JP2006016089A - Paper sheet conveying device, paper sheet conveying method, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a place of a cause for jamming cannot be specified correctly, and components are uselessly exchanged. <P>SOLUTION: A paper sheet conveying device used for an image forming device such as a copier comprises a conveying roll to convey paper sheets along a paper sheet conveying passage, a plurality of paper sheet detection sensors 18-24 to detect the passing of the paper sheets to be conveyed by the conveying roll at different positions in the conveying direction, a timer unit 27 to individually measure the detection timing to detect the passing of the paper sheets for each of the paper sheet detection sensors 18-24, and a control unit 25 to maintain conveying history information including the measured values of the detection timing by the timer unit 27 in a storage medium 28. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to a sheet conveying apparatus and a sheet conveying method used in the image forming apparatus.

  An image forming apparatus such as a copying machine incorporates a sheet conveying apparatus that conveys a sheet as an image forming target along a sheet conveying path. A plurality of transport rollers are disposed on the paper transport path. Each transport roller is rotationally driven using a motor or the like as a drive source, and the paper is transported from the upstream side to the downstream side in the transport direction according to the rotation of the transport roller.

  The paper transport device is provided with a plurality of detection sensors for detecting the passage of the paper on the paper transport path. Each detection sensor detects leading edge passage and trailing edge passage of the paper conveyed along the paper conveyance path. Conventionally, the detection timing when each detection sensor detects the passage of paper is measured, and a jam (paper jam) occurs when the measurement value of the detection timing exceeds a preset allowable limit value. The technique of judging is known.

  In general, a jam during sheet conveyance is likely to occur when slippage due to wear of the conveyance roll becomes significant. For this reason, if the jam occurs frequently, check the wear state of the transport rolls near the location where the jam frequently occurs, and replace it as necessary. ing. Patent Documents 1 and 2 below describe techniques for avoiding unnecessary parts replacement and operation stop by correcting or changing timer setting values and reference values for jam detection.

Japanese Patent No. 2565556 JP 2002-351281 A

  However, the cause of a jam that occurs during paper conveyance may exist in places other than where the occurrence of the jam is actually confirmed. For example, when transporting paper while sequentially delivering paper by a plurality of transport rolls, the delay due to one transport roll and the delay due to another transport roll are added together by the paper detection sensor downstream of those transport rolls. A jam may be detected. In such a case, the conventional paper transport device cannot locate the cause of the jam occurrence, and thus there is a risk that parts such as a transport roll provided near the jam occurrence position may be used unnecessarily.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a sheet conveying apparatus capable of accurately narrowing down the cause of the occurrence of a jam and an image forming apparatus including the same. It is in.

  A sheet conveying apparatus according to the present invention includes a conveying unit that conveys a sheet along a sheet conveying path, and a plurality of sheet detecting units that detect passage of the sheet conveyed by the conveying unit at different positions in the conveying direction. Each of the plurality of paper detection means includes a measurement means for measuring the detection timing when the passage of the paper is detected, and a holding means for holding conveyance history information including a measurement value of the detection timing by the measurement means. Further, an image forming apparatus according to the present invention includes the paper transport device having the above-described configuration.

  In the sheet conveying apparatus according to the present invention and the image forming apparatus including the same, the detection timing when the passage of the sheet is detected by a plurality of sheet detecting units at different positions in the conveying direction is measured, and the measured value is used as the conveyance history. By holding it as information, when the jam actually occurs, it is possible to indicate the conveyance history information at the time of maintenance of the device, etc. It is possible to confirm with reference.

According to the present invention, a situation in which jamming frequently occurs by measuring the detection timing when the passage of paper is detected for each of a plurality of paper detection means with a timer or the like and holding this measurement value as conveyance history information. In such a case, it is possible to accurately narrow down the cause of the occurrence of the jam by referring to the conveyance history information held so far. As a result, the cause of the occurrence of the jam can be quickly determined, so that the recovery work from the trouble such as the frequent occurrence of the jam can be completed in a short time. In addition, since unnecessary parts replacement can be avoided, maintenance costs can be reduced.
Parts replacement

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

  FIG. 1 is a schematic diagram showing a configuration example of an image forming apparatus to which the present invention is applied. The illustrated image forming apparatus includes a sheet conveying device. The paper transport device includes two paper storage cassettes 1 and 2 and transports paper stored in one of the paper storage cassettes 1 and 2 along the paper transport path. The sheet conveyance path is formed so as to pass through an image transfer section described later. The paper storage cassettes 1 and 2 each store a predetermined number of paper sheets and are arranged in two upper and lower stages. Each of the paper storage cassettes 1 and 2 basically has the same configuration although the size of the entire cassette differs depending on the size and type of paper to be stored.

