Tread strip for a vehicle tire and vehicle tire

Description

[0001] The invention relates to a tread for a vehicle tire, wherein a profile groove with a radially upper region and a radially lower region, as well as with a first groove flank and a second groove flank, is formed in the tread. Here, the maximum width of the profile groove measured in the radially lower region between a first point on the first groove flank and a second point on the second groove flank is greater than the upper width of the profile groove measured in the radially upper region between the two groove flanks. Furthermore, the bottom of the profile groove is concavely curved at a radially lowest point, wherein in the radially lower region the first groove flank at the first point and the second groove flank at the second point exhibit concave curvatures.Here, the curvature around the radially lowest point and the curvature around the first point are connected by a first straight line, and the curvatures around the radially lowest point and the curvature around the second point are connected by a second straight line.

[0002] Profile grooves that have a greater width in a radially lower region than in a radially upper region are known per se. US 2322505 A describes a tread comprising a plurality of functionally continuous, circumferentially extending ribs and lateral overhangs of substantial thickness that adjoin the ground contact surfaces of the ribs and project into grooves defined by the ribs, wherein the lateral dimensions of the overhangs are chosen such that, under load and in engagement with a support surface, they come into contact with adjacent units. This is intended to improve the stability and wear characteristics of the tread. DE 698 07 901 T2 describes a profile in which, when new, a block is bounded in cross-section by grooves and is provided with a channel that is radially inside and in a central position with respect to the block.This channel is essentially O-shaped and is connected to a groove whose course, in the thickness of the tread, follows a series of curved lines, with the groove opening onto the tread surface when new. This is intended to optimize the tread profile with regard to grip and handling performance, both in its initial state and throughout the tire's service life, without impairing the tire's performance under wear. DE 10 2020 212 560 A1 describes a vehicle tire with a circumferential groove, wherein a second radially inner groove section is axially wider than a first groove section. DE 10 2020 214 281 A1 describes a vehicle tire with a circumferential groove comprising different radial groove sections.

[0003] The invention is based on the objective of creating a tread or vehicle tire with a profile groove of the type described above, wherein the profile groove should have a simple, elegant and easily scalable design with a particularly low susceptibility to cracking.

[0004] The problem stated is solved according to the invention by the features of claim 1.

[0005] In other words, the basic shape of the radially lower region is based on an imaginary triangle, one apex of which lies at the radially lowest point and the other apex of which lies at the first and second points. In contrast, according to the prior art, the radially lower regions are oval, more closely resembling a quadrilateral. In any case, according to the prior art, straight flank segments in the radially lower region enclose smaller angles than those provided for in the invention. The invention recognizes that this allows the concave curves at both the lowest point and the first and second points to be executed with sufficiently large radii of curvature to reduce susceptibility to cracking. Furthermore, the triangular shape enables a particularly advantageous absorption of forces and their uniform distribution over the entire radially lower region.In particular, the shape according to the invention can prevent or reduce the focusing of the forces acting on the groove walls onto the groove bottom.

[0006] When the directional terms axial, radial, and circumferential are used, they refer to the tread as intended on a vehicle tire, which in turn is as intended on a vehicle tire. In this context, the radial direction refers to a direction perpendicular to and intersecting the axis of rotation of the vehicle tire. Radially inward refers to the orientation facing radially toward the axis of rotation. Radially outward refers to the orientation facing radially away from the axis of rotation. The circumferential direction denotes the direction of rolling motion around the axis of rotation.A tire positioned at the front of the circumference reaches a minimum distance to the road surface earlier during a 180° rotation of the tire when the vehicle is traveling forward than a tire positioned at the rear. The axial direction refers to a direction parallel to the axis of rotation. "Axially inward" refers to an orientation that is axially aligned with a tire equator, a tire equator plane, or a tire equator line. The tire equator plane is a plane perpendicular to the tire's axis of rotation that passes through the center of the tire's axial width, with the tire equator line lying within the tire equator plane and on the tire's surface. The lateral direction is defined as a direction consisting of components of the radial and / or axial directions.

