JP2003247182A - Steel cord for tire and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel cord for a tire capable of improving ride quality, driveability and belt endurance in a pneumatic tire and the pneumatic tire using the steel cord. <P>SOLUTION: One or two steel wires are used in a core filament and 1-6 steel wires are used in a sheath filament and the diameter of each wire is 0.2-0.38 mm. The sheath filament 2 has a twist structure twisting the steel wires around the core filament 1 at a twist pitch interval of 100-300 mm. A ratio (Dc/Ds) of the wire diameter Dc of the core filament 1 to the wire diameter Ds of the sheath filament 2 is 1.01-1.03 when the number of the sheath filament 2 is 1-3 and 1.04-1.07 when the number of the sheath filament 2 is 4-6. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord for a tire and a pneumatic tire using the same, and more specifically, to improve riding comfort, steering stability and belt durability of the pneumatic tire. And a pneumatic tire using the same.

[0002]

2. Description of the Related Art Conventionally, in a pneumatic tire, a steel cord has been used as a reinforcing cord for a belt layer. The steel cord used for the reinforcing cord of the belt layer mainly has a 1 × M structure in which a plurality of steel strands are twisted at a twist pitch of 20 mm or less for the purpose of improving rubber permeability and reducing cost. There is.

By the way, in recent years, in pneumatic tires for passenger cars in particular, in view of reduction of rolling resistance, improvement of riding comfort, and low cost, in place of the above-mentioned twisted structure steel cord, untwisted steel strands are aligned. It has been proposed to use the steel cord of the above as a reinforcing cord of the belt layer.

However, when the steel cord has a non-twisted structure as described above, the compression characteristics are deteriorated, the steel cord is easily broken, and a bundle of multiple layers is apt to be formed, and the rubber permeability into the cord is lowered. However, there is a problem that the belt durability is reduced. Further, since the steel cord does not act integrally, there is a problem that steering stability is deteriorated during cornering.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide, in a pneumatic tire, a steel cord for a tire capable of improving riding comfort, steering stability and belt durability, and a pneumatic cord using the same. To provide tires.

[0006]

Means for Solving the Problems A steel cord for a tire according to the present invention which achieves the above object, comprises a sheath filament made of a steel element wire disposed around a core filament made of a steel element wire. The wire diameter is set in the range of 0.20 to 0.38 mm, the number of the core filaments is set to 1 to 2, and the number of the sheath filaments is set to 1 to 6, and the core filament and the sheath filament are set. The total number of steel strands combined with is at least 3, and the sheath filament is twisted around the core filament at a twist pitch interval of 100 to 300 mm, and the strand diameter Dc of the core filament and When the number of sheath filaments is 1 to 3, the ratio Dc / Ds to the filament diameter Ds of the sheath filament is When present .01～1.03,4～6 is characterized in that the 1.04 to 1.07.

The pneumatic tire of the present invention is characterized in that the steel cord for a tire is used as a reinforcing cord for a belt layer.

According to the present invention, since the twisted cord having the core filament is used, the compression characteristic is improved, the cord breaking resistance of the steel cord can be enhanced, and the rubber can easily penetrate into the cord. As a result, the belt durability can be improved.

Further, by adopting the cord structure having the core filament, the vibration damping characteristic can be greatly improved as compared with the conventional steel cord having the 1 × M structure, so that the riding comfort can be enhanced.

Further, while adopting the twist structure, the twist pitch interval is increased as described above to bring the sheath filament closer to the untwisted straight structure, so that the cord tension can be effectively increased. This makes it possible to improve steering stability.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an example of a steel cord for tires of the present invention. This steel cord has a core filament 1 made of one steel wire and a sheath filament 2 made of N steel wires. Placed 1 + N
It is structured. N is in the range of 2 to 6, and the total number of steel strands including the core filament 1 and the sheath filament 2 is at least 3 in terms of the number of cords to be driven.

