Patent Application
20150078531
Embodiments described herein relate generally to a rotating-anode X-ray tube assembly and a rotating-anode X-ray tube apparatus.
In X-ray photography which is conducted in a medical field, etc., a rotating-anode X-ray tube assembly is generally used. The X-ray photography is, for instance, Roentgen photography, CT photography, etc. The rotating-anode X-ray tube assembly includes a housing, and a rotating-anode X-ray tube which is stored in the housing and radiates X-rays. A lead plate, which shields X-rays, is stuck to the inner surface of the housing. An X-ray radiation window, which passes X-rays radiated from the X-ray tube, is provided on the outer wall of the housing. A coolant, such as an insulation oil, is sealed in a space between the housing and the rotating-anode X-ray tube.
The rotating-anode X-ray tube includes an anode target, a cathode, and an envelope which accommodates the anode target and the cathode and has its inside reduced in pressure. The anode target can rotate at high speed (e.g. 10000 rpm). The anode target includes a target layer (umbrella-shaped portion) formed of a tungsten alloy. The cathode is located with eccentricity from the rotational axis of the anode target and is opposed to the target layer.
A high voltage is applied between the cathode and the anode target. Thus, if the cathode emits electrons, the electrons are accelerated and converged, and collide upon the target layer. Thereby, the target layer radiates X-rays, and the X-rays are discharged from the X-ray transmission window to the outside of the housing.
For example, the shape of a light-load X-ray tube assembly is substantially rotation-symmetric with respect to the axis of the X-ray tube. The housing is cylindrical, and includes a projection portion having a side surface to which a high-voltage receptacle is attached, an X-ray radiation window, and side plates which close both opening end portions of the cylindrical housing.
In the meantime, in recent years, in an X-ray tube assembly for CT photography use, etc., a housing including a first divisional part and a second divisional part has begun to be used in accordance with an increase in complexity of the shape of the X-ray tube, an increase in weight of the X-ray tube, and an increase in rotational speed of a rotating frame on which the X-ray tube assembly is mounted. The coupling surface between the first divisional part and second divisional part is parallel to the axis of the X-ray tube.
In general, according to one embodiment, there is provided a rotating-anode X-ray tube assembly comprising: an X-ray tube comprising an anode target including a target layer which emits X-rays, an anode target rotating mechanism configured to rotatably support the anode target, a cathode disposed opposite to the target layer in a direction along an axis of the anode target and configured to emit electrons, and an envelope accommodating the anode target, the anode target rotating mechanism and the cathode; a stator coil configured to generate a driving force for rotating the anode target rotating mechanism; a housing comprising an X-ray radiation port opening in a direction perpendicular to the axis, and storing and holding the X-ray tube and the stator coil; an X-ray radiation window configured to close the X-ray radiation port and to take out the X-rays to an outside of the housing; and a coolant filled in a space between the X-ray tube and the housing and absorbing at least part of heat produced by the X-ray tube. The housing includes a first divisional part which includes the X-ray radiation port and to which the X-ray tube is directly or indirectly fixed, and a second divisional part located on a side opposite to the anode target with respect to the anode target rotating mechanism and coupled to the first divisional part. A coupling surface between the first divisional part and the second divisional part is located on one plane, and is inclined to the axis, with exclusion of a direction perpendicular to the axis.
A rotating-anode X-tube assembly according to a first embodiment will be described hereinafter in detail with reference to the accompanying drawings. The rotating-anode X-ray tube assembly is used such that this assembly is fixed to, for example, a rotating frame of an X-ray CT scanner.
As illustrated in
The housing 20 includes an X-ray radiation port 20o1 which is open in a direction perpendicular to an axis a of the X-ray tube 30, and a through-hole 20o2 extending in a direction along the axis a. The housing 20 stores and holds the X-ray tube 30 and stator coil 90.
The housing 20 includes a first divisional part 20a and a second divisional part 20c, which are divided. The housing 20 is formed of a metallic material or a resin material. In this embodiment, the first divisional part 20a and second divisional part 20c are formed of moldings using an aluminum alloy. Incidentally, the first divisional part 20a may be formed of an aluminum alloy molding (or resin material), and the second divisional part 20c may be formed of a resin material (or aluminum alloy molding).
