JP2769434B2 - X-ray equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray apparatus having a built-in X-ray tube.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
US Patent 5,077,771, US Patent 4,646,3
38, U.S. Pat. No. 4,694,480 is known. These documents disclose a portable X-ray apparatus including an X-ray tube, a molded high-voltage power supply and a control circuit.

[0003]

As a method of applying a voltage to an X-ray tube, a method of varying a cathode ground, a target ground, or a focus voltage has been used. However, the generation of the microfocus microfocus is not mentioned in any of the above-mentioned documents, or even if it is mentioned, it is insufficient.

The voltage control method of the high voltage generating circuit is PWM.
And a pulse voltage control method. Among them, PWM
In the method, the effective voltage is controlled by changing the pulse width of the control pulse. Therefore, the followability of the secondary side of the transformer that generates a high voltage is poor, and the X-ray fluctuation is large. In the pulse voltage control method, since the operation of supplying a high voltage to the primary coil of the transformer is a current control method using a switching transistor, a large amount of power is lost due to heat generation, and cooling with a fan is required. The obstacle is that the X-ray micro-focus cannot be maintained due to the vibration of the fan.

Further, in the case of using a Cockcroft-Walton circuit for generating a high voltage, a container in which a capacitor and a diode are insulated is hardened with silicon rubber or epoxy resin. However, since the positions (arrangements) of the capacitor and the diode are shifted when the insulating material is filled, there is a large problem that the dispersion at the time of generating a high voltage is large and unstable.

An object of the present invention is to solve such a problem.

[0007]

In order to solve the above problems, an X-ray apparatus according to the present invention applies a high voltage between a cathode and a target so that electrons emitted from the cathode collide with the target. An X-ray tube for generating a line and a target voltage generating circuit for applying a positive high voltage to the target are provided. Furthermore, the target voltage generation circuit reduces the input voltage to a predetermined set voltage by a switching operation of the switch element, and increases an output voltage from the first voltage generation unit at a predetermined ratio. A second voltage generator. And
The first voltage generator is provided with a signal voltage obtained by dividing the output voltage from the second voltage generator, and the first voltage generator switches the switching of the switch element until the signal voltage is balanced with the set voltage. Perform the operation.

The first voltage generating section is provided with a capacitive element for charging an output current from the switch element.
The first voltage generator continues the switching operation by the switch element until the charging voltage of the capacitor reaches the set voltage, and supplies the charging voltage stored in the capacitor as an output voltage to the second voltage generator.

[0009]

According to the X-ray apparatus of the present invention, in the first voltage generation section provided in the target voltage generation circuit, the input voltage is reduced to a predetermined set voltage by switching (ON / OFF) operation of the switch element. I have. For this reason, the power loss is smaller than that of a circuit that performs constant voltage control linearly. The first voltage generator is provided with a signal voltage obtained by dividing the output voltage from the second voltage generator, and the first voltage generator uses the signal voltage as a control signal to operate the switch element. I have. For this reason, the switch element is driven within the minimum required operating range, and the power loss is smaller than that of a circuit that does not perform such feedback control. Further, since the first voltage generating section is provided with a capacitance element for charging the output current from the switching element, the output current from the switching element can be effectively used as a charging current for the capacitance element. Less power loss than no circuit. As described above, since the power loss of the first voltage generation unit is small and the heat generated in the first voltage generation unit is small, the target voltage generation circuit can be cooled by natural air cooling, and a cooling fan becomes unnecessary.

In the case where the Cockcroft-Walton circuit is provided in the second voltage generating section, the rectifying element and the capacitive element are connected to each other on the insulating substrate, so that each element is fixed by the insulating substrate. There is no displacement of each element. Therefore, there is no variation in the high voltage output due to the displacement of each element, and the second
A stable high voltage output can be obtained from the voltage generating section.

