Bicycle Electromechanical Derailleur Gearing for Precise Shift Positioning
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Solution Overview
Problem
Existing electromechanical actuating devices for bicycles face issues such as inaccurate position detection, hardening distortion of gearing elements, complex assembly due to material choice, and difficulty in coordinating motor and gearing positions, leading to unreliable operation and increased noise.
Innovation Solution
The actuating device features a gearing system with preloaded partial wheels for precise engagement, separate toothed wheels and gearing shafts for reduced distortion, and a trim device for adjusting shift positions, along with fault detection and reduced drive power to prevent overloading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torsion spring is used to preload the position detection wheel against the bracing wheel, then play between the position detection wheel and gearing output shaft is reduced, but the bracing force becomes too high at certain rotational angles, excessively influencing the output torque of the gearing
Solution Approach 1:
A compensating element (second torsion spring) is introduced as an intermediary between the bracing wheel and the position detection wheel. This compensating element generates a counteracting moment that balances the excessive bracing force from the first torsion spring at rotational angles where it would otherwise excessively influence the output torque, thereby maintaining measurement precision without adversely affecting the gearing's output torque characteristic
2Strength
If the pinion is hardened together with the gearing shaft to satisfy increasing torque demands, then strength is improved, but hardening distortion occurs in relatively long axles, impairing positioning accuracy
Solution Approach 1:
The pinion and gearing shaft are separated into two distinct components. The pinion can be hardened independently to achieve the required strength for torque transmission, while the gearing shaft remains separate and can be precisely positioned without suffering from hardening distortion. This segmentation allows each component to be optimized for its specific function without the adverse effects of combined hardening
3Weight of moving object
If screw connections are used to fasten motor or gearing components to the plastics housing, then weight is reduced, but the exact position of elements becomes dependent on tightening force and connections may distort or loosen over time
Solution Approach 1:
A positioning element is introduced as an intermediary between the motor or gearing components and the plastics housing. This positioning element provides precise mechanical positioning that is independent of screw tightening force, while still allowing the housing to be made of lightweight plastics material. The positioning element ensures consistent and accurate positioning without relying on the mechanical fastening force
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 design ensures precise and reliable operation, reduces play and hardening distortion, facilitates assembly, and compensates for manufacturing tolerances and wear, enhancing shift accuracy and reducing noise.
Implementation Method 1
the position detection wheel is additionally in engagement with a bracing wheel, which is continuously preloaded in a direction of rotation by a torsion spring
Implementation Method 2
The compensating element is in engagement with the position detection wheel and is configured to preload the position detection wheel in a direction of rotation opposite to the direction of rotation in which the bracing wheel preloads the position detection wheel
Data Source
AI summary
An Actuating device for a bicycle is provided. The actuating device may include a static element which is positionally fixed in relation to a bicycle frame, a movable element which is movable in relation to the static element, an electromechanical drive which provides drive force for a movement of the movable element. The electromechanical drive has a motor and a gearing driven by the motor. The gearing may include a first gearing wheel and a second gearing wheel which is in engagement with the first gearing wheel.