JP2006100032A - Rotating anode x-ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotating anode X-ray tube wherein a center of gravity is stable and whose size is reduced. <P>SOLUTION: A anode target 11 is rotated by a rotating magnetic field from outside. It is rotated by an action of the rotating magnetic field formed by a stator 31 to the anode target 11. A rotor structure generating rotational torque is removed from a rotating mechanism 21. The rotational torque is generated by directly applying the rotating magnetic field on the anode target 11. It is not necessary to provide a rotor mechanism in the rotating mechanism 21 rotatably supporting the anode target 11. The sizes of the rotating mechanism 21 and the stator 31 can be reduced. A compact and low cost rotating anode X-ray tube 1 with short full length can be provided. A rotating center of gravity of the anode target 11 can be easily stabilized. Reliability of the rotating anode X-ray tube 1 can be improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rotary anode X-ray tube in which a target rotates.

Conventionally, in this type of rotating anode X-ray tube, an anode target having a target layer that generates X-rays by bremsstrahlung by electron impact is mounted in a vacuum envelope. And this anode target is rotatably supported by the elongate cylindrical rotor as a rotation mechanism attached in the vacuum envelope. This rotor rotates the anode target at a high speed by a rotating magnetic field from the stator. And the structure installed in the outer side of the vacuum envelope is known so that this stator may surround a rotor concentrically (for example, refer patent document 1).
Japanese Patent Laid-Open No. 5-13029 (page 3-5, FIGS. 1 to 3)

  However, in the above-described rotary anode X-ray tube, in order to obtain the rotational torque necessary for rotating the anode target at a high speed, it is necessary to lengthen the overall axial length of the rotor to some extent. This is a factor that increases the overall length of the tube. In addition, the joining structure of the rotor and the anode target is complicated, which may increase the manufacturing cost. Therefore, since the balance between the center of gravity of the rotor and the center of gravity of the rotary anode X-ray tube is not so good, the life of the rotor may be adversely affected, and a large rotor may be used to adjust the center of gravity. There is a problem that there is a risk of increasing the manufacturing cost.

  The present invention has been made in view of these points, and an object of the present invention is to provide a rotary anode X-ray tube that has a stable center of gravity and can be miniaturized.

  The present invention relates to a vacuum envelope, a cathode that emits electrons, and a target that is provided in the vacuum envelope so as to be opposed to the cathode and emits X-rays upon incidence of electrons emitted from the cathode. A rotating body that rotatably supports the rotating body, and a drive unit that rotates the rotating body by generating a rotational torque concentrically at a certain angle with respect to the rotating body. Is.

  Then, a rotational torque is generated concentrically at a fixed angle with respect to the rotating body from the drive unit, and the target of the rotating body rotates by rotating the rotating body. Accordingly, since it is not necessary to provide a mechanism for rotating the target in the rotating mechanism that rotatably supports the rotating body, the rotational center of gravity can be easily stabilized and the mechanism for rotating the target can be reduced in size.

  According to the present invention, by rotating the rotating body by generating a rotational torque concentrically at a fixed angle with respect to the rotating body from the drive unit, the target of the rotating body is rotated. Since there is no need to provide a mechanism for rotating the target in the rotating mechanism that can be supported, the rotational center of gravity can be easily stabilized and the mechanism for rotating the target can be reduced in size, so that the center of gravity can be stabilized and reduced in size. Become.

  Hereinafter, the configuration of an embodiment of the rotary anode X-ray tube of the present invention will be described.

  1 and 2, reference numeral 1 denotes a rotary anode X-ray tube. The rotary anode X-ray tube 1 is mainly used in a medical X-ray apparatus and has a sliding bearing structure by liquid metal lubrication. The rotary anode X-ray tube 1 is provided with a vacuum envelope 2 as a vacuum container for keeping the inside in a high vacuum. The vacuum envelope 2 is provided with elongated cylindrical reduced diameter portions 3 and 4 at both ends in the longitudinal direction. A cylindrical enlarged portion 5 having a diameter larger than those of the reduced diameter portions 3 and 4 is provided in the central portion of the vacuum envelope 2 between the reduced diameter portions 3 and 4.

