JP5867811B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  In the present invention, after the sheet member separated into one sheet by the separating means is abutted against the abutting nip of the abutting roller pair in the rotation stopped state, the sheet member is conveyed toward the conveying destination by the rotational driving of the abutting roller pair. The present invention relates to a sheet conveying apparatus. The present invention also relates to an image reading apparatus and an image forming apparatus using such a sheet conveying apparatus.

  As this type of sheet conveying apparatus, an apparatus mounted on an image forming apparatus described in Patent Document 1 is known. This image forming apparatus transfers a toner image formed on the surface of a drum-shaped photoconductor by an electrophotographic process onto a recording sheet sandwiched between transfer nips by contact between the photoconductor and an endless transfer belt. ing. The sheet conveying device passes the recording sheet fed from the inside of the paper feed tray through the separating unit, the conveying unit, and the registration roller pair as the butting roller, and then feeds the recording sheet into the transfer nip at an appropriate timing.

  The separation means of the sheet conveying device separates and feeds only one recording sheet from a bundle of recording sheets sent out in a state where a plurality of sheets are overlapped from the inside of the paper feed tray. A separation pad that abuts to form a separation nip. The feed roller is rotationally driven so as to move in the sheet feeding direction while contacting the uppermost recording sheet among the plurality of recording sheets. In addition, the separation pad applies conveyance resistance to the lower recording sheet except the uppermost one among the plurality of recording sheets sandwiched between the feed rollers, so that the lower recording sheet is placed in the separation nip. Keep on. Patent Document 1 also describes a configuration in which a separation roller is provided instead of the separation pad. In this configuration, the lower side recording sheet is reversely conveyed from the inside of the separation nip toward the paper feed cassette by the rotational driving of the separation roller.

  Of the plurality of recording sheets sandwiched in the separation nip, the lower recording sheet remains in the separation nip by the action of the separation pad, or is reversely conveyed toward the paper feed cassette by driving the separation roller. . Thereby, the uppermost recording sheet in contact with the feed roller is separated from the lower recording sheet and fed out from the separation nip.

  The recording sheet separated into one sheet and fed out from the separation nip is sandwiched in the conveyance nip by the contact between the grip roller and the endless conveyance belt, and then is fed out from the conveyance nip. Then, the front end is abutted against the registration nip of the stopped registration roller pair. An optical sensor for detecting the recording sheet is disposed in the vicinity of the registration nip as the abutting nip. The driving of the grip roller is stopped after a predetermined delay stop time has elapsed after the leading edge of the sheet is detected by the optical sensor. In this process, the recording sheet with the leading end abutted against the registration nip is bent. When the recording sheet is not in a straight posture along the conveyance direction but in an oblique posture, the oblique posture is corrected straight by the bending force (skew correction). When rotation of the registration roller pair is started, the registration roller pair is fed out from the registration nip and enters the transfer nip.

  In the sheet conveying apparatus having such a configuration, due to the wear of the grip roller of the conveying means, the recording sheet feeding speed by the registration roller pair may become unstable and the image quality may be disturbed. Hereinafter, this phenomenon will be described in detail.

  The rear end side of the recording sheet immediately after the feeding from the registration nip to the transfer nip is still sandwiched by the separation nip on the most upstream side. In this state, an impact due to back tension or the like may be applied to the rear end side of the sheet in the separation nip. If the recording sheet is sufficiently bent immediately before the registration nip, the impact is absorbed by the deflection, so that transmission of the impact to the registration roller pair is avoided. However, if the recording sheet is not bent immediately before the registration nip, the impact applied to the rear end side of the recording sheet in the separation nip is applied to the registration roller pair via the recording sheet that is straightly stretched. It is transmitted. Then, due to a large fluctuation in torque due to the impact, the rotational speed of the registration roller pair is temporarily greatly reduced, and the recording sheet in the transfer nip is rubbed against the photoconductor, so that the toner image being transferred is disturbed. It is.

  The reason why the deflection of the recording sheet is not formed immediately before the registration nip is that the grip roller forming the conveyance nip between the registration nip and the separation nip on the most upstream side is worn. And the back tension by the feed roller which forms the separation nip upstream from the grip roller is involved in the wear of the grip roller. Specifically, the feed roller that forms the separation nip on the upstream side of the grip roller is driven to rotate at a lower linear velocity than the grip roller. When the leading edge of the recording sheet fed from the separation nip by the rotation of the feed roller enters the conveyance nip by the grip roller, the recording sheet is stretched between the conveyance nip and the separation nip with a strong tension, and is applied to the feed roller. A strong torque is applied. As a result, the torque limiter is actuated so that the feed roller follows the recording sheet, and the recording sheet is conveyed at the same linear velocity as the grip roller. At this time, an irregular back tension is applied to the recording sheet because the torque limiter operates irregularly due to subtle fluctuations in torque. As a result, the recording sheet slips on the surface of the grip roller to promote wear on the surface of the grip roller. When the linear velocity is reduced by reducing the diameter of the grip roller due to wear, the amount of the sheet sent out from the conveyance nip within the delay stop time described above is reduced, so that the recording sheet is sufficiently bent immediately before the registration nip. It will not be possible.

  In the state where the grip roller is worn, the image is disturbed by a sudden torque drop when the trailing edge of the recording sheet passes through the separation nip or the conveyance nip. Specifically, when the linear velocity of the grip roller is reduced below the design value due to wear, the pair of registration rollers existing downstream from the grip roller pulls the recording sheet while adjusting the linear velocity of the grip roller and the feed roller. It will follow the speed. In this state, if the trailing edge of the recording sheet passes through the separation nip on the uppermost stream side, the load on the registration roller pair suddenly decreases. The toner image will be disturbed. Also, when the trailing edge of the recording sheet passes through the conveyance nip, the load on the registration roller pair decreases rapidly, so the linear velocity of the registration roller pair increases temporarily, and the toner image in the transfer nip is displayed. It will be disturbed.

  Up to now, the problems that occur in an image forming apparatus that forms an image by an electrophotographic process have been described. However, an image forming apparatus that forms an image by a process different from the electrophotographic process or an image reading apparatus that includes an ADF is also used. Similar problems can arise. For example, in an inkjet image forming apparatus, if a configuration is adopted in which a recording sheet separated by a separation nip is bent between a conveyance nip and a registration nip and then sent to an image recording position by an inkjet head. This will disturb the ink image. In addition, when an image reading apparatus with an ADF adopts a configuration in which an original sheet separated by a separation nip is bent between a conveyance nip and a registration nip and then passed through an image reading position by an image reading sensor. A similar problem occurs. In this case, an image reading error occurs due to fluctuations in the conveyance speed of the original sheet at the image reading position.

  The present invention has been made in view of the above background, and an object thereof is to provide the following sheet conveying apparatus, and an image reading apparatus and an image forming apparatus using the sheet conveying apparatus. That is, a sheet conveying apparatus that can suppress image quality disturbance and image reading error due to wear of a conveying member (for example, a grip roller) of the conveying unit.

In order to achieve the above object, the present invention provides a feeding member that moves its surface endlessly in a feeding direction toward a destination, and forms a separation nip in contact with the feeding member. A conveyance resistance imparting member that imparts conveyance resistance to a sheet member that is not in direct contact with the feeding member in a state where a plurality of overlapping sheet members are sandwiched between the sheet feeding member and the feeding member. Separating means for separating the sheet member that is in direct contact with the feeding member from the sheet member that is not in direct contact and feeding it from the separation nip, and sheet detecting means for detecting the sheet member downstream of the separation nip in the sheet conveying direction If, surface to form a conveying nip is brought into contact with each other two conveying rollers to endlessly move, the sheet member passing through the separation nip in a state sandwiched himself of the transport nip, One of the conveying roller, a conveying means for transporting the transport destination by the endless movement of at least one of the surfaces, the abutment conveying nip two abutting transport member for a surface is endlessly moved by contact with each other In a state in which the sheet member that has passed through the conveyance nip is sandwiched between the abutting conveyance nip, at least one of the two abutting conveyance members is moved toward the conveyance destination by endless movement of one of the surfaces. Abutting and conveying means for conveying, a DC brushless motor that is a drive source of the conveying roller, an encoder for detecting the rotation amount of the conveying roller or the DC brushless motor, and between the conveying nip and the abutting and conveying nip a deflection detection means for detecting whether deflection of the amount of the sheet member that exceeds a predetermined threshold value is formed in the Deflection formation that forms the deflection of the sheet member by feeding the sheet member from the conveyance nip while abutting the leading end of the sheet member via the feeding nip against the abutting conveyance nip of the abutting conveyance unit in a non-driven state after carrying out the process, the sheet conveying device and a control means for performing a process of the abutting conveying means is driven feeding toward the conveyance destination of the sheet member from the abutting transport nip, said abutment a driving source for driving the conveying member provided separately from said DC brushless motor, in front Symbol deflection forming process, accumulation of a predetermined said rotation amount from the tip of the sheet member is detected by said sheet detecting means After performing the process of stopping the driving of the conveying means based on the target rotation amount , and after performing the bending formation process Based on the fact that the detection result by the bending detection means is no deflection, the conveyance in the subsequent bending forming process is performed by correcting the target rotation amount to a larger value so that the detection result of the presence of bending is obtained. When the control unit is configured to perform processing for increasing the driving amount of the unit and the sheet member is fed from the abutting conveyance nip toward the conveyance destination, the DC brushless motor At least one of the feedback control of the output voltage based on the detection result by the encoder and the target rotation position and the feedback control of the output voltage based on the detection result and the target rotation speed is performed on the coil, and feedback is performed. The amount of fluctuation per unit time of the output voltage when performing control is a predetermined threshold value. When exceeding, it is determined that a deflection exceeding the predetermined threshold is not formed between the conveyance nip immediately before starting the feeding of the sheet member from the abutting conveyance nip and the abutting conveyance nip. The control means is configured to perform a determination process, and the control means functions as the deflection detection means .

  In the present invention, in the bend forming process, after confirming that the bend is detected by the bend detecting means, the driving of the conveying means is temporarily stopped. Alternatively, if the detection result by the bending detection unit immediately after the driving of the conveying unit is temporarily stopped in the bending forming process becomes no bending, the driving amount of the conveying unit in the subsequent bending forming process is increased to cause bending. To be detected. In the configuration in which it is confirmed that the bending is detected and the driving of the conveying unit is stopped, even if the conveying member of the conveying unit is worn, the sheet member between the conveying nip and the abutting conveying nip in the bending forming process. Is bent with a predetermined bending amount. In addition, when the detection result by the bending detection unit immediately after the driving of the conveying unit is temporarily stopped in the bending formation process becomes no bending, in the configuration to increase the driving amount of the conveying unit in the subsequent bending formation process, Even if the predetermined bending amount cannot be obtained by the bending formation process due to the wear of the conveying member of the conveying means, the sheet member is bent by the predetermined bending amount in the next bending forming process. As described above, in any configuration, even if the conveying member of the conveying unit is worn, the sheet member can be reliably bent with a predetermined bending amount between the conveying nip and the abutting conveying nip. In such a configuration, the sheet member is sent out from the abutting conveyance nip in a state where the sheet member is bent by a predetermined deflection amount regardless of the wear of the conveyance member. Then, the impact applied to the rear end side of the sheet member at the separation nip of the separating means is absorbed at the bending portion of the recording sheet, so that the impact conveying member is stabilized without transmitting the impact to the impact conveying member. Drive at linear speed. Even if the linear velocity of the worn conveying member becomes slower than the linear velocity of the abutting conveying member and the amount of sheet deflection immediately before the abutting conveying nip gradually decreases during sheet conveyance, the sheet Since the sheet member is bent with a sufficient amount of deflection prior to the resumption of conveyance, the sheet member is continuously bent until the rear end of the sheet member passes through the separation nip and the conveyance nip. Alternatively, the timing at which the amount of bending becomes zero is delayed as compared with the case where the bending is hardly formed when the sheet conveyance is resumed. Thereby, the occurrence of torque fluctuation of the abutting conveyance member when the rear end of the sheet member passes through the separation nip or the conveyance nip is avoided or the time during which the torque fluctuation is caused is shortened. As described above, it is possible to avoid the transmission of impact from the separation nip to the abutting conveyance member via the sheet member, or the torque fluctuation of the abutting conveyance member when the trailing edge of the recording sheet passes through the separation nip or the conveyance nip. By avoiding the occurrence or shortening the time during which the torque fluctuation is caused, it is possible to suppress image quality disturbance and image reading error due to wear of the conveying member.

