Patent ID: 8870175

Claim:
A sheet stacking apparatus, comprising: a sheet stacking portion on which a plurality of sheets is sequentially stacked; a binding portion configured to perform a binding process on one edge portion in a sheet conveying direction of sheets stacked on the sheet stacking portion; a discharge stacking portion onto which the sheets or a sheet bundle, formed from a plurality of sheets and subjected to the binding process in the binding portion, is discharged, the discharge stacking portion being capable of being raised and lowered; a detecting portion configured to detect, on the one edge portion side, a stacking height of an upper surface of the sheets or the sheet bundle stacked on the discharge stacking portion; a raising/lowering portion configured to raise and lower the discharge stacking portion; a pressing portion which is movable, the pressing portion configured to press, from above, the sheets or the sheet bundle stacked on the discharge stacking portion; a moving portion configured to lower the pressing portion so as to press, from above, the sheets or the sheet bundle; and a control portion configured to control the raising/lowering portion so as to lower the discharge stacking portion in response to a signal from the detecting portion when the stacking height of the upper surface of the sheets or the sheet bundle increases, and the control portion is configured to control, when the sheet bundle is discharged onto the discharge stacking portion, the moving portion so that the pressing portion presses the sheet bundle with a pressing force greater than a pressing force in a case where the sheets are discharged onto the discharge stacking portion.