Rotating anode X-ray tube

Abstract

To provide a rotating anode type X-ray tube that can reduce frictional heat in the bearing section. [Solution] The rotating anode type X-ray tube 11 comprises a cathode 22 that emits electrons, an anode target 25 that generates X-rays when electrons generated from the cathode 22 strike it, a rotating body 24 that supports the anode target 25, a fixed shaft 23 that rotatably supports the rotating body 24, and a sliding bearing 34. The sliding bearing 34 has a bearing portion 36 that rotatably supports the rotating body 24 with respect to the fixed shaft 23, and a liquid metal material 37 interposed between the fixed shaft 23 and the rotating body 24. The bearing portion 36 has a bearing surface 39 provided on the fixed shaft 23 facing the inner surface of the rotating body 24. The bearing surface 39 is provided with a riblet structure 43 having a plurality of recesses 44 and protrusions 45 that extend along the circumferential direction of the bearing surface 39.

Description

Technical Field

[0001] Embodiments of the present invention relate to a rotating anode X-ray tube.

Background Art

[0002] In a rotating anode X-ray tube, by increasing the rotation speed of a rotating body that supports an anode target, the temperature of the focal plane of the anode target can be reduced, and more X-ray output can be obtained.

[0003] However, in proportion to the increase in the rotation speed of the rotating body, the friction in the bearing portion increases, and the generation of frictional heat also increases. When liquid metal is used as a lubricant for the bearing portion due to the increase in frictional heat, the metal contained in the liquid metal reacts with the metal constituting the bearing surface to form a product, and the product may inhibit the rotation of the rotating body. There is also a method of coating the bearing surface with a material having a low coefficient of friction to reduce the friction in the bearing portion, but the peeling of the coating becomes a problem. For these reasons, in a rotating anode X-ray tube, it is desired to reduce the friction in the bearing portion and the frictional heat.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a rotating anode X-ray tube capable of reducing frictional heat in the bearing portion.

Means for Solving the Problems

[0006] The rotating anode X-ray tube of this embodiment comprises an electron source that emits electrons, an anode target that generates X-rays when electrons generated from the electron source strike it, a rotating body that supports the anode target, a fixed shaft that rotatably supports the rotating body, and a sliding bearing. The sliding bearing has a bearing portion that rotatably supports the rotating body with respect to the fixed shaft, and a lubricant interposed between the fixed shaft and the rotating body. The bearing portion has a bearing surface provided on the fixed shaft opposite to the inner surface of the rotating body. At least one of the bearing surface and the inner surface of the rotating body opposite the bearing surface is provided with a riblet structure having a plurality of recesses and protrusions extending along the circumferential direction of the bearing portion. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view of a rotating anode type X-ray tube showing one embodiment. [Figure 2] This is a perspective view showing the riblet structure of the bearing section of the same rotating anode type X-ray tube. [Figure 3] This is a cross-sectional view of the bearing section of the same rotating anode type X-ray tube. [Modes for carrying out the invention]

[0008] One embodiment will be described below with reference to the drawings.

[0009] Figure 1 shows a rotating anode X-ray tube apparatus 10. The rotating anode X-ray tube apparatus 10 includes a rotating anode X-ray tube 11, a stator coil 12 that generates a magnetic field for rotating the rotating part of the rotating anode X-ray tube 11, and the like.

[0010] The rotating anode X-ray tube 11 comprises a vacuum enclosure 21, a cathode 22 which is an electron source, a fixed shaft 23, a rotating body 24, an anode target 25, and a rotor 26. The cathode 22, fixed shaft 23, rotating body 24, anode target 25, and rotor 26 are arranged inside the vacuum enclosure 21, while the stator coil 12 is located outside the vacuum enclosure 21.

[0011] The inside of the vacuum enclosure 21 is kept under vacuum. The vacuum enclosure 21 is provided with an X-ray transmission window through which X-rays generated by the anode target 25 are transmitted and output to the outside.

[0012] The cathode 22 emits electrons toward the anode target 25.

