Tire tread for heavy vehicle with improved resistance to attacks
By introducing an eccentric sipe bridge structure into the tread design of heavy vehicle tires, the wear problem caused by stones moving in the gaps is solved, thus improving the tire's durability and service life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- MICHELIN & CO (CIE GEN DES ESTAB MICHELIN)
- Filing Date
- 2021-06-07
- Publication Date
- 2026-07-21
AI Technical Summary
When existing heavy vehicle tires travel on hard surfaces, stones can easily get stuck in the gaps and move around, causing tread wear and reducing tire durability and lifespan.
Design a gap in a bridge structure with an eccentric sipe, including a groove and a sipe, the sipe being eccentrically directed to the bottom of the groove to reduce the probability of stone movement, and to reduce stone retention by introducing eccentricity into the gap.
It effectively reduces the risk of stones moving in the gaps, improves the durability and service life of the tire crown, and extends the overall life of the tire.
Smart Images
Figure CN115702083B_ABST
Abstract
Description
Technical Field
[0001] The subject of this invention is a tire tread for heavy-duty vehicles intended for mixed use (i.e., capable of traveling on paved or stony surfaces). Background Technology
[0002] The tread, located on the circumference of the tire and made of at least one rubber-based material, is designed to wear through contact with the ground via its surface. It typically includes a tread pattern, which is a system of gaps separating raised elements and is designed to provide the tire with grip on hard surfaces, loose surfaces, or surfaces that may be covered with water, snow, or mud.
[0003] In geometric terms, the tread can be defined by three dimensions: the thickness in the radial direction, the width in the lateral direction, and the length in the longitudinal direction.
[0004] These geometric features of the tread are measured on the tire as follows:
[0005] -Thickness is the radial distance between the tread surface and the bottom surface, which is substantially parallel to the tread surface and extends through the bottom of the deepest void.
[0006] - Width is the lateral distance between the endpoints of the tread surface when it is in contact with a hard ground under the pressure and load conditions specified by standards such as the European Tire and Rim Technology Organization (ETRTO) or ETRTO.
[0007] - The length is equal to the outer circumference of the tire.
[0008] When a tire is driven on the ground, the tread is subjected to wear loads caused by indentations on the ground. This wear leads to a gradual reduction in tread thickness. Furthermore, tread gaps can easily trap stones present on the ground. These stones may be expelled during driving or move towards the bottom of the gaps, creating cracks. These cracks can easily propagate from the bottom of the gaps to the tread and eventually to the tire's crown reinforcement. These cracks can eventually lead to crown deterioration, reducing tire durability and lifespan, thus requiring earlier replacement.
[0009] Tread clearances can be categorized into two types: grooves and sipes. Grooves define raised elements that can deform but do not come into contact with each other as the tread engages the contact patch with the ground. Sipes, narrower than grooves, have a width such that when the tread engages the contact patch, the opposing walls of the raised elements defining the sipes at least partially come into contact with each other. To determine the likelihood or impossibility of contact between the walls of a clearance, pressure and load conditions applied to the tire are, for example, those specified in ETRTO standards. Grooves are the widest clearances and are most likely to retain the largest stones that can easily move and attack the tread.
[0010] To reduce the impact of stone retention and movement in the tread gaps (especially grooves), tire designers have installed rubber protrusions (called bridges) at the bottom of the gaps. Thus, a bridge installed in the gap connects two protruding elements defining the gap and thereby locally reinforces the protruding elements, especially when subjected to shear stress perpendicular to the average direction of the gap. The bridge can be continuous or discontinuous along the average direction of the gap where the bridge is installed, or in a direction perpendicular to that average direction. It can also have a height greater than or less than the depth of the gap.
[0011] Introducing discontinuities in the bridge in the form of at least one sipe extending along the average direction of the gap in which the bridge is located ensures the flexibility of the bridge and thus the flexible connection between the protruding elements, which particularly helps to limit wear on the protruding elements. A first type of known discontinuous bridge comprises a single sipe leading to the gap and located at the center of the bridge, approximately equidistant from each protruding element. In this first type of bridge, it is noted that the presence of the sipe at the center of the bridge may reduce the bridge's protective performance against the bottom of the gap because stones can easily move into it. A second type of known discontinuous bridge comprises two sipes leading to the gap, each located at the junction between the bridge and one of the two protruding elements. Due to the presence of sipes at each end, a disadvantage of this second type of bridge is that it cannot connect the two adjacent protruding elements, thus failing to effectively function as a bridge.
