Bicycle Suspension Fork Air Volume Geometry for Stable Spring Rate
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Solution Overview
Problem
Existing bicycle suspension forks experience increased spring rate and speed-sensitive return forces due to the casting ramp spring effect, which affects the consistency of the riding experience.
Innovation Solution
Incorporating an increased internal air volume within the lower tube of the suspension fork, with varying cross-sectional areas and additional housing or cavities to reduce pressure spikes during compression, thereby minimizing the casting ramp spring effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the lower tube has a constant internal diameter, then the manufacturing is simpler, but the casting ramp spring effect causes increased spring rate and speed-sensitive return forces
Solution Approach 1:
The lower tube is designed with varying internal diameter along its length, creating different cross-sectional areas at different locations. This local variation in geometry allows the tube to have a larger internal volume in certain regions to reduce pressure spikes during compression, while maintaining manufacturing feasibility through controlled dimensional changes rather than requiring complex multi-component assemblies.
2Reliability
If the internal air volume is increased to reduce casting ramp spring effect, then the spring performance is improved, but the device complexity increases
Solution Approach 1:
The invention modifies the geometric parameters of the lower tube by varying the internal diameter along its length. This parameter change increases the internal air volume to reduce the casting ramp spring effect and minimize pressure fluctuations during compression. The variation in diameter is implemented as a controlled geometric feature rather than adding separate components, thereby managing complexity through intelligent design rather than component proliferation.
3Stress or pressure
If the cross-sectional area of the lower tube varies, then the air volume increases and pressure spikes are reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The lower tube is segmented into different sections with varying internal diameters, creating distinct zones with different cross-sectional areas. This segmentation allows the tube to have a larger internal volume in specific regions to reduce pressure spikes during compression events. The segmented design can be implemented through controlled manufacturing processes that create different dimensional characteristics in different sections, balancing pressure reduction needs with manufacturability.
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 increased air volume reduces the influence of the casting ramp spring, providing a more consistent feel and improved spring performance by minimizing pressure fluctuations, enhancing the riding experience.
Implementation Method 1
Incorporating an increased internal air volume within the lower tube of the suspension fork, with varying cross-sectional areas and additional housing or cavities to reduce pressure spikes during compression
Data Source
AI summary
Suspension forks for bicycles are described herein. An example suspension fork includes an upper tube and a lower tube. The upper tube having a first end and a second end opposite the first end, and the lower tube having a third end and a fourth end opposite the third end. The upper tube extends into the third end of the lower tube to provide a telescopic arrangement along an axis. A seal is coupled to the lower tube adjacent to the third end of the lower tube. The seal forms a sealed residual air space within the lower tube. A first cross sectional area of the sealed residual air space taken perpendicular to the axis at a first location of the lower tube adjacent the fourth end of the lower tube is larger than a second cross sectional area of the sealed residual air space of the lower tube taken perpendicular to the axis at a second location of the of the lower tube adjacent the third end of the lower tube.