WO2012007234A1

WO2012007234A1 - Steel cord for use as a strength support in a bracing ply of a pneumatic tyre for a vehicle

Info

Publication number: WO2012007234A1
Application number: PCT/EP2011/059549
Authority: WO
Inventors: Volkmar Fries; Jörn KRÜGER; Sadettin Fidan
Original assignee: Continental Reifen Deutschland Gmbh
Priority date: 2010-07-12
Filing date: 2011-06-09
Publication date: 2012-01-19
Also published as: DE102010036809A1

Abstract

The invention relates to a steel cord of 1+N construction, in which N is greater than 3, for use as a strength support in a bracing ply of a pneumatic tyre for a vehicle, the outer filaments (2) contacting the single inner filament (1). The inner filament (1) has a diameter (D₁) of between 0.30 mm and 0.45 mm and the outer filaments (2) have a diameter (D_N) of between 0.35 mm and 0.50 mm. The ratio of the diameter of the inner filament (1) to the diameter of the outer filaments (2) is between 0.7 and 1.1, and the number of outer filaments (2) is between four and six.

Description

description

Steel cord for use as a strength carrier in a belt layer of a

Vehicle tire

The invention relates to a two-ply steel cord of construction 1 + N with N greater than 3 for use as a strength member in a belt ply of a pneumatic vehicle tire, the outer filaments contacting the single inner filament. To the belt cords in the belt layers of pneumatic vehicle tires, in particular of

Commercial vehicle tires, high demands are made. In addition to a certain tensile and flexural strength and a certain strength are a high

Fatigue resistance and high corrosion resistance expected. Steel cords for belt plies usually have a multilayer construction of inner and outer steel filaments, with high stability of the steel cord against displacement of its filaments and good adhesion in the surrounding rubberizing composition being important for the durability and service life of the belt plies. Of course, the cost of producing the steel cords also play a role, the more expensive the cord construction, the higher the manufacturing costs. Target conflicts exist in particular between the determined by tread abrasion life of a pneumatic vehicle tire - the abrasion life -, the belt edge durability and the manufacturing cost of the belt package, which is mainly determined by the manufacturing cost of steel cords. If one of these parameters or one of these

Improved properties, this is usually at the expense of at least one of the other two properties or parameters. For example, the stiffness of the belt package, such as the use of stiffer steel cords or by increasing the steel cord density in the belt layers, increases the abrasion life of the tire. A lower steel cord density in the belt layers, however, improves the belt durability. In order to set a constant tensile stiffness for the sake of improving the abrasion life, larger diameter cords can provide a lower tensile strength

Steel cord density and thus a greater mutual steel cord spacing can be adjusted. This measure is therefore advantageous for the belt durability. With the same rigidity and equal left steel cord density in the belt layers are steel cords with larger

However, diameter detrimental to the belt durability and increase the cost because of the greater thickness of the belt layers and the associated larger

Gummierungsvolumens.

Two-ply steel cords are known in various embodiments from the prior art. For example, from DE 30 06 488 AI a steel cord for the belt layers of a pneumatic vehicle tire is known, which has a single inner filament with a diameter of 0.12 mm to 0.22 mm and at least three outer filaments with a diameter of 0.28 highest mm. This is an open cord construction in which the outer filaments touch the inner filament but are at a certain distance from each other. The use of such steel cords in the belt layers of pneumatic vehicle tires is intended to reduce the rolling resistance of the tire. Another steel cord with an open construction is from the

WO 89/09305 AI known. The steel cord has a single inner filament whose diameter is between 0.17 mm and 0.38 mm and which of six

Surrounded by steel filaments whose diameter deviates by at most 0.5 mm from that of the inner filament. The steel filaments should have a tensile strength of at least 2850 N / mm ² . This known cord should be particularly resistant to corrosion. Due to the small differences in the diameter of the inner and outer filaments, the six outer filaments almost completely surround the inner filament

Penetration of rubber material in the Filamentzwischenräume is hardly possible. The inner filament is therefore not fixed against displacement. This problem is circumvented in the steel cord constructions known from US Pat. No. 5,584,169 B and US Pat. No. 5,606,852 B in that the inner filament of the two-ply steel cord construction is waved or spiral pre-formed, resulting in a more open cross-section of the steel cord, since the outer filaments are now arranged at a greater mutual distance. This ensures a good penetration of the gum mixture between the outer filaments. The pre-deformation, however, suffers from the compactness of the steel cord, the larger diameter of the steel cord reduces the mutual cord spacing with the same cord density in the belt ply, which, as explained above, is detrimental to the belt durability as well as the thickness of the belt plies, thereby increasing the required volume Gum mixture and therefore the cost is increased.

