RU205833U1 - Pneumatic tire cover - Google Patents

Abstract

The utility model relates to the tire industry, namely to the structure of the tire carcass of pneumatic truck tires of a bias structure. load on the tire while maintaining or reducing the number of layers of cord in the carcass. The problem is solved by providing 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 different layers of the carcass and between the layers. the tire of a pneumatic tire of a diagonal structure, including a tread, sidewalls, a breaker, bead rings and a carcass, the carcass contains 6 layers of rubberized textile cord with a strength of more than 35 kgf / thread, a coefficient of specific strength of the cord less than 0.021 and and It has different cords in the inner, middle and outer carcass plies. The cords of the two inner and two outer carcass plies in a tire are 55 to 60 threads per 100 mm, the rubber content in these layers ranges from 46 to 49%. and the density of the cords in the two middle layers is higher than the density of the cords in the inner layers of the carcass by 20-24% and amounts to 72-76 threads per 100 mm. At the same time, the rubber content in the middle layers of the carcass with a density of cords from 72 to 76 threads per 100 mm less rubber content of the inner and outer layers of the carcass with a cord density of 55-60 threads per 100 mm by 35-40% and is 32-35%. the requirements for the necessary safety margin of the tire under load. Due to the different rubber content and the stiffness of the layers, increased shear stresses arise, which can cause delamination and destruction in the layers of the carcass during the operation of the tire.

Description

The utility model relates to the tire industry, namely to the structure of the tire carcass of pneumatic truck tires with a bias structure.

Consumers are constantly increasing the requirements for the load characteristics of truck tires without changing (increasing) their dimensions. One of the main load bearing elements of a tire and determining its load characteristic is the tire carcass. As a rule, the carcass of a biased 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.

When increasing the load characteristic of a tire in order to reduce the mass of the carcass and the tire as a whole, to increase the fuel efficiency and controllability of tires, the main task in the development of the carcass structure of modern truck tires is to maximize the reduction of the number of cord layers in the carcass.

The main direction in solving this problem is the use of cords of increased strength in the tire carcass. However, an increase in the load characteristic of tires by simply using stronger cords in the tire carcass is usually limited both by their cost and by the deterioration of their maintainability in the event of mechanical damage along the carcass with a significant decrease (for example, when using a steel cord up to 1-2 layers) of the number of cord layers.

Known design of the frame of pneumatic truck and light truck tires of radial and diagonal construction, 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 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", B60C 9/04, bulletin No. 20, Holding Company LLC LOIL NEFTEKHIM).

The disadvantages 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 difference in stiffness between the rubberized layers of the carcass cord and the outer rubber layers of the sidewall.

Also known is the design of a tire frame for 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", B60C 9/00, 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 carcass of pneumatic automobile tires, containing layers with different thread densities in the layer, with the breaking strength of the threads of 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). 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" , B60C 9/04, 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 layers during cyclic loading of the tire during operation, and the presence of significant shear deformations between the layers with different densities of the cords. In addition, increasing the rubber content in the lower density carcass plies increases the mass of the tire.

Another design drawback is the need to use cords with different strength characteristics in the carcass 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 in combination with the number of cords determines the strength of the carcass when the tire is loaded with an external load.

The use of rubberized cord with different densities in different layers of the tire carcass is due to differences in the types of stresses and deformations that occur in the inner, middle and outer layers of the multilayer tire carcass. In bias tires, the outer and inner layers of the carcass are subjected to more significant bending deformations than the middle layers, which necessitates their greater elasticity (flexibility).

In addition, the outer ply of the carcass cords should have a lower flexural stiffness to provide a smoother transition of stiffness from the rubberized ply of the carcass cord to the rubber of the tire sidewall.

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).

A decrease in the rubber content in the carcass ply increases the likelihood of cracking at the interface between the cord thread and the rubber and causes increased requirements for materials to ensure the required level of bond strength between the cord and the rubber compound used to rubberize it.

An excessive increase in the rubber content in the rubberized cord layer increases the mass of the rubber compound, reduces the rigidity of the carcass ply and increases the temperature that develops in the ply under dynamic stresses, and increases the mass of the tire carcass.

The technical problem to be solved by the proposed utility model is to create a carcass of a bias-structure tire 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 in combination with its density and rubber content in various layers of the carcass and between the layers.

To solve this problem, in a pneumatic tire of a diagonal structure, including a tread, sidewalls, a breaker, bead rings and a carcass, the carcass contains layers of rubberized textile cord with a strength of more than 35 kgf / thread, a coefficient of specific strength of the cord less than 0.021, and the carcass threads have different densities cords in the inner, middle and outer layers of the carcass.

The density of the cords of at least two inner and two outer layers of the carcass cords in the tire is from 55 to 60 threads per 100 mm, the rubber content in these layers is in the range from 46 to 49%, and the density of the cords in at least two middle layers more than the density of the cords in the inner layers of the carcass by 20-24% and is 72-76 threads per 100 mm.

In this case, the rubber content in the middle layers of the carcass with a cord density from 72 to 76 threads is 100 mm less than the rubber content of the inner and outer carcass layers with a cord density of 55-60 threads per 100 mm by 35-40% and is 32-35%.

In this case, the carcass contains, in particular, six layers of rubberized textile cord.

