Bicycle Crank Arm Sensor System Using Magnetic Flux Detection
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Solution Overview
Problem
Existing crank arm designs with strain gauges for detecting pedaling force require high accuracy installation, increasing manufacturing costs and time, and existing sensing arrangements are not efficient in accurately measuring pedaling force.
Innovation Solution
A crank arm design featuring a sensor support member with strain sensors mounted within a cavity of the crank body, which deforms upon pedaling force application, allowing for accurate measurement of pedaling force through a combination of strain gauges and semiconductor sensors, and an electric amplifier for signal amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are installed on the crank arm to detect pedaling force, then measurement precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces the traditional strain gauge installation method with a magnetic field-based detection system. A permanent magnet is embedded in the crank arm, and a magnetic sensor detects changes in magnetic flux as the crank arm deforms under pedaling force. This substitution eliminates the need for complex strain gauge installation while maintaining measurement precision, thereby reducing manufacturing complexity.
Solution Approach 2:
The patent introduces a permanent magnet as an intermediary between the crank arm structure and the detection system. The magnet converts mechanical deformation of the crank arm into changes in magnetic flux, which can be easily detected by magnetic sensors. This intermediary approach simplifies the overall system while improving measurement accuracy.
2Measurement precision
If strain gauges are installed on the crank arm to detect pedaling force, then measurement precision is improved, but manufacturing time increases
Solution Approach 1:
The patent replaces the time-consuming strain gauge installation process with a magnetic field-based detection system. The permanent magnet is embedded during crank arm manufacturing, and the magnetic sensor is mounted on the crank arm housing, eliminating the need for precise strain gauge installation and reducing manufacturing time significantly.
Solution Approach 2:
The permanent magnet is embedded in the crank arm during the manufacturing process itself, before the crank arm is assembled. This preliminary action ensures that the magnetic field detection capability is built into the crank arm structure, eliminating the need for separate sensor installation steps and reducing overall manufacturing time.
3Measurement precision
If high accuracy strain gauge installation is required, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent replaces the difficult strain gauge installation process with a magnetic field-based system. The permanent magnet is embedded in the crank arm using standard manufacturing techniques, and the magnetic sensor is simply mounted on the crank arm housing. This eliminates the need for precise alignment and complex installation procedures, significantly improving ease of manufacture.
Solution Approach 2:
The magnetic field detection system is designed to be self-aligning. The permanent magnet is fixed in the crank arm, and the magnetic sensor automatically detects changes in magnetic flux as the crank arm deforms. This self-service approach eliminates the need for complex alignment procedures and makes the system easy to manufacture and install.
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 enhances the accuracy and efficiency of pedaling force measurement, reducing manufacturing complexity and costs while providing reliable data for bicycle operation and user feedback.
Implementation Method 1
at least one strain sensor is disposed on the sensor support member
Implementation Method 2
an electric amplifier for signal amplification
Data Source
AI summary
A crank arm is provided that includes a crank body, a sensor support member and at least one sensor. The crank body has an axle mounting portion. The sensor support member is member attached to the crank body, and has an axle support portion that is configured to support an axle. The at least one strain sensor is disposed on the sensor support member.