Tire having an improved tread pattern

Abstract

According to aspects of the invention, a tire for a vehicle comprising a tread is provided. The tread comprises a set of consecutive block patterns arranged along a circumference of the tire, each block pattern of the set of consecutive block patterns comprising a block and a first groove adjacent to the block. The set of consecutive block patterns comprises a first subset of first block patterns having a first pitch length, a second subset of n 2 second block patterns having a second pitch length greater than the first pitch length, and a third subset of n3 third block patterns having a third pitch length greater than the second pitch length, wherein Formula (I), and Formula (II).

Description

Tire having an improved tread pattern DESCRIPTION Field of the invention

[0001] The present invention relates to a vehicle tire. One possible applicationof the disclosed tire relates to a winter tire intended to equip a passenger vehicle orcommercial van vehicles. The disclosure can also be applied to other tires, for exampleall-season tires or tires for off the road applications.Background

[0002] Winter tires – which are used here as a typical example to facilitatereadability – are known for providing good grip on snow covered road surfaces whilealso providing good performance on dry and wet road surfaces.

[0003] For example, winter tires are known that comprise grooves that extendfrom a center of the tire’s tread, i.e., from the equatorial plane of the tire, towards ashoulder (sometimes also referred to as “shoulder portion“ or “side portion”) of the tire.These grooves, which typically extend in substantial axial direction, are configured todeliver water from a contact patch of the tire with the road outwards to provide contact between tire blocks and the road surface. Contact between blocks and the road is necessary to provide friction which provides for lateral road holding and further allows a driver to control the movement of the vehicle by accelerating, braking and / or steering.

[0004] For tires which are intended to be used on various ground conditions,such as wet, dry and snow-covered grounds, there are several design parameters which have to be optimized to provide good performance for all ground conditions. In some cases, optimizing a design parameter for one type of road condition may include some performance loss for other conditions. Thus, there is a need of improvement in various design parameters, targeting at parameters which have synergistic effects.

[0005] Thus, it is an object of the present invention to provide a tire havingimproved performance on all types of road surfaces, such as wet, dry and snow-covered roads. Summary of the invention

[0006] This object is achieved by providing an improved vehicle tire accordingto the independent claim. Further embodiments are described in the dependent claims.

[0007] According to aspects of the invention, a tire for a vehicle comprising atread is provided. The tread comprises a set of consecutive block patterns arranged along a circumference of the tire, each block pattern of the set of consecutive blockpatterns comprising a block and a first groove adjacent to the block. The set ofconsecutive block patterns comprises a first subset offirst block patterns having afirst pitch length, a second subset of ^^ second block patterns having a second pitchlength greater than the first pitch length, and a third subset of ^^third block patternshaving a third pitch length greater than the second pitch length, wherein≥ 10, 1 ≥^^ ≥ 0.^^^^ 50, and 3 ≥^^ ≥ 1.50.

[0008] Such a tire provides for improved characteristics, in particular for wintertires on snow-covered grounds. Generally, two different mechanisms are responsiblefor traction on snow-covered and dry or wet grounds.

[0009] For snow traction, it is necessary for the edges of a tread profile to diginto a snow surface, in order to achieve a sufficient friction force between the tire andthe ground to provide stability to a vehicle equipped with the tire. This can readily beachieved by providing blocks having relatively high flexibility which allows fordeformation of the block under strain. The deformation of a block leads to enhanced edge efficiency, i.e., edges of the block can dig into a snow-covered surface more efficiently, thus increasing the tire’s traction on such snow-covered surfaces, especially during driving maneuvers such as braking, accelerating and steering, but also lateral road holding may be improved.

[0010] Tire treads usually have block patterns with different pitch lengths, forexample tire treads often have three different pitch lengths, such that a tread often has three subsets of block patterns, where each subset comprises block patterns of onespecific pitch length. Commonly, tire treads contain a relatively low number of blockpatterns with a low pitch length.

[0011] In contrast, the tire according to the independent claim may include 10or more block patterns of the smallest pitch length. The blocks of block patterns with alower pitch length are generally more flexible, since a lower pitch length usuallytranslates to a smaller width of the respective block measured in circumferentialdirection. A block with smaller width consequently deforms more readily upon strain. Therefore, a tread pattern containing more block patterns of the smallest pitch length contains more blocks with this increased flexibility, such that the performance of the tire on snow-covered surfaces is improved due to the above-described mechanism.

[0012] At the same time, for driving maneuvers on dry or wet grounds, thetraction force between the tire and the road surface strongly depends on the surface area of rubber in contact with the road. This surface area can be increased by providingstiffer blocks, which then do not deform as readily under strain, such that a largersurface area of the rubber is in contact with the road. Thus, an increased flexibility ofblocks, while increasing traction on snow, may at the same time impair the tire’sperformance on dry grounds by reducing the rubber surface in contact with the roadduring critical driving maneuvers such as braking, accelerating and steering.

[0013] Therefore, it is desired to also keep a number of blocks in block patternswith a larger pitch length and which are therefore stiffer than the blocks in the blockpatterns with low pitch length. Therefore, a trade-off between block patterns with lowpitch length and higher pitch lengths needs to be made in order to achieve optimal performance on both snow-covered and dry or wet grounds.

[0014] It has been found that this can be most efficiently achieved by providinga ratio between the numbers of block patterns of the first and second pitch length, i.e.^^^^, in the claimed range.

[0015] In some aspects of the invention, this ratio may fulfil one or more of thefollowing inequalities:^^^^ ≥ 0.60, preferably^^^^ ≥ 0.70, more preferably^^^^ ≥ 0.80, mostpreferably 0.90 ≥^^^^ ≥ 0.85. These ranges provide for optimal trade-off betweenperformance on snow-covered road surfaces and dry or wet road surfaces.

[0016] In some aspects of the invention, the ratio between ^^ and ^^ may fulfilone or more of the following inequalities: 2.95 ≥^^ ≥ 1.55, prefe^^^^ rably 2.9 ≥^^ ≥ 1.55,more preferably 2.85 ≥^^^^ ≥ 1.6. These ranges provide for optimal trade-off betweenperformance on snow-covered road surfaces and dry or wet road surfaces.

