Patent ID: 8682190

Claim:
An image forming apparatus, comprising: a photosensitive drum that has a drum surface on which a toner image is formed; a transfer member that forms, with the drum surface, a nip part through which a sheet passes while conveyed, and sequentially transfers onto the sheet in the nip part the toner image on the drum surface from a conveying direction leading end side of the sheet; a first application unit that selectively applies to the transfer member a fixed first forward bias, a variable second forward bias, and a reverse bias having a polarity opposite to polarities of the first forward bias and the second forward bias; a second application unit that applies to the drum surface a drum bias having a polarity opposite to polarities of the first and second forward biases; and a bias controller that controls the first application unit and the second application unit, and has a state acquiring unit for acquiring state information and a setting unit for setting the second forward bias in accordance with the state information, wherein the bias controller, while controlling the second application unit to apply the drum bias to the drum surface, first, controls the first application unit to apply the reverse bias or no bias to the transfer member, when a first region, which is located in a conveying direction at a farthest leading end of the sheet and to which the toner image is not transferred, passes through the nip part, then controls the first application unit to apply the first forward bias to the transfer member when a conveying direction leading end part of a second region begins to pass through the nip part, this second region being a region which is located on a rear end side of the first region in a conveying direction of the sheet and to which the toner image is transferred, and then controls the first application unit to apply the second forward bias to the transfer member when a third region, which is located on a further rear end side than the second region in the conveying direction of the sheet and to which the toner image is transferred, passes through the nip part, and wherein the first forward bias is set at a predetermined value or above regardless of the state information, and increases a potential of the transfer member to a level at which the toner image is transferred in the second region when the second region passes through the nip part, and the second forward bias is set in accordance with the state information.