X-ray tube

Abstract

An X-ray tube comprises a rod-shaped anode containing a target that receives electrons and generates X-rays, and having a main body extending along the tube axis; a vacuum housing that houses the distal end of the anode, where the target is located, and to which the proximal end of the anode is fixed via a housing connection; and a cover electrode disposed within the vacuum housing, connected to the anode via the cover connection, and surrounding the housing connection. The anode has a third expanded diameter portion that protrudes from the surface of the main body in a direction intersecting the tube axis. The cover connection portion is disposed closer to the proximal end of the anode than the third expanded diameter portion.

Description

Technical Field

[0001] One embodiment of the present invention relates to an X-ray tube. Background Art

[0002] Japanese Patent No. 4068332, Japanese Patent No. 4712727, and Japanese Patent Application Laid-Open No. 57-25660 disclose technologies related to X-ray tubes. The technology disclosed in Japanese Patent No. 4068322 relates to improving the assembly accuracy of components that constitute an X-ray tube. The technology disclosed in Japanese Patent No. 4712727 relates to suppressing discharge generation by simplifying the X-ray tube structure. The technology disclosed in Japanese Patent Application Laid-Open No. 57-25660 relates to increasing the precision of X-ray dose control.

[0003] The X-ray tubes disclosed in Japanese Patent Nos. 4068322, 4712727, and 57-25660 have a potential difference between the housing and the anode. Electrons emitted from the electron gun are guided toward a target mounted on the anode by this potential difference. A high voltage is applied to the anode to create this potential difference. When a high voltage is applied to the anode, a strong electric field is generated around the anode. As a result, unwanted discharges are likely to occur between the anode and the housing. Summary of the Invention

[0004] An object of the present invention is to provide an X-ray tube capable of suppressing discharge.

[0005] An X-ray tube according to one embodiment of the present invention comprises: a rod-shaped anode including a target that receives electrons and generates X-rays, and having a main body extending along an axis; a vacuum housing that houses the distal end of the anode, where the target is disposed, and to which the proximal end of the anode is fixed via a housing coupling; and a cover electrode disposed within the vacuum housing, connected to the anode via the cover coupling, and surrounding the housing coupling. The anode has a flange protruding from the surface of the main body in a direction intersecting the axis. The cover coupling is disposed closer to the proximal end of the anode than the flange. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a cross-sectional view showing the structure of an X-ray tube;

[0007] Figure 2 is a cross-sectional view showing an enlarged view of the frame connecting portion and the cover connecting portion;

[0008] Figure 3 is an enlarged cross-sectional view showing a frame connecting portion and a cover connecting portion according to a first modification;

[0009] Figure 4is an enlarged cross-sectional view showing a frame connecting portion and a cover connecting portion according to a second modification;

[0010] Figure 5 It is a cross-sectional view showing an enlarged view of a frame connecting portion and a cover connecting portion according to a third modification. DETAILED DESCRIPTION

[0011] An X-ray tube according to one embodiment of the present invention comprises: a rod-shaped anode including a target that receives electrons and generates X-rays, and having a main body extending along an axis; a vacuum housing that houses the distal end of the anode, where the target is disposed, and to which the proximal end of the anode is fixed via a housing coupling; and a cover electrode disposed within the vacuum housing, connected to the anode via the cover coupling, and surrounding the housing coupling. The anode has a flange protruding from the surface of the main body in a direction intersecting the axis. The cover coupling is disposed closer to the proximal end of the anode than the flange.

[0012] The state of the electric field generated within the vacuum housing is affected by the surface shape of the fixing portions of each component. The X-ray tube's housing connection secures the anode to the vacuum housing. The housing connection is surrounded by a shield electrode. The shield electrode, on the other hand, is secured to the anode by the shield connection. The shield connection is positioned closer to the anode's base end than the flange provided on the anode. As a result, these fixing portions are covered by the electrode. This mitigates the effect of the fixing portions on the electric field, thus suppressing localized increases in electric field intensity. This, in turn, suppresses discharge.

[0013] In the above-mentioned X-ray tube, the flange portion and the cover electrode may also be in contact with each other. According to this structure, the flange portion and the cover electrode are close to each other. As a result, the electric field around the flange portion and the cover electrode is easily stabilized.

[0014] In the aforementioned X-ray tube, the outer surface of the flange portion may include a first principal surface exposed to the interior space of the vacuum housing. The outer surface of the shield electrode may include a second principal surface exposed to the interior space of the vacuum housing. The first principal surface and the second principal surface may be contained within the same imaginary curved surface. This structure smoothes the boundary between the flange portion and the shield electrode. This mitigates the effect of the boundary on the electric field. Consequently, localized increases in electric field intensity are further suppressed. In other words, discharge can be further suppressed.

[0015] In the above-mentioned X-ray tube, the cover connection portion may be surrounded by a cover electrode. According to this configuration, the electric field around the cover connection portion can be further stabilized.

[0016] In the above-mentioned X-ray tube, the cover connecting portion may be joined to the cover electrode with respect to the flange portion. According to this configuration, the cover connecting portion can be covered by the flange portion. Furthermore, the cover electrode can be stably fixed.