[0017] In some aspects of the invention, one of the following inequalities maybe fulfilled: ^^ ≥ 13, preferably ^^ ≥ 15, more preferably ^^ ≥ 17. In other aspects ofthe invention, one of the following inequalities may be fulfilled: ^^ ≥ 20, preferably^^ ≥ 22, more preferably ^^ ≥ 25, even more preferably ^^ ≥ 27. The number of blockpatterns in these ranges provide for optimal performance on snow-covered roads by providing a large number of block patterns with low pitch length.

[0018] In some aspects of the invention, the first pitch length may be between22 and 27 mm, the second pitch length may between 27 and 33 mm, and the third pitchlength may be between 32 and 39 mm. In other aspects of the invention, the first pitchlength may be between 23 and 24 mm, the second pitch length may between 28 and 29mm, and the third pitch length may be between 33.5 and 34.5 mm.

[0019] In some aspects of the invention, the total number of block patterns maybe (^^ + ^^ + ^^) ≥ 60, preferably (^^ + ^^ + ^^) ≥ 64. In other aspects of theinvention, the total number of block patterns may be (^^ + ^^ + ^^) ≥ 70, preferably(^^ + ^^ + ^^) ≥ 72. This comparatively large number of block patterns providesadditional edges to the tread pattern, which enhances the tires performance on snow- covered surfaces.

[0020] In some aspects of the invention, if a ratio between a section width of thetire and an aspect ratio of the tire is between 2 mm and 5 mm, the tread tire may have afootprint width between 120 mm and 220 mm. In some aspects of the invention, if theratio between the section width of the tire and the aspect ratio of the tire is between 5mm and 8 mm, the tire may have a footprint width between 160 mm and 260 mm. Insome aspects of the invention, if the ratio between the section width of the tire and theaspect ratio of the tire is between 8 mm and 12 mm, the tire may have a footprint widthbetween 200 mm and 300 mm. This increased footprint width leads to a local stiffeningof the blocks again as well as to an increased surface area of rubber in contact with theroad, thus improving the tire’s traction on dry and wet grounds, especially during braking and accelerating, but also during cornering maneuvers. Thus, while the increased amount of block patterns with low pitch length provides increased traction on snow-covered grounds, as discussed above, the traction on dry and wet grounds may be impaired. By providing the same pitch configuration in combination with the increased footprint width mitigates this problem, such that performance on both snow-covered and dry or wet ground can be improved. In other words, the snow performancecan be improved without impairing the dry and wet performance.

[0021] In some aspects of the invention, the tread may have a skid depth ^^^^^,wherein 7.0 ≤ ^^^^^ ≤ 9.0, preferably 7.3 ≤ ^^^^^ ≤ 8.5, more preferably 7.4 ≤ ^^^^^ ≤8.4. In other aspects of the invention, the tread may have a skid depth ^^^^^, wherein8.0 ≤ ^^^^^ ≤ 8.6, preferably 8.1 ≤ ^^^^^ ≤ 8.5, more preferably 8.2 ≤ ^^^^^ ≤ 8.4. Thisskid depth also provides local stiffening of the blocks as compared to a greater skid depth, because with this lower skid depth, the blocks do not protrude as far radially outwards. Thus, this local stiffening of the blocks also improves the tire’s performance on dry and wet roads, leading to a good trade-off between snow-traction and dry / wet traction.

[0022] In some aspects of the invention, each block may comprise a plurality offirst sipes, and each first sipe may have a sipe depth ^ , where^^^^^ ^^^^ in 0.76 ≤^^^^^≤ 0.95,preferably 0.77 ≤^^^^^ ≤ 0.94, more preferably 0.78 ≤^^^^^^^^^^ ≤ 0.93. In other aspects ofthe invention, each first sipe may have a sipe depth ^^^^^, wherein 0.90^^^^^≤ 0.95,preferably 0.91 ≤^^^^^ ≤ 0.94, more pre^^^^^^^^^^ ferably 0.92 ≤^^^^^ ≤ 0.93. This ratio betweensipe depth and skid depth provides for sufficient flexibility on a block level, i.e., theflexibility of each individual block can be increased, leading to improved snowperformance. This further improves the trade-off between snow-covered and dry / wet road surfaces. In other words, on a scale of the entire tire tread, the tread provides improved flexibility via the block patterns with small pitch length. On a smaller scale, each block pattern may be stiffened by increasing the footprint width and decreasing the skid depth. On an even smaller scale, each block individually may increase its flexibility again by means of the sipe-to-skid-depth-ratio. Thus, snow performance of the tire can be improved while at the same time enhancing traction on dry and wet road surfaces. In some aspects of the invention, each block may comprise a first portion arranged at a central portion of the tire, and a second portion arranged in axial direction towards a shoulder of the tire with respect to the first portion. The first sipes may be arranged in at least one of the first portion and the second portion, and the atleast one of the first portion and the second portion may comprise a primary area and asecondary area located axially outward with respect to the primary area. Then, a first distance between two neighboring first sipes in the primary area may be smaller than asecond distance between two neighboring first sipes in the secondary area. In someaspects, the at least one of the first portion and the second portion may further comprises a tertiary area located axially outward with respect to the secondary area, and a third distance between two neighboring first sipes in the tertiary area may besmaller than the second distance between two neighboring first sipes in the secondaryarea. This further enhances traction on snow-covered roads, especially during braking,accelerating and steering, because by the increase in sipe density towards the edges ofthe block, the flexibility of the block is especially enhanced in those regions. Bydecreasing the distance between neighboring sipes near the outer areas of the block, e.g., near the leading and trailing edges, deformability of the block can be increased, leading to improved traction on snow, especially during braking and accelerating. By providing a higher distance between neighboring sipes in the central area of the block, in these regions the block is left less deformable, to still provide good traction on wet and dry grounds. Since the edges of the block are crucial for snow traction, it is especially advantageous to provide the lower distance between neighboring sipes especially near the edges of the block.

