FLEXIBLE FUEL TOLERANT CATALYTIC CONVERTER DIAGNOSTIC METHOD

• US 20080115486A1
• Filed: 11/20/2006
• Published: 05/22/2008
• Est. Priority Date: 11/20/2006
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Yurgil, James R.
• Granted Patent: US 7,891,168 B2
• Time in Patent Office: Days
• US Class Current: 60/277
• CPC Class Codes: F01N 11/007 the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F01N 2560/025 for measuring or detecting O2, e.g. lambda sensors
• CPC Class Codes: F02D 19/0623 Failure diagnosis or prevention; Safety measures; Testing
• CPC Class Codes: F02D 19/084 Blends of gasoline and alcohols, e.g. E85
• CPC Class Codes: F02D 19/087 with determination of densities, viscosities, composition, concentration or mixture ratios of fuels
• CPC Class Codes: F02D 2200/0611 Fuel type, fuel composition or fuel quality
• CPC Class Codes: F02D 41/0025 Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
• CPC Class Codes: F02D 41/0295 Control according to the amount of oxygen that is stored on the exhaust gas treating apparatus
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A monitoring system for a catalytic converter is provided. The system includes: a fuel determination module that determines a fuel composition based on a sensed composition of fuel in a fuel system; a fuel/air (F/A) determination module that selectively determines a stoichiometric F/A ratio based on the fuel composition; and an oxygen storage capacity (OSC) diagnostic module that computes a target OSC based on the stoichiometric F/A ratio, that compares the target OSC to a reference value and diagnosis the catalytic converter based on the comparison.

Claims

1. A monitoring system for a catalytic converter, comprising:

a fuel determination module that determines a fuel composition based on fuel in a fuel system;

a fuel/air (F/A) determination module that selectively determines a stoichioemetric F/A ratio based on the fuel composition; and

an oxygen storage capacity (OSC) diagnostic module that computes a target OSC based on the stoichiometric F/A ratio, that compares the target OSC to a reference value, and diagnosis the catalytic converter based on the comparison.

2. The system of claim 1 further comprising an enable module that detects a refuel event and wherein the fuel determination module determines the fuel composition after a refuel event occurs.

3. The system of claim 2 wherein the enable module detects the refuel event based on a current and a previous fuel level.

4. The system of claim 1 wherein the F/A ratio module sets the stoichiometric F/A ratio to a predetermined value when the fuel composition is a single specified hydrocarbon fuel.

5. The system of claim 1 wherein the F/A ratio module computes the stoichiometric F/A ratio when the fuel composition is composed of a blend of more than one hydrocarbon fuel.

6. The system of claim 1 further comprising a fuel sensor that generates a signal indicating a composition of fuel in the fuel system.

7. The system of claim 1 wherein the OSC diagnostic module initiates a rich condition based on the stoichiometric F/A ratio after a fuel cut-off period, computes a mass of oxygen released by the catalytic converter, and computes the target OSC over a target time period based on the mass of oxygen.

8. The system of claim 7 wherein the OSC diagnostic module determines the target time period based on an inlet delay time to detect a first F/A ratio and an outlet delay time to detect the first F/A ratio.

9. The system of claim 8 further comprising an inlet sensor that generates an inlet sensor signal indicating a first oxygen level of exhaust gases entering the catalytic converter and wherein the inlet delay time is determined based on the inlet sensor signal.

10. The system of claim 8 further comprising an outlet sensor that generates an outlet sensor signal indicating a second oxygen level of exhaust gases exiting the catalytic converter and wherein the outlet delay time is determined based on the outlet sensor signal.

11. A method of diagnosing a catalytic converter, comprising:

selectively determining a stoichiometric fuel/air ratio based on a fuel composition;

computing a target oxygen storage capacity (OSC) of the catalytic converter based on the stoichiometric fuel/air ratio; and

diagnosing the catalytic converter based on the oxygen storage capacity.

12. The method of claim 11 further comprising:

receiving a fuel sensor signal indicating a composition of fuel in a fuel system; and

determining a fuel composition based on the fuel sensor signal.

13. The method of claim 12 further comprising receiving a fuel event signal indicating an occurrence of a refuel event and wherein the determining a fuel composition occurs after a refuel event.

14. The method of claim 11 wherein the selectively determining further comprises determining the stoichiometric F/A ratio to be a predetermined value when the fuel composition indicates a single specified hydrocarbon fuel.

15. The method of claim 11 wherein the selectively determining further comprises computing a stoichiometric F/A ratio when the fuel composition indicates a blend of more than one hydrocarbon fuel.

16. The method of claim 11 further comprising:

saturating the catalytic converter with oxygen during a fuel cut-off period;

operating an engine in a rich condition based on the stoichiometric F/A ratio after the fuel cut-off period;

computing a mass of oxygen released by the catalytic converter based on mass air flow into the engine; and

wherein the computing the target OSC is further based on the mass of oxygen released over a target time period.

17. The method of claim 16 wherein the computing further comprises:

determining a first delay time for an inlet oxygen sensor to detect a first F/A ratio;

determining a second delay time for an outlet oxygen sensor to detect the first F/A ratio; and

computing the target time period based on the first and the second delay times.

18. The method of claim 17 further comprising:

determining a transport lag time required for a mass of air to flow through an inert catalytic converter; and

calculating the target time period based on the transport lag time.

19. The method of claim 11 wherein the diagnosing comprises diagnosing the catalytic converter based on a comparison of the target OSC and a reference value.

20. The method of claim 11 further comprising setting a malfunction code based on the diagnosing of the catalytic converter.