing screw 14 to a rotary shaft 13 protruding from one end of a cylindrical rotary body 12. .. A fixed body 15 is fitted inside the cylindrical rotating body 12, and a ring-shaped opening closing body 16 is provided at the lower end thereof.
Is fixed. The lower end 17 of the fixed body 15 is airtightly joined to a vacuum container 18 made of glass. Also, this fixed body 15
Has a cooling medium passage 19 whose central portion is hollowed out, into which a pipe 20 is inserted so that the cooling medium can be circulated as indicated by arrow C. Cylindrical rotating body 12
The fitting portion between the fixed body 15 and the fixed body 15 constitutes a dynamic pressure type slide bearing portion 21 as shown in the above-mentioned respective publications. for that reason,
Helical grooves 23 and 24 having a herringbone pattern as described in the above-mentioned publications are formed on the outer peripheral wall and both end walls of the fixed body 15 which becomes the slide bearing surface 22 on the fixed body side.
The slide bearing surface 25 on the rotor side facing this may be a simple smooth surface, or may have a spiral groove formed if necessary. Therefore, the rotating body 12 and the opening closing body 1
6, and the fixed body 15, the base material is, for example, iron.

(Fe), iron-nickel alloy, iron-chromium alloy, or iron-nickel-chromium alloy. Thin films 26, 27 made of ceramics are attached. The thin films 26 and 27 of the metal nitride ceramics are not particularly limited, but for example, the portions other than the bearing surfaces of the rotating body and the fixed body made of the above materials are appropriately masked, and CVD (chemical vapor deposition method) is used. ), A titanium nitride thin film on each bearing surface is 2 to 20 μm.
It can be formed by adhering to a thickness in the range of m and performing necessary heat treatment. This thin film of metal nitride ceramics has high adhesion strength, excellent high-temperature strength and abrasion resistance, excellent wettability with a liquid metal lubricant, and is hardly corroded by this lubricant. The fixed body 15 has spiral grooves 23, 24.
Is formed in advance, and the metal nitride thin film adheres to the inner surface of the groove with a substantially uniform thickness.

Both the bearing surfaces 22 and 25 of the rotating body and the fixed body are arranged to face each other with a gap g of about 20 μm, and a liquid metal lubricant (liquid metal lubricant) which is liquid during operation in the gap g and the spiral groove ( (Not shown) is filled and interposed. Then, a stator having an electromagnetic coil (not shown) is arranged at a position corresponding to the rotating body 12 outside the vacuum container 18 to generate a rotating magnetic field, and the rotating anode is rotated at a high speed as indicated by an arrow P. An electron beam emitted from a cathode (not shown) strikes the anode target 11 to generate X-rays,
Most of the heat generated in this target is radiated from the target by radiation, and part of it is passed from the rotating body 12 through the liquid metal lubricant of the bearing portion 21 to the outside through the fixed body 15 directly or via the cooling medium. Dissipated. The titanium nitride ceramic thin films 26 and 27 forming the bearing surface have high mechanical strength at high temperature and are not corroded by a liquid metal lubricant such as Ga or Ga alloy. Furthermore, the above-mentioned iron or iron alloy, which is the base material of the bearing, is relatively inexpensive and can be processed much more easily than Mo or W. Since it is also a ferromagnetic material, it has a high efficiency of magnetic coupling with a rotating magnetic field, which is desirable. Furthermore, since this bearing surface has high strength at high temperature, it is hard for the lubricant to attack at high temperature,
It is possible to raise the operating temperature of the bearing surface to, for example, about 500 ° C. Therefore, the operating temperature of the anode target can be increased, and the cooling rate of the anode target can be increased. Thereby, the average value of the input power to the anode target can be relatively increased. In this way, a rotary anode type X-ray tube having stable bearing operation performance and a high cooling rate can be easily obtained.

In the embodiment shown in FIG. 3, a cylindrical rotating body 12 which rotates integrally with the anode target 11 is arranged at the center. A substantially cylindrical fixed body 15 is provided so as to surround the rotary body 12. The fixing body 15 has a through hole through which the rotary shaft 13 penetrates at the upper end in the drawing, and a disc-shaped opening closing member 16 and an anode support 17 at the lower end opening in the drawing.
Are fixed by a plurality of metal screws 16a. The opening closing body 16 is in contact with the lower end surface of the rotating body 12, and the spiral groove 21 is formed on the surface. Further, on the outer circumference of the fixed body 15, a ferromagnetic cylinder functioning as a rotor of the motor is provided.
12a and outermost copper cylinder 12b fitted to the outside
A rotating cylinder 12c consisting of is arranged and its upper end 12d
Are mechanically and firmly fixed to the rotary shaft 13.

