JP4040313B2 - Rotating anode X-ray tube - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotary anode X-ray tube having improved heat dissipation characteristics.
[0002]
[Prior art]
The rotary anode type X-ray tube rotatably supports an anode target disposed in a vacuum vessel by a rotation support mechanism, and irradiates an electron beam to the anode target rotating at a high speed to emit X-rays from the anode target. It has a structure. The rotation support mechanism includes a rotating body and a fixed body that are fitted to each other, and a bearing is provided at a fitting portion between the two.
[0003]
The bearing is a rolling bearing such as a ball bearing or a spiral groove formed on the bearing surface, and liquid metal lubrication such as gallium (Ga) or gallium (Ga) -indium (In) -tin (Sn) alloy. A hydrodynamic slide bearing using a material is used. When the latter dynamic pressure type plain bearing is used, a bearing surface having a wide area where the rotating body and the fixed body face each other is formed in the fitting portion between the two through the liquid metal lubricant.
[0004]
Therefore, methods have been proposed in which the heat of the anode target is transmitted from the rotating body to the fixed body through the bearing surface and escapes to the outside of the tube through the fixed body (Japanese Patent No. 2960085 and Japanese Patent Laid-Open Nos. 7-226177 and 9- 9 171789).
[0005]
[Problems to be solved by the invention]
In the conventional rotary anode type X-ray tube, when the heat of the anode target is transferred from the rotary body to the fixed body via the bearing surface of the hydrodynamic slide bearing, the cooling mechanism formed inside the fixed body, for example, the cooling Heat is transferred to the cooling medium flowing through the service passage.
[0006]
The amount of heat transferred to the cooling medium increases as the effective contact area between the fixed body and the cooling medium increases. This effective contact area is a portion of the inner surface area of the cooling passage where heat is effectively transmitted, for example, a portion where the temperature of the inner surface of the cooling passage is high.
[0007]
For example, the dimensional change caused by the interaction between the heat transfer surfaces of the members constituting the rotating body and the stationary body and the liquid metal lubricant does not prevent stable bearing operation from being maintained, and the transfer of the liquid metal lubricant In a reference range having a difference ΔT = T1−T0 between the temperature T1 of the hot surface and the temperature T0 of the cooling medium (a range from an upper limit of about 200 ° C. to a lower limit of about 150 ° C. if the cooling medium is oil), Increasing the effective contact area is a standard for improving the cooling performance.
[0008]
However, if the distance from the joint between the joint and the rotating body where the heat of the anode target is transferred to the cooling passage inside the fixed body is short, most of the heat is transmitted through a narrow area with a short distance and the effective contact area is small. Become. In this case, a method of increasing the distance from the coupling portion between the joint portion and the rotating body to the cooling passage can be considered. However, when this distance is increased, the outer diameter of the rotating body increases, which is an obstacle to reducing the size and weight of the X-ray tube.
[0009]
An object of the present invention is to provide a rotating anode type X-ray tube which solves the above-described drawbacks and has improved heat dissipation characteristics.
[0010]
[Means for Solving the Problems]
The present invention has an anode target disposed in a vacuum vessel, and a rotating body and a fixed body provided with a hydrodynamic slide bearing using a liquid metal lubricant at a fitting portion, and rotatably supports the anode target. A rotating anode type X-ray tube having a rotating support mechanism configured to provide protrusions for transmitting heat of the anode target to the rotating body, and the outer surface of the rotating body positioned on both sides of the protruding parts. Further, the present invention is characterized in that a heat transfer promoting body having a higher thermal conductivity than the rotating body is joined and a cooling passage through which a cooling medium flows is provided in the fixed body .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. Reference numeral 10 denotes a vacuum vessel, and an anode target 11 is arranged in the vacuum vessel 10. The anode target 11 is connected to the joint portion 12. For example, the joint portion 12 is formed in a cylindrical shape as a whole, and has a heat insulating structure in which the area to which the heat of the anode target 11 is transmitted is reduced.
