JP2004250180A - Feeding device, image reading apparatus, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow accurate feeding by suppressing unevenness in speed without using accurate and high-cost position determination means, and obtain high quality images with a low-cost structure by suppressing unevenness in auxiliary scanning speed in the case of using a linear motor in a drive system. <P>SOLUTION: The feeding device includes a linear motor 21 as a driving source to feed a fed member, a liner encoder 25 for determining a feeding position of the fed member, controllers 31 to 36 for controlling the linear motor 21 by feeding back the determination result of the feeding position, and memory 39 for storing data about positional errors in each feeding position. The feeding device feeds back a correction position signal corrected with the determination result of the feeding position with data to a differential output portion 31. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transport device using a linear motor, an image forming device, and an image reading device.
[0002]
[Prior art]
Conventionally, it is known that a sub-scanning conveyance mechanism for sub-scanning a sheet-shaped recording medium for image recording and image reading is driven by a ball screw connected to a stepping motor or a DC motor, but uneven feeding or vibration occurs. Then, the image quality is reduced. An image forming apparatus using a linear motor to suppress the uneven feeding and the vibration is known from the following Patent Document 1.
[0003]
In order to control the speed of such an apparatus, Patent Document 2 below discloses a method of suppressing speed unevenness by a traveling body control unit of an image reading apparatus. Reference 3 below discloses a method of suppressing external disturbance by a servo control device of a tool table driving linear motor.
[0004]
When a linear motor is used, the tracking error is good, so that the measurement error of the position / speed appears as the unevenness of the sub-scanning speed as it is. However, Patent Documents 2 and 3 do not describe such measurement error. 2. Description of the Related Art Conventionally, in a device using a linear motor, a highly accurate and expensive detection means such as a linear encoder such as a glass scale has been used in order to improve measurement accuracy of position and speed.
[0005]
[Patent Document 1]
JP-A-11-216921
[0006]
[Patent Document 2]
JP-A-9-219986
[0007]
[Patent Document 3]
JP-A-2002-28858
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems of the related art, and when a linear motor is used for a drive system, a transport device capable of suppressing unevenness in speed and realizing accurate transport without using an accurate and expensive position measuring unit. The purpose is to provide. It is another object of the present invention to provide an image forming apparatus and an image reading apparatus capable of performing sub-scanning using such a transport device, suppressing unevenness in sub-scanning speed, and obtaining high image quality with an inexpensive configuration.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a transport device according to the present invention includes a linear motor as a drive source for transporting a transported object, a position measuring unit that measures a transport position of the transported object, Control means for controlling the linear motor by feeding back the measurement result, and storage means for storing data relating to a position error at each of the transfer positions, and a correction position obtained by correcting the measurement result of the transfer position with the data. A signal is fed back to the control means.
[0010]
According to this transport device, since the feedback control is performed using the corrected position signal in which the position error of the measured position of the transported object is corrected, accurate position control can be performed. Therefore, even if a linear motor is used for the drive system and high-precision and expensive position measuring means is not used, speed unevenness can be suppressed, accurate conveyance can be realized, and the cost of the conveyance device can be reduced.
[0011]
In the transport device, any one of a linear encoder, a laser interferometer and a rotary encoder can be used as the position measuring means.
[0012]
Further, the speed information calculated from the measurement result of the measurement position may be fed back to the control means.
[0013]
An image reading apparatus according to the present invention includes a main scanning unit that performs main scanning by irradiating a light beam on a scanned object in a main scanning direction, and a driving source that performs sub-scanning in a direction substantially perpendicular to the main scanning direction. An image reading unit that has a linear motor and reads image information from the object to be scanned by two-dimensional scanning of the object to be scanned, and a sub-scanning position that is a relative position between the object to be scanned and the main scanning unit Sub-scanning position measuring means, measuring means for controlling the linear motor by feeding back the measurement result of the sub-scanning position, and storage means for storing data relating to a position error at each of the sub-scanning positions, And a correction position signal obtained by correcting the measurement result of the sub-scanning position with the data is fed back to the control means.