  In addition, an anode target 11 that is a rotating body as a substantially annular rotating anode structure is rotatably disposed in the enlarged diameter portion 5 of the vacuum envelope 2. The anode target 11 is installed to be rotatable in the circumferential direction of the vacuum envelope 2. Here, on the outer peripheral edge of one side surface of the anode target 11, an inclined surface portion 12 that is inclined toward the other side surface in the radial direction of the anode target 11 is formed. The inclined surface portion 12 is formed along the circumferential direction of the anode target 11. A target layer 13 is formed on the inclined surface portion 12 as an electron impact surface that emits X-rays when irradiated with thermoelectrons e that are electron streams. The target layer 13 is formed in a disc shape along the circumferential direction of the anode target 11.

  Here, the anode target 11 rotates in the circumferential direction by the action of a rotating magnetic field from the outside. That is, the anode target 11 is provided with a portion that receives a rotating magnetic field from the outside and generates a rotational torque for the anode target 11 on the inclined surface portion 12 that is the peripheral portion of the anode target 11. . At this time, the anode target 11 is driven to rotate so that the target layer 13 of the anode target 11 does not melt at a high temperature.

  Further, an electron gun 15 as a cylindrical cathode assembly body that emits thermoelectrons e toward the target layer 13 is attached to the outside of the vacuum envelope 2 that is spaced apart from the target layer 13 of the anode target 11. It has been. The electron gun 15 is attached to the outside of one side surface along the axial direction of the enlarged diameter portion 5 of the vacuum envelope 2 and is electrically insulated from the target layer 13 of the anode target 11.

  That is, the electron gun 15 emits thermoelectrons e from the electron gun 15 toward the target layer 13, and X-rays generated by the bremsstrahlung due to the impact of the thermoelectrons e on the target layer 13 are the anode target. 11 is configured to be emitted in the radial direction R along the radial direction. Here, the electron gun 15 and the anode target 11 accelerate and rotate the hot electrons e emitted from the electron gun 15 by applying a high voltage between the electron gun 15 and the anode target 11. An X-ray L is generated by bombarding the anode target 11 with thermal electrons e.

  The anode target 11 is attached with a rotation mechanism 21 that rotatably supports the anode target 11. The rotating mechanism 21 includes a rotating member 22 as an elongated cylindrical rotating body. The rotating member 22 is fixed to the anode target 11 in a state of being concentrically inserted into the central portion of the anode target 11. The rotating member 22 is attached so as to protrude from both side surfaces of the anode target 11 by substantially the same length. Further, the rotating member 22 extends from the reduced diameter portion 3 on one end side to the reduced diameter portion 4 on the other end side on the side where the electron gun 15 of the vacuum envelope 2 is attached. The container 2 is attached concentrically.

  Fixing members 23 and 24 as fixing bodies that rotatably support the both end portions of the rotating member 22 are attached to both end portions of the rotating member 22. Here, the fixing member 23 that rotatably supports one end portion of the rotating member 22 is attached in the reduced diameter portion 3 on one end side of the vacuum envelope 2. A fixing member 24 that rotatably supports the other end of the rotating member 22 is attached to the reduced diameter portion 4 on the other end side of the vacuum envelope 2.

  On the other hand, on the outside of the enlarged diameter portion 5 of the vacuum envelope 2, a stator 31 is attached as a drive unit as a magnetic field forming means for rotationally driving the anode target 11 in the enlarged diameter portion 5. In the stator 31, an induction electromagnetic field is formed in a region where the inclined surface portion 12 of the anode target 11 is located, and this induction electromagnetic field is applied as a rotating magnetic field to the anode target 11 via the vacuum envelope 2 (Gap). ) 32 is provided. The magnetic gap 32 is provided to cause rotational torque to be generated concentrically at a fixed angle with respect to the anode target 11 and to rotate the anode target 11.

