EP4251433A1 - Tyre tread for a heavy vehicle with improved resistance to aggressive effects - Google Patents
Tyre tread for a heavy vehicle with improved resistance to aggressive effectsInfo
- Publication number
- EP4251433A1 EP4251433A1 EP21823964.8A EP21823964A EP4251433A1 EP 4251433 A1 EP4251433 A1 EP 4251433A1 EP 21823964 A EP21823964 A EP 21823964A EP 4251433 A1 EP4251433 A1 EP 4251433A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- tread
- height
- equal
- cavity
- external
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000000694 effects Effects 0.000 title abstract description 5
- 238000005096 rolling process Methods 0.000 claims description 12
- 239000004575 stone Substances 0.000 abstract description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 16
- 239000000463 material Substances 0.000 description 10
- 230000002787 reinforcement Effects 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
- B60C11/03—Tread patterns
- B60C11/0306—Patterns comprising block rows or discontinuous ribs
- B60C11/0309—Patterns comprising block rows or discontinuous ribs further characterised by the groove cross-section
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
- B60C11/03—Tread patterns
- B60C11/032—Patterns comprising isolated recesses
- B60C11/0323—Patterns comprising isolated recesses tread comprising channels under the tread surface, e.g. for draining water
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
- B60C11/03—Tread patterns
- B60C11/12—Tread patterns characterised by the use of narrow slits or incisions, e.g. sipes
- B60C11/1236—Tread patterns characterised by the use of narrow slits or incisions, e.g. sipes with special arrangements in the tread pattern
- B60C11/125—Tread patterns characterised by the use of narrow slits or incisions, e.g. sipes with special arrangements in the tread pattern arranged at the groove bottom
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
- B60C11/03—Tread patterns
- B60C11/12—Tread patterns characterised by the use of narrow slits or incisions, e.g. sipes
- B60C11/1272—Width of the sipe
- B60C11/1281—Width of the sipe different within the same sipe, i.e. enlarged width portion at sipe bottom or along its length
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
- B60C11/03—Tread patterns
- B60C11/032—Patterns comprising isolated recesses
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
- B60C11/03—Tread patterns
- B60C2011/0337—Tread patterns characterised by particular design features of the pattern
- B60C2011/0339—Grooves
- B60C2011/0341—Circumferential grooves
- B60C2011/0346—Circumferential grooves with zigzag shape
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
- B60C11/03—Tread patterns
- B60C2011/0337—Tread patterns characterised by particular design features of the pattern
- B60C2011/0339—Grooves
- B60C2011/0341—Circumferential grooves
- B60C2011/0355—Circumferential grooves characterised by depth
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B60C2200/00—Tyres specially adapted for particular applications
- B60C2200/06—Tyres specially adapted for particular applications for heavy duty vehicles
Definitions
- Tire tread for a heavy-duty vehicle having improved resistance to attacks
- the subject of the present invention is a tire tread for a heavy vehicle, more particularly for a mixed-use heavy vehicle, which can be driven both on the road, on tarmacked surfaces, and off the road, on stony ground.
- a tread consisting of at least one rubber-based material, is the wearing part of the tire, located at its periphery and intended to be worn when it comes into contact with the ground by means of a running surface. It most often includes a tread pattern which is a combination of cutouts, or hollows, and elements in relief, of the block type or of the rib type, intended essentially to ensure satisfactory performance in grip, more particularly on wet road surfaces.
- the cutouts allowing the evacuation of water are essentially wide cutouts called grooves.
- a groove has a width such that the walls of material facing it delimiting it do not come into contact with each other, during the passage of the tread in the contact surface, when the tire is subject to recommended inflation and load conditions as defined in particular by the European standards of the "European Tire and Rim Technical Organization” or "ETRT0" in its “Standards Manual 2020 - Commercial Vehicle Tyres”. commercial).
- the compression and shear deformations of the elements in relief delimiting the groove condition the pressures in contact with the ground and therefore the wear.
- these deformations by generating hysteretic losses in the material of the tread, impact the rolling resistance, and therefore the fuel consumption of the vehicle.
- a tread may also comprise narrow cutouts or incisions.
- An incision has a width such that the walls of material facing it delimiting it come into contact at least partially with each other, during the passage of the tread in the contact surface, under the conditions load and tire pressure specified by the E.T.R.T.O and seen previously.
- An incision does not make it possible to evacuate the water, but, vis-à-vis the grip, has an edge effect in the contact with the ground, which makes it possible in particular to break a film of water possibly present on floor.
- Treads comprising such complex cutouts have been described in particular in the documents WO 2011039194, WO 2011101495, WO 2012130735, WO 2016188956, WO 2019008276 and WO 2019122677. regular or not, on the running surface when new.
- Each complex cutout has external cavities, open to the tread surface and disjoint from each other in the main direction of the complex cutout.
- the main direction of the complex cutout generally corresponds to the direction of flow of the water in said cutout when driving on ground covered with water.
- This complex cutout includes, in addition to the external cavities, internal cavities formed inside the tread and generally connected to the running surface through incisions.
- These internal cavities are positioned radially and completely inside the running surface when new, and interposed between the external cavities.
- the internal cavities can be positioned at different levels of depth in the thickness of the strip.
- the continuity of the water flow in each complex cutout, when new, is ensured by connecting portions, generally connecting channels, between two consecutive outer and inner cavities respectively.
- the assembly formed by the external cavities, the internal cavities and the connecting channels thus forms a continuous groove.
- the juxtaposition of internal and external cavities not linked together, and therefore not allowing a flow of fluid from one to the other over the entire circumference of the tire does not constitute a continuous groove.
- the volume of all the internal cavities, the external cavities and the connecting channels is reduced compared to that of grooves that are entirely open on the tread surface when new and having a depth corresponding to the maximum depth of the internal or external cavities.
- the presence of complex cutouts thus makes it possible to limit the reduction in rigidity of the tread when new due to the presence of the grooves.
- a tread pattern can comprise both complex cutouts, emerging on the running surface intermittently, and conventional grooves, emerging on the running surface over their entire length.
- This stone retention phenomenon can be particularly marked in the case of complex cutouts. Indeed these can capture stones at the level of their external cavities, these stones being likely to remain blocked, more particularly, in the connection channels between the respectively external and internal cavities, and therefore to generate damage to the tread.
- the tread in new condition comprising at least one complex cutout comprising, along an average line, an alternation of external cavities, opening onto the rolling surface, and internal cavities, not opening onto the rolling surface, two consecutive external and internal cavities respectively being interconnected by a connecting channel,
- each external cavity having, in an average surface containing the average line and a radial direction perpendicular to the rolling surface, a height, measured, in the radial direction, between the rolling surface and an external cavity bottom, and a length , measured, along the mean line, at the level of the tread surface
- -each internal cavity having, in the mean surface, a height, measured, along the radial direction, between a top of the internal cavity and a bottom of the internal cavity radially interior to the bottom of the external cavity, and a length, measured, along the mean line, at the level of the bottom of the internal cavity
- each connecting channel having, in the middle surface, a height, measured, in the radial direction, between a connecting channel top and a connecting channel bottom, at the circumferential junction between the external cavity and the connecting channel , and a length, measured, along the mean line, between the external cavity and the internal cavity, non-zero, -each complex cut-out having, in the mean surface, a height measured, along the radial direction, between the rolling surface and the bottom of the internal cavity,
- each external cavity being at least equal to half the height of the complex cutout
- the height of each connecting channel being at most equal to one third of the height of the complex cutout
- the subject of the invention is therefore a tread comprising at least one complex cutout formed, along a mean line, by an alternation of external cavities, opening onto the tread surface, and internal cavities, not opening onto the rolling surface, two consecutive outer and inner cavities respectively being interconnected by a connecting channel providing a gradual transition between said outer and inner cavities respectively.
- the middle line of the complex cutout is not necessarily rectilinear, and may have, by way of example, a wavy shape or a zigzag shape. In addition, it can extend in any direction: longitudinal, transverse or oblique.
- the longitudinal direction is the direction of the longest tread dimension or length
- the transverse direction is the direction of the intermediate dimension or tread width
- the radial direction is the direction of the longest. small tread dimension or thickness.
- An oblique direction has an intermediate general orientation between the longitudinal direction and the transverse direction.
- An oblique direction is said to be substantially longitudinal, when it forms an angle at most equal to 45° with the longitudinal direction, and substantially transverse, when it forms an angle at most equal to 45° with the transverse direction.
- the complex cutout forms, in a section along an average surface defined by its average line and a radial direction perpendicular to the running surface, a continuous wavy groove comprising an alternation of external cavities, internal cavities and connecting channels between two consecutive internal and external cavities respectively.
- two consecutive external cavities along the mean line are separated by a single internal cavity and vice versa. Due to the undulation of the complex cutout in the circumferential direction, in the thickness of the tread, the bottom of any internal cavity is radially inside the bottom of an adjacent external cavity.
