Patent ID: 8233829
Filing Date: 2012-07-31
Classification: G03G

Abstract:
1. A transfer belt unit, comprising: a transfer belt that is endless and transfers a toner image transferred from an image carrier onto a transfer medium; a secondary transfer roller that forms a nip with the transfer belt at a position where the toner image is transferred onto the transfer medium; a plurality of stretching rollers that stretches the transfer belt; a drive unit that transmits a rotational driving force to at least one of the stretching rollers; a regulating member that prevents axial movement of the transfer belt at an axial end of at least one of the stretching rollers by having a diameter substantially 20% larger than a diameter of the stretching rollers at an end of the transfer belt where the regulating member contacts the transfer belt; and a primary transfer roller that faces the image carrier via the transfer belt, the primary transfer roller being offset with respect to the image carrier, wherein the transfer belt has a thickness not less than 100 micrometers and not more than 200 micrometers, a tension not less than 80 N/m and not more than 180 N/m, and a tensile elastic modulus not less than 1000 megapascals and not more than 2000 megapascals, the tension being obtained by dividing a tension [N] applied in an endless moving direction of the transfer belt by a belt width [m], which is a length of the transfer belt in a direction perpendicular to the endless moving direction, the secondary transfer roller has an Asker C hardness not less than 35 degrees and not more than 50 degrees, the stretching rollers have an outer diameter not less than 6 millimeters, and the primary transfer roller is a metal roller without a resin layer on a surface thereof.