Patent Application
20140373597
This invention relates generally to road wheels for testing tires on tire testing machines and more specifically, to tire operating surfaces employed by road wheels in testing or evaluating tire performance.
Tires are often tested to determine any of a variety of characteristics. In particular instances, in lieu of testing tires on a vehicle, where conditions are difficult to control, tires are tested on a rotating road wheel to better control the test conditions. Such road wheels include an outer tire operating surface along which the tire contacts and operates. Such outer tire operating surface forms a radially outer surface of the wheel. It can also be said the outer tire operating surface is an annular surface.
In operation, the tire is forcefully applied against, and rotates along, the outer tire operating surface of the rotating road wheel. Although the outer tire operating surface exhibits a curvature in a longitudinal direction as the surface extends about a circumference of the wheel, the outer tire operating surface is laterally flat, whereby the surface extends laterally along a path perpendicular to the circumferential direction of the wheel and parallel to the rotational axis of the wheel. In other words, the outer tire operating surface of the wheel forms a right circular cylindrical surface extending laterally a constant distance from relative the rotational axis of the wheel.
When a tire contacts a tire operating surface, whether it is a wheel surface or a ground surface, a portion of the tire tread contacts the operating surface. The portion of the tread contacting the operating surface forms an area of contact, which is referred to as a contact patch or footprint of the tire. A tire footprint includes an outer perimeter defining the area of contact, which may form a particular shape.
One goal of tire testing machines is to closely replicate real-world operating conditions for tires, such as conditions where the tire operates along a generally flat surface, such as a ground surface. Unfortunately, these cylindrical outer tire operating surfaces do not represent real-world conditions since it has been observed that tires tested on these cylindrical surfaces commonly exhibit notably higher wear on the shoulders of the tire treads than those tires tested on a generally flat surface. In other words, the wear distribution across a width of the tire tread is not representative of the wear distribution attained when the tire operates on a generally flat surface. It has also been observed that a footprint of a tire tested on a cylindrical outer wheel surface is different than the tire footprint achieved when operating along a generally flat surface. A tire footprint is the area of contact between a tire and a surface upon which the tire rests.
Therefore, there is a need to provide a road wheel having an outer tire operating surface better representing real-world conditions, and in particular, a wheel generating a wear distribution along a tire tread more consistent with tires operating along a generally flat operating surface. There is also a need to generate a tire footprint more consistent with tires operating along a generally flat operating surface.
The present invention includes methods and apparatus for testing tire performance using a wheel, the wheel having a laterally-contoured tire operating surface. The present invention also includes methods of forming a laterally-contoured tire operating surface for a road wheel. In particular embodiments, such methods comprise a step of providing a wheel configured to rotate, the wheel having an tire operating surface configured to engage a tire during operation, the tire operating surface being arranged outwardly from a rotational axis of the wheel in a radial direction of the wheel and having a width extending laterally relative a circumferential direction of the wheel, where the width of the operating surface extends laterally along a contoured path. Further steps of such methods include engaging forcefully a tread of a tire against the tire operating surface of the wheel and rotating the tire and the wheel while engaged according to the prior step for a sufficient duration to evaluate the tire.
In particular embodiments of the invention, a machine for testing tire performance, the machine includes a wheel configured to rotate, the wheel having an tire operating surface configured to engage a tire during operation, the tire operating surface being arranged outwardly from a rotational axis of the wheel in a radial direction of the wheel and having a width extending laterally relative a circumferential direction of the wheel, where the width of the operating surface extends laterally along a contoured path. Such embodiments include a drive source configured to rotate the wheel and a tire mount configured to rotatably maintain a tire and forcefully maintain the tire against the wheel.
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.
As suggested above, there is a need to provide an improved road wheel for performing tire testing operations. With reference to
Accordingly, particular embodiments of the present invention comprise methods of testing tire performance using a wheel having a laterally-contoured tire operating surface arranged along an annular side of the wheel. In testing tire performance, for example, tire durability may be tested and evaluated. It is understood that the testing of durability may evaluate the longevity of a tire tread by ascertaining the rate of wear, but may also (additionally or alternatively) test the longevity of other elements of the tires constituent components. In any event, it may be desirous, when testing a tire along a tire operating surface arranged along an annular side of the wheel, to better ensure that the tire wears as similar to a tire operating on a generally flat surface, such as a ground surface or a flat machine testing surface. Likewise, it may be desirous, when testing a tire on such a tire operating surface of the wheel, to better ensure that the tire has a footprint commensurate with the footprint of a tire operating on a generally flat surface. Accordingly, an annular road wheel is provided having a width extending laterally along a contoured path to form a laterally-contoured tire operating surface arranged along an annular side of the wheel. Accordingly, the tire operating surface may be arranged along an outer or inner annular side of the wheel, each of which are arranged in a radial direction outwardly from the rotational axis of the wheel. In certain embodiments, at least a portion of the laterally-contoured surface is convex, such as to form a road wheel having a laterally-convex, outer tire operating surface. In yet other embodiments, the laterally-contoured surface is at least partially concave. In particular embodiments, the wheel having laterally-contoured tire operating surface forms a portion of a tire testing machine. The following will now discuss various methods of testing tire performance using a wheel.
