Note: Descriptions are shown in the official language in which they were submitted.
II
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COMPOSITION FOR CORRECTING TIRE-WHEEL ASSEMBLY
IMBALANCES, FORCE VARIATIONS, AND VIBRATIONS
[0001] This international application claims priority to, and the benefit of,
pending
U.S. Provisional Patent Application No. 61/143,543, filed January 9, 2009, the
disclosure of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] This invention relates to a composition comprising a plurality of
particles for
use in reducing force variations and/or vibrations acting on a pneumatic tire
and/or
wheel during operation of a tire and wheel ("tire-wheel") assembly. More
specifically, the present invention provides a composition containing
particles or other
media having chambers containing fluid, such as air, or any other tire
balancing or
energy absorbing material.
Description of the Related Art
[0003] Tires are utilized by vehicles to improve vehicle handling and ride.
Tires,
however, are exposed to imbalances and abnormalities and disturbances, which
result
in force variations and vibrations acting upon the tire and ultimately the
vehicle.
Ultimately, imbalances, force variations, and vibrations reduce vehicle
handling,
stability, and ride, while also causing excessive tire wear. Accordingly, it
is generally
desirous to reduce, if not eliminate, imbalances, force variations, and
vibrations that
act upon the tire, the tire-wheel assembly, and ultimately the vehicle.
[0004] A vehicle generally comprises an unsprung mass and a sprung mass. The
unsprung mass generally includes portions of the vehicle not supported by the
vehicle
suspension system, such as, for example, the tire-wheel assembly, steering
knuckles,
brakes and axles. The sprung mass, conversely, generally comprises the
remaining
portions of the vehicle supported by the vehicle suspension system. The
unsprung
mass can be susceptible to disturbances and vibration originating from a
variety of
sources, such as worn joints, wheel misalignment, wheel non-uniformities, and
brake
I
NI
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drag. Disturbances and vibrations may also originate from a tire, which may be
caused by tire imperfections, such as tire imbalance, tire non-uniformities,
and
irregular tread wear.
[0005] A tire imbalance generally results from a non-uniform distribution of
weight
around the tire relative to the tire's axis of rotation. An imbalance may also
arise
when the tire weight is not uniform from side-to-side, or laterally, along the
tire. Tire
imbalances may be cured by placing additional weight at particular locations
to
provide a balanced distribution of weight about the tire. Balance weights,
such as
clip-on lead weights or lead tape weights, are often used to correct tire
imbalance and
balance the tire-wheel assembly. The balance weights are applied to the wheel
in a
position directed by a balancing machine. Balancing may also be achieved by
inserting a plurality of particulates or pulverant material into the tire
pressurization
chamber, which is forced against the tire inner surface by centrifugal forces
to correct
any imbalance. However, even perfect balancing of the tire-wheel assembly does
not
ensure that the tire will be exposed to other disturbances and vibrations.
Even a
perfectly balanced tire can have severe vibrations, which may result from non-
uniformities in the tire. Accordingly, a balanced tire-wheel assembly may not
correct
non-uniformities affecting the tire-wheel assembly during vehicle operation.
[0006] Tire non-uniformities are imperfections in the shape and construction
of a tire.
Non-uniformities affect the performance of a tire, and, accordingly, the
effects of
which can be measured and quantified by determining particular dynamic
properties
of a loaded tire. Non-uniformities also cause a variation of forces acting on
tire 11
through its footprint B. For example, a tire may have a particular conicity,
which is
the tendency of a tire to roll like a cone, whereby the tire translates
laterally as the tire
rotates under load. Also, a tire may experience ply steer, which also
quantifies a tire's
tendency to translate laterally during tire operation; however, this is due to
the
directional arrangement of tire components within the tire, as opposed to the
physical
shape of the tire. Accordingly, force variations may be exerted by the tire as
it rotates
under load, which means that different force levels may be exerted by the tire
as
portions of the tire having different spring constants enter and exit the tire
footprint
PI
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(the portion of the tire engaging the surface upon which the tire operates).
Non-
uniformities are measured by a force variation machine.
[0007] Force variations may occur in different directions relative to the
tire, and,
accordingly, may be quantified as radial (vertical), lateral (side-to-side),
and
tangential (fore-aft) force variations. Radial force variations operate
perpendicular to
the tire rotational axis along a vertical axis extending upward from the
surface upon
which the tire operates, and through the center of the tire. Radial forces are
strongest
in the vertical direction (e.g., wheel "hop"), such as during the first tire
harmonic
vibration. Radial forces may also have a horizontal (fore-aft, or "surge")
component
due to, for example, the radial centrifugal force of a net mass imbalance in
the
rotating tire. Lateral force variations are directed axially relative to the
tire's
rotational axis, while tangential force variations are directed
perpendicularly to both
radial and lateral force variation directions, which is generally in the
forward and
rearward direction of travel of the tire. Lateral forces cause either tire
wobble or a
constant steering force. Tangential forces, or fore-aft forces, generally act
along the
tire footprint in the direction of tire travel, or, in other words, in a
direction both
tangential to the tire's outer circumference (e.g., tread surface) and
perpendicular to
the tire's axis of rotation (thus also perpendicular to the radial and lateral
forces).
Tangential force variations are experienced as a "push-pull" effect on a tire.
Force
variations may also occur due to the misalignment of the tire-wheel assembly
[0008] Because tires support the sprung mass of a vehicle, any dynamic
irregularities
or disturbances experienced by the tire will cause the transmission of
undesirable
disturbances and vibrations to the sprung mass of the vehicle, and may result
in an
undesirable or rough vehicle ride, as well as a reduction in vehicle handling
and
stability. Severe vibration can result in dangerous conditions, such as wheel
tramp or
hop and wheel shimmy (shaking side-to-side). Radial force variations are
generally
not speed dependent, while fore/aft force variations may vary greatly with
speed.
