JP2021529124A - Pneumatic tires with optimized crown and tread pattern construction - Google Patents

Abstract

The present invention is a tire with a crown that includes at least one layer of reinforcing element. The outermost layer in the radial direction comprises at least one undulation (512). The undulations (512) in the outermost crown layer (5) in the radial direction have the points of the undulations (512) vertically below the center of the bottom surface (243) of the nearest main groove (24) by at least a radial distance of 1.5 mm. It is located on the outer side in the radial direction of the point of the outermost crown layer (5). The undulations (512) in the radial outermost crown layer constitute at least 10% of the radial outer surface (ROS) of the outermost crown layer (5). A rubber compound with a dynamic modulus G * of up to 3.25 MPa when measured at 10% peak strain at 40 ° C. and 10 Hz covers at least 30% of the rubber compound vertically above the undulations. Constitute. [Selection diagram] Fig. 2

Description

The present invention relates to a tire intended to be mounted on a passenger car, and more particularly to a crown of such a tire.

Since a tire has a geometric shape that exhibits rotational symmetry around the axis of rotation, the geometry of the tire is generally described by the meridional plane that includes the axis of rotation of the tire. For a given meridional plane, the radial, axial, and circumferential directions represent directions perpendicular to the tire rotation axis, parallel to the tire rotation axis, and perpendicular to the meridional plane, respectively. The midline, called the equatorial plane, divides the tire into two substantially symmetrical semicircular ring shapes, which can exhibit tread or structural asymmetry related to manufacturing accuracy or sizing. ..

In the text below, the expressions "inward in the radial direction of" and "outward in the radial direction of" are "closer to the axis of rotation of the tire in the radial direction than" and "radial than", respectively. It means "away from the axis of rotation of the tire in the direction". The expressions "inward in the axial direction of" and "outward in the axial direction of" are "closer to the equatorial plane in the axial direction than" and "away from the equatorial plane in the axial direction than", respectively. Means "is". The "radial distance" is the distance to the rotation axis of the tire, and the "axial distance" is the distance to the equatorial plane of the tire. The "radial thickness" is measured in the radial direction and the "axial width" is measured in the axial direction.

The tire comprises a crown with a tread intended to contact the road surface through the tread surface, two beads intended to contact the rim, and two sidewalls connecting the crown to the beads. Further, the tire comprises a carcass reinforcement arranged radially inside the crown and having at least one carcass layer connecting the two beads.

The tread of a tire is bounded by two peripheral surfaces in the radial direction, the outermost surface in the radial direction is the tread surface, and the innermost surface in the radial direction is called the bottom surface of the tread pattern. The bottom surface of a tread pattern, or bottom surface, is defined as the surface of a tread surface that is radially translated inward by a radial distance equal to the depth of the tread pattern. This depth usually decreases gradually over the outermost circumference of the tread, called the shoulder.

In addition, the tread of the tire is axially bounded by two sides. The tread is also composed of one or more rubber compounds. The expression "rubber compound" means a rubber composition with at least an elastomer and a filler.

The crown comprises at least one crown reinforcement inside the tread radially. The crown reinforcement comprises at least one working reinforcement with at least one working layer composed of reinforcing elements parallel to each other at an angle of 15 ° to 50 ° with respect to the circumferential direction. The crown reinforcement may also include a hoop reinforcement consisting of at least one hoping layer composed of reinforcement elements at an angle of 0 ° to 10 ° with respect to the circumferential direction, although not necessarily, hoop reinforcement. The body is usually located radially outside the working layer.

For any layer of reinforcement element for crown reinforcements, working reinforcements or other reinforcements, a continuous surface called the radial outer surface (ROS) of that layer is the radial outermost point of each reinforcement element for each meridian. Pass through. For any layer of reinforcement element for crown reinforcements, working reinforcements or other reinforcements, a continuous surface called the radial inner surface (RIS) of that layer is the radial innermost point of each reinforcement element for each meridian. Pass through. The radial distance between the layer of reinforcement element and any other point is measured from either of these surfaces so as not to incorporate the radial thickness of that layer. If the other measurement point is on the radial outside of the reinforcing element layer, the radial outer surface ROS to this point, and if the other measurement point is on the radial inside of the reinforcing element layer, the radial inner surface RIS. The radial distance from to this measurement point is measured for each. This makes it possible to consider coherent radial distances for each meridian without having to consider possible local variations associated with the cross-sectional shape of the layered reinforcement element.

The tread is notched for good grip on wet surfaces. A notch means either a well, a groove, or a sipe, or a circumferential follow, forming a spatial opening in the tread surface.

The sipe or groove has two characteristic main dimensions, width W and length L0, on the tread surface, the length L0 being at least equal to twice the width W. Thus, a sipe or groove determines its length Lo and is bounded by at least two main sides connected by a bottom surface, the two main sides being only a non-zero distance called the width W of the sipe or groove. They are separated from each other.

The depth of cut is the maximum radial distance between the tread surface and the bottom of the cut. The maximum value of the depth of cut is called the depth D of the tread pattern.

The Farrow is essentially a circumferential groove, meaning that its sides can vary locally at about ± 45 ° with respect to the circumferential direction, but all patterns belonging to the Farrow can be found on the entire surface of the tread. It forms a substantially continuous set, i.e., which exhibits a discontinuity of less than 10% in length as compared to the length of the pattern.

Circumferential fallows define the rib boundaries. The rib is composed of a tread pattern element contained between the axial edge of the tire and the outermost circumferential fellow in the adjacent axial direction, that is, contained between two adjacent circumferential fellows. ..

