Pawl Freewheel Ring Segmentation for Accurate Bicycle Torque Measurement
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Solution Overview
Problem
Existing bicycle drive arrangements face challenges in accurately measuring drive power due to interference variables caused by manufacturing tolerances, wear, and relative positions of components, leading to inaccuracies in recorded deformations and transmitted torque.
Innovation Solution
A drive arrangement featuring a jack freewheel with a first and second ring, where the second ring has an integration and the first ring has movable clinks, along with a sensor device that records deformations of the first ring to accurately measure drive power and torque, while compensating for interference variables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a freewheel is used to transmit drive force, then the drive force can be transmitted from the pedal crankshaft to the wheel, but disturbances occur due to radial forces and manufacturing tolerances that deform the freewheel and cause inaccurate deformation detection
Solution Approach 1:
The freewheel is divided into two separate rings: a first ring connected to the pedal crankshaft and a second ring connected to the output shaft. The pawls are mounted on the first ring and engage with the second ring. This segmentation allows the sensor device to measure deformations of the first ring independently, separating the measurement function from the torque transmission function and eliminating interference from radial forces and manufacturing tolerances.
Solution Approach 2:
The first ring serves as an intermediary element between the pedal crankshaft and the pawls. The sensor device detects deformations of this intermediary first ring, which accurately reflect the applied torque without being influenced by the engagement disturbances between pawls and the second ring. This intermediary structure enables precise measurement while maintaining reliable torque transmission.
2Force
If pawls are engaged with toothing in the locked state, then torque can be transmitted, but radial forces act on the freewheel causing deformation that does not directly correspond to transmitted drive force
Solution Approach 1:
By segmenting the freewheel into two separate rings with distinct functions, the first ring is dedicated to torque transmission while the second ring handles engagement with the pawls. This separation ensures that radial forces and engagement disturbances act on the second ring and do not interfere with the deformation measurements of the first ring, allowing accurate torque measurement despite the presence of harmful radial forces.
3Ease of operation
If individual pawls engage differently with toothing due to manufacturing tolerances and wear, then the freewheel can operate, but disturbances occur that do not directly correspond to transmitted drive force
Solution Approach 1:
The segmentation of the freewheel into two rings allows the measurement function to be isolated on the first ring. Variations in pawl engagement with the second ring due to manufacturing tolerances and wear do not affect the deformation measurements of the first ring, as the first ring's deformations directly correspond to the applied torque on the pedal crankshaft regardless of engagement conditions.
Solution Approach 2:
The sensor device continuously monitors deformations of the first ring and provides feedback about the transmitted torque. This feedback mechanism enables accurate measurement of drive force by focusing on the deformations of the first ring, which are directly caused by the applied torque and not influenced by variations in pawl engagement with the second ring.
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 enables precise measurement of drive power and torque by accurately recording deformations, thereby improving the control of the drive arrangement and allowing for more efficient operation and maintenance.
Implementation Method 1
a sensor device (28) which is designed to detect a deformation of the first ring (20) caused by an applied drive force
Data Source
Figure 1~2
Figure 3~5
AI summary
The invention relates to a drive arrangement for a bicycle, wherein the drive arrangement comprises a pawl freewheel (14). The pawl freewheel (14) has a first ring (20) with pawls (24) movably mounted thereon and a second ring (22) with a toothed section (26). Furthermore, the drive arrangement comprises at least one sensor device configured to detect deformation of the first ring (20) of the pawl freewheel (14) due to an applied drive force. The sensor device has an associated deformation sensor (28) for each pawl (24). The invention also relates to a method and a bicycle.