JP2017128436A - Sheet conveyance device and method of controlling the same, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for preventing step-out from repeatedly occurring in a motor used as a driving source of a conveyance system in a sheet conveyance device.SOLUTION: An engine control unit in a sheet conveyance device determines whether a delay has occurred in driving of a registration roller 10 using a conveyance sensor arranged between the registration roller 10 and a conveyance roller when conveyance of a sheet is started at a position of the registration roller 10 (S104). As a result of the determination, if the delay has occurred in the driving of the registration roller 10, an engine control unit 100 increases a time interval ΔT (S105). The time interval ΔT is a time interval from the start of the driving of the registration roller 10 by a registration clutch to the start of driving of the conveyance roller by a conveyance motor when the conveyance of the sheet by the registration roller 10 and the conveyance roller is started.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a sheet conveying apparatus, a control method therefor, and an image forming apparatus that forms an image on a sheet conveyed by the sheet conveying apparatus.

  In image forming apparatuses such as printers and copiers, stepping motors are widely used as a drive source for a conveyance system that conveys a sheet on which an image is formed. The stepping motor has a feature that can be realized in a small size and at a low cost. On the other hand, in a stepping motor, unlike a conventional servo motor, “step-out”, which is a phenomenon in which the rotation of the rotor of the motor cannot be synchronized with the input of a pulse signal, may occur. When the stepping motor used in the image forming apparatus is stepped out, the conveyance roller cannot be driven by the stepping motor, and jamming such as a paper jam occurs.

  Patent Document 1 describes that in an image forming apparatus using a stepping motor for a conveyance system, the motor step-out is detected based on the measurement result of the current flowing in the excitation coil of the stepping motor. Further, when the image forming apparatus detects a step-out of the motor, if there is no sheet on the conveyance roller driven by the motor, the image forming apparatus stops the current supply to the motor and then restarts the motor. To deal with the step-out that occurred.

JP 2001-158546 A

  In Japanese Patent Laid-Open No. 2004-260, a step-out generated in the motor at a timing when the sheet is not conveyed by the conveyance roller is dealt with, but it is also necessary to deal with a step-out generated in the motor during the conveyance of the sheet by the conveyance roller. This is because the step-out occurring during the conveyance of the sheet may be reproduced (occurs repeatedly) due to the same factor. Moreover, even if the motor is restarted in response to the occurrence of step-out, step-out may be reproduced again due to the same factor. Such step-out reproduction can cause a significant decrease in user convenience.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a technique for preventing a step-out from repeatedly occurring in a motor used as a drive source of a conveyance system of a sheet conveyance apparatus. .

  The present invention can be realized as, for example, a sheet conveying apparatus. A sheet conveying apparatus according to an aspect of the present invention includes a first roller that conveys a sheet, and a second roller that conveys the sheet and is disposed upstream of the first roller in the sheet conveying direction and driven by a stepping motor. And detecting means for detecting the state of the sheet conveyed by the second roller, and whether or not there is a delay in conveying the sheet based on the detection result of the sheet using the detecting means And a control means for increasing a time interval from the start of driving of the first roller to the start of driving of the second roller in response to the determination that the delay has occurred by the determining means. It is characterized by providing.

  According to the present invention, it is possible to prevent a step-out from occurring repeatedly in a motor used as a drive source for a conveyance system of a sheet conveyance apparatus. Thereby, it is possible to reduce the downtime caused in the image forming apparatus due to the jam caused by the step-out of the motor.

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus. FIG. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus. FIG. 4 is a diagram illustrating an example of the position of a sheet being conveyed in the image forming apparatus. FIG. 4 is a diagram illustrating an example of the position of a sheet being conveyed in the image forming apparatus. FIG. 4 is a diagram illustrating an example of the position of a sheet being conveyed in the image forming apparatus. The figure which shows the operation timing of a registration roller and a conveyance motor. The flowchart which shows the procedure of the drive control by an engine control part.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.

  Hereinafter, an example in which the present invention is applied to an image forming apparatus that employs a stepping motor as a drive source of a conveyance system that conveys a sheet will be described. The image forming apparatus according to the present embodiment is an apparatus that forms an image on a sheet by an electrophotographic method, such as a printing apparatus (printer), a copying machine, a multifunction peripheral (MFP), and a facsimile machine. It is an example of the apparatus to be used.

