AIR TIRES WITH CENTRAL CIRCUMFERENCE RIBBON

Description

[0001] The invention relates to a pneumatic vehicle tire with a tread having a profile. The profile of the tread has two circumferential grooves extending around the entire tire. A central circumferential rib of the profile is defined by two mutually parallel sides of these two circumferential grooves, which run perpendicular to the axial direction A of the pneumatic vehicle tire. This circumferential rib has fine cuts at regular intervals in the circumferential direction, which run from one of the mutually parallel sides of the two circumferential grooves to the other along a contour line. State of the art

[0002] Pneumatic vehicle tires suitable for winter use, commonly referred to as winter tires, must also keep a vehicle stable on a road surface even when it is covered in snow or ice. Furthermore, this winter performance, which includes snow and ice performance, also includes safe cornering, starting, and braking.

[0003] In order to achieve these properties, the tread of the pneumatic vehicle tire has a correspondingly designed profile.

[0004] Three main mechanisms contribute to the snow performance of the tire: rubber-snow friction, snow-snow friction and the edge (shear) effect of the tread structure.

[0005] The rubber-snow friction of a pneumatic vehicle tire is determined by the rubber material of the tread, in particular by the rubber material on the surface of the tread.

[0006] In order to increase snow-on-snow friction, the profile of the tread of the pneumatic vehicle tire has structures such as grooves that fill with snow picked up from the road surface. It is known from WO 2018 / 103924 A1 that circumferential grooves with a depth of 1.5 mm to 2.5 mm and a width 2.0 to 3.0 times this depth fill quickly and reliably with snow when driving on a snow-covered road surface. Rapidly filling a structure in the profile of the pneumatic vehicle tire with snow to generate snow-on-snow friction is particularly important if a vehicle has an anti-skid control system (ASR system) or an anti-lock braking system (ABS), since after short slip distances or short intervention times the profile of the pneumatic vehicle tire engages with the road surface and this requires snow-on-snow friction.

[0007] The edge (shear) effect of the tread structure is achieved by fine sipes, also known as sipes, at regular intervals in the tread. The width of these fine sipes is smaller than the width of grooves or grooves in the tread of a pneumatic vehicle tire and is between 0.2 mm and 0.7 mm, preferably between 0.4 and 0.6 mm and particularly preferably between 0.45 mm and 0.55 mm. The fine sipes are typically arranged in the tread blocks of the tread pattern, which are formed by grooves in the tread. When a tread block passes through the contact patch of the pneumatic vehicle tire, i.e. the tread block comes into contact with the road surface during tire rotation, the fine sipes in the tread block open up and grip edges are created that increase power transmission in snow. The tread block elements, which are defined by two fine sipes or one fine sipe and a tread block edge, tilt.The formation of the grip edges and the tilting of the profile block elements increases with the depth of the fine cuts in the profile.

[0008] However, the depth TF of the sipes can be reduced at the block edges, e.g., to improve the handling of the pneumatic vehicle tire. Such sipe edge structures, known as raised sipe edges, also reduce the formation of gripping edges and the tilting of the tread block elements.

[0009] However, on an icy road surface, the tilting of the tread block element is disadvantageous because, when a tread block passes through the ground contact patch, the contact area between the tread block elements present in the tread block and the icy road surface is reduced, so that only a reduced contact area can contribute to the power transmission between the vehicle's pneumatic tire and the road surface.

[0010] This conflicting objectives of snow and ice performance during snow and ice contact can be taken into account by providing a band profile in a circumferential rib of the profile of the pneumatic vehicle tire tread. The circumferential rib runs once around the tire circumference and has a fixed position in the axial direction A of the pneumatic vehicle tire. The axial direction A of the pneumatic vehicle tire is the direction of the axis around which the pneumatic vehicle tire mounted on a rim rotates in a vehicle. Accordingly, such a circumferential rib is delimited by two circumferential grooves in the axial direction A. The sides of these circumferential grooves that delimit the circumferential rib then preferably run parallel to one another and preferably run in the circumferential direction perpendicular to the axial direction A. The sides of the circumferential grooves that delimit the circumferential rib, or the edge of the circumferential rib, then have no directional component in the axial direction.The circumferential rib, as a band profile, features a fine cut at regular intervals in the circumferential direction. Since such a circumferential rib does not have tread blocks separated by grooves, especially transverse grooves perpendicular to the circumferential direction, tilting of the rib elements formed by the fine cuts in the circumferential rib as they pass through the ground contact area is reduced. On the other hand, the rib elements support each other so well that the fine cuts no longer open wide enough for the resulting grip edges to develop their full effect in snow. Snow-to-snow friction is also only slightly pronounced with such a circumferential rib and relies solely on the circumferential grooves with their full tread depth that border them.

[0011] The circumferential rib is positioned centrally in the axial direction A and preferably centrally. A circumferential rib is centrally positioned if there are other tread elements, such as tread blocks, between the circumferential rib and the tire shoulder closest to it in the axial direction A. A circumferential rib is a central circumferential rib if it is positioned centrally in the axial direction A in the tread of the pneumatic vehicle tire and thus the sides of the two circumferential grooves bordering it are at the same distance from the tire shoulder closest to it in the axial direction A.

[0012] If in such circumferential ribs the fine incisions of the belt profile have edge elevations at the edge of the circumferential rib, which follow one another in the circumferential direction, this leads to an increased circumferential stiffness of the circumferential rib at its edges, which increases the abrasion in this area of ​​the circumferential rib.

[0013] From EP 3 444 129 A1, central circumferential ribs with improved snow-snow friction are known with a belt profile in which straight fine incisions and grooves angled relative to the axial direction A alternate in the circumferential direction and the grooves additionally have a phase at their ends.

