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CN-122029056-A - Tire for heavy civil engineering vehicle with improved grip

CN122029056ACN 122029056 ACN122029056 ACN 122029056ACN-122029056-A

Abstract

The invention relates to a tyre (1) for heavy civil engineering vehicles and aims at improving the performance trade-off between the service life of its tread (2) in terms of wear, resistance to attack and grip. According to the invention, the arrangement of the incisions (3) varies as the tire wears, such that for a maximum incision depth (D) at least equal to 70% of the initial thickness (D0) and at most equal to 90% of the initial thickness (D0), the intermediate portion (21) of the tread (2) does not comprise an effective incision (3), and any side portion (22, 23) of the tread (2) comprises at least one effective incision (3), and for a maximum incision depth (D) at least equal to 20% of the initial thickness (D0) and at most equal to 40% of the initial thickness (D0), the intermediate portion (21) of the tread (2) comprises only a transversal effective incision (32), and any side portion (22, 23) of the tread (2) comprises at least one effective incision (3).

Inventors

  • O. Spencer

Assignees

  • 米其林集团总公司

Dates

Publication Date
20260512
Application Date
20241010
Priority Date
20231019

Claims (9)

  1. 1. Tyre (1) for a heavy construction site vehicle, said tyre (1) comprising a tread (2), said tread (2) comprising an arrangement of incisions (3), said incisions (3) separating raised elements (4), When the tire is new, the tread (2) has an initial width (L0) and has an initial thickness (D0), the initial width (L0) being measured between the two tread edges (24, 25) along an axial direction (YY ') parallel to the axis of rotation of the tire, the initial thickness (D0) being measured along a radial direction (ZZ') perpendicular to the tread surface (20) and being defined as the maximum initial depth of cut, -Said tread (2) comprising a middle portion (21) and two side portions (22, 23), said middle portion (21) extending symmetrically on both sides of a median plane (XZ) of the tyre and having an initial middle width (LC 0) equal to 50% of the initial width (L0), said two side portions (22, 23) extending from the middle portion (21) each up to a tread edge (24, 25), The cut is a longitudinal cut (31) or a transverse cut (32), the average line of the longitudinal cut (31) forming an angle of less than 45 DEG with the circumferential direction (XX '), the average line of the transverse cut (32) forming an angle of more than 45 DEG with the circumferential direction (XX'), At a given wear level, a cut (3) is considered to be effective when, at a given wear level, the width (W) of the cut (3) measured perpendicular to the average line of the cut (3) between the walls of the raised elements (4) separating the cuts (3) at the tread surface (20) is at least equal to 25% of the maximum depth (D0) of the tread when new, Characterized in that the arrangement of the incisions (3) varies as the tyre wears, Such that for a maximum incision depth (D) at least equal to 70% of the initial thickness (D0) and at most equal to 90% of the initial thickness (D0), the intermediate portion (21) of the tread (2) does not comprise an effective incision (3) and each side portion (22, 23) of the tread (2) comprises at least one effective incision (3), and for a maximum incision depth (D) at least equal to 20% of the initial thickness (D0) and at most equal to 40% of the initial thickness (D0), the intermediate portion (21) of the tread (2) comprises only a transversal effective incision (32) and each side portion (22, 23) of the tread (2) comprises at least one effective incision (3).
  2. 2. Tyre (1) according to claim 1, wherein each side portion (22, 23) of the tread (2) comprises at least one transversal effective incision (32) for a maximum incision depth (D) at least equal to 70% of the initial thickness (D0) and at most equal to 90% of the initial thickness (D0).
  3. 3. Tyre (1) according to any one of claims 1 and 2, wherein each side portion (22, 23) of the tread (2) comprises at least one longitudinal effective incision (31) for a maximum incision depth (D) at least equal to 70% of the initial thickness (D0) and at most equal to 90% of the initial thickness (D0).
  4. 4. A tyre (1) according to any one of claims 1 to 3, the intermediate area void ratio TESm of the intermediate tread portion (21) being equal to the ratio between the total area of its incisions SDm and the sum of the total area of its incisions SDm and the total area of raised elements SRm defined by these incisions, and the side area void ratio TESl of each side tread portion (22, 23) being equal to the ratio between the total area of its incisions SDl and the sum of the total area of its incisions SDl and the total area of raised elements SRl defined by these incisions 3524, wherein, for a maximum incision depth (D) at least equal to 70% of the initial thickness (D0) and at most equal to 90% of the initial thickness (D0), the intermediate area void ratio TESm is at most equal to the side area void ratio TESl, preferably at most equal to 70% of the side area void ratio TESl.
  5. 5. Tyre (1) according to claim 4, wherein said mid-area void ratio TES is at most equal to 12%.
  6. 6. Tyre (1) according to any one of claims 1 to 5, wherein each side portion (22, 23) of the tread (2) comprises at least one transversal effective incision (32) for a maximum incision depth (D) at least equal to 20% of the initial thickness (D0) and at most equal to 40% of the initial thickness (D0).
  7. 7. Tyre (1) according to any one of claims 1 to 6, the intermediate area void ratio TESm of the intermediate tread portion (21) being equal to the ratio between the total area of its incisions SDm and the sum of the total area of its incisions SDm and the total area of raised elements SRm defined by these incisions, and the side area void ratio TESl of each side tread portion (22, 23) being equal to the ratio between the total area of its incisions SDl and the sum of the total area of its incisions SDl and the total area of raised elements SRl defined by these incisions 3562, wherein, for a maximum incision depth (D) at least equal to 20% of the initial thickness (D0) and at most equal to 40% of the initial thickness (D0), the intermediate area void ratio TESm is at least equal to 70% of the side area void ratio TESl and at most equal to 130% of the side area void ratio TESl.
  8. 8. Tyre (1) according to claim 7, wherein said mid-area void ratio TES is at least equal to 10%.
  9. 9. Tyre (1) according to any one of claims 1 to 8, wherein the mid-area void ratio TESm for a maximum cut depth (D) at least equal to 70% and at most equal to 90% of the initial thickness (D0) is at most equal to the mid-area void ratio TESm for a maximum cut depth (D) at least equal to 20% and at most equal to 40% of the initial thickness (D0).

