BR112012017722A2 - TIRE - Google Patents

Abstract

TIRE. Tire (12) having a tread (2) comprising a central portion (L1) mounted on an equatorial plane (XX) and two shoulder portions (L2; L3), where the shoulder portions (L2; L3) have, each a row of side blocks (13; 14) circumferentially separated from each other by transverse shoulder grooves (23; 28); the central portion (L1) has a void / rubber ratio of less than 0.25 and comprises a first and second row (p; 10) of central blocks; each block (32) of the first central row (9) being substantially axially aligned with a block (33) of the second row to define a first, substantially continuous, transversal drainage channel (70), which crosses the central portion (L1); the first transverse drainage channel (70) being defined between a first pair of blocks, formed by a block (32) of the first row (9) and a block (33) of the second row (10) arranged axially side by side, and the first circumferentially adjacent pair of blocks, similarly formed; each block (32) of the first row (9) has an extension direction, forming an angle a1 between 45 < 198 > and 80 < 198 > in relation to the equatorial plane (XX), and each mouth (33) of the second row (10) lies on the extension direction of the preceding circumferential block (32) of the first row (9), in order to define a second drainage channel inclined and substantially continuous (71) that crosses the central portion (L1).

Description

. 1 . "TIRE" The present invention relates to a motor vehicle tire. In particular, the invention relates to a tire for motor vehicles having a large capacity engine, for example, from 2,000 to - 5 —3,000cm ”, whose tread provides excellent performance when driving on and off the road.

i Generally, tires for off-road vehicles are designed (tread, structure and profile) to be used particularly in extreme terrain or, in any case, unpaved, for example, for use on uneven terrain, dusty roads or muddy terrain and / or sandy.

"In recent years, so-called“ any terrain ”vehicles (4-wheel drive, abbreviated 4x4), that is, vehicles combining off-road and on-road performance have become increasingly popular and their flexibility has been greatly appreciated by the market .

“Any terrain” includes vehicles such as pick-ups, but also SUVs (sport utility vehicles) that combine space characteristics typical of high-performance vans (especially in terms of high torque and speed), typical of sports vehicles when used on roads.

Drivers of this type of vehicle are undoubtedly increasingly demanding tires that can provide excellent performance both on the road and off-road and, at the same time, good - handling characteristics, low noise levels and long life.

However, achieving the requirements mentioned above is mutually conflicting.

US 2003 / 00041.939 describes a tire having a tread for use both on and off road: the tread

- has at least a pair of intermediate ribs and a pair of shoulder ribs providing a plurality of groups of projecting tabs.

The groups of projecting tabs are formed and extend externally from and along the sidewalls of the tire.

Each group of projecting tabs - 5 preferably comprises three separate tabs.

Each flap has substantially a flat outer surface lying on a plane i different from the outer surface of the other flaps.

Two of the flaps are radially aligned with each other along the sidewall of the tire and the third flap lies in an intermediate position between the two aligned flaps.

US 2008 / 0047,642 describes a tire for light vehicles or automobiles.

The tread has a plurality of traction elements -. extending radially out of the base and a large circumferentially continuous groove.

The large groove has a circumferentially continuous window i extending from the tread to the radially outer contact surface.

The window, when viewed in the tread grip area, has a trapezoidal shape with two sides and a large radially external base.

The large base has an axial width corresponding to 7 to 20% of the width of the tread.

The large groove has a zigzag portion extending radially from the base of the tread - with a continuous circumferential stroke.

The sides of the window define the maximum axial extension or width of the zigzag portion of the large groove.

The Applicant has observed that a large number of blocks of considerable dimensions, as in the tread, as in the tread in the prior art, increase traction, especially in wet and / or muddy and / or uneven terrain, but an excessive use of blocks can compromise performance on dry roads and increase the level of tire noise.

In fact, one of the main causes of noise is the continuous sequence of impacts from the edges of blocks on the road surface.

: The Applicant also noted a higher tire / tire ratio in the central portion of the tires for off-road use of the prior art than in road tires.

This choice is usually due to the need to increase primarily the drainage over looked terrains and / or - 5 - Jacobins, and to ensure good flexibility and comfort of this portion.

However, the Applicant noted that a higher void / rubber ratio may | compromising performance on dry terrain, as well as increasing the level of noise and tire wear, in relation to both durability and irregularity of wear.

The Applicant has determined that the reciprocal contrasting problems described above are resolved by a tread pattern having a low void / rubber ratio and thus a greater one. * amount of rubber in relation to the terrain, in the innermost region, close to the equatorial plane and, at the same time, ensuring the formation in the —area and footprint of two main drainage channels, one transversal and the other oblique.

These drainage channels completely cross the tread from one shoulder to the other and prevent the retention of water and / or mud when running on muddy and / or wet terrain, while providing traction and lateral retention on sandy terrain and / or with grasses.

