Tires for mixed-use agricultural vehicles

Abstract

The subject of this invention is a tire (1) for agricultural vehicles, the tire (1) comprising a tread (2) composed of blocks (31, 32, 33) which are spaced in pairs by gaps (41, 42, 43, 51, 52) and arranged in a center row (21), two middle rows (22) and two side rows (23) across the width of the tread (2). According to the invention, in order to achieve the best trade-off between rolling resistance and service life in terms of wear during road use, the two consecutive blocks (31) of the center row (21) are separated by a lateral gap (41) with a width (E1) of at most 2.5 mm, the average circumferential aspect ratio of any block (31) of the center row (21) is at least equal to 0.95 and at most equal to 1.15, any block (32) of each intermediate row (22) includes a leading edge surface (321) in the circumferential direction of tire travel, the leading edge surface (321) forming an average angle (D2) of at least 30° with the radial direction (ZZ') of the tire, and the average circumferential aspect ratio of any block (33) of each side row (23) is at most equal to 0.9.

Description

Technical Field

[0001] The present invention relates to a tire for agricultural vehicles (e.g., agricultural tractors or agricultural industrial vehicles) used for mixed purposes (i.e., for use on roads and in fields), and more particularly to the tread of said tire. Background Technology

[0002] Like any tire, a tire for an agricultural vehicle includes a tread designed to contact the ground via a tread surface, the two axial ends of which are connected to two bead via two sidewalls, thereby providing a mechanical connection between the tire and the rim on which the tire is designed to be mounted.

[0003] In the following text and by convention, the circumferential (or longitudinal) direction, the axial (or lateral) direction, and the radial direction refer to the directions tangential to the tread surface and oriented in the direction of tire rotation, the directions parallel to the tire's axis of rotation, and the directions perpendicular to the tire's axis of rotation, respectively. The radial (or meridional) plane is defined by the radial and axial directions and includes the tire's axis of rotation. The circumferential plane is defined by the radial and circumferential directions and is therefore perpendicular to the tire's axis of rotation. The circumferential plane passing through the center of the tread is called the meridional circumferential plane or the equatorial plane.

[0004] Tires used for agricultural vehicles typically include a tread pattern consisting of multiple raised elements that extend radially outward from the support surface to the tread surface and are spaced apart from each other by gaps.

[0005] In the prior art, tire treads for agricultural vehicles typically include tread pattern elements in the form of bumps. The bumps generally have an elongated shape that is integrally parallelepiped, continuous or discontinuous, and composed of at least one straight or curved portion. The bumps are spaced apart from adjacent bumps by gaps or grooves. The bumps extend axially from the central region of the tread to the axial ends or shoulders of the tread. Each bump includes a contact surface, a leading edge surface, a trailing edge surface, and two side surfaces. The contact surface is located in the tread surface and is intended to make full contact with the ground. The leading edge surface intersects the tread surface, and its intersecting edge is intended to make initial contact with the ground. The trailing edge surface intersects the tread surface, and its intersecting edge is intended to make final contact with the ground.

[0006] The bumps are distributed circumferentially at a constant or variable spacing (measured between the centerlines of two consecutive bumps) and are typically positioned on either side of the tire's equatorial plane to form a V-shaped pattern. The apex of the V-shaped pattern (or herringbone pattern) is intended to be the first part of the contact patch that enters the ground. The bumps are generally symmetrical with respect to the tire's equatorial plane, and the circumferential offset between two rows of bumps is usually achieved by rotating one half of the tread relative to the other half about the tire's axis.

[0007] Tires for agricultural vehicles are designed to travel on a variety of terrains, such as more or less dense field soil, untreated paths leading to fields, and tarmac surfaces on roads. Given the versatility of their use in the field and on roads, tires for agricultural vehicles need to offer a performance trade-off between field traction on loose ground, shatter resistance, road abrasion resistance, forward travel resistance, and vibration comfort on roads (this list is not exhaustive).

