JP2019098819A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire which can be improved in flat spot resistance and high-speed durability without increasing weight of a belt reinforcing layer.SOLUTION: The pneumatic tire has a carcass 4 and a belt reinforcing layer 8 arranged at an outer periphery of a belt 6. The belt reinforcing layer has a main filament bundle formed by arranging four to six steel filaments of the same diameter in parallel to form a single layer without twisting the filaments, and comprises belt reinforcing plies, in which steel cords having n+1 structures (n=4-6) formed by winding, around the main filament bundle, one steel filament of a diameter smaller than the diameter of the steel filament as a wrapping filament, are arranged so that the longer diameter direction is parallel to the belt outer peripheral surface. A product of 0.5% elongation-time loads (N) per one steel cord, the number of the steel cords driven in the belt reinforcing plies (number/inch), and the number of the belt reinforcing plies is 2000-2500.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  In high performance tires such as ultra high performance, for the purpose of improving high speed durability, it is considered to improve the rigidity in the circumferential direction of the tire. As the means, laminating a plurality of belt reinforcing plies on the belt reinforcing layer may be mentioned.

  In addition, nylon fibers typified by 66 nylon and 6 nylon generally used for belt reinforcing plies may be shrunk and distorted due to heat generated during high speed running. Therefore, a pneumatic tire using a nylon fiber cord for the belt reinforcing layer has a problem that so-called flat spots are easily generated when the tire vibrates again.

  In order to ameliorate this problem, Patent Documents 1 and 2 propose applying a general-purpose steel cord to the belt reinforcing layer. However, as compared with the case of using a nylon fiber cord for the belt reinforcing layer, there is a problem that it leads to an increase in the weight of the belt reinforcing layer. Also, it is proposed to apply aramid fiber to the belt reinforcement layer, but since the rigidity is lower than steel cord, in order to obtain flat spot resistance and high-speed durability equivalent to steel cord, There is a problem that it is necessary to increase, leading to an increase in the weight of the belt reinforcing layer.

JP, 2009-40347, A JP 2004-322718 A Unexamined-Japanese-Patent No. 2015-227083

  An object of the present invention is to provide a pneumatic tire that can improve flat spot resistance and high speed durability without increasing the weight of the belt reinforcing layer.

  In Patent Document 3, a plurality of main filaments made of steel are aligned on a belt without twisting together to form a main filament bundle, and a single wrapping filament made of steel is wound around the main filament bundle. Although there is disclosed a pneumatic tire comprising a belt ply in which flat steel cords of an n + 1 structure (where n = 3 to 6) are arranged such that the major axis direction is parallel to the belt surface. There is no known tire using a steel cord of n + 1 structure in the layer.

  A pneumatic tire according to the present invention is a pneumatic tire having a carcass, a belt disposed on the outer periphery of a crown portion of the carcass, and a belt reinforcing layer disposed on the outer periphery of the belt, wherein the belt reinforcing layer is , 4 to 6 steel filaments of the same diameter are arranged in a single layer without twisting together to form a main filament bundle, and one steel filament smaller in diameter than the above steel filaments is used as the wrapping filament as the wrapping filament. A steel cord of n + 1 structure (n = 4 to 6) wound around a filament bundle is provided with a belt reinforcing ply arranged so that the major axis direction is parallel to the outer peripheral surface of the belt, 0 per steel cord .5% extension load (N), and the number of steel cords in the belt reinforcement ply (number / inch), The product of the number of belt reinforcing ply (N / inch) is assumed to be 2000 or more 2500 or less.

  According to the pneumatic tire of the present invention, excellent flat spot resistance and high speed durability can be obtained without increasing the weight of the belt reinforcing layer.

1 is a half sectional view of a pneumatic tire according to an embodiment of the present invention. The top view showing the composition of the steel cord concerning one embodiment of the present invention. 1 is a partial cross-sectional view of a belt reinforcing ply according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The perspective view which shows the structure of the steel cord which concerns on preferable embodiment of this invention. Sectional drawing which shows the structure of the steel cord which concerns on preferable embodiment of this invention.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The pneumatic tire according to the embodiment shown in FIG. 1 is a pneumatic radial tire for a passenger car, and includes a pair of left and right bead portions 1 and sidewall portions 2 and radially outer end portions of the left and right sidewall portions 2. A tread portion 3 provided between both side wall portions so as to connect is configured, and a carcass 4 extending across a pair of bead portions is provided.

