The structural parameters, material distribution, hysteresis loss, and dynamic physical properties of the bead parts of the BTR tire cannot meet the requirements. When tires are running at high speeds, heavy loads and relatively low pressures, the stress distribution at the end points of the carcass cords, wear-resistant adhesives, and the outer ends of the bead laps is unreasonable, stress concentration points appear, and radial distribution of material physical properties. The disparities are very different, radial shear stress is too large, and heat generation is high, leading to fatigue aging of the rubber compound.

The carcass cords are too low at the end of the bag, the material at the end of the bead banding is insufficient, and the sidewall rubber and the wear-resistant rubber are filled downwards, resulting in bending and bunching of the wear-resistant rubber. Stress is concentrated near the three end points and the wear-resistant adhesive is broken. Or the components form bubbles between the bonding surfaces. When the difference between the end point of the carcass cord and the outer end point of the bead wrapping is less than 6 mm, the problems of wear-resistant adhesive bending, assembly line breakage and bead debonding are likely to occur.

The thickness transition of the end points of the carcass ply and the chafer cloth is unreasonable, air is easily retained in the tire manufacturing process, and the tire gradually undergoes thermal delamination due to the fatigue aging of the rubber during the driving process, and expands into a bubble and escapes from the layer. The friction between each other produces a glue, and the accumulation of the glue causes the bulging of the assembly line, resulting in a rapid drop in the rigidity of the assembly line, resulting in a crack or even a spinning explosion.

The size of the bead () and the rim are too large, resulting in a tight joint between the bead and the rim, resulting in relative slip; the gap between the carcass cord and the wear rubber and the rim between the bead and the toe is too large. Under the conditions of heavy load and relatively low pressure, the carcass cords gradually withdraw, and drums are formed between the carcass and the toes, so that the cracks at the assembly line are gradually expanded, and even the beads are emptied, cracked, and drawn (see 1). ).

Improper use of tires is one of the major causes of bead breaks and voiding. Under standard inflation pressure and load, the actual horizontal axis of the tire is consistent with the horizontal axis of the design, and the tire performance can be fully exerted. Under the conditions of relatively large load and relatively low pressure, if the bead rigidity is insufficient, the actual horizontal tire axial position moves up. The stress is concentrated in the vicinity of the bead assembly line, resulting in excessive deformation of the part. The rubber compound forms air bubbles, voids, detonation and detonation under the complex stress (driving, braking, steering, etc.) When the large or relative inflation pressure is too low, the tire bead area is subjected to increased force, which may even cause the tire to lose air and the bead breaks.

(a) Inflatable pressure is too high (b) Inflatable pressure is normal (c) Insufficiency of inflation pressure The relationship between inflation pressure and bead deformation (7) The vehicle has not been replaced with a rim at the same time during the conversion process. For example, a 10.00R20 tire is assembled on a 7.0 rim, The 11.00R20 tire was assembled on a 7.5 rim, which was inconsistent with the load capacity of the original design, resulting in a change in the stress distribution at the bead of the tire. The stress concentration point shifted upward, causing a crack in the assembly line. It can be seen that the height of the rim is too high, the rim breaks into the bead, the stress concentration point moves downwards, and cracks and voids are easily formed above the assembly line; the rim height is too low, the bead position is not effectively supported, and the tire The stress concentration point of the circle moves upwards, and it is easy to appear cracks and voids below the assembly line.

(8) Improper setting of process parameters in the production process or impurities in the parts of the bead during the processing of the tire blank, frosting on the surface of the parts, scorching, incorporation of HIIR, and the presence of gas between the parts, causing the tire to be overloaded, During the process of high-speed driving, the defect area gradually expands, takes off, cracks, and even causes the bead to pull out.

Several types of assembly line voiding related to the production process are shown. (a) is caused by the poor adhesiveness of the apex. The crack extends upward and downward along the gap between the apex and the carcass ply and gradually tears; (b) and (c) are caused by poor adhesion of the sidewall rubber. Glue along the apex, bead wrapper film, wire wrapper and other components down; (d) cracks along the carcass cord down, the end of the wear rubber is not smooth and smooth, one of the reasons is The carcass ply remains air during the calendering process. During vulcanization, the gas accumulates at the end of the ply through the tiny space of the twisted steel wire.

(9) Inadequacy in adhesive properties such as apex and overedging adhesives, and excessive or small pressure of the pressure roller, etc., resulting in residual air between the parts of the bead or the joints of the parts.

(10) Improper positioning method or positioning lamp accuracy cannot reach the requirements during molding, resulting in too small a level difference between the end points of the carcass cord and the end point of the bead package, and the end points of the wear resistant rubber and the bead package. Structural adjustment of sidewall adhesive and wear-resistant rubber overlap surface thickness increase 0.51.0 rim height and tire force relationship between the instructions 107 Sun Qingjiang and other steel truck radial tire assembly and production process related to the assembly line to indicate the empty mm; bead package The method of pasting the film on the outer end of the cloth was changed from edging to lapping. The thickness of the film was increased from 0.6mm to 1.5mm to avoid uneven transition of the outer end of the bead wadding; the composite method of the sidewall was changed from two composites to three composites. And the rubber inside of the sidewall glue fills the material distribution at the outer ends of the carcass ply, the abrasion resistant rubber and the bead package, and effectively reduces the bending degree of the wear-resistant adhesive. At the same time, the height of the upper and lower apex rubbers was increased by 58mm, the height of the outer end points of the carcass ply and the bead fillers was increased by 23mm, and the thickness of the apex rubber at the outer ends of the carcass ply was increased by 1mm to enhance the rigidity of the bead area and to re-match the same. The rigid transition of the site. In addition, reduce the diameter of the bead ring and enhance the interference fit between the bead and the rim.

Process Improvement (1) Film manufacture reduces film extrusion temperature to avoid frosting on the film surface and improve film adhesion. Addition of small-scale film calendering equipment to reduce the change of plastic types in the press-type production process.

(2) Wire rolling Calendering The rubber conveyor belt is perpendicular to the film calender roll and swings left and right to reduce the amount of air bubbles for the glue clamp and to ensure uniform glue supply. Roller temperature, speed, and clearance meet requirements, avoiding air entering the film during wire rolling. By using the optical detection of the height of the glue on the calender rolls, the movement of the glue supply belt is controlled to ensure the amount and continuity of the glue. In addition, a squeegeeing device was added to the calendering roll, and fine needles with a punching length of 11.5 mm were gently blown over the surface of the film to remove air bubbles.

(3) The bead molding ensures that the parts of the bead area have proper adhesive properties, the surface is fresh, no impurities, no scorch, and the fitting pressure (such as sidewall pressure roller pressure) is properly adjusted to minimize the gas between the components. To avoid gas accumulation.

The tie-bubble device shows 1 calender roll; 2 stacking glue; 3 calendered cord fabrics; 4 glue supply conveyor belt; 5 squeegee device; 6 steel cords; 7 licker-in rollers; 8 idlers.

(4) The formation of green tires adopts laser light mark positioning, which reduces the width of the beacon and improves the positioning accuracy. It also changes the position of the bead package to external positioning. Proper use of the tire guides the user to properly maintain and use the tire, further extending the life of the tire.

Concluding remarks After taking the above-mentioned measures, the problem of cracking and bead debonding in the assembly line of all-steel radial truck tires is basically solved, and the tire's load capacity, high-speed performance and durability can be improved, and it is highly praised by users.

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January 28, 2019