CA3101639A1 - Pneumatic tire with optimized crown-and-tread-pattern architecture - Google Patents

Abstract

The invention relates to a pneumatic tire comprising a crown having at least one layer of reinforcing elements. The radially outermost layer includes at least one wave (512). The waves (512) of the radially outermost layer (5) are such that, for each meridian, radially inward from the center of the bottom surface (243) of the closest main groove (24), the points of the waves lie radially outside the points of said layer (5) by at least a radial distance of 1.5 mm. The waves (512) of the radially outermost crown layer constitute at least 10% of the radially outer surface (SRE) of said crown layer (5). A rubber compound having a maximum dynamic shear modulus G *, measured at 40°C at 10% peak-to-peak deformation at 10 Hz, of 3.25 MPa, constitutes at least 30% of the rubber compounds lying on top of said waves.

Description

FIELD OF THE INVENTION
The present invention relates to a tire intended to be mounted on a passenger vehicle, and more particularly the crown of such a tire.

A tire having a geometry of revolution relative to an axis of rotation, the geometry of the tire is generally described in a plane meridian containing the axis of rotation of the tire. For a given meridian plane, the radial, axial and circumferential directions denote respectively the directions perpendicular to the axis of rotation of the tire, parallel to the axis of rotation of pneumatic and perpendicular to the meridian plane. The circumferential plane median says equatorial plane divides the tire into two half tori approximately symmetrical, the tire which may have tread asymmetries, architecture, linked to manufacturing precision or dimensioning.

In what follows, the expressions radially inside and radially outside to mean closer to the axis of rotation of the .. pneumatic, in the radial direction, that and further from the axis of rotation pneumatic, in the radial direction, that. Expressions axially interior à and axially external to mean respectively closer to the plan equator, in the axial direction, than and further from the equatorial plane, according to axial direction, that. A radial distance is a distance from to the axis of rotation of the tire, and an axial distance is a distance by in relation to equatorial plane of the tire. A radial thickness is measured according to the radial direction, and an axial width is measured along the direction axial.

[0004] A tire comprises a crown comprising a tread intended to come into contact with the ground via a surface of rolling, two beads intended to come into contact with a rim and two sidewalls connecting the top to the beads. In addition, a tire comprises a reinforcement of carcass comprising at least one carcass layer, radially inner at the top and connecting the two beads.

The tread of a tire is delimited, according to the direction radial, by two circumferential surfaces, the most radially of which outside is the running surface and the most radially interior of which is called background surface of sculpture. The sculpture background surface, or background surface, is defined as the radially inwardly translated surface of the running surface from a distance WO 2020/00278

6 - 2 - PCT / FR2019 / 051166 radial equal to the tread depth. It is common that this depth either decreasing on the most axially circumferential portions external, called shoulders, tread.
[0006] In addition, the tread of a tire is delimited, according to the axial direction, by two side surfaces. The tread is in outraged consisting of one or more mixtures or rubber compounds. The expressions rubber mixture or rubber compound denotes a composition of rubber comprising at least one elastomer and a filler.

[0007] The crown comprises at least one radially crown reinforcement interior to the tread. The crown reinforcement includes at least one reinforcement of work comprising at least one working layer composed of elements of reinforcement parallel to each other forming, with the direction circumferential, an angle between 15 and 50. The crown reinforcement can also include a hooping reinforcement comprising at least one composite hooping layer reinforcing elements forming, with the circumferential direction, a angle between 0 and 10, the hooping reinforcement being most often but not necessarily radially outside the working layers.

[0008] For any layer of crown reinforcement elements, of work, or other, a continuous surface, called radially outer surface (SRE) of the said layer, passes through the most radially outer point of each element of reinforcement, of each meridian. For any layer of reinforcement elements of crown reinforcement, working, or other, a continuous surface, called surface radially interior (IRS) of said layer, passes through the most radially inside each reinforcing element, each meridian. The distances radials between a layer of reinforcing elements and any other point, are measured from one or the other of these surfaces and in such a way as not to to integrate the radial thickness of said layer. If the other measuring point is radially outside the layer of reinforcing elements, the radial distance is measured from the radially outer surface SRE at this point, and respectively since the radially inner surface SRI at the other measuring point if this is radially inside the layer of reinforcing elements. This makes it possible to take coherent radial distances from one meridian to another, without having to keep account of possible local variations linked to the shapes of the sections of the elements of reinforcement of layers.

