Developing device and process cartridge for an image forming apparatus

A developing device for developing a latent image formed on an image carrier with toner, comprising:

• a developer carrier, which faces said image carrier and accommodates a magnet therein, to support a developer made up of a toner and a magnetic carrier supporting said toner and convey said developer to a developing zone between said developer carrier and said image carrier,
• wherein an apparent coating ratio M of a surface of said developer carrier coated with said developer is, in a zone upstream of said developing zone in a direction of rotation of said developer carrier, expressed as:
• M=αA2+β(%),
• where α denotes a coefficient representative of the coating ratio, A2 denotes an amount of developer for a unit area, β denotes a value determined by a powder characteristic of said developer for an apparent coating ratio calculated with A2=0 and said coating ratio M is between 90% and 120%.

An image forming apparatus comprising:

• a photoconductive image carrier configured to allow a latent image to be formed thereon;
• a charger configured to uniformly charge said image carrier;
• a developing device configured to develop the latent image to thereby produce a toner image;
• and
• an image transferring device configured to transfer the toner image from said image carrier to a recording medium,
• wherein an apparent coating ratio M of a surface of a developer carrier included in said developing device and coated with said developer is, in a zone upstream of a developing zone in a direction of rotation of said developer carrier, expressed as:
• M=αA2+β(%),
• where a denotes a coefficient representative of the coating ratio, A2 denotes an amount of developer for a unit area, β denotes a value determined by a powder characteristic of a developer for an apparent coating ratio calculated with A2=0, and said coating ratio M is between 90% and 120%.

In a process cartridge removably mounted to a body of an image forming apparatus and comprising at least one of an image carrier, a charger, a developing device and a cleaning device, said developing device comprising:

• a photoconductive image carrier configured to allow a latent image to be formed thereon;
• a charger configured to uniformly charge said image carrier;
• a developing device configured to develop the latent image to thereby produce a toner image;
• and
• an image transferring device configured to transfer the toner image from said image carrier to a recording medium,
• wherein an apparent coating ratio M of a surface of a developer carrier included in said developing device and coated with said developer is, in a zone upstream of a developing zone in a direction of rotation of said developer carrier, expressed as:
• M=αA2+β(%),
• where α denotes a coefficient representative of the coating ratio, A2 denotes an amount of developer for a unit area, β denotes a value determined by a powder characteristic of a developer for an apparent coating ratio calculated with A2=0, and said coating ratio M is between 90% and 120%.