In the text below, the phrase "downward in the vertical direction of" means "for each meridian, it is radially inward within the boundaries of the axial coordinates bounded by." Therefore, the "points of the working layer below the vertical direction of the fallow" represent a set of points of the working layer inside the radial direction of the groove within the boundary of the axial coordinates defined by the fallow for each meridian. ..

In the text below, the phrase "vertically above" means "for each meridian, it is radially outside within the boundaries of the axial coordinates bounded by." Therefore, "the portion of the tread vertically above the undulations" represents a set of tread points on the radial outer side of the undulations within the boundary of the axial coordinates defined by the undulations for each meridian.

Tires need to meet a number of performance criteria in relation to phenomena such as wear, grip on various types of roads, rolling resistance, and dynamic behavior. These performance standards can sometimes provide solutions that undermine other standards. Therefore, in order to obtain good grip performance on a dry road surface, the rubber compound of the tread needs to be dissipative and soft. In contrast, in order to obtain a tire that works well with respect to behavior, especially with respect to the dynamic response to the lateral load of the vehicle and thus the load along the axis of rotation of the tire, the tire is high enough, especially under lateral load. Must have a level of rigidity. For a given size, the stiffness of the tire depends on the stiffness of the various elements of the tire: treads, crown reinforcements, sidewalls, and beads. Treads have traditionally reduced the depth of the tread pattern, or reduced the depth of the tread pattern, while providing a loss of grip on dry roads while stiffening the rubber compound or causing a loss of grip on wet roads. Rigidity is increased by either reducing the groove-to-rubber ratio of.

To alleviate this problem, tire manufacturers have used rubber compounds, for example, by stiffening the rubber compound, especially with fibers, as described in French Patent No. 3014442 and French Patent No. 29842430. Has changed.

French Patent No. 3014442 French Patent No. 2984230

These solutions are not always satisfactory. Reducing the depth of the tread pattern limits performance both in terms of wear and wet grip. By stiffening the rubber compound, the ability of wet grip and dry grip is limited, and tire noise during running is also increased. By reducing the void volume of the tread pattern, the grip capacity is reduced on wet road surfaces, especially when the pooled water is deep. Further, in order to ensure the durability of the tire, it is important to maintain a specific thickness of the rubber compound between the bottom surface of the notch, groove or fallow and the reinforcing element of the outermost radial crown layer.

Thus, using a particular rubber compound that is very soft and exhibits a high level of grip to make all or part of the tread should be done without compromising other performance aspects. I can't.

Therefore, a main object of the present invention is to use a tread rubber compound that exhibits "soft" or low levels of stiffness to improve performance and make its relevant properties available. These rubber compounds can have, for example, very hysteresis to enhance dry grip performance, or, in contrast, very small hysteresis to facilitate flattening to further improve rolling resistance. These low-rigidity rubber compounds can be placed over the entire tread or over a limited portion thereof so as not to adversely affect other performance aspects such as wear or behavior. This goal was achieved without altering its performance in terms of wear and crown durability, while complying with national standards for rolling resistance.

The purpose is
A tread intended to come into contact with the road surface through a grooved tread surface, the groove forming a space that opens into the tread surface and is bounded by two main sides connected at the bottom. A tread having a width W defined by the average distance between the two sides and a depth D defined by the maximum radial distance between the tread surface and the bottom surface.
A main groove, at least one groove having a width W equal to at least 1 mm and a depth D equal to at least 4 mm.
-At least one main groove is called a circumferential follow, which is substantially circumferential.
・ At least two ribs and
Passenger car tires equipped with
The tire also has a crown reinforcement inside the tread with at least one layer of reinforcement, represented by the crown layer.
-At least one layer of reinforcing element extends radially from the radial inner surface (RIS) to the radial outer surface (ROS).
The outermost radial crown layer has at least one undulation below the ribs in the vertical direction.
-At least one undulation in the radial outermost crown layer is a point of the radial outermost crown layer in which the radial outermost crown layer portion of the undulation is vertically below the center of the bottom surface of the circumferential fellow closest to the undulation. It is designed to be located on the outer side in the radial direction.
The at least one undulation in the radial outermost crown layer is the radius between the radial outer surface (ROS) and the tread surface of the radial outermost crown layer over at least 10% of the radial outer surface (ROS) of the crown layer. The radial distance (du) is the radial distance (ROS) between the radial outer surface (ROS) of the outermost crown layer in the radial direction and the tread surface, which is the distance vertically below the center of the bottom surface of the circumferential fellow that is closest to the undulations. It is at least 1.5 mm smaller than dc).
-The minimum radial distance (du) between the radial outer surface (ROS) and the tread surface of the outermost radial crown layer of the crown reinforcement is the maximum, equal to the closest circumferential fall depth D + 2 mm, and the minimum. Equal to the nearest circumferential follow depth D-2 mm,
The tread portion vertically above at least one undulation in the outermost crown layer in the radial direction has a rubber compound M of at least 30%, and its dynamic shear modulus G ^* is 10% of 10 Hz at 40 ° C. Achieved with passenger car tires, up to equal to 3.25 MPa when measured in inter-peak strain of.

The point on the layer of the reinforcing element is when the radial distance between the point and the point on the same crown layer vertically below the innermost point in the radial direction of the bottom surface of the nearest main groove exceeds 1 mm. , Belongs to the undulations in its crown layer. When there are two or more closest main grooves, the inspection of whether or not they belong to the undulations is performed in consideration of the main groove that maximizes the radial distance. To calculate the radial distance, consider points of the same type of reinforcing element: two points on the neutral axis, two radial outermost points of the reinforcing element, and two radial innermost points of the reinforcing element. become.

