High performance tire

Abstract

A tyre (1) for vehicle wheels, in particular high or ultra-high performance tyres for vehicle wheels also suitable for use on circuits, is described. The tread band (8) of the tyre has a central region (L1) having a limited extension and separated from two large shoulder regions, respectively an outer shoulder region (L2) and an inner shoulder region (L3). At least the outer shoulder region (L2) and the central region (L1) have a set of transverse grooves limited in type, number, size and extension. There are also annular portions (S1, S2, M) in the tread band (8) substantially free of grooves, so that the void rubber ratio is zero.

Description

Technical Field

[0001] This invention relates to a car tire, and more particularly to a high-performance or ultra-high-performance car tire designed for use both on roads and racetracks. Background Technology

[0002] The following documents disclose some examples of high-performance or ultra-high-performance car tires: WO2009004408, WO2015008137, WO02078982, WO2019111089. Summary of the Invention

[0003] High-performance and ultra-high-performance car wheels and tires (also designed for use on the track) need to provide performance, steering precision, and excellent ground grip so that high torque can be effectively transferred to the ground even at the high operating temperatures associated with track use.

[0004] Better results in terms of performance and grip can be achieved by using "smooth" tires (e.g., tires used in racing cars) and / or tires characterized by a very low, essentially zero, void-to-rubber ratio.

[0005] However, while these tires perform excellently on the track, their safety parameters are reduced in wet conditions, making them unsuitable for normal road use. Under certain weather conditions, precipitation wets the road surface, significantly reducing tire grip and compromising road handling, adequate traction, and effective braking.

[0006] The applicant has observed that attempts are typically made to increase the number and / or size of grooves in both the circumferential and lateral directions in order to affect drainage in the tire contact area (tire footprint area) when driving on wet surfaces.

[0007] The presence of wide and deep grooves increases the void-to-rubber ratio of the tread band, thus positively impacting the tire's drainage and grip characteristics when driving on wet surfaces.

[0008] However, the presence of wide and deep grooves in the circumferential and / or lateral directions reduces the stiffness of the tread belt, which can lead to a risk of performance degradation at high speeds on dry surfaces and generate noise.

[0009] Given the above, it is clear that high-performance or ultra-high-performance car tires designed for use both on the road and on the track—that is, tires suitable for transmitting high torque to the ground and / or achieving high speeds—must meet several conflicting requirements in order to provide good performance under a variety of different road and weather conditions.

[0010] The applicant therefore faces the problem of supplying automobile tires, particularly high-performance or ultra-high-performance automobile tires designed for use both on and off the road, which ensure high performance levels, braking and traction, without compromising drainage and safety features on wet surfaces.

[0011] The applicant has focused its efforts on achieving this improvement by producing tires with a tread band that is formed having a central region of finite extension separated from two wide shoulder regions. The shoulder regions and the central region have a series of lateral grooves. The tread band also includes an annular portion that is substantially without grooves: the applicant has found that this annular portion allows for substantially uniform tire stiffness in both the circumferential and lateral directions, which is beneficial for cornering traction / braking performance and road handling.

[0012] In a first aspect, the present invention relates to a car tire, the car tire having:

[0013] The tread belt includes a central region extending across the equatorial plane of the tire, an outer shoulder region positioned toward the outer side of the tire, and an inner shoulder region positioned toward the inner side of the tire.

[0014] The first circumferential groove axially defines the outer shoulder area relative to the central area of ​​the tread band, and the second circumferential groove axially defines the inner shoulder area relative to the central area.

[0015] The central region has a width that is less than or equal to 35% of the effective width of the tread strip;

[0016] The outer shoulder area and the inner shoulder area have a width greater than or equal to 30% of the effective width of the tread band;

[0017] The outer tire shoulder area is wider than the inner tire shoulder area;

[0018] The outer and inner shoulder areas include a plurality of first lateral grooves, the plurality of first lateral grooves having a first end located substantially at the corresponding edge of the tread band, having a maximum width of 4 mm or more, and having an extension length equal to at least 50% of the width of the shoulder area where the first lateral groove is located.

[0019] The central region includes a first circumferential rib and a second circumferential rib separated from each other by a third circumferential groove, the first circumferential rib and the second circumferential rib including a plurality of second transverse grooves;

[0020] in:

[0021] The outer shoulder region includes a shoulder annular portion located adjacent to the first circumferential groove, the shoulder annular portion having a void-to-rubber ratio that is substantially equal to zero.

[0022] The first circumferential rib includes a first annular portion positioned adjacent to the first circumferential groove, the first annular portion having a void-to-rubber ratio that is substantially equal to zero.