More particularly, according to a first aspect thereof, the present invention relates to a tire having a tread comprising a central portion L1 transversal to an equatorial plane (X-X) and two shoulder portions L2, L3. Each shoulder portion has at least one row of side blocks.

The central portion LI has a void / rubber ratio of less than 0.25 and comprises a first and second row of circumferential central blocks having an elongated shape.

Each block of the first row of circumferential central blocks is axially side by side with a block of the second row, in order to define a first substantially transverse drainage channel, substantially

At 4 - continuous, which crosses the central portion L1. This first transverse drainage channel is defined between a first pair of blocks, formed by a block from the first central row and a block from the second central row arranged axially side by side, and the first circumferentially adjacent pair, «+ S — formed in a similar manner.

In addition, each block on the block cover plate is | arranged according to an extension direction.

Each block of the second row of central blocks extends from: according to an extension direction substantially aligned with the extension direction of the preceding circumferential block of the first row, in order to define a second inclined and substantially continuous drainage channel that crosses the central portion L1. - This second drainage channel is defined between a second pair of blocks, formed by a block from the second row of central blocks and the block from the first row of central blocks that precedes the first in the circumferential direction and is aligned with it according to a substantially common extension direction, and the second pair of circumferentially adjacent blocks formed in a similar manner.

The expression "substantially continuous" referring to the channels - drainage can be interpreted as the condition in which, if the walls of the two blocks defining the channel and substantially arranged side by side circumferentially are continued, the continuations lying within the channel itself or, in in any case, at least one of these continuations, if not lying within the channel, passes at most to the wall of a block - circumferentially subsequent.

In other words, moving through the channel from one shoulder to the other & / or vice versa, you never find a wall of a block defining the channel arranged so as to completely obstruct the passage through the channel, retaining mud and / or water.

. 5 Furthermore, the aforementioned “extension direction” of the blocks of the central rows can generally correspond to the direction along which the largest dimension of the block having an elongated shape extends. For practical purposes, to identify the direction of extension of a block, it is possible, for example, to refer to u the straight line passing through midpoints of the short sides of an ideal rectangle in which the block is inscribed. | | For the purposes of the present invention, the width of the circumferential and / or transverse grooves can be detected by taking the width of the radially outer edges of the grooves themselves as a reference.

For the purposes of the present invention, the following i definitions also apply: - - by the tire's “equatorial plane”, we indicate a plane perpendicular to the tire's axis of rotation and which divides the tire into two symmetrically equal portions; - by “circumferential” direction we want to indicate a direction generally oriented according to the direction of rotation of the tire, or, in any case, only slightly inclined in relation to the direction of rotation of the tire; - By axial direction "or" axially "we want to indicate a parallel direction, or, in any case, only slightly inclined in relation to the axis of rotation of the tire; - by voids / rubber ratio ”we want to indicate the relationship between the total surface of the recesses of a given portion of the tire tread pattern (possibly the entire tread pattern) and the total surface of a given tire tread tread pattern (possibly the entire tread pattern).

The present invention, the aspect mentioned above, can have at least one of the preferred features described below.

Preferably, each block of the central portion L1 extends according to an extension direction adapted to form an angle al between 45º and 80º in relation to the equatorial plane (X-X). In addition, with reference to the angular arrangement of the grooves «5 and / or the straight lines formed in the tread in relation to the plane | : equatorial of the tire, such an angular arrangement must be aimed at each point of the! groove and / or straight line with reference to the angle defined by a rotation! completed from the equatorial plane to the direction tangent to the straight line passing through that point.

In order to provide the blocks in a particularly tensioned region of the tread with a certain stiffness, the blocks in the i of the central rows can be substantially polygons and, preferably,. substantially convex polygons.

For the purposes of the present invention, by substantially convex polygon we mean a polygon in which an extension of any of its sides substantially never crosses the surface of the polygon itself.

For practical purposes, the aforementioned blocks of the central rows can have small recesses (maximum Np, 1-2 mm, or, in percentage at most less than 5% of the largest dimension of the block itself), in any case, maintaining a adequate rigidity for the purposes of the invention.

Advantageously, the perimeter of the blocks of the central rows can comprise a broken line.

Preferably, each block of the central portion can have six sides.

Suitably, the blocks in the central rows have the same shape and size as the blocks in the second rows.

Advantageously, the first row blocks are arranged

: 7. rotated 180º in relation to the blocks of the second central row.

In order to provide an optimal balance of the traction / braking behavior on any type of surface, the blocks of the first central row are advantageously oriented with the vertex pointing in the direction. 5 opposite to the apex of the blocks of the second central row. Preferably, at least one first side in a plane substantially perpendicular to the equatorial plane (X-X) is substantially aligned with at least a second side of a second central row block to delimit the first transverse channel. : Similarly, at least one second side of a cover plate piece lies on planes substantially perpendicular to the heated liquid and is substantially axially aligned with at least - a first side of a second central row block to delimit | downwardly the first transverse channel. | ! Advantageously, the tire according to the present invention! it may comprise circumferential groove days to separate the central portion L1 from the shoulder pigs L2; L3.

