Shock Absorber Piston Bleed Circuit Tuning
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Solution Overview
Problem
Existing shock absorbers face challenges in generating damping forces at low piston velocities, particularly near zero speed, due to fixed orifice bleed valving systems, which lead to harshness and difficulties in tuning low-speed and high-speed valving circuits independently.
Innovation Solution
A separate low-speed variable orifice bleed circuit is introduced, interconnected with the mid/high-speed valving system to eliminate offset damping forces at zero speed, allowing independent tuning of each circuit for smoother transitions and improved damping characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a fixed orifice bleed valving system is used, then low-speed damping force is generated, but harshness occurs and independent tuning of low-speed and high-speed circuits is difficult
Solution Approach 1:
The bleed valving system is segmented into separate low-speed and high-speed circuits with distinct orifice structures. The low-speed circuit uses a first bleed orifice while the high-speed circuit uses a second bleed orifice, allowing independent tuning of each circuit's damping characteristics without interference, thereby eliminating harshness caused by fixed orifice systems.
Solution Approach 2:
The patent introduces variable orifice structures that dynamically adjust the bleed area based on piston velocity. The first and second bleed orifices have different geometric configurations that automatically engage at different speed ranges, creating a dynamic damping response that smooths the transition between low-speed and high-speed operation.
2Ease of operation
If a fixed orifice bleed circuit is used, then low-speed control is achieved, but the damping force is not a function of internal pressures and the velocity range is very small
Solution Approach 1:
Different regions of the bleed circuit are given different orifice characteristics - the first bleed orifice is optimized for low-speed operation with specific pressure sensitivity, while the second bleed orifice is optimized for high-speed operation. This local differentiation allows each circuit to function effectively across its designated velocity range while maintaining pressure-dependent damping characteristics.
Solution Approach 2:
The patent changes the geometric parameters of the bleed orifices to create pressure-dependent flow characteristics. The first and second bleed orifices have different cross-sectional areas and configurations that cause the damping force to vary as a function of internal chamber pressures, enabling effective control across a broad velocity range from very low speeds to high speeds.
3Force
If secondary valving is activated at low velocities, then damping is provided, but harshness is created due to mismatched force-velocity characteristics
Solution Approach 1:
The patent creates a dynamic transition between low-speed and high-speed valving circuits through carefully designed bleed orifice geometries. The first bleed orifice dominates at low velocities while the second bleed orifice becomes progressively more significant as velocity increases, creating a smooth, continuous damping characteristic that eliminates harsh transitions between valving stages.
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 solution enables independent tuning of damping forces at low piston velocities, reducing harshness and enhancing the overall damping performance by ensuring smooth transitions between low-speed and high-speed valving circuits, thereby improving vehicle handling and ride comfort.
Implementation Method 1
shock absorbers are generally connected between the sprung portion (body) and the unsprung portion (wheels) of the automobile. A piston is located within a working chamber defined by a pressure tube of the shock absorber... the piston being able, through valving, to limit the flow of damping fluid between opposite sides of the piston... the shock absorber is able to produce a damping force which dampens the unwanted vibration
Implementation Method 2
Because of the exponential relation between pressure drop and flow rate, it is a difficult task to obtain a damping force at relatively low piston velocities... a fixed low speed bleed orifice which provides a bleed passage which is always open across the piston
Data Source
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AI summary
A shock absorber includes a piston which has at least one compression fluid passage and at least one rebound fluid passage. A compression valve assembly closes the at least one compression passage and a rebound valve assembly closes the at least one rebound passage. An interconnecting passage connects the at least one compression fluid passage and the at least one rebound fluid passage to define an open flow path through the piston.