[0017] In the aforementioned X-ray tube, the frame connection portion may include a frame connection member fixed to the vacuum frame and an anode connection member fixed to the anode. The anode connection member may also be fixed relative to the frame connection member. When the vacuum frame and the anode are connected, internal stress may be generated. With this configuration, the frame connection member and the anode connection member can bear this internal stress. Consequently, it is possible to suppress the generation of unwanted deformation and stress in the vacuum frame and the anode.

[0018] In the above-mentioned X-ray tube, the vacuum frame may also include an inner cylindrical portion extending inwardly along the axis. The interior of the inner cylindrical portion and the interior of the vacuum frame may also be separated from each other by an anode and a frame connecting portion provided at one end of the inner cylindrical portion. The portion where the anode connecting member and the frame connecting member are joined may also be disposed within the inner cylindrical portion. According to this structure, the portion where the anode connecting member and the frame connecting member are joined is disposed within the inner cylindrical portion. Therefore, a cooling medium from the outside can easily enter the interior of the inner cylindrical portion. As a result, heat generated by the anode can be efficiently discharged.

[0019] According to the present invention, an X-ray tube capable of suppressing discharge is provided.

[0020] Hereinafter, the embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted.

[0021] The structure of the X-ray tube 3 will be described. Figure 1 As shown, the X-ray tube 3 is a so-called reflection-type X-ray tube. The X-ray tube 3 includes a vacuum housing 10, an electron gun 11, and a target T. The vacuum housing 10 is a vacuum enclosure that maintains a vacuum interior. The electron gun 11 is an electron generating unit. The electron gun 11 includes a cathode C. The cathode C includes a base made of, for example, a high-melting-point metal material and an easily electron-emitting substance impregnated within the base. The target T is plate-shaped. The target T is formed of a high-melting-point metal material, such as tungsten. The center of the target T is aligned with the tube axis AX of the X-ray tube 3. The electron gun 11 and the target T are housed within the vacuum housing 10. Electrons emitted from the electron gun 11 enter the target T. As a result, the target T generates X-rays. The generated X-rays are irradiated to the outside through the X-ray exit window 33a.

[0022] The vacuum housing 10 includes an insulating tube (bulb) 12 and a metal portion 13. The insulating tube 12 is formed of an insulating material. Glass is an example of the insulating material. The metal portion 13 includes an X-ray exit window 33a. The metal portion 13 includes a main body 31 (metal housing) and an electron gun housing 32. The main body 31 houses the target T, which serves as the anode. The electron gun housing 32 houses the electron gun 11, which serves as the cathode.

[0023] The main body 31 is cylindrical in shape. The main body 31 has an internal space S. A cover plate 33 is fixed to one end (outer end) of the main body 31. The cover plate 33 has an X-ray exit window 33a. The material of the X-ray exit window 33a is an X-ray transparent material. Examples of X-ray transparent materials include beryllium and aluminum. The cover plate 33 closes one end side of the internal space S. The main body 31 has a flange portion 311 and a cylindrical portion 312. The flange portion 311 is provided on the outer periphery of the main body 31. The flange portion 311 is fixed to an X-ray generating device (not shown). The cylindrical portion 312 is formed on one end side of the main body 31. The cylindrical portion 312 is cylindrical in shape.

[0024] The electron gun housing 32 is cylindrical in shape. It is fixed to a side portion of one end of the main body 31. The central axis of the main body 31 is approximately perpendicular to the central axis of the electron gun housing 32. In other words, the tube axis AX of the X-ray tube 3 is approximately perpendicular to the central axis of the electron gun housing 32. An opening 32a is provided at the end of the electron gun housing 32 on the main body 31 side. The interior of the electron gun housing 32 communicates with the internal space S of the main body 31 via the opening 32a.

[0025] The electron gun 11 includes a cathode C, a heater 111, a first grid electrode 112, and a second grid electrode 113. The electron gun 11 is capable of reducing the beam diameter of the electron beam generated by the cooperation of its components. In other words, the electron gun 11 can finely focus the electron beam. The cathode C, heater 111, first grid electrode 112, and second grid electrode 113 are mounted on a base substrate 115 via multiple power supply pins 114. These multiple power supply pins 114 extend parallel to each other. The cathode C, heater 111, first grid electrode 112, and second grid electrode 113 receive external power via their corresponding power supply pins 14.

[0026] The insulating tube 12 has a generally cylindrical shape. One end of the insulating tube 12 is joined to the main body 31. An inner tube portion 12a is provided at the other end of the insulating tube 12. The inner tube portion 12a extends inwardly of the insulating tube 12. The inner tube portion 12a is cylindrical in shape. The other end of the insulating tube 12 is folded inwardly along its entire circumference, defining a hole in the center of the insulating tube 12 when viewed in the Z direction.

