RUNNING STRIP FOR A VEHICLE TIRE

Description

[0001] The invention relates to a tread for a vehicle tire, comprising a profile groove with two groove flanks and a groove base extending between the groove flanks, wherein the groove base is set back from a base surface by one groove depth, wherein the groove base is modulated along a longitudinal extent of the profile groove with elevations reducing the groove depth, wherein the elevations along the longitudinal extent are each asymmetrically formed.

[0002] Typically, tread grooves have a flat groove base. For example, the tread depth usually does not vary along the longitudinal extent of a circumferential groove. However, there are a number of well-known problems with such conventionally designed tread grooves. For instance, the radial stiffness of a tread strip can decrease in the vicinity of tread grooves, which can increase the rolling resistance of the vehicle tire. In particular, uneven stiffness can result in combination with other tread elements, which in turn can lead to uneven wear. Furthermore, circumferential grooves with a flat groove base are poorly suited for the grip of a tire on snow-covered roads.

[0003] In accordance with the prior art, various designs and purposes are proposed for raised groove bases. For example, stiffening ribs and stone ejectors are arranged at specific points along the groove base. Furthermore, KR1302548B1 proposes a wave-shaped modulated groove depth to improve the wet grip of a vehicle tire. However, despite all these proposals, approaches capable of efficiently and convincingly solving all the aforementioned problems, particularly those concerning snow grip, are still lacking. EP 3 501 852 A1 describes a tire with a circumferential groove, wherein the groove base is provided with a groove base projection, the groove base projection comprising a first and a second inclined surface, the circumferential length of the first inclined surface being greater than the circumferential length of the second inclined surface.EP 2 985 157 A1 describes an aircraft tire wherein a circumferential groove has a wave shape with radially directed amplitude, wherein the wave shape can have a sawtooth shape, wherein the sawtooth shape can have a long and a short side in the circumferential direction.

[0004] The invention is based on the objective of creating a tread with profile grooves, in particular with circumferential grooves for efficient drainage, wherein the tread should simultaneously give a vehicle tire improved stability and winter properties.

[0005] The problem is solved according to the invention by forming pocket slats in the tread, wherein the pocket slats are arranged closer to a respective high point of the elevations than to a point full profile depth.

[0006] The invention recognizes that such raised sections on the base of a groove can also act as snow scoops, with one side of the raised section being optimized for collecting snow and the other side for stabilizing the raised section and the profile groove. Collecting snow in a profile groove creates advantageous snow-to-snow grip. This solution is particularly useful for directional tread patterns.

[0007] When the terms axial, radial, and circumferential are used, they refer to the vehicle tire as intended on a vehicle and its rolling motion. In this context, the radial direction refers to a direction perpendicular to and intersecting the axis of rotation of the vehicle tire. InRadial direction inwards refers to the orientation that faces the radial direction of the axis of rotation. In Radial direction outwards refers to the orientation that is radially away from the axis of rotation. Circumferential direction describes the direction of rolling motion around the axis of rotation. When the vehicle is moving forward, a tire positioned at the front circumferentially reaches its minimum distance to the road surface earlier during a 360° rotation than a tire positioned at the rear circumferentially, with the rear position reaching its minimum distance to the road surface less than 180° behind the front position.

[0008] The axial direction refers to a direction parallel to the axis of rotation. Pointing inwards axially refers to an orientation that is aligned with a tire equator plane or tire equator line. The tire equator plane is a plane perpendicular to the vehicle tire's axis of rotation, passing through the center of the tire's axial width, with the tire equator line running within the tire equator plane and on the tire's surface. The transverse direction is defined as a direction composed of components of the radial and / or axial directions.

[0009] 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 snow edges, 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 a 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.

[0010] A raised section at the base of the groove reduces the profile depth insofar as the raised section rises perpendicular to the base surface and the groove base running on a raised section is therefore less far back from the base surface than away from the raised section, i.e. in a position of full profile depth.

[0011] A raised area is asymmetrically formed along the longitudinal extent of the profile groove if no imaginary mirror plane can be constructed which would reflect the raised area back onto itself and runs perpendicular to the base surface and in the direction of a lateral extent of the profile groove.

[0012] The invention can be further developed with advantageous features as described below.

[0013] The profile groove is preferably a circumferential groove. In this way, the flank of a raised section, optimized for collecting snow, can engage the snow at the front in the circumferential direction, while the opposite flank of the raised section can absorb the resulting forces and transfer them into the tread.

[0014] Between 10 and 100 ridges per meter of the profile groove's length can be formed. With an even distribution, this results in both a good frequency of spaces for snow accumulation and high stability, without unduly disrupting the groove's water-shedding function. The ridges can be between 5 mm and 40 mm long along the profile groove's length. Here, length is defined as the distance between two points at full profile depth.

