Motorcycle Front Fork External Damping and Pressurization
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Solution Overview
Problem
The existing front fork systems for motorcycles experience variations in pressure balance and friction with piston speed, leading to a deteriorated feeling of damping force, which affects riding comfort and driving stability, and lack a wide range for adjusting damping force according to vehicle specifications.
Innovation Solution
A front fork design featuring a damping force generating portion external to the inner and outer tubes, with a working oil chamber and air chamber configuration that maintains stable pressure balance independent of piston speed and air chamber pressure, allowing for adjustable damping force through a wide range by utilizing a pressurization portion and adjustable valve units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional front fork design with internal flow paths is used, then the structure is compact, but the damping force cannot be adjusted over a wide range and pressure balance varies with piston speed
Solution Approach 1:
The front fork is divided into separate functional modules: an inner tube assembly containing the piston and flow paths, an outer tube assembly containing the damping force generating portion with external flow paths, and a pressurization portion. This segmentation allows independent optimization of each module and easy adjustment of damping specifications by replacing valve units without disassembling the entire fork.
Solution Approach 2:
A pressurization portion is introduced as an intermediary element to maintain stable pressure balance in the working oil chamber. This pressurization mechanism compensates for pressure variations caused by piston speed changes, providing consistent damping performance across different operating conditions.
2Ease of repair
If the damping force generating portion is placed inside the inner tube, then the structure is compact, but adjustment of damping specifications requires disassembly of fork components
Solution Approach 1:
The damping force generating portion with compression-side and extension-side flow paths is extracted from the inner tube and placed in the outer tube assembly. This extraction allows the damping specifications to be adjusted by simply replacing valve units in the outer tube without disassembling the inner tube or fork components, significantly easing maintenance and adjustment operations.
3Stability of the object's composition
If pressure balance varies with piston speed, then the damping force can be adjusted for different speeds, but the feeling of damping force becomes inconsistent and riding comfort deteriorates
Solution Approach 1:
The pressurization portion creates a stable pressure environment in the working oil chamber, effectively equalizing pressure conditions regardless of piston speed variations. This equipotential pressure state ensures consistent damping force characteristics and uniform riding comfort across different operating speeds.
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 design provides a stable and adjustable damping force, enhancing riding comfort and driving stability by maintaining consistent pressure balance and allowing for quick adjustments to damping specifications without disassembling the fork components, while preventing cavitation in the working oil chamber.
Implementation Method 1
a damping force generating portion forming an external flow path for circulating working oil to the lower oil chamber and the outer oil chamber at an outside of the inner tube
Implementation Method 2
a pressurization portion having an oil reservoir chamber communicated to the intermediate oil chamber and pressurizing working oil in the intermediate oil chamber by working oil filled in the oil reservoir chamber
Data Source
Figure 1
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AI summary
A front fork (21) includes an inner cylinder (135) disposed inside an inner tube (110), a piston rod (230) moving with an outer tube (210), a piston (220) attached to a lower end portion of the piston rod (230 )and sectioning an oil chamber (41) in the inner cylinder (135) into a lower oil chamber (51) and an upper oil chamber (52) and a damping force generating portion at an outside of the inner tube (110) having a first damping force generating portion generating resistance in working oil flowing in one direction in an external flow path, a second damping force generating portion disposed in series with the first damping force generating portion in the external flow path to generate resistance in working oil flowing in the other direction, and a pressurization portion (450) having an oil reservoir chamber (72) communicated to an intermediate oil chamber (63) and pressurizing working oil in the intermediate oil chamber (63).