[0008] When agricultural vehicles are primarily used on roads, and road travel accounts for, for example, 80% of total road and field travel, tire road performance becomes paramount. Tires designed for field efficiency must also possess high road performance, particularly in terms of energy efficiency and wear-related lifespan. Energy efficiency, due to limited rolling resistance (especially rolling resistance), translates into a significant contribution to vehicle fuel economy. Regarding road wear, tires must also achieve high mileage through moderate wear rates and controlled tread wear patterns.

[0009] However, in road use, finding the optimal trade-off between rolling resistance and service life in terms of wear must not result in a decrease in traction during road braking. Traction must be maintained at a level that meets the required safety requirements while ensuring the shortest possible braking distance. It must be acknowledged that simultaneously improving rolling resistance, service life, and traction is difficult. To reduce rolling resistance, reducing the hysteresis of the rubber material constituting the tread (i.e., reducing its heat dissipation capacity) is useful, but on the other hand, this will also reduce traction during braking. Similarly, increasing the volume of tread wear material can extend service life, but there is a risk of increasing rolling resistance.

[0010] Furthermore, seeking compromises in the aforementioned road performance must not result in a loss of field performance such as traction and suspension capabilities (i.e., the ability not to sink into the soil). Summary of the Invention

[0011] Therefore, the inventors set their own goal as to find an optimal trade-off between rolling resistance and service life of agricultural vehicle tires used on roads, without reducing adhesion during road braking or basic field performance such as traction and levitation.

[0012] This objective according to the invention is achieved by a tire for agricultural vehicles, the tire comprising a tread having an axial width and being composed of pairs of blocks spaced apart by gaps and arranged over the entire width of the tread in a center row, two intermediate rows and two side rows.

[0013] - The clearance is a lateral clearance that forms an angle of at least 60° with respect to the circumferential direction of the tire, or a circumferential clearance that forms an angle of at most 30° with respect to the circumferential direction.

[0014] - The center row is centered on the circumferential midplane of the tire. The two middle rows are located on either side of the center row in the axial direction and are separated by a circumferential gap. The two side rows are located on the outer side of the middle rows in the axial direction and are also separated by a circumferential gap.

[0015] - The center row, middle row, and side rows each comprise pairs of circumferentially distributed blocks, separated by lateral gaps, and each block has an average radial height, an average circumferential length, and an average circumferential slenderness ratio, wherein the average circumferential slenderness ratio is defined as the ratio between the average radial height and the average circumferential length of the block.

[0016] - The blocks on the same side row extend axially outward in the extensions of the blocks in the adjacent middle row, such that any two blocks in any pair of side rows and middle rows form protrusions in each other's extensions.

[0017] - The two continuous blocks in the center row are separated by a horizontal gap with a width of no more than 2.5mm.

[0018] - The average circumferential slenderness ratio of each block in the central row is at least equal to 0.95 and at most equal to 1.15.

[0019] - Each block in each intermediate row includes a leading edge face in the circumferential direction of tire rolling, the leading edge face forming an average angle of at least 30° with the radial direction of the tire.

[0020] - The average circumferential slenderness ratio of each block in each side row is at most 0.9.

[0021] The tire tread according to the invention includes tread pattern elements, which are not conventional protrusions extending axially from the middle region of the tread to the axial ends of the tread or the shoulder, but blocks distributed over the width of the tread.

[0022] These blocks are arranged in five circumferential rows: a central row, two intermediate rows located axially on either side of the central row, and two side rows located axially outside the intermediate rows. However, the arrangement of the blocks in the side rows and adjacent intermediate rows constitutes a local bump system.

[0023] The bump includes a contact surface, a leading edge surface, a trailing edge surface, and two side surfaces. The contact surface is located in the tread surface and is intended to make full contact with the ground. The leading edge surface intersects the tread surface, and its intersecting edge is intended to make initial contact with the ground. The trailing edge surface intersects the tread surface, and its intersecting edge is intended to make final contact with the ground. The individual leading and trailing edges are not necessarily contained within a single plane, but are typically characterized by the average angle they form with the radial direction of the tire.

