JPS61171043A - Rotating anode x-ray tube device - Google Patents

Abstract

PURPOSE:To provide a rotating anode X-ray tube device of greatly enhanced reliability, by using magnetic bearings so that a target for generating a large capacity of X-rays is rotatably supported out of contact with the bearings. CONSTITUTION:The rotors 114, 115 of magnetic thrust bearings are provided inside their stators 112, 113. An electric insulator 137 is shrink-fitted in the rotor 114 so that the insulator extends through the rotor. A metal plate 138 of molybdenum or the like is conjoined to the end face 137a of the electric insulator 137. An anode target 4 for generating X-rays is secured to the metal plate 138 by bolts 139. The rotors 114, 115 of the magnetic bearings are both kept at the ground potential by electricity supply diodes 124, 125 and other electricity supply diodes 128, 129 whose characteristics are inverse to those of the diodes 124, 125, so that the rotors have substantially the same potential as vacuum walls 102, 103 in the magnetic bearings. For that reason, the clearances between the rotors 114, 115 and the stators 112, 113 can be kept small enough to make the stiffness of each magnetic bearing very high.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a rotating anode type X-ray tube device, in which an anode target is rotated at high speed while being supported in a non-contact manner by a magnetic bearing. supply a high voltage of This invention relates to a rotating anode type X-ray tube device with a compact structure.

[Technical background of the invention]

Generally, X-ray tubes are used for medical purposes, for example, for X-ray diagnosis, and in the case of stomach examinations, etc., an X-ray tube as shown in FIG. 3 has been conventionally used. This X-ray tube is of the so-called rotating anode type, and has a cathode 2 disposed on one side of an envelope 1, and an eccentric cup 3 containing a cathode filament that emits thermionic electrons and a focusing electrode. . Further, near the center of the envelope 1, a substantially umbrella-shaped anode target 4 is arranged opposite to the cathode 2. This anode target 4 provides a high potential difference with the above-mentioned cathode 2, and the cathode filament -
This is to accelerate the electrons emitted from the components and cause them to collide, generating X-rays through bremsstrahlung radiation, as well as storing and dissipating the large amount of heat generated at this time, effectively expanding the heat generation area. This allows it to rotate at high speeds. Such an anode target 4 is supported by a support column 5.
It is connected to a covered cylindrical rotor 6 via.

This rotor 6 generates rotational force by receiving a rotating magnetic field generated by a stator 7 disposed outside the envelope 1.
Together with the stator 2, it forms an induction motor. Incidentally, the support column 5 and the rotor 6 are integrated into a trap. A rotating shaft 8 is disposed inside the rotor 6 along the axis, and one end of the rotating shaft 8 is fixed to the gerotor 6 with a screw or the like (not shown). A bottomed cylindrical stator 9 is coaxially disposed between the rotating shaft 6 and the rotor 6, and one end is fixed to the envelope 1 via a sealing ring 10.11. . Note that this stator 9 is partially exposed outside the tube and also serves to support and fix the entire X-ray tube to the outside. Between the stator 9 and the rotating shaft 8, a bearing 12.
13 is interposed so that the rotating shaft 8 can rotate freely. Now, during operation, the power generated when electrons emitted from the cathode filament reach the target 4 reaches 1 kW when the anode voltage is 50 kV and the current is 20 mA.

Since 91% or more of this /4 watt 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. Thermal radiation increases in proportion to the fourth power of temperature, so as the temperature rises, heat radiation increases significantly.
Reach thermal equilibrium in a short time. For example, under the above conditions, equilibration occurs at 1100t:' 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 then transferred to the rotor 6 and rotating shaft 8, making them hot. When the rotor 6 becomes high in temperature, thermal radiation increases and thermal equilibrium is reached as described above. Under the above conditions, the 0 point on the support column 5 reaches 800 approximately 15 minutes after the start of energization.
C. At 0 point of rotor 6, 55 Or in 30 minutes after starting energization.
At the zero point near the bearing 13, thermal equilibrium is reached at 400C approximately 50 minutes after the start of energization. If the heat conduction of the bearing 13 deteriorates, the temperature at point 0 will be the same as point 0, 550
It will also reach C. Depending on the rotational conditions of the balls 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.

Also, if the bearing 12.13 reaches 500C or more,
This results in a decrease in the hardness of the goal, resulting in damage to the tube such as rotation stoppage.

Also, the rotor 6 is connected via bearings 12 and 13 in a vacuum.
It has been found that when rotating the target 4, increasing the rotation speed significantly reduces the rotation life. The rotational speed of the X-ray tube actually used is about 10,000 rpm, but even in this case, the rotational life is not sufficient.

Furthermore, when the heat capacity of target 4 increases.