1 is a schematic configuration diagram showing a copying machine according to a reference embodiment. FIG. 2 is a partial configuration diagram illustrating an enlarged part of an image forming unit in the copier. FIG. 2 is a perspective view showing a scanner and an ADF of the copier. The expanded block diagram which shows the principal part structure of the same ADF with the upper part of a scanner. FIG. 4 is a schematic diagram illustrating a state of a recording sheet together with a paper feed path when “pause after skew correction” is performed in a printing unit in a state where the first conveyance roller is not worn. FIG. 6 is a schematic diagram illustrating a state when the trailing edge of the recording sheet has passed through the conveyance nip after feeding of the recording sheet is started from the state of FIG. 5. FIG. 6 is a schematic diagram illustrating a state of a recording sheet together with a paper feed path when “pause after skew correction” is performed in the printing unit in a state where the first conveyance roller is worn. FIG. 8 is a schematic diagram showing a state when the trailing edge of the recording sheet has passed through the separation nip after feeding of the recording sheet is started from the state of FIG. 7. FIG. 9 is a schematic diagram illustrating a state when the rear end of the recording sheet passes through the conveyance nip after the state of FIG. 8. FIG. 6 is a schematic diagram illustrating a state of a recording sheet together with a paper feed path when “pause after skew correction” is performed in the printing unit in a state where the first conveyance roller is further worn. FIG. 3 is a configuration diagram showing a paper feed path in a printing unit of the copier. FIG. 4 is a schematic diagram illustrating the sheet feeding path and a recording sheet forming a slight deflection in the sheet feeding path. FIG. 3 is a schematic diagram illustrating the sheet feeding path and a recording sheet that forms a large deflection in the sheet feeding path. Enlarged perspective view of a feed motor from the front of the printing unit of a copying machine according to the implementation embodiments. The expansion perspective view which shows the same feeding motor from back. The expansion perspective view which shows the code wheel mounted in the feed motor. The expansion perspective view which shows the modification of the same code wheel. The block diagram which shows the principal part of the electric circuit in the motor drive device of the printing part. The block diagram which shows the internal structure of the position and speed tracking control circuit of a motor control circuit.

Hereinafter, the present invention, an electrophotographic type copying machine (hereinafter, simply referred to as a copier) Before describing the implementation form of application to be described copying machine according to the reference embodiment.
First, the basic configuration of the copying machine according to the reference embodiment will be described. FIG. 1 is a schematic configuration diagram showing a copying machine according to a reference embodiment. In the figure, the copying machine includes a printing unit 100 as an image forming apparatus and an image reading unit 200. The image reading unit 200 as an image reading apparatus includes a scanner 201 fixed on the print unit 100 and an automatic document feeder (hereinafter referred to as ADF) 251 as a sheet conveying device supported by the scanner 201. Yes.

  The print unit 100 includes four image forming units 6Y, 6M, 6C, and 6K for forming yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K) toner images. . These use Y, M, C, and K toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached. As an example, an image forming unit 6Y for forming a Y toner image includes a drum-shaped photoreceptor 1Y, a drum cleaning device 2Y, a charge eliminating device (not shown), a charging device 4Y, as shown in FIG. A developing device 5Y and the like are provided. The image forming unit 6Y can be attached to and detached from the main body of the printing unit 100 so that consumable parts can be replaced at a time.

  The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is rotated clockwise in the drawing by a driving unit (not shown). The uniformly charged surface of the photoreceptor 1Y is exposed and scanned by a laser beam L emitted from an optical writing unit 7 as a latent image forming unit, and carries a Y electrostatic latent image. The Y electrostatic latent image is developed into a Y toner image by the developing device 5Y using Y toner. Then, intermediate transfer is performed on the intermediate transfer belt 8. The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the intermediate transfer process. The static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation. In the other image forming units 6M, C, and K, M, C, and K toner images are similarly formed on the photoreceptors 1M, C, and K, and are intermediately transferred onto the intermediate transfer belt 8.

  The developing device 5Y develops a latent image using a two-component developer (hereinafter referred to as a developer) containing a magnetic carrier (not shown) and non-magnetic Y toner. An agitating unit that conveys the developer accommodated in the interior and supplies it to the developing roll 51Y, and Y toner in the developer carried on the surface of the cylindrical developing sleeve of the developing roll 51Y. And a developing portion 53Y for transferring to the above. The developing roller 51Y includes a developing sleeve made of a non-magnetic pipe and a magnet roller that is included so as not to be rotated. The developer roller 51Y attracts the developer to the surface of the developing sleep by the magnetic force generated by the magnet roller. Let

  The agitating unit is provided at a position lower than the developing unit 53Y. The supplying unit 55Y supplies the developer to the developing roll 51Y while agitating and conveying the developer, and the supplying unit while agitating the developer received from the supplying unit 55Y. And a circulation part 54Y that circulates and conveys toward 55Y.

  The supply unit 55Y conveys the developer along the longitudinal direction of the screw by the rotational drive of the first agitating and conveying screw 56Y disposed so as to be parallel to the developing roll 51Y. In this process, the developer is supplied to the developing sleeve of the developing roll 51Y. The developer conveyed to the vicinity of the end in the longitudinal direction of the first agitating and conveying screw 56Y passes through a first communication port (not shown) provided near the end of the partition wall that partitions the supply unit 55Y and the circulation unit 54Y. Then, it enters the circulation part 54Y.

  The circulating portion 54Y rotates the second agitating / conveying screw 57Y disposed so as to be parallel to the developing roll 51Y and the first agitating / conveying screw 56Y, and causes the developer to move along the longitudinal direction of the screw. 1 stir transport screw 56Y is transported in the opposite direction. The developer conveyed to the vicinity of the end in the longitudinal direction of the second agitating and conveying screw 57Y returns to the supply unit 55Y through a second communication port (not shown) provided near the end of the partition wall.

  The developing unit 53Y includes a developing blade 51Y and a doctor blade 52Y whose tip is brought close to the developing sleeve of the developing roll 51Y. In the developing roll 51Y, the magnet roller included in the developing sleeve has a plurality of magnetic poles that are sequentially arranged from the position facing the doctor blade 52Y toward the rotation direction of the sleeve. Each of these magnetic poles applies a magnetic force to the developer on the sleeve at a predetermined position in the rotational direction. As a result, the developer supplied from the supply unit 55Y is attracted and carried on the surface of the developing sleeve, and a magnetic brush is formed along the magnetic field lines on the sleeve surface.

  The magnetic brush is regulated to an appropriate layer thickness when passing through the position facing the doctor blade 52Y as the developing sleeve rotates, and then conveyed to the developing area facing the photoreceptor 1Y. Then, Y toner is transferred onto the electrostatic latent image by the potential difference between the developing bias applied to the developing sleeve and the electrostatic latent image on the photoreceptor 1Y, thereby contributing to development. Further, it returns to the developing portion 53Y again with the rotation of the developing sleeve, and after returning from the sleeve surface due to the influence of the repulsive magnetic field formed between the magnetic poles of the magnet roller, it is returned to the supplying portion 55Y.

  An appropriate amount of toner is supplied to the circulation unit 54Y based on the detection result of the toner density sensor that detects the toner density of the developer in the circulation unit 54Y. In addition, as the developing device 5Y, a device using a one-component developer not containing a magnetic carrier may be employed instead of a device using a developer.

  In FIG. 1, an optical writing unit 7 is disposed below the image forming units 6Y, 6M, 6C, and 6K. The optical writing unit 7 serving as a latent image forming unit irradiates the respective photoconductors in the image forming units 6Y, 6M, 6C, and 6K with a laser beam L emitted based on the image information. By this exposure, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The optical writing unit 7 passes through a plurality of optical lenses and mirrors while deflecting the laser light L emitted from the light source in the main scanning direction (photoreceptor axial direction) by a polygon mirror that is rotationally driven by a motor. Irradiates the photoconductor.

  Below the optical writing unit 7, a sheet storage cassette 26, separation means 27 incorporated therein, and the like are disposed. The sheet storage cassette 26 stores a plurality of recording sheets P in a stack of sheets. The separation means 27 forms a separation nip by a feed roller 27a that can be driven to rotate and a separation pad 27b that abuts on the feed roller 27a.

  A feed roller 27 a of the separating unit 27 is in contact with the uppermost recording sheet P in the sheet bundle in the sheet storage cassette 26. The feed roller 27a feeds the recording sheet P into the separation nip by its own rotational drive. When a plurality of recording sheets P are fed into the separation nip, the feed roller 27a contacts only the uppermost recording sheet P among the recording sheets P. The uppermost recording sheet P follows the surface movement of the feed roller 27a and moves in the separation nip in the feeding direction. On the other hand, the load resistance due to the separation pad 27b that does not move the surface is applied to the lower recording sheet P excluding the uppermost recording sheet P. Thereby, the lower recording sheet P cannot move in the feeding direction following the uppermost recording sheet P, but remains in the separation nip. In this way, the separating means 27 separates only the uppermost recording sheet P from the plurality of recording sheets P sent out from the sheet storage cassette 26 into one sheet and directs it from the separation nip to the sheet feeding path. And send it out.

  Near the intermediate point in the length direction of the paper feed path, a transport roller pair 28 is disposed as a transport means. The transport roller pair 28 forms a transport nip by bringing a first transport roller 28a as a transport member into contact with a second transport roller 28b as a transport member. Of the two transport rollers, at least the first transport roller 28a is rotationally driven by a driving means (not shown).

  Also, a registration roller pair 29 as an abutting and conveying means is disposed near the end in the length direction of the paper feed path. The registration roller pair 29 includes a first registration roller 29a as an abutting and conveying member, and a second registration roller pair 29b that abuts on the first registration roller 29a and forms a registration nip as an abutting and conveying nip. Of the two registration roller pairs, at least the first registration roller 29a is rotationally driven by a driving means (not shown).

  The first transport roller 28a of the transport roller pair 28 is started to rotate at almost the same time as the feed roller 27a of the separating unit 27 is started to rotate or with a slight time lag. The leading end portion of the recording sheet P sent out from the separation nip of the separation means 27 to the paper feed path is eventually sandwiched between the conveyance nips of the conveyance roller pair 28. Since the first transport roller 28a is driven to rotate at a higher linear speed than the feed roller 27a, at this time, the recording sheet P is stretched with a strong tension between the separation nip and the transport nip. When a strong torque is applied to the feed roller, the torque limiter is activated and the feed roller is rotated around the recording sheet P. At this time, the back tension is irregularly applied to the recording sheet P because the torque limiter operates irregularly. Then, the recording sheet P slips on the first conveying roller 28a, thereby promoting wear of the first conveying roller 28a.

  Thereafter, the recording sheet P is sent out from the conveyance nip toward the registration roller pair 29 by the rotational driving of the first conveyance roller 28 a, and then the leading end abuts against the registration nip of the registration roller pair 29. At this time, since the rotational driving of the registration roller pair 29 is stopped, the recording sheet P cannot enter the registration nip and gradually bends. The skew of the recording sheet P is corrected by this bending.

  After the recording sheet P starts to be sent out from the conveyance nip of the conveyance roller pair 28, the rotation drive of the feed roller 27a of the separation unit 27 and the rotation drive of the conveyance roller pair 28 are stopped when a predetermined timing comes. . Thereby, conveyance of the recording sheet P is temporarily stopped in a state where the leading end is bent. Hereinafter, this pause is referred to as “pause after skew correction”.

  Above the image forming units 6Y, 6M, 6C, and 6K, an intermediate transfer unit 15 that moves the intermediate transfer belt 8 that is an intermediate transfer member endlessly while being stretched is disposed. In addition to the intermediate transfer belt 8, the intermediate transfer unit 15 includes four primary transfer bias rollers 9Y, M, C, and K, a cleaning device 10, and the like. A secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14 and the like are also provided.

  The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the figure by the rotational drive of at least one of the rollers while being stretched around the three rollers inside the loop. The primary transfer bias rollers 9Y, 9M, 9C, and 9K hold the intermediate transfer belt 8 that is moved endlessly in this manner between the photoreceptors 1Y, 1M, 1C, and 1K to form primary transfer nips. Yes. In these methods, a transfer bias having a polarity opposite to that of toner (for example, plus) is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 8. All of the rollers except the primary transfer bias rollers 9Y, M, C, and K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and Y, M, and C on the photoreceptors 1Y, M, C, and K , K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 8.