[0014]
According to this image reading apparatus, since the feedback control is performed using the corrected position signal obtained by correcting the position error of the measurement position of the object to be scanned, the sub-scanning position can be controlled with high accuracy. Therefore, even if a linear motor is used for the drive system and the high-precision and expensive position measuring means is not used, the unevenness of the sub-scanning speed can be suppressed, the accurate sub-scanning can be realized, and the cost of the image reading apparatus can be reduced. In addition, image reading can be performed with high accuracy, and high image quality can be obtained.
[0015]
In the image reading apparatus, any of a linear encoder, a laser interferometer, and a rotary encoder can be used as the sub-scanning position measuring means.
[0016]
Further, speed information calculated from the measurement result of the sub-scanning position may be fed back to the control unit.
[0017]
Further, the image reading means may include an optical unit including an optical system, and may be configured to convey the optical unit in the sub-scanning direction. Further, the scanning object may be transported in the sub-scanning direction.
[0018]
In addition, by arranging a magnetic shielding sheet or a magnetic shielding plate around the linear motor, it is possible to suppress the influence of the magnetism from the linear motor on other components and the like, and to prevent dust from entering. You can also.
[0019]
An image forming apparatus according to the present invention includes a main scanning unit that performs main scanning by irradiating an object to be scanned with a light beam in a main scanning direction, and a driving source that performs sub-scanning in a sub-scanning direction substantially orthogonal to the main scanning direction. A linear motor, and an image forming unit that forms an image on the scanned object by two-dimensional scanning of the scanned object, and a relative position between the scanned object and the main scanning unit. Sub-scanning position measuring means for measuring the sub-scanning position, control means for controlling the linear motor by feeding back the measurement result of the sub-scanning position, and storage means for storing data relating to a position error at each of the sub-scanning positions And a correction position signal obtained by correcting the measurement result of the sub-scanning position with the data is fed back to the control means.
[0020]
According to this image forming apparatus, since the feedback control is performed using the corrected position signal obtained by correcting the position error of the measured position of the scanned object, the sub-scanning position can be controlled with high accuracy. Therefore, even if a linear motor is used for the drive system and the high-precision and expensive position measuring means is not used, the unevenness in the sub-scanning speed can be suppressed, the sub-scanning with high accuracy can be realized, and the cost of the image forming apparatus can be reduced. At the same time, a high-quality image can be formed.
[0021]
In the image forming apparatus, any of a linear encoder, a laser interferometer, and a rotary encoder can be used as the sub-scanning position measuring means.
[0022]
Further, speed information calculated from the measurement result of the sub-scanning position may be fed back to the control unit.
[0023]
Further, the image forming unit may include an optical unit including an optical system, and may be configured to convey the optical unit in the sub-scanning direction. Further, the scanning object may be transported in the sub-scanning direction.
[0024]
In addition, by arranging a magnetic shielding sheet or a magnetic shielding plate around the linear motor, it is possible to suppress the influence of the magnetism from the linear motor on other components and the like, and to prevent dust from entering. You can also.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
<Image reading device>
[0027]
FIG. 1 is a perspective view schematically showing an image reading apparatus according to the present embodiment. FIG. 2 is a side view of a main part of the image reading apparatus of FIG. 1 viewed from the direction of arrow a in FIG. FIG. 3 is a block diagram (a) of a control system of the image reading apparatus of FIG. 1 and a block diagram (b) of an encoder correction / speed detection unit.
[0028]
An image reading apparatus 1 shown in FIG. 1 includes a main scanning unit 2, a reading unit 3, and a sub-scanning unit 4, and a main scanning unit 2 for a radiation image conversion panel 10 formed of a stimulable phosphor or the like. A laser beam is irradiated as excitation light from the scanning unit, and the radiation image conversion panel 10 is sub-scanned and conveyed in the sub-scanning direction H by the sub-scanning unit 4 to perform two-dimensional scanning. It reads the image information that has been detected and stored in the radiation image conversion panel 10 by radiation imaging. The radiation image conversion panel 10 is transported in the sub-scanning direction H while being guided by a guide member (not shown) fixed to the apparatus main body.
[0029]
As shown in FIG. 1, the main scanning unit 2 of the image reading apparatus 1 includes a light source 11 such as a laser diode (LD) for generating a laser beam for irradiating a radiation image conversion panel 10 and a laser beam from the light source 11. A polygon mirror 12 that irradiates the radiation image conversion panel 10 in the main scanning direction S to deflect laser light for performing main scanning, and a mirror 13 that reflects the laser light from the polygon mirror 12 toward the radiation image conversion panel 10 And. Note that an fθ lens or the like is further disposed as an optical system that guides the laser light from the light source 11 to the radiation image conversion panel 10, but is not shown in FIG.
