Seat Suspension Magnetic Spring Nonlinear Stiffness Control
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Solution Overview
Problem
The existing seat suspension systems using magnetic springs and torsion bars often result in a strong bottoming feeling due to rapid variations in spring constant when the upper frame approaches the lower limit position, leading to an unpleasant seating experience.
Innovation Solution
A suspension system with a combination of a linear spring and a magnetic spring, where the magnetic spring exhibits a nonlinear characteristic with a softer spring constant in the lower operating range, reducing the bottoming feeling by maintaining a lower spring constant when the upper frame displaces towards the lower limit position, and a higher spring constant when displacing towards the upper limit position, along with a damper that adjusts damping force based on the direction of movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a damper with high damping force is used to reduce bottoming of the upper frame, then the bottoming is reduced, but the seated person feels a stronger bottoming feeling
Solution Approach 1:
The damper's damping force is made variable rather than constant. The damping force increases as the compression amount increases, providing gentle damping during normal operation and strong damping only when necessary to prevent bottoming, thus avoiding the strong bottoming feeling caused by constant high damping force
Solution Approach 2:
The damping characteristic is changed from a constant high damping force to a variable damping force that depends on the compression amount. This parameter change allows the damper to adapt its behavior to different operating conditions, providing comfort during normal use and protection against bottoming only when needed
2Stability of the object's composition
If the spring constant of the magnetic spring increases rapidly when the upper frame approaches the lower limit position, then the guiding to a balanced point is improved, but the seated person feels a strong bottoming feeling
Solution Approach 1:
The spring mechanism is designed with different characteristics for different displacement ranges. In the lower operating range (near lower limit position), the magnetic spring exhibits softening characteristic with small spring constant for comfort. In the upper operating range (near upper limit position), the torsion bars provide strong restoring force for stable guiding. Each range has optimized local properties
Solution Approach 2:
The spring mechanism combines two different spring elements (magnetic spring and torsion bars) with different characteristics. The magnetic spring provides softening characteristic for comfort in the lower range, while the torsion bars provide strong positive spring characteristic for stability in the upper range, creating a composite system with superior overall performance
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 system effectively reduces the bottoming feeling by maintaining a softer spring characteristic throughout the lower operating range, allowing for better vibration absorption and impact alleviation, while ensuring stable support and damping efficiency across various displacements.
Implementation Method 1
a magnetic spring which includes: stationary magnets fixed to the lower frame; and a movable magnet which is linked to the upper frame through links and moves relative to the stationary magnets in accordance with the up-down movement of the upper frame
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(b)
AI summary
To enable damping force higher than conventional one to act and achieve a further reduction in thickness. A damper 60 is provided on an upper frame 10 which is a main vibrating body supported on upper portions of front links 21 and rear links 22 of a frame link mechanism 20, so as to be a sub-vibrating body which generates vibration whose behavior is different from that of vibration of the upper frame 10 caused by the rotary motion of the front links 21 and the rear links 22. When the upper frame is vibrated by input vibration, since the damper 60 exhibits the different vibration behavior, energy of the input vibration not only is distributed as vibrational energy of the upper frame 10 and heat energy generated by the elongation and contraction of the damper 60 but also is consumed as energy which vibrates the damper 60 itself provided as the vibrating body. Such arrangement and configuration of the damper 60 improve basic performance of vibration absorbency and impact absorbency that the suspension has.