Catalyst efficiency detection and heating method using cyclic fuel control

• US 6,651,422 B1
• Filed: 11/28/2000
• Issued: 11/25/2003
• Est. Priority Date: 08/24/1998
• Status: Expired due to Term

• Current Assignee: Joseph E. Legare
• Original Assignee: Joseph E. Legare
• Inventors: LeGare, Joseph E.
• Primary Examiner(s): Denion, Thomas
• Assistant Examiner(s): TRAN, DIEM T
• Application Number:
  US09/722,273
• Time in Patent Office: 1,092 Days
• Field of Search: 602/74, 602/84, 602/85, 602/77, 602/82, 602/99
• US Class Current: 60/277
• CPC Class Codes: F01N 11/002 the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• CPC Class Codes: F01N 2430/06 by varying fuel-air ratio, e.g. by enriching fuel-air mixture
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F01N 2900/0422 measuring the elapsed time
• CPC Class Codes: F02D 41/0085 Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio
• CPC Class Codes: F02D 41/0255 to accelerate the warming-up of the exhaust gas treating apparatus at engine start
• CPC Class Codes: F02D 41/1408 Dithering techniques
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An automobile engine'"'"'s catalytic converter is heated by inducing a change in the engine'"'"'s fuel injection delivery that varies from normal operating conditions. Heating the engine'"'"'s catalytic converter by changing the engine'"'"'s fuel injection delivery is useful in enabling the catalytic converter to achieve efficient operating temperature quicker and enables efficient and accurate diagnosis of catalyst degradation. Diagnosis of degraded catalyst performance is accomplished by measurements of the catalyst'"'"'s temperature characteristics following alternating of the fuel delivery to different cylinders from lean and rich fuel conditions that differ from the mass ratio of air to fuel being at chemical stoichiometric conditions. Measurements of the catalyst'"'"'s temperature characteristics with defined modifications of an engine'"'"'s operating conditions allows determining the catalytic converter'"'"'s gas conversion effectiveness. Commonly available temperature sensing devices are used to measure the exothermic heat generation in a portion of the evaluated catalytic converter for comparison to the temperature characteristics of a known catalyst'"'"'s conversion effectiveness.

Claims

1. A method of heating a catalytic converter of an internal combustion engine, including the steps of:

providing at least one temperature sensor in said catalytic converter;

sensing conditions from past and present engine control system parameters together with measurements of catalytic converter efficiency to determine sufficient levels of exothermic chemical reactions within the said catalytic converter; and

initiating cycling of exhaust gases'"'"' air-fuel ratios, from selected engine cylinders within the sensed limits of engine cylinder misfire, to produce air-fuel variations entering said catalytic converter so as to provide conditions sufficient for heating the catalyst to a temperature that reduces emission concentrations exiting said catalytic converter.

2. A method according to claim 1, whereby the quantity of fuel delivered to alternate groupings of engine cylinders are varied between non-stoichiometric conditions of excess fuel and insufficient fuel to cause sequentially alternating exhaust gas conditions entering the catalyst.

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

controlling the fuel quantity delivered to select cylinders of an internal combustion engine with a controller in an alternating manner for causing exhaust gas conditions that sufficiently deviate from extremes of normal engine stoichiometric closed loop fuel control conditions so as to increase the chemical energy content of the exhaust gases entering said catalytic converter; and

initiating said alternating fuel control only during pre-defined operating conditions to cause said heating of said catalytic converter.

4. The method of claim 1, wherein said step of controlling input fuel and air conditions includes operate the engine with large cyclic variations in the quantity of fuel delivered to each cylinder that sufficiently deviates from normal operation so as to cause a rise in said catalyst temperature as detected by said temperature sensor at a second temperature sufficient to cause said catalytic converter to operate at an operating temperature so that said catalytic converter effectively purifies said emissions from said catalytic converter.

5. The method of claim 4 wherein said step of controlling input fuel and air conditions further includes vary delivered fuel quantities to each cylinder, that feeds exhaust gases into a catalyst element of said catalytic converter so as to cause air-fuel ratio conditions sufficiently deviating from normal stoichiometric operation with the exhaust gases of alternating cylinders or groupings thereof feeding into the said catalyst to be alternately richer or leaner than chemical stoichiometric conditions, which increases the level of exothermic energy available to combine chemically at the active surfaces of said catalyst for producing a temperature change.

6. The method according to claim 1, wherein the step of controlling operates so that the groupings of cylinders'"'"' exhaust gases'"'"' air-fuel conditions, from selected engine cylinders are modified to minimize engine torque fluctuations while causing a change in quantities of chemically reactive gases entering said catalytic converter between richer and leaner than stoichiometric.

