Control method for a variable displacement refrigerant compressor in a high-efficiency AC System

摘要

A high efficiency air conditioning system (10) includes a pneumatically-controlled variable displacement compressor (12) and a compressor clutch (22) that is selectively cycled on and off to minimize series re-heating of conditioned air. Conditioned air is discharged after passing through an evaporator core (28), and a target value for the evaporator outlet air temperature is determined based on the desired air discharge temperature (88-92). The compressor clutch (22) is cycled off when the evaporator outlet air temperature falls below the target value by at least a calibrated amount (100-102), and is thereafter cycled on again when the evaporator outlet air temperature rises above the target value (98, 104). The target value is preferably biased to prevent compressor operation when the desired air discharge temperature exceeds outside air temperature by at least a calibrated amount (88-90) and to prevent the relative humidity in the air-conditioned space from rising above a desired level (94-96).