Steel cord for rubber reinforcement and off-road tire

Abstract

The steel cord comprises a core strand and a plurality of outer strands twisted on the periphery of the core strand, each of the core strand and the outer strands comprises M core monofilaments and N outer monofilaments, the N outer monofilaments are incompletely twisted on the periphery of the M core monofilaments, the core strand and the outer strands are asymmetrical in the radial section, and the M is larger than or equal to 1. The core strand and the outer strand form a spiral structure on the overall appearance, and part of the core strand is not covered by the outer strand and is exposed outside. The cross sections of the core strands and the outer strands are in asymmetric irregular shapes, the outer monofilaments are not completely wrapped on the inner monofilaments, gaps are formed between the strands, rubber can easily permeate, anchoring force of the center steel wire and the core steel wire is remarkably enhanced, and migration of the core monofilaments is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of steel cords, and in particular to a steel cord for rubber reinforcement and a corresponding tire. Background Art

[0002] The steel cord used to reinforce heavy-duty tires such as off-road tires needs to have high strength, so the steel cord has multiple strands including multiple monofilaments to achieve high strength, forming the corresponding OTR cord. The current OTR cord, such as the steel cord for rubber reinforcement and off-road tire disclosed in patent number CN209854313U, has a core strand and an outer strand twisted by a core monofilament and six outer monofilaments, i.e., a 1+6 structure, and the outer 6 outer monofilaments form a tight wrapping of the 1 core monofilament, resulting in the rubber not being able to penetrate well into the core monofilament. During the driving of the heavy-duty tire, the OTR cord is subjected to a very heavy load, which applies a strong force to the core monofilament in the core strand of the OTR cord. If the adhesive is not well attached and the anchor is not strong, the core monofilament migrates out of the rubber layer, and seriously punctures the outer rubber, exposing it, forming corrosion, and driving moisture to penetrate into the rubber layer to corrode the steel cord, seriously affecting the service life and safety of the tire.

[0003] Currently, there is also a method of optimization through single-filament deformation. However, after the single-filament is twisted, the deformation wave height will be suppressed, resulting in unsatisfactory final effect. Summary of the invention

[0004] The present invention aims to avoid the shortcomings of the prior art and provides a steel cord for rubber reinforcement.

[0005] The present invention solves the technical problem by adopting the following technical scheme: a steel cord for rubber reinforcement, comprising a core strand and a plurality of outer strands twisted around the core strand, the core strand and the outer strands each comprising M core monofilaments and N outer monofilaments, the N outer monofilaments being incompletely twisted around the M core monofilaments, the core strand and the outer strand being asymmetric in a radial cross section, the core strand and the outer strand forming a spiral structure in overall appearance, and part of the core strand being not covered by the outer strands and being exposed to the outside.

[0006] In several embodiments, the M core monofilaments are arranged in parallel and are not twisted, and the twist length of the outer monofilaments is less than 20 mm.

[0007] In several implementations, the value of M is between 2-4, and the value of N is between 3-6.

[0008] In several embodiments, the outer strands are further twisted with outer winding wires.

[0009] In several embodiments, the lay direction of the core strands, outer strands, and outer winding wires is the same, and the lay direction of the steel cord is opposite to that of the outer winding wires.

[0010] In several embodiments, the lay pitch of the core strands and outer strands is between 8 mm and 16 mm, and the lay pitch of the steel cord is between 16 and 32 mm.

[0011] In several embodiments, the diameters of the core single wires and outer single wires are between 0.15 mm and 0.28 mm.

[0012] In several embodiments, the average tensile strength Ts of the outer single wires is in the following range: 3800 - 2000×Ds < Ts < 4400 - 2000×Ds, where Ds is the diameter value of the outer single wire.

[0013] And, an off-the-road tire having the above-mentioned steel cord.

[0014] The effective effect of the present invention is as follows:

[0015] The cross-sections of the core strands and outer strands of the present invention are both asymmetric irregular shapes, and the outer single wires do not completely wrap around the inner single wires, forming gaps between the strands. Rubber can easily penetrate into the center steel wires, significantly enhancing the anchoring force of the core steel wires and avoiding the migration of the core single wires. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are only for the purpose of illustrating the selected embodiments and do not represent all possible embodiments, and should not be considered as a limitation on the scope of the present invention.

