Threaded Front Chainring Assembly for Easy Alignment and Power Meter Stability
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Solution Overview
Problem
Existing bicycle power meter devices face challenges when used with different chainrings, as the interface can result in changes to the zero-offset value of torque measurements, and multi-start threaded interfaces can be difficult to align.
Innovation Solution
A front chainring assembly with a chainring carrier and a chainring structure featuring blunt thread starts and axial projections/recesses, allowing for easy alignment and installation, and minimizing zero-offset changes when used with a power meter device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a multi-start threaded interface is used between the chainring structure and power meter device, then the chainring can be securely attached to the power meter device, but it becomes difficult to align the individual threads at the same time to initiate threading
Solution Approach 1:
The patent applies preliminary action by providing alignment features (such as alignment keys or keyed interfaces) that pre-align the multi-start threads before the threading operation begins. This allows the threads to be properly positioned relative to each other, making it easy to initiate threading while maintaining the secure attachment capability of the multi-start interface.
2Ease of repair
If the chainring structure is threadably engaged with the power meter device, then the chainring can be securely attached and easily replaced, but the interface results in a change in the zero-offset value of the torque measurement
Solution Approach 1:
The patent applies parameter changes by carefully designing the threaded interface parameters (thread pitch, diameter, engagement length, and material properties) to minimize the stiffness change and resulting zero-offset shift. The interface is engineered to maintain consistent mechanical properties that preserve torque measurement accuracy while allowing easy chainring replacement.
3Strength
If traditional lugs and bolts are used to attach the chainring to the power meter device, then the attachment is secure, but the overall weight of the assembly increases
Solution Approach 1:
The patent applies the taking out principle by removing the traditional lugs and bolts from the attachment system and replacing them with a integrated threaded interface. This extraction of unnecessary components reduces the overall weight of the assembly while maintaining secure attachment through the threaded engagement between the chainring structure and power meter device.
Data Source
AI summary
A chainring assembly includes a chainring carrier adapted to be coupled to a crank arm. The chainring carrier is rotatable about a rotation axis and includes an outer periphery having carrier threads. A chainring structure includes an inner periphery having chainring threads and an outer periphery comprising a plurality of teeth. The inner periphery of the chainring structure is threadably engaged with the outer periphery of the chainring carrier. In one embodiment, a power meter device includes a body having a torque input section and a torque output section, with the torque output section including an outer periphery having threads adapted to be coupled to a chainring structure.