Low-noise tires

Abstract

A tire (10) for a passenger vehicle has an axial central portion and axial lateral portions, the axial central portion and each axial lateral portion satisfying conditions I, II, and III: I - the part does not have transverse cutouts (90, 90'), II - the part comprises N transverse notches (90, 90') arranged such that π x OD / N ≥ 40 mm; III - the part comprises N transverse notches (90, 90') arranged such that π x OD / N≦24 mm; Condition I or II is satisfied by the axial central portion or by the axial lateral portion, and condition III is satisfied by the axial central portion or by the axial lateral portion.

Description

Technical Field

[0001] The present invention relates to a tire for a passenger car. The tire is understood to mean a casing intended to form, by cooperation with a support element, such as a rim, a cavity that can be pressurized up to a pressure higher than atmospheric pressure. The tire according to the present invention has a substantially donut-shaped structure that exhibits rotational symmetry around the main axis of the tire.

Background Art

[0002] A tire of size 245 / 45R 18 sold under the MICHELlN registered trademark and belonging to the PRIMACY 4 range is known from the prior art. Such tires provide an excellent performance compromise, among other things, between grip on wet or dry road surfaces and the exterior noise generated by the tire.

[0003] However, new regulations related to the exterior noise generated by tires, especially in Europe, require that this exterior noise be reduced.

[0004] Tire manufacturers have thus developed tires for reducing this exterior noise, for example, by modifying the tread pattern of the tire, as disclosed in International Publication No. WO 2018 / 199273, in which the grooves are provided with protrusions that shift the resonance frequency of the air columns in these grooves away from the frequency range audible to the human ear. Nevertheless, providing these protrusions in the grooves increases the complexity of the manufacture of the corresponding mold and thus the cost of the associated tire.

[0005] Another solution that is known today is disclosed in International Publication No. WO 2010 / 069510 and consists in modifying the architecture of a tire by radially interposing a sublayer of a material containing a high-density filler between the tread layer of the tire and the crown reinforcement of the tire. This sublayer makes it possible not to shift the frequency of the emitted noise, as in International Publication No. WO 2018 / 199273, but to attenuate the acoustic power of this noise. Nevertheless, providing such a sublayer in a tire increases not only the cost of the tire, but also its mass and thus its rolling resistance.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The object of the present invention is to reduce the external noise generated by a tire in a simple and cost - free way compared to tires of the prior art.

Means for Solving the Problems

[0008] For this purpose, the subject of the present invention is a tire for a passenger car comprising a tread intended to be in contact with a road surface through a tread surface having an outer diameter OD and axially delimited by first and second axially - extending edges of the tread surface when the tire is in motion, the tread being - An axial center portion having main circumferential grooves, with at least first and second main circumferential grooves each having a depth greater than or equal to 50% of the tread pattern height and axially disposed one on each side of the tire's median plane. The first and second main circumferential grooves are the main circumferential grooves furthest axially towards the outside of the tread. The axial center portion extends axially far from the axial outer edge of the first main circumferential groove to the axial outer edge of the second main circumferential groove. The axial center portion includes at least one center rib, and the center rib or each center rib is axially delimited by two main circumferential grooves having a depth greater than or equal to 50% of the tread pattern height, and the above-mentioned axial center portion, - Axially disposed one on each side of the axial center portion outside the axial center portion with respect to the median plane of the tire, and - The first axial transverse portion extends axially far from the first axial edge of the tread surface to the axial outer edge of the first main circumferential groove, - The second axial transverse portion extends axially far from the second axial edge of the tread surface to the axial outer edge of the second main circumferential groove, The first and second axial transverse portions are arranged as such, The center rib or each center rib and each first and second axial transverse portion have at least one axial portion satisfying one of the following conditions I, II, III. Each of the center rib or each center rib and one or more axial portions of each first and second axial transverse portion satisfying one of the conditions I, II, III has an axial width greater than or equal to 70% of the axial width of the center rib or each center rib and each first and second axial transverse portion. The above conditions are Only one - Without a transverse notch having a depth greater than or equal to 20% of the tread pattern height and an axial length greater than or equal to 20% of the axial width of the center rib or the axial transverse portion, and the axial portion has at least one circumferential notch having a depth strictly less than 50% of the tread pattern height Only one This, I - Without a transverse notch having a depth greater than or equal to 20% of the tread pattern height and an axial length greater than or equal to 20% of the axial width of the center rib or the axial transverse portion, and the axial portion has at least one circumferential notch having a depth strictly less than 50% of the tread pattern height May be provided That, The cross-sectional notches in the II-axis direction part have a depth greater than or equal to 20% of the tread pattern height or an axial length greater than or equal to 20% of the axial width of the center rib or the axial transverse part, and the total of N cross-sectional notches in the axial direction part having a depth greater than or equal to 20% of the tread pattern height or an axial length greater than or equal to 20% of the axial width of the center rib or the axial transverse part are arranged such that π×OD / N≧40mm, and the axial direction part has at least one circumferential notch having a depth strictly less than 50% of the tread pattern height May be provided such that The cross-sectional notches in the III-axis direction part have a depth greater than or equal to 20% of the tread pattern height or an axial length greater than or equal to 20% of the axial width of the center rib or the axial transverse part, and the total of N cross-sectional notches in the center rib or the axial direction part having a depth greater than or equal to 20% of the tread pattern height or an axial length greater than or equal to 20% of the axial width of the center rib or the axial transverse part are arranged such that π×OD / N≦24mm, and the axial direction part has at least one circumferential notch having a depth strictly less than 50% of the tread pattern height May be provided such that is Condition I or II is satisfied by at least one of the axial direction parts of the center rib or one of the center ribs, or by one of the axial direction parts of the first axial transverse part, or by one of the axial direction parts of the second axial transverse part Condition III is satisfied by at least one of the axial direction parts of the center rib or one of the center ribs, or by one of the axial direction parts of the first axial transverse part, or by one of the axial direction parts of the second axial transverse part the above-mentioned first and second axial transverse parts are provided with.

[0009] Due to either the one or two or more center ribs and the axial direction transverse portions having no or very few transverse notches or having a large number of transverse notches, the inventor behind the present invention has reduced the exterior vehicle noise generated by the tire.

[0010] Specifically, the inventor behind the present invention utilized the fact that the exterior vehicle noise generated by the tire is caused on the one hand by the excitation of the notches and on the other hand by the resonance of the mechanical structure formed by the tire. The inventor has found that by avoiding overlapping the frequency spectrum of the noise generated from the excitation of the notches with the frequency spectrum of the noise generated from the mechanical structure, the resonance of the frequencies and harmonics of these frequency spectra is avoided so that the exterior vehicle noise emitted by the tire can be significantly reduced.

[0011] More specifically, the frequency spectrum related to the noise generated from the mechanical structure is included between 600 Hz and 1100 Hz, and this spectrum depends, inter alia, on the length of the contact surface of the tire and on the dimensions and structure of the tire. According to the invention, the frequency spectrum related to the noise generated from the excitation of the central rib or of each central rib and of the transverse cutouts of each first and second axially transverse part is shifted with respect to the frequency spectrum in the range from 600 Hz to 1100 Hz so that the external noise emitted by the tire is reduced. That is, for each central rib and for each axial part of each first and second axially transverse part, the number of cutouts in the contact surface of the tire can be increased so as to shift the frequency spectrum of the noise generated from the excitation of the transverse cutouts towards higher frequencies (i.e., the average spacing π×OD / N can be reduced). Conversely, for each central rib and for each axial part of each first and second axially transverse part, the number of cutouts in the contact surface of the tire can also be reduced so as to shift the frequency spectrum of the noise generated from the excitation of the transverse cutouts towards lower frequencies (i.e., the average spacing π×OD / N can be increased). This excitation also depends on the traveling speed of the vehicle, and thus each value of N within the intervals of the invention can be selected according to the speed at which the vehicle is used.

[0012] According to the invention, condition I or II and condition III are satisfied at least once by at least one of the axial parts of the central rib or of one of the central ribs and by at least one of the axial parts of the first and second axially transverse parts. Specifically, if only condition I or II is satisfied by the rib or all the ribs and the first and second axial central parts, the tire is considered to have a grip problem on a wet road surface. If only condition III is satisfied by the rib or all the ribs and the first and second axial central parts, the rigidity of the tread is considered to be excessively reduced in the longitudinal direction due to an excessive number of transverse cutouts, which is considered to result in a drop in grip on a dry road surface.

[0013] In the context of the present invention, each axial portion either satisfies a single condition from among Conditions I, II, III or does not satisfy any of Conditions I, II, III. That is, the progression along the axial direction in the central rib or the axial transverse portion involves a passage from a plane perpendicular to a rotational axis for which one of Conditions I, II, III is satisfied to a plane perpendicular to a rotational axis for which none of Conditions I, II, III is satisfied, i.e., a passage from one axial portion to another axial portion. Similarly, the progression along the axial direction in the central rib or the axial transverse portion involves a passage from a plane perpendicular to a rotational axis for which one of Conditions I, II, III is satisfied to a plane perpendicular to a rotational axis for which another of Conditions I, II, III is satisfied, i.e., a passage from one axial portion to another axial portion. Finally, the progression along the axial direction in the central rib or the axial transverse portion involves a passage from a plane perpendicular to a rotational axis for which one of Conditions I, II, III is satisfied to a plane perpendicular to a rotational axis for which the same Conditions I, II, III are satisfied, i.e., remaining within one and the same axial portion.

[0014] The fact that the transverse cutouts to be taken into account when calculating the average spacing have both a depth greater than or equal to 20% of the tread pattern height and an axial length greater than or equal to 20% of the axial width of the associated central rib or axial transverse portion means that it is not necessary to take into account transverse cutouts that are not deep enough or not axially long enough to contribute to the exterior vehicle noise emitted by the tire.

[0015] Of Conditions I, II, III Only oneThe fact that the axial width of the central rib or each central rib and one or more axial portions of the entire axial portions of each of the first and second axially transverse portions that satisfy is greater than or equal to 70% of the axial width of the central rib or each central rib and each of the first and second axially transverse portions means that at least a non-significant portion of the axial width of the central rib or each central rib and each of the first and second axially transverse portions, in this case the portion corresponding to less than 30%, can consider embodiments that do not satisfy any of conditions I, II, and III. The fact that the axial width of one or more portions that do not satisfy any of conditions I, II, and III is relatively small guarantees that the one or more portions contribute little or nothing to the emitted external noise of the tire.

[0016] Furthermore, the fact that the central rib or each central rib and each of the first and second axially transverse portions has at least one axial portion that satisfies one of conditions I, II, III Only one makes it possible to consider embodiments in which different conditions I, II, III are satisfied or not satisfied by clearly different axial portions of the central rib or each central rib and each of the first and second axially transverse portions. According to the present invention, the sum of the axial widths of one or more axial portions that each satisfy one of conditions I, II, III Only one is greater than or equal to 70% of the axial width of the central rib or each central rib and each of the first and second axially transverse portions.

