JPH06223751A - Rotary anode x-ray tube device - Google Patents

Abstract

PURPOSE:To increase the number of filament in a rotary anode X-ray tube device in a simple constitution. CONSTITUTION:The common line COM of a cable 12 is connected to the current feeding terminals 11a of filaments 10a to 10d which are divided into two groups. The first select line SEL1 is connected to the current feeding ends 11b of the filaments 10a and 10b of the first group GR1 through rectifier elements 21a and 21b, while the second select line SEL2 is connected to the current feeding ends 11b of the filamrnts 10c and 10d of the second group GR2 through rectifier elements 21c and 21d. The cable 12 is connected to a DC power source 20 through the first switch 22 and the second switch 23. And the first switch 22 converts the current feeding into the first and the second select lines SEL1 and SEL2, while the second switch converts the polarity of the feeding current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary anode X-ray tube device mainly used in the medical field.

[0002]

As is well known, a rotary anode X-ray tube device is
The thermoelectrons emitted from the filament provided on the cathode are accelerated with a high voltage and collide with the surface of the target (rotary anode) that is rotationally driven to generate X-rays. The area where the thermoelectrons focused on the target surface collide is the so-called focal point. This focus is preferably set to a minimum size that can withstand the radiographic conditions in order to reduce geometric blurring of the X-ray image.

On the other hand, as the condition of X-ray irradiation, for example, X
The line intensity differs depending on the size of the subject, for example, the case of an adult and the case of a child, and also varies depending on the imaging site of the same subject. In order to increase the X-ray intensity, it is necessary to increase the value of the current flowing through the filament, so a filament of a size that can withstand this is used.

As described above, the conventional rotary anode X-ray tube is kept in a high vacuum because of the desire to make the focus as small as possible and the necessity of using a filament that can withstand the X-ray imaging conditions. Two filaments having different shapes are fixedly installed in the glass bulb, and these filaments are selectively used according to the photographing conditions.

This configuration will be described with reference to FIGS. 9 and 10. In FIG. 9, reference numeral 1 is a glass bulb that has been evacuated to vacuum, and inside the glass bulb 1, a cathode 2 that generates a thermoelectron A and a thermoelectron A that is emitted from the cathode 2 are received to emit an X-ray B. A target 3 that is a rotating anode that is generated and a motor rotor 4 that is connected to the target 3 are provided. The motor rotor 4 is rotated at high speed by a motor stator 5 arranged outside the glass bulb 1. The glass bulb 1, the motor stator 5 and the like are surrounded by a lead-lined casing 6 for shielding X-rays, and the generated X-rays B are emitted from a radiation window 7 provided in the casing 6 and are not shown. Emitted to the specimen.

The cathode 2 is, as shown in FIG.
Two filaments 10 (10a, 10
b) is provided. Each filament 10a, 10b
The three-core cable 1 is connected to the current supply terminal 11a on one side.
2 common lines COM are connected, and the filament 10
The first select line SEL1 of the cable 12 is connected to the current supply terminal 11b on the other side of a, and the second select line SEL2 of the cable 12 is connected to the current supply terminal 11b on the other side of the filament 10b. ing.

The current supplied from the AC power supply 13 is supplied to the common line COM and the first select line SEL.
1, or a changeover switch 14 for selectively energizing the common line COM and the second select line SEL2. The common line COM is always connected to the power supply 13, and by switching the connection between the terminal 14a in the switch 14 and the terminals 14b and 14c,
Power supply 13 and first select line SEL1 or second
The selection line SEL2 is switched to switch the current supply to the filaments 10a and 10b. This allows these filaments 10 to be used depending on the shooting conditions.
A and 10b are used properly.

The number of filaments 10 is determined according to the number of lines of the cable 12, but since the above-mentioned three-core cable 12 is generally used, the number of filaments is generally two in the conventional device. is there.

[0009]

However, the conventional example having such a structure has the following problems. That is, in the conventional device, the number of filaments 10 is 2 according to the number of select lines (two) of the cable 12 connecting the power source 13 and the filaments 10a and 10b.
However, since the X-ray imaging conditions are set to various values depending on the subject and the imaging region, the number (type) of filaments 10 should be as large as possible.

