JP3880897B2 - Rotating anode X-ray tube - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotary anode type X-ray tube in which an anode target rotates.
[0002]
[Prior art]
The rotating anode type X-ray tube is configured by housing an anode target for emitting X-rays and a cathode for irradiating an electron beam in a vacuum vessel, and the anode target is rotatably supported.
[0003]
A rotation support mechanism that rotatably supports the anode target is composed of a rotating body, a fixed body, and the like, and a bearing portion is provided between the rotating body and the fixed body. In the bearing portion, a rolling bearing using a ball bearing or a spiral groove is formed on the bearing surface, and a liquid metal lubricant such as gallium (Ga) or gallium-indium-tin (Ga-In-Sn) alloy is used. Hydrodynamic slide bearings that fill the spiral groove are used. When the latter hydrodynamic slide bearing is used, a bearing surface that is opposed in a wide area through the liquid metal lubricant is formed between the rotating body and the fixed body.
[0004]
In a rotary anode type X-ray tube using a hydrodynamic slide bearing, when heat generated by an anode target is released, the heat is transmitted from the rotary body of the rotary support mechanism to the fixed body via the bearing surface, for example. A method of escaping outside the X tube has been proposed. This method is disclosed in Japanese Patent Nos. 1828025 and 2983617, Japanese Patent No. 2856531, Japanese Patent Laid-Open No. 6-162973, Japanese Patent Laid-Open No. 7-105887, Japanese Patent Laid-Open No. 9-171789 (corresponding US Pat. No. 5,562,778), and the like. Is disclosed.
[0005]
[Problems to be solved by the invention]
The conventional rotary anode X-ray tube is a method for releasing the heat of the anode target, for example, transferring the heat from the anode target to the rotating body, and further transmitting the heat from the rotating body to the stationary body through the bearing surface of the hydrodynamic slide bearing. And finally, a method of dissipating heat using a cooling medium flowing inside the fixed body is employed.
[0006]
In this method, a fluid having a high heat transfer coefficient, such as an antifreeze for automobiles, is suitable for the cooling medium in order to improve the cooling performance. However, a fluid having a high heat transfer rate contains a lot of moisture, and its insulation resistance is lower than that of insulating oil. Therefore, it is difficult to adopt an X-ray tube having a structure in which a high voltage is applied to an anode portion, for example, a portion of a fixed body through which a cooling medium flows.
[0007]
Conventionally, an example in which pure water having a high heat transfer coefficient is used as a cooling medium can be seen in a fixed anode type analytical X-ray tube. In this method, it is indispensable to use a filter in order to prevent the metal forming the fixed body from dissolving into water or to prevent the purity of water from being lowered. If a filter is used, it must be replaced periodically. Further, in applications where the flow rate of the cooling medium is higher than that of an analytical X-ray tube or the like, the frequency of replacement of the filter becomes high, causing operational problems.
[0008]
Further, in the miniaturized rotary anode X-ray tube, the outer diameter of the fixed body constituting the rotation support mechanism is reduced. For this reason, there is a problem that the inner diameter of the cavity for the cooling passage provided in the fixed body is reduced, and the amount of heat transfer to the cooling medium is reduced.
[0009]
An object of the present invention is to solve the above-mentioned drawbacks and to provide a rotary anode type X-ray tube having good heat release characteristics.
[0010]
[Means for Solving the Problems]
In the present invention, an anode target provided in a vacuum vessel, a rotating body mechanically connected to the anode target, a sliding bearing is provided in a fitting portion between the rotating body, and a cavity is provided therein. In the rotary anode type X-ray tube having a fixed body, a protective member formed of ceramic is provided between a cooling passage formed in a cavity portion of the fixed body and a wall surface of the cavity. Features.
[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 constituting a rotary anode type X-ray tube, and a part thereof is shown in FIG. An anode target 11 is disposed in the vacuum vessel 10. The anode target 11 is rotatably supported by a rotation support mechanism 12. The rotation support mechanism 12 includes a rotation portion and a fixed portion, and the anode target 11 is mechanically connected to a rotation portion of the rotation support mechanism 12, for example, a portion of a bottomed cylindrical rotating body 13.
