JPH05299192A - X-ray generating device, x-ray diagnostic device, and x-ray ct device - Google Patents

Abstract

PURPOSE:To provide X-rays having a short rising time and little power consumption, reduce the ablation of a bearing portion due to heating, and reduce the maintenance work. CONSTITUTION:Three-phase power is fed to three-phase coils 10 of a three-phase motor section 11 to rotate a target 1. A current from a filament electrode 4 is fed to a filament 5 for heating. When negative high voltage is applied to a cathode electrode 3 and positive high voltage is applied to an anode electrode, electrons emitted from the filament 5 are accelerated and collide with the focal point portion of the target 1 to generate X-rays. The X-rays are radiated from an X-ray radiation port 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor for rotating a target of an X-ray generator, a controller for rotating the motor, an X-ray diagnostic apparatus and an X-ray CT apparatus using the X-ray generator.

[0002]

2. Description of the Related Art X-rays can be generated by causing electrons accelerated at high speed to collide with a substance. In reality, electrons are emitted from a cathode (filament) provided in a vacuum tube, accelerated at a high voltage and collided with an anode (target) to generate X-rays.

In such an X-ray generator, the kinetic energy of electrons striking the target is converted into X-rays at 1% or less, and most of them are converted into heat.
Therefore, the target becomes extremely hot. In particular, when the X-ray output is increased, the target temperature rises significantly,
There was a problem that the target melted.

Therefore, as a means for solving such a problem, a disk-shaped target is rotated by a motor,
There is a method in which accelerated electrons collide with the vicinity of the outer circumference of the rotating disk-shaped target. By rotating the target in this way, the area in which the electrons collide is substantially increased, so that it becomes possible to withstand a momentary heavy load with a small focus.

In the X-ray generator that rotates the target in this way, the area in which the electrons collide can be substantially increased by increasing the radius of the target. The output of the generator can be increased.

[0006]

FIG. 5 is a circuit diagram of a capacitor motor used in a conventional X-ray generator.

The capacitor motor section 22 includes a main winding 21.
And the auxiliary winding 20. Single-phase AC power is supplied from the single-phase power supply 18 to the main winding 21. A single-phase power supply 18 and a capacitor 19 are connected in series to the auxiliary winding 20, and single-phase power having a phase different from that of the main winding 21 is supplied. As a result, a rotational force is generated in the condenser motor unit 22 to rotate the target.

If the rotation speed of the target is low, the generated heat may not be well dispersed and a part of the target may momentarily become high temperature and melt. Therefore, until the rotation speed of the target exceeds the specified rotation speed, X Cannot generate lines. The time required for the target to reach the specified rotation speed from the stationary state is called the rise time, and the rise time should be as short as possible.

However, the conventionally used capacitor motor section has the advantage that it can be rotated by a single-phase AC power source, but on the other hand, it has the problem of poor efficiency and a long rise time. In particular, as the output of the X-ray generator has been increased, the size of the target has been increased, and thus the rise time until the target reaches the specified rotation speed has been further increased.

Such an X-ray generator irradiates an object with X-rays and displays a projected image of the object, or an X-ray diagnostic apparatus that irradiates the object with X-rays and uses the projection data to determine the inside of the object. It is used in an X-ray CT apparatus that obtains a tomographic image. As a result, the rise time is long and the diagnosis time is long, resulting in greater mental distress to the subject. In addition, the throughput of the apparatus is lowered due to the long diagnosis time for one person.

In order to shorten the rise time, it is sufficient to increase the capacity of the motor section and rotate the target, but generally the efficiency of the condenser motor is not so high. Therefore, if the capacity of the condenser motor section is increased,
The heat generated from the condenser motor increases, and this heat accelerates the deterioration of the bearing that supports the target.
There is a problem that the life of the X-ray generator is shortened. Therefore, it is an object of the present invention to provide an X-ray generator having a long service life by shortening the rise time and reducing heat generation from the motor section.

[0012]

In order to solve the above-mentioned problems, the present invention provides an electron emission means for emitting electrons, an electron acceleration means for accelerating the electrons emitted from the electron emission means, and the electron An X-ray generator comprising: a target that generates X-rays by colliding electrons accelerated by an accelerating unit; and a rotating unit that rotates the target using three-phase power. ..

[0013]

The electrons emitted from the electron emitting means are accelerated by the electron accelerating means and collided with the rotating target by the rotating means using three-phase electric power to generate X-rays.
As described above, by using the rotating means using the three-phase power, the rise time of the device can be shortened, and at the same time, the power consumption can be reduced.

[0014]

1 is a sectional view of an X-ray generator according to the present invention. The target 1 is a disk made of a heat-resistant conductive material such as tungsten.

