Tire with improved grip on wet and / or snow surfaces

Abstract

The invention relates to a stud tire comprising a tread comprising a stud pad (36c) comprising a receptacle (42) for receiving a stud (44), the maximum total diameter of the upper portion (51) of the stud extending over two thirds of the total height (H) of the stud being Dc. Each receptacle (42) is surrounded by a solid anchoring region (54) of a nail (44), said solid anchoring region (54) having a maximum total diameter Dmax. For each receptacle (42), each staple pad (36c) has a dimension Lmin that separates two opposing edges of the staple pad (36c) and a minimum distance through the center of the staple pin (48). The average value M of the Dmax / Lmin ratios of all the accommodating parts (42) and the nailing cushion blocks (36c) satisfies M < = 73%. The average value M'of the Dc / Dmax ratios of all the nails (44) and the accommodating parts (42) satisfies M '> = 37%.

Description

Technical Field

[0001] This invention relates to a tire. A tire is understood to mean a tire outer casing designed to form a cavity through interaction with a supporting element (e.g., a rim), the cavity being pressurized to a pressure greater than atmospheric pressure. The tire according to the invention has a generally toroidal shape structure exhibiting rotational symmetry about the tire's main axis. Background Technology

[0002] Studded tires sold under the MICHELIN® trademark in the X-ICE NORTH 4® series are known in the prior art. While these tires offer excellent performance, particularly in terms of grip on ice and low road wear, their grip on wet and snowy surfaces is not perfect. Summary of the Invention

[0003] The present invention aims to improve the grip of existing tires on wet and / or snowy surfaces without compromising their grip performance on ice.

[0004] Therefore, the present invention relates to a studded tire comprising a tread including pads, the pads including studded pads, each studded pad including at least one receiving portion for receiving a stud, the upper portion of the stud extending at two-thirds of the total height of the stud having a maximum total diameter Dc, each receiving portion being surrounded by a solid anchoring region for anchoring the stud, each solid anchoring region having a maximum total diameter Dmax, each studded pad having a dimension Lmin for each receiving portion, the dimension Lmin being the minimum distance separating the two opposite edges of the studded pad and passing through the center of the receiving portion, the average value M of the Dmax / Lmin ratio of all receiving portions and studded pads of the studded tire satisfying M≤73%, and the average value M' of the Dc / Dmax ratio of all studs and receiving portions of the studded tire satisfying M'≥37%.

[0005] Compared to existing tires, the tire according to the present invention provides improved grip on wet surfaces without compromising grip on ice. Specifically, by reducing the value of Dmax for a given Dc value, the present invention allows for a reduction in the value of Lmin; in other words, it allows for a reduction in the size of the pawl. This reduction in pawl size allows for an increase in the size of the slits defining the pawl, thereby enhancing grip on wet surfaces, and / or an increase in the number of pawls, thereby enhancing grip on snow. This is because increasing the size of the slits defining the pawl increases the porosity, allowing the tread to drain water more effectively. Increasing the number of pawls increases the number of edges that contact the snow layer covering the ground, thereby more effectively breaking down the snow layer.

[0006] Conversely, when the value of Dmax is reduced for a given Dc value, there is a risk that the reduced material surrounding the nail in the solid anchoring region may cause the nail to be less securely fixed within the solid anchoring region, resulting in decreased grip on ice. This invention allows this trade-off to be avoided by keeping the Dmax / Lmin ratio relatively low (in other words, by increasing the amount of material surrounding the solid anchoring region in the pad). Therefore, the reduction in the amount of material surrounding the nail in the solid anchoring region is compensated for by increasing the amount of material surrounding the solid anchoring region in the pad.

[0007] According to the invention, the maximum total diameter Dc is the maximum total diameter of the upper portion of the nail extending over two-thirds of the total height of the nail. Specifically, the upper portion of the nail relates to the degree of firmness of the nail's fixation in the solid anchorage region, particularly because it is close to the tread surface, unlike the innermost portion of the tread which is more firmly fixed in the tread due to anchorage at a deeper depth. The maximum total diameter Dc is determined by seeking the diameter of a circle inscribed within the portion of the upper portion extending over two-thirds of the total height of the nail that has the maximum diameter, the circle being contained in a plane substantially perpendicular to the overall direction of the nail's extension.

[0008] According to the invention, the solid anchoring region has the function of anchoring the nail and thus preventing it from dislodging from the receptacle. "Solid" means that the region does not include any cavities or holes that would prevent the nail from being securely fixed in the receptacle. The maximum total diameter Dmax is determined by finding the diameter of a circle inscribed within the portion of the solid anchoring region having the maximum diameter, the circle being contained in a plane substantially perpendicular to the overall direction of the nail's extension.

[0009] When the receiving part is axially symmetric, its center lies on the axis of symmetry. When the receiving part is not axially symmetric, its center coincides with the center of the circle inscribed within it that has the smallest diameter.

[0010] The average value M is determined by taking the arithmetic mean of the Dmax / Lmin ratio for each housing and each corresponding pad in the tire. Similarly, the average value M' is determined by taking the arithmetic mean of the Dc / Dmax ratio for each stud and each corresponding housing in the tire.

[0011] The cutout on the tread surface has two main characteristic dimensions: width and curve length, such that the curve length is at least twice the width. Therefore, the cutout is defined by at least two principal lateral faces, which determine its curve length and are connected by a bottom, with the two principal lateral faces spaced apart from each other by a non-zero distance, referred to as the width of the cutout.