The properties of the rubber compound are measured with a viscosity analyzer (Metrabib VA40000) in accordance with ASTM Standard D 5992-96. A sample of a sulfide composition that is subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz during a temperature sweep of 0 ° C to 100 ° C under a fixed stress of 0.7 MPa, preferably a sample of a sulfide composition having a thickness of 4 mm and a cross-sectional area of 400 mm2. The response of the cylindrical test piece is recorded. The dynamic shear modulus G ^* is also measured at a given temperature of 40 ° C. and 10 Hz with a 10% peak-to-peak strain, also in accordance with ASTM Standard D 5992-96. ^{Using the same procedure, the shear modulus G *} under stresses of 90 ° C, 10 Hz, and 0.7 MPa is measured.

Rubber compounds known to those of skill in the art can be used for certain applications, such as motor racing competitions, to improve certain performance aspects, such as dry grip, but these rubber compounds are completely present in passenger cars, even sports cars. Not suitable. This is because passenger cars need to comply with specific performance aspects such as maximum rolling resistance, minimum wear, durability, grip force, and behavioral performance aspects defined by environmental standards. Specifically, these vehicles are used on public roads under conditions of wet roads and wet grips that differ from the closed competition circuit for very short periods of time and ultimately for limited mileage. , You need to be able to drive. Owners of these vehicles do not have a team to change tires in the event of rain, and after one hour of running with worn tires, so after one hour of driving when these tires are worn. There are design parameters for tires according to the invention, such as the presence of grooves or circumferential fellows in the tread, the ability of the tire to travel thousands of kilometers, and thus sufficient tread pattern depth. Preferably, the grooves and circumferential fellows in the tire constitute a void ratio in the new tread that is equal to at least 10%. The void ratio is measured as the ratio of the volume of voids formed by all cuts in the tread to the radial outer tread volume of the bottom surface of the tread pattern containing the voids.

The rubber compound may suffer from poor wear performance due to low tread pattern height or normal tread pattern height that does not compensate for the low stiffness of the rubber compound, or with normal tread pattern height and low stiffness of the rubber compound. It exhibits low stiffness over a temperature range that cannot be used with conventional passenger car tires, regardless of whether the combination of tires excessively impairs performance related to behavior. When this low rigidity is accompanied by a large hysteresis, the performance related to rolling resistance is also impaired. Therefore, the use of these rubber compounds is itself a problem.

Dynamic shear modulus at 40 ° C, measured at 10 Hz with 10% inter-peak strain at 40 ° C, up to 3.25 MPa, preferably up to 3 MPa, preferably up to 2.5 MPa. Rubber compounds with a modulus G ^* are significantly adversely affected with respect to behavior associated with tread pattern height, such as those present for passenger cars.

Dynamic shearing at 90 ° C, measured under stresses of 90 ° C, 10 Hz, 0.7 MPa, up to 1 MPa, preferably up to 0.75 MPa, preferably up to 0.5 MPa Rubber compounds with a modulus of elasticity G ^* are significantly adversely affected by wear.

In the present invention, that is, by combining the undulations in the outermost crown layer in the radial direction with the low-rigidity rubber compound vertically above the undulations, it is possible to use the low-rigidity rubber compound regardless of the desired related characteristics. Become. This rubber compound in the tread, coupled with its low stiffness, reduces the volume of this rubber compound and the shear height of this rubber compound in the tread if it has excellent wear performance but high rolling resistance. By doing so, you can use it. Further, according to the present invention, it is possible to find an acceptable rolling resistance value. Similarly, performance degradation related to behavior or wear can be resolved by the present invention in order to obtain a high dry grip in combination with the low stiffness of this rubber compound.

One of the characteristics that characterizes the grip force is the tan δ 0 hysteresis value, which represents the tan δ value measured under stress at temperatures of 0 ° C., 10 Hz, and 0.7 MPa. Therefore, in a preferred embodiment of the present invention, the rubber compound M has a tan δ0 value equal to at least 0.5, preferably at least 0.6.

The undulations should necessarily affect the radial outermost layer of the crown reinforcement. The present invention affects behavior, wear and rolling resistance by reducing the volume of rubber compound in the tread vertically above the undulations. Other crown layers and carcass reinforcements may or may not be undulating. To be perceptible, the undulations must affect at least 10% of the surface of the outermost radial crown layer, and the amplitude of the undulations that can reduce the thickness of the rubber compound is at least 1.5 mm. Must be equal. For this, it is sufficient to have a vertical undulation on the single rib of the tread. The undulations can be, for example, central and symmetrical with respect to the median circumference.

This solution can have advantages with respect to uneven wear or with respect to axial thrust values that depend on the direction of axial thrust depending on the camber angle of the vehicle. Nevertheless, this single undulation can be evenly located under any rib, especially under one of the outermost radial ribs. Such selection can be made by considering the directional or axisymmetric sides of the tire and the camber angle of the vehicle on which the tire is used.

Similarly, the undulations need to be properly positioned with respect to the tread pattern depth D for optimum functionality. The minimum radial distance (du) between the radial outer surface (ROS) and the tread surface (21) of the radial outermost crown layer (5) of the crown reinforcement (3) is the largest and closest circumferential groove. It is equal to the depth D + 2 mm of (24), and is equal to the minimum depth D-2 mm of the nearest circumferential groove (24). If the position is too far inward in the radial direction, the undulations cannot solve the problem, because the height of the rubber compound above the undulations cannot be sufficiently reduced. If the undulations are positioned too far outward in the radial direction, wear will expose the crown layer and cause durability problems, or make more of the tread thinner to improve rolling resistance. It can, but this solution is not optimal.

Further, passenger car tires preferably have a tread pattern depth equal to at least 6 mm and a maximum of 10 mm. This depth is the maximum depth of the groove and circumferential fellow in the tread. This depth is generally measured near the equatorial plane of the tire. These values are current compromises, including wear, rolling resistance and behavioral aspects, among other performance aspects.

