Hydraulic End Stop Cavitation Prevention in Telescopic Forks
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Solution Overview
Problem
Existing telescopic spring fork legs for motorcycles and bicycles suffer from cavitation issues, leading to reduced effectiveness of the hydraulic end stop function, especially under dynamic stress, which results in decreased damping performance over time.
Innovation Solution
A telescopic spring fork leg design featuring a hydraulic end stop device with a pressure limiting mechanism and a damping needle that adjusts the throttle orifice cross-section, ensuring constant damping fluid pressure and preventing cavitation, while providing a spring deflection-dependent damping force that increases progressively, avoiding sudden blockages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the damping fluid is put under high pressure to prevent cavitation, then the formation of gas bubbles is avoided, but the device complexity increases due to the need for pressure limiting mechanisms and valve devices
Solution Approach 1:
The patent applies preliminary action by pre-filling the damping device with damping fluid at a controlled amount before operation. The filling device introduces the fluid to a predetermined level, ensuring the chamber is sufficiently filled without requiring complex real-time pressure control mechanisms during operation. This preliminary preparation prevents cavitation by ensuring adequate fluid volume from the start.
Solution Approach 2:
The damping device is designed to be self-regulating through the interaction of the piston, spring device, and damping fluid. The spring device automatically adjusts the piston position based on external forces, maintaining constant pressure on the damping fluid without requiring external pressure control systems. The system serves itself by using the mechanical elements already present to regulate fluid pressure.
2Ease of operation
If a hydraulic end stop is provided to prevent sudden blockages, then the damping force increases progressively, but the device complexity increases due to additional components like the end stop device and filling device
Solution Approach 1:
The patent merges the end stop function with the existing piston and spring device assembly. The hydraulic end stop is integrated into the same chamber where the piston moves, combining multiple functions (damping, spring support, and end stop) into a unified structure. This integration reduces the need for separate, complex end stop mechanisms while achieving smooth progressive damping force increase.
Solution Approach 2:
The patent uses hydraulic principles by employing damping fluid under constant pressure to provide the end stop function. Instead of a purely mechanical end stop that would create sudden blockages, the hydraulic system allows progressive compression of the damping fluid, which is nearly incompressible, to provide a smooth and controlled increase in damping force as the piston approaches the end of its travel.
3Adaptability or versatility
If the damping fluid flows through bores or valves to provide adjustable damping, then the damping properties can be adjusted to driver requirements, but very high flow velocities occur locally causing cavitation
Solution Approach 1:
The patent extracts the problematic high-velocity flow through narrow bores and valves by replacing it with a more open fluid path. The damping fluid flows directly from the compression chamber through the piston rod passage to the extension chamber without passing through constricted valve openings. This extraction of the fluid from the high-velocity path eliminates cavitation while preserving adjustable damping through the valve device that controls overall fluid volume.
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 effectively prevents cavitation, maintains damping performance even under hard and dynamic conditions, and ensures the hydraulic end stop remains effective over long use, providing a smooth and consistent damping experience without muscle fatigue.
Implementation Method 1
the damping fluid is put under high pressure so that gas bubbles cannot form in the first place
Implementation Method 2
gas bubbles form due to a gaseous fluid phase, and cavitation occurs
Implementation Method 3
a spring device (5), which is arranged in a first chamber (8) formed in the outer tube (3) and supports against a second chamber (9) formed by the damping device
Implementation Method 4
In order to bring about a damping function for damping the oscillating movement of the inner tube and outer tube relative to one another, known damping devices have bores through which a damping fluid in the form of, for example, telescopic fork oil can flow
Data Source
Figure 1
Figure 1A
Figure 2
AI summary
The telescopic spring leg (1) has an inner pipe (2), an outer pipe (3), a damping device (4) and a spring unit (5), which is arranged inside a chamber (8). The chamber is formed inside the outer pipe and is retained against another chamber (9) that is formed by the damping device. An end stop device (48) is arranged inside the damping device and is designed for the formation of a damping force that is dependent on the spring deflection. An independent claim is also included for a telescopic spring fork with an upper and a lower fork bridge.