TREAD FOR A TIRE

Abstract

A tire tread includes a middle rib formed by two circumferential main grooves extending along a tire circumferential direction, a first shoulder rib disposed axially outward from the center rib and one of the circumferential main grooves, and a second shoulder rib disposed axially outward from the center rib and the other of the two circumferential main grooves. The middle rib has a repeated group of three sipes: a first sipe being inclined radially inward a first angle relative to a radial direction, a second sipe being inclined radially inward a second angle relative to the radial direction, and a third sipe being inclined radially inward a third angle relative to the radial direction. The second angle is between −0.5 degrees and +0.5 degrees. The first and third angles are oppositely radially inclined to each other and the radial direction.

Claims

1. A tire tread comprising: a middle rib formed by two circumferential main grooves extending along a tire circumferential direction; a first shoulder rib disposed axially outward from the center rib and one of the circumferential main grooves; and a second shoulder rib disposed axially outward from the center rib and the other of the two circumferential main grooves, the middle rib having a repeated group of three sipes: a first sipe being inclined radially inward a first angle relative to a radial direction, a second sipe being inclined radially inward a second angle relative to the radial direction, and a third sipe being inclined radially inward a third angle relative to the radial direction, the second angle being between −0.5 degrees and +0.5 degrees, the first and third angles being oppositely radially inclined to each other and the radial direction.

2. The tire tread as set forth in claim 1 wherein the first and third angles are equal and oppositely radially inclined to each other and the radial direction.

3. The tire tread as set forth in claim 1 wherein the first sipe is inwardly angled circumferentially away from the second sipe.

4. The tire tread as set forth in claim 1 wherein the third sipe is inwardly angled circumferentially away from the second sipe.

5. The tire tread as set forth in claim 1 wherein the first shoulder rib has a second repeated group of three sipes: a first sipe being inclined radially inward a first angle relative to a radial direction, a second sipe being inclined radially inward a second angle relative to the radial direction, and a third sipe being inclined radially inward a third angle relative to the radial direction, the second angle being between −0.5 degrees and +0.5 degrees, the first and third angles being oppositely radially inclined to each other and the radial direction.

6. The tire tread as set forth in claim 5 wherein the second shoulder rib has a third repeated group of three sipes: a first sipe being inclined radially inward a first angle relative to a radial direction, a second sipe being inclined radially inward a second angle relative to the radial direction, and a third sipe being inclined radially inward a third angle relative to the radial direction, the second angle being between −0.5 degrees and +0.5 degrees, the first and third angles being oppositely radially inclined to each other and the radial direction.

7. The tire tread as set forth in claim 6 wherein the first group, the second group, and the third group each have equal first, second, and third angles.

8. The tire tread as set forth in claim 6 wherein the first group and the third group each have equal first, second, and third angles.

9. The tire tread as set forth in claim 6 wherein the first group and the second group each have equal first, second, and third angles.

10. The tire tread as set forth in claim 6 wherein the first group and the third group each have unequal first and third angles.

11. A tire tread comprising: an intermediate rib formed by two circumferential main grooves extending along a tire circumferential direction; a first shoulder rib disposed axially outward from the center rib and one of the circumferential main grooves; and a second shoulder rib disposed axially outward from the center rib and the other of the two circumferential main grooves, the middle rib having a repeated group of three sipes: a first sipe being inclined radially inward a first angle relative to a radial direction, a second sipe being inclined radially inward a second angle relative to the radial direction, and a third sipe being inclined radially inward a third angle relative to the radial direction.

