Concentric Bicycle Transmission with Variable Speed Motor
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Solution Overview
Problem
Bicycle transmissions using planetary gear mechanisms and variable speed motors face challenges in reducing size, weight, and complexity, with existing systems requiring multiple gear units and fixed reduction ratios, limiting shifting stages and increasing manufacturing costs.
Innovation Solution
A bicycle transmission design that concentrically arranges the input and output shafts and independently connects them with a planetary gear mechanism, utilizing a variable speed motor and a control unit to adjust rotational power, allowing for a single planetary gear mechanism and reduced part count, thereby simplifying the structure and reducing size and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple planetary gear units are installed to achieve desired transmission ratio, then the transmission ratio range is improved, but the device complexity increases
Solution Approach 1:
The patent applies dynamics by making the carrier rotatable relative to the sun gear, transforming a static single-stage planetary gear into a dynamic multi-ratio system. This rotational degree of freedom enables continuous variation of transmission ratios without requiring multiple discrete gear units, thus expanding the transmission ratio range while maintaining simple structure.
Solution Approach 2:
The patent introduces a new dimensional degree of freedom by allowing the carrier to rotate around the sun gear axis, adding a rotational dimension to the traditional planetary gear mechanism. This dimensional change enables multiple transmission ratios to be achieved within a single gear unit, avoiding the need for multiple stacked planetary stages.
2Adaptability or versatility
If two or more planetary gear devices are used for multi-stage shifts, then the shifting stages are increased, but the device complexity increases
Solution Approach 1:
The rotatable carrier mechanism provides continuous transmission ratio variation, effectively creating multiple shifting stages within a single planetary gear device. This dynamic adjustment capability replaces the need for multiple discrete planetary stages, achieving multi-stage shifting with simplified structure.
3Power
If a fixed reduction ratio is used, then the motor size is increased, but the transmission size is reduced
Solution Approach 1:
The patent changes the transmission ratio parameter dynamically through carrier rotation, allowing the system to adapt to different power requirements. This parameter variability enables the use of smaller motors with higher speed ranges, as the transmission can provide continuous ratio adjustment rather than relying on a fixed high reduction ratio, thereby reducing overall system size.
4Volume of moving object
If concentric arrangement of input and output shafts is implemented, then the transmission size is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The concentric arrangement nests the input shaft within the output shaft, with the carrier rotating around the sun gear that is mounted on the input shaft. This nested configuration achieves compact radial dimensions while the inherent mechanical constraints of the planetary gear meshing provide sufficient alignment tolerance, reducing manufacturing precision requirements compared to offset arrangements.
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
This design achieves a compact, lightweight, and cost-effective bicycle transmission with adjustable speed capabilities, enhancing aesthetics and ease of design modifications while reducing the number of parts and manufacturing complexity.
Implementation Method 1
The planetary gear mechanism includes a ring gear, a plurality of planet gears, a sun gear, and a carrier, and allows for the transmission of power
Data Source
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AI summary
Provided is a bicycle transmission using a variable speed motor and a planetary gear mechanism including: a first input rotary shaft (10) rotatably connected to a main power source (11); a second input rotary shaft (20) receiving a motor rotational power from a variable speed motor (21); a planetary gear mechanism (30) receiving first and second rotational power respectively from the first input rotary shaft (10) and the second input rotary shaft (20); an output shaft (40) receiving a third rotational power from the planetary gear mechanism (30); and a control unit (50) controlling the variable speed motor (21) and controlling a rotational direction and speed of the second input rotary shaft (20), wherein the first input rotary shaft (10) is arranged concentrically with the output shaft (40).