Upper frame opening and closing mechanism, and image forming apparatus using the same

An upper frame opening and closing mechanism, comprising:

• an upper frame pivotally attached to a main body unit so as to be opened and closed on a hinge, which receives a moment in an opening direction due to gravity when the upper frame is opened at an angle exceeding an inversion angle so as to expose an interior of the main body unit;
• an arm member, a base end of which is pivotally mounted on the upper frame;
• a rail member mounted on the main body unit, to guide a leading edge of the arm member along with opening and closing of the upper frame;
• and
• a biasing member to bias the upper frame in the opening direction,
• wherein a moment applied to the upper frame based on a biasing force from the biasing member is set to balance the moment applied to the upper frame based on gravity when the upper frame is opened at a maximum opening angle relative to the main body unit, except at a beginning and at an ending of the opening.