MT steel cord reinforced tire

Abstract

The invention provides an MT steel cord reinforced tire, the tire comprises a tread, a sidewall, a carcass, a belt, a bead, the carcass comprises one or more plies, the belt comprises two or more rubber reinforcement layers, and at least one belt rubber reinforcement layer or at least one carcass ply comprises at least one MT steel cord.

Description

Technical Field

[0001] This invention relates to a tire, and more particularly to a tire reinforced with MT steel cord. Background Technology

[0002] Tires are commonly used in vehicles such as cars, bicycles, motorcycles, and airplanes. Depending on their purpose, tires can be divided into passenger car tires, truck tires, and off-road tires such as construction machinery tires. They can be pneumatic or non-pneumatic tires.

[0003] A pneumatic tire is a ring-shaped structure made of rubber or other elastic materials, mounted on a rim. It is inflated with air to create pressure, giving it elasticity and cushioning properties to support the vehicle's weight and provide good grip and comfort. A pneumatic tire mainly consists of the tread, sidewall, carcass, belt layers, and bead. The tread, the outermost layer, is in direct contact with the ground and is crucial for tire performance (such as wet grip, rolling resistance, and noise). The sidewall connects the tread and bead, providing flexibility and cushioning. The carcass is the tire's skeleton structure, providing strength and shape retention. The belt layers, located between the tread and carcass, enhance stability, puncture resistance, and durability, maintaining tread shape at high speeds and improving handling. The bead is the part that contacts the rim, ensuring a secure fit and preventing slippage or come off the rim. Generally, pneumatic tires can be either tubed tires, where there is a separate rubber inner tube inside the tire to hold air, or tubeless tires, where air is directly filled into the sealed space between the tire and the rim.

[0004] The tire carcass and belt layers are typically composed of rubber layers containing reinforcements. The use of reinforcements increases the tire's strength and rigidity, preventing deformation or blowouts under high-speed or heavy-load conditions. Furthermore, it effectively resists punctures from sharp objects, enhancing tire safety. Additionally, reinforcements help the tire maintain its original shape, preventing tread deformation, thereby improving handling performance and comfort. These reinforcements can be made of polyester fibers, nylon, aramid fibers, or steel cords.

[0005] Tire lightweighting is a key trend in current tire technology development. Its main purpose is to reduce the overall weight of tires while ensuring safety and performance, thereby achieving energy conservation and emission reduction, lower manufacturing costs, and improved handling, comfort, and durability. The development of electric vehicles, in particular, has placed even higher demands on tire lightweighting.

[0006] Current main solutions for tire lightweighting include optimizing rubber materials, tire structure, tire manufacturing processes, and reducing the amount of reinforcing components. Among these, reducing the amount of reinforcing components primarily focuses on increasing the tensile strength of the steel wires to improve the strength of the steel cords and reduce their weight. By using steel wires with higher tensile strength and finer wires, sufficient cord breaking load can be provided, thus reducing the diameter and weight of the steel cords. Using finer and lighter steel cords or wires allows tires to be thinner and lighter.

[0007] The tensile strength of steel wire has evolved from ordinary strength (NT) or high strength (HT) to ultra-high strength (ST), and even extra-high strength (UT), and is currently developing towards super high strength (MT). Summary of the Invention

[0008] The primary objective of this invention is to provide a tire reinforced with MT steel cords.

[0009] According to the purpose of the present invention, a tire reinforced with MT steel cord is provided. The tire includes a tread, a sidewall, a carcass, a belt layer, and a bead. The carcass includes one or more ply layers, and the belt layer includes two or more rubber reinforcement layers. In this case, at least one belt layer rubber reinforcement layer or at least one carcass ply layer contains at least one MT steel cord.

