An image forming apparatus suppresses several kinds of inconveniences
caused by unnecessary contact of a belt-formed member with opposing
members and drives the belt-formed member accurately even when the
belt-formed member separated from a part of a plurality of opposing
members. In an image forming apparatus having a belt-formed member
supported by a plurality of supporting rollers and a plurality of opposing
members located side by side in a line to oppose and contact the
belt-formed member, a pivot mechanism is employed to temporarily separate
the belt-formed member from a part of the opposing members for color image
formation. The image forming apparatus also includes a tension roller dive
mechanism to increase a relative distance between the tension roller and
other supporting rollers to suppress a decrease in a tension of the
belt-formed member during the above-described separation of the
belt-formed member from the plurality of opposing members.
