Targeted stiffness vehicle tires

Description

[0001] The invention relates to a vehicle tire with a tread designed for contact with the road surface, which has an anisotropic stiffness profile.

[0002] The demands placed on the properties and performance characteristics of modern vehicle tires are constantly increasing, especially in high-performance applications, creating a need to optimize rolling and handling characteristics. The tread plays a crucial role in determining the handling characteristics of modern vehicle tires. The tread is the part of the tire that contacts the road, and its properties significantly influence the tire's behavior.

[0003] It is known from the prior art to deliberately create anisotropies and gradients in the physicochemical material properties of the tread to optimize driving characteristics, for example, with regard to stiffness or the hysteresis behavior of the rubber materials used, which is relevant for rolling resistance. In the prior art, these non-uniform material properties are often achieved by using different rubber materials, as is known, for example, from so-called MCT treads ("Multi Compound Tread"), i.e., through the deliberate use of chemically different rubber materials. For manufacturing reasons, the anisotropy of the material properties is usually generated transversely to the circumferential direction in the prior art, for example, by co-extrusion of two or more different rubber materials during the production of a tread.

[0004] In the field of vehicle tire manufacturing, there is a continued interest in optimizing tire performance. From a manufacturing perspective, it is desirable to avoid relying on the use of different rubber materials, particularly to allow for greater flexibility in tire design. Specifically, there is a need for design measures to reduce the susceptibility of vehicle tires to uneven wear or other defects, such as sawtooth wear or block depressions, especially on the non-driven axles of the vehicle, as many of the prior art MCT concepts are considered less than ideal in this respect.

[0005] US 5643374 A refers to a pneumatic tire that is capable of controlling complicated tire movements or the so-called wandering phenomenon, which cannot be predicted by the driver.

[0006] US patent 2018043736 A1 discloses a vehicle pneumatic tire that exhibits lower noise emissions and more even wear during driving.

[0007] The JP 2006168564 A reveals a pneumatic tire with good maneuverability and low rolling resistance.

[0008] EP 1870259 A1 relates to a tread made of a rubber compound for a vehicle tire and a vehicle tire containing this tread, wherein the tread is subdivided into profile blocks and / or profile bands by longitudinal and / or transverse grooves, wherein the tread has indentations which are filled and tightly closed with a material having different properties from the tread rubber compound.

[0009] US 5679186 A refers to a pneumatic tire whose resistance to tread wear is improved, especially against heel and toe wear caused by driving the tire.

[0010] DE 69202478 T2 discloses a tread strip with at least three circumferential ribs connected to each other via circumferential grooves, each rib having a plurality of transverse grooves extending in the transverse direction, which define a plurality of profile blocks lying one behind the other within each rib.

[0011] US 4986325 A reveals pneumatic tires with improved wet performance.

[0012] US 4836257 A relates to a radial pneumatic tire suitable for use in heavy-duty vehicles such as trucks, buses, etc.

[0013] The primary objective of the present invention was therefore to eliminate or at least reduce the disadvantages of the prior art.

[0014] In particular, the object of the present invention was to provide a vehicle tire which exhibits advantageous wear rates, especially on the driven axle. Furthermore, it was an object of the present invention that the vehicle tires to be provided should be less susceptible to uneven wear and the occurrence of defects such as sawtooth wear and block depressions, especially also on the non-driven axles.

[0015] It was an object of the present invention that the vehicle tires to be specified should have a high degree of flexibility with regard to the rubber materials to be used and, in particular, should also be feasible without the use of other rubber materials.

[0016] A further objective of the present invention was that the vehicle tires to be specified should be flexibly designed for specific tire types with regard to their configuration, in particular also as winter, summer and all-season tires.

[0017] Furthermore, it was an object of the present invention that, in the vehicle tires to be specified, a desired wear behavior should be promoted in a targeted manner by means of design measures, which should in particular also support the design of directional tires as well as the optimization for use on one side of the vehicle.

[0018] In this respect, it was an object of the present invention that the vehicle tires to be specified should be implementable both as pneumatic tires and as solid rubber tires.

[0019] The inventors of the present invention have now realized that the problems described above can surprisingly be solved by generating directed stiffness in the tread of a vehicle tire by tilting the structural elements arranged in the tread, for example the lamellar recesses, so to speak, and designing them as inclined stiffness elements, which thus do not extend substantially radially into the profile as defined in the claims.

[0020] The above finding resulted from initial tests on vehicle tires with so-called "shovel sipes," a feature familiar from winter tires designed for snow. These "shovel sipes" are grooves running largely along the radial direction in the tread blocks of winter tires, with a kink in the upper part, thus being partially inclined in the circumferential direction. These "shovel sipes" are structural elements primarily intended to optimize performance in snow. However, the inventors recognized that the use of "shovel sipes" could also yield fundamental advantages in the wear rate on the driven axle.However, it was also observed that the use of these "shovel sipes," which are only inclined at the end, results in disadvantages in wear behavior on the non-driven axle (so-called "irregular wear") and a higher susceptibility to defects such as sawtooth wear and block depressions. Furthermore, the concept of specifically shaped "shovel sipes" cannot be easily transferred from winter and all-season tires to summer tires, as the resulting reduction in stiffness would be unsuitable for summer tires.

[0021] The inventors have therefore set themselves the particular task of achieving a design, based on the promising advantages in the wear rate observed for "Shovel Sipes", that preserves the advantages in the wear rate, but reduces the disadvantages in "irregular wear" and the susceptibility to other defects on the non-driven axle, while ideally having no adverse effects on the suitability for summer tires.

[0022] Furthermore, the inventors set themselves the task of improving the "shovel sipes" concept, which is regularly only used for directional vehicle tires, so that advantageous wear behavior could also be achieved in non-directional tires.

