VEHICLE TIRES

Description

[0001] The invention relates to a vehicle tire having at least one structural region formed in the region of at least one tire shoulder and / or at least one tire sidewall, with a base surface having a particularly smooth surface on which a plurality of surface depressions which are circular in plan view are formed.

[0002] In order to reduce fossil fuel consumption and greenhouse gas emissions, particular attention has been paid in recent years to reducing vehicle fuel consumption. With regard to vehicle tires, the focus is primarily on measures that reduce rolling resistance. Recently, however, the aerodynamic properties of vehicle tires and their contribution to the vehicle's drag, especially in passenger cars, have also become more important. Since vehicle tires are not usually completely enclosed by the vehicle body, the tire sidewalls and tire shoulders are also exposed to airflow and contribute to the overall aerodynamic profile of the respective vehicle.Particularly at high vehicle speeds, high airflow velocities occur around the tire sidewalls, resulting in increased air resistance, which also impacts the vehicle's fuel consumption. The typically structured surfaces of tire sidewalls influence the development of turbulence and airflow separation in the boundary layer as the tires roll, so that, depending on the design, air resistance can even be undesirably increased.

[0003] It is already known to provide vehicle tires with specially structured surfaces on the tire sidewalls to achieve reduced air resistance. For example, DE 10 2010 036 765 A1 discloses a pneumatic vehicle tire with a surface structure on the tire sidewalls formed as a network of lattice-like structures curved concentrically to the tire axis. The lattice-like structures each closely enclose surface elements and are raised relative to the surface elements they enclose.This dense, tightly woven network of grid-like structures curved concentrically to the tire axis is intended to cause mini-turbulences to occur in the boundary layer of the air flowing around the tire sidewall surface in the depressions at high speeds, thus offsetting the separation edges of the laminar flow flowing around the tire sidewall surface and reducing air resistance. Another pneumatic vehicle tire intended to help reduce air resistance during rolling motion is known from DE 11 2014 000 477 T5. A plurality of dimple-shaped, in particular circular, depressions are formed on at least one region of the sidewall surface. These depressions vary periodically in size along the tire's circumferential direction and are embedded in a background hatching of elevations running parallel to one another. The circular depressions have a maximum depth of 0.3 mm to 1.5 mm.Another pneumatic vehicle tire with structured surface areas on the tire sidewalls, which are intended to enable reduced air resistance while maintaining good abrasion resistance of the structure, is known from WO 2013 / 010726 A1. For this purpose, the surface of at least one of the sidewalls is provided in at least one circumferential section with annular and linear structures distributed alongside one another in the radial and circumferential directions. The linear structures each directly and tightly enclose a surface element and form linear depressions.The dense, close-meshed network of ring-shaped, linear depressions formed in this way, which each closely enclose surface elements, causes mini-turbulences to form at high speeds in the boundary layer of the air flowing around the tire sidewall surface, which are intended to displace the separation edges of the laminar flow flowing around the tire sidewall surface and reduce air resistance.

[0004] It is known that the dimple pattern on the surface of golf balls reduces the drag coefficient by lowering the pressure drag, thus reducing the drag of golf balls by up to 50%. Small turbulences within the dimples transform the laminar boundary layer around the ball into a turbulent boundary layer. The flow separates with a delay, creating a negative pressure. The smaller the zone, the smaller the pressure difference to the upstream side and thus the deceleration in the direction of flight.

[0005] The invention is based on the object of transferring the concept of dimple patterns known from golf balls to vehicle tires in an innovative and particularly advantageous way for reducing air resistance.

[0006] The stated object is achieved according to the invention in that two depressions are connected to each other in pairs via a connection point which is narrower than the diameter of the depressions and form elongated structural elements which are each oriented in the circumferential direction of the tire.

[0007] The invention surprisingly provides a particularly aerodynamically advantageous surface structure on tire sidewalls or tire shoulders, which actually reduces the flow resistance of the vehicle tire. The structural elements oriented in the direction of tire rotation act particularly effectively as turbulators at higher driving speeds or with higher tire rotation. They transform a laminar boundary layer into a turbulent one, delaying flow separation, and thus ensuring a longer flow path, which reduces pressure drag.

[0008] These effects are supported and further enhanced by preferred designs and configurations of the structural elements oriented in the direction of rotation of the tire.

