JP2001276034A - Cathode scan type x-ray generator and x-ray ct scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and highly reliable cathode scan type X-ray generator for a very high speed X-ray CT scanner and the very high speed X-ray scanner using it, by which the inside of a subject is stereoscopically and instantly inspected and an excellent CT image is obtained. SOLUTION: The cathode scan type X-ray generator for the very high speed X-ray CT scanner is provided with a doughnut shape vacuum vessel VV, a cathode side rotary body assembly CR inside the vessel and a ring-shape cathode power supply mechanism SL1 to be operated in vacuum for energizing the cathode and generates X-rays circulating at high speed. The generator is used for the very high speed X-ray CT scanner. Then the rotary part of the cathode side rotary body assembly or the cathode power supply mechanism is supported by a bearing mechanism CBG consisting of a hydrodynamic slide bearing lubricated by liquid metal so as to be freely rotatable. A sufficient amount of liquid metallic lubricant is automatically supplied to the inside of the hydrodynamic slide bearing from a liquid metallic lubricant storing groove so that lubrication defect does not occur in any case.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode-scan type X-ray generator for an X-ray CT scanner which is small in size and emits X-rays from an X-ray orbit that rotates at a high speed and can perform ultra-high-speed scanning. The present invention relates to an X-ray CT scanner capable of performing ultra-high-speed scanning using this. By limiting the mechanism that rotates the X-ray focal point to small components in the vacuum vessel,
A small X-ray CT that can obtain a three-dimensional image by instantly photographing the subject by stably rotating the X-ray focus around the subject without having a mechanical rotating mechanism in the atmosphere at high speed. Provide a scanner. A dynamic pressure sliding bearing using a liquid metal as a lubricant is used to rotate the electron gun assembly in the vacuum vessel, and a component rotating inside the vacuum vessel is energized from outside the vacuum vessel.

[0002]

2. Description of the Related Art A conventional X-ray CT scanner will be described with reference to FIG. Conventional X
The line CT scanner includes a fixed base 1001 and a bearing 1003.
And a rotating gantry 1002 that rotates through the. The rotating gantry 1002 is rotated in the air by a rotation driving mechanism 1009 controlled using a controller 1008. An X-ray tube 1004 for generating X-rays, a high-voltage power supply (not shown) for supplying a high voltage thereto, a detector 1006 for receiving X-rays, and other electronic circuits 10
07 and the like are attached to the rotating frame 1002. A signal of an electronic circuit attached to the rotating gantry 1002 is transmitted to the fixed gantry 1001 by a slip ring (not shown). For this reason, the sum of the masses of the components attached to the rotary gantry 1002 is large, and if an attempt is made to increase the scanning speed of the X-ray CT scanner, a large centrifugal force acts, and the components mounted on the rotary gantry 1002 and the rotary gantry There is a disadvantage that the scanning speed cannot be increased because 1002 itself cannot withstand excessive stress.

[0003] X-rays used in conventional X-ray CT scanners
The wire tube 1004 is a disk-shaped X-ray target having a diameter of about 10 cm and 3,000 rpm in a cylindrical vacuum vessel.
The X-ray is rotated at a high speed of about m, and collides with electrons emitted from the cathode of the electron gun assembly to emit X-rays 1005 in one direction. The entire structure is cylindrical.
An X-ray tube for an X-ray CT scanner, which needs to generate a large amount of X-rays, requires a cooler, and the sum of both masses is 1
The rotation frame 1002 for attaching and rotating it in the air becomes large, and the entire X-ray CT scanner becomes large, which is not only inconvenient to handle, but also requires a large installation space. And the operating costs were large. Further, in recent years, as the use of X-ray CT scanners has expanded, there has been a demand for instantaneous observation of blood and a contrast agent. In order to respond to this, it is necessary to rotate the X-ray tube 1004 around the subject at a high speed. The highest orbiting speed so far is 2r
ps, which is considered the limit. on the one hand,
There is a demand to increase the X-ray dose to enhance the image quality and enhance the diagnostic performance, and it is necessary to increase the size and mass of the conventional X-ray tube 1004. Simultaneously satisfying these conflicting requirements has been impossible with an X-ray CT scanner having a conventional structure.

On the other hand, an X-ray CT scanner of the electronic scan type has been developed in the past in order to increase the scanning speed. In this method, electrons are taken out from an electron gun assembly fixed at the bottom of a vacuum vessel in the shape of a thermos placed on its side, and the position of the electrons is electromagnetically controlled while traveling about 100 cm in the vacuum vessel. After orbiting around the subject,
These electrons are made incident on an arc-shaped X-ray target to extract X-rays that make a half turn. In this structure,
High-speed scanning with a scan time of about 0.1 second is possible, but the image quality is poor due to the inability to obtain a sufficient amount of X-rays, the X-ray focus is too large, Are difficult to maintain, the whole device is large and difficult to handle, and it is expensive, and is used only for special applications.

[0005]

The problem to be solved is that the scan time of the X-ray CT scanner is greatly reduced to eliminate motion artifacts and to provide a sufficient level of X-ray dose in imaging a fast moving subject. An object of the present invention is to provide an X-ray CT scanner which can obtain a high-quality image with less photon noise by securing the X-ray CT scanner, and which is small in size and easy to handle. In addition, a ring mechanism that uses liquid metal, which is liquid during operation, as a lubricant is used as a bearing mechanism that can be used reliably in vacuum to achieve this, and a power supply mechanism that can supply power to components rotating in vacuum. Developed a pressure-sliding bearing, and stored a sufficient amount of liquid metal lubricant in the bearing mechanism and supplied it uniformly to the bearing despite the large diameter of the bearing and the large height drop of the bearing gap. An object of the present invention is to provide a cathode scan type X-ray generator which operates stably without running out of lubrication, and an X-ray CT scanner using the same.

