Electric Machine Torque Assist for Multi-Stage Turbocharger Transitions
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Solution Overview
Problem
Multi-stage series turbocharger systems face a trade-off between maximum power at high engine speeds and maximum torque in the mid-speed range, resulting in a 'mid-speed torque dip', where optimizing one aspect compromises the other.
Innovation Solution
A method and system that utilize an electric machine to assist the crankshaft rotation during transitions between stages of a multi-stage forced induction system, providing torque-assist by activating the electric machine when the first stage reaches peak performance and deactivating it when the second stage reaches peak performance, to reduce torque dip and improve torque response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the LP stage of the turbocharger system is configured to deliver a high flow capacity, then maximum power output at high engine speed is improved, but torque dip in the mid-speed range worsens
Solution Approach 1:
The electric machine provides preliminary torque assist to the crankshaft during the transition period between turbocharger stages, before the second stage fully engages. This anticipatory action prevents the torque dip from occurring by maintaining adequate torque levels during the handover period between stages.
Solution Approach 2:
The electric machine acts as an intermediary torque source between the two turbocharger stages. During the transition when the first stage is deactivating and the second stage is activating, the electric machine provides intermediate torque support to bridge the gap and prevent torque dip.
2Productivity
If the LP stage of the turbocharger system is configured to deliver a low flow capacity, then torque dip in the mid-speed range is eliminated, but maximum power output is reduced
Solution Approach 1:
The electric machine provides universal torque support across the entire engine operating range, particularly during transitions between turbocharger stages. It compensates for the limitations of both low-flow and high-flow LP stage configurations, enabling the system to achieve both smooth torque delivery and high power output.
3Productivity
If an electric machine is activated to assist crankshaft rotation during stage transitions, then torque response is improved and torque dip is reduced, but device complexity increases
Solution Approach 1:
The electric machine is integrated with the existing crankshaft and engine control systems, utilizing the vehicle's electrical infrastructure and control architecture. This self-integrating approach minimizes additional complexity while providing the needed torque assist function during turbocharger transitions.
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 electric machine assists in reducing torque dip during transitions, enhancing torque response and reducing back pressure in the exhaust system, thereby improving engine performance across the mid-speed range.
Implementation Method 1
assisting the rotation of the crankshaft using an electric machine
Data Source
AI summary
An exemplary method of providing torque-assist to a crankshaft of an internal combustion engine includes, among other things, assisting a rotation of the crankshaft using an electric machine during the transition between stages of a multi-stage forced induction system.