Tyre for vehicle wheels

Abstract

The present disclosure relates to a tyre (1) for a vehicle wheel, the tyre comprising a tread band (2) extending between a first axial end (4a) and a second axial end. A plurality of first grooves (10) arranged contiguously along the first shoulder region (7), a plurality of second grooves (20) arranged contiguously along the second shoulder region (8), and a plurality of third grooves (30) are defined on the tread band. Each third groove extends from a respective first end (31) defined between the equatorial plane (X) and a first axial end (4a) of the tread band to a respective second end (32) defined between the equatorial plane (X) and a second axial end (4b) of the tread band. Furthermore, each third groove is inclined at an angle (A) of between 8 DEG and 30 DEG with respect to the circumferential direction defined on the tread band (2).

Description

TECHNICAL FIELD

[0001] The present application relates to a tyre for vehicle wheels, in particular to a tyre for vehicle wheels of high-performance motor vehicles. BACKGROUND

[0002] In order to obtain sufficient road grip even on wet road surfaces, the tread band of the tyre is provided with grooves and possibly sipes having various configurations and geometries which delimit portions of the tread band, called blocks, which are intended to come into contact with the ground.

[0003] The overall configuration of the tread band defined by the group of grooves, sipes and / or blocks represents the tread pattern of the tyre.

[0004] The main function of the grooves and sipes is to allow the expulsion of the water present between the surface of the tyre and the road during the mutual contact of the two surfaces, thus preventing the hydrostatic pressure due to the impact of the water on the tyre in motion from causing the tyre to lift even partially from the road and thus causing the vehicle to lose control (phenomenon known as "hydroplaning").

[0005] The grooves and sipes formed on the tread band can further affect the traction performance of the tyre and the directional and stability performance of the tyre during the different driving phases of the vehicle, such as, for example, during acceleration or braking or cornering.

[0006] The term "tread surface" means the radially outer surface portion of the tread band which is intended to come into contact with the road surface when causing the tyre to roll on the road surface.

[0007] The term "tread pattern" means the overall configuration of the tread band defined by the combination of grooves and blocks.

[0008] Depending on the configuration of the tread pattern, a preferred direction of rolling can be defined on the tyre.

[0009] In this case, the tyre is said to be of the "directional" type and it is configured to be mounted on the vehicle so that the tyre rotates in the preferred direction of rolling during the travel of the vehicle in the forward direction.

[0010] The tread pattern can also be asymmetric with respect to the equatorial plane of the tyre, having a differentiated configuration between an outer region of the tyre, intended to be directed towards the outside when the tyre is mounted on the vehicle, and an opposite inner region of the tyre, closer to the central plane of the vehicle. In this way, it is possible to configure each portion of the tread band in a more selective manner, possibly in relation to the different stresses and requirements which can affect the outer region and the inner region of the tread band respectively during travel on the road surface.

[0011] The tyre having a tread pattern of the type simply described above is said to be of the "asymmetric" type.

[0012] The term "tread footprint" means the portion of the tread band that is in instantaneous contact with the road surface during the rolling motion of the tire. In actual conditions, the tread footprint is a function of different parameters, including the inflation pressure of the tire, the load supported by the tire, the road and driving conditions, but reference values can be defined for these parameters.

[0013] The term "equatorial plane" of the tire means a plane perpendicular to the axis of rotation of the tire and which divides the tire into two substantially identical parts, except for the asymmetric parts of the tread pattern.

[0014] The term "radial plane" of the tire means any plane that includes the axis of rotation of the tire.

[0015] The term "axial direction" means the direction parallel to the axis of rotation of the tire.

[0016] The term "circumferential" direction means the direction generally directed in the direction of rotation of the tire.

[0017] The term "sipe" means a recess formed in the tread band portion, and the width of this recess is preferably greater than or equal to 1.5 mm, more preferably greater than or equal to 3 mm. Preferably, the depth of the sipe is greater than 3 mm. The sipe preferably develops in a main longitudinal direction. This main longitudinal direction can have a linear development that can be substantially rectilinear, or it can have a development with successive rectilinear portions having different orientations (broken line development), or it can have a curved development with a constant or variable radius of curvature, or it can have a mixed linear development with rectilinear portions and curved portions.

[0018] The term "width" of a sipe or of a portion thereof means the dimension parallel to the tread surface and perpendicular to the main longitudinal extent of the sipe or of the portion thereof.

[0019] Two sipes "intersect" when they open toward each other to make fluid communication.

[0020] It can thus be noted that two sipes are defined as "intersecting" when they cross each other and when one sipe terminates in the other.

[0021] In other words, a sipe "intersects" another sipe when it extends through the other sipe and when one end of the sipe opens into the other sipe.

[0022] The term "longitudinal extent" of a sipe means the length extent of the sipe measured on the tread surface in the development direction of the sipe, regardless of the positioning or orientation of the sipe on the tread surface.

[0023] The term "circumferential extent" of a groove or of a portion thereof refers to the length extent of the groove or of the portion thereof measured in the circumferential direction of the tyre. In other words, the circumferential extent of a groove or of a portion thereof represents the orthogonal projection extent of the groove in the circumferential direction of the tyre.

[0024] Similarly, the term "axial extent" of a groove or of a portion thereof refers to the length extent of the groove or of the portion thereof measured in the axial direction of the tyre.

[0025] A groove is said to be "transversal" when it extends in a direction inclined at an acute angle greater than at least 5° with respect to the circumferential direction.