[0024] The geometry of each block can be defined by its radial height H in the radial direction, its axial width A in the axial direction, and its circumferential length B in the circumferential direction. These three dimensions, H, A, and B, are average values ​​measured on the block. Typically, the axial width and circumferential length vary with the height of the tread element: for example, due to the slope of the block surface, they may decrease from the support surface at the bottom of the gap all the way to the tread. In the case of radial tires used for driven wheels of agricultural tractors, the radial height H is typically at least 50 mm, and more often at least 60 mm. Based on these three dimensions H, A, and B, the circumferential slenderness ratio H / B, the axial slenderness ratio H / A, and the surface area aspect ratio B / A of a given tread element can be determined, thereby determining the rigidity of the tread element.

[0025] The blocks are separated in pairs by circumferential gaps. These gaps typically form an angle of at most 30° with respect to the circumferential direction. In other words, the average angle formed by its centerline relative to the tire's circumferential direction is not zero, but falls within the range of [0°; 30°]. The slope of the centerline relative to the circumferential direction is less than its slope relative to the axial direction. Therefore, the gaps are not strictly circumferential, but essentially circumferential.

[0026] Blocks in the same circumferential direction are separated in pairs by lateral gaps. These lateral gaps typically form an angle of at least 60° with respect to the circumferential direction. In other words, the average angle formed by its centerline relative to the tire's circumferential direction is not zero, but rather falls within the range of [60°; 90°]. The slope of the centerline relative to the circumferential direction is greater than its slope relative to the axial direction. Therefore, the gaps are not strictly lateral, but essentially lateral.

[0027] A gap is defined by the two walls of its separating blocks. During travel, as the blocks move to the contact patch between the tire and the ground and deform, these walls come together, and the gap they define closes. These deformations depend on the mechanical stresses experienced by the tire during travel, and these stresses themselves vary with the tire's operating conditions. The operating conditions (load, speed, pressure) for tires used on agricultural vehicles are defined in standards such as ETRTO (or "European Tire and Rim Technology Organization"), specifically in the "Agricultural Equipment Tires" section of its "Standards Manual-2019". When the tire is used under the standard-recommended operating conditions, the block walls defining the gap may or may not be in at least partial contact with each other, meaning the gap may or may not close. When the walls are not in contact, the gap is called a groove. When the walls are in at least partial contact, the gap is called a cut.

[0028] The geometry of a void typically consists of its width and depth. The width of the void is measured perpendicularly to its central surface, which is equidistant from the wall defining the void and flush with the tread, or in some cases, close to the tread if a chamfer exists on the opposing block. The void depth is measured perpendicularly to the tread between the open surface and the bottom of the void.

[0029] According to the first basic feature of the invention, the two continuous blocks in the center row are separated by a transverse gap with a width of at most 2.5 mm.

[0030] In other words, the central transverse gap is a cut that tends to close at least partially as it moves toward the ground surface.

[0031] Therefore, the central row formed by blocks separated by slits constitutes a quasi-continuous rib with periodic slits, which is highly beneficial for wear performance and rolling resistance during road use. Due to the small thickness of the transverse central gaps, the volume of rubber material worn through abrasion in the central portion is larger, which helps extend its service life in terms of wear resistance. Furthermore, the rubber material in the central portion has a large contact area with the ground, which reduces contact pressure on the ground, thereby reducing abrasion and wear. The presence of slits facilitates the flattening of the central row blocks in the circumferential direction, which firstly restricts the sliding of the blocks on the ground, thus limiting wear, and secondly restricts the deformation of the rubber material, thus limiting energy dissipation and reducing rolling resistance. In addition, the closure of the transverse central gaps in the ground contact area leads to the compactness of the central row blocks, i.e., the blocks are in contact with each other, thereby reducing the deformation of the central blocks due to Poisson's effect and shear stress. The result is reduced energy dissipation of the rubber material in the central row blocks, thus reducing rolling resistance.

[0032] In addition, when used in the field, limiting contact pressure (the contact pressure is greatest at the center of the tread) can prevent severe soil compaction, thus helping to protect the soil.

[0033] According to a second fundamental feature of the invention, the average circumferential slenderness ratio of each block in the central row is at least equal to 0.95 and at most equal to 1.15.

