Patent ID: 8824906

Claim:
An image forming apparatus, comprising: an image bearing member for bearing an electrostatic latent image and a toner image; a developer bearing member for bearing a developer layer containing toner particles and carrier particles while rotating in a predetermined direction; a toner bearing member for receiving the toner particles from the developer layer and carrying a toner layer while rotating in contact with the developer layer and supplying the toner particles of the toner layer to the image bearing member to develop the electrostatic latent image; a driving mechanism for driving and rotating the image bearing member, the developer bearing member and the toner bearing member; a sheet size discriminator for discriminating whether a sheet to which the toner image is to be transferred is a standard sized sheet or a long sheet, the size of which in a sub scanning direction is longer than the standard sized sheet; a first controller for controlling a linear velocity D of the image bearing member, a linear velocity M of the developer bearing member and a linear velocity S of the toner bearing member by controlling the driving mechanism; and a second controller for controlling the thickness of the toner layer carried on the toner bearing member; wherein: the first controller sets the linear velocity D at a predetermined first velocity and sets the linear velocity S so that S/D, which is a ratio of the linear velocity S to the linear velocity D, has a predetermined first value and the second controller sets the thickness of the toner layer carried on the toner bearing member at a predetermined first layer thickness when the sheet size discriminator discriminates that the sheet to which the toner image is to be transferred is the standard sized sheet; and the first controller sets the linear velocity D at a second velocity slower than the predetermined first velocity and sets the linear velocity S so that the S/D has a second value larger than the predetermined first value and the second controller sets the thickness of the toner layer at a second layer thickness smaller than the predetermined first layer thickness when the sheet size discriminator discriminates that the sheet to which the toner image is to be transferred is the long sheet.