JP2021054356A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that improves driving stability performance and ride comfort performance in a well-balanced manner.SOLUTION: A pneumatic tire has a belt layer 7 that includes first and second plies 8 and 9. Each of the first and second plies 8 and 9 includes a single and flat cord 12. In the single cord 12, a short-diameter direction is set to be a tire radius direction, and a long-diameter direction is set to be a tire axis direction. A between-cords distance D in the tire radius direction between the single cord 12 of the first ply 8 and the single cord 12 of the second ply 9 is in the range of 0.30-1.05 mm.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pneumatic tire.

Patent Document 1 below describes a pneumatic tire in which a belt layer including a single wire steel wire is embedded in a tread portion. The single wire steel wire has a flat cross-sectional shape.

Japanese Unexamined Patent Publication No. 2018-58515

In the pneumatic tire of Patent Document 1, there is room for improvement in improving the steering stability performance and the riding comfort performance in a well-balanced manner.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire capable of improving steering stability performance and riding comfort performance in a well-balanced manner.

The present invention includes a pneumatic tire, which includes a carcass bridged between a pair of bead portions and a belt layer arranged inside the tread portion on the outside of the carcass in the tire radial direction. The first ply and the second ply arranged outside the tire radial direction of the first ply are included, and each of the first ply and the second ply includes a single wire and a flat single wire cord, and the said The single wire cord is arranged in the minor axis direction in the tire radial direction and in the major axis direction in the tire axial direction, and the tire between the single wire cord of the first ply and the single wire cord of the second ply. The distance between the cords in the radial direction is 0.30 to 1.05 mm.

In the pneumatic tire according to the present invention, it is desirable that the minor axis of the single wire cord is 0.15 to 0.42 mm.

In the pneumatic tire according to the present invention, it is desirable that the flatness of the single wire cord is 70% or less.

In the pneumatic tire according to the present invention, it is desirable that each of the first ply and the second ply further includes a stranded cord in which filaments are twisted.

In the pneumatic tire according to the present invention, it is desirable that the number of twisted wire cords is larger than the number of single wire cords in each of the first ply and the second ply.

In the pneumatic tire according to the present invention, it is desirable that the number of twisted wire cords in each of the first ply and the second ply is twice or more the number of the single wire cords.

In the pneumatic tire according to the present invention, it is desirable that the number of filaments of the stranded cord is 3 or less.

In the pneumatic tire according to the present invention, it is desirable that the diameter of the filament of the stranded cord is smaller than the major diameter of the single wire cord.

In the pneumatic tire according to the present invention, it is desirable that the diameter of the filament of the twisted wire cord is 50% to 70% of the major axis of the single wire cord.

In the pneumatic tire according to the present invention, it is desirable that the bending rigidity of the twisted wire cord is larger than the bending rigidity of the single wire cord in the minor axis direction.

In the pneumatic tire according to the present invention, it is desirable that the bending rigidity of the stranded cord is 1.5 to 2.5 times the bending rigidity of the single wire cord in the minor axis direction.

The pneumatic tire of the present invention has a belt layer including a first ply and a second ply arranged outside the first ply in the radial direction of the tire. Each of the first ply and the second ply contains a single wire and a flat single wire cord. Further, in the single wire cord, the minor axis direction is arranged in the tire radial direction, and the major axis direction is arranged in the tire axial direction. In such a pneumatic tire, the bending characteristic of the belt layer in the tire radial direction is improved, and the riding comfort performance is improved. Further, since the rigidity of the belt layer in the tire axial direction of the tire is relatively large, a large cornering force is generated at the time of turning, and the steering stability performance is improved.

Further, the distance between the cords in the tire radial direction between the single wire cord of the first ply and the single wire cord of the second ply is 0.30 to 1.05 mm. By defining the distance between the cords in the above range on the premise of a flat cord, the belt layer maintains the strain relaxation function between the first ply and the second ply, and the first ply Deformation between the ply and the second ply is suppressed to be smaller to improve steering stability performance. Therefore, the tire of the present invention improves steering stability performance and ride comfort performance in a well-balanced manner.

