RU206929U1 - Pneumatic tire cover - Google Patents

Abstract

The utility model relates to the tire industry, namely to the structure of the tire frame of pneumatic truck tires of radial structure. The technical problem to be solved by the proposed utility model is to create a tire carcass with an optimal ratio of the number of layers and rubber content in them, providing an increase in the maximum load on the tire while maintaining or reducing the number of cord layers in the carcass. The task is achieved due to the presence in the tire of a pneumatic tire of a radial tread structure, belt, sidewalls, bead rings and a carcass containing 5 layers of rubberized textile cord with a ratio between the thickness of the cord thread and the tensile strength of the thread less than 0.021 and including layers with different densities threads, and the four inner layers of the carcass have the same density of cords, ranging from 48 to 52 threads per 100 mm, and the rubber content in the layer is from 50 to 55%, and one outer layer of the carcass contains from 42 to 44 threads per 100 mm and the rubber content in layer from 60 to 62%. 1 wp f-ly, 3 dwg

Description

The utility model relates to the tire industry, namely to the structure of the tire frame of pneumatic truck tires of radial structure.

Currently, there is a steady tendency to demand an increase in the load characteristics of truck tires without changing (increasing) their dimensions. The tire carcass is one of the main load bearing elements of the tire. Typically, the carcass of a truck tire consists of several layers of rubberized textile cord. An increase in the load characteristic of a truck tire can be achieved by increasing the number of layers of rubberized cord in the carcass; however, this solution increases the weight of the tire, increases its cost and reduces the indicators of fuel efficiency and speed endurance.

The task of developing the carcass structure of modern truck tires is to maximally reduce the number of cord layers in the carcass in order to reduce the mass of the carcass and the tire as a whole, improve fuel efficiency and controllability. The main direction in solving this problem is the use of cords of increased strength.

Known design of the frame of pneumatic truck and light truck tires of radial and diagonal design, made of textile cord fabric with a tensile strength of a thread of more than 400 N, with a number of twists of the thread 180-290 per meter, a specific strength of more than BS / tex more than 0.78 and an elongation of the cord thread less than 3% at a load of 39-45 N. At the same time, the rubber content in the cord layer is 18-27% (RF patent for invention RU 2456167 dated 20.12.2017 "Pneumatic tire", Bulletin No. 20, IPC B60C 9/04, Holding Loil NEFTEKHIM company).

The disadvantage of this design is the use of cord layers with the same rubber content for all layers of the carcass, which leads to:

- to increased consumption of textile cord;

- to the appearance of a sharp drop in stiffness between the layers of the frame and the outer rubber layers of the sidewall.

Also known is the design of the frame of a pneumatic tire with a landing diameter of 20 inches, consisting of layers of rubberized cord with a breaking strength of a thread not exceeding 35 kgf / thread and two types of density: denser in the inner layers and sparse in the outer layers of the frame (RF patent for utility model No. 17307 of March 27, 2001 "Pneumatic tire tire", Bulletin No. 9, State Unitary Enterprise "Research Institute of the Tire Industry").

The disadvantage of this design is the use of a low-strength cord for the carcass, which leads to an increase in the number of carcass plies with an increase in the load on the tire, increases its weight, worsens fuel efficiency and controllability.

The closest analogue to the proposed utility model is the structure of the frame of pneumatic automobile tires, containing layers with different thread density in the layer and the breaking strength of the threads more than 35 kgf / thread and the ratio between the thread thickness of the textile rubberized cord and the tensile strength of the thread is less than 0.021 (specific strength coefficient ) m² / s². At least in one layer of the carcass, the thread density is 25-30% less, and the rubber content is 1.6-3.5 times higher than in the rest of the carcass layers (RF patent for invention No. 2525344 dated 08/10/2014 "Pneumatic tire tire" , Bulletin No. 22, JSC "KORDIANT").

The disadvantage of this design is a significant difference in the rubber content between the layers of the carcass, which creates a temperature difference in the carcass array and the presence of significant shear deformations between the layers with different densities of the cords. In addition, increasing the rubber content also increases the mass of the tire.

Another design drawback is the need to use cords with different strength characteristics in the plies to ensure equal strength in the tire carcass plies with the conditions specified in the patent. This complicates the production process, increases the labor intensity and cost of tires.

The density of the cords in the carcass ply (and the number of plies) determines the strength of the carcass when the tire is loaded with an external load.

The use of rubberized cords with different densities in the inner and outer layers of the tire carcass is due to the differences in the types of stresses arising in the inner and outer layers of the multilayer tire carcass. (The inner layers of the carcass are the basis of the load-bearing structure of the carcass and for the most part are subjected to tension, the effect of circumferential and angular moments during tire operation. The outer layers of the carcass are auxiliary and work mainly for bending).

In carcass plies with different cord densities, the rubber content is also different.

