JP2025134219A - x-ray tube - Google Patents

Abstract

An X-ray tube capable of suppressing a rise in anode temperature is provided.
[Solution] The X-ray tube includes an anode (13) and a cathode. The anode (13) has an anode target body (14) and an anode target layer (15) provided on the anode target body (14). The cathode faces the anode target layer (15). The anode target body (14) has an anisotropic graphite portion (16) formed by stacking a plurality of graphite layers (17). The anode target layer (15) is provided on a plane intersecting with the stacking direction (a) of the graphite layers (17).
[Selected Figure] Figure 2

Description

An embodiment of the present invention relates to an X-ray tube.

X-ray tubes generate X-rays by causing electrons emitted from a cathode to collide with an anode, but the efficiency of converting the energy imparted to the electrons into X-rays is only about 1%, with the rest being converted into heat.

The heat generated by the electrons colliding with the anode is stored in the anode, and if the temperature of the electron impact surface of the anode exceeds the melting point of the material during electron impact, the electron impact surface will melt. For this reason, the power input to the X-ray tube must be limited so that the temperature of the anode does not exceed its melting point.

JP 2011-86463 A

The problem that this invention aims to solve is to provide an X-ray tube that can suppress temperature increases in the anode.

The X-ray tube of this embodiment includes an anode and a cathode. The anode has an anode target body and an anode target layer provided on the anode target body. The cathode faces the anode target layer. The anode target body has an anisotropic graphite portion formed by stacking multiple graphite layers. The anode target layer is provided on a plane that intersects with the stacking direction of the graphite layers.

1 is a side view of a fixed anode X-ray tube showing a first embodiment. FIG. 2 is a schematic cross-sectional view of the anode of the X-ray tube. FIG. 10 is a schematic cross-sectional view of a rotating anode type X-ray tube showing a second embodiment. FIG. 2 is a perspective view of the X-ray tube with a portion of the rotation shaft and the anode cut away. FIG. 2 is an enlarged cross-sectional view of the anode of the X-ray tube. 3A, 3B, and 3C are schematic cross-sectional views showing specific configuration examples in which an anode target layer is provided on an anode target body of the anode of the same X-ray tube. FIG. 10 is an enlarged cross-sectional view of an anode of a rotating anode type X-ray tube according to a third embodiment. FIG. 10 is an enlarged cross-sectional view of an anode of a rotating anode type X-ray tube according to a fourth embodiment. FIG. 10 is an enlarged cross-sectional view of an anode of a rotating anode type X-ray tube according to a fifth embodiment. FIG. 10 is a schematic diagram of an X-ray computed tomography diagnostic apparatus using a rotating anode X-ray tube according to the second to fifth embodiments.

The first embodiment will be described below with reference to Figures 1 and 2.

Figure 1 shows a side view of a fixed anode type X-ray tube 10. The X-ray tube 10 comprises a vacuum envelope 11, a cathode 12 sealed at one end of the vacuum envelope 11, and an anode (anode target) 13 sealed at the other end of the vacuum envelope 11.

The vacuum envelope 11 is made of, for example, glass, and maintains a vacuum inside.

The cathode 12 emits electrons toward the anode 13.

The anode 13 comprises an anode target body 14 and an anode target layer 15 provided on the anode target body 14. The anode target layer 15 faces the cathode 12, and electrons emitted from the cathode 12 collide with the anode target layer 15 to generate X-rays, which are then emitted outside the vacuum envelope 11.

Figure 2 shows a schematic cross-sectional view of the anode 13. The anode target body 14 of the anode 13 has an anisotropic graphite portion 16, and an anode target layer 15 is provided on this anisotropic graphite portion 16.

The anisotropic graphite portion 16 is formed by stacking multiple graphite layers 17, such as graphite sheets. The anisotropic graphite portion 16 has a stacking direction a of the graphite layers 17 and a plane direction, which is the graphene crystal plane of the graphite layers 17, that intersects with the stacking direction a. The thermal conductivity in the plane direction is higher than the thermal conductivity in the stacking direction a, and is also higher than the thermal conductivity of other metal materials such as copper.