  Further, in the vicinity of the paper storage cassette 1 arranged on the upper side, a calling roll 3 and a delivery roll 4 are arranged as paper feeding rolls. The calling roll 3 calls a sheet from the sheet storage cassette 1 by rotating in contact with the uppermost surface of the sheet stored in the sheet storage cassette 1. The delivery roll 4 separates and feeds the paper called by the call roll 3 one by one. Similarly, a call roll 5 and a feed roll 6 are also arranged as a paper feed roll in the vicinity of the paper storage cassette 2 arranged on the lower side.

  A plurality of (four in the illustrated example) transport rolls 7, 8, 9, and 10 are provided at predetermined intervals on a paper transport path that is a destination of paper fed from the respective paper storage cassettes 1 and 2. It has been. Each of the transport rolls 7, 8, 9, and 10 transports the paper downstream in the transport direction by rotating the paper while nipping (nipping) the paper. Among the plurality of transport rolls 7, 8, 9, and 10, the transport roll 10 arranged on the most downstream side is called a resist roll, and the transport roll 9 immediately before (upstream) the resist roll is a pre-resist. Also called a roll. Accordingly, in the following description, the transport roll 10 is referred to as a resist roll, and the transport roll 9 is referred to as a pre-registration roll.

  The registration roll 10 feeds a sheet on which an image is to be formed toward an image transfer unit (described later), and aligns the sheet when the sheet is fed. Therefore, the registration roll 10 is disposed in front (upstream side) of the image transfer unit in the sheet conveyance direction. The registration of the sheet by the registration roll 10 is performed by correcting the skew by abutting the leading edge of the sheet against the registration roll 10, or adjusting the sheet conveyance start timing (rotation start timing of the registration roll 10) after the skew correction. Is done.

  A photosensitive drum 11 and a vacuum transport unit 12 are disposed at the paper destination of the registration roll 10. The photosensitive drum 11 is rotationally driven in the counterclockwise direction in the figure. Around the photosensitive drum 11, as a means for forming an image (toner image) to be transferred onto a sheet, for example, a charger (not shown) for uniformly charging the surface of the photosensitive drum 11, and this An image writing device (not shown) for writing an electrostatic latent image by irradiating the surface of the photosensitive drum 11 charged by the charger with a laser beam, and a photosensitive drum on which the electrostatic latent image is written by the image writing device. A developing device (not shown) for supplying toner to the surface of the paper 11, a transfer roll 13 for transferring the toner image developed by the developing device to the paper, and the surface of the photosensitive drum 11 without being transferred to the paper. A cleaner (not shown) for removing the remaining unnecessary toner and a static eliminator (not shown) for discharging the surface of the photosensitive drum 11 are sequentially arranged in the rotation direction of the photosensitive drum 11.

  The vacuum transport unit 12 includes an endless transport belt 14 and two rolls 15 and 16 that support the transport belt 14. In the vacuum transport unit 12, the paper fed by the registration roll 10 is placed on the transport belt 14, and the back surface (the surface opposite to the surface on which the image is transferred) on the transport belt 14 is a vacuum system. The sheet is transported in accordance with the travel of the transport belt 14 accompanying the rotational driving of the belt support roll 15 (or 16).

  The transfer roll 13 is disposed at a position facing the photosensitive drum 11 via the conveyance belt 14 of the vacuum conveyance unit 12. Accordingly, the sheet conveyed by the vacuum conveying unit 12 passes through the opposite part of the photosensitive drum 11 and the transfer roll 13 during conveyance, and the image is transferred from the photosensitive drum 11 to the sheet at the opposite part. Therefore, the facing portion between the photosensitive drum 11 and the transfer roll 13 corresponds to the image transfer portion.

  A fixing device 17 is disposed at the destination of the sheet transported by the vacuum transport unit 12. The fixing device 17 fixes the image (toner image) transferred to the paper by the image transfer unit on the paper surface. The fixing unit 17 has a roll for heating and pressing, and the image is fixed to the sheet by heating and pressing when the sheet is conveyed while being nipped by the roll. Further, a discharge roll (not shown) is provided on the downstream side of the fixing device 17, and the paper is discharged to a discharge tray (not shown) by the discharge roll.