The index of rubber content in the rubberized cord layer, along with the density of the cord threads, is a characteristic for assessing the properties (performance, heat generation) of the rubber-cord layer under dynamic stress conditions.

The rubber content in the rubberized layer of the carcass cord is determined by the formula:

T = (1 - d / t) 100%, where:

t is the distance between the centers of adjacent threads in the carcass layer,

d is the diameter of the cord thread.

The value of the rubber content index in the rubberized layer of the carcass cord depends on the design and purpose of the tires (conditions of its operation). For radial tires, the rubber content in the ply is usually in the 40–65% range.

Reducing the rubber content in the carcass ply increases the likelihood of cracking at the interface between the cord thread and the rubber and requires increased material requirements to increase the bond strength between the cord and the rubber compound used to rubberize it.

An increase in the rubber content in the rubberized cord layer over 65% increases the rubber mass of the mixture, reduces the rigidity of the carcass layer and increases the temperature that develops in the layer under dynamic stresses.

The technical problem to be solved by the proposed utility model is to create a tire carcass with an optimal ratio of the number of layers and rubber content in them, providing an increase in the maximum load on the tire while maintaining or reducing the number of cord layers in the carcass.

The problem is solved by establishing a set of optimal parameters of the cord, namely, its strength and geometric characteristics, the diameter of the thread, with its density and rubber content in various layers of the carcass.

To solve the problem in the tire of a pneumatic tire of a radial structure, including a tread, sidewalls, a breaker and bead rings, the frame contains 5 layers of rubberized textile cord with a strength of more than 35 kgf / thread and with a specific strength coefficient of less than 0.021 and different density of cords in the inner and outer layers of the frame.

The density of the cords of at least three inner layers of the carcass cords in the tire is 48-52 threads per 100 mm, the rubber content in these layers is in the range from 50 to 55%, and the density of the cords in the outer layer is less than the density of the cords in the inner layers of the carcass by 12-16% and is 42-44 threads per 100 mm.

In this case, the rubber content in the outer casing layer with a cord density of 42–44 threads is 100 mm higher than the rubber content of the inner carcass layers with a cord density of 48–52 threads per 100 mm by 11–13% and is 60–62%.

The density of the cords in the inner and outer layers of the carcass is selected based on the characteristics of the used carcass cord and the requirement for the required safety margin of the tire.

The rubber content in the inner and outer layers is determined based on the following:

In the presence of rubberized cord layers in the carcass structure with different density of cords in the outer and inner layers at the boundaries between such carcass layers, due to the different rubber content and stiffness of the layers, increased shear stresses arise, which can cause delamination and destruction in the carcass layers in the process operation of the tire.

The index of interlayer rubber content makes it possible to evaluate the performance of a rubber-cord multilayer structure.

The value of the interlayer rubber content is determined by the formula:

r = (1 - d / h) 100%, where:

d is the diameter of the cord thread;

h is the distance between the centers of the cords in adjacent carcass plies.

The distance between the centers of the cords in adjacent carcass plies depends on the rubber coating thickness of each individual ply.

With an increase in the rubberizing thickness of the cord layer, the distance between the cords in adjacent layers increases and the interlayer rubber content increases.

An increase in the interlayer rubber content reduces the shear stresses between the rubberized cords, but increases the mass and decreases the thermal endurance of the tires.

Reducing the thickness of the rubberized ply of the cord and reducing the interlayer rubber content generally reduces the mass and increases the rigidity of the tire carcass, thereby increasing the thermal endurance of the tire, but increases the shear stresses between the rubberized cords of the carcass.

In addition, depending on the characteristics of the rubber compound used for rubberizing the cord and the accuracy of the equipment used for a particular tire manufacturer, the minimum value of the rubberizing thickness of the cord and, accordingly, the interlayer rubber content usually has technological limitations.

To improve the manufacturability, the thickness of the rubberizing of the cord in the carcass ply is usually assumed to be the same for all carcass plies, regardless of the density of the cords in them, and depends mainly on the diameter of the cord used.

The indicator of the interlayer rubber content in each case is selected empirically, taking into account the purpose of the tire and the technological capabilities of its production.

For a technologically feasible rubberizing thickness of cord threads with a strength of more than 35 kgf / thread and a specific strength coefficient of a card thread less than 0.021, the interlayer rubber content between the layers of the carcass to ensure reliable tire performance is from 27 to 33%.

FIG. 1 shows an example of a meridional section of a tire with a carcass according to the proposed utility model.

FIG. 2 shows a fragment of a cross-section of a tire carcass with layers of rubberized cord.

FIG. 3 shows a fragment of a cross-section of a tire frame with bead rings.

The tire shown in FIG. 1-3, contains:

1- protector,

2- sidewalls,

3- breaker,

4- side rings,

5- frame made of 5 layers of rubberized textile cord,

6- inner layers of rubberized cord,

7- outer layer of rubberized cord.

