Decoupler Assembly With Helical Axial Shoulder Spring
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Solution Overview
Problem
Decoupler assemblies for alternators are costly to manufacture due to the need for steel pulleys with tight tolerances and coatings, and they often require complex electric clutches in BAS systems, increasing complexity and cost.
Innovation Solution
A decoupler assembly featuring a pulley, hub, and coiled torsion spring with helical axial shoulders and driver walls allows for relative rotation and axial compression, reducing the need for precise coatings and eliminating the requirement for a wrap spring, enabling cost-effective and simplified manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a steel pulley with tight tolerances and coatings is used in the decoupler assembly, then the engagement with the wrap spring is predictable and reliable, but the manufacturing cost increases and the coating process becomes more difficult
Solution Approach 1:
The patent removes the wrap spring component from the decoupler assembly, eliminating the need for a precisely machined steel pulley with coatings. The isolation spring serves both the isolation function and provides sufficient engagement with the pulley and hub without requiring tight tolerances or protective coatings, thereby reducing manufacturing complexity and cost while maintaining reliability
Solution Approach 2:
The invention replaces the expensive, precisely machined steel pulley with a simpler pulley design that does not require tight tolerances or costly protective coatings. The isolation spring is designed to engage directly with the simplified pulley and hub, creating a more cost-effective assembly that maintains functional reliability without the need for expensive materials and processing
2Ease of operation
If a wrap spring is used in the decoupler assembly, then torque transfer in one direction is achieved, but the alternator shaft cannot drive the pulley in BAS systems, requiring additional complex electric clutches
Solution Approach 1:
The isolation spring performs multiple functions: it provides torque transfer in one direction during normal operation, allows reverse rotation when the alternator acts as a motor in BAS systems, and provides vibration isolation. This multi-functionality eliminates the need for separate electric clutches or additional components to enable BAS functionality, reducing overall system complexity while maintaining operational flexibility
Solution Approach 2:
The patent employs a dynamic spring-based isolation mechanism that automatically adapts its behavior based on the direction of torque application. The isolation spring naturally allows bidirectional rotation with different characteristics - providing isolation during motor operation and enabling reverse drive in BAS mode - without requiring complex control systems or additional clutch mechanisms
3Reliability
If the pulley is made with tight tolerances and coatings for wrap spring engagement, then the decoupler operates reliably, but the coating process becomes more expensive and the coating is prone to scratches causing rejection
Solution Approach 1:
By removing the wrap spring component, the patent eliminates the need for the pulley's interior surface to have tight tolerances and protective coatings. The isolation spring engages with a simpler pulley surface that does not require expensive coatings, thereby eliminating the harmful effect of coating scratches that could lead to component rejection while maintaining reliable operation
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 solution reduces manufacturing costs, simplifies the production process, and eliminates the need for complex clutches, while providing effective torque transfer and damping of oscillations, thereby enhancing the operating life and reducing stress on components.
Implementation Method 1
a coiled, torsion spring with helical axial shoulders and driver walls allows for relative rotation and axial compression
Implementation Method 2
an isolator spring that is preferably a coiled, torsion spring
Implementation Method 3
providing effective torque transfer and damping of oscillations
Data Source
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AI summary
In one aspect, a decoupler assembly is provided for use between a shaft and an endless drive member that is used to drive the shaft. The decoupler assembly includes a pulley, a hub and an isolator spring that is preferably a coiled torsion spring. The two ends of the spring are engageable, at least indirectly, with the pulley and the hub for the transfer of torque therebetween. At least one of the ends of the spring engages an engagement structure (on either the pulley or the hub) that includes a helical axial shoulder and a driver wall. The spring transfers torque in one direction through the driver wall (e.g. when the pulley overruns the hub), but the spring end is not fixedly connected to the driver wall. When the hub overruns the pulley, there is relative rotation between the spring and whichever of the hub and pulley it is not fixedly connected to. Accordingly, there is relative rotation between the spring end and the helical axial shoulder and the driver wall. This causes the spring end to separate from the driver wall and ride up the helical axial shoulder. This causes the spring to compress axially. The spring coils have a selected amount of spacing so that the spring can be compressed by a selected amount axially. This sets the amount of relative rotation (and the amount of overrun) that is available between the pulley and the hub in the situation when the hub overruns the pulley.