Brakes – Inertia of damping mass dissipates motion – Resiliently supported damping mass
Reexamination Certificate
2002-07-26
2004-08-24
Siconolfi, Robert A. (Department: 3683)
Brakes
Inertia of damping mass dissipates motion
Resiliently supported damping mass
C074S552000, C074S574300
Reexamination Certificate
active
06779637
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosures of Japanese Patent Application No. 2001-229681 filed on Jul. 30, 2001 including the specification, drawings and abstract, are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dynamic damper which is adapted to be mounted on a steering column or a steering wheel of an automotive vehicle for the purpose of damping or attenuating vibrations excited in a steering wheel.
2. Description of the Related Art
A steering wheel of an automotive vehicle is generally fixed to a free end of a longitudinal steering column that is supported by the vehicle at a bound end thereof. Therefore, the steering wheel is prone to be subjected to vibrations applied thereto in a direction perpendicular to an axial direction of the steering column. Further, a driver of the vehicle almost always handles directly the steering wheel during driving the vehicle, and eventually is able to sensitively feel minute vibrations excited in the steering wheel. Since the vibrations excited in the steering wheel greatly impact on a riding comfort of the vehicle as felt by the driver, there has been a great regard for absorbing the vibrations excited in the steering wheel.
In an attempt to damp or attenuate vibrations excited in the steering wheel, a dynamic damper, which includes a mass member and a spring member for elastically supporting the mass member, has been mounted on the steering wheel or other members of the steering system, thereby providing a secondary vibration system for the steering system as a primary vibration system. A natural frequency of the secondary vibration system is tuned to a natural frequency of the steering system, so that the vibrations excited in the steering wheel may be damped.
Keeping pace with recent advancement in recognition of safety and recent tendency of upgrading automotive vehicles, a telescopic steering column has been developed in order to allow a driver to adjust a position of the steering wheel in a longitudinal direction of the vehicle, depending upon his or her body-build or affinity.
An extensive study of the dynamic damper for use in the steering system conducted by the present inventor has revealed the fact that the conventional dynamic damper is not able to exhibit a desired damping effect for vibrations excited in a steering system equipped with the telescopic steering column. Described in detail, such a steering system experiences a change of the axial length of the steering column upon adjusting the position of the steering wheel supported by the steering column. This causes a relatively large amount of change in the spring constant of the steering column for supporting the steering wheel, thereby inevitably changing a natural frequency of the steering wheel supported by the steering column over a wide frequency range. Therefore, the conventional dynamic damper that is tuned to a specific frequency range may suffer from deterioration in its damping effect depending upon the selected position of the steering wheel. That is, the conventional dynamic damper is incapable of stably exhibiting a desired damping effect with respect to vibrations excited in the telescopic steering column.
To cope with this conventional problem, it has been proposed to install on the telescopic steering column a plurality of dynamic dampers that are tuned to different frequency ranges. However, since the axial length of the telescopic steering column may vary among a great number of possible values, or may be continuously changed over a given axial distance, it is not practical to install on the telescopic steering column a great number of dynamic dampers that are tuned to a great number of possible natural frequencies of the steering wheel, respectively.
SUMMARY OF THE INVENTION
It is therefore one object of this invention to provide a dynamic damping device for use in a steering system equipped with a telescopic steering column, which is novel in construction, and which is capable of stably exhibiting an excellent vibration damping effect with respect to vibrations excited in the steering wheel while assuring a reduced number of dynamic dampers to be mounted on the steering system.
The above and/or other objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending 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 principal of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A dynamic damping device for use in a steering system equipped with a telescopic steering column of an automotive vehicle, and adapted to be mounted on a steering column and/or a steering wheel of the steering system for damping vibrations excited in the steering wheel, the dynamic damping device comprising: (a) a plurality of dynamic dampers each including a mass member and a spring member for elastically supporting the mass member with respect to the steering column or the steering wheel, the plurality of dynamic dampers being independent of each other, wherein the plurality of dynamic dampers have respective natural frequencies that are arranged such that at least two of the natural frequencies of the plurality of dynamic dampers are tuned respectively to a higher and a lower frequency range in relation to a central value of a range of variation in a natural frequency of the steering wheel due to an expansion or contraction of the telescopic steering column, and held within the range of vibration in the natural frequency of the steering wheel, and such that differences between adjacent ones of the natural frequencies of the plurality of dynamic dampers are held within 10-40% of the central value of the range of vibration in the natural frequency of the steering wheel.
According to this mode of the invention, the dynamic damping device includes the plurality of dynamic dampers whose natural frequencies are uniquely tuned as described above. This arrangement enables the dynamic damping device to damp vibrations excited in the steering wheel with efficiency and stability with the help of a fewer number of dynamic dampers, even when the natural frequency of the steering wheel is changed due to a positioning operation of the steering wheel.
If the natural frequencies of the plurality of dynamic dampers are tuned to one of the higher and lower frequency ranges in relation to the central value of the range of vibration in the natural frequency of the steering wheel, the dynamic damping device may suffer from difficulty in exhibiting a desired damping effect with respect to vibrations excited in the steering wheel whose frequencies corresponding to the other one of the higher and lower frequency ranges. In addition, if the differences between the adjacent ones of the natural frequencies of the plurality of dynamic dampers are deviate from 10-40% of the central value of the range of vibration in the natural frequency of the steering wheel, the dynamic damping device become ineffective with respect to a frequency range within the range of vibration in the natural frequency of the steering wheel. As a result, the vibration condition of the steering wheel may be deteriorated depending upon the selected position of the steering wheel. Described in detail, if the difference between the adjacent ones of the natural frequencies of the dynamic dampers is made smaller than 10% of the central value of the possible natural frequency range of the steering wheel, damping effects of these two dynamic dampers overlap with each other in terms of frequency, and the two
Aoi Takahiro
Hamada Masaaki
Kato Rentaro
Oshima Hideki
Beyer Weaver & Thomas LLP
Kramer Devon
Siconolfi Robert A.
Tokai Rubber Industries Ltd.
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