The first divisional part 20a includes the X-ray radiation port 20o1 and through-hole 20o2. The X-ray tube 30 is directly or indirectly fixed to the first divisional part 20a. In this embodiment, an insulation member 8 and an X-ray shielding member 60 are interposed between the X-ray tube 30 and the first divisional part 20a, and the X-ray tube 30 is indirectly fixed to the first divisional part 20a.
The insulation member 8 is formed of a resin material or ceramics with high mechanical strength. The insulation member 8 prevents a positional displacement of the X-ray tube 30 in relation to the housing 20 in a direction perpendicular to the axis a. Furthermore, the insulation member 8 maintains electrical insulation between the X-ray tube 30 and the housing 20.
In addition, the stator coil 90 is directly or indirectly fixed to the first divisional part 20a. In this embodiment, a connection member 9 is interposed between the stator coil 90 and the first divisional part 20a, and the stator coil 90 is indirectly fixed to the first divisional part 20a via the connection member 9. Thus, the connection member 9 prevents a positional displacement of the stator coil 90 in relation to the housing 20 and X-ray tube 30. In addition, the connection member 9 is formed of a metal. Since the first divisional part 20a is set at a ground potential, the connection member 9 can also ground the stator coil 90.
The X-ray shielding member 60 is disposed along at least a part of the inner surface of the first divisional part 20a. In this embodiment, the X-ray shielding member 60 is stuck to at least a part of the inner surface of the first divisional part 20a. The X-ray shielding member 60 is formed of a material containing lead or a lead alloy as a main component.
The X-ray shielding member 60 is not provided in a region opposed to the connection member 9 and in a region on the second divisional part 20c side of the region opposed to the connection member 9. However, the X-ray shielding member 60 is provided with no gap in a region on the right side of the region opposed to the connection member 9 (i.e. the region opposed to the anode target 35, cathode 36, etc.). The X-ray shielding member 60 is also provided with no gap at a side edge of the X-ray radiation port 20o1 and at a side edge of the through-hole 20o2. Incidentally, the X-ray shielding member 60 is provided so as not to hinder the radiation of X-rays, which are used, to the outside of the housing 20 in the X-ray radiation port 20o1.
In addition, since the anode target 35 itself functions as an X-ray shielding member, the X-ray shielding member 60, together with the anode target 35, can prevent leakage of X-rays. Since the X-ray shielding member 60 (first divisional part 20a) extends in the direction along the axis a toward the second divisional part 20c side beyond an extension line of the surface of a target layer 35a (to be described later), the above-described advantageous effect can be obtained.
The second divisional part 20c is located on a side opposite to the anode target 35 with respect to the anode target rotating mechanism 14 (to be described later). The second divisional part 20c is coupled to the first divisional part 20a. In addition, the second divisional part 20c is formed so as not to affect the prevention of the above-described X-ray leakage. Specifically, the coupling surface between the first divisional part 20a and second divisional part 20c is located in a region where X-rays are shielded by the anode target 35.
Besides, the coupling surface is located on one plane, and is inclined to the axis a, with the exclusion of a direction perpendicular to the axis a. Thus, at one end face of the coupling surface, an angle formed relative to the axis a on the one hand is an acute angle, and an angle formed relative to the axis a on the other hand is an obtuse angle.
In this embodiment, in an attitude in which the axis a is parallel to a horizontal line, the X-ray radiation window 20w is located on the upper side of the anode target 35 and the cathode 36 is located on the right side of the anode target 35, the coupling surface is inclined in an upper-right direction. Thus, in this attitude, an upper-side one end face of the coupling surface forms an acute angle clockwise relative to the axis a, and forms an obtuse angle counterclockwise relative to the axis a.
By detaching the second divisional part 20c from the first divisional part 20a, the X-ray tube 30 and stator coil 90 can be exposed in a direction along the axis a and in a direction (upward) perpendicular to the axis a. Thus, the efficiency of manufacture of the rotating-anode X-ray tube assembly 10 can be enhanced. For example, after fixing the X-ray tube 30 to the first divisional part 20a, the stator 90 can be fixed to the first divisional part 20a.
Further, since the through-hole 20o2 is formed in the first divisional part 20a, and not in the second divisional part 20c, the first divisional part 20a and the second divisional part 20c can be coupled without requiring skill.