[0014] US 2020 / 0031171 A1 discloses a central circumferential rib having a straight fine cut angled relative to the axial direction A at regular intervals in the circumferential direction. Instead of a fine cut eight times the length of the spacing of the fine cuts in the circumferential direction, a thin transverse groove is arranged in the central circumferential rib, which is angled in the same way relative to the axial direction A. These transverse grooves have a depression in their end regions that is greater than the depth of the transverse groove and has the same depth as the circumferential grooves that border the circumferential rib. The sides of these circumferential grooves that border the circumferential rib have a zigzag shape with respect to the axial direction A and are not parallel to one another.

[0015] US 2018 / 0345734 A1 discloses central circumferential ribs of a pneumatic vehicle tire with good snow and ice performance. These ribs have a straight, fine sipe angled relative to the axial direction A at regular intervals in the circumferential direction. Instead of a fine sipe five times the length of the spacing of the fine sipes in the circumferential direction, a thin transverse groove is arranged in the central circumferential rib, which is angled at the same angle relative to the axial direction A. These transverse grooves have a depression in their end regions that is greater than the depth of the transverse groove in the center of the circumferential rib.

[0016] EP 3 421 263 B1 discloses central circumferential ribs of a pneumatic vehicle tire with good snow performance, which have a straight fine cut angled relative to the axial direction A at regular intervals in the circumferential direction, with every second fine cut being replaced by a transverse groove which is deeper than the fine cuts.

[0017] US 2018 / 0290498 A1 discloses circumferential ribs in the shoulder area of ​​a pneumatic vehicle tire that have a fine sipe at regular intervals in the circumferential direction. At every fifth sipe in the circumferential direction, the end areas have a groove section that is wider and deeper than the sipe. The groove sections are designed to fill with snow when driving on a snow-covered roadway.

[0018] Another generic pneumatic vehicle tire is known from EP 1 961 586 A1.

[0019] Despite the already known tread structures, the task still remains to resolve the conflict between snow and ice performance even better while taking into account reduced tire wear due to abrasion. Summary of the invention

[0020] The problem is solved by a pneumatic vehicle tire according to patent claim 1.

[0021] Such a pneumatic vehicle tire has a tread with a profile that has a central circumferential rib, which is delimited by two sides, which run at least almost parallel to one another, of two circumferential grooves running around the entire pneumatic vehicle tire, which run at least almost perpendicular to the axial direction A of the pneumatic vehicle tire, by deviating only from the radial direction of a plane perpendicular to the axial direction A by an angle y which is less than 15°, such that the width of the circumferential rib remains constant or increases with increasing tread depth, wherein the circumferential rib has a fine cut at a regular distance d in the circumferential direction, which runs from one to the other of the mutually parallel sides of the two circumferential grooves along a contour line,and wherein instead of a fine cut at a distance three to seven times the length of the distance d between the fine cuts in the circumferential direction, a thin transverse groove is arranged in the central circumferential rib, the width BQ of which is at least 2.5 times the width BF of a fine cut and which has the contour line of the fine cuts, and wherein the depth TF of the fine cuts is at least partially reduced over a length L red of the contour line in the end regions of the fine cuts, and over 80% to 250% of this length L red of the contour line, the thin transverse grooves have a snow pocket in their end regions, which has a width BS perpendicular to the contour line that is at least 1.5 times the width B q of the thin transverse groove, and a depth TS that is a maximum of 65% of the tread depth TQ of the thin transverse groove.

[0022] A pneumatic vehicle tire according to the invention thus has a tread with a profile that includes two circumferential grooves extending around the entire tire. The two circumferential grooves are adjacent circumferential grooves, with a central circumferential rib located between them in the tread.

[0023] Each circumferential groove of a pneumatic vehicle tire has two sides in the axial direction A of the pneumatic vehicle tire, if its cross-section is viewed perpendicular to the circumferential direction. These two sides are located on one side or the other of the deepest point of the cross-section in the axial direction A, relative to the deepest point of the circumferential groove's cross-section, whose distance from the tread surface corresponds to the tread depth of the pneumatic vehicle tire. Both sides of the circumferential groove define a circumferential rib made of the tread rubber material. The facing sides of two adjacent circumferential grooves then jointly define a circumferential rib of the tread profile.

[0024] In a pneumatic vehicle tire according to the invention, the sides of the two circumferential grooves that delimit the circumferential rib run at least almost parallel to one another and at least almost perpendicular to the axial direction A of the pneumatic vehicle tire. In this case, the sides that delimit the circumferential rib only deviate from the radial direction of a plane perpendicular to the axial direction A by an angle γ that is less than 15°. This deviation of the sides that delimit the circumferential rib is such that the width of the circumferential rib remains constant or increases with increasing tread depth. Thus, both sides that delimit the circumferential rib run parallel to the circumferential direction of the pneumatic vehicle tire and only have the slight deviation from the radial direction of the pneumatic vehicle tire given by the angle γ. The radial direction of the pneumatic vehicle tire is perpendicular to its axial direction A, around which it rotates. Along the radial direction inwards, i.e.towards the center of the pneumatic vehicle tire, the tread depth of the tire tread increases. The sides delimiting the circumferential rib now deviate from the radial direction of the pneumatic vehicle tire by the angle γ such that the width of the circumferential rib remains constant or increases with increasing tread depth, i.e. inwards. Accordingly, the circumferential rib then has a constant width B in the axial direction A over the entire circumference of the pneumatic vehicle tire according to the invention on the surface and for each tread depth, which is determined by the distance between the at least almost parallel sides in the axial direction, but which can increase inwards according to the angle y, which varies with the tread depth. In a preferred embodiment, the two sides of the two parallel circumferential grooves delimiting the circumferential rib lie in two parallel planes that are perpendicular to the axial direction A.Then the angle γ is constant over the tread depth 0, apart from the base region of the circumferential grooves, and the width B is constant over the tread depth of the tread. In a particularly preferred embodiment, the two circumferential grooves themselves, which delimit the circumferential rib, run parallel to one another in two planes perpendicular to the axial direction A, i.e. the deepest point of the cross-section of the circumferential grooves perpendicular to the circumferential direction is located over the entire tire circumference in one of the two planes perpendicular to the axial direction A. Particularly preferably, both circumferential grooves have the same width in the axial direction A over the entire tire circumference. Pure manufacturing tolerances during production of the tire tread are not taken into account here with regard to the design of the circumferential grooves.

