Decoupler Assembly Lubricated Sliding Interface
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Solution Overview
Problem
Existing decoupling mechanisms for belt-driven accessories are costly, complex, and have limited operating life, with manual assembly processes and potential interference fits leading to wear and reduced fuel efficiency.
Innovation Solution
A decoupler assembly that eliminates the use of polymeric bushings by employing a hub, pulley, dampening spring, and helical clutch spring with a lubricated gap between the pulley and hub, allowing for improved surface area engagement and automated assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polymeric bushing is used between pulley and hub, then the assembly process requires manual fitting, but this increases assembly complexity and reduces productivity
Solution Approach 1:
The invention removes the polymeric bushing component entirely from the decoupler assembly. By eliminating this intermediate component, the patent enables direct metal-to-metal contact between the pulley bore and hub surface, which can be precisely machined and automatically assembled without manual bushing installation, thereby improving productivity and enabling automation.
Solution Approach 2:
The patent introduces a lubricant as an intermediary substance between the pulley and hub surfaces. This lubricant layer reduces friction and wear during operation, replacing the mechanical function previously provided by the polymeric bushing, while allowing for simpler assembly without manual fitting steps.
2Device complexity
If a polymeric bushing is used between pulley and hub, then assembly is simplified, but the surface area of engagement is reduced and pressure increases causing wear
Solution Approach 1:
By removing the polymeric bushing, the invention eliminates the component that limited the engagement surface area. The direct contact between the pulley bore and hub provides a larger surface area for load distribution, reducing contact pressure and wear while maintaining structural integrity through proper material selection and lubrication.
Solution Approach 2:
The invention changes the physical parameters of the interface by eliminating the bushing and introducing lubrication. This transforms the contact interface from a bushing-mediated connection to a direct lubricated metal-to-metal contact, altering friction characteristics, contact pressure distribution, and wear properties to improve reliability.
3Ease of manufacture
If a polymeric bushing is used, then assembly is easier, but friction increases reducing fuel economy
Solution Approach 1:
The removal of the polymeric bushing eliminates the high-friction interface that degraded fuel economy. The direct metal-to-metal contact with lubrication provides significantly lower friction coefficients compared to polymeric bushings, reducing energy losses and improving fuel efficiency despite requiring precision machining.
Solution Approach 2:
The invention applies lubrication (a fluid film) between the pulley and hub surfaces to reduce friction. This hydrodynamic or boundary lubrication regime minimizes contact friction during operation, reducing energy losses and improving fuel economy compared to dry or semi-dry polymeric bushing interfaces.
4Device complexity
If a polymeric bushing is used, then the decoupler assembly is simpler, but the operating life is reduced
Solution Approach 1:
By eliminating the polymeric bushing, the invention removes the wear-prone component with limited service life. The direct metal-to-metal contact with lubrication and larger surface area distribution provides superior wear resistance and extended operating life, while the structure remains sufficiently simple through the use of standard machining operations.
Solution Approach 2:
The invention employs composite material strategies by combining hardened steel surfaces with lubrication. The pulley and hub surfaces can be subjected to surface hardening treatments (such as nitriding or induction hardening) to create wear-resistant surfaces, while the lubricant provides additional protection, resulting in extended component life despite the elimination of the bushing.
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
This design reduces wear, improves fuel economy, and extends the decoupler's longevity by minimizing friction and preventing tilt, while allowing for efficient speed oscillation damping between the belt and shaft.
Implementation Method 1
There is a gap between the pulley and the pulley support surface. The gap has lubricant therein to facilitate sliding between the pulley and the pulley support surface.
Implementation Method 2
a dampening spring positioned to transmit torque between the hub and a carrier
Implementation Method 3
The clutch spring expands radially to operatively connect the pulley and the carrier when the pulley is rotated faster than the hub in a first rotational direction, thereby driving the hub with the pulley. The clutch spring contracts radially to operatively disconnect the pulley and the hub when the pulley rotates more slowly than the hub in the first rotational direction.
Data Source
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AI summary
In one aspect, the invention is directed to a decoupler assembly for between an endless drive element and a shaft. The endless drive element may be, for example, an accessory drive belt from a vehicular engine. The shaft may be, for example, the input shaft of a belt-driven accessory, such as an alternator or a compressor. The decoupler assembly includes a hub that mounts to the shaft, a pulley that is rotatable with respect to the hub, a dampening spring and a clutch member. A part of the pulley is supported on a pulley support surface on the hub. There is a gap between the pulley and the pulley support surface. The gap has lubricant therein to facilitate sliding between the pulley and the pulley support surface. By eliminating the use of a polymeric bushing between pulley and the hub, there are several advantages that are provided.