JPS61225742A - Rotary anode x-ray tube device - Google Patents

Abstract

PURPOSE:To heighten the stiffness of magnetic bearings, by using the bearings to support an X-ray generating target without contact, and using grounding diodes to set the rotors of the magnetic bearings at the ground potential without contact, so as to reduce the magnetic gaps of the bearings. CONSTITUTION:A target 4 is rotated by the rotors 114, 115 and stators 110-113 of radial and thrust magnetic bearings without contact. The target 4 is mounted with an electric insulator 137 inserted in the rotor 114. A positive high voltage is applied to the target 4 through an internal electroconductive line 140, a cathode 142 and a heater 114. A plurality of grounding diodes are formed between a fixed anode 122 or the like and a cathode 120 or the like on a heatresisting cylinder 118 at the end of the rotor 114. The rotor 114 is kept at the ground potential without contact. As a result, the magnetic gaps of the magnetic bearings can be reduced to heighten their stiffness to enable the use of a power supply of the neutral point grounding type.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a rotating anode type X@tube device, which rotates at high speed while supporting an anode target in a non-contact manner with a magnetic bearing, and furthermore, the present invention relates to a rotating anode type X@tube device. It supplies a positive high voltage, supplies a negative high voltage to the cathode, keeps the vacuum container and magnetic bearing rotor at substantially ground potential, maintains the distance between the magnetic bearing stator and rotor at 4W or less, and is compact. [Technical Background of the Invention] Generally, X-ray tubes are used for medical purposes, for example, for X-ray diagnosis. An X@ tube as shown in Figure 3 is used. This X-ray tube is a so-called rotating anode type, in which a cathode plate is disposed on one side of an envelope 1, and a cathode 3 containing a cathode filament that emits thermionic electrons and a focusing electrode is disposed eccentrically. There are others. A substantially umbrella-shaped anode target 4 is disposed near the center of the envelope 1, facing the cathode structure 2. This anode target 4 provides a high potential difference with the cathode structure 2, accelerates electrons emitted from the cathode filament, causes them to collide, and generates X-rays by bremsstrahlung radiation.
It is designed to store and dissipate the large amount of heat generated at this time, and is designed to be able to rotate at high speed in order to effectively spread the heat-generating surface structure. Such an anode target 4 is connected to a covered cylindrical loader 6 via a support column 5. This rotor 6 generates rotational force by receiving a rotating magnetic field generated by a stator 7 disposed outside the envelope 1, and forms an induction motor together with the stator 7. -Der 6 is integrated. A rotating shaft 8 is disposed inside the loader 6 along the axis.
One end of this rotating shaft 8 is fixed to the loader 6 by a screw or the like (not shown). This rotating shaft 8 and the rotor 6
A bottomed cylindrical stator 9 is disposed coaxially between the stator 9 and the stator 9, and one end thereof is fixed to the envelope 1 via a pair of weight rings 10 and 11. Furthermore, a bearing 12.13 is interposed between the stator 9 and the rotating shaft 8, and the rotating shaft 8
is designed to rotate freely. Now, during operation, the power when the electrons emitted from the cathode filament reach the target 4 is: anode voltage 50KV current 20mA
In this case, IKWK is reached. Since more than 99% of this power is converted into heat, the target 4 is heated to a high temperature with heat radiation to the outside and heat conduction to other parts. Heat radiation increases in proportion to the fourth power of the distance between the eyebrows, so when the temperature rises, heat radiation increases significantly and thermal equilibrium is reached in a short time. For example, under the above conditions #'i equilibrates at 1100°C after 5 minutes.

On the other hand, when heat is transferred by thermal conduction, if the other end of the conductive medium is thermally free, the end gradually becomes hotter over a long period of time. The heat of the target 4 is transmitted to the loader 6 and the rotating shaft 8, making them high temperature. When the rotor 6 becomes high in temperature, thermal radiation increases as described above and thermal equilibrium is reached. Under the above conditions, the 0 point on the support column 5 is 800 degrees Celsius approximately 15 minutes after the start of energization, the 0 point on the rotor 6 is 550 degrees Celsius 30 minutes after the start of energization, and the 0 point near the bearing 13 is approximately 800 degrees Celsius after the start of energization. Thermal equilibrium is reached at 400°C in 50 minutes.