Therefore, the cylindrical rotating body 12 and the cylindrical fixed body 15 are made of the same iron material as in the above-mentioned embodiment.
Then, the metal nitride thin films 26 and 27 are attached to the surface of the sliding bearing portion 21 which is fitted with each other. On the other hand, the disc-shaped opening closing body 16 is itself entirely formed of metal nitride ceramics, and the upper surface thereof, that is, the bearing surface in contact with the cylindrical rotating body 12, has the herringbone pattern as described above. The spiral groove 21 is formed in advance.

The rotating body and the fixed body may be entirely made of metal nitride ceramics, or one of the rotating body and the fixed body may be made of metal nitride ceramics and the other is made of metal. The material may be made of a material having a thin film of metal nitride attached to at least the bearing surface.

The metal nitride, which is ceramics, is
The above-mentioned titanium nitride is particularly preferable, but not limited to, for example, vanadium nitride, hafnium nitride, tungsten nitride, molybdenum nitride, zirconium nitride, tantalum nitride, niobium nitride, chromium nitride,
At least one metal nitride selected from iron nitrides can be used. It should be noted that these ceramic materials are mainly composed of metal nitride and may naturally contain a small amount of another substance. Further, these are excellent in mechanical and physical stability at high temperature, and have a relatively small specific resistance and a relatively large thermal conductivity, and therefore they are suitable as an anode structure of an X-ray tube. In addition to the above-mentioned CVD (Chemical Vapor Deposition) method on the surface which becomes the bearing surface of the base material, these also use a PACVD (Plasma Activated Chemical Vapor Deposition) method,

A MOCVD (metal organic chemical vapor deposition) method or a PVD (physical vapor deposition) method is used to form a film by depositing it to a predetermined thickness and performing a necessary heat treatment, a molten salt bath dipping method,
Alternatively, they can be attached by a thermal nitriding method in a nitrogen gas atmosphere.

Furthermore, the liquid metal lubricant is Ga, Ga
-In or Ga-In-Sn, which is not limited to those mainly containing Ga, for example, a Bi-In-Pb-Sn alloy containing a relatively large amount of bismuth (Bi) or a relatively large amount of In. In-Bi alloy, or In-Bi-S
An n alloy or the like may be used. Since these have a melting point of room temperature or higher, it is desirable that the lubricant is preheated to a temperature higher than this temperature to be in a liquid state before rotating the anode target, and then rotated.

[0017]

As described above, according to the present invention, since the bearing surface of the sliding bearing portion is made of metal nitride ceramics, it has high mechanical strength at high temperature and wets the liquid metal lubricant. It is possible to obtain an inexpensive rotary anode type X-ray tube which has excellent properties, is hardly corroded by this lubricant, has stable bearing operation performance at high temperature for a long time, and has a high cooling rate.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing an embodiment of the present invention,

2 is a partially enlarged view of FIG. 1,

FIG. 3 is a longitudinal sectional view of a main part showing another embodiment of the present invention.

[Explanation of symbols] 11 ... Anode target, 12 ... Rotating body, 15 ... Fixed body, 18 ... Vacuum container, 21 ... Sliding bearing part, 22, 25 ... Bearing surface, g ... Gap, 26, 27 ... Metal nitride Thin film, 23, 24 ... spiral groove.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takayuki Kitami 1385-1 Shimoishigami, Otawara-shi, Tochigi Stock Company Toshiba Nasu Electronic Tube Factory

Claims (3)

[Claims] 1. A rotating body to which an anode target is fixed,
A sliding bearing portion comprising a fixed body rotatably holding the rotating body, and a metallic lubricant which is provided on a part of the rotating body and the fixed body and which is liquid at least during operation between the bearing surfaces. A rotary anode X-ray tube comprising: a rotary anode X-ray tube, wherein at least one bearing surface of the sliding bearing portion is made of a metal nitride. 2. At least one bearing surface has vanadium nitride, hafnium nitride, titanium nitride, tungsten nitride, molybdenum nitride, zirconium nitride, tantalum nitride, niobium nitride, chromium nitride, iron nitride. The rotating anode type X-ray tube according to claim 1 or 2, which is composed of at least one kind of metal nitride selected from materials. 3. A bearing according to claim 1, wherein at least one of the bearing surfaces has a spiral groove for receiving a liquid metal lubricant.
The rotating anode type X-ray tube described in.