[0023] During development, the inventors realized that this is surprisingly achievable by using stiffening elements that—unlike shovel sipes—do not have a pronounced kink, but are essentially straight, similar to shovel sipes, yet inclined at a moderate angle. This largely straight design, combined with the inclination, surprisingly increases the effectiveness of the stiffening elements and leads to greater advantages in terms of wear behavior, on both the driven and non-driven axles.

[0024] Without wishing to be bound by this theory, the inventors assume that the angle set in the largely straight stiffening elements partially redirects the radial force acting during use into a horizontal component. This force component can be used to specifically reduce the wear rate by optimally adjusting the angle of inclination. For the circumferential inclination based on the "Shovel Sipes" design, it was found that the circumferentially inclined stiffening elements in the tread must be predominantly inclined in the same direction to achieve this positive effect.This can be implemented without problems in many tires and is only a design-limiting problem in exceptional cases, as it makes implementation more difficult, for example, in vehicle tires in which the so-called RAT ("Residual Aligning Torque") is to be set, since in these vehicle tires there would probably have to be an even distribution of structural elements inclined in one or the other circumferential direction in order to achieve the desired RAT effects.It is assumed that the introduction of a force acting against the external driving force into the tread by the inclined stiffness elements in the longitudinal direction shifts the force transmission away from the run-out area of ​​the contact surface and towards the inlet, so that a flatter gradient of force action is obtained, which reduces a so-called "snap-out" at the run-out of the contact area (also known as "slapping" or "footprint"), which has a positive effect on the abrasion rate and the occurrence of other undesirable wear effects.

[0025] Advantageously, unlike the "shovel sipes", the straight stiffness elements are also suitable for use in summer tires and, since they do not have to fulfill a function in the area of ​​snow performance, can even be advantageously moved into the tread, where they create an advantageous anisotropy of stiffness below the tread surface, which is reflected in the above-described

[0026] This offers advantages. Furthermore, the inventors have found that moving away from optimizing snow performance makes it possible to also incorporate a lateral tilt, which can lead to advantages in wear behavior even with non-directional tires, as well as an optimization of running characteristics compared to tires with sidewalls.

[0027] Our own tests and complementary abrasion simulations yielded favorable results with various tilt angles. A steeper tilt led to a significant reduction in abrasion rates in the center of the tire, achieving a reduction of more than 80%. However, it was also observed that this could increase abrasion in the shoulder areas, leading to the development of compensatory measures, which are described below. Without further measures, particularly at low tilt angles, an overall beneficial reduction in the maximum abrasion rate of approximately 33% is achieved, corresponding to a reduction from 3 mm to 2 mm, thus improving tire life by 50%, without significantly impairing abrasion performance in the sidewall areas.

[0028] The aforementioned problems are thus solved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention are described in the dependent claims and the following descriptions.

[0029] Such embodiments, which are hereinafter referred to as preferred, are combined in particularly preferred embodiments with features of other embodiments referred to as preferred. Combinations of two or more of the embodiments referred to below as particularly preferred are therefore especially preferred. Also preferred are embodiments in which a feature of one embodiment, referred to as preferred to any degree, is combined with one or more further features of other embodiments, which are referred to as preferred to any degree.

[0030] The invention relates to a vehicle tire with a tread provided for contact with the road surface, wherein the tread comprises a plurality of profile blocks separated from one another by profile grooves, each having a contact surface provided for contact with the road surface. wherein the tread comprises a plurality of planar structural elements, each structural element having a central centroid line in the longitudinal direction, which extends radially from an inner point P(r 1 ) with radius r 1 to an outer point P(r 2 ) with radius r 2 through the tread, and comprising the points P(r) as a function of the radius r, wherein the structural elements are independently selected from the group consisting of recesses in the tread and material areas with a stiffness increased or decreased compared to the surrounding tread, wherein the central centroid line of each structural element at each point P(r) forms a radially inward tangent angle α(r) with the circumferential direction,wherein the central centroid line of each structural element at each point P(r) forms a radially inward tangent angle β(r) with the axial direction, wherein at least some of the structural elements are designed as stiffness elements for which, in the respective region from r1 to r2: i) that these are circumferentially inclined stiffness elements whose mean tangent angle <α(r)> is less than 89°, wherein the difference Δα(r) between the maximum and the minimum of the tangent angle a(r) is less than 15°, and ii) that these are transversely inclined stiffness elements whose mean tangent angle <β(r)> is less than 89°, wherein the difference Δβ(r) between the maximum and the minimum of the tangent angle β(r) is less than 15°, wherein the stiffness elements are related to the total number of stiffness elements. are arranged in the profile blocks to 80% or morewherein, with respect to the total number of stiffness elements, 50% or more of the stiffness elements are circumferentially inclined stiffness elements, wherein 60% or more of the circumferentially inclined stiffness elements have a mean tangent angle <α(r)>, circumferentially inclined stiffness elements have a mean tangent angle <α(r)> pointing in the same direction, wherein the mean tangent angle <α(r)> varies between separate stiffness elements transversely to the circumferential direction, wherein the mean tangent angle <α(r)> has a minimum in the central region of the tread, the central region comprising the middle 60% of the tread transversely to the circumferential direction.

[0031] The invention relates to a vehicle tire which, in accordance with the skilled person's understanding, comprises a tread. A vehicle tire according to the invention is preferably a pneumatic tire. A vehicle tire according to the invention is particularly preferred, wherein the tire is a truck or passenger car tire, preferably a passenger car tire.

[0032] The tread comprises a multitude of planar structural elements, as is known from the prior art. Such structural elements are, in particular, groove-shaped recesses that, in the prior art, regularly extend parallel to the radial direction of the vehicle tire into the tire and serve to adjust the tread characteristics. With respect to the radial direction of the vehicle tire, such structural elements thus extend from an inner point or inner base surface to an outer point or outer surface. Using the example of a groove-shaped recess known from the prior art, which is also referred to by those skilled in the art as a "sipe," this means that the base of the sipe is closer to the center of the vehicle tire than the opening of the sipe on the surface of the tread.

