Printer engine and color image forming device using this printer engine

A color image forming device comprising:

• a printer engine;
• a recording medium accommodating part which accommodates a recording medium that is supplied to said printer engine;
• a fixing device which fixes color toner images that are transferred onto said recording medium;
• and
• a recording medium discharge part to which the recording medium on which a toner image has been fixed is discharged, said 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 the amount of positional deviation of the transfer positions of the toner images of the 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 transfer 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.

An image forming device comprising:

• a plurality of image carriers which carry visible images on moving surfaces;
• driving means which individually drives the respective image carriers;
• visible image forming means which forms visible images on the respective image carriers;
• an endless moving body whose surface is caused to move endlessly so as to successively pass through positions facing the respective image carriers;
• transfer means which transfers the visible images formed on the surfaces of the respective image carriers onto a recording medium held on the surface of said endless moving body, or which transfers said images onto the surface of said endless moving body, and then transfers said images onto the recording medium;
• image detection means which detects the visible images carried on the surface of said endless moving body;
• and
• control means which performs speed setting processing of forming specified reference images on the respective image carriers at a specified timing, transferring these reference images onto the surface of said endless moving body, calculating the relative amount of mutual positional deviation in the respective reference images on the basis of the timing at which the respective reference images are detected by said image detection means, and individually setting the driving speeds of the respective image carriers on the basis of said calculation results, wherein
• said control means is constructed so that the driving speeds of the respective image carriers are individually set within a range in which the driving speed differences between the respective image carriers are kept at a specified upper limit value or lower.