  In addition, a plurality of (seven in the illustrated example) paper detection sensors (paper) are detected on the paper conveyance path including the paper feeding portion in order to detect the occurrence of the jam when the paper is conveyed. Detection means) 18 to 24 are provided. Each of the paper detection sensors 18 to 24 is arranged at a different position in the paper transport direction. That is, the paper detection sensor 18 is disposed in the vicinity (downstream side) of the feed roll 4 provided in the paper feeding unit of the upper paper storage tray 1, and the paper detection sensor 19 is supplied to the lower paper storage tray 2. It is arranged in the vicinity (downstream side) of the feed roll 6 provided in the paper section. The paper detection sensor 20 is disposed in the vicinity (downstream side) of the transport roll 7 disposed on the most upstream side in the transport direction, and the paper detection sensor 21 is in the vicinity of the transport roll 8 on the downstream side of the transport roll 7 ( The sheet detection sensor 22 is disposed in the vicinity (downstream side) of the pre-registration roll 9 on the further downstream side than the transport roll 8. The paper detection sensor 23 is disposed in the vicinity (upstream side) of the registration roll 10, and the paper detection sensor 24 is disposed in the vicinity (downstream side) of the fixing device 17.

  Each of the paper detection sensors 18 to 24 is composed of, for example, a reflective photosensor in which a light emitting element and a light receiving element are arranged on the same sensor surface, and a position facing the sensor surface in the vicinity (hereinafter referred to as a sensor detection position). When a sheet is present, the printer is turned on, and when not present, the printer is turned off. Therefore, each of the paper detection sensors 18 to 24 switches from the off state to the on state when the leading edge of the paper passes through the sensor detection position, and then when the trailing edge of the paper passes through the sensor detection position. Switch from on to off. Accordingly, it is possible to detect the passage of the paper (passing through the leading edge and passing through the trailing edge) based on the on / off state of each of the paper detection sensors 18 to 24.

  FIG. 2 is a block diagram showing the configuration of the control system related to jam detection in the sheet conveying device, particularly as the configuration of the control system of the image forming apparatus according to the embodiment of the present invention. In the figure, a control unit 25 comprehensively controls the processing operation of the entire image forming apparatus including the sheet conveying device, and includes an internal memory that temporarily stores various data. The control unit 25 is electrically connected to the plurality of paper detection sensors 18 to 24 described above, and detection signals (on / off signals) output from the respective paper detection sensors 18 to 24 are individually taken into the control unit 25. It is supposed to be. Although not shown, the control unit 25 is connected to an actuator such as a motor (roll rotation driving motor) serving as a paper conveyance drive source and a clutch for intermittently transmitting power to the motor. These actuators are driven in accordance with drive signals given from the control unit 25.

  The operation panel 26 serves as an interface for a user using the image forming apparatus to perform various input operations. The timer unit 27 performs time measurement according to an instruction from the control unit 25. The timer unit 27 has as many timers as the number of the paper detection sensors 18 to 24. More specifically, the timer unit 27 includes a timer (hereinafter referred to as a first timer) for measuring the detection timing when the paper detection sensor 18 detects the passage of the paper, and the detection when the paper detection sensor 19 detects the passage of the paper. A timer for measuring timing (hereinafter referred to as a second timer), a timer for measuring detection timing when the paper detection sensor 20 detects the passage of paper (hereinafter referred to as a third timer), and a paper detection sensor 21 for paper A timer (hereinafter referred to as a fourth timer) for measuring the detection timing when the passage of paper is detected, a timer (hereinafter referred to as a fifth timer) for measuring the detection timing when the paper detection sensor 22 detects the passage of paper, A timer (hereinafter referred to as a sixth timer) for measuring the detection timing when the paper detection sensor 23 detects the passage of the paper, and a paper detection Timer for sensor 24 measures the detection timing of detecting the passage of the sheet (hereinafter, the seventh timer) and a. Time measurement in the timer unit 27 is performed by counting a reference clock having a fixed period.

  The storage medium 28 is used for storing and holding various data necessary for the control unit 25 to control the processing operation of the apparatus. The storage medium 28 is configured using, for example, a magnetic disk such as a hard disk or an optical disk. Reading and writing of data with respect to the storage medium 28 is performed by the control unit 25. The storage medium 28 is used when storing control data relating to jam detection or holding history information relating to jam detection.

  More specifically, in the storage medium 28, standard values (design data) when the paper detection sensors 18 to 24 detect the passage of paper (passing the leading edge and passing the trailing edge) as control data related to jam detection. (Theoretical value based) and allowable limit values are stored in a table format. As a specific example, with respect to the paper detection sensor 18, as shown in FIG. 3, the standard value T1 and the allowable limit value T2 when the paper detection sensor 18 detects passage of the leading edge of the paper, and the paper detection sensor 18 A standard value T3 and an allowable limit value T4 for detecting end passage are stored in a table format. In this case, the standard values T1 and T4 and the permissible limit values T2 and T4 are values that define the passage of time from the timing at which paper feeding from the paper storage tray 1 is started by the rotation of the calling roll 3.

