JP2011068245A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of reducing road noise without degrading ride comfort and drive stability. <P>SOLUTION: The pneumatic radial tire 1 includes a belt cover layer 6 composed of a steel cord 6s spirally wound at a substantial angle of 0° to a tire peripheral direction in the whole range on the outer-periphery side and/or both-end ranges of belt layers 4, 5. A damping ratio ζ of the steel cord 6s constituting the belt cover layer 6 is set at 0.008-0.017. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire in which road noise is reduced without impairing ride comfort and steering stability.

  Conventionally, as a technique for ensuring high-speed durability of a tire and reducing road noise, a belt cover in which a heat-shrinkable organic fiber cord made of nylon or the like is spirally wound around the outer circumferential side of the belt layer in the tire circumferential direction. Arranging layers has been widely done. In recent years, as automobiles have become more sophisticated and quieter, there has been a strong demand for further reduction of high-speed durability and road noise. As a countermeasure, high-elasticity machine fiber cords and steel cords are used for the belt cover layer. Attempts to use have been made (see, for example, Patent Document 1).

  However, when a steel cord with a high elastic modulus is used for the belt cover layer, the steel cord has a low elongation, so the ride comfort deteriorates. At the same time, the steel cord is belted in the lift process during vulcanization molding. There is a problem that the layer gauge bites into the layer, and an interlayer gauge between the belt cover layer and the belt layer cannot be secured, and it is extremely difficult to obtain desired high-speed durability and road noise.

  As a countermeasure, Patent Document 2 proposes to use a composite fiber cord in which a steel monofilament is wound around an organic fiber cord at a specific angle as a cover cord constituting the belt cover layer. However, in this proposal, the tagging effect due to the belt cover layer is insufficient, and it is difficult to ensure the steering stability, and further, the improvement effect of road noise is limited, and further improvement has been demanded.

JP 2000-255214 A JP 2000-301911 A

  An object of the present invention is to solve the above-described conventional problems, and to provide a pneumatic radial tire that reduces road noise without impairing riding comfort and driving stability. .

In order to achieve the above object, a pneumatic radial tire of the present invention is provided with a plurality of belt layers whose cord directions intersect each other on the outer periphery of a carcass layer in a tread portion, In a pneumatic radial tire provided with a belt cover layer made of a steel cord spirally wound at an angle of substantially 0 ° with respect to the tire circumferential direction at both end regions, the pneumatic radial tire is defined by the following formula of the steel cord: The damping ratio ζ is 0.008 to 0.017.
ζ = [1 / {2π (m−1)}] × ln (Hα / Hβ)
(However, Hα is the height of the vibration wave after α seconds have passed since the vibration was input to the steel cord, Hβ is the vibration after β seconds (α <β) has elapsed since the vibration was input to the steel cord. Wave height, m: Number of vibration waves from the time α seconds passed after the vibration was input to the steel cord to the time β seconds passed)

  Furthermore, in the above-described configuration, the steel cord is made of M strands (provided that N strands (however, N = 3 to 4) of strands having a strand diameter of 0.08 to 0.15 mm are twisted in advance). , M = 3 to 5) It is preferable to form an M × N structure by drawing them together and twisting them together. In this case, the twist direction of the steel strand in the strand and the twist direction of the strand in the steel cord may be the same. Furthermore, the strand pitch of the steel strands in the strand is preferably 1.0 to 2.0 mm, and the strand pitch of the strands in the steel cord is preferably 2.0 to 5.0 mm.

  According to the present invention described above, since the damping ratio of the steel cord constituting the belt cover layer disposed on the outer peripheral side of the belt layer is set to 0.008 to 0.017, the steel cord is used in the lift process during vulcanization molding. It is possible to reduce road noise without hindering the ride comfort and steering stability in the tire after vulcanization molding while efficiently preventing the belt from biting into the belt layer.

  Here, if the damping ratio of the steel cord is less than 0.008, the vibration during running cannot be resolved and the damping performance deteriorates, so that the ride comfort and the handling stability are insufficient, and at the same time the road noise reduction effect is insufficient. Thus, if it exceeds 0.017, the damping performance is too good, and the ride comfort and the handling stability are insufficient.

It is sectional drawing which shows an example of the pneumatic radial tire which consists of embodiment of this invention. It is sectional drawing which shows an example of the steel cord which comprises the belt cover layer in the tire of FIG. It is explanatory drawing which shows an example of the method of measuring the attenuation ratio of a steel cord. It is explanatory drawing which shows the attenuation | damping condition of the vibration wave of the steel cord obtained by the measurement of FIG.

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

  FIG. 1 is a cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing an example of a steel cord constituting a belt cover layer in the tire of FIG.