<Image forming apparatus>
FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus according to the present embodiment. The image forming apparatus may be an image forming apparatus that forms a multicolor image using a plurality of color toners (developers), but an image forming apparatus that forms a single color image using a single color toner will be described. The image forming apparatus includes a printer unit 1 that forms an image on a sheet and a reader unit 2 that reads an image of a document. The image forming apparatus may include an ADF unit that conveys a document to be read. The sheet may be referred to as recording paper, recording material, recording medium, paper, transfer material, transfer paper, or the like.

  In the printer unit 1, the sheets P stored in the paper feed cassette 3 are fed to the transport path one by one by the pickup roller 31 and the separation roller 32. The sheet P fed from the sheet feeding cassette 3 is transported downstream by the transport roller 33 along the transport path. The sheet P may be fed from the manual sheet feeding unit 4 to the conveyance path. When the sheet P reaches the position of the registration roller (registration roller pair) 10, skew correction is performed by the leading end of the sheet P abutting against the stopped registration roller 10. When a predetermined time elapses after the registration sensor 9 detects the sheet P, the rotation of the registration roller 10 is started, so that the sheet P is conveyed to the transfer nip portion between the photosensitive drum 7 and the transfer roller 11. The

  In the printer unit 1, a laser scanner unit 6, a photosensitive drum (photosensitive member) 7, a charging roller 40, a transfer roller 11, a developing device 5, and a fixing device 8 are image forming units (images in FIG. 2) that form an image on a sheet P. Forming part 110). In the image forming unit 110, the outer peripheral surface of the rotationally driven photosensitive drum 7 is uniformly charged to a predetermined polarity potential by the action of the charging roller 40. The laser scanner unit 6 exposes the charged photosensitive drum 7 with a light beam (laser light). Specifically, the laser scanner unit 6 outputs a laser beam L modulated in accordance with image information (time-series digital pixel signal), and scans the charged photosensitive drum 7 with the laser beam L, thereby performing photosensitive. An electrostatic latent image is formed on the drum 7. The laser scanner unit 6 is configured to read the laser beam L based on image data (image information) obtained by reading an image of a document by the reader unit 2 or image data received from an external device such as a PC via a network. Is output.

  The developing device 5 includes a developing roller, and develops the electrostatic latent image on the photosensitive drum 7 using toner supplied from a toner replenishing unit (not shown) in which a replaceable toner bottle is installed. A toner image is formed on the photosensitive drum 7. The toner image formed on the photosensitive drum 7 moves to the transfer nip portion as the photosensitive drum 7 rotates. When a transfer bias having a polarity opposite to that of the photosensitive drum 7 is applied to the transfer roller 11, the toner image on the photosensitive drum 7 is transferred to the surface of the sheet P at the transfer nip portion.

  The sheet P on which the toner image is transferred in the image forming unit 110 is conveyed into the fixing device 8. The fixing device 8 fixes the toner image on the sheet P to the sheet P by applying heat and pressure to the sheet P by a fixing heater and a pressure roller. In this way, an image is formed on the sheet P. When performing single-sided printing on the sheet P, the sheet P is discharged to the discharge tray 18 outside the apparatus by the discharge roller 12 after passing through the fixing device 8 or discharged from the apparatus by the discharge roller 13. The paper is discharged to the paper tray 19.

  When performing double-sided printing on the sheet P, the sheet P on which image formation on the first surface has been completed is conveyed by the reversing roller 14 to a predetermined reversal start position. Thereafter, the rotation direction of the reverse roller 14 is reversed in the reverse direction, whereby the sheet P is conveyed in the reverse direction and guided to the double-sided conveyance path 20. The reversing roller 14 is controlled to reverse the rotation direction in response to, for example, detection of the rear end of the sheet P in the sheet conveyance direction by the reversing sensor 17. The reversing roller 14 is rotationally driven by a reversing motor (reversing motor 112 in FIG. 2).

  The double-sided conveyance path 20 feeds a sheet from a position on the downstream side of the registration roller 10 to a position on the upstream side of the registration roller 10 in the conveyance path where the registration roller 10 is arranged (conveyance path from the separation roller 32 to the reverse roller 14). It is a conveyance path for conveying. That is, the double-sided conveyance path 20 is a position on the upstream side of the registration roller 10 for forming the image on the second surface after passing the position of the registration roller 10 and forming the image on the first surface. Used to transport to. Conveying rollers 21 and 22 that convey the sheet P in the conveying path are arranged in the duplex conveying path 20. The conveyance roller 21 is disposed on the duplex conveyance path 20 upstream of the conveyance roller 22 in the sheet conveyance direction. The conveyance rollers 21 and 22 are disposed upstream of the registration rollers 10 in the sheet conveyance direction, and are driven by a driving source different from the registration rollers 10 as described later.

