JP2001080313A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire in which weight of a belt cord is reduced to improve rolling resistance, a noise level is reduced, and vibration convergence, that is, ride quality is improved. SOLUTION: This pneumatic tire comprises: a carcass that is folded around a bead core of a bead portion through a tread portion and side wall portion; and a belt layer disposed in a radial direction and the outside of the carcass, and inside the tread. The belt layer is constituted by burying a belt code formed of a steel solid wire having a flat cross section. In a shape of a cross section, a ratio between a long diameter LD and a short diameter SD is 1.05-1.35, and the long diameter LD is 0.30-0.50 mm. The steel solid wire is corrugated in a long diameter direction and short diameter direction, and the corrugation pitch P is in a range of 3.0 mm-10.0 mm and the corrugation height H is in a range of 0.05 mm-0.15 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a reduced noise level during running and improved vibration convergence, that is, improved riding comfort.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for lower fuel consumption of vehicles, and therefore, fuel-efficient tires having reduced rolling resistance have been developed. In order to reduce the rolling resistance, reducing the weight of the tire is one of the effective means, and the belt layer cord material is being reviewed from such a viewpoint.

[0003] A belt layer of a radial tire is formed by arranging a belt cord at a relatively shallow angle with respect to a tire circumferential direction in order to tighten a radially extending carcass cord like a tag. Conventionally, a steel cord obtained by twisting a plurality of steel strands is used as a belt cord of a belt layer, for example, a 1 × steel cord whose cross-sectional structure is shown in FIG.
Although a three-structure steel cord has been employed, a belt cord using a so-called single cord made of a single steel wire has been proposed with a reduction in tire weight. For example, it is a steel cord having a 1 × 1 structure and a diameter of 0.35 to 0.50 mm whose cross-sectional structure is shown in FIG.

[0004] However, when such a single wire cord is used for the belt cord, when the cord diameter is increased in order to prevent the occurrence of the cord breakage during tire running, the rigidity of the steel cord increases, the belt layer becomes hard, and the tire layer becomes hard. Noise during driving increases, vibration convergence is poor,
Reduce ride comfort.

Japanese Patent Application Laid-Open No. Hei 11-91311 discloses a prior art for improving the riding comfort of a pneumatic tire using a single steel cord for a belt layer. This uses a belt cord having a damping ratio of 0.018 to 0.25 and a spirally corrugated wire diameter of 0.40 to 0.50 mm. However, this technique is not sufficient as a pneumatic tire having an overall balance of reduced rolling resistance, reduced noise level and improved ride comfort.

[0006]

SUMMARY OF THE INVENTION The present invention reduces the weight of a belt cord in order to improve the rolling resistance, and further reduces the noise level and the vibration convergence by appropriately reducing the rigidity of the belt layer. That is, an object of the present invention is to provide a pneumatic tire with improved riding comfort.

[0007]

The present invention comprises a carcass folded from a tread portion through a sidewall portion around a bead core of a bead portion, and a belt layer disposed radially outside the carcass and inside a tread portion, A pneumatic tire in which the belt layer is formed by embedding a belt cord made of a single steel wire having a flat cross section having the following characteristics (1) and (2) in rubber.

(1) In the cross-sectional shape, the major axis LD / minor axis SD is 1.05 to 1.35, and the major axis LD is 0.
30 to 0.50 mm.

(2) The steel single wire is corrugated in the major axis direction and the minor axis direction, and the corrugation pitch P is 3.0 m.
m to 10.0 mm, and the corrugated height H is 0.0
5 to 0.15 mm.

In the present invention, preferably, the complex elastic modulus E _S ^* of the cord-coated rubber of the belt layer is in the range of 5 to 10 MPa, and the complex elastic modulus E _T ^* of the rubber of the tread portion is 5 to 10 MPa.
The pneumatic tire has a range of 20 MPa and further satisfies the following expression (1).

E _T ^* ≦ 2E _S ^* (1) The complex elastic modulus was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho at a frequency of 10 Hz, a strain of 2%, and a temperature of 25 ° C.
Was measured.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The pneumatic tire 1 of the present embodiment includes:
As shown in FIG. 1, a pair of bead portions 3 each having a bead core 2, a sidewall portion 4 extending radially outward from each bead portion 3, and a tread portion 5 connecting between the sidewall portions 4. Prepare. In the drawings, passenger car tires are illustrated.

