JP2989079B2 - X-ray equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray apparatus,
More particularly, the present invention relates to an X-ray apparatus including an X-ray tube having a built-in slide bearing using a liquid metal as a lubricant.

[0002]

2. Description of the Related Art For example, a rotating anode X-ray tube is incorporated as an X-ray radiation source in an X-ray apparatus such as an X-ray imaging apparatus and an X-ray exposure apparatus which are widely used as a CT scanner. ing. This rotary anode type X-ray tube is, as is well known,
A disk-shaped anode target is mechanically supported by a rotating body and a fixed body having a bearing part therebetween, and an electromagnetic coil of a stator arranged outside the vacuum vessel is energized to emit an electron beam from the cathode while rotating at high speed. To the anode target
Emits rays. The bearing portion includes a rolling bearing such as a ball bearing, a spiral groove formed on a bearing surface, and gallium (Ga) or gallium-indium-tin (Ga).
-In-Sn) alloy is composed of a hydrodynamic sliding bearing using a liquid metal lubricant which becomes liquid during operation. An example using the latter plain bearing is described, for example, in Japanese Patent Publication No. 60-2146.
No. 3, JP-A-60-97536, JP-A-60-117531, JP-A-60-17531
No. 60-160552, JP-A-62-287555, JP-A-2-27947
Or Japanese Unexamined Patent Publication (Kokai) No. 2227948/1990.

[0003]

The liquid metal lubricant filled between the bearing surfaces of the plain bearing of the rotary anode type X-ray tube disclosed in each of the above publications has a relatively low melting point that can be practically used. However, its melting point is about 10 ° C. That is,
For example, the melting point of a Ga—In—Sn alloy is 10.7 ° C. even for a low melting point, and is 57 ° C. for a Bi—In—Pb—Sn alloy containing a relatively large amount of bismuth (Bi). Since the X-ray device may be used in a temperature environment not less than the melting point of the liquid metal lubricant, the lubricant in the bearing of the X-ray tube may be frozen before the device is operated. I have. In this state, the anode target cannot be rotated, and if a rotational force is forcibly applied, the bearing surface will be damaged. Therefore, before the rotation of the anode target of the X-ray tube, it is necessary to start the operation after the bearing is heated to a temperature equal to or higher than the melting point to melt the lubricant into a liquid state. For that purpose, the above-mentioned Japanese Patent Application Laid-Open No. 60-160552 discloses that a heat source such as a heating coil, a heat radiator, or a high-frequency radiator is provided inside or outside the X-ray tube, and a cathode filament is provided. The use of thermal radiation is disclosed.

However, providing a heat source such as a heating coil, a heat radiator, or a high-frequency radiator inside or outside the X-ray tube is inconvenient because an extra heat source needs to be arranged. In addition, utilizing the heat radiation of the cathode filament has a disadvantage that it takes a long time to raise the temperature of the bearing portion.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned disadvantages, and can efficiently melt a metal lubricant in a bearing portion without adding an extra part to an X-ray tube and stably start rotation. It is intended to provide a device.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an operation control for applying an alternating voltage from a stator drive power supply to a stator electromagnetic coil to cause electromagnetically induced heating of components of a spiral groove bearing and melting a lubricant in the bearing. An X-ray apparatus comprising means .

[0007]

According to the present invention, even when the lubricant is frozen, heat due to electromagnetic induction current loss is generated in the rotating body or the fixed body including the spiral groove bearing by the AC voltage applied to the stator electromagnetic coil, The temperature of the lubricant in the bearing increases efficiently. Therefore, it is possible to reliably start rotating the rotating body in a state in which the lubricant reaches a temperature equal to or higher than the melting point and is in a liquid state. Thus, safe and stable operation of the X-ray apparatus is guaranteed even under a temperature environment lower than the melting point of the metal lubricant.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.
The same parts are denoted by the same reference numerals. The X-ray apparatus of the embodiment shown in FIG. 1 includes a rotating anode type X-ray tube 10, a cathode and anode energizing power supply (not shown), a stator 11, a stator driving power supply 12, and a main controller 13 of the X-ray imaging apparatus. And