Preferably, the circumferential grooves have a wavy course.

Preferably, the shoulder portion blocks can be circumferentially separated from one another by transverse shoulder grooves.

Suitably, the path of the circumferential grooves can be circumferentially interrupted by at least the transverse shoulder grooves.

The circumferential grooves with a corrugated path can preferably have a width greater than 6 mm.

Suitably, the circumferential grooves with a wavy path can be less than 15 mm wide. Advantageously,

, circumferential grooves with a wavy path may have a depth greater than 12 mm, preferably between 10 and 17 mm. Preferably, the rows of central circumferential blocks "can be separated from each other by a circumferential groove.

115 Preferably, the aforementioned circumferential groove may have a "serrated" path.

: In the present invention, by "serrated" path of a groove we want to indicate the path of a groove having a cyclically repeated pattern and formed by at least one substantially transversal section and perpendicular to the equatorial plane (XX) and by at least one inclined section in relation to the equatorial plane (XX) and by at least one section inclined in relation to the equatorial plane (XX). The latter being arranged and - dimensioned so as to intersect the substantially cross section, preferably at one end thereof.

The circumferential groove can preferably have a width greater than 5 mm.

Suitably, the circumferential groove can be less than 15 mm wide. Advantageously, the circumferential groove can have a depth greater than 12 mm, preferably between 10 and 17 mm.

In order to increase the adhesion with the floor in the presence of wet terrains, the rows of central and / or shoulder blocks can have a plurality of cracks.

The cracks can be between 2 and 10 mm deep and less than 2 mm wide.

These slits are capable of providing excellent braking / traction characteristics at the same time, typically, from the tire's rolling condition over a straight path and / or in a curve.

The tire of the invention has an excellent rolling behavior on the road, both on dry and wet terrain, as well as,

: 9, a low noise level under these conditions. In addition, the tire of the invention also has excellent off-road handling characteristics, in particular over the entire range related to water drainage and / or mud and, at the same time, traction and lateral grip on dusty roads or on «5 sandy / grassy terrain.

. Features and advantages of the invention will now be presented with reference to the embodiments shown to indicate, and not limit, the purposes in the attached drawings, in which: - the figure | it is a perspective view of a tire with a tread made according to an example of the invention; figure 2 is a plan view of the tire tread of figure 1; Figure 2a is an enlarged plan view of a variant of the tread of figure 2; figure 3 is an enlarged cross-sectional view of the tread of the tire in figure 2.

In figures 1, 2, 2a, a tire 1 is shown with a first embodiment of the tread 2 according to the present invention.

The structure of the tire | it is, per se, a typical, conventional one and comprises a carcass, a tread crowning the carcass, a pair of axially opposite side walls ending in bead reinforced with bead rings and respective bead inserts. Preferably, the tire also comprises a belt structure interposed between the carcass and the tread. The carcass comprises one or more carcass linings anchored to the bead, rings, while the strap structure comprises two strap strips radially arranged one on top of the other. The strap strips are formed by sections of a rubberized fabric incorporating metallic strings, whose strings are parallel to each other within each strip and having

. 10. a cross-orientation in relation to those of the adjacent strips, with slopes preferably symmetrical in relation to the equatorial plane. Preferably, the belt structure also comprises a third belt strip, in a radially outermost position, provided with ropes «5 substantially parallel to the equatorial plane. y Tire 1 preferably has an H / C ratio of the height of the right cross section with the maximum width of the cross section between 0.60 € 0.90. To ensure long life and, at the same time, high performance throughout the life of the tire, particularly as far as use on road terrain is concerned, the tread 2 has, overall, an empty / rubber ratio that is low compared to - a tire also intended for off-road use, ie less than 0.5, preferably less than 0.47, for example, equal to about 0.4.

D the vacuum / rubber ratio is, in any case, greater than 0.35.

The tread 2 comprises a center hold L1 and two shoulder portions L2; L3. The tread 2 shown in figures 1, 2 and 2a is of the symmetrical type, that is, it does not have a preferred rolling direction and does not involve any restrictions on the side of the tire (internal / external) on the vehicle.

The can L1, arranged transversely to the equatorial plane (X-X) is visually separated from the shoulder portions L2; L3 through two circumferential grooves 3, 3º.

According to the present invention, the circumferential grooves 3. 3º are mainly intended to provide the tread 2 with longitudinal flexibility and to ensure, at the same time, drainage of water and mud in the footprint area, over any type of terrain that the tire is used.

More preferably, the circumferential grooves 3.31 have a wavy stroke, as best described below. The corrugated course of grooves 3, 3º increases the lateral stiffness of the tire, providing greater “handling”.

The circumferential grooves 3, 31 with corrugated travel can preferably be wider than 6 mm.