This solution has been maintained to solve behavioral problems as a result of the crown layer being laid on a substantially cylindrical formwork and having a regular curvature with no inflection points in the meridional plane. This is contrary to the tire manufacturing method that has been used. Creating substantially torus-shaped undulations under the ribs, which are themselves torus-shaped, is advantageous from the standpoint of ease of manufacture and productivity. Specifically, tools for manufacturing tires before curing typically utilize the axisymmetry of the tire, creating undulations with the same axisymmetry to provide standard tire manufacturing means. It will be possible to use it.

The undulating layer of the reinforcing element under compressive load violates the recommendations for preventing buckling of the structure. Specifically, by creating a discontinuity in the radius of curvature, additional stress is generated, which may cause buckling. However, in tires the load is very local, which means that when one part of the crown is in the compressed state, another part of the crown is in the tensioned state, on a much smaller scale than the undulation scale. Therefore, the undulations produced within the scope of the present invention do not impair the durability of the tire.

These undulations no longer aim to improve rolling resistance and behavior, but have low stiffness, i.e. 40 ° C, 10 Hz, to improve behavior and acceptable rolling resistance and improve dry grip. ^{Use a tread rubber compound with a maximum dynamic shear modulus G * at} 10% inter-peak strain equal to 3.25 MPa, up to 3 MPa, preferably up to 2.5 MPa, at least vertically above the undulations. It becomes possible to do.

Depending on the desired performance aspect and its aging, the rubber compound above the undulations in the outermost radial crown layer is, in whole or in part, a rubber compound M with low stiffness and good dry grip. Can be. Preferably, the tread surface has this rubber compound in new condition.

The distance (du) is reduced by creating at least one undulation in the outermost radial crown layer, where this undulation or undulation of the crown layer is above the crown layer vertically below the circumferential fellow closest to the undulation. It is located on the radial outside of the undulating part. It is not a problem to consider a crown layer that is not undulating, but meets the criteria of reducing the distance du by reducing the tread pattern depth in a given area, as undulating. This feature is further known, especially for passenger car tires, where the depth of the tread pattern is smaller at the axial outer edge of the tire, known as the shoulder, than the closest circumferential fellow. In prior art tires, in the portion of the shoulder where the radial distance (du) is reduced, the outermost radial crown layer is the portion of the same crown layer that is at the same radius or vertically below the nearest circumferential fellow. Is on the inside in the radial direction of.

The present invention also works when one or more undulations are positioned on one or more parts of one or more shoulders of the tire.

The gap lower distance (d1) is preferably maintained in the main groove and the circumferential follow. Grooves or sipes are less sensitive to punctures and impacts from obstacles. They are protected by a rubber compound that imparts its technical characteristics of shallow or narrow grooves.

Vertically below the undulations in the outermost crown layer in the radial direction, all or part of the other crown layers can be undulated, and the carcass layer can also be undulated depending on the structural rigidity desired for the crown. The outermost radial crown layer must be undulating and is of appropriate thickness buried between the outermost radial crown layer and the adjacent crown layer, typically the working layer. By using a rubber compound for inclusion, it can be made the only undulating layer. However, it is also possible to undulate two, three or all of the crown layers in this way. The protective layer or hopping layer is optional in the tire and does not affect the benefits of the solution.

10% of the radial outer surface of the outermost radial crown layer is considered to be measurable at 10% of the tread surface, which is an improved rubber compound in terms of dry grip, so that 10% of the radial outer surface is in the undulating portion. It suffices to be at a radial distance equal to at least 1.5 mm from the radial innermost point of the crown layer vertically below the nearest main groove.

The amplitude of this undulation should be at least equal to 1.5 mm to have a significant effect on the tire scale. Therefore, the radial distance (du) between the radial outer surface (ROS) and the tread surface of the outermost radial crown layer over at least 10% of the radial outer surface (ROS) of the crown layer having one or more undulations. ) Is at least the radial distance (dc) between the radial outer surface (ROS) and the tread surface of the outermost radial crown layer, which is the distance vertically below the center of the bottom surface of the main groove closest to the undulations. It is 1.5 mm smaller.

In order to increase the rigidity of the crown and increase the bond between the undulations and the rubber compound M located vertically below the undulations (s), the preferred solution is multiple crown layers, the outermost crown layer in the radial direction and The crown layers adjacent to it in the radial direction, or all of the crown layers, are undulating, that is, they are substantially relative to each other over the entire width of the crown, except for the last 3 centimeters of the axial end. It is at a certain distance. This is because these axial ends are, in some cases, subject to the decoupling treatment of the rubber compound.

The optimal solution takes into account tire characteristics and possibly vehicle characteristics. Optimization can be done according to tire orientation, tire asymmetry, and vehicle camber angle.

Preferably, the radial outer surface (ROS) and tread surface of the radial outermost crown layer span at least 10%, preferably at least 20%, and up to 85% of the radial outer surface (ROS) of the outermost radial crown layer. The radial distance (du) between is the distance vertically below the center of the bottom surface of the main groove closest to the undulation, the radial direction between the radial outer surface (ROS) of the outermost crown layer in the radial direction and the tread surface. It is at least 1.5 mm, preferably 2 mm smaller than the distance (dc). Design parameters that allow adjustment of performance aspects of grip, wear, rolling resistance and behavior are as follows:
The range of contact surfaces formed by the low-rigidity, high-grip rubber compound M, and the range of undulations in the outermost radial crown layer (the void ratio of the tread pattern, which rarely falls below 10% or 15%). With the knowledge to limit it to a maximum of 85% (100% -15%). The wider the range of undulations (s), or the more ribs with undulations vertically downward, the greater the advantage of using the rubber compound in terms of grip and the less adverse effect it has on rolling resistance. Therefore, it is possible to adjust the number of undulations and the proportion of low-rigidity, high-grip rubber compound M, depending on the desired performance with respect to dry grip, rolling resistance and dynamic behavior.
The amplitude of undulations, which is equal to at least 1.5 mm but is limited to 5 mm due to the radius of curvature imposed on the rigid and therefore less variable metal working layer (thus related to rolling resistance and dynamic behavior). It is possible to adjust the shearing force of the rubber compound of the tread.

