Abstract: An ink jet system printer of the charge amplitude controlling type includes a carriage travelling across the printing region. A nozzle for emitting ink droplets and a slidable member are disposed on the carriage. The slidable member supports a charging tunnel and a cleaning pad for cleaning the front surface of the nozzle. When the carriage is positioned at the leftmost position before initiating the actual printing operation, the slidable member is slided on the carriage so that the cleaning pad contacts the front surface of the nozzle for cleaning purposes. Thereafter, the slidable member is held stationary on the carriage at a position wherein the charging tunnel confronts the nozzle.

Abstract: In an ink jet system printer of the charge amplitude controlling type, an electric current flows through an ink droplet issuance unit to ink liquid when an ink droplet is properly charged by charging means. A detection circuit is connected to the ink droplet issuance unit for detecting the electric current flowing through the ink droplet issuance unit, thereby developing a phase OK signal when a predetermined electric current is detected.

Abstract: A printer head is mounted on a carriage which is driven to travel in the row direction at a predetermined constant speed. A pulse generation device is provided for developing a pulse signal in response to the travel of the carriage in order to determine print width. A detection device develops a detection signal when the carriage reaches the first print position to initiate printing of the first character. The detection signal is applied to a counter which counts a time interval from a time at which the last pulse is developed from the pulse generation device to a time at which the detection signal is developed. The following character printing is effected each time the pulse generation device develops a predetermined number of pulses indicative of one character width or print pitch and the time interval determined by the counter has passed from the time at which the last pulse of the predetermined number is developed.

Abstract: A primary matrix pattern such as 5 .times. 7 matrix structure and an auxiliary matrix pattern such as 4 .times. 6 matrix structure are combined with each other in an ink jet system printer in such a manner that auxiliary dots contributing to the auxiliary matrix pattern are shifted in both column and row directions by a half dot position with respect to the primary matrix pattern. These auxiliary dots function to increase dot density along oblique lines in the dot matrix pattern.