[0009] Particularly preferred is an embodiment in which the connecting points on the base surface are each delimited by edges which are curved inwards towards one another and which each merge tangentially into the circular edges of the depressions.

[0010] The tangential transitions are preferably located at the end region of the end points of a chord of the circular edges of the depressions, wherein these chords have a length of 20% to 70%, in particular of 30% to 40%, of the diameter of the depressions.

[0011] In order to create mini-turbulences or turbulators in the desired manner during rotation of the tire, it is advantageous if the narrowed connecting points have an extension length determined between the centers of the two chords and a smallest width of 15% to 30% of the diameter of the depressions in their center and between the edges on the base surface.

[0012] The recesses, which are circular except for the points where the connections between the two recesses are located, preferably have a diameter of 3.5 mm to 6.0 mm and, at their deepest point, a depth of 0.3 mm to 1.2 mm relative to the level of the base surface. This dimensioning of the recesses promotes a particularly aerodynamically advantageous surface structure.

[0013] Also aerodynamically advantageous are depressions which either have a base at a constant depth and, from this, an edge flank running along the outer edge, which is inclined at an angle of 10° to 45° towards the base and relative to the base surface, or which are designed as rounded troughs with their deepest point in the center of their circular shape.

[0014] The narrowed connection points are advantageously provided with a bottom which, relative to the level of the base surface, extends to a depth corresponding at most to the greatest depth of the recesses and is at least 0.1 mm. In the narrowed connection points, edge flanks can also extend from the bottom to the edges, preferably extending in continuation of the edge flanks extending from the edge of the recesses.

[0015] Further, additional measures that contribute to reducing pressure resistance include structuring the bottom or the inner area of ​​the recesses. In a preferred embodiment in this regard, at least one elevation, in particular a plurality of elevations extending seamlessly to one another, is formed on the bottom of the recesses and preferably also on the bottom of the narrowed connection points.

[0016] According to a further preferred embodiment, the elevation(s) is / are trapezoidal in cross-section, in particular isosceles trapezoidal, wherein, in the case of a plurality of elevations, these either directly adjoin one another at their base or extend at a mutual distance of in particular up to 0.8 mm, and wherein the elevation(s) is / are preferably designed such that its highest point(s) is / are located at least 0.1 mm within the level of the base surface. Elevations designed in this way can be particularly well impressed into the tire sidewall or tire shoulders using vulcanization moldings provided with milled structures in a conventional manner.

[0017] There are a number of ways to create effective and, at the same time, visually appealing elevations in the depressions. One of these options involves forming a plurality of elevations at the bottom of the depressions that run parallel to one another and, in particular, extend in a straight line to the edges of the depressions or to the edge flanks. In an alternative embodiment, at least one elevation is formed at the bottom of the depressions that runs along a circle that is, in particular, concentric to the outer edge of the depressions. In this case, two or three elevations that run concentrically to one another and to the edge of the depressions can be formed at the bottom of the depressions. These elevations can, furthermore, end at different heights relative to the level of the base surface.

[0018] Further features, advantages and details of the invention will now be described in more detail with reference to the drawing, which largely shows schematic embodiments. Fig. 1 schematically shows a section of a side view of a vehicle tire with a sidewall with structural areas, Fig. 2 a detail of a structural area Fig. 1 in enlarged view, Fig. 3 the outer contour of a structural element of a structural area, Fig. 4a und Fig. 4b a variant of a structural element, Fig. 4a top view, Fig. 4b in enlarged section along the line IVb-IVb of the Fig. 4a , Fig. 5a und Fig. 5b another variant of a structural element, Fig. 5a top view, Fig. 5b in the enlarged section along the line Vb-Vb of the Fig. 5a , Fig. 6a und Fig. 6b a third variant of a structural element, Fig. 6a in oblique view, Fig. 6b in section along the line VIb-VIb of the Fig. 6a and Fig. 7a und Fig. 7b a fourth variant of a structural element, Fig. 7a in oblique view, Fig. 7b in section along the line VIIb-VIIb of the Fig. 7a .

[0019] Vehicle tires designed according to the invention are tires of any design, in particular radial tires, and tires of any type, in particular pneumatic vehicle tires for motor vehicles, such as passenger cars, light trucks or commercial vehicles.