- the respectively external and internal cavities, as well as the connecting channels, are characterized by their respective geometries defined in the average surface of the complex cutout, namely a height measured along the radial direction, in the thickness of the tread, and a length, measured along the mean line of the complex cutout, between two references depending on the complex cutout portion considered.
- the respective heights can be defined with respect to the height of the complex cutout, measured between the running surface in new condition, on which the external cavities open, and a bottom surface passing through the bottom of the internal cavities, c' that is, the radially innermost points of the complex cutout.
- each external cavity is at least equal to half the height of the complex cutout, which guarantees a sufficient volume of external cavity, necessary for the storage of water on wet ground, when the tread is in new condition.
- the length of any connecting channel is non-zero, which guarantees a gradual transition between the respectively external and internal cavities connected by said connecting channel.
- the essential characteristic of the invention is to limit the height of the connecting channel, measured at the level of the connection of the channel with the external cavity, in other words at the level of its section opening into the external cavity. According to the invention, this height is optimized to prevent the passage of too large stones, that is to say of a size such that they would be likely to cause significant damage to the crown of the tire.
- the inventors have estimated a critical stone size characterized by a diameter greater than one third of the height of the complex cutout, hence a height of the connecting channel at the level of its connection with the external cavity at most equal to one third of the height complex cutting.
- each connecting channel is at least equal to one tenth of the height of the complex cutout. Below this value, the flow of water in the complex cutout becomes insufficient to guarantee sufficient grip of the tread on a wet road surface, due to too great a constriction of the complex cutout at the level of the connecting channel. .
- each external cavity is at most equal to three quarters of the height of the complex cutout.
- This maximum external cavity height guarantees the presence, radially inside the external cavity, of a thickness of rubber-based material sufficient to ensure the protection of the portion crown insert radially positioned inside the tread, directly above the external cavity.
- each connecting channel is at least equal to the height of the connecting channel.
- the connecting channel is effective for blocking stones captured by the external cavity to which it is connected, if it is of sufficient length, i.e. if it provides striction over a sufficient distance.
- each internal cavity is at least equal to one third of the height of the complex cutout.
- This minimum internal cavity height guarantees a sufficient external cavity volume, necessary for the storage of water on wet ground, when the tread reaches a level of wear corresponding to the top of the internal cavity, in other words when the cavity internal in turn opens on the running surface in the worn state.
- each internal cavity is at most equal to three quarters of the height of the complex cutout.
- This maximum internal cavity height guarantees the presence, radially outside the internal cavity, of a thickness of rubber-based material sufficient to ensure, when new, the protection of the crown reinforcement portion. radially positioned inside the tread, directly above the internal cavity.
- the ratio between the internal cavity length and the external cavity length is advantageously at least equal to 0.8. Below this value, the external cavity length becomes excessive and penalizes the volume of material to be worn.
- the ratio between the internal cavity length and the external cavity length is again advantageously at most equal to 1.5, preferably at most equal to 1.2. Above this value, the length of the external cavity becomes insufficient to guarantee good collection of the water present on the ground.
- each internal cavity has an internal cavity top extended radially outwards by an incision as far as the rolling surface, due to a technological constraint for manufacturing the cavities. external by molding from the outside of the tread.
- each external cavity has an external cavity bottom extended radially inwards by at least one incision up to, at most, a bottom surface passing through the internal cavity bottom. .
- the tread wear level reaches the bottom of the external cavity, at least one incision appears which will contribute to grip, particularly on wet ground, by creating a ridge effect making it possible to break the film of water present on the ground.
- the middle line of at least one complex cutout is substantially longitudinal, forming at all points an angle at most equal to 45°, preferably at most equal to 20° , with respect to a longitudinal direction of the tread.
- this mean line is preferably oriented in a longitudinal direction, which is the direction of advancement of the tire and the main direction of flow of the water evacuated in the contact surface with the ground.
- At least one complex cutout having a substantially longitudinal mean line is axially positioned in a median portion of the tread having an axial width at most equal to two-thirds of the axial width of the tread, said middle portion being centered on a median plane passing through the middle of the tread surface and perpendicular to the tread surface.
- the axial width of the tread is the axial distance between the axial ends of the running surface, when the tire is inflated and crushed under the pressure and load conditions recommended by the ETRTO standards.
- - Figure 2 Cross-sectional view, along an average complex cut-out surface, of a complex cut-out portion comprising an external cavity, an internal cavity and a connecting channel connecting them.
- Figure 1 is a top view of a tread 1 according to the invention in new condition.
- the tread 1 of the tire intended to come into contact with the ground via a running surface 2, comprises cutouts 3, delimiting elements in relief 4.
- two grooves can be distinguished substantially longitudinal each delimiting a lateral rib and a middle portion 11, said middle portion 11 having, in a transverse direction YY' of the tread, an axial width Wm at most equal to two thirds of the axial width W of the tread .
- the middle portion 11 further comprises two complex cutouts 5 substantially longitudinal, each separating two longitudinal rows of relief elements 4 of block type two by two separated by incisions.
- Each complex cutout 5 comprises, along an average line Lm, an alternation of external cavities 6, opening onto the running surface 2, and internal cavities 7, not opening onto the running surface 2, two cavities respectively external 6 and internal 7 consecutive being interconnected by a connecting channel 8.
- the internal cavities 7 and the connecting channels 8, not visible in the new state of the tread, are shown in dotted lines.
- the average line Lm of each complex cutout 5 has a substantially longitudinal zigzag shape, with a tangent at any point forming, with a longitudinal direction XX' of the tread, an angle at most equal to 45 °, preferably at most equal to 20°.
- Figure 2 is a sectional view, along an average surface Sm of complex cutout, of a portion of complex cutout 5 comprising an external cavity 6 connected at each of its ends to an internal cavity 7 by a connecting channel 8. Only half a internal cavity 7 is represented at each end of the external cavity 6.
- the external cavity 6 has, in an average surface Sm containing the average line Lm and a radial direction ZZ' perpendicular to the running surface 2 of the tread 1, a height H11, measured, along the radial direction ZZ', between running surface 2 and an external cavity bottom 62, and a length L1, measured, along mean line Lm, at running surface 2.
- Each cavity internal 7 has, in the average surface Sm, a height H22, measured, in the radial direction ZZ', between an internal cavity top 71 and an internal cavity bottom 72 radially inside the external cavity bottom 62, and a length L2 , measured along the mean line Lm, at the level of the bottom of the internal cavity 72.
- FIG. 2 are shown two internal half-cavities 7 of length L2/2.
- Each connecting channel 8 has, in the mean surface Sm, a height H3, measured, along the radial direction ZZ', between a connecting channel top 81 and a connecting channel bottom 82, at the circumferential junction between the cavity external 6 and the connecting channel 8, and a length L3, measured along the mean line Lm, between the external cavity 6 and the internal cavity 7, non-zero.
- the complex cutout 5 has, in the average surface Sm, a height H, measured, along the radial direction ZZ', between the rolling surface 2 and the bottom of the internal cavity 72.
- the height H11 of each external cavity 6 is at least equal to half the height H of the complex cutout 5.
- each connecting channel 8 is at most equal to a third of the height H of the complex cutout 5.
- the external cavity 6 has an external cavity bottom 62 extended radially inwards by an incision 63 up to a bottom surface 10 passing through the internal cavity bottom 72.
- each internal cavity 7 has a top of internal cavity 71 extended radially outwards by an incision 73 up to running surface 2.
- the inventors have more particularly studied this invention for a tire of size 13 R 22.5 intended to equip a steering axle for a mixed-use heavy vehicle and to carry a load equal to 4000 kg with an inflation pressure equal to 8.75 bars, according to the "Standards Manual 2020" of the E.T.R.T.O.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Tires In General (AREA)
Abstract
The present invention relates to a tyre tread (1) for a heavy vehicle and is intended to improve its resistance to aggressive effects resulting from stones. The tread (1), in the new state, comprises at least one complex cut-out (5) comprising, according to a mean line (Lm), an alternating arrangement of external cavities (6) which open at the tread surface (2), and internal cavities (7) which do not open at the tread surface (2), two consecutive cavities, an external one (6) and internal one (7), respectively, which are connected to each other by a connection channel (8) with a non-zero length, the height (H11) of each external cavity (6) being at least equal to half of the height (H) of the complex cut-out (5), the height (H3) of each connection channel (8) being at most equal to one third of the height (H) of the complex cut-out (5).