Depending on the rotation of the poles in the bearings 12 and 13, thermal expansion may cause problems such as poor clearance between the outer ring and the inner ring, and damage to the bearing. Furthermore, if the temperature of the bearings 12, 13 exceeds 500°C, the hardness of the ball will decrease, resulting in loss of bulb performance such as stoppage of rotation.

In addition, the loader 6 is
It has been found that when rotating the target 4, increasing the rotation speed significantly reduces the rotation life. The X-ray tubes actually used have a rotational speed of about 10.00 Orpm, but even in this case the rotational life is not sufficient.

Furthermore, when the heat capacity of the target 4 increases, the weight of the target increases, resulting in a shortened rotational life. To solve this problem, U.S. Patent No. 114
, 417.171, Japanese Patent Publication No. 58-43860, and Japanese Patent Publication No. 59-63646.
Although tubes have been proposed, they have the following drawbacks. That is, in U.S. Patent No. 4,417.171, the outer diameter of the rotor becomes extremely large, which not only increases the size of the entire X-shaped tube, but also requires a high voltage to be applied to the central pillar, which makes it difficult to maintain it. is difficult. Special Public Service 1987
In No. 43860, the rigidity of the rotor and target is low, the resonance frequency is low, and high speed rotation is not possible. In Japanese Patent Application Laid-Open No. 59-63646, the anode must be kept at ground potential, which is inconvenient as a special high voltage power supply and high voltage cable are required.

[Key points of background technology]

However, the conventional X-ray tube as described above has the following drawbacks. That is, as mentioned above, when the temperature of the grooves of the bearing 12, 13 increases, not only does the clearance between the balls and the inner and outer rings become insufficient, but also the lubricant existing between the balls evaporates. Bearings 12.13 may be damaged. For these reasons, there is a drawback that rotation stoppage accidents tend to occur frequently. To prevent this, increase the degree of blackening of target 4, increase the degree of blackness of the surface of target 4,
Although it has been considered to install a heat shield plate between the target 4 and the rotor 6, the effect of these is relatively small, and the reality is that the input power to the target 4 is too small.

In addition, when this structure is rotated at high speed, the rotational life becomes extremely short. And if we increase the heat capacity of target 4,
In order to eliminate these problems in which the weight of the target 4 increases, the rotational life becomes increasingly short, a rotating anode type X-ray tube using a magnetic bearing is disclosed in US Patent Specification 4.
No. 417.171, Japanese Patent Publication No. 5B-43860, and Japanese Patent Application Laid-Open No. 59-63646.

However, each of these has drawbacks as mentioned above.

[Purpose of the invention]

The object of the present invention is to use a large-capacity turbulent magnetic bearing for X-ray generation to rotatably support the magnetic bearing in a non-contact manner, maintain sufficiently high rigidity of the magnetic bearing, and increase the rigidity of the rotating part to reduce the resonance frequency. iJ high-speed, low-vibration, ultra-high-speed rotation
(By keeping the target at a positive high voltage, the cathode at a negative high voltage, and the vacuum vessel, magnetic bearing a-tar and stator at substantially earth potential). To provide a rotating anode type X-tube device which has a small magnetic gap and high rigidity, and which has significantly improved reliability by preventing noise from entering a position sensor for detecting displacement of a rotor.

[Summary of the invention]

In this invention, an insulator is inserted and fixed inside a rotor for a magnetic bearing, and an X-ray generating target is mechanically fixed at a separated position on the outer periphery of this insulator through this insulator.
The target and the magnetic bearing rotor are electrically insulated by the separated insulating part, the magnetic bearing rotor is maintained at substantially ground potential, and the target is provided by penetrating the inside of at least one rotor. A high positive voltage is supplied to the target from outside the tube through a conductive path formed by the tube. A negative high voltage can be applied to the cathode, and it can be used with the same high voltage power supply with the same neutral point grounding as a conventional rotating anode XM tube, and it has the same weight as a conventional X-ray tube. This is a rotary anode type X@ tube device that has an external dimension of 1,000 yen and can rotate a large-capacity target at an ultra-high speed, has an extremely long life, and has low vibration and noise.

