JPH05144396A - Rotary anode type x-ray tube - Google Patents

Abstract

PURPOSE:To provide a comparatively low cost rotary anode type X ray tube in which wettability of the bearing surfaces to liquid metal lubricant is excellent and a stable bearing operation can be maintained by restraining errorsion caused by this lubricant. CONSTITUTION:In a rotary anode type X-ray tube, at least one bearing surfaces 22 and 25 of a slide bearing part 21 arranged in a part of a rotary body 12 and a fixed body 15 are formed of ceramics which belong to an IVa group, a Va group or a VIa group except chromium and are mainly composed of at least one nitride, boride or carbide group of at least one transition metal positioned in 4, 5 or 6 period.

Description

Detailed Description 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 an improvement of a rotary mechanism section for supporting an anode target.

[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 having a bearing portion and a fixed body, and energizes an electromagnetic coil arranged outside a vacuum container. While rotating the anode target at a high speed, an electron beam emitted from the cathode is applied to the surface of the anode target to emit X-rays. The bearing portion includes a rolling bearing such as a ball bearing, a spiral groove formed on the bearing surface, and gallium (Ga) or gallium-indium-tin (Ga-).
It is composed of a dynamic pressure type slide bearing using a metal lubricant that becomes liquid during operation, such as an In-Sn) alloy. Examples of the latter slide bearing are disclosed in, for example, Japanese Patent Publication No. 60-21463, Japanese Patent Laid-Open No. 60-97536, Japanese Patent Laid-Open No. 60-113817, and Japanese Patent Laid-Open No. 60-1175.
No. 31, JP-A-61-2914, JP-A-62-287555, or JP-A-2-227947.

By the way, the rotating body which supports the anode target is usually a rotating shaft made of a high melting point metal which is fixed to and supports the anode target, and iron which is connected to the rotating shaft and functions as a rotor of an induction motor. It is composed of a cylindrical core made of a ferromagnetic material, and an outer cylinder having a high electric conductivity such as copper, which is fitted to the outer periphery of the cylindrical core and fixed by brazing. A columnar fixed body is provided inside the rotating body via a bearing. Then, a rotating magnetic field is applied to the rotating body from the stator outside the tube to rotate the rotating body at a high speed by the principle of the induction motor.

[0004]

In the rotary anode type X-ray tube disclosed in the above publications, molybdenum (Mo) or Mo alloy, or tungsten (W) or W alloy is used as the material of the sliding bearing. is doing. However, if the bearing is made of such a material, the bearing surface is likely to be oxidized during the manufacturing process of the X-ray tube, and the wettability with the liquid metal lubricant may be impaired. Further, at the high temperature reached by heat treatment at high temperature or operation of the X-ray tube, mutual permeation of the bearing surface and the liquid metal lubricant occurs, and the bearing surface is apt to be roughened or change in dimension. As a result, the gap size of the bearing surface may change, and stable bearing operation may not be maintained.

The present invention eliminates the above-mentioned inconvenience, improves the wettability between the bearing surface and the liquid metal lubricant, and suppresses the erosion of the bearing member by this lubricant to maintain stable bearing operation. An object of the present invention is to provide a relatively inexpensive rotary anode type X-ray tube that can be manufactured.

[0006]

According to the present invention, at least one bearing surface of a sliding bearing provided on a part of a rotating body and a fixed body is a group IVa, a group Va, or a group VIa excluding chromium.
A rotating anode type X which is a group and is composed of ceramics containing at least one of the group of carbides, borides or nitrides of at least one transition metal located in 4, 5, or 6 periods as a main component. It is a line tube.

[0007]

According to the present invention, the bearing surface made of these ceramics has excellent wettability with the liquid metal lubricant and has a sufficiently high melting point so that the reaction with the lubricant is small and corrosion of the bearing surface is unlikely to occur. .. It is also possible to use an inexpensive bearing base material. Furthermore, since these ceramics have sufficient conductivity to form the anode current path of the X-ray tube, a dynamic pressure slide bearing can be formed without complicating the structure. Therefore, stable bearing operation can be maintained for a long time.