[0012] The presence of sipes in the axle means that the gap has a stepped structure, which includes a first radially outer wide gap of the groove type leading to the tread surface and a second radially inner narrow gap of the sipe type leading to the groove. Summary of the Invention
[0013] The inventors set a goal for themselves to improve the durability of the tread of tires used on heavy vehicles by reducing the risk of stones lodged in the gaps moving while the tire is in motion. The tire includes a tread with recesses having bridges with sipes.
[0014] The objective has been achieved by the tread of a tire for heavy vehicles, the tread being designed to contact the ground via its surface and including gaps defined by raised elements relative to the bottom surface and extending over a specific length.
[0015] - At least one void includes, over at least a portion of its length, a first radially outer void portion leading to the tread surface and a second radially inner void portion leading to the first void portion.
[0016] - The first gap is a groove having a width W11 and a depth H1. The width W11 is measured on the tread surface perpendicular to the average surface of the groove, and the depth H1 is measured from the tread surface perpendicular to the bottom of the groove having a width W12.
[0017] - The second gap is a cutting groove, which has a width W2 and a depth H2. The width W2 is measured perpendicular to the average surface of the cutting groove, and the depth H2 is measured perpendicular to the bottom of the groove.
[0018] - The cutting groove extends to the bottom of the trench at a distance E, which is measured between the average surface of the trench and the average surface of the cutting groove.
[0019] - The distance E from the cutter groove to the bottom of the trench is at least equal to the width W12 of the bottom of the trench divided by 6.
[0020] Basically, according to the invention, when the tread of a tire for a heavy vehicle includes a gap having a bottom with a bridge having sipes (i.e., a bridge having a single sipe extending in the average direction of the gap), the sipes extend eccentrically toward the radially outer surface of the bridge relative to the average surface of the gap. This eccentricity is defined by a distance E between the intersection of the planar surface of the gap and the intersection of the average surface of the sipe with the radially outer surface of the bridge, the surface corresponding to the bottom of a first gap portion of the groove type located radially outside the bridge. According to the invention, the distance E is at least equal to the width W12 of the groove bottom divided by 6, meaning the sipe extends to the outer side of the central third of the bridge.
[0021] In other words, the clearance of a bridge with sipes can be described as a stepped clearance, comprising a first radially outer clearance portion of the groove type and a second radially inner clearance portion of the sipe type. The first radially outer clearance portion is defined by two protruding elements and extends to the tread surface, while the second radially inner clearance portion at least partially passes through the bridge and extends to the first clearance portion on the radially outer surface of the bridge. The total depth of the stepped clearance is the radial distance between the tread surface and the bottom of the clearance.
[0022] The first radially outer void is a groove, the walls of which do not contact each other when the tread enters the contact patch with the ground. It extends along an average surface substantially perpendicular to the tread surface. The first void has a width W11 on the tread surface and a width W12 at its bottom, the widths W11 and W12 being measured perpendicular to the average surface and between the opposing walls of the protruding element defining the groove, respectively. The first void has a depth H1, measured perpendicularly from the tread surface to the bottom of the groove. In other words, the depth H is the maximum radial distance between the tread surface and the bottom of the groove.
[0023] The second radial internal clearance is a sipe, the walls of which are at least partially in contact with each other as the tread enters the contact patch with the ground. It extends along an average surface, which may be inclined relative to the bottom of the groove and therefore not necessarily vertical. The second clearance has a width W2 and a depth H2, the width W2 being measured perpendicularly to the average surface of the sipe between the walls of the sipe, and the depth H2 being measured perpendicularly to the bottom of the sipe from the bottom of the groove. In other words, the depth H2 is the radial distance between the bottom of the groove and the bottom of the sipe. The width W2 of the sipe is substantially constant over the entire depth H2 and can therefore be measured at any radial level between the bottom of the groove and the bottom of the sipe.
[0024] Therefore, the distance E from the cutter groove to the bottom of the groove is the distance between the intersection of the average surface of the groove and the bottom of the groove and the intersection of the average surface of the cutter groove and the bottom of the groove.
[0025] The advantage of this eccentric sipe in the tire groove is that it reduces the probability of a captured stone moving out of the groove, because the stone's initial path along the groove's axis is deflected by the eccentricity of the sipe. Therefore, the probability of a stone moving into the sipe is reduced, and the stone may be blocked in the groove or even expelled from the gap. Consequently, the risk of impact to the radially inner tread reinforcement is reduced, and its durability is improved, thus extending tire life.
