Pressure measurement system

• US 6,595,043 B2
• Filed: 09/12/2001
• Issued: 07/22/2003
• Est. Priority Date: 09/12/2001
• Status: Expired due to Term

• Current Assignee: FCA US LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Corporation (Mercedes-Benz Group AG)
• Inventors: Jaye, John R
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US09/951,077
• Publication Number:
  US 20030046989A1
• Time in Patent Office: 678 Days
• Field of Search: 731/12, 731/15, 731/16, 731/172, 731/173, 731/181, 731/182
• US Class Current: 73/114.06
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• CPC Class Codes: G01M 15/08 by monitoring pressure in cylinders
• CPC Class Codes: G01M 15/09 by monitoring pressure in fluid ducts, e.g. in lubrication or cooling parts

Abstract

An engine combustion diagnostic system and method for diagnosing an engine improve combustion quality determinations. The method includes the step of linking manifold absolute pressure (MAP) to in-cylinder pressure during calibration of the engine such that a table results. A single in-cylinder pressure measurement is collected during real-time operation of the engine. The method further provides for determining combustion quality for the engine based on the real-time in-cylinder pressure measurement and the table.

Claims

1. A method for diagnosing an engine, the method comprising the steps of:

(a) linking manifold absolute pressure (MAP) to in-cylinder pressure during calibration of the engine such that a table results;

(b) collecting a single in-cylinder pressure measurement during real-time operation of the engine;

(c) determining combustion quality for the engine based on the real-time in-cylinder pressure measurement and the table;

(d) determining a real-time ratio based on the real-time in-cylinder pressure measurement and a real-time MAP measurement;

(e) matching the real-time MAP measurement to an entry in the table having a calibration MAP measurement that is approximately equal to the real-time MAP measurement; and

(f) dividing the real-time ratio by a calibration ratio corresponding to the entry, the calibration ratio being based on a calibration in-cylinder pressure measurement and the calibration MAP measurement such that a combustion quality calculation results.

2. The method of claim 1 further including the step of determining whether the engine has misfired based on the combustion quality calculation.

3. The method of claim 1 further including the steps of:

repeating steps b) and c) of claim 1 for a predetermined period of time; and

conducting transient combustion analysis based on the combustion quality calculations.

4. The method of claim 1 further including the step of searching a computer readable medium for the calibration MAP measurement.

5. The method of claim 1, step (a) further including the steps of:

accelerating the engine over a predetermined engine speed range;

obtaining a plurality of calibration MAP measurements during acceleration;

obtaining a plurality of calibration in-cylinder pressure measurements during acceleration;

calculating calibration ratios based on the calibration MAP measurements and the calibration in-cylinder pressure measurements; and

storing the calibration ratios, the calibration MAP measurements and the in-cylinder pressure measurements to the table which is contained in a computer readable medium.

6. The method of claim 5 further including the step of accelerating the engine from idle to wide open throttle.

7. A method for determining combustion quality for an engine, the method comprising the steps of:

determining a real-time ratio based on a real-time in-cylinder pressure measurement and a real-time manifold absolute pressure (MAP) measurement;

matching the real-time MAP measurement to an entry in a table having a calibration MAP measurement that is approximately equal to the real-time MAP measurement; and

dividing the real-time ratio by a calibration ratio corresponding to the entry, the calibration ratio being based on a calibration in-cylinder pressure measurement and the calibration MAP measurement such that a combustion quality calculation results.

8. The method of claim 7 further including the step of determining whether the engine has misfired based on the combustion quality calculation.

9. The method of claim 7 further including the step of searching a computer readable medium for the calibration ratio.

10. A method for diagnosing combustion quality of a vehicle internal combustion engine, the method comprising the steps of:

accelerating the engine over a predetermined engine speed range;

obtaining a plurality of calibration manifold absolute pressure (MAP) measurements during acceleration;

obtaining a plurality of calibration in-cylinder pressure measurements during acceleration;

calculating calibration ratios based on the calibration MAP measurements and the calibration in-cylinder pressure measurements;

storing the calibration ratios to a computer readable medium such that a table results;

collecting a single in-cylinder pressure measurement during real-time operation of the vehicle;

determining a real-time ratio based on the real-time in-cylinder pressure measurement and a real-time MAP measurement;

matching the real-time MAP measurement to an entry in the table having a calibration MAP measurement that is approximately equal to the real-time MAP measurement;

dividing the real-time ratio by a calibration ratio corresponding to the entry such that a combustion quality calculation results.

11. The method of claim 10 further including the step of accelerating the engine from idle to wide open throttle.

12. The method of claim 10 further including the step of determining whether the engine has misfired based on the combustion quality calculation.

13. The method of claim 10 further including the step of replacing one or more on board diagnostic calculations of the vehicle with the combustion quality calculation.