7. A method of heating a catalytic converter of an internal combustion engine including the steps of:

providing at least one temperature sensor in said catalytic converter;

sensing, with said temperature sensor, a first temperature indicating that a catalyst in said catalytic converter is not operating at an operating temperature at which said catalyst will effectively purify emissions from said catalytic converter;

measuring other engine and vehicle parameters in addition to the catalyst temperature for comparing to respective threshold values that determine initiation of catalyst heating;

initiating a change in the fuel quantities, delivered to individual engine cylinders connected to said catalytic converter, that differs from normal engine operation;

adjusting a magnitude of fuel delivered to selected ones of each of said individual engine cylinders such that the air-fuel ratio characteristics of the exhaust gases entering said catalytic converter cycle between levels alternating from leaner than stoichiometric to richer than stoichiometric conditions so that said catalytic converter increases in temperature faster than under normal operating conditions without said adjusting the magnitude of fuel delivered to each individual engine cylinder; and

adjusting the magnitude of fuel to each of said engine cylinders, individually, such that the air-fuel ratio characteristics of the exhaust gases entering said catalytic converter cycle is approximately at stoichiometric conditions when said temperature sensor is measuring a second temperature is indicative of said catalytic converter operating at an operating temperature such that said catalytic converter is effectively purifying said emissions output from said catalytic converter.

8. The method of claim 7, further comprising the steps of:

controlling the time duration of fuel delivered to each of said engine cylinders, individually, such that the air-fuel ratio characteristics of the exhaust gases entering said catalytic converter alternate between rich and lean conditions;

controlling frequency of the lean to rich to lean cycle of exhaust gases feeding into said catalytic converter by delivering to groupings of firing cylinders a fuel quantity, that causes each cylinder in the group to have a common air-fuel ratio, either richer or leaner than stoichiometric;

producing a gas stream entering the catalyst that cycles between non-stoichiometric conditions having exhaust air-fuel ratios alternating from lean and rich conditions; and

monitoring the catalyst temperature for comparing to threshold values that determine the termination of catalyst heating, and wherein said leaner than stoichiometric conditions is such that λ

is more than 1.07 and said richer than stoichiometric conditions is such that λ

s less then 0.93.

9. An engine control system for heating a catalytic converter of an internal combustion engine, comprising:

a temperature sensor disposed in said catalytic converter; and

an electronic engine control system configured to;

sensing with said temperature sensor a first temperature condition together with other past and present control system parameters indicating that said catalytic converter has reached conditions sustaining exothermic chemical reactions within the catalyst; and

controlling cycling of exhaust gases'"'"' air-fuel ratios, from selected engine cylinders, to produce air-fuel variations of and thereby produce additional quantities of chemically reactive gases entering said catalytic converter so as to provide conditions sufficient for heating the catalyst to a temperature that reduces emission concentrations exiting said catalytic converter.

10. The system of claim 9, further comprising:

a second temperature sensor disposed in said catalytic converter at a different location than said first temperature sensor, said second temperature sensor for determining a temperature of a different catalyst element than said first sensor so as to ensure that both catalyst elements are heated to a temperature sufficient for said catalytic converter to operate effectively to purify said emissions from said catalytic converter.

11. The system of claim 9 wherein said step of controlling input fuel and air conditions further includes modifying the delivered fuel quantities to each cylinder for preventing operation within the detected limits of engine misfire to thereby more consistently increase the level of exothermic energy available to combine chemically at the active surfaces of said catalyst for producing a temperature change while minimizing air pollutants.

12. The system of claim 11, wherein said step of controlling input fuel and air conditions includes operating the engine with large cyclic variations in the quantity of fuel delivered to each cylinder that sufficiently deviates from normal operation so as to cause a rise in said catalyst temperature as detected by said temperature sensor at a second temperature sufficient to cause said catalytic converter to operate at an operating temperature so that said catalytic converter effectively purifies said emissions from said catalytic converter.

13. The system according to claim 9, wherein the electronic engine controller modifies the exhaust gases'"'"' air-fuel conditions from selected engine cylinders to cause a change in quantities of chemically reactive gases entering said catalytic converter between richer and leaner than stoichiometric, while remaining outside the detected limits of engine cylinder misfiring.

