Tire tread for heavy vehicle with improved robustness

Abstract

The present invention relates to a tire tread (1) for heavy civil engineering vehicles, which has an improved compromise between resistance to mechanical impacts caused by stony ground and grip on muddy ground. The tread (1) comprises five rows (41, 42, 43), which are separated in pairs by longitudinal cuts (51, 52) and distributed along the transverse direction (YY') as a center row (43), two intermediate rows (42) and two side rows (41). The tread blocks (31, 32, 33) in a single row (41, 42, 43) are separated in pairs by transverse cuts (61, 62, 63). Each transverse cut in the side row (41) is a transverse groove, and each transverse cut (62) in the intermediate row (42) is a transverse non-penetrating groove (621) or a transverse slit (622). The transverse non-penetrating groove (621) and the transverse slit (622) are arranged alternately along the longitudinal direction XX'. Correspondingly, each internal longitudinal cut (52) separating two adjacent intermediate rows and center rows (42, 43) is a longitudinal groove.

Description

Technical Field

[0001] The present invention relates to a tire tread for heavy-duty vehicles designed to carry heavy loads and travel on uneven, stony and / or muddy surfaces, such as dump truck-type construction site vehicles used in mines or quarries. Background Technology

[0002] The tread comprises at least one rubber-based material and is intended to form the outer periphery of the tire, and is also intended to be worn down when its tread surface comes into contact with the ground.

[0003] The tread can be defined by three geometrical terms: the smaller dimension or thickness along the direction perpendicular to the tread surface; the middle dimension or width along the lateral direction; and the larger dimension or length along the longitudinal direction. When the tread is attached to the tire, the lateral direction is also called the axial direction because it is parallel to the tire's axis of rotation, and the longitudinal direction is also called the circumferential direction because it is tangent to the tire's circumference in the tire's direction of travel.

[0004] To ensure satisfactory longitudinal grip performance (under engine torque and braking torque) and lateral grip performance, a combination of cuts, known as tread patterns, is required to form separating raised elements in the tread.

[0005] There are two types of cuts: grooves and sipes. Grooves are wide cuts primarily used to store and drain water or mud present on the ground. When a tire is subjected to recommended inflation and load conditions (as defined specifically by, for example, standard ISO 4250 and standards of the Tire & Rim Association or TRA), the tread enters the contact patch, and the cut width is such that the opposing material walls defining the cut do not come into contact with each other; this cut is called a wide cut. Sipes are narrow cuts whose intersection with the tread surface or edge corners contribute to grip on wet surfaces due to the corner effect in the contact patch that can disrupt the water film present on the ground. When the tread enters the contact patch under the tire load and pressure conditions specified by TRA as described above, the cut width is such that the opposing material walls defining the cut at least partially come into contact with each other; this cut is called a narrow cut.

[0006] A cut is typically characterized by an average surface that is equidistant from the wall that defines the cut and intersects the tread. The line of intersection of this average surface and the tread surface is called the average line of the cut. The average line of the cut is not necessarily a straight line; for example, it can be wavy or zig-shaped. When the angle between the tangent to the average line of the cut at any point and the longitudinal direction of the tread is between 0° and 45°, the cut is broadly referred to as a longitudinal cut. When the angle between the tangent to the average line of the cut at any point and the transverse direction of the tread is between 0° and 45°, the cut is broadly referred to as a transverse cut.

[0007] In the case of tire treads used on heavy-duty construction site vehicles, the raised elements are typically tread blocks. A tread block is a volume of material defined by a contact surface, a bottom surface, and a side surface connecting the contact and bottom surfaces contained within the tread surface. These tread blocks can be arranged in longitudinal rows forming the tread blocks, these rows being separated in pairs by longitudinal cuts of the type of grooves or sipes (also called longitudinal gaps). Furthermore, within the same longitudinal row of tread blocks, the tread blocks are typically separated in pairs by lateral cuts of the type of grooves or sipes.

[0008] The geometry of the tread in a tire typically consists of a width L in the lateral direction and a thickness H in the direction perpendicular to the tread surface. Width L is defined as the lateral width of the surface of a new tire's tread that contacts a smooth surface (e.g., tarmac) when the tire is subjected to nominal pressure and load conditions recommended by TRA standards, for example. Thickness H is typically defined as the maximum radial depth, measured in the tread cut when the tire is new, corresponding to the maximum radial height of the tread blocks. In the case of tires used on dump truck-type construction vehicles, for example, the width L is at least 600 mm and the thickness H is at least 60 mm or even 70 mm.

