Sliding bearing unit and rotating anode type X-ray tube

Abstract

According to an embodiment of the present invention, a sliding bearing unit includes a fixed shaft, a rotating body, and liquid metal. The fixed shaft includes a radial bearing surface. The rotating body has a first cylinder and a second cylinder. The second cylinder includes another radial bearing surface, and its rotational movement is restricted to prevent rotation relative to the first cylinder. The liquid metal, together with the radial bearing surface and the other radial bearing surface, forms a hydrodynamic radial sliding bearing.

Description

Technical Field

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

[0002] In medical and industrial equipment that uses X-rays to diagnose subjects, X-ray tube devices are commonly used as the X-ray source. Rotating anode type X-ray tube devices, which incorporate rotating anode type X-ray tubes, are well-known as X-ray tube devices.

[0003] A rotating anode X-ray tube device includes a rotating anode X-ray tube that emits X-rays, a stator coil, and a housing that houses the rotating anode X-ray tube and the stator coil. The rotating anode X-ray tube includes a fixed shaft, an electron-generating cathode, an anode target, a rotating body, and peripheral components. The rotating body is cylindrical. The anode target is fixed to the rotating body. The gap between the fixed shaft and the rotating body is filled with lubricant. The rotating anode X-ray tube employs a hydrodynamic sliding bearing. The rotating body rotates together with the anode target under the influence of the magnetic field generated by the stator coil. Furthermore, electrons emitted from the cathode strike the anode target, emitting X-rays.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-60517

[0007] Patent Document 2: Japanese Patent Application Publication No. 2012-510136 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] This embodiment provides a sliding bearing unit capable of achieving good bearing operation and a rotating anode type X-ray tube having the sliding bearing unit.

[0010] Technical means for solving technical problems

[0011] One embodiment involves a sliding bearing unit.

[0012] The device includes a fixed shaft extending along a rotation axis and having a first radial bearing surface on its outer circumferential surface, a rotating body freely rotating about the fixed shaft, and a lubricant. The rotating body has: a first cylinder extending along the rotation axis to form a cylindrical shape and positioned around the fixed shaft; and a second cylinder extending along the rotation axis to form a cylindrical shape, located between the fixed shaft and the first cylinder, having a second radial bearing surface on its inner circumferential surface, and the rotational movement of the second cylinder is restricted to prevent relative rotation with respect to the first cylinder. The lubricant is filled in a plurality of gaps between the fixed shaft, the first cylinder, and the second cylinder, and together with the first radial bearing surface and the second radial bearing surface, forms a hydrodynamic radial sliding bearing.

[0013] Furthermore, one embodiment involves a rotating anode type X-ray tube.

[0014] The device includes: a sliding bearing unit comprising a fixed shaft extending along a rotation axis and having a first radial bearing surface on its outer circumferential surface; a rotating body freely rotatable about the fixed shaft; and a lubricant; an anode target; a cathode disposed opposite to the anode target; and an outer casing accommodating the sliding bearing unit, the anode target, and the cathode and fixing the fixed shaft. The rotating body has: a first cylinder extending along the rotation axis in a cylindrical shape and positioned around the fixed shaft; and a second cylinder extending along the rotation axis in a cylindrical shape, located between the fixed shaft and the first cylinder, and having a second radial bearing surface on its inner circumferential surface. The rotational movement of the second cylinder is restricted to prevent relative rotation with respect to the first cylinder. The lubricant is filled in a plurality of gaps between the fixed shaft, the first cylinder, and the second cylinder, and forms a hydrodynamic radial sliding bearing with the first radial bearing surface and the second radial bearing surface. The anode target surrounds the outer circumferential surface of the first cylinder and is fixed to the first cylinder. Attached Figure Description

[0015] Figure 1 This is an enlarged cross-sectional view showing a portion of the X-ray tube of Comparative Example 1, and a diagram showing the state of the anode target before it is heated.

[0016] Figure 2 This is an enlarged cross-sectional view showing a portion of the X-ray tube of Comparative Example 1 above, and is a diagram showing the state of the anode target from the time it is heated until it is cooled.

[0017] Figure 3 This is an enlarged cross-sectional view showing a portion of the X-ray tube of Comparative Example 2, and a diagram showing the state of the anode target from the time it is heated until it is cooled.

[0018] Figure 4This is an enlarged cross-sectional view showing a portion of the X-ray tube of Comparative Example 3, and a diagram showing the state of the anode target from the time it is heated until it is cooled.

[0019] Figure 5 This is a cross-sectional view showing the X-ray tube apparatus according to the first embodiment.

[0020] Figure 6 It is shown Figure 5 An enlarged cross-sectional view of a portion of the X-ray tube shown.

[0021] Figure 7 It is shown Figure 5 A side view of a portion of the fixed shaft shown.

[0022] Figure 8 It is shown Figure 5 The second cylinder is shown in a three-dimensional view.

[0023] Figure 9 It is shown Figure 5 A perspective view of the first limiting member shown.

[0024] Figure 10 This is an enlarged cross-sectional view showing a portion of the X-ray tube involved in the first embodiment described above, and is a diagram showing the state from when the anode target is heated until the anode target is cooled.

[0025] Figure 11 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to the second embodiment.

[0026] Figure 12 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to the third embodiment.

[0027] Figure 13 This is a cross-sectional view showing the X-ray tube apparatus according to the fourth embodiment.

[0028] Figure 14 It is shown Figure 13 The three-dimensional view of the fixed axis shown.

[0029] Figure 15 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to the fifth embodiment.

[0030] Figure 16 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to the sixth embodiment.

[0031] Figure 17 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to the seventh embodiment.

[0032] Figure 18This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to the eighth embodiment.

[0033] Figure 19 This is a cross-sectional view showing the X-ray tube apparatus according to the ninth embodiment.

[0034] Figure 20 This is a cross-sectional view showing the X-ray tube apparatus according to the tenth embodiment.

[0035] Figure 21 This is a cross-sectional view showing the X-ray tube apparatus according to the eleventh embodiment.

[0036] Figure 22 This is a cross-sectional view showing the X-ray tube apparatus according to the twelfth embodiment. Detailed Implementation

[0037] Hereinafter, various embodiments and comparative examples of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the disclosed content is merely an example, and appropriate modifications will readily conceive of by those skilled in the art while retaining the spirit of the invention; such modifications are also naturally included within the scope of the invention. In addition, for the purpose of clearer explanation using the drawings, the width, thickness, shape, etc., of various parts are sometimes schematically represented compared to the actual embodiment; however, this is merely an example and should not be used to limit the interpretation of the invention. Moreover, in this specification and the various drawings, the same reference numerals are used for the same parts that have appeared in existing drawings, and detailed descriptions are appropriately omitted.

[0038] In the following embodiments and comparative examples, a sliding bearing unit and a rotating anode type X-ray tube apparatus having the sliding bearing unit will be described. The rotating anode type X-ray tube apparatus includes rotating anode type X-ray tubes, etc. 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 peripheral components. The sliding bearing unit includes a fixed shaft, a rotating body, and liquid metal (metal lubricant) as a lubricant, and it uses a sliding bearing.

[0039] (Comparative Example 1)

[0040] First, the X-ray tube apparatus involved in Comparative Example 1 will be described. Figure 1 This is an enlarged cross-sectional view showing a portion of the X-ray tube 1 of Comparative Example 1, and a diagram showing the state of the anode target 50 before it is heated. Figure 2 This is an enlarged cross-sectional view showing a portion of the X-ray tube 1 of Comparative Example 1, and a diagram showing the state from when the anode target 50 is heated to when the anode target 50 is cooled.

[0041] like Figure 1 As shown, the X-ray tube apparatus involved in Comparative Example 1 includes an X-ray tube 1. The X-ray tube 1 includes a sliding bearing unit U, an anode target 50, etc. The sliding bearing unit U includes a fixed shaft 10, a rotating body 20, liquid metal LM, etc.

[0042] The fixed shaft 10 is cylindrical and extends along the rotation axis a. A radial bearing surface S11a is formed on the outer circumferential surface of the fixed shaft 10. The rotating body 20 is cylindrical and extends along the rotation axis a, surrounding the fixed shaft 10. A radial bearing surface S21a is formed on the inner circumferential surface of the rotating body 20. Liquid metal LM fills the gap between the fixed shaft 10 and the rotating body 20. The liquid metal LM, together with the radial bearing surfaces S11a and S21a, forms a hydrodynamic radial sliding bearing Ba.

[0043] The anode target 50 has an anode target body 51 and a target layer 52 disposed on a portion of the outer surface of the anode target body 51. The anode target body 51 has an annular shape, is connected to the outer peripheral surface of the rotating body 20, is fixed to the rotating body 20, and is integral with the rotating body 20. The target layer 52 has a target surface (electron impact surface) S52 that impacts electrons emitted from the cathode.

