Method of determining windshield fogging based on inference from presence of rain

• US 6,155,061 A
• Filed: 12/23/1999
• Issued: 12/05/2000
• Est. Priority Date: 12/23/1999
• Status: Expired due to Fees

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Ford Motor Company
• Inventors: Dage, Gerhard Allen, Hoeschele, John David, Davis, Leighton Ira Jr.
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US09/472,085
• Time in Patent Office: 348 Days
• Field of Search: 62/133, 62/176.1, 62/176.2, 62/176.5, 62/176.6, 62/244, 165/204, 165/222, 165/224, 165/230, 165/42, 165/43, 236/44 A, 236/44 R, 236/44 C, 236/91 C, 236/49.3, 454/75
• US Class Current: 62/176.6
• CPC Class Codes: B60H 1/00785 by the detection of humidity or frost

Abstract

A method is provided of determining windshield fog secondary for automatically controlling a heating, ventilation and air conditioning (HVAC) system of a vehicle. The method includes the steps of determining whether rain is occurring on a windshield of a vehicle, determining a windshield parameter as a function of the rain occurring and determining a temperature difference based on temperature within a cabin of the vehicle and ambient temperature. The method also includes the steps of determining a fog boundary based on the windshield parameter and temperature difference, determining a relative humidity based on the windshield parameter and the temperature difference and fog boundary and determining a fog probability based on the fog boundary relative humidity and a nominal base relative humidity for rain conditions. The method further includes the steps of determining anti-fog actions to be taken based on the fog probability and taking the anti-fog actions determined to control the HVAC system.

Claims

1. A method of determining windshield fog boundary for automatically controlling a heating, ventilation and air conditioning (HVAC) system of a vehicle, said method comprising the steps of:

determining whether rain is occurring on a windshield of a vehicle;

determining a windshield parameter as a function of the rain occurring;

determining a temperature difference based on temperature within a cabin of the vehicle and ambient temperature;

determining a fog boundary based on the windshield parameter and temperature difference;

determining a relative humidity based on the windshield parameter and the temperature difference and fog boundary;

determining a fog probability based on the fog boundary relative humidity and a nominal base relative humidity for rain conditions;

determining anti-fog actions to be taken based on the fog probability; and

taking the anti-fog actions determined to control the HVAC system.

2. A method as set forth in claim 1 wherein said step of determining whether rain is occurring is based on a signal from a rain sensor or a wiper motor for a predetermined period of time.

3. A method as set forth in claim 2 wherein said step of determining the windshield parameter is a function of vehicle speed, time and rain occurring.

4. A method as set forth in claim 3 wherein including the step of determining a fog boundary comprises calculating the fog boundary based on the ambient temperature (T_amb) and windshield parameter (F_w) and temperature difference (T_in -T_amb).

5. A method as set forth in claim 4 wherein said step of calculating the fog boundary according to the equation rh_bd =100-h^-1 [(1-F_w) (T_in -T_amb)].

6. A method as set forth in claim 5 wherein said step of determining the anti-fog actions comprises determining whether to adjust blower speed, turn on the air conditioning, change an air distribution mode, adjust a fresh/recirculation air door, add heat or any combination of these actions.

7. A method as set forth in claim 6 wherein said step of taking the anti-fog actions comprises adjusting blower speed, turning on the air conditioning, changing an air distribution mode, adjusting a fresh/recirculation air door, or adding heat.

8. A method as set forth in claim 2 wherein said step of determining fog probability is based on the windshield parameter (F_w) and the temperature difference (T_in -T_amb) and a nominal base relative humidity for rain conditions.

9. A method as set forth in claim 8 wherein said fog probability is determined from a range of relative humidity approximately from 75% to 95% and temperature difference of approximately from 30°

F. to 50°

F.

10. A method of determining windshield fog boundary for automatically controlling a heating, ventilation and air conditioning (HVAC) system of a vehicle, said method comprising the steps of:

determining whether rain is occurring on a windshield of a vehicle;

determining a windshield parameter as a function of the rain occurring;

determining a temperature difference based on temperature within a cabin of the vehicle and ambient temperature;

calculating a fog boundary relative humidity based on the ambient temperature (T_amb) and the windshield parameter (F_w) and the temperature difference (T_in -T_amb);

determining a fog probability based on the fog boundary relative humidity and a nominal base relative humidity for rain conditions;

determining anti-fog actions to be taken based on the fog probability; and

taking the anti-fog actions determined to control the HVAC system.

11. A method as set forth in claim 10 wherein said step of determining whether rain is occurring is based on a signal from a rain sensor or a wiper motor for a predetermined period of time.

12. A method as set forth in claim 11 wherein said step of determining the windshield parameter is a function of vehicle speed, time and rain occurring.

13. A method as set forth in claim 10 wherein said step of calculating the fog boundary according to the equation rh_bd =100-h^-1 [(1-F_w) (T_in -T_amb)].

14. A method as set forth in claim 10 wherein said step of determining the anti-fog actions comprises determining whether to adjust blower speed, turn on the air conditioning, change an air distribution mode, adjust a fresh/recirculation air door, add heat, or any combination of these actions.

15. A method as set forth in claim 14 wherein said step of taking the anti-fog actions comprises adjusting blower speed, turning on the air conditioning, changing an air distribution mode, adjusting a fresh/recirculation air door, or adding heat.

16. A method as set forth in claim 10 wherein said step of determining fog probability is based on the windshield parameter (F_w) and the temperature difference (T_in -T_amb) and a nominal base relative humidity for rain conditions.

17. A method as set forth in claim 16 wherein said fog probability is determined from a range of relative humidity approximately from 75% to 95% and temperature difference of approximately from 30°

F. to 50°

F.

18. A method of determining windshield fog boundary for automatically controlling a heating, ventilation and air conditioning (HVAC) system of a vehicle, said method comprising the steps of:

determining whether rain is occurring on a windshield of a vehicle based on a signal from a rain sensor or a wiper motor for a predetermined period of time;

determining a windshield parameter as a function of the rain occurring;

determining a temperature difference based on temperature within a cabin of the vehicle and ambient temperature;

calculating a fog boundary on the ambient temperature (T_amb) and the windshield parameter (F_w) and the temperature difference (T_in -T_amb);

determining a relative humidity based on the windshield parameter and the temperature difference and fog boundary;

determining a fog probability based on the windshield parameter (F_w) and the temperature difference (T_in -T_amb) and a nominal base relative humidity for rain conditions;

determining anti-fog actions to be taken based on the fog probability; and

taking the anti-fog actions determined to control the HVAC system.

19. A method as set forth in claim 18 wherein said step of determining the windshield parameter is a function of vehicle speed, time and rain occurring.

20. A method as set forth in claim 18 wherein said fog probability is determined from a range of relative humidity approximately from 75% to 95% and temperature difference of approximately from 30°

F. to 50°

F.