[0006]

SUMMARY OF THE INVENTION In the present invention, all rotating parts of an X-ray CT scanner are mounted in a donut-shaped vacuum vessel to minimize the size of the rotating parts, eliminating the need for mechanical rotating parts in air. By doing so, an X-ray CT scanner capable of ultra-high-speed scanning is realized. The vacuum container is formed in a donut shape, and the subject is placed on a bed in the atmosphere near the central axis of the vacuum container. Electrons are emitted from the cathode of the electron gun assembly that circulates in the vacuum vessel, and accelerated electrons collide with the annular X-ray target mounted in the vacuum vessel in opposition to the orbit of the cathode to generate X-rays. generate. The generated X-rays are applied to the subject in the atmosphere through an X-ray emission window provided on the small-diameter wall of the vacuum vessel. The X-rays that have passed through the subject are detected by an annular X-ray detector arranged in the atmosphere coaxially with the vacuum vessel, reconstructed into a tomographic image by a computer, and displayed on a display device.
The rotating part for rotating the X-ray focal point in the vacuum vessel is limited to lightweight electron gun assembly, etc., and its volume is small,
The rotation period is 0.1
Even when rotating at a high speed of less than a second, the stress applied to the rotating body can be sufficiently reduced, and the high-speed rotation can be stably continued.
Also, since about three electron gun assemblies are attached to the same cathode side rotating body assembly, ultra-high-speed scanning with a scan time of about 0.03 seconds can be performed.

An X-ray CT scanner of the type in which an electron gun is rotated inside a donut-shaped vacuum vessel has been proposed in the past, but has not been realized so far. One of the reasons is that a means for continuing stable rotation in a vacuum and a reliable means for stably setting the potential of the rotating body to a constant value have not been found. In the present invention, as a bearing mechanism that can be used reliably in a vacuum, an annular hydrodynamic sliding bearing using a liquid metal that is a liquid during operation as a lubricant is adopted, and the diameter of this bearing is large and the height difference of the opening of the bearing is reduced. Provide a means for automatically supplying liquid metal lubricant to the interior of the bearing despite the large size. Further, the potential of the rotating body is set to a constant value via the liquid metal lubricant.

In the X-ray CT scanner of the present invention, the center axis of rotation is substantially horizontal, and the diameter of the bearing is approximately 100.
cm, the head drop in the bearing gap is large,
When the rotating portion of the bearing stops rotating, the liquid metal lubricant concentrates on the portion located vertically below the bearing gap due to the influence of the gravitational acceleration, and runs short on the portion located vertically above. When the rotating part starts rotating again, the liquid metal lubricant is insufficient in the part located vertically above, and an excessive torque is required. In order to prevent this, a mechanism for pumping the liquid metal lubricant to the rotating part of the bearing mechanism and supplying it to the part located vertically above the bearing was attached. A liquid metal lubricant supply mechanism in which a sufficient amount of liquid metal lubricant is stored in a non-rotating portion of the bearing mechanism, and the liquid metal lubricant stored in this portion is attached to a rotating portion. With this, it is supplied evenly in the bearing. This liquid metal lubricant storage mechanism is composed of a ring-shaped groove or a number of well-shaped wells with a bottom that are annularly recessed inside the bearing fixed body, and is mounted at a position where the dynamic pressure of the bearing is small. I have. The liquid metal lubricant storage mechanism comprises a portion filled with the liquid metal lubricant and a vacuum portion, and the vacuum portion communicates with a vacuum space outside the bearing mechanism CBG by a vent provided vertically above. are doing.

Even when the residual gas comes out of the liquid metal lubricant or the bearing rotating body or the bearing fixed body, or when the space volume changes due to the movement of the liquid metal lubricant, the bearing is provided by the vent hole. The pressure is maintained at the same level as the vacuum space outside the mechanism CBG. Therefore, the liquid metal lubricant stored vertically below the liquid metal lubricant storage mechanism easily moves, for example, by adhering to the bearing rotating body, and is uniformly supplied to the inside of the bearing, so that the liquid metal lubricant is sufficiently supplied even at the time of starting. Smooth rotation can be started with a small rotation torque. Also, even when the bearing rotating body is stopped, if the liquid level is lowered, the static pressure of the liquid metal lubricant at the opening of the bearing does not increase, so that the liquid metal lubricant is not pushed out from the inside of the bearing. .

[0010] The bearing surface is in thermal communication with the vacuum vessel,
Since the vacuum vessel is forcibly cooled from the outside, the temperature of the bearing surface does not rise, the thermal expansion is small, and stable operation can be performed for a long time despite the heat generated in the bearing. Further, components that generate heat, such as an electron gun assembly and an X-ray target, are also forcibly cooled via the liquid metal lubricant in the bearing gap, thereby suppressing thermal expansion and the like.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cathode scan type X-ray generator is wrapped in a donut-shaped vacuum vessel, and the vacuum vessel is installed so that its central axis is substantially horizontal. A subject (human body) is placed in the atmosphere, and the vacuum container is arranged so as to surround the subject. The vacuum container is fixed without rotating, and the angle with the subject and the position in the horizontal direction can be changed. X-rays are generated toward the subject while moving the X-ray focus so that the X-ray focal point orbits around the subject inside the vacuum vessel. By using the orbiting X-rays, an X-ray CT scanner having no rotating mechanism in the atmosphere is realized. A cathode scan type X-ray generator for an X-ray CT scanner capable of performing an ultra-high-speed scan and obtaining a large output, which cannot be realized with an X-ray CT scanner having a conventional structure, and an ultra-high-speed X-ray generator using the same An X-ray CT scanner was realized with a simple structure at low cost and with high reliability.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a cathode scan type X-ray generator according to one embodiment of the present invention and an X-ray CT scanner using the same will be described below with reference to the drawings. FIG. 2 shows a cathode scan type X-ray generator of the present invention and an X-ray using the same.
FIG. 3 is a schematic cross-sectional view of the entire structure of the X-ray CT scanner, FIG. 3 is a principle view, and FIG. 4 is a cross-sectional view of a part of a cathode scan type X-ray generator according to the present invention which is located vertically above at a certain moment. FIG. 5 is an enlarged sectional view of a part of a cathode side rotating body assembly which is a main part of the cathode scan type X-ray generator of the present invention, and FIG. 6 is a partial lower part of FIG. It is sectional drawing which expanded.

