E-Bike Drive Unit Mounting via Orthogonal Shaft Nesting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The limited installation space in the area of the bottom bracket of electric bicycles restricts the free space for joints or connection points for chain stays, limiting the design flexibility and mechanical efficiency of drive units with orthogonal designs.
Innovation Solution
A space-optimized drive unit mounting system where the drive unit is partially surrounded by a frame interface with recesses that allow the output shaft to be positioned close to the center, enabling direct force transmission and a lightweight, cost-effective construction, using screws for attachment and a tolerance compensation element for gap adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the drive unit is mounted using traditional bolts on protruding tabs, then the drive unit can be securely attached to the frame, but the mounting areas restrict the space for joints or connection points where chainstays of a suspension rear triangle could be attached
Solution Approach 1:
The output shaft is nested within the frame interface structure, with the shaft positioned inside the frame interface rather than mounted on external tabs. This nesting arrangement allows the chainstay connection points to be located in the previously occupied tab areas, thereby increasing space for suspension components while maintaining secure mounting through the integrated structure.
Solution Approach 2:
The mounting system transitions from a two-dimensional tab-based attachment to a three-dimensional integrated structure where the output shaft is positioned within the frame interface. This dimensional change allows mounting areas to extend closer to the center of the output shaft while providing space in other dimensions for chainstay connections, resolving the space conflict.
2Strength
If the mounting areas extend close to the center of the output shaft, then direct force transmission and mechanical efficiency are improved, but the complexity of the frame interface structure increases
Solution Approach 1:
The frame interface structure merges multiple functions into a single integrated component: it provides structural support, serves as the mounting interface for the output shaft, and creates the recesses that enable close-center mounting. This consolidation achieves strong force transmission while avoiding the complexity of separate mounting brackets and adjustment mechanisms.
3Force
If the output shaft is positioned closer to the center, then mechanical loads are better transmitted directly to the frame, but the precision required for alignment and assembly increases
Solution Approach 1:
The recesses in the frame interface are designed with dimensions and tolerances that accommodate normal manufacturing variations. This beforehand cushioning through generous recess design absorbs alignment errors and tolerance deviations, allowing the output shaft to be positioned close to the center for optimal force transmission without requiring extreme manufacturing precision.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a drive arrangement (1) of an electric bicycle (100), comprising a drive unit (2) and a frame interface (3), wherein the drive unit (2) has an output shaft (21), a motor (25) with a motor shaft (22), and a gearbox (26) which connects the output shaft (21) and the motor shaft (22), wherein the output shaft (21) is orthogonal to the motor shaft (22), wherein the frame interface (3) has a first wall (31) and a second wall (32), wherein the drive unit (2) is arranged at least partially between the first wall (31) and the second wall (32), wherein each wall (31, 32) has a retaining area (34) with a recess (30) which penetrates the respective retaining area (34) along a direction parallel to the output shaft (21), wherein the output shaft (21) is at least partially in the recesses (30) of the retaining areas (34) is orderedand wherein the drive unit (2) is attached to the frame interface (3) at each holding area (34) at at least one attachment point (5).