[0009] The typical driving conditions for tires used on construction site vehicles are particularly demanding. For example, such vehicles are designed to travel uphill (requiring good grip under traction) or downhill (requiring good grip under braking) on ​​often sloping paths. Furthermore, these paths are often winding, requiring good lateral grip. Finally, the paths are typically made of locally available materials, such as compacted gravel that is periodically watered to ensure the integrity of the wear layer as vehicles pass over it, and is often covered in mud and water: this necessitates good tread resistance to ensure satisfactory service life, and the ability to allow this mixture of mud and water to penetrate and drain from the tread to ensure satisfactory grip on muddy surfaces. Moreover, these demanding driving conditions create considerable mechanical compressive and shear stresses in the tread blocks. Deformation of the tread blocks results in heat dissipation in the viscoelastic material that makes up the tread. This heat dissipation will cause the temperature in the tire crown to rise, which may lead to serious damage or even rupture of the tire crown reinforcement located radially inside the tread.

[0010] For example, a tread pattern including tread blocks has been described in document WO 2014170283, which is designed to ensure good longitudinal grip, satisfactory lateral grip, mud shedding capacity and limited heat level under traction and braking. Summary of the Invention

[0011] The inventors set their own objective as to further improve the trade-off between tread grip (especially under traction on muddy surfaces) and tire crown heat level for tires used on heavy-duty vehicles (especially heavy-duty construction site vehicles).

[0012] This objective has been achieved by a tire tread for heavy-duty vehicles, the tread being designed to contact the ground via its surface and comprising tread blocks arranged in rows along the longitudinal direction and defined by slits.

[0013] - The tread has a width measured in the lateral direction between the two side edges of the tread surface and a height equal to the maximum depth of a cut measured in the direction perpendicular to the tread surface.

[0014] - The cut can be at least partially a groove or slit, the groove having a depth at least equal to 50% of the tread height and a width at least equal to 20% of the depth, and the slit having a depth at least equal to 50% of the tread height and a width strictly less than 20% of the depth.

[0015] The tread comprises five rows, which are separated in pairs by longitudinal cuts and distributed laterally as a center row, two intermediate rows, and two side rows. The center row is centered on a central plane perpendicular to the tread surface. The two intermediate rows are located on either side of the center row and are symmetrical with respect to the central plane. The two side rows are located on the outermost side of the tread and are symmetrical with respect to the central plane.

[0016] - Patterned blocks in the same row are separated in pairs, at least partially, by transverse cuts.

[0017] - Each lateral cut in the side row is a lateral groove extending from the side edge of the tread surface to the outer longitudinal cut.

[0018] - Each transverse cut in the middle row is a transverse non-penetrating groove or a transverse slit, the transverse non-penetrating groove continuing the transverse grooves in the adjacent side rows and extending from the outer longitudinal cut to the transverse inner end of the transverse non-penetrating groove, the transverse slit extending from the outer longitudinal cut to the inner longitudinal cut, such that along the longitudinal direction, each transverse non-penetrating groove alternates with a transverse slit.

[0019] - Each internal longitudinal cut separating two adjacent rows, namely the middle row and the center row, is a longitudinal groove.

[0020] Therefore, the tread of the present invention includes five rows of tread blocks distributed with a center row of tread blocks, two side rows of tread blocks and two intermediate rows of tread blocks. The center row of tread blocks is centered on the center plane of the tread. The two side rows are symmetrical with respect to the center plane and are located on the outer side in the lateral direction (i.e., at the edge of the tread). Each intermediate row is located in the lateral direction between the center row and the side rows.

[0021] Each lateral groove present in each side row tread block has a depth at least equal to 50% of the tread height and a width at least equal to 20% of the depth. These lateral grooves extend to the lateral exterior of the nearest center row tread block via non-through lateral grooves, i.e., they do not completely penetrate the center row. This ensures a continuous channel between the lateral exterior of the center row and the side rows, allowing for the lateral expulsion of water or mud from the ground, thereby improving tire grip. These channels also help cool the radially inner portion of the tire crown, thus contributing to the durability of the tire crown.

[0022] The lateral sipes in each center row alternate with lateral non-penetrating grooves. Each lateral sipe has a depth at least equal to 50% of the tread height and a width at most equal to 20% of the depth. This ensures the closure of the center row, protecting the tire crown in this central area from impacts caused by stones on the ground. Specifically, this refers to the area in the contact patch that exhibits high pressure and is sensitive to stone impacts.