[0020] Fig. 1 shows a circumferential section of the side view of a vehicle tire with a sidewall 1 and a tire shoulder 3 adjoining this in the direction of the tread of the vehicle tire, which is not visible. The sidewall 1 is a circular ring in plan view of the tire with the tire axis as the center, marked with M. In Fig. 1 Furthermore, the radial direction of the vehicle tire is indicated by the double arrow R and the circumferential direction around the tire axis is indicated by the double arrow U.

[0021] On the side wall 1, in the circumferential direction U, circumferential sections designed as structural areas 2 alternate with circumferential sections in which, for example, on an unstructured, in particular smooth, background, characters designed as elevations or depressions, such as characters forming a lettering, or logos and the like, are formed.

[0022] Fig. 1 shows a circumferential section of a structural region 2, which extends in the circumferential direction of the sidewall 1 preferably over a circular ring section, which has a width in the radial direction R, which, depending on the tire dimension and tire type, is in the order of 1.5 cm to 50.0 cm. In the circumferential direction, the structural regions 2 preferably extend over central angles of 5° to 90°. Each structural region 2 has a base surface 1a provided with a smooth surface ( Fig, 2 ) with structural elements 4, which are evenly distributed over a large part of the area occupied by the respective structural area 2 and thus occupy in particular 50% to 80% of this area. Fig. 1 shows, by reducing the size of the structural elements 4 and increasing their distances, a transition area to a circumferential section of a different design can be created.

[0023] For example Fig. 2 , Fig. 3 , Fig. 4a , Fig, 5a , Fig. 6a and Fig. 7a show, the structural elements 4 are each pairs of recesses 5 connected to one another via a connection point 6 - a constriction -, extending from the base surface 1a, delimited on the base surface 1a by circular edges, according to the preferred embodiment, designed to match in plan view and thus elongated. According to the Fig. 1 und 2 In the preferred embodiment shown, the structural elements 4 run in the circumferential direction U and within circumferential rows at mutual distances a 1 of preferably 1.0 mm to 2.5 mm.

[0024] The structural elements 4, which are arranged in adjacent rows, are each offset from one another in the radial direction, for example such that, viewed in the radial direction, one recess 5 of each structural element 4 is opposite a connection point 6 from the adjacent row of structural elements 4 and the second recess 5 is assigned to a distance between the structural elements 4 running in the circumferential direction U within a row. As a result of the mutually offset arrangement of the rows of structural elements 4, spaces arise between the recesses 5 of structural elements 4 in adjacent rows with a width b 1 of in particular 1.0 mm to 2.5 mm.

[0025] Fig. 2 shows the outer contour of a structural element 4 with two, except for the junction points of the connection point 6, circular depressions 5 with a diameter d which is 3.5 mm to 6.0 mm, in particular on the order of 5.0 mm. The connection point 6 is delimited on the base surface 1a by edges which are curved inwards towards one another and which each merge tangentially into the circular edges of the depressions 5 in the region of the end points of a chord s of the depressions 5. The chords s have a length of 20% to 70%, in particular 30% to 40%, of the diameter of the depressions 5. In their center, the connection points 6 have their narrowest point with a width b 2 which is 15% to 30% of the diameter d of the depressions 5, in particular 0.5 mm to 2.0 mm.

[0026] The extension length e of the connecting points 6 determined between the centers of the two circular chords s is 15% to 30% of the diameter d, preferably in the order of magnitude of 0.5 mm to 1.5 mm, so that the structural elements 4 have an extension length I of preferably 8.5 mm to 13.5 mm.

[0027] Preferred embodiments of the design of the recesses 5 of the structural elements 4 will now be described with reference to the further figures.

[0028] In the Fig. 4a und Fig. 4b , Fig. 5a und Fig. 5b as well as in Fig. 6a und 6b In the embodiments shown, the depressions 5 and the connecting point 6 each have a continuous base 8 located at a constant level or at a constant depth t 1 of 0.3 mm to 1.2 mm and, between the base edge and the outer edge of the structural element 4, an edge flank 8a which is inclined inwards at an angle α, wherein α, viewed from a perpendicular to the base 8, is 10° to 45°.