[0023] The second circumferential rib includes a second annular portion having a void-to-rubber ratio that is substantially equal to zero.

[0024] The applicant has discovered that, due to these features, the tires of the present invention achieve high performance levels even on the racetrack, while still maintaining excellent handling and hydroplaning characteristics on wet surfaces. Not wishing to be bound by any particular theory, the applicant believes that by having the lateral grooves as described above in the ribs in the central region and at least in the outer shoulder region, and by having annular portions without recesses and / or grooves in adjacent regions, the tread band stiffness distribution in both the circumferential and lateral directions is optimized to achieve high performance levels in handling, traction, and braking, without compromising drainage characteristics and safety on wet surfaces and limiting noise.

[0025] For the purposes of this invention, the following definitions apply:

[0026] "Tread pattern" refers to the representation of all points (including recesses) in the tread band in a plane perpendicular to the equatorial plane of the tire and tangent to the maximum diameter of the tire.

[0027] Measurements of angles and / or linear quantities (distance, width, length, etc.) and / or surface area are intended to reference the tread pattern as defined above.

[0028] Furthermore, considering the angular arrangement of the grooves formed in the tread band relative to the equatorial plane of the tire, for each point of the groove, this angular arrangement should be understood as a reference acute angle (i.e., an absolute value between 0° and 90°), defined by rotating from the equatorial plane to a direction tangent to the groove passing through that point.

[0029] The term "equatorial plane" in tire terminology refers to the plane perpendicular to the tire's axis of rotation and that divides the tire into two substantially equal parts.

[0030] The “circumferential” direction refers to the direction that is basically in line with the direction of rotation of the tire, or the direction that is slightly inclined (e.g., up to about 20°) relative to the direction of rotation of the tire.

[0031] The "axial" direction refers to a direction that is generally parallel to the tire's axis of rotation, or slightly inclined (e.g., up to about 20°) relative to the tire's axis of rotation. Typically, the axial direction is generally perpendicular to the circumferential direction.

[0032] The term “effective width” refers to the width of the outermost radial portion of the tread strip intended to contact the ground (from one edge to the other).

[0033] "Void-to-Rubber Ratio" refers to the ratio between the total surface area of ​​the grooves in a given annular portion (which may be the entire tread belt) of the tire and the total surface area of ​​that given annular portion (which may be the entire tread belt).

[0034] "A void-to-rubber ratio that is substantially zero" refers to the void-to-rubber ratio of the tread band portion that has substantially no significant effect on drainage and / or the hardness of the tread band portion, such as a void-to-rubber ratio less than or equal to 0.005.

[0035] The invention may include one or more of the features set forth below in one or more preferred aspects thereof.

[0036] Preferably, the second annular portion located on the second circumferential rib is arranged adjacent to the third circumferential groove.

[0037] Preferably, the second transverse grooves of the first transverse rib and the second transverse rib may have an extension length equal to at least 30% of the width of the circumferential rib to which they are located.

[0038] Advantageously, the second transverse groove of the first circumferential rib is inclined in the opposite direction to the second transverse groove of the second circumferential rib.

[0039] Conveniently, the second transverse grooves of the first and second circumferential ribs can be tilted relative to the direction parallel to the equatorial plane to form an angle greater than 60°.

[0040] Preferably, the first circumferential rib has a void-to-rubber ratio of less than or equal to 0.01.

[0041] Advantageously, the void rubber ratio of the first circumferential rib can be determined solely by the second transverse groove.

[0042] Conveniently, the first annular portion located on the first circumferential rib has a width greater than or equal to 30% of the width of the first circumferential rib.

[0043] Preferably, the second transverse groove of the second circumferential rib may have an extension length greater than the extension length of the second transverse groove of the first circumferential rib.

[0044] Advantageously, the second annular portion located on the second circumferential rib has a width greater than or equal to 25% of the width of the second circumferential rib.

[0045] Preferably, the first annular portion may have a width greater than that of the second annular portion.

[0046] Conveniently, the first annular portion has a width greater than that of the shoulder annular portion.

[0047] Preferably, the second circumferential rib has a void-to-rubber ratio of less than 0.02.

[0048] Conveniently, the void rubber ratio of the second circumferential rib can be determined solely by the second transverse groove.

[0049] Advantageously, the second transverse groove of the first circumferential rib and the second circumferential rib can have a maximum width of less than 2 mm.

[0050] Preferably, the second transverse grooves of the first circumferential rib and the second circumferential rib can have a maximum depth of less than 4 mm.

[0051] Conveniently, the number of first lateral grooves in the outer tire shoulder region can be less than the number of first lateral grooves in the inner tire shoulder region.

