Sliding bearing unit and rotating anode type X-ray tube

Abstract

To provide a slide bearing unit which can obtain a favorable bearing motion for a long period of time, and a rotating anode-type X-ray tube having the slide bearing unit.SOLUTION: A slide bearing unit comprises a fixed shaft 10, a rotating body, and a lubricant. The fixed shaft 10 has a large-diameter part 11 including a first radial bearing face, and a small-diameter part 13. The rotating body has a rotating body main body 27 including a second radial bearing face, and a seal component 90. The seal component 90 includes an external peripheral face S90a, an internal peripheral face S90b, a capturing recessed face S90c opened at the internal peripheral face S90b, recessed to the external peripheral face S90a side, and capable of capturing the lubricant, and a through-hole h. The through-hole h has a first opening OP1 and a second opening OP2, and connects a space surrounded by the capturing recessed face S90c to a first clearance between the first radial bearing face and the second radial bearing face.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] Embodiments of the present invention relate to a sliding bearing unit and a rotating anode type X-ray tube.

Background Art

[0002] Generally, in medical devices and industrial devices that diagnose a subject using X-rays, an X-ray tube device is used as an X-ray generation source. As an X-ray tube device, a rotating anode type X-ray tube device including a rotating anode type X-ray tube is known.

[0003] The rotating anode type X-ray tube device includes a rotating anode type X-ray tube that emits X-rays, a stator coil, and a housing that houses these rotating anode type X-ray tube and stator coil. The rotating anode type X-ray tube includes a fixed shaft, a cathode that generates electrons, an anode target, a rotating body, and an envelope. The rotating body is formed in a cylindrical shape. The anode target is fixed to the rotating body. A lubricant is filled in the gap between the fixed shaft and the rotating body. The rotating anode type X-ray tube uses a hydrodynamic sliding bearing. The rotating body rotates together with the anode target by a magnetic field generated from the stator coil. Further, X-rays are emitted when electrons emitted from the cathode collide with the anode target.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] This embodiment provides a sliding bearing unit capable of obtaining good bearing operation over a long period, and a rotating anode type X-ray tube including this sliding bearing unit.

Means for Solving the Problems

[0006] A sliding bearing unit according to an embodiment includes a fixed shaft extending along a rotation axis and having a large-diameter portion including a first radial bearing surface on a first outer peripheral surface, and a small-diameter portion formed integrally with the large-diameter portion and having a second outer diameter smaller than a first outer diameter of the large-diameter portion, a rotating body rotatable about the fixed shaft, and a lubricant. The rotating body includes a rotating body main body extending along the rotation axis and formed in a cylindrical shape, positioned to surround the large-diameter portion, and including a second radial bearing surface on a first inner peripheral surface, a seal component fixed to the rotating body main body, formed in a cylindrical shape, positioned to surround the small-diameter portion, and including a second outer peripheral surface, a second inner peripheral surface, a capture concave surface that opens to the second inner peripheral surface and is recessed toward the second outer peripheral surface side to capture the lubricant, and a through hole. The lubricant is filled in a gap between the fixed shaft and the rotating body, and forms a hydrodynamic radial sliding bearing together with the first radial bearing surface and the second radial bearing surface. The through hole has a first opening that opens to the capture concave surface and a second opening that opens to a surface of the seal component other than the second inner peripheral surface and the capture concave surface, penetrates the seal component from the first opening to the second opening, and connects a space surrounded by the capture concave surface to a first gap between the first radial bearing surface and the second radial bearing surface. and in a direction perpendicular to the rotation axis, when the longest distance from the rotation axis to the first opening is defined as a first distance and the longest distance from the rotation axis to the second opening is defined as a second distance, the second distance is equal to or greater than the first distance, a second gap is provided between the first inner peripheral surface and the second outer peripheral surface, the capture concave surface includes a bottom surface located on the second outer peripheral surface side, the first opening opens to the bottom surface of the capture concave surface, the second opening opens to the second outer peripheral surface, the second gap connects the through hole to the first gap.

[0007] In addition, the rotating anode type X-ray tube according to one embodiment includes a fixed shaft having a large-diameter portion that extends along the rotation axis and includes a first radial bearing surface on the first outer peripheral surface, and a small-diameter portion that is formed integrally with the large-diameter portion and has a second outer diameter smaller than the first outer diameter of the large-diameter portion; a rotating body that is rotatable about the fixed shaft; a lubricant; a sliding bearing unit including; the male fixed to the rotating body a positive electrode target; a cathode disposed opposite to the anode target; an outer container that houses the sliding bearing unit, the anode target, and the cathode, and fixes the fixed shaft. The rotating body includes a rotating body main body that extends along the rotation axis and is formed in a cylindrical shape, is located surrounding the large-diameter portion, and includes a second radial bearing surface on the first inner peripheral surface; a seal component that is fixed to the rotating body main body, is formed in a cylindrical shape, is located surrounding the small-diameter portion, and includes a second outer peripheral surface, a second inner peripheral surface, a capture concave surface that opens on the second inner peripheral surface and is recessed toward the second outer peripheral surface side to capture the lubricant, and a through hole; The lubricant is filled in a gap between the fixed shaft and the rotating body, and forms a hydrodynamic radial sliding bearing together with the first radial bearing surface and the second radial bearing surface. The through hole has a first opening that opens to the capture concave surface and a second opening that opens to a surface of the seal component other than the second inner peripheral surface and the capture concave surface, penetrates the seal component from the first opening to the second opening, and connects the space surrounded by the capture concave surface to a first gap between the first radial bearing surface and the second radial bearing surface. and in a direction perpendicular to the rotation axis, when the longest distance from the rotation axis to the first opening is defined as a first distance and the longest distance from the rotation axis to the second opening is defined as a second distance, the second distance is equal to or greater than the first distance, a second gap is provided between the first inner peripheral surface and the second outer peripheral surface, the capture concave surface includes a bottom surface located on the second outer peripheral surface side, the first opening opens to the bottom surface of the capture concave surface, the second opening opens to the second outer peripheral surface, the second gap connects the through hole to the first gap.

Brief Description of the Drawings

[0008]

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Mode for Carrying Out the Invention

[0009] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. Note that the disclosure is merely an example, and for those that can be easily conceived by those skilled in the art with appropriate modifications while maintaining the gist of the invention, they are naturally included in the scope of the present invention. In addition, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but this is merely an example and does not limit the interpretation of the present invention. Also, in this specification and each figure, elements similar to those described above with respect to the previously shown figures may be assigned the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0010] In the following embodiments, a sliding bearing unit and a rotating anode type X-ray tube apparatus including the sliding bearing unit will be described. The rotating anode type X-ray tube apparatus includes a rotating anode type X-ray tube and the like. Hereinafter, the rotating anode type X-ray tube apparatus will be simply referred to as an X-ray tube apparatus, and the rotating anode type X-ray tube will be simply referred to as an X-ray tube. The X-ray tube includes a sliding bearing unit, an anode target, a cathode, and an envelope. The sliding bearing unit includes a fixed shaft, a rotating body, and liquid metal (metal lubricant) as a lubricant, and uses a sliding bearing.

[0011] (First Embodiment) First, the X-ray tube apparatus according to the first embodiment will be described. FIG. 1 is a cross-sectional view showing the X-ray tube apparatus according to the first embodiment. FIG. 2 is an enlarged cross-sectional view showing a part of the X-ray tube 1 shown in FIG. 1. FIG. 3 is a side view showing a part of the fixed shaft 10 shown in FIG. 1. FIG. 4 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to the first embodiment, and shows the fixed shaft 10 and the rotating body 20.

[0012] As shown in FIG. 1, the X-ray tube apparatus includes a rotating anode type X-ray tube 1, a stator coil 2 as a coil that generates a magnetic field, and the like. The X-ray tube 1 includes a sliding bearing unit U, an anode target 50, a cathode 60, and an envelope 70. The sliding bearing unit U includes a fixed shaft 10, a rotating body 20, and liquid metal LM as a lubricant, and uses a sliding bearing.

[0013] As shown in FIGS. 1 to 3, the fixed shaft 10 is formed in a cylindrical shape, extends along the rotation axis a, and has radial bearing surfaces S11a and S11b formed on the outer peripheral surface. The fixed shaft 10 includes a large-diameter portion 11 and a small-diameter portion 13. The large-diameter portion 11 and the small-diameter portion 13 are coaxially and integrally formed. The fixed shaft 10 is formed of a metal such as an Fe (iron) alloy or a Mo (molybdenum) alloy.

[0014] The large-diameter portion 11 of the fixed shaft 10 is located in regions A1, A2, A3, A4, and A5 arranged along the rotation axis a. Region A2 is spaced from region A1 in the direction along the rotation axis a. Region A3 is located between region A1 and region A2 and is adjacent to each of region A1 and region A2. Region A4 is located beyond region A1 from region A3 and is adjacent to region A1. Region A5 is located beyond region A2 from region A3 and is adjacent to region A2.

[0015] The large-diameter portion 11 is formed in a cylindrical shape and has an outer peripheral surface S11. The outer peripheral surface S11 has a radial bearing surface S11a, a radial bearing surface S11b, a concave surface S11c, a concave surface S11d, and a concave surface S11e. Further, the large-diameter portion 11 has one end surface S11f and the other end surface S11g located on the opposite side of the one end surface S11f in the direction along the rotation axis a.

[0016] The one end surface S11f has a thrust bearing surface S11i and a concave surface S11m. The concave surface S11m opens to the one end surface S11f and is recessed toward the other end surface S11g side. When the one end surface S11f is viewed from the direction along the rotation axis a, the thrust bearing surface S11i has an annular shape, and the concave surface S11m has a circular shape and is surrounded by the thrust bearing surface S11i.

[0017] The other end surface S11g has a thrust bearing surface S11j and a concave surface S11n. The thrust bearing surface S11j faces a seal component 90 described later. The concave surface S11n opens to the other end surface S11g and is recessed toward the one end surface S11f side. When the other end surface S11g is viewed from the direction along the rotation axis a, the thrust bearing surface S11j has an annular shape, and the concave surface S11n has an annular shape and is surrounded by the thrust bearing surface S11j. Note that the small-diameter portion 13 is continuously formed from the region surrounded by the concave surface S11n in the other end surface S11g.

[0018] The radial bearing surfaces S11a and S11b are each formed over the entire circumference on the outer peripheral surface S11 of the large-diameter portion 11. In the present first embodiment, the concave surfaces S11c, S11d, and S11e are each formed over the entire circumference on the outer peripheral surface S11 of the large-diameter portion 11. However, the concave surfaces S11c, S11d, and S11e may be formed intermittently in the circumferential direction, respectively.

[0019] The radial bearing surface S11a is formed on the large-diameter portion 11 in the region A1. The radial bearing surface S11b is formed on the large-diameter portion 11 in the region A2. The radial bearing surface S11a and the radial bearing surface S11b are spaced apart in the direction along the rotation axis a.

[0020] The radial bearing surface S11a has a plane surface Sa and a plurality of scraping concave surfaces (a plurality of pattern portions) Pa. The plane surface Sa has a smooth outer peripheral surface. The plurality of scraping concave surfaces Pa each open to the plane surface Sa, are recessed toward the rotation axis a side, and are formed for scraping the liquid metal LM. The plurality of scraping concave surfaces Pa are formed by indenting the plane surface Sa and are arranged over the entire circumference on the outer peripheral surface S11 of the large-diameter portion 11 in the region A1. Each scraping concave surface Pa extends obliquely with respect to the circumferential direction and is arranged. The scraping concave surface Pa includes a bottom surface Sc located on the rotation axis a side. In the direction along the rotation axis a, the plurality of scraping concave surfaces Pa are formed at intervals. However, the plurality of scraping concave surfaces Pa may be connected in the direction along the rotation axis a. Also, among the plurality of scraping concave surfaces Pa, the scraping concave surfaces Pa on the concave surface S11c side do not contact the concave surface S11c, but may contact the concave surface S11c. Similarly, among the plurality of scraping concave surfaces Pa, the scraping concave surfaces Pa on the concave surface S11d side do not contact the concave surface S11d, but may contact the concave surface S11d.

