JPH01213487A - Steel cord - Google Patents

Abstract

PURPOSE:To obtain the above cord useful for reinforcing material of tire, etc., preventing fretting wears, by twisting plural or more single wires or strands and wrapping synthetic monofilaments on the most outside layer. CONSTITUTION:Two or more single wires or strands are twisted one or more times and synthetic monofilaments (d) are wrapped on the most outside layer to afford the aimed steel cord.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a steel cord used as a reinforcing material for rubber products such as tires for automobiles and conveyor belts.

<Prior art> Steel cord is used as a reinforcing material for rubber products such as tires and belts, so its strength is high.
It must also have adhesive properties with rubber.

Therefore, high carbon fA wire such as piano wire specified by JIS G-3502 is used as the material, and in order to improve adhesion to the rubber, plating of copper or copper-zinc binary alloy or multi-component alloy is used. A film is attached and this is φ0.1
Stretched to ~0.4 fin, 250-350 K9f
After making a filament with a tensile strength of 4, twist these multiple filaments several times, and if necessary, wrap the φ0.15 dark filament manufactured in the above manner in a spiral at a predetermined twisting pitch. It has been obtained.

This kind of wrapped steel cord is used for trucks,
It is often used as a reinforcing material for bus tires.

Tires used for trucks and buses differ from passenger car tires in that each part, such as the breaker, carcass, and filler, is reinforced with steel cords, and even if the tread wears out, the tire body remains strong, so only the tread is 2.3 It is often used for 300,000 to 400,000 floors with a rotating cap.

However, when we dismantled a tire that had been driven 100,000 to 200,000 times and examined the degree of damage to the steel cord in the carcass, we found that, although there were varying degrees of damage, there was damage between the wrapping wire that made up the steel cord and the steel filament on the outer layer of the cord. There are some filaments whose cross-sectional area has decreased due to fretting (abrasion), resulting in a 20-50% reduction in breaking load, and some filaments that have already broken due to fatigue failure, and the breaking load in this area is 50-80%. You can see the code decreasing.

Therefore, if adverse conditions such as overloading or driving on rough roads are added to the usage conditions, the cord may break by the time the vehicle reaches 300,000 to 400,000 floors, causing problems such as tire bursting. .

As a solution to this problem, for example,
As shown in No. 7, attempts have been made to reduce the hardness of the wrapping wire, but this is also made of the same material (steel to steel).
, fretting is unavoidable.

Furthermore, as a solution to this problem, a steel cord without wrapping wire may be considered, but it has problems with shaping during tire forming or birdcage (local bulging of the cord) when the steel cord is subjected to a compressive load. Some cords required wrapping wires, which created new problems.

<Problems to be Solved by the Invention> As mentioned above, wrapped steel cords cause 7 retting between the wrapping wire and the outer filament that constitutes the cord, but if this is removed, another new problem arises. There was a problem in that it could not be removed because it caused

For example, 3+9+15x 0.175+1 is used as carcass reinforcement cord for truck and bus tires.
In the case of a steel cord with a configuration of xo, 15, 15 φ0.175mm wires and φ0.1
5rR.

The wrapping wires are in contact with each other, and there is point contact at every wrapping pitch (usually 3.5 mm).

However, since the twist pitch and twist direction of the above two are extremely different, fretting wear is particularly noticeable.
There is a problem in that when a tensile load is applied to the cord, stress concentration occurs in the worn portion of the cord, eventually leading to breakage.

Measures to solve the problem〉 Considering that fretting wear occurs in both filaments due to their performance being similar to that of the filament, the material of the wrapping wire should be made softer than the material of the steel cord. Moreover, we considered whether it could be made of a different material.

The present inventors investigated various materials for wrapping wires from the above point of view, and found that synthetic 11il monofilament (e.g. nylon,
This invention was achieved as a result of learning that vinylon, polypropylene, polyester) were suitable for wrapping wire.

That is, in this invention, two or more T11 wires or strands are twisted together once or multiple times and then synthesized into the outermost layer! a
The present invention provides a steel cord wrapped with fiber monofilament.

In the case of polyester with a diameter of 0.23a, the synthetic fiber monofilament has a low breaking load of 2 kg, but it has adequate rigidity for molding, the ends do not come apart, and the adhesive property is improved by using resorcinol, formalin, and latex on the surface. (RFL
) and learned that it can be obtained by processing.