[0012]
The joint portion 12 includes, for example, a first tubular portion 121 located on the anode target 11 side and a second tubular portion 122 having both an inner diameter and an outer diameter larger than the first tubular portion 121. A flange 121a is formed at the end of the first tubular portion 121 on the anode target 11 side, and the anode target 11 is joined to the upper surface of the flange 121a by a friction welding method or the like. Moreover, the 2nd cylindrical part 122 is connected with the rotation support mechanism 13 which supports the anode target 11 rotatably.
[0013]
The rotation support mechanism 13 includes a rotating portion and a fixed portion, and the joint portion 12 is connected to, for example, a bottomed cylindrical inner rotating body 14 that forms the rotating portion. For example, an annular projecting portion 14a is formed on the outer peripheral portion of the inner rotating body 14, and the end surface of the second cylindrical portion 122 of the joint portion 12 is connected to the upper surface of the projecting portion 14a, for example, the anode target 11 side by diffusion bonding or the like. It is joined. Both are fixed simultaneously with screws 15.
[0014]
A copper outer rotator 16 is joined to the outer peripheral surface below the protrusion 14 a of the inner rotator 14. The outer rotating body 16 has a structure in which, for example, a heat transfer promoting body 16a portion located on the anode target 11 side and a rotor 16b portion located on the side far from the anode target 11 are integrated. The inner rotator 14 and the outer rotator 16 are joined in the region L1 on the anode target 11 side, and a space L2 is provided between the inner rotator 14 and the outer rotator 16 in the region L2 below. The upper end portion of the outer rotating body 16, that is, the upper end portion of the heat transfer promoting body 16a is in contact with the lower surface of the protruding portion 14a.
[0015]
Copper heat transfer promotion bodies 17a and 17b are joined to, for example, the entire outer peripheral surface of the inner rotator 14 and the outer end surface of the bottom of the inner rotator 14 located above the protrusion 14a. The annular portion at the lower end of the heat transfer promoting body 17 is in contact with the upper surface of the protrusion 14a.
[0016]
The lower opening of the inner rotating body 14 is sealed with a thrust ring 18. The thrust ring 18 is fixed to the inner rotating body 14 and forms a rotating portion of the rotation support mechanism 13 together with the inner rotating body 14 and the outer rotating body 16. A fixed body 19 is fitted in a space surrounded by the inner rotating body 14 and the thrust ring 18.
[0017]
The fixed body 19 forms a fixed portion of the rotation support mechanism 13, and has a large-diameter portion 191 that fits inside the inner rotary body 14 and the thrust ring 18, and a small-diameter portion 192 that has a smaller outer diameter. The small diameter portion 192 passes through the thrust ring 18, and the lower end portion 19 a extends to the outside of the vacuum vessel 11. A lower end portion 19 a of the fixed body 19 is fixed to the vacuum vessel 11 via a holding member 20.
[0018]
A hole 21 is formed along the tube axis m in the fixed body 19, and a pipe 22 is disposed in the hole 21. At this time, as indicated by the arrow Y, the cooling passage through which the cooling medium flows from the outside of the vacuum vessel 11 through the hole 21 outside the pipe 22, from the upper end thereof through the inside of the pipe 22, and further to the outside of the vacuum vessel 11. Is formed.
[0019]
Further, a dynamic pressure type plain bearing is provided at a rotating portion of the rotation support mechanism 13, for example, at a fitting portion between the inner rotating body 14 or the thrust ring 18 and the fixed body 19. For example, spiral grooves 23a and 23b are formed in two regions separated in the tube axis m direction at the fitting portion between the inner peripheral surface of the inner rotating body 14 and the outer peripheral surface of the fixed body 19, and the spiral grooves 23a and 23b Liquid metal lubricant is supplied to the portion to form radial dynamic pressure bearings Ra and Rb. Further, spiral grooves 24a and 24b are formed on the upper end surface of the fixed body 19 facing the inner bottom surface of the inner rotating body 14 and the stepped surface of the fixed body 19, and a liquid metal lubricant is supplied to the spiral grooves 24a and 24b. Thus, dynamic pressure type sliding bearings Sa and Sb in the thrust direction are formed.