The anisotropic graphite portion 16 has a stacking end surface 18 formed by the end faces of multiple graphite layers 17 on a surface that intersects with the stacking direction a of the graphite layers 17. The tip surface of the anode target body 14 facing the cathode 12 is the stacking end surface 18, and is provided on an inclined surface that is inclined relative to the direction facing the cathode 13.

The anode target layer 15 is provided on the leading end surface of the anode target body 14, on the stacking end surface 18, which is a surface that intersects with the stacking direction a of the anisotropic graphite portion 16, and is in contact with and thermally connected to the multiple graphite layers 17. An electron collision surface 19, on which electrons emitted from the cathode 12 collide, is formed on the surface of the anode target layer 15.

The anode target layer 15 is formed of a heavy metal with a high melting point, such as molybdenum (Mo), tungsten (W), or an alloy of these. For example, a molybdenum alloy layer is formed on the stacked end surface 18 of the anisotropic graphite portion 16, a tungsten alloy layer is formed on this molybdenum alloy layer, and an electron collision surface 19 is formed on the surface of the molybdenum alloy layer.

When the X-ray tube 10 is in operation, electrons emitted from the cathode 12 collide with the anode target layer 15 of the anode 13, generating X-rays that are then emitted outside the vacuum envelope 11.

Heat is generated when electrons collide with the anode target layer 15 of the anode 13. The heat generated in the anode target layer 15 is transferred to the multiple graphite layers 17 of the anisotropic graphite portion 16, spreads in the plane direction of the multiple graphite layers 17 where thermal conductivity is high, and escapes to the outside of the X-ray tube 10.

The anode target body 14 is typically made of a highly thermally conductive metal such as copper to dissipate heat generated in the anode target layer 15 to the outside of the X-ray tube 10. However, by using the anisotropic graphite portion 16, the heat generated in the anode target layer 15 can be quickly dissipated to the outside of the X-ray tube 10. This suppresses temperature rise in the anode 13 and keeps the temperature of the anode target layer 15 below the melting point of the material of the anode target layer 15, thereby easing restrictions on the power input to the X-ray tube 10.

Next, Figures 3 to 6 show the second embodiment.

Figure 3 shows a schematic cross-sectional view of a rotating anode type X-ray tube 20. The X-ray tube 20 comprises a vacuum envelope 21, a cathode 22, a fixed shaft 23, a rotating body 26 having a rotating shaft 24 and an anode 25, a rotor 27, and a stator coil 28. The cathode 22, fixed shaft 23, rotating body 26, and rotor 27 are arranged within the vacuum envelope 21, and the stator coil 28 is arranged outside the vacuum envelope 21.

The vacuum envelope 21 maintains a vacuum inside. The vacuum envelope 21 is provided with an X-ray transmission window that emits X-rays generated by the anode 25 to the outside.

The cathode 22 emits electrons toward the anode 25.

The fixed shaft 23 is made of metal and has a roughly cylindrical shape, with one end supported by the vacuum envelope 21. A cooling passage 29 is formed inside the fixed shaft 23, through which a refrigerant, a liquid coolant for cooling, passes. A cooling device equipped with a heat exchanger (not shown) circulates the refrigerant between the cooling passage 29 and the heat exchanger.

The rotating shaft 24 is cylindrical and rotatably arranged around the fixed shaft 23, for example, using a fluid metal bearing structure.

The anode 25 is disk-shaped and is arranged around the rotation axis 24.

The rotor 27 is cylindrical and is arranged around the rotation shaft 24.

The stator coil 28 is positioned opposite the rotor 27 across the vacuum envelope 21 and generates a magnetic field that rotates the rotor 27.

Figure 4 also shows a perspective view with parts of the rotating shaft 24 and anode 25 cut away.

A rotating shaft-side mounting portion 30 for mounting the anode 25 is provided around the rotating shaft 24. The rotating shaft-side mounting portion 30 has mounting holes 31 at multiple locations around the circumference for mounting the anode 25 with bolts. The axial direction of the mounting holes 31 is parallel to the axial direction of the rotating shaft 24.