  The sheet P guided to the double-sided conveyance path 20 is conveyed to a position on the upstream side of the registration roller 10 by the arranged conveyance rollers 21 and 22. At that time, the sheet P is in a state in which the first surface and the second surface are reversed as compared with the image formation on the first surface. After that, the sheet P is discharged to the discharge tray 18 by the discharge roller 12 after the image formation on the second surface is performed in the same manner as the image formation on the first surface, or the discharge roller. 13 is discharged to a discharge tray 19.

  In the present embodiment, the registration roller 10 rotates when the driving force from the main motor (the main motor 111 in FIG. 2) of the image forming apparatus is applied via the registration clutch 50. When the registration clutch 50 is in the ON state, the driving force from the main motor 111 is transmitted to the registration roller 10 and the registration roller 10 rotates. When the registration clutch 50 is in the OFF state, the driving force from the main motor 111 is not transmitted to the registration roller 10, and the rotation of the registration roller 10 is stopped. As described above, the registration clutch 50 transmits the driving force from the main motor 111 to the registration roller 10 to rotationally drive the registration roller 10. Further, the transport rollers 21 and 22 are rotated by being driven by a common transport motor 51. The conveyance motor 51 rotationally drives the conveyance rollers 21 and 22 by transmitting a driving force to the conveyance rollers 21 and 22 via a gear and a belt (not shown).

  In the conveyance path of the sheet P in the image forming apparatus, a large number of sheet sensors 9, 34, 15 to 17, 23, 34 for detecting the sheet P are provided. The sheet sensor 34 is disposed at a position where the sheet fed from the sheet feeding cassette 3 can be detected. The registration sensor 9 is disposed at a position where the sheet conveyed to the position of the registration roller 10 can be detected. The sheet sensor 15 is disposed at a position before the sheet discharge roller 12, the sheet sensor 16 is disposed at a position before the sheet discharge roller 13, and the reverse sensor 17 is disposed at a position before the reverse roller 14. The conveyance sensor 23 is disposed on the duplex conveyance path 20 downstream of the conveyance roller 22 in the sheet conveyance direction, and is disposed on the conveyance path between the registration roller 10 and the conveyance roller 22.

<MFP control system>
FIG. 2 is a block diagram showing a configuration of a control system of the image forming apparatus according to the present embodiment, and particularly shows a configuration related to sheet conveyance. The image forming apparatus includes an engine control unit 100 and an image controller 101 as a control system.

  The engine control unit 100 includes a CPU, a ROM, a RAM (not shown), and the like, reads a control program stored in the ROM into the RAM, executes the control program, and controls each device in the image forming apparatus, thereby controlling the sheet. Controls conveyance and image forming operations. The engine control unit 100 is connected to an image controller 101 that generates image data for image formation, and can communicate with the image controller 101 by serial communication.

  The image controller 101 receives and generates image data by performing control of an operation unit that receives user operations, control of the reader unit 2, control of communication with a host computer that can communicate via USB connection or LAN connection, and the like. Do. The image controller 101 transmits the generated image data to the engine control unit 100 and instructs the engine control unit 100 to start an image forming operation. The engine control unit 100 controls devices such as the image forming unit 110, the main motor 111, the reverse motor 112, the registration clutch 50, and the conveyance motor 51 according to instructions from the image controller 101, thereby performing sheet conveyance and image formation operations. Control.

  The engine control unit 100 receives signals output from the registration sensor 9, the reverse sensor 17, the conveyance sensor 23, and the other sheet sensors 15, 16, and 34. Each sensor outputs an ON signal when the sheet P is detected, and outputs an OFF signal when the sheet P is not detected. The engine control unit 100 can detect the leading edge and the trailing edge of the sheet P conveyed on the conveying path in the sheet conveying direction based on the ON / OFF signal output from each sensor.

  The engine control unit 100 performs drive control of the main motor 111, the reverse motor 112, and the transport motor 51. Although not shown in FIG. 2, motor drive circuits for driving the motors are provided for the main motor 111, the reverse motor 112, and the transport motor 51, respectively. The engine control unit 100 performs drive control of each motor by controlling each motor drive circuit. Further, the engine control unit 100 performs rotation control of the registration roller 10 by performing switching control of the connection state between the ON state and the OFF state of the registration clutch 50.