[0011]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a perspective view showing the configuration of the X-ray apparatus according to the present embodiment, and FIGS. 2A and 2B are sectional views showing the configuration of the X-ray apparatus according to the present embodiment. 1 and 2 (a) and (b)
Thus, the X-ray apparatus according to the present embodiment includes a microfocus X-ray tube 10 that emits X-rays and a microfocus X-ray tube 1.
Cockcroft-Walton circuit 2 for applying high voltage to zero
0a, control circuits 23 and 31 for applying a high voltage to the microfocus X-ray tube 10, and a control device 40 for externally controlling these circuits. The Cockcroft-Walton circuit 20a includes a support substrate 20b made of an insulating member that supports the configuration. Cockcroft-Walton circuit 20a and support substrate 20b
Is molded in a mold block 21, and is provided on an insulating oil bath 21 provided on a front side surface of the mold block 21.
The target high voltage supply terminal 22 and the microfocus X-ray tube 10 are connected through a.

On the mold block 21, a substrate 23 provided with a step-down inverter circuit and a push-pull inverter circuit for driving the Cockcroft-Walton circuit 20a, and a microfocus X-ray tube 1
A Cockcroft-Walton circuit 30 for supplying high-voltage power to the 0 cathode electrode is mounted. Furthermore, housing 5
A connector 25 for connecting the control device 40 with a cable is provided on the rear side surface of the control device 40.

FIG. 3 shows a cross-sectional structure of the microfocus X-ray tube 10. As shown in the figure, the microfocus X-ray tube 10 is configured by combining a metal envelope 12 and a glass envelope 13. A ceramic stem 11 is fitted into one end of the envelope 12, and a beryllium X-ray emission window 14 is formed on a side surface of the envelope 12.

Inside the envelopes 12 and 13, the envelope 12
The electron gun 15 is arranged on the side, and the oxygen-free copper target base 16 is arranged on the envelope 13 side. The electron gun 15 is
Heater electrode 15a, cathode 15b, grid electrode 1
5c and a focus electrode 15d. At the tip of the target base 16, a tungsten target 16a is brazed with silver.

The cathode 15b is formed by the heater electrode 15a.
Is heated, electrons are emitted from the surface of the cathode 15b at a certain temperature. The emitted electrons are accelerated by the grid electrode 15c, are focused by the focus electrode 15d, and collide with the target 16a. Due to the collision, the electrons are converted into X-rays and heat, and the generated X-rays are emitted from the X-ray emission window 14 to the outside. The generated heat is released to the outside through the target base 16 having high thermal conductivity.

The target 16a is arranged at an angle of 25 ° with respect to a plane perpendicular to the trajectory of the electrons toward the target 16a. Since the target 16a is arranged at an angle in this manner, most of the generated X-rays are
, And is emitted from the X-ray emission window 14 to the outside.

FIG. 4 is a perspective view showing the appearance of the mold block 21. In the mold block 21 shown in FIG.
0b is embedded. The Cockcroft-Walton circuit 20a is a circuit often used in a high-voltage power supply of about 70 kV. In the case of a high voltage of about 70 kV, it is necessary to mold with an insulating material so that the location where the voltage is increased to a high voltage is not affected by the surrounding environment. For this reason,
The molding is performed by the mold block 21. Conventionally, when a Cockcroft-Walton circuit is fixed with a mold block, a plurality of diodes and a capacitor constituting the Cockcroft-Walton circuit are often misaligned. The high-voltage output from the Cockcroft-Walton circuit in which the displacement has occurred often varies, and it has been difficult to supply a stable high-voltage.

In this embodiment, as shown in FIGS. 5A to 5C, a plurality of diodes and capacitors constituting the Cockcroft-Walton circuit 20a are connected to the support substrate 20b.
Solder on top. Since the connected further diodes and a capacitor wiring 20b ₁ on the support substrate 20b, misalignment of the diode and the capacitor does not occur when the mold is poured a resistance to dielectric edge material from the top. Therefore, the high voltage output from the Cockcroft-Walton circuit 20a is stabilized.

