US Patent 7458654 Liquid ejection apparatus and ejection abnormality determination method

The liquid ejection apparatus comprises: a liquid ejection head having a nozzle which ejects liquid, a pressure chamber which is provided correspondingly to the nozzle, and a pressure measurement device which is provided correspondingly to the pressure chamber and measures pressure in the pressure chamber; a bubble removal device which removes a bubble from the pressure chamber; an error extraction device which extracts an error in capacitance of the pressure measurement device of the pressure chamber from which the bubble has been removed by the bubble removal device; a threshold value setting device which sets a corrected threshold value to be used for determination of pressure abnormality in the pressure chamber, the corrected threshold value having been corrected for the error in the capacitance of the pressure measurement device extracted by the error extraction device; a storage device which stores the corrected threshold value set by the threshold value setting device; and a pressure abnormality determination device which performs the determination of the pressure abnormality in the pressure chamber, according to a result of comparison between a measurement result obtained from the pressure measurement device and the corrected threshold value read out from the storage device.