JP2015077884A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that is improved in ride comfort performance and tire durability while suppressing increase in mass.SOLUTION: In the pneumatic tire, a side reinforcing layer 10 including a steel cord is embedded in a region ranging from a bead part 1 to a side wall part 2. The steel cord of the side reinforcing layer 10 has a n×2 double twisted structure where a plurality of metal filaments with wire diameters of 0.15 to 0.18 mm are twisted (n=2 or 3), and a load at the time of elongation of 0.5% in a rubber attached state after vulcanization of the tire is 40 to 100 N.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire provided with a side reinforcing layer.

  With the recent high performance of vehicles, pneumatic radial tires with further improved handling stability are strongly demanded. Therefore, as a countermeasure, a technique has been proposed in which a side reinforcing layer extending in the tire radial direction from the vicinity of the bead core is embedded from the bead portion to the sidewall portion. A tire provided with such a side reinforcing layer has a problem that although the driving stability is improved, the riding comfort performance is deteriorated. In addition, an increase in the mass of the tire due to the provision of the side reinforcing layer cannot be denied.

  Therefore, in Patent Document 1, in order to suppress an increase in mass and a decrease in riding comfort performance, it is proposed to use a steel cord in which ultrafine wire metal filaments having a wire diameter of 0.09 to 0.12 mm are twisted together. As the twist structure, an m + n multi-layer twist structure (m = 1 to 3, n = 5 to 15), a 1 × n single twist structure (n = 5 to 15), an m × n double twist structure ( m = 3-5, n = 2-4) and the like are exemplified.

  Patent Document 2 discloses that a metal filament having a wire diameter of 0.12 to 0.22 mm is made of an mxn multi-layer twist structure (in order to improve riding comfort performance without impairing steering stability and durability. It is disclosed that the twist directions of the upper twist and the lower twist are made different from each other after m = 3 to 7, n = 2 to 7).

JP 2012-106568 A JP 2011-131682 A

  However, if the filament diameter is too small as in Patent Document 1, the cord strength is not sufficient, so that it is necessary to increase the number of driven wires, and there is a problem that adhesion failure is likely to occur. In addition, when steel cords with a 1xn single twist structure or m + n multi-layer twist structure are used, excessive stress concentration occurs due to cord distortion, resulting in reduced steel cord durability and load durability. There is. Further, in the case of the m × n double twist structure, for example, in the case of the 3 × 3 structure specifically disclosed in Patent Document 2, the number of filaments increases, so that the mass of the steel cord increases and the tire mass increases. There is a problem of increasing.

  Patent Documents 1 and 2 do not specifically disclose an n × 2 double twisted structure (n = 2, 3), and together with such a specific twisted structure, a wire diameter of a metal filament and a steel cord It is also not disclosed that the ride comfort performance and the tire durability are improved while the increase in mass is suppressed by defining the load at the time of specific extension.

  This invention is made | formed in view of the above point, and it aims at providing the pneumatic tire which can improve riding comfort performance and tire durability, suppressing an increase in mass.

  A pneumatic tire according to the present invention includes a pair of left and right bead portions and sidewall portions, and a tread portion provided between the left and right sidewall portions, and has a steel in an area from the bead portions to the sidewall portions. In a pneumatic tire in which a side reinforcing layer including a cord is embedded, the steel cord is an n × 2 double twist structure in which a plurality of metal filaments having a wire diameter of 0.15 to 0.18 mm are twisted (where n = 2 or 3), and the load at the time of 0.5% elongation in the state with rubber after vulcanization of the tire is 40 to 100 N.

  According to the present invention, by using the steel cord having the specific double twist structure as the side reinforcing layer, it is possible to improve riding comfort performance and tire durability while suppressing an increase in mass.

1 is a half sectional view of a pneumatic radial tire according to one embodiment.

  Hereinafter, embodiments of the present invention will be described in detail.

  As shown in FIG. 1, the pneumatic tire according to the embodiment is a pneumatic radial tire for passenger cars, and includes a pair of left and right bead portions (1) and sidewall portions (2), and left and right sidewall portions (2). And tread portions (3) provided between the side wall portions (2) so as to connect the radially outer ends of the two.

  A carcass (4) is embedded in the radially inner portion of the tread portion (3), and the carcass (4) is disposed between the pair of bead portions (1). That is, both ends of the carcass (4) are locked by the annular bead core (5) embedded in the bead portion (1) through the sidewall portion (2) on both sides from the tread portion (3). . The carcass (4) is composed of at least one carcass ply (one in the example shown in the figure) formed by arranging carcass cords as a reinforcing material in parallel with a predetermined number of driving and covering with a covering rubber. The carcass ply is arranged so as to be substantially perpendicular to the circumferential direction.