[0012] On a new tire, the width of the slit is the maximum distance between the two main sidewalls, measured as follows: by default, when the slit does not include a chamfer, it is measured at a radial dimension coinciding with the tread surface; by default, when the slit includes a chamfer, it is measured at the outermost radial dimension of the slit and the innermost radial dimension of the chamfer. The width is measured substantially perpendicular to the main sidewalls. If a width other than the default width is specified, such as a width at a specific dimension, that width is equal to the minimum distance between the two main sidewalls at that specific dimension of the slit.

[0013] The depth of the slit on a new tire is the maximum radial distance between the bottom of the slit and its projection onto the ground when the tire is in motion. The maximum depth of the slit is called the tread height. Advantageously but optionally, the tread height ranges from 6.5 mm to 10.0 mm, preferably from 8.0 mm to 9.5 mm.

[0014] The average direction of the cut is the shortest straight line connecting the two ends of the cut.

[0015] At the radial dimension that determines the slit width, the overall direction of the slit is defined by a line equidistant from the main sidewall of the slit.

[0016] In some embodiments, all or some of the main cuts may be chamfered. The chamfer on the main cut can be a straight chamfer or a rounded chamfer. A straight chamfer is formed by a plane inclined relative to the main surface of the cut, extending to the edge defining the cut. A rounded chamfer is formed by a curved surface tangentially connected to the main surface of the cut to which it extends. The chamfer of the cut is characterized in that its height and width are equal to a radial distance and a distance along a direction perpendicular to the main surface of the cut between the common point of the main surface of the cut extended by the chamfer and the cut edge defining the cut, respectively.

[0017] The tire according to the invention has a generally toroidal shape about an axis of rotation substantially coincident with the tire's axis of rotation. This axis of rotation defines three directions commonly used by those skilled in the art: the axial direction, the circumferential direction, and the radial direction.

[0018] The axial direction refers to the direction that is substantially parallel to the tire's axis of rotation (in other words, the tire's axis of rotation).

[0019] The circumferential direction refers to the direction that is essentially perpendicular to both the axial direction and the tire radius (in other words, tangent to a circle centered on the tire's axis of rotation).

[0020] The radial direction refers to the direction along the tire's radius; in other words, any direction that intersects the tire's axis of rotation and is substantially perpendicular to that axis.

[0021] The midplane of a tire (denoted by Me) is a plane perpendicular to the tire's axis of rotation, located axially between the two bead surfaces.

[0022] The circumferential equatorial plane of a tire refers to the plane in the meridional section plane that passes through the tire's equator and is perpendicular to the midplane and radial direction. The tire's equator is the axis in the meridional section plane (a plane perpendicular to the circumferential direction and parallel to the radial and axial directions), which is parallel to the tire's axis of rotation and is equidistant between the outermost radial point of the tread intended to contact the ground and the innermost radial point of the tire intended to contact a support (such as a rim).

[0023] The meridional plane refers to a plane that is parallel to, contains, and is perpendicular to the circumferential direction of the tire's axis of rotation.

[0024] Radial inner / inner and radial outer / outer refer to those closer to and further away from the tire's axis of rotation, respectively. Axial inner / inner and axial outer / outer refer to those closer to and further away from the tire's midplane, respectively.

[0025] The bead refers to the portion of a tire designed to attach the tire to a mounting support (such as a wheel, including a rim). Therefore, each bead is specifically designed to contact the flange of the rim for attachment.

[0026] Any range of values ​​expressed as “between a and b” refers to the range of values ​​from greater than a to less than b (i.e., excluding the extreme values ​​a and b), while any range of values ​​expressed as “from a to b” means the range of values ​​from a to b (i.e., including the strict extreme values ​​a and b).

[0027] In a preferred embodiment of the invention, the tire is intended for use in passenger vehicles as defined by the 2023 ETRTO (European Tyre and Rim Technology Organization) standard. The cross-section of such a tire in the meridional plane is characterized by a section height H and nominal section width S, within the meaning of the 2023 ETRTO standard, satisfying: an H / S ratio, expressed as a percentage, at most 90 (preferably at most 70) and at least 30; and a nominal section width S at least 115 mm (preferably at least 175 mm) and at most 385 mm (preferably at most 315 mm). Furthermore, the diameter D at the flange (which defines the diameter of the rim on which the tire is mounted) is at least 12 inches (preferably at least 16 inches) and at most 24 inches. Tires intended for use in passenger vehicles include tires for vehicles referred to as “light trucks” in the United States or for vans as defined by the 2023 ETRTO standard.

[0028] In view of the nature of the present invention, in addition to the studs, the tire is preferably marked with M+S (representing “mud + snow”) and / or 3PMSF (representing “Sanfengshan snowflakes”).

[0029] Advantageously, each stud includes an anchoring base for anchoring the stud in the tread, a stud (mise) intended to contact the ground surface on which the tire travels, and a sheath disposed between the anchoring base and the stud.

[0030] In a preferred embodiment that optionally improves the anchorage of each nail in each corresponding receptacle, the receptacle includes an anchoring portion for the base of the nail, wherein the maximum total diameter Dlt of the anchoring portion for the base of the nail in the absence of a nail is strictly smaller than the maximum total diameter Dct of the base of the nail.

[0031] The maximum total diameter Dlt is determined by seeking the diameter of a circle in which the portion with the maximum diameter of the anchoring portion for the base of the nail is inscribed, and the circle is contained in a plane substantially perpendicular to the overall direction of the extension of the receiving portion.

[0032] The maximum total diameter Dct is determined by finding the diameter of a circle in which the portion of the base of the nail with the maximum diameter is inscribed, and this circle is contained in a plane substantially perpendicular to the overall direction of the nail's extension.

