| 摘要 |
PURPOSE:To prevent any cooling effect drop from occurring by making an on-off setting temperature in a compressor so as to be varied by the specified range for a specified period, in a controller, bearing the above caption, which turns the compressor on or off with evaporator temperature and prevents an evaporator from frosting. CONSTITUTION:A certain latitude is given to on setting temperature TON and off setting temperature TOFF of a compressor by a Schmitt circuit made up of an operational amplifier OP1 and a resistor R2 of a comparator 1, and the detected temperature is compared with on-off setting temperatures TON and TOFF, whereby the compressor is turned on or off via a drive circuit 2. On the other hand, an oscillator 3 consists of operational amplifiers OP2 and OP3, resistors R6-R9 and a condenser C, and it determines a variation width Tw and a variation period Tp of these on-off setting temperatures TON and TOFF, outputting them to the comparator 1. Consequently, the variation width of an on-off command of the comparator is periodically varied so that it comes to defrost in consequence. Accordingly, at the time of a drop in the on-off setting temperature, cooling capacity is fully utilizable so that its efficiency is improvable. |