  The secondary transfer backup roller 12 disposed on the inner side of the belt loop sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 disposed on the outer side of the belt loop to form a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 8 is transferred to the recording sheet P at the secondary transfer nip. Untransferred toner that has not been transferred to the recording sheet P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the belt cleaning device 10.

  After the rotational driving of the feed roller 27a and the conveyance roller pair 28 is temporarily stopped, when the timing at which the recording sheet P can be synchronized with the four-color toner image on the intermediate transfer belt 8 in the secondary transfer nip comes, the feed roller 27a. And the rotational driving of the conveying roller pair 28 is resumed. Further, the rotational driving of the registration roller pair 28 is started. As a result, the recording sheet P is sandwiched between the registration nips of the registration roller pair 29 and then sent out from the registration nip toward the secondary transfer nip. Then, the toner image is superimposed on the four-color toner image on the intermediate transfer belt 8 at the secondary transfer nip.

  When the recording sheet P sent out from the secondary transfer nip passes between the rollers of the fixing device 20, the four-color toner image transferred to the surface is fixed by heat and pressure. Thereafter, the recording sheet P is discharged out of the apparatus through a pair of discharge roller pairs 30. A stack portion 31 is formed on the upper surface of the printer main body, and the recording sheets P discharged to the outside by the discharge roller pair 30 are sequentially stacked on the stack portion 31.

  A bottle container 33 is disposed between the intermediate transfer unit 15 and the stack portion 31 located above the intermediate transfer unit 15. The bottle container 33 stores toner bottles 32Y, 32M, 32C, and 32K as replenishment toner storage units that store Y, M, C, and K toners. The toner bottles 32Y, 32M, 32C, and 32K are installed on the bottle container 33 so as to be placed from above for each toner color. The Y, M, C, and K toners in the toner bottles 32Y, 32M, 32C, and 32K are appropriately replenished to the developing devices of the image forming units 6Y, 6M, 6C, and 6K, respectively, by a toner replenishing device that serves as a toner transport unit described later. Is done. These toner bottles 32Y, 32M, 32C, and 32K are detachable from the main body of the printing unit 100 independently of the image forming units 6Y, 6M, 6C, and 6K.

  A switchback device is disposed in the vicinity of the fixing device 20. In the double-sided printing mode in which images are formed on both sides of the recording sheet P, the recording sheet P that has passed through the fixing device 20 after the toner image is formed only on one side is turned upside down by the switchback device while being registered upside down. Retransmitted toward the pair 29 registration nip. After the toner image is formed on the other surface after being sent from the registration nip to the secondary transfer nip, the fixing device 20 performs the fixing process on the toner image on the other surface, and then the discharge roller. Stacked on the stack unit 31 via the pair 30.

In FIG. 1, a copying machine according to a reference embodiment is shown from the front side. An image reading unit 200 including a scanner 201 and an ADF 251 is disposed on the print unit 100. The image reading unit 200 is fixed on a gantry 299 supported by two legs fixed to the back surface of the print unit 100, and between the stack unit 31 of the print unit 100 and the gantry 299. There is a large space in between. The recording sheets P stacked on the stack unit 31 are located in the space.

  The scanner 201 of the image reading unit 200 includes a fixed reading unit 202 and a moving reading unit 203. The movable reading unit 203 is disposed immediately below a second contact glass (not shown) fixed to the upper wall of the casing of the scanner 201 so as to come into contact with the document MS, and illustrates an optical system including a light source and a reflection mirror. It can be moved in the middle / left / right direction. Then, in the process of moving the optical system from the left side to the right side in the figure, the light emitted from the light source is reflected by a document (not shown) placed on the second contact glass and then passed through a plurality of reflecting mirrors. Then, light is received by the image reading sensor 204 fixed to the scanner body.

  On the other hand, the fixed reading unit 202 includes a light source, a reflection mirror, an image reading sensor such as a CCD, and the like. The fixed reading unit 202 is a first contact glass (not shown) fixed to the casing upper wall of the scanner 201 so as to come into contact with the document MS. It is arranged directly below. Then, when a document MS conveyed by the ADF 251 described later passes through the first contact glass, the light emitted from the light source is sequentially reflected by the document surface and received by the image reading sensor via a plurality of reflection mirrors. To do. Thus, the first surface of the document MS is optically scanned without moving the optical system including the light source and the reflection mirror. The ADF 251 described later includes a second fixed reading unit that optically scans the second surface of the document MS.

  As shown in FIG. 3, the ADF 251 disposed on the scanner 201 is supported by a hinge 249 fixed to the scanner 201 so as to be swingable in the vertical direction. Then, by swinging, it moves like an open / close door, and the first contact glass 211 and the second contact glass 212 on the upper surface of the scanner 201 are exposed in the opened state.

  In the case of a single-sided original such as a book in which one corner of the original bundle is bound, the original cannot be separated one by one, and therefore cannot be conveyed by the ADF 251. Therefore, in the case of a single-sided original, the ADF 251 is opened as shown in FIG. 3, and then the single-sided original on which the page to be read is opened is placed face down on the second contact glass 212, and then the ADF 251 is close up. Then, the image of the page is read by the moving reading unit (203) of the scanner 201.

  On the other hand, in the case of a document bundle in which a plurality of independent documents MS are simply stacked, the documents MS are automatically conveyed one by one by the ADF 251 while the fixed reading unit (202) in the scanner 201 or the first document MS in the ADF 251. The two-surface fixed reading unit can sequentially read. In this case, after setting the original bundle on the original placement table 253, a copy start button (not shown) is pressed. Then, the ADF 251 conveys the original MS of the original bundle placed on the original placement table 253 in order from the top. In the course of this conveyance, immediately after the original MS is reversed, the original MS is passed directly above the surface fixed reading unit (202) of the scanner 201. At this time, the image on the first surface of the document MS is read by the fixed reading unit (202) of the scanner 201.

  FIG. 4 is an enlarged configuration diagram showing the main configuration of the ADF 251 together with the upper portion of the scanner 201. The ADF 251 includes a document setting unit A, a separation feeding unit B, a conveyance unit C, a turn unit D, an abutting conveyance unit E, a first reading conveyance unit F, a second reading conveyance unit G, a paper discharge unit H, and a stacking unit I. Etc.

  The document setting unit A includes a document table 253 on which a bundle of documents MS is set. The separation feeding unit B separates and feeds the originals MS one by one from the set of originals MS set. The transport unit C transports the fed document MS to the downstream turn unit D. Further, the turn portion D has a curved conveyance portion that is curved in a C-shape, and the document MS is turned upside down in the curved conveyance portion so as to be turned upside down. The abutting conveyance unit E corrects the skew of the document MS or conveys the document MS toward the first reading conveyance unit F on the downstream side. In addition, the first reading and conveying unit F conveys the document MS on the first contact glass 211, and the fixed reading unit (202) disposed inside the scanner (not shown) below the first contact glass 211. Is to read the first side of the document MS. The second reading / conveying unit G causes the second fixed reading unit 295 to read the second surface of the document MS while conveying the document MS under the second fixed reading unit 295. The paper discharge unit H discharges the original MS from which both-side images have been read toward the stack unit I. The stack unit I stacks the original MS on the stack table 255.

  The original MS is placed on the movable original table 254 that can swing in the directions of arrows a and b in the drawing according to the thickness of the bundle of originals MS, and the rear end of the original is placed on the original table 253. It is set in the state of being put on. At this time, the position in the width direction is adjusted by abutting side guides (not shown) against both ends in the width direction (direction orthogonal to the drawing surface) on the document placing table 253. The document MS set in this way pushes up a lever member 262 that is swingably disposed above the movable document table 254. Accordingly, the document set sensor 263 detects the setting of the document MS and transmits a detection signal to a controller (not shown). This detection signal is sent from the controller to the reading control unit of the scanner via the I / F.

  The document placing table 253 holds a first length sensor 257 and a second length sensor 258 that are made of a reflective photosensor that detects the length of the document MS in the conveyance direction. These length sensors detect the length of the document MS in the conveyance direction.

  Above the bundle of documents MS placed on the movable document table 254, a pickup roller 280 supported by a cam mechanism so as to be movable in the vertical direction (arrow c and d directions in the figure) is disposed. . This cam mechanism moves the pickup roller 280 up and down by driving a pickup motor (not shown). When the pickup roller 280 moves upward, the movable document table 254 swings in the direction of arrow a in the drawing, and the pickup roller 280 comes into contact with the uppermost document MS in the bundle of documents MS. When the movable document table 254 further rises, the table rise detection sensor 259 eventually detects the rise of the movable document table 254 to the upper limit. As a result, the pick-up motor stops and the rising of the movable document table 254 stops.

  The main body operation unit including a numeric keypad and a display (not shown) is operated by the operator for key operation for setting the reading mode indicating the double-sided reading mode or the single-sided reading mode, or pressing the copy start key. Is called. When the copy start key is pressed, a document feed signal is transmitted from a main body control unit (not shown) to the controller of the ADF 251. Then, the pick-up roller 280 is rotationally driven by a normal rotation of a paper feed motor (not shown), and sends the document MS on the movable document table 254 from the movable document table 254.

  Regarding the setting of the double-sided reading mode or the single-sided reading mode, it is possible to set the double-sided or single-sided setting for all the originals MS placed on the movable original table 254 at once. Also, the first and tenth originals MS are set to the double-sided reading mode, while the other originals MS are set to the single-sided reading mode. Can also be set.

  The document MS sent out by a pickup roller 280 as a sending member enters the separation conveyance unit B and is sent to a contact position with the paper feed belt 284. The sheet feeding belt 284 is stretched by a driving roller 282, a driven roller 283, and the like, and is endlessly moved in the clockwise direction in the drawing by the rotation of the driving roller 282 accompanying the normal rotation of the sheet feeding motor. A separation roller 285 that is driven to rotate in the clockwise direction in the drawing by the forward rotation of the paper feed motor is in contact with the lower tension surface of the paper feed belt 284. At the contact portion, the surface of the paper feed belt 284 moves in the paper feed direction. On the other hand, the separation roller 285 is in contact with the paper feeding belt 284 with a predetermined pressure, and when the paper is in direct contact with the paper feeding belt 284 or only one original MS is sandwiched between the contact portions. At that time, it is carried around to the belt or the document MS. However, when a plurality of documents MS are sandwiched between the contact portions, the accompanying force is lower than the torque of the torque limiter, so that the document is rotated clockwise in the figure opposite to the accompanying direction. As a result, a moving force in the direction opposite to the paper feed is applied to the original MS below the uppermost position by the separation roller 285, and only the uppermost original MS is separated from several originals.

  The document MS separated into one sheet by the action of the sheet feeding belt 284 and the separation roller 285 enters the conveyance unit C. In the transport unit C, the first transport roller in which the document MS sandwiched in the transport nip by the contact between the first transport roller 286 and the second transport roller 287 as a transport member is rotationally driven by the drive of the paper feed motor. 286 is conveyed toward the turn part D on the downstream side. Since the linear velocity of the first conveying roller 286 is higher than the linear velocity of the upstream sheet feeding belt 284, the document MS is stretched with a strong tension between the separation nip and the conveying nip. Since a strong torque is applied to the paper feed belt 284, the torque limiter is activated, and the driving roller 282 that drives the paper feed belt 284 follows the document MS. At this time, an irregular back tension is applied to the document MS, so that the document MS slips on the first transport roller 286 and promotes wear of the first transport roller 286.

  The document MS sent out from the conveyance nip toward the turn part D passes directly under the document width sensor 273. The document width sensor 273 has a plurality of paper detection units including reflection type photosensors and the like, and these paper detection units are arranged in the document width direction (direction perpendicular to the drawing sheet). Based on which paper detection unit detects the document MS, the size of the document MS in the width direction is detected.

  The leading edge of the document MS whose size in the width direction is detected by the document width sensor 273 enters the turn portion D. The turn part D as the transport part forms a turn transport nip by the contact of the first turn roller 266 and the second turn roller 273. The document MS sandwiched between the turn conveyance nips is conveyed toward the abutting conveyance unit E on the downstream side by a first turn roller 266 that is rotationally driven by a paper feed motor. At this time, the upper and lower sides are reversed by moving along the curved conveyance path. Even on the surface of the first turn roller 266, the document MS slips due to the back tension, so that the wear of the first term roller 266 is promoted.