Tangential force variations are generally insignificant below 40 mph; however,
tangential force variations surpass radial force variations as the dominant
cause of
unacceptable vibration of a balanced tire rotating at over 60 mph and can
quickly
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grow to be a magnitude of twice the radial force variation at speeds
approaching 80
mph. Currently, there are no viable methods for reducing tangential force
variations.
[0009] Methods have been developed to correct for excessive force variations
by
removing rubber from the shoulders and/or the central region of the tire tread
by
means such as grinding. These methods are commonly performed with a force
variation or uniformity machine which includes an assembly for rotating a test
tire
against the surface of a freely rotating loading drum. This arrangement
results in the
loading drum being moved in a manner dependent on the forces exerted by the
rotating tire whereby forces may be measured by appropriately placed measuring
devices. A computer interprets the force measurements and grinders controlled
by the
computer remove rubber from the tire tread. However, grinding of the tire has
certain
disadvantages. For example, grinding can reduce the useful tread life of the
tire, it
may render the tire visually unappealing or it can lead to the development of
irregular
wear when the tire is in service on a vehicle. Studies have shown that
grinding does
not reduce tangential force variation (Dorfi, "Tire Non-Uniformities and
Steering
Wheel Vibrations," Tire Science & Technology, TSTCA, Vol. 33, no. 2, April-
June
2005 p 90-91). In fact, grinding of the tire can also increase tangential
force
variations within a tire.
[0010] Presently, there is a need to effectively reduce tire imbalance, force
variations,
and vibrations. This would allow tires having excessive force variations to be
used.
For example, new tires having excessive force variations may be used instead
of being
discarded. Further, there is a need to reduced and/or correct force variations
and
vibrations that develop during the life of a tire, such as due to tire wear or
misalignment of a vehicle component, where such reduction and/or correction
may
occur concurrently as any such force variation and/or vibration develops
(i.e., without
dismounting to analyze and/or correct each such tire after a performance issue
is
identified). There also remains a need to reducing rolling resistance and
reduce
impact energy loss at the tire footprint.
WO 2010/081016 CA 02748744 2011-06-29 PCT/US2010/020519
SUMMARY OF THE INVENTION
[0011] The present invention comprises compositions and methods for improved
correction of force imbalances, force variations, and/or dampening of
vibrations in a
tire-wheel assembly. In particular embodiments, the composition includes a
plurality
of particles for positioning within the tire-wheel assembly, wherein each of
said
particles include a void.
[0012] In other embodiments, the present invention comprises a method for
improved
correction of force imbalances, force variations, and/or dampening of
vibrations in a
tire-wheel assembly. In particular embodiments, the methods include the steps
of
providing a tire-wheel assembly and providing a plurality of particles
positioned
within the tire-wheel assembly, wherein each of said particles include a void.
A
further step includes placing said plurality of particles into a
pressurization chamber
within said tire-wheel assembly.
[0013] The foregoing and other objects, features and advantages of the
invention will
be apparent from the following more detailed descriptions of particular
embodiments
of the invention, as illustrated in the accompanying drawings wherein like
reference
numbers represent like parts of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows a single wheel model of a vehicle showing the relationship
of
the sprung mass and the unsprung mass;
[0015] FIG. 2 is a fragmentary side elevational view of a conventional tire-
wheel
assembly including a tire carried by a rim, and illustrates a lower portion or
"footprint" of the tire tread resting upon and bearing against an associated
supporting
surface, such as a road;
[0016] FIG. 3 is an axial vertical cross sectional view of a conventional rear
position
unsprung mass of vehicle including the tire-wheel assembly of FIG. 2 and
additionally illustrates the lateral extent of the footprint when the tire
rests under load
upon the road surface;
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[0017] FIG. 4 is a cross sectional view of the tire-wheel assembly of FIG. 3
during
rotation, and illustrates a plurality of radial load forces of different
variations or
magnitudes reacting between the tire and the road surface as the tire rotates,
and the
manner in which the particle mixture is forced in position in proportion to
the variable
radial impact forces;
[0018] FIG. 5 is a graph, and illustrates the relationship of the impact
forces to the
location of the particle mixture relative to the tire when under
rolling/running
conditions during equalizing in accordance with FIG. 4;
[0019] FIG. 6A is a cross-sectional view of a spherical particle having a
central
chamber (i.e., void) to provide a rotationally weight balanced particle,
according to
one embodiment of the present invention.
[0020] FIG. 6B is a cross-sectional view of an ellipsoid-shaped particle
having a
central chamber, according to an alternative embodiment of the disclosed
invention.
[0021] FIG. 7A is a cross-sectional view of a spherical particle having a non-
central
internal chamber to provide a rotationally weight imbalanced particle,
according to
another alternative embodiment of the present invention.
[0022] FIG. 7B is a cross-sectional view of an ellipsoid-shaped particle
having a non-
central internal chamber, according to another alternative embodiment of the
present
invention.
[0023] FIG. 8 is a cross-sectional view of a spherical particle having a
central
chamber partially filled with a second material or medium, according to
another
alternative embodiment of the present invention.
[0024] FIG. 9 is a cross-sectional view of a spherical particle having a
plurality of
chambers located internally and along an exterior surface of such particle,
according
to another alternative embodiment of the present invention.
[0025] FIG. 10 is a perspective view of a spheroid-shaped particle, such as is
shown
in FIGS. 6A, 7A, and 8.
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[0026] FIG. 11 is a perspective view of an ellipsoid-shaped particle, such as
is shown
in FIGS. 6B and 7B.
