JP3045906B2 - Rotating anode X-ray tube - Google Patents

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 a rotating mechanism for supporting an anode target.

[0002]

2. Description of the Related Art As is well known, a rotating anode type X-ray tube includes a stator electromagnetic coil in which a disk-shaped anode target is supported by a rotating body and a fixed body having a bearing therebetween and arranged outside a vacuum vessel. An electron beam is emitted from the cathode while being energized and rotated at a high speed, and the X-ray is emitted by hitting the anode target.
Rolling bearings such as ball bearings, helical grooves on the bearing surface and gallium (Ga)
Alternatively, it is constituted by a dynamic pressure bearing using a liquid metal such as a gallium-indium-tin (Ga-In-Sn) alloy as a lubricant. Examples using the latter plain bearing are disclosed, for example, in JP-B-60-21463 and JP-A-60-9753.
No. 6, JP-A-60-117531, JP-A-61-29
No. 14, or JP-A-60-287555.

The rotating body supporting the anode target usually has a target supporting portion in which an outer cylindrical rotor made of copper having high electric conductivity is integrally joined by brazing. A rotating magnetic field is applied to this rotor from a stator electromagnetic coil outside the tube, and the rotor is rotated at a high speed by the principle of an induction motor.

[0004]

The prior art described above has the following disadvantages. In other words, when liquid metal is used as a lubricant, the bearing has little wear and there is almost no rotation noise.However, the rotating body and fixed body that support the anode target are It gets hot. However, since the liquid metal lubricant is very active, it reacts with the bearing constituent material, and the gap between the bearings may gradually change to deteriorate the rotation characteristics. In order to solve this inconvenience, there is also known a structure in which a refrigerant is fed into a bearing component to perform forced cooling. However, in such an X-ray tube, it is necessary to add a refrigerant circulation device, which complicates the X-ray device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotating anode type X-ray tube capable of suppressing a rise in temperature of a bearing portion and maintaining stable rotating characteristics for a long period of time. I do.

[0006]

According to the present invention, a fixed body for rotatably holding a rotating body to which an anode target is fixed via a dynamic pressure sliding bearing lubricated with a liquid metal is provided by a high heat transfer.
The surface of the core made of conductive material, that is, the sliding bearing surface
The surface is different from the core material and the metal that constitutes the lubricant.
The other hard metal element is diffused to a predetermined depth, and the axis of high hardness
It is a rotating anode type X-ray tube having a receiving surface . Or
In addition, the fixed body is made of a core made of high thermal conductive material and a sliding bearing.
The content of the hard material on the surface that becomes the bearing surface gradually increases
Anode type X-rays composed of functionally gradient materials
Tube.

[0007]

According to the present invention, since the heat reaching the fixed body is quickly radiated to the outside of the tube, the temperature rise of the bearing portion is suppressed, the stable bearing rotation performance is maintained for a long time , and the anode
The heat input to the get can be increased. Also,
The core part of the fixed body and the surface part that becomes the sliding bearing surface peel off or
Has a highly reliable hydrodynamic sliding bearing
X-ray tube is obtained.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.
The same parts are denoted by the same reference numerals. 1 and 2 show a completed state and a used state. The rotating anode X-ray tube 10 of this embodiment is a disk-shaped anode target 1 made of heavy metal.
1 is integrally connected and fixed by a fixing screw 14 to a target support shaft 13 protruding from one end of the cylindrical rotating body 12. A fixed body 15 is provided inside the cylindrical rotating body 12.
Are inserted coaxially and closely, and a thrust ring 16 for closing the opening of the rotating body is fixed to the lower end of the rotating body with a plurality of screws. Lower end 17 of fixed body 15
Is hermetically joined to a glass cylindrical portion 22 of a vacuum vessel 21 via a connection ring 18 and sealing rings 19 and 20. The vacuum container 21 has a large-diameter metal container 23 surrounding the anode target 11, and an X-ray emission window 24 is provided in a part thereof. Further, the vacuum vessel 21 has a glass cylindrical portion 26 that supports a cathode structure 25 disposed to face the anode target 11.

[0009] Therefore, a cylindrical fixed body 15, the preferred method of assembly will be described later, the core portion 27 made of a highly thermal conductive material such as copper, high speed tool covering around the tube outer extension 27a, and its Surface portions 28, 29 of a hard material such as steel
have. As described later, the high-hardness material surface portions 28 and 29 constitute a hydrodynamic sliding bearing surface together with the inner surface of the rotating body, and therefore have a high hardness such as high-speed tool steel such as SKD-11 (JIS standard). And high temperature strength, and well wet with liquid metal lubricant such as Ga alloy
Configured in that wood material.

