JP2008006890A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire improved in belt durability in a high-load condition, reducing the load noise, in the case of using an organic fiber cord having high heat shrinkage stress for a belt cover layer. <P>SOLUTION: The belt cover layer formed by winding the organic fiber cord having 3.5 N or more of heat shrinkage stress at 150°C in the tire circumferential direction is arranged at least in both ends of the belt layers 4 and 5 on the peripheral side thereof. Rubber strips 7 and 7 for covering terminals of the belt layers 4 and 5 are respectively inserted between the belt cover layer 6 and both the ends of the belt layers 4 and 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a pneumatic radial tire, and more particularly, a pneumatic radial tire that improves belt durability while reducing road noise when a belt cover layer is composed of a highly heat-shrinkable organic fiber cord. Regarding tires.

  In general, a pneumatic radial tire for high-speed running forms a belt cover layer in which a heat-shrinkable organic fiber cord is wound in the tire circumferential direction on the outer peripheral side of the belt layer, and the belt layer at the time of high-speed running is formed by this belt cover layer. High-speed durability is improved by suppressing the rising of the end, but this belt cover layer simultaneously increases the rigidity of the shoulder area at the end of the belt layer, thus reducing road noise especially in the mid-frequency range. (See, for example, Patent Document 1).

The above-described road noise reduction effect can be increased as the heat shrinkage stress of the fiber cord used for the belt cover layer is increased. However, if the heat shrinkage stress of the fiber cord is made too high, the fiber cord bites into the belt layer side due to heat at the time of tire vulcanization, and the rubber thickness between the belt layer and the belt cover layer is reduced. Separation is likely to occur at the end portion. As a result, particularly when a high load is applied, there is a problem that the belt end portion flutters during high-speed running, and the belt cover layer breaks in the vicinity of the end of the belt layer due to its behavior.
JP 7-310251 A

  The object of the present invention is to eliminate such conventional problems, and in the case where an organic fiber cord having a high heat shrinkage stress is used as a belt cover layer, the belt durability in a high load state is achieved while reducing road noise. An object of the present invention is to provide a pneumatic radial tire with improved performance.

  In order to achieve the above object, the pneumatic radial tire of the present invention has a plurality of belt layers that intersect the cord direction on the outer periphery of the carcass layer in the tread portion, and at least both ends on the outer peripheral side of the belt layer. A pneumatic radial tire having a belt cover layer in which an organic fiber cord having a thermal shrinkage stress at 150 ° C. of 3.5 N or more is wound in a tire circumferential direction, the belt cover layer and both ends of the belt layer The gist is that rubber strips are inserted so as to cover the ends of the belt layers.

Furthermore, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(3).
(1) The thickness of the rubber strip is 0.5 to 1.0 mm.
(2) A ratio of 100% modulus A of the rubber strip to 4.5 to 7.0 MPa, and a ratio A / B of the modulus A and 100% modulus B of the coated rubber covering the belt layer adjacent to the rubber strip. Is set to 0.95 to 1.05.
(3) The organic fiber cord is a material selected from polyester fiber, polyamide fiber, and polyketone fiber.

  According to the present invention, when the belt cover layer is composed of an organic fiber cord having a thermal shrinkage stress at 150 ° C. of 3.5 N or more, the end of the belt layer is provided between the belt cover layer and both ends of the belt layer. Since the rubber strip is arranged so as to cover, even if a large heat shrinkage force acts on the belt cover layer during the vulcanization process of the tire, at both ends of the belt layer, there is a gap between the belt layer and the belt cover layer. Since an appropriate rubber thickness can be ensured, separation at the belt layer end portion and breakage of the belt cover layer accompanying the separation can be suppressed, and belt durability can be improved.

  In addition, at least both end portions of the belt layer are restrained by the belt cover layer having a high heat shrinkage stress, so that it is possible to further reduce road noise.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a half cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view showing an arrangement relationship of a belt layer and a belt cover layer in the tire of FIG. is there.