<Example of sheet conveyance control>
3 to 5 are diagrams illustrating examples of the position of the sheet being conveyed in the image forming apparatus. In these drawings, the positions of the sheets P1, P2, and P3 that are sequentially fed from the sheet feeding cassette 3 and conveyed through the conveyance path when performing double-sided printing on three sheets P1, P2, and P3 continuously. Showing the relationship.

  When performing double-sided printing, the engine control unit 100 causes the registration clutch 50 and the conveyance motor 51 to temporarily stop the sheet P at the position where the leading edge of the sheet P conveyed on the double-sided conveyance path 20 contacts the registration roller 10. To control. Thereafter, the engine control unit 100 controls the registration clutch 50 and the conveyance motor 51 to start (restart) conveyance of the sheet P by the registration roller 10 and the conveyance roller 22.

  In FIG. 3, after image formation on the first surface is performed, the sheet P1 is transported by the transport rollers 21 and 22 through the duplex transport path 20, and waits at a position where the leading edge of the sheet P1 contacts the registration roller 10. Is in a state of being. The sheet P2 is being conveyed downstream of the registration rollers 10 on the conveyance path, and is in a state where an image is formed on the first surface by the image forming unit 110. The sheet P3 is waiting to be fed in the sheet feeding cassette 3.

  After the image formation on the first surface is performed, the sheet P2 is sent to the duplex conveyance path 20 by the reversing roller 14 as described above. The sheet P1 is resumed from the position of the registration roller 10 so as to be conveyed at a predetermined interval from the sheet P2. At that time, the sheet P1 is conveyed downstream from the position of the registration roller 10 by starting the driving of the registration roller 10 and the conveyance roller 22 by the registration clutch 50 and the conveyance motor 51, and an image on the second surface is conveyed. Formation takes place.

  FIG. 4 shows a case where the conveyance motor 51 does not step out when the conveyance of the sheet P1 shown in FIG. 3 from the position of the registration roller 10 is resumed. On the other hand, FIG. 5 shows a case where a step-out occurs in the conveyance motor 51 when the conveyance of the sheet P1 shown in FIG. 3 from the position of the registration roller 10 is resumed.

  In FIG. 4, the sheet P <b> 1 is conveyed downstream from the position of the registration roller 10, and after the image is formed on the second surface, the sheet P <b> 1 is being discharged to the discharge tray 18 by the discharge roller 12. is there. The sheet P3 is fed from the sheet feeding cassette 3 to the conveyance path so that the sheet P3 is conveyed at a predetermined interval from the sheet P1 which has been resumed from the position of the registration roller 10, and is supplied to the first surface by the image forming unit 110. An image is formed on the screen. Meanwhile, the sheet P2 is conveyed by the conveyance rollers 21 and 22 in the double-sided conveyance path 20.

  On the other hand, when a step-out occurs in the conveyance motor 51, the rotation of the conveyance rollers 21 and 22 driven by the conveyance motor 51 stops. As a result, as shown in FIG. 5, the sheet P <b> 2 stops on the double-sided conveyance path 20 with the leading end in contact with the conveyance roller 21. In this case, the engine control unit 100 does not normally convey the sheet P2 in the duplex conveyance path 20 based on the output signals from the reversal sensor 17 and the conveyance sensor 23 (that is, a jam occurs in the duplex conveyance path 20). Can be detected.

  Specifically, the engine control unit 100 does not detect the leading edge of the sheet P2 by the conveyance sensor 23 within a predetermined time after the reverse roller 14 starts conveying the sheet P2 to the double-sided conveyance path 20. It can be determined that P2 is not normally conveyed. In this case, the engine control unit 100 can determine that a step-out has occurred in the transport motor 51 that drives the transport rollers 21 and 22, as will be described later. Based on such a determination result, the engine control unit 100 stops or restarts the operation of the transport motor 51.

  Here, with reference to FIG. 6, a mechanism that causes a step-out in the conveyance motor 51 when the conveyance of the sheet is started (restarted) from the position of the registration roller 10 will be described. FIG. 6 shows the state of the registration clutch 50, the rotational speed (peripheral speed) of the registration roller 10 driven by the registration clutch 50, and the driving frequency of the transport motor 51.

  When the engine control unit 100 switches the registration clutch 50 from the OFF state to the ON state, the driving of the registration roller 10 is started by the driving force from the main motor 111, and the registration roller 10 starts to rotate. Further, when the engine control unit 100 starts the conveyance motor 51, the conveyance motor 51 starts driving the conveyance rollers 21 and 22, and the conveyance rollers 21 and 22 begin to rotate.

