Composite Spring Isolating Decoupler for Engine Vibration
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Solution Overview
Problem
Diesel and gasoline engine accessory drive systems face increased vibrations and belt chirp noise due to higher crankshaft vibrations and alternator inertia, leading to reduced belt operating life and noise issues.
Innovation Solution
An isolating decoupler with a composite spring featuring a clutch portion, transition portion, and variable diameter portion, which provides isolation, damping, and infinite overrun capability without bumper stops, using a single multi-purpose composite spring instead of a combination of wrap and torsion springs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a combination of wrap spring and torsion spring coupled by a spring carrier is used, then isolation and damping functions are achieved, but device complexity increases and infinite overrun capability is limited by bumper stops
Solution Approach 1:
The patent combines the wrap spring and torsion spring into a single composite spring that integrates both functions. The composite spring has a first portion providing wrap spring functionality and a second portion providing torsion spring functionality, eliminating the need for separate springs and a spring carrier, thus reducing device complexity while maintaining isolation and damping functions
Solution Approach 2:
The composite spring serves multiple functions simultaneously: it provides both wrap spring and torsion spring functionality, enables infinite overrun capability without bumper stops, and provides isolation and damping. This multi-functional design replaces the need for multiple separate components and their associated mounting structures
2Device complexity
If a single composite spring is used instead of spring combination, then device complexity is reduced and infinite overrun capability is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The composite spring is divided into distinct portions: a first portion providing wrap spring functionality and a second portion providing torsion spring functionality. The transition between portions is defined by specific geometric parameters (radii, coil diameters, pitch angles) that can be controlled during manufacturing, allowing complex functionality to be achieved through segmented design with controlled interfaces
Solution Approach 2:
The patent specifies precise geometric parameters for the composite spring including coil diameters, pitch angles, radii of curvature, and transition zone dimensions. By controlling these parameters during manufacturing, the complex multi-functional behavior is achieved through precise parameter specification rather than complex assembly procedures
3Adaptability or versatility
If composite spring with variable diameter portion is used, then adaptability to torque changes is improved, but manufacturing complexity increases
Solution Approach 1:
The composite spring includes a variable diameter portion where the coil diameter changes along the length of the spring. This dynamic geometric variation allows the spring to adapt its stiffness characteristics to different torque conditions, providing optimized performance across a range of operating conditions while maintaining a continuous manufacturable 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 solution effectively reduces angular vibration transmission to belt-driven accessories, extends their operational life, and minimizes belt chirp noise by utilizing a single composite spring that adapts to torque changes, ensuring efficient torque transmission and decoupling during rapid deceleration events.
Implementation Method 1
a composite spring having a clutch portion, a transition portion and a variable diameter portion
Implementation Method 2
the frictional engagement with the pulley can be released
Data Source
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AI summary
An isolating decoupler comprising a hub (11) for connection to a shaft, a pulley (16) journalled to the hub, the pulley having a belt engaging surface, a composite spring (12) having a clutch portion (22), a transition portion (23) and a variable diameter portion (24), the composite spring engaged between the hub and the pulley, the clutch portion diameter reducible in a loading direction for a frictional engagement with the pulley in the loading direction, the frictional engagement of the clutch portion progressively releasable from the pulley in an unloading direction, the variable diameter portion having a diameter which varies according to a torque load; and an inertial member (74) engaged with the hub through a damping member (75).