JP2006179231A - Rotary positive electrode x-ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary positive electrode x-ray tube equipped with a foreign matter scatter prevention mechanism capable of preventing the scatter of foreign matters generated at a roller bearing of a rotary positive electrode in an envelope and of facilitating its mounting work. <P>SOLUTION: A nearly L-shaped cap 38 comprising a cylindrical part 38 facing the peripheral surface of a shaft part 24b of a rotating shaft 24 so as to cover a roller bearing 26 on the side close to an opening of a bearing box 28 out of two roller bearings 26 supported to the inside wall surface of a hollow part 32 of the bearing box 28a of a fixed part 28 of a rotary positive electrode 14, and having an inside surface generally parallel to it, and a ring-like flat part 38b connected to the end of the cylindrical part 38a is installed, and the peripheral edge of the flat part 38a of the cap 38 is fixed to the inside wall surface of the bearing box 28a with a retaining ring 40 together with an outer ring 26a of the roller bearing 26. A clearance 44 between the shaft part 24b of the rotating shaft 24 and the cylindrical part 38b of the cap 38 is kept small. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mounting structure for a rolling bearing part of a rotating anode of a rotating anode X-ray tube, and more particularly to a mounting structure for a rolling bearing part suitable for preventing a lubricant of a rolling bearing and foreign matter generated from the rolling bearing from falling off.

  A rotating anode X-ray tube has a cathode that generates an electron beam, a target that generates X-rays when the electron beam from the cathode collides, a rotating anode whose target portion rotates, and the cathode and the rotating anode are vacuum-tight. And an envelope that insulates and supports both electrodes. The target portion of the rotating anode is rotatably supported by a rolling bearing and is rotated at a high speed when the rotating anode X-ray tube is used. The envelope is mostly made of an insulating material such as heat-resistant glass, and insulates the high voltage (X-ray tube voltage) applied to the rotating anode X-ray tube.

  When using a rotating anode X-ray tube, the X-ray tube voltage of about 50 kV to 150 kV is usually between the cathode and the rotating anode of the rotating anode X-ray tube, and the filament heating voltage on the cathode filament causes the rotating anode to rotate. A stator driving voltage is applied to each of the stators. By applying these voltages, the rotating anode rotates at high speed, the thermoelectrons emitted from the cathode filament are focused into an electron beam, accelerated by the X-ray tube voltage, and collided with the target of the rotating anode. Radiate a line. The X-ray source on the target is called the focal point, but this focal point is convenient for obtaining X-ray images that are better for X-ray photography, but it is large when a large amount of X-ray dose is required. Is more convenient. In a rotating anode X-ray tube, the effective focal area on the target increases due to rotation of the rotating anode, and a large X-ray tube load (multiplying the X-ray tube voltage and the X-ray tube current) can be applied. This makes it possible to emit a large amount of X-rays with a small focus. For this reason, rotating anode X-ray tubes are widely used in the field of medical diagnosis.

  FIG. 5 shows a cross-sectional view of an example of the structure of the rotary anode of a conventional rotary anode X-ray tube. In FIG. 5, a rotating anode 100 is attached to an umbrella-shaped target 102, a rotor 104 that supports the target 102, a rotating shaft 106 that supports the rotor 104, and a rotating shaft 106. The bearing 108 and a fixed portion 110 that fixes and supports the outer ring of the rolling bearing 108 are configured.

  The target 102 is a large-diameter umbrella-shaped disk, and has an inclined surface on the upper surface where an electron beam collides from the cathode to form a focal point. Since at least the inclined surface of the target 102 is made of a metal material having a high atomic number and a high melting point, such as tungsten, which has good X-ray generation efficiency, the weight of the target 102 is usually heavy. The rotor 104 includes a target support portion 104a that supports the target 102, and a cylindrical large-diameter portion 104b that serves as a rotor in combination with a stator disposed on the outside. The target support portion 104a is made of a high-strength, high-melting metal material such as molybdenum, and the large-diameter portion 104b is made of a highly conductive metal material such as copper. The shoulder 104c of the rotor 104 is coupled to the rotating shaft 106. A screw or the like is used for this connection. The rotor shoulder 104c is made of a high-strength metal material like the target support 104a. The rotating shaft 106 includes a flange portion 106a that is coupled to the rotor 104, and a shaft portion 106b that is coupled to the inner ring of the rolling bearing 108. The rotating shaft 106 is made of a high-strength metal material.