  The carcass 4 is composed of at least one carcass ply having its both ends locked by an annular bead core 5 embedded in the bead portion 1 from the tread portion 3 to the sidewall portion 2. The carcass ply is formed by arranging carcass cords made of an organic fiber cord or the like substantially at right angles to the circumferential direction of the tire.

  A belt 6 is disposed between the carcass 4 and the tread rubber portion 7 on the outer peripheral side (that is, the outer side in the tire radial direction) of the carcass 4 in the tread portion 3. The belt 6 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 plies, usually at least two belt plies, and in the present embodiment, the carcass side The first belt ply 6A and the second belt ply 6B on the tread rubber portion side are composed of two belt plies. The belt plies 6A and 6B are formed by inclining steel cords at a predetermined angle (for example, 15 to 35 degrees) with respect to the tire circumferential direction and arranging the steel cords at predetermined intervals in the tire width direction. Each belt ply has a steel cord coated with a coating rubber. The steel cords are disposed to intersect each other between the two belt plies 6A and 6B.

  A belt reinforcing layer 8 is provided between the belt 6 and the tread rubber portion 7 on the outer peripheral side of the belt 6 (that is, on the outer side in the tire radial direction). The belt reinforcing layer 8 is a cap ply which covers the belt 6 with its entire width by a belt reinforcing ply 8A (see FIG. 3), and is made of a steel cord 20 which is arranged substantially parallel to the tire circumferential direction. That is, as shown in FIG. 3, the belt reinforcing layer 8 has the steel cords 20 arrayed along the tire circumferential direction, and the steel cord 20 is arranged in the tire circumferential direction so as to cover the entire width direction of the belt 6. It can be formed by spirally winding at an angle of 0 to 5 degrees.

  The belt reinforcing layer 8 of the present embodiment has a load (N) at 0.5% elongation per steel cord, the number (inch / inch) of steel cords in the belt reinforcing ply, and the number of belt reinforcing plies 8A. The product of (N / inch) with is preferably 2000 or more and 2500 or less, more preferably 2100 or more and 2400 or less, and still more preferably 2150 or more and 2300 or less. By being 2000 or more, the rigidity in the tire circumferential direction is high, and excellent high-speed durability can be easily obtained. Moreover, by being 2500 or less, it can suppress that the cord of the belt reinforcement layer 8 bites into the belt layer 6 at the time of expansion of the tire at the time of tire vulcanization molding, and a tire excellent in durability is easily obtained. . Here, "a load at 0.5% elongation per steel cord (N)" is a load at a 0.5% elongation when a tensile test is performed in accordance with JIS G 3510.

  The load at 0.5% elongation (N) per steel cord is not particularly limited, but is preferably 100 to 300 N, more preferably 120 to 280 N, and still more preferably 140 to 250 N preferable.

  The 0.5% elongation load (N) can be adjusted by the number of main filaments 12 described later, the diameter d of the main filaments 12, the carbon content (mass%) of the main filaments 12, and the like.

  As shown in FIG. 3, the belt reinforcing ply 8A is formed by arranging the steel cord 20 so that the major axis direction B is parallel to the belt surface (i.e., the belt outer peripheral surface). That is, in the belt reinforcing ply 8A, the steel cord 20 is embedded in the coating rubber 11 at a predetermined interval so that the minor axis direction A coincides with the thickness direction K of the belt reinforcing ply 8A. Therefore, the steel cord 20 is disposed such that the major axis direction B is parallel to the tread surface. With this configuration, the steel cord 20 can be easily processed when it is rubber-coated, and the thickness of the belt reinforcing ply 8A can be reduced to suppress an increase in tire weight. Further, in the obtained belt reinforcing ply 8A, since the bending rigidity in the tire width direction is high, the steering stability can be improved, and the bending rigidity in the tire radial direction is low. Can raise

