Image forming apparatus and control method by the same with toner quantity monitoring

A method performed by an image forming apparatus, a sensor, comprising:

• acquiring a physical quantity relating to an amount of toner supplied from a supply device into a developing device by a sensor;
• driving the supply device comprising a cartridge for accommodating a toner and configured to supply the toner in the cartridge to the developing device until the acquired physical quantity reaches a predetermined value;
• counting a time during which the supply device is being driven with a timer;
• and
• determining that the amount of toner in the cartridge becomes smaller than a predetermined amount if the time counted by the timer is longer than a predetermined threshold value.

A toner processing device, comprising:

• a supply device comprising a cartridge for accommodating a toner and configured to supply the toner in the cartridge to a developing device;
• a sensor configured to acquire a physical quantity relating to an amount of toner;
• a timer configured to count a time;
• and
• a controller configured to
• acquire the physical quantity relating to the amount of toner supplied from the supply device into the developing device by the sensor,
• drive the supply device until the acquired physical quantity reaches a predetermined value,
• count a time during which the supply device is being driven with the timer, and
• determine that the amount of toner in the cartridge becomes smaller than a predetermined amount if the time counted by the timer is longer than a predetermined threshold value.