JPH06168667A - X-ray tube ageing method and device - Google Patents

Abstract

PURPOSE:To provide a highly accurate and stable X-ray tube ageing method and a device by which ageing electric power is not changed substantially even if the ageing electric power composed of a tube electric current and tube voltage is changed into plural setting steps. CONSTITUTION:A tube voltage and a tube electric current 7 impressed actually upon an X-ray tube are fed back, and a preset value of a coil ratio of the primary side to the secondary side of a primary side variable transformer 10 of a high voltage transformer 9 is selected in the optimum preset value A as a parameter according to a correcting characteristic by a computer. Thereby, substantially unchanged and preset plural step ageing can be carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for aging an X-ray tube, and more particularly to setting the aging power thereof.

[0002]

2. Description of the Related Art An X-ray tube usually has at least a cathode filament and an anode facing the cathode filament. For example, in a rotary anode type X-ray tube, an electric power is actually applied to the X-ray tube so that a focus trajectory is obtained. An aging process is performed for the purpose of melting foreign matter such as protrusions on the surface and smoothing it to enhance high voltage withstand characteristics. These aging steps are usually performed after exhausting the X-ray tube and tipping it off.

In the aging process of such an X-ray tube, it is necessary to keep the electric power applied to the tube constant. That is, the aging power referred to here is the product of the tube voltage set so that the anode becomes positive with respect to the cathode filament and the tube current that reaches the anode from the cathode filament by this tube voltage.

The conventional aging method for an X-ray tube uses feedback control as shown in FIG. 6 in order to maintain one tube current at a certain set value. In FIG. 6, an AC voltage 1 is applied to the cathode filament 4 to heat the cathode filament 4. On the other hand, a high voltage transformer 9 connected between the anode 8 and the cathode filament 4 applies a tube voltage having a positive side to the anode side, and the thermoelectron flow emitted from the heated cathode filament 4 is a positive high voltage anode voltage. Flows to the side and forms a tube current 16. The tube current 16 is converted into a voltage signal 18 by the feedback shunt 17 and input to the current regulator 30. The current regulator 30 uses this voltage signal 1
The thyristor unit 2 adjusts the cathode filament so that 8 becomes constant. Here, the tube voltage is set by the variable transformer 10 on the primary side of the high voltage transformer 9, but it is independent of the tube current.

[0005]

In the conventional aging process of an X-ray tube, the tube current is fed back and the filament current is controlled to stabilize the aging power, in order to stabilize the aging power. However, one tube voltage keeps the setting of the variable transformer on the primary side of the high-voltage transformer constant, but the tube voltage actually generated when the setting of the tube current becomes large is due to the internal impedance of the cable and variable transformer. The value drops below the set value. It is also affected by power fluctuations. Therefore, the aging power, which is the product of the tube current and the tube voltage, becomes indefinite, resulting in unstable aging.

The present invention has been made in view of the above circumstances, and the tube voltage is fed back together with the tube current, and the variable transformer on the primary side of the high-voltage transformer is controlled based on these values to achieve high accuracy. The purpose is to perform extremely stable aging of X-ray tubes.

[0007]

The present invention provides a high-voltage transformer having at least a cathode filament and an anode facing the cathode filament, the output voltage of which is determined by the number of primary windings and the number of secondary windings. A method for aging an X-ray tube, in which a tube voltage set so that the anode is positive with respect to the cathode filament through the cathode filament and a tube current reaching the anode from the cathode filament by the tube voltage are changed in a plurality of steps. In, in each of the plurality of steps, the winding ratio of the variable transformer on the primary side of the high voltage transformer is selected in accordance with the tube current and the tube voltage,
An aging method for an X-ray tube, characterized in that an aging power composed of a product of the tube current and the tube voltage can be selected in each of a plurality of steps, and a cathode filament and an anode facing the cathode filament. A tube voltage set so that the anode is positive with respect to the cathode filament and a tube current that reaches the anode from the cathode filament by the tube voltage. In an aging device for an X-ray tube that is correspondingly aged, a shunt that extracts a tube current signal proportional to the tube current, a high resistance that steps down the tube voltage and generates a tube voltage signal, the tube current signal, and the tube current signal A memory function for storing the peak value of the voltage signal, the tube current peak value as the tube current set value, and the tube voltage pin A computer having a comparator function for respectively comparing the tube value with a tube voltage set value, and a function for calculating an optimum filament current operation amount and a high voltage generation amount based on the result of the comparison of the tube current and the tube voltage, Aging of an X-ray tube comprising a thyristor unit that actually changes the filament current according to the new filament current operation amount, and an automatic variable transformer that actually operates the input voltage of the high voltage transformer according to the new high voltage generation amount. It is a device.