Another two-layer steel cord construction is known from JP 60038208 A. This document relates to a 1 + 5 cord construction with a maximum

Filament diameter of 0.342 mm. To ensure sufficient tensile rigidity of

To achieve belt layers, especially in commercial vehicle tires, these steel cords would have to be arranged with a higher cord density, which, however, as mentioned, for the

Belt edge durability is disadvantageous.

Multilayer steel cord constructions with two or more filaments in the first layer are also known in different embodiments. The most of

Belt cords of these constructions have cross-sectional areas greater than 0.5 mm ² and are 2- or 3-ply cords with two to four filaments in the first ply. Apart from the more expensive cord production, which is associated with higher costs, these belt cords have a relatively low compactness and low rigidity at a given cord diameter. This affects the abrasion life and conflicts with belt edge durability.

The invention has for its object to improve a steel cord of the type mentioned for use as Gürtelkord in belt layers of commercial vehicle tires, so that the mentioned goal conflicts between Abrieblebensdauer, belt edge durability and manufacturing costs are eliminated. The object is achieved according to the invention in that the inner filament has a diameter between 0.30 mm and 0.45 mm and the outer filaments have a diameter between 0.35 mm and 0.50 mm, wherein the ratio of the diameter of the inner filament to the diameter of the outer filaments between 0.7 and 1.1 and the number of outer filaments between four and six.

In accordance with the invention executed steel cords, the diameter of the filaments and the number of outer filaments are optimally matched to one another, that a good penetration of the rubber material of the belt layer is ensured in the spaces between the outer filaments and thus the inner filament is fixed against displacement. Steel cords according to the invention have a cord diameter which allows to place the steel cords in the belt ply at mutual distances which are advantageous for belt edge durability. At the same time can be with

Steel cords according to the invention achieve a rigidity of the belt plies or of the belt package, which is advantageous for the abrasion service life.

To fix the inner filament, it is important to ensure a certain openness of the second layer to ensure a good penetration of rubber material into spaces between the filaments of the second layer. The openness O of the outer filaments is determined according to equation III, according to which O [%] = N × A _M / π × Do with A _M as the arithmetic mean of the smallest mutual spacings of the outer filaments. In this case, steel cords designed according to the invention are designed such that the openness is between 10% and 25%. For the belt edge durability and the rigidity of the belt plies it is particularly advantageous if the diameter of the inner filament is between 0.35 mm and 0.42 mm and the diameter of the outer filaments is between 0.38 mm and 0.45 mm. In this context, it is also particularly advantageous if the ratio of

Diameter of the inner filament to the diameter of the outer filaments between 0.8 and 1.0. Steel cords according to the invention are particularly suitable as reinforcements in the

Belt layers of the belt package of commercial vehicle tires.

Further features, advantages and details of the invention will now be described with reference to the drawing, which illustrates an embodiment in more detail. It shows

Fig. 1 shows a cross section through a steel cord designed according to the invention.

Cords made according to the invention are of the type 1 + N, where N is between four and six. The steel cord exemplified in Fig. 1 has the construction 1 + 5 and therefore consists in the first layer of a single inner filament 1 and five outer filaments 2 in contact with its outer side in the second layer. The outer filaments 2 are twisted together in a known manner about their longitudinal axis and around the inner filament 1.

The filaments 1 and 2 can be considered in cross-section as circles, wherein the diameter Di of the inner filament 1 between 0.30 mm and 0.45 mm, the same for all outer filaments 2 diameter D of the outer filaments 2 between 0.35 mm and 0.50 mm. The diameter Di of the inner filament 1 is in particular between 0.35 mm and 0.42 mm, the diameter D _{N of} the outer filaments 2 in particular between 0.38 mm and 0.45 mm. Steel cords designed according to the invention are designed such that the ratio of the diameter Di of the inner filament 1 to the diameter D of the outer filaments 2 is between 0.7 and 1.1, in particular between 0.8 and 1.0.

