US 6,324,354 B1 · Image forming process and an image forming apparatus

Abstract

The present invention relates to an image forming process and an image forming apparatus, which have a refresh means which refreshes the developing sleeve by allowing the toner on the developing sleeve to jump toward the photoreceptor drum when transfer to recording medium is not done. Refresh is performed by applying an AC bias between the photoreceptor drum and the developing sleeve. The number of dots of latent image corresponding to actual image pattern is counted and the ratio of this number of dots to the number of dots corresponding to full black original image is defined as print rate, and cumulative average print rate is calculated each time when a page or a predetermined number of pages is printed. When the average print rate falls short of proper print rate, refresh is performed. It is suitable to set several proper print rate, and the duration of application of the AC bias is varied according to the average print rate. It is also effective to apply AC bias for refresh higher in effective voltage than applied for developing. It is also effective to prevent “fog” by applying transfer reverse bias to transfer part until the toner on the photoreceptor passes the transfer part and transfer positive bias after cleaning of the toner on the photoreceptor is finished. Generally, when an image forming apparatus is used for an extended period of time or when low print rate original image is copied in large quantity, deterioration such as reduction in print density and “fog” is liable to occur. According to the present invention, even if images of low print rate is copied in large quantity, deterioration does not occur.

Claims78

Dependent claims

An image forming process, in an image forming apparatus having a toner carrier which faces an electrostatic latent image carrier and carries toner to the developing zone thereon, provided with a refresh process in which an alternating electric field for refresh is applied between said electrostatic latent image carrier and said toner carrier to refresh the surface of said toner carrier by carrying the toner on said toner carrier to said electrostatic latent image carrier side when the image is not transferred to a recording medium, wherein:

said refresh process is performed in a case where print rate of image falls short of proper print rate.

An image forming apparatus provided with a toner carrier which faces an electrostatic latent image carrier and carries toner to the developing zone thereon, and performs refresh of the toner on said toner carrier when image transfer to a recording medium is not executed, further comprising

a counting means for counting the number of pages of the recording medium;
an average print rate processing means for obtaining average print rate by numerically processing print rate corresponding to image pattern;
and
a refresh means which applies an alternating electric field for refresh between said electrostatic latent image carrier and said toner carrier to carry toner on the said toner carrier to the said electrostatic latent image carrier side when said print rate falls short of proper print rate;
and
said refresh means is actuated in a case where the average print rate calculated by said average print rate processing means falls short of proper print rate when proper number of pages is counted.

3 more elements

an average print rate processing means which computes average print rate corresponding to image pattern every time image formation on recording medium is performed;
a rotation control means to control rotation of said electrostatic latent image carrier and said toner carrier;
a refresh means which applies an alternating electric field for refresh between said electrostatic latent image carrier and said toner carrier to carry toner on said toner carrier, which toner exists on the part thereof facing said electrostatic latent image carrier, to said electrostatic latent image carrier side, while said electrostatic latent image carrier and said toner carrier are stopped of their rotations, when said print rate falls short of proper print rate;
and
refresh of the surface of said toner carrier is performed, rotating said electrostatic latent image carrier after said alternating electric field for refresh is applied.

2 more elements

an average print rate processing means which computes average print rate corresponding to image pattern every time image formation on recording medium is performed;
a rotation control means to control rotation of said electrostatic latent image carrier and said toner carrier;
a memory to memorize said average print rate when it falls short of proper print rate;
a refresh means which applies an alternating electric field for refresh between said electrostatic latent image carrier and said toner carrier to carry toner on said toner carrier, which toner exists on the part thereof facing said electrostatic latent image carrier, to said electrostatic latent image carrier side, when next printing is directed with reference to the content of said memory;
and
printing is started after refresh of the surface of said toner carrier, rotating said electrostatic latent image carrier after said alternating electric field is applied.

3 more elements

Dependencies are inferred from the claim text.

Image forming process and an image forming apparatus

Life of this patent

Image forming process and an image forming apparatus

Life of this patent

Abstract

Claims78