CA3197350A1 - Pneumatic vehicle tyre with central circumferential rib - Google Patents

Abstract

A pneumatic vehicle tire having a tread (1) which has a profile and has 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 encircle the entire pneumatic vehicle tire, which circumferential channels run at least approximately perpendicular to the axial direction A of the pneumatic vehicle tire in that they only deviate by an angle ? 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. The circumferential rib (3) has, at regular spacing intervals d in a circumferential direction, a sipe (6) which runs from one to the other of the mutually parallel sides (4, 4') of the two encircling circumferential channels (2, 2') along a contour line (10). At three to seven times the length of the spacing interval d of the sipes (6) in the circumferential direction, in each case one thin transverse channel (8) is arranged in the middle circumferential rib (3) in place of a sipe (6), the width BQ of which thin transverse channel is at least 2.5 times the width BF of a sipe (6) and which thin transverse channel has the contour line (10) of the sipes (6). 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 said length Lred of the contour line (10), the thin transverse channels (8) have in their end regions a snow pocket (20). The snow pockets (20) have 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 has a depth TS of at most 65% of the profile depth TQ of the thin transverse channel (8).

Description

Pneumatic vehicle tyre with central circumferential rib Description [0001]The invention relates to a pneumatic vehicle tire having a tread which has a profile. The profile of the tread has two circumferential channels that encircle the entire tire. A middle circumferential rib of the profile is delimited by two sides, running parallel to one another, of these two circumferential channels, which sides run perpendicular to the axial direction A of the pneumatic vehicle tire. Said circumferential rib has, at regular spacing intervals in a circumferential direction, sipes which run from one to the other of the mutually parallel sides of the two circumferential channels along a contour line.
Prior art

(0002] Pneumatic vehicle tires that are also suitable for use in winter, normally referred to for short as winter tires, must keep a vehicle stable on a roadway even when said roadway is covered in snow or ice. This winter performance, which encompasses snow and ice performance, also includes safe cornering with the vehicle, and safe launching and braking with the vehicle.

(0003] To achieve these characteristics, the tread of the pneumatic vehicle tire has a correspondingly designed profile.

[0004]The snow performance of the tire is contributed to primarily by three mechanisms of action: rubber-on-snow friction, snow-on-snow friction, and the edge (shear) action of the profile structure.

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

[0006]To increase the snow-on-snow friction, the profile of the tread of the pneumatic vehicle tire has structures such as grooves that fill with snow taken in from the roadway. It is known here from WO 2018/103924 Al that circumferential grooves with a depth of 1.5 mm to 2.5 mm and a width of 2.0 to 3.0 times this depth quickly and reliably fill with snow when driving on a snow-covered roadway.
Fast filling of a structure in the profile of the pneumatic vehicle tire with snow in order to generate snow-on-snow friction is particularly important if a vehicle has an anti-slip control (ASR) system or an anti-lock (ABS) system, because the profile of the pneumatic vehicle tire then grips the roadway after short slip distances or short gripping times, and snow-on-snow friction is then required for this purpose.

[0007] The edge (shear) action of the profile structure is achieved using sipes, also referred to as lamellae, at regular spacing intervals in the profile. The width of these sipes is smaller than the width of channels or grooves in the profile of the tread of a pneumatic vehicle tire, and amounts to 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 sipes are typically arranged in the profile blocks of the profile of the tread, which are formed by channels in the profile. If a profile block now passes through the ground contact patch of the pneumatic vehicle tire, that is to say the profile block makes contact with the roadway as the tire rotates, the sipes in the profile block open, resulting in grip edges that increase the traction in snow. Here, the profile block elements that are delimited by two sipes, or by a sipe and a profile block edge, tilt. The formation of grip edges, and the tilting of the profile block elements, increase with the depth of the sipes in the profile.

[0008] The depth TF of the sipes may however be reduced at the block edges, for example in order to improve the handling of the pneumatic vehicle tire. On the other hand, such structures of the sipes, referred to as edge elevations of the sipes, reduce the formation of grip edges and the tilting of the profile block elements.

[0009] In the case of an ice-covered roadway, the tilting of the profile block element is however disadvantageous because, as a profile block passes through the ground contact patch, the contact area between the profile block elements present in the profile block and the ice-covered roadway is reduced as a result, such that only a reduced contact area can contribute to the traction between pneumatic vehicle tire and roadway.