Moreover, since it is possible to suppress an interference during working between the X-ray tube 30 and stator coil 90, on the one hand, which are installed in the first divisional part 20a, and the second divisional part 20c, on the other hand, it becomes possible to suppress damage which is mutually suffered by at least one of the X-ray tube 30 and stator coil 90, and the second divisional part 20c.
Furthermore, after the X-ray tube 30 and stator coil 90 are installed in the first divisional part 20a, a gap between the X-ray tube 30 and stator coil 90 can be confirmed. Since the relative position between the X-ray tube 30 and stator coil 90 can be corrected where necessary, this can make it less likely that problems will arise with the rotational characteristics of the anode target rotating mechanism 14 of the X-ray tube 30 and the cooling capability of the X-ray tube 30.
The first divisional part 20a includes a frame portion 20b on the outer edge side of the opening. The second divisional part 20c includes a frame portion 20d on the outer edge side of the opening. In the frame portion 20b, a frame-shaped groove portion, which is formed on the side opposed to the frame portion 20d, is formed.
The first divisional portion 20a and second divisional portion 20c are touched such that the frame portions 20b and 20d are opposed, and the first divisional portion 20a and second divisional portion 20c are joined by a screw 20f serving as a fastening member. The gap between the frame portions 20b and 20d is liquid-tightly sealed by an O-ring which is provided in the above-described groove portion. The O-ring has a function of preventing leakage of the coolant 7 to the outside of the housing 20.
The inner surface of the housing 20 and the surface of the X-ray shielding member 60 are in contact with the coolant 7.
In this case, the rotating-anode X-ray tube assembly 10 includes a mounting portion 20e. The mounting portion 20e is formed so as to project from the outer surface of the first divisional part 20a. For example, the mounting portion 20e is directly or indirectly fixed to the rotating frame of an X-ray CT scanner.
The X-ray radiation window 20w is located in the outside of the housing 20. The X-ray radiation window 20w can be formed by using a material with high mechanical strength. In this embodiment, the X-ray radiation window 20w is formed by using aluminum, but can also be formed by using other metallic material such as beryllium, or a resin. Thus, the X-ray radiation window 20w can take out X-rays to the outside of the housing 20. The X-ray radiation window 20w has a concave shape, and is configured to reduce the distance between the X-ray tube 30 and the X-ray radiation window 20w.
The X-ray radiation window 20w includes an attachment region which is directly attached to the first divisional part 20a, and an X-ray transmission region. An attachment surface is formed on an outer wall of the first divisional part 20a, which is opposed to the X-ray radiation window 20w. The attachment surface is flat. A frame-shaped groove portion is formed in the attachment surface of the first divisional part 20a in a manner to surround the X-ray radiation port 20o1. An O-ring is disposed in the groove portion.
A screw 21 serving as a fastening member is passed through a through-hole formed in the attachment region of the X-ray radiation window 20w, and is fastened in a screw hole formed in the attachment surface of the first divisional part 20a. The screw hole formed in the first divisional part 20a forms, together with the screw 21, a pushing mechanism. Thereby, the position of the X-ray radiation window 20w relative to the first divisional part 20a (housing 20) can be fixed.
The O-ring is interposed between the first divisional part 20a and the X-ray radiation window 20w. The O-ring has a function of preventing leakage of the coolant 7 to the outside of the housing 20. Thus, the X-ray radiation window 20w, together with the O-ring, can liquid-tightly close the X-ray radiation port 20o1.
The X-ray tube 30 includes an envelope 31, an anode target 35, an anode target rotating mechanism 14, and a cathode 36. The envelope 31 accommodates the anode target 35, anode target rotating mechanism 14 and cathode 36.
The envelope 31 includes a container 32. The container 32 is formed of, for example, glass, or a metal such as copper, stainless steel or aluminum. An X-ray radiation window 33 is airtightly provided on the container 32. In this case, the X-ray radiation window 33 is formed of beryllium. A part of the envelope 31 is formed of a high-voltage insulation member.
In this embodiment, the envelope 31 (X-ray tube 30) includes a high-voltage connection part 34 which extends in the direction along the axis a, passes through the through-hole 20o2, and is exposed to the outside of the housing 20. The high-voltage connection part 34 is formed of a high-voltage insulation member and a high-voltage supply terminal. The high-voltage insulation member is formed of ceramics. The high-voltage supply terminal is a metallic terminal. The high-voltage supply terminal is provided so as to penetrate the high-voltage insulation member, has one end exposed to the outside of the housing 20 from the surface of the high-voltage insulation member (the high-voltage connection part 34), and has the other end electrically connected to the cathode 36.
