Dual Fuel Injector Control for Air-Fuel Ratio Accuracy
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Solution Overview
Problem
At lower to middle engine loads, it is challenging to control the engine's air-fuel ratio due to small changes in fuel injection, leading to undesirable variations in the air-fuel ratio, especially when changes in air inducted into the cylinder occur after fuel delivery.
Innovation Solution
The method involves adjusting the port fuel injection amount in response to engine operating conditions and selectively adjusting the direct fuel injection pulse widths, ensuring that the sum of port and direct injected fuel amounts closely matches the desired cylinder fuel amount, even after intake valve closing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If small amounts of fuel are injected to the cylinder, then the desired fuel amount is achieved, but the air-fuel ratio control accuracy deteriorates due to larger variations from small changes in injection amount
Solution Approach 1:
The fuel injection system is divided into two separate injectors: a port fuel injector that delivers a baseline fuel amount, and a direct fuel injector that delivers additional fuel. This segmentation allows the control system to manage fuel delivery in two distinct stages, improving overall control accuracy when small total fuel amounts are required by using the port injector for precise metering and the direct injector for supplemental delivery.
Solution Approach 2:
The system dynamically changes the operating parameters of the two injectors based on engine conditions. The port fuel injector pulse width is adjusted based on initial engine operating conditions, and the direct fuel injector pulse width is subsequently adjusted based on actual air amount measurements. This parameter adaptation compensates for variations and maintains accurate air-fuel ratio control.
2Reliability
If port fuel injection is used, then fuel atomization is improved during cold conditions, but the response time to changing engine conditions is delayed
Solution Approach 1:
The port fuel injector delivers fuel in advance during the intake stroke, allowing fuel atomization to occur before combustion. This preliminary fuel delivery ensures good atomization quality, particularly during cold conditions, while the subsequent direct fuel injection can quickly respond to changing engine conditions by adding or reducing fuel as needed.
Solution Approach 2:
The system maintains continuous fuel delivery through the combination of port injection during the intake stroke and direct injection during the compression stroke. This continuity ensures that fuel atomization benefits are maintained while the system can continuously adapt to changing engine conditions without interruption.
3Temperature
If direct fuel injection is used, then cylinder charge cooling is increased, but the control accuracy deteriorates when small fuel amounts are required
Solution Approach 1:
The system applies different injection strategies to different locations and timing within the cylinder cycle. The port fuel injector operates during the intake stroke when the intake valve is open, providing precise fuel metering. The direct fuel injector operates during the compression stroke, providing charge cooling. Each injector is optimized for its specific function and timing, achieving both precision and cooling benefits.
Solution Approach 2:
The system dynamically switches between and combines two injection modes based on engine conditions. The control system adjusts the pulse widths of both injectors in real-time, enabling the engine to maintain accurate fuel control while utilizing the charge cooling effect of direct injection when needed.
Data Source
AI summary
Methods and systems for simultaneously operating port fuel injectors and direct fuel injectors of an internal combustion engine are described. In one example, a port fuel injection window is shorted to provide time for scheduling a direct fuel injector pulse width so that the direct fuel injector pulse width may be adjusted so that a desired amount of fuel enters a cylinder.