[0010] This conflict of aims between snow performance and ice performance in the context of grip on snow and grip on ice can be allowed for by providing a band profile in a circumferential rib of the profile of the pneumatic vehicle tire tread.
Here, the circumferential rib runs once around the circumference of the tire and has a fixed position in an axial direction A of the pneumatic vehicle tire. The axial direction A of the pneumatic vehicle tire is in this case the direction of the axis about which the pneumatic vehicle tire mounted on a wheel rim rotates in a vehicle. Such a circumferential rib is correspondingly delimited in the axial direction A by two circumferential channels. Those sides of said circumferential channels which delimit the circumferential rib then preferably run parallel to one another and preferably run in a circumferential direction perpendicular to the axial direction A. Those sides of the circumferential channels which delimit the circumferential rib, or the edge of the circumferential rib, then have/has no directional component in the axial direction.
Here, the circumferential rib in the form of a band profile has sipes at regular spacing intervals in the circumferential direction. Since such a circumferential rib has no profile blocks that are separated by channels, in particular transverse channels that are transverse with respect to the circumferential direction, the rib elements formed in the circumferential rib by the sipes tilt to a reduced degree as said rib elements pass through the ground contact patch. On the other hand, the rib elements are in this case even supported so well that the sipes no longer open far wide enough to allow the grip edges that arise as a result to impart their full action on snow. In the case of such a circumferential rib, the snow-on-snow friction is also only low, and is based only on the circumferential channels of full profile depth that delimit said circumferential rib.
[0011 'The circumferential rib is positioned in the middle, and preferably centrally, in the axial direction A. A circumferential rib is situated in the middle if, in the axial direction A, there are further profile elements such as profile blocks situated between the circumferential rib and the tire shoulder situated closest to said circumferential rib. A circumferential rib is a central circumferential rib if it is positioned centrally in the tread of the pneumatic vehicle tire in the axial direction A, and thus those sides of the two circumferential channels which delimit said circumferential rib have the same spacing to the tire shoulder that is situated closest in the axial direction A.
[001211f, in such circumferential ribs, the sipes of the band profile have edge elevations at the edge of the circumferential rib, which edge elevations are situated in succession in the circumferential direction, this leads to increased circumferential stiffness of the circumferential rib at its edges, increasing wear in this region of the circumferential rib.
[0013]EP 3 444 129 Al has disclosed middle circumferential ribs with improved snow-on-snow friction, with a band profile in which straight sipes and channels, which are angled relative to the axial direction A, alternate in a circumferential direction, and the channels additionally have a bevel at their ends.
[0014]US 2020/0031171 Al has disclosed a central circumferential rib which, at regular spacing intervals in a circumferential direction, has straight sipes which are angled relative to the axial direction A, wherein, at eight times the length of the spacing interval of the sipes in the circumferential direction, a thin transverse channel is arranged in the central circumferential rib in place of a sipe, which thin transverse channel is angled to the same degree relative to the axial direction A.
Said transverse channels have, in their end regions, a depression with a greater depth than the transverse channel and with the same depth as the circumferential channels that delimit the circumferential rib. Those sides of said circumferential channels which delimit the circumferential rib have a zigzag shape relative to the axial direction A, and do not run parallel to one another.
[0015]US 2018/0345734 Al has disclosed middle circumferential ribs of a pneumatic vehicle tire with good snow and ice performance, which, at regular spacing intervals in a circumferential direction, have straight sipes which are angled relative to the axial direction A, wherein, at five times the length of the spacing interval of the sipes in the circumferential direction, a thin transverse channel is arranged in the middle circumferential rib in place of a sipe, which thin transverse channel is angled to the same degree relative to the axial direction A. These transverse channels have, in their end regions, a depression with a greater depth than the transverse channel in the middle of the circumferential rib.
[0016]EP 3 421 263 B1 has disclosed middle circumferential ribs of a pneumatic vehicle tire with good snow performance, which middle circumferential ribs have, at regular spacing intervals in a circumferential direction, straight sipes that are angled relative to the axial direction A, wherein part of every second sipe is replaced by a transverse channel that is deeper than the sipes.
[0017]US 2018/0290498 Al has disclosed circumferential ribs in the shoulder region of a pneumatic vehicle tire, which circumferential ribs have sipes at regular spacing intervals in a circumferential direction, wherein, in the case of every fifth sipe in the circumferential direction, the end regions have a channel portion that has a greater width than the sipe and a greater depth than the sipe. The channel portions are provided for filling with snow when driving on a snow-covered roadway.
[0018] Despite the profile structures that are already known, the problem addressed remains that of even more effectively resolving the conflict between snow and ice performance, whilst allowing for reduced tire wear resulting from abrasion.
Summary of the invention (0019] The object is achieved by a pneumatic vehicle tire as claimed in claim 1.
[0020]Such a pneumatic vehicle tire has a tread which has a profile and has a middle circumferential rib delimited by two sides, running at least approximately parallel to one another, of two circumferential channels which encircle the entire pneumatic vehicle tire, which circumferential channels run at least approximately perpendicular to the axial direction A of the pneumatic vehicle tire in that they only deviate by an angle y 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 thus remains constant or increases with increasing profile depth, wherein the circumferential rib has, at regular spacing intervals d in a circumferential direction, a sipe which runs from one to the other of the mutually parallel sides of the two encircling circumferential channels along a contour line, and wherein, at three to seven times the length of the spacing interval d of the sipes in the circumferential direction, in each case one thin transverse channel is arranged in the middle circumferential rib in place of a sipe, the width BQ of which thin transverse channel is at least 2.5 times the width BF of a sipe and which thin transverse channel has the contour line of the sipes, and wherein the depth TF of the sipes is at least partially reduced, over a length Lred of the contour line, in the end regions of the sipes, and, over 80% to 250% of said length Lred of the contour line, the thin transverse channels have in their end regions a snow pocket which has a width Bs perpendicular to the contour line of at least 1.5 times the width Bq of the thin transverse channel and has a depth Ts of at most 65% of the profile depth To of the thin transverse channel.
(0021]A pneumatic vehicle tire according to the invention thus has a tread with a profile that has two circumferential channels that encircle the entire tire.
The two circumferential channels are adjacent circumferential channels, between which a middle circumferential rib is situated in the tread.
[0022] Each circumferential channel of a pneumatic vehicle tire now has two sides in the axial direction A of the pneumatic vehicle tire, if one considers the cross section thereof perpendicular to the circumferential direction. In relation to the lowest point of the cross section of the circumferential channel, the spacing of which to the surface of the tread corresponds to the profile depth of the pneumatic vehicle tire, the two sides are situated on one or the other side of the lowest point of the cross section in the axial direction A. Here, the two sides of the circumferential channel delimit a circumferential rib composed of the rubber material of the tread.
The sides, facing toward one another, of two adjacent encircling circumferential channels then jointly delimit a circumferential rib of the profile of the tread.
[0023] In a pneumatic vehicle tire according to the invention, those sides of the two circumferential channels which delimit the circumferential rib run at least approximately parallel to one another and at least approximately perpendicular to the axial direction A of the pneumatic vehicle tire. Here, the sides that delimit the circumferential rib only deviate by an angle y of less than 150 from the radial direction of a plane perpendicular to the axial direction A. 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 profile depth. The two sides that delimit the circumferential rib thus run parallel to the circumferential direction of the pneumatic vehicle tire and have only the small deviation, defined by the angle y, from the radial direction of the pneumatic vehicle tire. The radial direction of the pneumatic vehicle tire is perpendicular to the axial direction A thereof, about which said pneumatic vehicle tire rotates. Inwardly along the radial direction, that is to say in the direction of the middle of the pneumatic vehicle tire, the profile depth of the tire profile increases. The sides that delimit the circumferential rib now deviate from the radial direction of the pneumatic vehicle tire by the angle y such that the width of the circumferential rib remains constant or increases with increasing profile depth, that is to say inwardly. The circumferential rib then correspondingly has a constant width B in the axial direction A, at the surface and at every profile depth, over the entire circumference of the pneumatic vehicle tire according to the invention, said width being defined by the spacing of the at least approximately parallel sides in the axial direction, though said width may increase inwardly in accordance with the angle y, which varies with the profile depth. In one preferred embodiment, the two sides, which delimit the circumferential rib, of the two parallel circumferential channels are situated in two parallel planes that are perpendicular to the axial direction A. Then, other than in the bottom region of the circumferential channels, the angle y is 0 over the profile depth, and the width B is constant over the profile depth of the profile. In one particularly preferred embodiment, the two circumferential channels themselves, which delimit the circumferential rib, also run parallel to one another in two planes perpendicular to the axial direction A, that is to say the lowest point of the cross section of the circumferential channels perpendicular to the circumferential direction is situated, over the entire tire circumference, in in each case one of the two planes perpendicular to the axial direction A. Here, the two circumferential channels particularly preferably both have the same width in the axial direction A
over the entire tire circumference. Here, pure manufacturing tolerances in the production of the tire profile are not taken into consideration with regard to the design of the circumferential channels.
[0024]Typically, the width B in the axial direction A of the circumferential rib at the surface thereof is 17 mm to 40 mm, preferably 20 mm to 30 mm, and particularly preferably 22 mm to 28 mm, in the new state of the pneumatic vehicle tire.
[0025] Here, the circumferential rib has sipes at regular spacing intervals d in the circumferential direction. The sipes present in the circumferential rib run from one to the other of the mutually parallel sides, which delimit the circumferential rib, of the two encircling circumferential channels along a contour line. The sipes thus run from one end of the circumferential rib in the axial direction A, which is formed by one side of one of the two encircling circumferential channels, to the other end of the circumferential rib in the axial direction A, which is formed by one side of the second of the two encircling circumferential channels. Here, all of the sipes run along a fixed contour line which likewise runs from one end of the circumferential rib in the axial direction A to the other end of the circumferential rib in the axial direction A. The contour line defines the course of the sipes at the surface of the tread irrespective of the circumferential position of the sipe. The contour line is in this case merely the main line along which the sipes run from one end of the circumferential rib to the other end of the circumferential rib. The actual course of the sipe at the surface of the tread may deviate from this main line, because the main line may in this case also have added to it a course of the sipe which, substantially in the surface of the tread, has a component perpendicular to the main line, that is to say which, in the surface of the tread, runs primarily perpendicular to the contour line. Here, the dimension of the deviation from the main line is considerably smaller than the width B of the circumferential rib in the axial direction A. Typically, the dimension of the deviation is at most 15% of the width B of the circumferential rib, preferably at most 5% of the width B of the circumferential rib and particularly preferably 3% of the width B of the circumferential rib. The course thus added has its main component, that is to say its main course direction, in a direction that typically deviates by no more than 20 from the perpendicular to the contour line in the surface of the tread, preferably deviates by no more than 50 from the perpendicular to the contour line on the surface of the tread, and particularly preferably deviates by no more than 2 from the perpendicular to the contour line on the surface of the tread. The added course typically oscillates or meanders in the direction of the main component about the contour line, or in this direction has a zigzag course or some other periodic course, wherein the period may vary along the contour line. The added course is preferably present only over a part of the contour line. The sipes extend in a radial direction of the pneumatic vehicle tire from the surface of the circumferential rib to a depth TF, whilst following their course at the surface of the tread. Here, sipes which are adjacent in the circumferential direction have approximately the same spacing interval dn in the circumferential direction, and preferably run parallel to one another.
The spacing interval dn of adjacent sipes in the circumferential direction typically varies here, over the entire circumference of the tire, by at most 10% of the average spacing interval d, preferably by at most 5% of the average spacing interval d and particularly preferably by at most 2% of the average spacing interval d. This is based in particular only on manufacturing tolerances during the course of the production of the pneumatic vehicle tire. Typically, the regular spacing interval d of the sipes in the circumferential direction at 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.
[0026]At three to seven times the length of the spacing interval d of the sipes in the circumferential direction, in each case one thin transverse channel is arranged in the circumferential rib of the pneumatic vehicle tires according to the invention in place of these sipes. These thin transverse channels may each be arranged in the circumferential channel with uniform spacing intervals, or preferably with different spacing intervals, in the circumferential direction, wherein the spacing of the thin transverse channels in the circumferential direction is in each case a multiple of the spacing interval d of the sipes in the circumferential direction. Improved acoustic behavior of the pneumatic vehicle tire according to the invention is achieved with an arrangement of the thin transverse channels with different spacings in the circumferential direction, because vibrations owing to a particular resonance period in the circumferential direction are thereby avoided owing to the thin transverse ribs in the circumferential rib.
[0027]The width BQ of the thin transverse channel in the middle 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 middle circumferential rib, preferably 2.5 to 5 times the width BF
of a sipe, particularly preferably 2.75 to 4.5 times the width BE of a sipe, and most preferably 2.8 to 4 times the width BE of a sipe. The width BQ of the thin transverse channels and the width BE of the sipes is the width perpendicular to the common contour line of the thin transverse channels and sipes.
[0028]Specifically, the thin transverse channels in the middle circumferential rib of the pneumatic vehicle tire according to the invention have the contour line of the sipes. In this way, the transverse channels and sipes of the middle circumferential rib have substantially the same shape at the surface of the tread of a vehicle tire according to the invention. The thin transverse channels thus follow the same contour line as the sipes. Here, the contour line of a thin transverse channel and that of an adjacent sipe run parallel to one another so as to be offset in the circumferential direction by the spacing interval d. It is essential that each thin transverse channel runs along the contour line and cannot also, like a sipe, have an added course that substantially has a component perpendicular to the contour line.
The thin transverse channels extend in a radial direction of the pneumatic vehicle tire from the surface of the circumferential rib to a depth TQ, whilst following their course at the surface of the tread.
[0029] The depth TF of the sipes of the middle circumferential rib of the pneumatic vehicle tire according to the invention is at least partially reduced, over a length Lred of the contour line, in the end regions of the sipes. The depth TF of such a sipe is thus limited to a reduced depth TF,1 in one end region or both end regions of the sipe, which are adjacent to the two circumferential channels that delimit the circumferential rib. Such a sipe then has one edge elevation or two edge elevations.
It is possible for only some of the sipes or for all of the sipes of the middle circumferential rib to have one or two such edge elevations. The reduction of the depth TF may be the same or different for all sipes with an edge elevation.
The length Lred Of the contour line in which an edge elevation is present begins in each case at one end of the surface of the circumferential rib in the axial direction A, that is to say at one of the two sides of one of the two circumferential channels that delimit the circumferential rib, and then ends at a particular point of the contour line.
[0030] Over an approximately equal or greater length Ls, specifically over 80%
to 250% of said length Lred of the contour line, the thin transverse channels of the circumferential rib have a snow pocket in their end regions. Such a snow pocket at the ends of the thin transverse channel thus extends over said length Ls along the contour line, likewise beginning at one of the two sides of one of the two circumferential channels that delimit the circumferential rib. The task of such a snow pocket, which constitutes a cavity in the tire profile, is to quickly fill with snow from the roadway during driving operation, such that increased grip on snow is achieved, owing to snow-on-snow friction, correspondingly quickly.
[0031] Here, the snow pockets at the ends of the thin transverse channels have a width Bs perpendicular to the contour line of the thin transverse channels, and measured parallel to the tire surface on which the contour line runs, of at least 1.5 times the width Bo of the thin transverse channel, and a depth Is of at most 65% of the profile depth TQ of the thin transverse channel. The further geometrical dimensions of the snow pockets provided in the middle circumferential rib of a pneumatic vehicle tire according to the invention are thus coupled to the dimensions of the thin transverse channels in the circumferential rib. Said snow pockets are wider than the thin transverse channels, specifically at least 1.5 times the width of the thin transverse channels, perpendicularly with respect to the contour line of the thin transverse channels, which is indeed also the contour line of the sipes.
By contrast, the depth TS of said snow pockets is smaller than the profile depth To of the thin transverse channel, specifically such that the depth TS of said snow pockets amounts to at most 65% of the profile depth To of the thin transverse channel.
Here, the depth TS of the snow pockets and the profile depth To of the thin transverse channels respectively denotes the extent of the snow pockets or thin transverse channels in the radial direction of the pneumatic vehicle tire proceeding from the surface of the tread of the pneumatic vehicle tire. Here, the radial direction points inward from the tire surface to the axis of rotation of the pneumatic vehicle tire, and is perpendicular thereto. Thus, in a middle circumferential rib of a pneumatic vehicle tire according to the invention, at the ends of thin transverse channels which run from one side of the circumferential rib to the other, there are provided snow pockets which, laterally, that is to say parallel to the tire surface, have an extent defined by a length LS along the contour line of the associated thin transverse channel and by a width Bs perpendicular to the contour line. Here, the width Bs is intentionally made greater than the width Bo of the thin transverse channel, and the length LS is chosen to be of a similar dimension to, or to be greater to a certain extent than, the length Lred of the edge elevations of the sipes of the circumferential rib.
Altogether, the snow pockets thus have, at the tire surface, a large cross-sectional area that can fill with snow during driving operation on a snow-covered roadway. Furthermore, the limited depth TS of the snow pockets results in fast filling of the snow pocket with snow, such that increased grip on snow owing to snow-on-snow friction is made possible quickly. Such grip is particularly advantageous if a vehicle has an anti-slip control (ASR) or anti-lock (ABS) system and is thus capable of quickly utilizing the improved friction.
[0032] Furthermore, a length LS of the snow pockets that amounts to over 80%
to 250% of the length Lred of the edge elevations of the sipes along the contour line has approximately the same dimension as the length Lred of the edge elevations, or is greater than the length Lred of the edge elevations. The snow pockets are thus intentionally positioned at the same position as the edge elevations of the sipes in