[0020]
Here, FIGS. 2A and 2B show cross sections of the line segment aa in the region L1 and the line segment bb in the region L2. As shown in FIG. 2A, the outer rotating body 16 in the region L1, that is, the heat transfer promoting body 16a, is divided into, for example, four by a slit SL extending in the tube axis m direction. As shown in FIG. 2B, the outer rotating body 16 in the region L2, that is, the rotor 16b is formed in a cylindrical shape. The length of the slit SL in the tube axis m direction is longer than the joint portion with the inner rotator 14 to reduce the stress generated at the joint portion with the inner rotator 14 during manufacturing.
[0021]
In the configuration described above, a rotational force is generated in the rotor 16b portion of the outer rotating body 16 by a rotating magnetic field generated by a stator coil (not shown) arranged outside the vacuum vessel 11. This rotational force is transmitted to the anode target 11 through the joint portion 12, and the anode target 11 rotates. In this state, the anode target 11 is irradiated with an electron beam, and X-rays are emitted from the anode target 11.
[0022]
When the rotating anode X-ray tube enters an operating state, the temperature of the anode target 11 rises due to the irradiation of the electron beam. Most of the heat of the anode target 11 is dissipated by radiation. A part of the heat is transmitted from the joint 12 that is thermally and mechanically connected to the inner rotating body 14 via the protrusion 14a. The heat transmitted to the inner rotating body 14 is transferred to the fixed body 19 through a gap, for example, a bearing region, between the inner rotating body 14 and the fixed body 19 located on the back side of the protruding portion 14a.
[0023]
At this time, a part of the heat transmitted to the projecting portion 14a is transmitted to the upper portion of the projecting portion 14a of the inner rotating body 14 through the heat transfer promoting bodies 17a and 17b, and the inner rotating body 14 and the fixed body are transmitted from the bottom surface portion thereof. It is transmitted to the fixed body 19 through a gap 19. Further, part of the heat is transmitted to the lower part of the protrusion 14 a via the heat transfer promoting body 16 a of the outer rotating body 16, and is transmitted from the inner rotating body 14 to the fixed body 19. And it is dissipated outside from the fixed body 18 directly or by the cooling medium flowing through the cooling passage.
[0024]
The fitting portion between the inner rotating body 14 and the fixed body 19 is filled with the liquid metal lubricant in both the bearing area and the non-bearing area that is not the bearing area. Therefore, heat is favorably transferred from the inner rotating body 14 to the fixed body 19 through the liquid metal lubricant.
[0025]
According to the above configuration, the heat of the anode target 11 is transmitted from the protruding portion 14a to the upper and lower sides in the figure in the tube axis direction by the heat transfer promoting bodies 16a, 17a, and 17b, and the fixed body from the wide range of the inner rotary body 14 19 is transmitted. Therefore, the effective contact area with the cooling medium is increased and the cooling efficiency is improved. Moreover, since the heat transmitted to the inner rotating body 14 is dispersed over a wide range by the heat transfer promoting body, it is not necessary to increase the thickness of the inner rotating body 14, and an increase in the size of the structure is avoided.
[0026]
In the case of the above-described configuration, the heat transfer promoting bodies 16a, 17a, and 17b are provided on both sides of the protruding portion 14a in the tube axis m direction, and heat is transmitted from the wide range of the inner rotating body 14 to the fixed body 19. However, a configuration in which the heat transfer promoting body is provided only on one side of the protruding portion 14a can also be adopted. Further, the heat transfer promoting body does not need to be provided on the entire outer surface of the inner rotating body 14, but can be selectively provided in a region where the heat of the anode target 11 is transmitted, for example, in the vicinity of the protruding portion 14a.
[0027]
Moreover, the anode target 11 and the joint part 12 are couple | bonded by metal joining, such as a friction welding method, and the joint part 12 and the inner side rotary body 14 are connected by diffusion joining. In this case, all the heat transfer paths from the anode target 11 to the inner rotating body 14 are coupled metallurgically. Therefore, there is no portion in the heat transfer path where the metals merely mechanically contact each other, and there is an effect that variation in the thermal resistance value in the heat transfer path is prevented.
