JP5531224B2 - Rotating anode X-ray tube - Google Patents

Description

  Embodiments described herein relate generally to a rotary anode X-ray tube.

  The rotary anode type X-ray tube is mainly applied to a medical X-ray apparatus or the like.

  In the case of a rotating anode X-ray tube with a structure that conducts heat of the anode target through the hydrodynamic slide bearing and cools the anode target, a hole is formed along the central axis of the fixed body constituting the bearing. A structure has been proposed in which a cooling medium is introduced and sprayed in the back of the pipe to take away the heat conducted toward the center of the fixed body.

  In addition, a structure in which a fixed body is configured by members having different thermal conductivities has been proposed.

JP 2001-118534 A JP 2001-189143 A

  An object of the present embodiment is to provide a rotary anode X-ray tube capable of improving the cooling performance.

According to this embodiment,
A cathode that emits electrons; an anode target that emits X-rays when electrons emitted from the cathode are incident; a rotator coupled to the anode target; and a columnar shape that rotatably supports the rotator. A hydrodynamic slide bearing composed of a fixed body and a liquid metal filled between the rotating body and the fixed body, and a vacuum containing the anode target, the cathode, and the hydrodynamic slide bearing An envelope, and the fixed body is a flow path through which a cooling medium circulates and extends in a direction parallel to the central axis of the fixed body, and the rotating body, A flow path that can take in the liquid metal from between the fixed body and is located on the center axis side of the fixed body with respect to the first flow path and extends in a direction parallel to the central axis. A rotary anode X-ray tube characterized by comprising: It is provided.

FIG. 1 is a diagram schematically showing an example of the configuration of a rotating anode type X-ray tube in the present embodiment. FIG. 2 is a cross-sectional view showing a structural example of a dynamic pressure type plain bearing applicable to the rotary anode X-ray tube shown in FIG. FIG. 3 is a diagram schematically showing a cross-sectional structure when the fixed body shown in FIG. 2 is cut along line A-A ′. FIG. 4 is a diagram schematically showing a cross-sectional structure when the fixed body shown in FIG. 2 is cut along line B-B ′. FIG. 5 is a diagram schematically showing a cross-sectional structure when the fixed body shown in FIG. 2 is cut along the C-C ′ line. FIG. 6 is a diagram for explaining a modification of the present embodiment.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. In each figure, the same reference numerals are given to components that exhibit the same or similar functions, and duplicate descriptions are omitted.

  FIG. 1 is a diagram schematically showing an example of the configuration of a rotating anode type X-ray tube in the present embodiment.

  That is, the rotary anode X-ray tube 1 includes a vacuum envelope 2, a cathode 3, an anode target 4, a dynamic pressure slide bearing 10, and the like. The vacuum envelope 2 is formed of, for example, glass, and the internal space 2A is maintained at a high vacuum. The vacuum envelope 2 has an X-ray output window 2W provided in a part thereof. In such a vacuum envelope 2, a cathode 3, an anode target 4, a dynamic pressure type slide bearing 10, and the like are accommodated.

  The cathode 3 is an electron source that emits electrons. The cathode 3 is disposed at a position away from the tube axis O of the rotary anode X-ray tube 1. Such a cathode 3 is supported inside the vacuum envelope 2 by a support mechanism (not shown).

  The anode target 4 emits X-rays when electrons emitted from the cathode 3 enter. The anode target 4 is formed in a substantially disc shape, and a part of the anode target 4 faces the cathode 3. The anode target 4 formed in a disk shape in this manner is connected to a hydrodynamic slide bearing 10 which is a rotation support mechanism at a substantially center thereof and is rotatably supported.

  The hydrodynamic slide bearing 10 includes a rotating body 11, a fixed body 12, and a liquid metal 13 filled between the rotating body 11 and the fixed body 12.

  The rotating body 11 includes a rotating column 11A connected to the anode target 4, a rotating shaft 11B connected to the rotating column 11A, and a rotor 11C formed outside the rotating shaft 11B. . The rotating shaft 11B is formed in a cylindrical shape extending along the tube axis O. One end side of the rotating shaft 11B along the tube axis O is closed, and the other end side of the rotating shaft 11B along the tube axis O is open. The rotary support 11A is connected to one end of the rotary shaft 11B. The rotor 11 </ b> C is formed of a metal material having a low electrical resistance such as copper, and is formed in a cylindrical shape extending along the tube axis O. The rotor 11C is fixed to one end side of the rotating shaft 11B.

