Patent ID: 8764003

Claim:
A control method of a feeder including: a feeding portion which stores a sheet of paper containing an envelope with a predetermined size and feeds the stored sheet of paper, the envelope containing an opened portion and a closed portion; and a pair of registration rollers containing an upper roller and a lower roller, each roller having a longitudinal length longer than a width of the fed sheet of paper, the registration rollers correcting a posture of the sheet of paper fed from the feeding portion to convey the sheet of paper toward a downstream side along a sheet-conveying direction, wherein, when conveying the envelope, the posture of the envelope is corrected by hitting the closed portion of the envelope, which is opposite side of the opened portion of the envelope, against a nip portion between the upper and lower rollers of the registration rollers and the envelope is then conveyed with the envelope being nipped by the upper and lower rollers of the registration rollers, the method comprising: a setting step of setting an envelope mode to control a conveying speed of the envelope based on a coverage rate of an image to be formed on the envelope; and a control step of controlling the conveying speed of the envelope by adjusting a rotation speed of the registration rollers based on the coverage rate of the envelope mode set in the setting step.