The present invention relates to a tire tread. More particularly, the present invention relates to a tire tread with an asymmetric shoulder groove.
In order to improve handling, tires are conventionally provided with grooves in their treads, wherein increased groove cross sections may increase the tire's drainage capacity. However, such grooves may negatively influence the tire's steering stability and grip. During cornering, grooves of tires may be subjected to buckling and tread portions laterally adjacent to these grooves may be raised from the road's surface such that they no longer contact the road.
This phenomenon may impair the adherence contact between the road and the tire tread, and may result in a loss of control when making sudden maneuvers at high speed. Specifically, typical tire grooves may generate high stress concentrations in the adjacent tread and undergo buckling during frequent handling of a tire resulting in limited dry performances. Moreover, in wet conditions, the groove's cross sectional area may be reduced, thereby impeding its drainage capacity.
A conventional asymmetric tread portion may be provided with circumferentially extending grooves having tilted/angled sidewalls. An outermost groove may have sidewall cross sections or profiles with different tilts in respect of a line perpendicular to the planar tread. Other grooves may have sidewall cross sections which are more tilted than the counterparts of the outermost groove. This arrangement is intended to maintain a safe cornering stability and also a low noise level. However, cornering stability may still be improved, especially at high speed on a vehicle having a non-zero, positive camber angle.
It is a continuing goal of tire makers to overcome one or more of the afore-mentioned disadvantages.
A first tire in accordance with the present invention includes an annular tread portion including a first circumferentially extending asymmetric shoulder groove having an angled axially inner sidewall with an axially inner sidewall radial angle between 170° and 180° , an angled axially outer sidewall with an axially outer sidewall radial angle between 155° and 170° , and a curved base surface with a radius of curvature ranging from 40.0 mm at an axially inner edge and 20.0 mm at an axially outer edge.
According to another aspect of the first tire, the curved base surface has a radius of curvature as low as between 1.5 mm and 4.0 mm, or 2.5 mm, from the axially inner edge to the axially outer edge.
According to still another aspect of the first tire, the axially inner sidewall radial angle is about 175°.
According to yet another aspect of the first tire, the axially outer sidewall radial angle is about 161°.
According to still another aspect of the first tire, a second circumferentially extending asymmetric shoulder groove has an angled axially inner sidewall with an axially inner sidewall radial angle between 167° and 177°, an angled axially outer sidewall with an axially outer sidewall radial angle between 155° and 170°, and a curved base surface with a radius of curvature ranging from 40.0 mm at an axially inner edge and 8.0 mm at an axially outer edge.
According to yet another aspect of the first tire, the curved base surface of the second shoulder groove has a radius of curvature as low as between 1.5 mm and 4.0 mm, or 1.5 mm, from the axially inner edge to the axially outer edge.
According to still another aspect of the first tire, the axially inner sidewall radial angle of the second shoulder groove is about 172°.
According to yet another aspect of the first tire, the axially outer sidewall radial angle of the second shoulder groove is about 161°.
According to still another aspect of the first tire, the first tire includes a third circumferential central groove.
According to yet another aspect of the first tire, the third circumferential central groove includes bridge structures at circumferential intervals about the third groove and contoured pockets therebetween.
A second tire in accordance with the present invention includes a first circumferentially extending asymmetric shoulder groove and a second circumferentially extending asymmetric shoulder groove, the first circumferentially extending asymmetric shoulder groove having an angled axially inner sidewall with an axially inner sidewall radial angle between 170° and 180°, an angled axially outer sidewall with an axially outer sidewall radial angle between 155° and 170°, and a curved base surface with a radius of curvature ranging from 40.0 mm at an axially inner edge and 20.0 mm at an axially outer edge, the second circumferentially extending asymmetric shoulder groove having an angled axially inner sidewall with an axially inner sidewall radial angle between 167° and 177°, an angled axially outer sidewall with an axially outer sidewall radial angle between 155° and 170°, and a curved base surface with a radius of curvature ranging from 40.0 mm at an axially inner edge and 8.0 mm at an axially outer edge.
According to another aspect of the second tire, the curved base surface of the first groove has a radius of curvature as low as between 1.5 mm and 4.0 mm, or 2.5 mm, from the axially inner edge to the axially outer edge.
According to still another aspect of the second tire, the axially inner sidewall radial angle of the first groove is about 175°.
According to yet another aspect of the second tire, the axially outer sidewall radial angle of the first groove is about 161°.
According to still another aspect of the second tire, the curved base surface of the second shoulder groove has a radius of curvature as low as between 1.5 mm and 4.0 mm, or 1.5 mm, from the axially inner edge to the axially outer edge.
According to yet another aspect of the second tire, the axially inner sidewall radial angle of the second shoulder groove is about 172°.
According to still another aspect of the second tire, the axially outer sidewall radial angle of the second shoulder groove is about 161°.
According to yet another aspect of the second tire, the second tire includes a third circumferential central groove.
According to still another aspect of the second tire, the third circumferential central groove includes bridge structures at circumferential intervals about the third groove and contoured pockets therebetween.
The above aspects and features of this disclosure of the present invention may be combined with or replaced by one another.
“Apex” or “Bead Filler Apex” means an elastomeric filler located radially above the bead core and between the plies and the turn-up plies.
“Axial” and “Axially” mean the lines or directions which are parallel to the axis of rotation of the tire.
“Bead” means that part of the tire comprising an annular tensile member commonly referred to as a “bead core” wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
“Belt structure” or “reinforcing belts” means at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17 degrees to 27 degrees with respect to the equatorial plane of the tire.
“Camber angle” or “camber” means an angle between the equatorial plane of the tire and a line perpendicular to the road. This angle is positive when the upper portion of the tire is tilted outwardly when mounted to the vehicle, and negative when the upper portion of the tire is tilted inwardly.