[0021] The radial bearing surface S11b has a plane surface Sb and a plurality of scraping concave surfaces (a plurality of pattern portions) Pb. The plane surface Sb has a smooth outer peripheral surface. The plurality of scraping concave surfaces Pb each open to the plane surface Sb, are recessed toward the rotation axis a, and are formed for scraping in the liquid metal LM. The plurality of scraping concave surfaces Pb are formed by denting the plane surface Sb and are arranged over the entire circumference on the outer peripheral surface S11 of the large-diameter portion 11 in the region A2. The scraping concave surfaces Pb are arranged to extend obliquely with respect to the circumferential direction. The scraping concave surface Pb includes a bottom surface Sc located on the rotation axis a side. In the direction along the rotation axis a, the plurality of scraping concave surfaces Pb are formed at intervals. However, the plurality of scraping concave surfaces Pb may be connected in the direction along the rotation axis a. Also, among the plurality of scraping concave surfaces Pb, the scraping concave surface Pb on the concave surface S11c side does not contact the concave surface S11c, but may contact the concave surface S11c. Similarly, among the plurality of scraping concave surfaces Pb, the scraping concave surface Pb on the concave surface S11e side does not contact the concave surface S11e, but may contact the concave surface S11e.

[0022] Each scraping concave surface Pa and each scraping concave surface Pb are formed by grooves having a depth of several tens of μm. The plurality of scraping concave surfaces Pa and the plurality of scraping concave surfaces Pb each form a herringbone pattern. For this reason, the radial bearing surfaces S11a and S11b are each an uneven surface, can scrape in the liquid metal LM, and can easily generate dynamic pressure by the liquid metal LM.

[0023] The concave surface S11c is formed in the large-diameter portion 11 in the region A3. The concave surface S11d is formed in the large-diameter portion 11 in the region A4. The concave surface S11e is formed in the large-diameter portion 11 in the region A5. The concave surface S11c, the concave surface S11d, and the concave surface S11e are positioned at intervals from each other in the direction along the rotation axis a and are offset from the radial bearing surface S11a and the radial bearing surface S11b.

[0024] The concave surface S11c is aligned with each of the radial bearing surfaces S11a and S11b in the direction along the rotation axis a. The concave surface S11d is aligned with the radial bearing surface S11a in the direction along the rotation axis a. The concave surface S11e is aligned with the radial bearing surface S11b in the direction along the rotation axis a. The concave surfaces S11c, S11d, and S11e are each a smooth outer peripheral surface and a plane surface. Note that the fixed shaft 10 may include a shelter and a plurality of through holes connected to the shelter. The shelter is an internal space of the fixed shaft 10 filled with an appropriate amount of liquid metal LM. The plurality of through holes includes one or more through holes opening to the concave surface S11c. The plurality of through holes further includes one or more through holes opening to the concave surface S11d. Alternatively, the plurality of through holes further includes one or more through holes opening to the concave surface S11e instead of the concave surface S11d. Alternatively, the plurality of through holes further includes one or more through holes opening to the concave surface S11d and one or more through holes opening to the concave surface S11e. The shelter and the plurality of through holes can form a circulation path for the liquid metal LM.

[0025] The concave surfaces S11c, S11d, and S11e are formed to be recessed compared to the radial bearing surfaces S11a and S11b. In other words, the concave surfaces S11c, S11d, and S11e are located on the rotation axis a side from the virtual extension surface Se of the plane surfaces Sa and Sb. More specifically, in the fixed shaft 10, the outer diameter DO2 of the section where the concave surfaces S11c, S11d, and S11e are formed is smaller than the minimum outer diameter DO1 of the outer diameters of the sections where the radial bearing surfaces S11a and S11b are formed.

[0026] In the direction perpendicular to the rotation axis a, the gap between the concave surfaces (concave surfaces S11c, S11d, and S11e) and the rotating body 20 is larger than the gap between the radial bearing surface S11a (plane surface Sa) and the rotating body 20, and larger than the gap between the radial bearing surface S11b (plane surface Sb) and the rotating body 20.

[0027] In the first embodiment, in the direction perpendicular to the rotation axis a, the gaps between the radial bearing surfaces S11a (plane surface Sa) and the rotating body 20 (inner peripheral surface S20a), and between the radial bearing surfaces S11b (plane surface Sb) and the rotating body 20 are each 10 to 40 μm. Note that the above gaps may be less than 10 μm. Also, in the direction perpendicular to the rotation axis a, the gaps between the concave surfaces (concave surfaces S11c, S11d, S11e) and the rotating body 20 are 0.1 to 3 mm.

[0028] The spaces between the concave surface S11c and the rotating body 20, between the concave surface S11d and the rotating body 20, and between the concave surface S11e and the rotating body 20 can function as reservoirs for accommodating the liquid metal LM. Since the liquid metal LM can be supplied from both adjacent sides to each of the radial bearing surfaces S11a, S11b, depletion of the liquid metal LM in the bearing gap can be suppressed.

[0029] Contact between the radial bearing surface of the fixed shaft 10 and the radial bearing surface of the rotating body 20 that occurs when the liquid metal LM becomes thin or disappears in the bearing gap can be suppressed. Furthermore, since generation of foreign matter in which at least one of the bearing surfaces is worn can be suppressed, contamination of the liquid metal LM by foreign matter can be suppressed.

[0030] The smaller diameter portion 13 is formed in a cylindrical shape and is located on one end side of the larger diameter portion 11. The smaller diameter portion 13 has an outer diameter DO4 that is smaller than the outer diameter DO3 of the larger diameter portion 11 (the outer diameter of the plane surface Sa or the outer diameter of the plane surface Sb). The smaller diameter portion 13 is located on the rotation axis a side from the thrust bearing surface S11j.

[0031] As shown in FIGS. 1 and 2, the rotating body 20 is configured to be rotatable about the fixed shaft 10. The rotating body 20 includes a rotating body main body 27, a seal component 90, and a cylindrical portion 25. The rotating body main body 27 and the seal component 90 are each formed of a metal such as an Fe alloy or an Mo alloy. The cylindrical portion 25 is formed of a metal such as copper (Cu) or a copper alloy.

[0032] The rotating body main body 27 includes a first cylinder 21 and a lid portion 29. The first cylinder 21 extends along the rotation axis a, is formed in a cylindrical shape, and is positioned surrounding the fixed shaft 10 (large-diameter portion 11). In the present first embodiment, the first cylinder 21 has a uniform inner diameter and outer diameter over its entire length. The first cylinder 21 has an inner peripheral surface S20a. The inner peripheral surface S20a includes a radial bearing surface S20b. The radial bearing surface S20b is located at least in regions A1 and A2. In the present first embodiment, the radial bearing surface S20b is a smooth inner peripheral surface and is a plane surface.

[0033] The lid portion 29 is formed in a disk shape, is integrally formed with the first cylinder 21, and liquid-tightly closes one end side of the first cylinder 21. The lid portion 29 includes a thrust bearing surface S20i that faces the thrust bearing surface S11i of the fixed shaft 10 in the direction along the rotation axis a.

[0034] As shown in FIGS. 2 and 4, the seal component 90 is fixed to the rotating body main body 27, is formed in a cylindrical shape, and is positioned surrounding the small-diameter portion 13. The seal component 90 has a cylindrical portion 91 and a flange portion 92. The cylindrical portion 91 includes an outer peripheral surface S90a, an inner peripheral surface S90b, a plurality of catching concave surfaces S90c, S90d, S90e, and a through hole h. Further, the seal component 90 includes a thrust bearing surface S20j that faces the thrust bearing surface S11j of the fixed shaft 10.

[0035] The clearance (clearance) between the inner peripheral surface S90b of the seal component 90 and the fixed shaft 10 (small-diameter portion 13) is set to a value that can maintain the rotation of the rotating body 20 and suppress the leakage of the liquid metal LM. From the above, the above clearance is small, and the seal component 90 (cylindrical portion 91) functions as a labyrinth seal ring. The above clearance between the inner peripheral surface S90b and the small-diameter portion 13 in the direction perpendicular to the rotation axis a is within the range of 50 to 300 μm.

[0036] The capturing concave surfaces S90c, S90d, and S90e each open to the inner peripheral surface S90b, are recessed toward the outer peripheral surface S90a side, and are configured to capture the liquid metal LM. The capturing concave surfaces S90c, S90d, and S90e are each formed over the entire circumference on the inner peripheral surface S90b of the cylindrical portion 91. In that case, the capturing concave surfaces S90c, S90d, and S90e are each an annular groove. The capturing concave surfaces S90c, S90d, and S90e each include a bottom surface located on the outer peripheral surface S90a side. For example, the capturing concave surface S90c includes the bottom surface Sd.

[0037] In the capturing concave surfaces S90c, S90d, and S90e, the capturing concave surface S90c is closest to the largest diameter portion 11, and the capturing concave surface S90e is farthest from the largest diameter portion 11. In the direction along the rotation axis line a, the capturing concave surface S90d is located between the capturing concave surface S90c and the capturing concave surface S90e. Note that the seal component 90 does not necessarily have to have a plurality of capturing concave surfaces S90c, S90d, and S90e. The seal component 90 only needs to have at least the capturing concave surface S90c.

[0038] The through hole h has a first opening OP1 that opens to the capturing concave surface S90c and a second opening OP2 that opens to a surface of the seal component 90 (cylindrical portion 91) other than the inner peripheral surface S90b and the capturing concave surfaces S90c, S90d, and S90e. The through hole h penetrates the seal component 90 (cylindrical portion 91) from the first opening OP1 to the second opening OP2. Here, let the gap between the radial bearing surface S11b of the fixed shaft 10 and the radial bearing surface S20b of the rotating body 20 be the first gap g1. Then, the through hole h connects the space surrounded by the capturing concave surface S90c to the first gap g1.

[0039] In the first embodiment, the first opening OP1 opens to the bottom surface Sd of the capture concave surface S90c. The second opening OP2 opens to the outer peripheral surface S90a. The outer peripheral surface S90a of the seal component 90 is surrounded with a gap by the inner peripheral surface S20a of the rotating body 20. Here, in the sliding bearing unit U, let the gap between the inner peripheral surface S20a and the outer peripheral surface S90a be the second gap g2. Then, the second gap g2 connects the through hole h to the first gap g1. In this embodiment, g2 > g1. The upper limit of the second gap g2 may be about 3 mm. Note that the second gap g2 can function as a reservoir for accommodating the liquid metal LM. Since the liquid metal LM can be supplied to each of the radial sliding bearing Bb and the thrust sliding bearing Bd from the side, depletion of the liquid metal LM in the bearing can be suppressed.

[0040] The flange portion 92 has an annular shape, surrounds the outer peripheral surface S90a over the entire circumference, and is continuously and integrally formed from the outer peripheral surface S90a. Among the seal component 90, the flange portion 92 is fixed to the first cylinder 21. For example, as in the first embodiment, in order to fix the relative position of the seal component 90 with respect to the first cylinder 21, an annular stepped portion may be formed on the outer peripheral side of the flange portion 92. The stepped portion of the flange portion 92 can be fitted to the first cylinder 21.

[0041] The seal component 90 is fixed to the rotating body main body 27 (the first cylinder 21) using a screw 120. The boundary between the first cylinder 21 and the seal component 90 is welded over the entire circumference. Since the welding portion 130 can liquid-tightly block the gap between the first cylinder 21 and the seal component 90, leakage of the liquid metal LM through the gap between the first cylinder 21 and the seal component 90 can be suppressed.

[0042] As shown in FIGS. 1 and 2, the cylindrical portion 25 is joined to the outer peripheral surface of the first cylinder 21 and is fixed to the first cylinder 21. Note that in FIG. 2, the illustration of the cylindrical portion 25 is omitted. When assembling into the sliding bearing unit U, the fixed shaft 10 is fitted inside the integrated unit of the first cylinder 21 and the lid portion 29. Then, in order to cover it with the seal component 90, the seal component 90 is fixed to the first cylinder 21.

[0043] In the present embodiment, the lid portion 29 is formed integrally with the first cylinder 21, but the lid portion 29 may be a lid physically independent from the first cylinder 21. The fixed shaft 10 and the rotating body 20 are provided with a gap therebetween in all the opposing regions. The large-diameter portion 11 is covered by the rotating body 20. The small-diameter portion 13 protrudes outside the rotating body 20. The fixed shaft 10 rotatably supports the rotating body 20.

[0044] The liquid metal LM is filled in the gap between the fixed shaft 10 (large-diameter portion 11) and the rotating body 20. As the material of the liquid metal LM, materials such as GaIn (gallium-indium) alloy and GaInSn (gallium-indium-tin) alloy can be used. The liquid metal LM is filled in an appropriate amount in the above gap. During the rotation operation of the rotating body 20, the liquid surface on the rotation axis a side of the liquid metal LM is located on the rotation axis a side with respect to the bottom surface Sc of the radial bearing surfaces S11a and S11b. Thereby, depletion of the liquid metal LM in the bearing gap can be suppressed.

