US Patent No. 9,874,843

IMAGE FORMING APPARATUS


Patent No. 9,874,843
Issue Date January 23, 2018
Title Image Forming Apparatus
Inventorship Hiroki Takayanagi, Abiko (JP)
Assignee Canon Kabushiki Kaisha, Tokyo (JP)

Claim of US Patent No. 9,874,843

1. An image forming apparatus, comprising:
a movable image bearing member;
an image forming unit configured to form a test toner image on said image bearing member;
a sensor provided opposed to said image bearing member and including a detecting portion configured to detect the test toner
image formed on said image bearing member;

a changing portion configured to change an image forming condition of said image forming unit on the basis of a detection
result of said detecting portion;

a shielding member having an opening and provided between said detecting portion and said image bearing member, said shielding
member being reciprocable between a first position and a second position, wherein when said shielding member is in the first
position, said detecting portion is exposed to said image bearing member at a position where said opening is opposed to said
detecting portion, and when said shielding member is in the second position, said shielding member shields said detecting
portion from said image bearing member;

a first opposing portion includes a first member of porous resin material or rubber disposed opposed to said image bearing
member and provided at a position opposing said image bearing member through said opening in a process of movement of said
shielding member from the second position to the first position;

an electrically grounded electroconductive member disposed on a side opposite a side of said first member opposed to said
image bearing member; and

a second opposing portion includes a second member of a dielectric material or insulative material disposed opposed to said
image bearing member and provided at a position opposing said image bearing member through said opening in the process of
movement of said shielding member from the second position to the first position;

wherein said second opposing portion is disposed at a position closer to said sensor than said first opposing portion, and
said second opposing portion has an electrostatic capacity smaller than that of said first opposing portion.