ROTARY X-RAY ANODE HAVING AN INTEGRATED LIQUID METAL BEARING OUTER SHELL

Abstract

A rotary x-ray anode with an integrated liquid metal bearing outer shell has an anode disc made of Mo or a Mo-based alloy formed with a hole, which is formed centrally in the region of the axis of rotation and extends in the axial direction at least through part of the anode disc, and a bearing bushing made of Mo or a Mo-based alloy. The bearing bushing is connected to the anode disc via a material bond and its inner wall extends the hole in the anode disc. At least an axial portion of an inner wall of the hole in the anode disc and at least an axial portion of an inner wall of the bearing bushing are formed circumferentially as a liquid metal bearing running surface and they form at least a part of a liquid metal bearing outer shell. There is also described a corresponding production method.

Claims

1-15. (canceled)

16. A rotary x-ray anode with an integrated liquid metal bearing outer shell, comprising: an anode disk made of Mo or a Mo-based alloy, said anode disk being formed with a central hole in a region of an axis of rotation and extending in an axial direction through at least a portion of said anode disk; a bushing made of Mo or a Mo-based alloy bonded to said anode disk via a material bonding connection; said bushing having an inner wall continuing said central hole of said anode disk and being formed circumferentially as a liquid metal bearing running surface, at least over an axial section thereof, and forming a first subsection of a liquid metal bearing outer shell; said central hole of said anode disk having an inner wall formed circumferentially as a liquid metal bearing running surface, at least over an axial section thereof, and forming at least a part of a second subsection of the liquid metal bearing outer shell; said first and second subsections of the liquid metal bearing outer shell adjoining one another and together forming a continuous liquid metal bearing running surface of the liquid metal bearing outer shell.

17. The rotary x-ray anode according to claim 16, wherein said material bonding connection is a bond formed by a process selected from the group consisting of diffusion bonding, friction welding, and beam welding.

18. The rotary x-ray anode according to claim 16, wherein said Mo-based alloy is at least one alloy selected from the group consisting of alloy MHC and alloy TZM, and wherein: MHC has the following composition: a Hf content of 1.00-1.30% by weight; a C content of 500-1200 μg/g; and balance Mo; where a content of any metallic impurities is ≤5000 μg/g and a total content of any impurities selected from the group consisting of H, N, and O is ≤1000 μg/g; TZM has the following composition: a Ti content of 0.40-0.55% by weight; a Zr content of 0.06-0.12% by weight; a C content of 50-500 μg/g; balance Mo; where a content of any metallic impurities is ≤5000 μg/g and a total content of any impurities selected from the group consisting H, C, N, and O is ≤1500 μg/g.

19. The rotary x-ray anode according to claim 16, wherein said anode disk and said bushing are each formed of molybdenum or are each formed from the same molybdenum-based alloy.

20. The rotary x-ray anode according to claim 16, wherein said material bonding connection is a friction welding bond.

21. The rotary x-ray anode according to claim 16, wherein a side of said anode disk facing toward said bushing is formed with a connection port, said connection port having an inner wall extending said central hole in said anode disk and said connection port protruding with respect to a peripheral face on an outside of said anode disk, with at least an axial section of said inner wall of said connection port being formed circumferentially as a liquid metal bearing running surface and forming a portion of said second subsection of said liquid metal bearing outer shell, and wherein said material bond is formed between said protruding connection port of said anode disk and said bushing.

22. The rotary x-ray anode according to claim 16, wherein said central hole in said anode disk is a passage hole and said anode disk, on a side opposite from said bushing, is formed with an extension port, said extension port having an inner wall extending said passage hole of said anode disk and said extension port protruding with respect to a peripheral face on an outside of the anode disk, with at least an axial section of said inner wall of said extension port being formed circumferentially as a liquid metal bearing running surface and forming a portion of said second subsection of said liquid metal bearing outer shell.

23. The rotary x-ray anode according to claim 16, wherein said anode disk has a thickness that increases in a radial direction toward the axis of rotation, with an increase in the thickness proceeding from a reference thickness measured radially in a middle of a beveled focal track surface up to the thickness in the region of said central hole being 30-300%.

24. The rotary x-ray anode according to claim 16, wherein said anode disk is formed with a plurality of slits arranged uniformly over a circumference and passing through a thickness of said anode disk, each of said slits extending over a radial section in a region between an outer circumference of said anode disk and said central hole in said anode disk.

25. A rotary x-ray anode system, comprising: a rotary x-ray anode with an integrated liquid metal bearing outer shell according to claim 16; and a liquid metal bearing inner shell inserted into said liquid metal bearing outer shell and having a liquid metal bearing running surface; said liquid metal bearing outer shell and said liquid metal bearing inner shell being matched to one another to form a defined bearing gap therebetween.