Description
Bande de roulement de pneumatique pour un véhicule poids lourd ayant une résistance aux agressions améliorée Tire tread for a heavy-duty vehicle having improved resistance to attacks
[0001] La présente invention a pour objet une bande de roulement de pneumatique pour un véhicule poids lourd, plus particulièrement pour un véhicule poids lourd à usage mixte, pouvant rouler à la fois sur route, sur des sols goudronnés, et hors la route, sur des sols pierreux. [0001] The subject of the present invention is a tire tread for a heavy vehicle, more particularly for a mixed-use heavy vehicle, which can be driven both on the road, on tarmacked surfaces, and off the road, on stony ground.
[0002] Une bande de roulement, constituée par au moins un matériau à base de caoutchouc, est la partie usante du pneumatique, située à sa périphérie et destinée à être usée lors de son entrée en contact avec un sol par l’intermédiaire d’une surface de roulement. Elle comprend le plus souvent une sculpture qui est une combinaison de découpures, ou creux, et d’éléments en relief, de type blocs ou de type nervures, destinée essentiellement à assurer une performance satisfaisante en adhérence, plus particulièrement sur une chaussée mouillée. [0002] A tread, consisting of at least one rubber-based material, is the wearing part of the tire, located at its periphery and intended to be worn when it comes into contact with the ground by means of a running surface. It most often includes a tread pattern which is a combination of cutouts, or hollows, and elements in relief, of the block type or of the rib type, intended essentially to ensure satisfactory performance in grip, more particularly on wet road surfaces.
[0003] De façon connue, les conditions de roulage par temps de pluie d’un véhicule, et plus particulièrement celles d’un véhicule poids lourd, requièrent une évacuation rapide de l'eau présente dans la surface de contact entre la bande de roulement et la chaussée. Cette évacuation permet d'assurer un contact direct du matériau constituant la bande de roulement avec cette chaussée par l’intermédiaire de la surface de roulement. L’eau qui n’est pas repoussée vers l’avant ou les côtés du pneumatique s'écoule ou est captée en partie dans les découpures formées dans la bande de roulement. [0003] In known manner, the conditions for driving a vehicle in rainy weather, and more particularly those of a heavy vehicle, require rapid evacuation of the water present in the contact surface between the tread and the pavement. This evacuation makes it possible to ensure direct contact of the material constituting the tread with this roadway via the running surface. Water that is not pushed to the front or the sides of the tire runs off or is partially captured in the cutouts formed in the tread.
[0004] L’évacuation de l’eau est assurée par les découpures qui forment un réseau d’écoulement de fluide qui doit être efficace pendant toute la durée d’utilisation du pneumatique, depuis son état neuf jusqu’à son état d’usure maximal. L’état d’usure maximal, fixé par la réglementation en vigueur, est l’état d’usure à partir duquel le pneumatique doit être retiré du véhicule pour des raisons de sécurité. [0004] The evacuation of water is ensured by the cutouts which form a fluid flow network which must be effective throughout the service life of the tire, from its new condition to its worn condition. maximum. The maximum state of wear, fixed by the regulations in force, is the state of wear from which the tire must be removed from the vehicle for safety reasons.
[0005] Plus précisément, les découpures permettant l’évacuation de l’eau sont essentiellement des découpures larges appelées rainures. Une rainure a une largeur telle que les parois de matière en vis-à-vis la délimitant n’entrent pas en contact l’une avec l’autre, lors du passage de la bande de roulement dans la surface de contact, lorsque le pneumatique est soumis à des conditions de gonflage et de charge recommandées telles que définies
notamment par les normes européennes de la « European Tyre and Rim Technical Organization » (Organisation technique européenne du pneu et de la roue) ou « E.T.R.T.0 » dans son « Standards Manual 2020 - Commercial Vehicle Tyres » (Manuel de normes 2020 - Pneus pour véhicules commerciaux). Les déformations en compression et en cisaillement des éléments en relief délimitant la rainure conditionnent les pressions dans le contact avec le sol et donc l’usure. De plus ces déformations, en générant des pertes hystérétiques dans le matériau de la bande de roulement, impactent la résistance au roulement, et donc la consommation de carburant du véhicule. [0005] More specifically, the cutouts allowing the evacuation of water are essentially wide cutouts called grooves. A groove has a width such that the walls of material facing it delimiting it do not come into contact with each other, during the passage of the tread in the contact surface, when the tire is subject to recommended inflation and load conditions as defined in particular by the European standards of the "European Tire and Rim Technical Organization" or "ETRT0" in its "Standards Manual 2020 - Commercial Vehicle Tyres". commercial). The compression and shear deformations of the elements in relief delimiting the groove condition the pressures in contact with the ground and therefore the wear. Moreover, these deformations, by generating hysteretic losses in the material of the tread, impact the rolling resistance, and therefore the fuel consumption of the vehicle.
[0006] Une bande roulement peut également comprendre des découpures étroites ou incisions. Une incision a une largeur telle que les parois de matière en vis-à-vis la délimitant entrent en contact au moins partiellement l’une avec l’autre, lors du passage de la bande de roulement dans la surface de contact, dans les conditions de charge et de pression du pneumatique spécifiées par l’E.T.R.T.O et vues précédemment. Une incision ne permet pas d’évacuer l’eau, mais, vis-à-vis de l’adhérence, a un effet d’arête dans le contact au sol, qui permet en particulier de casser un film d’eau éventuellement présent sur le sol. [0006] A tread may also comprise narrow cutouts or incisions. An incision has a width such that the walls of material facing it delimiting it come into contact at least partially with each other, during the passage of the tread in the contact surface, under the conditions load and tire pressure specified by the E.T.R.T.O and seen previously. An incision does not make it possible to evacuate the water, but, vis-à-vis the grip, has an edge effect in the contact with the ground, which makes it possible in particular to break a film of water possibly present on floor.
[0007] Pour limiter la réduction du volume de matière à user de la bande de roulement résultant de la présence de rainures et d’incisions, il a été proposé des découpures dites complexes qui permettent, par rapport à des rainures usuelles, ouvertes en totalité sur la surface de roulement, d’augmenter le volume de matière de la bande de roulement tout en respectant le volume de creux pour un stockage de l’eau au-delà d’un seuil déterminé, quel que soit le niveau d’usure du pneumatique. [0007] To limit the reduction in the volume of material to be worn out of the tread resulting from the presence of grooves and incisions, so-called complex cutouts have been proposed which, compared to the usual grooves, are entirely open on the running surface, to increase the volume of material of the tread while respecting the hollow volume for water storage beyond a determined threshold, whatever the level of wear of the pneumatic.
[0008] Des bandes de roulement comprenant de telles découpures complexes ont été décrites en particulier dans les documents WO 2011039194, WO 2011101495, WO 2012130735, WO 2016188956, WO 2019008276 et WO 2019122677. Une découpure complexe débouche d’une façon discontinue, à intervalle régulier ou non, sur la surface de roulement à neuf. Chaque découpure complexe présente des cavités externes, ouvertes sur la surface de roulement et disjointes les unes des autres dans la direction principale de la découpure complexe. La direction principale de la découpure complexe correspond généralement à la direction d’écoulement de l’eau dans ladite découpure lors d’un roulage sur un sol recouvert d’eau. Cette découpure complexe comprend, outre les cavités externes, des cavités internes formées à l’intérieur de la bande de roulement et généralement reliées
à la surface de roulement par des incisions. Ces cavités internes sont positionnées radialement et totalement à l'intérieur de la surface de roulement à l'état neuf, et intercalées entre les cavités externes. Les cavités internes peuvent être positionnées à différents niveaux de profondeur dans l’épaisseur de la bande. En outre, la continuité de l’écoulement d’eau dans chaque découpure complexe, à l’état neuf, est assurée par des portions de liaison, généralement des canaux de liaison, entre deux cavités respectivement externe et interne consécutives. L’ensemble constitué par les cavités externes, les cavités internes et les canaux de liaison forme ainsi une rainure continue. En revanche, la juxtaposition de cavités internes et externes non liées entre elles, et donc ne permettant pas un écoulement de fluide des unes vers les autres sur toute la circonférence du pneumatique, ne constitue pas une rainure continue. [0008] Treads comprising such complex cutouts have been described in particular in the documents WO 2011039194, WO 2011101495, WO 2012130735, WO 2016188956, WO 2019008276 and WO 2019122677. regular or not, on the running surface when new. Each complex cutout has external cavities, open to the tread surface and disjoint from each other in the main direction of the complex cutout. The main direction of the complex cutout generally corresponds to the direction of flow of the water in said cutout when driving on ground covered with water. This complex cutout includes, in addition to the external cavities, internal cavities formed inside the tread and generally connected to the running surface through incisions. These internal cavities are positioned radially and completely inside the running surface when new, and interposed between the external cavities. The internal cavities can be positioned at different levels of depth in the thickness of the strip. In addition, the continuity of the water flow in each complex cutout, when new, is ensured by connecting portions, generally connecting channels, between two consecutive outer and inner cavities respectively. The assembly formed by the external cavities, the internal cavities and the connecting channels thus forms a continuous groove. On the other hand, the juxtaposition of internal and external cavities not linked together, and therefore not allowing a flow of fluid from one to the other over the entire circumference of the tire, does not constitute a continuous groove.
