Belt Integrated Starter Generator Engine Speed Synchronization
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Solution Overview
Problem
In hybrid vehicles, matching engine speed with electric machine speed during engine starts is challenging, leading to driveline disturbances, which can be mitigated by reducing engine torque before connection to prevent shock.
Innovation Solution
A controller is configured to produce excess torque beyond demand torque during engine starts, using a starter-generator to load the engine and adjust its speed to match the electric machine speed, and then engaging a clutch to couple the engine with the driveline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the engine speed is reduced during engine starts to match electric machine speed, then driveline disturbances are prevented, but engine torque must be reduced requiring spark retardation which increases start time
Solution Approach 1:
The system applies preliminary loading to the engine via the starter-generator before clutch engagement to pre-synchronize engine speed with electric machine speed. This preliminary speed matching eliminates the need for post-engagement speed adjustment and avoids spark retardation, thereby reducing overall start time while maintaining driveline stability.
Solution Approach 2:
The starter-generator acts as an intermediary device between the engine and the driveline during the transition phase. It provides controlled loading to regulate engine speed and absorbs speed mismatches, enabling smooth clutch engagement without spark retardation and reducing both driveline disturbances and start time.
2Use of energy by moving object
If the engine is isolated from drivetrain components during startup using a disconnect clutch, then efficiency is enhanced, but driveline disturbances may occur during engagement
Solution Approach 1:
The controller performs preliminary speed synchronization of the engine with the electric machine before disconnect clutch engagement. This ensures that when the clutch connects the isolated engine to the drivetrain, speed mismatch is minimized, preventing driveline disturbances while maintaining the efficiency benefits of isolation during startup.
Solution Approach 2:
The system continuously monitors engine speed and electric machine speed during the startup phase and uses feedback control to adjust starter-generator loading. This real-time feedback ensures precise speed matching before clutch engagement, eliminating driveline shocks while preserving energy efficiency during the isolated startup period.
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 ensures a smooth engine start by synchronizing engine and electric machine speeds, reducing driveline disturbances and enhancing efficiency by isolating the engine from drivetrain components during startup.
Implementation Method 1
operate the starter-generator to load the engine to consume the excess torque and drive the engine speed toward an electric machine speed
Data Source
AI summary
A controller is configured to respond to an engine start command, operate the engine to produce excess torque beyond a demand torque, and in response to engine speed achieving a threshold, operate the starter-generator to load the engine to consume the excess torque and drive the engine speed toward an electric machine speed, and engage a clutch to couple the engine and an electric machine.