[0023] According to the invention, the internal longitudinal cuts separating two adjacent rows, namely the middle row and the center row, are longitudinal grooves. These internal longitudinal grooves form a continuous channel between the middle and center rows, thus allowing water or mud present on the ground to drain longitudinally, thereby improving tire grip. This channel also helps cool the radially inner portion of the tire crown, thus contributing to the durability of the tire crown.

[0024] Therefore, at any point on the tread surface, the tread can effectively expel water or dirt present on the ground by either lateral passage formed by the lateral grooves in the side row (which are continued by the lateral non-through grooves in the center row) or longitudinal passage formed by the internal longitudinal grooves located between the center row and the middle row.

[0025] This network of lateral and longitudinal channels also contributes to effective ventilation of the tread and cooling of the tire crown.

[0026] Advantageously, each external longitudinal cut has an average line positioned laterally at an average distance relative to the center plane of the tread, said average distance being at least 20% of the tread width. The average line of the cut is a line on the tread surface of the average surface of the cut, equidistant from the walls of the tread blocks defining the cut. Since the average line of the cut is not necessarily strictly longitudinal, its average distance relative to the center plane is the average of the distances of all its points from the center plane. The above features define a minimum average distance between each external longitudinal cut and the center plane, and thus correspondingly define a maximum width of the sidewall. The resulting technical effect is to ensure that the heat level in the radially inner part of the tire crown sidewall, which is typically subjected to high temperatures, is acceptable.

[0027] Advantageously, each outer longitudinal slit has an average line positioned in the lateral direction at an average distance relative to the center plane of the tread, said average distance being at most 35% of the tread width. This feature defines the maximum average distance between each outer longitudinal slit and the center plane, and thus correspondingly defines the minimum width of the sidewall. The resulting technical effect is to ensure that the tread wear-related stiffness level of each sidewall is acceptable when the tire is subjected to lateral cornering stress.

[0028] Advantageously, the inner lateral end of each lateral non-penetrating groove in the center row is positioned laterally at a distance equal to at least 20% of the tread width relative to the center plane of the tread. This feature implicitly defines the maximum engagement of the lateral non-penetrating grooves in the center row. If the lateral non-penetrating groove portion over-engages, i.e., if its inner lateral end is too close to the center plane, it extends into an area exhibiting strong pressure in the contact patch and being particularly sensitive to stone-induced attacks. This makes the center row even more sensitive to stone-induced attacks.

[0029] Furthermore, each lateral inner end of the lateral non-penetrating groove in the center row is positioned at a distance from the center plane of the tread along the lateral direction equal to at most 35% of the tread width. This feature implicitly defines the minimum engagement of the lateral non-penetrating grooves in the center row. If the lateral non-penetrating groove engages sufficiently, that is, if its lateral inner end is close enough to the center plane, it extends into the contact patch when the tire is subjected to a light load (typically 20% of its nominal load) and mounted in pairs on the rear axle of an unloaded vehicle. Under these conditions, the presence of the lateral non-penetrating grooves in the contact patch ensures the lateral expulsion of water or mud present on the ground, thereby improving tire grip.

[0030] Advantageously, each internal longitudinal slit has an average line positioned laterally at an average distance relative to the center plane of the tread, said average distance being at least 5% of the tread width. The average line of the slit is a line on the tread surface of the average surface of the slit equidistant from the walls of the tread blocks defining the slit. Since the average line of the slit is not necessarily strictly longitudinal, its average distance relative to the center plane is the average of the distances of all its points from the center plane. This feature defines the minimum average distance of each internal longitudinal slit from the center plane, and thus correspondingly defines the minimum width of the center row. An insufficiently wide center row will consist of narrow tread blocks, resulting in lower stiffness and greater sensitivity to chipping.

[0031] Furthermore, each internal longitudinal slit has an average line positioned in the lateral direction at an average distance relative to the center plane of the tread, said average distance being at most 20% of the tread width. This feature defines the maximum average distance between each internal longitudinal slit and the center plane, and thus correspondingly defines the maximum width of the center row. An excessively wide center row would consist of wide tread blocks, which is detrimental to the thermal performance of the tire tread.

[0032] Preferably, each external longitudinal cut separating two adjacent rows, namely the side row and the center row, is a longitudinal sipe. These longitudinal sipes ensure closure, thereby ensuring protection of the tread from impacts caused by stones present on the ground. Furthermore, when the tire is subjected to lateral stress, such as during cornering, these longitudinal sipes restrict the lateral movement of the tread blocks in those rows through a shoulder effect between the rows. Therefore, this lateral hardening of the tread limits the wear of the tread blocks in those rows during cornering.