[0007] In particular, the circumferential and transverse directions can run along a base surface of the vehicle tire. The base surface coincides with the smooth surface that the vehicle tire would have if no small-scale tread elements, such as grooves or radially projecting ribs, were provided. Small-scale tread elements are characterized in at least one of the three dimensions—radial, axial, and circumferential—by a dimension and / or radius of curvature that is less than or equal to the maximum tread depth in the vehicle tire. The base surface remains physically intact wherever no such tread elements are provided. The remaining portions of the base surface can be at least partially intended for contact with a road surface.Where, for example, a groove runs through a tread of the vehicle tire, the base surface continues as an imaginary surface above the groove; where, for example, a radially protruding rib is arranged on the tread, the base surface continues as an imaginary surface below the radially protruding rib.

[0008] All described features relate specifically to the new condition of the tread. The effects achieved with the features of the main claim can be supported and further enhanced by preferred embodiments and configurations.

[0009] The first and second straight connections are preferably aligned at an angle of 45° to 70°, and more preferably at an angle of 55° to 65° to each other. These sections include an angle of 60°, which is characteristic of an equilateral triangle. An equilateral triangle is characterized by a particularly high degree of symmetry, which in turn can promote a uniform distribution of forces.

[0010] The curvature around the radially lowest point and the curvatures around the first and second points preferably transition smoothly into the first and second straight lines. A smooth transition can be described throughout using well-defined tangents.

[0011] The concave curvatures at the radially deepest point and at the first and second points on the groove flanks can each be described by one or more radii of curvature. In a preferred embodiment, the concave curvatures are each formed as circular arcs with a single radius of curvature. When dimensions of radii of curvature are specified, either a radius of curvature corresponding to such a circular arc of a uniform curvature is meant, or the smallest radius of curvature of a correspondingly largest local curvature along the path of a more complex concave curvature with various radii of curvature.

[0012] A radius of curvature describing the curvature at the radially lowest point can have a length between one-third and two-thirds of the upper width of the profile groove measured in the radially upper region between the two groove flanks. Alternatively, the radii of curvature can be scaled over further regions, preferably scaling the maximum width of the profile groove measured between the first point on the first groove flank and the second point on the second groove flank, so that the entire radially lower region can be adapted in size to the requirements and dimensions of a given tread.

[0013] According to the invention, the radii of curvature describing the curves at the first and second points are in a ratio of no more than 2:1 and no less than 1:2, respectively, and preferably have the same length. This creates symmetry between the opposing groove flanks. Furthermore, according to the invention, the radii of curvature at the radially lowest point and at the first and second points are arranged in pairs in a ratio of no more than 2:1 and no less than 1:2, respectively, and preferably have the same length. This allows forces acting in the radially lower region to be distributed particularly evenly across the three concave curves, resulting in minimal stress at each curve.

[0014] The centers of curvature of the circles of curvature corresponding to the curvatures at the radially lowest point, at the first point, and at the second point can be equidistant from each other and consequently located at the vertices of an imaginary equilateral triangle. This results in a particularly high degree of symmetry with a correspondingly advantageous distribution of forces and stresses in the radially lower region of the profile groove.

[0015] The radially lower region can transition into the radially upper region along a convex curve on both the first and second groove flanks. This convex curve can be located radially directly above the concave curve centered on the first and second points, respectively, with the curves preferably transitioning smoothly into one another. This creates a flowing contour not only of the radially lower region but also of the transition to the radially upper region, which can have a positive effect on force distribution and crack susceptibility on the groove walls.

[0016] The radii of curvature describing the convex curves can be of equal length. The radii of curvature describing the convex curves and the radii of curvature describing the curves at the radially lowest point, at the first point, and / or at the second point can also be of equal length. The convex curves can each be described by one or more radii of curvature. In a preferred embodiment, the convex curves are each designed as a circular arc with a single radius of curvature. A particularly symmetrical and uniform distribution of forces can be achieved by designing the concave and convex curves in a similar or identical manner.

[0017] The maximum width in the radially lower region of the tread groove can be between 2 mm and 20 mm, preferably between 4 mm and 8 mm. A greater width can contribute to a higher drainage capacity of the tread groove, while a smaller width may be advantageous, for example, in terms of ensuring sufficient stiffness of the tread.

