阅读说明：本技术 具有带盲微纹沟的周向纹沟的卡车轮胎 (Truck tire with circumferential groove having blind microgrooves ) 是由 S·沃斯 R·C·勒杜列斯库 于 2019-04-05 设计创作，主要内容包括：本文提供了一种滚动方向为胎面的纵向方向的重型卡车轮胎胎面。存在周向纹沟(20),所述周向纹沟在纵向上完全围绕胎面延伸。所述周向纹沟并不约束牺牲肋纹。多个微纹沟(22)与周向纹沟接合,并位于周向纹沟在横向方向上的相对侧。所述微纹沟从周向纹沟延伸出来,使得在末端处终止于所述胎面的橡胶中。(A heavy truck tire tread having a rolling direction that is the longitudinal direction of the tread is provided herein. There is a circumferential groove (20) extending completely around the tread in the longitudinal direction. The circumferential grooves do not constrain the sacrificial ribs. A plurality of microgrooves (22) are engaged with the circumferential groove and located on opposite sides of the circumferential groove in the lateral direction. The micro-groove extends from the circumferential groove so as to terminate in the rubber of the tread at a terminal end.)

1. A heavy truck tire tread comprising:

a longitudinal direction, a transverse direction, and a thickness direction, wherein the tread is a directional tread and has a rolling direction in the longitudinal direction;

a circumferential groove extending completely around the tread in a longitudinal direction, wherein the circumferential groove does not constrain a sacrificial rib;

a plurality of micro-grooves engaged with the circumferential groove and located on opposite sides of the circumferential groove in a lateral direction, wherein the micro-grooves extend from the circumferential groove so as to terminate in rubber of the tread at a terminal end.

2. The tread of claim 1, where the circumferential groove is located within a rib of the tread that is bounded on opposite sides in a lateral direction by two grooves of the tread, where the microgroove terminates within rubber of the tread such that the microgroove does not extend to and engage any of the two grooves on opposite sides of the rib in the lateral direction.

3. The tread of claim 1 or 2, wherein an outer surface of the tread engaged with the circumferential groove on opposite sides of the circumferential groove in the lateral direction is not offset in the thickness direction.

4. The tread of any of claims 1-3, wherein the circumferential groove has a body and a tear drop, wherein the tear drop is farther in a thickness direction from an outer surface of the tread than the body, wherein the body and the tear drop extend completely around the tread in a linear orientation in a longitudinal direction.

5. The tread of any one of claims 1-4, wherein the sipe extends from the circumferential groove in a direction that includes a component of the lateral direction and a component of the longitudinal direction.

6. The tread of claim 5, wherein the lateral reference line extends in the lateral direction through a junction at a junction where the sipe and the circumferential groove join, wherein a surface extension line extends through the junction to a terminal end of the sipe, wherein the surface extension line is oriented from-30 degrees to +30 degrees from the lateral reference line.

7. The tread of claim 5 or 6, wherein the component in the longitudinal direction is arranged such that the sipe extends from the circumferential groove in a longitudinal direction opposite the rolling direction.

8. The tread of any one of claims 1-7, wherein the sipe has a sipe bottom, wherein a sipe bottom point is located at the sipe bottom, wherein a sipe apex is located on the sipe of the tread outer surface at the same position in the lateral direction as the sipe bottom point, wherein a sipe diagonal line extends from the sipe bottom point to the sipe apex, wherein a reference line extends through the sipe bottom point in the thickness direction, and wherein the reference line has no component in the longitudinal or lateral direction, wherein a sipe inclination angle of the sipe diagonal line to the reference line is not zero degrees.

9. The tread of claim 8, wherein the groove inclination angle is greater than or equal to 5 degrees and less than or equal to 20 degrees, wherein the tread base point is configured to approach a ground contact surface before the groove apex when the tread moves forward.

10. The tread of any of claims 1-9, wherein a terminal end of the sipe extends from 4 to 6 millimeters and includes 4 to 6 millimeters from the circumferential groove in the lateral direction.

11. The tread of any one of claims 1-10, wherein the sipe is spaced from a successive sipe of the sipe in the longitudinal direction by a distance that is 4 millimeters to 6 millimeters and includes 4 millimeters and 6 millimeters.