[0026] Advantageously, the distance E is at most equal to half the width W12 of the groove bottom. The greater the distance E, the more the stone's path deflects, meaning the risk of the stone moving into the groove is reduced. When the distance E is equal to half the width W12 of the groove bottom, the groove leads to the bottom of one of the two protruding elements defining the groove, which is the extreme position of the groove's open end.
[0027] Preferably, the width W11 of the groove is at least equal to the width W12 of the groove bottom. This condition means that the groove walls are not radial, and in a radial plane perpendicular to the average direction of the groove, the groove has a trapezoidal cross-section, the larger base of which extends to the tread surface, and the smaller base of which forms the bottom of the groove. This trapezoidal cross-section helps to expel stones during tire travel by forming a discharge cone, and also facilitates tire manufacturing, particularly the removal of voids from the mold after the tire has cured.
[0028] Preferably, the width W11 of the trench is at least 4 mm. Below this value, the trench no longer serves as a channel that cannot contact itself, and there is no longer a risk of stones being retained and thus moved.
[0029] Furthermore, the ratio W11 / W12 must be limited, typically to a maximum of 3. This condition limits the inclination angle of the groove walls and thus the volume of the groove, which, relative to the protruding elements defining the groove, ensures sufficient volume of wear-prone material to give the tread good wear performance.
[0030] The groove depth H1 is advantageously at least 0.5 times the kerf depth H2. In other words, the groove depth H1 is at least one-third of the total depth H of the clearance, which is defined as the sum of the groove depth H1 and the kerf depth H2. This is within the typical design range and ensures sufficient groove volume for grip.
[0031] The groove depth H1 is more advantageously at most twice the kerf depth H2. In other words, the groove depth H1 is at most two-thirds of the total depth H of the void, which is defined as the sum of the groove depth H1 and the kerf depth H2. This is within the typical design range and ensures sufficient bridge height in protecting the bottom of the void.
[0032] Preferably, the width W2 of the cutting groove is at most 2 mm. If it is higher than this value, the cutting groove no longer functions as a cutting groove because its walls can no longer contact each other.
[0033] Preferably, the width W2 of the groove is at least 0.4 mm. The value of 0.4 mm is the technical minimum for manufacturing; below this value, problems will occur when producing groove inserts for molding grooves.
[0034] Advantageously, the average surface of the sipe forms an angle D of at most 15° relative to the radial direction perpendicular to the tread surface. Given that the preferred direction of stone movement is known to be radial, the angle of the average surface of the sipe can slow the stone's movement into it. Furthermore, assigning this upper limit of 15° to the angle significantly facilitates radial removal from the mold when the tire has finished curing.
[0035] The bottom of the groove advantageously has a circular profile, the minimum radius R of which is at least 1.5 times the width W2 of the groove. This circular shape at the bottom of the groove (often referred to by designers as a "droplet") is a crack-prevention device that delays cracking at the bottom of the groove by reducing localized stress.
[0036] According to a specific embodiment, the average surface of the groove forms an angle of at most 45° with respect to the longitudinal direction. In other words, the groove (and the stepped gaps that form the first radially outer portion) are substantially longitudinal, i.e., longitudinal or inclined with an average surface having an angle of less than or equal to 45° with respect to the longitudinal direction. This is because such longitudinal or inclined gaps are more likely to trap stones due to their orientation, which is substantially parallel to the tire's direction of travel; therefore, the bridge according to the invention has an advantage in this type of gap.
[0037] According to the preferred variant of the substantially longitudinally spaced gap defined above, the gap is continuous over the entire length of the tread. Therefore, the substantially longitudinally spaced gap, including the bridge according to the invention, over the entire length of the tread, effectively protects against stone trapping throughout the entire circumference of the tire.
[0038] According to another particular embodiment, the average surface of the trench forms an angle of at most 45° with respect to the transverse direction. In other words, the trench (and the stepped gaps that form the first radial outer portion) are substantially transverse, that is, transverse or their average surface is inclined with an angle of less than or equal to 45° with respect to the transverse direction.
