Compact Filtering Pulley for Bi-Directional Start-Stop Torque
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Solution Overview
Problem
Existing filtering pulleys for motor vehicle alternators are not optimized for use in start-stop systems and are radially and axially bulky, failing to ensure desired technical performance and compactness.
Innovation Solution
A filtering pulley design featuring a tubular hub, a coaxial tubular crown with a rolling/sliding support system, a torsion spring, and a torque-limiting joint that allows bi-directional coupling and decoupling between the hub and crown, enabling efficient torque transmission while maintaining compactness and reducing noise.
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 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 replaces the static free wheel mechanism with a dynamic torsion spring-based filtering unit that can adapt its coupling state. The torsion spring (11) allows the crown (3) to rotate relative to the hub (2) and enables bi-directional torque transmission while maintaining filtering functionality, thus resolving the contradiction between handling speed reductions and compatibility with start-stop systems.
2Reliability
If known filtering pulley designs are used to ensure filtering functionality, then torsion vibrations are reduced, but the pulley becomes radially and axially bulky
Solution Approach 1:
The patent employs a nested structure where the torsion spring (11) is positioned within the space between the hub (2) and crown (3). The spring holder element (12) and damping ring (13) are also nested within this internal space. This nesting arrangement achieves filtering functionality without increasing the external radial and axial dimensions of the pulley.
3Reliability
If a spring is attached with predetermined width relative freedom of rotation to provide filtering, then torsion vibrations are dampened, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple functions into integrated components. The spring holder element (12) serves both to mount the torsion spring (11) and to provide a sliding contact surface with the hub head portion (2b). The damping ring (13) integrates damping functionality within the existing structural space. This merging reduces the number of separate parts and simplifies the overall structure.
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, allowing its use in start-stop systems, is compact, and inexpensive to manufacture, with reduced noise and complexity.
Implementation Method 1
a torsion spring (11), a spring holder element (12), said spring holder element (12) cooperating with one end of the spring (11)
Implementation Method 2
a tubular crown (3) externally coaxial to the hub (2) and supported so that it is rotationally free on the latter
Implementation Method 3
a tubular crown (3) externally coaxial to the hub (2) and supported so that it is rotationally free on the latter
Implementation Method 4
a torque-limiting joint (20) configured to decouple the crown (3) from the hub (2) when the torsion spring (11) has reached its torque transmission capacity
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 or transmitting the torque interposed between the hub and the crown, a torsion spring, a carrier, and a torque limiting joint. The torque limiting joint is coupled to interface with one of the surfaces between the crown and has an open-loop strip spring. The torque limiting joint and is configured to slide with respect to said surface when the torque transmitted between the crown and the hub reaches a predetermined level.