[0025] Typically, the width B in the axial direction of the circumferential rib on its surface in the new state of the pneumatic vehicle tire is 17 mm to 40 mm, preferably 20 mm to 30 mm and particularly preferably 22 mm to 28 mm.

[0026] The circumferential rib has a fine cut at a regular distance d in the circumferential direction. The fine cuts in the circumferential rib run from one to the other of the parallel sides of the two circumferential grooves that border the circumferential rib along a contour line. The fine cuts therefore run from one end of the circumferential rib in axial direction A, which is formed by one side of one of the two circumferential grooves, to the other end of the circumferential rib in axial direction A, which is formed by one side of the second of the two circumferential grooves. All fine cuts run along a defined contour line, which also runs from one end of the circumferential rib in axial direction A to the other end of the circumferential rib in axial direction A. The contour line defines the course of the fine cuts on the surface of the tread, regardless of the circumferential position of the fine cut.The contour line is merely the main line along which the fine incisions run from one end of the circumferential rib to the other end of the circumferential rib. The actual course of the fine incision on the surface of the tread may deviate from this main line, since a further course of the fine incision to the main line may be added, which essentially has a component perpendicular to the main line in the surface of the tread, i.e. which runs mainly perpendicular to the contour line in the surface of the tread. The dimension of the deviation from the main line is significantly smaller than the width B of the circumferential rib in the axial direction A. Typically, the dimension of the deviation is a maximum of 15% of the width B of the circumferential rib, preferably a maximum of 5% of the width B of the circumferential rib and particularly preferably 3% of the width B of the circumferential rib. The course supplemented in this way has its main component, i.e.its main direction of progression, in a direction which typically does not deviate by more than 20° from the perpendicular to the contour line in the surface of the tread, preferably does not deviate by more than 5° from the perpendicular to the contour line in the surface of the tread, and particularly preferably does not deviate by more than 2° from the perpendicular to the contour line in the surface of the tread. Typically, the supplemented progression oscillates or meanders around the contour line in the direction of the main component, or has a zigzag or other periodic progression in this direction, wherein the period can vary along the contour line. The supplemented progression is preferably only present over part of the contour line. The sipes extend from the surface of the circumferential rib in the radial direction of the pneumatic vehicle tire to a depth TF, following their progression on the surface of the tread.Adjacent fine sipes in the circumferential direction have almost the same distance dn in the circumferential direction and preferably run parallel to one another. The distance dn between adjacent fine sipes in the circumferential direction typically varies over the entire tire circumference by a maximum of 10% of the average distance d, preferably by a maximum of 5% of the average distance d and particularly preferably by a maximum of 2% of the average distance d. This is based in particular only on manufacturing tolerances during production of the pneumatic vehicle tire. Typically, the regular distance d in the circumferential direction of the fine sipes on the surface of the circumferential rib in the new state of the pneumatic vehicle tire is 3 mm to 9 mm, preferably 4 mm to 7 mm and particularly preferably 5 mm to 6 mm.

[0027] Instead of these fine sipes, a thin transverse groove is arranged in the circumferential rib of the pneumatic vehicle tire according to the invention, each having a length three to seven times the distance d between the fine sipes in the circumferential direction. These thin transverse grooves can be arranged at the same distance or, preferably, at different distances in the circumferential direction in the circumferential groove, wherein the distance between the thin transverse grooves in the circumferential direction is a multiple of the distance d between the fine sipes in the circumferential direction. By arranging the thin transverse grooves at different distances in the circumferential direction, improved acoustic behavior of the pneumatic vehicle tire according to the invention is achieved, since this prevents vibrations due to a specific resonance period in the circumferential direction caused by the thin transverse ribs in the circumferential rib.

[0028] The width BQ of the thin transverse groove in the central circumferential rib of the pneumatic vehicle tire according to the invention is at least 2.5 times the width BF of a sipe in the central circumferential rib, preferably 2.5 to 5 times the width BF of a sipe, particularly preferably 2.75 to 4.5 times the width BF of a sipe, and most preferably 2.8 to 4 times the width BF of a sipe. The width BQ of the thin transverse grooves and the width BF of the sipes are the widths perpendicular to the common contour line of the thin transverse grooves and sipes.

[0029] The thin transverse grooves in the central circumferential rib of the pneumatic vehicle tire according to the invention have the contour line of the sipes. As a result, the transverse grooves and sipes of the central circumferential rib have essentially the same shape on the surface of the tread of a vehicle tire according to the invention. The thin transverse grooves thus follow the same contour line as the sipes. The contour line of a thin transverse groove and an adjacent sipe run parallel to one another, offset by the distance d in the circumferential direction. It is essential that each thin transverse groove runs along the contour line and not, as a sipe can have, an additional course that essentially has a component perpendicular to the contour line.The thin transverse grooves extend from the surface of the circumferential rib in the radial direction of the pneumatic vehicle tire to a depth TQ , following their course on the surface of the tread.

[0030] The depth TF of the sipes of the central circumferential rib of the pneumatic vehicle tire according to the invention is at least partially reduced over a length L red of the contour line in the end regions of the sipes. Thus, the depth TF of such a sipe is limited to a reduced depth TF,1 in one end region or both end regions of the sipe that are adjacent to the two circumferential grooves delimiting the circumferential rib. Such a sipe then has one edge elevation or two edge elevations. Only some of the sipes of the central circumferential rib may have one or two such edge elevations, or all of the sipes may have one or two such edge elevations. The reduction in depth TF may be the same or different for all sipes with edge elevations.The length L red of the contour line in which an edge elevation is present begins at one end of the surface of the circumferential rib in the axial direction A, i.e. at one of the two sides of one of the two circumferential grooves that delimit the circumferential rib, and then ends at a specific point on the contour line.

