Lean Burn Engine Control via Air Follows Fuel Inversion
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Solution Overview
Problem
Conventional internal combustion engine control systems face instability and power reduction during load increases due to the 'fuel follows air' approach, leading to potential engine stalling, especially when transitioning from lean to rich burn operations.
Innovation Solution
An engine operation control system that employs an 'air follows fuel' approach, where the engine control unit adjusts fuel injection duration and throttle position to maintain a target air-fuel ratio, using an electronic throttle control system and fuel injection system to manage engine speed and load, allowing for seamless switching between lean and rich burn operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional 'fuel follows air' approach is used during load increases, then the throttle position is adjusted to maintain air flow, but engine stability deteriorates and power reduction occurs due to delayed fuel response
Solution Approach 1:
The patent inverts the conventional control sequence by implementing an 'air follows fuel' approach instead of 'fuel follows air'. The ECU determines target air-fuel ratio based on throttle position and engine speed, then adjusts fuel injection duration to achieve the target ratio. This inversion allows fuel injection to lead the control action, preventing the delay and instability associated with adjusting throttle position first during load increases.
Solution Approach 2:
The ECU proactively determines the target air-fuel ratio based on anticipated load conditions and throttle position changes before the actual load increase fully impacts engine operation. By calculating the required fuel injection duration in advance based on engine speed data and throttle position, the system prepares the optimal fuel quantity ahead of time, ensuring immediate response to load changes without the instability caused by reactive throttle adjustments.
2Loss of energy
If lean burn operation is used to improve fuel efficiency, then brake-specific fuel consumption decreases, but engine stability deteriorates during load transitions requiring rich burn operations
Solution Approach 1:
The patent implements dynamic switching between lean burn and rich burn operations based on real-time engine conditions. The ECU continuously monitors engine speed data, throttle position, and load conditions to determine the optimal air-fuel ratio. During light load conditions, the system maintains lean burn operation for fuel efficiency, while automatically transitioning to rich burn operation during load increases or transient conditions to ensure engine stability and prevent stalling.
Solution Approach 2:
The system dynamically changes the air-fuel ratio parameter based on operating conditions. By adjusting the fuel injection duration to achieve target air-fuel ratios that vary with engine speed and load, the system optimizes the balance between fuel efficiency and stability. The ECU modifies the air-fuel ratio from lean (higher ratio) during light load to rich (lower ratio) during heavy load or transient conditions, resolving the contradiction between fuel efficiency and engine stability.
3Measurement precision
If the throttle position is adjusted frequently to maintain air-fuel ratio during load changes, then air-fuel ratio control precision improves, but engine response time increases due to mechanical throttle lag
Solution Approach 1:
The patent replaces mechanical throttle position adjustment with electronic fuel injection control for air-fuel ratio management. Instead of physically moving the throttle plate to maintain air-fuel ratio during load changes, the ECU electronically adjusts the fuel injection duration based on engine speed data and throttle position sensors. This substitution eliminates mechanical throttle lag while achieving precise air-fuel ratio control through direct electronic control of fuel quantity.
Solution Approach 2:
The ECU acts as an intermediary that processes throttle position sensor data and engine speed data to calculate the optimal fuel injection duration. Rather than directly adjusting throttle position, the ECU uses this intermediate calculation to determine the precise fuel quantity needed to maintain target air-fuel ratio, bypassing the mechanical lag of throttle actuation while maintaining accurate ratio control through electronic fuel injection timing and duration adjustments.
Data Source
AI summary
An internal combustion engine includes an engine block including a cylinder a piston positioned within the cylinder and configured to reciprocate in the cylinder, an electronic throttle control system comprising a motor and a throttle plate, a fuel system for supplying a controlled amount of fuel to the cylinder including a fuel injector, and an engine control unit coupled to the fuel system and the electronic throttle control system. The engine control unit is configured to determine engine speed data comprising a current engine speed, a previous engine speed, and a desired engine speed and control a fuel injection duration based on the engine speed data.