Commercial-vehicle tire

Abstract

The invention relates to a commercial-vehicle tire comprising bead regions, each of which has a bead core (5), a flange profile (3) and an apex (6) which is composed of a radially outer apex portion (6a) and a radially inner apex portion (6b) which contacts the bead core (5), the radially outer apex portion (6a) and the radially inner apex portion (6b) differing from one another in terms of their rubber material. The aim of the invention is to resolve the conflict existing between the objectives rolling resistance and bead durability in a considerably more favorable way than before. This aim is achieved in that the radially inner apex portion (6b) has a cross-sectional area having a surface area (A6b) ranging from 60% to 160% of the surface area (A5) of the cross-sectional area of the bead core (5), wherein the rubber material of the radially inner apex portion (6b) has a tensile stress at 100% elongation which is greater than the tensile stress of the rubber material of the radially outer apex portion (6a) by 2.00 MPa to 30.00 MPa, and wherein the rubber material of the radially outer apex portion (6a) has a rebound resilience at 70°C, which is greater than the rebound resilience of the rubber material of the radially inner apex portion (6b) by 5.0 percentage points to 50.0 percentage points.

Description

[0001] Description

[0002] Commercial vehicle tires

[0003] The invention relates to a commercial vehicle tire with bead regions each having a bead core, a two-part apex sitting radially outward on the bead core and a horn profile, as well as a single- or multi-layer carcass insert folded over the bead cores, wherein each apex is composed of a radially outer apex part and a radially inner apex part contacting the bead core, wherein the radially outer apex part and the radially inner apex part each consist of a rubber material and the rubber material of the radially outer apex part differs from the rubber material of the radially inner apex part.

[0004] A commercial vehicle tire of the type mentioned above is known, for example, from DE 102014 211 525 A1. The commercial vehicle tire has a steel cord bead reinforcer running along the outer side of the carcass ply, a two-part apex in each bead area, and two reinforcement layers made of textile reinforcements embedded in rubber running along the outer side of the steel cord bead reinforcer. The apex has a radially outer apex part and a radially inner apex part, whereby in one embodiment, the rubber material of the radially outer apex part differs from the rubber material of the radially inner apex part in terms of its hardness.The reinforcement layers terminate radially within the bead core and extend radially to a height that is at least 70 mm, relative to a line running axially through the rim corner point. The ends of the reinforcement layers located at this height are spaced apart from each other by up to 10 mm in the radial direction. The reinforcement layers provide greater rigidity in the upper bead and sidewall areas, thereby reducing the rolling resistance of the commercial vehicle tire by 2% to 5%. Another commercial vehicle tire of the type mentioned above, which is a bias-shoulder tire, is known from DE 10 2014 213240 A1.The commercial vehicle tire has an inner layer, optionally combined with a filler profile, a carcass ply forming carcass roll-ups, a steel cord bead reinforcer running on the outside of the carcass ply in each bead area with a section running on the outside of the tire and a section running on the inside of the tire, and an apex consisting of a radially outer apex part and a radially inner apex part. The rubber material of the radially outer apex part can differ from the rubber material of the radially inner apex part. Between the inner layer or the filler profile and the section of the steel cord bead reinforcer running on the inside of the tire and the section of the carcass ply adjoining it in the radial direction runs a reinforcement layer made of textile strength members embedded in rubber, which ensures particularly high load capacity and high mileage.

[0005] JP 2000 108 616 A discloses a commercial vehicle tire with bead regions, each with a multi-part apex consisting of at least two apex parts. According to one embodiment, the apex is composed of a radially inner apex part and a radially outer apex part, with the rubber material of the radially inner apex part having a greater hardness than the rubber material of the radially outer apex part. This is intended to ensure good bead durability.

[0006] It is also known that the design of the bead areas of a commercial vehicle tire significantly influences driving stability, steering behavior, suspension comfort, and the tire's fit on the rim. It is particularly important to avoid stiffness jumps in the bead areas and to ensure the most even (smooth) stiffness progression possible. Stiffness is greatest in the area of ​​the bead cores, where the bead cores are responsible for the tire's secure and firm fit on the rim. In the thinner sidewall areas, stiffness is lower than near the bead cores, which can cause the tire to periodically compress during rolling (flexion work). Excessive deflection leads to greater flexion work and thus to thermal heating, which can cause tire damage. The apex influences the stiffness and stiffness progression in the bead and sidewall areas.The deflection should not occur too close to the rim flanges, as this increases the risk of the tire deforming at the rim flanges and damaging the bead areas. If damage occurs in the bead areas, retreading the tire in the tread area is no longer an option.

