Engine and emission monitoring and control system utilizing gas sensors

• US 5,426,934 A
• Filed: 02/10/1993
• Issued: 06/27/1995
• Est. Priority Date: 02/10/1993
• Status: Expired due to Term

• Current Assignee: Hitachi America Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi America Limited (Hitachi, Ltd.)
• Inventors: Hunt, Frank W., Kaneyasu, Masayoshi, Saikalis, George
• Primary Examiner(s): Hart, Douglas
• Application Number:
  US08/015,930
• Time in Patent Office: 867 Days
• Field of Search: 60/276, 60/277, 60/278, 123/691, 123/688
• US Class Current: 60/276
• CPC Class Codes: B01D 53/9495 Controlling the catalytic process
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 2250/12 absorption or adsorption, and catalytic conversion
• CPC Class Codes: F01N 2550/00 Monitoring or diagnosing the deterioration of exhaust systems
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F01N 2550/03 of sorbing activity of adsorbents or absorbents
• CPC Class Codes: F02D 41/005 according to engine operating conditions
• CPC Class Codes: F02D 41/146 the characteristics being an NOx content or concentration
• CPC Class Codes: F02D 41/1495 Detection of abnormalities in the air/fuel ratio feedback system
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: G01M 15/102 by monitoring exhaust gases
• CPC Class Codes: G01M 15/104 using oxygen or lambda-sensors testing catalytic converters F01N3/18, F01N11/007
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An engine monitoring system and/or emission reduction system is provided for use in conjunction with an internal combustion engine. The system includes a plurality of sensors which detect various engine operating conditions and in which each sensor generates an output signal representative of its particular engine operating condition. At least one of these sensors is a gas sensor associated with the exhaust system which produces an output signal indicative of the concentration of nitric oxides in the exhaust emissions and which has an output which varies as a function of the concentration of such nitric oxides. A central processing unit receives inputs from the various engine sensors and, in accordance with preprogrammed algorithms, monitors the engine for failure and/or deterioration of various components in the emission reduction system as well as the various engine sensors. The processing unit further generates output signals which controls the operation of various engine components to optimize the operating condition of the engine as well as to meet governmental standards relating to engine emissions.

Claims

1. For use in conjunction with an internal combustion engine which emits nitric oxides as a part of its engine emissions, an exhaust system for the engine and means in said exhaust system for reducing undesirable engine emissions, an engine monitoring system comprising:

a plurality of sensors for detecting various engine operating conditions and for generating output signals representative thereof,

at least one of said sensors comprising a gas sensor associated with said exhaust system which produces an output signal N1 indicative of the concentration of a preselected gas in the engine exhaust emissions,

means responsive to the output signals from said sensors for indicating the state of selected engine components,

wherein said means for reducing emissions in the engine exhaust comprises a three way catalytic converter which reduces hydrocarbons, nitric oxides and carbon monoxide in the exhaust gas stream,

wherein said gas sensor is operatively positioned downstream from the three way converter and wherein said means for reducing emissions in the exhaust gas stream comprises a nitric oxide catalytic converter which receives the exhaust gas steam from the three way converter, and means for detecting a malfunction of the nitric oxide catalytic converter comprising;

a second gas sensor positioned in the exhaust gas stream downstream from the nitric oxide converter, said second gas sensor producing an output signal N2 which varies as a function of the concentration of nitric oxide in the exhaust gas stream,

means for reading the output signal N1 from the first gas sensor and for reading the output signal N2 from the second sensor,

means for generating an efficiency factor for the nitric oxide catalytic converter equal to the value (N1 - N2)/K where K is a preselected constant,

means for comparing said efficiency factor to a preset threshold, and

means for generating an output indicator signal when said efficiency factor exceeds said threshold.

2. The invention as defined in claim 1 wherein said preselected gas is nitric oxide.

3. The invention as defined in claim 1 wherein said sensors further comprise an air/fuel sensor which provides an output signal representative of the air/fuel ratio of the engine.