In the rotary anode type X-ray tube 10, a disk-shaped anode target 15 made of heavy metal is integrally formed with a rotary shaft 17 projecting from one end of a cylindrical rotary body 16 by a fixed nut 18 in a vacuum vessel 14. It is fixed to. A cylindrical fixed body 19 is coaxially fitted inside the cylindrical rotating body 16, and a ring-shaped opening closing body 20 is fixed to the lower end opening of the rotating body. The lower end of the fixed body 19 is connected to the anode support 17, which is air-tightly joined to the glass cylindrical container 14a of the vacuum container. The fitting portion between the rotating body 16 and the fixed body 19 constitutes a dynamic pressure spiral groove bearing 22 as shown in the above-mentioned publications. Therefore, spiral grooves 23 and 24 having a herringbone pattern as described in each of the above-mentioned publications are formed in the outer peripheral wall of the fixed body, the end face, and the opening closing body 20 which become the sliding bearing surface on the fixed body side. . The sliding bearing surface on the rotating body side facing this may be a simple smooth surface,
Alternatively, a spiral groove may be formed as necessary. The bearing surfaces of the rotating body and the fixed body are approximately 20
They are close together with a micrometer bearing gap. The fixed body 19 on the rotation center axis has a lubricant accommodating chamber 25 formed of a hole whose central portion is hollowed out in the axial direction. The outer peripheral wall of the intermediate portion of the fixed body 19 is slightly cut to form a small-diameter portion 26. The four radial passages 27 leading from the lubricant accommodating chamber 25 to the small-diameter portion 26 are symmetrical at equal angles. Is formed. Thus, the radial lubricant passage 27 extending from the lubricant accommodating chamber 25 is opened at an intermediate portion between the spiral grooves 23 of the two sets of radial bearings, that is, at a position where there is no spiral groove. Furthermore, the lubricant storage chamber 25 at the center
The upper end opening 25a shown in the figure is a spiral groove 24 made of a circular herringbone pattern forming a thrust bearing.
Located in the center of the bearing surface with
The thrust bearing is in communication with the bearing gap. A ferromagnetic cylinder 16b such as iron and a copper cylinder 16c are integrally fitted and fixed to an outer peripheral portion of a bottomed cylinder 16a constituting a main part of the rotating body 16. These operate as a rotor of the electromagnetic induction motor in cooperation with the stator 11 disposed outside the glass cylindrical container portion 14a on the outer periphery of the rotating body. The stator 11 includes a cylindrical iron core 11a and a stator electromagnetic coil 11b wound therearound. The stator electromagnetic coil 11b is circuit-connected so that a drive voltage is applied from a stator drive power supply, and generates a rotating magnetic field that reaches inside the rotating body during operation.

[0010] Therefore, a temperature detector 28 is attached to the anode support portion 17 extended outside the tube together with the fixed body of the X-ray tube. Temperature sensor from spiral groove bearing to anode support 28
By taking the heat transfer coefficient up to the above into consideration, the signal level obtained by the temperature detector 28 can be treated as corresponding to the temperature of the spiral groove bearing. Therefore, the temperature detector 28
Is supplied to the temperature detection comparator 29. Further, the output control signal of the temperature detection comparator 29 is configured to be supplied to the stator drive power supply 12 via the controller 30. The temperature detection comparator 29 converts the signal level corresponding to the detected temperature supplied from the temperature detector 28 into
A comparison operation is performed with a reference level corresponding to a predetermined melting point of the lubricant, and when the temperature corresponding signal level is lower than the reference level, conversely, each control output signal corresponding to the case where the temperature corresponding signal level is higher is sent to the controller 30. send. When the signal level corresponding to the bearing temperature is lower than the reference level, the controller 30 outputs the commercial power frequency (50 Hz or 60 Hz) from the stator driving power source 12.
The control output signal is supplied to the stator drive power supply 12 so as to supply the stator electromagnetic coil 11b with an AC voltage having a frequency higher than (Hz) and a range in which the rotating body does not start rotating. An inverter power supply circuit that generates a voltage having a frequency higher than the commercial power supply frequency is incorporated in the stator drive power supply 12. On the other hand, when the bearing temperature corresponding signal level is higher than the reference level, if there is a rotating body start command signal supplied from the main controller 13, a steady rotating drive voltage is immediately applied from the stator drive power supply 12 to the stator electromagnetic coil 11b. It is being supplied. Each part is provided with a microcomputer so that such operations and signal processing can be performed, and a sequence control program is set therein.

