Crankshaft Speed Evaluation for Uncontrolled Combustion Detection
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Solution Overview
Problem
Existing methods for detecting uncontrolled combustion in internal combustion engines, such as self-ignitions caused by hot spots or oil droplets, are limited as they cannot detect low-frequency pressure profiles which do not significantly impact structure-borne noise, potentially leading to engine damage.
Innovation Solution
The method evaluates the speed curve of the crankshaft to detect uncontrolled combustion by comparing parameters like gas torque and combustion position with reference values from controlled combustion, eliminating the need for a knock sensor and utilizing existing rotational speed measurements for engine control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If knock sensors are used to detect uncontrolled combustion, then high-frequency pressure components can be detected, but low-frequency pressure profiles cannot be detected
Solution Approach 1:
The patent replaces the mechanical knock sensor system with an evaluation of the crankshaft speed curve. The crankshaft speed variations reflect the pressure fluctuations in the combustion chamber, allowing detection of both high-frequency and low-frequency pressure profiles through a single measurement system that already exists in the engine.
2Reliability
If additional knock sensors are installed to detect all types of self-ignition, then detection coverage improves, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing crankshaft speed measurement serve multiple functions: it is used both for engine control/regulation and for detecting uncontrolled combustion. This multi-functional use eliminates the need for separate knock sensors while maintaining comprehensive detection capability across different combustion conditions.
Solution Approach 2:
The crankshaft speed measurement system serves itself by providing combustion detection functionality without requiring additional dedicated sensors. The same measurement infrastructure that monitors engine performance also detects abnormal combustion events, making the system self-sufficient.
3Device complexity
If crankshaft speed evaluation is used to detect uncontrolled combustion, then no additional hardware is needed, but detection precision for subtle combustion events may be reduced
Solution Approach 1:
The patent uses the crankshaft speed curve as an intermediary that translates combustion chamber pressure fluctuations into measurable speed variations. The crankshaft speed acts as a mediator that reflects the underlying pressure dynamics, allowing indirect but accurate detection of combustion events without direct pressure measurement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for reliable detection of uncontrolled combustion events independent of spark plug ignition, enhancing engine safety by identifying shifts in pressure profiles and preventing damage, particularly in high-power density and downsizing engine concepts.
Implementation Method 1
the pressure fluctuations in the combustion chamber caused by the combustion being detected and evaluated
Implementation Method 2
combustion of the supplied fuel-air mixture causes the vehicle to start driving or to maintain driving
Data Source
Figure 1
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AI summary
The invention relates to a method for recognizing uncontrolled combustion in a combustion engine which occurs independently of ignition by a spark plug, wherein the pressure vibrations in the combustion chamber triggered by the combustion are detected and evaluated. In order to be able to detect uncontrolled combustion before ignition by the spark plug and/or before normal combustion start for a given ignition time point at any time, according to the invention the rotational speed (n) of a crankshaft (10) of the combustion engine (1), which is influenced by the pressure vibrations, is evaluated.