Hybrid Engine Deceleration Cylinder Cut-Off NVH Mitigation
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Solution Overview
Problem
Deceleration cylinder cutoff (DCCO) is hindered by challenges such as undesirable noise, vibration, and harshness (NVH) characteristics due to intake manifold pressure issues when transitioning from DCCO to operational modes, and existing solutions like spark retard are wasteful and inefficient.
Innovation Solution
Implementing a method where some or all cylinders are briefly activated to pump air before fueling and firing, reducing manifold pressure to mitigate NVH issues and avoid the need for fuel-wasting techniques like spark retard, by transitioning through a deceleration fuel cut-off (DFCO) mode before resuming normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If deceleration cylinder cutoff (DCCO) is implemented to improve fuel economy, then fuel savings increase, but noise, vibration, and harshness (NVH) characteristics deteriorate due to intake manifold pressure issues
Solution Approach 1:
The system performs preliminary action by briefly activating cylinders to pump air and reduce intake manifold pressure before transitioning from DCCO to operational modes. This pre-conditioning of the intake manifold pressure prevents NVH issues during mode transition while maintaining the fuel economy benefits of extended DCCO operation.
Solution Approach 2:
The system implements a transitional DFCO mode that briefly skips the fuel injection phase while maintaining cylinder activation for air pumping. This allows rapid pressure equalization in the intake manifold during the transition period, resolving NVH characteristics quickly while minimizing the time spent in the transitional state, thus preserving overall fuel economy.
2Loss of energy
If deceleration cylinder cutoff (DCCO) operates for extended periods to maximize fuel savings, then fuel economy improves, but emissions control becomes problematic due to oxygen saturation of exhaust catalyst
Solution Approach 1:
The system employs periodic action by implementing intermittent transitions to DFCO mode during extended DCCO operation. Rather than continuous DCCO operation, the system periodically activates cylinders for brief DFCO periods to manage catalyst oxygen saturation, then returns to DCCO mode. This periodic intervention maintains emissions control while preserving overall fuel economy through extended DCCO operation.
3Object-affected harmful factors
If spark retard is used to mitigate NVH issues during DCCO transition, then NVH characteristics improve, but fuel efficiency deteriorates due to wasteful fuel consumption
Solution Approach 1:
The system extracts the harmful effect of high intake manifold pressure by separately addressing it through brief cylinder activation for air pumping during DFCO transition. By removing the pressure issue through mechanical means rather than fuel management (spark retard), the system avoids the fuel waste associated with spark retard while still achieving NVH mitigation.
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 improves NVH characteristics and reduces the need for wasteful techniques, allowing for longer DCCO mode operation with enhanced fuel economy and emissions control.
Implementation Method 1
some or all cylinders are briefly activated to pump air before fueling and firing, reducing manifold pressure
Data Source
AI summary
Methods and arrangements for transitioning an engine between a deceleration cylinder cutoff (DCCO) state and an operational state are described. In one aspect, transitions from DCCO begin with reactivating cylinders to pump air to reduce the pressure in the intake manifold prior to firing any cylinders. In another aspect, transitions from DCCO, involve the use of an air pumping skip fire operational mode. After the manifold pressure has been reduced, the engine may transition to either a cylinder deactivation skip fire operational mode or other appropriate operational mode. In yet another aspect a method of transitioning into DCCO using a skip fire approach is described. In this aspect, the fraction of the working cycles that are fired is gradually reduced to a threshold firing fraction. All of the working chambers are then deactivated after reaching the threshold firing fraction.