[0026] The inclination of the direction of a groove (for example, the longitudinal direction) with respect to the circumferential direction identified on the tread band is defined by the acute angle formed by the direction and the circumferential direction. As an extreme example, a direction extending parallel to the tyre axis has an inclination of 90° with respect to the circumferential direction.

[0027] The inclination of a groove with respect to the circumferential direction identified on the tread band is defined by the acute angle formed by a straight line passing through the end portions of the groove and the circumferential direction.

[0028] The inclination of a portion of a groove with respect to the circumferential direction identified on the tread band is defined by the acute angle formed by a straight line passing through the end portions of the portion of the groove and the circumferential direction.

[0029] If the groove or the portion thereof is rectilinear, the inclination of the groove or of the portion thereof coincides with the inclination of the longitudinal direction of the groove or of the portion thereof.

[0030] Conversely, when the groove or the portion thereof does not have a rectilinear course, the inclination of the groove or of the portion thereof does not coincide (or can only partially coincide) with the inclination of the longitudinal direction thereof. If considered on a Cartesian plane positioned on the tread band (tangent to the tread band), in which the longitudinal axis of the coordinates is parallel to the circumferential direction and the transversal axis of the coordinates is parallel to the axis of the tyre, the groove maintains "the same sign of inclination" when each portion of the groove has an ascending course or each portion of the groove has a descending course.

[0031] In other words, the groove will maintain the same sign of inclination when the course of the groove can be represented on the Cartesian plane as defined above by an increasing monotonic function or by a decreasing monotonic function.

[0032] When two grooves are considered on a Cartesian plane positioned on the tread band (tangent to the tread band), in which the longitudinal axis of the coordinates is parallel to the circumferential direction and the transversal axis of the coordinates is parallel to the axis of the tyre, the two grooves have "the same sign of inclination" or are "inclined in the same way" if both the courses of the two grooves are ascending or descending.

[0033] Therefore, if two grooves are considered on the Cartesian plane as defined above, they have "opposite sign" slopes or are "inconsistently" inclined when one groove is rising in its run and the other groove is falling in its run. Two grooves or two groove portions are "axially aligned" or aligned along the axial direction of the tyre when their respective projections on the equatorial plane overlap each other over at least 80% of the longitudinal extent of the two grooves or two groove portions.

[0034] Two grooves or two groove portions are "substantially parallel" when they extend at the same inclination angle with respect to the circumferential direction or when the difference between their respective inclination angles with respect to the circumferential direction is at most 10°, preferably at most 5°.

[0035] Two grooves or two groove portions are "substantially perpendicular" when they are inclined at an angle of 90° with respect to each other, with a maximum tolerance of 10°, preferably a maximum tolerance of 5°.

[0036] A plurality of grooves is arranged "in succession" along the circumferential development of the tread band or of a portion thereof when each groove of the plurality is circumferentially spaced apart from a similar groove by a predetermined extent, which is not necessarily constant and can vary by up to 50% of the predetermined extent, preferably by up to 30% of the predetermined extent.

[0037] The term "void-to-rubber ratio" means the ratio between the total surface of the grooves and the sipes contained in the predetermined portion of the tread pattern of the tyre intended to rest on the ground (in the applicable cases, the entire tread pattern) and the total surface of the predetermined portion of the tread pattern (in the applicable cases, the entire tread pattern).

[0038] EP1930185, JP2020125085 and JP2016002886 disclose respective examples of tyres having a tread band on which at least one circumferential groove is defined having a spiral or partially spiral configuration.

[0039] The Applicant has initially observed that, when travelling on wet road surfaces, a relevant portion of the water present in the footprint area of the tyre is thrown into the air in the form of fine water spray and droplets, which significantly limits the visibility for the vehicles following.

[0040] The Applicant has further observed that this phenomenon is particularly enhanced in the case of high speed travel of the vehicle and of large size tyres, to the point of becoming one of the main safety problems in the case of races held on wet road conditions.

[0041] For example, the Applicant has verified that, in racing vehicles, the amount of water that can be expelled through the footprint area and therefore the amount of water that can be sprayed into the air by each individual tyre is of the order of tens of litres per second.

[0042] The Applicant has further verified that many racing events are particularly affected by the low visibility of the vehicle drivers in the event of travel on wet road surfaces, with consequent serious safety problems, which can lead to the adoption of measures to limit the race or even to suspend it.

[0043] On the other hand, the Applicant has observed that this phenomenon is a direct consequence of the draining behaviour implemented by the tread band, which has grooves of different shapes and sizes on its surface specifically for this purpose. As already mentioned above, in fact, in order to be able to obtain a proper road grip during travel of the vehicle on wet road surfaces and in particular to avoid aquaplaning phenomena, a sufficient ability to drain the water present in the footprint area is necessary.

[0044] The Applicant therefore believes that there is a need to provide a tyre whose tread pattern is configured to obtain the best performance level in terms of road grip on wet road surfaces, even in extreme stress conditions, such as in the case of use in motor vehicles with high performance levels and in racing events, configured so as to improve the visibility of the vehicle following behind.

[0045] To meet this requirement, the Applicant has observed that the majority of the water expelled by the vehicle wheel and thrown in the opposite direction to the direction of travel is mainly that portion of water expelled by the circumferential grooves formed on the tread band.

[0046] The Applicant has in particular verified that, as a result of the high draining capacity of the circumferential grooves, the presence of the circumferential grooves also causes the generation of a water spray that is generally longer and higher, thus limiting the visibility of the following vehicle even at relatively long distances.

