Abstract: A developing unit using a bicomponent developer and capable of collecting only carrier included in the developer and deteriorated due to aging while recycling toner, and a method of collecting the developer from the developing unit. The developing unit separate the developer into toner and carrier before the collection of the developer.

Abstract: In an image forming apparatus, a toner collection mode is executed when a series of image formation modes ends and when the image formation mode is continuously repeated a preselected number of times. A toner image sensing mode for sensing a reflection density from a reference toner image is executed every time the image formation mode is repeated a preselected number of times. The apparatus is capable of surely and efficiently removing toner left on an image carrier after image transfer, and collecting the reference toner image with a developing unit. The reference toner image is prevented from contaminating an image transferring unit and a cleaning unit.

Abstract: In an image forming apparatus, during the course of recording, a cleaning roller is rotated together with an image carrier. The roller frictionally charges toner left on the image carrier after image transfer to the same polarity. A cleaning member electrostatically collects the charged toner. At the same time, a voltage is applied to the cleaning member by a voltage applying device in order to cause it to attract the charged toner, thereby cleaning the image carrier. Hence, even when the toner remaining on image carrier is charged partly to the positive polarity and partly to the negative polarity, the toner can be entirely transferred to the cleaning member by a simple construction.

Abstract: A cartridge for replenishing a two-ingredient developer to an image forming apparatus, and a developer replenishing device using it are disclosed. The cartridge is made up of two containers each storing a content of particular kind. One of the containers has an annular portion and a bore formed at the center by the annular portion. The other container has a cylindrical configuration and coaxially mates with the above container to form a single unit. Coaxial openings are respectively formed in the containers. Spiral grooves inclined in opposite directions to each other are respectively formed on the inner peripheries of the containers.