Filtering Pulley Torque-Limiting Joint for Start-Stop 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 fail to provide bi-directional torque transmission.
Innovation Solution
A pulley design incorporating a torque-limiting joint with a torsion spring and rolling/sliding bearings, allowing bi-directional torque transmission and decoupling under specific conditions, 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 under reverse torque, then the pulley can handle instantaneous speed reductions, but it becomes impossible to use in start-stop systems where bi-directional torque transmission is required
Solution Approach 1:
The patent removes the free wheel component from the filtering unit, extracting the one-way coupling mechanism that prevented bi-directional torque transmission. This allows the pulley to function in start-stop systems while maintaining filtering capabilities through the spring-based damping mechanism alone
Solution Approach 2:
The filtering unit is designed to perform multiple functions without requiring a free wheel: it provides both vibration filtering through the spring element and bi-directional torque transmission. The spring-based mechanism handles both normal operation and reverse torque conditions, making the pulley universal for both conventional and start-stop systems
2Reliability
If known filtering pulley designs are used to ensure filtering performance, then torsion vibrations are reduced, but the pulley becomes radially and axially bulky
Solution Approach 1:
The spring element is nested within the space between the hub and crown, utilizing the existing radial space efficiently. The spring coils are arranged to fit within the pulley's radial envelope without requiring additional radial clearance, while the axial height is minimized through optimized spring geometry and direct mounting to the hub and crown surfaces
Solution Approach 2:
The spring element acts as a flexible component that provides filtering functionality with minimal material volume. The coiled spring structure achieves the required compliance and damping with a compact form factor, replacing bulkier rigid filtering mechanisms with a flexible, space-efficient elastic element
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
Enables efficient operation in both start-stop and conventional systems with reduced noise and increased durability, ensuring optimal torque transmission and reduced assembly costs.
Implementation Method 1
a torque-limiting joint (20) basically comprising a torsion spring (21) housed in the space (9) and configured to fulfil, at the same time, the function of free wheel in both relative rotation directions between crown (3) and hub (2)
Implementation Method 2
The crown (3) is supported on the hub (2) using rolling/sliding support means. In particular, the pulley (1) comprises a rolling bearing (6), for example a sphere bearing, radially interposed between the crown (3) and the first end (2a') of the hub (2)
Implementation Method 3
The torque-limiting joint (20) is sized in order to cooperate in contact with the hub (2) and the carrier (12) in order to decouple the crown (3)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A filtering pulley (1) for an accessory transmission of an internal combustion engine, comprising a hub (2), a crown (3), and a filtering unit (4) for transmitting the torque that is interposed between the hub (2) and the crown (3) and comprising a torsion spring (11), a carrier (12), and a torque limiting joint (20), the torque limiting joint (20) comprising an open-loop strip spring (21) and being configured to slide with respect to said surface (3' ' ) when the torque transmitted between the crown (3) and the hub (2) reaches a predetermined level (T1, T2).