DETAILED DESCRIPTION OF THE DRAWINGS
[0027] Reference is first made to FIG. 1 of the drawings which shows a single
wheel
model of a vehicle where symbol M5 denotes the mass of a sprung vehicle
structure
(hereafter referred to as sprung mass) and Mõ denotes the mass of an unsprung
structure (hereafter referred to as unsprung mass). The unsprung mass M.
generally
consists of all of the parts of the vehicle not supported by the vehicle
suspension
system such as the tire-wheel assembly, steering knuckles, brakes and axles.
The
sprung mass M5, conversely is all of the parts of the vehicle supported by the
vehicle
suspension system. Symbol K5 denotes the spring constant of a vehicle spring,
and CS
denotes the damping force of the shock absorber. The unsprung mass Mõ can be
susceptible to disturbances and vibration from a variety of sources such as
worn
joints, misalignment of the wheel, brake drag, irregular tire wear, etc.
Unsprung mass
Mõ may also be susceptible to imbalances in the tire or wheel, or tire-wheel
assembly.
The vehicular tires are resilient and support the sprung mass M5 of a vehicle
on a road
surface as represented by the spring rate of the tires as symbol Kt. Any tire
or wheel
non-uniformities result in a variable spring rate Kt which, as the tire
rotates, can cause
vibration of the unsprung mass M. Further, any obstacle encountered by the
tire
during its operation results in an impact, which causes force variations and
vibrations
that propagate through the tire and ultimately to the sprung mass M5 of the
vehicle. In
each instance, the imbalances, force variations, and/or vibrations are
transmitted to the
sprung mass M5, thereby reducing vehicle ride, stability, and/or handling.
[0028] Referring now to FIGS. 2 and 3 of the drawings, a tire-wheel assembly
10 is
illustrated, which is an element of the unsprung mass Mõ referred to in FIG.
1. A tire
11 and a wheel (i.e., rim) 12 having a tire inflation valve define the tire-
wheel
assembly 10. A tire tends to flex radially, and sidewalls SW1, SW2 (FIGS. 2, 3
and
4) which tend to bulge outwardly under load when resting or running upon an
operating surface R, which may be, for example, a ground or a road surface.
The
I
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amount of flex will vary depending upon the tire construction and inflation,
as well as
the loads acting upon the tire 11.
[0029] Tire 11 engages an operating surface R with a tread T, which forms a
footprint
B as the tread is forced against operating surface R. Footprint B forms a
shape having
a length L and a lateral width W. Tire 11 also includes beads B1, B2 for
securing tire
11 upon wheel 12. Due to tire deflection, tread compression, and/or frictional
losses,
tire 11 resists rolling under load. Accordingly, each tire 11 has a measurable
rolling
resistance when operating under load.
[0030] Correction of tire-wheel imbalances and non-uniformities associated
with the
unsprung mass Mõ of a vehicle is beneficial for reducing undesired vibrations
that are
detrimental to the handling, longevity, and overall performance of the vehicle
and its
tires. If imbalances and non-uniformities are not corrected, excessive force
variations
may cause excessive vibrations and/or less than optimum vehicle handling,
stability,
and ride, as well as excessive wear of the tires and other vehicle components.
As
previously mentioned, non-uniformities and vibrations may exist even if the
tire-
wheel assembly 10 is balanced (i.e., mass balanced with weights), as non-
uniformities
may independently exist in the tire, and/or result from brake drag, worn
steering or
suspension linkages, changing road conditions, tire wear or misalignment, and
one or
more tires impacting an obstacle ("obstacle impact"), for example. Therefore,
in
addition to correcting any tire or wheel imbalance, there is also a present
need to
reduce, minimize, and/or correct force variations and vibrations arising
during
operation of tire-wheel assembly 10, and to achieve such in a short period of
time
(i.e., to minimize the response time for making these force and vibration
corrections).
This response period is also referred to as the restitution period.
[0031] To substantially reduce, minimize, or correct mass or weight
imbalances, force
variations, and/or vibrations associated with a tire-wheel assembly, a
plurality of
particulates (or particles) 20 are inserted into a pressurization chamber I
within tire-
wheel assembly 10. Pressurization chamber I is generally positioned between
tire 11
and wheel 12. In particular embodiments, particles 20 are able to reduce
and/or
substantially eliminate any mass or weight imbalance associated with tire-
wheel
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assembly 10 (i.e., associated with the tire 11 or wheel 12). Further,
particles 20 may
also be able to reduce radial, lateral, and even tangential force variations,
and reduce
or dampen vibrations operating through tire 11 and the unsprung mass Mõ of a
vehicle. Still further, particles 20 may also reduce tire rolling resistance.
Because
particles 20 are free flowing within pressurization chamber I, particles 20
are able to
alter their positions within the chamber, as necessary, to adapt to and reduce
any mass
or weight imbalance, force variations, and/or vibrations that may arise during
tire 11
operation, and during the operational life of the tire 11 and/or wheel 12 of
the tire-
wheel assembly 10. Reduction and/or correct of any mass or weight imbalance of
the
tire 11 and/or wheel 12 may be achieved in lieu of using other tire balancing
products,
such as, for example, lead weights or other balancing strips, which may be
mounted to
an interior or exterior surface of the wheel. Still, such tire balancing
products or
weights may also be used in conjunction with particles 20, such as when, for
example,
the tire-wheel assembly 10 is first balanced and a plurality of particles 20
are
subsequently inserted into the tire-wheel assembly 10.
