JP5267150B2 - X-ray tube device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray tube device capable of restraining temperature rise at a magnetic field generator. <P>SOLUTION: The magnetic field generator 4 is made up in a laminated structure of a magnetic part 4A and a high thermally conductive part 4B by adopting iron for the former 4A and copper for the latter 4B as a plurality of components with different coefficients of thermal conductivity. A coolant represented by cooling oil or the like or a fixing part for fixing the magnetic field generator 4 is to be kept in contact with the high thermally conductive part 4B so that the same 4B may have a heat radiation action as one with a higher coefficient of thermal conductivity. Heat generated at the magnetic field generator 4, due to such heat radiation action, is thermally conducted to the high thermally conductive part 4B to be dissipated. As a result, rise of temperature at the magnetic field generator 4 can be restrained. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an X-ray tube apparatus that generates X-rays by collision of an electron beam with an anode.

  As a conventional X-ray tube device, there is an envelope rotation type X-ray tube device in which an anode rotates integrally with an envelope (for example, see Patent Documents 1 and 2). In such an envelope rotation type X-ray tube apparatus, a magnetic field generator provided outside the X-ray tube main body with an electron beam generated from a cathode electron source provided at the axial center in the X-ray tube main body. And focus and deflect to form a focal point at a predetermined position on the target disk of the anode. The magnetic field generator includes a coil, a magnetic pole, and a yoke, and generates a focusing magnetic field for focusing the electron beam. At the same time, it can generate a superposed deflection magnetic field for deflecting the electron beam. Examples of such a magnetic field generator include a quadrupole magnetic lens and an octopole magnetic lens. Since the anode of the envelope rotating X-ray tube rotates together with the envelope, the focused and deflected electron beam does not collide with one point on the target disk. Therefore, the heat generated by the collision of the electron beam spreads to the circumferential region on the target disk, and the target disk can be prevented from melting. The heat generated by the collision of the electron beam is dissipated by heat conduction from the anode target integrated with the envelope to the outside of the X-ray tube. Therefore, the cooling efficiency of the X-ray tube is good, and continuous X-ray irradiation is possible without taking cooling time.

US Pat. No. 4,993,055 US Pat. No. 5,883,936

  However, since the magnetic field generator is placed outside the envelope that is the main body of the X-ray tube, it is far from the electron beam, and the magnetic field generator has a high magnetomotive force (the product of the current flowing through the magnetic field generator and the number of turns of the coil). ) Is required and the amount of heat generated by the coil increases. In the magnetic field generator described in Patent Document 2, since the yoke is composed only of iron having low thermal conductivity, the heat generated in the coil is not efficiently radiated outside the magnetic field generator. Therefore, the temperature of the coil or yoke rises, causing a problem that X-rays cannot be continuously irradiated from the X-ray tube. In addition, there is a problem that high energy X-rays cannot be irradiated due to an increase in coil temperature. In order to prevent this, there is a means of increasing the wire diameter of the coil or increasing the number of turns of the coil, but there arises a problem that the coil becomes large. Further, in order to focus and deflect a higher energy electron beam, it is necessary to generate a strong magnetic field, and a larger amount of heat radiation is required for the magnetic field generator.

  This invention is made in view of such a situation, and it aims at providing the X-ray tube apparatus which can suppress the raise of the temperature in a magnetic field generator.

In order to achieve such an object, the present invention has the following configuration.
That is, the invention described in claim 1 is an X-ray tube device that generates X-rays by collision of an electron beam with an anode, and includes a magnetic field generator that generates a magnetic field to focus and deflect the electron beam. , the magnetic field generator comprises a magnetic pole and the yoke, at least one of the yoke and the magnetic pole, and provided in a multilayer structure thermal conductivity consists of a plurality of different components, at least one of the components One is formed of a magnetic material.