4. The invention as defined in claim 1 and comprising means for determining the air excess ratio of the engine combustion, and wherein said system includes means for detecting a malfunction of said gas sensor associated with said exhaust system said means for detecting a malfunction of said gas sensor associated with said exhaust system comprising:

means for determining if engine operation is substantially at a stoichiometric air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a stoichiometric value N1_STOIC,

means for determining if engine operation is substantially at a predetermined lean air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a lean value N1_LEAN,

means for calculating a signal ratio SR in accordance with the formula SR=N1_LEAN /N1_STOIC,

means for comparing the calculated value of SR with a preset threshold for SR, and

means for generating an output indicator signal when said calculated value for SR is less than said threshold value for SR.

5. The invention as defined in claim 1 wherein said sensors include a sensor which generates a signal representative of the air excess ratio, and wherein said system comprises means for detecting a malfunction of the three way converter comprising:

means for determining if engine operation is substantially at a predetermined rich air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a rich air/fuel value N1_RICH,

means for determining if engine operation is substantially at a predetermined lean air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a lean air/fuel value N1_LEAN,

means for calculating a threshold value N1_THRESH(TWC) in accordance with the formula N1_THRESH(TWC) =(N1_RICH +N1_LEAN)/K where K is a preselected constant,

means for determining if engine operation is substantially at stoichiometric air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a stoichiometric air/fuel value N1_STOIC,

means for comparing said threshold value N1_STOIC with the calculated threshold value N1_THRESH(TWC) and for generating an output signal representative of a malfunction of the three way converter when N1_STOIC exceeds N1_THRESH(TWC).

6. The invention as defined in claim 1 wherein said sensor comprises an air/fuel sensor which generates an output signal representative of the air/fuel ratio of the engine, and wherein said system comprises means for detecting a malfunction of the air/fuel sensor comprising:

means for determining if engine operation is substantially at a preset rich air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a rich air/fuel value N1_RICH,

means for determining if engine operation is substantially at a predetermined lean air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a lean air/fuel value N1_LEAN,

means for calculating a median value N1_MEDIAN in accordance with the formula N1_MEDIAN =(N1_RICH +N1_LEAN)/K where K is a preselected constant,

means for reading the current output signal N1 from the gas sensor and for determining when current output signal N1 is within a preset range of N1_MEDIAN for thereafter comparing the current air excess ratio with a present range of the air excess ratio, and

means for generating an output signal indicative of a malfunction of the air/fuel sensor when the current air excess ration is outside said preset range of the air excess ratio.

7. The invention as defined in claim 1 wherein said engine sensors comprises an engine speed sensor, an engine knock sensor and an air/fuel sensor, and further comprising means for detecting an engine misfire comprising:

means for reading the output signals from the gas sensor, speed sensor, knock sensor and air/fuel sensor,

means for comparing each said sensor output signal with preselected threshold values wherein one threshold value is associated with each sensor, and

means for generating an indicator output signal indicative of an engine misfire when each said sensor output signal exceeds its associated threshold value.

8. The invention as defined in claim 1 wherein said gas sensor comprises titanium oxide.

9. The invention as defined in claim 1 wherein said gas sensor comprises tin oxide.

10. The invention as defined in claim 1 wherein said gas sensor comprises niobium oxide.

11. For use in conjunction with an internal combustion engine which emits nitric oxides as a part of its engine emissions, an exhaust system for the engine and means in said exhaust system for reducing undesirable engine emissions, an engine monitoring system comprising:

a plurality of sensors for detecting various engine operating conditions and for generating output signals representative thereof,

at least one of said sensors comprising a gas sensor associated with said exhaust system which produces an output signal N1 indicative of the concentration of a preselected gas in the engine exhaust emissions,

means responsive to the output signals from said sensors for indicating the state of selected engine operating conditions,

wherein said engine sensors comprises an engine speed sensor, an engine knock sensor and an air/fuel sensor, and further comprising means for detecting an engine misfire comprising;

means for reading the output signals from the gas sensor, speed sensor, knock sensor and air/fuel sensor,

means for comparing each said sensor output signal with preselected threshold values wherein one threshold value is associated with each sensor, and

means for generating an indicator output signal indicative of an engine misfire when each said sensor output signal exceeds its associated threshold value.

