Telescopic Suspension Fork Fluid Duct and Sealing
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Solution Overview
Problem
Existing telescopic suspension fork designs face issues with oil volume equalization between the damping arrangement and reservoir, leading to inconsistent response behavior, especially under varying travel profiles, which can result in a hardening of the damping arrangement and discomfort for the rider.
Innovation Solution
A telescopic suspension fork leg with a piston rod featuring a fluid duct and a sealing arrangement that allows for continuous fluid communication between the spring and damping chambers, even in unstressed states, preventing premature wear and maintaining consistent damping behavior by allowing regular fluid exchange and relieving pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing arrangement is provided between the first and second chamber to prevent oil mixing, then fluid separation is improved, but the sealing arrangement undergoes premature wear due to continuous movement over abrupt transitions
Solution Approach 1:
The transition region is designed with a curved, continuous surface instead of abrupt steps or sharp transitions. This curved transition surface allows the sealing arrangement to move smoothly without sudden directional changes, reducing wear while maintaining effective fluid separation between chambers.
Solution Approach 2:
The transition region gradually changes geometric parameters (radius, curvature) to create a smooth continuous surface. This gradual parameter change eliminates abrupt transitions that cause sealing lip damage, extending the service life of the sealing arrangement while maintaining chamber separation.
2Ease of manufacture
If the fluid duct is designed with abrupt transitions for manufacturing simplicity, then manufacturing ease is improved, but the sealing arrangement experiences rapid wear due to continuous movement over step jumps
Solution Approach 1:
Instead of manufacturing simple abrupt steps, the fluid duct incorporates curved transition regions that guide the sealing arrangement smoothly. This maintains manufacturability through standard machining while eliminating the wear-causing sharp transitions.
Solution Approach 2:
The transition region is designed to accommodate the dynamic movement of the sealing arrangement, providing a continuously varying surface that adapts to the sealing lip's position during operation, thereby reducing impact and wear.
3Reliability
If the damping arrangement is placed under high pressure to prevent cavitation, then cavitation prevention is improved, but air bubbles still form locally causing inconsistent damping behavior
Solution Approach 1:
An air chamber is introduced as an intermediary element between the damping fluid and the high-pressure zones. This air chamber absorbs pressure fluctuations and prevents direct contact between air bubbles and the damping fluid, maintaining consistent damping behavior while preventing cavitation.
Solution Approach 2:
The air chamber creates an inert gas environment that isolates the damping fluid from direct exposure to pressure-induced air bubble formation. This inert atmosphere prevents cavitation-related inconsistencies in damping performance.
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 a consistent response behavior of the suspension fork, independent of the travel profile, by allowing fluid equalization and preventing the hardening of the damping arrangement, thus providing a more comfortable and dynamic riding experience.
Implementation Method 1
When the damping fluid flows through the bores or valves, respectively, very high pressures are formed locally
Implementation Method 2
which are so great that air bubbles develop. This potentially can cause cavitation in some known damping arrangements
Implementation Method 3
a spring arrangement (5), which is arranged in a first chamber (21) formed in the outer tube (3)
Implementation Method 4
a sealing arrangement (23), displaceable along the piston rod (22), is provided between the first and second chamber (21, 24)
Data Source
AI summary
A telescopic suspension fork leg, such as may be used in a motorcycle. The fork leg has an inner tube and an outer tube and a damping arrangement and a spring arrangement, which is arranged within a first chamber which is formed in the outer tube and is supported against a second chamber formed by the damping arrangement and arranged beneath the first chamber, which is constructed to receive a damping fluid. The damping arrangement has a piston, on a piston rod, with upper and lower piston surfaces. The piston is displaceable within a damping tube arranged largely concentrically to the inner tube, and the damping tube is surrounded by an annulus chamber arranged largely concentrically to the damping tube, and a sealing arrangement, displaceable along the piston rod, is provided between the first and second chambers.