Continuously Variable Planetary Gear for Electric Bicycle Drivetrain
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Solution Overview
Problem
Existing electric bicycles with rear wheel shifting devices suffer from suboptimal coordination between electric drives and shifting mechanisms, leading to weight distribution issues, complex assembly, and high costs due to the presence of heavy hub gears and separate shifting devices.
Innovation Solution
Integration of a continuously adjustable planetary gear within the crank drive area, combining the electric drive with a reduction gear and a planetary gear, allowing for a compact and lightweight design by eliminating the need for a separate shifting device on the rear wheel, with the planetary gear's input connected to both the crank drive and electric drive, enabling stepless torque summation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a separate switching device on the rear wheel is used, then gear shifting functionality is achieved, but the weight of the rear wheel increases and assembly becomes complex
Solution Approach 1:
The patent merges the switching device with the rear wheel hub to create an integrated hub gear system. The switching device is not separate but integrated into the hub structure, allowing gear shifting functionality while reducing overall weight and simplifying assembly. The hub gear mechanism combines the wheel hub and gear shifting components into a single unified structure.
2Device complexity
If jumping between discrete gear stages is used, then simple gear ratios are achieved, but coordination between electric drive and shifting device becomes suboptimal
Solution Approach 1:
The patent implements a continuously variable transmission (CVT) mechanism within the hub gear system, replacing discrete gear stages with a dynamic transmission ratio system. This allows the gear ratio to vary continuously rather than jumping between fixed stages, enabling optimal coordination between the electric drive motor and the shifting device. The CVT mechanism adjusts the transmission ratio dynamically based on driving conditions, improving adaptability while maintaining coordination with the electric drive system.
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 configuration enhances handling, suspension, and driving dynamics by reducing weight, simplifying assembly, and achieving optimal coordination between electric and pedal power, while allowing for modular expansion and improved ground clearance.
Implementation Method 1
a planetary gear with an infinitely variable ratio in the area of the crank drive of the vehicle
Implementation Method 2
an input element of the continuously variable planetary gear is also connected to the crank drive and the electric drive, with a pedal drive torque applied by a driver and an electric drive torque applied by the electric drive being introduced via the same input element of the continuously variable planetary gear, so that the summation of the two torques takes place in front of the infinitely variable planetary gear
Data Source
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AI summary
The invention relates to a vehicle which can be driven by motor power and/or pedal power, in particular an electric bicycle, comprising a crank drive (2) with a crankshaft (20), an output element, which outputs a drive torque for the vehicle, in particular to a chain or the like, an electric drive (3) with a reduction gear, and a continuously variable planetary gear unit (10). An output element (12) of the continuously variable planetary gear unit transmits the torque to the output element.