Image forming apparatus with developer density and remaining amount detection

An image forming apparatus comprising:

• a developing container for containing therein a developer including a toner and a carrier;
• means for detecting a density of the developer in said developing container;
• a developing device including a toner container containing the toner therein, and a toner replenishing device for replenishing said developing container with the toner in said toner container;
• comparing means for comparing the density of the developer in said developing container with a predetermined reference value;
• remaining amount detecting means for detecting the remaining amount of toner in said toner container;
• selecting means for selecting one of a plurality of values which is to be used as said predetermined reference value, in conformity with the remaining amount of toner in said toner container;
• and
• toner absence judging means for judging an absence of the remaining amount of toner in said toner container when the density of the developer in said developing container becomes lower than the predetermined reference value selected by said selecting means.

An image forming apparatus including at least one developing device having a developing container for containing therein a developer having a toner and a carrier, means for detecting a density of the developer in said developing container, and a toner replenishing device provided with a toner container containing the toner therein, and for replenishing said developing container with a proper amount of the toner in said toner container, said toner replenishing device being a cartridge detachably mountable to the image forming apparatus, wherein by the density of the developer in said developing container becoming smaller than a predetermined limit value, the absence of the toner in said toner container is judged, comprising:

• remaining amount detecting means for detecting the remaining amount of toner in said toner container;
• and
• informing means for generating a signal indicative of a small remaining amount of toner when the remaining amount of toner in said toner container becomes equal to or less than a predetermined amount;
• said limit value being effective only in a state in which the signal indicative of a small remaining amount of toner is being outputted.