The three-phase motor unit 11 is composed of the rotor 7 and the three-phase coil 10 and generates a rotational force for rotating the target 1. The target 1 is supported by the rotor 7 of the three-phase motor unit 11, and is rotated by rotating the rotor 7. The rotor 7 is made of a conductive material such as iron or aluminum in a cylindrical shape, and has a shaft for supporting the target 1 at one end. Rotor 7
Is attached to the anode electrode 9 via a bearing 8 so that it can freely rotate.
The three-phase coil 10 generates a rotating magnetic field by the three-phase power supplied from the three-phase power supply 12. When this rotating magnetic field is applied to the cylindrical portion of the rotor 7, a rotating force is generated by the electromagnetic induction phenomenon and the rotor 7 rotates. The outer atmosphere 2 covers the target 1, the filament 5, the rotor 7, and the bearing 8 and keeps the inside vacuum. Filament 5
It is heated by the electric current supplied from the filament electrode 4 so that electrons are easily emitted.

The cathode electrode 3 is electrically connected to the filament 5 and supplies the filament 5 with the high voltage supplied to the cathode electrode 3. The anode electrode 9 is electrically connected to the target 1, and the anode electrode 9
Is supplied to the target 1.

At this time, when a negative high voltage is applied to the cathode electrode 3 and a positive high voltage is applied to the anode electrode, the filament 5 is charged to a negative voltage and the target 1 is charged to a positive voltage. As a result, an electric field is generated between the target 1 and the filament 5. This electric field causes the filament 5
The electrons emitted from the electron beam are accelerated and collide with the focal portion of the target 1 to generate X-rays. This X-ray is emitted from the X-ray irradiation port 6. Next, the three-phase coil 10 of the X-ray generator according to the present invention will be described. FIG. 2 shows a circuit diagram of the three-phase coil 10.

The three-phase coil 10 is formed by connecting one end of each of the three coils 13 in common and connecting them in a Y-shape. At this time, when a three-phase power supply is applied to the other end of each coil, the three-phase coil 10 generates a rotating magnetic field to rotate the rotor 7.

As described above, the three-phase motor section that generates the rotational force using the three-phase power source converts the electric power into the rotational force more efficiently than the conventional condenser motor section that generates the rotational force using the single-phase power source. be able to.

Table 1 shows an example of actual measurement of power and rise time during steady rotation in the X-ray generator having the three-phase motor section 11 and the X-ray generator having the condenser motor section.

[0021]

[Table 1]

The power at the time of steady rotation in Table 1 represents how much power should be supplied in order to continue rotating the target 1 at the specified rotation speed. The rising time in Table 1 shows the rising time when a voltage of 200 V was applied to the motor unit whose electric power was measured during steady rotation.

In order to maintain the specified number of revolutions in the condenser motor unit 22, it is necessary to supply electric power of 250 W at a voltage of 60 V, whereas the three-phase motor unit 11 is 40 V.
If the power of 100 W is supplied with the voltage of, the specified rotation speed can be maintained. A part of the supplied electric power is converted into kinetic energy for rotating the target 1, and the rest is released as heat.

Since the kinetic energy required for continuing to rotate the target 1 is almost equal in the X-ray generator having the three-phase motor unit 12 and the X-ray generator having the condenser motor unit 22, it is supplied to the motor unit. The motor with a large amount of electricity generates more heat. From this, it can be seen that in the actual measurement example of Table 1, the three-phase motor unit 11 generates less than half the heat of the capacitor motor unit. Since this heat generation shortens the life of the bearing 8 of the X-ray generator, it is better to minimize it.

Since the three-phase motor section 12 generates less heat than the conventional condenser motor section 22, the life of the bearing 8 can be extended, and the maintenance work of the apparatus can be reduced. In terms of heat generation,
The three-phase motor unit 11 is extremely superior to the condenser motor unit 22. At the same time, since the power consumption during steady rotation can be greatly reduced, the running cost for operating the X-ray generator for a long time can be reduced. Further, since the rising time is half the time of the conventional condenser motor, it is possible to shorten the time from the driving of the device to the start of X-ray irradiation.

Thus, the X having the three-phase motor section 11
The X-ray generator is superior to the X-ray generator having the conventional condenser motor unit 22 in terms of heat generation, power consumption, and rise time. Next, a method of controlling the rotation speed of the three-phase motor unit 11 will be described. FIG. 3 is a circuit configuration diagram of a rotation control unit that controls the rotation speed of the three-phase motor unit 11 by switching the voltage.

When the target 1 is stopped and the prescribed number of revolutions is reached, the changeover switch 15 is turned on to the side a, and a voltage of, for example, 200 V is applied to the three-phase coil 10 to reach the prescribed number of revolutions. After that, the changeover switch 15 is changed over to the b side and lowered by the transformer 14, for example, 40V.
The voltage of 3 is applied to the three-phase coil 10 for use.

In this way, a high voltage is initially applied to the three-phase coil 10
It is possible to shorten the time required to reach the specified rotation speed by applying the voltage to the engine to start the rotation. Further, after reaching the specified number of revolutions, the voltage can be lowered to reduce unnecessary power consumption and at the same time reduce heat generation from the three-phase motor unit 12. In addition, by lowering the applied voltage, it is possible to prevent the number of rotations of the three-phase motor unit 12 from increasing more than necessary. If the number of rotations of the three-phase motor unit 12 becomes higher than necessary, the load on the bearing 8 will increase and the life of the bearing 8 will be shortened. Therefore, switching the voltage to prevent the number of rotations from increasing more than necessary. This has the effect of reducing the maintenance work of the device.