It is sectional drawing of the pneumatic tire of this invention. It is an enlarged view of the belt layer of FIG. It is a schematic diagram which shows the procedure of measuring the flexural rigidity of a cord. (A) and (b) are cross-sectional views of filaments of other prevailing forms. (A) is a side view of the single-line cord of another actual form, and (b) is a plan view of the single-line cord of (a). It is sectional drawing of the belt layer of another embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of the right half of the tire meridian including the tire rotation axis (not shown) in the normal state of the pneumatic tire (hereinafter, may be simply referred to as “tire”) 1 of the present embodiment. FIG. 1 shows, for example, a tire 1 for a passenger car. However, the present invention can also be applied to tires 1 for motorcycles, heavy loads, and the like.

The "normal state" is a state in which the tire 1 is rim-assembled on a normal rim (not shown), the normal internal pressure is applied, and there is no load. Unless otherwise specified in the present specification, the dimensions of each part of the tire 1 are values measured in a normal state.

The "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire 1 is based. For example, "standard rim" for JATMA and "Design Rim" for TRA. ", ETRTO is" Measuring Rim ".

The "regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire 1 is based. For JATMA, the "maximum air pressure", and for TRA, the table "TIRE LOAD". The maximum value described in "LIMITS AT VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

The tire 1 includes a tread portion 2, a pair of sidewall portions 3 connected to both ends of the tread portion 2 and extending inward in the tire radial direction, and a pair of bead portions 4 connected to the sidewall portion 3 and extending inward in the tire radial direction. Includes.

The tire 1 of the present embodiment includes a carcass 6 bridged between the bead portions 4 and a belt layer 7 arranged outside the carcass 6 in the tire radial direction and inside the tread portion 2.

The carcass 6 is formed of, for example, one carcass ply 6A. The carcass ply 6A is formed by, for example, covering a carcass cord arranged at an angle of 75 to 90 ° with respect to the tire equator C with a rubber material (not shown).

The carcass ply 6A includes, for example, a main body portion 6a and a folded-back portion 6b. The main body portion 6a extends in a toroid shape between the bead cores 5 embedded in each bead portion 4, for example. The folded-back portion 6b is connected to the main body portion 6a and is folded back around the bead core 5 from the inside to the outside in the tire axial direction, for example.

In the present embodiment, the belt layer 7 includes a first ply 8 and a second ply 9 arranged outside the first ply 8 in the tire radial direction. The belt layer 7 may further include other plies (not shown).

FIG. 2 is an enlarged view of the belt layer 7 of FIG. As shown in FIG. 2, each of the first ply 8 and the second ply 9 includes a single wire and flat single wire cord 12 in the present embodiment. Further, each of the first ply 8 and the second ply 9 further includes, for example, a twisted wire cord 13 in which a plurality of filaments 13a are twisted together, and a topping rubber 14. In the present embodiment, the single wire cord 12 is arranged in the minor axis direction in the tire radial direction and in the major axis direction in the tire axial direction. In such a tire 1, the bending characteristic of the belt layer 7 in the tire radial direction is improved, and the riding comfort performance is improved. Further, since the rigidity of the belt layer 7 in the tire axial direction of the tire 1 is relatively large, a large cornering force is generated at the time of turning, and the steering stability performance is improved. Further, the stranded cord 13 causes energy loss due to friction between the filaments 13a. Since each of the plies 8 and 9 of the present embodiment includes the single wire cord 12, energy loss is suppressed and rolling resistance performance is enhanced. In the present specification, the minor axis direction and the major axis direction are the directions when the belt layer 7 is arranged parallel to the tire axial direction. In addition, the minor axis direction and the major axis direction shall include deviations (inclinations) of the degree of manufacturing error.