As shown in FIG. 2, the donut-shaped vacuum vessel VV is installed so that the central axis CC 'is substantially horizontal, and is constantly evacuated to a high vacuum state from an exhaust port VC by a vacuum pump (not shown). I have. As shown in FIG. 2 or FIG. 4, a cylindrical cathode-side rotating body assembly CR is provided in a vacuum space inside the vacuum vessel VV. The cathode-side rotating body assembly CR uses liquid metal, which is liquid at room temperature, as a lubricant. The bearings are rotatably supported in a vacuum by a bearing mechanism CBG comprising a dynamic pressure sliding bearing, and their central axes coincide with CC '.
Three electron gun assemblies EG are attached to the cathode side rotating body assembly CR separately in the circumferential direction. As shown in FIG. 5, a cylindrical rotor RT2 made of copper is coaxially attached to the cathode side rotating body assembly CR, and a magnetic path cylinder MT2 made of a magnetic material is attached coaxially thereto. I have. Rotor R
An arcuate stator LM2 is attached along the vacuum vessel wall outside the vacuum vessel VV in a state facing T2. The rotor RT2 is disposed so as to be sandwiched between the magnetic path cylinder and the stator LM2. Rotor RT
2 receives a rotational torque from the stator LM2 through the wall made of a non-magnetic material of the vacuum vessel VV and receives a rotational torque, so that the cathode side rotating body assembly CR rotates. The cathode side rotating body assembly CR is a bearing mechanism CBG comprising a dynamic pressure sliding bearing.
It is electrically and thermally connected to the vacuum vessel VV through the liquid metal lubricant therein.

As shown in FIG. 4, a cathode 1 for emitting thermoelectrons 2 is attached to the tip of the electron gun assembly EG. An annular X-ray target TG is attached to face the orbit of the cathode 1. As shown in FIG. 2, the X-ray target TG is a cylindrical anode-side rotating body assembly A.
It is mechanically coupled to R. The anode side rotating body assembly AR is rotatably attached to a part of the vacuum vessel VV via a bearing mechanism ABG including a dynamic pressure sliding bearing using liquid metal which is liquid at room temperature as a lubricant. Anode rotating body assembly AR
Is equipped with a rotor RT1 made of a copper tube.
A magnetic path cylinder made of a magnetic material is mounted coaxially with the magnetic path cylinder. An arc-shaped stator LM is formed along the vacuum vessel wall outside the vacuum vessel VV in a state facing the rotor RT1.
1 is attached. The rotor RT1 is disposed between the magnetic path cylinder and the stator LM1. The rotor RT1 is connected to the vacuum vessel VV from the stator LM1.
The rotation torque is given by the electromagnetic induction through the wall made of the non-magnetic material, so that the anode side rotating body assembly AR rotates. The center axis of rotation of the X-ray target TG coincides with the center axis CC 'of rotation of the cathode 1 of the electron gun assembly EG, and the cathode 1 always faces the surface of the X-ray target TG, and the two oppose each other. To rotate.

Referring to FIG. 2 or FIG. 4, cathode feeding mechanism SL
1 will be described. In the embodiment shown in FIG. 2 or FIG.
The two cathode power supply mechanisms SL1 are coaxially mounted, and form three independent current paths. In these figures, the internal structure of the cathode power supply mechanism SL1 is simplified. The cathode 1 of the electron gun assembly EG is electrically connected to the high voltage terminal HT through an annular cathode power supply mechanism SL1 having a central axis substantially the same as the orbiting central axis CC ′ of the electron gun assembly EG in a vacuum space in the vacuum vessel VV. It is connected to the. The high voltage terminal HT is connected to a negative high voltage of about -150 KV from an unillustrated high voltage power supply outside the vacuum vessel VV and the electron gun assembly EG.
Is supplied to heat the negative electrode 1. Each cathode power supply mechanism SL1 has a fixed portion and a rotating portion, and the fixed portion is mechanically fixed to a part of the vacuum vessel VV via an insulator 220 while maintaining electrical insulation. The rotating part and the fixed part of the cathode power supply mechanism SL1 constitute a dynamic pressure sliding bearing using liquid metal as a lubricant, and electricity is supplied between the two via the liquid metal lubricant. The rotating part of the cathode power supply mechanism SL1 is an electron gun assembly EG
The cathode power supply mechanism SL1 rotates together with the electron gun assembly with a certain degree of eccentricity and axial displacement allowed.

The X-ray target TG is an anode side rotating body assembly A
It is electrically and thermally connected to the vacuum vessel VV via the liquid metal lubricant present in the R bearing mechanism ABG. The vacuum vessel VV is at the ground potential and is forcibly cooled with cooling water or the like. Therefore, the X-ray target TG is set to the ground potential, and a large amount of heat generated from the X-ray target TG is efficiently removed by the cooling water flowing through the wall of the vacuum vessel VV via the liquid metal lubricant. Since the thermal resistance between the X-ray target TG and the cooling water is sufficiently small,
Since the temperature of the line target TG is kept low, a large power input is allowed, and an extremely large amount of X-rays can be generated in a short time.

The electron gun assembly EG includes F1 and F shown in FIG.
As shown in F2 and F3, three are mounted at equal intervals around the cathode side rotating body assembly CR. Here, F1, F2, and F3 indicate three focal points of X-rays that are generated when the electrons 2 are accelerated and collide with the X-ray target TG. X-ray focus F
1, F2 and F3 simultaneously rotate in the same direction as shown in FIG. 3 while simultaneously generating X-rays. The current positions of these X-ray focal points are detected by an angle detection mechanism (not shown) attached to the cathode side rotating body assembly CR. The X-rays emitted from the X-ray focal points F1, F2, F3 are shown in FIG.
As shown in the figure, the fan is shaped like a fan by the X-ray distribution limiting mechanism inside the X-ray target TG, passes through the fan direction distribution shaper WF (see FIG. 4) attached to the cathode side rotating body assembly CR, and the fan X-ray emission window XW of the vacuum vessel VV after the X-ray intensity distribution in the direction is optimized (see FIG. 4)
, And after passing through an external annular slit SLT, passing through the subject M, and opposing surfaces of two annular X-ray detectors DF and DB mounted coaxially with the X-ray target TG. To reach.