12. The tread of any of claims 1-11, wherein the sipe has a width of 0.4 to 0.6 millimeters, and comprises 0.4 to 0.6 millimeters.

13. A heavy truck tire having a tread according to any one of claims 1 to 12.

Technical Field

The subject matter of the present invention relates to a truck tire having improved overall wear life and/or rolling resistance. More particularly, the present application relates to a long-distance steered tire for a truck, the steered tire having a circumferential groove with blind microgrooves that exhibit directionality in orientation.

Background

Manufacturers of heavy commercial vehicle tires have historically been challenged to increase the wear life of these tires, particularly steer tires, because the occurrence of irregular wear will lead to early retirement of these tires. Attempts to increase wear life include increasing lateral stiffness by reducing the number of ribs (rib) in the sculpture. However, this modification can result in a decrease in wet traction performance due to the loss of the sipes. One design feature implemented to protect a steered tire from irregular wear is the use of small, directional microgrooves on the rib edges. While these microgrooves protect the rib edges by reducing edge stress, they introduce longitudinal forces due to vertical loading. These rib edges are either at the two lateral ends of the tread or adjacent to the sacrificial ribs of the tire, which in turn are at the two lateral ends of the tread. The height of the sacrificial ribs is different from the height of the rib edges, including the microgrooves.

It is known to provide circumferential grooves in the continuous rib of a tire. Furthermore, it is known to include full-width lateral grooves, which extend from these circumferential grooves to the adjacent circumferential grooves of the tread. These full width side grooves are effective in generating directional coupling forces to protect the tread. However, full width side grooves are also more prone to irregular heel/toe wear and other localized wear patterns. While mechanisms for increasing tire wear life are known, they accept at least one related performance tradeoff. Accordingly, there remains room for variation and improvement in the art.

Drawings

A full and enabling disclosure of the present invention, 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:

FIG. 1 is a perspective view of a heavy truck tire.

FIG. 2 is a front view of the tread of FIG. 1.

Fig. 3 is a close-up front view of the tire of fig. 1.

FIG. 4 is a perspective view of a portion of a tread according to another exemplary embodiment.

FIG. 5 is a close-up front view of the tread of FIG. 4.

FIG. 6 is a close-up perspective view of a portion of the tread, illustrating internal features below the outer surface of the tread.

FIG. 7 is a close-up perspective view of circumferential grooves and microgrooves, illustrating portions of these features below the outer surface.

FIG. 8 is a perspective cross-sectional view of a portion of the tread taken along the circumferential groove.

FIG. 9 is a front cross-sectional view of a portion of the tread taken along the circumferential groove.

The use of the same or similar reference symbols in different drawings indicates the same or similar features.

Detailed Description

Reference now will 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 is 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 to include these and other modifications and variations.

The present invention provides a tread 10 for a heavy truck tire 58 having ribs 26 with circumferential grooves 20 located therein. A plurality of microgrooves 22 extend from the inner and outer sides of the circumferential groove 20 in the transverse direction 14. The microgrooves 22 may be angled relative to the transverse direction 14 such that they extend from the circumferential groove 20 so as to have portions that extend in both the longitudinal and transverse directions 12, 14. Additionally, the microgrooves 22 may be angled with respect to the thickness direction 16 such that the microgrooves 22 also have portions that extend in both the longitudinal direction 12 and the thickness direction 16. The circumferential groove 20 having the micro-groove 22 feature improves the overall wear life of the tread 10 while maintaining wet traction performance. The ribs 26 are not blocks of the tread 10, but rather are features that extend a full 360 degrees around the tire 58, not separated by sipes or other openings.