Suitably, the circumferential grooves 3, 31 with undulating stroke can be less than 15 mm wide. Advantageously, the circumferential grooves with a wavy stroke can have a depth — greater than 12 mm, preferably between 10 and 17 mm, for example, equal to mm.

| The central portion L1 has two circumferential rows 9 and 10 of - blocks 32, 33, while the shoulder portions individually have a row of blocks, respectively, 13, 14.

15 The shoulder portions L2, L3 will be described first and only later will a detailed description of the central portion L] 1 be presented. In detail, the PB L2 has a row 13 of shoulder blocks 22, separated from each other by transverse grooves. of the shoulder 23.

Preferably, the grooves transverse to the shoulders 23, at least in their first section, can be arranged according to the radial planes of the tire 1.

The transverse grooves 23 have substantially a constant width and, even more preferably, a width between 14 mm and 28 mm, for example, equals 22 mm.

In addition, the grooves 23 preferably have a depth greater than 12 mm, preferably between 10 mm and 17 mm, for example, equal to 15 mm.

According to the embodiment shown in the figures, the shoulder blocks 22 have a substantially rectangular shape. In their axially outermost portion (the portion furthest from the equatorial plane (X-X)) the shoulder blocks 22 are arranged substantially perpendicular to the equatorial plane (X-X). Moving further into the equatorial plane (X-X), the transverse grooves of the shoulders 23, while remaining parallel to each other, are inclined and form an angle a2 in relation to the equatorial plane (X-X). Preferably, the transverse grooves of the shoulders 23 are inclined by an angle 02 with respect to the equatorial plane (X-X) which is less than 120 °. The inclination of the transverse grooves of the shoulders 23 also determines the inclination of the second section of the shoulder blocks 22. The shoulder blocks 22 end substantially facing the central portion L1, with - an axially internal end formed by three sides 24, 25, 26 , of which two sides 24, 26 are oblique connecting sides, and one side 25 is substantially parallel to the equatorial plane (XX) and comprised between the two oblique connecting sides 24, 26. Preferably, u on both connecting sides obliques 24, 26, indicated in 24, have a lesser extent.

As for row 14 of blocks 27 of the shoulder portion L3, it should be noted that, in addition to the orientation of the axially internal end of the blocks, taper 14 of blocks 27 is totally similar to row 13 of blocks 22 and can be obtained simply by turning the 180º of the latter.

The blocks 27 of row 14, however, are not arranged in a circumferentially corresponding position to that of blocks 22 of row 13, instead of being circumferentially staggered. In addition, the blocks 27 of row 14 are separated by transverse grooves in the shoulders 28 totally similar to the transverse grooves in the shoulders 23 of the row 13.

As mentioned above, it should be noted that the axially internal ends of the shoulder blocks of the same row are oriented in the same circumferential direction, while, according to what is known in the embodiments of figures 1-3, the axially internal ends of two distinct rows, in particular rows 13 and 14 are oriented in the opposite circumferential direction. To immediately recognize the feature mentioned above in figures 2 and 2a, the ends of the axially internal sides of the blocks 27 have, in addition to a quotation mark, the same reference number of the corresponding sides of the axially internal ends of the blocks

22. In detail, considering, for example, figure 2, - while the axially internal ends of the blocks 22, formed by the sides 24, 25, 26, are descendedly oriented, the i axially internal ends of the blocks 27, formed by the 24º, 25º, 26º sides are | - upwardly oriented. | The sides 24, 25, 26 and 24º, 25º, 26º of the ends of the

15. shoulder blocks 22, 27 face and delimit the groove 3, 3 ". In other words, the sequence in the circumferential direction of the axially internal ends of blocks 22 and 27, particularly on sides 24, 25, 26 and 24º, 25º, 26º, defines the axially external side wall of the groove 3, respectively,

3.

As mentioned above, preferably the circumferential groove 3 is provided with a substantially undulating course, which means that the side walls have a substantially undulating course, which is interrupted by the transverse grooves in the shoulders 23.

Likewise, with regard to the 3rd grooves, it can be seen that their —condulated course is interrupted by the shoulder transverse blocks 28.

It can be noted that, according to the present invention, shoulder blocks 22, 27 can be provided with slits 30.

The slots 30, normally provided in the axially innermost portion of blocks 22 and 27, have a “hockey stick” type course, with the club cable arranged in the direction of the block's extension.

In other words, the slots 30 have two substantially straight sections connected, in order to define an angle less than 180º between them, for example, of about 130º-150º.

One of the two substantially straight sections has a greater length, equal to about 2-3 times the length of the other substantially straight section.

Slots 30 can have a depth between 2 and 10 mm, for example, equal to 3 mm, and a width less than 2 mm.

As mentioned above, the circumferential grooves 3, 3º separate the central portion L1 from the shoulder portions L2, respectively, L3. Á The central portion L1 is designed to have a large amount of rubber in relation to the ground in the most central portion close to the equatorial plane (XX) of the tire 1. For this purpose, the central portion L1 has an empty / rubber less than 0.25, for example, equal to 0.2.

