Image forming apparatus employing touchdown developing method

An image forming apparatus, comprising:

• an image carrier including a circumferential surface configured to carry an electrostatic latent image and a toner image thereon;
• a developer carrier including a circumferential surface configured to carry a developer layer containing toner, an additive, and carriers thereon;
• a toner carrier including a circumferential surface configured to come into contact with the developer layer and to carry a toner layer by receiving toner from the developer layer so as to supply toner of the toner layer to the image carrier for developing the electrostatic latent image;
• a bias voltage control unit configured to apply a bias voltage to the image carrier, the developer carrier, and the toner carrier, and to control the bias voltages;
• and
• a detection unit configured to electrically detect a toner adhesion condition with respect to the circumferential surface of the toner carrier, wherein the bias voltage control unit changes bias voltage setting from an ordinary developing mode to a toner removing mode when the detection unit detects toner adhesion in excess of a threshold value, and
• in the toner removing mode, the bias voltage control unit sets the bias voltage to be applied to the image carrier, the developer carrier, and the toner carrier in such a manner that only the additive remains on the circumferential surface of the toner carrier, and the developer layer carried on the developer carrier comes into contact with the circumferential surface of the toner carrier with a large force, as compared with the ordinary developing mode.