[0033] In accordance with expert understanding, these are planar structural elements, i.e., structural elements that have a significantly larger extent in the plane spanned by two spatial directions than in the spatial direction perpendicular to them. Accordingly, these structural elements are, for example, groove-shaped recesses or thin layers of material, but not, for example, cubic blocks of material.

[0034] A person skilled in the art understands that defining the inclination of structural elements in a complex system such as a vehicle tire requires specifying a meaningful reference system for each element, allowing for a precise determination of its inclination. While determining the inclination is generally straightforward for the structural elements that are likely most relevant in practice—namely, the essentially straight cuts—the inventors believe that for certain applications, it is advantageous to also design structural elements with more complex surfaces and larger volumes with an inclination.

[0035] To describe this meaningfully, the present invention defines a central center of gravity line as a reference system for each structural element. This line extends longitudinally, i.e., from the radial inside to the radial outside of the structural element, as visualized in the accompanying figures. For a given radius r, this center of gravity line includes the point P(r). Determining the center of gravity line is not a problem for those skilled in the art and, in cases of doubt, can be reliably approximated for typical vehicle tires and structural elements of usual size by drawing the line connecting the centers M(r) of the respective cross-sectional surfaces of the structural elements with the circumferential surface for each radius, thus taking into account the basic curvature of the vehicle tire in the circumferential direction.This approach also creates a clearly defined reference system for more complex structural elements, such as wave-shaped, groove-like recesses.

[0036] The structural elements can, in principle, be any type of planar structural element that allows for influencing the local stiffness. In their simplest form, these are recesses in the material, such as cuts running parallel to the radial direction and groove-like depressions, which are well known in the prior art. However, it is also possible to use material areas in which a material with a different stiffness than the surrounding components of the tread is used locally, i.e., within the dimensions of the respective structural element.Naturally, rubber materials are particularly suitable for this purpose, which differ in terms of stiffness from the surrounding rubber materials of the tread, for example due to the conditions used for vulcanization and / or the chemical nature of the rubber material used.

[0037] The orientation of the structural elements in space can be determined in light of the above definition of the central center of gravity line relative to the circumferential direction or the axial direction in order to determine the degree of inclination.

[0038] In the case of structural elements that are particularly relevant in practice and have an essentially straight central center of gravity line (i.e., a center of gravity line with a constant slope), the angle between the central center line and the circumferential direction or the axial direction is particularly easy to determine.

[0039] In the case of a central centroid line that deviates from the shape of an ideal straight line, the angle with the adjacent tangent can be determined for each point P(r) with radius r, as is known to those skilled in the art from the fundamental areas of analysis when determining slopes. Accordingly, it is to the understanding of those skilled in the art that, within the scope of the present invention, the tangent angles are always referred to, which, in the case of straight central lines, become the angle of intersection of the centroid line with the circumferential direction or the axial direction, respectively.

[0040] Those skilled in the art understand that a precise description of angular relationships requires a clear definition of the angle serving as the reference system. The intersection of the central centroid line with, for example, the circumferential direction forms four angles, namely two pairs of vertex and opposite angles of the same magnitude. In accordance with the usual procedure for intersection angles, the smaller of the intersection angles is used in the present invention. Furthermore, in order to define the direction in which the corresponding angle points, the angle that points radially inward, i.e., on the side facing the inside of the tire, is used in the present invention, as will be further illustrated below.

[0041] To determine the circumferential inclination, the tangent angle between the central center of gravity and the circumferential direction can be determined. For straight, uninclined cuts known from the prior art, this angle is 90°. The reference direction for evaluating the lateral inclination is the axial direction of the vehicle tire, which is orthogonal to the circumferential direction. For structural elements known from the prior art, this angle is also essentially 90°.

[0042] A person skilled in the art understands that curvature can occur in the shoulder areas of the tread of vehicle tires. Structural elements located in these shoulder areas, which have structural elements known from the prior art and extend essentially orthogonally to the surface of the tread, exhibit at least potentially an angle other than 90° with the axial direction in this shoulder area. However, this angle is caused by the inherent curvature of the tire surface in the shoulder area.The person skilled in the art understands that the foregoing definition, that the relevant tread is provided for road contact, means that the definition for the inclined structural elements applies to the part of the tread that is provided for road contact and consequently runs substantially parallel to the axial direction, and that the curved shoulder areas are accordingly not assigned to the tread within the scope of the present invention.

[0043] The inclination of the specific structural elements according to the invention is now expressed within the scope of the present invention by the fact that the angle of intersection of the central center of gravity line with the circumferential direction or the axial direction deviates from 90°. In order to meaningfully distinguish such inclined structural elements from other, non-inclined structural elements, these specific structural elements are referred to here as stiffness elements to account for their function in generating directional stiffness, whereby a further distinction is made between stiffness elements inclined in the circumferential direction and in the transverse direction, whereby inclination in both directions is also possible.

[0044] For essentially straight centroid lines, the tangent angle can advantageously be determined directly as the angle of intersection at any given point. However, to also allow the definition of centroid lines that deviate from a straight course, at least section by section, the inclination is determined within the scope of the present invention via the mean tangent angle, which, in the case of straight centroid lines, always merges into the angle of intersection. A person skilled in the art can readily determine the mean tangent angle by referring to fundamental mathematical concepts, and in particular by dividing the integral of the corresponding trigonometric function between r1 and r2 by the difference between r2 and r1.

[0045] Furthermore, it is defined above for both types of stiffness elements that the difference between the maximum and minimum tangent angles is less than 15°. This means that the stiffness elements are designed with a relatively uniform slope of the centroid line and, for example, do not include pronounced kinks, such as those that occur in "shovel sipes," where the difference between the extreme tangent angles is regularly on the order of 45° or more.

