Image forming apparatus and controlling method therefor

摘要

An image forming apparatus includes a first station including a first photosensitive drum, a second station including a second photosensitive drum, and an intermediate transfer member for receiving the first toner image from the first drum and the second toner image from the second drum sequentially. In addition, a first sensor detects a first index image on the intermediate transfer member, and a second sensor detects a second index image on the second drum. A controller controls a peripheral speed of the second drum, and an executing device executes a test mode using a first test inclined index image and a second test inclined index image. The controller controls image forming conditions for the first and second index images in accordance with outputs of the first and second sensors in the test mode.

主权项

1. An image forming apparatus comprising:
a first image forming station including a first photosensitive member, a first electrostatic image forming device configured to form an electrostatic image on said first photosensitive member, and a first developing device configured to develop the electrostatic image on said first photosensitive member to form a first toner image with first color toner; a second image forming station including a second photosensitive member, a second electrostatic image forming device configured to form an electrostatic image on said second photosensitive member, and a second developing device configured to develop the electrostatic image on said second photosensitive member to form a second toner image with second color toner of which color is different from color of the first color toner; an intermediate transfer member configured to receive the first toner image from said first photosensitive member and the second toner image from said second photosensitive member sequentially in this order so as to superimpose the second toner image on the first toner image; a first sensor including a first probe extended in a first direction and configured to detect a first index electrostatic image, on said intermediate transfer member, formed by said first electrostatic image forming device so that the first index electrostatic image is substantially parallel to the first direction and transferred from said first photosensitive member; a second sensor including a second probe extended in a second direction and configured to detect a second index electrostatic image on said second photosensitive member formed by said second electrostatic image forming device so that the second index electrostatic image is substantially parallel to the second direction; a controlling device configured to control a peripheral speed of said second photosensitive member so that the second index electrostatic image is superimposed on the first index electrostatic image at a transfer position where the second toner image is transferred from said second photosensitive member to said intermediate transfer member, in accordance with the detection result of said first sensor and the detection result of said second sensor; and an executing device configured to execute a test mode in which a first test index electrostatic image, which is inclined relative to the first direction by a predetermined nonzero angle, is formed on said first photosensitive member and then the first test index electrostatic image is transferred on said intermediate transfer member from said first photosensitive member and detected by said first sensor, and a second test index electrostatic image, which is inclined relative to the second direction by a predetermined nonzero angle, is formed on said second photosensitive member and then the second test index electrostatic image is detected by said second sensor; wherein said controlling device controls an electrostatic image forming condition for the first index electrostatic image in accordance with the detection result of said first sensor in the test mode, and an electrostatic image forming condition for the second index electrostatic image in accordance with the detection result of said second sensor in the test mode.