Sheet feeding apparatus and image forming apparatus with curvature formation portion and reversely rotatable feeding roller

An image forming apparatus comprising:

• a sheet support portion configured to support a plurality of sheets;
• a forwardly or reversely rotatable feeding roller configured to send an uppermost sheet from among the sheets supported by the sheet support portion;
• a separation claw having pressing portions configured to press both ends of the sheet supported by the sheet support portion in the width direction thereof and orthogonal to a direction in which the sheet is fed, and configured to separate the uppermost sheet in response to a forward or reverse rotating of the feeding roller;
• a curvature formation portion configured to form a curvature so both ends, in the width direction of the sheet supported by the sheet support portion, become lower than a center portion thereof;
• a control unit configured to control the feeding roller and the curvature formation portion to rotate the feeding roller in a direction opposite to the direction in which the sheet is fed to remove the uppermost sheet from the separation claw, move the separation claw so that the pressing portions lie at a position separated from and lower than the uppermost sheet, and rotate the feeding roller in the direction in which the sheet is fed;
• and
• an image forming unit configured to form an image on the sheet fed by the feeding roller.

A sheet feeding method comprising:

• reversely feeding an uppermost sheet from among a plurality of sheets supported by a sheet support portion by a feeding roller rotating in a direction opposite to a direction in which the sheet is fed;
• drawing out the leading end of the uppermost sheet from pressing portions provided on a separation claw and configured to press both ends of the sheet supported by a sheet support portion in the width direction thereof orthogonal to the direction in which the sheet is fed, and curving the sheet in the direction in which the sheet is fed;
• forming curvature by a curvature formation portion so that both ends in the width direction of the sheet supported by the sheet support portion become lower than a center portion;
• moving the pressing portions to a position separated from the uppermost sheet along with the curvature of the sheet;
• and
• sending out the uppermost sheet along the upper surface of the separation claw by rotating the feeding roller in the direction in which the sheet is fed.