Patent ID: 7949265

Claim:
A toner supply device for supplying toner to a developing device for developing an electrostatic latent image formed on an image bearer, comprising: a first toner supply portion for supplying toner to a developing hopper of the developing device; a second toner supply portion for supplying toner stored therein to the first toner supply portion; a first toner supply driver for driving the first toner supply portion when supplying the toner fed from the second toner supply portion to the developing device; a first residual toner quantity detector for detecting the residual quantity of toner stored in the first toner supply portion; a second toner supply driver for driving the second toner supply portion when supplying the toner stored in the second toner supply portion to the first toner supply portion; a second residual toner quantity detector for detecting the residual quantity of toner stored in the second toner supply portion; and a controller for controlling the drives of the first and second toner supply drivers by switching on and off the drives of the first and second toner supply drivers in accordance with the residual toner quantities detected by the first and second residual toner quantity detectors, wherein when, while both the first and second toner supply drivers are being driven, the controller detects that the residual quantity of toner in the first toner supply portion is equal to or lower than a predetermined level, by means of the first residual toner quantity detector, the controller controls the drives of the first and second toner supply drivers so as to keep driving the first toner supply driver and stop driving the second toner supply driver.