A single rib can correspond to 15% of the axial width of the outermost radial working layer. It generally has three, four or five ribs and the fallow corresponds to about 20% of this width.

Therefore, the preferred solution is the radial outer surface (ROS) of the radial outermost crown layer over at least 10%, preferably at least 20%, and up to 85% of the radial outer surface (ROS) of the radial outermost crown layer. The radial distance (du) between the surface and the tread surface is the distance vertically below the center of the bottom surface of the circumferential Farrow closest to the undulations. It is up to 5 mm, preferably up to 3 mm less than the radial distance (dc) between them.

For optimum performance with respect to crown puncture and impact without compromising rolling resistance, between the radial outer surface (ROS) of the outermost radial crown layer and the bottom surface of the circumferential fall (s). The radial distance (d1) of is equal to at least 1 mm and equal to a maximum of 5 mm, preferably equal to at least 2 mm and equal to a maximum of 4 mm. Below the lower limit, the tire may prove to be too impact sensitive. If the upper limit is exceeded, the rolling resistance of the tire becomes disadvantageous.

It is advantageous for the tread, eg, the main groove of the tread, to include at least one wear indicator, the minimum radial distance (du) between the radial outer surface (ROS) of the radial outermost layer of the crown reinforcement and the tread surface. ) Is preferably at least equal to the radial distance (df) between the tread surface and the radial outermost point of the wear indicator. Specifically, the user can use the wear indicator to check for tire wear, which can be done before the radial outermost reinforcement elements of the crown reinforcement begin to appear on the tread surface. This is very important.

Advantageously, the entire portion of the tread, as well as the entire portion of the tread surface vertically above the undulations in the radial outermost crown layer (5), is at least 50% to maximize the properties of the rubber compound M. It comprises a rubber compound M of preferably 75%, more preferably 100%.

In a preferred embodiment of the invention, the radial outer tread portion of the wear indicator is made up of 100% rubber compound M to take advantage of the properties of rubber compound M until the tire is removed due to wear. ..

To maximize the benefits of the solution, it is advantageous that the undulations of the outermost working layer in the radial direction be vertically below all ribs on the tread surface.

One of the preferred solutions is the undulation of the radial outermost working layer in order to obtain just the right performance advantage over the increased manufacturing overheads that the step of undulating the radial outermost working layer means. However, it exists only vertically below the rib of the tread surface closest to the axial direction on any side of the median peripheral surface.

Preferably, the depth D of the main groove (24) is equal to at least 6 mm and at most 10 mm. A tread pattern depth of 6-10 mm allows a good compromise between the performance aspects of wear and rolling resistance in many passenger car tires.

When the radial outermost layer of the reinforcing element of the crown reinforcing body is a hoping layer, the radial outermost layer of the reinforcing element of the crown reinforcing body is a woven fabric, preferably a type of aliphatic polyamide or aromatic polyamide, aliphatic polyamide. It is advantageous to have reinforcing elements made of a type containing a combination of and aromatic polyamides, a polyethylene terephthalate type or a rayon type, these reinforcing elements are parallel to each other and in the circumferential direction of the tire (XX' ) And an absolute value equal to a maximum of 10 °.

One preferred solution is that at least one embedding rubber compound having a radial thickness equal to at least 0.3 mm is positioned vertically below any undulation in the outermost radial crown layer. be. The purpose is to allow the crown layer to undulate during manufacturing and curing. These embedding rubber compounds may be present all around the tire or may be placed on specific parts of the tire, as required. It is possible to lay a plurality of embedding rubber compounds vertically below one or more undulations with different radius values that have different characteristics depending on the tire specifications. When laying a single embedding rubber compound, its maximum thickness is the radial outermost point of the radial outer surface of the radial outermost crown layer in the undulations and the circumferential direction closest to the undulations for a given undulation. It is approximately equal to the radial distance from the radial outer surface of the outermost radial crown layer vertically below the center of the bottom of the Farrow.

When the tread is formed from one or more rubber compounds, the embedded rubber compound has a maximum dynamic loss tan δ1 measured at a temperature of 23 ° C. and 10 Hz in the radial direction of the bottom surface of the main groove or circumferential fall. The rubber compound with the lowest hysteresis of the outer tread should be up to equal to, preferably 30% less than the maximum dynamic loss tan δ2 measured under a stress of 0.7 MPa at a temperature of 23 ° C. and 10 Hz. It is advantageous. For an embedded rubber compound having the same hysteresis, improvement in rolling resistance is achieved simply by reducing the shear stress load that the rubber compound receives. Since the embedded rubber compound does not receive the same stress as the rubber compound that makes the tread, its properties can be modified to further improve rolling resistance. A 30% reduction in hysteresis leads to a significant improvement in the present invention. The rubber compound having the smallest hysteresis of the tread is a rubber compound that forms a part of the radial outer side of the bottom surface of the tread pattern, and the maximum value of tan δ1 measured under a stress of 0.7 MPa at a temperature of 23 ° C. and 10 Hz. Is the smallest of all rubber compounds that make up the radial outer part of the bottom of the tread pattern.