  The document MS sent out from the turn conveyance nip toward the abutting conveyance unit E passes through the position facing the reading entrance sensor 267 and then reaches the abutting conveyance unit E. The abutting and conveying unit E forms an abutting and conveying nip by the contact between the first abutting and conveying roller 289 as the abutting and conveying member and the second abutting and conveying roller 290. The original MS that has passed the position facing the reading entrance sensor 267 eventually comes into contact with the conveying nip by abutting its leading end. At this time, since the rotation driving of the first butting conveyance roller 289 is stopped, the document MS cannot enter the butting conveyance nip. And it bends gradually with conveyance. The skew of the original MS is corrected by the bending force.

  Thereafter, rotation driving of the first abutting conveyance roller 289 is started at a predetermined timing, and the leading end portion of the document MS passes through the abutting conveyance nip. The document MS that has passed through the abutting conveyance nip passes through the first reading conveyance unit F while being pressed against the first contact glass 211 of the scanner 201 by the pressing roller 265. At this time, the image on the first surface (the surface facing downward in the drawing) of the document MS is read by the first fixed reading unit 202 of the scanner 201.

  The document MS that has passed through the first reading conveyance unit F passes through a pair of reading exit rollers 292, which will be described later, and the leading edge of the document MS is detected by the paper discharge sensor 261. When the single-sided reading mode is set, reading of the second side of the document MS by the second fixed reading unit 95 described later is not necessary. Therefore, when the leading edge of the document MS is detected by the paper discharge sensor 261, the forward rotation drive of the paper discharge motor is started, and the lower paper discharge roller in the drawing roller pair 294 is rotated in the clockwise direction in the drawing. Driven by rotation. At the timing when the trailing edge of the document MS comes out of the nip of the paper discharge roller pair 294, the drive of the paper discharge motor is stopped.

  On the other hand, when the double-sided reading mode is set, the timing until the paper MS reaches the second fixed reading unit 295 after the leading edge of the document MS is detected based on the pulse count of the reading motor. Calculated. At that timing, a gate signal indicating an effective image area in the sub-scanning direction on the second surface of the document MS is transmitted from the controller to the reading control unit. This transmission is continued until the rear end of the document MS leaves the reading position of the second fixed reading unit 295, and the image on the second surface of the document MS is read by the second fixed reading unit 295.

  The second fixed reading unit 295 includes a contact image sensor (CIS). A second reading roller 296 that supports the document MS from the non-reading surface side is disposed at a position facing the second fixed reading unit 295. The second reading roller 296 serves to prevent the original MS from floating at the reading position by the second fixed reading unit 295 and to function as a reference white portion for acquiring shading data in the second fixed reading unit 295. I'm in charge.

  FIG. 5 is a schematic diagram illustrating the state of the recording sheet P together with the paper feed path and the like when the “pause after skew correction” is performed in the printing unit in a state where the first conveyance roller 28a of the conveyance roller pair 28 is not worn. It is. In an initial state immediately after shipment from the factory, the intermediate transfer belt 7, the secondary transfer roller 19, two registration rollers in the registration roller pair 29, two conveyance rollers in the conveyance roller pair 28, and a feed roller 27 a in the separating unit 27. Move on the surface at the same linear velocity. In this state, as shown in the figure, “pause after skew correction” is performed with the recording sheet sufficiently bent immediately before the registration nip.

  Thereafter, when the driving of the various rollers is resumed and the recording sheet P is conveyed from the registration nip toward the secondary transfer nip, the various rollers move on the surface at the same linear velocity, thereby conveying the conveying roller pair 28. The sheet deflection formed between the nip and the registration nip of the registration roller pair 29 is maintained as it is immediately after the “pause after skew correction” (hereinafter referred to as “initial deflection amount”). The amount of bending does not change until the trailing edge of the recording sheet P passes through the conveyance nip of the conveyance roller pair 28 as shown in FIG.

  During the period from when the leading edge of the recording sheet P enters the secondary transfer nip until the trailing edge of the recording sheet passes through the separation nip of the separation means, the trailing edge of the recording sheet P is pressed by the separation pad 27b of the separation nip. An irregular transport load is applied to the side. This may cause momentary conveyance failure of the recording sheet P in the separation nip. The impact due to this momentary conveyance failure causes the conveyance nip of the conveyance roller pair 28 and the registration nip of the registration roller pair 29. Is absorbed by the bending of the sheet between them, and does not reach the registration roller pair 29. For this reason, the registration roller pair 29 is driven at a stable linear velocity.

  In the conventional image forming apparatus, when the linear velocity of the first conveying roller 28a of the conveying roller pair 28 is reduced below the design value due to wear, “pause after skew correction” is performed as shown in FIG. The amount of sheet deflection between the conveyance nip and the resist nip immediately after this becomes smaller than the design value. Even though the sheet feeding speed from the separation nip and the sheet feeding speed from the conveyance nip are slower than the design values due to a decrease in the linear speed, the “Pause after skew correction” "Is done.

  When the sheet feeding from the registration nip to the secondary transfer nip is started in this state, the sheet feeding speed from the conveyance nip by the first conveyance roller 28a is the sheet feeding speed from the registration nip by the first registration roller 29a. Therefore, the amount of sheet deflection between the conveyance nip and the resist nip is further reduced. As shown in FIG. 8, when the trailing edge of the recording sheet P passes through the separation nip, there is almost no sheet bending between the conveyance nip and the registration nip.

  Then, the first registration roller 29a causes the linear velocity of the first conveying roller 28a to follow its own linear velocity while pulling the recording sheet P. In this state, as shown in FIG. 9, when the trailing edge of the recording sheet P passes through the conveyance nip, the load on the first registration roller 29a is suddenly reduced. It suddenly rises and disturbs the toner image in the secondary transfer nip.

  When the wear of the first conveying roller 28a further progresses and the “initial deflection amount” further decreases, the sheet between the conveying nip and the resist nip before the trailing edge of the recording sheet P passes through the separating nip of the separating unit 27. Deflection disappears. Then, while the first registration roller 29a pulls the recording sheet P, the linear velocity of the first conveying roller 28a and the feed roller 27a follows the linear velocity of itself. Then, when the trailing edge of the recording sheet P passes through the separation nip and when the trailing edge of the recording sheet P passes through the conveyance nip, the linear speed of the registration roller pair 29 temporarily rises, and the secondary transfer. The toner image in the nip is disturbed.

  Further, when the wear of the first transport roller 28a further progresses and the “initial deflection amount” is almost eliminated, as shown in FIG. 10, the separation nip passes through the transport nip and the resist nip to the secondary transfer nip. The recording sheet P is stretched with tension in the entire section. In this state, the impact applied to the rear end side of the recording sheet P at the separation nip of the separating means 27 is transmitted to the registration roller pair 27 via the recording sheet P, and the driving speed of the registration roller pair 27 is changed. This disturbs the toner image in the secondary transfer nip.

FIG. 11 is a configuration diagram showing a paper feed path in the printing unit 100 of the copying machine according to the reference embodiment. A deflection amount detection sensor 35 is disposed on the left side of the sheet feed path in the drawing. The deflection amount detection sensor 35 can detect the distance between its tip and the test object using sound waves, infrared rays, or the like. When the recording sheet P is not present between the conveyance nip and the registration nip, the deflection amount detection sensor 35 detects the distance between its leading end and the right guide plate in the drawing in the sheet feeding path. On the other hand, as shown in FIG. 12, when the recording sheet P exists between the conveyance nip and the registration nip, the deflection amount detection sensor 35 detects that the leading edge of the recording sheet P Detect distance. FIG. 12 shows a state in which the recording sheet P is not bent at all between the conveyance nip and the registration nip. However, as shown in FIG. 13, when the recording sheet P is bent, the above-described distance becomes shorter. . The greater the amount of bending of the recording sheet P, the shorter the distance. Therefore, the deflection amount detection sensor 35 detects the deflection amount of the recording sheet P.

In addition, as the deflection amount detection sensor 35, a sensor that detects the deflection amount by another method instead of detecting the deflection amount using light or sound waves may be provided. For example, a method of detecting a deflection amount based on a posture change amount of a posture changing member that is pushed by a bent recording sheet P to change the posture may be used. Further, in the copying machine according to the reference embodiment, the bending amount detection sensor 35 that quantitatively detects the bending amount of the recording sheet P is used as the bending detection unit. However, a bending amount that exceeds a predetermined threshold is formed. It is also possible to use one that qualitatively detects whether or not it is present (whether or not it is bent).

  A sheet detection sensor 36 is disposed near the exit of the conveyance nip of the conveyance roller pair 28. The sheet detection sensor 36 detects the recording sheet P in the sheet feed path on the upstream side in the sheet conveyance direction with respect to the deflection amount detection sensor 35. Then, the sheet detection signal is output to the motor control circuit. The motor control circuit is configured to perform the following bending forming process. That is, after the sheet detection signal is sent by the sheet detection sensor 36, the sheet deflection amount detected by the deflection amount detection sensor 35 has increased to a predetermined value (the presence of deflection is detected for a deflection exceeding a predetermined threshold). The driving of the feeding motor is temporarily stopped. Accordingly, the “pause after skew correction” is performed by temporarily stopping the rotation of the feed roller 27a and the first transport roller 28a.

  In such a configuration, regardless of the wear of the feed roller 27a of the separating unit 27 and the first conveyance roller 28a of the conveyance roller pair 27, the sheet deflection amount of a predetermined value is surely ensured between the conveyance nip and the registration nip. With the recording sheet P bent, the “pause after skew correction” is completed. After the conveyance of the recording sheet P is resumed, the impact applied to the trailing end side of the sheet at the separation nip is absorbed by the bent portion of the recording sheet P, so that the impact is not transmitted to the registration roller pair 29, and the registration roller The pair 29 is driven at a stable linear velocity. In addition, even if the worn feed roller 27a or the first transport roller 28a has a linear velocity that is slower than the linear velocity of the registration roller pair 29, the amount of sheet deflection immediately before the registration nip gradually decreases during sheet conveyance. Even if the recording sheet P is bent with a sufficient amount of deflection prior to restarting the sheet conveyance, the recording sheet P is bent until the trailing edge of the recording sheet P passes through the separation nip and the conveyance nip. to continue. Alternatively, the timing at which the amount of bending becomes zero is delayed as compared with the case where the bending is hardly formed when the sheet conveyance is resumed. This avoids the occurrence of torque fluctuation of the registration roller pair 29 when the trailing edge of the recording sheet P passes through the separation nip or the conveyance nip, or shortens the time during which the torque fluctuation is caused. As described above, it is possible to avoid the transmission of impact from the separation nip to the registration roller pair 29 via the recording sheet, or to change the torque of the registration roller pair 29 when the trailing edge of the recording sheet P passes through the separation nip or the conveyance nip. By avoiding the occurrence of this phenomenon or shortening the time during which torque fluctuations are caused, it is possible to suppress image quality disturbance due to wear of the first transport roller 28a.

  In FIG. 4 described above, a deflection amount detection sensor 299 for detecting the deflection amount of the document MS is disposed between the turn portion D and the abutting conveyance portion E. This bend amount detection sensor 299 is based on the same principle as the bend amount detection sensor (35) of the print unit (100), and the turn conveyance nip by the contact between the first turn roller 266 and the second turn roller 273, and the first The amount of deflection of the document MS between the abutting conveyance nip caused by the contact between the abutting conveyance roller 289 and the second abutting conveyance roller 290 is detected. Similar to the printer unit, as the bend detection means, instead of the bend amount detection sensor 299 for quantitatively detecting the bend amount, it is qualitatively detected whether a bend exceeding a predetermined threshold is formed. May be used.

  A paper feed motor, which is a driving source of various rollers disposed upstream of the first reading conveyance unit F in the document conveyance direction, is temporarily stopped as follows when skew correction of the document MS is performed. That is, a predetermined deflection amount is detected by the deflection amount detection sensor 299 after the leading edge of the document MS is detected by the reading entrance sensor 267 disposed upstream of the deflection amount detection sensor 299 in the document conveyance direction. Based on (a deflection exceeding the threshold value is detected), the drive is stopped.

  In such a configuration, the document MS is reliably bent at a predetermined deflection amount at the time of skew correction regardless of wear of the paper feed belt 284 as a feeding member, the first conveyance roller 286 as a conveyance member, and the first turn roller 266 as a conveyance member. I will. As a result, regardless of the wear of these rollers, the document MS can be conveyed at a stable speed by the first reading conveyance unit F or the second reading conveyance unit G, and the occurrence of reading errors can be suppressed.

