Image forming apparatus

An image forming apparatus, which has a plurality of image forming stations each comprising an image forming unit for forming an image, superimposes images of a plurality of colors formed in the plurality of image forming stations on a recording medium, said apparatus operable in a first image forming mode for forming images of a plurality of colors by at least two image forming stations from among the plurality of image forming stations, and a second image forming mode for forming monochromatic images by a single image forming station from among the plurality of image forming stations, comprising:

• a controller which controls formation of the monochromatic images by partially stopping the driving of the image forming units in the image forming stations except for the single image forming station used in the second image forming mode in accordance with switching to the second image forming mode during image formation in the first image forming mode.

An image forming apparatus, which has a plurality of image forming stations each comprising an image forming unit for forming an image, superimposes images of a plurality of colors formed by the plurality of image forming stations on a recording medium, said apparatus operable in a first image forming mode for forming images of a plurality of colors by at least two image forming stations from among the plurality of image forming stations, a second image forming mode for forming monochromatic images by a single image forming station from among the plurality of image forming stations, and a third image forming mode for driving the image forming unit in the single image forming station used in the second image forming mode, partially stopping the driving of the image forming units in the image forming stations except for the single image forming station used in the second image forming mode, and forming monochromatic images, comprising:

• a controller which forms monochromatic images in the third image forming mode up to a predetermined number of images and forms monochromatic images in the second image forming mode when the number of images exceeds the predetermined number in accordance with switching during forming images in the first image forming mode to the second image forming mode.

An image forming apparatus, which has a plurality of image forming stations each comprising an image forming unit for forming images, superimposes images of a plurality of colors formed by the plurality of image forming stations on a recording medium, said apparatus operable in a first image forming mode for forming images of a plurality of colors by at least two image forming stations from among the plurality of image forming stations, and a second image forming mode for forming monochromatic images by a single image forming station from among the plurality of image forming stations, comprising:

• a controller which controls formation of monochromatic images by partially stopping the driving of the image forming units in the image forming stations except for the single image forming station used in the second image forming mode for an image forming period and thereafter, driving the image forming units stopped in accordance with the switching during forming of images in the first image forming mode to the second image forming mode.

An image forming apparatus, which has a plurality of image forming stations each comprising an image forming unit for forming images, superimposes images of a plurality of colors formed by the plurality of image forming stations on a recording medium, said apparatus operable in a first image forming mode for forming images of a plurality of colors by at least two image forming stations from among the plurality of image forming stations, a second image forming mode for forming monochromatic images by a single image forming station from among the plurality of image forming stations, and a third image forming mode for driving the image forming unit in the single image forming station used in the second image forming mode, partially stopping the driving of the image forming units in the image forming stations except for the single image forming station used in the second image forming mode, and forming monochromatic images, comprising:

• a controller for forming monochromatic images in the third image forming mode up to a predetermined number of images in accordance with the switching during image formation in the first image forming mode to the second image forming mode.