E-bike Driving Unit Rotation Detection Resolution
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Solution Overview
Problem
Existing electric assist bicycles face limitations in increasing the detection resolution of the rotation detection device, which is essential for accurate pedaling monitoring and assistance, due to the constraints of cogs on the collar coupling the crankshaft with the torsion bar.
Innovation Solution
The driving unit incorporates a rotation detection device with a ring magnet and detector positioned on the rotating member, allowing for improved detection resolution without the need for increasing the number of cogs on the crankshaft, thereby enhancing the monitoring of pedaling and assistance provided by the electric motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of cogs on the collar is increased to increase detection resolution, then the detection resolution of the rotation detection device is improved, but the axial dimension of the crankshaft must be increased, which is not realistic
Solution Approach 1:
The patent moves the detected portion from the axial direction (collar with cogs) to the radial direction (rotating member surrounding the crankshaft axis). This dimensional change allows the detection resolution to be improved by increasing the number of magnetic poles on the ring magnet without increasing the axial dimension of the crankshaft, as the detection occurs in a different spatial plane.
Solution Approach 2:
The patent introduces a ring magnet with multiple magnetic poles as an intermediary element on the rotating member. This ring magnet serves as a mediator between the crankshaft rotation and the detector, enabling high-resolution detection without requiring direct modification of the crankshaft structure or increase of its axial dimension.
2Measurement precision
If the number of cogs is increased to improve detection resolution, then the detection precision is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the detection function from the crankshaft structure itself and relocates it to a separate rotating member. The ring magnet with multiple magnetic poles is placed on the rotating member rather than integrating cogs into the crankshaft collar, thereby improving detection resolution while reducing the structural complexity of the crankshaft assembly.
Solution Approach 2:
The patent replaces the mechanical cog-based detection system with a magnetic field-based detection system. Instead of using physical cogs on the crankshaft collar, a ring magnet with magnetic poles on the rotating member creates a magnetic field that the detector reads, thereby achieving higher detection resolution with simpler mechanical structure.
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 enhances the detection resolution of the rotation detection device, enabling more precise monitoring of pedaling and improved assistance to the rider, while allowing for a smaller axial dimension of the crankshaft, thus improving the overall efficiency and accuracy of the electric assist system.
Implementation Method 1
a magnetostrictive torque detection device located in the housing for detecting a torque generated in the crankshaft
Implementation Method 2
a magnetic rotation detection device located in the housing for detecting rotation of the crankshaft
Data Source
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AI summary
A driving unit for use in an electric assist bicycle that includes a rotation detection device in addition to a torque detection device is provided, where the detection resolution of the rotation detection device is increased. The driving unit 50 may be used in an electric assist bicycle 10 and includes a housing 52, a crankshaft 54, a torque detection device 56B, a rotating member 56, and a rotation detection device 130. The rotating member includes a connecting shaft 56A and an output shaft 118. The connecting shaft is located at one of the ends of the rotating member disposed along its axis, and is coupled with the crankshaft in the housing. The output shaft is located at the other one of the ends of the rotating member disposed along its axis, and a driving sprocket is attached to the output shaft. The rotation detection device includes a detected portion 132 and a detector 134. The detected portion is provided on the rotating member, and located around the central axis of the crankshaft in the housing. The detector detects that the detected portion rotates together with the rotating member.