E-Bike Transmission Assembly for Smooth Shifting Under Load
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Solution Overview
Problem
Existing electrically-assisted bicycles face issues with gear ratio shifting under load, particularly when riders encounter hills, and there is a need for improved gearboxes that prevent lubricating oil leakage and facilitate energy recovery during braking.
Innovation Solution
A drivetrain system with an electric motor and gearshift device that includes a reduction gear, freewheel, and control unit for automatic gear ratio adjustment, along with a casing design that prevents oil leakage in various orientations, and incorporates regenerative braking and anti-theft features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional gearbox is used in electrically-assisted bicycles, then the structure is simple and easy to manufacture, but the gear ratio cannot shift smoothly under load particularly when riders encounter hills
Solution Approach 1:
The patent applies dynamics by making the gear ratio adjustable rather than fixed. The gearbox incorporates multiple gear ratios that can be dynamically selected based on riding conditions, allowing the system to adapt to varying loads and terrain. The electric motor's variable speed and torque characteristics enable smooth transitions between gear ratios under load, resolving the contradiction between reliability and complexity.
Solution Approach 2:
The patent changes the parameter of gear ratio from fixed to variable. By incorporating multiple gear ratios and enabling dynamic selection, the system can optimize performance under different loading conditions. The electric motor's ability to vary its operating parameters (speed, torque) complements the variable gear ratio system, allowing smooth shifting even under hill-climbing loads.
2Reliability
If seals are provided at the junction of casing parts to prevent oil leakage, then oil leakage is prevented, but air circulation in the gears is restricted
Solution Approach 1:
The patent uses a flexible oil seal at the casing junction that can accommodate relative movement between parts. This flexible seal maintains oil containment while allowing for thermal expansion and contraction, and permits controlled air circulation pathways that do not compromise the sealing integrity. The seal design balances oil retention with adequate ventilation for gear cooling.
Solution Approach 2:
The patent introduces an intermediary sealing mechanism that mediates between the conflicting requirements of oil retention and air circulation. The seal design allows it to maintain oil containment while permitting controlled air flow through designated pathways, effectively mediating between the need for lubrication and the need for cooling ventilation.
3Extent of automation
If the electric motor is connected to the output sprocket of the gearshift device, then automatic gear ratio adjustment is enabled, but the device complexity increases
Solution Approach 1:
The patent applies universality by making the electric motor serve multiple functions: it provides propulsion power and simultaneously acts as the actuating mechanism for automatic gear ratio adjustment. The motor's torque and speed control capabilities are utilized both for driving the bicycle and for selecting optimal gear ratios, reducing the need for separate actuation systems and justifying the increased complexity through multi-functionality.
Solution Approach 2:
The patent merges the propulsion function and gear selection function into a single integrated system. The electric motor is directly connected to the output sprocket, combining the drive train and gear control mechanisms. This integration allows the motor to simultaneously provide propulsion and control gear ratio selection, merging two functions into one component 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
The system provides smooth gear shifting, prevents oil leakage, enhances energy recovery, and offers automatic gear adjustment, improving the performance and reliability of electrically-assisted bicycles.
Implementation Method 1
an electric motor, in particular disposed to provide a portion of the energy for the propulsion of the device
Implementation Method 2
a reduction gear, wherein the electric motor is connected to the output sprocket of the gearshift device via the reduction gear
Implementation Method 3
freewheel
Data Source
AI summary
A drivetrain for a mobility vehicle includes: an electric motor and a gearshift device having a plurality of gear ratios between a first gear ratio and an upper gear ratio, the electric motor being connected to at least one output sprocket of the gear shift device.