Air/Fuel Switching Torque Compensation for Stable Engine Speed
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Solution Overview
Problem
Existing engine control systems experience noticeable fluctuations in engine speed due to air-fuel ratio (A/F) switching, particularly at idle, leading to consumer-noticeable variability in engine sound and vehicle speed.
Innovation Solution
An A/F switching torque compensation system that proactively adjusts engine load requests in real-time or near-real-time based on air-fuel ratio changes, using processors to determine throttle, spark, and variable valve timing actuator outputs to maintain engine speed stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the engine switches between rich and lean air-fuel ratios to optimize catalytic converter functioning, then emissions are minimized at stoichiometric levels, but engine speed fluctuations and torque variability occur particularly at idle
Solution Approach 1:
The system proactively adjusts the engine load request before the A/F switching event occurs. The controller detects the upcoming A/F ratio change and preemptively modifies the throttle angle or other load control parameters to compensate for the anticipated torque fluctuation, thereby preventing engine speed variations rather than reacting to them after they occur.
Solution Approach 2:
The system applies an opposing control action to counteract the expected harmful effect of A/F switching. When a rich-to-lean transition is anticipated (which would cause torque decrease), the system increases the engine load request in advance to offset the upcoming torque drop, and vice versa for lean-to-rich transitions, thereby neutralizing the engine speed fluctuations.
2Productivity
If the engine operates at idle with A/F ratio switching every 15 seconds, then catalytic converter efficiency is maximized, but noticeable torque flares and dips occur that affect driveability
Solution Approach 1:
The controller proactively modifies the engine load request in real-time or near-real-time based on detected A/F ratio changes. By adjusting the throttle angle or other load control parameters before the torque flare or dip fully manifests, the system maintains smooth engine operation and preserves driveability while continuing to operate the catalytic converter at optimal efficiency.
3Stability of the object's composition
If reactive torque compensation is used after torque changes are detected, then engine speed stability can be restored, but the compensation response is delayed causing prolonged flares or dips
Solution Approach 1:
The system performs preliminary compensation by detecting A/F ratio changes and adjusting the engine load request in real-time or near-real-time before the torque fluctuation fully develops. This proactive approach eliminates the time delay inherent in reactive systems that wait to detect torque changes before responding, thereby minimizing the duration of engine speed fluctuations.
Data Source
AI summary
A vehicle includes one or more processors configured to select an air/fuel ratio for the engine that is different from the stoichiometric air/fuel ratio. The one or more processors are further configured to select a torque request for the engine, determine a load request for the engine based on at least the torque request and the selected air/fuel ratio, and determine an output to a throttle actuator based on the load request for the engine.