The steel filaments of the core filament 1 and the sheath filament 2 have a filament diameter (diameter) of 0.20 to 0.20.
The one with 0.38 mm is used. The sheath filament 2 has a twist structure in which it is twisted around the core filament 1, and the twist pitch interval is 100 to 30.
The range is 0 mm, which is much larger than before.

The ratio Dc / Ds between the filament diameter Dc of the core filament 1 and the filament diameter Ds of the sheath filament 2 is 1.01-1.1 when the number of sheath filaments 2 is 1-3.
When the number is 03, 4 to 6, it is set to 1.04 to 1.07.

FIG. 2 shows another example of the steel cord for a tire of the present invention, which is the same as that shown in FIG.
In the steel cord of No. 2, the core filament 1 is composed of two steel strands and has a 2 + N structure. Here, N is in the range of 1 to 6, and the total number of steel strands including the core filament 1 and the sheath filament 2 is at least three.

FIG. 3 shows an example of a pneumatic tire using the above-mentioned steel cord for tire as a reinforcing cord for a belt layer. Reference numeral 11 is a tread portion, 12 is a sidewall portion, and 13 is a bead portion. Inside the tire, a carcass layer 14 is mounted between the left and right bead portions 13, and both end portions 1
4a is folded back from the inside of the tire to the outside so that the bead filler 16 is sandwiched around the bead core 15 embedded in the bead portion 13. A plurality of belt layers 17 are provided on the outer peripheral side of the carcass layer 14 of the tread portion 11.

Each belt layer 17 has a large number of reinforcing cords f arranged in an inclined manner with respect to the tire circumferential direction, and the reinforcing cords f are laminated so as to intersect with each other with the inclination direction being opposite to the tire circumferential direction. There is. The steel cords described above are used as the reinforcing cords f.

According to the steel cord for a tire of the present invention described above, the twisted cord having the core filament 1 improves the compression characteristics and makes it difficult for the steel cord to break, and the rubber inside the cord can be made more durable. Since the permeability can be increased, the belt durability can be improved.

Further, since the cord structure having the core filament 1 is adopted, the vibration damping characteristic is greatly improved as compared with the conventional steel cord having the 1 × M structure, and as a result, the riding comfort can be improved. .

If the twist pitch interval of the sheath filament 2 is smaller than 100 mm, the number of twists becomes too large and the cord tension cannot be sufficiently exerted, and as a result, the steering stability is lowered. On the other hand, if it exceeds 300 mm, the rubber permeability into the inside of the cord decreases, and the belt durability deteriorates. Also,
Since it becomes difficult to act as a twisted cord as a unit, it is difficult to improve steering stability, and the cord damping property is lowered, so that riding comfort is lowered.

If the ratio Dc / Ds is less than 1.01 when the number N of the sheath filaments 2 is 1 to 3, or less than 1.04 when the number N of the sheath filaments 2 is 4 to 6, it is difficult for rubber to penetrate into the cord. Therefore, the belt durability is adversely affected. Conversely, when the number N of sheath filaments 2 is 1 to 3, 1.03
When it is more than 1.0, or when it is more than 1.07 when the number of wires is 4 to 6, the core wire diameter must be increased as a result, and it becomes difficult to improve riding comfort.

If the number N of the sheath filaments 2 is more than 6, it becomes difficult to form a gap between the sheath filaments 2 because it is close to the closest packing structure, and as a result, the rubber permeability into the inside of the cord is lowered.

If the wire diameter of the steel wire is smaller than 0.20 mm, the number of cords to be driven must be increased in order to maintain the tire strength, and the belt separation resistance is lowered, and conversely 0.38 mm. If it exceeds, the wire diameter becomes too thick and the fatigue resistance decreases.

In the present invention, the above-mentioned core filament 1 may be untwisted or may have a twisted structure.
In the case of the twisted structure, it is preferable to twist at the same twist pitch as that of the sheath filament 2 or at a twist pitch less than that.