In the conventional Cockcroft-Walton circuit disclosed in Japanese Patent Application Laid-Open No. 63-186,566, a stopper hole is provided in a support substrate to fix a diode and a capacitor. However, in this circuit, from 70 kV to 1
When used at 00 kV, the withstand voltage is poor, and since a protruding wiring is exposed on the substrate, discharge occurs in this portion. On the other hand, in the structure of the present embodiment, the projection on the substrate can be minimized by providing the printed wiring on the support substrate. For this reason, the withstand voltage characteristics are greatly improved.

FIG. 6 is a block diagram showing the operation of the X-ray apparatus according to this embodiment. This block diagram shows an operation block unit 100 for operating the microfocus X-ray tube 10.
And a control block unit 2 for controlling the operation block unit 100
00.

The operation block unit 100 includes a target control unit 110 for controlling a target voltage of the microfocus X-ray tube 10, a target overcurrent detection unit 120 for detecting an overcurrent of the target 16a, and a target Grid controller 1 for controlling grid voltage
30. Further, a cathode control unit 140 for controlling the cathode voltage of the microfocus X-ray tube 10
And a heater control unit 150 for controlling a heater voltage of the microfocus X-ray tube 10.

The control block unit 200 includes a voltage setting D / A converter 210 for supplying a target voltage setting voltage to the target control unit 110 and the cathode control unit 140, and a current setting D / A for supplying a target current setting voltage to the grid control unit 130. The converter includes a converter 220 and an interlock detector 230 for detecting an interlock.
Further, an aging unit 240 that performs warm-up,
A key switch 250 for stopping generation of X-rays and a power supply control unit 260 for performing voltage conversion are provided. Further, a ROM 270 and a RAM 280 in which a control program is stored
And a voltage setting switch 290 for setting a voltage, a current, and an X-ray mode, a current setting switch 300, and a mode switch 310, respectively. Further, a mode display section 320 for displaying an X-ray mode, a target overcurrent, a target voltage, and a target current respectively, and an overcurrent display section 33
0, a target voltage display meter 340, a target current display meter 350, and a CPU 360 for controlling each device.

FIG. 7 is a block diagram showing a detailed configuration of the operation block unit 100. As shown in the figure, the target control unit 110 receives a target voltage setting voltage from the voltage setting D / A converter 210 and controls the target voltage. A target high voltage generator 112 for generating a target high voltage.
The target overcurrent detection unit 120 includes an overcurrent detection unit 121 that detects an overcurrent of the target current generated by the target high voltage generation unit 112, and a target high voltage generation unit 11
And an overvoltage detection unit 122 for detecting an overvoltage of the target voltage generated in Step 2.

The grid control unit 130 includes a target current detection unit 131 for detecting a target current, and a target for comparing the target current detected by the target current detection unit 131 with a set current signal output from the current setting D / A converter 220. A current comparison unit 132 and a cutoff voltage control setting unit 133 are provided. Further, a grid voltage control unit 134 that controls a grid voltage based on a comparison result in the target current comparison unit 132 and a grid voltage generation unit 135 that generates a desired grid voltage in response to an instruction from the grid voltage control unit 134 Have.

The cathode control unit 140 has a voltage setting D / A
Cathode voltage control section 141 which receives a target voltage setting voltage from converter 210 and controls a cathode voltage
And a cathode voltage generator 142 that generates a desired cathode voltage in response to an instruction from the cathode voltage controller 141. The heater control unit 150 includes a heater voltage control unit 151 that controls a heater voltage, and a heater voltage generation unit 152 that receives a command from the heater voltage control unit 151 and generates a desired heater voltage.

The most important thing in the microfocus X-ray tube 10 is that the focal diameter of the microfocus X-ray tube 10 is small and does not change even if the target voltage is variable. For this reason, it is necessary for the target high voltage generation unit 112 to generate a voltage that changes linearly from a low voltage to a high voltage. However, U.S. Pat.
In the conventional target high voltage generator disclosed in US Pat. No. 6,338 and US Pat. No. 4,694,480, the voltage control method is the PWM method, and the voltage fluctuates particularly on the low voltage side, so that the voltage can be changed linearly. Did not.