[0044] 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 metal parts of the anode target 50, the rotating body 20, the fixed shaft 10, and the peripheral devices (not shown) are at ground potential.

[0045] While the X-ray tube 1 is in operation, the rotating body 20 and the anode target 50 rotate together. Furthermore, the cathode irradiates the anode target 50 with an electron beam. Thus, the anode target 50 emits X-rays when struck by electrons.

[0046] When an electron beam continuously irradiates the target surface S52 for a certain period of time, heat accumulates in the anode target 50, and the temperature of the target surface S52 rises. There is a problem that when the heat generated by the electron beam exceeds the heat capacity of the anode target 50 and exceeds its allowable temperature, the target surface S52 begins to be damaged. This problem can be solved by increasing the size of the anode target 50 to increase its heat capacity. Enlarging the anode target 50 also improves the cooling rate of the anode target 50 through radiation.

[0047] However, the increase in the size of the anode target 50 leads to an increase in the size, weight, and cost of the X-ray tube 1. Therefore, increasing the size of the anode target 50 is not a preferred method to solve the above problems.

[0048] Therefore, by utilizing the liquid metal LM of the hydrodynamic sliding bearing (radial sliding bearing Ba) as the heat transfer medium, heat can be transferred from the anode target 50 to the fixed shaft 10, and the aforementioned heat can be transferred to the coolant flowing through the heat transfer section 10a formed inside the fixed shaft 10. The heat generated on the anode target 50 can be removed by the aforementioned cooling unit. To improve cooling performance, the heat transfer rate from the anode target 50 to the fixed shaft 10 must be increased. Therefore, the anode target 50 is firmly attached to the rotating body 20.

[0049] like Figure 2 As shown, when the anode target 50 reaches a high temperature, the stress generated by thermal expansion propagates to the rotating body 20. Furthermore, the heat (thermal energy) generated by electron impacts on the target surface S52 is sequentially transferred from the target surface S52 to the interior of the target layer 52, the portion of the anode target body 51 near the target layer 52, and the portion of the anode target body 51 near the rotating body 20, causing the temperature of the anode target 50 to rise. Therefore, in the X-ray tube 1 of Comparative Example 1, when the anode target body 51 reaches a high temperature, the gap (bearing clearance) between the radial bearing surface S11 and the radial bearing surface S21a changes (expands), leading to a decrease in the performance of the radial sliding bearing Ba.

[0050] (Comparative Example 2)

[0051] Next, the X-ray tube apparatus involved in Comparative Example 2 will be described. Figure 3 This is an enlarged cross-sectional view showing a portion of the X-ray tube 1 of Comparative Example 2, and a diagram showing the state of the anode target 50 from being heated to being cooled.

[0052] like Figure 3 As shown, the anode target body 51 has a circumferentially shaped cutout 51a. The cutout 51a is located at the root of the anode target body 51 and is positioned on the inner circumferential side of the target layer 52. When the cutout 51a is formed on the anode target body 51, compared to the case where the cutout 51a is not formed on the anode target body 51, the negative impact of the thermal expansion of the anode target 50 on the rotating body 20 can be reduced.

[0053] However, since the anode target 50 is firmly bonded to the rotating body 20, the negative impact of the thermal expansion of the anode target 50 on the rotating body 20 will remain to a large extent. Therefore, the X-ray tube 1 of Comparative Example 2 is the same as the X-ray tube 1 of Comparative Example 1, resulting in a decrease in the performance of the radial sliding bearing Ba.

[0054] (Comparative Example 3)

[0055] Next, the X-ray tube device involved in Comparative Example 3 will be described. Figure 4This is an enlarged cross-sectional view showing a portion of the X-ray tube 1 of Comparative Example 3, and a diagram showing the state of the anode target 50 from being heated to being cooled.

[0056] like Figure 4 As shown, the fixed shaft 10 is cylindrical. The anode target body 51 is held in place by the nut 31 of the X-ray tube 1 pressed against the protrusion 28 of the rotating body 20. Thus, the anode target 50 is fixed to the rotating body 20. The anode target body 51 is spaced apart from the rotating body 20 in the radial direction of the anode target 50. A protrusion 29 is formed on the outer peripheral surface of the rotating body 20. The protrusion 29 extends toward the anode target body 51 but does not contact the anode target body 51. The liquid contact material 32 of the X-ray tube 1 is sealed in the space surrounded by the rotating body 20, the anode target 50, and the nut 31. The heat generated on the anode target 50 can be transferred to the rotating body 20 via the liquid contact material 32.

[0057] As described above, the anode target body 51 is disposed at a distance from the rotating body 20 in the radial direction of the anode target 50. Therefore, while transferring the heat generated on the anode target 50 to the rotating body 20, the negative impact of the thermal expansion of the anode target 50 on the rotating body 20 can be mitigated.

[0058] However, the structure of the X-ray tube 1 in Comparative Example 3 becomes more complex. Furthermore, since the anode target 50 is firmly bonded to the rotating body 20, the negative impact of the thermal expansion of the anode target 50 on the rotating body 20 will remain to a large extent. Therefore, the X-ray tube 1 in Comparative Example 3, like the X-ray tubes 1 in Comparative Examples 1 and 2, will lead to a decrease in the performance of the radial sliding bearing Ba.

[0059] As can be seen from Comparative Examples 1 to 3 above, what is needed is an X-ray tube 1 in which the thermal expansion of the anode target 50 will not negatively affect the bearing. Furthermore, a sliding bearing unit U and an X-ray tube 1 capable of achieving good bearing operation are needed. Additionally, a small X-ray tube 1 with excellent thermal properties is required.

[0060] (First Implementation)

[0061] Next, the X-ray tube apparatus according to the first embodiment will be described. Figure 5 This is a cross-sectional view showing the X-ray tube apparatus according to the present first embodiment. Figure 6 It is shown Figure 5 An enlarged cross-sectional view of a portion of the X-ray tube 1 shown. Figure 7 It is shown Figure 5 A side view of a portion of the fixed shaft 10 shown. Figure 8 It is shown Figure 5 The third-dimensional view of the second cylinder 22 shown. Figure 9 It is shown Figure 5A perspective view of the first limiting member 23 shown.

[0062] like Figure 5 As shown, the X-ray tube device includes a rotating anode type X-ray tube 1, a stator coil 2 which serves as a coil for generating a magnetic field, etc. The X-ray tube 1 includes a sliding bearing unit U, an anode target 50, a cathode 60, and peripheral devices 70. The sliding bearing unit includes a fixed shaft 10, a rotating body (rotation shaft) 20, and liquid metal LM, which uses a sliding bearing.

[0063] like Figures 5 to 7 As shown, the fixed shaft 10 is cylindrical and extends along the rotation axis a, having radial bearing surfaces S11a and S11b formed on its outer circumferential surface and a heat transfer portion 10a. The fixed shaft 10 includes a large-diameter portion 11, a first small-diameter portion 12, and a second small-diameter portion 13. The large-diameter portion 11, the first small-diameter portion 12, and the second small-diameter portion 13 are formed coaxially as a single unit. The fixed shaft 10 is formed of a metal such as an Fe (iron) alloy or a Mo (molybdenum) alloy.

[0064] 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 A1 is surrounded by the anode target 50. Region A2 is spaced apart from region A1 along the rotation axis a. Region A3 is located between regions A1 and A2, adjacent to both regions A1 and A2. Region A4 is located from region A3 towards and across region A1, adjacent to region A1. Region A5 is located from region A3 towards and across region A2, adjacent to region A2.

[0065] The large-diameter portion 11 is cylindrical and has radial bearing surfaces S11a, S11b, S11c, S11d, and S11e located on its outer circumferential surface. Furthermore, the large-diameter portion 11 has a thrust bearing surface S11i at one end and a thrust bearing surface S11j at the other end. Radial bearing surfaces S11a and S11b are formed across the entire outer circumferential surface of the large-diameter portion 11. In the first embodiment, concave surfaces S11c, S11d, and S11e are formed across the entire outer circumferential surface of the large-diameter portion 11. However, concave surfaces S11c, S11d, and S11e may also be formed discontinuously in the circumferential direction.

[0066] Radial bearing surface S11a is formed in region A1 on the large-diameter portion 11. Radial bearing surface S11b is formed in region A2 on the large-diameter portion 11. Radial bearing surfaces S11a and S11b are provided at intervals along the rotation axis a.

[0067] The radial bearing surface S11a has a smooth surface Sa and multiple patterned portions Pa. The smooth surface Sa has a smooth outer peripheral surface. The multiple patterned portions Pa are formed by recesses in the smooth surface Sa and are arranged across the entire outer peripheral surface of the large-diameter portion 11 in region A1. Each patterned portion Pa is arranged in a diagonal manner relative to the circumference.

[0068] Multiple patterned portions Pa are formed at intervals along the direction of rotation axis a. However, the multiple patterned portions Pa may also be connected to each other in the direction of rotation axis a.