[0017] When an axial portion of a rib or an axially transverse portion does not satisfy the same conditions I, II, III as two adjacent axial portions of the same rib or the same axially transverse portion, or when an axial portion of a rib or an axially transverse portion does not satisfy any of conditions I, II, III, but two adjacent axial portions of the same rib or the same axially transverse portion each satisfy one of conditions I, II, III Only oneWhen the following is satisfied, there are two transition zones between the relevant axial part and each adjacent axial part, and these two transition zones emit external noise in a frequency spectrum that is likely to overlap with the structural noise spectrum of the tire. Therefore, the number of transition zones will be minimized if not eliminated. Further, this means, firstly, that the number of conditions I, II, and III satisfied on one and the same central rib or one and the same axial transverse part will be minimized, and secondly, that among conditions I, II, and III on one and the same rib or one and the same axial transverse part Only one When the following is satisfied, none of conditions I, II, and III are satisfied, and the axial parts that may be axially sandwiched between various axial parts that surely satisfy the single conditions I, II, and III will be minimized if not eliminated.

[0018] OD is the outer diameter of the tire measured on the median plane of the tire. Therefore, π×OD is the circumference of the tire measured on the median plane of the tire. N and OD or π×OD are measured on the unloaded tire, and can be measured whether inflated or not, and what is important for N and OD or π×OD is that they are measured under the same conditions.

[0019] The axial width of the axial part of the axial central part or the axial transverse part of the central rib, of the axial part of the central rib, of the axial part of the axial transverse part, is the axial distance between two planes perpendicular to the axis of rotation of the tire through which the axial inner edge and the axial outer edge of the axial part of the axial transverse part of the axial part of the central rib, of the axial central part or the axial transverse part of the central rib, respectively, pass.

[0020] The axial length of the transverse notch is the axial distance between two planes perpendicular to the axis of rotation of the tire through which the axial inner end and the axial outer end of the transverse notch, respectively, pass.

[0021] According to the present invention, at least a part of the central rib or one of the central ribs, at least a part of the first axial transverse part, or at least a part of the second axial transverse part is provided with a transverse notch. The notch means either a groove or a sipe, and forms a space opening on the tread surface.

[0022] The sipe or groove has two main characteristic dimensions on the tread surface, namely width and curve length, and these dimensions are such that the curve length is at least equal to twice the width. Thus, the sipe or groove determines its curve length, is connected by a bottom surface, and is delimited by at least two main side surfaces that are separated from each other by a non-zero distance called the width of the notch.

[0023] In a new tire, the width of the notch is the maximum distance between the two main side surfaces, and is measured at the location of the radial dimension that coincides with the tread surface when the notch is not chamfered, and is measured at the location of the outermost radial dimension of the notch and the location of the innermost radial dimension of the chamfer when the notch is chamfered. In the case where the notch has two clearly different parts with different widths W1 and W2 such that 0.67≦W1 / W2≦1.50, the width of the notch is the width of the part with the maximum curve length. The clearly different parts are separated from each other by an interruption in the curvature of each side surface of each part, such as a local or sudden step or a local or sudden narrowing.

[0024] On a new tire, the depth of the notch is the maximum radial distance between the bottom of the notch and the projection point of this bottom on the road surface when the tire is running. The maximum value for the depth of the notch is called the tread pattern height.

[0025] The sipe is such that the distance between the main side surfaces is suitable to enable at least a partial contact state when the main side surfaces that define the boundary of the sipe pass through the ground contact surface, especially when the tire is new and especially under normal running conditions including when the tire is under nominal load and nominal pressure.

[0026] The groove is such that the distance between the main sides is a distance such that, in particular, under normal running conditions including when the tire is under the nominal load and nominal pressure, these main sides cannot come into contact with each other.

[0027] The notch may be in the transverse or circumferential direction.

[0028] The transverse notch extends in an average direction forming an angle greater than 30°, preferably greater than or equal to 45°, with the circumferential direction of the tire. The average direction is the shortest curve parallel to the tread surface connecting the two ends of the notch. The transverse notch can be continuous such that the two main sides determining its length are continuous over the length of the transverse notch, i.e., not interrupted by a tread block or another notch. Equally, the transverse notch can be discontinuous such that the two main sides determining its length are interrupted by one or more tread blocks and / or one or more notches, i.e., interrupted by one or more tread blocks and / or one or more other notches.

[0029] The circumferential notch extends in an average direction that forms an angle with the circumferential direction of the tire that is less than or equal to 30°, preferably less than or equal to 10°. The average direction is the shortest curve parallel to the tread surface connecting the two ends of the notch. In the case of a continuous circumferential notch, the two ends coincide with each other and are joined by the curve that constitutes the entire circumference of the tire. The circumferential notch can be continuous such that the two main sides that determine its length are continuous over the entire circumference of the tire, i.e., not interrupted by a tread block or another notch. Equally, the circumferential notch can be discontinuous such that the two main sides that determine its length are interrupted by one or more tread blocks and / or one or more notches over the entire circumference of the tire, i.e., interrupted by one or more tread blocks and / or one or more other notches.

[0030] The main direction of the notch is the direction in which a curve extends equidistant from each of the edges of the notch at a location of the radial dimension of the tread surface. The curve length is the length between each of the ends of the notch measured along this curve that is equidistant from each of the edges of the notch at a location of the radial dimension of the tread surface.

[0031] In the case of a circumferential notch located outside the median plane of the tire, the sides are called the axial inner surface and the axial outer surface, and the axial inner surface is arranged axially inside the axial outer surface with respect to the median plane at a given azimuth angle.

[0032] In the case of a transverse notch, the sides are called the front surface and the rear surface, and the front surface is the surface whose edge enters the ground surface in front of the edge of the rear surface with respect to a given circumferential line.

[0033] A circumferential groove having a depth greater than or equal to 50% of the tread pattern height and including a first axially transverse portion, a second axially transverse portion, and one or more center ribs therein is referred to as a main rib. Thus, in cases where the tread pattern height is at least twice as large as the height of the legal tread wear indicator and represents most of a passenger car tire, these main circumferential grooves have a depth such that they persist over more than half of the wearable tread height of the tire. Thus, such main circumferential grooves, which are greater than or equal to 50% of the tread pattern height, do not disappear until the tire wears at least 50% of its wearable tread height. The wearable tread height is defined as the radial height between the radially outermost point of the legal tread wear indicator when the tire is new and the projected point of the legal tread wear indicator onto the road surface when the tire is in motion. Such legal tread wear indicators are mandated, for example, by United Nations regulations R30 and R54, US standard FMVSS139, or Chinese standard GB97743, and are intended to indicate to the user of the tire a legal tire tread wear threshold that is dangerous to drive beyond, especially on a wet road surface.

[0034] In the conventional method, the tread surface is determined on a tire mounted on a nominal rim and inflated to nominal pressure within the meaning of the 2019 specifications of the European Tyre and Rim Technical Organisation or "ETRTO". When there is a clear boundary between the tread surface and the remainder of the tire, the axial width of the tread surface is easily measured. When the tread surface is continuous with the outer surface of the tire sidewall, the axial boundary of the tread surface passes through the point where the angle between the tangent of the tread surface and a straight line parallel to the axial direction is equal to 30°. When there are several points in the meridian section where this angle is equal to 30° in absolute value, the radially outermost point is adopted.

[0035] The tire according to the present invention has a substantially donut shape around a swivel axis that substantially coincides with the rotation axis of the tire. This swivel axis defines the three directions conventionally used by those skilled in the art, namely, the axial direction, the circumferential direction, and the radial direction.

[0036] The expression "axial direction" means a direction substantially parallel to the swivel axis of the tire, i.e., the rotation axis of the tire.

[0037] The expression "circumferential direction" means a direction substantially perpendicular to both the axial direction and the radius of the tire (i.e., the tangent of a circle centered on the rotation axis of the tire).

[0038] The expression "radial direction" means a direction along the radius of the tire, i.e., any direction that intersects the rotation axis of the tire and is substantially perpendicular to this axis.

[0039] The expression "midplane of the tire" (denoted as M) means a plane that is perpendicular to the rotation axis of the tire, is axially intermediate between the two beads, and passes through the axial center of the crown reinforcement.

[0040] The expression "equatorial circumferential plane of the tire" (denoted as E) means a plane that passes through the equator of the tire in the meridian section and is perpendicular to the midplane and the radial direction. The equator of the tire is an axis that is parallel to the rotation axis of the tire in the meridian section (perpendicular to the circumferential direction and parallel to the radial and axial directions), and is equidistant between the radially outermost point of the tread intended to contact the road surface and the radially innermost point of the tire intended to contact a support, such as a rim, and the distance between these two points is equal to H.

[0041] The expression "meridian plane" means a plane that is parallel to the rotation axis of the tire, includes it, and is perpendicular to the circumferential direction.

[0042] "Radially inner" and "radially outer" respectively mean "being close to the rotational axis of the tire" and "being far from the rotational axis of the tire". "Axially inner" and "axially outer" respectively mean "being close to the center plane of the tire" and "being far from the center plane of the tire".

[0043] The term "bead" means a portion of the tire that is intended to enable the attachment of the tire to a mounting support, such as a wheel having a rim. Accordingly, each bead is, among other things, intended to be in contact with the flange of the rim and to enable attachment thereto.

[0044] Any range of values represented by the expression "between a and b" represents a range of values extending from greater than a to less than b (i.e., excluding the endpoints a and b), while any range of values represented by the expression "from a to b" means a range of values extending from a to b (i.e., including the exact endpoints a and b).

[0045] The tyre according to the invention is intended for passenger cars as defined according to the 2019 standards of the European Tyre and Rim Technical Organisation or "ETRTO". Such a tyre has a ratio H / S, expressed as a percentage within the meaning of the 2019 standards of the European Tyre and Rim Technical Organisation or "ETRTO", equal to a maximum of 90, preferably equal to a maximum of 80, more preferably equal to a maximum of 70 and at least equal to 30, preferably at least equal to 40, and a nominal cross-sectional width S equal to at least 115 mm, preferably at least equal to 155 mm, more preferably at least equal to 175 mm and at most equal to 385 mm, preferably at most equal to 315 mm, more preferably at most equal to 285 mm, even more preferably at most equal to 255 mm, and is characterised by a cross-section having a meridian cross-section with a cross-sectional height H and a nominal cross-sectional width S. In addition, the diameter D at the flange defining the diameter of the tyre mounting rim is equal to at least 12 inches, at least 16 inches and at most equal to 24 inches, preferably at most equal to 20 inches.

[0046] Advantageously, in order to consider only the transverse notches that contribute maximally to the external vehicle noise emitted by the tyre due to their depth, the total of the N transverse notches to be taken into account for calculating the average spacing has a depth greater than or equal to 30% of the tread pattern height, preferably greater than or equal to 40%.