[0009] Pour une bande de roulement à découpures complexes, le volume de l’ensemble des cavités internes, des cavités externes et des canaux de liaison est réduit par rapport à celui de rainures ouvertes en totalité sur la surface de roulement à neuf et ayant une profondeur correspondant à la profondeur maximale des cavités internes ou externes. La présence de découpures complexes permet ainsi de limiter la réduction de rigidité de la bande de roulement à l'état neuf liée à la présence des rainures. [0009] For a tread with complex cutouts, the volume of all the internal cavities, the external cavities and the connecting channels is reduced compared to that of grooves that are entirely open on the tread surface when new and having a depth corresponding to the maximum depth of the internal or external cavities. The presence of complex cutouts thus makes it possible to limit the reduction in rigidity of the tread when new due to the presence of the grooves.
[0010] Une sculpture de bande de roulement peut comporter à la fois des découpures complexes, débouchant sur la surface de roulement par intermittence, et des rainures classiques, débouchant sur la surface de roulement sur toute leur longueur. [0010] A tread pattern can comprise both complex cutouts, emerging on the running surface intermittently, and conventional grooves, emerging on the running surface over their entire length.
[0011] Lorsque le pneumatique roule sur un sol pierreux, sa bande de roulement est susceptible de retenir des pierres dans ses découpures, et en particulier dans ses rainures. Ces pierres retenues par les rainures de la bande de roulement sont alors susceptibles de créer des perforations de la bande de roulement, pouvant entraîner un endommagement de l’armature de sommet du pneumatique, radialement intérieure à la bande de roulement, et, à terme, une rupture de ladite armature de sommet rendant le pneumatique inutilisable. [0011] When the tire rolls on stony ground, its tread is likely to retain stones in its cutouts, and in particular in its grooves. These stones retained by the grooves of the tread are then likely to create perforations in the tread, which can cause damage to the crown reinforcement of the tire, radially inside the tread, and, ultimately, a rupture of said crown reinforcement rendering the tire unusable.
[0012] Ce phénomène de rétention de pierres peut être particulièrement marqué dans le cas de découpures complexes. En effet celles-ci peuvent capter des pierres au niveau de leurs cavités externes, ces pierres étant susceptibles de rester bloquées, plus
particulièrement, dans les canaux de liaison entre les cavités respectivement externes et internes, et donc de générer un endommagement de la bande de roulement. [0012] This stone retention phenomenon can be particularly marked in the case of complex cutouts. Indeed these can capture stones at the level of their external cavities, these stones being likely to remain blocked, more particularly, in the connection channels between the respectively external and internal cavities, and therefore to generate damage to the tread.
[0013] Ainsi les inventeurs se sont donnés pour objectif d’améliorer la résistance aux agressions par des pierres d’une bande de roulement pour véhicule poids lourd, comprenant des découpures complexes constituées par une alternance de cavités externes, de cavités internes et de canaux de liaison entre cavités externes et cavités internes. [0013] Thus the inventors have set themselves the objective of improving the resistance to attack by stones of a tread for a heavy vehicle, comprising complex cutouts consisting of an alternation of external cavities, internal cavities and channels connection between external cavities and internal cavities.
[0014] Cet objectif a été atteint par une bande de roulement de pneumatique pour un véhicule poids lourd, destinée à entrer en contact avec un sol par l’intermédiaire d’une surface de roulement, comprenant des découpures délimitant des éléments en relief,[0014] This objective has been achieved by a tire tread for a heavy vehicle, intended to come into contact with the ground by means of a running surface, comprising cutouts delimiting elements in relief,
-la bande de roulement à l’état neuf comprenant au moins une découpure complexe comprenant, selon une ligne moyenne, une alternance de cavités externes, débouchant sur la surface de roulement, et de cavités internes, ne débouchant pas sur la surface de roulement, deux cavités respectivement externe et interne consécutives étant reliées en entre elles par un canal de liaison, - the tread in new condition comprising at least one complex cutout comprising, along an average line, an alternation of external cavities, opening onto the rolling surface, and internal cavities, not opening onto the rolling surface, two consecutive external and internal cavities respectively being interconnected by a connecting channel,
-chaque cavité externe ayant, dans une surface moyenne contenant la ligne moyenne et une direction radiale perpendiculaire à la surface de roulement, une hauteur, mesurée, selon la direction radiale, entre la surface de roulement et un fond de cavité externe, et une longueur, mesurée, selon la ligne moyenne, au niveau de la surface de roulement, -chaque cavité interne ayant, dans la surface moyenne, une hauteur, mesurée, selon la direction radiale, entre un sommet de cavité interne et un fond de cavité interne radialement intérieur au fond de cavité externe, et une longueur, mesurée, selon la ligne moyenne, au niveau du fond de la cavité interne, -each external cavity having, in an average surface containing the average line and a radial direction perpendicular to the rolling surface, a height, measured, in the radial direction, between the rolling surface and an external cavity bottom, and a length , measured, along the mean line, at the level of the tread surface, -each internal cavity having, in the mean surface, a height, measured, along the radial direction, between a top of the internal cavity and a bottom of the internal cavity radially interior to the bottom of the external cavity, and a length, measured, along the mean line, at the level of the bottom of the internal cavity,
-chaque canal de liaison ayant, dans la surface moyenne, une hauteur, mesurée, selon la direction radiale, entre un sommet de canal de liaison et un fond de canal de liaison, à la jonction circonférentielle entre la cavité externe et le canal de liaison, et une longueur, mesurée, selon la ligne moyenne, entre la cavité externe et la cavité interne, non nulle, -chaque découpure complexe ayant, dans la surface moyenne, une hauteur mesurée, selon la direction radiale, entre la surface de roulement et le fond de cavité interne, -each connecting channel having, in the middle surface, a height, measured, in the radial direction, between a connecting channel top and a connecting channel bottom, at the circumferential junction between the external cavity and the connecting channel , and a length, measured, along the mean line, between the external cavity and the internal cavity, non-zero, -each complex cut-out having, in the mean surface, a height measured, along the radial direction, between the rolling surface and the bottom of the internal cavity,
-la hauteur de chaque cavité externe étant au moins égale à la moitié de la hauteur de la découpure complexe,
-la hauteur de chaque canal de liaison étant au plus égale au tiers de la hauteur de la découpure complexe. -the height of each external cavity being at least equal to half the height of the complex cutout, the height of each connecting channel being at most equal to one third of the height of the complex cutout.
[0015] L’invention a donc pour objet une bande de roulement comprenant au moins une découpure complexe constituée, selon une ligne moyenne, par une alternance de cavités externes, débouchant sur la surface de roulement, et de cavités internes, ne débouchant pas sur la surface de roulement, deux cavités respectivement externe et interne consécutives étant reliées en entre elles par un canal de liaison assurant une transition progressive entre lesdites cavités respectivement externe et interne. [0015] The subject of the invention is therefore a tread comprising at least one complex cutout formed, along a mean line, by an alternation of external cavities, opening onto the tread surface, and internal cavities, not opening onto the rolling surface, two consecutive outer and inner cavities respectively being interconnected by a connecting channel providing a gradual transition between said outer and inner cavities respectively.
[0016] La ligne moyenne de la découpure complexe n’est pas nécessairement rectiligne, et peut avoir, à titre d’exemples, une forme ondulée ou une forme en zigzag. De plus elle peut s’étendre selon une direction quelconque : longitudinale, transversale ou oblique. Par convention, la direction longitudinale est la direction de la plus grande dimension ou longueur de la bande de roulement, la direction transversale est la direction de la dimension intermédiaire ou largeur de la bande de roulement, et la direction radiale est la direction de la plus petite dimension ou épaisseur de la bande de roulement. Une direction oblique a une orientation générale intermédiaire entre la direction longitudinale et la direction transversale. Une direction oblique est dite sensiblement longitudinale, lorsqu’elle forme un angle au plus égal à 45° avec la direction longitudinale, et sensiblement transversale, lorsqu’elle forme un angle au plus égal à 45° avec la direction transversale. [0016] The middle line of the complex cutout is not necessarily rectilinear, and may have, by way of example, a wavy shape or a zigzag shape. In addition, it can extend in any direction: longitudinal, transverse or oblique. By convention, the longitudinal direction is the direction of the longest tread dimension or length, the transverse direction is the direction of the intermediate dimension or tread width, and the radial direction is the direction of the longest. small tread dimension or thickness. An oblique direction has an intermediate general orientation between the longitudinal direction and the transverse direction. An oblique direction is said to be substantially longitudinal, when it forms an angle at most equal to 45° with the longitudinal direction, and substantially transverse, when it forms an angle at most equal to 45° with the transverse direction.
