Bicycle Transmission Shared Carrier Design

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Solution Overview

Problem

Existing bicycle transmissions with complex designs and multiple series-connected planetary gears require high assembly effort and are costly, making them difficult to assemble and maintain.

Innovation Solution

A simplified transmission design featuring a first and second planetary gear set with a shared carrier, eliminating the need for stepped planetary gears, and utilizing four shift elements to achieve a 4-speed configuration suitable for bicycles, with optional integration of an electric machine for assistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If three series-connected planetary transmissions with seven gear planes are used, then a speed increasing ratio is achieved, but the design becomes complex and assembly effort becomes very high

Engineering Contradiction:

Improvespeed increasing ratioVSAvoidtransmission design complexity

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent merges multiple planetary gear functions into a single integrated planetary transmission unit. Instead of using three separate series-connected planetary transmissions, the invention combines the gear planes and planetary gears into one unified structure that achieves the same speed increasing ratio with significantly reduced complexity and assembly requirements

Inventive Principle:

Principle #5Merging (Combining)

2Power

If three series-connected planetary transmissions with seven gear planes are used, then a speed increasing ratio is achieved, but the number of parts increases and assembly becomes time-consuming

Engineering Contradiction:

Improvespeed increasing ratioVSAvoidassembly speed

Core Design Contradiction:

PowerVSProductivity

Solution Approach 1:

The patent consolidates seven separate gear planes into a single integrated planetary transmission structure. This merging reduces the total number of parts that need to be assembled and eliminates the need for complex series connections, thereby significantly improving assembly speed and productivity while maintaining the required speed increasing ratio

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If multiple stepped planetary gears are used, then gear ratio variation is achieved, but manufacturing costs and assembly complexity increase

Engineering Contradiction:

Improvegear ratio variationVSAvoidmanufacturing cost and assembly ease

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent employs dynamically selectable gear planes within the integrated planetary transmission. Instead of using multiple stepped planetary gears with fixed differentials, the invention allows for dynamic engagement and disengagement of different gear planes during operation, achieving gear ratio variation while maintaining a simpler, more cost-effective manufacturing and assembly process

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11649009B2Transmission for a bicycle

Publication Date: 2023.05.16 ZF FRIEDRICHSHAFEN AG

AI summary

A transmission for a bicycle includes at least four shift elements, one input shaft (1), a first planetary gear set (PS1) which is operatively connected to the input shaft (1), and a second planetary gear set (PS2). A carrier of the first planetary gear set is rotationally fixed to a carrier of the second planetary gear set (PS2).