[0030]
In addition, the reading section 3 of the image reading apparatus 1 shown in FIG. 1 has an elongated end face in the main scanning direction S in order to collect stimulated light emitted from the radiation image conversion panel 10 by being excited by irradiation of laser light. A light collector 16 is provided so as to extend, and a photoelectric conversion element 15 such as a photomultiplier for photoelectrically converting the stimulated light condensed and guided by the light collector 16. In the reading unit 3, the electric signal photoelectrically converted from the stimulated emission is subjected to predetermined signal processing as image data, and then is operated from the image reading device 1 via a communication cable through an operation terminal, an image storage device, and an image display device. The image is output to an image output device such as a device or a dry imager (both are not shown). Note that the reading unit 3 may have a configuration other than the present embodiment as long as it is a unit that reads image information from the radiation image conversion panel 10.
[0031]
A sub-scanning unit 4 of the image reading apparatus 1 of FIG. 1 includes a linear motor 21 which is a driving source for transporting the radiation image conversion panel 10 and performing sub-scanning in a sub-scanning direction H substantially orthogonal to the main scanning direction S. And a linear encoder 25 that detects and measures the position of the radiation image conversion panel 10 when the radiation image conversion panel 10 is transported and moved.
[0032]
The linear motor 21 is disposed so as to extend along the radiation image conversion panel 10 in parallel with the sub-scanning direction H, has a long rail-like shape, and has a U-shaped cross-sectional member 22 fixed to the apparatus body. A pair of magnet yokes 22a and 22b provided on two opposing inner surfaces of the cross-sectional member 22 and a distance between the pair of magnet yokes 22a and 22b so as to protrude from the side end surface of the radiation image conversion panel 10. And a movable coil portion 23 located in a non-contact manner. The linear motor 21 conveys the radiation image conversion panel 10 in the sub-scanning direction H and performs sub-scanning by controlling the energization of the movable coil unit 23.
[0033]
Also, as shown by broken lines in FIGS. 1 and 2, it is preferable to arrange a magnetic shielding plate 49 around the linear motor 21 so as to cover the entire linear motor 21. The influence of the magnetism from the linear motor 21 on the electric components and the like of the reading unit 3 can be suppressed, and the entry of dust into the linear motor 21 can also be prevented.
[0034]
The linear encoder 25 includes a measuring unit 25a formed of a linear scale or the like attached near the side end surface of the radiation image conversion panel 10 so as to extend in parallel with the sub-scanning direction H, and irradiates the measuring unit 25a with light to generate reflected light. A detection unit 25b fixed to the apparatus main body so as to detect the position of the received light and measure the position. When the radiation image conversion panel 10 is transported in the sub-scanning direction, the measurement unit 25a moves together with the radiation image conversion panel 10 with respect to the detection unit 25b, and the detection unit 25b detects the position of the radiation image conversion panel 10.
[0035]
FIG. 4 shows a specific example of the linear encoder 25. As shown in FIG. 4, light from a light source 41 composed of an LED or the like is irradiated on the scale surface 25c of the measuring unit 25a via the condenser lens 44 and the scanning grating 45, and the reflected light is transmitted via the scanning grating 45 and the condenser lens 44. The light is received by the light receiving elements 42 and 43. Light from the condenser lens 44 is transmitted through a scanning grating 45 in which two phase gratings are alternately inserted, becomes a parallel light beam, is incident on the scale surface 25c, and the scale interval is shifted by 1/4 from the scale surface 25c. Four grating images are formed, and the reflected light is incident on the light receiving elements 42 and 43, and four sine wave signals having a phase difference of 90 degrees are generated. When the measuring unit 25a formed of a linear scale moves in the sub-scanning direction, an encoder signal is generated from the light receiving elements 42 and 43 according to the moving distance.
[0036]
In FIG. 1, the radiation image conversion panel 10 is transported for sub-scanning. However, the main scanning unit 2 and the reading unit 3 may be transported to the radiation image conversion panel 10 for sub-scanning. Of course, both the radiation image conversion panel 10 and the main scanning unit 2 and the reading unit 3 may be transported.