Therefore, three or more filaments 10 (1
0a to 10d) in the device, for example, as shown in FIG. 11, select lines SEL1 to SELn
It is sufficient to use the cables 12 'having an increased number of cables, but such a cable 12' must be specially manufactured, which causes a problem of high manufacturing cost.

Further, as shown in FIG. 12, a plurality of three-core cables 12 are used to make filaments 10 (10a-1a).
It is possible to increase the number of 0d), but in this case, there is a problem that the switch 15 for the current supplied to each cable 12 is required and the device becomes large.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a rotary anode X-ray tube device capable of increasing the number of filaments with a simple structure.

[0013]

The present invention has the following constitution in order to achieve such an object. That is, according to the present invention, a common cathode of a three-core cable including a common line, a first select line, and a second select line is provided with 3 to 4 thermionic emission filaments in a cathode arranged to face a rotating anode. One side of the current supply terminal of each filament is connected to the line, each filament is divided into two groups by one or two filaments, and the common line of the filaments belonging to the first group is not connected. For each current supply terminal,
According to the direction of the supplied current, the current supply to each filament of the first group is switched,
The first select line of the cable is connected to each current supply terminal on the side to which the common line of the filament belonging to the second group is not connected, according to the direction of the current supplied, The second select line of the cable is connected so that the current supply to each filament of the two groups is switched, and the DC power source is connected to the cable, and further, the common line of the cable and the first line. Or a first switch for selectively switching between a common line and a second select line to supply a current from the DC power supply, and the common line of the cable and the first select line, or A second switch that switches the polarity of the current supplied to the common line and the second select line A.

[0014]

The operation of the present invention is as follows. By selectively switching the current supplied from the DC power supply to the common line and the first select line or the common line and the second select line of the cable by the first switch, the first group An electric current is supplied to each of the filaments or the second filaments.

Further, by switching the polarity of the current supplied to the common line and the first select line of the cable, or the common line and the second select line by the second switch, it is possible to select which of the groups within each group. It is switched so that the filament is supplied with current.

That is, the combination of the switching of the first switch and the second switch is switched so that the current is supplied to any one of the three to four filaments.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a main part of a rotary anode X-ray tube device according to an embodiment of the present invention. In addition, FIG.
Since the parts denoted by the same reference numerals as those in FIG. 10 have the same configuration as the conventional example, detailed description thereof will be omitted here. FIG. 1 shows an example device in which four filaments 10a to 10d having different shapes are provided in the device and the current supplied to them is switched to selectively use each filament 10a to 10d.

As shown in FIG. 1, each filament 10a
The cable 12 for connecting the DC power supply 20 and the 10 d
It is a three-core cable that has been generally used in the past. Current supply terminal 1 on one side of each filament 10a to 10d
The common line COM of the three-core cable 12 is connected to 1a.

The filaments 10a to 10d are
Two filaments 10a and 10b and two filaments 10c and 10d are divided into two groups.

The filaments 10a, 10b belonging to the first group GR1 are supplied to the respective current supply terminals 11b on the side of the filaments 10a, 10b not connected to the common line COM, according to the direction of the current supplied thereto. 1
The first select line SEL1 of the cable 12 is arranged in opposite directions as shown in FIG. 1 so that the current supply to 0a and 10b can be switched.
It is connected via a and 21b.

Further, according to the direction of the current supplied to the current supply terminals 11b of the filaments 10c and 10d belonging to the second group GR2 on the side to which the common line COM is not connected, according to the direction of the current supplied to the second group GR2. The second select line SEL2 of the cable 12 is arranged so that the current supply to the filaments 10c and 10d can be switched.
As shown in FIG. 1, they are connected via rectifying elements 21c and 21d arranged in opposite directions.

On the other hand, the DC power source 20 is connected to the cable 12,
It is connected via the first switch 22 and the second switch 23.

