Patent ID: 9645528
Date: 2017-05-09
CPC Classifications: G03G

Claim:
1. An image forming apparatus comprising: a plurality of image forming units, each including a photosensitive member, an electrostatic image forming unit, and a developing device, the electrostatic image forming unit being configured to form an electrostatic image on said photosensitive member, the developing device being configured to develop the electrostatic image into a toner image and capable of collecting transfer residual toner deposited on said photosensitive member; an intermediary transfer member configured to carry the toner image primary transferred from at least one of said photosensitive members at each of primary transfer portions, each of the primary transfer portions being provided at a position opposing a corresponding photosensitive member and including a most downstream primary transfer portion and a most upstream primary transfer portion with respect to a rotational direction of said intermediary transfer member; a rotatable transfer member configured to secondary transfer the toner image from said intermediary transfer member onto a recording material while sandwiching the recording material between said rotatable transfer member and said intermediary transfer member at a secondary transfer portion; a constant voltage element, electrically connected between said intermediary transfer member and a ground potential, configured to maintain a predetermined voltage by flow of a current therethrough; a power source configured to form a secondary transfer electric field at the secondary transfer portion by applying a voltage to said rotatable transfer member and configured to form a primary transfer electric field at the primary transfer portion by passing the current through said constant voltage element; a cleaning device configured to remove toner deposited on said intermediary transfer member at a side downstream of the secondary transfer portion and upstream of the primary transfer portion with respect to the rotational direction of said intermediary transfer member; and a controller configured to execute, during interruption of an image forming operation due to occurrence of a jam of the recording material, an operation in a collecting mode in which said photosensitive members and said intermediary transfer member are rotationally driven under application of a predetermined voltage to said rotatable transfer member, and collect untransferred toner, by said cleaning device, carried on said photosensitive members and said intermediary transfer member without being subjected to a secondary transfer process at the secondary transfer portion, wherein when the untransferred toner is carried on said intermediary transfer member at a side upstream of the most downstream primary transfer portion and downstream of the most upstream primary transfer portion with respect to the rotational direction of said intermediary transfer member, said controller executes the following operations during execution of the operation in the collecting mode: (i) during passing of the untransferred toner through each of the primary transfer portions during the execution of the operation in the collecting mode, said controller effects control so that a voltage of an opposite polarity to a charge polarity of the toner is applied to said rotatable transfer member, and (ii) after passing of the untransferred toner through each of the primary transfer portions during the execution of the operation in the collecting mode, said controller effects control so that a voltage of an identical polarity to the charge polarity of the toner is applied to said rotatable transfer member.