[0032] A plurality of particles 20 may be inserted into pressurization chamber
I
through the tire pressurization valve, or, when particles 20 are sized larger
than the
valve opening, particles 20 may be placed into chamber I prior to tire 11
being fully
mounted on wheel 12. When placing particles 20 within chamber I other than
through the pressurization valve, particles 20 may be placed into chamber I in
a free-
form or in a collective form, such as, for example, within a degradable bag or
as a
briquette of particles 20. In operation, the bag or briquette would
deteriorate during
subsequent tire operation, as the chamber I warms and/or the bag or briquette
tumbles
during tire operation, to provide particles 20 in a free-form. This process
may be
repeated with each tire-wheel assembly 10 of a vehicle, and, once completed,
each
tire-wheel assembly 10 may be rotated with reduced force variations and
vibrations,
which are dampened and/or absorbed by the particles 20.
[0033] Referring now to FIGS. 6A and 6B, the particles 20 may include one or
more
voids (i.e., chambers) 40 within particle body 30. Voids 40 may be provided to
increase the balancing and/or energy absorbing capabilities of particles 20.
For
example, voids 40 may contain air or any other gas, or may be at least
partially filled
it
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with any other solid or fluid material, such as, for example, a viscous or
viscoelastic
energy absorbing material, to affect the deformation and/or rebound of
particle 20.
For example, a particle 20 having a void 40 may more significantly deform when
particle 20 impacts the interior of a tire during tire operation, than a
particle 20 not
having a void 40. By increasing the deformation of particle 20, more energy is
absorbed by particle 20, and the force variations and/or vibrations operating
through
or within the tire are further reduced. In particular arrangements, the
particle interior
or void 40 may be filled with a viscoelastic material for improved energy
absorption
capabilities, while the exterior of particle 20 may be formed of a more
durable
material, which may better withstand the environment and impact within the
tire and
increase the useful life of particle 20. Further, voids 40 may contain weight
material
or tire balancing material that improves that capability of particles 20 to
reduce or
correct any mass or weight imbalance of tire-wheel assembly 10, where such
balancing material may, for example, have a higher density or specific gravity
than
the material forming the surrounding body 30 of particle 20.
[0034] In particular embodiments, such as shown by example in FIG. 7A, one or
more holes or apertures 42 may extend from a void 40, and between such void 40
and
the exterior of the corresponding particle 20, so to allow the void 40 to vent
and allow
the particle 20 to deform (or compress) more upon particle impact during tire
operation, and/or reduce the compression or increased pressurization of any
air or gas
within the void 40. This may operate to further reduce the particle's ability
to
rebound upon particle impact during tire operation (or, in other words,
increase the
energy-absorbing capacity of the particle 20 during tire operation), since the
gas or air
is allowed to vent into the tire's interior chamber I during tire impact,
which reduces
the ability of the particle to further compress the air or gas contained
within the void
40 as it is deformed during impact. It is contemplated that each hole or
aperture 42
may comprise any shape or size.
[0035] Particles 20 may form any desired shape, regular or irregular. For
example,
with reference to the examples shown in FIGS. 6A and 6B, particles 20 may
comprise
spheroids or ellipsoids, respectively. Specifically, spheroids comprise
spherically-
shaped particles or spheres as shown by example in FIGS. 6A and 10. Particles
20
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may be shaped to improve the reduction or correction of any new or changing
imbalance, force variation, or vibration of tire-wheel assembly 10. For
example,
spherically-shaped particles 20 may facilitate improved rolling capabilities
for
improved relocation or maneuverability of any such particle 20 within chamber
I to
improve the responsiveness of a particle 20 for correction or reducing any new
or
changing imbalance, force variation, or vibration of tire-wheel assembly 10.
By
further example, non-spherical particle shapes (such as ellipsoids, cylinders,
cubes or
other hexahedrons, for example) may resist rotation by geometric resistance
and/or by
creating a mass or weight imbalance within a particle 20 about a particle's
central or
rotational axis to resist rotation thereof, which may better allow a particle
20 to more
quickly settle and position itself within chamber I to reduce or correct any
new or
changing imbalance, force variation, or vibration. Examples of such non-
spherically
imbalanced particles 20 that resist rotation are shown in FIGS. 6B, 7B, and
11. In can
be said that spherical particles 20 have a rotationally balanced shape, while
ellipsoids
and other shaped objects are not rotationally balanced about at least one axis
of
rotation.
[0036] Any particle 20 may contain one or more voids 40 forming any desired
shape,
regular or irregular. For example, with continued reference to FIGS. 6A and
6B,
voids 40 may be spheroids or ellipsoids, respectively. Spheroids include voids
40
having a spherical shape, as shown by example in FIG. 6A, while ellipsoids
comprise
a non-spherical shape, such as is shown in FIG. 6B. By further example, any
void 40
may comprise any shape contemplated herein with reference to particle 20. As
with
the exterior shape of a particle 20, the shape and/or positioning of any void
40 within
such particle 20 may improve the reduction or correction of any new or
changing
imbalance, force variation, or vibration of tire-wheel assembly 10. For
example, a
single symmetrical void 40 positioned centrally (i.e., concentrically) within
a particle
20 may provide a better mass or weight balanced particle 20, to facilitate
improved
rolling capabilities for improved relocation or maneuverability of any such
particle 20
within chamber I, which may improve the responsiveness of a particle 20 to
correct or
reduce any new or changing imbalance, force variation, or vibration of tire-
wheel
assembly 10. With reference to FIG. 6A, by example, a single spherically-
shaped
it
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(symmetrical) void 40 is shown within a spherical (symmetrical) particle 20.