[0069] The radial bearing surface S11b has a smooth surface Sb and multiple patterned portions Pb. The smooth surface Sb has a smooth outer peripheral surface. The multiple patterned portions Pb are formed by recesses in the smooth surface Sb and are arranged across the entire outer peripheral surface of the large-diameter portion 11 in region A2. The patterned portions Pb are arranged in a diagonal manner relative to the circumferential direction.

[0070] Multiple patterned portions Pb are formed at intervals along the direction of rotation axis a. However, the multiple patterned portions Pb may also be connected to each other in the direction of rotation axis a.

[0071] Each patterned portion Pa and each patterned portion Pb are formed by grooves with a depth of tens of μm. Multiple patterned portions Pa and multiple patterned portions Pb respectively form Herringbone peak patterns. Therefore, the radial bearing surfaces S11a and S11b are concave and convex surfaces, which can sweep liquid metal LM into them and easily generate dynamic pressure caused by liquid metal LM.

[0072] Concave surface S11c is formed in region A3 of the large-diameter portion 11. Concave surface S11d is formed in region A4 of the large-diameter portion 11. Concave surface S11e is formed in region A5 of the large-diameter portion 11. Concave surfaces S11c, S11d, and S11e are spaced apart from each other in the direction along the rotation axis a, and are separate from the radial bearing surfaces S11a and S11b.

[0073] Concave surface S11c is parallel to radial bearing surfaces S11a and S11b along the direction of rotation axis a. Concave surface S11d is parallel to radial bearing surface S11a along the direction of rotation axis a. Concave surface S11e is parallel to radial bearing surface S11b along the direction of rotation axis a. Concave surfaces S11c, S11d, and S11e are smooth outer peripheral surfaces and are smooth surfaces.

[0074] Concave surfaces S11c, S11d, and S11e are formed by recesses compared to radial bearing surfaces S11a and S11b. In other words, concave surfaces S11c, S11d, and S11e are located on the rotation axis a side of the imaginary extension surface Se of radial bearing surfaces S11a and S11b. Furthermore, at the fixed shaft 10, the outer diameter DO2 of the interval forming concave surfaces S11c, S11d, and S11e is smaller than the smallest outer diameter DO1 among the outer diameters of the intervals forming radial bearing surfaces S11a and S11b.

[0075] In the direction perpendicular to the rotation axis a, the gap between the concave surface (concave surfaces S11c, S11d, S11e) and the second cylinder 22 is greater than the gap between the radial bearing surface S11a (smooth surface Sa) and the second cylinder 22, and is also greater than the gap between the radial bearing surface S11b (smooth surface Sb) and the second cylinder 22.

[0076] In this first embodiment, in the direction perpendicular to the rotation axis a, the gaps between the radial bearing surface S11a (smooth surface Sa) and the second cylinder 22, and the gaps between the radial bearing surface S11b (smooth surface Sb) and the second cylinder 22, are 10 to 40 μm, respectively. Alternatively, the gaps may be less than 10 μm. Furthermore, in the direction perpendicular to the rotation axis a, the gaps between the concave surfaces (concave surfaces S11c, S11d, and S11e) and the second cylinder 22 are 0.1 to 3 mm.

[0077] The spaces between the concave surface S11c and the second cylinder 22, the spaces between the concave surface S11d and the second cylinder 22, and the spaces between the concave surface S11e and the second cylinder 22 can be used as reservoirs for containing liquid metal LM. Since liquid metal LM can be supplied from both sides to each radial bearing surface S11a, S11b, the depletion of liquid metal LM in the bearing gap can be suppressed.

[0078] It can suppress contact between radial bearing surfaces when the liquid metal LM becomes thin or absent in the bearing clearance. Furthermore, since it can suppress the generation of foreign matter by the bearing surface itself due to at least one side being cut away, it can suppress the introduction of foreign matter into the liquid metal LM.

[0079] The first minor diameter portion 12 is formed as a cylinder with an outer diameter smaller than that of the major diameter portion 11, and is located at one end of the major diameter portion 11. The first minor diameter portion 12 is located on the rotation axis a side of the thrust bearing surface S11i.

[0080] The second minor diameter portion 13 is formed as a cylinder with an outer diameter smaller than that of the major diameter portion 11, and is located at the other end of the major diameter portion 11. The second minor diameter portion 13 is located on the rotation axis a side of the thrust bearing surface S11j.

[0081] 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 first embodiment, the first bottom surface 10b1 is located in the first small diameter portion 12, and the second bottom surface 10b2 is located in the second small diameter portion 13.

[0082] A heat transfer section 10a extends along the rotation axis a and opens on at least one of the first bottom surface 10b1 and the second bottom surface 10b2. In a first embodiment, the heat transfer section 10a is a heat transfer hole that opens on the second bottom surface 10b2. The heat transfer section 10a forms a refrigerant flow channel. The heat transfer section 10a transfers heat through forced convection of the refrigerant flowing inward. In this first embodiment, the refrigerant is a coolant L. Water cooling or oil cooling can improve the cooling rate of the anode target 50 of the X-ray tube 1. However, the refrigerant can also be air, and air cooling can also improve the cooling rate of the anode target 50.

[0083] The heat transfer section 10a is preferably located at least in region A1. This allows for the cooling of areas in the fixed shaft 10 where heat is easily transferred to the anode target 50.

[0084] like Figure 5 and Figure 6 As shown, the rotating body 20 is configured to rotate freely about a fixed axis 10. The rotating body 20 includes a first cylinder 21, a second cylinder 22, a first limiting member 23, a second limiting member 24, and a cylindrical portion 25. The first cylinder 21, the second cylinder 22, the first limiting member 23, and the second limiting member 24 are each formed of a metal such as an Fe alloy or a Mo alloy. The cylindrical portion 25 is formed of a metal such as copper (Cu) or a copper alloy. In the rotating body 20, the first cylinder 21 is the outer cylinder located on the outer side, while the second cylinder 22 is the inner cylinder located relatively on the inner side.

[0085] The first cylinder 21 extends along the axis of rotation a, forming a cylindrical shape, and is positioned around the fixed shaft 10 (large diameter portion 11). In this first embodiment, the first cylinder 21 has a uniform inner diameter and outer diameter along its entire length.

[0086] like Figure 5 , 6 As shown in Figure 8, 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 fixed shaft 10 and the first cylinder 21. In this first embodiment, the second cylinder 22 has a uniform inner diameter and outer diameter along its entire length. The inner diameter of the second cylinder 22 is larger than that of the fixed shaft 10 (large diameter portion 11), and the outer diameter of the second cylinder 22 is smaller than that of the inner diameter of the first cylinder 21.

[0087] The second cylinder 22 includes a radial bearing surface S22 on its inner circumferential surface. The radial bearing surface S22 is located at least in regions A1 and A2. In this first embodiment, the radial bearing surface S22 is a smooth inner circumferential surface. The second cylinder 22 can be moved to a position eccentric to the fixed shaft 10 and the first cylinder 21, respectively, by a size corresponding to the gap between the second cylinder 22 and the fixed shaft 10 and the gap between the second cylinder 22 and the first cylinder 21. The rotational movement of the second cylinder 22 is restricted to prevent relative rotation with respect to the first cylinder 21. Therefore, the rotational speed of the second cylinder 22 is the same as the rotational speed of the first cylinder 21.

[0088] Along the axis of rotation a, the length of the second cylinder 22 is shorter than the length of the large-diameter portion 11. The length of the second cylinder 22 is adjusted so as not to impair the function of the radial sliding bearing and the thrust sliding bearing, which will be described later.

[0089] 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 the end of the second cylinder 22 along the rotation axis a. The second end face 22e2 is located at the end of the second cylinder 22 along the rotation axis a, and is located on the opposite side of the first end face 22e1. In this 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 on the first end face 22e1 and is recessed along the rotation axis a.

[0090] In this first embodiment, the gap between the first cylinder 21 and the second cylinder 22 in a direction perpendicular to the rotation axis a ranges from 10 μm to 40 μm.

[0091] like Figure 5 , Figure 6 and Figure 9 As shown, the first limiting member 23 has a first member 23a and one or more second members 23b. In this embodiment, the first limiting 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 this first embodiment, in order to fix the relative position of the first member 23a with respect to the first cylinder 21, an annular stepped portion can be formed on the outer periphery of the first member 23a. The stepped portion of the first member 23a can be fitted to the first cylinder 21.

[0092] Along the axis of rotation a, the first component 23a can be fixed to the first cylinder 21 by keeping it pressed against the first cylinder 21. Alternatively, the first component 23a can be fixed to the first cylinder 21 by welding or brazing, or it can be detachably fixed to the first cylinder 21 using screws.

