JP2005245126A - Motor controller, image reader, and image recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform accurate motor control, using an inexpensive encoder. <P>SOLUTION: This motor controller gets shift information such as shift velocity, etc. by calculating an A-phase signal and a B-phase signal being encoder output, in the unit of (the number of partitions of interpolation/2)×M, and performs the feedback control of the motor, on the basis of the gotten shift information. But, M is a positive integer which does not include 0. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a motor control technique, and more particularly to a motor control device having a motor control unit that feedback-controls a motor using an encoder, and an image reading device and an image recording device having such a motor control device.

  In image reading apparatuses and image recording apparatuses, there is an increasing demand for obtaining high-quality images, and in order to improve the image quality by reducing the movement unevenness of a moving body that moves for reading scanning or recording scanning, It is necessary to improve the performance of moving means for scanning during image recording.

  In many cases, the scanning means has an encoder for controlling the movement of the medium carrying the image information or the medium on which the image information is recorded, or for controlling the movement of the reading means or the recording means, and performs high-precision movement control. In particular, it is desired to develop a high-performance encoder.

  In Patent Document 1, it is proposed to improve the accuracy of an encoder without increasing the number of magnetic sensors by devising a processing circuit that processes the output of a magnetic sensor that detects the rotation of a rotating magnetic drum.

Patent Document 2 proposes an encoder that corrects an interpolation error by correcting the voltage of a sine wave signal output by moving reading.
JP 2000-105134 A JP 2000-314638 A

  Conventionally, as in Patent Documents 1 and 2, the accuracy of movement control has been improved by increasing the accuracy of the encoder by increasing the resolution or increasing the accuracy of the encoder.

  However, there is a limit to improving the performance of the encoder, and there is a problem that a high-precision encoder becomes expensive.

  If high-accuracy movement control can be performed using a relatively inexpensive encoder that is commercially available, the manufacturing cost of the image reading apparatus and the image recording apparatus can be reduced, and the high-quality image reading apparatus and the image recording can be reduced. The device can be realized.

  If such a technique is used for movement control of a medium carrying image information in an image reading apparatus and movement control of a medium on which image information is recorded in an image recording apparatus, high-quality image reading performance and high-quality image These devices having output performance can be provided at low cost.

  An object of the present invention is to provide a low-cost and high-performance image reading apparatus and image recording apparatus. Another object of the present invention is to provide a motor control device capable of high-precision movement control without using a high-precision encoder.

  Prior to the description of the present invention, an interpolation error included in the phase signal obtained from the output of the interpolation division encoder will be described with reference to FIGS.

  FIG. 1A shows an ideal phase signal of an encoder output, that is, a phase signal that does not include an error.

  The A-phase signal and the B-phase signal are rectangular wave pulses having 1 level and 0 level, and are pulse train signals proportional to the position and having a constant width and interval. The B phase signal has a phase difference of 90 ° with respect to the A phase signal.

  FIG. 1B shows a phase signal obtained from a practical encoder, that is, an encoder having an interpolation error.

  The output of the A phase signal and the B phase signal is not output in proportion to the position, but a pulse having a width deviating from the normal value is output from the encoder as indicated by “large” and “small”. “Positive” indicates a normal width. Further, not only the pulse width but also the interval between pulses includes an error.

  FIG. 1C shows an integrated value of the encoder output. As shown in FIG. 1B, an ideal encoder output (shown by a solid line) showing an integrated value proportional to the position is shown in FIG. From the encoder output having an interpolation error, an integrated value having a periodic error is obtained as shown by a one-dot chain line.

  Accordingly, when the movement amount or movement speed is detected using a phase signal including an error, an error occurs in the detected movement information, that is, the movement speed or movement position. For example, even during conveyance at a constant speed, the phase signal output by the movement detection has an error, so that the pulse width P0 ≠ P1 ≠ P2, and the calculated movement amount based on such a phase signal And the speed are different from the movement amount and speed calculated based on the regular pulse width P.

  Such an encoder error is as shown in FIG. 2 using a Lissajous figure.

  FIG. 2A is an ideal output Lissajous figure, and FIG. 2B is an output Lissajous figure including an error.

  In the ideal case of FIG. 2A, the Lissajous figure is a circle, and the phases x0 to x7 are equiangular. On the other hand, the Lissajous figure of the output including an error is an ellipse as shown in FIG. 2B, and the phases x0, x3, x4, and x7 have small angles, and the phases x1, x2, x5, and x6 are large. With an angle.

  However, as in x0 + x1 + x2 + x3, the interpolation division number / 2, that is, equivalent to 180 °, which is a half of one cycle, cancels the error even in the signal including the error, and removes the error.

  Accordingly, by processing a signal having a phase difference of the number of interpolation divisions / 2, it is possible to obtain a detection result obtained by removing the error from the signal including the error. Naturally, a signal from which an error has been removed can be obtained even by an integral multiple of the number of interpolation divisions / 2, that is, the number of interpolation divisions / 2 × M.

