US 2008/0173437 A1 · FOG DETECTION ERROR PROTECTION FOR WINDOW FOG CONTROL

Abstract

A method for controlling a vehicle HVAC system to automatically defog a windshield glass and to prevent fogging or condensation of the windshield glass. In-cabin air temperature and relative humidity are measured and used to determine a dewpoint. Further, ambient or outside temperature is measured. If windshield wipers are being used or if the cabin air temperature is less than a predetermined temperature, the ambient air temperature value is used as a glass temperature, otherwise the glass temperature is determined from the ambient air temperature and vehicle speed. A fog margin, which is a measure of the likelihood of fog formation, is based upon the difference between dewpoint and the windshield glass temperature. The fog margin is used to control the HVAC system to anticipate and respond to potential fogging conditions.

Claims9

Dependent claims

A method for controlling a vehicle HVAC system to reduce a likelihood of fog forming on a window glass of the vehicle, comprising the steps of:

calculating a dewpoint of air within a cabin of said vehicle;
sensing operation of windshield wipers;
measuring ambient air temperature;
measuring a moving speed of the vehicle;
wherein, when the windshield wipers are not operating, calculating a window glass temperature based upon vehicle speed and ambient air temperature;
wherein, when the windshield wipers are operating, using the ambient air temperature as the window glass temperature;
determining a fog margin based upon the window glass temperature and said calculated dewpoint, said fog margin being a measure of the likelihood of fog forming on said vehicle window;
and
operating said HVAC system in accordance with a predetermined algorithm based upon said fog margin.

6 more elements

Dependencies are inferred from the claim text.

Fog detection error protection for window fog control

Life of this patent

Fog detection error protection for window fog control

Life of this patent

Abstract

Claims9