The first switch 22 is a switch for selectively supplying current to the common line COM and the first select line SEL1 of the cable 12 or the common line COM and the second select line SEL2. Yes, the changeover switch 1 that has been commonly used from the past
4 (see FIG. 10). That is, the common line COM is always connected to the line L1 connected to the DC power source 20, and the line connected to the DC power source 20 by switching the connection between the terminal 22a and the terminals 22b and 22c in the switch 22. L2,
The first and second select lines SEL1 of the cable 12,
Switch to SEL2.

The second switch 23 is connected to the cable 1
2 common lines COM and 1st select line SEL
1 or a switch for switching the polarity of the current supplied to the common line COM and the second select line SEL2. That is, the terminal 23a in the switch 23 connected to the “+” side of the DC power source 20, and the terminal 23
c, 23d, the terminal 23b connected to the "-" side of the DC power source 20, and the connection with the terminals 23e, 23f are simultaneously switched to set the polarities ("+") of the lines L1, L2.
"-").

With this structure, the filaments 10a to 10d can be switched as follows. First, with the second switch 23, the terminal 23
By switching so that a is connected to the terminal 23c and the terminal 23b is connected to the terminal 23e, the line L1 becomes "-" and the line L2 becomes "+". Then, the first switch 22
By switching the connection between the terminal 22a and the terminal 22b, the "-" line L1 is connected to the common line COM of the cable 12, and the "+" line L2 is the first select line SEL1 of the cable 12. Connected with. As a result, the common line COM is "-", and the first
The current from the DC power supply 20 flows to the first group GR1 side with the select line SEL1 of "+". The current supplied in this manner flows through the rectifying element 21a side connected in the forward direction toward the filament side, so that the current is supplied only to the filament 10a.

Further, in the above-mentioned state, the connection of the second switch 23 is made by connecting the terminal 23a and the terminal 23d and the terminal 23b and the terminal 2.
If switched to 3f, the common line COM is "+",
When the first select line SEL1 is "-",
Current from the DC power source 20 flows to the group GR1 side of
Since the current flows through the rectifying element 21b side connected in the opposite direction toward the filament side, the filament 10
The current is supplied only to b.

Further, the terminal 22a of the first switch 22.
When the polarity of the current is switched by the above-mentioned second switch 23 in a state where the terminal 22c is connected with the terminal 22c, the filaments 10c, 10d on the second group GR2 side can be switched and used.

That is, the filaments 10a to 10d can be switched by a combination of switching by the first switch 22 and the second switch 23.

Each of the filaments 10a to 10a having the above construction
10d is placed in the cathode structure 30 as shown in FIG. 2 (a) is a front view of the cathode structure 30, FIG. 2 (b) is a plan view thereof, and FIG. 2 (c) is a sectional view taken along the line AA of FIG. 2 (b). 2 (d) is BB of FIG. 2 (b).
FIG. Then, as shown in FIG. 3, the cathode structure 30 is arranged so as to face the target 3 and a magnetic field is applied to the thermoelectrons A emitted from the filaments 10a to 10d, whereby the thermoelectrons A are always The same focal point TG can be collided. Further, each of the filaments 10a to 10d is provided in the concave focusing electrode 30a,
It is configured to reduce the focus TG.

Next, three filaments 1 having different shapes
An example in which 0a to 10c are provided in the apparatus, the electric current supplied to them is switched, and each filament 10a to 10c is selectively used will be described with reference to FIG.

As shown in FIG. 4A, in this embodiment, the four filaments 10a to 10a described above are used except that the second group GR2 is composed of the filaments 10c.
The configuration is similar to that of the embodiment including d.

Filaments 10a-1 according to this embodiment
The switching of 0c will be described below. First, the filaments 10a and 10b are switched by switching the polarity of the current with the second switch 23 in a state where the first switch 22 is switched to supply the current to the first group GR1. This is the same as the above-mentioned embodiment.

Next, in a state where the first switch 22 is switched so that current is supplied to the second group GR2,
By supplying the current to the filament 10c by switching the polarity of the current with the second switch 23,
Not supplied (at this time, all filaments 10a
It is possible to switch between (i.e., current is not supplied to 10c).

