Compression Ratio Determination via Intake Pressure Oscillations
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Solution Overview
Problem
Current methods for determining the current compression ratio of internal combustion engines are either indirect and uncertain or require additional costly sensors, making it difficult to optimize engine operation and detect wear or external interventions.
Innovation Solution
Measuring dynamic pressure oscillations in the intake or exhaust tract and applying discrete Fourier transformation to generate a pressure oscillation signal, which is then analyzed to determine the compression ratio using reference values associated with specific signal frequencies, without the need for additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional sensors are installed to directly measure compression ratio, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses existing sensors (intake manifold pressure sensor, crankshaft position sensor) that are already installed for other engine control functions to determine compression ratio. The existing sensor data is repurposed to provide compression ratio information without requiring additional measurement devices, making the system self-sufficient and avoiding increased complexity.
Solution Approach 2:
The patent replaces direct mechanical pressure measurement (which would require additional pressure sensors in the combustion chamber) with an indirect measurement approach using acoustic/cyclic pressure oscillation analysis from the intake manifold. This substitution uses signal processing of existing sensor data rather than direct mechanical measurement, reducing device complexity while maintaining measurement capability.
2Device complexity
If indirect methods are used to determine compression ratio, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The system analyzes cyclic pressure oscillations in the intake manifold that are directly related to the compression process. These pressure oscillations occur at frequencies related to engine operating parameters and contain information about compression ratio. By measuring and analyzing these natural vibrations/oscillations, the system achieves precise compression ratio determination indirectly through the physical relationship between compression process and intake manifold pressure dynamics.
Solution Approach 2:
The system determines compression ratio by analyzing changes in pressure oscillation parameters (frequency, amplitude, phase) in the intake manifold rather than directly measuring combustion chamber pressure. The compression ratio is derived from these oscillation parameter changes which are functionally related to compression ratio through the engine's breathing dynamics, achieving precise indirect measurement through parameter transformation.
3Device complexity
If compression ratio is kept constant for simple design, then device complexity is reduced, but adaptability to different operating conditions deteriorates
Solution Approach 1:
The system enables dynamic determination of compression ratio during engine operation by continuously analyzing intake manifold pressure oscillations. This allows the compression ratio to be identified as a variable parameter that can change with operating conditions, engine wear, or external interventions, rather than being a fixed design parameter. The dynamic measurement capability provides real-time information for adaptive engine control.
Solution Approach 2:
The system provides feedback about the actual compression ratio during engine operation by continuously analyzing pressure oscillation signals. This feedback information can be used by the engine control unit to detect deviations from expected compression ratio values, identify wear or mechanical issues, and potentially adjust engine operating parameters to optimize performance for the current compression ratio condition.
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
Enables precise determination of the current compression ratio for each cylinder, allowing for adaptive control parameters to optimize engine operation and detect mechanical issues without additional apparatus or complexity.
Implementation Method 1
From the pressure oscillation signal, using discrete Fourier transformation, at least one actual value of at least one characteristic of at least one selected signal frequency of the measured pressure oscillations in relation to the crankshaft phase angle signal is then determined
Data Source
AI summary
In the method according to example embodiments, dynamic pressure oscillations in the inlet tract of the respective internal combustion engine are measured during normal operation, and from these a corresponding pressure oscillation signal is generated. A crankshaft phase angle signal is acquired at the same time. The pressure oscillation signal is used to determine an actual value of at least one characteristic of at least one selected signal frequency of the measured pressure oscillations in relation to the crankshaft phase angle signal, and the current compression ratio is determined on the basis of the determined actual value and using reference values of the corresponding characteristic of the respective same signal frequency for different compression ratios.