Filtering Pulley Torque Limiting for Start-Stop Belt Drives
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Solution Overview
Problem
Existing filtering pulleys for alternators in motor vehicles are not optimized for use in start-stop systems and are either too bulky or inefficient, and they decouple the electric motor from the belt transmission when torque is reversed.
Innovation Solution
A filtering pulley with a torque-limiting joint and torsion spring system that allows bi-directional coupling between the hub and crown, using a strip spring that slides when a predetermined torque level is reached, ensuring efficient torque transmission while maintaining compact size and reducing noise and wear.
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 be protected from reverse torque, but the electric motor is decoupled from the belt transmission in start-stop systems when driving
Solution Approach 1:
The patent replaces the static free wheel mechanism with a dynamic friction-based torque limiting joint that can adapt its coupling state based on torque direction and magnitude. The friction elements allow bidirectional torque transmission under normal conditions but automatically decouple when reverse torque exceeds the friction threshold, enabling compatibility with both conventional alternator systems and start-stop systems with reversible electric motors.
2Adaptability or versatility
If known filtering pulley solutions are used to enable bi-directional coupling, then the pulley can work in start-stop systems, but the design becomes radially and axially bulky
Solution Approach 1:
The patent merges the torque limiting function with the filtering unit by integrating friction elements directly into the existing pulley structure between the hub and crown. This consolidation eliminates the need for separate bulky mechanisms, achieving bidirectional coupling capability while maintaining a compact design that fits within the existing pulley radial and axial dimensions.
3Adaptability or versatility
If known filtering pulley solutions are used to achieve bi-directional coupling, then the pulley can operate in start-stop systems, but manufacturing costs increase
Solution Approach 1:
The patent employs friction elements made from cost-effective materials such as friction plates, washers, or pads that can be manufactured using standard machining or molding processes. These relatively simple components replace complex free wheel mechanisms, significantly reducing manufacturing costs while providing the required bidirectional coupling functionality for start-stop systems.
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 effectively operates in both start-stop and conventional systems, providing efficient torque transmission with reduced noise and wear, while maintaining a compact design and low manufacturing costs.
Implementation Method 1
a torsion spring operatively interposed between the carrier and one of the hub and crown
Implementation Method 2
a torsion spring operatively interposed between the carrier and one of the hub and crown and provided with two ends cooperating in contact with respective spring holders integral with the carrier and one of the hub and crown
Implementation Method 3
The torque limiting joint is an open loop strip spring that is configured to slide with respect to the surface when the torque transmitted between the crown and the hub reaches a predetermined level
Data Source
AI summary
A filtering pulley for an accessory transmission of an internal combustion engine has a hub, a crown, a filtering unit for transmitting the torque that is 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 a surface of the crown when the torque transmitted between the crown and the hub reaches a predetermined level.