[0045] The liquid metal LM forms a hydrodynamic sliding bearing together with the bearing surface of the fixed shaft 10 and the bearing surface of the rotating body 20. The liquid metal LM forms a hydrodynamic radial sliding bearing Ba together with the radial bearing surface S11a and the radial bearing surface S20b. The radial sliding bearing Ba is located in the region A1. The liquid metal LM forms a hydrodynamic radial sliding bearing Bb together with the radial bearing surface S11b and the radial bearing surface S20b. The radial sliding bearing Bb is located in the region A2. The liquid metal LM forms a hydrodynamic thrust sliding bearing Bc together with the thrust bearing surface S11i and the thrust bearing surface S20i. The liquid metal LM forms a hydrodynamic thrust sliding bearing Bd together with the thrust bearing surface S11j and the thrust bearing surface S20j.

[0046] As shown in FIG. 1, the anode target 50 is formed in an annular shape and is provided coaxially with the fixed shaft 10 and the rotating body 20. The anode target 50 has an anode target body 51 and a target layer 52 provided on a part of the outer surface of the anode target body 51. The anode target body 51 is formed in an annular shape. The anode target body 51 is fixed to the rotating body 20 and is integrated with the rotating body 20.

[0047] In the present embodiment, the anode target body 51 is indirectly fixed to the rotating body main body 27 (lid portion 29) via a cylindrical connecting portion 110 and is integrated with the connecting portion 110 and the rotating body main body 27. The connecting portion 110 is formed of a metal such as an Mo alloy. The connecting portion 110 functions as a heat insulating portion and makes it difficult to transfer heat from the anode target 50 to the rotating body 20.

[0048] The anode target body 51 is formed of Mo, W (tungsten), or an alloy using these. The target layer 52 has a target surface (electron collision surface) S52 where electrons emitted from the cathode collide. The melting point of the metal forming the target layer 52 is the same as or higher than the melting point of the metal forming the anode target body 51. In the present first embodiment, the anode target body 51 is formed of an Mo alloy and the target layer 52 is formed of a W alloy.

[0049] The anode target 50 is rotatable together with the rotating body 20. When electrons collide with the target surface S52 of the target layer 52, a focal point is formed on the target surface S52. Thereby, the anode target 50 emits X-rays from the focal point.

[0050] The cathode 60 is spaced from the target layer 52 of the anode target 50 and is disposed opposite to the anode target 50 (target layer 52). The cathode 60 is attached to the inner wall of the outer enclosure 70. The cathode 60 has a filament 61 as an electron emission source that emits electrons to irradiate the target layer 52.

[0051] The outer enclosure 70 is formed in a cylindrical shape. The outer enclosure 70 is formed of glass, ceramic, and metal. In the outer enclosure 70, the outer diameter of the portion facing the anode target 50 is larger than the outer diameter of the portion facing the cylindrical portion 25. The outer enclosure 70 has an opening 72. The outer enclosure 70 is sealed and houses the slide bearing unit U, the anode target 50, the connection portion 110, and the cathode 60. The inside of the outer enclosure 70 is maintained in a vacuum state (reduced pressure state).

[0052] The opening 72 is hermetically joined to the reduced diameter portion 13 of the fixed shaft 10 so as to maintain the airtight state of the outer enclosure 70. In this embodiment, the X-ray tube 1 employs a one-end support bearing structure. The outer enclosure 70 fixes the reduced diameter portion 13 of the fixed shaft 10. That is, the reduced diameter portion 13 functions as a cantilever support portion of the bearing.

[0053] The stator coil 2 is provided to face the outer peripheral surface of the rotating body 20, more specifically, the outer peripheral surface of the cylindrical portion 25, and surround the outer enclosure 70. The shape of the stator coil 2 is annular. The stator coil 2 generates a magnetic field applied to the cylindrical portion 25 (rotating body 20) to rotate the rotating body 20 and the anode target 50.

[0054] In the operating state of the X-ray tube device, since the stator coil 2 generates a magnetic field applied to the rotating body 20 (particularly the cylindrical portion 25), the rotating body 20 rotates. As a result, the anode target 50 also rotates together with the rotating body 20. Further, a current is applied to the cathode 60 and a negative voltage is applied, and a relatively positive voltage is applied to the anode target 50. The potentials of the rotating body 20 and the fixed shaft 10 are the same as the potential of the anode target 50. In the case of an anode-grounded X-ray tube, the anode target 50, the rotating body 20, the fixed shaft 10, and the metal parts of the outer enclosure (not shown) are at the ground potential.

[0055] As a result, a potential difference is generated between the cathode 60 and the anode target 50. The filament 61 emits electrons. These electrons are accelerated and collide with the target surface S52. Thereby, a focal spot is formed on the target surface S52, and the focal spot emits X-rays when colliding with electrons. The electrons (thermoelectrons) that have collided with the anode target 50 are converted into X-rays, and the rest are converted into thermal energy. Note that the electron emission source of the cathode 60 is not limited to a filament, and may be, for example, a flat emitter. Further, the X-ray tube 1 may be a cold cathode X-ray tube instead of a hot cathode X-ray tube.

[0056] As shown in FIGS. 2 and 4, in the operating state of the sliding bearing unit U, liquid metal LM may be extruded from the bearing (for example, the thrust sliding bearing Bd). For example, during the operation of the X-ray tube 1, due to the expansion of the gas existing between the fixed shaft 10 and the rotating body 20, a part of the liquid metal LM together with the gas may be instantaneously ejected outside the bearing from the gap between the fixed shaft 10 and the rotating body 20.

[0057] However, the fixed shaft 10 has a concave surface S11n. Even if the gas and the liquid metal LM are extruded from the bearing toward the smaller-diameter portion 13 side of the fixed shaft 10, the impact of the extruded gas and liquid metal LM can be absorbed by the concave surface S11n. Note that by forming the concave surface S11n on the fixed shaft 10, the thrust bearing surface S11j can be formed with high precision on the other end surface S11g.

[0058] Furthermore, the sliding bearing unit U is provided with a seal component 90. Therefore, even if the liquid metal LM is extruded between the inner peripheral surface S90b of the seal component 90 and the smaller-diameter portion 13, the plurality of capture concave surfaces S90c, S90d, S90e of the seal component 90 can capture the extruded liquid metal LM.

[0059] This can suppress the leakage of the liquid metal LM to the outside of the sliding bearing unit U. Since the scattering of the liquid metal LM into the outer vessel 70 is suppressed, the occurrence of discharge that may occur in the X-ray tube 1 can be suppressed. As a result, the product life of the X-ray tube 1 can be extended, and the product reliability of the X-ray tube 1 can be improved. And the X-ray tube 1 can continue to operate without losing its function.

[0060] The through hole h connects the space surrounded by the capture concave surface S90c to the first gap g1 and the third gap g3 via the second gap g2. Here, the third gap g3 is a gap between the large-diameter portion 11 and the seal component 90 in the direction along the rotation axis a. The through hole h constitutes a circulation path for the liquid metal LM together with the capture concave surface S90c, the second gap g2, etc. When the liquid metal LM is captured by the capture concave surface S90c, the liquid metal LM can be used for the bearing again. Therefore, the depletion of the liquid metal LM in the bearing can be suppressed.

[0061] Here, the dimensions of the fixed shaft 10 and the seal component 90 will be described. As shown in FIGS. 3 and 4, in the direction perpendicular to the rotation axis a, the longest distance from the rotation axis a to the first opening OP1 of the through hole h is defined as the first distance DI1, and the longest distance from the rotation axis a to the second opening OP2 of the through hole h is defined as the second distance DI2. The distance from the rotation axis a to the bottom surface Sc of each of the scraping concave surfaces Pa and Pb is defined as the third distance DI3.

[0062] The second distance DI2 is equal to or greater than the first distance DI1. Due to the centrifugal force, the liquid metal LM can be moved inside the through hole h from the first opening OP1 to the second opening OP2. Since the liquid metal LM can be moved from the inside of the capture concave surface S90c to the second gap g2 through the through hole h, the liquid metal LM can be circulated well.

[0063] The third distance DI3 is equal to or greater than the first distance DI1. Compared with the case where the third distance DI3 is less than the first distance DI1, the liquid metal LM inside the capture concave surface S90c can be better supplied to the scraping concave surfaces Pa and Pb. As a result, when the rotating body 20 rotates, the liquid surface on the rotating axis a side of the liquid metal LM becomes easier to be positioned on the rotating axis a side from the bottom surface Sc of each of the scraping concave surfaces Pa and Pb, and depletion of the liquid metal LM in the bearings (radial sliding bearings Ba and Bb) can be suppressed.

[0064] Furthermore, the third distance DI3 is equal to or greater than the second distance DI2. In the present embodiment, the third distance DI3 exceeds the second distance DI2. Compared with the case where the third distance DI3 is less than the second distance DI2, the liquid metal LM inside the through hole h can be better supplied to the scraping concave surfaces Pa and Pb. And depletion of the liquid metal LM in the bearings can be further suppressed. An X-ray tube apparatus including the X-ray tube 1 is formed as described above.

[0065] According to the X-ray tube apparatus according to the first embodiment configured as described above, the X-ray tube apparatus includes a rotating anode type X-ray tube 1. The X-ray tube 1 includes a sliding bearing unit U, an anode target 50, a cathode 60, an outer container 70, and the like. The sliding bearing unit U includes a fixed shaft 10, a rotating body 20 rotatable about the fixed shaft 10, a liquid metal LM, and the like. The fixed shaft 10 has a large-diameter portion 11 extending along the rotation axis a and including a radial bearing surface S11a and a radial bearing surface S11b on the outer peripheral surface S11, and a small-diameter portion 13 having an outer diameter DO4 smaller than the outer diameter DO3 of the large-diameter portion 11.

[0066] The rotating body 20 has a rotating body main body 27 and a seal component 90. The rotating body main body 27 extends along the rotation axis a and is formed in a cylindrical shape, surrounds the large-diameter portion 11, and includes a radial bearing surface S20b on the inner peripheral surface S20a. The seal component 90 is fixed to the rotating body main body 27, is formed in a cylindrical shape, surrounds the small-diameter portion 13, and includes an outer peripheral surface S90a, an inner peripheral surface S90b, capture concave surfaces S90c, S90d, S90e that open to the inner peripheral surface S90b and are recessed toward the outer peripheral surface S90a side to capture the liquid metal LM, and a through hole h.

[0067] The liquid metal LM is filled in the gap between the fixed shaft 10 and the rotating body 20. The liquid metal LM forms a hydrodynamic radial sliding bearing Ba together with the radial bearing surface S11a and the radial bearing surface S20b. The liquid metal LM forms a hydrodynamic radial sliding bearing Bb together with the radial bearing surface S11b and the radial bearing surface S20b.

[0068] The through hole h has a first opening OP1 that opens to the capture concave surface S90c and a second opening OP2 that opens to a surface of the seal component 90 other than the inner peripheral surface S90b and the capture concave surfaces S90c, S90d, S90e. The through hole h penetrates the seal component 90 from the first opening OP1 to the second opening OP2 and connects the space surrounded by the capture concave surface S90c to the first gap g1 between the radial bearing surface S11b and the radial bearing surface S20b.

[0069] The through hole h constitutes a circulation path for the liquid metal LM together with the capture concave surfaces S90c, etc. When the liquid metal LM is captured by the capture concave surface S90c, the liquid metal LM can be used for the bearing again. Therefore, depletion of the liquid metal LM in the bearing can be suppressed.

[0070] The first opening OP1 of the through hole h is formed at the position farthest from the rotation axis a in the capture concave surface S90c. Thereby, a situation where the liquid metal LM is left in the space surrounded by the capture concave surface S90c can be avoided. From the above, it is possible to obtain a sliding bearing unit U that can achieve good bearing operation over a long period of time and an X-ray tube 1 equipped with this sliding bearing unit.

[0071] (Modification Example 1 of the First Embodiment) Next, Modification Example 1 of the above-described first embodiment will be described. The X-ray tube 1 (sliding bearing unit U) is configured in the same manner as the first embodiment except for the configuration described in this Modification Example 1. FIG. 5 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to this Modification Example 1, and is a view showing the fixed shaft 10 and the rotating body 20.

[0072] As shown in FIG. 5, the third distance DI3 may be the same as the second distance DI2. In this Modification Example 1, g2 = g1. The liquid metal LM inside the through hole h can be satisfactorily supplied to the scraping concave surfaces Pa and Pb. And the depletion of the liquid metal LM in the bearing can be further suppressed. In addition, this Modification Example 1 can obtain the same effects as the first embodiment.

