Car tyre
The car tire design addresses the challenges of braking, traction, and durability by incorporating a symmetrical tread pattern with circumferential ribs and transverse grooves, resulting in improved performance and longevity.
Patent Information
- Application Number
- PCT/IB2024/062692
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-12-20
- Filing Date
- 2024-12-16
- Publication Date
- 2025-06-26
AI Technical Summary
Existing summer car tires face challenges in achieving improved braking and traction on dry roads, ensuring driving safety on wet roads, while also providing long mileage, even wear, and low noise.
A car tire design featuring a substantially symmetrical tread pattern with a central region and shoulder regions, incorporating three circumferential ribs and transverse grooves with specific inclination angles, which enhances drainage and even rubber distribution for improved performance and durability.
The tire design achieves better braking and traction on dry roads, ensures driving safety on wet roads, and provides long mileage, even wear, and low noise, thanks to its optimized tread pattern and groove configuration.
Smart Images
Figure IB2024062692_26062025_PF_FP_ABST
Abstract
Description
[0001] CAR TYRE
[0002] Field of the invention
[0003] The present invention relates to a car tyre. More specifically, to a so-called “summer” tyre.
[0004] Prior art
[0005] The following documents describe some examples of summer car tyres: W02009 / 004408, W02015 / 008137, WO02 / 078982, WO2019 / 111089,
[0006] W02009 / 060476.
[0007] Summary of the invention
[0008] Car wheel tyres intended particularly for use in summer are generally characterized by tread bands formed with blocks or tread band portions that are substantially continuous, i.e., do not have large recesses (grooves or sipes), as well as by the presence of a limited number of sipes. This increases the amount of rubber in contact with the road surface, resulting in better handling, braking stability, and shorter braking distance.
[0009] The Applicant has observed an increasing attention of the users to the ability of car tyres to offer long mileage, even wear, and low noise.
[0010] The Applicant has observed that it is generally believed that the achievement of the above-mentioned goals can be obtained simply by increasing the amount of rubber in contact with the road surface, and that, therefore, these goals should already be intrinsic in the manufacturing of “summer” tyres.
[0011] However, the Applicant has observed that this is often not the case because of the excessive stiffness variation between adj acent tread band portions or blocks, particularly in axial direction.
[0012] Therefore, the Applicant has faced the problem of providing a car tyre, particularly a summer car tyre, capable of improving braking and traction on dry roads, to ensure driving safety on wet roads, as well as long mileage, even wear, and low noise.
[0013] The Applicant has focused its efforts to achieve this improvement by making a tyre having a substantially symmetrical tread pattern, provided with a tread band having a central region separated from two shoulder regions. In addition, the central region of the tyre has been designed so as to form three circumferential ribs defined by grooves respectively located at the two shoulder regions and by further grooves located in the central region which are substantially larger than the grooves located at the shoulder regions.
[0014] Moreover, advantageously, such a central region further comprises transverse grooves extending in a respective circumferential rib. Further advantageously, the transverse grooves in the first rib have an inclination angle relative to a direction parallel to the equatorial plane smaller than or equal to 40°, whereas the transverse grooves in the second and third ribs have an inclination angle greater than the inclination angle of the transverse grooves in the first rib.
[0015] In a first aspect thereof, the invention thus relates to a car tyre having a tread band comprising a central region, extending across an equatorial plane of the tyre, a first shoulder region and a second shoulder region.
[0016] Such a tyre comprises a first circumferential groove axially delimiting the first shoulder region relative to the central region and a second circumferential groove axially delimiting the second shoulder region relative to the central region.
[0017] Advantageously, said first circumferential groove has substantially the same width as the second circumferential groove.
[0018] Advantageously, said central region comprises a first, a second, and a third circumferential rib separated from one another by a third and a fourth circumferential groove.
[0019] The third circumferential groove has substantially the same width as the fourth circumferential groove.
[0020] The third and fourth circumferential grooves have a width larger than the width of the first and second circumferential grooves.
[0021] Said first, second, and third circumferential ribs respectively comprise a plurality at least of first, second, and third transverse grooves.
[0022] Advantageously, the first, second, and third transverse grooves have maximum width smaller than or equal to 3 mm.
[0023] Preferably, the first, second, and third transverse grooves extend over at least 50% of the width of the rib where they are located.
[0024] Advantageously, said first transverse grooves, at least for a major portion of their extension, are inclined relative to a direction parallel to the equatorial plane so as to form a first inclination angle smaller than or equal to 40°.
[0025] Said second and said third transverse grooves have a second inclination angle relative to a direction parallel to the equatorial plane greater than said first inclination angle.
[0026] The Applicant has verified that, due to these features, the tyre of the invention allows better braking and traction performance on dry roads to be achieved, while still ensuring driving safety on wet roads, as well as long mileage, even wear, and low noise.
[0027] Without wishing to be bound by any particular theory, the Applicant believes that the presence of four circumferential channels having widths not too much different from one another provides good draining properties together with a more even partition of the tread band in the axial direction, which favors road holding and long mileage, whereas the presence of the transverse grooves with similar distribution and extension in the central portion favors low noise and even wear.
[0028] For the purposes of the present invention, the following definitions apply:
[0029] By “tread pattern” it is meant the representation of all points of the tread band (including recesses) in a plane perpendicular to the equatorial plane of the tyre and tangential to the maximum diameter of the tyre.
[0030] The measurements of angles and / or linear quantities (distances, widths, lengths, etc.) and / or surface areas shall be understood as referring to the tread pattern as defined above.
[0031] Furthermore, considering the angular arrangement of the grooves formed in the tread band relative to the equatorial plane of the tyre, such angular arrangement shall be understood, for each point of the groove, as referring to the acute angle (i.e., an angle comprised between 0° and 90° in absolute value) defined by a rotation starting from the equatorial plane to the direction tangent to the groove passing through that point.
[0032] By the term “equatorial plane” of the tyre it is meant a plane perpendicular to the rotation axis of the tyre and dividing the tyre into two substantially equal portions.
[0033] By “circumferential” direction it is meant a direction generally directed according to the rotation direction of the tyre, or slightly inclined (e.g., by at most about 15°) relative to the rotation direction of the tyre.
