Sprag Cage Freewheel With Bearing Disk for Compact E-Bike Drives
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Solution Overview
Problem
Conventional cage freewheels and external rolling contact bearings required for e-bike drives occupy significant installation space, increasing the axial distance between pedals and drive housing, making them undesirable for compact designs.
Innovation Solution
A sprag cage freewheel with a bearing disk arranged axially adjacent to the sprag cage, acting as a plain bearing, reduces the need for a second rolling contact bearing, allowing for a more compact shaft/hub connection and enabling the use of a single rolling contact bearing, which is integrated on one side of the freewheel, thus reducing the overall axial length and allowing for higher load capacity or smaller dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cage freewheels are installed with external rolling contact bearings on both sides, then reliable shaft/hub mounting is achieved, but axial installation space increases
Solution Approach 1:
The bearing disk is integrated directly into the freewheel assembly, merging the bearing function with the freewheel structure. This eliminates the need for separate external bearings on both sides, reducing axial space while maintaining mounting reliability through the combined structure
Solution Approach 2:
The bearing disk serves multiple functions simultaneously: it acts as a plain bearing for radial support, provides a mounting surface for the freewheel, and enables single-side installation. This multi-functionality reduces the number of separate components needed while maintaining reliable shaft/hub mounting
2Reliability
If three separate components (two bearings and a freewheel) are used, then reliable mounting is ensured, but device complexity and cost increase
Solution Approach 1:
The bearing disk and freewheel are combined into a single integrated assembly, reducing the component count from three separate parts (two bearings plus freewheel) to two main components (one bearing disk assembly and one freewheel), simplifying the overall structure while maintaining mounting reliability
Solution Approach 2:
The bearing disk assembly performs multiple functions that previously required separate components: it provides bearing support, enables mounting, and supports the freewheel operation. This multi-functionality reduces component complexity while ensuring reliable mounting
3Ease of manufacture
If sprags and bearing rollers are arranged consecutively in the circumferential direction, then mounting is simplified, but clamping surface area and load capacity are reduced
Solution Approach 1:
The bearing disk is divided into multiple segments arranged in the circumferential direction, with each segment containing sprags. This segmentation allows continuous circumferential coverage with sprags while maintaining a compact structure that is easy to manufacture and install
4Length of moving object
If a compact axial design is achieved with fewer bearings, then installation space is reduced, but manufacturing complexity may increase
Solution Approach 1:
The bearing disk is designed as a multi-functional component that combines bearing support, mounting surface, and structural support functions. This integration simplifies the overall assembly process and manufacturing while achieving compact axial dimensions, as the multi-functional design reduces the number of separate parts that need to be manufactured and assembled
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 design results in a more compact, cost-effective, and robust construction that can absorb radial, axial, and tilting forces, enhancing operational reliability while minimizing construction space, particularly beneficial for e-bike drives with helically toothed gearwheels.
Implementation Method 1
the bearing disk acts as a plain bearing between shaft component and hub component
Implementation Method 2
the sprags being loaded resiliently in the engagement direction
Data Source
AI summary
A cage freewheel for installing in the clamping gap between a shaft and a hub, in particular in the drive of an e-bike, having a sprag cage which, in one embodiment, is fitted continuously in the circumferential direction with sprags arranged pivotably in the sprag cage, with the sprags being loaded resiliently in the engagement direction. Here, a bearing disk is arranged axially adjacent to the sprag cage. In a further embodiment, the cage ring is fitted consecutively in the circumferential direction both with bearing rollers and with sprags. In addition, a shaft and hub arrangement and to an e-bike drive having a cage freewheel with the abovementioned features is also provided.