Filtering Pulley Damping for Start-Up Torsional Vibrations
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Solution Overview
Problem
Existing filtering pulleys for internal combustion engines face challenges in effectively filtering torsional vibrations at start-up and low speeds, as the damping required to manage high amplitude oscillations conflicts with the need for low damping during engine acceleration.
Innovation Solution
A filtering pulley design featuring a dynamic damper with a C-bushing and metallic ring, along with arched elastic assemblies and an actuator, provides adjustable damping by utilizing angular clearances and asymmetric behavior to decouple the hub and pulley ring during high amplitude oscillations, allowing for optimal filtering of torsional vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high damping is provided to manage high amplitude oscillations at start-up, then the filtering of torsional vibrations is improved, but the damping during engine acceleration becomes excessive causing inefficiency
Solution Approach 1:
The damping device dynamically adjusts its damping characteristics based on operating conditions. The friction element engages selectively to provide high damping during start-up transients with high amplitude oscillations, then disengages during normal engine acceleration to minimize energy loss. This dynamic adaptation resolves the contradiction between needing high damping for reliability and low damping for efficiency.
Solution Approach 2:
The device changes the damping parameter (friction force) based on the amplitude of torsional oscillations. During high amplitude oscillations at start-up, the friction element engages to increase damping. During normal operation with lower amplitude oscillations, the friction element disengages to reduce damping. This parameter change allows the system to optimize performance across different operating phases.
2Reliability
If a damping device is added to the filtering pulley, then the damping of high amplitude oscillations is improved, but the device complexity increases
Solution Approach 1:
The damping device is integrated into the existing filtering pulley structure by combining the friction element with the elastic element that already exists in the pulley. The friction element is positioned within the same assembly, sharing common components such as the hub and pulley ring. This merging approach adds the damping function without significantly increasing overall device complexity.
Solution Approach 2:
The damping device is self-regulating through the interaction between the friction element and elastic element. The system automatically engages the friction element when high amplitude oscillations occur and disengages it when oscillations subside, without requiring external control mechanisms. This self-service characteristic simplifies the control system and reduces overall device complexity.
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 design achieves effective filtering of torsional vibrations by maintaining low damping during normal operation and increased damping during high amplitude oscillations, reducing impact on the belt and ancillaries, while ensuring efficient torque transmission.
Implementation Method 1
a friction damper 27 radially interposed between the wall 14 of the closing element 11 and the hub portion 22 of the dynamic damper 19
Implementation Method 2
a plurality of arched elastic assemblies 40 arranged circumferentially in the chamber 15
Data Source
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AI summary
A filtering pulley (1) comprising a hub (2) adapted to be fixed to a rotating shaft, a pulley ring (3) mounted coaxial and rotationally free on said hub (2), at least one elastic assembly (40) interposed between the hub (2) and the pulley ring (3) and a damper (27) for damping the relative oscillations between the hub (2) and the pulley ring (3); the damper (27) has a first damping level for relative rotations between the hub (2) and the pulley ring (3) which are smaller than a predetermined angle and a second damping level, which is greater than the first level, for relative rotations between the hub (2) and the pulley ring (3) which are larger than the predetermined angle.