[0031] The thin transverse grooves of the circumferential rib have a snow pocket in their end regions over almost the same or a greater length LS, namely over 80% to 250% of this length L red of the contour line. Such a snow pocket therefore extends at the ends of the thin transverse groove over this length LS along the contour line, also starting on one of the two sides of one of the two circumferential grooves that border the circumferential rib. The purpose of such a snow pocket, which represents a cavity in the tire tread, is to quickly fill with snow from the road surface while driving, so that increased snow grip occurs correspondingly quickly due to snow-on-snow friction.

[0032] The snow pockets at the ends of the thin transverse grooves have a width BS perpendicular to the contour line of the thin transverse grooves, which is determined parallel to the tire surface in which the contour line runs, which is at least 1.5 times as large as the width BQ of the thin transverse groove, and a depth TS that is a maximum of 65% of the tread depth TQ of the thin transverse groove. Thus, the further geometric dimensions of the snow pockets provided in the central circumferential rib of a pneumatic vehicle tire according to the invention are linked to the dimensions of the thin transverse grooves in the circumferential rib. They are wider than the thin transverse grooves perpendicular to the contour line of the thin transverse grooves, which is also the contour line of the sipes, and are at least 1.5 times as wide as the thin transverse grooves. Its depth Ts, however, is less than the tread depth TQ of the thin transverse groove, in such a way that its depth TS is a maximum of 65% of the tread depth TQ of the thin transverse groove.The depth TS of the snow pockets and the tread depth TQ of the thin transverse grooves each indicate the extent of the snow pockets or thin transverse grooves in the radial direction of the pneumatic vehicle tire, starting from the surface of the tread of the pneumatic vehicle tire. The radial direction points inwards from the tire surface towards the axis of rotation of the pneumatic vehicle tire and is perpendicular to this. Thus, in a central circumferential rib of a pneumatic vehicle tire according to the invention, snow pockets are provided at the ends of thin transverse grooves that run from one side of the circumferential rib to the other. These snow pockets have a lateral extent, i.e. parallel to the tire surface, which is given by a length Ls along the contour line of the associated thin transverse groove and a width Bs perpendicular to the contour line.The width BS is deliberately increased compared to the width BQ of the thin transverse groove, and the length LS is selected to be similar to, or a certain amount greater than, the length L red of the raised edges of the fine incisions of the circumferential rib. Overall, the snow pockets have a large cross-sectional area on the groove surface, which can fill with snow when driving on a snow-covered road. Furthermore, the limited depth Ts of the snow pockets means that the snow pockets fill quickly with snow, so that quickly increased snow grip is enabled by snow-on-snow friction. Such an intervention is particularly advantageous when a vehicle is equipped with an anti-skid control (ASR) or an anti-lock braking system (ABS), and is thus able to quickly utilize the improved friction.

[0033] Furthermore, the length Ls of the snow pockets, which is over 80% to 250% of the length L red of the raised edges of the fine sipes along the contour line, has almost the same dimension as the length L red of the raised edges or is greater than the length L red of the raised edges. The snow pockets are therefore specifically positioned in the same position in the axial direction as the raised edges of the fine sipes, since the snow pockets, as cavities, counteract any stiffening of the circumferential rib in this axial position, i.e. at their ends in the axial direction A, by the raised edges and the circumferential stiffness, i.e. the elasticity of the circumferential rib, is thus evened out in the axial direction A. This promotes more even wear of the tread of a pneumatic vehicle tire according to the invention. This evening out is based on all dimensions of the snow pockets, i.e. in addition to their length LS, also their width BS and their depth TS.

[0034] By providing precisely defined snow pockets in the tread structure of a central circumferential rib with uniform fine cuts, which are partially replaced by thin transverse grooves, both the snow-snow friction of a pneumatic vehicle tire and, at the same time, the abrasion behavior of the pneumatic vehicle tire can be improved.

[0035] In a preferred embodiment, the central circumferential rib of the pneumatic vehicle tire according to the invention is its central circumferential rib. In this position, the circumferential rib is in direct contact with the road surface at least most of the time during driving, so that the snow pockets in the circumferential direction are most reliably filled with snow quickly on a snowy road surface, and the snow-to-snow friction builds up accordingly quickly.

[0036] In another embodiment, the thin transverse grooves are arranged in the circumferential direction in the central circumferential groove of the pneumatic vehicle tire according to the invention, instead of a sipe, over different multiples of the spacing d of the sipes in the circumferential direction. By arranging the thin transverse grooves at different spacings around the tire circumference, whereby the sequence of the different multiples can nevertheless repeat periodically around the tire circumference, the acoustic behavior of the pneumatic vehicle tire according to the invention is improved, as already mentioned. The sequence of multiples can, for example, consist of exactly two different multiples, e.g., fourfold and fivefold, which repeat irregularly or regularly. In this example, every fourth or fifth sipe is then replaced by a thin transverse groove having a snow pocket with the dimensions described above at its ends.

[0037] In a preferred embodiment, instead of a fine sipe at a distance four to six times the length of the spacing d between the fine sipes in the circumferential direction, particularly preferably at a distance four to five times the length of the spacing d between the fine sipes in the circumferential direction, the previously described thin transverse groove with its snow pockets is arranged in the central circumferential rib of a pneumatic vehicle tire according to the invention. Particularly with these spacings of the thin transverse grooves, a tilting of the tread block elements is achieved in an appropriate manner in order to achieve both advantageous snow and ice performance due to the circumferential rib.

[0038] Preferably, in the central circumferential rib of a pneumatic vehicle tire according to the invention, the width BQ of the thin transverse grooves is a maximum of five times the width BF of a fine sipe. This also supports the tilting of the tread block elements in an appropriate manner and prevents excessive tilting of individual tread block elements.