[0046] Furthermore, the vehicle tire according to the invention is limited with regard to the orientation of the mean tangent angles of the circumferentially inclined stiffness elements such that these must point in the same direction for 60% or more of the time. In accordance with the skilled person's understanding, this refers to the direction in which the angle opens, i.e., the direction away from the intersection of the center line with the circumferential direction or the axial direction.

[0047] In the inventors' experiments, the desired beneficial effect on wear behavior was observed only for a preferred circumferential orientation and the resulting anisotropy or directional stiffness. In this respect, the inventors consider it an advantage of the laterally inclined stiffness elements that it has been shown that no preferred orientation needs to be set to produce a positive effect. On the contrary, designs are even preferred in which the laterally inclined stiffness elements on the different sides of the vehicle tire are deliberately oriented in different directions, for example, pointing outwards, so that essentially 50% point in one direction and 50% in the other.

[0048] According to the inventors, even relatively small deviations from right-angled tangent angles, and also certain deviations from the ideal straight shape, result in beneficial effects on the abrasion behavior. At the same time, the inventors have found that a particularly advantageous influence on the abrasion properties occurs when the tangent angle deviates noticeably from 90°. Conversely, in the absence of countermeasures as described below, relatively large inclinations, i.e., deviations from 90°, sometimes lead to adverse effects on the abrasion behavior in the edge regions, at least with circumferential inclinations.Accordingly, the inventors have identified particularly suitable angles, and it is especially preferred to set the same values ​​for the circumferentially and transversely inclined stiffness elements, or to define the resulting ranges from the maxima and minima listed below. A preferred vehicle tire according to the invention is therefore one in which, for the circumferentially inclined stiffness elements, the mean tangent angle <α(r)> is 87° or less, preferably 85° or less, and particularly preferably 80° or less, and the mean tangent angle <α(r)> is preferably 45° or more, and particularly preferably 60° or more.Preferably, or alternatively, a vehicle tire according to the invention is used, wherein for the stiffness elements inclined in the transverse direction, the mean tangent angle <β(r)> is 87° or less, preferably 85° or less, particularly preferably 80° or less, wherein the mean tangent angle <β(r)> is preferably 45° or more, particularly preferably 60° or more.

[0049] Even though the vehicle tires according to the invention can tolerate a certain curvature of the stiffening elements, as defined above, the inventors' experiments clearly show that the best results are achieved with stiffening elements that have the straightest possible central center of gravity line. Since such stiffening elements are also significantly easier to manufacture, the use of such stiffening elements for both directions of inclination is explicitly preferred, with it being particularly preferred that the central center of gravity line is a straight line with a substantially constant slope. A vehicle tire according to the invention is preferred in that, for the circumferentially inclined stiffening elements, the difference Δα(r) is less than 10°, preferably less than 5°, and particularly preferably less than 1°.Preferably, or alternatively, a vehicle tire according to the invention is used, wherein for the laterally inclined stiffness elements the difference Δβ(r) is less than 10°, preferably less than 5°, and particularly preferably less than 1°. Here too, the same upper limits are preferably defined for both inclinations.

[0050] As explained above, in addition to the recesses known from the prior art, which are also ideally suited for the present invention, material areas with altered stiffnesses can also be used as structural elements, which makes it possible, in particular, to create areas of increased stiffness and to generate directional stiffness without having to create recesses in the material, which is particularly preferred when the stiffness elements are not to be arranged on the surface of the tread but inside it, as disclosed below.Although it is theoretically possible to use both types of structural elements in the same vehicle tire, the inventors believe that, with regard to manufacturing efficiency, it is particularly preferable to provide only one type of structural element at a time, with rubber materials being particularly suitable for use in the material areas. Therefore, a preferred option is a vehicle tire according to the invention in which the structural elements or the stiffness elements are selected independently from the group consisting of recesses, in particular groove-shaped recesses, in the tread.Alternatively, a preferred vehicle tire according to the invention is one in which the structural elements or the stiffness elements among the structural elements are selected independently of one another from the group consisting of material areas with a reduced or increased, preferably reduced, stiffness compared to the surrounding tread. A preferred vehicle tire according to the invention is one in which the material areas comprise one or more materials selected from the group consisting of rubber materials. A preferred additional or alternative vehicle tire according to the invention is one in which the material in the material area has a modulus of elasticity that differs from the modulus of elasticity of the surrounding tread by 2 MPa or more, preferably by 3 MPa or more, and particularly preferably by 4 MPa or more.

[0051] Within the scope of the present invention, the term E-modulus denotes the mean dynamic storage modulus E', which is determined for rubber materials from a dynamic-mechanical measurement at 55 °C according to DIN 53513:1990-03, wherein the mean dynamic storage modulus E' is the mean value of two measurements at 0.15 % elongation and 8 % elongation.

[0052] Regardless of the type of structural element, it is preferred to design the stiffness elements with a comparatively small volume, which can be achieved by making them particularly planar, being especially advantageous when using recesses. A preferred vehicle tire according to the invention is therefore one in which the stiffness elements have a width in the direction of their smallest dimension that corresponds to 20% or less, preferably 15% or less, particularly preferably 10% or less, and most preferably 5% or less, of the length or depth in the direction of their greatest dimension.

[0053] Preferably, or alternatively, a vehicle tire according to the invention is used, wherein the stiffness elements have the same basic shape to 80% or more, preferably 90% or more, particularly preferably 95% or more, and most preferably essentially 100%, in relation to the total number of stiffness elements.