Next, a copying machine according to an embodiment to which the present invention is applied will be described. Incidentally, unless otherwise noted below, the configuration of the copying machine according to the actual embodiment are identical to those of the reference embodiment.
FIG. 14 is an enlarged perspective view showing a feed motor 110 as a drive source of a feed roller (27a in FIG. 1) and a first transport roller (28a in FIG. 1) (not shown) from the front. FIG. 15 is an enlarged perspective view showing the feeding motor 110 from the rear. As shown in these drawings, the motor shaft 113 of the feeding motor 110 protrudes forward from the motor body at the front portion of the motor body while passing through the motor body in the front-rear direction. The rear part projects rearward from the motor body.

  A driver board 116 is fixed to the rear side of the motor body, and a driver circuit for exciting the three-phase coils of the feeding motor 110 in a predetermined order is mounted on the driver board 116. The motor shaft 113 also protrudes rearward through the driver board 116.

  The code wheel 111a of the motor encoder 111 is fixed at a position behind the driver board 116 in the motor shaft 113, and rotates on the same rotational axis as the motor shaft 113 as the motor shaft 113 rotates. As shown in FIG. 16, the code wheel 111 a includes a plurality of slits SL arranged at a predetermined pitch in the rotation direction. An optical sensor 111b composed of a transmissive photosensor is fixed to the driver board 116 of the feed motor 110 so as to sequentially detect the slits SL as the code wheel 111a rotates (see FIG. 15). Although not shown for convenience, a cover member that covers the driver board 116 and the motor encoder 111 is fitted into the rear end portion of the motor body of the feeding motor 110.

  In order to ensure that the code wheel 111a is rotated in synchronization with the motor shaft 113 even if expansion and contraction occurs due to a temperature change, the code wheel 111a is not only press-fitted into the motor shaft 113 but also attached to the motor shaft 213 by an adhesive. It is desirable to adhere.

  As the code wheel 111a, the one obtained by processing the wheel main body and the slit SL by punching a metal plate is used. Since the code wheel 111a is made of metal, it is possible to suppress the expansion and contraction due to the temperature change and reduce the variation with time of the slit pitch. However, it is easy to attach foreign matters such as dust to the burrs generated during the punching process. Therefore, instead of the code wheel 111a shown in FIG. 16, the code wheel 111a shown in FIG. 17 may be used. The code wheel 111a includes a plurality of dark portions DP that are arranged at a predetermined pitch in the rotation direction as marks. The dark part DP is formed by a half etching process using a photolithography method. A part having a mirror-finished layer coated on the surface is used as a substrate, and the part where the mirror-finished layer is removed by half etching to expose the dark part layer is the dark part DP. The dark portion DP can be processed with high accuracy. However, the cost is increased by half-etching. In addition, since it is weak against oils and fats, handling is required.

  When the code wheel 111a shown in FIG. 17 is used, the optical sensor 111b is made of a reflective photosensor instead of the transmissive photosensor, and the dark portion DP is changed depending on the light reflectivity. May be detected.

Thus, in the copying machine according to the implementation mode, the driver circuit, and a motor encoder 111, it is mounted to the feed motor 110.

FIG. 18 is a block diagram illustrating a main part of an electric circuit in the motor driving device of the printing unit of the copying machine according to the embodiment . A motor control circuit 180 that controls the driving of the feeding motor 110 formed of a DC brushless motor is formed separately from the feeding motor 110 and is fixed to the main body of the printing unit (100 in FIG. 1). The motor control circuit 180 includes a target position / speed calculation circuit 181, a position / speed tracking control circuit 182, a motor rotation amount / speed calculation circuit 183, and the like.

  The target signal generation means 190 shown in the figure generates target signals such as the target rotation amount, target rotation speed, target rotation stop position of the first transport roller (28a) prior to “pause after skew correction”. . A print control unit that controls the overall control of various devices of the print unit may function as the target signal generation unit 190. As the motor control circuit 180, a circuit composed of a one-chip microcomputer or a circuit composed of a control ASIC (Application Specific Integrated Circuit) is used.

  The target signal sent from the target signal generation unit 190 to the motor control circuit 180 is input to the target position / speed calculation circuit 181 of the motor control circuit 180. Based on the input target signal, the target position / speed calculation circuit 181 calculates a target motor stop position for stopping the first transport roller (28a) in a target rotation posture, and uses the result as a target position signal. Output. Further, based on the target signal, a target motor rotation speed for rotating the first transport roller (28a) at the target rotation speed is calculated, and the result is output as a target speed signal.

  As an optical sensor of the motor encoder 111 mounted on the feeding motor 110, a two-channel optical sensor having two light receiving portions that receive light after passing through the slit SL is used. The two light receiving units are arranged so as to satisfy the following conditions. That is, when the slit SL of the code wheel 111a is opposed to the first light receiving portion, the second light receiving portion is opposed to the wheel non-slit portion existing on the side of the slit SL. Based on the change in the ratio of the amount of light received by the first light-receiving unit and the amount of light received by the second light-receiving unit, the moment when the slit SL of the code wheel 111 is opposed to each light-receiving unit without deviation is accurately grasped. Is done. The first light receiving unit outputs a voltage corresponding to the amount of received light as a pulse signal A. The second light receiving unit outputs a voltage corresponding to the amount of received light as a pulse signal B.

  The pulse signal A and the pulse signal B output from the optical sensor 111 b are input to the motor rotation amount / speed calculation circuit 183 of the motor control circuit 180. The motor position / speed calculation path 183 calculates the motor rotation amount based on the result of calculating the pulse rising number and the pulse frequency for the pulse signal A and the pulse signal B, respectively, and outputs the result as a motor rotation amount signal. Also, the motor rotation speed is calculated, and the result is output as a motor rotation speed signal.

  The position / speed tracking control circuit 182 constantly supplies GND (-power supply) to the driver circuit 112. Further, if necessary, an excitation + power supply (+24 V) and a signal + power supply (+5 V) are supplied to the driver circuit 112. Furthermore, a brake signal, a PWM signal, and a direction signal (CW, CCW) are individually output to the driver circuit 112 as necessary. As the direction signal, either a normal rotation signal for performing a normal rotation command or a reverse rotation signal for performing a reverse rotation command is output. The PWM signal is for instructing an excitation voltage value output from the driver circuit 112 to the coil of the feeding motor 110.

  The feed motor 110 has a hall element 117. This Hall element 117 has become 0 [°] (360 °) as a reference, or 120 [°] and 240 [°] with respect to the rotational angle posture of the motor shaft 113 of the feeding motor 110. Is output to the driver circuit 112.

  The driver circuit 112 includes an output adjustment unit that adjusts the output of the excitation voltage for the coil of the feed motor 110 based on the PWM signal output from the position / speed tracking control circuit 182 of the motor control circuit 180, and the feed motor 110. A coil switching unit that switches a coil that outputs an excitation voltage among the three-phase coils is provided. The output adjusting unit adjusts the value of the excitation voltage per unit time flowing through the coil via the coil switching unit by turning on and off the output of the voltage of +24 [V] to the coil switching unit based on the PWM signal. The coil switching unit includes a pre-driver and a plurality of FETs (field effect transistors). As the plurality of FETs, at least the first FET for turning on / off the output of the U excitation voltage for exciting the first phase coil, and the on / off of the output of the V excitation voltage for exciting the second phase coil. And a third FET for turning on and off the output of the W excitation voltage for exciting the third phase coil. The FETs individually output gate voltages for controlling switching by the FETs from the pre-drivers.

  The pre-driver individually controls on / off of the gate voltage for the three FETs based on the Hall signal from the Hall element 217, so that the excitation voltage to be output to the feeding motor 110 is changed to the U excitation voltage and the V excitation voltage. And W excitation voltage. By this switching, a rotational force by switching the magnetic field is applied to the motor shaft 113 of the feeding motor 110.

  The position / speed tracking control circuit 182 calculates a deviation amount of the motor rotation speed signal sent from the motor rotation amount / speed calculation circuit 183 from the target speed signal, and adjusts the PWM signal based on the deviation amount. Thus, the excitation voltage for the feed motor 110 is adjusted, and a speed adjustment process for controlling the rotation speed of the feed motor 110 to the target rotation speed is performed. By this speed adjustment processing, the rotational speed of the first transport roller (28a) that is a driven body driven by the feeding motor 110 can be freely adjusted.

  The motor drive device directly adjusts the rotation speed of the feed motor 110 by the motor encoder 111 mounted on the feed motor 110 without detecting the rotation speed of the first transport roller (28a) that is rotationally driven by the feed motor 110. To detect automatically. In such a configuration, the change in the rotation speed of the feed motor 110 is compared with the conventional case where the change in the rotation speed of the feed motor 110 is indirectly detected based on the change in the rotation speed of the first transport roller (28a). Detect quickly. Then, according to the detection result, the rotation speed of the feeding motor 110 is quickly returned to the original speed, so that the rotation speed instability of the first transport roller (28a) due to the load fluctuation can be suppressed. .

In the copying machine according to the implementation embodiments, by mounting the driver board 116 by the driver circuit 112 is incorporated in the feeding motor 110, conventionally which has been disposed at a position away driver circuit 112 from the feeding motor 110 The distance between the driver circuit 110 and the coil of the feeding motor 110 is made shorter than that of FIG. Accordingly, an excitation voltage is applied from the driver circuit 112 to the motor coil by the electrode on the driver board 116 without providing a harness in which a plurality of driving power supply wires and signal wires are bundled between the driver circuit 112 and the feeding motor 110. Or a Hall signal as a sensing signal can be transmitted from the feeding motor 110 to the driver circuit 112. As a result, by suppressing the generation of noise when switching the coil to be excited at high speed, or by suppressing the mixing of the generated noise into the Hall signal, the motor rotation caused by the mixing of noise into the Hall signal can be reduced. Instability can be suppressed.

  In addition, between the driver circuit 112 and the motor control circuit 180, excitation + power supply, GND, brake signal, PWM signal, direction signal, signal + power supply, pulse signal A, and pulse signal B are individually led. A harness made up of eight electric wires is wound around. In this harness, only one electric wire is provided for guiding the excitation + power source that is the source of the excitation voltage, and +24 V is stably supplied to this electric wire over a long period of time. Unlike between the driver circuit 112 and the feed motor 110, the high-speed switching of the + 24V conduction line that accompanies the switching of the coil to be excited is not performed, so that no noise is generated due to the high-speed switching. For this reason, even if the electric wire for leading the exciting power source, the electric wire for guiding the pulse signal A, and the electric wire for guiding the pulse signal B are wound together, the pulse signal A and the pulse signal B No noise mixing occurs.

  Based on the motor rotation amount signal sent from the motor rotation amount / speed calculation circuit 183, the position / speed tracking control circuit 182 detects the sheet detection sensor 36 with the leading edge of the recording sheet near the exit of the conveyance nip with respect to the feeding motor 110. To know the total amount of rotation since it was detected. Then, based on the comparison between the grasp result and the target position signal, the brake timing for the feed motor 110 is determined to become the target rotation amount, and the output of the PWM signal to the driver circuit 112 is stopped at the brake timing. Then, a brake signal is output, and target stop processing for stopping the feed motor 110 at the target rotation angle posture is performed. Thereby, the 1st conveyance roller (28a) driven by the feeding motor 110 and the 2nd conveyance roller (28b) to rotate with this can be stopped by a target rotation angle posture.

  In a state where the feed motor 110 is stopped, the position / speed tracking control circuit 182 performs a hold process. In this hold process, the presence or absence of forward rotation or reverse rotation of the motor shaft 113 is monitored based on the motor rotation amount signal sent from the motor rotation amount / speed calculation circuit 183. When forward rotation is detected, the feed motor 110 is driven in reverse rotation by an amount corresponding to the forward rotation amount. On the other hand, when reverse rotation is detected, the feed motor 110 is moved forward by an amount corresponding to the reverse rotation amount. Roll drive. As a result, the feed roller (27a), the first transport roller (28a), and the first registration roller (29a) driven by the rotational driving force of the feed motor 110 are constrained to the target rotational posture. In such a configuration, the apparatus can be downsized and the apparatus configuration can be simplified by restraining the feeding motor 110 to a desired rotation angle posture by hold control regardless of the attachment of the helical gear.

