Image forming apparatus including reciprocatable fixing unit next to heating unit

An image forming apparatus, comprising:

• a heating unit which includes a heater and is disposed to extend along a first direction in a main body;
• a fixing unit which includes a first rotation member that is heated by the heater and a second rotation member that biases a sheet toward the first rotation member, and is disposed next to the heating unit to extend along the first direction in the main body;
• a unit bias portion which biases the heating unit toward the fixing unit;
• and
• a fixed unit fixed to the main body,
• wherein
• the unit bias portion retains a position of the heating unit with respect to the fixing unit at a reference position in a second direction along which the heating unit and the fixing unit are arranged,
• the heating unit includes a plurality of first to-be-engaged portions and a second to-be-engaged portion,
• the fixing unit includes a plurality of first engagement portions which respectively engage with the plurality of first to-be-engaged portions to restrict a movement of the heating unit in a third direction intersecting with the first direction and the second direction,
• the fixed unit includes a second engagement portion which engages with the second to-be-engaged portion to restrict a movement of the heating unit in the first direction,
• the fixing unit further includes:
• a movable unit including the first rotation member and the second rotation member,
• a supporting member which supports the movable unit such that the movable unit is movable along the first direction, and
• a reciprocating mechanism which causes the movable unit to reciprocate along the first direction,
• the reciprocating mechanism causes the movable unit to reciprocate once every time a plurality of the sheets pass between the first rotation member and the second rotation member, and
• when the heating unit moves from a position farther away from the fixing unit than the reference position to the reference position along the second direction under a bias force of the unit bias portion, the first engagement portions move from positions of not engaging with the first to-be-engaged portions to positions of engaging with the first to-be-engaged portions, respectively, and the second engagement portion moves from a position of not engaging with the second to-be-engaged portion to a position of engaging with the second to-be-engaged portion.