[0027] The inner cylinder portion 12a of the insulating tube 12 holds the anode 61 (target support portion 60) via the frame connecting portion 15 (fixing portion). A target T is fixed to the front end side of the target support portion 60. The target support portion 60 is in the shape of a rod. In addition, the target support portion 60 is in the shape of a cylinder. The target support portion 60 is formed using a material such as copper. The target support portion 60 extends in the Z direction. An inclined surface 60a is formed on the front end side of the target support portion 60. The inclined surface 60a is inclined in a manner that moves away from the electron gun 11 as it moves from the insulating tube 12 side toward the main body 31 side. The target T is buried in the end portion of the target support portion 60. The target T and the inclined surface 60a are flush with each other.

[0028] The base end portion 60b of the target support portion 60 protrudes further outward than the lower end portion of the insulating tube 12. The base end portion 60b of the target support portion 60 is the front end portion on the base end side. The base end portion 60b of the anode 61 protrudes further outward than the folded-back position. The base end portion 60b of the target support portion 60 (anode 61) is connected to a power supply (not shown). In this embodiment, the vacuum frame 10 (metal portion 13) is at ground potential. Therefore, the metal portion 13 is at ground potential. The anode 61 (target support portion 60) receives a positive high voltage from the power supply. In addition, the anode 61 may also receive a voltage in a manner different from the positive high voltage from the power supply.

[0029] The base end of the target support portion 60 (anode 61) comprises a base end portion 60b, a cylindrical portion 60c, a first expanded diameter portion 60d, a second expanded diameter portion 60e, and a third expanded diameter portion 60f, in this order. The cylindrical portion 60c, the first expanded diameter portion 60d, the second expanded diameter portion 60e, and the third expanded diameter portion 60f are each cylindrical in shape. The base end of the target support portion 60 can also be defined as the base end of the anode 61. The third expanded diameter portion 60f can also be defined as a flange. The base end of the target support portion 60 is connected to the extension portion 60k. The extension portion 60k extends toward the distal end (the inclined surface 60a side). The base end of the target support portion 60 can also be defined as the base end of the anode 61. The distal end can also be defined as the inclined surface 60a side. The first expanded diameter portion 60d is cylindrical in shape. The first expanded diameter portion 60d can also be annular in shape. The outer diameter of the first expanded diameter portion 60d is larger than that of the cylindrical portion 60c. The outer diameter of the first expanded diameter portion 60d is the diameter of the cross section perpendicular to the tube axis AX. The second expanded diameter portion 60e is cylindrical. The second expanded diameter portion 60e may also be annular. The outer diameter of the second expanded diameter portion 60e is larger than the outer diameter of the first expanded diameter portion 60d. The third expanded diameter portion 60f is cylindrical. The third expanded diameter portion 60f may also be annular. The outer diameter of the third expanded diameter portion 60f is larger than the outer diameter of the second expanded diameter portion 60e. The outer diameter of the third expanded diameter portion 60f is the largest among the outer diameters of the target support portion 60 (anode 61). The outer diameter of the third expanded diameter portion 60f is larger than the inner diameter of the inner cylindrical portion 12a of the insulating tube 12. The inner diameter of the inner cylindrical portion 12a is the diameter of the hole provided in the center of the insulating tube 12. The base end of the target support portion 60 is inserted into the insulating tube 12. The base end of the target support portion 60 may also be defined as the base end of the anode 6X. Furthermore, the outer diameter of the third enlarged diameter portion 60 f may be smaller than the inner diameter of the inner cylindrical portion 12 a of the insulation tube 12 .

[0030] The frame connecting portion 15 is made of metal or the like. The frame connecting portion 15 includes a first fixing portion 16 and a second fixing portion 17. The first fixing portion 16 and the second fixing portion 17 fix the anode 61 (target support portion 60) to the other end of the insulating tube 12. The first fixing portion 16 is cylindrical in shape. The inner diameter of the first fixing portion 16 is substantially identical to the outer diameter of the first enlarged diameter portion 60d. The outer diameter of the first fixing portion 16 is substantially identical to the outer diameter of the second enlarged diameter portion 60e. The first enlarged diameter portion 60d is inserted through one end of the first fixing portion 16. The first fixing portion 16 is fixed to the target support portion 60 (anode 61).

[0031] The second fixing portion 17 includes an inner cylindrical portion 17a, an outer cylindrical portion 17b, and a connecting portion 17c. The inner diameter of the inner cylindrical portion 17a is approximately identical to the outer diameter of the first fixing portion 16. The diameter of the outer cylindrical portion 17b is approximately identical to the diameter of the inner cylindrical portion 12a of the insulating tube 12. The connecting portion 17c connects the upper end of the inner cylindrical portion 17a to the upper end of the outer cylindrical portion 17b. The connecting portion 17c is annular when viewed from the Z direction. The lower end of the outer cylindrical portion 17b is welded to the end surface of the other end of the insulating tube 12. The other end is the upper end of the inner cylindrical portion 12a. The inner cylindrical portion 17a is fixed to the first fixing portion 16. The first fixing portion 16 is inserted through the inner cylindrical portion 17a. The position of the lower end of the inner cylindrical portion 17a is approximately identical to the position of the lower end of the first fixing portion 16. The first fixing portion 16 is fixed to the target support portion 60 (anode 61). The first fixing portion 16 is joined to the inner cylindrical portion 17a. The anode 61 (target support portion 60 ) is fixed to the other end portion of the insulating tube 12 via the first fixing portion 16 and the second fixing portion 17 .