  The stator 31 has a thickness dimension substantially equal to the outer diameter dimension of the rotating member 22. Further, as shown in FIG. 2, the stator 31 is disposed on the periphery of the enlarged diameter portion 5 of the vacuum envelope 2 except in the position where the electron gun 15 is attached. At least two or more, more preferably three or more, for example, three are attached with a predetermined phase angle θ (degrees) apart at equal intervals. Specifically, each of these stators 31 is attached to the opposite side of the enlarged diameter portion 5 of the vacuum envelope 2 to the side where the electron gun 15 is attached. The stators 31 are divided for each phase.

  Further, each of the stators 31 is attached in a state where the width direction of each of the stators 31 is aligned with the radial direction of the vacuum envelope 2. That is, the stators 31 are arranged so that the inclined surface portion 12 of the anode target 11 is sandwiched between the magnetic gaps 32 of the stators 31 so as to generate torque concentrically at a constant angle. In other words, these stators 31 are attached in a state where the diameter-enlarged portion 5 of the vacuum envelope 2 is inserted into the magnetic gap 32 of the stator 31 so that a concentric rotating magnetic field acts on the anode target 11. Thus, a rotational torque for rotating the anode target 11 is generated.

  Therefore, these stators 31 are magnetically bonded to the anode target 11. Furthermore, the stator 31 is driven to rotate the anode target 11 by being controlled by an inverter (not shown) which is a control device as a control means. That is, the stator 31 is a direct drive system in which a rotational torque is directly generated by the anode target 11 and the anode target 11 is directly rotated.

  The stator 31 has a stator core 33 as a core portion as a mechanism portion fitted and attached to the periphery of the enlarged diameter portion 5 of the vacuum envelope 2 over the axial direction of the enlarged diameter portion 5. I have. The stator core 33 is formed in a U-shaped section or a C-shaped section having a magnetic gap 32. The stator core 33 includes a prismatic main body 34 having a longitudinal direction along the longitudinal direction of the stator core 33. A pair of prismatic side pieces 35 and 36 projecting in the same direction are integrally provided at both ends of the main body 34. Between these side piece portions 35 and 36 and the main body portion 34, a concave fitting concave portion 37 is provided to be fitted to the peripheral edge of the enlarged diameter portion 5 of the vacuum envelope 2. The fitting recess 37 has a width dimension larger than the width dimension of the enlarged diameter portion 5 of the vacuum envelope 2. Further, fitting piece portions 38 and 39 attached to both end surfaces of the enlarged diameter portion 5 of the vacuum envelope 2 are attached to the sides of the tip edges of the both side piece portions 35 and 36 that are in contact with each other. ing. The fitting piece portions 38 and 39 are formed so that the space between the fitting piece portions 38 and 39 is substantially equal to the width dimension of the enlarged diameter portion 5 of the vacuum envelope 2. Specifically, the fitting piece portions 38 and 39 are attached at positions facing the inclined surface portion 12 of the anode target 11.

  Here, the outer peripheral surface of the reduced diameter portion 4 on the other end side of the vacuum envelope 2 to which the fitting piece portions 38 and 39 are connected has high magnetic permeability, heat resistance, vacuum tightness, and withstand voltage. A coating layer 41 made of a fine ceramic having excellent properties is formed. The coating layer 41 is formed along the circumferential direction on the outer peripheral surface of the reduced diameter portion 4 on the other end side. Furthermore, the coating layer 41 is also provided on each of the outer peripheral surface of the reduced diameter portion 4 on the other end side of the portion to which the fitting piece portions 38 and 39 of the stator core 33 are connected and the end surface of the reduced diameter portion 4. Is formed. The covering layer 41 is provided on the outer peripheral surface of the reduced diameter portion 4 located on the path of the magnetic gap 32 of the rotating magnetic field acting from the stator 31 to the anode target 11. That is, the coating layer 41 is attached at a position where the magnetic lines of force from the stator 11 pass. Further, in the covering layer 41, each stator 31 is magnetically coupled to the reduced diameter portion 4 on the other end side of the vacuum envelope 2 through the covering layer 41.

