Patent ID: 7770998

Claim:
A color image forming apparatus, comprising: a conveying member having a surface configured to convey a plurality of transfer sheets, the surface including a spacing area between at least two adjacent transfer sheets on the surface of the conveying member; a plurality of image carrying members that are arranged in tandem, configured to carry images and configured to transfer the images onto the transfer sheets conveyed by the conveying member; a signal generator configured to generate a first timing signal for at least one of a plurality of colors formed by the color image forming apparatus, the first timing signal including a first sub-scan image area signal that indicates an effective image area in a sub-scanning direction of one of the plurality of transfer sheets, and configured to generate a second timing signal for at least one of the plurality of colors formed by the image forming apparatus, the second timing signal including a second sub-scan image area signal that is generated for a short period of time when the color image forming apparatus is in a stand-by mode such that image formation is not performed onto the transfer sheets; a counter configured to count delay lines to determine whether a first predetermined time has elapsed from a first negation timing of the first sub-scan image area signal, the first negation timing occurring at a negation edge of the first sub-scan image area signal and the negation edge corresponds to a trailing edge of the one of the plurality of transfer sheets, and configured to count delay lines to determine whether a second predetermined time has elapsed from a second negation timing of the second sub-scan image area signal, the second negation timing occurring at a negation edge of the second sub-scan image area signal; and a pattern formation mechanism configured to form a first maintenance pattern on the spacing area after the first predetermined time has elapsed from the first negation timing of the sub-scan image area signal, and configured to form a second maintenance pattern, when the color image forming apparatus is in the stand-by mode such that image formation is not performed onto the transfer sheets, on the conveying member after the second predetermined time has elapsed from the second negation timing of the sub-scan image area signal.