[0093] The first member 23a is opposite to the first end face 22e1 of the second cylinder 22. Therefore, 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 S23a that is opposite to the thrust bearing surface S11i of the fixed shaft 10 in the direction along the rotation axis a. The thrust bearing surface S23a is located on the inner circumferential side of the first member 23a and has an annular shape. Furthermore, in... Figure 9 The thrust bearing surface S23a has a dotted pattern.

[0094] Each second component 23b protrudes from the first component 23a in a direction along the rotation axis a. The second components 23b are provided in a one-to-one correspondence with the recesses 22r of the second cylinder 22. Each second component 23b is fitted into the recesses 22r of the second cylinder 22. In this first embodiment, sufficient clearance is ensured between the second components 23b and the recesses 22r for fitting. Therefore, the second components 23b can be fitted into the recesses 22r without an interference fit. Furthermore, the clearance between the second components 23b and the recesses 22r allows for the circulation path of the liquid metal LM.

[0095] The second member 23b is configured together with the recess 22r of the second cylinder 22 to restrict the rotational movement of the second cylinder 22. The second cylinder 22 is restricted so as not to rotate relative to the first cylinder 21.

[0096] The gap between the first limiting member 23 (first member 23a) and the fixed shaft 10 (first minor diameter portion 12) is set to a value that can maintain the rotation of the rotating body 20 and suppress leakage of liquid metal LM. As described above, the gap is very small, and the first member 23a functions as a labyrinth seal ring.

[0097] like Figure 5 and Figure 6 As shown, the second limiting member 24 has an annular shape and is fixed to the first cylinder 21. In the first embodiment, the second limiting member 24 is integrally formed from the same material as the first cylinder 21. The second limiting member 24 is opposite to the second end face 22e2 of the second cylinder 22. Thus, the second limiting member 24 can restrict the movement of the second cylinder 22 along the direction of the rotation axis a.

[0098] The second limiting member 24 includes a thrust bearing surface S24 that is opposite to the thrust bearing surface S11j of the fixed shaft 10 in the direction along the rotation axis a. The thrust bearing surface S24 is located on the inner circumferential side of the second limiting member 24 and has an annular shape.

[0099] Furthermore, the gap (clearance) between the second limiting member 24 and the fixed shaft 10 (second small diameter portion 13) is set to a value that can maintain the rotation of the rotating body 20 and suppress leakage of liquid metal LM. As described above, the gap is very small, and the second limiting member 24 functions as a labyrinth seal ring.

[0100] The cylindrical portion 25 engages with the outer peripheral surface of the first cylinder 21 and is fixed to the first cylinder 21. Additionally, in Figure 6 The illustration of the cylindrical part 25 is omitted in the text.

[0101] When assembling into the sliding bearing unit U, the second cylinder 22 is inserted into the integral part of the first cylinder 21 and the second limiting member 24, and then the fixed shaft 10 is assembled into the second cylinder 22. After that, the first limiting member 23 is covered, thus fixing the first limiting member 23 to the first cylinder 21.

[0102] In this embodiment, the second limiting member 24 is integrally formed with the first cylinder 21, and the first limiting member 23 is a cover that is physically independent of the first cylinder 21.

[0103] However, the first limiting member 23 may be integrally formed with the first cylinder 21, and the second limiting member 24 may be a cover that is physically independent of the first cylinder 21.

[0104] Alternatively, the first limiting member 23 and the second limiting member 24 may be caps that are physically independent of the first cylinder 21.

[0105] The fixed shaft 10 and the rotating body 20 are spaced apart from each other in completely opposite regions. The large-diameter portion 11 is covered by the rotating body 20. The first small-diameter portion 12 and the second small-diameter portion 13 protrude to the outside of the rotating body 20. The fixed shaft 10 supports the rotating body 20, allowing it to rotate.

[0106] Liquid metal LM is filled in multiple gaps between the fixed shaft 10 (large diameter portion 11), the first cylinder 21, the second cylinder 22, the first limiting member 23, and the second limiting member 24. The liquid metal LM can be made of materials such as GaIn alloy or GaInSn alloy. The liquid metal LM is appropriately filled in the aforementioned gaps. When the rotating body 20 rotates, the liquid surface on the rotation axis a side of the liquid metal LM is located on the rotation axis a side of the radial bearing surfaces S11a and S11b. This prevents the liquid metal LM in the bearing gaps from drying up.

[0107] The liquid metal LM, together with the bearing surface of the fixed shaft 10 and the bearing surface of the rotating body 20, forms a hydrodynamic sliding bearing.

[0108] Liquid metal LM, together with radial bearing surfaces S11a and S22, forms a hydrodynamic radial sliding bearing Ba. The radial sliding bearing Ba is located in region A1.

[0109] Liquid metal LM, together with radial bearing surfaces S11b and S22, forms a hydrodynamic radial sliding bearing Bb. Radial sliding bearing Bb is located in region A2.

[0110] Liquid metal LM, together with thrust bearing surface S11i and thrust bearing surface S23a, forms a hydrodynamic thrust sliding bearing Bc.

[0111] Liquid metal LM, together with thrust bearing surface S11j and thrust bearing surface S24, forms a hydrodynamic thrust sliding bearing Bd.

[0112] The gap between the first end face 22e1 (recess 22r) of the second cylinder 22 and the first limiting member 23 connects 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, forming the circulation path of the liquid metal LM. The gap between the second end face 22e2 of the second cylinder 22 and the second limiting member 24 connects 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, forming the circulation path of the liquid metal LM.

[0113] As described above, the liquid metal LM can move in multiple gaps between the fixed shaft 10 (large diameter portion 11), the first cylinder 21, the second cylinder 22, the first limiting member 23, and the second limiting member 24.

[0114] The anode target 50 is formed in an annular shape and is coaxially disposed with the fixed shaft 10, the first cylinder 21, and the second cylinder 22. The anode target 50 has an anode target body 51 and a target layer 52 disposed on a portion 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 surrounds the outer circumferential surface of the first cylinder 21 and is fixed to the first cylinder 21. In this embodiment, the anode target body 51 is fixed to the first cylinder 21.

[0115] The anode target body 51 is formed of molybdenum, tungsten, or alloys thereof. 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 this first embodiment, the anode target body 51 is formed of a molybdenum alloy, and the target layer 52 is formed of a tungsten alloy.

[0116] The anode target 50 can rotate together with the rotating body 20. When electrons strike the target surface S52 of the target layer 52, a focal point is formed on the target surface S52. As a result, the anode target 50 emits X-rays from the focal point.

[0117] 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.

[0118] The choice of materials for the first cylinder 21 and the second cylinder 22 is highly flexible. Therefore, the second cylinder 22 can be formed from the same material as the first cylinder 21, or it can be formed from a different material than the first cylinder 21.

[0119] The second cylinder 22 can be formed of the same material as the fixed shaft 10. The thermal expansion coefficient of the second cylinder 22 can be the same as that of the fixed shaft 10. For example, it can suppress variations in radial bearing clearance.

[0120] The first cylinder 21 can be formed of the same material as the fixed shaft 10. The thermal expansion coefficient of the first cylinder 21 can be the same as that of the fixed shaft 10. For example, it can suppress variations in the thrust bearing clearance.

[0121] Furthermore, the fixed shaft 10 can be formed from a material different from that of the first cylinder 21, or from a material different from that of the second cylinder 22. For example, the fixed shaft 10 can be formed from a metal softer than that of the first cylinder 21, or from a metal softer than that of the second cylinder 22. Since the fixed shaft 10 is easy to machine, its production efficiency can be improved.

[0122] When the anode target body 51 and the outer peripheral surface of the first cylinder 21 are spaced apart, the first cylinder 21 can be formed of the same material as the anode target body 51 or of a different material.

[0123] When the anode target body 51 is connected to and 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 thermal expansion coefficient of the anode target body 51 can be the same as that of the first cylinder 21. For example, it can prevent the anode target body 51 from detaching from the first cylinder 21, or prevent damage to at least one of the first cylinder 21 and the anode target body 51.

[0124] like Figure 5 As shown, the cathode 60 is spaced apart from the target layer 52 of the anode target 50 and is disposed opposite to the target layer 52. The cathode 60 is mounted on the inner wall of the peripheral device 70. The cathode 60 has a filament 61 that serves as an electron emission source, which emits electrons to irradiate the target layer 52.

[0125] The peripheral device 70 is cylindrical. It is made of glass, ceramic, or metal. In the peripheral device 70, the outer diameter of the portion opposite the anode target 50 is larger than the outer diameter of the portion opposite the cylindrical portion 25. The peripheral device 70 has openings 71 and 72. The peripheral device 70 is sealed and houses the sliding bearing unit U, the anode target 50, and the cathode 60. The interior of the peripheral device 70 is maintained in a vacuum state (depressurized state).