[0012]
The rotating body 13 includes, for example, a bottomed cylindrical small-diameter portion 13a located on the anode target 11 side, a cylindrical large-diameter portion 13b having a larger inner diameter than the small-diameter portion 13a, a small-diameter portion 13a, and a large-diameter portion 13b. It is comprised from the flange-shaped level | step-difference part 13c etc. which ties. The lower opening of the large diameter portion 13 b is sealed with a thrust ring 14.
[0013]
The thrust ring 14 is fixed to the large-diameter portion 13 b and constitutes a rotating portion of the rotation support mechanism 12 together with the rotating body 13. A cylindrical rotor 15 is fixed to the large diameter portion 13 b of the rotating body 13 and the outer peripheral side wall portion of the thrust ring 14.
[0014]
The cylindrical rotor 15 is made of copper or the like having high heat and electrical conductivity, and generates a rotational force by a rotating magnetic field applied from the outside. The rotational force of the cylindrical rotor 15 is transmitted to the anode target 11 through the rotating body 13 and the like, and the anode target 11 is rotated. A columnar fixed body 16 is fitted in an internal space surrounded by rotating parts such as the rotating body 13 and the thrust ring 14.
[0015]
The fixed body 16 constitutes a fixed portion of the rotation support mechanism 12. For example, the first small diameter portion 16 a fitted into the small diameter portion 13 a of the rotary body 13 and the outer diameter is larger than the first small diameter portion 16 a. The large-diameter portion 16b fits into the 13 large-diameter portions 13b, and the second small-diameter portion 16c has a smaller outer diameter than the large-diameter portion 16b and penetrates the thrust ring 14 portion. Inside the fixed body 16, for example, a cavity 17 having a closed cross section and a circular cross section is provided. A protection member 18 made of a material different from that of the fixed body 16 is fitted into the cavity 17, and the protection member 18 is joined to the inner wall surface of the cavity 17.
[0016]
The protective member 18 is made of a material having electrical insulation properties and corrosion resistance against moisture, such as silicon nitride (Si3 N4, eg, TSN-90 manufactured by Toshiba Corporation). The protective member 18 is desirably a material having a thermal conductivity equal to or higher than that of the fixed body 16, for example, a thermal conductivity at room temperature of 50 W / mK or more. The thermal conductivity of Si3 N4 is 90 W / mK. The protective member 18 is made of ceramics mainly composed of at least one selected from aluminum nitride, beryllia, silicon carbide, and alumina.
[0017]
The protection member 18 has a bottomed cylindrical shape with a cavity 18 a formed therein, and for example, the outer bottom surface thereof is joined to the bottom inner surface of the fixed body 16, and the outer peripheral surface thereof is joined to the inner peripheral surface of the fixed body 16. The lower end of the protective member 18 extends to the outside of the vacuum vessel 10, and the lower end thereof opens to the outside of the vacuum vessel 10. A pipe 19 is disposed in the internal space of the protection member 18, and the lower end of the pipe 19 is also open to the outside of the vacuum vessel 10.
[0018]
At this time, as indicated by an arrow Y, for example, the cooling medium flowing in from the lower end opening of the pipe 19 rises in the pipe 19, moves from the upper end to the outside of the pipe 19, and lowers the outside, thereby lowering the lower end of the protection member 18. A cooling passage that flows out of the opening is formed.
[0019]
The anode support portion 20 is connected to the second small diameter portion 16 c of the fixed body 16. Further, a hydrodynamic slide bearing is formed between the rotating portion and the fixed portion of the rotation support mechanism 12, for example, in a fitting portion between the rotating body 13 or the thrust ring 14 and the fixed body 16.
