Image forming apparatus

摘要

An image forming apparatus includes a primary transfer bias adjuster to adjust, in a second mode, a primary transfer bias by a correction amount in accordance with a degree of deterioration of a developing agent detected by a first developing agent condition detector so as to reduce a primary transfer current of the primary transfer bias upon transferring a toner image from a first image bearing member onto an intermediate transfer member, and to adjust, in a first mode, the primary transfer bias by a correction amount less than the correction amount in the second mode or not to adjust the primary transfer bias in accordance with the degree of deterioration of the developing agent detected by the first developing agent condition detector upon primarily transferring the toner image from the first image bearing member onto the intermediate transfer member.

主权项

1. An image forming apparatus, comprising:
an intermediate transfer member to move in a first direction; a plurality of image bearing members to bear toner images thereon, the plurality of image bearing members disposed along the first direction; a plurality of toner image forming devices to form the toner images on the plurality of image bearing members using different developing agents; a primary transfer device to apply a primary transfer bias to primarily transfer each of the toner images formed on the plurality of image bearing members onto a surface of the intermediate transfer member to form a composite toner image; a secondary transfer device to apply a secondary transfer bias to secondarily transfer the composite toner image formed on the intermediate transfer member to a recording medium; a controller to selectively control image forming operation between a first mode and a second mode such that in the first mode the composite toner image is formed using at least two of the plurality of image bearing members including a first image bearing member and a second image bearing member and after the composite toner image is formed on the intermediate transfer member the secondary transfer bias is applied to secondarily transfer the composite toner image from the intermediate transfer member to the recording medium, and in the second mode the toner image is formed on the first image bearing member used in the first mode which is disposed downstream from the second image bearing member in the first direction and after the toner image is primarily transferred from the first image bearing member onto the intermediate transfer member the secondary transfer bias less than that in the first mode is applied to transfer the toner image from the intermediate transfer member to the recording medium; a first developing agent condition detector to detect a degree of deterioration of a developing agent used to form the toner image on the first image bearing member; and a primary transfer bias adjuster to adjust, in the second mode, the primary transfer bias by a correction amount in accordance with the degree of deterioration of the developing agent detected by the first developing agent condition detector so as to reduce a primary transfer current of the primary transfer bias upon transferring the toner image from the first image bearing member onto the intermediate transfer member, and to adjust, in the first mode, the primary transfer bias by a correction amount less than the correction amount in the second mode or not to adjust the primary transfer bias in accordance with the degree of deterioration of the developing agent detected by the first developing agent condition detector upon primarily transferring the toner image from the first image bearing member onto the intermediate transfer member.