Filtering Pulley With Progressive Rigidity for Torsional Vibration
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Solution Overview
Problem
Existing filtering pulleys for internal combustion engines face a challenge in effectively filtering torsional vibrations from the crankshaft while maintaining sufficient rigidity to handle high loads, as the elastic elements' rigidity needs to be low to absorb oscillations but cannot be reduced further due to high load constraints.
Innovation Solution
A filtering pulley design featuring a hub with a coaxial ring and an elastic assembly with progressive rigidity, where the rigidity increases from a predetermined angle of rotation, utilizing a combination of springs and an anti-warping device to manage torque transmission efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the rigidity of the elastic elements is lowered to filter torsional oscillations, then the filtering capability is improved, but the ability to handle high loads deteriorates
Solution Approach 1:
The elastic element's rigidity is made variable rather than constant. The spring geometry is designed so that its rigidity changes dynamically with compression: at low torques the spring coils are spaced apart providing low rigidity for vibration filtering, while at high torques the coils compress together providing high rigidity for load handling. This dynamic adaptation resolves the contradiction between filtering capability and load handling.
Solution Approach 2:
The physical parameters of the elastic element (specifically the spacing and compression state of spring coils) are changed based on operating conditions. The spring is designed with variable pitch where the distance between adjacent coils varies along its length, creating different rigidity characteristics at different compression levels. This parameter change allows the same element to provide both low rigidity for filtering and high rigidity for load bearing.
2Strength
If the rigidity of the elastic elements is increased to handle high loads, then the load handling capability is improved, but the filtering capability deteriorates
Solution Approach 1:
The elastic element transitions from a static rigidity design to a dynamic one where the rigidity adapts to the applied load. During normal operation with high loads, the spring is compressed to a state where coil spacing is reduced, increasing rigidity for load handling. During torsional oscillations with low torques, the spring remains in a less compressed state with greater coil spacing, providing low rigidity for effective vibration filtering.
Solution Approach 2:
The geometric parameters of the spring, particularly the pitch or spacing between coils, are designed to change with compression. The variable pitch design ensures that at different compression levels (corresponding to different torque levels), the effective rigidity changes appropriately. This allows the system to automatically adjust the rigidity parameter based on operating conditions without external control.
3Object-affected harmful factors
If a progressive rigidity spring is used to resolve the rigidity contradiction, then both filtering and load handling are improved, but the device complexity increases due to anti-warping requirements
Solution Approach 1:
The anti-warping function is merged with the load-bearing function by designing the guide elements as integral parts of the spring assembly rather than separate components. The guide elements are positioned and shaped to simultaneously prevent warping and distribute loads evenly across the spring coils. This integration reduces the number of separate parts and simplifies the overall structure while achieving both objectives.
Solution Approach 2:
Guide elements are introduced as intermediary components between the spring and the surrounding structure. These guides mediate the interaction by constraining the spring's movement to prevent warping while allowing the necessary compression and expansion. The guides act as intermediaries that translate the spring's elastic deformation into controlled motion, preventing unwanted warping without adding significant complexity to the overall system.
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 pulley achieves high rigidity for high torques and lower rigidity for low torques, effectively filtering vibrations while preventing spring warping, thus enhancing the reliability and performance of the system.
Implementation Method 1
an elastic assembly having one elastic element with a progressive rigidity increasing starting from a predetermined threshold value of the angle of relative rotation between the hub and the ring
Implementation Method 2
In order to 'filter' the torsional oscillations transmitted by the crank shaft to the belt, a filtering pulley is generally used... one elastic element with a progressive rigidity increasing starting from a predetermined threshold value of the angle of relative rotation
Data Source
AI summary
Filtering pulleys have a hub adapted to be fixed to a rotating shaft, a ring assembled coaxial and rotationally free on the hub, and an elastic assembly arranged circumferentially with respect to the hub and the ring and interposed between a pair of first elements integral with the hub and between a pair of second elements integral with the ring. The elastic assembly includes an elastic element having a progressive rigidity increasing starting from a predetermined threshold value of the angle of relative rotation between the hub and the ring.