26. The rotary x-ray anode system according to claim 25, which comprises at least one circumferential mechanical boundary element disposed in a region of at least one axial end section of said liquid metal bearing running surface of said liquid metal bearing outer shell and/or of said liquid metal bearing running surface at said liquid metal bearing inner shell, said at least one circumferential mechanical boundary element, during a use of the x-ray anode system, limiting a flow of liquid metal present in the bearing gap in the axial direction.

27. The rotary x-ray anode system according to claim 25, which comprises a circumferential coating provided in a region of at least one axial end section of said liquid metal bearing running surface at the liquid metal bearing outer shell and/or in a region of the liquid metal bearing running surface at the liquid metal bearing inner shell, said circumferential coating being formed to suppress wetting by the liquid metal in the bearing gap during a use of the x-ray anode system.

28. The rotary x-ray anode system according to claim 25, wherein said liquid metal bearing inner shell is formed on an insert spigot guided through said bushing at least into the central hole formed in said anode disk.

29. The rotary x-ray anode system according to claim 25, wherein at least one of said liquid metal bearing running surface at said liquid metal bearing outer shell or said liquid metal bearing running surface at said liquid metal bearing inner shell is formed with at least two circumferential, superficially structured running sections that are spaced apart in axial direction.

30. A method of producing a rotary x-ray anode, the method comprising: providing an anode disk made of molybdenum or a molybdenum-based alloy; providing a stub of Mo or an Mo-based alloy; materially bonding the stub to the anode disk centrally relative to an axis of rotation of the anode disk; and mechanically working the anode disk and the stub to form the rotary x-ray anode with an integrated liquid metal bearing outer shell, wherein the stub forms a bushing with a liquid metal bearing running surface and the anode disk has a hole with an inner wall and the inner wall has at least an axial section that is formed circumferentially as a liquid metal bearing running surface.

31. The method according to claim 30, which comprises working the anode disk and the stub to form a rotary x-ray anode with an integrated liquid metal bearing outer shell, including: an anode disk made of Mo or a Mo-based alloy, said anode disk being formed with a central hole in a region of an axis of rotation and extending in an axial direction through at least a portion of said anode disk; a bushing made of Mo or a Mo-based alloy bonded to said anode disk via a material bonding connection; said bushing having an inner wall continuing said central hole of said anode disk and being formed circumferentially as a liquid metal bearing running surface, at least over an axial section thereof, and forming a first subsection of a liquid metal bearing outer shell; said central hole of said anode disk having an inner wall formed circumferentially as a liquid metal bearing running surface, at least over an axial section thereof, and forming at least a part of a second subsection of the liquid metal bearing outer shell; and said first and second subsections of the liquid metal bearing outer shell adjoining one another and together forming a continuous liquid metal bearing running surface of the liquid metal bearing outer shell.

Description

[0053] Further advantages and expediencies of the invention will be apparent from the description of working examples that follows, with reference to the appended figures.

[0054] The figures show:

[0055] FIG. 1: a perspective view of a rotary x-ray anode of the invention in cross section according to a first embodiment;

[0056] FIG. 2A, 2B: two cross-sectional views of the rotary x-ray anode from FIG. 1 for illustration of the production;

[0057] FIG. 3: a cross-sectional view of a rotary x-ray anode of the invention according to a second embodiment;

[0058] FIG. 4: a cross-sectional view of a rotary x-ray anode of the invention according to a third embodiment;

[0059] FIG. 5: a cross-sectional view of a rotary x-ray anode of the invention according to a fourth embodiment;

[0060] FIG. 6: a cross-sectional view of a rotary x-ray anode of the invention according to a fifth embodiment;

[0061] FIG. 7: a cross-sectional view of a rotary x-ray anode of the invention according to a sixth embodiment;

[0062] FIG. 8: a cross-sectional view of a rotary x-ray anode of the invention according to a seventh embodiment; and

[0063] FIG. 9: a cross-sectional view of a rotary x-ray anode system of the invention with inserted spigot, showing two variants A and B of the spigot above the cross-sectional view, each once in top view and once in cross-sectional view.

[0064] FIGS. 1-9 are schematic diagrams in which the size ratios are not exactly reproduced, and the details of the axially terminal ends of the liquid metal bearing outer shell and of the liquid metal bearing are not shown. For the axially terminal ends of the liquid metal bearing—as is known in the specialist field—different configurations are possible, examples of which include those shown in DE 10 2015 204 488 A1, US 2016/0086760 A1, U.S. Pat. No. 5,204,890 A, JP 2012/084400 A and US 2017/0169984 A1. In other words, in the diagrams of FIGS. 1-9, the bushing, the anode disk and the spigot may also continue further in axial direction—possibly with a different progression or different configuration—and/or also be connected to further components.

