Fuel volatility detection and compensation during cold engine start

• US 6,360,726 B1
• Filed: 07/31/2000
• Issued: 03/26/2002
• Est. Priority Date: 07/31/2000
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Javaherian, Hossein
• Primary Examiner(s): WOLFE JR, WILLIS RAY
• Application Number:
  US09/630,313
• Time in Patent Office: 603 Days
• Field of Search: 123/435, 123/436, 123/478, 123/480, 123/486, 123/179.5, 123/179.16, 123/491, 731/173, 731/181, 731/16
• US Class Current: 123/491
• CPC Class Codes: F02D 19/061 by controlling fuel injectors
• CPC Class Codes: F02D 19/0636 by estimation, i.e. without using direct measurements of a corresponding sensor
• CPC Class Codes: F02D 2200/0612 determined by estimation
• CPC Class Codes: F02D 2200/1012 Engine speed gradient
• CPC Class Codes: F02D 2200/1015 Engines misfires
• 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 41/064 at cold start F02D41/067 takes precedence
• CPC Class Codes: F02D 41/1498 measuring engine roughness
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

An adaptive same-ignition-cycle passive method is disclosed for the real-time detection and compensation of fuel volatility (or equivalently, the fuel driveability index, DI) during cold start of a multi-cylinder engine. The method detects a signature of fuel volatility on engine speed (rpm) immediately after engine starts to run. In accordance with this method, a local short-duration high-amplitude speed droop is associated with fuels of various volatility which can be detected within the first second after engine ignition while engine is in idle-neutral operation mode. The speed droop is uniquely correlated with the fuel DI value in the form of calibration tables at different temperatures. The actual fuel DI is thus detected and the optimum fuel enrichment/enleanment is quickly determined within few events after engine is flagged as running even before the transmission is engaged (vehicle still in P/N mode). Hence, optimum tradeoff between vehicle driveability and low tailpipe emissions is simultaneously achieved on-line.

Claims

1. A method for cold start of a gasoline fueled, multi-cylinder, internal combustion engine in an automotive vehicle;

said vehicle comprising an engine control module containing a programmed microprocessor for controlling fuel delivery to said engine and timing the ignition of said fuel in the cylinders of said engine, an engine speed sensor for providing engine speed data to said microprocessor, a fuel tank with gasoline of unknown volatility properties and a vehicle operator activated starter motor for cranking said engine for starting;

said engine comprising at least one fuel injector for receiving fuel from said fuel tank and delivering fuel to said cylinders, said method being executed under the control of said microprocessor and comprising

upon cranking of said engine, initiating delivery of said fuel to said cylinders by one or more said injectors at a first pre-calibrated fuel-rich rate and initiating ignition to achieve engine running operation,

sensing the speed of said engine to detect commencement of engine running operation,

upon sensing engine running operation, reducing the rate of delivery of said fuel to a second pre-calibrated fuel rate,

sensing speed values of said engine over subsequent cylinder ignition events to detect a peak engine speed value and a minimum engine speed value lower than said peak value,

calculating the difference in engine speed between said peak value and minimum value, and

using said difference as a measure to determine the volatility properties of said fuel.

2. A method for cold start as recited in claim 1 comprising setting a detection window of engine events within which to detect said peak value and a minimum or terminal speed value within said window.

3. A method for cold start as recited in claim 1 comprising adjusting said pre-calibrated fuel-rich injection rate to a fuel injection rate based on the volatility properties determined for said fuel.

4. A method for cold start as recited in claim 2 comprising adjusting said pre-calibrated fuel-rich injection rate to a fuel injection rate based on the volatility properties determined for said fuel.

11. A method for cold start as recited in any of claims 1-10 comprising determining the volatility properties of said fuel by comparing said difference in engine speed or time rate of change of said speed with a correlation of such differences with the known volatility properties of reference gasolines stored in the memory of said module.

5. A method for cold start of a gasoline fueled, multi-cylinder, internal combustion engine in an automotive vehicle;

said vehicle comprising an engine control module containing a programmed microprocessor for controlling fuel delivery to said engine and timing the ignition of said fuel in the cylinders of said engine, an engine speed sensor for providing engine speed data to said microprocessor, a fuel tank with gasoline of unknown volatility properties and a vehicle operator activated starter motor for cranking said engine for starting;

said engine comprising at least one fuel injector for receiving fuel from said fuel tank and delivering fuel to said cylinders, said method being executed under the control of said microprocessor and comprising

upon cranking of said engine, initiating delivery of said fuel to said cylinders by one or more said injectors at a first pre-calibrated fuel-rich rate and initiating ignition to achieve engine running operation,

sensing the speed of said engine to detect commencement of engine running operation,

upon sensing engine running operation, reducing the rate of delivery of said fuel to a second pre-calibrated fuel rate,

sensing speed values of said engine over subsequent cylinder ignition events,

calculating the time rate of change of said engine speed to detect at least one peak value and one minimum value on the said rate of speed change values, and

using said peak value and said minimum value as a measure to determine the volatility properties of said fuel.

6. A method for cold start as recited in claim 5 comprising calculating the difference between said peak and minimum rate of speed change values over a specified detection window and using the said difference value as a measure of the volatility properties of said fuel.

7. A method for cold start as recited in claim 5 comprising sensing speed values of said engine over subsequent cylinder ignition events,

calculating the time rate of change of said engine speed to detect the number of zero-crossings on the said rate of speed change values over a specified detection window, and

using the said number of zero-crossings as a measure to determine the volatility properties of said fuel.

8. A method for cold start as recited in claim 5 comprising adjusting said pre-calibrated fuel-rich injection rate to a fuel injection rate based on the volatility properties determined for said fuel.

9. A method for cold start as recited in claim 6 comprising adjusting said pre-calibrated fuel-rich injection rate to a fuel injection rate based on the volatility properties determined for said fuel.

10. A method for cold start as recited in claim 7 comprising adjusting said pre-calibrated fuel-rich injection rate to a fuel injection rate based on the volatility properties determined for said fuel.

12. A method as recited in any of claims 3, 4 or 8-10 comprising adjusting said pre-calibrated fuel injection rate by reference to a correlation of fuel injection rates with the known volatility properties of reference gasolines stored in the memory of said module.