Bicycle Bottom Bracket Radially Inward Force Reducing Structure
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Solution Overview
Problem
Conventional bicycle bottom bracket assemblies experience radially inward deformation due to tightening or press-fitting forces, which increases rotational torque requirements and can damage bearing units, reducing their service life.
Innovation Solution
The bicycle bottom bracket assembly incorporates a radially inward force reducing structure, featuring support members with specific designs such as non-threaded outer surfaces, varying thread heights, deformable members, radially extending recesses, and connecting tubes with increased wall thickness, to mitigate the radially inward forces transmitted to the bearing units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If support members are screwed into or press-fitted into the hanger part, then the bottom bracket assembly is securely mounted, but radially inward forces deform the support members and damage the bearing units
Solution Approach 1:
A force reducing structure is introduced as an intermediary component between the support member and the bearing unit. This structure intercepts and reduces the radially inward forces generated during mounting, preventing full transmission of these forces to the bearing unit, thereby resolving the contradiction between secure mounting and bearing unit protection
Solution Approach 2:
The force reducing structure is designed to cushion or absorb radially inward forces before they reach the bearing unit. By providing this protective function in advance during the mounting process, the bearing unit is shielded from damaging forces that would otherwise occur during installation
2Ease of manufacture
If resin material is used for support members, then manufacturing complexity is reduced, but radially inward deformation increases due to material flexibility
Solution Approach 1:
The force reducing structure serves as a mediator that compensates for the inherent flexibility of resin material. It intercepts radially inward forces before they can cause excessive deformation of the resin support member, enabling the use of easier-to-manufacture resin materials while maintaining dimensional stability
Solution Approach 2:
The force reducing structure modifies the force transmission parameters by reducing the magnitude of radially inward forces. This parameter change allows resin support members to maintain their shape under load despite their material flexibility, resolving the contradiction between ease of manufacture and shape stability
Data Source
AI summary
A bicycle bottom bracket assembly having a rotational central axis includes a support member, a bearing unit and a radially inward force reducing structure. The support member includes a hanger mounting portion and a bearing mounting portion. The bearing mounting portion is configured to be at least partly positioned within a hanger part of a bicycle frame. The bearing unit includes an outer race, an inner race and at least one roller element disposed between the outer and inner races in a radial direction with respect to the rotational central axis. The outer race is fixed to the bearing mounting portion of the support member. The radially inward force reducing structure reduces a radially inward force being transmitted to the bearing unit.