[0034] By “axial” direction it is meant a direction substantially parallel to the rotation axis of the tyre, or at most slightly inclined (e.g., by at most about 15°) relative to the rotation axis of the tyre. Generally, the axial direction is substantially perpendicular to the circumferential direction.
[0035] By the term “effective width” referred to the tread band it is meant the width of the radially outermost portion of the tread band (from one edge to the other) intended to contact the ground.
[0036] By “void-to-rubber ratio” it is meant the ratio between the total surface area of the recesses or grooves of a given tread band portion (possibly of the whole tread band) and the total surface area of the given tread band portion (possibly of the whole tread band). By the term “major portion” referred to a groove and / or sipe it is meant a portion of a groove and / or sipe measured along the extension thereof greater than or equal to 45% of the total extension of the groove and / or sipe.
[0037] By the term “width of a groove” it is meant the distance between the lateral walls defining the same groove measured at a depth of about 1 mm from the radially outermost surface of a new tyre.
[0038] The present invention, in one or more preferred aspects thereof, may comprise one or more of the features hereafter presented.
[0039] Conveniently, the first inclination angle of the first transverse grooves and the second inclination angle of the second and third transverse grooves are concordant.
[0040] Preferably, the third and fourth circumferential grooves have a width larger than or equal to 1 times and smaller than or equal to 1.5 times the width of the first and second circumferential grooves.
[0041] Advantageously, the third and fourth circumferential grooves have a width larger than or equal to 7 mm.
[0042] Preferably, the first and second circumferential grooves may be located substantially at the same distance from the equatorial plane.
[0043] Advantageously, the tread band has an effective width; the first and second circumferential grooves are located at a distance from the equatorial plane smaller than or equal to 37% of said effective width and larger than or equal to 17% of said effective width.
[0044] Preferably, the third and fourth circumferential grooves may be located substantially at the same distance relative to the equatorial plane.
[0045] Advantageously, the third and fourth circumferential grooves are located at a distance from the equatorial plane smaller than or equal to 12% of said effective width and larger than or equal to 6% of said effective width.
[0046] Preferably, the first transverse grooves may comprise a first, a second, and a third segment arranged consecutively to one another.
[0047] Preferably, the second segment may have an extension greater than 50% of the total extension of the first transverse groove.
[0048] Advantageously, the first segment of the first transverse grooves may extend from the first circumferential groove.
[0049] Conveniently, the first segment of the first transverse grooves may have an extension smaller than 30% of the total extension of the first transverse groove.
[0050] Conveniently, the third segment of the first transverse grooves may extend from the second segment up to merging into the third circumferential groove.
[0051] Preferably, the third segment of the first transverse grooves may have an extension smaller than or equal to 10% of the total extension of the first transverse groove.
[0052] Conveniently, the first circumferential rib comprises first transverse grooves and fourth transverse grooves
[0053] The fourth transverse grooves may have an extension smaller than the first transverse grooves.
[0054] Advantageously, the fourth transverse grooves may have a maximum width smaller than or equal to 3 mm.
[0055] Preferably, the fourth transverse grooves, at least for a major portion of their extension, may be inclined relative to a direction parallel to the equatorial plane so as to form a third inclination angle smaller than or equal to 40°.
[0056] Conveniently, the fourth transverse grooves may be substantially parallel to the first transverse grooves over at least 80% of their extension.
[0057] Advantageously, the fourth transverse grooves may be circumferentially alternated with the first transverse grooves, preferably in a one-to-one ratio.
[0058] Preferably, the second transverse grooves may extend form the third circumferential groove to the fourth circumferential groove.
[0059] Advantageously, the second inclination angle of the second transverse grooves is smaller than or equal to 75°.
[0060] Conveniently, the second circumferential rib comprises second transverse grooves and fifth transverse grooves. The fifth transverse grooves may have an extension smaller than the second transverse grooves.
[0061] Preferably, the fifth transverse grooves may extend from the fourth circumferential groove over at most 70% of the width of the second circumferential rib.
[0062] Conveniently, the fifth transverse grooves may be inclined relative to a direction parallel to the equatorial plane so as to form a fourth inclination angle smaller than or equal to 75°.
[0063] Preferably, the fifth transverse grooves may be substantially parallel to the second transverse grooves over at least 80% of their extension.
[0064] Conveniently, the fifth transverse grooves are circumferentially alternated with the second transverse grooves, preferably in a one-to-one ratio.
[0065] Preferably, the third circumferential rib comprises third transverse grooves.
[0066] Conveniently, the third transverse grooves may extend from the fourth circumferential groove to the second circumferential groove.
[0067] Advantageously, in order to avoid substantial stiffness variations in axial direction, at least some of the third transverse grooves, at least in a portion of their extension, may be arranged along the extension direction of the second transverse grooves.
[0068] Preferably, in order to avoid substantial stiffness variations in axial direction, at least some of the third transverse grooves, at least in a portion of their extension, may be arranged along the extension direction of the fifth transverse grooves.
[0069] Conveniently, the third transverse grooves may comprise a first and a second segment arranged consecutively to each other. The first segment of the third transverse grooves may have an extension greater than 50% of the total extension of the third transverse groove.
[0070] The second segment of the third transverse grooves may have an extension smaller the extension of the first segment.
[0071] Conveniently, the outer shoulder region has substantially the same width as the inner shoulder region.
[0072] Preferably, the outer shoulder region and the inner shoulder region may comprise, respectively, a plurality of sixth and seventh transverse grooves having a first end substantially located at a respective edge of the tread band.
[0073] The sixth and seventh transverse grooves may a have maximum width larger than or equal to 3 mm and an extension equal to at least 50% of the width of the shoulder region where they are located.
[0074] Conveniently, the sixth and seventh transverse grooves may extend respectively from the first and second circumferential grooves.
[0075] Advantageously, the sixth and seventh transverse grooves may have an extension equal to or smaller than 90% of the width of the tread band region where they are located. Conveniently, the void-to-rubber ratio of the outer shoulder region and of the inner shoulder region is respectively achieved through the contribution of just the sixth and seventh transverse grooves.
