| CPC G03G 15/1605 (2013.01) [G03G 15/80 (2013.01)] | 23 Claims |
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1. An image forming apparatus comprising:
an image bearing member configured to bear a toner image;
an intermediate transfer belt that is rotatable, endless, and onto which the toner image is to be transferred from the image bearing member; and
a plurality of current supply devices capable of supplying currents to the intermediate transfer belt,
wherein the plurality of current supply devices includes:
a first current supply device including
a primary transfer member configured to primarily transfer the toner image from the image bearing member onto the intermediate transfer belt by supplying a primary transfer current to the intermediate transfer belt at a primary transfer portion,
a first power source configured to apply a voltage to the primary transfer member, and
a first detecting unit configured to detect a current supplied from the first power source;
a second current supply device including
a secondary transfer member configured to secondarily transfer the toner image from the intermediate transfer belt onto a recording material by supplying a secondary transfer current to the intermediate transfer belt at a secondary transfer portion,
a second power source configured to apply a voltage to the secondary transfer member, and
a second detecting unit configured to detect a current supplied from the second power source;
a third current supply device including
a discharge member configured to supply a discharge current to the intermediate transfer belt at a discharge portion downstream of the secondary transfer portion and upstream of the primary transfer portion in a rotation direction of the intermediate transfer belt,
a third power source configured to supply a current to the discharge member, and
a third detecting unit configured to detect the current supplied from the third power source; and
a control unit configured to control the plurality of current supply devices,
wherein, among currents supplied by the plurality of current supply devices at an image forming time, if Ia is a sum of current densities of positive currents, per unit length of the intermediate transfer belt in a width direction in regions where the currents are supplied by the plurality of current supply devices at the image forming time, supplied in a direction from an outer peripheral surface side of the intermediate transfer belt to an inner peripheral surface side of the intermediate transfer belt, Ib is a sum of current densities of positive currents, per unit length of the intermediate transfer belt in the width direction in the regions where the currents are supplied by the plurality of current supply devices at the image forming time, supplied in a direction from the inner peripheral surface side to the outer peripheral surface side of the intermediate transfer belt, and a value of Ia−Ib is a value of a current balance of a current supplied to the intermediate transfer belt,
an electric resistance of the intermediate transfer belt with respect to the current balance is larger when the value of the current balance is a negative value of a predetermined value than when the value of the current balance is a positive value of the predetermined value, and
wherein, during execution of a print job of continuous image formation in which the toner image is continuously transferred onto a plurality of recording materials, the control unit performs constant current control on the discharge current such that, based on a detection result detected by the first detecting unit during the print job and a detection result detected by the second detecting unit during the print job, the current balance is positive.
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