The central portion L1 has two rows 9, 10 of circumferential central blocks 32,33.

Rows 9, 10 of circumferential central blocks 32, 33 are - separated from each other by a circumferential groove 4 having a "serrated" course.

The circumferential groove 4 is thus formed by a sequence of substantially transverse sections and a sequence of inclined sections. Each substantially cross section alternates, preferably, with a sloping section.

Suitably, as shown in the embodiments of figures 1-3, all the inclined sections of the groove 4 are inclined in the same direction.

Slot 4 is arranged in the equatorial plane (X-X) so

! 15! that its substantially transversal sections cross such a plane a short distance from its intersection with the inclined sections.

The circumferential groove 4 is preferably wider than 5 mm.

Preferably, the circumferential groove 4 has, in any case, a width less than 15 mm, for example, equal to 14 mm.

Advantageously, the circumferential groove 4 has a depth greater than 12 mm, preferably between 10 and 17 mm, for example, equal to 15 mm.

In the embodiment of figures 2 and 2a, the row 9 of central blocks 32 is interposed between the circumferential groove 3 and the circumferential groove 4, while the row 10 of central blocks 33 is interposed between - the groove 4 and the circumferential groove 3 .

Advantageously, in order to provide more resistance, blocks 32 of row 9, as well as blocks 33 of row 10, can be substantially polygons, preferably convex polygons.

The central blocks 32, as well as the blocks 33, have, at least partially, a perimeter defined by a broken line, such as, for example, defined by a regular hexagon, as shown in figure2.

Since the blocks 33 of row 10 are totally similar, in terms of shape and dimension, to blocks 32 of row 9 and are obtained by rotating this row 180º, only the shape and arrangement of the central blocks 32, as shown in the figures 1-3, will be described below.

For this reason, in figures 2 and 2a, the sides of blocks 33 have, in addition to a quotation mark, the same reference number as the corresponding sides of blocks 32.

Preferably, the central blocks 32 have an elongated shape and an extension direction inclined with respect to the equatorial plane (X-X).

Advantageously, the extension direction of each central block 32 defines a straight line of extension r adapted to form an angle al between 45º and 80º, preferably between 47º and 60º, for example, equal to 55º, with the equatorial plane (XX ). | The central blocks 32 of the same row define straight extension lines parallel to each other and spaced apart.

Preferably, also the central blocks 33 of row 10 are arranged according to a defined extension direction, for example, in the embodiment shown in the figures, by a straight line of extension r - adapted to form an angle al between 45º and 80º, preferably between 47º and 60º, for example, equal to 55º, with the equatorial plane (XX). According to an advantageous aspect of the present invention,. each block 33 of the second row 10 and the preceding block 32 in the circumferential direction have substantially the same extension direction defined by the common line.

This means that each block 33 of the second row 10 lies substantially on the continuation of the straight line of extension r defined by the preceding circumferentially block 32 of the first row.

In other words, on the straight line of extension r of block 32 who, with reference to figures 2 or 2a, lies in a “lower” position on the circumferential development.

In fact, the Applicant found that such an inclination of the blocks forming the central portion L1 of the pattern, together with the arrangement of rows of shoulder blocks 22, 27, allows improvements to be obtained - notable in contrast to the noise level of the pattern, particularly as much as the noise generated during tire turn maneuver provided with these blocks is of interest.

In addition, the irregular shape of the blocks 32 allows a final portion 32a formed by

17 is three sides 34, 35, 36 and a vertex portion 32b, also formed by three sides 38, 39, 40 arranged so as to taper the block 32, thereby forming a vertex.

In the final portion 32a, shown in figure 2, two sides 34, 36 bottom section oblique connecting sides, and one side 35, facing circumferential groove 3, is delimited by the two oblique connecting sides 34, 36. Preferably, one of the two oblique connecting sides 34, 36, indicated by 36, have a smaller extension and one, indicated by 34, is inclined in relation to the equatorial plane (XX), thus forming an angle, for example, - between 75º% 105º .

In the apex portion 32b, shown in figure 2, there are two sides: connection 38, 40 arranged substantially parallel to each other, and one - front side 39 interposed between the other two and arranged substantially perpendicular to the equatorial plane (X-X).

Advantageously, the front side 39 of the apex portion 32b is parallel to the oblique side 34 with less extension of the final portion 32a.

The circumferential groove 3 is thus axially bounded inwards by the sides 35, 36 and partially by the side 40 of the central blocks 32.

In other words, the sequence in the circumferential direction of sides 35, 36 and 40 of the central blocks 32, at least partially, defines the axially internal side wall of the groove 3.

Similarly, the circumferential groove 3º is delimited axially inward by the 35º, 36º sides and, partially, by the 40º side of the - central blocks33.

In other words, the sequence in the circumferential direction of the sides 351, 36º and 40º of the central blocks 33, at least partially, defines the axially internal side wall of the groove 3º.

