Bicycle Chainring Tooth Layout for Rough-Terrain Chain Guidance

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Managing chain engagement and tension in bicycle drivetrain systems, especially over rough terrain, is challenging due to potential chainring contact with the bicycle frame, leading to damage and inefficiencies in propulsion.

Innovation Solution

A solitary chainring design with alternating groups of teeth, featuring protrusions, chamfers, and recesses to guide and maintain the chain effectively, ensuring secure engagement and reduced frame deformation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional chainring design is used, then the structure is simple, but the chain engagement is unreliable and frame damage occurs over rough terrain

Engineering Contradiction:

Improvechain engagement reliabilityVSAvoidchainring structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The chainring teeth are segmented into two distinct groups: first group teeth with outboard protrusions and second group teeth without protrusions. This segmentation allows different tooth types to perform different functions - the protruding teeth engage and guide the chain while the non-protruding teeth provide structural support, improving chain engagement reliability without requiring a completely complex redesign

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the chainring teeth are given different local qualities through the protrusion feature. The outboard side of first group teeth has enlarged protrusions that create cross-shaped cross sections, providing enhanced chain guidance and engagement at specific locations, while other regions maintain simpler geometries for structural integrity

Inventive Principle:

Principle #3Local quality

2Ease of operation

If the chainring teeth are made with uniform structure, then manufacturing is simple, but chain guidance and engagement are insufficient

Engineering Contradiction:

Improvechain guidanceVSAvoidtooth structure manufacturing

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The tooth structure incorporates local quality variations through protrusions on the outboard side of first group teeth. These protrusions create cross-shaped cross sections that provide superior chain guidance and engagement characteristics at critical locations, while the rest of the tooth structure maintains manufacturable geometries

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The alternating pattern of protruding and non-protruding teeth segments the chain engagement function across different tooth types, allowing the chain to be guided and retained through a series of localized features rather than requiring complex overall tooth geometry

Inventive Principle:

Principle #1Segmentation

3Productivity

If the chainring is positioned close to the chain stay, then the drivetrain is compact, but frame deformation and damage occur under high loads

Engineering Contradiction:

Improvedrivetrain compactnessVSAvoidframe deformation

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The protrusions on the first group teeth create preliminary engagement features that guide the chain onto the chainring teeth before full load is applied. This preliminary action ensures proper chain positioning and reduces the likelihood of chain derailment or frame contact under subsequent high-load conditions

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The protruding teeth act as intermediaries between the chain and the chainring body, providing enhanced chain guidance and engagement. This intermediary function ensures reliable chain retention that prevents chain derailment and subsequent contact between the chainring and chain stay under high loads

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP3072799B1chainring

Publication Date: 2023.11.08 SRAM LLC

Figure 1~2
Figure 3
Figure 4

AI summary

A solitary chainring (50) of a bicycle front crankset for engaging a drive chain (10), including a plurality of teeth (52) formed about a periphery of the chainring, the plurality of teeth (52) consisting of an even number. The plurality of teeth (52) includes a first group of teeth (58) and a second group of teeth (60) arranged alternatingly between the first group of teeth. The first group of teeth (58) and the second group of teeth (60) are equal in number. Each of the first and second group of teeth include an outboard side (54) and an inboard side (56) opposite the outboard side and each tooth of the first group of teeth (58) includes at least a first protrusion on the outboard side thereof and each tooth of the second group of teeth (60) are free of the first protrusions on the outboard side and the inboard side.