[0037]
As shown in FIG. 3A, the control system of the image reading device 1 of FIG. 1 controls the entire image reading device 1 and generates a speed command signal to the linear motor 21. A first difference output unit 31 that generates a difference signal in accordance with a difference between the input speed command signal and a measured speed signal obtained from the corrected position signal from the linear encoder 25, and a PID ( A speed control unit 32 that performs speed control by a proportional-integral-derivative) control operation; and a second control unit that generates a difference signal according to a difference between a speed control signal input from the speed control unit 32 and a drive signal input to the linear motor 21. A difference output unit 33.
[0038]
The control system shown in FIG. 3A includes a current control unit 34 that generates a PWM (pulse width modulation) control signal based on a difference signal from the second difference output unit 33 and a PWM control signal based on the PWM control signal. An inverter circuit 35 that outputs a drive signal to the movable coil unit 23 of the linear motor 21; and a current detection that detects the drive signal of the inverter circuit 35 and feeds it back to a second difference output unit 33 to compensate for an error in the speed control signal. And a vessel 36.
[0039]
The control system in FIG. 3A further calculates a measurement position signal indicating the sub-scanning position of the radiation image conversion panel 10 based on the encoder signal input from the detection unit 25b of the linear encoder 25, and converts the measurement position signal. A position correction / speed detection unit 37 is provided that corrects based on the error signal, obtains a measured speed signal from the corrected position signal, and feeds it back to the first difference output unit 31.
[0040]
As shown in FIG. 3B, specifically, the position correction / speed detection unit 37 integrates the encoder signal of the pulse waveform input from the detection unit 25b of the linear encoder 25 to obtain an encoder signal integration that obtains a measurement position signal. A circuit 38, a memory 39 for measuring a position error at each sub-scanning position in the sub-scanning direction in advance and storing it as an error signal, and correcting the measured position signal from the encoder signal integrating circuit 38 with the error signal to represent an accurate position A correction unit 40 for obtaining a position signal, and a speed calculation circuit 41 including a differentiating circuit for obtaining a speed signal from the corrected position signal are provided.
[0041]
In the position correction / speed detection unit 37, for example, as shown in the graph in the correction unit 40 in FIG. 3B, the actual position m is measured at a coordinate position indicated by a small white circle in the figure from the measurement position m corresponding to the measurement position signal. By obtaining ', the measured position signal can be corrected to a position signal representing an accurate position. The memory 39 stores, for example, a plurality of coordinates (m, m ') representing the measured position m and the actual position m' as error signals.
[0042]
In the linear encoder 25, for example, a pitch error of the scale surface 25c in FIG. 4 appears as a speed measurement error, and such a pitch error is unique to each rear air encoder and differs for each encoder. As described above, the error is corrected based on the relationship between the measurement position measured in advance for each encoder 25 and the actual position, so that the measurement position measured by the encoder 25 can be accurately determined regardless of the detection accuracy of the encoder 25. Can be corrected to a suitable position. For this reason, it is not necessary for the encoder 25 to have a high detection accuracy leading to an increase in cost.
[0043]
In addition to the linear encoder as the sub-scanning position measuring means, a laser interferometer or a rotary encoder may be used. In this case, as described above, since the detection accuracy is not so required, a relatively inexpensive device may be used. It can be used, and the cost of the device can be reduced.
[0044]
The operation of the image reading device 1 of FIGS. 1 to 3 will be described. First, the main scanning unit 2 performs main scanning on the radiation image conversion panel 10 in the main scanning direction S with the laser light 143 by the control unit 30 in FIG. Image information is read by condensing stimulated emission generated from the image conversion panel 10 and performing photoelectric conversion.
[0045]
Based on the speed command signal calculated from the main scanning period and the reading pitch by the control unit 30, the signal is output via the first difference output unit 31, the speed control unit 32, the second difference output unit 33, and the current control unit 34. The linear motor 21 is driven by the PWM control signal, starts the conveyance of the radiation image conversion panel 10 in the sub-scanning direction H in FIG. 1, and converts the radiation image converted based on the encoder signal measured by the linear encoder 25. A position signal representing an accurate position of the measured position signal of the panel 10 based on the coordinates (m, m ′) representing the measured position m and the actual position m ′ stored in the memory 39 by the correction unit 40 in FIG. To be corrected.
