RU2805565C1 - Pneumatic tire case - Google Patents

Abstract

FIELD: automotive industry.

SUBSTANCE: invention relates to a case of a cargo pneumatic tire of a radial design. The case includes a tread, a breaker, sidewalls, bead rings and a carcass containing inner and outer layers of rubberized textile cord with different thread densities. The interlayer rubber content of at least one outer carcass layer is 40-55% higher than the interlayer content of the carcass inner layers. The interlayer rubber content of the outer layers of the carcass is in the range of 0.49-0.55.

EFFECT: improvement in the operational characteristics of the tire.

2 cl, 1 dwg, 1 tbl

Description

The invention relates to the tire industry, namely to the design of the frame of pneumatic truck tires of radial design.

Load-bearing capacity indicator, i.e. maximum load on the tire is one of the main characteristics of truck tires, the requirements for which are constantly increasing while maintaining or increasing the requirements for the level of speed endurance of the tire.

One of the main elements of a tire that determines its performance characteristics, such as performance, speed endurance and handling, is the tire carcass. This is the most important power part of the design of a car tire, ensuring its strength, perceiving internal air pressure and transmitting loads from external forces acting from the road to the wheel. The task of the carcass is to maintain the shock-absorbing properties of the tire, as well as to hold the amount of air necessary for this.

As a rule, the carcass of a truck tire consists of several layers of rubberized cord (textile or metal cord). Thus, for passenger cars, the strength of a tire is usually ensured by 1-2 layers of carcass; for trucks, the average number is 4-8 layers. For large tires, the carcass can contain up to 30 or more layers; the largest number of layers is needed for agricultural machinery and tires for heavy-duty vehicles.

The goal of developing the carcass design of modern truck tires is to increase its strength while minimizing the weight of the carcass and the tire as a whole, increasing speed endurance, as well as fuel efficiency and controllability.

A known tire carcass design for a pneumatic tire of radial design, containing a breaker, tread, sidewalls, bead rings and a frame made of cord threads of the same structure and strength, characterized in that the strength of the carcass cord threads is 23-32 kgf/thread, the relative rubber content between adjacent frame layers is 0.24-0.45, while the number of frame layers is not less than two and not more than three. (RF Patent No. 22907 for the utility model “Tyre of a pneumatic tire”; IPC: B60C 9/02 (2000.01); publ. 05.10.2002. The patent went into the public domain (previously the patent holder: Limited Liability Company Scientific, Production and Commercial Center " WEIGHT."))

The disadvantage of this design is the use of the same interlayer rubber content, which leads to a sharp drop in rigidity at the boundary of the outer layers of the carcass and the sidewall cover rubber, which reduces the performance of the tire.

Also known is the design of a tire for a pneumatic tire with a radial design, including a tread, belt, sidewalls, bead rings and a frame containing six layers of rubberized textile cord, the rubber content in the layer being from 0.50 to 0.55, two outer layers of the carcass have rubber content in the layer is from 0.60 to 0.62, and the interlayer rubber content in the frame is from 0.27 to 0.33 (RF patent No. 206932 for the utility model “Tyre of a pneumatic tire”; publ. 10/01/2021 Bulletin No. 28; patent holder : JSC "Research Institute of Rubber and Polymer Products").

The use of this technical solution with a low constant interlayer rubber content in the carcass layers does not reduce the shear stresses at the interface between the cord threads and the rubber in the outer layers of the carcass, reduces its performance and increases the lateral rigidity of the tire, which worsens the tire's operational characteristics, such as speed endurance and controllability and fuel efficiency.

The design of a pneumatic car tire with a frame having layers of rubberized textile cord with a strength of more than 35 kgf/thread and the ratio between the thickness of the rubberized textile cord thread and the tensile strength of the thread is less than 0.021 (specific strength) is also known. In at least 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 remaining layers of the carcass (RF patent No. 2525344 for the invention “Tire of a pneumatic tire”; publ. 10.08 .2014 Bulletin No. 22; patent holder: KORDIANT JSC).