[0039] Preferably, the snow pockets of the thin transverse grooves of the central circumferential rib of a pneumatic vehicle tire according to the invention are arranged symmetrically to the contour line of the thin transverse grooves. This contributes to the uniform tilting of the tread block elements adjacent to the thin transverse groove.

[0040] Preferably, the snow pockets of the thin transverse grooves of the central circumferential rib of a pneumatic vehicle tire according to the invention have a width BS perpendicular to the contour line that is 2 to 3 times the width BQ of the thin transverse groove. Particularly preferably, the width BS of the snow pockets is 2.2 to 2.5 times the width BQ of the thin transverse groove. This contributes to good snow-to-snow friction while simultaneously providing appropriate tilting of the tread block elements and uniform elasticity in the axial direction A of the central circumferential rib.

[0041] Preferably, the snow pockets of the thin transverse grooves of the central circumferential rib of a pneumatic vehicle tire according to the invention have a depth Ts that is 35 to 60% of the tread depth TQ of the thin transverse groove, particularly preferably 40% to 58% of the tread depth TQ of the thin transverse groove, and very particularly preferably 50% to 55% of the tread depth of the thin transverse groove. This also contributes to good snow-to-snow friction after a short time, while simultaneously providing appropriate tilting of the tread block elements and uniform elasticity, thus ensuring uniform tire wear in the axial direction A of the central circumferential rib.

[0042] Preferably, the thin transverse grooves of the central circumferential rib of a pneumatic vehicle tire according to the invention have a snow pocket of length Ls in their end regions over 95% to 200% of the length L red of the contour line, over which the depth TF of the sipes is reduced in the end regions of the sipes, and particularly preferably these thin transverse grooves have a snow pocket of length Ls over 105% to 130% of the length L red of the contour line, over which the depth of the sipes is reduced in the end regions of the sipes. In particular, the correspondence between the position of the raised portions of the sipes and the position of the snow pockets contributes to the elasticity in axial direction A of the central circumferential rib being quite uniform in axial direction A. In particular, even on the sides of the circumferential rib, despite the raised portions of the sipes, the circumferential stiffness is almost the same as in the center of the circumferential rib.As a result, the abrasion of the rubber material of the circumferential rib is at least almost uniform across the entire width of the circumferential rib in the axial direction.

[0043] Preferably, the thin transverse grooves of the central circumferential rib of a pneumatic vehicle tire according to the invention have a snow pocket in their end regions over a contour line length Ls of 2.5 mm to 8 mm, particularly preferably over a contour line length Ls of 3.5 mm to 7 mm, and most preferably over a contour line length of 4 mm to 5.5 mm. This achieves both good snow-to-snow friction and fairly uniform elasticity in the axial direction A of the central circumferential rib.

[0044] The snow pockets of the thin transverse grooves of the central circumferential rib of a pneumatic vehicle tire according to the invention have a base region and side surfaces. The base region delimits the snow pockets in the radial direction at a depth Ts. However, the depth TS can vary in the axial direction and circumferential direction by up to 20%, preferably by up to 5%, and particularly preferably by up to 1%. The side surfaces delimit the snow pockets by surfaces that extend from the base surface to the surface of the pneumatic vehicle tire. In particular, a side surface can run parallel to the contour line or, as the end surface of the snow pocket, can be perpendicular to the contour line. Preferably, the surface of the base region of the snow pockets merges into the side surfaces with a radius of curvature of 0.2 mm to 1.5 mm, particularly preferably with a radius of curvature of 0.5 mm to 1.25 mm, and most preferably with a radius of curvature of 0.8 mm to 1.1 mm.This further improves the rapid filling of the snow pockets with snow while driving on snow, which leads to good snow-to-snow friction more quickly.

[0045] In one embodiment, the snow pockets of the thin transverse grooves of the central circumferential rib of a pneumatic vehicle tire according to the invention have a bottom region and an end surface as a side surface. Typically, the surface of the bottom region transitions into the end surface with a radius of curvature of 0.2 mm to 1.5 mm, preferably with a radius of curvature of 0.5 mm to 1.25 mm, and particularly preferably with a radius of curvature of 0.8 mm to 1.1 mm. This further improves the rapid filling of the snow pockets with snow during driving on snow, which correspondingly leads to good snow-to-snow friction more quickly.

[0046] Typically, the snow pockets of the thin transverse grooves of the central circumferential rib of a pneumatic vehicle tire according to the invention have a base region that extends radially inward, i.e., toward the center of the pneumatic vehicle tire, with a fine cut along the contour line. This promotes the tilting of the tread block elements in the circumferential rib, in particular the tilting of the tread block elements adjacent to the respective transverse groove, which is thus not reduced by the depth TS of the snow pockets, which is reduced compared to the tread depth TQ of the thin transverse ribs.

[0047] Typically, the fine cuts in the base area of ​​the snow pockets have the same width BF as the fine cuts in the circumferential rib that have not been replaced by a thin transverse groove. This promotes a uniform tilting of the tread block elements across the circumference and further promotes the uniform elasticity of the circumferential rib in the axial direction A.

[0048] Preferably, the fine cuts in the bottom area of ​​the snow pockets have the same depth TF as the fine cuts in the center of the circumferential rib that have not been replaced by a thin transverse groove. This also promotes uniform tilting of the tread block elements across the circumference and further promotes the uniform elasticity of the circumferential rib in the axial direction.

[0049] In one embodiment, the contour line of the fine incisions of the central circumferential rib of a pneumatic vehicle tire according to the invention is a straight line which is preferably perpendicular to the parallel sides of the two circumferential grooves.

[0050] In one embodiment, the contour line of the fine sipes of the central circumferential rib of a pneumatic vehicle tire according to the invention is slightly angled in the center of the circumferential rib. Thus, the contour line can be formed by two straight lines angled to each other, which enclose an angle β of 140° to 170°, preferably an angle β of 150° to 165°.

