System and method for vehicle defogging condition calculation and control

• US 20060000597A1
• Filed: 06/30/2004
• Published: 01/05/2006
• Est. Priority Date: 06/30/2004
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Errington, Bradley C., Kanemaru, Junichi
• Granted Patent: US 7,392,838 B2
• Time in Patent Office: Days
• US Class Current: 165/204
• CPC Class Codes: B60H 1/00785 by the detection of humidity or frost
• CPC Class Codes: B60H 1/00814 Control systems or circuits characterised by their output, for controlling particular components of the heating, cooling or ventilating installation
• CPC Class Codes: B60H 1/00828 Ventilators, e.g. speed control B60H1/00864 takes precedence

Abstract

A method and apparatus for controlling a vehicle HVAC system to automatically defog a windshield glass and to prevent fogging or condensation of the windshield glass. The ambient air temperature and vehicle speed are measured and used to determine a windshield glass temperature. The in-cabin air temperature and relative humidity are measured and used to determine a dewpoint. An dewpoint margin is calculated to compensate for sensor accuracy and fog predictability. A fog margin, which is based upon calculated windshield glass temperature and dewpoint, is calculated and used, in conjunction with the dewpoint margin, to control the HVAC system to anticipate potential fogging conditions and to scale the intensity of the HVAC system response based upon the severity of fogging conditions.

Claims

1. A method for controlling a vehicle HVAC system, comprising the steps of:

calculating a temperature of a window in said vehicle;

calculating a dewpoint of air within a cabin of said vehicle;

sensing relative humidity of air within said vehicle cabin;

determining a fog margin based upon said calculated window temperature and said calculated dewpoint, said fog margin being related to condensation formation on said vehicle window;

wherein said HVAC system is operated in accordance with a predetermined algorithm based upon said fog margin and said sensed relative humidity.

2. The method according to claim 1, wherein said window temperature calculating step includes the steps of:

measuring a vehicle speed;

measuring a temperature of ambient air outside said vehicle;

calculating said window glass temperature based upon at least one of said measured vehicle speed and said measured ambient air temperature.

3. The method according to claim 2, comprising the further steps of:

measuring air temperature within the vehicle cabin; and

,

if said cabin air temperature is above a predetermined temperature, using said ambient air temperature as said window glass temperature.

4. The method according to claim 1, wherein said dewpoint calculating step includes the steps of:

measuring air temperature within the vehicle cabin; and

,

determining said dewpoint based upon said measured air temperature and relative humidity.

5. A method for controlling a vehicle HVAC system, comprising the steps of:

calculating a temperature of a window in said vehicle;

sensing a temperature of air within said vehicle cabin;

sensing relative humidity of air within said vehicle cabin with a relative humidity sensor, said relative humidity sensor having a predetermined sensor accuracy;

determining a fog margin based upon said calculated window temperature and said calculated dewpoint, said fog margin being related to condensation formation on said vehicle window;

determining a fog predictability, which is a difference between a calculated relative humidity for condensation at a given temperature and a measured relative humidity for condensation at the given temperature;

calculating a dewpoint based upon said sensed air temperature and sensed relative humidity within said vehicle cabin;

calculating a humidity margin based upon said sensor accuracy and said fog predictability;

determining a dewpoint margin based upon said calculated dewpoint and said humidity margin;

wherein said HVAC system is operated in accordance with a predetermined algorithm based upon said fog margin, said sensed relative humidity, and said dewpoint margin.

6. The method according to claim 5, wherein said window temperature calculating step includes the steps of:

measuring a vehicle speed; and

, calculating said window glass temperature based upon at least one of said measured vehicle speed and said measured ambient air temperature.

7. The method according to claim 6, wherein, if said cabin air temperature is above a predetermined temperature, using said ambient air temperature as said window glass temperature.