[0034] For centering blocks, the optimal trade-off between circumferential flattening for wear and rolling resistance and the level of slip achieved at the contact surface during braking on wet surfaces is considered to be a circumferential slenderness ratio close to 1.

[0035] According to a third fundamental feature of the invention, each block of each intermediate row includes a leading edge surface in the circumferential direction of tire rolling, the leading edge surface forming an average angle of at least 30° with the radial direction of the tire.

[0036] The average angle of the leading edge face of the intermediate block is at least 30°, which gives the intermediate block a large material volume and high circumferential stiffness. The large material volume ensures a satisfactory service life in terms of wear. The high circumferential stiffness restricts the slippage of the intermediate block in the contact area, thereby reducing wear and thus reducing friction. Furthermore, the circumferential deformation of the intermediate block is also limited due to the Poisson effect and shear stress. As a result, energy dissipation of the rubber material in the intermediate block is reduced, thereby lowering rolling resistance.

[0037] When used in the field, the average angle of the leading edge of the middle row of blocks should be at least 30°. This larger angle increases the cohesion of the soil in front of and below the blocks, thus allowing for greater traction.

[0038] According to the fourth fundamental feature of the invention, the average circumferential elongation ratio of each block in each side row is at most equal to 0.9.

[0039] Compared to the near-1 circumferential slenderness ratio of existing blocky tires, increasing the circumferential length of the blocks reduces the average circumferential slenderness ratio of each block in each side row, resulting in a larger volume of wear material (beneficial for wear) and higher circumferential stiffness. The larger material volume ensures a satisfactory service life in terms of wear. Higher circumferential stiffness limits slippage of the middle row blocks in the contact patch, thus reducing wear and abrasion. Furthermore, circumferential deformation of the middle row blocks is also limited due to the Poisson effect and shear stress. This results in reduced energy dissipation of the rubber material in the middle row blocks, thereby reducing rolling resistance.

[0040] Preferably, the axial width of the center row is at least 15% and at most 25% of the axial width of the tread.

[0041] The axial width of the center row must be large enough to significantly improve the technical advantages in terms of wear and rolling resistance during road use, but it cannot be too large so as to properly ensure field traction function.

[0042] Advantageously, the local volumetric porosity of the central row is at most 20%.

[0043] The proportion of tire voids is typically quantified by the total volumetric void ratio, defined as the ratio between the void volume and the total tread volume assuming no voids. This total volume corresponds to the geometric volume defined by the bearing surface and the tread surface. The total volumetric void ratio is also known as the total volumetric cut ratio. Because the tread surface varies depending on the degree of tread wear, the total volumetric void ratio typically (but not necessarily) varies with the degree of wear. Therefore, the total volumetric void ratio can be defined for a brand-new tire or a tire in a given wear condition. For example, tires used as driven wheels for agricultural tractors typically have a total volumetric void ratio of at least 50% and at least 60% when brand-new. In the following text, the term "total volumetric void ratio" implies "the total volumetric void ratio of the tire when it is brand-new."

[0044] Local volumetric porosity can also be defined for any tread portion extending circumferentially along the entire circumference of the tire and axially extending from a first circumferential plane to a second circumferential plane. The distance between these two circumferential planes defines the axial width of said tread portion, more simply referred to as the width. Local volumetric porosity is defined as the ratio between the void volume and the total volume of the tread portion assuming no voids, corresponding to the geometric volume defined by the bearing surface, the tread surface, and the two circumferential planes. Local volumetric porosity is also known as local volumetric cut ratio. Similar to total volumetric porosity, local volumetric porosity can be defined for tires that are brand new or in a given wear condition. In the following text, the expression "local volumetric porosity" implies "local volumetric porosity when the tire is brand new."

[0045] The local volumetric porosity of the center row is at most 20%, which ensures a significant and beneficial effect on performance in terms of wear and rolling resistance during road use.

[0046] Advantageously, each transverse gap separating the two continuous blocks in the central row forms an angle of at least 70° with the circumferential direction.

[0047] An angle as close as possible to the axial direction of the transverse gap (i.e., as close as possible to 90°) is beneficial for circumferential flattening of the center row. The inventors have discovered that an angle value of 70° is the minimum value for this flattening effect.