[0126] To maintain the airtightness of the peripheral device 70, the opening 71 is airtightly connected to one end of the fixed shaft 10 (first minor diameter portion 12), and the opening 72 is airtightly connected to the other end of the fixed shaft 10 (second minor diameter portion 13). In this embodiment, the X-ray tube 1 adopts a two-end support bearing structure. The peripheral device 70 fixes the first minor diameter portion 12 and the second minor diameter portion 13 of the fixed shaft 10. That is, the first minor diameter portion 12 and the second minor diameter portion 13 function as double-sided support portions of the bearing.

[0127] The X-ray tube 1 has a tube portion 40 disposed inside the fixed shaft 10. An 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 outward from the fixed shaft 10. The fixed shaft 10 and the tube portion 40 together form a flow channel for the coolant L.

[0128] The pipe section 40 has an inlet 40a for introducing coolant into its interior and an outlet 40b for discharging coolant L into the interior of the fixed shaft 10. The inlet 40a is located on a side extending outward from the second bottom surface 10b2 of the fixed shaft 10. Furthermore, the outlet 40b is provided with a gap between it and the bottom surface of the heat transfer section 10a in the direction along the rotation axis a.

[0129] An opening is formed on the fixed shaft 10 on the outer side of the peripheral device 70, and the tube section 45 is liquid-tightly connected to this opening. The tube section 45 has an outlet 45a for discharging coolant L to the outside. As described above, the coolant L circulating inside the X-ray tube 1 is introduced through the inlet 40a, passes through the interior of the tube section 40, is discharged from the outlet 40b into the interior of the fixed shaft 10, passes between the tube section 40 and the fixed shaft 10, and is discharged from the outlet 45a of the tube section 45. Alternatively, the coolant L can also circulate in the reverse direction. In this case, the tube section 45 forms the inlet of the coolant L, and the tube section 40 forms the outlet of the coolant L.

[0130] The stator coil 2 is positioned opposite the outer peripheral surface of the rotating body 20, and more specifically, opposite the outer peripheral surface of the cylindrical portion 25 and surrounding the outer side of the peripheral device 70. The stator coil 2 is ring-shaped. The stator coil 2 generates a magnetic field applied to the cylindrical portion 25 (rotating body 20) to cause the rotating body 20 and the anode target 50 to rotate.

[0131] As described above, an X-ray tube apparatus having an X-ray tube 1 is formed.

[0132] During the operation of the X-ray tube apparatus, the status coil 2 generates a magnetic field applied to the rotating body 20 (particularly the cylindrical section 25), thereby causing the second cylinder 22 to rotate. Consequently, the first cylinder 21 and the anode target 50 also rotate together. Furthermore, a current and a negative voltage are applied to the cathode 60, while a relatively positive voltage is applied to the anode target 50.

[0133] This creates a potential difference between the cathode 60 and the anode target 50. The filament 61 releases electrons. These electrons are accelerated and strike the target surface S52. This forms a focal point on the target surface S52, which emits X-rays upon being struck by electrons. Electrons striking the anode target 50 (hot electrons) are converted into X-rays, while the remainder are converted into heat energy. Furthermore, the electron emission source of the cathode 60 is not limited to a filament; it could also be a planar emitter, for example. Additionally, the X-ray tube 1 can be a cold cathode X-ray tube, rather than a hot cathode X-ray tube.

[0134] Figure 10 This is an enlarged cross-sectional view showing a portion of the X-ray tube 1 according to the first embodiment, and a diagram showing the state from when the anode target 50 is heated to when the anode target 50 is cooled.

[0135] like Figure 10 As shown, when heat is generated on the anode target 50, the anode target 50 undergoes thermal expansion. Consequently, the stress generated by this thermal expansion propagates to portions integral with or firmly bonded to the anode target 50, resulting in thermal deformation. In this first embodiment, the portion of the first cylinder 21 located in region A1 is prone to thermal deformation. For example, the portion of the first cylinder 21 located in region A1 can extend outward in the radial direction by a maximum of 100 μm.

[0136] However, in the first embodiment, the second cylinder 22 is not physically fixed to the first cylinder 21. A gap exists between the second cylinder 22 and the first cylinder 21. Since the second cylinder 22 is not firmly connected to the first cylinder 21, stress caused by deformation of the first cylinder 21 is difficult to propagate to the second cylinder 22. This suppresses deformation of the second cylinder 22 caused by the thermal expansion of the anode target 50 and also suppresses the degradation of bearing performance.

[0137] Furthermore, due to the increased volume between the first cylinder 21 and the second cylinder 22, the liquid metal LM accumulates on the side of the first cylinder 21 due to centrifugal force, thereby creating a vacuum space on the side of the large-diameter portion 11. However, since a reserved space for the liquid metal LM is pre-formed through the concave surfaces S11c, S11d, and S11e, the liquid metal LM can be supplied to the gap between the first cylinder 21 and the second cylinder 22 or the bearing gap. As described above, the degradation of bearing performance can be suppressed. In addition, heat transfer from the anode target 50 to the large-diameter portion 11 side is not hindered.

[0138] Alternatively, when fitting the second member 23b into the recess 22r, unlike the first embodiment, the second member 23b can be assembled into the recess 22r using an interference fit. In this case, deformation of the second cylinder 22 caused by the thermal expansion of the anode target 50 can also be suppressed. This is because even if the anode target 50 undergoes thermal expansion, the end of the first cylinder 21 is not easily deformed, and the second cylinder 22 is indirectly fixed to the less deformable end of the first cylinder 21.

[0139] As described above, the relative position of the second cylinder 22 with respect to the first cylinder 21 can be fixed by an interference fit. In this case, it is possible to prevent the second cylinder 22 from moving to a position eccentric to the first cylinder 21. In addition, the method of fixing the relative position of the second cylinder 22 with respect to the first cylinder 21 is not limited to an interference fit, but can also be performed by brazing, welding or using screws.

[0140] In this embodiment, the end of the second cylinder 22 on the first end face 22e1 side is indirectly fixed to the first cylinder 21 via the first limiting member 23.

[0141] However, since the relative position of the second cylinder 22 with respect to the first cylinder 21 is fixed, the end of the second cylinder 22 on the first end face 22e1 side may not be fixed. The end of the second cylinder 22 on the second end face 22e2 side may be indirectly fixed to the first cylinder 21 via the second limiting member 24. The heat transfer path from the anode target 50 from the first end face 22e1 to the second end face 22e2 is long, thus further suppressing the deformation of the second cylinder 22.

[0142] Alternatively, the end of the second cylinder 22 on the first end face 22e1 side can be indirectly fixed to the first cylinder 21 via the first limiting member 23, and the end of the second cylinder 22 on the second end face 22e2 side can be indirectly fixed to the first cylinder 21 via the second limiting member 24.

[0143] According to the first embodiment of the X-ray tube apparatus 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, and an outer peripheral device 70. The sliding bearing unit U includes a fixed shaft 10, a rotating body 20 that can rotate freely around the fixed shaft 10, and liquid metal LM. The fixed shaft 10 includes radial bearing surfaces S11a and S11b extending along the rotation axis a and having radial bearing surfaces on its outer peripheral surface.

[0144] The rotating body 20 has a first cylinder 21 and a second cylinder 22. The first cylinder 21 extends along the rotation axis a, is cylindrical, and is disposed around the fixed shaft 10. The second cylinder 22 extends along the rotation axis a, is cylindrical, and is located between the fixed shaft 10 and the first cylinder 21. Its inner circumferential surface includes a radial bearing surface S22, and its rotational movement is restricted to prevent rotation relative to the first cylinder 21. The second cylinder 22 can be moved to positions eccentric to both the fixed shaft 10 and the first cylinder 21.

[0145] Liquid metal LM fills multiple gaps between the fixed shaft 10, the first cylinder 21, and the second cylinder 22, and together with the radial bearing surfaces S11a and S22, forms a hydrodynamic radial sliding bearing Ba, and together with the radial bearing surfaces S11b and S22, forms a hydrodynamic radial sliding bearing Bb. An anode target 50 surrounds the outer circumferential surface of the first cylinder 21 and is fixed to the first cylinder 21.

[0146] The rotating body 20 has a double-cylinder structure. The first cylinder 21, which is firmly bonded to or integrally formed with the anode target 50, and the second cylinder 22, which forms the radial sliding bearings Ba and Bb, are physically independent. The second cylinder 22 is less susceptible to the negative effects of the thermal expansion of the anode target 50.

[0147] According to the X-ray tube apparatus of the first embodiment configured as described above, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 equipped with the sliding bearing unit U can be obtained.

[0148] (Second Implementation)

[0149] Next, the X-ray tube apparatus according to the second embodiment will be described. The X-ray tube 1 is configured in the same way as in the first embodiment, except for the structure described in this second embodiment. Figure 11 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to this second embodiment.

[0150] like Figure 11As shown, the second cylinder 22 also has a plurality of circulation holes h22. Each circulation hole h22 extends from the outer peripheral surface of the second cylinder 22 to the inner peripheral surface. In this second embodiment, each circulation hole h22 extends linearly in a direction perpendicular to the rotation axis a. The positions of each circulation hole h22 are offset from the region A1 opposite to the radial bearing surface S11a and the radial bearing surface S22, and the region A2 opposite to the radial bearing surface S11b and the radial bearing surface S22.

