Bicycle Hub Axial Force Reduction via Segmented Freewheel
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Solution Overview
Problem
Existing hubs for muscle-powered vehicles, particularly bicycles, face issues with deformation under load, leading to reduced durability and increased weight due to high axial forces, which can result in gear shifts, wear, and potential malfunction.
Innovation Solution
A hub design featuring a freewheel device with two interacting components, a hub-side and rotor-side freewheel component, utilizing a threaded connection with a larger thread groove gradient to reduce axial forces on the hub shell, combined with a lightweight material construction and enhanced bearing support, to minimize deformation and increase stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a toothed disk freewheel is used to transmit driving force quickly, then response speed is improved, but high loads cause bending moments that tilt the toothed disk, increasing wear and limiting durability
Solution Approach 1:
The toothed disk is divided into two separate disks (first and second toothed disks) that work together to transmit force. This segmentation distributes the mechanical loads across multiple components, reducing the bending moments and tilt on any single disk, thereby improving durability while maintaining quick response speed.
Solution Approach 2:
Different regions of the hub assembly are given different properties: the toothed disks use hardened materials resistant to wear, while the hub shell uses lightweight materials. The bearing seats are specifically designed with enhanced support characteristics to prevent deformation under load, allowing each component to optimize its local function.
2Reliability
If axial forces are increased to secure the freewheel component, then reliability is improved, but deformation of the hub shell increases, requiring heavier construction
Solution Approach 1:
Instead of relying solely on axial forces to secure the freewheel component, the invention introduces radial support through specifically designed bearing seats. This shifts part of the load-bearing function from the axial dimension to the radial dimension, allowing the hub shell to maintain lightweight construction while achieving reliable component securing through multi-directional support.
3Loss of time
If the number of ratchet pawls is increased to reduce re-engagement angle, then response time is improved, but the complexity of the freewheel device increases
Solution Approach 1:
The invention extracts the ratchet pawl mechanism from the traditional axial freewheel design and integrates it into a toothed disk system where force transmission occurs through tooth engagement rather than pawl-ratchet interaction. This eliminates the need for multiple pawls and complex spring mechanisms, reducing device complexity while maintaining fast re-engagement through the inherent mechanical coupling of the toothed disks.
Data Source
AI summary
A hub for bicycles or the like including a hub shell which is rotatably supported relative to a hub axle, a rotor rotatably supported relative to the hub axle, and a freewheel device having two interacting freewheel components namely, a hub-side freewheel component and a rotor-side freewheel component. The two freewheel components each contain axial engagement components. The hub-side freewheel component is non-rotatably and axially fixedly connected with the hub shell. The rotor-side freewheel component is non-rotatably connected with the rotor and is movable in the axial direction relative to the rotor and the hub shell between a freewheel position and an engagement position. Rolling members are provided for defined accommodation in the hub-side freewheel component to support the hub shell relative to the hub axle. The hub-side freewheel component is connected with the hub shell through a multiple thread having at least two separate, axially spaced apart thread grooves.