Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2001-09-26
2003-05-20
Schwartz, Christopher P. (Department: 3613)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S140150
Reexamination Certificate
active
06565072
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-297404 filed on Sep. 28, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a damping actuator applicable to an active vibration-damping device attached to a subject member for exhibiting an active damping effect with respect to vibrations excited in the subject member, and such an active vibration-damping device equipped with the damping actuator. In particular, the invention is concerned with a damping actuator suitably usable in a vibration-damping device for an automotive vehicle, such as an engine mount, a body mount and a vibration damper, and an active vibration-damping device equipped with such a damping actuator.
2. Description of the Related Art
For damping or reducing a vibration of a subject member or a member of a vibration transmitting system, there have been generally used vibration damping means which utilize a damping effect exhibited by a shock absorber or an elastic body member, or vibration isolating or insulating means which utilize a spring effect exhibited by a coil spring or an elastic body member. These vibration-damping devices are all adapted to provide a passive vibration damping or isolating effect, and are not capable of sufficiently damping or isolating a vibration whose characteristics tend to vary. In the light of this drawback of the known vibration device, there have been developed active vibration damping devices adapted to apply an oscillating force to the subject member for actively or positively offsetting or attenuating vibrations to be damped. Known examples of such active vibration damping devices are disclosed in JP-A-11-351322 and JP-A-2000-35083.
The active vibration-damping device requires a damping actuator for generating the oscillating force. Such a damping actuator is required to be capable of accurately controlling a frequency of the oscillating force. To meet this requirement, a known damping actuator, which has been suitably used in the active vibration damping devices as disclosed in the above-indicated publications, includes: an inner shaft member and an outer sleeve member disposed radially outwardly of said inner shaft member with a radial spacing therebetween; a permanent magnet fixed to the inner shaft member; and a coil fixed to the outer sleeve member. Upon energization of the coil, magnetic poles or fields are given on the side of the outer sleeve member and act on magnetic poles or fields given on the side of the inner shaft member owing to the permanent magnet, to thereby generate an oscillating force which causes a relative movement of the inner shaft member and the outer sleeve member in an axial direction of the inner shaft member. In the known damping actuator, therefore, an electric current applied to the coil is regulated so as to control generated electromagnetic force or magnetic force functioning as the oscillating force.
In particular, when the active vibration-damping device is used for damping vibrations excited in an automotive vehicle, the damping actuator is further required to generate a sufficiently large oscillating force with a reduced power consumption, as well as to be compact and lightweight.
However, the known damping actuator is insufficient to meet the above-mentioned requirements. Thus, the known damping actuator has been desired to be improved in all of the above-mentioned requirements, namely to be more (i) compact in size, (ii) light in weight, and (iii) efficient in generating the oscillating force in terms of power consumption.
SUMMARY OF THE INVENTION
It is therefore a first object of this invention to provide a novel damping actuator which is simple in construction and reduced in size and weight, and which is capable of generating an oscillating force with improved efficiency in terms of a required amount of electric power consumption.
It is a second object of this invention to provide an active vibration-damping device which is equipped with the damping actuator according to the present invention.
The first object may be attained according to the following modes (1)-(7) of the invention, and the second object may be attained according to the following modes (8)-(11) of the invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the present invention is not limited to the following modes or combinations of technical features, but may otherwise be recognized based on the thought of the present invention that described in the whole specification and drawings or that may be recognized by those skilled in the art in the light of the disclosure in the whole specification and drawings.
(1) A damping actuator comprising: (a) an inner shaft member; (b) an outer sleeve member disposed coaxially with and radially outwardly of the inner shaft member with a radial spacing therebetween such that the outer sleeve member being movable relative to the inner shaft member; (c) a coil disposed coaxially with and fixedly mounted on the inner shaft member; (d) an inner yoke fixedly disposed on the coil so as to form at an outer circumferential portion thereof a plurality of inner magnetic pole portions located in axially opposite sides of the coil, the plurality of inner magnetic pole portions being given magnetic poles upon energization of the coil; (e) a permanent magnet disposed radially outwardly of said coil and/or said inner yoke with a radial spacing therebetween and fixedly mounted in the outer sleeve member in a coaxial relation with each other so as to extend in a circumferential direction of the outer sleeve member; and (f) an outer yoke fixedly disposed on the permanent magnet and associated with the permanent magnet to form a plurality of outer magnetic pole portions, the plurality of outer magnetic pole portions being given magnetic poles by the permanent magnet, the inner magnetic pole portions and the outer magnetic pole portions are opposed to each other in a radial direction perpendicular to an axial direction of the inner shaft member with a predetermined radial gap therebetween, and are offset from each other in the axial direction, while the coil is in a non-energized state, the coil being energized for generating a magnetic axial driving force acting between the inner and outer magnetic pole portions so that the inner and outer magnetic pole portions are moved relative to each other in the axial direction.
In the damping actuator constructed according to the first mode (1) of this invention described above, the coil is fixed to the inner shaft member, unlike the conventional damping actuator in which the coil is fixed to the outer sleeve member. In this arrangement, a diameter of the coil is made small, whereby a length of a wire winding around the coil is made small to the number of winding of the coil. Since a resistance value of the wire to flow of an electric current therethrough is made small in proportion as the length of the wire is reduced, an amount of electric power consumption of the damping actuator can be reduced. Likewise, the weight of the damping actuator is made small in proportion as the length of the wire is reduced. In addition, the number of winding of the coil to the length of the wire is increased, so that a magnetic flux density of a magnetic field, i.e., a magnetic force generated by the coil is increased in proportion as the number of winding of the coil is increased. Thus, the present damping actuator is capable of generating a large magnetic axial driving force and a resultant sufficiently increased oscillating force.
Further, the damping actuator constructed according to the present mode (1) of the invention, the permanent magnet is fixed to the outer sleeve member, while the permanent magnet is conventionally fixed to the inner shaft member. In this
Goto Katsuhiro
Hagino Yoshihiko
Kramer Devon
Rossi & Associates
Schwartz Christopher P.
Tokai Rubber Industries Ltd.
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