[0151] Multiple circulation holes h22 are located in regions A3, A4, and A5, and are arranged at intervals along the direction of the rotation axis a. Alternatively, although not shown, multiple circulation holes h22 may also be arranged at intervals circumferentially in their respective regions A3, A4, and A5.

[0152] Multiple circulation holes h22 are 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, thus forming a circulation path for the liquid metal LM. Therefore, the liquid metal LM can move rapidly between the two gaps mentioned above.

[0153] According to the second embodiment configured as described above, the same effects as the first embodiment can be obtained. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0154] (Third Implementation)

[0155] Next, the X-ray tube apparatus according to the third embodiment will be described. The X-ray tube 1 is configured in the same way as in the second embodiment, except for the structure described in this third embodiment. Figure 12 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to this third embodiment.

[0156] like Figure 12 As shown, the fixed shaft 10 (large diameter portion 11) also has a plurality of grooves 11r. Each groove 11r opens on a concave surface S11c, S11d, or S11e and is recessed toward the rotation axis a. In this third embodiment, each groove 11r is not formed around the entire circumference of the large diameter portion 11. The plurality of grooves 11r are provided in the region opposite to the circulation hole h22 and are spaced apart from each other in the direction along the rotation axis a and in the circumferential direction.

[0157] However, the groove 11r can be formed across the entire circumference of the large diameter portion 11. Furthermore, the second cylinder 22 can be formed without the circulation hole h22.

[0158] According to the third embodiment configured as described above, the same effects as those of the second embodiment can be obtained. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0159] (Fourth Implementation)

[0160] Next, the X-ray tube apparatus according to the second embodiment will be described. The X-ray tube 1 is configured in the same way as in the second embodiment, except for the structure described in this fourth embodiment. Figure 13 This is a cross-sectional view showing the X-ray tube apparatus according to the present fourth embodiment. Figure 14 It is shown Figure 13 The three-dimensional view of the fixed shaft 10 shown.

[0161] like Figure 13 and Figure 14 As shown, the fixed shaft 10 has a receiving portion and a circulation hole. The receiving portion is disposed inside the fixed shaft 10 to receive liquid metal LM. The circulation hole extends from the receiving portion of the fixed shaft 10 to the outer peripheral surface, and its position is offset from the radial bearing surfaces S11a and S11b. In this fourth embodiment, the fixed shaft 10 includes a receiving portion 10c, a receiving portion 10d, a receiving portion 10e, and a plurality of circulation holes h11.

[0162] Receiving portions 10c, 10d, and 10e are respectively disposed inside the fixed shaft 10 and formed by through holes extending linearly along the direction of the rotation axis a. In this fourth embodiment, the receiving portions 10c, 10d, and 10e extend at least from region A4 to region A5. The receiving portions 10c, 10d, and 10e are provided at intervals in the circumferential direction. The openings of the receiving portions 10c, 10d, and 10e located on the first bottom surface 10b1 are sealed by sealing material 15 to prevent liquid metal LM from leaking to the outside of the X-ray tube 1.

[0163] Multiple circulation holes h11 communicate with receiving portions 10c, 10d, or 10e and extend linearly in a direction perpendicular to the rotation axis a. The multiple circulation holes h11 open into one of the concave surfaces S11c, S11d, and S11e. The circulation holes h11 allow liquid metal LM to circulate between the receiving units 10c, 10d, 10e and the fixed shaft 10 and the second cylinder 22.

[0164] The receiving portions 10c, 10d, and 10e can function as reservoirs for containing liquid metal LM. Therefore, the liquid metal LM temporarily contained in the receiving portions 10c, 10d, and 10e can be provided to the gap between the fixed shaft 10 and the second cylinder 22, and further, the liquid metal LM can be provided to the gap between the first cylinder 21 and the second cylinder 22.

[0165] In this fourth embodiment, the circulation holes h11 are spaced apart from each other in the direction along the rotation axis a and in the circumferential direction. The circulation holes h11 and their corresponding circulation holes h22 are located on the same straight line. However, the circulation holes h11 may not be located on the same straight line as the circulation holes h22. Furthermore, the plurality of circulation holes h11 may not be provided in all regions A3, A4, and A5. For example, the plurality of circulation holes h11 may be provided only in region A3, and may only open on the concave surface S11c.

[0166] Alternatively, the circulation hole h11 may also be located on at least one of the radial bearing surfaces S11a and S11b.

[0167] According to the fourth embodiment configured as described above, the same effects as those of the second embodiment can be obtained. Furthermore, the depletion of the liquid metal LM in the bearing clearance can be further suppressed. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0168] (Fifth Implementation)

[0169] Next, the X-ray tube apparatus according to the fifth embodiment will be described. The X-ray tube 1 is configured in the same way as in the third embodiment, except for the structure described in this fifth embodiment. Figure 15 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to this fifth embodiment.

[0170] like Figure 15 As shown, the second cylinder 22 can have multiple regions with different outer diameters. The inner diameter of the first cylinder 21 is uniform along its entire length. As described above, multiple regions Aa, Ab, Ac, Ad, Ae, Af, and Ag exist along the direction of the rotation axis a, and the gap between the first cylinder 21 and the second cylinder 22 is different in these multiple regions. The second cylinder 22 has multiple concave surfaces 22c. The multiple concave surfaces 22c are formed across the entire outer circumferential surface of the second cylinder 22 in regions Ab, Ad, and Af, respectively. The concave surfaces 22c are formed by recessing towards the rotation axis a.

[0171] The circulation hole h22 opens onto the concave surface 22c.

[0172] Here, the gap between the first cylinder 21 and the second cylinder 22 of regions Aa and Ag is set as g1, the gap between the first cylinder 21 and the second cylinder 22 of regions Ac and Ae is set as g2, and the gap between the first cylinder 21 and the second cylinder 22 of regions Ab, Ad, and Af is set as g3.

[0173] Therefore, g1 ≤ g2 < g3. In this fifth embodiment, although g1 = g2, g1 < g2 is also possible. Thus, in regions Aa and Ag, the first cylinder 21 and the second cylinder 22 can be aligned. In regions Ac and Ae, a path for transferring heat from the first cylinder 21 to the second cylinder 22 can be realized. In regions Ab, Ad, and Af, it can function as a reservoir for containing liquid metal LM.

[0174] Alternatively, g2 < g3 = g1. In other words, the outer diameter of the second cylinder 22 in regions Aa and Ag can be the same as the outer diameter of the second cylinder 22 in regions Ab, Ad, and Af.

[0175] The second cylinder 22 has an outer diameter DO3 in region Ac and an outer diameter DO4 in region Ad. The outer diameter DO3 is also the outer diameter of the region surrounded by the anode target 50 within the second cylinder 22. The outer diameter DO4 is also the outer diameter of the region in the second cylinder 22 adjacent to region Ac (the region surrounded by the anode target 50). The outer diameter DO3 is larger than the outer diameter DO4.

[0176] According to the fifth embodiment configured as described above, the same effects as those of the third embodiment can be obtained. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0177] (Sixth Implementation Method)

[0178] Next, the X-ray tube apparatus according to the sixth embodiment will be described. The X-ray tube 1 is configured in the same way as in the fifth embodiment, except for the structure described in this sixth embodiment. Figure 16 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to the sixth embodiment.

[0179] like Figure 16 As shown, the first cylinder 21 has multiple portions with different inner diameters. The first cylinder 21 includes a first portion 21A with an inner diameter DI1 and a second portion 21B with an inner diameter DI2. The inner diameter DI1 is larger than the inner diameter DI2. The first portion 21A is located in regions Aa, Ab, Ac, and Ad. The second portion 21B is located in regions Ae, Af, and Ag.

[0180] The second cylinder 22 has multiple sections with different outer diameters. The second cylinder 22 includes a first section 22A with an outer diameter DO5 and a second section 22B with an outer diameter DO6 smaller than DO5. The first section 22A is located in regions Aa, Ab, and Ac. The second section 22B is located in regions Ad, Ae, Af, and Ag.

[0181] Here, the gap between the first cylinder 21 and the second cylinder 22 of regions Aa and Ag is set as g1, the gap between the first cylinder 21 and the second cylinder 22 of regions Ac and Ae is set as g2, and the gap between the first cylinder 21 and the second cylinder 22 of regions Ab, Ad, and Af is set as g3.

[0182] Therefore, g1 ≤ g2 < g3. In this sixth embodiment, although g1 = g2, g1 < g2 is also possible. Thus, in regions Aa and Ag, the first cylinder 21 and the second cylinder 22 can be aligned. In regions Ac and Ae, a path for transferring heat from the first cylinder 21 to the second cylinder 22 can be realized. In regions Ab, Ad, and Af, it can function as a reservoir for containing liquid metal LM.