[0009] In order to obtain performance in wet grip, cutouts are arranged in the tread. A cut designates either a well, either a groove, either an incision or a circumferential groove and forms a space opening onto the running surface.
.. [0010] An incision or a groove present on the running surface, of them main characteristics dimensions: a width W and a length Lo, such as length Lo is at least equal to twice the width W. An incision or groove is therefore delimited by at least two main lateral faces determining its length Lo and connected by a bottom face, the two main side faces being distant one from the other by a non-zero distance, known as the width W of the incision or of the groove.
The depth of the cutout is the maximum radial distance between the area bearing and the bottom of the cutout. The maximum value of depths of cutouts is called tread depth D.
A groove is a substantially circumferential groove, the faces lateral are substantially circumferential in that their orientation may vary locally around plus or minus 45 around the circumferential direction but that all patterns belonging to the groove are found all around the band of rolling, forming a substantially continuous assembly, that is to say having discontinuities less than 10% in length compared to the length of the patterns.
.. [0013] The circumferential grooves define the ribs. A rib is composed patterns of the tread lying between an axial edge of the tire and a furrow neighboring most axially outer circumferential, i.e. between two furrows neighboring circumferentials.
In what follows, the expression in line with means, for each meridian, radially inside within the limit of the axial coordinates delimited by.
So the points of a working layer directly above a furrow designate for each meridian, the set of radially interior points of the working layer to the groove within the limit of the axial coordinates delimited by the groove.
In what follows, the overhanging expression of means, for each meridian, radially outward within the limit of the axial coordinates delimited by.
Thus the part of the tread overhanging a corrugation designate for each meridian, the set of points of the tread radially outside the corrugation within the limit of the delimited axial coordinates through ripple.
STATE OF THE ART
[0016] A tire must meet multiple performance criteria wearing on phenomena such as wear, adhesion on different types of ground, rolling resistance, dynamic behavior. These criteria performance sometimes lead to solutions opposing other criteria. So for a good dry grip performance, the rubber compound of the tread bearing must be dissipative and soft. On the other hand, to obtain a tire efficient in behavior, especially in dynamic response to an effort transverse to the vehicle and therefore mainly in the axis of rotation of the pneumatic, the tire must have a level of rigidity, in particular under load transverse, sufficiently high. For a given dimension, the stiffness of the tire depend on the rigidity of the various elements of the tire, which are the rolling, the crown reinforcement, the sides and the beads. The stiffening of the Band bearing is traditionally obtained either through the stiffening of compounds rubbery resulting in a loss of dry ground adhesion, either through the decrease in tread depth or decrease in the notch level of the sculpture leading to a loss of grip on wet surfaces.
To overcome the problem, tire manufacturers have by example changed the rubbery compound by stiffening it in particular with fibers, as mentioned in documents FR 3 014 442 and FR 2 984 230.
These solutions are not always satisfactory. Decrease the depth tread pattern limits performance in wear and grip on wet roads.
Rigidize the rubbery compound limits the wet grip capacity and dry soil, and also increases the noise emissions of the tire when driving. Reduce the tread cavity volume reduces grip capacity on the ground wet and more particularly in case of high water height on the ground. It is otherwise important to maintain a certain thickness of rubbery compounds between the face of bottom of cutouts, grooves or grooves and the reinforcing elements of the layer of most radially outer top to guarantee the endurance of the pneumatic.

Thus the use of certain very soft rubbery compounds and very adherents to achieve, all or part of the tread, is not feasible without degrading other performance.
SUMMARY OF THE INVENTION
[0020] The main objective of the present invention is therefore to improve a performance using rubbery tread compounds soft or of low rigidity, in order to be able to use their properties associated. These rubbery compounds, for example, can be very hysteretic in order to to increase performance in dry ground grip or on the contrary very little hysteretic for facilitate flattening in order to further improve resistance to rolling. Not to not penalize other performances such as wear or behavior these compounds low rigidity rubbery can be arranged over the entire strip of rolling or on a limited part. This objective is achieved without modifying its performance in wear and endurance of the top, while respecting national standards in rolling resistance.
This objective is achieved by a tourism tire comprising:
= a tread intended to come into contact with the ground by via a running surface comprising grooves, a groove forming a space opening onto the running surface and being delimited through two main side faces connected by a bottom face, and having a width W defined by the average distance between the two side faces and a depth D defined by the maximum radial distance between the surface of bearing and the bottom face, = at least one groove, being a major groove, having a width W at the less equal to 1 mm and a depth D at least equal to 4 mm, = at least one major groove being substantially circumferential, called circumferential groove = at least two ribs, = the tire further comprising a crown reinforcement, radially inner to the tread, comprising at least one layer of elements reinforcement, called top layer, = the at least one layer of radially extending reinforcing elements from a radially interior surface (IRS) to a surface radially external (SRE), = the most radially outer crown layer comprising at least a undulation directly above a rib, = the at least one corrugation of the top layer most radially outer