US Patent 7428400 Primary transfer unit of image forming apparatus

A primary transfer unit includes transfer units for performing a toner transfer from image carriers onto a transfer belt. Each of the transfer units is formed with a metallic roller. The metallic roller is arranged so as to satisfy θ1<θ2, where an angle of the endless belt with respect to a tangent to the image carrier, on a side upstream of rotation of the endless belt to a transfer nip region where the image carrier and the endless belt are in contact is θ1, and an angle of the endless belt with respect to the tangent, on a side downstream of rotation of the endless belt to the transfer nip region is θ2.