[0008]

Embodiments will be described below with reference to the drawings.
The same parts are denoted by the same symbols. (Example 1) As shown in FIGS. 1 and 2, a disk-shaped anode target 11 made of a heavy metal is a rotating body 12 having a substantially bottomed cylindrical shape.
It is fixed by a nut 14 to a rotary shaft 13 protruding from one end of the. An iron cylinder and a copper cylinder (not shown) functioning as a rotor of the induction motor are closely fitted to the outer peripheral portion of the rotating body 12 ,
It is fixed. A substantially cylindrical fixed body 15 is fitted inside the rotating body 12 . A small diameter portion 15a is formed at the tip of the fixed body 15 . At the position of the step of the fixed body, the thrust bearing disc 16 is fixed to the opening of the rotating body. The lower end of the small-diameter portion 15a of the fixed body is joined to an anode support ring 17, and this support ring 17 is airtightly joined to a vacuum container 18 made of glass. Further, the fixed body 15 has a cooling medium passage 19 whose central portion is hollowed out, and a pipe 20 is inserted therein, so that the cooling medium can be circulated as shown by an arrow C. The fitting portion between the rotating body 12 and the fixed body 15 constitutes a dynamic pressure type slide bearing portion 21 as shown in the above-mentioned respective publications. Therefore, the outer peripheral sliding bearing surface 22 of the fixed body 15 is formed with spiral grooves 23, 23 having two sets of herringbone patterns of a radial bearing. Helical grooves 24, 24 having a circular herringbone pattern of a thrust bearing are formed on the slide bearing surfaces at both ends of the fixed body 15 , respectively. These spiral grooves
The depth of 23,24 is approximately 20 micrometers.
The slide bearing surface 25 on the inner peripheral surface of the rotary body is merely a smooth surface, or a spiral groove may be formed if necessary. Both the bearing surfaces 22 and 25 of the rotating body and the fixed body are arranged to face each other with a bearing gap g of about 20 μm, and a metal lubricant which is liquid during operation is present in the bearing gap g and the spiral groove. (Not shown) is filled and intervened.

Therefore, the rotating body 12 and the fixed body 15 have bearing surfaces 22 and 25 in which ceramic thin films 26 and 27 are adhered to the surface of a bearing base material made of metal. The bearing base material of the rotating body 12 and the fixed body 15 is an iron alloy such as stainless steel, or high speed steel, for example, SK4 of carbon tool steel defined by Japanese Industrial Standards (JIS), or SKD of alloy tool steel.
It is composed of a steel material such as 11 containing a small amount of carbon (that is, 0.5 to 2.5% by weight). Then, ceramic thin films 26 and 27 made of carbide (VC) of vanadium (V) which is a transition metal of Va group of the periodic table of elements and a period of 4 are attached and formed on the surface portion of each bearing base material which becomes the bearing surface. ing. As a method of forming the ceramic thin films 26 and 27, first, a portion of the bearing base material other than the portion to be the bearing surface is appropriately masked, and this is kept in the electric furnace at a temperature of 500 to 1250 ° C. It was immersed in a molten salt bath containing V) for several hours. As a result, a thin film of vanadium carbide (VC) was deposited on each bearing surface to a thickness of about 10 micrometers. This was heat treated.

The melting point of vanadium carbide (VC) ceramics is about 2850.degree. This is also 20-2
Coefficient of thermal expansion between 00 ° C is 7.2-6.5 × 10 ^-6 / ° C
Therefore, there is not so much difference from the coefficient of thermal expansion of the bearing base material, and there is little risk of cracks and the like. In particular, this ceramic thin film made of vanadium carbide (VC) has a high adhesive strength, excellent high-temperature strength, and wear resistance because a part of carbon in the base steel is diffusion-bonded. Further, it has excellent wettability with a liquid metal lubricant such as Ga or a Ga alloy, and has a sufficiently high melting point so that it hardly reacts with the lubricant, and is therefore unlikely to be corroded by this lubricant. Since this ceramic thin film has conductivity, it can form a part of the anode current path together with the liquid metal lubricant. It should be noted that the fixed body 15 has spiral grooves 23 and 24 formed in advance, and the ceramic thin film adheres to the inner surfaces of the grooves with a substantially uniform thickness. Thus, this ceramic thin film is suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube. Further, the above-mentioned iron alloy, stainless steel, carbon tool steel, etc., which are the bearing base materials, are cheaper than Mo and W, and are remarkably easy to process. Further, since this bearing surface has high strength at high temperature and is not easily corroded by the lubricant 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, in other words, 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 structure of FIG. 1, the fixed body 15 is made of a non-ferromagnetic material having a relative magnetic permeability close to 1 (that is, generally called a non-magnetic material), and is used as a bearing and a fixed body. It is desirable to obtain a desired rotating performance by making the rotating magnetic field hardly reach.

