| 摘要 |
<p>PURPOSE:To perform heating in a short time and to prevent overshooting by powering on a heater fully for quick heating up to critical temperature set between set temperature and control point temperature, and then decreasing the duty cycle speedily. CONSTITUTION:The outut of a temperature detecting element 1 is inputted to a V/F converter 2 which varies in duty cycle with temperature to be converted into a pulse interval, and also inputted to a comparator 3. The outputs of the circuits 2 and 3 are supplied to an OR circuit 4, whose output is supplied to a solid-state relay SSR5 to intermit a current to the heater 6. Quick heating is carried out with a 100% duty cycle initially, but the output of the comparator 3 goes down to L when the temperature attains to the critical temperature between the set temperature and control temperature to decrease the duty cycle speedily under the control of the V/F converter 2, so that the temperature rises gradually. Consequently, the temperature rises in a short time without overshooting. This is suitable for the fixing device of a copying machine.</p> |
