Patent ID: 7261399

Claim:
An image forming apparatus comprising: a plurality of ink tanks which store ink; a plurality of ink jet heads which jet the ink supplied from the respective ink tanks to thereby form an image on an image forming medium; a pressurizing pump which supplies air; an air tank which communicates with the pressurizing pump; a plurality of pressurizing valves which connect the air tank to the respective ink tanks, respectively; atmosphere open valves which are disposed in the respective ink tanks and at least one of the air tanks in such a manner that the inside of the air tank is openable to the atmosphere; an ink discharge control unit which opens the respective pressurizing valves and which drives the pressurizing pump and which supplies air to the respective ink jet heads from the air tank through the respective ink tanks to raise head inner pressures of the respective ink jet heads and which discharges the ink from the respective ink jet heads; and a pressure averaging control mechanism which discharges the ink from the respective ink jet heads and which thereafter opens the respective pressurizing valves and which opens the atmosphere open valve to thereby average the pressures in the respective ink tanks.