(Example 2) A ceramic thin film of vanadium boride (VB ₂ ) was formed on the surface of a bearing base material made of metal to form a bearing surface. This vanadium boride (VB
The ceramic thin film of ₂ ) has a melting point of about 2400 ° C and 2
Coefficient of thermal expansion between 0 and 200 ℃ is about 7.6 × 10 ^-6 / ℃
Is. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 3) A ceramic thin film of vanadium nitride (VN) was formed on the surface of the bearing base material to form a bearing surface. This vanadium nitride ceramic thin film is
It has a melting point of about 2050 ° C. and a coefficient of thermal expansion between 20 and 200 ° C. of about 8.1 × 10 ⁻⁶ / ° C. Since this thin film has a slightly lower melting point, it can also be used as a liquid metal lubrication type dynamic sliding bearing surface for an X-ray tube by suppressing the manufacturing process and operating temperature of the X-ray tube to a slightly lower level.

(Example 4) As shown in FIGS. 3 to 8, the fixed body 15 has spiral grooves 23 and 24 formed on the radial sliding bearing surface 22 on the outer periphery and the thrust bearing surface at the tip. An axial hole 28 for storing and circulating the liquid metal lubricant and a radial hole 30 which is bored in four radial directions from the center and opens to the small diameter portion 29 of the fixed body are formed in the central portion of the fixed body. There is. Further, a circumferential groove 31 is formed on the stepped portion of the small fixed body diameter portion 15a. By appropriately masking a region other than the bearing surface of this fixed body, and by CVD (chemical vapor deposition),
A ceramic thin film 27 made of nitride (TiN) of titanium (Ti) which is a transition metal of Group IVa and period 4 is 0.5 to 1
The thickness was deposited in the range of 0 micrometer, for example 5 micrometer. In addition, as shown in an enlarged view in FIG. 2, the spiral groove portion formed in the base material of the fixed body is preliminarily rounded so that a sharp projection of the coating film by CVD does not occur at the apex angle 23a between adjacent grooves. It is shaped like an arc or taper.

On the other hand, in order to form the rotating body 12 , a bearing cylindrical body 32 having an inner peripheral surface serving as a radial bearing surface, a fixed body bearing disk 33 coupled to the upper opening thereof, and a bearing ring coupled to the lower opening. 16 is prepared in advance as a separate part. These bearing base materials are made of the metal as exemplified in the above (Example 1). A disc fitting step and a welding bead 34 are formed in the upper opening portion of the bearing cylindrical body 32, and a plurality of protrusions 35 for maintaining a gap are formed on the outer peripheral wall thereof. Further, a step 36 for maintaining a gap, a rotor cylinder fitting step 37, a welding bead 38, a bearing ring fitting step 39, and a plurality of female screw holes 40 are formed on the outer peripheral wall near the lower opening. This bearing cylinder
On the inner peripheral surface of 32, a ceramic thin film 26 made of titanium nitride (TiN) was formed by CVD to a thickness of about 5 μm. In this case, since the bearing cylindrical body 32 is a simple cylinder, the CVD reaction gas spreads all over the inner peripheral surface, so that a good-quality coating can be formed in the entire region with a uniform thickness. On the other hand, the bearing disc 33 has a recess 41 on the outer surface.
Further, the welding bead 42 is formed, and the ceramic thin film 26 also made of titanium nitride (TiN) in the state of a single component is formed in advance on the inner surface serving as the thrust bearing surface in a thickness of about 10 micrometers. .. Bearing ring
A spiral groove 24 is previously formed on the inner surface, which is a thrust bearing surface around the central hole 16a, and a ceramic thin film 26 made of titanium nitride (TiN) is also formed on this surface in a single component state. It was formed with a thickness of 5 micrometers. A plurality of through holes 16b for screw penetration are formed in the outer peripheral flange portion. These bearing disks 33
Since the bearing ring 16 has a ceramic thin film formed on a flat surface, it is possible to easily deposit a uniform film having a uniform thickness by CVD or the like. In addition,
A circular herringbone pattern spiral groove of the thrust bearing may be formed on the inner surface of the bearing disc 33.

