Vehicle tyre with carcass ply

Abstract

The invention relates to a radial vehicle tyre having a radial carcass and having at least one carcass ply composed of steel cords (1) embedded in rubber and having bead regions having bead cores and core profiles, around which the carcass ply extends forming a turn-up, wherein the steel cords each comprise exactly six equal-sized filaments (2) in a 1+5 construction, wherein the diameter (D1) of the steel cords is at most 0.75 mm, wherein, underneath the bead core, the steel cords are arranged in the carcass ply with more than 70 epdm, preferably more than 80 epdm, more preferably more than 90 epdm, wherein the diameter (D2) of each of the six filaments is at least 0.15 mm and at most 0.25 mm.

Description

[0001] 202405973

[0002] - 1 - Description

[0003] Vehicle tires with carcass layer

[0004] The invention relates to a carcass cord for a vehicle tire, a carcass for a vehicle tire containing the cord, and a vehicle tire, preferably a commercial vehicle tire, for example for trucks, in radial construction with the carcass.

[0005] Vehicle tires, especially commercial vehicle tires, have a radial carcass, in particular a steel cord carcass, with at least one carcass layer made of steel cords embedded in rubber and further bead areas with bead cores and core profiles, around which the carcass layer forms high points.

[0006] Commercial vehicle tires typically have a cross-sectional height of 120 mm to 400 mm, especially 175 mm to 280 mm.

[0007] Commercial vehicle tires still predominantly have a load index of 121 to 160.

[0008] It is common practice in commercial vehicle tires of the type mentioned above - with a cross-sectional height of 120 mm to 400 mm and a load index of 121 to 160 - to reinforce the carcass ply with steel cords of the construction 3 x 0.20 mm + 9 x 0.175 mm, whereby the steel filaments have a tensile strength in the NT (normal tensile) range of 2700 N / mm2 to 3050 N / mm2 and are arranged under the bead core with 65 to 80 epdm (ends per decimeter, also referred to as "thread density under the bead core" or "thread density under the core").

[0009] The described steel cord construction gives the carcass layer good strength properties, but has the disadvantage that when the finished raw tire is molded into a vulcanization mold, the steel cords can be forced through the inner layer in the shoulder areas of the tire.

[0010] Another disadvantage of steel cords in general is that they require a certain minimum thickness of the rubber coating on the carcass ply so that the 202405973

[0011] -2 - Steel cords can be stably embedded in the rubber coating. The rubber coating should have approximately 150% to 200% of the thickness or diameter of the steel cords used.

[0012] Typically, the cords used have a diameter of 0.75 to 1.0 mm to achieve the necessary strength of the tire casing. A correspondingly thicker tire casing results in high rolling resistance.

[0013] On the other hand, sufficient rubber must be able to penetrate between the filaments of the steel cords to prevent the filaments from rubbing against each other within the steel cords, thus avoiding rapid wear and premature fatigue of the steel cords. To achieve this, prior art, such as in application US 2019 0152261 A1, typically employs different filament diameters, which, however, complicates processing during manufacturing.

[0014] The invention is based on the objective of overcoming the disadvantages of the prior art.

[0015] The problem is solved according to the invention by providing steel cords for a tire carcass layer that have exactly six filaments. The steel cords have a maximum diameter of 0.75 mm, preferably a maximum of 0.69 mm, and particularly preferably a maximum of 0.66 mm.

[0016] Such a small diameter allows the required rubber thickness for the steel cord to be significantly reduced.

[0017] This conserves resources and saves on manufacturing costs, but above all, it also results in a significantly lower rolling resistance for the tire due to the use of steel cords. 202405973

[0018] - 3 - The filaments can be arranged in the steel cords according to construction 1 + 5, with five outer filaments (layer filaments) evenly wound around a central filament (core filament).

[0019] The lay length with which the layer filaments are wound around the core filament is preferably between 6 mm and 14 mm, more preferably between 8 mm and 13 mm.

[0020] The use of such steel cords, together with an arrangement at certain mutual distances, is particularly well suited to preventing the steel cords from being pushed through into the shoulder areas of the tire when it is molded into the tire vulcanization mold.

[0021] In comparison to a 1 + 6 arrangement with seven filaments, the present embodiment has the further advantage that the five layer filaments present here can be advantageously arranged in such a way that during calendering sufficient rubber mass is drawn between the individual filaments, both between the individual layer filaments and between layer filaments and core filament, so that friction effects between the filaments and resulting fatigue effects are reduced.