  Both ends of the carcass (4) are locked by being folded back from the inner side in the tire axial direction by the bead core (5). Accordingly, the carcass (4) has a toroidal body portion (4A) straddling between the left and right bead cores (5), and the bead core (5) at both ends of the body portion (4A) from the inner side to the outer side in the tire axial direction. It consists of a folded back part (4B). And between the main-body part (4A) and the folding | turning part (4B), the bead filler (6) made from the hard rubber which makes a cross-sectional triangle shape is distribute | arranged to the radial direction outer peripheral side of the bead core (5).

  A belt (7) is disposed on the outer peripheral side of the carcass (4) in the tread portion (3) (that is, on the outer side in the tire radial direction). The belt (7) is provided on the outer periphery of the crown portion of the carcass (4), and can be constituted by one or a plurality of belt layers, usually at least two belt layers. Then, it is composed of two belt layers. Then, on the outer peripheral side of the belt (7) (that is, the outer side in the tire radial direction), a belt reinforcing layer formed by spirally winding an organic fiber cord between the belt (7) and the tread rubber portion (8) ( 9) is provided. The belt (7) is formed by inclining a conventional steel cord for a belt at a constant angle (for example, 15 to 35 degrees) with respect to the tire circumferential direction and arranging it at predetermined intervals in the tire width direction. The steel cords are arranged so as to cross each other between the two belt layers.

  In the above configuration, in the present embodiment, the side reinforcing layer (10) extending in the tire radial direction is provided in the region from the bead portion (1) to the sidewall portion (2). The side reinforcing layer (10) is a rubber layer in which a plurality of steel cords are arranged in parallel at predetermined intervals and covered with rubber.

  In the side reinforcing layer (10), the steel cord is disposed to be inclined with respect to the tire circumferential direction. The inclination angle of the steel cord is not particularly limited, but the inclination angle with respect to the tire circumferential direction is preferably 15 ° to 50 °, and more preferably, in order to improve the radial rigidity and circumferential rigidity of the tire in a balanced manner. Is 20 ° to 40 °.

  The side reinforcing layer (10) may be provided only in the bead part (1) or only in the side wall part (2) as long as it is within the region from the bead part (1) to the side wall part (2). Even if it provides, it may be provided so that a bead part (1) may straddle a sidewall part (2). In this example, the side reinforcing layer (10) extends outward in the tire radial direction from the vicinity of the bead core (5) so as to straddle the side wall portion (2) from the bead portion (1), and the side wall portion (2). The tire ends in the tire radial direction inner side than the maximum width position (2A) so as not to reach the tire maximum width position (2A).

  More specifically, the side reinforcing layer (10) is provided along the outer surface in the tire axial direction of the bead filler (6), that is, the folded portion (4B) of the bead filler (6) and the carcass (4). It is interposed between and. Further, the radially outer end (4B) of the folded portion (4B) is covered with the folded portion (4B) of the carcass (4) from the outer side in the tire axial direction so that the radially outer end (10A) of the side reinforcing layer (10) is covered. 4BE) extends to the outer side in the tire radial direction from the radial outer end (10A) of the side reinforcing layer (10).

  The arrangement of the side reinforcing layer (10) is not limited to the case where the side reinforcing layer (10) is interposed between the bead filler (6) and the carcass folded portion (4B) as described above. 4B) may be arranged on the outer side in the tire axial direction, and may be interposed between the bead filler (6) and the carcass main body (4A).

  As the steel cord as the reinforcing cord constituting the side reinforcing layer (10), a steel cord having an n × 2 double twist structure (where n = 2 or 3) in which a plurality of metal filaments are twisted is used. That is, the steel cord is formed by twisting n strands (that is, 2 or 3 strands) of strands formed by twisting two metal filaments. As described above, the number of filaments constituting the strand is two, and the number of strands is two or three, thereby suppressing the increase in the total number of filaments and increasing the mass of the steel cord. The increase can be suppressed. The twist directions of the lower twist and the upper twist are preferably different from each other. In one embodiment, the lower twist is an S twist and the upper twist is a Z twist.