[0028]
The heat transfer promoting bodies 16a and 17a are formed on the outer surface of the inner rotating body 14 in an annular shape having a predetermined width, for example, a constant width in the tube axis m direction. As described above, even when the heat transfer promoting bodies 16a and 17a are set to have a constant width, variations in the heat resistance value of the heat transfer path are eliminated.
[0029]
Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same reference numerals are given to the portions corresponding to FIG.
[0030]
In this embodiment, a thin portion 11 a having a small thickness is provided around a through hole at the center of the anode target 11. Further, an annular stepped portion 12 a that protrudes outward is provided on the outer peripheral portion of the tubular joint portion 12, and an annular protrusion 12 b that protrudes inward is provided at the lower end of the joint portion 12 in the figure. The thin portion 11a of the anode target 11 is fastened and fixed between the fixing screw 31 and the stepped portion 12a. At the same time, the thin portion 11 a and the stepped portion 12 a are joined by diffusion bonding using the titanium foil 32. Further, the annular projecting portion 12b of the joint portion 12 and the projecting portion 14a of the inner rotating body 14 are joined, for example, by brazing.
[0031]
The inner rotating body 14 includes a bottomed cylindrical small diameter portion 141 having a small inner diameter and a large diameter portion 142 having a larger inner diameter than that. The small-diameter portion 141 and the large-diameter portion 142 are formed in an integral structure, for example. Further, an annular recess is formed on the outer peripheral surface of the inner rotary body 14 in the lower part of the figure, and the outer rotary body 16 is fitted and joined to the recess. In this case, the outer rotating body 16 functions as a rotor that generates a rotational force with a magnetic field applied from the outside.
[0032]
In the fixed body 19, a small diameter portion 192 a having an outer diameter smaller than that of the large diameter portion 191 is formed in an integral structure on the anode target 11 side of the large diameter portion 191. The small diameter portion 192 a is fitted inside the small diameter portion 141 of the inner rotating body 14, and the large diameter portion 191 is fitted inside the large diameter portion 142 of the inner rotating body 14.
[0033]
In addition, a spiral groove is formed in the step surface of the fixed body 19 located on the anode target 11 side, and a thrust hydrodynamic slide bearing Sa located on the anode target 11 side is provided in this portion.
[0034]
And on the outer peripheral surface of the small-diameter portion 141 located below the protruding portion 14a of the inner rotating body 14 and the outer peripheral surface of the small-diameter portion 141 positioned above the protruding portion 14a, 34 is formed in an annular shape, and the heat transfer promoting body 35 is joined to the entire outer end surface of the bottom surface of the small-diameter portion 141. The annular upper end of the heat transfer promoting body 33 and the annular lower end of the heat transfer promoting body 34 are in contact with the protruding portion 14a.
[0035]
In this case, the gap between the fitting portions where the small-diameter portion 141 of the inner rotating body 14 and the small-diameter portion 192a of the fixed body 19 face each other is set, for example, in the range of 30 μm to 500 μm, and the bearing region in which the helical groove is formed. It is formed in a non-bearing region larger than the gap. This non-bearing region is filled with a liquid metal lubricant as in the bearing region. The non-bearing region has a larger gap than the bearing region and hardly functions as a bearing. A structure in which the non-bearing region is enlarged is shown in a circle R. As indicated by the circle R, the liquid metal lubricant LM is filled in the gap between the small-diameter portion 141 of the inner rotating body 14 and the small-diameter portion 192a of the fixed body 19.
[0036]
Further, the cooling passage is formed beyond the coupling portion between the joint portion 12 and the inner rotating body 14, for example, the protruding portion 14 a, and further upward.
[0037]
Also in the case of the above-described configuration, the heat of the anode target 11 is transferred from the joint portion 12 that is connected to the anode target 11 in order thermally and mechanically to the protruding portion 14a of the inner rotating body 14. And it transmits to the wide range of the inner side rotary body 14 through the heat transfer promotion bodies 33-35, and transmits to the fixed body 19 from the wide range of the inner side rotary body 14. FIG. Then, it is dissipated to the outside directly from the fixed body 18 or through a cooling medium flowing through the cooling passage. Therefore, the effective contact area with the cooling medium is increased and the cooling efficiency is improved.