11 an axial direction, because the snow pockets, as cavities, thus counteract stiffening of the circumferential rib at this axial position, that is to say at its ends in the axial direction A, caused by the edge elevations, and thus the circumferential stiffness, that is to say the elasticity of the circumferential rib, is made more uniform in the axial direction A. This is conducive to more uniform wear of the tread of a pneumatic vehicle tire according to the invention. This homogenization is based on all dimensions of the snow pockets, that is to say not only their length Ls but also their width Bs and their depth Is.
[0033]Through the described provision of exactly defined snow pockets in the profile structure of a middle circumferential rib with uniform sipes, which are in part replaced by thin transverse channels, it is thus possible for both the snow-on-snow friction of a pneumatic vehicle tire, and at the same time the wear behavior of the pneumatic vehicle tire, to be improved.
[0034] In one preferred embodiment, the middle circumferential rib of the pneumatic vehicle tire according to the invention is its central circumferential rib. In this position, the circumferential rib is at least normally in direct contact with the roadway during driving operation, such that the snow pockets of the circumferential direction then quickly fill with snow with the greatest certainty in the case of a snow-covered roadway, with snow-on-snow friction being established correspondingly quickly.
[0035]1n another embodiment, the thin transverse channels are, in the circumferential direction, arranged in the middle circumferential channel of the pneumatic vehicle tire according to the invention in place of a sipe over different multiples of the spacing interval d of the sipes in the circumferential direction.
Through this arrangement of the thin transverse channels at different spacing intervals over the tire circumference, wherein the sequence of the different multiples may nevertheless periodically repeat over the tire circumference, the acoustic behavior of the pneumatic vehicle tire according to the invention is improved, as already discussed above. The sequence of the multiples may for example consist of exactly two different multiples, for example four times and five times, which repeat irregularly or regularly. In this example, it is then the case that every fourth or fifth sipe is replaced by a thin transverse channel which, at its ends, has a snow pocket with the above-described dimensions.