In the belt layer 7 of the present embodiment, the distance D between the cords in the tire radial direction between the single wire cord 12 of the first ply 8 and the single wire cord 12 of the second ply 9 is 0.30 to 1.05 mm. .. In this way, by defining the distance D between the cords in the above range on the premise of the so-called flat cord, the first ply 8 and the second ply 9 maintain the strain relaxation function. The deformation between the ply 8 and the second ply 9 can be suppressed to be smaller. Therefore, the tire 1 has excellent steering stability performance and rolling resistance performance.

In the present embodiment, the single wire cord 12 is formed by including a steel cord and a so-called ternary plating layer made of copper, zinc and cobalt, or a plating layer made of bronze or brass (not shown) on the surface of the steel cord. ing. As a result, the adhesiveness between the topping rubber 14 and the single wire cord 12 is enhanced, and energy loss can be effectively suppressed.

The minor axis SD of each single wire cord 12 is preferably 0.15 to 0.42 mm. If the minor axis SD is less than 0.15 mm, the rigidity of the belt layer 7 becomes small, and the steering stability performance may deteriorate. If the minor axis SD exceeds 0.42 mm, the bending characteristic of the belt layer 7 in the tire radial direction is deteriorated, so that the riding comfort performance may be deteriorated.

The flatness of each single wire cord 12 is preferably 70% or less. Such a single wire cord 12 enhances the bending characteristic of the belt layer 7 in the tire radial direction and the rigidity in the tire axial direction in a well-balanced manner. If the flatness ratio is excessively small, the bending characteristic of the belt layer 7 in the tire radial direction becomes too large, and the riding comfort performance may be deteriorated. Therefore, the flatness is preferably 40% or more. The flatness is the ratio (SD / LD) of the minor axis SD and the major axis LD of the single wire cord 12 in the present specification.

It is desirable that the distance D between the cords is larger than that of the short diameter SD. As a result, a large drag force is generated against the shearing force of the single wire cord 12, so that damage to the topping rubber 14 is suppressed and the riding comfort performance is maintained high. If the distance D between cords is excessively larger than that of the short diameter SD, the steering stability performance and rolling resistance performance may deteriorate. From this point of view, the difference (D-SD) between the cord-to-cord distance D and the minor axis SD is preferably 0.15 mm or more, and more preferably 0.20 mm or more. The difference (D-SD) is preferably 0.63 mm or less, and more preferably 0.45 mm or less.

The single wire cord 12 has a small bending rigidity in the minor axis direction, and is prone to bending deformation in the minor axis direction. Therefore, by including the stranded wire cord 13 in each of the first ply 8 and the second ply 9, a sheet-shaped top fabric (not shown) in which the cords 12 and 13 are coated with the topping rubber 14 is manufactured. Occasionally, it is suppressed that the top rubber is curled in the minor axis direction. Further, such a top roll is prevented from causing waviness in the minor axis direction when it is conveyed. In the manufacturing process, the top roll is cut at an arbitrary angle in the width direction to form a plurality of ply pieces (not shown). Each of the ply pieces is formed as a first ply 8 or a second ply 9 by joining the ends thereof.

In each of the first ply 8 and the second ply 9, in the present embodiment, the number of stranded cords 13 is larger than the number of single wire cords 12. As a result, the rigidity of the top roll in the minor axis direction is increased, and the curl-like deformation and the occurrence of waviness are further suppressed.

In each of the first ply 8 and the second ply 9, for example, the number of stranded cords 13 is set to be twice or more the number of single cords 12 in order to effectively exert the above-mentioned action. If the number of stranded cords 13 is excessively large, the effect of providing the single wire cords 12 is less likely to be exhibited. From this point of view, it is desirable that the number of stranded cords 13 is 3 times or less the number of single cords 12.

It is desirable that the diameter Da of the filament 13a of the stranded cord 13 is smaller than the major diameter LD of the single wire cord 12. Such a stranded cord 13 suppresses an increase in the mass of the belt layer 7, and enhances rolling resistance performance and ride comfort performance. If the diameter Da of the filament 13a of the stranded cord 13 is excessively small, the top roll in the above-mentioned manufacturing process may be curled and the effect of suppressing the waviness of the top roll may be reduced. , There is a risk that the steering stability performance will deteriorate. From this point of view, it is more desirable that the diameter Da of the filament 13a of the stranded cord 13 is 50% to 70% of the major diameter LD of the single wire cord 12.

