Bicycle Bottom Bracket Torque Sensing With Optical Torsion Detection
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Solution Overview
Problem
Existing bicycle bottom bracket torque sensor arrangements are complex and costly to produce, making them impractical for widespread adoption in pedelecs.
Innovation Solution
A simplified torque sensor arrangement using a bottom bracket shaft with a torsion shaft and a reference arm, combined with an optically detectable reference scale and a digital camera or position sensor, allows for cost-effective detection of torque without requiring complex magnetic field detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic field sensor and magnetized hollow torsion shaft are used for torque detection, then torque measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces the magnetic field-based detection system with an optical detection system. Instead of using a magnetized hollow torsion shaft and magnetic field sensor, the invention uses an optically detectable reference scale attached to the torsion shaft and a digital camera or optical position sensor to detect the rotation angle. This substitution of mechanical/magnetic components with optical components simplifies the device structure while maintaining measurement precision.
Solution Approach 2:
The patent uses an optically detectable reference scale that creates a visual pattern (copy of the rotation angle) which can be detected by the digital camera. The reference scale acts as a simplified representation of the torsion shaft's angular position, allowing optical detection without complex magnetic field interactions.
2Measurement precision
If a magnetic field sensor and magnetized hollow torsion shaft are used for torque detection, then torque measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive magnetic field sensors and magnetized components with more cost-effective optical components. The digital camera or optical position sensor combined with a simple optically detectable reference scale provides a lower-cost alternative to precision magnetic field detection systems, while maintaining the ability to accurately measure torque through optical angle detection.
Solution Approach 2:
The optically detectable reference scale can be implemented as a simple, inexpensive component that may be a printed pattern or attached marker, replacing expensive magnetic encoding structures. This approach uses cheaper materials and manufacturing processes while achieving the same functional goal of encoding angular position information.
3Reliability
If multiple torsion sensors are distributed over the circumference, then continuous torque detection during complete revolution is improved, but device complexity increases
Solution Approach 1:
The patent uses a single digital camera or optical position sensor that can detect the reference scale at any angular position of the torsion shaft. This single sensor provides universal detection capability throughout the complete revolution, replacing the need for multiple distributed sensors. The optical system maintains continuous detection capability while using fewer components.
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
Enables accurate and efficient detection of torque for controlling electric drive support, reducing production costs while maintaining precision and functionality.
Implementation Method 1
In principle, the reference indicator, the reference scale and the position sensor can be physically configured so that, for example, a magnetic/inductive detection of the position of the reference indicator in relation to the reference scale is carried out. The reference scale of some embodiments is in the form of an optically detectable reference scale and the position sensor is a digital camera.
Data Source
AI summary
A bicycle bottom bracket arrangement (10) has a bottom bracket shaft (21) and at least one pedal crank (24) connected in a rotationally secure manner to the bottom bracket shaft (21). The bicycle bottom bracket arrangement (10) also has a torque sensor (30) with a torsion shaft (32) that is driven by the bottom bracket shaft (21) at an introduction location (E) of the torque sensor (30). An output shaft (40) is driven by the torsion shaft (32) at an output location (A) that is remote from the introduction location (E). A reference arm (39) is fixed at the introduction location (E) and has an indicator (38) that refers to a reference scale (66; 66′) associated with the torsion shaft at the output location (A) in a rotationally secure manner. A stationary electric torsion sensor detects the position of the reference indicator (38) in relation to the reference scale.