Ultra-precision temperature control system for machine tool and control method therefor

An ultra-precision temperature control system for a machine tool, comprising:

• a component constituting a part of a machining apparatus and having a heat source;
• a heat transfer fluid brought into contact with said component to control a temperature of said component to a set temperature;
• precooling means for cooling said heat transfer fluid coming out of said machining apparatus to a predetermined temperature;
• a heater for heating said heat transfer fluid sent from said precooling means;
• heating control means for controlling a heating power of said heater, wherein said heating control means includes a constant-power thyristor phase controller for controlling electric power supplied to said heater for heating control;
• a closed, heat-insulated damping tank for temporarily storing said heat transfer fluid coming out of said heater and for sending it to said machining apparatus;
• a machine body temperature sensor for detecting a temperature of said machining apparatus;
• a supply fluid temperature sensor for detecting a supply fluid temperature of said heat transfer fluid at an outlet of said heater;
• a machine outlet fluid temperature sensor for detecting a return fluid temperature of said heat transfer fluid at an outlet of said component;
• a digital computer for calculating a target temperature for said supply fluid temperature and for outputting a command signal representative of said target temperature to said heating control means;
• and
• wherein said digital computer includes:
• (a) means for calculating a target temperature (To,NEW) based on a temperature difference from a prior target temperature (To,OLD) and a difference between a set value (Tc) and an actually controlled temperature value (Tx) which is based on at least one of said machine body temperature sensor and said machine outlet fluid temperature sensor, according to the following formula:
• To,New=To,OLD+(Tc-Tx),
• and
• (b) means for sending a signal to said heating control means to effect heating towards said target temperature (To,NEW);
• and
• (c) means for maintaining said target temperature not changed when said actually controlled temperature value (Tx) is within a predetermined temperature range with respect to a target value therefor.