Rear Derailleur Motor Nesting for Reduced Protrusion
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Solution Overview
Problem
Conventional rear derailleurs with electric motor units often protrude significantly from the bicycle frame, compromising aesthetics and potentially increasing weight and complexity.
Innovation Solution
A rear derailleur design featuring a base member, movable member, linkage, and electric motor unit where the motor unit is partially disposed inward of the center pulley plane, minimizing protrusion, with a linkage and saver structure to protect the motor unit and enhance shifting precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the derailleur is designed to minimize outward protrusion from the frame, then the aesthetic appearance and weight are improved, but the integration of electric motor units and linkage mechanism becomes more difficult
Solution Approach 1:
The patent positions the electric motor unit and linkage mechanism inward of the center pulley plane rather than outward, utilizing the internal space of the derailleur body. This dimensional repositioning reduces outward protrusion while accommodating all necessary components within the compact inward space, resolving the contradiction between minimal protrusion and integration feasibility
Solution Approach 2:
The linkage mechanism and electric motor unit are nested within the derailleur body structure, with components arranged concentrically and hierarchically. The inner link, outer link, and motor unit are positioned one within another or adjacent to each other in a space-efficient manner, allowing complex integration without increasing outward dimensions
2Shape
If the electric motor unit is positioned inward of the center pulley plane, then the derailleur protrusion is minimized, but the linkage mechanism space becomes constrained
Solution Approach 1:
The linkage mechanism employs a dynamic four-bar linkage design with rotatable joints and movable links that adapt their configuration based on operational requirements. The inner link and outer link can rotate and reposition dynamically, maximizing the utilization of constrained inward space while maintaining full functional range of motion for chain guide movement
Solution Approach 2:
The linkage mechanism is divided into separate functional segments: the inner link connected to the motor unit, the outer link connected to the chain guide, and various joint mechanisms. This segmentation allows each component to be optimized for its specific function while fitting within the limited inward space, as each segment can be independently sized and positioned
Data Source
AI summary
A rear derailleur includes a base member, a movable member, a linkage and an electric motor unit. The base member includes a bicycle mounting portion for attaching to a bicycle. The movable member includes a chain guide having a first pulley that rotates around a first pulley axis in a center pulley plane that bisects the first pulley. The linkage movably supports the movable member relative to the base member. The electric motor unit is stationary with respect to at least a part of the base member and operatively coupled to the linkage to move the movable member relative to the base member between an outermost lateral position and an innermost lateral position. The electric motor unit is at least partially disposed inward of the center pulley plane while the movable member is disposed in the outermost lateral position.