[Embodiments of the invention]

The rotary anode type X-tube device of the present invention is constructed as shown in FIG. 1, and the same parts as in the conventional example (FIG. 3) are given the same reference numerals.

That is, the central portion of the housing L, which is a vacuum container, is made of gold sm and is maintained at a ground potential. And this housing 1 is X? Generation for fM generation - Get! a heat-absorbing container portion 101 that absorbs heat from the magnetic bearing;
103, vacuum partitions 104 and 105 within the position sensor,
It consists of auxiliary bearing support plates 106, 107 and end insulating containers 108, 109. This flexible housing 1 forms a vacuum container as described above with the above-mentioned portions, and its V:J portion is maintained at a high vacuum.

Radial magnetic bearing stators 110 and 111 that generate an attractive force in the radial direction are provided outside the magnetic shaft internal vacuum partition walls 102 and 103. Thrust magnetic bearing stators 112 and 113 that generate an attractive force in the thrust direction are provided beside the radial magnetic bearing stators 110 and 111, respectively.

Inside each stator, there is a magnetic bearing 9 made of Kawaguchi magnetic material, and on its outer periphery there is a 1 m I# made of magnetic material.
The plates 116, 117 are coated with this laminate plate 116.1
17 and the stator 110, 11 for the radial magnetic bearing.
A radial magnetic bearing is constructed by generating a suction force between the bearing and the bearing.

The ends of the magnetic bearing loaders 114 and 115 are made of a thin heat-resistant metal such as tantalum or a ceramic with a metalized surface such as 8i3N4. A grounding diode 124, 125 is formed between the heat-resistant cylinders 118, 119 and a low-temperature operation cathode 120, 121, such as a Parisian cathode, and the diode anode 122, 123. ing. Furthermore, a fixed cathode 126 is located further away from the target 4.
, 127 are provided, and the above-mentioned rotating heat-resistant cylinder 1
18. The above-mentioned current-carrying diode 12 is connected between a part of 119.
Grounding diode 128°129 with characteristics opposite to 4°125
is formed.

These fixed cathodes 126 and 127 are made of metal that can be heated to high temperatures, such as tungsten wire, and when heated to, for example, 2250°C, they not only operate as cathodes for generating thermionic electrons, but also emit light from their surfaces. Strong thermal radiation is applied to heat the opposing heat-resistant cylinders 118 and 119 to a high temperature. And the cathode 120.1 attached to the stiffener
21 is heated to approximately 900°C and acts as a cathode as described above.

Diode anodes 122°123 facing these cathodes
is made of a filament, such as a tungsten wire, and is heated by being energized from outside the vacuum envelope, thereby additionally heating the opposing cathodes 120° and 121.

Fixed cathode above! 26 and 127 are grounded, and a positive voltage, for example 5, is applied to the fixed anode 122 via a resistor 153.
0v is applied. Therefore, although the current value is limited to a low value, the potential of the rotors 114, 115 is substantially always at ground potential. In FIG. 1, the connection of another grounding diode is omitted. Moreover, the heat-resistant cylinder 118
, 119 has the outer diameter of the magnetic bearing rotor 114.11.
Since the outer diameter is smaller than that of No. 5, the centrifugal force is small despite the high temperature, and it can withstand high-speed rotation.

With these diodes, magnetic bearing a-tar 114,
115 are both kept at substantially ground potential, and are at substantially the same potential as the vacuum partition walls 102 and 103 within the magnetic axis. Therefore, the distance between them can be kept within t''0.5M0.5M, and the stator 110 for the radial magnetic bearing and the rotor 114 for the magnetic bearing 114.
5 can be reduced to within lva. As a result, bearing rigidity can be extremely increased.

