1. Field of the Invention
The present invention relates to an image forming apparatus transferring a toner image to a transfer material.
2. Description of the Related Art
Conventionally, there has been known an image forming apparatus having a plurality of photosensitive drums arranged laterally in a line and having an intermediate transfer belt as a transfer belt or a conveyor belt conveying a transfer material. Japanese Patent Application Laid-Open No. 2009-048051 discloses an image forming apparatus having a transfer device including a sheet member and an elastic member, wherein the elastic member presses the sheet member to the intermediate transfer belt at a position facing a photosensitive drum so as to be stably in contact with each other to form a desired nip portion. In comparison with a transfer device contacting a transfer roller with the intermediate transfer belt, the transfer device including the sheet member and the elastic member can form a desired contact region between the sheet member and the intermediate transfer belt and thus has the advantage of providing a high-quality image and a small-sized device.
When a single color image is formed, it is desirable to suppress an increase in rotation torque of the intermediate transfer belt by releasing the contact state between the transfer device corresponding to other colors and the intermediate transfer belt.
However, the configuration in which the transfer device including the sheet member and the elastic member is abutted against and separated from the intermediate transfer belt has a difficulty in suppressing a change in position of the contact region. The configuration of separating the entire transfer device from the intermediate transfer belt complicates the separation mechanism.