[0007] Currently, it is still common practice to use single-piece apexes made of a single rubber material with "medium" or "low" stiffness. Due to their triangular cross-sectional shape, single-piece apexes also provide a corresponding stiffness profile in the bead and sidewall areas, although single-piece apexes are significantly inferior to multi-piece apexes in this respect. Single-piece apexes are therefore not optimal in terms of bead durability, but have proven to be favorable in terms of rolling resistance with the appropriate selection of rubber material.

[0008] The previously known multi-part apexes consisting of at least two apex parts, in which it is usual for one apex part to be made of a rubber material with greater stiffness and the other apex part to be made of a rubber material with lower stiffness, are particularly advantageous for bead durability, so that the risk of tire damage in the bead area is reduced and the commercial vehicle tire is therefore usually considered for retreading.

[0009] In the design and configuration of apexes, there is a previously inadequately resolved conflict between rolling resistance and bead durability, which is directly related to retreadability. The invention is therefore based on the object of resolving the conflict between rolling resistance and bead durability in a commercial vehicle tire of the type mentioned above in a significantly more favorable manner than previously.

[0010] The stated object is achieved according to the invention in that o the radially inner apex part has a cross-sectional area with a surface area of ​​60% to 160% of the surface area of ​​the cross-sectional area of ​​the bead core, o the rubber material of the radially inner apex part has a stress value at 100% elongation - determined according to DIN 53504 with test specimen type S3 - which is 2.00 MPa to 30.00 MPa greater than the stress value at 100% elongation of the rubber material of the radially outer apex part and o the rubber material of the radially outer apex part has a rebound resilience at 70°C - determined according to ISO 4662, with a test specimen with a thickness of 6.3 mm ± 0.5 mm according to Annex A of ISO 4662 - which is 5.0 percentage points to 50.0 percentage points greater than the rebound resilience at 70°C of the Rubber material of the radially inner apex part.

[0011] According to the invention, the radially inner apex part has a significantly smaller cross-sectional area than previously usual, whereby the cross-sectional area of ​​the radially inner apex part is at least one-third, and even tends to be at least 50% smaller, than in previously conventional apexes. Although the radially inner apex part is "small", its stiff rubber material (higher stress value at 100% elongation) maintains overall high bead stability (good bead durability), making the commercial vehicle tire ideally suited for retreading. In particular, bead durability is significantly improved compared to currently conventional one-piece apexes. The radially outer apex part, which is therefore larger than previously usual in terms of its cross-sectional area, is made of a rubber material whose rebound resilience at 70°C is significantly greater than that of the rubber material of the radially inner apex part.The rubber material of the radially outer apex part is thus optimized with regard to the tire's rolling resistance. The rolling resistance is significantly improved (low rolling resistance), especially compared to known commercial vehicle tires with the previously common two-part apex. The commercial vehicle tire according to the invention is thus significantly improved with regard to the trade-off between rolling resistance and bead stability.

[0012] According to a preferred embodiment, the cross-sectional area of ​​the radially inner apex portion is 70% to 140%, in particular 75% to 130%, preferably 80% to 120%, and particularly preferably up to 100%, of the cross-sectional area of ​​the bead core. This is particularly advantageous in view of the conflicting objectives to be resolved.

[0013] According to a further preferred embodiment, the stress value at 100% elongation of the rubber material of the radially inner apex part is 3.00 MPa to 25.00 MPa, preferably 4.00 MPa to 18.00 MPa, particularly preferably 4.50 MPa to 16.00 MPa, and most preferably 6.00 MPa to 12.00 MPa greater than the stress value at 100% elongation of the rubber material of the radially outer apex part. These differences have proven particularly advantageous for the tire's bead durability.

