| 摘要 |
PURPOSE:To prevent the drying of ink in and near a nozzle by a method in which when nonprinting state continues for a given time period, blank injection of the nozzle is made prior to printing. CONSTITUTION:In an on-demand type ink jet printer in which plural ink jet nozzles are provided and selectively driven in such a way as to inject ink only at the time of printing, a means to measure the time of nonprinting state, e.g., a circuit consisting of a clock pulse generator CLK, a flip-flop 32, and a counter 40, is provided, and in case where nonprinting state exceeds a given period of time, blank injection of the nozzle is made prior to printing. Also, a means to detect the change in print colors is provided, and when ink jet nozzles not used immediately before printing are used, blank injection of the nozzles should be made prior to the printing preferably. |