  As the optical sensor 211, one having a resolution of 45 [LPI] is used. In addition, as the code wheel 111a, one having 100 slits SL per round is used. The reason for this is as follows. That is, conventionally, an HB type stepping motor has been generally used as a drive source for the transport roller pair. The basic resolution of the HB type stepping motor is 200 pulses (two-phase excitation). It is 400 pulses for 1-2 phase excitation and 800 pulses for W1-2 phase excitation. It is desirable to obtain the same capability as the resolution with the feeding motor 110 made of a DC brushless motor. Since a DC brushless motor is generally used at a rotational speed more than twice that of a stepping motor, considering the reduction ratio, the basic resolution is half of 100 pulses and the basic resolution of the stepping motor (two-phase It is possible to demonstrate the same ability as (excitation). Also, by using the pulse signals A and B respectively output from the two light receiving units of the optical sensor 111b, it is possible to generate 200 pulses multiplied by 2 and 400 pulses multiplied by 4 for one rotation of the motor. Therefore, it is also possible to exhibit the same ability as the resolution at the time of 1-2 phase excitation or W1-2 phase excitation of the stepping motor. Therefore, the code wheel 111a provided with 100 slits SL per round is used.

  Further, by using an optical sensor 111b having a resolution of 45 [LPI], the central circle diameter φ of the code wheel 111a provided with 100 slits SL is kept at 17.97 [mm]. Thereby, the code wheel 111a can be accommodated within the diameter of the feed motor 110, and an increase in the diameter of the feed motor 110 due to the mounting of the code wheel 111a can be avoided. If the code wheel pulse is doubled to 200 pulses, the central circle diameter φ of the code wheel 111a increases to 35.93 [mm]. It is very difficult to keep the central circle φ within the diameter of the feeding motor 110. In addition, even if the code wheel pulse is 1.5 times 150 pulses, since the response frequency does not exceed the use limit, the resolution is preferably 45 [LPI].

  In FIG. 15, a connector 115 is fixed to the driver board 116. The connector 115 is engaged with a harness connector provided at the end of the harness that is wound around from the motor control circuit 180. The number of pins of the connector 115 is as follows: excitation + power receiving pin, GND receiving pin, brake signal receiving pin, PWM signal receiving pin, direction signal receiving pin, signal + power receiving pin, pulse signal A output 8 pins for receiving a pulse signal and a pin for receiving a pulse signal. In FIG. 18, although not shown for convenience, a +5 [V] power supply wiring and a GND wiring extend from the driver circuit 112 to the optical sensor 111b.

  The arrangement pitch of pins in the connector 115 is 1.5 [mm]. Further, the arrangement order of the pins is as follows. That is, pin 1 = excitation + power supply reception pin, pin 2 = GND reception pin, pin 3 = brake signal reception pin, pin 4 = PWM signal reception pin, pin 5 = direction signal reception Pin 6, Pin = Signal + Power Supply Acceptance Pin, Pin 7 = Pulse Signal A Output Pin, Pin 8 = Pulse Signal Acceptance Pin. By moving the combination of the pulse signal A output pin (No. 7) and the pulse signal reception pin (No. 8) away from the 24 [V] excitation + power supply reception pin (No. 1), the pulse signal It is possible to efficiently suppress noise from being mixed in.

  Conventionally, the most frequently used drive source for the conveying roller pair is that the plane perpendicular to the rotation axis is 42 [mm] × 42 [mm] and the length in the axial direction is 42 [mm]. It is a certain “□ 42 × L42”. The next most frequently used is “□ 56 × L42”. These two types accounted for about 90% of the HB type stepping motor used as a driving source for the pair of conveying rollers. Therefore, it is desirable that the feed motor 110 has a size that can be replaced with these two types of HB type stepping motors.

  In order for the feeding motor 110 to exhibit the same controllability as the HB stepping motor, it is necessary to read the slit SL and the dark portion DP with high accuracy. Therefore, it is necessary to keep the positional error in the rotational direction at the sensor reading position within one rotation of the code wheel 111a in the state where it is assembled to the motor at 0.3 [%] or less. For such a position error, it is desirable to use components in which the dimensional accuracy of the code wheel 111a, the assembly accuracy of the code wheel 111a with respect to the motor shaft 113, the straightness of the motor shaft, and the like are strictly controlled.

  The motor control circuit 180, at the time when the accumulation of the motor rotation amount (accumulation of reception of the pulse signal) after the leading edge of the recording sheet is detected by the sheet detection sensor 36 reaches a predetermined target rotation amount in the bending formation process. Processing for stopping the driving of the feeding motor 110 is performed. When the first conveying roller (28a in FIG. 1) is not worn, the amount of bending of the recording sheet between the conveying nip and the registration nip becomes a predetermined target bending amount by this process. Therefore, the detection result by the deflection amount detection sensor (35 in FIG. 13) becomes the target deflection amount (the deflection of the target deflection amount is detected).

  However, since the linear velocity of the first conveyance roller decreases when the first conveyance roller is worn, the amount of deflection of the recording sheet when the first conveyance roller stops at the target rotation amount is the target deflection amount. Less than. And the detection result by the deflection amount detection sensor 35 becomes smaller than the target deflection amount (the deflection of the target deflection amount is not detected). The deflection amount detection sensor 35 transmits the detection result of the deflection amount to the target signal generation unit 190 as a deflection amount signal. The target signal generation unit 190 is configured so that the difference between the deflection amount of the recording sheet grasped based on the deflection amount signal and the target deflection amount exceeds a predetermined threshold value. Correct the target rotation amount to a larger value. Specifically, a value obtained by multiplying the above-described difference by a predetermined coefficient is added to the target rotation amount. With this correction, in the next and subsequent bend forming processes, the first conveying roller (28a) stops after rotating more, and the bend amount of the recording sheet immediately after “pause after skew correction” is almost equal to the target bend. It becomes quantity.

  Even in such a configuration, the recording sheet P is reliably bent by the target deflection amount between the conveyance nip and the registration nip regardless of the wear of the first conveyance roller (28a). "Can complete the image quality disturbance due to the wear of the rollers.

  The target signal generation unit 190 also feeds the feed motor used in the deflection forming process when the difference between the deflection amount of the recording sheet grasped based on the deflection amount signal and the target deflection amount exceeds a predetermined threshold. By increasing the target rotational speed of 110, the linear speed of the feed roller (27a) and the first transport roller (28a) is brought close to the original linear speed. As a result, it is possible to suppress the lengthening of the bending forming process caused by increasing the target rotation amount of the feeding motor 110 in accordance with the shortage of the bending amount due to wear of the feed roller and the first transport roller.

  As described above, the feed motor 110 is shared not only as a drive source for the first transport roller (28a) as a transport member but also as a drive source for the feed roller (27a) as a feed member. By sharing the driving source of the two rollers with one feeding motor 110, the cost can be reduced.

FIG. 19 is a block diagram showing an internal configuration of the position / speed tracking control circuit 182 of the motor control circuit. The position / speed tracking control circuit 182 includes a position feedforward control circuit 182a, a speed feedforward control circuit 182b, a position feedback control circuit 182c, a speed feedback control circuit 182d, a speed detection circuit 182e, a first addition / subtraction circuit 182f, and a second addition / subtraction circuit. 182g, an adder circuit 182h, and the like. The feeding motor (110) made of a DC brushless motor is inevitably inferior in position follow-up and speed follow-up at start-up and stop as compared to a stepping motor. Therefore, in the implementation form, previously investigated the operating characteristics of the startup and stop of the feed motor, on the basis of their operating characteristics, improving the position tracking ability and speed trackability during startup and stop A position follow-up profile and a speed follow-up profile are constructed and stored in the target position / velocity calculation circuit (181). The target position / speed calculation circuit generates a target position signal and a target speed signal based on these profiles.

  The target position signal received by the position / speed tracking control circuit 182 is input as an addition value to the first addition / subtraction circuit 182f. The first addition / subtraction circuit 182f receives as a subtraction value a position detection signal constructed based on the motor rotation amount detection result by the encoder. When the actual motor rotation position (position detection signal) and the target rotation position (target position signal) are the same, the total value becomes zero. On the other hand, when the actual motor rotation position is ahead of the target rotation position, the total value becomes negative. Further, when the actual motor rotation position is delayed from the target rotation position, the total value becomes positive. The total value is input to the position feedback control circuit 182c. The position feedback control circuit 182c converts the input total value from position to speed and outputs it as a first feedback signal.

  The target position signal received by the position / speed tracking control circuit 182 is also input to the position feedforward control circuit 182a. The position feedforward control circuit 182a converts the target position into a speed and outputs it as a first feedforward signal. The first feedback signal output from the position feedback control circuit 182c and the first feedforward signal output from the position feedforward control circuit 182a are respectively input as addition values to the second addition / subtraction circuit 182g.

  The position detection signal received by the position / speed tracking control circuit 182 is also input to the speed detection circuit 182e. The speed detection circuit 182e calculates the rotational speed of the motor based on the time change of the input position detection signal, and outputs the result as a speed detection signal. This speed detection signal is input as a subtraction value to the second addition / subtraction circuit 182g.

  The total value in the second addition / subtraction circuit 182g is input to the speed feedback circuit 182d. The speed feedback circuit 182d converts the total value of the input speeds into a voltage value for realizing an increase / decrease of the speed (increase in the case of a plus sign, decrease in the case of a minus sign), and an adder circuit 182h. Output to.

  On the other hand, the target speed signal received by the position / speed tracking control circuit 182 is input to the speed feedforward control circuit 182b. The speed feedforward control circuit 182b converts the input target speed into a voltage value for realizing it, and outputs the voltage value to the adder circuit 182b. Then, the voltage addition result in the adding circuit 182b is output to the driver circuit as a PWM signal.

  In such a configuration, a feedback control value based on the difference between the speed detection result and the target speed and a feedback control value based on the difference between the position detection result and the target position with respect to the feedforward control value based on the position tracking profile or the speed tracking profile. As a result, the DC brushless motor can exhibit position followability and speed followability comparable to a stepping motor.

Then, the copying machine according to the implementation mode describes more characteristic adding configure embodiments of the copying machine.
[First embodiment]
The copier according to the first embodiment does not include the deflection amount detection sensor 35 shown in FIG. Instead, the combination of the motor control circuit 180 and the motor encoder 111 is made to function as a deflection detection means.

  The registration roller pair 29 is driven by a registration motor different from the feeding motor 110. In the bending forming process, the feeding motor 110 is driven in a state where the driving of the registration motor is stopped, and the recording sheet is sent out from the conveyance nip toward the registration nip. When the amount of bending formed by this bending forming process is less than the target amount of bending, the recording sheet is then fed from the registration nip toward the secondary transfer nip by driving the registration motor or the feeding motor 110. The amount of sheet deflection between the conveyance nip and the registration nip gradually decreases. Eventually, no deflection occurs, and the recording sheet is stretched with a strong tension between the conveyance nip and the registration nip. This is because the linear speeds of the registration rollers (29a, 29b) in the unworn state are faster than the linear speeds of the transport rollers (28a, 28b) in the worn state. Since the recording sheet stretched with a strong tension is conveyed at the entire area in the longitudinal direction at the linear velocity of the registration rollers, the linear velocity is increased by promoting the rotation of the conveyance roller pair at the conveyance nip. Thereby, since the load with respect to the feeding motor 110 falls rapidly, the rotational speed of the feeding motor 110 becomes faster than the reference speed. Therefore, when the recording sheet is fed from the registration nip toward the secondary transfer nip, the rotation speed of the feeding motor 110 becomes faster than the reference speed, and the difference exceeds a predetermined threshold value. In such a case, it can be considered that the deflection of the target deflection amount is no longer formed in the deflection forming process.

  Therefore, when the motor control circuit 180 starts the feeding of the recording sheet from the registration nip to the secondary transfer nip after performing the bending forming process, the sheet detection result by the sheet detection sensor 36 becomes “no sheet”. The following determination processing is performed until the end of the sheet (until the trailing edge of the sheet passes through the conveyance nip). That is, based on the pulse number (motor rotation amount) of the pulse signal sent from the motor encoder 111, the rotational speed of the feed motor 110 is periodically calculated at predetermined time intervals. Then, it is determined whether or not the calculation result satisfies a condition that it is faster than the reference speed and a difference from the reference speed (hereinafter referred to as a speed difference) exceeds a predetermined threshold. In the case where it is provided, it is determined that a deflection exceeding the predetermined threshold has not been formed between the conveyance nip and the registration nip immediately before starting the sheet feeding from the registration nip. Then, the target rotation amount of the feed motor 110 used in the subsequent deflection forming process is corrected to a larger value. With such a configuration, it is possible to detect whether or not the recording sheet is bent without providing a bending amount detection sensor that optically detects the bending amount of the recording sheet.