In each of the parts formed with the thin film as described above, first, the bearing disc 33 is fitted to the disc fitting step of the bearing cylindrical body 32, and the welding beads 34 and 42 of both are integrally joined by heli-arc welding. did. This welded portion is represented by reference numeral 43.
Since this welding is local heating at a position distant from the bearing surface, there is no risk of deterioration of the ceramic thin film on the bearing surface. Next, the rotor cylinder 45 made of a ferromagnetic material, to which the rotating shaft 13 is fixed and the copper cylinder 44 is fixed to the outer periphery, is fitted into the assembly of the bearing cylinder 32 and the bearing disc 33 from the upper side of the drawing until it hits the step 37. I inserted it. Then, the lower end weld bead 46 of the rotor cylinder and the weld bead 38 of the bearing cylinder are integrally joined by helicopter arc welding as indicated by reference numeral 47. In this state, between the rotor cylinder and the bearing cylinder, a heat insulating gap 48 is formed which is maintained by the gap maintaining protrusion 35 and the gap maintaining step 36. The heat insulating gap 48 lengthens the heat conduction path from the anode target to the slide bearing, and thus suppresses the heat generated in the target from reaching the slide bearing portion. The heat insulating gap 48 is practically 0.1 mm.
It is desirable to set the radial dimension to 1 mm or less. The upper welded portion 43 is located in the upper gap 49 that receives the rotating shaft, and is kept in non-contact with the inner surface of the shoulder portion 45a of the rotor cylinder. The rotary shaft 13 is formed with a vent hole 13a for allowing the space including the gaps 48, 49 to be evacuated to a high vacuum in the evacuation process.

Next, the rotating body 12 assembled in this way is
Arranged in the vacuum heating furnace so that the rotating shaft 13 faces downward,
The built-in gas is released from each component, and in that state the bearing cylinder
A predetermined amount of liquid metal lubricant (not shown) such as Ga—In—Sn alloy was injected into the inner space of 32. After that, the fixed body 15 was slowly inserted into the inside of the bearing cylindrical body 32, the bearing ring 16 was fitted, and tightened and fixed with a plurality of bolts 50.
Since a bearing gap of about 20 μm is provided between the bearing surface of the rotating body and the bearing surface of the fixed body assembled in this way, liquid in the bearing gap, the spiral groove, and the hole in the center is formed. Full of metal lubricant. After that, the anode support ring 17 was airtightly welded to the small diameter portion 15a of the fixed body, and the thin sealing ring and the sealing ring of the vacuum container 18 were also airtightly welded. Then, the inside of the vacuum container was evacuated to complete the X-ray tube.

Titanium nitride (Ti) forming the bearing surface
The ceramic thin film of N) has a melting point of about 3080 ° C. and a coefficient of thermal expansion between 20 and 200 ° C. of 9.8 to 9.
It is 2 × 10 ⁻⁶ / ° C., which is relatively large. Therefore, the coefficient of thermal expansion of a nonmagnetic iron alloy such as stainless steel or high speed steel as the bearing base material is 9.0 to 14.0 × 1.
It is preferable to use a metal in the range of 0 ^-6 / ° C, because there is no occurrence of cracks or peeling on the bearing surface of the ceramic thin film. As described above, this ceramic thin film has high adhesion strength to the base material and is excellent in high temperature strength and abrasion resistance. Further, the wettability of the liquid metal lubricant is excellent, and the liquid metal lubricant is unlikely to be corroded. Therefore, stable operation of the dynamic pressure sliding bearing can be guaranteed for a long period of time.