[0033] In a preferred embodiment that optionally improves the anchorage of each nail in each corresponding receptacle, the receptacle includes an anchoring portion for the sheath of the nail, wherein the maximum total diameter Dlc of the anchoring portion for the sheath of the nail in the absence of a nail is strictly smaller than the maximum total diameter Dcc of the sheath of the nail.

[0034] The maximum total diameter Dlc is determined by seeking the diameter of a circle in which the portion of the anchoring part of the sheath for the nail has the largest diameter, and this circle is contained in a plane substantially perpendicular to the overall direction of the extension of the receiving portion.

[0035] The maximum total diameter Dcc is determined by finding the diameter of a circle in which the portion of the sheath containing the nail has the largest diameter, and this circle is contained in a plane substantially perpendicular to the overall direction of the nail's extension.

[0036] In the preferred but optional implementation, M ≤ 70%, and more preferably M ≤ 67%. The lower the value of M, the more secure the solid anchoring area within the pad is.

[0037] Preferably, but optionally, M ≥ 50%, and more preferably M ≥ 60%.

[0038] In a preferred but optional embodiment, M' ≥ 40%, preferably M' ≥ 43%. For a given Dc value, the lower the value of M' and the higher the value of Dmax, the lower the value of Lmin can be and the larger the size of the slit defining the pad can be, thereby increasing the grip on wet and / or snow surfaces.

[0039] Preferably, but optionally, M'≤70%, and more preferably M'≤60%.

[0040] In a preferred but optional embodiment, the average value of Dmax is strictly less than 14 mm, preferably less than or equal to 12 mm, and more preferably less than or greater than 11 mm. Reducing the value of Dmax allows for a further reduction in the value of Lmin, thereby allowing for a further reduction in the size of the pad. As mentioned above, reducing the size of the pad allows for an increase in the size of the slits defining the pad, which improves grip performance on wet and / or snowy surfaces.

[0041] In a preferred but optional embodiment, the average value of Lmin is strictly less than 19 mm, preferably less than or equal to 17 mm. As mentioned above, reducing Lmin allows for a reduction in pad size, thereby improving grip performance on wet and / or snowy surfaces.

[0042] In a preferred but optional embodiment, the average value of Dc is strictly less than 10 mm, preferably less than or equal to 6 mm. For a given Lmin and Dmax value, reducing Dc improves the fixation of the nail in the solid anchorage area and the pad.

[0043] Each of the above average values ​​is determined by averaging the relevant values ​​Dmax, Lmin, or Dc for each pad or housing of the tire.

[0044] In a preferred but optional implementation, each pad is defined by at least a main cut.

[0045] Preferably, but optionally, the depth of each main cut in the defining pad is greater than or equal to 50% of the tread height, and more preferably greater than or equal to 75% of the tread height.

[0046] Preferably, but optionally, each main cut defining the pad has a width greater than or equal to 2.0 mm. Preferably, but optionally, the main cut or each main cut has a width less than or equal to 10.0 mm.

[0047] In a preferred but optional embodiment, the pad is defined at least by main slits comprising N lateral main slits, where N / C ≥ 36 lateral main slits / meter, and C is the circumference of the studded tire in meters. A relatively high N / C ratio improves grip on snow. Specifically, a larger number of lateral main slits means a larger number of lateral edges, as described above, which allows for more effective disruption of the snow cover. This increase in the number of lateral main slits is achieved by the invention, which, as described above, allows for a reduction in the size of the pads and thus an increase in their number by reducing Lmin.

[0048] To determine C, the diameter of the tire used is the diameter measured on a tire mounted on a measuring rim according to the 2023 ETRTO Standard Manual and inflated to 2.5 bar.

[0049] A lateral cut refers to a cut that extends along an average direction forming an angle strictly greater than 30° (preferably greater than or equal to 45°) with respect to the tire's circumferential direction (in other words, forming an angle less than or equal to 60°, preferably strictly less than 45°, with respect to the tire's axial direction). The average direction is the shortest curve connecting the two ends of the cut and parallel to the tread surface. A lateral cut can be continuous, meaning it is not interrupted by blocks or other cuts, such that the two principal sides determining its length are uninterrupted along the length of the lateral cut. A lateral cut can also be discontinuous, meaning it is interrupted by one or more blocks and / or one or more cuts, such that the two principal sides determining its length are interrupted by one or more blocks and / or one or more cuts.

[0050] Conventionally, the tread surface is defined axially by a first axial edge and a second axial edge. The axial width of the tread is the width measured between the first and second axial edges along the axial direction. The first and second axial edges of the tread are determined on a tire mounted on a nominal rim as defined in the 2023 ETRTO (European Tyre and Rim Technology Organization) standard manual and inflated to a pressure of 2.5 bar. The first and second axial edges of the tread are arranged on either side of the tire's midplane and are formed by lines substantially parallel to the tire's circumferential direction. The first and second axial edges of the tread are easily determined if there is a clear boundary between the tread and the rest of the tire. If the tread is continuous relative to the outer surface of the tire sidewall, the first and second axial edges can be determined, for example, by loading the tire to 80% of its load capacity as defined in the 2023 ETRTO standard manual, and the first and second axial edges can be considered as the axial limits of the tread in contact with the ground.

[0051] Preferably, but optionally, N / C ≥ 38 transverse main cuts / meter.

[0052] In a preferred but optional embodiment, the pad is defined at least by the main slit, and the volumetric porosity of the studded tire in relation to the main slit is greater than or equal to 25.0%, preferably strictly greater than 28.5%. As mentioned above, a high volumetric porosity improves wet grip performance.