[0183] As described above, the first cylinder 21 includes a first portion 21A with a larger inner diameter DI1, and the second cylinder 22 includes a second portion with a smaller outer diameter DO6. Therefore, when assembled into the sliding bearing unit U, the second cylinder 22 can be easily inserted into the integral part of the first cylinder 21 and the second limiting member 24.

[0184] According to the sixth embodiment configured as described above, the same effects as those of the fifth embodiment can be obtained. Since the first portion 21A has a relatively large inner diameter DI1, the liquid metal LM is less likely to dry up in the gap between the first portion 21A and the first portion 22A. In other words, in the region surrounded by the anode target 50, the liquid metal LM is less likely to dry up in the gap between the first cylinder 21 and the second cylinder 22. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having this sliding bearing unit U can be obtained.

[0185] Furthermore, unlike the sixth embodiment described above, the inner diameter of the first cylinder 21 can be formed uniformly along its entire length. In other words, the first cylinder 21 can have an inner diameter DI1 along its entire length. In this case, the same effect as the sixth embodiment described above can also be obtained.

[0186] (Seventh Implementation)

[0187] Next, the X-ray tube apparatus according to the seventh embodiment will be described. The X-ray tube 1 is configured in the same way as in the first embodiment, except for the structure described in this seventh embodiment. Figure 17 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to this seventh embodiment. Additionally, in Figure 17 For convenience, the illustrations of the recess 22r and the second component 23b are omitted.

[0188] like Figure 17As shown, the second cylinder 22 has multiple concave surfaces 22c. The multiple concave surfaces 22c are formed across the entire outer circumferential surface of the second cylinder 22. The concave surfaces 22c are recessed towards the axis of rotation a.

[0189] The X-ray tube 1 has a ring-shaped spring 80. In this seventh embodiment, the X-ray tube 1 has two springs 80. The springs 80 are located between the first cylinder 21 and the second cylinder 22, with their inner ends pressing against the concave surface 22c and their outer ends pressing against the inner circumferential surface of the first cylinder 21.

[0190] The gap between the concave surface 22c and the inner circumferential surface of the first cylinder 21 can be used as a reservoir to hold the liquid metal LM, or as a space to house the spring 80. Thus, for example, the first cylinder 21 and the second cylinder 22 can remain coaxial.

[0191] According to the seventh embodiment configured as described above, the same effects as those of the first embodiment can be obtained. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0192] (Eighth Implementation Method)

[0193] Next, the X-ray tube apparatus according to the eighth embodiment will be described. The X-ray tube 1 is configured in the same way as in the first embodiment, except for the structure described in this eighth embodiment. Figure 18 This is an enlarged cross-sectional view showing a portion of the X-ray tube apparatus according to this eighth embodiment.

[0194] like Figure 18 As shown, the rotation of the second cylinder 22 can also be limited by the second limiting member 24.

[0195] The second cylinder 22 also includes one or more recesses 22t. In this eighth embodiment, the second cylinder 22 has three recesses 22t. These recesses 22t are spaced apart from each other in the circumferential direction. Each recess 22t opens on the second end face 22e2 and is recessed in the direction along the axis of rotation a.

[0196] Second limiting member 24 and Figure 9 The first limiting member 23 shown is also constructed in the same way. The second limiting member 24 has a first member 24a and one or more second members 24b. In this eighth embodiment, the second limiting member 24 has three second members 24b. The first member 24a has an annular shape and is fixed to the first cylinder 21.

[0197] The first member 24a is opposite to the second end face 22e2 of the second cylinder 22. Thus, the first member 24a can restrict the movement of the second cylinder 22 in the direction along the rotation axis a. The first member 24a includes a thrust bearing surface S24. The thrust bearing surface S24 is located on the inner circumferential side of the first member 24a and has an annular shape.

[0198] Each second member 24b protrudes from the first member 24a in a direction along the rotation axis a. Each second member 24b is provided in a one-to-one correspondence with a recess 22t in the second cylinder 22. Each second member 24b is fitted into a recess 22t in the second cylinder 22. In this eighth embodiment, the second member 24b may be fitted into the recess 22t without an interference fit. However, an interference fit may also be used. The second member 24b is configured to, together with the recess 22t in the second cylinder 22, restrict the rotational movement of the second cylinder 22.

[0199] According to the eighth embodiment configured as described above, the same effects as those of the first embodiment can be obtained. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0200] (Ninth Implementation)

[0201] Next, the X-ray tube apparatus according to the ninth embodiment will be described. The X-ray tube 1 is configured in the same way as in the first embodiment, except for the structure described in this ninth embodiment. Figure 19 This is a cross-sectional view showing the X-ray tube apparatus according to the present ninth embodiment.

[0202] like Figure 19 As shown, the X-ray tube 1 is formed without the tube section 40, the annular section 16, and the tube section 45. The heat transfer section 10a is a heat transfer hole. The heat transfer section 10a opens on both the first bottom surface 10b1 and the second bottom surface 10b2, extends along the rotation axis a, and is penetrated by the fixed shaft 10. The refrigerant (coolant L) flows into the fixed shaft 10 from the first bottom surface 10b1 side and flows out to the outside of the fixed shaft 10 from the second bottom surface 10b2 side. Alternatively, the refrigerant (coolant L) flows into the fixed shaft 10 from the second bottom surface 10b2 side and flows out to the outside of the fixed shaft 10 from the first bottom surface 10b1 side.

[0203] According to the ninth embodiment configured as described above, the same effects as those of the first embodiment can be obtained. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0204] (Tenth Implementation)

[0205] Next, the X-ray tube apparatus according to the tenth embodiment will be described. The X-ray tube 1 is configured in the same way as in the first embodiment, except for the structure described in this tenth embodiment. Figure 20 This is a cross-sectional view showing the X-ray tube apparatus according to the tenth embodiment.

[0206] like Figure 20 As shown, the X-ray tube 1 adopts a single-end bearing structure. The peripheral device 70 fixes the second minor diameter portion 13 of the fixed shaft 10. That is, the second minor diameter portion 13 functions as a cantilever support portion of the bearing.

[0207] The fixed shaft 10 includes a large-diameter portion 11 and a second small-diameter portion 13, but lacks a first small-diameter portion 12. A first bottom surface 10b1 is located on the large-diameter portion 11, and a thrust bearing surface S11i is located on the first bottom surface 10b1. The first limiting member 23 is formed in the shape of a circular plate, and one end of the first cylinder 21 is liquid-tightly closed. The first limiting member 23 has a thrust bearing surface S23a opposite to the thrust bearing surface S11i.

[0208] In this tenth embodiment, the second cylinder 22 has a recess 22t, and the second limiting member 24 has a first member 24a and a second member 24b. The second limiting member 24 is detachably fixed to the first cylinder 21, for example, using screws. The rotational movement of the second cylinder 22 is restricted to prevent it from rotating relative to the first cylinder 21.

[0209] According to the tenth embodiment configured as described above, the same effects as those of the first embodiment can be obtained. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0210] (Eleventh Implementation Method)

[0211] Next, the X-ray tube apparatus according to the eleventh embodiment will be described. The X-ray tube 1 is configured in the same way as in the tenth embodiment, except for the structure described in this eleventh embodiment. Figure 21 This is a cross-sectional view showing the X-ray tube apparatus according to the eleventh embodiment.

[0212] like Figure 21 As shown, the fixed shaft 10 also has a flange portion 17. The flange portion 17 is located on the outer peripheral surface of the large diameter portion 11 and is integrally formed with the large diameter portion 11.

[0213] The rotating body 20 also includes a bearing member 26. The bearing member 26 is integrally formed from a cylindrical portion surrounding the flange portion 17 and an annular portion opposite to the flange portion 17 in the direction along the rotation axis a. The second restraining member 24, for example, together with the bearing member 26, is detachably fixed to the first cylinder 21 using screws. Furthermore, the structure of the rotating body 20 and the assembly method of the sliding bearing unit U are not limited to... Figure 21 The example shown is not the only one that can be transformed in various ways.

[0214] The second limiting member 24 and the flange portion 17 together with the liquid metal LM form a hydrodynamic thrust sliding bearing Bc. On the other hand, the bearing member 26 and the flange portion 17 together with the liquid metal LM also form a hydrodynamic thrust sliding bearing Bd.

[0215] According to the eleventh embodiment configured as described above, the same effects as those of the tenth embodiment can be obtained. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0216] (Twelfth Implementation)

[0217] Next, the X-ray tube apparatus according to the twelfth embodiment will be described. The X-ray tube 1 is configured in the same way as the first embodiment, except for the structure described in this twelfth embodiment. Figure 22 This is a cross-sectional view showing the X-ray tube apparatus according to the twelfth embodiment.