Particular embodiments of such methods include a step of providing a wheel configured to rotate, the wheel having a tire operating surface arranged along an annular side of the wheel and configured to engage a tire during operation, the tire operating surface having a width extending laterally relative a circumferential direction of the wheel along a contoured path. In such embodiments, the wheel has a laterally-contoured tire operating surface configured to engage a tire during operation. The tire operating surface is arranged along an annular side of the wheel and in a outwardly in radial direction from the rotational axis of the wheel. The annular side may comprise an inner or outer side of the wheel. Because the tire operating surface is arranged along an annular side of the wheel, when describing the shape of either the tire operating surface or the tire operating side of the wheel, the description of one herein also describes the other unless specifically noted otherwise, and vice versa.
It is understood that the tire operating surface may extend continuously around an annular side of the wheel to form an annular tire operating surface. In such instances, it can be said that the tire operating surface extends circumferentially about a rotational axis of the wheel. It is also understood that the tire operating surface may extend discontinuously or intermittently around an annular side of the wheel. In any event, the tire operating surface is a laterally-contoured surface, extending laterally across a width of the surface transverse to the radial direction of the wheel along a contoured path. The contoured path may comprise any non-linear path, such as a contoured path, which may extend fully or partially across the width of the wheel. Accordingly, the laterally-contoured surface at least comprises a non-linear segment or portion, which may be coupled with one or more linear segments or portions.
In particular embodiments, the laterally-contoured tire operating surface tapers radially inward toward the rotational axis of the wheel as the surface extends laterally outward relative a centerline of the tire operating surface, the centerline extending circumferentially around the tire operating surface. In certain instances of such embodiments, when the tire operating surface is arranged along an outer annular side of the wheel, the portion of the tire operating surface tapering radially inward forms a convex tire operating surface. Accordingly, it can be said that the laterally-contoured tire operating surface extends laterally along a convex path to form a laterally-convex outer surface. In other instances of such embodiments, when the tire operating surface is arranged along an inner annular side of the wheel, the portion of the tire operating surface tapering radially inward forms a concave tire operating surface. It is understood, however, that laterally-contoured inner and outer operating surfaces may each include concave and/or convex portions. Moreover, as otherwise noted herein, it is appreciated that the full width, or only a portion, of a laterally-contoured surface may be contoured. Accordingly, it can be said that at least a portion of the width of the laterally-convex surface extends along a convex or concave path. It is understood that a convex tire operating surface is curved or rounded outwardly relative the rotational axis of the wheel, whereby the lateral extents of the surface width are located closer to the rotational axis of the wheel than more intermediate portions of the surface width. For a concave tire operating surface, the opposite is true. The convex, outer tire operating surface provides a tread wear distribution across a tire footprint more similar to the distribution attained when the tire operates on generally flat surface. The convex, outer tire operating surface also provides a tire footprint that more closely resembles the tire footprint arising along a generally flat surface. The same benefits appreciated for a convex, outer tire operating surface are also appreciated for a concave, inner tire operating surface.
It is understood that the laterally-contoured tire operating surface may be symmetrical or asymmetrical relative a plane bisecting a width of the wheel and extending radially outward and normal to the rotational axis of the wheel (referred to herein as the “bisecting plane”). By further example, the widthwise extension of the surface may extend along any non-linear path, including a constant radius path or a path comprising multiple curved and/or linear segments defined by two or more different radii, which may result in a curvilinear or non-linear path. In particular instances, the convexity or concavity of tire operating surface has a constant curvature defined by a constant radius of curvature. The origin of the radius of curvature may be located at any radial or lateral location relative the rotational axis and the bisecting plane, respectively. For example, the origin of the radius of curvature may be located on the axis of rotation, on the bisecting plane, or may be spaced a desired distance from the axis of rotation and/or the bisecting plane. In more specific examples, the origin is located at the intersection of the bisecting plane and the axis of rotation. The resulting radius of curvature creates a spherical surface, although the surface does not extend 360 degrees around the origin. It is possible to create more or less curvature by moving the origin closer to, or farther from, the axis of rotation. It is also possible to provide asymmetry by moving the origin in a lateral direction away from the bisecting plane.
In performing tire performance testing, at least a portion of the laterally-contoured tire operating surface may be texturized to include a texture. The texture may be provided to facilitate tire traction and/or to facilitate tread wear. It is understood that such texture may comprise any known or desired texture formed to or applied by any desired process. For example, the texture may be formed into the tire operating surface, such as by any manual or mechanized process, such as molding, mechanical or chemical etching, cold or hot working, or any grinding or abrasion process. Any such or otherwise desired texture may be applied or attached to the tire operating surface, such as by way of applying a layer of desired material to the laterally-contoured surface. Exemplary texture includes texturized tape (such as safety walk tape), particulate, or stone, but may include any other material providing a desired texture upon which it is desired for a tire to operate whether natural or unnatural. It is appreciated that the tire operating surface may have a smooth texture. It is noted that while the presence of texture may provide a non-linear micro surface, the presence of such texture does not negate or alter the more generally formation of a laterally-contoured tire operating surface or side, and the laterally-contoured path along which the tire operating surface or side extends.