“Carcass” means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads.
“Circumferential” means lines or directions extending along or in parallel to the perimeter of the surface of the annular tread perpendicular to the axial direction.
“Cross section” means in the present application a cross section following or lying in a plane which extends along the axial direction and the radial direction of the tire. A “cross section” with regard to the tread or its components, as for instance its grooves, may also be considered as the profile of the tread or its components.
“Equatorial plane” means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread; or the plane containing the circumferential centerline of the tread.
“Groove” means an elongated void area in a tread that may extend circumferentially. A groove width or depth may be equal to its average width or depth over its length.
“Inboard” means a direction axially oriented toward a center of the vehicle.
“Inner” means, if not otherwise defined, an inner axial direction.
“Lateral” means a direction parallel to the axial direction.
“Normal Load” means the specific design inflation pressure and load assigned by the appropriate standards organization for the service condition for the tire.
“Outboard” means a direction axially oriented away from the center of the vehicle.
“Outer” means, if not otherwise defined, an outer axial direction.
“Overlay” means a ply arranged radially on the top of the belt or belt plies. Such overlays are often used for reinforcement of high-speed tires.
“Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire. In connection with “inner” or “outer” it refers to the tire axis.
“Sidewall” means that portion of a tire between the tread and the bead, or, in the context of the present disclosure, also a lateral boundary of a tread groove.
“Slip angle” or “slip” means the angle between a rolling tire's direction of travel and the orientation of the equatorial plane of the tire.
“Tread” or “Tread portion” means one or more rubber components which when bonded to a tire carcass include that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load.
“Tread width” means the arc length of the tread surface in the plane including the axis of rotation of the tire.
“Undertread” means a layer of rubber placed under an extruded tread to boost adhesion of the tread to the stabilizer plies during tire assembly and preferably to cover the end of the cut belts.
The structure, operation, and advantages of the present invention will become more apparent upon contemplation of the following description taken in conjunction with the accompanying drawings, wherein:
U.S. patent application Ser. No. 16/997,972 to the present Applicant, filed Aug. 20, 2020, is incorporated herein by reference in its entirety.
As shown in
Each main groove 20, 21, 22 may comprise a cross section with a groove bottom or base 25, 28, 31 laterally separating a pair of essentially radially extending sidewalls 23, 24, 26, 27, 29, 30, and a groove opening essentially radially opposite to the groove bottom 25, 28, 31. The groove opening may be considered as lying in a plane of the tread's surface which contacts the ground when rolling. Alternatively, the groove opening's cross section or profile may be considered as a straight line extending between the radially outer surfaces of two circumferential ribs forming the sidewalls of, or delimiting, the respective groove 20, 21, 22. Each sidewall 23, 24, 26, 27, 29, 30 may extend over the majority of the groove's depth and the main grooves 20, 21, 22 may generally increase their width in a radially outer direction R.
The groove bottom 25, 28, 31 may extend axially over the majority of the maximum width of the corresponding groove 20, 21, 22. However, in other examples, a groove bottom may be optional. For example, the sidewalls of a groove may laterally meet in just one point in cross section or in one circumferential line.
As shown in
The outermost groove's cross section may further include portions 35, 36 joining the groove bottom 25 with the inner sidewall 24 and the outer sidewall 23. The joining portions 35, 36 may be straight, or may be curved and comprise an axially outer joining portion 35 with a radius of curvature R1, and an axially inner joining portion 36 with a radius of curvature R2 inferior to R1. Preferably, the radius of curvature R1 is at least twice the radius of curvature R2.
Further, the middle groove 21 may include a chamfer 38 at the radially outer end of the outer sidewall 26, which may be tilted with respect to the groove opening 37 by an angle θ between 10° and 45°, or between 20° and 35°, and wherein the height of the chamfer may be between 5% and 15% of the maximum depth of the middle groove 21. The cross sectional width of the chamfer may be about 5% to 15% of the width of the groove opening. On the axially opposite side of the middle groove 21, instead of a chamfer, the middle groove may include an edge 39 intended to contact the road.
The groove bottom 28 of the middle groove 21 may also be tilted with respect to the groove opening 37 such as to reduce the depth of the middle groove in an outboard direction. Similar to the outer groove, the middle groove 21 may include portions 40, 41 joining the groove bottom 28 with the inner sidewall 27 and the outer sidewall 26. The joining portions 40, 41 may be straight, or may be curved. A curved outer joining portion 40 may have a first radius of curvature R3, and an inner joining portion 41 may have a second radius of curvature R4 superior to R3. For example, the radius of curvature R4 may be at least twice times the radius of curvature R3.
The innermost groove 22, as depicted in
The width of the middle groove 21 may be larger than the width of the outermost groove 20. The cross sectional area of the middle groove 21 may correspondingly be larger than the cross sectional area of the outermost groove 20. Such a feature may further improve the stability of the tire under cornering maneuvers. However, the width and/or the cross sectional area of the grooves 20, 21, 22 may also be equal.
As stated above, a tread 100 may have one or more circumferential grooves 101, 102, 103, 104 in accordance with the present invention for improving durability (
As shown in
As shown in
In general, and in addition to the above described features, it is possible to further reinforce at least the bottom of one or more grooves in order to further improve the groove stiffness under cornering conditions and/or to reduce groove buckling. The combination of groove bottom reinforcements and the groove designs mentioned herein may further improve the groove stiffness and handling performance of the example tire 1.
While certain representative examples and details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the scope of the present invention as defined by the following appended claims. In any case, the above described examples shall not be understood in a limiting sense. In particular, features of the above examples may also be replaced by one another or combined with one another.