| 摘要 |
PROBLEM TO BE SOLVED: To enable a power control for a PTC heater not to lengthen the time to finish drying and not to raise the costs of products. SOLUTION: The temperature of air fed to the PTC heater when the drying operation is started is detected (S1), a frequencyχof control for turning on and off electric power to the PTC heater is set according to the result of detection (S4 to S8), the power is turned on and off to a second PTC heater of the set frequency PTC heater (S13 to S18), and the power fed to the PTC heater is controlled. Alternatively, the drying operation may be started with a weak heater intensity, and thereafter the drying operation may be controlled to continue with switching the heater intensity to strong one when the exhaust air in the drying chamber is judged to have raised to a predetermined temperature from the result of detection of temperature.
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