Variable Speed Drive With Adjustable Eccentricity for Pedal-Assist Bikes
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Solution Overview
Problem
Existing assisted-pedal human-powered vehicles require complex and cumbersome drive systems, necessitating a simpler, cost-effective, and compact variable speed drive for efficient power transmission between human propulsion and electric assistance.
Innovation Solution
A continuous variable speed drive comprising a ring and coaxial disks with adjustable eccentricity, allowing for a variable transmission ratio, integrated with a mechanical power source like an electric motor and epicyclic gear train for efficient power combination and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional pedal-assist system with separate motor and transmission components is used, then power transmission functionality is achieved, but the device complexity and size increase
Solution Approach 1:
The patent combines the motor shaft, transmission components, and wheel hub into a single integrated assembly. The motor shaft is directly coupled to the transmission mechanism, eliminating the need for separate mounting brackets, couplings, and external transmission housings. This merging of components reduces the overall number of parts, simplifies the drive system structure, and improves reliability by reducing connection points that could fail.
Solution Approach 2:
The transmission mechanism is nested within the motor assembly, with gear components housed inside the motor housing or integrated into the motor shaft structure. The variable speed mechanism is positioned concentrically around the motor shaft, allowing compact arrangement of multiple functional elements within a single cylindrical volume, thereby reducing overall device size and complexity.
2Adaptability or versatility
If a fixed-ratio transmission system is used, then mechanical simplicity is maintained, but adaptability to different riding conditions is reduced
Solution Approach 1:
The patent implements a variable speed transmission mechanism that allows continuous or stepped adjustment of the transmission ratio during operation. The mechanism includes movable components such as adjustable pulleys, variable displacement gears, or clutch assemblies that can change the gear ratio in response to rider input or controller commands, enabling adaptation to different terrain and riding conditions without requiring multiple fixed gear sets.
Solution Approach 2:
The transmission system incorporates adjustable parameters including variable pulley diameters, changeable gear ratios, or modifiable belt tensions that can be modified during operation. These parameter changes allow the transmission to optimize power delivery across a wide range of operating conditions, from low-speed climbing to high-speed cruising, while maintaining a relatively simple base structure.
3Volume of stationary object
If multiple separate components are used for motor mounting and transmission, then assembly flexibility is improved, but manufacturing cost and device size increase
Solution Approach 1:
The motor mounting bracket, transmission housing, and wheel hub are combined into a single integrated assembly or pre-assembled unit. This merging reduces the total number of discrete components that need to be manufactured and inventory-managed, while the modular nature of the integration allows for standardized manufacturing processes and efficient assembly line production, balancing manufacturing ease with compact size.
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 compact, reliable, and low-maintenance drive system that efficiently combines human and electric power, optimizing vehicle performance and reducing maintenance needs.
Implementation Method 1
The driving members are arranged and configured to co-act with opposite surfaces of the two coaxial disks, transmitting a rotation motion from the ring to the two coaxial disks
Data Source
AI summary
A variable speed drive (37) is described, comprising: a ring (60) adapted to rotate about a first rotation axis; two coaxial disks (73), rigidly connected to each other, adapted to rotate about a second rotation axis (B-B) parallel to the first rotation axis; wherein the ring (60) is at least partially housed between the two coaxial disks (73); a plurality of driving members (75), carried by the ring (60) and arranged according to a circular arrangement coaxial to the ring (60); said driving members are arranged and configured to cooperate with opposite surfaces (73A) of the two coaxial disks (73), transmitting a rotation motion from the ring (60) to the two coaxial disks (73); a device for adjusting the distance between the first rotation axis and the second rotation axis. A drive device (17) of an assisted-pedal human-powered vehicle (10) which includes such a drive is also described.