[0053] The volumetric porosity related to the main incision means that only the main incision is considered when determining the volumetric porosity. Therefore, in particular, the grooves formed in each pad are not taken into account.

[0054] Therefore, the volumetric porosity associated with the main slit is the ratio of the total volume of the main slit of the tire in its new, uninstalled, and uninflated state to the total volume of the tread in its new state excluding any slits (whether main slits or sipes). One of the methods described in WO2021 / 089958 can be used in particular to measure this volumetric porosity associated with the main slit.

[0055] In a preferred but optional embodiment, the surface density of studs per square decimeter of tread is greater than or equal to 8.0, preferably greater than or equal to 8.7, more preferably greater than or equal to 9.3, and even more preferably greater than or equal to 9.5. Reducing the value of Dmax for a given Dc value allows for a decrease in constraints on tread studability. Specifically, for studable pads, the value of Lmin needs to be at least equal to the value of Dmax. Therefore, reducing Dmax increases the number of studable locations, thereby providing the possibility of increasing the surface density of studs and thus improving grip on ice.

[0056] To determine the surface density, the total number of nails present on the tire is counted, and the total tread area is calculated as a value equal to 3.14 × D × LBDR, where LBDR is the axial width of the tread as defined above, and D is the diameter measured on a tire mounted on a rim inflated to 2.5 bar according to the 2023 ETRTO Standard Manual.

[0057] In a preferred but optional embodiment, each stud pad includes one or more secondary cuts formed therein, the width of which is less than or equal to 2.0 mm, preferably less than or equal to 1.2 mm. These secondary cuts (commonly referred to as grooves) allow for improved grip on wet and snowy surfaces.

[0058] In a preferred but optional embodiment of the tread, the pad includes a first group having at least one pad and a second group having at least one pad, each of the first group and the second group being at least partially defined in the circumferential direction by a pair of circumferentially successive first lateral main cuts and a pair of circumferentially successive second lateral main cuts, each of the first lateral main cuts and the second lateral main cuts being: - Extending axially from the outer ends of the first and second lateral main cuts to the inner ends of the first and second lateral main cuts respectively, the outer end of each first lateral main cut is located on one side of the tire's midplane, and the outer end of each second lateral main cut is located on the other side of the tire's midplane. - A first circumferential azimuth angle extends from the inner end of the axial direction to a second circumferential azimuth angle at the outer end of the axial direction. When the tire is mounted on a forward-moving vehicle, the first circumferential azimuth angle enters the area in contact with the ground where the tire travels before the second circumferential azimuth angle.

[0059] In an embodiment that can increase the amount of snow that can be stored in the tread, the axial length of each of the first lateral main cut and the second lateral main cut is equal to at least 30%, preferably at least 40%, of the axial width of the tread.

[0060] In a preferred embodiment, the tire has a direction of rotation such that, when mounted on a vehicle moving forward and conforming to its direction of rotation, a first circumferential azimuth angle enters the area of ​​contact with the ground where the tire travels before a second circumferential azimuth angle. In these embodiments, the tire has a predetermined direction of rotation when mounted on the vehicle. This means that the tire is designed such that as the vehicle moves forward, the tire rotates in a predetermined direction, referred to as the direction of rotation. Typically, the tire has markings indicating the direction of rotation. Mounting a tire in a manner that does not conform to its direction of rotation can lead to unpredictable tire performance.

[0061] Optionally, the first transverse main incision and the second transverse main incision each extend axially from the outer end to the inner end along an average direction, the average direction forming an average angle with the circumferential direction ranging from 45° to 75°.

[0062] Optionally, the first and second transverse main incisions each extend axially along a principal direction, and as they move from their respective outer axial ends to their respective inner axial ends, the angle formed by the principal direction and the circumferential direction decreases by at least 75% of the curve length of each of the first and second transverse main incisions. The curve length is determined along a line extending in the general direction following the transverse main incisions.

[0063] Preferably, but optionally, the depth of each of the first and second lateral main cuts is greater than or equal to 50% of the tread height, and more preferably greater than or equal to 75% of the tread height.

[0064] Preferably, but optionally, the first and second transverse main incisions each have a width greater than or equal to 2.0 mm. Preferably, but optionally, the transverse main incisions, or each transverse main incision, have a width less than or equal to 10.0 mm.

[0065] In a variant of the aforementioned embodiment of the tread, the first group and the second group each include a first axial inner end and a second axial inner end, each of the first axial inner end and the second axial inner end of the first group and the second group at least partially defining a central main cutout, the central main cutout extending along a general direction forming a variable angle with the circumferential direction of the tire over the entire circumference of the tire, such that: - Each first axial inner end of each first group at least partially defines one of the second transverse main incisions, the second transverse main incision forming a central main incision or a portion of each central main incision, and - Each second axial inner end of each second group at least partially defines one of the first transverse main incisions, the first transverse main incision forming a central main incision or another part of each central main incision.

[0066] This variant design allows for improved tire grip on snow by enhancing the tire's ability to grip snow on snow. Specifically, to improve tire grip on snow, the tire tread needs to store snow so that the stored snow itself adheres closely to the snow covering the ground and properly transmits force between the tire and the snow-covered surface. If the snow stored in the tread slips within the tread, this reduces the force transmission between the tire and the snow covering the ground, thus impairing the tire's grip on the snow-covered surface. By means of the arrangement of the first and second axial inner ends, the snow is circumferentially captured, thereby reducing the slippage of this snow stored in the center cutout. This differs from a variant where the center cutout, or each center cutout, extends along an overall direction forming a substantially constant angle with the tire's circumferential direction over the entire circumference of the tire.

