| 摘要 |
PURPOSE:To maintain a specified image density constant by setting upper and lower limits to the toner density of a developer and replenishing the toner in such a way that the actual condition of the toner density is made to conform to the set upper/lower limits. CONSTITUTION:When a main switch is turned on, a sequence controller operates and investigates the bias voltage of a developing unit and the heating temp. of a photosensitive drum D. When the controller confirms that said voltage and temp. comply with set values, a developing sleeve turns to supply the developer in a developing tank T to a toner density detector 1, the value thereof is then inputted to a toner density range setter 2. When the density signal is below the lower limit value, an L signal is outputted from a detecting circuit 2c for the lower limit of the toner density and operates a driving circuit 7 for a toner replenishing member to replenish the toner until an H signal is outputted from the circuit 2c, thereby the toner is replenished until the toner density conforms to the upper/lower limits. A copying operation is started in the stage when such preparation is completed. |