12. The invention as defined in claim 11 wherein said preselected gas is nitric oxide.

13. The invention as defined in claim 11 wherein said sensors further comprise an air/fuel sensor which provides an output signal representative of the air/fuel ratio of the engine.

14. The invention as defined in claim 11 wherein said means for reducing emissions in the engine exhaust comprises a three way catalytic converter which reduces hydrocarbons, nitric oxides and carbon monoxide in the exhaust gas stream.

15. The invention as defined in claim 14 wherein said gas sensor is operatively positioned downstream from the three way converter and wherein said means for reducing emissions in the exhaust gas stream comprises a nitric oxide catalytic converter which receives the exhaust gas stream from the three way converter, and means for detecting a malfunction of the nitric oxide catalytic converter comprising:

a second gas sensor positioned in the exhaust gas stream downstream from the nitric oxide converter, said second gas sensor producing an output signal N2 which varies as a function of the concentration of nitric oxide in the exhaust gas stream,

means for reading the output signal N1 from the first gas sensor and for reading the output signal N2 from the second sensor,

means for generating an efficiency factor for the nitric oxide catalytic converter equal to the value (N1 - N2)K where K is a preselected constant,

means for comparing said efficiency factor to a preset threshold, and

means for generating an output indicator signal when said efficiency factor exceeds said threshold.

16. The invention as defined in claim 11 and comprising means for determining the air excess ratio of the engine combustion, and wherein said system includes means for detecting a malfunction of said gas sensor associated with said exhaust system, said means for detecting a malfunction of said gas sensor associated with said exhaust system comprising:

means for determining if engine operation is substantially at a stoichiometric air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a stoichiometric value N1_STOIC,

means for determining if engine operation is substantially at a predetermined lean air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a lean value N1_LEAN,

means for calculating a signal ratio SR in accordance with the formula SR=N1_LEAN /NI_STOIC,

means for comparing the calculated value of SR with a preset threshold for SR, and

means for generating an output indicator signal when said calculated value for SR is less than said threshold value for SR.

17. The invention as defined in claim 14 wherein said sensors include a sensor which generates a signal representative of the air excess ratio, and wherein said system comprises means for detecting a malfunction of the three way converter comprising:

means for determining if engine operation is substantially at a predetermined rich air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a rich air/fuel value N1_RICH,

means for determining if engine operation is substantially at a predetermined lean air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a lean air/fuel value N1_LEAN,

means for calculating a threshold value N1_THRESH(TWC) in accordance with the formula N1_THRESH(TWC) =(N1_RICH +N1_LEAN)/K where K is a preselected constant,

means for determining if engine operation is substantially at stoichiometric air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a stoichiometric air/fuel value N1_STOIC,

means for comparing said threshold value N1_STOIC with the calculated threshold value N1_THRESH(TWC) and for generating an output signal representative of a malfunction of the three way converter when N1_STOIC exceeds N1_THRESH(TWC).

18. The invention as defined in claim 11 wherein said sensor comprises an air/fuel sensor which generates an output signal representative of the air/fuel ratio of the engine, and wherein said system comprises means for detecting a malfunction of the air/fuel sensor comprising:

means for determining if engine operation is substantially at a preset rich air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a rich air/fuel value N1_RICH,

means for determining if engine operation is substantially at a predetermined lean air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a lean air/fuel value N1_LEAN,

means for calculating a median value N1_MEDIAN in accordance with the formula N1_MEDIAN =(N1_RICH +N1_LEAN)/K where K is a preselected constant,

means for reading the current output signal N1 from the gas sensor and for determining when current output signal N1 is within a preset range of N1_MEDIAN for thereafter comparing the current air excess ratio with a present range of the air excess ratio and

means for generating an output signal indicative of a malfunction of the air/fuel sensor when the current air excess ration is outside said preset range of the air excess ratio.