Next, the pneumatic tire 1 is provided with a bead core 2 of a bead portion 3 from a tread portion 5 through a sidewall portion 4.
And a carcass 6 that is folded back from the inside in the tire axial direction and locked, and a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 5. The carcass 6 has a so-called semi-radial or radial structure in which carcass cords are arranged at an angle of 65 to 90 degrees, preferably 80 to 90 degrees with respect to the tire equator.
An organic fiber cord such as polyester, nylon and rayon is usually used as the carcass cord.

The belt layer 7 is composed of one or more belt cords each composed of a single steel wire shown in the figure arranged at a relatively shallow angle with respect to the tire equator, for example, at an angle of 5 to 30 degrees.
In this example, the belt ply is formed from two belt plies 7a and 7b,
Each of the belt plies 7a and 7b is disposed so as to change directions so that belt cords intersect with each other.

In the present invention, the steel single wire used for the belt cord has a long diameter LD / short diameter SD (see FIG. 3) in the cross-sectional shape in the range of 1.05 to 1.35.
If it is less than 1.05, reduction in noise level and improvement in vibration convergence cannot be expected. On the other hand, if it exceeds 1.35, the working degree for flattening a single steel wire is too large, and the strength is reduced. During running of the tire, breakage may occur due to cracking of a single steel wire.

Further, in order to maintain the strength of the steel single wire, the long diameter LD needs to be 0.30 mm or more. However, if the diameter of the single steel wire is too large, the rigidity of the belt layer is increased and the riding comfort is deteriorated.
m.

Next, the steel single wire 8 is corrugated in a so-called spiral shape in the major axis direction and the minor axis direction as shown in FIG. 2, and the corrugation pitch P is in the range of 3.0 to 10.0 mm. Here, the corrugated pitch P is a length of one pitch in the longitudinal direction of the corrugated steel single wire, and the corrugated pitch is preferably substantially constant in the longitudinal direction, but is not necessarily limited to the above range. It does not need to be constant.

When the corrugated pitch P is less than 3.0 mm,
If the degree of corrugation is too large, the strength of the steel single wire is reduced, while if it exceeds 10.0 mm, the reduction in noise level and the improvement in vibration convergence are not sufficient.

Further, the corrugation height H is 0.05 to 0.15.
mm. When the thickness is less than 0.05 mm, reduction in noise level and vibration convergence cannot be expected, while
If it exceeds mm, the strength of the steel single wire decreases. Here, the corrugation height H means a so-called amplitude in corrugation as shown in FIG. The corrugated height H is preferably substantially constant in the longitudinal direction of the single steel wire, but need not be constant within the above range.

As described above, in the present invention, since the belt cord 8 is corrugated in a so-called spiral shape, the circumscribed circle of the cord is larger than in the case where the belt cord 8 is corrugated in a two-dimensional plane. Therefore, when viewed as a composite material with the rubber covering the steel single wire 8 of the belt cord, the compression rigidity is increased. As a result, for example, even under severe conditions such as a tire eight-turn test, the cord breakage is reduced,
The durability of the cord can be improved. Further, since the present invention comprises a belt layer of a single steel wire, compared to a cord in which a plurality of strands are twisted, the adhesion of rubber around the cord is improved, so that it is possible to effectively prevent moisture from entering the cord. And the reduction in durability due to the generation of rust can be reduced.

Next, in the present invention, the complex elastic modulus (E _S ^* ) of the rubber used for the belt layer is in the range of 5 to 10 MPa.
Complex elastic modulus of the tread rubber (E _T ^*) is in the range of 5 to 20 mPa.

Conventionally, when a steel cord in which a plurality of strands are twisted is used for a belt layer, a relatively hard rubber is used in accordance with the rigidity of the steel cord to reduce the peeling of the steel cord end and its covering rubber. The way had been taken.
In the present invention, since a steel single wire corrugated in a spiral shape is used, stress concentration can be reduced, and a relatively soft coated rubber can be used. As a result, the vibration convergence of the tire can be further improved. Furthermore, by making the complex elastic modulus E ^* of the tread rubber and the rubber covering the belt layer close to each other, the two follow together as a unit during repeated deformation during tire running, so that stress concentration at both ends of the belt cord is relieved. Rubber exfoliation at parts can be effectively reduced.
Therefore, the complex elastic modulus E ^* of the tread rubber and the rubber of the belt layer preferably satisfies the following relationship.

