Crank Angle Sensor Combustion Pressure Detection
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Solution Overview
Problem
Existing combustion state detection methods using crank angle sensors face challenges in accurately detecting combustion pressure due to excessive torsional vibrations, which current technologies are unable to effectively mitigate.
Innovation Solution
A method and apparatus that utilize a memory to record the relationship between reference crank sensor signals and in-cylinder pressure, allowing a processor to accurately obtain in-cylinder pressure by collating detected crank angle sensor signals with pre-stored relationships, enabling precise combustion pressure detection even under torsional vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensing element is placed near the combustion chamber to detect combustion pressure, then the detection accuracy is improved, but the thermal shock and load on the sensing element increase causing failure
Solution Approach 1:
The patent introduces a crank angle sensor as an intermediary device to indirectly detect combustion state by measuring crankshaft angular velocity variations, rather than directly exposing a pressure sensing element to the harsh combustion environment. This mediator approach allows combustion pressure detection while protecting the sensor from thermal shock and mechanical load.
Solution Approach 2:
The patent replaces the direct mechanical pressure sensing system with an optical/electrical detection system using a crank angle sensor. By substituting the mechanical pressure sensor with an electrical sensor that detects crankshaft position and velocity, the system avoids the reliability issues of direct pressure measurement while maintaining detection capability.
2Measurement precision
If a hole is formed to communicate combustion chamber pressure to a sensing element, then pressure detection is enabled, but air column vibration in the hole causes detection errors
Solution Approach 1:
The patent extracts the harmful air column vibration element (the communication hole) from the detection system and replaces it with a completely different detection approach using a crank angle sensor. This eliminates the source of vibration-induced errors while maintaining the ability to detect combustion pressure through crankshaft velocity variations.
3Object-affected harmful factors
If the hole length is shortened to suppress air column vibration, then vibration error is reduced, but the pressure sensing element is located too near the combustion chamber increasing thermal load
Solution Approach 1:
The crank angle sensor serves as an intermediary that allows the system to benefit from both short hole positioning (reduced vibration) without suffering from the thermal consequences. The mediator detects combustion effects through crankshaft velocity changes rather than direct pressure measurement, decoupling the vibration solution from the thermal problem.
4Reliability
If torsional vibrations occur due to resonance between natural frequency and engine vibration, then detection accuracy deteriorates, but current methods cannot correct this variation
Solution Approach 1:
The patent employs feedback mechanisms by continuously monitoring crankshaft angular velocity and using this information to infer combustion pressure. The system uses the crank angle sensor signals to detect torsional vibrations and compensates for their effects through signal processing and comparison with predetermined relationships, maintaining accuracy despite resonance conditions.
Solution Approach 2:
The patent stores predetermined relationships between crank angle sensor signals and combustion pressure in advance. By having pre-established reference data, the system can compare actual readings against these predetermined relationships to accurately determine combustion pressure even when torsional vibrations cause signal variations, without needing real-time correction algorithms.
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 accurate and easy detection of combustion pressure using a crank angle sensor, maintaining combustion control quality even when the combustion pressure sensor fails, by estimating pressure based on recorded relationships between crank angle and pressure signals.
Implementation Method 1
This crank angle sensor is for detecting the crank angular velocity of the crankshaft of the internal combustion engine, but indirectly detects the combustion state in the combustion chamber and detects a change in the angular velocity of the crankshaft due to a change in the combustion state
Implementation Method 2
there is recorded in a memory a relationship between a cycle of an output signal of the crank angle sensor and in-cylinder pressure
Implementation Method 3
the measured cycle of the output signal of the crank angle sensor is compared with the measured output signal of the combustion pressure sensor in a processor, and the in-cylinder pressure is determined
Data Source
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AI summary
A combustion pressure detection method and a combustion pressure detection apparatus of an internal combustion engine that can detect combustion pressure by using a crank angle sensor in an accurate and easy way. A relationship between a crank angle sensor signal and a combustion pressure signal is previously recorded. As a result, even if the combustion pressure sensor fails, the combustion pressure is detected by collating the crank angle sensor signal with the relationship.