  The present invention is based on the detection of movement information with very little error, that is, movement speed, movement position, movement acceleration, and the like, by utilizing such characteristics of the interpolation division type encoder output.

  In the case of detecting the speed V, according to the present invention, when R is the number of interpolation divisions, the speed V, which is movement information, is calculated from the information of the period unit of R × M / 2 by the following equation.

V = (R × M) / 2 × ΔB / ΔT (M) (1)
Here, ΔB is the resolution (distance) of the encoder, and ΔT (M) is the time for the moving body to move the distance ΔX × M / 2, where ΔX is the length of one cycle of the encoder.

  When the formula (1) is modified, the following formula (2) is obtained.

V = {(ΔX × M) / 2} / ΔT (M) (2)
In the above formulas (1) and (2), M is a positive integer not including 0.

  Thus, the moving speed V is obtained from the calculation in units of (R / 2) × M.

  FIG. 3 shows an example of the movement speed calculation according to the present invention, and shows an example of calculation when the interpolation division number R = 16 and M = 1.

  In FIG. 3, the A-phase signal and the B-phase signal are shown as ideal rectangular pulses, but in an actual control system, these signals include errors as shown in FIG. However, as described above, since the movement distance ΔX / 2 × M corresponding to (R / 2) × M is an amount excluding the error, the movement speed V is a value that does not include the error.

The following invention is based on the basics described above, and the object is achieved by the following invention.
1.
An encoder that outputs an A-phase signal and a B-phase signal having at least a 90 ° phase difference by interpolation division according to the movement of the moving body;
A calculation unit for calculating and outputting movement information of the moving body including a moving speed by calculating the output of the encoder;
In a motor control device having motor control means for controlling a motor based on the movement information obtained by the arithmetic unit,
The calculation unit calculates a movement amount corresponding to (interpolation division number / 2) × M, and outputs the movement information, where M is a positive value not including 0 Is an integer.
2.
The calculation unit includes a storage unit, and the storage unit stores change points of the A-phase signal and the B-phase signal, and the calculation unit stores the movement information based on information stored in the storage unit. The motor control device according to 1, wherein the motor control device is calculated.
3.
3. The motor control apparatus according to 1 or 2, wherein the motor control means performs control in synchronization with a change point of the A-phase signal and the B-phase signal.
4).
4. The motor control device according to 3, wherein the motor control means performs control at a cycle of (interpolation division number / 2) × M × N, where N is a positive integer not including 0. is there.
5).
Reading means for reading and scanning a medium carrying image information;
Holding means for holding the medium; and
In the image reading apparatus having a moving means for relatively moving the reading means and the holding means,
5. The image reading apparatus according to claim 1, wherein the moving unit includes a motor and the motor control device according to any one of 1 to 4.
6).
A recording means for recording the image information by scanning a medium on which the image information is recorded;
Holding means for holding the medium; and
In the image reading apparatus having a moving means for relatively moving the recording means and the holding means,
5. The image recording apparatus according to claim 1, wherein the moving unit includes a motor and the motor control device according to any one of 1 to 4.

  The invention according to any one of claims 1 to 6 enables high-precision motor control with few errors using an encoder with relatively low accuracy.

  According to the third or fourth aspect of the invention, it is possible to perform motor control with higher accuracy by synchronizing the sampling period of the movement information detection such as speed and the control period.

  According to the fifth aspect of the present invention, an image reading apparatus capable of high-quality and high-quality reading even with an inexpensive encoder is realized.

  According to the sixth aspect of the invention, an image recording apparatus capable of recording a high-quality and high-quality image even using an inexpensive encoder is realized.

  FIG. 4 shows a motor control apparatus according to the embodiment of the present invention.

  Reference numeral 1 denotes an interpolation division type encoder, which is a linear encoder or a rotary encoder. Further, either an optical encoder or a magnetic encoder may be used. An encoder using laser interference can also be used.

  1a is an encoder scale as a moving body that rotates or moves one-dimensionally, 1b is an encoder head composed of an optical sensor or a magnetic sensor that reads an encode pattern on the encoder scale 1a, 1c is an output of the encoder head 1b, that is, an analog sin wave signal, and It is a signal processing unit that outputs an A-phase signal interpolated from an analog cos wave signal and a B-phase signal having a phase difference of 90 ° from the A-phase signal. Note that the encoder head 1b may be configured by integrally forming a sensor and signal processing.

  In the figure, the encoder scale 1a is driven. However, the encoder head 1b may be driven to relatively move the encoder scale 1a and the encoder head 1b.

  The encoder scale 1a and the encoder head 1b move relative to each other. Reference numeral 1d denotes a motor that moves the encoder scale 1a or the encoder head 1b as a moving body, and a rotary motor or a linear motor is used. A linear motor of the type is preferred and can be composed of a three-phase motor or a DC motor.