As shown in FIG. 3, X-ray focal points F1, F2,
The X-rays emitted from F3 are the opposite parts D of the detector.
1, D2 and D3. The irradiation field range and the like are determined so that the detector portions D1, D2, and D3 do not overlap each other. Since the sum of the detector portions D1, D2, and D3 occupies almost the entire annular detector, all the detection elements in the X-ray detectors DF and DB are effectively used, and the cost / performance ratio is improved. Each of the annular detectors DF and DB is also divided into a large number of detection element rows in the direction of the central axis CC ′, and a signal detected by each detection element is converted into a digital signal by an electronic circuit (not shown). The image is reconstructed into a tomographic image by a computer (not shown) and displayed on an image display device (not shown) to obtain a multi-slice CT image.

FIG. 4 is an enlarged view of a part of the cross section around the electron gun assembly at a moment when it is positioned vertically above, and the same parts are denoted by the same symbols. In FIG. 4, the internal structure of the bearing mechanism CBG is shown in a simplified manner. The cathode-side rotating body assembly CR has a generally rotationally symmetrical structure as a whole, and the components such as the electron gun assembly EG attached thereto are small and lightweight, so that they can sufficiently withstand high-speed rotation of about 10 rps. In this case, the X-ray focus is 3
Since the number of scans is one, the scan time can be reduced to 0.03 seconds. The X-ray target TG has a large diameter of 120 cm, rotates in the direction opposite to the X-ray focal points F1, F2, and F3, and is forcibly cooled as described above, so that the surface temperature of the X-ray target TG increases. Since it is difficult to input a large amount of power, a sufficient amount of X-rays can be generated in a short time, and a high-quality CT image with little photon noise can be obtained despite ultra-high-speed scanning. In addition, since the multi-slice scan is realized, X-rays can be effectively used, not only can the resolution in the direction parallel to the central axis CC 'be increased, but also a wide range of imaging can be completed in a short time to achieve three-dimensional scanning. Real-time CT image can be obtained.

In order to realize the X-ray CT scanner having the above configuration, it is inevitable to realize the bearing mechanisms CBG and ABG and the cathode power supply mechanism SL which can be practically used in the above-described device configuration.
An object of the present invention is to realize a dynamic pressure sliding bearing that rotatably supports a rotating part in a vacuum. Conventionally, a hydrodynamic sliding bearing having a small diameter of 5 cm or less and an opening of the bearing on only one side has been put to practical use. In this case, the liquid metal lubricant inserted into the dynamic pressure sliding bearing is retained inside the bearing opening by the action of surface tension at the bearing opening. In order to obtain a sufficient bearing pressure of the hydrodynamic sliding bearing, the size of the gap between the rotating part and the fixed part has been limited to several tens of μm. For example, when the size of the gap at the opening of the bearing is 50 μm, when the height drop of the liquid metal lubricant exceeds about 18 cm, the static pressure of the liquid metal lubricant due to gravitational acceleration overcomes the surface tension at the opening of the bearing, and Lubricant leaks out. This becomes a serious problem when the rotating part of the bearing stops rotating. Particularly, a dynamic pressure sliding bearing having a height drop of about 100 cm in the circumferential direction of the opening of the bearing as in the case of the present invention cannot be realized by the conventional technology.

An embodiment of a bearing mechanism CBG comprising a hydrodynamic sliding bearing will be described with reference to FIGS. FIG. 5 is an enlarged view of a part of the cross section of the cathode side rotating body assembly CR and the cathode side bearing mechanism CBG, and the upper part of FIG. 5 is a part located vertically above at a certain moment in actual use. , And the lower part indicates the part located vertically below at the same moment. In FIG. 5, the central part is omitted and is shortened and displayed. FIG. 6 is an enlarged view of a part located below FIG. 5 and shows a cross section of the bearing mechanism CBG. FIG.
As shown in the figure, the cathode side rotating body assembly CR includes a bearing mechanism CB.
A bearing rotating body 102, which is a rotating part of G, is coaxially mounted. A bearing fixed body 101 which is a fixed part of the bearing mechanism CBG is fitted to the bearing rotating body 102 with a gap. A part of the bearing fixing body 101 is mechanically and thermally connected to the vacuum vessel VV. The vacuum vessel VV is attached to a support base (not shown) so that an appropriate posture and a horizontal position with respect to the installation floor can be maintained. The bearing fixed body 101 and the bearing rotating body 102 have surfaces facing each other, and the facing surfaces are the first bearing gaps 103 and 108, the second bearing gaps 104 and 109,
It has third bearing gaps 106,111. At least one of the opposing surfaces forming the bearing gap has a herringbone-shaped bearing groove. The first, second, and third bearing gaps are filled with a liquid metal that is liquid at room temperature, preferably a lubricant made of an alloy of gallium, indium, and tin, and each of the bearing gaps has a radial shape. The bearing gaps coincide with the respective bearing gaps of the first thrust bearing and the second thrust bearing which are mounted facing each other with a distance therebetween with respect to the bearing. The bearing gaps 103 and 108, the bearing gaps 104 and 109, and the bearing gaps 106 and 111 are the same, respectively, and different numbers indicate different positions. Here, at least one of the surfaces facing the bearing gap has the bearing groove. In the embodiment shown in FIGS. 5 and 6, the radial bearing is divided into two independent bearings, each having a bearing gap, but these are collectively referred to as 103, 10 in FIG.
It is represented by 8. It should be understood that in FIG. 6, the bearing gap 108 is clearly shown as being divided into a bearing gap 185 and a bearing gap 186.

When a rotational torque is applied to the cathode side rotating body assembly CR, a dynamic pressure is generated in these bearings, so that the rotating portion can be floated and rotatably supported. When the bearing rotating body 102 is rotating, the liquid metal lubricant in each bearing gap is subjected to the action of being confined inside the bearing, so that it does not leak from the bearing gap to the outside vacuum space.