[0052] Advantageously, the number of first lateral grooves in the inner shoulder area can be approximately twice the number of first lateral grooves in the outer shoulder area.

[0053] To improve lateral drainage, the first lateral grooves in the first and second shoulder regions may have a width that increases with distance from the equatorial plane of the tire.

[0054] Conveniently, the maximum width of the first lateral groove in the outer tire shoulder region can be greater than the maximum width of the first groove in the inner tire shoulder region.

[0055] Advantageously, the first lateral grooves in the first shoulder region and the second shoulder region can have a maximum depth of less than 4 mm.

[0056] Preferably, the first lateral grooves in the inner shoulder region and the outer shoulder region do not have intersections with the first circumferential groove and the second circumferential groove.

[0057] Conveniently, the first transverse groove can have a generally straight course.

[0058] Advantageously, the second transverse groove can have a generally straight orientation.

[0059] Preferably, the first circumferential groove has a width of less than 5 mm.

[0060] Advantageously, the first, second and third circumferential grooves can have a width that increases as they move away from the outer shoulder area.

[0061] Conveniently, the maximum depth of the first transverse trench can be greater than the maximum depth of the second transverse trench.

[0062] Further features and advantages of the invention will become clearer from the detailed description of some preferred, but not exclusive, embodiments of high-performance or ultra-high-performance car tires intended for use on the racetrack, according to the invention. Attached Figure Description

[0063] The following description will be made with reference to the accompanying drawings, which are for illustrative purposes only and not for limiting purposes, wherein:

[0064] - Figure 1 A view showing an example of a tire according to the present invention;

[0065] - Figure 2 yes Figure 1 An enlarged view of the cross-section of the tire;

[0066] - Figure 3 yes Figure 1 A schematic plan view of a portion of the tire tread band;

[0067] - Figure 4 This is a diagram illustrating the axial variation of tire stiffness from the outer shoulder to the inner shoulder; and

[0068] - Figure 5 and Figure 6 This is a diagram illustrating the indoor noise test results of a tire according to the invention compared to two different contrasting tires. Detailed Implementation

[0069] Referring to the accompanying drawings, the tire used for automobile wheels is generally indicated by 1, particularly for tires used for wheels of high-performance or ultra-high-performance automobiles, which are also intended for use on the racetrack.

[0070] The tire 1 itself has a conventional structure and includes a carcass, a tread band 8 placed in the crown of the carcass, and a pair of axially opposed sidewalls terminating in a bead reinforced by a bead core and associated bead filler. The tire preferably also includes a belt structure inserted between the carcass and the tread band. The carcass includes one or more carcass plies anchored to the bead core, while the belt structure includes two belt strips radially stacked on top of each other. The belt strips are formed from multiple pieces of rubber-treated fabric bonded with metal cords parallel to each other in each belt strip and having a cross orientation relative to the cords of adjacent belt strips, preferably symmetrically inclined relative to the equatorial plane. Preferably, the belt structure also includes a third belt strip located at the outermost radial position, the third belt strip having cords oriented substantially parallel to the equatorial plane. Preferably, although not mandatory, the tire according to the invention has a nominal section width of at least about 225, more preferably at least about 245. For example, the tire may have nominal section widths of 225, 245, 275, or 295. Preferably, the tire according to the invention has a reduced section height. For example, the section height may be less than or equal to 60% of the nominal section width, more preferably less than or equal to 50% of the nominal section width.

[0071] The tire 1 preferably has an H / C ratio between the height of the straight section and the maximum section width, which is between 0.25 and 0.60.

[0072] The tread band 8 generally has a low porosity rubber ratio, that is, a porosity rubber ratio of less than 0.25, preferably less than 0.20.

[0073] Preferably, the total void rubber ratio of the tread 1 is greater than 0.15.

[0074] Preferably, but not necessarily, the tires according to the invention are asymmetrical, meaning that the pattern of the tread strip 7 of the tire on the right side of the equatorial plane XX is significantly different from the pattern of the tread strip of the tire on the left side. The tire 1 and / or the tread strip 8 thus have an inner side that is preferably arranged towards the interior of the vehicle (the right side in the example shown in the figure) and an outer side that is preferably arranged towards the exterior of the vehicle (the left side in the example shown in the figure) when assembled.

[0075] The tread band 8 is provided with three circumferential grooves extending in a generally circumferential direction, namely the first circumferential groove 2, the second circumferential groove 3 and the third circumferential groove 4.

[0076] The first circumferential groove 2 and the second circumferential groove 3 separate the central region L1 of the tread belt 8 from the outer shoulder region L2 and the inner shoulder region L3 of the tread belt 8. The outer shoulder region and the inner shoulder region are respectively located on the left and right sides of the central region L1. The outer shoulder region L2 is located on the outer side of the tire, while the inner shoulder region L3 is located on the inner side of the tire.

