JPH0668605B2 - X-ray speed photography device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quick-shooting device for an X-ray imaging apparatus, and in particular, to a quick-shooting drive control device suitable for suppressing vibration generated in the X-ray imaging apparatus main body during quick shooting. It relates to a quick-shooting device.

[Background of the Invention]

X-ray imaging device quick-shooting device (hereinafter simply referred to as a quick-shooting device)
Transports a holder holding an image medium such as an X-ray film or an image storage medium from a standby position to an imaging position by an actuator such as a DC motor, and the X-rays emitted from the X-ray device pass through the subject. It is a device that performs a series of operations until the transmission X-ray image obtained by the above is printed on the image medium and then returned to the standby position.

Hereinafter, such a quick-shooting device will be described with reference to the drawings.
FIG. 5 shows an outline of the X-ray imaging apparatus with a part cut away. In FIG. 5, when the DC motor 1 is driven by the quick drive control device 2, the pulley 6 fixed to the motor shaft 3
Is rotated, and a holder 8 mounted on a belt 7 wound around a pulley 5 rotatably mounted on a shaft 4 and the pulley 6, that is, mounted on a holder transport mechanism The sheet is conveyed from the position A to the shooting position B.
An encoder 9 is provided on the motor shaft 3 and outputs a signal corresponding to the position of the rotary holder 8 of the motor shaft 3 to the quick-drive control device 2.

In such a quick-shooting device, the time required to convey the holder 8 from the standby position A to the shooting position B is required to be as short as possible for timely shooting. Therefore, the holder 8 must be transported with a large acceleration / deceleration (hereinafter referred to as unit acceleration). At this time, the impact force generated by the acceleration vibrates the X-ray imaging apparatus main body 10 through the holder transport mechanism, and causes a large vibration (see arrow B) on the subject lying table (not shown).

FIG. 6 is a block diagram of a conventional quick-shoot drive controller 2 having such a problem, which will be described below. When the holder is started to be conveyed, the comparison means 11 first uses the position of the photographing position B as a position command from a system controller (not shown).
To enter. On the other hand, the output pulse from the encoder 9 is input to the position detecting means 12 to detect the current position of the holder 1. This is compared with the position command by the comparison means 11 to obtain a position deviation, which is input to the speed command means 13. The speed command means 13 outputs a speed command corresponding to the position deviation, and the comparing means 15 compares the speed command with the current speed of the holder 8 obtained by the speed detecting means 14 to obtain the speed deviation. Pulse width modulation signal according to this speed deviation (hereinafter referred to as PWM signal)
And a drive method signal for selecting the drive direction of the motor are generated by the PWM signal generating means 16, and this signal is input to the motor drive circuit 17 to drive and control the DC motor 1, and the holder 8
To transport.

FIG. 7 is a time chart when the holder is conveyed in such a conventional device, (a) is a conveying position, (b) is a conveying speed,
(c) is the conveyance acceleration, and (d) is the above-mentioned X due to the conveyance of the holder 8.
The vibrations generated in the radiographic apparatus body 10 are shown respectively. As shown in FIG. 7 (a), the position command input to the comparison means 11 is constant from the start of conveyance of the holder 8 to the stop thereof, which is a characteristic of the conventional quick-drive control device.

That is, the conventional quick-shooting drive control device 2 described above controls the electric power supplied to the DC motor 1 so that the position deviation, which is the difference between the position command and the current position obtained by the position detecting means 12, is minimized. , The holder 8 as shown in the transfer curve of FIG.
To transport. At this time, as shown in FIG. 7 (b), the conveyance speed reaches the maximum speed determined by the characteristics of the quick-shoot drive controller 2 and the DC motor 1 immediately after the start of conveyance, and the holder 8 is kept in the vicinity of the position command as it is. Transport. When the holder 8 approaches the position command, the position deviation obtained by the comparison means 11 becomes small, and accordingly, the speed command output from the speed command means 13 becomes small, and eventually the rotation speed of the DC motor 1 and the accompanying rotation speed. The transport speed decreases. After that, as shown in FIGS. 7 (a) and 7 (b), the holder 8 goes beyond the position command and goes too far, and then returns to the position command again.

