Cam Phaser Valve Timing for Catalyst Oxygen Management
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Solution Overview
Problem
Existing fuel cutoff systems in motor vehicles deliver excess oxygen to catalysts during deceleration, leading to oxygen storage capacity saturation, which reduces the catalyst's ability to convert NOx emissions and diminishes fuel economy improvements.
Innovation Solution
A control system that includes a fuel cutoff module, an oxygen storage module, and an intake valve timing module, which determines deceleration fuel cutoff events and adjusts valve timing by actuating cam phasers to reduce oxygen flow to the catalyst, preventing oxygen storage capacity saturation and optimizing fuel economy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If fuel cutoff is implemented during deceleration to improve fuel economy, then fuel economy improves, but excess oxygen accumulates in the catalyst reducing NOx conversion efficiency
Solution Approach 1:
The valve timing is dynamically adjusted during fuel cutoff events by actuating cam phasers to modify intake valve closing timing. This dynamic adjustment reduces oxygen flow to the catalyst during deceleration, preventing oxygen storage capacity saturation and maintaining NOx conversion efficiency while preserving fuel economy benefits
Solution Approach 2:
The system changes the valve timing parameter by actuating cam phasers to different positions. This parameter change controls the amount of oxygen delivered to the catalyst during fuel cutoff, optimizing both fuel economy and emissions performance by preventing excessive oxygen accumulation
2Reliability
If rich fuel conditions are applied after fuel cutoff to release oxygen from the catalyst and improve NOx conversion, then NOx conversion improves, but fuel economy improvements are diminished
Solution Approach 1:
Instead of applying full rich fuel conditions to clear the catalyst, the system uses partial action by dynamically adjusting valve timing to prevent excessive oxygen accumulation in the first place. This approach maintains adequate NOx conversion without requiring aggressive fuel enrichment, thereby preserving fuel economy benefits
3Reliability
If valve timing is modified to reduce oxygen flow to the catalyst, then oxygen storage capacity saturation is prevented, but system complexity increases due to cam phaser actuation requirements
Solution Approach 1:
The cam phaser actuation system serves multiple functions: it controls valve timing for oxygen flow management during fuel cutoff events, maintains NOx conversion efficiency, and works within the existing variable valve timing infrastructure. This multi-functionality justifies the added complexity by delivering multiple benefits from a single system
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
The system effectively reduces oxygen flow to the catalyst, maintaining NOx conversion efficiency and improving fuel economy by preventing oxygen storage capacity saturation during deceleration fuel cutoff events.
Implementation Method 1
A cam phaser is actuated to modify a valve timing of the intake valves to reduce a flow rate of oxygen to the catalyst
Implementation Method 2
The catalyst stores oxygen when operating under lean fuel conditions and consumes the stored oxygen when operating under rich fuel conditions
Implementation Method 3
a catalyst that reduces the levels of CO, NOx, and HC in the exhaust gas by chemically converting these gases into carbon dioxide, nitrogen, and water
Data Source
AI summary
A control system for a fuel cutoff system of a motor vehicle includes a fuel cutoff module that generates a fuel cutoff signal for disabling a supply of fuel to an engine, in response to the fuel cutoff module detecting a deceleration fuel cutoff (DFCO) event. The control system further includes an oxygen storage module determining an amount of oxygen accumulated in a catalyst and comparing this amount to an oxygen storage capacity (OSC) of the catalyst, in response to the fuel cutoff module determining the DFCO event. The control system further includes an intake valve timing module generating a phasing signal to actuate a plurality of cam phasers to reduce a flow rate of oxygen to the catalyst, in response to the fuel cutoff module determining the DFCO event and the oxygen storage module determining that the amount of oxygen stored in the catalyst is less than the OSC.