[0038]
Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 4, parts corresponding to those in FIG.
[0039]
In the case of this embodiment, the rotating portion constituting the rotation support mechanism 13 includes a cylindrical portion 41 and a first thrust ring 42, a second thrust ring 43, and a second thrust ring that seal the upper and lower openings of the cylindrical portion 41. It is comprised from the cylindrical rotor 44 etc. which are located under 43. The cylindrical rotor 44 generates a rotational force by a rotating magnetic field generated by a stator coil (not shown) located outside the vacuum vessel 10. This rotational force is transmitted to the anode target 11, and the anode target 11 rotates.
[0040]
An annular projecting portion 41a is formed on the outer peripheral surface of the cylindrical portion 41, and the joint portion 12 is fixed to the projecting portion 41a. An annular step 45 is provided at the edge of the central through hole of the anode target 11, and an outer protrusion 46 positioned at the upper end of the joint portion 12 is joined to the step 45. Further, the inner projecting portion 47 located at the lower end of the joint portion 12 and the annular projecting portion 41 a of the cylindrical portion 41 are diffusion-bonded and simultaneously fixed by screws 48. And the heat-transfer promotion bodies 49 and 50 are joined to the outer peripheral surface of the cylindrical part 41 located above and the downward direction of the cyclic | annular protrusion part 41a in the pipe-axis m direction. In this case, the end portions of any of the heat transfer promoting bodies 49 and 50 are in contact with the annular projecting portion 41a.
[0041]
The fixed body 19 includes a large-diameter portion 51 fitted to the cylindrical portion 41, a first small-diameter portion 52 and a second small-diameter portion 53 that are respectively continuous above and below the large-diameter portion, and the first small-diameter portion 52. Is fixed to a part of the vacuum vessel 10.
[0042]
For example, a cylindrical first fixing member 54 is hermetically joined to a part of the vacuum vessel 10. A cylindrical second fixing member 55 is hermetically joined to the bent portion 54 a that is bent inside the upper end of the first fixing member 54, and a cylindrical third fixing member 56 is hermetically joined to the inside of the second fixing member 55. ing. The illustrated upper end of the fixed body 19 is fixed in an airtight manner inside the third fixing member 56.
[0043]
The second small diameter portion 53 of the fixed body 19 passes through the second thrust ring 43, extends to the outside of the vacuum container 10, and is fixed to the vacuum container 10 by the holding member 57. The fixed body 19 is provided with a hole 58 penetrating in the tube axis direction from the upper end surface to the lower end surface thereof to form a cooling passage. The upper and lower ends of the hole 58 are opened to the outside of the vacuum vessel 10, and as indicated by an arrow Y, the cooling medium enters, for example, from the lower end opening 58a and exits from the upper end opening 58b.
[0044]
In addition, the hydrodynamic slide bearings Ra and Rb in the radial direction and the thrust hydrodynamic slide bearing Sa are fitted to a fitting portion between the cylindrical portion 41, the first thrust ring 42, the second thrust ring 43, and the large diameter portion 51 of the fixed body 19. , Sb are formed. In this case, for example, the back side of the cylindrical portion 41 in the region where the heat transfer promoting bodies 49, 50 are formed and the fitting portion of the fixed body 19 are larger than the gaps of the hydrodynamic slide bearings Ra, Rb, Sa, Sb. It is a non-bearing part.
[0045]
In the embodiment of FIG. 4, both ends of the fixed body 19 are fixed to the vacuum vessel 10. Therefore, the anode target 11 and the rotation support mechanism 13 are stably supported. Further, since the dynamic pressure type sliding bearings Ra, Rb, Sa, and Sb are disposed on both sides of the anode target 11, the load load applied to the upper and lower bearings is well balanced and a stable bearing function is realized.
[0046]
In the case of said embodiment, the heat-transfer promoter is formed with copper. However, it is also possible to use a copper alloy, a composite reinforced metal material mainly composed of copper, or a metal having high thermal conductivity such as molybdenum.
[0047]
Moreover, the metal material containing at least one of copper and silver is impregnated into the pores of the sintered material containing at least one of molybdenum, molybdenum alloy, tantalum, tantalum alloy, tungsten, tungsten alloy, and tungsten carbide. It is also possible to use a composite material that has been allowed to enter.