[0014] In addition, it is favorable for the bead durability if the stress value at 100% elongation of the rubber material of the radially outer apex part is 0.50 MPa to 9.00 MPa, in particular 0.75 MPa to 7.50 MPa, preferably 1.00 MPa to 6.00 MPa, and particularly preferably 2.50 MPa to 5.00 MPa.

[0015] A further preferred embodiment is characterized in that the rebound resilience at 70°C of the rubber material of the radially outer apex part is 7.5 percentage points to 45.0 percentage points, preferably 9.0 percentage points to 40.0 percentage points, and particularly preferably 10.0 percentage points to 30.0 percentage points, greater than the rebound resilience at 70°C of the rubber material of the radially inner apex part. This contributes to a further reduction in the rolling resistance of the tire.

[0016] Furthermore, it is favorable for the rolling resistance of the tire if the rebound elasticity at 70°C of the rubber material of the radially inner apex part is 25% to 65%, in particular 30% to 60%, and preferably at least 45%.

[0017] According to a further preferred embodiment, the carcass ply is designed as a single layer and ends in each bead region as a carcass turnup with a height determined in the radial direction. The radially inner apex portion, on its side facing the inside of the tire and contacting the carcass ply, has a maximum height determined in the radial direction of 60% to 100%, in particular 70% to 90%, of the height of the carcass turnup. The maximum height and the height refer to a line which, viewed in the tire cross-section, runs in the axial direction through a point on the bead region of the commercial vehicle tire that corresponds to the rim corner point. This design is also of additional advantage for rolling resistance and bead durability.

[0018] According to an alternative, further preferred embodiment, the carcass ply is designed in multiple layers, with each layer of the carcass ply ending in each bead region as a carcass turnup with a height determined in the radial direction. The radially inner apex part, on its side facing the inside of the tire and contacting the carcass ply, has a maximum height determined in the radial direction of 60% to 100%, in particular 70% to 90%, of the height of the highest carcass turnup, wherein the maximum height and the height refer to a line which, viewed in the tire cross-section, runs in the axial direction through a point on the bead region of the commercial vehicle tire that corresponds to the rim corner point. This design is also of additional advantage for rolling resistance and bead durability.In the last two preferred embodiments, the height of the carcass turn-up is in particular 25.0 mm to 50.0 mm, preferably 30.0 mm to 45.0 mm.

[0019] Preferably, the cross-sectional area of ​​the radially inner apex portion is triangular, with the radially inner apex portion tapering off at its end facing away from the bead core. This design is further advantageous with regard to the trade-off between rolling resistance and bead durability.

[0020] Furthermore, in the last two embodiments, it is advantageous if the radially outer apex part, viewed in the tire cross-section, runs between the or each carcass turn-up and the radially inner apex part.

[0021] The commercial vehicle tire is preferably designed for mounting on a 15° drop-center rim with a width code of 5.25 to 18.00, as per ETRTO standards.

[0022] The use of the commercial vehicle tire according to the invention on a 15° drop-center rim with a width code of 5.25 to 18.00, standardized according to ETRTO standards, is therefore particularly advantageous.

[0023] Further features, advantages and details of the invention will now be explained with reference to the single figure, Fig. 1, which schematically shows a cross section through one of the bead regions of a commercial vehicle tire with an embodiment of the invention.

[0024] Commercial vehicle tires designed according to the invention are tires for multi-track commercial vehicles, preferably for medium-duty trucks (7.5 t < GVW < 18.0 t), for heavy trucks (GVW > 18.0 t) or for buses, and in particular commercial vehicle tires of radial design. The heights specified below are measured in the radial direction (indicated by the double arrow R) and each refer to a line L which, when the commercial vehicle tire is mounted on a suitable rim and not inflated, viewed in the tire cross-section, runs in the axial direction (indicated by the double arrow A) through a point X corresponding to the rim corner point on the respective bead area of ​​the commercial vehicle tire. The axial direction is understood to be the direction running parallel to the axis of rotation of the commercial vehicle tire. The radial direction corresponds to the direction running perpendicular to the axial direction in the tire cross-section.The rim corner point is known to be the intersection point of the rim shoulder with the rim flange. The heights are determined using a tire circumferential section cut from a vulcanized pneumatic tire, which is attached to the rim. Alternatively, the heights can be determined using computed tomography.