12 [0036] In one preferred embodiment, at four to six times the length of the spacing interval d of the sipes in the circumferential direction, particularly preferably at four to five times the length of the spacing interval d of the sipes in the circumferential direction, the above-described thin transverse channel with its snow pockets is arranged in the middle circumferential rib of a pneumatic vehicle tire according to the invention in place of a sipe. In particular, with these spacing intervals of the thin transverse channels, tilting of the profile block elements in an appropriate form is achieved in order to realize both advantageous snow performance and advantageous ice performance owing to the circumferential rib.
[0037] Preferably, in the middle circumferential rib of a pneumatic vehicle tire according to the invention, the width Bo of the thin transverse channels is at most 5 times the width BF of a sipe. This, too, assists the tilting of the profile block elements in an appropriate form and prevents excessive tilting of individual profile block elements.
[0038] The snow pockets of the thin transverse channels of the middle circumferential rib of a pneumatic vehicle tire according to the invention are preferably arranged symmetrically with respect to the contour line of the thin transverse channels. This is conducive to uniform tilting of the profile block elements that are adjacent to the thin transverse channel.
[0039] The snow pockets of the thin transverse channels of the middle circumferential rib of a pneumatic vehicle tire according to the invention preferably have a width Bs perpendicular to the contour line of 2 to 3 times the width Bo of the thin transverse channel. The width BS of the snow pockets is particularly preferably 2.2 to 2.5 times the width BQ of the thin transverse channel. This is conducive to good snow-on-snow friction, at the same time with appropriate tilting of the profile block elements and uniform elasticity of the middle circumferential rib in the axial direction A.
[0040] The snow pockets of the thin transverse channels of the middle circumferential rib of a pneumatic vehicle tire according to the invention preferably have a depth Ts of 35 to 60% of the profile depth To of the thin transverse channel, particularly preferably 40% to 58% of the profile depth To of the thin transverse

