Belted layer steel wire structure for enhancing durability of engineering radial tire

Abstract

The invention discloses a belted layer steel wire structure for enhancing the durability of an engineering radial tire, and relates to the technical field of tires. According to the invention, the end part of the belted layer steel wire is designed into a stepped structure to realize stepped transition, and then U-shaped edge covering is carried out, so that the bonding strength of the steel wire end point and rubber can be effectively enhanced, and meanwhile, the situation that initial small cracks are generated too early due to sharp corners of the steel wire end point in the prior art is avoided.

Description

Technical Field

[0001] This invention relates to the field of tire technology, and more specifically to a belt layer steel wire structure for enhancing the durability of engineered radial tires. Background Technology

[0002] In engineering radial tires, the cord direction of the belt layer skeleton material is laid at a certain angle to the meridian direction. This structure can effectively enhance the circumferential stiffness of the tire and improve its load-bearing capacity. In existing technology, to achieve the oblique laying of the belt layer, the calendered steel cord fabric is cut at an angle using a cutting tool. Figure 1 As shown in the diagram, the strands are then laid out along the entire length of the auxiliary drum to achieve a certain angle between the angle of the steel wire cord in the belt layer and the meridian direction.

[0003] In existing cutting techniques, the ends of the steel wires in the belt layer of engineering radial tires often develop sharp corners during the beveling process, especially at small angles, where the ends become even sharper. Figure 2-3 As shown. After cutting and U-shaped edging, the adhesion between the steel wire and rubber at the sharp corners is poor, and the continuity between the steel wire and rubber is poor at the microscopic level. During the use of the formed tire, initial small cracks are prone to appear at this location.

[0004] Because the end area of ​​the belt layer in engineering radial tires experiences significant stress and deformation, coupled with high temperatures, initial small cracks can propagate further and cause shoulder delamination, resulting in tire damage. Therefore, optimizing the design of the belt layer wire ends to avoid sharp corner structures and delay the initiation of initial cracks can effectively improve the durability of the belt layer ends. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a belt layer steel wire structure that enhances the durability of engineering radial tires. The ends of the belt layer steel wires are stepped to achieve a stepped transition. When U-shaped edge is applied, the adhesion strength between the steel wire ends and the rubber can be effectively strengthened. At the same time, it will not cause the premature generation of initial small cracks due to the presence of sharp corners at the steel wire ends, as is the case in the prior art.

[0006] The technical solution of this invention is as follows: A belt layer steel wire structure for enhancing the durability of engineering radial tires is disclosed. The belt layer steel wire is divided into a single-strand steel wire structure and a multi-strand steel wire structure. Each steel wire includes at least two coils from the inside to the outside. For the single-strand steel wire, the lengths of the steel wires in different coils are different and decrease from the inner coil to the outer coil, so that the end of the single-strand steel wire has a stepped structure. For the multi-strand steel wire, each steel wire is the same length, but the lengths of adjacent steel wires at the outer coil are staggered by D1 and D2, and the length of the steel wire at the center is D1, where D1 > D2, so that the end of the multi-strand steel wire has a stepped structure.

[0007] Preferably, for a single strand of steel wire, the length difference between adjacent coils of steel wire is L. n =[1.5-0.1(n-1)]d n Where L1 represents the length difference between the innermost layer of steel wire and the adjacent second layer of steel wire, L2 represents the length difference between the second layer of steel wire and the adjacent third layer of steel wire, and so on, in mm; d1 represents the diameter of the innermost layer of steel wire, d2 represents the diameter of the second layer of steel wire, and so on, in mm.

[0008] Preferably, D1-D2=2D, where D represents the diameter of the steel wire in mm.

[0009] The bonding strength between steel wires and rubber is crucial to tire durability. The structure of the steel wire ends directly affects its contact area and adhesion to the rubber. In traditional designs, the sharp corners of the steel wire ends often lead to uneven contact and reduced adhesion. This invention, however, designs the ends of the belt layer steel wires with a stepped structure, which effectively improves the bonding strength through a smooth transition.

[0010] This is because of the adhesive force between the steel wire and the rubber. Typically affected by contact area interfacial bond strength The influence of surface roughness. Based on the theory of adhesion, the relationship can be expressed as:

[0011] in: For adhesive force, N; The interfacial bond strength is expressed in MPa. For contact area, mm 2 .

