Patent ID: 6839531

Claim:
A belt apparatus used for image formation structured such that a belt is extended between at least two rollers provided opposite to and at a distance from each other and the belt is rotated by the rotation of the rollers, and structured such that processing means used for image formation are arranged around the belt and the processing means are made to function while the belt is being rotated, the belt apparatus including an intermediate transfer means comprising a transfer brush and a transfer roller, and at least one of the processing means acts on any one of the two rollers while an image is being formed on the belt thereby imparting a rotational load variation to that roller, wherein the roller to which a rotational load variation is directly imparted by the processing means is set as a roller that drives the belt, wherein a structure is employed in which the drive roller is linked to a drive source via a roller drive system equipped with a power transmission system that uses frictional contact, and rotational force from the drive source is transmitted to the drive roller via the roller drive system, wherein, when there are a plurality of processing means imparting a load variation, the roller to which a rotational load variation is being imparted by the processing means imparting the largest load variation is set as the roller that drives the belt, and wherein the transfer brush and the transfer roller have an electrical potential difference and a bias power supply is provided to apply a bias voltage to the transfer brush and the transfer roller to form a bias circuit.