  The fixed body 12 rotatably supports the rotating body 11 having the above configuration. In FIG. 1, the cross-sectional structure of the fixed body 12 is omitted, and a more specific description will be given later.

  The liquid metal 13 is made of a liquid metal having a relatively low vapor pressure in vacuum, for example, an indium (In) -gallium (Ga) alloy. The liquid metal 13 is filled in a gap between the rotating shaft 11B and the fixed body 12.

  FIG. 2 is a cross-sectional view showing a structural example of a dynamic pressure type plain bearing 10 applicable to the rotary anode X-ray tube 1 shown in FIG. Here, only the configuration necessary for the description is illustrated, and the rotating body 11 is illustrated in a simplified manner.

  The fixed body 12 is formed in a cylindrical shape extending along the tube axis O. The tube axis O corresponds to the central axis of the fixed body 12. Such a fixed body 12 is fitted to the rotating body 11. A side surface 12A of the fixed body 12 is a cylindrical surface facing the inner surface 11D of the fitted rotating body 11. Further, the front end surface 12B of the fixed body 12 is circular. The liquid metal 13 is sealed between the side surface 12A and the front end surface 12B of the fixed body 12 and the inner surface 11D of the rotating body 11.

  Such a fixed body 12 includes a target-side radial bearing 121 located on the anode target side (not shown), an anti-target-side radial bearing 122 located on the rear end side of the target-side radial bearing 121, and an anti-target. And a thrust side bearing 123 located on the rear end side of the side radial bearing 122. A herringbone pattern 12C for scraping the liquid metal 13 is provided on the side surface 12A of the fixed body 12 having such a configuration.

  The fixed body 12 has first to fifth flow paths P1 to P5. The 1st flow path P1, the 3rd flow path P3, and the 4th flow path P4 comprise some flow paths for circulating insulating oil as a cooling medium, for example. The second flow path P <b> 2 and the fifth flow path P <b> 5 constitute a part of the flow path that can take in the liquid metal 13 from between the rotating body 11 and the fixed body 12.

  The first flow path P1 is a cylindrical space (cooling jacket) extending in a direction parallel to the central axis O of the fixed body 12, and is formed close to the side surface 12A. The second flow path P2 is located on the inner side of the first flow path P1, that is, on the side of the central axis O of the fixed body 12, and is a substantially linear space extending in a direction parallel to the central axis O. . The second flow path P2 penetrates to the front end surface 12B, communicates with the space between the inner surface 11D of the rotating body 11 and the front end surface 12B of the fixed body 12, and can take in the liquid metal 13.

  The third flow path P <b> 3 is a substantially linear space (reflux hole) extending along the central axis O of the fixed body 12. That is, the third flow path is located further inside than the second flow path P2. The fourth flow path P4 communicates the first flow path P1 and the third flow path P3, and is a substantially straight line extending in the radial direction of the fixed body 12 without communicating with the second flow path P2. It is a shaped space. The fifth flow path P5 is a flow path communicating with the second flow path P2, and is a linear space extending in the radial direction of the fixed body 12 without communicating with the first flow path P1.

  The fixed body 12 further has a sixth flow path P6 that communicates with the third flow path P3 and is formed coaxially with the third flow path P3 at the rear end thereof. The sixth flow path P6 is a space having an inner diameter larger than that of the third flow path P3, and communicates with the outside of the vacuum envelope (not shown). A pipe PP that is inserted into the third flow path P3 and drawn out of the vacuum envelope is attached to the sixth flow path P6. The pipe PP partitions the sixth flow path P6, and forms a seventh flow path P7 communicating with the third flow path P3 on the inside thereof. That is, the seventh flow path P7 formed inside the pipe PP is separated from the sixth flow path P6.

  The fixed body 12 further has an eighth flow path P8 that communicates the first flow path P1 and the sixth flow path P6. The eighth flow path P8 is a substantially linear space extending in the radial direction of the fixed body 12 without communicating with the second flow path P2.