[0047] Similarly, in order to consider only the transverse notches that contribute maximally to the external vehicle noise emitted by the tyre due to their width, the total of the N transverse notches to be taken into account for calculating the average spacing has an axial length greater than or equal to 30% of the axial width of the central rib or of the axial transverse part, preferably greater than or equal to 50%, even more preferably greater than or equal to 75%.

[0048] Of course, in order to take into account the transverse notches that contribute maximally to the vehicle exterior noise emitted by the tire due to both the width and the axial length, in a highly preferred embodiment, the consideration of transverse notches having a depth greater than or equal to 40% of the tread pattern height and an axial length greater than or equal to 75% of the axial width of the central rib or the axial transverse portion will advantageously act on the calculation of the average spacing.

[0049] In one preferred embodiment, at least one of the central rib or the axial portion of each central rib satisfies condition I or II, and at least one of the axial portions of each of the first and second axial transverse portions satisfies condition III. Preferably, at least one of the central rib or the axial portion of each central rib satisfies condition I, and at least one of the axial portions of each of the first and second axial transverse portions satisfies condition III.

[0050] During the acceleration phase, the vehicle is less heavily loaded at the front, and thus the axial central portion comes into contact with the road surface during driving, while the first and second axial transverse portions, even if they come into contact with the road surface, only have a relatively light contact state. Therefore, in order to reduce the noise generated during this acceleration phase, especially in the case of a vehicle using front-wheel drive, it is preferable to make the axial central portion as quiet as possible, and thus to have one or more central ribs with only a small number of transverse notches or even no transverse notches at all.

[0051] Advantageously, in order to avoid as much as possible any potential overlap between the frequency spectrum of the noise generated by the excitation of the notch and the frequency spectrum of the noise generated by the mechanical structure, there are provided transverse notches having a depth greater than or equal to 20% of the tread pattern height and an axial length greater than or equal to 20% of the axial width of the central rib or each central rib or the axial transverse part or each axial transverse part, and the total of the N transverse notches of the central rib or each central rib or the axial transverse part or each axial transverse part satisfying condition II is preferably arranged such that π×OD / N≧60 mm, and even more preferably such that π×OD / N≧80 mm.

[0052] In one preferred embodiment, there are provided transverse notches having a depth greater than or equal to 20% of the tread pattern height and an axial length greater than or equal to 20% of the axial width of the central rib or each central rib or the axial transverse part or each axial transverse part, and the total of the N transverse notches of the central rib or each central rib or the axial transverse part or each axial transverse part satisfying condition III is arranged such that π×OD / N≧10 mm, and preferably such that π×OD / N≧15 mm.

[0053] By limiting the number of transverse notches within the contact patch of the tire, an excessive reduction in the area of the tread in contact with the road surface is avoided, and thus an excessive increase in the pressure applied by the road surface to each of the edge corners forming the edges of the transverse notches is avoided. Further, this avoids impairing the grip on a dry road surface, which is an inverse function of the pressure applied by the road surface to the tread.

[0054] Advantageously, in order to avoid potential overlap between the frequency spectrum of the noise generated by the excitation of the notch and the frequency spectrum of the noise generated by the mechanical structure as much as possible, it has a depth greater than or equal to 20% of the tread pattern height and an axial length greater than or equal to 20% of the axial width of the central rib or each central rib or the axial transverse portion or each axial transverse portion, and the totality of the N transverse notches of the central rib or each central rib or the axial transverse portion or each axial transverse portion satisfying Condition III is preferably arranged such that π×OD / N≦22 mm, and even more preferably, π×OD / N≦20 mm.

[0055] Very advantageously, in order to limit as much as possible the exterior noise emitted by one or more parts that do not satisfy any of Conditions I, II, and III, each of the central rib or each central rib and one or more axial parts of each of the first and second axial transverse portions that satisfy Only one any of Conditions I, II, and III has an axial width of the whole that is greater than or equal to 80%, preferably greater than or equal to 90% of the axial width of the central rib or each central rib and each of the first and second axial transverse portions.

[0056] As described above, in order to minimize the diversity of the transition zone by reducing the number of conditions satisfied on one and the same central rib or one and the same axial transverse portion, when the central rib or each central rib or the first axial transverse portion or the second axial transverse portion each comprises several axial parts that satisfy Only one any of Conditions I, II, and III, the totality of the axial parts of the central rib or each central rib or the first axial transverse portion or the second axial transverse portion Only one satisfies any of Conditions I, II, and III.

[0057] As described above, by minimizing the number of axial portions that do not satisfy any of conditions I, II, and III, which are sandwiched between various axial portions that satisfy the single conditions I, II, and III in the axial direction, the number of transition zones is minimized. The central rib or each central rib and each first and second axial transverse portions satisfy one of conditions I, II, and III Only one and include an axial portion having an axial width that is greater than or equal to 70%, preferably 80%, more preferably 90% of the axial width of the central rib or each central rib and each first and second axial transverse portions.

[0058] In one advantageous embodiment, the ratio of the axial width of the central portion to the axial width of each first and second axial transverse portions is greater than or equal to 3.0, preferably in the range from 3.0 to 5.0, more preferably from 4.0 to 4.5.

[0059] In this embodiment, the axial central portion has the largest axial width compared to the first and second axial transverse portions. This embodiment is particularly advantageous in that when the rib or each rib satisfies condition I or II, the smaller the axial width of the axial central portion, the higher the degree to which the noise generated by the transverse notch can be reduced.

[0060] Advantageously, the axial central portion has an axial width that is greater than or equal to 50%, preferably greater than or equal to 60% of the axial width of the tread surface of the tire when new. Advantageously, the axial central portion has an axial width that is less than or equal to 80%, preferably less than or equal to 70% of the axial width of the tread surface of the tire when new.

[0061] Advantageously, each of the first and second axial lateral portions has an axial width that is less than or equal to 25%, preferably less than or equal to 20%, of the axial width of the tread surface of the tire when new. Advantageously, each of the first and second axial lateral portions has an axial width that is greater than or equal to 5%, preferably greater than or equal to 10%, of the axial width of the tread surface of the tire when new.

[0062] Due to the advantageous features of each main circumferential groove, - each main circumferential groove has a depth in the range from 4.0 mm to the tread pattern height, preferably from 5.0 mm to the tread pattern height, more preferably still from 5.5 mm to the tread pattern height, - each main circumferential groove has a width greater than or equal to 1.0 mm, preferably greater than or equal to 5.0 mm, more preferably greater than or equal to 8.0 mm, and even more preferably in the range from 8.0 mm to 15.0 mm.

[0063] Advantageously, when each of the first and second axial lateral portions comprises a transverse notch extending axially from the axial outer end to the axial inner end, at least 50%, preferably 75%, more preferably still, of each of the transverse notches of each of the first and second axial lateral portions is at least partially blocked by a connecting bridge connecting the front face and the rear face to form the axial inner end of the transverse notch. In order to take into account only the transverse notches that contribute most to noise, preferably, the above-mentioned features apply to the totality of N transverse notches having a depth greater than or equal to 20% of the tread pattern height and an axial length greater than or equal to 20% of the axial width of each of the first and second axial lateral portions.

[0064] In other words, the connecting bridge forms part of the axial outer surface of the first or second main circumferential groove. Furthermore, due to the presence of the connecting bridge, the air communication between the transverse notch and the main circumferential groove in the axial central portion is restricted or even completely eliminated, and thus the acoustic resonance of the potential air column established between the transverse notch and the circumferential groove is also restricted or even completely eliminated.

[0065] Even more advantageously, the connecting bridge is arranged so as to completely block the communication between the transverse notch and the first or second main circumferential groove when the transverse notch enters the contact surface when the tire is running on the road surface. Furthermore, this eliminates any risk of acoustic resonance of the air column between the transverse notch and the circumferential groove.

[0066] Due to the advantageous features of each transverse notch, - each transverse notch has a depth in the range from 2.0 mm to the tread pattern height, preferably in the range from 4.0 mm to the tread pattern height, even more preferably in the range from 5.0 mm to the tread pattern height, - each transverse notch has a width smaller than or equal to 2.0 mm, preferably in the range from 0.5 mm to 2.0 mm.

[0067] Advantageously, at least one, preferably at least 25%, more preferably at least 40% of the transverse notches of at least one of the first and second axial transverse portions - the main portion extends over a main curve length that is strictly greater than 50% of the total curve length of the transverse notch, - the supplementary portion extends over a supplementary curve length that is strictly smaller than 50% of the total curve length of the transverse notch, is arranged axially outside the main portion, and has a width greater than the width of the main portion, and are provided with the main portion and the supplementary portion separated from each other by an interruption at the curvature of each side surface.

[0068] Such supplementary parts enable effective drainage and thus better grip performance on wet road surfaces.

[0069] Due to the preferred characteristics of the tire, the surface area porosity of the tread ranges from 27% to 45%, preferably from 30% to 40%.

[0070] Due to the preferred characteristics of the tire, the volume porosity of the tread ranges from 17% to 35%, preferably from 20% to 30%.

[0071] Such surface area porosity and volume porosity ensure effective drainage under driving conditions on wet road surfaces.

[0072] Preferably, the surface area porosity of each of the first and second axially transverse portions ranges from 20% to 30%.

[0073] Also preferably, the volume porosity of each of the first and second axially transverse portions ranges from 5% to 10%.

[0074] Preferably, the surface area porosity of the axially central portion ranges from 35% to 45%.

[0075] Also preferably, the volume porosity of the axially central portion ranges from 25% to 35%.

[0076] Preferably, the surface area porosity of the central rib or each central rib ranges from 5% to 10%.

[0077] Also preferably, the volume porosity of the central rib or each central rib ranges from 0.5% to 5%, preferably from 0.5% to 2%.

[0078] Advantageously, the ratio of the surface area porosity of the central rib or each central rib to the surface area porosity of each of the first and second axial transverse portions is less than or equal to 0.35, preferably less than or equal to 0.30, and more preferably in the range from 0.10 to 0.30.

[0079] Also advantageously, the ratio of the volume porosity of the central rib or each central rib to the volume porosity of each of the first and second axial transverse portions is less than or equal to 0.20, preferably less than or equal to 0.15, and more preferably in the range from 0.10 to 0.15.

[0080] The surface area porosity of the tread, a portion of the tread, or a rib is - a new product, inflated to nominal pressure, under nominal load, and thus the difference between the total contact area AT of the ground contact surface of the tread, a portion of the tread, or a rib of the tire in contact with a smooth road surface, e.g., a glass plate, and the contact area AC of the elements of the tread, a portion of the tread, or a rib in contact with the road surface during running, and - the total contact area AT of the ground contact surface of the tread, a portion of the tread, or a rib of the tire that is a new product, inflated to nominal pressure, under nominal load, and thus in contact with a smooth road surface, and is a ratio that associates them.

[0081] The volume porosity of the tread, a part of the tread, or a rib is the ratio of the total volume of the notch in the tread, a part of the tread, or the rib of a new tire to the total volume of the tread, a part of the tread, or the rib of the new tire without any notch. The tread is axially delimited by two planes perpendicular to the tire's axis of rotation and passing through the axial edges of the tread surface. A part of the tread or a rib is axially delimited by two planes perpendicular to the tire's axis of rotation and passing through the axial edge ends of this part or rib. The tread, a part of it, or a rib is radially delimited by a curved surface parallel to the tread surface of the new tire and passing through the radially innermost point of the deepest notch in the tread of the new tire.