14. A method of heating a catalytic converter of an internal combustion engine, comprising the steps of:

providing at least one temperature sensor in said catalytic converter;

sensing with said temperature sensor a first temperature indicating that said catalytic converter is operating at conditions producing exothermic chemical reactions; and

changing quantities of chemically reactive gases by varying selected engine cylinders exhaust gases'"'"' air-fuel ratios entering said catalytic converter so as to heat the catalyst to an increased temperature sufficient to reduce emission concentrations exiting said catalytic converter.

15. A method according to claim 14, whereby the step of changing quantities of chemically reactive gases entering said catalytic converter includes changing the amount of hydrocarbon, CO, and oxygen.

16. A method according to claim 14, further comprising the steps of:

sensing a second temperature condition of said catalytic converter at a second time period with said at least one temperature sensor;

comparing actual catalytic converter temperature versus time characteristic as derived from said first temperature conditions and said second temperature conditions to reference values stored in memory and determining an existence of a malfunctioning catalytic converter based upon said comparison between actual and reference catalytic converter temperature characteristics.

17. The method according to claim 16, whereby results from said comparisons to determine an existence of a malfunctioning catalytic converter are used to modify both the starting point for initiating cycling of exhaust gases'"'"' air-fuel ratios and their magnitudes to heat the catalyst when the temperature is between approximately 100°

C. and 500°

C.

18. The system according to claim 14, wherein the step of changing quantities of chemically reactive gases operates so that the exhaust gases entering said catalytic converter varies between conditions richer and leaner than stoichiometric.

19. A method according to claim 17, wherein the first temperature is below 200°

C.

20. A method according to claim 14, wherein the first temperature is below 200°

C.

21. A method of determining the gas conversion efficiency of a catalytic converter connected to an engine having one or more cylinders, including the steps of:

measuring an initial temperature for exhaust gases in a said catalytic converter at one or more location(s);

monitoring temperature characteristics of said catalytic converter together with past and present engine control unit parameters to determine stable operating conditions suitable for providing consistent evaluation of gas conversion efficiency characteristics of said catalytic converter;

activating an engine control unit for cycling of fuel levels delivered to selected engine cylinders, each of said selected engine cylinder'"'"'s gas flow having conditions of either excess fuel or excess air that sufficiently deviate from stoichiometric chemical requirements;

cycling a quantity of fuel delivered to alternate groups of engine cylinders to provide feed gases to said catalytic converter with consistent levels of chemical energy for the purpose of creating a sufficient change in the unburned exhaust gas entering said catalytic converter during a predetermined time period;

measuring a temperature versus time profile at said location of said catalytic converter from a time near initiation of said cycling a quantity of fuel delivered to alternate groups of engine cylinders and subsequent to disabling said cycling;

comparing said measured temperatures to temperature profiles stored in a memory, said temperature profiles representative of a near malfunctioning catalytic converter;

determining from said monitored catalytic converter'"'"'s temperature profile a second average time rate of temperature change and the corresponding maximum average exhaust gas temperature change attained since said initial temperature measurement;

comparing said second average time rate of temperature change in a calibrated time period with temperature change rates stored in said memory;

comparing a maximum average exhaust gas temperature change attained since said initial temperature measurement, after another time period, with a delta temperature threshold value stored in said memory;

updating a magnitude of a catalyst diagnostic flag counter value stored in said memory by a value determined by a comparison of the maximum average exhaust gas temperature change and the second average time rate of temperature change after a calibrated time period for said thresholds stored in said memory, said values depending on past and present operating parameters; and

activating a catalyst state malfunction indicator when the catalyst diagnostic flag counter value reaches a predetermined value.

22. A method according to claim 21, whereby magnitudes of the induced fluctuations in exhaust air-fuel ratio for each respectively firing engine cylinder are selected from values stored in said memory depending on past and present operating parameters.

23. A method according to claim 21, whereby a frequency of cycling said fuel rate to the engine cylinders is selected from stored values in said memory depending on past and present operating parameters in order to maximize a temperature rise of the engine exhaust gases.

24. A method according to claim 21, whereby magnitude and frequency of the air-fuel ratio perturbations from stoichiometric conditions flowing into said catalytic converter are selected from stored values in said memory depending on past and present operating parameters.

25. A method according to claim 21, whereby the engine operating conditions, for initiating cyclic fuel control modulation to cause exhaust air-fuel ratio fluctuations, are selected so as to minimize concentrations of CO, HC and nitrogen oxide gases exiting the catalytic converter.

26. A method according to claim 21, whereby the magnitude and timing of an intentionally induced rise in catalyst temperature is selected together with an appropriately positioned temperature measuring device based upon the engine design characteristics to allow detection of an unacceptable degradation in said monitored catalytic converter conversion efficiency.