[0054] As explained above, an advantage of the invention is that the directional stiffness can be generated in various ways. It is not necessarily required that the stiffness elements extend to the surface of the tread, since, according to the inventors, the advantageous influence on the wear characteristics can also be achieved if the stiffness elements are arranged within the tread. The inventors believe this is particularly feasible in pneumatic vehicle tires whose treads utilize a so-called "cap / base" construction, where the stiffness elements can be arranged in the cap layer or in the underlying base layer, or even partially in both layers.In this respect, the inventors believe there is a certain preference for designing stiffness elements in the surface layer as recesses, while to avoid cavities inside the vehicle tire, a design with material areas for stiffness elements in the base layer is particularly suitable. A preferred vehicle tire according to the invention comprises a multi-layered structure with a surface layer intended for road contact and a base layer arranged radially below the surface layer.A preferred vehicle tire according to the invention is one in which the stiffness elements are arranged in the plywood layer to a extent of 60% or more, preferably 80% or more, particularly preferably 90% or more, very preferably 95% or more, and particularly preferably substantially 100%, over at least a portion of the length of the stiffness elements, preferably over the predominant portion of the length, and particularly preferably over substantially the entire length. It is also preferred that, in some cases, the stiffness elements are additionally arranged in the plywood layer.Alternatively, a vehicle tire according to the invention, wherein the stiffness elements are arranged in the base position to 60% or more, preferably 80% or more, particularly preferably 90% or more, very preferably 95% or more, and particularly preferably substantially 100%, with respect to the total number of stiffness elements.

[0055] Building on this and independent of any "cap / base" construction of the tread, the two extreme embodiments described above, i.e., that the stiffening elements extend to the surface of the tread or are arranged completely within the tread, can be formulated alternatively. A preferred embodiment in this sense is a vehicle tire according to the invention in which the stiffening elements, in relation to the total number of stiffening elements, are located partially on the surface of the tread to the extent of 80% or more, preferably 90% or more, particularly preferably 95% or more, very preferably 98% or more, and particularly preferably substantially 100%.Alternatively, a vehicle tire according to the invention is preferred, wherein the stiffness elements, with respect to the total number of stiffness elements, are arranged completely inside the tread to 80% or more, preferably 90% or more, particularly preferably 95% or more, very preferably 98% or more, and particularly preferably substantially 100%.

[0056] In practice, vehicle tires with a tread pattern are particularly relevant. According to the invention, a vehicle tire is defined as follows: the tread comprises a plurality of tread blocks separated from one another by tread grooves, each block having a contact surface intended for road contact.

[0057] It has been successfully demonstrated that the teaching of the preceding invention is particularly well suited to providing corresponding profiled treads with directional stiffness. Since the tread blocks are particularly relevant for road contact and are subjected to especially high forces during operation, the inventors consider it particularly advantageous to provide the stiffness elements in these very tread blocks, and advantageously to design the tread blocks with at least a majority of several stiffness elements. According to the invention, a vehicle tire is characterized in which the stiffness elements, relative to the total number of stiffness elements, are arranged in the tread blocks to a extent of 80% or more, preferably 90% or more, particularly preferably 95% or more, most preferably 98% or more, and most preferably substantially 100%.Preferably, or alternatively, a vehicle tire according to the invention is used, wherein the tread blocks comprise at least one, preferably at least two, particularly preferably at least three stiffness elements, based on the total number of tread blocks, to 60% or more, preferably 80% or more, particularly preferably 90% or more, very preferably 95% or more, and particularly preferably substantially 100%.

[0058] When using tread blocks, suitable dimensions for the stiffness elements can be specified particularly easily, and the corresponding size relationships are also generally suitable for use inside the vehicle tire for stiffness elements that do not extend at least into the tread blocks. A preferred vehicle tire according to the invention has a radial extension of the stiffness elements in the tread blocks in the range of 0.2h to 1.0h, preferably in the range of 0.4h to 0.9h, and particularly preferably in the range of 0.6h to 0.8h, where h is the mean height of the tread blocks relative to the base of the surrounding tread grooves.A vehicle tire according to the invention is also preferred, either additionally or alternatively, wherein the extent of the stiffness elements in the tread blocks transversely to the circumferential direction is in the range of 0.5*b1 to 1.0*b1, preferably in the range of 0.7*b1 to 1.0*b1, and particularly preferably in the range of 0.9*b1 to 1.0*b1, where b1 is the mean width of the tread blocks transversely to the circumferential direction. A vehicle tire according to the invention is also preferred, either additionally or alternatively, wherein the extent of the stiffness elements in the tread blocks parallel to the circumferential direction is in the range of 0.5*b2 to 1.0*b2, preferably in the range of 0.7*b2 to 1.0*b2, and particularly preferably in the range of 0.9*b2 to 1.0*b2, where b2 is the mean width of the tread blocks in the circumferential direction.

[0059] Particularly when using recesses as stiffness elements, the inventors believe it is advantageous to arrange them as much as possible within the tread blocks and not, for example, in the interior of the tread, since this can also have beneficial effects on other driving characteristics, such as water drainage from the tread or friction on snow. A vehicle tire according to the invention is therefore particularly preferred in which the recesses, based on the total number of recesses, are arranged within the tread blocks to a degree of 96% or more, preferably 97% or more, particularly preferably 98% or more, most preferably 99% or more, and most preferably substantially 100%.

[0060] According to the inventors, advantageous effects on wear behavior can be achieved even with the use of relatively shallowly inclined stiffening elements. At the same time, it has been shown that particularly advantageous effects on wear behavior can be achieved when as many of the structural elements as possible are designed as stiffening elements, with particularly preferred embodiments essentially omitting conventional, i.e., non-inclined, structural elements such as groove-shaped recesses. A preferred vehicle tire according to the invention is one in which, relative to the total number of structural elements, 30% or more, preferably 50% or more, particularly preferably 70% or more, most preferably 90% or more, and most preferably essentially 100%, of the structural elements are designed as stiffening elements.

[0061] According to the inventors, particularly advantageous directional vehicle tires are obtained when the stiffening elements are predominantly inclined, at least in part, in the circumferential direction. Similarly, the inventors consider it advantageous if the stiffening elements are also inclined, at least in part, in the transverse direction. According to the invention, a vehicle tire is characterized in which, with respect to the total number of stiffening elements, 50% or more, preferably 70% or more, particularly preferably 90% or more, most preferably 95% or more, and in particular substantially 100%, of the stiffening elements are inclined in the circumferential direction.A vehicle tire according to the invention is also preferred, wherein, with respect to the total number of stiffness elements, 50% or more, preferably 70% or more, particularly preferably 90% or more, most preferably 95% or more, and in particular substantially 100%, of the stiffness elements are stiffness elements inclined in the transverse direction.

