Transfer roller with voltage polarity control

An image forming apparatus, comprising:

• an image bearing member movable along an endless path;
• image forming means for forming a toner image on said image bearing member, said image forming means including charging means for charging said image bearing member and developing means for developing an image on said image bearing member with toner;
• transfer means for transferring the toner image from said image bearing member onto a transfer material at a transfer position, and transfer means having a transfer member contactable to a backside of the transfer material, the transfer member being supplied with a voltage of the same polarity as the toner during a developing operation to transfer the toner from said transfer member to said image bearing member, when the transfer material is absent at the transfer position;
• means for causing a region of said image bearing member to have a potential of the polarity which is the same as the charging polarity of said charging means before said region reaches the transfer position, so that said region does not have a polarity opposite from the charging polarity of said charging means after said region passes through the transfer position, wherein said transfer member is supplied with the voltage when said region is at the transfer position.

An image forming apparatus, comprising:

• an image bearing member movable along an endless path;
• image forming means for forming a toner image on said image bearing member, said image forming means including charging means for charging said image bearing member;
• a member contactable to said image bearing member, said contactable member being supplied with a voltage having the same polarity as the toner during a developing operation to transfer the toner from said contactable member to said image bearing member;
• and
• means for causing a region of said image bearing member to have a potential of a polarity which is the same as the charging polarity of said charging means before said region reaches a position at which said region contacts said contactable member so that said region does not have a polarity opposite from the charging polarity of said charging means after said region passes through said position.

An image forming apparatus, comprising:

• an image bearing member movable along an endless path;
• image forming means for forming a toner image on said image bearing member, said image forming means including charging means for charging said image bearing member and developing means for developing an image on said image bearing member;
• transfer means for transferring the toner image from said image bearing member to a transfer material at a transfer position, said transfer means including a transfer member contactable to a backside of the transfer material, said transfer member being supplied with a voltage having a polarity which is opposite from charging polarity of said charging means to transfer the toner from said transfer member to said image bearing member when the transfer material is absent at the transfer position;
• and
• means for causing a region of said image bearing member to have a potential of the same polarity as the charging polarity of said charging means before said region is charged by said charging means for image formation, wherein said charging means charges said region and said image forming means forms an image on said region after said region has a potential of the same polarity as the charging polarity of said charging means.

An image forming apparatus, comprising:

• an image bearing member movable along an endless path;
• image forming means for forming a toner image on said image bearing member, said image forming means including charging means for charging said image bearing member and developing means for developing an image on said image bearing member with toner;
• transfer means for transferring the toner image from said image bearing ember onto a transfer material at a transfer position, said transfer means having a transfer member contactable to a backside of the transfer material, said transfer member being supplied with a voltage of a polarity which is opposite from a charging polarity of said charging means to transfer the toner from said transfer member to said image bearing member, when the transfer material is absent at the transfer position;
• and
• means for causing a region of said image bearing member to have a potential of a polarity which is the same as the charging polarity of said charging means before said region reaches the transfer position, so that said region does not have a polarity opposite from the charging polarity of said charging means after said region passes through the transfer position, wherein said region is at the transfer position when said voltage is supplied to said transfer member.

An image forming apparatus, comprising:

• an image bearing member movable along an endless path;
• image forming means for forming a toner image on said image bearing member, said image forming means including charging means for charging said image bearing member;
• a member contactable to said image bearing member, said contactable member being supplied with a voltage having a polarity which is opposite from the charging polarity of said charging means to transfer the toner from said contactable member to said image bearing member;
• and
• means for causing a region of said image bearing member which a potential of a polarity which is the same as the charging polarity of said charging means before said region reaches a position of contact with said contactable member, so that said region does not have a polarity opposite from the charging polarity of said charging means after said region passes through said position.