The parameters of the density of the cords in the inner and outer layers of the carcass are selected based on the characteristics of the carcass cord available for use and ensuring the required safety margin of the tire under load.

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

An additional indicator of the 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. As a rule, with an increase in the diameter of the cord, the thickness of the rubber coating also increases.

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 weight of the carcass and decreases the thermal endurance of the tires. The value of the circumferential stiffness of the carcass also decreases, thereby reducing the tire handling performance.

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. This increases the likelihood of delamination between the cord layers and cracks in the tire.

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, the required technical characteristics in terms of load and speed, as well as the technological capabilities of its production.

In the proposed utility model, the rubber content in the inner and outer layers is determined based on the following.

For the technologically optimal thickness of rubberizing of the cords with a strength of more than 35 kgf / thread and with a specific strength coefficient of the 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.

The tire shown in FIG. 1, 2, contains:

1 - protector,

2 - sidewalls,

3 - breaker,

4 - side rings,

5 - a frame made of 6 layers of rubberized textile cord,

6 - inner layers of the rubberized cord of the carcass,

7 - outer layers of rubberized carcass cord,

8 - the middle layers of the rubberized cord of the carcass,

9 - inner rubber layer.

The carcass 5 of the tire has six layers of rubberized textile cord. The two inner layers 6 and two outer layers 7 of the carcass 5 are made of 452A cord and have a density of 58 threads per 100 mm, and the two middle layers 8 are made of 45A cord and have a density of 72 threads per 100 mm.

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

The inner and outer layers of the carcass operate in the mode of increased bending stresses and, in order to reduce the shear stresses in the layers, they have a low density of cords 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 two inner and two outer layers is 55-60 threads per 100 mm with a rubber content of 46-49%.

Studies have shown that if the rubber content in the carcass layer at a cord density of 55-60 threads per 100 mm is less than 46%, this will require the use of a cord with a large thread diameter and, accordingly, an increase in its rubberizing thickness, which, in turn, will lead to to an increase in mass and a decrease in the thermal endurance of the tire.

If the rubber content in the carcass ply at a cord density of 55-60 threads per 100 mm is more than 49%, then this will require the use of a cord with a smaller thread diameter while maintaining or increasing their strength, i.e. increasing the cost of the cord. In addition, the lateral rigidity of the carcass will decrease, and the tire handling will deteriorate.

For the proposed design parameters of the middle layers of the frame, taking into account the provision of the necessary margin of safety under load, it was experimentally established that to achieve the set goals, the density of the cord in at least two middle layers should be 72-76 threads per 100 mm with a rubber content of 32-35%.

A decrease in density in the middle layers of the carcass less than 72 threads per 100 mm leads to a decrease in the safety margin of the tire, reduces its rigidity and performance. The mass also increases.

An increase in cord density above 76 threads per 100 mm leads to a decrease in the rubber content in the layer and increases shear stresses between the cord thread and the surrounding rubber, which leads to an increased risk of loss of bond between the cord thread and the rubber compound and destruction of the tire carcass during operation.

If the density of the cord in the middle layers is less than 72 threads per 100 mm with a rubber content of 32-35%, then this will require the use of a cord with a large diameter of threads, leads to the need to increase the thickness of the rubberized cord, and increases the mass of the tire.

If the density of the cord in the middle layers is more than 76 threads per 100 mm with a rubber content of 32-35%, then this will require the use of a different cord with a smaller thread diameter, different from that adopted in the inner and outer 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 middle layers of the carcass at a cord density of at least one outer layer of 72-76 threads per 100 mm is less than 32%, this will require the use of a cord with a large thread diameter and an increase in its rubberizing thickness, which in turn , will increase the mass and reduce the thermal endurance of the tire.

If the rubber content in the middle plies of the carcass with a cord density in at least one middle ply of 72 to 76 threads per 100 mm is more than 35%, then this will require the use of a cord with threads of a smaller diameter and higher strength, i.e. increasing the cost of the cord. In addition, the flexural 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 diagonal tires 1150-400-457 with a carcass of a serial design and 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 2 + 4 + 2 2 + 2 + 2 Density of cords in the inner and outer layers of the carcass, pcs / 100mm 72-76 * 56-60 * Density of cords in the middle layers of the carcass, pcs / 100mm 88 76 Rubber content in the inner and outer layers of the frame,% 47-50 * 46-49 * Rubber content in the middle layers of the carcass,% 39 35 Interlayer rubber content in the carcass layers,% 40 31 Tire weight,% 100 95 Maximum load on tires,% 100 110 Maximum tire speed,% 100 105

* - different indicators of density and rubber content in the layers of the carcass of the finished tire are due to the different percent of drawing of layers in the manufacture of tires

Thus, the proposed utility model provides an increase in load characteristics while reducing the mass and increasing the speed endurance of 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 bias structure, including a tread, a belt, sidewalls, bead rings and a carcass, containing 6 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 of cords with different thread densities, differing the fact that the two inner and two outer layers of the carcass have the same density of cords, ranging from 55 to 60 threads per 100 mm, and the rubber content in the layer is from 46 to 49%, and the two carcass plies located between the inner and outer layers of the carcass contain from 72 to 76 threads per 100 mm and have a rubber content in the layer from 32 to 35%. 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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