The anode target 35 is provided within the envelope 31. The anode target 35 is formed in a disc shape. The anode target 35 includes a target layer 35a which is provided on a part of the outer surface of the anode target. Electrons radiated from the cathode 36 collide upon the target layer 35a, and thereby the target layer 35a emits X-rays. The anode target 35 is formed of a metal such as molybdenum or a molybdenum alloy. The target layer 35a is formed of a metal such as a tungsten alloy. The anode target 35 is rotatable.
The cathode 36 is provided within the envelope 31. The cathode 36 is disposed opposite to the target layer 35a in a direction along the axis a. The cathode 36 emits electrons which are radiated on the anode target 35. A relatively negative voltage is applied to the cathode 36 via the high-voltage supply terminal of the high-voltage connection part 34, and a filament current is supplied to a filament (electron emission source), not shown, of the cathode 36.
The anode target rotating mechanism 14 rotatably supports the anode target 35. The anode target rotating mechanism 14 includes a rotor, a bearing, a fixed body and a rotary body. The fixed body is formed in a columnar shape, and is fixed to the envelope 31. The fixed body rotatably supports the rotary body. The rotary body is formed in a cylindrical shape and is provided coaxial with the fixed body. The rotor is fixed to the outer surface of the rotary body. Incidentally, the rotor receives a driving force which is generated by the stator coil 90. The anode target 35 is fixed to the rotary body. The bearing is formed between the fixed body and the rotary body. The rotary body is provided so as to be rotatable together with the anode target 35.
In the meantime, the anode target 35 is grounded. For example, the anode target 35 is connected to a ground terminal (not shown) which is electrically insulatively provided on the housing 20, via the anode target rotating mechanism 14, a conductor line (not shown), etc.
The rotating-anode X-ray tube assembly 10 further includes a seal ring 26. The seal ring 26 is configured to liquid-tightly seal the coolant 7 coming through a gap between the through-hole 20o2 and the high-voltage connection part 34, and to prevent leakage of the coolant 7 to the outside of the housing 20.
The seal ring 26 is formed in a frame shape. The shape of the seal ring 26 is associated with the shape of the through-hole 20o2 and high-voltage connection part 34. In this case, the seal ring 26 is formed in an annular shape.
An annular groove portion is formed in an inner peripheral edge of the seal ring 26, which is opposed to the high-voltage connection part 34. A gap between the seal ring 26 and the high-voltage connection part 34 is sealed by an annular O-ring which is provided in the annular groove portion. The O-ring has a function of preventing leakage of the coolant 7 to the outside from the gap between the seal ring 26 and the high-voltage connection part 34.
A frame-shaped groove portion is formed in the outer surface of the first divisional part 20a, which surrounds the through-hole 20o2 and is opposed to the seal ring 26. An O-ring is disposed in the frame-shaped groove portion.
A screw 27 serving as a fastening member is passed through a through-hole formed in the seal ring 26, and is fastened in a screw hole formed in the first divisional part 20a. The screw hole formed in the first divisional part 20a forms, together with the screw 27, a pushing mechanism. Thereby, the position of the seal ring 26 relative to the first divisional part 20a (housing 20) can be fixed.
The O-ring is interposed between the first divisional part 20a and the seal ring 26. The O-ring has a function of preventing leakage of the coolant 7 to the outside from the gap between the first divisional part 20a and the seal ring 26.
From the above, the seal ring 26, together with the O-ring and high-voltage connection part 34, can liquid-tightly close the through-hole 20o2.
The coolant 7 is filled in the space between the X-ray tube 30 and housing 20. The coolant 7 absorbs at least part of the heat produced by the X-ray tube 30. Incidentally, the coolant 7 also absorbs heat produced by the stator col 90, etc., other than the X-ray tube 30. As the coolant 7, an insulation oil or a water-based coolant can be used. In this embodiment, a water-based coolant is used as the coolant 7.
In the rotating-anode X-ray tube assembly 10 with the above-described structure, a predetermined current is applied to the stator coil 90, and thereby the rotor of the anode target rotating mechanism 14 rotates and the anode target 35 rotates. Next, a predetermined high voltage is applied between the anode target 35 and the cathode 36. In this case, the anode target 35 is grounded, and a negative high voltage and filament current are supplied to the cathode 36.
