Apparatus and method for cleaning a transfer device of an image forming apparatus

An image forming apparatus, comprising:

• an image carrier for carrying a toner image;
• a charging device which charges said image carrier;
• a transferring device which is in direct contact with said image carrier when a sheet of paper is not at a nip between said image carrier and said transferring device;
• a power source which applies a bias voltage to said transferring device;
• and
• a control device which controls said power source so as to apply a first bias voltage having a first polarity as said bias voltage to said transferring device in order to transfer material having said first polarity from said transferring device to said image carrier, switching a polarity of said bias voltage and applying a second bias voltage having a second polarity which is opposite to the first polarity to the transferring device in order to transfer material having said second polarity from said transferring device to said image carrier, and controlling the charging device to charge said image carrier when at least one of said first and second bias voltages are being applied to the transferring device,
• wherein the control device controls said charging device to charge the image carrier only when one of the first and second bias voltages are being applied to the transferring device.

A method of cleaning a transferring device of an image forming apparatus, comprising the steps of:

• applying a first bias voltage having a first polarity to the transferring device in order to transfer material having said first polarity from said transferring device to an image carrier which contacts the transferring device;
• applying a second bias having a second polarity which is opposite to the first polarity in order to transfer material having said second polarity from said transferring device to said image carrier;
• and
• charging said image carrier when at least one of said first and second bias voltages are being applied to the transferring device,
• wherein the step of charging the image carrier is performed only when one of the first and second bias voltage are being applied to the transferring device.

An image forming apparatus, comprising:

• an image carrier for carrying a toner image;
• a charging device which charges said image carrier;
• a transferring device which is in direct contact with said image carrier when a sheet of paper is not at a nip between said image carrier and said transferring device;
• a power source which applies a bias voltage to said transferring device;
• and
• a control device which controls said power source so as to apply a first bias voltage having a first polarity as said bias voltage to said transferring device for more than five rotations of said transferring device in order to transfer material having said first polarity from said transferring device to said image carrier, and switching a polarity of said bias voltage and applying a second bias voltage as said bias voltage to said transferring device, said second bias voltage having a second polarity which is opposite to the first polarity in order to transfer material having said second polarity from said transferring device to said image forming device.