Patent Description:
Vibrations generated when a tire rolls on a surface can cause undesirable NVH issues including wheel hop, vehicle vibrations, and noise. Typically, dampers in vehicle suspensions or viscoelastic damping in the tire itself can reduce the amplitude of these NVH issues. However, as tires are designed for ever-lower rolling resistance targets, the mass and damping of the tires are reduced which, in turn, reduces their ability to damp vibrations. If a vehicle has low suspension damping and/or low tire damping, NVH issues can be exacerbated.

An apparatus according to the preamble of claim <NUM> is known from <CIT>. In addition, <CIT> discloses another apparatus comprising a wheel/hub assembly including an axle shaft, a wheel, and a hub supporting the wheel on the axle shaft with a tuned mass-spring damper (TMSD) being vibrationally coupled to the wheel/hub assembly and having a counteracting resonant frequency of vibration that is predetermined with reference to a target resonant frequency of vibration of the wheel/hub assembly.

According to the invention, an apparatus as defined in claim <NUM> is provided. The dependent claims define preferred and/or advantageous embodiments of the invention. According to the invention, a tuned-mass-spring damper (TMSD) is provided, the TMSD coupled to the wheel/hub assembly of the apparatus. This TMSD may absorb vibrational energy from the wheel/hub assembly such that the vibrational energy transmitted to the vehicle itself is tuned and reduced. However, unlike a tire with high damping, this invention may not contribute significantly to rolling resistance. Additionally, unlike a vehicle with high suspension damping, this invention may not cause vibrations to be transmitted to the vehicle itself. In other words, this invention may reduce vibrations without increasing rolling resistance.

The TMSD may be connected to the wheel or hub or axle by means of a bearing such that the TMSD can rotate independently from the wheel. This arrangement may permit the TMSD to remain rotationally fixed (i.e. not rotating) even if the wheel itself is rotating. In one embodiment, the primary advantage of the arrangement comes from the fact that the TMSD would not need to rotate with the wheel. Because the TMSD does not need to rotate with the wheel, it may eliminate two potentially detrimental effects on vehicle performance that could be caused if the TMSD was forced to rotate with the wheel:.

The TMSD is configured in distinct portions of elastic material that establish the counteracting resonant frequency of vibration. These may include a spring portion overlying a part of the wheel/hub assembly, and a mass portion overlying the spring portion. An embodiment of the TMSD may thus include distinct portions of rubber or other elastic material configured as layers of an elastic structure mounted on the wheel/hub assembly.

The distinct portions of the elastic structure may have properties of density and stiffness that are predetermined with reference to the counteracting resonant frequency. The portions of elastic material may thus include a first portion having stiffness that is predetermined with reference to the counteracting resonant frequency, and a second portion having density that is predetermined with reference to the counteracting resonant frequency.

The structures illustrated in the drawings include examples of the elements recited in the claims. The illustrated structures thus include examples of how a person of ordinary skill in the art can make and use the claimed invention. These examples are described to meet the enablement requirements of the patent statute without imposing limitations that are not recited in the claims. One or more of the elements of one embodiment may be used in combination with, or as a substitute for, one or more elements another as needed for any particular implementation of the invention.

As shown schematically in <FIG>, an apparatus <NUM> includes a tire <NUM>, which may be mounted on a vehicle wheel/hub assembly <NUM>. The wheel/hub assembly <NUM> may include at least two of a wheel <NUM>, a hub <NUM> and an axle shaft <NUM>. In use, the tire <NUM> and the wheel/hub assembly <NUM> may be subjected to dynamic forces from the road surface. Such forces can induce NVH. The applied dynamic forces may vary throughout a band of frequencies. The tire <NUM> and the wheel/hub assembly <NUM> may then experience a corresponding range of vibrational modes induced by the applied dynamic forces. A narrow band of frequencies may include frequencies at which the wheel/hub assembly <NUM> has a resonant vibratory response. The wheel/hub assembly <NUM> may then experience a corresponding resonant mode of vibration. Such a resonant mode of vibration may generate excessive NVH.

For example, the solid curves in <FIG> indicates levels of NVH generated by a wheel/hub assembly across a range of force input frequencies. The peaks in the solid line curves indicate NVH levels generated by resonant vibratory responses in the wheel/hub assembly. The peaks in the solid line curves thus occur at resonant frequencies of vibration in the wheel/hub assembly. Accordingly, a wheel/hub assembly as represented here will vibrate in a resonant mode at each force input frequency corresponding to a peak in a solid line curve.

