JPS57175423A - Controller for refrigeration cycle of automobile - Google Patents

Abstract

PURPOSE:To avoid the deterioration of the feeling of cooling, by providing a variable-capacity compressor in a refrigeration cycle and by reducing the capacity of the compressor when the rotational frequency of an engine has become lower than a prescribed level, to diminish the load upon the engine to prevent the temperature just downstream to an evaporator from rising due to the stoppage of the compressor. CONSTITUTION:When the rotational frequency of an engine has become lower than a prescribed level due to idling or the like, the output level of a rotational frequency detection circuit 25 becomes so high that the transistors 164a, 165 of a control circuit 16 are forcedly turned on. As a result, a transistor 164b is turned off, transistors 166, 167, 171 are turned on and transistors 168, 169, 170 are turned off so that an electrical current flows to a servomotor 17 through the emitter and collector of the transistor 171 and the collector and emitter of the transistor 167. For that reason, the servomotor 17 rotates backward to decrease the rotation angle of the variable ring of a variable-capacity compressor to reduce its capacity. Since the capacity is set at the minimum (one third of the maximum), the load upon the engine is reduced so that it does not overheat.