Engine starting and warm-up fuel control method having low volatility fuel detection and compensation

• US 6,655,358 B2
• Filed: 09/13/2001
• Issued: 12/02/2003
• Est. Priority Date: 09/14/2000
• Status: Expired due to Term

• Current Assignee: Delphi Technologies Ip Limited (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Herman, Andrew D., Yoo, In Kwang, Maloney, Peter James, Breidenbach, Hallett D., Carlson, Craig A., Yoo, Deog H.
• Primary Examiner(s): Vo, Hieu T.
• Assistant Examiner(s): HUYNH, HAI H
• Application Number:
  US09/952,012
• Publication Number:
  US 20020112699A1
• Time in Patent Office: 810 Days
• Field of Search: 123/491, 123/339.12, 123/339.19, 123/436, 123/536, 123/1.A, 123/350, 123/352, 731/173, 701/110
• 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 19/0649 Liquid fuels having different boiling temperatures, volatilities, densities, viscosities, cetane or octane numbers
• CPC Class Codes: F02D 2041/1432 the system including a filter, e.g. a low pass or high pass filter
• CPC Class Codes: F02D 2200/0611 Fuel type, fuel composition or fuel quality
• 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 41/06 for engine starting or warming up F02D41/0255 takes precedence
• CPC Class Codes: F02D 41/1498 measuring engine roughness
• CPC Class Codes: F02D 41/16 for idling
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

An improved engine fuel control detects combustion instability due to the use of high DI fuel during cold start and warm-up and compensates the fuel control for detected combustion instability through temporary enrichment of the delivered air/fuel ratio. When the engine idle speed error magnitude is less than a calibrated threshold, usage of high DI fuel is detected by identifying a surge signal based on the engine speed error fluctuation in a predetermined frequency range attributable to combustion instability due to the presence of high DI fuel in a cold engine. When the average amplitude of the surge signal exceeds a calibrated surge threshold, the presence of high DI fuel is detected. Additionally, the method is disabled for a prescribed period following commanded load transitions associated with the air conditioning system and the automatic transmission.

Claims

1. A method of operation for an internal combustion engine having an open-loop fuel control for maintaining an air/fuel ratio of said engine at a target value during engine starting and warm-up, comprising the steps of:

measuring a speed of said engine during engine idling following starting;

determining an engine speed error based on deviations of said measured speed from a desired idle speed;

bandpass filtering an error signal based on said determined engine speed error to form a surge signal representative of speed error fluctuation in a predetermined frequency range attributable to usage of high driveability index fuel in a cold engine;

low-pass filtering said surge signal to determine a sustained amplitude of said surge signal;

detecting usage of high driveability index fuel if the sustained amplitude of the surge signal exceeds a calibrated threshold; and

temporarily enriching said air/fuel ratio relative to said target value when the presence of high driveability index fuel is detected.

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

detecting engine load transitions that influence engine speed; and

detecting the presence of high driveability index fuel if said engine load transitions are not detected and the sustained amplitude of the surge signal exceeds a calibrated threshold.

3. The method of operation of claim 2, including the step of:

disabling the step of detecting the presence of high driveability index fuel for a prescribed time interval following detection of an engine load transition.

4. The method of operation of claim 1, including the step of:

disabling the step of detecting the presence of high driveability index fuel unless a temperature of the engine is within a prescribed range and a run time of the engine is less than a calibrated run time.

5. The method of operation of claim 1, wherein the step of temporarily enriching said air/fuel ratio includes the steps of:

holding said air/fuel ratio at a first value determined as a function of said target value and a temperature of said engine;

controlling said air/fuel ratio according to a second value intermediate said first value and said target value; and

adjusting said air/fuel ratio to a closed-loop target value when the engine upon completion of said warm-up.

6. The method of operation of claim 1, including the step of:

forcing said error signal to zero when the determined engine speed error exceeds a threshold error.

7. The method of operation of claim 1, including the step of:

forcing said surge signal to zero when the determined engine speed error exceeds a threshold error.