[0077] The central area L1 extends across the equatorial plane XX of the tire. The outer shoulder area L2 and the inner shoulder area L3 extend near the axial ends of the tread band 8.

[0078] Although not indicated by clearly discernible edges, the end of the tread band 8 may be defined by the intersection between the radially outermost portion of the tread band 8 extending in a generally axial direction and the axially outermost portion of the tread band 8 extending in a generally radial direction.

[0079] The central area L1 of this tire occupies a limited portion of the tread band 8.

[0080] In fact, the central area L1 can have a width that is less than or equal to 35% of the effective width of the tread band 8 (i.e., the width of the area of ​​the tread band 1 intended to contact the ground).

[0081] The central region L1 of the tread band 8 preferably has a width smaller than that of the outer shoulder region L2.

[0082] Preferably, the central region L1 of the tread band 8 has a width greater than or equal to the width of the inner shoulder region L3.

[0083] The outer shoulder area L2 has a width greater than 30% of the effective width of the tread band 8. The inner shoulder area L3 has a width less than 35% of the effective width of the tread band 8. The outer shoulder area L2 has a width greater than that of the inner shoulder area L3.

[0084] The first circumferential groove 2 defines a first outer shoulder region L2 in the axial direction relative to the central region L1 of the tread band 8, while the second circumferential groove 3 defines a second inner shoulder region L3 in the axial direction relative to the central region L1.

[0085] Preferably, the first circumferential groove 2 and the second circumferential groove 3 extend in the circumferential direction along the entire circumference of the tire and have a generally straight orientation.

[0086] The first circumferential groove 2 has a different width compared to the second circumferential groove 3.

[0087] Specifically, the first circumferential groove 2 has a width significantly smaller than that of the second circumferential groove 3. Preferably, the first circumferential groove 2 has a width less than 50% of the width of the second circumferential groove 3.

[0088] The first lateral groove 2 is not particularly wide because it is primarily used to provide behavioral continuity between the outer shoulder area L2 and the central area L1, thus the function of draining water from the outer portion of the tire mark area is mainly handled by the lateral grooves, which will be described in more detail below.

[0089] In fact, the first circumferential groove 2 may have a width of less than or equal to about 5 mm, more preferably less than or equal to about 4 mm, and in any case greater than or equal to about 2 mm.

[0090] Preferably, the second circumferential groove 3 may have a width of about 6 mm, more preferably about 8 mm, and in any case less than or equal to about 15 mm.

[0091] Preferably, the first circumferential groove 2 and the second circumferential groove 3 may have a depth of about 8 mm, more preferably about 6 mm, and in any case about 2 mm. Preferably, the first circumferential groove 2 has a depth less than the depth of the second circumferential groove 3.

[0092] The tread band 8 also includes a third circumferential groove 4 located in the central region L1.

[0093] Compared to the first circumferential groove 2, the third circumferential groove 4 has a larger width. Compared to the width of the second circumferential groove 3, the third circumferential groove 4 has a smaller width.

[0094] Preferably, the third circumferential groove 4 may have a width greater than or equal to about 5 mm, more preferably greater than or equal to about 6 mm, and in any case less than or equal to about 12 mm.

[0095] The third circumferential groove 4 may have a depth of about 8 mm, more preferably about 6 mm, and in any case about 4 mm. Preferably, the first circumferential groove 2 has a depth less than that of the third circumferential groove 4. Preferably, the second circumferential groove 3 has a depth substantially equal to that of the third circumferential groove 4.

[0096] Referring again to the embodiment shown in the figure, the second and third circumferential grooves 3 and 4 are configured with straight cross sections having a generally trapezoidal shape.

[0097] The third week's trench 4 also has a straight direction.

[0098] The first, second, and third circumferential grooves may have a width that increases as they move away from the outer shoulder area L2.

[0099] As described above, the first circumferential groove 2 and the second circumferential groove 3 define the outer shoulder region L2 and the inner shoulder region L3, respectively, located on the left and right sides of the central region L1 in the tread band 8.

[0100] The outer shoulder area L2 and the inner shoulder area L3 have good stiffness to help the tire prepare for response, especially at high speeds and when cornering.

[0101] To make the tire shoulder area rigid, the outer shoulder area L2 and the inner shoulder area L3 have a limited ratio of void rubber.

