Hub Assembly Rotation Control for Coasting Gear Shift
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Solution Overview
Problem
Human-powered vehicles face challenges in efficiently shifting gears during coasting, as existing systems struggle to adjust rotational speeds and sprocket engagement effectively, leading to inefficient energy transfer and gear shifting.
Innovation Solution
A hub assembly with a rotation control structure that includes a first and second rotatable member and a one-way clutch, allowing for differential rotational speeds and ratios to facilitate smooth gear shifting during pedaling and coasting, utilizing a ring gear, sun gear, and planetary gears to transmit rotations at specific ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional hub assembly is used during coasting, then the chain remains engaged with a single sprocket, but gear shifting cannot be performed during coasting
Solution Approach 1:
The hub assembly employs a rotation control structure that dynamically changes the rotational relationship between the first and second rotatable members based on operating conditions. During coasting, the structure allows differential rotation to enable chain shifting, while during pedaling it synchronizes rotation for efficient power transfer. This dynamic adaptability resolves the contradiction by making the system versatile without requiring completely separate mechanisms for different operating modes.
Solution Approach 2:
The rotation control structure serves multiple functions: it enables gear shifting during coasting, maintains synchronized rotation during pedaling, and provides rotational speed reduction. By integrating these functions into a single mechanism that couples two rotatable members with different rotation ratios, the invention achieves versatility without proportionally increasing device complexity.
2Adaptability or versatility
If the first rotatable member rotates at the same speed as the second rotatable member during coasting, then the structure is simple, but chain shifting between sprockets cannot occur
Solution Approach 1:
The rotation control structure dynamically adjusts the rotational speed relationship between the first and second rotatable members. During coasting, it permits differential rotation where the first rotatable member rotates at a different speed than the second, enabling the chain to move between sprockets. This dynamic speed adjustment resolves the contradiction by allowing versatility when needed while maintaining simplicity when not required.
3Adaptability or versatility
If the chain rotates at high speed during coasting, then power transfer is maintained, but gear shifting becomes difficult and energy loss increases
Solution Approach 1:
The rotation control structure dynamically reduces the rotational speed of the first rotatable member relative to the second rotatable member during coasting operations. This speed reduction facilitates smooth chain shifting between sprockets by decreasing the kinetic energy that would otherwise resist the shifting action, thereby reducing energy loss while maintaining the versatility to perform gear changes during coasting.
4Adaptability or versatility
If a rotation control structure with different rotation ratios is introduced, then gear shifting during coasting is enabled, but the device complexity increases
Solution Approach 1:
The rotation control structure is designed as a multi-functional mechanism that simultaneously enables gear shifting during coasting, maintains synchronized rotation during pedaling, and provides rotational speed reduction. By integrating these multiple functions into a single coupled mechanism between two rotatable members, the invention achieves versatility without proportionally increasing complexity compared to having separate mechanisms for each function.
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
Enables efficient gear shifting during coasting by adjusting rotational speeds and reducing output rotations, allowing for seamless chain shifting between sprockets while maintaining a lower rotational speed, thereby improving energy transfer and pedaling assistance.
Implementation Method 1
a first one-way clutch provided between the first rotatable member and the second rotatable member to transmit the first input rotation of the first rotatable member to the second rotatable member
Implementation Method 2
at least one planetary gear engaged with the ring gear and the sun gear to transmit the second input rotation of the second rotatable member to the first rotatable member at the second ratio
Data Source
AI summary
A hub assembly for a human-powered vehicle comprises a hub axle, a first rotatable member, a second rotatable member, and a rotation control structure. The rotation control structure couples the first rotatable member to the second rotatable member to transmit a first input rotation of the first rotatable member to the second rotatable member at a first ratio of a first output rotation of the second rotatable member to the first input rotation of the first rotatable member. The rotation control structure couples the second rotatable member to the first rotatable member to transmit a second input rotation of the second rotatable member to the first rotatable member at a second ratio of a second output rotation of the first rotatable member to the second input rotation of the second rotatable member. The second ratio is different from the first ratio. The second ratio is larger than 0.