[0032] The frame connection portion 15 includes a third fixing portion 18 (cover connection portion). The third fixing portion 18 secures a cover electrode 19 to the anode 61 (target support portion 60). The cover electrode 19 is an electrode member. It covers the portion of the insulating tube 12 where the inner cylindrical portion 12a is welded to the outer cylindrical portion 17b of the second fixing portion 17. The welded portion can also be defined as the portion where the inner cylindrical portion 12a and the outer cylindrical portion 17b meet. The cover electrode 19 prevents damage to the insulating tube 12. Damage to the insulating tube 12 is caused by discharge into the welded portion. The cover electrode 19 includes a ring portion 19a and an outer peripheral portion 19b. The ring portion 19a abuts the lower surface of the third expanded diameter portion 60f. The outer peripheral portion 19b forms the surrounding surface of the cover electrode 19. The surrounding surface can also be defined as the outer peripheral surface. The inner diameter of the ring portion 19a is substantially identical to the outer diameter of the second expanded diameter portion 6e. The second expanded diameter portion 60e is inserted through the ring portion 19a. The third fixing portion 18 is cylindrical in shape. The inner diameter of the third fixing portion 18 is substantially identical to the outer diameter of the second expanded diameter portion 60e. The third fixing portion 18 is embedded in the second expanded diameter portion 60e and a portion of the first fixing portion 16. The second expanded diameter portion 60e and a portion of the first fixing portion 16 are inserted through the third fixing portion 18. The ring portion 19a is press-fitted into the third expanded diameter portion 60f by the third fixing portion 18. The cover electrode 19 is fixed to the anode 61 (target support portion) via the third fixing portion 18.

[0033] Below, refer to Figure 2 The frame connecting portion 15 will be described in more detail. The frame connecting portion 15 connects the anode 61 and the vacuum frame 10. In the following description, the inner peripheral surface is the surface on the tube axis AX side. The outer peripheral surface is the surface on the opposite side of the tube axis AX side.

[0034] The frame connecting portion 15 includes a first fixing portion 16 (anode connecting member) and a second fixing portion 17 (frame connecting member). The first fixing portion 16 is fixed to the anode 61 (target support portion 60) using a joint B1. The joint B1 is formed by brazing or welding. The second fixing portion 17 is fixed to the insulating tube 12. The first fixing portion 16 is fixed to the second fixing portion 17 using a joint B2. The joint B2 is formed by brazing or welding. The anode 61 (target support portion 60) is fixed to the insulating tube 12 via the first fixing portion 16 and the second fixing portion 17. The frame connecting portion 15 allows the length of the cylindrical portion 60c exposed to the outside of the vacuum frame 10 to be extended. The cylindrical portion 60c contacts a cooling medium supplied from the outside. The cooling medium is, for example, insulating oil. This structure increases the contact area that facilitates heat transfer. Therefore, heat can be efficiently transferred from the anode 61 (target support portion).

[0035] The first fixing portion 16 has a cylindrical shape. A first expanded diameter portion 60d is inserted into the end portion 16a of the first fixing portion 16. The end portion 16a abuts the end surface 60g of the anode 61 (target support portion 60). The abutment between the end portion 16a and the end surface 60g determines the position of the first fixing portion 16 relative to the anode 61 (target support portion 60) in the direction of the tube axis AX. A joint B1 is provided between the first fixing portion 16 and the first expanded diameter portion 60d. The joint B1 is formed by brazing, welding, or the like. The first fixing portion 16 is fixed to the first expanded diameter portion 60d.

[0036] The length of the first fixing portion 16 along the tube axis AX is longer than the length of the first expanded diameter portion 60d along the tube axis AX. The first fixing portion 16 protrudes further toward the base end portion 60b than the end surface 60h. The inner circumferential surface of the first fixing portion 16 includes a portion facing the first expanded diameter portion 60d and a portion facing the cylindrical portion 60c. The outer diameter of the cylindrical portion 60c is smaller than the outer diameter of the first expanded diameter portion 60d. A gap D1 is formed between the first fixing portion 16 and the cylindrical portion 60c. Gap D1 increases the contact area between the anode 1 (target support portion 60) and the coolant. The coolant is, for example, insulating oil. Therefore, heat easily transfers from the anode 61 (target support portion) to the coolant.

[0037] The second fixing portion 17 is an integral component and includes an inner tube portion 17a, an outer tube portion 17b, and a connecting portion 17c.