  Two rolling bearings 108 are used, each of which is composed of an inner ring 108a, an outer ring 108b, and a rolling element (ball) 108c. The inner ring 108a of the rolling bearing 108 may be omitted by providing a rolling surface (groove) for the rolling element 108c on the surface of the shaft portion 106b of the rotating shaft 106. In this case, the rotating shaft 106 and the rolling bearing 108 are often handled as an integral component. The rolling bearing 108 is also made of a high-strength metal material like the rotating shaft 106. The fixed part 110 includes a bearing box 110a that supports the rolling bearing 108, an anode end 110b to which an anode potential is supplied, and the like. The bearing box 110a has a shaft portion 106b of the rotating shaft 106 and a hollow portion 112 that accommodates the rolling bearing 108, and an outer ring 108b of the rolling bearing 108 is fixed to an inner wall 112a of the hollow portion 112. Since the two rolling bearings 108 are arranged at intervals, spacers 114 and 116 are disposed between the inner ring 108a and the outer ring 108b, respectively. The large-diameter spacer 116 is attached to the fixed portion 110 side, and the small-diameter spacer 114 is attached to the rotating shaft 106 side. The anode end 110b of the fixed portion 110 is usually processed to have an outer diameter thinner than that of the bearing box 110a, and is used to support the rotating anode 100 of the X-ray tube. The fixed part 110 is made of a metal material such as stainless steel or copper. A metal ring or the like used for connection with the envelope is also attached around the anode end 110b of the fixed portion 110. A lid 118 for fixing the outer side 108b of the rolling bearing 108 and the spacer 116 to the inner wall of the hollow part 112 of the fixed part 110 is attached to the inlet side of the hollow part 112 of the fixed part 110.

  The rolling bearing 108 is coated with a lubricant in order to increase the rotation life in vacuum. As the lubricant, a solid lubricant is used, and a soft metal such as silver or lead or a compound such as molybdenum disulfide is used. These lubricants are applied to the surface of the rolling element (ball) 108c of the rolling bearing 108 and the rolling surfaces of the inner ring 108a and the outer ring 108b. Before the rolling bearing 108 coated with the lubricant is mounted on the rotary anode X-ray tube, the rolling bearing 108 may be rotated and the amount of lubricant adhering to the rolling bearing 108 may be optimized.

  When a rotating anode X-ray tube is used, a large X-ray tube load is repeatedly applied. Therefore, a large heat input is repeatedly input to the target 102 of the rotating anode 100, and the target 102 rises to a high temperature of about 1000 degrees. As a result, the rolling bearing 108 that rotatably supports the target 102 of the rotating anode 100 rotates for a long time under conditions in which the temperature constantly fluctuates in a high vacuum. Accordingly, the lubricant of the rolling bearing 108 melts into a fluid at a high temperature and may fall off the surface of the rolling bearing 108. In addition, when the rotary anode X-ray tube is used for a long time, wear powder is generated from the rolling bearing 108 and may fall off as foreign matter. In addition, there is a mixture of the above-described lubricant and wear powder, which are integrated into a foreign substance.

  These foreign substances are initially attached to the periphery of the rolling bearing 108 and remain in the hollow portion 112 in the bearing housing 110a of the fixed portion 110. It may scatter in the vacuum envelope of the X-ray tube, adhere to the surface of the target 102, the surface of the cathode, the inner surface of the vacuum envelope, etc., and generate a discharge when an X-ray tube voltage is applied. This is a big problem.

For this reason, some countermeasures for preventing the scattering of foreign matters from the rolling bearing of the rotary anode X-ray tube have been taken so far, and are disclosed in Patent Documents 1 to 3 below.
Japanese Unexamined Patent Publication No. 55-139739 Japanese Utility Model Publication No. 55-142884 Japanese Utility Model Publication No. 6-58547

  In Patent Document 1, an end on the target side of a rolling bearing (ball bearing) closer to the target is covered with a groove-shaped member, and a ring-shaped cover plate is arranged so as to cover the ball bearing on the inner side. There is disclosed a rotating anode in which an outer edge portion of a groove-shaped member and a cover plate is fixed to an inner wall of a hollow portion of a fixed portion together with an outer ring of a ball bearing. On the inner peripheral side of the groove-shaped member, there is provided a folded portion that is parallel to the axial direction of the rotating shaft and is folded back to the ball bearing side, and a small gap as large as the bearing clearance is provided between the folded portion and the rotating shaft. In addition, the gap between the inner periphery of the cover plate and the rotating shaft is also held in the same gap. By adopting such a structure, a space (first space) around the ball bearing covered with the cover plate and a space (second space) between the groove-shaped member and the cover plate are formed. These spaces serve as spaces for collecting foreign matter separated from the ball bearings. First, the foreign matter separated from the ball bearing in the first space is collected, but the foreign matter leaked from the first space through the gap between the cover plate and the rotating shaft is collected in the second space. As a result, almost no foreign matter leaks from the second space into the envelope, and the foreign matter collecting effect is greatly improved.