As shown in FIG. 5, the bearing fixed body 10
The first end gaps 105 and 110, the second end gap 107,
112, the radial bearing gap 103, 1
08 and the center axes of the opposing surfaces forming the first end gaps 105 and 110 and the second end gaps 107 and 112 coincide with CC ′ in a state where they are substantially horizontal. Bearing gaps 104, 10 of the first thrust bearing
9, and the bearing gap 106, 1 of the second thrust bearing
11 are flat, and the bearing gaps 104 and 109 of the first thrust bearing are formed.
Are the radial bearing gaps 103 and 108 and the first end gaps 105 and 110, the second thrust bearing gaps 106 and 111 are the radial bearing gaps 103 and 108 and the second end gap 107. , 1
And 12. First end gap 105,1
10 and the diameter of the respective opposing surfaces constituting the second end gaps 107 and 112 are equal to the bearing gap 1 of the radial bearing.
03, 108 are smaller than the diameter of the facing surface. The size of the first end gaps 105 and 110 and the size of the second end gaps 107 and 112 are larger than the size of the bearing gaps 103 and 108 of the radial bearing. And the second end gaps 107, 112 are both in communication with the vacuum space, and have opposing surfaces (not shown) that are not wetted by the liquid metal lubricant described above. Between the bearing gaps 104, 109 of the first thrust bearing and the first end gaps 105, 110 there are annular bearing openings 121, 121 ', and the bearing gaps 106, 111 of the second thrust bearing and the second. The second end gap 107,
Between them, there are annular bearing openings 120, 120 '. These bearing openings have opposing surfaces that are not wetted by the liquid metal lubricant and a gap sandwiched therebetween, and form a substantial boundary between a region where the liquid metal lubricant is present and a vacuum space. Has formed. Bearing opening 120,
The diameter of each of the opposing surfaces constituting the bearing openings 121, 121 ′ is the same as the diameter of the bearing gap 10 of the radial bearing.
3, 108 are smaller than the diameter of the facing surface. End gaps 105 and 110, end gap 107
, 112, bearing openings 120 and 120 ′, bearing opening 121
And 121 'are the same, and different numbers indicate the difference in the indicated position. Here, at least one of the surfaces facing the end gap has the non-wetting surface.

When the bearing rotator 102 stops rotating, the bearing opening 12 which substantially forms a boundary between the region where the liquid metal lubricant is present and the vacuum region in the bearing mechanism CBG.
Surface tension acts on the liquid metal lubricant at 0, 120 'and the bearing openings 121, 121', preventing the liquid metal lubricant from leaking out of these bearing openings. The static pressure in the liquid metal lubricant due to gravitational acceleration is proportional to the depth of the liquid metal lubricant from the waterline. In other words, the static pressure in the liquid metal lubricant becomes higher as it is located vertically downward. On the other hand, the pressure effect of pushing the liquid metal lubricant by the surface tension is inversely proportional to the size of the gap of the bearing opening. Therefore, the bearing opening 1
If the gap between the bearings 20, 120 'and the bearing openings 121, 121' is made sufficiently small, it is possible to prevent the liquid metal lubricant from leaking from the inside of the hydrodynamic sliding bearing having a large diameter. This can be achieved by configuring the bearing openings 120, 120 'and the bearing openings 121, 121' at the end of the first thrust bearing and the end of the second thrust bearing, respectively. The reason is that the diameter of the bearing used in the present invention is as large as about 100 cm, so that it is difficult to keep the gap of the radial bearing at a sufficiently small value, but it is difficult to reduce the size of the bearing gap in the thrust bearing. And the size of the gap in the bearing opening can be as small as the size of the bearing gap in the adjacent thrust bearing. The reason why the size of the bearing gap of the thrust bearing can be reduced is that the thrust bearing is hardly affected by thermal expansion because the distance between the opposed bearings is short, and is mounted so as to have a horizontal rotation center axis CC '. Therefore, the bearing is hardly affected by gravity and centrifugal force.The bearing surface is made flat so that high accuracy can be easily maintained. That is, the loss can be prevented from becoming excessive.

In the X-ray CT scanner of the present invention, the center of rotation is substantially horizontal, and the diameter of the bearing is approximately 100c.
m, the height drop in the bearing gap is large, and when the bearing rotor 102 stops rotating, the liquid metal lubricant concentrates on the vertically lower portion of the bearing gap due to the effect of gravitational acceleration, There is a shortage in the part. When the bearing rotor 102 starts to rotate again, the liquid metal lubricant runs short in the vertically upper part, and an excessive torque is required.
In order to prevent this, a liquid metal lubricant supply mechanism for pumping the liquid metal lubricant to the bearing rotating body 102 and supplying it to the vertically upper part of the bearing was attached. A liquid metal lubricant storage mechanism for storing a sufficient amount of liquid metal lubricant in the bearing fixed body 101, and a liquid metal lubricant supply mechanism in which the liquid metal lubricant stored in this portion is attached to the bearing rotating body 102 With this, it is supplied evenly in the bearing. The liquid metal lubricant supply mechanism has a structure in which the liquid metal lubricant can be pumped up, for example, like a bottomed recess attached to the bearing rotor 102, but is not shown.
The liquid metal lubricant storage mechanism will be described with reference to FIG. The description here will be made only for the vertically lower part shown in the figure. In this embodiment, annular liquid metal lubricant storage grooves 180, 181 and 182 attached to the bearing fixing body 101 are formed at locations between the bearings. The bearing gap 108 is divided into two parts 185 and 186 by a liquid metal lubricant storage groove 180, which are independent radial bearing bearing gaps.
The liquid metal lubricant storage groove 181 is located at the boundary between the bearing gap 111 and the bearing gap 185, and the liquid metal lubricant storage groove 182 is formed between the bearing gap 109 and the bearing gap 18.
6 at the boundary. Liquid metal lubricant storage groove 180,
Numerals 181 and 182 are covered with the outer surface of the bearing rotating body 102 and form an annular cavity. Each of the liquid metal lubricant storage grooves is connected by communication holes 183 and 184 formed of a number of holes. The portions located vertically below the annular liquid metal lubricant storage grooves 180, 181, and 182 are filled with the liquid metal lubricant, but the portion above the vertical is free of the liquid metal lubricant and the vacuum state is established. Has become.