[0013] The fixed shaft 23 is provided in a substantially cylindrical shape, with its end fixed to the vacuum enclosure 21. The fixed shaft 23 has a fixed shaft portion 31 and support shaft portions 32 provided at both ends of the fixed shaft portion 31, which have a smaller diameter than the fixed shaft portion 31. Inside the fixed shaft 23, a cooling passage 30 is formed through which a refrigerant, which is a cooling liquid for cooling, passes. The refrigerant is circulated between the cooling passage 30 and the heat exchanger by a cooling device equipped with a heat exchanger (not shown).

[0014] The rotating body 24 is cylindrical and rotatably positioned around the fixed shaft portion 31 of the fixed shaft 23 with a gap 33 in between.

[0015] The rotating body 24 is rotatably supported with respect to the fixed shaft 23 by a bearing structure. The bearing structure includes a hydrodynamic sliding bearing 34, which is a radial bearing that rotatably supports the radial side of the rotating body 24 with respect to the fixed shaft 23, and thrust bearings 35 that rotatably support both axial ends of the rotating body 24 with respect to the fixed shaft 23.

[0016] The sliding bearing 34 comprises two bearing portions 36 spaced apart in the axial direction of the fixed shaft 23 and the rotating body 24, and a liquid metal 37, which is a lubricant, interposed in the gap between the fixed shaft 23 and the rotating body 24.

[0017] The bearing portion 36 includes a bearing forming portion 38 which is a large-diameter portion that protrudes from the outer circumferential surface of the fixed shaft portion 31 of the fixed shaft 23, a fixed-side bearing surface 39 provided on the outer circumferential surface of the bearing forming portion 38, and a rotating-side bearing surface 40 provided on the inner circumferential surface of the rotating body 24 that faces the fixed-side bearing surface 39.

[0018] A groove pattern 41 with a groove shape for holding the liquid metal 37 is formed on the bearing surface 39 of the fixed shaft 23. The groove pattern 41 has a plurality of grooves 42 arranged in parallel in the circumferential direction at positions spaced apart in the axial direction on both sides of the bearing surface 39, and inclined with respect to the axial and circumferential directions of the bearing surface 39. The groove pattern 41 is formed in a symmetrical or asymmetrical shape in the axial direction of the bearing surface 39.

[0019] On the bearing surface 39 of the fixed shaft 23, a riblet structure 43 is formed in the area other than the groove portion 42, extending along the circumferential direction of the bearing surface 39. As shown in Figures 2 and 3, the riblet structure 43 has recesses 44 in which the cross section along the axial direction of the bearing surface 39 is recessed in a substantially triangular shape (inverted triangular shape) and protrusions 45 that protrude in a substantially triangular shape. Multiple recesses 44 and multiple protrusions 45 are arranged alternately and at equal intervals in the axial direction of the bearing surface 39 and extend along the circumferential direction. The direction in which the recesses 44 and protrusions 45 extend along the circumferential direction of the bearing surface 39 corresponds to the direction in which the liquid metal 37 interposed between the bearing surface 39 and the bearing surface 40 of the rotating body 24 flows as the rotating body 24 rotates.

[0020] The recesses 44 and protrusions 45 are formed in the entire area of ​​the bearing surface 39, excluding the grooves 42. In the area between the grooves 42 on both sides in the axial direction of the bearing surface 39, the recesses 44 and protrusions 45 are continuously provided around the entire circumference. However, they may be provided only in a portion of the area of ​​the bearing surface 39, excluding the grooves 42, in which case it is preferable that they are provided in at least the area between the grooves 42 on both sides in the axial direction of the bearing surface 39.

[0021] The recesses 44 and protrusions 45 are provided on the bearing surface 39, for example, by laser processing or cutting. The recesses 44 and protrusions 45 are isosceles triangular in shape, and the vertex formed by the isosceles of the protrusion 45 is at an acute angle, but it may be curved or flat. The depth h1 of the recesses 44 from the bearing surface 39 is shallower than the depth h2 of the grooves 42 from the bearing surface 39. The pitch p of the recesses 44 and protrusions 45 in the axial direction of the bearing surface 39 is smaller than the distance w between the bearing surface 39 of the fixed shaft 23 and the bearing surface 40 of the rotating body 24.

