TIRE TREAD

Abstract

A tread for a tire includes a first circumferential main groove; a second circumferential main groove; a third circumferential main groove; and a fourth circumferential main groove. The fourth circumferential main groove has a stabilizing structure for increasing tread stiffness. The stabilizing structure is axially offset a predetermined amount from a centerline of the fourth circumferential main groove. The fourth circumferential main groove has an angled axially inner sidewall, an angled axially outer sidewall, and a curved base surface. The stabilizing structure extends radially inward from the curved base surface of the fourth circumferential main groove.

Claims

1. A tread for a tire comprising: a first circumferential main groove; a second circumferential main groove; a third circumferential main groove; and a fourth circumferential main groove, the fourth circumferential main groove having a stabilizing structure for increasing tread stiffness, the stabilizing structure being axially offset a predetermined amount from a centerline of the fourth circumferential main groove, the fourth main groove having an angled axially inner sidewall, an angled axially outer sidewall, and a curved base surface, the stabilizing structure extending radially inward from the curved base surface.

2. The tread as set forth in claim 1 wherein the stabilizing structure has a subgroove with a curved, cylindrical radially innermost surface for mitigating cracking and increasing axial flexibility of the stabilizing structures.

3. The tread as set forth in claim 2 wherein an axial width of the subgroove shrinks to 0.0 mm under a predetermined operating condition.

4. The tread as set forth in claim 3 wherein the subgroove has a first sidewall and a second sidewall interconnected by the curved, cylindrical radially innermost surface of the subgroove.

5. The tread as set forth in claim 4 wherein the first sidewall abuts the second sidewall under the predetermined operating condition.

6. The tread as set forth in claim 5 wherein relative motion between the first sidewall and the second sidewall is prevented by a frictional engagement of the first sidewall and the second sidewall.

7. A method for stiffening a tire tread comprising the steps of: extending a first circumferential main groove across the tire tread; extending a second circumferential main groove across the tire tread; circumferentially extending a subgroove across a radially innermost curved bottom surface of the first main groove; axially offsetting the subgroove a predetermined amount from a centerline of the first main groove; and curving a radially innermost surface of the subgroove, the radially innermost surface of the subgroove being radially inside the radially innermost curved bottom surface of the first main groove.

8. The method as set forth in claim 7 wherein the radially innermost surface of the subgroove mitigates cracking and increases axial flexibility of the first main groove.

9. The method as set forth in claim 8 wherein an axial width of the subgroove shrinks to 0.0 mm under a predetermined operating condition.

10. The method as set forth in claim 9 wherein the subgroove has a first sidewall and a second sidewall interconnected by the radially innermost surface of the subgroove.

11. The method as set forth in claim 10 further including the step of abutting the first sidewall against the second sidewall under the predetermined operating condition.

12. The method as set forth in claim 7 wherein relative motion between the first sidewall and the second sidewall is prevented by a frictional engagement of the first sidewall and the second sidewall.

13. A system for increasing cornering stiffness of a tire tread comprising: a first circumferential main groove; a second circumferential main groove; and a stabilizing structure for increasing tread stiffness, the stabilizing structure having a circumferentially extending subgroove in a radially innermost curved bottom of the first main groove, the subgroove being axially offset a predetermined amount from a centerline of the first circumferential main groove.

14. The system as set forth in claim 13 wherein the subgroove has a curved, cylindrical radially innermost surface for mitigating cracking and increasing axial flexibility of the stabilizing structures.

15. The system as set forth in claim 14 wherein an axial width of the subgroove shrinks to 0.0 mm under a predetermined operating condition.

16. The system as set forth in claim 15 wherein the subgroove has a first sidewall and a second sidewall interconnected by the curved, cylindrical radially innermost surface of the subgroove.

17. The system as set forth in claim 16 wherein the first sidewall abuts the second sidewall under the predetermined operating condition.

18. The system as set forth in claim 17 wherein relative motion between the first sidewall and the second sidewall is prevented by a frictional engagement of the first sidewall and the second sidewall.

19. The system as set forth in claim 13 wherein the radially innermost bottom of the first main groove has a radius of curvature ranging from 40.0 mm at an axially inner edge and 20.0 mm at an axially outer edge.

20. The system as set forth in claim 13 wherein the radially innermost bottom of the first main groove has a radius of curvature as low as between 1.5 mm and 4.0 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0092] The present invention will be better understood through reference to the following description and the appended drawings, in which:

[0093] FIG. 1 is a schematic perspective view of a tire in accordance with the present invention;

[0094] FIG. 2 is a schematic orthogonal view of the tread of the tire of FIG. 1;

[0095] FIG. 3 is a schematic detail view of the tread of FIG. 2;

[0096] FIG. 4 is a schematic section view taken along the line “4-4” in FIG. 2;

[0097] FIG. 5 is a detailed schematic view of part of the tread of FIG. 4;

[0098] FIG. 6 represents a schematic detail perspective view of an asymmetric tread groove from FIG. 4; and

[0099] FIG. 7 represents a schematic detail perspective view of another asymmetric tread groove from FIG. 4.