[0025] Fig. 1 shows a cross-section through a bead region of a vulcanized commercial vehicle tire. The second bead region, not shown, is designed to match the bead region shown.

[0026] The commercial vehicle tire is specifically designed for mounting on a 15° drop-center rim, which is designed in accordance with the European Tire and Rim Technical Organization Standards Manual (“ETRTO Standards”) in the currently applicable version (as of July 19, 2022), section 15° Drop-Center Rims (width codes 5.25 to 18.00) with nominal diameters of 17.5 inches, 19.5 inches, 20.5 inches, 22.5 inches or 24.5 inches.

[0027] Fig. 1 shows the components of the commercial vehicle tire: a section of an airtight inner layer 1, a section of a sidewall 2, a flange profile 3, a section of a single-ply carcass insert 4, a bead core 5, a two-part apex 6 seated on the bead core 5, a core flap 7, a steel cord bead reinforcement 8, a filler profile 9, and a filler profile 10. All of these components extend over the entire circumference of the tire, thus forming a ring around components running in the circumferential direction.

[0028] The sidewall 2 overlaps the horn profile 3 on the outside of the tire. The carcass ply 4 consists of steel cords embedded in rubber, running cross-free and essentially parallel to one another, wherein the carcass ply 4 runs in a known manner between the two bead cores 5, is folded over around each bead core 5 from the inside of the tire facing the inner layer 1 towards the outside of the tire and ends on the outside of the tire next to the apex 6 as a carcass turnup 4a at a height hi of 25.0 mm to 50.0 mm, preferably 30.0 mm to 45.0 mm. The core lug 7 consists of a rubberized textile fabric, in particular of rubberized nylon fabric, and is placed around the bead core 5 in such a way that it separates the carcass ply 4 from the bead core 5.The steel cord bead reinforcer 8 consists of steel cords embedded in rubber, running cross-free and essentially parallel to each other. It runs in contact with the side of the carcass ply 4 facing away from the bead core 5 and ends on the inside and outside of the tire in the area of ​​the apex 6, while on the outside of the tire it ends before the end of the carcass turnup 4a. The filler profile 9 is located on the outside of the tire, on the bead core 5 and the apex 6, and runs - in sections - between the steel cord bead reinforcer 8 and the flange profile 3, between the carcass turnup 4a and the flange profile 3, and between the apex 6 and the flange profile 3 or the sidewall 2.The filling profile 10 runs between the two bead areas, is located in each bead area on the inside of the bead core 5 and the apex 6 and runs in each bead area in sections between the steel cord bead reinforcer 8 and the inner layer 1 as well as in sections between the inner layer 1 and the carcass ply 4.

[0029] The bead core 5 consists of a tensile core wire 5a, which is embedded in rubber material and runs circumferentially, is made in particular of metal, and preferably has a circular cross-section. The bead core 5a is formed in a known manner by winding a single core wire 5a embedded in rubber material or by winding a plurality of core wires 5a embedded in rubber material. The bead core 5 has, viewed in the tire cross-section, a cross-sectional area with an area As. For a bead core 5 made of a single core wire 5a, the area As of the cross-sectional area of ​​the bead core 5 is calculated from the maximum number of turns multiplied by the area of ​​the cross-sectional area of ​​the core wire 5a. The number of turns can vary by one turn, depending on the location of the cross-section.The "maximum number of turns" is the number of turns at a location where the largest number of turns is present. For a bead core 5 composed of a plurality of core wires 5a, the surface area As of the cross-sectional area of ​​the bead core 5 is calculated from the number of core wires 5a multiplied by the surface area of ​​the cross-sectional area of ​​one core wire 5a. Therefore, when determining the surface area As, the rubber material surrounding the core wire 5a(s) is not taken into account.

[0030] The two-part apex 6 consists of a radially outer apex part 6a made of a rubber material, preferably not in contact with the bead core 5, and a radially inner apex part 6b made of a rubber material, preferably not in contact with the bead core 5. The rubber materials of the apex parts 6a, 6b differ in their stress values ​​at 100% elongation and in their rebound resilience at 70°C, as explained below.

