Image forming apparatus having control structure for cleaning the transfer device

An image forming apparatus, comprising:

• an image carrier for forming thereon an electrostatic latent image corresponding to image information;
• a developing device for developing said electrostatic latent image formed on the surface of said image carrier to thereby form a toner image;
• a transfer roller contactable with said image carrier through a transfer sheet being fed for transferring said toner image carried on said image carrier to said transfer sheet;
• contacting and separating means for contacting said transfer roller with said image carrier and separating said transfer roller from said image carrier in accordance with a signal from a transfer sheet detect sensor;
• a cleaning member contactable with said transfer roller at a position where said transfer roller is separated from said image carrier by said contacting and separating means;
• and,
• transfer roller rotation speed control means for increasing the rotation speed of said transfer roller when said transfer roller is in contact with said cleaning member at the position thereof separated from said image carrier over the rotation speed of said transfer roller when said transfer roller is in contact with said image carrier.

An image forming apparatus, comprising:

• an image carrier for forming thereon an electrostatic latent image corresponding to image information;
• a developing device for developing said electrostatic latent image formed on the surface of said image carrier to thereby form a toner image;
• and,
• an intermediate transfer member for transferring primarily said toner image formed on the surface of said image carrier, the primary transfer being repeatedly performed on said intermediate transfer member for each of a plurality of colors to thereby superimpose toner images of a plurality of colors on top of each other on said intermediate transfer member and, after then, said color toner images of a plurality of colors being transferred secondarily to a transfer sheet as a whole;
• a secondary transfer roller contactable with said intermediate transfer member through said transfer sheet for transferring secondarily said color toner image carried on said intermediate transfer member to said transfer sheet;
• a registration roller for deciding the supply timing of said transfer sheet being supplied into between said intermediate transfer member and said secondary transfer roller and also for feeding said transfer sheet to a tucking point provided on the surface of said intermediate transfer member;
• a transfer sheet detect sensor disposed downstream of said tucking point in the feeding direction of said transfer sheet and upstream of a point of contact at which said intermediate transfer member and said secondary transfer roller are contacted with each other;
• and,
• a contacting and separating means, when said transfer sheet is detected by said transfer sheet detect sensor, for bringing said secondary transfer roller into contact with said intermediate transfer member.

An image forming apparatus, comprising:

• an image carrier for forming thereon an electrostatic latent image corresponding to image information;
• a developing device for developing said electrostatic latent image formed on the surface of said image carrier to thereby form a toner image;
• an intermediate transfer member for transferring primarily said toner image formed on the surface of said image carrier, the primary transfer being repeatedly performed on said intermediate transfer member for each of a plurality of colors to thereby superimpose toner images of a plurality of colors on top of each other on said intermediate transfer member and, after then, said color toner images of a plurality of colors being transferred secondarily to a transfer sheet as a whole;
• a secondary transfer roller contactable with said intermediate transfer member through said transfer sheet for transferring secondarily said color toner image carried on said intermediate transfer member to said transfer sheet;
• contacting and separating means for contacting and separating said secondary transfer roller with respect to said intermediate transfer member in accordance with a signal from a transfer sheet detect sensor;
• a cleaning member contactable with said secondary transfer roller at a position thereof where said secondary transfer roller is separated from said intermediate transfer member by said contacting and separating means;
• and
• secondary transfer roller rotation speed control means for increasing the rotation speed of said secondary transfer roller when said secondary transfer roller is in contact with said cleaning member at the position thereof separated from said intermediate transfer member over the rotation speed of said secondary transfer roller when said secondary transfer roller is in contact with said intermediate transfer member.