[0048] Further advantageously, the depth of each lateral gap separating the two continuous blocks in the central row is at least equal to 50% of the average radial height of the blocks, preferably at least equal to 70%.

[0049] When the depth of the lateral clearance in the center row is less than 50% of the average radial height of the block, it is insufficient to guarantee the hinge effect that allows the center row to flatten out circumferentially, which has a significant impact on rolling resistance.

[0050] According to a particularly advantageous implementation, each lateral gap separating the two continuous blocks in the central row extends radially inward through the cavity.

[0051] The bottom of the transverse void contains a cavity that is typically spherical, which reduces the risk of cracking starting from the bottom of the void by avoiding stress concentration. Furthermore, at the end of its service life, when the wear level reaches the bottom of the void, two interlocking edges form, which helps maintain minimal adhesion on wet surfaces.

[0052] Advantageously, the axial width of each intermediate row is at least 15% and at most 25% of the axial width of the tread.

[0053] This range of axial width values ​​for each intermediate row ensures effective traction for most of the tire tread in the field.

[0054] Further advantageously, the local volumetric porosity of each intermediate row is at least 40%, preferably at least 55%.

[0055] For effective traction in the field, the local volumetric porosity of the middle row must reach a minimum of 40%.

[0056] Furthermore advantageously, the average circumferential elongation of each block in each intermediate row is at least equal to 0.5 and at most equal to 1.

[0057] The average circumferential slenderness ratio of each block in the middle row is in the range of [0.5; 1], which, combined with the average angle of the leading edge face of the block being at least 30°, results in optimal circumferential stiffness of the block relative to the trade-off between road performance and field traction in terms of wear and rolling resistance.

[0058] Preferably, each block in the middle row includes a leading edge face that forms an average angle of at least 35° with the radial direction of the tire.

[0059] When used in the field, the larger the average angle of the leading edge of the middle row of blocks, the greater the cohesion of the soil in front of and below the blocks, which generates greater traction in the field.

[0060] Advantageously, the axial width of each side row is at least 15% and at most 25% of the axial width of the tread.

[0061] Further advantageously, the local volumetric porosity of each side row is at least 40%, preferably at least 55%.

[0062] The combination of the side rows and the middle rows, with axial width and local volumetric porosity within the aforementioned defined range, constitutes a local bump system that is effective for field traction.

[0063] Advantageously, the average circumferential slenderness ratio of each block in each side row is at most equal to 0.8.

[0064] Advantageously, the average circumferential slenderness ratio of each block in each side row is at least equal to 0.6.

[0065] The average circumferential slenderness ratio of each block in the side row ranges from [0.6; 0.8], which makes the circumferential stiffness of the block optimal relative to the trade-off between road performance in terms of wear and rolling resistance and field performance in terms of traction and soil removal.

[0066] Further advantageously, each block of the side row includes a leading edge surface that forms an average angle of at least 10° and at most 30° with respect to the radial direction of the tire.

[0067] If the average angle of the leading edge exceeds 30°, the width of the lateral gap separating the two continuous blocks of the side row becomes too small to guarantee sufficient traction and soil removal capacity. To compensate for the risk of field traction loss, the reduction in the width of the lateral gap can be partially compensated for by any increase in the depth of the lateral gap.

[0068] According to a specific implementation, each block of the sidewall includes a leading edge and a trailing edge, which form an average angle with the radial direction of the tire that is of equal absolute value. Therefore, this configuration means that the slopes of the leading and trailing edges of the sidewall are symmetrical.

[0069] Preferably, each middle row and side row comprises at least 26 blocks.

[0070] More preferably, each middle row and side row includes up to 32 blocks.

[0071] For each side row or middle row, the choice of the number of circumferentially distributed blocks is the result of a trade-off between road wear (which depends on the volume of wear material and the area of ​​material in contact with the ground) and road noise and vibration comfort (which depends especially on the distance between two consecutive blocks in the same row). Attached Figure Description

[0072] With the help of the following description Figures 1 to 6 To better understand the present invention:

[0073] - Figure 1 A perspective view of a tire according to the present invention is shown.

