Image forming apparatus with drive control of a driven member based on a between-sheets time

摘要

An image forming apparatus is provided in which, during a continuous sheet passing, in the case where a between-sheets time is short, none of a cleaning mode and a drive OFF mode is performed; in the case where the between-sheets time is of a medium length of time, the cleaning mode is performed but the drive OFF mode is not performed; and in the case where the between-sheets time is long, both the cleaning mode and the drive OFF mode are performed. As a result, degradation of an image bearer due to the cleaning bias is alleviated, decreased productivity due to the cleaning mode is alleviated, a problem is alleviated in which a back surface of a recording medium gets dirty due to toner adhered to a transfer rotation body, and another problem is alleviated in which the service life of a driven member is shortened.

主权项

1. An image forming apparatus, comprising:
an image bearer configured to be driven to run in a first predetermined direction; a transfer rotation body configured to rotate in a second predetermined direction and abut the image bearer to form a transfer nip unit; a bias applying unit configured to transfer a toner image onto a recording medium conveyed to the transfer nip unit by applying a transfer bias to the transfer rotation body; and a driven member configured to be driven by a drive unit during an image forming operation, wherein the bias applying unit is configured to apply a cleaning bias for removing toner adhered to the transfer rotation body and apply a non-image area bias whose absolute value is less than the cleaning bias to the transfer rotation body, time X, which is defined as between-sheets time from when the recording medium is fed out at the transfer nip unit to when the next recording medium is fed into the transfer nip unit while the image bearer is in a driven state and a plurality of the recording media are continuously conveyed, varies based on a predetermined condition, in the case where the time X does not exceed a threshold value A, the bias applying unit is controlled to apply the non-image area bias during all of the time X and the drive unit is controlled to drive the driven member during all of the time X, in the case where the time X exceeds the threshold value A and does not exceed a threshold value B which is greater than the threshold value A, the bias applying unit is controlled to apply the non-image area bias during time Z within the time X and apply the cleaning bias during time (X-Z), and the drive unit is controlled to drive the driven member during all of the time X, and in the case where the time X exceeds the threshold value B, the bias applying unit is controlled to, during the time Z within the time X, turn OFF bias application so that none of the transfer bias, the cleaning bias, and the non-image area bias is applied, or to apply the non-image area bias which is equivalent to the bias application being turned OFF, and, during the time (X-Z), apply the cleaning bias, wherein the drive unit is controlled to stop driving the driven member during time W within the time X and drive the driven member during time (X-W).