Electric Bicycle Drive with Single Torque Element
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Solution Overview
Problem
Existing drives for electric bicycles, particularly those designed for cargo bikes, are complex and costly due to intricate gears and sensor systems required for automatic torque support, making them inefficient and expensive to produce.
Innovation Solution
A drive system for cargo bikes utilizing a single torque-transmitting element, such as a belt or chain, with a simple rotatable connection between the electric motor and output shaft, along with field-oriented control and a manually operable actuator, allowing for robust and cost-effective power assistance without the need for complex sensors or specialized motor adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If complex gears and sensor systems are used for automatic torque support, then power assistance is improved, but device complexity and production costs increase
Solution Approach 1:
The patent extracts and eliminates the complex sensor system and automatic torque detection mechanisms from the drive system. Instead of using sensors to detect torque and control the motor, the invention uses a mechanically simple direct connection where the motor is coupled to the wheel via a torque-transmitting element, removing the need for complex control systems while maintaining power assistance capability
Solution Approach 2:
The drive system is segmented into independent functional components: the motor unit with its own control electronics housed separately, the torque-transmitting element (belt or chain), and the wheel. This segmentation allows each component to be optimized independently and simplifies the overall system architecture by eliminating the need for integrated complex gear systems
2Power
If complex gears and sensor systems are used for automatic torque support, then power assistance is improved, but production costs increase
Solution Approach 1:
The patent employs commercially available off-the-shelf components such as standard motors, belts, or chains as torque-transmitting elements, and inexpensive control electronics. These components can be sourced from standard suppliers without custom engineering, significantly reducing production costs while maintaining adequate performance for cargo bike applications
Solution Approach 2:
The control electronics are housed within the motor unit itself, creating a self-contained module that requires minimal assembly and integration work. This self-service arrangement eliminates the need for complex wiring harnesses and reduces assembly steps, thereby lowering production costs
3Force
If the electric motor is placed on the pedal crankshaft with complex gears, then torque transmission is improved, but device complexity increases
Solution Approach 1:
The patent introduces a torque-transmitting element (belt or chain) as an intermediary between the motor and the wheel. This intermediary allows for flexible power transmission while maintaining a simple system architecture. The belt or chain can accommodate misalignments and provides a clean, decoupled connection between the motor unit and the wheel, avoiding the need for complex direct-drive gear systems
4Ease of operation
If control electronics are placed outside the housing, then accessibility is improved, but compactness decreases
Solution Approach 1:
The control electronics are merged with the motor unit and housed within the same enclosure. This integration creates a compact, self-contained module that reduces the overall system volume. The electronics are positioned to work in conjunction with the motor, eliminating the need for separate housing and reducing the number of discrete components
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 results in a compact, robust, and cost-effective drive system that provides optimized power assistance, suitable for heavy loads, with reduced production costs and simplified control, enabling efficient torque transmission and motor support.
Implementation Method 1
an electric motor (12) which is rotatably connected to the output shaft (16) as a direct drive, namely via a single torque transmission element (18)
Implementation Method 2
The double chain (18) thus comprises two chains revolving side by side, which rotatably connect a gear wheel (23) mounted on a shaft (20) of the electric motor (12) and a gear wheel (25) mounted on the output shaft (16)
Data Source
AI summary
A drive for an electric bicycle comprises a pedal crank shaft, an electric motor and a switchable gearbox, as well as an output shaft separate from the pedal crank shaft, which are arranged in a common housing, wherein the electric motor is rotatably connected to the output shaft, and the pedal crank shaft is rotatably connected to the output shaft via the switchable gearbox.