FIG. 7 (c) shows the acceleration from the start of conveyance of the holder 8 to the end thereof, and it can be seen from this figure that a rapid change in acceleration occurs immediately after the start of conveyance and immediately before the end. The product of this acceleration and the mass of the holder 8 becomes the force that the holder 8 applies to the X-ray imaging apparatus main body 10 through the holder transport mechanism. This force is shocking, as can be seen from the acceleration curve of FIG. 7 (c), so that a large vibration occurs in the X-ray imaging apparatus main body 10 as shown in FIG. 7 (d).

The vibration generated in the X-ray imaging apparatus main body 10 not only makes the subject uncomfortable during X-ray imaging, but also adversely affects the image quality of the image obtained by the image blurring. Conventionally, this point is improved. Was requested.

In order to solve the above problem, a method of changing the position command with the passage of time to suppress a rapid change in acceleration can be considered. Hereinafter, such a quick drive control device will be described.

FIG. 8 is a block diagram of the quick-shooting drive control device 2a of a system in which the position command is changed with the passage of time and the transport position of the holder 8 is controlled along with it. FIG. 9 is a time chart when the holder is conveyed by the quick drive control device 2a. (A) is a conveying position, (b) is a conveying speed, (c) is a conveying acceleration, and (d) is a conveying of the holder 8. Therefore, the vibrations generated in the X-ray imaging apparatus main body 10 are shown.

Since there are a plurality of types of holder transport distances depending on the size of the image medium and the shooting mode, the transport distance code for selecting the required transport distance and the transport start command for instructing the timing of transport start Input to the position command means 18 in the figure. The position command means 18 generates a position command, which changes corresponding to the elapsed time from the start of the transfer, as shown in FIG. 9A, based on the transfer distance code and the transfer start command. The position command that changes according to the elapsed time is
Since the holder 8 is optimized so that the conveyance acceleration does not change suddenly, the vibration generated in the X-ray imaging apparatus main body 10 should be suppressed. However, the conventional motor drive circuit 17 shown in FIG. 6 and FIG. 8 uses the DC motor 1 when the holder 8 is decelerated.
It is difficult to smoothly control the drive current (hereinafter, referred to as armature current), and as shown in FIG. 9 (c), the carrier acceleration is interrupted to vibrate the X-ray imaging apparatus main body 10. Remains.

The reason why it is difficult to smoothly control the armature current when the conventional motor drive circuit 17 decelerates the holder 8 will be described below.

FIG. 10 is an equivalent circuit diagram in which the conventional motor drive circuit 17 and the DC motor 1 are configured by the inductance 36, the resistor 37, and the induced voltage source 38.

FIG. 11 is a time chart before and after the start of deceleration in the conventional motor drive circuit 17. The conventional motor drive circuit
When driving the holder 8 in the direction of rotating the holder 8 to the photographing position B (hereinafter referred to as forward rotation), the transistors 23 and 24 are turned off, the transistor 25 is turned on, and the transistor 22 is turned on in FIG. ON / OFF control is performed by the PWM signal. When the holder 8 is driven to rotate in the direction of conveying to the standby position A (hereinafter referred to as reverse rotation), the transistors 22 and 25 are turned off, the transistor 23 is turned on, and the transistor 24 is turned on by the PWM signal. Turn off.

In order to rotate the DC motor 1 in the normal rotation direction by the conventional motor drive circuit 17, the drive direction signal is set to high level and PW
Power supply 30-transistor 22
An armature current flows in the circuit of DC motor 1-transistor 25-power supply 30, and the electric power stored in the inductance 36 of DC motor 1 at this time causes DC motor-transistor 25-diode 27-circuit of DC motor 1 The current continues to flow. At this time, the DC motor 1 performs a power generation action by its normal rotation, generates an induced voltage, and forms an induced voltage source 38.

To reversely drive the DC motor 1 to start deceleration from this state, the drive direction signal is changed from the high level to the low level, and while the PWM signal is at the high level, the power supply 30-transistor 24-DC motor 1- A voltage (hereinafter referred to as armature voltage) is applied to the DC motor 1 by the circuit of the transistor 23 and the power source 30. However, in the conventional motor drive circuit 17, the induced voltage source generates a DC voltage while the PWM signal is at a low level. Motor 1
-Transistor 23-Diode 29-DC motor 1 circuit causes short-circuit current to flow, resulting in excessive armature current as shown in FIG. Since the armature current of the DC motor 1 is almost proportional to the output torque of the DC motor 1, the torque generated by the excessive armature current causes the holder 8 to change the carrier acceleration, and the torque shown in FIG. X-ray imaging device body 10 as shown in d)
Vibrate. It is difficult for the conventional motor drive circuit 17 to control this excessive armature current. In the motor drive circuit 17 shown in FIGS. 6, 8 and 10, AND circuits 19, 20 are provided.
As described above, the inverting circuit 21 is used as a logic circuit for switching the transistors 22 to 25 based on the PWM signal and the driving direction signal.

