Sheet post-processing apparatus and image forming system including the apparatus

A sheet post-processing apparatus, comprising:

• a conveying member which is configured to convey a sheet, the sheet including a plurality of sheets;
• a processing tray on which the plurality of sheets that are carried in along a predetermined carry-in direction by the conveying member are stacked;
• a processing unit which is configured to execute a predetermined post process onto the plurality of sheets that are stacked on the processing tray;
• a reference plate which is configured to align the plurality of sheets in the predetermined carry-in direction by abutting against edges of the plurality of sheets, the plurality of sheets being carried in onto the processing tray, the edges being on a downstream side in an alignment direction that is opposite to the predetermined carry-in direction;
• a pair of width regulating members
• which are configured to reciprocate in a width direction that is orthogonal to the predetermined carry-in direction, and
• which are configured to align the plurality of sheets that are carried in onto the processing tray in the width direction;
• a drive unit which is configured to reciprocate the pair of width regulating members;
• and
• a control portion which is configured to control the drive unit,
• the control portion repetitively performing a width-direction alignment operation every time each of the plurality of sheets is carried in onto the processing tray, the width-direction alignment operation including
• a first alignment operation of moving the pair of width regulating members from standby positions to first regulating positions after each of the plurality of sheets that are carried in onto the processing tray has been aligned in the predetermined carry-in direction by the abutting of the edge of each of the plurality of sheets against the reference plate, and
• a second alignment operation of
• moving the pair of width regulating members from the first regulating positions to the standby positions after performing the first alignment operation, and
• then moving the pair of width regulating members to second regulating positions,
• the sheet post-processing apparatus satisfying the following formula (1)
• C1>C2>P1≥C3 (1)
• where
• P1 is a size in the width direction of each of the plurality of sheets,
• C1 is an interval between the pair of width regulating members at the standby positions,
• C2 is an interval between the pair of width regulating members at the first regulating positions, and
• C3 is an interval between the pair of width regulating members at the second regulating positions.