  Patent Document 2 discloses a rotating anode in which a shield is attached to both a rolling bearing on the target side and a rolling bearing on the anode end side in order to prevent foreign matter separated from the rolling bearing from dropping out of the fixed portion. It is disclosed. A double shield is attached to the rolling bearing on the target side, the outer shield is fixed to the outer periphery of the fixed portion, and the inner shield is fixed to the rotating shaft. As a foreign matter fall-off prevention mechanism, in the case of the outer shield, the gap between the inner periphery of the shield and the outer periphery of the rotating shaft is narrowed. In the case of the inner shield, this is used as the outer shield. It is arranged close to the body to narrow the gap between the shields. In addition, a single shield is attached to the rotating shaft of the rolling bearing on the anode end side, and the gap between the outer periphery of the shield and the inner wall of the hollow portion of the fixed portion is narrowed. In this way, the effect of preventing foreign matter from falling off the rolling bearing is improved by using a double shield.

  In Patent Document 3, an opening is directed to the ball bearing side at the portion of the rotating shaft and the lid (coupled to the fixed portion) adjacent to the side surfaces of the inner ring and outer ring of the rolling bearing (ball bearing) on the target side. There is disclosed a rotating anode in which a rotating shaft side circumferential groove and a lid side circumferential groove are provided, and a clearance between both circumferential groove edges is a distance close to a radial clearance of the ball bearing. The foreign matter separated from the ball bearing is generated from the boundary between the ball and the rolling contact surface of the ball bearing, so that the foreign matter circulates by providing circular grooves on both the rotating shaft side and the fixed part side toward the ball bearing side. It is received and held by the groove. In addition, the edges (the side with the clearance) of the two circumferential grooves are arranged away from the circumferential groove from the ball rolling surface of the ball bearing, and the clearance between both circumferential groove edges is extremely narrow. Even if the use position of the X-ray tube is changed, the foreign matter is received by the circumferential groove, and the foreign matter is hardly scattered through the gap and into the envelope.

  In the above-described conventional rotary anode X-ray tube, when the rolling bearing is in use, the rolling bearing rotates under conditions where the temperature constantly fluctuates in a high vacuum, and the rolling bearing lubricant melts into a fluid at high temperatures. There is also. In such a case, the lubricant may be separated from the surface of the rolling bearing and fall off as foreign matter. In addition, when the rolling bearing is used for a long time, wear powder of the constituent material is generated, and the wear powder falls off the rolling bearing as a foreign matter. Most of these foreign matters in the rolling bearings stay around the rolling bearing in the hollow part of the fixed part of the rotating anode, but only a small part is scattered in the envelope and discharged by the high voltage X-ray tube voltage. This discharge is a big problem.

  Examples of techniques for preventing scattering of foreign matters separated from rolling bearings of the rotating anode include those disclosed in Patent Documents 1 to 3 above, and the rotating anode X-ray tube disclosed in these documents. Then, a mechanism for preventing scattering of foreign matters is provided around the rolling bearing on the target side of the rotating anode. In the technique of Patent Document 1, a groove-shaped member or a multilayer cover plate is fixed together with the outer ring of the rolling bearing on the target side to the hollow inner wall of the fixed portion of the rotating anode, and the rolling bearing side is positioned on the inner peripheral side of the groove-shaped member Therefore, there is a problem that the structure around the rolling bearing on the target side is complicated, and it is difficult to fix the groove-shaped member or the cover plate.

  In the technique described in Patent Document 2, a shielding body for preventing foreign matter scattering is attached to a rotating shaft of a rotating anode together with two inner rings of rolling bearings. Since the rotating shaft side is rotated at a high speed together with the inner ring of the rolling bearing, an unbalance occurs during use due to the attachment of the shield, and the reliability of the rotational life becomes a problem. Further, in the technique described in Patent Document 3, a groove for collecting foreign matter is provided in the vicinity of the inner ring of the rolling bearing on the target side of the rotating shaft of the rotating anode. There is a similar problem.

  In view of the above, in the present invention, a rotary anode X-ray tube equipped with a foreign matter scattering prevention mechanism that effectively prevents foreign matter generated in the rolling bearing of the rotary anode from scattering into the envelope and is easy to install. The purpose is to provide.

  In order to achieve the above object, a rotating anode X-ray tube of the present invention comprises a disk-shaped target, a rotor that supports the target, a rotating shaft that supports the rotor, and a plurality of rolling members that rotatably support the rotating shaft. In a rotary anode X-ray tube (hereinafter abbreviated as X-ray tube) including a bearing and a rotating anode having a fixed portion that supports the rolling bearing in the bearing housing, the outer surface of the shaft portion of the rotary shaft is opposed to the outer surface. A cap comprising a cylindrical portion having an inner peripheral surface substantially parallel to the cylindrical portion and a ring-shaped flat plate portion coupled to an end opposite to the target of the cylindrical portion is disposed on the opening side of the bearing box of the fixed portion. The clearance between the inner peripheral surface of the cylindrical portion of the cap and the outer peripheral surface of the shaft portion of the rotating shaft is larger than the radial clearance of the rolling bearing. (Claim 1).