[0047] Furthermore, in certain situations, such as high-speed travel, some of the water present in the circumferential grooves can rotate with the wheel for more than half a turn before being expelled by the tread band. In this case, the water is in fact thrown in the forward direction along the direction of travel of the vehicle, so as to splash on the road surface in front of the vehicle itself, with the clearly undesirable consequence of causing an increase in the amount of water present on the road surface involved in the rolling of the tyre.

[0048] The Applicant therefore believes, in evaluating these aspects, that in order to improve the visibility of the vehicle following behind without affecting the necessary draining capacity, the tread pattern of the tyre would have to be configured so as to not only limit the amount of water expelled by the grooves from the footprint area, but also to limit the direction of the expelled water that must be expelled by the grooves themselves.

[0049] Finally, the Applicant has found that, on a tread band of a tyre formed with grooves extending between two opposite shoulder regions axially opposite and inclined at a suitable angle with respect to the circumferential direction, the tyre allows the water present in the footprint region, especially the water present in the central region of the tread band, to be effectively discharged mainly towards one side of the tyre, thus avoiding that the long water spray is directly flung to the rear of the vehicle, also avoiding the possibility that some of the discharged water can be brought to the front of the vehicle itself. SUMMARY

[0050] In particular, in a first aspect of the present application, the present application relates to a tyre for vehicle wheels, comprising a tread band extending between a first axial end and a second axial end.

[0051] Preferably, a first shoulder region is defined on the tread band, delimited by the first axial end in an axially external position.

[0052] Preferably, a second shoulder region is defined on the tread band, delimited by the second axial end in an axially external position.

[0053] Preferably, a central region is defined on the tread band, interposed between the first shoulder region and the second shoulder region.

[0054] Preferably, the central region extends so as to span the equatorial plane of the tread band.

[0055] Preferably, a plurality of first grooves is defined on the tread band.

[0056] Preferably, the first grooves are arranged in succession along the circumferential development of the first shoulder region.

[0057] Preferably, each first groove extends transversely from the first axial end towards the central region.

[0058] Preferably, each first groove is located in a position spaced from the second axial end.

[0059] Preferably, a plurality of second grooves is defined on the tread band.

[0060] Preferably, the second grooves are arranged in succession along the circumferential development of the second shoulder region.

[0061] Preferably, each second groove extends transversely from the second axial end towards the central region.

[0062] Preferably, each second groove is located in a position spaced from the first axial end.

[0063] Preferably, a plurality of third grooves is defined on said tread band.

[0064] Preferably, each of said third grooves extends from a respective first end portion as far as a respective second end portion.

[0065] Preferably, said first end portion is defined between said equatorial plane and said first axial end portion.

[0066] Preferably, said second end portion is defined between said equatorial plane and said second axial end portion.

[0067] Preferably, each of said third grooves is inclined at an angle comprised between 8° and 30° with respect to the circumferential direction of said tread band.

[0068] Applicant believes that, thanks to these characteristics and in particular to the particular configuration of the third grooves, the tyre according to the present application will, when driving on wet road surfaces, including in high speed driving conditions, direct a relevant portion of the water expelled from the footprint area towards one side of the wheel, rather than directly in the opposite direction to the direction of travel of the vehicle.

[0069] In this way, the area of poor or zero visibility behind the vehicle is greatly reduced, thus improving the driving safety of the driver of the vehicle located behind the vehicle, in driving conditions on wet road surfaces, including at high speed. Applicant further believes that the provision of the first and second grooves allows to quickly expel water in the shoulder areas, while maintaining sufficient rigidity of the tread band in these areas, which allows to effectively counteract the tangential stresses with strong axial component generated during the phases of turning of the vehicle.

[0070] In the above aspects, the present application can have at least one of the additional features indicated below.

[0071] Preferably, each of said third grooves maintains the same sign of inclination of said first end portion with respect to the circumferential direction of the tread band and of said second end portion with respect to the circumferential direction of the tread band.

[0072] Preferably, in each of said third grooves, said first end portion is spaced apart from said second end portion by a predetermined circumferential extent which is not zero.

[0073] In some embodiments, each of said plurality of third grooves intersects at least one first groove, more preferably at least two first grooves, even more preferably at least three first grooves, and in a very preferred manner at least four first grooves.

[0074] In this manner, each third groove is in fluid communication with at least one first groove (or with at least two, three or four first grooves, respectively) to facilitate and accelerate the flow of water out of the central region of the tread band, up to the point where water is also discharged from the tire in the region of the first axial end of the tread band using one or more first grooves. These first grooves also pass through the first shoulder region for this purpose, opening at the first axial end.

[0075] In some embodiments, each third groove of the plurality of third grooves intersects at least one second groove, more preferably at least two second grooves, even more preferably at least three second grooves, and in a very preferred manner at least four second grooves.

[0076] In this manner, each third groove is in fluid communication with at least one second groove (or with at least two, three or four second grooves, respectively) to facilitate and accelerate the flow of water out of the central region of the tread band, up to the point where water is also discharged from the tire in the region of the second axial end of the tread band using one or more second grooves. These second grooves also pass through the second shoulder region for this purpose, opening at the second axial end.

[0077] In some embodiments, the first end of each third groove is spaced apart from the first axial end in a range comprised between 15% and 30% of the tread band width.

[0078] In some embodiments, the second end of each third groove is spaced apart from the second axial end in a range comprised between 15% and 30% of the tread band width.

[0079] In some embodiments, the third grooves of the plurality of grooves are substantially identical to each other.

[0080] In some embodiments, the third grooves of the plurality of grooves are substantially parallel to each other.

[0081] In some embodiments, the circumferential extent of each third groove of the plurality of grooves is less than the circumferential length of the tread band, preferably less than 70% of the circumferential length of the tread band.

