Alternator Isolator Decoupler Size Reduction via Nested Clutch
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Solution Overview
Problem
Current alternator isolating decoupler devices have a large overall diameter due to the need for various components, which is undesirable in the context of smaller automotive engine sizes and increased fuel efficiency requirements.
Innovation Solution
An isolator decoupler design featuring a pulley journalled to a shaft on a low friction bushing, with a spring carrier also journalled to the shaft on a low friction bushing, utilizing a torsion spring and a one-way clutch with a wrap spring to reduce size while maintaining functionality, and incorporating an overload feature to prevent excessive torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional components (isolating spring, one way clutch, bearing) are used in alternator isolating decoupler devices, then the required functionality is achieved, but the overall diameter of the device becomes excessively large
Solution Approach 1:
The patent combines the one-way clutch and isolating spring into a single integrated assembly where the one-way clutch is positioned inside the spring carrier. This merging of functions allows the device to maintain torque transmission capability and isolation functionality while reducing the overall diameter compared to traditional designs that use separate components.
Solution Approach 2:
The design nests the one-way clutch within the spring carrier structure, and further nests the low friction bushings within the existing component interfaces. This nested arrangement allows multiple functional elements to occupy overlapping spatial volumes, significantly reducing the external diameter while preserving all required functions.
2Ease of manufacture
If standard friction bushings are used for journaling the pulley and spring carrier to the shaft, then manufacturing and assembly are simplified, but friction torque increases causing excessive wear and reduced durability
Solution Approach 1:
The patent changes the material parameters of the bushings from standard friction materials to low friction materials with specifically optimized coefficients of friction. This parameter change reduces the friction torque at the journal interfaces between the pulley-spring carrier assembly and the shaft, thereby reducing wear and improving durability while maintaining the simple bushing-based design approach.
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 allows for a smaller device diameter while maintaining effective torque transmission and reducing friction torque, particularly during overrunning conditions, thereby enhancing durability and reducing wear on bushings.
Implementation Method 1
a pulley journalled to a shaft on a low friction bushing
Implementation Method 2
a spring carrier journalled to the shaft on a low friction bushing
Implementation Method 3
a torsion spring coupled between the pulley and the spring carrier
Implementation Method 4
a one way clutch spring frictionally engaged with the shaft
Data Source
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AI summary
An isolator decoupler comprising a pulley, a shaft, the pulley journalled to the shaft on a low friction bushing, a spring carrier, the pulley journalled to the spring carrier on a low friction bushing, the spring carrier journalled to the shaft on a low friction bushing, a torsion spring coupled between the pulley and the spring carrier, a one way clutch spring frictionally engaged with the shaft, the one way clutch spring coupled to the spring carrier, the one way clutch spring is disposed radially inward of the torsion spring, and the pulley temporarily engagable with an end of the one way clutch spring whereby the frictional engagement of the one way clutch spring with the shaft is temporarily diminished.