  When the conveyance of the sheet P1 (FIG. 3) is started from the position of the registration roller 10, the engine control unit 100 causes the registration clutch 50 and the conveyance motor 51 so that the registration roller 10 starts rotating before the conveyance roller 22. The drive control is performed. Specifically, the engine control unit 100 switches the registration clutch 50 from the OFF state to the ON state at time T1, and starts the conveyance motor 51 at time T2 when a preset time ΔT has elapsed from time T1. The driving of the roller 22 is started. In this drive control, as shown at 601 in FIG. 6, the registration roller 10 starts to rotate before the conveyance motor 51 (conveyance roller 22), and the rotation speed of the registration roller 10 reaches a constant rotation before the conveyance motor 51. The goal is to reach speed. This is because the conveyance roller 22 assists the conveyance of the sheet P1 after the conveyance of the sheet P1 by the registration roller 10 is started.

  However, there may be a delay in driving the registration roller 10 by the registration clutch 50. Specifically, the time required from when the registration clutch 50 switches to the ON state until the clutch is actually connected varies depending on the individual difference of the registration clutch 50. Further, the time required for the rotation speed of the registration roller 10 to reach a certain rotation speed varies depending on the type and basis weight of the sheet to be conveyed by the registration roller 10. Due to such factors, there may be a delay in the start timing of rotation of the registration roller 10 as indicated by 602 in FIG. In this case, the conveyance motor 51 (conveyance roller 22) starts to rotate before the registration roller 10, and the rotation speed of the conveyance motor 51 may reach a certain rotation speed before the rotation speed of the registration roller 10. .

  Thus, when the driving of the registration roller 10 is delayed and the conveyance motor 51 starts to rotate before the registration roller 10, only the conveyance roller 22 conveys the sheet P1 while the registration roller 10 is not rotating. Will start. As a result, the sheet P1 is pushed out in the direction of the registration roller 10 by the conveyance roller 22 with the leading end of the sheet P1 being in contact with the registration roller 10, and the registration loop amount of the sheet P1 between the registration roller 10 and the conveyance roller 22 gradually increases. To increase. As a result, the load applied to the transport motor 51 through the transport roller 22 gradually increases, and when the transport motor 51 is loaded with a predetermined amount or more, the transport motor 51 is stepped out. When a step-out occurs in the conveyance motor 51 in this way, the sheet cannot be conveyed in the double-sided conveyance path 20, and a jam occurs.

<Drive control of registration clutch and transport motor>
In the present embodiment, it is determined whether or not there is a step out of the transport motor 51 or a step out of the transport motor 51 by the mechanism described above, and the registration clutch 50 and the transport motor 51 are driven based on the determination result. Take control. Specifically, the engine control unit 100 determines whether or not there is a delay in driving the registration roller 10 by the registration clutch 50 based on the detection result of the sheet P using the conveyance sensor 23. If the engine control unit 100 determines that a delay has occurred, it controls the registration clutch 50 and the transport motor 51 so that the time interval ΔT shown in FIG. 6 increases. That is, when the conveyance of the sheet P by the registration roller 10 and the conveyance roller 22 is started, the time interval ΔT from the start of the driving of the registration roller 10 by the registration clutch 50 to the start of the driving of the conveyance roller 22 by the conveyance motor 51. Increase.

  Accordingly, the conveyance roller 22 does not start to rotate before the registration roller 10 by relatively delaying the timing at which the conveyance roller 22 starts to be driven relative to the timing at which the registration roller 10 starts to be driven. To do. By such drive control, it is possible to prevent step-out from occurring in the transport motor 51 by the mechanism described above, and it is possible to prevent step-out from occurring repeatedly by the mechanism described above. In addition, it is possible to reduce downtime caused in the image forming apparatus due to a jam caused by the step-out of the conveyance motor 51.

  Below, with reference to FIG. 7, the specific procedure of the drive control of the above-mentioned registration clutch 50 and the conveyance motor 51 is demonstrated. Here, as described with reference to FIGS. 3 to 5, a case where double-sided printing is executed in the image forming apparatus will be described as an example. FIG. 7 is a flowchart illustrating a drive control procedure by the engine control unit 100 when the conveyance of the sheet P1 stopped at the position of the registration roller 10 is resumed as shown in FIG. As described above, the processing of each step in the flowchart is realized in the image forming apparatus by the CPU of the engine control unit 100 reading and executing the control program stored in the ROM.