[0022] The diameters of the filaments are preferably all the same, with the filaments preferably having a diameter of at least 0.15 mm and preferably having a diameter of at most 0.25 mm.

[0023] Preferably, the minimum diameter of the filaments is 0.19 mm.

[0024] Using only one type of filament allows for simple processing during the production of the steel cord.

[0025] The smaller the diameter of the filaments, the smaller the overall diameter of the steel cord. 202405973

[0026] -4 - By using thinner filaments, the amount of rubber used can be further reduced, which has a beneficial effect on the rolling resistance of the corresponding tire (see above). However, with smaller steel filament diameters, the requirements for the strength of the steel in the filaments increase. Furthermore, the brittleness of the filaments must also be considered. The stiffness of the cord generally decreases when thinner filaments are used.

[0027] When weighing the requirements regarding the steel properties of the filaments against the goal of reducing the rubber volume, this can lead to a preferred diameter of the steel filaments used, selected as follows.

[0028] A preferred filament diameter is at least 0.22 mm, particularly preferably at least 0.23 mm and at most 0.25 mm. This facilitates processing during the cord's production.

[0029] The small diameter of the filaments and the construction shown result in the required small diameter of the cords.

[0030] To ensure sufficient durability, the steel filaments according to the invention preferably comprise or consist of a steel or steels exhibiting a tensile strength in the NT, HT, or ST range, i.e., in the normal tensile, high tensile, or super-high tensile range (normal, high, or super-high tensile strength) of preferably over 3300 MPa to 3800 MPa. Compared to steels with higher tensile strengths, such steels advantageously exhibit lower brittleness and higher fatigue strength.

[0031] For filaments with a minimum diameter of 0.15 mm, this results in a maximum desired tensile strength of 3800 N / mm² (MPa). For filaments with larger diameters, steels with a lower maximum tensile strength are sufficient. The desired maximum tensile strength in MPa can be calculated as a function of the filament diameter d in mm using the following formula:

[0032] Maximum tensile strength [MPa] = 4100 - (2000*d [mm])202405973

[0033] - 5 -llm To further increase durability or reduce brittleness, only steels in the NT or HT range are preferably used.

[0034] For filaments with a minimum diameter of 0.15 mm, this results in a maximum desired tensile strength of 3500 N / mm² (MPa). For filaments with larger diameters, steels with a lower maximum tensile strength are sufficient. The desired maximum tensile strength in MPa can be calculated as a function of the filament diameter d in mm using the following formula:

[0035] Maximum tensile strength [MPa] = 3800 - (2000*d [mm])

[0036] To further increase durability and / or further reduce brittleness, only steels in the low-temperature range are still preferably used.

[0037] However, the use of steels with higher tensile strength has the advantage that the filaments have a higher strength.

[0038] To ensure high strength and thus high robustness, the steel filaments according to one embodiment of the invention comprise or consist of a steel or steels that have a tensile strength in the UT to MT range, i.e. in the ultra-high tensile to mega-high tensile range (ultra-high to mega-high tensile strength) of over 3800 N / mm2 and preferably over 4100 N / mm2 up to 4500 N / mm2.

[0039] The required tensile strength in MPa for a UT steel can be calculated as a function of the filament diameter d in mm using the following formula:

[0040] Maximum tensile strength [MPa] = 4400 - (2000*d [mm])

[0041] The required tensile strength in MPa for an MT steel can be calculated as a function of the filament diameter d in mm using the following formula:

[0042] Maximum tensile strength [MPa] = 4800 - (2000*d [mm])

[0043] The thinner the filament, the higher the tensile strength of the steel used is preferred. 202405973

[0044] -6 -

[0045] The linear density of the steel filaments used is preferably between 77 g / 100 m (grams per 100 m of filament) and 247 g / 100 m, with the filament diameters varying between 0.15 mm and 0.25 mm.

[0046] The tensile density of the filaments is therefore preferably between 13 and 58 MPa / (g / 100m).

[0047] The HT / ST / UT steels used for the invention are particularly preferably characterized by a carbon content of 0.6% to 1.1% in the steel, in the special case of UT steels used of at least 0.75%, preferably at least 0.80%.

[0048] The wires are preferably coated with an alloy comprising copper and zinc, or copper, zinc, and iron. The alloys can consist of the aforementioned metals, wherein in a binary coating the proportion of copper is preferably between 61% and 66% and the proportion of zinc is preferably between 29% and 34% (by mass).