The anode 25 comprises an anode target body 32 and a target layer 33 provided on the anode target body 32.

The anode target body 32 is disk-shaped and has a central insertion hole 34 through which the rotary shaft 24 passes. An anode-side mounting portion 35 is provided around the insertion hole 34 and attached to the rotary shaft-side mounting portion 30 of the rotary shaft 24. The anode-side mounting portion 35 has multiple mounting holes 36 at multiple circumferential locations corresponding to the multiple mounting holes 31 in the rotary shaft-side mounting portion 30. The axial direction of the mounting holes 36 is parallel to the axial direction of the disk-shaped anode target body 32. The anode-side mounting portion 35 is positioned on the rotary shaft-side mounting portion 30, and multiple bolts are attached to the mounting holes 31 in the rotary shaft-side mounting portion 30 through the mounting holes 36 in the anode-side mounting portion 35. The anode target body 32 is fixed to the rotary shaft 24 and thermally connected to the rotary shaft 24. The anode target body 32 has an inclined surface 37 on the outer periphery of one axial surface facing the cathode 22.

The anode target layer 33 is provided circumferentially on the outer periphery of one axial surface of the anode target body 32 facing the cathode 22. The anode target layer 33 is provided on an inclined surface 37 of the anode target body 32. The anode target layer 33 is formed of a heavy metal with a high melting point, such as molybdenum (Mo), tungsten (W), or an alloy thereof. An electron collision surface 38 is formed on the surface of the anode target layer 33, with which electrons emitted from the cathode 22 collide.

Figure 5 also shows an enlarged cross-sectional view of the anode 25. The anode target body 32 of the anode 25 has an anisotropic graphite portion 39, and the anode target layer 33 is provided on this anisotropic graphite portion 39. In this embodiment, the entire anode target body 32 is formed from the anisotropic graphite portion 39.

The anisotropic graphite portion 39 is formed by stacking multiple graphite layers 40, such as graphite sheets. The anisotropic graphite portion 39 has a stacking direction a of the graphite layers 40 and a plane direction, which is the graphene crystal plane of the graphite layers 40, that intersects with the stacking direction a. The thermal conductivity in the plane direction is higher than the thermal conductivity in the stacking direction a, and is also higher than the thermal conductivity of other metal materials such as copper.

The stacking direction a of the graphite layers 40 is aligned along the circumferential direction Z, which is the rotational direction of the anode target body 32, and the surface direction of the graphite layers 40 is aligned along the radial direction X and axial direction Y, which is the thickness direction of the anode target body 32. Therefore, stacking end surfaces 41, which are composed of the end faces of multiple graphite layers 40 that intersect with the stacking direction a of the graphite layers 40, are formed on one axial surface, the other axial surface, the outer circumferential surface, and the inner axial surface of the anode target body 32.

The anode target body 32 is attached so that the other axial surface and the stacked end surface 41 on the inner peripheral surface of the anode target body 32 are in contact with the rotating shaft 26, and the multiple graphite layers 40 are fixed in contact with and thermally connected to the rotating shaft 26.

The anode target layer 33 is provided along the circumferential direction Z on the stacking end surface 41 on one axial surface of the anode target body 32, which is a surface that intersects with the stacking direction a of the graphite layers 40, and is in contact with and thermally connected to the multiple graphite layers 40.

Figures 6(a) to 6(c) show schematic cross-sectional views of specific configuration examples in which an anode target layer 33 is provided on an anode target body 32. The anode target layer 33 has a first layer 43 made of, for example, a tungsten alloy that forms the electron impact surface 38, and a second layer 44 that is a bonding layer that bonds this first layer 43 to the anisotropic graphite portion 39.

In the configuration example shown in Figure 6(a), an inclined surface 37 is formed on the stacking end surface 41 on one axial surface of the anode target body 32, which is a surface that intersects with the stacking direction a of the graphite layer 40, and a first layer 43 is provided on this inclined surface 37 via a second layer 44.