  Each steel cord 20 for the belt reinforcing ply of the pneumatic tire according to the present embodiment, as shown in FIGS. 2 and 3, is made of only steel filaments and has 4 to 6 main filaments 12 of the same diameter, and And one wrapping filament 14 for bundling. The diameter d of the main filament 12 is preferably 0.15 to 0.30 mm, more preferably 0.15 to 0.25 mm. If the diameter d of the main filament 12 is 0.15 mm or more, the rigidity of the steel cord 20 can be reduced and the ride comfort can be easily improved while maintaining the steering stability at the time of mounting the tire. When the diameter d is 0.30 mm or less, it does not become too rigid and can suppress an increase in surface distortion due to compressive deformation, so the fatigue resistance of the belt reinforcing ply 8A can be maintained, and the tire durability is maintained. Easy to do. The wrapping filament 14 may have a bending stiffness less than that of the main filament 12, for example 10 to 40% of the main filament 12. The diameter d0 of the wrapping filament 14 is preferably 0.10 to 0.15 mm. When the diameter d0 of the wrapping filament 14 is within this range, it is easy to secure the cohesion while suppressing the increase in diameter of the steel cord 20.

  The carbon content (% by mass) of the main filament 12 is not particularly limited, but is preferably 0.80% by mass or more, and more preferably 0.90% by mass or more.

  These main filaments 12 are juxtaposed in one layer along one plane. That is, in a cross section perpendicular to the longitudinal direction of the steel cord 20, the steel cords 20 are aligned in a line. Therefore, each steel cord 20 is flat and has a major diameter D1 and a minor diameter D2 as shown in FIG. The values of the major diameter D1 and the minor diameter D2 are not particularly limited. For example, the major diameter D1 can be 1.00 to 1.50 mm, and the minor diameter D2 can be 0.30 to 0.60 mm, and the major diameter / minor diameter The ratio of is, for example, 1.5 to 5 times, preferably 2 to 4 times.

  The number of main filaments 12 juxtaposed in one cord is 4 to 6 from the viewpoint of increasing the flatness of the cord and reducing the thickness of the belt layer etc. while keeping the shape as a bundle stable. Books are preferred, and more preferably four to five. That is, when the number of main filaments 12 exceeds six, it becomes difficult to arrange them in a line so that the shape as a bundle tends to be irregular. The main filament 12 may not necessarily have a circular cross section. For example, the steel cord 20 can be further flattened by using an elliptical cross section as the main filament 12.

  On the other hand, the wrapping filament 14 is not particularly limited, but one having no corrugation, that is, a so-called "straight" one is preferably used. In the case of straightness, winding is easy and the restraining force of winding is easy to be uniformly high. In addition, the restraining force by the wrapping filament 14 enables the aligned main filaments 12 to have a sense of unity as the steel cord 20, which is high against in-plane deformation of the belt material when changing the route during traveling or bending a curve. Stiffness is obtained.

  As a further preferable aspect of the above embodiment, as shown in FIGS. 4 and 5, a flat steel cord 20 formed by winding a wrapping filament 14 around a main filament bundle 13 is pressed in its short diameter direction A to wrap the filament A variation of 14 can be used. The pressing causes the wrapping filament 14 to deform along the shape of the space into at least a part of the space formed between the adjacent main filaments 12 so that the part thereof penetrates. That is, at least a portion of the space is filled with at least a portion of the wrapping filament 14. Therefore, the restraining force of the main filament 12 by the wrapping filament 14 can be increased. In addition, relatively large plastic deformation is applied to the wrapping filament 14 to reduce the rotational torque and repulsive force inherent to the wrapping filament 14. Therefore, the main filament bundles 13 can easily maintain the shape in which the main filament bundles 13 are arranged in one row, and can easily exhibit the excellent effect of the flat cords.

  The thickness of the steel cord 20 according to the present embodiment having the wrapping filament 14 deformed by pressing in the minor axis direction A as described above, that is, the minor axis Da after pressing has the wrapping filament 14 before deformation. The thickness of the steel cord 20 can be smaller than the short diameter Db (not shown) before pressing. The ratio (Da / Db) of the minor axis Da of the steel cord 20 after pressing to the minor axis Db of the steel cord 20 before pressing is preferably 0.80 or less, and more preferably 0.65 to 0.75. is there. Thus, by pressing with a force having a magnitude such that Da / Db ≦ 0.80, penetration of the deformed wrapping filament 14 into the space between the main filaments 12 is sufficient, and the restraining force of the wrapping filament 14 is obtained. Can be secured enough. Also, the rotational torque and the repulsive force inherent to the wrapping filament 14 can be sufficiently reduced.

