Pressure Sensor Calibration via Compression Phase Offset
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for calibrating cylinder pressure sensors in internal combustion piston engines are inadequate, leading to inaccurate measurements and suboptimal engine performance due to variations in cylinder and receiver pressures, especially when sensors operate in harsh conditions.
Innovation Solution
A method involving measuring pressure during the compression phase before ignition, determining the heat release characteristic, calculating the change in cylinder volume, estimating a pressure offset, and using this offset to calibrate the pressure sensor, thereby improving measurement accuracy and engine control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensor is placed in harsh combustion environment to measure cylinder pressure directly, then measurement information quality is improved, but sensor reliability deteriorates due to damage from incomplete combustion
Solution Approach 1:
The patent uses the compression phase as an intermediary measurement window. By measuring pressure during compression (before ignition), the sensor avoids exposure to harsh combustion conditions while still obtaining calibration data. The compression phase pressure measurements serve as a mediator to derive the pressure offset that corrects combustion phase measurements, thus protecting the sensor from damage while maintaining measurement accuracy.
2Ease of operation
If pressure sensor is calibrated using receiver pressure assuming equal cylinder and receiver pressure at inlet valve closure, then calibration process is simplified, but measurement precision deteriorates due to pressure variations from standing oscillation waves and long distance
Solution Approach 1:
The patent performs preliminary measurement and calculation during the compression phase to determine the pressure offset before actual combustion measurements are taken. By measuring pressure at multiple crank angles during compression, calculating the corresponding volume changes, and deriving the pressure offset through heat release analysis, the system establishes a correction factor in advance. This preliminary action ensures accurate calibration without relying on the simplified (but inaccurate) assumption of equal receiver and cylinder pressures.
3Device complexity
If traditional calibration methods are used without accounting for heat release and volume change, then calibration process is simpler, but measurement precision deteriorates due to uncorrected pressure offset
Solution Approach 1:
The patent implements a feedback mechanism where pressure measurements during compression are used to calculate the pressure offset, which then feeds back to correct the combustion phase pressure measurements. The system continuously monitors pressure at multiple crank angles, calculates volume changes based on piston position, determines heat release characteristics, and uses this information to compute and apply a pressure offset correction factor, ensuring accurate measurements while providing a systematic method to manage the increased complexity.
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 enhances the accuracy of pressure measurements, reducing fuel consumption and emissions by enabling more precise engine operation and automatic calibration from cycle to cycle.
Implementation Method 1
Measuring a pressure pm indicative to a pressure in the cylinder at a crank angle (θ0-θ1)
Implementation Method 2
Determining a heat release characteristic during the crank angle range (θ0-θ1)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Invention relates to a method of calibrating a pressure sensor (80) adapted to measure pressure in an internal combustion piston engine (12), which the method comprises during a compression phase before start of the ignition at least steps of i. Measuring pressure p m in the cylinder at a crank angle (ϑ0), ii. Determining a heat release value during a crank angle range (ϑ0 – ϑ1), iii. Estimating a pressure offset ∆p of the pressure measured in the step i. using the heat release value determined in the step ii., and Calibrating the cylinder pressure measurement with the estimated pressure offset. The invention relates also to an internal combustion piston engine (12).