In the configuration example shown in Figure 6(b), a recess 45 is provided from the stacking end surface 41 on one axial surface of the anode target body 32, which is a surface that intersects with the stacking direction a of the graphite layer 40, to the outer peripheral surface. A second layer 44 is provided in this recess 45, and a first layer 43 is provided on an inclined surface 37 provided on this second layer 44.

In the configuration example shown in Figure 6(c), a second layer 44 is laminated on a lamination end surface 41 on one axial surface of the anode target body 32, which is a surface that intersects with the lamination direction a of the graphite layer 40, and a first layer 43 is provided on an inclined surface 37 provided on this second layer 44.

When the X-ray tube 20 is in operation, electrons emitted from the cathode 22 collide with the electron collision surface 38 of the anode target layer 33 of the rotating anode 25, generating X-rays, which are then emitted to the outside through the X-ray transmission window of the vacuum envelope 21.

Heat is generated when electrons collide with the anode target layer 33. The heat generated in the anode target layer 33 is transferred from the stacked end surface 41 of the anisotropic graphite portion 39 to the multiple graphite layers 40, spreading in the planar direction where thermal conductivity is high. It is then quickly and efficiently transferred to the rotating shaft 24 to which the anode 25 is attached, and is then released to the outside from the rotating shaft 24 via the fixed shaft 23, etc.

As a result, the heat generated in the anode target layer 33 can be quickly and efficiently transferred to the rotating shaft 24 by the anisotropic graphite portion 39 and dissipated, suppressing temperature increases in the anode target layer 33 and keeping the temperature of the anode target layer 33 below the melting point of the material of the anode target layer 33, thereby easing restrictions on the power input to the X-ray tube 20.

Next, Figure 7 shows a third embodiment. Figure 7 shows an enlarged cross-sectional view of the anode 25 of a rotating anode type X-ray tube 20. Note that the same components as in the second embodiment are designated by the same reference numerals and their description will be omitted.

The anode target body 32 has an anisotropic graphite portion (first anisotropic graphite portion) 39 in which the stacking direction a of the graphite layers 40 is arranged along the circumferential direction Z of the anode target body 32, and a second anisotropic graphite portion 50 in which the stacking direction a of the graphite layers 40 is arranged along the axial direction of the anode target body 32.

The anisotropic graphite portion 39 is provided on the outer periphery of the anode target body 32, and the anode target layer 33 is provided on the stacking end surface 41 on one side of the anode target body 32 in the axial direction, which is a surface that intersects with the stacking direction a of the graphite layer 40.

The second anisotropic graphite portion 50 is located closer to the inner periphery of the anode target body 32 than the anisotropic graphite portion 39, and is positioned between the anisotropic graphite portion 39 and the rotation axis 24.

The stacking end face 41 on the inner peripheral surface of the anisotropic graphite portion 39 and the stacking end face 41 on the outer peripheral surface of the second anisotropic graphite portion 50 are joined. The stacking direction a of the graphite layers 40 at the stacking end face 41 on the inner peripheral surface of the anisotropic graphite portion 39 intersects with the stacking direction a of the multiple graphite layers 40 at the stacking end face 41 on the outer peripheral surface of the second anisotropic graphite portion 50, so that the multiple graphite layers 40 of the anisotropic graphite portion 39 and the multiple graphite layers 40 of the second anisotropic graphite portion 50 are in contact in a crossing (lattice) pattern.

The laminated end surface 41 on the inner circumferential surface of the second anisotropic graphite portion 50 is attached in contact with the rotating shaft 24.

When the X-ray tube 20 is in operation, heat generated in the anode target layer 33 by electron collisions is transferred from the stacking end surface 41 of the anisotropic graphite portion 39 to the multiple graphite layers 40, spreading in the planar direction with high thermal conductivity. The heat is then transferred from the multiple graphite layers 40 of the anisotropic graphite portion 39 to the multiple graphite layers 40 of the second anisotropic graphite portion 50, spreading in the planar direction with high thermal conductivity. The heat is then quickly and efficiently transferred to the rotating shaft 24 to which the second anisotropic graphite portion 50 is attached, and then escapes from the rotating shaft 24 to the outside via the fixed shaft 23, etc.