[0076] Further features and advantages of the invention shall become clearer from the detailed description of some preferred, although not exclusive, embodiments of a car tyre according to the present invention.
[0077] Brief description of the drawings
[0078] Such description shall be made hereafter with reference to the accompanying drawings, provided only for indicating, and thus non-limiting, purposes, wherein: figure 1 shows a view of a first example of a tyre according to the invention; figure 2 is an enlarged view of a cross section of the tyre according in figure 1; figure 3 is a schematic plan view of a tread band portion of the tyre in figure 1.
[0079] Detailed description of embodiments of the invention
[0080] With reference to the attached figures, a tyre for car wheels is generally indicated at 100. The structure of the tyre 100 is per se of a conventional type and comprises a carcass, a tread band 20 placed in crown to the carcass, a pair of axially opposed sidewalls, ending in beads reinforced by bead cores and associated bead fillers. The tyre preferably also comprises a belt structure interposed between the carcass and the tread band. The carcass comprises one or more carcass plies anchored to the bead cores, whereas the belt structure comprises two radially superimposed belt strips. The belt strips are formed of pieces of a rubberized fabric incorporating metal cords parallel to one another in each strip and having a crossed orientation, preferably with a symmetrical inclination relative to the equatorial plane, relative to the cords of adjacent strips. Preferably, the belt structure also comprises, in a radially outer position, a third belt layer provided with cords oriented substantially parallel to the equatorial plane. Preferably, although not necessarily, the tyre according to the invention has a nominal section width of at least about 205, more preferably of at least about 225. For example, the tyre may have a nominal section width of 225, 245, 275, 295, and 355. Preferably, the tyre according to the invention has a reduced section height. For example, the section height may be smaller than or equal to 60%, more preferably smaller than or equal to 50%, of the nominal section width.
[0081] The tread band 20 has overall a reduced void-to-rubber ratio, preferably a void-to-rubber ratio smaller than or equal to 0.30, more preferably smaller than or equal to 0.28, even more preferably smaller than or equal to 0.20
[0082] Preferably, the overall void-to-rubber ratio of the tread band 20 is greater than 0.14.
[0083] The tread band 20 is provided with at least two circumferential grooves, respectively a first 1 and a second 2 circumferential groove, extending in a substantially circumferential direction.
[0084] The first and second circumferential grooves 1 and 2 respectively separate a central region LI of the tread band 20 from a first shoulder region L2 and from a second shoulder region L3, respectively located to the left and right of the central region LI. In the embodiment shown in the figures, preferably, the first shoulder region L2 is located on the outer side of the tyre, whereas the second shoulder region L3 is located on the inner side of the tyre. The central region LI extends across the equatorial X-X plane of the tyre. The first L2 and second L3 shoulder regions extend close to the axial ends of the tread band 20.
[0085] As shown by way of example in the embodiments of figures 1-3, the central region LI takes up a substantial portion of the tread band 20.
[0086] In particular, the central region LI may have a width larger than or equal to 35% of the effective width of the tread band 20, i.e., the width of the tread band portion intended to contact the ground; the first shoulder region L2 may have a width smaller than 25% of the effective width M of the tread band 20; the second shoulder region L3 may have a width smaller than 25% of the effective width M of the tread band 20.
[0087] Moreover, the central region LI may have a width smaller than or equal to 50% of the effective width of the tread band 20, the first shoulder region L2 may have a width larger than 20% of the effective width of the tread band 20, and the second shoulder region L3 may have a width larger than 20% of the effective width of the tread band 20.
[0088] Preferably, the first shoulder region L2 has a width substantially equal to the width of the second shoulder region L3.
[0089] The first circumferential groove 1 delimits the first shoulder region L2 from the central region LI of the tread band 7 in axial direction, whereas the second circumferential groove 2 delimits the second shoulder region L3 from the central region LI in axial direction.
[0090] Preferably, the first 1 and second 2 circumferential grooves have a substantially straight course in the circumferential direction, preferably over the whole circumferential development of the tyre.
[0091] For the purpose of making the stiffness of the tread band 20 homogeneous in axial direction, the first 1 and second 2 circumferential grooves may be located substantially at the same distance from the equatorial plane X-X.
[0092] Preferably, the first 1 and second 2 circumferential grooves may be located at a distance from the equatorial plane X-X smaller than or equal to 37% of the effective width M of the tread band 20 and larger than or equal to 17% of said effective width M. The first circumferential groove 1 may have a width substantially equal to the width of the second circumferential groove 2. The first circumferential groove 1 and the second circumferential groove 2 may, for example, have a width smaller than or equal to about 12.5 mm, preferably smaller than or equal to about 11 mm, preferably larger than or equal to about 7 mm.
[0093] Preferably, the first 1 and second 2 circumferential grooves may have a depth smaller than or equal to about 12 mm, more preferably smaller than, or equal to, about 11 mm, preferably greater than, or equal to, about 7 mm. Preferably, the first circumferential groove 1 has a depth substantially equal to the depth of the second circumferential groove 2.
[0094] The first and second circumferential grooves 1 and 2, in combination with the third 3 and fourth 4 circumferential grooves, which are described in more detail below, are mainly provided with the purpose of draining water from the footprint area.
[0095] In fact, the tread band 20 preferably comprises, in the central region LI, a third 3 and a fourth 4 circumferential groove.
[0096] Preferably, the third 3 and fourth 4 circumferential grooves have a substantially straight course in the circumferential direction, preferably over the whole circumferential development of the tyre.
[0097] Still for the purpose of making the stiffness of the tread band 20 homogeneous in the axial direction, the third 3 and fourth 4 circumferential grooves may be located substantially at the same distance from the equatorial X-X plane.
[0098] Preferably, the third 3 and fourth 4 circumferential grooves may be located at a distance from the equatorial plane X-X smaller than or equal to 12% of the effective width M of the tread band and larger than or equal to 6% of said effective width M.
[0099] The third circumferential groove 3 may have a width substantially equal to the width of the fourth circumferential groove 4.
