Filtering Pulley Strip-Spring Coupling for Start-Stop Systems
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Solution Overview
Problem
Existing filtering pulleys with free wheels are not suitable for start-stop systems as they decouple the electric motor when it is driving, and known solutions are not optimized for technical performance and are radially and axially bulky.
Innovation Solution
A filtering pulley with a torque-limiting joint that includes a strip spring and a lever, allowing bi-directional coupling between the hub and pulley within a predetermined range of torques, making it suitable for start-stop systems while maintaining compact dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a free wheel is incorporated in the filtering unit to decouple the hub from the crown when torque is reversed, then the alternator can handle instantaneous speed reductions, but the electric motor is decoupled when driving in start-stop systems
Solution Approach 1:
The patent replaces the static free wheel mechanism with a dynamic torque-limiting joint comprising a strip spring and lever assembly. This dynamic system automatically adjusts coupling status based on real-time torque conditions, enabling bidirectional torque transmission within a predetermined range while maintaining engagement for the electric motor in start-stop systems.
Solution Approach 2:
The invention changes the operational parameters by introducing a torque threshold mechanism through the strip spring and lever. The system transitions from binary coupled/decoupled states to a continuous torque-dependent engagement state, allowing the pulley to maintain connection while limiting transmitted torque to predetermined levels during electric motor operation.
2Adaptability or versatility
If known filtering pulley solutions are used for start-stop systems, then the electric motor remains coupled, but the device becomes radially and axially bulky
Solution Approach 1:
The patent employs a nested arrangement where the strip spring is positioned within the space between the hub and crown, the lever assembly is integrated into the crown structure, and the torque-limiting joint components are housed within the pulley's existing dimensional envelope. This nesting approach achieves bidirectional torque transmission functionality without increasing radial or axial dimensions.
Solution Approach 2:
The invention merges the torque-limiting function with the existing filtering unit structure by integrating the strip spring and lever assembly into the space between the hub and crown. The lever is incorporated into the crown's structure, combining multiple functions (filtering, torque limiting, and bidirectional transmission) into a single compact assembly.
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 pulley achieves bi-directional torque transmission within a predetermined range, enabling its use in start-stop systems while maintaining compactness and ease of assembly, thus addressing the limitations of existing solutions.
Implementation Method 1
a strip spring and a lever, allowing bi-directional coupling between the hub and pulley within a predetermined range of torques
Implementation Method 2
a torque-limiting joint that includes a strip spring and a lever, allowing bi-directional coupling between the hub and pulley within a predetermined range of torques
Data Source
AI summary
A filtering pulley for an accessory transmission of an internal combustion engine that has a hub, a crown, a filtering unit for transmitting the torque interposed between the hub and the crown, a torsion spring, a carrier, and a torque limiting joint. The torque limiting joint has an open-loop strip spring and is configured to slide with respect to said surface when the torque transmitted between the crown and the hub reaches a predetermined level.