[0039] According to the preferred variant of the substantially lateral voids defined above, the voids are located in the middle portion of the tread, the width of which is preferably equal to the width of the tread divided by 3. Conventionally, since lateral voids are voids where the average surface forms an angle of at most 45° with the lateral direction, they are closer to the lateral direction than the longitudinal direction of travel, making it particularly difficult to expel stones from them. Therefore, when the tread includes lateral voids in its middle portion (which is typically defined as the central third of the tread), it is particularly advantageous that these voids are protected by the sipes-equipped bridges according to the invention, as this tread portion is subjected to high contact pressure, which facilitates the possible collection of stones present in the tire-ground contact area.
[0040] Another subject of the present invention is a tire for heavy-duty vehicles, the tire comprising the tread described in any of the above embodiments. Attached Figure Description
[0041] The following illustrations are not drawn to scale. Figures 1 to 3 The features of the present invention are described in the following:
[0042] - Figure 1 : A view of the radial section of the stepped void according to the present invention.
[0043] - Figure 2 : A perspective view of an exemplary portion of the tread according to the present invention.
[0044] - Figure 3 : Figure 2 The diagram shows a radial cross-sectional view of an exemplary portion of the tread according to the invention, representing a stepped gap. Detailed Implementation
[0045] Figure 1 This is a view of a radial section of the stepped gap according to the invention. The radial section is formed by a plane defined by a radial direction zz' and a direction yy' perpendicular to the average direction xx' of the gap. The gap 3 of the tread 1 of a tire for heavy vehicles (the tread is intended to contact the ground through the tread surface 2) is defined by a protruding element 4 relative to the bottom surface 5 and extends over a certain length. The gap 3 includes, over at least a portion of its length, a first radially outer gap portion 31 leading to the tread surface 2 and a second radially inner gap portion 32 leading to the first gap portion 31. The first gap portion 31 is a groove having a width W11 and a depth H1, the width W11 being measured on the tread surface 2 perpendicular to the average surface S1 of the groove 31, and the depth H1 being measured from the tread surface 2 perpendicular to the bottom 311 of the groove having a width W12. The second gap 32 is a groove having a width W2 and a depth H2. The width W2 is measured perpendicularly to the average surface S2 of the groove 32, and the depth H2 is measured perpendicularly from the bottom 311 of the groove to the bottom 321 of the groove. The groove 32 extends to the bottom 311 of the groove at a distance E, which is measured between the average surface S1 of the groove 31 and the average surface S2 of the groove 32. According to the invention, the distance E from the groove 32 to the bottom 311 of the groove is at least equal to the width W12 of the bottom 311 of the groove divided by 6. Figure 1 In the illustrated embodiment, the average surface S2 of the sipe 32 forms an angle D of at most 15° with respect to the radial direction zz' perpendicular to the tread surface 2. Furthermore, the bottom 321 of the sipe has a circular profile, the minimum radius R of which is at least 1.5 times the width W2 of the sipe 32.
[0046] Figure 2 This is a perspective view of an exemplary portion of the tread 1 according to the present invention. The directions shown in the figure are the circumferential direction XX', the lateral direction YY', and the radial direction ZZ' of the tread, respectively. Figure 2A portion of the tread 1 of a tire for heavy-duty vehicles is shown. The tread is designed to contact the ground via a tread surface 2 and includes gaps 3 according to the invention, defined by raised elements 4 relative to a bottom surface 5. At least a portion of the gaps 3 (particularly the substantially longitudinal gaps 3) includes a first radially outer gap portion 31 leading to the tread surface 2 and a second radially inner gap portion 32 leading to the first gap portion 31. The tread 2 also includes substantially transverse gaps 3 arranged in a central portion and two side portions, leading to the substantially longitudinal gaps. Therefore, this tread pattern is a block tread pattern, which is particularly suitable for the drive axles of heavy-duty vehicles.
[0047] Figure 3 for Figure 2 The diagram shows a radial cross-section of an exemplary portion of the stepped void in a tire tread according to the invention. The radial cross-section is formed by a plane defined by a radial direction zz' and a direction yy' perpendicular to the average direction xx' of the void. Figure 2 As shown, directions xx', yy', and zz' define a local reference frame relative to the void under consideration, with the local radial direction zz' corresponding to the radial direction ZZ' of the tread. Figure 2 The features shown are Figure 1 The features shown are the same. In the specific case shown, the groove 32 extends towards the bottom of the groove 311 at a distance E relative to the average surface S1 of the groove 31, said distance E being equal to half the width W12 of the bottom of the groove 311, i.e., at the wall base with the maximum eccentricity. Furthermore, the groove 32 is perpendicular to the bottom of the groove 311, which means that its average surface S2 is parallel to the average surface S1 of the groove 31.