19. The invention as defined in claim 11 wherein said gas sensor comprises titanium oxide.

20. The invention as defined in claim 11 wherein said gas sensor comprises tin oxide.

21. The invention as defined in claim 11 wherein said gas sensor comprises niobium oxide.

22. For use in conjunction with an internal combustion engine which emits nitric oxides as a pan of its engine emissions, an exhaust system for the engine, means in said exhaust system for reducing undesirable engine emissions comprising a three way converter, and further comprising a plurality of control means for varying engine operating parameters, an engine emission reduction system comprising:

a plurality of sensors for detecting various engine operating conditions and for generating output signals representative thereof,

at least one of said sensors comprising a gas sensor associated with said exhaust system which produces an output signal indicative of the concentration of a preselected gas in the engine exhaust emissions,

means responsive to the output signals from said sensors for regulating said control means during preselected engine operating conditions in a fashion to reduce undesirable engine emissions during said preselected engine operation conditions,

wherein said regulating means comprises means to recirculate a portion of the exhaust emissions from the engine to the intake for the engine,

wherein said exhaust system includes a nitric oxide catalytic converter capable of reducing a preset concentration of nitric oxide, and wherein said system comprises means for detecting the emissions of nitric oxide from the exhaust from the exhaust system, and means for controlling said recirculation means so that the quantity of exhaust gas recirculation is sufficient to reduce the nitric oxide concentration in the exhaust gas stream to said preset concentration.

23. The invention as defined in claim 22 wherein said preselected gas is nitric oxide.

24. The invention as defined in claim 22 and comprising means for introducing air into said three way converter, means for determining the air/fuel ratio, and means for activating said air introducing means when the air/fuel ratio is in a lean or stoichiometric condition and the value from the gas sensor exceeds a preset threshold.

25. The invention as defined in claim 22 wherein said sensors comprise a throttle sensor which produces an output signal indicative of the position of the throttle, wherein the engine includes fuel injectors and means for selectively introducing air into the fuel injectors, means for controlling the introduction of air into the fuel injectors comprising:

means for reading the throttle position sensor,

means responsive to a throttle open condition less than wide open throttle for activating the fuel injector air introducing means in pulses synchronized with the injection of fuel by the fuel injectors.

26. For use in conjunction with an internal combustion engine which emits nitric oxides as a part of its engine emissions, an exhaust system for the engine and means in said exhaust system for reducing undesirable engine emissions, an engine monitoring system comprising:

a plurality of sensors for detecting various engine operating conditions and for generating output signals representative thereof,

at least one of said sensors comprising a gas sensor associated with said exhaust system which produces an output signal N1 indicative of the concentration of a preselected gas in the engine exhaust emissions,

means responsive to the output signals from said sensors for indicating the state of selected engine components,

means for determining the air excess ratio of the engine combustion, and wherein said system includes means for detecting a malfunction of said gas sensor associated with said exhaust system, said means for detecting a malfunction of said gas sensor associated with said exhaust system comprising;

means for determining if engine operation is substantially at a stoichiometric air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a stoichiometric value N1_STOIC,

means for determining if engine operation is substantially at a predetermined lean air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a lean value N1_LEAN,

means for calculating a signal ratio SR in accordance with the formula SR=N1_LEAN /NI_STOIC,

means for comparing the calculated value of SR with a preset threshold for SR, and

means for generating an output indicator signal when said calculated value for SR is less than said threshold value for SR.

