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, and the N outer monofilaments are not completely twisted on the periphery of the M core monofilaments. The core strand and the outer strand are asymmetrical on the radial cross section, 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 is easy to 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] This utility model relates to the field of steel cord technology, specifically to a steel cord for rubber reinforcement and a corresponding tire. Background Technology

[0002] Steel cords used to reinforce heavy-duty tires, such as off-highway tires, require high strength. Therefore, steel cords consist of multiple strands comprising multiple monofilaments to achieve this high strength, forming the corresponding OTR cords. Current OTR cords, such as the steel cord for rubber reinforcement and off-highway tires disclosed in patent number CN209854313U, have a core strand and outer strands both composed of one core monofilament and six outer monofilaments twisted together (1+6 structure). The six outer monofilaments tightly wrap around the single core monofilament, preventing proper rubber penetration. During heavy-duty tire operation, the OTR cord endures extremely heavy loads, which exert a strong force on the core monofilaments. If the rubber adhesion is poor and the anchoring is weak, the core monofilaments can migrate from the rubber layer, potentially puncturing the outer rubber layer, exposing them, causing corrosion, and allowing moisture to penetrate the rubber layer and corrode the steel cord, severely impacting tire lifespan and safety.

[0003] Currently, there is also a method to optimize the process by deforming the monofilament. However, this method suppresses the deformation wave height after the monofilament is twisted, resulting in an unsatisfactory final effect. Utility Model Content

[0004] This invention aims to overcome the shortcomings of existing technologies by providing a steel cord for rubber reinforcement.

[0005] The present invention solves the technical problem by adopting the following technical solution: a steel cord for rubber reinforcement, comprising a core strand and multiple outer strands twisted around the core strand. Each core strand and outer strand comprises M core monofilaments and N outer monofilaments. The N outer monofilaments are incompletely twisted around the M core monofilaments. The core strand and outer strands are asymmetrical in radial cross-section. The core strand and outer strands form a spiral structure in overall shape, and some core strands are not covered by the outer strands and are exposed.

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

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

[0008] In several embodiments, the outer strand is further twisted with an outer winding thread.

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

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

[0011] In several embodiments, the diameters of the core single wires and the 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 utility model is as follows:

[0015] In the present utility model, the cross-sections of the core strands and the outer strands are both asymmetric irregular shapes, and the outer single wires do not completely wrap the inner single wires, and gaps are formed between the strands. Rubber can easily penetrate into the central steel wires, and the anchoring force of the core steel wires is significantly enhanced, 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 limiting the scope of the present utility model.

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

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

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

[0020] Therefore, 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 present invention claimed, 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, multiple 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 both 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, and the core strand 10 and the outer strands 20 are asymmetrical in the 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 layer, 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 and not twisted. 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, and 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 within 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 4 outer single wires 12. The 4 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 and a strength of 3500 MPa to 3800 MPa, while the outer winding filament 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 with a twist pitch of 12.5 mm and a twist direction of S, thereby forming seven strands, namely one core strand 10 and six outer strands 20. The six outer strands 20 are twisted around the core strand 10 with a twist pitch of 20 mm and a twist direction of Z. Finally, an outer winding filament 30 is wound around the outer strands 20 with a twist pitch of 5 mm and a twist direction of S. The core monofilaments 11 and outer monofilaments 12 have a diameter of 0.21 mm and a strength of 3500 MPa to 3800 MPa, while the outer winding filament 30 has a diameter of 0.15 mm.

[0031] Example 3

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

[0033] Comparative Example 1

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

[0035] The samples formed in Comparative Example 1 and Examples 1-4 were tested. The samples contained four parallel steel cords, with a distance of 5 mm measured from the center of one steel cord to the center of the other between two adjacent steel cords. The rubberized sample had dimensions of 220 x 25 x 15 mm (length x width x height). Next, one end of the rubberized sample was selected, the rubber compound at the selected end was removed, and the steel cords were left inside, ensuring that the remaining rubberized sample had a length of 1 inch. Third, the outer strands and the first outer monofilament were untied from the steel cord at the selected end to expose the first core monofilament. Fourth, one of the first core monofilaments was pulled out of the rubberized sample, and the required force was recorded. The recorded force is the core monofilament anchoring force.

[0036] The data obtained based on the above testing method is shown in the table below:

[0037]

[0038] Based on the above test structure, it can be seen that the steel cord in this embodiment has higher anchoring force and lower linear density.

[0039] All descriptions herein may be presented in any suitable order. Any and all instances used, or exemplary language provided herein (such as "for example"), are merely for the purpose of better illustrating the invention and are not intended to limit the scope of the invention, except as provided in the claims. The language used in the detailed description should not be construed as indicating any essential elements for practicing the invention beyond the claims.

[0040] This utility model describes preferred embodiments, including the best mode known to the inventors for carrying out the utility model. Of course, variations of these preferred embodiments will be readily apparent to those skilled in the art. The inventors intend that those skilled in the art may use these variations as appropriate, and the inventors indicate that the utility model can be implemented in other ways than those specifically described herein. Therefore, this utility model includes all improvements encompassed by the spirit and scope of the utility model as defined by the claims. Moreover, unless otherwise stated or there is a clear contradiction in the content, this utility model includes any of the foregoing elements 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 asymmetric in the radial cross-section. The M core filaments 11 are arranged in parallel without twist. The twist pitch of the outer filaments (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.

2. 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).

3. A steel cord for rubber reinforcement according to claim 2, 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 the twist direction of the outer winding wire (30).

4. A steel cord for rubber reinforcement according to claim 3, 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.

5. A 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.

6. A 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).

7. An off-road tire, characterized in that, The off-road tire includes the steel cord according to any one of claims 1 - 6.

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