Conductive roller transfer device with improved transfer efficiency and pollution control

A toner image transferring device for electrostatically transferring a charged toner image electrostatically held by a toner image carrying body means to a sheet or paper, which comprises:

• a conductive elastic transfer roller means disposed in contact with said toner image carrying body means to form a nip therebetween for passing the sheet or paper;
• and
• an electric source means for selectively applying a first electric energy and a second electric energy to said conductive elastic transfer roller means, said first electric energy giving the sheet or paper an electric charge having a polarity opposite to that of a charge of the toner image, during passage of the sheet or paper through the nip between said toner image carrying body means and said conductive elastic transfer roller means, whereby the charged toner image can be transferred from said toner image carrying body means to the sheet or paper, said second electric energy giving said conductive elastic transfer roller means an electric charge having the same polarity as the charge of the toner image, whereby a toner pollution of said conductive elastic transfer roller means can be electrostatically removed therefrom,
• wherein said conductive elastic transfer roller means being formed of a conductive foam rubber material such that pore openings appear over a surface of said conductive elastic transfer roller means, whereby a residual part of the toner pollution of said conductive elastic transfer roll means can leave no stain on a rear surface of the sheet or paper during the passage of the sheet or paper through the nip between said toner image carrying body means and said conductive elastic transfer roller means, and wherein said electric source means includes a constant current source having a substantially constant current output as said first electric energy, and a constant voltage source having a substantially constant voltage output as said second electric energy.

An electrophotographic recording apparatus comprising:

• a photosensitive body means on which an electrically charged area can be produced;
• an optical writing means for optically writing a latent image on the charged area of said photosensitive body means;
• a toner developing means for electrostatically developing said latent image with an electrically charged toner to form a charged toner image thereon;
• a conductive elastic transfer roller means disposed in contact with said photosensitive body means to form a nip therebetween for passing a sheet or paper;
• and
• an electric source means for selectively applying a first electric energy and a second electric energy to said conductive elastic transfer roller means, said first electric energy giving the sheet or paper an electric charge having a polarity opposite to that of a charge of the toner image, during passage of the sheet or paper through the nip between said photosensitive body means and said conductive elastic transfer roller means, whereby the charged toner image can be transferred from said photosensitive body means to the sheet or paper, said second electric energy giving said conductive elastic transfer roller means an electric charge having the same polarity as the charge of the toner image, whereby a toner pollution of said conductive elastic transfer roller means can be electrostatically removed therefrom,
• wherein an electric potential of said photosensitive body means is maintained at substantially zero by said optical writing means during the application of said second electric energy to said conductive elastic transfer roller means for the removal of the toner pollution therefrom.