Fig. 1 shows a tire 58, which is a heavy truck tire 58. In this regard, the tire 58 is not designed for use with an automobile, motorcycle, or light truck (payload capacity less than 4000 pounds), but is instead designed for and used with a heavy truck (e.g., an 18-wheel vehicle, a garbage truck, or a box truck). The tire 58 may be a steering tire, a drive tire, a trailer tire, or an all-wheel tire. The tire 58 includes a casing 60 upon which the tread 10 is disposed. The tread 10 may be manufactured with the casing 60 and formed into a new tire 58, or the tread 10 may be a retread band that is attached to the carcass 60 at some point after the casing 60 has been used to form the retreaded tire 58. This is the case for all designs shown and described herein. They may be either the tread design of a new tire 58 or the tread design of the tread 10 for a retreaded tire 58. The central axis of the tire 58 extends through the center of the casing 60, and the lateral direction 14 of the tire 58 is parallel to the central axis. The radial direction 16 (also referred to as the thickness direction 16) of the tire 58 is perpendicular to the central axis, and the tread 10 is located farther from the central axis than the casing 60 in the thickness direction 16. The tread 10 extends around the entire casing 60 in the circumferential direction 12 (also referred to as the longitudinal direction 12) of the tire 58 and 360 degrees around the central axis. The tread 10 includes a series of grooves and ribs that form a tread pattern. Rolling tread width extending in the lateral direction 14 from one shoulder tread edge 62 to an opposite shoulder tread edge 64 of the tread 10 rolling tread width represents the portion of the tread 10 that engages the ground through normal operation of the tire 58, and the shoulder tread edges 62, 64 may engage the ground and the area in the lateral direction 14 between these locations.

The tread 10 may be a portion of a tire 58 or retread band that is produced and subsequently attached to a casing 60 to form a retreaded tire 58. The same tread pattern may be repeated throughout the longitudinal length of the tread 10. Referring to fig. 2 and 3, the tread 10 includes a number of circumferential ribs and grooves. There are two internal ribs 26 and 70 separated by a circumferential groove 28, these features surrounding the entire tire 58 in the longitudinal direction 12. There are two further shoulder ribs 72 and 74, which also surround the entire tire 58 in the longitudinal direction 12 and are separated from the inner ribs 26, 70 by further circumferential grooves. The sacrificial rib 66 is adjacent to the shoulder rib 72 and the sacrificial rib 68 is adjacent to the shoulder rib 74. The height of the sacrificial ribs 66 and 68 in the thickness direction 16 is not the same as the height of the shoulder ribs 72, 74. In this regard, the height of the sacrificial ribs 66, 68 is less than the height of the shoulder ribs 72, 74 in the thickness direction 16. The heights of both internal ribs 26, 70 and both shoulder ribs 72, 74 are the same in the thickness direction 16. Again, this thickness direction 16 may be referred to as the radial direction 16, such that the distances from the axial center of the tire 58 to the inner ribs 26, 70 and shoulder ribs 72, 74 of the outer surface 48 of the tread 10 are all the same. The sacrificial ribs 66, 68 are present to reduce irregular wear of the tread 10. The circumferential cut separates the sacrificial ribs 66, 68 from their adjacent shoulder ribs 72, 74. At the circumferential cut with the sacrificial rib 66, there is a micro-groove in the shoulder rib 72, but at this circumferential cut there is no micro-groove in the sacrificial rib 66. Also, at the circumferential cut with the sacrificial rib 68, there is a micro-groove in the shoulder rib 74, but at this circumferential cut there is no micro-groove in the sacrificial rib 68.

The grooves of the tread 10 (e.g., the pair of circumferential grooves 28, 30 adjacent to the circumferential rib 26) have a width of 2 millimeters or more. A groove is a feature of the tread 10, being a small cut in the tread 10, having a width less than the width of the groove. These grooves (e.g., microgrooves 22) are less than 2 millimeters wide. While four ribs 26, 70, 72, 74 are present with two sacrificial ribs 66, 68, according to other embodiments, any number of ribs may be present, and in these other embodiments, two sacrificial ribs 66, 68 may or may not be present. The tread 10 is oriented such that it is designed for forward rotation of the tire 58, but the tread 10 need not be oriented in other exemplary embodiments. The rolling direction 18 is the direction in which the tread 10 is designed to rotate in the longitudinal direction 12. Various features of the tread 10 may be arranged such that when the tread 10 is rotated in the rolling direction 18, irregular wear performance characteristics of the tread 10 are improved relative to opposite rolling direction 18. Such improvements typically result in an increased removal mileage (removal milege) because an irregularly worn tire 58 may be removed before reaching a normal removal tread depth or wear strip. Some of these directional characteristics may be the angles of the grooves and sipes within the tread 10.

