Image forming apparatus having curling device for holding transfer material and method of curling sheet

摘要

A developing device which develops an electrostatic latent image formed on an image carrier by toner, thereby forming a toner image; a transferring device which transfers the toner image to a fed transfer material; a registration device which provides a timing of feeding the transfer material; a curling device which nips the transfer material so as to produce a curl which is curved in the same direction as the transferring device; a curling control device which controls a nip operation mechanism of the curling device; and mode setting means for instructing the curling control device to operate are disclosed. In accordance with a thick sheet mode set in the mode setting means, the nip operation of the curling device is executed and a dummy transfer period in which the transfer operation of the transferring device is stopped is set.