Engine control having fuel volatility compensation

• US 6,178,949 B1
• Filed: 10/04/1999
• Issued: 01/30/2001
• Est. Priority Date: 10/04/1999
• 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: Matekunas, Frederic Anton, Chang, Chen-Fang, Kirwan, John E., Jorgensen, Scott Willis
• Primary Examiner(s): Kwon, John
• Application Number:
  US09/411,273
• Time in Patent Office: 484 Days
• Field of Search: 123/435, 123/486, 123/406.47, 123/406.22
• US Class Current: 123/435
• 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 19/0649 Liquid fuels having different boiling temperatures, volatilities, densities, viscosities, cetane or octane numbers
• CPC Class Codes: F02D 2200/0612 determined by estimation
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• 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: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

An improved engine control in which the fuel volatility is detected based on a measure of the fired-to-motored cylinder pressure ratio, and used to trim fuel and spark timing controls during engine warm-up and transient fueling periods. In a first embodiment, a matrix of empirically determined pressure ratio values that occur with fuels of differing volatility is stored and compared to the measured pressure ratio to identify the closest stored pressure ratio, and the fuel volatility is determined based on the fuel volatility associated with the identified pressure ratio. In a second embodiment, the actual fuel vapor-to-air equivalence ratio is computed based on the measured pressure ratio, and the fuel volatility is determined based on the deviation between the actual ratio and the desired fuel vapor-to-air equivalence ratio.

Claims

1. A control method for a spark ignition internal combustion engine in which fuel delivery to an engine cylinder is determined based on an assumed fuel volatility, the control method comprising the steps of:

measuring fired and motored pressures in said cylinder during a combustion cycle, and determining a pressure ratio based on such measured pressures;

determining an actual volatility of the delivered fuel as a function of the determined pressure ratio; and

adjusting the fuel delivery to said engine cylinder based on the determined actual volatility.

2. The control method of claim 1, including the steps of:

storing the actual fuel volatility determined in a first period of engine operation, and

in a subsequent period of engine operation, retrieving the stored actual volatility and delivering fuel to the engine cylinder based on the retrieved volatility.

3. The control method of claim 1, wherein the step of determining an actual volatility of the delivered fuel comprises the steps of:

storing a matrix of empirically determined pressure ratios associated with various fuel volatilities;

identifying a stored pressure ratio that most closely corresponds to the determined pressure ratio; and

determining the actual volatility based on the fuel volatility associated with the identified stored pressure ratio.

4. The control method of claim 1, wherein the fuel delivery is calibrated to achieve a desired fuel vapor-to-air equivalence ratio, and the step of determining an actual volatility of the delivered fuel comprises the steps of:

determining an actual fuel vapor-to-air equivalence ratio based on the determined pressure ratio; and

determining the actual volatility of the delivered fuel based on a deviation of the actual fuel vapor-to-air equivalence ratio from the desired fuel vapor-to-air equivalence ratio.

5. A control method for a spark ignition internal combustion engine in which spark timing and fuel delivery to an engine cylinder during an engine warm-up period are determined based on an assumed fuel volatility, the control method comprising the steps of:

measuring fired and motored pressures in said cylinder during a combustion cycle of said warm-up period, and determining a pressure ratio based on such measured pressures;

determining an actual volatility of the delivered fuel as a function of the determined pressure ratio; and

adjusting the spark timing and fuel delivery to said engine cylinder during said warm-up period based on the determined actual volatility.

6. A control method for a spark ignition internal combustion engine in which spark timing and fuel delivery to an engine cylinder are determined based on a measure of an fuel vapor-to-air ratio in an exhaust stream of the engine, the control method comprising the steps of:

identifying a period of transient fuel delivery;

measuring fired and motored pressures in said cylinder during a combustion cycle of said identified period, and determining a pressure ratio based on such measured pressures;

determining an actual volatility of the delivered fuel as a function of the determined pressure ratio; and

adjusting the spark timing and fuel delivery to said engine cylinder during said identified period based on the determined actual volatility.