Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
2000-04-10
2001-09-25
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S229000, C062S176600, C062S176300, C062S228500, C236S04400R, C165S230000
Reexamination Certificate
active
06293116
ABSTRACT:
TECHNICAL FIELD
This invention relates to a vehicle climate control system having a variable capacity refrigerant compressor and more particularly to a system that regulates passenger compartment humidity without requiring a humidity sensor.
BACKGROUND OF THE INVENTION
A vehicle climate control system performs two primary functions: temperature regulation and dehumidification. In a system having a variable capacity refrigerant compressor, this is generally achieved by adjusting the stroke of the compressor based on the cooling load, and then reheating the cooled and dehumidified air as required to regulate the temperature of the passenger compartment air at the desired temperature. In this type of control the principal feedback variable is passenger compartment temperature, and the relative humidity within the passenger compartment varies significantly depending on cooling load, ambient humidity, and so on.
While widely used, the above-described approach exhibits significant drawbacks in terms of both compressor power consumption and passenger comfort. System efficiency suffers due to overcooling and then reheating for purposes of temperature regulation, while passenger comfort suffers under conditions where the relative humidity of the passenger compartment falls below a comfortable level. Clearly, reducing the compressor capacity under certain conditions will improve both vehicle fuel economy and passenger comfort without degrading the passenger compartment temperature control.
For the above reasons, it has been proposed to measure the relative humidity in the passenger compartment and to regulate the system operation to control both temperature and humidity. However, an accurate humidity sensor significantly increases system cost, and therefore limits the system applicability to primarily luxury vehicles. Accordingly what is needed is a cost effective approach for controlling both temperature and humidity in a vehicle climate control system.
SUMMARY OF THE INVENTION
The present invention is directed to an improved vehicle climate control system in which the passenger compartment temperature and humidity are controlled without requiring a humidity sensor. This invention is based on the recognition that the air temperature at the evaporator outlet represents the dew point of the air supplied to the passenger compartment, and may be specified based on the desired passenger compartment air temperature to achieve a desired relative humidity in the vehicle once the desired passenger compartment temperature has been achieved. According to a first embodiment, the desired relative humidity is predetermined, and the corresponding values of evaporator outlet air temperature are determined as a function of the desired passenger compartment temperature. According to a second embodiment, the operator of the vehicle is permitted to select a desired relative humidity, and the corresponding values of evaporator outlet air temperature are determined as a function of the desired passenger compartment temperature and the selected humidity level.
REFERENCES:
patent: 4540040 (1985-09-01), Fukumoto et al.
patent: 4848444 (1989-07-01), Heinle et al.
patent: 4878358 (1989-11-01), Fujii
patent: 5191768 (1993-03-01), Fujii
patent: 5884497 (1999-03-01), Kishita et al.
Bhatti Mohinder Singh
Forrest Wayne Oliver
Keen Elliott D.
Delphi Technologies Inc.
Griffin Patrick M.
Tanner Harry B.
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