[0082] To determine the surface area porosity, the nominal load is equal to 80% of the rated load indicated by the European Tyre and Rim Technical Organisation or "ETRTO" in 2019, and the nominal pressure is equal to 2.5 bar.

[0083] In one advantageous embodiment, the axial central portion comprises at least a third main circumferential groove and at least first and second central ribs - the first central rib is axially included between the first main circumferential groove and the third main circumferential groove, - the second central rib is axially included between the second main circumferential groove and the third main circumferential groove, in an arranged state.

[0084] Therefore, by increasing the number of central ribs for a given axial width of the axial central portion, the drainage across the entire axial width of the tread is improved.

[0085] In an even more preferred embodiment, the axial central portion comprises a third and a fourth main circumferential groove and at least first, second, and third central ribs - the first central rib is axially included between the first main circumferential groove and the third main circumferential groove, - The second central rib is axially included between the third main circumferential groove and the fourth main circumferential groove, - The third central rib is axially included between the fourth main circumferential groove and the second main circumferential groove, and is provided in such an arranged state.

[0086] The presence of the three central ribs further improves drainage.

[0087] In this more preferred embodiment, - The first central rib extends axially far from the axially inner edge of the first main circumferential groove to the axially outer edge of the third main circumferential groove, - The second central rib extends axially from the axially outer edge of the third main circumferential groove to the axially inner edge of the fourth main circumferential groove, - The third central rib extends axially from the axially outer edge of the fourth main circumferential groove to the axially inner edge of the second main circumferential groove.

[0088] In the embodiments shown so far, the central rib or each central rib has an axial width that is less than or equal to 30% of the axial width of the axial central portion, preferably less than or equal to 25%. Therefore, regardless of the number of central ribs, drainage by each of these central ribs is facilitated by reducing the axial width of each of these central ribs.

[0089] To have a sufficient tread surface to reduce the local pressure applied by the road surface to the tire, thereby ensuring good grip on a dry road surface, the central rib or each central rib has a sufficient axial width that is greater than or equal to 10% of the axial width of the axial central portion, preferably greater than or equal to 15%.

[0090] In one very preferred embodiment, the central rib or each central rib has an axial width in the range of 20 mm to 40 mm, preferably 25 mm to 35 mm.

[0091] In an embodiment that improves grip on a wet road surface, while generating little or no additional noise within the axial center portion and not deteriorating the behavior of the tire, the center rib or at least one of them, preferably each center rib, - is axially disposed between the center rib or each center rib and two circumferential grooves provided therebetween, - is strictly less than 50% of the tread pattern height, preferably less than or equal to 30% of the tread pattern height, more preferably in the range of 10% to 30% of the tread pattern height, and includes at least one additional circumferential notch.

[0092] Specifically, the additional circumferential notch or each additional circumferential notch, especially due to its circumferential orientation, and thus the circumferential orientation of the edge of its side surface, there is no edge corner of the additional circumferential notch or each additional circumferential notch hitting the road surface when the tire is running, so it contributes little or no to the generation of noise caused by the vibration of the notch.

[0093] The additional circumferential notch or each additional circumferential notch can store water when running on a wet road surface due to the void volume it generates, thereby improving grip on the wet road surface. Further, each additional circumferential notch divides the center rib, and with this division, the center rib is formed into two axially separated portions by the main circumferential notch on one hand and the additional circumferential notch on the other hand. This is because each of the axially separated portions of the center rib has a shorter axial width than when the center rib has no additional circumferential notch, and thus has a higher function of removing water from the center of each axially separated portion towards each of the main circumferential notch and the additional circumferential notch.

[0094] Finally, the additional circumferential notch or each additional circumferential notch does not deteriorate the behavior of the tire, especially regarding lateral rigidity, due to its relatively small depth.

[0095] Due to advantageous features, - The axial width of the central rib or an additional circumferential notch of each central rib or the axial width of each additional circumferential notch is from 4% to 15% of the axial width of the central rib or each central rib, preferably in the range of 4% to 10%. In a highly preferred embodiment, the axial width of the additional circumferential notch or each additional circumferential notch is in the range of 1.0 mm to 4.0 mm, - The depth of the additional circumferential notch or each additional circumferential notch is less than or equal to 3.0 mm, preferably in the range of 1.0 mm to 3.0 mm.

[0096] By making the additional circumferential notch with a width greater than the depth preferable, the axial width of each axial portion of the central rib disposed on both sides of the additional circumferential notch is reduced. Accordingly, the function of the tire to remove water into each of the main circumferential notches is enhanced, and this effect is even more significant as the axial width of the additional circumferential notch or each additional circumferential notch is larger. Nevertheless, in order to have a sufficient tread area to reduce the local pressure applied by the road surface to the tire, thereby ensuring good grip on a dry road surface, this axial width should not be excessively large.

[0097] In an embodiment that improves grip on a wet road surface, simultaneously generates little or no extra noise within the first axial transverse portion, and does not deteriorate the behavior of the tire, the first axial transverse portion, similar to the axial central portion, - is disposed axially between the first circumferential groove and the first axial end of the tread surface, - is strictly less than 50% of the tread pattern height, preferably less than or equal to 30% of the tread pattern height, more preferably having a depth in the range of 10% to 30% of the tread pattern height, and includes at least one additional circumferential notch.

[0098] Similarly, in order to improve the grip on a wet road surface, and at the same time generate little or no extra noise within the second axial lateral portion and not deteriorate the behavior of the tire, the second axial lateral portion, like the axial center portion and the first axial lateral portion, - is arranged axially between the second circumferential groove and the second axial end of the tread surface, - is strictly less than 50% of the tread pattern height, preferably less than or equal to 30% of the tread pattern height, more preferably having a depth in the range of 10% to 30% of the tread pattern height, and comprises at least one additional circumferential notch.

[0099] Similar to the additional circumferential notches in the axial center portion, with the advantageous features that improve the function of the tire to remove water and at the same time guarantee good grip on a dry road surface, - the axial width of the additional circumferential notch or each additional circumferential notch in the first axial lateral portion is in the range of 3% to 15% of the axial width of the first axial lateral portion, preferably in the range of 3% to 10%, - the axial width of the additional circumferential notch or each additional circumferential notch in the second axial lateral portion is in the range of 3% to 15% of the axial width of the second axial lateral portion, preferably in the range of 3% to 10%.

[0100] In one highly preferred embodiment, - the axial width of the additional circumferential notch or each additional circumferential notch is in the range of 1.0 mm to 4.0 mm, regardless of whether the additional circumferential notch is made in the first axial lateral portion or the second axial lateral portion, - the depth of the additional circumferential notch or each additional circumferential notch is less than or equal to 3.0 mm, preferably in the range of 1.0 mm to 3.0 mm, regardless of whether the additional circumferential notch is made in the first axial lateral portion and / or the second axial lateral portion.

[0101] In an embodiment that enables reducing the pressure received by the edge corners that form the edges of the notches, and thus enables improving the grip on a dry road surface, at least one of the main circumferential grooves is chamfered. In other words, when the boundaries of each main circumferential groove that includes the center rib or one of them are defined axially inward and outward by the bottom surface that connects the axially inward surface and the axially outward surface that define the boundaries of the main circumferential groove that face radially inward, at least one of the circumferential grooves, preferably each main circumferential groove, is arranged such that at least one of the axially inward surface and the axially outward surface is connected to at least one of the axially inward edge and the axially outward edge of the main circumferential groove by a chamfered portion, preferably each of the axially inward surface and the axially outward surface is connected to each of the axially inward edge and the axially outward edge of each main circumferential groove by a chamfered portion.

[0102] The chamfered portion on the circumferential notch can be a linear chamfered portion or a rounded chamfered portion. The linear chamfered portion is formed by a plane that is inclined with respect to the axially inward surface and the axially outward surface and extends to the axially inward edge or the axially outward edge that defines the boundary of the circumferential notch in the axial direction. The rounded chamfered portion is formed by a curved surface that continues to the axially inward surface or the axially outward surface and merges tangentially with these surfaces. The chamfered portion on the circumferential notch is characterized by a height and a width that are respectively equal to the radial distance and the axial distance between the common point with the axially inward surface or the axially outward surface extended by the chamfered portion and the axially inward edge or the axially outward edge that defines the boundary of the circumferential notch in the axial direction.

[0103] From the perspective of improving grip on a drier road surface, when Condition II and / or III are satisfied, at least 50%, preferably at least 75%, more preferably each transverse notch is chamfered. In other words, when the boundaries of each transverse notch are defined radially by a front surface and a rear surface that are connected to each other by a bottom surface that defines the boundary of the transverse notch in the circumferential direction and faces radially inward, at least 50%, preferably at least 75%, more preferably each transverse notch is such that at least one of the front surface and the rear surface is connected to at least one of the leading edge and the trailing edge of the transverse notch by a chamfered portion, and preferably each front surface and rear surface are arranged such that they are each connected to each of the leading edge and the trailing edge of each transverse notch by a chamfered portion.

[0104] The chamfered portion on the transverse notch can be a linear chamfered portion or a rounded chamfered portion. The linear chamfered portion is formed by a plane that is inclined with respect to the front surface or the rear surface and extends to the leading edge or the trailing edge that defines the boundary of the transverse notch in the circumferential direction. The rounded chamfered portion is formed by a curved surface that continues from the front surface or the rear surface and merges tangentially with these surfaces. The chamfered portion on the transverse notch is characterized by a height and a width that are respectively equal to the radial distance between a common point with the front surface or the rear surface extended by the chamfered portion and the leading edge or the trailing edge that defines the boundary of the transverse notch in the circumferential direction and the distance in a direction perpendicular to the front surface or the rear surface.

[0105] In the conventional method, a tire includes a crown, two sidewalls, and two beads, and each sidewall connects each bead to the crown. The crown also includes a tread and a crown reinforcement disposed radially inside thereof in the conventional method. Further, the tire includes a carcass reinforcement fixed within each bead and extending radially inside the crown within each sidewall.

[0106] In the conventional method, the crown reinforcement comprises at least one crown layer containing reinforcing elements. These reinforcing elements are preferably textile or metallic filamentary elements.

[0107] In embodiments that enable achieving the performance aspects of a tire known as a radial tire as defined by ETRTO, the carcass reinforcement comprises at least one carcass layer, and the carcass layer or each carcass layer comprises carcass filamentary reinforcing elements, and each carcass filamentary reinforcing element extends substantially along a main direction forming an angle in the range of 80° to 90° in absolute value with the circumferential direction of the tire.

[0108] The present invention will be better understood by reading the following description provided as a mere non - limiting example with reference to the drawings.