From the above, in order to suppress the vibration of the X-ray imaging apparatus main body 10, in accordance with the transport distance and the time from the start of transport,
Position command means 18 for generating a position command effective for vibration suppression
In addition to the above, it is understood that it is important to control the DC motor 1 with a motor drive circuit capable of controlling the armature current of the DC motor 1 even during deceleration.

[Object of the Invention]

The present invention has been made in view of the above problems, and an object of the present invention is to provide a quick-shooting drive control device capable of suppressing the vibration of the X-ray imaging apparatus main body that occurs when the holder is transported.

[Outline of Invention]

The present invention prepares a position command for the holder corresponding to the elapsed time from the start of transport of the holder, generates a speed command according to the deviation between this position command and the current position of the holder, and the current speed of the holder. A PWM signal is generated according to the deviation between the armature voltage and the armature voltage in the specified direction when the PWM signal is at the high level and in the opposite direction when the PWM signal is at the low level. The DC motor is driven by the voltage to smoothly convey the holder.

Example of Invention

Embodiments of the present invention will be described below with reference to the drawings. First
The figure is a block diagram showing an embodiment of a quick-shoot drive controller according to the present invention. In the figure, 18 is a position command means for generating a position command corresponding to the elapsed time from the start of conveyance of the holder 8 (see FIG. 5). In the figure, 16b is a PWM signal generating means for controlling the armature current of the DC motor 1, 17b is a predetermined method when the PWM signal is at a high level, and 17b is a predetermined direction when the PWM signal is at a low level. 2 is a motor drive circuit that generates an armature voltage in the opposite direction. FIG. 2 shows the motor drive circuit 17b.
3 is an equivalent circuit diagram in which the DC motor 1 is composed of an inductance 36, a resistance 37, and an induced voltage source 38. 1 in Figures 1 and 2
3,9,11 to 15,18,21 to 30 are the same as those in FIGS. 8 and 10.
FIG. 4 is a time chart showing the transfer position, the transfer speed, the transfer acceleration, and the vibration generated in the X-ray imaging apparatus main body 10 (see FIG. 5) when the holder is transferred according to the present invention.

Next, the operation of the apparatus of this embodiment will be described. First, in FIG. 1, when a holder is started to be transported, a transporting distance code indicating a required transporting distance and a transporting start signal are input to the position commanding means 18 from a host system controller (not shown). The position command means 18 generates a position command shown in FIG. 4 (a) corresponding to the elapsed time from the start of conveyance and gives it to the comparison means 11. On the other hand, the output pulse of the encoder 9 is input to the position detecting means 12 to detect the current position of the holder 8,
This is compared with the position command by the comparison means 11 to obtain a position deviation and input to the speed command means 13. Speed command means 13
Outputs a speed command according to the position deviation, and compares the current speed obtained by the speed detection means 14 with the comparison means 15 to obtain a speed deviation. The PWM signal generating means 16b obtains a signal in which a high level period and a low level period of the pulsed signal are controlled according to the speed deviation, that is, a PWM signal. The P
DC motor 1 by motor drive circuit 17b based on WM signal
Drive control. That is, when the PWM signal is at the high level, only the transistors 22 and 25 are turned on, and when the PWM signal is at the low level, only the transistors 23 and 24 are turned on and the armature voltage of the DC motor 1 is alternately applied to the armature current. When the high level period is longer than the low level period, the PWM signal acts as driving during forward rotation of the motor or braking during reverse rotation, and when the high level period is shorter than the low level period. It works as a drive for the reverse rotation of the motor or as a braking for the normal rotation. That is, the motor drive circuit 17b of the device of the present invention performs forward rotation drive and reverse rotation drive of the motor only with the PWM signal, and does not require a drive direction signal as compared with the conventional motor drive circuit.

When the above operation is executed by a position command that changes with the passage of time, the carrying position of the holder 8, the carrying speed,
The conveyance acceleration and the vibration of the X-ray imaging apparatus main body 10 are shown as a time chart in FIG.

