| 摘要 |
PURPOSE:To control the density of printing at high accuracy by providing an element that detects the quantity of developer in a developing device and determining the quatity of replenishment of toner according to the quantity of developer. CONSTITUTION:At the time of installing elements 11, 11' that detect the quantity of developer, a sensor sensitive to magnetism is effective as the element 11 since the carrier of developer 12 is magnetic substance. When the quantity of developer 12 is at a position higher than the position of 11, the toner of the quantity, for instance, 3alpha is replenished to a developing device. When the quantity of developer 12 is between 11 and 11' the toner of the quantity 2alpha is supplied, and when the quantity of developer 12 is below 11' the toner of the quantity alpha is supplied to the developing device 5. Thus, the ratio of toner in the developer 12 to the carrier can be maintained almost constant, and the control of printing density does not go wrong. |