  Further, a substantially cylindrical stator coil 42 which is a winding coil as a stator winding is attached to the stator core 33 of each stator 31. The stator coil 42 is formed in a substantially cylindrical shape having an outer diameter dimension larger than the thickness dimension of the stator core 33 and a length dimension smaller than the length dimension of the stator core 33. The stator coil 42 is attached to the central portion of the stator core 33 in the longitudinal direction. That is, the stator coil 42 is formed in a shape in which a winding for one phase is wound substantially at the center of the main body 34 of the stator core 33 as shown in FIG.

  At this time, three-phase alternating current is supplied to the stator coil 42 of each stator 31 from the inverter. Then, an eddy current is generated from each stator 31 by electromagnetic induction by the supply of alternating current, and this eddy current acts as a rotational torque of the anode target 11. Specifically, the rotation principle of the anode target 11 by each of the stators 31 is the same as that used for the rotation principle of a meter that measures the amount of mechanical household power consumption. That is, the rotational frequency of the anode target 11 is a value obtained by subtracting the slip from the synchronous speed given by the synchronous magnetic field speed = f / (360 degrees / θ) with respect to the inverter drive frequency f.

  Next, the operation of the above embodiment will be described.

  First, three-phase alternating current is supplied from the inverter to the stator coils 42 of the stators 31 to generate eddy currents in the stator coils 42 of the stators 31. At this time, due to the generation of eddy currents in the stator coils 42 of the stators 31, a rotating magnetic field is generated from the stators 31 by electromagnetic induction.

  Then, this rotating magnetic field acts on the anode target 11 from the stator core 33 of each stator 31 through the coating layer 41 and the vacuum envelope 2, and rotational torque is generated in the anode target 11. Rotates at high speed.

  In this state, thermoelectrons e are emitted from the electron gun 15 toward the target layer 13 of the anode target 11 rotating at high speed.

  At the same time, a high voltage is applied between the electron gun 15 and the anode target 11 to accelerate the thermoelectrons e emitted from the electron gun 15, and the thermoelectrons e are applied to the target layer 13 of the anode target 11. The X-rays L are generated by the bremsstrahlung by the impact of the thermal electrons e from the target layer 13 by collision.

  At this time, the X-ray L is emitted to the outside of the vacuum envelope 2 in the radial direction R along the radial direction of the anode target 11 by the inclined surface portion 12 on which the target layer 13 is provided.

  As described above, according to the above-described embodiment, the anode target 11 that is rotatably mounted in the enlarged diameter portion 5 of the vacuum envelope 2 is configured to rotate by a rotating magnetic field from the outside. At the same time, the stator 31 is fitted and magnetically coupled to the enlarged diameter portion 5 in which the anode target 11 is mounted, and a rotating magnetic field is formed by the stator 31. The anode target 11 is made to act on the anode target 11 via the envelope 2 to rotate.

  As a result, the rotor structure, which is a mechanism for generating rotational torque with respect to the rotating mechanism 21, is removed, and a rotational magnetic field is directly applied to the anode target 11 to generate rotational torque. For this reason, it is not necessary to provide a rotor mechanism that rotationally drives the rotating mechanism 21 in the rotating mechanism 21 that rotatably supports the anode target 11. Therefore, the length along the longitudinal direction of the rotating mechanism 21 can be reduced as compared with the case where a rotor mechanism is provided at one end in the longitudinal direction of the rotating mechanism 21 and the stator 31 is attached so as to cover the rotor mechanism.

  Therefore, the total length along the longitudinal direction of the rotating mechanism 21 can be reduced, and the rotating mechanism 21 and the stator 31 for rotating the anode target 11 can be reduced in size. Therefore, the rotary anode X-ray tube 1 having a short overall length and a compact cost can be provided. That is, since the entire length of the rotary anode X-ray tube 1 can be shortened and miniaturized, the rotary anode X-ray tube 1 having a shape suitable for a portable X-ray apparatus can be provided.

