Patent ID: 8746675

Claim:
A sheet feeder that attracts an uppermost sheet of a sheet stack of a plurality of stacked sheets and feeds the uppermost sheet in a sheet feeding direction, the sheet feeder comprising: an endless belt made of a dielectric material, entrained around an upstream roller and a downstream roller and disposed above the sheet stack to face the sheet stack on a sheet-facing side thereof; a charging device configured to apply an alternating voltage to an outer circumferential surface of the endless belt to form thereon an alternating charge pattern; a belt tension adjuster to adjust tension on the endless belt; and a control device configured to control the belt tension adjuster to change a state of the endless belt from a first state, in which the endless belt is slack on the sheet-facing side thereof, to a second state, in which the endless belt is taut on the sheet-facing side thereof, as the endless belt attracts and conveys the uppermost sheet from the sheet stack, wherein the belt tension adjuster includes: an upstream drive source configured to drive the upstream roller; and a downstream drive source configured to drive the downstream roller, wherein the control device controls the timing of driving of the upstream drive source and the downstream drive source separately when the endless belt attracts and conveys the uppermost sheet from the sheet stack.