Commercial vehicle tires with high tread base

Abstract

Commercial vehicle tyres with a belt (8) extending in the circumferential direction U of the tyre over the circumference of the tyre, with at least two belt layers with reinforcements embedded in a rubber mixture and with a profiled tread (6) constructed radially outside the belt (8), • wherein the tread (6) has at least two circumferential grooves (9) extending in the circumferential direction U of the tire over the entire circumference of the tire, with a groove base (10) and with a groove base thickness G, wherein the groove base thickness G in each cross-section of the tire containing the tire axis indicates the distance of the lowest point of the groove base (10) to the radially outer surface which encloses the strength members of the radially outermost belt layer, • wherein the tread (6) has at least one profile rib (11) extending in the circumferential direction U of the tire over the entire circumference of the tire, which is limited in its axial extent by one or two circumferential grooves (9), • wherein the tread (6) has a profile depth (12) which is defined by an envelope extending in the tread (6) and touching the groove bases (10) of the circumferential grooves (9) from the radial inside, • wherein the tread (6) has two layers consisting of different rubber compounds, a tread cap (13) and a tread base (14), from radially outside to radially inside • and wherein the tread base (14) extends at least partially radially outside the profile depth (12), characterized in that • that at least one profile rib (11) is designed as a base profile rib (11), wherein the tread base (14) within each base profile rib (11) has a maximum radial extension Bmax with a value of 0.5 mm ≤ Bmax ≤ 2.0 mm, measured from the profile depth (12) vertically to the radially outside, • that at least one circumferential groove (9) axially delimiting the base profile rib (11) is designed as a deep circumferential groove (9), each deep circumferential groove (9) having a groove base thickness G of 3.5 mm ≤ G ≤ 7.0 mm, • that the tread base (14) is formed from a rubber mixture which has a rebound elasticity at 70°C of at least 70 points, preferably of at least 75 points, measured according to DIN 53 512, and • that the tread (6) has a regrooving reserve with a maximum regrooving depth of 0 mm to 1 mm.

Description

[0001] The invention relates to a commercial vehicle tire with a belt extending in the circumferential direction U of the tire over the circumference of the tire, having at least two belt plies with reinforcements embedded in a rubber mixture, and having a profiled tread constructed radially outside the belt, wherein the tread has at least two circumferential grooves extending in the circumferential direction U of the tire over the entire circumference of the tire, with a groove base and a groove base thickness G, wherein the groove base thickness G in each cross-section of the tire containing the tire axis indicates the distance from the deepest point of the groove base to the radially outer surface that encloses the reinforcements of the radially outermost belt ply, wherein the tread has at least one profile rib extending in the circumferential direction U of the tire over the entire circumference of the tire, which profile rib is limited in its axial extent by one or two circumferential grooves,wherein the tread has a profile depth which is defined by an envelope extending in the tread and touching the groove bases of the circumferential grooves from radially inward, wherein the tread has two layers consisting of different rubber compounds from radially outward to radially inward, a tread cap and a tread base, and wherein the tread base extends at least partially radially outside the profile depth.

[0002] It is common practice to equip pneumatic vehicle tires, especially commercial vehicle tires, with a two-part tread consisting of a tread cap, which comes into contact with the ground as the tire rolls, and a tread base, which is arranged essentially radially inside the tread cap. The tread cap is made of a rubber compound optimized for abrasion and other tire properties, and the tread base is made of a rubber compound optimized for hysteresis.

[0003] Such a hysteresis-optimized rubber compound typically exhibits poorer abrasion properties, such as a higher wear rate, than the rubber compound used in the tread cap. To adequately ensure a low tire wear rate, it is important to ensure that the tread base does not come into extensive contact with the road surface over the entire service life of the tread.

[0004] EP 2 477 824 B1 discloses a commercial vehicle tire of the type mentioned above, the tread base of which comprises a rubber compound in the two axially outermost tread ribs of the tread with a rebound resilience of 72.4 points at 70°C. The rubber compound, with a radial thickness of approximately 4.5 mm, extends at least partially radially outside the tread depth. The rubber compound of the tread base in the tread ribs arranged axially between these two axially outermost tread ribs has a rebound resilience of 50 points at 70°C. This design of the tread base has a positive effect on the tire's durability.