  After the sheet P <b> 1 (FIG. 3) conveyed on the double-sided conveyance path 20 is temporarily stopped at the position of the registration roller 10, conveyance to the downstream side of the registration roller 10 is resumed. When the resumption timing of the conveyance of the sheet P1 is reached, the engine control unit 100 switches the registration clutch 50 from the OFF state to the ON state in S101. Thereby, the driving of the registration roller 10 is started.

  Thereafter, in S102, the engine control unit 100 determines whether or not the time ΔT has elapsed since the registration clutch 50 was switched to the ON state. When the time ΔT has elapsed, the process proceeds to S103. The time ΔT is set in advance based on various data such as the size of the sheet used for image formation, the type of the sheet, and the current sheet conveyance control state. In step S <b> 103, the engine control unit 100 activates the transport motor 51. Thereby, driving of the transport rollers 21 and 22 by the transport motor 51 is started.

  Next, in S104, it is determined whether or not there is a delay in driving the registration roller 10 started in S101. If it is determined that there is a delay, the engine control unit 100 proceeds to S105, and if it is determined that there is no delay, the engine control unit 100 ends the process according to the procedure illustrated in FIG. The determination process in S104 can be realized by, for example, the following determination process 1 or determination process 2, and both determination processes are executed in the present embodiment.

(Judgment process 1)
In determination processing 1, it is determined whether or not there is a delay in driving the registration roller 10 based on the detection result by the conveyance sensor 23 on the trailing edge of the sheet P <b> 1 conveyed by the registration roller 10 and the conveyance roller 22. If the driving of the registration roller 10 is delayed when the conveyance of the sheet P1 is started from the position of the registration roller 10, the conveyance of the sheet P1 is delayed, and as a result, the conveyance sensor 23 detects the trailing edge of the sheet P1. Timing is delayed. Therefore, it is possible to determine whether or not there is a delay in driving the registration roller 10 based on the timing at which the trailing edge of the sheet P1 is detected.

  Specifically, the elapsed time from when the driving of the registration roller 10 is started in a state where the leading edge of the sheet P1 is in contact with the registration roller 10 until the trailing edge of the sheet P1 is detected by the conveyance sensor 23 is measured. A determination process is performed based on the measurement result. In this case, when the elapsed time does not exceed the predetermined threshold, it is determined that there is no delay in driving the registration roller 10, and when the elapsed time exceeds the predetermined threshold, there is a delay. It may be determined that Alternatively, it may be determined whether or not there is a delay in driving the registration roller 10 based on a comparison result between the measured elapsed time and the elapsed time when there is no delay in the driving of the registration roller 10. . For example, the difference between the measured elapsed time and the elapsed time when there is no delay in driving the registration roller 10 may be compared with a predetermined threshold value. These threshold values can be determined in correspondence with the driving delay amount of the registration roller 10 to such an extent that the conveyance motor 51 is stepped out by the load applied to the conveyance roller 22 when the conveyance of the sheet P1 is started.

(Judgment process 2)
In the determination process 2, determination is performed using the sheet P2 conveyed next to the sheet P1. In the determination process 2, whether or not there is a delay in driving the registration roller 10 based on the detection result by the conveyance sensor 23 at the leading edge of the sheet P <b> 2 conveyed on the double-sided conveyance path 20 after passing the position of the registration roller 10. Determine whether. For example, by determining whether or not the leading edge of the sheet P2 is detected by the conveyance sensor 23 within a predetermined time from the conveyance start timing of the sheet P2 from the reversal start position, the driving of the registration roller 10 is delayed. It is determined whether or not.

  When the leading edge of the sheet P2 cannot be detected by the transport sensor 23 within a predetermined time, the transport of the sheet P2 by the transport rollers 21 and 22 is stopped in the middle of the duplex transport path 20. This may occur due to a step-out in the transport motor 51 due to a delay in driving the registration roller 10. In this case, the sheet P cannot be conveyed to the position of the conveyance sensor 23 by the conveyance rollers 21 and 22, and the sheet P cannot be detected by the conveyance sensor 23. Therefore, based on the detection result of the leading edge of the sheet P2 by the conveyance sensor 23, it is possible to determine whether or not there is a delay in driving the registration roller 10.