[0067] A variable angle means that the angle takes on at least two different values ​​at at least two different azimuth angles at the central cut. In some variants, the overall direction extends along a generally sinusoidal curve. In other variants, the overall direction extends along a generally zigzag-shaped broken line.

[0068] Regardless of the variant form, the center cut allows for improved lateral grip on wet surfaces due to the presence of edges on each of the first and second axial inner ends.

[0069] Therefore, regardless of the variant, the tire tread can store snow, allowing the stored snow to adhere closely to the snow covering the ground and properly transfer force between the tire and the snow-covered surface. Thus, the center cutout further improves the tire's grip on snow.

[0070] The center cutout preferably extends along the entire circumference of the tire. In one variant, the center cutout extends continuously around the entire circumference of the tire. Continuous means that air can circulate freely around the circumference of the tire using only the center cutout. In another variant, the center cutout extends discontinuously around the entire circumference of the tire. In this variant, air cannot circulate freely around the circumference of the tire using only the center cutout, for example, due to the presence of tread pattern elements (such as pads) located within the center cutout.

[0071] In a preferred and optional embodiment, the first and second transverse main incisions each lead directly to at least one central incision. Each of the first and second main incisions facilitates water drainage by leading to the central incision or each central incision.

[0072] Directly refers to each and / or the center cut of the first and second lateral main cuts, or each center cut connected to each other, with no other cuts in the tread between them.

[0073] Preferably, but optionally, the depth of the central main cut is greater than or equal to 50% of the tread height, and more preferably greater than or equal to 75% of the tread height.

[0074] Preferably, but optionally, the central main incision has a width greater than or equal to 2.0 mm. Preferably, but optionally, the central main incision has a width less than or equal to 7.0 mm.

[0075] This is because a center cut that is too wide may reduce the tire's ability to compact the snow within that cut, thus reducing the force transfer between the tire and the snowy surface. A cut that is too narrow will reduce the amount of snow stored, thus reducing the tire's ability to promote snow-on-snow grip.

[0076] In an advantageous embodiment, the first group or each of the first group and / or the second group or each of the second groups includes at least one pad, preferably the first group or each of the first group and / or the second group or each of the second groups includes a plurality of pads separated by one or more additional main cuts.

[0077] The additional main cut, created by the gaps between the pads in the first and second groups, improves grip on wet surfaces.

[0078] Preferably, but optionally, the depth of the additional main cut or each additional main cut is greater than or equal to 50% of the tread height, preferably greater than or equal to 75% of the tread height.

[0079] Preferably, but optionally, the additional main incisions, or each additional main incision, have a width greater than or equal to 2.0 mm. Preferably, but optionally, the additional main incisions, or each additional main incision, have a width less than or equal to 5.0 mm.

[0080] Conventionally, a tire includes a crown, two sidewalls, and two beads, with each sidewall connecting each bead to the crown. Still conventionally, the crown includes a tread and a crown reinforcement disposed radially inward of the tread. The tire also includes a carcass reinforcement anchored in each bead, extending radially in each sidewall, and extending axially in the crown radially inward of the crown reinforcement.

[0081] Conventionally, a tread reinforcement comprises at least one tread layer containing reinforcing elements. These reinforcing elements are preferably fabric or filament elements.

[0082] In embodiments that enable the achievement of tire performance as defined by, for example, ETRTO, as a radial tire, the carcass reinforcement includes at least one carcass ply, and each carcass ply or each carcass ply includes carcass filament reinforcing elements, each carcass filament reinforcing element extending substantially along a principal direction forming an angle with respect to the circumferential direction of the tire, the absolute value of which ranges from 80° to 90°. Alternatively, a variable angle ranging from 80° to 90° may be present in at least a portion of the sidewall, and a variable angle strictly less than 80° may be present in at least a portion of the tread. Attached Figure Description

[0083] The invention will be more clearly understood by referring to the following description, which is provided by way of non-limiting example only, in conjunction with the accompanying drawings, wherein: - Figure 1 This is a meridional cross-sectional plan view of a tire according to an embodiment of the present invention. - Figure 2 for Figure 1 A top view of the tread of a medium-sized tire. - Figure 3 for Figure 2 A detailed view of the studded pads in the tread shown, which include studs. - Figure 4 for Figure 3 A cross-sectional view of the center stud pad in a plane passing through the stud and substantially parallel to the radial direction of the tire. - Figure 5 for Figure 3 and Figure 4 The pad shown is with Figure 4 A similar cross-sectional view without nails. - Figure 6 For use in molding Figures 3 to 5 Detailed views of the molded elements of the stud pad block shown, and - Figure 7 To and Figure 4 A similar view shows a studded pad of a tire according to another embodiment of the invention. Detailed Implementation

[0084] Reference frames X, Y, and Z are shown, which correspond to the tire's usual axial direction (Y), radial direction (Z), and circumferential direction (X).

[0085] refer to Figure 1 and Figure 2 The tire according to the invention is indicated by the overall designation 10. The tire 10 has a generally toroidal shape about an axis of rotation substantially parallel to the axial direction Y. The tire 10 is intended for use in passenger vehicles and is sized 205 / 55R16. The tire 10 is a studded tire marked M+S and 3PMSF. The studded tire 10 is shown as new, i.e., before it has been driven. The studded tire 10 has a rotation direction R, which indicates the direction along which the studded tire 10 must rotate as the vehicle moves forward after being mounted on it.

