A belt layer structure for ultra-low pressure agricultural radial tires

Abstract

This invention belongs to the field of tire manufacturing technology and discloses a belt layer structure for an ultra-low pressure agricultural radial tire, including belt layer one, belt layer two, and tackifying rubber sheet. This invention optimizes the belt layer angle by specifying the ratio of the belt layer to the tire's running surface, adjusting the difference in belt layer endpoints, and improving the belt layer angle. This results in a more uniform pressure distribution during tire rolling, effectively avoiding stress concentration at the belt layer ends. Simultaneously, a dedicated tackifying rubber sheet system is added between the belt layers to enhance interlayer adhesion strength, buffer shear deformation, and reduce interfacial heat generation. Structurally, this reduces belt layer gaps and early failures that occur when the tire is subjected to large deformation under low pressure, significantly improving tire durability and extending tire lifespan. By using suitable cord materials, a reasonable number of layers, and precision manufacturing processes, a balance between rigidity and flexibility is achieved while ensuring heavy load-bearing capacity and puncture resistance. The overall solution extends tire lifespan.

Description

Technical Field

[0001] This invention belongs to the field of tire manufacturing technology, specifically a belt layer structure for ultra-low pressure agricultural radial tires. Background Technology

[0002] Agricultural radial tires typically use fiber cords arranged in a near-circumferential direction for their belt layer, which restricts the tire's circumferential deformation. The belt layer bears 60%-70% of the tire's internal stress and is the tire's main load-bearing component. Its structural design parameters directly affect the overall tire's stress and deformation.

[0003] With the expansion of agricultural production, large agricultural machinery is increasingly used in actual production. At the same time, in order to avoid soil compaction caused by the operation of large agricultural machinery, which affects crop production and yield, ultra-low pressure agricultural radial tires are widely chosen by customers due to their high load capacity, large ground contact area, and strong passability. The increased number of belt layers in existing ultra-low pressure agricultural radial tires has improved the tire's strength and puncture resistance. However, under heavy load or cyclic operation, the tire's stress deformation increases, and the shear force at the ends between the belt layers is concentrated, which can easily cause premature end failure, forming shoulder gaps, reducing the tire's durability and affecting its service life. Therefore, a reasonable belt layer structure design is needed to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide an ultra-low pressure agricultural radial tire belt layer structure to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a belt layer structure for an ultra-low pressure agricultural radial tire, comprising a belt layer one, a belt layer two, and an adhesive film. The belt layer one and the belt layer two are arranged at an angle of 18°-29° to the center line of the tire crown. The width of the belt layer one is 0.85-0.87 times the width of the tire tread, and the width of the belt layer two is 0.82-0.84 times the width of the tire tread. The belt layer one and the belt layer two are centered and the difference between their two endpoints (a) is 10-30 mm. An adhesive film 3 is provided at both ends of each belt layer one and the belt layer two.

[0006] As a preferred embodiment of the present invention, both the first belt layer and the second belt layer are three- or four-layer fiber fabric layers.

[0007] As a preferred embodiment of the present invention, the fiber fabric of the first belt layer and the second belt layer is nylon 66 or polyester cord, the cord linear density is 1500D-2500D and it has been impregnated with resin.

[0008] As a preferred embodiment of the present invention, the fabric cutting angle error between the first belt layer and the second belt layer is ≤ ±0.5°, and the dimensional deviation of the two side grade a is ≤ ±1mm.

[0009] As a preferred embodiment of the present invention, the width b of the tackifying film is 60-80 mm, and it is symmetrically distributed with the endpoints of the first and second belt layers as the center lines.

[0010] As a preferred embodiment of the present invention, the thickness of the tackifying film is 1.0-1.5 mm.

[0011] As a preferred embodiment of the present invention, the tackifying film uses a matrix material made of natural rubber and butadiene rubber, wherein the natural rubber content is 60%-70%, the butadiene rubber content is 30%-40%, and it contains carbon black, tackifying resin, antioxidant and vulcanizing agent.

[0012] As a preferred embodiment of the present invention, the tackifying film has a Shore A hardness of 55-65 degrees and an elastic modulus lower than that of the fabric adhesives of belt layer one and belt layer two.

[0013] As a preferred embodiment of the present invention, the first belt layer, the second belt layer, and the adhesive film are bonded together using a two-stage bonding process. The adhesive film is heat-bonded after the endpoints of the first belt layer and the second belt layer are aligned. The bonding temperature is 90-110℃ and the bonding pressure is 0.5-0.8MPa.