[0100] The third circumferential groove 3 and the fourth circumferential groove 4 have a width larger than the width of the first 1 and second 2 circumferential grooves.
[0101] Preferably, the third 3 and fourth 4 circumferential grooves have a width larger than or equal to 1 times and smaller than or equal to 1.5 times the width of the first 1 and second 2 circumferential grooves. Preferably, the third 3 and fourth 4 circumferential grooves have a width smaller than or equal to 1.2 times the width of the first 1 and second 2 circumferential grooves.
[0102] The third 3 and fourth 4 circumferential grooves may have, for example, a width smaller than or equal to about 16 mm, preferably smaller than or equal to about 14 mm, preferably larger than or equal to about 7 mm.
[0103] Preferably, the third and fourth circumferential grooves 3 and 4 may have a depth smaller than or equal to about 12 mm, more preferably smaller than or equal to about 11 mm, preferably greater than, or equal to, about 7 mm.
[0104] Preferably, the third circumferential groove 3 has a depth substantially equal to the depth of the fourth circumferential groove 4.
[0105] The central region LI is designed to make the stiffness of this portion of the tread band 20 as uniform as possible.
[0106] To this end, the central region LI has a low void-to-ratio ratio along with a homogeneous distribution of transverse grooves.
[0107] Preferably, the central region LI has a void-to-rubber ratio smaller than about 0.30, preferably smaller than about 0.25. Preferably, the central region LI has a void-to- rubber ratio greater than about 0.20.
[0108] In the embodiments shown in Figs 1-3, the third 3 and fourth 4 circumferential grooves, together with the first 1 and second 2 circumferential grooves, define in the central region LI a first 5, a second 6, and a third 7 circumferential rib.
[0109] In the embodiment shown in Figs 1-3, preferably, the first circumferential rib 5 is located between the first circumferential groove 1 and the third circumferential groove 3, the second circumferential rib 6 is located between the third circumferential groove 3 and the fourth circumferential groove 4, and the third circumferential rib 7 is located between the fourth circumferential groove 4 and the second circumferential groove 2.
[0110] For increasing the amount of “rubber to the ground” at the central region LI, thus improving handling properties, noise, and rolling resistance, the circumferential ribs in the central region LI, respectively the first 5, second 6, and third 7 circumferential ribs, are characterized by low void-to-rubber ratios. At least one among the first 5, second 6, and third 7 circumferential ribs, preferably all of them, has, in fact, a void-to-rubber ratio smaller than or equal to about 0.035, more preferably smaller than or equal to about 0.033.
[0111] In the embodiment shown in the figures, the void-to-rubber ratio of the first circumferential rib 5 is achieved just by means of first 10 and fourth 13 transverse grooves.
[0112] The first transverse grooves 10 extend in the first circumferential rib 5, preferably starting from the first circumferential groove 1, over at least 50% of the width of the first circumferential rib 5.
[0113] Preferably, the first transverse grooves 10 extend over at least 70% of the width of the first circumferential rib 5, even more preferably the first transverse grooves 10 extend over 100% of the width of the first circumferential rib 5, i.e., up to merging into the third circumferential groove 3.
[0114] In embodiment shown in the figures, the first grooves 10 have a first 10’, a second 10”, and a third 10’” segment arranged consecutively to one another.
[0115] Preferably, the first segment 10’ extends in the first circumferential rib 5 starting from the first circumferential groove 1 and has an extension smaller than 30% of the total extension of the first transverse groove 10.
[0116] The second segment 10”, arranged consecutively to the first segment 10’, has an extension greater than or equal to 50% of the total extension of the first transverse groove 10.
[0117] The third segment 10’”, arranged consecutively to the second segment 10”, has an extension smaller than the extension of the first segment 10’.
[0118] The third segment 10’” has an extension smaller than or equal to 10% of the total extension of the first transverse groove 10.
[0119] In the embodiments shown in Figs 1-3, the second segment 10” represents the major portion of the extension of the first transverse grooveslO, and is inclined so as to form a first inclination angle a smaller than or equal to 40° with the equatorial X-X plane. Still referring to the embodiment shown in the figures, the first segment 10’, has a substantially curvilinear course and is arranged so as to connect the first circumferential groove 1 with the second segment 10” of the first transverse grooves 10.
[0120] Similarly, the third segment 10’” has a substantially curvilinear course and is arranged so as to connect the second segment 10” of the first transverse grooves 10 with the third circumferential groove 3.
[0121] The first segment 10’ and the third segment 10’” have opposite concavity in the circumferential direction.
[0122] Preferably, the first transverse grooves 10 have a width smaller than or equal to about 3 mm. For example, they may have a width of between about 0.6 and about 1.5 mm.
[0123] In embodiment shown in the figures, the first transverse grooves 10 may have, when the tyre is new, a width which is not constant in the radial direction. In particular, they may have a section widening at their radially outermost portion so as to form a flare.
[0124] The flare affects a groove portion smaller than or equal to 1 mm starting from the radially outermost surface of the tread band, when the tyre is new.
[0125] The first transverse grooves 10 may have a depth greater than or equal to about 2 mm. Preferably, the first transverse grooves 10 may have a depth smaller than about 6.5 mm. For example, they may have a depth of between about 2.5 and about 5.5 mm.
[0126] The first transverse grooves 10 may have a constant depth along their respective extension.
[0127] The first circumferential rib 5 may comprise, as in the examples in Figs 1-3, a plurality of fourth transverse grooves 13.
[0128] Preferably, the fourth transverse grooves 13 have an extension smaller than the first transverse grooves 10.
[0129] Preferably, the fourth transverse grooves 13 extend over at most 80% of the width of the first circumferential rib 5, even more preferably the fourth transverse grooves 13 extend over at most 60% of the width of the first circumferential rib 5.
[0130] The fourth transverse grooves 13 extend over at least 30% of the width of the first circumferential rib 5. The fourth transverse grooves 13 extend in the first circumferential rib 5 preferably starting from the first circumferential groove 1.
[0131] In the embodiments shown in Figs 1-3, the fourth transverse grooves 13, at least for a major portion of their extension, are inclined so as to form a third inclination angle a’ smaller than or equal to 40° with the equatorial X-X plane.