[0029] At the Fig. 4a und 4b In the embodiment shown, a plurality of elevations 7 running parallel to one another are formed on the bottom 8 of the recesses 5 and the connecting point 6, which Fig. 4a are only indicated by lines and extend to the edge flanks 8a. As Fig. 4b As shown in an enlarged view, the elevations 7, for example, have a particularly isosceles trapezoidal cross-sectional area and matching heights h of 0.3 mm to 1.0 mm, where h is at least 0.1 mm less than the depth t 1 , so that the elevations 7 do not project beyond the depressions 5. The elevations 7 forming a hatching have side flanks 7a which are inclined relative to a perpendicular to the base 8 preferably at correspondingly large angles β, where β is 10° to 45°. Due to their trapezoidal shape, the elevations 7 have narrow plateau surfaces 7b with a particularly constant width in the order of 0.15 mm. At their base on the base 8 of the depressions 5, the elevations 7 can directly adjoin one another or, as in Fig. 4b shown, have a mutual distance a 2 of 0.2 mm to 1.0 mm.

[0030] At the Fig. 5a und 5b In the embodiment shown, several grooves (three in the embodiment shown) are arranged on the bottom 8 of the recesses 5, which are concentric to one another and concentric to the outer edge of the recesses 5 and are Fig. 5a Elevations 9a, 9b and 9c indicated by lines are formed, with elevation 9a being the innermost and elevation 9c the outermost elevation. In the embodiment shown, the elevations 9a, 9b and 9c have different heights ha, hb and hc relative to the level of the base 8, with the innermost elevation 9a having the lowest height ha and the outermost elevation 9c having the greatest height hc. The height ha of the innermost elevation 9a is 0.1 mm to 0.3 mm, the height hb of the adjacent elevation 9b is 0.2 mm to 0.6 mm, and the height hc of the outermost elevation 9c is 0.3 mm to 0.9 mm, with elevations 9a, 9b and 9c not projecting beyond the outer edge of the depression 5. The elevations 9a, 9b and 9c can also have matching heights of 0.1 mm to 0.9 mm.Otherwise, the elevations 9a, 9b, and 9c are designed, analogous to the elevations 7, in an isosceles trapezoidal cross-section, with side flanks 9a 1 , 9b 1 , and 9c 1 , which are inclined relative to a perpendicular to the base 8, preferably at correspondingly large angles β of 10° to 45°, and with narrow, here annular, circumferential plateau surfaces with a particularly constant width of the order of 0.15 mm. At the base 8, thus at the base, the elevations 9a, 9b, and 9c directly adjoin one another; alternatively, the elevations 9a, 9b, and 9c have a mutual distance a 2 of up to 1.0 mm.

[0031] Fig. 6a with Fig. 6b as well as Fig. 7a with Fig. 7b show further variants of recesses connected in pairs 5. In the Fig. 6a und Fig. 6b In the embodiment shown, the recesses 5 have a circular bottom 8 at a constant level, i.e., at a depth t 1 of 0.30 mm to 1.2 mm; the depth of the connecting point 6 is adapted to the depth of the bottom 8. No elevations are formed on the bottom 8. From the bottom 8 to the outer edges of the recesses 5 and the connecting point 6, an edge flank 8a runs continuously relative to the bottom 8 at the aforementioned angle of inclination α.

[0032] At the Fig. 7a und Fig. 7b In the embodiment shown, the recesses 5 are generally rounded depressions with a trough-shaped base 8 and their deepest point with the depth t 1 in the region of the center of their circular shape. The connecting point 6 is a local shallower constriction between the two recesses 5. Also in the embodiment according to Fig. 7a with Fig. 7b elevations may be present on the ground 8 in an analogous manner as described.

[0033] Tires with structural regions designed according to the invention are vulcanized in a vulcanization mold, which has corresponding embossed structures in the area of ​​the tire shoulders and / or tire sidewalls to form these structural regions, complementary to the structural regions and structural elements. The relevant components of the vulcanization mold are therefore side shells for forming the sidewalls and the shoulder-side regions of profile segments, which imprint the tread pattern of the vehicle tire. The structures are preferably produced using a material-removing process, for example, using a milling tool. List of reference symbols

[0034] 1Sidewall 1aBase area 2Structural area 3Tire shoulder 4Structural element 5Recess 6Connection point 7Protrusion 7aSide flank 7bPlateau area 8Ground 8aEdge flank 9a, 9b, 9cProtrusion 9a 1 , 9b 1 , 9c 1 Side flank α, βAngle a 1 , a 2 Distance b 1 , b 2 Width dDiameter e, lExtension length h, ha , hb , hc Height RRadial direction sChord t 1 Depth UCircumferential direction

Claims

1. Vehicle tyre with at least one structural region (2) which is formed in the region of at least one tyre shoulder (3) and / or at least one tyre sidewall (1) and has a base area (1a) which has an in particular smooth surface and on which a multiplicity of superficial depressions (5) which are circular when seen from above are formed, characterized in that two depressions (5) in each case are connected to one another in pairs by way of a connecting point (6) that is narrowed in comparison with the diameter of the depressions (5) and form elongated structural elements (4), which are in each case oriented in the circumferential direction of the tyre.

