JPS5495247A - Temperature controller of fixing heater - Google Patents

Abstract

PURPOSE: To set fixing temperatures in multiple stages with a simple constitution by selecting a plurality of resistances provided to a temperature detection circuit according to recording speeds and controlling the heating temperature of the fixing heater.

CONSTITUTION: The negative temperature coefficient thermistor Th of a temperature detection circuit 2 is connected to resistances R₁ thru R₃. When the signals corresponding to the high speed, low speed and fixing recording of recording paper are applied to a logic circuit 10, a relay switch 3 or 4 go ON or both switches go OFF and resistances R₁, R₁ + R₂, R₁ + R₂ + R₃ are selected. As a result, the time until a comparator 5 generates its comparison output through coincidence of a reference voltage by a constant voltage and the detection voltage via the thermistor Th becomes subsequently shorter according to high speed setting, low speed settng and recording. Hence, a relay 7 is de-energized by the inversion output of an FF 6 by the coincidence output of the comparator 5 and the fixing temperature are set in multiple stages according to the time when a heater 1 is heated through thriode AC switch, thus setting of plural fixing temperatures of different preheating temperatures, recording temperatures, etc. according to the high and low speeds may be accomplished with the simple constitution wherein the heating circuit is cmmonly used.

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