Internal Combustion Engine Control for Catalyst Activation
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Solution Overview
Problem
In-cylinder direct injection spark ignition engines face challenges in achieving early activation of the exhaust gas purifying catalyst while maintaining combustion stability, particularly during cold starts, due to fuel adhesion to cylinder walls and increased unburned HC emissions.
Innovation Solution
The engine control system adjusts the fuel injection timing and amount to ensure a stable air-fuel mixture by injecting fuel in the expansion stroke, shortening the interval between fuel injection end and ignition timing, and increasing fuel injection in the expansion stroke as the ignition timing is retarded, to promote catalyst temperature increase and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fuel is injected in the expansion stroke to activate the catalyst early, then the exhaust gas temperature increases and catalyst activation is promoted, but the air-fuel mixture around the ignition plug becomes insufficient leading to poor combustion stability
Solution Approach 1:
The fuel injection is divided into two separate stages: first injection during the compression stroke to form a base air-fuel mixture, and second injection during the expansion stroke to increase exhaust temperature. This segmentation allows each injection to serve its specific function without compromising the other, resolving the contradiction between catalyst activation and combustion stability
Solution Approach 2:
The first fuel injection during the compression stroke performs a preliminary action of creating a sufficient air-fuel mixture around the ignition plug before combustion begins. This preliminary mixture formation ensures combustion stability is maintained even when the second expansion stroke injection occurs, which prioritizes exhaust temperature increase for catalyst activation
2Object-generated harmful factors
If ignition timing is retarded after compression top dead center to reduce emissions, then HC and NOx emissions are reduced, but combustion stability deteriorates especially at cold start
Solution Approach 1:
The system dynamically adjusts the ignition timing parameter based on engine operating conditions, particularly cold start status. During cold start, ignition timing is set earlier (less retarded) to ensure combustion stability, while under normal operating conditions, more retarded ignition timing is used to maximize emission reduction. This parameter adaptation resolves the contradiction between emission control and combustion reliability
3Temperature
If fuel injection timing is delayed to promote catalyst temperature increase, then exhaust gas temperature rises, but the interval between injection and ignition becomes too long causing fuel dispersion and mixture inhomogeneity
Solution Approach 1:
Fuel injection is segmented into two distinct timing phases: compression stroke injection with a shorter delay to ignition that ensures proper mixture formation and homogeneity, and expansion stroke injection with a longer delay that prioritizes exhaust temperature increase. The segmentation allows the system to accept some mixture inhomogeneity from the second injection while maintaining overall combustion stability through the first injection's proper timing
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 approach enables early activation of the exhaust gas purifying catalyst while ensuring combustion stability by maintaining a rich air-fuel mixture around the ignition plug and optimizing fuel distribution, thereby reducing emissions and improving engine performance.
Implementation Method 1
a fuel injection valve that directly injects fuel into a cylinder of the engine to form an air-fuel mixture
Implementation Method 2
a spark plug that ignites the air-fuel mixture
Implementation Method 3
a piston that performs reciprocating motions
Implementation Method 4
the fuel easily vaporizes as compared to the case where the fuel is injected during a compression stroke
Data Source
AI summary
An internal combustion engine control device controls an in-cylinder direct injection type spark ignition internal combustion engine including a fuel injection valve for injecting fuel into a cylinder and an ignition plug for igniting an air-fuel mixture in the cylinder and configured to inject the fuel in an expansion stroke and ignite the fuel after injection in the expansion stroke under a specific operating condition. The internal combustion engine control device shortens an interval between a fuel injection timing in the expansion stroke and an ignition timing as the ignition timing is retarded.