[0218] like Figure 22 As shown, the fixed shaft 10 can be a solid component formed in a cylindrical shape. The portion of the fixed shaft 10 exposed outside the outer casing 70 can be used to cool the fixed shaft 10.

[0219] According to the twelfth embodiment configured as described above, the same effects as those of the tenth embodiment can be obtained. Thus, a sliding bearing unit U capable of achieving good bearing operation and an X-ray tube 1 having the sliding bearing unit U can be obtained.

[0220] Several embodiments of the present invention have been described, but these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, 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, and also within the scope of the invention and its equivalents as set forth in the claims.

Claims

1. A sliding bearing unit, characterized in that, include: A fixed shaft extending along the axis of rotation and including a first radial bearing surface on its outer circumferential surface; A rotating body that can rotate freely about the fixed axis; as well as Lubricant The rotating body has: A first cylinder extends along the axis of rotation and forms a cylindrical shape, and the first cylinder is located around the fixed axis; and A second cylinder extends along the axis of rotation and forms a cylindrical shape. This second cylinder is located between the fixed shaft and the first cylinder. It includes a second radial bearing surface on its inner circumferential surface, and the rotational movement of the second cylinder is restricted to prevent rotation relative to the first cylinder. The lubricant fills the gaps between the fixed shaft and the first cylinder, the fixed shaft and the second cylinder, and the first cylinder and the second cylinder, and together with the first radial bearing surface and the second radial bearing surface, forms a hydrodynamic radial sliding bearing.

2. The sliding bearing unit as described in claim 1, characterized in that, The second cylinder can be moved to a position that is eccentric to both the fixed axis and the first cylinder.

3. The sliding bearing unit as described in claim 1, characterized in that, The rotating body also has a first limiting member. The second cylinder includes a first end face located at one end along the direction of the rotation axis, and a recess that is open on the first end face and recessed along the direction of the rotation axis. The first limiting member has: A first component fixed to the first cylinder and opposite to the first end face of the second cylinder, the first component restricting the movement of the second cylinder in the direction along the axis of rotation; as well as A second member protrudes from the first member and is fitted into the recess along the direction of the rotation axis. This second member is configured to, together with the recess, restrict the rotational movement of the second cylinder. The fixed shaft includes a first thrust bearing surface. The first component includes a second thrust bearing surface opposite to the first thrust bearing surface. The lubricant fills multiple gaps between the fixed shaft, the first cylinder, the second cylinder, and the first limiting member, and together with the first thrust bearing surface and the second thrust bearing surface, forms a hydrodynamic thrust sliding bearing.

4. The sliding bearing unit as described in claim 3, characterized in that, The rotating body also has a second limiting member. The second cylinder includes a second end face located at one end along the direction of the rotation axis and on the opposite side of the first end face. The second limiting member is fixed to the first cylinder, opposite to the second end face of the second cylinder, and is configured to limit the movement of the second cylinder in the direction along the rotation axis. The gap between the first end face and the first limiting member, and the gap between the second end face and the second limiting member, are respectively connected to the gap between the fixed shaft and the second cylinder, and the gap between the first cylinder and the second cylinder, thereby forming the circulation path of the lubricant.

5. The sliding bearing unit as described in claim 1, characterized in that, The second cylinder includes a circulation hole that connects to the gap between the fixed shaft and the second cylinder, and the gap between the first cylinder and the second cylinder, thereby forming a circulation path for the lubricant. The circulation hole extends from the outer circumferential surface of the second cylinder to the inner circumferential surface.

6. The sliding bearing unit as described in claim 1, characterized in that, The second cylinder is formed of a different material than the first cylinder.

7. The sliding bearing unit as described in claim 1, characterized in that, The second cylinder is formed of the same material as the fixed shaft.

8. The sliding bearing unit as described in claim 1, characterized in that, The first cylinder is formed of the same material as the fixed shaft.

9. A rotating anode type X-ray tube, characterized in that, include: A sliding bearing unit comprising a fixed shaft, a rotating body, and a lubricant, wherein the fixed shaft extends along a rotation axis and includes a first radial bearing surface on its outer circumferential surface, and the rotating body rotates freely about the fixed shaft; Anode target; A cathode disposed opposite to the anode target; and An external device that houses the sliding bearing unit, the anode target, and the cathode, and fixes the fixed shaft. The rotating body has: A first cylinder extending along the axis of rotation and forming a cylindrical shape, the first cylinder being positioned around the fixed axis; and A second cylinder extends along the axis of rotation and forms a cylindrical shape. This second cylinder is located between the fixed shaft and the first cylinder. It includes a second radial bearing surface on its inner circumferential surface, and the rotational movement of the second cylinder is restricted to prevent rotation relative to the first cylinder. The lubricant fills the gaps between the fixed shaft and the first cylinder, the fixed shaft and the second cylinder, and the first cylinder and the second cylinder, and together with the first radial bearing surface and the second radial bearing surface, forms a hydrodynamic radial sliding bearing. The anode target surrounds the outer circumferential surface of the first cylinder and is fixed to the first cylinder.

10. The rotating anode type X-ray tube as described in claim 9, characterized in that, The second cylinder can be moved to a position that is eccentric to both the fixed axis and the first cylinder.

11. The rotating anode type X-ray tube as described in claim 9, characterized in that, The rotating body also has a first limiting member. The second cylinder includes a first end face located at one end along the direction of the rotation axis, and a recess that is open on the first end face and recessed along the direction of the rotation axis. The first limiting member has: A first member fixed to the first cylinder and opposite to the first end face of the second cylinder, the first member restricting the movement of the second cylinder in the direction along the axis of rotation; as well as A second member protrudes from the first member and is fitted into the recess along the direction of the rotation axis. This second member is configured to, together with the recess, restrict the rotational movement of the second cylinder. The fixed shaft includes a first thrust bearing surface. The first component includes a second thrust bearing surface opposite to the first thrust bearing surface. The lubricant fills multiple gaps between the fixed shaft, the first cylinder, the second cylinder, and the first limiting member, and together with the first thrust bearing surface and the second thrust bearing surface, forms a hydrodynamic thrust sliding bearing.

12. The rotating anode type X-ray tube as described in claim 11, characterized in that, The rotating body also has a second limiting member. The second cylinder includes a second end face located at one end along the direction of the rotation axis and on the opposite side of the first end face. The second limiting member is fixed to the first cylinder, opposite to the second end face of the second cylinder, and is configured to limit the movement of the second cylinder in the direction along the rotation axis. The gap between the first end face and the first limiting member, and the gap between the second end face and the second limiting member, are respectively connected to the gap between the fixed shaft and the second cylinder, and the gap between the first cylinder and the second cylinder, thereby forming the circulation path of the lubricant.

13. The rotating anode type X-ray tube as described in claim 9, characterized in that, The second cylinder includes a circulation hole that connects to the gap between the fixed shaft and the second cylinder, and the gap between the first cylinder and the second cylinder, thereby forming a circulation path for the lubricant. The circulation hole extends from the outer circumferential surface of the second cylinder to the inner circumferential surface.

14. The rotating anode type X-ray tube as described in claim 9, characterized in that, The second cylinder has a first outer diameter in the first region surrounded by the anode target. A second outer diameter is present in a second region adjacent to the first region along the direction of the rotation axis. The first outer diameter is larger than the second outer diameter.

15. The rotating anode type X-ray tube as described in claim 14, characterized in that, The first cylinder has a first inner diameter in the first region. The second region has a second inner diameter. The first inner diameter is larger than the second inner diameter.

16. The rotating anode type X-ray tube as described in claim 14, characterized in that, The radial sliding bearing is located in the first region.

17. The rotating anode type X-ray tube as described in claim 9, characterized in that, The second cylinder is formed of a different material than the first cylinder.

18. The rotating anode type X-ray tube as described in claim 9, characterized in that, The second cylinder is formed of the same material as the fixed shaft.

19. The rotating anode type X-ray tube as described in claim 9, characterized in that, The first cylinder is formed of the same material as the fixed shaft.

20. The rotating anode type X-ray tube as described in claim 9, characterized in that, The fixed shaft further includes: First bottom surface; A second bottom surface located on the opposite side of the first bottom surface along the direction of the rotation axis; and A heat transfer section extending along the axis of rotation, which opens at least one of the first bottom surface and the second bottom surface, transfers heat to the refrigerant flowing inside.

21. The rotating anode type X-ray tube as described in claim 20, characterized in that, The heat transfer section is located in a first region surrounded by the anode target.

22. The rotating anode type X-ray tube as described in claim 9, characterized in that, The fixed shaft also includes a concave surface parallel to the first radial bearing surface in the direction along the axis of rotation. The concave surface is located on the rotation axis side of the imaginary extended surface of the first radial bearing surface.

23. The rotating anode type X-ray tube as described in claim 9, characterized in that, The fixed shaft further includes: An internally disposed portion for receiving the lubricant; and A circulation hole extends from the receiving portion to the outer peripheral surface.

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