RU2076805C1 - Method for manufacture of radial-ply pneumatic tyres - Google Patents

Abstract

FIELD: tyre industry; manufacture of pneumatic tyres for cars and trucks including tubeless tyres. SUBSTANCE: during first stage carcass is assembled and formed by applying layers of breaker and tread and then forming process is completed. During first stage tread is applied with thickness decreasing from crown to shoulders found from equation h_s= (0,90-0,93)h_c, where h_s - thickness of tread in shoulder zone, and h_c - thickness of tread in over tyre crown zone. During second stage tyre blank is formed in mould with radius of tread curvature made to hyperbolic spiral described by relationship R_i = ±(0,45-0,60)B/Φ_i±(0,04-0,05)rad, where R_i - variable radius of curvature, mm; B - width of tyre section, mm; Φ_i - actual angle of hyperbolic spiral, rad. During the second stage tyre is exposed to forming and curing in mould with radii of curvature in zone of change from side to cap of tread R1 equal to (0.19-0.25)B and in zone of shoulder R2 equal to (0.40-0.50)B, where B - width of tyre section in mould. Tyre mould is formed with curvature of tread in mould described by four radii, minimum. EFFECT: improved quality of tyre. 3 cl, 4 dwg, 1 tbl

Description

 The invention relates to the tire industry, in particular the production of radial pneumatic passenger and truck tires, including tubeless.

A known method of manufacturing tires of pneumatic tires, in which they assemble a frame bracelet, mold it, apply a belt and tread, and then vulcanize the tire in the mold [1]
However, the known method cannot provide a finished tire with a tread thickness along the crown that is less than the tread thickness in the shoulder region and a radius of curvature in the shoulder region that is much smaller than the radius of curvature along the crown in the finished tire and in the mold, which leads to a decrease in the total area contact of the tire with the road and does not allow more evenly distribute the contact voltage of the tire with the road during its operation.

There is another method for the manufacture of radial pneumatic tires, in which at the first stage the carcass is assembled, molded, the layers of the breaker and tread are applied during molding, the molding process is completed and then, in the second stage, the tire blank is vulcanized in the mold [2]
However, the known method also does not allow to produce a tire with a configuration of the running and shoulder zones, which provides an increase in the total area of contact of the tire with the road, reduces the specific pressure of the tire in contact with the road and increases the safety of the tire during its operation.

 The technical result of the proposed method is to obtain a finished tire, which will increase the total contact area of the tire with the road and will more evenly distribute the contact voltage of the tire with the road during its operation and increase tire safety and its durability.

где R_i переменный радиус кривизны, мм;
В ширина профиля покрышки, мм;
Φ_i текущий угол гиперболической спирали, рад.To achieve a technical result, at the first stage, the tread is applied with a thickness decreasing from the crown to the shoulders, determined by the ratio
h _n (0.90-0.93) h _k ,
where h _{n the} thickness of the tread in the shoulder region;
h _{k the} thickness of the tread on the crown of the tire,
and at the second stage, the tire blank is molded in a mold with a radius of curvature of the tread made in a hyperbolic spiral described by the dependence

where R _{i the} variable radius of curvature, mm;
The width of the tire profile, mm;
Φ _i current angle of the hyperbolic spiral, rad.

 At the second stage, the tire is molded in a mold with radii of curvature in the transition zone from the sidewall to the running part of the tread R1 equal to (0.19-0.25) B, and in the shoulder zone R2 equal to (0.40-0.50 ) B, where B is the width of the tire profile in the mold. The tire blank is molded with the tread curvature in a mold described by at least four radii.

 In FIG. 1 shows a first step in manufacturing a tire; in FIG. 2 and 3 - profile of the tire in the mold, options; in FIG. 4 tire in the mold in the second stage.

 The method is as follows.

At the first stage, layers of rubberized cord 1 are applied to the assembly drum (not shown conditionally in FIG. 1) in a certain sequence, rolled them in, and wings are planted 2. Then the board is machined and the frame is formed. When forming the framework, layers of the belt 3 and the tread 4 are applied (Fig. 1). The tread 4 is applied with a thickness decreasing from the crown to the shoulders, determined by the ratio
h _n (0.90-0.93) h _k ,
where h _{n is the} thickness of the projector in the shoulder region;
h _{k the} thickness of the tread on the crown of the tire.