[0033] Preferably, each lateral cut in the center row is a lateral sipe, which continues the lateral sipes in the adjacent center row and extends from the first inner longitudinal cut to the second inner longitudinal cut. Each lateral sipe present in the center row has a depth at least equal to 50% of the tread height and a width at most equal to 20% of the depth. This ensures the closure of the center row, protecting the tire crown in this central region against impacts from stones present on the ground. Specifically, this refers to the area in the contact patch that exhibits high pressure and is sensitive to stone impacts.

[0034] Advantageously, each tread block in the side row, defined by two consecutive lateral grooves, has a tread block height in a direction perpendicular to the tread surface and a tread block length in a longitudinal direction, wherein the tread block height is at most equal to 80% of the tread block length. Beyond 80%, the side row tread blocks become insufficiently stiff and therefore more sensitive to wear, especially under cornering stress.

[0035] Advantageously, each tread block in the sidewall has a tread block length along the longitudinal direction, and each lateral groove defined by two tread blocks has a lateral groove width along the longitudinal direction, the lateral groove width being at least 18% of the sum of the lateral groove width and the tread block length. This feature defines a minimum void ratio for the sidewall tread blocks; below this minimum void ratio, insufficient water or mud is expelled from the tread sidewalls, which adversely affects tire grip.

[0036] Furthermore, each tread block in the sidewall has a tread block length along the longitudinal direction, and each lateral groove defined by two tread blocks has a lateral groove width along the longitudinal direction, the lateral groove width being at most 35% of the sum of the lateral groove width and the tread block length. This feature defines a maximum void ratio for the sidewall tread blocks, beyond which the stiffness of the tread blocks in the sidewall becomes insufficient to ensure good tire wear resistance.

[0037] Advantageously, at least one ventilation cavity is provided between at least two consecutive lateral grooves in the same sidewall tread along the longitudinal direction. This ventilation cavity opens to the tread surface and has a depth at least 70% of its height. The ventilation cavity is a recess formed in the tread in a generally radial direction and has a surface opening to the tread surface with a closed profile; therefore, it is not a cut as described above. Such a ventilation cavity is sometimes referred to as a ventilator. The presence of ventilation cavities in the sidewall tread blocks allows for ventilation of the tread edges, thus cooling the radially inner crown portion, which serves as a tire hotspot, thereby limiting tire crown degradation and improving its durability.

[0038] According to a specific embodiment, the ventilation cavity includes a radially outer first portion extending radially inward from a radially inner second portion, the inner wall of the radially outer first portion being inclined at a first angle relative to a direction perpendicular to the tread surface, and the inner wall of the radially inner second portion being inclined at a second angle, strictly less than the first angle, relative to a direction perpendicular to the tread surface. The double-inclined internal ventilation walls restrict the acquisition and retention of stones within the cavity, which are prone to causing cracks detrimental to the durability of the tire tread.

[0039] Advantageously, the tread includes two outer side surfaces, each intersecting the tread surface at a side edge. All lateral grooves in the side row open to the side surfaces of the tread along their openings. At least one ventilation cavity is provided between at least two surfaces to which consecutive lateral grooves in the same side row open in the longitudinal direction. This ventilation cavity, when the tire is new, opens to the side surfaces of the tread rather than to the tread surface. In this case, the ventilation cavity is a recess formed in the side surface of the tread in a generally transverse direction, having a surface that opens to the tread surface with a closed profile. The presence of the ventilation cavity opening to the side surfaces of the tread allows ventilation of the side surfaces, thus cooling the ends of the crown reinforcement layer extending transversely to the inner side of the side surfaces of the tread, thereby limiting the degradation of the tire crown and improving its durability. This ventilation cavity does not open to the tread surface when the tire is new to avoid irregular wear starting at the tread edge.

[0040] The present invention also relates to a tire for heavy-duty vehicles (preferably heavy-duty construction site vehicles), the tire comprising a tread according to any of the above embodiments. Attached Figure Description

[0041] From not drawn to scale Figures 1 to 6 To illustrate the features of this invention, the tire size is 59 / 80R 63:

[0042] - Figure 1 A top view of a portion of the tire tread according to the present invention.

[0043] - Figure 2 A top view of a portion of the tread according to the invention, which shows... Figures 3 to 6 The cross-sectional plane,

[0044] - Figure 3 According to the present invention, the meridional section of the tread along the dashed line AA is...

[0045] - Figure 4 The circumferential section passing through the center row of the tread according to the invention passes through the plane BB of the center circumferential section.

[0046] - Figure 5 A circumferential section passing through the middle row of the tread according to the invention, outside the transverse non-penetrating grooves, passes through the circumferential section plane CC.

