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

Abstract

A sheet post-processing apparatus includes a first conveying member, a processing tray, a first processing unit, a reference plate, an alignment member, a home-position detection unit, a drive unit, and a control portion. The alignment member has a shaft joined to a drive unit to rotate, and one or more alignment paddles protruding in a radial direction of the shaft. The control portion calculates a contact assumed interval in which the trailing end of the sheets may make contact with the alignment paddle and an interference timing at which the alignment paddle interferes with a carry-in path of the sheets. If the interference timing falls within the contact assumed interval, the control portion temporarily changes the rotation speed of the alignment member from a reference speed to shift the phase of the alignment paddle so that the interfere timing falls outside the contact assumed interval.