In order to effectively exert the above-mentioned action, it is desirable that the diameter Da of the filament 13a of the stranded cord 13 is 0.15 to 0.45 mm.

The number of filaments 13a of the stranded cord 13 is preferably 3 or less, for example. As a result, the topping rubber 14 is filled between the filaments 13a without any gaps, so that the adhesiveness between the stranded cord 13 and the topping rubber 14 is further enhanced, and the friction between the filaments 13a is greatly reduced. The number of filaments 13a of the stranded cord 13 is 2 in this embodiment.

In the present embodiment, the stranded cord 13 is formed by including a filament 13a made of steel, a ternary plating layer on the surface of the filament 13a, and a plating layer such as bronze or brass (not shown). As a result, the adhesiveness between the filament 13a and the topping rubber 14 is enhanced.

The flexural rigidity E2 of the stranded cord 13 is preferably larger than the flexural rigidity E1 of the single wire cord 12 in the minor axis direction. As a result, the top roll in the above-mentioned manufacturing process becomes curled, the effect of suppressing the waviness of the top roll is exhibited, and the steering stability performance is enhanced. From this point of view, it is more desirable that the bending rigidity E2 of the stranded cord 13 is 1.5 to 2.5 times the bending rigidity E1 of the single wire cord 12 in the minor axis direction.

The "flexural rigidity" is measured as shown below. FIG. 3 is a schematic view showing a procedure for measuring the flexural rigidity of each of the cords 12 and 13. The "flexural rigidity" is defined as the rigidity of the test piece 100 measured using, for example, a rigidity tester (Model 150-D) manufactured by Taber, USA. The test piece 100 is obtained by fusing the cords 12 and 13 to a length of 150 mm.

Specifically, one end 101 of the test piece 100 is fixed to the jig 201, and a force in the direction perpendicular to the test piece 100 is applied to the other end 102 of the test piece 100 extending at a length of 130 mm from the fixed end. Will be done. Then, the drag force (flexural rigidity) N when the opening angle at the other end 102 of the test piece 100 becomes 40 ° is measured. The "flexural rigidity in the minor axis direction" is the rigidity when the minor axis direction of the single wire cord 12 is made to coincide with the vertical direction.

Although not particularly limited, it is desirable that the bending rigidity of the single wire cord 12 of the first ply 8 in the minor axis direction is smaller than the bending rigidity of the single wire cord 12 of the second ply 9 in the minor axis direction. Since the first ply 8 is arranged inside the tire radial direction with respect to the second ply 9, the radius of curvature of the first ply 8 in the tire circumferential direction is relatively smaller than that of the second ply 9. Therefore, by making the bending rigidity of the single wire cord 12 of the first ply 8 smaller than the bending rigidity of the single wire cord 12 of the second ply 9, both plies 8 and 9 have a large tag with respect to the carcass 6. It is effective and improves steering stability.

The cross section of the filament 13a of the stranded cord 13 is circular in the present embodiment. As shown in FIG. 4A, the cross section of the filament 13a may be elliptical. Further, as shown in FIG. 4B, the cross section of the filament 13a includes a pair of linear portions 15a extending linearly in the major axis direction and a pair of arcuate portions 15b extending linearly in the minor axis direction. It may have a substantially rectangular shape including.

As shown in FIG. 2, in the present embodiment, the single wire cord 12 of the first ply 8 and the single wire cord 12 of the second ply 9 are arranged at the same position in the tire axial direction. Further, the stranded cord 13 of the first ply 8 and the stranded cord 13 of the second ply 9 are arranged at the same position in the tire axial direction. The single wire cord 12 of the first ply 8 and the single wire cord 12 of the second ply 9 may be misaligned in the tire axial direction. Further, the stranded cord 13 of the first ply 8 and the stranded cord 13 of the second ply 9 may be misaligned in the tire axial direction.