Furthermore, metal rings 130 and 131 made of non-magnetic metal are fixed to the outer periphery of the magnetic bearing rotors 114 and 115 following the n11 layer plates 116 and 117. Following this, a copper ring 132 and a non-magnetic ring 133 are fixed. A stator 134 for one rotation of the rotor is provided outside the steel ring 132, which forms an induction motor to rotate the loader at high speed. On the outside of the metal ring 130 and non-magnetic ring 133, there is a
Radial sensor 1 via IJ song 04, 105
35, 136 are provided for the rotor 114 for the n1 magnetic bearing.
, 115 is detected.

Furthermore, a penetrating electrical insulator 132 is mechanically and rigidly fixed to the inside of the magnetic bearing rotor 114 by shrink fitting or the like. A metal plate 138 made of molybdenum or the like is bonded to an end surface 137-a of the electrical insulator 137 on the target side of the rotor 114. Experiments have shown that this joining can be achieved by brazing or the like. And, on this metal plate 138, XII!
Generation pole target for generation! The magnetic bearing rotor 114 is mechanically and tightly fixed by a bolt 139.
The electrical insulator 1
37 has a larger diameter withstand voltage part 137-b than other parts.
is formed, and the target 4 and the magnetic bearing roller 114
It maintains a high breakdown pressure (for example, 8QKV or higher). In this case, the voltage-withstanding portion 137-b of the electrical insulator 137 has an uneven surface to increase the creepage distance.

A conductive path 140 is provided in the center of the electric insulator 137, and a conductor body 141t-
It is electrically coupled to the terminal (terminal) 4 through the terminal. A heat-resistant cylinder 142 is provided at the other end of the conductive path 140, and a thermionic emission cathode 143 is attached to a part of the cylinder.
A heater 144 installed on the outside of the cathode J4
J#: t Heated to a high temperature of about 1000°C. The heater 144 is supplied with a high voltage (for example, 7 volts) from outside the tube during operation.
5KV) is applied and heated as described above to the cathode 14.
Due to the inflow of thermionic electrons from No. 3, they are electrically coupled at low impedance. This cathode 143 and heater 144
Since the perveance of the diode consisting of n is larger than the perveance of the diode consisting of the cathode 3 and targt, the voltage drop in this part is smaller. 4 can be supplied with high voltage from outside the pipe without contact. ◎ Also on the inside part of the other magnetic bearing rotor 115.
When the electrical insulator 145 is inserted by shrink-fitting, etc., the target mounting metal plate 138 and the rotor 115 have a high voltage (e.g. It is maintained at 80KV). As described above, the rotor 115 is kept at the ground potential and the target 4Fi is kept at a positive high voltage.

Note that the withstand voltage portion 145-a is provided with an uneven portion to increase the creepage distance.

Also, cathode 3! lc is a target 4 to which a negative high voltage (for example, -75 KV) is supplied by a conductor (not shown), and thermionic electrons are kept at a positive high voltage (for example, +75 KV).
and generates X-rays 146. This X-ray 146 is
The X-rays are irradiated to the outside of the tube through an X-ray emission window 142 made of, for example, beryllium and attached to the heat-absorbing container 101.

Father, Tergutu) Secondary electrons emitted from 4 (not shown)
is a withstand voltage section 137- of n% electrical insulation @137°145, which is shielded by a shielding plate 148°149 provided inside the pipe.
b, 145-a.

Further, on the outside of the ends of the rotors 114, 115,
The auxiliary bearings 150 and 151 are connected to the support plates 106 and 1.
It is strongly supported by 071fC. rotor 11
4. When 115 is working normally, rotor 1
Although not in contact with 14 and 115, the rotating part is supported by these auxiliary bearings 150 and 151 before operation or in case of abnormal operation.

A position sensor 152 is attached to the end of the a-tar 115 to detect displacement in the thrust direction.
3 to perform position control in the thrust direction.

Note that it is preferable to use ceramics such as silicon nitride (for example, 8i1N) as the material for the receiving insulators 137/145 because of their high mechanical strength.

[Modified example of the invention]

In the above embodiment, the rotors 114 and 115.

Although a non-contact current path is used to maintain substantially the ground potential, a structure may be adopted in which one or both of the current paths are brought into mechanical contact.

