E-bike Drive Device with External Speed Sensor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electric bicycles face challenges in providing a reliable and space-efficient drive system that allows high power transfer while maintaining a compact design, especially for mounting on frames like the down tube or seat tube.
Innovation Solution
A drive device comprising a motor unit, gearbox, and speed sensor unit with a spiral-shaped speed disc arranged outside the motor housing, along with a two-part or multi-part pedal crankshaft design, allowing for a compact and space-saving structure with the motor unit and gearbox positioned coaxially around the pedal crankshaft, enabling efficient torque transmission and speed measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the speed sensor unit is arranged inside the motor housing, then the structure is more integrated, but the serviceability and accessibility of the speed disc and speed sensor deteriorate
Solution Approach 1:
The speed sensor unit is segmented from the motor housing by placing the speed disc and speed sensor outside the motor housing, while the motor unit remains integrated within the housing. This segmentation allows the speed sensor unit to be accessed, serviced, or replaced independently without disassembling the motor housing, thus improving serviceability while maintaining structural integration through the external mounting arrangement.
2Volume of moving object
If the motor unit and gearbox are arranged coaxially around the pedal crankshaft, then the space utilization is improved, but the manufacturing complexity increases
Solution Approach 1:
The motor unit and gearbox are nested coaxially around the pedal crankshaft, with the motor unit positioned at one end and the gearbox at the other end of the crankshaft axis. This nesting arrangement maximizes space utilization by efficiently arranging components along the same axis, reducing the overall volume required for the drive device while maintaining manufacturability through standardized coaxial mounting interfaces.
3Ease of repair
If the speed disc is arranged outside the motor housing, then the serviceability is improved, but the structural compactness deteriorates
Solution Approach 1:
The speed disc is positioned outside the motor housing in a spatial arrangement that utilizes the external dimension of the pedal crankshaft. This dimensional placement allows the speed sensor unit to be accessed from the outside without compromising the internal compactness of the motor housing, achieving both serviceability and structural efficiency through three-dimensional spatial optimization.
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
The solution enables a reliable, compact, and efficient electric bicycle drive system with a slim frame design, improved serviceability, and enhanced riding comfort by allowing for a robust and space-saving integration of components like the ring motor and planetary gear, while maintaining reliable speed and torque measurement.
Implementation Method 1
The speed sensor unit can be designed in such a way that another tachometer method can be implemented, for example by means of a magnetized speed disc
Data Source
AI summary
In an embodiment a drive device includes a motor unit having an electric motor configured to drive an electric bicycle, a pedal crankshaft rotatable about an axis of rotation, a gearbox coupled, on the one hand, to the motor unit and, on the other hand, to the pedal crankshaft, the gearbox configured to output a torque for driving the electric bicycle, a motor housing in which the motor unit and the gearbox are arranged and through which the pedal crankshaft extends and a speed sensor unit including a speed sensor and a speed disc, wherein the speed disc is coupled to the pedal crankshaft so as to be rotatable about the axis of rotation, and is arranged outside the motor housing.