[Operation / Effect] According to the invention of claim 1, the magnetic field generator includes a magnetic pole and a yoke, and at least one of the above-described yoke and the above-described magnetic pole has a plurality of different thermal conductivities. By forming at least one of the above-mentioned components with a magnetic material, the heat generated by the magnetic field generator is heated to the component having the higher thermal conductivity among the components. Conducted and dissipated by heat dissipation action. As a result, temperature rise due to heat generated in the coil of the magnetic field generator can be suppressed. As a result, the X-ray continuous differential time can be lengthened by suppressing the temperature rise. In addition, it is possible to generate a stronger magnetic field than before and to generate high energy X-rays. Also, by suppressing the rise in temperature, there is no need to increase the wire diameter of the coil of the magnetic field generator or increase the number of turns of the coil, so the coil wire diameter is reduced, the number of turns of the coil is reduced, It can also be made smaller.

In X-ray tube apparatus of the invention described above, the yoke is constituted by an annular yoke that surrounds the outer periphery of the X-ray tube body to support the magnetic pole, to only the yoke described above may be provided in a multilayer structure as described above (Invention described in claim 2) Only the magnetic poles described above may be configured in the above-described laminated structure (invention described in claim 3). Therefore, depending on the heat generation location, the magnetic pole may be configured in a stacked structure without the yoke having a stacked structure, the yoke may be configured in the stacked structure without forming the magnetic pole in a stacked structure, Both yokes may have a laminated structure.

Moreover, the following are mentioned as a specific example of the structure mentioned above. For example, the component has a heat dissipation effect by bringing the refrigerant into contact with a component having the higher thermal conductivity among the components described above. Among the components described above, a component having a higher thermal conductivity has a heat radiation effect as a result of being cooled by the refrigerant in contact with the component .

According to the X-ray tube apparatus according to the present invention, the magnetic field generator includes a magnetic pole and a yoke, and at least one of the above-described yoke and the above-described magnetic pole is composed of a plurality of components having different thermal conductivities. By configuring at least one of the above-described components with a magnetic material, the heat generated by the magnetic field generator is thermally conducted to the component having the higher thermal conductivity among the components, Heat is dissipated by heat dissipation. As a result, the temperature rise in the magnetic field generator can be suppressed.

(A) is a schematic side view of the X-ray tube apparatus according to each embodiment, (b) is a schematic front view of a magnetic field generator of the X-ray tube apparatus according to Embodiment 1, and (c) is a magnetic field generation of (b). It is a side view of the yoke in a container. (A) is a schematic front view of the magnetic field generator of the X-ray tube apparatus concerning Example 2, (b) is a side view of the yoke in the magnetic field generator of (a), and the fixing | fixed part which fixes it. (A)-(c) is a side view of the yoke in the magnetic field generator concerning a modification.

  Embodiment 1 of the present invention will be described below with reference to the drawings. 1A is a schematic side view of an X-ray tube apparatus according to each embodiment, and FIG. 1B is a schematic front view of a magnetic field generator of the X-ray tube apparatus according to Embodiment 1. FIG.1 (c) is a side view of the yoke in the magnetic field generator of FIG.1 (b).

  As shown in FIG. 1A including Example 2 to be described later, an envelope rotating X-ray tube device 1 according to Example 1 includes a cathode 2 for generating an electron beam B, and the cathode 2 is installed in the groove, the magnetic field generator 4 generates a magnetic field for focusing and deflecting the electron beam B from the cathode 2, and the electron beam B focused and deflected by the magnetic field generator 4. An anode 5 that generates X-rays by the collision, and an envelope 6 that accommodates the cathode 2, the cylindrical electrode 3, and the anode 5 and rotates together with the anode 5.

  A cylindrical electrode 3 is disposed together with the cathode 2 at the center of the axis O of the electron beam B. The cathode 2 is composed of a filament made of, for example, tungsten. The filament is heated to a high temperature to emit thermoelectrons to generate an electron beam B. The cathode 2 may be a field emission type in addition to a thermionic emission type typified by a filament or the like, and is not particularly limited.