As can be seen from fig. 2, the ribs 26 in which the circumferential grooves 20 are located have the same height over the entire length in the transverse direction 14. The circumferential groove 20 divides the rib 26 in half, each of which has an outer surface 48 that is the same distance from the tire center 58 in the thickness direction 16. However, the outer surface 48 may be curved due to inflation of the tire 58. It should be understood that when referring to the height/distance of the outer surface 48, they may be measured by measuring the flat tread band from the bottom of the flat tread band to the outer surface 48. Alternatively, when two outer surfaces 48 or any other number of surfaces are described as being at the same height in the thickness direction 16, they are described as having no depth offset of the tread 10 between the surfaces 48. Thus, in the illustrated embodiment, there is no tread depth offset or step across the circumferential groove 20 in the lateral direction 14, such that there is no tread depth step or offset between the two outer surfaces 48 on either side of the circumferential groove 20. It is likely that the outer surface 48 of the tire 58, when inflated, will have multiple heights in the thickness direction 16 at different locations in the lateral direction 14, but that there will be no offset or step between these surfaces 48, all of which will exhibit the same height if the tread 10 is removed from the carcass 60 as measured.

Placing the circumferential grooves 20 and microgrooves 22 in the ribs is different from placing the microgrooves in the shoulder ribs 72, 74 because the shoulder ribs 72, 74 are adjacent to the sacrificial ribs 66, 68 whose outer surfaces 48 have a different height in the thickness direction 16 than the outer surfaces 48 of the shoulder ribs 72, 74. The circumferential groove 20 may be located at a midpoint of the rib 26 in the flank direction 14 such that equal portions of the rib 26 are located inside and outside the circumferential groove 20 in the flank direction 14.

Fig. 4 shows a portion of the tread 10 in perspective view with a series of arrows on the outer surface 48 of the tread 10 to indicate the rolling direction 18 to the user. The indicia of the rolling direction 18 may additionally or alternatively be placed on the casing 60 or on the tread edges 62, 64. The inner rib 26 has a circumferential groove 20 along its entire length such that the circumferential groove 20 encircles the entire tire 58 360 degrees about its central axis in the longitudinal direction 12. A plurality of micro grooves 22 extend from the circumferential groove 20 on both sides of the circumferential groove 20 such that the micro grooves 22 extend from the inner and outer sides of the circumferential groove 20 in the transverse direction 14. The circumferential groove 20 has a body 32 located at the outer surface 48 and extending into the interior of the tread 10. Circumferential groove 20 also has a tear drop (teardrop)34 at the lower end of body 32, within tread 10, and closest to the center of tire 58 in the thickness direction 16. The other internal rib 70 has circumferential grooves and microgrooves arranged in the same manner as the grooves in the internal rib 26. The arrangement of these features 20, 22 in the internal ribs 70 need not be described, as the description thereof discussed with reference to the internal ribs 26 also applies. The shoulder ribs 72, 74 and the sacrificial ribs 66, 68 do not include similar circumferential grooves having microgrooves, but according to other exemplary embodiments, one or more of these ribs may be included.

Fig. 5 shows a front view of a portion of the tread 10, in which the rib 26 between two circumferential grooves 28, 30 is visible. The circumferential groove 20 is straight and extends linearly in the longitudinal direction 12. The micro grooves 22 are engaged with the circumferential grooves 20 and are located on both sides of the circumferential grooves 20 in the transverse direction 14. Both circumferential grooves 20 and sipes 22 are present on the outer surface 48 and extend into the interior of the tread 10. The microgrooves 22 are arranged such that the microgrooves on opposite sides of the circumferential groove 20 are not staggered, but are at the same position in the longitudinal direction 12. According to other exemplary embodiments, the microgrooves 22 may also be staggered. The microgrooves 22 are linear in shape, extending from the circumferential groove 20, but have rounded ends 24. In other arrangements, the microgrooves 22 have a linear shape without rounded ends 24. All of the microgrooves 22 may be arranged in the same manner, i.e., they all have the same shape and size and all have the same angle with respect to the lateral direction 14.

