Planetary Bicycle Gear Hub With Low-Resistance Downshifting

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Solution Overview

Problem

Existing bicycle gear hubs face complexity and potential damage during gear shifting, particularly when switching from high to low gear, due to intricate mechanisms and reverse control pawl operations, which complicate the process and increase labor requirements.

Innovation Solution

A bicycle gear hub design featuring a series of planetary gear modules, one-way clutches, and a shift mechanism with a shift actuator and control pawls, where the shift actuator's rotational direction aligns with the control pawl closure direction when shifting from high to low gear, allowing the fastest planetary gear module to be closed first, reducing resistance and labor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If traditional control pawl mechanisms are used to switch between high and low gear, then gear shifting can be achieved, but the operational complexity increases and potential damage occurs due to reverse control pawl operations

Engineering Contradiction:

Improvegear shifting operationVSAvoidcontrol mechanism complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent inverts the traditional control pawl mechanism by using a control cam with eccentric lobes instead of pawls that must open and close. The cam's eccentric shape automatically engages and disengages the sun gear from the axle through rotational motion, eliminating the need for reverse operations and reducing mechanical complexity.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent replaces the mechanical control pawl system with a cam-based mechanical system. The control cam converts rotational motion into the required engagement and disengagement actions, simplifying the control mechanism and eliminating the complexity of coordinating multiple pawl operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If multiple axial pawls are used to provide different speed ratios, then versatile gear ratios are achieved, but the operational difficulty increases when determining which pawl to open or close

Engineering Contradiction:

Improvegear ratio versatilityVSAvoidpawl control operation

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent segments the control function by providing a separate control cam for each planetary gear module. Each cam is independently responsible for controlling the engagement of its corresponding sun gear, allowing simple rotational control to achieve different gear ratios without the complexity of coordinating multiple pawls.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control cam acts as an intermediary between the shift actuator and the sun gear engagement. The cam's eccentric lobes translate the simple rotational input into the complex engagement and disengagement motions required, making the system easier to operate while maintaining versatility.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If control pawls are opened and closed during gear shifting, then speed ratio changes are achieved, but the mechanism becomes vulnerable to damage

Engineering Contradiction:

Improvespeed ratio adjustmentVSAvoidmechanism durability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

Instead of using control pawls that must open and close (prone to damage), the patent uses a control cam with eccentric lobes that continuously rotates. The cam's shape automatically provides engagement and disengagement without requiring the control element to open or close, reducing mechanical stress and improving reliability.

Inventive Principle:

Principle #13The other way round (Inversion)

4Ease of operation

If the shift actuator rotates in reverse direction to close control pawls, then gear shifting is achieved, but the labor and complexity increase

Engineering Contradiction:

Improvegear shifting easeVSAvoidcontrol direction complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent inverts the control mechanism so that a single rotational direction of the shift actuator controls all gear changes. The eccentric cam lobes are shaped so that rotation in one direction sequentially engages different sun gears, eliminating the need for reverse rotation and simplifying the control operation.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11904981B2Bicycle gear hub

Publication Date: 2024.02.20 SUN RACE STURMEY ARCHER

AI summary

A bicycle gear hub includes an axle, planetary gear modules, one-way clutches and a shift mechanism. The planetary gear modules are connected in series at the axle. The shift mechanism includes a shift actuator and control pawls movably disposed at different positions of the axle. The shift actuator includes recess portions to control opening and closing of a control protrusion of one control pawl, and further to control a sun gear of the corresponding planetary gear module to the axle. When a high gear is shifted to a low gear, a rotational direction of the shift actuator is identical to a rotational direction for closing the control pawl.