Image forming apparatus

An image forming apparatus, comprising:

• a first image forming unit configured to form a first toner image;
• a second image forming unit configured to form a second toner image of a color different from a color of the first toner image;
• an intermediate transfer member to which the first toner image and the second toner image are transferred, and configured to convey the transferred first and second toner images to a sheet transfer position;
• a contact/separation unit configured to switch a mode between a first mode in which the intermediate transfer member is in contact with the first image forming unit disposed on a downstream side of the second image forming unit in a conveyance direction of the first and second toner images by the intermediate transfer member and the intermediate transfer member is separated from the second image forming unit, and a second mode in which the intermediate transfer member is in contact with the first image forming unit and the second image forming unit;
• and
• a controller configured to control an operation of he image forming apparatus,
• wherein, in a case where a first image, that is a monochrome image formed using the first image forming unit without using the second image forming unit, a second image, that is the monochrome image, and a third image, that is a color image formed using the first image forming unit and the second image forming unit, are formed in order on sheets, the controller controls the contact/separation unit to switch the mode from the first mode to the second mode after transfer of the first image to the intermediate transfer member is completed and before formation of the second image by the first image forming unit is started if a first image length that is a length of the first image in the conveyance direction is smaller than a predetermined length, and
• wherein, after the first image is transferred to the sheet, the controller controls the contact/separation unit to switch the mode from the first mode to the second mode if the first image length in the conveyance direction is greater than the predetermined length.