2. Vehicle tyre according to Claim 1, characterized in that the narrowed connecting points (6) on the base area (1a) are each delimited by peripheries which are curved inwardly relative to one another and in each case tangentially transition into the circularly extending peripheries of the depressions (5).

3. Vehicle tyre according to Claim 1 or 2, characterized in that the narrowed connecting points (6) in each case in the region of the end points of a chord (s) of the circular peripheries of the depressions (5) tangentially transition into the circularly extending peripheries of the depressions (5), wherein the chords (s) have a length of 20% to 70%, in particular of 30% to 40%, of the diameter (d) of the depressions (5).

4. Vehicle tyre according to Claim 3, characterized in that the narrowed connecting points (6) have a length of extent (e), determined between the centres of the two chords (s), of 15% to 30% of the diameter (d) of the depressions (5).

5. Vehicle tyre according to one or more of Claims 1 to 4, characterized in that the narrowed connecting points (6) have, determined in their middle and between their peripheries at the base area (1a), their smallest width (b2) of 15% to 30% of the diameter (d) of the depressions (5).

6. Vehicle tyre according to one or more of Claims 1 to 5, characterized in that the depressions (5) have a diameter of 3.5 mm to 6.0 mm and at their lowest point, in relation to the level of the base area (1a), a depth (t1) of 0.3 mm to 1.2 mm.

7. Vehicle tyre according to one or more of Claims 1 to 6, characterized in that the depressions (5) have a circular base (8) at a constant depth (t1) and a peripheral flank (8a) which extends from its outer, circularly extending periphery to the base (8) and is inclined towards the base (8) at an angle (α) of 10° to 45°.

8. Vehicle tyre according to one or more of Claims 1 to 7, characterized in that the narrowed connecting points (6) have a base (8) which, in relation to the level of the base area (1a), extends at a depth which corresponds at most to the greatest depth (t1) of the depressions (5) and is at least 0.1 mm.

9. Vehicle tyre according to one or more of Claims 1 to 8, characterized in that peripheral flanks (8a) run from the peripheries of the narrowed connecting points (6) towards their base (8) and extend in the continuation of the peripheral flanks (8a) that run from the periphery of the depressions (5).

10. Vehicle tyre according to one or more of Claims 1 to 9, characterized in that the depressions (5) are overall in the form of hollows with a hollow-like base (8).

11. Vehicle tyre according to one or more of Claims 1 to 10, characterized in that, at the base (8) of the depressions (5) and preferably also at the base (8) of the narrowed connecting points (6), in each case at least one elevation (7, 9a, 9b, 9c), in particular a multiplicity of elevations (7, 9a, 9b, 9c) that extend relative to one another without intersecting, are formed.

12. Vehicle tyre according to Claim 11, characterized in that the elevation(s) (7, 9a, 9b, 9c) in cross section is or are in the form of a trapezium, in particular in the form of an isosceles trapezium, and, in the case of a multiplicity of elevations (7, 9a, 9b, 9c), at their base either adjoin one another directly or extend at a mutual distance (a2) of in particular up to 1.0 mm, wherein the elevation(s) (7, 9a, 9b, 9c) is or are preferably designed in such a way that their highest point is at least 0.1 mm within the level of the base area (1a).

13. Vehicle tyre according to Claim 11 or 12, characterized in that the elevations (7) extend parallel to one another, and in particular rectilinearly, and up to the peripheries of the depressions (5) or up to the peripheral flanks (8a).

14. Vehicle tyre according to Claim 11 or 12, characterized in that at least one elevation (9a, 9b, 9c) is formed at the base (8) of the depressions (5) and extends along a circle that extends in particular concentrically with respect to the outer periphery of the depressions (5).

15. Vehicle tyre according to Claim 14, characterized in that two or three elevations (9a, 9b, 9c) that extend concentrically with respect to one another and to the periphery of the depressions are formed at the base (8) of the depressions (5).