[0048] Figure 2 and Figure 3 The exemplary tread shown is an embodiment studied by the inventors for a mixed-use tire with a tire size of 13R22.5, specifically designed for mounting to a drive axle. According to the ETRTO Standards Manual 2019, this tire is designed to carry a load equal to 4000 kg at an inflation pressure of 8.6 bar.
[0049] Table 1 below shows the characteristics of the tested tread:
[0050] [Table 1]
[0051] characteristic numerical values The width W11 of groove 31 10.4mm The width W12 of groove 31 4mm The height H1 of trench 31 10mm The width W2 of the tool groove 32 0.8mm The height H2 of the tool groove 32 11.2mm The inclination angle D of the tool groove 32 0° Distance E 2mm
[0052] The tread according to the invention (which is developed for conventional tires to withstand inflation pressure) can also be used in non-pneumatic tires, and also in any non-pneumatic rolling assembly that a vehicle is intended to be fitted with.
Claims
1. A tread (1) for a tire of a heavy vehicle, the tread being intended to contact the ground via a tread surface (2) and including a gap (3) defined by a raised element (4) relative to a bottom surface (5) and extending over a specific length, - At least one gap (3) includes, along at least a portion of its length, a first radially outer gap portion (31) leading to the tread surface (2) and a second radially inner gap portion (32) leading to the first radially outer gap portion (31). - The first radially outer void (31) is a groove having a width W11 and a depth H1. The width W11 is measured on the tread surface (2) perpendicular to the average surface (S1) of the groove (31). The depth H1 is measured from the tread surface (2) perpendicular to the bottom (311) of the groove with a width W12 along the radial direction of the tread. The bottom (311) of the groove is a plane. - In a radial plane perpendicular to the average direction of the groove (31), the groove (31) has a trapezoidal cross-section, the larger base of which is the portion leading to the tread surface (2), and the smaller base of which is the bottom of the groove (311). - The second radial internal void (32) is a sipe, the sipe having a width W2 and a depth H2, the width W2 being measured perpendicular to the average surface (S2) of the sipe (32), the depth H2 being measured from the bottom of the groove (311) perpendicular to the bottom of the sipe (321) along the radial direction of the tread, the bottom of the sipe (321) having a circular profile, the minimum radius R of the circular profile being at least equal to 1.5 times the width W2 of the sipe (32). - The opposite walls of the cutter groove (32) are parallel to each other. - The depth H1 of the groove (31) is at least 0.5 times the depth H2 of the cutting groove (32), and at most twice the depth H2 of the cutting groove (32). - The cutting groove (32) extends to the bottom of the trench (311) at a distance E, said distance E being measured between the average surface (S1) of the trench (31) and the average surface (S2) of the cutting groove (32). Its features are, The distance E from the cutter groove (32) to the bottom of the groove (311) is at least equal to the width W12 of the bottom of the groove (311) divided by 6. The average surface (S1) of the groove (31) forms an angle of at most 45° with the lateral direction (YY') of the tread. The width W11 of the groove (31) is at least 4 mm. The width W2 of the tool groove (32) is at most 2 mm, and The width W2 of the groove (32) is at least 0.4 mm.
2. The tread (1) according to claim 1, wherein, The distance E is at most equal to half the width W12 of the bottom (311) of the trench.
3. The tread (1) according to any one of claims 1 and 2, wherein, The width W11 of the trench (31) is at least equal to the width W12 of the bottom of the trench (311).
4. The tread (1) according to claim 1, wherein, The average surface (S2) of the sipe (32) forms an angle D of up to 15° relative to the radial direction (ZZ') perpendicular to the tread surface (2).
5. The tread (1) according to claim 1, wherein, The average surface (S1) of the groove (31) forms an angle of up to 45° with the longitudinal direction (XX') of the tread.
6. The tread (1) according to claim 5, wherein, The gap (3) is continuous along the entire length of the tread.
7. The tread (1) according to claim 1, wherein, The gap (3) is located in the middle part of the tread, and the width of the middle part is equal to the width of the tread divided by 3.
8. A tire for heavy vehicles, said tire comprising a tread (1) according to any one of claims 1 to 7.