Patent ID: 8081905
Filing Date: 2011-12-20
Classification: G03G

Abstract:
1. An image forming apparatus comprising: at least one image bearing member which is a rotating member and on which an electrostatic latent image is formed at an image writing position; at least one image forming device configured to form the electrostatic latent image on the at least one image bearing member and to develop the electrostatic latent image with a developer including a toner to form a toner image on the at least one image bearing member; a transfer device configured to transfer the toner image onto a receiving material, said transfer device including a moving member selected from a feeding member configured to feed the receiving material so that the toner image on the at least one image bearing member is transferred onto the receiving material at an image transfer position, and an intermediate transfer medium configured to receive the toner image from the at least one image bearing member at an image transfer position and to transfer the toner image to the receiving material; a drive controller configured to control driving of the at least one image bearing member so that a rotation angular speed of the at least one image bearing member is identical to a targeted rotation angular speed; a pattern detection device configured to detect plural detection pattern images formed on the moving member in a moving direction thereof by forming plural electrostatic latent images of the plural detection pattern images on the at least one image bearing member, developing the plural electrostatic latent images with the developer to form plural detection pattern toner images on the at least one image bearing member, and then transferring the detection pattern toner images onto the moving member at the image transfer position; a second rotating member influencing an interval of the pattern toner images; and a correction device configured to correct the targeted rotation angular speed in such a manner that a pattern interval variation component representing a periodical variation in moving speed of the at least one image bearing member is extracted from a data of the detection pattern images; the thus extracted pattern interval variation component is corrected on the basis of a phase difference representing an angle between a first virtual line connecting the image writing position and a rotation center of the at least one image bearing member and a second virtual line connecting the image transfer position and the rotation center of the at least one image bearing member to determine an amount of variation in rotation angle or rotation angular speed per one revolution of the at least one image bearing member; the targeted rotation angular speed is corrected by superimposing a correction value, which is an inversion value negating the variation in rotation angle or rotation angular speed per one revolution of the at least one image bearing member on the targeted rotation angular speed, wherein the correction device is configured to repeat correction processing for the extracted pattern interval variation component (N-1) times to obtain an average of the variation in rotation angle or rotation angular speed per one revolution of the at least one image bearing member, a product of N and the phase difference being substantially identical to a product of M and 2π, M and N being positive integers, and the average is used as the variation in rotation angle or rotation angular speed per one revolution of the at least one image bearing member, and the detection pattern toner images are formed at regular time intervals throughout a length that is a common multiple of a peripheral length of the second rotating member and a peripheral length of the at least one image bearing member.