Such voltage switching may be carried out by manually switching the changeover switch 13, or a three-phase motor unit 12 may be provided with a rotation speed detector so that the voltage automatically changes when a predetermined rotation speed is reached. You may switch to. Also,
After the change-over switch 13 is turned to the a side, it may be automatically switched to the b side after a certain time has elapsed.

Further, as a method for finely controlling the rotation speed, a method of changing only the frequency of the three-phase power source applied to the three-phase coil 10 by the inverter circuit 16 as in the rotation speed control section shown in the circuit configuration diagram of FIG. Alternatively, there is a method of changing the frequency and the voltage. X-ray irradiation level setting device 1 in FIG.
Reference numeral 7 is a device for setting the intensity of the generated X-rays.

The inverter circuit 16 changes the frequency and voltage of the three-phase power source steplessly based on the X-ray irradiation level set by the X-ray irradiation level setter 17. By applying the output from the inverter circuit 16 to the three-phase coil 10, the rotation speed of the target 1 can be changed in accordance with the X-ray irradiation level.

When the X-ray output is large, the target 1 is rotated at a high speed so as not to melt the target 1, and when the X-ray output is small, the rotation speed is low in terms of power consumption and device life. It is desirable to rotate with.
Therefore, when the X-ray output is large, the frequency and voltage of the three-phase power supply output from the inverter circuit 16 are increased, and when the X-ray output is small, the three-phase power output from the inverter circuit 16 is output. Lower the frequency and voltage of the power supply.
Thereby, the rotation speed of the target 1 can be rotated at high speed when the output of X-ray is large, and can be rotated at a low rotation speed when the output of X-ray is small, and the rotation of the target 1 can be efficiently controlled. ..

When the conventional capacitor motor is applied with a voltage whose frequency and voltage are changed by an inverter circuit to control the rotation speed, it is necessary to change the capacity of the capacitor 20 according to the output frequency of the inverter circuit. It was difficult to control the rotation speed steplessly. However, in the X-ray generator having the three-phase motor unit of the present invention, since it is not necessary to use a capacitor, the rotation speed can be easily controlled.

By using the X-ray generator described above in an X-ray diagnostic apparatus or an X-ray CT apparatus, the time required for X-ray diagnostic imaging or tomographic imaging can be shortened, and the subject can be examined. You can reduce the emotional distress you give. At the same time, the throughput of these devices can be increased. Further, since the heat generation is small, the consumption of the X-ray generator part can be reduced, and the cost and time required for maintenance can be reduced. Further, since the power consumption is low, the running cost of the device can be reduced.

It is needless to say that the present invention is not limited to the above-mentioned embodiments, but can be variously modified without departing from the spirit of the present invention. For example, although the three coils are connected in a Y shape in the above embodiment, the connection may be made by a Δ connection in which the three coils are connected in a Δ shape.

[0036]

As described above in detail, according to the present invention, it is possible to provide an X-ray generator having a short rise time and low power consumption. Further, it is possible to reduce heat generation from the motor section and prolong the life of the X-ray generator. Further, since the rotation of the motor unit is easily controlled, the power consumption can be reduced and the life of the X-ray generator can be extended.

[Brief description of drawings]

FIG. 1 is a sectional view of an X-ray generator according to the present invention.

FIG. 2 is a circuit diagram of a three-phase motor unit of the X-ray generator according to the present invention.

FIG. 3 is a circuit configuration diagram showing an embodiment of a rotation speed control unit.

FIG. 4 is a circuit configuration diagram showing an embodiment of a rotation speed control unit.

FIG. 5 is a circuit diagram of a conventionally used capacitor motor unit.

[Explanation of symbols]

 1 Target 2 Surrounding Air 3 Cathode Electrode 4 Filament Electrode 5 Filament 6 X-Ray Irradiation Port 7 Rotor 8 Bearing 9 Anode Electrode 10 Three-Phase Coil 11 Three-Phase Motor Section 12 Three-Phase Power 13 Coil 14 Transformer 15 Change Switch 16 Inverter Circuit 17 X-ray irradiation level setting device 18 Single-phase power supply 19 Capacitor 20 Auxiliary winding 21 Main winding

Claims (5)

[Claims] 1. X-rays are produced by colliding electrons accelerated by the electron emission means, electron acceleration means for accelerating the electrons emitted from the electron emission means, and electrons accelerated by the electron acceleration means. A target to be generated, and a rotating means for rotating the target using three-phase power,
An X-ray generator comprising: 2. The X-ray generator according to claim 1, further comprising voltage control means for changing the voltage of the three-phase power. 3. The X-ray generator according to claim 1, further comprising frequency conversion means for changing the frequency of the three-phase power. 4. An X-ray diagnostic apparatus comprising the X-ray generator according to claim 1. 5. An X-ray CT apparatus comprising the X-ray generator according to any one of claims 1 to 3.