  The diameter of the wrapping filament 14 before pressing, that is, the filament diameter d0 is preferably smaller than the diameter d of the main filament 12 as described above, and more preferably 0.10 to 0.15 mm. When it is 0.15 mm or less, the rotational torque and repulsive force inherent in the wrapping filament 14 can be easily reduced by pressing, and when it is 0.10 mm or more, the possibility of breaking at the time of pressing can be further reduced.

  The pressing can be performed using a rolling roll (not shown), and the flat cord after winding of the wrapping filament 14 is sandwiched and pressed from both upper and lower sides by the rolling roll. Since the wrapping filament 14 is located outside and its hardness is lower than that of the main filament 12, pressing can preferentially deform the wrapping filament 14. A space having a substantially fan-shaped cross section is formed between the adjacent main filaments 12, and when pressed by a rolling roll, the inner peripheral side of the wrapping filament 14 is deformed to fill the space to form the space. Protrusions 14a are formed along. At the same time, a recess is formed between the protrusions 14a, and the outer circumferential side portion 14b of the wrapping filament is deformed in a planar manner.

  In one embodiment, the carbon content (mass%) of the main filament 12 is Cc, and the carbon content (mass%) of the wrapping filament 14 is Cw. The content is preferably 40% by mass, more preferably 0.10 to 0.30% by mass. When Cc-Cw is 0.05% by mass or more, the wrapping filament 14 is easily deformed by pressure, and when it is 0.40% by mass or less, the possibility of disconnection of the wrapping filament 14 by pressure is reduced. can do.

  The type of pneumatic tire according to the present embodiment is not particularly limited, and various types of tires such as tires for passenger cars, heavy duty tires used for trucks, buses and the like can be mentioned.

  In the above-mentioned embodiment, although belt reinforcement layer 8 explained what is a cap ply which covers belt 6 with the full width, it is not limited to this, but covers the end of the tire width direction outside of belt 6, and its circumference The edge ply may be an edge ply, and the edge ply may be a portion in which both ends in the tire width direction of the cap ply are folded back.

  Hereinafter, although the example of the present invention is shown, the present invention is not limited to these examples.

  A steel cord having a structure shown in Table 1 below was produced. In the belt reinforcing layer of the conventional example, a belt reinforced ply was formed into two plies using a 940 dtex / 2 66 nylon cord as an organic fiber cord. The steel cords of Comparative Examples 1 and 2 have a 2 + 1 multi-layered twist structure (2 + 1 × 0. 6) in which one metal filament of the same diameter is twisted around a core consisting of two metal filaments aligned. 27) is a conventional steel cord. All other steel cords are wrapped with one straight wrapping filament (diameter d0 = 0.15 mm), with the main filament bundle in which multiple main filaments are arranged in a line without twisting. Further, it is a steel cord of an n + 1 structure formed by pressing with a rolling roll so as to be Da / Db shown in Table 1. In addition, the winding pitch p of the wrapping filament was 5.0 mm. Incidentally, 0.22 of “4 × 0.22 + 1” in Table 1 indicates that the main filament diameter d is 0.22 mm.

  The measurement method for the steel cord is as follows.

-Carbon content of filament: Infrared absorption method according to JIS G 1211 (Annex 3: total carbon determination method-high frequency induction furnace combustion). In more detail, steel was melt | dissolved by high frequency heating using the apparatus made from LECO "CS-400", and it quantitatively analyzed by the infrared absorption method.

Filament diameter, cord diameter: In accordance with JIS G 3510, the diameter of the cord and the filament was measured with a predetermined thickness meter.

-Load at 0.5% elongation: A tensile test was conducted in accordance with JIS G 3510, and a load at 0.5% elongation was measured.

  Further, using the obtained cord as a cord for a belt reinforcing layer, a radial tire having a tire size of 245 / 35R20 95W was vulcanized and formed according to a conventional method. About each tire, all the configurations other than the belt reinforcing layer were common. The steel cord in the belt ply had a 2 + 2 × 0.25 structure, and the number of drive was 20 / inch. The angle of the steel cord in the belt ply (6A) / (6B) was + 24 ° / −24 ° with respect to the tire circumferential direction. The belt reinforcing ply was produced by arranging the steel cords in the number of insertions described in Table 1 so that the major axis direction was parallel to the belt surface, and then using a calender device to make it topping opposite.

  The carcass ply had two cords of polyester cord 1100 dtex / 2, and the number 28 of punched sheets / 25 mm.

