A heptagonal steel cord

Abstract

The application discloses a heptagonal steel cord, which comprises a center layer twisted by center steel wires, an intermediate layer twisted by intermediate steel wires, and an outer layer twisted by outer layer steel wires, wherein the intermediate layer is sleeved on the outer periphery of the center layer, and the outer layer is sleeved on the outer periphery of the intermediate layer. The heptagonal steel cord can effectively avoid the problem of cord arching caused by layer torsion release during cord cutting, reduce the risk of core protrusion of single steel wire in the center layer of the tire, and effectively improve the fatigue resistance and service life of the tire.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel cord production, and relates to a heptagonal steel cord. BACKGROUND

[0002] The steel cord is an important component of the tire framework material, and the existing 1+6+12 steel cord for tires is composed of a center layer, an intermediate layer and an outer layer of steel wires, the center layer is composed of one d1 steel wire, the intermediate layer is composed of six d2 steel wires, and the outer layer is composed of twelve d3 steel wires, wherein the diameters of the steel wires satisfy d1>d2=d3; however, when the cord is cut, the arch edge problem caused by the release of layer torsion increases the risk of core protrusion of the single steel wire in the tire center layer, and reduces the fatigue resistance and service life of the tire. SUMMARY

[0003] The present application aims to overcome the deficiencies in the prior art, and provides a heptagonal steel cord, which effectively avoids the arch edge problem caused by the release of layer torsion when the cord is cut, reduces the risk of core protrusion of the single steel wire in the tire center layer, and effectively improves the fatigue resistance and service life of the tire body of the tire.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0005] A heptagonal steel cord, the steel cord comprising:

[0006] a center layer composed of two center steel wires;

[0007] an intermediate layer composed of seven intermediate steel wires, the intermediate layer being sleeved on the outer periphery of the center layer;

[0008] an outer layer composed of fourteen outer layer steel wires, the outer layer being sleeved on the outer periphery of the intermediate layer;

[0009] the diameter of the center steel wire is d1, the diameter of the intermediate steel wire is d2, and the diameter of the outer layer steel wire is d3, wherein d1

[0010] The cross-sectional shape of the steel cord is heptagonal.

[0011] Optionally, the diameter d1 of the two center steel wires of the center layer is 0.15 mm.

[0012] Optionally, the diameter d2 of the seven intermediate steel wires of the intermediate layer is 0.20-0.215 mm.

[0013] Optionally, the diameter d3 of the fourteen outer layer steel wires of the outer layer is 0.18-0.195 mm.

[0014] Optionally, the twist direction of the center steel wire is the same as the twist direction of the outer layer steel wire, and the twist direction of the intermediate steel wire is the same as the twist direction of the outer layer steel wire.

[0015] Optionally, the twist direction of the outer layer steel wire is Z.

[0016] Optionally, the twist pitch of the outer layer steel wire is 2 times the twist pitch of the center steel wire, and the twist pitch of the intermediate steel wire is equal to the twist pitch of the outer layer steel wire.

[0017] Optionally, the twist pitch of the center steel wire is 7.5-8.0 mm, and the twist pitch of the intermediate steel wire and the outer layer steel wire is 15.0-16.0 mm.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The present application provides a heptagonal steel cord, which is formed by one-time twisting, ensuring the tightness of each layer of the steel cord. Since the diameter d1 of the center layer 2x1 steel wire is smaller than the diameter d2 of the intermediate layer steel wire, and the diameter d2 of the intermediate layer steel wire is larger than the diameter d3 of the outer layer steel wire, the torque of the center layer is small, and the anchoring force of the intermediate layer steel wire is large, which effectively avoids the problem of arching of the cord due to layer torsion release during cord cutting, and the risk of core protrusion of the center layer single steel wire during long-term use of the tire.

[0020] The cord of the present application can effectively improve the fatigue resistance of the tire body of the tire, thereby improving the service life of the tire. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The figure shows the cross-sectional view of a heptagonal steel cord according to an embodiment of the present application.

[0022] Figure 2 The figure shows the cross-sectional view of a heptagonal steel cord according to an embodiment of the present application.