[0017] Figure 1 Schematically shows the overall structure of the steel cord for rubber reinforcement in Example 1;

[0018] Figure 2 Schematically shows the structure of the core strands 10 of the steel cord for rubber reinforcement in Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Next, embodiments of the present invention will be described in detail with reference to the drawings. To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0020] Accordingly, the following detailed description of the embodiments of the present invention provided in conjunction with the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0021] The steel cord for rubber reinforcement mainly includes a core strand 10, a plurality of outer strands 20 twisted around the periphery of the core strand 10, and an outer winding wire 30 twisted around the outer periphery of all the outer strands 20. The core strand 10 and the outer strands 20 each include M core single wires 11 and N outer single wires 12. The N outer single wires 12 are incompletely twisted around the periphery of the M core single wires 11. The core strand 10 and the outer strands 20 are asymmetrical in a radial cross-section.

[0022] The above-mentioned core single wires 11, outer single wires 12, and outer winding wire 30 can be coated with a zinc-coated copper coating, that is, copper is plated on the steel wire, zinc is plated on the copper layer, and finally through thermal diffusion, copper and zinc are fused together to form a brass coating.

[0023] Among them, the M core single wires 11 are arranged in parallel without twisting. The twist pitch of the outer single wires 12 is less than 20 mm. The value of M is between 2 and 4, and the value of N is between 3 and 6.

[0024] Among them, the core strand 10, the outer strands 20, and the outer winding wire 30 have the same twist direction. The twist direction of the steel cord is opposite to the twist direction of the outer winding wire 30. The twist pitch of the core strand 10 and the outer strands 20 is between 8 mm and 16 mm. The twist pitch of the steel cord is between 16 and 32 mm. The twist pitch of the outer winding wire 30 is 3.5 mm - 5 mm.

[0025] In addition, the diameters of the core single wires 11 and the outer single wires 12 are between 0.15 mm and 0.28 mm. The average tensile strength Ts of the outer single wires 12 is in the following range: 3800 - 2000×Ds < Ts < 4400 - 2000×Ds, where Ds is the diameter value of the outer single wires 12.

[0026] Embodiment 1

[0027] As Figure 1 shown, the steel cord has 3 core single wires 11 arranged in parallel and four outer single wires 12. The four outer single wires 12 are wound around the 3 core single wires 11 with a twist pitch of 12.5 mm and a twist direction of S, thus forming 7 strands, that is, 1 core strand 10 and 6 outer strands 20. The 6 outer strands 20 are twisted around 1 core strand 10 with a twist pitch of 20 mm and a twist direction of Z. Finally, the outer winding wire 30 is wound around the outer strands 20 with a twist pitch of 5 mm and a twist direction of S.

[0028] The core monofilament 11 and the outer monofilament 12 have a diameter of 0.21 mm, a strength of 3500 MPa to 3800 MPa, and the outer winding wire 30 has a diameter of 0.15 mm.

[0029] Example 2

[0030] In this embodiment, the steel cord has two parallel core monofilaments 11 and five outer monofilaments 12, the five outer monofilaments 12 are wound around the two core monofilaments 11, the twisting pitch is 12.5 mm, the twisting direction is S, thereby forming seven strands, namely one core strand 10 and six outer strands 20, the six outer strands 20 are twisted on one core strand 10, the twisting pitch is 20 mm, the twisting direction is Z, and finally the outer winding 30 is wound around the outer strand 20, the twisting pitch is 5 mm, and the twisting direction is S. The core monofilament 11 and the outer monofilament 12 have a diameter of 0.21 mm, a strength of 3500 MPa to 3800 MPa, and the outer winding 30 has a diameter of 0.15 mm.

[0031] Example 3

[0032] In this embodiment, the steel cord has four parallel core filaments 11 and three outer filaments 12, the three outer filaments 12 are wound around the four core filaments 11, the twisting pitch is 12.5 mm, the twisting direction is S, thereby forming seven strands, namely one core strand 10 and six outer strands 20, the six outer strands 20 are twisted on one core strand 10, the twisting pitch is 20 mm, the twisting direction is Z, and finally the outer winding 30 is wound around the outer strand 20, the twisting pitch is 5 mm, and the twisting direction is S. The core filaments 11 and the outer filaments 12 have a diameter of 0.21 mm, a strength of 3500 MPa to 3800 MPa, and the outer winding 30 has a diameter of 0.15 mm.