In lieu
of a centrally positioning a single symmetrical void 40, a plurality of voids
40 may be
arranged about the particle center to provide a balanced particle 20. In the
alternative,
a non-symmetrical void 40 may provide a mass or weight imbalance within a
particle
20 relative to the particle's central axis or center to resist rotation, which
may better
allow a particle to more quickly position itself within chamber I to reduce or
correct
any new or changing imbalance, force variation, or vibration, and resist any
unnecessary relocation due to any minor disturbance or anomaly. With reference
to
FIG. 6B, a non-spherical (non-symmetrical) void 40 is positioned centrally
(concentrically) within particle 40 to provide a weight imbalanced particle
20. It is
contemplated that an unbalanced (i.e., weight imbalanced) particle 20 may
include a
symmetrical, centrally positioned void 40. And in the alternative, because it
is
understood that any particle 20 can include any shaped void 40, a spherical
particle
such as shown in FIG. 6A, for example, may include a non-spherical or weight
imbalanced void shape, such as the ellipsoid shape shown in FIG. 6B, for
example.
Further, a plurality of voids 40 may be arranged to provide a weight
imbalanced
particle 20. In any of the embodiments considered, void 40 may or may not be
partially filled with any weighted solid or fluid.
[0037] A mass or weight imbalance within a particle 20 may also be achieved by
positioning a void 40 non-centrally (i.e., non-concentrically) within a
particle 20, such
as is shown by example in FIGS. 7A and 7B, such as for the purpose of creating
a
weight imbalance within particle 20 to resist rotation of such particle.
Still, voids 40
may be positioned at any location and arranged as desired within particle 20,
such as,
for example, centrally (i.e., concentrically) within a particle 20 as shown by
example
in FIGS. 6A and 6B such as to facilitate a weight balanced particle 20. The
placement
of a void 40 within a particle 20 may provide a non-uniform thickness t of
body 30,
such as shown by example in FIGS. 7A and 7B. It is contemplated that any
combination of symmetrical and non-symmetrical particles 20 and voids 40 may
be
arranged as desired to provide weight balanced or unbalanced particles 20.
[0038] Referring now to FIG. 8, the particle 20 may comprise a body 30 formed
of a
first material, and a void 40 at least partially filled with, or at most
substantially
I I
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completely filled with, a second material 50. In one embodiment, the first
material
may form a shell, characterized by a thickness t about a single void 40.
Depending
upon the position of the single void 40 within particle 20, body thickness t
may be
substantially constant or uniform, or variable. As mentioned above, it is
understood
that the second material 50 may comprise, for example, a weight or tire
balancing
material or an energy absorbing material, such as a viscous or viscoelastic
material.
Further, second material 50 may form any fluid (i.e., liquid or gas), solid,
or
composite. Tire balancing material or compositions may comprise any of those
disclosed by Fogal in U.S. Patent Nos. 7,022,753 or 6,979,060, which includes
metallic balls or particles, such as, for example, stainless-steel balls or
particles, as
well as any other tire balancing composition known to one of ordinary skill in
the art,
such as, for example, beads, shot, particles, dust, and powders made of
ferrous and
non-ferrous metals, ceramics, plastics (including thermoplastics), glass
beads, and
alumina.
[0039] As shown in FIG. 9, a particle 20 may also include a plurality of voids
40
spaced as desired throughout particle body 30. For example, with continued
reference
to FIG. 9, voids 40 may extend entirely within body 30, or may be exposed to
an
exterior surface of particle 20. Whether particle 20 contains a single void 40
or
multiple voids 40, any such void 40 maybe in communication with the exterior
of
particle 20, such as by way of any aperture or orifice extending from an
exterior
surface of particle 20 to the embedded void 40. For example, if any void 40 is
exposed to the air contained within a chamber I, the air or other material
contained
within void 40 would not substantially compress during any particle
deformation
during tire operation, which would reduce any elastic rebound or response by
particle
20 to any such deformation and thereby enhance the energy absorbing properties
of
particle 20. Accordingly, particle 20 may be an open cell or closed cell
particle 20,
which may form, for example, open and closed cell sponges, foams, or other
plastics
or polymers. A particle 20 having voids 40 may also be described as having at
least a
second material 50 dispersed within particle 20. It is contemplated that
particle 20
may include other materials additional to second material 50 for inclusion in
any void
40, which may or may not contain second material 50.
11
I
WO 2010/081016 CA 02748744 2011-06-29 PCT/US2010/020519
14
[0040] Referring now to the composition of the particles 20, particle body 30
may be
formed of, and/or voids 40 may be at least partially filled with, or at most
substantially completely filled with, any desired material, which may
comprise, alone
or in combination, a polymer, plastic (which includes thermoplastic),
elastomer, fluid,
or metal. In particular embodiments, each such material may also comprise an
energy
dampening or absorbing material, which may be any viscous or viscoelastic
material.
Because the viscous and viscoelastic materials are less reactive (i.e.,
provides very
little reactive bounce) than other elastic materials, particles 20 may more
quickly
become positioned along the tire, and may also better maintain any such
position,
during tire operation to correct tire force variations. Further, the dampening
properties may also absorb any vibrations being transmitted through tire 11. A
viscoelastic material possesses both elastic and viscous properties. For
example,
when applying a load to a purely elastic material, all of the energy stored
during the
corresponding strain of the material is returned after the loading is removed.
To the
contrary, a purely viscous material does not return any of the strain energy
stored after
the corresponding loading is removed to provide pure damping. Accordingly, a
viscoelastic material combines both elastic and viscous behaviors to provide
an
energy dampening material that is capable of absorbing energy, so to reduce
the
impact forces and vibrations acting upon, or being produced by, tire-wheel
assembly
10.
[0041] The dampening properties of a viscoelastic material can be quantified
as
having a storage modulus E' and a loss modulus E". Storage modulus E' relates
to
the elastic behavior (i.e., elastic response) of the viscoelastic material,
while loss
modulus E" relates to the viscous behavior (i.e., viscous response) of the
viscoelastic
material, or, in other words, the material's ability to dissipate energy.