[0005] One of the key considerations in tread development is achieving low rolling resistance while maintaining sufficiently positive abrasion properties. Rolling resistance correlates with the rebound resilience at 70°C (according to DIN 53512) of the tread rubber compound(s), with high rebound resilience resulting in low rolling resistance. Retreadability also plays a major role in the tread development of commercial vehicle tires, as good retreadability positively influences the tire's economic efficiency.

[0006] US 2013 / 0220500 A1 and DE 602005001427 T2 each disclose a commercial vehicle tire for heavy vehicles with a split tread. US 4407346 A, EP 1531064 A1, and JP 2011-173438 A each disclose a pneumatic vehicle tire with a split tread.

[0007] The invention is based on the object of providing a commercial vehicle tire which has improved rolling resistance with sufficient abrasion properties and good retreadability.

[0008] The stated object is achieved according to the invention in that at least one tread rib is designed as a base tread rib, the tread base within each base tread rib having a maximum radial extension Bmax with a value of 0.5 mm ≤ Bmax ≤ 2.0 mm, measured from the tread depth perpendicularly to the radial outside, that at least one circumferential groove axially delimiting the base tread rib is designed as a deep circumferential groove, each deep circumferential groove having a groove base thickness G of 3.5 mm ≤ G ≤ 7.0 mm, that the tread base is formed from a rubber mixture which has a rebound resilience at 70°C of at least 70 points, preferably of at least 75 points, measured in accordance with DIN 53 512, and that the tread has a regrooving reserve with a maximum regrooving depth of 0 mm to 1 mm.

[0009] The base thickness G of each deep circumferential groove is 3.5 mm ≤ G ≤ 7.0 mm. This increased distance and the resulting amount of rubber material between the tread base of the deep circumferential groove and the reinforcement members of the radially outermost belt ply results in improved durability and improved retreadability.

[0010] The base thickness G of the circumferential grooves also influences the profile depth, which is defined by an envelope running within the tread and touching the groove bases of the circumferential grooves from the radial inside. In the shoulder areas axially outside the axially outermost circumferential grooves, the profile depth is parallel to the tread periphery.

[0011] The rubber compound from which the tread base is formed has a rebound resilience at 70°C of at least 70 points, preferably at least 75 points, measured according to DIN 53 512. Such high rebound resilience has a positive effect on the rolling resistance of the pneumatic vehicle tire. The rubber material arranged radially between the tread depth and the reinforcement member of the radially outermost belt layer is largely formed by the rubber compound of the tread base. Due to the great base thickness of the deep circumferential grooves, the high rebound resilience of the rubber compound of the tread base is particularly important for ensuring improved rolling resistance of the pneumatic vehicle tire.

[0012] Rolling resistance is further optimized by increasing the proportion of the tread base volume to the total tread volume. To achieve this, the tread base extends beyond the tread depth into the base rib. The extension is such that the maximum extension Bmax of the tread base within the base rib has a value of 0.5 mm ≤ Bmax ≤ 2.0 mm, measured radially outward from the tread depth normal to the tread depth.

[0013] A maximum extension Bmax of at least 0.5 mm ensures that a relevant proportion of the volume of the base profile rib is occupied by the low-rolling resistance rubber compound of the tread base.

[0014] Limiting Bmax to a maximum of 2.0 mm ensures that the rubber compound of the tread base, which generally has poorer abrasion properties than the rubber compound of the tread cap, does not come into extensive contact with the road surface throughout the entire service life of the tread. The service life of a tread is limited, among other things, by wear and thus by the decreasing depth of the circumferential grooves with wear. The legally prescribed minimum depth of the tire's circumferential grooves in operating condition is 1.8 mm.

[0015] A tread rib is a tread rib extending in the circumferential direction U of the tire over the entire circumference of the tire or a tread block extending in the circumferential direction U of the tire over the entire circumference of the tire, optionally divided by transverse grooves.

