Image forming apparatus including a duct for airflow having a sectional area that becomes gradually smaller toward a part of a rotating shaft exposed into the duct

An image forming apparatus comprising:

• an optical scanning device including a rotating polygon mirror that deflects and scans beam light from a light source unit with respect to a surface to be scanned, a motor having a rotating shaft to which the rotating polygon mirror is fixed and rotationally driving the rotating polygon mirror, and a housing that accommodates the rotating polygon mirror and the motor;
• a duct having a rectangular section and disposed adjacent to the optical scanning device, a part of the rotating shaft being exposed into the duct;
• and
• a cooling fan that generates airflow which flows inside the duct,
• wherein, at a position close to where the part of the rotating shaft is exposed into the duct and upstream of the part of the rotating shaft exposed into the duct with respect to a flow direction of the airflow in the duct, a sectional area of the duct becomes gradually smaller toward the part of the rotating shaft exposed into the duct in the flow direction of the airflow in the duct, the sectional area of the duct is smallest at a position where the part of the rotating shaft is provided, and downstream of the position where the part of the rotating shaft is provided, the sectional area of the duct becomes larger than the smallest sectional area.