Preferably, the central blocks 32 are separated from each other

18! another by transverse grooves 43. This means that, due to what happens with reference to the central portion Ll, the wavy course of the circumferential groove 3, respectively, 3rd, is interrupted by the transverse grooves 43. Row 10 of blocks, as previously mentioned, it is interposed between the groove 4 and the circumferential groove 3º.

In addition, the central blocks 33 of the row 10 of blocks are separated from each other by the grooves 43. According to an important aspect of the present invention, the transverse grooves 43 not only separate the central blocks 32, 33, but also completely cross each other the central portion L1, forming a substantially continuous transversal drainage channel 70, which provides characteristics - high traction and braking.

As shown in figures 2 and 2a, preferably at least one side 34 of the end portion 32a of each block 32 of the first row 9 is substantially aligned with at least one side 39 ° of the apex portion 33b of a block 33 of the second row 10 to delimit upwardly the transverse groove 43. Similarly, at least one side 39 of the apex portion 32b of each block32 of the first central row 9 lies in a plane substantially perpendicular to the equatorial plane (XX) and is substantially aligned with at least one side 34º of the final portion 33a of a block 33 of the second row 10 to descendently delimit the first transverse groove 43. In other words, the side 34 of the block 32 and the 39th side of the axially aligned block 33 delimit the upper walls of the first drainage channel 70 , while side 39 of block 32 and side 34º of block 33 delimit the lower walls of the first drainage channel 70, represented by transverse groove 43. Preferably, in achievement shown in figures 1-

3, the upper and lower walls of the transverse groove 43 are interrupted by the circumferential grooves 3, 3, 4.

The transverse grooves 43, which substantially form the first drainage channel 70, preferably have a greater depth - doquel2mm, preferably between about 10 and 17mm, for example, equal to l15mm.

The transverse grooves 43, with the exception of the final sections, in which they end in the circumferential grooves 3, 3 °, can have a substantially constant width throughout their lengths.

Preferably, the transverse grooves 43 can have a cooling step greater than 6mm in width, for example, equal to about | 9mm. | - The transverse grooves 43 extend from groove 3 to groove 3º.

The grooves 43 are not arranged in a position corresponding to the transverse grooves of the shoulders 23, but instead, they are circumferentially staggered with respect to these.

Similarly, in the preferred embodiment shown in Figure 2, the transverse grooves 43 are not circumferentially - aligned with the transverse grooves 28 of the shoulder portion L3, but instead, they are circumferentially staggered with respect to them.

The grooves 43 are preferably joined to the shoulder transverse grooves 23, 28 by means of sections of circumferential groove 3 and circumferential groove 3, respectively.

According to an important aspect of the present invention, in the central portion L1, blocks 32 and 32 are arranged in the footprint areas: a first transverse channel 70, substantially coincident, as already mentioned, with transverse groove 43, the second oblique channel 71 .

The formation of the second inclined drainage channel 71,

substantially continuous, which crosses the central portion L1, is obtained thanks to each block 33 of the second row 10 being aligned with the circumferentially preceding block 32 of the first row 9 according to a straight line of common extension r.

The second inclined drainage channel 71 is thus arranged preferably substantially parallel to the straight line of extension t common to the two blocks 32, 33. The second drainage channel 71 is defined, as best shown in figures 2, 2a, between a first pair of blocks, formed by a block 33 of the second row 10 and the block 32 of the first row 9 preceding it in the circumferential direction and aligned with it according to the straight line of extension r common, and a second pair of blocks 32 , 33 - similarly formed and circumferentially adjacent.

Preferably, at least one side 38 of a block 32 of the first row 9 lies in a plane substantially parallel to the straight line of common extension r and is substantially aligned with at least one 40º side of a bit 33 of the second row 10 to delimit upwardly the second drain channel 71. Similarly, at least one side 40 of a block 32 of the first row 10 lies in a plane substantially parallel to the aforementioned straight line of extension r common and is substantially aligned with at least one side 38 'of a block 33 of the second row 10 to downwardly delimit the second drainage channel 71. Similarly, side 38 of block 32 and side 40º of block 33, - respectively, circumferentially adjacent to those mentioned above, and aligned with each other according to the line straight extension r common, delimiting the upper wall of the drain channel 71. The lower and upper walls of the second drain channel 71 are interrupted by substantially transverse sections of the circumferential hura 4.

Preferably, the second drainage channel 71 ends at the circumferential groove 3 ° and is connected to a transverse groove 28 of the shoulder portion to provide continuity of drainage.

Advantageously, for the same purpose, the drainage channel 71 ends at the circumferential groove 3 and is connected to the transverse groove 23.