[0022] The liquid metal 37 is enclosed in the gap 33 between the fixed shaft 23 and the rotating body 24, and a lubricating material having fluidity such as a gallium-indium (Galn) alloy or a gallium-indium-tin (GaInSn) alloy is used.

[0023] As shown in FIG. 1, the thrust bearing 35 has a disc-shaped thrust bearing member 46 attached to the end of the rotating body 24. The thrust bearing 35 is composed of the thrust bearing surface 47 of the thrust bearing member 46, the end face of the fixed shaft portion 31, and the liquid metal 37 interposed therebetween. The thrust bearing 35 is provided with a hole 48 through which the fixed shaft 23 is inserted at the center, and a thrust seal portion 49 for sealing the space between the peripheral surface of the fixed shaft 23 and the inner peripheral surface of the hole 48 is provided.

[0024] Further, the anode target 25 is provided in a disc shape and protrudes from the outer peripheral surface of the rotating body 24. On the facing surface of the anode target 25 with the cathode 22, an anode 50 for generating X-rays when electrons emitted from the cathode 22 collide is provided. The anode 50 is formed of a heavy metal with a high melting point, and as the heavy metal, for example, molybdenum (Mo), tungsten (W), or an alloy thereof is used.

[0025] Further, the rotor 26 is cylindrical and is provided around the rotating body 24.

[0026] Further, the stator coil 12 is disposed at a position facing the rotor 26 via the vacuum enclosure 21 and generates a magnetic field for rotating the rotor 26.

[0027] In the rotating anode type X-ray tube 11, the anode target 25 rotates together with the rotating body 24, and electrons emitted from the cathode 22 collide with the anode 50 of the anode target 25 to generate X-rays. The temperature of the anode target 25 rises due to the heat generated by the collision of electrons, and the heat of the anode target 25 is conducted from the rotating body 24 to the fixed shaft 23 through the sliding bearing 34 and is absorbed by the refrigerant flowing through the fixed shaft 23, thereby suppressing the temperature rise of the anode target 25.

[0028] When the rotating body 24 rotates, dynamic pressure is generated in the liquid metal 37 interposed between the bearing surface 39 of the fixed shaft 23 and the bearing surface 40 of the rotating body 24, supporting the rotating body 24 without contact with the fixed shaft 23. Multiple grooves 42 provided on the bearing surface 39 of the fixed shaft 23 allow the liquid metal 37 to be scraped between the bearing surface 39 of the fixed shaft 23 and the bearing surface 40 of the rotating body 24, making it easier to generate dynamic pressure from the liquid metal 37.

[0029] Incidentally, when the rotating body 24 is rotating, the frictional resistance at the bearing portion 36 increases in proportion to the increase in the rotational speed of the rotating body 24, and the generation of frictional heat also increases. Due to the increase in frictional heat, the metal contained in the liquid metal 37 reacts with the metal of the fixed shaft 23 and the rotating body 24 that constitute the bearing surfaces 39 and 40, generating products, and these products may hinder the rotation of the rotating body 24. The friction at the bearing portion 36 is due to turbulent flow generating vortices in the liquid metal 37 flowing between the bearing surface 39 and the bearing surface 40, and these vortices generate frictional resistance.

[0030] In the rotating anode type X-ray tube 11 of this embodiment, a riblet structure 43 is provided on the bearing surface 39 of the fixed shaft 23, having a plurality of recesses 44 and a plurality of protrusions 45 that are aligned axially and extend along the circumferential direction. Therefore, even if turbulent vortices are generated in the liquid metal 37 that flows circumferentially with the rotating body 24, the contact area between the vortices and the fixed shaft 23 is reduced, and the frictional resistance due to the vortices is reduced. This reduction in frictional resistance reduces the generation of frictional heat in the bearing portion 36, which reduces the obstruction of the rotation of the rotating body 24 caused by the above-mentioned products, and stabilizes the rotation of the rotating body 24.