As shown in FIG. 4B, if the current supply terminal 11b of the filament 10c and the second select line SEL2 are directly connected to each other without the rectifying element 21c, the first By switching the switch 22 so that the current is supplied to the second group GR2, it is possible to always supply the current to the filament 10c regardless of the switching state of the polarity of the current in the second switch 23.

As shown in FIG. 5, the respective arrangements 10a to 10c having the constructions shown in FIGS. 4 (a) and 4 (b) are arranged in the cathode structure 31 and opposed to the target 3. Similarly to the above-described embodiment, the thermoelectrons A emitted from the filaments 10a to 10c can always collide with the same focal point TG, and the focal point TG can be converged.

Although there are constant voltage, constant current and constant power DC power supplies, in the present invention, it is preferable to use constant current or constant power. This is because when a constant voltage DC power supply is used, a constant voltage is supplied to the filaments 10a to 10d, but if the filaments 10a to 10d are heated, the resistance value changes, and accordingly,
This is because the current flowing through the filaments 10a to 10d fluctuates, and as a result, the tube current becomes unstable. On the other hand, when a constant current or constant power DC power supply is used, regardless of fluctuations in the resistance values of the filaments 10a to 10d,
A constant current always flows through the filaments 10a to 10d,
It is possible to stabilize the tube current.

By the way, it is possible that the tube current becomes unstable when a current is supplied from the DC power source 20 to the filaments 10a to 10d as in the above-described embodiments. This will be described with reference to FIG. For example, a tube current of 0.
To obtain 2 A, the filament 10 has a constant current i of 5 A.
Let's say that you shed. At this time, when the current i of 5 A is supplied from the DC power supply 20, the current i always flows in a fixed direction, and the thermoelectrons A are emitted from the filament 10 toward the target 3, and the thermoelectrons A are accompanied by the flow of the thermoelectrons A. Therefore, 0.2 A (tube current) will additionally flow at the “−” side terminal of the filament 10. This allows the filament 10
The temperature rises excessively, the emission of thermoelectrons further increases, and the tube current rises. As described above, it is also considered that the tube current rises due to the emission of the thermoelectrons A, even though the constant current i of 5 A is flown so that the initially planned tube current is 0.2 A. Tube current becomes unstable.

Therefore, it is preferable to provide a correction mechanism for correcting the supply current so that the above problems can be dealt with even if they occur. The configuration of this correction mechanism will be described with reference to FIGS. 7 and 8.

First, as shown in FIG. 7, the supply current correction circuit 40 is provided in the high voltage generator 50. The high voltage generator 50 is for accelerating thermoelectrons A emitted from the filaments 10a to 10d toward the target 3, and for example, generates a high voltage of + 50000V on the anode side and -50000V on the cathode side. . The supply current correction circuit 40 is provided near the ground (0V) of the high voltage generator 50. This is because if the supply current correction circuit 40 is provided near the high voltage, it becomes difficult to insulate the supply current correction circuit 40.

As shown in FIG. 8, this supply current correction circuit 40 is provided with a known resistor 41, converts the tube current ix into a voltage, amplifies the voltage with an amplifier 42, and outputs the differential amplifier 4
3 is supplied to one end side. A reference voltage is supplied from the reference voltage generator 44 to the other end of the differential amplifier 43.

The reference voltage generator 44 inputs the type of the selected filaments 10a to 10d from the input line IL1 and also selects the selected filaments 10a to 10d.
The set value of the tube current to be generated at d is input line I
Input from L2 and select filaments 10a-10
When the tube current of the set value is generated at d,
1. The voltage value to be supplied to the differential amplifier 43 via the amplifier 42 is generated as a reference voltage.

That is, the difference between the reference voltage and the actually measured value is calculated by the difference amplifier 43. If the measured value is the same as the reference voltage, the difference value, that is, the output value from the difference amplifier 43 is “0”, and if the measured value is different from the reference voltage, the calculated difference value is calculated from the difference amplifier 43. Is output. Then, the output value from the differential amplifier 43 is input to the supply current adjusting circuit 45, and the current value generated from the DC power supply 20 is adjusted according to the input value.