[0020]
For example, a herringbone-pattern spiral groove is formed in an upper region and a lower region sandwiching an annular recess 21 located approximately in the middle of the first small diameter portion 16a of the fixed body 16, and liquid metal lubricant is supplied to the spiral groove portion. As a result, radial hydrodynamic slide bearings Ra and Rb are formed. Further, a herringbone-pattern spiral groove is formed on both upper and lower surfaces perpendicular to the tube axis m of the large-diameter portion 16b of the fixed body 16, and a liquid metal lubricant is supplied to the spiral groove portion to provide a hydrodynamic slide bearing in the thrust direction. Sa and Sb are formed. A stator 22 that generates a rotating magnetic field is disposed outside the vacuum vessel 10.
[0021]
Here, a method of joining the cavity 17 inside the fixed body 16 and the protective member 18 will be described. For example, a metallized layer is formed on the outer surface of the ceramic forming the protective member 18, and gold plating is further applied on the metallized layer. On the other hand, the inner surface of the cavity 17 is also plated with gold. Then, an intermediate member such as a copper pipe (not shown) and the protective member 18 are coaxially fitted in the cavity 17. In this state, heat treatment is performed at 750 ° C. for about 30 minutes or more in a hydrogen furnace or a vacuum furnace, and the cavity 17, the intermediate member, and the protective member 18 are diffusion bonded.
[0022]
At this time, gold functions as a diffusion promoting material. Since the copper of the intermediate member has a larger coefficient of thermal expansion than the iron alloy or molybdenum alloy, which is a material of the fixed body, the contact surfaces to be joined are heated when heated, and the pressure necessary for diffusion bonding acts.
[0023]
In the above-described configuration, a current is passed through the coil 22a of the stator 22 to generate a rotating magnetic field, and the cylindrical rotor 15 is rotated. The anode target 11 is rotated by the rotation of the cylindrical rotor 15. In this state, the anode target 11 is irradiated with an electron beam, and X-rays are emitted from the anode target 11.
[0024]
According to the configuration described above, the protective member 18 is provided in the cavity 17 of the fixed body 16, and the electrically insulating protective member 18 is in contact with the cooling medium. Therefore, even in a configuration in which a high voltage is applied to the fixed body 16, a cooling medium having a high heat transfer coefficient such as water or a water-free antifreeze can be used, and the cooling efficiency is improved. Further, since the ceramics of the protective member 18 has corrosion resistance, corrosion of the fixed body 16 due to the cooling medium can be prevented. Further, since the protective member 18 has a higher thermal conductivity than the fixed body 16 and the protective member 18 and the fixed body 16 are metallicly bonded by diffusion bonding or the like, the heat of the fixed body 16 is a cooling medium. Is transmitted well.
[0025]
In the above embodiment, the protective member 18 and the fixed body 16 are diffusion bonded. However, a metallized layer may be formed on at least a part of the outer peripheral surface of the protective member 18, and the protective member 18 and the fixed body 16 may be brazed with each other through the metallized layer.
[0026]
Next, another embodiment of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view of the small-diameter portion 13a of the rotating body 13 in FIG. 1 in a direction orthogonal to the tube axis, and the same reference numerals are given to portions corresponding to FIG.
[0027]
In the case of this embodiment, a plurality of convex portions 31 are formed in a wave shape in the circumferential direction on the surface of the protective member 18 on the cooling passage side, for example, on the inner wall surface in contact with the cooling medium. The plurality of convex portions 31 extend in the extending direction of the tube axis, for example, parallel to the tube axis, for example, over the entire length of the protection member 18. In this case, the area where the protective member 18 and the cooling medium come into contact increases, and the cooling efficiency is improved.
[0028]
Next, another embodiment of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view of the small-diameter portion 13a of the rotating body 13 in FIG. 1 in a direction perpendicular to the tube axis. The same reference numerals are given to portions corresponding to FIG.
[0029]
In the case of this embodiment, the cooling medium guide structure 35 is fitted over a cavity 18a (FIG. 1) portion provided in the protection member 18, for example, a region surrounded by the thrust ring 14 from slightly below the upper end in the figure.
