| 摘要 |
PURPOSE:To obtain an on-demand type ink jet head free of air-troubles by providing an air sensor to detect the mixing condition of air inside the head. CONSTITUTION:A pieze-electic element 21 is connected to a drive circuit 23, and vibrated initially to an extent that no ink particles are jetted, and then the element 21 is switched to a sensor circuit 24 to let it detect the secondary effect of vibration. Since the secondary effect frequency of vibration is of nearly 50KHz, it can be taken out in the form of a signal if the secondary effect frequency of vibration is amplified by a differential amplifier. In case where air is present, a high-frequency component (C portion) appears. |
