Sprag Freewheel Cage Structure for Compact E-Bike Torque Transfer
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Solution Overview
Problem
Existing sprag freewheel units face challenges in electric bicycles due to space constraints and tolerance requirements, particularly when integrating rolling elements and sprags, leading to complex designs and increased costs.
Innovation Solution
A common cage design integrates both sprags and rolling elements, allowing for a more compact and cost-effective sprag freewheel unit with improved robustness and reduced drag torque, suitable for electric bicycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate cages are provided for rolling elements and sprags, then the sprag freewheel unit can function properly, but the device complexity and manufacturing costs increase
Solution Approach 1:
The patent merges the previously separate cages for rolling elements and sprags into a single common cage structure. This common cage integrates both types of bearing elements, reducing the number of separate components while maintaining the functional independence of rolling elements and sprags through their respective receptacles within the unified cage structure.
Solution Approach 2:
The common cage serves multiple functions simultaneously: it holds both rolling elements and sprags, provides structural support for the entire bearing assembly, and maintains the spatial relationships between different bearing elements. This multi-functional design eliminates the need for separate specialized cages for each type of bearing element.
2Ease of manufacture
If larger tolerance ranges are accepted, then manufacturing costs decrease, but the precision and performance of the sprag freewheel unit deteriorate
Solution Approach 1:
The patent changes the tolerance parameters by designing the common cage and its receptacles to accommodate a wider range of dimensional variations in rolling elements and sprags. The receptacle geometry and positioning features are specifically designed to absorb tolerance variations, allowing manufacturing with relaxed tolerances while maintaining proper function of the bearing elements.
3Volume of moving object
If the sprag freewheel unit is designed for compact size, then space constraints are satisfied, but the robustness against maximum torque decreases
Solution Approach 1:
The patent employs a nested arrangement where rolling elements and sprags are integrated within the common cage structure in a space-efficient manner. The receptacles for both types of elements are arranged to maximize space utilization, with elements positioned to interlock and support each other, achieving compact dimensions without sacrificing the load-bearing capacity needed for torque resistance.
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 integrated cage design reduces costs, simplifies assembly, and enhances the sprag freewheel's robustness against high torques while minimizing drag torque, enabling efficient operation without motor resistance during muscle-powered pedaling.
Implementation Method 1
several rolling elements for the rotatable mounting of an inner and an outer shaft relative to one another
Implementation Method 2
torque is transmitted via the sprags in a force-locking manner
Data Source
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AI summary
The proposed solution relates to a clamping body freewheel unit (3) and to a drive device (A) for motor-assisted driving of an electric bicycle (1) having a clamping body freewheel unit (3). The proposed clamping body freewheel unit (3) comprises - a plurality of clamping bodies (5) via which force transmission between an inner shaft and an outer shaft, which can be coupled together via the clamping body freewheel unit (3), is allowed only in one of two opposite directions of rotation, - a cage (35) via which the plurality of clamping bodies (5) of the clamping body freewheel unit (3) are kept together at a defined spacing in a circumferential direction (U), and - a plurality of rolling elements (6) via which the inner and outer shafts are mounted so as to be rotatable relative to one another when the inner and outer shafts are coupled together via the clamping body freewheel unit (3), wherein at least some of the plurality of rolling elements (6) and the clamping bodies (5) are held jointly on the one cage (35).