Rear Sprocket Assembly With Internal Splines for Wider Gear Range
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Solution Overview
Problem
Current bicycle rear sprocket assemblies face challenges in achieving a wider gear range while maintaining durability and material flexibility, as well as efficient torque transmission and attachment to the hub assembly.
Innovation Solution
The bicycle rear sprocket assembly features a first sprocket with a smaller pitch-circle diameter and a second sprocket with at least ten internal spline teeth, which engage with the sprocket support body, allowing for reduced rotational force distribution and increased radial lengths of internal-spline driving surfaces, enhancing durability and strength, and enabling a wider gear range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pitch-circle diameter of the sprocket is reduced to achieve a wider gear range, then the gear range is improved, but the strength and durability of the sprocket may deteriorate
Solution Approach 1:
The sprocket is divided into multiple independent sprockets with different pitch-circle diameters, allowing each to be optimized for specific strength requirements while collectively providing a wide gear range. The first sprocket has a smaller pitch-circle diameter for high-speed gear range, while the second sprocket has a larger pitch-circle diameter for strength and durability.
2Reliability
If the number of internal spline teeth is increased to improve torque transmission, then the durability is improved, but the device complexity increases
Solution Approach 1:
The internal spline teeth are designed with non-uniform radial lengths, where specific teeth have extended radial lengths to concentrate torque transmission on fewer teeth. This local enhancement of torque capacity allows the use of fewer total spline teeth while maintaining or improving durability, thereby reducing device complexity.
3Strength
If the radial length of internal-spline driving surfaces is increased to improve strength, then the sprocket strength is improved, but the manufacturing complexity increases
Solution Approach 1:
The internal-spline driving surfaces are segmented into multiple teeth with different radial lengths. This segmentation allows the strength enhancement to be concentrated on specific critical teeth rather than uniformly increasing the radial length of all teeth, thereby improving strength while managing manufacturing complexity through selective reinforcement.
4Device complexity
If fewer internal spline teeth are used to reduce device complexity, then the manufacturing is simplified, but the torque transmission capacity and durability deteriorate
Solution Approach 1:
Instead of uniformly distributing torque across many teeth, the design concentrates torque transmission on a fewer number of teeth with extended radial lengths. This local quality enhancement allows each tooth to handle higher loads, maintaining durability while reducing the total number of teeth and simplifying the device structure.
Data Source
AI summary
A bicycle rear sprocket assembly comprises a plurality of bicycle sprockets comprising a first sprocket and a second sprocket. The first sprocket includes a first opening having a first minimum diameter that is smaller than a minimum outer diameter of a sprocket support body of a bicycle rear hub assembly. The second sprocket includes a second opening and at least ten internal spline teeth. The second opening has a second minimum diameter that is equal to or larger than the minimum outer diameter. The at least ten internal spline teeth are configured to engage with the sprocket support body of the bicycle rear hub assembly. The at least ten internal spline teeth include a plurality of internal-spline driving surfaces each including a radial length. A total of the radial lengths of the plurality of internal-spline driving surfaces is equal to or larger than 7 mm.