Bottom Bracket Planetary Gearbox With Low-Load 12-Speed Shifting
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Solution Overview
Problem
Existing bicycle and pedelec pedal bearing gears require complex structures and high component loads to achieve efficient gear shifting, which increases manufacturing effort and reduces efficiency.
Innovation Solution
A pedal bearing gear with a bottom bracket transmission featuring a two-stage step planet wheel set and two planetary wheel sets, coupled with six switching elements to implement a simple and compact gear shifting mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a complex gear structure is used to achieve efficient gear shifting, then gear efficiency is improved, but device complexity and manufacturing effort increase
Solution Approach 1:
The patent combines multiple planetary gear sets (first and second planetary gear sets with sun gears, planet gears, and ring gears) into a single integrated bottom bracket transmission system. This merging of gear functions into one compact unit achieves efficient gear shifting while reducing overall device complexity compared to separate gear systems, directly resolving the contradiction between gear efficiency and structure complexity
Solution Approach 2:
The planetary gear sets are nested within the bottom bracket housing, with the first and second planetary gear sets arranged in a compact configuration where components are interlocked and space-efficiently positioned. This nesting approach maximizes gear efficiency within a limited space while minimizing the external footprint and structural complexity of the transmission system
2Reliability
If multiple planetary gear sets are used to reduce component loads, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent merges two planetary gear sets into a single integrated transmission system where the first planetary gear set and second planetary gear set share common components and housing space. This combining approach distributes component loads across multiple gear elements (improving reliability) while maintaining a unified structure that avoids the complexity of completely separate gear systems
Solution Approach 2:
The bottom bracket transmission system performs multiple gear shifting functions through the coordinated operation of the first and second planetary gear sets. Each planetary gear set can operate independently or in combination, providing versatile gear ratio options while maintaining a compact unified structure that reduces overall system complexity compared to multiple independent transmission units
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 proposed solution achieves a particularly simple and compact structure with low component loads and high gear efficiency, compared to traditional gear systems.
Implementation Method 1
The bottom bracket transmission has a first gear shift group (3) and a second gear shift group (4), which are coupled to one another to form a multi-speed gear system
Data Source
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AI summary
A planetary bottom bracket gearbox for a bicycle or pedelec (1) is proposed, comprising a crankshaft (WAn) as the input and a gearbox output shaft (WAb) as the output, and further shafts (W1, W2, W3, W4, W5, W6, W7), as well as a first gearbox shift group (3) and a second gearbox shift group (4) coupled to each other to implement several gears (G1, G2, G3, G4, G5, G6, G7, G8, G9, G10, G11, G12). The first gearbox shift group (3) includes a two-stage stepped planetary gear set (StRS) to which a first shift element (B1), a second shift element (B2), and a fifth shift element (F1I, F1II, F1III, F1IV, F1V, F1VI) are assigned. Furthermore, a bicycle or pedelec (1) with a bottom bracket gearbox is proposed.