[0049] The use of HT / ST / UT steels for carcass cord filaments enables the provision of advantageously thin cords with the required high tensile strengths for use in large commercial vehicle tires as defined in the introduction.

[0050] The described cords particularly meet the requirements for use in commercial vehicle tires with rim diameters of 17.5 inches to 22.5 inches (also “inch”; = 17.5” and 22.5” tires), preferably 19.5 inches ( = 19.5”) to 22.5 inches.

[0051] Application in larger tires requires higher strength and the use of stronger steels or a higher number of cords.

[0052] In a carcass layer according to the invention, the steel cords according to the invention are used for reinforcement, preferably with more than 70 epdm, preferably more than 80 epdm, more202405973

[0053] - 7 - preferably more than 90 epdm below the bead core, arranged. The rim diameter is preferably 19.5 inches to 22.5 inches.

[0054] The high number of cords in the carcass layer according to the invention is made possible by the thin cords with low filament count and small diameters provided according to the invention.

[0055] The high number of cords, each with high tensile strength, ensures sufficient strength, stability and service life of the carcass, which, due to the small diameter of the cords, can also be advantageously thin.

[0056] The required rubber thickness, and thus the amount of rubber used during calendering of the carcass ply, scales with the cord diameter. By using the steel cords according to the invention (as described), the rubber thickness can be significantly reduced without impairing the tire's performance. The rolling resistance of such a tire can be reduced.

[0057] At the same time, the arrangement of the filaments (1 + 5) according to the invention ensures a sufficient rubber thickness between the steel filaments. This prevents rapid material fatigue of the cords.

[0058] The use of six identical filaments further simplifies the manufacturing process of the carcass cords.

[0059] A tire according to the invention contains the carcass layer according to the invention with the cords according to the invention.

[0060] A reduced amount or thickness of rubber in the carcass layer, as described in the invention, advantageously leads to an improvement in the rolling resistance behavior of the tire according to the invention, i.e., the rolling resistance decreases. 202405973

[0061] - 8 - A reduced rolling resistance also advantageously correlates with lower energy consumption due to friction losses of the tire according to the invention and thus enables fuel savings.

[0062] Furthermore, a reduced amount of rubber leads to a beneficial reduction in rubber requirements, resulting in lower manufacturing costs and greater sustainability of the tire.

[0063] The preferred features are not limiting. The preferred features may relate to the filaments, the steel cord, the carcass with the stamped cord, or the tire according to the invention.

[0064] The steel cord according to the invention is preferably used in the carcass layer of a commercial vehicle tire, in particular a truck tire. However, its use in other vehicle tires, for example passenger car tires, is also possible.

[0065] The truck tire in which the steel cord according to the invention is used in the carcass layer is preferably a tire with a steel carcass, which is furthermore designed for an internal pressure between 6 and 10 bar, particularly preferably for an internal pressure of at least 9 bar.

[0066] According to a further aspect, the present invention can also be applied to radial tires for passenger cars (cars) with a radial carcass. All features described above apply analogously, unless they explicitly relate to truck tires.

[0067] However, due to the lower internal tire pressure of passenger car tires, fewer steel cords can be used in passenger car tires than previously described for truck tires.

[0068] The minimum number of ends required per decimeter (on steel cords) under the EPDM_PKW bead core can be calculated according to the invention using the following formula: 202405973

[0069] - 9 - EPDM_PKW > {[(internal pressure of the vehicle tire) / 9 bar] * 90 epdm}.

[0070] Further features, advantages and details of the invention (in particular of the first aspect) will now be described in more detail with reference to Figure 1, which schematically shows a cross-section of an embodiment of a steel cord intended for a carcass layer of a commercial vehicle tire.

[0071] The commercial vehicle tire features the usual components, such as a profiled tread, a multi-ply belt reinforced in particular with steel cords, an inner layer, bead areas with bead cores and core profiles, and a radial carcass consisting of at least one carcass ply reinforced with steel cords. The steel cords of the carcass ply run radially in the sidewalls and axially beneath the tread and belt (in other words, closer to the tire axis than the tread).

[0072] Figure 1 shows a cross-section of a steel cord 1, designed according to the invention for use in the carcass layer of a commercial vehicle tire, which has the construction (1 + 5) x0.23 HT / ST / UT and accordingly six filaments 2 of equal dimensions and twisted around each other, wherein the central filament is processed without twisting. The remaining five layer filaments are wound around the core filament 2a.

[0073] The diameter D2 of each of the filaments is, by definition, 0.23 mm in this example.