[0132] The fourth transverse grooves 13 extend, at least for a major portion of their extension, according to a direction substantially parallel to the direction of the first transverse grooves 10.
[0133] In the embodiment shown in Figs 1-3, the fourth transverse grooves 13 extend, at least over 80% of their extension, according to a direction substantially parallel to the direction of the first transverse grooves 10.
[0134] Furthermore, in the first rib 5, the fourth transverse grooves 13 are circumferentially alternated with the first transverse grooves 10, preferably in a one-to-one ratio.
[0135] The fourth transverse grooves 13 have substantially the same width as the first transverse grooves 10. Preferably, the fourth transverse grooves 13 have a width equal to or smaller than about 3 mm.
[0136] For example, they may have a width of between about 0.6 and about 1.5 mm.
[0137] In embodiment shown in the figures, the fourth transverse grooves 13 may have, when the tyre is new, a width which is not constant in the radial direction. In particular, they may have a section widening at their radially outermost portion so as to form a flare.
[0138] The flare affects a groove portion smaller than or equal to 1 mm starting from the radially outermost surface of the tread band, when the tyre is new.
[0139] The fourth transverse grooves 13 may have a depth greater than or equal to about 2 mm. For example, they may have a depth of between about 2.5 and about 5.5 mm. The fourth transverse grooves 13 may have a constant depth along their respective extension.
[0140] In the embodiment shown in the figures, the void-to-rubber ratio of the second circumferential rib 6 is achieved just by means of second 11 and fifth 14 transverse grooves. The second transverse grooves 11 extend in the second circumferential rib 6, preferably starting from the third circumferential groove 3, over at least 50% of the width of the second circumferential rib 6.
[0141] Preferably, the second transverse grooves 11 extend over at least 70% of the width of the second circumferential rib 6, even more preferably the second transverse grooves 11 extend over 100% of the width of the second circumferential rib 6, i.e., up to merging into the fourth circumferential groove 4.
[0142] In the embodiment shown in the figures, the second grooves 11 have a substantially straight course.
[0143] Preferably, the second transverse grooves 11 are inclined so as to form a second inclination angle P with the equatorial plane which is greater than the first inclination angle a of the first transverse grooves 10.
[0144] In the embodiments shown in the figures, the second inclination angle P of the second transverse grooves 11 is concordant with the first inclination angle a of the first transverse grooves 10.
[0145] The second transverse grooves 11 are inclined so as to form a second inclination angle P smaller than or equal to 75° with the equatorial X-X plane.
[0146] Preferably, the second transverse grooves 11 are inclined so as to form a second inclination angle P greater than or equal to 45° with the equatorial X-X plane.
[0147] Preferably, the second transverse grooves 11 have substantially the same width as the first transverse grooves 10.
[0148] The second transverse grooves 11 have a width equal to or smaller than about 3 mm. For example, they may have a width of between about 0.6 and about 1.5 mm.
[0149] In the embodiment shown in the figures, the second transverse grooves 11 may have, when the tyre is new, a width which is not constant in the radial direction. In particular, they may have a section widening at their radially outermost portion so as to form a flare.
[0150] The flare affects a groove portion smaller than or equal to 1 mm starting from the radially outermost surface of the tread band, when the tyre is new. The second transverse grooves 11 may have a depth greater than or equal to about 2 mm. For example, they may have a depth of between about 2.5 and about 5.5 mm. The second transverse grooves 11 may have a constant depth along their respective extension.
[0151] As in the examples shown in the figures, the second circumferential rib 6 may comprise a plurality of fifth transverse grooves 14.
[0152] Preferably, the fifth transverse grooves 14 have an extension smaller than the second transverse grooves 11.
[0153] Preferably, the fifth transverse grooves 14 extend over at most 80% of the width of the second circumferential rib 6, even more preferably the fifth transverse grooves 14 extend over at most 60% of the width of the second circumferential rib 6.
[0154] The fifth transverse grooves 14 extend over at least 30% of the width of the second circumferential rib 6.
[0155] The fifth transverse grooves 14 extend in the second circumferential rib 6 preferably starting from the fourth circumferential groove 4.
[0156] In the embodiments shown in Figs 1-3, the fifth circumferential grooves 14 have a substantially straight course.
[0157] Preferably, the fifth transverse grooves 14 are inclined so as to form a fourth inclination angle P’ smaller than or equal to 75° with the equatorial X-X plane.
[0158] The fifth transverse grooves 14 extend, at least for a major portion of their extension, according to a direction substantially parallel to the direction of the second transverse grooves 11.
[0159] In the embodiment shown in the figures, the fifth transverse grooves 14 extend, over the total extension thereof, according to a direction substantially parallel to the direction of the second transverse grooves 11.
[0160] Furthermore, in the second rib 6, the fifth transverse grooves 14 are circumferentially alternated with the second transverse grooves 11, preferably in a one-to-one ratio.
[0161] The fifth transverse grooves 14 have substantially the same width as the second transverse grooves 11. Preferably, the fifth transverse grooves 14 have a width equal to or smaller than about 3 mm.
[0162] For example, they may have a width of between about 0.6 and about 1.5 mm.
[0163] In embodiment shown in the figures, the fifth transverse grooves 14 may have, when the tyre is new, a width which is not constant in the radial direction. In particular, they may have a section widening at their radially outermost portion so as to form a flare.
[0164] The flare affects a groove portion smaller than or equal to 1 mm starting from the radially outermost surface of the tread band, when the tyre is new.
[0165] The fifth transverse grooves 14 may have a depth greater than or equal to about 2 mm. For example, they may have a depth of between about 2.5 and about 5.5 mm. The fifth transverse grooves 14 may have a constant depth along their respective extension.
[0166] In the embodiment shown in the figures, the void-to-rubber ratio of the third circumferential rib 7 is achieved just by means of third transverse grooves 12.
[0167] Preferably, the third transverse grooves 12 extend starting from the fourth circumferential groove 4, over at least 70% of the width of the third circumferential rib 7.
