Skip Fire Engine Control for Pumping Loss Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Internal combustion engines operate at suboptimal efficiency due to varying loads, leading to inefficient air and fuel delivery, which results in reduced thermodynamic efficiency and increased fuel consumption, particularly at partial throttle conditions.
Innovation Solution
Implementing a skip fire operation method where selected working cycles are deactivated by holding intake and exhaust valves closed, using a sigma delta controller to dynamically determine cylinder firings and adjust fuel injection quanta based on operating conditions, allowing for continuous variable displacement mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the engine operates at partial throttle to control power output, then the power delivery matches the desired load, but thermodynamic efficiency decreases due to reduced compression and increased pumping losses
Solution Approach 1:
The engine operates in periodic skip-fire mode, alternating between firing and skipping cycles in selected cylinders. This periodic action allows the engine to maintain unthrottled operation with high thermodynamic efficiency during firing cycles while reducing average power output to match load requirements, thereby resolving the contradiction between power control and efficiency
Solution Approach 2:
The engine dynamically adjusts its operating mode between conventional continuous firing and skip-fire variable displacement modes based on real-time load conditions. This dynamic adaptation allows the engine to maintain optimal efficiency during skip-fire operation while still meeting varying power demands, resolving the efficiency-loss contradiction
2Loss of energy
If conventional variable displacement engines shut down cylinders to improve efficiency, then fuel efficiency improves, but the engine kicks out of variable displacement mode quickly when additional power is requested
Solution Approach 1:
The skip-fire system provides continuous, dynamic adjustment of effective displacement through on-the-fly firing pattern modifications, enabling rapid response to power demand changes without the delay and complexity of mechanical cylinder shutdown systems. This dynamic control maintains both fuel efficiency and adaptability
Solution Approach 2:
The system changes operational parameters (firing patterns, cylinder selection, fuel injection timing) to smoothly transition between displacement modes. This parameter-based control allows the engine to maintain variable displacement operation during transient conditions, preventing premature exit from efficiency mode while meeting power demands
3Adaptability or versatility
If all cylinders operate continuously to meet varying load demands, then power delivery is maintained, but pumping losses increase and thermodynamic efficiency decreases
Solution Approach 1:
The engine segments its cylinders into active and inactive groups during skip-fire operation. By deactivating selected cylinders through closed intake and exhaust valves, the engine eliminates pumping losses in those cylinders while maintaining adequate power output from active cylinders, thereby reducing overall energy losses while handling varying loads
Data Source
AI summary
A variety of methods and arrangements for improving the fuel efficiency of internal combustion engines based on skip fire operation of the engine are described. In one aspect the skip fire decisions are made on a working cycle by working cycle basis. During selected skipped working cycles, the corresponding cylinders are deactivated such that air is not pumped through the cylinder during the selected skipped working cycles. In some implementations, the cylinders are deactivated by holding associated intake and exhaust valves closed such that an air charge is not present in the working chamber during the selected skipped working cycles.