[0047] - Figure 6 : A circumferential section passing through the side row of the tread according to the invention, which passes through the circumferential section plane DD. Detailed Implementation

[0048] exist Figures 1 to 6 In this system, various geometric dimensions are defined in the reference frame XYZ, which is defined by the longitudinal or circumferential direction XX' (tangent to the tire's circumference along the tire's direction of travel), the lateral or axial direction YY' (parallel to the tire's axis of rotation), and the radial direction ZZ' (perpendicular to the tire's axis of rotation). When the tire tread surface has generatrices that are substantially straight and the tire's axis of rotation is a cylinder, the radial direction ZZ' is substantially perpendicular to the tread surface at any point on the tread surface.

[0049] Figure 1This is a top view of a portion of the tread 1 according to the invention. The tread 1 of a tire for heavy-duty vehicles is intended to contact the ground via the tread surface 2 and includes tread blocks (31, 32, 33) arranged in rows (41, 42, 43) along the longitudinal direction XX' and defined by cuts (51, 52, 61, 62, 63). The tread 1 has a width L measured along the lateral direction YY' between the two side edges 21 of the tread surface 2. The cuts (51, 52, 61, 62, 63) are at least partially wide cuts (or grooves) or narrow cuts (or sipes). The tread 1 comprises five rows (41, 42, 43), which are separated in pairs by longitudinal cuts (51, 52) and distributed along the transverse direction YY' with a central row 43, two intermediate rows 42, and two side rows 41. The central row 43 is centered on a central plane XZ perpendicular to the center of the tread surface 2. The two intermediate rows 42 are located on either side of the central row 43 and are symmetrical with respect to the central plane XZ. The two side rows 41 are located on the outermost side in the transverse direction and are symmetrical with respect to the central plane XZ. Tread blocks (31, 32, 33) in the same row (41, 42, 43) are at least partially separated in pairs by transverse cuts (61, 62, 63). According to the invention, each transverse cut 61 in the side row 41 is a transverse groove extending from the side edge 21 of the tread surface 2 to the outer longitudinal cut 51. According to the invention, each transverse cut 62 in the intermediate row 42 is a transverse non-penetrating groove 621 or a transverse slit 622, wherein the transverse non-penetrating groove 621 continues the transverse groove 61 in the adjacent side row 41 and extends from the outer longitudinal cut 51 to the transverse inner end E2 of the transverse non-penetrating groove 621, and the transverse slit 622 extends from the outer longitudinal cut 51 to the inner longitudinal cut 52, such that each transverse non-penetrating groove 621 alternates with the transverse slit 622. Therefore, unlike the transverse slit 622, the transverse non-penetrating groove 621 does not completely penetrate the intermediate row 42. Also according to the invention, each inner longitudinal cut 52 separating two adjacent rows (42, 43) respectively, the intermediate row and the center row, is a longitudinal groove. Each external longitudinal cut 51 has an average line M1 positioned at an average distance D1 relative to the center plane XZ of the tread 1 along the lateral direction YY', said average distance D1 being at least 20% and at most 35% of the width L of the tread 1. Each lateral inner end E2 of the lateral non-through groove 621 in the center row 42 is positioned at a distance D2 relative to the center plane XZ of the tread 1 along the lateral direction YY', said distance D2 being at least 20% and at most 35% of the width L of the tread 1. The line M2 passes through all inner ends E2.Each internal longitudinal cut 52 has an average line M3 positioned at an average distance D3 relative to the center plane XZ of the tread 1 along the lateral direction YY', the average distance D3 being at least 5% and at most 20% of the width L of the tread 1. Each external longitudinal cut 51 separating two adjacent rows (41, 42) respectively, the side row and the center row, is a longitudinal groove. Each lateral cut 63 in the center row 43 is a lateral groove, the lateral groove continuing the lateral groove 622 in the adjacent center row 42 and extending from the first internal longitudinal cut 52 to the second internal longitudinal cut 52. A ventilation cavity 7 leading to the tread surface 2 is disposed along the longitudinal direction XX' between two consecutive lateral grooves 61 in the same side row 41. When the tire is new, a ventilation cavity 8 leading to the side surface 22 of the tread, rather than to the tread surface 2, is disposed between the two surfaces 611 along the longitudinal direction XX', wherein a continuous transverse groove 61 in the same side row 41 leads to the two surfaces 611.

