Engine Cylinder Deactivation for NVH and Catalyst Temperature Control
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Solution Overview
Problem
Existing engine cylinder deactivation methods, such as variable displacement engines and active decompression technologies, increase noise, vibration, and harshness (NVH) due to differences in torque output profiles from active and deactivated cylinders, which can lead to reduced exhaust catalyst efficiency and increased emissions.
Innovation Solution
Implementing a combination of modified eight stroke and four stroke combustion cycles in engine cylinders, where one set of cylinders operates with eight strokes and another with four strokes, using variable displacement engine (VDE) and active decompression technology (ADT) mechanisms to maintain a uniform torque profile, thereby reducing NVH and increasing exhaust temperature to keep catalysts above light-off temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cylinder deactivation is implemented using variable displacement engine or active decompression technology, then engine efficiency is improved and emissions are reduced, but noise, vibration, and harshness (NVH) increase due to differences in torque output profile
Solution Approach 1:
The patent divides the cylinder group into multiple sub-groups, where each sub-group can be independently deactivated. This segmentation allows for more granular control over torque output, reducing the abrupt changes that cause NVH issues while still achieving fuel savings during light-load operation.
Solution Approach 2:
The patent implements dynamic transition strategies where cylinders are deactivated and reactivated in a controlled sequence, and intake throttling is dynamically adjusted to maintain smooth torque output. This dynamic control prevents sudden torque changes that would otherwise cause vibration and harshness.
2Use of energy by moving object
If cylinder deactivation is implemented, then fuel consumption is reduced, but exhaust catalyst temperature may fall below light-off temperature reducing emission treatment effectiveness
Solution Approach 1:
The patent deactivates only a portion of the cylinders (partial action) rather than all cylinders, and dynamically adjusts the number of active cylinders based on exhaust temperature feedback. This ensures sufficient exhaust flow and temperature to maintain catalyst light-off while still achieving fuel savings.
Solution Approach 2:
The patent implements a feedback control system that monitors exhaust catalyst temperature and adjusts cylinder deactivation status accordingly. When catalyst temperature approaches light-off threshold, cylinders are reactivated to maintain temperature, ensuring continuous effective emission treatment.
3Use of energy by moving object
If all cylinders are deactivated simultaneously, then maximum fuel savings are achieved, but torque output becomes non-uniform causing increased vibration and harshness
Solution Approach 1:
The patent segments cylinders into multiple sub-groups that can be deactivated independently. This allows gradual deactivation rather than simultaneous deactivation of all cylinders, maintaining more uniform torque output and reducing vibration while still achieving significant fuel savings.
Solution Approach 2:
The patent employs periodic activation and deactivation of cylinder sub-groups in a controlled sequence. This periodic action smooths out torque fluctuations by ensuring that not all cylinders are deactivated at the same time, thereby reducing vibration and harshness while maintaining fuel efficiency benefits.
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 NOx emissions, maintains emissions quality, and ensures smooth engine operation by trapping air in deactivated cylinders, increasing intake throttling, and combining four and eight stroke cycles to maintain catalyst functionality.
Implementation Method 1
At catalyst light-off temperature (e.g., operational temperature), the exhaust catalyst may oxidize and reduce exhaust constituents in an exhaust gas
Implementation Method 2
operating a first set of cylinders in a first combustion cycle over eight strokes and a second set of cylinders in a second combustion cycle over four strokes
Data Source
AI summary
Methods and systems are provided for cylinder deactivation to reduce tailpipe emissions and increase exhaust temperature. In one example, a method may include operating a first set of cylinders in a first combustion cycle over modified eight strokes and a second set of cylinders in a second combustion cycle over modified four strokes. Each cylinder in the first set of cylinders may be selectively deactivated via a variable displacement engine (VDE) mechanism while each cylinder in the second set of cylinders may be selectively deactivated via an active decompression technology (ADT) mechanism.