[0102] Preferably, the outer tire shoulder region L2 and / or the inner tire shoulder region L3 have a void-to-rubber ratio of less than about 0.25, preferably less than about 0.23. Preferably, the outer tire shoulder region L2 and / or the inner tire shoulder region L3 have a void-to-rubber ratio of greater than about 0.05, preferably greater than about 0.07.

[0103] The void rubber ratio in the outer tire shoulder region L2 is mainly determined by the first lateral groove 6, while the void rubber ratio in the inner tire shoulder region L3 is mainly determined by the first lateral groove 7.

[0104] In other words, other types of grooves and / or recesses are preferably absent in the outer tire shoulder region L2 and the inner tire shoulder region L3 (ignoring the first and second circumferential grooves 2 and 3).

[0105] Therefore, the outer tire shoulder region L2 includes a circumferentially repeating first lateral groove 6, while the inner tire shoulder region L3 includes a circumferentially repeating first lateral groove 7.

[0106] The first transverse grooves 6 and / or 7 each have a straight orientation.

[0107] The first transverse grooves 6 and / or 7 each have a generally transverse orientation or an orientation that is slightly inclined relative to the axial direction.

[0108] Specifically, the first grooves 6 and 7 form an angle ω with the equatorial plane XX, the absolute value of which is between 60° and 90°, preferably between 70° and 90°. The first transverse grooves 6 and 7 have a maximum width greater than or equal to about 4 mm. Preferably, the first transverse grooves 6 and 7 have a maximum width less than about 10 mm. For example, their maximum width can be between about 4 mm and about 8 mm.

[0109] The first transverse grooves 6 and / or 7 may have the following characteristics: Figure 1 , 3 The width shown in the example decreases as it moves toward the equatorial plane XX.

[0110] The first transverse grooves 6 and / or 7 may, for example, have the shape of an elongated droplet.

[0111] Each of the first lateral grooves 6 and / or 7 may have a non-constant depth along its respective extension length, for example, a depth that decreases (preferably gradually) toward the axial outer edge of the tire.

[0112] Each of the first transverse grooves 6 and 7 has a maximum depth of at least about 1.5 mm and less than about 4 mm. Preferably, each of the first transverse grooves 6 and 7 has a maximum depth between about 2 mm and about 3.5 mm.

[0113] The number of first lateral grooves 6 in the outer tire shoulder region L2 is less than the number of first lateral grooves 7 in the inner tire shoulder region L3. (Reference) Figure 1 , 3 In the embodiment shown, the number of first lateral grooves 7 in the inner shoulder region L3 is approximately twice the number of first lateral grooves 6 in the outer shoulder region L2.

[0114] As for the ratio between the number of grooves 7 in the inner shoulder region L3 and the number of grooves 6 in the outer shoulder region L2, it is certainly conceivable that it may deviate reasonably from the exact value 2: for example, considering that seventy grooves are arranged in the inner shoulder region L3, it is conceivable that thirty to forty grooves are provided in the outer shoulder region L2.

[0115] The first lateral grooves 6 and / or 7 each have a first end generally located at the corresponding axial outer edge of the tread band 8, and the first lateral groove 6 extends from the first end in a generally axial direction for at least 50% of the width of the outer shoulder region L2 where the first lateral groove is located, and the first lateral groove 7 extends from the first end in a generally axial direction for at least 50% of the width of the inner shoulder region L3 where the first lateral groove is located. Thus, the first lateral grooves 6 and 7 respectively affect the hardness of the tread band regions in which they are formed.

[0116] In the embodiment shown in the figure, the first lateral groove 6 of the outer shoulder region L2 has a smaller extension length compared to the first lateral groove 7 of the inner shoulder region L3.

[0117] The first lateral groove 6 of the tire shoulder region L2 may have an extension length equal to at least 60% of the width of the tire shoulder region L2. Preferably, the first lateral groove 6 of the tire shoulder region L2 may have an extension length equal to at least 70% of the width of the tire shoulder region L2 and in any case less than 90% of the width of the first tire shoulder region L2.

[0118] Therefore, the first lateral groove 6 in the outer tire shoulder area L2 does not intersect with the first circumferential groove 2.

[0119] The significant but still limited extension length of the first lateral groove 6 results in the annular shoulder portion M in the outer shoulder region L2 having a void-to-rubber ratio that is substantially zero in the circumferential direction.

[0120] The annular shoulder portion M is therefore the essentially groove-free portion of the outer shoulder region L2.

[0121] Preferably, the annular shoulder portion M is positioned adjacent to the circumferential groove 2.

[0122] The annular shoulder portion M has a width greater than or equal to 5% of the effective width L of the tread band 8.

[0123] Preferably, the annular shoulder portion M has a width less than or equal to 8% of the effective width L of the tread band 8.