[0016] A regrooving reserve is a rubber layer of the tread, radially adjacent to the inside of the tread depth, into which the tread geometry of the largely worn treaded area can be subsequently cut. The maximum regrooving depth and thus the radial thickness of the regrooving reserve is the regrooving depth recommendation specified by the tire manufacturer for regroovable tires. Truck tires, in particular, are known to be regroovable by installing a regrooving reserve to increase the tire's mileage. Regrooving recommendations up to a depth of 4.5 mm are known.

[0017] In order to ensure positive abrasion properties such as a low wear rate over the entire service life of the tire, the tread has a regrooving reserve with a maximum regrooving depth of 0 mm to 1 mm.

[0018] A commercial vehicle tire with such a combination of geometry and rubber compound of the tread base exhibits improved rolling resistance while simultaneously maintaining sufficient abrasion properties and good retreadability. Surprisingly, it has been shown that the pneumatic vehicle tire according to the invention, due to the reduced rolling resistance combined with sufficiently positive abrasion properties and good retreadability, offers improved cost-effectiveness compared to conventional retreadable tires, even with a low maximum regrooving depth of 0 mm to 1 mm.

[0019] The advantages mentioned also apply when the tread has a maximum regrooving depth of 0 mm, i.e. when the tyre cannot be regrooved.

[0020] For tires with a regrooving reserve, it is customary to indicate the regrooving ability on the tire sidewall. This is often done by the notation “regroovable” on the tire sidewall. It is useful for a pneumatic vehicle tire with a regrooving reserve and a maximum regrooving depth of 0 mm to have a corresponding indication on its outer surface, in particular on the sidewall, which contains the information that the tread cannot be regrooved. This information can be a marking that can be detected and interpreted by a human observer and / or an electronic device. The marking can be colored and / or with a light-dark contrast and / or formed by elevation(s) and / or depression(s) on the surface.The marking may, for example, be a label and / or a symbol indicating that the profile is not regroovable and / or that the maximum regrooving depth is 0 mm. This is indicated, for example, by the words "nicht nachschneidbar" or "non-regroovable."

[0021] It is advantageous if at least one base tread rib is arranged not as the axially outermost tread rib, i.e., not as a shoulder rib, but as an axially inner tread rib bordered by two circumferential grooves. Such a tread pattern ensures good tire properties throughout the entire tread life, even with highly asymmetrical wear in the shoulder area.

[0022] It is particularly advantageous in terms of cost-effectiveness if the base profile rib has a maximum radial extension Bmax of the tread base within the base profile rib with a value of 1.0 mm ≤ Bmax ≤ 1.8 mm, measured from the profile depth vertically to the radially outside.

[0023] It is also advantageous if the deep circumferential groove is designed with a groove base thickness G of 5 mm ≤ G ≤ 7.0 mm, preferably 6.0 mm ≤ G ≤ 7.0 mm. Such a high groove base thickness ensures particularly good retreadability.

[0024] It is particularly advantageous for the rolling resistance of the commercial vehicle tire if the rubber compound of the tread base has a rebound elasticity at 70° that is at least 5 points higher than the rubber compound of the tread cap, each measured according to DIN 53 512.

[0025] In an advantageous embodiment, the base tread rib in the area between the tread depth and a surface running within the base tread rib, parallel to the tread depth and spaced 0.5 mm to 1.8 mm apart, is formed to at least 70 vol.% (volume percent), preferably at least 80 vol.%, of the rubber compound of the tread base. This optimizes the volume fraction of low-rolling-resistance rubber compound.

[0026] It is advantageous if the tread has two, three, or more axially adjacent base tread ribs. This further increases the volume fraction of the low-rolling-resistance rubber compound of the tread base relative to the total volume of the tread, thus further improving the rolling resistance of the commercial vehicle tire. Preferably, all inner tread ribs are base tread ribs. The proportion of low-rolling-resistance rubber compound is further increased if all tread ribs are base tread ribs.

[0027] It is also advantageous if all circumferential grooves bordering at least one base tread rib are deep circumferential grooves. It is also practical if all circumferential grooves are deep circumferential grooves.

[0028] The rebound resilience of the tread base compound can be influenced in various ways. For example, rebound resilience can be influenced by special rubbers, special cross-linking systems, the filler content, such as carbon black, and / or the bonding of the filler to the surrounding rubber matrix.