  As shown in FIG. 1B, the magnetic field generator 4 of the present invention includes a plurality of (four in FIG. 1B) magnetic poles 4a and polygons that support them (octagons in FIG. 1B). Yoke 4b. As shown in FIG. 1A, the yoke 4b is formed in an annular shape that surrounds the outer periphery of the envelope 6 that is an X-ray tube main body. A coil 4c is directly wound around the magnetic pole 4a. As another configuration, the coil 4c may be wound around a bobbin (cylinder), and the coil 4c may be wound around the magnetic pole 4a by inserting the bobbin into the magnetic pole 4a. In order to release heat generated in the coil 4c, which will be described later, via the yoke 4b, the magnetic part 4A (see FIG. 1C) of the magnetic pole 4a or the yoke 4b (see FIG. 1C) is brought into contact with the coil 4c, so that the magnetic It fixes to part 4A so that contact thermal resistance may become low. The magnetic pole 4a corresponds to the magnetic pole in the present invention, and the yoke 4b corresponds to the yoke in the present invention.

  Conventionally, heat generated in the coil is radiated through the magnetic pole and oil. Conventionally, an iron-only yoke conducts to oil around the coil (indicated as “Oil” in FIG. 1A) and the like, and most of the heat is conducted from the coil surface. Therefore, the heat dissipation efficiency is low and the coil temperature rises. Thus, it is conceivable to form the yoke with a material having higher thermal conductivity than iron (for example, copper or aluminum), but copper or aluminum is a non-magnetic material and is not suitable as a yoke.

  In Example 1, including Example 2 to be described later, as shown in FIG. 1 (c), at least a yoke 4b is composed of a magnetic part 4A made of iron and a high heat conduction part 4B in which the magnetic part 4A is sandwiched and laminated. It is characterized by comprising. That is, the yoke 4b is formed in a laminated structure including a plurality of magnetic parts 4A and high heat conduction parts 4B, which are parts having different thermal conductivities, and at least one of the parts described above is formed of a magnetic material. And Here, the magnetic part 4A is formed as a magnetic material. The high thermal conductivity portion 4B is formed of a material having a higher thermal conductivity than the magnetic portion 4A, for example, copper. By sandwiching the magnetic part 4A between the high heat conduction part 4B, the high heat conduction part 4B comes into contact with the oil as the refrigerant, and the high heat conduction part 4B has a larger heat dissipation action than iron. That is, not only the surface of the coil 4c but also the high heat conduction part 4B conducts heat, the effective heat radiation area increases, and heat radiation becomes easy.

  In summary, the magnetic field generator 4 is composed of the coil 4c, the magnetic pole 4a, and the annular yoke 4b that supports the coil 4c and surrounds the outer peripheral portion of the X-ray tube main body (envelope 6). As a plurality of parts having different rates, a magnetic part 4A and a high heat conduction part 4B are adopted, and at least the yoke 4b is configured in a laminated structure of the magnetic part 4A and the high heat conduction part 4B. The high thermal conductivity portion 4B, which is a component having a higher thermal conductivity than iron, has a large heat dissipation effect.

  If at least the yoke 4b has a laminated structure of the magnetic part 4A and the high heat conducting part 4B, only the yoke 4b may have a laminated structure of the magnetic part 4A and the high heat conducting part 4B. Both the 4a and the yoke 4b may be formed in a laminated structure of the magnetic part 4A and the high heat conduction part 4B. In addition, the yoke 4b is not necessarily configured to have the above-described stacked structure, and the magnetic pole 4a may be configured to have a stacked structure without using the yoke 4b having the above-described stacked structure, depending on the heat generation location. Thus, the magnetic field generator 4 is composed of the magnetic pole 4a and the annular yoke 4b that supports the magnetic pole 4a and surrounds the outer peripheral portion of the X-ray tube main body (envelope 6), and at least the yoke 4b is the laminated structure described above. Alternatively, at least the magnetic pole 4a may be configured in the laminated structure described above. Therefore, depending on the heat generation location, the magnetic pole 4a may be configured in a stacked structure without the yoke 4b having a stacked structure, or the yoke 4b may be configured in a stacked structure without forming the magnetic pole 4a. In addition, both the magnetic pole 4a and the yoke 4b may be configured in a laminated structure.