27. A method according to claim 21, whereby the catalytic converter temperature is measured using a single temperature sensor placed at the specified location, that has been predetermined to allow sensing the aggregate exothermic temperature characteristics of said catalytic converter below a specified level of gas conversion efficiency.

28. A method according to claim 21, whereby a duration of the time period used for detection of catalytic converter efficiency performance is selected to provide accurate monitoring of said catalytic converter'"'"'s efficiency performance.

29. A method according to claim 21, whereby both frequency and magnitude of each individual cylinder'"'"'s air-fuel ratio fluctuations are selected to cause a sufficiently large catalyst temperature change to determine efficiency of said catalytic converter, without interrupting the engine'"'"'s combustion event and ignition.

30. A method according to claim 21, whereby said time period that the catalytic converter operates below 500°

C. may be reduced by detecting the initiation of catalyst exothermic energy release at temperatures above 100°

C. and enabling catalyst heating using cyclic fuel control modulation.

31. A method according to claim 21, whereby the conditions of engine operation can be temporarily stabilized during the catalytic converter'"'"'s conversion efficiency detection period on engines having motorized throttle control, so as to improve accuracy and consistency of said catalytic converter temperature characteristics evaluation.

32. A method according to claim 21, whereby the engine control unit is used to control aggregate air-fuel ratio entering the catalytic converter, during catalyst heating using cyclic fuel control modulation, to be at a desired level relative to stoichiometric conditions.

33. A method according to claim 24, whereby the magnitude and frequency of the air-fuel ratio perturbations are modified as the catalytic converter'"'"'s performance degrades based upon past and present operating parameters.

34. A method of heating a catalytic converter of an internal combustion engine, including the steps of:

varying the delivered fuel quantities to each cylinder, that feeds exhaust gases into a catalyst element so as to cause air-fuel ratio conditions sufficiently deviating from normal stoichiometric operation with the exhaust gases of alternating cylinders or groupings thereof feeding into the said catalyst to be alternately richer or leaner than chemical stoichiometric conditions, which increases the level of exothermic energy available to combine chemically at the active surfaces of said catalyst for producing a temperature change; and

operating the engine with large cyclic variations in the quantity of fuel delivered to each cylinder that sufficiently deviates from normal operation so as to cause a significant rise in said catalyst temperature change.

35. A method according to claim 34, whereby the quantity of fuel delivered to alternate groupings of engine cylinders are varied between non-stoichiometric conditions of excess fuel and insufficient fuel to cause sequentially alternating exhaust gas conditions entering the catalyst.

36. A method according to claim 35, further comprising the steps of:

controlling the fuel quantity delivered to select cylinders of an internal combustion engine with a controller in an alternating manner for causing exhaust gas conditions that sufficiently deviate from extremes of normal engine stoichiometric closed loop fuel control conditions so as to increase the chemical energy content of the exhaust gases entering said catalytic converter; and

initiating said alternating fuel control only during pre-defined operating conditions to cause said heating of said catalytic converter.

37. A method of heating a catalytic converter of an internal combustion engine including the steps of:

measuring engine and vehicle parameters including the catalyst temperature for comparing to respective threshold values that determine the initiation of catalyst heating;

initiating a change in the fuel quantities, delivered to individual engine cylinders connected to said catalytic converter, that differs from normal engine operation;

adjusting the magnitude of fuel delivered to each of said individual engine cylinder such that the air-fuel ratio characteristics of the exhaust gases entering said catalytic converter cycle between levels alternating from leaner than stoichiometric to richer than stoichiometric conditions so that said catalytic converter increases in temperature faster than under normal operating conditions without said adjusting the magnitude of fuel delivered to each individual engine cylinder.

38. The method of claim 37, further comprising the steps of:

controlling timing of fuel delivered to each of said individual engine cylinders such that the air-fuel ratio characteristics of the exhaust gases entering said catalytic converter alternate between rich and lean conditions;

controlling frequency of the lean to rich to lean cycle of exhaust gases feeding into said catalytic converter by delivering to groupings of firing cylinders a fuel quantity, that causes each cylinder in the group to have a common air-fuel ratio, either richer or leaner than stoichiometric;

producing a gas stream entering the catalyst that cycles between non stoichiometric conditions having exhaust air-fuel ratios alternating from lean and rich conditions; and

monitoring the catalyst temperature for comparing to threshold values that determine the termination of catalyst heating, and wherein said leaner than stoichiometric conditions is such that λ

is more than 1.07 and said richer than stoichiometric conditions is such that λ

is less then 0.93.