  The signal processing unit 1c outputs a Z signal that is an origin signal. The Z signal is used to calculate the absolute position. The Z signal may not be used, and the absolute position may be determined by providing a sensor separately from the encoder 1.

  Reference numeral 2 denotes a calculation unit, which includes a calculation unit 2a composed of a CPU and a memory 2b as a storage unit. The calculation unit 2a outputs a speed signal v and a position signal x from the A phase signal and the B phase signal.

  Note that the position signal x may not be output. Moreover, the calculating part 2 can also be comprised so that an acceleration may be calculated and output.

  The calculating means 2 calculates the speed V using the above equation (2), that is, V = (ΔX / 2) × M / ΔT, and outputs a speed signal v.

  The computing means 2a further outputs a position signal x from the A phase signal, the B phase signal, and the Z phase signal.

  The position X of the moving body is obtained by the sum of the position displacements ΔX in each scan, that is, X = ΣΔX, but X is reset to 0 by the Z signal.

  The motor control means 3 controls the drive voltage of the motor 1d using the speed signal v that is the output of the calculation unit 2a, and the speed of the motor 1d (rotational speed in the case of a rotary motor, linear in the case of a linear motor). (Moving speed) is feedback controlled.

  The control of the motor control means 3 calculates the speed in synchronization with the change in the position of the encoder during the conveyance at a conveyance speed equal to or higher than a predetermined set value, performs feedback control at the timing of the completion of the speed calculation, and conveys below the set value. During conveyance at a speed or during stoppage, feedback control is performed for each period of a predetermined time T0.

  Further, the motor control means 3 calculates the speed in synchronization with the (R / 2) × M × N encoder position change during the conveyance of the set value or more, and performs feedback control at the timing of the end of the speed calculation. You may do it. In particular, it is preferable to calculate N as 1. This is preferable because it is possible to suppress the occurrence of periodic vibrations and speed irregularities that can occur when a linear motor with high motor responsiveness is used.

  The control cycle is not limited to the above, and feedback control may be performed with the control cycle fixed for each cycle of the predetermined time T0.

  In this case, the accuracy is slightly reduced, but can be realized with a simple configuration.

  Here, R is the number of interpolation divisions, and M and N are positive integers that do not include 0. By such control, the sampling period and the control synchronization in the speed detection in units of time for moving the distance corresponding to the pulse (R / 2) × M are taken, so that smooth and stable control is performed.

  FIG. 5 is a flowchart of the calculation performed by the calculation means 2a.

  In step F1, the output of the encoder 1 is read. That is, the A phase signal and the B phase signal are read.

  In step F2, change points of the output of the encoder 1, that is, 1 → 0 and 0 → 1 are detected.

  When a change point is detected (Y in F2), the detection time is held in the memory 2b (F3).

  In step F4, a time ΔT required to detect (R / 2) × M pulses is calculated. That is, ΔT (M) = T (0) −T (0−j) is calculated. Here, j = (R / 2) × M. The calculation of ΔT is performed using the detection time stored in the memory 2b.

In step F5, the speed V is calculated using the following equation.
V = (ΔX / 2) × M / ΔT (M)
Note that ΔT (M) may be obtained by directly measuring the time from the (R / 2) × M change point without using a memory.

  Finally, a speed signal v indicating the speed V is output in F6. Here, in addition to the velocity V, the absolute position X may be obtained from ΣΔX and the position signal x may be output.

  FIG. 6 shows a control system including the motor control means 3 in FIG.

  The motor control means 3 includes a difference detection circuit 3a, a PI control unit 3b, and a motor drive unit 3c that compare the speed V from the calculation unit 2 and the target speed V0 in FIG. In this example, a three-phase motor 4 that is a linear motor is used as the motor 1d in FIG. 4, and the motor drive unit 3c outputs a U-phase drive current, a V-phase drive current, and a W-phase drive current.

  As the control means, in addition to the PI control shown in the figure, any known control method such as PID control, modern control, or H∞ control can be used. In addition to speed information, position information and acceleration information can be used. In addition to the three-phase motor shown in the figure, a servo motor, a DC motor, and the like can be controlled.

  In FIG. 4, the calculation unit 2 and the motor control unit 3 are shown as separate blocks, but actually, the control unit 2 a and the motor control unit 3 may be configured by one CPU.

  FIG. 7 is a flowchart of the control of the CPU constituting the calculation means 2a and the motor control means 3 in FIG.

  As described with reference to FIG. 5, the speed V is obtained by steps F1 to F5.

  In step F7 following step F5, a difference between the target speed V0 and the detected speed V is detected, and in F8, a driving current for driving the three-phase motor 4 is output based on the detected difference.