[0048]
A composite material composed of a metal material containing at least one of copper and silver and a ceramic material dispersed in the metal without forming a solid solution with the metal material can also be used. Furthermore, a composite material of a metal material containing at least one of copper and silver and graphite can also be used.
[0049]
Moreover, a heat-transfer promoter is normally formed in a cylindrical shape, for example according to the shape of the outer peripheral surface of an inner side rotary body or a cylindrical part. However, in the case of deformation at the time of joining due to a difference in thermal expansion with the inner rotating body or the cylindrical part, a slit can be provided in the joined part, for example, in the tube axis direction. Moreover, the structure which joins to the outer peripheral surface of an inner side rotary body or a cylindrical part may be sufficient as the several heat-transfer acceleration | stimulation body piece with a predetermined | prescribed width and length instead of a cylinder shape.
[0050]
In addition, it is desirable that the heat transfer promoting body has a thermal conductivity of 100 W / m · K or more at room temperature. Also, for example, brazing or diffusion bonding is desirable for joining the inner rotating body or the cylindrical portion to the heat transfer promoting body.
[0051]
Also, when connecting the anode target to the joint, the heat of the anode target is directly transferred, so molybdenum or molybdenum alloy is used for the joint, and the joint with the joint of the rotating body is, for example, molybdenum. Or molybdenum alloy, iron, iron alloy, etc. are used. Moreover, it can also be set as the structure which connects an anode target directly to rotary bodies, such as an inner side rotary body or a cylindrical part, without using a coupling part.
[0052]
Further, as a cooling mechanism inside the fixed body, a cooling passage is provided and a cooling medium is allowed to flow through the cooling passage. However, a heat pipe or the like can be used for the cooling mechanism.
[0053]
【The invention's effect】
According to the present invention, a rotating anode X-ray tube with improved heat dissipation characteristics can be realized.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an essential part for explaining an embodiment of the present invention.
2 is a cross-sectional view taken along line aa and line bb in FIG. 1;
FIG. 3 is a longitudinal sectional view of an essential part for explaining another embodiment of the present invention.
FIG. 4 is a longitudinal sectional view of an essential part for explaining another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Vacuum container 11 ... Anode target 12 ... Joint part 13 ... Rotation support mechanism 14 ... Inner rotary body 15 ... Screw 16 ... Outer rotary body 16a ... Heat transfer promotion body 16b ... Rotor 17a, 17b ... Heat transfer promotion body 18 ... Thrust Ring 19 ... Fixed body 20 ... Holding member 21 ... Hole 22 ... Pipes 23a, 23b ... Spiral grooves 24a and 24b ... Spiral grooves Ra and Rb ... Radial dynamic pressure-type slide bearings Sa and Sb ... Thrust-direction dynamic pressure-type slide bearings

Claims (2)

A rotation support mechanism that has a rotating body and a fixed body provided with an anode target disposed in a vacuum vessel and a hydrodynamic slide bearing using a liquid metal lubricant at a fitting portion, and rotatably supports the anode target. In the rotary anode type X-ray tube comprising: a projecting portion for transferring heat of the anode target to the rotating body, and the rotating body on the outer surface of the rotating body located on both sides of the projecting portion. A rotary anode type X-ray tube characterized in that a heat transfer promoting body having a higher thermal conductivity than the body is joined, and a cooling passage through which a cooling medium flows is provided in the fixed body . A fitting part is provided with an anode target arranged in a vacuum vessel, a joint part having a cylindrical part at least partially and transmitting a rotational force to the anode target, and a hydrodynamic slide bearing using a liquid metal lubricant A rotating anode type X-ray tube having a rotating support mechanism and a rotating support mechanism that rotatably supports the anode target, and provided with a projecting portion coupled to the joint portion on the rotating body, A cooling passage having a heat conductivity higher than that of the rotator is joined to the outer surface of the rotator located on both sides of the protrusion , and a cooling passage through which the cooling medium flows is fixed to the fixed body. A rotary anode X-ray tube characterized by being provided .

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