DETECTION OF TONER CONCENTRATION

摘要

PURPOSE:To exactly detect the toner concn. of a developer contg. toner particles which do not substantially reflect the light of a wavelength region of detecting light over a long period of time by using the developer mixed with magnetic carrier particles higher in the spectral light reflectivity in a prescribed wavelength region than that of the toner particles. CONSTITUTION:The two-component developer 7 mixed with the nonmagnetic toner particles and the magnetic carrier particles is housed in a container 6 of a developing device 5. The magnetic carrier particles provided with the higher spectral reflectivity in the wavelength region of the detecting light which is detected by a photodetector 21 and is converted to an electric signal than the spectral reflectivity of the colornts of the toner particles by contg. a magnetic material having the spectral reflectivity higher than the spectral reflectivity of the colornts of the toner particles are used as the magnetic carrier particles. For example, the magnetic carrier particles formed by using maghemite (gamma-Fe2O3) which is a brown coloring pigment having magnetism and coating the surfaces of such cores with a resin in order to improve triboelectrostatic chargeability, environmental stability and durability are used as the magnetic cores of the magnetic carrier particles.