[0010] According to the present invention, 'MT steel cord' refers to a steel cord comprising at least two steel wires, wherein at least one steel wire has a tensile strength of MT. 'MT' refers to a steel wire tensile strength between 4600-2000×d and 5000-2000×d MPa, where d is the diameter of the steel wire in mm. Preferably, all steel wires in the MT steel cord have a tensile strength of MT.

[0011] The belt-layer rubber reinforcement layer refers to a rubber layer of a certain size, in which multiple reinforcing elements are embedded. In this invention, the reinforcing elements in the belt-layer rubber reinforcement layer are all MT steel cords; or a mixture of MT steel cords and steel cords containing lower tensile strength steel wires, such as UT or ST steel cords; or a mixture of MT steel cords and polymer material cords, such as cords made of polyester fiber, nylon, or aramid. The belt-layer rubber reinforcement layer includes multiple reinforcing elements arranged in parallel at a certain spacing.

[0012] The belt-layer rubber reinforcement has a certain layer strength to meet the requirements of tire durability, handling, and high-speed performance. The layer strength of the belt-layer rubber reinforcement mainly depends on the number of reinforcing members (i.e., MT steel cords) and the breaking strength of the reinforcing members. The layer strength of the belt-layer rubber reinforcement can be calculated using known formulas. It is generally in the range of tens to hundreds of kN / dm, such as 20-200 kN / dm. Typically, the number of reinforcing members per decimeter width ('EPD') is used as one of the parameters for calculating the layer strength of the rubber reinforcement. For passenger car tires, EPD is typically 50-110, such as 70, 80, or 90; for truck tires, EPD is typically 35-75, such as 45, 55, or 65. The breaking strength of each reinforcing member can be hundreds or even thousands of N, such as 200-3500 N, such as 330 N, 1500 N, 3000 N, or 3500 N. The spacing between adjacent reinforcing members is related to the EPD and the diameter of the reinforcing members. Taking MT steel cord as a reinforcement element as an example, the spacing between adjacent MT steel cords is between 0.1 and 1.5 mm. The spacing between adjacent MT steel cords in the same rubber reinforcement layer can be the same or different. When the belt layer has multiple rubber reinforcement layers, the spacing between adjacent MT steel cords in different rubber reinforcement layers can be the same or different. For example, when the belt layer has two rubber reinforcement layers, the spacing between adjacent MT steel cords in the first rubber reinforcement layer is 0.6 mm, and the spacing between adjacent MT steel cords in the second rubber reinforcement layer is 0.6 mm or 0.8 mm.

[0013] When the belt layer has multiple rubber reinforcement layers, for passenger car tires, the distance between the centers of the MT steel cords in adjacent layers in the radial direction is typically between 0.8 and 1.7 mm; for truck tires, the distance is typically between 1.4 and 3.2 mm. Alternatively, when the belt layer has multiple rubber reinforcement layers, for passenger car tires, the rubber spacing between the MT steel cords in adjacent layers in the radial direction is typically between 0.4 and 0.8 mm; for truck tires, the rubber spacing is typically between 0.6 and 1.2 mm.

[0014] The belt layer rubber reinforcement has a certain flexural stiffness, which characterizes its ability to resist deformation under bending moment, directly affecting tire handling, comfort, and durability. The flexural stiffness of the belt layer rubber reinforcement can be calculated using known formulas, and typically ranges from several to tens or even hundreds of kN·mm. 2 / dm, for example, 3-130kN·mm 2 / dm.

[0015] Depending on the application requirements, the belt layer of a tire can include two, three, or more layers of rubber reinforcement. For example, the belt layer of pneumatic radial tires used in heavy-duty vehicles (such as heavy-duty trucks or buses) typically has four rubber reinforcement layers: a first working layer, a second working layer, a protective layer, and a transition layer. The transition layer is located closest to the tire carcass; the protective layer is furthest from the carcass; and the first and second working layers are located between the transition and protective layers. The reinforcements in the transition layer are arranged parallel to each other at a relatively large angle, for example, greater than 40 degrees relative to the tire's circumference. The reinforcements in the first working layer are arranged parallel to each other at a first angle α1, with an angle range of 15 to 30 degrees relative to the tire's circumference; the reinforcements in the second working layer are arranged parallel to each other at a second angle α2, also with an angle range of 15 to 30 degrees, but their arrangement direction is opposite to that of the steel wires in the first working layer (relative to the tire's circumference). The reinforcements in the protective layer are also arranged parallel to each other at a certain angle relative to the tire's circumference. To reduce tire weight and rolling resistance, the belt layer can have three rubber reinforcement layers: a first working layer, a second working layer, and a protective layer or transition layer.

