TONER QUANTITY DETECTING SYSTEM FOR AN IMAGE RECORDING APPARATUS, A METHOD OF DETECTING THE QUANTITY OF TONER AND A DEVELOPING DEVICE FOR THE IMAGE RECORDING APPARATUS

摘要

A toner quantity detecting system has a toner quantity detector (4c) and is capable of accurately detecting the decrease of the quantity of toner contained in the toner container of the developing unit of an image recording apparatus to an upper threshold quantity and to a lower threshold quantity regardless of the inherent output characteristic of the toner quantity detector (4c) and determining a prewarning voltage (E nep) representing the upper threshold quantity and a warning voltage (E emp) representing the lower threshold quantity so that the difference between the prewarning voltage (E nep) and the warning voltage (E emp) is sufficiently large. The prewarning voltage (E nep) and the warning voltage (E emp) are determined on the basis of the inherent output characteristic of the toner quantity detector (4c). The output voltage (E s) of the toner quantity detector (4c) is compared with the prewarning voltage (E nep) and the warning voltage (E emp) to provide a prewarning signal (NAL) upon the reduction of the quantity of the toner to the upper threshold quantity and to provide a warning signal (EAL) upon the reduction of the quantity of the toner to the lower threshold quantity.