An operation example will be described with reference to FIG. The metal lubricant filled in the sliding bearing part of the X-ray tube is approximately 10 ° C.
It is assumed that the material has a melting point of The reference level preset in the temperature detection comparator 29 is set to a level sufficiently higher than the melting point of the lubricant, for example, 15 ° C. now,
It is assumed that the environment where the X-ray apparatus is placed is about 5 ° C. The temperature (T) of the fixed part of the bearing is also about 5 ° C. The lubricant at approximately this temperature is, of course, frozen. This temperature is detected by the detector 28, and a signal corresponding thereto is input to the temperature detection comparator 29. This state is represented as the time point (a) on the time axis (t) in FIG.
The temperature detection comparator 29 calculates, compares and determines that the temperature of the bearing portion is lower than the reference level, and as described above, the controller 30 supplies the stator drive power supply 12 with a frequency higher than the commercial power supply frequency (for example, 210 Hz). ) And sends a control output signal to supply a low voltage (E) (for example, 50 V) to the stator electromagnetic coil 11b within a range in which the rotating body is not started to rotate. Accordingly, a high-frequency rotating magnetic field (210 Hz in the above example) is generated from the stator electromagnetic coil 11b, and X
Electromagnetically induced eddy current loss occurs in the rotating body and fixed body of the wire tube, and the temperature (T) of the bearing portion gradually increases. Particularly, in this embodiment, since the spiral groove bearing is coaxially arranged in the inner region of the stator electromagnetic coil 11b, the AC magnetic field generated in the stator electromagnetic coil is efficiently applied to the bearing components, and the induced current loss is efficient. Fever. Thus, for example, after about 3 minutes, the temperature of the bearing section exceeds the reference level of 15 ° C. In this state, the metal lubricant in the bearing is melted and is completely liquid. This temperature relationship is compared and determined by a temperature detection comparator 29, and the stator electromagnetic coil 11b is determined.
A control signal is supplied from the controller 30 to the stator drive power supply 12 so that the power supplied to the power supply is switched to a voltage (for example, 400 V) sufficient for starting rotation of the rotating body. This switching point is point (b) in FIG. Thereafter, when the rotation speed of the rotating body reaches a predetermined number of revolutions, the frequency and the voltage (for example, 70 Hz, 150 V) of the steady rotation are switched from the time (c). When the temperature of the bearing portion in the initial stage (a) is higher than the reference level, the control from (a) to (b) is not necessary, and the start from (b) is started immediately. The X-ray apparatus according to the present invention has a configuration automatically controlled by such a sequence. In order to melt the lubricant, the voltage supplied to the stator electromagnetic coil 11b between (a) and (b) may be a high frequency voltage of, for example, about 1 kHz.

In the above embodiment, the temperature detector is fixed to an anode support thermally connected to the bearing, and has a structure for indirectly detecting the temperature of the bearing. However, the present invention is not limited to this. It may be configured. That is, a small hole reaching the vicinity of the bearing from outside the tube may be formed in the fixed body, and a temperature detector such as a thermocouple may be embedded in the vicinity of the bearing. Thereby, the temperature of the bearing portion can be detected almost directly, and more precise control can be performed. Alternatively, the temperature of the insulating oil in the X-ray tube accommodating container (housing) in which the X-ray tube is housed and filled with the insulating oil is detected, so that the rotation start of the anode target of the X-ray tube is started. The temperature of the lubricant may be detected indirectly, and the sequence control for reducing the lubricant preheating process as described above may be performed based on the bearing temperature correspondence signal. Alternatively, the configuration may be such that the room temperature at which the X-ray apparatus is placed is detected and the temperature of the bearing portion is further indirectly detected. In this case, by setting the reference level to an appropriate temperature, it is possible to prevent a strong starting moment from being applied to the rotating body when the lubricant is frozen.