[0046]
As described above, the speed command signal is corrected by feeding back the measured speed signal obtained by the speed calculation circuit 41 from the position signal corrected to the accurate position to the first difference output unit 31 to correct the speed signal. Can drive the linear motor 21 and can suppress unevenness in the sub-scanning speed. Therefore, the radiation image conversion panel 10 can be moved to the correct sub-scanning position, and the next main scanning and reading are performed at the accurate sub-scanning position.
[0047]
As described above, according to the image reading apparatus of the present embodiment, the scale pitch error of the linear encoder 25 is measured in advance by using the linear motor 21 for the drive system for the sub-scanning conveyance. By correcting the measurement position measured by the linear encoder 25 to the actual accurate position when performing the speed control, accurate speed measurement can be performed, and therefore, sub-scanning without speed unevenness can be performed. High-quality image reading can be performed. Further, since it is not necessary to use a highly accurate and expensive position measuring means such as an encoder, the cost of the image reading apparatus can be reduced.
[0048]
<Image forming apparatus>
[0049]
FIG. 5 is a schematic view of the entire image forming apparatus according to the present embodiment as viewed from the side. 6A is a plan view of a main part of the image forming apparatus of FIG. 5, and FIG. 3B is a sectional side view of the main part. FIG. 7 is a perspective view of a main part of the image forming apparatus of FIG.
[0050]
An image forming apparatus 600 shown in FIG. 5 forms an image by directly or indirectly exposing image information obtained by radiographing a human body or the like in a medical field onto a recording medium which is a sheet-like image forming material (sheet film). It is.
[0051]
In the image forming apparatus 600 of FIG. 5, a plurality of sheet-shaped recording media 100 of a laser heating system are placed and stored in a cassette 210 which is a loading table of a loading device 200 in a stacked state. The recording medium 100 placed on the cassette 210 is separated one by one by a suction cup 220 serving as a sending means and sent out. The fed recording medium 100 is transported by a transport roller 230 to a cylindrical drum 240 serving as a sheet holding unit. In the drum 240, the leading end of the recording medium 100 is held by a gripper 250 as a sheet holding member. The recording medium 100 is adhered and held on the peripheral surface of the drum 240 by the rotation of the drum 240 (clockwise in FIG. 5) and the sliding roller 260 that slides on and follows the drum 240. The sliding roller 260 has a mechanism for pressing and separating from the drum 240.
[0052]
As shown in FIG. 5 and FIG. 6, a multi-channel, which is a laser light emitting element provided in the laser device 310 of the exposure optical system 300, is applied to the sheet-shaped recording medium 100 held and rotated on the peripheral surface of the drum 240. The recording medium 100 is irradiated with the light beam L emitted from the laser head 31 </ b> A of the mold, performs main scanning in the rotation direction (main scanning direction) R, and performs sub-scanning in the rotation axis direction (sub-scanning direction) H of the drum 240. Ablation of material occurs between the color material layer and the base layer to form an image.
[0053]
When the irradiation scan on the recording medium 100 is completed, the drum 240 is rotated in the reverse direction (counterclockwise in FIG. 1), and the recording medium 100 is separated from the drum 240 by a separating unit (not shown) such as a separation claw, and is conveyed. The sheet is conveyed by conveying means 270 such as a roller. At this time, the recording medium 100 is separated and conveyed such that the end of the recording medium 100 held by the gripper 250 is on the rear end side.
[0054]
The first sheet 110 and the second sheet 120 are peeled from the transported recording medium 100 by the peeling means 400. Due to this separation, a portion irradiated by the light beam L of the laser device 310 is transferred to the second sheet 120, and an unexposed portion of the color material layer remains on the first sheet 110, thereby forming an image. When the recording medium 100 is peeled, the first sheet 110 used as an image-formed sheet is discharged by a discharge roller 280 onto a discharge tray 290 outside the apparatus. The second sheet 120 is wound and collected by the collecting unit 500.
[0055]
As described above, in the image forming apparatus 600 of the present embodiment, the recording medium 100 wound on the outer peripheral surface of the drum 240 is irradiated with the light beam L emitted from the laser device 310 to form an image. Therefore, in order to achieve high-quality image formation and image recording, it is necessary to smoothly drive the laser device 310 in the sub-scanning direction without unevenness in speed. explain.
