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

An apparatus for transferring a toner image on an image carrier to a sheet, comprising:

• a charging device which charges said image carrier;
• a first power source which applies a charging voltage to said charging device;
• a transferring device which is in direct contact with said image carrier when said sheet is not at a nip between said image carrier and said transferring device;
• a second power source which applies a transferring voltage to said transferring device;
• and
• at least one control board which controls said first and second power sources so as to apply the charging voltage to said charging device and the transferring voltage to said transferring device when said transferring device is in direct contact with said image carrier,
• wherein said second power source is switched over between a negative polarity and a positive polarity,
• wherein said second power source is switched over from the negative polarity to the positive polarity when said sheet is not at the nip between said image carrier and said transferring device, and
• wherein an absolute value of the transferring voltage outputted from said second power source is greater than an absolute value of the charging voltage outputted from said first power source.

An apparatus for transferring a toner image on an image carrier to a sheet, comprising:

• a charging device which charges said image carrier;
• a first power source which applies a charging voltage to said charging device;
• a transferring device which is in direct contact with said image carrier when said sheet is not at a nip between said image carrier and said transferring device;
• a second power source which applies a transferring voltage to said transferring device;
• and
• at least one control board which controls said first and second power sources so as to apply the charging voltage to said charging device and the transferring voltage to said transferring device when said transferring device is in direct contact with said image carrier,
• wherein said transferring voltage has a polarity which is opposite to a polarity of said toner image,
• said apparatus further comprising:
• a paper separating electrode which separates the sheet from said image carrier;
• and
• a power source which is connected to said paper separating electrode and applies a separating voltage to said paper separating electrode,
• wherein said at least one control board turns the separating voltage on when the sheet is not at a nip between said image carrier and said transferring device.

A method for transferring a toner image on an image carrier to a sheet, comprising the steps of:

• applying a first voltage to said image carrier when said sheet is not at a nip between said image carrier and a contact transferring device;
• and
• applying a second voltage to said contact transferring device during a time period between consecutive image forming operations when the contact transferring device is in direct contact with said image carrier when said sheet is not at the nip,
• wherein said second voltage is constant over a period of time during which a first image is formed, no image is formed, and a second image is formed.

A method for transferring a toner image on an image carrier to a sheet, comprising the steps of:

• applying a first voltage to said image carrier when said sheet is not at a nip between said image carrier and a contact transferring device;
• and
• applying a second voltage to said contact transferring device which is in direct contact with said image carrier when said sheet is not at the nip,
• wherein said second voltage is switched over between a negative polarity and a positive polarity,
• wherein said second voltage is switched over from the negative polarity to the positive polarity when said sheet is not at the nip between said image carrier and said contact transferring device, and
• wherein an absolute value of said second voltage is greater than an absolute value of said first voltage.

A method for transferring a toner image on an image carrier to a sheet, comprising the steps of:

• applying a first voltage to said image carrier when said sheet is not at a nip between said image carrier and a contact transferring device;
• and
• applying a second voltage to said contact transferring device which is in direct contact with said image carrier when said sheet is not at the nip,
• wherein said second voltage has a polarity which is opposite to a polarity of said toner image,
• said method further comprising the step of:
• applying a separating voltage to a paper separating electrode which separates the sheet from said image carrier when said sheet is not at the nip between said image carrier and said contact transferring device.

An apparatus for transferring a toner image on an image carrier to a sheet, comprising:

• a charging device which charges said image carrier;
• a first power source which applies a charging voltage to said charging device;
• a transferring device which is in direct contact with said image carrier when said sheet is not at a nip between said image carrier and said transferring device;
• a second power source which applies a transferring voltage to said transferring device;
• and
• at least one control board which controls said second power source so that said second power source is switched over between a negative polarity and a positive polarity.

An apparatus for transferring a toner image on an image carrier to a sheet, comprising:

• a charging device which charges said image carrier;
• a first power source which applies a charging voltage to said charging device;
• a transferring device which is in direct contact with said image carrier when said sheet is not at a nip between said image carrier and said transferring device;
• a second power source which applies a transferring voltage to said transferring device;
• at least one control board which controls said first and second power sources;
• a paper separating electrode which separates the sheet from said image carrier;
• and
• a power source which is connected to said paper separating electrode and applies a separating voltage to said paper separating electrode,
• wherein said at least one control board turns the separating voltage on when the sheet is not at a nip between said image carrier and said transferring device.

A method for transferring a toner image on an image carrier to a sheet, comprising the steps of:

• applying a first voltage to said image carrier when said sheet is not at a nip between said image carrier and a contact transferring device;
• and
• applying a second voltage to said contact transferring device which is in direct contact with said image carrier when said sheet is not at the nip,
• wherein said second voltage is switched over between a negative polarity and a positive polarity.

A method for transferring a toner image on an image carrier to a sheet, comprising the steps of:

• applying a first voltage to said image carrier when said sheet is not at a nip between said image carrier and a contact transferring device;
• applying a second voltage to said contact transferring device which is in direct contact with said image carrier when said sheet is not at the nip;
• and
• applying a separating voltage to a paper separating electrode which separates the sheet from said image carrier when said sheet is not at the nip between said image carrier and said contact transferring device.