Image forming apparatus, and image carrier moving apparatus for use in image forming apparatus

An image forming apparatus comprising:

• a plurality of image carriers;
• an exposure portion that scans, in an axial direction, light which is emitted from a light source based on image data of a document sheet, and applies the light to a surface of each of the image carriers, to form an electrostatic latent image on each of the image carriers;
• a developing device that develops the electrostatic latent image formed by the exposure portion into a toner image;
• an intermediate transfer medium which travels in a direction in which the plurality of image carriers are aligned, and on which the toner image obtained by development on each image carrier by the developing device is sequentially superimposed;
• a cleaning member that is disposed so as to contact with each image carrier and that removes residual toner on each image carrier to perform cleaning;
• a driving mechanism that causes each image carrier to shuttle in the axial direction with a predetermined amplitude while the image carrier is driven to rotate;
• a detecting member that detects positional information representing a position, in the axial direction, obtained when each image carrier shuttles;
• and
• a control portion that controls, based on a result of detection by the detecting member, a time when scanning on each of the image carriers by the exposure portion is to be started;
• wherein
• the driving mechanism includes:
• a first gear member that is provided in each of the image carriers;
• a second gear member that is disposed so as to oppose the first gear member and be rotatable coaxially with the first gear member, the second gear member disposed so as not to be movable in the axial direction, the second gear member having teeth formed such that the number of the teeth of the second gear member is different from the number of teeth of the first gear member;
• a driving gear that meshes with the first gear member and the second gear member;
• a cam surface that is provided in one of the first gear member and the second gear member such that a distance in the axial direction varies in a circumferential direction;
• a cam follower that is provided in the other of the first gear member and the second gear member so as to contact with the cam surface;
• and
• an urging member that urges each of the image carriers in a direction in which the cam surface and the cam follower come into contact with each other;
• the first gear member includes a reflecting surface by which light is reflected, such that the reflecting surface is positioned at a predetermined position, in a circumferential direction, of a side surface portion;
• the second gear member includes a through hole opposing the reflecting surface;
• and
• the detecting member:
• includes a light emitting portion that applies light through the through hole to the reflecting surface, and a light receiving portion that receives, through the through hole, light reflected by the reflecting surface;
• and
• detects peak positions of amplitudes with which the image carriers shuttle, based on an output time period in which the reflected light is outputted, the output time period being changed according to a difference between a rotation angle of the first gear member and a rotation angle of the second gear member.