Patent ID: 7497543

Claim:
A liquid ejection apparatus, comprising: a liquid ejection head including a nozzle which ejects liquid, a pressure chamber which is connected to the nozzle and is to be filled with the liquid, a pressure generating element which pressurizes the liquid in the pressure chamber, and a pressure determination element which determines a pressure inside the pressure chamber and outputs a pressure determination signal; a storage device which stores a peak value of the pressure determination signal output by the pressure determination element in a state where the nozzle ejects the liquid normally; a first ejection abnormality factor extraction device which extracts a first ejection abnormality factor by comparing the peak value stored previously in the storage device with the pressure determination signal output by the pressure determination element during a prescribed period for ejection abnormality determination; a threshold value variably setting device which sets a threshold value for extracting a second ejection abnormality factor according to a differential between the peak value stored previously in the storage device and a peak value of the pressure determination signal output by the pressure determination element during the prescribed period for ejection abnormality determination; a pulse generation device which is capable of generating pulses according to a comparison result between the threshold value set by the threshold value variably setting device and the pressure determination signal output by the pressure determination element during the prescribed period for ejection abnormality determination; and a measurement device which extracts the second ejection abnormality factor by measuring a time interval of the pulses generated by the pulse generation device.