[0051] In certain embodiments of a pneumatic vehicle tire according to the invention, the contour line of the fine sipes in the end region of the fine sipes deviates from the axial direction A of the pneumatic vehicle tire by an angle α of less than 20°, preferably less than 15° and particularly preferably less than 8°.

[0052] In certain embodiments of a pneumatic vehicle tire according to the invention, the sipes of the central circumferential rib running along the contour line are wave-shaped over a portion of the contour line. In this portion of the contour line, the actual course of the sipe deviates from the main contour line. The course of the sipe is supplemented by a wave-shaped component perpendicular to the contour line. Instead of the wave-shaped component, the course of the sipe can also be supplemented by a zigzag line and another oscillating component.

[0053] In certain embodiments, the depth TF of the fine incisions is partially reduced over a length L red of the contour line of 7% to 35% in one end region or preferably both end regions of the fine incisions, preferably over a length L red of the contour line of 12% to 30%, and particularly preferably over a length L red of the contour line of 16% to 23%. Preferably, the depth TF of all fine incisions is reduced over such a length L red of the contour line in both end regions of the fine incisions.

[0054] In certain other embodiments, the depth TF of the fine incisions is partially reduced in each case over a length L red of the contour line of 1.5 mm to 9 mm in one end region or preferably in both end regions of the fine incisions, preferably in each case over a length L red of the contour line of 2.5 mm to 7.5 mm and in particular in each case over a length L red of the contour line of 3.5 mm to 5.5 mm. Preferably, the depth TF of all fine incisions is reduced over such a length L red of the contour line in both end regions of the fine incisions.

[0055] In the aforementioned embodiments, the depth TF,1 , TF,2 of the fine incisions can be reduced differently in their end regions for different fine incisions in order to make the circumferential rigidity more uniform in the circumferential direction. In particular, in the case of successive fine incisions in the circumferential direction, the depth TF of the fine incisions can be reduced alternately to a first depth TF,1 and a second depth TF,1 in their end regions.

[0056] Typically, the depth TF of the fine cuts of the central circumferential rib of a pneumatic vehicle tire according to the invention is reduced in the end regions by 25% to 85%, preferably by 35% to 75% and particularly preferably by 40% to 55%.

[0057] In embodiments in which the depth TF,1 , TF,2 of the fine incisions is reduced differently in their end regions for different fine incisions, typically the first depth TF,1 is reduced by 25% to 60% and the second depth TF,2 is reduced by 60% to 85%, preferably the first depth TF,1 is reduced by 35% to 55% and the second depth TF,2 is reduced by 65% ​​to 80%, and particularly preferably the first depth TF,1 is reduced by 40% to 50% and the second depth TF,2 is reduced by 70% to 75%. This promotes the uniformity of the elasticity of the circumferential rib in the circumferential direction on its sides. Brief description of the drawings

[0058] The invention will now be explained in more detail using an exemplary embodiment. It shows: Fig. 1: Section of the surface of a tread of a pneumatic vehicle tire according to the invention over the entire width of the tread Fig. 2: Section of the central circumferential rib of the Fig. 1shown pneumatic vehicle tire according to the invention in the circumferential direction Fig. 3: 3-dimensional section of the profile of the central circumferential rib of the Fig. 1 shown pneumatic vehicle tire according to the invention Detailed description of the invention

[0059] In the Figures 1 to 3 An embodiment of a pneumatic vehicle tire according to the invention is shown. Such a pneumatic vehicle tire has a tread provided with a profile. In Figure 1a section of the surface of the tread 1 of the pneumatic vehicle tire according to the invention is shown across its entire width. Various profile elements can be seen in the profile of the tread 1; a circumferential rib 3, a central circumferential rib, is shown in the center of the tread 1. This circumferential rib 3 extends in the circumferential direction over the entire circumference of the pneumatic vehicle tire according to the invention and is delimited by two circumferential grooves 2, 2' that run around the entire circumference of the pneumatic vehicle tire according to the invention. The two circumferential grooves 2, 2' run parallel to one another and perpendicular to the axial direction A of the pneumatic vehicle tire. Both circumferential grooves 2, 2' have the same cross-section perpendicular to the circumferential direction over the entire tire circumference. Both circumferential grooves 2, 2' have two sides that delimit the two circumferential grooves 2, 2' in the axial direction A.Each of the two sides 4, 4' of the circumferential grooves 2, 2' delimits the circumferential rib 3. A section of the circumferential rib 3 in the circumferential direction is also shown in the . Figure 2 shown. In this figure, the circumferential grooves 2, 2' defining the circumferential rib 3 are also shown with their sides 4, 4' defining the circumferential rib 3. Also in Figure 3 the circumferential rib 3 is shown, this time in three-dimensional representation, whereby the circumferential rib 3 itself as in Figure 2is developed in one plane. Here, in particular, the view of the circumferential rib 3 in the axial direction A is shown, with a short section of the circumferential rib 3 in the circumferential direction U being shown. Here, too, the circumferential grooves 2 and 2' can be seen, which delimit the circumferential rib 3. Only in the case of the circumferential groove 2 at the lower end of the illustration can side 4 of the circumferential groove 2 be seen, which forms the edge of the circumferential rib 3. The sides 4, 4' of the circumferential grooves 2, 2' that delimit the circumferential rib 3 run in two parallel planes perpendicular to the axial direction A. The straight sides 4, 4' are thus perpendicular to the tread surface and extend along the circumferential direction. The distance between the sides 4, 4' in the axial direction A then specifies a width B of the circumferential rib 3 that is constant in the radial direction of the tire and is 27 mm in the exemplary embodiment.The sides 4, 4' then merge with a curvature in the bottom area of ​​the circumferential grooves 2, 2' into the groove base of the circumferential grooves 2, 2', as shown in . Figure 3 shown.