Often
dampening properties are quantified by tangent delta (tan delta or tan 6),
which is the
ratio of loss modulus E" (i.e., viscous response) to the storage modulus E'
(i.e.,
elastic response), or E"/E. Tan delta is a measure of hysteresis, which is a
measure
of the energy dissipated by a viscoelastic elastomer during cyclic deformation
(loading and unloading). The use of tangent delta to characterize the
viscoelastic
properties of materials is well known to one having ordinary skilled in the
art. The
PI
WO 2010/081016 CA 02748744 2011-06-29 PCT/US2010/020519
higher the tan delta, the higher the energy loss. For a perfectly elastic
material or
polymer, tan delta equals zero. Tan delta is affected by temperature, as well
as the
structure of the material, such as, for example, the degree of crystallinity,
crosslinking, and molecular mass. As the temperature experienced by a
pneumatic
tire is known to range from the ambient temperature to several hundred degrees
during tire operation, the energy dampening material may be selected to have
desired
tangent delta values for use with an intended tire temperature range.
[0042] In particular embodiments, a particle 20 or particle body 30 are formed
of,
and/or void 40 at least partially filled with, or at most substantially
completely filled
with, a viscoelastic material having desired hysteresis, or energy absorption
or force
dampening, properties. In one embodiment, the viscoelastic material is
Sorbothane ,
a viscoelastic urethane polymer material manufactured by Sorbothane, Inc. of
Kent,
Ohio. For Sorbothane material having a durometer of 30 Shore 00, at ambient
temperature such material is characterized as having tan delta values of
approximately
0.30 at 5 Hertz excitation, 0.38 at 15 Hertz excitation, and 0.45 at 30 Hertz
excitation,
each taken at 2% strain and 20% compression. For Sorbothane material having a
durometer of 50 Shore 00, at ambient temperature such material is
characterized as
having tan delta values of approximately 0.56 at 5 Hertz excitation, 0.58 at
15 Hertz
excitation, and 0.57 at 30 Hertz excitation, each taken at 2% strain and 20%
compression. For Sorbothane material having a durometer of 70 Shore 00, at
ambient temperature such material is characterized as having tan delta values
of
approximately 0.56 at 5 Hertz excitation, 0.60 at 15 Hertz excitation, and
0.59 at 30
Hertz excitation, each taken at 2% strain and 20% compression. Ambient
temperature
is room temperature, which is generally between approximately 60-80 degrees
Fahrenheit, which means that it may be slightly higher or lower. Other
viscoelastic or
viscous materials may be used in lieu of Sorbothane. For example, the polymer
may
be a thermoplastic vulcanizate which includes a mixture of polypropylene and
vulcanized ethylene propylene diene monomer where the polypropylene is a
continuous phase of the thermoplastic vulcanizate. One such material is
Sarlink
3140 manufactured by DSM. In another embodiment, the polymer may be a
viscoelastic material which includes an amorphous mixture of butyl and
chloroprene
I
WO 2010/081016 CA 02748744 2011-06-29 PCT/US2010/020519
16
polymers such as NAVCOMTT', which is a product of Allsop/Sims Vibration. In
other
embodiments, the viscoelastic material for forming particles 20 may be a
polyvinyl
chloride.
[0043] It is contemplated that viscoelastic materials having tangent delta
values other
than those disclosed above may be used. For example, a particle 20 or particle
body
30 are formed of, and/or void 40 at least partially filled with, a
viscoelastic material
having a durometer of 30 Shore 00, at ambient temperature such material is
characterized as having tan delta values of at least approximately 0.15 or
0.20 at 5
Hertz excitation, 0.20 or 0.25 at 15 Hertz excitation, and/or 0.30 or 0.35 at
30 Hertz
excitation, each taken at 2% strain and 20% compression. A particle 20 or
particle
body 30 may be formed of, and/or void 40 at least partially filled with, a
viscoelastic
material having a durometer of 50 Shore 00, at ambient temperature such
material is
characterized as having tan delta values of approximately 0.30 or 0.35 at 5
Hertz
excitation, 0.40 or 0.45 at 15 Hertz excitation, and/or 0.40 or 0.45 at 30
Hertz
excitation, each taken at 2% strain and 20% compression. A particle 20 or
particle
body 30 are formed of, and/or void 40 at least partially filled with, a
viscoelastic
material having a durometer of 70 Shore 00, at ambient temperature such
material is
characterized as having tan delta values of at least approximately 0.40 or
0.45 at 5
Hertz excitation, 0.45 or 0.50 at 15 Hertz excitation, and/or 0.45 or 0.50 at
30 Hertz
excitation, each taken at 2% strain and 20% compression. Ambient temperature
is
room temperature, which is generally between approximately 60-80 degrees
Fahrenheit, which means that it may be slightly higher or lower.
[0044] In other embodiments, a particle 20 or particle body 30 are formed of,
and/or
void 40 at least partially filled with, or at most substantially completely
filled with, a
material that is selected based on a predetermined minimum specific gravity.
Specific
gravity is defined as the ratio of the density of a given solid or liquid
substance to the
density of water at a specific temperature and pressure. Substances with a
specific
gravity greater than one are denser than water, and so (ignoring surface
tension
effects) such substances will sink in water, and those with a specific gravity
of less
than one are less dense than water, and therefore will float in water. In one
embodiment, a material having a minimum specific gravity of at least 0.90 may
be
WO 2010/081016 CA 02748744 2011-06-29 PCT/US2010/020519
17
utilized. In other embodiments, the specific gravity is at least approximately
1.1, or at
least approximately 1.3. It is contemplated, however, that materials having
other
specific gravities may be used.
