Bicycle Rear Hub Torque Detection via Magnetostriction
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Solution Overview
Problem
The existing rear bicycle hubs face challenges in accurately measuring driving force due to the direct adhesion of strain gauges, which is affected by the accuracy of assembly.
Innovation Solution
A rear bicycle hub design incorporating a magnetostrictive element and a detection coil in the driving force transmission path, allowing for non-contact detection of torque changes, thereby reducing the impact of assembly accuracy. The detection coil can be positioned on the hub spindle, attachment member, or hub shell, and the system may include a wireless transmitter and power supply for efficient data transmission and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauge is affixed directly to the coupling part, then driving force can be measured, but measurement precision deteriorates due to assembly accuracy requirements
Solution Approach 1:
The patent replaces the mechanical adhesion-based strain gauge system with a magnetostrictive sensing system. The magnetostrictive element detects torque through magnetic field changes caused by twisting, eliminating the need for direct mechanical adhesion and associated assembly precision requirements.
Solution Approach 2:
The magnetostrictive element acts as an intermediary between the mechanical torque and the detection coil. Instead of directly measuring mechanical deformation through adhesion, the system uses magnetic permeability changes as an intermediate phenomenon to transmit torque information to the detection coil non-contactly.
2Reliability
If strain gauge is affixed directly to the coupling part, then driving force can be measured, but reliability deteriorates due to adhesive uniformity requirements
Solution Approach 1:
The patent eliminates the adhesive-based mechanical attachment system by using a magnetostrictive sensing mechanism. The magnetostrictive element is coupled to the drive part through mechanical connection rather than adhesion, and detection occurs through magnetic field interaction, removing reliability concerns related to adhesive uniformity.
Solution Approach 2:
The magnetic field serves as an intermediary that transmits torque information without requiring direct physical contact or adhesion between the sensing element and the drive part, thereby eliminating reliability issues associated with adhesive bonding.
3Ease of operation
If detection coil is installed on the rotating hub shell, then driving force can be detected, but device complexity increases due to signal routing requirements
Solution Approach 1:
Instead of placing the detection coil on the rotating hub shell as in conventional designs, the patent inverts the arrangement by placing the detection coil on the stationary hub spindle. This allows the coil to remain stationary while still detecting the magnetic field changes from the rotating magnetostrictive element, simplifying signal routing.
Solution Approach 2:
The patent creates a stationary copy of the detection function on the hub spindle rather than moving the detection coil with the rotating hub shell. This stationary detection point simplifies the overall system architecture and signal routing while maintaining full detection 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
This design enables accurate and reliable measurement of driving force in a manner unaffected by assembly accuracy, with the non-contact detection method and wireless transmission providing enhanced reliability and ease of use.
Implementation Method 1
the magnetic permeability of the magnetostrictive element disposed to the driving force transmission path changes in a manner reflective of torque that is generated on the driving force transmission path, in response to the driving force
Implementation Method 2
The inductance of the detection coil changes due to change in the magnetic permeability of the magnetostrictive element. The driving force can be measured by detecting the change in inductance of the magnetostrictive element, as an electrical signal
Data Source
AI summary
A bicycle rear hub includes a hub spindle, a drive part, a hub shell and a driving force measuring part. The drive part is rotatably supported on the hub spindle, and configured to receive a driving-force-input member. The hub shell is rotatably supported on the hub spindle and operatively coupled to the drive part for rotation by the drive part on the hub spindle. The driving force measuring part includes a magnetostrictive element disposed in a driving force transmission path between the drive part and the hub shell, and a detection coil disposed in opposition to the magnetostrictive element.