Then, the cylindrical high hardness material surface portion 2 is formed.
8, two sets of dynamic pressure type radial sliding bearings 3
A pair of herringbone pattern helical grooves 32 and 33 that are part of 0 and 31 are formed. In the vicinity of the center of the high-hardness material surface portion 28, a circumferential recess 35 for forming the first lubricant reservoir 34 is formed.
The connection ring 18 made of an iron alloy is hermetically joined to the lower end portion 17 of the hard material surface portion 28 extended in a cylindrical shape by the helic arc welding as described above.
Further, a flat flange portion 29a of a high-hardness material surface portion 29 having a substantially U-shaped vertical section is air-tightly joined to and integrated with an upper end portion of the cylindrical high-hardness material surface portion 28 in the figure. The space inside the U-shaped high hardness material surface portion 29 constitutes a second lubricant reservoir 36, while the flat flange portion 29a
On the upper surface, a circular herringbone pattern spiral groove 38 to be one thrust slide bearing 37 is formed. The surface of the thrust ring 16 in contact with the lower shoulder of the hard material surface portion 28 is provided with the other thrust sliding bearing 3.
Nine circular herringbone pattern spiral grooves 40 are formed. And a core 27 made of a high thermal conductive material.
Has a cylindrical outer extension 2 also made of a high thermal conductive material.
7a is thermally and mechanically integrally connected by a screw portion 27b. The outer extension 27a of the core portion of the high heat conductive material is extended to the outside of the vacuum vessel in close contact with the inside of the lower end portion 17 of the surface of the high hardness material, and the radiator 41 made of a high heat conductive material such as copper or aluminum is transmitted therethrough. It is thermally connected and fixed. The connection ring 18 integrally fixed to the lower end portion 17 of the hard material surface is supported and fixed at a predetermined position inside the X-ray tube container 43 by an X-ray tube support 42 made of an electrical insulator. .

Such a fixed body 15 can be assembled as shown in FIGS. That is, first, as shown in FIG. 3A, two cylindrical and substantially U-shaped high-hardness material surface portions 2 are formed by pressing or cutting.
8, 29 are manufactured. Then, as shown in FIG.
These are combined and integrally joined at a hermetic joint B by laser welding, and then placed in a hydrogen furnace upside down so that the U-shaped cross section 29 faces down. The molten copper to be the part 27 is injected, and the casting is performed while maintaining the temperature at or above the melting point of copper for a predetermined time. As the casting method, a lost wax method, a casting method, or the like can be adopted.

In this way, a material in which a core made of copper is cast inside the surface of the high-hardness material is completed, and then, as shown in FIGS. , 29 are formed by cutting or etching to form a central recess 35 and spiral grooves 32, 33, 38. Further, a copper external extension 27a prepared separately is screwed and fixed to the core 27. The screwing portion 27b may perform brazing. Thus,
The fixed body 15 is completed.

On the other hand, the cylindrical rotating body 12 is fitted with an intermediate cylinder 44 to which the anode target 11 is integrally connected via a shaft 13 while maintaining a first adiabatic gap G1. It has a bottom inner cylinder 45 and a copper outer cylinder 46 fitted around the outer periphery of the intermediate cylinder 44.
Four small projections 4 are provided on the outer periphery of the upper end of the bottomed inner cylinder 45.
5a are formed, which are in contact with the inner peripheral wall of the intermediate cylinder 44 with a small contact area, and maintain a precise coaxial positional relationship between the two while maintaining the first adiabatic gap G1. The copper outer cylinder 46 has its upper end in the figure partially fixed to the intermediate cylinder 44 so as to rotate integrally with the copper outer cylinder 46, and a second adiabatic gap G2 is provided in most of the space therebetween. The width in the radial direction of both adiabatic gaps G1, G2 is in the range of 0.1 to 1 mm, for example, 0.5 mm. And copper outer cylinder 4
In a region occupying about two thirds of the lower side of the outer peripheral surface of No. 6, a black film 47 excellent in heat radiation is attached.

Since the inner cylinder 45 with a bottom has a part of the inner surface which constitutes a dynamic pressure sliding bearing surface together with the surface of the fixed body, also the molybdenum (Mo), stainless steel, or SKD-11 (JIS standard). has high hardness and high-temperature strength such as high-speed tool steel, such as, composed of wood fees Ru wetted well with the liquid metal lubricant.

The intermediate cylinder 44 has a thermal conductivity sufficiently smaller than that of the dull iron, and is 0.1 (ca) in the range of 0 to 500 ° C.
1 / cm · sec · ° C.) or less, more preferably 0.08
(Cal / cm · sec · ° C.) or less.
The upper end of the intermediate cylinder is fixed to the shaft 13, and the lower end is the inner cylinder 45 that is farther from the anode target in terms of heat transfer.
Are integrally joined by welding. As the intermediate cylinder 44, for example, an alloy mainly composed of iron / nickel,
Alloys mainly composed of nickel / cobalt, alloys mainly composed of iron / chromium, alloys mainly composed of iron / chromium / nickel, tool steel mainly composed of iron / chromium / carbon / molybdenum or tungsten, or ceramics Selected materials may be used. Incidentally, at least one of the intermediate cylinder and the inner cylinder may be formed of a ferromagnetic material.
It is preferable from the viewpoint of the magnetic action efficiency with the rotating magnetic field of the stator 48.