  In the X-ray tube of the present invention, the length of the cylindrical portion of the cap is at least twice the thickness of the flat plate portion, and the inner peripheral surface of the cylindrical portion of the cap and the outer peripheral surface of the shaft portion of the rotary shaft Is approximately twice or more than the radial clearance of the rolling bearing.

  In the X-ray tube of the present invention, the outer peripheral edge portion of the flat plate portion of the cap is fixed to the inner wall surface of the bearing box of the fixed portion.

  Further, in the X-ray tube of the present invention, a groove (hereinafter referred to as a retaining ring groove) for fitting a retaining ring at a position near the opening end of the bearing box on the inner wall surface of the bearing box of the fixed portion. The outer peripheral edge portion of the flat plate portion of the cap is fixed to the inner wall surface of the bearing housing of the fixed portion together with the outer ring of the rolling bearing closest to the target by fitting and retaining the retaining ring in the retaining ring groove. Is.

  In the X-ray tube of the present invention, at least the cylindrical portion of the cap is magnetized (Claim 2).

  In the X-ray tube of the present invention, a groove is provided on the inner peripheral surface of the cylindrical portion of the cap (claim 3). The shape of the groove is a triangle or a rectangle.

  In the X-ray tube of the present invention, a cylindrical portion parallel to the outer peripheral surface of the shaft portion of the rotating shaft so as to cover the rolling bearing closest to the target among the rolling bearings supported in the bearing box of the fixed portion of the rotating anode. And a cap having a flat plate portion coupled to the end of the cylindrical portion, the outer peripheral edge portion of the flat plate portion of the cap is fixed to the inner wall surface of the bearing box of the fixed portion, and the inner peripheral surface of the cylindrical portion of the cap Is placed close to the outer peripheral surface of the shaft portion of the rotating shaft more than the radial clearance of the rolling bearing, so most of the foreign matter separated from the rolling bearing during use of the X-ray tube is the periphery of the rolling bearing. The cap cylindrical part also extends for a very small amount of foreign matter that is collected by the flat part of the cap and enters the narrow gap between the cylindrical part of the cap and the shaft part of the rotating shaft. Therefore, it will be collected until this plow, and will be scattered in the envelope The amount of foreign matter is greatly reduced compared to conventional products. As a result, the discharge caused by the scattering of foreign matter in the X-ray tube is suppressed (Claim 1).

  In the X-ray tube of the present invention, the length of the cylindrical portion of the cap is at least twice the thickness of the flat plate portion, and the clearance between the cylindrical portion of the cap and the shaft portion of the rotating shaft is the radial clearance of the rolling bearing. Because the foreign matter separated from the rolling bearing and entering the clearance between the cylindrical portion of the cap and the shaft portion of the rotating shaft is collected by the cylindrical portion of the cap. The scattering of foreign matter into the envelope is reduced, and a clearance is secured between the rotating shaft and the cap to prevent contact during rotation. Can do.

  Further, in the X-ray tube of the present invention, the outer peripheral edge of the flat plate portion of the cap is fixed to the inner wall surface of the bearing box of the fixed portion, so that the rolling system does not have any influence on the rotating system of the rotating anode. The bearing can be safely rotated at high speed, and high rotational reliability can be maintained.

  In the X-ray tube of the present invention, the outer peripheral edge portion of the flat plate portion of the cap is fixed to the inner wall surface of the bearing box of the fixed portion together with the outer ring of the rolling bearing by the retaining ring. In addition, the cap can be fixed with a simple structure without adding a complicated part, and the effect of preventing scattering of foreign matters separated from the rolling bearing can be improved.

  In the X-ray tube of the present invention, since at least the cylindrical portion of the cap of the rotating anode is magnetized, the inner peripheral surface of the magnetized cylindrical portion is between the cylindrical portion of the cap and the shaft portion of the rotating shaft. Foreign matter from the intruding rolling bearing can be efficiently collected (claim 2).

  In the X-ray tube of the present invention, since a groove having a shape such as a triangle or a rectangle is provided on the inner peripheral surface of the cylindrical portion of the cap, the cylindrical portion of the cap among foreign matters separated from the rolling bearing. Foreign matter that has entered the clearance between the shaft and the shaft portion of the rotary shaft is efficiently collected and retained in the groove on the inner peripheral surface of the cylindrical portion. Inward scattering is greatly reduced (Claim 3).