  FIG. 8 shows an image recording apparatus according to an embodiment of the present invention.

  As shown in the drawing, a roll-shaped photosensitive material 30 as a recording material is loaded (two in the figure), a paper loading section 14, a paper feeding section 15 that cuts and feeds the photosensitive material 30 to a desired length, A main scanning unit 16 having a drum 17 that is rotatably supported and winds the photosensitive material 30 around a predetermined position and fixes the photosensitive material 30 to the body, and a light beam applied to the photosensitive material 30 on the drum 17 facing the drum 17. It comprises a sub-scanning unit 18 having an optical unit 19 for exposing and writing an image, and each part of the exposure unit 11 is provided with driving means (not shown) for driving each part.

  The optical unit 19 includes a red LED unit 31, a green LED unit 32, and a blue LED unit 33, and a light beam from the red LED unit 31, the green LED unit 32, and the blue LED unit 33 is reflected by a mirror 34, a collecting light. An image is exposed to the photosensitive material 30 on the drum 17 through the optical lens 35. At this time, as the drum 17 rotates, scanning in the main scanning direction is performed, and the optical unit 19 is moved in the direction perpendicular to the paper surface of the drawing, scanning in the sub scanning direction is performed, and image exposure is performed.

  The exposed photosensitive material 30 is developed in the development processing unit 12 and image recording is performed.

  Reference numeral 20 denotes an encoder that detects the rotation of the drum 17. Based on the output of the encoder 20, the motor 21 that drives the drum 17 is feedback-controlled, and the rotation speed of the drum 17 is controlled to be constant.

  Since the output of the encoder 20 is processed as described above with reference to FIGS. 2 to 7, high-precision control of the motor 21 is performed, and the drum 17 rotates at a constant speed.

  9 to 13 are radiation image reading apparatuses that use a linear encoder to control a linear motor, and show an image reading apparatus according to an embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. 9 is a side view of the radiographic image reading apparatus according to the present embodiment, FIG. 10 is a perspective view of essential parts of the radiographic image reading apparatus of FIG. 9, FIG. 11 is a partial side view of the radiographic image reading apparatus of FIG. FIG. 13 is a main part plan view showing a linear motor of the radiographic image reading apparatus of FIG. 10, and FIG. 13 is a side view showing a vibration damping mechanism of the radiographic image reading apparatus of FIG.

  The radiographic image reading apparatus of FIG. 9 conveys a cassette 111 composed of a front plate 110 and a back plate 120 (FIG. 11), and accumulates as an image information carrier fixed to the back plate 120 (FIG. 11). Radiation image information is read from a phosphor sheet (hereinafter also referred to as “stimulable phosphor sheet”) 128 (FIG. 11). The back plate 120 (FIG. 11) of the cassette 111 has a ferromagnetic portion made of iron or the like on a part of both sides of the attachment. In FIG. 9, the cassette 111 is assumed to be a half-cut cassette, but is not limited to this.

  As shown in FIG. 9, the radiographic image reading apparatus inserts the cassette 111 on which radiographic imaging has been performed into the insertion port 113 in the direction of arrow A1. At this time, the cassette 111 is inserted so that the front plate 110 side faces obliquely downward, but the stimulable phosphor sheet faces the front plate 110 side. When the cassette 111 is inserted into the insertion slot 113, the presence of the cassette 111 is recognized by a cassette detection sensor (not shown), and the cassette is moved to the center of the insertion slot 113 by the width adjusting means 147 disposed in the insertion slot 113. It is justified.

  Next, the insertion roller 142 is operated so that the cassette 111 is conveyed along the dotted line a in the direction of the arrow A2 and taken into the apparatus main body 112. The transport mechanism 140 that transports the cassette 111 stands by at the position of the dotted line a when the insertion roller 142 is operating, and receives the cassette 111 that is transported by the insertion roller 142 from the insertion port 113. When the cassette grip 402a (FIG. 11) on the lifting platform 402 operating along the transport mechanism 140 catches the lower end of the cassette 111, the lifting platform 402 transports the cassette 111 along the transport mechanism 140 in the direction of arrow A2, It is controlled to stop at the cassette receiving position.

  Next, when the cassette 111 is unlocked and shifts to the lock OFF state, the transport mechanism 140 rotates in the direction of the arrow A3 and stops at the retracted position (for example, the position of the dotted line b). By this operation, the back plate 120 and the front plate 110 are completely separated. At this time, the transport mechanism 140 stops at the retracted position as shown in FIG. By retracting the front plate 110 from the back plate 120 at a sufficient angle, it is possible to prevent the back plate 120 and the front plate 110 from interfering when the back plate 120 performs a sub-scanning operation.

