Patent ID: 8447202
Filing Date: 2013-05-21
Classification: G03G

Abstract:
1. An image forming apparatus, comprising: a plurality of image carriers, on which an electrostatic latent image is formed; a plurality of exposure units forming the electrostatic latent image on corresponding image carriers respectively; a plurality of developers for developing the electrostatic latent image on corresponding image carriers respectively; an intermediate transfer belt, on which a toner image is primarily transferred from the plurality of image carriers; a plurality of primary transfer units transferring the toner image on corresponding image carriers to the intermediate transfer belt in a primary transfer position respectively; a secondary transfer unit for transferring the toner image on the intermediate transfer belt to a printing material in a secondary transfer portion; a registration roller that restricts a position of the printing material, and conveys the printing material to the secondary transfer portion at a predetermined timing; a printing material detection unit being arranged at a position upstream from a position of the registration roller in a conveying direction of the printing material, and detecting a leading edge and a trailing edge of the printing material in order to determine a printing material length in the conveying direction, a printing material position in an orthogonal direction to the conveying direction, and a printing material length in the orthogonal direction; and a matching unit for controlling the plurality of exposure units; wherein, the image forming apparatus is capable of forming two types of images including an image with margins and an image without margins, when the image is formed with margins, the printing material detection unit bypasses detection of the printing material length in the conveying direction, the printing material position in the orthogonal direction, and the printing material length in the orthogonal direction, and when the image is formed without margins, the registration roller stops the conveying of the printing material after the printing material detection unit detects the printing material length in the conveying direction, the printing material position in the orthogonal direction, and the printing material length in the orthogonal direction, then the plurality of exposure units respectively start an exposure for a corresponding image carrier in accordance with a control of the matching unit after detecting by the printing material detection unit, and then the plurality of exposure units respectively form the electrostatic latent image having a size matching the printing material length and the printing material position detected by the printing material detection unit, and wherein the image forming apparatus does not form toner images that are larger than the printing material, thereby reducing an amount of spent toner and suppressing generation of waste toner.