[0023] In some aspects of the invention, each block may be incised by at leastone second groove. Each second groove may comprise a protrusion protruding radiallyoutwardly from a bottom of the second groove. The protrusion may comprise a secondsipe. The second sipe may substantially follow a shape of the second groove. A ratiobetween a height of the protrusion and a skid depth of the tire may be between 0.3 and0.5 mm from a bottom of the tread. A width of the protrusion may match a width of thesecond groove. The second sipe may have a depth of between 40 and 70 % of a height ofthe protrusion.

[0024] The sipe allows for a local increase in flexibility of the block, while theprotrusion limits said flexibility. Thus, the second groove with the protrusion –particularly in the described dimensions – also provides for good trade-off betweenflexibility and stiffness, and thus for good performance on both snow-covered and dry or wet ground.

[0025] In some aspects of the invention, a ratio between void surface andrubber surface in a central portion of the tread may be higher than the ratio between the void surface and the rubber surface in a portion of the tread axially outwards withrespect to the central portion. In some aspects of the invention, the ratio between voidsurface and rubber surface in the central portion may be between 35.5 and 38.5.

[0026] In some aspects of the invention, the ratio between void surface andrubber surface in the portion of the tread axially outwards with respect to the centralportion may be between 31.5 and 34.5.

[0027] A higher ratio between void and rubber translates to increased flexibilityof the rubber parts. Thus, a void to rubber ratio in the described range provides for increased flexibility of the blocks at a central portion of the tire, while providing stiffer blocks at the shoulder of the tire. This further improves the balance between performance on snow-covered grounds and dry or wet grounds, especially in braking condition. Brief description of the drawings

[0028] Fig. 1 illustrates a sketch of a vehicle tire according to the presentinvention.

[0029] Fig. 2 illustrates a tread pattern of a tire according to the presentinvention.

[0030] Fig. 3 illustrates two blocks of the tread pattern according to the presentinvention.

[0031] Fig. 4 illustrates a portion of the tread pattern, particularly the distancesbetween neighboring sipes.

[0032] Fig. 5 illustrates a three-dimensional view of a block according to thepresent invention. Detailed description

[0033] Fig. 1 shows a sketch of a vehicle tire according to the present disclosure.

[0034] According to Fig. 1, the tire 100 comprises a tread 110. The treadcomprises a set of consecutive blocks 10 as well as grooves 20 arranged between twoblocks 10 of the set of consecutive blocks. Moreover, a sipe may be arranged within each of the set of consecutive blocks 10.

[0035] The blocks may be arranged consecutively along a circumferentialdirection 120 of the tire.

[0036] A “groove” represents an incision in the tread pattern. A width of thegroove may vary, for example, the first groove may be of larger width than the second groove, or may be of equal or even smaller width. For example, the width of a groove may be at least 2 mm. The width of a single groove does not necessarily have to be constant: For example, a groove can have a wider width towards the opening of the tread pattern, and a smaller width in radial inward direction. Also, a depth of a groovemay vary, and sometimes a groove may extend at full tread depth (with the full tread depth being the maximum distance between the radially outermost part of the tire to the bottom of the deepest groove, measured in radial direction), but this does not necessarily have to be the case. The full tread depth is sometimes also denoted as the“skid depth”. For example, a groove depth of least 1 mm, preferably at least 3 mm, isconsidered.

[0037] A “sipe” also represents an incision in the tread pattern. For example,the width of sipe may be smaller than the width of a groove, and may for example be less than 2 mm. Just as is the case for the groove, the width of a sipe does not have to be constant, and means can be applied to allow for a wider width towards the opening of the tread pattern, and a smaller width in radial inward direction. Also, a depth of a sipemay vary, and sometimes a sipe may extend at full depth, but this does not necessarilyhave to be the case. For example, a sipe depth of least 1 mm, preferably at least 20% of the skid depth is considered.

[0038] Within the context of the present disclosure, “circumferential direction”120 means a direction perpendicular to an axial direction 130 which is parallel to thedirection in which the tire usually rolls, i.e., parallel to a tangential direction with respect to the circumference of the tire. With respect to Fig.1, the circumferential direction 120 is thus a direction which is within a plane parallel to the yz-plane.

[0039] Within the context of the present disclosure, “axial direction” 130 meansa direction parallel to the direction of an axis of a vehicle on which the tire is usually mounted. Thus, according to Fig.1, the axial direction 130 is parallel to the x-axis and thus perpendicular to the yz-plane.

[0040] Within the context of the present disclosure, “radial direction” 140means a direction perpendicular to the axial direction. The radial direction is parallel to a connection of a center 150 of the tire with the tread surface. Thus, the radial direction is within a plane parallel to the yz-plane and generally perpendicular to the axial direction 130 and the circumferential direction 120.

[0041] Within the context of the present disclosure, the “equatorial plane” refersto a plane which is perpendicular to the axial direction 130 and cuts the section width ofthe tire in two halves of equal width. Thus, the equatorial plane is parallel to the yz- plane and corresponds to the widthwise centerline of the tread.

[0042] Within the context of the present disclosure, the “pitch length” meansthe length of a block pattern, i.e, a block and a first groove adjacent to the block,measured in the circumferential direction of the tire. For example, the “pitch length”may correspond to the arc length, measured alongside the circumference of the tire,between one point belonging to a pitch and a homologous point of a subsequent pitch. E.g., the pitch length may be the arc length between a point on a leading / trailing edge of one block and the corresponding point on the leading / trailing edge of the subsequent block.

[0043] Also, any numeral angles given herein are to be considered absolutevalues, i.e., not limiting to the orientation of the respective angle.

[0044] Fig. 2 illustrates a tread pattern of a tire according to the presentinvention. The tread pattern of Fig. 2 may for example be placed on the tread 110 of tire100 according to Fig.1.

[0045] According to Fig. 2, the tread may comprise a set of consecutive blockpatterns 12, 14, 16 arranged along a circumference of the tire, each block pattern of theset of consecutive block patterns comprising a block 12a, 14a, 16a and a first groove 12b,14b, 16b adjacent to the block. Block patterns 12, 14, 16 may be arranged on both sidesof equatorial plane 18 of the tire. In some cases, the width of both, the blocks 12a, 14a,16a and the grooves 12b, 14b, 16b may be different for each pitch. In other examples,the width of only one of the blocks 12a, 14a, 16a and the grooves 12b, 14b, 16b may bedifferent for each pitch, while the other of the blocks 12a, 14a, 16a and the grooves 12b,14b, 16b may be the same for all pitches.