For example, if the output value from the differential amplifier 43 is "0", the measured value and the reference voltage are the same, and the current value currently supplied from the DC power source 20 may be the same, so The current supplied from the power source 20 is not changed. If the output value from the differential amplifier 43 is “+ α”,
Since the actually measured value is lower than the reference voltage, the supply current from the DC power source 20 is increased by a predetermined amount (adjusted current amount corresponding to “+ α”) to adjust the tube current. Furthermore, if the output value from the differential amplifier 43 is “−α”, the measured value is higher than the reference voltage, so the supply current from the DC power supply 20 is a predetermined amount (adjusted current component corresponding to “−α”). ) Drop it,
Adjust to lower the tube current.

By incorporating such a correction circuit in the apparatus, it is possible to cope with the case where the tube current becomes unstable due to the use of the DC power supply 20.

[0045]

As is apparent from the above description, according to the present invention, the combination of the switching of the first and second select lines of the three-core cable and the switching of the polarity of the current to be supplied results in three or more. The configuration is such that the supply current to the four filaments can be switched, and a rotary anode X-ray tube device having three to four filaments can be realized with a simple configuration.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a main part of a rotary anode X-ray tube device according to an embodiment of the present invention.

FIG. 2A is a front view showing the configuration of a cathode structure that houses each filament. (B): It is a top view which shows the structure of the cathode structure. (C): It is a sectional view taken along the line AA of FIG. (D): It is the BB arrow sectional drawing of FIG.2 (b).

FIG. 3 is a diagram showing an arrangement of a cathode and a target housed in a cathode structure.

FIG. 4 (a) is a diagram showing a configuration of a main part of an embodiment apparatus provided with three filaments. (B): It is a figure which shows the structure of the principal part of the modified example of (a).

FIG. 5 is a diagram showing an arrangement of a cathode structure containing three filaments and a target.

FIG. 6 is a diagram for explaining a state in which the tube voltage becomes unstable.

FIG. 7 is a diagram showing a mounting position of a mechanism for correcting a supply current.

FIG. 8 is a block diagram showing a configuration of a mechanism for correcting a supply current.

FIG. 9 is a sectional view showing a configuration of a rotary anode X-ray tube device according to a conventional example.

FIG. 10 is a diagram showing a configuration of a main part of a rotary anode X-ray tube device according to a conventional example.

FIG. 11 is a diagram for explaining a problem of the conventional example.

FIG. 12 is a diagram for explaining the problems of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass bulb 2 ... Cathode 3 ... Target (rotating anode) 10 (10a-10d) ... Filament 11a, 11b ... Current supply terminal 12 ... 3-core cable 20 ... DC power supply 21a-21d ... Rectifier 22 ... 1st switch 23 ... Second switch GR1 ... First group GR2 ... Second group COM ... Common line SEL1 ... First select line SEL2 ... Second select line A ... Thermoelectron 40 ... Supply current correction circuit 50 ... High voltage Generator

Claims (1)

[Claims] 1. A common line of a three-core cable comprising a common line, a first select line, and a second select line, which is provided with 3 to 4 thermionic emission filaments on a cathode arranged to face a rotating anode. , One side of the current supply terminal of each filament is connected, each filament is divided into two groups by one or two filaments, and the common line of the filaments belonging to the first group is not connected to each side. A first select line of the cable is connected to the current supply terminal so that the current supply to each filament of the first group is switched according to the direction of the supplied current, and
The current supply terminals on the side of the filaments belonging to the second group, to which the common line is not connected, can switch the current supply to the filaments of the second group according to the direction of the current supplied. Is connected to a second select line of the cable, and a direct current power source is connected to the cable, and further, a common line and a first select line of the cable or a common line and a second select line of the cable. And a current supplied to the common line and the first select line of the cable, or the common line and the second select line of the cable. 2. A rotating anode X-ray tube device comprising a second switch for switching the polarity of.