layer being such that the portion of the top layer radially exterior of the corrugation is radially exterior to the points of said layer of the most radially outer vertex plumb with the center of the face of background the circumferential groove closest to said corrugation, = the at least one corrugation of the top layer most radially outer being such that, over at least 10% of the radially surface exterior (SRE) of said top layer, the radial distance (du) between the surface radially outer (SRE) of the most radially top layer outer surface and running surface, is at least 1.5 mm less than the radial distance (dc) between the radially outer surface (SRE) of the layer of most radially outer crown and tread surface, distance at plumb with the center of the bottom face of the nearest circumferential groove of said corrugation, = the minimum radial distance (du) between the radially outer surface (SRE) of the most radially outer crown layer of the crown reinforcement and the running surface, being at most equal to the depth D of the groove nearest circumferential increased by 2 mm and at least equal to the depth D of the nearest circumferential groove reduced by 2 mm, = the part of the tread that overhangs at least one corrugation of the most radially outer crown layer, comprising at least 30%
of a rubbery compound M whose dynamic shear modulus G *, measured at 40 C at 10% peak-to-peak strain at 10Hz, is at most equal to 3.25 MPa.
A point of a layer of reinforcing elements belongs to the ripple of this said top layer if the radial distance between the point considered and point of the same top layer plumb with the most radially interior point of the bottom surface of the nearest major groove, is greater than 1 mm. Yes it exists more than one nearest major groove, we will test for belonging to ripple taking into account the major groove which maximizes the radial distance considered.
For the calculation of the radial distance, one will consider points of the elements of reinforcement of the same nature: two points of the neutral fiber, two points more radially outwardly of the reinforcing elements, the two most radially interior reinforcement elements.
The properties of the rubbery compounds are measured on a viscoanalyst (Metravib VA4000), according to ASTM D 5992-96. We record the response of a sample of vulcanized composition preferably a test tube cylindrical 4 mm thick and 400 mm2 in section, subjected to solicitation sinusoidal in alternating simple shear, at a frequency of 10Hz, during a scanning at temperature between 0 and 100 C, under a fixed stress of 0.7 MPa. The module dynamic shear G * are measured at a given temperature, 40 C at 10% of peak-to-peak strain at 10Hz also according to ASTM D 5992 ¨ 96.
According to the same procedures a shear modulus G * at 90 C at 10 Hz and under a stress of 0.7MPa is measured.
To improve certain performances, such as for example the adhesion ground dry it is possible to use rubbery compounds known to man of trade for particular uses such as motor racing but these rubber compounds are absolutely unsuitable for vehicles of tourism even with a sporting tendency. Indeed, passenger vehicles must respect certain performances such as rolling resistance values maximum set by environmental and performance standards minimum wear, endurance, grip and handling. Indeed these vehicles have to be able to travel on open roads and in travel conditions and wet grip that is not that of a competition circuit, closed on a very short time for ultimately reduced mileage. Like the owners of these vehicles do not have a stable to change their tires in case of rain and after an hour of racing when these are worn, it is parameters design for tires according to the invention that it is impossible to rule out such as the presence of circumferential grooves or furrows in the strip of bearing capacity and the ability to cover several thousand kilometers with the pneumatic, therefore with sufficient depth of sculpture. Preferably the grooves and the furrows circumferentials of the tire constitute a rate of depression in the bearing in new condition at least equal to 10%. The dip rate is measured by the ratio of the void volume formed by all the cutouts of the strip of bearing on the volume of the tread radially outside the surface of sculpture base, hollow included.
The rubbery compounds in question have low rigidity on the temperature ranges which make them unusable for tires depending on the state art for passenger vehicles either that the performance wear is degraded by a low sculpture height or by a usual sculpture height do not not compensating the low rigidity of the rubber compound, i.e. the performance behavior either too degraded due to the combination of a usual tread height and the weak stiffness of the rubbery compound. If this low rigidity is accompanied by a high hysteresis, rolling resistance performance will also be degraded.
The use of these rubbery compounds is therefore a problem in itself.
Rubber compounds having a modulus G * at 40 C modulus of dynamic shear G *, measured at 40 C at 10% peak-to-peak strain at 10Hz, at most equal to 3.25 MPa, preferably at most equal to 3 MPa, of preference to more equal to 2.5 MPa are for example very penalized in behavior with a sculpture height as it exists for passenger vehicles.
Rubber compounds having a G * modulus at 90 C modulus of dynamic shear, measured at 90 C at 10 Hz under a stress of 0.7 MPa, at more equal to 1 MPa, preferably at most equal to 0.75 MPa, preferably at more equal at 0.5 MPa, are very penalized in wear.
The invention, namely to combine the corrugations of the top layer most radially outer to a rubber compound of low stiffness in overhang of said corrugation, makes it possible to use a rubbery compound of low how stiff regardless of the associated property referred to. If the rubbery compound of the strip of bearing has associated with its low rigidity, performance in wear excellent, but a high rolling resistance, the invention allows its use in reducing the volume of this rubbery compound and the shear height of this compound rubbery in the tread. The invention also makes it possible to find an acceptable rolling resistance value. Likewise for a property high dry grip combined with low compound stiffness rubbery, degradation of performance behavior or wear can be resolved by invention.

