US 12,393,135 B2
Image forming apparatus
Norihiro Shirahata, Tokyo (JP); Shuhei Tokiwa, Tokyo (JP); and Satoru Motohashi, Chiba (JP)
Assigned to Canon Kabushiki Kaisha, Tokyo (JP)
Filed by CANON KABUSHIKI KAISHA, Tokyo (JP)
Filed on Dec. 20, 2023, as Appl. No. 18/389,937.
Claims priority of application No. 2022-212422 (JP), filed on Dec. 28, 2022.
Prior Publication US 2024/0219859 A1, Jul. 4, 2024
Int. Cl. G03G 15/02 (2006.01)
CPC G03G 15/0266 (2013.01) [G03G 15/0258 (2013.01)] 18 Claims
OG exemplary drawing
 
1. An image forming apparatus, comprising:
an image bearing member configured to rotate;
a charging member configured to contact with the image bearing member and to rotate while forming a charging portion, the charging member charging a surface of the image bearing member at the charging portion;
a charging voltage applying portion configured to apply charging voltage to the charging member;
an exposure unit configured to expose the surface of the image bearing member charged by the charging member;
a developer bearing member configured to bear developer, face the image bearing member at a developing portion, and supply the developer to the surface of the image bearing member;
a developing voltage applying portion configured to apply developing voltage to the developer bearing member;
a transfer member configured to transfer the developer, which has been supplied to the surface of the image bearing member at a transfer portion, onto a transferred member;
a transfer voltage applying portion configured to apply transfer voltage to the transfer member;
a cleaning member configured to contact the image bearing member at a cleaning portion which is formed on a downstream side of the transfer portion and on an upstream side of the charging portion in a rotating direction of the image bearing member; and
a control portion configured to control the charging voltage applying portion, the developing voltage applying portion and the transfer voltage applying portion, wherein
the control portion can execute
a first operation to move the developer from a surface of the charging member to the surface of the image bearing member by controlling the charging voltage applying portion, and
a second operation to supply the developer to the cleaning portion by controlling the charging voltage applying portion, the developing voltage applying portion and the transfer voltage applying portion, wherein
in the first operation, between the charging member and the image bearing member, the control portion controls the charging voltage applying portion so as to generate
a first potential difference that generates an electrostatic force to move developer, which is charged to an opposite polarity to a normal charging polarity, from the charging member to the image bearing member, and
a second potential difference that generates an electrostatic force to move developer, which is charged to the normal charging polarity, from the charging member to the image bearing member, wherein
in the second operation, the control portion controls the charging voltage applying portion, the developing voltage applying portion, and the transfer voltage applying portion, so that
in the developing portion, developer is supplied to the surface of the image bearing member, and
in the transfer portion, the developer is supplied to the cleaning portion by generating an electrostatic force in the developer supplied to the surface of the image bearing member, such that the developer charged to the normal charging polarity moves from the transfer member to the image bearing member, and wherein
a region of the surface of the image bearing member, to which developer is supplied in the second operation, includes a region where the second potential difference has been generated in the first operation immediately before the developer is supplied.