Bicycle Gearshift Four-Bar Linkage Angular Adjustment
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Solution Overview
Problem
Bicycle gearshifts face challenges in achieving precise control, particularly between higher gears, due to a substantial vertical spacing between the chain guide and smaller sprockets, leading to reduced sensitivity and control precision.
Innovation Solution
A four-bar linkage kinematic mechanism with a base body and mobile body connected through connecting rods, featuring a kinematic adjustment mechanism that alters the relative angular position between the base body and the frame, allowing the chain guide to maintain a consistent distance from sprockets of varying diameters, enhancing sensitivity and control precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the chain guide is positioned close to the largest sprocket to improve control sensitivity, then the sensitivity of control increases, but the precision of gearshifting between higher gears deteriorates due to substantial vertical spacing between the chain guide and smaller sprockets
Solution Approach 1:
The base body is made rotatable relative to the frame around a first axis, allowing the system to dynamically adjust its angular position. This dynamic adjustment enables the chain guide to maintain optimal distance from sprockets of different sizes, resolving the contradiction between control sensitivity and gearshifting precision by adapting the position according to the engaged sprocket.
Solution Approach 2:
The relative angular position between the base body and the frame is changed as a function of the primary displacement of the chain guide. This parameter change allows the system to optimize the vertical spacing between the chain guide and sprockets of different diameters, thereby maintaining both control sensitivity and gearshifting precision across all gears.
2Manufacturing precision
If the chain guide is positioned close to smaller sprockets to improve gearshifting precision between higher gears, then the precision improves, but the control sensitivity deteriorates due to increased vertical spacing from the largest sprocket
Solution Approach 1:
The rotatable base body enables dynamic repositioning of the chain guide relative to both the largest and smallest sprockets. By adjusting the angular position around the first axis, the system maintains optimal control sensitivity with the largest sprocket while simultaneously achieving precise gearshifting with smaller sprockets.
Solution Approach 2:
The system changes the relative angular position parameter between the base body and frame based on the chain guide's displacement, allowing optimization of spacing for different sprocket sizes. This parameter adjustment resolves the contradiction by enabling the chain guide to be optimally positioned for each gear configuration.
3Device complexity
If the relative angular position between the base body and frame is fixed, then the structure is simple, but the precision of gearshifting control deteriorates due to inability to adapt to different sprocket sizes
Solution Approach 1:
The base body is made rotatable relative to the frame around a first axis, introducing a dynamic element that allows adjustment of the relative angular position. This simple rotational degree of freedom enables adaptation to different sprocket sizes without significantly increasing structural complexity, thereby improving gearshifting precision.
Solution Approach 2:
The relative angular position between the base body and frame is made variable rather than fixed. This parameter change allows the system to adapt to different sprocket diameters, improving gearshifting precision while maintaining relatively simple structure through a single rotational degree of freedom.
4Manufacturing precision
If the base body is made rotatable to adjust relative angular position, then the gearshifting precision improves, but the device complexity increases due to additional kinematic mechanism
Solution Approach 1:
The base body is made rotatable relative to the frame around a first axis, adding a single rotational degree of freedom. This dynamic element improves gearshifting precision by enabling adjustment of the relative angular position, while the simplicity of a single rotational joint minimizes the increase in device complexity.
Solution Approach 2:
The relative angular position parameter is made adjustable through a rotatable base body. This change improves gearshifting precision by allowing optimization of chain guide positioning for different sprockets, while the mechanism required to achieve this parameter change remains relatively simple.
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
The solution provides improved precision in gearshifting by modifying the trajectory of the chain guide towards smaller sprockets, increasing sensitivity and control, especially between lower gears, while avoiding the drawbacks of bringing the chain guide too close to the largest sprocket.
Implementation Method 1
a four-bar linkage-kinematic mechanism with a base body and a mobile body connected together through a pair of connecting rods articulated to the base body and to the mobile body at four pin elements
Implementation Method 2
a rotary body with a toothed sector and pinion for precise actuation
Data Source
AI summary
The present invention refers to a bicycle gearshift with improved precision control, comprising a kinematic mechanism in the form of a four-bar linkage with a base body and a mobile body connected together through a pair of connecting rods articulated to the base body and to the mobile body at four pin elements, each pair of opposite pin elements of the four pin elements defining a diagonal of the four-bar linkage kinematic mechanism, and a first attachment group of the base body to a bicycle frame, the mobile body being connected to a chain guide at a second attachment group, the four-bar linkage kinematic mechanism being associated with gearshift actuation means suitable for deforming the four-bar linkage kinematic mechanism so as to determine a displacement of the mobile body with respect to the base body and consequently a primary displacement of the chain guide in the axial direction with respect to the axis (A) of a cogset, and it is characterised in that the first attachment group comprises a kinematic mechanism for changing the relative angular position between the base body of the four-bar linkage kinematic mechanism and the frame as a function of the primary displacement of the chain guide.