JP2007273102A - Rotating anode x-ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotating anode X-ray tube with increase of loss of a bearing restrained, in the case an anode target makes an high-speed rotation. <P>SOLUTION: For the rotating anode X-ray tube provided with a cathode 21 generating electron beams 23, an anode target 12 emitting X rays 24 with irradiation of the electron beams 23, a rotation supporting mechanism 14 equipped with a rotating part 15 and a fixed part 16 having a bearing area comprising a dynamic-pressure sliding bearing at one part of the opposed area and a non-bearing area at the other for supporting the anode target 12 in free rotation, and a vacuum envelope 11 for containing the cathode 21, the anode target 12, and the rotation supporting mechanism 14, at least a part of the surface of either or both of the rotating part 15 and the fixed part 16 in the non-bearing area is formed of a material with poorer wettability to a liquid metal lubricating material J than the surface of the rotating part 15 and the fixed part 16 in the bearing area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotary anode type X-ray tube in which a bearing portion of a rotation support mechanism that rotatably supports an anode target is formed by a dynamic pressure type slide bearing.

  The rotating anode type X-ray tube has a structure in which an electron beam is irradiated to a rotating anode target and X-rays are emitted from the anode target.

  Here, a conventional rotary anode X-ray tube will be described with reference to FIG.

  The rotary anode type X-ray tube 40 includes a vacuum envelope 41 and the like, and a disk-shaped anode target 42 is disposed in the vacuum envelope 41. The anode target 42 is connected to the rotation support mechanism 44 via the rotation shaft portion 43 and is rotatably supported by the rotation support mechanism 44. The rotation support mechanism 44 includes a rotation part 45 and a fixed part 46.

  The rotating portion 45 has a three-layer structure of an inner rotating body 47a, an intermediate rotating body 47b, and an outer rotating body 47c, and a rotating shaft 43 is connected to the intermediate rotating body 47b. The inner rotating body 47a has a bottomed cylindrical shape having a bottom on the anode target 42 side and an opening on the opposite side of the anode target 42, and constitutes a fixed portion 46 of the rotation support mechanism 44 in the inner space of the inner rotating body 47a. A fixed body 48 is fitted. The fixed body 48 passes through a thrust ring 49 that seals the lower opening of the inner rotating body 47a, and further passes through an anode support member 50 that seals the lower end of the vacuum envelope 41. 41 extends to the outside.

  A hydrodynamic slide bearing is provided in a region where the rotating portion 45 and the fixed portion 46 are fitted with a small gap, for example, in a part of a region where the inner rotating body 47a or the thrust ring 49 and the fixed body 48 face each other.

  For example, herringbone-pattern spiral grooves are formed in two regions on the surface of the fixed body 48 in the direction of the tube axis m, and hydrodynamic slide bearings so-called radial bearings Ra and Rb are provided.

  A helical groove having a herringbone pattern is formed on the upper end surface of the fixed body 48 facing the upper bottom surface of the inner rotating body 47a, and a hydrodynamic slide bearing, so-called thrust bearing Sa, is provided. Further, a helical groove having a herringbone pattern is formed on the annular surface at the lower end of the fixed body 48 facing the thrust ring 49, and a hydrodynamic slide bearing so-called thrust bearing Sb is provided.

  A liquid metal lubricant such as gallium (Ga) or a gallium-indium-tin (Ga-In-Sn) alloy is supplied to a gap between the rotating portion 45 and the fixed portion 46, for example, a bearing region in which a spiral groove is formed. Yes.

  A cathode 51 is disposed opposite the anode target 42, and a stator 52 that generates a rotating magnetic field for rotating the anode target 42 is disposed outside the vacuum envelope 41.

  When the rotating anode X-ray tube described above enters an operating state, the rotating portion 45 is rotated by the rotating magnetic field generated by the stator 52. The rotation of the rotating portion 45 is transmitted to the anode target 42 via the rotating shaft portion 43, and the anode target 42 rotates at a high speed. The rotating anode target 42 is irradiated with the electron beam 53 from the cathode 51, and X-rays 54 are emitted from the target surface of the anode target 42. The emitted X-ray 54 is taken out from an X-ray window 41 a provided in the vacuum envelope 41.

