Brushless Starter Motor Closed-Loop Speed Synchronization
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Solution Overview
Problem
Internal combustion engines face challenges in managing noise, vibration, and harshness (NVH) effects during change-of-mind events, where an acceleration request is made before the engine has a chance to stop completely, leading to inefficient engine starting and cranking processes.
Innovation Solution
An electric starter system incorporating a brushless starter motor, a solenoid device, and a controller that employs closed-loop speed control to ensure a permissible speed delta between the starter motor and engine speeds, facilitating rapid tip-in responses and minimizing NVH through selective engagement of the pinion gear with the flywheel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine is allowed to stop completely before starting, then the engine starting process is more stable and controlled, but the response time to acceleration requests increases significantly
Solution Approach 1:
The system performs preliminary synchronization of the starter motor speed with the engine speed before pinion-flywheel engagement. The closed-loop speed control adjusts the starter motor to match engine speed within a predetermined delta range, ensuring the engine is already rotating at the correct speed when cranking begins, thus eliminating startup delay while maintaining stability
2Productivity
If the pinion gear is engaged with the flywheel at high speed differential, then the engine can start faster, but noise, vibration, and harshness (NVH) effects increase significantly
Solution Approach 1:
The system implements closed-loop speed control that continuously monitors the speed differential between the starter motor and engine, and adjusts the starter motor speed accordingly. This feedback mechanism ensures the speed delta remains within a predetermined acceptable range, allowing fast engagement while minimizing NVH effects through active control
3Productivity
If the starter motor delivers maximum torque immediately upon engagement, then the engine cranking speed is achieved faster, but the speed synchronization precision is compromised
Solution Approach 1:
The system performs preliminary speed synchronization before full torque delivery. The closed-loop control first matches the starter motor speed to the engine speed within a predetermined delta range, establishing precise speed alignment before the pinion gear engages the flywheel and maximum torque is applied, thus achieving both fast cranking and precise synchronization
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 engine starts with reduced NVH and delay, improving tip-in performance during change-of-mind events by maintaining a controlled speed differential and delivering maximum motor torque efficiently.
Implementation Method 1
The electric starter system includes a solenoid device coupled to a pinion gear
Implementation Method 2
brushless starter motor, i.e., an electric machine using an electronic commutator instead of physical conductive brushes
Data Source
AI summary
An electric starter system for a powertrain or other system having an engine includes a solenoid device coupled to a pinion gear, a brushless starter motor, and a controller. The starter motor has actual machine speed, and is connectable to the flywheel via the pinion gear during a change-of-mind event when a commanded engine auto-stop sequence is interrupted before completion. When engine speed exceeds a threshold speed and is less than a calibrated starting speed, the controller executes a method in which closed-loop speed control of the starter motor is enabled using the engine speed as a reference value until an effective machine speed is within a permissible speed delta of engine speed. The controller causes the solenoid device to translate the pinion gear into engagement with the flywheel and starter motor, disables closed-loop speed control, and commands the starter motor to start the engine.