Image forming apparatus that detects a presence of a conductive foreign object on a recording material

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.