[0031] Since the recesses 44 and protrusions 45 of the riblet structure 43 are provided with a triangular cross-section in the axial direction of the bearing surface 39, the frictional resistance against turbulent vortices in the liquid metal 37 flowing circumferentially with the rotating body 24 is highly effective in reducing frictional resistance, thereby further reducing the generation of frictional heat.

[0032] Since the recesses 44 and protrusions 45 are provided in areas of the bearing surface 39 other than the grooves 42, it is possible to ensure the generation of dynamic pressure by the grooves 42 while reducing the generation of frictional heat by reducing frictional resistance due to the riblet structure 43.

[0033] Since the depth h1 of the recess 44 from the bearing surface 39 is shallower than the depth h2 of the groove 42, it is possible to ensure the generation of dynamic pressure by the groove 42 while reducing the generation of frictional heat by reducing frictional resistance by the riblet structure 43.

[0034] Since the pitch p of the recesses 44 and protrusions 45 in the axial direction of the bearing surface 39 is smaller than the distance w between the bearing surface 39 and the rotating body 24, it is possible to reduce the vortices generated by turbulence in the liquid metal 37 that flows circumferentially with the rotating body 24, thereby reducing frictional resistance.

[0035] In this way, by providing a riblet structure 43 on the bearing surface 39 of the fixed shaft 23, frictional resistance is reduced, frictional heat in the bearing section 36 is reduced, and a rotating anode type X-ray tube 11 can be provided that stabilizes the rotation of the rotating body 24.

[0036] Furthermore, the riblet structure 43 is not limited to being provided on the bearing surface 39 of the fixed shaft 23, but may also be provided on the bearing surface 40 which is the inner surface of the rotating body 24, or it may be provided on both the bearing surface 39 of the fixed shaft 23 and the bearing surface 40 of the rotating body 24. In any case, frictional resistance is reduced, frictional heat in the bearing portion 36 is reduced, and the rotation of the rotating body 24 can be stabilized.

[0037] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0038] 11. Rotating anode type X-ray tube 22 The cathode, the source of electrons 23 Fixed axis 24. Rotating bodies 25 Anode Target 34 Plain bearings 36 Bearing section 37. Liquid metal as a lubricant 39 Bearing surface 42 Groove 43 Riblet structure 44 recess 45 Convex part

Claims

1. An electron source that emits electrons, An anode target that generates X-rays when electrons generated from the electron source strike it, A rotating body supporting the anode target, A fixed shaft that rotatably supports the aforementioned rotating body, A bearing portion that rotatably supports the rotating body with respect to the fixed shaft, and a sliding bearing having a lubricant interposed between the fixed shaft and the rotating body, A rotating anode type X-ray tube equipped with, The bearing portion has a bearing surface provided on the stationary shaft facing the inner surface of the rotating body, and at least one of the bearing surface and the inner surface of the rotating body facing the bearing surface is provided with a riblet structure having a plurality of recesses and protrusions extending along the circumferential direction of the bearing portion. A rotating anode type X-ray tube characterized by its features.

2. The recess and the protrusion are each provided with a triangular cross-section in the axial direction of the bearing portion. The rotating anode type X-ray tube according to feature 1.

3. The bearing surface has a plurality of grooves arranged in parallel in the circumferential direction, which are inclined with respect to the axial and circumferential directions of the bearing surface. The recess and the protrusion are provided in areas of the bearing surface other than the groove. The rotating anode type X-ray tube according to feature 1.

4. The depth of the recess from the bearing surface is shallower than the depth of the groove. The rotating anode type X-ray tube according to feature 3.

5. The pitch between the recess and the protrusion in the axial direction of the bearing portion is smaller than the distance between the bearing surface and the inner surface of the rotating body. The rotating anode type X-ray tube according to feature 1.

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