Asymmetric Chain Tensioning for Higher Drivetrain Jump Torque
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Solution Overview
Problem
Current chain tensioning devices in drivetrain transfer cases compromise system efficiency to achieve higher jump torque, as they apply constant loads that increase tensioning forces, leading to reduced efficiency and increased jump torque, whereas in engine timing systems, tensioning devices cause noise, vibration, and harshness (NVH) issues.
Innovation Solution
The implementation of a chain tensioning device that applies tension asymmetrically towards the driven sprocket, using multi-pivot torsion spring or blade spring tensioners, to force chain jumps to occur at the drive sprocket, reducing chain width and mass while maintaining efficiency, by allowing slack accumulation near the drive sprocket and using low-force springs to minimize system inefficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a tensioning device applies constant load to increase chain tension, then jump torque capacity is improved, but system efficiency deteriorates
Solution Approach 1:
The patent employs a dynamic tensioning system where the tensioning force is not constant but varies with operating conditions. The system allows the chain tension to be maintained at optimal levels during normal operation while automatically reducing tension during conditions that would otherwise cause excessive force application, thereby preserving system efficiency while maintaining jump torque capacity.
Solution Approach 2:
The patent changes the parameter of tensioning force from a fixed constant value to a variable parameter that adapts to operating conditions. By adjusting the tensioning force dynamically based on chain slack, operational direction, and load conditions, the system achieves high jump torque capacity only when needed while minimizing energy losses during normal operation.
2Strength
If high tensioning force is applied to delay tooth jump, then jump torque increases, but system efficiency decreases significantly
Solution Approach 1:
The tensioning device transitions from static high-force tensioning to dynamic tensioning that applies high force only during reverse rotation or failure conditions. During normal forward operation, the tensioning force is reduced to minimal levels, eliminating continuous energy losses while preserving the ability to achieve high jump torque when required.
Solution Approach 2:
The system applies high tensioning force periodically or event-driven rather than continuously. The tensioning force is activated during specific events such as reverse rotation detection or chain slack thresholds, and deactivated during normal operation, creating a periodic or conditional action pattern that maintains performance while reducing energy consumption.
3Object-affected harmful factors
If chain slack is controlled to improve NVH, then noise and vibration are reduced, but jump torque capacity is compromised
Solution Approach 1:
The patent applies different tensioning strategies to different portions of the chain system based on local requirements. The tensioning device focuses control efforts on managing chain slack in specific zones that affect NVH during normal operation, while allowing greater slack in zones that would otherwise require constant high tensioning to maintain jump torque capacity.
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
This approach enhances jump torque performance by forcing chain jumps at the drive sprocket, allowing for narrower chain and sprocket designs, reducing mass and cost, while maintaining system efficiency at approximately 98.9% compared to conventional systems, which typically achieve 96.8% efficiency with higher tensioning forces.
Implementation Method 1
at least one tensioning device including a resilient blade or a multi-pivot arm and a torsion spring
Implementation Method 2
the chain transmits power from a driving shaft to a driven shaft
Implementation Method 3
it is important to impart and maintain a certain degree of tension in the chain
Data Source
AI summary
A chain tensioning device which combats natural build-up of chain slack. In controlling the chain slack, the torque at which a chain jumps occurs is delayed resulting in a higher jump torque performance.