The micro-grooves 22 are blind grooves in that they extend from the circumferential groove 20, terminating in the tread 10 before reaching the grooves 28, 30 or simply any other feature beyond the interior of the rib 26. The microgrooves 22 are not full width grooves that extend all the way to the ribs 26. If the circumferential groove 20 is located exactly in the middle of the ribs 26 in the transverse direction 14, such that half of the ribs 26 are inside the circumferential groove 20 and the other half of the ribs 26 are outside the circumferential groove 20, the microgrooves 22 extend less than half the total width of the ribs 26 in the transverse direction 14. The circumferential groove 20 may be located in the middle of the rib 26 such that the two halves of the rib 26 have the same length as each other in the transverse direction 14. The microgrooves 22 generate a coupling force to reduce or eliminate irregular wear.

At the outer surface 48 of the tread 10, and extending to at least a majority of the depth of the microgrooves 22 in the thickness direction 16, the microgrooves 22 are angled with respect to the lateral direction 14. Specifically, the microgrooves 22 are angled such that they have an extension in the lateral direction 14 and an extension in the longitudinal direction 12 as they extend from the circumferential groove 20. The outer surface 48 of the circumferential groove 20 at the juncture 38 engages the microgrooves 22. A transverse reference line 36 extends in the transverse direction 14 and passes through this junction 38. The microgrooves 22 extend from the junction 38 to the ends 24 thereof. Surface extension line 40 is a line on outer surface 48 that extends from junction 38 through tip 24. If the microgrooves 22 are wavy or curved or have an irregular shape, the surface extension lines 40 will still be straight lines extending from the junction 38 to the end 24.

The surface extension line 40 is aligned at an angle 56 to the transverse reference line 36. The angle 56 is measured such that it is less than 90 degrees, as this angle 56 may alternatively be measured to be greater than 270 degrees. The microgrooves 22 are arranged such that their portions extending from the circumferential groove 20 in the longitudinal direction 12 are opposite to the portions of the rolling direction 18. Although only the sipes 22 are described as having the angle 56, all of the sipes 22 extending from the circumferential groove 20 may have these characteristics and all may be arranged in the same manner. The microgrooves 22 on the other side of the circumferential groove 20 are likewise arranged in the same manner and have an extension in the longitudinal direction 12 opposite to the rolling direction 18. Other sipes in the tread 12, such as those in the internal ribs 70 shown in fig. 5, extend in the longitudinal direction 12 in the same direction as the rolling direction 18.

The extent of the microgrooves 22 in the transverse direction 14 may be measured by a straight line measurement from the tip 24 to the circumferential groove 20 in the transverse direction 14. In addition, the extension across rib 26 may be measured by drawing a straight line from junction 38 in the transverse direction 14 to the transverse position of end 24, which line is not necessarily on end 24, but is exactly at its transverse position if microgrooves 22 are angled. The extension in the transverse direction 14 may be 2 mm to 10 mm. If the length of extension is less than this range, the microgrooves 22 may not be effective in providing irregular wear protection. If the extended length is greater than this range, the wider microgrooves 22 may cause the ribs 26 to be too flexible and reduce wear performance. The microgrooves 22 preferably extend between 4 and 6 millimeters in the transverse direction 14.

The spacing of the microgrooves 22 in the transverse direction 12 (sometimes referred to as density because it determines the number of each length) also affects the reduction of irregular wear performance. If the pitch of the microgrooves 22 is small, the microgrooves 22 will be weak, and if the pitch is too large, the microgrooves 22 will not be effective against irregular wear. The pitch of the microgrooves 22 may be measured by measuring the linear distance between successive junctions 38 of successive microgrooves 22 in the longitudinal direction 12. An acceptable micro-groove 22 pitch is 3 mm to 10 mm. The preferred microgroove spacing is 4 mm to 6 mm.

The width of the microgrooves 22 is the distance between their walls. The width of the microgrooves 22 may or may not be the same along their entire length. The width of the microgrooves 22, if varied, may be measured as the width of a majority of the length of the microgrooves 22. If not, the maximum width of the sipe 22 may be specified as the thickness of the sipe 22. The width of the acceptable microgrooves 22 may be 0.1 to 2.0 millimeters. The preferred width of the microgrooves 22 is 0.4 millimeters to 0.6 millimeters. Thinner sipes 22 are not practical, and sipes 22 that are greater than an acceptable range may reduce the wear performance of the tread 10.

