Starter Motor Disengagement Control for Engine Restart NVH
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Solution Overview
Problem
Current automatic start-stop systems in vehicles face challenges in efficiently restarting the engine after a 'Change of Mind Event' due to insufficient driveline state information, leading to suboptimal starter motor disengagement times that affect engine launch robustness and noise vibration harshness (NVH).
Innovation Solution
The system adjusts the starter motor disengagement speed limit based on whether the driveline is fully open, using distinct cranking speed limits for open and closed driveline states, determined by engine speed and coolant temperature, to optimize engine restart and reduce NVH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single speed limit is used for starter motor disengagement, then the robustness of engine start is improved, but the NVH and starter motor wear increase due to excessive cranking duration
Solution Approach 1:
The patent applies dynamics by making the starter motor disengagement speed limit variable rather than fixed. The control system dynamically adjusts the disengagement speed limit based on real-time detection of driveline state (open or closed), allowing the system to adapt to different operating conditions and resolve the contradiction between reliable start and reduced NVH/wear
Solution Approach 2:
The patent changes the parameter of starter motor disengagement speed limit based on driveline state. When the driveline is detected to be closed, the system uses a higher speed limit to ensure robust engine start, while using a lower speed limit when the driveline is open to reduce NVH and starter motor wear, thus resolving the technical contradiction
2Object-affected harmful factors
If the starter motor is disengaged early to reduce NVH and wear, then the harmful factors are reduced, but the engine may fail to start successfully due to insufficient rotational speed
Solution Approach 1:
The patent uses feedback from driveline state detection to control the starter motor disengagement timing. The control system continuously monitors the driveline state and adjusts the disengagement speed limit accordingly, ensuring that the engine starts successfully when needed while minimizing NVH and wear when the driveline is open
3Object-affected harmful factors
If the starter motor is engaged later to reduce wear, then the harmful factors are reduced, but the engine launch responsiveness deteriorates
Solution Approach 1:
The patent applies dynamics by making the starter motor engagement timing adaptive. The system dynamically decides when to engage the starter motor based on the driveline state detection, allowing for earlier engagement when the driveline is closed for responsive launch, and later engagement when the driveline is open to reduce wear
Data Source
AI summary
Methods and systems are provided for dealing with a change of mind event during an automatic shut-down of an engine in which the speed at which a starter motor used to restart the engine is disengaged is based upon the comparison of current engine speed (N) with a cranking speed limit (SLIM). In one example, during an engine restart while the engine is spinning down, the starter motor may crank the engine to a threshold cranking engine speed adjusted based on a position of the gear.