Piston Assembly with Open Bleed Circuit for Shock Absorber Damping
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Solution Overview
Problem
Existing shock absorbers face challenges in generating low damping forces at low piston velocities, leading to harshness during low-speed movements due to fixed or variable orifice bleed valving systems that fail to independently tune low-speed and high-speed damping characteristics effectively.
Innovation Solution
A separate low-speed variable orifice bleed circuit is introduced, with two fluid flow paths that close at specified piston velocities, allowing independent tuning of low-speed damping characteristics and smooth transitions between low-speed and high-speed valving systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed orifice bleed valving system is used, then the structure is simple, but the low-speed damping force is insufficient and harshness occurs during low-speed movements
Solution Approach 1:
The bleed circuit is divided into two separate flow paths: a first flow path with a first orifice and a second flow path with a second orifice. This segmentation allows each path to be optimized for different speed ranges, with the first path handling low-speed flow and the second path handling high-speed flow, thereby resolving the contradiction between structural simplicity and low-speed damping performance.
Solution Approach 2:
The system transitions from a static fixed orifice to a dynamic multi-path system where flow distribution changes based on piston velocity. At low speeds, fluid primarily flows through the first orifice providing adequate damping; at high speeds, fluid shifts to the second orifice. This dynamic adaptation eliminates harshness while maintaining performance across the full velocity range.
2Ease of operation
If a variable orifice bleed valving system is used, then low-speed damping force is improved, but the transition between low-speed and high-speed valving creates harshness
Solution Approach 1:
The bleed circuit is divided into two separate flow paths: a first flow path with a first orifice and a second flow path with a second orifice. This segmentation allows each path to be optimized for different speed ranges, with the first path handling low-speed flow and the second path handling high-speed flow, thereby resolving the contradiction between structural simplicity and low-speed damping performance.
Solution Approach 2:
The design accepts that each individual orifice produces a harsh force-velocity characteristic, but converts this harm into benefit by combining two such circuits in parallel. The superposition of two harsh characteristics with different timing creates a smooth overall characteristic, transforming the harmful sharp transitions into a beneficial gradual transition.
3Ease of operation
If the orifice cross-sectional area is reduced to increase low-speed damping force, then low-speed damping is improved, but the velocity range for effective low-speed control becomes very small
Solution Approach 1:
The bleed circuit is divided into two separate flow paths: a first flow path with a first orifice and a second flow path with a second orifice. This segmentation allows each path to be optimized for different speed ranges, with the first path handling low-speed flow and the second path handling high-speed flow, thereby resolving the contradiction between structural simplicity and low-speed damping performance.
Solution Approach 2:
The system uses two different orifice cross-sectional areas (first area and second area) to create two distinct flow characteristics. The first orifice is sized for low-speed flow control while the second orifice handles high-speed flow. This parameter differentiation allows the system to maintain adaptability across a wide velocity range while providing sufficient low-speed damping force.
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 improved low-speed damping characteristics, reducing harshness and allowing for independent tuning of damping forces, enhancing ride comfort and vehicle handling by effectively managing damping forces across a range of piston velocities.
Implementation Method 1
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
Implementation Method 2
All damping forces produced by the shock absorber are the result of piston valving when a full displacement valving system is used
Data Source
AI summary
A shock absorber includes a piston which has at least one compression fluid passage, at least one rebound fluid passage and at least one bleed 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. A bleed valve assembly with the bleed fluid passage defines a first, always open flow path through the piston and a second flow path, separate from the first flow path, through the piston. A bleed disc is movable between a first position where the second flow path is open and a second position where the second flow path is closed.