[0082] Preferably, the circumferential extent of each third groove of the plurality of grooves is greater than 20% of the circumferential length of the tread band, and more preferably, the circumferential extent of each third groove is comprised between 30% and 50% of the circumferential length of the tread band.

[0083] In some embodiments, in each third groove of the plurality of grooves, the first end is spaced apart from the second end by a circumferential extent greater than 25% of the circumferential length of the tread band.

[0084] In some embodiments, the plurality of third grooves is formed by a number of third grooves greater than 3, preferably greater than 5, more preferably greater than 9.

[0085] In some embodiments, the plurality of third grooves is formed by a number of third grooves less than 20, more preferably less than 15.

[0086] In some embodiments, each radial plane intersects at the tread band at least three of the third grooves.

[0087] In some embodiments, each radial plane intersects at the tread band no more than five of the third grooves.

[0088] In some embodiments, each of the plurality of third grooves has a width comprised between 5 mm and 15 mm, preferably between 8 mm and 12 mm.

[0089] In some embodiments, each of the plurality of third grooves has a depth greater than 3 mm, preferably less than 8 mm. Preferably, each of the plurality of third grooves has a depth comprised between 3 mm and 6 mm.

[0090] In some embodiments, each third groove comprises a first end portion at the first end, a second end portion at the second end, and a central portion interposed between the first end portion and the second end portion. Preferably, the central portion is substantially rectilinear.

[0091] Preferably, the central portions of the third grooves are substantially parallel to each other.

[0092] Preferably, the central portions constitute at least 70%, more preferably at least 80%, even more preferably at least 90% of the longitudinal extent of the third grooves.

[0093] In some embodiments, the central portion of each of the third grooves is inclined with respect to the circumferential direction by an angle comprised between 8° and 30°, more preferably between 10° and 20°, even more preferably between 10° and 15°.

[0094] In some embodiments, the first end portion extends along a substantially circumferential direction.

[0095] In some embodiments, the first end portion constitutes no more than 10%, more preferably no more than 5% of the longitudinal extent of the third grooves.

[0096] In some embodiments, the second end portion extends along a substantially circumferential direction.

[0097] In some embodiments, the second end portion constitutes no more than 10%, more preferably no more than 5%, of the longitudinal extent of the third groove.

[0098] In some embodiments, each first groove intersects at least one of the third grooves.

[0099] In some embodiments, each second groove intersects at least one of the third grooves.

[0100] In some embodiments, each first groove is inclined at an angle comprised between 70° and 85° with respect to the circumferential direction.

[0101] In some embodiments, each first groove is inclined with respect to the circumferential direction in a manner consistent with the inclination of the third groove with respect to the circumferential direction.

[0102] In some embodiments, each second groove is inclined at an angle comprised between 70° and 85° with respect to the circumferential direction.

[0103] In some embodiments, each second groove is inclined with respect to the circumferential direction in a manner consistent with the inclination of the third groove with respect to the circumferential direction.

[0104] In some embodiments, each second groove is inclined with respect to the circumferential direction in a manner inconsistent with the inclination of the first groove with respect to the circumferential direction.

[0105] In some embodiments, each second groove is substantially perpendicular to the third groove.

[0106] In some embodiments, the central portion of each third groove comprises a first side wall and a second side wall, the first side wall joining the third groove to the tread surface at a side proximal to the first axial end, the second side wall joining the third groove to the tread surface at a side proximal to the second axial end. Preferably, the first side wall is inclined with respect to the radial direction at an angle greater than the angle at which the second side wall is inclined with respect to the radial direction.

[0107] Preferably, the first side wall is inclined with respect to the radial direction at an angle comprised between 30° and 40°.

[0108] Preferably, the second side wall is inclined with respect to the radial direction at an angle comprised between 10° and 20°.

[0109] In some embodiments, the plurality of first grooves comprises a plurality of first short grooves.

[0110] In some embodiments, the plurality of first grooves comprises a plurality of first long grooves.

[0111] Preferably, the longitudinal extent of the first long grooves is greater than the longitudinal extent of the first short grooves.

[0112] Preferably, each first short groove intersects a single third groove.

[0113] Preferably, each first short groove terminates in the single third groove.

[0114] Preferably, each first long groove intersects at least two third grooves, more preferably three third grooves.

[0115] Preferably, each first long groove terminates in one of the third grooves.

[0116] Preferably, each first long groove extends at most as far as the equatorial plane, more preferably substantially as far as the equatorial plane.

[0117] In some embodiments, each first long groove is interposed between two first short grooves.

[0118] In some embodiments, the plurality of first grooves comprises a plurality of first intermediate grooves.

[0119] Preferably, the longitudinal extent of the first intermediate grooves is greater than the longitudinal extent of the first short grooves.

[0120] Preferably, the longitudinal extent of the first intermediate grooves is less than the longitudinal extent of the first long grooves.

[0121] Preferably, each first intermediate groove intersects at least two third grooves, more preferably two third grooves.

[0122] Preferably, each first intermediate groove terminates in one of the third grooves.

[0123] In some embodiments, each first intermediate groove is interposed between two first short grooves.

[0124] In some embodiments, each first short groove is interposed between a first long groove and a first intermediate groove.

[0125] In some embodiments, the plurality of second grooves comprises a plurality of second short grooves.

[0126] In some embodiments, the plurality of second grooves comprises a plurality of second long grooves.

[0127] Preferably, the longitudinal extent of the second long grooves is greater than the longitudinal extent of the second short grooves.

[0128] Preferably, each second short groove intersects a single third groove.