  In the third flow path P3, it is desirable to provide a diffuser DF that diffuses the flow of the cooling medium in order to eliminate the stagnation of the cooling medium, in front of the position communicating with the fourth flow path P4.

  According to such a configuration, when the heat generated in the anode target is conducted to the hydrodynamic slide bearing 10, it is radiated and cooled as follows. That is, the heat generated in the anode target is conducted to the rotating body 11 constituting the hydrodynamic slide bearing 10. The heat conducted to the rotating body 11 is transmitted to the side surface 12 </ b> A of the fixed body 12 through the liquid metal 13. That is, the side surface 12 </ b> A serves as a heat transfer surface that receives heat conducted to the rotating body 11.

  On the other hand, the cooling medium is circulated through a route described below, for example. That is, the cooling medium introduced into the sixth flow path P6 from the outside of the vacuum envelope is guided to the first flow path P1 through the eighth flow path P8. Further, the cooling medium is guided from the first flow path P1 to the third flow path P3 via the fourth flow path P4, and then passed through the seventh flow path P7 inside the pipe PP to the outside of the vacuum envelope. Led to. The heat transmitted to the side surface 12A of the fixed body 12 is transmitted to the cooling medium flowing through the first flow path P1, and is carried away by the cooling medium.

  Note that the second flow path P2 and the fifth flow path P5 serve as gas vent holes for venting gas contained in the liquid metal 13 between the rotating body 11 and the fixed body 12. The second flow path P2 and the fifth flow path P5 communicate with the space inside the vacuum envelope. For this reason, the gas inside the hydrodynamic slide bearing 10 is discharged into the space inside the vacuum envelope, and the pressure inside the hydrodynamic slide bearing 10 in which the liquid metal 13 is sealed and the inside of the vacuum envelope. The pressure can be the same.

  FIG. 3 is a diagram schematically showing a cross-sectional structure when the fixing body 12 shown in FIG. 2 is cut along the line A-A ′.

  The illustrated cross section is a cross section orthogonal to the central axis O. As illustrated, the first flow path P1 has a substantially ring-shaped cross section close to the side surface 12A. The third flow path P3 provided with the diffuser DF is located in the center of the fixed body 12 and has a substantially circular cross section. The first flow path P1 and the third flow path P3 are connected by a fourth flow path P4.

  In the example shown here, the fourth flow path P4 is formed at three locations. These fourth flow paths P4 are formed radially along the radial direction from the central axis O toward the side surface 12A. These three fourth flow paths P4 are formed at equal intervals in the direction of 120 ° with the central axis O as the center.

  The second flow path P2 is located between the first flow path P1 and the third flow path P3 and has a substantially circular cross section. In the example shown here, the second flow path P2 is formed at three locations. These three second flow paths P2 are formed at equal intervals in the direction of 120 ° with the central axis O as the center. In addition, each of these second flow paths P2 is located between each of the three fourth flow paths P4, and the first flow path P1, the third flow path P3, which are the flow paths of the cooling medium, And it is not connected with the 4th channel P4.

  FIG. 4 is a diagram schematically showing a cross-sectional structure when the fixed body 12 shown in FIG. 2 is cut along the line B-B ′.

  The cross section shown in the figure is also a cross section orthogonal to the central axis O, like the cross section of FIG. As illustrated, the eighth flow path P8 is located between the third flow path P3 and the side surface 12A and has a substantially rectangular cross section. Note that the eighth flow path P8 does not directly communicate with the third flow path P3. In the example shown here, the eighth flow path P8 is formed in three places. These three eighth flow paths P8 are formed at equal intervals in the direction of 120 ° with the central axis O as the center.

  Each of the three second flow paths P2 is positioned between each of the three eighth flow paths P8. What are the third flow path P3 and the eighth flow path P8 that are the flow paths of the cooling medium? Not communicating. Further, each of the second flow paths P2 is connected to a fifth flow path P5 that penetrates to the side surface 12A. These fifth flow paths P5 are formed radially along the radial direction from the central axis O toward the side surface 12A. The three fifth flow paths P5 are formed at equal intervals in the direction of 120 ° with the central axis O as the center.