The problem is that the target weight is large, and the rotation life is shortened. To solve this problem, magnetically levitated X-ray tubes have been proposed as described in U.S. Pat. These have the following drawbacks. That is, U.S. Pat. No. 4,417,17
In No. 1, the outer diameter of the rotor is extremely large, which not only increases the size of the entire X-ray tube, but also requires a high voltage to be applied to the central column, making it difficult to maintain it. In Japanese Patent Publication No. 5g-43860, the rotor and target have low rigidity, 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 (requiring a special high voltage power supply and high voltage cable).

[Problems with background technology]

However, the conventional X-ray tube as described above has the following drawbacks. That is, as mentioned above, the inner ring of the bearing 12.13 tends to get hot, but the outer ring J is at a low temperature, and the temperature at this point is between 60C and 550C, and the temperature of the inner ring of the bearing 12.13 is high. It changes depending on the rotation status of the wheel. ? -What happens when the temperature of the tube increases? - Not only is there insufficient clearance between the bearing ring and the inner and outer rings, but the lubricant existing between them evaporates, causing the bearing 12.
13 may be damaged. For these reasons, there is a drawback that rotational stoppage accidents tend to occur frequently. In order to prevent this, increasing the degree of blackening of the target 4, increasing the degree of blackening of the surface of the rotor 6, and installing a heat shield plate between the target 4 and the rotor 6 have been considered, but these effects are Relatively few;
The actual situation is that the input to target 4/4 watts is too small.

Furthermore, when this structure is rotated at high speed, the rotational life becomes extremely poor. Increasing the heat capacity of the target 4 increases the weight of the target 4, which further shortens the rotational life. In order to eliminate these problems, a rotating anode type X-ray tube using a magnetic bearing has been developed as described in US Patent Specification 4.
417,171, Japanese Patent Publication No. 58-43860, and Japanese Patent Publication No. 59-63646.

However, each of these has drawbacks as described above.

[Purpose of the invention]

The purpose of this invention is to rotatably support a large-capacity X-ray generation target using a magnetic bearing without contact, maintain the rigidity of the magnetic bearing sufficiently high, and increase the rigidity of the rotating part to achieve a resonance frequency. It makes high-speed rotation with low vibration possible, extremely long rotation life, and also makes the target a positive high voltage, the cathode a negative high voltage, and virtually protects the rotor and stator of the vacuum vessel and magnetic bearing. A rotating anode type X-ray tube that significantly improves reliability by keeping it at ground potential, making the magnetic gear lug smaller and increasing its rigidity, and preventing noise from entering the position sensor that detects the displacement of the rotor. The goal is to provide the following.

[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 the insulator via this insulator.
The rotor for magnetic bearings is electrically insulated by the portion of the insulating material that separates the rotor for magnetic bearings, and the rotor for magnetic bearings is maintained at substantially ground potential. It is configured to supply a positive high voltage to the target from outside the tube through a conductive path provided through the tube.A negative high voltage can be applied to the cathode, and the conventional rotating It can be used with the same high-voltage power supply with the same neutral point grounding as anode-type X-ray tubes, has the same weight and external dimensions as conventional X-ray tubes, and can target large-capacity targets at ultra-high speeds. It is a rotating anode type X-ray tube device that can be rotated, has an extremely long life, and has low vibration and noise.

[Embodiments of the invention]

The rotating anode type X-ray 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 1, which is a vacuum container, is made of metal and is maintained at ground potential. The housing 1 includes a heat absorbing container portion 101 that absorbs heat from the anode 4 for generating X-rays, a vacuum partition 102 in the magnetic bearing,
103, vacuum partitions 104 and 105 within the position sensor,
Auxiliary bearing support plates 106, 107 and end insulating container 108
, 109. Housing J like this
The above-mentioned parts form a vacuum container as described above, and the inside of the container is kept at a high vacuum.

Radial magnetic bearing stators 110 and 111 that generate an attractive force in the radial direction are provided outside the vacuum partition walls 102 and 103 within the magnetic bearings. 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 of these stators is a magnetic bearing rotor 1.
14 and 115 are arranged. This J magnetic bearing rotor LL4.115 is made of a magnetic material such as pure iron, and has laminated plates 116, 111 made of magnetic material on its outer periphery.
A suction force is generated between the laminated plates 116, 117 and the radial magnetic bearing stators 110, 111 to form a radial magnetic bearing.

Furthermore, the ends of the magnetic bearing rotors 114 and 115 are provided with heat-resistant metals 218 and 119, for example, low-temperature operating cathodes 120 and 121 such as barium imbre cathode.
are attached to form current-carrying diodes 124 and 125 with diode anodes 122 and 123. Furthermore, a fixed cathode 126.12'l is provided on the outside thereof, and a current-carrying diode 128 having a characteristic opposite to that of the current-carrying diode 124, 125 is provided between the fixed cathode 126.12'l and a part of the rotating heat-resistant metal 118.119.

