Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2000-05-24
2001-12-04
Swann, J. J. (Department: 3611)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S140140, C188S161000, C188S267000
Reexamination Certificate
active
06325365
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibration mechanism having a magneto-spring that can be used for a vibration isolator such, for example, as a suspension unit, a cab mount, an engine mount or the like.
2. Description of the Related Art
Various types of damping materials, dampers, and other control methods have been proposed to prevent vibration and noise that occur in machines and structures built from materials with low internal damping properties, which are required for their strength and rigidity.
In particular, with motor vehicles progressively being made to run at faster and faster speeds, damage to the muscular and nervous systems of vehicle occupants due to exposure to vibration is becoming an issue. Symptoms of these types of damage include fatigue, headaches, stiff shoulders, lower back pain, and vision problems. Normally, springs and damping materials, such as metal springs, air springs, rubber, viscoelastic materials, and dampers, are combined to optimize vibration isolating properties. However, this combination often exhibits opposing characteristics, as in the relationship between the dynamic magnification and the loss factor. That is, if the dynamic magnification is reduced to improve the low-frequency characteristics, this results in a hard spring having a small loss factor, which deteriorates the high-frequency characteristics. In contrast, if the loss factor is increased to improve the high-frequency characteristics, this results in a soft spring having a large dynamic magnification, which is analogous to the damping materials and deteriorates the low frequency characteristics. For that reason, many studies are being conducted on controlling vibration using passive vibration isolators including dynamic dampers, or quasi-active or active control systems. There is a demand for the dampers which can cope with a characteristic change of an object for which vibration isolation is intended, or which is not subject to deterioration with age and influenced by the environment such as temperatures, oils, ozone or the like.
From among these studies, a suspension seat that combines a suspension mechanism set at a low spring constant under a relatively hard cushion has been proposed as a seat that would reduce the vibrational energy from a motor vehicle. Conventional suspension seats attempt to find a point of compromise between isolating high-frequency components of vibrational input and reducing the shocks due to the cushion hitting its bottom point (bottoming or bottom end stop), to optimize the suspension's parameters, but with passive control, limitations always exist.
In recent years, accompanying the practical use of permanent magnets that have a high coercive force and high residual magnetic flux density, research is flourishing in area such as mechanical structures and magnetic systems that utilize magnetic levitation, magnetic bearings, MR dampers, etc., which use magnetic force and magnetic fluidity to control vibration. In particular, magnetic dampers in which eddy currents caused by electromagnetic induction and magnetic damping caused by the effects of magnetic flux are utilized are useful as an attenuating means, and the practical use thereof is expanding.
Meanwhile, because magnetic levitation damping technology makes it possible to support physical objects with no actual physical contact, its merits include reduction of problems related to friction and wear, the capability for motion at very high speeds, and low levels of vibration and noise. Moreover, it can be used in special situations (also a special characteristic of magnets), as well as having the advantage of its force being effective in all directions. For those reasons, magnetic levitation vehicles, magnetic bearings, etc. which apply these special characteristics are being developed.
Of the levitation technologies that utilize these types of magnetic forces, the majority utilizes attractive forces. Magnetic circuits that make use of repulsive forces are difficult to utilize in vibration control systems, due to their instability, the fact that the marked non-linear characteristics of the repulsive forces are difficult to control, and their large spring constant.
SUMMARY OF THE INVENTION
The present invention has been developed to overcome the above-described disadvantages.
It is accordingly an objective of the present invention to provide a vibration mechanism capable of effectively absorbing vibration input from the outside when incorporated into a suspension unit for an automobile seat, an engine mount or the like.
In accomplishing the above and other objectives, the vibration mechanism according to the present invention includes first and second permanent magnets spaced from each other, and the second permanent magnet is movable relative to the first permanent magnet. The first and second permanent magnets constitute a repulsive magneto-spring having a spring constant, wherein magnetic energy accumulated in the magneto-spring is made substantially constant by appropriately selecting a locus of motion of the second permanent magnet relative to the first permanent magnet, thereby setting the spring constant to substantially zero.
By this construction, although the stroke varies depending on input even if vibration is input to the first permanent magnet, the second permanent magnet is not much affected by such vibration, making it possible to efficiently absorb the vibration.
If each of the first and second permanent magnets is a multi-pole magnet, a leakage magnetic field created between neighboring magnet poles can be effectively utilized, resulting in an efficient magneto-spring.
Advantageously, the repulsive force acting between the first and second permanent magnets is made substantially constant by appropriately selecting a relationship between the opposing area of the first and second permanent magnets and the distance between the first and second permanent magnets. Although the construction is very simple, vibration can be effectively absorbed by making use of a phase shift.
Conveniently, the first permanent magnet is secured to a stationary frame, while the second permanent magnet is secured to a movable frame movably mounted on the stationary frame. By this construction, movement of the movable frame relative to the stationary frame changes the opposing area of the two permanent magnets depending on the distance therebetween. As a result, the spring constant is maintained substantially zero, making it possible to efficiently absorb vibration.
If the first and second permanent magnets are inclined on the stationary and movable frames, respectively, the opposing area of the magnets can be easily changed depending on the distance between the magnets, making it possible to simplify the construction of the vibration mechanism.
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Fujita Etsunori
Kawasaki Seiji
Kojima Shigeyuki
Delta Tooling Co., Ltd.
Devine David
Swann J. J.
Wenderoth , Lind & Ponack, L.L.P.
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