Variable Valve Timing for Cylinder Deactivation Flow Control
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Solution Overview
Problem
Existing engine technologies face issues with tailpipe emissions and catalyst efficiency when cylinders are reactivated, leading to fuel economy penalties due to additional fuel required for exhaust catalyst regeneration and minor variations in cam timing affecting flow through deactivated cylinders.
Innovation Solution
Adjusting valve timing on a second engine bank to maintain a substantially smaller flow and alternating flow direction based on the exhaust air-to-fuel ratio, allowing for selective cylinder deactivation without degrading the exhaust catalyst efficiency, and enabling reverse flow for cooled EGR benefits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If valve timing is adjusted to reduce flow through deactivated cylinders, then cylinder deactivation benefits are achieved, but exhaust catalyst efficiency degrades due to oxygen saturation
Solution Approach 1:
The patent applies periodic action by continuously alternating the flow direction through the deactivated cylinder bank between forward flow (intake to exhaust) and reverse flow (exhaust to intake). This periodic reversal prevents sustained oxygen saturation of the exhaust catalyst while maintaining the benefits of cylinder deactivation. The controller switches the flow direction periodically based on detected oxygen levels in the exhaust manifold.
Solution Approach 2:
The patent applies inversion by reversing the normal flow direction through the deactivated cylinder bank. Instead of allowing only forward flow from intake to exhaust, the system creates reverse flow from exhaust to intake, which pulls oxygen-rich exhaust gases through the deactivated cylinders and prevents oxygen saturation of the exhaust catalyst, thereby maintaining catalyst efficiency during deactivation.
2Use of energy by moving object
If flow is reduced through deactivated cylinders, then fuel economy improves, but catalyst regeneration requires additional fuel
Solution Approach 1:
The patent applies preliminary action by proactively managing the flow direction through the deactivated cylinder bank before oxygen saturation occurs. The controller continuously monitors oxygen levels and preemptively reverses flow direction to prevent excessive oxygen accumulation, thereby avoiding the need for subsequent fuel-rich regeneration events that would consume additional energy.
3Productivity
If cam timing is adjusted to control flow through deactivated cylinders, then flow can be reduced, but minor variations in cam timing affect flow and reduce catalyst efficiency
Solution Approach 1:
The patent applies feedback by using an oxygen sensor to continuously detect oxygen levels in the exhaust manifold and using this information to control the flow direction through the deactivated cylinder bank. The controller adjusts the flow direction based on real-time oxygen detection, providing closed-loop control that maintains catalyst efficiency while managing flow through the deactivated bank.
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 reduces catalyst regeneration requirements, maintains engine performance, and improves fuel economy by minimizing oxygen saturation in the exhaust catalyst and utilizing reverse flow for cooled EGR benefits.
Implementation Method 1
minor changes in exhaust pressure and intake pressure can result in some net flow between the intake and exhaust manifolds
Implementation Method 2
additional fuel is required to reactivate the exhaust catalyst of the deactivated bank
Data Source
AI summary
Methods and systems are provided for adjusting cylinder valve timings to enable a group of cylinders to operate and combust while another group of cylinders on a second are selectively deactivated. Valve timing may be adjusted to allow flow of air through the inactive cylinders to be reduced, lowering catalyst regeneration requirements upon reactivation. The valve timing may alternatively be adjusted to enable exhaust gas to be recirculated to the active cylinders via the inactive cylinders, providing cooled EGR benefits.