[0046] For example, the first block pattern 12 may comprise block 12a andgroove 12b. The second block pattern 14 may comprise block 14a and groove 14b. Thethird block pattern 16 may comprise block 16a and groove 16b.

[0047] In some aspects of the invention, each block pattern of the set ofconsecutive block patterns may consist of a block and a first groove adjacent to theblock.

[0048] In some embodiments, the tread may comprise blocks on both sides ofthe equatorial plane 18 of the tire. In some embodiments described elsewhere herein,these blocks may have axisymmetric configuration, such that the overall pattern is V-Shaped. In other embodiments described elsewhere herein, the blocks on both sides ofthe equatorial plane 18 may be point-symmetric, such that the overall pattern is S- shaped. In any case, the present disclosure is not directed at a specific orientation of the blocks but can be applied to blocks of various shapes and orientations.

[0049] Moreover, while the present disclosure is described with respect to treadpatterns which are generally symmetric, i.e., having same or similar tread configuration on both sides of the equatorial plane, it will be understood that the concept described herein can also be applied in asymmetric tread patterns, i.e., in patterns have substantially different tread configurations on both sides of the equatorial plane of the tire.

[0050] Generally, the blocks 12a, 14a, 16a of each block pattern 12, 14, 16 havethe purpose of providing contact to the ground when the tire is in rolling condition. The edges as well as the surfaces of the blocks are configured to provide a friction force between the tire and the ground for grip, allowing general roadholding as well as movement control of the vehicle by a driver of a vehicle by acceleration, braking or steering.

[0051] According to Fig. 2, each block pattern 12, 14, 16 may further comprise afirst groove 12b, 14b, 16b. Each of the first grooves may be arranged adjacent to a block12a, 14a, 16a of the respective block pattern. Preferably, alternating blocks and firstgrooves may be placed over the entire circumference of the tire.

[0052] “Consecutive block patterns” within the context of this disclosure meansthat the tread comprises multiple block patterns following one another in succession over the circumference of the tire. While it is preferred that the invention according to the present disclosure is provided for all block patterns of the tire, it is possible that some individual block patterns, which may be arranged between other block patterns of the set of consecutive block patterns, are not arranged as described herein.

[0053] Although Fig. 2 illustrates a specific order in which block patterns maybe arranged (i.e., a first block pattern 12, followed by a second block pattern 14, followed by a third block pattern 16), other orders of block patterns of the different subsets of block patterns are possible. The order of block patterns of different subsets of block patterns may vary over the circumference of the tire. If block patterns are arranged on both sides of the equatorial plane 18 of the tire, the order of the blockpatterns may be the same on both sides of the equatorial plane 18.

[0054] Preferably, the first grooves 12b, 14b, 16b may start near the equatorialplane 18 of the tire and extend towards a shoulder end of the tread to open at the outeredge of the tire. Each first groove 12b, 14b, 16b may be delimited by two adjacent blocks12a, 14a, 16a, and more precisely by the two adjacent blocks’ respective edges facingtowards the first groove. For example, groove 14b may be delimited by block 12a andblock 14a, and groove 16b may be delimited by block 14a and block 16a.

[0055] The purpose of the first grooves 12b, 14b, 16b is mainly the drainage ofwater from the contact patch by guiding the water along the first groove 12b, 14b, 16btowards the shoulder of the tire and eject the water from there, as the tire rolls on theground. Thus, the first grooves 12b, 14b, 16b provide for improved performance of thetire, especially in wet road conditions. Further, as the first grooves 12b, 14b, 16b delimitthe blocks 12a, 14a, 16a, they also provide edges for the blocks for improved snowperformance. Moreover, the first grooves 12b, 14b, 16b allow for improved wearperformance, as they allow more flexibility of the tread elements, such that slippage ofthe blocks 12a, 14a, 16a over the ground is reduced, leading to a decrease in theabrasion effects leading to wear.

[0056] In some aspects, the set of consecutive block patterns may comprise afirst subset of ^^first block patterns 12 having a first pitch length 122, a second subset of ^^second block patterns 14 having a second pitch length 142 greater than the firstpitch length 122, and a third subset of ^^ third block patterns 16 having a third pitchlength 162 greater than the second pitch length 142.

[0057] In some aspects, the set of consecutive block patterns may consist of afirst subset of ^^first block patterns 12 having a first pitch length 122, a second subset of ^^second block patterns 14 having a second pitch length 142 greater than the first pitch length 122, and a third subset of ^^third block patterns 16 having a third pitch length 162 greater than the second pitch length 142.

[0058] In other words, the tread may comprise block patterns with threedifferent pitch lengths, namely ^^block patterns with the first, shortest pitch length, ^^block patterns with the second, intermediate pitch length and ^^ block patterns withthe third, largest pitch length.

[0059] Thus, in some aspects, the complete tire tread may consist of orcomprise (^^ + ^^ + ^^) block patterns in total. In some aspects, the total number ofblock patterns may be at least 60, i.e., (^^ + ^^ + ^^) ≥ 60. In some aspects, the totalnumber of block patterns may be at least 64, i.e., (^^ + ^^ + ^^) ≥ 64. In otherembodiments, the total number of block patterns may be at least 70, or at least 72, i.e.,(^^ + ^^ + ^^) ≥ 70 or (^^ + ^^ + ^^) ≥ 72. A large number of block patterns directlytranslates to a large number of blocks. Thus, the large number of block patterns furtherprovides an increased number of block edges. The block edges contribute to the frictionforce between the tire and the ground and especially allow for the tread to dig into snowy surfaces, leading to improved traction of the tire, especially on snow-covered roads.

