Torque Limited Decoupler Spring Expansion Control
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Solution Overview
Problem
Existing decoupler systems in automotive vehicles face durability issues due to excessive torques during aggressive start profiles and rapid acceleration, which overstress the torsion spring, reducing long-term durability.
Innovation Solution
A decoupler assembly with a torque limiter, such as a sleeve or wire coil, is used to limit the expansion of the torsion spring, ensuring it fully couples the hub and pulley only at or above a predetermined torque, preventing overloading and maintaining durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torsion spring is allowed to expand freely to couple the hub and pulley, then the decoupler can accommodate torsional vibrations and speed oscillations, but excessive torques during aggressive start profiles and rapid acceleration will overstress the torsion spring reducing long term durability
Solution Approach 1:
A torque limiter is introduced as an intermediary component between the torsion spring and the coupling mechanism. This torque limiter prevents excessive expansion of the torsion spring during high-torque conditions, thereby protecting the spring from overstress while still allowing normal torsional vibrations and speed oscillations to be accommodated through the decoupler mechanism.
Solution Approach 2:
The system changes the operational parameters of the torsion spring by limiting its maximum expansion through the torque limiter. This ensures that the spring operates within safe stress boundaries during aggressive start profiles and rapid acceleration, while maintaining its ability to absorb minor torsional vibrations under normal operating conditions.
2Strength
If the torsion spring is made more robust to withstand excessive torques, then durability is improved, but the decoupler becomes less able to allow speed oscillations and torsional flexibility
Solution Approach 1:
The decoupler system is segmented into distinct functional components: the torsion spring for accommodating normal torsional vibrations, the torque limiter for preventing excessive torque transmission, and the coupling mechanism for connecting the hub and pulley. This segmentation allows each component to be optimized for its specific function without compromising the overall system performance.
Solution Approach 2:
The torque limiter serves as a mediator that protects the torsion spring from excessive torques while allowing the spring to maintain its torsional flexibility for normal speed oscillations. This intermediary component enables the system to have both strength and flexibility simultaneously.
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 decoupler assembly effectively prevents torques above a predetermined value from overstressing the torsion spring, enhancing the long-term durability of the decoupler by ensuring full coupling only at specific torque levels, thereby improving the system's operational stability and longevity.
Implementation Method 1
A clutch spring is secured to the carrier and has a plurality of helical coils frictionally engaging with the inner surface of the pulley to selectively couple the hub and pulley
Implementation Method 2
A torsion spring extends between the hub and the carrier for transferring torque therebetween... enabling the torsion spring to absorb minor torsional vibrations
Implementation Method 3
A torque limiter, in the form of a sleeve, is fitted about the torsion spring and is sized to limit expansion of the torsion spring enabling the torsion spring to fully couple the hub with the pulley at or above a predetermined torque
Data Source
AI summary
A decoupler assembly is provided for allowing an alternator to be rotatably driven by a serpentine belt in an engine of an automotive vehicle and for allowing the speed of the belt to oscillate relative to the alternator. A hub is fixedly carried by a drive shaft from the alternator for rotation therewith. A pulley is rotatably journaled to the hub by a ball bearing assembly. A bare, helical clutch spring is operatively coupled between the hub and pulley for transferring rotational movement from the pulley to the hub during acceleration of the pulley relative to the hub by the serpentine belt and for allowing the hub to overrun the pulley during deceleration of the pulley relative to the hub. A torque limiter, preferably a spring or sleeve, is wrapped about the torsion limiting outward expansion of the torsion isolating the torsion spring from torques above a predetermined limit.