[0073] (Modification Example 2 of the First Embodiment) Next, Modification Example 2 of the above-described first embodiment will be described. The X-ray tube 1 (sliding bearing unit U) is configured in the same manner as the first embodiment except for the configuration described in this Modification Example 2. FIG. 6 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to this Modification Example 2, and is a view showing the fixed shaft 10 and the rotating body 20.

[0074] As shown in FIG. 6, for example, due to the fluidity of the liquid metal LM, the third distance DI3 may be less than the second distance DI2. g2 < g1. Also in this Modification Example 2, the through hole h constitutes a circulation path for the liquid metal LM together with the capture concave surface S90c and the like. Therefore, this Modification Example 2 can obtain the same effects as the first embodiment.

[0075] (Modification Example 3 of the First Embodiment) Next, a modification example 3 of the first embodiment will be described. The X-ray tube 1 (sliding bearing unit U) is configured in the same manner as the first embodiment except for the configuration described in this modification example 3. FIG. 7 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to this modification example 3, and is a view showing the fixed shaft 10 and the rotating body 20.

[0076] As shown in FIG. 7, the seal component 90 may have a reservoir concave surface S90f that opens to the outer peripheral surface S90a and is recessed toward the inner peripheral surface S90b. The reservoir concave surface S90f can accommodate the liquid metal LM. The second opening OP2 of the through-hole h opens to the reservoir concave surface S90f. The reservoir concave surface S90f and the second gap g2 connect the through-hole h to the first gap g1 and the third gap g3.

[0077] According to this modification example 3, in addition to the second gap g2, the liquid metal LM can also be accommodated in the space surrounded by the reservoir concave surface S90f. The depletion of the liquid metal LM in the bearing can be further suppressed. In addition, this modification example 3 can obtain the same effects as the first embodiment.

[0078] (Modification Example 4 of the First Embodiment) Next, a modification example 4 of the first embodiment will be described. The X-ray tube 1 (sliding bearing unit U) is configured in the same manner as the first embodiment except for the configuration described in this modification example 4. FIG. 8 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to this modification example 4, and is a view showing the fixed shaft 10 and the rotating body 20.

[0079] As shown in FIG. 8, the volume of the space surrounded by the capture concave surface S90c may gradually decrease as it approaches from the inner peripheral surface S90b side to the outer peripheral surface S90a side. It is possible to make it easier for the liquid metal LM captured by the capture concave surface S90c to move toward the first opening OP1 of the through-hole h. In addition, this modification example 4 can obtain the same effects as the first embodiment.

[0080] (Modification Example 5 of the First Embodiment) Next, a modification example 5 of the first embodiment will be described. The X-ray tube 1 (the sliding bearing unit U) is configured in the same manner as the first embodiment except for the configuration described in this modification example 5. FIG. 9 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to this modification example 5, and is a view showing the fixed shaft 10 and the rotating body 20.

[0081] As shown in FIG. 9, the seal component 90 may include a plurality of through holes h. Each through hole h has a first opening OP1 that opens to the bottom surface Sd of the capture concave surface S90c and a second opening OP2 that opens to the outer peripheral surface S90a of the seal component 90. In this modification example 5, the seal component 90 includes two through holes h, but may include three or more through holes h. Compared with the case where the seal component 90 has one through hole h, the liquid metal LM captured by the capture concave surface S90c can be more easily returned to the bearing side. In addition, this modification example 5 can obtain the same effects as the first embodiment.

[0082] (Second Embodiment) Next, an X-ray tube device according to the second embodiment will be described. The X-ray tube 1 is configured in the same manner as the first embodiment except for the configuration described in this second embodiment. FIG. 10 is a cross-sectional view showing the X-ray tube device according to this second embodiment. FIG. 11 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to this second embodiment, and is a view showing the fixed shaft 10 and the rotating body 20. Note that, in FIG. 11, the illustration of the cylindrical portion 25 is omitted.

[0083] As shown in FIG. 10, the fixed shaft 10 further includes a flange portion 17. The flange portion 17 is located on the outer peripheral surface side of the large-diameter portion 11 and is integrally formed with the large-diameter portion 11. In this embodiment, the flange portion 17 is continuously formed from the concave surface S11e of the large-diameter portion 11. In other words, the flange portion 17 and the large-diameter portion 11 are formed of the same material at the same time. However, the flange portion 17 and the large-diameter portion 11 that are physically independent of each other may be prepared, and the fixed shaft 10 may be formed by fixing the flange portion 17 to the large-diameter portion 11.

[0084] The rotating body 20 further includes a bearing member 26. The bearing member 26 is formed in a cylindrical shape. In the direction along the rotation axis line a, the bearing member 26 sandwiches the flange portion 17 together with the rotating body main body 27 (the first cylinder 21). For example, as in the present second embodiment, in order to fix the relative position of the bearing member 26 with respect to the first cylinder 21, an annular stepped portion may be formed on the outer peripheral side of the bearing member 26. The stepped portion of the bearing member 26 can be fitted to the first cylinder 21.

[0085] Similarly, in order to fix the relative position of the seal component 90 with respect to the first cylinder 21 and the bearing member 26, an annular stepped portion may be formed on the outer peripheral side of the flange portion 92. The stepped portion of the flange portion 92 can be fitted to the bearing member 26.

[0086] As shown in FIG. 11, the seal component 90 and the bearing member 26 are fixed to the rotating body main body 27 (the first cylinder 21) using a screw 120. The boundary between the first cylinder 21 and the bearing member 26 is welded over the entire circumference. Since the gap between the first cylinder 21 and the bearing member 26 can be hermetically closed by the welded portion 140, leakage of the liquid metal LM through the gap between the first cylinder 21 and the bearing member 26 can be suppressed. The boundary between the bearing member 26 and the seal component 90 is welded over the entire circumference. Since the gap between the bearing member 26 and the seal component 90 can be hermetically closed by the welded portion 150, leakage of the liquid metal LM through the gap between the bearing member 26 and the seal component 90 can be suppressed.

[0087] The flange portion 17 includes a thrust bearing surface S11i and a thrust bearing surface S11j located on the opposite side of the thrust bearing surface S11i in the direction along the rotation axis line a. The rotating body main body 27 (the first cylinder 21) includes a thrust bearing surface S20i facing the thrust bearing surface S11i of the flange portion 17 in the direction along the rotation axis line a. The bearing member 26 includes a thrust bearing surface S20j facing the thrust bearing surface S11j of the flange portion 17 in the direction along the rotation axis line a.

[0088] The liquid metal LM forms a hydrodynamic thrust sliding bearing Bc together with the thrust bearing surface S11i of the flange portion 17 and the thrust bearing surface S20i of the first cylinder 21. The liquid metal LM forms a hydrodynamic thrust sliding bearing Bd together with the thrust bearing surface S11j of the flange portion 17 and the thrust bearing surface S20j of the bearing member 26. Here, in the sliding bearing unit U, the second gap g2 is the gap between the outer peripheral surface S90a of the seal component 90 and the inner peripheral surface S26 of the bearing member 26.

[0089] The seal component 90 has an annular portion 91a. The annular portion 91a includes a first end surface 91b that is part of the capture concave surface S90c and a second end surface 91c that is located on the opposite side of the first end surface 91b in the direction along the rotation axis a and faces the large diameter portion 11. The first opening OP1 of the through hole h opens to at least one of the first end surface 91b and the bottom surface Sd. In the present embodiment, the first opening OP1 opens to the first end surface 91b. The second opening OP2 of the through hole h opens to the second end surface 91c. The through hole h penetrates the seal component 90 (annular portion 91a) from the first opening OP1 to the second opening OP2. In the present embodiment, the through hole h extends in the direction along the rotation axis a. The second distance DI2 is the same as the first distance DI1.

[0090] The through hole h connects the space surrounded by the capture concave surface S90c to the third gap g3. In the present embodiment, the large diameter portion 11 and the seal component 90 do not form a thrust sliding bearing together with the liquid metal LM. Therefore, the second opening OP2 of the through hole h can be directly connected to the third gap g3. The third gap g3 connects the through hole h to the first gap g1 and the like.

[0091] According to the X-ray tube device according to the second embodiment configured as described above, the X-ray tube 1 includes a sliding bearing unit U, an anode target 50, a cathode 60, an outer container 70, and the like. The sliding bearing unit U has a thrust sliding bearing at a position away from the third gap g3.

[0092] The through hole h has a second opening OP2 that leads directly to the third gap g3, and together with the capture concave surface S90c and the like, constitutes a circulation path for the liquid metal LM. When the liquid metal LM is captured by the capture concave surface S90c, the liquid metal LM can be used again for the bearing without adversely affecting the thrust sliding bearing.

[0093] From the above, in this second embodiment as well, the same effects as those of the first embodiment can be obtained. This second embodiment can provide a sliding bearing unit U capable of obtaining good bearing operation over a long period and an X-ray tube 1 equipped with this sliding bearing unit. Note that in this second embodiment, one or more techniques of the above-described modification example 1 (FIG. 5), modification example 2 (FIG. 6), modification example 3 (FIG. 7), modification example 4 (FIG. 8), and modification example 5 (FIG. 9) can be applied.

[0094] (Modification Example 1 of the Second Embodiment) Next, modification example 1 of the second embodiment will be described. The X-ray tube 1 (sliding bearing unit U) is configured in the same manner as the second embodiment except for the configuration described in this modification example 1. FIG. 12 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to this modification example 1, and is a view showing the fixed shaft 10 and the rotating body 20.

[0095] As shown in FIG. 12, the through hole h does not necessarily extend in the direction along the rotation axis a. The second distance DI2 may exceed the first distance DI1. That is, in the direction perpendicular to the rotation axis a, the longest distance from the rotation axis a to the second opening OP2 of the through hole h may exceed the longest distance from the rotation axis a to the first opening OP1 of the through hole h. Also in this modification example 1, the same effects as those of the second embodiment can be obtained.

[0096] (Third Embodiment) Next, an X-ray tube device according to a third embodiment will be described. The X-ray tube 1 is configured in the same manner as in the first embodiment except for the configuration described in this third embodiment. FIG. 13 is a cross-sectional view showing the X-ray tube device according to this third embodiment. FIG. 14 is an enlarged cross-sectional view showing a part of the X-ray tube 1 shown in FIG. 13. In FIG. 14, the illustration of the cylindrical portion 25 is omitted. FIG. 15 is a cross-sectional view showing a further enlarged part of the X-ray tube 1 shown in FIG. 14. FIG. 16 is a perspective view showing the second cylinder 22 shown in FIG. 13. FIG. 17 is a perspective view showing the first restricting member 23 shown in FIG. 13.

[0097] As shown in FIGS. 13 and 14, the fixed shaft 10 further includes a reduced-diameter portion 12. The reduced-diameter portion 12 is formed in a cylindrical shape with an outer diameter smaller than that of the large-diameter portion 11 and is located on the other end side of the large-diameter portion 11. The reduced-diameter portion 12 is located on the rotation axis a side from the thrust bearing surface S11i. When one end surface S11f is viewed from the direction along the rotation axis a, the concave surface S11m has an annular shape and is located between the thrust bearing surface S11i and the reduced-diameter portion 12.

[0098] The fixed shaft 10 includes a first bottom surface 10b1, a second bottom surface 10b2, and a heat transfer portion 10a. The second bottom surface 10b2 is located on the opposite side of the first bottom surface 10b1 in the direction along the rotation axis a. In this embodiment, the first bottom surface 10b1 is located at the reduced-diameter portion 12, and the second bottom surface 10b2 is located at the reduced-diameter portion 13.

[0099] The heat transfer portion 10a extends along the rotation axis a and opens to at least one of the first bottom surface 10b1 and the second bottom surface 10b2. In this embodiment, the heat transfer portion 10a is a heat transfer hole, opens to the second bottom surface 10b2, and does not open to the first bottom surface 10b1. The heat transfer portion 10a forms a flow path for the refrigerant. The heat transfer portion 10a transfers heat to the refrigerant flowing inside by forced convection. In this embodiment, the refrigerant is the coolant L. The cooling rate of the anode target 50 of the X-ray tube 1 can be improved by water cooling or oil cooling. However, the refrigerant may be air, and the cooling rate of the anode target 50 may be improved by air cooling. The heat transfer part 10a is preferably located at least in the region A1. Thereby, among the fixed shafts 10, the portions where the heat of the anode target 50 easily transfers can be cooled. Note that the region A1 is a region surrounded by the anode target 50.

