Auto-ignition Detection in Spark Ignition Engines
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Solution Overview
Problem
Modern, highly supercharged Otto-cycle internal combustion engines face issues with premature firing and spontaneous ignition, leading to uncontrolled combustion, extreme pressures, and potential engine damage, which existing methods struggle to reliably identify and prevent.
Innovation Solution
A method and device that measure segment time periods for individual cylinders during engine operation, determine running irregularity values, and compare them to a threshold to identify potential spontaneous ignition, allowing for the confirmation or rejection of such events by interrupting fuel supply and assessing the impact on cylinder performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing methods (rotational speed measurement, knocking signal detection, pressure difference analysis) are used to identify spontaneous ignition, then detection capability is provided, but reliability of identification is insufficient under high load conditions
Solution Approach 1:
The patent segments the detection approach by analyzing running irregularity values of individual cylinders separately and comparing them sequentially. The method divides the detection process into: measuring segment time periods for each cylinder, determining running irregularity values for each cylinder, comparing values in ignition sequence, and selectively confirming spontaneous ignition based on the comparison. This segmentation allows reliable identification even when only one cylinder exhibits abnormal behavior.
Solution Approach 2:
The patent implements feedback by using the running irregularity value of a preceding cylinder as a reference for detecting the current cylinder. The control device compares the running irregularity value of cylinder (x-1) with that of cylinder (x) in the ignition sequence. This feedback mechanism enables the system to distinguish between general engine conditions affecting all cylinders and true spontaneous ignition events occurring in specific cylinders, significantly improving detection reliability.
2Reliability
If fuel supply is interrupted to confirm spontaneous ignition suspicion, then reliable confirmation is achieved, but engine performance and productivity are temporarily reduced
Solution Approach 1:
The patent applies partial action by interrupting fuel supply to only the specific cylinder suspected of spontaneous ignition rather than shutting down the entire engine. The control device selectively closes the fuel supply to cylinder (x) while other cylinders continue to operate normally. This partial intervention maintains overall engine productivity while providing sufficient verification data for the suspected cylinder, achieving reliable confirmation with minimal productivity loss.
3Reliability
If spontaneous ignition is detected early before knocking occurs, then prevention of engine damage is enabled, but detection system complexity increases
Solution Approach 1:
The patent employs self-service by utilizing the engine's existing operational parameters (segment time periods, crankshaft position, fuel injection timing) that are already measured for normal engine control. The control device calculates running irregularity values from these existing measurements without requiring additional dedicated sensors or measurement systems. This approach enables early detection of spontaneous ignition while avoiding increased device complexity, as the system uses data already being collected for routine engine management.
Data Source
AI summary
In a spark-ignition internal combustion engine having multiple cylinders, successive segment time periods assigned to the individual cylinders during working strokes thereof, and subsequently irregular running values are determined from the segment time periods. In a predefined speed range of the engine, the irregular running values of the cylinders are compared with a predefined threshold, and suspected auto-ignition for a first cylinder is detected if the irregular running value of a second cylinder located before the first cylinder in terms of timing of the ignition sequence undershoots the threshold. Fuel to the first cylinder suspected of auto-ignition is interrupted for a predefined number of cycles, and the fuel interruption influence on the irregular running values of the second cylinder during the cycles is detected. The suspected auto-ignition of the first cylinder is either confirmed or rejected based on the irregular running values occurring at the second cylinder.