Image forming apparatus

An image forming apparatus comprising:

• an intermediate transfer belt that is endless;
• a plurality of rollers around which the intermediate transfer belt is rotatably stretched;
• a density sensor that outputs a sensed value of a toner density of a toner image transferred to an outer circumferential surface of the intermediate transfer belt;
• and
• a positioning portion that is disposed opposite the density sensor, at an inner circumferential side of the intermediate transfer belt, the positioning portion contacting an inner circumferential surface of the intermediate transfer belt to keep a predetermined distance across a gap between the intermediate transfer belt and the density sensor,
• wherein
• the positioning portion includes:
• a support member that is disposed at the inner circumferential side of the intermediate transfer belt so as to face the intermediate transfer belt;
• and
• a non-woven fabric that is laid on a surface of the support member facing the intermediate transfer belt so as to contact the inner circumferential surface of the intermediate transfer belt, the non-woven fabric being electrically conductive, and
• the image forming apparatus further comprises:
• a primary transfer portion that is disposed upstream of the density sensor with respect to a rotational direction of the intermediate transfer belt, the primary transfer portion primarily transferring the toner image formed on an outer circumferential surface of a photosensitive drum to the outer circumferential surface of the intermediate transfer belt;
• a first support roller that is disposed between the density sensor and the primary transfer portion so as to have the intermediate transfer belt rotatably stretched therearound;
• a second support roller that is disposed between the primary transfer portion and the first support roller so as to have the intermediate transfer belt rotatably stretched therearound;
• a secondary transfer roller that is disposed, across the intermediate transfer belt, opposite the first support roller, the secondary transfer roller secondarily transferring the toner image primarily transferred to the outer circumferential surface of the intermediate transfer belt to a sheet passing between the secondary transfer roller and the intermediate transfer belt;
• a bias applying portion that applies a secondary transfer bias to the first support roller;
• and
• a feedback portion that electrically connects the support member and the second support roller to the bias applying portion such that, when the secondary transfer bias is applied to the first support roller, the feedback portion returns, to the bias applying portion, an influx current that has flowed from the first support roller via the intermediate transfer belt into the support member and the second support roller.