Brief Description of the Drawings

[0109]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0110] A coordinate system X, Y, Z corresponding to the axial direction (Y), radial direction (Z), and circumferential direction (X) of the tire is shown in the figure related to the tire.

[0111] In the following description, the measured values obtained are those obtained from the tire in the unloaded and non-expanded state, except for the measured values of the volume porosity and surface porosity.

[0112] FIG. 1 illustrates a tire denoted by the overall reference numeral 10 according to the present invention. The tire 10 has a substantially donut shape around a turning axis substantially parallel to the axial direction Y. The tire 10 has a size of 245 / 45R18 with respect to a passenger car. In various figures, the tire 10 is depicted as new, i.e., when it has not yet been run. The outer diameter OD of the tire 10 is equal to 678 mm.

[0113] The tire 10 includes a crown 12, and the crown 12 includes a tread 14 intended to be in contact with the road surface during running and a crown reinforcement 16 extending in the circumferential direction X within the crown 12. Further, the tire 10 includes an airtight layer 18 that is airtight with respect to an inflation gas that, when mounted on a mounting support therefor, e.g., a rim, defines the boundary of a closed internal cavity together with this mounting support.

[0114] The crown reinforcement 16 includes an active reinforcement 20 and a hoop reinforcement 22. The active reinforcement 16 includes at least one active layer, and here includes two active layers 24, 26. In this particular case, the active reinforcement 16 is composed of two active layers 24, 26. The radially inner active reinforcement 24 is disposed radially inside the radially outer active layer 26.

[0115] The hoop reinforcement 22 comprises at least one hooping layer, here comprising one hooping layer 28. The hoop reinforcement 22 here consists of the hooping layer 28.

[0116] The crown reinforcement 16 has the tread 14 resting thereon in the radial direction. In this case, the hoop reinforcement 22, here the hooping layer 28, is disposed radially outside the working reinforcement 20 and is thus sandwiched radially between the working reinforcement 20 and the tread 14. Preferably, the hoop reinforcement 22 has an axial width that is at least as large as the axial width of the working reinforcement 20 and in this particular case in the illustrated embodiment of FIG. 1, it can be assumed that the hoop reinforcement 22 has an axial width that is larger than the axial width of the working reinforcement 20.

[0117] The tire 10 comprises two sidewalls 30 that extend radially inwards from the crown 12. Further, the tire 10 has two beads 32 radially inside the sidewalls 30. Each sidewall 30 connects each bead 32 to the crown 12.

[0118] The tire 10 comprises a carcass reinforcement 34 that is secured within each bead 32 and in this case wound around a bead wire 33. The carcass reinforcement 34 extends radially inside the crown 12 within each sidewall 30. The crown reinforcement 16 is disposed radially between the tread 14 and the carcass reinforcement 34. The carcass reinforcement 34 comprises at least one carcass layer, here comprising a single carcass layer 36. In this particular case, the carcass reinforcement 34 consists of the single carcass layer 36.

[0119] Each working layer 24, 26, hooping layer 28, and carcass layer 36 comprises an elastomeric matrix in which one or more filamentary reinforcing elements of the corresponding layer are embedded. These layers will be described below with reference to FIG. 2.

[0120] Hoop reinforcement 22, here the hooping layer 28 is axially delimited by two axial edges 28A, 28B of the hoop reinforcement 22. The hoop reinforcement 22 comprises one or more hooping filamentary reinforcing elements 280, and the hooping filamentary reinforcing elements 280 are helically wound circumferentially so as to extend in the main direction D0 of each hooping filamentary reinforcing element from the axial edge 28A of the hooping layer 28 to the other axial edge 28B in the axial direction. The main direction D0 forms an angle AF with the circumferential direction X of the tire 10 that is less than or equal to 10° in absolute value, preferably less than or equal to 7°, more preferably less than or equal to 5°. In this case, AF = -5°. The hooping layer 28 has a density of 98 hooping filamentary reinforcing elements per decimeter, and this density is measured perpendicular to the direction D0.

[0121] The radially inner working layer 24 is axially delimited by two axial edges 24A, 24B. The radially inner working layer 24 comprises working filamentary reinforcing elements 240 that extend in a substantially parallel manner to each other along the main direction D1 from the axial edge 24A to the other axial edge 24B in the axial direction. Similarly, the radially outer working layer 26 is axially delimited by two axial edges 26A, 26B. The radially outer working layer 26 comprises working filamentary reinforcing elements 260 that extend in a substantially parallel manner to each other along the main direction D2 from the axial edge 26A to the other axial edge 26B in the axial direction. The main direction D1 in which each working filamentary reinforcing element 240 of the radially inner working layer 24 extends, and the main direction D2 in which each working filamentary reinforcing element 260 of the other radially outer working layer 26 extends, respectively form angles AT1 and AT2 in the direction opposite to the circumferential direction X of the tire 10. Each main direction D1, D2 forms an angle AT1, AT2 in the range of strictly greater than 10° in absolute value with the circumferential direction X of the tire 10, preferably in the range of 15° to 50°, more preferably in the range of 15° to 30°. In this case, AT1 = -26° and AT2 = +26°.

[0122] The carcass layer 36 is axially delimited by two axial edges 36A, 36B. The carcass layer 36 extends along a main direction D3 that forms an angle AC, here AC = +90°, with the circumferential direction X of the tire 10 that is greater than or equal to 60° in absolute value, preferably in the range from 80° to 90°, from its one axial edge 36A to the other axial edge 36B in the axial direction. The carcass layer 36 comprises carcass filamentary reinforcing elements 360.

[0123] Conventionally, each hoop filamentary reinforcing element 280 comprises two multifilament strands each constituted by a spun yarn of aliphatic polyamide, in this case a nylon monofilament having a yarn count equal to 140 tex. These two multifilament strands are each helically twisted 250 turns per meter in one direction and further helically twisted 250 turns per meter in opposite directions with respect to each other. These two multifilament strands are helically wound around each other. As a variant, it is considered possible to use a hoop filamentary reinforcing element 280 comprising one multifilament strand with a spun yarn of aliphatic polyamide, in this case a nylon monofilament having a yarn count equal to 140 tex, and one multifilament strand with a spun yarn of aromatic polyamide, in this case an aramid monofilament having a yarn count equal to 167 tex. These two multifilament strands are each helically twisted 290 turns per meter in one direction and further helically twisted 290 turns per meter in opposite directions with respect to each other. These two multifilament strands are helically wound around each other. This variant results in AT1 = -29° and AT2 = +29°.

[0124] Each actuating filamentary reinforcing element 180 is an assembly of two steel monofilaments each having a diameter equal to 0.30 mm and helically wound with a pitch of 14 mm. As a variation, an assembly of six steel monofilaments can be used, which includes an inner layer of two monofilaments each having a diameter equal to 0.23 mm and helically wound with a pitch of 12.5 mm in a first direction, for example, the Z direction, and an outer layer of four monofilaments helically wound around the inner layer with a pitch of 12.5 mm in a second direction opposite to the first direction, for example, the S direction. In another variation, each actuating filamentary reinforcing element 180 is composed of a steel monofilament having a diameter equal to 0.30 mm. More generally, the steel monofilament has a diameter in the range of 0.25 mm to 0.32 mm.

[0125] Conventionally, each carcass filamentary reinforcing element 340 includes two multifilament strands each composed of a spun yarn of polyester, here a PET monofilament. These two multifilament strands are individually helically twisted 240 times per meter in one direction and further helically twisted 240 times per meter in opposite directions to each other. Each of these multifilament strands has a yarn count equal to 220 tex. In other variations, it is considered possible to use a yarn count equal to 144 tex and a twist equal to 420 twists per meter, or a yarn count equal to 334 tex and a twist equal to 270 twists per meter.

[0126] Referring to FIGS. 1, 3, and 4, the tread 14 includes a tread surface 38 that brings it into contact with the road surface. The tread surface 38 is intended to be in contact with the road surface when the tire 10 is traveling along the road surface, and is axially delimited by first and second axial edges 41, 42 passing through points N such that the angle between the tangent T of the tread surface 38 passing through each point N disposed on each side of the center plane M and the straight line R parallel to the axial direction Y is equal to 30°.

[0127] Referring to FIGS. 1 and 3 to 5, the tread 14 includes an axially central portion P0 and first and second axially lateral portions P1, P2 that are axially disposed outside the axially central portion P0, one on each side of the axially central portion P0 with respect to the median plane M of the tire 10.

[0128] The axially central portion P0 has an axial width L0 that is greater than or equal to 50%, preferably greater than or equal to 60%, and less than or equal to 80%, preferably less than or equal to 70% of the axial width L of the tread surface 38 of the tire 10 when new.

[0129] Each of the first and second axially lateral portions P1, P2 has an axial width L1 that is less than or equal to 25%, preferably less than or equal to 20%, and greater than or equal to 5%, preferably greater than or equal to 10% of the axial width L of the tread surface 38 of the tire 10 when new.

[0130] The ratio of the axial width L0 of the central portion P0 to the axial widths L1, L2 of the first and second axially lateral portions P1, P2 is greater than or equal to 3.0, preferably in the range of 3.0 to 5.0, more preferably in the range of 4.0 to 4.5.

[0131] In this case, L0 = 140 mm, L1 = L2 = 33 mm, and L = 206 mm.

[0132] The axially central portion includes first, second, third, and fourth main circumferential grooves respectively designated by reference numerals 52, 54, 56, 58. The first and second grooves 52, 54 are each disposed on one side of the median plane M of the tire 10 in the axial direction and are the main circumferential grooves that are furthest axially outward of the tread 14.

[0133] Referring to FIGS. 3 to 5, the first, second, third, and fourth main circumferential grooves 52, 54, 56, 58 are delimited by an axial outer edge indicated by reference numerals 521, 541, 561, 581 respectively at a location having a radial dimension equal to the radial dimension of the tread surface 38, and an axial inner edge indicated by reference numerals 522, 542, 562, 582 respectively.

[0134] Referring to FIGS. 4 and 5, each of the main circumferential grooves 52, 54, 56, 58 is axially delimited by an axially inner surface Fr1 and an axially outer surface Fr2 that define the boundaries of each of the main circumferential grooves 52, 54, 56, 58 in the axial direction at a location having a radial dimension inside the radial dimension of the tread surface 38. Each of the main circumferential grooves 52, 54, 56, 58 is delimited by a bottom surface Frd towards the radially inner side.

[0135] Each of the main circumferential grooves 52, 54, 56, 58 is chamfered, that is, each of the main circumferential grooves 52, 54, 56, 58 is arranged such that at least one of the axially inner surface Fr1 and the axially outer surface Fr2, in this case each is connected to each of the axially inner edge 522, 542, 562, 582 and the axially outer edge 521, 541, 561, 581 of the respective main circumferential groove 52, 54, 56, 58 by a chamfered portion Cf.