Another embodiment of the present invention will be described with reference to a sequence control diagram shown in FIG. Before turning on the main power supply of the X-ray apparatus, the helical groove bearing portion of the rotary anode X-ray tube is at a temperature lower than the melting point of the lubricant, and therefore the lubricant is frozen. Therefore, first, at the time (a),
AC voltage E of 70 Hz and 160 V from the stator drive power supply
Is applied to the stator electromagnetic coil, and this voltage is continuously supplied for 2 minutes until time (b). During this time, the temperature of the bearing portion rises due to electromagnetic induction heating, the lubricant melts, and the anode target starts rotating. At the point (b), the voltage supplied to the stator electromagnetic coil is reduced to 50V. The frequency is 7
It remains at 0 Hz. The target rotation speed R stabilizes at about 3,000 rpm after once increasing as indicated by the dotted line. In this state, at time (d), a voltage between the cathode and the anode is applied to the X-ray tube, a fluoroscopic diagnosis is performed, and a part requiring imaging, a timing, and the like are determined. Then, at the time (e) after the fluoroscopy is completed, the voltage supplied from the stator drive power supply to the stator electromagnetic coil is switched to 210 Hz and 400 V. Thereby, the rotation speed of the anode target is about 10,000.
rpm. At this point (f), a high cathode-anode voltage is applied to the X-ray tube and an X-ray photograph is taken. At the same time as the end of this photographing, the voltage supplied to the
Hz, 130 V, and 7 (g)
Change to 0Hz, 50V. As a result, the number of revolutions of the anode target is stabilized at about 3,000 rpm, and the process proceeds to the next fluoroscopic diagnosis. Such control is repeated.

Incidentally, a conventional X-ray apparatus using an X-ray tube having a ball bearing lubricated with a solid metal lubricant, as shown in FIG. 4, requires less than 5 seconds before the fluoroscopic diagnosis (h) as shown in FIG. For a short period of time, a rotation drive voltage of 180 Hz and 200 V is supplied to the stator electromagnetic coil to start rotation. Immediately at the time (i), the frequency was reduced to 60 Hz and 50 V, and fluoroscopy was performed.
Thereafter, photographing is performed in the same manner as described above. After the photographing is completed, the voltage supply to the stator electromagnetic coil is stopped, or a reverse rotating magnetic field is applied to cause a braking action, in order to minimize bearing abrasion and lubricant scattering and wear. The rotation of the is stopped early. Therefore, it is necessary to perform the start control from (h) to (i) again before the next fluoroscopy. As a result of performing such repetition, although the rotational driving power is small, excessive stress is repeatedly applied to the rotating mechanism in the X-ray tube, and bearing wear, vibration, and noise are likely to occur.

On the other hand, according to the present invention, although the rotational driving power is slightly high, once the lubricant is once melted, it can be constantly rotated at about 3,000 rpm with low vibration and low noise. The fluoroscopy can also be performed relatively quickly when needed. Further, undesired stress is less likely to be applied to the rotating mechanism inside the X-ray tube, and the X-ray tube can be used stably for a long time.

Incidentally, the main winding of the stator electromagnetic coil,
Each current or the phase difference between the currents of the auxiliary winding has a remarkable difference between the rotating body and the non-rotating state. Therefore, the configuration is such that these currents of the stator electromagnetic coil are detected, and a comparison is made between a non-rotating state and a steady rotating state to calculate and control the presence or absence of freezing of the lubricant in the bearing portion. It may be. That is, first, a predetermined AC voltage is applied to the stator electromagnetic coil for a predetermined time to detect the current of each coil or its phase, and when the rotating body is a coil current or a phase difference corresponding to the non-rotating state,
Appropriate current and supply time for melting the lubricant are obtained by arithmetic processing, and the supply voltage to the stator electromagnetic coil is automatically controlled. In this case, the voltage to be applied first is set to a value sufficient to start rotation immediately if the lubricant is in a molten state. In the case where each current and phase of the stator electromagnetic coil corresponds to a state in which the lubricant is in a molten state and immediately starts rotating, the control configuration is such that a voltage of a steady rotation is directly applied to the stator electromagnetic coil. .
According to this, the apparatus can be configured such that the molten or non-melted state of the lubricant in the bearing portion can be almost directly detected, and appropriate rotational drive control can be performed according to each state. Therefore, the reliability is high, the temperature detecting means for the bearing portion is not required, and a relatively simple device configuration can be achieved.