The vibration damping ratio obtained under the following conditions is preferably 0.8 or less. That is, FIG.
As shown in (a), the length m is 100 mm and the width w is 10 m.
A composite piece 20 is formed by embedding five steel cords 22 having the above-mentioned configuration at approximately equal intervals in a rubber piece 21 having a thickness m and a thickness t of 2 mm. As shown in FIG. 4 (b), this composite piece 20 is cantilevered with a supporting margin v of 10 mm.

Subsequently, as shown in FIG. 4 (c), the composite piece 20 is pushed down and bent so that the bending amount r of the tip 20a thereof is 30 mm. Next, the flexure of the composite piece 20 is released. At this time, the deflection amount r of the tip 20a of the vibrating composite piece 20 is measured by a laser displacement meter from the start of vibration.

The obtained deflection amount r is plotted on a graph in which the horizontal axis x is time and the vertical axis y is the deflection amount, as shown in FIG. 4 (d). The position of the maximum value of the bending amount r of the tip 20a of the composite piece 20 that bends to the opposite side (upper side in the figure) immediately after the start of vibration is defined as the origin (0) of the horizontal axis x, and 0.05 seconds from that origin.
Tip 2 that periodically bends to the opposite side for 0.4 seconds (area E)
For the peak value of the deflection amount of 0a in each cycle, y = A.
e ^−bx (where A is the apparent deflection of the composite piece tip 20a at the origin, b is the vibration damping coefficient of the composite piece, and e is the exponential function) To do. Bending amount r'after 0.2 seconds from the origin in this approximate curve S and the composite piece tip 20 at the origin
The vibration damping ratio represented by the ratio r ′ / A ₀ of the actual bending amount A _{0 of a} is set to 0.8 or less. If the vibration damping ratio is larger than 0.8, riding comfort is deteriorated, which is not preferable.

The steel cord for tires of the present invention can be preferably used as a reinforcing cord for a belt layer in a pneumatic tire for passenger cars, but is not limited thereto.

[0029]

EXAMPLES In the pneumatic tire having the same tire size of 185 / 65R14 and having the configuration shown in FIG. 3, the structure of steel cords used for the reinforcing cords of the belt layer, the number of arrangements, the twist pitch interval of the sheath filaments, and the ratio Dc / D
s, the tires of the present invention having the vibration damping ratio as shown in Table 1, comparative tires 1 to 5, and conventional tires were produced.

Each of these test tires was subjected to an evaluation test of riding comfort, steering stability and belt durability under the following measurement conditions, and the results shown in Table 1 were obtained. Further, when a rubber permeability evaluation test was conducted under the following measurement conditions, the results shown in Table 1 were obtained. Rubber PermeabilityEach steel cord used in each test tire was embedded in an unvulcanized coated rubber layer, the cord was taken out after vulcanization, and the rubber permeability inside the taken out cord was visually observed, and the observed cord length On the other hand, the ratio (%) of the length of the portion where the rubber completely penetrates between the strands is shown. Ride comfort Each test tire was attached to a rim of rim size 14 x 5 1/2 JJ, air pressure was set to 200 kPa, and it was attached to a 1800 cc vehicle. A feeling test was conducted by a test driver on the test course, and the results were compared with the conventional results. The tire was evaluated with an index value of 100. The larger this value is,
Excellent riding comfort. Steering stability Each test tire was mounted on a 1800cc vehicle in the same manner as above, and a feeling test was conducted by a test driver on a test course, and the result was evaluated by an index value with the conventional tire being 100. The larger this value, the better the steering stability. Belt durability Each test tire was assembled on a rim of 14 × 5 1/2 JJ at an air pressure of 170 kPa, left to stand in an atmosphere of 70 ° C. × 98% RH (relative humidity) for 30 days, and then wetted to have a diameter of 1707 mm. Slip angle 0 ± 5 ° on the drum of JATM
73 ± 47 of the load corresponding to the air pressure conditions specified in A
% Load and slip angle 0.067H under fluctuating load condition
The vehicle was run for 300 km while being changed by a rectangular wave of z. After running, the test tire was incised, and the presence or absence of wire breakage in the belt portion was examined and evaluated.

