Sheet conveying apparatus and image forming apparatus

Abstract

A sheet conveying apparatus including: a skew feed amount detecting portion for detecting a skew feed amount of a sheet; a pair of skew feed correcting portions for correcting the skew feed by conveying the sheet by their independent rotations; a conveying amount detecting portion for detecting the sheet conveying amounts by the correcting portions; and a controller for controlling rotations of the correcting portions based on detection results obtained by the skew feed amount detecting portion and the conveying amount detecting portion, wherein, after a skew feed correcting operation-is started, the controller detects a sheet correction amount by the correcting portions based on a detection result obtained by the conveying amount detecting portion, and controls the rotations of the correcting portions so that the sheet correction amount equals to the skew feed amount of the sheet detected by the skew feed amount detecting portion.

1 . A sheet conveying apparatus, comprising: 
 a skew feed amount detecting portion configured to detect a skew feed amount of a sheet;    a pair of skew feed correcting portions arranged in a direction perpendicular to a sheet conveying direction, configured to correct a skew feed of the sheet by conveying the sheet through independent rotations of said pair of skew feed correcting portions;    a conveying amount detecting portion configured to detect respective sheet conveying amounts of said pair of skew feed correcting portions; and    a control portion configured to control rotations of said pair of skew feed correcting portions according to detection results obtained by said skew feed amount detecting portion and said conveying amount detecting portion,    wherein, after a skew feed correcting operation by said pair of skew feed correcting portions is started, said control portion calculates a sheet correction amount by said pair of skew feed correcting portions based on a detection result obtained by said conveying amount detecting portion, and controls the rotations of said pair of skew feed correcting portions so that the sheet correction amount becomes equal to the skew feed amount of the sheet detected by said skew feed amount detecting portion.    
     
     
         2 . A sheet conveying apparatus according to  claim 1 , 
 wherein said pair of skew feed correcting portions effect a skew feed correction by a difference between sheet conveying speeds, and    wherein said control portion controls the sheet conveying speeds of said pair of skew feed correcting portions so that a difference between the sheet conveying amounts of said pair of skew feed correcting portions when the skew feed correction is performed becomes equal to a difference between sheet conveying amounts of said pair of skew feed correcting portions set based on the skew feed amount of the sheet detected by said skew feed amount detecting portion.    
     
     
         3 . A sheet conveying apparatus according to  claim 2 , wherein, when correcting the skew feed of -the sheet, said control portion controls the sheet conveying speeds of said pair of skew feed correcting portions so as to change the difference between the sheet conveying speeds of said pair of skew feed correcting portions according to the skew feed amount of the sheet.  
     
     
         4 . A sheet conveying apparatus according to  claim 1 , 
 wherein said pair of skew feed correcting portions effect a skew feed correction by a difference between sheet conveying speeds, and    wherein said control portion controls the sheet conveying speeds of said pair of skew feed correcting portions so that the sheet correction amount based on a difference between the sheet conveying amounts of said pair of skew feed correcting portions when the skew feed correction of the sheet is effected becomes equal to the skew feed amount of the sheet detected by said skew feed amount detecting portion.    
     
     
         5 . A sheet conveying apparatus according -to  claim 1 , 
 wherein said conveying amount detecting portion is provided with rotary members respectively provided in said pair of skew feed correcting portions so as to be opposed to each other, and a rotation amount detecting portion for detecting rotation amounts of said rotary members,    wherein said rotation amount detecting portion detects the rotation amounts when the rotary members rotate in association with a movement of the sheet conveyed by said pair of skew feed correcting portions, and    wherein said control portion detects the sheet conveying amount based on detection results obtained by said rotation amount detecting portions.    
     
     
         6 . A sheet conveying apparatus according to  claim 5 , 
 wherein said rotary members are arranged along a curved path and on an inner side of the curved path for guiding the sheet, and    wherein said pair of skew feed correcting portions are arranged along the curved path and on outer peripheral surfaces of said rotary members, the sheet being conveyed while undergoing a skew feed correction by said pair of skew feed correcting portions and said rotary members.    
     
     
         7 . A sheet conveying apparatus according to  claim 6 , wherein said pair of skew feed correcting portions are provided with driving rollers and driven rollers arranged along the outer peripheral surfaces of said rotary members, and conveyor belts stretched around said driving rollers and said driven rollers, and conveys the sheet while effecting the skew feed correction on the sheet between said conveyor belts and said rotary members.  
     
     
         8 . A sheet conveying apparatus according to  claim 1 , wherein said conveying amount detecting portion is provided with a sensor for detecting a speed fluctuation of the sheet in a non-contact fashion, and detects the sheet conveyed by said pair of skew feed correcting portions by said sensor in a non-contact fashion to detect the sheet conveying amount.  
     
     
         9 . A sheet conveying apparatus according to  claim 8 , wherein said sensor also serves as a skew feed amount detecting means for detecting a leading edge of the sheet conveyed to said sensor.  
     
     
         10 . An image forming apparatus which has an image forming portion to form an image to the sheet conveyed by a sheet conveying apparatus, comprising: 
 a skew feed amount detecting portion configured to detect a skew feed amount of a sheet;    a pair of skew feed correcting portions arranged in a direction perpendicular to a sheet conveying direction, configured to correct a skew feed of the sheet by conveying the sheet through independent rotations of said pair of skew feed correcting portions;    a conveying amount detecting portion configured to detect respective sheet conveying amounts of said pair of skew feed correcting portions; and    a control portion configured to control rotations of said pair of skew feed correcting portions according to detection results obtained by said skew feed amount detecting portion and said conveying amount detecting portion,    wherein, after a skew feed correcting operation by said pair of skew feed correcting portions is started, said control portion detects a sheet correction amount by said pair of skew feed correcting portions based on a detection result obtained by said conveying amount detecting portion, and controls the rotations of said pair of skew feed correcting portions so that the sheet correction amount becomes equal to the skew feed amount of the sheet detected by said skew feed amount detecting portion.