[0129] Preferably, each second short groove terminates in one of the third grooves.

[0130] Preferably, each second long groove intersects at least two third grooves, more preferably three third grooves.

[0131] Preferably, each second long groove terminates in one of the third grooves.

[0132] Preferably, each second long groove extends at most as far as the equatorial plane, more preferably substantially as far as the equatorial plane.

[0133] In some embodiments, each second long groove is interposed between two second short grooves.

[0134] In some embodiments, the plurality of second grooves comprises a plurality of second intermediate grooves.

[0135] Preferably, the longitudinal extent of the second intermediate grooves is greater than the longitudinal extent of the second short grooves.

[0136] Preferably, the longitudinal extent of the second intermediate grooves is less than the longitudinal extent of the second long grooves.

[0137] Preferably, each second intermediate groove intersects at least two third grooves, more preferably three third grooves.

[0138] Preferably, each second intermediate groove terminates in one of the third grooves.

[0139] In some embodiments, each second intermediate groove is interposed between two second short grooves.

[0140] In some embodiments, each second short groove is interposed between a second long groove and a second intermediate groove.

[0141] In some embodiments, each first short groove is axially aligned with a corresponding second long groove or second intermediate groove.

[0142] In some embodiments, each first long groove is axially aligned with a corresponding second short groove.

[0143] In some embodiments, each first intermediate groove is axially aligned with a corresponding second short groove.

[0144] In some embodiments, the equatorial plane divides the tread band into an outer region of the tread band and an inner region of the tread band, the outer region being located proximal to the exterior of the vehicle when the tyre is mounted on the vehicle, and the inner region being axially opposite the outer region.

[0145] Preferably, said first shoulder region is defined in an outer region of said tread band.

[0146] In some embodiments, when said tyre is mounted on a vehicle and the tyre is rotated during travel of said vehicle in a preferred rolling direction, said second end portion enters a footprint region before said first end portion.

[0147] In some embodiments, said tread band is devoid of circumferential grooves.

[0148] In some embodiments, said tread band is devoid of any groove extending between said first shoulder region and said second shoulder region and inclined in a manner not coinciding with said third groove.

[0149] In some embodiments, said tread band is devoid of any groove other than said first groove, said second groove and said third groove.

[0150] In some embodiments, said tread band has a void-to-rubber ratio comprised between 0.30 and 0.35. BRIEF DESCRIPTION OF DRAWINGS

[0151] The features and advantages of the present application can be better understood with reference to the detailed description of preferred exemplary embodiments thereof in conjunction with the attached drawings, in which:

[0152] - Figure 1 is a perspective view of a tyre for vehicle wheels according to the present application,

[0153] - Figure 2 is Figure 1 a front view of the tyre of

[0154] - Figure 3 is Figure 1 a schematic view, drawn to an enlarged scale, of a significant portion of the tread band of the tyre of

[0155] - Figure 4 is Figure 1 a schematic cross-sectional view in a transversal section of the tread band of the tyre of

[0156] - Figure 5 is a schematic view of a tyre according to the prior art. DETAILED DESCRIPTION

[0157] With reference to the attached Figures 1 to 4 , indicated as a whole with 1 is a tyre for vehicle wheels realized according to the present application.

[0158] The tyre 1 comprises a tread band 2 and a tyre structure, which is itself conventional and not shown in the drawings, on which a tread surface 3 is defined, which is arranged in a radially external position with respect to the tread band 2 and is intended to come into contact with the road surface.

[0159] The tyre 1 has a conventional substantially toroidal form, which develops around an axis of rotation, so as to define on the tread surface 3 an axial direction Y parallel to the axis of rotation and to be crossed by an equatorial plane X perpendicular to the axis of rotation, and to define on the tread surface 3 a circumferential direction parallel to said equatorial plane.

[0160] The tyre 1 is preferably arranged to be mounted on a high-performance car, for example a racing car, and can have a nominal cross-sectional width of approximately 305 mm, with a rim diameter of 18 inches.

[0161] The tread band 2 extends axially between a first axial end 4a and a second axial end 4b, so as to define a width L of approximately 300 mm, which is intended to come into contact with the road surface in standard conditions of use.

[0162] The equatorial plane X divides the tread band 2 into an outer region 5 of the tread band, which is intended to be located proximal to the outside of the vehicle when the tyre is mounted on the vehicle, and an inner region 6 of the tread band, which is axially opposite the outer region 5.

[0163] A first shoulder region 7 of the tread band is also defined on the tread band 2, which is delimited in an axially external position by the first axial end 4a, a second shoulder region 8 of the tread band is defined on the tread band 2, which is delimited in an axially external position by the second axial end 4b, and a central region 9 is interposed between the first shoulder region 7 and the second shoulder region 8.

[0164] The first shoulder region 7 and the second shoulder region 8 extend axially over approximately 20% to 25% of the width L of the tread band in a substantially symmetrical manner with respect to the central region 9, which also extends symmetrically so as to span the equatorial plane X.

[0165] The first shoulder region 7 is defined in the outer region 5 of the tread band 2, while the second shoulder region 8 is defined in the inner region 6 of the tread band 2.

[0166] On the tread band 2, a plurality of first grooves 10 is defined, which are arranged in succession along the circumferential development of the first shoulder region 7, a plurality of second grooves 20 is defined, which are arranged in succession along the circumferential development of the second shoulder region 8, and a plurality of third grooves 30 is defined, which are arranged in succession along the circumferential development of the central region 9.

[0167] No other grooves are present on the tread band 2, so that the tread pattern of the tyre is defined exclusively by the first grooves 10, the second grooves 20 and the third grooves 30.