  Instead of calculating the rotation speed of the feed motor 110 based on the number of pulses (motor rotation amount), the following may be performed. That is, the relationship between the elapsed time from the start of driving of the feeding motor 110 to feed the recording sheet from the registration nip toward the secondary transfer nip and the theoretical rotation amount of the feeding motor 110 is shown. Remember the function. Then, when the difference between the rotation amount theoretical value calculated based on the function and the elapsed time and the rotation amount calculated based on the number of pulses exceeds a predetermined threshold, it may be determined that there is no deflection.

  Further, when the registration motor is configured by a DC brushless motor having the same configuration as the feeding motor 110 and the driving of the registration motor is controlled by the registration motor control circuit having the same configuration as the motor control circuit 180, It may be as follows. That is, instead of causing the combination of the motor control circuit 180 and the motor encoder 111 to function as a deflection detection means, a registration motor control circuit and a motor encoder with a built-in registration motor (or an encoder that detects the rotation speed of the registration roller) are detected. It functions as a means. In this case, if the recording sheet is stretched between the conveyance nip and the registration nip with a strong tension, the load on the registration motor increases rapidly, so that the rotation speed of the registration motor becomes lower than the reference speed or the registration motor. The amount of rotation may be less than the theoretical amount of rotation. Therefore, when the rotation speed of the registration motor becomes slower than the reference speed and the difference exceeds a predetermined threshold, it can be considered that the deflection of the target deflection amount is not formed in the deflection forming process.

[Second Embodiment]
The copying machine according to the second embodiment also does not include the deflection amount detection sensor 35 shown in FIG. Instead, the motor control circuit 180 is caused to function as a deflection detection means.

  As described above, when the deflection of the target deflection amount is not formed in the deflection forming process, the recording sheet is stretched with a strong tension when the recording sheet is subsequently fed from the resist nip toward the secondary transfer nip. Thus, the load on the feeding motor 110 is abruptly reduced. Then, the rotation speed of the feeding motor 110 increases rapidly. At this time, since the motor control circuit 180 performs feedback control by the position feedback control circuit 182c and the speed feedback control circuit 182d, the output voltage to the feeding motor 110 is further reduced, and the target rotational speed, So that the rotation position can be obtained. For this reason, the value of the PWM signal to be output is rapidly reduced.

  The motor control circuit 180 is provided with a bending presence / absence determination circuit (not shown). This bend presence / absence determination circuit has a fluctuation amount per unit time of a PWM signal for the feeding motor 110 when the recording sheet is fed from the registration nip to the secondary transfer nip by driving the registration motor and the feeding motor 110. When a predetermined threshold value is exceeded, determination is made as follows. In other words, it is determined that the amount of deflection exceeding the predetermined threshold is not formed between the conveyance nip and the registration nip immediately before starting the sheet feeding from the registration nip. Then, the target rotation amount of the feed motor 110 used in the subsequent deflection forming process is corrected to a larger value. Even in such a configuration, it is possible to detect whether or not the recording sheet is bent without providing a bending amount detection sensor that optically detects the bending amount of the recording sheet.

  When the registration motor is configured by a DC brushless motor having the same configuration as the feeding motor 110 and the driving of the registration motor is controlled by the registration motor control circuit having the same configuration as the motor control circuit 180, It may be as follows. That is, instead of causing the motor control circuit 180 to function as a deflection detection unit, the registration motor control circuit functions as a deflection detection unit. In this case, when the recording sheet is stretched between the conveyance nip and the registration nip with a strong tension, the rotation speed of the registration motor is rapidly reduced, and the PWM signal for the registration motor is rapidly increased. Therefore, when the fluctuation amount per unit time of the PWM signal exceeds a predetermined threshold, it may be considered that the deflection of the target deflection amount is not formed in the deflection forming process.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
[Aspect A]
In the aspect A, a feed member (for example, the feed roller 27a or the feed belt 284) that moves its surface endlessly in a feeding direction toward the transport destination, and a separation nip is formed by contacting the feed member. In addition, a conveyance resistance applying member (for example, a separation pad) that applies conveyance resistance to a sheet member lower than the uppermost sheet member in a state where a plurality of sheet members that overlap each other are sandwiched between the feeding members. 27b and separation roller 285), and separating means (for example, separation means 27 or separation means) that separates the uppermost sheet member that is in contact with the feeding member from the lower sheet member and feeds it from the separation nip. Part B) and two conveying members that move the surface endlessly (for example, a first conveying roller 28a, a second conveying roller 28b, a first conveying roller 286, a second conveying roller 287, a first tape) The roller 266 and the second turn roller 273 are in contact with each other to form a conveyance nip, and in a state where the sheet member that has passed through the separation nip is sandwiched between the conveyance nips, at least one of the two conveyance members Conveying means (for example, conveying roller pair 28, conveying unit C, turn part D) that conveys toward the conveying destination by endless movement of one surface, and two abutting conveying members (for example, registration rollers) that move the surface endlessly And abutting and conveying rollers) are brought into contact with each other to form an abutting and conveying nip, and the sheet member that has passed through the conveying nip is sandwiched between the abutting and conveying nips of the two abutting and conveying members. Abutting conveyance means (for example, a pair of registration rollers 2) that conveys toward the conveyance destination by endless movement of at least one of the surfaces. Abutting and conveying unit E), and feeding the sheet member out of the conveying nip while abutting the leading end of the sheet member that has passed through the conveying nip against the abutting and conveying nip of the non-driven abutting and conveying means. Control means for performing a process of feeding the sheet member from the abutting conveyance nip toward the conveying destination by driving the abutting conveying means after performing the bending forming process for forming the bending of the sheet member. For example, in a sheet conveying apparatus having a target signal generating unit 190 and a motor control circuit 180)), is the sheet member bent by an amount exceeding a predetermined threshold between the conveying nip and the abutting conveying nip? And a bend detecting means (e.g., bend amount detecting sensors 35, 299) for detecting whether or not the bend is formed in the bend forming process. The bend detecting means that performs the process of stopping the driving of the conveying means based on the fact that the detection result by the detecting means is deflected, or immediately after the driving of the conveying means is stopped in the bending forming process. When the detection result according to (1) indicates that there is no deflection, the control means is configured to perform a process of correcting the drive stop timing of the conveying means in the subsequent bending formation process so that the detection result is the presence of deflection. It is characterized by comprising.

[Aspect B]
Aspect B uses, in aspect A, a DC brushless motor as a drive source for the transport member, an encoder (for example, 111) for detecting the rotation amount of the transport roller as the transport member or the DC brushless motor, and the separation Sheet detection means (for example, a sheet detection sensor 36 and a reading entrance sensor 267) that detects the sheet member downstream of the nip in the sheet conveyance direction is provided, and the leading edge of the sheet member is moved by the sheet detection means in the bending forming process. Based on the fact that the accumulated rotation amount after detection has reached a predetermined target rotation amount, a process for stopping the driving of the conveying unit is performed, and the driving of the conveying unit is stopped in the bending forming process. The target rotation amount is increased based on the fact that the detection result by the bending detection means immediately after the bending is no To perform the process of correcting the, it is characterized in that constitutes the control means. In such a configuration, by correcting the target rotation amount to a larger value, the insufficient sheet conveyance amount can be increased and the deflection amount can be brought close to the target deflection amount.

[Aspect C]
Aspect C is the difference between the rotational speed calculated based on the rotation amount and the reference speed when the sheet member is fed from the abutting conveyance nip toward the conveyance destination in aspect B, or the rotation When the difference between the rotation amount and the rotation amount theoretical value exceeds a predetermined threshold value, a predetermined interval is set between the conveyance nip immediately before starting the feeding of the sheet member from the abutting conveyance nip and the abutting conveyance nip. The control means is configured to carry out a determination process for determining that the amount of deflection exceeding the threshold value is not formed, and the combination of the encoder and the control means functions as the deflection detection means. It is what. In this configuration, as described above, it is possible to detect the presence / absence of a deflection exceeding a threshold without providing a deflection amount detection sensor that optically detects the deflection amount of the recording sheet.

[Aspect D]
Aspect D is based on the detection result by the encoder and the target rotational position with respect to the coil of the DC brushless motor when the sheet member is fed from the abutting conveyance nip toward the conveyance destination in the aspect B. Per unit time of the output voltage when at least one of the feedback control of the output voltage and the feedback control of the output voltage based on the detection result and the target rotation speed is performed and the feedback control is performed. When the amount of fluctuation exceeds a predetermined threshold, the amount of deflection exceeding the predetermined threshold is between the transport nip and the butting transport nip immediately before starting the feeding of the sheet member from the butting transport nip. The control means is configured to carry out a determination process for determining that is not formed, Serial is characterized in that the control means is made to function as the deflection detection means. Even in such a configuration, it is possible to detect the presence or absence of a deflection exceeding the threshold without providing a deflection amount detection sensor that optically detects the deflection amount of the recording sheet.

[Aspect E]
Aspect E provides a second DC brushless motor different from the DC brushless motor as a driving source for driving the abutting conveying member in aspect B, and an abutting conveying roller as the abutting conveying member, Alternatively, a second encoder that detects the amount of rotation of the second DC brushless motor is provided, and when a sheet member is fed from the abutting conveyance nip toward the conveyance destination, the detection result by the second encoder is obtained. When the difference between the rotation speed calculated based on the reference speed or the difference between the detection result and the rotation amount theoretical value exceeds a predetermined threshold, feeding of the sheet member from the abutting conveyance nip is started. No deflection exceeding the predetermined threshold was formed between the immediately preceding transport nip and the abutting transport nip. Determination processing constitutes the control means to perform, is characterized in that to function as the deflection detecting means a combination of the second encoder and the control unit. Even in such a configuration, it is possible to detect the presence or absence of a deflection exceeding the threshold without providing a deflection amount detection sensor that optically detects the deflection amount of the recording sheet.

[Aspect F]
Aspect F provides a second DC brushless motor different from the DC brushless motor as a driving source for driving the abutting conveying member in aspect B, and an abutting conveying roller as the abutting conveying member, Alternatively, a second encoder that detects the amount of rotation of the second DC brushless motor is provided, and when the sheet member is fed from the abutting conveyance nip toward the conveyance destination, the coil of the second DC brushless motor is And performing at least one of feedback control of the output voltage based on the detection result by the second encoder and the target rotational position, and feedback control of the output voltage based on the detection result and the target rotational speed, and feedback Unit of the output voltage when performing control An amount that exceeds a predetermined threshold value between the conveying nip and the abutting conveyance nip immediately before starting the feeding of the sheet member from the abutting conveyance nip when the fluctuation amount per interval exceeds a predetermined threshold value The control means is configured to carry out a determination process for determining that no bending has been formed, and the control means functions as the deflection detecting means. Even in such a configuration, it is possible to detect the presence or absence of a deflection exceeding the threshold without providing a deflection amount detection sensor that optically detects the deflection amount of the recording sheet.

[Aspect G]
Aspect G is the back of the sheet member according to any one of aspects B to F, based on the fact that the detection result by the bending detection means immediately after the drive of the conveying means is stopped by the bending formation processing is no deflection. While the end side is conveyed from the conveyance nip toward the abutting conveyance nip by driving the conveyance means, the leading end side of the sheet member is directed from the abutting conveyance nip to the conveyance destination by driving the abutting conveyance means. The control means is configured to perform processing for correcting the driving speed of the DC brushless motor to a faster value when being conveyed. In such a configuration, as already described, it is possible to suppress an increase in the length of the bending forming process caused by increasing the target rotation amount of the DC brushless motor in accordance with the shortage of the bending amount due to wear of the conveying member.

[Aspect H]
Aspect H is characterized in that, in aspect G, the motor is shared as a drive source for the feeding member. In such a configuration, the cost can be reduced as compared with the case where the drive source is not shared.