One of the properties marking the adhesion is the value of the hysteresis tan 50 designating the value of tan O measured at the temperature from 0 C to 10 Hz and under a stress of 0.7 MPa. Thus a preferred embodiment of the invention is that the rubbery compound M has a tan 50 value at least equal to 0.5, from preference to less equal to 0.6.
The corrugations must necessarily impact the layer of elements of reinforcement of the most radially outer summit. The invention has an effect on the behavior, wear, rolling resistance by reducing the volume of compound rubbery of the tread overhanging the corrugations. Others top layer as well as the carcass reinforcement may or may not be corrugated.
For be noticeable, the ripples must impact at least 10% of the surface of the most radially outer crown layer and the amplitude of the ripple who allows the thickness of the rubber compound to be reduced, must be at least equal 1.5 mm. To do this, a corrugation plumb with a single rib of the Band bearing may be sufficient. The ripple can be for example central and symmetrical with respect to the median circumferential plane.
This solution may have an advantage in terms of irregular wear, or valuable axial thrust as a function of the thrust direction as a function of the camber of vehicle. However, this single undulation can also be located under a any rib and in particular under one of the most radially ribs exterior. These choices can be made taking into account the aspect directional or axisymmetric of the tires and camber of the vehicle to which the pneumatic is destined.
Similarly for optimal operation, the ripple must be good positioned in relation to the tread depth D. The radial distance minimal (du) between the radially outer surface (SRE) of the crown layer (5) most radially outer crown reinforcement (3) and running surface (21), is at most equal to the depth D of the nearest major groove (24) augmented 2 mm and at least equal to the depth D of the deepest major groove (24) close decreased by 2 mm. For a position that is too radially interior, the undulation born will not solve the problem because it will not decrease enough the height of rubbery compound overhanging the corrugation. If the ripple is positioned too radially to the outside, or wear will show the layers of summit, which will pose a problem of endurance, that is to say a greater part of the tread could be thinned in order to gain in resistance to bearing and the solution would not be optimal.
[0033] Furthermore, passenger car tires preferably have a depth of sculpture at least equal to 6 mm and at most equal to 10 mm. This depth is the maximum depth of circumferential grooves and grooves on the belt of rolling. It is generally measured near the equatorial plane of the pneumatic. These values are a compromise today including the aspects wear, rolling resistance and behavior among others performance. .
This solution goes against the methods of manufacturing tires for in which the top layers are laid on substantially cylindrical, the top layers presenting in the meridian plane, a curvature regular without inflection point and therefore are reserved so far for solve behavior problems. Create noticeably toric undulations under the ribs, themselves substantially toric is interesting from a point of view of the .. ease of manufacture, and productivity. Indeed the tools of making a pneumatic before firing most often uses the properties axisymmetric of pneumatic, create corrugations with the same axisymmetry property allows to use standard tire production facilities.
Corrugate layers of reinforcing elements subjected to forces of compression goes against the recommendations to fight against buckling structures. Indeed, to create a discontinuity of radius of curvature amounts to create some over-stresses where buckling could take place. However in the pneumatic, the forces are very localized so that part of the top is in voltage when another is in compression, at a scale much lower than that of ripples.
Thus the corrugations made within the limits of the invention do not harm not at the endurance of the tire.
These corrugations allow the use of a rubbery compound of the low rigidity tread, i.e. whose shear modulus dynamic G * at 40 C at 10% peak-to-peak strain at 10Hz, at most equal to 3.25 MPa, at .. more equal to 3 MPa, preferably at most equal to 2.5 MPa, at least in overhang of say ripples, no longer with the objective of making a gain in resistance to bearing and in behavior but for a gain in dry ground grip with a behavior improved and acceptable rolling resistance.