13 channel, and very particularly preferably 50% to 55% of the profile depth of the thin transverse channel. This, too, is conducive to good snow-on-snow friction after a short time, at the same time with appropriate tilting of the profile block elements and uniform elasticity and thus uniform tire wear of the middle circumferential rib in the axial direction A.
[0041 I The thin transverse channels of the middle circumferential rib of a pneumatic vehicle tire according to the invention preferably had a snow pocket of length Ls in their end regions over 95% to 200% of the length Lred of the contour line over which the depth TF of the sipes is reduced in the end regions of the sipes, and said thin transverse channels particularly preferably had a snow pocket of length Ls over 105% to 130% of the length Led 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 elevations of the sipes and the position of the snow pockets is conducive to highly uniform elasticity, in the axial direction A, of the middle circumferential rib in the axial direction A. There is then in particular also approximately the same circumferential stiffness at the sides of the circumferential rib, despite the elevations of the sipes, as in the middle of the circumferential rib. As a result, the wear of the rubber material of the circumferential rib is also at least approximately uniform over the entire width of the circumferential rib in the axial direction.
[0042] The thin transverse channels of the middle circumferential rib of a pneumatic vehicle tire according to the invention preferably have a snow pocket in their end regions over a length Ls of the contour line of 2.5 mm to 8 mm, particularly preferably over a length Ls of the contour line of 3.5 mm to 7 mm and very particularly preferably over a length of the contour line of 4 mm to 5.5 mm. Here, both good snow-on-snow friction and highly uniform elasticity of the middle circumferential rib in the axial direction A are achieved.
[0043] The snow pockets of the thin transverse channels of the middle circumferential rib of a pneumatic vehicle tire according to the invention have a bottom region and side faces. The bottom region delimits the snow pockets in a radial direction at a depth Ts. Here, the depth Ts may however vary by up to 20%, preferably by up to 5% and particularly preferably by up to 1%, in the axial direction