  9 to 11, the sub-scanning unit 150 includes a linear sub-scanning rail 151 that is fixed to a frame (not shown) and extends in the vertical direction, and the sub-scanning rail 151 is moved in the vertical direction by movable units 152 a and 152 b. And a rubber magnet 154 provided on the sub-scanning moving plate 153 for attracting and fixing the back plate 120, and the sub-scanning moving plate 153 is a linear motor 453 (FIG. 10). ) To move vertically.

  When the back plate 120 is completely separated from the front plate 110, the ferromagnetic portion of the back plate 120 is attracted to the rubber magnet 154. It is conveyed in the sub-scanning direction H along the sub-scanning rail 151 in the direction of arrow A4 (upward). While the sub-scanning is performed, the photostimulable phosphor sheet 128 is main in the direction perpendicular to the sub-scanning direction H (the direction perpendicular to the paper surface in FIG. 9) by the laser light B emitted from the laser scanning unit 161 of the reading unit 160. It is configured to be scanned.

  As shown in FIG. 9, in addition to the laser scanning unit 161, the reading unit 160 collects the photostimulated light generated from the photostimulable phosphor sheet 128 by the irradiation of the laser light via the light guide 162. And the like.

  When laser light acts on the photostimulable phosphor sheet 128, photostimulated light (image information) proportional to the radiation energy accumulated in the photostimulable phosphor sheet 128 is emitted, and this photostimulated light passes through the light guide 162. Collected in the condenser tube 163 through. The condensed photostimulated light is converted into an electrical signal by a photoelectric conversion element such as a photomultiplier provided on the end face of the condenser tube 163. The photostimulated light converted into an electrical signal is subjected to predetermined signal processing as image data, and then an image of an operation terminal, an image storage device, an image display device, a dry imager, or the like from the device main body 112 via a communication cable. Output to an output device (both not shown). Of course, the reading unit 160 may have a configuration other than that of the present embodiment as long as it is a means for reading image information from the photostimulable phosphor sheet 128.

  Further, it is preferable that the image data capturing start time is determined by detecting the upper end of the back plate 120 by the sensor 190 of FIG. When the back plate 120 is not present, the sensor 190 receives the laser beam B and continues to output a signal having a predetermined intensity. However, when the upper end of the back plate 120 moves to a position where the laser beam B is blocked, the sensor 190 Since the signal strength of the electrical signal output from the lowering of the back plate 120 is reduced, the upper end of the back plate 120 can be detected.

  When the reading of the image information from the photostimulable phosphor sheet 128 is completed, the back plate 120 starts to be conveyed in the direction of arrow A5 (downward) by the linear motor 453 (FIG. 10). While the back plate 120 is conveyed in the direction of the arrow A5, the erasing light C is emitted from the erasing lamp 164, and the image information remaining on the photostimulable phosphor sheet 128 is erased. As the erasing lamp 164, a halogen lamp, a high-intensity fluorescent lamp, an LED array, or the like can be used.

  When the back plate 120 is lowered to the position where it has moved to the rubber magnet 154, the movement of the back plate 120 by the sub-scanning unit 150 is stopped. When the back plate 120 stops at the transition position, the transport mechanism 140 that has been retracted to the retracted position rotates again to the position indicated by the dotted line c in FIG. 9 and unites the back plate 120 and the front plate 110. When the back plate 120 and the front plate 110 are combined, the lock pin 402c of FIG. 11 housed in the lifting platform 402 is raised, and the tip of the lock pin 402c is inserted into the insertion hole of the front plate 110, thereby locking the lock plate 402c. The cassette 111 that has been in the OFF state is locked and shifts to the lock ON state, so that the back plate 120 and the front plate 110 cannot be separated. When the cassette 111 shifts to the lock ON state, the lock pin 402c is lowered and stored in the lifting platform 402 again.

  When the combination of the back plate 120 and the front plate 110 is completed, the transport mechanism 140 again rotates and moves in the direction of arrow A6 in FIG. 9 to the position of the dotted line b, thereby peeling the back plate 120 from the rubber magnet 154. As described above, the operation of peeling off the back plate 120 from the rubber magnet 154 is performed with rotational movement. Therefore, the back plate 120 (cassette 111) is removed with a small force compared to the case of peeling off by parallel movement. Can be peeled off.

  When the transport mechanism 140 stops at the position of the dotted line b, the fixed state of the front plate 110 by the grip claws 403a is released, and the cassette 111 becomes transportable on the transport mechanism 140. When the fixed state of the front plate 110 is released, the lifting platform 402 transports the cassette 111 along the transport mechanism 140 in the direction of the arrow A7 of the discharge port 114, and delivers the cassette 111 to the discharge roller 143. Upon receiving the cassette 111, the discharge roller 143 performs a discharge operation until the cassette 111 is completely discharged to the discharge port 114. When the cassette 111 is completely discharged to the discharge port 114, the transport mechanism 140 rotates and moves to the position of the dotted line a in the direction of the arrow A6, and shifts to a state where the next cassette 111 can be received.