[0100] The rotating body 20 includes a first cylinder 21, a second cylinder 22, a first restricting member 23, a second restricting member 24, a cylindrical portion 25, and a seal component 90. The first cylinder 21, the second cylinder 22, the first restricting member 23, and the second restricting member 24 are each formed of a metal such as an Fe alloy or a Mo alloy. In the rotating body 20, the first cylinder 21 is an outer cylinder located on the outside, and the second cylinder 22 is an inner cylinder located relatively on the inside.

[0101] As shown in FIGS. 13 to 16, the first cylinder 21 extends along the rotation axis a and is formed in a cylindrical shape, and is located surrounding the large-diameter portion 11. The second cylinder 22 extends along the rotation axis a and is formed in a cylindrical shape. The second cylinder 22 is located between the large-diameter portion 11 of the fixed shaft 10 and the first cylinder 21. In the present embodiment, the second cylinder 22 has a uniform inner diameter and outer diameter over the entire length. The inner diameter of the second cylinder 22 is larger than the outer diameter (outer diameter DO3) of the fixed shaft 10 (large-diameter portion 11), and the outer diameter of the second cylinder 22 is smaller than the inner diameter of the first cylinder 21.

[0102] The first cylinder 21 does not include a radial bearing surface S20b. The second cylinder 22 has an inner peripheral surface S20a including a radial bearing surface S20b. The radial bearing surface S20b is located at least in the regions A1 and A2. In the present embodiment, the radial bearing surface S20b is a smooth inner peripheral surface and is a plane surface. Due to the gaps between the second cylinder 22 and the fixed shaft 10 and between the second cylinder 22 and the first cylinder 21, the second cylinder 22 is movable to an eccentric position with respect to each of the fixed shaft 10 and the first cylinder 21. The rotation operation of the second cylinder 22 is restricted so as not to rotate relative to the first cylinder 21. Therefore, the rotation speed of the second cylinder 22 is the same as the rotation speed of the first cylinder 21.

[0103] The length of the second cylinder 22 in the direction along the rotation axis a is adjusted so as not to impair the functions of the radial sliding bearing and the thrust sliding bearing. The second cylinder 22 includes a first end face 22e1, a second end face 22e2, and one or more recesses 22r. The first end face 22e1 is located at an end of the second cylinder 22 in the direction along the rotation axis a. The second end face 22e2 is located at an end of the second cylinder 22 in the direction along the rotation axis a and is on the opposite side of the first end face 22e1. In the present embodiment, the second cylinder 22 has three recesses 22r. These recesses 22r are spaced apart from each other in the circumferential direction. Each recess 22r opens to the first end face 22e1 and is recessed in the direction along the rotation axis a. In the present embodiment, in the direction perpendicular to the rotation axis a, the gap between the first cylinder 21 and the second cylinder 22 is 10 to 40 μm.

[0104] As shown in FIGS. 13, 14, and 17, the first restricting member 23 has a first member 23a and one or more second members 23b. In the present embodiment, the first restricting member 23 has three second members 23b. The first member 23a has an annular shape and is fixed to the first cylinder 21. For example, as in the present embodiment, an annular stepped portion may be formed on the outer peripheral side of the first member 23a in order to fix the relative position of the first member 23a with respect to the first cylinder 21. The stepped portion of the first member 23a can be fitted into the first cylinder 21.

[0105] The first member 23a can be fixed to the first cylinder 21 by holding the first member 23a in a state of being pressed against the first cylinder 21 in the direction along the rotation axis a. Alternatively, the first member 23a may be fixed to the first cylinder 21 by welding or brazing, or the first member 23a may be removably fixed to the first cylinder 21 using screws.

[0106] The first member 23a faces the first end face 22e1 of the second cylinder 22. Thereby, the first member 23a can restrict the movement of the second cylinder 22 in the direction along the rotation axis a. The first member 23a includes a thrust bearing surface S20i that faces the thrust bearing surface S11i of the fixed shaft 10 in the direction along the rotation axis a. The thrust bearing surface S20i is located on the inner peripheral side of the first member 23a and has an annular shape. In FIG. 17, a dot pattern is applied to the thrust bearing surface S20i.

[0107] Each second member 23b protrudes from the first member 23a in the direction along the rotation axis a. The second members 23b are provided in one-to-one correspondence with the recesses 22r of the second cylinder 22. Each second member 23b is fitted into the recess 22r of the second cylinder 22. In the present embodiment, a sufficient gap for fitting is secured between the second member 23b and the recess 22r. Therefore, the second member 23b can be fitted into the recess 22r without using interference fit. Further, the gap between the second member 23b and the recess 22r can be used as a circulation path for the liquid metal LM.

[0108] The second member 23b is configured to restrict the rotation operation of the second cylinder 22 together with the recess 22r of the second cylinder 22. The second cylinder 22 is restricted from rotating with respect to the first cylinder 21.

[0109] The gap (clearance) between the first restricting member 23 (first member 23a) and the fixed shaft 10 (diameter-reduced portion 12) is set to a value that can maintain the rotation of the rotating body 20 and suppress the leakage of the liquid metal LM. From the above, the gap is small, and the first member 23a functions as a labyrinth seal ring.

[0110] As shown in FIGS. 13 to 15, the second restricting member 24 has an annular shape and is fixed to the first cylinder 21. In the present embodiment, the second restricting member 24 is integrally formed of the same material as the first cylinder 21. The second restricting member 24 faces the second end face 22e2 of the second cylinder 22. Thereby, the second restricting member 24 can restrict the movement of the second cylinder 22 in the direction along the rotation axis a. The second restricting member 24 and the first cylinder 21 function as a rotating body main body 27.

[0111] The seal component 90 is fixed to the rotating body main body 27 using a screw 120. The seal component 90 only needs to be fixed to the first cylinder 21 indirectly at least. The boundary between the rotating body main body 27 (the second restricting member 24) and the seal component 90 is welded over the entire circumference. Since the welding portion 130 can liquid-tightly block the gap between the second restricting member 24 and the seal component 90, leakage of the liquid metal LM through the gap between the second restricting member 24 and the seal component 90 can be suppressed.

[0112] When assembling into the sliding bearing unit U, the second cylinder 22 is inserted into the inside of the rotating body main body 27 which is an integral body of the first cylinder 21 and the second restricting member 24, and then the fixing shaft 10 is fitted to the second cylinder 22. Thereafter, in order to cover with the first restricting member 23, the first restricting member 23 is fixed to the first cylinder 21. Next, the seal component 90 is fixed to the rotating body main body 27.

[0113] In the present embodiment, the second restricting member 24 is formed integrally with the first cylinder 21, and the first restricting member 23 is physically independent from the first cylinder 21. However, the first restricting member 23 may be formed integrally with the first cylinder 21, and the second restricting member 24 may be physically independent from the first cylinder 21. Alternatively, the first restricting member 23 and the second restricting member 24 may each be physically independent from the first cylinder 21.

[0114] The fixed shaft 10 and the rotating body 20 are provided with a gap therebetween in the entire facing region. The large-diameter portion 11 is covered by the rotating body 20. The small-diameter portions 12 and 13 protrude outside the rotating body 20. The fixed shaft 10 rotatably supports the rotating body 20.

[0115] The liquid metal LM is filled in a plurality of gaps between the fixed shaft 10 (large-diameter portion 11), the first cylinder 21, the second cylinder 22, the first restricting member 23, the second restricting member 24, and the sealing component 90.

[0116] The gap between the first end face 22e1 (recess 22r) of the second cylinder 22 and the first restricting member 23 is connected to the gap between the fixed shaft 10 and the second cylinder 22 and the gap between the first cylinder 21 and the second cylinder 22, constituting a circulation path for the liquid metal LM. The gap between the second end face 22e2 of the second cylinder 22 and the second restricting member 24 is connected to the gap between the fixed shaft 10 and the second cylinder 22 and the gap between the first cylinder 21 and the second cylinder 22, constituting a circulation path for the liquid metal LM.

[0117] From the above, the liquid metal LM can move in a plurality of gaps between the fixed shaft 10 (large-diameter portion 11), the first cylinder 21, the second cylinder 22, the first restricting member 23, the second restricting member 24, and the sealing component 90.

[0118] Here, the materials of the fixed shaft 10, the first cylinder 21, the second cylinder 22, and the anode target body 51 will be described. The degree of freedom in selecting the materials of the first cylinder 21 and the second cylinder 22 is high. Therefore, the second cylinder 22 may be formed of the same material as the first cylinder 21 or a different material from the first cylinder 21.

[0119] The second cylinder 22 may be formed of the same material as the fixed shaft 10. The coefficient of thermal expansion of the second cylinder 22 and the coefficient of thermal expansion of the fixed shaft 10 can be made to coincide. For example, the variation in the radial bearing clearance can be suppressed. The first cylinder 21 may be formed of the same material as the fixed shaft 10. The coefficient of thermal expansion of the first cylinder 21 can be made to match that of the fixed shaft 10. For example, fluctuations in the thrust bearing clearance can be suppressed.

[0120] Note that the fixed shaft 10 may be formed of a material different from that of the first cylinder 21 and may also be formed of a material different from that of the second cylinder 22. For example, the fixed shaft 10 can be formed of a metal softer than the first cylinder 21, or the fixed shaft 10 can be formed of a metal softer than the second cylinder 22. Since the fixed shaft 10 is easier to process, the productivity of the fixed shaft 10 can be improved.

[0121] When the anode target body 51 is positioned at a distance from the outer peripheral surface of the first cylinder 21, the first cylinder 21 may be formed of the same material as the anode target body 51 or may be formed of a material different from that of the anode target body 51. When the anode target body 51 is connected to the outer peripheral surface of the first cylinder 21 and the anode target body 51 is fixed to the outer peripheral surface of the first cylinder 21, the first cylinder 21 is formed of the same material as the anode target body 51. The coefficient of thermal expansion of the anode target body 51 can be made to match that of the first cylinder 21. For example, it is possible to suppress a situation where the anode target body 51 comes off from the first cylinder 21 or at least one of the first cylinder 21 and the anode target body 51 is damaged.

[0122] The outer container 70 further has an opening 71. The opening 71 is hermetically joined to the reduced-diameter portion 12 of the fixed shaft 10 so as to maintain the airtight state of the outer container 70. In the present embodiment, the X-ray tube 1 employs a both-end support bearing structure. The outer container 70 fixes the reduced-diameter portions 12 and 13 of the fixed shaft 10. That is, the reduced-diameter portions 12 and 13 function as both-end support portions of the bearing.

[0123] The X-ray tube 1 includes a tube portion 40 provided inside a fixed shaft 10. The annular portion 16 is liquid-tightly joined to the second bottom surface 10b2 of the fixed shaft 10. The outer peripheral surface of the tube portion 40 is liquid-tightly joined to the opening of the annular portion 16 and extends outside the fixed shaft 10. The fixed shaft 10 forms a flow path for the coolant L together with the tube portion 40.

[0124] The tube portion 40 has an inlet 40a for taking in the coolant L therein and an outlet 40b for discharging the coolant L into the fixed shaft 10. The inlet 40a is located on the side extending outward from the second bottom surface 10b2 of the fixed shaft 10. Also, the outlet 40b is positioned with a gap from the bottom surface of the heat transfer portion (heat transfer hole) 10a in the direction along the rotation axis a.

[0125] On the outside of the outer container 70, an opening is formed in the fixed shaft 10, and a tube portion 45 is liquid-tightly joined to this opening. The tube portion 45 has an outlet 45a for taking out the coolant L to the outside. From the above, the coolant L circulating inside the X-ray tube 1 is taken in from the inlet 40a, passes through the inside of the tube portion 40, is discharged into the fixed shaft 10 from the outlet 40b, passes between the tube portion 40 and the fixed shaft 10, and is taken out from the outlet 45a of the tube portion 45. Note that the above coolant L may circulate in the reverse direction. In this case, the tube portion 45 forms an inlet for the coolant L, and the tube portion 40 forms an outlet for the coolant L.

[0126] FIG. 18 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to the present embodiment, and is a view showing a state until heat is input to the anode target 50 and the anode target 50 is cooled. As shown in FIG. 18, when heat is generated in the anode target 50, the anode target 50 thermally expands. Then, stress due to thermal expansion propagates to a portion integral with the anode target 50 or a portion firmly coupled to the anode target 50, and thermal deformation occurs. In the present embodiment, thermal deformation is likely to occur in the portion of the first cylinder 21 located in the region A1. For example, the portion of the first cylinder 21 located in the region A1 can expand outward in the radial direction by up to 100 μm at most.