The disadvantage of this design is the significant difference in rubber content between the inner and outer layers of the frame, which creates various deformations and causes the formation of a temperature difference in the frame mass.

The closest analogue to the proposed invention is the design of a pneumatic diagonal tire tire, including a large one, containing a tread, sidewalls, bead rings, a breaker and a frame made of layers of rubberized cord wrapped around the bead rings in the outer and inner directions, and rubber layers, while between groups of carcass cord layers wrapped around the bead rings in the outer direction contain layers of textile rubberized cord, the interlayer rubber content of which is 1.25-1.45 times greater than the interlayer rubber content of the cord layers wrapped around the bead rings in the outer direction.

Between the breaker and the group of cord layers wrapped around the side rings in the outer direction, there are layers of textile rubberized cord, similar in rubber content to the textile rubberized cord located between the groups of carcass cord layers wrapped around the rings in the outer direction. (RF Patent No. 2113362 for the invention “Pneumatic Tire Tire”; IPC: B60C 9/00 (1995.01); publ. 06/20/1998. The patent went into the public domain (previously the patent holder: Limited Liability Company Transocean Commerce Limited.))

The disadvantage of this technical solution due to an increase in the interlayer rubber content is the formation of an area with low flexural rigidity inside the load-bearing main layers of the frame, which leads to an increase in heat generation in the frame and a decrease in its performance.

The technical problem to be solved by the present invention is to reduce heat generation in the carcass and increase its performance, increase the speed endurance of the tire while maintaining the load characteristics of the tire and reducing its weight by establishing the optimal interlayer rubber content between the layers of the tire carcass.

The problem is solved by the fact that in a pneumatic truck tire tire of a radial design, including a tread, breaker, sidewalls, bead rings and a frame containing inner and outer layers of rubberized textile cord with different thread densities, the interlayer rubber content of at least one outer layer of the frame is 40-55% more interlayer content of the inner layers of the frame. In this case, the interlayer rubber content of the outer layers of the frame is in the range of 0.49-0.55.

In fig. 1 shows an example of a meridional section of a tire with a frame according to the invention.

The tire shown in FIG. 1, contains:

1 - protector;

2 - sidewalls;

3 - breaker;

4 - side rings;

5 - internal layers of the frame made of rubberized cord;

6 - outer layers of the frame made of rubberized cord.

The tire shown in FIG. 1, contains a tread 1, sidewalls 2, breaker 3, side rings 4 and a frame made of 6 layers of rubberized textile cord wrapped around the side rings, with a tensile strength of 45 kgf/thread. The four inner layers 5 of the frame have a density of 48 threads/100 mm, and the two outer layers 6 have a density of 44 threads/100 mm. In this case, the interlayer content in the inner layers of the frame is 0.33-0.35, and the value of the interlayer rubber content in the outer layers of the frame is 0.49-0.53, i.e. the interlayer rubber content of the outer layers of the frame is 1.5 times greater than the interlayer rubber content of the inner layers of the frame.

The interlayer rubber content determines the performance of the layers of a multilayer carcass when exposed to stresses arising during loading and deformation during tire operation due to the heterogeneity of its structure and differences in the characteristics (rubber and cord) of the materials.

Interlayer rubber content is determined by the formula:

r = (1 - d/h),

Where:

d is the diameter of the cord thread;

h is the distance between the centers of the threads in adjacent layers of the frame.

The distance between the centers of the cord threads in adjacent layers of the frame (h) is determined by the thickness of the rubber coating of each individual layer of the frame cord. As the thickness of the rubberized cord layer increases, the distance between the cord threads in adjacent layers increases and the interlayer rubber content between them increases. An increase in the interlayer rubber content reduces the shear stresses at the interface between the cord and rubber.

