Hybrid Engine Stop Position Control via Disconnect Clutch
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Solution Overview
Problem
Hybrid vehicle engines face increased emissions and limited torque upon restarting, as current methods do not effectively manage engine stopping to minimize emissions and ensure quick torque availability upon restart.
Innovation Solution
Adjusting the disconnect clutch application force and slip to stop the engine at a desired position, such as a predetermined interval after the top-dead-center compression stroke, allows for controlled spark and fuel injection upon restart, reducing emissions and accelerating engine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is stopped to conserve fuel, then fuel economy is improved, but emissions increase during engine restart
Solution Approach 1:
The engine is stopped at a predetermined position (after TDC compression stroke and before exhaust stroke) in advance of the restart event. This preliminary positioning ensures that when the engine restarts, the cylinders are in optimal positions for immediate combustion, reducing the time the engine needs to run before producing useful work and minimizing emissions during the transition from stop to operational state.
2Use of energy by moving object
If the engine is stopped to conserve fuel, then fuel economy is improved, but torque availability is limited after restart
Solution Approach 1:
The engine stopping position is pre-determined to be after the top-dead-center compression stroke and before the exhaust stroke. This preliminary positioning ensures that upon restart, the pistons are already in positions favorable for immediate combustion and torque generation, allowing the engine to deliver full torque much sooner after restart compared to stopping at other positions.
3Object-generated harmful factors
If the disconnect clutch slip is adjusted to stop the engine at a desired position, then emissions are reduced and torque availability is improved, but the control system complexity increases
Solution Approach 1:
The controller monitors engine position and adjusts the disconnect clutch application force based on feedback regarding whether the engine has stopped at the desired position. This feedback mechanism ensures the engine stops at the optimal position (after TDC compression stroke and before exhaust stroke) while providing a systematic method to achieve the dual benefits of reduced emissions and improved torque availability without excessive complexity.
Data Source
AI summary
A method and a system for improving operation of a hybrid vehicle are presented. In one example, a disconnect clutch is operated in response to an engine stop request to adjust an engine stopping position during an engine shutdown. The approach may reduce engine starting time after the engine stop.