39. A method of determining the gas conversion efficiency of a catalytic converter composed of one or more catalysts and connected to an engine having one or more cylinders controlled by an engine control unit, including the steps of:

measuring initial temperature conditions of a catalytic converter at one or more location(s);

determining from past and present engine control unit parameters and monitored temperature characteristics of said catalytic converter the conditions suitable for providing consistent evaluation of gas conversion efficiency characteristics of said catalytic converter during a first period;

activating an engine control unit to cause a temporary duration of changes in selected engine cylinders'"'"' properties, such properties differing from said first period, for effecting a change in the exhaust gases'"'"' chemical energy levels entering said catalytic converter during a second time period causing a significant temperature change exceeding normal exhaust temperature operational fluctuations;

measuring changes in said catalytic converter'"'"'s temperature versus time characteristic'"'"'s profile subsequent to changing exhaust gas chemical energy levels entering said catalytic converter from such temporary changes activated in second time period;

comparing said measured temperature profile changes to reference temperature profiles stored in a memory, said reference profiles representative of desired catalyst diagnostic limit conditions;

updating the magnitude of a catalyst diagnostic status indicator stored in memory based upon comparison of said measured and said reference catalytic converter temperature profiles; and

activating a catalyst state malfunction indicator when the catalyst diagnostic status indicator value reaches a predetermined limit.

40. A method of determining the gas conversion efficiency of a catalytic converter, composed of one or more catalyst elements, connected to an engine having one or more cylinders that are controlled by an engine control unit, including the steps of:

measuring a first temperature condition of said catalytic converter at a first time period with one or more temperature sensors;

cycling gas mixture properties entering said catalytic converter between conditions significantly leaner and richer than stoichiometric operating conditions by varying delivered fuel quantities to said one or more cylinders;

measuring a second temperature condition of said catalytic converter at a second time period with said one or more temperature sensors;

comparing actual catalytic converter temperature versus time characteristic as derived from said first temperature and said second temperature to reference values stored in memory and determining an existence of a malfunctioning catalytic converter based upon said comparison between actual and reference catalytic converter temperature characteristics.

41. A method according to claim 40, wherein said step of cycling gas mixture properties includes varying the delivered fuel quantities to each said cylinder, that feeds exhaust gases into a catalyst element, so as to cause air-fuel ratio conditions sufficiently deviating from normal stoichiometric operation with the exhaust gases of alternating cylinders or groupings thereof feeding into the said catalyst to be alternately richer or leaner than chemical stoichiometric conditions, which increases the level of exothermic energy available to combine chemically at the active surfaces of said catalyst for producing a temperature change.

42. A method according to claim 41, whereby the quantity of fuel delivered to alternate groupings of engine cylinders are varied between non-stoichiometric conditions of excess fuel and insufficient fuel to cause sequentially alternating exhaust gas conditions entering the catalyst.

43. A method according to claim 42, further comprising the steps of:

controlling the fuel quantity delivered to select cylinders of an internal combustion engine with a controller in an alternating manner for causing exhaust gas conditions that sufficiently deviate from extremes of normal engine stoicchiometric closed loop fuel control conditions so as to increase the chemical energy content of the exhaust gases entering said catalytic converter; and

initiating said alternating fuel control only during pre-defined operating conditions to cause said heating of said catalytic converter.

44. A method according to claim 40, whereby a magnitude and timing of an intentionally induced rise in catalytic converter temperature is selected together with an appropriately positioned temperature measuring device based upon the engine design characteristics to allow detection of an unacceptable degradation in said monitored catalytic converter conversion efficiency.

45. A method according to claim 40, whereby the catalytic converter temperature is measured using a single temperature sensor placed at the specified location, that has been predetermined to allow sensing the aggregate exothermic temperature characteristics of said catalytic converter below a specified level of gas conversion efficiency.

46. A method according to claim 40, whereby a duration of the time period used for detection of catalytic converter efficiency performance is selected to provide accurate monitoring of said catalytic converter'"'"'s efficiency performance.

47. A method according to claim 40, whereby both frequency and magnitude of each individual cylinder'"'"'s air-fuel ratio fluctuations are selected to cause a sufficiently large catalyst temperature change for determining the efficiency of said catalytic converter, without interrupting the engine'"'"'s combustion event and ignition.

48. A method according to claim 40, whereby said time period that the catalytic converter operates below 500°

C. may be reduced by detecting the initiation of catalyst exothermic energy release at temperatures above 100°

C. and enabling catalyst heating using cyclic fuel control modulation.