Thereby, an electron beam is radiated from the cathode 36 to the target layer 35a of the anode target 35, X-rays are radiated from the anode target 35, and the X-rays are radiated to the outside through the X-ray radiation window 33 and X-ray radiation window 20w.
According to the rotating-anode X-ray tube assembly 10 of the first embodiment with the above-described structure, the rotating-anode X-ray tube assembly 10 includes the rotating-anode X-ray tube 30, stator coil 90, housing 20, X-ray radiation window 20w, and coolant 7.
The housing 20 includes the first divisional part 20a and second divisional part 20c. The first divisional part 20a includes the X-ray radiation port 20o1, and the X-ray tube 30 is directly or indirectly fixed to the first divisional part 20a. The second divisional part 20c is located on the side opposite to the anode target 35 with respect to the anode target rotating mechanism 14, and is coupled to the first divisional part 20a. The coupling surface between the first divisional part 20a and second divisional part 20c is located on one plane, and is inclined to the axis a, with the exclusion of the direction perpendicular to the axis a.
After disposing only the X-ray tube 30 in the first divisional part 20a, the stator coil 90 can be disposed in the first divisional part 20a. The workability can be enhanced since there is no need to dispose the X-ray tube 30 and stator coil 90 as one body in the first divisional part 20a in the state in which the stator coil 90 is inserted over the X-ray tube 30. For example, a simple work can be made. Then, the stator coil 90 can be disposed with high precision.
The gap between the X-ray tube 30 and the stator coil 90 can be confirmed. Since the relative position between the X-ray tube 30 and stator coil 90 can be corrected where necessary, it becomes possible to avoid such a situation that problems will arise with the rotational characteristics of the anode target rotating mechanism 14 of the X-ray tube 30 and the cooling capability of the X-ray tube 30.
In addition, since there is no need to set a wide gap between the X-ray tube 30 and stator coil 90, it is possible to prevent degradation in the efficiency of rotary drive by a produced magnetic field of the stator coil 90, and to prevent an increase in power consumption of the stator coil 90.
The X-ray shielding member 60 (first divisional part 20a) extends in the direction along the axis a toward the second divisional part 20c side beyond the extension line of the surface of the target layer 35a. Specifically, the coupling surface between the first divisional part 20a and second divisional part 20c is located in a region where there is no fear of X-ray leakage. Thus, the X-ray shielding member 60, together with the anode target 35, can prevent leakage of X-rays.
In addition, since there is no need to adopt a special structure by providing an X-ray shielding member in the second divisional part 20c in a manner to overlap the X-ray shielding member 60, an increase in processing cost of the housing 20 can be suppressed.
Further, the first divisional part 20a includes the through-hole 20o2 extending in the direction along the axis a. The high-voltage connection part 34 extends in the direction along the axis a, passes through the through-hole 20o2, and is exposed to the outside of the housing 20. Since the through-hole 20o2 is formed in the first divisional part 20a, and not in the second divisional part 20c, the first divisional part 20a and the second divisional part 20c can be coupled without requiring skill.
Moreover, since it is possible to suppress an interference during working between the X-ray tube 30 and stator coil 90, on the one hand, which are installed in the first divisional part 20a, and the second divisional part 20c, on the other hand, this can make it less likely that damage is mutually suffered by at least one of the X-ray tube 30 and stator coil 90, and the second divisional part 20c.
From the above, the rotating-anode X-ray tube assembly 10 can be obtained which can prevent leakage of X-rays, has high product reliability, has a good manufacturing yield, and can suppress an increase in manufacturing cost and power consumption.
Next, a rotating-anode X-ray tube apparatus 1 according to a second embodiment will be described. In this embodiment, the same functional parts as in the above-described first embodiment are denoted by like reference numerals, and a detailed description thereof is omitted. The rotating-anode X-ray tube apparatus 1 is used such that this apparatus 1 is fixed to, for example, a rotating frame of an X-ray CT scanner.
As illustrated in
The conduit 11 includes a first conduit 11a, a second conduit 11b and a third conduit 11c. The first conduit 11a has one end portion connected liquid-tightly to an opening of the first divisional part 20a, and has the other end portion connected liquid-tightly to an intake port of the circulating pump 120. The second conduit 11b has one end portion connected liquid-tightly to a discharge port of the circulating pump 120, and has the other end connected liquid-tightly to the radiator 130. The third conduit 11c has one end portion connected liquid-tightly to the radiator 130, and has the other end connected liquid-tightly to the other opening of the first divisional part 20a.