The steel cord has an open construction in which the outer filaments 2, while in contact with the inner filament 1, but at least partially do not touch each other. Therefore, the outer filaments 2 may all be spaced apart from each other, however, some, for example, two or three outer filaments 2 may contact each other. As the figure shows, the mutual distances A _N i to A _N5 of

Filaments 2 - determined in those places where the mutual distance of each other adjacent outer filaments 2 is the lowest - be different sizes. Straight lines drawn at the least spaced locations are, viewed in cross-section, chords of a circle of diameter D _o , which is given by the equation below

1 can be determined as follows:

Equation I: D ₀ = (Di + D _N ) × cos (360 2N)

The average distance A M (arithmetic mean) of the outer filaments 2, the average chord length at the circle with the diameter Do, can be determined according to equation II:

Equation II: A _NM = avg (A ... _Nh A _NN) = [(Di + D _N) x sin (360 2 N)] - D _N

The equations I and II apply exactly only with a uniform arrangement of the outer filaments 2 around the inner filament 1, in a non-uniform arrangement, at different mutual distances A _N i to A _N N results in a low

Inaccuracy, which can be ignored.

In steel cords according to the invention, it is essential to ensure a certain openness of the second ply which ensures a good penetration of the rubber material into the interstices between the filaments 2 of the second ply so that the inner filament 1 is fixed against displacement. The openness O of the outer filaments

2 results from Equation III: Equation III: O [%] = N × A _NM / π × D ₀

Steel cords designed according to the invention are designed such that O is between 10% and 25%. With an openness O smaller than 10% is sufficient

Gummipenetration between the outer filaments 2 is no longer ensured and there is a risk of displacement of the inner filament 1, the steel cord is susceptible to corrosion. With an openness greater than 25%, the cord stiffness suffers on the cord outside diameter. Lower cord stiffness generally results in a reduction in the abrasion performance of the tread of the tire. If you also increase the number of cords and thus reduce the mutual cord spacing, the belt edge durability is impaired.

Some examples of steel cords made according to the invention and the openness determined according to equation III are given below:

Steel cords designed according to the invention are primarily suitable as reinforcements in belt layers of pneumatic vehicle tires, in particular belt layers of commercial vehicle tires. In the production of the belt layers, the steel cords aligned in parallel with each other and arranged at a predetermined mutual distance become one

Rubber compound, the gum mixture, embedded.

Both the inner filament 1 and the outer filaments 2 are steel filaments with conventional tensile strengths of at least 2800 N / mm ² (normal Tensile- execution) up to 4100 N / mm ² (Ultra High Tensile- execution).

11 059549

LIST OF REFERENCE NUMBERS

1 filament

2 filament

ANI distance

A _N2 distance

A _N? distance

AN4 distance

A _N5 distance

Do diameter

Di diameter

D _N diameter

Claims

claims:

A steel cord of construction 1 + N with N greater than 3 for use as a strength member in a belt ply of a pneumatic vehicle tire, the outer filaments (2) contacting the single inner filament (1),

characterized,

the inner filament (1) has a diameter (Di) between 0.30 mm and 0.45 mm and the outer filaments (2) have a diameter (D _N ) between 0.35 mm and 0.50 mm, the ratio the diameter of the inner filament (1) to the diameter of the outer filaments (2) is between 0.7 and 1.1, and the number of outer filaments (2) is between four and six.

2. Steel cord according to claim 1, characterized in that the openness (O) of

outer filaments (2) according to equation (III)

Equation III: O [%] = N × A _NM / π × D ₀

is between 10% and 25%, where A _N M is the arithmetic mean of the minimum mutual spacing of the outer filaments (2).

3. Steel cord according to claim 1 or 2, characterized in that the diameter of the inner filament (1) is between 0.35 mm and 0.42 mm.

4. Steel cord according to claim 1 or 2, characterized in that the diameter of the outer filaments (2) is between 0.38 mm and 0.45 mm. Steel cord according to one of claims 1 to 4, characterized in that the ratio of the diameter of the inner filament (1) to the diameter of the outer filaments (2) is between 0.8 and 1.0.

Use of the steel cord according to one or more of Claims 1 to 5 as a strength carrier in at least one belt ply of a pneumatic vehicle tire, in particular of a utility vehicle tire.