The inner layers of the carcass with a higher density of cord threads in them are the power skeleton of the tire carcass, taking on the main impact of the vertical load on the tire, providing the strength and necessary load-bearing capacity of the tire.

An increase in the interlayer rubber content in the inner layers of the carcass has a beneficial effect on the elasticity of the tire, its ability to withstand shock loads and improves driving comfort during operation, but increases the weight of the tire, reduces its speed endurance and fuel efficiency.

The external additional layers of the frame operate in the mode of increased bending stresses and, in order to reduce the resulting shear stresses, have a reduced density of cord threads and an increased rubber content in the layer.

An increase in the interlayer rubber content in the outer layers of the carcass leads to a decrease in the torsional rigidity of the tire, which is responsible for transmitting torque from the steering wheel when turning, and increases the elasticity and controllability of the tire.

The maximum and minimum values of interlayer rubber content generally depend on the characteristics of the rubber mixture used for rubberizing the cord, the technological capabilities and accuracy of the equipment used by a particular manufacturer.

A specific indicator of the optimal interlayer rubber content in each specific case is selected empirically, taking into account the purpose, required technical characteristics of the tire and the technological capabilities of the manufacturer.

Experimentally, using the example of a cord with a tensile strength of 45 kgf/thread and a thread diameter of 0.95 mm, it was established that the technologically feasible thickness of the interlayer rubber content to ensure the necessary load-bearing capacity and reliable performance in the internal layers of the frame should be 0.33-0.35.

To ensure the necessary speed endurance and performance, the interlayer rubber content of the outer layers of the frame should be in the range of 0.49-0.55, i.e. 40-55% more interlayer rubber content in the inner layers of the frame.

Research has shown that if the inter-ply rubber content of the outer carcass layers exceeds the inter-ply rubber content of the inner carcass layers by less than 40% (i.e., the inter-ply rubber content of the outer carcass layers will be less than 0.49), the performance of the tire carcass is reduced due to an increase in rigidity and the magnitude of shear stresses in the outer layers of the frame.

An increase in the interlayer rubber content of the outer layers of the carcass by more than 55% (i.e., the interlayer rubber content of the outer layers of the carcass will be 0.55 or higher) than the interlayer content of the inner layers of the carcass leads to an increase in the mass of the carcass and tire, an increase in the temperature developing in the carcass mass and reducing the speed and thermal endurance of the tire.

As an example of a specific design, a 24R21 tire design is proposed, the carcass of which contains 6 rubberized layers, while the cord density in the inner/outer layers of the carcass is 48/44 pcs/100 mm, the interlayer rubber content of the four inner layers of the carcass is 0.33-0.35 , and the two outer layers of the frame - 0.53.

Table 1 presents the characteristics and results of comparative bench tests of 24R21 tires of a serial design and tires containing a carcass according to the present invention.

Table 1 Indicator name Serial design Proposed design Number of cord layers in the frame 4+2 4+2 Density of cord threads in the inner/outer layers of the frame, pcs/100 mm 48/44 48/44 Interlayer rubber content in the inner/outer layers of the frame 0.54/0.54 0.33-0.35/0.53 Tire weight,% 100 97 Maximum tire load,% 100 100 Maximum bus speed,% 100 100-105

Thus, the proposed technical solution ensures the preservation of 100% of the maximum load on the tire while reducing the tire weight by 3% of the mass of the serial design and increasing the maximum tire speed by 4%.

The proposed technical solution can be implemented in production conditions on standard equipment using known technologies

Claims (2)

1. A pneumatic truck tire tire of radial design, including a tread, belt, sidewalls, bead rings and a frame containing inner and outer layers of rubberized textile cord with different thread densities, characterized in that the interlayer rubber content of at least one outer layer of the frame is 40 -55% more inter-ply rubber content of the inner carcass layers. 2. A tire according to claim 1, characterized in that the interlayer rubber content of the outer layers of the carcass is in the range of 0.49–0.55.