E-bike Bottom Bracket Bearing Torque Measurement
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Solution Overview
Problem
Existing systems for determining torque on a shaft in muscle-powered vehicles with electric assistance face measurement deviations due to non-concentric orientations and coaxiality errors between the shaft and sensors, leading to inaccurate torque detection.
Innovation Solution
A bottom bracket bearing with a torsion element connected to the shaft, featuring measuring triggers on both sides to detect deformation through precise time measurement, allowing for accurate calculation of torque by determining the time difference and rotational speed, thereby improving measurement resolution and driving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is arranged outside the shaft with a sensor holder to measure the magnetic field, then the torque can be determined using magnetostriction effects, but static measurement deviations occur due to non-constant distance or air gap between the sensor and shaft
Solution Approach 1:
A magnetically conductive shaft extension is introduced as an intermediary between the torsion element and the sensor. This extension serves as a magnetic field mediator that transmits the magnetic field changes from the torsion element to the sensor, ensuring a constant magnetic coupling path and eliminating measurement deviations caused by variable air gaps.
Solution Approach 2:
The patent replaces direct mechanical contact or complex mechanical positioning systems with a magnetic field-based measurement system. The magnetostriction effect in the shaft extension allows torque measurement through magnetic field changes rather than mechanical sensor contact, simplifying the system while improving reliability.
2Ease of operation
If the shaft and sensor are not oriented relative to each other in a constant concentric manner, then the sensor can be positioned outside the shaft, but dynamic errors occur that negatively affect the sensor signal and evaluation
Solution Approach 1:
The magnetically conductive shaft extension acts as a mediator that decouples the sensor positioning from the shaft orientation requirements. It maintains a constant magnetic coupling path even when the sensor and shaft are not perfectly concentric, thereby preserving measurement precision while allowing operational flexibility.
Solution Approach 2:
The patent changes the measurement parameter from direct physical distance or angular position to magnetic field intensity. By measuring magnetic field changes in the shaft extension rather than physical displacements, the system becomes insensitive to concentricity errors and orientation variations.
3Measurement precision
If measuring triggers are positioned on both drive side and driven side of the torsion element, then high measurement resolution is achieved through precise time measurement, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical deformation measurement systems with a time-based measurement approach using magnetic triggers. By measuring the time difference for magnetic field changes to propagate through the torsion element, the system achieves high measurement resolution with simpler electronic timing circuits rather than complex mechanical sensors.
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 provides high measurement resolution, enhancing driving comfort and efficiency by precisely adapting motor support to the driving situation, particularly in sporting applications, and enabling effective energy recovery during braking.
Implementation Method 1
a deformation of the torsion region is detected during loaded operation by means of a precise time measurement
Implementation Method 2
The resulting time difference, together with the determined rotational speed (cadence), forms an indication of the present deformation of the torsion region
Data Source
AI summary
Bottom bracket bearing (40), with a bottom bracket bearing shaft (42), a torsion element (44) connected on the driving side to the bottom bracket bearing shaft (42) for conjoint rotation and having a torsion region (50) bounded by a driving-side end (46) and a driven-side end (48), and measurement elements (52, 54, 56, 58) which are designed to measure a time difference, resulting from a deformation of the torsion region (50) in the rotation load mode, between driven-side end (48) and driving-side end (46).