[0086] The studded tire 10 includes a tread 14 designed to contact the ground during driving. Furthermore, the studded tire 10 has a conventional structure as described, for example, in patent applications WO2021250331, WO2022074341, or WO2022069819.

[0087] The tread 14 includes a tread surface 16, which is intended to contact the ground when the tire 10 is traveling on the ground. The tread surface 16 is defined axially by a first axial edge 18 and a second axial edge 20.

[0088] The tread 14 includes a first lateral main cut 22 and a second lateral main cut 24, a central main cut 26 extending over the entire circumference of the studded tire 10, and additional main cuts 28 and 30. The tread 14 further includes a first group 32 and a second group 34, each group 32 and 34 including a plurality of pads 36 and 38, each pad 36 and 38 including a plurality of secondary cuts 40 formed therein, the pads of each group 32 and 34 being separated from each other by one of the additional main cuts 28 and 30. The pads 36 and 38 include studded pads 36c and 38c and unstudded pads 36u and 38u. The pads 36 and 38 are defined by the main cuts 22, 24, 26, 28, and 30.

[0089] The depth of each of the main cuts 22, 24, 26, 28 and 30 defining the pads 36 and 38 is greater than or equal to 50% of the tread height, preferably greater than or equal to 75% of the tread height. Each of the main cuts 22, 24, 26, 28 and 30 defining the pads has a width greater than or equal to 2.0 mm and less than or equal to 10.0 mm.

[0090] Each first transverse main incision 22 extends axially from an outer end 22A to an inner end 22B. The outer end 22A is located on a first side of the midplane Me. Similarly, each second transverse main incision 24 extends axially from an outer end 24A to an inner end 24B. The outer end 24A is located on a second side of the midplane Me, in other words, it is located on the opposite side to the side where the outer end 22A is located.

[0091] Each first lateral main cut 22 extends circumferentially from a circumferential first azimuth angle AZ1 at the axial inner end 22B to a circumferential second azimuth angle AZ2 at the axial outer end 22A. When the studded tire 10 is mounted on a vehicle moving forward and conforming to its direction of rotation R, the circumferential first azimuth angle AZ1 enters the area of ​​contact with the ground on which the studded tire 10 travels before the circumferential second azimuth angle AZ2. Similarly, each second lateral main cut 24 extends circumferentially from a circumferential first azimuth angle AZ1' at the axial inner end 24B to a circumferential second azimuth angle AZ2' at the axial outer end 24A. When the studded tire 10 is mounted on a vehicle moving forward and conforming to its direction of rotation R, the circumferential first azimuth angle AZ1' enters the area of ​​contact with the ground on which the studded tire 10 travels before the circumferential second azimuth angle AZ2'.

[0092] The axial length of each of the first lateral main cut 22 and the second lateral main cut 24 is equal to at least 30%, preferably at least 40%, of the axial width LBDR of the tread 14, in which case it is 52%.

[0093] The first transverse main incision 22 and the second transverse main incision 24 each extend axially from the outer end 22A, 24A to the inner end 22B, 24B along an average direction, wherein the average direction forms an average angle with the circumferential direction X ranging from 45° to 75°, and in this case equal to 65°.

[0094] The first transverse main incision 22 and the second transverse main incision 24 each extend axially along the main direction. When they move from their respective outer axial ends 22A and 24A to their respective inner axial ends 22B and 24B, the angle formed by the main direction and the circumferential direction X decreases at least 75% of the curve length of the first transverse main incision 22 and the second transverse main incision 24, and in this case, decreases at 100% of the curve length.

[0095] The depth of each of the first lateral main cut 22 and the second lateral main cut 24, the central main cut 26, and the additional main cuts 28 and 30 is greater than or equal to 50% of the tread height, preferably greater than or equal to 75% of the tread height. The tread height ranges from 6.5 mm to 10.0 mm, preferably from 8.0 mm to 9.5 mm. In this case, the tread height, the depth of each of the first lateral main cut 22 and the second lateral main cut 24, the depth of the central main cut 26, and the depth of each of the additional main cuts 28 and 30 are approximately equal to 8.5 mm.

[0096] The first transverse main incision 22 and the second transverse main incision 24 each have a width greater than or equal to 2.0 mm and less than or equal to 10.0 mm.

[0097] The width of the central main incision 26 is greater than or equal to 2.0 mm and less than or equal to 7.0 mm, and in this case equal to 5.0 mm.

[0098] The widths of the additional main incisions 28 and 30 are each greater than or equal to 2.0 mm and less than or equal to 5.0 mm, and in this case are essentially equal to 4.0 mm.

[0099] The width of each secondary cut 40 is less than or equal to 2.0 mm, preferably less than or equal to 1.2 mm, and in this case equal to 1.0 mm.

[0100] Each first group 32 is at least partially defined in the circumferential direction by a pair of circumferentially successive first transverse main incisions 22. Each first group 32 includes an axial inner end 32A. Each second group 34 is at least partially defined in the circumferential direction by a pair of circumferentially successive second transverse main incisions 24. Each second group 34 includes an axial inner end 34A.

[0101] Each of the first axial inner ends 32A and the second axial inner ends 34A partially defines a central cutout 26. Each of the first lateral main cutouts 22 and the second lateral main cutouts 24 leads directly to the central cutout 26. The central cutout 26, extending over the entire circumference of the studded tire 10, extends along a general direction G that forms a variable angle with the circumferential direction of the studded tire 10. In this case, the general direction extends along a generally zigzag-shaped zigzag line. Specifically, the central cutout 26 extends over the entire circumference of the studded tire 10 such that each of the first axial inner ends 32A at least partially defines one of the second lateral main cutouts 24, which forms a portion of the central cutout 26, and each of the second axial inner ends 34A at least partially defines one of the first lateral main cutouts 22, which forms another portion of the central cutout 26.

