| 摘要 |
PURPOSE:To appropriately start a defrosting cycle by starting the defrosting operation by utilizing such a phenomenon that the charge ratio of the temperature of a coolant evaporator to the time increases with the progress of the defrosting and a condition exceeding a certain preset value continues for a specific period of time. CONSTITUTION:The defrosting operation is carried out only when the temperature theta of the coolant evaporator 3 becomes less than a preset value to prevent such an erroneous operation that when no frost exists, a defrosting mode operation is started. Furthermore, the change ratio I of the temperature theta of the coolant evaporator 3 to the time (t) is noticed. The time when the change ratio I of the evaporator temperature theta to the time is negative and is larger than the preset value C1 which is an absolute value of (l) is continued for a predetermined period of time C2, is determined as a time for starting the defrosting, and a signal is emitted from an electronic control part 7. Then, a four-way changeover valve 2 is switched through an electromagnetic contactor 15, and the coolant passage is switched to carry out the defrosting operation. When the temperature theta of the evaporator 3 exceeds the preset value, the defrosting operation is terminated. |