[0168] Each first groove 10 extends transversely from the first axial end 4a in a substantially rectilinear longitudinal direction inclined at an angle C of about 75° with respect to the circumferential direction, towards the equatorial plane X. Similarly, each second groove 20 extends transversely from the second axial end 4b in a substantially rectilinear longitudinal direction inclined at an angle D of about 75° with respect to the circumferential direction, having the sign of the inclination opposite to that of the first grooves 10, towards the equatorial plane X.

[0169] Each first groove 10 and each second groove 20 has a depth P comprised between 3 mm and 6 mm, a width comprised between 10 mm and 20 mm, and tapers slightly from the axial end towards the equatorial plane X.

[0170] The third grooves 30 are substantially identical and parallel to each other, each of said third grooves extending from a respective first end 31 defined in the outer region 5 to a second end 32 defined in the inner region 6.

[0171] Each third groove 30 is inclined with respect to the circumferential direction at an angle A comprised between about 12° and 13°, defined as the acute angle between the circumferential direction and the direction of a straight line passing through the first end 31 and the second end 32 of the third groove 30, having the sign opposite to that of the inclination of the second grooves 20 and the same as that of the inclination of the first grooves 10.

[0172] In particular, on each third groove 30 a first end portion 33, comprising the first end 31, a second end portion 34, comprising the second end 32, and a central portion 35 interposed between the first end portion 33 and the second end portion 34 are defined.

[0173] The first end portion 33 and the second end portion 34 are substantially parallel to the circumferential direction and extend in opposite directions to each other, delimiting the central region 9 from the first shoulder region 7 and the second shoulder region 8.

[0174] The longitudinal extent of the first end portion 33 and of the second end portion 34 does not exceed 5% of the total longitudinal extent of the third groove 30.

[0175] The central portion 35 forms the main part of the longitudinal extent of the third groove 30 and extends along a substantially rectilinear longitudinal direction inclined at an angle B comprised between about 13° and 14° with respect to the circumferential direction.

[0176] The width of the central portion 35 is substantially constant and is about 10 mm, while the width of the first end portion 33 and of the second end portion 34 narrows towards the first end 31 and the second end 32, respectively.

[0177] The depth of the third groove 30 is, for example, between 3 mm and 6 mm and remains constant in the central portion 35, while in the first end portion 33 and the second end portion 34, the depth gradually decreases until it substantially disappears at the first end 31 and the second end 32, respectively.

[0178] Preferably, the depth P of the third groove 30 is substantially the same as the depth of the first groove 10 and the depth of the second groove 20.

[0179] The circumferential range of each third groove 30 is approximately 40% of the circumferential length of the tread band 2.

[0180] The total number of third grooves 30 provided on the tread belt 2 is 11, and the third grooves 30 are arranged in such a way that each radial plane of the tire 1 intersects with at least four third grooves 30, especially with five third grooves 30 in the region of the first end portion 33 or the second end portion 34, and with four third grooves 30 in the region of the central portion 35.

[0181] Furthermore, each third groove 30 is preferably shaped asymmetrically to counteract lateral forces at bends. More specifically, for example, it can be... Figure 4 As can be seen more clearly, the normal section of each central portion 35 along the longitudinal axis has an inclination relative to the radial direction defined on the tread band and passing through the central portion 35, with the inclination at the outer side being greater than that at the inner side.

[0182] Specifically, the central portion 35 of each third groove 30 includes a first sidewall 36 and a second sidewall 37, the first sidewall connecting the third groove 30 to the tread surface 3 located on the side near the first axial end 4a, and the second sidewall connecting the third groove to the tread surface 3 located on the side near the second axial end 4b.

[0183] The first wall 36 is inclined at an angle E between 30° and 40° (e.g., 35°) relative to the radial direction, while the second wall 37 is inclined at an angle G between 10° and 20° (e.g., 15°) relative to the radial direction.

[0184] In this way, when the vehicle travels around the curved section, the large tilt angle on the outer side helps the block at that location to withstand the increased lateral force caused by the load transfer due to travel along the curve.

[0185] The first groove 10 is formed by a first short groove 11, a first intermediate groove 12 and a first long groove 13. Preferably, the first short groove, the first intermediate groove and the first long groove are arranged alternately along the circumference of the tread belt in a pattern of successive repetition of the first short groove, the first intermediate groove, the first short groove and the first long groove.

[0186] Each first short groove 11 intersects with a single third groove 30, and in particular intersects with and terminates within the third groove 30 closest to the first axial end 4a.

[0187] Each of the first intermediate grooves 12, which has a longitudinal range greater than that of the first short groove, intersects with the two third grooves 30 and terminates in the third groove 30 furthest from the first axial end 4a and passes through the third groove 30 closest to the first axial end 4a.

[0188] Each first long groove 13 with a longitudinal range greater than the first intermediate groove 12 intersects with three third grooves 30 and terminates in the third groove 30 furthest from the first axial end 4a and passes through the third groove 30 closest to the first axial end 4a.

[0189] Specifically, each first long groove 13 extends through the outer region 5 of the tread band 2 as far as the equatorial plane X.

[0190] The second groove 20 is formed in a similar manner within the inner region 6 of the tread band 2.

[0191] Therefore, the second groove 20 is formed by the second short groove 21, the second intermediate groove 22 and the second long groove 23. Preferably, the second short groove, the second intermediate groove and the second long groove are arranged alternately along the circumferential development of the tread belt in a pattern of successive repetition of the second short groove, the second intermediate groove, the second short groove and the second long groove.