  Here, the standard value is a standard (average) value that is expected to be detected by the paper detection sensor when the paper is conveyed in an ideal state. On the other hand, the permissible limit value is the maximum value that is allowed when the paper detection sensor detects the passage of the paper, and is a reference value (threshold) for detecting the occurrence of a jam. Therefore, the allowable limit value is set to a value larger than the standard value. If the detection timing at which the paper detection sensor detects the passage of paper is measured with a timer, the allowable limit value corresponds to a jam timer value set for jam detection. Therefore, if the measured value of the timer exceeds the allowable limit value before the paper detection sensor detects the passage of the paper, it is determined that a jam has occurred.

  The output unit 29 outputs various information for which an output instruction has been received from the control unit 25 using a display function, a print function, or a data transmission function.

  Next, the basic operation of the image forming apparatus based on the control process of the control unit 25 will be described. First, the user inputs desired image forming conditions (for example, paper size, number of copies, image density, etc.) using the operation panel 26, and then presses a start button in the operation panel 26. Thereby, one job is started. At this time, assuming that the paper storage cassette that stores the paper specified by the user's input operation using the operation panel 26 or the paper storage cassette selected by the automatic selection function is the upper paper storage cassette 1, for example. By the rotation of the calling roll 3 and the delivery roll 4 corresponding to the paper storage cassette 1, the paper stored in the paper storage cassette 1 is separated and sent out one by one in order from the top.

  The paper thus sent out from the paper storage cassette 1 to the paper transport path is then transported to the downstream side in the transport direction (upper side in FIG. 1) by the rotation of the transport roll 8 and sent to the pre-registration roll 9. Next, the sheet is fed into the registration roll 10 according to the rotation of the pre-registration roll 9. The rotation of the registration roll 10 is stopped before the paper is fed by the pre-registration roll 9. Therefore, the leading edge of the paper fed by the pre-registration roll 9 is abutted against the nip portion of the registration roll 10 in a rotation stopped state. Further, by feeding a predetermined amount of paper by the pre-registration roll 9 in this abutting state, the paper is bent in a loop shape before the registration roll 10, that is, the paper skew is corrected, and this state Press to pause the paper.

  Thereafter, the resist roll driving clutch is turned on in accordance with the timing at which the electrostatic latent image written on the surface of the photosensitive drum 11 by the image writing device (not shown) is developed into a toner image and sent to the image transfer unit. As a result, the rotation of the resist roll 10 is started. As a result, the sheet whose skew has been corrected as described above is sent to the image transfer unit according to the rotation of the registration roll 10. In the image transfer unit, the sheet fed by the registration roll 10 is placed on the conveyance belt 14 of the vacuum conveyance unit 12, and the image transfer unit (transferred to the photosensitive drum 11 and the transfer drum 14) by the traveling of the conveyance belt 14. It moves so as to pass through a portion facing the roll 13). At this time, the toner image arrives at the image transfer portion in accordance with the timing when the leading edge of the paper reaches the image transfer portion, and the transfer roll 13 imparts a charge having a polarity opposite to that of the toner, whereby the surface of the photosensitive drum 11 is exposed. The toner image is transferred to the paper.

  Thereafter, the sheet is sent to the fixing device 17 by the vacuum conveyance unit 12, and the image is fixed on the sheet surface of the sheet by the pressurizing action and heating action applied between the rolls. Next, the sheet fed from the fixing device 17 is transferred to a discharge roll (not shown), and is discharged to a discharge tray (not shown) by this discharge roll. Although the case where an image is formed on one side of a sheet has been described here, an image forming apparatus having a “double-sided printing function” that forms an image on both sides of a sheet may be used.

  When the image forming apparatus is operated as described above, the control unit 25 executes processing related to jam detection according to the flowchart of FIG. Note that the processing relating to jam detection is repeatedly performed for each of the paper detection sensors 18 to 24 provided at a predetermined interval on the paper conveyance path, and here, when the paper detection sensor 18 is used to detect jam. The processing will be described as an example.

  First, when paper is supplied from the paper storage cassette 1, paper supply (paper feeding) is started by rotation of the calling roll 3, and at the same time, the value of the first timer of the timer unit 27 is reset to zero ( Step S1), the time measurement by the first timer is started (Step S2).

  Next, it is confirmed whether or not the paper detection sensor 18 is turned on (detection of the passage of the leading edge of the paper) (step S3). If the paper detection sensor 18 is not turned on, it is checked whether or not the measured value of the first timer exceeds the allowable limit value (step S4). The permissible limit value applied in this case is a permissible limit value from the start of paper supply from the paper storage tray 1 until the paper detection sensor 18 detects passage of the front end of the paper.