Thus, a bearing gap of about 20 μm is maintained between the inner cylinder 45 of the rotating body 12 and the hard material surface portions 28, 29 of the fixed body 15, but as described above, between them. Since the radial and thrust dynamic pressure sliding bearings are constructed, the bearing gap, the first and second
The lubricant reservoirs 34 and 36 are filled with a metal lubricant such as a Ga alloy. In addition, the amount of the lubricant is the lubricant reservoir 3
It is not always necessary to completely satisfy 4, 36, but it is sufficient if the amount can guarantee a long-term bearing operation.

The X-ray tube 10 to which the rotating anode type X-ray tube 10 is fixed
The inside of the wire tube housing 43 is filled with insulating oil and is circulated and used by a cooler and a pump (not shown).
It is more preferable that the cooling oil is applied to the radiator 41 fixed to the outward extension 27a of the high thermal conductive material of the fixed body and forcedly cooled by applying the cooling oil as shown by a dotted line arrow because the cooling action of the bearing portion is enhanced. Alternatively, in the manufacturing process of the X-ray tube, particularly in the evacuation process, a radiator or a cooler is connected to the outer extension 27a of the fixed body to cool the same while the electron beam collides with the anode target to release gas at a high temperature. Exhaust can be performed. Thereby, good vacuum for a long time,
X-ray tube operation performance with high reliability can be maintained.

As described above, in the rotating anode type X-ray tube of the present invention, on the one hand, the rotating body 12 prevents the heat generated in the anode target 11 from reaching the bearing portion as much as possible, and on the other hand, the fixed body 15 prevents the heat generated by the bearing portion from being generated. Is efficiently conducted and dissipated outside the tube by a core portion made of a high heat conductive material. As a result, during the assembly process or operation of this rotary anode type X-ray tube, the temperature rise of the liquid metal lubricated hydrodynamic slide bearing is suppressed, and the undesired reaction between the bearing surface and the lubricant is effectively promoted. Can be suppressed.

The high thermal conductive material core 27 and the external extension 27a of the fixed body 15 are preferably made of copper or an alloy mainly composed of copper, but are not limited thereto. Is 0.07 (cal / cm · sec · ° C)
Above, more preferably 0.1 (cal / cm · sec ·
° C) or higher. Specific examples thereof include aluminum or an alloy mainly composed of aluminum, pure iron or an alloy mainly composed of iron, nickel or an alloy mainly composed of nickel.

The surface portions 28 and 29 of the high-hardness material are not limited to high-speed tool steel as described above. For example, molybdenum (Mo) or Mo alloy, tantalum (Ta) or Ta alloy, niobium (Nb) or Nb Alloys, stainless steels, alloys mainly composed of iron / nickel, alloys mainly composed of iron / nickel / cobalt, alloys mainly composed of iron / chromium, alloys mainly composed of iron / chromium / nickel, iron / chromium / Tool steel or the like mainly composed of carbon / molybdenum or tungsten can be used.

The embodiment shown in FIG.
7 and its external extension 27a are made of an integral body of a high thermal conductive material, and at least the surface portion of the portion located inside the rotating body is impregnated with another metal element to a predetermined depth to obtain a high hardness material surface portion 28. As. Specifically, the core is made of pure iron, and the surface of the core is made of chromium (Cr), carbon (C),
Or, at least one of boron (B) has a depth of 50 to 20.
Diffuse to 0 μm. It is particularly effective to simultaneously diffuse chromium (Cr) and carbon (C). The bearing surface composed of these surface layers is more preferable because the reaction speed with the Ga alloy at a high temperature is relatively low and the high-temperature hardness is high. The bearing surface may be formed with a spiral groove before the diffusion, or may be formed by cutting the surface after the diffusion and etching.

In addition, a second lubricant reservoir 36 formed of a long hole extending in the axial direction is formed in the center shaft portion of the fixed body 15. Further, four lubricant passages 36a are formed which extend from the second lubricant reservoir 36 in the radial direction and open to the wall surface of the depression 35 serving as the first lubricant reservoir.
This allows the lubricant to flow in different directions.

According to this embodiment, most of the fixed body other than the very surface portion including the bearing surface is substantially made of a high heat conductive material, so that the heat dissipation of the bearing portion is further enhanced, and the bearing surface is improved. Of the reaction between the lubricant and the lubricant can be further suppressed.