[0136] Each of the main circumferential grooves 52, 54, 56, 58 is respectively indicated by reference numerals Hr2, Hr4, Hr6, Hr8 and has a depth in the range from 4.0 mm to the tread pattern height Hs, particularly preferably in the range from 5.0 mm to the tread pattern height Hs, even more preferably in the range from 5.5 mm to the tread pattern height Hs. Each depth Hr2, Hr4, Hr6, Hr8 is greater than or equal to 50% of the tread pattern height Hs. In this case, Hs = Hr6 = Hr8 = 6.5 mm and Hr2 = Hr4 = 6.0 mm.

[0137] Each of the main circumferential grooves 52, 54, 56, 58 is denoted by reference numerals Lr2, Lr4, Lr6, Lr8 respectively, and has a width greater than or equal to 1.0 mm, preferably greater than or equal to 5.0 mm, more preferably greater than or equal to 8.0 mm, and even more preferably in the range of 8.0 mm to 15.0 mm. In this case, Lr2 = Lr4 = 10.0 mm and Lr6 = Lr8 = 12.5 mm.

[0138] The axial center portion P0 extends in the axial direction from the axial outer edge 521 of the first main circumferential groove 52 to the axial outer edge 541 of the second main circumferential groove 54.

[0139] The axial center portion P0 includes first, second, and third center ribs denoted by reference numerals 62, 64, 66 respectively. Each of the center ribs 62, 64, 66 is separated in the axial direction by two main circumferential grooves, here by two of the first, second, third, and fourth main circumferential grooves 52, 54, 56, 58.

[0140] The first center rib 62 is arranged to be included between the first main circumferential groove 52 and the third main circumferential groove 56 in the axial direction. In this case, the first center rib 62 extends in the axial direction from the axial inner edge 522 of the first main circumferential groove 52 to the axial outer edge 561 of the third main circumferential groove 56.

[0141] The second center rib 64 is arranged to be included between the third main circumferential groove 56 and the fourth main circumferential groove 58 in the axial direction. In this case, the second center rib 64 extends in the axial direction from the axial inner edge 562 of the third main circumferential groove 56 to the axial inner edge 582 of the fourth main circumferential groove 58.

[0142] The third center rib 66 is arranged to be included between the fourth main circumferential groove 58 and the second main circumferential groove 54 in the axial direction. In this case, the third center rib 66 extends in the axial direction from the axial outer edge 581 of the fourth main circumferential groove to the axial inner edge 542 of the second main circumferential groove 54.

[0143] Each of the central ribs 62, 64, 66 is denoted by reference numerals Ln2, Ln4, Ln6 respectively, and has an axial width that is less than or equal to 30%, preferably less than or equal to 25%, and greater than or equal to 10%, preferably greater than or equal to 15% of the axial width L0 of the axial center portion P1. Each of the axial widths Ln2, Ln4, Ln6 ranges from 20 mm to 40 mm, preferably in the range of 25 mm to 35 mm. In this case, Ln2 = Ln4 = Ln6 = 29.5 mm.

[0144] The axial center portion P0 includes at least one additional circumferential notch formed in one of the central ribs 62, 64, 66. In this case, each of the central ribs 62, 64, 66 includes additional circumferential notches 72, 74, 76 respectively. Each of the additional circumferential notches 72, 74, 76 is disposed axially between two circumferential grooves 52 and 56, 56 and 58, 58 and 54 that sandwich each of the central ribs 62, 64, 66.

[0145] Each of the additional circumferential notches 72, 74, 76 is strictly less than 50% of the tread pattern height Hs, preferably less than or equal to 30% of the tread pattern height Hs, and more preferably has a depth in the range of 10% to 30% of the tread pattern height Hs. Each of the additional circumferential notches 72, 74, 76 has an axial width Lc2, Lc4, Lc6 respectively in the range of 4% to 15% of each of the axial widths Ln2, Ln4, Ln6, preferably in the range of 4% to 10%. Each of the axial widths Lc2, Lc4, Lc6 ranges from 1.0 mm to 4.0 mm, and here Lc2 = Lc4 = Lc6 = 2.0 mm. Each of the additional circumferential notches 72, 74, 76 has a depth Hc2, Hc4, Hc6 respectively that is less than or equal to 3.0 mm, preferably in the range of 1.0 mm to 3.0 mm, and here Hc2 = Hc4 = Hc6 = 1.0 mm.

[0146] Referring to FIG. 9, each of the central ribs 62, 64, 66 has an axial portion that is P62, P64, P66 respectively, and here it is composed of each axial portion P62, P64, P66. Each axial portion P62, P64, P66 has an axial width equal to each of the axial widths Ln2, Ln4, and Ln6. Each axial portion P62, P64, P66 does not include a transverse notch having a depth greater than or equal to 20% of the tread pattern height Hs and an axial length greater than or equal to 20% of the axial widths Ln2, Ln4, and Ln6 of the respective central ribs 62, 64, 66 such that each of them satisfies only one of the conditions I, II, III, here condition I. All axial widths of the axial portions P62, P64, P66, here the axial widths of the axial portions P62, P64, P66 of each of the central ribs 62, 64, 66, are greater than or equal to 70%, preferably 80%, more preferably 90% of the axial widths of the respective central ribs 62, 64, 66, and here are equal to 100% of each of the axial widths Ln2, Ln4, and Ln6.

[0147] Referring to FIG. 3, the first axial transverse portion P1 is arranged to extend axially from the first axial edge 41 of the tread surface 38 to the axial outer edge 521 of the first main circumferential groove 52.

[0148] The second axial transverse portion P2 is arranged to extend axially from the second axial edge 42 of the tread surface 38 to the axial outer edge 541 of the second main circumferential groove 54.

[0149] Referring to FIGS. 4 to 6, each of the first and second axial transverse portions P1, P2 is provided with additional circumferential notches 82, 84 formed therein. The additional circumferential notch 82 is arranged axially between the first circumferential groove 52 and the first axial edge 41 of the tread surface 38. The additional circumferential notch 84 is arranged axially between the second circumferential groove 54 and the second axial edge 42 of the tread surface 38.

[0150] Each additional circumferential notch 82, 84 is strictly less than 50% of the tread pattern height Hs, preferably less than 30% of the tread pattern height Hs, and more preferably has a depth in the range of 10% to 30% of the tread pattern height Hs. Each additional circumferential notch 82, 84 has an axial width L1, L2 in the range of 3% to 15%, preferably 3% to 10% of the respective axial widths Ll2, Ll4. Each axial width Ll2, Ll4 is in the range of 1.0 mm to 4.0 mm, and here Ll2 = Ll4 = 2.0 mm. Each additional circumferential notch 82, 84 has a depth Hl2, Hl4 less than or equal to 3.0 mm, preferably in the range of 1.0 mm to 3.0 mm, and here Hl2 = Hl4 = 1.0 mm.

[0151] Referring to FIG. 6, each axial transverse portion P1, P2 includes transverse notches 90, 90' having a depth greater than or equal to 20% of the tread pattern height Hs. In this particular case, all the transverse notches 90, 90' of each axial transverse portion P1, P2 have a depth Ht greater than or equal to 20%, preferably 30%, more preferably 40% of the tread pattern height Hs. Each transverse notch 90, 90' has a depth Ht in the range from 2.0 mm to the tread pattern height Hs, preferably from 4.0 mm to the tread pattern height Hs, and even more preferably from 5.0 mm to the tread pattern height Hs, and here Ht = 6.0 mm.

[0152] Referring to FIGS. 7 and 8, each transverse notch 90, 90' is circumferentially delimited by a leading edge 901 and a trailing edge 902 at a location having a radial dimension equal to the radial dimension of the tread surface 38. Each transverse notch 90, 90' is circumferentially delimited by a front face Ft1 and a rear face Ft2 at a location of a dimension radially inside the radial dimension of the tread surface 38. Each transverse notch 90, 90' is delimited by a bottom face Ftd towards the radially inner side. Each transverse notch 90, 90' is chamfered, that is, each transverse notch 90, 90' is arranged such that each of the front face Ft1 and the rear face Ft2 is connected to each of the leading edge 901 and the trailing edge 902 of each transverse notch 90, 90' by a chamfer portion Cf. Each transverse notch 90, 90' extends far axially from an axially outer end E1 to an axially inner end E2, and defines a total curve length TI of each transverse notch 90, 90' and an axial length La, La' of each transverse notch 90, 90'.

[0153] Between the transverse notches 90, 90' having a depth greater than or equal to 20% of the tread pattern height Hs, there is a distinction between the transverse notch 90 which is a four-component group including transverse notches 92, 94, 96, 98 formed in the first axial transverse portion P1, and the transverse notch 90' which is a three-component group including transverse notches 92', 94', 96' formed in the second axial transverse portion P2. These notches have different widths and are irregularly arranged circumferentially to avoid high noise and further maintain the uniformity of the tire. The width of each transverse notch 90, 90' is less than or equal to 2.0 mm, preferably in the range of 0.5 mm to 2.0 mm. Accordingly, each of the transverse notches 92, 94, 96, 98, 92', 94', 96' has widths Lt2, Lt4, Lt6, Lt8, Lt2', Lt4', Lt6' such that Lt2 = Lt2' = 1.2 mm, Lt4 = Lt4' = Lt8 = 1.5 mm, and Lt6 = Lt6' = 0.8 mm.

[0154] Referring to FIGS. 3, 7, and 8, the first axial transverse portion P1 includes transverse notches 92, 94, 96, 98 each having a main portion indicated by reference numerals 921, 941, 961, 981 respectively and a supplementary portion indicated by reference numerals 922, 942, 962, 982 respectively. The main portion and the supplementary portion are separated from each other by discontinuities 923, 943, 963, 983 within the curved portions of each front face Ft1 and rear face Ft2. Each supplementary portion 922, 942, 962, 982 is disposed axially outside each main portion 921, 941, 961, 981 and here has a width Ls2, Ls4, Ls6, Ls8 greater than the widths Lp2, Lp4, Lp6, Lp8 of the respective main portions 921, 941, 961, 981 which are equal to each width Lt2, Lt4, Lt6, Lt8. Each main portion 921, 941, 961, 981 extends over a main curve length Tp that is strictly greater than 50% of the total curve length TI of each transverse notch 92, 94, 96, 98. Each supplementary portion 922, 942, 962, 982 extends over a supplementary curve length Tc that is strictly less than 50% of the total curve length TI of each transverse notch 92, 94, 96, 98.

[0155] Each transverse notch 92, 94, 96, 98 has an axial length La that is greater than or equal to 20%, preferably 30%, more preferably 50%, even more preferably 75% of the axial width L1 of the first axial transverse portion P1. In this case, La = 42 mm.

[0156] Here, there are transverse notches 90 composed of the transverse notches 92, 94, 96, 98, having a depth greater than or equal to 20% of the tread pattern height Hs and an axial length La greater than or equal to 20% of the axial width of the first axial transverse portion P1, and the number thereof is N = 125 through the circumferential direction of the tire 10. In a modification of the first embodiment, N = 98.

[0157] As can be seen in FIG. 3, the second axial transverse portion P2 includes transverse notches 92', 94', 96' each composed of a main portion having a curve length equal to the curve length of the notch.