[0050] Figure 2 A top view of a portion of the tread 1 according to the present invention, which is labeled Figures 3 to 6 The radial cross-sectional planes along the dashed line AA define the meridional cross-sections through the tread in two radial cross-sectional regions YZ, respectively distributed between the side row, middle row, and center row. The circumferential cross-sectional plane BB defines the circumferential cross-section through the center row. The circumferential cross-sectional plane CC defines the circumferential cross-section through the middle row. The circumferential cross-sectional plane DD defines the circumferential cross-section through the side row.

[0051] Figure 3 The section is a meridional section passing through the tread according to the invention along the dashed line AA. The tread intended to contact the ground via the tread surface 2 comprises tread blocks arranged in rows (41, 42, 43) along the longitudinal direction XX' and defined by longitudinal cuts (51, 52) in the transverse direction. Figure 3A cross-sectional view is shown passing through the two side racks 41, the two middle racks 42, and the center rack 43. Each middle rack 42 is separated from the adjacent side rack 41 by an outer longitudinal cut 51 and from the center rack 43 by an inner longitudinal cut 52, the outer longitudinal cut 51 being positioned at an average distance D1 relative to the center plane XZ, and the inner longitudinal cut 52 being positioned at an average distance D3 relative to the center plane XZ. Each outer longitudinal cut 51 is a groove with a depth PI at least equal to 50% of the tread height H and a width WI strictly less than 20% of the depth PI. Each inner longitudinal cut 52 is a groove with a depth PR at least equal to 50% of the tread height H and a width WR at least equal to 20% of the depth PI. The tread height H is equal to the maximum cut depth measured along a direction perpendicular to the tread surface 2: therefore, it is the distance between the tread surface 2 and an imaginary surface 23 parallel to the tread surface 2 and tangent to the bottom of the cut with the maximum depth. The tread has a width L measured along the lateral direction YY' between the two side edges 21 of the tread surface 2. Figure 3 The image shows a single side edge 21, and it should be noted that the symmetrical portion of the tread relative to the center plane XZ is shown at the horizontal height of the meridional section of the transverse cut 61 passing through the side row 41. Figure 3 Ventilation chamber 7 is also shown in the meridional section, which opens to the tread surface 2 and has a depth PC at least equal to 70% of the height H (100% of the height H in the case shown). The ventilation chamber 7 is located along the longitudinal direction XX' in two consecutive lateral grooves in the same side row 41. Figure 3 (Not shown in the image). A ventilation cavity 8 is also shown, which, when the tire is new, leads to the side surface 22 of the tread instead of the tread surface 2, and is located along the longitudinal direction XX' between two surfaces led to by continuous transverse grooves 61 in the same side row 41. Figure 3 (not shown in the text)

[0052] Figure 4 The circumferential section of the center row 43 of the tread according to the invention passes through the plane BB of the center circumferential section. The center row 43 comprises tread blocks 33 separated from each other by transverse cuts 63. Each transverse cut 63 is a groove with a depth PI at least equal to 50% of the tread height H and a width WI strictly less than 20% of the depth PI. The tread height H is equal to the maximum cut depth measured along a direction perpendicular to the tread surface 2: therefore, it is the distance between the tread surface 2 and an imaginary surface 23 parallel to the tread surface 2 and tangent to the bottom of the cut with the maximum depth.

[0053] Figure 5The circumferential section of the intermediate row 42 of the tread according to the invention passes through the circumferential section plane CC outside the transverse non-penetrating grooves. The tread blocks 32 in the intermediate row 42 are separated in pairs by transverse sipes 622 in their transverse inner portions, the depth PI of which is at least equal to 50% of the height H of the tread (which is measured between the tread surface 2 and the imaginary surface 23, which is parallel to the tread surface 2 and tangent to the bottom of the cut with the maximum depth) and its width WI is strictly less than 20% of the depth PI.

[0054] Figure 6 The circumferential section of the sidewall 41 according to the invention passes through the circumferential section plane EE. The sidewall 41 includes tread blocks 31 spaced apart by lateral cuts 61. Each lateral cut 61 is a groove with a depth PR at least equal to 50% of the tread height H (measured between the tread surface 2 and an imaginary surface 23 parallel to the tread surface 2 and tangent to the bottom of the cut with the maximum depth) and a width WR at least equal to 20% of the depth PR. Each tread block 31 in the sidewall 41, defined by two consecutive lateral grooves 61, has a tread block height H1 in a direction perpendicular to the tread surface and a tread block length B1 in the longitudinal direction XX'. Advantageously, the tread block height H1 is at most equal to 80% of the tread block length B1. Each lateral groove 61 defined by two tread blocks 31 has a lateral groove width W1 in the longitudinal direction XX'. Advantageously, the transverse groove width W1 is at least 18% of the sum of the transverse groove width W1 and the pattern block length B1 and at most 35% of the sum of the transverse groove width W1 and the pattern block length B1. Figure 6 A ventilation cavity 7 is also shown, which opens to the tread surface 2 and has a depth PC of at least 70% of the height H (100% of the height H in the case shown), the ventilation cavity being located between two consecutive transverse grooves 61 in the same side row 41 along the longitudinal direction XX'.

