Humidity compensation system for an internal combustion engine

• US 6,575,148 B1
• Filed: 02/22/2002
• Issued: 06/10/2003
• Est. Priority Date: 02/22/2002
• Status: Active Grant

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Bhargava, Sumit, Dunnuck, David
• Primary Examiner(s): NGUYEN, HOANG M
• Application Number:
  US10/080,722
• Time in Patent Office: 473 Days
• Field of Search: 606/02, 606/051, 123/564, 123/406.12, 123/406.19, 123/406.55
• US Class Current: 123/564
• CPC Class Codes: F02B 29/0406 Layout of the intake air cooling or coolant circuit
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02B 37/18 by bypassing exhaust from the inlet to the outlet of turbine or to the atmosphere
• CPC Class Codes: F02B 37/22 by varying cross-section of exhaust passages or air passages , e.g. by throttling turbine inlets or outlets or by varying effective number of guide conduits F02B37/24 takes precedence
• CPC Class Codes: F02B 37/24 by using pumps or turbines with adjustable guide vanes
• CPC Class Codes: F02D 2200/0402 the parameter being determined by using a model of the engine intake or its components
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 2200/0418 Air humidity
• CPC Class Codes: F02D 2200/703 Atmospheric pressure
• CPC Class Codes: F02D 37/02 one of the functions being ignition
• CPC Class Codes: F02D 41/00 Electrical control of supply of combustible mixture or its constituents F02D43/00 takes precedence ; control of engine starters F02N11/08, electrical control of engine ignition timing F02P5/145
• CPC Class Codes: F02D 41/1487 Correcting the instantaneous control value
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• CPC Class Codes: F02M 26/05 High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• CPC Class Codes: F02M 26/10 having means to increase the pressure difference between the exhaust and intake system, e.g. venturis, variable geometry turbines, check valves using pressure pulsations or throttles in the air intake or exhaust system
• CPC Class Codes: F02M 26/23 Layout, e.g. schematics
• CPC Class Codes: F02P 5/1506 with particular means during starting
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A humidity compensation system for an internal combustion engine includes a humidity sensor sensing relative humidity of intake air, a temperature sensor sensing intake air temperature, a pressure sensor sensing intake air pressure and a control circuit computing a specific humidity (SH) value based on the sensor outputs. The control circuit is configured to compute one or more of an adjusted air-to-fuel ratio command as a function of SH and a default air-to-fuel ratio command, an adjusted ignition timing command as a function of SH, engine speed and a default ignition timing command and an adjusted boost pressure command as a function of SH and a default boost pressure command. The control circuit is operable to control any of fueling, ignition timing and boost pressure based on the corresponding adjusted air-to-fuel ratio, ignition timing and boost pressure commands to thereby compensate for humidity effects on engine operation.

Claims

1. A humidity compensation system for an internal combustion engine, comprising:

means for determining a specific humidity of air entering an intake manifold of an internal combustion engine;

a fuel system responsive to a fueling command to supply fuel to said engine; and

a control circuit determining an adjusted air-to-fuel ratio command as a function of said specific humidity and a default air-to-fuel ratio command, said control circuit producing said fueling command as a function of said adjusted air-to-fuel ratio command.

2. The system of claim 1 wherein said control circuit is configured to determine an air-to-fuel multiplier as a function of said specific humidity and to determine said adjusted air-to-fuel ratio command as a product of said air-to-fuel multiplier and said default air-to-fuel command.

3. The system of claim 2 wherein said control circuit includes an air-to-fuel multiplier map mapping a number of specific humidity values to a corresponding number of air-to-fuel multiplier values, said control circuit determining said air-to-fuel multiplier by mapping said specific humidity to an appropriate one of said number of air-to-fuel multiplier values.

4. The system of claim 1 further including:

a turbocharger having a turbine configured to discharge engine exhaust gas therefrom; and

means responsive to an airflow signal to modify a swallowing capacity of said turbine;

and wherein said control circuit is configured to determine an adjusted boost pressure command as a function of said specific humidity and a default boost pressure command, said control circuit producing said airflow signal as a function of said adjusted boost pressure command.

