Sheet stacking device

A sheet stacking device comprising:

• a sheet discharge platform where sheets, which have been subjected to heating and drying processing after images are formed using ink liquid, are conveyed and stacked;
• a blowing mechanism that includes a nozzle having an opening, a whole surface of the opening being positioned so as to face a portion on a side surface of a sheet bundle stacked on the sheet discharge platform below an upper portion of the sheet bundle by a distance corresponding to a predetermined number of sheets, and the nozzle blowing air to the side surface of the sheet bundle via the opening;
• a height adjustment mechanism that changes the position of the sheet discharge platform relative to the nozzle in a vertical direction according to a height of the sheet bundle;
• a height detecting device that detects the height of the sheet bundle stacked on the sheet discharge platform;
• a control device that controls the height adjustment mechanism according to the height of the sheet bundle detected by the height detecting device;
• and
• a sheet alignment mechanism that aligns the sheet by coming into contact with the side surface of the sheet bundle below the portion to which air is blown from the nozzle;
• wherein
• the sheet alignment mechanism includes a sheet alignment member that includes an air passage portion allowing air to pass therethrough and aligns the sheet of the sheet bundle by coming into contact with a side surface of the sheet bundle crossing the side surface of the sheet bundle to which air is blown, and an area changing device that changes an air passage area of the air passage portion.