| 摘要 |
The present invention is to provide, for each nozzle, a temperature sensor that detects a temperature change accompanying driving an ejection heater. In the temperature change, an inflection point appears when an ink is ejected normally. Then, calculated is a summation of absolute values of the differences between a value of second derivative in each point of temperature data in a predetermined section including the timing at which this inflection point appears and a first threshold value based on the second derivative when an ejection-failure occurrence. Since the second derivative when the ejection-failure has occurred does not vary virtually, the summation becomes to be approximately zero. Therefore, appears clearly the difference with the time of normal ejection. From the magnitude relation between the summation and a second threshold value predetermined with respect to the summation, it can be determined whether the normal ejection is being carried out for every nozzle.
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