It is understood that the wheel may be formed in any manner and of any construction. For example, the lateral-contour of a tire operating surface may be formed by molding or machining the convexity into the wheel's tire operating surface. By further example, such as when the tire operating surface is obtained by affixing one or more plates around the outer or inner circumference of the wheel, the lateral-contour may be achieved by molding, bending, or shaping each plate through any hot or cold forming process.
Further steps in performing the method of testing tire durability using a wheel include (1) engaging forcefully the tread of the tire with the tire operating surface of the wheel and (2) rotating the tire and the wheel while engaged according to the prior step for a desired duration to evaluate the durability of the tire. Each of these steps may be performed in accordance with known principles and techniques.
With regard to the step of engaging forcefully the tread of the tire with the tire operating surface, tire and/or wheel may be translated toward the other to forcefully engage the tire and the wheel. Because the tire and wheel maybe mounted on the same machine, portions of the machine corresponding to the tire or wheel may translate to achieve such engagement. Of course, the tire and wheel may be mounted on separate machines or apparatus while still achieving the desired engagement. It is also understood that any orientation of the tire relative the wheel may be employed to provide any desired test condition. For example, by altering the positional relationship between the rotational axes of the tire and wheel, a slip angle may be provided between the tire and wheel or camber introduced to the tire.
With regard to the step of rotating the tire and wheel, it is understood that the tire and/or wheel may be driven to accomplish the step of rotating. In doing so, a drive source is arranged in operable communication with tire and/or the wheel. The drive source may comprise any drive source known to one of ordinary skill in the art, and may comprise, for example, a motor.
These methods for testing tire durability on a laterally-contoured tire operating surface may be achieved manually or automatically, in whole or in part. Exemplary embodiments of a tire testing device for use in performing such methods are discussed in further detail below. The device(s) shown in the figures only exemplify any of a variety of tire testing devices that may be employed within the scope of this invention.
With reference to
The wheel 18 includes a laterally-contoured outer side 19o generally forming a laterally-contoured outer tire operating surface 20g. Both the outer side 19o and the outer surface 20o extend lengthwise in a circumferential direction about the wheel to form an annular side and surface, respectively. Outer side 19o and outer surface 20o are shown to have a width W18, which can be any size, including a size equal to or greater than the width W16 of the tire 16. In the embodiment shown in
While it is understood that the laterally-convex surface may extend laterally along any curved path, which may comprise any curvilinear or non-linear path, the lateral path shown in
It is appreciated that origin O may be arranged any distance Δrad from the rotational axis Aw-Aw to achieve any desired radius of curvature Rc. Accordingly, the curvature may be increased or decreased by altering the distance Δrad between the origin O and the rotational axis Aw-Aw. For example, in
With continued reference to
As noted otherwise herein, the outer tire operating surface may include texture. With reference
As noted otherwise herein, the outer tire operating surface and/or side may extend in a widthwise direction of wheel along any desired non-linear path, including any variable or multi-curvature laterally-contoured path. Exemplary embodiments thereof are shown in
In lieu of, or in addition to, employing a counter-curvature portion, a linearly-extending portion may extend from the central, convex portion as the outer tire operating surface extends toward a lateral side of the surface width. In such instances, the provide a smooth transition between the central portion and the linearly-extending portion, the linearly-extending portion extends laterally an angle greater than zero relative the rotational axis of the wheel. In any event, by providing counter-curvature or a linear taper, any further increase in the slope of the surface taper or curvature is eliminated as the tire operating surface approaches any lateral side of the wheel (or, in other words, as the tire operating surface extends away from the centerline of the wheel).
By further example, with reference now to the embodiment of
As discussed otherwise herein, the tire operating surface may be formed along an inner annular side of the wheel. By example, with reference to
As mentioned above, the present invention includes methods of forming a laterally-contoured tire operating surface for a road wheel. The tire operating surface may be formed along an outer, annular side of the road wheel, or may be formed along components for forming a road wheel having a laterally-contoured operating surface. Exemplary embodiments for performing these methods are shown in
With reference now to the exemplary embodiments of
With reference to
With reference to
To evaluate the benefits of using a laterally-contoured tire operating surface, laterally-contoured outer tire operating surfaces of different radii were evaluated. In particular, tire footprints were taken along laterally-contoured outer tire operating surfaces and compared to footprints taken along a laterally flat outer tire operating surface (being a common road wheel) and a flat surface representing a common ground surface. With reference to
With continued reference to
In
While this invention has been described with reference to particular embodiments thereof, it shall be understood that such description is by way of illustration and not by way of limitation. Accordingly, the scope and content of the invention are to be defined by the terms of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCTUS2011067994 | Dec 2011 | WO | international |
This application claims priority to, and the benefit of, International Patent Application No. PCT/US2011/067994, filed Dec. 29, 2011 with the United States Receiving Office, which is hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US12/72188 | 12/28/2012 | WO | 00 | 6/27/2014 |