  In addition, since the length of the rotation mechanism 21 can be shortened, the balance of the center of gravity position between the rotation mechanism 21 and the anode target 11 can be improved, so that the rotation center of gravity of the anode target 11 can be easily stabilized. Therefore, the life of the rotating mechanism 21 is not adversely affected, and it is not necessary to enlarge the rotating mechanism 21 in order to adjust the position of the center of gravity. That is, since the structure of the rotating mechanism 21 can be simplified, the joining structure of the rotating mechanism 21 and the anode target 11 can be facilitated, so that the manufacturing cost of the rotating anode X-ray tube 1 can be reduced. The reliability of the anode type X-ray tube 1 can be improved.

  In the above embodiment, the three stators 31 are attached to the enlarged diameter portion 5 of the vacuum envelope 2. However, the portion of the enlarged diameter portion 5 of the vacuum envelope 2 to which the electron gun 15 is attached. In addition, if the configuration is such that at least one stator 31 is attached and the anode target 11 in the vacuum envelope 2 can be rotationally driven, the same operational effects as in the above-described embodiment can be obtained.

  Further, the anode target 11 provided with the target layer 13 is directly acted on by the rotating magnetic field from the stator 31, and the anode target 11 is driven to rotate. As a rotating body that rotates by the action of the rotating magnetic field from the outside. The drive mechanism (not shown) is configured separately from the anode target 11, and the drive mechanism is disc-shaped and attached concentrically to the anode target 11 via a predetermined gap, and the stator is attached to the drive mechanism. The anode target 11 can also be driven to rotate by applying a rotating magnetic field from 31.

  In this case, when the anode target 11 is directly driven to rotate, heat generated in the anode target 11 can be generated not in the anode target 11 but in the drive mechanism unit. Therefore, the amount of heat generated by the anode target 11 can be reduced, and the heat generated by the rotation of the anode target 11 can be radiated more easily. Furthermore, when the anode target 11 is rotationally driven by this drive mechanism portion, a plurality of stators 31 can be attached over the entire circumference of the drive mechanism portion. At this time, when the stator 31 covers the drive mechanism portion more widely in the circumferential direction, the rotation of the drive mechanism portion can be stabilized. On the other hand, when the drive mechanism portion is not covered much in the circumferential direction, the displacement of the rotating magnetic field applied to the drive mechanism portion can be increased, so that the drive mechanism portion can be rotated faster.

It is an explanatory side view showing one embodiment of a rotating anode type X-ray tube of the present invention. It is an explanatory top view which shows a rotary anode type X-ray tube same as the above.

Explanation of symbols

1 Rotating anode X-ray tube 2 Vacuum envelope
11 Anode target, which is the anode as a rotating body
13 Target layer as target
15 Electron gun as cathode
21 Rotating mechanism
31 Stator as drive unit
41 Coating layer

Claims (4)

A vacuum envelope,
A cathode that emits electrons;
A rotating body having a target which is provided in the vacuum envelope so as to be opposed to the cathode and emits X-rays upon incidence of electrons emitted from the cathode;
A rotating mechanism that rotatably supports the rotating body;
A rotary anode type X-ray tube comprising: a drive unit that generates a rotational torque concentrically at a fixed angle with respect to the rotating body and rotates the rotating body. The rotating anode type X-ray tube according to claim 1, wherein the rotating body is an anode. The rotary anode type X-ray tube according to claim 1 or 2, wherein a plurality of magnetic field forming means are provided apart from each other in the rotating direction of the rotating body. The magnetic field forming means is provided outside the vacuum envelope and causes a rotating magnetic field to act on the rotating body via the vacuum envelope,
4. The vacuum envelope according to claim 1, further comprising a coating layer that is provided on a side surface on a path of a rotating magnetic field that acts on the rotating body from the magnetic field forming means and is made of fine ceramic. The rotary anode type X-ray tube as described.

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