[0033] Comparative Example 1

[0034] For example, the structure of the steel cord used for rubber reinforcement is disclosed in the patent number CN209854313U in the background technology.

[0035] The sample formed by the above-mentioned comparative example 1 and examples 1-4 was tested. The sample was embedded with 4 steel cords arranged in parallel, the distance between two adjacent steel cords measured from the center of one steel cord to the center of another steel cord was 5 mm, and the rubberized sample had a size of 220x25x15mm (length x width x height); secondly, one end of the rubberized sample was selected, the rubber compound of the selected end was removed and the steel cord was left therein, and it was ensured that the remaining rubberized sample had a length of 1 inch; thirdly, the outer strands and the first outer monofilaments were untied from the steel cord at the selected end to expose the first core monofilaments; fourthly, one of the first core monofilaments was pulled out from the rubberized sample and the required force was recorded, and the recorded force was the core monofilament anchoring force.

[0036] According to the above test method, the data obtained are shown in the following table:

[0037]

[0038] According to the above test structure, it can be known that the steel cord in this embodiment has a higher anchoring force and a lower linear density.

[0039] All the methods described herein can be performed in any suitable order. Any and all examples used, or exemplary language (such as "for example") provided herein are merely to better illustrate the present invention and are not intended to limit the scope of the present invention, unless the claims are included. The language in the detailed description should not be construed as indicating any essential factors for practicing the present invention that are not claimed.

[0040] The present invention describes preferred embodiments, including the best mode of carrying out the invention known to the inventors. Of course, variations of these preferred embodiments will be apparent to those skilled in the art. The inventors anticipate that the skilled artisan may use such variations as appropriate, and the inventors indicate that the present invention may be implemented in other ways than those specifically described herein. Therefore, the present invention includes all modifications encompassed by the spirit and scope of the invention as defined by the claims. Furthermore, unless otherwise stated or clearly contradictory in context, the present invention includes any of the above-described factors and all possible variations thereof.

Claims

1. A steel cord for rubber reinforcement, characterized in that: It includes a core strand (10) and a plurality of outer strands (20) twisted around the periphery of the core strand (10). Both the core strand (10) and the outer strands (20) include M core filaments (11) and N outer filaments (12). The N outer filaments (12) are not completely twisted around the periphery of the M core filaments (11), and the core strand (10) and the outer strands (20) are asymmetrical in the radial cross-section.

2. A steel cord for rubber reinforcement according to claim 1, characterized in that: The M core filaments 11 are arranged in parallel without twisting, and the twist pitch of the outer filaments (12) is less than 20 mm.

3. The steel cord for rubber reinforcement according to claim 1, characterized in that: The value of M is between 2 and 4, and the value of N is between (3) and (6).

4. The steel cord for rubber reinforcement according to claim 1, characterized in that: An outer winding wire (30) is also twisted around the periphery of the outer strand (20).

5. A steel cord for rubber reinforcement according to claim 4, characterized in that: The twist directions of the core strand (10), the outer strands (20) and the outer winding wire (30) are the same, and the twist direction of the steel cord is opposite to that of the outer winding wire (30).

6. A steel cord for rubber reinforcement according to claim 5, characterized in that: The twist pitch of the core strand (10) and the outer strands (20) is between 8 mm and 16 mm, and the twist pitch of the steel cord is between 16 and 32 mm.

7. The steel cord for rubber reinforcement according to claim 1, characterized in that: The diameters of the core filaments (11) and the outer filaments (12) are between 0.15 mm and 0.28 mm.

8. The steel cord for rubber reinforcement according to claim 1, characterized in that: The average tensile strength Ts of the outer filaments (12) is in the following range: 3800 - 2000×Ds < Ts < 4400 - 2000×Ds, where Ds is the diameter value of the outer filaments (12).

9. An off-road tire, characterized in that: The off-road tire includes the steel cord according to any one of claims 1 - 8.

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