[0065] Elucidated hereinafter, with reference to FIGS. 1 and 2A, 2B, is a first embodiment of an inventive rotary x-ray anode 2. In its basic form, this has an anode disk 5 made of MHC formed in a rotationally symmetric manner with respect to an axis of rotation 4 (axial direction). On one side of the anode disk 5 is a circumferential focal track 6 with a focal track coating of a W—Re alloy (W: 95% by weight; Re: 5% by weight). In the region of the focal track 6, the anode disk 5 has a circumferential beveled focal track surface 10 which is angled (at an angle α) relative to a reference plane 8 that extends at right angles to the axis of rotation 4. A hole 12 extends through the anode disk 5, the inner wall 14 of which is formed as a liquid metal bearing running surface. On the opposite side from the focal track 6, the anode disk has a tubular connection port 16 in monolithic form which has been attached by forging and is made of the material of the anode disk 5, and which protrudes with respect to the peripheral face on the outside of the anode disk 5. The inner wall 18 thereof extends the hole 12 in the anode disk 5 and likewise takes the form of a liquid metal bearing running surface. A tubular bushing 20 likewise formed from MHC is bonded by its axial (annular) end face via a material bond 21 to the correspondingly formed axial (annular) end face of the connection port 16. The inner wall 22 of the bushing 20 is formed circumferentially as a liquid metal bearing running surface. The liquid metal bearing running surfaces of the anode disk 5, of the connection port 16 and of the bushing 20 together form a continuous liquid metal bearing running surface which, in the present case, extends in a linear manner in the form of an outer cylinder face, which forms part of a liquid metal bearing outer shell. FIG. 2A shows the bushing 20 and the anode disk 5 still as separate components, and FIG. 2B shows them in the ultimate state after establishment of the material bond 21 via friction welding (and further mechanical processing). As elucidated, the friction welding in axial direction leads to truncation of the connection port 16 and of the bushing 20 in the region of the connection zone.

[0066] In the description of further embodiments that follows—where identical or largely identical components are affected—identical reference numerals are used, and predominantly the differences with respect to the first embodiment are addressed.

[0067] In the second embodiment shown in FIG. 3, the thickness (measured in axial direction) of the anode disk 5′ increases continuously in the radially inward direction. In particular, the thickness increases by 30-300% proceeding from a reference thickness d.sub.R (measured radially in the middle in the region of the beveled focal track surface 10) up to a maximum thickness dii in the region of the hole 12 (with inclusion of all components monolithically bonded to the anode disk 5′, i.e. in the present case of the connection port 16). In addition, the thickness increases in the radially inward direction by 20-150% proceeding from the reference thickness d.sub.R even without including the monolithically formed connection port 16, in which case the thickness di in the inner region which is crucial for this purpose is measured directly (radially) outside the connection port 16.

[0068] In the third embodiment shown in FIG. 4, the anode disk 5—by comparison with the first embodiment—on the opposite side from the bushing 20 has an extension port 24 that extends the (passage) hole 12 of the anode disk 5 with its inner wall 26 and which protrudes with respect to the peripheral face on the outside of the anode disk 5. The inner wall 26 of the extension port 24 is likewise formed circumferentially as a liquid metal bearing running surface and hence forms part of the liquid metal bearing outer shell. In addition, FIG. 4 shows the increase in thickness proceeding from the reference thickness d.sub.R up to the maximum thickness dii (including all components monolithically bonded to the anode disk 5, i.e. in the present case the connection port 16 and the extension port 24). In the fourth embodiment shown in FIG. 5, the anode disk 5″—by comparison with the first embodiment—does not have a connection port. Instead, the bushing 20 is bonded via a diffusion bond directly to the planar face of the anode disk 5″.

[0069] In the embodiments shown in FIGS. 6-9, the bushing 20 is disposed on the same side as the focal track 6. By comparison with the first embodiment, in the fifth embodiment shown in FIG. 6, the connection port 16′ is disposed on the anode disk 5′″, likewise on the side of the focal track 6. In the sixth embodiment shown in FIG. 7, the anode disk 5″—similarly to the fourth embodiment (see FIG. 5)—does not have a connection port. Instead, the bushing 20 is bonded via a diffusion bond directly to the planar face of the anode disk 5″. The seventh embodiment shown in FIG. 8 differs from the sixth embodiment in that the thickness of the anode disk 5″″ increases continuously in the radially inward direction.