[0056]
As shown in FIGS. 6 and 7, one end of a rotating shaft 241 of the drum 240 is connected to a drive motor 244 via a coupling 243, and a rotary encoder 50 is provided at an end of the drive motor 244. The rotation speed of the motor 244 is detected. The rotation shaft 241 of the drum 240 may be extended so as to be integrated with the rotor of the drive motor 244.
[0057]
The laser device 310 having the laser head 31A is mounted on the upper surface side of a base member (carriage) 320. On the bottom surface side of the base member 320, two main sliders 330 are provided on the side near the rotation shaft 241. One sub-slider 340 is fixed on a side far from the rotation shaft 241.
[0058]
The main slider 330 is slidable in the sub-scanning direction on a main guide member (guide rail) 350 having a smooth surface horizontally arranged in parallel with the rotation shaft 241. The sub-slider 340 is fitted to a sub-guide member (guide bar) 370 having a smooth surface horizontally supported by the support members 36A and 36B in parallel with the main guide member 350, and is slidable in the sub-scanning direction H. is there. Therefore, the base member 320 on which the laser device 310 is mounted is supported at three points on the main guide member 350 and the sub-guide member 370 by the two main sliders 330 and the one sub-slider 340, and the sub-scanning direction H To slide.
[0059]
The base member 320 has a laser device 310 mounted thereon and is moved in the sub-scanning direction H by a linear motor 380. The linear motor 380 is disposed so as to extend in parallel with the sub-scanning direction H, has a long rail shape, and has a U-shaped cross-section member 38C fixed to the apparatus main body. A pair of magnet yokes 38A, 38A provided on two surfaces to be provided, and a movable coil 38B attached to the movable base member 320 and separated from the pair of magnet yokes 38A and 38A and located in a non-contact manner. ing. The base member 320 on which the laser device 310 is mounted slides on the two guide members 350 and 370 under the control of energizing the movable coil portion 38B of the linear motor 380, and moves while being guided in the sub-scanning direction H.
[0060]
As shown in FIGS. 6 and 7, a linear encoder 390 is provided as a sub-scanning position measuring means between the guide rail 350 on the recording medium 100 side and the recording medium 100, and a laser provided by a detection unit provided on the laser device 310 side. The position and speed of the head 31A can be detected. The linear encoder 390 may have the same configuration as that described with reference to FIG.
[0061]
The linear motor 380 is controlled based on the position and speed of the laser head 31A detected by the detection unit of the linear encoder 390, and moves the laser head 31A at a constant speed in the sub-scanning direction. The rotary encoder 50 provided on the drive motor 244 controls the rotation speed of the drive motor 244 to be constant.
[0062]
The control system of the image forming apparatus 600 shown in FIGS. 5 to 7 can be configured in the same manner as in FIGS. 3A and 3B described above, and in the same figure, the laser is controlled based on the encoder signal input from the detection unit of the linear encoder 390. A measurement position signal representing the sub-scanning position of the head 31A is calculated, the measurement position signal is corrected based on the error signal, a measurement speed signal is obtained from the corrected position signal, and the measurement speed signal is fed back to the first difference output unit 31. .
[0063]
The operation of the control system of the image forming apparatus 600 shown in FIGS. 5 to 7 will be described. First, the laser device 310 slides on the two guide members 350 and 370 and moves in the sub-scanning direction H by controlling the energization of the movable coil portion 38B of the linear motor 380, and moves from the laser head 31A to the recording medium on the drum 240. 100 is irradiated with a laser beam, and then the drum 240 is rotated by a predetermined amount in the rotation direction R, and then the laser beam is similarly irradiated to form an image on the recording medium 100.
[0064]
When the laser device 310 is moved in the sub-scanning direction H by the linear motor 380 during image formation as described above, the control unit 30 in FIG. 3A outputs a predetermined speed command signal to the linear motor 380 for sub-scanning. Based on the above-mentioned speed command signal, the linear motor 380 is driven by the PWM control signal output through the first difference output unit 31, the speed control unit 32, the second difference output unit 33, and the current control unit 34, and the laser 6A, the sub-scanning is started in the sub-scanning direction H in FIG. 6A, and the measured position signal of the laser head 31A of the laser device 310 obtained based on the encoder signal measured by the linear encoder 390 is shown in FIG. The correction unit 40 in (b) corrects the position signal representing the accurate position by the coordinates (m, m ') representing the measured position m and the actual position m' stored in the memory 39.