[0012] The stepped structure at the end of the wire in the bundle layer of this invention results in a smoother shape at the wire end and a larger contact area. The increased size enhances adhesion. The stepped structure reduces the sharp angles at the wire ends, preventing excessively small local contact areas and thus improving the bonding effect between the wire and the rubber.

[0013] Tires undergo repeated load cycles during driving, which can lead to material fatigue. Fatigue cracks typically initiate and propagate from areas of stress concentration. Traditional wire designs, due to the presence of sharp corners, generate high stress concentrations in these areas. The stepped structure of this invention effectively reduces this phenomenon, improving tire fatigue life. By reducing stress concentration at the wire ends through the stepped structure, fatigue life is improved. Simultaneously, the stepped design ensures more even load distribution, effectively slowing crack formation.

[0014] Furthermore, during high-speed driving, the temperature of the belt layer rises significantly due to friction and air resistance. Temperature changes cause material expansion or contraction, especially when there is a large difference in the coefficients of thermal expansion between the rubber and the steel wire, leading to thermal stress and potentially cracking. Traditional sharp-corner designs at the steel wire ends cannot effectively accommodate these thermal stress changes, easily causing early crack propagation. The stepped structure of this invention helps alleviate this problem by reducing thermal stress concentration. The theoretical analysis is as follows: Thermal stress caused by temperature It can be calculated using the following formula:

[0015] in: It is thermal stress, Pa; It is the Young's modulus of the material, in Pa; It is the coefficient of linear expansion of the material, / ℃; It refers to temperature change, in °C.

[0016] Because steel wires and rubber have different coefficients of thermal expansion, temperature changes can generate thermal stress at their interface. This invention designs the ends of the belt layer steel wires with a stepped structure, smoothing the wire ends and reducing areas of thermal stress concentration, thereby mitigating the risk of crack propagation at high temperatures. In practical applications, temperature has a significant impact on tire materials. At high temperatures, the fatigue performance of the belt layer material decreases drastically, while the optimized design of this invention effectively reduces thermal stress and crack propagation, extending tire lifespan.

[0017] The belt layer steel wire structure for enhancing the durability of engineered radial tires provided by this invention, through innovative optimization of the end structure of single-strand and multi-strand steel wires, has the following significant advantages compared to existing technologies: 1. In existing technologies, the sharp-angled structure formed by the oblique cutting of the bundled steel wires leads to uneven contact and insufficient adhesion between the steel wire and the rubber interface, resulting in microscopic continuity defects. This invention designs single-strand steel wires as a stepped structure with a "long inner coil and short outer coil," and multi-strand steel wires as a stepped structure with "differentiated lengths between the central and outer strands," creating a smooth transition contact interface at the wire ends. This structure significantly increases the effective contact area between the steel wire and the rubber. According to adhesion theory, this improves the interfacial bonding strength. With the contact area A remaining constant, the increase directly improves the adhesive force, while eliminating the problem of localized weak adhesion caused by sharp corners, significantly enhancing the interfacial continuity between the steel wire and the rubber, and fundamentally reducing the risk of adhesive failure.

[0018] 2. The ends of the belt layer in engineered radial tires are subjected to repeated load cycles during driving. Existing sharp-angle structures are prone to becoming stress concentration points, leading to premature initiation and rapid propagation of initial small cracks, ultimately causing shoulder delamination. The stepped structure of this invention, through its smoothly transitioned end shape, effectively disperses the load transmission path and avoids stress accumulation in localized areas. Finite element simulation results show that, compared to traditional 30°, 45°, and 60° sharp-angle structures, the stepped structure of this invention significantly reduces the peak stress at the wire ends and provides a more uniform stress distribution. This can significantly delay the initiation time of initial cracks and slow down crack propagation, thereby significantly improving the fatigue resistance of the belt layer ends.

[0019] 3. When a tire travels at high speed, the belt layer experiences a significant temperature rise due to friction and air resistance. The difference in thermal expansion coefficients between the steel wire and the rubber induces thermal stress, and sharp-angled structures exacerbate this stress concentration, leading to crack propagation. The stepped structure of this invention, by optimizing the end shape, reduces areas of thermal stress concentration, distributing the thermal stress generated by temperature changes evenly across the interface and lowering the risk of interfacial delamination due to differences in thermal expansion and contraction. Even under high-temperature conditions, it effectively maintains the adhesion stability between the steel wire and the rubber, preventing a rapid decline in material fatigue performance and extending the tire's service life in complex temperature environments.

