| 摘要 |
PURPOSE:To enable the detection of frosting in relation with room temp. and to improve reliability by utilizing reversely the characteristic of the 1st thermistor for detecting frosting in the stage of measuring temp. CONSTITUTION:The 1st thermistor is attached in a frosting place in a cooler 2, for example, between fins 3, and the temp. in an air conditioning chamber 1 is detected with the 2nd thermistor Th2. When power sources V1, V2 are turned on, the operation for a defrosting command is stopped until the thermistor Th1 evolves thoroughly heat and the measurement of the room temp. by the thermistor Th2 is started. Constant current flows from the emitter of an npn type transistor Tr1 to the thermistor Th1 when a timer T turns off, by which the thermistor Th1 is maintained at a specified temp. When frosts are successively deposited, the frosts are thawed and evaporated, by which heat is deprived and the temp. of the thermistor Th1 falls. The voltage of the thermistor Th1 increases and when the voltage of the thermistor Th1 rises above the reference voltage while the room temp. measured by the thermistor Th2 is at the temp. at which condensed dew is changed to a frost or below, a defrosting relay DF operates and a defrosting command is emitted. |
