Asymmetrical Bicycle Gear Teeth for Compact Transmission
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Solution Overview
Problem
Existing bicycle gear change mechanisms lack miniaturization capabilities, limiting the compactness and efficiency of bicycle components.
Innovation Solution
The implementation of a gear change mechanism with asymmetrical teeth on gears, where the first pressure angle is larger than the second, and the third pressure angle is larger than the fourth, allowing for miniaturization by optimizing tooth geometry and engagement, enabling the use of spur gears and planetary gear mechanisms to change the speed of rotation efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional symmetrical gear teeth are used, then the gear structure is simple and easy to manufacture, but the gear mechanism cannot be miniaturized and occupies larger space
Solution Approach 1:
The patent applies asymmetry by designing gear teeth with different pressure angles on opposite sides. Specifically, one side of each tooth has a pressure angle of 20 degrees while the other side has a pressure angle of 25 degrees. This asymmetric tooth geometry allows the gear mechanism to be miniaturized by optimizing the space utilization within the gear body, enabling compact design without compromising load-bearing capacity.
Solution Approach 2:
The patent applies local quality by varying the pressure angle parameter locally across different regions of the same tooth. The first side of the tooth uses a 20-degree pressure angle while the second side uses a 25-degree pressure angle, allowing each region to be optimized for its specific functional requirements. This enables compact gear design while maintaining adequate strength in different loading zones.
2Volume of moving object
If gear size is reduced for miniaturization, then the gear mechanism becomes more compact, but the load capacity of the teeth decreases
Solution Approach 1:
The patent applies parameter changes by modifying the pressure angle parameter to different values on opposite sides of the teeth (20 degrees and 25 degrees). This parameter variation allows optimization of the tooth root strength and contact area distribution, enabling the gear to maintain adequate load capacity despite reduced overall size. The higher pressure angle side provides enhanced root strength while the lower pressure angle side optimizes contact mechanics.
3Volume of moving object
If asymmetrical teeth with different pressure angles are used, then miniaturization and load capacity increase, but manufacturing precision requirements become more stringent
Solution Approach 1:
The patent employs specific discrete pressure angle values (20 degrees and 25 degrees) that balance the need for miniaturization with manufacturability. These standardized angular parameters can be implemented using conventional gear cutting methods with appropriate tooling, making the asymmetric geometry achievable with moderate precision requirements rather than extreme tolerances.
Data Source
AI summary
A bicycle gear change mechanism includes a first gear including first teeth and a second gear including second teeth. Each of the first teeth includes a first surface and a second surface. The first surface defines a first pressure angle. The second surface defines a second pressure angle. The first pressure angle differs from the second pressure angle. Each of the second teeth includes a third surface and a fourth surface. The third surface defines a third pressure angle. The fourth surface defines a fourth pressure angle. The third pressure angle differs from the fourth pressure angle. The second gear engages the first gear.