[0074] The filaments 2 are twisted in a known manner with a twist length of 6.0 mm to 14.0 mm, preferably of about 12.0 mm to 13.0 mm.

[0075] The filaments are made of steel of strength classes HT, ST, or UT and have a tensile strength of more than 3300 N / mm². In a preferred embodiment, the filaments have a tensile strength of at least 3500 N / mm². 202405973

[0076] - 10 - The filaments 2 each have a substantially circular or exactly circular cross-section.

[0077] The total diameter D1 of the formed cord is, in this example, a maximum of 0.69 mm, namely, for example, exactly 0.69 mm.

[0078] To produce a carcass layer containing such steel cords, the steel cords are embedded in one of the usual rubberizing compounds by calendering, wherein the number of steel cords in the non-vulcanized calendered carcass layer is over 70, preferably over 80, more preferably over 90 epdm.

[0079] In the finished, vulcanized commercial vehicle tire, the number of steel cords under the bead core is also over 70, preferably over 80, more preferably over 202405973

[0080] - 11 -

[0081] Reference symbol list

[0082] 1 steel cord

[0083] 2 Filament

[0084] 2a Core filament

[0085] D1 Korddurchmesser

[0086] D2 Filamentdurchmesser

Claims

202405973 - 12 - Patent claims 1. Radial-type vehicle tires with a radial carcass and with at least one carcass ply made of steel cords (1) embedded in rubber and with bead areas with bead cores and core profiles around which the carcass ply forms raised sections, wherein the steel cords each comprise exactly six filaments (2) of equal size in a construction 1 + 5, wherein the diameter (D1) of the steel cords is a maximum of 0.75 mm, wherein under the bead core the steel cords in the carcass ply are arranged with more than 70 epdm, preferably more than 80 epdm, more preferably more than 90 epdm, wherein the diameter (D2) of each of the six filaments is at least 0.15 mm and a maximum of 0.25 mm.

2. Vehicle tire according to claim 1, wherein the diameter of each of the filaments is at least 0.19 mm, preferably at least 0.22 mm, particularly preferably at least 0.23 mm.

3. Vehicle tire according to one of claims 1 or 2, wherein the diameter of the steel cords is a maximum of 0.69 mm, preferably a maximum of 0.66 mm.

4. Vehicle tire according to any one of claims 1 to 3, wherein the steel used in the steel cords is a normal-tensile, high-tensile or super-high-tensile steel, preferably having a tensile strength between 3300 N / mm2 and 3800 N / mm2.

5. Vehicle tire according to any one of claims 1 to 3, wherein the steel used in the steel cords is an ultra-high tensile or mega-high tensile steel having a tensile strength of up to 4500 N / mm2.

6. Vehicle tire according to any one of claims 1 to 5, wherein the steel used in the steel cords is a high-tensile steel having a carbon content of 0.6% to 1.1% inclusive, or wherein the steel used in the steel cords is an ultra-high-tensile steel having a carbon content of 0.75% inclusive, preferably 0.8% inclusive, to 1.1% inclusive. 202405973 - 13 - 7. Vehicle tires according to any one of claims 1 to 6, wherein the rim diameter of the vehicle tires is at least 17.5 inches, preferably at least 19.5 inches, and furthermore up to a maximum of 22.5 inches.

8. Vehicle tire according to any one of claims 1 to 7, wherein the vehicle tire has a cross-sectional height of 120 mm to 280 mm and a load index of 121 to 160.

9. Vehicle tire according to any one of claims 1 to 8, wherein the vehicle tire is a commercial vehicle tire.

10. Use of steel cords (1) for reinforcing carcass plies of vehicle tires, each comprising exactly six filaments (2) of equal size in construction 1 + 5, wherein the diameter (D1) of the steel cords is a maximum of 0.75 mm, wherein the steel used in the steel cords is a high tensile or an ultra-high tensile steel.

11. Radial-type vehicle tires for passenger cars with a radial carcass and with at least one carcass ply made of steel cords (1) embedded in rubber and with bead areas with bead cores and core profiles around which the carcass ply forms raised sections, wherein the steel cords each comprise exactly six filaments (2) of equal size in the construction 1 + 5, wherein the diameter (D1) of the steel cords is a maximum of 0.75 mm, wherein the steel used in the steel cords is a high-tensile or an ultra-high-tensile steel, and wherein the steel cords are arranged in the carcass ply with a number of EPDM_PKW under the bead core, wherein: EPDM_PKW > {[(internal pressure of the vehicle tire) / 9 bar] * 90 epdm}.

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