Sheet conveying apparatus and image forming apparatus

Abstract

A sheet conveying apparatus includes a detecting unit configured to detect a sheet; a conveying unit including a driving roller and a driven roller that rotates in conformity with the driving roller and configured to convey the sheet by holding the sheet between the driving roller and the driven roller; a disk configured to rotate in correspondence with the driven roller and including multiple slits arranged in a periphery thereof; first and second sensors configured to detect the multiple slits and output detection signals, the first and second sensors being provided substantially opposite to each other where a rotational axle of the disk is positioned at a center between the first and second sensors; and a conveyance distance calculating unit configured to calculate a sheet conveying distance based on a detection result of the detecting unit and the detection signals.

What is claimed is: 
     
         1 . A sheet conveying apparatus comprising:
 a detecting unit configured to detect a sheet;   a conveying unit including a driving roller and a driven roller that rotates in conformity with the driving roller and configured to convey the sheet by holding the sheet between the driving roller and the driven roller;   a disk configured to rotate in correspondence with the driven roller and including a plurality of slits arranged in a periphery thereof;   first and second sensors configured to detect the plurality of slits and output detection signals, the first and second sensors being provided substantially opposite to each other where a rotational axle of the disk is positioned at a center between the first and second sensors; and   a conveyance distance calculating unit configured to calculate a sheet conveying distance based on a detection result of the detecting unit and the detection signals.   
     
     
         2 . The sheet conveying apparatus as claimed in  claim 1 , wherein the plurality of slits are arranged to cause a phase of the detections signals output from the first sensor to be different from a phase of the detection signals output from the second sensor. 
     
     
         3 . The sheet conveying apparatus as claimed in  claim 1 , wherein the detecting unit includes
 an upstream detecting unit provided on an upstream side of the conveying unit with respect to a sheet conveying direction for detecting the sheet, and   a downstream detecting unit provided on an downstream side of the conveying unit with respect to the sheet conveying direction for detecting the sheet.   
     
     
         4 . The sheet conveying apparatus as claimed in  claim 3 , wherein the conveyance distance calculating unit is configured to calculate the sheet conveying distance based on the detection signals during a period between detection of the sheet by the downstream detecting unit and detection of the sheet by the upstream detecting unit. 
     
     
         5 . The sheet conveying apparatus as claimed in  claim 4 , wherein the conveyance distance calculating unit is further configured to calculate a length of the sheet in the sheet conveying direction by adding the sheet conveying distance to a distance between the upstream detecting unit and the downstream detecting unit. 
     
     
         6 . An image forming apparatus comprising:
 the sheet conveying apparatus as claimed in  claim 1 .   
     
     
         7 . The image forming apparatus as claimed in  claim 6 , further comprising:
 a transfer unit configured to transfer an image to the sheet;   wherein the sheet conveying apparatus is provided directly above the transfer unit.   
     
     
         8 . The image forming apparatus as claimed in  claim 6 , further comprising:
 an image forming unit configured to form the image to be transferred based on image data; and   a correcting unit configured to correct the image data based on the sheet conveying distance calculated by the conveyance distance calculating unit.