Patent ID: 7624976

Claim:
A post-processing apparatus comprising: a compile tray that contains a recording sheet, and has a sheet end position determination portion which contacts with and determines a position of an end edge of the contained recording sheet; a first sheet end alignment member that carries the recording sheet received in the compile tray to the sheet end position determination portion and aligns the end edge of the recording sheet; a second sheet end alignment member that moves between the sheet carrying position and a standby position, wherein the sheet carrying position is where the second sheet end alignment member contacts with the recording sheet to carry the recording sheet to a side of the first sheet end alignment member, and the standby position is separated from the recording sheet; a second sheet end alignment member control unit that moves the second sheet end alignment member between the sheet carrying position and the standby position, and changes a carrying position sustaining time to sustain the second end alignment member at the sheet carrying position according to a sheet number of the recording sheets contained in the compile tray; a contained sheet number counting unit that counts a sheet number of the recording sheets contained in the compile tray; a sheet number storage unit that stores the sheet number for changing the carrying position sustaining time; and a carrying position sustaining time setting unit that sets the carrying position sustaining time to a predetermined sustaining time for small sheet number when a contained sheet number of the compile tray is smaller than the sheet number that changes the carrying position sustaining time, and sets the carrying position sustaining time to a predetermined sustaining time for large sheet number when a contained sheet number of the compile tray is equal to or larger than the sheet number for changing the carrying position sustaining time, wherein the second sheet end alignment member control unit sustains the second sheet end alignment member at the sheet carrying position until the end edge of the received recording sheet contacts with the sheet end position determination portion when the contained sheet number of the compile tray is smaller than the sheet number for changing the carrying position sustaining time, and sustains the second sheet end alignment member at the sheet carrying position until the end edge of the received recording sheet is carried to the first sheet end alignment member when the contained sheet number of the compile tray is larger than the sheet number for changing the carrying position sustaining time, and wherein the predetermined sustaining time for small sheet number is longer than the predetermined sustaining time for large sheet number, thereby preventing buckling of the end edge of the received recording sheet.