[0014] The beneficial effects of this invention are as follows: This invention specifies the ratio of the belt layer to the tire tread surface in ultra-low pressure agricultural radial tires, adjusts the difference in the end points of the belt layer, and optimizes the belt layer angle. This results in a more uniform pressure distribution during tire rolling, effectively avoiding stress concentration at the ends of the belt layer. Simultaneously, a dedicated tackifying rubber system is added between the belt layers to improve interlayer adhesion strength, buffer shear deformation, and reduce interfacial heat generation. Structurally, this reduces belt layer gaps and early failures that occur when tires are subjected to large deformations under low pressure, significantly improving tire durability and extending tire lifespan. By employing suitable cord materials, a reasonable number of layers, and precision manufacturing processes, a balance between rigidity and flexibility is achieved while ensuring heavy load-bearing capacity and puncture resistance. The overall solution extends tire lifespan, improves reliability under ultra-low pressure conditions, and better meets the needs of large agricultural machinery in field operations. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention.

[0016] In the diagram: 1. Belt layer one; 2. Belt layer two; 3. Adhesive film. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figure 1 As shown, this embodiment of the invention provides a belt layer structure for an ultra-low pressure agricultural radial tire, including belt layer 1, belt layer 2, and tackifying film 3. Belt layer 1 and belt layer 2 are arranged at an angle of 18°-29° to the center line of the tire crown. The width of belt layer 1 is 0.85-0.87 of the tire tread width, and the width of belt layer 2 is 0.82-0.84 of the tire tread width. Belt layer 1 and belt layer 2 are centered and the difference between their two endpoints (a) is 10-30 mm. Each belt layer 1 and belt layer 2 has a tackifying film 3 at both ends.

[0019] The 18°-29° cross arrangement can balance circumferential rigidity and lateral stability, adapting to the requirements of ultra-low pressure and large deformation; the belt layer 1 and belt layer 2 are designed according to the width ratio of the driving surface to achieve a rigidity gradient transition; the center differential structure makes the forces on both sides symmetrical, avoiding uneven wear and stress load; the adhesive film 3 set at the end directly acts on the high stress area to improve the structural reliability.

[0020] Among them, both belt layer 1 and belt layer 2 are three or four layers of fiber fabric.

[0021] Three or four layers of fiber curtain fabric can meet the heavy load requirements of large agricultural machinery, providing sufficient strength and puncture resistance. Too few layers can easily lead to insufficient strength and excessive deformation, while too many layers can result in excessive rigidity and intensified interlayer shear. Three or four layers of fiber curtain fabric can achieve the optimal match between load-bearing capacity, flexural strength, and weight.

[0022] Among them, the fiber fabric of belt layer 1 and belt layer 2 is nylon 66 or polyester cord, the cord linear density is 1500D-2500D and it has been impregnated.

[0023] Nylon 66 and polyester cords are high in strength, dimensionally stable, and fatigue-resistant, making them suitable for the stress requirements of belt layers; a linear density of 1500D-2500D provides appropriate skeleton strength; impregnation treatment improves the bonding between the cord and the rubber interface, prevents cord fraying and debonding, and enhances the overall structural stability.

[0024] Among them, the fabric cutting angle error of belt layer 1 and belt layer 2 is ≤ ±0.5°, and the dimensional deviation of the two side grade a is ≤ ±1mm.

[0025] Precise control of the cutting angle ensures consistent cross angles and uniform stress distribution; strict control of differential dimensional deviations ensures left-right symmetry, avoiding tire runaway, uneven wear, and localized stress overload. High-precision manufacturing requirements can improve tire uniformity and high-speed durability.

[0026] Among them, the width b of the tackifying film 3 is 60-80mm, and it is symmetrically distributed with the endpoints of belt layer 1 and belt layer 2 as the center line.

[0027] A width of 60-80mm can completely cover the stress concentration area at the end of the belt layer. The symmetrical arrangement with the endpoint as the center ensures that the film is evenly stressed and has stable adhesion. Insufficient width will lead to reinforcement failure, while excessive width will increase the consumption of rubber and the weight of the tire crown. A width of 60-80mm can balance the reinforcement effect and economy.

[0028] The thickness of the tackifying film 3 is 1.0-1.5mm.

[0029] A thickness of 1.0-1.5mm provides sufficient bonding interface and buffering capacity. If the thickness is too small, insufficient bonding and easy flexing and cracking may occur. If the thickness is too large, it will cause sudden changes in local rigidity and increased heat generation. A thickness of 1.0-1.5mm is suitable for belt layer rubber system, and the interface bonding is strong after vulcanization.

