JPS6149094B

PURPOSE:To maintain a temperature of melted resin at a prescribed value with excellent responsiveness, by calculating the temperature of resin based on the measured value of a cylinder temperature compensated by using a parameter related to the temperature of melted resin in a cylinder, and by controlling the cylinder temperature by using a differential value between said temperature of resin and a desired temperature of resin. CONSTITUTION:Thermocouples C1-C4 are provided in the respective zones of the cylinder 2 of an extruder 1, and a cylinder temperature in each zone is thereby measured. Next, a signal from a radiation thermocouple and a signal from a room-temperature measuring resistor 11 are inputted in a microprocessor 14 via a scanner 13, while a signal in a relation to the number of rotation of a screw is inputted in a microprocessor 14 (numeral 12 is a linearizer and numerals 15 and 16 A/D converters), and thereby the temperature of melted resin is calculated. This is compared with a so-called resin temperature. Then, a differential value thus obtained is used for controlling a heater 20 or a blower 21 for cooling in each cylinder zone via a scanner 17 (numeral 18 denotes a D/A converter and 19 a temperature regulator).