A rotary anode type X-ray tube using a dynamic pressure type plain bearing as described above is disclosed in Patent Documents 1 to 3 and the like.
JP 60-117531 A JP-A-2-227948 JP-A-5-144396

  In a conventional rotary anode X-ray tube, a hydrodynamic slide bearing, for example, is provided at a bearing portion of a rotation support mechanism that rotatably supports an anode target. In the hydrodynamic slide bearing, in order to obtain a good bearing function, for example, the rotating portion is set to float and rotate. Therefore, the liquid metal lubricant is supplied to the gap between the rotating portion and the fixed portion constituting the rotation support mechanism. Further, the rotating portion and the fixed portion are formed of a metal material having good wettability with the liquid metal lubricant.

  By the way, when the rotating anode X-ray tube is operated, the temperature of the anode target is increased by the irradiation of the electron beam. Therefore, when more X-rays are obtained, the number of revolutions of the anode target is increased in order to suppress the temperature increase of the anode target.

  When the rotation speed of the anode target is increased, wettability with the liquid metal lubricant in the rotating part or the fixed part is affected, for example, the frictional resistance of the bearing, that is, the bearing loss increases, and the temperature rises. When the temperature of the bearing portion rises, a reaction product is generated due to the interaction between the rotating portion or the fixed portion and the liquid metal lubricant. As a result, a stable bearing operation cannot be maintained, for example, the distance between the bearing surfaces changes.

  The increase in the bearing loss described above becomes prominent particularly when the ratio of the area of the non-bearing area where the dynamic pressure type sliding bearing is not formed to the area of the bearing area where the dynamic pressure type sliding bearing is provided is large.

  An object of the present invention is to solve the above-described drawbacks and to provide a rotary anode type X-ray tube that suppresses an increase in bearing loss when the anode target rotates at a high speed.

  In the present invention, a cathode that generates an electron beam, an anode target that emits X-rays by irradiation of the electron beam, a bearing region including a hydrodynamic slide bearing is provided in a part of a region facing each other, A rotating support mechanism having a rotating portion and a fixed portion whose opposing regions are non-bearing regions, and rotatably supporting the anode target, and a vacuum outside housing the cathode, the anode target, and the rotating support mechanism In the rotary anode X-ray tube including the envelope, at least a part of one or both surfaces of the rotating portion and the fixed portion in the non-bearing region are connected to the rotating portion and the fixed portion in the bearing region. It is characterized in that it is made of a material having poor wettability with respect to the liquid metal lubricant than the surface.

  In the present invention, at least a part of the surface of one or both of the rotating part and the fixed part in the non-bearing region is made of a material having a poor wettability with respect to the liquid metal lubricant than the surfaces of the rotating part and the fixed part in the bearing region. Forming. Therefore, even when the anode target rotates at a high speed, the friction resistance of the bearing generated in the non-bearing region, for example, the bearing loss is reduced, and a rotating anode type X-ray tube capable of maintaining stable bearing operation is realized.

  An embodiment of the present invention will be described with reference to the schematic structural diagram of FIG. FIG. 1 shows a part in section.

  The rotary anode type X-ray tube 10 includes a vacuum envelope 11 and the like, and a disk-shaped anode target 12 made of heavy metal is disposed in the vacuum envelope 11. The anode target 12 is connected to the rotation support mechanism 14 via the rotation shaft portion 13 and is rotatably supported by the rotation support mechanism 14. The rotation support mechanism 14 includes a rotation portion 15 and a fixed portion 16.

  The rotating portion 15 is formed by sequentially joining an inner rotating body 17a made of a high-strength metal material, an intermediate rotating body 17b made of a ferromagnetic metal such as iron, and an outer rotating body 17c made of a metal having good electrical conductivity such as copper. For example, in the three-layer structure, the rotating shaft portion 13 is connected to the intermediate rotating body 17b.

  The inner rotator 17a has a bottomed cylindrical shape having a bottom on the anode target 12 side and an opening on the opposite side of the anode target 12, and constitutes a fixed portion 16 of the rotation support mechanism 14 in the inner space of the inner rotator 17a. A cylindrical fixed body 18 is fitted. The base material of the fixed body 18 is formed of, for example, the same metal material as that of the inner rotary body 17a. The fixed body 18 passes through a thrust ring 19 that seals the lower opening of the inner rotating body 17a, and further passes through an anode support member 20 that seals the lower end of the vacuum envelope 11 in the illustrated manner. 11 to the outside.