[0074] - Figure 2 A front view of a tire according to the present invention is shown.

[0075] - Figure 3A meridional cross-sectional view of the tread of a tire according to the present invention is shown.

[0076] - Figure 4 The diagram shows a circumferential cross-sectional view of the center row portion of the tread of a tire according to the present invention.

[0077] - Figure 5 The diagram shows a circumferential cross-sectional view of the middle row portion of the tread of a tire according to the present invention.

[0078] - Figure 6 The diagram shows a circumferential cross-sectional view of the side row portion of the tread of a tire according to the present invention. Detailed Implementation

[0079] Figure 1 This is a perspective view of a tire according to the present invention. The tire 1 for agricultural vehicles includes a tread 2 composed of pairs of blocks (31, 32, 33), which are separated by gaps (41, 42, 43, 51, 52) and arranged in a center row 21, two intermediate rows 22, and two side rows 23 across the width of the tread 2. The gaps (41, 42, 43, 51, 52) are either lateral gaps (41, 42, 43) or circumferential gaps (51, 52).

[0080] Figure 2This is a front view of a tire according to the present invention; the tire 1 for agricultural vehicles, in its unloaded and inflated state, has a diameter D and includes a tread 2, the tread 2 having an axial width L in the axial direction YY' and being composed of pairs of blocks (31, 32, 33), the blocks (31, 32, 33) being separated by gaps (41, 42, 43, 51, 52) and arranged in a center row 21, two intermediate rows 22 and two side rows 23 across the width of the tread 2. The gaps (41, 42, 43, 51, 52) are lateral gaps (41, 42, 43) forming an angle of at least 60° with the circumferential direction XX' of the tire 1, or circumferential gaps (51, 52) forming an angle of at most 30° with the circumferential direction XX'. The center row 21, having an axial width L1, is centered on the circumferential midplane E of the tire. Two intermediate rows 22 (each with an axial width L2) are axially located on either side of the central row 21 and separated by circumferential gaps 51, each circumferential gap 51 having a width E2. Two side rows 23 (each with an axial width L3) are axially located outside the intermediate rows 22 and separated by circumferential gaps 52, each circumferential gap having a width E3. The central row 21, intermediate rows 22, and side rows 23 are each composed of circumferentially distributed pairs of blocks (31, 32, 33), which are separated by transverse gaps (41, 42, 43) and each have an average circumferential length (B1, B2, B3). The circumferential length B1 of the block 31 of the central row 21 is the circumferential distance measured between the two cut-type transverse gaps 41 defining the block 31. The circumferential length B2 of block 32 in the middle row 22 is the average circumferential distance measured between the leading edge surface 321 and the trailing edge surface 322 of block 32. The circumferential length B3 of block 33 in the side row 23 is the average circumferential distance measured between the leading edge surface 331 and the trailing edge surface 332 of block 33. Block 33 of the same side row 23 extends axially outward in the extension of block 32 in the adjacent middle row 22, such that any pair of blocks (33, 32) in the side row 23 and the middle row 22 respectively form a protrusion in each other's extension.

[0081] Figure 3 A meridional section of the tread of a tire according to the present invention is shown. The tread has an axial width L and is divided into a center row 21 with an axial width L1, two intermediate rows 22 with an axial width L2, and two side rows 23 with an axial width L3. Each intermediate row 22 is separated from the center row 21 by a circumferential gap 51 of width E2 and depth P2, and is separated from the nearest side row 23 by a circumferential gap 52 of width E3 and depth P3.

[0082] Figure 4A circumferential cross-section of a portion of the center row 21 of the tire tread according to the present invention is shown in the plane XZ. The center row 21 is composed of circumferentially distributed blocks 31, each block having a circumferential length B1 and a height H1. The blocks 31 are separated in pairs by lateral cut-type gaps 41 with a width E1. According to the present invention, two consecutive blocks 31 of the center row 21 are separated by lateral gaps 41 with a width E1 of at most 2.5 mm. In the illustrated embodiment, lateral cuts 41 with a depth of H1 alternate with lateral cuts 41 with a depth less than H1. Because some lateral cuts are shallow, tire production is facilitated by reducing the force required to remove the tire from the mold after curing.

