| 摘要 |
PURPOSE:To prevent a refrigerant from being brought to an abnormal temperature, by a system wherein when the difference between a room temperature set point and the actual room temperature reaches or exceeds a predetermined limit value, a control signal stepped UP or DOWN by a predetermined step width at a time for each predetermined period of time is outputted so as to reduce the temperature difference to zero. CONSTITUTION:A room temperature is compared with a set point. When the difference between the two is not substantially zero, the condition of the difference is judged as UP or DOWN according as the difference is positive or negative. Time is counted by an UP timer when the difference condition is judged as UP, whereas time is counted by a DOWN counter when the difference condition is judged as DOWN. The set time for the timers are, for example, about 1sec. When the set time is up, a control signal is stepped UP or DOWN by one step width through a stepping-UP/DOWN circuit 22. By the control signal, the opening of a proportional control valve 15 is controlled in the direction for opening or closing by one step width through a driving circuit 19, and accordingly, the heating value of a refrigerant heater 12 is controlled by one step width.
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