[0062] In principle, particularly for the implementation of directional or side-mounted vehicle tires, designs are conceivable in which the stiffness elements are inclined only in the circumferential direction or only in the transverse direction, with the proportions described above applying accordingly. However, in the inventors' opinion, a particularly advantageous design, in which the advantages of both inclination directions can be combined, arises when the structural elements are inclined to a large extent in both directions, i.e., both in the circumferential direction and in the axial direction.A preferred vehicle tire according to the invention is therefore one in which, with respect to the total number of stiffness elements, 50% or more, preferably 70% or more, particularly preferably 90% or more, most preferably 95% or more, and in particular substantially 100%, of the stiffness elements are inclined in the circumferential direction and inclined in the transverse direction.

[0063] As explained above, it has been found that, with regard to the circumferentially inclined stiffness elements, these should point predominantly in the same direction to achieve the desired effect, with at least the 6:4 ratio defined above being set with respect to the orientation (i.e., 60% pointing in one direction and 40% in the other direction). However, the inventors consider particularly advantageous embodiments to result precisely when the circumferentially inclined stiffness elements point as far as possible in the same direction. Thus, a vehicle tire according to the invention is preferred in which 70% or more, preferably 80% or more, particularly preferably 90% or more, most preferably 95% or more, and most preferably substantially 100% of the circumferentially inclined stiffness elements have a mean tangent angle <α(r)> pointing in the same direction.

[0064] As explained above, particularly with relatively steep circumferential slopes in the lateral region of the tread, the wear behavior may only be marginally improved or even negatively affected in some areas. To avoid this and, in particular, to fully exploit the advantages of greater circumferential slopes in the central part of the tire, the inventors propose varying the slope angles transverse to the circumferential direction, thereby creating a non-uniform distribution of the tangent angles. A particularly preferred configuration is one in which smaller slopes are used in the lateral region and more pronounced slopes, i.e., smaller average tangent angles, are used in the central region.According to the invention, in this background, a vehicle tire according to the invention is wherein the mean tangent angle <α(r)> between separate stiffness elements varies transversely to the circumferential direction, wherein the mean tangent angle <α(r)> has a minimum in the central region of the tread, wherein the central region comprises the middle 60% of the tread transversely to the circumferential direction.

[0065] In addition or alternatively to the above, it is also possible to provide at least small quantities of stiffening elements that are oriented opposite to the main direction of the other circumferentially inclined stiffening elements, with it being particularly preferred to arrange these in the side areas of the vehicle tire, with an arrangement that is as symmetrical as possible being preferred.A preferred vehicle tire according to the invention is one in which the mean tangent angles <α(r)> of the stiffness elements in the two edge regions of the tread point at least partially, preferably predominantly, and particularly preferably substantially completely, in the opposite direction to the mean tangent angles <α(r)> of the stiffness elements in the central region, wherein the central region comprises the middle 60% of the tread transversely to the circumferential direction and wherein the two edge regions each comprise the outer 20% of the tread transversely to the circumferential direction.

[0066] As explained above, a pronounced inclination of the stiffness elements in the circumferential direction, in combination with a high proportion of these circumferentially inclined stiffness elements, results in significantly improved wear behavior depending on the direction of travel of the vehicle tire. Accordingly, it is particularly preferred to explicitly design such vehicle tires as directional tires. More precisely, a vehicle tire according to the invention is preferred, wherein the vehicle tire is a directional tire, and wherein 70% or more, preferably 80% or more, particularly preferably 90% or more, most preferably 95% or more, and particularly preferably substantially 100%, of the circumferentially inclined stiffness elements have a mean tangent angle <α(r)> that points opposite to the intended direction of travel.In accordance with expert understanding, the intended direction of travel is the direction of rotation of the vehicle tire, which is directed against the direction of travel in the area of ​​road contact.

[0067] A vehicle tire according to the invention is preferred in addition or alternatively to the above embodiments, wherein, with respect to the total number of stiffness elements inclined in the circumferential direction, 50% or more, preferably 70% or more, particularly preferably 90% or more, and most preferably substantially 100% of the stiffness elements are arranged in the central area of ​​the tread, wherein the central area comprises the middle 60% of the tread transversely to the circumferential direction.

[0068] Regarding the preferred direction of the lateral tilt, the inventors consider two options particularly advantageous. By setting a preferred tilt in one direction, i.e., by designing the stiffness elements with a mean tangent angle that points largely in the same direction, it is possible to obtain vehicle tires that are explicitly preferred for use on the left or right side of the vehicle, since the vehicle tires can then be precisely adjusted to the load profile expected during cornering. For example, the wear on the right tire from left-hand turns is significantly greater than that from right-hand turns, so aligning the angle with the force expected during the respective cornering maneuvers allows for left / right-specific adjustment of the vehicle tires.A vehicle tire according to the invention is preferred for this purpose, wherein 70% or more, preferably 80% or more, particularly preferably 90% or more, very particularly preferably 95% or more, and especially preferably substantially 100% of the stiffness elements inclined in the transverse direction have a mean tangent angle <β(r)> pointing in the same direction.