FIG. 3 shows D by the motor drive circuit 17b of FIG. 1 and FIG.
6 is a time chart showing the armature voltage and the armature current before and after the start of deceleration when the C motor 1 is driven. PW
During the period when the M signal is high level, the transistor 2 in FIG.
Only 2,25 are turned on, the armature voltage is generated in the direction in which the DC motor 1 rotates in the normal direction, and only the transistors 23,24 are turned on while the PWM signal is at the low level, and the armature voltage in the opposite direction is generated. To do. If the DC motor 1 is rotating normally, the second
Although the induced voltage source 38 is formed as shown in the figure, according to the present embodiment, since there is no period in which a short-circuit current flows due to this induced voltage, the armature current can be controlled even during deceleration. Therefore, the holder 8 moves along with the position command that changes according to the elapsed time.
Since the carriage can be controlled, the vibration of the X-ray imaging apparatus main body 10 can be effectively suppressed as shown in FIG.

Further, according to the present embodiment, since the position command means also regulates the transportation time of the holder, the transportation operation is always finished at the same time at any transportation distance among several transportation distances, and the timing is aligned. There is also an effect that it is possible to take an X-ray image.

Incidentally, in the above embodiment, the position command means 18, the comparison means 11, 1
It goes without saying that the speed command means 13 and the like may be configured by software of a microcomputer.

In the first embodiment, the motor drive circuit is composed of four transistors each pairing two as shown in FIG. 2, but may be composed of two transistors as a pair as shown in FIG. .

In the embodiment of FIG. 2 and the embodiment of FIG. 12, the motor drive circuit is composed of bipolar transistors, but it may be composed of switching elements such as thyristors and field effect transistors.

〔The invention's effect〕

As described above, according to the present invention, the position command of the holder that changes according to the elapsed time from the start of the transportation of the holder is prepared, and the speed command is generated according to the deviation between this position command and the current position of the holder. PWM signal is generated according to the deviation between this and the current speed of the holder, and the armature voltage is alternately applied to the DC motor based on this PWM signal to optimize the DC motor from the start to the stop. Since it can be controlled in the state, the holder can be transported more smoothly than the conventional apparatus, and the vibration of the X-ray imaging apparatus at this time can be suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of the motor drive circuit of the present invention and a DC motor, and FIG.
FIG. 4 is a time chart showing the operation of the circuit of FIG. 2, FIG. 4 is a time chart when the holder is conveyed according to the present invention, and FIG. ，
FIG. 8 is a block diagram of a conventional device, FIGS. 7 and 9 are time charts when a holder is conveyed by the conventional device of FIGS. 6 and 8, and FIG. 10 is a motor drive circuit and a DC motor of the conventional device. An equivalent circuit diagram, FIG. 11 is a time chart showing the operation of the circuit of FIG. 10, and FIG. 12 is a motor drive circuit according to another embodiment. 1 ... DC motor, 2 (2a, 2b) ... quick-shooting drive controller,
8 ... Holder, 9 ... Encoder, 10 ... X-ray imaging apparatus main body, 11, 15 ... Comparison means, 13 ... Speed command means, 16 (1
6b) ... PWM signal generating means, 17 (17b, 17c) ... motor drive circuit, 18 ... position command means, 22 to 25, 33, 34 ... transistors.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-58-11927 (JP, A) JP-A-59-9652 (JP, A) JP-A-58-212394 (JP, A) Actual development Sho-48- 63660 (JP, U)

Claims (1)

[Claims] 1. A holder for holding an image storage medium, a transport mechanism for causing the holder to reciprocate between a standby position and a photographing position, an actuator for driving the transport mechanism, and a control circuit for the actuator. In the X-ray rapid copying apparatus, the control circuit detects the current position of the holder from a position command means for generating a position command of the holder which changes corresponding to the elapsed time from the start of transport of the holder, and an output signal of the actuator. Position detecting means, speed commanding means for generating a speed command according to the deviation between the position command and the current position of the holder, speed detecting means for detecting the current speed of the holder from the output signal of the actuator, and the speed command And PWM signal generating means for outputting a pulse width modulation signal according to the deviation between the current speed of the holder and Actuator to apply a voltage in a predetermined orientation, X-rays rapid photographing apparatus characterized by comprising a pair of switching-means for applying a voltage to the opposite direction to the low-level period.