Lean-Burn Engine Controller Firing Density Transitions
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Solution Overview
Problem
Skip fire engine control systems face challenges in transitioning between firing densities to meet torque requests while minimizing Noise, Vibration, and Harshness (NVH), maintaining proper air-fuel ratios, and controlling air flow to avoid excessive emissions, especially in lean burn internal combustion engines.
Innovation Solution
The engine controller separately determines firing and pumping densities during transitions, allowing for intermixing of cylinder firing and deactivation with air and exhaust gas pumping to balance torque demand, NVH reduction, air-fuel ratio control, and emissions management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If firing density is increased to meet torque request, then power output is improved, but NVH increases
Solution Approach 1:
The patent segments the control of firing density and pumping density into separate independent control loops. The firing density controller manages cylinder firing patterns to meet torque requests, while the pumping density controller manages air flow and pumping operations. This segmentation allows each controller to optimize its parameter independently, enabling the firing density to be increased for torque while the pumping density is adjusted to mitigate NVH, resolving the contradiction between power output and NVH.
2Object-affected harmful factors
If firing density is decreased to reduce NVH, then noise and vibration are reduced, but torque output decreases
Solution Approach 1:
By segmenting the control functions, the patent allows the firing density to be reduced for NVH mitigation while the pumping density is independently increased to maintain torque output. The pumping density controller compensates for the reduced firing density by optimizing air flow and pumping operations, ensuring that torque requirements are met even with lower firing density, thus resolving the contradiction between NVH reduction and torque maintenance.
3Object-generated harmful factors
If pumping density is increased to control air flow, then emissions are reduced, but air-fuel ratio control becomes more difficult
Solution Approach 1:
The patent segments air flow control into pumping density (managed by the pumping density controller) and fuel injection control (managed by the fuel injection controller). The pumping density controller increases pumping density to control air flow and reduce emissions, while the fuel injection controller independently adjusts fuel injection to maintain the correct air-fuel ratio. This segmentation simplifies the overall control by dividing the complex air-fuel ratio management into two independent control loops, resolving the contradiction between emissions reduction and air-fuel ratio control complexity.
4Speed
If firing density transitions quickly to meet torque demand, then responsiveness is improved, but emissions control deteriorates
Solution Approach 1:
The patent segments the transition control into firing density transitions (for torque responsiveness) and pumping density transitions (for emissions control). When torque demand changes, the firing density controller可以快速调整 firing density to meet the new torque requirement, while the pumping density controller independently manages the transition of pumping density to ensure emissions remain controlled. This segmentation allows rapid torque response without compromising emissions control, resolving the contradiction between responsiveness and emissions control.
Data Source
AI summary
A skip fire engine controller and method of control is described wherein during transitions from a first firing density to a second firing density, a firing density and a pumping density are separately set so as to balance the conflicting demands of (a) torque control, (b) Noise, Vibration and Harshness (NVH), (c) air flow through the engine and (d) air-fuel ratio.