[0038] The inner tube portion 17a is cylindrical in shape. End 17a1 is continuous with the connecting portion 17c. The first fixing portion 16 is inserted into the inner tube portion 17a. End 16b of the first fixing portion 16 is inserted from end 17a1 of the inner tube portion 17a. End 16b of the first fixing portion 16 is substantially flush with end 17a2 of the inner tube portion 17a. The entire inner circumferential surface of the inner tube portion 17a faces the outer circumferential surface of the first fixing portion 16. The outer circumferential surface of the inner tube portion 17a faces the outer tube portion 17b and the inner tube portion 12a of the insulating tube 12. For example, the outer diameter of the inner tube portion 17a is smaller than the inner diameter of the inner tube portion 12a of the insulating tube 12. Therefore, a gap D2 is formed between the inner tube portion 17a and the inner tube portion 12a of the insulating tube 12.

[0039] The outer tube portion 17b is cylindrical. One end 17b1 of the outer tube portion 17b is continuous with the connecting portion 17c. The end 12a1 of the insulating tube 12 is connected to the end 17b2. The radial size of the outer tube portion 17b corresponds to the size of the inner tube portion 12a of the insulating tube 12. The end 17b2 of the outer tube portion 17b faces the end 12a1 of the inner tube portion 12a of the insulating tube 12. The end 17b2 is welded to the insulating tube 12 and fixed by being embedded in the end surface of the insulating tube 12. Therefore, the wall thickness of the outer tube portion 17b is thinner than that of the insulating tube 12.

[0040] End 17a2 is connected to end 16b of first fixing portion 16. A joint B2, for example, is formed at the portion where end 17a2 and end 16b are connected. This connected portion is located on the opening side of inner cylindrical portion 12a of insulating tube 12. This position improves ease of connection.

[0041] A high voltage is applied to the anode 61 (target support portion) from an external power source via the base end 60b. This voltage generates a strong electric field around the anode 61 (target support portion). The first fixing portion 16 and the second fixing portion 17 are metal components. Therefore, a high voltage is also applied to the first fixing portion 16 and the second fixing portion 17. As a result, a state of discharge is generated around the frame connecting portion 15. The distribution of the electric field is affected by the shape of the frame connecting portion 15, etc. For example, the intensity of the electric field tends to be high at right-angled corners. Therefore, the intensity of the electric field tends to be high near the corners of the frame connecting portion 15. For example, the intensity of the electric field tends to be high near the corner between the outer cylindrical portion 17b of the second fixing portion 17 and the connecting portion 17c. When the intensity of the electric field increases, the possibility of discharge increases. Therefore, a shield electrode 19 is provided to mitigate the intensity of the electric field generated around these shapes. The cover electrode 19 is fixed to the anode 61 (target support portion 60 ). Furthermore, the cover electrode 19 is electrically connected to the anode 61 (target support portion 60 ). Therefore, the potential of the cover electrode 19 is the same as that of the anode 61 (target support portion 60 ) and the frame connecting portion 15 .

[0042] The shield electrode 19 is cylindrical. Its outer shape smoothly connects the cylindrical base end to the tapered, roughly conical tip end. The shield electrode 19 has an internal space S1 of approximately the same shape. The tip of the shield electrode 19 abuts against the anode 61 (target support 60). The ring portion 19a is secured to the anode 1 (target support 60) by the shield connector 70.

[0043] The base end portion 19c on the opposite side of the ring portion 19a has an opening 19c1. The other base end portion 19c is positioned closer to the base end portion 60b than the end portion 16b of the first fixing portion 16 in the direction of the tube axis AX. The base end portion 19c is positioned closer to the base end portion 60b than the end portion 17a2 of the second fixing portion 1 in the direction of the tube axis AX. The first fixing portion 16 and the second fixing portion 17 are located within the internal space S1 of the cover electrode 19. The entire frame connecting portion 15 is located within the internal space S1 of the cover electrode 19.

[0044] The cover electrode 19 covers the frame connecting portion 15 .

[0045] The cover electrode 19 has an opening 19a1 provided in the ring portion 19a. The second expanded diameter portion 60e of the anode 61 (target support portion 60) is inserted into the opening 19a1. The main surface 19a2 of the ring portion 19a, which surrounds the opening 19a1, is an annular, flat surface. The main surface 19a2 abuts against the back surface 60f1 of the third expanded diameter portion 60f. In other words, the main surface 19a2 and the back surface 60f1 of the third expanded diameter portion 60f are in surface contact. The back surface 60f1 of the third expanded diameter portion 60f is the surface on the base end side of the target support portion 60. The abutment of the ring portion 19a against the back surface 60f1 determines the position of the cover electrode 19 relative to the anode 61 (target support portion 60) in the direction of the tube axis AX. The back surface 60f1 of the third expanded diameter portion 60f serves as a positioning portion for the cover electrode 19.

