Sheet conveying apparatus and image forming apparatus

Abstract

A sheet conveying apparatus includes a sheet conveying unit including a drive roller and a driven roller; a downstream detection unit and an upstream detection unit; a conveying amount measuring unit that measures a conveying amount of the sheet; and a conveying distance calculation unit that calculates a conveying distance of the sheet, wherein a distance between the downstream detection unit and the upstream detection unit or a perimeter of one of the drive roller and the driven roller is set such that an expected conveying distance calculated based on a set sheet length of an expected value of the sheet becomes a substantially integer multiple of a perimeter of the one of the drive roller and the driven roller.

1 . A sheet conveying apparatus comprising:
 a sheet conveying unit that conveys a sheet including
 a drive roller which is driven to be rotated by a driving unit, and 
 a driven roller which is rotated in accordance with the drive roller while the sheet is interposed between the drive roller and the driven roller; 
   a downstream detection unit that detects the sheet downstream of the sheet conveying unit in a conveying direction of the sheet;   an upstream detection unit that detects the sheet upstream of the sheet conveying unit in the conveying direction of the sheet;   a conveying amount measuring unit that measures a conveying amount of the sheet conveyed by the sheet conveying unit; and   a conveying distance calculation unit that calculates a conveying distance of the sheet conveyed by the sheet conveying unit based on the conveying amount measured by the conveying amount measuring unit within a period determined by detections made by the first detection unit and the second detection unit,   wherein an expected value of the conveying distance calculated based on a set sheet length of an expected sheet for which the conveying distance is to be calculated becomes a substantially integer multiple of a perimeter of one of the drive roller and the driven roller.   
     
     
         2 . The sheet conveying apparatus according to  claim 1 , further comprising a sensor provided upstream or downstream of the sheet conveying unit to function as the upstream detection unit or the downstream detection unit, respectively. 
     
     
         3 . The sheet conveying apparatus according to  claim 2 ,
 wherein the conveying distance calculation unit selects a combination of the upstream detection unit and the downstream detection unit such that the expected conveying distance calculated based on the set sheet length of the expected sheet and the distance between the selected downstream detection unit and the upstream detection unit becomes a substantially integer multiple of a perimeter of the one of the drive roller and the driven roller.   
     
     
         4 . The sheet conveying apparatus according to  claim 1 , further comprising a sensor position adjusting unit that adjusts the position of at least one of the upstream detection unit and the downstream detection unit in the conveying direction of the sheet. 
     
     
         5 . The sheet conveying apparatus according to  claim 4 ,
 wherein the sensor position adjusting unit adjusts the position of the at least one of the upstream detection unit and the downstream detection unit in the conveying direction of the sheet such that the expected conveying distance calculated based on the set sheet length of the expected sheet and the distance between the selected downstream detection unit and the upstream detection unit becomes a substantially integer multiple of a perimeter of one of the drive roller and the driven roller.   
     
     
         6 . The sheet conveying apparatus according to  claim 1 ,
 wherein the conveying distance calculation unit calculates a length of the sheet in the conveying direction of the sheet by adding a distance between the first detection unit and the second detection unit to the calculated conveying distance of the sheet.   
     
     
         7 . The sheet conveying apparatus according to  claim 1 ,
 wherein a conveying amount measuring unit measures the conveying amount of the sheet conveyed by the sheet conveying unit based on a rotation amount of one of the drive roller and the driven roller.   
     
     
         8 . The sheet conveying apparatus according to  claim 7 ,
 wherein a distance between the downstream detection unit and the upstream detection unit or a perimeter of the one of the drive roller and the driven roller is set such that an expected conveying distance calculated based on a set sheet length of an expected sheet for which the conveying distance is to be calculated becomes a substantially integer multiple of a perimeter of one of the drive roller and the driven roller.   
     
     
         9 . An image forming apparatus comprising:
 a transfer unit that transfers a toner image onto a sheet; and   the sheet conveying apparatus according to  claim 1 .