Despite the low void / rubber ratio in the central L1 portion and, therefore, the large amount of rubber in relation to the ground, the formation of the two drainage channels mentioned above allows to avoid obstacles to the evacuation of water and / or mud between one shoulder and the other, thereby providing excellent drainage characteristics,. particularly when driving off-road. At the same time, the vacuum / rubber ratio is low - when referring to a tire intended for off-road use as well, it allows excellent handling, handling and durability characteristics to be combined in a tire particularly designed for off-road use.

As previously mentioned, for the purposes of the present invention, the expression “substantially continuous” with reference to drainage channels, can be interpreted as the condition in which, if the walls of the two blocks defining the channel and substantially arranged side by side are circumferentially continuations, the continuation lies within the channel itself or, in any case, at least one of these continuations, - if not lying within the channel, at most it will pass through the wall of a subsequent circumferentially block. For the purposes of this definition, abrupt reductions in the groove depth, due to reinforcing elements arranged between adjacent blocks, are not considered.

In other words, when moving the channel from one shoulder to the other and / or vice versa, a block wall will never be found defining the channel arranged so as to completely obstruct the passage through the channel, thus capturing water and / or mud.

According to an advantageous embodiment, the blocks - of the central rows can be provided with slots 53. The slits 53 of the central blocks 32, 33 have a “hockey stick” type curl, with the club cable arranged in the direction block extension.

In other words, the slots 53 have two substantially straight sections connected in order to define an angle less than 180º between them, for example, from about 130º to 150º. | One of the two substantially straight sections has a length: greater, equal to about 2-3 times the length of the other substantially. straight. In addition, the slots 53, like the slots 30 previously described, can have a depth between 2 and 10mm, and a width less than 2mm.

To provide tire 1 with greater structural strength and prevent excessive mobility of the blocks, they can be attached to each other by means of reinforcement elements, that is, by an amount of - rubber that reduces the groove depth in a section of separation between two adjacent blocks.

In the embodiment shown in figure 2a, the reinforcement element 133 is provided for this purpose between blocks 32, 33 of central rows 9 and 10, while reinforcement element 134 is provided between blocks 33 and shoulder blocks 27.

Finally, still with reference to the embodiment of figure 2a, reinforcement element 135 is provided between the blocks 32 of row 3 and the shoulder blocks 22.

A sample of the tire of the invention having the tread

2 of figures 1-2 was made and tested against a commercially available tire having a tread with four rows of blocks, two center rows and two shoulder rows, and known to users for excellent off-road behavioral characteristics, both on wet and dry floors, and homologated motor vehicles with large capacity engines.

Both tires were 265/76 R15, with the 8J16 ”rim and an inflation pressure of 2.3 bar.

A Mitsubishi L200 motor vehicle was initially equipped with four tires of the invention and then with four comparison tires.

Rolling behavior tests, both on terrain - paved, dry and wet, as well as off-road terrain, particularly muddy, sandy and small gravel terrain

15. rock blocks, as well as, comfort and noise inside and outside the motor vehicle were made.

The rolling behavior test on paved terrain, with dry and wet ground, is performed on predetermined paths, typically trails closed to traffic. By simulating some maneuvering characteristics (such as changing lanes, overtaking, slalom between traffic cones, entering and exiting curves) at a constant speed, as well as during acceleration and deceleration, the test driver evaluates the tire's performance by score a scoreboard for the latter's behavior during the aforementioned maneuvers.

In addition, rolling behavior tests on off-road terrain are performed on predetermined paths, closed to traffic, which comprise different types of terrain (ie mud, sand, gravel, etc.).

In this case, the test driver, performing some characteristic maneuvers on the different types of terrain, evaluates, by notes, the traction, maneuverability, controllability and directionality of the rear axle of the tire during the test.

In addition, two different types of noise tests outside the vehicle were performed, one with instruments and the other subjective.

The noise test with instruments outside the vehicle is carried out! over a straight stretch of a paved path provided with microphones. According to the test, the motor vehicle enters the segment of the route at a predetermined speed, then the engine is turned off and the noise outside the vehicle is measured. As engine idling until the vehicle comes to a stop. The subjective noise test outside the vehicle is carried out on the same type of route and following the same procedure, but in this case, the - evaluation is carried out only by the test driver. The results of the test are reproduced in Table 1, where the —notes are expressed as a percentage, establishing the values for the comparison tire as 100. The rating scale represents a subjective assessment made by the test driver who tests the equipment one after the other. Table 1 [the Teomparação cc—— | Invention = | Eamaçento Og oo | Gravel and small blocks of rock - | 190 190 In Table 1, values greater than 100 indicate an improvement over the reference tire.

The test results demonstrate that the tire of the invention overall performed better compared to the reference tire.