12. The tire tread as set forth in claim 11 wherein the first angle is between +10 degrees and +30 degrees.

13. The tire tread as set forth in claim 12 wherein the second angle is between −0.5 degrees and +0.5 degrees.

14. The tire tread as set forth in claim 13 wherein the third angle is between −10 degrees and −30 degrees.

15. The tire tread as set forth in claim 11 wherein the first angle is between +17 degrees and +23 degrees.

16. The tire tread as set forth in claim 15 wherein the second angle is between −0.5 degrees and +0.5 degrees.

17. The tire tread as set forth in claim 16 wherein the third angle is between −17 degrees and −23 degrees.

18. The tire tread as set forth in claim 11 wherein the first angle is between +19.5 degrees and +20.5 degrees.

19. The tire tread as set forth in claim 18 wherein the second angle is between −0.5 degrees and +0.5 degrees.

20. The tire tread as set forth in claim 19 wherein the third angle is between −19.5 degrees and −20.5 degrees.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The accompanying drawings, which are incorporated in, and constitute a part of, this specification, illustrate examples of the present invention and, together with a general description of the present invention given above, and the detailed description given below, serve to explain the present invention.

[0094] FIG. 1 is a schematic orthogonal view of a tire tread in accordance with the present invention;

[0095] FIG. 2 is a schematic sectional view of part of the tire tread of FIG. 1;

[0096] FIG. 3 is another schematic sectional view of the tire tread of FIG. 1 under acceleration; and

[0097] FIG. 4 is still another schematic sectional view of the tire tread of FIG. 1 under braking.

DETAILED DESCRIPTION OF EXAMPLES OF THE PRESENT INVENTION

[0098] This description is made for the purpose of illustrating the general principles of the present invention and should not be understood in a limiting sense. The scope of the present invention is best determined by reference to the appended claims. The reference numerals as depicted in the drawings are the same as those referred to in this specification. Any further structural limitations of the example tire and tread may be specified in U.S. Pat. No. 9,174,495, herein incorporated by reference in its entirety.

[0099] FIGS. 1-4 show an example pneumatic or non-pneumatic tire tread 1 having a contact surface 3, such as a road, and a first circumferential shoulder rib 11, a second circumferential center rib 12, and a third circumferential shoulder 13, each separated axially by a circumferential groove 9. The first rib 11, the second rib 12, and the third rib 13 may have axially extending sipes 111. The sipes 111 may be axially extending, angled in the direction of rotation, or angled opposite the direction of rotation (FIG. 2). The sipes 111 may have a circumferential thickness between 0.4 mm and 2.0 mm. The sipes 111 may have axial lengths between 15.0 mm and 30.0 mm, or 17.0 mm and 26.0 mm, or between 21.0 mm and 23.0 mm, or 21.5 mm. The sipes 111 may have radial depths between 6.0 mm and 12.0 mm.

[0100] As shown in FIG. 2, a group of three of the sipes 111 may extend directly radially inward (middle sipe), radially inward (and circumferentially) at an angle +k to a radial depth d from the contact surface 3 (left sipe), and radially inward (and circumferentially) at an opposite angle −k to a radial depth d from the contact surface 3 (right sipe). The value of angle k may be between +10 degrees and +30 degrees, or between +17 degrees and +23 degrees, or +20 degrees, and correspondingly between −10 degrees and −30 degrees, or between −17 degrees and −23 degrees, or −20 degrees. The radial depth d may be between 5.0 mm and 7.0 mm, or 5.5 mm and 6.5 mm, or 6.0 mm.

[0101] Conventionally, tread design optimization for braking tends to impact wet and dry braking in opposite directions. A general trend is that lower tread stiffness improves wet braking, but penalizes dry braking. The above grouping of sipes 111 may allow optimization of wet braking without the trade-off in dry braking. FIG. 3 illustrates an example of the sipes 111 operating under accelerating conditions. FIG. 4 illustrates an example of the sipes 111 operating under braking conditions.

[0102] In accordance with the present invention, this grouping of sipes 111 may mitigate block stiffness locally and correspondingly enable block deformation locally. As seen FIGS. 3-4, the trailing edges at each sipe 111 (right edge in FIG. 3 and left edge in FIG. 4) may open and thereby increase the capacity to retain the snow during both acceleration and braking. Traction in both cases is thereby enhanced.

[0103] The present invention has been described with reference to the above examples. Modifications and alterations may occur to others upon reading and understanding of this specification. The specification is intended to include all such modifications and alterations in so far as they come within the scope of the appended claims or the equivalents thereof.