In other words, synthetic LA fibers are usually weak, and this is applied to the surface of the -tan steel cord. Even when the filament is wound in a spiral, the 11 strands unravel one after another from the wound end, but in the case of monofilament, the diameter of the filament is much larger than that of normal fibers, so it is also stronger. When wrapped around a cord, it becomes curly and does not easily unravel from the end.

In other words, it has the characteristic of not easily losing its shape.

As described above, by changing the material of the wrapping wire from steel to synthetic AM fiber monofilament, no fretting occurred in the outermost layer of the steel filament.

After repeatedly bending and pulling a cord using a synthetic fiber monofilament as a wrapping wire, we investigated the fretting wear between this monofilament and the outer filament of the steel cord, and found that there was no wear. . This is because when the cord is repeatedly bent and deformed, the monofilament, which is the wrapping wire, can expand and contract following the deformation of the cord, so there is no need for it to move on the outer filament of the cord or compress the outer filament of the cord. It is also believed that this is because monofilament is extremely soft compared to steel filament.

This means that this steel cord cannot be bent or pulled by tires, etc.
When used as a reinforcing material for rubber composites that are often subjected to compressive deformation, it is thought to contribute to improving their lifespan and durability.

FIG. 1 is an explanatory diagram showing the structure of the steel cord according to the present invention, and the left end portion thereof shows the arrangement of the constituent filaments. That is, the steel cord A is made up of three layers: the center layer is made up of three wood filaments, the inner layer is made up of nine filaments, and the outer layer is made up of 15 wood filaments a, b, and c.
As the wrapping wire d, polyester monofilament with a diameter of 0.20 mm was twisted at a twist pitch of 3.5 m #Ix with the winding direction in the S direction.

On the other hand, Fig. 2 shows φ0 as wrapping wire 〇.
．． It is an explanatory view of a normal steel cord manufactured using 15 m of steel wire.

<Example> As an example, 3÷9÷15xO, 175 shown in Figure 1 is used for carcass cords of truck and bus tires.
Polyester monofilament with a diameter of 0.20 ffil is twisted as a wrapping wire on the outer layer of the steel cord with a twist pitch of 3. A steel cord was obtained by winding the SmtrS winding direction in the S direction.

In addition, as a comparison amount, the conventional φ
A steel cord having the structure shown in FIG. 2 was obtained by winding a 0.15ffij+ steel wire under the same conditions.

Both of these steel cords were adhered to rubber to make a composite body (a rubber belt in this example), and a fatigue test was conducted on the composite body.

In addition, in the fatigue test using the same belt, the cord inside the belt was 200.
After 100,000 bends, the belt was bent and each cord was extracted from the belt to examine changes in cord performance.

(The reduction rate of the cutting load by the '2J cord tensile test, that is, the cutting load of the cord after the test was evaluated based on two test items.

The results are shown in Table 1.

Table 1 As a result, for the cord of the present invention, no traces of fretting wear were observed on the cord outer layer filament and wrapping wire side after the fatigue test. Furthermore, the reduction rate of the cord cutting load after the fatigue test was also found to be less than 1% for the cord of the present invention, which was found to be significantly improved compared to the conventional cord.

<Effects of the Invention> As explained above, since the steel cord of the present invention uses synthetic fiber monofilament as the wrapping wire, it is possible to prevent fretting wear between the outer layer steel wire and the wrapping wire. When used as a carcass cord for steel radial tires for trucks and buses, the cord has good fatigue performance (i.e., fretting wear resistance), so it can also improve the durability of the tire. This is possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the structure of the steel cord of the present invention, and FIG. 2 is an explanatory diagram showing the structure of a conventional steel cord. A... Steel cord a... Filament in the center layer b... Filament in the inner layer C... Filament in the outer layer d... Wrapping wire made of synthetic II monofilament e... Wrapping wire made of steel material Applicant's agent Patent attorney Kazu 1) Showa 1 Figure 2

Claims (1)

[Claims] A steel cord characterized by having two or more single wires or strands twisted together once or multiple times and then wrapping the outermost layer with synthetic fiber monofilament.