[0023] In the figure: 1, center layer; 2, intermediate layer; 3, outer layer; 4, center steel wire; 5, intermediate steel wire; 6, outer layer steel wire. DETAILED DESCRIPTION

[0024] The present application will be further described below in conjunction with the drawings. The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0025] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can be explicitly or implicitly included one or more. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0026] In the description of the present application, it needs to be understood that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0027] Comparative example

[0028] As shown in Figure 2 , a steel cord is a 1+6+12 steel cord, which includes a center layer, an intermediate layer and an outer layer of steel wires. The center layer of the steel cord is twisted by one d1 steel wire, the intermediate layer is twisted by six d2 steel wires, and the outer layer is twisted by twelve d3 steel wires. The steel wire diameter d1>d2=d3, the center layer has no twist, the twist direction of the six steel wires in the intermediate layer is the same as that of the twelve steel wires in the outer layer, and the p2 twist pitch of the six steel wires in the intermediate layer is 0.468-0.52 times the p3 twist pitch of the twelve steel wires in the outer layer. The steel cord structure is processed and formed by secondary twisting. Example

[0029] As shown in Figures 1 to 2 , a heptagonal steel cord includes:

[0030] a center layer 1 twisted by two center steel wires 4;

[0031] an intermediate layer 2 twisted by seven intermediate steel wires 5, the intermediate layer 2 being sleeved on the outer periphery of the center layer 1;

[0032] An outer layer 3 is formed by twisting fourteen outer layer steel wires 6, and the outer layer 3 is sleeved on the outer periphery of the intermediate layer 2.

[0033] The diameter of the center steel wire 4 is d1, the diameter of the intermediate steel wire 5 is d2, and the diameter of the outer layer steel wire 6 is d3, wherein d1 is designed as 0.15 mm, d2 is designed as 0.20 mm, and d3 is designed as 0.18 mm.

[0034] The twisting direction of the center steel wire 4 is the same as that of the outer layer steel wire 6, and the twisting direction of the intermediate steel wire 5 is the same as that of the outer layer steel wire 6; the twist pitch p3 of the outer layer steel wire 6 is twice the twist pitch p1 of the center steel wire 4; the twist pitch p2 of the intermediate steel wire 5 is equal to the twist pitch p3 of the outer layer steel wire 6, wherein p1 is designed as 7.5 mm, and p3 is designed as 15.0 mm.

[0035] The cross-sectional shape of the steel cord is a heptagon.

[0036] The following table is a comparison of the parameters of the present embodiment and the comparative examples

[0037] Item Prior art standard Invention technology - example Structure 0.22+6+12x0.20 ST 2x0.15+7x0.20+14x0.18 ST Center layer steel wire diameter d1 ±0.01 (mm) 0.22 0.151 Intermediate layer steel wire diameter d2 ±0.01 (mm) 0.20 0.199 Outer layer steel wire diameter d3 ±0.01 (mm) 0.20 0.181 Center layer steel wire lay p1 (mm) ±5% / 7.70 Center layer steel wire lay direction / Z Intermediate layer steel wire lay p2 (mm) ±5% 6.3 15.18 Intermediate layer steel wire lay direction Z Z Outer layer steel wire lay p3 (mm) ±5% 12.5 15.18 Outer layer steel wire lay direction Z Z Cord diameter (mm) ±5% 1.02 1.05 Linear density (g / m) ±5% 4.86 4.85 Breaking load (N) ≥2010 2072 Pull-out force (N / 25mm) ≥1000 1123 Coating rate (%) ≥70 85 Embodiment

[0038] As shown in Figures 1 to 2 a heptagonal steel cord, the steel cord comprising:

[0039] a center layer 1 formed by twisting two center steel wires 4;

[0040] an intermediate layer 2 formed by twisting seven intermediate steel wires 5, and the intermediate layer 2 is sleeved on the outer periphery of the center layer 1;

[0041] an outer layer 3 formed by twisting fourteen outer layer steel wires 6, and the outer layer 3 is sleeved on the outer periphery of the intermediate layer 2.

[0042] The diameter of the center steel wire 4 is d1, the diameter of the intermediate steel wire 5 is d2, and the diameter of the outer layer steel wire 6 is d3, wherein d1 is designed as 0.15 mm, d2 is designed as 0.205 mm, and d3 is designed as 0.185 mm.

[0043] The twisting direction of the center steel wire 4 is the same as that of the outer layer steel wire 6, and the twisting direction of the intermediate steel wire 5 is the same as that of the outer layer steel wire 6; the twist pitch p3 of the outer layer steel wire 6 is twice the twist pitch p1 of the center steel wire 4; the twist pitch p2 of the intermediate steel wire 5 is equal to the twist pitch p3 of the outer layer steel wire 6, wherein p1 is designed as 7.5 mm, and p3 is designed as 15.0 mm.

[0044] The cross-sectional shape of the steel cord is a heptagon.