[0046] Viewing the back surface 60f1 from the direction of the tube axis AX, the back surface 60f1 is an annular plane surrounding the second expanded diameter portion 60e. Viewing the ring portion 19a from the direction of the tube axis AX, the shape of the ring portion 19a corresponds to the shape of the back surface 60f1. The inner diameter of the back surface 60f1 is approximately equal to the inner diameter of the ring portion 19a. In other words, the outer diameter of the second expanded diameter portion 60e is approximately equal to the inner diameter of the opening 19a1. The outer diameter of the back surface 60f1 is approximately equal to the outer diameter of the ring portion 19a. In other words, the maximum outer diameter of the third expanded diameter portion 60f is approximately equal to the outer diameter of the ring portion 19a. The outer diameter of the ring portion 19a refers to the length from the tube axis AX to the portion continuous with the surface 19f of the cover electrode 19. The ring portion 19a does not protrude from the third expanded diameter portion 60f in a direction intersecting the tube axis AX. The third expanded diameter portion 60f has a surface 60f2. Surface 60f2 forms a smooth surface that is substantially continuous with surface 19f of cover electrode 19 at the boundary with cover electrode 19. In other words, the third expanded diameter portion 60f has a first principal surface at the boundary with cover electrode 19. This first principal surface is contained within the same imaginary curved surface as surface 19f of cover electrode 19. Surface 60f2 (first principal surface) of the third expanded diameter portion 60f protrudes from the surface of the extension portion 60k of the anode 61 (target support portion 60) in a cross-section along tube axis AX. In other words, the first principal surface of the third expanded diameter portion 60f protrudes from the surface of the extension portion 60k of the target support portion 60 in a cross-section along tube axis AX. Thus, surface 60f2 is a smooth surface with a substantially continuous change in shape until it reaches rear surface 60f1. Furthermore, the shape of surface 60f2 is such that a protrusion that smoothly protrudes from the surface of anode 61 (target support portion 60) is cut at a desired position along the protrusion direction. In other words, the shape of the surface 60 f 2 is a shape obtained by cross-sectioning a protrusion that smoothly protrudes from the surface of the target support portion 60 at a desired position.

[0047] The cover connecting portion 70 will now be described. The cover connecting portion 70 attaches the cover electrode 19 to the anode 61 (target support portion 60). The cover electrode 19 is fixed to the anode 61 (target support portion 60) by the third fixing portion 18 that constitutes the cover connecting portion 70. The third fixing portion 18 is cylindrical in shape. The second expanded diameter portion 60e of the anode 61 (target support portion 60) is inserted into the end portion 18a of the third fixing portion 18. The end portion 18a abuts the back surface 19a3 of the ring portion 19a.

[0048] The length of the third fixing portion 18 along the tube axis AX is longer than the length of the second expanded diameter portion 60e along the tube axis AX. The inner circumferential surface of the third fixing portion 18 includes a portion in contact with the outer circumferential surface of the second expanded diameter portion 60e and a portion in contact with the outer circumferential surface of the first fixing portion 16. The end 18b of the third fixing portion 18 is fixed to the first fixing portion 16 via a joint B3. Joint B3 is formed by brazing, welding, or other means. The end 18b of the third fixing portion 18 protrudes further toward the base end 60b than the lower end surface of the first expanded diameter portion 60d. The end 18b of the third fixing portion 18 does not contact the second fixing portion 17. The end 18b of the third fixing portion 18 is separated from the connecting portion 17c in the direction of the tube axis AX. The end 18b of the third fixing portion 18 does not necessarily need to protrude further toward the base end 60b than the lower end surface of the first expanded diameter portion 60d. For example, the end 18b of the third fixing portion 18 may be located opposite the first expanded diameter portion 60d.

[0049] The inner diameter of the third fixing portion 18 is approximately equal to the inner diameter of the opening 19a1 of the ring portion 19a. The outer diameter of the third fixing portion 18 is larger than the inner diameter of the opening 19a1 of the ring portion 19a. The end 18a of the third fixing portion 18 abuts against the back surface 19a3 of the ring portion 19a. The edge of the ring portion 19a on the side of the opening 19a1 is clamped between the back surface 60f1 of the third expanded diameter portion 60f and the end 18a of the third fixing portion 18. This clamping structure secures the cover electrode 19 to the target support portion 60 at its base end (base end 60b) closer to the anode 61 than the third expanded diameter portion 60f (flange). In other words, the cover electrode 19 is secured to the target support portion 60 at its base end 60b closer to the anode 61 than the flange. The cover electrode 19 of the cover coupling portion 70 is directly secured to the anode 61 (target support portion 60) without brazing, welding, or other methods of joining. The cover connection portion 70 is not limited to this structure. Other structures of the cover connection portion 70 will be described later.

[0050] [Operation and Effect] Hereinafter, the operation and effect of the X-ray tube 3 according to the embodiment will be described.

[0051] The X-ray tube 3 includes a rod-shaped anode 61 (target support portion 60) containing a target T that receives electrons and generates X-rays, and a main body extending along the tube axis AX. A vacuum housing 10 houses the distal end of the anode 61 (target support portion 60), where the target T is located, and secures the proximal end of the anode 61 (target support portion 60) via a housing coupling 15. A cover electrode 19 is disposed within the vacuum housing 10 and connected to the anode 61 (target support portion 60) via a cover coupling 70, surrounding the housing coupling 15. The anode 61 (target support portion 60) includes a third expanded diameter portion 60f (flange portion) protruding from the surface of the main body in a direction intersecting the tube axis AX. The cover coupling 70 is disposed closer to the proximal end of the anode 61 than the third expanded diameter portion 60f.