In addition, although the rotor 114 (or 115) and the insulator 137 (or 145) are bonded over the entire surface, it is of course better to limit the bonding surface to a part and connect it to the electrically insulating material 4. Between things 137 and 145,
Although both are connected via a metal plate 138,
These may be directly joined.

Moreover, in the above embodiment, the target! is supported on both sides, but it goes without saying that it may be moved to the magnetic bearing stator 1llf110 side to form a so-called cantilevered structure.

Next, another modification will be explained using FIG. 2. Note that the second factor represents only the leftmost portion of FIG. 1, and the same parts as in FIG. 1 are given the same reference numerals.

That is, the shield plate 160 is attached between the rotors 114 and 115 yen insulator 137 and the heat-resistant cylinder 118 attached to one end of the rotor. This shield plate 160 is mechanically supported by the end insulating container 108, and its potential is kept at a lower potential than the ground potential or the potential of the target 4.

Now, during operation, the cathode 126.12 of the current-carrying diode
Since it is heated to a high temperature of 0td, the metal evaporates, but it is captured by the shield plate 160, so the electrical insulator 13
It is possible to provide a rotating anode type X-tube device which maintains high withstand voltage without contaminating the surface of 7,108 and has high reliability.

Furthermore, the radiant heat from the heat-resistant cylinder 118 heated to a high temperature is shielded by the shield plate 118, and the electrical insulator 13
Since the electrical insulator 7 is not heated, the reliability of the electrical insulator 137 is increased.

It goes without saying that the same concept holds true for other current-carrying diodes not shown.

〔Effect of the invention〕

According to this invention, the following excellent effects can be obtained. Namely, since the rotating body is strong against centrifugal stress,
It is possible to rotate at ultra-high speeds on the order of Orpm, and the peak input value of the XN tube can be increased to about 1.7 compared to conventional tubes. In addition, since the rotating body is completely non-contact, there is low vibration and
Can we provide a low noise XN tube and is it even more mechanical? -Since no wheel bearings are used, the rotational life is extremely long.

In addition, the target 4 is set to a positive high voltage, and the cathode 120°121
Since it is maintained at a negative high voltage, a so-called neutral point grounded high voltage power supply can be used.

Since a conventional X-ray tube power supply can be used, the rotating anode type X-tube device of the present invention can be used in a conventional X-ray generator. Also, the rotors 114 and 115 are substantially at ground potential. Therefore, the magnetic gap of the magnetic bearing can be made small and strong rigidity can be obtained.
Kp ) target 4 at high speed (e.g. 30.00 O
It can be rotated at a high speed (rpm), making it extremely large
(e.g. 6 MHU) x-ray tubes can be provided.

Furthermore, since the rotors 114 and 115 are substantially at ground potential, noise entering the position sensor 152 can be reduced, allowing stable operation.

Further, the structure of the rotors 114 and 115 is simple, and as a result, a compact and low-cost X-ray tube can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a rotating anode type X-ray tube according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a modified example of the invention.
FIG. 3 is a sectional view showing a conventional rotating anode type X-ray tube. 1...Heunong, 110,111...Stator for radial magnetic bearing, 112.113...Stator for thrust magnetic bearing, 114,115...Rotor for magnetic bearing, 120,121...Grounding diode cathode, 137
．． 145...Electric insulator, 4...Target, 3.
··cathode.

Claims (13)