[0016] For example, the belt layer of pneumatic radial tires used in passenger vehicles (such as cars) typically has two rubber reinforcement layers: a first working layer and a second working layer. The reinforcements in the first working layer are arranged in parallel at a first angle α1, with an angle range of 15 to 30 degrees relative to the tire circumference. The reinforcements in the second working layer are arranged in parallel at a second angle α2, also with an angle range of 15 to 30 degrees, but their arrangement direction is opposite to that of the steel wires in the first working layer (relative to the tire circumference). In addition, the belt layer may include a third layer, in which the reinforcements are arranged in parallel at a relatively large angle (e.g., greater than 40 degrees) relative to the tire circumference.

[0017] The belt layer rubber reinforcement has a certain thickness and width. When the belt layer includes two or more rubber reinforcement layers, the thickness and width of each individual rubber reinforcement layer can be the same or different.

[0018] According to the present invention, the belt layer comprises two or more rubber reinforcing layers. When the belt layer has two or more rubber reinforcing layers, some layers may contain MT steel cords, or each layer may contain MT steel cords. All rubber reinforcing layers may use only MT steel cords; otherwise, some rubber reinforcing layers may use MT steel cords, and some rubber reinforcing layers may use UT / ST steel cords or polymer material cords.

[0019] The same belt layer rubber reinforcement layer can use MT steel cords of the same structure, or MT steel cords of different structures. Different belt layers rubber reinforcement layers can use MT steel cords of the same structure, or MT steel cords of different structures.

[0020] Besides the belt layer rubber reinforcement layer containing MT steel cord, the carcass ply may or may not contain MT steel cord. The carcass ply refers to a rubber layer of a certain size, in which multiple reinforcing members are embedded. In this invention, the reinforcing members in the carcass ply may contain only MT steel cord; or they may be a mixture of MT steel cord and steel cord containing lower tensile strength steel wires, such as UT or ST steel cord; or they may be a mixture of MT steel cord and polymer material cords, such as cords made of polyester fiber, nylon, or aramid; or they may contain only steel cords with lower tensile strength steel wires, such as UT or ST steel cord; or they may contain only polymer material cords, such as cords made of polyester fiber, nylon, or aramid. The rubber reinforcement layer includes multiple reinforcing members arranged in parallel at a certain spacing.

[0021] The tire carcass may include one, two, three, or more ply layers. When the tire carcass has two or more ply layers, some layers may contain MT steel cord, or each layer may contain MT steel cord. All ply layers may use only MT steel cord; alternatively, some ply layers may use MT steel cord, while others may use UT / ST steel cord or polymer material cord. The same ply layer may use MT steel cord of the same structure or different structures. Different ply layers may use MT steel cord of the same structure or different structures.