Claims (5)

1. Tire (1), characterized by the fact that it has a tread (2) comprising a central portion (L1) mounted on an equatorial plane (XX) and two shoulder portions (1.2, L3), in which: the portions shoulder (L1; L2) each have at least one row of side blocks (13; 14); the central portion (LI) has a void / rubber ratio of less than 0.25 and comprises a first and second row (9; 10) of central blocks having an elongated shape; each block (32) of the first central row (9) is substantially arranged axially side by side with a block (33) of the second row, so as to define a first substantially transverse drainage channel (70),. substantially continuous, which crosses the central portion (L1); ! the aforementioned first drainage channel substantially 15. Transverse (70) is defined between a first pair of blocks, formed by a block (32) of the first row (9) and a block (33) of the second row (10) arranged axially side by side, and the first pair circumferentially adjacent blocks, similarly formed; each block (32) of the first row (9) is arranged according to an extension direction; each block (33) of the second row (10) extends according to an extension direction substantially aligned with the extension direction of the block (32) circumferentially preceding the first row (9) in order to define a second inclined drainage channel and substantially continuous (71) that crosses the central portion (L1); the aforementioned second drainage channel (71) being defined between a second pair of nozzles, formed by a block (33) of the second row (10) and the block (32) of the first row (9) that precedes the first in the circumferential direction and is aligned therewith in a substantially common direction of extension, and the second pair of circumferentially adjacent blocks formed in a similar manner. 2. Tire according to claim 1, characterized by the fact that each block of the central portion (L1) extends according to an extension direction adapted to form an angle between 45º and 80º with the equatorial plane (X-X). Tire according to claim 1, characterized in that the blocks (32; 33) of the central rows (9; 10) comprise substantially convex polygons I. Tire according to any one of the preceding claims, characterized in that the perimeter of the blocks (32; 33) of the central rows (9; 10) comprise a broken line. f 5. Tire according to claim 4, characterized by the fact that each block has six sides. 6. Tire according to any of the preceding claims, characterized in that the blocks (32; 33) of the central rows (9; 10) have substantially the same shape and dimension. 7. Tire according to any of the preceding claims, characterized in that the blocks (32; 33) of the central rows (9; —10) have at least one tapered portion in order to form a vertex. 8. Tire according to claim 7, characterized in that the blocks (32) of the first row (9) are oriented with a vertex pointing in the opposite direction in relation to the apex of the blocks (33) of the second row (10). Tire according to any one of claims 5 to 8, characterized in that at least one first side (34) of a block (32) of the first central row (9) lies in a plane substantially perpendicular to the equatorial plane (XX ) and be substantially axially aligned with at least a second side (39º) of a block of the second central leaf (10) to delimit the first transverse channel (70) upwards. Tire according to any one of claims 5 to 9, characterized in that at least a second side (39) of a block (32) of the first central row (9) lies in a plane substantially - perpendicular to the equatorial plane ( XX) and be substantially axially aligned with at least one first side (34º) of a block of the second center row (10) to descend the first transverse channel (70). Tire according to any one of claims 5 to 10, characterized in that at least one side (40) of a block (32) of the first row (9) lies in a plane substantially parallel to the mentioned common extension direction and be substantially aligned with at least one side (387) of a block (33) of the second row (10) to delimit. downwardly the second drainage channel (71). Tire according to any one of claims 5 to | 11, characterized by the fact that at least one Jado (38) of a block (32) of the first row (9) lies in a plane substantially parallel to the mentioned common extension direction and is substantially aligned with at least one side (407) of a block (33) of the second row (9) for upwardly delimiting the second drain channel (71). 13. Tire according to any of the preceding claims, characterized in that the shoulder portion blocks (LI; L2) are circumferentially separated by transverse shoulder grooves (23; 28). 14. Tire according to any one of the preceding claims, characterized by the fact that it comprises two circumferential grooves (3; 3º) to separate said central portion L1 from shoulder portions L2; L3. 15. Tire according to any of the preceding claims, characterized by the fact that the circumferential grooves (3, 3 °) have a wavy course. 16. Tire according to claim 14 or 15, characterized by the fact that the path of the circumferential grooves (3; 3 ") is interrupted at least by the transverse shoulder grooves (23; 28). 17. Tire according to any one of the preceding claims, characterized in that the rows (9,10) of central circumferential blocks (32,33) are separated from each other by an additional circumferential groove (4). 18. Tire according to claim 17, characterized by the fact that the additional circumferential groove (4) has a sawtooth-like course. Ô =. "= A [ES 3, =; |; E, = ZE * 3 9 hello 3 Hu 20 so F A 7 + '| EZRA) EDS DA 23 Í FA of ES 3 Í AEDI IEA E fe Db 53 71/7) FE 7 28 31 = UA, Lo ie AASE PR and NÃ V /% = 28 23 1 LS = 7 2 2 2 A “53 QE | 23 ASS You 38 | | E dh 28 .-- | EE 4 and RFPADE EL lh A o A a. 12 n S Fig.2 3 135 3 59 ns 3rd 70. 2 | | : 5 | - S / Lo Ldo 133 E E DO Aa O) ESA OE of Fig. 2A : '; ; 4/4 * o [E <* õ, | =: - 2 eo <- = - So a on [5a] o: | -: mo> a, | The "