Referring again to <FIG>, a resonant frequency of NVH in the wheel/hub assembly <NUM> may be determined in a known manner. The determined resonant frequency may be selected as a target resonant frequency for which the resulting NVH is sought to be attenuated. One or more TMSDs <NUM> may then be tuned to have a resonant frequency of vibration equal or substantially equal to the target frequency. When a TMSD <NUM> is operatively coupled to the wheel/hub assembly <NUM>, as shown for example in <FIG>, it can be oriented to vibrate at the target frequency in a resonant mode that acts oppositely to the resonant mode of vibration in the wheel/hub assembly <NUM>. The counteracting vibrational force inputs from the TMSD <NUM> can suppress vibrational displacement that might otherwise occur. This can attenuate the NVH generated by vibration at the target frequency, as indicated by the dashed line curves shown in <FIG>.

The wheel/hub assembly <NUM> of <FIG> may be equipped with a TMSD <NUM> for suppressing vibration as described above. In this embodiment, the TMSD <NUM> is configured as a circumferentially continuous ring centered coaxially over the axle shaft <NUM>. The TMSD <NUM> has distinct portions of elastic material with properties of density and stiffness that are predetermined with reference to the counteracting resonant frequency. The portions of elastic material may include a first portion in which the stiffness is predetermined with reference to the counteracting resonant frequency, and a second portion in which the density is predetermined with reference to the counteracting resonant frequency.

More specifically, the distinct portions of elastic material in the illustrated TMSD <NUM> include an inner layer <NUM> of rubber, and an outer layer <NUM> of rubber that overlies and is bonded to the inner layer <NUM>. The inner layer <NUM> may be mounted on the outer race <NUM> of a bearing <NUM> on the axle shaft <NUM>. The bearing <NUM> may couple the TMSD <NUM> vibrationally with the wheel/hub assembly <NUM> at the axle shaft <NUM>, but may permit the TMSD <NUM> to float rotationally relative to the axle shaft <NUM>.

The inner and outer layers <NUM> and <NUM> of the TMSD <NUM> may have the same stiffness or differing stiffness, but in either case the stiffness of the inner layer <NUM> may be predetermined with reference to the counteracting resonant frequency. The inner and outer layers <NUM> and <NUM> may also have the same density or differing density, but in either case the density of the outer layer <NUM> may be predetermined with reference to the counteracting resonant frequency. This enables the inner layer <NUM> to serve as a spring portion of the TMSD <NUM>, with the outer layer <NUM> serving as a mass portion coupled to the spring portion. When the wheel/hub assembly <NUM> vibrates, the TMSD <NUM> may act as a spring/mass system to counteract the vibration. The counteracting spring/mass actions of the TMSD <NUM> are optimal at the resonant frequency of vibration to which the TMSD <NUM> is tuned. Since the TMSD <NUM> is tuned to the target resonant frequency of the wheel/hub assembly <NUM>, it applies optimal resistance to vibration of the wheel/hub assembly <NUM> in the corresponding resonant mode.

The TMSD <NUM> can be coupled, and/or vibrationally coupled, with the wheel/hub assembly <NUM> in other arrangements. For example, in the embodiment of <FIG>, an apparatus <NUM> is illustrated in which the TMSD <NUM> may be mounted directly on the axle shaft <NUM>. In the embodiment of <FIG>, an apparatus <NUM> is illustrated in which the TMSD <NUM> may be coupled to a constant velocity (CV) joint <NUM> through a bearing <NUM> similar to the bearing <NUM> of <FIG>. As shown in <FIG>, an apparatus <NUM> is illustrated in which the TMSD <NUM> can be mounted directly on the CV joint <NUM>, without the use of a bearing. In the embodiment of <FIG>, an apparatus <NUM> is illustrated in which the TMSD <NUM> may be located within the tire <NUM>, and may be coupled to the wheel/hub assembly <NUM> through a bearing <NUM> having an inner race <NUM> fixed to the wheel <NUM> to rotate with the wheel <NUM>. Other arrangements could include, for example, mounting the TMSD <NUM> on the wheel <NUM> without a bearing, on the hub <NUM> either with or without a bearing, at another location on the axle shaft <NUM>, or at any other suitable location on the wheel/hub assembly <NUM>.