  As a result of the determination processing in S104, if it is determined that there is a delay in driving the registration roller 10, the engine control unit 100 next increases the set value of time ΔT in S105. As a result, when no step-out occurs in the transport motor 51, the occurrence of step-out is prevented in advance. Further, when a step-out occurs in the transport motor 51, the step-out is prevented from repeatedly occurring (reproduced). In S105, for example, the set value of time ΔT may be increased by a predetermined amount, or the set value of time ΔT may be increased by a predetermined ratio (for example, 10% of the current set value). The process of S105 is performed every time it is determined in S104 that there is a delay in driving the registration roller 10, and the step-out of the conveyance motor 51 does not occur or the possibility of the step-out does not occur. May be repeated.

  After S105, in S106, the engine control unit 100 determines whether or not a step-out has occurred in the transport motor 51. When the engine control unit 100 determines that no step-out has occurred in the transport motor 51, the engine control unit 100 ends the process according to the procedure illustrated in FIG. 7 and determines that the step-out has occurred in the transport motor 51. In step S107, the process proceeds to step S107. In S106, for example, if the conveyance sensor 23 cannot detect the leading edge of the sheet P within a predetermined time from the start timing of conveyance of the sheet P2 from the reverse start position, the engine control unit 100 causes the conveyance motor 51 to step out. It is determined that it has occurred. That is, the determination result of the above-described determination process 2 can be used for this determination process.

  When a step-out occurs in the conveyance motor 51, the conveyance rollers 21 and 22 cannot convey the sheet P, and a jam occurs. In this case, in order to resume the sheet conveyance and the image forming operation, it is necessary to eliminate the step-out of the conveyance motor 51 and to eliminate the jam of the sheet that can no longer be conveyed, if necessary.

  Therefore, in S107, the engine control unit 100 executes a recovery process for eliminating the step-out of the transport motor 51. Specifically, after stopping the conveyance motor 51, the engine control unit 100 rotates the conveyance motor 51 in a direction opposite to that during conveyance of the sheet by a predetermined number of pulses. The number of pulses may be the number of pulses corresponding to the initial phase alignment for returning the conveyance motor 51 from the step-out state, or may be a pulse number N times the number of pulses for the initial phase alignment. . For example, 4 pulses may be used when the excitation method of the transport motor 51 is 2-phase excitation, and 8 pulses may be used when the excitation method is 1-2 phase excitation. Alternatively, the number of pulses may be determined according to the job being executed in the image forming apparatus. Thereafter, the engine control unit 100 reverses the rotation direction of the conveyance motor 51 again and rotates it in the rotation direction during conveyance of the sheet.

  If the sheet P2 cannot be detected by the conveyance sensor 23 within a predetermined time after the completion of the motor recovery process, the conveyance of the sheet remaining on the conveyance path cannot be resumed, and the jam is not resolved. In this case, the engine control unit 100 determines that the jam has not been eliminated, and uses the operation unit of the image forming apparatus to notify the user to remove the remaining sheet from the conveyance path, thereby eliminating the jam. Plan.

  When the motor recovery process is completed and the conveyance of the sheet P2 in the double-sided conveyance path 20 is resumed, the engine control unit 100 ends the process according to the procedure shown in FIG. Thereafter, the engine control unit 100 temporarily stops the conveyance of the sheet P2 in response to the detection of the sheet P2 by the registration sensor 9 (in response to the sheet P2 reaching the position of the registration roller 10). At that time, the engine control unit 100 switches the registration clutch 50 from the ON state to the OFF state and stops the operation of the transport motor 51.

  As described above, in this embodiment, when the conveyance of the sheet by the registration roller 10 and the conveyance roller 22 is started from the position of the registration roller 10, a delay occurs in driving the registration roller 10 using the conveyance sensor 23. It is determined whether or not. As a result of the determination, when the driving of the registration roller 10 is delayed, the registration clutch 50 and the conveyance motor 51 are controlled so that the time interval ΔT is increased. The time interval ΔT is from when the registration roller 50 starts driving the registration roller 10 when the registration roller 10 and the conveyance roller 22 start conveying the sheet P to when the conveyance motor 51 starts driving the conveyance roller 22. It is a time interval. By such processing, it is possible to prevent the step-out of the conveyance motor 51 from occurring repeatedly, and to reduce the downtime caused in the image forming apparatus due to a jam caused by the step-out of the conveyance motor 51.