5. The system of claim 4 wherein said control circuit is configured to compute a boost multiplier as a function of said specific humidity and to compute said adjusted boost pressure command as a product of said boost multiplier and said default boost pressure command.

6. The system of claim 5 wherein said control circuit includes a boost multiplier map mapping a number of specific humidity values to a corresponding number of boost multiplier values, said control circuit determining said boost multiplier by mapping said specific humidity to an appropriate one of said number of boost multiplier values.

7. The system of claim 1 further including:

an engine speed sensor producing an engine speed signal indicative of rotational speed of said engine; and

an ignition system responsive to a timing signal to ignite an air-fuel mixture within said engine;

and wherein said control circuit is configured to determine an adjusted ignition timing command as a function of said specific humidity, said engine speed signal and a default ignition timing command, said control circuit producing said timing signal as a function of said adjusted ignition timing command.

8. The system of claim 7 wherein said control circuit is configured to determine a timing multiplier as a function of said engine speed signal and to determine a timing modifier as a product of said timing multiplier and said specific humidity, said control circuit determining said adjusted ignition timing command as a sum of said timing modifier and said default ignition timing command.

9. The system of claim 8 wherein said control circuit includes a timing multiplier map mapping a number of specific engine speed values to a corresponding number of timing multiplier values, said control circuit determining said timing multiplier by mapping a current value of said engine speed signal to an appropriate one of said number of timing multiplier values.

10. The system of claim 9 further including:

a turbocharger having a turbine configured to discharge engine exhaust gas therefrom; and

means responsive to an airflow signal to modify a swallowing capacity of said turbine;

and wherein said control circuit is configured to determine an adjusted boost pressure command as a function of said specific humidity and a default boost pressure command, said control circuit producing said airflow signal as a function of said adjusted boost pressure command.

11. The system of claim 10 wherein said control circuit is configured to compute a boost multiplier as a function of said specific humidity and to compute said adjusted boost pressure command as a product of said boost multiplier and said default boost pressure command.

12. The system of claim 11 wherein said control circuit includes a boost multiplier map mapping a number of specific humidity values to a corresponding number of boost multiplier values, said control circuit determining said boost multiplier by mapping said specific humidity to an appropriate one of said number of boost multiplier values.

13. The system of claim 1 wherein said means for determining a specific humidity of air entering said intake manifold of said internal combustion engine includes:

a humidity sensor producing a humidity signal indicative of relative humidity of air entering said intake manifold;

a temperature sensor producing a temperature signal indicative of a temperature of air entering said intake manifold; and

a pressure sensor producing a pressure signal indicative of a pressure of air entering said intake manifold;

and wherein control circuit responsive to said humidity signal, said temperature signal and said pressure signal to determine said specific humidity.

14. The system of claim 1 further wherein said means for determining a specific humidity of air entering said intake manifold of said internal combustion engine includes:

a humidity sensor producing a humidity signal indicative of relative humidity of ambient air;

a temperature sensor producing a temperature signal indicative of ambient air temperature; and

a pressure sensor producing a pressure signal indicative of ambient air pressure;

and wherein control circuit responsive to said humidity signal, said temperature signal and said pressure signal to determine said specific humidity.

15. A method of compensating for atmospheric humidity effects on the operation of an internal combustion engine, comprising:

determining a specific humidity of air entering an intake manifold of an internal combustion engine;

computing an adjusted air-to-fuel ratio command as a function of said specific humidity and a default air-to-fuel ratio command; and

fueling said engine based on said adjusted air-to-fuel ratio command.

16. The method of claim 15 wherein the computing step further includes:

computing an air-to-fuel multiplier as a function of said specific humidity; and

computing said adjusted air-to-fuel ratio command as a product of said air-to-fuel multiplier and said default air-to-fuel ratio command.

17. The method of claim 15 further including:

computing an adjusted boost pressure command as a function of said specific humidity and a default boost pressure command; and

controlling pressure of air entering an intake manifold of said engine based on said adjusted boost pressure command.