[0029] According to a preferred embodiment of the invention, the rubber compound of the tread base has a filler content of 20 phr to 30 phr, preferably 24 phr to 26 phr, particularly preferably 25 phr. Carbon black and / or silica, for example, can be used as fillers. The phr (parts per hundred parts of rubber by weight) is the standard quantity used in the rubber industry for compound formulations. The dosage of the weight fractions of the individual substances is always based on 100 parts by weight of the total mass of all rubbers present in the mixture.

[0030] Such a commercial vehicle tire is particularly suitable for trucks or buses.

[0031] Further features, advantages and details of the invention will now be explained in more detail with reference to the schematic drawing, which shows an embodiment. Fig. 1 a schematic partial cross-section through a commercial vehicle tire according to the invention.

[0032] The Fig. 1 shows the right half of a partial cross-section through a pneumatic vehicle tire according to the invention for a commercial vehicle. Fig. 1 shows, of the usual components of a commercial vehicle tire, a largely air-impermeable inner layer 1, a carcass 2 containing at least one reinforcement layer, which extends in a conventional manner from the zenith region of the pneumatic vehicle tire over the side walls 3 into the bead regions and is anchored there by wrapping tensile bead cores, a profiled tread 6 located radially above the carcass 2 and a belt 8 arranged between the tread 6 and the carcass 2 and extending in the circumferential direction U of the tire over the circumference of the tire with four belt layers with reinforcements made of steel cords embedded in a rubber mixture.

[0033] The profiled tread 6 comprises, in the area shown, two circumferential grooves 9 extending in the circumferential direction U of the tire over the entire circumference of the tire, with a groove base 10 and a groove base thickness G, wherein the groove base thickness G in each cross-section of the tire containing the tire axis indicates the distance of the lowest point of the groove base 10 to the radially outer surface which envelops the strength members of the radially outermost belt layer.

[0034] Furthermore, the tread has at least one profile rib 11 extending in the circumferential direction U of the tire over the entire circumference of the tire, which is limited in its axial extent by one or two circumferential grooves 9.

[0035] The profile depth 12 of the tread 6 is given by an envelope running in the tread 6 and touching the groove bottoms 10 of the circumferential grooves 9 from the radial inside.

[0036] The tread 6 has, from radially outside to radially inside, two layers consisting of different rubber compounds, a tread cap 13 and a tread base 14, wherein the tread base 14 extends at least partially radially outside the tread depth 12.

[0037] In the illustrated embodiment, all profile ribs 11 are designed as base profile ribs. The maximum radial extent Bmax of the tread base 14 within these base profile ribs 11 is designed with a value of 1 mm ≤ Bmax ≤ 1.8 mm, measured perpendicularly radially outward from the profile depth 12. At least the axially inner profile ribs 15 are formed by the rubber compound of the tread base 14 to an extent of at least 70 vol.%, preferably at least 80 vol.%, in the region between the profile depth 12 and a surface running within the base profile rib, parallel to the profile depth and spaced 0.5 mm to 1.8 mm apart.

[0038] The circumferential grooves 10 delimit the profile ribs 11 in the axial direction and are all designed as deep circumferential grooves 10, ie they have a groove base thickness G of 6 mm ≤ G ≤ 7.0.

[0039] Furthermore, the tread base 14 is formed from a rubber compound having a rebound resilience at 70°C of at least 70 points, preferably at least 75 points, measured according to DIN 53 512. The rubber compound of the tread base 14 has a rebound resilience at 70°C that is at least 5 points higher than the rubber compound of the tread cap 13, each measured according to DIN 53 512. The rubber compound of the tread base 14 has a filler content of 20 phr to 30 phr, preferably of 24 phr to 26 phr.

[0040] The tread has a regrooving reserve n with a maximum regrooving depth of 0 mm. The profile is therefore not regroovable. Sidewall 3 is marked with the word "non-regroovable" (not shown). This is formed by raised areas on the surface of sidewall 3.