[0083] Figure 5 A circumferential cross-section of a portion of the intermediate row 22 of the tire tread according to the invention is shown in the plane XZ. The intermediate row 22 is composed of circumferentially distributed blocks 32, each block 32 having a circumferential length B2 (an average distance measured between a leading edge surface 321 and a trailing edge surface 322) and a height H2. The blocks 32 are spaced apart in pairs by lateral groove-type gaps 42. According to the invention, each block 32 of each intermediate row 22 includes a leading edge surface 321 and a trailing edge surface 322 in the circumferential direction of tire rolling, the leading edge surface 321 forming an average angle D2 of at least 30° with the radial direction ZZ' of the tire, and the trailing edge surface 322 forming an average angle D'2 with the radial direction ZZ' of the tire.

[0084] Figure 6 A portion of the sidewall row 23 of the tire tread according to the invention is shown in a circumferential cross section on the plane XZ. The sidewall row 23 is composed of circumferentially distributed blocks 33, each block 33 having a circumferential length B3 (the average distance measured between the leading edge surface 331 and the trailing edge surface 332) and a height H3. The blocks 33 are spaced in pairs by lateral groove-type gaps 43. According to the invention, the average circumferential aspect ratio of each block 33 of each sidewall row 23 is at most equal to 0.9. Furthermore, each block 33 of each sidewall row 23 includes a leading edge surface 331 and a trailing edge surface 332 in the circumferential direction of tire rolling, the leading edge surface 331 forming an average angle D3 with the radial direction ZZ' of the tire at least equal to 10° and at most equal to 30°, and the trailing edge surface 332 forming an average angle D'3 with the radial direction ZZ' of the tire.

[0085] This invention specifically addresses agricultural tires with a size of 600 / 70R 30.

[0086] Table 1 below lists the following: Figures 1 to 6 The technical features of the preferred exemplary embodiments of the present invention are shown.

[0087] Table 1

[0088]

[0089]

[0090]

[0091] The inventors compared the performance level of the tire according to the invention with that of the reference tire 600 / 70R 30 Michelin MACHXBIB through digital simulation and / or internal testing. For a tire bearing a load Z = 3801 kg, inflated to a pressure P = 1.8 bar, and traveling at a speed V = 15 km / h, the rolling resistance during road use decreased from 14.8 kg / t of the reference tire to 11.6 kg / t of the tire according to the invention, a reduction of 21%. The tire according to the invention has a 20% longer service life in terms of wear (defined as the number of miles traveled on the road before the tire is completely worn out) than the reference tire.

Claims

1. A tire (1) for an agricultural vehicle, the tire (1) comprising a tread (2) having an axial width (L) and consisting of pairs of blocks (31, 32, 33) separated by gaps (41, 42, 43, 51, 52) and arranged in a center row (21), two intermediate rows (22) and two side rows (23) across the width of the tread (2). - The gaps (41, 42, 43, 51, 52) are lateral gaps (41, 42, 43) that form an angle of at least 60° with the circumferential direction (XX') of the tire (1), or circumferential gaps (51, 52) that form an angle of at most 30° with the circumferential direction (XX'). - The center row (21) is centered on the circumferential midplane (E) of the tire. The two intermediate rows (22) are located on both sides of the center row (21) in the axial direction and are separated by a circumferential gap (51). The two side rows (23) are located on the outside of the intermediate rows (22) in the axial direction and are separated by a circumferential gap (52). - The central row (21), the middle row (22), and the side row (23) each include circumferentially distributed pairs of blocks (31, 32, 33), which are separated by transverse gaps (41, 42, 43) and each have an average radial height (H1, H2, H3), an average circumferential length (B1, B2, B3), and an average circumferential slenderness ratio, wherein the average circumferential slenderness ratio is defined as the ratio between the average radial height and the average circumferential length of the block. - The blocks (33) of the same side row (23) extend outward along the axial direction in the extension of the blocks (32) of the adjacent middle row (22), such that any pair of blocks (33, 32) of the side row (23) and the middle row (22) respectively form protrusions in each other's extensions. Its features are, Two consecutive blocks (31) in the center row (21) are separated by a lateral gap (41) of width (E1) of at most 2.5 mm. The average circumferential slenderness ratio of any block (31) in the center row (21) is at least 0.95 and at most 1.