[0017] La découpure complexe forme, dans une coupe selon une surface moyenne définie par sa ligne moyenne et une direction radiale perpendiculaire à la surface de roulement, une rainure ondulée continue comprenant une alternance de cavités externes, de cavités internes et de canaux de liaison entre deux cavités consécutives respectivement interne et externe. En d’autres termes, deux cavités externes consécutives selon la ligne moyenne sont séparées par une seule cavité interne et réciproquement. Du fait de l’ondulation de la découpure complexe selon la direction circonférentielle, dans l’épaisseur de la bande de roulement, le fond de toute cavité interne est radialement intérieur au fond d’une cavité externe adjacente. [0017] The complex cutout forms, in a section along an average surface defined by its average line and a radial direction perpendicular to the running surface, a continuous wavy groove comprising an alternation of external cavities, internal cavities and connecting channels between two consecutive internal and external cavities respectively. In other words, two consecutive external cavities along the mean line are separated by a single internal cavity and vice versa. Due to the undulation of the complex cutout in the circumferential direction, in the thickness of the tread, the bottom of any internal cavity is radially inside the bottom of an adjacent external cavity.
[0018] Les cavités respectivement externes et internes, ainsi que les canaux de liaison, sont caractérisés par leurs géométries respectives définies dans la surface moyenne de la
découpure complexe, à savoir une hauteur mesurée selon la direction radiale, dans l’épaisseur de la bande de roulement, et une longueur, mesurée selon la ligne moyenne de la découpure complexe, entre deux références dépendant de la portion de découpure complexe considérée. Les hauteurs respectives peuvent être définies par rapport à la hauteur de la découpure complexe, mesurée entre la surface de roulement à l’état neuf, sur laquelle débouche les cavités externes, et une surface de fond passant par le fond des cavités internes, c’est-à-dire les points les plus radialement intérieurs de la découpure complexe. Dans le contexte de l’invention la hauteur de chaque cavité externe est au moins égale à la moitié de la hauteur de la découpure complexe, ce qui garantit un volume de cavité externe suffisant, nécessaire au stockage de l’eau sur un sol mouillé, lorsque la bande de roulement est à l’état neuf. En outre la longueur de tout canal de liaison est non nulle, ce qui garantit une transition progressive entre les cavités respectivement externe et interne reliées par ledit canal de liaison. The respectively external and internal cavities, as well as the connecting channels, are characterized by their respective geometries defined in the average surface of the complex cutout, namely a height measured along the radial direction, in the thickness of the tread, and a length, measured along the mean line of the complex cutout, between two references depending on the complex cutout portion considered. The respective heights can be defined with respect to the height of the complex cutout, measured between the running surface in new condition, on which the external cavities open, and a bottom surface passing through the bottom of the internal cavities, c' that is, the radially innermost points of the complex cutout. In the context of the invention, the height of each external cavity is at least equal to half the height of the complex cutout, which guarantees a sufficient volume of external cavity, necessary for the storage of water on wet ground, when the tread is in new condition. Furthermore, the length of any connecting channel is non-zero, which guarantees a gradual transition between the respectively external and internal cavities connected by said connecting channel.
[0019] La caractéristique essentielle de l’invention est de limiter la hauteur du canal de liaison, mesurée au niveau de la connexion du canal avec la cavité externe, autrement dit au niveau de sa section débouchant dans la cavité externe. Selon l’invention cette hauteur est optimisée pour empêcher le passage de pierres de taille trop importante, c’est-à-dire d’une dimension telle qu’elles seraient susceptibles de générer un endommagement important du sommet du pneumatique. Les inventeurs ont estimé une taille critique de pierre caractérisée par un diamètre supérieur au tiers de la hauteur de la découpure complexe, d’où une hauteur du canal de liaison au niveau de sa connexion avec la cavité externe au plus égale au tiers de la hauteur de la découpure complexe. The essential characteristic of the invention is to limit the height of the connecting channel, measured at the level of the connection of the channel with the external cavity, in other words at the level of its section opening into the external cavity. According to the invention, this height is optimized to prevent the passage of too large stones, that is to say of a size such that they would be likely to cause significant damage to the crown of the tire. The inventors have estimated a critical stone size characterized by a diameter greater than one third of the height of the complex cutout, hence a height of the connecting channel at the level of its connection with the external cavity at most equal to one third of the height complex cutting.
[0020] Préférentiellement la hauteur de chaque canal de liaison est au moins égale au dixième de la hauteur de la découpure complexe. En dessous de cette valeur, le débit d’eau dans la découpure complexe devient insuffisant pour garantir une adhérence suffisante de la bande de roulement sur une chaussé mouillée, en raison d’une striction trop importante de la découpure complexe au niveau du canal de liaison. [0020] Preferably, the height of each connecting channel is at least equal to one tenth of the height of the complex cutout. Below this value, the flow of water in the complex cutout becomes insufficient to guarantee sufficient grip of the tread on a wet road surface, due to too great a constriction of the complex cutout at the level of the connecting channel. .
[0021] Encore avantageusement la hauteur de chaque cavité externe est au plus égale aux trois quarts de la hauteur de la découpure complexe. Cette hauteur maximale de cavité externe garantit la présence, radialement à l’intérieur de la cavité externe, d’une épaisseur de matériau à base de caoutchouc suffisante pour assurer la protection de la portion
d’annature de sommet radialement positionnée à l’intérieur de la bande de roulement, à l’aplomb de la cavité externe. Again advantageously the height of each external cavity is at most equal to three quarters of the height of the complex cutout. This maximum external cavity height guarantees the presence, radially inside the external cavity, of a thickness of rubber-based material sufficient to ensure the protection of the portion crown insert radially positioned inside the tread, directly above the external cavity.
[0022] Avantageusement la longueur de chaque canal de liaison est au moins égale à la hauteur du canal de liaison. Le canal de liaison est efficace pour le blocage des pierres captées par la cavité externe à laquelle il est relié, s’il a une longueur suffisante, c’est-à- dire s’il assure une striction sur une distance suffisante. [0022] Advantageously, the length of each connecting channel is at least equal to the height of the connecting channel. The connecting channel is effective for blocking stones captured by the external cavity to which it is connected, if it is of sufficient length, i.e. if it provides striction over a sufficient distance.
[0023] Avantageusement la hauteur de chaque cavité interne est au moins égale au tiers de la hauteur de la découpure complexe. Cette hauteur minimale de cavité interne garantit un volume de cavité externe suffisant, nécessaire au stockage de l’eau sur un sol mouillé, lorsque la bande de roulement arrive à un niveau d’usure correspondant au sommet de cavité interne, autrement dit lorsque la cavité interne s’ouvre à son tour sur la surface de roulement à l’état usé. [0023] Advantageously, the height of each internal cavity is at least equal to one third of the height of the complex cutout. This minimum internal cavity height guarantees a sufficient external cavity volume, necessary for the storage of water on wet ground, when the tread reaches a level of wear corresponding to the top of the internal cavity, in other words when the cavity internal in turn opens on the running surface in the worn state.
[0024] Encore avantageusement la hauteur de chaque cavité interne est au plus égale aux trois quarts de la hauteur de la découpure complexe. Cette hauteur maximale de cavité interne garantit la présence, radialement à l’extérieur de la cavité interne, d’une épaisseur de matériau à base de caoutchouc suffisante pour assurer, à l’état neuf, la protection de la portion d’armature de sommet radialement positionnée à l’intérieur de la bande de roulement, à l’aplomb de la cavité interne. Again advantageously the height of each internal cavity is at most equal to three quarters of the height of the complex cutout. This maximum internal cavity height guarantees the presence, radially outside the internal cavity, of a thickness of rubber-based material sufficient to ensure, when new, the protection of the crown reinforcement portion. radially positioned inside the tread, directly above the internal cavity.
[0025] Le rapport entre la longueur de cavité interne et la longueur de cavité externe est avantageusement au moins égal à 0.8. En dessous de cette valeur, la longueur de cavité externe devient excessive et pénalise le volume de matière à user. The ratio between the internal cavity length and the external cavity length is advantageously at least equal to 0.8. Below this value, the external cavity length becomes excessive and penalizes the volume of material to be worn.
[0026] Le rapport entre la longueur de cavité interne et la longueur de cavité externe est encore avantageusement au plus égal à 1.5, de préférence au plus égal à 1.2. Au-dessus de cette valeur, la longueur de cavité externe devient insuffisante pour garantir une bonne captation de l’eau présente sur le sol. The ratio between the internal cavity length and the external cavity length is again advantageously at most equal to 1.5, preferably at most equal to 1.2. Above this value, the length of the external cavity becomes insufficient to guarantee good collection of the water present on the ground.