[0052] The state of the electric field generated inside the vacuum housing 10 is influenced by the surface shape and surface condition of the fixing portions of each component. Here, the housing connection portion 15 of the X-ray tube 3 secures the anode 61 to the vacuum housing 10. The housing connection portion 15 is surrounded by the shield electrode 19. Meanwhile, the shield electrode 9 is secured to the anode 61 by the shield connection portion 70. The shield connection portion 70 is located closer to the base end of the anode 61 than the third expanded diameter portion 60f provided on the anode 61. As a result, the housing connection portion 15, which secures the anode 61 to the vacuum housing 10, and the shield connection portion 70, which secures the shield electrode 19 to the anode 61, are located in locations covered by electrodes with the same potential. These electrodes are, for example, the shield electrode 19 and the third expanded diameter portion 60f. This mitigates the effects of the electric field inside the vacuum housing 10. Consequently, localized increases in electric field intensity are suppressed. In other words, discharge is suppressed.

[0053] The third enlarged diameter portion 60f contacts the cover electrode 19. This structure brings the third enlarged diameter portion 60f and the cover electrode 19 closer together. As a result, the electric field around the flange and the cover electrode is easily stabilized. In addition, the cover electrode 19 can be positioned closer together.

[0054] The outer surface of the third expanded diameter portion 60f includes a surface 60f2 exposed to the interior space of the vacuum housing 10. The outer surface of the cover electrode 19 includes a surface 19f (second main surface) exposed to the interior space of the vacuum housing 10. Surface 60f2 and surface 19f are contained within the same imaginary curved surface. This structure smoothes the boundary between the third expanded diameter portion 60f and the cover electrode 19. This mitigates the effects of the boundary on the electric field. As a result, localized increases in electric field intensity are further suppressed. In other words, discharge can be further suppressed.

[0055] The cover connection portion 70 is surrounded by the cover electrode 19. According to this structure, the electric field around the cover connection portion 70 can be further stabilized.

[0056] The frame connection portion 15 includes a second fixing portion 17 fixed to the vacuum frame 10 and a first fixing portion 16 fixed to the anode 6 (target support portion 60). The first fixing portion 16 is fixed to the second fixing portion 17. With this structure, the first fixing portion 16 and the second fixing portion 17 can be used to support the internal stress caused by the connection between the vacuum frame 10 and the anode 61 (target support portion 60). This can suppress the generation of unnecessary deformation and stress in the vacuum frame 10 and the anode 61 (target support portion 60).

[0057] The vacuum frame 10 includes an inner cylindrical portion 12a extending inward along the tube axis AX. The interior of the inner cylindrical portion 12a and the interior of the vacuum frame 10 are separated from each other by the anode 61 (target support portion 60) and the frame connecting portion 15 provided at one end of the inner cylindrical portion 12a. The portion where the second fixing portion 17 and the first fixing portion 16 are joined is arranged inside the inner cylindrical portion 12a. According to this structure, the portion where the second fixing portion 17 and the first fixing portion 16 are joined is arranged inside the inner cylindrical portion 12a. The portion where the second fixing portion 17 and the first fixing portion 16 are joined is, for example, the joining portion B2. Therefore, the cooling medium provided from the outside can easily enter the interior of the cylindrical portion 12a. As a result, the heat generated by the anode 61 can be efficiently discharged.

[0058] While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Various modifications can be made to the present invention without departing from the spirit and scope of the present invention.

[0059] The shield electrode 19 of the X-ray tube 3 according to the embodiment is clamped between the third expanded diameter portion 60f and the third fixing portion 18. This structure secures the shield electrode 19 to the anode 61 (target support portion 60). The shield connection portion 70A included in the X-ray tube 3A of the first modification may be used as the securing structure. Alternatively, the shield connection portion 70B included in the X-ray tube 3B of the second modification may be used as the securing structure. Alternatively, the shield connection portion 70C included in the X-ray tube 3C of the third modification may be used as the securing structure.

[0060] [First Modification] Figure 3 As shown, the X-ray tube 3A of the first modified example includes a cover connecting portion 70A. The cover connecting portion 70A directly connects the ring portion 19a to the back surface 60f1 of the third expanded diameter portion 60f by brazing, welding, or the like.

[0061] Specifically, the shield electrode 19A includes a cylindrical portion 19d. The cylindrical portion 19d extends from the ring portion 19a in the direction of the tube axis AX. The shape of the cylindrical portion 19d is the same as, for example, the third fixing portion 18. The inner circumferential surface of the cylindrical portion 19d is in contact with the second enlarged diameter portion 60e and the first fixing portion 16. The length of the shield electrode 19A in contact with the anode 61 (target support portion 60) and the first fixing portion 16 is increased. For example, in the absence of the cylindrical portion 19d, the length of the shield electrode 19 in contact with the second enlarged diameter portion 60e is equal to the wall thickness of the ring portion 19a. The cylindrical portion 19d allows the shield electrode 19A to be stably fixed to the anode 61 (target support portion 60).