DETAILED DESCRIPTION OF EXAMPLES OF THE PRESENT INVENTION

[0100] A similar tread construction is disclosed in US 2019/0168546, incorporated by reference herein in its entirety. Referring now in more detail to the drawings, the present invention will below be described in more detail. The pneumatic, or non-pneumatic, tire 10 illustrated in FIGS. 1-7 may have a tread 11 defined by intermediate circumferential first shoulder ribs 12, intermediate circumferential second ribs 14, and a center intermediate circumferential third rib 16. The intermediate circumferential ribs 12, 14, 16 may be defined by two stabilizing circumferential grooves 22 and two central circumferential grooves 24. The two central circumferential grooves 24 may each have a trapezoidal cross-section with slanted walls and a curved bottom (FIG. 4). The intermediate circumferential second ribs 14 and the center intermediate circumferential third rib 16 may have wavy blind sipes 15, 17, respectively, for improving performance of the tread 11.

[0101] The two stabilizing circumferential grooves 22 may also have a trapezoidal cross-section with slanted walls and a curved bottom, similar to the two central circumferential grooves 24. The radial depth of each stabilizing groove 22 may be more shallow (FIG. 4) or less (not shown) than the depth of the central circumferential grooves 24. The stabilizing groove depths may be about 50% of the central groove depths (FIG. 4). At the curved bottom of each stabilizing groove 22 may be a stabilizing structure 220. The stabilizing structures 220 may define circumferentially extending linear subgrooves 222 in the bottoms of the stabilizing grooves 22. As shown in FIG. 3, the axial width of the subgrooves 222 may be less than the axial width of the bottoms of the stabilizing grooves 22. The subgrooves 222 may have curved, cylindrical radially innermost surfaces 229 to mitigate cracking and to increase axial flexibility of the stabilizing structures 222 (FIGS. 5-7).

[0102] When an axially inward load is placed on the tread 11, such as while the vehicle is cornering, the axial width of the subgrooves 222 may shrink to as little as 0.0 mm (e.g., touching). Because of the linear pattern of the subgrooves 222, the walls of the subgrooves may frictionally lock thereby preventing relative circumferential movement between the walls of the subrooves. This may provide an increase in stiffness of the tread 11 while cornering, without requiring increased overall stiffness of the tread during straight line movement of the vehicle.

[0103] The subgrooves 222 may be axially offset a predetermined amount 228 from a centerline 227 of the grooves 22. The amount 228 of offset may be varied to tune the cornering stiffness of the tread 11. If a subgroove 222 is offset toward the center rib 16 (FIGS. 5-7), the tread 11 around that subgroove may have less cornering stiffness than a subgroove at the centerline 227 of the groove 22. Conversely, if a subgroove 222 is offset away from the center rib 16 (not shown), the tread 11 around that subgroove may have greater cornering stiffness than a subgroove at the centerline 227 of the groove 22. No matter the axial position relative to the centerline 227 of the groove 22, the stabilizing structure 220 may mitigate cracking and increase axial flexibility of the tread 11 during non-cornering, straight line motion and rotation of the tire 10.

[0104] In accordance with the present invention and as shown in FIGS. 4-7, the asymmetric first left-hand shoulder groove 22 may have a radially angled inner sidewall 161 with a first sidewall radial angle between 170° and 180°, or 175° and a radially angled outer sidewall 162 with a second sidewall radial angle between 155° and 170°, or 161°. The first left-hand shoulder groove 22 may further have a curved base surface 163 with a radius of curvature ranging from 40.0 mm at its axially inner edge 164 and 20.0 mm at its axially outer edge 165. The curved base surface 163 may have a radius of curvature as low as between 1.5 mm and 4.0 mm, or 2.5 mm, as it extends from edge 164 to edge 165. The first left-hand shoulder groove 22 may still further have a stabilizing structure 220 nearer the center of the tread 11 than the centerline of the first left hand shoulder groove (See FIG. 5).

[0105] In accordance with the present invention and as shown in FIGS. 4-7, the asymmetric second right-hand shoulder groove 22 may have a radially angled inner sidewall 171 with a first sidewall radial angle between 167° and 177°, or 172° and a radially angled outer sidewall 172 with a second sidewall radial angle between 155° and 170°, or 161°. The second right-hand shoulder groove 22 may further have a curved base surface 173 with a radius of curvature ranging from 40.0 mm at its axially inner edge 174 and 8.0 mm at its axially outer edge 175. The curved base surface 173 may have a radius of curvature as low as between 1.5 mm and 4.0 mm, or 1.5 mm, as it extends from edge 174 to edge 175. The second right-hand shoulder groove 22 may still further have a stabilizing structure 220 nearer the center of the tread 11 than the centerline of the second right-hand shoulder groove (FIG. 5).

[0106] While the present invention has been described in connection with what is considered the most practical and preferred example, it is to be understood that the present invention is not to be limited to these described examples, but is intended to cover various arrangements which are included within the spirit and scope of the broadest possible interpretation of the appended claims so as to encompass all modifications and equivalent arrangements which are possible.