Patent ID: 6112807
Filing Date: 2000-09-05
Classification: B60H

Abstract:
A method for controlling a heating, ventilation and air conditioning (HVAC) system of a vehicle which discharges a flow of air to a passenger cabin of the vehicle, the system including a variable speed blower, a ducting, a compressor, an evaporator, a heater core for heating air in the ducting, a control element having control positions for varying refrigerating and heating capacity of the HVAC system, a pressure cycling switch for controlling operation of the compressor, a plurality of blend doors having various control positions for controlling direction of air flow and ratio of fresh air to recirculated air, a humidity sensor for sensing relative humidity within the passenger cabin and providing a corresponding relative humidity signal, and temperature sensors for sensing temperature within the passenger cabin, the evaporator, and ambient temperature and providing a corresponding passenger cabin temperature signal, an evaporator temperature signal and an ambient temperature signal, the method comprising the steps of:measuring the ambient temperature and generating the ambient temperature signal;measuring the temperature of the evaporator and generating the evaporator temperature signal;bypassing the pressure cycling switch when the ambient temperature signal is below 42.degree. F.;cycling the control element on and off according to a predetermined duty cycle when the ambient temperature signal is below 42.degree. F. and above 20.degree. F.; andmoving the plurality of blend doors to a predetermined position based upon the ambient temperature signal and the evaporator temperature signal.