The depth of the sipe 22 in the thickness direction 16 on the outer surface 48 may be one-third of the depth of the entire tread 10 to the entire tread depth. The preferred depth of the sipe 22 may be 3/4 a full tread 10 depth to a full tread 10 depth minus 2 millimeters.

The microgrooves 22 are blind grooves in that they extend across a portion of the ribs 26 in the transverse direction 14, but not all of the ribs 26. The micro-grooves 22 extend from the circumferential groove 20 to the transverse direction 14 by an amount and then terminate short of the grooves 28, 30 so that they do not contact another tread 10 feature other than the circumferential groove 20. In this regard, if adjacent grooves 28, 30 have extended microgrooves, the microgrooves 22 do not contact the grooves 28, 30 or the microgrooves of the grooves 28, 30. Likewise, the microgrooves that engage the grooves 28, 30 extend to the internal ribs 26 and terminate short of the circumferential grooves 20 and microgrooves 22, and thus the only tread 10 that they engage is the circumferential grooves 28, 30 themselves. The width of the microgrooves 22 may be the same or greater than the width of the microgrooves of the shoulder ribs 72, 74 located adjacent the sacrificial ribs 66, 68. The extension of the microgrooves 22 may be the same as or greater than the extension of the microgrooves at the shoulder ribs 72, 74 (located adjacent to the sacrificial ribs 66, 68) in the transverse direction 14. The extent in the transverse direction 14 may be measured by measuring the transverse position in the transverse direction 14 from the juncture 38 to the terminus 24. This length will be a line in the lateral direction 14 that extends from the junction point 38 and ends at the same location on the outer surface 48 of the tread 10 as the location of the terminal end 24 of the lateral direction 14.

Fig. 6 and 7 show details of the circumferential grooves 20 and microgrooves 22 below the outer surface 48. The circumferential groove 20 has a body 32 that is linear in cross-sectional shape and extends from the outer surface 48 to the interior of the tread 10. In other embodiments, the shape of the body 32 is not linear, but may be undulating, angled, curved, non-linear, have sections of different widths, or may be irregularly shaped. In thickness direction 16, tear drop 34 is at the bottom of body 32, expands from body 32 to the widest of circumferential groove 20 in lateral direction 14, and then closes on itself at the bottom of tear drop 34. The microgrooves 22 are engaged with the body 32 and, thus, open into the body and extend in the thickness direction 16 along the entire height of the body 32. Microgroove 22 also engages tear drop 34 and opens into tear drop 34. However, microgrooves 22 do not extend along the entire height of tear drop 34 in thickness direction 16, but rather only extend along an upper portion of tear drop 34 in thickness direction 16. The microgrooves 22 have a rectangular cross-sectional shape along a majority of their length. However, the portion of the microgrooves 22 furthest from the circumferential groove 20 at the tip 24 has a circular cross-sectional shape, as does the bottommost portion of the microgrooves 22 that contacts the tear drop 34 in the thickness direction 16. Tear drop 34 is an optional feature that need not be included in circumferential groove 20 in all embodiments. The circumferential groove 20 is shown as straight, but in other embodiments may be wavy, arcuate, angled, or irregularly shaped in the longitudinal direction 12 around the circumference of the tire 58.

Referring now to fig. 8, a cross-section of the tread portion is shown through circumferential groove 20. Microgroove 22 engages with tear drop 34 and body 32 of circumferential groove 20 such that a fluid communication channel is established between all of these features. The angles of the sipes 22 may be the same such that their overall structure is positioned the same relative to the respective tread 10 directions 12, 14, 16. Alternatively, the microgrooves 22 may be angled or undulating, or have various shapes such that their orientation in each direction 12, 14, 16 is different in different portions of the microgrooves 22.

