Image forming apparatus having control device for applying control biases to collection members

摘要

An image forming apparatus includes: a first image forming unit for a monochrome printing including a first photosensitive member for black, a first charging member and a first collection member; a second image forming unit for a multi-color printing including a second photosensitive member for a color, a second charging member and a second collection member; and a control device configured to, at the color printing mode, apply a first charging bias to the second charging member and apply a first bias having a reverse polarity to a charged polarity of developer to the first and second collection members, and at the monochrome printing mode, apply a second charging bias to the second charging member, apply a second bias having the reverse polarity to the first collection member and apply a third bias to the second collection member.

主权项

1. An image forming apparatus comprising:
a conveyance belt configured to convey a recording sheet; a first image forming unit configured to form a monochrome image at a monochrome printing mode, the first image forming unit comprising:
a first photosensitive member for black configured to contact the conveyance belt;a first charging member configured to charge the first photosensitive member; anda first collection member configured to collect a substance attached on the first photosensitive member; a second image forming unit provided at a more upstream side than the first image forming unit in a moving direction of the conveyance belt and configured to form a multi-color image at a multi-color printing mode, the second image forming unit comprising:
a second photosensitive member for a color except for black configured to contact the conveyance belt;a second charging member configured to charge the second photosensitive member; anda second collection member configured to collect a substance attached on the second photosensitive member; and a control device configured to control biases to be applied to the first charging member, the second charging member, the first collection member and the second collection member, wherein at the color printing mode, the control device is configured to:
apply a first charging bias to the second charging member; andapply a first bias having a reverse polarity to a charged polarity of developer to the first collection member and the second collection member, and wherein at the monochrome printing mode, the control device is configured to:
apply a second charging bias having an absolute value smaller than that of the first charging bias to the second charging member;apply a second bias having a reverse polarity to the charged polarity of developer to the first collection member; andapply a third bias having the same polarity as the charged polarity of the developer to the second collection member.