  The metal filament constituting the steel cord has a wire diameter (also referred to as filament diameter or strand diameter) in the range of 0.15 to 0.18 mm. In a metal filament having a wire diameter thinner than 0.15 mm, it is necessary to use a large number of steel cords in order to ensure the total strength, and the cord occupancy increases, and as a result, edge separation is also adversely affected. If a metal filament with a wire diameter larger than 0.18 mm is used, the unit mass of the steel cord itself and the mass of the side reinforcing layer are increased, which is contrary to the weight reduction of the tire. The wire diameter of the metal filament is more preferably 0.16 to 0.18 mm.

  Here, the measurement of a filament diameter is performed by measuring the diameter of a metal filament with a predetermined thickness meter according to JIS G3510.

  When a plurality of metal filaments are twisted to form a steel cord, each metal filament may be twisted with the same diameter or different wire diameters as long as it is within the range of the above-mentioned wire diameters. The plurality of metal filaments are twisted together.

  The steel cord has a load at 0.5% elongation (0.5% ASE) of 40 to 100 N in a state with rubber after vulcanization of the tire. In order to make 0.5% LASE less than 40N, it is necessary to shorten the twist pitch, and the cord strength is lowered by the twist strain. As a result, the load durability of the tire decreases with an increase in the number of steel cords to be driven. On the other hand, when 0.5% LASE exceeds 100 N, excessive stress concentration occurs due to distortion of the steel cord, the durability of the steel cord is lowered, and the load durability of the tire is lowered. Moreover, the improvement effect of riding comfort performance is not acquired. 0.5% ASE is more preferably 50 to 80N.

  Here, the measurement of 0.5% ASE is based on the state of rubber attached after vulcanization of the tire by a tensile test in accordance with JIS G3510 (grip spacing: 5 cm, tensile speed: 1/10 (mm / min) of cord gripping interval). The load-elongation curve is obtained, and the load at 0.5% elongation obtained from the curve.

  The specific means for setting 0.5% ASE of the steel cord within the above range is not particularly limited. 0.5% ASE tends to increase as the number of metal filaments increases, the wire diameter of the metal filaments increases, and the twist pitch increases, so these specifications should be set appropriately. Thus, 0.5% ASE can be set within the above range.

  The pneumatic tire according to this embodiment is manufactured in the same manner as a normal tire manufacturing method except that the side reinforcing layer (10) is provided, and can be manufactured according to the manufacturing method. For example, when folding both ends of the carcass (4) on the tire forming drum, the reinforcement ply (the steel cord is aligned and then the rubber-coated topping) that constitutes the belt reinforcement layer (10) is used as a bead filler (6 ) Overlaid on top, and the raw tire (green tire) is made so that the folded part (4B) of the carcass (4) is overlaid on it, and the resulting raw tire is vulcanized and molded into air A radial tire is obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples.

  A radial tire having a tire size of 215 / 45R17 having a cross-sectional shape shown in FIG. The configuration of the side reinforcing layer (10) is as shown in Table 1 below, and the configuration other than the side reinforcing layer (10) is the same for each tire.

  Specifically, the belt (7) has two steel cords having a structure of 2 + 1 × 0.27 mm, which are generally used, with the number of ends being 21 / 25.4 mm (cord angle is + 25 ° / −25). °). Carcass (4) was a single ply of polyester fiber 1670 dtex / 2 cord arranged with 22 ends / 25 mm. The inclination angle of the steel cord in the side reinforcing layer with respect to the tire circumferential direction was 30 °.

  Each measurement / evaluation method about each physical property of the steel cord and side reinforcement layer in Table 1 and tire performance is as follows.

Filament diameter and cord diameter: Values obtained by measuring the diameters of the metal filament and the steel cord with a predetermined thickness meter in accordance with JIS G3510 after being left for 24 hours or more under constant temperature conditions of 20 ° C. and 65% RH.

・ Strong cord, 0.5% LASE: Steel cords with rubber taken out from vulcanized tires are left for 24 hours or more under constant temperature conditions of 20 ° C. and 65% RH, and then pulled according to JIS G3510. The tensile strength is measured with a testing machine (grip interval: 5 cm, tensile speed: 1/10 (mm / min) of cord grasp interval). The cord strength is the maximum load required to cut the steel cord at that time, and 0.5% ASE is the load at the time of 0.5% elongation obtained from the load-elongation curve obtained at the time of the measurement. is there. The steel cord with rubber used for the tensile test is a steel cord coated with approximately 1 mm of rubber around the steel cord.

Code occupancy (%): Cord diameter (mm) x number of cords driven (pieces / 25.4mm) x 100 / 25.4 (mm).

-Side reinforcement layer total strength: Tensile strength per 25.4 mm of the side reinforcement layer calculated by multiplying the cord strength by the number of cords to be driven in the side reinforcement layer.