(Example 5) A ceramic thin film made of titanium carbide (TiC) was formed on the surface of a bearing base material made of metal to form a bearing surface. This titanium carbide (Ti
The ceramic thin film of C) has a melting point of about 3150 ° C.
Coefficient of thermal expansion between 0 to 200 ° C. is about 8.3 to 7.6 × 1
It is 0 ^-6 / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 6) A ceramic thin film of titanium boride (TiB ₂ ) was formed on the surface of a bearing base material made of metal to form a bearing surface. This ceramic thin film has a melting point of about 2920 ° C. and a coefficient of thermal expansion between 20 and 200 ° C. of about 4.6 to 4.8 × 10 ⁻⁶ / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

Example 7: Molybdenum (M) which is a transition metal of Group VIa and period 5 is formed on the surface of a bearing base material made of metal.
A ceramic thin film of carbide (Mo ₂ C) of o) was formed to form a bearing surface. This ceramic thin film has a melting point of about 2580 ° C. and a thermal expansion coefficient of about 7.8 × 10 ⁻⁶ / ° C. between 20 and 200 ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 8) ... Molybdenum (M) which is a transition metal of group VIa and period 5 is formed on the surface of a bearing base material made of metal.
A ceramic thin film of boride (MoB ₂ or MoB) of o) was formed to form a bearing surface. This ceramic thin film has a melting point of about 2200 or 2550 ° C.
The coefficient of thermal expansion between 00 ° C. is about 8.6 × 10 ⁻⁶ / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 9) A ceramic thin film of a carbide (Nb ₂ C or NbC) of niobium (Nb) which is a transition metal of Va group and period 5 is formed on the surface of a bearing base material made of metal. The bearing surface was used. This niobium carbide ceramic thin film has a melting point of about 3080 or 3600 ° C.
Coefficient of thermal expansion between 0 to 200 ° C is about 7.0 to 6.5 x 1
It is 0 ^-6 / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 10) A ceramic thin film of niobium boride (NbB ₂ ) was formed on the surface of a bearing base material made of metal to form a bearing surface. This ceramic thin film has a melting point of about 3000 ° C. and a coefficient of thermal expansion between about 20 and 200 ° C. of about 8.0 × 10 ⁻⁶ / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 11) A ceramic thin film of niobium nitride (NbN) was formed on the surface of a bearing base material made of metal to form a bearing surface. This ceramic thin film has a melting point of about 2100 ° C. and a coefficient of thermal expansion between about 20 and 200 ° C. of about 10.1 × 10 ⁻⁶ / ° C. Since this thin film has a slightly lower melting point, it can also be used as a liquid metal lubrication type dynamic sliding bearing surface for an X-ray tube by suppressing the manufacturing process and operating temperature of the X-ray tube to a slightly lower level.

Example 12: Zirconium (Z) which is a transition metal of group IVa and period 5 is formed on the surface of a bearing base material made of metal.
A ceramic thin film of carbide (ZrC) of r) was formed and used as a bearing surface. This zirconium carbide ceramic thin film has a melting point of about 3420 ° C. and a thermal expansion coefficient of about 6.9 × 10 ⁻⁶ / ° C. between 20 and 200 ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 13) A ceramic thin film of zirconium boride (ZrB ₂ ) was formed on the surface of a metal bearing base material to form a bearing surface. This ceramic thin film has a melting point of about 3040 ° C. and a coefficient of thermal expansion between 20 and 200 ° C. of about 5.9 × 10 ⁻⁶ / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

Example 14 A zirconium nitride (ZrN) ceramic thin film was formed on the surface of a metal bearing base material to form a bearing surface. This ceramic thin film
It has a melting point of about 2980 ° C. and a coefficient of thermal expansion between 20 and 200 ° C. of about 7.9 × 10 ⁻⁶ / ° C. This thin film can also be used as a liquid metal lubrication type dynamic pressure sliding bearing surface of an X-ray tube.