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, the structure of the first embodiment of the rotary anode X-ray tube according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing an outline of the overall structure of a first embodiment of a rotary anode X-ray tube according to the present invention, FIG. 2 is a cross-sectional view of the main part of the rotary anode of this embodiment, and FIG. 3 is this embodiment It is an expanded sectional view showing the detail of the principal part of. The overall structure of the rotary anode X-ray tube of the present embodiment will be described with reference to FIGS. 1 and 2, and the structure of the rotary anode as the main part of the present embodiment will be described with reference to FIGS.

  In FIG. 1, a rotary anode X-ray tube (hereinafter abbreviated as X-ray tube) 10 of the present embodiment includes a cathode 12, a rotary anode 14 disposed facing the cathode 12, a cathode 12 and a rotary anode 14 And an envelope 16 that is vacuum-tightly enclosed. The cathode 12 is a part that generates an electron beam, a filament that emits thermoelectrons, a focusing electrode 12a that focuses the thermoelectrons into an electron beam, a support 12b that supports the focusing electrode 12a, and an insulating support for the support 12b It consists of stem 12c and so on. The filament is accommodated in the focusing electrode 12a.

  1 and 2, the rotating anode 14 includes a disk-shaped target 20 that generates X-rays when an electron beam from the cathode 12 collides, a rotor 22 that supports the target 20, and a rotating shaft that supports the rotor 22. 24, a plurality of (two in the illustrated example) rolling bearings 26 that rotatably support the rotating shaft 24, a fixed portion 28 that fixes the outer ring 26a of the rolling bearing 26, and the like. The target 20 has an inclined surface 20a on which the electron beam from the cathode 12 collides with the upper surface of the disk. At least the inclined surface 20a is made of a high melting point metal material such as tungsten or a tungsten alloy. The target 20 is coupled to the rotor 22 at the center of the disk. The rotor 22 includes a thin-axis target support portion 22a that supports the target 20, and a large-diameter cylindrical portion 22b with a bottom. The target support portion 22a is a bottom portion of the cylindrical portion 22b (hereinafter referred to as a shoulder portion). Combined with 22c. The target support portion 22a is made of a refractory metal material such as molybdenum, the large diameter cylindrical portion of the cylindrical portion 22b is made of a highly conductive metal material such as copper, and the shoulder portion 22c is the same material as the target support portion 22a or others. Made of high strength metal material. A rotational driving force is applied to the cylindrical portion 22b of the rotor 22 by a stator disposed outside the X-ray tube 10, and the rotor 22 rotates around a central axis (rotating axis) 34 of the rotating anode 14. The rotor 22 and the rotating shaft 24 are coupled by a screw or the like at the shoulder 22c of the rotor 22a.

  The rotating shaft 24 has a disk-shaped flange portion 24a coupled to the rotor 22 and a columnar shaft portion 24b coupled to the rolling bearing 26, and is made of a high-strength steel material. The rolling bearing 26 is a ball bearing, has an outer ring 26a, a ball (rolling element) 26b, and an inner ring 26c, and is made of a high-strength steel material. The inner ring 26c of the rolling bearing 26 is coupled to the outer periphery of the shaft portion 24b of the rotating shaft 24, thereby rotatably supporting the rotating shaft 24. In the present embodiment, the shaft portion 24b of the rotating shaft 24 The inner ring 26c of the rolling bearing 26 is omitted by providing a groove (rolling groove) for rolling the ball 26b of the rolling bearing 26 on the outer peripheral surface. Since the rolling groove of the shaft portion 24b of the rotating shaft 24 is functionally the same as the rolling surface of the inner ring 26c of the rolling bearing 26, in the following description, the rolling groove of the shaft portion 24b of the rotating shaft 24 is used. Will be described as the inner ring 26c of the rolling bearing 26. In the present embodiment, since the two rolling bearings 26 are arranged at intervals, when distinguishing the two, the rolling bearing 26 on the side closer to the target 20 is far from the target side rolling bearing 26 and the target 20. The side rolling bearing 26 will be referred to as the anode end side rolling bearing 26. The outer rings 26a of the two rolling bearings 26 are fixed to the fixing part 28 with a spacer 36 at an appropriate interval. When the inner ring 26c of the rolling bearing 26 is attached to the shaft portion 24b of the rotating shaft 24, a spacer is also disposed between the two inner rings 26c.

  A lubricant 30 is applied or attached to the rolling surfaces of the outer ring 26a and the inner ring 26c of the rolling bearing 26 and the surface of the ball 26b. As the lubricant, a soft metal such as silver or lead or a lubricating compound such as molybdenum disulfide is used.

