Patent ID: 7593655
Filing Date: 2009-09-22
Classification: G03G

Abstract:
1. An image forming apparatus, comprising: an image bearing member; an intermediate transfer member; a transfer unit which transfers toner images formed on the image bearing member to the intermediate transfer member at a primary transfer bias, and then transfers the toner images on the intermediate transfer member to a substrate at a secondary transfer bias; a control unit which forms a plurality of toner patches on the image bearing member, which are categorized into at least two groups according to their width in the main scanning direction, and transfers the toner patches to the intermediate transfer member at various primary transfer biases; and a density sensor which measures densities of the toner patches transferred to the intermediate transfer member; wherein the toner patches are categorized into a first group in which toner patches have a long length in the ,main scanning direction and a second group in which toner patches have a short length in the main scanning direction, and wherein the control unit sets the optimum primary transfer bias based on the measuring results of the toner patches in the first group and in the second group.