Filtering Pulley With Bidirectional Torque Damping for Start-Stop Drives
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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 machine from the belt transmission when it is a driving electric machine, and existing solutions are not optimized for technical performance and are radially and axially bulky.
Innovation Solution
A compact filtering pulley design featuring a torsion spring, a torque limiting joint with a ribbon spring, and integrated damping means, which allows bidirectional coupling between the hub and pulley within a predetermined torque range, enabling use in both start-stop and conventional transmission systems.
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 in case of torque inversion, then the belt is protected from dynamic overloads, but the electric machine is decoupled from the belt transmission when it is a driving electric machine in start-stop systems
Solution Approach 1:
The patent replaces the static free wheel mechanism with a dynamic viscous coupling device that allows bidirectional torque transmission. The viscous coupling comprises a rotor and stator with viscous material between them, enabling torque transmission in both directions while providing damping, thus eliminating the need for a free wheel and enabling compatibility with start-stop systems.
Solution Approach 2:
The patent substitutes the mechanical free wheel mechanism with a viscous fluid-based coupling system. The viscous material (shear-thickening fluid) provides torque transmission through fluid dynamics rather than mechanical interlocking, allowing bidirectional coupling without the decoupling function of a free wheel.
2Adaptability or versatility
If existing solutions are used to enable bidirectional coupling, then compatibility with start-stop systems is achieved, but the device becomes radially and axially bulky
Solution Approach 1:
The viscous coupling device is nested within the existing filtering pulley structure. The rotor is coupled to the hub, the stator to the crown, and the viscous material is contained between them within the existing radial and axial space of the filtering unit, avoiding additional bulk.
Solution Approach 2:
The viscous coupling device performs multiple functions simultaneously: it provides bidirectional torque transmission, damping of torsional vibrations, and protection against dynamic overloads, replacing the need for separate free wheel and damping mechanisms that would increase dimensions.
3Reliability
If a free wheel is used to protect the belt from dynamic overloads, then reliability is improved, but the device complexity increases
Solution Approach 1:
The patent merges the filtering function, bidirectional torque transmission, and damping functions into a single integrated viscous coupling device. This eliminates the need for separate free wheel mechanisms and simplifies the overall structure while maintaining or improving reliability.
Solution Approach 2:
The complex mechanical free wheel mechanism is replaced with a simpler viscous fluid-based system that provides the same protection function along with additional damping capabilities, reducing overall device complexity.
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 improved torque transmission and damping, ensuring efficient operation in both drive and overrun conditions, while being compact and economical to produce, thus addressing the limitations of existing solutions.
Implementation Method 1
a spring, e.g., a helical or spiral spring, or a plurality of springs or other resilient members arranged circumferentially between the hub and the crown
Implementation Method 2
a viscous coupling device (40) arranged between the hub (2) and the pulley (3) and comprising a rotor (41) coupled to the hub (2), a stator (42) coupled to the pulley (3), and a viscous material (43) arranged between the rotor (41) and the stator (42)
Implementation Method 3
a torque limiting joint with a ribbon spring
Data Source
AI summary
Filtering pulleys for an accessory transmission of an internal combustion engine have a hub, an annular crown provided with a profile configured to cooperate with a transmission belt positioned externally coaxial around an axis (A) to the hub and supported in rotationally free motion on the hub itself, and a filtering unit for transmitting the torque interposed between the hub and the annular crown. The filtering unit has a torsion spring, a carrier, and a torque limiting joint cooperating with each other to transmit a torque between the hub and the crown. The filtering pulleys can include a damping means carried by a member that is integral with one of the hub and crown and configured to provide variable damping according to the torque.