If you select a ratio less than the proposed limits, the curvature of the inner radius R _in the shoulder will increase, which will lead to the appearance of cracks between the cord cords in the shoulder area.

 If you select a ratio greater than the proposed limits, the total thickness of the tire in the shoulder area will increase, which will lead to increased heat generation and premature destruction of the edges of the belt.

где R_i переменный радиус кривизны, мм;
В ширина профиля покрышки, мм;
Φ_i текущий угол гиперболической спирали, рад.Then complete the molding process. The assembled tire is passed to the second stage and vulcanized in the mold 5 (in Fig. 4, the mold is shown conditionally). The molding of the tire in the mold 5 is carried out to obtain the required curvature of the tread, the radius of curvature of which is made along a hyperbolic spiral, described by the dependence

where R _{i the} variable radius of curvature, mm;
The width of the tire profile, mm;
Φ _i current angle of the hyperbolic spiral, rad.

 In FIG. 2 shows a profile of a passenger radial tire; FIG. 3 profile of a truck radial tire. In these figures, the tire tread profile is described by a hyperbolic spiral centered at point 0, the direction of the X axis of the spiral at an angle (0.04-0.05) radian to the horizontal axis of the tire profile with a variable radius of curvature R and the current spiral angle.

 A special case is the molding of a tire blank with a tread curvature in a mold described by at least four radii R1, R2, R3, R4 (Fig. 4).

 In the event that the tread profile is described by less than four radii of curvature, it will not be possible to ensure a smooth change in the curvature of the tire profile from the crown to the shoulder region, which leads to an uneven distribution of stresses in the tire contact with the road and impairs tire performance such as uniformity tread wear, temperature field distribution, noise generation, etc. The optimal change in the curvature of the tread profile is achieved when the radius of curvature of the tread R is made along a hyperbolic spiral with the condition that it touches the tire crown.

 At the second stage (Fig. 4), the tire is molded in a mold with radii of curvature in the transition zone from the sidewall to the running part of the tread R1 equal to (0.19-0.25) B and in the shoulder zone R2 equal to (0, 40-0.50) B, where B is the width of the tire profile in the mold.

 When choosing the ratios R1 and R2 less than the proposed limits, stress concentrations arise when the shoulder area of the tire comes into contact with the road.

 When choosing the ratios R1 and R2 over the proposed limits, the total contact area between the tire and the road decreases, the tire grip deteriorates and the tire wear rate increases.

 The table shows the comparative profile characteristics of known models of pneumatic tires of size 175 / 70R13 and an example of a tire manufactured by the proposed method.

 After vulcanization, the tire is transferred to the final operations for its manufacture. Next, the tire manufacturing cycle is repeated.

 The proposed method allows to produce tires with the configuration of the running and shoulder zones, which reduces the specific pressure in contact with the road, and to produce tires with increased wear resistance and safety.

Claims (3)

1. A method of manufacturing radial pneumatic tires, in which the carcass is assembled at the first stage, molded, the breaker and tread layers are applied during molding, the molding process is completed and then the tire blank is vulcanized in the mold, characterized in that at the first stage the tread is applied with a thickness decreasing from the crown to the shoulders, determined by the ratio h _n = (0.90 0.93) h _k , where h _n is the tread thickness in the shoulder area, h _k is the tread thickness along the tire crown, and in the second step tires are molded into ss-shape with a radius of curvature of the tread taken along a spiral giperbollicheskoy described dependence

where R _{i the} variable radius of curvature, mm;
B tire profile width, mm;
Φ _i current angle of the hyperbolic spiral, rad. 2. The method according to claim 1, characterized in that at the second stage the tire is molded in a mold with radii of curvature in the transition zone from the sidewall to the running part of the tread R ₁ = (0.19 0.25) B, and the shoulder area R ₂ = (0.40 0.50) B, where B is the width of the tire profile in the mold.  3. The method according to p. 1, characterized in that the tire blank is molded with the tread curvature in the mold described by at least four radii.

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