[0030] Among them, the tackifying film 3 uses a matrix material that combines natural rubber and butadiene rubber, with natural rubber content of 60%-70% and butadiene rubber content of 30%-40%, and contains carbon black, tackifying resin, antioxidant and vulcanizing agent.

[0031] Natural rubber provides high adhesion and high elasticity, while butadiene rubber enhances flexural strength and low-temperature performance. The system balances adhesion and mechanical properties, and is reinforced with carbon black, strengthens interfacial bonding with tackifying resin, and extends lifespan with antioxidants, ensuring the film remains stable under long-term heavy loads and high-frequency flexing.

[0032] Among them, the Shore A hardness of the tackifying film 3 is 55-65 degrees, and its elastic modulus is lower than that of the fabric adhesive of belt layer 1 and belt layer 2.

[0033] With a hardness of 55-65 degrees, it falls between soft cushioning rubber and belt layer rubber. Its lower modulus effectively absorbs interlayer shear deformation, avoids stress concentration, and its moderate hardness ensures support without causing abrupt changes in rigidity. This significantly reduces cyclic heat generation in the tire shoulder area and improves durability.

[0034] Among them, the first belt layer 1, the second belt layer 2 and the tackifying film 3 are bonded together by a two-stage bonding process. After the ends of the tackifying film 3 are aligned with those of the first belt layer 1 and the second belt layer 2, they are heat-bonded and formed. The bonding temperature is 90-110℃ and the bonding pressure is 0.5-0.8MPa.

[0035] Secondary lamination ensures precise film positioning, no bubbles, and no misalignment. Heat bonding improves film flowability and adhesive activity. Temperatures of 90-110℃ and pressures of 0.5-0.8MPa ensure a tight bond at the interface, forming a whole after vulcanization, thus avoiding manufacturing defects such as delamination and bubbles.

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A belt layer structure for ultra-low pressure agricultural radial tires, characterized in that: It includes belt layer one (1), belt layer two (2) and tackifying film (3). The belt layer one (1) and belt layer two (2) are arranged at an angle of 18°-29° to the center line of the tire crown. The width of the belt layer one (1) is 0.85-0.87 of the tire tread width, and the width of the belt layer two (2) is 0.82-0.84 of the tire tread width. The belt layer one (1) and belt layer two (2) are centered and the difference between the two ends is 10-30mm. Each belt layer one (1) and belt layer two (2) is provided with tackifying film (3) at both ends.

2. The ultra-low pressure agricultural radial tire belt layer structure according to claim 1, characterized in that: Both the first belt layer (1) and the second belt layer (2) are three or four layers of fiber fabric.

3. The ultra-low pressure agricultural radial tire belt layer structure according to claim 1, characterized in that: The fiber fabric of the first belt layer (1) and the second belt layer (2) is nylon 66 or polyester cord, with a cord linear density of 1500D-2500D and is treated with impregnation.

4. The ultra-low pressure agricultural radial tire belt layer structure according to claim 1, characterized in that: The fabric cutting angle error of the first belt layer (1) and the second belt layer (2) is ≤ ±0.5°, and the size deviation of the two sides of the difference a is ≤ ±1mm.

5. The ultra-low pressure agricultural radial tire belt layer structure according to claim 1, characterized in that: The width b of the adhesive film (3) is 60-80 mm, and it is symmetrically distributed with the endpoints of the first belt layer (1) and the second belt layer (2) as the center line.

6. The ultra-low pressure agricultural radial tire belt layer structure according to claim 1, characterized in that: The thickness of the tackifying film (3) is 1.0-1.5 mm.

7. The ultra-low pressure agricultural radial tire belt layer structure according to claim 1, characterized in that: The tackifying film (3) uses a matrix material made of natural rubber and butadiene rubber, wherein the natural rubber content is 60%-70%, the butadiene rubber content is 30%-40%, and it contains carbon black, tackifying resin, antioxidant and vulcanizing agent.

8. The ultra-low pressure agricultural radial tire belt layer structure according to claim 1, characterized in that: The tackifying film (3) has a Shore A hardness of 55-65 degrees and an elastic modulus lower than that of the fabric adhesive of belt layer one (1) and belt layer two (2).

9. The ultra-low pressure agricultural radial tire belt layer structure according to claim 1, characterized in that: The first belt layer (1), the second belt layer (2) and the adhesive film (3) are bonded together by a two-stage bonding process. The adhesive film (3) is heat-bonded after the ends of the first belt layer (1) and the second belt layer (2) are aligned. The bonding temperature is 90-110℃ and the bonding pressure is 0.5-0.8MPa.

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