[0069] Alternatively, according to the inventors, favorable abrasion properties in non-sidewall tires can be achieved particularly well if the lateral inclination of the stiffness elements in the two edge regions of the tire is inverted, with a mirroring of the stiffness elements on the central plane of the tire orthogonal to the axial direction being particularly preferred. A preferred option is a tire according to the invention in which, with respect to the total number of laterally inclined stiffness elements, 50% or more, preferably 70% or more, particularly preferably 90% or more, and most preferably essentially 100% of the stiffness elements are arranged in the two edge regions of the tread, wherein the two edge regions each comprise the outer 20% of the tread transversely to the circumferential direction.Particularly preferred is a vehicle tire according to the invention, wherein the mean tangent angles <β(r)> of the stiffness elements inclined in the transverse direction in one of the two edge regions of the tread point at least partially, preferably predominantly, particularly preferably substantially completely, in the opposite direction as the mean tangent angles <β(r)> of the stiffness elements in the opposite edge region, wherein the two edge regions each comprise the outer 20% of the tread transversely to the circumferential direction.

[0070] Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying figures, in which the radial direction R, the circumferential direction U, or the A are shown as needed for clarity. Fig. 1 is a highly simplified schematic representation of a vehicle tire according to the invention; Fig. 2 shows schematic representations of profile blocks with different structural elements or stiffness elements; Fig. 3 is a schematic visualization of central centroid lines in exemplary structural elements; Fig. 4 is a schematic visualization of the resulting angles of intersection of the central centroid line with the circumferential direction; Fig. 5 is a schematic visualization of the resulting angles of intersection of the central centroid line with curved centroid lines; Fig. 6 is a schematic cross-sectional view transverse to the circumferential direction through an exemplary tread with various stiffness elements inclined in the transverse direction; and Fig. 7 is a schematic visualization of the influence of stiffness elements inclined in the circumferential direction on the forces acting when passing through the contact patch.

[0071] Figure 1Figure 1 shows a very schematic representation of a vehicle tire 10 according to the invention with a profiled tread 12 provided for road contact, wherein the vehicle tire 10 is designed as a pneumatic vehicle tire, in particular a passenger car tire.

[0072] Figure 2a Figure 1 shows a schematic representation of a profile block 22 in a cross-sectional view parallel to the circumferential direction U, as known from the prior art. Three structural elements 14, designed as lamellar recesses, extend within the profile block 22 from a point P(r₁) with radius r₁ located radially inside R to a point P(r₂) with radius r₂ located radially outside. The schematic representation of the Figure 2A) the structural elements 14 are neither inclined in the circumferential direction U nor in the axial direction and accordingly have a tangent angle of 90° with both directions over the entire length.

[0073] Figure 2b ) visualized in contrast to the Figure 2a ) an inclination of the structural elements 14 in the circumferential direction U. In the profile block 22 shown, the three structural elements 14 are now designed as stiffness elements 18, which enclose an angle α with the circumferential direction U at every point of the radius r that is not 90°. Since the stiffness elements 18 are designed as straight cuts and accordingly have a central centroid line 16 whose slope does not change over its entire length, the mean tangent angle <α(r)> corresponds in this case to the angle of intersection α. Figure 2c ) visualizes a corresponding cross slope of the stiffness elements 18 in the profile block 22 and the associated angle β.

[0074] Figure 3 This serves to explain how the central center of gravity line 16, running radially from inside to outside between points P(r 1 ) and P(r 2 ), is oriented in a stiffness element 18 or a structural element 14 and illustrates the identification in schematic exemplary inclined stiffness elements 18.

[0075] Figure 4 A schematic representation illustrates, with the circumferential direction U and the radial direction R shown, which angle of intersection within the scope of the present invention can be read at a point P(r) as the radially inward directed tangent angle.

[0076] Figure 5a) visualizes using the example of a structural element 14, which is designed as a "shovel sipe" known from the prior art, how the angles relative to the circumferential direction U can be read at each point along the radial direction and clearly visualizes that in this case the difference between the maximum and the minimum tangent angle is significantly greater than 15°, namely about 45°.

[0077] Figure 5b ) now illustrates the concept familiar to those skilled in the art of determining the respective angle at each point P(r) of a curved function via the tangent angle when the central centroid line 16, where in this case a structural element 14 is shown which is not a stiffness element 18, since the difference between the maximum and the minimum of the tangent angle α is again greater than 15°, as this lies at essentially 90° in the difference between the outermost points.

[0078] Figure 6 Figure 1 shows a schematic cross-sectional view transverse to the circumferential direction through the tread 12 of a vehicle tire 10 according to the invention, wherein the profile blocks 22 are aligned with the tread pattern intended for the

[0079] The contact surface 24 intended for road contact and the profile grooves 20 between it are schematically shown. For better clarity, in Figure 6 Furthermore, the central area Z is shown, which comprises the middle 60% of the tread 12 perpendicular to the circumferential direction and is flanked on both sides by the two edge areas S 1 and S 2. The Figure 6Using the example of transversely inclined stiffness elements 18, possible arrangements of these stiffness elements in a tread 12 with a "cap / base" construction are shown. The schematically drawn stiffness elements 18 can, for example, extend only through the profile blocks 22 and reach, for example, to the surface of the tread 12. An arrangement in the area of ​​the profile groove 20 is possible, although less preferred, whereby it is also conceivable that the stiffness elements 18 extend from the surface of the tread 12 into the "base", wherein in Figure 6 Furthermore, an embodiment is shown in which the stiffness elements 18 inclined in the transverse direction do not extend to the surface of the tread 12, but are arranged exclusively in the "base".

