Patent ID: 8177313

Claim:
An image forming apparatus comprising: a print head to eject droplets; a subtank to supply ink to the print head; a main tank to supply the ink to the subtank; a supply pump to supply the ink from the main tank to the subtank; a pump driver to drive the supply pump in response to a driving voltage supplied to the pump driver; an amount sensor to sense an ink amount in the subtank and output a signal when the ink amount in the subtank is at a predetermined level; and a unit to supply the driving voltage to the pump driver to drive and control the pump driver, wherein the unit is configured to decrease an ink supply rate of the supply pump, by changing the driving voltage applied to the pump driver from a first voltage value Vin 1 to a second voltage value Vin 2 where Vin 1 >Vin 2 >0, to cause the pump driver to change an operation rate of the supply pump from a normal operation rate Vp 1 to a lower operation rate Vp 2 , where Vp 1 >Vp 2 >0, in response to the signal outputted by the amount sensor indicating that the ink amount in the subtank is at the predetermined level, and to stop the supply pump, by no longer applying the driving voltage to the pump driver when a predetermined allowable time Tt 1 for operation at the lower operation rate Vp 2 has passed after the signal indicating that the ink amount in the subtank is at the predetermined level is outputted by the amount sensor.