[0127] However, in this embodiment, the second cylinder 22 is not physically fixed to the first cylinder 21. There is a gap between the second cylinder 22 and the first cylinder 21. Since the second cylinder 22 is not firmly coupled to the first cylinder 21, the stress due to the deformation of the first cylinder 21 is difficult to propagate to the second cylinder 22. The deformation of the second cylinder 22 caused by the thermal expansion of the anode target 50 can be suppressed, and the deterioration of the bearing performance can be suppressed.

[0128] Also, since the volume between the first cylinder 21 and the second cylinder 22 increases, the liquid metal LM gathers on the first cylinder 21 side due to centrifugal force, and a vacuum space is generated on the large-diameter portion 11 side. However, since the concave surfaces S11c, S11d, and S11e form a reservoir space for the liquid metal LM in advance, the liquid metal LM can be supplied to the gap between the first cylinder 21 and the second cylinder 22 and the bearing gap. From the above, the deterioration of the bearing performance can be suppressed. Also, the heat transfer from the anode target 50 to the large-diameter portion 11 side is not inhibited.

[0129] When fitting the second member 23b into the concave portion 22r, unlike this embodiment, interference fitting may be used to fit the second member 23b into the concave portion 22r. Also in this case, the deformation of the second cylinder 22 caused by the thermal expansion of the anode target 50 can be suppressed. This is because even if the anode target 50 thermally expands, the end portion of the first cylinder 21 is difficult to deform, and the second cylinder 22 is indirectly fixed to the end portion of the first cylinder 21 that is difficult to deform.

[0130] As described above, the relative position of the second cylinder 22 with respect to the first cylinder 21 may be fixed by interference fitting. In that case, the second cylinder 22 can be prevented from moving to an eccentric position with respect to the first cylinder 21. Note that the method of fixing the relative position of the second cylinder 22 with respect to the first cylinder 21 is not limited to interference fitting, and it may be performed by brazing, welding, using screws, or the like.

[0131] In the present embodiment, the end portion of the second cylinder 22 on the first end face 22e1 side is indirectly fixed to the first cylinder 21 via the first restricting member 23. However, in order to fix the relative position of the second cylinder 22 with respect to the first cylinder 21, it is not necessary to fix the end portion of the second cylinder 22 on the first end face 22e1 side. The end portion of the second cylinder 22 on the second end face 22e2 side may be indirectly fixed to the first cylinder 21 via the second restricting member 24. Since the heat transfer path from the anode target 50 is longer on the second end face 22e2 side than on the first end face 22e1, deformation of the second cylinder 22 can be further suppressed.

[0132] Alternatively, the end portion of the second cylinder 22 on the first end face 22e1 side may be indirectly fixed to the first cylinder 21 via the first restricting member 23, and the end portion of the second cylinder 22 on the second end face 22e2 side may be indirectly fixed to the first cylinder 21 via the second restricting member 24.

[0133] Here, the dimensions of the fixing shaft 10 and the seal component 90 will be described. As shown in FIGS. 3 and 15, the second distance DI2 is equal to or greater than the first distance DI1. In the present embodiment, the second distance DI2 exceeds the first distance DI1. The third distance DI3 is equal to or greater than the first distance DI1. In the present embodiment, the third distance DI3 exceeds the first distance DI1. Further, the third distance DI3 is equal to or greater than the second distance DI2. In the present embodiment, the third distance DI3 exceeds the second distance DI2.

[0134] Furthermore, here, in the sliding bearing unit U, the gap between the inner peripheral surface of the first cylinder 21 and the outer peripheral surface of the second cylinder 22 is defined as the fourth gap g4, and the gap between the inner peripheral surface of the first cylinder 21 and the outer peripheral surface S90a of the seal component 90 is defined as the fifth gap g5. The second gap g2 connects the through hole h to the first gap g1. The fifth gap g5 connects the through hole h to the fourth gap g4.

[0135] According to the X-ray tube device according to the third embodiment configured as described above, the X-ray tube device includes a rotating anode type X-ray tube 1. The X-ray tube 1 includes a sliding bearing unit U, and the sliding bearing unit U has a sealing component 90. The sealing component 90 of the present embodiment is formed in the same manner as the sealing component 90 of the first embodiment. Therefore, the present embodiment can obtain the same effects as the first embodiment.

[0136] The rotating body 20 has a first cylinder 21 and a second cylinder 22. The first cylinder 21 extends along the rotation axis a and is formed in a cylindrical shape, and is located surrounding the fixed shaft 10. The second cylinder 22 extends along the rotation axis a and is formed in a cylindrical shape, and is located between the fixed shaft 10 and the first cylinder 21, and includes a radial bearing surface S20b on the inner peripheral surface S20a, and the rotational movement is restricted so as not to rotate relative to the first cylinder 21. The second cylinder 22 may be movable to a position eccentric with respect to each of the fixed shaft 10 and the first cylinder 21.

[0137] The liquid metal LM is filled in a plurality of gaps between the fixed shaft 10, the first cylinder 21, and the second cylinder 22, and forms a hydrodynamic radial sliding bearing Ba together with the radial bearing surface S11a and the radial bearing surface S20b, and forms a hydrodynamic radial sliding bearing Bb together with the radial bearing surface S11b and the radial bearing surface S20b. The anode target 50 surrounds the outer peripheral surface of the first cylinder 21 and is fixed to the first cylinder 21.

[0138] The rotating body 20 has a double cylinder structure. The first cylinder 21 that is firmly coupled to the anode target 50 or is integrally formed with the anode target 50 and the second cylinder 22 that forms the radial sliding bearings Ba and Bb are physically independent. The second cylinder 22 is hardly affected by the thermal expansion of the anode target 50. According to the present embodiment, a sliding bearing unit U capable of obtaining good bearing operation and an X-ray tube 1 including this sliding bearing unit U can be obtained. In addition, in the third embodiment, one or more techniques of the above-described Modification 1 (FIG. 5), Modification 2 (FIG. 6), Modification 3 (FIG. 7), Modification 4 (FIG. 8), and Modification 5 (FIG. 9) can be applied.

[0139] (Modification 1 of the Third Embodiment) Next, Modification 1 of the third embodiment will be described. The X-ray tube 1 (the sliding bearing unit U) is configured in the same manner as in the third embodiment except for the configuration described in this Modification 1. FIG. 19 is an enlarged cross-sectional view showing a part of the X-ray tube 1 according to this Modification 1, and is a view showing the fixed shaft 10 and the rotating body 20.

[0140] As shown in FIG. 19, the rotating body 20 may be formed without the second restricting member 24. The seal component 90 is fixed to the first cylinder 21 using a screw 120. The seal component 90 faces the second end face 22e2 of the second cylinder 22. Thereby, the seal component 90 can restrict the movement of the second cylinder 22 in the direction along the rotation axis a.

[0141] In the direction perpendicular to the rotation axis a, the seal component 90 faces the first cylinder 21 but does not face the second cylinder 22. In the sliding bearing unit U, the gap between the second end face 22e2 of the second cylinder 22 and the second end face 91c of the seal component 90 is defined as the sixth gap g6. The fifth gap g5 connects the through hole h to the fourth gap g4. Further, the fifth gap g5 connects the through hole h to the first gap g1 via the sixth gap g6.

[0142] As shown in FIGS. 3 and 19, the third distance DI3 is equal to or greater than the first distance DI1. In this Modification 1, the third distance DI3 exceeds the first distance DI1. Also in this Modification 1, the same effects as those of the third embodiment can be obtained.

[0143] Although some embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

[0144] For example, the large-diameter portion 11 may be formed without the concave surface S11d called the running-up section. In this case, the radial bearing surface S11a may exist up to the end of the large-diameter portion 11. The large-diameter portion 11 may be formed without the concave surface S11e called the running-up section. In this case, the radial bearing surface S11b may exist up to the end of the large-diameter portion 11. The through-hole h opens into the capture concave surface S90c closest to the large-diameter portion 11, but may also open into capture concave surfaces other than the capture concave surface S90c. For example, the through-hole h may open into the capture concave surface S90d. Or, the seal component 90 may include both a through-hole h that opens into the capture concave surface S90c and a through-hole h that opens into the capture concave surface S90d. 。 The invention described in the original claims of the present application is appended below. [1] A fixed shaft having a large-diameter portion that extends along a rotation axis and includes a first radial bearing surface on a first outer peripheral surface, and a small-diameter portion that is formed integrally with the large-diameter portion and has a second outer diameter smaller than the first outer diameter of the large-diameter portion, a rotating body that is rotatable about the fixed shaft, and a lubricant, wherein the rotating body includes a rotating body main body that extends along the rotation axis and is formed in a cylindrical shape, surrounds the large-diameter portion, and includes a second radial bearing surface on a first inner peripheral surface, and a seal component that is fixed to the rotating body main body, is formed in a cylindrical shape, surrounds the small-diameter portion, and includes a second outer peripheral surface, a second inner peripheral surface, a capture concave surface that opens to the second inner peripheral surface and is recessed on the second outer peripheral surface side to capture the lubricant, and a through hole, the lubricant is filled in a gap between the fixed shaft and the rotating body, and forms a hydrodynamic radial sliding bearing together with the first radial bearing surface and the second radial bearing surface, The through hole has a first opening that opens to the capture concave surface and a second opening that opens to a surface of the seal component other than the second inner peripheral surface and the capture concave surface. The through hole penetrates the seal component from the first opening to the second opening, connecting the space surrounded by the capture concave surface to a first gap between the first radial bearing surface and the second radial bearing surface. Sliding bearing unit. [2] In a direction perpendicular to the rotation axis, when the longest distance from the rotation axis to the first opening is defined as a first distance and the longest distance from the rotation axis to the second opening is defined as a second distance, the second distance is equal to or greater than the first distance. The sliding bearing unit according to [1]. [3] A second gap is provided between the first inner peripheral surface and the second outer peripheral surface. The capture concave surface includes a bottom surface located on the second outer peripheral surface side. The first opening opens to the bottom surface of the capture concave surface. The second opening opens to the second outer peripheral surface. The second gap connects the through hole to the first gap. The sliding bearing unit according to [2]. [4] The large-diameter portion includes a first thrust bearing surface facing the seal component. The seal component includes a second thrust bearing surface facing the first thrust bearing surface. The lubricant forms a hydrodynamic thrust sliding bearing together with the first thrust bearing surface and the second thrust bearing surface. The sliding bearing unit according to [3]. [5] The first radial bearing surface has a smooth plane surface and a plurality of scraping concave surfaces that open to the plane surface and are recessed toward the rotation axis to scrape the lubricant. The scraping concave surface includes a bottom surface located on the rotation axis side. [2] In a direction perpendicular to the rotation axis, when the distance from the rotation axis to the bottom surface of the scraping concave surface is defined as a third distance, the third distance is equal to or greater than the second distance. The sliding bearing unit according to [2]. [6] The first radial bearing surface has a smooth plane surface and a plurality of scraping concave surfaces that open to the plane surface and are recessed toward the rotation axis to scrape the lubricant. The scraping concave surface includes a bottom surface located on the rotation axis side. [2] In a direction perpendicular to the rotation axis, when the distance from the rotation axis to the bottom surface of the scraping concave surface is defined as a third distance, the third distance is less than the second distance. The sliding bearing unit according to [2]. [7] A second gap is provided between the first inner peripheral surface and the second outer peripheral surface. The seal component further has a reservoir concave surface that opens to the second outer peripheral surface, is recessed toward the second inner peripheral surface side, and can accommodate the lubricant. The capture concave surface includes a bottom surface located on the second outer peripheral surface side. The first opening opens to the bottom surface of the capture concave surface. The second opening opens to the reservoir concave surface. The reservoir concave surface and the second gap connect the through hole to the first gap. The sliding bearing unit according to [2]. [8] The fixed shaft further has a flange portion that is located on the first outer peripheral surface side and is integrally formed with the large-diameter portion. The flange portion includes a first thrust bearing surface and a third thrust bearing surface located on the opposite side of the first thrust bearing surface in the direction along the rotation axis. The rotating body has a second thrust bearing surface facing the first thrust bearing surface and a fourth thrust bearing surface facing the third thrust bearing surface. The lubricant forms a hydrodynamic first thrust sliding bearing together with the first thrust bearing surface and the second thrust bearing surface. The lubricant forms a hydrodynamic second thrust sliding bearing together with the third thrust bearing surface and the fourth thrust bearing surface. In the direction along the rotation axis, there is a third gap between the large-diameter portion and the seal component. The capture concave surface includes a bottom surface located on the second outer peripheral surface side. The seal component has an annular portion including a first end surface that is a part of the capture concave surface and a second end surface that is located on the opposite side of the first end surface in the direction along the rotation axis and faces the large-diameter portion. The first opening opens to at least one of the first end surface and the bottom surface of the capture concave surface. The second opening opens to the second end surface. The third gap connects the through hole to the first gap. The sliding bearing unit according to [2]. [9] The rotating body main body has a first cylinder that extends along the rotation axis and is formed in a cylindrical shape and surrounds the large-diameter portion. has a second cylinder that extends along the rotation axis and is formed in a cylindrical shape, is located between the large-diameter portion and the first cylinder, has the first inner peripheral surface including the second radial bearing surface, and is restricted from rotating relative to the first cylinder. The seal component is fixed to the first cylinder. The lubricant is filled in a plurality of gaps between the fixed shaft, the first cylinder, and the second cylinder. The sliding bearing unit according to [2].

