Skip Fire Engine Controller Firing Profile Optimization
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Solution Overview
Problem
Skip fire engine control systems face challenges in reducing noise, vibration, and harshness (NVH) to an acceptable level while maintaining fuel efficiency and delivering desired engine torque output, which has hindered their widespread adoption.
Innovation Solution
A skip fire engine controller with a skip fire profile module and firing controller that determines an operational firing fraction and directs firings to deliver a desired engine output, utilizing a lookup table to select the optimal firing fraction based on cylinder load, engine speed, and transmission gear, allowing for varying cylinder load levels to improve fuel efficiency and reduce NVH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If skip fire engine control is implemented to improve fuel efficiency, then fuel economy is significantly improved, but noise, vibration and harshness (NVH) increases making the engine run rougher
Solution Approach 1:
The system dynamically adjusts the firing fraction based on operating conditions such as engine speed, load, and temperature. The controller continuously monitors these parameters and modifies the skip fire pattern in real-time to maintain acceptable NVH levels while maximizing fuel efficiency benefits.
Solution Approach 2:
The invention changes the firing fraction parameter as a function of cylinder load, with more firing fractions available at lower cylinder loads than at higher cylinder loads. This parameter adjustment allows the system to optimize the balance between fuel economy and NVH performance across different operating conditions.
2Loss of energy
If skip fire operation is used to reduce fuel consumption, then fuel efficiency improves, but vibration control becomes significantly more challenging
Solution Approach 1:
The controller uses feedback from sensors monitoring engine vibrations, NVH levels, and operating conditions to continuously adjust the firing fraction and cylinder selection. This closed-loop control enables the system to maintain acceptable vibration levels while achieving fuel consumption reductions through skip fire operation.
Solution Approach 2:
The system dynamically adapts the skip fire pattern based on real-time vibration measurements and operating conditions, making vibration control manageable through continuous adjustment of firing fractions and cylinder deactivation strategies.
3Use of energy by moving object
If a fixed set of cylinders is deactivated under low load conditions, then fuel efficiency improves, but engine adaptability to different operating conditions decreases
Solution Approach 1:
Instead of a fixed cylinder deactivation strategy, the system dynamically determines which cylinders to deactivate and the firing fraction based on current operating conditions including engine speed, load, temperature, and NVH levels. This enables the engine to adapt to a wide range of operating conditions while maintaining fuel efficiency benefits.
Solution Approach 2:
The invention changes the firing fraction parameter as a function of cylinder load and operating conditions, allowing more firing fractions to be available at lower cylinder loads. This parameter adaptation enables the engine to maintain versatility across different operating conditions while achieving fuel efficiency improvements.
Data Source
AI summary
In one aspect, a skip fire engine controller is described. The skip fire engine controller includes a skip fire module arranged to determine an operational firing fraction and associated cylinder load for delivering a desired engine output. The skip fire engine controller also includes a firing controller arranged to direct firings in a skip fire manner that delivers the selected operational firing fraction. Various methods, modules, lookup tables and arrangements related to the selection of a suitable operational firing fraction are also described.