[0060] In some aspects, the tread may comprise at least 10 block patterns of thefirst, shortest pitch length, i.e.,≥ 10. In some preferred embodiments, the numberof block patterns with the shortest pitch length may be higher, for example≥ 13,^^ ≥ 15, or ^^ ≥ 17. In other embodiments, the number of block patterns with theshortest pitch length may be even higher, for example≥ 20,≥ 22,≥ 25, or^^ ≥ 27. As discussed in more detailed above, a great number of block patterns withlow pitch length provides for a larger quantity of more flexible blocks. The blocks with improved flexibility provide for enhanced performance on snow-covered road surfaces. Therefore, increasing said number of block patterns with the shortest pitch length improves the overall snow performance of the tire.

[0061] In some aspects of the invention, the first pitch length may be between23 and 24 mm, the second pitch length may be between 28 and 29 mm, and the thirdpitch length may be between 33.5 and 34.5 mm.

[0062] In some aspects of the invention, the ratio between the numberoffirst block patterns and the number ^^of second block patterns may be between 0.50and 1, i.e., 1 ≥^^≥ 0.50. In other words, the quantity of first block patterns may be atleast half the number of second block patterns, and at most equal the number of secondblock patterns. In some aspects of the invention, the ratio between ^^ and ^^ may bleast 0.50, i.e.,^e at^^^ ≥ 0.50. In some aspects of the invention, the ratio betweenand ^^may be at least 0.55, i.e.,^^≥ 0.55. In some aspects of the invention, the ratio between^ and ^^may be at least 0.70, i.e.,^^≥ 0.70. In some aspects of the invention, thebetweenand ^^ may be at least 0.55 and at most 0.90, i.e., 0.90 ≥^^≥ 0.55.

[0063] As discussed above, a higher number of block patterns with small pitchlengths may improve snow performance of the tire, while at the same time, the performance on dry and / or wet road surfaces may be impaired. Thus, especially forwinter tires, it is desirable to provide a satisfactory tradeoff between snow and dry orwet performance. Such a tradeoff can be readily achieved by providing numbers of the first block patterns and second block patterns in the above-described ranges.

[0064] In some aspects of the invention, a ratio between the number ^^ of blockpatterns with the third, largest pitch length and the number ^^ of block patterns withthe second pitch length may be between 1.50 and 3, i.e., 3 ≥^^^^ ≥ 1.50. In some aspectsof the invention, the ratio between ^^ and ^^ may be between 1.55 and 2.95, i.e., 2.95 ≥^^^^ ≥ 1.55. In some aspects, the ratio between ^^ and ^^ may be between 1.6 and 2.85,i.e., 2.85 ≥^^^^ ≥ 1.6.

[0065] In some aspects of the invention, the number ^^ of block patterns withthe third, largest pitch length may be lower or equal to the numberof block patternswith the first, smallest pitch length, i.e., ^^ ≤ ^^. The block patterns with the largestpitch length particularly contribute to the traction of the tire on dry and wet grounds,especially during braking and accelerating. Thus, a number of said block pattern in theabove-defined range provides for a good trade-off between snow and dry / wet traction.

[0066] In some aspects of the invention, if a ratio between a section width of thetire and an aspect ratio of the tire is between 2 mm and 5 mm, the tread tire may have afootprint width between 120 mm and 220 mm. In some aspects of the invention, if theratio between the section width of the tire and the aspect ratio of the tire is between 5mm and 8 mm, the tire may have a footprint width between 160 mm and 260 mm. Insome aspects of the invention, if the ratio between the section width of the tire and theaspect ratio of the tire is between 8 mm and 12 mm, the tire may have a footprint widthbetween 200 mm and 300 mm.

[0067] The section width may correspond to the nominal width of the tire,measured in axial direction, and is usually given in millimeters. The section width maycorrespond to the widest extension of the tire in axial direction. The aspect ratio maycorrespond to the tire’s height off the rim, measured in radial direction, divided by thesection width, and is usually given in %. The tire’s height off the rim corresponds to theradial extension of the tire parts radially outwards from the rim. Thus, an aspect ratio of 70 means that the ratio between the height off the rim and the section width equals 0.7.

[0068] To calculate the ratio between the section width and the aspect ratio, thesection width in mm is divided by the aspect ratio in %. For example, for a tire having asection width of 255 mm and an aspect ratio of 70, the ratio between the section width and the aspect ratio is equal to 255 mm / 70 ≈ 3.6 mm.

[0069] The procedure for measuring a tire footprint according to the presentdisclosure is described elsewhere herein. The footprint width may be measured in axialdirection at the widest axial extension of the footprint.

[0070] This increased footprint width leads to a local stiffening of the blocksagain, thus improving the tire’s traction on dry and wet grounds, especially duringbraking and accelerating. Thus, while the increased amount of block patterns with low pitch length provides increased traction on snow-covered grounds, as discussed above, the traction on dry and wet grounds may be impaired. By providing the same pitch configuration in combination with the increased footprint width mitigates this problem, such that performance on both snow-covered and dry or wet ground can be improved. In other words, the snow performance can be improved without impairing the dry and wet performance.

[0071] In some aspects, the tread may have a skid depth ^^^^^, wherein 7.0 ≤^^^^^ ≤ 9.0, preferably 7.3 ≤ ^^^^^ ≤ 8.5, more preferably 7.4 ≤ ^^^^^ ≤ 8.4. In otherembodiments, the tread may have a skid depth ^^^^^, wherein 8.0 ≤ ^^^^^ ≤ 8.6,preferably 8.1 ≤ ^^^^^ ≤ 8.5, more preferably 8.2 ≤ ^^^^^ ≤ 8.4.

[0072] The skid depth may be the maximum distance between the radiallyoutermost part of the tire to the bottom of the deepest incision (e.g., groove or sipe),measured in radial direction.

[0073] Smaller skid depths generally lead to increased stability of the individualblocks, because due to the smaller radial extension of the block, the flexibility decreases. Thus, a lower skid depth provides for stiffer blocks and thus for enhanced performance on dry and wet grounds. However, a skid depth which is too low may impair the water ejection capacity because the cross-sectional area of the first grooves drops. Moreover, with the increased stiffness of the blocks, the performance on snow- covered roads may be impaired. Thus, also for the skid depth a trade-off between the properties is necessary, which is present especially for the above-described ranges.

