Cylinder Equalization via Exhaust Back Pressure Correlation
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Solution Overview
Problem
Current methods for internal combustion engines fail to accurately detect and compensate for cylinder-specific differences in air charge due to pressure waves and temperature effects, leading to suboptimal fuel/air ratios and increased emissions, as they rely on averaged values and do not account for fluctuations dependent on the operating point.
Innovation Solution
A method that determines and adjusts cylinder-specific charge quantities by measuring and correlating exhaust gas back pressure values with camshaft position and operating cycle, allowing for precise detection and compensation of differences in fresh air and fuel distribution between cylinders, using a control unit to adjust intake and fuel injection accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional measurement and calculation methods are used, then the fuel/air ratio is averaged over all cylinders as a mean value, but cylinder-specific differences in air charge cannot be detected
Solution Approach 1:
The invention segments the measurement approach by determining exhaust gas back pressure values for each individual cylinder separately over multiple operating cycles, rather than using a single averaged measurement. This allows cylinder-specific air charge differences to be detected while maintaining operational simplicity through the use of existing sensor infrastructure.
Solution Approach 2:
The invention performs preliminary determination of exhaust gas back pressure values over at least two operating cycles before calculating the final air charge values. This preliminary action allows the system to capture fluctuations dependent on the operating point and establish a baseline for detecting cylinder-specific differences.
2Productivity
If cylinder-specific differences are not compensated, then the fuel/air ratio does not correspond to the desired optimal value, but emissions increase and catalytic converter efficiency decreases
Solution Approach 1:
The invention implements a feedback mechanism where exhaust gas back pressure values are continuously determined over multiple operating cycles, compared between cylinders, and used to adjust fuel injection quantities. This closed-loop control ensures that cylinder-specific differences are compensated, maintaining optimal fuel/air ratios and minimizing emissions.
Solution Approach 2:
The invention changes the parameter being measured from averaged values to cylinder-specific exhaust gas back pressure values determined over multiple operating cycles. This parameter change enables the detection and compensation of cylinder-specific air charge differences, improving both engine efficiency and emission control.
3Reliability
If overdimensioned catalytic converters are used to compensate for unequal distributions, then storage capacity increases, but cost, space requirements, and heat input needs increase
Solution Approach 1:
The invention performs preliminary detection and compensation of cylinder-specific air charge differences through exhaust gas back pressure measurement and fuel injection adjustment. By addressing the root cause of unequal distributions before emissions occur, the system reduces the burden on the catalytic converter, allowing for smaller, more cost-effective converter design.
Solution Approach 2:
The invention converts the potentially harmful effect of cylinder-specific air charge differences into a beneficial control signal by measuring exhaust gas back pressure and using it to adjust fuel injection. This transforms what would otherwise require oversized emission control components into an opportunity for precise engine management.
Data Source
AI summary
A method and control unit for cylinder equalization of an internal combustion engine having at least two cylinders, and includes the following steps: Determination of exhaust gas back pressure values of the individual cylinders over at least two operating cycles, correlation of the exhaust gas back pressure values with the camshaft position and/or the operating cycle, determination of the exhaust gas back pressure maxima for each cylinder, comparison of the exhaust gas back pressure maxima between the individual cylinders and detection of differences, adjustment of the cylinder-specific charge quantities of fresh air and/or fuel. In addition, the invention relates to a controller for carrying out the method and a motor vehicle having such a controller. The method improves the previously known methods and makes them more efficient, especially with regard to the efficiency of the combustion process and thus also of exhaust-gas aftertreatment.