E-Bike Transmission With Offset Output Gears for Quiet Torque Sharing
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Solution Overview
Problem
Conventional electric drives for bicycles face challenges in cost-efficiency and noise reduction due to the high torque requirements and material costs associated with metal components, which often lead to noise issues.
Innovation Solution
The implementation of a transmission system with at least two offset output gears that distribute the drive power to the driven gear, allowing for reduced torque at each engagement point, enabling the use of plastic components and a compact design that increases ground clearance and reduces noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal components are used for driven gear and output gear to transmit large torques, then the transmission reliability is improved, but the production cost increases and noise problems occur
Solution Approach 1:
The patent divides the single torque transmission path into multiple parallel paths by introducing at least two output gears (first output gear and second output gear) that both engage with the driven gear. This segmentation distributes the torque across multiple engagement points, reducing the load on each individual gear component and enabling the use of cost-effective plastic materials while maintaining transmission reliability.
Solution Approach 2:
The patent applies different material properties to different components based on their functional requirements. By reducing the torque load per engagement point through multiple output gears, the local stress conditions change, allowing plastic materials (which are cheaper and quieter) to be used instead of metal, while still meeting the reliability requirements for torque transmission.
2Reliability
If metal components are used for driven gear and output gear to transmit large torques, then the transmission reliability is improved, but noise problems occur
Solution Approach 1:
The patent segments the torque transmission into multiple parallel paths through at least two output gears engaging with the driven gear. This distribution of torque across multiple engagement points reduces the impact forces and vibrations at each individual engagement, thereby significantly reducing noise generation while maintaining reliable torque transmission.
Solution Approach 2:
The patent replaces expensive and noisy metal components with plastic components for the output gears and driven gear. Plastic materials inherently generate less noise during engagement while still providing sufficient durability for the application, thus eliminating noise problems associated with metal-on-metal contact.
3Length of stationary object
If the driven gear diameter is limited to maintain ground clearance, then the ground clearance is improved, but the torque transmission capability is reduced
Solution Approach 1:
The patent introduces at least two output gears that engage with the driven gear at different circumferential positions. This segmentation allows the driven gear to have a smaller diameter (maintaining ground clearance) while still achieving the required total torque transmission capability through the combined effect of multiple engagement points distributed around the gear circumference.
Solution Approach 2:
The patent utilizes the circumferential dimension of the driven gear by positioning multiple output gears at different angular positions around the driven gear's circumference. This dimensional distribution allows efficient torque transmission without increasing the radial size of the driven gear, thus maintaining ground clearance while achieving the required torque capability.
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 solution reduces production costs, minimizes noise, and allows for a more compact and efficient electric drive system that maintains performance while enhancing the bicycle's ground clearance.
Implementation Method 1
The transmission has at least two output gears, which serve to drive the driven gear and which, for this purpose, in each case individually engage with the driven gear
Implementation Method 2
Via a suitable power distribution realized in the transmission, the drive power of the electric motor is distributed to the at least two output gears
Data Source
AI summary
An electric drive for a bicycle is disclosed. The drive includes an electric motor including an drive shaft, a driven shaft connected in a rotationally fixed manner to a driving gear for coupling to a wheel drive, and a transmission structured and arranged to drivingly connect the drive shaft to the driven shaft. The transmission includes a driven wheel, which is connected in a rotationally fixed manner to the driven shaft in a rotational drive direction, and at least two output gears. The at least two output gears includes a first output gear and a second output gear that each engage with the driven gear offset to one another in a circumferential direction to drive the driven wheel.