Non-linear Orifice Contour for Shock Absorber Damping Control
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Solution Overview
Problem
Existing shock absorbers face challenges in generating adequate damping forces at low piston velocities while maintaining acceptable damping forces at high velocities, and their damping characteristics are affected by temperature changes due to fluid viscosity variations.
Innovation Solution
A bleed disc with a substantially non-linear orifice contour is introduced, forming multiple portions with varying areas, which restricts fluid flow between the upper and lower working chambers, providing controlled damping at low piston speeds and minimizing temperature-related issues by optimizing the orifice design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed low speed bleed orifice with straight channel is used, then low speed damping control is achieved, but the system fails to maintain consistent performance across temperature variations
Solution Approach 1:
The patent applies curvature by replacing the straight channel with a curved or serpentine flow path in the bleed orifice. This curved geometry increases the effective flow path length and creates more resistance to fluid flow, particularly at low velocities. The curved path also promotes better mixing and reduces the impact of temperature-induced viscosity changes, allowing the orifice to maintain more consistent damping characteristics across varying temperatures while still providing effective low-speed control.
2Force
If small notches are used to create restriction at low velocities, then low speed damping is improved, but the flow of fluid operates over a very small range of velocity
Solution Approach 1:
The curved flow path design extends the effective velocity range by creating progressive resistance. At very low velocities, the curved path provides sufficient restriction to generate adequate damping force. As velocity increases, the curved geometry continues to provide controlled resistance through its extended path length, allowing the system to maintain effective damping across a broader velocity spectrum compared to straight-channel designs with equivalent restriction.
3Force
If the bleed orifice is designed to restrict flow at low speeds, then damping control is achieved, but at high temperatures the fluid may not be restricted and at low temperatures the discs may deflect prematurely
Solution Approach 1:
The curved or serpentine flow path creates inherently higher flow resistance compared to a straight channel of equivalent dimensions. This increased resistance helps maintain effective fluid restriction even when fluid viscosity decreases at high temperatures. The curved geometry also distributes pressure more evenly along the flow path, reducing localized stress concentrations that could cause premature disc deflection at low temperatures, thereby extending the operational temperature range.
4Force
If highly restricted fluid flow is used to produce firm ride, then damping force is increased, but damping force at low piston velocities becomes difficult to obtain
Solution Approach 1:
The curved flow path design provides progressive resistance that is more effective at low velocities while maintaining acceptable performance at higher velocities. The extended path length and geometric complexity of the curved channel create sufficient resistance at low flow rates to generate adequate damping force, while avoiding the overly restrictive conditions that would prevent low-speed operation. This geometry effectively decouples the restriction level from velocity dependence.
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 enhances damping control at low piston speeds and maintains consistent performance across varying temperatures, improving vehicle handling and ride quality by ensuring appropriate damping forces across a range of velocities.
Implementation Method 1
the viscosity of the fluid is higher (thick fluid) at cold temperatures and is low (thin fluid) at high temperatures
Implementation Method 2
Due to an exponential relationship between pressure drop and flow rate, it is difficult to obtain a damping force at relatively low piston velocities
Implementation Method 3
the shock absorber is able to produce a damping force which counteracts the unwanted vibration
Data Source
AI summary
A shock absorber for a vehicle includes a pressure tube that defines a fluid chamber. A piston disposed within the fluid chamber divides the fluid chamber into an upper working chamber and a lower working chamber. The piston defines a compression passage and a rebound passage which extend through the piston between the upper working chamber and the lower working chamber. A valve disc assembly engages the piston and controls the flow of fluid between the upper working chamber and the lower working chamber. The valve disc assembly includes a bleed disc that defines an orifice with a substantially non-linear contour. The orifice extends to an outer diameter of the bleed disc, and forms a bleed channel between the upper working chamber and the lower working chamber.