[0031] In the exemplary embodiment shown, the radially inner apex part 6b, viewed in the tire cross-section, has a substantially triangular cross-sectional area, runs at its end facing away from the bead core 5 along a section of the carcass ply 4 running inside the tire, and extends to a maximum height h2 (height at the highest point), which is 60% to 100%, in particular 70% to 90%, of the aforementioned height hi of the carcass turnup 4a. The cross-sectional area of ​​the radially inner apex part 6b has a surface area Aeb, which is 60% to 160%, in particular 70% to 140%, preferably 75% to 130%, particularly preferably 80% to 120%, most preferably up to 100%, of the surface area As of the cross-sectional area of ​​the bead core 5.

[0032] The radially outer apex part 6a runs, viewed in the tire cross-section, between the carcass turn-up 4a and the radially inner apex part 6b, thus separating, together with the core lug 7, the radially inner apex part 6b from the carcass turn-up 4a and extending in the radial direction to a height ho which is greater than the already mentioned height hi of the carcass turn-up 4a.

[0033] The stress values ​​at 100% elongation mentioned above were determined according to DIN 53504 (Testing of rubber and elastomers - Determination of tear strength, tensile strength, elongation at break and stress values ​​in tensile tests (edition 2017-03), test specimen type S3).

[0034] The rebound resilience at 70°C was determined according to ISO 4662 (Rubber-rubber or thermoplastic elastomers - Determination of rebound resilience of vulcanizates (Edition 2017-06, Pendulum method according to Section 5)), with a test piece thickness of 6.3 mm ± 0.5 mm, as mentioned in Annex A (Use of non-standard test pieces).

[0035] The rebound resilience at 70°C serves as an indicator of the rolling resistance of the tire, with high rebound resilience at 70°C meaning low rolling resistance.

[0036] The rubber material of the radially outer apex part 6a has a stress value at 100% elongation which is 0.50 MPa to 9.00 MPa, in particular 0.75 MPa to 7.50 MPa, preferably 1.00 MPa to 6.00 MPa, and particularly preferably 2.50 MPa to 5.00 MPa. The rubber material of the radially inner apex part 6b has a stress value at 100% elongation which is 2.00 MPa to 30.00 MPa, in particular 3.00 MPa to 25.00 MPa, preferably 4.00 MPa to 18.00 MPa, particularly preferably 4.50 MPa to 16.00 MPa, most preferably 6.00 MPa to 12.00 MPa greater than the stress value at 100% elongation of the rubber material of the radially outer apex part 6a.

[0037] The rubber material of the radially outer apex part 6a further has a rebound resilience at 70°C that is 5.0 percentage points to 50.0 percentage points, in particular 7.5 percentage points to 45.0 percentage points, preferably 9.0 percentage points to 40.0 percentage points, and particularly preferably 10.0 percentage points to 30.0 percentage points, greater than the rebound resilience at 70°C of the rubber material of the radially inner apex part 6b. The rubber material of the radially inner apex part 6b has a rebound resilience at 70°C that is 25% to 65%, in particular 30% to 60%, and preferably at least 45%.

[0038] In the illustrated embodiment, three rubber reinforcing strips 11, 12, 13 are installed on the outer side of the tire's apex 6, running circumferentially. The reinforcing strip 11 runs between the carcass turnup 4a and the steel cord bead reinforcement 8. The reinforcing strip 12 runs over its entire extent in contact with the filler profile 9 and, in sections, in contact with the steel cord bead reinforcement 8, the carcass turnup 4a, and the radially outer apex part 6a. The reinforcing strip 13 covers the free end of the carcass turnup 4a and, in sections, in contact with the radially outer apex part 6a and the reinforcing strip 12.

[0039] Table 1 shows examples of rubber compounds A and B. The quantities of the components of rubber compounds A and B are given in the unit phr (parts per hundred parts rubber), which is common in rubber technology. The quantities refer to 100 parts by mass of the base polymer. Tires with correspondingly constructed apexes, as shown in Table 2, were manufactured from rubber compounds A and B and compared as explained below in Table 1. Table 1: Recipes

[0040] Commercial vehicle tires in the dimension 315 / 70 R 22.5 were manufactured for a steering axle. These tires differed only in the design of the apex. The apexes had a similar cross-sectional shape and thus similarly large cross-sectional areas. The differences in the apex are shown in Table 2. Table 2 also contains tire test results, which included a rolling resistance test according to ISO 28580 (Passenger car, truck, and bus tires - Rolling resistance measurement method - Single-point test and correlation of measurement results, edition 2018-07) and a specially developed bead durability test (drum test). The test result for the bead durability of the reference tire Ref. 1 was set to a value of 100. Values ​​less than 100 indicate a deterioration in bead durability.