Annular liquid metal lubricant storage grooves 180, 18
1, 182 are also provided with communication holes 183, 184 in a portion in a vacuum state located vertically above.
There is a ventilation hole (not shown) communicating with the vacuum space outside the BG, so that the same vacuum state as the vacuum space outside the bearing mechanism CBG is maintained. Even if the liquid metal lubricant or the residual gas comes out from the bearing rotating body 102 or the bearing fixed body 101 or if the liquid metal lubricant moves and the space volume changes, the bearing mechanism CBG is formed by the vent hole.
Is maintained in the same vacuum state as the external vacuum space. Therefore,
The liquid metal lubricant stored vertically below the liquid metal lubricant storage mechanism easily moves, for example, by adhering to the bearing rotating body 102, and is uniformly supplied to the inside of the bearing. Smooth rotation can be started with the rotation torque. Further, even when the bearing rotor 102 stops rotating, the static pressure of the liquid metal lubricant does not increase as described above, so that the liquid metal lubricant is not pushed out from the bearing opening.

Next, the function of supplying the liquid metal lubricant will be described with reference to FIG. When the bearing rotator 102 stops rotating, the liquid metal lubricant storage grooves 180, 18
The 1,182 vertically lower portion, for example, 5 cm above the lowest position, is filled with liquid metal lubricant.
At a higher position, a vacuum state is established. As described above, each of the liquid metal lubricant storage grooves is provided with the communication hole 18.
Since the liquid metal lubricants communicate with each other at 3,184, the liquid metal lubricants in the respective liquid metal lubricant storage grooves have the same liquid level. The bearing gaps 109, 111, 185, 186 at portions within the height filled with liquid metal lubricant
Is also filled with a liquid metal lubricant. At a position higher than this height, at least a part of the liquid metal lubricant flows out of the bearing gap, and there is a state in the bearing gap that is not filled with the liquid metal lubricant. When the bearing rotor 102 starts rotating, the liquid metal lubricant filled vertically below each bearing gap moves in the circumferential direction of the bearing and approaches a uniform distribution in the circumferential direction. As a result, the portion filled with the liquid metal lubricant vertically below is filled with the liquid metal lubricant storage groove 18.
The effect of sucking the liquid metal lubricant from 0,181,182 occurs. This is repeated so that each bearing gap is filled with the liquid metal lubricant. In order to ensure this effect, the liquid metal lubricant supply mechanism (not shown) operates effectively.

By this operation, a sufficient amount of the liquid metal lubricant is supplied to the portion vertically above. Therefore, in the cathode scan type X-ray generator of the present invention, the liquid metal lubricant is uniformly supplied to the inside of the bearing, so that even at the time of starting, smooth rotation can be started with sufficiently small rotation torque. When rotating at high speed, the liquid metal lubricant in the liquid metal lubricant storage groove is separated from the bearing rotating body by centrifugal force and does not adversely affect the rotation characteristics.

In the above description, the cathode side rotating body assembly CR
Bearing mechanism composed of a dynamic pressure sliding bearing used for
However, the bearing mechanism ABG composed of a dynamic pressure sliding bearing used for the anode side rotating body assembly AR is also a bearing composed of a dynamic pressure sliding bearing used for the rotating part of the cathode power feeding mechanism SL1. The mechanism has a similar structure.

When the bearing rotating body 102 is rotating at a sufficiently high speed, a relatively large bearing loss occurs in each of the above-described bearing gaps.
Is kept at a low temperature because it is also thermally coupled to the vacuum vessel VV which is forcibly cooled from the outside. The bearing rotator 102 is thermally coupled to the bearing fixed body 101 via the liquid metal lubricant present in the respective bearing gap and is kept at a sufficiently low temperature. Further, a cathode side rotating body assembly CR is mechanically connected to the bearing rotating body 102, and a heating element such as an electron gun assembly EG is attached to the cathode side rotating body assembly CR. In particular, the anode side bearing mechanism AGB
In this case, a large amount of heat flows from the X-ray target TG that generates a large amount of heat. Even in these cases,
The temperature of the bearing mechanism can be kept sufficiently low.

Although the present invention has been described with reference to illustrative embodiments, the present invention is not intended to be limited to the structure and form of the embodiments illustrated herein, but to be departed from the spirit and scope of the invention. It is to be understood that various embodiments are possible and that various changes and modifications can be made. For example, in the present invention, three electron gun assemblies are attached, but one or three or more electron gun assemblies may be used. Although the present invention shows a structure in which both the cathode rotating body assembly CR and the X-ray target TG are rotated, a cathode scan type X-ray generator having a structure in which the X-ray target TG and a portion connected thereto are fixed is provided. It includes, of course, a scanner and an X-ray CT scanner. The same effect can be obtained even if the annular liquid metal lubricant storage is constituted by a large number of cylindrical depressions.
Needless to say, the bearing fixing body 101 may be configured as a part of a vacuum vessel. Further, in the above embodiment, an example is shown in which a liquid metal that is liquid at room temperature is used as a lubricant, but even if it is a solid at room temperature, it has a slightly higher melting point and is heated and liquefied before operation. Of course, the same effect can be obtained by operating afterwards. Further, the X-ray emission window for taking out the X-rays generated from the X-ray target outside the vacuum vessel may be integrated with the vacuum vessel or may be configured as a part of the vacuum vessel. If the X-ray attenuation rate at a portion is small, it can be regarded as an X-ray emission window. Needless to say, the vacuum vessel VV does not have to have a rotationally symmetric shape. It goes without saying that the center axis of the vacuum vessel and the center axis of the cathode side rotating body assembly or the anode side rotating body assembly may be deviated to some extent. It is needless to say that the X-ray target is divided and each divided part may have a gap. Needless to say, the rotating part of the cathode power supply mechanism SL1 may be the bearing rotating body itself that constitutes the bearing mechanism of the cathode power supply mechanism SL1.
Of course, the cathode power supply mechanism SL1 may be integrally formed with the bearing mechanism CBG. In the present invention, the size of the gap means the shortest distance from any point on one of the opposing surfaces forming the gap to the other of the opposing surfaces forming the gap. .