[0030]
The cooling medium guide structure 35 is made of, for example, a metal mainly composed of copper or a copper alloy. For example, a plurality of concave grooves 36 extending in parallel with the tube axis m are formed on the outer peripheral portion in the circumferential direction, and a plurality of protrusions 37 are formed between the adjacent concave grooves 36. The concave grooves 36 are formed, for example, in parallel with opposing wall surfaces to a predetermined depth, and the plurality of projecting portions 37 extend, for example, in parallel with the tube axis m. The front end surface 37a of each protrusion 37 is located on a common cylindrical surface with the tube axis m as the center. And the front end surface 37a of the protrusion part 37 fits into the cavity 18a wall surface of the protection member 18, and is joined by diffusion bonding etc. simultaneously. At this time, a cooling passage through which the cooling medium flows is formed in a region surrounded by the groove 36, for example, the wall surface of two adjacent projecting portions 37 and the wall surface of the cavity 18a.
[0031]
Next, a method of joining the fixed body 16, the protection member 18, and the cooling medium guide structure 35 will be described. First, a metallized layer is formed on the outer peripheral surface of the protective member 18 and the wall surface of the internal cavity, and further gold (Au) plating is performed thereon. An intermediate member copper pipe (not shown) and the protective member 18 are coaxially fitted in the cavity of the fixed body 16, and the cooling medium guide structure 35 is coaxially inserted in the cavity of the protective member 18. To fit.
[0032]
In this state, heat treatment is performed at 750 ° C. for about 30 minutes or more in a hydrogen furnace or a vacuum furnace. At this time, the fixed body 16 and the protection member 18 are diffusion-bonded by the same method as described in FIG. Further, the protrusion 37 of the cooling medium guide structure 35 and the wall surface of the cavity 18a of the protection member 18 are diffusion-bonded in the same manner. In this case, since the cooling medium guide structure 35 has a higher coefficient of thermal expansion than the protective member 18, when heated, the contact surfaces of both the members are brought into close contact with each other, and the pressure necessary for diffusion bonding acts, and good diffusion bonding is achieved. Realized.
[0033]
In addition, the plurality of protrusions 37 are in mechanical and thermal surface contact with the protection member 18. Therefore, the coolant guide structure 35 is heated over a wide range at a relatively uniform temperature. At the same time, a plurality of projecting portions 37 are formed on the outer peripheral portion of the cooling medium guiding structure 35, and the cooling medium guiding structure 37 and the cooling medium are in contact with each other over a wide area. Therefore, the effective contact area between the cooling medium guide structure 35 and the cooling medium is increased, the amount of heat transmitted to the cooling medium is increased, and the heat dissipation characteristics are improved.
[0034]
Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 4, parts corresponding to those in FIG.
[0035]
In the case of this embodiment, the vacuum vessel 10 has a portion 10a on the anode side and a portion 10b on the cathode side. The anode target 11 is provided with a through hole 41 in the center, and an annular step portion 11a is provided at the edge on the through hole 31 side. The anode target 11 is connected to the joint portion 42. The joint portion 42 is provided with an outward projecting portion 42 a at the upper end and an inward projecting portion 42 b at the lower end, and the step portion 11 a of the anode target 11 and the outward projecting portion 42 a of the joint portion 42 are joined. Further, the inward protruding portion 42 b of the joint portion 42 is connected to the rotation support mechanism 12.
[0036]
The rotation support mechanism 12 includes a rotation part and a fixed part. The rotating portion includes a cylindrical rotating body 13, a first thrust ring 43 that seals the upper and lower openings of the rotating body 13, a second thrust ring 44, and a cylindrical rotor 15 that is connected to the lower side of the second thrust ring 44. Has been. An annular protrusion 131 provided on the rotating body 13 is diffusion-bonded to the inward protrusion 42 b of the joint portion 42 and is simultaneously fixed with a screw 45.