  Next, the sub-scanning unit 150 will be further described with reference to FIGS. The sub-scanning unit 150 includes a moving mechanism 400 that moves the sub-scanning moving plate 153 in the vertical scanning direction H in order to perform sub-scanning of the photostimulable phosphor sheet 128.

  The moving mechanism 400 in FIG. 10 includes a linear motor 453 that drives the sub-scanning moving plate 153 in the vertical direction along the sub-scanning rail 151 and performs sub-scanning, and a position of the sub-scanning moving plate 153 that extends in the vertical direction. A linear encoder 454 that detects a speed and the like, and a counterweight 460 connected via a sub-scanning moving plate 153 and a belt 440 are provided. As the linear motor 453, the three-phase motor 4 shown in FIG. 6 is used.

  As shown in FIGS. 10 and 12, the linear motor 453 is fixed to a frame (not shown) and extends vertically on two opposing surfaces of the inner surface of the U-shaped cross-section member having a long rail shape. A pair of magnet yokes 453a, and a movable coil 453b that is positioned between the pair of magnet yokes 453a in a non-contact manner and attached to the sub-scanning moving plate 153 via an attachment portion 453c.

  The linear encoder 454 is fixed to a frame (not shown) and extends parallel to the sub-scanning direction H (in the vertical direction). The linear encoder 454 is fixed to the sub-scanning moving plate 153 so as to face the scale 454a. It has an opposing encoder head 454b and can detect the position and speed of the sub-scanning moving plate 153. The encoder head 454b includes a line sensor and a light source that illuminates the scale 454a.

  The output of the linear encoder 454 is processed by the arithmetic unit and speed control means shown in FIGS. 4 and 6, and the linear motor 453 is controlled by the transport control means shown in FIGS.

  The counterweight 460 is movable along a pair of guides 410 that are fixed to a frame (not shown) and extend in the vertical direction. The mass of the counterweight 460 is movable together with the sub-scanning moving plate 153 and the sub-scanning moving plate 153. The mass of the encoder head 454b, the movable coil 453b, and the movable parts 152a and 152b is substantially equal to the total mass of the members. Since the counterweight 460 is substantially equal to the total mass of the sub-scanning moving plate 153 and each member, even if the energization to the movable coil 453b of the linear motor 453 is stopped when the apparatus power is turned off, the sub-scanning moving plate 153 The sub-scanning moving plate 153 is not dropped due to its own weight, and damage due to the dropping of the sub-scanning moving plate 153 can be prevented in advance.

  Further, driven pulleys 459 and 470 driven by the belt 440 are disposed between the sub-scanning moving plate 153 and the counterweight 460. If the sub-scanning moving plate 153 moves upward, the counterweight 460 moves downward. The counterweights 460 and the sub-scanning moving plate 153 are moved in opposite directions.

  As shown in FIGS. 10 and 13, a vibration damping mechanism 500 for attenuating the vibration of the moving belt 440 is provided between the driven pulley 470 and the counterweight 460. The vibration damping mechanism 500 includes a roller 501 that is rotatably provided on a rotation shaft 505, and a shaft 507 and a shaft 504 that urge the roller 501 and press the belt 440 in a direction substantially perpendicular to the moving direction. A tension spring 502 provided between them, a shaft 507 and a rotary shaft 505 are attached, and can be rotated around a fulcrum shaft 503 around a fulcrum shaft 503 rotatably held in a frame (not shown). The rotating member 506 provided on both sides of the roller 501 as described above. These rotating members 506 and the like are rotatably held as an integral unit. The tension spring 502 always rotates the rotating member 506 around the fulcrum shaft 503 to urge the roller 501 in the rotating direction R and press it against the belt 440.

  According to the vibration damping mechanism 500, even if the belt 440 vibrates for some reason during the movement, the belt 440 is always pressed in a state where the roller 501 is urged in the rotation direction R. The vibration of the belt 440 can be absorbed while rotating in the rotation directions R and R ′, the vibration of the belt 440 can be attenuated, and the amplification of the vibration of the sub-scanning moving plate 153 can be prevented. Thereby, since the belt 440 can move stably, the sub-scanning moving plate 153 can move stably together with the photostimulable phosphor sheet 128.

  The tension force of the tension spring 502 is appropriately selected according to the tension of the belt 440. Adjustment of the tension force of the tension spring 502 may be performed by changing the spring constant, or the mounting position of the shaft 504 may be changed. The vibration damping mechanism 500 may be arranged so that the pressing direction of the belt 440 is opposite to that in FIG. 10, and between the sub-scanning moving plate 153 and the driven pulley 459 or the driven pulley 459 and the driven pulley. 470 may be arranged between them, or a plurality of combinations may be arranged at these positions.