[0027] Selon une variante de réalisation préférée des cavités internes, chaque cavité interne a un sommet de cavité interne prolongé radialement vers l’extérieur par une incision jusqu’à la surface de roulement, en raison d’une contrainte technologique de fabrication des cavités externes par moulage par l’extérieur de la bande roulement.
[0028] Selon une variante de réalisation des cavités externes, chaque cavité externe a un fond de cavité externe prolongé radialement vers l’intérieur par au moins une incision jusqu’à, au plus, une surface de fond passant par le fond de cavité interne. Lorsque le niveau d’usure de la bande de roulement atteint le fond de la cavité externe, il apparaît alors au moins une incision qui va contribuer à l’adhérence, en particulier sur sol mouillé en créant un effet d’arête permettant de casser le film d’eau présent sur le sol. [0027] According to a preferred embodiment of the internal cavities, each internal cavity has an internal cavity top extended radially outwards by an incision as far as the rolling surface, due to a technological constraint for manufacturing the cavities. external by molding from the outside of the tread. According to an alternative embodiment of the external cavities, each external cavity has an external cavity bottom extended radially inwards by at least one incision up to, at most, a bottom surface passing through the internal cavity bottom. . When the tread wear level reaches the bottom of the external cavity, at least one incision appears which will contribute to grip, particularly on wet ground, by creating a ridge effect making it possible to break the film of water present on the ground.
[0029] Selon un mode de réalisation préféré de la bande de roulement, la ligne moyenne d’au moins une découpure complexe est sensiblement longitudinale, formant en tout point un angle au plus égal à 45°, de préférence au plus égal à 20°, par rapport à une direction longitudinale de la bande de roulement. En d’autres termes cette ligne moyenne est préférentiellement orientée selon une direction longitudinale, qui est la direction d’avancement du pneumatique et la direction principale d’écoulement de l’eau évacuée dans la surface de contact avec le sol. According to a preferred embodiment of the tread, the middle line of at least one complex cutout is substantially longitudinal, forming at all points an angle at most equal to 45°, preferably at most equal to 20° , with respect to a longitudinal direction of the tread. In other words, this mean line is preferably oriented in a longitudinal direction, which is the direction of advancement of the tire and the main direction of flow of the water evacuated in the contact surface with the ground.
[0030] Selon une variante du mode de réalisation préféré de la bande de roulement, au moins une découpure complexe ayant une ligne moyenne sensiblement longitudinale est axialement positionnée dans une portion médiane de bande de roulement ayant une largeur axiale au plus égale aux deux tiers de la largeur axiale de la bande roulement, ladite portion médiane étant centrée sur un plan médian passant par le milieu de la surface de roulement et perpendiculaire à la surface de roulement. La largeur axiale de la bande roulement est la distance axiale entre les extrémités axiales de la surface de roulement, lorsque le pneumatique est gonflé et écrasé dans les conditions de pression et de charge recommandées par les normes de l’E.T.R.T.O. L’avantage d’avoir une découpure complexe dans la portion médiane de la bande de roulement, par rapport à une rainure classique est de diminuer la surface débouchante de la découpure sur la surface de roulement, et donc le risque de captation de pierres, sachant que cete portion médiane, caractérisée par une distribution de pressions de contact élevées, a une grande aptitude à capter les pierres. En effet cette portion centrale est caractérisée par un grand rayon méridien, donc par un profil externe relativement plat et ne permettant pas un effet de charnière apte à libérer les pierres captées sur la chaussée. De plus elle correspond à une portion de rigidité élevée du sommet du pneumatique.
[0031] L ’ invention a également pour obj et un pneumatique pour un véhicule poids lourd comprenant une bande de roulement selon l’un quelconque des modes de réalisation précédemment décrits. [0030] According to a variant of the preferred embodiment of the tread, at least one complex cutout having a substantially longitudinal mean line is axially positioned in a median portion of the tread having an axial width at most equal to two-thirds of the axial width of the tread, said middle portion being centered on a median plane passing through the middle of the tread surface and perpendicular to the tread surface. The axial width of the tread is the axial distance between the axial ends of the running surface, when the tire is inflated and crushed under the pressure and load conditions recommended by the ETRTO standards The advantage of having a complex cutout in the middle portion of the tread, compared to a conventional groove, is to reduce the emerging surface of the cutout on the tread surface, and therefore the risk of picking up stones, knowing that this middle portion, characterized by a distribution of high contact pressures, has a great ability to capture stones. Indeed this central portion is characterized by a large meridian radius, therefore by a relatively flat external profile and not allowing a hinge effect capable of releasing the stones captured on the roadway. Moreover, it corresponds to a portion of high rigidity of the crown of the tire. [0031] The object of the invention is also a tire for a heavy vehicle comprising a tread according to any one of the embodiments described above.
[0032] Les caractéristiques de l’invention sont illustrées par les figures 1 et 2 schématiques et non représentées à l’échelle : The characteristics of the invention are illustrated by Figures 1 and 2 schematic and not shown to scale:
-Figure 1 : Vue de dessus d’une bande de roulement selon l’invention à l’état neuf,-Figure 1: Top view of a tread according to the invention in new condition,
-Figure 2 : Vue en coupe, selon une surface moyenne de découpure complexe, d’une portion de découpure complexe comprenant une cavité externe, une cavité interne et un canal de liaison les reliant. -Figure 2: Cross-sectional view, along an average complex cut-out surface, of a complex cut-out portion comprising an external cavity, an internal cavity and a connecting channel connecting them.
[0033] La figure 1 est une vue de dessus d’une bande de roulement 1 selon l’invention à l’état neuf. La bande de roulement 1 de pneumatique, destinée à entrer en contact avec un sol par l’intermédiaire d’une surface de roulement 2, comprend des découpures 3, délimitant des éléments en relief 4. Parmi les découpures 3 représentées, on distingue deux rainures sensiblement longitudinales délimitant chacune une nervure latérale et une portion médiane 11, ladite portion médiane 11 ayant, selon une direction transversale YY’ de la bande roulement, une largeur axiale Wm au plus égale aux deux tiers de la largeur axiale W de la bande de roulement. La portion médiane 11 comprend en outre deux découpures complexes 5 sensiblement longitudinales, séparant chacune deux rangées longitudinales d’éléments en relief 4 de types blocs deux à deux séparés par des incisions. Chaque découpure complexe 5 comprend, selon une ligne moyenne Lm, une alternance de cavités externes 6, débouchant sur la surface de roulement 2, et de cavités internes 7, ne débouchant pas sur la surface de roulement 2, deux cavités respectivement externe 6 et interne 7 consécutives étant reliées entre elles par un canal de liaison 8. Les cavités internes 7 et les canaux de liaison 8, non apparents à l’état neuf de la bande de roulement, sont représentés en traits pointillés. Dans le mode de réalisation représenté, la ligne moyenne Lm de chaque découpure complexe 5 a une forme en zigzag sensiblement longitudinale, avec une tangente en tout point formant, avec une direction longitudinale XX’ de la bande roulement, un angle au plus égal à 45°, de préférence au plus égal à 20°. Figure 1 is a top view of a tread 1 according to the invention in new condition. The tread 1 of the tire, intended to come into contact with the ground via a running surface 2, comprises cutouts 3, delimiting elements in relief 4. Among the cutouts 3 represented, two grooves can be distinguished substantially longitudinal each delimiting a lateral rib and a middle portion 11, said middle portion 11 having, in a transverse direction YY' of the tread, an axial width Wm at most equal to two thirds of the axial width W of the tread . The middle portion 11 further comprises two complex cutouts 5 substantially longitudinal, each separating two longitudinal rows of relief elements 4 of block type two by two separated by incisions. Each complex cutout 5 comprises, along an average line Lm, an alternation of external cavities 6, opening onto the running surface 2, and internal cavities 7, not opening onto the running surface 2, two cavities respectively external 6 and internal 7 consecutive being interconnected by a connecting channel 8. The internal cavities 7 and the connecting channels 8, not visible in the new state of the tread, are shown in dotted lines. In the embodiment shown, the average line Lm of each complex cutout 5 has a substantially longitudinal zigzag shape, with a tangent at any point forming, with a longitudinal direction XX' of the tread, an angle at most equal to 45 °, preferably at most equal to 20°.
