Bicycle Hub Gear Compact Design via Planetary Extraction
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Solution Overview
Problem
Existing bicycle hub gears for mountain and trekking bikes face challenges such as large space requirements, high weight, complex mechanisms, and limited gear spread due to the use of multiple chainrings and pawls, making them unsuitable for compact and lightweight designs.
Innovation Solution
A bicycle hub transmission system featuring a multi-speed gearbox with axial teeth and spring elements that function as freewheels, allowing for compact design and reduced weight by eliminating the need for pawls and providing a large gear spread with a three-speed planetary gear, enabling efficient power transmission and freewheeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three chainrings are provided to achieve a large gear spread, then the gear range is increased, but the space required at the bottom bracket area increases significantly
Solution Approach 1:
The invention extracts the multiple chainring system from the bottom bracket area and replaces it with a single chainring combined with a planetary gear mechanism in the rear hub. This removes the space-consuming multi-chainring arrangement while preserving the gear spread functionality through the planetary gear's multiple gear ratios.
Solution Approach 2:
The planetary gear mechanism employs a nested structure where planet gears are arranged around a sun gear, and the entire planetary mechanism is contained within the rear hub assembly. This nesting allows multiple gears to occupy a compact space, achieving high gear density without increasing the bottom bracket area.
2Adaptability or versatility
If three chainrings are provided to achieve a large gear spread, then the gear range is increased, but the device weight increases
Solution Approach 1:
The invention merges the functions of multiple chainrings and the rear derailleur into a single integrated planetary gear mechanism. By combining these separate components into one unified system in the rear hub, the total weight is reduced while maintaining the capability for multiple gear ratios.
Solution Approach 2:
The planetary gear mechanism serves multiple functions simultaneously: it provides the gear multiplication effect of multiple chainrings, incorporates the shifting mechanism, and includes the freewheel function. This multi-functionality eliminates the need for separate components, reducing overall system weight.
3Ease of operation
If multiple pawls are used for shifting between different gear ratios, then the gear changing capability is achieved, but the mechanism complexity increases significantly
Solution Approach 1:
The invention extracts the complex multi-pawl shifting mechanism and replaces it with a simplified single-pawl design that acts on the planetary gear's sun gear or planet carrier. This single pawl controls the engagement between different gear elements, achieving gear shifting without requiring multiple pawls and their associated complex actuation mechanisms.
4Ease of operation
If a conventional rear derailleur is used with a Hammerschmidt gear, then the sprocket shifting is achieved, but the overall device weight and space requirements increase
Solution Approach 1:
The invention merges the rear derailleur function directly into the planetary gear mechanism by integrating the shifting pawl and actuation system within the hub assembly. This integration eliminates the need for a separate rear derailleur component, reducing weight and space while maintaining sprocket shifting capability through the planetary gear's inherent design.
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
The solution achieves a compact and lightweight design with a large gear spread, reducing weight to less than 1 kg, including the sprocket cassette, and simplifying gear shifting while maintaining low resistance and efficient power transmission.
Implementation Method 1
at least one spring element is also provided, by which the engaged axial toothings are held in engagement. The spring element and the engaged axial teeth are designed in such a way that they also act as a freewheel
Data Source
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AI summary
The bicycle hub gear has a drive element (12) and an output element (62), where a multi-speed gear mechanism is arranged between the drive element and output element. A transmission element (14,16) is equipped, which slides axially in different transmission positions. The transmission element transmits power from the drive element to the output element through different gear wheel groups.