[0045] In still other embodiments, a particle 20 or particle body 30 are
formed of,
and/or void 40 at least partially filled with, or at most substantially
completely filled
with, a material that is selected based on a predetermined durometer.
Durometer is a
measurement of the material hardness. In particular embodiments, particles 20
are
formed of a material having a durometer of approximately 70 shore 00 or less,
50
shore 00 or less, or 30 shore 00 or less. In other embodiments, the durometer
is
approximately 70 shore A or less, 50 shore A or less, or 30 shore A or less.
It is
contemplated, however, that materials having other durometers may be used. In
particular embodiments, particles 20 having a lower durometer are sized or
weighted
smaller than particles 20 having a higher durometer.
[0046] It is understood that particles 20 may comprise any size. However,
pneumatic
tires are pressurized with an air or other gas, usually through a valve stem
having a
passageway extending between the pressurization chamber I and the outside of
tire
11. Presently, a filter is used with the valve stem to prevent the inadvertent
release of
particles 20 from the pressurization chamber, and/or to otherwise prevent
particles 20
from become lodged in the valve stem. In an effort to eliminate the use of a
filter, in
particular embodiments, particles 20 have a predetermined minimum particle
size or
diameter which is greater than the passageway of the valve stem. Therefore, in
particular embodiments, particles 20 are at least 0.1875 inches in diameter,
or at least
0.25 inches in diameter. In other embodiments, particles 20 have a diameter
approximately equal to at least 0.50 inches, to at least 0.575 inches, to at
least 0.600
inches, to at least 0.700 inches, to at least 0.850 inches, to at least 0.950
inches, or to
at least 1.0 inches. In other embodiments, the diameter of particles 20 may be
4
inches or more. Consistent with other shaped particles 20, the dimensions
associated
with all previously identified diameters may instead refer to a particle's
height, width,
or length. For example, a particle 20 may have a height, width, or length of
at least
0. 1875 inches.
WO 2010/081016 CA 02748744 2011-06-29 PCT/US2010/020519
18
[0047] As stated before, vibrations and force variations may arise during
loaded tire
operation, where the forces and vibrations arise at least in part due to the
tire
deflecting as it enters and exits the tire footprint. Further, forces and
vibrations arise
when the tire impacts an object, such as a pothole or other object present on
the
operating or road surface R. Accordingly, by providing particles 20 that
freely
operate within the pressurization chamber I of a tire 11, particles 20 are
able to
migrate to particular interior surfaces of the tire for the purpose of
correcting, at least
in part, the force variations and vibrations operating within and/or upon the
tire.
Further, the energy absorbing properties of particles 20 improve the
effectiveness of
the particles 20 by allowing the particles 20 to absorb and/or interfere with
at least a
portion of the vibrations (i.e., frequencies) and forces operating within and
upon the
tire 11. This not only continues to allow the particles 20 to operate as
particle
dampers, whereby particles dampen the forces and vibrations by impacting the
surfaces of the tire to interfere with the undesired forces and/or vibrations,
it also
provides a material that also dampens the forces and vibrations. Now, in
effect, there
are two means of dampening occurring - particle (impact) dampening, and
material
dampening, each of which disrupt and destructively interfere with the forces
and
vibrations operating upon tire 11. Still further, by utilizing a dampening
(energy and
force absorbing) material, particles 20 rebound less after impacting the inner
tire
surface or another particle, which now allows the particles to adapt and
settle into
place more quickly about the tire. This may also improve tire rolling
resistance.
[0048] Rolling resistance is the tendency of a loaded tire to resist rolling,
which is at
least partially caused by the tire deflecting as it enters the tire footprint.
As the tire
enters the footprint, the tire deflects and the tread impacts the operating or
road
surface R, which generates resistive forces as well as force variations and
vibrations
extending from the footprint. By using particles 20 that more readily absorb
energy
upon impact, particles 20 are better able to overcome a tire's tendency to
resist rolling
by absorbing the forces and vibrations. Further, by increasing the overall
weight of
the total quantity of particles 20 present in the pressurization chamber I,
more
momentum is provided by the particles as the tire rotates. This is beneficial
to
overcoming (improving) the rolling resistance of a tire 11, as the additional
it
WO 2010/081016 CA 02748744 2011-06-29 PCT/US2010/020519
19
momentum is useful to overcome the forces resisting tire rotation. The overall
increase in weight is provided by increasing size and mass of particles 20,
and/or
increasing the quantity of particles 20 present within the pressurization
chamber I.
For example, by providing 20 ounces of particles 20 within the pressurization
chamber I of a 22 inch diameter tire, the particles 20 provide approximately
61
pounds of force as the tire rotates on a vehicle traveling at approximately 67
miles per
hour. In comparison, providing 12 ounces of particles 20 within the
pressurization
chamber I of the same tire 11 provides approximately 36 pounds of force.
Accordingly, by providing more particle weight within the pressurization
chamber I,
higher levels of force variations and vibrations may be reduced and/or
overcome, and
rolling resistance may be reduced due to the increase in momentum, as well as
the
reduction in force variations and vibrations. In particular embodiments, at
least
approximately 10 ounces of particles 20 are placed within pressurization
chamber I of
a passenger car tire-wheel assembly 10. In other embodiments, at least
approximately
15 ounces or at least approximately 20 ounces of particles 20 are placed
within the
pressurization chamber I of a passenger car tire-wheel assembly 10. In other
embodiments, smaller weight amounts of particles 20 may be placed within a
pressurization chamber I of a motorcycle tire, for example, or larger amounts
in
earthmover or airplane tires, for example. As suggested above, one or more
tire or
wheel balance weight products, such as lead weights, for example, or any other
known balance weight product adapted for attachment to a tire or wheel, may
also be
used to correct tire or wheel mass imbalances, in concurrent use with
dampening
particles 20, which are used for the correction of force variations and
vibrations.
