Patent ID: 8534785

Claim:
An inkjet printer comprising: an ink circulation path comprising an ink head comprising a nozzle surface where a plurality of nozzles which eject an ink are formed, a first tank which is positioned above the nozzle surface along a gravitational direction and stores the ink to be supplied for the ink head, a second tank which is provided below the nozzle surface in the gravitational direction and stores the ink collected from the ink head, and a pump which pumps the ink from the second tank to the first tank; first and second liquid surface detectors which respectively detect ink liquid surfaces in the first and second tanks; an ink supply unit which supplies the ink circulation path with the ink; a supplementary feed valve which makes the ink supply unit and the ink circulation path communicate with or shut from each other; a control unit which controls driving and a stop operation of the pump, an open/close operation of the supplementary feed valve, and the whole inkjet printer; a storage unit which stores information detected by the first and second liquid surface detectors; and a determination unit which determines whether or not an abnormality occurs in the first and second liquid surface detectors, based on the information, wherein when the ink circulates through the ink circulation path, the second liquid surface detector detects whether or not the ink liquid surface in the second tank is higher than a predetermined level, the detected information is accumulatively stored into the storage unit, the determination unit determines whether or not an abnormality occurs in the second liquid surface detector, based on the accumulatively stored information, the first liquid detector thereafter detects whether or not the ink liquid surface in the first tank is higher than a predetermined level, the detected information is accumulatively stored into the storage unit, and the determination unit determines whether or not an abnormality occurs in the first liquid surface detector, based on the accumulatively stored information.