  In step S3 and step S4, if the measured value of the first timer exceeds the allowable limit value before the paper detection sensor 18 is turned on, it is determined that a jam has occurred before the paper passes the paper detection sensor 18. Then, the process proceeds to step S9. If the paper detection sensor 18 is turned on before the measured value of the first timer exceeds the allowable limit value, the measured value of the first timer is read from the timer unit 27 and stored in the internal memory at the same time (step S5). . At this time, the measurement value of the first timer read from the timer unit 27 is a value indicating the timing at which the paper detection sensor 18 detects the passage of the leading edge of the paper.

  Next, it is confirmed whether or not the paper detection sensor 18 is turned off (detection of passage of the rear end of the paper) (step S6). If the sheet detection sensor 18 is not turned off, it is confirmed whether or not the measured value of the first timer exceeds the allowable limit value (step S7). The permissible limit value applied in this case is a permissible limit value from the start of paper supply from the paper storage tray 1 until the paper detection sensor 18 detects the passage of the rear end of the paper.

  In step S6 and step S7, if the measurement value of the first timer exceeds the allowable limit value before the paper detection sensor 18 is turned off, it is determined that a jam has occurred after the paper reaches the paper detection sensor 18. Then, the process proceeds to step S9. If the paper detection sensor 18 is turned off before the measurement value of the first timer exceeds the allowable limit value, the measurement value of the first timer is read from the timer unit 27 and stored in the internal memory at the same time (step S8). . At this time, the measurement value of the first timer read from the timer unit 27 is a value indicating the timing when the paper detection sensor 18 detects the passage of the trailing edge of the paper.

  In step S9, the timer measurement value (measurement value of the detection timing) stored in the internal memory when the occurrence of the error is detected is written and held in the storage medium 28 as one of the transfer history information. For example, if one or more timer measurement values are stored in the internal memory at the time when the occurrence of an error is detected (when it is determined Yes in step S3 or S6), all the stored timer measurements are stored. The value is held in the storage medium 28 in the form of a table so that it can be seen which paper detection sensor detects the passage of the paper (passing the leading edge and passing the trailing edge). Therefore, for example, when the paper supplied from the paper storage tray 1 is conveyed, the jam detection process using the paper detection sensors 18, 21, and 22 does not detect the occurrence of the jam, and the jam detection using the paper detection sensor 23 is performed. If the occurrence of a jam is detected during the detection process, all the timer measurement values stored in (stored in) the internal memory of the control unit 25 in the jam detection process up to that time (from the paper detection sensor 23 that detected the occurrence of the jam) Also, the measurement value of the detection timing corresponding to the paper detection sensors 18, 21, and 22 arranged on the upstream side in the transport direction) is held in the storage medium 28 as the transport history information.

  Such processing relating to jam detection is similarly executed when jam detection is performed using the other paper detection sensors 19 to 24. At that time, each time one sheet is transported, the value measured by each timer of the timer section 27 is sequentially added and stored in the internal memory of the control unit 25. As a result, when the occurrence of a jam is not detected during conveyance, the measurement values (measurement results) by seven timers are stored in the internal memory for each sheet. When the conveyance of one sheet is completed, the timer measurement value stored in the internal memory during the conveyance of the sheet is deleted at that time (or when the job is completed).

  Further, the allowable limit value applied for jam detection is read from the storage medium 28 for each of the paper detection sensors 19 to 24 and set individually. For example, when jam detection is performed using the paper detection sensor 19, from the start of paper supply from the paper storage tray 2 to when the paper detection sensor 19 detects the passage of the paper (passing the leading edge and passing the trailing edge). Apply acceptable limits. In this case, the value of the second timer corresponding to the paper detection sensor 19 is reset to zero at the timing when the paper supply (paper feeding) is started by the rotation of the calling roll 5.

  When jam detection is performed using the paper detection sensor 20, the paper detection sensor 19 on the upstream side detects the passage of the leading edge of the paper, and then the paper detection sensor 20 passes the paper (passing the leading edge, trailing edge). Apply the limit values allowed before detecting (passing). In this case, the value of the third timer corresponding to the paper detection sensor 20 is reset to zero when the paper detection sensor 19 is turned on.

  When jam detection is performed using the paper detection sensor 21, the paper detection sensor 21 or the paper detection sensor 20 on the upstream side of the paper detection sensor 21 detects the passage of the leading edge of the paper, and then the paper detection sensor 21 passes the paper ( The limit value allowed until the detection of the passage of the leading edge and the trailing edge is applied. In this case, the value of the fourth timer corresponding to the paper detection sensor 21 is simultaneously reset to zero when the paper detection sensor 18 or the paper detection sensor 20 is turned on.

