| 摘要 |
PURPOSE:To prevent deterioration in follow-up performance or duplication capabilities by prolonging an energization time for a printing head at lower temperatures than a thermal protection operating temperature. CONSTITUTION:A first operating point A on a high temperature side and a second operating point B on a low temperature side are detected respectively by means of resistance variations following an increase in thermister temperatures. A thermal protection circuit 13 operates at the time when the first operating point has been detected, applying thermal protection to the action of a printing head. A printing head drive control circuit 14 operates when the second operating point has been detected to prolong an energization time for the printing head. Consequently, a faulty follow-up action or deterioration of copying capability due to a decrease in printing pressure at the time of temperature of the printing head being risen is prevented. At the same time, the degradation of the printing head also can be prevented because of the shortening of a time in which the printing head is exposed to a high temperature area. |