[0041] Table 2: Tire test results

[0042] Table 2 shows that the commercial vehicle tire according to the invention has significantly lower rolling resistance compared to the reference tire Ref. 1 and remains consistently good in terms of bead durability. Furthermore, Table 2 shows that the commercial vehicle tire according to the invention remains consistently good in terms of rolling resistance compared to the reference tire Ref. 2 and is significantly improved in terms of bead durability.

[0043] Furthermore, consistent tests were conducted with a tire of the specified dimension intended for a drive axle and a tire of the specified dimension intended for a trailer axle. These tests also demonstrate corresponding improvements in rolling resistance and bead durability for tires according to the invention. The invention is not limited to the described embodiment.

[0044] In the bead area of ​​the tire, additional reinforcement layers containing strength members as well as additional reinforcement strips made of rubber can be installed. The carcass ply 4 can be multi-layered, in particular two- or three-layered. In a multi-layer carcass ply, the carcass turnups of the layers of the carcass ply can end at different heights. The radially inner apex part 6b, viewed in the tire cross-section, can have a cross-sectional area that deviates from the triangular cross-sectional area. The aforementioned maximum height h2 of the radially inner apex part 6b is 60% to 100%, in particular 70% to 90%, of the height of the highest carcass turnup. The core tab 7, the steel cord bead reinforcement 8 and the reinforcement strips 11, 12, 13 are optional. The cross-sectional area of ​​the bead core is in particular hexagonal or circular. Alternatively, the cross-sectional area of ​​the bead core has a shape of a hexagon ora shape derived from a circle. Such a derived shape is, for example, a cross-sectional area in the shape of a hexagon with a corner region roughly shaped like a parallelogram.

[0045] List of reference symbols

[0046] 1 inner layer

[0047] 2 Side wall 3 Horn profile

[0048] 4 Carcass insert

[0049] 4a Carcass roll-up

[0050] 5. Bead core

[0051] 5a Core wire 6 Apex

[0052] 6a radial outer apex part

[0053] 6b radial inner apex part

[0054] 7 core flag

[0055] 8 Steel cord bead reinforcement 9 Filler profile

[0056] 10 Filling profile

[0057] 11 Reinforcement layer

[0058] 12 reinforcement layer

[0059] 13 Reinforcement layer A double arrow (axial direction)

[0060] As, Aeb Area ho, hi Height h2 Maximum height

[0061] L Line R Double arrow (radial direction)

[0062] X point

Claims

Patent claims 1. Commercial vehicle tire with bead areas each having a bead core (5), a two-part apex (6) sitting radially outwardly on the bead core (5) and a horn profile (3), as well as a single- or multi-ply carcass insert (4) folded over the bead cores (5), each apex (6) being composed of a radially outer apex part (6a) and a radially inner apex part (6b) contacting the bead core (5), the radially outer apex part (6a) and the radially inner apex part (6b) each consisting of a rubber material and the rubber material of the radially outer apex part (6a) being different from the rubber material of the radially inner apex part (6b), characterized in that the radially inner apex part (6b) has a cross-sectional area with an area content (Aeb) of 60% to 160% of the area content (As) of the cross-sectional area of ​​the bead core (5),o wherein the rubber material of the radially inner apex part (6b) has a stress value at 100% elongation - determined according to DIN 53504 with test specimen type S3 - which is 2.00 MPa to 30.00 MPa greater than the stress value at 100% elongation of the rubber material of the radially outer apex part (6a), and o wherein the rubber material of the radially outer apex part (6a) has a rebound resilience at 70°C - determined according to ISO 4662, with a test specimen with a thickness of 6.3 mm ± 0.5 mm according to Annex A of ISO 4662 - which is 5.0 percentage points to 50.0 percentage points greater than the rebound resilience at 70°C of the rubber material of the radially inner apex part (6b).