  The anode 5 is disposed integrally with the envelope 6 inside the envelope 6. The anode 5 is provided with a target inclined portion 5a, and the focused and deflected electron beam B is accelerated toward the anode 5 by an electric field generated by a high voltage, and generates X-rays by colliding with the target inclined portion 5a. . The envelope 6 is evacuated. A cathode side rotating shaft 7 is disposed on the cathode 2 side of the envelope 6, and an anode side rotating shaft 8 is disposed on the anode 5 side of the envelope 6. By rotating both the rotating shafts 7 and 8, the envelope 6 rotates together with the anode 5. The outside of the envelope 6 is filled with cooling oil (indicated as “Oil” in FIG. 1A) or air.

According to the X-ray tube apparatus 1 according to the first embodiment, the magnetic field generator 4 is configured in a laminated structure including a plurality of parts having different thermal conductivities (in each embodiment, the magnetic portion 4A and the high thermal conductivity portion 4B). Then, by forming the magnetic part 4A out of the parts described above with a magnetic material, the heat generated by the magnetic field generator 4 has the higher thermal conductivity of the parts (the high heat conduction part 4B in each embodiment). Conducts heat to the part and dissipates heat by heat dissipation. The effective contact area with the oil was, for example, 40 cm ² in the case of conventional iron alone, but the laminated structure of iron (magnetic part 4A) and copper (high heat conduction part 4B) as in Example 1 was used. If in is approximately eight times the 320cm ^2. Therefore, the temperature rise in the magnetic field generator 4 can be suppressed. As a result, the X-ray continuous differential time can be lengthened by suppressing the temperature rise, and high-energy X-rays can be generated. Further, since the temperature rise is suppressed, it is not necessary to increase the wire diameter of the coil 4c of the magnetic field generator 4 and increase the number of turns of the coil 4c. Therefore, the wire diameter of the coil 4c is reduced and the number of turns of the coil 4c is reduced. Thus, the coil 4c can be made smaller. Furthermore, the heat radiation efficiency is high, and it is not necessary to place the magnetic field generator 4 in the cooling oil, and there is an effect that it can be placed in the air or in a vacuum.

  Next, Example 2 will be described as an example of placing the magnetic field generator in a vacuum. FIG. 2A is a schematic front view of the magnetic field generator of the X-ray tube apparatus according to the second embodiment, and FIG. 2B is a view illustrating a yoke in the magnetic field generator of FIG. It is sectional drawing of a fixing | fixed part. Since the schematic side view of the X-ray tube apparatus according to the second embodiment is the same as that of the X-ray tube apparatus according to the first embodiment, FIG. Further, the configuration of the X-ray tube apparatus 1 other than the magnetic field generator 4 is the same as that of the first embodiment, and thus the description thereof is omitted.

  In the present Example 2, as shown to Fig.2 (a), the fixing | fixed part 9 which fixes the magnetic field generator 4 in a vacuum is provided. Further, as shown in FIG. 2 (b), the fixing portion 9 is brought into contact with the high heat conduction portion 4B which is a component having a higher thermal conductivity among the components. Therefore, the high heat conduction part 4B has a heat radiation action through the fixing part 9. As in the first embodiment, a refrigerant represented by oil or the like may be filled outside the envelope 6 (see FIG. 1A). The fixing portion 9 corresponds to the fixing portion in the present invention.