Fig. 9 is a cross-sectional view taken through the circumferential groove 20 along a portion of the tread 10 in the longitudinal direction 12. The bodies 32 of the microgrooves 22 are oriented with respect to the thickness direction 16 such that they have an extension not only in the thickness direction 16, but also in the longitudinal direction 12 and the thickness direction 16. The microgrooves 22 may be angled relative to the thickness direction 16 such that they extend from the circumferential groove 20 in the longitudinal direction 12, away from the rolling direction 18. Such a slope may be referred to as a negative microgroove 22 slope. The groove apex 46 is located at the top of the microgroove 22 at the outer surface 48. The sipe 22 extends into the tread 10 until it terminates at a sipe bottom 42, which is the furthest position from the opening at the sipe apex 46. A groove bottom point 44 is marked at the position of the groove bottom 42. The groove slope 50 extends from the groove bottom point 44 to the groove apex 46. The bottom 42 of the microgrooves 22 have a circular cross-sectional shape, but this feature is optional in other embodiments. The groove slope 50 is a straight line passing through the points 44 and 46, and is still a straight line even if the body 32 is wavy, curved, angled, or irregularly shaped.

Reference line 52 extends through the groove bottom point 44 and through the outer surface 48. The reference line 52 is oriented entirely in the radial direction 16 and has no component in the longitudinal/circumferential direction 12 or the transverse/axial direction 14. When comparing the orientation of the groove slope line 50 with the reference line 52, the microgrooves 22 are observed to be slanted. The groove slope line 50 is oriented at a groove slope angle 54 from the reference line 52. According to various exemplary embodiments, the groove inclination angle 54 may be from 10 degrees to 45 degrees, from 11 degrees to 45 degrees, from 10 degrees to 20 degrees, from 11 degrees to 20 degrees, from 10 degrees to 15 degrees, from 5 degrees to 15 degrees, from 13 degrees to 23 degrees, from 15 degrees to 28 degrees, from 15 degrees to 30 degrees, from 18 degrees to 28 degrees, from 20 degrees to 25 degrees, from 20 degrees to 45 degrees, or from 12 degrees to 23 degrees.

The inclination of the groove slope line 50 with respect to the reference line 52 is negative in its direction opposite to the rolling direction 18 of the tread 10. In this regard, the groove bottom point 44 is configured to enter the ground-contacting surface of the tread 10 before the groove apex 46 when it engages the ground. The reference line 52, the groove bottom point 44, the groove slope line 50, the groove top point 46, and the groove inclination angle 54 all fall within a common plane. The cross-section in fig. 9 is also in the reference plane, so that all these elements can be viewed relative to each other. This common reference plane extends in the longitudinal direction 12, and the transverse direction 14 is perpendicular to this common reference plane. All the micro grooves 22 engaged with the circumferential groove 20 may be provided to have the same groove inclination angle 54.

Thus, the microgrooves 22 may be arranged such that they have a groove slope angle greater than zero and such that they have a non-zero angle 56. Alternatively, the microgrooves 22 may be arranged such that one of the angles 54 or 56 is zero and the other angle 54 or 56 is non-zero. Further, there are exemplary embodiments in which both angles 54 and 56 are zero. The angle 56 may be greater than or equal to the corresponding angle of the microgrooves in the shoulder ribs 72, 74 adjacent to the sacrificial ribs 66, 68.

The groove inclination angle 54 may be 0 to 30 degrees. In a preferred embodiment, the groove angle 54 is 5 to 20 degrees. In some embodiments, the groove inclination angle 54 may be higher than the corresponding groove inclination angle of the micro-grooves in the shoulder ribs 72, 74 adjacent to the sacrificial ribs 66, 68, which is typically 8.5 degrees. Such a groove rake angle may be effective to provide global irregular wear protection. However, the microgrooves 22 not at the shoulder ribs 72, 74/sacrificial ribs 66, 68 interface are less sensitive to the formation of irregular wear and may be higher than 8.5 degrees. With respect to the angle 56 of the microgrooves 22, an acceptable angle 56 may be plus or minus 45 degrees. Angles steeper than plus or minus 45 degrees may affect the firmness of the tread 10. In a preferred embodiment, the angle 56 is in the range of plus or minus 30 degrees.

While the present subject matter has been described in detail with respect to specific embodiments and methods thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, the scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not preclude inclusion of such modifications, variations and/or additions to the present subject matter.