Belt Integrated Starter Generator Reverse Rotation Engine Start
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Solution Overview
Problem
Belt integrated starter/generators (BISG) for engines are costly and inefficient for starting engines with lower torque capacity, especially in cold conditions, as they require larger torque reserves to ensure robust engine starting.
Innovation Solution
The engine operating method involves rotating the crankshaft in a reverse direction to increase the angular rotational distance before compression, allowing the engine to reach higher cranking speeds using inertia, thus reducing the torque requirements for starting with a BISG of lower output capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a BISG with larger torque capacity is used to ensure robust engine starting in cold conditions, then engine starting reliability is improved, but system cost increases
Solution Approach 1:
The engine is rotated in reverse direction before starting to build up rotational momentum and position the crankshaft at an optimal starting position. This preliminary action allows the engine to coast through the high-torque compression stroke, reducing the peak torque requirement of the BISG while maintaining starting reliability
Solution Approach 2:
Instead of rotating the engine only in the forward direction during starting, the method incorporates reverse direction rotation to manipulate engine momentum and positioning. This inversion of the conventional starting approach reduces the torque capacity requirement of the BISG
2Reliability
If a BISG with larger torque capacity is used to overcome compression and friction losses, then engine starting robustness is improved, but electrical power consumption increases
Solution Approach 1:
The engine is rotated in reverse direction and held at a specific crankshaft position before starting, allowing the pistons to be positioned where compression losses are minimized. This preliminary positioning reduces the energy required during the actual starting process
Solution Approach 2:
The starting process incorporates periodic reverse and forward rotation phases. The engine is rotated backward, held momentarily, then rotated forward to start. This periodic action pattern optimizes energy efficiency by utilizing engine inertia and minimizing compression work during the critical starting phase
3Ease of manufacture
If the engine is started with a BISG of lower output torque capacity, then system cost is reduced, but the ability to overcome compression and friction losses is insufficient
Solution Approach 1:
The crankshaft is rotated in reverse direction to position the engine at an optimal starting position where the pistons are near bottom dead center on the compression stroke. This preliminary positioning reduces the torque required to overcome compression forces, enabling a lower-capacity BISG to successfully start the engine
Solution Approach 2:
The method changes the operational parameters of engine starting by introducing reverse direction rotation and holding the crankshaft at specific positions. These parameter changes manipulate engine momentum and positioning to reduce peak torque requirements, allowing a lower-capacity BISG to overcome compression and friction losses
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 method enhances engine starting robustness, reduces system costs, and conserves electrical power by enabling engine starting with a smaller BISG and battery, while minimizing excess torque capacity.
Implementation Method 1
Rotating the engine at a higher cranking speed may allow the engine's inertia to help the BISG rotate the engine trough top-dead-center compression stroke of a cylinder
Implementation Method 2
holding the engine stopped at the crankshaft position via supplying current to the BISG
Data Source
AI summary
Systems and methods for operating an internal combustion engine that may be automatically stopped and started are described. In one example, an engine is rotated in a reverse direction after an engine stop so that a belt integrated starter/generator may rotate the engine in a forward direction and utilize the inertia of the engine to rotate trough top-dead-center compression stroke, thereby starting the engine.