| 摘要 |
PURPOSE:To prevent the deformation of a recording sheet caused by the long- time contact with a heater, by providing a control means for making the surface humidity of the heater lower than that at the time of usual recording provided that the recording sheet is present on the heater for a definite time or more. CONSTITUTION:A thermistor 40 changes in its internal resistance corresponding to heat-sensitive temp. and generates a change in the voltage dividing ratio with a resistor 41. The terminal voltage VIN of the resistor 41 becomes the input voltages of comparators 42, 43 to be compared with the reference voltages Vref1, Vref2 of reference power supplies 44, 45. The reference voltage Vref1 is set to VIN=Vref1 at heater set temp. T1 at a usual printing time and the reference voltage Vref2 is set to VIN=Vref2 at the heater set temp. T2 when recording paper is present on a printing platen for a definite time or more and, herein, T1>T2 and Vref1>Vref2 are set. A thyristor 55 is made operable or inoperable based upon the comparing result of VIN and Vref2 to control the temp. of a heater 11 so as to hold the same to a set value T2. Even when the recording paper 9 is present on the heater 11, temp. can be lowered and the deformation of the recording paper 9 is suppressed to the min. |