[0158] Each of the transverse notches 92’, 94’, 96’ has an axial length La’ that is greater than or equal to 20%, preferably 30%, more preferably 50%, even more preferably 75% of the axial width L2 of the second axial transverse portion P2. In this case, La2’ = 42 mm.

[0159] The transverse notch 90’ formed by the transverse notches 92’, 94’, 96’ and having a depth greater than or equal to 20% of the tread pattern height Hs and an axial length La’ greater than or equal to 20% of the axial width of the second axial transverse portion P2 has a number N’ = 125 through the circumferential direction of the tire 10. In the above-described deformation, N’ = 98.

[0160] Each of the transverse notches 90, 90’ of each of the first and second axial transverse portions P1, P2 is at least partially closed by a connecting bridge 100 that connects the front face Ft1 and the rear face Ft2 and forms the axial inner end E2 of each of the transverse notches 90, 90’. Here, each connecting bridge 100 is arranged so as to completely block the communication between each of the transverse notches 90, 90’ and the first and second main circumferential grooves 52, 54 when the transverse notch enters the ground contact surface when the tire is running.

[0161] Therefore, referring to FIG. 9, each of the first and second axial transverse portions P1, P2 includes a first axial portion that is P11, P21 each having N, N’ transverse notches 90, 90’, and a second axial portion that is P12, P22 each composed of a connecting bridge 100. Each of the second axial portions P12, P22 is arranged axially inside each of the first axial portions P11, P21.

[0162] Each axial direction portion P11, P21 has an axial direction width that is greater than or equal to 70%, preferably 80%, more preferably 90% of the axial direction width of each axial direction lateral portion P1, P2, and in this case is equal to 91%. In this case, each first axial direction portion P11, P21 has an axial direction width equal to 30 mm. To supplement that, each second axial direction portion P12, P22 has an axial direction width equal to 3 mm. Each axial direction portion P11, P21 satisfies only condition III by π×OD / N≦24 mm being satisfied. Further, π×OD / N≧10 mm is satisfied. In this specific case, π×OD / N = 17 mm is satisfied. In the above-described modification having N = 98, π×OD / N≦24 mm and π×OD / N≧10 mm, and more specifically π×OD / N = 22 mm is satisfied.

[0163] In the first embodiment, in order to limit the transition zone, each central rib 62, 64, 66 and each first and second axial direction lateral portions P1, P2 satisfy among conditions I, II, III Only one and it should be noted that each has an axial direction portion P62, P64, P66, P11, P21 having an axial direction width greater than or equal to 70%, preferably 80%, more preferably 90% of the axial direction width of each central rib 62, 64, 66 and each first and second axial direction lateral portions P1, P2.

[0164] The surface area porosity of the tread 14 is in the range of 27% to 45%, preferably in the range of 30% to 40%, and in this case is equal to 36%. The volume porosity of the tread 14 is in the range of 17% to 35%, preferably in the range of 20% to 30%, and in this case is equal to 24%.

[0165] The surface area porosity of each first and second axial direction lateral portions P1, P2 is in the range of 20% to 30%, and in this case is equal to 25%. The volume porosity of each first and second axial direction lateral portions P1, P2 is in the range of 5% to 10%, and in this case is equal to 8%.

[0166] The surface area porosity of the axial center portion P0 ranges from 35% to 45%, and is equal to 41% here. The volume porosity of the axial center portion P0 ranges from 25% to 35%, and is equal to 30% here.

[0167] The surface area porosity of each of the central ribs 62, 64, 66 ranges from 5% to 10%, and is equal to 7% here. The volume porosity of each of the central ribs 62, 64, 66 ranges from 0.5% to 5%, preferably from 0.5% to 2%, and is equal to 1% here.

[0168] The ratio of the surface area porosity of each of the central ribs 62, 64, 66 to the surface area porosity of each of the first and second axial lateral portions P1, P2 is less than or equal to 0.35, preferably less than or equal to 0.30, more preferably in the range of 0.10 to 0.30, and is equal to 0.28 here. The ratio of the volume porosity of each of the central ribs 62, 64, 66 to the volume porosity of each of the first and second axial lateral portions P1, P2 is less than or equal to 0.20, preferably less than or equal to 0.15, more preferably in the range of 0.10 to 0.15, and is equal to 0.13 here.

[0169] Next, the tire according to the second embodiment of the present invention will be described below with reference to FIG. 10. Elements similar to those of the first embodiment are denoted by the same reference numerals.

[0170] Unlike the case of the first embodiment, the central rib 64 does not have a circumferential notch having a depth of strictly less than 50% of the tread pattern height. In this case, the central rib does not include an additional circumferential notch 74.

[0171] Furthermore, the central rib 64 has each of conditions I, II, III Only oneIt has several axial portions that satisfy the following. In this particular case, the central rib 64 has, on the one hand, an axial width equal to 50% of the axial width Ln4 of the central rib 64 and has a first axial portion P641 that satisfies only condition III, and on the other hand, an axial width equal to 50% of the axial width Ln4 of the central rib 64 and has a second axial portion P642 that satisfies only condition I. Each of the total axial widths of the first and second axial portions P641 and P642 of the central rib 64 satisfies Only one and is 70%, preferably 80%, more preferably 90% of the axial width of the central rib 64, and here it is 100% of the axial width Ln4.

[0172] More specifically, the axial portion P641 has a transverse notch 91 having a depth Ht greater than or equal to 20% of the tread pattern height Hs and an axial length Lb greater than or equal to 20% of the axial width of the central rib 64, and here equal to 50%. The number of notches 91 is N = 125 through the circumferential direction of the tire. The totality of the N transverse notches 91 is arranged such that π×OD / N≦24 mm so as to satisfy only condition III. In a variation of this second embodiment, N = 98 and π×OD / N≦24 mm also holds.

[0173] Unlike the first embodiment, the central rib 64 has a transition zone between the first axial portion P641 and the second axial portion P642, and the axial widths of the first and second axial portions P641 and P642 are such that the central rib 64 does not include any axial portion having an axial width greater than or equal to 70% of the axial width of the central rib 64 that satisfies Only one Note that it satisfies the following.

[0174] Next, the tire according to the third embodiment of the present invention will be described below with reference to FIG. 11. Elements similar to those of the conventional embodiment are denoted by the same reference numerals.

[0175] Unlike the first embodiment, each central rib 62, 64, 66 does not have any circumferential notches having a depth strictly less than 50% of the tread pattern height. In this case, each central rib 62, 64, 66 does not include each additional circumferential notch 72, 74, 76.

[0176] Furthermore, as in the second embodiment, each of the central ribs 62, 64, and 66 is formed so as to satisfy one of conditions I, II, and III. Only one In this particular case, each central rib 62, 64, 66 has an axial portion P621, P641, P661, which has an axial width equal to 50% of the axial width Ln2, Ln4, Ln6 of each central rib 62, 64, 66 on the one hand and satisfies only condition III, and an axial portion P622, P642, P662, which has an axial width equal to 50% of the axial width Ln2, Ln4, Ln6 of each central rib 62, 64, 66 on the other hand and satisfies only condition I. Thus, among conditions I, II, III, Only one The overall axial width of the first and second axial portions P621 and P622, P641 and P642, P661 and P662 of each central rib 62, 64, 66 satisfying the above is greater than or equal to 70%, preferably 80%, more preferably 90% of the axial width of the central rib 64, and here equal to 100% of each axial width Ln2, Ln4, Ln6.

[0177] A tire according to a fourth embodiment of the invention will now be described below with reference to Figure 12. Elements similar to those of the prior art embodiment are indicated with the same reference numerals.

[0178] Unlike in the first embodiment, the central rib 64 does not have a circumferential notch having a depth strictly less than 50% of the tread pattern height. In this case, the central rib does not include the additional circumferential notch 74.

[0179] Furthermore, the central rib 64 is a member that satisfies any one of conditions I, II, and III. Only oneIt includes several axial portions P641, P643 that satisfy [condition], and a central portion P642 that does not satisfy any of conditions I, II, and III.

[0180] In this particular case, the total axial width of the axial portions P641 and P643, each of which satisfies one of conditions I, II, and III, here only condition III, is greater than or equal to 70% of the axial width of the central rib 64, here equal to 75% of the axial width Ln4. On the one hand, the axial portion P641 has an axial width equal to 50% of the axial width Ln4 of the central rib 64 and satisfies only condition III. On the other hand, the axial portion P643 has an axial width equal to 25% of the axial width Ln4 of the central rib 64 and satisfies only condition III.

[0181] Furthermore, unlike in the case of the second and third embodiments, the central rib 64 includes several axial portions P641 and P643 that each satisfy one of conditions I, II, and III Only one However, the entire axial portions P641 and P643 of the fourth embodiment satisfy one of conditions I, II, and III, here only condition III.

[0182] Unlike in the case of the first embodiment, the central rib 64 includes two transition zones between the various axial portions P641, P642, and P643, and the axial widths of the axial portions P641, P642, and P643 are such that the central rib 64 does not include any axial portion having an axial width greater than or equal to 70% of the axial width of the central rib 64 and satisfying one of conditions I, II, and III. Only one It should also be noted that.

[0183] More specifically, each of the axial direction portions P641 and P643 has a depth Ht greater than or equal to 20% of the tread pattern height Hs and an axial length Lb and Lc greater than or equal to 20% of the axial width of the center rib 64, here equal to 50% and 25% respectively, and includes transverse notches 91 and 93. The number of the notches 91 and 93 is N1 = N3 = 125 respectively through the circumferential direction of the tire. The whole of the N1 transverse notches 91 and the whole of the N3 transverse notches 93 are arranged such that π×OD / N1≦24mm and π×OD / N3≦24mm so as to satisfy only Condition III. A modification of this fourth embodiment will give N1 = N3 = 98, and thus will also give π×OD / N1≦24mm and π×OD / N3≦24mm so as to satisfy only Condition III.

[0184] The axial direction portion P642 does not satisfy any of Conditions I, II, and III. In particular, the axial direction portion P642 includes N2 transverse notches 95 through the circumferential direction of the tire of FIG. 12. These N2 = 65 transverse notches 95 have a depth Ht greater than or equal to 20% of the tread pattern height Hs and an axial length greater than or equal to 20% of the axial width Ln4 of the center rib 64, here equal to 25%, but the whole of the N transverse notches 95 are arranged such that 24mm < π×OD / N2 < 40mm.

[0185] Next, a tire according to a fifth embodiment of the present invention will be described below with reference to FIG. 13. Elements similar to those in the conventional embodiments are denoted by the same reference numerals.