[0034] La figure 2 est une vue en coupe, selon une surface moyenne Sm de découpure complexe, d’une portion de découpure complexe 5 comprenant une cavité externe 6 reliée à chacune de ses extrémités à une cavité interne 7 par un canal de liaison 8. Seule une demi-
cavité interne 7 est représentée à chaque extrémité de la cavité externe 6. La cavité externe 6 a, dans une surface moyenne Sm contenant la ligne moyenne Lm et une direction radiale ZZ’ perpendiculaire à la surface de roulement 2 de la bande roulement 1, une hauteur H11, mesurée, selon la direction radiale ZZ’, entre la surface de roulement 2 et un fond de cavité externe 62, et une longueur Ll, mesurée, selon la ligne moyenne Lm, au niveau de la surface de roulement 2. Chaque cavité interne 7 a, dans la surface moyenne Sm, une hauteur H22, mesurée, selon la direction radiale ZZ’, entre un sommet de cavité interne 71 et un fond de cavité interne 72 radialement intérieur au fond de cavité externe 62, et une longueur L2, mesurée, selon la ligne moyenne Lm, au niveau du fond de la cavité interne 72. Sur la figure 2 sont représentées deux demi-cavités internes 7 de longueur L2/2. Chaque canal de liaison 8 a, dans la surface moyenne Sm, une hauteur H3, mesurée, selon la direction radiale ZZ’, entre un sommet de canal de liaison 81 et un fond de canal de liaison 82, à la jonction circonférentielle entre la cavité externe 6 et le canal de liaison 8, et une longueur L3, mesurée, selon la ligne moyenne Lm, entre la cavité externe 6 et la cavité interne 7, non nulle. En outre la découpure complexe 5 a, dans la surface moyenne Sm, une hauteur H, mesurée, selon la direction radiale ZZ’, entre la surface de roulement 2 et le fond de cavité interne 72. La hauteur H11 de chaque cavité externe 6 est au moins égale à la moitié de la hauteur H de la découpure complexe 5. Conformément à l’invention, la hauteur H3 de chaque canal de liaison 8 est au plus égale au tiers de la hauteur H de la découpure complexe 5. Dans le mode de réalisation représenté, la cavité externe 6 a un fond de cavité externe 62 prolongé radialement vers l’intérieur par une incision 63 jusqu’à une surface de fond 10 passant par le fond de cavité interne 72. De plus chaque cavité interne 7 a un sommet de cavité interne 71 prolongé radialement vers l’extérieur par une incision 73 jusqu’à la surface de roulement 2. [0034] Figure 2 is a sectional view, along an average surface Sm of complex cutout, of a portion of complex cutout 5 comprising an external cavity 6 connected at each of its ends to an internal cavity 7 by a connecting channel 8. Only half a internal cavity 7 is represented at each end of the external cavity 6. The external cavity 6 has, in an average surface Sm containing the average line Lm and a radial direction ZZ' perpendicular to the running surface 2 of the tread 1, a height H11, measured, along the radial direction ZZ', between running surface 2 and an external cavity bottom 62, and a length L1, measured, along mean line Lm, at running surface 2. Each cavity internal 7 has, in the average surface Sm, a height H22, measured, in the radial direction ZZ', between an internal cavity top 71 and an internal cavity bottom 72 radially inside the external cavity bottom 62, and a length L2 , measured along the mean line Lm, at the level of the bottom of the internal cavity 72. In FIG. 2 are shown two internal half-cavities 7 of length L2/2. Each connecting channel 8 has, in the mean surface Sm, a height H3, measured, along the radial direction ZZ', between a connecting channel top 81 and a connecting channel bottom 82, at the circumferential junction between the cavity external 6 and the connecting channel 8, and a length L3, measured along the mean line Lm, between the external cavity 6 and the internal cavity 7, non-zero. In addition, the complex cutout 5 has, in the average surface Sm, a height H, measured, along the radial direction ZZ', between the rolling surface 2 and the bottom of the internal cavity 72. The height H11 of each external cavity 6 is at least equal to half the height H of the complex cutout 5. In accordance with the invention, the height H3 of each connecting channel 8 is at most equal to a third of the height H of the complex cutout 5. In the mode embodiment shown, the external cavity 6 has an external cavity bottom 62 extended radially inwards by an incision 63 up to a bottom surface 10 passing through the internal cavity bottom 72. In addition, each internal cavity 7 has a top of internal cavity 71 extended radially outwards by an incision 73 up to running surface 2.
[0035] Les inventeurs ont plus particulièrement étudié cette invention pour un pneumatique de dimension 13 R 22.5 destiné à équiper un essieu directeur pour un véhicule poids lourd à usage mixte et à porter une charge égale à 4000 kg avec une pression de gonflage égale à 8.75 bars, selon le « Standards Manual 2020 » de la norme E.T.R.T.O. The inventors have more particularly studied this invention for a tire of size 13 R 22.5 intended to equip a steering axle for a mixed-use heavy vehicle and to carry a load equal to 4000 kg with an inflation pressure equal to 8.75 bars, according to the "Standards Manual 2020" of the E.T.R.T.O.
[0036] Le tableau 1 ci-dessous présente les caractéristiques de la bande de roulement testée : [0036] Table 1 below presents the characteristics of the tread tested:
[Tableau 1]
[Table 1]
Claims
1. Bande de roulement (1) de pneumatique pour un véhicule poids lourd, destinée à entrer en contact avec un sol par l’intermédiaire d’une surface de roulement (2), comprenant des découpures (3) délimitant des éléments en relief (4), 1. Tire tread (1) for a heavy-duty vehicle, intended to come into contact with the ground via a running surface (2), comprising cutouts (3) delimiting elements in relief ( 4),
-la bande de roulement (1) à l’état neuf comprenant au moins une découpure complexe (5) comprenant, selon une ligne moyenne (Lm), une alternance de cavités externes (6), débouchant sur la surface de roulement (2), et de cavités internes (7), ne débouchant pas sur la surface de roulement (2), deux cavités respectivement externe (6) et interne (7) consécutives étant reliées entre elles par un canal de liaison (8), - the tread (1) in new condition comprising at least one complex cutout (5) comprising, along a mean line (Lm), an alternation of external cavities (6), opening onto the running surface (2) , and internal cavities (7), which do not open onto the running surface (2), two consecutive external (6) and internal (7) cavities respectively being interconnected by a connecting channel (8),
-chaque cavité externe (6) ayant, dans une surface moyenne (Sm) contenant la ligne moyenne (Lm) et une direction radiale (ZZ’) perpendiculaire à la surface de roulement (2), une hauteur (H11), mesurée, selon la direction radiale (ZZ’), entre la surface de roulement (2) et un fond de cavité externe (62), et une longueur (Ll), mesurée, selon la ligne moyenne (Lm), au niveau de la surface de roulement (2), -chaque cavité interne (7) ayant, dans la surface moyenne (Sm), une hauteur (H22), mesurée, selon la direction radiale (ZZ’), entre un sommet de cavité interne (71) et un fond de cavité interne (72) radialement intérieur au fond de cavité externe (62), et une longueur (L2), mesurée, selon la ligne moyenne (Lm), au niveau du fond de la cavité interne (72) , -each external cavity (6) having, in an average surface (Sm) containing the average line (Lm) and a radial direction (ZZ') perpendicular to the rolling surface (2), a height (H11), measured, according to the radial direction (ZZ'), between the tread surface (2) and an external cavity bottom (62), and a length (Ll), measured, along the mean line (Lm), at the level of the tread surface (2), -each internal cavity (7) having, in the average surface (Sm), a height (H22), measured, in the radial direction (ZZ'), between an internal cavity top (71) and a bottom of internal cavity (72) radially inside the bottom of the external cavity (62), and a length (L2), measured, along the mean line (Lm), at the level of the bottom of the internal cavity (72),
-chaque canal de liaison (8) ayant, dans la surface moyenne (Sm), une hauteur (H3), mesurée, selon la direction radiale (ZZ’), entre un sommet de canal de liaison (81) et un fond de canal de liaison (82), à la jonction circonférentielle entre la cavité externe (6) et le canal de liaison (8), et une longueur (L3), mesurée, selon la ligne moyenne (Lm), entre la cavité externe (6) et la cavité interne (7), non nulle, -each connecting channel (8) having, in the average surface (Sm), a height (H3), measured, in the radial direction (ZZ'), between a connecting channel top (81) and a channel bottom link (82), at the circumferential junction between the external cavity (6) and the connecting channel (8), and a length (L3), measured, along the mean line (Lm), between the external cavity (6) and the internal cavity (7), non-zero,
-chaque découpure complexe (5) ayant, dans la surface moyenne (Sm), une hauteur (H), mesurée, selon la direction radiale (ZZ’), entre la surface de roulement (2) et le fond de cavité interne (72), - each complex cutout (5) having, in the average surface (Sm), a height (H), measured, in the radial direction (ZZ'), between the running surface (2) and the bottom of the internal cavity (72 ),
-la hauteur (H11) de chaque cavité externe (6) étant au moins égale à la moitié de la hauteur (H) de la découpure complexe (5),
caractérisée en ce que la hauteur (H3) de chaque canal de liaison (8) est au plus égale au tiers de la hauteur (H) de la découpure complexe (5). -the height (H11) of each external cavity (6) being at least equal to half the height (H) of the complex cutout (5), characterized in that the height (H3) of each connecting channel (8) is at most equal to one third of the height (H) of the complex cutout (5).