The present invention realizes an X-ray CT scanner capable of ultra-high-speed scanning as described above. The present invention can be applied to an electron beam irradiation device for irradiating an electron beam from a device. That is, the X-ray target and the parts related thereto, the X-ray X-ray distribution limiting mechanism, the fan direction distribution shaper WF, and other X-ray related parts are omitted from the device configuration described in the above embodiment, and the X-ray The emission window XW is changed to an electron beam emission window made of a thin titanium plate, and the direction of emitting electrons from the electron gun assembly EG is changed to the direction of the electron beam emission window. When this is used, it is possible to provide an electron beam irradiation apparatus which can be used for plastics, glass, and other modification treatments and has a large industrial effect.

[0033]

As described above, when the cathode scan type X-ray generator of the present invention is employed, the rotating part can be formed into a structure in which light parts are attached to a substantially rotationally symmetric structure inside the vacuum vessel, so that centrifugation is performed. Ultra-high-speed scan type X-ray C with less influence of force, for example, a scan time of 0.03 seconds
The T scanner can be realized at a low cost with a simple structure. In particular, a large amount of X
Lines can be generated, and a sufficiently high-quality image with little photon noise can be obtained. The generated X-rays are effectively received by the annular surface detector, and a large number of cross-sections in a wide area can be instantaneously photographed. Using this data, the three-dimensional internal structure of the subject can be instantaneously obtained. Be able to inspect. For this reason, it is possible to provide an X-ray CT scanner capable of faithfully and immediately imaging even a portion that moves quickly, such as a human heart, inside the subject. The bearing mechanism uses a hydrodynamic sliding bearing that uses liquid metal as a lubricant, so it can be used stably in a vacuum for a long time, and can keep the potential of the rotating part constant, and it is very small. The occurrence of unstable phenomena such as discharge can be prevented. Further, the heat generated inside through the dynamic pressure sliding bearing can be effectively guided to the outside of the vacuum vessel to be cooled. A sufficient amount of liquid metal lubricant is stored inside the bearing mechanism and is automatically supplied into the bearing gap, so that insufficient lubrication does not occur and stable operation is maintained with sufficient reliability can do. There is no external mechanical rotation mechanism, and related power supplies and electronic circuits can be used in a stationary state, so overall reliability is high,
The whole X-ray CT scanner becomes compact.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic cross section of a conventional X-ray CT scanner.

FIG. 2 is a cross-sectional view of a main part of an overall structure of a cathode scan type X-ray generator according to the present invention and an X-ray CT scanner using the same.

FIG. 3 is a diagram illustrating the principle of a cathode scan type X-ray generator according to the present invention and an X-ray CT scanner using the same.

FIG. 4 is an enlarged view of a cross section of a part of the cathode scan type X-ray generator according to the present invention, which is located vertically above at a certain moment.

FIG. 5 is an enlarged sectional view of a part of a cathode side rotating body assembly which is a main part of a cathode scan type X-ray generator according to the present invention.

FIG. 6 is a further enlarged sectional view of a part of FIG. 5, which is a main part of the cathode scan type X-ray generator according to the present invention.

[Explanation of symbols]

ABG Anode-side bearing mechanism AR Anode-side rotating body assembly B Bed CBG Cathode-side bearing mechanism CR Cathode-side rotating body assembly DB Rear detector assembly DF Front detector assembly D1 Part of detector DF, DB D2 Detector DF, Part of DB D3 Detector DF, Part of DB EG Electron gun assembly F1 X-ray focus F2 X-ray focus F3 X-ray focus HT High voltage terminal LM1 Arc-shaped stator LM2 Arc-shaped stator M Subject MT2 Magnetic path cylinder RT1 rotor RT2 rotor SL1 cathode power supply mechanism SLT slit TG X-ray target VC exhaust port VV vacuum vessel WF fan direction distribution shaper XW X-ray emission window 1 cathode 2 electron beam 101 bearing fixed body 102 bearing rotating body 103 vertical of radial bearing gap Upper part 104 Vertical upper part of the bearing gap of the first thrust bearing 105 End Vertical upper part of the bearing 106 Vertical upper part of the bearing gap of the second thrust bearing 107 Vertical upper part of the end gap 108 Vertical lower part of the radial bearing gap 109 Vertical lower part of the bearing gap of the first thrust bearing 110 End gap 111 Vertically lower part of the bearing gap of the second thrust bearing 112 Vertically lower part of the end gap 120 Vertically lower part of the bearing opening 120 'Vertically upper part of the bearing opening 121 Vertically lower part of the bearing opening 121' Bearing opening Vertical portion 132 annular recess 133 annular recess 180 liquid metal lubricant storage groove 181 liquid metal lubricant storage groove 182 liquid metal lubricant storage groove 183 communication hole 184 communication hole 217 rotational torque transmission mechanism 220 insulator 1001 conventional X-ray CT scanner fixed stand 1002 Rotary mount of conventional X-ray CT scanner 1003 Bearing of conventional X-ray CT scanner 1004 X-ray tube of conventional X-ray CT scanner 1005 X-ray of conventional X-ray CT scanner 1006 Detector of conventional X-ray CT scanner 1007 Electronic circuit of conventional X-ray CT scanner 1008 Controller of conventional X-ray CT scanner 1009 Rotary drive mechanism of conventional X-ray CT scanner

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01J 35/24 H01J 35/24

Claims (8)

