Bicycle Hub Torque Sensor With Flexible Ribs for Power Measurement
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Solution Overview
Problem
There is a need for a torque-measuring device that can be inserted between an inner shaft or hub and an outer structure to measure torque between a sprocket-cassette or sprocket and the hub of a driven bicycle wheel, as existing technologies do not effectively address this application.
Innovation Solution
A torque-measuring apparatus comprising a sprocket cassette holder with flexible ribs that connect an outer tubular structure to an inner tubular structure, allowing for rotational displacement measurement between chain-driven sprockets and a hub, using a rotational-displacement-measurement device to measure applied torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque-measuring device is inserted between the sprocket-cassette and hub, then torque measurement capability is improved, but device complexity increases
Solution Approach 1:
The torque-measuring apparatus is divided into separate components: an outer tubular structure that fits over the sprocket-cassette and an inner tubular structure that fits over the hub, connected by flexible ribs. This segmentation allows the device to be installed without replacing the entire drivetrain system, reducing overall system complexity while maintaining measurement capability.
Solution Approach 2:
The flexible ribs act as intermediary elements that transmit torque from the outer tubular structure to the inner tubular structure while allowing for elastic deformation. This intermediary mechanism enables torque measurement through elastic deflection without requiring direct coupling between the sprocket-cassette and hub, simplifying the measurement principle.
2Measurement precision
If flexible ribs are used to connect outer and inner tubular structures, then torque measurement accuracy is improved, but manufacturing precision requirements increase
Solution Approach 1:
The flexible ribs are designed with specific geometric parameters (cross-sectional shape, thickness, length) that determine their elastic properties. By carefully selecting these parameters, the ribs can be made from standard materials and manufacturing processes while achieving the required measurement accuracy through controlled elastic deformation under torque load.
Solution Approach 2:
The flexible ribs can be constructed from composite materials or materials with tailored mechanical properties that provide both the necessary flexibility for torque measurement and sufficient strength to withstand drivetrain loads. This allows for manufacturing with standard tolerances while maintaining measurement precision.
3Measurement precision
If a rotational-displacement-measurement device is added to measure angular displacement, then torque measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical torque measurement mechanisms (such as strain gauges, torque tubes, or bending beams) with a simpler system based on rotational displacement measurement. By measuring the angular displacement of the inner tubular structure relative to the outer structure and using the known elastic properties of the flexible ribs, torque can be calculated without requiring complex mechanical sensing elements.
Solution Approach 2:
The flexible ribs serve as a mechanical intermediary that converts torque application into measurable rotational displacement. This allows the use of simple angular position sensors rather than complex torque sensors, reducing device complexity while maintaining measurement capability.
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 apparatus effectively measures torque between the sprocket-cassette and the hub, providing accurate power measurement data to the rider through a bicycle computer display.
Implementation Method 1
a plurality of ribs configured to connect the first tubular structure to the second tubular structure such that the second outer tubular structure and the first inner tubular structure are configured to rotate relative to each other about the central axis of rotation
Data Source
Figure 1A~1D
Figure 1E~1H
Figure 1J~1i1
AI summary
A torque-measurement device that has a rotational axis, and wherein the torque-measurement device includes an inner tubular structure, an outer tubular structure, and a plurality of ribs that each have a length dimension in a rib-length direction parallel to the rotational axis, a rib-width dimension in a width direction perpendicular to the length direction and extending radially rotational axis, and a minimun rib-thickness dimension in a thickness direction perpendicular to the length direction and perpendicular to the width direction, wherein the length dimension is greater than the width dimension and the width dimension is greater than the thickness dimensions, wherein each of the plurality of ribs has a center plane that lies in the rib-length direction and the rib-width direction, and wherein a torque applied between the inner tubular structure and the outer tubular structure results in an angular displacement of inner tubular structure relative to the outer tubular structure.