TIRE WITH LAMELLE IN BRIDGE

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a tire having tread features that provide improved resistance to wear and, more particularly, irregular wear. More specifically, lamellae are provided along tread elements of the tire and along a groove between such tread elements to provide for improved wear patterns and particularly to provide resistance to irregular wear at the leading and trailing edges of the tread element.

BACKGROUND OF THE INVENTION

[0002] Tires, particularly commercial vehicle tires as used on trucks, must be periodically removed from service and replaced as the tires eventually wear from use. Depending upon the application and maintenance of each tire, anomalies in the tread region can also develop during use that lead to the tire being removed from service before reaching the normal useful life of the tread. Typically, such anomalies are discovered as the driver senses a change in the ride of the vehicle or a change in the tire noise during vehicle use, and removal of a tire having anomalies is frequently a subjective determination. Such anomalies can include, for example, depressions or uneven wear in the tread region, which is generally caused by unequal stress distribution laterally across the tread region. "Heel and toe" wear is a form of irregular wear that can occur in which one side of a tread element - such as the leading edge of a tread block - wears more quickly than the opposing side. An explanation of various types of irregular tire wear can be found in a guide entitled "Radial Tire Conditions Analysis Guide: A Comprehensive Review of Tread Wear and Conditions", published by The Truck Maintenance Council (TMC).

[0003] Many different factors can contribute to irregular tire wear. For example, the operating conditions of the vehicle as well as the type of load carried can both have an impact on tire wear. In addition to the existence of many possible causes, it is common that a combination rather than a single factor will start uneven wear or cause it to increase. Determining a solution where a combination of factors is contributing can be particularly difficult.

[0004] Accordingly, a need remains to reduce the irregular wear occurring on tread elements such as e.g., tread blocks. The present invention provides one or more features than can help resist the onset and continuation of irregular wear. The onset of "heel to toe" wear is a particular concern that the present invention can be useful in addressing.

SUMMARY QF EXEMPLARY EMBODIMENTS

[0005] Objects and advantages of the invention will be set forth in part in the following summary description, or may be obvious from the description, or may be learned through practice of the invention. A summary of certain exemplary embodiments of the present invention will now be set forth. [0006] In one exemplary embodiment of the invention, a tire having tread features that can improve traction and wear is provided. The tire defines axial, radial, and circumferential directions and includes at least one circumferential groove of radial depth H ₀ , a plurality of axial grooves of radial depth H, and a plurality of tread elements positioned circumferentially about the tire and having a height equal to the radial depth H ₀ . The tread elements are defined by the circumferential grooves and the axial grooves. The axial grooves separate the tread elements. Each tread element has a length L along the circumferential direction. A plurality of lamellae are positioned in each tread element. Each lamella extends through the tread element along the axial direction and has a depth along the radial direction. At least one lamella is positioned in each axial groove, extends axially through the tire, and has a depth along the radial direction. [0007] In another exemplary embodiment, the present invention provides a tread for a tire. The tire defines axial, radial, and circumferential directions. The tread includes at least two tread elements defined by circumferential grooves of radial depth H ₀ and axial grooves of radial depth H. The tread elements have a length L along the circumferential direction. A bridge connects the tread elements along at least one of the axial grooves. A plurality of lamellae are positioned in each tread element with each lamella extending through the tread element along the axial direction and having a depth along the radial direction. Each lamella within a tread element is separated from adjacent lamella by a distance I. At least one lamella is positioned in the bridge and extends axially through the tire at a depth along the radial direction. [0008] The present invention includes numerous variations providing still other embodiments of the present invention. For example, the ratio I / L may be in the range of about 0.15 < I / L < 0.35 or, more particularly, in the range of about 0.2 < I / L < 0.3. The ratio H / H ₀ may be in the range of about 0.8 > H / H ₀ > 0.5 or, more particularly, in the range of about 0.7 > H / H ₀ > 0.6. The lamellae positioned in each tread element may be equally spaced over the tread element along the circumferential direction. The spacing between lamellae may be less than or equal to about thirty-five percent of the length L of each tread element. The axial grooves may each have a width W along the circumferential direction that is in the range of about 2 mm to about 20 mm. In some embodiments, the tire has at least two lamella positioned in each axial groove or bridge, extending axial Iy through the tire, and a having a depth along the radial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A full and enabling disclosure of the present subject matter, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

[0010] Fig. 1 illustrates a partial perspective view of a tread strip from a tire constructed according to an exemplary embodiment of the present invention.

[0011] Fig. 2 is schematic representation and partial elevation view of a tread strip constructed according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0012] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a third embodiment. It is intended that the present invention include these and other modifications and variations. [0013] As used herein with reference to an exemplary embodiment, the following terms have these definitions:

[0014] The term "radial" refers to the direction perpendicular to the axis of rotation of the tire and is designated with arrows R in Fig. 2

[0015] The term "axial" refers to the direction parallel to the axis of rotation of the tire and is designated with arrows A in Fig. 1.

[0016] The term "circumferential" refers to the circular direction defined by a radius of fixed length as it is rotated about the axis of rotation of the tire and is designated with arrows C in

Figs. 1 and 2.