[0168] Even more preferably, the third transverse grooves 12 extend over 100% of the width of the third circumferential rib 7, i.e., up to merging into the second circumferential groove 2.
[0169] In the embodiment shown in Figs 1-3, the third transverse grooves 12 comprise a first 12’ and a second segment 12”arranged consecutively to each another.
[0170] Preferably, the first segment 12’ has an extension greater than 50% of the total extension of the third transverse groove 12.
[0171] The second segment 12” has instead an extension smaller than the extension of the first segment 12’.
[0172] For example, the second segment 12” has an extension smaller than 30% of the total extension of the third transverse groove 12.
[0173] The third transverse grooves 12, at least for a major portion of their extension, are inclined relative to a direction parallel to the equatorial plane X-X so as to form a second inclination angle P greater than the first inclination angle a of the first transverse grooves 10.
[0174] In the embodiments shown in the figures, the second inclination angle P of the third transverse grooves 12 is concordant with the first inclination angle a of the first transverse grooves 10 and with the second inclination angle P of the second transverse grooves 11.
[0175] Preferably, the third transverse grooves 12, at least for a major portion of their extension, are inclined relative to a direction parallel to the equatorial plane X-X so as to form a second inclination angle P smaller than or equal to 75°.
[0176] Preferably, the third transverse grooves 12 are inclined so as to form a second inclination angle P greater than or equal to 45° with the equatorial plane X-X.
[0177] In the embodiment shown in figure 3, the major portion coincides with the first segment 12’ of the third transverse grooves.
[0178] In the embodiment shown in the figures, the inclination angle of the second segment 12” of the third transverse grooves 12 is greater than the second inclination angle P of the first segment 12’.
[0179] In order to avoid substantial stiffness variations in axial direction, at least some of the third transverse grooves 12 may be arranged, at least in a portion of their extension, along the extension direction of the second transverse grooves 11.
[0180] In the embodiment shown in the figures, some first segments 12’ of the third transverse grooves 12 may be arranged along the extension direction of the second transverse grooves 11.
[0181] Still in order to avoid substantial stiffness variations in axial direction, at least some of the third transverse grooves may be arranged, at least in a portion of their extension, along the extension direction of the fifth transverse grooves 14.
[0182] In the embodiment shown in the figures, some first segments 12’ of the third transverse grooves 12 may be arranged along the extension direction of the fifth transverse grooves 14.
[0183] In the embodiment shown in Figs 1-3, a third transverse groove 12 arranged, at least in a portion of its extension, along the extension direction of a second transverse groove 11 is followed, in circumferential direction, by a third transverse groove 12 arranged, at least in a portion of its extension, along the extension direction of a fifth transverse groove 14.
[0184] Preferably, the third transverse grooves 12 have substantially the same width as the first transverse grooves 10 and the second transverse grooves 11.
[0185] The third transverse grooves 12 have a width equal to or smaller than about 3 mm.
[0186] For example, they may have a width of between about 0.6 and about 1.5 mm.
[0187] In embodiment shown in the figures, the third transverse grooves 12 may have, when the tyre is new, a width which is not constant in the radial direction. In particular, they may have a section widening at their radially outermost portion so as to form a flare.
[0188] The flare affects a groove portion smaller than or equal to 1 mm starting from the radially outermost surface of the tread band, when the tyre is new.
[0189] The third transverse grooves 12 may have a depth greater than or equal to about 2 mm. For example, they may have a depth of between about 2.5 and about 5.5 mm. The third transverse grooves 12 may have a constant depth along their respective extension.
[0190] The first shoulder region L2, as well as the second shoulder region L3 have a good stiffness for providing the tyre with readiness of response particularly at high speed and in cornering.
[0191] To make the tyre shoulder regions stiff, the first L2 and L3 shoulder regions have a limited void-to rubber ratio.
[0192] Preferably, the first shoulder region L2 and / or the second shoulder region L3 have a void-to-rubber ratio smaller than about 0.20, preferably smaller than about 0.18. Preferably, the first shoulder region L2 and / or the second shoulder region L3 have a void-to-rubber ratio greater than about 0.05, preferably greater than about 0.07.
[0193] Preferably, the first L2 and the second L3 shoulder regions have substantially the same voi d-to-rubb er-rati o .
[0194] In particular, the first shoulder region L2 and the second shoulder region L3 have a plurality of sixth 16 and seventh 17 transverse grooves, respectively.
[0195] The first shoulder region L2 comprises circumferentially repeating sixth transverse grooves 16.
[0196] In the embodiment shown in the figures, the void-to-rubber ratio of the first shoulder region L2 is achieved just by means of these sixth transverse grooves 16.
[0197] In other words, in the first shoulder region L2 preferably there are no other kinds of grooves and / or recesses.
[0198] The sixth transverse grooves 16 of the first shoulder region L2 have a first end located substantially at the respective axially outer edge of the tread band 20, and extend from said end in a substantially axial direction for at least 50% of the width of the first shoulder region L2.
[0199] Preferably, the sixth transverse grooves 16 of the first shoulder region L2 may have an extension equal to at least 70% of the width of the first shoulder region L2. The sixth transverse grooves 16 of the first shoulder region L2 may have an extension equal to or smaller than 90% of the width of the first shoulder region L2.
[0200] Preferably, the sixth transverse grooves 16 extend in the first shoulder region L2 up to merging into the first circumferential groove 1.
[0201] Preferably, the sixth transverse grooves 16 of the first shoulder region L2 have a substantially transverse course or in any case a course which is only slightly inclined relative to the axial direction.
[0202] In particular, the course of the sixth transverse grooves 16 forms an angle of between 75° and 90° in absolute value with the equatorial plane X-X.
[0203] The sixth transverse grooves 16 of the first shoulder region L2 have a maximum width larger than or equal to about 3 mm. Preferably, they have a maximum width smaller than about 8 mm. For example, they may have a maximum width of between about 3.5 and about 7 mm.
[0204] In embodiment shown in the figures, the sixth transverse grooves 16 may have, when the tyre is new, a width which is not constant in the radial direction. In particular, they may have a section widening at their radially outermost portion so as to form a flare.