  The fixed portion 28 has a substantially cylindrical bearing box 28a and a rod-like anode end 28b, and is made of a metal material such as copper or stainless steel. The bearing box 28a of the fixed portion 28 has a deep hole 32 opened on one side, and the shaft portion 24b of the rotating shaft 24 and the rolling bearing 26 are accommodated in the hole 32. The outer rings 26a of the two rolling bearings 26 are fixed to the inner wall 33 of the bearing box 28a of the fixed portion 28 with a spacer 36 therebetween. The anode end 28b of the fixed portion 28 is a portion connected to the envelope 16, and the anode potential to the X-ray tube 10 is fed to the anode end 28b.

  In FIG. 1, an envelope 16 includes a large-diameter portion 16a that accommodates the target 20 of the rotating anode 14, the head of the cathode 12, and the like, a cathode insulating portion 16b that accommodates the stem 12c portion of the cathode 12, and the rotating anode 14 The anode insulating portion 16c that accommodates the rotor 22 is provided. In the present embodiment, the large-diameter portion 16a, the cathode insulating portion 16b, and the anode insulating portion 16c of the envelope 16 are integrated and made of an insulating material such as heat resistant glass or ceramic. The cathode insulating portion 16b is insulated and supported by coupling the cathode 12 with the stem 12c of the cathode 12, and the anode insulating portion 16c is insulated and supported by coupling with the anode end 28b of the fixed portion 28 of the rotating anode 14. . X-rays generated at the focal point 21 formed on the inclined surface 20a of the target 20 are radiated to the outside through the large portion 16a of the envelope 16. In the present embodiment, the case where the large-diameter portion 16a is made of an insulating material has been shown. However, the large-diameter portion 16a may be made of a metal material such as copper or stainless steel. An X-ray radiation window made of a beryllium plate or the like is attached to a portion close to the focal point 21 of the lens.

  Next, with reference to FIGS. 2 and 3, the detailed structure of the rotating anode, which is a main part of the present embodiment, will be described. In FIG. 2, in the rotating anode 10 of the present embodiment, a cap 38 is attached to the opening of the hole 32 of the bearing box 28a of the fixing portion 28 for fixing the target side rolling bearing 26 so as to cover the entire target side rolling bearing 26. Yes. The cross section of the cap 38 is generally L-shaped, and the thickness thereof is about 0.5 mm to about 2 mm, and may be thinner or thicker depending on the case. As a material, a metal material such as steel is mainly used, but a heat-resistant insulating material such as ceramic may be used.

  FIG. 3 is an enlarged view of the periphery of the target-side rolling bearing 26. The cap 38 includes a flat plate portion 38a and a cylindrical portion 38b, and an end of the cylindrical portion 38b opposite to the target 20 is coupled to the inner peripheral portion of the flat plate portion 38a. The cap 38 is made by pressing or cutting a thin plate. The outer peripheral edge portion of the flat plate portion 38a of the cap 38 is fixed to the inner wall 33 of the bearing box 28a of the fixed portion 28 together with the outer ring 26a of the target side rolling bearing 26. In the present embodiment, a retaining ring (for example, a commercially available C-shaped retaining ring) 40 is used to fix the flat plate portion 38a of the cap 38. For retaining and retaining the retaining ring 40, a circulating groove (hereinafter referred to as a retaining ring groove) 42 of an appropriate depth provided in the inner wall 33 of the hole 32 of the fixing portion 28 is used. In the anode, the structure is almost the same as that used for fixing the outer ring 26a of the rolling bearing 26. The cylindrical portion 38b of the cap 38 faces the shaft portion 24b of the rotating shaft 24 from the inner periphery of the flat plate portion 38 toward the target 20, and extends in parallel along the surface thereof.

  The clearance 44 between the inner peripheral surface of the cylindrical portion 38b of the cap 38 and the outer peripheral surface of the shaft portion 24b of the rotating shaft 24 is preferably as narrow as possible from the viewpoint of preventing the scattering of foreign matters from the rolling bearing 26. In the rotating anode 14 using the rolling bearing 26, it is necessary to make it larger than the radial clearance of the rolling bearing 26 in consideration of the radial clearance of the rolling bearing 26 itself. Further, in the rotating anode 14 having a large weight of the target 20, in addition to the radial clearance of the rolling bearing 28, the amount of deformation due to the load of the rotating anode 14 itself or the amount of deformation due to the centrifugal force generated by mounting on the CT scanner device, etc. Since factors influence, it is necessary to determine the dimension value of the clearance 44 in consideration of these factors. For example, when the outer diameter of the outer ring 26a normally used for an X-ray tube is 26 mm, the radial clearance of the rolling bearing 26 is combined with the amount of deformation caused by the load of the rotating anode 14 itself or the centrifugal force load. Since the clearance in the radial direction is about twice (about 0.05 mm), the clearance 44 between the cylindrical portion 38 of the cap 38 and the shaft portion 24b of the rotating shaft 24 is preferably larger than that and about 0.05 to 0.5 mm. The longer the length of the cylindrical portion 38b of the cap 38, the greater the effect of preventing foreign matter from scattering from the rolling bearing 26, and it is appropriate that the length of the flat plate portion 38a is at least twice and about 5 to 10 times.