[0018] The radially lower section can extend over a quarter to a half of the radial depth of the tread groove. Generally, the smaller the proportion of the radially lower section, the lower the drainage capacity. Furthermore, the extent of the radially upper and lower sections determines at what degree of wear the radially lower section contacts the running surface of the tread. An optimal setting can be determined in conjunction with the design of the rest of the tread, considering a property of the tread often referred to as "performance over lifetime."

[0019] The upper width of the profile groove, measured in the radially upper area between the two groove flanks, can be between 0.5 mm and 6 mm, preferably between 1 mm and 3 mm. Such comparatively small dimensions prevent stones from penetrating the groove. The wider radially lower area still ensures sufficient drainage capacity. The groove flanks in the radially upper area, radially above the transitions to the radially lower area, preferably run parallel to each other and in the radial direction, as is known in principle from so-called U-grooves.

[0020] The features described above and / or below can be continuously fulfilled along a longitudinal section of the tread groove, wherein the longitudinal section can be at least five times as long, preferably at least ten times as long, as the maximum width. This allows the advantageous effect of the cross-sectional shape to be scaled along the longitudinal direction and, according to some embodiments, can also be selectively provided only in sections, so that the effect according to the invention only applies in selected areas of the tread.

[0021] The profile groove designed according to the invention is preferably a circumferential groove, but can also be advantageously designed as a transverse or oblique groove.

[0022] The invention also relates to a vehicle tire with a tread as described above and / or below. Vehicle tires designed according to the invention are tires of any construction, in particular radial tires, and tires of any type, in particular pneumatic tires for motor vehicles such as passenger cars, light trucks or commercial vehicles.

[0023] The invention is described below by way of example with reference to the accompanying drawings and advantageous embodiments. The drawings show: Figure 1 schematically a perspective view of a section of an embodiment of a running strip according to the invention, Figure 2 schematically a sectional view of another embodiment of the running track according to the invention.

[0024] Figure 1Figure 1 shows a perspective view of an embodiment of a tread strip according to the invention, wherein the upper part of the image shows a running surface of the tread strip with a groove opening and the lower part of the image shows a side view of a cross-section of an embodiment of a profile groove 1 according to the invention. The groove flanks 4, 5 of the profile groove 1 extend in the cross-section over a large part of a radially upper region 2 of the profile groove 1 parallel to the radial direction. In a radially lower region 3, the profile groove 1 assumes a special shape, which is determined by means of Figure 2 will be described in more detail below. Along the longitudinal extent of the profile groove 1, the profile groove 1 has a constant cross-section at least along the longitudinal section 19 shown.

[0025] Figure 2 shows a sectional view of another embodiment of the running track according to the invention, which is shown in Figure 1The embodiment shown is very similar. The section plane, which coincides with the drawing plane, is defined by the radial direction (from bottom to top in the drawing plane) and another direction perpendicular to the longitudinal extent of the profile groove 1. In the radially upper region 2, the first groove flank 4 and the second groove flank 5 extend essentially parallel to each other, with an upper width 9 determined between the groove flanks 4 and 5 in the Figure 2The radially lower region 3 is concavely curved at a radially lowest point 10. Furthermore, the first and second groove flanks 4, 5 are concavely curved at a first and second point 6, 7, respectively. Between the first and second points 6, 7, the profile groove has its maximum width 8. The concave curves at the first and second points 6, 7 are connected to the concave curve at the radially lowest point 10 by a first and second straight connection 15, 16, respectively. In the illustrated embodiment, the straight connections 15, 16 are at an angle of approximately 60° to each other. Transitions between the radially upper region 2 and the concavely curved sections at the first and second points 6, 7 are designed as convex curves projecting into the profile groove 1 in the illustrated embodiment. The concave and convex curves are designed as circular arcs that intersect tangentially.transition into the straight lines 15, 16. A radius of curvature 11 for the curvature at the radially lowest point 10, radii of curvature 12, 13 for the curvatures at the first and second points 6, 7, and radii of curvature 17, 18 for the convex curvatures are identical in the illustrated embodiment. The centers of curvature 14 of the circles of curvature for the three concave curvatures are equidistant in the illustrated embodiment, arranged at the vertices of an imaginary equilateral triangle. Reference symbol list

