Clutched Decoupler with Wrap Spring and Overrunning Capability
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Solution Overview
Problem
Existing decouplers between engine crankshafts and belt or endless drive members do not effectively provide overrunning capability and can be complex, especially when incorporating powered clutches for belt/alternator start functionality.
Innovation Solution
A clutched device comprising a hub, pulley, and hub drive clutch with an isolation spring and optional pulley overrun clutch, utilizing a wrap spring clutch for controlled torque transfer and overrunning, allowing the belt to briefly overrun the crankshaft while providing BAS capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a decoupler is designed to provide overrunning capability and BAS functionality, then the decoupling performance and belt/alternator start capability are improved, but the device complexity increases due to the need for powered clutches and multiple clutch mechanisms
Solution Approach 1:
The patent combines the hub drive clutch and pulley overrun clutch into a single integrated decoupler assembly. The hub drive clutch (23) and pulley overrun clutch (99) are merged within the same structural framework, sharing common components such as the wrap spring clutch mechanism and actuator assembly (24). This merging reduces overall device complexity while maintaining both overrunning capability and BAS functionality.
Solution Approach 2:
The wrap spring clutch mechanism serves multiple functions: it provides the hub drive clutch functionality for BAS operation and the pulley overrun clutch functionality for overrunning capability. The actuator assembly (24) can control both clutch engagements, making it a universal control system that handles multiple operational modes (normal driving, overrunning, and BAS) through a single multi-functional component set.
2Adaptability or versatility
If a decoupler uses powered clutches to provide decoupling and BAS capability, then the belt/alternator start functionality is achieved, but the manufacturing complexity and cost increase
Solution Approach 1:
The wrap spring clutch mechanism is designed to engage and disengage automatically based on rotational direction and torque conditions, without requiring complex external control systems. The isolation spring (26) and pulley overrun clutch (99) self-regulate the engagement state based on the operational mode, reducing manufacturing complexity by eliminating the need for sophisticated electronic controls and sensors.
Solution Approach 2:
The actuator assembly (24) serves as an intermediary mechanism that simplifies the control of both clutch engagements. Rather than requiring separate complex control systems for the hub drive clutch and pulley overrun clutch, the actuator assembly provides a unified mechanical interface that manages both functions through a single actuation system, thereby reducing manufacturing complexity.
3Stability of the object's composition
If a decoupler isolates the belt from torsional vibrations using springs, then the belt speed stability is improved, but the device complexity increases due to additional spring mechanisms
Solution Approach 1:
The isolation spring (26) is integrated into the existing clutch mechanism structure rather than being a separate isolated component. The spring is positioned within the hub drive clutch assembly, sharing space with the wrap spring clutch and actuator components. This merging approach provides vibration isolation functionality while utilizing the same structural framework, thereby minimizing additional complexity.
4Adaptability or versatility
If a decoupler allows the pulley to overrun the hub, then the overrunning capability is improved, but the torque transfer efficiency may be reduced during normal operation
Solution Approach 1:
The pulley overrun clutch (99) is designed to dynamically engage and disengage based on rotational speed differences between the pulley and hub. During normal operation when the pulley and hub rotate at similar speeds, the clutch remains engaged, ensuring efficient torque transfer. When the pulley speed exceeds hub speed (overrunning condition), the clutch automatically disengages, allowing overrunning without penalty to normal operation efficiency. This dynamic behavior eliminates the trade-off between overrunning capability and torque transfer efficiency.
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 isolates the belt from torsional vibrations, enables overrunning, and provides boost capability, simplifying the decoupling mechanism while maintaining efficiency and reliability.
Implementation Method 1
The hub drive clutch is a wrap spring clutch and is controllable to operatively connect the pulley to the hub for driving the hub in a first rotational direction
Implementation Method 2
An isolation spring is provided and operatively connects the hub to the pulley when the hub drives the pulley in the first rotational direction
Implementation Method 3
a pulley overrun clutch is provided and permits the pulley to overrun the hub in the first rotational direction
Data Source
AI summary
In an aspect, a clutched device is provided, including a hub, a pulley and a hub drive clutch. The hub defines an axis and is connectable to a rotatable shaft of a rotary device. The pulley is rotatable relative to the hub and is engageable with an endless drive member. The hub drive clutch is a wrap spring clutch and is controllable to operatively connect the pulley to the hub for driving the hub in a first rotational direction. An isolation spring is provided and operatively connects the hub to the pulley when the hub drives the pulley in the first rotational direction. Optionally, a pulley overrun clutch is provided and permits the pulley to overrun the hub in the first rotational direction.