Belt Starter Generator Tuning for Torsional Vibration Isolation
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Solution Overview
Problem
Belt drive systems in vehicles face noise and performance issues due to torsional vibrations from internal combustion engines and high acceleration/deceleration rates, which traditional alternator isolator decouplers cannot address since they prohibit the driving function.
Innovation Solution
A belt tuning device with a torsional spring connecting a pulley to a shaft, featuring a spring stop ring with outwardly extending tabs that fit within recesses on the shaft, allowing the pulley to angularly advance and absorb speed fluctuations, providing vibration attenuation during both motoring and generation functions while enabling the device to function as both a driver and driven unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a traditional alternator isolator decoupler is used, then vibration attenuation is achieved, but the driving function is prohibited
Solution Approach 1:
The patent employs a dynamic engagement mechanism where the isolator decoupler transitions between engaged and disengaged states based on operational requirements. During motoring mode, the decoupler engages to provide vibration attenuation; during generation mode, it disengages to allow the alternator to drive the belt. This dynamic state change resolves the contradiction by making the vibration isolation feature active only when needed, rather than permanently prohibiting the driving function.
Solution Approach 2:
The patent introduces an intermediary engagement mechanism (including elements such as a spring, retainer, and engagement surfaces) that mediates between the isolator decoupler and the alternator assembly. This intermediary structure enables selective coupling and decoupling, allowing the system to achieve both vibration attenuation and driving capability through controlled engagement states rather than direct permanent coupling.
2Device complexity
If the pulley is rigidly connected to the rotor, then structural simplicity is maintained, but vibration attenuation is reduced
Solution Approach 1:
The patent segments the connection between the pulley and rotor by introducing an isolator decoupler assembly with distinct components (isolator element, decoupler, retainer, spring). This segmentation allows the system to maintain overall structural simplicity while incorporating vibration attenuation features through the segmented isolator mechanism, rather than requiring a completely complex flexible coupling system.
Solution Approach 2:
The patent changes the connection parameter from rigid (fixed stiffness) to flexible (variable stiffness through spring engagement). The isolator decoupler uses a spring element that provides flexible connection during motoring mode to attenuate vibrations, while maintaining sufficient rigidity during generation mode when engaged. This parameter change enables both structural simplicity and effective vibration attenuation.
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 device effectively attenuates vibrations during both motoring and generation functions, improving the smooth operation of belt drive systems by allowing the pulley to advance ahead of the rotor, and decoupling the rotor from the pulley structure, thereby reducing noise and performance issues.
Implementation Method 1
a torsion spring positioned internal to the pulley structure, with a first end of the torsion spring fixed to a spring retainer fixed to the pulley structure and a second end of the torsion spring fixed to a spring stop ring
Implementation Method 2
the torsion spring inside the tuning device allows the pulley to angularly advance ahead of the rotor. This allows the tuning device to absorb the speed fluctuation induced by the engine's torsional vibration and to attenuate vibrations during both motoring and generation functions
Implementation Method 3
The spring stop ring has at least one outwardly extending tab configured to fit within the at least one recess in the flange and the tab has an arcuate length less than the arcuate length of the recess
Data Source
AI summary
A belt tuning device to an accessory belt drive system (ABDS) that utilizes a torsional spring to connect the belt pulley to the shaft of a motor generator unit to isolate the system and allow the pulley to advance ahead of the motor or to be behind the motor. The tuning device also has a free running zone providing a decoupling function for the system, allowing the tuning device to be both a driver and a generator of power. The tuning device has all of the belt pulley, a spring retainer, a torsion spring, a stop ring, and a shaft fixed in relation to each other.