Electric Bicycle Crankshaft Torque Sensor Mounting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing electric bicycle designs face issues with accurately detecting human pedal force due to bending moments affecting the crankshaft and torque detection cylinder, leading to potential damage and deformation, and increased manufacturing costs due to unconventional frame structures and limited space for torque sensor components.
Innovation Solution
The design includes a crankshaft and torque detection cylinder within a hanger with an engaging portion between the crankshaft and torque detection cylinder positioned at the intermediate portion between bearings, utilizing a tubular member or serration extended portion to regulate axial movement and increase bending strength, while maintaining a conventional frame structure and using a metallic inner cylinder to protect the torque sensor from external elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the torque sensor is disposed at the front of the motor unit below the hanger to detect force transmitted from the crankshaft to the crank gear, then the pedal force can be measured in a relatively satisfactory manner, but the frame structure becomes different from a typical bicycle, leading to uncomfortable feeling and higher manufacturing cost
Solution Approach 1:
The torque sensor is extracted from the motor unit and integrated directly into the hanger body. This separates the torque detection function from the motor mounting structure, allowing the use of a conventional bicycle frame while maintaining accurate pedal force measurement capability.
Solution Approach 2:
The torque sensor is merged with the hanger structure, combining two previously separate components (hanger and torque sensor housing) into a single integrated unit. This simplifies the overall structure and reduces manufacturing complexity while preserving measurement accuracy.
2Device complexity
If the crankshaft and torque detection cylinder are engaged via an engaging portion near the bearing location to dispose the torque sensor component on the outer surface, then the structure is compact, but the crankshaft is subjected to considerable bending moment, causing potential damage and deformation
Solution Approach 1:
The engaging portion is repositioned from a location near the bearing (radial/axial proximity) to the intermediate portion between bearings, utilizing the longitudinal dimension of the crankshaft. This spatial redistribution reduces the bending moment arm while maintaining structural compactness.
Solution Approach 2:
The tubular member is introduced as an intermediary component between the crankshaft and the second bearing. This mediator regulates axial movement of the bearing and provides additional structural support, distributing the bending moment and protecting the crankshaft from excessive stress.
3Ease of operation
If the hanger and lower pipe are located as in a typical bicycle to allow easy foot movement, then the rider can easily get on and off, but the crankshaft cannot be considerably increased in diameter due to limited hanger space, increasing bending moment influence
Solution Approach 1:
The crankshaft is segmented into multiple functional zones: the intermediate portion between bearings houses the engaging portion for the torque detection cylinder, while other portions maintain standard dimensions. This segmentation allows optimized local geometry without increasing overall crankshaft diameter, preserving ease of mounting while reducing bending moment effects.
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 configuration effectively minimizes bending moment influence on the crankshaft, prevents damage and deformation, maintains high stiffness, and reduces manufacturing costs by allowing the use of conventional torque sensor sizes, while ensuring reliable and efficient pedal force detection and protection from rain and noise.
Implementation Method 1
a magnetostriction portion of a torque sensor is disposed on the outer periphery of the torque detection cylinder
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is an electric bicycle that can properly detect a human driving force as a rotary force according to a pedal force and prevent damage and deformation on a crankshaft. Engaging portions 17Aba and 24a between a crankshaft 17 and a torque detection cylinder 34 are disposed at the intermediate portion between a first bearing 29A near a crank gear that rotatably supports the crankshaft 17 and a second bearing 29B opposite to the crank gear, and a tubular member 40 is fit onto a point between a portion supported by the second bearing 29B on the crankshaft 17 and the engaging portions 17Aba and 24a. The tubular member 40 is brought into contact with the second bearing 29B and regulates an axial movement of the second bearing 29B to the engaging portions 17Aba and 24a.