Epicyclic Bicycle Drivetrain With Chainless Variable Gear Ratio
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Solution Overview
Problem
Human powered vehicles, such as bicycles and unicycles, face challenges with traditional chain-driven drivetrains that suffer from maintenance burdens, aerodynamic inefficiencies, and exposure risks, as well as limitations in power transmission and torque due to reliance on intermediary components like chains and belts.
Innovation Solution
A pedal cycle drivetrain utilizing an epicyclic gear train with direct drive between components, including an input, output, and electric motors, which reduces potential losses and provides a compact, variable transmission ratio, eliminating the need for chains and belts while integrating an electric generator and energy storage for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chain drive system is used to transmit power from pedals to wheel, then power transmission is achieved, but maintenance burden increases and reliability decreases due to jamming and chain jumping
Solution Approach 1:
The patent removes the chain drive system entirely from the drivetrain, replacing it with a direct drive mechanism where the crank arm directly rotates the wheel hub. This extraction of the intermediary chain component eliminates maintenance issues related to chain jamming, lubrication, and alignment while simplifying the overall drivetrain structure.
Solution Approach 2:
The patent employs an asymmetric direct drive configuration where the crank arm is directly coupled to the wheel hub through a non-symmetric connection mechanism. This asymmetric design allows for efficient power transmission while eliminating the need for symmetric chain-driven sprockets, thereby reducing complexity and improving reliability.
2Power
If a lubricated chain is used for power transmission, then power transfer is enabled, but harmful factors increase due to soil contamination and maintenance requirements
Solution Approach 1:
The patent extracts and removes the lubricated chain component from the drivetrain, replacing it with a direct drive system. This eliminates the source of soil contamination and maintenance burden while preserving power transmission capability through direct mechanical coupling between the crank arm and wheel hub.
3Length of moving object
If an extended chain run is used in recumbent bicycles, then power transmission over distance is achieved, but reliability worsens due to increased exposure to contamination and jamming
Solution Approach 1:
The patent removes the extended chain run entirely by implementing a direct drive system where the crank arm directly rotates the wheel hub. This eliminates the long chain path that would be exposed to contamination and potential jamming, thereby improving reliability while accommodating the extended distance requirements of recumbent bicycle designs.
4Ease of operation
If an upright bicycle position is used, then steering and balance are simplified, but aerodynamic drag increases reducing maximum speed
Solution Approach 1:
The patent implements a universal direct drive mechanism that can be applied to various bicycle configurations including both upright and recumbent positions. The crank arm to wheel hub direct coupling provides efficient power transmission in all configurations, allowing riders to choose aerodynamic recumbent positions without sacrificing drivetrain reliability or power transmission efficiency.
Data Source
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AI summary
A pedal cycle drivetrain (1) comprising: an epicyclic gear train (3) comprising: a sun gear (11) rotatable around a main axis; a planet carrier (13) rotatable around the main axis and carrying one or more planet gears (15) meshed with the sun gear (11); and an annulus (17) rotatable around the main axis and meshed with the one or more planet gears (15). The sun gear (11), the planet carrier (13), and the annulus (17) are each exclusively in direct drive with one of: an input (5) including one or more pedals; an output (7) including a wheel hub (8) rotatable around the main axis; and a first electric motor (19). Varying angular velocity of the first electric motor (19) corresponds to a varying effective transmission ratio between the input (5) and the output (7). An example application for the pedal cycle drivetrain (1) is use as a transmission in a human powered vehicle (100, 200, 400) such as a unicycle, a recumbent bicycle, or a tricycle.