Sheet stacking apparatus and image forming apparatus

The sheet stacking apparatus further comprising:

• a first detection sensor disposed at the sheet stacking portion configured to generate a signal based on presence or absence of a sheet stacked on the sheet stacking portion;
• and
• a second detection sensor disposed at the cover portion configured to generate a signal based on a position of a sheet stacking surface of the sheet stacking portion or a position of an uppermost surface of a sheet stacked on the sheet stacking portion,
• wherein the controller controls the driving portion according to detection signals from the first detection sensor and the second detection sensor.

An image forming apparatus comprising:

• an image forming device for forming an image on a sheet;
• and
• a sheet stacking apparatus for stacking the sheet on which the image is formed,
• the sheet stacking apparatus including:
• a sheet stacking portion on which the sheet discharged from a sheet discharge port is stacking;
• a cover portion disposed above the sheet stacking portion and having a facing surface facing a sheet stacking surface of the sheet stacking portion;
• a driving portion configured to lift and lower the sheet stacking portion;
• and
• a controller for controlling the driving portion,
• wherein the controller controls the driving portion such that, when a sheet is not stacked on the sheet stacking portion, a distance between the facing surface of the cover portion and the sheet stacking surface of the sheet stacking portion is kept within a predetermined range, and when a sheet is stacked on the sheet stacking portion, a distance between the facing surface of the cover portion and an uppermost surface of the sheet stacked on the sheet stacking portion is kept within the predetermined range.