Motor-Generator Unit for Engine Accessory Drive and Starter Integration
Solution Overview
Problem
Conventional starter motors and engine accessory drive systems are inadequate for the high operational cycles required in start-stop systems, leading to inefficiencies and increased wear, and accessories are non-functional when the engine is shut down, resulting in reduced fuel efficiency and increased emissions.
Innovation Solution
An engine accessory drive system incorporating a motor-generator unit (MGU) with a gearbox assembly and an EAD controller that selectively operates in generator, accessory drive, and starter modes, allowing the MGU to power accessories and start the engine while the engine is shut down, reducing the need for discrete components and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional starter motors are used in start-stop systems, then the system can perform the required number of starting cycles, but the starter motor becomes inadequate and fails due to excessive wear and operational demands
Solution Approach 1:
The motor-generator unit (MGU) is designed to perform multiple functions: it operates as a starter motor to crank the engine, as an alternator to generate electrical power when driven by the engine, and as an accessory drive motor to power accessories independently. This multi-functionality eliminates the need for separate starter motors and alternators, resolving the contradiction by providing a single component that can reliably handle the high cycle demands of start-stop systems while maintaining durability through proper design for frequent operation
Solution Approach 2:
The patent combines the starter motor and alternator functions into a single motor-generator unit (MGU). The MGU includes a motor-stator assembly and a generator-stator assembly that share common structural elements, allowing the same mechanical component to function as both a high-cycle starter motor and an electrical generator. This merging resolves the reliability issue by consolidating functions into a single unit designed to withstand the operational demands of start-stop systems
2Loss of energy
If the engine is shut down to reduce fuel consumption and emissions, then fuel economy improves, but the accessories become non-functional
Solution Approach 1:
The motor-generator unit serves dual purposes: when the engine is running, it functions as an alternator to charge the battery; when the engine is shut down, it functions as an electric motor to power the accessories. This multi-functionality allows the system to maintain accessory operation during engine-off periods, resolving the contradiction between fuel economy and accessory functionality
Solution Approach 2:
The energy storage system (battery) acts as an intermediary between the engine and accessories. When the engine is running, the MGU charges the battery; when the engine is shut down, the battery provides electrical power to the MGU, which then drives the accessories. This intermediary energy storage mechanism enables accessory operation during engine-off periods while maintaining fuel economy benefits
3Reliability
If separate components (starter motor, alternator, accessory drive) are used, then each component can be optimized for its specific function, but the overall system complexity and part count increase
Solution Approach 1:
The patent merges the starter motor, alternator, and accessory drive functions into a single motor-generator unit. The MGU includes a motor-stator assembly for starter function, a generator-stator assembly for alternator function, and a shared rotor that can be driven by the engine or drive accessories. This consolidation reduces the number of separate components while maintaining the specialized functions needed for reliable operation
Solution Approach 2:
The motor-generator unit is designed with universal functionality to replace multiple discrete components. The same mechanical structure serves as both a high-cycle starter motor and an electrical generator, eliminating the need for separate alternator and accessory drive components. This multi-functionality reduces system complexity and part count while maintaining the reliability of specialized functions through integrated design
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 reduces fuel consumption, emissions, and part count, weight, and cost by enabling the MGU to operate accessories and start the engine while the engine is off, enhancing engine performance and efficiency compared to conventional systems.
Implementation Method 1
a motor-generator unit (MGU) configured to selectively operate as an electric motor and an electric generator
Data Source
AI summary
An engine accessory drive (EAD) system for an engine includes a motor-generator (MGU) unit operably coupled to an accessory. The EAD system also includes a gearbox assembly, which includes a first gear train operably coupled to the MGU, and a second gear train operably coupled to an output of the engine. The gearbox assembly also includes a clutch selectively coupling the first gear train with a second gear train. The EAD system further includes a starter assembly, which includes a starter shaft operably coupled to the second gear train. The starter assembly also includes a starter pinion coupled to the starter shaft, and an actuator configured to selectively engage the starter pinion with a flywheel of the engine. Further yet, the EAD system includes an EAD controller configured to selectively operate the EAD system in one of a generator mode, an accessory drive mode, and a starter mode.