초록 ▼

A low charge protection method for an electronically controlled variable displacement compressor. In each period of compressor operation, a low charge test sequence is carried out to monitor the system performance once the system control pressure has been reduced below a specified level. In a set-up

A low charge protection method for an electronically controlled variable displacement compressor. In each period of compressor operation, a low charge test sequence is carried out to monitor the system performance once the system control pressure has been reduced below a specified level. In a set-up phase of the test, the compressor is down-stroked to near-minimum displacement for a predetermined time or until the system control pressure rises above a reference level. At such point, the compressor is up-stroked to near-maximum displacement to initiate a pull-down phase of the test. If the system pressure is reduced by specified amount within a reference interval, a failed test is indicated and the count in a nonvolatile counter is incremented. If the pull-down duration exceeds the reference interval, a passed test is indicated, and the count, if any, is decremented. When the nonvolatile count exceeds a specified threshold, the compressor is disabled and further operation is prevented until the count is reset by a service technician.

대표청구항 ▼

In a vehicle air conditioning system including a refrigerant compressor, the displacement of which is controlled to maintain a measured refrigerant vapor pressure at a desired value, a control method for protecting said compressor from damage due to continued operation with insufficient refrigerant

In a vehicle air conditioning system including a refrigerant compressor, the displacement of which is controlled to maintain a measured refrigerant vapor pressure at a desired value, a control method for protecting said compressor from damage due to continued operation with insufficient refrigerant charge, comprising the steps of: controlling the compressor to a minimum displacement once the vapor pressure of the refrigerant reaches the desired value, to thereby initiate a set-up period in which the measured vapor pressure is permitted to increase; controlling the compressor to a maximum displacement once the measured vapor pressure reaches a first reference pressure, thereby to terminate said set-up period and define a pull-down period in which the measured vapor pressure is decreased by the compressor at a maximum rate; measuring a pull-down time required for the measured vapor pressure to decrease from the first reference pressure to a second reference pressure lower than said first reference pressure; and indicating the detection of an insufficient refrigerant condition if the pull-down time is shorter than a reference pull-down time characteristic of a sufficient refrigerant condition.