[0037] Depending on the desired performance and their evolution over time, it is possible that the rubbery compound overhanging the ripple of the layer of most radially outer vertex either wholly or partially in a rubber compound M of low rigidity and with a good level of adhesion dry soil.
Preferably the running surface comprises this rubbery compound to state new.
The distance (du) is reduced by creating at least one undulation in the most radially outer crown layer, so that this corrugation or corrugated part of the crown layer is radially outside the part of the crown layer in line with the circumferential groove closest to said ripple. It is not a question of considering a top layer as wavy no wavy but respecting the criterion of reducing the distance due to a decrease of the depth of sculpture in a given area. This feature is through elsewhere known in particular for tires for passenger vehicles whose tread depth is less axially on the edges exterior of pneumatic, say shoulders, that in the most circumferential grooves relatives.
In tires according to the state of the art, in the shoulder area where the radial distance (du) decreases, the most radially outer crown layer is either at the same radius, or radially inside the parts of the same layer of Mountain peak plumb with the nearest circumferential groove.
The invention also operates by positioning one or more corrugations in one or more parts of one or more shoulders of the tire.
The sub-hollow (dl) will preferably be kept in the grooves major and circumferential grooves. Minor grooves or incisions are less sensitive to punctures and attacks by obstacles. They are protected by the rubbery compound giving them their technical characteristic of groove shallow or shallow.
Plumb with the undulation of the top layer most radially outer layer, all or part of the other crown layers may be wavy as well as the carcass layer depending on the structural rigidity wanted for the Mountain peak. The most radially outer crown layer must be wavy, it can be the sole corrugated layer using a rubbery compound of stuffing of the appropriate thickness placed between the top layer most radially exterior and the top layer, generally a working layer, radially adjacent. But two, three, all top layers can be waved like this.
The protective or shrinking layers are optional in a tire and born not condition the interest of the solution.
It appears that 10% of the running surface with a compound Improved rubbery in dry ground grip allows measurement of an improvement of performance so that it is sufficient that 10% of the radially surface exterior of the most radially outer crown layer is in the part of the undulations at a radial distance at least equal to 1.5mm from the most radially interior of said crown layer in line with the groove major closer.
The amplitude of this undulation must be at least equal to 1.5 mm for to have significant effects on the tire scale. So the difference between the distance radial (du) between the radially outer surface (SRE) of the layer of top there more radially outer and the running surface, is less than at minus 1.5 mm at the radial distance (dc) between the radially outer surface (SRE) of the the most radially outer crown layer and the tread surface, distance to plumb with the center of the bottom face of the major groove closest to said corrugation, over at least 10% of the surface of the surface radially outdoor (SRE) of the top layer in one or more corrugations.
To increase the rigidity of the top and amplify the coupling between the corrugations and the rubbery compound M located directly above the ripples, a preferred solution is that several top layers, the top layer the more radially outer and the crown layer radially adjacent to this one, or even all the top layers are wavy, namely at a distance them each other substantially constant over the entire width of the top to the exception the last 3 centimeters of their axial ends. These axial ends receive in fact sometimes rubbery decoupling compounds.
The optimal solution takes into account the characteristics of the pneumatic and possibly from the vehicle. Optimization can be carried out depending on the character direction of the tire, its asymmetry, the camber of the vehicle.
Preferably over at least 10%, preferably at least 20% and at plus 85%, of the radially outer surface (SRE) of the top layer more radially outer, the radial distance (du) between the radially surface exterior (SRE) of the most radially outer crown layer and the surface of bearing is at least 1.5 mm, preferably 2 mm, less than the distance radial (dc) between the radially outer surface (SRE) of the layer of top there more radially outward and the tread surface, distance directly from the center of the bottom face of the major groove closest to said corrugation. The design parameters allowing the adjustment of grip performance, wear, rolling resistance, behavior are:
= the extent of the contact surface formed by the rubbery compound M from low rigidity and high adhesion and therefore corrugations of the layer of most radially outer vertex, knowing that the notch rate of the sculpture, rarely less than 10% or 15%, the limit at most 85% (100% -15%).
The more the corrugation (s) are extended or the more there are plumb ribs of which there are ripples, plus the use of the rubbery compound is interesting in terms of grip and less penalizing in rolling resistance. We will be able to adjust the number of waves and the percentage of compound rubbery M of low rigidity and high adhesion depending on the desired performance in dry grip, rolling resistance and dynamic behavior.
= The amplitude of the ripple at least equal to 1.5 mm but limited to 5 mm in due to the radii of curvature to be imposed on the metallic working layers, rigid and therefore not very deformable which makes it possible to adjust the shear of rubber compound of the tread in relation to the resistance to rolling and dynamic behavior.
A single rib can represent 15% of the axial width of the layer of most radially outer work. It is common to have 3, 4 to 5 ribs and that the furrows represent around 20% of this width.
A preferred solution is therefore that over at least 10%, preferably at less 20% and not more than 85%, of the radially outer surface (SRE) of the layer of most radially outer vertex, the radial distance (du) between the area radially outer (SRE) of the most radially top layer exterior and the running surface is at most 5 mm less, preferably at least more 3 mm at the radial distance (dc) between the radially outer surface (SRE) of the the most radially outer crown layer and the tread surface, distance to plumb with the center of the bottom face of the nearest circumferential groove of said ripple.