[0124] Therefore, the first lateral groove 7 of the inner tube shoulder region L3 does not have an intersection with the second circumferential groove 3.

[0125] In the embodiment shown in the figure, the first lateral groove 7 of the inner shoulder region L3 may have an extension length equal to at least 70% of the width of the inner shoulder region L3.

[0126] Preferably, the first lateral groove 7 of the inner tire shoulder region L3 may have an extension length equal to at least 80% of the width of the inner tire shoulder region L3 and in any case less than 90% of the width of the inner tire shoulder region L3.

[0127] The significant but still limited extension length of the first lateral groove 7 results in the circumferential shoulder portion N in the inner shoulder region L3 having a void-to-rubber ratio that is substantially zero.

[0128] Preferably, the annular shoulder portion N has a void-to-rubber ratio of less than or equal to 0.02 and is positioned adjacent to the circumferential groove 3.

[0129] Therefore, the annular shoulder portion N is the part of the inner shoulder region L3 that is generally without grooves.

[0130] Preferably, the annular shoulder portion N has a width that is less than or equal to 7% of the effective width L of the tread band 8.

[0131] The annular shoulder portion N has a width greater than or equal to 4% of the effective width L of the tread band 8.

[0132] The central area L1 is designed to ensure a large amount of rubber in contact with the ground, while also ensuring proper drainage in the very center (i.e., near the equatorial plane XX of tire 1).

[0133] For this purpose, Figure 1-3 The tread band 8 shown has a void rubber ratio of less than about 0.3, preferably less than about 0.25, in the central region L1.

[0134] The third circumferential groove 4, together with the first circumferential groove 2 and the second circumferential groove 3, defines the first circumferential rib 9 and the second circumferential rib 10 in the central region L1.

[0135] exist Figure 1-3In the tire shown, the first circumferential rib 9 is located between the first circumferential groove 2 and the third circumferential groove 4. The second circumferential rib 10 is located between the third circumferential groove 4 and the second circumferential groove 3.

[0136] exist Figure 1-3 In the tire shown, in order to increase the amount of "rubber in contact with the ground" at the central region L1 and thus optimize handling, noise and rolling resistance characteristics, the central region L1 and the circumferential ribs 9 and 10 are characterized by a low void-to-rubber ratio.

[0137] At least one of the first circumferential rib 9 and the second circumferential rib 10, preferably both of them, actually have a void rubber ratio of less than about 0.02, more preferably less than about 0.015.

[0138] For this purpose, the first circumferential rib 9 and the second circumferential rib 10 include a plurality of second transverse grooves 11, 12.

[0139] The ratio of the void rubber between the first circumferential rib 9 and the second circumferential rib 10 is determined solely by the second transverse grooves 11 and 12.

[0140] exist Figure 1-3 In the tire shown, the second lateral groove 11 is located in the first circumferential rib 9, while the second lateral groove 12 is located in the second circumferential rib 10.

[0141] The second transverse grooves 11 and 12 are preferably thin cuts and have a maximum width of less than or equal to about 2 mm.

[0142] Preferably, the second transverse grooves 11 and 12 have a maximum depth of less than 3 mm, preferably less than 2.5 mm. Preferably, the second transverse grooves 11 and 12 have a maximum depth of greater than 1 mm.

[0143] Preferably, the first transverse grooves 6 and 7 can have a maximum depth greater than the maximum depth of the second transverse grooves 11 and 12.

[0144] The second transverse grooves 11 and / or 12 may have a generally straight orientation along their entire length.

[0145] The distance between the second transverse grooves 11 and / or 12 in the circumferential direction is preferably between 25 mm and 80 mm.

[0146] The second transverse groove 11 is inclined to form an angle α with the equatorial plane XX.

[0147] In detail, the orientation of the second transverse groove 11 forms an angle α with the equatorial plane XX, with an absolute value between 45° and 90°, preferably between 50° and 70°.

[0148] The second transverse groove 12 is inclined to form an angle β with the equatorial plane XX.

[0149] In detail, the orientation of the second transverse groove 12 forms an angle β with the equatorial plane XX, with an absolute value between 45° and 90°, preferably between 50° and 70°.

[0150] The second transverse groove 11 of the first circumferential rib 9 is inclined in the opposite direction to the second transverse groove 12 of the second circumferential rib 10.

[0151] Compared with the extension length of the second transverse groove 11 of the first circumferential rib 9, the second transverse groove 12 of the second circumferential rib 10 has a larger extension length.

[0152] Preferably, the second transverse grooves 11 extend over at least 30%, preferably 40%, of the width of the circumferential ribs 9 to which they are located. Preferably, the second transverse grooves 12 also extend over at least 30%, preferably 40%, of the width of the circumferential ribs 10 to which they are located.