  In FIG. 1, a pneumatic radial tire 1 has a plurality (two layers in the figure) of belt layers 4 and 5 that cross the cord direction on the outer periphery of the carcass layer 3 in the tread portion 2, and the belt layers 4 and 5. A belt cover layer 6 in which an organic fiber cord having a thermal shrinkage stress at 150 ° C. of 3.5 N or more is wound in the tire circumferential direction at least at both ends on the outer peripheral side (the full width of the belt layers 4 and 5 in the figure). Yes.

  For the organic fiber cord constituting the belt cover layer 6, high heat shrinkable fibers having a heat shrinkage stress at 150 ° C. of 3.5 N or more, preferably 20.0 N or less, more preferably 4.0 to 15.0 N are used. Between the belt cover layer 6 and both end portions of the belt layers 4 and 5, rubber strips 7 and 7 are arranged so as to cover the ends of the belt layers 4 and 5, respectively.

  As a result, even if a large thermal contraction force acts on the belt cover layer 6 in the vulcanization process of the tire, the belt layers 4 and 5 are properly disposed between the belt layers 4 and 5 and the belt cover layer 6 at both ends. Since the rubber thickness can be ensured, it is possible to suppress separation at the belt layer 4 and 5 end portions and breakage of the belt cover layer 6 accompanying the separation, and belt durability can be improved. In addition, since at least both ends of the belt layers 4 and 5 are restrained by the belt cover layer 6 having a high thermal shrinkage stress, it is possible to further reduce road noise.

  FIG. 2 is a schematic cross-sectional view showing the arrangement relationship of the belt layer and the belt cover layer in the tire of FIG. In the present invention, the thickness t of the rubber strips 7 and 7 inserted between the belt cover layer 6 and both ends of the belt layers 4 and 5 is preferably 0.5 to 1.0 mm. If it is less than 0.5 mm, the effect of suppressing the breakage of the belt cover layer 6 cannot be sufficiently obtained, and if it exceeds 1.0 mm, the riding comfort of the tire is reduced. On the other hand, since the width w of the rubber strip 7 is naturally determined by the distance between the ends of the belt layers 4 and 5, it is not particularly limited, but it is assumed that the rubber strip 7 covers both ends of the belt layers 4 and 5. Usually, it is set to about 10 to 20 mm. If the width w of the rubber strip 7 is excessively increased, the riding comfort of the tire is reduced.

  In the present invention, the rubber strip 7 is preferably made of rubber having the same physical properties as the coated rubber covering the belt cords of the adjacent belt layers 4 and 5. From this point of view, the 100% modulus A of the rubber strip 7 is set to 4.5 to 7.0 MPa, preferably 5.0 to 6.0 MPa, and the belt layers 4 and 5 adjacent to the modulus A are covered. The ratio A / B of the coated rubber to 100% modulus B is preferably 0.95 to 1.05. Thereby, the separation in the edge part of the belt layers 4 and 5 can be prevented reliably.

  As described above, the organic fiber cord constituting the belt cover layer 6 has a heat shrinkage stress of 3.5 N at 150 ° C. in order to ensure an excellent road noise reduction effect and belt durability improvement effect at the same time. The organic fiber cords described above are used. As the organic fiber cords, cord materials selected from polyester fibers, polyamide fibers, and polyketone fibers are preferably used.

  In the above-described embodiment, the case where the belt cover layer 6 is disposed over the entire width of the belt layers 4 and 5 has been described. However, the belt cover layer 6 is disposed only at both ends of the belt layers 4 and 5. Further, as shown in FIG. 1, the belt cover layer 6 is disposed over the entire width of the belt layers 4 and 5, and another belt cover layer 6 is disposed on the outer peripheral side at both ends of the belt cover layer 6. In some cases.

  The tire size is 195 / 65R15 91H, the tire structure is the same as in FIG. 1, and as shown in Table 1, a conventional tire without a rubber strip (conventional example) and a rubber strip with a width of 15 mm as shown in FIG. Comparison between the tires of the present invention (Examples 1 to 3) arranged at the left and right ends of the layers 4 and 5 and the rubber strips protruding from both ends of the belt layer 4 by 5 mm and arranged over the entire width of the belt layers 4 and 5 Tires (comparative examples) were produced.

