Bottom Bracket Planetary Transmission With More Gears, Less Complexity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bottom bracket transmissions for bicycles and pedelecs require significant construction effort and do not offer improved properties compared to prior art.
Innovation Solution
A bottom bracket transmission with a planetary design that includes a pedal crankshaft as a drive and a transmission output shaft as an output, featuring a first and second transmission shifting group coupled for implementing multiple gears, utilizing a two-stage stepped planetary gear set with specific shifting elements for compact and efficient gear shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional transmission design with multiple planetary gear sets is used, then multiple gears can be implemented, but the construction effort and device complexity increase significantly
Solution Approach 1:
The patent combines two planetary gear sets into a single integrated unit where they share common components (sun gear, ring gear, planet gears). This merging reduces the total number of independent components while maintaining the ability to provide multiple gear ratios through selective blocking of different element combinations.
Solution Approach 2:
The planetary gear elements serve multiple functions simultaneously - the sun gear and ring gear can each serve as input, output, or fixed elements depending on which shifting element is engaged. This multi-functionality allows a single compact structure to provide multiple gear ratios without requiring separate dedicated pathways for each gear.
2Adaptability or versatility
If more shifting elements are added to achieve more gears, then gear versatility improves, but the construction effort and component count increase
Solution Approach 1:
The shifting elements are designed to control blocking of gear elements within a shared planetary structure rather than requiring separate shifting mechanisms for each gear set. This consolidation reduces the overall number of shifting elements needed while maintaining comprehensive gear control.
3Volume of moving object
If a compact planetary gear design is used, then the transmission size is reduced, but component loads increase
Solution Approach 1:
The transmission is divided into two functional stages (first and second planetary gear sets) that can be selectively engaged. This segmentation allows the load to be distributed across different element combinations in each stage, preventing any single component from bearing excessive loads while maintaining a compact overall structure.
4Productivity
If conventional transmission designs are used, then gear implementation is achieved, but gearing efficiency decreases due to higher component loads
Solution Approach 1:
By segmenting the transmission into two stages with selective engagement, the patent reduces the number of meshing interfaces that simultaneously bear load. This allows for more efficient power transmission through fewer engaged components at any given time, reducing overall energy losses.
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 achieves a simple and compact construction with reduced component loads and high gearing efficiency, offering improved performance compared to prior art transmissions.
Implementation Method 1
a two-stage stepped planetary gear set with three shifting elements
Data Source
AI summary
A bottom bracket transmission with a planetary design for a bicycle or a pedelec (1) includes a pedal crankshaft (WAn), a transmission output shaft (WAb), further shafts (W1, W2, W3, W4, W5, W6, W7), and a first transmission shifting group (3) and a second transmission shifting group (4) coupled together for implementing a plurality of gears (G1, G2, G3, G4, G5, G6, G7, G8, G9, G10, G11, G12). The first transmission shifting group (3) includes a two-stage stepped planetary gear set (StRS1).