(Example 15) A ceramic thin film of carbide (W ₂ C or WC) of tungsten (W) which is a transition metal of Group VIa and period 6 is formed on the surface of a bearing base material made of metal. The bearing surface was used. This tungsten carbide ceramic thin film has a melting point of about 2795 ° C or 27
At 85 ° C, the coefficient of thermal expansion between 20 and 200 ° C is about 6.2.
˜5.2 × 10 ⁻⁶ / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 16) A ceramic thin film of tungsten boride (WB ₂ or WB) was formed on the surface of a metal bearing base material to form a bearing surface. This ceramic thin film has a melting point of about 2370 ° C or 2800 ° C.
And the coefficient of thermal expansion between 20 and 200 ° C. is about 7.8 to 6.
It is 7 × 10 ⁻⁶ / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 17) A ceramic thin film of tantalum (Ta) carbide (Ta ₂ C or TaC) which is a transition metal of Va group and period 6 is formed on the surface of a bearing base material made of metal. The bearing surface was used. This tantalum carbide ceramic thin film has a melting point of about 3400 ° C or 3880 ° C.
And the coefficient of thermal expansion between 20 and 200 ° C. is about 8.3 to 6.
It is 6 × 10 ^-6 / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 18) A ceramic thin film of tantalum boride (TaB ₂ ) was formed on the surface of a bearing base material made of metal to form a bearing surface. This ceramic thin film has a melting point of about 3100 ° C. and a thermal expansion coefficient of about 8.2 to 7.1 × 10 ⁻⁶ / ° C. between 20 and 200 ° C. This thin film is
Similarly, it is suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 19) A ceramic thin film of tantalum nitride (TaN) was formed on the surface of a bearing base material made of metal to form a bearing surface. This ceramic thin film has a melting point of about 3090 ° C. and a thermal expansion coefficient of about 5.0 × 10 ⁻⁶ / ° C. between 20 and 200 ° C. This thin film can also be used as a liquid metal lubrication type dynamic pressure sliding bearing surface of an X-ray tube.

Example 20 ... Hafnium (H) which is a transition metal of group IVa and period 6 is formed on the surface of a bearing base material made of metal.
A ceramic thin film of carbide (HfC) of f) was formed to form a bearing surface. This ceramic thin film has a melting point of about 3700 ° C. and a thermal expansion coefficient of about 7.0 to 6.7 × 10 ⁻⁶ / ° C. between 20 and 200 ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 21) A ceramic thin film of hafnium boride (HfB ₂ ) was formed on the surface of a bearing base material made of metal to form a bearing surface. This ceramic thin film
It has a melting point of about 3250 ° C. and a coefficient of thermal expansion between 20 and 200 ° C. of about 6.3 × 10 ⁻⁶ / ° C. This thin film is also suitable as a liquid metal lubrication type dynamic pressure sliding bearing surface for an X-ray tube.

(Example 22) A ceramic thin film of hafnium nitride (HfN) was formed on the surface of a bearing base material made of metal to form a bearing surface. This ceramic thin film has a melting point of about 3310 ° C. and a coefficient of thermal expansion between 20 and 200 ° C. of about 7.4 to 6.9 × 10 ⁻⁶ / ° C. This thin film is
Similarly, it can be used as a liquid metal lubrication type dynamic pressure sliding bearing surface of an X-ray tube.

In the embodiment shown in FIG. 9, a rotating column 51 that rotates integrally with the anode target 11 is arranged at the center. According to a preferred assembly procedure, a ceramic thin film is formed in advance on the inner peripheral surface of the fixed body cylinder 52 in which both ends of the fixed body 15 are open and on the respective bearing surfaces of the upper and lower fixed body disks 53, 54. The base material of each of these parts is the same as that of the above-mentioned embodiment. A spiral groove 24 of the thrust bearing is formed in advance on the inner surface of the lower fixed body disk 54. Further, a ceramic thin film is previously formed on the bearing surface of the inner rotary bearing cylinder 55 of the rotating body 12 and the lower end bearing surface of the rotary cylinder 51. Helical grooves 23 and 24 are formed on the outer peripheral surface and the upper surface of the rotary bearing cylinder 55. A rotary bearing cylinder 55 is fitted to the outer periphery of a rotary cylinder 51 to which the rotary shaft 13 is brazed and fixed, and a lower portion 56 is brazed to be integrated. On the other hand, the fixed body cylinder 52 and the lower fixed body disk 54 are welded at the welded portion 56 to be integrated. Next, this fixed body cylinder 52 and lower fixed body disk 54
The assembly is subjected to gas release treatment in a vacuum heating furnace, and Ga alloy lubricant is injected into the inner space. The assembly of the rotary cylinder 51 and the rotary bearing cylinder 55 is inserted into this, and the fixed body disk 53 is fixed to the upper part by a plurality of bolts 50. Further, a rotor cylinder 45 having a copper cylinder 44 is fitted on the outer side of the rotor cylinder 45, and the upper cylinder part 45 and the rotary shaft 13 are fixed to each other by a pin. Then, the target 11 is fixed to the rotating shaft 13. After that, the X-ray tube is completed by the same assembly process as that of the above-described embodiment. In the configuration shown in the figure, it is desirable that the fixed body 15 is made of a non-magnetic material in order to obtain the required rotation performance.

