Image forming apparatus and control method therefor

An image forming apparatus that forms an image on a sheet, the apparatus comprising:

• a plurality of image forming stations which form toner images;
• and
• a control unit adapted to control a first image forming station of said plurality of image forming stations, which is not used for forming an image on a sheet, to perform an adjustment processing operation for said first image forming station while a second image forming station of said plurality of image forming stations is used for forming an image on a sheet,
• wherein at least said first image forming station of said plurality of image forming station includes an image carrier which carries a toner image, and a sensor which reads a toner pattern on said image carrier, and
• wherein the adjustment processing operation includes an operation to form a toner pattern on said image carrier of said first image forming station at a predetermined condition and to read the toner pattern by said sensor of said first image forming station in order to adjust a parameter of said first image forming station.

An image forming apparatus that forms an image on a sheet, the apparatus comprising:

• a plurality of image forming stations which form toner images;
• and
• a control unit adapted to control a first image forming station of said plurality of image forming stations, which is not used for forming an image on a sheet, to perform an adjustment processing operation for said first image forming station while a second image forming station of said plurality of image forming stations is used for forming an image on a sheet,
• wherein the adjustment processing operation includes an operation to adjust at least one of a toner supply amount and a transfer voltage in said first image forming station.