[Aspect I]
Aspect I is characterized in that in any of the aspects B to H, the DC brushless motor is mounted with the encoder for detecting the rotation amount of the motor shaft and a driver circuit for exciting the coil. is there. In such a configuration, the linear speed of the conveying member driven by the DC brushless motor can be freely adjusted by adjusting the rotational speed of the DC brushless motor to an arbitrary speed based on the result of detecting the rotational speed of the DC brushless motor. can do. Further, the rotational speed of the DC brushless motor is detected directly and with high accuracy by an encoder mounted on the DC brushless motor without detecting the speed of the conveying member driven by the DC brushless motor. Then, compared to the conventional method in which the rotation speed of the conveying member is detected, a change in the rotation speed of the DC brushless motor is quickly detected and quickly returned to the original rotation speed, so that the conveying member caused by load fluctuations can be obtained. The speed instability can be suppressed. In addition, since the driver circuit is mounted on the DC brushless motor, the distance between the driver circuit and the coil of the DC brushless motor is made shorter than in the conventional case where the driver circuit is disposed at a position away from the DC brushless motor. . As a result, an excitation voltage can be supplied from the driver circuit to the motor coil by the electrode on the circuit board without providing a harness in which a plurality of drive power supply wires and signal wires are bundled between the driver circuit and the DC brushless motor. The rotation sensing signal can be transmitted from the motor to the driver circuit. As a result, by suppressing the generation of noise when switching the coil to be excited at high speed, or by suppressing the mixing of the generated noise into the rotation sensing signal, the motor caused by the mixing of noise into the rotation sensing signal Instability of rotation can be suppressed.

[Aspect J]
Aspect J provides feedforward control of the output voltage based on the target rotational position and output based on the detection result by the encoder and the target rotational position for the coil of the DC brushless motor in the deflection forming process according to aspect I. The control means is configured to perform voltage feedback control, output voltage feedforward control based on a target rotational speed, and output voltage feedback control based on the detection result and target rotational speed. To do. In this configuration, as described above, the DC brushless motor can exhibit excellent position followability and speed followability comparable to a stepping motor.

27a: Feed roller (feeding member)
27b: Separation pad (conveyance resistance applying member)
27: Separating means 28a: First conveying roller (conveying member)
28b: 2nd conveyance roller (conveyance member)
28: Conveying roller pair (conveying means)
29a: first registration roller (abutting and conveying member)
29b: Second registration roller (abutting and conveying member)
29: Registration roller pair (abutment conveying means)
36: Deflection amount detection sensor (deflection detection means)
110: Feed motor (drive source, DC brushless motor)
111: Encoder 112: Driver circuit 113: Motor shaft 190: Target signal generation means 190 (part of control means)
180: Motor control circuit (part of control means)
266: First turn roller (conveying member)
273: Second turn roller (conveying member)
284: Paper feed belt (feeding member)
285: Separation roller (conveyance resistance applying member)
286: First conveying roller 286 (conveying member)
287: Second transport roller 287 (transport member)
289: first abutting conveyance roller (abutting conveyance member)
290: First abutting conveyance roller (abutting conveyance member)
299: Deflection amount detection sensor (deflection detection means)
B: Separation part (separation means)
C: Conveying section (conveying means)
D: Turn part (conveying means)

JP 2008-207922 A

Claims (6)

A feeding member that moves its surface endlessly in a feeding direction toward the conveyance destination, and a separation nip that is in contact with the feeding member to form a plurality of sheet members that overlap each other A conveyance resistance applying member that applies conveyance resistance to a sheet member that is not in direct contact with the feeding member in a state where the sheet member is sandwiched between the sheet member and the sheet member that is in direct contact with the feeding member. Separation means for separating from a sheet member that is not in contact and feeding out from the separation nip;
Sheet detecting means for detecting a sheet member downstream of the separation nip in the sheet conveying direction;
Two conveying rollers that move the surface endlessly are brought into contact with each other to form a conveying nip, and at least one of the two conveying rollers in a state where the sheet member that has passed through the separation nip is sandwiched between the conveying nips of the sheet. Transport means for transporting toward the transport destination by endless movement of one of the surfaces;
Two abutting and conveying members that move the surface endlessly are brought into contact with each other to form an abutting and conveying nip, and in the state where the sheet member that has passed through the conveying nip is sandwiched between the abutting and conveying nips of the two, Abutting and conveying means for conveying toward the conveying destination by endless movement of at least one of the surfaces of the abutting conveying member;
A DC brushless motor which is a drive source of the conveying roller;
An encoder for detecting a rotation amount of the transport roller or the DC brushless motor;
Deflection detecting means for detecting whether or not the amount of sheet member deflection exceeding a predetermined threshold is formed between the conveyance nip and the abutting conveyance nip;
Deflection that forms the deflection of the sheet member by feeding the sheet member out of the conveying nip while abutting the leading end of the sheet member that has passed through the conveying nip against the abutting conveying nip of the abutting conveying means in a non-driven state. In a sheet conveying apparatus having a control unit that performs a process of driving the abutting conveying unit and feeding the sheet member from the abutting conveying nip toward the conveying destination after performing the forming process .
A drive source for driving the abutting conveying member is provided separately from the DC brushless motor,
Processing at pre Symbol deflection forming process, the amount of rotation of the accumulation from the tip of the sheet member is detected by said sheet detecting means stops the driving of the conveying means on the basis that becomes a predetermined target rotation amount carried out, and the deflection forming process based especially became without deflection detection result by the deflection detection means after performing, the target rotation amount so that the detection result that there flexing to a larger value By correcting , the control means is configured to perform a process of increasing the driving amount of the conveying means in the subsequent bending formation process ,
and,
When a sheet member is being sent out from the abutting conveyance nip toward the conveyance destination, feedback control of an output voltage based on a detection result by the encoder and a target rotation position for the coil of the DC brushless motor, and The amount of fluctuation per unit time of the output voltage exceeds a predetermined threshold when at least one of the feedback control of the output voltage based on the detection result and the target rotation speed is performed and the feedback control is performed. A determination is made that there has been no deflection exceeding the predetermined threshold between the transport nip immediately before starting the feeding of the sheet member from the butting transport nip and the butting transport nip. The control means is configured to perform processing, and the control means is Sheet conveying apparatus is characterized in that to function as a. A feeding member that moves its surface endlessly in a feeding direction toward the conveyance destination, and a separation nip that is in contact with the feeding member to form a plurality of sheet members that overlap each other A conveyance resistance applying member that applies conveyance resistance to a sheet member that is not in direct contact with the feeding member in a state where the sheet member is sandwiched between the sheet member and the sheet member that is in direct contact with the feeding member. Separation means for separating from a sheet member that is not in contact and feeding out from the separation nip;
Sheet detecting means for detecting a sheet member downstream of the separation nip in the sheet conveying direction;
Two conveying rollers that move the surface endlessly are brought into contact with each other to form a conveying nip, and at least one of the two conveying rollers in a state where the sheet member that has passed through the separation nip is sandwiched between the conveying nips of the sheet. Transport means for transporting toward the transport destination by endless movement of one of the surfaces;
Two abutting and conveying members that move the surface endlessly are brought into contact with each other to form an abutting and conveying nip, and in the state where the sheet member that has passed through the conveying nip is sandwiched between the abutting and conveying nips of the two, Abutting and conveying means for conveying toward the conveying destination by endless movement of at least one of the surfaces of the abutting conveying member;
A DC brushless motor which is a drive source of the conveying roller;
An encoder for detecting a rotation amount of the transport roller or the DC brushless motor;
Deflection detecting means for detecting whether or not the amount of sheet member deflection exceeding a predetermined threshold is formed between the conveyance nip and the abutting conveyance nip;
Deflection that forms the deflection of the sheet member by feeding the sheet member out of the conveying nip while abutting the leading end of the sheet member that has passed through the conveying nip against the abutting conveying nip of the abutting conveying means in a non-driven state. In a sheet conveying apparatus having a control unit that performs a process of driving the abutting conveying unit and feeding the sheet member from the abutting conveying nip toward the conveying destination after performing the forming process .
As a drive source for driving the abutting conveying member, a second DC brushless motor different from the DC brushless motor is provided,
A second encoder for detecting a rotation amount of the butting conveying roller as the butting conveying member or the second DC brushless motor;
In the bending forming process, a process of stopping the driving of the conveying unit based on the accumulation of the rotation amount after the leading edge of the sheet member is detected by the sheet detection unit reaches a predetermined target rotation amount. The target rotation amount is corrected to a larger value so as to obtain a detection result of the presence of deflection, based on the fact that the detection result by the deflection detection means after the execution of the deflection formation process has been performed is no deflection. Thus, the control unit is configured to perform a process of increasing the driving amount of the transport unit in the subsequent bending formation process,
and,
When the sheet member is sent out from the abutting conveyance nip toward the conveyance destination, feedback control of the output voltage based on the detection result by the second encoder and the target rotation position for the coil of the second DC brushless motor. , And at least one of the output voltage feedback control based on the detection result and the target rotation speed, and the amount of fluctuation per unit time of the output voltage when the feedback control is performed is predetermined. When the threshold value is exceeded, a deflection exceeding the predetermined threshold value is not formed between the conveyance nip immediately before starting the feeding of the sheet member from the abutting conveyance nip and the abutting conveyance nip. The control unit is configured to perform a determination process for determining that the control unit has Sheet conveying apparatus is characterized in that to function as viewed detecting means. In the sheet conveying apparatus according to claim 1 or 2 ,
Based on the fact that the detection result by the bending detection means after the bending forming process is not bent, the rear end side of the sheet member is driven from the conveying nip to the abutting conveying nip by driving the conveying means. A process of correcting the driving speed of the DC brushless motor when the front end side of the sheet member is conveyed from the abutting conveyance nip toward the conveyance destination by driving the abutting conveyance means while conveying toward the sheet is performed. As described above, a sheet conveying apparatus comprising the control means. In the sheet conveying apparatus according to claim 3 ,
The DC brushless motor is commonly used as a drive source for the feeding member. A feeding member that moves its surface endlessly in a feeding direction toward the conveyance destination, and a separation nip that is in contact with the feeding member to form a plurality of sheet members that overlap each other A conveyance resistance applying member that applies conveyance resistance to a sheet member that is not in direct contact with the feeding member in a state where the sheet member is sandwiched between the sheet member and the sheet member that is in direct contact with the feeding member. Separation means for separating from a sheet member that is not in contact and feeding out from the separation nip;
Sheet detecting means for detecting a sheet member downstream of the separation nip in the sheet conveying direction;
Two conveying rollers that move the surface endlessly are brought into contact with each other to form a conveying nip, and at least one of the two conveying rollers in a state where the sheet member that has passed through the separation nip is sandwiched between the conveying nips of the sheet. Transport means for transporting toward the transport destination by endless movement of one of the surfaces;
Two abutting and conveying members that move the surface endlessly are brought into contact with each other to form an abutting and conveying nip, and in the state where the sheet member that has passed through the conveying nip is sandwiched between the abutting and conveying nips of the two, Abutting and conveying means for conveying toward the conveying destination by endless movement of at least one of the surfaces of the abutting conveying member;
A DC brushless motor which is a drive source of the conveying roller;
An encoder for detecting a rotation amount of the transport roller or the DC brushless motor;
Deflection detecting means for detecting whether or not the amount of sheet member deflection exceeding a predetermined threshold is formed between the conveyance nip and the abutting conveyance nip;
Deflection that forms the deflection of the sheet member by feeding the sheet member out of the conveying nip while abutting the leading end of the sheet member that has passed through the conveying nip against the abutting conveying nip of the abutting conveying means in a non-driven state. In a sheet conveying apparatus having a control unit that performs a process of driving the abutting conveying unit and feeding the sheet member from the abutting conveying nip toward the conveying destination after performing the forming process.
A drive source for driving the abutting conveying member is provided separately from the DC brushless motor,
In the bending forming process, a process of stopping the driving of the conveying unit based on the accumulation of the rotation amount after the leading edge of the sheet member is detected by the sheet detection unit reaches a predetermined target rotation amount. The target rotation amount is corrected to a larger value so as to obtain a detection result of the presence of deflection, based on the fact that the detection result by the deflection detection means after the execution of the deflection formation process has been performed is no deflection. Thus, the control unit is configured to perform a process of increasing the driving amount of the transport unit in the subsequent bending formation process,
The DC brushless motor is equipped with the encoder for detecting the rotation amount of the motor shaft and a driver circuit for exciting the coil,
and,
In the deflection forming process, with respect to the coil of the DC brushless motor, an output voltage feedforward control based on a target rotation position, a detection result by the encoder and an output voltage feedback control based on the target rotation position, and a target rotation The sheet conveying apparatus according to claim 1, wherein the control means is configured to perform feed-forward control of the output voltage based on speed and feedback control of the output voltage based on the detection result and the target rotation speed. In an image forming apparatus comprising: an image recording unit that records an image on a recording sheet; and a sheet conveying unit that conveys the recording sheet toward a recording position by the image recording unit.
Wherein as a sheet conveying unit, the image forming apparatus characterized by using any one of a sheet conveying apparatus according to claim 1 to 5.

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