[0008]

According to the present invention, in order to keep the aging power, which is the product of the tube current and the tube voltage, constant, the fluctuation from the set value of the tube voltage due to the step change of the tube current is fed back, and the correction obtained thereby is obtained. By selecting the set value of the winding ratio of the variable transformer on the primary side of the high voltage transformer by the value, it is possible to stabilize the aging power corresponding to the tube current and the tube voltage in a plurality of steps.

[0009]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, an AC power supply 1 is connected to a thyristor unit 2,
The output of the transformer 3 is connected to the cathode filament 4 of the X-ray tube. On the other hand, a high voltage transformer 9 is connected to the middle point of the transformer 8 and the anode 8 of the X-ray tube. High voltage transformer 1 of 9
AC power supply 11, variable transformer 10 and switch 1 on the next side
2 is connected, and the variable transformer 10 can be selected by changing the set value A depending on the winding ratio of the primary side and the secondary side by the motor 19.

The tube current 16 is converted into a tube current signal 18 by the shunt 17, and the filament current 5 is converted into a filament current signal 7 by the current transformer 6. The output voltage of the high voltage transformer 9 is divided by the high resistance 13 and the low resistance 14 and converted as a tube voltage signal 15. Converted filament current signal 7 and tube current signal 1
8 and the tube voltage signal 15 are A / D converters 20 and 2, respectively.
Converted into a digital signal at 1 and 22 and computer 2
6 is input. From the computer 26, D /
The variable transformer control signal 28 is output through the A converter 24 and the motor driver 27.

The circuit shown in FIG. 1 can be represented by the equivalent circuit shown in FIG. In FIG. 2, R1, R2 and R3
Is the resistance of each power transmission line. The voltage supplied to this circuit is E1, and the primary side voltage of the variable transformer 10 is E
2. Similarly, the secondary side voltage is E3, and the high voltage transformer 1 is 1.
The secondary voltage is E4, the secondary voltage is E5, the voltage applied to the anode 8 and the cathode 4 is Ep, and the current flowing in each circuit is I.
1, I2 and Ip, and the winding ratios of the primary side and the secondary side of the variable transformer 10 and the high voltage transformer 9 are 1: respectively.
By setting A and 1: B, the following equation can be derived.

I2 = BIp I1 = AI1 = ABIp E2 = E1-R1I1 E3 = AE2 = AE1-AR1I1 = AE1-AABR1Ip = A (E1-ABR1Ip) E4 = E3-R2I2 = A (E1-ABR1Ip) -BI BE4 = AB (E1-ABR1Ip) -BBIpR2-R3Ip Ep = E5-R3Ip = AB (E1-ABR1Ip) -BBIpR2-R3Ip = ABE1- [BB (AAR1 + R2) + R3] Ip Furthermore, the respective parameter values are as follows. Set to.

E1 = 400 V B = 1000 [times] R1 = 1 [Ω], R2 = 1 [Ω], R3 = 1 [Ω]

At this time, FIG. 3 shows the Ep / Ip characteristic with the winding ratio setting value A of the variable transformer 10 as a parameter in the above equation. From FIG. 3, when the set value A of the variable transformer 10 is fixed, the tube voltage E increases when the tube current Ip increases.
It can be seen that p becomes smaller and the rate of decrease differs for each set value A. Therefore, when the tube current Ip increases, it is necessary to change the set value A of the variable transformer 10.

