E-Bike Motor Unit Torque Sensing With Integrated Load Cell
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor units and electrically assisted bicycles lack precise and efficient systems for measuring external forces applied to spindles, leading to inefficiencies in torque calculation and motor control.
Innovation Solution
An external force measurement unit comprising a load cell with strain gauges and an evaluation unit to measure and calculate external forces applied to a spindle, integrated with a freewheel and angular encoder for improved precision and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are arranged on flaps of the load cell to measure external forces, then measurement precision is improved, but device complexity increases due to additional components and arrangement requirements
Solution Approach 1:
The patent combines the load cell structure with the bearing support integration, where the flaps are arranged on the support ring of the load cell and strain gauges are mounted directly on these flaps. This merging of measurement and support functions reduces overall device complexity while maintaining measurement precision.
Solution Approach 2:
The offset caused by spindle weight is pre-determined and stored in the evaluation unit before actual measurements. This preliminary calibration action allows the system to automatically compensate for gravitational effects during operation, improving measurement precision without requiring complex real-time calculations or additional sensors.
2Measurement precision
If an evaluation unit is added to measure resistance changes and calculate external forces, then measurement precision improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The evaluation unit is designed to perform multiple functions: measuring resistance changes from strain gauges, determining offset values, calculating external forces, and controlling the electric motor. This multi-functionality consolidates what could be separate complex systems into a single integrated unit, balancing precision improvement with manageable complexity.
Solution Approach 2:
The patent replaces complex mechanical force measurement mechanisms with an electrical measurement system using strain gauges and an evaluation unit. This substitution simplifies the overall system architecture while achieving high measurement precision through electrical resistance changes that are easier to measure and process than direct mechanical measurements.
3Measurement precision
If the load cell support ring with flaps is used to transmit forces from the spindle, then measurement accuracy improves, but the weight of the stationary object increases
Solution Approach 1:
The load cell support ring features localized flaps with strain gauges only in the regions where force transmission and measurement are required. This local quality approach concentrates material and measurement components only where needed, rather than uniformly distributing weight throughout the entire support structure, thus improving measurement accuracy while minimizing unnecessary weight increase.
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
Enhances the accuracy of torque calculation and motor control, allowing for more precise and efficient operation of electrically assisted bicycles.
Implementation Method 1
a first strain gauge which is arranged on the first flap and a second strain gauge, which is arranged on the second flap, wherein depending on a change of length of the first flap or the second flap due to a material expand the first strain gauges and/or the second strain gauge is adapted to change their respective resistance
Implementation Method 2
change of length of the first flap or the second flap due to a material expand
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a motor unit for an electrically assisted bicycle, the motor unit having only one freewheeling device, and to an electrically assisted bicycle.