According to the rotating-anode X-ray tube apparatus 1 of the second embodiment with the above-described structure, the rotating-anode X-ray tube apparatus 1 includes the rotating-anode X-ray tube assembly 10. The rotating-anode X-ray tube assembly 10 includes the rotating-anode X-ray tube 30, stator coil 90, housing 20, X-ray radiation window 20w, and coolant 7. Thus, the same advantageous effects as in the above-described first embodiment can be obtained.
The rotating-anode X-ray tube apparatus 1 includes the circulating pump 120. Since forced convection can be caused to occur in the coolant 7 in the housing 20, the temperature distribution of the coolant 7 in the housing 20 can be made uniform.
The rotating-anode X-ray tube apparatus 1 includes the radiator 130 and fan unit 140. Thus, the radiation to the outside of the heat produced by the X-ray tube 30, etc. can be further promoted.
From the above, the rotating-anode X-ray tube assembly 10 and rotating-anode X-ray tube apparatus 1 can be obtained which can prevent leakage of X-rays, has high product reliability, has a good manufacturing yield, and can suppress an increase in manufacturing cost and power consumption.
Next, a modification of the rotating-anode X-ray tube apparatus 1 according to the second embodiment will be described. Incidentally, in this modification, too, the same advantageous effects as in the second embodiment can be obtained.
As illustrated in
In the meantime, in this example, the third conduit 11c is liquid-tightly attached to the other opening of the first divisional part 20a, and the other end portion of the third conduit 11c is directly attached to the intake port of the cooling passage 30a. Thereby, the coolant 7, which has been cooled through the radiator 130, can be introduced into the cooling passage 30a.
Next, another modification of the rotating-anode X-ray tube apparatus 1 according to the second embodiment will be described. Incidentally, in this another modification, too, the same advantageous effects as in the second embodiment can be obtained.
As illustrated in
In this example, an insulation oil is used as the coolant 7, and a water-based coolant is used as the coolant 70. The coolant 70 is filled in the cooling passage 30b and conduit 11, and absorbs at least part of the heat produced by the X-ray tube 30.
The conduit 11 is made to communicate with the cooling passage 30b of the X-ray tube 30 through the housing 20. To be more specific, one end portion of the first conduit 11a is made to communicate with the discharge port of the cooling passage 30b, and the other end portion of the third conduit 11c is made to communicate with the intake port of the cooling passage 30b. The circulating pump 120 circulates the coolant 70. The radiator 130 radiates the heat of the coolant 70.
Next, a rotating-anode X-ray tube assembly according to a third embodiment will be described. In this embodiment, the same functional parts as in the above-described first embodiment are denoted by like reference numerals, and a detailed description thereof is omitted.
As illustrated in
The second divisional part 20c is formed so as not to affect the prevention of X-ray leakage. Specifically, the coupling surface between the first divisional part 20a and second divisional part 20c is located in a region where X-rays are shielded by the anode target 35.
The X-ray shielding member 60 (first divisional part 20a) extends in the direction along the axis a toward the second divisional part 20c side beyond an extension line of the surface of the target layer 35a. Thus, the X-ray shielding member 60, together with the anode target 35, can prevent leakage of X-rays.
By detaching the second divisional part 20c from the first divisional part 20a, the X-ray tube 30 and stator coil 90 can be exposed in a direction along the axis a and in a direction (downward) perpendicular to the axis a. Thus, the efficiency of manufacture of the rotating-anode X-ray tube assembly 10 can be enhanced. For example, after fixing the X-ray tube 30 to the first divisional part 20a, the stator 90 can be fixed to the first divisional part 20a. Incidentally, by varying the attitude of the first divisional part 20a where necessary, it becomes possible to make it easier to fix the X-ray tube 30 and stator coil 90 to the first divisional part 20a.
In addition, in this embodiment, too, the mounting portion 20e is formed on the first divisional part 20a. In this case, two mounting portions 20e are formed on the first divisional part 20a with an interval in the direction along the axis a.
