Patent ID: 8892023

Claim:
An image forming apparatus comprising: an image-forming portion that forms an image on a sheet; a detecting unit that detects an amount and direction of deflection of the sheet from a previously set reference position along a sheet width direction which is perpendicular to a transporting direction of the sheet, the detecting unit being positioned at an upstream side of the image-forming portion; a registration roller that is biased to one side of the sheet width direction by a predetermined urging force of a spring and that shifts along the sheet width direction, the registration roller being positioned at an upstream side of the detection unit; and a control unit that is configured to determine, based on the amount and direction of deflection of the sheet detected by the detecting unit, a first required shift amount of the sheet in a first direction or a second required shift amount of the sheet in a second direction and to control the registration roller to perform first or second registration roller shift corrections, to shift the sheet along the sheet width direction to the reference position based on the first or second required shift amounts of the sheet and to send the shifted sheet to the image-forming portion, wherein the control unit is also configured to determine a first specific shift value for the first registration roller shift correction based on the first required shift amount of the sheet when shifting the sheet in the first direction along the sheet width direction, the first specific shift value including a first amount of correction for correcting an influence by the urging force of the spring by which the registration roller is biased, or to determine a second specific shift value for the second registration roller shift correction, which is different from the first registration roller shift correction, based on the second required shift amount of the sheet when shifting the sheet in the second direction along the sheet width direction, the second specific shift value including a second amount of correction for correcting an influence by the urging force of the spring by which the registration roller is biased, wherein the first specific shift value is determined using a first correction equation which uses the first required shift amount of the sheet based on the amount of deflection and a first correction coefficient based on the urging force of the spring when shifting the sheet to the first direction in the sheet width direction, or the second specific shift value is determined using a second correction equation which uses the second required shift amount of the sheet based on the amount of deflection and a second correction coefficient constant based on the urging force of the spring when shifting the sheet to the second direction in the sheet width direction.