14 and circumferential direction. The side faces delimit the snow pockets by way of faces which extend from the bottom face to the surface of the pneumatic vehicle tire. In particular, a side face may in this case run parallel to the contour line or, as an end face of the snow pocket, be perpendicular to the contour line. The face of the bottom region of the snow pockets preferably transitions with a curvature radius of 0.2 mm to 1.5 mm, particularly preferably with a curvature radius of 0.5 mm to 1.25 mm, and very particularly preferably with a curvature radius of 0.8 mm to 1.1 mm, into the side faces. This further improves the fast filling of the snow pockets with snow during driving operation on snow, which correspondingly leads more quickly to good snow-on-snow friction.
[0044] In one embodiment, the snow pockets of the thin transverse channels of the middle circumferential rib of a pneumatic vehicle tire according to the invention have a bottom region and an end face as a side face. The face of the bottom region typically transitions with a curvature radius of 0.2 mm to 1.5 mm, preferably with a curvature radius of 0.5 mm to 1.25 mm, and particularly preferably with a curvature radius of 0.8 mm to 1.1 mm, into the end face. This further improves the fast filling of the snow pockets with snow during driving operation on snow, which correspondingly leads more quickly to good snow-on-snow friction.
[0045]Typically, the snow pockets of the thin transverse channels of the middle circumferential rib of a pneumatic vehicle tire according to the invention have a bottom region that continues inward in a radial direction, that is to say in the direction of the middle of the pneumatic vehicle tire, with a sipe along the contour line. This promotes the tilting of the profile block elements in the circumferential rib, in particular the tilting of the profile block elements adjacent to the respective transverse channel, which is thus not reduced by the depth Ts of the snow pockets being reduced in relation to the profile depth To of the thin transverse ribs.
[0046] Here, the sipes in the bottom region of the snow pockets typically have the same width BF as those sipes of the circumferential rib which have not been replaced by a thin transverse channel. This further promotes uniform tilting of the profile block elements over the circumference, and the uniformity of the elasticity of the circumferential rib in the axial direction A.

[0047] The sipes in the bottom region of the snow pockets preferably have the same depth TF as those sipes of the circumferential rib which have not been replaced by a thin transverse channel have in the middle of the circumferential rib. This, too, further promotes uniform tilting of the profile block elements over the circumference, and the uniformity of the elasticity of the circumferential rib in the axial direction.
[0048] In one embodiment, the contour line of the sipes of the middle 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 encircling circumferential channels.
[0049] In one embodiment, the contour line of the sipes of the middle circumferential rib of a pneumatic vehicle tire according to the invention is angled slightly in the middle of the circumferential rib. In this case, the contour line may thus be formed by two straight lines which are angled relative to one another and which enclose an angle 8 of 140 to 170 , preferably an angle 13 of 150 to 165 .
[0050] In particular embodiments of a pneumatic vehicle tire according to the invention, the contour line of the sipes in the end region of the sipes deviates from the axial direction A of the pneumatic vehicle tire by an angle a of less than 20 , preferably less than 15 and particularly preferably less than 8 .
[005111n particular embodiments of a pneumatic vehicle tire according to the invention, the sipes, running along the contour line, of the middle circumferential rib are of undulating form over a part of the contour line. In this part of the contour line, the actual course of the sipe deviates from the main line of the contour line.
The course of the sipe has added to it an undulating component perpendicular to the contour line. Instead of the undulating component, the course of the sipe may also have added to it a zigzag line and some other oscillating component.
[0052] In particular embodiments, the depth TF of the sipes is partially reduced, in each case over a length Lred of the contour line of 7% to 35% in one end region or preferably both end regions of the sipes, preferably over in each case a length Lred of the contour line of 12% to 30%, and particularly preferably over a length Lred of the contour line of 16% to 23%. The depth TF of all sipes is preferably reduced over such a length Lred of the contour line in both end regions of the sipes.
[0053] In other particular embodiments, the depth TF of the sipes is partially reduced, in each case over a length Lred of the contour line of 1.5 mm to 9 mm in one end region or preferably in both end regions of the sipes, preferably in each case over a length Lred of the contour line of 2.5 mm to 7.5 mm, and particularly in each case over a length Lred of the contour line of 3.5 mm to 5.5 mm. The depth TF of all sipes is preferably reduced over such a length Lred of the contour line in both end regions of the sipes.
(0054] In the abovementioned embodiments, the depth TF,1, TF,2 of the sipes in their end regions may be reduced to different extents in different sipes in order to make the circumferential stiffness more uniform in the circumferential direction.
In particular, in sipes that are successive in the circumferential direction, the depth TF
of the sipes in their end regions may be reduced alternately to a first depth TF,1 and a second depth TF,1-[0055]Typically, the depth TF of the sipes of the middle 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%.
(0056] In embodiments in which the depth TF,1, TF,2 of the sipes in their end regions is reduced to different extents in different sipes, the first depth TF,1 is typically reduced by 25% to 60% and the second depth TF,2 is typically 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 at its sides.
Brief description of the drawings [0057]The invention will now be explained in more detail on the basis of an exemplary embodiment, in which:

figure 1:
shows a detail of the surface of a tread of a pneumatic vehicle tire according to the invention across the entire width of the tread figure 2: shows a detail of the central circumferential rib of the pneumatic vehicle tire according to the invention shown in figure 1, in a circumferential direction figure 3: shows a 3-dimensional detail of the profile of the central circumferential rib of the pneumatic vehicle tire according to the invention shown in figure 1 Detailed description of the invention (0058] Figures 1 to 3 show an exemplary embodiment of a pneumatic vehicle tire according to the invention. A pneumatic vehicle tire of said type has a tread that is equipped with a profile. Figure 1 shows a detail of the surface of the tread 1 of the pneumatic vehicle tire according to the invention across its entire width.
Visible in the profile of the tread 1 are various profile elements, with a circumferential rib 3, a central circumferential rib, being shown in the middle of the tread 1. Said circumferential rib 3 extends in a direction of revolution over the entire circumference of the pneumatic vehicle tire according to the invention and is delimited by two circumferential channels 2, 2' that encircle the entire circumference of the pneumatic vehicle tire according to the invention. The two circumferential channels 2, 2' run parallel to one another and run perpendicular to the axial direction A of the pneumatic vehicle tire. Both circumferential channels 2, 2' have the same cross section, perpendicular to the circumferential direction, over the entire tire circumference. Here, both circumferential channels 2, 2' have two sides that delimit the two circumferential channels 2, 2' in the axial direction A. In each case one of the two sides 4, 4' of the circumferential channels 2, 2' delimits the circumferential rib 3. A detail of the circumferential rib 3 in a circumferential direction is likewise shown in figure 2. Said figure likewise shows the circumferential channels 2, 2' that delimit the circumferential rib 3, with their sides 4, 4' that delimit the circumferential rib 3. Figure 3 likewise shows the circumferential rib 3, this time in a three-dimensional illustration, with the circumferential rib 3 itself being shown in a developed view in a plane, as in figure 2. Here, in particular, a view of the circumferential rib 3 in an axial direction A is shown, with a short detail of the circumferential rib 3 in a circumferential direction U being shown. Here, too, it is possible to see the circumferential channels 2 and 2' that delimit the circumferential rib 3. Only in the case of the circumferential channel 2 at the bottom of the illustration is it also possible to see the side 4 of the circumferential channel 2, which side forms the edge of the circumferential rib 3. The sides 4, 4', which delimit the circumferential rib 3, of the circumferential channels 2,2' 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 spacing of the sides 4, 4' in the axial direction A then predefines a width B of the circumferential rib 3 which is constant in a radial direction of the tire, and which in the exemplary embodiment is 27 mm. The sides 4, 4' then transition, with a curvature in the bottom region of the circumferential channels 2, 2', into the channel base of the circumferential channels 2, 2', as shown in figure 3.
(0059] The circumferential rib is divided by sipes 6 which run across the entire width B of the circumferential rib 3 from one to the other of the mutually parallel sides 4, 4' of the two encircling circumferential channels 2, 2'. The sipes 6 have a regular spacing interval d to one another in the circumferential direction U, which in the exemplary embodiment is 5.5 mm at the surface of the circumferential rib 3.
Here, each sipe 6 runs along a contour line 10. The shape of the contour line 10 is the same for all sipes 6 in the circumferential rib 3. The contour line 10 is formed by two straight lines which each enclose an angle a of 15 with the axial direction A
and which intersect in the middle of the circumferential rib 3. Correspondingly, the two straight lines enclose an angle 8 of 150 with one another. Other than in the edge regions of the circumferential rib 3, an undulating line is superposed on said contour line 10 in the course of the sipes 6, such that the sipes 6 have an undulating course in the middle of the circumferential rib 3. Whilst the profile depth of the circumferential channels 2, 2' in the new state of the pneumatic vehicle tire is 8 mm, the depth TF of the sipes 6 in the middle of the circumferential rib 3 is 7 mm. In the end region of the sipes 6, the depth IF of the sipes 6 is reduced. In the exemplary embodiment, the depth TF is reduced at both end regions over 21% of the length Lred Of the contour line 10. In the exemplary embodiment, the depth TF of the contour line is reduced over the length Lred 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 sipes is reduced in the end regions to 50% of the profile depth TF, and is therefore 3.5 mm, over the same length Lred.

[0060]In the circumferential rib 3, the sipes 6 are replaced at certain spacing intervals in the circumferential direction U by a thin transverse channel 8.
In the exemplary embodiment shown, this spacing interval amounts alternately to four, five or six times the length of the spacing interval d of the sipes 6, in an irregular sequence. Here, the thin transverse channels 8 are arranged at irregular spacing intervals in order to avoid vibrations of the circumferential rib 3 owing to resonance that can result from a regular spacing of the thin transverse channels 8. In the exemplary embodiment, the width BQ of the thin transverse channels 8 is three times the width BE of the sipes 6. In the exemplary embodiment, the width BE of the sipes 6 is 0.5 mm, and the width BQ of the thin transverse channels 8 is correspondingly 1.5 mm. The profile depth TQ of the thin transverse channels is 8 mm. The transverse channels 8 run along the same contour line 10 as the sipes 6. Here, the sipes 8 run only along the contour line 10 and have no further component perpendicular to the contour line, as in the case of the undulating course of the sipes 6.
[0061] Furthermore, the thin transverse channels 8 each have a snow pocket 20 in their end regions. Here, the end region of the contour line 10 that extends from one circumferential channel 2 to the other circumferential channel 2', which circumferential channels delimit the circumferential rib 3, is that region of the contour line 10 which begins in each case at the circumferential channels 2 and 2' and then extends inward into the circumferential rib 3. Here, the snow pockets 20 then have a length LS along the contour line 10. In the exemplary embodiment, the snow pockets 20 have a length LS equal to the length Led of the elevations of the sipes 6.
Correspondingly, the length LS of the snow pockets also amounts to 21% of the length of the contour line 10. Furthermore, the snow pockets 20 also have an extent parallel to the surface of the tread 1 perpendicularly with respect to the contour line 10. In the exemplary embodiment, this width BS of the snow pockets 20 is twice the width BQ of the thin transverse channels 8, and is therefore 3 mm.
Furthermore, the snow pockets 20 also have a depth TS in a radial direction. In the exemplary embodiment, the depth TS of the snow pockets 20 is exactly half the profile depth TQ of the thin transverse channels 8. Correspondingly, the profile depth Ts of the snow pockets has a value of 4 mm. Further details of the design of the snow pockets 20 can be seen in particular from figure 3. At the depth Ts, the snow pockets have a bottom region 21. In the exemplary embodiment shown, said bottom region 21 is substantially parallel to the surface of the tread 1. The snow pockets furthermore have side faces 22. In the exemplary embodiment shown, the side faces 22 firstly run parallel to the contour line 10 and perpendicular to the surface of the tread 1, such that the surfaces have a component in a radial direction.
Furthermore, one side face 22 of the snow pockets is configured as an end face 23, which is a face perpendicular to the contour line 10. Between the bottom region 21 and the side faces 22, in particular the end face 23, there is a transition with a curvature radius of 1 mm. Furthermore, the bottom region 21 of the snow pockets 20 has, in its middle, a sipe 25 that runs along the contour line 10 of the thin transverse channels 8. The width of the sipes 25 corresponds to the width BF of the sipes 6.
The depth of said sipes 25 corresponds to the depth TF of the other sipes 6 of the circumferential rib 3. As in all embodiments of the pneumatic vehicle tire according to the invention, the central circumferential rib 3 of the exemplary embodiment is distinguished by the fact that, owing to the snow pockets 20 that are provided, said central circumferential rib exhibits good snow-on-snow friction, which is available after a short time because the snow pockets 20 fill up quickly, and furthermore by uniform tilting of the profile block elements that are provided, resulting in a good compromise between snow behavior (snow performance) and ice behavior (ice performance) of the circumferential rib 3. The design of the snow pockets 20 furthermore allows very uniform elasticity or circumferential stiffness of the transverse rib 3 in the axial direction A. Here, the snow pockets 20 that are provided at the edge of the circumferential rib 3 substantially compensate for the elevations at the end of the sipes 6 of the circumferential rib 3. The structure of a middle circumferential rib of the pneumatic vehicle tire according to the invention has been discussed in detail on the basis of the described parameters of this description. This structure must be correspondingly adapted in each case 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 with a width of between 195 mm and 315 mm. The height of the tire may in this case amount to between 35% of the width of the pneumatic vehicle tire and 65% of the width of the pneumatic vehicle tire. The wheel rims on which such pneumatic vehicle tires are mounted can have a diameter of between 15 inches and 22 inches. A different number of sipes 6 and thin transverse channels 8 may be provided over the circumference of the pneumatic vehicle tire depending on the corresponding circumference of such a tire. Here, a number of sipes 6 and transverse channels 8 may increase with the circumference, or may increase with the circumference only to a certain proportion. Such a proportion may for example be between 5 and 20%.
In general, pneumatic vehicle tires according to the invention may of course also have other dimensions, as long as the advantageous characteristics of the described circumferential rib can be utilized in the pneumatic vehicle tire.
It is finally pointed out that the invention has been discussed on the basis of numerous detailed exemplary embodiments. These are however examples of the invention. Other embodiments of the pneumatic vehicle tire according to the invention may correspondingly also have only individual features of an exemplary embodiment, or features of different described exemplary embodiments simultaneously, unless explicitly stated otherwise.