[0074] The increased footprint width and lowered skid depth particularlyprovide for enhanced performance of the tire on dry and wet grounds. Thus, while the block pattern arrangements as discussed above improve snow traction and at the same time may impair dry and wet performance, the disadvantages can be mitigated byadapting the footprint width and / or the skid depth as discussed above. This way, bothsnow and dry / wet performance of the tire can be increased.

[0075] In some aspects of the invention, a ratio between void surface andrubber surface in a central portion of the tread may be higher than the ratio betweenthe void surface and the rubber surface in a portion of the tread axially outwards withrespect to the central portion.

[0076] The ratio between void surface and rubber surface may be measured infootprint condition. The measurement of a tire footprint is described elsewhere herein.The rubber surface ^^^^^^^may be obtained by measuring the surface area of all rubber parts in contact with the ground during the footprint measurement. The void surface ^^^^^may then be calculated as the difference between the total surface ^^^^^^and therubber surface ^^^^^^^, such that ^^^^^ = ^^^^^^ − ^^^^^^^.

[0077] If the ratio between void surface in a specific portion of the tire is to beevaluated, the rubber surface ^^^^^^^may be obtained similarly by measuring the surface area of all rubber parts in contact with the ground in the specific portion. Thevoid surface can then be obtained by ^^^^^ = ^^^^^^^^ − ^^^^^^^ , with ^^^^^^^^ being thetotal surface area of the specific portion.

[0078] In some aspects of the invention, the central portion of the tread maymake up 30% of the footprint width in axial direction.

[0079] In some aspects of the invention, the ratio between void surface andrubber surface in the central portion may be between 35.5 and 38.5.

[0080] In some aspects of the invention, the ratio between void surface andrubber surface in the portion of the tread axially outwards with respect to the centralportion may be between 31.5 and 34.5.

[0081] In some aspects of the invention, the ratio between void surface andrubber surface may vary continuously from a central portion of the tire towards theportions of the tread axially outwards with respect to the central portion.

[0082] The higher ratio between void surface and rubber surface in the centralportion leads to a local increase in flexibility of the blocks, thus achieving improved traction of the tire on snow-covered roads.

[0083] Fig. 3 illustrates two blocks of the tread pattern according to the presentinvention. The blocks of Fig. 3 may correspond to the blocks 10 of block patterns 12, 14or 16 of any one of the first, second or third subset of block patterns.

[0084] According to Fig. 3, each of the blocks 10 may comprise a first portion112 arranged at a central portion of the tire. The central portion of the tire may be theportion which is closest to or adjacent to the equatorial plane 18 of the tire. Moreover,according to Fig.3, each of the blocks 10 may comprise a second portion 114, whichmay be arranged in axial direction towards a shoulder of the tire with respect to thefirst portion 112, and immediately next to first portion. Additionally, according to Fig. 3, each of the blocks 10 may comprise a third portion 116, which may be arranged in axial direction towards a shoulder of the tire with respect to the second portion 114, andimmediately next to second portion 114. The first portion 112 may be denoted as“central portion”. The second portion 114 may be denoted as “intermediate portion”.The third portion 116 may be denoted as “shoulder portion”.

[0085] According to Fig. 3, the first portion 112, the second portion 114 and thethird portion 116 may be separated by second grooves 22, 24. However, in someaspects, the first portion 112, the second portion 114 and the third portion 116 may alsobe formed continuously, meaning that there may be no complete disruption betweenthe three portions 112, 114, 116. Instead, they may be formed as one continuousarrangement. According to Fig. 3, each block 10 may comprise a plurality of first sipes310. As illustrated in Fig. 3, the first sipes 310 may be arranged in all three portions ofthe block. However, in other embodiments, the first sipes 310 may be arranged only insome of the block portions and not in others. Although the first sipes 310 according toFig.3 are shaped as straight lines, they may as well have other shapes, for example zig- zag shapes, as illustrated in Fig.2. Sipes are capable of trapping snow therein, such that, once snow is trapped, the friction coefficient between the tire and a snow-coveredroad surface can be increased. Moreover, each sipe may provide an additional edge tothe tread. This improves traction on snow-covered grounds.

[0086] The density of the first sipes 310 may vary over an axial extension of eachblock portion 112, 114, 116. In other words, the distance between two neighboring firstsipes 310 may vary over an axial extension of each block portion 112, 114, 116. Themeasurement of the distance between neighboring first sipes is described elsewhereherein.

[0087] The block 10 of Fig. 3 may correspond to any one of blocks 12a, 14a, 16aof Fig.2.

[0088] The distance between neighboring first sipes 310 may be constant withina portion of the block. However, in other embodiments, as for example illustrated in Fig.4, the distance between neighboring first sipes 310 may also vary, for examplecontinuously, over the axial extension of each block portion 112, 114, 116. Preferably,the distance between neighboring first sipes 310 may be lowest near the equatorial plane 18 of the tire and may increase along the axial extension of the block in adirection axially outwards towards the second portion 114 of the block 10. In someaspects, the distance between neighboring first sipes 310 may be low near the shoulder of the tire, i.e., in the third portion 116 of block 10, and may increase along the axial extension of the block in a direction axially inwards towards the second portion 114 of the block 10.

[0089] As illustrated in Fig. 3, each block 10 may be incised by one or moresecond grooves 22, 24. Each second groove 22, 24 may comprise a protrusionprotruding radially outwardly from a bottom of the second groove 22, 24. In some aspects, the protrusion may match a width of the second groove 22, 24. The width 222, 242 may be measured perpendicular to the direction of extension of the second groove 22, 24. Thus, the protrusion may reach from one edge of the second groove 22, 24 to an opposing edge of the second groove 22, 24.

[0090] The protrusion may comprise a second sipe 312. The second sipe 312may substantially follow a shape of the second groove 22, 24. That is, an angle betweena second sipe and at least one edge of the respective second groove 22, 24 may be lower or equal to 10°, preferably lower or equal to 5°.

[0091] Fig. 4 illustrates a portion of the tread pattern, particularly the distancesbetween neighboring sipes.