  When jam detection is performed using the paper detection sensor 22, the paper detection sensor 21 on the upstream side detects the passage of the leading edge of the paper, and then the paper detection sensor 22 passes the paper (passing the leading edge, trailing edge). Apply the limit values allowed before detecting (passing). In this case, the value of the fifth timer corresponding to the paper detection sensor 22 is reset to zero when the paper detection sensor 21 is turned on.

  When jam detection is performed using the paper detection sensor 23, the upstream paper detection sensor 22 detects the passage of the leading edge of the paper and the paper detection sensor 23 detects the passage of the leading edge of the paper. The permissible limit value or the rotation of the registration roll 10 is started with the front end of the paper abutting against the registration roll 10 (the registration roll driving clutch is turned on), and then the rear end of the paper is detected by the paper detection sensor 23. Apply the limit value allowed before detecting passage. In this case, the value of the sixth timer corresponding to the paper detection sensor 23 is reset to zero at the timing when the paper detection sensor 22 is turned on and when the registration roller driving clutch is turned on.

  Further, when jam detection is performed using the paper detection sensor 24, as described above, the limit value that is permitted from the start of the rotation of the registration roll 10 until the paper detection sensor 24 detects the passage of the leading edge of the paper, A limit value that is allowed after the paper detection sensor 24 detects the passage of the front end of the paper until the paper detection sensor 24 detects the passage of the rear end of the paper is applied. In this case, the value of the seventh timer corresponding to the paper detection sensor 24 is reset to zero at the timing when the registration roll driving clutch is turned on and when the paper detection sensor 24 is turned on.

  By repeatedly performing the above processing, new conveyance history information is sequentially added and held (stored) in the storage medium 28 whenever a jam occurs. For this reason, for example, when the number of jam occurrences in the image forming apparatus reaches two, two history information # 1 to # 2 are held in the storage medium 28 as shown in FIG.

  Further, when referring to the transfer history information stored in the storage medium 28, a request code for requesting output of the transfer history information is input from the operation panel 26. Then, in response to the request code input from the operation panel 26, the control unit 25 reads the transfer history information in the storage medium 28 and gives an output instruction for the transfer history information to the output unit 29. Thereby, for example, the transport history information as shown in FIG. 5 is output as visible information to a monitor or a sheet by the display function, printing function, or data transmission function provided in the output unit 29.

  Accordingly, the service person in charge of maintenance of the image forming apparatus refers to the conveyance history information output by the output unit 29, and for each jam that actually occurs, the jam from the start of sheet conveyance (start of sheet feeding) to the jam. It is possible to check in detail at what timing each paper detection sensor detects the passage of the paper before the occurrence. Therefore, for example, when the transport history information including the two history information # 1 to # 2 remains in the storage medium 28 as shown in FIG. 5, the cause of the jam occurrence can be narrowed down based on the transport history information. .

  For example, looking at the history information # 1, the occurrence of a jam is detected because the timer measurement value when the paper detection sensor B detects the passage of the leading edge of the paper exceeds the allowable limit value. In this stage, the timer measurement value when the paper detection sensor A detects the passage of the rear end of the paper is much higher than the standard value and is close to the allowable limit value. The timer measurement value when the paper detection sensor A detects the passage of the leading edge of the paper is a value close to the standard value. Accordingly, the history information # 1 indicates that a conveyance delay occurs when the sheet passes the position of the sheet detection sensor A. Therefore, it can be understood that the cause of the paper jam is not in the vicinity of the paper detection sensor B but in a component (roll or the like) in the vicinity of the paper detection sensor A.

  On the other hand, regarding the history information # 2, the occurrence of a jam is detected when the timer measurement value when the paper detection sensor B detects the passage of the rear end of the paper exceeds the allowable limit value. In the previous stage, the timer measurement value when the paper detection sensor B detects the passage of the trailing edge of the paper and the timer measurement value when the paper detection sensor A detects the passage of the leading edge and the trailing edge of the paper, Is close to the standard value. Therefore, the history information # 2 indicates that a conveyance delay occurs when the sheet passes the position of the sheet detection sensor B. Therefore, it can be understood that the cause of the paper jam is not in the vicinity of the paper detection sensor A but in a component (roll or the like) in the vicinity of the paper detection sensor B.