[0153] To improve driving accuracy and gripping force, the first and second circumferential ribs are respectively provided with a first circumferential annular portion S1 and a second circumferential annular portion S2 with a gap rubber ratio of approximately zero.

[0154] The presence of a central rib in the first and second circumferential annular portions, where the clearance rubber ratio is substantially zero, in conjunction with the annular portion M in the outer shoulder region L2, which also has a clearance rubber ratio substantially zero, and preferably also in conjunction with the annular portion N in the inner shoulder region L3, which also has a clearance rubber ratio substantially zero, increases tire stiffness, thereby improving grip (especially on the track), track accuracy, and noise reduction.

[0155] The first annular portion S1 of the first circumferential rib 9 is adjacent to the first circumferential groove 2.

[0156] Preferably, the first annular portion S1 of the first circumferential rib 9 is arranged to form an annular portion Z with the annular shoulder portion M, the annular portion Z being at least about 10% of the effective width of the tread band 8 and having a substantially zero void rubber ratio (ignoring the factor of the first circumferential groove 2).

[0157] The first annular portion S1 has a width greater than or equal to 6% of the effective width L of the tread band 8.

[0158] The first annular portion S1 has a width that is less than or equal to 10% of the effective width L of the tread band 8.

[0159] Preferably, the first annular portion S1 has a width greater than or equal to 30% of the width A9 of the first circumferential rib 9.

[0160] The width of the first annular portion S1 is greater than the width of the second annular portion S2, and the width of the second annular portion S2 is greater than the width of the annular shoulder portion M.

[0161] The second annular portion S2 of the second circumferential rib 10 is adjacent to the third circumferential groove 4.

[0162] Preferably, the width of the second annular portion S2 is greater than or equal to 25% of the width A10 of the second circumferential rib 10.

[0163] The width of the second annular portion S2 is less than or equal to 9% of the effective width L of the tread band 8 and greater than or equal to 6% of the effective width L of the tread band 8.

[0164] The hardness of the tread band of the tire according to the invention was simulated in order to measure its variation in the axial direction. The same type of test was also performed on the tread bands of two comparative tires currently manufactured by the applicant for the same market segment.

[0165] Therefore, the tire tread band is divided into five adjacent circumferential rings of equal width.

[0166] The simulation results show that Figure 4 In the diagram, C and C1 refer to the comparison tires, while B refers to the tire according to the present invention.

[0167] It can be seen that the tire according to the present invention has significantly higher hardness in almost all circumferential rings, and these circumferential rings as a whole do not show any significant change in hardness.

[0168] Indoor noise tests were also conducted.

[0169] Noise testing was conducted in an external soundproof chamber (semi-anechoic chamber) using a fixed turntable that rotatably supports the tire under test. The turntable was first fitted with a tire according to the invention, and then with two different comparison tires from the same market segment.

[0170] In the noise test, one tire in each group was kept in contact with the drum and rotated at different speeds. Additionally, microphones were placed both inside and outside the vehicle to measure internal and external noise separately.

[0171] Figure 5 and Figure 6 The image shows the exterior views of the vehicle as a function of speeds (km / h) between 150 km / h and 20 km / h. Figure 5 ) and inside the car ( Figure 6The diagram shows the noise level in dB(A). Figures A and A1 refer to the comparison tires, while Figure B refers to the tire according to the invention. It can be noted that the tire according to the invention has an average noise level 5 dB(A) lower than the lowest noise level among these compared tires (measured both outside and inside the vehicle). Test results show that, in the conducted indoor noise tests, the tire according to the invention exhibits significantly better performance compared to the comparison tires.

[0172] Various modifications can be made to the embodiments described in detail herein, while still remaining within the scope of protection of the invention as defined by the appended claims.