In one embodiment, an apparatus is provided, the apparatus comprising: a wheel/hub assembly including an axle shaft, a wheel, and a hub supporting the wheel on the axle shaft, the wheel/hub assembly having a target resonant frequency of vibration; and a tuned mass-spring damper vibrationally coupled to the wheel/hub assembly and having a counteracting resonant frequency of vibration that is predetermined with reference to the target resonant frequency of vibration. In one embodiment, the damper is configured as a circumferentially continuous ring and is mounted concentrically on the wheel/hub assembly. In one embodiment, the counteracting resonant frequency is equal or substantially equal to the target resonant frequency. In one embodiment, the damper is configured in distinct portions of elastic material having properties of density and stiffness that are predetermined with reference to the counteracting resonant frequency. In one embodiment, the distinct portions of elastic material include a first portion having stiffness predetermined with reference to the counteracting resonant frequency, and a second portion having density predetermined with reference to the counteracting resonant frequency. In one embodiment, the distinct portions of elastic material have the same stiffness. In one embodiment, the distinct portions of elastic material have differing stiffness. In one embodiment, the distinct portions of elastic material have the same density. In one embodiment, the distinct portions of elastic material have differing density. In one embodiment, the distinct portions of elastic material include a spring portion overlying a part of the wheel/hub assembly and having stiffness predetermined with reference to the counteracting resonant frequency, and further include a mass portion overlying the spring portion and having density predetermined with reference to the counteracting resonant frequency. In one embodiment, the distinct portions of elastic material are configured as layers of a circumferentially continuous ring. In one embodiment, the damper is coupled to the wheel/hub assembly through a bearing on the axle shaft. In one embodiment, the damper is mounted directly on the axle shaft. In one embodiment, the wheel/hub assembly includes a CV joint, and the damper is coupled to the wheel/hub assembly through a bearing on the CV joint. In one embodiment, the wheel/hub assembly includes a CV joint, and the damper is mounted directly on the CV joint. In one embodiment, the damper is coupled to the wheel/hub assembly through a bearing mounted on the wheel at a location within the tire.

To the extent that the term "includes" or "including" is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term "comprising" as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term "or" is employed (e.g., A or B) it is intended to mean "A or B or both. " When the applicants intend to indicate "only A or B but not both" then the term "only A or B but not both" will be employed. Thus, use of the term "or" herein is the inclusive, and not the exclusive use. See Bryan A. Garner, A Dictionary of Modern Legal Usage <NUM> (2d. Also, to the extent that the terms "in" or "into" are used in the specification or the claims, it is intended to additionally mean "on" or "onto. " To the extent that the term "substantially" is used in the specification or the claims, it is intended to take into consideration the degree of precision available in tire manufacturing, which in one embodiment is ± <NUM> millimeters (± <NUM> inches). To the extent that the term "selectively" is used in the specification or the claims, it is intended to refer to a condition of a component wherein a user of the apparatus may activate or deactivate the feature or function of the component as is necessary or desired in use of the apparatus. To the extent that the term "operatively connected" is used in the specification or the claims, it is intended to mean that the identified components are connected in a way to perform a designated function. As used in the specification and the claims, the singular forms "a," "an," and "the" include the plural. Finally, where the term "about" is used in conjunction with a number, it is intended to include ± <NUM> % of the number. In other words, "about <NUM>" may mean from <NUM> to <NUM>.

Claim 1:
An apparatus comprising:
a wheel/hub assembly (<NUM>) including an axle shaft (<NUM>), a wheel (<NUM>), and a hub (<NUM>) supporting the wheel (<NUM>) on the axle shaft (<NUM>), the wheel/hub assembly (<NUM>) having a target resonant frequency of vibration; and
a tuned mass-spring damper (<NUM>) vibrationally coupled to the wheel/hub assembly (<NUM>) and having a counteracting resonant frequency of vibration that is predetermined with reference to the target resonant frequency of vibration,
wherein the damper (<NUM>) is configured in distinct portions of elastic material having properties of density and stiffness that are predetermined with reference to the counteracting resonant frequency,
characterized in that
the damper (<NUM>) comprises:
an inner layer (<NUM>) of rubber; and
an outer layer (<NUM>) of rubber that overlies and is bonded to the inner layer (<NUM>);
wherein the inner layer (<NUM>) is configured to be mounted on an outer race (<NUM>) of a bearing (<NUM>) on the axle shaft (<NUM>).