129 is formed. By means of these diodes, both the magnetic bearing rotors 114 and 115 are maintained at substantially ground potential, and are substantially at the same potential as the vacuum partitions 102 and 103 within the magnetic bearings. Therefore, the distance between them can be kept small within O, SW, and the distance between the stators 110, 111 for radial magnetic bearings and the rotors 114, 115 for magnetic bearings can be reduced to within IW.゛. As a result, bearing rigidity can be extremely increased.

Further, on the outer periphery of the magnetic bearing rotors 114 and 115, a metal ring 130 is provided following the laminated plates 116 and 117.
, 131 are fixedly attached thereto, and a copper ring 132 and a non-magnetic ring 133 are fixedly attached to the outer periphery of one rotor 115 following the metal ring 131. A stator 134 for rotating the rotor is provided on the outside of the steel ring 132, and these form an induction motor to rotate the rotor at high speed. On the outside of the metal ring 130 and non-magnetic ring 133.

Fradial sensors 135 and 136 are provided via rings 104 and 105, respectively, and the magnetic bearing roller 1
14,115 deviations are detected.

Furthermore, a penetrating electrical insulator 137 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 137-1 of the electric insulator 137 on the TAG4 side. Experiments have shown that this joining can be achieved by brazing or the like.

And this metal plate 13 & IC has an anode terminal (4) for generating X-rays? It is mechanically and tightly fixed by a bolt 139.

The end of the magnetic bearing rotor 114 and the metal plate 13
8, a withstand voltage part 137-b is formed in which the diameter of the electrical insulator 137 is larger than that of other parts.
4 and the high withstand voltage of the magnetic bearing roller 114 (e.g. 80
kV or higher). In this case, the electrical insulator 13
The withstand voltage portion 137-b of No. 7 has a roughened surface to increase the creepage distance.

A conductive path 140 is provided in the center of the electrical insulator 137, and is connected to the target via a conductor 141 attached to the end face of the electrical insulator 137 on the target 4 side by metallization or the like. electrically coupled to. A heat-resistant metal 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 heat-resistant metal 142. heated to high temperatures. Above heater 1
44 is supplied with a high voltage (e.g. 75 kV) from outside the tube during operation.
) is applied, heated as described above, and is electrically coupled with low impedance due to the inflow of thermoelectrons from the cathode 143. Therefore, high voltage can be supplied to the terminal (4) from outside the tube without contact.

Also in a part of the inside of the other magnetic bearing rotor 115,
The electric insulator 145 is inserted and fixed by shrink fitting or the like, and similarly to the above, the target mounting metal plate 138 and the rotor 115 have a high withstand voltage (for example, 80 kV) K is maintained.

As described above, the rotor 115 is kept at the ground potential, and the terminal 4 is kept at a positive high voltage. Note that the withstand voltage portion 145-* is provided with an uneven portion to increase the creepage distance.

In addition, a negative high voltage (
e.g. -75 kV) and thermionic electrons are kept at a positive high voltage (e.g. +75 kV).
4 and generates X-rays 146. The X-rays 146 are irradiated to the outside of the tube through an X-ray emission window 147 made of, for example, beryllium and attached to the heat-absorbing container section 101. In addition, secondary electrons (not shown) emitted from the electrical insulators 137, 145 are shielded by shielding plates 148, 149 provided inside the tube, and the withstand voltage portions J, ? 7-b
, 145-aK is prevented from flying into the air.

Further, auxiliary bearings 150, 151 are provided on the outer sides of the ends of the rotors 114, 115, respectively, on support plates 106, 1.
It is strongly supported by 01. rotor 114,
When rotor 115 is operating normally, rotor 114
, 115, but the rotating part is supported by these auxiliary earrings 150, 151 before operation or in case of abnormal operation.

Further, a position sensor 152 is attached to the end of the rotor 115 to detect deviation in the thrust direction, and its output is used to control the stators 112, 11 for syst thrust magnetic bearings.
3 to control the position in the thrust direction.

Note that it is preferable to use ceramics such as silicon nitride (for example, 81.N4) as the material for the electrical insulators 137 and 145 because the mechanical strength increases.

[Modified example of the invention]

In the above embodiment, a non-contact current path is used to maintain the rotors 114, 115 at substantially ground potential, but one or both of them may be in mechanical contact.

Similarly, the non-contact conductive parts 143 and 144 for supplying voltage from outside the target 41C may be changed to a conductive mechanism using mechanical contact.