Claims

1. A car tyre (1) having a tread band (8) comprising a central region (LI) extending across the equatorial plane (X-X) of the car tyre, an outer shoulder region (L2) located towards the outer side of the car tyre, and an inner shoulder region (L3) located towards the inner side of the car tyre; a first circumferential groove (2) axially delimiting the outer shoulder region (L2) with respect to the central region (LI) and a second circumferential groove (3) axially delimiting the inner shoulder region (L3) with respect to the central region (LI); the width of the central region (LI) is less than or equal to 35% of the effective width (L) of the tread band (8); the width of the outer shoulder region (L2) and of the inner shoulder region (L3) is greater than or equal to 30% of the effective width (L) of the tread band (8); the width of the outer shoulder region (L2) is greater than the width of the inner shoulder region (L3); the outer shoulder region (L2) and the inner shoulder region (L3) comprise a plurality of first transverse grooves (6, 7) having a first end located at the respective edge of the tread band (8), a maximum width greater than or equal to 4 mm, and an extension length equal to at least 50% of the width of the shoulder region in which they are located; the central region (LI) comprises a first circumferential rib (9) and a second circumferential rib (10) separated from each other by a third circumferential groove (4), the first circumferential rib (9) and the second circumferential rib (10) comprising a plurality of second transverse grooves (11, 12); wherein the outer shoulder region (L2) comprises a shoulder annular portion (M) located adjacent to the first circumferential groove (2), the shoulder annular portion having a void-to-rubber ratio equal to zero; the first circumferential rib (9) has a first annular portion (SI) located adjacent to the first circumferential groove (2), the first annular portion having a void-to-rubber ratio equal to zero; the second circumferential rib (10) has a second annular portion (S2), the second annular portion having a void-to-rubber ratio equal to zero.

2. A vehicle tyre (1) according to claim 1, characterized in that, the second annular portion (S2) is located adjacent to the third circumferential groove (4).

3. A vehicle tyre (1) according to claim 1 or 2, characterized in that, the extension length of the second transverse grooves (11, 12) is equal to at least 30% of the width of the circumferential rib (9, 10) in which they are located.

4. A vehicle tyre (1) according to claim 1 or 2, characterized in that, the second transverse grooves (11) of the first circumferential rib (9) are inversely inclined with respect to the second transverse grooves (12) of the second circumferential rib (10).

5. A vehicle tyre (1) according to claim 1 or 2, characterized in that, the second transverse grooves (11, 12) are inclined with respect to a direction parallel to the equatorial plane (X-X) so as to form an angle greater than 60°.

6. A vehicle tyre (1) according to claim 1 or 2, characterized in that the first circumferential rib (9) has a void-to-rubber ratio less than 0.

01.

7. A vehicle tyre (1) according to claim 6, characterized in that the void-to-rubber ratio of the first circumferential rib (9) is determined only by the second transverse grooves (11).

8. A vehicle tyre (1) according to claim 1 or 2, characterized in that, the width of the first annular portion (SI) is greater than or equal to 30% of the width (A9) of the first circumferential rib (9).

9. A vehicle tyre (1) according to claim 1 or 2, characterised in that The second transverse groove (12) of the second circumferential rib (10) has an extension length greater than that of the second transverse groove (11) of the first circumferential rib (9).

10. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The second annular portion (S2) has a width greater than or equal to 25% of the width (A10) of the second circumferential rib (10).

11. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The first annular portion (S1) has a width greater than that of the second annular portion (S2).

12. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The first annular portion (S1) has a width greater than that of the shoulder annular portion (M).

13. A vehicle tyre (1) according to claim 1 or 2, characterised in that The second circumferential rib (10) has a void-to-rubber ratio less than 0.

02.

14. A vehicle tyre (1) according to claim 13, characterized in that, The void-to-rubber ratio of the second circumferential rib (10) is determined only by the second transverse groove (12).

15. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The second transverse groove (11, 12) has a maximum width less than 2 mm.

16. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The second transverse groove (11, 12) has a maximum depth less than 4 mm.

17. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The number of the first transverse grooves (6) of the outer shoulder region (L2) is less than that of the first transverse grooves (7) of the inner shoulder region (L3).

18. A vehicle tyre (1) according to claim 17, characterized in that The number of the first transverse grooves of the inner shoulder region (L3) is twice that of the first transverse grooves of the outer shoulder region (L2).

19. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The first transverse grooves (6, 7) have a width that increases away from the equatorial plane (X-X) of the vehicle tire.

20. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The maximum width of the first transverse grooves (6) of the outer shoulder region (L2) is greater than that of the first transverse grooves (7) of the inner shoulder region (L3).

21. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The first transverse grooves (6, 7) have a maximum depth less than 4 mm.

22. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The first transverse grooves (6, 7) have no intersection with the first and second circumferential grooves (2, 3).

23. A vehicle tyre (1) according to claim 1 or 2, characterised in that The first transverse grooves (6, 7) have a straight course.

24. A vehicle tyre (1) according to claim 1 or 2, characterised in that The second transverse grooves (11, 12) have a straight course.

25. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The first circumferential groove (2) has a width less than 5 mm.

26. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The first, second, and third circumferential grooves (2, 3, 4) have a width that increases away from the outer shoulder region (L2).

27. A vehicle tyre (1) according to claim 1 or 2, characterized in that, The maximum depth of the first transverse grooves (6, 7) is greater than that of the second transverse grooves (11, 12).

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