The target high voltage generator 112 of this embodiment
Adopts a double inverter system using a step-down type inverter for a low voltage part and a push-pull type inverter for a high voltage part. Therefore, it is possible to obtain a variable voltage that linearly changes from a low voltage to a high voltage. FIG. 8 shows the results measured using this example. FIG. 3 is a graph showing the relationship between the input voltage and the output voltage. From this graph, it can be seen that in this embodiment, the input voltage and the output voltage linearly change from a low voltage of about 10 kV to a high voltage of about 100 kV.

FIG. 9 shows a specific circuit configuration of the target high voltage generator 112. The target voltage circuit 400 of this embodiment includes a step-down type inverter circuit 410 in the low voltage section and a push-pull type inverter circuit 420 in the high voltage section. By providing two types of inverter circuits 410 and 420 having different characteristics as described above,
A wide range of variable voltage from low to high can be obtained stably.

The principle of operation of the target voltage circuit 400 will be described with reference to the circuit diagram of FIG. 9 and the waveform diagram of FIG. First, a target voltage setting voltage (Vi) is applied to the primary side of the transformer 430 (see FIG. 10A).
And the error amplifier IC through the buffer amplifier IC _1-a
A set voltage signal is supplied from _1-b to the comparator IC _1-c (see FIGS. 10B and 10C). Transformer 430-2
On the next side, the initial state is 0 (V), and the detection voltage divided by the voltage divider 440 and given through the operational amplifier IC _5-a is also 0 (V). Error amplifier IC _1-b is supply voltage +2
It saturates to a voltage of 4 (V) and is supplied to the comparator IC _1-c (see FIG. 10B). Capacitor C
The voltage of ₁ is also 0 (V) in the initial state, and the comparator IC _1-c saturates to +24 (V) (see FIG. 10C). As a result the transistor Q _1, Q _2, Q ₃ is turned ON, the capacitor C ₁ through the inductor L ₁
There is charged, the transistor Q ₁ is switched to reach the set voltage, continued charging of the capacitor C ₁ (FIG. 1
0 (d) (e)). Inductance L ₁ is provided between the transistor Q _1, a capacitor C _1, the optimization of the time constant of the charging current to the capacitor C ₁ can be achieved.
When the voltage (V ₂ ) of the capacitor C ₁ exceeds the target voltage setting voltage (Vi), the comparator IC _{1 -c} outputs 0
(V), and the operations of the transistors Q ₁ , Q ₂ , and Q ₃ are turned off (see FIG. 10D). Therefore, the voltage (V ₂ ) is stabilized around the target voltage setting voltage (Vi).

Further, the primary voltage of the transformer 430 is
Transistor Q corresponding to oscillation frequency by oscillator IC _4
6, given by the ON / OFF operation of the Q _7. When an ON voltage is applied from the target voltage ON / OFF terminal, the transmitter IC ₄ outputs the comparators IC _2-a , IC _2-b ,
Oscillates by ON operation by IC _2-c . Transformer 430
Is increased to a voltage corresponding to the turns ratio, and further increased to a higher voltage by the Cockcroft-Walton circuit 20a. The boosted output voltage is divided into a resistance ratio by a voltage divider 440, and the error amplifier IC is _supplied through an operational amplifier IC5 _-a.
A detection voltage is applied to _1-b (see FIG. 10 (g)). The error amplifier IC _{1 -b} compares the detected voltage with the target voltage setting voltage (Vi), and drives the comparator IC _{1 -c} until the state becomes balanced.

As described above, the high voltage output can be controlled by linking the step-down type inverter circuit 410 and the push-pull type inverter circuit 420. Circuit of the primary side of the transformer 430 (step-down inverter circuit 410, a push-pull type inverter circuit 420) features is driven by the comparator IC _1-c, the transistor Q ₁ the charging current of the capacitor C ₁ to Q
That is, control is performed by the ON / OFF operation of ₃ . For this reason, it can be driven with the minimum necessary power, and a circuit configuration with extremely low power loss is possible.