[0092] According to Fig. 4, each block 10 may comprise a first portion 112arranged near or at a central portion of the tire and a second portion 114 arranged inaxial direction towards a shoulder of the tire with respect to the first portion.

[0093] The first sipes 310 may be arranged in at least one of the first portionand the second portion, and the at least one of the first portion 112 and the secondportion 114 may comprise a primary area 112a, 114a and a secondary area 112b, 114blocated axially outward with respect to the primary area 112a, 114a. In some aspects ofthe invention, the at least one of the first portion 112 and the second portion 114 may further comprise a tertiary area 112c, 114c located axially outward with respect to the secondary area 112b, 114b.

[0094] In some aspects of the invention, a primary, secondary or tertiary areamay be delimited by sipes. However, a primary, secondary or tertiary area may also bedelimited in other ways, such as by grooves, by change in angle of block edges, or the like.

[0095] In some aspects of the invention, a first distance ^^ between twoneighboring first sipes 310 in the primary area 112a may be smaller than a seconddistance ^^ between two neighboring first sipes 310 in the secondary area 112b. In someaspects of the invention, a third distance ^^between two neighboring first sipes 310 in the tertiary area 112c may be smaller than the second distance ^^between twoneighboring first sipes 310 in the secondary area 112b.

[0096] Two areas, e.g. a primary area 112a, 114a and a secondary area 112b, 114bmay be adjacent to each other. If the areas are delimited by first sipes, the first sipe located between the primary area 112a, 114a and the secondary area 112b, 114b may be part of both the primary area 112a, 114a and the secondary area 112b, 114b. Thus, threefirst sipes may comprise two separate pairs of neighboring first sipes in two areas.

[0097] The distances ^^, ^^, ^^ between neighboring first sipes 310 may bemeasured by neglecting potential zig-zag or other shapes of the individual first sipes 310. Thus, to measure the distance between neighboring first sipes, a straight line maybe generated for each first sipe by connecting two end points of each first sipe. Thedistance between the so generated lines may then be measured perpendicularly to theselines. The distance between the two neighboring first sipes may then be equal to thedistance between said lines.

[0098] The high density of first sipes towards the edges of the block 10 furtherenhances the traction of the tire on snow by improving the edge efficiency of the block10. That is, by decreasing the distance between neighboring sipes near the edges of theblock, deformability of the block can be increased near these edges, leading toimproved traction on snow, especially during braking and accelerating. By providing a higher distance between neighboring sipes in the central area of the block, in these regions the block is left less deformable, to still provide good traction on wet and dry grounds. Since the edges of the block are crucial for snow traction, it is especially advantageous to provide the lower distance between neighboring sipes especially near the edges of the block.

[0099] Fig. 5 illustrates a three-dimensional view of a block 10 according to thepresent invention. The block 10 of Fig. 5 may correspond to a block 10 as described inany of the preceding Figs.

[0100] Similar to the block 10 of Figs. 3 or 4, the block 10 as illustrated in Fig. 5may also comprise a first portion 112, a second portion 114 and a third portion 116. Asillustrated in Fig.5, the block 10 may also comprise first sipes 310. The distance Δ^^^^between neighboring first sipes 310 may vary along the axial extension of the block 10as described with respect to Figs. 3 and 4. Although the first sipes 310 according to Fig.5 are illustrated as straight lines, it will be understood that they may have other shapesas well, as for example the zig zag shapes as illustrated in some of the preceding Figs.

[0101] As illustrated in Fig. 5, the tread may have a skid depth ^^^^^, wherein7.0 ^^ ≤ ^^^^^ ≤ 9.0 ^^, preferably 7.3 ^^ ≤ ^^^^^ ≤ 8.5 ^^, more preferably7.4 ^^ ≤ ^^^^^ ≤ 8.4 ^^. In other embodiments of the invention, the tread may have askid depth ^^^^^, wherein 8.0 ≤ ^^^^^ ≤ 8.6, preferably 8.1 ≤ ^^^^^ ≤ 8.5, morepreferably 8.2 ≤ ^^^^^ ≤ 8.4.

[0102] As further illustrated in Fig. 5, each first sipe may have a sipe depth^ , wherei^^^^^^^^^^ ^^^^ n 0.76 ≤^^^^^≤ 0.95, preferably 0.77 ≤^^^^^≤ 0.94, more preferably0.78 ≤^^^^^^^^^^ ≤ 0.93. In other aspects of the invention, each first sipe may have a sipedepth ^ , wherein 0.90 ≤^≤ 0.95, preferably 0.91 ≤^^^^^^^^^^≤ 0.94, more0.92 ≤^^^^^^^^^^ ≤ 0.93.

[0103] As further illustrated by Fig. 5, each block 10 may be incised by at leastone second groove 22, 24. Each second groove 22, 24 may comprise a protrusion 25 protruding radially outwardly from a bottom of the second groove 22, 24. In someaspects, the protrusion 25 may have a height ^^. A ratio between the height ^^ of theprotrusion 25 and the skid depth ^ may be between 0.3 and^^^^^^ 0.5, i.e., 0.3 ≤^^^^^≤ 0.5.

[0104] In some aspects of the invention, the protrusion 25 may comprise asecond sipe 312. The second sipe 312 may have a depth ^^^, measured from the radiallyoutwardmost point of the protrusion 25. The depth ^^^ of the second sipe 312 may bebetween 40 and 70 % of the height ^^ of the protrusion 25.

[0105] In some aspects of the invention, the width ^^ of the protrusion 25 maymatch the width ^^of the second groove 22, 24.

[0106] Numeral values, especially regarding the measurements of skid depths,sipe depths, etc. given in the present disclosure refer to measurements conducted onnew tires, which have not been exposed to wear prior to the measurements.

[0107] Within the context of this disclosure, value ranges defined by bordervalues are meant to encompass said border values. In other words, a value range given as “between a and b” is meant to encompass the values a and b. Tire footprint measurement

[0108] Within the context of this disclosure, a “tire footprint” means all parts ofthe tire that come into contact with the ground when the tire is in inflated and loaded condition. The tire footprint gives information about the behavior of a tread profile in normal condition, i.e., from the tire footprint it can be seen, which parts of the blocks come into contact with the ground under static loading conditions.