[10] The first radial bearing surface has a smooth plane surface and a plurality of scraping concave surfaces that open to the plane surface respectively, are recessed toward the rotation axis side, and scrape in the lubricant. The scraping concave surface includes a bottom surface located on the rotation axis side. When, in a direction perpendicular to the rotation axis, the distance from the rotation axis to the bottom surface of the scraping concave surface is defined as a third distance. The third distance is equal to or greater than the first distance. The sliding bearing unit according to [2].

[11] A fixed shaft that extends along the rotation axis and has a large-diameter portion including a first radial bearing surface on a first outer peripheral surface and a small-diameter portion that is integrally formed with the large-diameter portion and has a second outer diameter smaller than the first outer diameter of the large-diameter portion, a rotating body that is rotatable about the fixed shaft, and a lubricant. An anode target fixed to the rotating body. A cathode disposed opposite to the anode target. An outer casing that houses the sliding bearing unit, the anode target, and the cathode and fixes the fixed shaft. The rotating body is formed in a cylindrical shape extending along the rotation axis, located surrounding the large-diameter portion, and having a rotating body main body including a second radial bearing surface on a first inner peripheral surface. A seal component that is fixed to the rotating body main body, formed in a cylindrical shape, located surrounding the small-diameter portion, and includes a second outer peripheral surface, a second inner peripheral surface, a capture concave surface that opens to the second inner peripheral surface and is recessed toward the second outer peripheral surface side to capture the lubricant, and a through hole. The lubricant is filled in a gap between the fixed shaft and the rotating body, and together with the first radial bearing surface and the second radial bearing surface, forms a hydrodynamic radial sliding bearing. The through hole has a first opening that opens to the capture concave surface and a second opening that opens to a surface of the seal component other than the second inner peripheral surface and the capture concave surface, penetrates the seal component from the first opening to the second opening, and connects the space surrounded by the capture concave surface to a first gap between the first radial bearing surface and the second radial bearing surface. Rotating anode type X-ray tube.

[12] When, in a direction perpendicular to the rotation axis, the longest distance from the rotation axis to the first opening is defined as a first distance, and the longest distance from the rotation axis to the second opening is defined as a second distance. The second distance is equal to or greater than the first distance. The rotating anode type X-ray tube according to

[11] .

[13] There is a second gap between the first inner peripheral surface and the second outer peripheral surface. The capture concave surface includes a bottom surface located on the second outer peripheral surface side, the first opening opens to the bottom surface of the capture concave surface, the second opening opens to the second outer peripheral surface, the second gap connects the through hole to the first gap, The rotating anode type X-ray tube according to

[12] .

[14] The large diameter portion includes a first thrust bearing surface facing the seal component, the seal component includes a second thrust bearing surface facing the first thrust bearing surface, the lubricant forms a hydrodynamic thrust sliding bearing together with the first thrust bearing surface and the second thrust bearing surface, The rotating anode type X-ray tube according to

[13] .

[15] The first radial bearing surface has a smooth plane surface and a plurality of scraping concave surfaces that open to the plane surface and are recessed toward the rotation axis side for scraping the lubricant, the scraping concave surface includes a bottom surface located on the rotation axis side, when the distance from the rotation axis to the bottom surface of the scraping concave surface in a direction perpendicular to the rotation axis is defined as a third distance, the third distance is equal to or greater than the second distance, The rotating anode type X-ray tube according to

[12] .

[16] The first radial bearing surface has a smooth plane surface and a plurality of scraping concave surfaces that open to the plane surface and are recessed toward the rotation axis side for scraping the lubricant, the scraping concave surface includes a bottom surface located on the rotation axis side, when the distance from the rotation axis to the bottom surface of the scraping concave surface in a direction perpendicular to the rotation axis is defined as a third distance, the third distance is less than the second distance, The rotating anode type X-ray tube according to

[12] .

[17] There is a second gap between the first inner peripheral surface and the second outer peripheral surface, the seal component further has a reservoir concave surface that opens to the second outer peripheral surface and is recessed toward the first inner peripheral surface side for accommodating the lubricant, The capture concave surface includes a bottom surface located on the second outer peripheral surface side, the first opening opens to the bottom surface of the capture concave surface, the second opening opens to the reservoir concave surface, the reservoir concave surface and the second gap connect the through hole to the first gap, The rotating anode type X-ray tube according to

[12] .

[18] The fixed shaft further has a flange portion located on the first outer peripheral surface side and integrally formed with the large diameter portion, the flange portion includes a first thrust bearing surface and a third thrust bearing surface located on the opposite side of the first thrust bearing surface in the direction along the rotation axis, The rotating body has a second thrust bearing surface facing the first thrust bearing surface and a fourth thrust bearing surface facing the third thrust bearing surface. The lubricant forms a hydrodynamic first thrust sliding bearing together with the first thrust bearing surface and the second thrust bearing surface. The lubricant forms a hydrodynamic second thrust sliding bearing together with the third thrust bearing surface and the fourth thrust bearing surface. In the direction along the rotation axis, there is a third gap between the large-diameter portion and the seal component. The capture concave surface includes a bottom surface located on the second outer peripheral surface side. The seal component has an annular portion including a first end surface that is a part of the capture concave surface and a second end surface that is located on the opposite side of the first end surface in the direction along the rotation axis and faces the large-diameter portion. The first opening opens to at least one of the first end surface and the bottom surface of the capture concave surface. The second opening opens to the second end surface. The third gap connects the through hole to the first gap. The rotating anode type X-ray tube according to

[12] .

[19] The rotating body main body extends along the rotation axis and is formed in a cylindrical shape, and a first cylinder that surrounds the large-diameter portion and is located; extends along the rotation axis and is formed in a cylindrical shape, is located between the large-diameter portion and the first cylinder, has the first inner peripheral surface including the second radial bearing surface, and a second cylinder whose rotational movement is restricted so as not to rotate relative to the first cylinder. The seal component is fixed to the first cylinder. The lubricant is filled in a plurality of gaps between the fixed shaft, the first cylinder, and the second cylinder. The rotating anode type X-ray tube according to

[12] .

[20] The first radial bearing surface has a smooth plane surface and a plurality of scraping concave surfaces that open to the plane surface and are recessed toward the rotation axis side to scrape in the lubricant. The scraping concave surface includes a bottom surface located on the rotation axis side. When the distance from the rotation axis to the bottom surface of the scraping concave surface in the direction perpendicular to the rotation axis is defined as a third distance, The third distance is equal to or greater than the first distance. The rotating anode type X-ray tube according to

[12] .

Explanation of Symbols

[0145] 1…X-ray tube, U…bearing unit, 10…fixed shaft, 11…large diameter part, 12, 13…small diameter parts, 17…flange part, Sa, Sb…plane surfaces, Sc…bottom surface, Pa, Pb... scraping concave surface, S11... outer peripheral surface, 20... rotating body, 21... first cylinder, 22... second cylinder, 23... first limiting member, 24... second limiting member, 26... bearing member, S26... inner peripheral surface, S20a... inner peripheral surface, 50... anode target, 52... target layer, 51... anode target body, 60... cathode, 61... filament, 70... outer enclosure, 90... seal component, 91... cylindrical portion, 92... flange portion, S90a... outer peripheral surface, S90b... inner peripheral surface, S90c, S90d, S90e... capture concave surface, Sd... bottom surface, S90f... reservoir concave surface, 91a... annular portion, 91b... first end face, 91c... second end face, h... through hole, OP1... first opening, OP2... second opening, L... coolant, LM... liquid metal, Ba, Bb, Bc, Bd... bearings, S11a, S11b, S20b... radial bearing surfaces, S11i, S11j, S20i, S20j... thrust bearing surfaces, a... axis of rotation, DI1, DI2, DI3... distances, g1, g2, g3, g4, g5, g6... gaps.

Claims

1. a fixed shaft including a large diameter portion extending along a rotation axis and including a first radial bearing surface on a first outer circumferential surface, and a small diameter portion formed integrally with the large diameter portion and having a second outer diameter smaller than the first outer diameter of the large diameter portion; A rotor that is rotatable around the fixed shaft; A lubricant, The rotating body is a rotor main body extending along the rotation axis and formed in a cylindrical shape, the rotor main body being positioned to surround the large diameter portion and including a second radial bearing surface on a first inner circumferential surface; a sealing component that is fixed to the rotating body, is formed in a cylindrical shape, is positioned to surround the small diameter portion, and includes a second outer circumferential surface, a second inner circumferential surface, a capturing concave surface that opens into the second inner circumferential surface and is recessed toward the second outer circumferential surface so as to be capable of capturing the lubricant, and a through hole; the lubricant is filled in the gap between the fixed shaft and the rotating body, and forms a dynamic pressure type radial plain bearing together with the first radial bearing surface and the second radial bearing surface, the through hole has a first opening that opens into the capturing concave surface and a second opening that opens into a surface of the seal component other than the second inner circumferential surface and the capturing concave surface, passes through the seal component from the first opening to the second opening, and connects a space surrounded by the capturing concave surface to a first gap between the first radial bearing surface and the second radial bearing surface, In a direction perpendicular to the rotation axis, the longest distance from the rotation axis to the first opening is defined as a first distance, and the longest distance from the rotation axis to the second opening is defined as a second distance. the second distance is greater than or equal to the first distance, a second gap between the first inner circumferential surface and the second outer circumferential surface; The capturing concave surface includes a bottom surface located on the second outer circumferential surface side, the first opening opens into the bottom surface of the trapping concave surface; the second opening opens to the second outer circumferential surface, The second gap connects the through hole to the first gap. Plain bearing unit.

2. the large diameter portion includes a first thrust bearing surface facing the seal component, the seal component includes a second thrust bearing surface opposing the first thrust bearing surface, the lubricant forms a hydrodynamic thrust sliding bearing together with the first thrust bearing surface and the second thrust bearing surface; 2. The plain bearing unit according to claim 1.

3. the first radial bearing surface has a smooth plain surface and a plurality of raking concave surfaces each of which opens onto the plain surface and is recessed toward the rotation axis line to raking in the lubricant, The recessed surface includes a bottom surface located on the rotation axis side, In a direction perpendicular to the rotation axis, a distance from the rotation axis to the bottom surface of the concave scraping surface is defined as a third distance. The third distance is greater than or equal to the second distance.

2. The plain bearing unit according to claim 1.

4. the first radial bearing surface has a smooth plain surface and a plurality of raking concave surfaces each of which opens onto the plain surface and is recessed toward the rotation axis line to raking in the lubricant, The recessed surface includes a bottom surface located on the rotation axis side, In a direction perpendicular to the rotation axis, a distance from the rotation axis to the bottom surface of the concave scraping surface is defined as a third distance. the third distance is less than the second distance; 2. The plain bearing unit according to claim 1.

5. The rotating body includes: a first cylinder extending along the rotation axis and formed in a cylindrical shape, the first cylinder surrounding the large diameter portion; a second cylinder extending along the rotation axis and formed in a cylindrical shape, being located between the large diameter portion and the first cylinder, having the first inner circumferential surface including the second radial bearing surface, and having a rotational movement restricted so as not to rotate relative to the first cylinder, The sealing component is fixed to the first cylinder, The lubricant is filled in a plurality of gaps between the fixed shaft and the first cylinder and between the fixed shaft and the second cylinder.

2. The plain bearing unit according to claim 1.

6. the first radial bearing surface has a smooth plain surface and a plurality of raking concave surfaces each of which opens onto the plain surface and is recessed toward the rotation axis line to raking in the lubricant, The recessed surface includes a bottom surface located on the rotation axis side, In a direction perpendicular to the rotation axis, a distance from the rotation axis to the bottom surface of the concave scraping surface is defined as a third distance. The third distance is greater than or equal to the first distance.