  In the above-described embodiment, the registration roller 10 is driven using the registration clutch 50 for transmitting the driving force from the main motor 111 to the registration roller 10. However, the registration roller 10 is driven using an individual motor. May be. Further, a sensor for detecting whether or not the conveyance motor 51 is out of step may be provided for the conveyance motor 51, and the determination process of S106 may be performed using the sensor.

  In the above-described embodiment, it has been described that the timing for starting the driving of the conveyance roller 22 is relatively delayed with respect to the timing for starting the driving of the registration roller 10. The timing at which the driving of the registration roller 10 is started may be relatively advanced with respect to the timing at which the driving is started.

1: printer unit, 2: reader unit, 5: developing device, 7: photosensitive drum, 9: registration sensor, 10: registration roller, 20: duplex conveyance path, 21, 22: conveyance roller, 23: conveyance sensor, 50: Registration clutch 51: Conveyance motor 100: Engine control unit 110: Image forming unit 111: Main motor

Claims (13)

A first roller for conveying the sheet;
A second roller for conveying the sheet, which is disposed upstream of the first roller in the sheet conveying direction and driven by a stepping motor;
Detecting means for detecting the state of the sheet conveyed by the second roller;
A determination unit that determines whether or not a delay occurs in the conveyance of the sheet based on a detection result of the sheet using the detection unit;
Control means for increasing a time interval from the start of driving of the first roller to the start of driving of the second roller in response to the determination that the delay is caused by the determining means;
A sheet conveying apparatus comprising: The sheet conveying apparatus according to claim 1, wherein the determination unit determines whether the delay has occurred based on a detection result of a trailing edge of the sheet by the detection unit. The determination unit determines whether or not the delay has occurred based on an elapsed time from when the conveyance of the sheet is started by the first roller until the trailing edge of the sheet is detected by the detection unit. The sheet conveying device according to claim 2, wherein: The determination means determines that the delay does not occur when the elapsed time does not exceed the threshold, and determines that the delay occurs when the elapsed time exceeds the threshold. The sheet conveying device according to claim 3. The threshold value corresponds to a driving delay amount of the first roller that causes a step-out of the stepping motor due to a load applied to the second roller when the conveyance of the sheet is started. Item 5. The sheet conveying apparatus according to Item 4. The first roller is disposed in the first conveyance path,
The second roller is disposed in a second conveyance path for conveying the sheet from a position downstream of the first roller in the first conveyance path to a position upstream of the first roller,
The determination unit determines whether or not the delay has occurred based on a detection result of the leading end of a sheet conveyed through the second conveyance path after passing the position of the first roller by the detection unit. The sheet conveying apparatus according to claim 1. The sheet according to any one of claims 1 to 6, wherein the control unit increases the time interval by a predetermined ratio when the determination unit determines that the delay has occurred. Conveying device. The sheet conveying apparatus according to claim 6, wherein the determination unit determines that a step-out has occurred in the stepping motor if the detection unit cannot detect the leading edge of the sheet. The said control means performs the process for eliminating the step-out of the said stepping motor, when it determines with the said stepping motor having stepped out by the said determination means. Sheet conveying device. The control means stops the sheet at a position where the leading edge of the sheet conveyed on the conveyance path contacts the first roller, and then starts conveying the sheet by the first roller and the second roller. The sheet conveying apparatus according to any one of claims 1 to 9, wherein driving of the first roller and the second roller is controlled. 11. The sheet conveying apparatus according to claim 1, wherein the driving of the first roller is transmitted by a clutch with a driving force from a main motor of the sheet conveying apparatus. An image forming apparatus comprising the sheet conveying device according to any one of claims 1 to 11,
The first roller is a registration roller that starts driving in accordance with the timing of image formation on a sheet.
The second roller passes the position of the registration roller and forms a sheet on the first surface, and the downstream side of the registration roller in the transport direction for image formation on the second surface. An image forming apparatus, wherein the image forming apparatus is disposed on a transport path for transporting from the position to a position upstream of the registration roller. A method for controlling a sheet conveying apparatus,
The sheet conveying device includes: a first roller that conveys a sheet; a second roller that is disposed upstream of the first roller in the sheet conveying direction and is driven by a stepping motor; and the second roller Detecting means for detecting the state of the sheet conveyed by
The control method is:
A determination step of determining whether or not there is a delay in conveying the sheet based on a detection result of the sheet using the detection unit;
A control step of increasing a time interval from the start of driving of the first roller to the start of driving of the second roller in response to the determination that the delay has occurred in the determining step;
A control method for a sheet conveying apparatus, comprising:

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