Bicycle Hub Freewheel Mechanism for Load Distribution
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Solution Overview
Problem
Bicycle hubs face challenges in maintaining functionality across a wide range of rotational speeds, requiring reliable force transmission at high loads while minimizing friction and deformation, especially under dynamic loads encountered in sports and professional cycling.
Innovation Solution
A hub design featuring a freewheel with two interacting components, a hub-side and rotor-side freewheel component, biased via a biasing device, where the hub-side component is axially displaceable within a threaded ring with a helical thread groove, reducing axial forces and allowing for a stiffer, lighter structure by distributing loads through a larger thread pitch and gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a narrow threaded ring with a single thread is used to protect the hub shell from direct contact with the toothed disk, then the hub shell is protected, but the threaded ring is permanently driven into the hub shell under pedaling loads, causing locally high loads that may dilate or burst the hub shell, requiring increased wall thickness and adding weight
Solution Approach 1:
The patent introduces a freewheel mechanism as an intermediary between the toothed disk and the hub shell. This freewheel allows torque transmission in the driving direction while preventing the permanent driving-in effect that caused hub shell damage. The intermediary mechanism protects the hub shell without requiring increased wall thickness, thus avoiding weight increase.
Solution Approach 2:
The patent changes the operational parameters of the threaded ring by introducing a freewheel mechanism that allows axial movement. This enables the threaded ring to be permanently driven into the hub shell in a controlled manner during assembly, while the freewheel prevents further permanent driving-in during operation, eliminating the problem of load-induced dilation and burst.
2Strength
If the wall thickness of the hub shell is increased to dissipate loads and prevent dilation or burst, then the hub shell strength is improved, but the total weight of the hub considerably increases
Solution Approach 1:
The freewheel mechanism serves as an intermediary that protects the hub shell from excessive loads without requiring increased wall thickness. By allowing controlled axial movement and preventing permanent driving-in during operation, the freewheel eliminates the need for over-engineering the hub shell thickness, thus maintaining optimal weight-strength ratio.
3Reliability
If the freewheel is designed to quickly establish force closure under driving force, then torque transmission reliability is improved, but the freewheel must also show minor friction during back-pedaling or non-pedaling, creating a design challenge
Solution Approach 1:
The patent employs a dynamic freewheel mechanism that automatically adapts its friction characteristics based on the direction of rotation. During forward pedaling, the mechanism establishes force closure for reliable torque transmission. During back-pedaling or non-pedaling, the mechanism transitions to a low-friction state, allowing free rotation with minimal energy loss. This dynamic adaptation resolves the contradiction between reliability and energy efficiency.
Data Source
AI summary
A hub for bicycles comprising a hub axle, a hub shell, a rotor, and a toothed disk freewheel including a pair of interacting freewheel components namely, a hub-side freewheel component and a rotor-side freewheel component. The freewheel components each comprise axial engagement components biased in the engagement position through a biasing device. The hub-side freewheel component is axially displaceably received in a threaded ring and non-rotatably coupled with the hub shell in the driving direction. The rotor-side freewheel component is non-rotatably provided at the rotor for transmitting rotational movement from the rotor to the hub shell in the engagement position of the two freewheel components. The threaded ring comprises a thread with a thread groove that extends along a helical line in an axial direction around a circumference of the threaded ring, where the helical line shows less than five full revolutions around the circumference of the threaded ring. The thread is screw-connected with a thread of the hub shell.