[0022] MT steel cord can be any known structure comprising multiple steel wires, such as: 1) n×m multi-strand steel cord, where n is the number of strands in the steel cord, at least 2, and m is the number of steel wires in each strand, at least 2. Examples: 3×3, 3×4, 7×7. 2) 1×n single-strand steel cord, where n is the number of steel wires in the steel cord, at least 2. Examples: 1×2, 1×3, 1×4, 1×5, 1×6, 1×7, 1×8. 3) n+m structure steel cord, which has two sets of steel wires. These two sets of wires are twisted together to form spiral shapes with the same twist pitch. The first set has n steel wires, where n is at least 2. The n steel wires are essentially not twisted together and are parallel to each other. The second set has m steel wires, where m is at least 1. Examples: 2+2, 2+3, 3+2, 3+3, 4+3, 4+6. 4) L+m(+n) (also known as "L+M(+N)") multilayer steel cord structure. This type of steel cord has a core layer with l steel wires, a first layer with m steel wires, and possibly a second layer with n steel wires. There may also be an outer winding wire. Examples include 1+3, 1+4, 1+5, 1+6, 2+5, 2+5cc, 2+6, 2+7, 2+7cc, 2+8, 3+6, 3+8, 3+8cc, 3+9, 3+9cc, 4+9, 5+10, 1+3+8, 1+4+8cc, 1+4+9, 1+5+10, 1+5+10cc, 1+6+11, 1+6+12, 1+6+12cc, 2+5+10, 2+6+12, 3+8+13, 3+9+15, 4+10+16.

[0023] Alternatively, MT steel cord can be a composite cord comprising at least one steel wire with MT tensile strength. The steel cord may also include other monofilaments made of non-steel materials, such as monofilaments made of polymer materials, including nylon, rayon, polyester, and aramid yarns. Typically, composite cords are made by twisting multiple steel wires around a single polymer monofilament. Such composite cords offer better elongation performance and are suitable for reinforcing the 0-degree ply or crown belt ply of tires.

[0024] Steel cords, which are made of multiple steel wires twisted together, have a certain twist pitch, such as 4-40mm, preferably 6-38mm.

[0025] The diameter of MT steel cord ranges from 0.3 to 2.0 mm. The diameter is mainly related to the cord's structure and the diameter of the steel wires. For example, a 2×0.30 MT steel cord structure has a diameter of 0.60 mm. Another example is a 3+8×0.35 MT structure with a diameter of 1.45 mm. Yet another example is a 3×0.24+9×0.225 MT structure with a diameter of 0.94 mm.

[0026] The cross-section of MT steel cord can be circular or non-circular.

[0027] MT steel cord can be either standard or open-type. Open-type cord has a larger cord diameter and better rubber permeability. For example, the steel cord structure is 5×0.35 MT OC with a diameter of 0.88 mm; 4×0.225 MT OC with a diameter of 0.54 mm; 3×0.225 MT OC with a diameter of 0.47 mm; 6×0.35 MT OC with a diameter of 1.01 mm; 6×0.335 MT OC with a diameter of 0.99 mm; and 6×0.32 MT OC with a diameter of 0.97 mm. The steel wires in these open-type steel cords can be pre-deformed steel wires.

[0028] In MT steel cord, the steel wires can be straight or pre-deformed. The pre-deformed wires can have any known pre-deformation method, such as single-gear pre-deformation, double-gear pre-deformation, polygonal pre-deformation, etc. Pre-deformed wires also allow for larger cord diameters and better rubber permeability. For example, a steel cord structure of 5×0.35 MTBETRU with BETRU polygonal pre-deformed wires has a cord diameter of 0.94mm; a steel cord structure of 5×0.30 MTBETRU with BETRU polygonal pre-deformed wires has a cord diameter of 0.81mm; and a steel cord structure of 5×0.30MT HI with single-gear pre-deformed wires has a cord diameter of 1.03mm.

[0029] MT steel cord possesses a certain degree of bending stiffness. Bending stiffness refers to the ability of steel cord to resist deformation when subjected to a bending moment, and is commonly used to measure its flexibility and bending resistance. It is closely related to the structure, material properties, and geometry of the steel cord, and can be calculated using known formulas. In tire manufacturing, bending stiffness affects the maneuverability of the cord during the forming process and the flexibility of the final tire carcass. Excessive stiffness can lead to difficulties in tire forming, while insufficient stiffness may affect the tire's durability and load-bearing capacity. The bending stiffness of MT steel cord typically ranges from tens to hundreds or even thousands of N·mm. 2 For example, the theoretically calculated bending stiffness of 2×0.25 MT is 77 N·mm. 2 The theoretically calculated bending stiffness of 3×0.17 MT is 25 N·mm. 2 The theoretically calculated bending stiffness of 6×0.45 MT is 2415 N·mm. 2 .