  FIG. 5 is a diagram schematically showing a cross-sectional structure when the fixed body 12 shown in FIG. 2 is cut along the line C-C ′.

  The cross section shown in the figure is also a cross section orthogonal to the central axis O, like the cross section of FIG. As illustrated, the sixth flow path P6 is located in the center of the fixed body 12 and has a substantially circular cross section. The pipe PP is located inside the sixth flow path P6. A seventh flow path P7 is formed inside the pipe PP. The three second flow paths P2 are located between the sixth flow path P6 and the side surface 12A.

  According to the present embodiment configured as described above, a cylindrical space extending substantially parallel to the side surface 12 </ b> A at a position close to the side surface 12 </ b> A of the fixed body 12 in contact with the liquid metal 13 inside the fixed body 12. And this space is used as the first flow path P1 as a part of the flow path for circulating the cooling medium. For this reason, a wide heat transfer area can be secured, and the heat transfer path from the side surface 12A of the fixed body 12 to the cooling medium can be shortened. Therefore, sufficient heat transfer can be performed and the cooling performance can be improved.

  Further, the second flow path P2 for exhausting the gas accumulated in the hydrodynamic slide bearing 10 during the manufacturing process for creating a vacuum or during operation to the space 2A inside the vacuum envelope 2 is the first flow path P2. It is formed closer to the central axis O than the flow path P1. Such a gas vent path including the second flow path P2 communicates with the vacuum space 2A inside the vacuum envelope 2, while a circulation path for circulating the cooling medium including the first flow path P1. Is atmospheric pressure, but they are separated without communicating with each other. That is, the degassing path three-dimensionally intersects the circulation path inside the fixed body 12, and passes through the space between the inner surface 11D of the rotating body 11 and the side surface 12A of the fixed body 12 and the fifth flow path P5. Communicate.

  Therefore, without increasing the diameter of the fixed body 12, the first flow path P <b> 1 is a space for transferring heat to the cooling medium in the circulation path, leaving a thickness for reliably separating the gas vent path and the circulation path. Can be formed larger. At the same time, by shortening the path of heat conducted through the liquid metal 13 to a minimum, a large conduction cooling rate can be secured while keeping the bearing surface temperature low.

  In the present embodiment, the first flow path P1 is formed within a depth range of a distance of 0.1 mm to 15 mm from the side surface 12A of the fixed body 12 toward the central axis O along the radial direction of the fixed body 12. Yes. The first flow path P1 is desirably as close to the side surface 12A as possible from the viewpoint of heat transfer, and the plate thickness between the first flow path P1 and the side surface 12A is the inner surface 11D of the rotating body 11 and the fixed body. It is desirable that the thickness be sufficient to maintain a space in which the liquid metal 13 between the 12 side surfaces 12A is sealed in a vacuum-tight manner. As a result of repeated studies by the inventors based on such grounds, it has been confirmed that it is desirable to form the first flow path P1 within the above range.

  In the present embodiment, a flow path having a shape that cannot be machined by inserting a tool from the outside is formed inside the fixed body 12, but a plurality of parts are joined by friction welding or electron beam welding. And can be formed easily. For example, the fixed body 12 is divided into two or more bodies in a cross section perpendicular to the direction of the central axis O at a portion corresponding to a position where the gas vent hole and the circulation path intersect three-dimensionally, and the gas vent is formed inside. After processing the hole and the circulation path, each part is joined by the above-described method, so that the fixed body 12 having the structure of the present embodiment can be realized without leaving a defect or a processing distortion causing a leak. .

  In the present embodiment, the fixed body 12 is formed using an iron-based material. Such iron-based materials are inferior in thermal conductivity to molybdenum (Mo) -based materials, but are low in cost, have good workability, and form a complicated flow path. Suitable for

  FIG. 6 is a diagram for explaining a modification of the present embodiment.

  In the present embodiment, as illustrated, the fixed body 12 may have a turbulence promoter TP on the inner wall P1A on the side close to the side surface 12A in the first flow path P1. The turbulence promoter TP is a protrusion that protrudes from the inner wall P1A toward the center axis (not shown) (that is, the side away from the side surface 12A), and is formed in a ring shape that extends the entire inner wall P1A. .