List of reference signs 1 Tread 2, 2' Circumferential channel 3 Circumferential rib 4, 4' Side of a circumferential channel 6 Sipe 8 Thin transverse channel Contour line Snow pocket 21 Bottom region of a snow pocket 22 Side face of a snow pocket 23 End face of a snow pocket Sipe below a snow pocket A Axial direction B Width of the circumferential rib in axial direction A
BE Width of a sipe BQ Width of the thin transverse channel Bs Width of the snow pocket perpendicular to the contour line d Spacing of the sipes in circumferential direction dn Spacing of adjacent sipes in circumferential direction Lmd 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 region TF,2 Reduced depth of a second sipe in the edge region TQ Depth of the thin transverse channel Ts Depth of the snow pocket U Circumferential direction a Angle by which the contour line of the sipes in the end region of the sipes deviates from the axial direction A of the pneumatic vehicle tire 13 Angle enclosed between two straight lines which are at an angle with respect to one another and which form a contour line y Angle by which the two sides of two encircling circumferential channels that delimit the circumferential rib deviate in a radial direction from a plane perpendicular to the axial direction A

Claims (10)

Patent claims

1. A pneumatic vehicle tire having a tread (1) which has a profile and has 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 encircle the entire pneumatic vehicle tire, which circumferential channels run at least approximately perpendicular to the axial direction A of the pneumatic vehicle tire in that they only deviate by an angle y 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 regular spacing intervals d in a circumferential direction, a sipe (6) which runs from one to the other of the mutually parallel sides (4, 4') of the two encircling circumferential channels (2, 2') along a contour line (10), and wherein, at three to seven times the length of the spacing interval d of the sipes (6) in the circumferential direction, in each case one thin transverse channel (8) is arranged in the middle circumferential rib (3) in place of a sipe (6), the width BQ of which thin transverse channel is at least 2.5 times the width BF of a sipe (6) and which thin transverse channel has the contour line (10) of the sipes (6), and wherein 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 said 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 has a depth TS of at most 65% of the profile depth TQ of the thin transverse channel (8).

2. The pneumatic vehicle tire as claimed in patent claim 1, characterized in that the middle circumferential rib (3) is the central circumferential rib (3) of the pneumatic vehicle tire.

3. The pneumatic vehicle tire as claimed in patent claim 1 or 2, characterized in that the thin transverse channels (8) are, in the circumferential direction, arranged in the middle circumferential channel (3) in place of a sipe (6) over different multiples of the spacing interval d of the sipes (6) in the circumferential direction.

4. The pneumatic vehicle tire as claimed in 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. The pneumatic vehicle tire as claimed in 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. The pneumatic vehicle tire as claimed in 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. The pneumatic vehicle tire as claimed in at least one of patent claims 1 to 6, characterized in that the snow pockets (20) have a bottom region (21) that continues inward in a radial direction with a sipe (25) along the contour line (10).

8. The pneumatic vehicle tire as claimed in 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. The pneumatic vehicle tire as claimed in at least one of patent claims 1 to 8, characterized in that the sipes (6) running along the contour line (10) are of undulating form over a part of the contour line (10).

10. The pneumatic vehicle tire as claimed in 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%.