Patent ID: 7991315

Claim:
An image forming apparatus comprising: a developing apparatus for developing an electrostatic latent image formed on an image bearing member with a developer, the developing apparatus including a developer carrying member for carrying the developer to develop the electrostatic latent image with the developer and a developer supplying member having a foam layer into which the developer can enter for supplying the developer to the developer carrying member, the developer carrying member having a core electrode for rotatably supporting the developer carrying member, and the developer supplying member having a core electrode for rotatably supporting the developer supplying member; and a detector for detecting information relating to capacitance between the core electrode of the developer carrying member and the core electrode of the developer supplying member by detecting a voltage induced from the core electrode of the developer carrying member when the alternating bias is applied to the core electrode of the developer supplying member, wherein a surface aeration amount L (liter/minute) of the developer supplying member satisfies 1.8≦L when the surface aeration amount L is measured by: (i) inserting the developer supplying member into a measurement jig including a hollow cylinder having an inner diameter smaller by 1 mm than an outer diameter of the developer supplying member, and two through-holes each having a diameter of 10 mm in a side surface of the hollow cylinder, one through-hole being exposed to ambient air and the other through-hole being communicated with a flowmeter and a decompression pump, and (ii) measuring a value of the flowmeter when the decompression pump evacuates air from the measurement device under the same exhaust condition as an exhaust condition in which a value of the flowmeter is 10.8 liters/minute in a state in which the developer supplying member is not inserted into the hollow cylinder.