NOx Sensor Combustion Control Without Cylinder Pressure Sensors
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Solution Overview
Problem
The use of cylinder pressure sensors for combustion control in vehicle engines is costly, requires multiple sensors, and is susceptible to physical disturbances, leading to inefficiencies in data processing and increased costs due to the need for high-speed calculation by a dedicated ECU.
Innovation Solution
A combustion control method that uses NOx sensors to measure NOx concentration in exhaust gas, estimating heat generation rates and adjusting ignition timing and boost pressure to maintain optimal combustion conditions without relying on cylinder pressure sensors, thereby reducing costs and improving robustness against physical disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If cylinder pressure sensors are used for combustion control, then combustion mode can be grasped for each crank angle with high responsiveness, but the cost increases and a dedicated high-speed ECU is required
Solution Approach 1:
The patent replaces the mechanical/cylinder pressure sensor-based combustion detection system with a chemical/NOx sensor-based detection system. The NOx sensor detects nitrogen oxide concentration in exhaust gas, which correlates with combustion characteristics, thereby substituting the direct mechanical pressure measurement approach with an indirect chemical measurement approach that uses standard ECUs.
Solution Approach 2:
The patent introduces NOx concentration in exhaust gas as an intermediary parameter to infer combustion mode. Instead of directly measuring cylinder pressure or combustion characteristics, the system uses NOx concentration as a mediator that reflects combustion state, enabling standard ECUs to perform combustion control without high-speed processing requirements.
2Reliability
If multiple cylinder pressure sensors are installed, then combustion control can be improved, but mounting space requirements increase and costs rise
Solution Approach 1:
The patent makes the NOx sensor serve multiple functions: it not only detects NOx concentration for emission control but also provides combustion mode information for combustion control. This multi-functionality eliminates the need for separate cylinder pressure sensors, reducing mounting space requirements while maintaining combustion control accuracy.
3Productivity
If cylinder pressure sensor data is processed at high speed, then real-time control is achieved, but the calculation speed of standard ECU cannot keep up, requiring data thinning
Solution Approach 1:
The patent replaces the high-speed data processing requirement with a slower-response NOx sensor measurement approach. Since NOx concentration changes more slowly than cylinder pressure, standard ECUs can process the data without requiring high-speed calculation capabilities or data thinning, while still achieving effective combustion control.
4Measurement precision
If cylinder pressure sensor output is used for control, then combustion information is obtained, but the system is susceptible to pressure fluctuations from road reactions
Solution Approach 1:
The patent uses NOx concentration in exhaust gas as an intermediary measurement that is less sensitive to mechanical disturbances. While cylinder pressure is directly affected by road reactions and physical shocks, NOx concentration in the exhaust stream provides a more stable indicator of combustion characteristics, reducing the impact of physical disturbances on measurement accuracy.
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 method allows for effective combustion control with equivalent controllability to cylinder pressure sensor systems, reducing costs and enhancing robustness against physical disturbances, while maintaining optimal combustion conditions.
Implementation Method 1
a NOx sensor provided on an upstream side of the catalyst
Implementation Method 2
an exhaust path for an exhaust gas discharged from the engine includes a catalyst and a NOx sensor provided on an upstream side of the catalyst
Data Source
AI summary
A combustion control method in an engine of a vehicle wherein an exhaust path includes a catalyst and a NOx sensor provided on an upstream side of the catalyst, the method includes the following steps. A step of determining whether a NOx concentration in an exhaust gas falls within a predetermined reference range; a step of estimating a heat generation rate profile indicating crank angle dependency of a heat generation rate in the engine when the NOx concentration is determined out of the reference range; and a step of comparing a value of an index characterizing the estimated heat generation rate profile with a value of an index in an ideal heat generation rate profile specified from a driving condition of the vehicle and controlling a combustion condition in the engine based on a result.