Continuous cylinder misfire detection method

Abstract

A method and system for detection of continuous single cylinder misfire, by more completely analyzing an estimated periodic sequence of reference period signals, and comparing the periodic sequence with a sample corresponding to an immediately prior revolution, is offered. Data occurring periodically, with a period of one revolution, are eliminated, whereas signals associated with a period of one engine cycle are enhanced. This comprises measuring a sequence of engine reference periods corresponding to a single engine revolution. Transient noise is removed. A first difference is calculated, and a disturbance sequence is estimated, correlatable to a single engine cycle. A difference is calculated and compared to a threshold. The threshold comprises an array of calibrated values, determined based upon engine operating speed and engine load.

Description

TECHNICAL FIELD [0001] This invention pertains generally to internal combustion engine control systems, and more specifically to detection of engine misfire events. INCORPORATION BY REFERENCE [0002] Applicant incorporates by reference U.S. Pat. No. 5,668,725, entitled: Internal Combustion Engine Misfire Detection, issued to Naik, in that the method and apparatus for monitoring engine speed to detect intermittent engine misfire events, including removal of transient changes in engine speed variation that vary in a periodic sense with a period of one engine revolution or one engine cycle, need not be fully described in detail herein. BACKGROUND OF THE INVENTION [0003] Engine manufacturers are mandated to detect engine misfire events as an element of state and federal on-board diagnostics regulations. The regulations require detection of various forms of engine misfire, including intermittent misfire, one cylinder continuous misfire, and two opposing cylinder misfire tests. Designers a...

AI Technical Summary

Benefits of technology

The present invention offers an improvement for detecting continuous cylinder misfire in an internal combustion engine. This is achieved by measuring a periodic sequence of reference periods and comparing it with a sample corresponding to an immediately prior engine revolution. This eliminates any components periodic with a period of one revolution, while enhancing signals associated with a period of one engine cycle. The invention provides a system and method to monitor operation of an engine for occurrence of a continuous single cylinder engine misfire, which can be detected at specific engine operating conditions. The invention also involves measuring the sequence of reference periods occurring immediately prior to each cylinder firing event. A threshold is selected based upon engine operating speed and engine load to improve the accuracy of the detection.

Problems solved by technology

Crankshaft speed variation monitoring algorithms to monitor engine operation may be unable to identify all occurrences of engine misfire, due to variations in system implementation that introduce errors inducing signal noise.

Signal noise may affect the ability of a misfire detection method to detect misfire, especially at high engine speeds on some engine applications.

Issues related to system implementation that may affect signal noise include, for example, part-to-part variation in crankshaft wheel tooth machining, and variations in engine torque between cylinders, due to variations in delivery of fuel, air, spark, and exhaust gas recirculation.

In general, misfire detection is difficult under low load, high-speed conditions, especially for engines with a large number of cylinders and large levels of powertrain and driveline inertia.

Furthermore, misdiagnosis of engine misfire events may lead to costly, and potentially ineffective service procedures.

The method may be unable to detect continuous single cylinder misfires in specific engine applications, e.g., wherein an individual cylinder continuously misfires within a specific speed / load operating range otherwise undetectable using normal monitoring methods.

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