Patent ID: 7891786

Claim:
An ink-jet printer, comprising: an ink-jet recording head having an ink inlet into which an ink inflows; an ink tank which has a known volume and stores the ink and which has an ink outlet from which the ink outflows and additionally has an air inlet into which an air inflows; a first connector having an ink supply passage which communicates, at one end thereof, with the ink outlet of the ink tank and communicates, at an other end thereof, with the ink inlet of the ink-jet recording head, wherein the ink-jet recording head includes a plurality of nozzles each of which communicates with the ink tank via the ink supply passage and at least one of which ejects a droplet of the ink in a printing operation; an air-pressure regulating device which has an air outlet from which the air outflows and additionally has a second connector having an air supply passage which communicates, at one end thereof, with the air outlet and communicates, at an other end thereof, with the air inlet of the ink tank; a volume obtaining portion which obtains at least one of (a) a volume of the ink present in the ink tank and (b) a volume of the air present in the ink tank, wherein a sum of (a) the volume of the ink present in the ink tank and (b) the volume of the air present in the ink tank is equal to the known volume of the ink tank; and an operation control portion which controls, based on the volume obtained by the volume obtaining portion, an operation of the air-pressure regulating device to regulate a pressure of the air present in the ink tank, to a predetermined value so as to perform, in a state in which the ink jet recording head does not perform the printing operation, a purging operation in which the ink present in the nozzles of the ink-jet recording head is forcedly discharged into an outside space owing to the pressure of the air in the ink tank, regulated to the predetermined value.