Abstract
With the public interest in environment conservation in recent years, the automobile industry now requires technological innovations to reduce fuel consumption. Innovative technologies demand that the air-conditioning system be of “a power-saving design”, which would reduce the engine emissions. In regulatory testing, the US EPA has included air conditioning operation as part of the Supplemental Federal Test Procedure (SFTP) known as SC03. With these new requirements, enhanced compressor control is essential to power saving. With this in mind, the variable displacement compressor is more advantageous than other types. This paper describes the power saving air-conditioning control algorithms through cooperative control of the Power Train (P/T) and an externally controlled air conditioning (A/C) compressor. By coordinating the A/C system with the P/T, the algorithms reduce compressor displacement during vehicle acceleration to prevent excessive A/C cooling, and increase the compressor displacement to store the cool air during vehicle deceleration which will improve fuel consumption when driving. The power saving compressor control algorithms which do not affect passenger comfort is the main focus of this paper.
The compressor variable displacement control for the reduction of fuel consumption requires various signal selections and a domain definition which can be used to judge the vehicle’s driving condition whether accelerating or decelerating.
To maximize power saving and reduce fuel consumption, a careful consideration and application for an allowable wide range of target temperature of evaporator air outlet is essential to achieve this goal (the highest comfort temperature in acceleration and the lowest temperature in deceleration).
A prototype test vehicle is operational and undergoing validation for thermal comfort and drivability. These evaluations include climatic wind tunnel tests and field tests. Fuel consumption in the air conditioning operation has been tested through the measurement of the fuel usage and the compressor torque. A 7~8% potential reduction in SC03 mode was found and acceleration performance was also improved by about 0.34% compared with typical A/C cut off logic.
Keywords: variable displacement compressor, cooperative P/T-A/C control, fuel consumption, ECV duty