FIG. 11 shows X in Japanese Patent Application No. 5-175734.
FIG. 5 is a circuit diagram of a target voltage circuit 500 in the line device. The difference between this target voltage circuit 500 and the target voltage circuit 400 of the present embodiment is that the error amplifier IC _6-1
ON / OFF control of the transistor Q ₅ (corresponding to the transistor Q ₁ of the present embodiment) with the output from the error amplifier IC _1-b of the present embodiment, and the output from the transistor Q ₅ (corresponding to the capacitor C ₂ of the present embodiment) capacitors for charging the current is that is not provided. Therefore, the current flowing through the transistor Q ₅ is turned power loss, heating value of the circuit there were many. Further, the transistors Q ₁ and Q ₂ provided in the inverter circuit are current controlling switching transistors, and have lower efficiency than the voltage controlling switching transistors Q ₆ and Q ₇ and generate considerable heat. Therefore, there is a disadvantage that the operation becomes unstable unless a cooling fan is provided and cooled by the fan.

FIGS. 12A and 12B show a graph of the power loss of the target voltage circuit 500 and a graph of the power loss of the target voltage circuit 400 of this embodiment. From these graphs, it can be seen that the power loss of the target voltage circuit 400 of this embodiment is smaller in any region in the high voltage output range of 10 to 70 kV. In this case, the configuration of the Cockcroft-Walton circuit is the same in both circuits.

Using the graphs of FIGS. 13A and 13B, the output intensity of the X-ray tube according to the present embodiment and the PWM intensity according to the conventional example will be described.
The output intensity of the X-ray tube provided with the high voltage generating circuit using the method is compared. FIG. 13A is a graph showing the output intensity of an X-ray tube provided with a high voltage generation circuit using a PWM method. FIG. 13B is a graph showing the output intensity of the X-ray tube according to the present embodiment. From these graphs, it can be seen that the output intensity of the X-ray tube according to the present embodiment is more stable than that of the conventional example. In this case, it is assumed that a target voltage of 40 kV is applied to both X-ray tube targets and a target current of 10 μA is flowing.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified. For example, the microfocus X-ray tube 10 may be of an end window type in addition to the side window type shown in FIG.

[0037]

As described in detail above, the X of the present invention
In the case of a line device, the first voltage generation unit included in the target voltage generation circuit switches the switch element (ON).
/ OFF) to reduce the input voltage to a predetermined set voltage. Further, the switching operation of the switch element is controlled by a signal voltage from the second voltage generator. For this reason, there is almost no power loss in the first voltage generator, and heat generation from the circuit is very small. Therefore,
The circuit can be cooled by natural air cooling without using a special air cooling fan. As described above, since the circuit can be cooled by natural air cooling, there is no problem of the conventional apparatus that the X-ray micro focus cannot be maintained due to the vibration of the cooling fan.

The Cockcroft-Walton circuit of the second voltage generating section has a configuration in which a rectifying element and a capacitive element are connected by wiring on an insulating substrate, so that each element is fixed by the insulating substrate and each element is fixed. Does not occur. Therefore, a stable high-voltage output can be obtained from the second voltage generator without causing a variation in the high-voltage output due to the displacement of each element.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of an X-ray apparatus according to an embodiment.

FIG. 2 is a cross-sectional view illustrating a configuration of an X-ray apparatus according to the present embodiment.

FIG. 3 is a cross-sectional view showing a structure of a microfocus X-ray tube.

FIG. 4 is a perspective view showing an appearance of a mold block.

FIG. 5 is a diagram showing a structure of a Cockcroft-Walton circuit.

FIG. 6 is a block diagram illustrating an operation of the X-ray apparatus according to the embodiment.

FIG. 7 is a block diagram showing a detailed configuration of an operation block unit.

