Image forming apparatus equipped with register rollers for curling

Abstract

An image forming apparatus of the present invention includes a photoreceptor drum on which a toner image is formed, a transfer drum for transferring the toner image formed to transfer paper by bringing the transfer paper into contact with the photoreceptor drum, and a pair of register rollers for supplying the transfer paper to the transfer drum at a predetermined time and for curling the transfer paper in an arc. The register rollers include first and second rollers pressed against each other, the first roller being a predetermined hardness and the second roller being a hardness larger than the first roller. The transfer drum is disposed on the same side as the second roller with respect to an imaginary tangent line touching the surface of the second roller at one end of a contact section between the first and second rollers. The image forming apparatus also includes transporting means for supplying the transfer paper to the register rollers so that a front edge of the transfer paper comes into contact with the second roller, temporarily stops, and then continues to the transfer drum. The image forming apparatus also includes a means for changing the pressure that the register rollers are pressed together. Paper type, quality, thickness, and size are detected and the pressure is adjusted accordingly. The means for changing pressure includes a resilient member for the pressing the second roller against the first, and a changing member for changing the amount of deformation of the resilient member.