[0041] It is a tire for trucks or buses. List of reference symbols 1 inner layer 2 carcass 3 side wall 6 treads 7 Contact surface with the road 8 belts 9 circumferential groove 10 groove base 11 profile rib 12 tread depth 13 tread cap 14 Tread base 15 axial inner profile rib G Groove base thickness Bmax maximum radial extension of the tread base U circumferential direction aR axial direction rR radial direction

Claims

[1] Commercial vehicle tyres with a belt (8) extending in the circumferential direction U of the tyre over the circumference of the tyre, with at least two belt layers with reinforcements embedded in a rubber mixture and with a profiled tread (6) constructed radially outside the belt (8), • wherein the tread (6) has at least two circumferential grooves (9) extending in the circumferential direction U of the tire over the entire circumference of the tire, with a groove base (10) and with a groove base thickness G, wherein the groove base thickness G in each cross-section of the tire containing the tire axis indicates the distance of the lowest point of the groove base (10) to the radially outer surface which encloses the strength members of the radially outermost belt layer, • wherein the tread (6) has at least one profile rib (11) extending in the circumferential direction U of the tire over the entire circumference of the tire, which is limited in its axial extent by one or two circumferential grooves (9), • wherein the tread (6) has a profile depth (12) which is defined by an envelope extending in the tread (6) and touching the groove bases (10) of the circumferential grooves (9) from the radial inside, • wherein the tread (6) has two layers consisting of different rubber compounds, a tread cap (13) and a tread base (14), from radially outside to radially inside • and wherein the tread base (14) extends at least partially radially outside the profile depth (12), characterized by , that • that at least one profile rib (11) is designed as a base profile rib (11), wherein the tread base (14) within each base profile rib (11) has a maximum radial extension Bmax with a value of 0.5 mm ≤ Bmax ≤ 2.0 mm, measured from the profile depth (12) vertically to the radially outside, • that at least one circumferential groove (9) axially delimiting the base profile rib (11) is designed as a deep circumferential groove (9), each deep circumferential groove (9) having a groove base thickness G of 3.5 mm ≤ G ≤ 7.0 mm, • that the tread base (14) is formed from a rubber mixture which has a rebound elasticity at 70°C of at least 70 points, preferably of at least 75 points, measured according to DIN 53 512, and • that the tread (6) has a regrooving reserve with a maximum regrooving depth of 0 mm to 1 mm. [2] Commercial vehicle tyre according to claim 1, characterized bythat the recutting reserve has a maximum recutting depth of 0 mm. [3] Commercial vehicle tyres according to one or more of the preceding claims, characterized by that at least one base profile rib (11) is an axially inner profile rib (15). [4] Commercial vehicle tyres according to one or more of the preceding claims, characterized by that the maximum radial extension Bmax of the tread base (14) within the base profile rib (11) has a value of 1.0 mm ≤ Bmax ≤ 1.8 mm, measured from the profile depth (12) vertically to the radial outside. [5] Commercial vehicle tyres according to one or more of the preceding claims, characterized by that the deep circumferential groove (9) is formed with a groove base thickness G of 5 mm ≤ G ≤ 7.0 mm, preferably of 6.0 mm ≤ G ≤ 7.0 mm. [6] Commercial vehicle tyres according to one or more of the preceding claims, characterized bythat the rubber compound of the tread base (14) has a rebound elasticity at 70° that is at least 5 points higher than the rubber compound of the tread cap (13), each measured according to DIN 53 512. [7] Commercial vehicle tyres according to one or more of the preceding claims, characterized by that the base profile rib (11) in the area between the profile depth (12) and a surface running within the base profile rib (11), parallel to the profile depth (12) and spaced by 0.5 mm to 1.8 mm, is formed by the rubber mixture of the tread base (14) to an extent of at least 70 vol.%, preferably at least 80 vol.%. [8] Commercial vehicle tyres according to one or more of the preceding claims, characterized by that all circumferential grooves (9) which delimit at least one base profile rib (11) are deep circumferential grooves (9). [9] Commercial vehicle tyres according to one or more of the preceding claims, characterized bythat the tread (6) has two, three or more axially adjacent base profile ribs (11). [10] Commercial vehicle tyres according to one or more of the preceding claims, characterized by that the rubber mixture of the tread base (14) has a filler content of 20 phr to 30 phr, preferably 24 phr to 26 phr. [11] Commercial vehicle tyres according to one or more of the preceding claims, characterized by that it is a tire for trucks or buses.

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