  A hydrodynamic slide bearing is formed in a region where the rotating portion 15 and the fixed portion 16 are fitted with a small gap, for example, in a part of a region where the inner rotating body 17a or the thrust ring 19 and the fixed body 18 face each other. For example, a herringbone pattern helical groove is formed on the surface of two regions of the fixed body 18 separated in the tube axis m direction, and dynamic pressure type sliding bearings, so-called first and second radial bearings Ra and Rb are provided. The outer diameter of the fixed body 18 is, for example, a non-bearing without a spiral groove sandwiched between the first and second radial bearings Ra and Rb in the bearing region provided with the first and second radial bearings Ra and Rb. It is larger than the area. In this case, the gap between the inner rotating body 17a and the fixed body 18 is smaller in the bearing area than in the non-bearing area.

  A spiral groove having a herringbone pattern is formed on the upper end surface of the fixed body 18 facing the upper bottom surface of the inner rotating body 17a, and a hydrodynamic slide bearing, so-called first thrust bearing Sa is provided. A herringbone pattern helical groove is formed in the annular region of the lower end surface of the fixed body 18 shown in the figure facing the thrust ring 19 that is mechanically fixed to the inner rotary body 17a and forms part of the rotating portion 15. A pressure type slide bearing is provided with a so-called second thrust bearing Sb.

  A liquid metal lubricant such as gallium (Ga) or a gallium-indium-tin (Ga-In-Sn) alloy is supplied to a gap between the rotating portion 15 and the fixed portion 16, for example, a bearing region in which a helical groove is formed. Yes. During operation, the liquid metal lubricant circulates in the gap between the rotating portion 15 and the fixed portion 16 including, for example, the bearing region and the non-bearing region.

  The bearing body, for example, the first and second radial bearings Ra and Rb in which spiral grooves are formed, and the fixed body 18 portion of each of the first and second thrust bearings Sa and Sb can obtain a good bearing function. Thus, for example, the entirety is formed of a metal having good wettability with the liquid metal lubricant. On the other hand, the non-bearing region, that is, the region where the spiral groove is not formed, for example, the fixed body 18 in the region sandwiched between the radial bearings Ra and Rb and the inner side of the region where the spiral groove is formed on the upper end surface of the fixed body 18 A ceramic layer is formed on the metal surface of the base material forming the fixed body 18, for example, inside the region where the spiral groove on the lower end surface is formed. The surface on which the ceramic layer is formed has poor wettability with the liquid metal lubricant as compared with the inner rotating body 17a and the fixed body 18 in the bearing region.

  As the ceramic, for example, alumina, titania, silica, or nitridation is used. As a method for forming the ceramic layer, there are, for example, a method in which powdered ceramic is mixed with a liquid and applied to a non-bearing region of a fixed body and heated and fixed, or a method of spraying and fixing a film.

  A cathode 21 is disposed opposite to the anode target 12, and a stator 22 that generates a rotating magnetic field for rotating the anode target 12 is disposed outside the vacuum envelope 11.

  When the rotating anode X-ray tube enters an operating state, the rotating portion 15, for example, the intermediate rotating body 17 b is rotated by the rotating magnetic field generated by the stator 22. The rotation of the rotating portion 15 is transmitted to the anode target 12 via the rotating shaft portion 13, and the anode target 12 rotates at a high speed. In this state, the anode 21 is irradiated with the electron beam 23 from the cathode 21, and the X-ray 24 is emitted from the anode target 12. The emitted X-ray 24 is taken out from the X-ray window 11 a provided in the vacuum envelope 11.

  Here, the pattern of the non-bearing region in a state where the anode target 12 rotates at a high speed will be described with reference to an enlarged view A of FIG. Enlarged view A is an enlarged view of the circled portion of FIG.

  The surface of the fixed body 18 in the non-bearing region is formed of a material having poor wettability with a liquid metal lubricant such as ceramic. For this reason, the liquid metal lubricant J adheres to the inner rotating body 17 a side, and a gap G is generated between the liquid metal lubricant J and the fixed body 18. Therefore, no frictional resistance is generated between the liquid metal lubricant J and the fixed body 18, bearing loss is reduced, and heat generation is suppressed. As a result, the generation of reaction products by the liquid metal lubricant J is suppressed, and the stable bearing operation is maintained without changing the interval between the bearing surfaces.

  The rotating portion of the bearing region, for example, the bearing surface of the inner rotating body 17a and the thrust ring 19 may be a smooth surface, or may form a spiral groove or other groove.

  Next, the fixed body 18 will be described with reference to FIG. FIG. 2 is a diagram in which the fixed body 18 portion is extracted. The same reference numerals are given to the portions corresponding to FIG.

