Adaptive method for detecting misfire in an internal combustion engines using an engine-mounted accelerometer

• US 6,388,444 B1
• Filed: 01/13/2000
• Issued: 05/14/2002
• Est. Priority Date: 01/13/2000
• Status: Expired due to Fees

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Scholl, David James, Hahn, Stephen L., Carlstrom, Kevin Ronald
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Hamdan, Wasseem H.
• Application Number:
  US09/482,469
• Time in Patent Office: 852 Days
• Field of Search: 324/378, 123/406.24, 123/435, 123/406.41, 123/406.42, 123/406.43, 73/350.3, 73/350.4, 731/173
• US Class Current: 324/378
• CPC Class Codes: G01M 15/11 by detecting misfire

Abstract

A method for detecting misfire in an internal combustion engine comprising the steps of measuring instantaneous angular velocity of the engine crankshaft during combustion in the combustion chamber of a piston and cylinder assembly, determining if combustion has occurred using crankshaft acceleration data, measuring engine block combustion energy vibrations by means of an accelerometer, determining whether combustion has occurred using the accelerometer data, identifying the cylinder where the acceleration data originates, comparing the results of the crankshaft acceleration information with the accelerometer information to detect whether each set of data detects misfire, decreasing the threshold for detecting a misfire using accelerometer data if a misfire is detected only by the crankshaft acceleration data whereby a reliable misfire signal can be obtained during those instances when the crankshaft acceleration data is unreliable and increasing the threshold for the accelerometer when the crankshaft acceleration data indicates no misfire but a misfire is detected by the accelerometer information.

Claims

1. An adaptive method for detecting misfire in a combustion chamber of a piston and cylinder assembly for a spark-ignition, automotive, internal combustion engine, the engine having a cylinder housing, a crankshaft and a camshaft, an accelerometer being mounted on the exterior of the cylinder housing;

the method comprising the steps of;

measuring engine combustion vibration energy in a frequency range of about 2 KHz to 4.5 KHz by recording and processing accelerometer output data to detect whether a misfire has occurred;

measuring instantaneous crankshaft and camshaft positions;

determining the location in the combustion cycle at which combustion is expected to occur using instantaneous crankshaft position and camshaft angle data;

determining whether combustion has occurred using accelerometer output data;

determining instantaneous crankshaft acceleration using crankshaft position data;

determining whether combustion has occurred using crankshaft acceleration data, and;

determining whether a misfire in the combustion chamber is detected by comparing processed accelerometer output data with processed crankshaft position data and signaling a misfire if the processed accelerometer output data and the processed crankshaft position data both indicate a misfire.

2. The method set forth in claim 1 wherein the accelerometer output data and the crankshaft position data are processed simultaneously in parallel;

and

filtering the accelerometer output data to establish a threshold value for vibration data below which the vibration data does not indicate a misfire.

3. The method set forth in claim 2 including the adaptive step of decreasing the threshold value for accelerometer output data for the identified combustion chamber;

and

signaling a misfire if the processed accelerometer output data and the processed crankshaft position data both indicate a misfire following a decrease in the threshold value.

4. The method set forth in claim 2 including the step of increasing the threshold value for accelerometer output data for the identified combustion chamber if a misfire is indicated by the accelerometer output data but is not indicated by the crankshaft position data.

5. An adaptive method for detecting misfire in a combustion chamber of a piston and cylinder assembly for a spark-ignition, automotive internal combustion engine, the engine having a cylinder housing, a crankshaft and a camshaft, an accelerometer being mounted on the exterior of the cylinder housing;

the method comprising the steps of;

measuring engine combustion energy vibrations in a frequency range below about 5 KHz by recording and processing accelerometer output data to detect whether a misfire has occurred;

measuring instantaneous crankshaft and camshaft positions;

determining the location in the combustion cycle in which combustion is expected to occur using instantaneous crankshaft position and camshaft angle data;

determining whether combustion has occurred using accelerometer output data;

determining instantaneous crankshaft acceleration using crankshaft position data;

determining whether combustion has occurred using crankshaft acceleration data, and;

determining whether a misfire in the combustion chamber has occurred by comparing processed accelerometer output data with processed crankshaft position data and signaling a misfire if the processed accelerometer output data and the processed crankshaft position data both indicate a misfire.

6. The method set forth in claim 5 wherein the accelerometer output data and the crankshaft position data are processed simultaneously in parallel;

and

filtering the accelerometer output data to establish a threshold value for vibration data below which the vibration data does not indicate a misfire.

7. The method set forth in claim 6 including the adaptive step of decreasing the threshold value for accelerometer output data for the identified combustion chamber;

and

signaling a misfire if the processed accelerometer output data and the processed crankshaft position data both indicate a misfire following a decrease in the threshold value.

8. The method set forth in claim 6 including the step of increasing the threshold value for accelerometer output data for the identified combustion chamber if a misfire is indicated by the accelerometer output data but is not indicated by the crankshaft position data.