Image forming apparatus and sheet processing apparatus

An image forming apparatus comprising:

• an image forming unit configured to form an image on a sheet;
• a discharge rotary member pair configured to discharge the sheet on which the image has been formed by the image forming unit;
• a sheet supporting unit configured to support the sheet discharged through the discharge rotary member pair, the sheet supporting unit comprising a first support surface, and a second support surface provided downstream, in a sheet discharge direction, of the first support surface, and having a smaller inclination angle than the first support surface with respect to a horizontal plane;
• an abutment surface configured to abut against an upstream end, in the sheet discharge direction, of the sheet supported on the sheet supporting unit;
• an elevation unit configured to move the sheet supporting unit up and down;
• and
• a control unit, in a state where no sheet is supported on the sheet supporting unit, configured to execute
• (1) a first discharge mode of controlling the elevation unit such that the sheet supporting unit is positioned at a first position where a first intersection between a first extension line of the second support surface and a plane including the abutment surface is positioned higher than a nip of the discharge rotary member pair before the discharge rotary member pair starts discharging the sheet, and
• (2) a second discharge mode of controlling the elevation unit such that the sheet supporting unit is positioned at a second position lower than the first position and where a second intersection between a second extension line of the second support surface and the plane including the abutment surface is positioned lower than the nip of the discharge rotary member pair before the discharge rotary member pair starts discharging the sheet,
• wherein the control unit executes the first discharge mode in a case where a type of sheet to be discharged by the discharge rotary member pair is a first type, and executes the second discharge mode in a case where a type of sheet to be discharged by the discharge rotary member pair is a second type, and
• the sheet of the second type has a higher stiffness than that of the sheet of the first type.