In the present embodiment, the single wire cords 12 and the stranded wire cords 13 of the plies 8 and 9 are aligned in parallel, and are formed at an angle of 15 to 45 degrees with respect to the tire equator C (not shown), for example. Has been done.

The topping rubber 14 preferably has a complex elastic modulus E * of 6.0 to 14.0 MPa. Such a topping rubber 14 enhances riding comfort performance and steering stability performance in a well-balanced manner. In order to effectively exert the above-mentioned action, it is desirable that the loss tangent tan δ of the topping rubber 14 is 0.04 to 0.14.

In this specification, the complex elastic modulus E * and the loss tangent tan δ are the values measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the following conditions in accordance with the provisions of JIS-K6394. is there.
Initial distortion: 10%
Amplitude: ± 2%
Frequency: 10Hz
Deformation mode: Tensile temperature: 70 ° C

Although not particularly limited, the thickness T of the first ply 8 and the second ply 9 is 0.8 to 2.3 mm.

5 (a) and 5 (b) are side views and plan views of the single-line cord 12 of another embodiment. The same reference numerals are given to the same configurations as the single wire cord 12 of the present embodiment, and the description thereof will be omitted. As shown in FIGS. 5A and 5B, the single wire cord 12 of this embodiment is wavy in the major axis direction and the minor axis direction, for example. Such a single wire cord 12 absorbs vibration at the time of rolling of the tire 1 to further enhance the riding comfort performance.

The single wire cord 12 preferably has a wavy pitch P of 3.0 to 10.0 mm. Further, it is desirable that the single wire cord 12 has a wavy height H of 0.05 to 0.15 mm. When the wave pitch P is large and the wave height H is small, the vibration absorption effect becomes small and the ride comfort performance may not be improved. When the wave pitch P is small and the wave height H is large, the strength of the single wire cord 12 may decrease and the steering stability performance may deteriorate.

FIG. 6 is an enlarged view of the first ply 8 of the belt layer 7 of still another embodiment. The same components as those of the first ply 8 of the present embodiment are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 6, the single wire cord 12 of the first ply 8 is inclined in the major axis direction with respect to the tire axial direction. In such a single wire cord 12, the length D1 in the tire axial direction is smaller than the length in the tire axial direction of the single wire cord 12 arranged in the major axis direction in the tire axial direction, so that the single wire cord adjacent to the tire axial direction A large distance can be taken between 12 and the other cords 12 and 13. In other words, a large amount of topping rubber 14 between the single wire cord 12 and the other cords 12 and 13 is secured. As a result, the generation of cracks generated between the cords 12 and 13 and the topping rubber 14 is suppressed, so that the steering stability performance is maintained high.

As the major axis direction approaches the tire radial direction, the bending characteristic of the belt layer 7 in the tire radial direction deteriorates, and the riding comfort performance may deteriorate. Further, since the rigidity of the belt layer 7 in the tire axial direction is relatively small, the steering stability performance may be deteriorated. Therefore, in the single wire cord 12 of this embodiment, the major axis direction is set to an angle θ of 10 to 35 degrees with respect to the tire axial direction. The single wire cord 12 of the second ply 9 can also have an angle θ of 10 to 35 degrees with respect to the tire axial direction in the major axis direction (not shown).

Although the particularly preferable embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments, and can be modified into various embodiments.