Response of a sample of crosslinked composition (preferably a cylindrical test piece with a thickness of 4 mm and a cross-sectional area of 400 mm2) that is subjected to the shear stress of a simple alternating sinusoidal wave at a frequency of 10 Hz and 23 ° C in accordance with ASTM standard D 5992-96. Is recorded. Inter-peak strain amplitude sweep is performed from 0.1% to 100% (outward cycle) and then from 100% to 0.1% (return cycle). This result utilized is the loss factor (tan (δ)). For the return cycle, the maximum observed value of tan (δ) (tan (δ) max at 23 ° C) is shown.

The crown reinforcement is preferably composed of a hoping layer and a working reinforcement having two working layers at opposite angles, as in many current crown structures.

The features and other advantages of the present invention will be better understood with the help of FIGS. 1-4, but the figures are not at a constant scale and have been simplified to make the invention easier to understand. Is drawn.

It is a partial view of a structure and a tread including a tire, particularly a groove and a circumferential follow. A cross-sectional view of the meridian penetrating the crown of the tire according to the present invention is shown, with different radial distances du, d1, D, df, dc and a padding suitable for creating undulations in the outermost radial crown layer, working layer or hopping layer. The rubber compound (6) for inclusion is described, and the undulations include a low-rigidity rubber compound M vertically above the undulations. A cross-sectional view of the meridian penetrating the crown of the tire according to the present invention is shown and is suitable for creating undulations in different radial distances du, d1, D, df, dc and in the outermost radial crown reinforcement, working layer and hopping layer. A rubber compound for embedding (6) is described, wherein the undulations are 100% above the undulations and part of the radial outer tread of the wear indicator, and the low rigidity rubber compound M is provided. A cross-sectional view of the meridian penetrating the crown of the tire according to the present invention is shown, and different radial distances du, d1, D, df, dc and undulations in the outermost radial crown reinforcement, working layer or hopping layer are described. This undulation is provided vertically above it and on a portion of the radial outer tread of the wear indicator, including a low rigidity rubber compound M. These undulations form undulations while laminating different layers of carcass and crown reinforcements prior to curing, or while curing the tire with a tread volume suitable for creating this type of undulation. It is formed without the use of embedding rubber, using a manufacturing tool designed as described above.

FIG. 1 is a perspective view of a part of a tire crown. A Cartesian frame of reference (XX', YY', ZZ') is associated with each meridional plane. The tire has a tread 2 intended to come into contact with the road surface through the tread surface 21. Arranged in the tread are a groove 24 having a width W that may vary from groove to groove, and a circumferential follower 25 that defines the boundaries of the ribs 26. The tire also includes a working reinforcement 4 and, in this case, a crown reinforcement 3 with, for example, a hoop reinforcement 5. The working reinforcements include at least one working layer, in this case, for example, two working layers 41 and 42, each with parallel reinforcing elements (411 for crown layer 41). The radial outer surface (ROS) of the radial outermost working layer (41) is also shown.

FIG. 2 schematically shows a meridional cross section penetrating a tire crown according to the present invention. This particularly illustrates the undulations (512) of the carcass layer 1, the outermost crown layer (5) in the radial direction, and the embedding rubber compound (6) positioned vertically downward in the undulations over the entire width of the ribs 26. do. FIG. 2 also shows the following radial distances:
D: Groove depth, which is the maximum radial distance between the tread surface (21) and the bottom surface of the groove (243).
Dc: The radial distance between the radial outer surface (ROS) and the tread surface (21) of the outermost radial crown layer (5), which is the bottom surface of the main groove (24) closest to the undulations (512). It is measured vertically downward from the innermost point in the radial direction of (243).
Du: The minimum radial distance between the radial outer surface (ROS) and the tread surface (21) of the radial outermost crown layer (5) of the crown reinforcement.
Df: The radial distance between the tread surface (21) and the outermost point in the radial direction of the wear indicator (7).
D1: The minimum distance between the radial outer surface (ROS) of the radial outermost crown layer (5) and the bottom surface (243) of the circumferential fall (25).

FIG. 3 schematically shows a meridional cross section penetrating a tire crown according to the present invention. This is especially the undulations in the crown reinforcement composed of the two working layers (41 and 42) and, in this case, the hoping layer (5), which is the outermost radial crown layer, and the vertical of each rib of the tread. A rubber compound for embedding (6) arranged below the outermost working layer (42) in the radial direction, which is vertically below the undulations in the lower direction, is shown.

FIG. 4 schematically shows a meridional cross section penetrating a tire crown according to the present invention. This is the undulations in the carcass reinforcement without the use of the rubber compound for embedding (6), the undulations in the crown reinforcement composed of two working layers (41 and 42), and in this case the outermost radial. The undulations in the hoping layer (5), which is the crown layer, are particularly illustrated.

A meridional cross section that penetrates a tire is obtained by cutting the tire at two meridional planes. This cross section is used to determine various radial distances, the center of the bottom of the groove, and the center of the circumferential fellow.