The embodiment shown in FIG.
The high thermal conductive material of No. 7 and the high hardness material of the surface portion 28 are made of a functionally graded material whose content gradually changes on the way. The region S in the figure is a portion where the contents of both materials gradually change in the radial direction.

Thus, even if the high thermal conductive material and the high hardness material have relatively different coefficients of thermal expansion, there is no possibility that the distortion due to the difference between them may be locally concentrated, so that the stable bearing performance and the X-ray tube performance can be improved. Stable operation can be maintained.

It should be noted that the present invention provides a rotary anode having a structure in which a columnar rotating body which is integrally connected to an anode target and rotates is disposed at the center, and a substantially cylindrical fixed body is provided so as to surround the rotating body 12. It can also be applied to a fixed body of a type X-ray tube. That is, the surface of the fixed body as a bearing surface is made of a hard material,
The main part which holds it and extends to the outside of the tube is made of high thermal conductive material.

The liquid metal lubricant is Ga or G
Not limited to the a alloy, for example, a Bi—In—Pb—Sn alloy containing a relatively large amount of bismuth (Bi), an In—Bi alloy containing a relatively large amount of In, or In—Bi—Sn
Alloys may be used. Since these materials have a melting point of room temperature or higher, it is desirable to rotate the metal lubricant after preheating the metal lubricant to a temperature equal to or higher than the melting point before rotating the anode target.

[0028]

As explained above, according to the present invention,
Temperature rise of the bearing portion can be suppressed, therefore, Rutotomoni fixed undesired reactions with the bearing surface of the material and lubricant can be suppressed
The core of the body and the surface of the sliding bearing
There is no danger that the bearing's rotational performance will be maintained over a long period of time.

[Brief description of the drawings]

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

FIG. 2 is a schematic longitudinal sectional view showing an example of an apparatus equipped with the X-ray tube of the present invention.

FIG. 3 is an exploded vertical sectional view illustrating an assembled state of the fixed body of FIG. 1;

FIG. 4 is a longitudinal sectional view illustrating the assembled state of the fixed body of FIG. 1 and a top view thereof.

FIG. 5 is a partial side view showing another embodiment of the present invention in which a part thereof is enlarged.

FIG. 6 is a longitudinal sectional view of a main part showing still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Anode target 12 ... Rotating body 15 ... Fixed body 27 ... Core part 27a ... Extra-tube extension part 28, 29 ... Surface part 30, 31 , 37, 39 ... Bearing 41 ... Heat sink

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-259445 (JP, A) JP-A-2-227947 (JP, A) JP-A-62-140661 (JP, U) (58) Investigation Field (Int.Cl. ⁷ , DB name) H01J 35/10

Claims (4)

(57) [Claims] 1. A rotating body inside a vacuum vessel having an anode target fixed to a part thereof, a fixed body fitted to the rotating body and rotatably holding the rotating body, the rotating body and the fixed body A dynamic pressure sliding bearing having a spiral groove provided in a fitting portion of the body, and a mutual contact between the spiral and the bearing surface of the sliding bearing;
The metal fluid supplied to the gap and at least liquid during operation
In a rotary anode type X-ray tube comprising a lubricant , the fixed body has a core portion in a temperature range of 0 ° C to 300 ° C.
Conductivity higher than 0.1 (cal / cm · sec · ° C)
It is made of heat conductive material and the end is directly or other high heat transfer
Extending outside the vacuum vessel through an extra-tube extension member made of a conductive material.
The core material and the core material
Another metal element different from the metal that constitutes the lubricant is
The above-mentioned slide shaft which is diffused to a higher degree and has a higher hardness than the core portion
A rotating anode type X-ray tube, wherein a bearing surface of a bearing is formed . 2. The core of the fixed body is made of pure iron.
The metal elements diffused to the surface of the core are chromium and charcoal.
At least one gold selected from elemental or boron
The rotating anode type X-ray tube according to claim 1, which is a genus element . 3. The diffusion depth of the metal element is 50 to 20.
3. The rotating anode type X-ray tube according to claim 2, wherein the diameter is in a range of 0 μm . 4. A rotating body inside the vacuum vessel, a part of which has an anode target fixed thereto, a fixed body fitted to the rotating body and rotatably holding the rotating body, the rotating body and the fixed body A dynamic pressure sliding bearing having a spiral groove provided in a fitting portion of the body, and a mutual contact between the spiral and the bearing surface of the sliding bearing;
The metal fluid supplied to the gap and at least liquid during operation
In a rotary anode type X-ray tube comprising a lubricant , the fixed body comprises a core made of a high thermal conductive material and the slide shaft.
Characterized in that the surface portion of the high-hardness material comprising a bearing surface for receiving is configured with functionally graded material that changes gradually content in the middle
Rotating anode X-ray tube according to.