US 7,613,406 B2
Image forming apparatus that detects a presence of a conductive foreign object on a recording material
Masami Takeda, Mishima (Japan)
Assigned to Canon Kabushiki Kaisha, Tokyo (Japan)
Filed on Apr. 19, 2006, as Appl. No. 11/406,251.
Claims priority of application No. 2005-132311 (JP), filed on Apr. 28, 2005; and application No. 2005-253932 (JP), filed on Sep. 01, 2005.
Prior Publication US 2006/0245768 A1, Nov. 02, 2006
Int. Cl. G03G 15/00 (2006.01)
U.S. Cl. 399—16 3 Claims
OG exemplary drawing
 
1. An image forming apparatus comprising:
an image bearing member on which a toner image is formed;
a transfer member that forms a transfer nip portion with said image bearing member, wherein said transfer member transfers the toner image formed on said image bearing member onto a recording material by applying a voltage into said transfer member;
a fixing device that fixes the toner image transferred onto the recording material, on the recording material, said fixing device having a heater, a film and a roller that forms a fixing nip portion with the heater through the film, wherein the film contacts a recording material at the fixing nip portion;
a current detecting device that detects a current flowing in said transfer member, when the recording material passes through the transfer nip portion;
a judgment device for judging, based on an output from said current detecting device, whether or not a conductive foreign object is present on the recording material;
a leading edge detecting device that is provided at an upstream side of said transfer member with regard to a conveyance direction of the recording material and detects a leading edge of a recording material; and
a controller that controls said image forming apparatus,
wherein when t1 denotes a timing to detect the leading edge of a recording material by said leading edge detecting device, t2 denotes a timing to detect a conductive foreign object by said current detecting device and T denotes a time in which a recording material passes through the nip portion between the leading edge detecting device and said fixing nip portion, if (t2−t1) is less than T, said controller stops conveying a recording material before the leading edge of the recording material comes into said fixing nip portion, and if (t2−t1) is equal to or more than T, said controller stops conveying a recording material and notifies a user that the recording material is to be removed in an upstream direction of said fixing device with regard to the conveyance direction of the recording material.