1. Field of the Invention
The present invention relates to an image forming apparatus, such as an electronic copying apparatus and a laser printer, and more particularly to an image forming apparatus which has a fixing unit for fixing a developer (e.g., powdered toner) transferred onto a sheet.
2. Description of the Related Art
In recent years, an image forming apparatus (e.g., an electronic copying apparatus and a laser printer) has come to employ the so-called clam shell structure, for easy maintenance and for easy removal of sheets causing an abnormal transfer state. In the clam shell structure, the housing is divided into first and second units (i.e., upper and lower units), with the boundary therebetween defined by a sheet transport path formed inside the apparatus, and wherein the first unit can be opened in a direction away from the second unit.
The image forming apparatus comprises a fixing means for fixing a developer image to a sheet. Normally, the fixing means is of a heating roller type. It includes a pair of fixing rollers (namely, a heating roller and a pressing roller) which are in rolling contact with each other, and a releasing claw which is used for releasing a sheet from the fixing rollers, to prevent the sheet from being wound around the fixing rollers.
Published Unexamined Japanese Patent Application (PUJPA) No. 63-6588 discloses an example of a conventional image forming apparatus which is the clam shell type and which employs a fixing means of the heating roller type. As may be understood from the example in the reference, the releasing claw remains engaged with the fixing rollers even after the first unit is opened or separated from the second unit.
In the conventional image forming apparatus, the releasing claw remains engaged with the fixing rollers even after the first unit is opened, as mentioned above. If the releasing claw is touched by something and is thus subject to an external force, an impact is applied between the releasing claw and the fixing rollers. In such a case, it is likely that the tip end of the releasing claw will be broken or the surfaces of the fixing rollers will be scratched, so that a satisfactory fixing operation or a reliable releasing operation cannot be performed thereafter.