2. The plain bearing unit according to claim 1.

7. a fixed shaft including a large diameter portion extending along a rotation axis and including a first radial bearing surface on a first outer circumferential surface, and a small diameter portion formed integrally with the large diameter portion and having a second outer diameter smaller than the first outer diameter of the large diameter portion; A rotor that is rotatable around the fixed shaft; A lubricant, The rotating body is a rotor main body extending along the rotation axis and formed in a cylindrical shape, the rotor main body being positioned to surround the large diameter portion and including a second radial bearing surface on a first inner circumferential surface; a sealing component that is fixed to the rotating body, is formed in a cylindrical shape, is positioned to surround the small diameter portion, and includes a second outer circumferential surface, a second inner circumferential surface, a capturing concave surface that opens into the second inner circumferential surface and is recessed toward the second outer circumferential surface so as to be capable of capturing the lubricant, and a through hole; the lubricant is filled in a gap between the fixed shaft and the rotating body, and forms a dynamic pressure type radial plain bearing together with the first radial bearing surface and the second radial bearing surface; the through hole has a first opening that opens into the capturing concave surface and a second opening that opens into a surface of the seal component other than the second inner circumferential surface and the capturing concave surface, the through hole penetrates the seal component from the first opening to the second opening, and connects a space surrounded by the capturing concave surface to a first gap between the first radial bearing surface and the second radial bearing surface, In a direction perpendicular to the rotation axis, the longest distance from the rotation axis to the first opening is defined as a first distance, and the longest distance from the rotation axis to the second opening is defined as a second distance. the second distance is greater than or equal to the first distance, a second gap between the first inner circumferential surface and the second outer circumferential surface; the seal component further includes a reservoir concave surface that opens to the second outer circumferential surface, is concave toward the second inner circumferential surface, and is capable of storing the lubricant; The capturing concave surface includes a bottom surface located on the second outer circumferential surface side, the first opening opens into the bottom surface of the trapping concave surface; the second opening opens into the reservoir concave surface; The reservoir concave surface and the second gap connect the through hole to the first gap. Plain bearing unit.

8. a fixed shaft including a large diameter portion extending along a rotation axis and including a first radial bearing surface on a first outer circumferential surface, and a small diameter portion formed integrally with the large diameter portion and having a second outer diameter smaller than the first outer diameter of the large diameter portion; A rotor that is rotatable around the fixed shaft; A lubricant, The rotating body is a rotor main body extending along the rotation axis and formed in a cylindrical shape, the rotor main body being positioned to surround the large diameter portion and including a second radial bearing surface on a first inner circumferential surface; a sealing component that is fixed to the rotating body, is formed in a cylindrical shape, is positioned to surround the small diameter portion, and includes a second outer circumferential surface, a second inner circumferential surface, a capturing concave surface that opens into the second inner circumferential surface and is recessed toward the second outer circumferential surface so as to be capable of capturing the lubricant, and a through hole; the lubricant is filled in a gap between the fixed shaft and the rotating body, and forms a dynamic pressure type radial plain bearing together with the first radial bearing surface and the second radial bearing surface; the through hole has a first opening that opens into the capturing concave surface and a second opening that opens into a surface of the seal component other than the second inner circumferential surface and the capturing concave surface, the through hole penetrates the seal component from the first opening to the second opening, and connects a space surrounded by the capturing concave surface to a first gap between the first radial bearing surface and the second radial bearing surface, In a direction perpendicular to the rotation axis, the longest distance from the rotation axis to the first opening is defined as a first distance, and the longest distance from the rotation axis to the second opening is defined as a second distance. the second distance is greater than or equal to the first distance, the first radial bearing surface has a smooth plain surface and a plurality of raking concave surfaces each of which opens onto the plain surface and is recessed toward the rotation axis line to raking in the lubricant, The recessed surface includes a bottom surface located on the rotation axis side, In a direction perpendicular to the rotation axis, a distance from the rotation axis to the bottom surface of the concave scraping surface is defined as a third distance. The third distance is greater than or equal to the second distance. Plain bearing unit.

9. a sliding bearing unit including: a fixed shaft having a large diameter portion extending along a rotation axis and including a first radial bearing surface on a first outer circumferential surface, and a small diameter portion formed integrally with the large diameter portion and having a second outer diameter smaller than the first outer diameter of the large diameter portion; a rotating body rotatable around the fixed shaft; and a lubricant; an anode target fixed to the rotor; A cathode disposed opposite the anode target; an enclosure that accommodates the sliding bearing unit, the anode target, and the cathode and fixes the fixed shaft; The rotating body is a rotor main body extending along the rotation axis and formed in a cylindrical shape, the rotor main body being positioned to surround the large diameter portion and including a second radial bearing surface on a first inner circumferential surface; a sealing component that is fixed to the rotating body, is formed in a cylindrical shape, is positioned to surround the small diameter portion, and includes a second outer circumferential surface, a second inner circumferential surface, a capturing concave surface that opens into the second inner circumferential surface and is recessed toward the second outer circumferential surface so as to be capable of capturing the lubricant, and a through hole; the lubricant is filled in a gap between the fixed shaft and the rotating body, and forms a dynamic pressure type radial plain bearing together with the first radial bearing surface and the second radial bearing surface; the through hole has a first opening that opens into the capturing concave surface and a second opening that opens into a surface of the seal component other than the second inner circumferential surface and the capturing concave surface, the through hole penetrates the seal component from the first opening to the second opening, and connects a space surrounded by the capturing concave surface to a first gap between the first radial bearing surface and the second radial bearing surface, In a direction perpendicular to the rotation axis, the longest distance from the rotation axis to the first opening is defined as a first distance, and the longest distance from the rotation axis to the second opening is defined as a second distance. the second distance is greater than or equal to the first distance, a second gap between the first inner circumferential surface and the second outer circumferential surface; The capturing concave surface includes a bottom surface located on the second outer circumferential surface side, the first opening opens into the bottom surface of the trapping concave surface; the second opening opens to the second outer circumferential surface, The second gap connects the through hole to the first gap. Rotating anode type X-ray tube.

10. the large diameter portion includes a first thrust bearing surface facing the seal component, the seal component includes a second thrust bearing surface opposing the first thrust bearing surface, the lubricant forms a hydrodynamic thrust sliding bearing together with the first thrust bearing surface and the second thrust bearing surface; 10. The rotating anode X-ray tube according to claim 9.

11. the first radial bearing surface has a smooth plain surface and a plurality of raking concave surfaces each of which opens onto the plain surface and is recessed toward the rotation axis line to raking in the lubricant, The recessed surface includes a bottom surface located on the rotation axis side, In a direction perpendicular to the rotation axis, a distance from the rotation axis to the bottom surface of the concave scraping surface is defined as a third distance. The third distance is greater than or equal to the second distance.

10. The rotating anode X-ray tube according to claim 9.

12. the first radial bearing surface has a smooth plain surface and a plurality of raking concave surfaces each of which opens onto the plain surface and is recessed toward the rotation axis line to raking in the lubricant, The recessed surface includes a bottom surface located on the rotation axis side, In a direction perpendicular to the rotation axis, a distance from the rotation axis to the bottom surface of the concave scraping surface is defined as a third distance. the third distance is less than the second distance; 10. The rotating anode X-ray tube according to claim 9.

13. The rotating body includes: a first cylinder extending along the rotation axis and formed in a cylindrical shape, the first cylinder surrounding the large diameter portion; a second cylinder extending along the rotation axis and formed in a cylindrical shape, being located between the large diameter portion and the first cylinder, having the first inner circumferential surface including the second radial bearing surface, and having a rotational movement restricted so as not to rotate relative to the first cylinder, The sealing component is fixed to the first cylinder, The lubricant is filled in a plurality of gaps between the fixed shaft and the first cylinder and between the fixed shaft and the second cylinder.

10. The rotating anode X-ray tube according to claim 9.

14. the first radial bearing surface has a smooth plain surface and a plurality of raking concave surfaces each of which opens onto the plain surface and is recessed toward the rotation axis line to raking in the lubricant, The recessed surface includes a bottom surface located on the rotation axis side, In a direction perpendicular to the rotation axis, a distance from the rotation axis to the bottom surface of the concave scraping surface is defined as a third distance. The third distance is greater than or equal to the first distance.

10. The rotating anode X-ray tube according to claim 9.

15. a sliding bearing unit including: a fixed shaft having a large diameter portion extending along a rotation axis and including a first radial bearing surface on a first outer circumferential surface, and a small diameter portion formed integrally with the large diameter portion and having a second outer diameter smaller than the first outer diameter of the large diameter portion; a rotating body rotatable around the fixed shaft; and a lubricant; an anode target fixed to the rotor; A cathode disposed opposite the anode target; an enclosure that accommodates the sliding bearing unit, the anode target, and the cathode and fixes the fixed shaft; The rotating body is a rotor main body extending along the rotation axis and formed in a cylindrical shape, the rotor main body being positioned to surround the large diameter portion and including a second radial bearing surface on a first inner circumferential surface; a sealing component that is fixed to the rotating body, is formed in a cylindrical shape, is positioned to surround the small diameter portion, and includes a second outer circumferential surface, a second inner circumferential surface, a capturing concave surface that opens into the second inner circumferential surface and is recessed toward the second outer circumferential surface so as to be capable of capturing the lubricant, and a through hole; the lubricant is filled in a gap between the fixed shaft and the rotating body, and forms a dynamic pressure type radial plain bearing together with the first radial bearing surface and the second radial bearing surface; the through hole has a first opening that opens into the capturing concave surface and a second opening that opens into a surface of the seal component other than the second inner circumferential surface and the capturing concave surface, the through hole penetrates the seal component from the first opening to the second opening, and connects a space surrounded by the capturing concave surface to a first gap between the first radial bearing surface and the second radial bearing surface, In a direction perpendicular to the rotation axis, the longest distance from the rotation axis to the first opening is defined as a first distance, and the longest distance from the rotation axis to the second opening is defined as a second distance. the second distance is greater than or equal to the first distance, a second gap between the first inner circumferential surface and the second outer circumferential surface; the seal component further includes a reservoir concave surface that opens to the second outer circumferential surface, is concave toward the second inner circumferential surface, and is capable of storing the lubricant; The capturing concave surface includes a bottom surface located on the second outer circumferential surface side, the first opening opens into the bottom surface of the trapping concave surface; the second opening opens into the reservoir concave surface; The reservoir concave surface and the second gap connect the through hole to the first gap. Rotating anode type X-ray tube.

16. a sliding bearing unit including: a fixed shaft having a large diameter portion extending along a rotation axis and including a first radial bearing surface on a first outer circumferential surface, and a small diameter portion formed integrally with the large diameter portion and having a second outer diameter smaller than the first outer diameter of the large diameter portion; a rotating body rotatable around the fixed shaft; and a lubricant; an anode target fixed to the rotor; A cathode disposed opposite the anode target; an enclosure that accommodates the sliding bearing unit, the anode target, and the cathode and fixes the fixed shaft; The rotating body is a rotor main body extending along the rotation axis and formed in a cylindrical shape, the rotor main body being positioned to surround the large diameter portion and including a second radial bearing surface on a first inner circumferential surface; a sealing component that is fixed to the rotating body, is formed in a cylindrical shape, is positioned to surround the small diameter portion, and includes a second outer circumferential surface, a second inner circumferential surface, a capturing concave surface that opens into the second inner circumferential surface and is recessed toward the second outer circumferential surface so as to be capable of capturing the lubricant, and a through hole; the lubricant is filled in a gap between the fixed shaft and the rotating body, and forms a dynamic pressure type radial plain bearing together with the first radial bearing surface and the second radial bearing surface; the through hole has a first opening that opens into the capturing concave surface and a second opening that opens into a surface of the seal component other than the second inner circumferential surface and the capturing concave surface, the through hole penetrates the seal component from the first opening to the second opening, and connects a space surrounded by the capturing concave surface to a first gap between the first radial bearing surface and the second radial bearing surface, In a direction perpendicular to the rotation axis, the longest distance from the rotation axis to the first opening is defined as a first distance, and the longest distance from the rotation axis to the second opening is defined as a second distance. the second distance is greater than or equal to the first distance, the first radial bearing surface has a smooth plain surface and a plurality of raking concave surfaces each of which opens onto the plain surface and is recessed toward the rotation axis line to raking in the lubricant, The recessed surface includes a bottom surface located on the rotation axis side, In a direction perpendicular to the rotation axis, a distance from the rotation axis to the bottom surface of the concave scraping surface is defined as a third distance. The third distance is greater than or equal to the second distance. Rotating anode type X-ray tube.

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