FIG. 4 shows that the tube voltage Ep is 100 KV and 15
When 0 KVk is kept constant, the relationship between the set value A of the variable transformer 10 and the tube current Ip is obtained from FIG. That is, when it is desired to keep the tube voltage Ep constant, it is necessary to set the set value A of the variable transformer 10 to the most suitable value by the motor 19 in accordance with the change of the tube current Ip as shown in FIG. is there.

On the other hand, the aging process that is actually carried out is carried out through a plurality of steps as shown in Table 1. This is because such a weak condition is set because the load on the X-ray tube cannot be increased at the start of aging, and the load is gradually increased at each step.

[0017]

[Table 1]

Therefore, when the steps as described above are performed, for example, as in steps 7 to 13, the tube voltage Ep is
Even if the settings are the same, the set value of the tube current Ip may be changed. In the case of conventional aging, the tube current Ip
When the set value of is changed, the tube voltage Ep fluctuates accordingly, which causes a problem that the aging power deviates from the predetermined set value. However, in the present invention, as described above, the tube voltage Ep actually applied to the X-ray tube is fed back, and the computer shown in FIG.
By selecting the most suitable setting value A of the variable transformer 10 according to the correction characteristic shown in (1), it becomes possible to execute aging in a plurality of steps as set substantially without fluctuation.

[0019]

As described above, according to the present invention, even if the tube current and the tube voltage of the aging power are changed in accordance with a plurality of steps in the aging process, the aging power is stable with substantially high accuracy. It is possible to always obtain the aging effect as set.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an aging device showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a high voltage circuit section of the circuit shown in FIG.

FIG. 3 is a characteristic diagram of tube voltage vs. tube current using the setting value of the variable transformer of FIG. 1 as a parameter.

FIG. 4 is a characteristic diagram of the set value of the variable transformer versus the tube current with the set value of the tube voltage of FIG. 3 as a parameter.

FIG. 5 is a circuit diagram of a conventional aging device.

[Explanation of symbols]

 7 ... Tube current 8 ... Anode 9 ... High voltage transformer 10 ... Variable transformer

Claims (2)

[Claims] 1. A cathode filament and an anode facing the cathode filament are provided at least, and the cathode filament is connected to the cathode filament through a high voltage transformer whose output voltage is determined by the number of primary windings and the number of secondary windings. In an aging method for an X-ray tube, the tube voltage set so that the anode is positive and the tube current reaching the anode from the cathode filament by the tube voltage are changed in a plurality of steps, respectively, in each of the plurality of steps. The winding ratio of the variable transformer on the primary side of the high-voltage transformer is selected according to the tube current and the tube voltage, and the aging power that is the product of the tube current and the tube voltage is selected in each of a plurality of steps. An aging method for an X-ray tube, which is characterized in that 2. A tube voltage including at least a cathode filament and an anode facing the cathode filament, a tube voltage set so that the anode is positive with respect to the cathode filament, and the tube voltage causes the cathode filament to move to the anode. In an aging device for an X-ray tube that is aged corresponding to a plurality of steps by the aging power that is a product of the reaching tube current, a shunt that extracts a tube current signal proportional to the tube current, and the tube voltage is stepped down. A high resistance for generating a tube voltage signal, a memory function for storing the tube current signal and a peak value of the tube voltage signal, a tube current peak value as a tube current set value, and the tube voltage peak value as a tube voltage set value. Comparing function to compare with each, and based on the result of the comparison of the tube current and tube voltage, the optimum filament current operation amount and A computer having a function of calculating the high voltage generation amount, a thyristor unit that actually changes the filament current by the new filament current operation amount, and an automatic operation that actually operates the input voltage of the high voltage transformer by the new high voltage generation amount. An aging device for an X-ray tube, which is equipped with a variable transformer.