Method and a color image forming apparatus forming a positioning mark

A color image forming apparatus comprising:

• a photoconductive element;
• latent image forming means for selectively forming on said photoconductive element latent images respectively corresponding to images of particular colors and a position mark latent image representative of position information;
• a developing unit developing said latent images with developers of respective colors to thereby produce corresponding color images, and developing said position mark latent image to thereby produce a position mark;
• an intermediate transfer belt for causing the color images to be transferred thereto one above another and then transferred therefrom to a recording medium, and causing said position mark to be transferred thereto to form a position information portion;
• a position information detecting unit generating a detection signal on detecting said position information portion formed on said intermediate transfer belt;
• starting means for starting said photoconductive element in response to said detection signal fed from said position information detecting unit;
• and
• control means for forming said position information portion on said intermediate transfer belt for each recording medium.

A color image forming apparatus comprising:

• a photoconductive element;
• latent image forming means for selectively forming on said photoconductive element latent images respectively corresponding to images of particular colors and a position mark latent image representative of position information;
• a developing unit developing said latent images with developers of respective colors to thereby produce corresponding color images, and developing said position mark latent image to thereby produce a position mark;
• an intermediate transfer belt for causing the color images to be transferred thereto one above another and then transferred therefrom to a recording medium, and causing said position mark to be transferred thereto to form a position information portion;
• a position information detecting unit generating a detection signal on detecting said position information portion formed on said intermediate transfer belt;
• starting means for starting said photoconductive element in response to said detection signal fed from said position information detecting unit;
• and
• distance measuring means for forming at least one position information portion on said intermediate transfer belt at least once when said apparatus is started up, and measuring, based on said position information portion, a distance which said intermediate transfer belt travels during one turn thereof.

A color image forming apparatus comprising:

• a photoconductive element;
• latent image forming means for selectively forming on said photoconductive element latent images respectively corresponding to images of particular colors and a position mark latent image representative of position information;
• a developing unit developing said latent images with developers of respective colors to thereby produce corresponding color images, and developing said position mark latent image to thereby produce a position mark;
• an intermediate transfer belt for causing the color images to be transferred thereto one above another and then transferred therefrom to a recording medium, and causing said position mark to be transferred thereto to form a position information portion;
• a position information detecting unit generating a detection signal on detecting said position information portion formed on said intermediate transfer belt;
• starting means for starting said photoconductive element in response to said detection signal fed from said position information detecting unit;
• and
• order determining means for effecting image formation with, at first, a developer of a color used to form said position information portion.

A color image forming apparatus comprising:

• a photoconductive element;
• latent image forming means for selectively forming on said photoconductive element latent images respectively corresponding to images of particular colors and a position mark latent image representative of position information;
• a developing unit developing said latent images with developers of respective colors to thereby produce corresponding color images, and developing said position mark latent image to thereby produce a position mark;
• an intermediate transfer belt for causing the color images to be transferred thereto one above another and then transferred therefrom to a recording medium, and causing said position mark to be transferred thereto to form a position information portion;
• a position information detecting unit generating a detection signal on detecting said position information portion formed on said intermediate transfer belt;
• starting means for starting said photoconductive element in response to said detection signal fed from said position information detecting unit;
• and
• wherein said position information detecting unit emits a beam greater in spot diameter than a beam for writing image data on said photoconductive element.

A color image forming apparatus comprising:

• a photoconductive element;
• latent image forming means for selectively forming on said photoconductive element latent images respectively corresponding to images of particular colors and a position mark latent image representative of position information;
• a developing unit developing said latent images with developers of respective colors to thereby produce corresponding color images, and developing said position mark latent image to thereby produce a position mark;
• an intermediate transfer belt for causing the color images to be transferred thereto one above another and then transferred therefrom to a recording medium, and causing said position mark to be transferred thereto to form a position information portion;
• a position information detecting unit generating a detection signal on detecting said position information portion formed on said intermediate transfer belt;
• starting means for starting said photoconductive element in response to said detection signal fed from said position information detecting unit;
• and
• wherein a beam incident to said position information detecting unit is smaller in spot diameter than a beam issuing from said position information detecting unit.

A color image forming apparatus comprising:

• a photoconductive element;
• latent image forming means for selectively forming on said photoconductive element latent images respectively corresponding to images of particular colors and a position mark latent image representative of position information;
• a developing unit developing said latent images with developers of respective colors to thereby produce corresponding color images, and developing said position mark latent image to thereby produce a position mark;
• an intermediate transfer belt for causing the color images to be transferred thereto one above another and then transferred therefrom to a recording medium, and causing said position mark to be transferred thereto to form a position information portion;
• a position information detecting unit generating a detection signal on detecting said position information portion formed on said intermediate transfer belt;
• starting means for starting said photoconductive element in response to said detection signal fed from said position information detecting unit;
• and
• control means for starting writing said position information portion before image data begins to be written and after said intermediate transfer belt has been fed to a position short of a position where said position information detecting unit is located.

A method of forming a color image formed on a photoconductive element, comprising the steps of:

• selectively forming on said photoconductive element latent images respectively corresponding to images of particular colors and a position mark latent image representative of position information;
• developing said latent images with developers of respective colors to thereby produce corresponding color images, and developing said position mark latent image to thereby produce a position mark;
• causing the color images to be transferred onto an intermediate transfer belt one above another and then transferred therefrom to a recording medium, and causing said position mark to be transferred thereto to form a position information portion;
• generating a detecting signal on detecting said position information portion formed on said intermediate transfer belt;
• and
• starting the operation for forming the latent images on said photoconductive element in response to said detection signal.