| 摘要 |
PURPOSE:To ensure that air pressure-time characteristics are not affected by the variations in external factors, to obtain a constant pressure rise time and enhance operability of an air-supplying system, by causing a controlling means for a command voltage signal and a feedback signal from a pressure sensor to output a pulse signal to an air valve, thereby controlling pressurization in an ink tank. CONSTITUTION:An output from a signal generator 36 is connected to one terminal of a comparator 37, and a feedback signal is inputted to the other terminal from a feedback circuit comprising a pressure sensor 38, which is disposed at a supplying pipe between an air valve and an air duct 19a for a purging tip valve 14, and an amplifier 39. A comparator 37 controls a preset command voltage signal E1 and the feedback signal E2 so that the relationship of E1=E2 is constantly maintained, and outputs a binarized signal to a coil of a solenoid valve, i.e., an air valve 41 through an air valve-driving circuit 40, thereby operating the solenoid valve. Then, air is supplied to the air duct 19a for the valve 14 through an MPU 26, an air pump-driving circuit 29, an air pump 30 and an air tank 31. |