[0026] 1 Profile groove 2 Radial upper area 3 Radial lower area 4 First groove flank 5 Second groove flank 6 First point (on the first groove flank) 7 Second point (on the second groove flank) 8 Maximum width 9 Upper width 10 Radially lowest point 11 Radius of curvature (for the curvature at the radially lowest point) 12 Radius of curvature (for the curvature at the first point) 13 Radius of curvature (for the curvature at the second point) 14 Centers of curvature of circles of curvature 15 First straight connection 16 Second straight connection 17 Radius of curvature (for a first convex curvature) 18 Radius of curvature (for a second convex curvature) 19 Longitudinal section of the profile groove

Claims

1. Tread for a vehicle tyre, wherein formed in the tread is a profile groove (1) having a radially upper region (2) and a radially lower region (3) and having a first groove flank (4) and a second groove flank (5), wherein a maximum width (8) of the profile groove (1), measured in the radially lower region (3) between a first point (6) on the first groove flank (4) and a second point (7) on the second groove flank (5), is larger than an upper width (9) of the profile groove measured in the radially upper region (2) between the two groove flanks (4, 5), wherein a base of the profile groove (1) is curved concavely at a radially lowest point (10), wherein in the radially lower region (2) the first groove flank (4) at the first point (6) and the second groove flank (5) at the second point (7) have concave curvatures, wherein the curvature about the radially lowest point (10) and the curvature about the first point (6) are connected by a first rectilinear connection (15), and wherein the curvature about the radially lowest point (10) and the curvature about the second point (7) are connected by a second rectilinear connection (16), wherein the first and the second rectilinear connection (15, 16) are at a mutual angle of 20° to 80°, characterized in that the curvature radii (11, 12, 13) describing curvatures at the radially lowest point (10) and at the first and the second point (6, 7) are in pairs at a mutual ratio of not more than 2:1, or not less than 1:2, respectively.

2. Tread according to Claim 1, characterized in that the first and the second rectilinear connection (15, 16) are at a mutual angle of 45° to 70°, preferably of 55° to 65°.

3. Tread according to either of Claims 1 or 2, characterized in that the curvature radii (12, 13) describing curvatures at the first and at the second point (6, 7) are at a mutual ratio of not more than 2:1, or not less than 1:2, respectively, and are preferably identical in terms of length.

4. Tread according to Claim 3, characterized in that the curvature radii (11, 12, 13) describing curvatures at the radially lowest point (10) and at the first and the second point (6, 7) are identical in terms of length.

5. Tread according to one of Claims 1 to 4, characterized in that the centres of curvature (14) of curvature circles to the curvatures are disposed so as to be equidistant to one another at the radially lowest point (10), at the first point (6) and at the second point (7).

6. Tread according to one of Claims 1 to 5, characterized in that the radially lower region (3) on the first and second groove flanks (4, 5) transitions in each case along a convex curvature into the radially upper region (2).

7. Tread according to Claim 6, characterized in that the curvature radii (17, 18) describing convex curvatures are identical in terms of length.

8. Tread according to Claim 7, characterized in that the curvature radii (17, 18) describing the convex curvatures and the curvature radii (11, 12, 13) describing curvatures at the radially lowest point (10), at the first point (6) and / or at the second point (7) are identical in terms of length.

9. Tread according to one of Claims 1 to 8, characterized in that the maximum width (8) in the radially lower region (3) of the profile groove (1) is between 2 mm and 20 mm, preferably between 4 mm and 8 mm.

10. Tread according to one of Claims 1 to 9, characterized in that the upper width (9) of the profile groove (1), measured in the radially upper region (2) between the two groove flanks (4, 5), is between 0.5 mm and 6 mm, preferably between 1 mm and 3 mm.

11. Tread according to one of Claims 1 to 10, characterized in that the radially lower region (3) extends over a quarter to a half of a radial depth of the profile groove (1).

12. Tread according to one of Claims 1 to 11, characterized in that the features of one of Claims 1 to 11 are satisfied continuously along a longitudinal portion (19) of the profile groove (1), wherein the longitudinal portion (19) is at least five times, preferably at least ten times, the maximum width (8).

13. Vehicle tyre having a tread according to one of Claims 1 to 12.