Engine Stop Position Control via Reverse Rotation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Engines with pistons near top-dead-center compression stroke pose challenges for electric machines to rotate them efficiently, leading to increased in-rush current and potential degradation, especially when starting the engine again.
Innovation Solution
The method involves rotating the engine in a reverse direction when the piston is within a threshold crankshaft angle of top-dead-center compression stroke to reduce the effort required for subsequent starts and conserving electric energy by avoiding rotation when not needed, thereby reducing electric machine degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric machine rotates the engine when the piston is near top-dead-center compression stroke, then the engine can be started, but the in-rush current increases and the electric machine degrades faster
Solution Approach 1:
The controller detects when the engine stops with the piston near top-dead-center compression stroke and preemptively rotates the engine in reverse using the electric machine. This preliminary action positions the piston away from the high-compression position before a subsequent start is needed, preventing the in-rush current problem from occurring in the first place
2Power
If the electric machine rotates the engine away from top-dead-center position, then the subsequent engine start requires less effort and current, but the electric machine consumes energy during the reverse rotation
Solution Approach 1:
The system uses the engine's own inertia and mechanical structure to its advantage. By rotating the engine in reverse when stopped near top-dead-center, the system leverages the existing mechanical configuration to reposition the piston, and then allows the engine's momentum to carry it through the starting cycle with minimal additional energy input
3Reliability
If the engine is stopped with piston near top-dead-center compression stroke, then the engine stop position is achieved, but the subsequent engine start becomes difficult and increases electric machine load
Solution Approach 1:
Instead of trying to start the engine directly from the problematic top-dead-center position, the controller inverts the approach by first rotating the engine in reverse to move the piston away from this position. This reverse action transforms the difficult starting condition into a favorable one, making subsequent engine starts easier and reducing the load on the electric machine
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 approach reduces the effort to rotate the engine during starting, decreases electric machine degradation, and shortens engine starting time by allowing the belt integrated starter/generator to start the engine without assistance from the integrated starter/generator.
Implementation Method 1
rotating an engine via an electric machine in a first direction in response to the engine having stopped rotating in a position where a piston of a cylinder of the internal combustion engine is within a predetermined crankshaft angle of top-dead-center compression stroke
Implementation Method 2
rotating the engine via the electric machine in a second direction without rotating the engine in the first direction in response to the engine having stopped rotating in a position where the piston of the cylinder is not within the predetermined crankshaft angle of top-dead-center compression stroke
Data Source
AI summary
A method and system for controlling a stop rotation position of an engine is described. In one example, the system includes an integrated starter/generator that may be selectively coupled to the engine. The integrated starter/generator may rotate the engine in a first direction (e.g., reverse direction) or a second direction (e.g., a forward direction) in response to a position at which the engine stops rotating following cessation of combustion in the engine.