[Claims] 1. A donut-shaped vacuum container for forming a vacuum space by maintaining a vacuum state inside the vacuum container, and supported in the vacuum space inside the vacuum container so as to be rotatable coaxially with a center axis of the vacuum container. A cathode side rotating body assembly, an electron gun assembly attached to a part of the cathode side rotating body assembly, a cathode attached to the electron gun assembly and emitting electrons, and A rotating portion of a cathode power supply mechanism for supplying power from the outside, an annular X-ray target mounted facing a surface including the orbital path of the cathode, and an X-ray generated on the surface of the X-ray target. An X-ray emission window for taking out of the vacuum vessel, a rotation drive mechanism for applying a rotational force to the cathode-side rotating body assembly, and a bearing rotatably supporting the cathode-side rotating body assembly in the vacuum vessel. Mechanism and the cathode And a bearing mechanism for rotatably supporting a rotating part of the power supply mechanism in the vacuum vessel. At least one of these bearing mechanisms is a part for fixing the bearing mechanism. Bearing fixed body,
A plurality of hydrodynamic sliding bearings having a liquid metal, which is a liquid during operation, as a lubricant between the bearing stationary body and the bearing rotating body; Each dynamic pressure sliding bearing has a bearing surface opposed with a gap, and at least one of these bearing surfaces is provided with a herringbone-shaped bearing groove, Any 2 of the hydrodynamic sliding bearings
There is a low pressure area where the bearing pressure is small between the bearings,
In the part of the bearing fixed body located in this low pressure area,
A cathode scan type X-ray generator comprising a liquid metal lubricant storage mechanism for storing the liquid metal lubricant, and an X-ray CT scanner using the same. 2. A donut-shaped vacuum vessel for forming a vacuum space by holding the inside of the vacuum state, and supported so as to be coaxially rotatable in the vacuum space inside the vacuum vessel with the center axis of the vacuum vessel. An anode-side rotator assembly, an annular X-ray target attached to the anode-side rotator assembly, and an electron gun assembly attached to orbit around an X-ray target in a trajectory facing the surface of the X-ray target. A cathode mounted on the electron gun assembly and emitting electrons,
A cathode power supply mechanism for supplying power to the cathode from outside the vacuum vessel, and X-rays generated from the surface of the X-ray target.
An X-ray emission window for taking out the radiation outside the vacuum vessel;
It has a rotary drive mechanism that applies a rotational force to the anode-side rotating body assembly, and a bearing mechanism that rotatably supports the anode-side rotating body assembly in a vacuum vessel. A bearing fixed body that is a part for fixing the bearing mechanism, and a bearing rotating body that is fitted to and rotated by the bearing fixed body. Liquid is present between these bearing fixed body and the bearing rotating body during operation. A plurality of hydrodynamic sliding bearings using a liquid metal as a lubricant, each hydrodynamic sliding bearing has an opposing bearing surface with a gap, and at least one of these bearing surfaces Is provided with a herringbone-shaped bearing groove, there is a low pressure region where the bearing pressure is small between any two of the dynamic pressure sliding bearings, and the low pressure region is located in the low pressure region. In the part of the bearing fixed body of Cathode scanning X-ray generator, characterized in that the liquid metal lubricant storage mechanism that stores the lubricant is provided, and X-ray CT scanner using this. 3. The liquid metal lubricant storage mechanism according to claim 1, wherein the liquid metal lubricant storage mechanism includes a plurality of annular grooves or a plurality of annularly disposed recesses in the bearing fixed body and facing the bearing rotating body. 3. A cathode scan type X-ray generator according to claim 1 or 2, and an X-ray CT scanner using the same. 4. The liquid metal lubricant storage mechanism according to claim 1, wherein said liquid metal lubricant storage mechanism is closed on a side having a large radius.
3. The cathode scan type X-ray generator according to any one of the above items 3, and an X-ray CT scanner using the same. 5. The liquid metal lubricant storage mechanism according to claim 3, wherein a plurality of the liquid metal lubricant storage mechanisms are provided coaxially, and at least some of them are connected to each other through a passage. And a X-ray CT scanner using the same. 6. The liquid metal lubricant storage mechanism according to claim 1, further comprising a ventilation hole at a position vertically above and communicating with a vacuum space of the vacuum vessel.
And a X-ray CT scanner using the same. 7. The liquid metal lubricant storage mechanism is provided with a passage communicating with the outside of the vacuum vessel. Through the passage, the liquid metal lubricant stored in the liquid metal lubricant storage mechanism is provided. The amount can be changed from the outside of the vacuum vessel while the inside of the vacuum vessel is maintained in a high vacuum state.
A cathode scan type X-ray generator according to any one of the above, and an X-ray CT scanner using the same. 8. A donut-shaped vacuum container for forming a vacuum space by holding the inside of the vacuum state, and supported so as to be coaxial with the center axis of the vacuum container in the vacuum space inside the vacuum container. A cathode side rotating body assembly, an electron gun assembly attached to a part of the cathode side rotating body assembly, a cathode attached to the electron gun assembly and emitting electrons, and A rotating portion of a cathode power supply mechanism for externally supplying power, an electron beam emission window for extracting electrons emitted from the cathode and accelerated, and a rotation drive mechanism for applying a rotating force to the cathode side rotating body assembly And a bearing mechanism for rotatably supporting the cathode side rotating body assembly in the vacuum vessel, and a bearing mechanism for rotatably supporting the rotating part of the cathode power supply mechanism in the vacuum vessel. Have these axes At least one of the bearing mechanisms of the receiving mechanism has a bearing fixed body that is a part for fixing the bearing mechanism, and a bearing rotating body that is fitted into and rotated by the bearing fixed body. A plurality of hydrodynamic sliding bearings using liquid metal, which is liquid during operation, as a lubricant are configured between the bearing rotating body and each of the hydrodynamic sliding bearings has an opposing bearing surface with a gap. A herringbone-shaped bearing groove is provided on at least one of these bearing surfaces, and a low-pressure region in which the bearing pressure is small is present between any two of the dynamic pressure sliding bearings. An electron beam irradiator, wherein a liquid metal lubricant storage mechanism for storing the liquid metal lubricant is provided at a portion of the bearing fixed body located in the low pressure region.