[0030] To meet the adhesion performance requirements of MT steel cord to rubber, the steel wires in the MT steel cord with MT tensile strength are coated with a metallic coating that promotes rubber adhesion. The metallic coating can be any of the existing steel wire coatings known in the field of rubber reinforcement, providing adhesion to the rubber compound and corrosion resistance. Preferably, the metallic coating of the steel wire is a zinc plating layer, a zinc alloy coating such as a zinc-silver coating, a copper alloy coating such as a brass coating or a bronze coating, or a ternary or quaternary coating comprising three or four metals selected from the group consisting of copper, zinc, cobalt, nickel, tin, indium, titanium, manganese, iron, silver, bismuth, and molybdenum, such as Zn-Cu-Co, Zn-Cu-Fe, and Zn-Cu-Ni ternary coatings.

[0031] The diameter d of the steel wire with MT tensile strength is preferably in the range of 0.15-0.55 mm or more preferably in the range of 0.16-0.45 mm, such as 0.18 mm, 0.20 mm, 0.23 mm, 0.26 mm, 0.28 mm, 0.30 mm, 0.33 mm, 0.35 mm, 0.38 mm, 0.40 mm, and 0.42 mm.

[0032] The steel wire with MT tensile strength is made of high-carbon steel. Generally, increasing the carbon content in the steel leads to higher tensile strength of the wire, but also increases production costs. According to the present invention, the carbon content of the steel wire with MT tensile strength is 0.70%-1.05% (weight percentage), preferably 0.86%-0.95%.

[0033] Steel wire with MT tensile strength can be made from wire rod of pure new steel that contains no recycled steel (such as direct reduced iron, hot-pressed iron, or pig iron), or from wire rod of steel containing recycled steel. Preferably, steel wire with MT tensile strength is made from wire rod of recycled steel with a recycled steel content of at least 15%, at least 30%, at least 45%, or even 100%.

[0034] The rubber used in the belt reinforcement layer and the carcass ply can be any known rubber compound. Typically, rubber compounds include natural rubber (such as smoked sheet or latex) or synthetic rubber, carbon black, zinc oxide, stearic acid, sulfur, antioxidants, accelerators, binders, resorcinol, cobalt neodecanoate, etc., mixed in specific proportions to form a rubber compound. Accelerators (such as CZ, DZ) are used to increase the vulcanization speed of the rubber. Antioxidants (such as 4020, RD, H) are used to enhance tire life. Carbon black (such as N220, high abrasion furnace black) is the main reinforcing agent, affecting abrasion resistance and strength. Softeners (such as rubber oil, paraffin wax, coumarone) improve processing performance and flexibility. The combination of sulfur and accelerators determines the vulcanization speed and final properties. Example: 100 parts by weight of SMR20 granular adhesive, 60 parts by weight of carbon black N326, 8.0 parts by weight of zinc oxide, 0.2 parts by weight of stearic acid, 5.0 parts by weight of insoluble sulfur, 1.0 parts by weight of antioxidant TMQ, 1.0 parts by weight of antioxidant 6PPD, 1.0 parts by weight of accelerator DCBS, 5.0 parts by weight of adhesive RA-65, 1.2 parts by weight of resorcinol, and 1.0 parts by weight of cobalt neodecanoate.

[0035] The properties of the rubber compound must meet the standard requirements. Depending on the application and the bonding system required for different MT steel cord coatings, the vulcanized rubber has different performance requirements. For example, the elongation at break of the vulcanized rubber must be ≥300%, the tensile strength ≥16MPa or ≥20MPa, and the Mooney viscosity (ML(1+4)) of the compound at 100℃ must be 50 to 90.