[0109] When analyzing a tire footprint, generally, the respective tire is inflated,with the pressure depending on the type of the tire. For a standard radial passenger tirewith nominal section widths of 195 mm and below, a tire pressure of 1.9 bar is used. Fora standard radial passenger tire with nominal section widths of 205 mm and above, a tire pressure of 2.0 bar is used. For reinforced radial passenger tires of all sizes, a pressure of 2.3 bar is used. For tires of commercial vans, trucks, etc., the standardized inflation pressure according to the European Tyre and Rim Technical Organisation (ETRTO) is used. All measurements are conducted under room ambient temperature.

[0110] The tire is then loaded at the following load conditions: For a radialpassenger tire, the tire is loaded with weight corresponding to 88% of the tire loadindex according to ETRTO charts. Tires for commercial vans, trucks, etc. are loadedwith weight corresponding to the ETRTO single load rated standard. To conduct themeasurement, ink may be applied to the tread profile and the tire may then be pushedagainst a card according to the above specifications, leaving an ink footprint which canthen be analyzed. A footprint is evaluated on three tire portions which are equally spaced by 120° over the circumference of the tire. The metrics that are analyzed in the footprint are then averaged over the three measured portions.

Claims

CLAIMS 1. A tire for a vehicle comprising a tread, the tread comprising:a set of consecutive block patterns arranged along a circumference of the tire,each block pattern of the set of consecutive block patterns comprising a block and afirst groove adjacent to the block; the set of consecutive block patterns comprising a first subset of ^^ first blockpatterns having a first pitch length, a second subset of ^^ second block patterns havinga second pitch length greater than the first pitch length, and a third subset of ^^ thirdblock patterns having a third pitch length greater than the second pitch length,wherein: ^^^ ≥ 10,^ 1 ≥^^^^ ≥ 0.50, and^ 3 ≥^^^^ ≥ 1.50.

2. The tire of claim 1, wherein^^^^ ≥ 0.50, preferably^^^^ ≥ 0.55, , mostpreferably 0.90 ≥^^^^ ≥ 0.55.

3. The tire of any one of the preceding claims, wherein 2.95 ≥^^^^ ≥ 1.55,preferably 2.9 ≥^^^^ ≥ 1.55, more preferably 2.85 ≥^^^^ ≥ 1.6.

4. The tire of any one of the preceding claims, wherein≥ 13, preferably^^ ≥ 15, more preferably ^^ ≥ 17.

5. The tire of any one of the preceding claims, wherein the first pitch lengthis between 22 and 27 mm, the second pitch length is between 27 and 33 mm, and thethird pitch length is between 32 and 39 mm.

6. The tire of any one of the preceding claims, wherein (^^ + ^^ + ^^) ≥60, preferably (^^ + ^^ + ^^) ≥ 64.

7. The tire of any one of the preceding claims, wherein, if a ratio between asection width of the tire and an aspect ratio of the tire is between 2 mm and 5 mm, thetire has a footprint width between 120 mm and 220 mm, andwherein, if the ratio between the section width of the tire and the aspect ratio ofthe tire is between 5 mm and 8 mm, the tire has a footprint width between 160 mm and260 mm, andwherein, if the ratio between the section width of the tire and the aspect ratio ofthe tire is between 8 mm and 12 mm, the tire has a footprint width between 200 mmand 300 mm.

8. The tire of any one of the preceding claims, wherein the tread has a skiddepth ^^^^^, wherein 7.0 ^^ ≤ ^^^^^ ≤ 9.0 ^^, preferably 7.3 ^^ ≤ ^^^^^ ≤ 8.5 ^^,more preferably 7.4 ^^ ≤ ^^^^^ ≤ 8.4 ^^.

9. The tire of any one of the preceding claims, wherein the tread has a skid depth^^^^^, and wherein each block comprises a plurality of first sipes, each first sipe havinga sipe depth ^ , wherein 0.76 ≤^^^^^ ≤ 0.95, preferably 0.77^^^^^^^^^^^^^^ ≤^^^^^ ≤ 0.94, morepreferably 0.780.93.

10. The tire of claim 9, wherein each block comprises:a first portion arranged at a central portion of the tire; and a second portion arranged in axial direction towards a shoulder of the tire with respect to the first portion, wherein the first sipes are arranged in at least one of the first portion and the second portion, and the at least one of the first portion and the second portioncomprises a primary area and a secondary area located axially outward with respect tothe primary area, such that:a first distance between two neighboring first sipes in the primary area is smallerthan a second distance between two neighboring first sipes in the secondary area.

11. The tire of claim 10, wherein the at least one of the first portion and thesecond portion further comprises a tertiary area located axially outward with respect tothe secondary area, and wherein a third distance between two neighboring first sipes inthe tertiary area is smaller than the second distance between two neighboring first sipes in the secondary area.

12. The tire of any one of the preceding claims, wherein the block of eachblock pattern is incised by at least one second groove, each second groove comprising a protrusion protruding radially outwardly from a bottom of the second groove, the protrusion comprising a second sipe.

13. The tire of claim 12, wherein the second sipe substantially follows ashape of the second groove.

14. The tire of any one of claims 12 to 13, wherein a ratio between a height ofthe protrusion and a skid depth of the tire is between 0.3 and 0.5.

15. The tire of any one of claims 12 to 14, wherein a width of the protrusionmatches a width of the second groove.

16. The tire of any one of claims 12 to 15, wherein the second sipe has adepth of between 40 and 70 % of a height of the protrusion.

17. The tire of any one of the preceding claims, wherein a ratio between voidsurface and rubber surface in a central portion of the tread is higher than the ratio between the void surface and the rubber surface in a portion of the tread axially outwards with respect to the central portion.

18. The tire of claim 17, wherein the ratio between void surface and rubbersurface in the central portion is between 35.5 and 38.5.

19. The tire of claim 17 or 18, wherein the ratio between void surface andrubber surface in the portion of the tread axially outwards with respect to the central portion is between 31.5 and 34.5.

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