Ink jet printer

Abstract

An ink jet printer performs adjustments such that even if the ink ejection speed decreases, the ink droplet landing position on a recording sheet will not deviate. Based on the ink droplet transit time between ejection of an ink droplet and the landing thereof on the recording sheet, and the moving speed of the print head carriage, a control unit controls the time of applying a drive voltage to a piezoelectric element of a print head so that an ejected ink droplet lands at a predetermined position on the recording sheet being conveyed. During printing, the control unit receives a pulse signal from an encoder and detects the reception time thereof. The control unit then determines the next reception time by adding to the previous time, an encoder signal period based on the signals received. The control unit also determines an ink droplet transit time which depends on the characteristics of the piezoelectric elements, the power-on time, and the like. The control unit determines an ejection time by subtracting the droplet transit time from the reception time, so that the ink droplet ejected at the ejection time will land at an intended position on the recording sheet. The next ink droplet ejection time is determined by adding an ejection cycle to the ejection time, and the next ink droplet is ejected at that time. This ink ejecting operation is repeated upon arrival of later pulse signals.