  In the above embodiment, when the measured value by each timer exceeds the allowable limit value (when occurrence of a jam is detected), the timer measured value stored in the internal memory of the control unit 25 until then ( Although the measurement result is held in the storage medium 28, the present invention is not limited to this. For example, instead of the permissible limit value, a jam predictor value smaller than the permissible limit value is applied, and when the measured value of the paper passage detection timing measured by one of the timers exceeds the jam predictor value, the transport history information is displayed. It may be held in the storage medium 28. In addition, for the storage medium 28, a paper detection sensor on the upstream side in the transport direction with respect to the paper detection sensor determined that the measured value of the paper passage detection timing exceeds the jam predictive value in the same manner as the jam detection process. The measurement value of the paper passage detection timing corresponding to the above may be held as the conveyance history information, or only the timer measurement value measured exceeding the jam predictive value may be held as the conveyance history information.

  The jam predictor value is set to a value larger than the standard value and close to an allowable limit value for jam detection (for example, a value about 90% of the allowable limit value). Therefore, when the conveyance history information is held in the storage medium 28 by applying the jam predictor value, if the timer measurement value measured exceeding the jam indication value is held as the conveyance history information, the storage medium 29 All timer measurement values to be written are smaller than the allowable limit value.

  FIG. 6 shows an example of the conveyance history information when the jam predictor value is applied. In the conveyance history information shown in the drawing, when the paper detection sensor 18 detects the passage of the leading edge of the paper, there are five timer measurement values measured exceeding the jam predictive value, and the paper detection sensor 21 detects the passage of the leading edge of the paper. There is one history of timer measurement values measured exceeding the jam predictive value. By referring to this history information, there is a high frequency (the possibility of occurrence of jam) that the timer measurement value corresponding to the paper detection sensor 18 exceeds the jam predictive value before the occurrence of jam is actually detected. You can grasp the fact that is. Therefore, whether or not damage (roll wear, etc.) has occurred on the rolls (calling roll 3, feeding roll 4) and other parts in the vicinity of the paper detection sensor 18 based on the history information during periodic maintenance. By investigating and replacing or repairing parts as necessary, the occurrence of jams can be prevented. Further, as a result of referring to the transfer history information, when it is found that the allowable limit value set for jam detection is inappropriate, by changing the setting of the allowable limit value by an input operation on the operation panel 26, Unnecessary jams can be prevented from occurring. Furthermore, it is possible to appropriately predict the replacement time of parts such as rolls from the transition of the timer measurement value accumulated as the conveyance history information, or to notify the user of the necessity for replacement of parts.

  Further, when holding the transfer history information in the storage medium 28, it is also possible to hold the transfer history information separately for each paper transfer condition. Examples of paper conveyance conditions include paper conveyance speed and paper size. The paper transport speed is controlled to be switched between two stages, for example, high speed and low speed, depending on the thickness and quality of the paper. There is a difference in the timing at which each sheet detection sensor detects the passage of the sheet when the sheet is conveyed at a high speed and when the sheet is conveyed at a low speed. Even when the paper size (particularly, the paper length in the transport direction) changes, there is a difference in the timing at which each paper detection sensor detects the passage of the paper (particularly, the trailing edge passage). For this reason, an allowable limit value and a standard value for jam detection are set according to the paper conveyance speed and the paper size.

  Therefore, the control unit 25 grasps the conveyance conditions such as the sheet conveyance speed and the sheet size in accordance with the input operation of the user using the operation panel 26 when starting the sheet conveyance (sheet feeding). When the occurrence of a jam is actually detected in the jam detection process using the paper detection sensor, the transport history information is held in the storage medium 28 for each transport condition as shown in FIG. As described above, by holding the conveyance history information separately for each conveyance condition, the service person can check the occurrence state of the jam for each conveyance condition and narrow down the cause. In addition, if a jam predictor value is applied instead of the allowable limit value as described above, the presence or absence of a jam occurrence predictor is checked for each transport condition, the setting of the allowable limit value is reviewed, and the time for parts replacement is predicted. You can do it.

  Furthermore, the measured value of the paper passage detection timing measured by each timer of the timer unit 27 while the plurality of preset sheets (for example, three sheets) are conveyed is sequentially stored in the internal memory of the control unit 25. At the same time, the stored data in the internal memory is updated so that the latest measurement value obtained every time one sheet is conveyed (the old measurement value is deleted). When the measured value of the paper passage detection timing measured by the timer exceeds a predetermined value (allowable limit value or jam sign value), the measured value of the detection timing is measured by the timer unit 27 before the predetermined value is exceeded. Alternatively, the measurement value of the detection timing for a predetermined number of times may be read from the internal memory and stored in the storage medium 28 as conveyance history information. Further, the transport history information may be held separately for each transport condition (transport speed, paper size, etc.) as described above.