[0192] Each second short groove 21 intersects with a single third groove 30, and in particular intersects with the third groove 30 closest to the second axial end 4b and terminates within the third groove.

[0193] Each of the second intermediate grooves 22, which has a longitudinal range greater than that of the second short groove 21, intersects with the three third grooves 30 and terminates in the third groove 30 furthest from the second axial end 4b and passes through the third groove 30 closest to the second axial end 4b.

[0194] Each of the second long grooves 23, which has a longitudinal range greater than the second intermediate groove 22, intersects with the three third grooves 30 and terminates in the third groove 30 furthest from the second axial end 4b and passes through the third groove 30 closest to the second axial end 4b.

[0195] Specifically, each of the second longest grooves 23 extends through the inner region 6 of the tread band 2 as far as the equatorial plane X.

[0196] The first groove 10 and the second groove 20 are arranged along the outer region 5 and the inner region 6 of the tread belt 2, respectively, such that each first short groove 11 is axially aligned with the corresponding second long groove 23 or second intermediate groove 22, and similarly, each second short groove 21 is axially aligned with the corresponding first long groove 13 or first intermediate groove 12.

[0197] The tread pattern of the tire 1 defined by the above-mentioned groove configuration defines a void-to-rubber ratio of approximately 0.33 on the tread belt.

[0198] The tread pattern features shown above make tire 1 a directional asymmetric tire, so as to define both the preferred rolling direction (marked as F in the figure, which is used when the vehicle is moving forward normally) and a specific assembly position on the vehicle (that is, on the right or left side).

[0199] Specifically, the tires are mounted on the vehicle in such a manner that when they rotate in the preferred rolling direction, the second end 32 of each third groove 30 enters the tire imprint area before the corresponding first end 31.

[0200] In this way, most of the water discharged from the central region 9 of the tread belt 2 through the third groove 30 is transported toward the first axial end 4a of the tire 1.

[0201] In this way, any water spray generated while driving on a wet road surface is directed laterally toward the outside of the vehicle relative to the direction of travel, rather than toward the rear of the vehicle, in order to improve the visibility of other vehicles following behind the vehicle equipped with tire 1.

[0202] Furthermore, due to the characteristics described in detail above and shown in the accompanying drawings, tire 1 also has optimal longitudinal stiffness and axial stiffness characteristics, which allows for a high level of road grip, traction, and maneuverability on both wet and dry surfaces.

[0203] Example

[0204] The characteristics and performance level of the aforementioned tire 1 have been calculated and compared with... Figure 5 The diagram is schematic and compared with tire 100, which is still manufactured by the applicant according to the prior art.

[0205] Tire 100 has the same dimensions as tire 1 and is made of the same elastomer compound as tire 1, and is currently used in racing cars under medium wet road conditions (so-called "intermediate" tires).

[0206] The tread pattern of tire 100 includes only blind grooves, which extend from the central region of the tread belt toward the opposite axial ends of the tread belt.

[0207] The comparison has been conducted using an appropriate mathematical model prepared by the applicant, which allows for the calculation of the most relevant parameters in the definition of the behavior of the two tires on dry and wet surfaces.

[0208] Specifically, the following parameters have been calculated for both types of tires:

[0209] -Longitudinal stiffness, that is, the resistance of the tread belt to tangential stresses that are parallel to the circumferential direction, is calculated at the position where the tread belts are aligned axially.

[0210] - Lateral stiffness, that is, the resistance of the tread belt to tangential stresses parallel to the tire's axis of rotation, is calculated at the axial alignment of the tread belt joints.

[0211] - The ratio between longitudinal stiffness and lateral stiffness, which is also calculated at the position where the tread belts are aligned axially.

[0212] The calculations performed demonstrate how the stiffness characteristics of the tire of the present invention allow for a sufficient level of performance in terms of road grip.

[0213] In particular, the model shows that in the tire of the present invention, the ratio of longitudinal stiffness to lateral stiffness remains substantially constant along the cross section of the tread belt, thereby exhibiting optimal uniformity in stiffness at different portions of the tread belt, which generally indicates favorable balance behavior on the road.

[0214] The applicant also simulated the behavior of the two types of tires under hydroplaning conditions.

[0215] Specifically, for each tire, the force released by the tire on the ground in the tire track area when traveling at preset speeds of 70 km / h and 80 km / h and carrying a 600 kg load with 3 mm of water on the road surface has been calculated. This force was then set to be correlated with the force released by the corresponding tire on the ground under dry conditions, thereby obtaining the percentage of remaining force for each tire.

[0216] Calculation and simulation results have shown that tire 1, implemented according to the present invention, behaves far better than tire 100 on wet roads.

[0217] In fact, at lower speeds (70 km / h), the tire of the present invention shows a residual force percentage that is about twice that of the comparative tire, while at higher speeds (80 km / h), the residual force percentage of the tire of the present invention is even about ten times that of the comparative tire.

[0218] Therefore, the simulation demonstrates how the tire of the present invention allows its respective road grip characteristics to be maintained on wet surfaces in a more efficient manner than that of comparative tires.