As a method of forming the above-mentioned ceramic thin film on the surface of the metal bearing base material, CVD is used.
Not limited to the (chemical vapor deposition) method, a PVD (physical vapor deposition) method is applied to form a film having a predetermined thickness and a necessary heat treatment, a molten salt bath dipping method, or a thermal nitriding method in a nitrogen gas atmosphere. Can be attached with.

In the embodiment shown in FIG. 10, the bearing cylinder 61 of the rotating body 12 and the substantially cylindrical fixed body 15 itself are the same as the ceramic thin film in each of the above-mentioned embodiments except for chromium, IVa group, Va. Group VIa or VIa group, which is composed of a ceramic containing a transition metal nitride, boride, or carbide located in 4, 5, or 6 periods as a main component. The bearing surfaces of the rotating body 12 and the fixed body 15 are made of this ceramic itself. Then, the fixed body small diameter portion 15a made of ceramics and the iron anode support 17 are brazed with silver brazing, and are mechanically and electrically coupled. Thereby, the anode current path is also completed.

In the embodiment shown in FIG. 11, the fixed body 15 itself is made of an insulating ceramics such as silicon nitride (Si ₃ N ₄ ) and the above-mentioned ceramic thin film 27 is formed on the surface thereof, that is, the bearing surface. It is a thing. The rotating body 12 may be similarly made of an insulating ceramic material or may be made of a conductive ceramic material as described above. Then, in order to form an anode current path, the end face 13a of the rotary shaft 13 made of Mo connected to the anode target 11 is exposed on the same surface as the thrust bearing surface, and the bearing surface and the central hole are formed.
It is configured to make electrical contact with the liquid metal lubricant filled in 28. Then, a conductor rod 62 is provided penetrating the other end of the fixed body 15 , one end 62a thereof is electrically connected to the iron anode support 17 by brazing, and the other end 62b extends into the central hole 28. And is in electrical contact with the liquid metal lubricant. This constitutes a current path from the anode target 11 to the anode support 17.

It should be noted that either one of the portion forming the bearing surface of the cylindrical body or the cylindrical body is made of, for example, molybdenum (Mo) or tungsten (W), and the other is used without forming a ceramic thin film on the bearing surface. The ceramic bearing surface may be formed as described above. Furthermore, molybdenum or tungsten may be used as the bearing base material when the above-mentioned ceramic thin film is coated on the bearing surface.

Among the transition metals located in the IVa group, the Va group, or the VIa group and located in the 4, 5, or 6 period from the ceramics constituting the bearing surface, especially chromium (C
The reason for excluding r) is that chromium carbides, borides, or nitrides are not practical because they have a considerably low melting point and react significantly with liquid metal lubricants such as Ga or Ga alloys.

Furthermore, an X-ray tube is manufactured at a relatively high temperature,
Alternatively, when operating, vanadium or molybdenum carbide ceramics are particularly suitable. Alternatively, niobium or tungsten carbide or boride ceramics are preferred as they withstand higher temperatures. Similarly, titanium, zirconium, hafnium, or tantalum carbide, boride, or nitride ceramics are preferred as they withstand even higher temperatures. These have a melting point of 2610 ° C. or higher and have excellent corrosion resistance to liquid metal lubricants.

Furthermore, carbides of the above-mentioned transition metals,
A ceramic having a composition containing one of boride or nitride as a main component and at least one of carbide, boride, or nitride of another transition metal mixed therein may be used. As an example, titanium carbonitride [Ti (C,
N)] ceramics and the like.