[0055] According to TRA standard (TRA Yearbook 2019), the inventors studied the invention more specifically for a tire of size 59 / 80R 63, which is designed to be mounted on a dump truck and to carry a load of 100,000 kg when inflated to a pressure of 7 bar.

[0056] For a tire size of 59 / 80R 63, the inventors compared a tire I including the tread according to the invention with a reference tire R of the Michelin XDR3 series with a size of 59 / 80R63.

[0057] Table 1 below shows the corresponding features of the tread according to the present invention and a reference tread:

[0058] [Table 1]

[0059]

[0060] Tire I, comprising a tread according to the invention, and a reference tire R were compared through tests related to grip on wet surfaces conducted on vehicles at a construction site, and through digital simulations using the finite element method (to establish a mapping of temperatures reached in the tire crown). Regarding grip on wet surfaces, the tire according to the invention had a braking distance approximately 11% shorter than the reference tire on wet muddy surfaces, primarily due to the greater width and length of the lateral cutouts on the sidewalls. Regarding the temperature levels reached in the tire crown, the digital simulations showed a possible temperature drop of 3°C between the sidewalls of the tire according to the invention and the reference tire, and a possible temperature drop of 2°C between the center portion of the tire according to the invention and the reference tire.

Claims

1. A tread (1) for a tire for a heavy-duty vehicle, which is intended to contact the ground via a tread surface (2) and includes tread blocks (31, 32, 33) arranged in rows (41, 42, 43) along a longitudinal direction (XX') and defined by cutouts (51, 52, 61, 62, 63). - The tread (1) has a width (L) of at least 600 mm and a height (H) of at least 60 mm, the width (L) being measured along the lateral direction (YY') between the two side edges (21) of the tread surface (2), and the height (H) being equal to the maximum depth of the cuts (51, 52, 61, 62, 63) measured along a direction perpendicular to the tread surface (2). - The cuts (51, 52, 61, 62, 63) are either internal longitudinal grooves or external longitudinal slits. The depth (PR) of the internal longitudinal groove is at least equal to 50% of the tread height (H) and the width (WR) of the internal longitudinal groove is at least equal to 20% of the depth (PR). The depth (PI) of the external longitudinal slit is at least equal to 50% of the tread height (H) and the width (WI) of the external longitudinal slit is strictly less than 20% of the depth (PI). - The tread (1) comprises five rows (41, 42, 43), which are separated in pairs by internal longitudinal grooves and external longitudinal sipes (51, 52) and distributed along the transverse direction (YY') as a center row (43), two intermediate rows (42) and two side rows (41). The center row (43) is centered on a central plane (XZ) perpendicular to the center of the tread surface (2). The two intermediate rows (42) are located on both sides of the center row (43) and are symmetrical with respect to the central plane (XZ). The two side rows (41) are located on the outermost side in the transverse direction and are symmetrical with respect to the central plane (XZ). - The patterned blocks (31, 32, 33) in the same row (41, 42, 43) are at least partially separated in pairs by transverse cuts (61, 62, 63). Its features are, Each lateral cut (61) in the side row (41) is a lateral groove extending from the side edge (21) of the tread surface (2) to the outer longitudinal sipe (51). Each lateral cut (62) in the middle row (42) is a lateral non-penetrating groove (621) or a lateral sipe (622). The lateral non-penetrating groove (621) continues the lateral groove (61) in the adjacent side row (41) and extends from the outer longitudinal sipe (51) to the lateral inner end (E2) of the lateral non-penetrating groove (621). The lateral sipe (622) extends from the outer longitudinal sipe (51) to the inner longitudinal groove (52), such that along the longitudinal direction (XX'), each lateral non-penetrating groove (621) alternates with the lateral sipe (622). Each inner longitudinal cut (52) separating two adjacent rows (42, 43) of the middle row and the center row is an inner longitudinal groove. The lateral grooves in the side row (41) and the lateral non-penetrating grooves (621) in the center row (42) have a depth at least equal to 50% of the height of the tread and a width at least equal to 20% of the depth; the lateral sipes (622) in the center row (42) have a depth at least equal to 50% of the height of the tread and a width strictly less than 20% of the depth.