[0060] The circumferential rib is divided by fine incisions 6, which run from one of the mutually parallel sides (4, 4') of the two circumferential grooves (2, 2') to the other over the entire width B of the circumferential rib 3. The fine incisions 6 are spaced apart in the circumferential direction U by a regular distance d, which in the exemplary embodiment is 5.5 mm on the surface of the circumferential rib 3. Each fine incision 6 runs along a contour line 10. The shape of the contour line 10 is the same for all fine incisions 6 in the circumferential rib 3. The contour line 10 is formed by two straight lines, each forming an angle α of 15° with respect to the axial direction A and intersecting in the center of the circumferential rib 3. Accordingly, the two straight lines enclose an angle β of 150° with each other.Apart from the edge regions of the circumferential rib 3, a wavy line is superimposed on this contour line 10 along the course of the sipes 6, so that the sipes 6 have a wavy course in the center of the circumferential rib 3. While the tread depth of the circumferential grooves 2, 2' is 8 mm when the pneumatic vehicle tire is new, the depth TF of the sipes 6 in the center of the circumferential rib 3 is 7 mm. In the end region of the sipes 6, the depth TF of the sipes 6 is reduced. In the exemplary embodiment, the depth TF is reduced by over 21% of the length L red of the contour line 10 at both end regions. In the exemplary embodiment, the depth TF of the contour line is reduced over the length L red of 5.5 mm along the contour line 10. Every second sipe 6 has a depth TF,1 of only 1.75 mm in its end region.The depth TF,2 of the other fine cuts is reduced to 50% of the profile depth TF in the end areas over the same length L red and is therefore 3.5 mm.

[0061] In the circumferential rib 3, the fine incisions 6 are replaced at certain intervals in the circumferential direction U by a thin transverse groove 8. In the exemplary embodiment shown, this spacing is alternately four, five, or six times the length of the spacing d between the fine incisions 6 in an irregular sequence. The thin transverse grooves 8 are arranged at an irregular spacing to avoid vibrations of the circumferential rib 3 due to resonances that can arise from a regular spacing of the thin transverse grooves 8. The width BQ of the thin transverse grooves 8 in this exemplary embodiment is three times as large as the width BF of the fine incisions 6. The width BF of the fine incisions 6 in this exemplary embodiment is 0.5 mm and correspondingly the width BQ of the thin transverse grooves 8 is 1.5 mm. The tread depth TQ of the thin transverse grooves is 8 mm. The transverse grooves 8 run along the same contour line 10 as the fine incisions 6.Here, the fine incisions 8 run only along the contour line 10 and have no further component perpendicular to the contour line, as in the wave-shaped course of the fine incisions 6.

[0062] In addition, the thin transverse grooves 8 each have a snow pocket 20 in their end regions. Here, the end region of the contour line 10, which extends from one circumferential groove 2 to the other circumferential groove 2', which borders the circumferential rib 3, is the region of the contour line 10 that begins at the circumferential grooves 2 and 2' and then extends inward into the circumferential rib 3. The snow pockets 20 then have a length Ls along the contour line 10. In the exemplary embodiment, the snow pockets 20 have the same length Ls as the length L red of the elevations of the fine incisions 6. Accordingly, the length Ls of the snow pockets is 21% of the length of the contour line 10. Furthermore, the snow pockets 20 also have an extension parallel to the surface of the tread 1 and perpendicular to the contour line 10. In the exemplary embodiment, this width BS of the snow pockets 20 is twice as large as the width BQ of the thin transverse grooves 8 and is therefore 3 mm.In addition, the snow pockets 20 also have a depth TS in the radial direction. In the exemplary embodiment, the depth TS of the snow pockets 20 is exactly half the tread depth TQ of the thin transverse grooves 8. Accordingly, the tread depth TS of the snow pockets has a value of 4 mm. In particular, the . Figure 3Further details of the design of the snow pockets 20 can be found in the figure. At depth TS, the snow pockets 20 have a base region 21. In the exemplary embodiment shown, this base region 21 is essentially parallel to the surface of the tread 1. Furthermore, the snow pockets 20 have side surfaces 22. In the exemplary embodiment shown, the side surfaces 22 run parallel to the contour line 10 and perpendicular to the surface of the tread 1, so that the surfaces have a component in the radial direction. In addition, one side surface 22 of the snow pockets is designed as an end surface 23, which is a surface perpendicular to the contour line 10. Between the base region 21 and the side surfaces 22, in particular the end surface 23, there is a transition with a radius of curvature of 1 mm. Furthermore, the base region 21 of the snow pockets 20 has a fine incision 25 in its center, which runs along the contour line 10 of the thin transverse grooves 8.The width of the sipes 25 corresponds to the width BF of the sipes 6. The depth of these sipes 25 corresponds to the depth TF of the remaining sipes 6 of the circumferential rib 3. Like all embodiments of the pneumatic vehicle tire according to the invention, the central circumferential rib 3 of the exemplary embodiment is characterized by the fact that, due to the provided snow pockets 20, it has good snow-to-snow friction, which is available after a short time due to the rapid filling of the snow pockets 20, as well as by a uniform tilting of the provided tread block elements, whereby a good balance is achieved between the snow behavior (snow performance) and ice behavior (ice performance) of the circumferential rib 3. In addition, the design of the snow pockets 20 further enables a very uniform elasticity or circumferential stiffness of the transverse rib 3 in the axial direction A.Here, the provided snow pockets 20 at the edge of the circumferential rib 3 largely compensate for the elevations at the end of the fine cuts 6 of the circumferential rib 3. The structure of a central circumferential rib of the pneumatic vehicle tire according to the invention has been comprehensively explained using the parameters described in this description. This structure must be adapted to the size of a pneumatic vehicle tire. In particular, the circumferential ribs 3 of the pneumatic vehicle tires according to the invention are used in pneumatic vehicle tires whose width is between 195 mm and 315 mm. The height of the tire can be between 35% of the width of the pneumatic vehicle tire and 65% of the width of the pneumatic vehicle tire. The rims on which such pneumatic vehicle tires are mounted can have a diameter between 15 inches and 22 inches.Depending on the corresponding circumference of such a tire, a different number of fine sipes 6 and thin transverse grooves 8 can be provided over the circumference of the pneumatic vehicle tire. The number of fine sipes 6 and transverse grooves 8 can grow with the circumference or only grow with the circumference to a certain extent. Such a proportion can, for example, be between 5 and 20%. In general, pneumatic vehicle tires according to the invention can of course also have other dimensions, as long as the advantageous properties of the described circumferential rib can be utilized in the pneumatic vehicle tire. Finally, it should be noted that the invention has been explained using many detailed exemplary embodiments. These are nevertheless examples of the invention.Accordingly, other embodiments of the pneumatic vehicle tire according to the invention may also have only individual features of one embodiment or simultaneously features of various described embodiments, unless explicitly stated otherwise. List of reference symbols