The inner layers 6 of the carcass 5 are made of cord 45A and have a density of 48 threads / 100 mm, and the outer layer 7 is made of cord 452A and has a density of 42 threads / 100 mm.

In this case, the interlayer content in all layers of the framework is the same and amounts to 31%.

A decrease in density in the main, so-called bearing layers of the carcass less than 48 threads / 100 mm leads to a decrease in the safety margin of the tire and reduces its performance. The mass also increases. Increasing the cord density above 52 strands / 100 mm leads to a decrease in the rubber content in the ply and increases shear stresses between the cord and the surrounding rubber, which leads to an increased risk of loss of bond between the cord and the rubber compound and destruction of the tire carcass during operation.

The outer, additional layer of the carcass operates in the mode of increased bending stresses and, in order to reduce the shear stresses in the layers, has a reduced density of cord threads and an increased rubber content.

It has been experimentally established that in order to achieve the set goals, the density of the cord of at least three inner layers is 48–52 threads per 100 mm with a rubber content of 50–55%

Studies have shown that if the rubber content in the carcass layer at a cord density of 48–52 threads per 100 mm is less than 50%, this will require the use of a cord with a large thread diameter and an increase in its rubber coating thickness, which, in turn, will lead to an increase in weight and reducing the thermal endurance of the tire.

If the rubber content in the carcass ply at a cord density of 48–52 threads per 100 mm is more than 55%, then this will require the use of a cord with a smaller thread diameter and higher strength, i. E. increasing the cost of the cord. In addition, the rigidity of the carcass will decrease, and the tire handling will deteriorate.

For the proposed design parameters of the inner layers of the carcass, it was experimentally established that in order to achieve the set goals, the density of the cord in the outer layer should be 42–44 threads per 100 mm with a rubber content of 60–62%.

If the density of the cord is less than 42 threads per 100 mm with a rubber content of 60–62%, this will reduce the strength characteristics of the tires.

If the density of the cord is more than 44 threads per 100 mm with a rubber content of 60–62%, then this will require the use of a different cord with a smaller thread diameter, different from that adopted in the inner layers of the carcass cord. The use of an additional type of cord increases the labor intensity and cost of manufacturing tires.

If the rubber content in the outer ply of the carcass with a cord density in the outer ply of 42-44 threads per 100 mm is less than 60%, this will require the use of a cord with a larger thread diameter and an increase in its rubber coating thickness, which, in turn, will lead to an increase in mass and a decrease in the thermal endurance of the tire.

If the rubber content in the outer ply of the carcass with a cord density in the outer ply of 42–44 threads per 100 mm is more than 62, then this will require the use of a cord with a smaller thread diameter and greater strength, that is, an increase in the cost of the cord. In addition, the rigidity of the carcass will decrease, and the tire handling will deteriorate.

A decrease in the interlayer rubber content of less than 27% for the selected type of cord requires a complication (and an increase in the cost) of the rubberizing technological process to achieve a smaller rubber coating thickness, an increase in the level of bond strength of the rubber compound with the cord thread due to an increase in shear stresses between adjacent layers of rubberized cord, an increase in the cost of rubber mixtures.

An increase in the interlayer rubber content in the layers of the carcass over 33% requires an increase in the thickness of the rubber coating of the cord, leads to a decrease in the rigidity of the carcass, increases the mass of the tire and reduces the controllability and thermal endurance.

Table 1 shows the characteristics and results of comparative bench tests of 12.00R18 tires of a serial design and tires with a carcass according to the proposed utility model.

Table 1

Indicator name Serial design Proposed design Relative strength of the cord in the carcass 0.028 0.020 The number of layers of cord in the carcass 3 + 2 4 + 1 Density of cords in the inner / outer layers of the carcass, pcs / 100 mm 60/48 48/44
according to the formula 48-52 and 42-44 Rubber content in the inner / outer layers of the frame,% 58/66 55/61
according to the formula 50-55 and 60-62 Interlayer rubber content in the carcass layers,% 39 31 Tire weight,% 100 100 Maximum load on tires,% 100 109 Maximum tire speed,% 100 100-105

Thus, the proposed utility model provides an increase in load characteristics while maintaining the mass and speed endurance of the tires.

The utility model can be realized on standard equipment under conditions of mass production.

Claims (2)

1. A tire of a pneumatic tire of a radial structure, including a tread, a belt, sidewalls, bead rings and a carcass containing 5 layers of rubberized textile cord with a ratio between the thickness of the cord thread and the tensile strength of the thread less than 0.021 and including layers with different thread densities, which differ in that the four inner layers of the carcass have the same density of cords, ranging from 48 to 52 threads per 100 mm, and the rubber content in the layer is from 50 to 55%, and one outer layer of the carcass contains from 42 to 44 threads per 100 mm and the rubber content in layer from 60 to 62%. 2. A tire according to claim 1, characterized in that the interlayer rubber content in the carcass is from 27 to 33%.

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