[0062] The cover connecting portion 70A joins the main surface 19a2 of the ring portion 19a with the back surface 60f1 of the third expanded diameter portion 60f. The main surface 19a2 of the cover connecting portion 70A is joined to the back surface 60f1 using a joint B4. The joint B4 is formed by brazing or welding, etc. The joint B4 is not exposed at the boundary between the surface 60f2 and the surface 19f. The inner circumferential surface of the cylindrical portion 19d of the cover connecting portion 70A can also be directly joined to the second expanded diameter portion 60e using a joint B4, etc. The inner circumferential surface of the cylindrical portion 19d can also be further joined to the outer circumferential surface of the first fixing portion 16. According to this structure, the cover connecting portion 70A joins the cover electrode 19A to the anode 61 (target support portion 60). Therefore, the number of components can be reduced.

[0063] [Second modification] Figure 4 As shown, the X-ray tube 3B of the second modified example has a cover connection portion 70B. The cover connection portion 70B, similar to the cover connection portion 70 of the first modified example, directly secures the cover electrode 19B to the anode 61 (target support portion 60). The cover connection portion 70B secures the cover electrode 19B to the anode 61 (target support portion 60) via a spring structure. The cover electrode 19B has a cylindrical portion 19e. The cylindrical portion 19e has a female thread 19e1 provided on the inner circumference. The second enlarged diameter portion 60e of the anode 61 (target support portion 60) has a male thread 60e1 provided on the outer circumference. The female thread 19e1 of the cylindrical portion 19e screws into the male thread 60e1. As a result, the anode 61 (target support portion 60) is secured to the cover electrode 19B. The cover connection portion 70B makes it possible to easily attach the cover electrode 19B to the anode 61 (target support portion 60).

[0064] [Third Modification] Figure 5 As shown, the X-ray tube 3C of the third modified example includes a cover connection portion 70C. Unlike the cover electrode 19B of the second modified example, the cover connection portion 70C does not directly secure the cover electrode 19C to the anode 61 (target support portion 60). The X-ray tube 3C shares the same fixing components as the X-ray tube 3. The cover connection portion 70C of the third modified example includes a so-called C-ring 71 and a groove 60e2. The groove 60e2 is provided in the second enlarged diameter portion 60e. The C-ring 71 fits into the groove 60e2. This fit determines the position of the C-ring 71 relative to the anode 61 (target support portion 60) in the direction of the tube axis AX. The outer periphery of the C-ring 71 is larger than the inner diameter of the ring portion 19a. The main surface of the C-ring 71 faces the back surface 19a3 of the ring portion 19a. The inside of the C-ring 71 fits into the groove 60e2. Therefore, the C-ring 71 does not move relative to the anode 61 (target support portion 60) in the direction of the tube axis AX. The ring portion 19a is sandwiched between the back surface 60f1 of the third expanded diameter portion 60f and the main surface of the C-ring 71. The cover coupling portion 70C also allows the cover electrode 19C to be easily attached to the anode 61 (target support portion 60).

Claims

1. An X-ray tube, wherein: have: a rod-shaped anode including a target for receiving electrons and generating X-rays and having a main body extending in the direction of the axis; a vacuum frame that houses the front end side of the anode on which the target is arranged and to which the base end side of the anode is fixed by a frame connecting portion; a cover electrode disposed inside the vacuum housing and connected to the anode via a cover connection portion and surrounding the housing connection portion; The anode includes an expanded diameter portion protruding from the surface of the main body in a direction intersecting the axis, and a flange portion protruding from the surface of the main body in a direction intersecting the axis and having an outer diameter larger than that of the expanded diameter portion. The cover electrode has a ring portion, the ring portion including: an opening having an inner diameter equal to an outer diameter of the expanded diameter portion and into which the expanded diameter portion is inserted; and a main surface in contact with the back surface of the flange portion. The cover connecting portion is arranged closer to the base end side of the anode than the flange portion, and is surrounded by the cover electrode.

2. The X-ray tube according to claim 1, wherein The flange portion is in contact with the cover electrode.

3. The X-ray tube according to claim 1, wherein The outer surface of the flange portion includes a first main surface exposed to the inner space of the vacuum frame. The outer surface of the cover electrode includes a second main surface exposed to the inner space of the vacuum frame. The first main surface and the second main surface are included in the same imaginary curved surface.

4. The X-ray tube according to claim 1, wherein The cover coupling portion joins the cover electrode to the flange portion.

5. The X-ray tube according to claim 1, wherein The frame connecting portion includes a frame connecting member fixed to the vacuum frame and an anode connecting member fixed to the anode. The anode connecting member is fixed relative to the frame connecting member.

6. The X-ray tube according to claim 5, wherein The vacuum frame includes an inner cylinder portion extending inwardly along the axis. The interior of the inner cylinder and the interior of the vacuum frame are separated from each other by the anode provided at one end of the inner cylinder and the frame connecting portion. A portion where the anode connecting member and the frame connecting member are joined is disposed inside the inner cylindrical portion.

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