As a result, the heat generated in the anode target layer 33 can be quickly and efficiently transferred to the rotating shaft 24 by the anisotropic graphite sections 39, 50 and dissipated, suppressing temperature increases in the anode target layer 33 and keeping the temperature of the anode target layer 33 below the melting point of the material of the anode target layer 33, thereby easing restrictions on the power input to the X-ray tube 20.

Next, Figure 8 shows a fourth embodiment. Figure 8 shows an enlarged cross-sectional view of the anode 25 of a rotating anode type X-ray tube 20. Note that the same reference numerals are used for components similar to those of the second and third embodiments, and their description will be omitted.

The anode target body 32 has an anisotropic graphite portion (first anisotropic graphite portion) 39 in which the stacking direction a of the graphite layers 40 is arranged along the circumferential direction Z of the anode target body 32, and a second anisotropic graphite portion 50 in which the stacking direction a of the graphite layers 40 is arranged along the axial direction of the anode target body 32.

The anisotropic graphite portion 39 is provided on the outer and inner peripheral sides of the anode target body 32. The anisotropic graphite portion 40 on the outer peripheral side has an anode target layer 33 provided on a stacking end surface 41 on one axial surface of the anode target body 32, which is a surface that intersects with the stacking direction a of the graphite layer 40. The anisotropic graphite portion 39 on the inner peripheral side has an anode side mounting portion 35 that is attached to the rotation shaft 24.

The second anisotropic graphite portion 50 is located between the anisotropic graphite portion 39 on the outer periphery side and the anisotropic graphite portion 39 on the inner periphery side.

The lamination end face 41 on the inner peripheral surface of the outer anisotropic graphite portion 39 and the lamination end face 41 on the outer peripheral surface of the inner anisotropic graphite portion 39 are bonded to the lamination end face 41 on the outer peripheral surface and the lamination end face 41 on the inner peripheral surface of the second anisotropic graphite portion 50, respectively. The lamination direction a of the graphite layers 40 at the lamination end face 41 of each anisotropic graphite portion 39 intersects with the lamination direction a of the graphite layers 40 at the lamination end face 41 of the second anisotropic graphite portion 50, so that the multiple graphite layers 40 of the anisotropic graphite portion 39 and the multiple graphite layers 40 of the second anisotropic graphite portion 50 are in contact with each other in a crossing (lattice) pattern.

The anisotropic graphite portion 39 on the inner periphery is attached so that the other axial surface of the anode target body 32 and the stacked end surface 41 on the inner periphery are in contact with the rotation shaft 24.

When the X-ray tube 20 is in operation, heat generated in the anode target layer 33 by electron collisions is transmitted from the stacking end surface 41 of the outer anisotropic graphite portion 39 to the multiple graphite layers 40, spreading in the planar direction where thermal conductivity is high. Then, the heat is transmitted from the multiple graphite layers 40 of the outer anisotropic graphite portion 39 to the multiple graphite layers 40 of the second anisotropic graphite portion 50, spreading in the planar direction where thermal conductivity is high. Then, the heat is transmitted from the multiple graphite layers 40 of the second anisotropic graphite portion 50 to the multiple graphite layers 40 of the inner anisotropic graphite portion 39, spreading in the planar direction where thermal conductivity is high. Finally, the heat is quickly and efficiently transmitted to the rotating shaft 24 to which the inner anisotropic graphite portion 39 is attached, and then escapes from the rotating shaft 24 to the outside via the fixed shaft 23, etc.

As a result, the heat generated in the anode target layer 33 can be quickly and efficiently transferred to the rotating shaft 24 by the anisotropic graphite sections 39, 50 and dissipated, suppressing temperature increases in the anode target layer 33 and keeping the temperature of the anode target layer 33 below the melting point of the material of the anode target layer 33, thereby easing restrictions on the power input to the X-ray tube 20.

Next, Figure 9 shows a fifth embodiment. Figure 9 shows an enlarged cross-sectional view of the anode 25 of a rotating anode type X-ray tube 20. Note that the same reference numerals are used for components similar to those in the second to fourth embodiments, and their description will be omitted.

