| 摘要 |
PURPOSE:To constantly uniformalize typeprinting density, even when a typeprinting speed is changed, without necessity of adjusting voltage to be charged to a thermal head, by controlling the temperature of a platen in response to the typeprinting speed. CONSTITUTION:A thermal printer utilizes the phenomenum that deep typeprinting density can be obtained, even if voltage to be applied to a thermal head 1 is small, by properly heating a thermal paper sheet 2, running on a platen 3, through the platen. That is, the output voltage of a constant-voltage power source 5 to be applied to a resistance heater 4 arranged in the platen 3 is controlled by a voltage-controlling part 6 which is driven by a signal from a typeprinting speed-detecting part 7, to hold the thermal paper sheet 2 at a proper temperature through the platen 3 (the thermal paper sheet 2 is held at a high temperature when the typeprinting speed is high, while it is held at a low temperature when the typeprinting speed is slow). In addition, a signal from a sensor 8 having detected the temperature of the platen 3 may be utilized to drive the voltage-controlling part 6, so that influence from the change of an atmospheric temperature can be eliminated. |