[0017] The term "tread strip" refers to that portion of a tire intended for contact with a support surface,

[0018] The terms "tread element" refers to structures projecting from the "tread strip" and may include, for example, a plurality of blocks which are arranged about the circumference of the tire and defined by grooves as described further below.

[0019] The terms "lamellae" (plural) and "lamella" (singular) refer to narrow incisions or cracks in the tire tread, which are represented in the figures as lines in the tread strip. A lamella may have a zig-zag configuration along both the radial and axial directions of the tire, but other configurations may also be used.

[0020] An exemplary embodiment of a tread strip 100 as may be used with a tire according to the present invention is illustrated in Figs. 1 and 2. Tread strip 100 includes a plurality of tread elements 1 15 (e.g., tread blocks) arranged circumferentially about the tire. The tread elements

1 15 are defined in part by circumferential grooves 105 that extend about the circumferential direction C of the tire and by axial grooves 1 10 that are oriented substantially along the axial direction A of the tire. As shown in Fig. 2, circumferential grooves 105 have a radial depth H ₀ while axial grooves 1 10 have a radial depth H and a width W along circumferential direction C. The particular ornamentation for the tread pattern shown in Figs. 1 and 2 is provided by way of example only and the present invention may be used with numerous other tread patterns. For example, circumferential grooves 105 and axial grooves 1 10 may be provided in various other shapes and orientations to define multiple other configurations for tread elements 1 15 and the overall appearance of the tread pattern.

[0021] Tread elements 1 15 also define multiple lamellae 120. Each lamella 120 is a thin incision that extends completely through the tread element 1 15 along the axial direction A and has a certain depth into the tread element 1 15 along the radial direction R. Preferably, each lamella has a zig-zag configuration along both axial direction A and radial direction R as illustrated in the figures. Within a tread element 1 15, each lamella is separated from adjacent lamella by a distance I. While three lamellae 120 are illustrated for each tread element 1 15, other configurations may be used as well.

[0022] A single lamella 120 in tread element 1 15 can provide improvements not only in tire traction but also in the wear performance of the tire. Furthermore, the addition of multiple lamellae 120 to tread element 1 15 can further improve the traction and wear performance of the tire. Unfortunately, the addition of multiple lamellae 120 to each tread element 1 15 can reduce the rigidity of the tread element 1 15 and lead to chunking or cracking of the same. [0023] It was discovered that bridging between tread elements 115 can reduce or prevent the chunking of tread element 1 15 that may occur with multiple lamellae. More specifically, each tread element 1 15 is defined in part by axial grooves 1 10 that separate the leading and trailing edges 140 and 150 of adjacent tread elements 1 15. By reducing the depth H of axial groove 1 10, a bridge 160 can be created that connects adjacent tread elements 1 15. However, it was also discovered that while such bridging can reduce or eliminate the chunking previously described, the addition of bridge 160 led to other irregular wear problems such as a "heel to toe" wearing effect on the leading and trailing edges 140 and 150 of the tread element 1 15. [0024] To alleviate this problem, Applicant discovered that the addition of a lamella 130 to bridge 160 can reduce or eliminate the irregular wear induced by the addition of bridge 160. More specifically, lamella 130 is positioned at the bottom of axial groove 1 10 and in bridge 160. As with lamellae 120 in tread elements 1 15, lamella 130 preferably has a zig-zag configuration along both axial direction A and radial direction R but other configurations may be used. In addition, while preferably only one lamella 130 is positioned in axial groove up to two lamellae 130 may be used.

[0025] In order to increase the benefits of the invention, certain physical parameters should be maintained for tread strip 100. The width W of axial groove 1 10 should be in the range of about 2 mm to about 20 mm. The ratio H / H ₀ , which is the ratio of the radial depth H of axial groove 1 10 to the radial depth H ₀ of circumferential groove 105, should be in the range of about 0.8 > H / H ₀ > 0.5. More particularly, the ratio H / H ₀ is in the range of about 0.7 > H / H ₀ > 0.6. Similarly, the ratio I / L, which is the ratio of the distance L between adjacent lamella 1 1 5 to the length L of tread elements 1 15 along the circumferential direction, should be in the range of about 0.15 < 1 / L < 0.35. More particularly, the ratio I / L is in the range of about 0.2 < I / L < 0.3.

[0026] Controlled testing confirms the benefits of the invention. The wear and traction of three tires were compared: i) a Witness; ii) Design I - a tire with a single lamella in the center of the tread elements, and iii) Design II - a tire with a plurality of lamella in the tread elements and a single lamella in the axial groove separating the tread elements. As compared to the Witness, Design I provides about a 5 percent improvement in the mileage life of the tire and a 10 percent improvement in traction. Design II provides a 15 percent improvement in the mileage life and a 30 percent improvement in traction as compared to the witness.

[0027] It should be understood that the present invention includes various other modifications that can be made to the exemplary embodiments described herein that come within the scope of the appended claims and their equivalents. These and other embodiments of the present invention are with the spirit and scope of the claims that now follow.