Sheet processing apparatus

An image forming system comprising:

• an image forming portion configured to form an image on a sheet;
• a first conveyance portion configured to convey a sheet on which the image has been formed by the image forming portion in a first conveyance direction;
• a placement portion on which the sheet conveyed by the first conveyance portion is placed;
• an abutment portion against which an upstream edge in the first conveyance direction of the sheet on the placement portion abuts;
• a second conveyance portion configured to convey the sheet in a second conveyance direction in which the upstream edge in the first conveyance direction of the sheet on the placement portion moves toward the abutment portion;
• a shifting portion configured to move in a shift direction in a state of abutting one edge following the first conveyance direction of the sheet conveyed in the first conveyance direction by the first conveyance portion, and thus to move, in the shift direction, the sheet conveyed by the first conveyance portion;
• a driving portion configured to drive the shifting portion to move the shifting portion in the shift direction;
• a stapler configured to perform a binding process on a plurality of sheets that are positioned at a binding position by being conveyed in the second conveyance direction by the second conveyance portion to cause the downstream edge thereof in the second conveyance direction to abut the abutment portion and then being moved in the shift direction by the shifting portion;
• a stacking portion disposed downstream of the placement portion in the first conveyance direction and configured to stack the sheet conveyed in the first conveyance direction by the first conveyance portion;
• a pair of discharge rollers including an upper discharge roller and a lower discharge roller, and being configured to discharge, onto the stacking portion, the sheet conveyed by the first conveyance portion;
• an upper discharge roller moving member configured to move the upper discharge roller to a nipping position, a first separated position, and a second separated position, the nipping position being a position where the sheet is nipped by the upper discharge roller and the lower discharge roller, the first separated position being a position where the upper discharge roller and the lower discharge roller are separated from each other, and the second separated position being a position where the upper discharge roller is located, in a vertical direction, between the position where the upper discharge roller is at the nipping position and the position where the upper discharge roller is at the first separated position;
• a sensor configured to detect the sheet;
• and
• a control portion configured to control the first conveyance portion, the second conveyance portion, the driving portion, the pair of discharge rollers and the upper discharge roller moving member based on a signal of the sensor,
• wherein the control portion is capable of executing:
• (1) a binding discharge process in which (a) the binding process is performed on the plurality of sheets by the stapler and (b) the plurality of sheets subjected to the binding process are discharged onto the stacking position by the pair of discharge rollers, the plurality of sheets being positioned at the binding position by repeating a process in which, after the sheet is conveyed in the first conveyance direction by the first conveyance portion, the sheet is conveyed in the second conveyance direction on the placement portion by the second conveyance portion to cause a downstream edge of the sheet in the second conveyance direction to abut the abutment portion, and the sheet caused to abut the abutment portion is moved in the shift direction and positioned at the binding position by the shifting portion by driving the shifting portion by the driving portion;
• and
• (2) a switchbackless shift discharge process in which (a) the first conveyance portion conveys the sheet in the first conveyance direction until a downstream end of the sheet in the first conveyance direction has passed between the upper discharge roller and the lower discharge roller in a state in which the upper discharge roller is at the first separated position, (b) the upper discharge roller moving member moves the upper discharge roller from the first separated position toward the second separated position to cause the sheet to press down, (c) the shifting portion moves the sheet in the shift direction by driving the driving portion without conveying the sheet in the second conveyance direction by the second conveyance portion while the upper discharge roller is at the second separated position, and (d) after the upper discharge roller moves to the nipping position, the pair of discharge rollers discharges the sheet onto the stacking portion.