A pneumatic tire for a passenger car of size 195 / 65R15 having the basic structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1. Then, tests were conducted on the steering stability performance, riding comfort performance, and rolling resistance performance of each test tire. In addition, the curl resistance and wave resistance of the top fabric of the first ply during manufacturing were tested. The common specifications of each test tire and top roll, and the test method are as follows.
T: 0.83mm (1st ply, 2nd ply)

<Maneuvering stability / riding comfort>
Each test tire was mounted on all wheels of a 2000cc passenger car under the following conditions. Then, the test driver ran the vehicle on a circuit course on a dry asphalt road surface, and the responsiveness, rigidity, grip force, steering stability performance and ride comfort performance related to transient characteristics at this time were evaluated by the test driver's sensuality. .. The result is represented by a score of 100 in Comparative Example 1, and the larger the value, the better.
Rim: 15x6JJ
Internal pressure: 230kPa

<Rolling resistance performance>
Using a rolling resistance tester, the rolling resistance of the test tire was measured under the following conditions based on ISO28580. The result is represented by an exponent with the value of Comparative Example 1 as 100, and the smaller the value, the better.
Rim: 15x6JJ
Internal pressure: 230kPa
Load: 3.43kN
Speed: 80km / h

<Curl resistance / wave resistance>
In the manufacturing process of the belt layer, curl resistance and waviness resistance were confirmed. The curl resistance was evaluated by visual inspection of a tester for the state of curl generated on the sheet-like top roll. As for the wave resistance performance, the state of waviness generated during the transportation of the top roll was evaluated visually by a tester. Both the curl resistance performance and the wave resistance performance are based on the occurrence rate of top rolls judged to be unacceptable by the tester. Those with the occurrence rate of less than 3% are good, and the occurrence rate is from 3% to Those with an incidence of more than 8% were allowed, and those with an incidence of more than 8% were not allowed.
The test results are shown in Table 1. Each tire of the example and the comparative example has the same configuration as the first ply and the second ply. Further, "ends" in Table 1 is the total number of single wire cords and stranded wire cords included in each ply with a length of 5 cm in the tire axial direction.

As a result of the test, it is understood that the test tires of the examples have various performances improved as compared with the test tires of the comparative examples. Further, it is understood that the top fabric including the stranded cord is excellent in curl resistance and waviness resistance.

1 Pneumatic tire 7 Belt layer 8 1st ply 9 2nd ply 12 Single wire cord

Claims (11)

Pneumatic tires
It includes a carcass bridged between a pair of bead portions and a belt layer arranged inside the tread portion on the outside in the tire radial direction of the carcass.
The belt layer includes a first ply and a second ply arranged outside the first ply in the tire radial direction.
Each of the first ply and the second ply includes a single wire and a flat single wire cord.
In the single wire cord, the minor axis direction is arranged in the tire radial direction, and the major axis direction is arranged in the tire axial direction.
The distance between the cords in the tire radial direction between the single wire cord of the first ply and the single wire cord of the second ply is 0.30 to 1.05 mm.
Pneumatic tires. The pneumatic tire according to claim 1, wherein the minor axis of the single wire cord is 0.15 to 0.42 mm. The pneumatic tire according to claim 1 or 2, wherein the flatness of the single wire cord is 70% or less. The pneumatic tire according to any one of claims 1 to 3, wherein each of the first ply and the second ply further includes a stranded cord in which filaments are twisted. The pneumatic tire according to claim 4, wherein in each of the first ply and the second ply, the number of the twisted wire cords is larger than the number of the single wire cords. The pneumatic tire according to claim 4 or 5, wherein in each of the first ply and the second ply, the number of the twisted wire cords is twice or more the number of the single wire cords. The pneumatic tire according to any one of claims 4 to 6, wherein the number of filaments of the stranded cord is 3 or less. The pneumatic tire according to any one of claims 4 to 7, wherein the diameter of the filament of the stranded cord is smaller than the major axis of the single wire cord. The pneumatic tire according to claim 8, wherein the filament diameter of the stranded cord is 50% to 70% of the major axis of the single wire cord. The pneumatic tire according to any one of claims 4 to 9, wherein the flexural rigidity of the stranded cord is larger than the flexural rigidity of the single wire cord in the minor axis direction. The pneumatic tire according to claim 10, wherein the flexural rigidity of the stranded cord is 1.5 to 2.5 times the flexural rigidity of the single wire cord in the minor axis direction.

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