[0036] The tires of this invention can be passenger car tires, truck tires, and off-road tires such as construction machinery tires; they can be pneumatic tires or non-pneumatic tires. Detailed Implementation

[0037] The first embodiment of the present invention is a passenger car tire. The tire includes a pair of bead cores, a carcass, and a belt layer.

[0038] The bead core is located in the bead portion of the tire and includes a ring-shaped cable bead extending circumferentially along the tire. The cross-section of the bead core is circular or substantially circular; alternatively, it can be rectangular or substantially rectangular, or square or hexagonal. The cable bead is made by looping bead wires together, or it can be made of wire rope.

[0039] The tire carcass consists of a ply layer. This ply layer is also a rubber layer, within which multiple cords are embedded. The cords in the ply layer are made of polymer materials, such as polyester, nylon, or aramid. The cords in the ply layer extend along the width of the tire. Specifically, the tire carcass extends in a ring between a pair of bead cores, folding back around the bead cores from the inside to the outside of the tire width direction, thus securing the tire carcass to the pair of bead cores.

[0040] The belt layer comprises two belt layer rubber reinforcement layers, namely a first working layer and a second working layer. The first and second working layers are located on the radially outer side of the tire carcass. The first working layer contains multiple parallel 2+2×0.25MT steel cords with an EPD of 65. The second working layer contains multiple parallel 1×5×0.21MT steel cords with an EPD of 65.

[0041] A second embodiment of the present invention is a truck tire. The tire includes a pair of bead cores, a carcass, and a belt layer.

[0042] The bead core is located in the bead portion of the tire and includes a ring-shaped cable bead extending circumferentially along the tire. The cross-section of the bead core is circular or substantially circular; alternatively, it can be rectangular or substantially rectangular, or square or hexagonal. The cable bead is made by looping bead wires together, or it can be made of wire rope.

[0043] The tire carcass includes a ply layer. This ply layer is also a rubber layer, and multiple MT steel cords are embedded within it. The MT steel cords in the ply layer are 3×0.24+9×0.225 CC MT. The cords in the ply layer extend along the tire width direction. Specifically, the tire carcass extends in a ring between a pair of bead cores and folds back around the bead cores from the inside to the outside of the tire width direction, thus securing the tire carcass to the pair of bead cores. The belt layer includes three belt layer rubber reinforcement layers: a first working layer, a second working layer, and a transition layer. The transition layer, the first working layer, and the second working layer are sequentially disposed on the radially outer side of the tire carcass, with the transition layer disposed between the tire carcass and the first working layer. The first working layer contains multiple parallel 4+3×0.33 MT steel cords with an EPD of 55. The second working layer also contains multiple parallel 4+3×0.33 MT steel cords with an EPD of 55. The transition layer contains multiple parallel 4+3×0.33 MT steel cords with an EPD of 40.

Claims

1. A tire reinforced with MT steel cord, the tire comprising a tread, sidewall, carcass, belt layer, and bead, wherein the carcass comprises one or more ply layers, and the belt layer comprises two or more rubber reinforcing layers, characterized in that, At least one belt layer rubber reinforcement layer or at least one carcass ply contains at least one MT steel cord.

2. The tire according to claim 1, characterized in that, Each rubber reinforcement layer or each carcass ply in the belt layer contains at least one MT steel cord.

3. The tire according to claim 1 or 2, characterized in that, The reinforcing elements in at least one belt layer rubber reinforcement layer or at least one carcass ply layer are MT steel cords.

4. The tire according to any one of claims 1 to 3, characterized in that, Each rubber reinforcement layer in the belt layer or each carcass ply layer contains MT steel cord as the reinforcing element.

5. The tire according to any one of claims 1 to 6, characterized in that, MT steel cord has an n×m, 1×n, n+m or l+m(+n) structure.