[0102] The volumetric porosity of the studded tire 10 related to the main cuts, in other words, the volumetric porosity related to the main cuts 22, 24, 26, 28 and 30, is greater than or equal to 25.0%, preferably strictly greater than 28.5%, and in this case equal to 29.0%.

[0103] As described above, given the diameter measured on a tire inflated to 2.5 bar and mounted on a measuring rim according to the 2023 ETRTO standard manual, and the measured axial width LBDR equal to 0.175 meters, the circumference C of the studded tire 10 is equal to 1.984 meters, and the tread area is equal to 34.7 square decimeters. The studded tire 10 has N first and second lateral main slits 22, 24, where N satisfies N / C ≥ 36 lateral main slits / meter, preferably N / C ≥ 38 lateral main slits / meter. In this case, N = 156, such that N / C = 39 lateral main slits / meter.

[0104] The studded tire 10 comprises 300 studs, such that the surface density of studs per square decimeter of tread is greater than or equal to 8.0, preferably greater than or equal to 8.7, which in this case equals 9.0 studs / decimeter. Variations are possible where the surface density of studs per square decimeter of tread is greater than or equal to 9.3, even more preferably greater than or equal to 9.5, for example equal to 9.8 studs / decimeter, which corresponds to 340 studs for the tire.

[0105] Figure 3 and Figure 4 A pad 36c is shown. The description of each pad 38c can be deduced from the following description with necessary modifications. Each pad 36c includes at least one receiving portion 42 for receiving a nail 44. Each nail 44 includes an anchoring base 46 for anchoring the nail 44 in the tread 14, a pin 48 (e.g., made of tungsten carbide) intended to contact the ground surface where the tire travels, and a sheath 50 disposed between the anchoring base 46 and the pin 48. The sheath 50 is made of a different material than the pin 48, in this case, aluminum. The nail 44 extends to a total height equal to H, which is measured between the upper end (in this case, the end of the pin 48) and the lower end (in this case, the end of the anchoring base 46). Figure 4 In the diagram, the receiving portion 42 is shown by a dashed line. Due to the elasticity of the material surrounding the nail 44, the receiving portion 42 conforms to the shape of the nail 44.

[0106] like Figure 3As can be seen, for each receiving portion 42, each stud pad 36c has a dimension Lmin, which is the minimum distance separating the two opposite edges 37, 39 of the stud pad 36c and passing through the center of the receiving portion 42. Depending on the stud pad, the value of dimension Lmin for the stud pads 36c, 38c ranges from 11 mm to 23 mm, and the average value of Lmin is strictly less than 19 mm, preferably less than or equal to 17 mm, in which case it is equal to 17 mm.

[0107] Each stud pad 36c includes a decorative area 52 disposed on the tread surface 16 surrounding the stud pin 48 of the stud 44. In this case, the decorative area 52 includes two concentric rings 52a, 52b surrounding the stud pin 48 of the stud 44, each of which has a different texture to provide a favorable aesthetic appearance to the stud pad 36c. Other shapes and textures may be used for the decorative area 52.

[0108] like Figure 4 As can be seen, each receiving portion 42 is used to surround the solid anchoring region 54 of the anchoring pin 44. The solid anchoring region 54 has a maximum total diameter Dmax. The maximum total diameter Dmax of the pin pads 36c and 38c is the same, equal to 11 mm. The average value of Dmax is strictly less than 14 mm, preferably less than or equal to 12 mm, more preferably less than or equal to 11 mm, and therefore equal to 11 mm in this case.

[0109] On the upper part 51 of the nail 44, which extends two-thirds of the total height H, the nail 44 has a maximum total diameter Dc. In this case, the maximum total diameter Dc is the maximum total diameter Dcc of the sheath 50. The maximum total diameter Dc of the nail 44 is the same for all nails, and in this case, it is equal to 5 mm. The average value of Dc is strictly less than 10 mm, preferably less than or equal to 6 mm, and therefore equal to 5 mm in this case.

[0110] like Figure 5 As shown, the receiving portion 42 includes an anchoring portion 42t for the base 46 of the nail 44 and an anchoring portion 42c for the sheath 50 of the nail 44. To conform to the shape of the nail 44 and anchor it in the solid anchoring region 54, the maximum total diameter Dlt of the anchoring portion 42t of the receiving portion 42 in the absence of the nail 44 is strictly smaller than the maximum total diameter Dct of the base 46 of the nail 44. Similarly, the maximum total diameter Dlc of the anchoring portion 42c of the receiving portion 42 in the absence of the nail 44 is strictly smaller than the maximum total diameter DCc of the sheath 50.

[0111] Figure 6A molding element 60 for molding the pad 36c shown in the aforementioned figures is illustrated. The molding element 60 includes a molding element 62 for molding the secondary cutout 40 and a molding element 64 for molding the receiving portion 42. The molding element 64 includes a molding portion 64t for molding the anchoring portion 42t for the base 46, a molding portion 64c for molding the anchoring portion 42c for the sheath 50, and a molding portion 66 for molding the decorative area 52.

[0112] The average value M of the Dmax / Lmin ratio of all receiving portions 42 and stud pads 36c and 38c of the studded tire 10 satisfies M≤73%, preferably M≤70%, more preferably M≤67%, and satisfies M≥50%, preferably M≥60%. In this case, M=66%.