[Claims] (1) At least one tube current passing cathode, a rotatable X-ray generating target provided opposite to the tube current passing cathode, and a rotatable X-ray generating target for supporting the target in a non-contact manner. A heat-resistant cylinder is provided at the end of the rotor that constitutes the magnetic bearing on the side far from the target, and the cathode and anode installed on the heat-resistant cylinder and the anode and the anode installed in the vacuum container are not in contact with each other. 1. A rotating anode type X-ray tube device, characterized in that a plurality of grounding diodes each comprising an anode and a cathode that operate together are provided, and at least one of the grounding diodes has a characteristic opposite to that of the others. (2) Among the plurality of grounding diodes, at least one cathode is fixed to a vacuum container, heated by electricity from outside the vacuum, and acts as a cathode by emitting thermoelectrons; The rotary anode type X-ray tube device according to claim 1, wherein the cathode of another rotatable grounding diode mounted on the heat-resistant cylinder can be heated. (3) Among the plurality of grounding diodes, at least one cathode is fixed to the vacuum container, and energized from outside the vacuum.
The second of the other rotatable grounding diodes is heated and acts as a cathode by emitting thermoelectrons, and the first cathode together with another heating body fixed to the vacuum container.
3. The rotating anode X-ray tube according to claim 1, wherein the cathode is heated and both the first cathode and the second cathode are maintained at a good operating temperature. (4) The rotating anode X-ray tube device according to any one of claims 1 to 3, wherein the heat-resistant circumference is made of a thin heat-resistant metal, preferably tantalum. (5) Among the plurality of grounding diodes, at least one cathode is made of a material with a high thermionic emission temperature, preferably tungsten or an alloy thereof, is fixed in a vacuum container, and is heated by electrical current from outside the vacuum. , which itself emits thermionic electrons and acts as a cathode, and the cathode of another rotatable grounding diode mounted close to the heat-resistant cylinder is made of a material having a low thermionic emission temperature, preferably impregnated with barium. Claims 1 to 4 are made of type oxide cathodes.
The rotary anode type X-tube device described in . (6) The rotating anode type X-ray tube device according to any one of claims 1 to 5, wherein the heat-resistant cylinder is made of ceramic. (7) Claims 1 to 6, wherein the outer diameter of the heat-resistant cylinder is smaller than the outer diameter of the rotor constituting the magnetic bearing.
Rotating anode type X-ray tube device as described in . (8) Among the plurality of grounding diodes, the grounding diode whose cathode is on the side of the vacuum vessel is placed outside of the grounding diode whose cathode is on the rotatable heat-resistant cylinder, in other words, from the magnetic bearing loader. A rotating anode type X-ray tube device according to any one of claims 1 to 7, which is installed at a remote location. (9) Among the plurality of grounding diodes, at least one of the grounding diodes whose cathode is attached to the heat-resistant cylinder has an opposing anode composed of a heater, and operates as an anode while also receiving air from outside the vacuum. 9. The rotating anode X-ray tube device according to claim 1, wherein the opposing cathode is heated by power supply. (10) Among the plurality of grounding diodes, the cathode of the grounding diode on the vacuum vessel side is grounded, and the positive electrode is connected to the anode of the grounding diode mounted on the rotatable heat-resistant cylinder through a resistor. A rotating anode type X-ray tube apparatus according to claim 1, which supplies a voltage of . (11) providing a diode for supplying a high voltage to the target from the outside of the vacuum container without contact through at least one of the rotors constituting the magnetic bearing;
11. The rotating anode X-ray tube device according to claim 1, wherein the perveance of the diode is greater than the perveance of the diode comprising the cathode for passing tube current and the target. (12) An electric insulator is provided inside at least one of the rotors constituting the magnetic bearing, and a high voltage is supplied to the target from the outside of the vacuum container through the inside of the electric insulator without contact. a diode, a heat-resistant cylinder attached to the end of the rotor that constitutes the magnetic bearing that is far from the target, and an anode or a cathode of the plurality of grounding diodes provided on the heat-resistant cylinder, and the heat-resistant cylinder 12. The rotary anode type X-ray tube device according to claim 1, further comprising a heat shield plate provided substantially coaxially between the electric insulator and the electric insulator. (13) At least one tube current passing cathode, a rotatable X-ray generation target provided opposite to the accumulated current passing cathode, and a rotatable X-ray generating target for supporting the target in a non-contact manner. magnetic bearings on both sides of the target, heat-resistant cylinders are provided at the ends of the rotors of the magnetic bearings on both sides that are far from the target, and a cathode, an anode, and A rotating anode characterized in that it is provided with a plurality of grounding diodes consisting of an anode and a cathode that operate together in a non-contact manner with these attached to a vacuum container, and at least one of the grounding diodes has a characteristic opposite to that of the others. Type X-ray tube device.