E _T ^* ≦ 2E _S ^* The belt ply composed of a single steel wire of the present invention is preferably formed by laminating two belt layers on a tire, but in another embodiment, the belt ply is composed of the single steel wire. It is also possible to use only one belt ply, and to use another belt ply in combination with one or two plies made of a conventional steel cord or organic fiber cord.

[0024]

EXAMPLE A radial tire for a passenger car having a tire size of TL175 / 70R13 was prototyped in accordance with the specifications shown in Table 1, assembled with a regular rim, filled with a regular internal pressure and filled with a displacement of 500 mm.
The vehicle was mounted on the front and rear wheels of the cc, and an actual vehicle test was conducted.

The specifications of the tire carcass not shown in Table 1 are as follows. (1) Polyester cord 1000d / 2 (2) Number of ends (lines / 5cm) 37 (3) Cord angle 88 ° (4) Number of plies Two pieces The tire performance was measured by the following method.

(1) Tire strength The plunger energy was measured by a plunger test. That is, it is the energy until the tire bursts when the tire is struck by a protrusion, and the relative value is indexed with Comparative Example 1 being 100. The larger the value, the higher the strength.

(2) Wire breaking ratio A figure-shaped course consisting of two circles each having a diameter of 14 m is 300
After turning twice, the tire was disassembled and the number of broken belt cords was counted. This was shown as a code breaking rate (%). 0
Means that there is no code break. The load is the front wheel 3
00 kgf and lateral G are 0.7 G.

(3) Noise Noise The magnitude of the noise (frequency 120 Hz) generated when the vehicle travels on an uneven road surface is measured.
It was indexed as 00. The higher the value, the lower the noise sound.

(4) Vibration Convergence The vibration convergence (time from excitation to convergence) was measured by applying vibration to the tire with a vibrator. Comparative Example 1 was 100
And is indicated by an index. The larger the numerical value, the better the convergence and the better the riding comfort.

The results of these evaluations are shown in Table 1. Comparative Examples 1 and 2 are examples in which the major axis LD / minor axis SD is out of the range of the present invention.

Comparative Examples 3 and 4 are examples in which the corrugated pitch P is out of the range of the present invention. Comparative Examples 5 and 6 are examples in which the corrugated height H is out of the range of the present invention.

Comparative Examples 7 and 8 are examples in which the long diameter LD is out of the range of the present invention. It can be seen that Examples 1, 2 and 3 of the present invention are all excellent in reduction of tire strength and noise level and furthermore in vibration convergence.

[0033]

[Table 1]

[0034]

[Table 2]

The embodiments disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0036]

As described above, according to the present invention, since the belt cord is made of a single steel wire flat and corrugated in a predetermined range, fuel consumption can be reduced by reducing the weight of the tire.
Moreover, the noise level can be reduced, and the vibration convergence, that is, the riding comfort can be improved.

[Brief description of the drawings]

FIG. 1 is a meridional section of a right half molecule of a tire showing an example of the present invention.

FIG. 2 is a conceptual diagram of an example of a single steel wire.

FIG. 3 is a sectional view taken along line II of FIG. 2;

FIG. 4 is a sectional view of a conventional steel cord (1 × 3).

FIG. 5 is a sectional view of a conventional steel single wire 1 × 1.

[Explanation of symbols]

1 tire, 2 bead core, 3 bead section, 4 sidewall section, 5 tread section, 6 carcass, 7 belt layer, 8 belt cord.

Claims (2)

[Claims] 1. A carcass which is folded around a bead core of a bead portion from a tread portion via a sidewall portion, and a belt layer disposed radially outside the carcass and inside a tread portion, the belt layer comprising: Next (1)
A pneumatic tire comprising a belt cord made of a single steel wire having a flat cross section and having the characteristics of (2) embedded in rubber. (1) The major axis LD / minor axis SD in the cross-sectional shape of a single steel wire is 1.05 to 1.35, and the major axis LD is 0.30 to 0.50 mm. (2) The steel single wire is corrugated in the major axis direction and the minor axis direction, and the corrugation pitch P is 3.0 mm to 10.0.
mm, and the corrugated height H is 0.05 to 0.15.
mm. 2. The complex elastic modulus E _S ^* of the rubber of the belt layer is 5 to 5.
In the range of 10 MPa, a range ^* complex elastic modulus E _T is 5~20MPa rubber of the tread portion, the pneumatic tire according to claim 1, characterized by further satisfying the following equation (1). E _T ^* ≦ 2E _S ^* (1)