[0037]
The cylindrical rotor 15 generates a rotational force by a rotating magnetic field generated by a stator (not shown) located outside the vacuum vessel 10. This rotational force is transmitted to the anode target 11 through the rotating portion of the rotation support mechanism 12 and the joint portion 42, and the anode target 11 rotates.
[0038]
The fixed portion of the rotation support mechanism 12 is composed of a fixed body 16 and the like. The fixed body 16 has a large-diameter portion 161 fitted into the rotating body 13 and a small-diameter portion 162 extending below the large-diameter portion 161. The lower end of the small-diameter portion 162 extends to the outside of the vacuum vessel 10. Yes. For example, a cavity 46 having a uniform diameter that penetrates in the upper and lower tube axis m directions is provided in the fixed body 16, and a protective member 47 is fitted in the cavity 46. The protection member 47 has a cylindrical shape with a cavity 471 provided therein, and the same material as that of the protection member 18 used in FIG. 1 is used, and the protection member 47 and the wall surface of the cavity 46 are joined.
[0039]
The protection member 47 extends along the tube axis, its upper and lower ends extend to the outside of the vacuum vessel 10, and the upper portion in the drawing is fixed to a part of the vacuum vessel 10. For example, a cylindrical first fixing member 48 is hermetically joined to a part 10 b of the vacuum vessel 10, and a second fixing member 49 is brazed to the outer peripheral surface of the protection member 47, so that the first fixing member 48 and the second fixing member 49 are joined. Are, for example, TIG welded.
[0040]
The openings at the upper and lower ends of the cavity 471 of the protection member 47 are located outside the vacuum vessel 10. In this case, a cooling passage is formed in the cavity 471 inside the protection member 47, and the cooling medium enters, for example, from the lower end opening 47a and exits from the upper end opening 47b as indicated by an arrow Y.
[0041]
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 rotary body 13, the first thrust ring 43, the second thrust ring 44 and the large diameter portion 161 of the fixed body 16. , Sb are formed.
[0042]
Also in the embodiment of FIG. 4, the bonding between the cavity 46 of the fixed body 16 and the protection member 47 is performed by the same method as described with reference to FIG. 1.
[0043]
In the embodiment of FIG. 4, both end portions of the protection member 47 are fixed to the vacuum vessel 10. Therefore, the anode target 11 and the rotation support mechanism 12 are stably supported. Further, since the dynamic pressure type sliding bearings Ra, Rb, Sa, and Sb are located 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.
[0044]
Also in this configuration, the protective member 47 is provided in the cavity 46, and the electrically insulating and corrosion-resistant protective member 47 is in contact with the cooling medium. Therefore, similarly to the case of FIG. 1, even in a configuration in which a high voltage is applied to the stationary body, a cooling medium having a high heat transfer coefficient such as water or a non-freezing liquid having a high water content can be used, and the cooling efficiency is improved. Moreover, corrosion of the fixed body 16 by a cooling medium is also prevented.
[0045]
Next, another embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view of the rotating body 13 in FIG. 4 in a direction perpendicular to the tube axis. The same reference numerals are given to the portions corresponding to FIG. In the case of this embodiment, the cooling medium guide structure 51 is fitted in a cavity 471 portion of the protection member 47, for example, a region sandwiched between two thrust rings 43 and 44 (FIG. 4) positioned above and below.
[0046]
The cooling medium guiding structure 51 is formed of, for example, copper or a metal mainly composed of copper, and has a plurality of concave grooves 52 having a triangular cross section, for example. The plurality of recessed grooves 52 extends, for example, in parallel with the tube axis m, and a plurality of protrusions 53 extending, for example, in parallel with the tube axis m are formed between the adjacent recessed grooves 52. The front end surface 53a of each protrusion 53 is located on a common cylindrical surface with the tube axis m as the center, for example. And the front end surface 53a of the protrusion part 53 fits into the wall surface of the cavity 471 of the protection member 47, and is joined by diffusion bonding, for example simultaneously. At this time, a medium passage through which the cooling medium flows is formed in a region surrounded by the groove 52, for example, the wall surface of the adjacent protrusion 53 and the wall surface of the cavity 471.