According to the rotating-anode X-ray tube assembly 10 of the third embodiment with the above-described structure, the rotating-anode X-ray tube assembly 10 includes the rotating-anode X-ray tube 30, stator coil 90, housing 20, X-ray radiation window 20w, and coolant 7.
The housing 20 includes the first divisional part 20a and second divisional part 20c. The first divisional part 20a includes the X-ray radiation port 20o1, and the X-ray tube 30 is directly or indirectly fixed to the first divisional part 20a. The second divisional part 20c is located on the side opposite to the anode target 35 with respect to the anode target rotating mechanism 14, and is coupled to the first divisional part 20a. The coupling surface between the first divisional part 20a and second divisional part 20c is located on one plane, and is inclined to the axis a, with the exclusion of the direction perpendicular to the axis a.
The coupling surface between the first divisional part 20a and second divisional part 20c is inclined in a lower-right direction. In this case, too, the same advantageous effects as in the above-described first embodiment can be obtained.
From the above, the rotating-anode X-ray tube assembly 10 can be obtained which can prevent leakage of X-rays, has high product reliability, has a good manufacturing yield, and can suppress an increase in manufacturing cost and power consumption.
Next, a rotating-anode X-ray tube assembly according to Comparative Example 1 will be described.
As illustrated in
Thus, such a special structure is adopted that an X-ray shielding member 60 is provided on the first divisional part 20a, an X-ray shielding member 80 is provided on the second divisional part 20c, and the X-ray shielding member 60 and X-ray shielding member 80 oppose each other. The reason for this is that it is highly possible that X-rays leak from the coupling surface of the housing 20. In the case of Comparative Example 1, however, an increase in processing cost of the housing 20 will occur. The second divisional part 20c includes the X-ray radiation port 20o1 and through-hole 20o2. The X-ray radiation window 20w is attached to the second divisional part 20c, and closes the X-ray radiation port 20o1.
According to the rotating anode X-ray tube assembly 10 of the comparative example 1 with the above-described structure, the stator coil 90 cannot be disposed in the first divisional part 20a, after disposing only the X-ray tube 30 in the first divisional part 20a. It is necessary to dispose the X-ray tube 30 and stator coil 90 as one body in the first divisional part 20a in the state in which the stator coil 90 is inserted over the X-ray tube 30.
The gap between the X-ray tube 30 and the stator coil 90 cannot be confirmed. Since it is difficult to correct the relative position between the X-ray tube 30 and stator coil 90, problems may arise with the rotational characteristics of the anode target rotating mechanism 14 of the X-ray tube 30 and the cooling capability of the X-ray tube 30.
In addition, there may be a need to set a wide gap between the X-ray tube 30 and stator coil 90. This may lead to degradation in the efficiency of rotary drive by a produced magnetic field of the stator coil 90, and to an increase in power consumption of the stator coil 90.
Further, since the through-hole 20o2 is formed in the second divisional part 20c, skill is required to couple the first divisional part 20a and the second divisional part 20c.
Moreover, it is possible that the X-ray tube 30 and stator coil 90, on the one hand, which are installed in the first divisional part 20a, and the second divisional part 20c, on the other hand, interfere during working, and are mutually damaged. After the assembling in the housing, it is not possible to confirm whether the X-ray tube, stator coil, second divisional part, etc. have been damaged. Thus, there is concern that a problem will arise in a subsequent manufacturing process or during the use by the user.
Next, a rotating-anode X-ray tube assembly according to Comparative Example 2 will be described.
As illustrated in
The structure of the rotating-anode X-ray tube assembly 10 of Comparative Example 2 is described below.
The rotating-anode X-ray tube assembly 10 is, in general terms, a neutral-grounding-type X-ray tube assembly including the housing 20, X-ray tube 30, coolant 7 (insulation oil), high-voltage insulation member 6, stator coil 90, and receptacles 300, 400.
The housing 20 includes a cylindrically formed housing body 20n, and cover parts (side plates) 20f, 20g, 20h. In a direction along the axis a of the X-ray tube 30, a peripheral edge portion of the cover part 20f is in contact with a stepped portion of the housing body 20n. A rubber member 2a is formed of an O-ring and is provided between the housing body 20n and the cover part 20f. A C type retaining ring 20i is fitted in the groove portion of the housing body 20n.