  FIG. 2A shows the upper end surface of the fixed body 18 located on the anode target side, and a spiral groove 31a that becomes the thrust bearing Sa is formed in an annular region near the outer peripheral edge. The central portion 18a of the upper end surface has no spiral groove and is a non-bearing region. For example, a ceramic layer is formed on the surface portion of the non-bearing region.

  FIG. 2B shows the side surface of the fixed body 18, and spiral grooves 31 b and 31 c that become radial bearings Ra and Rb are formed. A region 18b sandwiched between the radial bearings Ra and Rb and a region 18c located inside the anode support member from a portion penetrating the thrust ring are non-bearing regions. For example, a ceramic layer is formed on the surface portion of the non-bearing region.

  FIG. 2C shows the lower end surface of the fixed body 18 located on the side opposite to the anode target. A spiral groove 31d that becomes the thrust bearing Sb is formed in an annular region facing the thrust ring. A region 18d inside the spiral groove 31d is a non-bearing region. A ceramic layer is formed on the surface portion of the non-bearing region.

  Next, another embodiment of the present invention will be described with reference to FIG. FIG. 3 is a diagram in which a fixed body portion is extracted. The same reference numerals are given to the portions corresponding to those in FIG. 1 and FIG.

  In this embodiment, the base material of the bearing regions R1 and R2 is formed of a metal material having good wettability with the liquid metal lubricant, and the base material of the non-bearing region R3 is, for example, ceramic with poor wettability with the liquid metal lubricant. These are joined together to form a fixed body 18.

  Also in this case, the frictional resistance with the liquid metal lubricant in the non-bearing region is reduced, and the same effect as in the case of FIG. 1 can be obtained.

  As shown in FIG. 1, in the case of a configuration in which a ceramic layer is provided on the surface of a metal that is a base material of the non-bearing region, compared to the case where the entire base material of the non-bearing region is formed of ceramic, There is an advantage that heat conductivity and conductivity can be secured.

  In each of the above embodiments, a ceramic layer is formed on the fixed portion of the non-bearing region, or the base material is formed of ceramic. However, an oxide may be formed on the surface of the fixed part in the non-bearing region, and the wettability with the liquid metal lubricant may be deteriorated. Even when an oxide is formed on the surface of the fixed portion, the contact angle between the surface and the liquid metal lubricant is 90 degrees or more, and an area having poor wettability with the liquid metal lubricant is formed.

  In each of the above embodiments, only the fixed portion of the non-bearing region is provided with a portion having poor wettability with the liquid metal lubricant. However, the portion having poor wettability with the liquid metal lubricant may be provided in both the fixed portion and the rotating portion in the non-bearing region, or may be provided only in a part of the non-bearing region. You may provide only in the rotation part side of a non-bearing area | region, without providing in a fixed part.

  According to said structure, the temperature rise of the rotation support mechanism which supports an anode target rotatably is suppressed, and the rotation anode X-ray tube which can maintain a stable bearing function is implement | achieved.

1 is a schematic structural diagram illustrating an embodiment of the present invention. FIG. 2 is a schematic structural diagram in which a fixed body portion in FIG. 1 is extracted. It is a general | schematic structural drawing explaining other embodiment of this invention. It is a schematic structure figure explaining a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Rotating anode X-ray tube 11 ... Vacuum envelope 12 ... Anode target 13 ... Rotating shaft part 14 ... Rotation support mechanism 15 ... Rotating part 16 ... Fixed part 17a ... Inner rotating body 17b ... Intermediate rotating body 17c ... Outer rotating body 18 ... fixed body 19 ... thrust ring 20 ... anode support member 21 ... cathode 22 ... stator 23 ... electron beam 24 ... X-ray m ... tube axis J ... liquid metal lubricant G ... clearance Ra, Rb ... radial bearings Sa, Sb ... Thrust bearing

Claims (2)

  A cathode region that generates an electron beam, an anode target that emits X-rays when irradiated with the electron beam, and a bearing region that includes a hydrodynamic slide bearing are provided in a part of a region facing each other. A rotating support mechanism having a rotating part and a fixed part which are non-bearing regions, and rotatably supporting the anode target; and a vacuum envelope storing the cathode, the anode target and the rotating support mechanism. In the rotary anode X-ray tube provided, at least part of the surface of one or both of the rotating portion and the fixed portion in the non-bearing region is more liquid than the surface of the rotating portion and the fixed portion in the bearing region. A rotary anode X-ray tube characterized by being formed of a material having poor wettability with respect to a metal lubricant.   The rotary anode X-ray tube according to claim 1, wherein the material having poor wettability with respect to the liquid metal lubricant is ceramic or oxide.

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