The present invention has been implemented for tire A of size 305 / 30ZR20 intended to be mounted on a passenger car. The groove depth D of the tread pattern is between 5 mm at the shoulder and 7 mm at the equator, the width W varies between 4 and 15 mm, and the tread contains four circumferential fellows. .. The crown reinforcing body is composed of two working layers in which the reinforcing elements form an angle of ± 38 ° with the circumferential direction, and a woven fabric hoping layer in which the reinforcing elements form an angle of ± 3 ° with the circumferential direction. The hoping layer 5, which is the outermost crown layer in the radial direction, undulates under the five ribs of the tread, occupying 50% or more of its surface area. This undulation was made using an embedding rubber compound located radially inside the innermost working layer in the radial direction, which more specifically includes the carcass layer and the innermost crown layer in the radial direction. It is located between. The undulations have an amplitude of 2 mm, that is, the radial distance (du) between the radial outer surface (ROS) and the tread surface of the radial outermost crown layer (5) in the undulations (512) is the radial maximum. 2 mm smaller than the radial distance (dc) between the radial outer surface (ROS) of the outer crown layer (5) and the tread surface (21), these are the circumferential followers (24) closest to the undulations (512). It is the distance vertically downward from the innermost point in the radial direction of the bottom surface of. The radial distance between the radial outer surface (ROS) of the radial outermost crown layer (5) and the bottom surface (243) of the circumferential fellow (25) is equal to 1.5 mm. The tread consists of a single rubber compound CC1 with the following characteristics:
G ^* is measured at 10 Hz with 10% inter-peak strain at 40 ° C and is equal to 2.3 MPa.
The dynamic shear modulus G ^* is measured under stresses of 90 ° C., 10 Hz, and 0.7 MPa and is equal to 0.45 MPa.
Tanδ is measured under stress at temperatures of 0 ° C., 10 Hz, and 0.7 MPa and is equal to 0.58.

Tire A was compared to tires B and C of the same size with the same characteristics except:
-The crown layer of the tire B is not undulating, and the tread is composed of a single rubber compound CC2.
-The crown layer of the tire C is not undulating, and the tread is composed of the same single rubber compound CC1 as the tire A.

Although the rubber compound CC2 does not fall under the present invention, it is a rubber compound suitable for use in treads and has the following characteristics.
G ^* is measured at 10 Hz with 10% inter-peak strain at 40 ° C and is equal to 3.3 MPa.
The dynamic shear modulus G ^* is measured under stresses of 90 ° C, 10 Hz, and 0.7 MPa and is equal to 1.05 MPa.
Tanδ is measured under stress at temperatures of 0 ° C., 10 Hz, and 0.7 MPa and is equal to 0.48.

The embedding rubber compound used to create the undulations of tire A has a dynamic loss tan δ1 measured under stress at a temperature of 23 ° C., 10 Hz and a stress of 0.7 MPa, which is tire A. Tread is 60% less than the dynamic loss of the rubber compound CC1 produced.

The performance aspect of the tire according to the present invention can be seen in the table below with a reference value of 100. A rating greater than 100 means that the performance of the tires of the present invention is superior to that of the controls. Superior performance in terms of rolling resistance, and thus a rating of over 100, means that the rolling resistance of the tires of the present invention is less than that of the control. A dry grip of more than 100 means that one lap of the test lap circuit takes less time than a control tire.

表１：本発明の性能

Table 1: Performance of the present invention

An object of the present invention is to allow the use of "soft" or low-rigidity rubber compounds in treads. The prior art tire B serves as a control without a rugged crown layer or low stiffness rubber compound in the tread.

Obviously in tire C, the use of the specified low stiffness rubber compound in the tread based on a flat structure is unacceptable in all aspects of rolling resistance, wear and behavior compared to control tire B. There is a reduction and only the dry grip is improved. Given the size of sports applications and their high rolling resistance, the deterioration of rolling resistance is no longer acceptable to tire C in terms of environmental standards.

The present invention, as evidenced by tire A, not only allows all deterioration due to the use of the low-rigidity rubber compound CC1 to be ameliorated, but surprisingly, through the combination of the structure and the low-rigidity rubber compound. It makes it possible to improve the dry grip a priori provided by the rubber compound CC1 by an additional 25%.

Improvements of the present invention with respect to rolling resistance were evaluated on a standard machine for measurement standardized according to ISO2850: 2009.

The behavior was evaluated at a pressure of 3 bar and a high temperature by measuring the characteristic Dz of the Pacejka tire behavior model well known to those skilled in the art.

The tires were also mounted on sports-type vehicles and tested on winding circuits that could generate significant lateral loads. A professional driver trained to evaluate a tire will use the tire A according to the invention according to a rigorous test process under the same temperature and road conditions without knowing the characteristics of the tire to be tested. The measurement was repeated with comparison with tire C. The driver assigned points to the tires. In all the tests carried out, tire A according to the present invention outperformed tires B and C in terms of vehicle behavior, road holding, dry road surface, and grip.

Wear was evaluated in tests in which vehicles of the same type follow each other on a given circuit that represents the customer's application. The vehicle is driven by a professional driver trained to evaluate the tires in the same type of driving style, under the same temperature and road conditions, without knowing the characteristics of the tires to be tested, according to a rigorous test process. The measurement was repeated. After each test day, the height of the remaining tread pattern was measured. The wear shown here corresponds to an improvement in post-roll wear that corresponds to 30% of the tire life.

Claims (15)

