Patent ID: 7877030
Filing Date: 2011-01-25
Classification: G03G

Abstract:
1. An image forming apparatus comprising: an image bearing member for bearing an electrostatic image; and a developing device, including a developer carrying member for carrying a developer including a magnetic carrier and toner having an average charge amount Q/M satisfying: 30 μC/g≦|Q/M|≦100 μC/g and for feeding the developer toward an opposite portion between said developing device and said image bearing member, for developing the electrostatic image by applying to the developer carrying member a developing bias comprising a DC voltage component and an AC voltage component; wherein the developing bias has a waveform portion including a collecting period, in which a voltage produces an electrostatic force for moving the toner toward the developer carrying member, and including a developing period in which a voltage produces an electrostatic force for moving the toner toward said image bearing member, and wherein the waveform portion satisfies the following formulas (1), (2), and (3): wherein f represents a frequency of the waveform portion, α represents a change rate of voltage per time at the time when a voltage value of the developing bias is equal to an electrostatic image potential VL, at a maximum density portion of an image formed on said image bearing member, during transition from the developing period to the collecting period, Vpp represents a peak-to-peak voltage which is a difference between a peak voltage in the developing period of the developing bias and a peak voltage in the collecting period of the developing bias, T represents a period of the waveform portion and is 1/f, S S Vcon represents a developing contrast value represented by Vcon=|Vdc−VL| where Vdc represents the DC voltage component of the developing bias.