[0113] The average value M' of the Dc / Dmax ratio of all studs 44 and the receiving portion 42 of the studded tire 10 satisfies M'≥37%, preferably M'≥40%, more preferably M'≥43%, and satisfies M'≤70%, preferably M'≤60%. In this case, M'=45%.

[0114] Figure 7 A stud pad 36c for a tire according to another embodiment of the present invention is shown. Elements similar to those in the foregoing embodiments are indicated by the same reference numerals.

[0115] Unlike the studded pad 36c of the studded tire 10 described with reference to the aforementioned figures, Figure 7 The stud pad 36c includes a stud 44 in which the anchoring base 46 and the stud pin 48 are integrally formed and therefore made of the same material (in this case, tungsten carbide). The anchoring base 46 and the stud pin 48 pass through a sheath 50 along the general direction in which the stud 44 extends. The sheath 50 is made of a polymer (e.g., as described in WO2020119984).

[0116] Comparative Test Several comparative tests were conducted. Therefore, a braking test (Test 1) was performed on a road surface covered with a water film approximately 2 mm high, with the vehicle traveling at 80 km / h. The distance required for the vehicle to come to a complete stop was measured. Test 1 was conducted without any nails in the tires.

[0117] Traction on snow-covered ground was also tested (Test 2): the time required for the vehicle to accelerate from idle to 25 km / h was measured.

[0118] Braking on snow-covered ground was also tested (Test 3), with the vehicle traveling at 50 km / h. The distance required to reach 5 km / h was measured.

[0119] Speed ​​tests were also conducted on the snow-covered track (Test 4) by measuring the vehicle’s average lap time.

[0120] Finally, grip on the ice was tested (Test 5), where the distance required to accelerate from 25 km / h to 5 km / h was measured in the first time period, and the time required to accelerate from 5 km / h to 25 km / h was measured in the second time period. The results from the two time periods were averaged.

[0121] The results are summarized in Table 1 and shown as a base of 100 relative to the control tire T, where M = 75%, M' = 36%, Lmin varies from 14 mm to 24 mm, Dmax = 14 mm or 16 mm, and Dc = 5 mm. Tire T and the studded tire 10 according to the invention comprise the same studs and the same number of studs. A score higher than 100 indicates improved tire performance.

[0122] Table 1 Results showed that the present invention can improve grip on wet and snowy surfaces without compromising grip on ice.

[0123] The present invention is not limited to the embodiments described above.

Claims

1. A studded tire (10) comprising a tread (14) including pads (36u, 38u, 36c, 38c), the pads (36u, 38u, 36c, 38c) including studded pads (36c, 38c), each studded pad (36c, 38c) including at least one receiving portion (42) for receiving a stud (44), the maximum total diameter of the upper portion (51) of the stud (44) extending at two-thirds of the total height (H) of the stud (44) being Dc. Each receiving portion (42) is used to anchor the nail (44) surrounded by a solid anchoring region (54), each solid anchoring region (54) having a maximum total diameter Dmax. For each receiving portion (42), each stud pad (36c, 38c) has a dimension Lmin, which is the minimum distance between the two opposite edges (37, 39) of the stud pad (36c, 38c) and passing through the center of the receiving portion (42). Its features are, The average value M of the Dmax / Lmin ratio of all the receiving portions (42) and the stud pads (36c, 38c) of the studded tire (10) satisfies M≤73%, and the average value M' of the Dc / Dmax ratio of all the studs (44) and the receiving portions (42) of the studded tire (10) satisfies M'≥37%.

2. The studded tire (10) according to the preceding claim, wherein, M≤70%, preferably M≤67%.

3. The studded tire (10) according to any one of the preceding claims, wherein, M'≥40%, preferably M'≥43%.

4. The studded tire (10) according to any one of the preceding claims, wherein, The average value of Dmax is strictly less than 14 mm, preferably less than or equal to 12 mm, and more preferably less than or equal to 11 mm.

5. The studded tire (10) according to any one of the preceding claims, wherein, The average value of Lmin is strictly less than 19 mm, preferably less than or equal to 17 mm.

6. The studded tire (10) according to any one of the preceding claims, wherein, The average value of Dc is strictly less than 10 mm, preferably less than or equal to 6 mm.

7. The studded tire (10) according to any one of the preceding claims, wherein, The pad blocks (36u, 38u, 36c, 38c) are defined by at least the main cuts (22, 24, 26, 28, 30), which include N transverse main cuts (22, 24), where N satisfies N / C ≥ 36 transverse main cuts (22, 24) / meter, and C is the circumference of the studded tire (10) in meters.

8. The studded tire (10) according to any one of the preceding claims, wherein, The pads (36u, 38u, 36c, 38c) are defined at least by main cuts (22, 24, 26, 28, 30), and the volumetric porosity of the studded tire (10) in relation to the main cuts is greater than or equal to 25.0%, preferably strictly greater than 28.5%.

9. The studded tire (10) according to any one of the preceding claims, wherein, The surface density of the nails (44) per square decimeter of tread (14) is greater than or equal to 8.0, preferably greater than or equal to 8.7, more preferably greater than or equal to 9.3, and even more preferably greater than or equal to 9.

5.

10. The studded tire (10) according to any one of the preceding claims, wherein, Each stud pad (36c, 38c) includes one or more secondary cutouts (40) formed in the stud pad (36c, 38c), the width of the secondary cutouts (40) being less than or equal to 2.0 mm, preferably less than or equal to 1.2 mm.

Images