  Care must be taken that the cylindrical portion 38b of the cap 38 does not contact the end of the inner ring 26c of the rolling bearing 26. When the inner ring of the rolling bearing 26 is omitted as in the present embodiment, the cylindrical portion 38b of the cap 38 may be extended to the ball 26b side of the rolling bearing 26. Further, regarding the shape of the inner peripheral surface of the cylindrical portion 38b of the cap 38 on the target 20 side, if the shape of the outer periphery of the shaft portion 24b of the rotating shaft 24 is not a straight line but a curve or the like, the shaft portion 24b In accordance with the shape, a curve or the like may be processed to secure the dimension of the clearance 44 between the cylindrical portion 38b of the cap 38 and the shaft portion 24b of the rotating shaft 24. The flat plate portion 38a of the cap 38 is shown as a flat plate shape in the drawing, but is not limited to this, and it may be a ring shape and have a flat outer peripheral edge, and it may be thick in the radial direction. Even if the thickness changes, the shape may partially include a curved surface.

  As in this embodiment, an L-shaped cap 38 is disposed so as to cover the rolling bearing 26 on the target 20 side, and the clearance 44 between the cylindrical portion 38 of the cap 38 and the shaft portion 24b of the rotating shaft 24 is kept narrow. By doing so, it is possible to prevent foreign matter generated in the rolling bearing 26 from being scattered inside the envelope 16 of the X-ray tube 10. If the dimension of the clearance 44 is D and the length of the cylindrical portion 38b of the cap 38 is T, if the size of the foreign matter is larger than the dimension D of the clearance 44, the foreign matter does not enter the clearance 44. If the size of the foreign matter is smaller than the dimension D of the clearance 44, the foreign matter can enter the clearance 44, but the foreign matter has entered the clearance 44. In the gap 44, collision and reflection are repeated between the inner peripheral surface of the cylindrical portion 38b of the cap 38 and the outer peripheral surface of the shaft portion 24b of the rotating shaft 24. As a result, most of the invading foreign matter adheres to the circumferential surface of the cylindrical portion 38b of the cap 38 and the outer circumferential surface of the shaft portion 24b of the rotary shaft 24, or returns to the bearing box 28a of the fixed portion 28. Only a very small part of the dust is scattered in the envelope 16, so that the scattering of foreign matter into the envelope 16 is significantly reduced as compared with the conventional product. The effect of preventing the scattering of such foreign matter into the envelope 16 is obtained as the ratio T / D between the length dimension T of the cylindrical portion 38b of the cap 38 and the dimension D of the clearance 44 increases.

  In the rotating anode 14 of the present embodiment, the outer peripheral edge portion of the flat plate portion 38a of the cap 38 is sandwiched between the outer ring 26 and the retaining ring 40 of the target side rolling bearing 26, and the retaining ring 40 is fitted into the retaining ring groove 42. Since the cap is fixed to the inner wall of the bearing box 28a of the fixing portion 28, the structure of the cap 38 is simple, and the structure of fixing the cap 38 by the retaining ring 40 is also simple. Further, in this rotating anode 14, only the cap 38 is added to the stationary part 28 side which is a stationary system, and nothing is added to the rotating shaft 24 side which is a rotating system. It does not affect the reliability such as vibration and life during high-speed rotation. As described above, by adding a simple structure to the rotating anode, it is possible to suppress discharge caused by scattering of foreign matters in the envelope of the X-ray tube without impairing reliability at high speed rotation. became.

  Next, a second embodiment of the rotary anode X-ray tube according to the present invention will be described. The X-ray tube of this embodiment is the same as that of the first embodiment except that the specifications of the rotating anode cap are different, and will be described below with reference to FIGS. In the present embodiment, the structure and dimensions of the cap 38 are the same as those in the first embodiment, and the material is a magnetic material and magnetized. Since the cap 38 using a magnetic steel material is composed of a flat plate portion 38a and a cylindrical portion 38b, at least the cylindrical portion 38b may be made of a magnetic material and magnetized. The cap 38 is usually magnetized in advance using a magnetizing device or the like before being incorporated into the rotating anode.

  Since the rolling bearing 26 and the rotating shaft 24 are usually made of a magnetic steel material, among the foreign matters separated from the rolling bearing 26, the wear powder of the rolling bearing 26 or a mixture of this wear powder and lubricant has magnetism. . For this reason, when the foreign matter having magnetism separated from the rolling bearing 28 enters the clearance 44 between the cylindrical portion 38b of the cap 38 and the shaft portion 24b of the rotary shaft 24, it is magnetically applied to the inner peripheral surface of the cylindrical portion 38b. By adhering, the effect of preventing foreign matter from being collected and scattered from the rolling bearing 26 from entering the envelope is further improved than in the first embodiment.