  When the magnetic field generator 4 has a laminated structure of the magnetic part 4A and the high heat conduction part 4B, and the fixing part 9 fixes the magnetic field generator 4, the effect of improving the heat dissipation of the heat generation of the coil 4c is obtained by calculation. Yes. The calculation will be specifically described below.

As shown in FIG. 2A, a fixing position by the fixing portion 9 is P, and a path between the heat source (coil 4c) and the fixing position P is a heat conduction path L. It is assumed that the temperature of the yoke 4b at the fixed position P is constant at 25 ° C., and the coil heating value is Q. The thermal conductivity of iron is 73 W / m · K, and the thermal conductivity of copper is 394 W / m · K.
If only conventional iron, the cross-sectional area of the yoke 4b and S, when the temperature in the vicinity of the coils 4c and _{T 1,} temperatures _{T 1} is determined from the heat conduction equation _{T 1 = 25 ℃ + Q [} W] × L [m ] / (S [m ² ] × 73 [W / m · K]) (1)
It becomes.
On the other hand, if the laminated structure of iron as in the second embodiment (magnetic portion 4A) and copper (high thermal conductive portion 4B), and the cross-sectional area of the yoke 4b _S F, and _{S C,} the temperature in the vicinity of the coil 4c _{T 2} Then, the temperature T ₂ is obtained from the heat conduction equation. T ₂ = 25 ° C. + Q [W] × L [m] / (S _F [m ² ] × 73 [W / m · K] +
S _C [m ² ] × 394 [W / m · K]) (2)
It becomes.
According to the above formulas (1) and (2), the temperature T ₁ near the coil in the case of conventional iron only, and the lamination of iron (magnetic part 4A) and copper (high heat conduction part 4B) as in the second embodiment determining the temperature T ₂ of the vicinity of the coils 4c in the case of the structure. For example, if Q = 50 W, L = 0.03 m, S = 1 × 10 ⁻⁴ m ² , S _F = S _C = 0.5 × 10 ⁻⁴ m ² , T ₁ = 230 ° C., T ₂ = 89 ° C.

Thus, in the case of only conventional iron, the temperature T ₁ near the coil reaches 230 ° C., and the coil copper wire is damaged by heat. On the other hand, in the case of a laminated structure of iron as in the second embodiment (magnetic portion 4A) and copper (high thermal conductivity portion. 4B), temperature T ₂ in the vicinity of the coil 4c is 89 ° C., and the there is no problem.

  According to the X-ray tube apparatus 1 according to the second embodiment, similarly to the first embodiment, the magnetic field generator 4 includes a plurality of components having different thermal conductivities (in each embodiment, the magnetic part 4A and the high heat conduction part 4B). ), And the magnetic part 4A among the above-described parts is formed of a magnetic material, so that the heat generated by the magnetic field generator 4 has a higher thermal conductivity (high heat conduction part 4B). ) Is conducted to the part having heat and is dissipated by the heat radiation action. As a result, the temperature rise in the magnetic field generator 4 can be suppressed.

  Unlike the first embodiment described above, in the second embodiment, the magnetic field generator 4 is fixed in a vacuum, and the fixing portion 9 has a higher thermal conductivity among the components described above (high heat in each embodiment). By contacting the component having the conductive portion 4B), the component has a heat dissipation action.

  The present invention is not limited to the above-described embodiment, and can be modified as follows.

  (1) The present invention can also be applied to industrial devices such as non-destructive inspection equipment and medical devices such as an X-ray diagnostic device.

  (2) In each of the above-described embodiments, the magnetic part 4A is sandwiched between the high thermal conduction parts 4B. However, as shown in FIG. 3A, the magnetic parts 4A and the high thermal conduction parts 4B are alternately laminated. It may be a structure. Further, as shown in FIG. 3 (b), a structure in which the high heat conducting portion 4B is laminated on the side contacting the refrigerant or the fixed portion typified by oil or the like may be used. In addition, the magnetic field generator has a laminated structure composed of three or more parts having different thermal conductivities so as to gradually increase the thermal conductance toward the side of the refrigerant or the fixed part typified by oil. You may comprise. In FIGS. 3A and 3B, the thickness of each layer is uniform, but each layer may have a different thickness.

