Patent ID: 7373097

Claim:
A printer engine comprising: a plurality of photosensitive bodies which are rotationally driven, and which have toner images formed on the outer circumferential surfaces thereof; an endless belt which is disposed facing the outer circumferential surfaces of said photosensitive bodies, and which runs while carrying toner images that have been transferred from said photosensitive bodies, or while holding a recording medium onto which the toner images on said photosensitive bodies are transferred; means for forming detection pattern toner images on said photosensitive bodies which are used to detect an amount of positional deviation of transfer positions of the toner images of respective colors when the toner images formed on said photosensitive bodies are superimposed and transferred onto said endless belt or the recording medium held on said endless belt; means for transferring the detection pattern toner images formed on said respective photosensitive bodies onto said endless belt or the recording medium held on said endless belt; means for detecting the detection pattern toner images that have been transferred onto said endless belt or the recording medium held on said endless belt; means for judging the amount of positional deviation in the transfer positions of the detection pattern toner images of the respective colors on the basis of the detection results of said means for detecting the detection pattern toner images; and means for adjusting the rpm of driving parts that drive said photosensitive bodies on the basis of the judgment results of said means for judging the amount of positional deviation in the transfer positions so that the linear velocities of said photosensitive bodies are caused to agree with each other.