[0065]
As described above, the speed command signal is corrected by feeding back the measured speed signal obtained by the speed calculation circuit 41 from the position signal corrected to the accurate position to the first difference output unit 31 to correct the speed signal. Can drive the linear motor 380, and can suppress unevenness in the sub-scanning speed. For this reason, the laser device 310 can be moved in the sub-scanning direction in a stable state without uneven speed, and image formation is performed stably.
[0066]
Also, in the linear encoder 390, as in FIG. 4, the pitch error of the scale surface appears as a speed measurement error, and such a pitch error is unique to each rear air encoder and differs for each encoder. Since the error is corrected based on the relationship between the measurement position measured in advance for each encoder 390 and the actual position, the measurement position measured by the encoder 390 can be corrected to an actual accurate position regardless of the detection accuracy of the encoder 390. . For this reason, the encoder 390 does not need high detection accuracy that leads to high cost.
[0067]
In addition to the linear encoder as the sub-scanning position measuring means, a laser interferometer or a rotary encoder may be used. In this case, as described above, since the detection accuracy is not so required, a relatively inexpensive device may be used. It can be used, and the cost of the device can be reduced.
[0068]
As described above, according to the image forming apparatus of the present embodiment, the linear motor 380 is used for the driving system for sub-scanning conveyance, and the scale pitch error of the linear encoder 390 is measured in advance, and the sub-scanning is performed. By correcting the measurement position measured by the linear encoder 390 to the actual accurate position when performing the speed control, accurate speed measurement can be performed, and therefore, sub-scanning without speed unevenness can be performed. High quality image formation can be performed. Further, since it is not necessary to use a highly accurate and expensive position measuring unit such as an encoder, the cost of the image forming apparatus can be reduced.
[0069]
Note that, similarly to FIGS. 1 and 2, by arranging a magnetic shielding plate around the linear motor 380 so as to cover the entire linear motor 380, the influence of magnetism from the linear motor 380 on electric components and the like can be reduced. In addition, it is possible to prevent dust from entering the linear motor 380.
[0070]
As described above, the present invention has been described with the embodiments, but the present invention is not limited to these, and various modifications can be made within the technical idea of the present invention. For example, in the image reading apparatus of FIG. 3, an example is shown in which the radiation conversion plate 10 is conveyed in the sub-scanning direction in the horizontal direction. However, the present invention is not limited to this, and is applicable to, for example, sub-scanning in the vertical direction. Of course. The image forming apparatus may be an apparatus that forms an image by performing two-dimensional scanning on a planar photosensitive material, for example.
[0071]
【The invention's effect】
According to the present invention, it is possible to provide a transfer device that uses a linear motor for a drive system and suppresses unevenness in speed and realizes accurate transfer without using an accurate and expensive position measuring unit. Further, it is possible to provide an image forming apparatus and an image reading apparatus capable of performing sub-scanning using such a transport device, suppressing unevenness in sub-scanning speed, and obtaining high image quality with an inexpensive configuration.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing an image reading apparatus according to an embodiment.
FIG. 2 is a side view of a main part of the image reading apparatus of FIG. 1 as viewed from an arrow direction a of FIG.
FIGS. 3A and 3B are a block diagram of a control system of the image reading apparatus of FIG. 1 and a block diagram of an encoder correction / speed detection unit;
FIG. 4 is a perspective view showing a specific example of the linear encoder shown in FIGS. 1 and 2;
FIG. 5 is a schematic view of the entire image forming apparatus according to the present embodiment, as viewed from the side.
6A is a plan view of a main part of the image forming apparatus of FIG. 5 and FIG.