[0020] 4. Belt end delamination is one of the main forms of damage in engineering radial tires. Its core causes are weak adhesion due to sharp-angled structures, stress concentration, and the superposition of thermal stress. This invention solves these three major problems simultaneously through a stepped structure, blocking the delamination failure path at the structural design level. In practical applications, it can effectively reduce the probability of belt end delamination, extend tire service life, and reduce maintenance costs and safety risks caused by tire damage, significantly improving the overall reliability and economic value of engineering radial tires. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the steel wire curtain after it has been cut diagonally with a cutting knife.

[0022] Figure 2 This is a schematic diagram of the sharp-angled end structure of the steel wire in the belt layer caused by the existing bias cutting process.

[0023] Figure 3 This is a side view of the sharp-angled end structure of the steel wire in the belt layer caused by the existing oblique cutting process.

[0024] Figure 4 This is a schematic diagram of a single-strand steel wire structure with specifications of 3+9+15×0.22+0.15 in Embodiment 1 of the present invention.

[0025] Figure 5 This is a side view of a single strand of steel wire with specifications of 3+9+15×0.22+0.15 in Embodiment 1 of the present invention.

[0026] Figure 6 This is a schematic diagram of a single-strand steel wire structure with specifications of 3×0.2+6×0.35 in Embodiment 2 of the present invention.

[0027] Figure 7 This is a schematic diagram of a multi-strand steel wire structure with a specification of 7×7×0.22 in Embodiment 3 of the present invention.

[0028] Figure 8 This is a schematic diagram of a multi-strand steel wire structure with specifications of 7×(3+9+15)×0.22+0.2 in Embodiment 4 of the present invention.

[0029] Figure 9 These are finite element simulation diagrams of stress concentration at the end positions of the belt layer steel wires with traditional 30° sharp corner structure, 45° sharp corner structure, and 60° sharp corner structure, as well as the belt layer steel wires of Embodiments 1-2 of the present invention, under one load; wherein, Figure a corresponds to the belt layer steel wire of Embodiment 1, Figure b corresponds to the belt layer steel wire of Embodiment 2, Figure c corresponds to the belt layer steel wire with 60° sharp corner structure, Figure d corresponds to the belt layer steel wire with 45° sharp corner structure, and Figure e corresponds to the belt layer steel wire with 30° sharp corner structure.

[0030] Figure 10 These are finite element simulation diagrams of stress concentration at the end positions of the belt layer steel wires with traditional 30° sharp corner structure, 45° sharp corner structure, and 60° sharp corner structure, as well as the belt layer steel wires of Embodiments 1-2 of the present invention, under double load; wherein, Figure a corresponds to the belt layer steel wire of Embodiment 1, Figure b corresponds to the belt layer steel wire of Embodiment 2, Figure c corresponds to the belt layer steel wire with 60° sharp corner structure, Figure d corresponds to the belt layer steel wire with 45° sharp corner structure, and Figure e corresponds to the belt layer steel wire with 30° sharp corner structure.

[0031] In the diagram, 1 represents a steel wire. Detailed Implementation

[0032] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention.

[0033] Example 1 like Figure 4 As shown in the figure, this embodiment designs a bundled layer steel wire structure for a single strand steel wire 1 with specifications of 3+9+15×0.22+0.15. As can be seen from the figure, it is formed by winding three loops of steel wire 1 sequentially from the inside out. The innermost loop has three steel wires 1, the middle loop has nine steel wires 1, and the outermost loop has fifteen steel wires 1. Simultaneously, a steel wire 1 with a diameter of 0.15mm is wrapped around the outside to connect the three loops of steel wire 1 into a single unit. In this embodiment, the end of the single strand steel wire 1 is designed in a three-layer stepped style: as shown... Figure 5As shown, the length of the three coils of steel wire 1 decreases from the inside to the outside, and the length difference between the innermost coil of steel wire 1 and the middle coil of steel wire 1 is L1=1.5d1=1.5×0.22mm=0.33mm; the length difference between the middle coil of steel wire 1 and the outermost coil of steel wire 1 is L2=1.4d2=1.4×0.22mm=0.308mm.

