Belt-Integrated Starter Generator Engine Shutdown Control
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Solution Overview
Problem
Modern internal combustion engines with low internal friction and flywheels, when equipped with engine stop/start features, face challenges in efficiently shutting down the engine due to reduced engine shutdown speed, leading to increased fuel consumption and emissions.
Innovation Solution
A vehicle system incorporating a belt-integrated starter generator (BISG) mechanically coupled to the crankshaft, which applies a load to slow the engine and capture electric power, with the initial load magnitude proportional to engine temperature and clutch state, allowing for controlled engine shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is equipped with low internal friction and a flywheel to improve fuel economy and idle speed stability, then the engine shutdown speed is reduced, but this leads to increased fuel consumption and emissions during shutdown
Solution Approach 1:
The patent replaces the purely mechanical engine shutdown process with an electromechanical system. The BISG (belt-integrated starter generator) converts the mechanical shutdown process into an electrical energy capture process, where the BISG acts as a generator during engine deceleration to recover energy that would otherwise be lost, thereby resolving the contradiction between maintaining low shutdown speed and improving fuel economy
Solution Approach 2:
The patent converts the harmful effect of low engine shutdown speed (which causes increased fuel consumption and emissions) into a beneficial effect by using the BISG to capture the kinetic energy during engine deceleration. The energy that would be wasted during the extended shutdown process is now recovered and stored in the battery, turning the disadvantage of slower shutdown into an opportunity for energy recovery
2Loss of time
If the BISG applies a high load to the crank shaft to speed up engine shutdown, then shutdown time is reduced, but this may cause increased vibrations and mechanical stress
Solution Approach 1:
The patent applies dynamic control to the BISG load application. The controller continuously monitors engine speed, vibration levels, and clutch state, dynamically adjusting the BISG torque output throughout the shutdown process. This allows the system to apply higher loads when safe and reduce loads when vibrations become excessive, optimizing the trade-off between shutdown speed and mechanical stress
Solution Approach 2:
The patent changes the operational parameters of the BISG based on real-time engine conditions. The initial magnitude of the load is adjusted according to engine temperature and clutch state, and the load is progressively modified during shutdown. This parameter adaptation allows the system to achieve fast shutdown while staying within safe vibration and stress thresholds
3Loss of energy
If the initial magnitude of the load is increased to capture more electric power, then energy recovery is improved, but this may overload the battery or electrical system
Solution Approach 1:
The patent implements a feedback control system where the controller continuously monitors battery state of charge, electrical system capacity, and current draw. Based on this feedback, the controller dynamically adjusts the BISG torque to maximize energy recovery while preventing battery overload or electrical system stress. The feedback loop ensures the system operates within safe boundaries while capturing maximum available energy
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
The system enables faster and smoother engine shutdown, reducing fuel consumption and emissions, while improving user experience by minimizing vibrations and extending the life of engine components.
Implementation Method 1
a belt-integrated starter generator (BISG) mechanically coupled to the crank shaft and configured to generate electric power from motion of the engine to charge the battery
Implementation Method 2
a controller configured to operate the BISG to apply a load to the crank shaft to slow the engine and capture electric power for storage in the battery
Data Source
AI summary
A vehicle includes an engine including a crank shaft; a battery; a belt-integrated starter generator (BISG) mechanically coupled to the crank shaft and configured to generate electric power from motion of the engine to charge the battery; and a controller configured to operate the BISG to apply a load to the crank shaft to slow the engine and capture electric power for storage in the battery, wherein an initial magnitude of the load is proportional to a temperature of the engine, responsive to a speed of the BISG or engine achieving a predetermined non-zero threshold, remove the load from the crank shaft, and bring the engine to a stop.