Post-processing apparatus and image forming system

A post-processing apparatus comprising:

• a conveyance portion conveying a sheet;
• a processing tray on which the sheet having passed through the conveyance portion can be stacked;
• a post-processing portion that performs post-processing on the sheet on the processing tray;
• a discharge tray to which the sheet is discharged;
• a discharge portion disposed downstream of the conveyance portion in a sheet conveyance direction, the discharge portion discharging the sheet to the discharge tray;
• and
• a control portion controlling the discharge portion,
• wherein
• the discharge portion includes:
• an arm pivotable such that, about a one end part thereof, another end part thereof being movable up and down;
• a driving roller that is supported on the other end part of the arm so as to be rotatable, the driving roller making contact with the sheet from above and rotating forward so as to discharge the sheet to the discharge tray;
• and
• a driven roller disposed below the driving roller across a sheet conveyance passage, the driven roller nipping the sheet with the driving roller as the driving roller moves downward,
• when stacking the sheet on the processing tray, the control portion moves the driving roller downward to bring, from above, the driving roller into contact with the sheet having passed through the conveyance portion and rotates the driving roller backward so as to retract the sheet from a trailing edge thereof onto the processing tray,
• except when the sheet as a target of the post-processing is retracted onto the processing tray, the control portion sets a downward movement speed of the driving roller to a predetermined normal speed, and
• when the sheet as the target of the post-processing is retracted onto the processing tray, the control portion sets the downward movement speed of the driving roller to a speed lower than the normal speed.