  In preparing each tire, the cord material and cord heat shrinkage stress of the belt cover layer were made different as shown in Table 1. In the tire of the present invention and the comparative tire, the thickness of the rubber strip was 0.6 mm, and the 100% modulus of the coated rubber covering the belt layers 4 and 5 in each tire was set to 5.5 MPa. In Table 1, 66N represents nylon 66 fiber, PET represents polyester fiber, and POK represents polyketone fiber.

These five types of tires were evaluated for belt durability, road noise and riding comfort by the following test methods, respectively, and the results are also shown in Table 1.
[Belt durability]
Each tire is filled with an air pressure of 240 kPa, and a load corresponding to 88% of the maximum load capacity specified by JATMA is applied by an indoor drum endurance test (drum diameter: 1707 mm), and the running speed is 81 km / h for 2 hours. Each time the vehicle was run while increasing the load by 13%, the running distance until the tire broke was measured. The result was displayed by the index | exponent which sets the conventional example to 100. Larger values indicate better belt durability.
[Road noise]
Each tire is filled with an air pressure of 200 kPa and attached to the front and rear wheels of the vehicle (Mark II, 2.0 Grande). The test course consisting of an asphalt road is run at an average speed of 100 km / h and attached to the backrest of the driver's seat. The sound pressure (decibel) in the range of 31.5 to 1250 Hz was measured with a sound collecting microphone. The result was displayed by the index | exponent which sets the conventional example to 100. It shows that the reduction effect of road noise is excellent, so that a numerical value is large.
[Ride comfort]
Sensory evaluation of riding comfort was also performed through the above-mentioned [road noise] test. The result was displayed by the index | exponent which sets the conventional example to 100. Larger values indicate better ride comfort.

  From Table 1, it can be seen that the tire of the present invention (Example 1) is improved in belt durability in a high load state while maintaining the same road noise reduction effect as compared with the conventional tire (Conventional example). Recognize. In the tire of the present invention (Example 2), the heat shrinkage stress of the belt cover layer is made higher than that of Example 1, so that the effect of reducing road noise and the durability of the belt in a high load state are further improved. . Further, in the tire of the present invention (Example 3), the heat shrinkage stress of the belt cover layer is made higher than that in Example 2, so that the road noise reduction effect is further improved, but the belt durability is improved. The effect is slightly reduced.

  In contrast, the comparative tire (comparative example) in which the rubber strip is disposed over the entire width of the belt layer is found to have reduced riding comfort.

1 is a half sectional view showing a pneumatic radial tire according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a positional relationship between a belt layer and a belt cover layer in the tire of FIG.

Explanation of symbols

l Pneumatic radial tire 2 Tread part 3 Carcass layer 4, 5 Belt layer 6 Belt cover layer 7 Rubber strip

Claims (4)

A plurality of belt layers crossing the cord direction are arranged on the outer periphery of the carcass layer in the tread portion, and an organic fiber cord having a heat shrinkage stress of 3.5 N or more at 150 ° C. is applied to at least both ends on the outer peripheral side of the belt layer. A pneumatic radial tire having a belt cover layer wound around the tire in the circumferential direction,
A pneumatic radial tire in which a rubber strip is inserted between the belt cover layer and both ends of the belt layer so as to cover the ends of the belt layer.   The pneumatic radial tire according to claim 1, wherein the rubber strip has a thickness of 0.5 to 1.0 mm.   The 100% modulus A of the rubber strip is set to 4.5 to 7.0 MPa, and the ratio A / B of the modulus A to the 100% modulus B of the coated rubber covering the belt layer adjacent to the rubber strip is set to 0.00. The pneumatic radial tire according to claim 1 or 2, wherein the pneumatic radial tire is 95 to 1.05. The pneumatic radial tire according to claim 1, 2 or 3, wherein the organic fiber cord is made of a material selected from a polyester fiber, a polyamide fiber, and a polyketone fiber.

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