[0070] FIG. 9 shows a rotary x-ray anode system 27 in which the rotary x-ray anode 2 together with anode disk 5′″, connection port 16′ and bushing 20 is formed in accordance with the fifth embodiment (cf. FIG. 6). Also shown is a spigot 28 inserted on the inside, on which the liquid metal bearing inner shell is formed. A bearing gap 30 is formed between the liquid metal bearing inner shell of the spigot 28 and the liquid metal bearing outer shell, which, in use, is filled with liquid metal (not shown). Above the rotary x-ray anode are shown two illustrative variants for the formation of the spigot 28. In the first variant A (shown at the top in FIG. 9, once on the left in top view, and once in cross section to the right and within the rotary x-ray anode 2), the spigot 28 has a tubular basic form, and a smooth surface on the outside. In the second variant B (shown at the top in FIG. 9 as the third figure from the left, once in top view, and to the right once in cross section), the spigot 28′ has two superficially structured running sections 32, 34 that are spaced apart in axial direction. The spigot 28′ also has a coolant duct 36 that runs on the inside, which has a coolant tube 40 inserted into a blind hole 38, with the diameter of the coolant tube 40 chosen so as to be correspondingly smaller than that of the blind hole 38, such that coolant, for example, can flow in via the coolant tube 40 and flow back on the outside through the annular duct formed between the coolant tube 40 and the blind hole 38.

Production Examples

[0071] Example 1: There follows a description of a production process for a rotary x-ray anode of the invention, in which the anode disk and the bushing are formed from MHC and are bonded to one another via friction welding. First of all, the anode disk and a stub with a cylindrical basic form are produced by powder metallurgy, which comprises the steps of providing corresponding starting powders (for MHC), pressing and sintering, and in the present case subsequent forming (forging of the anode disk; radial forging of the stub). The stub is processed mechanically, such that it has a tubular basic form, in order to form the later bushing. In addition, in the course of forming (forging), a protruding tubular connection port (with an axial length of 40 mm) is forged centrally onto the anode disk on one side, meaning that the connection port is formed monolithically from the material of the anode disk. Both the end face of the tubular stub and the end face of the connection port have an area to be welded of 2000 mm.sup.2 and an internal diameter of 44 mm (the external diameter is determined thereby). In the present case, a friction welding machine with direct driving of the spindle is used. The tubular stub is clamped into the (non-rotating) holder of the friction welding machine, and the anode disk into the (rotating) spindle holder. Subsequently, the anode disk is set in rotation (2000 revolutions per minute) and pressed against the stub with a friction pressure of 30 bar. Subsequently, the drive of the anode disk is stopped and the compression pressure is increased to 65 bar. The total friction time, i.e. that within which relative rotary motion takes place between anode disk and stub, is 3 seconds. There then follows a mechanical processing operation for establishment of the final geometry, with the tubular stub then forming the bushing. Further fitted components, coatings, coverings, etc. may—as elucidated at the outset—also be added on. Depending on the geometry of the components and the processing steps, it is possible to include low-stress annealing (for example at temperatures in the range of 1100° C.-1300° C.) once or more than once during the production process.

[0072] Example 2: There follows a description of a production process for a rotary x-ray anode of the invention, in which the anode disk and the bushing are formed from TZM and are bonded to one another via friction welding. The same steps and parameters as in example 1 are employed, except for the following differences: starting powders for production of the anode disk and the stub from TZM (and not from MHC) are provided. The friction pressure used is only 25 bar, and the compression pressure is increased to only 60 bar after the driving of the anode disk has ended.

[0073] Example 3: There follows a description of a production process for a rotary x-ray anode of the invention, in which the anode disk and the bushing are formed from TZM and are bonded to one another via diffusion bonding. First of all, in the same way as in the second working example, the anode disk and a tubular stub are produced from TZM. Both the end face (to be bonded) of the tubular stub and the end face (to be bonded) of the connection port are processed mechanically and then ground and/or polished in order to provide a smooth planar surface. Subsequently, the diffusion bonding of the two components with mutually adjoining end faces is conducted at a temperature of 1700° C. and a pressure of 10 MPa and for a duration of at least 5 minutes (preferably in the range of 6-15 minutes).

[0074] The present invention is not limited to the working examples shown in the figures. More particularly, the liquid metal bearing running surface of the liquid metal bearing outer shell need not necessarily have a linear progression in the form of an outer cylinder face; it may also, as elucidated at the outset, have a stepped progression, a circumferential ridge, etc., in which case the liquid metal bearing inner shell then typically has a correspondingly adapted progression.