  As shown in FIG. 10, the coupling portion 464 between the counterweight 460 and the belt 440 is provided with a rotation mechanism that can freely rotate in a direction substantially perpendicular to the traveling direction of the belt 440. Therefore, even if a reciprocating bending motion of the belt 440 occurs, there is no breakage. Further, since it is rotatable about an axis substantially perpendicular to the traveling direction, even if the relative positional relationship between the guide 410 and the belt 440 is not parallel to the traveling direction, the belt 440 is not twisted and reading is performed. Image unevenness does not occur due to the restoring impact of the belt 440 during operation. In addition, even in the joint portion between the sub-scanning moving plate 153 and the belt 440, a similar effect can be obtained by adopting the same configuration.

  Next, the operation of the moving mechanism 400 of the sub-scanning unit 150 will be described. As described above, when the energization of the movable coil 453b of the linear motor 453 is started in the state shown in FIGS. Due to the action of the magnet yoke 453a of the motor 453 and the movable coil 453b, the sub-scanning moving plate 153 moves along the sub-scanning rail 151 in the direction A4 in FIG. When the sensor 90 in FIG. 9 detects the upper end of the back plate 120, the stimulable phosphor sheet 128 is moved in a direction perpendicular to the sub-scanning direction H by the laser light B emitted from the laser scanning unit 161 of the reading unit 160. Start main scan.

  The linear motor 453 is controlled to move the sub-scanning moving plate 153 at a constant speed based on the position / velocity detection of the linear encoder 454, so that the main scanning is performed while the sub-scanning moving plate 153 performs sub-scanning in the vertical direction. Then, the radiographic image is read. When the main scanning is completed over the almost entire surface of the photostimulable phosphor sheet 128 and the image reading is completed, the sub-scanning moving plate 153 is moved in the direction A5 in FIG. The photostimulable phosphor sheet 128 is irradiated with erasing light C from 164 to erase the remaining image.

  As described above, the photostimulable phosphor sheet 128 whose image reading has been completed as described above is re-stored in the cassette 111 after the back plate 120 and the front plate 110 are combined, and the cassette 111 is discharged to the discharge port 114. And discharged.

  According to the moving mechanism 400 that moves the sub-scanning unit 150 as described above, the linear motor 453 is different from the conventional configuration using a ball screw or the like, and the photostimulable phosphor sheet is interposed via the sub-scanning moving plate 153. Since 128 is driven precisely, uneven feeding in the sub-scanning direction H can be suppressed, feeding accuracy is good, and the photostimulable phosphor sheet 128 can be accurately sub-scanned. For this reason, the photostimulable phosphor sheet 128 can be scanned stably and reliably with the laser beam, and the image information can be read stably and reliably, and a good image without image unevenness can be obtained. In addition, a radiographic image for medical diagnosis in the medical field is required to have high image quality, but a good image suitable for this medical diagnostic image can be obtained. In particular, for example, when sub-scanning is performed at a low speed of 10 mm / second or less, the feeding accuracy is very good, and a good medical diagnostic image without image unevenness can be obtained.

  When the linear motor 453 is used for driving in the vertical direction, when the apparatus power is turned off, the linear motor is not energized and the movable coil 453b cannot be held, but the sub-scanning moving plate 153 is not used. Since the counterweight 460 is connected to the sub-scanning moving plate 153, the sub-scanning moving plate 153 does not move unexpectedly due to gravity when the apparatus power is turned off and the linear motor 453 does not operate. Since the tension can be maintained, the sub-scanning moving plate 153 can move stably.

  It is also conceivable to prevent the above-described movement due to gravity, for example, by equipping the belt with a brake mechanism or the like.

  Further, the sub-scanning moving plate 153 and the counterweight 460 vibrate in the moving direction via the belt 440, so that the uneven feeding of the sub-scanning moving plate 153 is deteriorated. As a result, the unevenness of the image becomes a medical diagnostic image. Although there is a risk of hindrance, the vibration damping mechanism 500 of the belt 440 is provided between the sub-scanning moving plate 153 and the counterweight 460, and uneven feeding in the sub-scanning direction H is reduced. The phosphor sheet 128 can be sub-scanned with higher accuracy.

  Note that the erasing unit 164 may be positioned above the position in FIG. 9, and the stimulable fluorescent plate may be moved downward during reading and may be moved upward during erasing. The erasing may be started immediately after reading the image.

  Further, the belt 440 may be configured to be applied in parallel by using one or a plurality of combinations using a metal belt such as stainless steel, a metal wire, a resin belt, or the like.

  One belt 440 may be arranged on the center line in the sub-scanning direction H, or a plurality of belts 440 may be arranged in a line symmetrical position with respect to the center line. However, in consideration of the assembly process, the belt 440 is configured with only one belt. As a matter of course, the assembly time is reduced compared to a configuration in which a plurality of belts are configured in parallel, and the adverse effects that may occur due to component accuracy between the plurality of belts or errors in assembly are considered. This is preferable because there is substantially no need to do this, and the requirements for component accuracy and assembly accuracy can be relaxed.

