| 摘要 |
PROBLEM TO BE SOLVED: To keep the dispersion of charge in a narrow range as much as possible so that only preset charges can be imparted to a surface to be developed by providing a filter for selecting toner grains on a developing device. SOLUTION: A roller 2 is cooperated with a doctor 6, and the doctor 6 strongly presses toner grains 10 to the roller surface of the roller 2. The charging of the toner grains 10 is reinforced by this pressing. This process is further helped by adding a voltage between the roller 2 and the doctor 6. The action of the doctor 6 regulates the diameter of the toner grains on the roller 2. Namely, the diameter of the toner grains is limited by the doctor 6 pressed onto the roller 2. A potential is given to the roller 2 so that a constant electric field is generated between the roller 2 and a roller 3. The intensity of the electric field is such that the strongly charged particles 12 are attracted from the roller 2 to the roller 3 to regulate the upper limit and lower limit of the grain charges. |