Furthermore, although the rotor 114 (or 115) and the insulator 137 (or 145) are bonded over the entire surface, it goes without saying that the bonding surface may be limited to only a portion.

In addition, in the above embodiment, the magnetic bearing stator 4 is supported on both sides, but the stator 111 for the magnetic bearing is moved to the 110 side,
Of course, a so-called cantilevered structure may also be used.

Next, another modification will be explained using FIG.
The same parts as in Figure 1 are given the same symbols.

That is, if the electrical insulators 137 and 145 are made columnar and the voltage-withstanding portions 137-b and 145-h are made to have a high voltage by increasing the creeping distance, the same effect as in the above embodiment can be obtained. Furthermore, it goes without saying that the creepage distance may be increased by providing uneven portions in the voltage withstanding portions 1st-b and x4s-mVc.

Alternatively, a conventional mechanical bearing may be used for the bearing portion.

〔Effect of the invention〕

According to this invention, the following excellent effects can be obtained.

In other words, since the rotating body is completely non-contact, 3(b)00r
It is possible to rotate at extremely high speeds of about 100 pm, and the peak input value of the X-ray tube can be increased to about 1.7 compared to conventional tubes. Furthermore, since the rotating body is completely non-contact, it is possible to provide an X-ray tube with low vibration and low noise, and since no mechanical sol 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.

In other words, since a conventional X-ray tube power source can be used, the rotating anode X-ray tube of the present invention can be used in a conventional X-ray generator.

In addition, since the rotors 114 and 115 are substantially at ground potential, the magnetic gap of the magnetic bearing can be made small and strong rigidity can be obtained.
) 4 to high speed (e.g. 30.00 Orpm)
), it is possible to provide a JX-ray tube with an extremely large capacity (for example, 6 MHU). 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, an inexpensive X-ray tube with a conductive duct can be provided.

[BRIEF DESCRIPTION OF THE DRAWINGS] 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 modification of the invention.
FIG. 3 is a sectional view showing a conventional rotating anode type X-ray tube. 1...Housing! ...Anode target, 11o
. 111... Stator for radial magnetic bearing, 112°1
13...Stator for thrust magnetic bearing, 114°11
5... Rotor for magnetic bearing, 120, 121... Cathode, 137, 145... Electrical insulator. Applicant's agent Patent attorney Takehiko SuzueN3

Claims (9)

[Claims] (1) having at least one cathode, a rotatable X-ray generating anode target provided opposite to the cathode, and a bearing portion rotatably supporting the anode target;
A rotating anode X-ray tube device, characterized in that a bearing rotor constituting the bearing portion and the anode target are mechanically attached via an electrical insulator. (2) The bearing part is a magnetic bearing that magnetically supports the anode target in a non-contact manner, and a part of the electrical insulator is coaxially inserted and fixed into the rotor part for this magnetic bearing, and the electrical insulator is The outer end portion of the magnetic bearing rotor has a larger outer diameter than the insertion portion, and the anode target is machined on the side opposite to the magnetic bearing rotor with respect to the larger outer diameter portion. A rotary anode type X-ray tube device according to claim 1, which is fixed in aspect. (3) A rotating anode type X-ray tube device according to claim 1 or 2, wherein the electrical insulator is a silicon nitride ceramic. (4) A rotating anode type X-ray according to claim 2, wherein an uneven portion is provided in an intermediate portion between the magnetic bearing rotor and the anode target of the electrical insulator to increase the creeping distance between the two. tube device. (5) A conductive path passing through the center of the electrical insulator is provided, and a high voltage is supplied from the outer end of the electrical insulator to the anode target through the conductive path to drive the magnetic bearing rotor. The rotating anode type X-ray tube device according to claim 2, wherein the rotating anode type X-ray tube device is set to a ground potential. (6) Magnetic bearings are provided at both ends of the anode target via the electrical insulator, each rotor is maintained at ground potential, and the magnetic bearing is provided by penetrating the central part of the electrical insulator that passes through at least one of the rotors. Claim 2: Supplying high voltage to the anode target from outside the tube through the conductive path
Rotating anode type X-ray tube device as described in . (7) The rotating anode type X-ray tube device according to claim 2, wherein the outer peripheral portion of the magnetic bearing rotor has a laminated structure. (8) A claim that includes a vacuum wall made of a non-magnetic thin plate between the magnetic bearing rotor and the stator, the magnetic bearing rotor side being kept in a high vacuum, and the magnetic gap set to 4 mm or less. 2. The rotating anode X-ray tube device according to item 2. (9) The method according to any one of claims 1 to 8, wherein a metal is bonded to the anode target side of the electrical insulator, and the anode target is mechanically fixed to the metal. Rotating anode type X-ray tube device.