Harmonic Bicycle Drive Unit With Buffer-Decoupled Outer Bushing
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Solution Overview
Problem
Existing drive units for manually driven vehicles, such as bicycles, have complex structures with numerous components, leading to issues with reliability, noise, and space efficiency.
Innovation Solution
A compact drive unit design incorporating a harmonic drive with a buffer system for acoustic decoupling and torque damping, featuring a freewheel clutch mechanism for torque addition and a premountable unit for simplified assembly, which includes a non-rotatable outer bushing for structural support and a deformable inner bushing for high transmission ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a complex structure with numerous components is used in existing drive units, then the drive unit can provide manual and electric drive functions, but the reliability decreases and noise increases
Solution Approach 1:
The patent combines the manual drive (bottom bracket shaft) and electric drive (electric motor with harmonic drive) into a single integrated drive unit with a common output shaft. This merging of functions into one compact structure reduces the number of separate components and bearing points, thereby improving reliability while maintaining both manual and electric drive capabilities.
2Adaptability or versatility
If a complex structure with numerous components is used in existing drive units, then the drive unit can provide manual and electric drive functions, but the noise increases
Solution Approach 1:
The patent introduces a buffer element as an intermediary between the harmonic drive's outer bushing and the housing. This buffer acts as a mediator that acoustically decouples the harmonic drive from the housing, preventing noise transmission while allowing the integrated drive unit to maintain both manual and electric drive functions.
3Object-generated harmful factors
If a harmonic drive with buffer system is used, then acoustic decoupling and torque damping are achieved, but the device complexity increases
Solution Approach 1:
The patent applies the buffer element locally at the specific location where the harmonic drive's outer bushing contacts the housing. This localized application of acoustic decoupling provides noise reduction exactly where needed without requiring complex modifications throughout the entire drive unit structure.
4Volume of moving object
If a compact transmission unit with high transmission ratios is used, then coaxial arrangement is achieved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes the harmonic drive's ability to achieve high transmission ratios in a compact form factor through its wave generator mechanism. The buffer element compensates for manufacturing tolerances and misalignments, allowing the system to achieve the desired compact coaxial arrangement without requiring extremely tight manufacturing precision.
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 provides a quiet, reliable, and compact drive unit with improved torque transmission and assembly efficiency, enabling a coaxial and space-saving design for both manual and electrically assisted drives.
Implementation Method 1
The outer bushing of the harmonic drive is coupled to the housing via a buffer, for example a rubber/metal bearing. The outer bushing and the housing can in this way be advantageously acoustically decoupled.
Implementation Method 2
Independently thereof, it is possible to compensate eccentricities caused, for example, by axial misalignment and/or tilting.
Implementation Method 3
The torque of the electric motor is transmitted to the output shaft via the harmonic drive and the first freewheel clutch.
Implementation Method 4
The harmonic drive can expediently have a wave generator and a deformable, for example, cylindrical inner bushing with external teeth (flex spine).
Implementation Method 5
The outer bushing of the harmonic drive can advantageously be coupled non-rotatably to the housing. The outer bushing can thus serve as a torque support mechanism relative to the housing.
Implementation Method 6
The bottom bracket shaft and the harmonic drive can expediently each be coupled to the output shaft by a freewheel clutch, wherein the harmonic drive, the freewheel clutches, and the output shaft can be arranged coaxially with one another in the housing.
Data Source
AI summary
A drive unit (10) for a manually driven vehicle, in particular a bicycle or an EPAC, includes a housing (12), an electric motor (18) with a rotor (44), a bottom bracket shaft (14), a harmonic drive (20) coupled to the rotor (44), and an output shaft (22). The harmonic drive (20) includes an outer bushing with an inner toothing. The outer bushing (38) of the harmonic drive (20) is coupled to the housing (12) via a buffer (64).