Alternator Isolating Decoupler with Nested Wrap Springs
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Solution Overview
Problem
Conventional alternator isolators are bulky, costly, and inefficient in managing dynamic belt loading fluctuations, leading to belt noise, slippage, and vibration due to their limited ability to accommodate varying engine rotational speeds and torsional forces.
Innovation Solution
An alternator isolating decoupler with a first and second wrap spring in parallel, each arranged in series with a torsion spring and releasably engaged with a one-way clutch, which is integrated with the alternator rotor to manage torque fluctuations and reduce frictional wear by decoupling during peak torque events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional torsional isolator is used at the crankshaft, then the dynamic belt loading fluctuations can be reduced, but the device becomes bulky, heavy, and costly with limited effectiveness
Solution Approach 1:
The patent extracts the torsional isolator function from the crankshaft and relocates it to the alternator rotor. By placing the isolator mechanism within the alternator assembly rather than at the crankshaft, the system achieves belt loading fluctuation reduction without adding bulk to the engine's critical rotating components. The isolator is integrated into the alternator's existing structure, avoiding the need for a separate heavy crankshaft-mounted device.
Solution Approach 2:
The patent introduces a spring-based isolator mechanism as an intermediary between the belt drive system and the alternator rotor. This intermediary component absorbs and dampens dynamic belt loading fluctuations through elastic deformation, protecting both the belt system and the alternator from excessive forces while maintaining a compact design.
2Force
If the spring rate is increased to accommodate high torsional forces, then the torsion transmitting function is improved, but the coupling/decoupling function deteriorates due to increased frictional wear and heat
Solution Approach 1:
The patent employs a one-way clutch mechanism that dynamically adjusts the coupling state between the isolator spring and the alternator rotor based on operating conditions. During normal operation, the clutch engages to transmit torque; during overrun or decoupling events, the clutch automatically disengages, allowing the spring to rotate freely without generating frictional wear or heat. This dynamic switching resolves the contradiction between maintaining high torsion capability and minimizing energy loss during decoupling.
Solution Approach 2:
The one-way clutch mechanism is designed to automatically engage and disengage based on the direction and magnitude of torque, without requiring external control. The mechanism self-regulates the coupling state, enabling the system to optimize between torque transmission and wear reduction based on real-time operating conditions, thereby resolving the spring rate contradiction without external intervention.
3Device complexity
If a single spring mechanism is used, then the device complexity is reduced, but the ability to manage dynamic belt loading fluctuations across varying engine speeds is limited
Solution Approach 1:
The patent combines multiple spring elements (first spring and second spring) with a one-way clutch mechanism into a single integrated isolator assembly. This merged design allows the system to handle a broader range of dynamic loading conditions through the combined elastic properties of multiple springs and the directional control of the clutch, while maintaining a compact, unified structure that does not significantly increase overall device complexity.
Solution Approach 2:
The isolator mechanism is designed to perform multiple functions: torque transmission, dynamic loading dampening, and overrun protection. The combination of spring elements and one-way clutch enables the same mechanism to adapt to varying engine speeds and torque conditions, providing universal functionality across different operating regimes without requiring multiple separate devices.
4Use of energy by moving object
If the alternator rotor is directly coupled to the crankshaft, then the power transmission efficiency is maximized, but the belt noise, slippage, and vibration increase under dynamic loading conditions
Solution Approach 1:
The patent incorporates a spring-based isolator mechanism that provides beforehand cushioning against dynamic belt loading fluctuations. The spring elements are pre-loaded and positioned to immediately absorb shock loads and dampen vibrations before they can propagate through the belt system, thereby reducing noise and slippage while maintaining efficient power transmission under normal operating conditions.
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 reduces the physical size and weight of the torsion spring and one-way clutch, optimizing component performance by limiting excessive torque and minimizing wear, thereby enhancing the durability and efficiency of the belt-driven accessory system.
Implementation Method 1
a first spring (40) and a second spring (50) in parallel, each in turn arranged in series with a torsion spring (20)
Implementation Method 2
each spring being releasably engaged with a one way clutch (70)
Data Source
AI summary
An alternator isolating decoupler comprising an alternator shaft (100), a one-way clutch (70) engaged with the alternator shaft, a first wrap spring (40) releasably engaged with the one-way clutch, a second wrap spring (50) releasably engaged with the one-way clutch, the second wrap spring arranged in parallel with the first wrap spring, the first wrap spring and the second wrap spring in nested relation, the first wrap spring and the second wrap spring each having an end (41,51) releasably engagable with an end cap (90), the end cap fixedly connected to an outer housing (10), the first wrap spring and the second wrap spring each engaged in series with a torsion spring (20), the torsion spring engaged with the outer housing, and the outer housing engaged with an alternator rotor (110).