Electrophotographic apparatus

An electrophotographic apparatus comprising a developing means for forming a toner image on a photosensitive body by forming a latent image combining exposed portions and non-exposed portions on said photosensitive body by exposing said charged photosensitive body using an exposing means, and developing said exposed portions by a developing agent having a magnetic carrier and a toner containing magnetite fine particles as main components using a first developing roller and a second developing roller rotated in directions opposite to each other and arranged along a moving direction of said photosensitive body;

• developing means for forming a toner image on said photosensitive body;
• and
• a cleaning means having a blade member for removing toner remaining on the photosensitive body after transferring said toner image to printing paper, said blade member being provided so as to push against a surface of said photosensitive body;
• wherein
• the moving direction of said first developing roller is opposite to the moving direction of said photosensitive body, and a circumferential speed ratio (S1=Vd1/Vp) of a circumferential speed (Vd1) of the first developing roller to a circumferential speed (vp) of the photosensitive body is restricted in a range of 0.5 to 2.5;
• the moving direction of said second developing roller is equal to the moving direction of said photosensitive body, and a circumferential speed ratio (S2=Vd2/Vp) of a circumferential speed (Vd2) of the second developing roller to a circumferential speed (Vp) of the photosensitive body is restricted in a range of 1.5 to 3.5;
• and
• said first developing roller and said second developing roller also have a funtion to remove unnecessary toner remaining on said photosensitive body in the relationship of said circumferential speed ratios.

An electrophotographic apparatus comprising:

• an organic photosensitive body having a film thickness of 20 to 60 .mu.m;
• charging means for charging said organic photosensitive body;
• exposing means for forming a latent image combining exposed portions and non-exposed portions on said photosensitive body by exposing said charged photosensitive body;
• developing means for developing said exposed portions using a first developing roller and a second developing roller rotated in directions opposite to each other and arranged along a moving direction of said photosensitive body, and a developing agent containing a toner to which is added any one of magnetic fine particles of 0.1 to 2 wt % for a toner surface and magnetic fine particles of 0.5 to 20 wt % inside the toner;
• cleaning means having a blade member for removing toner remaining on the photosensitive body after transferring a toner image to printing paper, provided so as to push onto a surface of said photosensitive body, wherein
• the moving direction of said first developing roller is opposite to the moving direction of a photosensitive body, a circumferential speed ratio (S1=Vd1/Vp) of a circumferential speed (Vd1) of the first developing roller to a circumferential speed (Vp) of the photosensitive body being restricted in a range of 0.5 to 2.5;
• the moving direction of said second developing roller being equal to the moving direction of said photosensitive body, a circumferential speed ratio (S2=Vd2/Vp) of a circumferential speed (Vd2) of the second developing roller to a circumferential speed (Vp) of the photosensitive body being restricted in a range of 1.5 to 3.5;
• a developing bias voltage applied to said first developing roller being restricted to approximately 35 to 70% of a latent image voltage of said non-exposed portions;
• a developing bias voltage applied to said second developing roller being restricted to a voltage higher than the developing bias voltage applied to said first developing roller;
• and
• a linear pressure of said blade member pushed so as to be in contact to the surface of said photosensitive body being restricted to 5 to 15 g/cm.sup.2.