[0063] 1Tread 2, 2'Circumferential groove 3Circumferential rib 4, 4'Side of a circumferential groove 6Sipe 8Thin transverse groove 10Contour line 20Snow pocket 21Bottom area of ​​a snow pocket 22Side surface of a snow pocket 23End surface of a snow pocket 25Sipe below a snow pocket AAxial direction BBidth of the circumferential rib in axial direction ABF Width of a sipe BQ Width of the thin transverse groove BS Width of the snow pocket perpendicular to the contour line dSpacing of the sipes in the circumferential direction dn Spacing of adjacent sipes in the circumferential direction L red Length of the contour line over which the depth of a sipe is reduced LS Length of the snow pocket along the contour line TF Depth of the sipes TF,1 Reduced depth of a first sipe in the edge area TF,2 Reduced depth of a second sipe in the edge area TQ Depth of the thin transverse groove TS Depth of the snow pocket U Circumferential direction α Angle,by which the contour line of the fine sipes in the end area of ​​the fine sipes deviates from the axial direction A of the pneumatic vehicle tyre β included angle between two straight lines angled to each other which form a contour line γ angle by which the two sides of two circumferential grooves which limit the circumferential rib deviate in the radial direction from a plane perpendicular to the axial direction A,

Claims

1. Pneumatic vehicle tyre with a tread (1) which has a profile and a middle circumferential rib (3) delimited by two sides (4, 4'), running at least approximately parallel to one another, of two circumferential channels (2, 2') which surround the entire pneumatic vehicle tyre and run at least approximately perpendicular to the axial direction A of the pneumatic vehicle tyre in that they only deviate by an angle γ of less than 15° from the radial direction of a plane perpendicular to the axial direction A, such that the width of the circumferential rib (3) thus remains constant or increases with increasing profile depth, wherein the circumferential rib (3) has, at a regular spacing d in the circumferential direction, a sipe (6) which runs from one to the other of the mutually parallel sides (4, 4') of the two surrounding circumferential channels (2, 2') along a contour line (10), and wherein, at three to seven times the length of the spacing d of the sipes (6) in the circumferential direction, arranged in the middle circumferential rib (3) instead of a sipe (6) there is in each case a thin transverse channel (8), the width BQ of which is at least 2.5 times the width BF of a sipe (6) and which has the contour line (10) of the sipes (6), characterized in that the depth TF of the sipes (6) is at least partially reduced over a length Lred of the contour line (10) in the end regions of the sipes (6) and, over 80% to 250% of this length Lred of the contour line (10), the thin transverse channels (8) have in their end regions a snow pocket (20) which has a width Bs perpendicular to the contour line (10) of at least 1.5 times the width BQ of the thin transverse channel (8) and a depth Ts of at most 65% of the profile depth TQ of the thin transverse channel (8).

2. Pneumatic vehicle tyre according to Patent Claim 1, characterized in that the middle circumferential rib (3) is the central circumferential rib (3) of the pneumatic vehicle tyre.

3. Pneumatic vehicle tyre according to Patent Claim 1 or 2, characterized in that the thin transverse channels (8) are arranged in the middle circumferential rib (3) in the circumferential direction instead of a sipe (6) over various multiples of the spacing d of the sipes (6) in the circumferential direction.

4. Pneumatic vehicle tyre according to at least one of Patent Claims 1 to 3, characterized in that the snow pockets (20) are arranged symmetrically with respect to the contour line (10) of the thin transverse channels (8).

5. Pneumatic vehicle tyre according to at least one of Patent Claims 1 to 4, characterized in that the snow pockets (20) have a width Bs perpendicular to the contour line (10) of 2 to 3 times the width BQ of the thin transverse channel (8) and preferably of 2.2 to 2.5 times the width BQ of the thin transverse channel (8).

6. Pneumatic vehicle tyre according to at least one of Patent Claims 1 to 5, characterized in that the snow pockets (20) have a depth Ts of 35 to 60% of the profile depth TQ of the thin transverse channel (8), preferably 40% to 58% of the profile depth TQ of the thin transverse channel (8), and particularly preferably 50% to 55% of the profile depth TQ of the thin transverse channel (8).

7. Pneumatic vehicle tyre according to at least one of Patent Claims 1 to 6, characterized in that the snow pockets (20) have a bottom region (21) that continues inwards in a radial direction with a sipe (25) along the contour line (10).

8. Pneumatic vehicle tyre according to Patent Claim 7, characterized in that the sipes (25) in the bottom region (21) of the snow pockets (20) have the same depth TF as those sipes (6) of the circumferential rib (3) which have not been replaced by a thin transverse channel (8) have in the middle of the circumferential rib (3).

9. Pneumatic vehicle tyre according to at least one of Patent Claims 1 to 8, characterized in that the sipes (6) running along the contour line (10) are of an undulating form over a part of the contour line (10).

10. Pneumatic vehicle tyre according to at least one of Patent Claims 1 to 9, characterized in that the depth TF of the sipes (6) is partially reduced in each case over a length Lred of the contour line (10) of 7% to 35% in one end region or both end regions of the sipes (6), preferably over a length Lred of the contour line (10) of 12% to 30%, and particularly preferably over a length Lred of the contour line (10) of 16% to 23%.