Bicycle Electric Assistance Device with Tangential Tire Drive
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Solution Overview
Problem
Existing electric assistance devices for bicycles face challenges such as increased mass sensitivity due to hub-mounted electric machines, complex wheel removal due to electrical connections, and architectural impacts on bicycles from geared motor systems, as well as issues with rim toothing retaining stones.
Innovation Solution
An electric assistance device where the electric machine is fixed close to the tire, with a motor pinion meshing tangentially with integral toothing on the tire, and a separable sub-assembly including the electric machine and control means carried by the frame, allowing for easy assembly and disassembly, and a battery that can be manually separated, with a quick electrical connector and oscillating arm for secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the electric machine is placed in the hub of the wheel, then the wheel can be driven directly or via reduction system, but the mass increases and is located at the wheel level making it very sensitive for the cyclist
Solution Approach 1:
The electric machine is extracted from the wheel hub and mounted on the bicycle frame instead. The drive mechanism is separated into two parts: the electric machine (on frame) and the drive wheel assembly (on wheel), connected through a flexible coupling. This extraction removes the heavy mass from the wheel, reducing rotational inertia and improving handling while maintaining driving capability.
Solution Approach 2:
The drive system is segmented into separate components: the electric machine assembly mounted on the frame, the drive wheel with toothing on the wheel, and a flexible coupling connecting them. This segmentation allows the heavy electric machine to be positioned on the frame rather than the wheel, reducing wheel mass sensitivity while preserving the driving function.
2Ease of operation
If the electric machine is placed in the hub of the wheel, then the wheel can be driven, but the removal of the wheel becomes complex due to electrical connections and specific fixings
Solution Approach 1:
The electric machine is extracted from the wheel hub, eliminating the need for electrical connections between the wheel and motor. The wheel can now be removed independently as a simple mechanical assembly without dealing with electrical connectors, sensors, or motor mountings, greatly simplifying maintenance and repairs.
Solution Approach 2:
The drive system is divided into electrically independent modules: the electric machine assembly on the frame and the mechanical drive wheel on the wheel. This segmentation allows the wheel to be removed and reinstalled as a purely mechanical operation, independent of the electrical systems, improving ease of repair.
3Adaptability or versatility
If a geared motor group drives the pedals using the existing transmission, then the transmission is utilized, but the architecture of the bicycle must be specifically designed to accommodate these devices
Solution Approach 1:
Instead of integrating the motor into the pedal transmission system (one-dimensional integration), the electric machine is mounted on the frame in a separate location, driving the wheel through a flexible coupling. This dimensional separation allows the motor to be added without redesigning the bicycle frame or transmission architecture, maintaining compatibility with standard bicycles.
Solution Approach 2:
The drive system is designed to be universally applicable to different bicycle types without requiring specific architectural modifications. The electric machine mounts to the frame in a location that accommodates various frame geometries, and the flexible coupling adapts to different wheel positions, making the system compatible with multiple bicycle architectures.
4Ease of operation
If the toothing is integral with the circle of the front rim, then the electric motor can drive the wheel, but the toothing is likely to retain stones
Solution Approach 1:
The toothing is applied locally only to the specific region of the tire that contacts the motor pinion, rather than being integral with the entire rim circle. This localized toothing on the tire surface provides the necessary driving engagement while leaving the rest of the rim smooth and free of stone-retaining features, reducing the harmful effect of stone accumulation.
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 provides a lightweight, easy-to-maintain electric assistance system that minimizes architectural changes to the bicycle, reduces the risk of stone retention, and allows for efficient energy transfer while enabling easy installation and removal of components.
Implementation Method 1
A motor pinion 3 meshes tangentially with a toothing 51 integral with the tire 5 and can thus transmit to it a driving force which assists the cyclist
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates, in particular, to an electric power-assist device for bicycles, said device comprising: an electric machine (2) comprising a rotor; means (4) for securing the electric machine; a driving pinion (3) driven by the rotor of the electric machine; and a frame (10), said device being characterised in that the driving pinion can mesh tangentially with complementary teeth (51) solidly connected to a tyre (5) of a rear wheel (61) of the bicycle, and in that the securing means are borne by the frame, said securing means, together with the electric machine, forming a sub-assembly (20) that can be manually separated from the frame.