Wrap Spring Isolator Decoupler for Engine Vibration and Torque Management
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Solution Overview
Problem
Diesel and gasoline engine accessory drive systems experience increased crankshaft vibrations and belt slip noise due to higher engine efficiency, leading to reduced belt life and challenges in engine start-up and shut-down, where existing isolators and decouplers fail to effectively manage torque and vibrations.
Innovation Solution
An isolator decoupler with a wrap spring engagable with a one-way clutch carrier, coupled to a torsion spring, loadable in the unwinding direction to lockably engage through friction in the driving direction, incorporating a slip feature to prevent overloading and damage from excessive torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional isolator or decoupler is used to filter crankshaft vibrations during engine operation, then vibration filtering is effective in the engine running speed range, but the isolator presents problems during engine start-up or shut-down due to its natural frequency
Solution Approach 1:
The isolator incorporates a one-way clutch mechanism that allows the isolator to dynamically change its behavior. During normal engine operation, the isolator functions as a vibration filter. During start-up or shut-down, the one-way clutch disengages, allowing the isolator to freely rotate and avoid resonance issues, thus adapting to different operating conditions
2Reliability
If the wrap spring is made stiffer to prevent overloading during peak torque, then torque protection is improved, but the belt slip noise and vibration increase during normal operation
Solution Approach 1:
The wrap spring is designed with specific physical parameters (wire diameter, mean coil diameter, number of active coils) that allow it to provide torque limiting protection while maintaining flexibility during normal operation. The spring rate is optimized to slip at peak torque conditions but remain compliant during normal belt operation, preventing both overloading and excessive noise
3Power
If the one-way clutch carrier is designed with high friction engagement to prevent slippage, then power transmission efficiency is improved, but the wrap spring cannot effectively limit torque during overloading
Solution Approach 1:
The friction surface of the one-way clutch carrier is designed with specific local properties (surface area, material composition, surface roughness) that create optimal friction characteristics. This allows the carrier to maintain strong frictional engagement for efficient power transmission during normal operation while still permitting the wrap spring to slip and limit torque when overloaded
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 decouples locked elements when peak torque is exceeded, preventing damage to the spring and one-way clutch, ensuring efficient power transmission and minimizing noise and vibration, thereby extending the life of the belt and maintaining system integrity during engine start-up.
Implementation Method 1
the wrap spring through friction is able to lockably engage the inner surface in a driving direction
Implementation Method 2
a torsion spring having an end engaged with the pulley, the torsion spring loadable in an unwinding direction
Data Source
Figure 1
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AI summary
An isolator decoupler comprising a pulley (5), the pulley journalled to a shaft (1), a torsion spring (6) having an end (61) engaged with the pulley (5), the torsion spring (6) loadable in an unwinding direction, a one-way clutch carrier (8), a one-way clutch (14) disposed between the shaft (1) and the one-way clutch carrier (8), a wrap spring (7) engagable with an inner surface (81) of the one-way clutch carrier (8), the wrap spring (7) coupled to the torsion spring (6), and the wrap spring (7) loadable in the unwinding direction such that the wrap spring (7) through friction is able to lockably engage the inner surface (81) in a driving direction.