Claims

1. A tire (1) for a vehicle wheel, said tire comprising a tread band (2) extending between a first axial end (4a) and a second axial end (4b), wherein: - First shoulder region (7), the first shoulder region is defined by the first axial end (4a) in an axially external position; - Second shoulder region (8), the second shoulder region is defined by the second axial end (4b) in an axially external position; - Central region (9), which is inserted between the first shoulder region (7) and the second shoulder region (8) and extends to cross the equatorial plane (X) of the tread band (2). - Multiple first grooves (10) are arranged in succession along the circumferential development of the first shoulder region (7), and each first groove (10) extends laterally from the first axial end (4a) toward the central region (9) at a position spaced apart from the second axial end (4b). - Multiple second grooves (20) are arranged in succession along the circumferential development of the second shoulder region (8), and each second groove (20) extends laterally from the second axial end (4b) toward the central region (9) at a position spaced apart from the first axial end (4a). - Multiple third grooves (30), each of which is: i. Extending from the respective first end (31) defined between the equatorial plane (X) and the first axial end (4a) to the respective second end (32) defined between the equatorial plane (X) and the second axial end (4b), and ii. Inclined at an angle (A) between 8° and 30° relative to the circumferential direction of the tread band (2).

2. The tire according to claim 1, wherein, Each of the plurality of third grooves (30) intersects with at least one first groove (10).

3. The tire according to claim 1 or 2, wherein, Each of the plurality of trenches, the third trench (30), intersects with at least one of the second trenches (20).

4. The tire according to any one of the preceding claims, wherein, The circumferential extent of each of the third grooves (30) is smaller than the circumferential length of the tread strip (2).

5. The tire according to any one of the preceding claims, wherein, The circumferential extent of each of the third grooves (30) is greater than 20% of the circumferential length of the tread strip (2).

6. The tire according to any one of the preceding claims, wherein, In each of the third grooves, the circumferential extent of the distance between the first end (31) and the second end (32) is greater than 25% of the circumferential length of the tread strip (2).

7. The tire according to any one of the preceding claims, wherein, Each radial plane of the tire (1) intersects at least three third grooves in the third groove (30) at the tread strip (2).

8. The tire according to any one of the preceding claims, wherein, Each radial plane of the tire (1) intersects with no more than five third grooves (30) at the tread strip (2).

9. The tire according to any one of the preceding claims, wherein, Each third groove (30) includes a first end portion (33) located at the first end (31), a second end portion (34) located at the second end (32), and a central portion (35) inserted between the first end portion (33) and the second end portion (34), wherein the central portion (35) is substantially straight and constitutes at least 70% of the longitudinal extent of the third groove (30).

10. The tire according to claim 9, wherein, The central portion (35) of each of the third grooves (30) is inclined at an angle (B) between 8° and 30° relative to the circumferential direction.

11. The tire according to claim 9 or 10, wherein, The central portion (35) of each third groove (30) includes a first sidewall (36) and a second sidewall (37), the first sidewall connecting the third groove (30) to the tread surface (3) located on one side near the first axial end (4a), and the second sidewall connecting the third groove (30) to the tread surface (3) located on one side near the second axial end (4b), the first sidewall (36) having a greater tilt angle relative to the radial direction than the second sidewall (37) having a greater tilt angle relative to the radial direction.

12. The tire according to any one of the preceding claims, wherein, Each of the first grooves (10) intersects with at least one of the third grooves (30).

13. The tire according to any one of the preceding claims, wherein, Each second groove (20) intersects with at least one of the third grooves (30).

14. The tire according to any one of the preceding claims, wherein, Each first groove (10) is inclined relative to the circumferential direction in a manner consistent with that of the third groove (30) relative to the circumferential direction.

15. The tire according to any one of the preceding claims, wherein, Each second groove (20) is inclined relative to the circumferential direction in a manner inconsistent with that of the third groove (30) and / or the first groove (10) relative to the circumferential direction.

16. The tire according to any one of the preceding claims, wherein, The plurality of first grooves (10) include a plurality of first short grooves (11) and a plurality of first long grooves (13), wherein the longitudinal range of the first long grooves (13) is greater than the longitudinal range of the first short grooves (11).

17. The tire according to claim 16, wherein, Each first short groove (11) intersects with a single third groove (30).

18. The tire according to claim 16 or 17, wherein, Each first long groove (13) intersects with at least two third grooves (30).

19. The tire according to any one of claims 16 to 18, wherein, Each of the first longest grooves (13) extends substantially to the equatorial plane (X).

20. The tire according to any one of claims 16 to 19, wherein, Each first long groove (13) is inserted between two first short grooves (11).

21. The tire according to any one of the preceding claims, wherein, The plurality of second trenches (20) include a plurality of second short trenches (21) and a plurality of second long trenches (23), wherein the longitudinal range of the second long trenches (23) is greater than the longitudinal range of the second short trenches (21).

22. The tire according to claim 21, wherein, Each second short groove (21) intersects with a single third groove (30).

23. The tire according to claim 21 or 22, wherein, Each second long groove (23) intersects with at least two third grooves (30).

24. The tire according to any one of claims 21 to 23, wherein, Each of the second longest grooves (23) extends substantially to the equatorial plane (X).

25. The tire according to any one of the preceding claims, wherein, The equatorial plane (X) divides the tread band (2) into an outer region (5) and an inner region (6) of the tread band. When the tire is mounted on the vehicle, the outer region is located near the outside of the vehicle, and the inner region is axially opposite to the outer region (5). The first shoulder region (7) is defined in the outer region (5) of the tread band.

26. The tire according to claim 25, wherein, When the tire (1) is mounted on the vehicle and causes the tire to rotate in the preferred rolling direction (F) during the vehicle's operation, the second end (32) enters the tire imprint area before the first end (31).

27. The tire according to any one of the preceding claims, wherein, Each of the third grooves (30) maintains the same sign for the inclination of the first end (31) relative to the circumferential direction of the tread strip (2) as the inclination of the second end (32) relative to the circumferential direction of the tread strip.

Images