Bicycle Gear Hub Shift Mechanism Reducing Resistance
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Solution Overview
Problem
Existing bicycle gear hubs with planetary gear systems face complexity in gear shifting operations, potential mechanism damage, and reverse control pawl operations, making them labor-intensive and prone to mechanical stress.
Innovation Solution
A bicycle gear hub design featuring a shift mechanism with a shift actuator and control pawls, allowing for sequential planetary gear modules connected in series, where the rotational direction of the shift actuator aligns with the closing direction of control pawls during gear shifts, particularly from high to low gears, reducing resistance and labor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If control pawls are used to fix sun gears to axles for achieving speed-up ratios, then versatile speed ratios can be obtained, but the operation complexity increases and the mechanism becomes prone to damage
Solution Approach 1:
The patent divides the control mechanism into multiple independent control pawls (first control pawl and second control pawl), each responsible for controlling different planetary gear modules. This segmentation allows for simpler individual operations while maintaining versatile speed ratio capabilities through coordinated operation of multiple pawls.
Solution Approach 2:
The control pawls are designed to be movable rather than fixed, allowing them to dynamically engage and disengage from sun gears based on the desired gear ratio. This dynamic control enables versatile speed ratios while simplifying operations through intuitive engagement mechanisms.
2Adaptability or versatility
If axial pawls are opened and closed to achieve different gear ratios, then speed ratios greater than 1 can be obtained, but the control becomes difficult and the mechanism is vulnerable to damage
Solution Approach 1:
The control pawls are designed with spring-loaded mechanisms that provide cushioning during engagement. The springs absorb shock and reduce impact forces when pawls engage with sun gears, preventing mechanism damage while maintaining reliable operation across different speed ratios.
Solution Approach 2:
The control pawls are designed to automatically engage and disengage through spring mechanisms and geometric constraints, reducing the need for complex manual control. The system self-regulates the engagement process, improving reliability by eliminating human error in control operations.
3Adaptability or versatility
If control pawls are closed in reverse direction during gear shifting, then gear ratio changes can be achieved, but the operation becomes labor-intensive and complex
Solution Approach 1:
The patent inverts the traditional control pawl design by making the pawls movable and spring-loaded rather than fixed. This inversion allows the pawls to be engaged in the same rotational direction as the gear shifting operation, eliminating the need for reverse direction control and significantly improving ease of operation.
Data Source
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AI summary
A bicycle gear hub (100) includes an axle (110), planetary gear modules (120, 130), one-way clutches (140, 150) and a shift mechanism (170). The planetary gear modules (120, 130) are connected in series at the axle (110). The shift mechanism (170) includes a shift actuator (172) and control pawls (174, 176) movably disposed at different positions of the axle (110). The shift actuator (172) includes recess portions (112, 114) to control opening and closing of a control protrusion (174C, 176C) of one control pawl (174, 176), and further to control a sun gear (126, 136) of the corresponding planetary gear module (120, 130) to the axle (110). When a high gear is shifted to a low gear, a rotational direction of the shift actuator (172) is identical to a rotational direction for closing the control pawl (174, 176).