  A cooling medium such as insulating oil flows through the first flow path P1, but when the flow of the cooling medium becomes a laminar flow, the heat transfer rate from the side surface 12A to the cooling medium decreases. That is, the flow velocity of the cooling medium flowing near the inner wall P1A is slower than the flow velocity of the cooling medium flowing near the inner wall P1B on the side close to the central axis in the first flow path P1. For this reason, the cooling medium flowing in the vicinity of the inner wall P1A is likely to have a higher temperature than the cooling medium flowing in the vicinity of the inner wall P1B. Since the high-temperature cooling medium stays in the vicinity of the inner wall P1A, the heat transfer coefficient from the side surface 12A is reduced.

  Therefore, as shown in the figure, by arranging the turbulence promoter TP on the inner wall P1A, the boundary layer in the vicinity of the inner wall P1A is peeled off, and transition to turbulent flow TF occurs. Thereby, it becomes possible to generate a vortex by the turbulent flow TF and to stir the boundary layer to improve the heat transfer coefficient.

  The turbulence promoter TP is arranged at an appropriate interval W and a height H according to the viscosity and flow velocity of the cooling medium.

  As described above, according to this embodiment, it is possible to provide a rotary anode X-ray tube capable of improving the cooling performance.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the spirit of the invention in the stage of implementation. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  For example, in the present embodiment, the hydrodynamic slide bearing 10 has been described as an example in which only the rear end portion of the fixed body 12 is supported, but the rotating shaft 11B is formed in a cylindrical shape, and the anode target 4 May be attached to substantially the center of the rotating shaft 11B, and the both ends of the fixed body 12 may be supported (both-end bearings).

DESCRIPTION OF SYMBOLS 1 ... Rotating anode type X-ray tube 2 ... Vacuum envelope 3 ... Cathode 4 ... Anode target 10 ... Dynamic pressure type plain bearing 11 ... Rotating body 11D ... Inner surface 12 ... Fixed body 12A ... Side surface 12B ... End surface 12C ... Herringbone pattern 13 ... Liquid metal P1 to P8 ... Flow path PP ... Pipe DF ... Diffuser TP ... Turbulence promoter

Claims (7)

A cathode that emits electrons;
An anode target from which electrons emitted from the cathode are incident to emit X-rays;
A moving body composed of a rotating body connected to the anode target, a columnar fixed body that rotatably supports the rotating body, and a liquid metal filled between the rotating body and the fixed body. A pressure-type plain bearing,
A vacuum envelope containing the anode target, the cathode, and the hydrodynamic slide bearing;
With
The fixed body is a flow path through which a cooling medium circulates, and extends from the cylindrical first flow path extending in a direction parallel to the central axis of the fixed body, and between the rotating body and the fixed body. A substantially linear second channel that is capable of taking in liquid metal and that is positioned closer to the central axis of the fixed body than the first channel and extends in a direction parallel to the central axis. A rotating anode X-ray tube characterized by comprising:   The fixed body further communicates the substantially straight third flow path extending along the central axis of the fixed body, the first flow path, and the third flow path, and the second flow path. The rotary anode type X-ray tube according to claim 1, further comprising a substantially straight fourth flow path extending in a radial direction of the fixed body without communicating with the rotary anode.   The fixed body further includes a linear fifth flow path that communicates with the second flow path and extends in a radial direction of the fixed body without communicating with the first flow path. The rotary anode X-ray tube according to claim 1.   2. The rotary anode X-ray according to claim 1, wherein the first flow path is formed within a distance of 0.1 mm to 15 mm in a radial direction of the fixed body from a side surface of the fixed body. tube.   The rotary anode X-ray tube according to claim 1, wherein the fixed body is formed by joining a plurality of parts by friction welding or electron beam welding.   The rotary anode X-ray tube according to claim 1, wherein the fixed body is formed using an iron-based material.   2. The rotary anode X-ray tube according to claim 1, wherein the fixed body has a turbulence promoter disposed on an inner wall on a side close to a side surface in the first flow path.

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