27. For use in conjunction with an internal combustion engine which emits nitric oxides as a pan of its engine emissions, an exhaust system for the engine and means in said exhaust system for reducing undesirable engine emissions, an engine monitoring system comprising:

a plurality of sensors for detecting various engine operating conditions and for generating output signals representative thereof,

at least one of said sensors comprising a gas sensor associated with said exhaust system which produces an output signal N1 indicative of the concentration of a preselected gas in the engine exhaust emissions,

means responsive to the output signals from said sensors for indicating the state of selected engine components,

wherein said sensor comprises an air/fuel sensor which generates an output signal representative of the air/fuel ratio of the engine, and wherein said system comprises means for detecting a malfunction of the air/fuel sensor comprising;

means for determining if engine operation is substantially at a preset rich air/fuel ratio and means for then reading the output signal NI from the gas sensor and for storing a rich air/fuel value N1_RICH,

means for determining if engine operation is substantially at a predetermined lean air/fuel ratio and means for then reading the output signal N1 from the gas sensor and for storing a lean air/fuel value N1_LEAN,

means for calculating a median value N1_MEDIAN in accordance with the formula N1_MEDIAN =(N1_RICH +N1_LEAN)/K where K is a preselected constant,

means for reading the current output signal N1 from the gas sensor and for determining when current output signal N1 is within a preset range of N1_MEDIAN for thereafter comparing the current air excess ratio with a present range of the air excess ratio, and

means for generating an output signal indicative of a malfunction of the air/fuel sensor when the current air excess ration is outside said preset range of the air excess ratio.

28. For use in conjunction with an internal combustion engine which emits nitric oxides as a pan of its engine emissions, an exhaust system for the engine, means in said exhaust system for reducing undesirable engine emissions comprising a three way converter, and further comprising a plurality of control means for varying engine operating parameters, an engine emission reduction system comprising:

a plurality of sensors for detecting various engine operating conditions and for generating output signals representative thereof,

at least one of said sensors comprising a gas sensor associated with said exhaust system which produces an output signal indicative of the concentration of a preselected gas in the engine exhaust emissions,

means responsive to the output signals from said sensors for regulating said control means during preselected engine operating conditions in a fashion to reduce undesirable engine emissions during said preselected engine operation conditions,

means for introducing air into said three way converter, means for determining the air/fuel ratio, and means for activating said air introducing means when the air/fuel ratio is in a lean or stoichiometric condition and the value from the gas sensor exceeds a preset threshold.

29. The invention as defined in claim 28 and comprising means for activating said air introducing means during a rich air/fuel engine operating condition.

30. For use in conjunction with an internal combustion engine which emits nitric oxides as a part of its engine emissions, an exhaust system for the engine, means in said exhaust system for reducing undesirable engine emissions comprising a three way converter, and further comprising a plurality of control means for varying engine operating parameters, an engine emission reduction system comprising:

a plurality of sensors for detecting various engine operating conditions and for generating output signals representative thereof,

at least one of said sensors comprising a gas sensor associated with said exhaust system which produces an output signal indicative of the concentration of a preselected gas in the engine exhaust emissions,

means responsive to the output signals from said sensors for regulating said control means during preselected engine operating conditions in a fashion to reduce undesirable engine emissions during said preselected engine operation conditions,

wherein said sensors comprise a throttle sensor which produces an output signal indicative of the position of the throttle, wherein the engine includes fuel injectors and means for selectively introducing air into the fuel injectors, means for controlling the introduction of air into the fuel injectors comprising;

means for reading the throttle position sensor,

means responsive to a throttle open condition less than wide open throttle for activating the fuel injector air introducing means in pulses synchronized with the injection of fuel by the fuel injectors.

31. The invention as defined in claim 30 wherein said air introducing pulses precede their associated fuel injection pulse by a predetermined amount.

32. The invention as defined in claim 30 and comprising means for activating the fuel injector air introducing means in pulses synchronized with the injection of fuel by the fuel injector during a warm engine, idle operating condition.

33. The invention as defined in claim 32 wherein said air introducing pulses precede their associated fuel injection pulse by a predetermined amount.

34. The invention as defined in claim 30 and comprising means for continuously activating said fuel injector air introducing means during a throttle closed, cold engine operating condition.