[0045] The following table is a comparison of the parameters of the present embodiment and the comparative examples

[0046] Item Prior art standard Invention technology - example Structure 0.25+6+12x0.225 HT 2x0.15+7x0.205+14x0.185 ST Center layer steel wire diameter d1 ±0.01 (mm) 0.25 0.151 Intermediate layer steel wire diameter d2 ±0.01 (mm) 0.225 0.206 Outer layer steel wire diameter d3 ±0.01 (mm) 0.225 0.185 Center layer steel wire lay p1 (mm) ±5% / 7.75 Center layer steel wire lay direction / Z Intermediate layer steel wire lay p2 (mm) ±5% 7.5 15.20 Intermediate layer steel wire lay direction Z Z Outer layer steel wire lay p3 (mm) ±5% 16.0 15.20 Outer layer steel wire lay direction Z Z Cord diameter (mm) ±5% 1.15 1.07 Linear density (g / m) ±5% 6.14 5.12 Breaking load (N) ≥2225 2264 Pull-out force (N / 25mm) ≥1250 1379 Coating rate (%) ≥75 90 Embodiment

[0047] As Figures 1 to 2 shown, a heptagonal steel cord, the steel cord comprising:

[0048] a center layer 1 twisted by two center steel filaments 4;

[0049] a middle layer 2 twisted by seven middle steel filaments 5, the middle layer 2 being sleeved on the outer periphery of the center layer 1;

[0050] an outer layer 3 twisted by fourteen outer layer steel filaments 6, the outer layer 3 being sleeved on the outer periphery of the middle layer 2.

[0051] The diameter of the center steel filament 4 is d1, the diameter of the middle steel filament 5 is d2, and the diameter of the outer layer steel filament 6 is d3, wherein d1 is designed as 0.15 mm, d2 is designed as 0.215 mm, and d3 is designed as 0.195 mm.

[0052] The twist direction of the center steel filament 4 is the same as that of the outer layer steel filament 6, and the twist direction of the middle steel filament 5 is the same as that of the outer layer steel filament 6; the twist pitch p3 of the outer layer steel filament 6 is twice the twist pitch p1 of the center steel filament 4; the twist pitch p2 of the middle steel filament 5 is equal to the twist pitch p3 of the outer layer steel filament 6, wherein p1 is designed as 8.0 mm, and p3 is designed as 16.0 mm.

[0053] The cross-sectional shape of the steel cord is heptagonal.

[0054] The following table is a comparison of the parameters of the embodiment and the comparative examples

[0055] Item Prior art standard Invention technology - example Structure 0.25+6+12x0.225 HT 2x0.15+7x0.215+14x0.195 HT Center layer steel wire diameter d1 ±0.01 (mm) 0.25 0.151 Intermediate layer steel wire diameter d2 ±0.01 (mm) 0.225 0.214 Outer layer steel wire diameter d3 ±0.01 (mm) 0.225 0.195 Center layer steel wire lay p1 (mm) ±5% / 8.10 Center layer steel wire lay direction / Z Intermediate layer steel wire lay p2 (mm) ±5% 7.5 15.92 Intermediate layer steel wire lay direction Z Z Outer layer steel wire lay p3 (mm) ±5% 16.0 15.92 Outer layer steel wire lay direction Z Z Cord diameter (mm) ±5% 1.15 1.11 Linear density (g / m) ±5% 6.14 5.66 Breaking load (N) ≥2225 2318 Pull-out force (N / 25mm) ≥1250 1405 Coating rate (%) ≥75 90

[0056] In order for the direct contact of each layer, it is necessary to optimize the design value of the diameter of the middle steel filament and the diameter of the outer layer steel filament, so that the contact between the steel filaments has good geometric characteristics, and such contact load depends on the load that each steel filament can resist, i.e. the load on the cord divided by the number of steel filaments.

[0057] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A heptagonal steel cord, characterized in that, The steel cord comprises: a center layer twisted by two center steel filaments; an intermediate layer twisted by seven intermediate steel filaments, the intermediate layer being sleeved on the outer periphery of the center layer; an outer layer twisted by fourteen outer layer steel filaments, the outer layer being sleeved on the outer periphery of the intermediate layer; the diameter of the center steel filament is d1, the diameter of the intermediate steel filament is d2, and the diameter of the outer layer steel filament is d3, wherein d1 the cross-sectional shape of the steel cord is a heptagon; the diameter d1 of the two center steel filaments of the center layer is 0.15 mm; the diameter d2 of the seven intermediate steel filaments of the intermediate layer is 0.20-0.215 mm; the diameter d3 of the fourteen outer layer steel filaments of the outer layer is 0.18-0.195 mm; the twist direction of the center steel filament is the same as that of the outer layer steel filament, and the twist direction of the intermediate steel filament is the same as that of the outer layer steel filament; the twist direction of the outer layer steel filament is Z; the twist pitch of the outer layer steel filament is twice that of the center steel filament; the twist pitch of the intermediate steel filament is equal to that of the outer layer steel filament; the twist pitch of the center steel filament is 7.5-8.0 mm, and the twist pitch of the intermediate steel filament and the outer layer steel filament is 15.0-16.0 mm.

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