In the direction along the axis a of the X-ray tube 30, a peripheral edge portion of the cover part 20g is in contact with a stepped portion of the housing body 20n. The cover part 20g includes an opening portion 20k through which the coolant 7 comes in and goes out. A vent hole 20m, through which air as an atmosphere comes in and goes out, is formed in the cover part 20h. A C type retaining ring 20j is fitted in a groove portion of the housing body 20n. A seal portion of a rubber member 2b is formed like an O-ring.
A fixed shaft of the X-ray tube 30 is fixed to the container 32 and high-voltage insulation member 6. The high-voltage insulation member 6 is directly fixed to the housing 20, or indirectly fixed to the housing 20 via the stator coil 90. The high-voltage insulation member 6 is configured to effect electrical insulation between the fixed shaft (X-ray tube 30), and the housing 20 and stator coil 90.
The rotating-anode X-ray tube assembly 10 further includes X-ray shielding members 510, 520 and 530.
The X-ray shielding member 510 is provided on one side of the housing 20 and shields X-rays which are radiated from the target layer 35a. The X-ray shielding member 510 includes a first shielding portion 511 and a second shielding portion 512.
The X-ray shielding member 520 is formed in a cylindrical shape. One end portion of the X-ray shielding member 520 is close to the first shielding portion 511. The X-ray shielding member 530 is formed in a cylindrical shape and is provided in a cylindrical portion 20r of the housing 20. One end portion of the X-ray shielding member 530 is close to the X-ray shielding member 520.
A holding member 3 and rubber members 2d, 2e are provided between the X-ray tube 30 and the housing 20. The stator coil 90 is fixed to the housing body 20n. The receptacle 300 for the anode is located inside a cylindrical portion 20q of the housing 20 and is attached to the cylindrical portion 20q. A ring nut 310 is fastened to a stepped portion of the cylindrical portion 20q and pushes the receptacle 300. The receptacle 400 for the cathode is located inside the cylindrical portion 20r of the housing 20 and is attached to the cylindrical portion 20r. A ring nut 410 is fastened to a stepped portion of the cylindrical portion 20r and pushes the receptacle 400.
According to the rotating-anode X-ray tube assembly 10 of the comparative example with the above-described structure, the end portion of the anode of the X-ray tube can relatively easily be fixed to the high-voltage insulation member 6 which is attached to the cylindrical housing 20. However, the cathode side of the X-ray tube is merely elastically supported and fixed to the cylindrical housing 20 via the holding member 3 and rubber members 2d, 2e.
In the meantime, in recent years, in an X-ray tube assembly for CT photography use, etc., with an increase in complexity of the shape of the X-ray tube 30, an increase in weight of the X-ray tube 30, and an increase in rotational speed of a rotating frame to which the X-ray tube assembly is mounted, there may be a case which cannot be coped with by the fixing structure of the X-ray tube to the housing in the above-described comparative example.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
For example, in the above embodiments, the X-ray shielding member 60 is stuck to only the inner surface of the first divisional part 20a, but the embodiments are not limited to this example. The X-ray shielding member may be stuck to the inner surface of the second divisional part 20c. In this case, it is possible to contribute to further reduction in the amount of leakage of scattered X-rays.
The X-ray shielding member (60) does not need to be stuck to the inner surface of the housing 20, and may be disposed within the housing 20 while being spaced apart from the inner surface of the housing 20.
It is desirable that the entire surface of the X-ray shielding member (60) be coated with an organic coating film. The reason for this is that, for example, when the coolant 7 is a water-based coolant, if the X-ray shielding member is in a state of immersion in the water-based coolant, such problems will arise that the lead, of which the X-ray shielding member is formed, is gradually corroded and dissolved during use and the electrical conductivity of the coolant 7 increases, or that a deposit containing lead as a main component forms on a metallic outer surface of the X-ray tube 30.
The embodiments of the invention are applicable not only to the above-described rotating-anode X-ray tube assembly 10 and rotating-anode X-ray tube apparatus 1, but also to various kinds of rotating-anode X-ray tube assemblies and rotating-anode X-ray tube apparatuses. For example, the rotating-anode X-ray tube assembly is not limited to a rotating-anode X-ray tube assembly of an anode-grounding type, but may be a rotating-anode X-ray tube assembly of a cathode-grounding type or a rotating-anode X-ray tube assembly of a neutral-grounding type.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-191449 | Sep 2013 | JP | national |
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-191449, filed Sep. 17, 2013, the entire contents of which are incorporated herein by reference.