[0047]
The fixing body 16, the protection member 47, and the cooling medium guide structure 51 are joined by the same method as described in the embodiment of FIG. 3. Also in this case, at least the cavity 46 portion of the fixed body 16 is formed of, for example, an iron alloy or a molybdenum alloy, and the cooling medium guide structure 51 is formed of, for example, a metal material mainly composed of copper or a copper alloy.
[0048]
According to the configuration of the present invention described above, even when a high voltage is applied to the anode portion, the rotating support mechanism fixed body can be cooled using a cooling fluid having a high heat transfer coefficient, and rotation with good heat release characteristics can be achieved. An anode type X-ray tube can be realized.
[0049]
【The invention's effect】
According to the present invention, a rotary anode type X-ray tube having good heat release 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.
FIG. 2 is a longitudinal sectional view of an essential part for explaining another embodiment of the present invention.
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.
FIG. 5 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 ... Rotation support mechanism 13 ... Rotating body 14 ... Thrust ring 15 ... Cylindrical rotor 16 ... Fixed body 17 ... Cavity 18 ... Protection member 19 ... Pipe 20 ... Anode support part 21 ... Annular recessed part 22 ... Stator Ra, Rb ... Radial dynamic pressure type slide bearing Sa, Sb ... Thrust direction dynamic pressure type slide bearing m ... Pipe shaft

Claims (10)

An anode target provided in a vacuum vessel, a rotating body mechanically connected to the anode target, and a fixed body provided with a sliding bearing in a fitting portion with the rotating body and having a cavity therein. The rotating anode X-ray tube provided is provided with a protective member formed of ceramics between a cooling passage formed in a cavity portion of the fixed body and a wall surface of the cavity. Anode X-ray tube. The rotary anode type X-ray tube according to claim 1, wherein the thermal conductivity of the protective member is equal to or greater than the thermal conductivity of the material constituting the fixed body. 2. The rotating anode type X-ray tube according to claim 1, wherein a convex portion extending in an extending direction of the tube axis is formed on a wall surface facing the cooling passage of the protective member. 2. The rotary anode X-ray tube according to claim 1, wherein the protective member is cylindrical, and one end opening of the protective member is an inlet for the cooling medium, and the other end opening is an outlet for the cooling medium. An anode target provided in a vacuum vessel, a rotating body mechanically connected to the anode target, and a fixed body provided with a sliding bearing in a fitting portion with the rotating body and having a cavity therein. In the rotary anode X-ray tube provided, a protective member made of ceramics having a cavity provided therein is disposed in the cavity portion of the fixed body, and the cavity wall surface of the protective member is disposed in the cavity portion of the protective member. A rotating anode X-ray tube characterized in that a cooling medium guide structure constituting a cooling passage is disposed. 6. The rotary anode type X-ray tube according to claim 5, wherein each of the cooling medium guide structures has a plurality of protrusions whose front end surfaces are joined to the wall surface of the cavity portion of the protection member and extend in the extending direction of the tube axis. The rotary anode type X-ray tube according to claim 5 or 6, wherein the cooling medium guide structure has a cavity through which the cooling medium flows. The rotary anode X-ray tube according to any one of claims 5 to 7, wherein the cooling medium guide structure and the protective member are joined. The rotary anode X-ray tube according to any one of claims 1 to 8, wherein the protective member and the cavity wall surface of the fixed body are joined. An intermediate member made of a material having a thermal expansion coefficient larger than that of the protective member and the fixed body is disposed between the protective member and the cavity wall surface of the fixed body, and the protective member, the intermediate member, and the The rotary anode X-ray tube according to any one of claims 1 to 8, wherein the intermediate member and the cavity wall surface of the fixed body are joined to each other.

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