Patent Application
20070137749
The invention generally relates to a pneumatic tire having a tread pattern and, more particularly, to a pneumatic tire for a vehicle having a tread pattern that provides superior performance characteristics.
Tire design and more specifically tread pattern design plays a critical role in the safe and efficient operation of a vehicle. For example, it is known that the tread pattern assists in the generation of steering forces, as well as driving and braking forces. Also, the tread pattern can improve vehicle performance by reducing road noise, providing superior grip capabilities in both wet and/or dry driving conditions, as well as minimizing rolling resistance to increase the overall fuel economy of the vehicle.
In examining the complex mechanisms involved in proper tread pattern design, several factors play a role in the final design of the tread pattern. These factors include industry standards, government regulations, customer specifications, marketing requirements and the like. On the other hand, the complex mechanisms which are taken into account in the design of the tread pattern include, amongst other mechanisms, stresses generated upon the tire during driving conditions, energy losses due to rolling resistance, sidewall flexing, to a host of other mechanisms. Thus, the design of a tread pattern is not a trivial task and, in fact, is quite complex requiring the need to take into account many different considerations.
In practice, the design of a tire tread pattern also requires the balancing of many contradictory demands. Finding the proper structure that balances these demands for any given tire is thus a great challenge. For this and other reasons, engineers typically focus on a large array of considerations, placing emphasis on certain design criteria over others, depending on the specific application of the tire. However, by focusing on these design criteria, other criteria such as tire wear or stress components may not have been weighed as heavily during the design stage.
By way of a more specific illustration, one design approach has been to form grooves between ribs with negatively sloped walls to increase gripping capabilities. However, in such an approach, the grooves are more likely to trap and retain stones, which can damage the tire. Another example is in the use of all-season tires, which customarily employ block elements in their tread design. These designs have superior grip performance but tend to have increased noise level, as well as have a tendency toward irregular wear due primarily to their lack of stiffness in the circumferential direction of the tread. Such noise generation and irregular wear are accentuated at acute or sharp angles in the rubber blocks formed by intersections of groove walls.
In any event, tire patterns have common pattern traits. These common pattern traits include, for example, grooves with sharp or acute angles in transitional areas, e.g., between treads, vertical walls forming the grooves or treads, etc. It has been theorized that such designs have large stress components which conjugate at the sharp angles, as well as result in increased road noise and rolling resistance. Of course, engineers are constantly designing tread patterns to increase overall tire efficiency, but these design traits remain pervasive.
In a first aspect of the invention, a tire comprises a lug pattern. Each lug of the lug pattern has a substantially oval shaped contacting surface and a plurality of variable angle sidewalls extending from a base to the substantially oval shaped contacting surface.
In another aspect of the invention, the tire comprises a plurality of same shaped lugs. Each of the plurality of same shaped lugs is offset with respect to one another in adjacent rows and includes a substantially rectangular base with convex sides and a substantially oval shaped contacting surface. A plurality of sidewalls extends from the substantially rectangular base to the substantially oval shaped contacting surface.
In another aspect of the invention, the tire comprises a plurality of lugs, each comprising: a substantially rectangular base with convex sides; a substantially oval shaped contacting surface; and a plurality of tapered and variable angle sidewalls extending from the substantially rectangular base to the substantially oval shaped contacting surface. The transition between each of the tapered and variable angle sidewalls for each of the plurality of lugs is devoid of sharp edges. A groove bottom positioned between adjacent lugs of the plurality of lugs has a rounded portion.
The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:
The present invention is directed to a tire with a tread pattern having superior performance characteristics. In embodiments of the invention, the tread pattern includes a lug pattern, where each lug of the lug pattern has a generally rectangular base with convex sides and an oval shaped contacting surface. The lug further has variable angle or flank angle sidewalls extending from the oval shaped contacting surface to the generally rectangular base. In the design of the invention, the sidewalls are also tapered with respect to a vertical axis. In use, the tread pattern of the present invention exhibits superior stone trapping resistance, groove cracking resistance, pressure distribution, as well as increased wet traction and tread mileage properties. It has also been found that the tread pattern of the present invention contributes to a decrease in road noise and further has a low rolling resistance thereby increasing vehicle efficiently.
The lugs 100 each include a contacting surface “S” which is substantially oval in shape and, in one embodiment, has a length to width ratio with may be in the range of approximately 1.28:1 to 1.4:1, and more preferably approximately 1.3:1. It should be understood, though, that other length to width ratios are also contemplated by the invention, depending on such variables as tread width and tire outer diameter.
In the non-limiting embodiment of
In addition, each of the variable angle sidewalls 1001A, 1002A, 1003A and 1004A is at an angle with respect to a vertical axis thus creating a tapered or pyramid-like appearance. A bottom 200 of the groove between each base “B” is rounded with a radius that may vary with respect to a location on the sidewall 1001A, 1002A, 1003A and 1004A of neighboring lug(s) in the same or different row, as discussed with reference to
In further embodiments, the transition area “T” or corners between each of the sidewalls 1001A, 1002A, 1003A and 1004A as well as the contacting surface “S” of the lug and the sidewalls is rounded, eliminating any sharp edges.
The sidewalls 1001A, 1002B, 1003C and 1004D provide a variable groove angle and/or variable wall contour during rolling of the tire, thus reducing stone or other debris trapping. That is, using the tread design of the present invention, an angle is constantly changing on the side of the groove during roll of the footprint (e.g., rotating and flanking angles) thus contributing significantly to the release stones and/or other debris. Additionally, the varying wall contour and rounded edges improves the pressure distribution of the tire (due to the elimination of any sharp angles) which, in turn, results in:
(i) superior tread wear properties;
(ii) superior wet traction;
(iii) reduced noise; and
(iv) longer tread mileage.
It has also been found that the varying wall contour and/or rounded edges of the present invention reduces stress points in the tire due to the fact that forces cannot conjugate in one area, e.g., at any point or corner. Instead, by using the tread pattern of the present invention, the varying wall contour and rounded corners allows forces to travel upwards on the lug 100, thus eliminating places for forces to collect. This leads to improved groove cracking resistance. As one of ordinary skill in the art would recognize, the substantial reduction or elimination of stresses is due mainly to the elimination of any sharp edges or angles in the tire pattern design.
Still referring to
Additionally, each sidewall 1001A, 1002B, 1003C and 1004D is tapered and has a variable angle. By having the tapered sidewall, the volume and hence surface area of the of the lug 100 will increase from the contact surface to the base “B”. The radius R1 and R2 also increases gradually and continuously from the contact surface to the base “B”.
From a manufacturing standpoint, the material to produce the tread patterns should flow better into the mold since there are no sharp corners. Thus, the material does not have to squeeze into corners, but instead flows smoothly around rounded corners. This results in better material (e.g., rubber) flow in the mold during manufacturing, thus resulting in fewer defects.
The foregoing examples have been provided for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. The present invention is not r intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.