  Next, a third embodiment of the rotary anode X-ray tube according to the present invention will be described. The X-ray tube of this embodiment is the same as that of the first embodiment except that the specifications of the rotating anode cap are different. FIG. 4 shows a cross-sectional view of the cap used in this embodiment. In FIG. 4, the cap 50 used in this embodiment is also composed of a donut-shaped flat plate portion 50a and a cylindrical cylindrical portion 50b. The structure of the flat plate portion 50 and the material of the cap 50 are the same as those in the first embodiment. The cylindrical portion 50b is usually made thicker than the flat plate portion 50a. A plurality (six in the illustrated example) of rectangular grooves 52 are provided on the inner peripheral side of the cylindrical portion 50. The groove 52 is processed so that the depth dimension is larger than the normal width dimension. In the illustrated case, the grooves are processed by a circular method, but may be performed by a spiral method.

  In the present embodiment, since a plurality of grooves 52 are provided on the inner peripheral surface of the cylindrical portion 50b of the cap 50, the foreign matter separated from the rolling bearing 26 is separated from the cylindrical portion 50b of the cap 50 and the shaft portion 24b of the rotating shaft 24. Most of the foreign matter is collected in this groove 52 when it enters the clearance 44 between them, and the amount of foreign matter scattered through the clearance 44 and into the envelope 16 is significantly reduced. Is done. The effect of collecting foreign matter by the grooves 52 is improved as the number of the grooves 52 is increased and the depth of the grooves 52 is increased.

  In the above description of the present embodiment, the shape of the groove 52 is a rectangle. However, the shape is not limited to this, and may be a triangle or other shapes. Further, even if the depth dimension of the groove 52 is smaller than the width dimension, the presence of the groove 52 improves the effect of collecting foreign matter, and thus is not particularly limited. Further, if the number of the grooves 52 is one or more, the foreign matter collecting effect is improved, and this number is not particularly limited. As for the processing of the groove 52, the spiral method seems to be slightly more advantageous than the circulation method, but the circulation method seems to be more advantageous for collecting foreign matter.

1 is a cross-sectional view schematically showing the overall structure of a first embodiment of a rotary anode X-ray tube according to the present invention. Sectional drawing of the principal part of the rotating anode of this embodiment. The expanded sectional view showing the detail of the principal part of this embodiment. Sectional drawing of the cap used for 3rd Embodiment of the rotating anode X-ray tube which concerns on this invention. Sectional drawing of an example of the rotating anode of the conventional rotating anode X-ray tube.

Explanation of symbols

10 ... Rotary anode X-ray tube (X-ray tube)
12 ... Cathode
12c ... Stem
14 ... Rotating anode
16 ... Envelope
20 ... Target
22 ... Rotor
24 ・ ・ ・ Rotation axis
24a ... Flange
24b ... Shaft
26 ・ ・ ・ Rolling bearing
26a ... Outer ring
26b ... Ball
26c ... Inner ring
28 ・ ・ ・ Fixed part
28a ... Bearing box
28b ... Anode end
30 ... Lubricant
32 ... Hole
33 ... Inner wall
34 ・ ・ ・ Center axis (rotary axis)
38, 50 ... Cap
38a, 50a ... Flat plate
38b, 50b ... cylindrical part
40 ... retaining ring
42 ... Groove (groove for retaining ring)
44: Clearance
52 ... Groove

Claims (3)

  A rotor for supporting a disk-shaped target, a rotating shaft for supporting the rotor, a plurality of rolling bearings for rotatably supporting the rotating shaft, and a rotating anode having a fixed portion for supporting the rolling bearing in a bearing box In the rotating anode X-ray tube, a cylindrical portion having an inner peripheral surface facing and substantially parallel to the outer peripheral surface of the shaft portion of the rotating shaft, and a ring coupled to the end of the cylindrical portion opposite to the target A cap composed of a flat plate portion is disposed on the opening side of the bearing box of the fixed portion so as to cover the rolling bearing closest to the target, and the inner peripheral surface of the cylindrical portion of the cap and the shaft portion of the rotary shaft A rotary anode X-ray tube characterized in that the clearance with the outer peripheral surface is larger than the radial clearance of the rolling bearing.   2. The rotary anode X-ray tube according to claim 1, wherein at least a cylindrical portion of the cap is magnetized. 3. The rotary anode X-ray tube according to claim 1, wherein a groove is provided on the inner peripheral surface side of the cylindrical portion of the cap.

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