[0049] Reference is made to FIGS. 4 and 5 which illustrate the innumerable
radial
impact forces (Fn) which continuously react between the road R and the tread T
at
the lower portion or footprint B during tire-wheel assembly rotation. There
are an
infinite number of such forces Fn at virtually an infinite number of locations
(Pn)
across the lateral width W and the length L of the footprint B, and FIGS. 4
and 5
diagrammatically illustrate five such impact forces F1-F5 at respective
locations Pl-
P5. As is shown in FIG. 5, it may be assumed that the forces F1-F5 are
different from
each other because of such factors as tire wear at the specific impact force
location,
~I
WO 2010/081016 CA 02748744 2011-06-29 PCT/US2010/020519
the road condition at each impact force location, the load upon each tire-
wheel
assembly, etc. Thus, the least impact force may be the force Fl at location P1
whereas
the greatest impact force may be the force F2 at location P2. Once again,
these forces
Fl-F5 are merely exemplary of innumerable/infinite forces laterally across the
tire 11
between the sidewalls SW1 and SW2 and circumferentially along the tire
interior
which are created continuously and which vary as the tire-wheel assembly 10
rotates.
[0050] As these impact forces are generated during tire-wheel assembly
rotation, the
particles 20 operate as impact or particle dampers to provide another means of
dampening vibrations, frequencies, and/or resistive rolling forces, which is
in addition
to each being absorbed at least in part due to the viscous properties of the
viscoelastic
material used to form particles 20, as discussed above. Subsequently,
particles 20
may relocate from their initial position in dependency upon the location and
the
severity of the impact forces Fn to correct any existing force variations. The
relocation of the particles 20 may be inversely related to the magnitude of
the impact
forces. For example, the greatest force Fl (FIG. 5) may be at position P1, and
due to
these greater forces Fl, the particles 20 may be forced away from the point P1
and the
smallest quantity of the particles remains at the point P1 because the load
force
thereat is the highest. Contrarily, the impact force F may be the lowest at
the impact
force location point P2 and, therefore, more of the particles 20 will remain
thereat
(FIG. 4). In other words, at points of maximum or greatest impact forces (F1
in the
example), the quantity of the particles 20 is the least, whereas at points of
minimum
force impact (point P2 in the example), the quantity of particles 20 may be
proportionately increased, thereby providing additional mass which may absorb
and
dampen the vibrations or impact forces Fn. Accordingly, the vibrations or
impact
forces Fn may force the particles 20 to continuously move away from the higher
or
excessive impact forces F1 and toward the areas of minimum impact forces F2.
[0051] Particles 20 may be moved by these impact forces Fn radially, as well
as
laterally and circumferentially, but if a single force and an individual
particle of the
particles 20 could be isolated, so to speak, from the standpoint of cause and
effect, a
single particle located at a point of maximum impact force Fn would be
theoretically
moved 180 degrees there from. Essentially, with an adequate quantity of
particles 20,
WO 2010/081016 CA 02748744 2011-06-29 PCTIUS2010/020519
21
the variable forces Fn create, through the impact thereof, a lifting effect
within the
chamber I which at least in part equalizes the radial force variation applied
against the
footprint until there is a total force equalization circumferentially and
laterally of the
complete tire-wheel assembly 11. Thus the rolling forces created by the
rotation of the
tire-wheel assembly 11 in effect create the energy or force Fn which is
utilized to
locate the particles 20 to achieve lift and force equalization and assure a
smooth ride.
Furthermore, due to the characteristics of the particles 20 as described
below, road
resonance may be absorbed as the tire-wheel assemblies 10 rotate.
[0052] It is contemplated that more than one type of particle 20 may be
provided in
chamber I to form a multimodal composition. Accordingly, a mixture of varying
amounts of different particles 20 may be provided, where such particles 20 may
differ, such as by size, weight, shape, and material, and/or by void 40
quantity,
location, shape, and the material at least partially filling any such void 40.
A benefit
of this multimodal particle composition is that particular particles may
respond more
quickly to smaller forces, while other particles may provide more quickly
respond to
larger forces. Additionally, a particular group of particles 20 may operate to
correct
tire imbalances, while others correct particular force variations and/or
vibrations.
[0053] As the tire-wheel assembly 10 is rotating, the particles 20 may be
tumbling
within the assembly 10 until the assembly 10 and particles 20 are subjected to
sufficient centripetal force such that the particles 20 may be "pinned" to the
interior
surface of the tire 11. While tumbling in the assembly 10, the particles 20
may
repeatedly impact the interior surfaces of the assembly 10 as well as others
of the
plurality of particles 20, which may lead to surface wear and degradation of
the
particles 20. Thus, the particles 20 may be selected to have a predetermined
hardness
or hardness range which is sufficient to prevent the particles 20 from
degrading while
tumbling in the assembly 10. In one embodiment, the hardness range of the
particles
20 may be from no more than approximately 30 to 70 Shore 00 hardness, or 30 to
70
Shore A hardness.
[0054] Particles 20, as disclosed and contemplated herein, may be formed by
any
process or processes known to one of ordinary skill in the art. For example, a
particle
WO 2010/081016 CA 02748744 2011-06-29 PCT/US2010/020519
22
20 may be formed by joining two pre-molded halves or independent portions of
particle 20, such as by use of an adhesive or the like.
[0055] Although the invention has been described with reference to certain
preferred
embodiments, as will be apparent to those skilled in the art, certain changes
and
modifications can be made without departing from the scope of the invention as
defined by the following claims.