FIG. 8 is a diagram illustrating a relationship between an input voltage and an output voltage of a target high voltage generation unit.

FIG. 9 is a circuit diagram illustrating a configuration of a target voltage circuit according to the present embodiment.

FIG. 10 is a waveform chart showing the operation of the target voltage circuit of the present embodiment.

FIG. 11 is a circuit diagram showing a configuration of a conventional target voltage circuit.

FIG. 12 is a diagram illustrating a relationship between an output voltage of a target voltage circuit and power loss.

FIG. 13 is a diagram showing the relationship between the output intensity of the X-ray tube and time.

[Explanation of symbols]

10: Micro focus X-ray tube, 11: Stem, 1
2, 13 ... envelope, 14 ... X-ray emission window, 15 ... electron gun,
15a: heater electrode, 15b: cathode, 15c: grid electrode, 15d: focus electrode, 15e: support,
16 target substrate, 16a target, 20a,
Reference numeral 30: Cockcroft-Walton circuit, 20b: Support substrate, 21: Mold block, 21a: Insulating oil tank, 22
... Target high voltage supply terminals, 23, 31 ... Substrate, 25
... Connector, 40 ... Control device, 50 ... Housing, 5
DESCRIPTION OF SYMBOLS 1 ... Lead plate, 52 ... Panel, 53 ... Evaporation prevention cover, 60
... Mold mold, 100 ... Operation block part, 110 ... Target control part, 111 ... Target voltage control part, 112
... Target high voltage generator, 120 ... Target overcurrent detector, 121 ... Overcurrent detector, 122 ... Overvoltage detector, 130 ... Grid controller, 131 ... Target current detector, 132 ... Target current comparator, 133 ... Cut-off voltage control setting unit, 134 ... grid voltage control unit,
135: grid voltage generator, 140: cathode controller, 141: cathode voltage controller, 142: cathode voltage generator, 150: heater controller, 151: heater voltage controller, 152: heater voltage generator, 200: control Block section, 210: voltage setting D / A converter, 2
20: current setting D / A converter, 230: interlock detecting unit, 240: aging unit, 250: key switch, 260: power control unit, 270: ROM, 280 ...
RAM, 290: voltage setting switch, 300: current setting switch, 310: mode switch, 320: mode display section, 330: overcurrent display section, 340: target voltage display meter, 350: target current display meter, 36
0: CPU, 400, 500: Target voltage circuit, 4
10 Step-down inverter circuit, 420 Push-pull inverter circuit, 430 Transformer, 440
… A voltage divider.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-181698 (JP, A) JP-A-57-9100 (JP, A) JP-A-2-32699 (JP, U) (58) Field (Int.Cl. ⁶ , DB name) H05G 1/32

Claims (2)

(57) [Claims] An X-ray tube for generating X-rays by applying a high voltage between a cathode and a target and causing electrons emitted from the cathode to collide with the target, and a target for applying a positive high voltage to the target An X-ray apparatus comprising: a first voltage generator configured to reduce an input voltage to a predetermined set voltage by a switching operation of a switch element; and the first voltage generator. And a second voltage generator for increasing an output voltage from the second voltage generator at a predetermined ratio. The first voltage generator is provided with a signal voltage obtained by dividing the output voltage from the second voltage generator. The first voltage generator performs a switching operation of the switch element until the signal voltage is balanced with the set voltage. A capacitance element for charging an output current from the switch element is provided, and the first voltage generation unit continues the switching operation by the switching element until the charging voltage of the capacitor reaches the set voltage. An X-ray apparatus, wherein the stored charge voltage is supplied to the second voltage generator as an output voltage. 2. The Cockcroft-Walton circuit is provided in the second voltage generator, and the Cockcroft-Walton circuit has a plurality of rectifying elements and a capacitive element between two insulating substrates arranged in parallel. 2. The X-ray apparatus according to claim 1, wherein the X-ray apparatus is mounted, and these elements are wired and connected on the insulating substrate.