  Further, one guide 410 of the counterweight 460 may be arranged on the center line in the sub-scanning direction H, or a plurality of guides 410 may be arranged in line-symmetrical positions with respect to the center line. A smaller number is preferable because the time required for adjusting the parallelism can be reduced. Furthermore, it is more preferable to arrange only one guide because it is not necessary to substantially adjust the parallelism between the plurality of guides.

  Further, as shown in FIG. 9, the back plate 120 is positioned in line symmetry with respect to the center line of the plane of the sub-scanning moving plate 153 along the moving direction (vertical direction) of the sub-scanning moving plate 153. Is held in. That is, the back plate 120 is held by the sub-scanning moving plate 153 so that the center lines of the planes along the moving direction (vertical direction) of the back plate 120 and the sub-scanning moving plate 153 coincide. Further, the center line in the vertical movement direction of the sub-scanning rail 151 for guiding the sub-scanning moving plate 153 is the center of gravity of the combination of the back plate 120 and the sub-scanning moving plate 153 (in this embodiment, the sub-scanning moving plate 153 is Since the shape is symmetrical, the sub-scanning moving plate 153 and the back plate 120 are moved to the sub-scanning rail 151 in a state where the weight balance is good by passing the sub-scanning moving plate 153 on the vertical center line). Since it can guide along, it is preferable.

  FIG. 14 shows an example of a shaft type linear motor 453 that can be used in the image reading apparatus shown in FIGS. A large number of magnet elements 453e connected in a rod shape are accommodated in a cylinder 453f, and a coil 453b constituting a movable portion is fitted outside the cylinder 453f to constitute a linear motor 453. By supplying current to the coil 453b, the coil 453b can be reciprocated as indicated by an arrow A8.

  The linear motor 453 shown in FIG. 14 has a feature that the motor itself can ensure high-accuracy movement because the movable part is guided by the motor drive part.

It is a figure which shows the phase signal output from an encoder. It is a figure which shows a Lissajous figure. It is a figure which shows the example of a calculation of the moving speed by this invention. It is a figure which shows the motor control apparatus which concerns on embodiment of this invention. It is a flowchart of the calculation which a calculating means performs. It is a figure which shows the control system containing a motor control means. It is a flowchart of the control which CPU which comprises a calculating means and a motor control means performs. 1 is a diagram illustrating an image recording apparatus according to an embodiment of the present invention. It is a side view of the radiographic image reading apparatus by this Embodiment. It is a principal part perspective view of the radiographic image reading apparatus of FIG. It is a partial side view of the radiographic image reading apparatus of FIG. It is a principal part top view which shows the linear motor of the radiographic image reading apparatus of FIG. It is a side view which shows the vibration damping mechanism of the radiographic image reading apparatus of FIG. It is a figure which shows the example of a shaft type linear motor.

Explanation of symbols

1a Encoder scale 1b Encoder head 1c Signal processing unit 1d Motor 2 Calculation unit 2a Calculation unit 2b Memory 3 Motor control unit ΔX Length of one cycle P Pulse width x0 to x7 Phase ΔT The moving body of the encoder is a distance (ΔX / 2) × Time to move M

Claims (6)

An encoder that outputs an A-phase signal and a B-phase signal having at least a 90 ° phase difference by interpolation division according to the movement of the moving body;
A calculation unit for calculating and outputting movement information of the moving body including a moving speed by calculating the output of the encoder;
In a motor control device having motor control means for controlling a motor based on the movement information obtained by the arithmetic unit,
The calculation unit calculates a movement amount corresponding to (interpolation division number / 2) × M, and outputs the movement information, where M is a positive value not including 0 Is an integer. The calculation unit includes a storage unit, and the storage unit stores change points of the A-phase signal and the B-phase signal, and the calculation unit stores the movement information based on the information stored in the storage unit. The motor control device according to claim 1, wherein: The motor control device according to claim 1, wherein the motor control unit performs control in synchronization with a change point of the A-phase signal and the B-phase signal. 4. The motor control device according to claim 3, wherein the motor control means performs control with a cycle of (number of interpolation divisions / 2) * M * N, wherein N is a positive integer not including 0 It is. Reading means for reading and scanning a medium carrying image information;
Holding means for holding the medium; and
In the image reading apparatus having a moving means for relatively moving the reading means and the holding means,
5. The image reading apparatus according to claim 1, wherein the moving unit includes a motor and the motor control device according to any one of claims 1 to 4. A recording means for recording the image information by scanning a medium on which the image information is recorded;
Holding means for holding the medium; and
In the image reading apparatus having a moving means for relatively moving the recording means and the holding means,
5. The image recording apparatus according to claim 1, wherein the moving unit includes a motor and the motor control device according to any one of claims 1 to 4.

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