[0034] Example 2 like Figure 6 As shown in the figure, this embodiment designs a bundled layer steel wire structure for a single strand steel wire 1 with specifications of 3×0.2+6×0.35. As can be seen from the figure, it is formed by winding two loops of steel wire 1 sequentially from the inside out. The innermost loop consists of three steel wires 1 with a diameter of 0.2mm, and the outermost loop consists of six steel wires 1 with a diameter of 0.35mm. In this embodiment, the end of the single strand steel wire 1 is designed with a two-layer stepped pattern: the length of the two loops of steel wire 1 decreases sequentially from the inside out, and the length difference between the two loops of steel wire 1 is L1=1.5d1=1.5×0.2mm=0.3mm.

[0035] Example 3 like Figure 7 As shown in the figure, this embodiment designs a bundled layer steel wire structure for a 7×7×0.22 specification multi-strand steel wire 1. As can be seen from the figure, it is composed of seven 7×0.22 steel wires 1 wound together, including a central steel wire 1 and six outer steel wires 1 surrounding the central steel wire 1. Each steel wire 1 consists of seven steel wires 1 with a diameter of 0.22mm. The seven steel wires 1 in each steel wire 1 are of the same length. The six outer steel wires 1 have lengths D1 and D2 arranged alternately, and the central steel wire 1 also has a length of D1. Furthermore, D1-D2=2×0.22mm=0.44mm, thus giving the ends of the multi-strand steel wire 1 in this embodiment a stepped structure.

[0036] Example 4 like Figure 8 As shown in the figure, this embodiment uses a bundled layer steel wire structure design for a multi-strand steel wire 1 with a specification of 7×(3+9+15)×0.22+0.2. As can be seen from the figure, it is composed of seven strands of (3+9+15)×0.22 steel wire 1 wound together, including one central strand and six outer strands surrounding the central strand. Each strand consists of three innermost strands, nine middle strands, and fifteen outermost strands. A 0.2mm diameter steel wire is used to wrap around the seven strands, binding them together. All strands have the same length. The six outer strands have lengths D1 and D2, which are arranged alternately. The central strand also has a length of D1, and D1-D2=2×0.22mm=0.44mm, resulting in a stepped structure at the ends of the multi-strand steel wire 1 in this embodiment.

[0037] Finite element simulations were performed on the belt layer steel wire 1 with traditional 30° sharp angle structure, 45° sharp angle structure, 60° sharp angle structure, and the belt layer steel wire 1 of Example 2, respectively. The results are as follows: Figure 9-10 As shown, when using the traditional sharp-angle structure for the belt layer steel wire 1, the larger the cutting angle, the more obvious the stress concentration in the sharp-angle region at the end. However, the stepped end structure of the belt layer steel wire 1 of this invention effectively reduces the stress concentration at the end of the steel wire 1 compared to the traditional sharp-angle structure. The peak stress at the end is significantly reduced, which can slow down the crack initiation time. At the same time, the stress distribution in the entire end region of the stepped structure is more uniform and the value is smaller, thus effectively improving the durability of the belt layer end.

Claims

1. A belt layer steel wire structure for enhancing the durability of engineering radial tires, wherein the belt layer steel wire (1) is divided into a single-strand steel wire structure and a multi-strand steel wire structure, and each steel wire (1) includes at least two turns of steel wire (1) from the inside to the outside; characterized in that, For a single-strand steel wire (1), the lengths of the steel wires (1) in different layers are different and decrease sequentially from the inner layer to the outer layer, so that the end of the single-strand steel wire (1) has a stepped structure; for a multi-strand steel wire (1), each steel wire (1) has the same length, but the lengths of the adjacent steel wires (1) at the outer layer are D1 and D2, which are arranged alternately, and the length of the steel wire (1) at the center is D1, where D1 > D2, so that the end of the multi-strand steel wire (1) has a stepped structure.

2. The belt layer steel wire structure for enhancing the durability of engineered radial tires as described in claim 1, characterized in that, For a single strand of steel wire (1), the length difference between adjacent layers of steel wire (1) is L. n =[1.5-0.1(n-1)]d n L1 represents the length difference between the innermost layer of steel wire (1) and the adjacent second layer of steel wire (1), L2 represents the length difference between the second layer of steel wire (1) and the adjacent third layer of steel wire (1), and so on, with the unit being mm; d1 represents the diameter of the innermost layer of steel wire (1), d2 represents the diameter of the second layer of steel wire (1), and so on, with the unit being mm.

3. The belt layer steel wire structure for enhancing the durability of engineered radial tires as described in claim 1, characterized in that, D1-D2=2D, where D represents the diameter of the steel wire (1), in mm.

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