[0205] The flare affects a groove portion smaller than or equal to 1 mm starting from the radially outermost surface of the tread band, when the tyre is new.
[0206] As in the examples shown in Figs 1-3, and leaving out the radially outer portion thereof, the sixth transverse grooves 16 of the first shoulder region L2 may have a substantially constant width along their extension. Preferably, the sixth transverse grooves 16 of the first shoulder region L2 have a maximum depth equal to at least about 2 mm and smaller than about 8 mm.
[0207] The sixth transverse grooves 16 of the first shoulder region L2 may have a depth which is not constant along their respective extension, for example a depth which decreases, preferably gradually, moving towards the axially outer edges of the tread band 20.
[0208] In the embodiment shown in the figures, the void-to-rubber ratio in the second shoulder region L3 is achieved just by means of the seventh transverse grooves 17.
[0209] In other words, in the second shoulder region L3 there are no other kinds of grooves and / or recesses.
[0210] The seventh transverse grooves 17 of the second shoulder region L3 have a first end located substantially at the respective axially outer edge of the tread band 20, and extend from said end in a substantially axial direction for at least 50% of the width of the second shoulder region L3.
[0211] Preferably, the seventh transverse grooves 17 of the second shoulder region L3 may have an extension equal to at least 70% of the width of the second shoulder region L3. The seventh transverse grooves 17 of the second shoulder region L3 may have an extension equal to or smaller than 90% of the width of the second shoulder region L3.
[0212] Preferably, the seventh transverse grooves 17 extend in the second shoulder region L3 up to merging into the second circumferential groove 2.
[0213] Preferably, the seventh transverse grooves 17 of the second shoulder region L3 have a substantially transverse course or in any case a course which is only slightly inclined relative to the axial direction.
[0214] In particular, the course of the seventh transverse grooves 17 forms an angle of between 75° and 90° in absolute value with the equatorial plane X-X.
[0215] The seventh transverse grooves 17 of the second shoulder region L3 have a maximum width larger than or equal to about 3 mm. Preferably, they have a maximum width smaller than about 8 mm. For example, they may have a maximum width of between about 3.5 and about 7 mm.
[0216] In embodiment shown in the figures, the seventh transverse grooves 17 may have, when the tyre is new, a width which is not constant in the radial direction. In particular, they may have a section widening at their radially outermost portion so as to form a flare.
[0217] The flare affects a groove portion smaller than or equal to 1 mm starting from the radially outermost surface of the tread band, when the tyre is new.
[0218] As in the examples shown in Figs 1-3, and leaving out the radially outer portion thereof, the seventh transverse grooves 17 of the second shoulder region L3 may have a substantially constant width along their extension.
[0219] Preferably, the seventh transverse grooves 17 of the second shoulder region L3 have a maximum depth of at least about 2 mm and smaller than about 8 mm.
[0220] EXAMPLE
[0221] Tyres having size 255 / 55 R17, model Cinturato P7, currently marketed by the Applicant (Comparison), were compared with tyres of the same size and having a tread pattern made according to the embodiment of the invention shown in the figures (Invention). Both tyres were fitted with an inflation pressure of 2.4 bar.
[0222] A VW Golf car was first equipped with four tyres made according to the invention and then with four comparison tyres.
[0223] Tests of the running behavior on road terrain, both dry and wet, as well as tests with instruments for measuring rolling resistance and braking space on dry and wet ground, were performed.
[0224] The running behavior test, on road terrain, with both dry and wet ground, is performed on predetermined paths, typically tracks closed to traffic. By simulating some typical maneuvers (such as change of lane, overtaking, slalom between traffic cones, entering and leaving a bend) at a constant speed, as well as under acceleration and deceleration, the test driver assesses the performance of the tyre by giving a numerical evaluation of the behavior of the latter during the aforementioned maneuvers.
[0225] Indoor noise tests were also performed.
[0226] The noise tests were carried out in a soundproof chamber (semi-anechoic chamber) using a fixed turret which rotatably supports the tyre to be tested, in particular equipped initially with a tyre according to the invention, and then with two different comparison tyres belonging to the same market segment.
[0227] In the noise test, a tyre of each set is kept in contact with a rotating drum and made to rotate at different speeds.
[0228] Furthermore, noise is measured with multiple microphones at different speeds and on different surfaces in terms of roughness.
[0229] The results of the tests are shown in Table I, where the values of the ratings, except for outer noise, are expressed as percentages, setting the values for the comparison tyre equal to 100.
[0230] As to the running behavior tests, the rating scale represents a subjective assessment made by the test driver testing the compared sets in sequence.
[0231] In the case of the mileage test, a value greater than 100 as compared to the comparison tyre indicates a percentual improvement in terms of lower tread wear (measured as recess depth) on a mixed route comprising distances on motorways, highways, secondary roads, and urban roads.
[0232] In the case of the braking distance measurement, a value greater than 100 as compared to the comparison tyre represents a shorter braking distance on the corresponding ground.
[0233] Table I
[0234] The tyre of the invention thus showed an overall improvement, and in particular a very pronounced improvement in terms of beahvior and braking on dry and wet grounds. Various modifications may be made to the embodiments described herein in detail, while remaining within the scope of protection of the invention, as defined by the following claims.
Claims
CLAIMS1. Car Tyre (100) having a tread band (20) comprising a central region (LI), extending across an equatorial plane (X-X) of the tyre, a first shoulder region (L2) and a second shoulder region (L3) opposed to each other relative to said central region (LI); a first circumferential groove (1) axially delimiting the first shoulder region (L2) relative to the central region (LI) and a second circumferential groove (2) axially delimiting the second shoulder region (L3) relative to the central region (LI); said first circumferential groove (1) having substantially a same width as said second circumferential groove (2); said central region (LI) comprising a first, a second, and a third circumferential rib (5, 6, 7) separated from each one another by a third (3) and a fourth (4) circumferential groove; said third circumferential groove (3) having substantially a same width as said fourth circumferential groove (4); said third and said fourth circumferential grooves (3, 4) having a width larger than said first and said second circumferential grooves (1, 2); said first, second, and third circumferential ribs (5, 6, 7) respectively comprising a plurality at least of first, second, and third transverse grooves (10, 11, 12) having a maximum width smaller than or equal to 3 mm and extending over at least 50% of the width of the rib where they are located; said first transverse grooves (10), at least for a major portion of their extension, being inclined relative to a direction parallel to the equatorial plane (X-X) so as to form a first inclination angle (a) smaller than or equal to 40°; said second and said third transverse grooves (11, 12), at least for a major portion of the respective extension, being inclined relative to a direction parallel to the equatorial plane (X-X) so as to form a second inclination angle (P) greater than said first inclination angle (a).
