Image forming apparatus having a plurality of image forming modes

An image forming apparatus for forming an image on a recording material, comprising:

• a recording material conveying member which is movable while carrying thereon the recording material;
• a plurality of image forming portions provided along a movement direction of said recording material conveying member, wherein each of said image forming portions includes a rotatable image bearing member, a rotatable charging roller for electrically charging uniformly a surface of said image bearing member in contact with said image bearing member, and developing means for developing an electrostatic latent image formed on said image bearing member into a developer image by reverse development;
• a plurality of transfer means, provided correspondingly to said image bearing members of said image forming portions, respectively, each for transferring the developer image from said image bearing member onto the recording material carried and conveyed by said recording material conveying member;
• a plurality of cleaning means, provided correspondingly to said image bearing members of said image forming portions, respectively, where each of said cleaning means includes a cleaning blade and is configured to remove a developer remaining on said image bearing member after the developer image is transferred from said image bearing member onto the recording material;
• and
• control means for executing, by mode selection, an operation in a multi-color image forming mode in which the developer images of a plurality of colors are superposed on the recording material carried and conveyed by said recording material conveying member by image forming operations of said image forming portions to effect multi-color image formation and an operation in a single-color image forming mode in which the developer image of a single color is transferred onto the recording material carried and conveyed by said recording material conveying member by an image forming operation of one of said image forming portions to effect single-color image formation,
• wherein said control means executes, during the execution of the operation in the single-color image forming mode, a sequence in which the developer image is formed on said image bearing member at said image forming portion which does not operate for the image formation, and a bias voltage for charging the developer for the developer image to an opposite polarity to a normal charge polarity of the developer is applied to said first transfer means to permit the developer charged to the opposite polarity to reach said cleaning means.

An image forming apparatus for forming an image on a recording material, comprising:

• a plurality of image forming portions for forming images, wherein each of said image forming portions includes an image bearing member, a charging member, for electrically charging a surface of said image bearing member, in contact with said image bearing member, and developing means for developing a latent image formed on said image bearing member into a developer image;
• a plurality of transfer means provided correspondingly to said image bearing members of said image forming portions;
• a plurality of cleaning means provided correspondingly to said image bearing members, where each of said cleaning means includes a cleaning blade which is in contact with said image bearing member and is configured to remove a developer remaining on said image bearing member after the developer image is transferred from said image bearing member;
• and
• control means for executing, by mode selection, an operation in a multi-color image forming mode in which developer images of a plurality of colors are formed by image forming operations to effect multi-color image formation and an operation in a single-color image forming mode in which the developer image of a single color is transferred by an image forming operation of one of said image forming portions to effect single-color image formation,
• wherein said control means executes, during or after the execution of the operation in the single-color image forming mode, a sequence in which the developer image is formed on said image bearing member at said image forming portion which does not operate for the image formation, and a bias voltage for charging the developer for the developer image to an opposite polarity to a normal charge polarity of the developer is applied to said transfer means to permit the developer charged to the opposite polarity to reach said cleaning means.

An image forming apparatus for forming an image on a recording material, comprising:

• a plurality of image forming portions for forming images, wherein each of said image forming portions includes an image bearing member, a charging member, for electrically charging a surface of said image bearing member, in contact with said image bearing member, and developing means for developing a latent image formed on said image bearing member into a developer image;
• transfer means for transferring the developer image from said image bearing member;
• cleaning means for removing the developer remaining on said image bearing member after the developer image is transferred from said image bearing member, where said cleaning means includes a cleaning blade which is in contact with said image bearing member;
• and
• control means for executing at least an operation in a single-color image forming mode in which a developer image of a single color is formed by an image forming operation of one of said image forming portions to effect single-color image formation,
• wherein said control means executes, during or after the execution of the single-color image forming mode operation, a sequence in which the developer image is formed on said image bearing member at said image forming portion which does not operate for the image formation, and a bias voltage for charging the developer for the developer image to an opposite polarity to a normal charge polarity of the developer is applied to said transfer means to permit the developer charged to the opposite polarity to reach said cleaning means.