Sheet conveying device, image processing apparatus, and sheet conveying method capable of preventing next sheet of sheet to be fed from being conveyed beyond sheet feed nip portion

A sheet conveying device comprising:

• a sheet placing portion on which a sheet is placed;
• a lift portion provided so as to be able to move up and down in the sheet placing portion and configured to lift the sheet placed on the sheet placing portion;
• a pickup roller provided above the sheet placing portion and configured to rotate in a first direction capable of conveying an uppermost sheet of one or more sheets lifted by the lift portion in a predetermined conveying direction;
• a conveying member provided so as to be able to come into contact with an upper surface of the sheet downstream of the pickup roller in the conveying direction and configured to rotate in a second direction capable of conveying the sheet conveyed by the pickup roller in the conveying direction;
• a separation roller forming, together with the conveying member, a sheet feed nip portion therebetween and configured to rotate in a fourth direction opposite to a third direction capable of conveying the sheet conveyed by the pickup roller in the conveying direction;
• a sheet feed processing portion configured to execute sheet feed processing for rotating the pickup roller, the conveying member, and the separation roller in the first direction, the second direction, and the fourth direction, respectively;
• a first determination processing portion configured to determine whether or not a leading edge in the conveying direction of the sheet conveyed by the sheet feed processing has passed through the sheet feed nip portion;
• and
• a lowering processing portion configured to lower the lift portion after the first determination processing portion determines that the leading edge in the conveying direction of the sheet has passed through the sheet feed nip portion and before the sheet feed processing is completed.