Patent ID: 8213835

Claim:
An image forming apparatus, comprising: a cylindrical image bearing member on which a toner image is to be formed; a transfer roller held in direct contact with a surface of the image bearing member for transferring a toner image on the image bearing member to one side of a transfer medium by applying a voltage having a polarity opposite to that of the toner image formed on the image bearing member from the other side of the transfer medium; a drive gear mounted coaxially with the image bearing member for rotating the image bearing member about an axis; a transfer gear mounted coaxially with the transfer roller and meshed with the drive gear to rotate the transfer roller about an axis; a driving mechanism for respectively rotating the transfer roller and the image bearing member with a specified speed difference; and a biasing member for biasing the transfer roller toward the surface of the image bearing member, wherein: the drive gear includes a first drive gear mounted on a first end portion of the image bearing member and a second drive gear mounted on a second end portion of the image bearing member opposite to the first end portion of the image bearing member, the transfer gear includes a first transfer gear mounted on a first end portion of the transfer roller and meshed with the first drive gear and a second transfer gear mounted on a second end portion of the transfer roller opposite to the first end portion of the transfer roller and meshed with the second drive gear, the first and second drive gears are mounted respectively on the first and second end portions of the image bearing member such that a gear pitch of the first drive gear and that of the second drive gear are shifted by a half phase, and the first and second transfer gears respectively are mounted on the first and second end portions to correspond to the half-phase shift.