・ Side reinforcement layer mass per tire: Topping for the side reinforcement layer obtained by topping rubber on steel cord and cutting, 150cm in the longitudinal direction and 4cm in the width direction at the center in the width direction The mass was indexed with the conventional example being 100. The smaller the number, the lighter the weight and the better.

-Tire load durability: Based on FMVSS109 (UTQG), measurement was performed as follows using a drum tester having a 1700 mm diameter rotating drum made of steel with a smooth surface. The tire internal pressure was 200 kPa, and the test speed was constant at 80 km / h. After running at 85% of the maximum load specified by JATMA for 4 hours, then at 90% of the maximum load for 6 hours, and further at 100% of the maximum load for 24 hours, it is run at 120% of the maximum load for 24 hours. At this time, if there is no abnormality in the appearance and the inner surface, the vehicle is further driven at 140% of the maximum load until a failure occurs. The distance traveled until the failure occurred was indexed with the conventional tire as 100. The larger the index, the better the load durability performance of the tire.

・ Ride comfort performance: Each tire is adjusted to 200kPa internal pressure using JIS standard rims, 4 kinds of same tires are mounted on a 2000cc domestic passenger car, 3 test drivers on the test course of good road and bad road The sensory evaluation of ride comfort performance was performed using the conventional example as a reference. “△” indicates the same as the conventional example, “X” indicates inferior, and “◯” indicates superior.

  The results are as shown in Table 1. In contrast to the conventional example in which a steel cord having a 2 + 1 × 0.27 multi-layer twist structure is used for the side reinforcing layer, the tire mass does not increase and the tire load durability is in Examples 1 to 3 according to the above embodiment. And ride performance was improved.

  On the other hand, the tire mass increased in Comparative Example 1 in which a 3 × 2 × 0.19 steel cord was used for the side reinforcing layer and the filament diameter was 0.19 mm, which was outside the specification. In Comparative Example 2 in which a steel cord of 3 × 2 × 0.14 is used for the belt reinforcing layer and the filament diameter is 0.14 mm which is not specified, the cord occupation ratio is high in order to obtain the necessary strength as the side reinforcing layer. As a result, load durability decreased.

  In Comparative Example 3, 4 × 2 × 0.15 steel cord was used for the side reinforcement layer, and the number of strands was four outside the specification, so the total number of filaments as the cord increased, Tire mass increased. In Comparative Example 7, which uses 1 × 2 × 0.17 steel cords for the side reinforcement layer and the number of strands is less than specified, the cord occupancy increases to obtain the necessary strength as the side reinforcement layer, and the load durability As a result, the riding performance was not reduced, and the riding comfort performance was not improved.

  In Comparative Example 4, 0.5% ASE of the steel cord was larger than specified, excessive stress concentration due to cord distortion occurred, the durability of the steel cord was lowered, and the tire load durability was lowered. Moreover, the improvement effect of riding comfort performance was not acquired. On the other hand, in Comparative Example 5 in which 0.5% ASE of the steel cord is smaller than specified, the twist strength of the steel cord is too much, and the cord strength is reduced due to the twist strain. As a result, along with the increase in the number of driven-in cords, the code occupancy rate increased and the tire load durability decreased.

  Comparative Example 6 is an example corresponding to Example 3 of Patent Document 2 described above. Since there are many metal filaments constituting the strand, the total number of metal filaments in the steel cord is increased, and the tire mass is increased. . Moreover, 0.5% LASE was too large, excessive stress concentration due to cord distortion occurred, the durability of the steel cord was lowered, and the tire load durability was lowered. Comparative Example 8 is an example corresponding to Conventional Example 1 of Patent Document 2 described above. No difference from the conventional example was observed when the steel cord configuration was 1 × 3 × 0.28.

  The present invention can be suitably used for various pneumatic radial tires including passenger vehicle tires.

1 ... bead part, 2 ... side wall part, 3 ... tread part,
4 ... carcass, 10 ... side reinforcement layer

Claims (1)

A pair of left and right bead portions and sidewall portions, and a tread portion provided between the left and right sidewall portions are provided, and a side reinforcing layer including a steel cord is embedded in an area from the bead portion to the sidewall portions. In pneumatic tires,
The steel cord has an n × 2 double twist structure (where n = 2 or 3) in which a plurality of metal filaments having a wire diameter of 0.15 to 0.18 mm are twisted, and after tire vulcanization. A pneumatic tire characterized by having a load of 40 to 100 N at 0.5% elongation in a state with rubber.

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