| 摘要 |
PURPOSE:To realize a low noise thermal printer made possible to automatically eliminate an inherent vibration region to be avoided, by limiting the drive current of a stepping motor when an avoiding speed range is judged to be within a low speed field. CONSTITUTION:A speed detection part 9 samples and counts the number of pulses per a required unit time of a motor pulse at every predetermined cycle and knows the rotational speed of a stepping motor 6 at every predetermined cycle from the counting number of pulses. The range of the aforementioned number of pulses per a required unit time is stored in an avoiding speed memory table 10 while rank sections of high, medium and low speeds are provided to the rotational speed range of the stepping motor 6 corresponding to inherent vibration frequency to be avoided preliminarily investigated by utilizing a ROM. The output of the speed detection part 9 is collated with the memory content of the avoiding speed memory table 10 by a collation part 11 and, when the collation result is judged to be within the aforementioned avoiding speed range, the cycle of the aforementioned printing pulse is controlled so as to become slower than the min. speed of the judge rank through a speed control part 12. When the judged degree corresponds to the low speed section, the supply current to the stepping motor 6 of a drive part 8 is limited through a current limit circuit 13. |