[0186] Unlike the case of the fourth embodiment, the center rib 64 includes several axial direction portions P641, P643, P644 each satisfying one of Conditions I, II, and III, and a center portion P642 that does not satisfy any of Conditions I, II, and III. Only one

[0187] ​In this particular case, the overall axial width of the axial portions P641, P643, and P644, each satisfying one of conditions I, II, and III, here only conditions I, II, and III, is greater than or equal to 70% of the axial width of the central rib 64, here equal to 75% of the axial width Ln4. On the one hand, the axial portion P641 has an axial width equal to 25% of the axial width Ln4 of the central rib 64, satisfies only condition III. On the other hand, the axial portion P643 has an axial width equal to 25% of the axial width Ln4 of the central rib 64, satisfies only condition I. And finally, the axial portion P644 has an axial width equal to 25% of the axial width Ln4 of the central rib 64, satisfies only condition II.

[0188] More specifically, the axial portion P641 includes a transverse notch 91 having a depth Ht greater than or equal to 20% of the tread pattern height Hs and an axial length Lc greater than or equal to 20% of the axial width of the central rib 64, here equal to 25%. The number of notches 91 in the circumferential direction of the tire is N1 = 125. The entire N1 transverse notches 91 are arranged such that π×OD / N1≦24 mm so as to satisfy only condition III. A modification of this fifth embodiment would give N1 = 98 such that π×OD / N1≦24 mm holds to satisfy only condition III.

[0189] Similar to the case of the fourth embodiment, the axial portion P642 does not satisfy any of conditions I, II, and III.

[0190] The axial portion P644 has a transverse notch 97 with a depth Ht greater than or equal to 20% of the tread pattern height Hs, and an axial length Lc greater than or equal to 20% of the axial width of the center rib 64, which is equal to 25% here. The number of these notches 97 is N4 = 25 through the circumferential direction of the tire. The totality of the transverse notches 97 of the axial portion P644 is arranged such that π×OD / N4≧40mm holds, preferably such that π×OD / N4≧60mm holds, and even more preferably such that π×OD / N4≧80mm.

[0191] Unlike the first embodiment, the center rib 64 has three transition zones between the various axial portions P641, P642, P643, and P644, and the axial widths of the axial portions P641, P642, P643, and P644 are such that the center rib 64 does not include any axial portion having an axial width greater than or equal to 70% of the axial width of the center rib 64 and satisfying only one of the conditions I, II, and III.

[0192] Comparative test

[0193] Tests were conducted on the tire 10 according to the first embodiment of the present invention. Together with this, unlike the tire 10 according to the first embodiment, each axial portion P62, P64, P66 has a depth greater than or equal to 20% of the tread pattern height Hs and an axial width greater than or equal to 20% of the axial widths Ln2, Ln4, and Ln6 of each center rib 62, 64, and 66. Therefore, tests were also conducted on a control tire W not according to the present invention, each of these axial portions P62, P64, P66 having a transverse notch that satisfies condition III.

[0194] During these tests, four identical tires 10 or W inflated to 2.5 bar were mounted on the vehicle, and the noise generated by the tires tested according to UNECE regulation 51-03 with a load of 470 daN applied was measured.

[0195] The first test measured the external vehicle noise generated by the tire tested at a constant speed, i.e., zero acceleration. The second test measured the external vehicle noise generated by the tire tested in an acceleration phase using an acceleration equal to 3 m.s-2. The results are shown collated in Table 1 below. In this table, the noise generated by tire W at a constant speed is denoted as R, and that generated in the acceleration phase is denoted as R'. TIFF2021250331000001.tif23155 Table 1

[0196] It should be noted that the tire 10 according to the present invention enables a significant reduction in the external vehicle noise generated by the tire regardless of whether it is in a constant speed or an acceleration phase.

[0197] The present invention is not limited to the above-described embodiments.

[0198] Specifically, without departing from the scope of the present invention, - the first central rib is included between the first main circumferential groove and the third main circumferential groove in the axial direction, - the second central rib is included between the second main circumferential groove and the third main circumferential groove in the axial direction, it is possible to consider an axial center portion provided with first, second, and third main circumferential grooves and first and second central ribs arranged as described above.

Explanation of reference numerals

[0199] 10 Tire 52, 54, 56, 58 Main circumferential groove 62, 64, 66 Central rib 72, 74, 76 Circumferential notch 90, 90' Transverse notch

Claims

1. A tire (10) for passenger vehicles having a tread (14) having an outer diameter OD and intended to come into contact with a road surface through a tread surface (38) axially bounded by first and second axial edges (41, 42) of the tread surface (38) when the tire (10) is in motion, comprising The tread (14) is an axially central portion (P0) comprising at least first and second main circumferential grooves (52, 54), one on each side of a median plane (M) of the tire (10), each having a depth (Hr) greater than or equal to 50% of a tread pattern height (Hs), the at least first and second main circumferential grooves (52, 54) being the main circumferential grooves axially furthest toward the outside of the tread (14); the at least first and second main circumferential grooves (52, 54) being the main circumferential grooves axially furthest toward the outside of the tread (14); an axially central portion (P0) extending axially from an axially outer edge (521) of the main circumferential groove (52) as far as an axially outer edge (541) of said second main circumferential groove (54), said axially central portion (P0) comprising at least one central rib (62, 64, 66), said central rib or each central rib (62, 64, 66) being axially bounded by two main circumferential grooves (52, 54, 56, 58) having a depth (Hr) greater than or equal to 50% of said tread pattern height (Hs); first and second axial lateral portions (P1, P2) arranged axially outwardly of the axial central portion (P0), one on each side of the axial central portion (P0) with respect to the median plane (M) of the tire (10), the first axial lateral portion (P1) extends axially from the first axial edge (41) of the tread surface (38) to the axial outer edge (521) of the first main circumferential groove (52); the second axial lateral portion (P2) extends axially from the second axial edge (42) of the tread surface (38) to the axial outer edge (541) of the second main circumferential groove (54); The or each central rib (62, 64, 66) and each first and second axial transverse portion (P1, P2) comprises at least one axial portion (P62, P64, P66, P11, P21, P641, P642, P643, P644, P622, P662) which satisfies only one of the following conditions I, II, III, and each of the axial portions (P62, P64, P66, P11, P21, P641, P642, P643, P644, P622, P662) which each satisfies only one of the conditions I, II, III. the total axial width of one or more axial portions of the or each central rib (62, 64, 66) or of each first and second axial lateral portion (P1, P2) is greater than or equal to 70% of the axial width (Ln2, Ln4, Ln6, L1, L2) of the or each central rib (62, 64, 66) and of each first and second axial lateral portion (P1, P2); The condition is I - said axial portions (P62, P64, P66, P642, P643, P622, P662) do not comprise transverse cut-outs (90, 90') having a depth (Ht) greater than or equal to 20% of said tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of said axial width (Ln2, Ln4, Ln6, L1, L2) of said central rib (62, 64, 66) or of said axial lateral portions (P1, P2), II- said axial portion (P644) comprises transverse cutouts (90, 90') having a depth (Ht) greater than or equal to 20% of said tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of said axial width of said central rib (62, 64, 66) or of said axial lateral portions (P1, P2), a set of N transverse notches (90, 90') of the axial portion having a depth (Ht) greater than or equal to 0% and an axial length (La, Lb, Lc) greater than or equal to 20% of the axial width (Ln2, Ln4, Ln6, L1, L2) of the central rib (62, 64, 66) or of the axial transverse portion (P1, P2) is arranged such that π×OD / N≧40 mm, III- said axial portions (P11, P21, P621, P641, P661, P643) comprise transverse cuts (90, 90') having a depth (Ht) greater than or equal to 20% of said tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of said axial width (Ln2, Ln4, Ln6, L1, L2) of said central rib (62, 64, 66) or of said axial lateral portions (P1, P2), the total of N transverse notches (90, 90') of the central rib (62, 64, 66) or of the axial portions (P1, P2) having a depth (Ht) greater than or equal to 20% of the dot pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of the axial width (Ln2, Ln4, Ln6, L1, L2) of the central rib (62, 64, 66) or of the axial transverse portions (P1, P2) are arranged such that π×OD / N≦24 mm; and condition I or II is satisfied at least by one of the axial portions of the central rib (62, 64, 66) or of one of the central ribs (62, 64, 66), or by one of the axial portions of the first axial transverse portion (P1), or by one of the axial portions of the second axial transverse portion (P2), condition III is satisfied at least by one of the axial portions of the central rib (62, 64, 66) or of one of the central ribs (62, 64, 66), or by one of the axial portions of the first axial transverse portion (P1), or by one of the axial portions of the second axial transverse portion (P2), said first and second axial transverse portions (P1, P2); Equipped with A tire (10).

2. 2. A tire (10) according to claim 1, characterized in that at least one of the axial portions of the or each central rib (62, 64, 66) satisfies condition I or II, and at least one of the axial portions of each of the first and second axial lateral portions (P1, P2) satisfies condition III.

3. 3. A tyre (10) according to claim 1, characterized in that it has a depth (La, Lb, Lc) greater than or equal to 20% of the tread pattern height (Hs) and an axial length (La, Lb, Lc) greater than or equal to 20% of the axial width (L1, L2, Ln1, Ln4, Ln6) of the or each central rib (62, 64, 66) or of the or each axial lateral portion (P1, P2), and that the totality of the N transverse notches (90, 90') of the or each central rib (62, 64, 66) or of the or each axial lateral portion (P1, P2) satisfying condition III is arranged such that π×OD / N≧10 mm.

4. 4. Tyre (10) according to any one of claims 1 to 3, characterized in that the total axial width of the or each central rib (62, 64, 66) and of each first and second axial lateral portion (P1, P2), each satisfying only one of conditions I, II, III, is greater than or equal to 80%, preferably 90%, of the axial width (Ln2, Ln4, Ln6, L1, L2) of the or each central rib (62, 64, 66) and of each first and second axial lateral portion (P1, P2).

5. 5. Tyre (10) according to any one of claims 1 to 4, characterized in that the or each central rib (62, 64, 66) or the first axial transverse portion (P1) or the second axial transverse portion (P2) comprises several axial portions each satisfying only one of conditions I, II, III, such that the entire axial portion of the or each central rib (62, 64, 66) or of the first axial transverse portion (P1) or of the second axial transverse portion (P2) satisfies only one of conditions I, II, III.

6. 6. Tyre (10) according to any one of claims 1 to 5, characterized in that the or each central rib (62, 64, 66) and each first and second axial lateral portion (P1, P2) comprises axial portions satisfying only one of conditions I, II, III, the axial width being greater than or equal to 70% of the axial width of the or each central rib (62, 64, 66) and of each first and second axial lateral portion (P1, P2).

7. 7. Tyre (10) according to any one of the preceding claims, characterized in that the surface area porosity of each of the first and second axial lateral portions (P1, P2) is in the range of 20% to 30%.

8. Tyre (10) according to any one of the preceding claims, characterized in that the volume void ratio of each of the first and second axial lateral portions (P1, P2) is in the range of 5% to 10%.

9. A tyre (10) according to any one of the preceding claims, characterized in that the or each central rib (62, 64, 66) has a surface area porosity in the range of 5% to 10%.

10. 10. Tyre (10) according to any one of the preceding claims, characterized in that the or each central rib (62, 64, 66) has a volume porosity in the range of 0.5% to 5%.

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