2. Tyre (100) according to claim 1, characterized in that said first inclination angle (a) and said second inclination angle (P) are concordant.
3. Tyre (100) according to claim 1, characterized in that said third (3) and said fourth(4) circumferential grooves have a width larger than or equal to 1 times and smaller than or equal to 1.5 times the width of said first (1) and second (2) circumferential grooves.
4. Tyre (100) according to any one of claims 1 to 3, characterized in that said third (3) and fourth (4) circumferential grooves have a width larger than or equal to 7 mm.
5. Tyre (100) according to claim 1, characterized in that said first (1) and second (2) circumferential grooves are located substantially at a same distance from said equatorial plane (X-X).
6. Tyre (100) according to claim 1, characterized in that said tread band (20) has an effective width (M); said first (1) and said second (2) circumferential grooves are located at distance from the equatorial plane (X-X) smaller than or equal to 37% of said effective width (M) and greater than or equal to 17% of said effective width (M).
7. Tyre (100) according to claim 1, characterized in that said third (3) and fourth (4) circumferential grooves are located substantially at a same distance relative to said equatorial plane (X-X).
8. Tyre (100) according to claim 1, characterized in that said third (3) and fourth (4) circumferential grooves are located at a distance from the equatorial plane (X-X) smaller than or equal to 12% of said effective width (M) and greater than or equal to 6% of said effective width (M).
9. Tyre (100) according to any one of the previous claims 1 to 8, characterized in that said first transverse grooves (10) comprise a first (10’), a second (10”), and a third (10’”) segment arranged consecutively to one another; said second segment (10”) having an extension greater than 50% of the total extension of said first transverse groove (10).
10. Tyre (100) according to any one of the previous claims 1 to 9, characterized in that said first segment (10’) extends from said first circumferential groove (1) and has an extension smaller than 30% of the total extension of said first transverse groove (10).
11. Tyre (100) according to any one of the previous claims 1 to 10, characterized in that said third segment (10’”) extends from said second segment (10”) up to merging into said third circumferential groove (3) and has an extension smaller than or equal to12. Tyre (100) according to any one of the previous claims 1 to 11, characterized in that said first circumferential rib (5) comprises fourth transverse grooves (13) having an extension smaller than said first transverse grooves (10).
13. Tyre (100) according to claim 12, characterized in that said fourth transverse grooves (13) have a maximum width smaller than or equal to 3 mm.
14. Tyre (100) according to claim 12 or 13, characterized in that said fourth transverse grooves (13), at least for a major portion of their extension, are inclined relative to a direction parallel to the equatorial plane (X-X) so as to form a third inclination angle (a’) smaller than or equal to 40°.
15. Tyre (100) according to any one of claims 12 to 14, characterized in that said fourth transverse grooves (13) are substantially parallel to said first transverse grooves (10) over at least 80% of their extension.
16. Tyre (100) according to any one of claims 12 to 15, characterized in that said fourth transverse grooves (13) are circumferentially alternated with said first transverse grooves (10), preferably in a one-to-one ratio.
17. Tyre (100) according to any one of the previous claims 1 to 16, characterized in that said second transverse grooves (11) extend form said third circumferential groove (3) to said fourth circumferential groove (4).
18. Tyre (100) according to any one of the previous claims 1 to 17, characterized in that said second inclination angle (P) is smaller than or equal to 75°.
19. Tyre (100) according to any one of the previous claims 1 to 18, characterized in that said second circumferential rib (6) comprises fifth transverse grooves (14) having an extension smaller than said second transverse grooves (11).
20. Tyre (100) according to claim 19, characterized in that said fifth transverse grooves (14) extend from said fourth circumferential groove (4) over at most 70% of the width of said second circumferential rib (6).
21. Tyre (100) according to claim 19 or 20, characterized in that said fifth transverse grooves (14) are inclined relative to a direction parallel to the equatorial plane (X-X) so as to form a fourth inclination angle (P’) smaller than or equal to 75°.
22. Tyre (100) according to any one of claims 19 to 21, characterized in that said fifthtransverse grooves (14) are substantially parallel to said second transverse grooves (11) over at least 80% of their extension.
23. Tyre (100) according to any one of claims 19 to 22, characterized in that said fifth transverse grooves (14) are circumferentially alternated with said second transverse grooves (11), preferably in a one-to-one ratio.
24. Tyre (100) according to any one of the previous claims 1 to 23, characterized in that said third circumferential rib (7) comprises only said third transverse grooves (12).
25. Tyre (100) according to any one of the previous claims 1 to 24, characterized in that said third transverse grooves (12) extend from said fourth circumferential groove (4) to said second circumferential groove (2).
26. Tyre (100) according to any one of the previous claims 1 to 25, characterized in that at least some of said third transverse grooves (12), at least in a portion of their extension, are arranged along the extension direction of said second transverse grooves (11) or along the extension direction of said fifth transverse grooves (14).
27. Tyre (100) according to any one of claims 1 to 26, characterized in that said third transverse grooves (12) comprise a first (12’) and a second (12”) segment arranged consecutively to each other; said first segment (12’) having an extension greater than 50% of the total extension of said third transverse groove (12).
28. Tyre (100) according to any one of the previous claims 1 to 27, characterized in that said first shoulder region (L2) and said second shoulder region (L3) respectively comprise a plurality of sixth and seventh transverse grooves (16, 17) having a first end substantially located at a respective edge of the tread band (20), having a maximum width larger than or equal to 3 mm and an extension equal to at least 50% of the width of the shoulder region where they are located.
Citation Information
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