Tires for passenger cars (1)
A tread (2) intended to come into contact with a road surface through a tread surface (21) provided with a groove (24), wherein the groove (24) opens into the tread surface (21) and has a bottom surface (21). A space defined by the two main side surfaces (241,242) connected by 243) is formed, and the width W defined by the average distance between the two side surfaces (241,242) and the tread surface (21). ) And the tread (2) having a depth D determined by the maximum radial distance between the bottom surface (243).
At least one groove (24), which is a principal groove, called a circumferential follow, having a width W equal to at least 1 mm and a depth D equal to at least 4 mm, and substantially circumferential.
With at least two ribs (26)
With
The tire (1) also comprises a crown reinforcing body (3) with at least one layer of reinforcing elements (41,42.5) represented by a crown layer inside the tread (2) in the radial direction.
The at least one layer of reinforcing elements (41, 42, 5) extends radially from the radial inner surface (RIS) to the radial outer surface (ROS).
In the tire (1)
The radial outermost crown layer (5) has at least one undulation (512) vertically below the rib (26).
The at least one undulation (512) in the radial outermost crown layer (5) is such that the radial outermost crown layer portion (5) of the undulation (512) is the circumference closest to the undulation (512). It is located vertically below the center of the bottom surface (243) of the directional follow (24) and is located radially outside the point of the outermost crown layer in the radial direction.
The at least one undulation (512) in the radial outermost crown layer (5) covers at least 10% of the radial outer surface (ROS) of the crown layer (5) and is said to be the radial outermost crown layer (5). The radial distance (du) between the radial outer surface (ROS) and the tread surface (21) is the center of the bottom surface (243) of the circumferential follow (24) closest to the undulation (512). At least 1.5 mm from the radial distance (dc) between the radial outer surface (ROS) and the tread surface (21) of the radial outermost crown layer (5), which is the distance vertically below. It's getting smaller,
The minimum radial distance (du) between the radial outer surface (ROS) and the tread surface (21) of the radial outermost crown layer (5) of the crown reinforcing body (3) is the maximum. Equal to the closest circumferential follow (24) depth D + 2 mm, and at least equal to the nearest circumferential follow (24) depth D-2 mm.
The tread portion vertically above at least one undulation in the outermost radial crown layer comprises at least 30% rubber compound M, the dynamic shear modulus G ^{* of which} is 10 at 10 Hz at 40 ° C. Equal to a maximum of 3.25 MPa when measured with% inter-peak strain,
A tire that features that. ^{The rubber compound M has a dynamic shear modulus G *} of up to 3 MPa, preferably up to 2.5 MPa when measured at 10 Hz with a 10% interpeak strain at 40 ° C.
The tire according to claim 1. The rubber compound M has a maximum of 1 MPa, preferably a maximum of 0.75 MPa, preferably a maximum of 0.5 MPa when measured under stresses of 90 ° C., 10 Hz, and 0.7 MPa. Have the same dynamic shear modulus G ^* ,
The tire according to claim 1 or 2. The rubber compound M has a tan δ0 value equal to at least 0.5, preferably at least 0.6, where tan δ is a tan δ value measured under stress at temperatures 0 ° C, 10 Hz, and 0.7 MPa. Is,
The tire according to any one of claims 1 to 3. The radial outer surface of the radial outermost crown layer (5) spans at least 10%, preferably at least 20%, and up to 85% of the radial outer surface (ROS) of the radial outermost crown layer (5). The radial distance (du) between (ROS) and the tread surface (21) is the distance vertically below the center of the bottom surface (243) of the closest circumferential follow (24). It is at least 1.5 mm, preferably 2 mm smaller than the radial distance (dc) between the radial outer surface (ROS) and the tread surface (21) of the outermost crown layer (5).
The tire according to any one of claims 1 to 4. The radial outer surface of the radial outermost crown layer (5) spans at least 10%, preferably at least 20%, and up to 85% of the radial outer surface (ROS) of the radial outermost crown layer (5). The radial distance (du) between (ROS) and the tread surface (21) is the distance vertically below the center of the bottom surface (243) of the closest circumferential follow (24). It is up to 5 mm, preferably up to 3 mm smaller than the radial distance (dc) between the radial outer surface (ROS) and the tread surface (21) of the outermost crown layer (5).
The tire according to any one of claims 1 to 5. The radial distance (d1) between the radial outer surface (ROS) of the radial outermost crown layer (5) and the bottom surface (243) of the circumferential fall (24) is equal to at least 1 mm and maximum. Is equal to 5 mm, preferably equal to at least 2 mm and at most equal to 4 mm.
The tire according to any one of claims 1 to 6. At least one main groove (24) of the tread (2) comprises at least one wear indicator (7) and the radial outer surface of the radial outermost crown layer (5) of the crown reinforcement (3). The minimum radial distance (du) between (ROS) and the tread surface 821) is said to be between the tread surface (21) and the radial outermost point (71) of the wear indicator (7). At least equal to the radial distance (df),
The tire according to any one of claims 1 to 7. The entire portion of the tread and the entire portion of the tread surface vertically above the undulations in the radial outermost crown layer (5) is at least 50%, preferably 75%, preferably 100% rubber compound M. With,
The tire according to any one of claims 1 to 8. The tread portion provided with at least one wear indicator and radially outside the wear indicator is made up of 100% of the rubber compound M.
The tire according to any one of claims 1 to 9. The depth D of the main groove (24) is equal to 10 mm at the maximum.
The tire according to any one of claims 1 to 10. The void ratio of the tread is equal to at least 10%,
The tire according to any one of claims 1 to 11. The radial outermost crown layer (5) of the reinforcing element of the crown reinforcing body (3) is a woven fabric, preferably a type of aliphatic polyamide or aromatic polyamide, or a type containing a combination of an aliphatic polyamide and an aromatic polyamide. A reinforcing element made of a polyethylene terephthalate type or a rayon type is provided, and the reinforcing elements are parallel to each other and form an angle B equal to a maximum of 10 ° in absolute value with the circumferential direction (XX') of the tire. ,
The tire according to any one of claims 1 to 12. At least one embedding rubber compound (6) having a radial thickness equal to at least 0.3 mm is positioned vertically below the undulations (512) in the radial outermost crown layer (5).
The tire according to any one of claims 1 to 13. The maximum dynamic loss tan δ1 measured at a temperature of 23 ° C. and 10 Hz of the rubber compound for embedding (6) has the smallest hysteresis of the tread (2) located on the radial outer side of the bottom surface of the circumferential follow. Maximum equal to, preferably 30% less, the maximum dynamic loss tan δ2 measured under a stress of 0.7 MPa at a rubber compound temperature of 23 ° C. and 10 Hz.
The tire according to any one of claims 1 to 14.

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