1. Field of the Invention
The present invention generally relates to a contacting and separating mechanism which causes a first member to contact a second member and separates the first member contacting the second member from the second member and an image forming apparatus using the contacting and separating mechanism such as a copying apparatus, a printer, a facsimile machine, and a multifunctional apparatus having the above functions.
2. Description of the Related Art
Conventionally, in an image forming apparatus such as a copying apparatus and a printer, a contacting and separating mechanism, which causes a member to be contacted such as a secondary transfer roller to contact a contacting member such as an intermediate transfer belt (image carrier) and separates the member contacting the contacting member from the contacting member, has been widely used (see Patent Documents 1 through 3).
In an image forming apparatus in Patent Document 1, four photoconductor drums are arrayed to face an intermediate transfer belt. On the four photoconductor drums, a black toner image, a yellow toner image, a magenta toner image, and a cyan toner image are formed, respectively. The four toner images are transferred onto the intermediate transfer belt by being superposed. The superposed toner image on the intermediate transfer belt is transferred onto a recording medium at a position where the intermediate transfer belt contacts a secondary transfer roller.
In the image forming apparatus, in order to reduce the wear and deterioration of the intermediate transfer belt and the secondary transfer roller caused by the friction between the intermediate transfer belt and the secondary transfer roller, or in order to remove a recording medium jammed at a position where the intermediate transfer belt contacts the secondary transfer roller, a contacting and separating mechanism is provided which automatically causes the secondary transfer roller to contact the intermediate transfer belt and automatically separates the secondary transfer roller from the intermediate transfer belt.
Specifically, in Patent Document 1, by a roller pressure applying lever (pressure applying member) whose rotation supporting point is near the secondary transfer roller, the secondary transfer roller is caused to contact the intermediate transfer belt. When a cam contacting the roller pressure applying lever is rotated to a predetermined angle, the roller pressure applying lever is pushed downward against a spring force which pushes the roller pressure applying lever. With this, the secondary transfer roller is separated from the intermediate transfer belt.
In Patent Document 1, in order to replace the secondary transfer roller with a new one, a rotation supporting point for moving the secondary transfer roller by its own weight is provided, in addition to the rotation supporting point of the roller pressure applying lever.
In Patent Document 2, a secondary transfer frame pressure applying metal plate and a secondary transfer member (pressure applying member) whose rotation supporting point is near the secondary transfer roller pushes the secondary transfer roller to the intermediate transfer belt. When a cam is rotated to a predetermined angle, which cam is disposed under the secondary transfer roller, and contacts the secondary transfer frame pressure applying metal plate, a spring force pushing the secondary transfer frame pressure applying metal plate and the secondary transfer member is released. With this, the secondary transfer roller is separated from the intermediate transfer belt.
In Patent Document 3, a secondary transfer unit (pressure applying member) whose rotation supporting point is separated from the secondary transfer roller causes the secondary transfer roller to contact the intermediate transfer belt. When a cam is rotated to a predetermined angle, which cam is disposed under the secondary transfer roller and contacts the secondary transfer unit, the secondary transfer roller is separated from the intermediate transfer belt.    [Patent Document 1] Japanese Unexamined Patent Publication No. 2004-252258    [Patent Document 2] Japanese Unexamined Patent Publication No. H11-030896    [Patent Document 3] Japanese Unexamined Patent Publication No. 2001-201954
However, in the image forming apparatus, when, for example, a power source of the apparatus is cut off and an automatic contacting and separating mechanism which is moved by a motor is not operated, in order to remove a recording medium jammed at a position where the intermediate transfer belt contacts the secondary transfer roller, or in order to perform maintenance of the intermediate transfer belt and the secondary transfer roller, a manual separating mechanism which manually separates the secondary transfer roller from the intermediate transfer belt must be provided.
However, in a case where the manual separating mechanism is attached to the automatic contacting and separating mechanism, when a manually operable cam (manual cam) contacts the pressure applying member of the automatic contacting and separating mechanism while using the pressure applying member and the rotation supporting point of the automatic contacting and separating mechanism as they are, a great force may be required for the manual operation or pressure deviation may be generated in the width direction of the secondary transfer roller which contacts the intermediate transfer belt.
That is, in order to increase the operability of the manual separating mechanism, in a case where the rotation supporting point of the pressure applying member rotating with the secondary transfer roller is disposed near the secondary transfer roller and the manual cam is disposed at a position separated from the secondary transfer roller, when the parallelism between the secondary transfer roller and the rotation supporting point of the pressure applying member is not accurately obtained, the pressure deviation in the width direction of the secondary transfer roller which contacts the intermediate transfer belt becomes great.
Specifically, in Patent Documents 1 and 2, since the rotation supporting point of the pressure applying member is near the secondary transfer roller, the pressure deviation in the width direction of the secondary transfer roller which contacts the intermediate transfer belt may be great.
In addition, in Patent Document 1, when the secondary transfer roller is replaced with a new one, the rotation supporting point for moving the secondary transfer roller by its own weight is formed, in addition to the rotation supporting point of the pressure applying member. However, the above problem is not solved and the size of the apparatus becomes large.
In Patent Document 3, since the rotation supporting point of the pressure applying member is at a position separated from the secondary transfer roller, the pressure deviation of the secondary transfer roller is relatively small at the contacting position with the intermediate transfer belt; however, when the cam is manually moved, a large force is required.
The above problems are not limited to the separating mechanism in which the secondary transfer roller is separated from the intermediate transfer belt. That is, the problems are common in all the separating mechanisms in which a member contacting another member is separated from the other member.