[0080] Figure 7Finally, the diagram visualizes, by way of example, the influence that the stiffness elements 18 have on the force experienced when passing through the contact surface, according to the inventors' assessment. Figure 7a ) shows a schematic representation of a force profile that results during driving between the inlet XE and the outlet XA of the contact area, wherein in particular the force acting at the outlet XA causes frictional energy. Figure 7b Figure 1 shows a schematic force curve during propulsion in a vehicle tire 10 according to the invention, which comprises circumferentially inclined stiffness elements 18 and is designed as a directional vehicle tire 10, in which essentially all circumferentially inclined stiffness elements 18 point in the same direction, namely against the direction of travel. This results in a flattening of the force curve and, advantageously, a reduced force at the runout XA. Reference symbol list

[0081] 10 Vehicle tire 12 Tread 14 Structural element 16 Central center of gravity line 18 Stiffness element 20 Profile grooves 22 Profile blocks 24 Contact surface

Claims

1. Vehicle tyre (10) having a tread (12) intended for contact with the roadway, wherein the tread (12) comprises a multiplicity of profile blocks (22) which are separated from one another by profile grooves (20) and respectively have a contact surface (24) intended for contact with the roadway, wherein the tread (12) has a multiplicity of two-dimensional structural elements (14), wherein each structural element (14) respectively has a central centre-of-gravity line (16) in the longitudinal direction, said lines each extending through the tread (12), with respect to the radial direction, from an inner point P(r1) with the radius r1 to an outer point P(r2) with the radius r2, and comprises the points P(r) as a function of the radius r, wherein the structural elements (14) are selected independently of one another from the group consisting of recesses in the tread (12) and material regions with a stiffness that is increased or reduced compared with the surrounding tread (12), wherein the central centre-of-gravity line (16) of each structural element (14) at each point P(r) respectively encloses with the circumferential direction a radially inwardly directed tangent angle αs(r), wherein the central centre-of-gravity line (16) of each structural element (14) at each point P(r) respectively encloses with the axial direction a radially inwardly directed tangent angle βs(r), wherein at least some of the structural elements (14) are in the form of stiffness elements (18) for which the following applies in the respective region of r1 to r2: i) they are stiffness elements (18) which are inclined in the circumferential direction and the mean tangent angle <α(r)> of which is less than 89°, wherein the difference Δα(r) between the maximum and the minimum of the tangent angle αs(r) is less than 15°, and ii) they are stiffness elements (18) which are inclined in the transverse direction and the mean tangent angle <β(r)> of which is less than 89°, wherein the difference Δβ(r) between the maximum and the minimum of the tangent angle βs(r) is less than 15°, wherein, with respect to the total number of the stiffness elements (18), 80% or more of the stiffness elements (18) are arranged in the profile blocks (22), wherein, with respect to the total number of the stiffness elements (18), 50% or more of the stiffness elements (18) are stiffness elements (18) that are inclined in the circumferential direction, wherein 60% or more of the stiffness elements (18) that are inclined in the circumferential direction have a mean tangent angle <α(r)> which faces in the same direction, wherein the mean tangent angle <α(r)> of the stiffness elements (18) that are inclined in the circumferential direction varies transversely to the circumferential direction between separate stiffness elements (18), wherein the mean tangent angle <α(r)> of the stiffness elements that are inclined in the circumferential direction has a minimum in the central region of the tread, wherein the central region comprises the central 60% of the tread transversely to the circumferential direction.

2. Vehicle tyre (10) according to Claim 1, wherein, with respect to the total number of the profile blocks (22), 60% or more of the profile blocks (22) comprise at least one stiffness element (18).

3. Vehicle tyre (10) according to either of Claims 1 and 2, wherein, with respect to the total number of the stiffness elements (18), 80% or more of the stiffness elements (18) lie partially on the surface of the tread (12).

4. Vehicle tyre (10) according to either of Claims 1 and 2, wherein, with respect to the total number of the stiffness elements (18), 80% or more of the stiffness elements (18) are arranged completely within the tread (12).

5. Vehicle tyre (10) according to one of Claims 1 to 4, wherein the structural elements (14) are selected independently of one another from the group consisting of recesses in the tread (12).

6. Vehicle tyre (10) according to one of Claims 1 to 4, wherein the structural elements (14) are selected independently of one another from the group consisting of material regions with a stiffness that is reduced compared with the surrounding tread (12).

7. Vehicle tyre (10) according to one of Claims 1 to 6, wherein, with respect to the total number of the stiffness elements (18), 50% or more of the stiffness elements (18) are stiffness elements (18) that are inclined in the transverse direction.

8. Vehicle tyre (10) according to one of Claims 1 to 7, wherein the mean tangent angle <β(r)> of the stiffness elements (18) that are inclined in the transverse direction varies transversely to the circumferential direction between separate stiffness elements (18).

9. Vehicle tyre (10) according to one of Claims 1 to 8, wherein the mean tangent angles <α(r)> of the stiffness elements (18) that are inclined in the circumferential direction situated in the two peripheral regions of the tread (12) face at least partially in the opposite direction to the mean tangent angles <α(r)> of the stiffness elements (18) that are inclined in the circumferential direction situated in the central region, wherein the central region comprises the central 60% of the tread (12) transversely to the circumferential direction and wherein the two peripheral regions respectively comprise the outer 20% of the tread (12) transversely to the circumferential direction.

10. Vehicle tyre (10) according to one of Claims 1 to 9, wherein the vehicle tyre (10) is a directional vehicle tyre (10), wherein 70% or more of the stiffness elements (18) that are inclined in the circumferential direction have a mean tangent angle <α(r)> which faces counter to the intended running direction.

11. Vehicle tyre (10) according to one of Claims 1 to 10, wherein, with respect to the total number of the stiffness elements (18) that are inclined in the transverse direction, 50% or more of the stiffness elements (18) are arranged in the two peripheral regions of the tread (12), wherein the two peripheral regions respectively comprise the outer 20% of the tread (12) transversely to the circumferential direction.

12. Vehicle tyre (10) according to one of Claims 1 to 11, wherein the mean tangent angles <β(r)> of the stiffness elements (18) that are inclined in the transverse direction that are situated in the two peripheral regions of the tread (12) face at least partially in the opposite direction to the mean tangent angles <β(r)> of the stiffness elements (18) in the opposite peripheral region, wherein the two peripheral regions respectively comprise the outer 20% of the tread (12) transversely to the circumferential direction.

13. Vehicle tyre (10) according to one of Claims 1 to 12, wherein 70% or more of the stiffness elements (18) that are inclined in the transverse direction have a mean tangent angle <β(r)> which faces in the same direction.