  FIG. 8 shows an example of the transfer history information. Looking at the illustrated history information, a jam occurs when the paper detection sensor B detects the passage of the leading edge of the paper, and a timer from the start of paper conveyance until the paper detection sensor B is turned on. It can be seen that the measured value is constantly close to the allowable limit value before the jam occurs. Further, in the paper detection sensor A arranged on the upstream side of the paper detection sensor B and the paper detection sensor C arranged on the downstream side, there is no significant delay in the paper passage detection timing (timer measurement value). I understand. For this reason, there is a delay in the conveyance of the paper for some reason between the detection of the leading edge of the paper by the paper detection sensor A and the detection of the leading edge of the paper by the paper detection sensor B. Therefore, the cause of the occurrence of jam can be narrowed down based on this.

  In the above-described embodiment, when the measurement value of each timer of the timer unit 27 exceeds a preset allowable limit value or jam sign value, the transport history information including the timer measurement value is held in the storage medium 28. However, in addition to this, the conveyance history information may be held when the measurement value of each timer of the timer unit 27 exceeds a preset standard value. In this case, the transition of the paper conveyance delay can be confirmed in a long time. Further, the conveyance history information may be held when the occurrence of a failure (for example, a mismatch between the sheet conveyance speed and the paper quality) designated by the user (or service person) using the operation panel 26 is detected.

  In addition, it is desirable that the predetermined values (allowable limit value, jam sign value, standard value) applied in the present invention can be arbitrarily set and changed by the service person using the operation panel 26. Further, regarding the setting change of the predetermined value, for example, the parameter of the setting change is used as a coefficient, and by specifying the value of this coefficient, a predetermined value corresponding to each paper detection sensor or a predetermined value set for each conveyance condition is set. It is desirable that the value can be changed uniformly.

1 is a schematic diagram illustrating a configuration example of an image forming apparatus to which the present invention is applied. FIG. 2 is a block diagram showing a configuration of a control system of the image forming apparatus according to the embodiment of the present invention. It is a figure which shows an example of the data for control concerning jam detection. It is a flowchart which shows the procedure of the process which concerns on jam detection. It is a figure which shows the 1st example of conveyance log information. It is a figure which shows the 2nd example of conveyance log information. It is a figure which shows the 3rd example of conveyance log information. It is a figure which shows the 4th example of conveyance log information.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,2 ... Paper storage tray, 3,5 ... Call roll, 4,6 ... Sending roll, 7,8 ... Conveyance roll, 9 ... Pre-registration roll (conveyance roll), 10 ... Registration roll (conveyance roll), 11 ... Photosensitive drum, 12 ... Vacuum transport unit, 13 ... Transfer roll, 17 ... Fixing device, 18-24 ... Paper detection sensor, 25 ... Control unit, 26 ... Operation panel, 27 ... Timer unit, 28 ... Storage medium, 29 ... Output section

Claims (10)

Conveying means for conveying the paper along the paper conveying path;
A plurality of paper detecting means for detecting the passage of the paper conveyed by the conveying means at different positions in the conveying direction;
Measuring means for measuring a detection timing at which passage of paper is detected for each of the plurality of paper detecting means;
And a holding unit that holds conveyance history information including a measurement value of the detection timing by the measurement unit. The sheet conveying apparatus according to claim 1, wherein the holding unit holds the conveyance history history when a measured value of the detection timing exceeds a predetermined value set in advance. The sheet conveying apparatus according to claim 1, wherein the holding unit holds the conveyance history information separately for each sheet conveyance condition. The sheet conveying apparatus according to claim 1, further comprising an output unit that outputs the conveyance history information. The sheet conveying apparatus according to claim 1, further comprising a changing unit that changes the setting of the predetermined value. The sheet conveying apparatus according to claim 2, wherein the predetermined value is an allowable limit value set for jam detection or a jam predictor value smaller than the allowable limit value. The holding means outputs the measurement value of the detection timing corresponding to the paper detection means arranged on the upstream side in the conveyance direction from the paper detection means determined that the measurement value of the detection timing exceeds the predetermined value. The sheet conveying device according to claim 2, wherein the sheet conveying device is held as information. When the measurement value of the detection timing exceeds the predetermined value, the holding unit measures the detection timing for a predetermined number of times measured by the measurement unit before the measurement value of the detection timing exceeds the predetermined value. The sheet conveying apparatus according to claim 2, wherein a value is held as the conveyance history information. An image forming apparatus comprising the sheet conveying device according to claim 1. A process of detecting the passage of the paper transported along the paper transport path by a plurality of paper detection means provided at different positions in the transport direction;
A process of measuring a detection timing at which passage of paper is detected for each of the plurality of paper detection means;
And a process of holding conveyance history information including a measurement value of the detection timing.

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