2. Bande de roulement (1) selon la revendication 1, dans laquelle la hauteur (H3) de chaque canal de liaison (8) est au moins égale au dixième de la hauteur (H) de la découpure complexe (5). 2. Tread (1) according to claim 1, in which the height (H3) of each connecting channel (8) is at least equal to one tenth of the height (H) of the complex cutout (5).
3. Bande de roulement (1) selon l’une des revendications 1 ou 2, dans laquelle la hauteur (H11) de chaque cavité externe (6) est au plus égale aux trois quarts de la hauteur (H) de la découpure complexe (5). 3. Tread (1) according to one of claims 1 or 2, wherein the height (H11) of each external cavity (6) is at most equal to three quarters of the height (H) of the complex cutout ( 5).
4. Bande de roulement (1) selon l’une quelconque des revendications 1 à 3, dans laquelle la longueur (L3) de chaque canal de liaison (8) est au moins égale à la hauteur (H3) du canal de liaison (8). 4. Tread (1) according to any one of claims 1 to 3, in which the length (L3) of each connecting channel (8) is at least equal to the height (H3) of the connecting channel (8 ).
5. Bande de roulement (1) selon l’une quelconque des revendications 1 à 4, dans laquelle la hauteur (H22) de chaque cavité interne (7) est au moins égale au tiers de la hauteur (H) de la découpure complexe (5). 5. Tread (1) according to any one of claims 1 to 4, in which the height (H22) of each internal cavity (7) is at least equal to one third of the height (H) of the complex cutout ( 5).
6. Bande de roulement (1) selon l’une quelconque des revendications 1 à 5, dans laquelle la hauteur (H22) de chaque cavité interne (7) est au plus égale aux trois quarts de la hauteur (H) de la découpure complexe (5). 6. Tread (1) according to any one of claims 1 to 5, in which the height (H22) of each internal cavity (7) is at most equal to three quarters of the height (H) of the complex cutout (5).
7. Bande de roulement (1) selon l’une quelconque des revendications 1 à 6, dans laquelle le rapport entre la longueur (L2) de cavité interne (7) et la longueur (Ll) de cavité externe (6) est au moins égal à 0.8. 7. Tread (1) according to any one of claims 1 to 6, in which the ratio between the length (L2) of the internal cavity (7) and the length (L1) of the external cavity (6) is at least equal to 0.8.
8. Bande de roulement (1) selon l’une quelconque des revendications 1 à 7, dans laquelle le rapport entre la longueur (L2) de cavité interne (7) et la longueur (Ll) de cavité externe (6) est au plus égal à 1.5, de préférence au plus égal à 1.2. 8. Tread (1) according to any one of claims 1 to 7, in which the ratio between the length (L2) of internal cavity (7) and the length (L1) of external cavity (6) is at most equal to 1.5, preferably at most equal to 1.2.
9. Bande de roulement (1) selon l’une quelconque des revendications 1 à 8, dans laquelle chaque cavité interne (7) a un sommet de cavité interne (71) prolongé radialement vers l’extérieur par une incision (73) jusqu’à la surface de roulement (2)· 9. Tread (1) according to any one of claims 1 to 8, in which each internal cavity (7) has an internal cavity top (71) extended radially outwards by an incision (73) up to to the running surface (2)
10. Bande de roulement (1) selon l’une quelconque des revendications 1 à 9, dans laquelle chaque cavité externe (6) a un fond de cavité externe (62) prolongé
radialement vers l’intérieur par au moins une incision (63) jusqu’à, au plus, une surface de fond (10) passant par le fond de cavité interne (72). 10. Tread (1) according to any one of claims 1 to 9, in which each external cavity (6) has an external cavity bottom (62) extended radially inward through at least one incision (63) to at most one bottom surface (10) passing through the internal cavity bottom (72).
11. Bande de roulement (1) selon l’une quelconque des revendications 1 à 10, dans laquelle la ligne moyenne (Lm) d’au moins une découpure complexe (5) est sensiblement longitudinale, formant en tout point un angle au plus égal à 45°, de préférence au plus égal à 20°, par rapport à une direction longitudinale (XX’) de la bande de roulement. 11. Tread (1) according to any one of claims 1 to 10, in which the mean line (Lm) of at least one complex cutout (5) is substantially longitudinal, forming at all points an angle at most equal at 45°, preferably at most equal to 20°, relative to a longitudinal direction (XX') of the tread.
12. Bande de roulement (1) selon la revendication 11, la bande de roulement (1) ayant une largeur axiale (W), dans laquelle au moins une découpure complexe (5) ayant une ligne moyenne (Lm) sensiblement longitudinale est axialement positionnée dans une portion médiane (11) de bande de roulement ayant une largeur axiale (Wm) au plus égale aux deux tiers de la largeur axiale (W) de la bande roulement, ladite portion médiane (11) étant centrée sur un plan médian (XZ) passant par le milieu de la surface de roulement (2) et perpendiculaire à la surface de roulement (2). 12. Tread (1) according to claim 11, the tread (1) having an axial width (W), in which at least one complex cutout (5) having a substantially longitudinal mean line (Lm) is axially positioned in a middle portion (11) of tread having an axial width (Wm) at most equal to two thirds of the axial width (W) of the tread, said middle portion (11) being centered on a median plane (XZ ) passing through the middle of the rolling surface (2) and perpendicular to the rolling surface (2).
13. Pneumatique pour véhicule poids lourd comprenant une bande de roulement (1) selon l’une quelconque des revendications 1 à 12.
13. A tire for a heavy-duty vehicle comprising a tread (1) according to any one of claims 1 to 12.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR2012247A FR3116763B1 (en) | 2020-11-27 | 2020-11-27 | Tire tread for a heavy-duty vehicle having improved resistance to attack |
PCT/FR2021/052039 WO2022112689A1 (en) | 2020-11-27 | 2021-11-19 | Tyre tread for a heavy vehicle with improved resistance to aggressive effects |
Publications (1)
Publication Number | Publication Date |
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EP4251433A1 true EP4251433A1 (en) | 2023-10-04 |
Family
ID=74183431
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP21823964.8A Pending EP4251433A1 (en) | 2020-11-27 | 2021-11-19 | Tyre tread for a heavy vehicle with improved resistance to aggressive effects |
Country Status (5)
Country | Link |
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US (1) | US20240092126A1 (en) |
EP (1) | EP4251433A1 (en) |
CN (1) | CN116568530A (en) |
FR (1) | FR3116763B1 (en) |
WO (1) | WO2022112689A1 (en) |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1225238A (en) * | 1967-04-21 | 1971-03-17 | ||
IT1185117B (en) * | 1985-06-26 | 1987-11-04 | Pirelli | TIRE FOR VEHICLE WHEELS WITH LOW ROLLING RESISTANCE TREAD |
FR2950565B1 (en) | 2009-09-29 | 2012-08-31 | Michelin Soc Tech | ROLLER BELT FOR IMPROVED RIGIDITY TIRES |
FR2956614B1 (en) | 2010-02-22 | 2012-03-23 | Michelin Soc Tech | TIRE TREAD GROOVE PROTECTION DEVICE OF TIRE |
FR2973285B1 (en) | 2011-04-01 | 2013-03-29 | Michelin Soc Tech | TREAD BAND COMPRISING AT LEAST ONE GROOVING ROD AND METHOD OF OBTAINING |
FR3036321A1 (en) | 2015-05-22 | 2016-11-25 | Michelin & Cie | TIRE FOR HEAVY WEIGHT WITH WEAR INDICATOR DEVICE |
WO2017176280A1 (en) * | 2016-04-08 | 2017-10-12 | Compagnie Generale Des Etablissements Michelin | Truck tire tread and truck tire |
WO2019008276A1 (en) | 2017-07-05 | 2019-01-10 | Compagnie Generale Des Etablissements Michelin | Tyre of which the tread comprises wavy grooves |
US11465450B2 (en) | 2017-12-19 | 2022-10-11 | Compagnie Generale Des Etablissements Michelin | Tire tread comprising undulating grooves |
-
2020
- 2020-11-27 FR FR2012247A patent/FR3116763B1/en active Active
-
2021
- 2021-11-19 EP EP21823964.8A patent/EP4251433A1/en active Pending
- 2021-11-19 US US18/038,918 patent/US20240092126A1/en active Pending
- 2021-11-19 WO PCT/FR2021/052039 patent/WO2022112689A1/en active Application Filing
- 2021-11-19 CN CN202180079462.5A patent/CN116568530A/en active Pending
Also Published As
Publication number | Publication date |
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FR3116763B1 (en) | 2024-04-05 |
CN116568530A (en) | 2023-08-08 |
WO2022112689A1 (en) | 2022-06-02 |
FR3116763A1 (en) | 2022-06-03 |
US20240092126A1 (en) | 2024-03-21 |
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