  (3) In each of the above-described embodiments, a component having a higher thermal conductivity among components is laminated on the side in contact with a refrigerant typified by oil or the like or a fixed portion. When the fixing portion 9 is provided as in the second embodiment described above, as shown in FIG. 3C, the parts other than the fixing position P (see FIG. 2A) by the fixing portion 9 A component having a higher thermal conductivity (for example, the high thermal conductivity portion 4B) may be included, and a component having a higher thermal conductivity among the components may be configured to contact the fixed position P.

  (4) In each of the embodiments described above, the magnetic part 4A is iron, and the high heat conduction part 4B, which is a part having a higher thermal conductivity among the parts, is copper. Is not particularly limited. If the magnetic field generator 4 is configured in a laminated structure composed of a plurality of parts having different thermal conductivities and at least one of the parts described above is formed of a magnetic material, the higher thermal conductivity of the parts. As a component having copper, a material other than copper may be used. For example, aluminum, brass, phosphor bronze, or a copper aluminum alloy may be used. In addition, the component having the higher thermal conductivity among the components is not necessarily limited to a non-magnetic material such as copper, and the magnetic field generator 4 is a laminated structure composed of a plurality of magnetic materials having different thermal conductivities. Alternatively, a component having a higher thermal conductivity among components may be formed of a magnetic material by forming a laminated structure including a plurality of magnetic materials and nonmagnetic materials having different thermal conductivities. Therefore, when applied to the embodiment, it is possible to bring the refrigerant or the fixed portion into contact with a component made of a magnetic material having a higher thermal conductivity among the components. Moreover, as long as it is a magnetic material, it may be a substance other than iron, or nickel or an iron-nickel alloy. Moreover, you may combine the substance illustrated here in the Example and modification (1)-(3) which were mentioned above.

  (5) In each of the above-described embodiments, the magnetic field generator (magnetic field generator 4) including the polygonal yoke 4b represented by an octagon has been described. However, the shape is not particularly limited as long as it is an annular yoke. For example, an annular shape may be used. Further, the number of magnetic poles of the magnetic field generator is not particularly limited, as exemplified by a quadrupole magnetic lens and an octupole magnetic lens.

  (6) As a method of laminating, screwing, adhesion, etc. can be considered, but it is not limited to these methods.

  (7) The high heat conduction portion 4B is preferably a continuous and integral structure, but may be divided into two or more in terms of production.

DESCRIPTION OF SYMBOLS 4 ... Magnetic field generator 4a ... Magnetic pole 4b ... Yoke 4A ... Magnetic part 4B ... High heat conduction part 5 ... Anode 6 ... Enclosure 9 ... Fixed part B ... Electron beam Oil ... Oil for cooling

Claims (4)

An X-ray tube device for generating X-rays by collision of an electron beam with an anode, comprising: a magnetic field generator for generating a magnetic field for focusing and deflecting the electron beam , the magnetic field generator comprising a magnetic pole, a yoke, And at least one of the yoke and the magnetic pole is formed in a laminated structure including a plurality of parts having different thermal conductivities , and at least one of the parts is formed of a magnetic material. X-ray tube device. In X-ray tube apparatus according to claim 1, wherein the yoke is composed of an annular yoke that surrounds the outer periphery of the X-ray tube body to support the pole, constituting only the yoke in the lamination structure X-ray tube device. In X-ray tube apparatus according to claim 1, wherein the yoke is composed of an annular yoke that surrounds the outer periphery of the X-ray tube body to support the pole, constituting only the pole to the laminated structure X-ray tube device.   The X-ray tube apparatus according to any one of claims 1 to 3, wherein the refrigerant is brought into contact with a component having a higher thermal conductivity among the components.

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