The anode target body 32 is formed using a highly thermally conductive metal such as copper.

The rotating shaft 24 has an anisotropic graphite portion formed by stacking multiple graphite layers along the circumferential direction of the rotating shaft 24.

When the X-ray tube 20 is in operation, heat generated in the anode target layer 33 by electron collisions is transferred through the anode target body 32 to the multiple graphite layers 40 of the anisotropic graphite portion 39 of the rotating shaft 24, spreading in the planar direction with high thermal conductivity, and then quickly and efficiently transferred from the rotating shaft 24 to the fixed shaft 23 and other parts, before being released to the outside.

As a result, the heat generated in the anode target layer 33 is transferred to the rotating shaft 24, allowing it to be quickly and efficiently dissipated to the outside, suppressing temperature increases in the anode target layer 33 and keeping the temperature of the anode target layer 33 below the melting point of the material of the anode target layer 33, thereby easing restrictions on the power input to the X-ray tube 20.

The anode 25 shown in the second to fourth embodiments may be combined with the rotating shaft 24 shown in the fifth embodiment. In this case, the heat generated in the anode target layer 33 can be quickly and efficiently transferred to the outside and dissipated.

Furthermore, the rotating anode type X-ray tube 20 shown in the second to fifth embodiments can be used in the X-ray computed tomography diagnostic apparatus 60 shown in Figure 10. Figure 10 is a schematic diagram of the X-ray computed tomography diagnostic apparatus 60.

The X-ray computed tomography diagnostic device 60 has a rotating stand 62 called a gantry arranged inside a housing 61, and an X-ray tube 20 is mounted on this stand 62.

The X-ray tube 20 mounted on the gantry 62 is positioned so that the axial direction of the rotation shaft 24 is parallel to the rotation axis of the gantry 62, and the X-ray transmission window faces the direction of the rotation center of the gantry 62.

By using anisotropic graphite portion 39 or anisotropic graphite portion 50 for the anode target body 32 of the anode 25, the density of the graphite material is low and it is lightweight, which makes it possible to stabilize the rotation of the pedestal 62 on which the rotating anode type X-ray tube 20 is mounted, compared to when a metal material such as copper is used for the anode target body 32 of the anode 25.

While several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in a variety of other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

REFERENCE SIGNS LIST 10 X-ray tube 12 Cathode 13 Anode 14 Anode target body 15 Anode target layer 16 Anisotropic graphite portion 17 Graphite layer 20 X-ray tube 22 Cathode 24 Rotation shaft 25 Anode 32 Anode target body 33 Anode target layer 39 Anisotropic graphite portion 40 Graphite layer 50 Second anisotropic graphite portion a Stacking direction Z Circumferential direction

Claims (4)

an anode having an anode target body and an anode target layer provided on the anode target body;
a cathode facing the anode target layer;
Equipped with
the anode target body has an anisotropic graphite portion formed by stacking a plurality of graphite layers;
The X-ray tube, wherein the anode target layer is provided on a plane intersecting a lamination direction of the graphite layers. an anode having an anode target body that rotates around a rotation axis and an anode target layer provided on the anode target body;
a cathode facing the anode target layer;
Equipped with
the anode target body has an anisotropic graphite portion formed by stacking a plurality of graphite layers along a circumferential direction of the anode target body,
The X-ray tube, wherein the anode target layer is provided on a plane intersecting a lamination direction of the graphite layers. 3. The X-ray tube according to claim 2, wherein the anode target body has the anisotropic graphite portion, in which the stacking direction of the graphite layers is along the circumferential direction of the anode target body, and a second anisotropic graphite portion, in which the stacking direction of the graphite layers is along the axial direction of the anode target body, and the second anisotropic graphite portion is provided between the anisotropic graphite portion and the rotation axis. A rotation axis;
an anode having an anode target body provided around the rotation axis and an anode target layer provided on the anode target body;
a cathode facing the anode target layer;
Equipped with
The X-ray tube according to claim 1, wherein the rotating shaft has an anisotropic graphite portion formed by stacking a plurality of graphite layers along a circumferential direction of the rotating shaft.