For optimum performance in perforation and attack on the top, without penalize the rolling resistance, the radial distance (dl) between the area radially outer (SRE) of the most radially top layer exterior and the bottom face of the circumferential groove (s) is at least equal to 1 mm and at most equal to 5 mm, preferably at least equal to 2 mm and at most equal to 4 mm. In below the lower limits, the tire could be too sensitive to assaults.
Beyond the upper limits, the rolling resistance of the tire would be penalized.
It is advantageous that the tread, for example a groove major of the tread, include at least one wear indicator, and that the distance minimum radial (du) between the radially outer surface (SRE) of the most layer radially outwardly of the crown reinforcement and the running surface is at less equal to the radial distance (df) between the running surface and the most point radially outside of the wear indicator. Indeed, it is important that the user can perceive that the tire is worn, thanks to the wear indicator and this before see the reinforcing elements of the most radially outer layer of the frame of peak appear at the level of the running surface.
Advantageously all parts of the tread and of the surface of bearing overhanging the undulations of the top layer (5) most radially outer, comprise at least 50% of the rubber compound M, preferably 75%, preferably 100%, in order to derive the greatest benefit from the properties of rubbery compound M.
In a preferred embodiment of the invention, the part of the band rolling radially outside the wear indicators is composed of 100% of the compound rubbery M, in order to take advantage of the properties of the compound rubbery M
until the tire is removed for wear.
It is advantageous that a corrugation of the most radially is present in line with all the ribs of the surface of the rolling in order to push the advantage of the solution to its optimum.
A preferred solution is that a corrugation of the working layer la more radially outer is present only in line with the ribs of the area bearing the closest axially to the median circumferential plane, from share and other of this plan, in order to obtain a performance just necessary by in relation to the increase in the manufacturing cost caused by the corrugation of the job the most radially outer.
Preferably the depth D of a major groove (24) is at less equal to 6 mm, and at most equal to 10 mm. The depths of sculpture between 6 and 10 mm allow a good compromise between performance in terms of wear and resistance to bearing in many touring tires.
In the case where the layer of reinforcing elements most radially exterior of the crown reinforcement is a layer of hooping, it is advantageous than the most radially outer layer of reinforcing elements of the frame of crown comprises reinforcing elements of textile, preferably of type aliphatic polyamide, aromatic polyamide, combination of polyamide aliphatic and of aromatic polyamide, polyethylene terephthalate or rayon, parallel between them and forming, with the circumferential direction (XX ') of the tire, an angle B at most equal to 100 in absolute value.
A preferred solution is that at least one rubbery compound of stuffing having a radial thickness at least equal to 0.3 mm is positioned plumb of any undulation of the most radially outer crown layer. This in order to allow corrugation of top layers during fabrication and firing.
These rubbery stuffing compounds can be present on all of the circumference of the tire or arranged in certain portions of the pneumatic as required. It is possible to have several compounds rubbery stuffing in line with the corrugation (s) at different radius values with different properties depending on the specifications of the tires. Yes just one rubber compound stuffing is arranged, its maximum thickness is approximately equal, for a given ripple, to the radial distance between the radially outer point of the radially outer surface of the layer of most radially outer vertex at the level of the corrugation and the surface radially outer crown layer most radially outer to plumb with the center of the bottom face of the nearest circumferential groove of said ripple.
It is advantageous that, the tread being constituted by one or several rubbery compounds, the rubbery stuffing compound has a maximum dynamic loss tan51, measured at a temperature of 23 C at 10 Hz, at more equal and preferably less than 30% of the dynamic loss maximum tan52 is the least hysteretic rubber compound in the tread and radially outside the bottom surfaces of major grooves or furrows circumferential, measured at a temperature of 23 C and under a stress of 0.7 MPa at 10 Hz. For a rubbery stuffing compound with the same hysteresis, the gain in rolling resistance is given only by the reduction of shear stresses that this rubbery compound undergoes. The compound rubbery stuffing not undergoing the same stresses as the compound rubber component of the tread, it is possible to modify his characteristics so as to further improve rolling resistance.
30% of lower hysteresis leads to a significantly higher gain for invention. The The least hysteretic rubber compound in the tread is the rubbery compound making up a portion of the tread radially outside the base surface of the sculpture, the maximum tan51 value of which, measured at a temperature of 23 C and under a stress of 0.7 MPa at 10 Hz is the most low of all the rubbery compounds composing a portion of the strip rolling radially outside the surface of the base of the sculpture.
The response of a sample of crosslinked composition is recorded (test tube cylindrical, preferably 4 mm thick and 400 mm2 in section), subject to a sinusoidal stress in alternating simple shear, at the frequency from 10 Hz, to 23 C according to standard ASTM D 5992 ¨ 96. An amplitude sweep of peak-to-peak strain from 0.1 to 100% (forward cycle) then from 100 to 0.1%
(cycle return). The result used is the loss factor (tan (5)). For the cycle back, we indicates the maximum value of tan (5) observed (tan (5) max at 23 C).
It is preferred that the crown reinforcement consists of a layer of shrinking and a working reinforcement of 2 working layers having opposite angles, such as of many current summit architectures.
BRIEF DESCRIPTION OF THE DRAWINGS
The characteristics and other advantages of the invention will be better included to using Figures 1 to 4, said figures not being shown in the scale but simplified way, in order to facilitate understanding of the invention:

= Figure 1 is a part of a tire, in particular its architecture and its tread provided with circumferential grooves and grooves.
= FIG. 2 represents a meridian section of the crown of a tire according to the invention and illustrates the different radial distances, du, dl, D, df, dc and a rubbery filling compound (6) capable of creating a corrugation of the top layer, working layer or hoop layer, the most radially outer, this corrugation comprising in its overhang a low stiffness rubber compound M.
= FIG. 3 represents a meridian section of the crown of a tire according to the invention and illustrates the different radial distances, du, dl, D, df, dc and rubbery filling compounds (6) capable of creating corrugations the crown reinforcement, the working layers and the hooping layer, this undulation comprising in its overhang and in 100% of the part of the tread radially outer to the wear indicators, a compound rubbery M of low rigidity.
= FIG. 4 represents a meridian section of the crown of a tire according to the invention and illustrates the different radial distances, du, dl, D, df, dc and corrugations of the crown reinforcement, the working layers and the hoop layer, carcass layer and sealing rubber, this undulation comprising in its overhang and in 100% of the part of the tread radially outer to the wear indicators, a compound rubbery M of low rigidity. These ripples are created without using of stuffing rubber or with manufacturing tools suitable for carry out during the laying of the different layers of reinforcing elements carcass and crown before baking, i.e. during baking of the tire by volumes of the tread adapted to create this type ripples.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 shows a perspective view of part of the top of a pneumatic. With each meridian plane is associated a Cartesian coordinate system (XX ', YY', ZZ ').
The tire has a tread 2 intended to come into contact with with a ground via a tread surface 21. In the tread rolling, are arranged grooves 24 of width W possibly different from a groove the other and circumferential grooves 25 delimiting the ribs 26. The pneumatic further comprises a crown frame 3 comprising a working frame 4 and here for the example, a hoop reinforcement 5. The working reinforcement comprises at least a working layer and here for the example two working layers 41 and 42 including each of the reinforcing elements parallel to each other (411 for the layer of top 41). Also shown is the radially outer surface (SRE) of the radially outermost working layer (41).
[0063] FIG. 2 schematically represents the meridian section of the top of the tire according to the invention. It illustrates in particular the layer of carcass 1, one corrugation (512) of the radially outermost crown layer (5) and a rubber compound stuffing (6) arranged directly above it, on all the width of the rib 26. Figure 2 also illustrates the distances radial following:
= D: the depth of a groove, maximum radial distance between the surface bearing (21) and the bottom face (243) of the groove, = dc: radial distance between the radially outer surface (SRE) of the radially outermost crown layer (5) and the surface of bearing (21), distance measured plumb with the most radially point inside the bottom face (243) of the nearest major groove (24) of said corrugation (512), = du: minimum radial distance (du) between the radially surface exterior (SRE) of the radially outermost crown layer (5) of the frame and the running surface (21), = df: radial distance between the rolling surface (21) and the most radially outside of the wear indicator (7), = dl: the minimum distance between the radially outer surface (SRE) of the radially outermost crown layer (5) and bottom face (243) circumferential grooves (25).
[0064] FIG. 3 schematically represents the meridian section of the top of the tire according to the invention. It illustrates in particular ripples of the frame top consisting of two working layers (41 and 42) and the top layer hooping (5) which is in this case the most radially top layer exterior, and rubber stuffing compounds (6) arranged under the working layer (42) the more radially inward in line with the undulations in line with each of tread ribs.
[0065] FIG. 4 schematically represents the meridian section of the top of the tire according to the invention. It illustrates in particular ripples of the frame carcass, the crown reinforcement made up of two working layers (41 and 42) and the hooping layer (5) which is in this case the top layer more radially outer, without the use of rubbery stuffing compounds (6).
A meridian section of the tire is obtained by cutting the pneumatic along two meridian planes. This cut is used to determine the different radial distances, the center of the bottom faces of the grooves and grooves circumferential.
The invention has been carried out on a tire A of dimension 305/30 intended to equip a passenger vehicle. The depths D of the grooves the sculpture are between 5 mm at the shoulders and 7 mm at the equator, for widths W varying between 4 and 15 mm, the tread contains 4 grooves circumferential. The top reinforcement is made up of two working layers whose reinforcement elements make an angle of + or ¨ 38 with the direction circumferential and a layer of textile hooping, the reinforcing elements of which form a angle of + or ¨ 3 with the circumferential direction. The most radially outer layer, the hooping layer 5, is corrugated under the 5 ribs of the Band bearing, constituting on 50% of its surface. The corrugations are made at ugly of rubber filling compounds radially internal to the layer of job most radially inner, located more precisely between the layer of carcass and the most radially inner crown layer. The ripples have amplitudes of 2mm, i.e. the radial distances (du) between the radially surface exterior (SRE) of the radially outermost crown layer (5) and the surface of bearing at the corrugations (512) are 2 mm smaller than the distances radial (dc) between the radially outer surface (SRE) of the layer of top (5) the most radially outer and the running surface (21), distances to the balance of most radially interior point of the bottom face of the grooves circumferential (24) closer to said undulations (512). The radial distance (dl) between the area radially outer (SRE) of the most radially top layer exterior (5) and the bottom face (243) of the circumferential grooves (24), is equal to 1.5 mm. The tread is composed of a unique CC1 rubbery compound having the following features:
= G * measured at 40 C at 10% peak-to-peak strain at 10Hz, is equal to 2.3 MPa = a dynamic shear modulus G *, measured at 90 C at 10 Hz and under a stress of 0.7 MPa, equal to 0.45 MPa, = tan O measured at a temperature of 0 C to 10 Hz and under a constraint of 0.7 MPa is equal to 0.58 The tires A were compared with the tires B, C likewise dimension, having the same characteristics except that:
= Tire B is such that its crown layers are not corrugated and its tread consists of a single rubber compound 002.
= The tire C is such that its crown layers are not corrugated and the tread is made of a unique CC1 rubbery compound similar to tire A.
The rubbery compound CC2, not corresponding to the invention, is a rubbery compound suitable for its use in the tread and has the following properties:
= G * measured at 40 C at 10% peak-to-peak strain at 10Hz, is equal to 3.3 MPa = a dynamic shear modulus G *, measured at 90 C at 10 Hz and under a stress of 0.7 MPa, equal to 1.05 MPa, = tan O measured at a temperature of 0 C to 10 Hz and under a constraint of 0.7 MPa is equal to 0.48 The rubbery filling compound used to create the corrugations of tire A, has a dynamic loss tan51, measured at a temperature of 23 C
and under a stress of 0.7 MPa at 10 Hz, 60% less than that of the compound rubbery CC1 constituting the tread of A.
The performance of the tire according to the invention can be seen according to the following table in base 100. An evaluation greater than 100 means that the tire performance is superior to that of the indicator. A better rolling resistance performance, therefore greater than 100, means that the rolling resistance of the tire is lower than that of the indicator light. A
dry ground grip, greater than 100, means that the lap time on the test circuit is lower than that of the control tire resistance to ground adhesion Wear behavior dry rolling A ¨ invention 100 102 100 100 C 92 101.5 90 90 Table I: performance of the invention The objective of the invention is to allow the use of compound rubbery soft or low stiffness in the tread. The tires of the state of art B, which have neither wavy top layers nor a rubbery compound of the low rigidity tread, serve as a witness.
The use of a rubber compound of low rigidity, such as defined in the tread on an architecture without corrugation, visible on the pneumatic C, leads to unacceptable lapses in all resistance performances at bearing, wear, behavior and a unique gain in ground-dry grip, vis-à-vis screw the witness tire B. In view of the sporting use of the size and its high value in rolling resistance, the degradation of rolling resistance, is such as the pneumatic C is no longer acceptable in view of environmental standards.
The invention, visible on the tire A, not only makes it possible to level all the degradations caused by the use of the rubbery compound of low rigidity CC1 but it surprisingly improves dry ground grip a priori supplied by the rubbery compound CC1 by an additional 25% by the coupling between the architecture and the low stiffness rubber compound.
The gain in rolling resistance of the invention was evaluated on a machine standard for ISO 2850: 2009 standardized measurements.