15. Each block (32) in each intermediate row (22) includes a leading edge face (321) in the circumferential direction of tire rolling. The leading edge face (321) of each block (32) in the intermediate row (22) forms an average angle (D2) of at least 30° with the radial direction (ZZ') of the tire. The average circumferential slenderness ratio of any block (33) in each side row (23) is at most 0.

9.

2. The tire (1) according to claim 1, wherein, The axial width (L1) of the center row (21) is at least 15% and at most 25% of the axial width (L) of the tread (2).

3. The tire (1) according to claim 1 or 2, wherein, The local volume void ratio of the center row (21) is at most equal to 20%, which is defined as the ratio between the void volume and the total volume of the tread portion assuming no voids, the total volume corresponding to the geometric volume defined by the support surface, the tread surface, and the two circumferential planes.

4. The tire (1) according to claim 1, wherein, Each transverse gap (41) of the two consecutive blocks (31) separating the central row (21) forms an angle of at least 70° with the circumferential direction (XX').

5. The tire (1) according to claim 1, wherein, The depth (P1) of each transverse gap (41) between the two consecutive blocks (31) separating the central row (21) is at least 50% of the average radial height (H1) of the block (31).

6. The tire (1) according to claim 1, wherein, Each transverse gap (41) of the two continuous blocks (31) separating the central row (21) extends radially inward through the cavity (411).

7. The tire (1) according to claim 1, wherein, The axial width (L2) of each intermediate row (22) is at least 15% and at most 25% of the axial width (L) of the tread (2).

8. The tire (1) according to claim 1, wherein, The local volume void ratio of each intermediate row (22) is at least 40%, which is defined as the ratio between the void volume and the total volume of the tread portion assuming no voids, the total volume corresponding to the geometric volume defined by the support surface, the tread surface, and the two circumferential planes.

9. The tire (1) according to claim 1, wherein, The average circumferential slenderness ratio of each block (32) in each intermediate row (22) is at least equal to 0.5 and at most equal to 1.

0.

10. The tire (1) according to claim 1, wherein, Each block (32) of the intermediate row (22) includes a leading edge surface (321) that forms an average angle (D2) of at least 35° with the radial direction (ZZ') of the tire.

11. The tire (1) according to claim 1, wherein, The axial width (L3) of each side row (23) is at least 15% and at most 25% of the axial width (L) of the tread (2).

12. The tire (1) according to claim 1, wherein, The local volume void ratio of each side row (23) is at least 40%, which is defined as the ratio between the void volume and the total volume of the tread portion assuming no voids, the total volume corresponding to the geometric volume defined by the support surface, the tread surface, and the two circumferential planes.

13. The tire (1) according to claim 1, wherein, The average circumferential slenderness ratio of each block (33) in each side row (23) is at most equal to 0.

8.

14. The tire (1) according to claim 1, wherein, The average circumferential slenderness ratio of each block (33) of each side row (23) is at least equal to 0.

6.

15. The tire (1) according to claim 1, wherein, Each block (33) of the side row (23) includes a leading edge surface (331) that forms an average angle (D3) with the radial direction (ZZ') of the tire at least equal to 10° and at most equal to 30°.

16. The tire (1) according to claim 1, wherein, Each block (33) of the side row (23) includes a leading edge surface (331) and a trailing edge surface (332), the leading edge surface (331) and the trailing edge surface (332) of each block (33) of the side row (23) forming an average angle (D3, D'3) with the radial direction (ZZ') of the tire with an absolute value equal.

17. The tire (1) according to claim 1, wherein, Each of the circumferentially distributed blocks (31, 32, 33) in the middle row (22) and side row (23) comprises at least 26 blocks.

18. The tire (1) according to claim 1, wherein, Each circumferentially distributed block (31, 32, 33) of the middle row (22) and side row (23) comprises up to 32 blocks.

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