18. The method of claim 15 further including:

determining an engine speed value corresponding to a rotational speed of said engine;

computing an adjusted ignition timing command as a function of said specific humidity, said engine speed value and a default ignition timing command; and

controlling ignition timing of said engine based on said adjusted ignition timing command.

19. The method of claim 18 further including:

computing an adjusted boost pressure command as a function of said specific humidity and a default boost pressure command; and

controlling pressure of air entering an intake manifold of said engine based on said adjusted boost pressure command.

20. A humidity compensation system for an internal combustion engine, comprising:

means for determining a specific humidity of air entering an intake manifold of an internal combustion engine;

an engine speed sensor producing an engine speed signal indicative of a rotational speed of said engine;

an ignition system responsive to a timing signal to ignite an air-fuel mixture within said engine; and

a control circuit determining an adjusted ignition timing command as a function of said specific humidity, said engine speed signal and a default ignition timing command, said control circuit producing said timing signal as a function of said adjusted ignition timing command.

21. The system of claim 20 wherein said control circuit is configured to determine a timing multiplier as a function of said engine speed signal and to determine a timing modifier as a product of said timing multiplier and said specific humidity, said control circuit determining said adjusted ignition timing command as a sum of said timing modifier and said default ignition timing command.

22. The system of claim 20 wherein said control circuit includes a timing multiplier map mapping a number of specific engine speed values to a corresponding number of timing multiplier values, said control circuit determining said timing multiplier by mapping a current value of said engine speed signal to an appropriate one of said number of timing multiplier values.

23. The system of claim 20 further including:

a turbocharger having a turbine configured to discharge engine exhaust gas therefrom; and

means responsive to an airflow signal to modify a swallowing capacity of said turbine;

and wherein said control circuit is configured to determine an adjusted boost pressure command as a function of said specific humidity and a default boost pressure command, said control circuit producing said airflow signal as a function of said adjusted boost pressure command.

24. The system of claim 23 wherein said control circuit is configured to compute a boost multiplier as a function of said specific humidity and to compute said adjusted boost pressure command as a product of said boost multiplier and said default boost pressure command.

25. The system of claim 24 wherein said control circuit includes a boost multiplier map mapping a number of specific humidity values to a corresponding number of boost multiplier values, said control circuit determining said boost multiplier by mapping said specific humidity to an appropriate one of said number of boost multiplier values.

26. The system of claim 20 wherein said means for determining a specific humidity of air entering said intake manifold of said internal combustion engine includes:

a humidity sensor producing a humidity signal indicative of relative humidity of air entering said intake manifold;

a temperature sensor producing a temperature signal indicative of a temperature of air entering said intake manifold; and

a pressure sensor producing a pressure signal indicative of a pressure of air entering said intake manifold;

and wherein control circuit responsive to said humidity signal, said temperature signal and said pressure signal to determine said specific humidity.

27. The system of claim 20 further wherein said means for determining a specific humidity of air entering said intake manifold of said internal combustion engine includes:

a humidity sensor producing a humidity signal indicative of relative humidity of ambient air;

a temperature sensor producing a temperature signal indicative of ambient air temperature; and

a pressure sensor producing a pressure signal indicative of ambient air pressure; and

wherein control circuit responsive to said humidity signal, said temperature signal and said pressure signal to determine said specific humidity.

28. A method of compensating for atmospheric humidity effects on the operation of an internal combustion engine, comprising:

determining a specific humidity of air entering an intake manifold of an internal combustion engine;

determining a rotational speed of said engine;

computing an adjusted ignition timing command as a function of said specific humidity, said rotational speed of said engine and a default ignition timing command; and

controlling ignition timing of said engine based on said adjusted ignition timing command.

29. The method of claim 28 wherein the computing step further includes:

computing a timing multiplier as a function of said rotational speed of said engine;

computing a timing modifier as a product of said timing multiplier and said specific humidity; and

computing said adjusted ignition timing command as a sum of said timing modifier and said default ignition timing command.

30. The method of claim 28 further including:

computing an adjusted boost pressure command as a function of said specific humidity and a default boost pressure command; and

controlling pressure of air entering an intake manifold of said engine based on said adjusted boost pressure command.