The behavior is evaluated by measuring the characteristic Dz of the model behavior of tires, says Pacejka, well known to the man of art, to hot pressure of 3b.
The tires have also been mounted on a vehicle of the type sporty and tested on a bending circuit suitable for generating transverse forces important.
A professional pilot, trained in tire evaluation, compares the tires A according to the invention, tires B and tires C
according to state of the art and following a rigorous testing process, within same temperature conditions, driving ground conditions, without knowing the characteristics of the tires tested, by repeating the measurement. The pilot note them tires. In all the tests carried out, the tires A according to the invention outclasses B and C tires in terms of vehicle behavior, resistance to road, on dry ground and in terms of grip.
The wear is evaluated on tests where vehicles of the same type are follow following a determined circuit representing customer use. The vehicles are led by professional pilots, trained in the assessment of tires and having the same type of pipe following a rigorous testing process, in the same temperature conditions, driving ground condition, without know the characteristics of the tires tested, by repeating the measurement. After each test day, the remaining tread heights are measured. Wear given here corresponds to the gain in wear after rolling corresponding to 30% of the life of the pneumatic.

Claims (15)

WO 2020/002786 - 23 - PCT / FR2019 / 051166 1. Tire (1), for passenger vehicle comprising:
= a tread (2) intended to come into contact with a ground by via a rolling surface (21) comprising grooves (24), a groove (24) forming a space opening onto the running surface (21) and being delimited by two main lateral faces (241, 242) connected by a bottom face (243), and having a width W defined by the mean distance Between the two side faces (241, 242) and a depth D defined by the distance maximum radial between the running surface (21) and the bottom face (243), = at least one groove (24), being a major groove, having a width W at the less equal to 1 mm and a depth D at least equal to 4 mm, = at least one major groove being substantially circumferential, called circumferential groove = at least two ribs (26), = the tire (1) further comprising a crown reinforcement (3), radially inside the tread (2), comprising at least one layer of reinforcing elements (41, 42, 5), called top layer, = the at least one layer of reinforcing elements (41, 42, 5) extending radially from a radially interior surface (IRS) to a area radially outer (SRE), characterized in that the radially outermost crown layer (5) comprises at least one corrugation (512) directly above a rib (26), in that the at least one corrugation (512) of the most radially outwardly is such that the portion of the top layer most radially outer (5) of the corrugation (512) is radially outer to the points of said most radially outer crown layer directly above the center of the bottom face (243) of the nearest circumferential groove (24) of said corrugation (512), in that the at least one corrugation (512) of the top layer (5) more radially outer is such that over at least 10% of the surface radially outer layer (SRE) of said top layer (5), the radial distance (du) enter here radially outer surface (SRE) of the top layer (5) most radially outer surface and the running surface (21), is less than less 1.5 mm at the radial distance (dc) between the radially outer surface (SRE) of the radially outermost crown layer (5) and the surface of rolling (21), distance plumb with the center of the bottom face (243) of the groove circumferential (24) closest to said corrugation (512), in that the minimum radial distance (du) between the radially surface outer layer (SRE) of the radially outermost crown layer (5) of the crown reinforcement (3) and the running surface (21), is at most equal to the depth D of the nearest circumferential groove (24) increased by 2 mm and at least equal to the depth D of the nearest circumferential groove (24) decreased by 2 mm.
in that the part of the tread overhanging at least one corrugation of the most radially outer crown layer, comprising at the less 30% of a rubber compound M whose shear modulus dynamic G *, measured at 40 C at 10% peak-to-peak strain at 10Hz, at plus equal to 3.25 MPa. 2. A tire according to claim 1, in which the rubber compound M
at a dynamic shear modulus G *, measured at 40 C at 10% deformation peak to peak at 10Hz, at most equal to 3 MPa, preferably at most equal to 2.5 MPa. 3. A tire according to either of claims 1 or 2 wherein the rubber compound M has a dynamic shear modulus G *, measured at 90 C at 10 Hz and under a stress of 0.7 MPa, is at most equal to 1 MPa, of preferably at most equal to 0.75 MPa, preferably at most equal to 0.5 MPa. 4. A tire according to any one of claims 1 to 3 wherein the rubbery compound M has a tan 50 value at least equal to 0.5, from preference at least equal to 0.6, where tan 50 denotes the value of tan O measured at temperature from 0 C to 10 Hz and under a stress of 0.7 MPa. 5. A tire according to any one of claims 1 to 4 wherein on at less 10%, preferably at least 20% and at most 85%, of the surface radially outer (SRE) of the most radially top layer (5) outer, the radial distance (du) between the radially outer surface (SRE) of the radially outermost crown layer (5) and the surface of rolling (21) is at least 1.5 mm, preferably 2 mm, less than the distance radial (dc) between the radially outer surface (SRE) of the layer of Mountain peak (5) the most radially outer and the running surface (21), distance to plumb with the center of the bottom face (243) of the circumferential groove (24) the more close. 6. A tire according to any one of claims 1 to 5 wherein on at less 10%, preferably at least 20% and at most 85%, of the surface radially outer (SRE) of the most radially top layer (5) outer, the radial distance (du) between the radially outer surface (SRE) of the radially outermost crown layer (5) and the surface of rolling (21), is at most 5 mm lower, preferably at most 3 mm lower than the distance radial (dc) between the radially outer surface (SRE) of the layer of Mountain peak (5) the most radially outer and the running surface (21), distance to plumb with the center of the bottom face (243) of the circumferential groove (24) the more close. 7. A tire according to any one of claims 1 to 6 wherein the radial distance (dl) between the radially outer surface (SRE) of the layer of most radially outer vertex (5) and the bottom face (243) of the groove circumferential (24) is at least equal to 1 mm and at most equal to 5 mm, preferably at least equal to 2 mm and at most equal to 4 mm. 8. A tire according to any one of claims 1 to 7, where at least a major groove (24) of the tread (2) comprising at least one witness wear (7), in which the minimum radial distance (du) between the surface radially outer (SRE) of the most radially top layer (5) outer edge of the crown frame (3) and the running surface (21) is at the less equal to the radial distance (df) between the running surface (21) and the point (71) on more radially outwardly of the wear indicator (7). 9. A tire according to any one of claims 1 to 8 wherein all parts of the tread and the tread surface overhanging the undulations of the most radially outer crown layer (5), comprise at least 50% of the rubber compound M, preferably 75%, of preferably 100%. 10. A tire according to any one of claims 1 to 9 and comprising at minus a wear indicator in which the part of the tread radially outside the wear indicators is composed of 100% of the compound rubbery M. 11. A tire according to any one of claims 1 to 10 wherein the depth D of a major groove (24) is at most equal to 10 mm. 12. A tire according to any one of claims 1 to 11 wherein the rate of depression in the tread is at least equal to 10%. 13. A tire according to any one of claims 1 to 12 wherein the crown layer (5) of radially outermost reinforcing elements of the crown reinforcement (3) comprises textile reinforcement elements, of preferably of the aliphatic polyamide, aromatic polyamide, combination of aliphatic polyamide and aromatic polyamide, polyethylene terephthalate or radiates, parallel to each other and forming, with the circumferential direction (XX ') of tire, an angle B at most equal to 100 in absolute value. 14. A tire according to any one of claims 1 to 13 wherein at least one rubbery stuffing compound (6) having a radial thickness at the less equal to 0.3 mm, is positioned in line with the corrugation (512) of the layer the most radially outer vertex (5). 15. A tire according to claim 14, in which the compound rubbery stuffing (6) has a maximum dynamic loss tanöl, measured at a temperature from 23 C at 10 Hz, at most equal to and preferably less than 30% than the loss maximum dynamic range tan52 of the least hysteretic rubbery compound of the tread (2) and radially outside the bottom surfaces of the furrows circumferential, measured at a temperature of 23 C and under a stress of 0.7 MPa at 10 Hz.