[0015] Adjacent ridges can be directly adjacent to one another, rising directly from a point with full profile depth in both directions of the longitudinal extent. Alternatively, a flat section can be located between two ridges, in which the groove base is flat and full profile depth. In addition to the asymmetrical ridges, further ridges can be present at the groove base, which may be symmetrical. For example, asymmetrical and symmetrical ridges can alternate at the groove base.

[0016] The raised sections extend perpendicular to the base surface over 20% to 80% of the full profile depth, preferably over 40% to 60%. This achieves a good balance between the drainage function of the profile groove on the one hand and the stabilization and snow collection function on the other.

[0017] The raised sections preferably extend across the full width of the profile groove between the groove flanks and merge into the groove flanks. This ensures a particularly effective stabilizing function of the raised sections. The groove bottom can have a constant groove depth at the highest point of the raised sections along a certain width of the profile groove. The radius of the rounding towards the groove flanks can be smaller at the highest point of the raised sections than at points with full profile depth. This further enhances the stabilizing function of the raised sections.

[0018] The asymmetrical shape of the ridges can be advantageously designed as follows: A maximum height of a ridge can be achieved at between 20% and 45%, preferably between 25% and 35% of the ridge's length. For a symmetrical ridge, this value would be 50%. By shifting the highest point away from the center of the ridge, its suitability for snow accumulation can be optimized. Preferably, the steeper flank of the ridge is positioned at the front in the circumferential direction, so that the path from the point where the ridge enters the snow to its highest point is shorter than the path from the highest point to where the ridge exits the snow. The opposite, shallower flank absorbs the forces acting on the steeper flank during snow accumulation particularly well, without causing significant deformation in the tread.

[0019] A raised section can rise along its longitudinal extent at a maximum angle of ascent and fall at a maximum angle of descent, the maximum angle of ascent being different from the maximum angle of descent and, in particular, being larger (in absolute terms). The maximum angles mark points of maximum (absolute) slope along a curved contour of the raised section, at which the second derivative of the contour would change sign if sufficiently differentiable. The angle of ascent is preferably defined on the circumferentially leading side of a raised section, and the angle of descent on the circumferentially trailing side. The maximum angle of ascent can be between 50° and 80°, and the maximum angle of descent between 30° and 60°. The angles are defined relative to the direction of the longitudinal extent of the profile groove.The difference between the maximum ascent and descent angles can be between 5° and 50°, preferably between 10° and 30°. The contour of the elevations, defined in a plane perpendicular to the base surface and in the longitudinal direction, can be continuous, preferably continuously differentiable, and further preferably twice continuously differentiable.

[0020] Preferably, the tread comprises several profile grooves with raised areas at the groove base according to the invention. For example, several parallel circumferential grooves with substantially identical modulation of the groove base can be formed in the tread. The raised areas of parallel grooves can be arranged at the same locations along the longitudinal extent or with an offset. For example, the raised areas in two adjacent circumferential grooves can be arranged with the same wavelength but with a phase shift, thereby achieving uniform stabilization of the tread.

[0021] It can be advantageous to have further profile grooves open into a profile groove modulated according to the invention. In this case, the opening preferably occurs between two raised sections, at a longitudinal position with the full profile depth, so that optimal drainage is ensured.

[0022] According to the invention, so-called pocket sipes are additionally formed in the tread. Pocket sipes have no open ends laterally; they are only open towards the base surface, but not, for example, towards the groove flanks. Such pocket sipes are arranged in a tread block or rib closer to a high point of a raised section according to the invention than at a point of full tread depth. In this way, the reduced stiffness in the tread at the pocket sipe can be compensated by the raised section, while the reduced stiffness at a point of full tread depth can, in turn, be compensated by a directly adjacent tread block or rib section without a sipe. Thus, uniform stiffness and, consequently, uniform tire wear are promoted.

[0023] The invention also relates to a vehicle tire with a tread pattern described above and / or below. The vehicle tire is preferably used in a directional manner, 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.

[0024] 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 sectional view of an embodiment of a running track according to the invention, Figure 2 schematically a top view of an embodiment of a running track according to the invention, Figure 3 schematically a sectional view according to the in Figure 2 drawn cutting line Figure 4 schematically a similar view to in Figure 3 an alternative embodiment.

[0025] Figure 1 Figure 1 shows a radially and axially outer section of a cross-section through an embodiment of a running strip 1 according to the invention. The section plane is perpendicular to the circumferential direction. Two parallel circumferential grooves 2, 2' are formed in the running strip 1. The axially inner circumferential groove 2 is modulated at the groove base 3 with protrusions 4 according to the invention. The section shown runs at a maximum height 5, measured along the circumferential direction (cf. Figure 1). Figure 3 ) such a rise 4 or at a corresponding minimum of the groove depth. In The elevation 4 extends to the shown circumferential position at a constant 50% of the full profile depth 6 (cf. Figure 3 ) in axial direction across the entire width of the profile groove 2.