Description

Tire for heavy civil engineering vehicle with improved grip Technical Field The present invention relates to a tire for a heavy construction site vehicle intended to carry heavy loads and to travel on uneven and stony ground (such as the ground of a mine). The invention relates in particular to a tread for such a tire, the grip of which is satisfactory at various wear levels of the tire. Background The invention relates more particularly to a tyre intended to be mounted to a heavy construction site vehicle, such as a dump truck intended for transporting material collected from a quarry or surface mine. Dump trucks can experience particularly severe driving conditions of high load, sustained speed, inclined and winding routes, uneven and stony ground. As an example, at the site of mining material (e.g., ore or coal), the use of dump truck type vehicles involves an alternation of full-load outbound cycles and empty-load return cycles in a simplified form. In a full-load off-station cycle, a full-load vehicle transports mined material from a loading area at the bottom of a mine or pit primarily uphill to an unloading area, requiring tires with good traction grip. In the empty return cycle, the empty vehicle returns mainly downhill into the loading area at the bottom of the mine, requiring good tire braking grip. The road, which is often inclined, also often includes curves, requiring good lateral grip of the tire. Furthermore, the roads on which the vehicles travel are composed of materials (e.g. crushed stone and tight rock) usually from mines, in order to ensure the integrity of the road wear layers as the vehicles pass, the rocks are regularly made moist, which means that they are usually covered with sludge and water. Thus, on the one hand, there is a need for a tread that is able to effectively remove this mixture of sludge and water, ensuring a satisfactory grip on muddy ground, and on the other hand, that is able to have good wear resistance and resistance to attacks by stones present on the ground. The special use of the dump truck as described above requires special management of the tires mounted thereon. When new, tires are typically mounted on the front axle or steering axle of the vehicle. In this front position, the load applied to the tyre is generally estimated to be between 60% and 100% of its nominal load-bearing capacity, depending on whether the vehicle is running in an empty or in a full state, as defined for example by standard ISO 4250 and the standard of "tyre and rim organization" or TRA. In this load range, the tire is in contact with the ground over the entire width of the tire tread, and the tire is subjected to limited or low longitudinal forces, but to high lateral forces due to the steering of the tire. When the tire wears up to about one third (i.e., when the tread thickness is reduced by one third as compared to the original thickness when new), the tire is removed from the front axle and mounted to the rear axle or drive axle to wear the remaining two-thirds of the tread. In this rear position, the load applied to the tyre is generally estimated to be between 30% and 100% of its nominal load-bearing capacity, depending on whether the vehicle is running in an empty or in a full state. In this lower load range (corresponding to running in an unloaded state), the tire is in contact with the ground over only a portion of the tread width. In this rear position, the tire is subjected to high longitudinal (driving and braking) forces (including when only the central or intermediate portion of the tread is in contact with the ground in an unloaded condition) and low lateral forces. Finally, according to current practice, the tire is permanently removed from the drive shaft when the tire tread reaches a residual thickness corresponding to a fully worn condition. Tire treads (intended to constitute the peripheral portion of the tire) generally comprise at least one rubber-based material and are intended to wear upon contact with the ground through the tread surface. Typically: Radial direction representing a direction perpendicular to the rotation axis of the tyre, An axial direction or transverse direction representing a direction parallel to the rotation axis of the tyre, A circumferential direction or longitudinal direction, representing a direction tangential to the outer circumference of the tyre and perpendicular to the radial direction and to the axial direction respectively, The equatorial plane or median circumferential plane, means the plane containing the radial and circumferential directions, perpendicular to the rotation axis of the tyre and dividing the latter into two equal parts. For any state of wear of the tire, the tread geometry is characterized by an axial width measured along the axial direction (width for short) and a radial thickness measured along the radial direction (thickness for short). Conventionally, width is defined as the width of the portion of the trea