  The weight of the belt reinforcing layer, the flat spot resistance, and the high speed durability were evaluated for each of the obtained pneumatic tires. The evaluation method of each evaluation item is shown below.

The weight of the belt reinforcing layer: The total weight of the belt reinforcing ply used per tire, and the total weight of the belt reinforcing ply of the conventional example was indexed as 100. The smaller the number, the lighter.

Flat spot resistance: After mounting a trial tire incorporating an internal pressure of 220 kPa on a test vehicle (sedan) with a displacement of 2500 cc and running the load at a speed of 100 km / h for 1 hour with a load per tire of 4.31 kN , Let stand for 16 hours. After that, sensory evaluation was performed by a test driver. The evaluation was performed on the magnitude of the vibration in the vertical direction and the front and back direction at the beginning of running, and those with large vibration were evaluated as "x" and those with almost no vibration were evaluated as "o".

-High speed durability: It conformed to ECE-R30 extension. That is, the internal pressure of the tire is 320 kPa, and the load is 80% of the maximum load defined by JATMA. After traveling for 10 minutes at 0 to 150 km / h, the vehicle was allowed to travel for 10 minutes at 150 km / h. After that, the speed was increased stepwise by 10 km / h every 10 minutes, and the vehicle was run until a failure occurred. The distance traveled until a failure occurs is indicated as an index of the conventional tire as 100. The larger the index, the better the high-speed durability.

· Tire extensibility: after vulcanization molding of the pneumatic tire obtained above, those with no defects such as waving in the belt reinforcement layer are regarded as excellent in extensibility as "○", and those with defects are reinforced at the time of expansion The layer was rated as "x" as unable to expand uniformly.

  The results are as shown in Table 1. As compared with the conventional example, in any of Examples 1 to 3, the weight of the belt reinforcing layer can be reduced, and excellent flat spot resistance and high-speed durability are obtained. Was found to be

  In Comparative Examples 1 and 2, the structure of the steel cord was not the n + 1 structure, and the weight of the belt reinforcing layer increased compared to the conventional example.

  In Comparative Examples 1 and 4, the load at 0.5% elongation (N) per steel cord, the number (inch / inch) of steel cords in the belt reinforcement ply, and the number of belt reinforcement plies. Since the product (N / inch) exceeds the upper limit of the predetermined numerical range and can not follow the expansion during vulcanization molding, the cord of the belt reinforcing layer bites into the belt layer, so tire expandability and high speed can be achieved. The durability was inferior.

  In Comparative Example 3, the product (N / N) of the load (N) at 0.5% elongation per steel cord, the number of the steel cords in the belt reinforcement ply (pieces / inch), and the number of belt reinforcement plies inch) was less than the lower limit value of the predetermined numerical range, the rigidity in the circumferential direction of the tire was low, and the high-speed durability was inferior.

  The pneumatic tire of the present invention can be used for various vehicles such as passenger cars, light trucks, buses and the like.

T ... tire 1 ... bead portion 2 ... sidewall portion 3 ... tread portion 4 ... carcass 5 ... bead core 6 ... belt 6A ... first belt ply 6B ... second belt ply 7 ... tread rubber portion 8: Belt reinforcing layer 8A: Belt reinforcing ply 11: Coating rubber 12: Main filament 13: Main filament bundle 14: Wrapping filament 20: Steel cord A: steel cord short diameter direction B: steel cord long diameter direction D1 ... Steel cord major diameter D2 ... Steel cord minor diameter Da ... Steel cord minor diameter after pressing K ... Belt ply thickness direction d ... Main filament diameter d0 ... Wrapping filament diameter

Claims (1)

A pneumatic tire comprising a carcass, a belt disposed on an outer periphery of a crown portion of the carcass, and a belt reinforcing layer disposed on an outer periphery of the belt,
The belt reinforcing layer is formed by arranging four to six steel filaments of the same diameter in a single layer without twisting together to form a main filament bundle, and one steel filament smaller in diameter than the steel filaments. A steel cord of n + 1 structure (n = 4 to 6) wound around the main filament bundle as a wrapping filament is provided with a belt reinforcing ply arranged so that the major axis direction is parallel to the belt outer peripheral surface,
The product (N / inch) of the load at the time of 0.5% extension (N) per steel cord, the number of steel cords in the belt reinforcement ply (pieces / inch) and the number of belt reinforcement plies (N / inch) is 2000 or more A pneumatic tire characterized by being 2500 or less.

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