FIG. 7 is a perspective view of a main part of the image forming apparatus of FIG. 5;
[Explanation of symbols]
1 ... image reading device
2 Main scanning unit
3 Reading unit
4: Sub-scanning unit
10. Radiation image conversion panel (transported object, scanned object)
21 ・ ・ ・ Linear motor
25 ... linear encoder
30 ... Control unit
31 first difference output unit
32 ・ ・ ・ Speed control unit
33... Second difference output unit
34 current control unit
35 ・ ・ Inverter
36 ... Current detector
37 ・ ・ ・ Position correction / speed detector
39 ・ ・ ・ Memory
40 ・ ・ ・ Correction unit
41 ・ ・ ・ Speed calculation circuit
100: sheet-shaped recording medium
240 ・ ・ ・ Drum
310 ・ ・ ・ Laser device
31A ・ ・ ・ Laser head
380 ・ ・ ・ Linear motor
390 ・ ・ ・ Linear encoder
H: Sub-scanning direction

Claims (21)

A linear motor as a drive source for transporting the transported object,
Position measuring means for measuring the transfer position of the transferred object,
Control means for performing feedback control of the linear motor based on the measurement result of the transport position,
Storage means for storing data relating to the position error at each of the transport positions,
A transfer device, wherein a correction position signal obtained by correcting the measurement result of the transfer position with the data is fed back to the control unit. The transport device according to claim 1, wherein a linear encoder is used as the position measuring unit. The transport apparatus according to claim 1, wherein a laser interferometer is used as the position measuring means. The transport device according to claim 1, wherein a rotary encoder is used as the position measuring unit. The transport device according to any one of claims 1 to 4, wherein speed information calculated from a measurement result of the measurement position is fed back to the control unit. Main scanning means for irradiating the scanned object with a light beam in the main scanning direction to perform main scanning, and a linear motor as a drive source for performing sub scanning in a sub scanning direction substantially orthogonal to the main scanning direction. Image reading means for reading image information from the scanned object by two-dimensional scanning of the scanned object,
Sub-scanning position measuring means for measuring a sub-scanning position which is a relative position between the scanned object and the main scanning means,
Control means for controlling the linear motor by feeding back the measurement result of the sub-scanning position,
Storage means for storing data relating to a position error at each of the sub-scanning positions,
An image reading apparatus, wherein a correction position signal obtained by correcting the measurement result of the sub-scanning position with the data is fed back to the control unit. The image reading apparatus according to claim 6, wherein a linear encoder is used as the sub-scanning position measuring means. The image reading apparatus according to claim 6, wherein a laser interferometer is used as the sub-scanning position measuring means. The image reading apparatus according to claim 6, wherein a rotary encoder is used as the sub-scanning position measuring means. 10. The image reading apparatus according to claim 6, wherein speed information calculated from the measurement result of the sub-scanning position is fed back to the control unit. The image reading apparatus according to claim 6, wherein the image reading unit has an optical unit including an optical system, and conveys the optical unit in the sub-scanning direction. The image reading apparatus according to claim 6, wherein the object to be scanned is transported in the sub-scanning direction. 13. The image reading apparatus according to claim 6, wherein a magnetic shielding sheet or a magnetic shielding plate is arranged around the linear motor. Main scanning means for performing main scanning by irradiating the scanned object with a light beam in the main scanning direction, and a linear motor as a driving source for performing sub scanning in a sub scanning direction substantially orthogonal to the main scanning direction. And an image forming means for forming an image on the scanned object by two-dimensional scanning with respect to the scanned object,
Sub-scanning position measuring means for measuring a sub-scanning position which is a relative position between the scanned object and the main scanning means,
Control means for controlling the linear motor by feeding back the measurement result of the sub-scanning position,
Storage means for storing data relating to a position error at each of the sub-scanning positions,
An image forming apparatus, wherein a correction position signal obtained by correcting the measurement result of the sub-scanning position with the data is fed back to the control unit. The image forming apparatus according to claim 14, wherein a linear encoder is used as the sub-scanning position measuring unit. The image forming apparatus according to claim 14, wherein a laser interferometer is used as the sub-scanning position measuring unit. The image forming apparatus according to claim 14, wherein a rotary encoder is used as the sub-scanning position measuring unit. 18. The image forming apparatus according to claim 14, wherein speed information calculated from the measurement result of the sub-scanning position is fed back to the control unit. The image forming apparatus according to claim 14, wherein the image forming unit includes an optical unit including an optical system, and conveys the optical unit in the sub-scanning direction. 20. The image forming apparatus according to claim 14, wherein the object to be scanned is transported in the sub-scanning direction. The image forming apparatus according to any one of claims 14 to 20, wherein a magnetic shielding sheet or a magnetic shielding plate is disposed around the linear motor.

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