Patent ID: 8626032

Claim:
An image forming apparatus comprising: an image carrier that rotates; an electrostatic latent image forming unit that sequentially forms electrostatic latent images corresponding to a plurality of colors on the image carrier; a developing device that includes a rotating body that rotates and stops, a plurality of developing units which are arranged on the rotating body, each of which stores therein a developer containing a carrier and a toner corresponding to one of the plurality of colors and comprises a developer carrying member on which the developer is carried, the rotating body rotates from a first waiting position to a developing position and from the developing position to a second waiting position and stops at the first waiting position, the developing position, and the second waiting position, each of the developer carrying members supplying the toner corresponding to one of the plurality of colors to the electrostatic latent image corresponding to the one of plurality of colors at the developing position at which the image carrier and the developer carrying member oppose each other; an intermediate transfer body that rotates; a first transfer unit that performs a first transfer operation for sequentially transferring toner images of the corresponding colors developed on the image carrier onto the intermediate transfer body at a first transfer position at which the image carrier and the intermediate transfer body oppose each other; a second transfer unit that performs a second transfer operation for simultaneously transferring the toner images of the corresponding colors, which have been transferred onto the intermediate transfer body, onto a recording material which is being transported; a supply unit that supplies a bias to the developer carrying member; and a setting unit that sets the bias to a first condition corresponding to a developing bias to develop the electrostatic latent image corresponding to the one of plurality of colors on the image carrier with the toner corresponding to the one of the plurality of colors at least while the electrostatic latent image corresponding to the one of plurality of colors is being located at the developing position, and that sets the bias to a second condition to suppress transferring of the toner in another one of the plurality of developing units to the image carrier after the rotating body starts rotating from the first waiting position and before the rotating body stops rotating and locates the another one of plurality of developing units at the developing position, wherein: the supply unit also supplies an alternating current voltage as the developing bias; and the setting unit sets a peak-to-peak value of the alternating current voltage under the second condition to be greater than a peak-to-peak value of the alternating current voltage under the first condition.