Catalyst Temperature Control via Spark and Valve Timing
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Solution Overview
Problem
Existing methods for controlling engine catalyst temperature during fuel cut conditions, such as transient fuel shut-off and auto-stop events, are inefficient and inaccurate, leading to increased emissions and decreased fuel economy due to inadequate heating strategies.
Innovation Solution
The method involves adjusting cylinder valve settings and spark timing to maintain catalyst temperature above a dynamic threshold, with more aggressive adjustments during transient fuel shut-off events and less aggressive adjustments during auto-stop events, using a continuously variable valve lift system to optimize catalyst heating based on predicted cooling amounts and vehicle conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is shut down during idle conditions to reduce fuel consumption, then fuel economy improves, but the catalyst temperature decreases below light-off temperature causing increased emissions
Solution Approach 1:
The system performs preliminary catalyst heating by retarding ignition timing and adjusting valve timing before the engine shut-down event occurs. This ensures the catalyst maintains sufficient temperature even after fuel injection is stopped, allowing the engine to shut down for fuel economy without causing emissions problems from catalyst cooling below light-off temperature.
2Temperature
If ignition timing is retarded to increase catalyst temperature before fuel cut-off, then catalyst temperature increases, but the temperature increase is insufficient compared to synergistic parameter adjustments
Solution Approach 1:
The system combines multiple parameter adjustments (ignition timing retardation, valve timing adjustment, and exhaust gas recirculation) to synergistically increase catalyst temperature. This merged approach achieves greater temperature increases than any single parameter adjustment alone, improving heating efficiency before fuel cut-off events.
3Device complexity
If a fixed threshold temperature is used to control catalyst heating, then the control logic simplifies, but it results in overheating during short fuel cut events and insufficient heating during long fuel cut events
Solution Approach 1:
The system dynamically adjusts the catalyst temperature threshold based on the predicted duration of the fuel cut event. For longer fuel cut events, a higher threshold is used to ensure sufficient heating, while for shorter events, a lower threshold prevents excessive heating. This dynamic threshold approach improves temperature control accuracy without requiring overly complex control logic.
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 effectively maintains catalyst temperature above the light-off temperature during fuel cut conditions, reducing emissions and improving fuel economy by dynamically adjusting heating strategies based on specific event durations and ambient conditions.
Implementation Method 1
a spark timing adjustment comprises actuating a spark plug of the cylinder at a retarded spark timing
Implementation Method 2
a cylinder valve adjustment comprises opening an exhaust valve of the cylinder at an advanced exhaust valve opening timing
Data Source
AI summary
Methods and systems are provided for increasing a catalyst temperature prior to entering a vehicle mode where combustion is temporarily discontinued. In one example, a method for increasing a temperature of an emission control device before a transient fuel shut-off (TFSO) event of an engine via a spark timing adjustment and an exhaust valve opening timing adjustments. Adjustments of the spark timing and the exhaust valve opening timing may change depending on whether a transient fuel shut off event of an auto-stop event occurs.