On the other hand, the frequency is arbitrary, and a low voltage in a range where the rotating body does not rotate even when the lubricant is in a liquid state is applied to the stator electromagnetic coil for a predetermined time (for example, an arbitrary set time of 10 seconds or more and 10 minutes or less). May be configured to be sequence-controlled so as to always go through the process of performing Thus, regardless of the operating temperature of the device, it is almost certain that the rotating body or the fixed body constituting the helical groove bearing is electromagnetically induced to generate heat to melt the metal lubricant of the bearing portion and then start the anode target in rotation. it can. Therefore, a temperature detector may not be provided, and safe and stable operation can be maintained with a relatively simple device configuration.

[0018]

As described above, according to the present invention,
Without adding extra heating means inside and outside the X-ray tube, the lubricant in the bearing portion can be efficiently heated and melted, and the rotation can be started. Therefore, stable operation of the X-ray apparatus is guaranteed even in a temperature environment lower than the melting point of the lubricant.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a main part of an embodiment of the present invention in a longitudinal section.

FIG. 2 is a sequence control diagram for explaining the operation of the apparatus shown in FIG. 1;

FIG. 3 is a sequence control diagram showing another embodiment of the present invention.

FIG. 4 is a sequence control diagram of an X-ray tube using a conventional ball bearing.

[Explanation of symbols]

 10 ... X-ray tube, 11 ... Stator, 11b ... Stator electromagnetic coil, 12 ... Stator drive power supply, 13 ... Main controller, 14 ... Vacuum container, 15 ... Anode target, 16 ... Rotating body, 19 ... Fixed body, 22 ... Helical groove bearing, 28… Temperature detector, 29… Temperature detection comparator, 30… Controller.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Makoto Tanaka 7-1, Nisshincho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Electronic Engineering Corporation (58) Field surveyed (Int. Cl. ⁶ , DB name) H01J 35 / Ten

Claims (5)

(57) [Claims] 1. A rotator anode target is fixed, the fixing member which is fitted coaxially to the rotating body, is Tsukin genus lubricant also a predetermined melting point in the fitting portion of the rotating body and the fixed body filling An X-ray tube having a helical groove bearing, a stator electromagnetic coil arranged on the outer periphery of a rotating body of the X-ray tube, and a stator drive power supply provided to apply a voltage to the stator electromagnetic coil. in X-ray apparatus, when starting rotation of the rotary member of the X-ray tube, by applying an AC voltage to the stator drive power supply or al the scan stator electromagnetic coil by electromagnetic induction heating the bearing part in the bearing
An X-ray apparatus comprising an operation control means for increasing the temperature of the metal lubricant . 2. A comprising a temperature detector for directly or indirectly detecting the temperature of the shaft receiving portion, corresponding to the bearing portion temperature corresponding signal level obtained through the temperature detector to the melting point of the metals lubricant 2. The X-ray apparatus according to claim 1, further comprising an operation control means for automatically controlling the rotation of the rotating body to be started only when the bearing temperature corresponding signal level exceeds the reference value corresponding to the melting point of the lubricant as compared with the reference value to be performed. apparatus. Wherein said scan stator electromagnetic coil current or phase
And the stator corresponding to the non-rotating state of the rotating body
When a current or a phase of the electromagnetic coil, the metals lubrication
The electric power that raises the temperature of the agent is applied to the stator electromagnetic coil.
2. The X-ray apparatus according to claim 1, further comprising operation control means for applying the voltage . 4. The X-ray apparatus according to claim 1, wherein the voltage applied to the stator electromagnetic coil before starting rotation of the rotating body is higher than the frequency of the commercial power supply. 5. A rotating body on which an anode target is fixed, a fixed body fitted coaxially with the rotating body, and a fitting portion of the rotating body and the fixed body filled with a metal lubricant having a predetermined melting point. An X-ray having an X-ray tube having a helical groove bearing, a stator electromagnetic coil arranged on the outer periphery of a rotating body of the X-ray tube, and a stator drive power supply provided to apply a voltage to the stator electromagnetic coil in the apparatus, before applying the starting voltage for starting rotation of the rotary member from the stator drive power to the stator electromagnetic coil, the AC voltage in the range of the Jun <br/> lubricant rotating body does not rotate in the molten state Operation control for applying a predetermined time to the stator electromagnetic coil
X-ray apparatus characterized by comprising means.