2. Commercial vehicle tire according to claim 1, characterized in that the surface area (Aeb) of the cross-sectional area of ​​the radially inner apex part (6b) is 70% to 140%, in particular 75% to 130%, preferably 80% to 120%, particularly preferably up to 100%, of the surface area of ​​the cross-sectional area (As) of the bead core (5).

3. Commercial vehicle tire according to claim 1 or 2, characterized in that the stress value at 100% elongation of the rubber material of the radially inner apex part (6b) is 3.00 MPa to 25.00 MPa, preferably 4.00 MPa to 18.00 MPa, particularly preferably 4.50 MPa to 16.00 MPa, most preferably 6.00 MPa to 12.00 MPa greater than the stress value at 100% elongation of the rubber material of the radially outer apex part (6a).

4. Commercial vehicle tire according to one of claims 1 to 3, characterized in that the stress value at 100% elongation of the rubber material of the radially outer apex part (6a) is 0.50 MPa to 9.00 MPa, in particular 0.75 MPa to 7.50 MPa, preferably 1.00 MPa to 6.00 MPa, and particularly preferably 2.50 MPa to 5.00 MPa.

5. Commercial vehicle tire according to one of claims 1 to 4, characterized in that the rebound resilience at 70°C of the rubber material of the radially outer apex part (6a) is 7.5 percentage points to 45.0 percentage points, preferably 9.0 percentage points to 40.0 percentage points, and particularly preferably 10.0 percentage points to 30.0 percentage points, greater than the rebound resilience at 70°C of the rubber material of the radially inner apex part (6b).

6. Commercial vehicle tire according to one of claims 1 to 5, characterized in that the rebound resilience at 70°C of the rubber material of the radially inner apex part (6b) is 25% to 65%, in particular 30% to 60%, and preferably at least 45%.

7. Commercial vehicle tyre according to one of claims 1 to 6, characterised in that the carcass ply (4) is designed in a single layer and ends in each bead region as a carcass turn-up (4a) with a height (hi) determined in the radial direction (double arrow R), wherein the radially inner apex part (6b) has, on its side facing the tyre inner side and contacting the carcass ply (4), a maximum height (h2) determined in the radial direction (double arrow R) of 60% to 100%, in particular from 70% to 90%, of the height (hi) of the carcass turn-up (4a), wherein the maximum height (h2) and the height (hi) relate to a line (L) which, viewed in the tire cross-section, runs in the axial direction (double arrow A) through a point (X) corresponding to the rim corner point on the bead area of ​​the commercial vehicle tire.

8. Commercial vehicle tire according to one of claims 1 to 6, characterized in that the carcass ply (4) is designed in multiple layers, wherein each layer of the carcass ply (4) ends in each bead region as a carcass turnup (4a) with a height (hi) determined in the radial direction (double arrow R), wherein the radially inner apex part (6b) has, on its side facing the inside of the tire and contacting the carcass ply (4), a maximum height (h2) determined in the radial direction (double arrow R) of 60% to 100%, in particular 70% to 90%, of the height (hi) of the highest carcass turnup (4a), wherein the maximum height (h2) and the height (hi) relate to a line (L) which, viewed in the tire cross-section, runs in the axial direction (double arrow A) through a point (X) on the bead region of the commercial vehicle tire corresponding to the rim corner point.

9. Commercial vehicle tire according to claim 7 or 8, characterized in that the height (hi) of the carcass turn-up (4a) is 25.0 mm to 50.0 mm, preferably 30.0 mm to 45.0 mm.

10. Commercial vehicle tire according to one of claims 1 to 9, characterized in that the cross-sectional area of ​​the radially inner apex part (6b) is triangular, wherein the radially inner apex part (6b) tapers off at its end facing away from the bead core (5).

11. Commercial vehicle tyre according to one of claims 7 to 10, characterised in that the radially outer apex part (6a), viewed in the tyre cross-section, extends between the or each carcass turn-up (4a) and the radially inner apex part (6b).

12. Commercial vehicle tyre according to one of claims 1 to 11, characterised in that it is intended for mounting on a 15° drop-centre rim with a width code of 5.25 to 18.00, standardised in accordance with ETRTO standards.

13. Use of the commercial vehicle tire according to one of claims 1 to 12 on a 15° drop-center rim with a width code of 5.25 to 18.00, standardized according to ETRTO standards.

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