[0031]

[Table 1] It can be seen from Table 1 that the tire of the present invention can improve rubber permeability, riding comfort, steering stability, and belt durability.

[0032]

As described above, according to the present invention, by specifying the steel cord for a tire, which is composed of the core filament and the sheath filament, as described above, the riding comfort, the driving stability, and the belt durability of the pneumatic tire can be improved. Can be improved.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing an example of a steel cord for tires of the present invention.

FIG. 2 is an enlarged cross-sectional view showing another example of the steel cord for tire of the present invention.

FIG. 3 is a cross-sectional view of a main part of a tire meridian showing an example of a pneumatic tire using the steel cord for tire of the present invention.

FIG. 4 shows a method for measuring the vibration damping ratio, (a) is an enlarged perspective view of a composite used to measure the vibration damping ratio, and (b) is a cantilevered support of the composite of (a). FIG. 6C is an explanatory view showing a state in which the composite body of FIG. 3B is bent, and FIG. 6D is a graph showing a change in the amount of flexure of the tip of the composite body, and an approximate curve is added to the graph. It is a figure.

[Explanation of symbols]

1 Core Filament 2 Sheath Filament 11 Tread Part 12 Sidewall Part 13 Bead Part 14 Carcass Layer 17 Belt Layer 20 Composite 20a Tip 21 Rubber Piece 22 Steel Cord S Approximate Curve m Composite Length r Composite Deflection t Composite thickness w Composite width

Claims (5)

[Claims] 1. A sheath filament made of a steel wire is arranged around a core filament made of a steel wire, and the diameter of the steel wire is 0.20 to 0.38.
Set in the range of mm and set the number of core filaments to 1 to
The number of sheath filaments is 1 to 2 while the number is 2
A twist structure in which the number of the steel filaments is six, and the total number of the steel filament wires including the core filament and the sheath filament is at least three, and the sheath filaments are twisted around the core filament at a twist pitch interval of 100 to 300 mm. And the ratio D of the strand diameter Dc of the core filament to the strand diameter Ds of the sheath filament.
c / Ds is 1.01 to 1.03 when the number of the sheath filaments is 1 to 3, and 1.04 when the number of the sheath filaments is 4 to 6
Steel cord for tires set to 1.07. 2. The steel cord for tire according to claim 1, wherein the core filament is untwisted. 3. The steel cord for tire according to claim 1, wherein the core filaments are twisted at a twist pitch interval of the sheath filament or less. 4. Using the steel cord for tire,
Form a composite piece in which five steel cords are embedded in a rubber piece having a length of 100 mm, a width of 10 mm and a thickness of 2 mm, and cantilever support the composite piece to bend it so that the bending amount of its tip is 30 mm. The amount of bending of the tip of the composite piece that vibrates when the bending is released was measured from the start of vibration, and the obtained amount of bending was plotted in a graph with the horizontal axis x as the time and the vertical axis y as the bending amount. At this time, the position of the maximum value of the amount of bending of the tip of the composite piece that bends to the opposite side immediately after the start of vibration is set as the origin of the horizontal axis, and the position on the opposite side is 0.05 seconds to 0.4 seconds from the origin. For the peak value of the amount of bending of the tip that bends periodically in each cycle, y = A · e
^-bx (where A is the apparent deflection of the tip of the composite piece at the origin, b is the vibration damping coefficient of the composite piece, and e is the exponential function). The vibration damping ratio represented by the ratio between the amount of deflection of the approximate curve 0.2 seconds after the origin and the actual amount of deflection A ₀ of the tip of the composite piece at the origin is 0.8.
The steel cord for tire according to claim 1, 2 or 3, which is as follows. 5. A pneumatic tire using the steel cord for tire according to claim 1 as a reinforcing cord for a belt layer.