Furthermore, at least one other intermediate layer may be formed between the bearing base material and the ceramic layer. In this case, the intermediate layer has a composition such that its coefficient of thermal expansion is between the coefficient of thermal expansion of the bearing base material and the ceramic layer, or a composition that enhances the degree of bonding with the bearing base material and the ceramic layer. May be.

Liquid metal lubricants are Ga and Ga-I.
It is not limited to an n alloy or a Ga-In-Sn alloy mainly composed of Ga, and for example, a Bi-In-Pb-Sn alloy relatively containing bismuth (Bi) or In
In-Bi alloy containing a relatively large amount of In, or In-Bi
-Sn alloy etc. can be used. Since these have a melting point of room temperature or higher, it is desirable that the lubricant is preheated to a temperature of the melting point or higher to be in a liquid state and then rotated before the anode target is rotated.

[0047]

As described above, according to the present invention,
The sliding bearing surface made of ceramics has excellent wettability with the liquid metal lubricant, and there is almost no erosion of the bearing surface by the lubricant, and a rotary anode type X-ray tube having stable bearing operation performance for a long time is obtained. be able to. It is also possible to use a relatively inexpensive bearing base material.

[Brief description of drawings]

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

FIG. 2 is a longitudinal sectional view showing an enlarged main part of FIG.

FIG. 3 is a vertical sectional view showing another embodiment of the present invention.

FIG. 4 is a vertical sectional view showing a main part of FIG.

5 is a top view of a main part of FIG. 3. FIG.

FIG. 6 is a vertical cross-sectional view showing the main part of the same as in FIG.

FIG. 7 is a top view taken along line 7-7 of FIG.

FIG. 8 is a semi-longitudinal cross-sectional view showing the main parts of FIG. 3 in an exploded manner.

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

FIG. 10 is a vertical sectional view showing still another embodiment of the present invention.

FIG. 11 is a vertical sectional view showing still 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, 23, 24 ... Helical groove, g ... Bearing gap, 32 ... Bearing cylinder, 16,33,53,54… Bearing disk, 26,27… Ceramic thin film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Sugiura 1385-1 Shimoishigami, Otawara-shi, Tochigi Stock Company Toshiba Nasu Electronic Tube Factory (72) Inventor Takayuki Kitami 1385-1 Shimoishigami, Otawara, Tochigi Company Toshiba Nasu Electronic Tube Factory (72) Inventor Hideo Yakoshi 1385-1 Shimoishigami, Otawara-shi, Tochigi Stock Company Toshiba Nasu Electronic Tube Factory (72) Inventor Shinto Ren 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Electronic Engineering Co., Ltd.

Claims (5)

[Claims] 1. A rotating body to which an anode target is partially fixed, a fixed body that rotatably holds this rotating body, and a spiral groove on a bearing surface provided on the rotating body and a part of the fixed body. A rotary anode X-ray tube comprising a formed slide bearing part and a metal lubricant which is interposed between bearing surfaces of the bearing part and which is liquid at least during operation, wherein at least one of the slide bearing parts is provided. Bearing surface of IVa group, Va group, or VIa group excluding chromium,
Alternatively, a rotating anode type X-ray tube characterized by being composed of a ceramic containing at least one of a group of at least one transition metal carbide, boride, or nitride located in 6 periods as a main component. 2. A rotary anode type X-ray tube in which the thin film of the ceramic according to claim 1 is adhered to the surface of a bearing base material made of metal to form a bearing surface. 3. The rotating anode type X-ray tube according to claim 2, wherein the bearing base material is iron or an iron alloy. 4. The bearing base material of the fixed body is a non-ferromagnetic material,
A rotary anode type X-ray tube having a bearing surface having the ceramic thin film according to claim 1 attached to the surface thereof. 5. One of the rotating body and the fixed body is located outside the other, which comprises a cylindrical portion whose inner peripheral surface serves as a bearing surface and a disk portion which substantially closes the opening thereof. 2. The rotating anode type X-ray tube according to claim 1, wherein a ceramic thin film is adhered to the inner peripheral bearing surface of said.