2. The tread (1) according to claim 1, wherein, Each external longitudinal cut (51) has an average line (M1) positioned at an average distance (D1) relative to the center plane (XZ) of the tread (1) along the lateral direction (YY'), the average distance (D1) being at least 20% of the width (L) of the tread (1).

3. The tread (1) according to any one of claims 1 and 2, wherein, Each external longitudinal cut (51) has an average line (M1) positioned at an average distance (D1) relative to the center plane (XZ) of the tread (1) along the lateral direction (YY'), the average distance (D1) being at most 35% of the width (L) of the tread (1).

4. The tread (1) according to any one of claims 1 and 2, wherein, Each lateral inner end (E2) of the lateral non-penetrating groove (621) in the middle row (42) is positioned at a distance (D2) relative to the center plane (XZ) of the tread (1) along the lateral direction (YY'), said distance (D2) being at least 20% of the width (L) of the tread (1).

5. The tread (1) according to any one of claims 1 and 2, wherein, Each lateral inner end (E2) of the lateral non-penetrating groove (621) in the middle row (42) is positioned at a distance (D2) relative to the center plane (XZ) of the tread (1) along the lateral direction (YY'), the distance (D2) being at most equal to 35% of the width (L) of the tread (1).

6. The tread (1) according to any one of claims 1 and 2, wherein, Each internal longitudinal cut (52) has an average line (M3) positioned at an average distance (D3) relative to the center plane (XZ) of the tread (1) along the lateral direction (YY'), the average distance (D3) being at least 5% of the width (L) of the tread (1).

7. The tread (1) according to any one of claims 1 and 2, wherein, Each internal longitudinal cut (52) has an average line (M3) positioned at an average distance (D3) relative to the center plane (XZ) of the tread (1) along the lateral direction (YY'), the average distance (D3) being at most 20% of the width (L) of the tread (1).

8. The tread (1) according to any one of claims 1 and 2, wherein, Each external longitudinal cut (51) separating two adjacent rows (41, 42) that are respectively side row and middle row is a longitudinal knife groove.

9. The tread (1) according to any one of claims 1 and 2, wherein, Each transverse cut (63) in the center row (43) is a transverse cutting groove that continues the transverse cutting groove (622) in the adjacent middle row (42) and extends from the first internal longitudinal cut (52) to the second internal longitudinal cut (52).

10. The tread (1) according to any one of claims 1 and 2, wherein, The tread blocks in the side row (41) are defined by two consecutive lateral grooves (61), and each tread block (31) in the side row (41) has a tread block height (H1) along a direction perpendicular to the tread surface (ZZ') and a tread block length (B1) along a longitudinal direction (XX'), wherein the tread block height (H1) is at most equal to 80% of the tread block length (B1).

11. The tread (1) according to any one of claims 1 and 2, wherein, Each pattern block (31) in the side row (41) has a pattern block length (B1) along the longitudinal direction (XX'), and each transverse groove (61) defined by two pattern blocks (31) has a transverse groove width (W1) along the longitudinal direction (XX'), wherein the transverse groove width (W1) is at least equal to 18% of the sum of the transverse groove width (W1) and the pattern block length (B1).

12. The tread (1) according to any one of claims 1 and 2, wherein, Each pattern block (31) in the side row (41) has a pattern block length (B1) along the longitudinal direction (XX'), and each transverse groove (61) defined by two pattern blocks (31) has a transverse groove width (W1) along the longitudinal direction (XX'), wherein the transverse groove width (W1) is at most equal to 35% of the sum of the transverse groove width (W1) and the pattern block length (B1).

13. The tread (1) according to any one of claims 1 and 2, wherein, Along the longitudinal direction (XX'), at least one ventilation cavity (7) is provided between at least two consecutive transverse grooves (61) in the same side row (41), the ventilation cavity (7) opening to the tread surface (2) and having a depth (PC) at least equal to 70% of the height (H).

14. The tread (1) according to any one of claims 1 and 2, wherein, The tread (1) includes two outer side surfaces (22), each of which intersects the tread surface (2) at the side edge (21) of the tread surface (21). All the lateral grooves (61) in the side row (41) lead to the side surface (22) of the tread along the opening (611). At least one ventilation cavity (8) is provided between at least two surfaces (611) led to by the continuous lateral grooves (61) in the same side row (41) along the longitudinal direction (XX'). The ventilation cavity (8) leads to the side surface (22) of the tread instead of the tread surface (2) when the tire is new.

15. A tire for heavy-duty construction site vehicles, said tire comprising the tread (1) according to any one of claims 1 to 14.

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