Hybrid Engine Cold Start Fuel Control via Electric Motor Torque
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Solution Overview
Problem
Hybrid vehicles face challenges in controlling fuel injection to reduce hydrocarbon emissions immediately after start-up, as oxygen sensors and catalytic converters take time to warm up, making it difficult to achieve accurate engine control and leading to excessive hydrocarbon emissions.
Innovation Solution
A system and method that use a calculated combustion stability value, determined from a torque signal of the electric motor, to modify the fuel injection pulsewidth, reducing hydrocarbon emissions by adjusting the fuel injected into the engine, especially during cold starts when oxygen sensor feedback is unreliable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen sensor feedback control is used to control fuel injection, then engine performance is improved, but hydrocarbon emissions increase during cold start when the sensor is too cold to provide accurate readings
Solution Approach 1:
The patent uses an intermediary feedback mechanism (engine roughness measurement via crankshaft position sensor) to bridge the gap when the primary feedback sensor (oxygen sensor) is unavailable. The crankshaft position sensor continuously measures engine speed variations to calculate roughness, providing indirect feedback about combustion quality without requiring thermal warming, thus enabling fuel injection control during cold start conditions.
Solution Approach 2:
The system performs preliminary determination of combustion stability using engine roughness measurements before the oxygen sensor becomes operational. By calculating the coefficient of variation of engine speed during the cold start period, the system proactively adjusts fuel injection parameters in advance of when traditional feedback would become available, preventing excessive hydrocarbon emissions from the outset.
2Object-generated harmful factors
If the catalytic converter is used to oxidize hydrocarbons, then emissions are reduced, but the catalyst requires extended warm-up time during which it remains ineffective
Solution Approach 1:
The system performs preliminary fuel injection adjustments based on engine roughness measurements before the catalytic converter becomes operational. By proactively optimizing the air-fuel ratio during the cold start period using crankshaft position-based combustion stability feedback, the system reduces hydrocarbon emissions at the source, preventing the catalyst from being overwhelmed with unburned fuel that would otherwise require extended warm-up time to process.
Solution Approach 2:
The patent converts the harmful effect of cold engine operation (poor combustion efficiency) into a beneficial control opportunity. By measuring engine roughness during cold start and using this information to adjust fuel injection, the system transforms the previously uncontrollable cold start emissions problem into a controllable parameter, reducing hydrocarbon emissions that would otherwise burden the catalytic converter.
3Reliability
If engine speed signals are processed to measure combustion stability, then engine control is improved, but the electric motor controls the combustion engine speed faster than the combustion engine at lower speeds, making roughness measurements impossible
Solution Approach 1:
The patent extracts the essential combustion stability information from the complex electric motor-controlled engine system by focusing specifically on crankshaft position variations. Rather than attempting to measure or control all aspects of the hybrid powertrain's complex speed interactions, the system isolates and measures only the combustion-induced speed variations through the crankshaft position sensor, filtering out the complexity of electric motor control.
Solution Approach 2:
The system uses the existing crankshaft position sensor, which is already part of the hybrid vehicle's control system, to provide dual functionality: both for controlling the electric motor's interaction with the combustion engine and for measuring combustion stability. This self-service approach eliminates the need for additional dedicated measurement devices, reducing system complexity while maintaining measurement capability.
Data Source
AI summary
A system and method for controlling an engine in a hybrid vehicle based on the use of a calculated combustion stability value to modify a pulsewidth signal to fuel injectors of the engine to reduce hydrocarbon emissions, especially following an engine start. The calculated combustion stability value is determined as a function of a torque signal obtained from an electric motor of the hybrid vehicle.