[0026] Figure 2Figure 1 shows a top view of an embodiment of a running track 1 according to the invention. This can be the one described in Figure 1. Figure 1 The embodiment shown is an example. In In the circumferential section of the radially inner profile groove 2 shown, three projections 4 according to the invention are formed along the longitudinal extent of the profile groove 2. The limiting lines, which are horizontal in the drawing, mark circumferential positions at which the projections 4 reach a height of 50% of their maximum height 5.

[0027] The elevation profile of the elevations 4 or the corresponding modulation of the rille base 3 is shown in Figure 3 even clearer. Here is a sectional view according to the one in Figure 2 drawn cutting line III-IIIThe drawing shows two horizontal lines marking the radial positions of the full tread depth 6 and the base surface 7 of the tread 1. It should be noted that for the sake of clarity, the curvatures that the tread 1 would assume in its intended form on a vehicle tire are not shown in the figures; instead of a horizontal straight line in Figure 3The base surface 7 on a vehicle tire, for example, would follow a circumferential curvature. The projections 4 extend at their maximum height 5 over approximately 50% of the full tread depth 6. The maximum height 5 is reached in the direction of the longitudinal extension of the tread groove 2 at approximately 30% of the length 8 of the projection 4, i.e., with a corresponding displacement 9 relative to an adjacent point of full tread depth. Preferably, the side shown on the right in the drawing is positioned circumferentially at the front of the vehicle tire, so that the steeper flank of the projections 4 can engage the snow when driving forward. According to the Figure 3 In the embodiment shown, the full profile depth 6 in the circumferential direction is only achieved at specific points, with the rises or falls of the adjacent elevations 4 directly following in the circumferential direction forwards and backwards.

[0028] Figure 4shows an alternative embodiment of a groove according to the invention in a sectional view similar to Figure 3 . As opposed to Figure 3 Between the two elevations 4 shown, a flat section 10 of the groove base 3 lies in the circumferential direction at full profile depth 6. Figure 4 This is further used as a demonstration example to illustrate a maximum angle of ascent 11 and a maximum angle of descent 12 of the protrusions. The angles 11 and 12 are measured relative to the longitudinal extent of the profile groove 2. In the illustrated embodiment, the maximum angle of ascent 11 is approximately 70° and the maximum angle of descent 12 is approximately 55°. The contours of the protrusions 4 follow a continuous, rounded profile, thus minimizing stress concentrations at the groove base 3. Reference symbol list

[0029] 1. Tread 2. Profile groove 2' (additional) profile groove 3. Groove base 4. Elevation 5. Maximum height 6. Full profile depth 7. Base area 8. Length 9. Displacement 10. Flat section 11. Maximum ascent angle 12. Maximum descent angle

Claims

1. Tread strip (1) for a vehicle tyre, comprising a profile groove (2) with two groove flanks and a groove bottom (3) extending between the groove flanks, wherein the groove bottom (3) is set back in relation to a base surface (7) by a groove depth, wherein the groove bottom (3) is modulated along a longitudinal extent of the profile groove (2) with elevations (4) which reduce the groove depth, wherein the elevations (4) are each of asymmetrical configuration along the longitudinal extent, characterized in that pocket lamellae are configured in the tread strip, wherein the pocket lamellae have no open ends to the groove flanks laterally, and wherein the pocket lamellae are arranged closer to a respective high point of the elevations than to a point of full profile depth.

2. Tread strip (1) according to Claim 1, characterized in that the profile groove (2) is a circumferential groove.

3. Tread strip (1) according to either of Claims 1 or 2, characterized in that between 10 and 100 elevations (4) are configured per metre of longitudinal extent of the profile groove (2).

4. Tread strip (1) according to one of Claims 1 to 3, characterized in that the elevations (4) along the longitudinal extent are each between 5 mm and 40 mm long.

5. Tread strip (1) according to one of Claims 1 to 4, characterized in that the elevations (4) extend perpendicularly with respect to the base surface (7) in each case over 20% to 80% of a full profile depth (6).

6. Tread strip (1) according to one of Claims 1 to 5, characterized in that the elevations (4) each extend over a full width of the profile groove (2) between the groove flanks.

7. Tread strip (1) according to one of Claims 1 to 6, characterized in that the groove bottom (3) at the highest point of the elevations (4) has a constant groove depth in each case along a width extent of the profile groove (2).

8. Tread strip (1) according to one of Claims 1 to 7, characterized in that a maximum height (5) of an elevation (4) is reached at between 20% and 45%, preferably between 25% and 35% of the length (8) of the elevation (4).

9. Tread strip (1) according to one of Claims 1 to 8, characterized in that the elevations (4) along the longitudinal extent each rise at a maximum rise angle (11) and fall at a maximum fall angle (12), wherein the maximum rise angle (11) is greater than the maximum fall angle (12).

10. Tread strip (1) according to Claim 9, wherein the maximum rise angle (11) is between 50° and 80° and the maximum fall angle (12) is between 30° and 60°.

11. Vehicle tyre having a tread strip (1) according to one of Claims 1 to 10.