  In FIG. 1, a pneumatic radial tire 1 has a plurality of belt layers 4 and 5 (two layers in the figure) in which the cord directions intersect each other on the outer periphery of the carcass layer 3 in the tread portion 2, and the belt layer 4, A belt cover layer 6 made of a steel cord spirally wound at an angle of substantially 0 ° (more specifically, an angle of 5 ° or less) with respect to the tire circumferential direction is provided on the entire outer peripheral side and both end regions of the tire 5. ing.

The steel cord 6s constituting the belt cover layer 6 has a form as illustrated in FIG. 2, and a damping ratio ζ defined by the following formula is 0.008 to 0.017, preferably 0.011 to 0.00. 014 is set.
ζ = [1 / {2π (m−1)}] × ln (Hα / Hβ)
(However, Hα: the height of the vibration wave after the passage of α seconds after the vibration is input to the steel cord 6s, Hβ: after the passage of β seconds (α <β) after the vibration is input to the steel cord 6s. Vibration wave height, m: Number of vibration waves from the time α seconds passed after the vibration was input to the steel cord 6s to the time β seconds passed)

  Thus, by setting the damping ratio ζ of the steel cord 6s constituting the belt cover layer 6 to 0.008 to 0.017, the steel cord 6s bites into the belt layer 5 in the lift process during vulcanization molding. Road noise can be reduced without hindering riding comfort and steering stability in a vulcanized tire while preventing it efficiently.

  Here, if the damping ratio ζ of the steel cord 6s is less than 0.008, the vibration during running cannot be resolved and the damping performance is deteriorated, so that the riding comfort and the handling stability are insufficient, and at the same time the road noise reduction effect is insufficient. Therefore, if it exceeds 0.017, the damping performance is too good, and the ride comfort and the handling stability are insufficient.

  The above-described damping ratio ζ of the steel cord 6s is measured based on the steel cord 6s separated from the belt cover layer 6 after the belt cover layer 6 is taken out from the vulcanized tire.

  The damping ratio ζ of the steel cord 6s in the present invention is defined as described above. More specifically, for example, it is obtained as follows.

  That is, as shown in FIG. 3, the length of the sample of the steel cord 6s is set to 320 mm, the sample is bridged over the support tools 10 and 10 separated by 300 mm, and the sample protrudes from both ends of the support tools 10 and 10 respectively. A 500 g weight 11, 11 is attached, and a reflective tape 12 for measuring the displacement of the vibration wave using a laser is attached to the center position in the length direction of the sample.

Then, a thread 13 having a length of 20 mm is attached to a position P 50 mm away from one end of the sample (the position of the right support 10 in the figure), and the lower end Q of the thread 13 is held by hand and pulled downward by 20 mm. The steel cord 6s is vibrated by releasing it. Then, the heights Hα and Hβ of the vibration waves after α seconds have elapsed after the vibration is input (for example, after 100 milliseconds have elapsed) and β seconds have elapsed (for example, after 160 milliseconds have elapsed), The number m is read by a laser device (not shown), and the attenuation ratio (ζ) is obtained by the following equation. In addition, the attenuation state of the vibration wave of the steel cord 6s after inputting the vibration is shown in FIG.
Damping ratio (ζ) = [1 / {2π (m−1)}] × ln (Hα / Hβ)
Therefore, the damping ratio (ζ) obtained by this equation indicates that the larger the numerical value, the easier it is to attenuate.

  In the embodiment of FIG. 1 described above, the belt cover layer 6 is disposed in the entire outer peripheral side and both end regions of the belt layer 5, but the position where the belt cover layer 6 is disposed is limited to this. Instead, the belt cover layer 6 may be disposed only in the entire outer peripheral side of the belt layer 5 or only in both end regions. Furthermore, the belt cover layer 6 may be divided into a plurality of parts in the tire width direction.

  In the present invention, the steel cord 6s constituting the belt cover layer 6 has N steel wires 7 having a wire diameter of 0.08 to 0.15 mm in advance (N = 3 to 3) as illustrated in FIG. 4) When strand S is formed by twisting, M strands (where M = 3 to 5) are aligned and twisted together to form an M × N structure (3 × 3 structure in the figure). Good. Thereby, the flexibility of the steel cord 6s is ensured, and the steel cord 6s can be efficiently prevented from biting into the belt layer 5 in the lift process during vulcanization molding.

  Here, when the wire diameter is less than 0.08 mm, the effect of reducing road noise is insufficient, and when the wire diameter exceeds 0.15 mm, the steel cord belt layer 5 in the lift process during vulcanization molding is obtained. It becomes difficult to suppress the biting of the material, and the effect of improving the high-speed durability is insufficient.

  The steel cord 6s constituting the belt cover layer 6 of the present invention may be formed so that the twist direction of the steel strand 7 in the strand S and the twist direction of the strand S in the steel cord 6s are the same. Thereby, the flexibility of the steel cord 6s is ensured, and the steel cord 6s can be more efficiently prevented from biting into the belt layer 5 in the lift process during vulcanization molding.

  More preferably, the twist pitch Ps of the steel strand 7 in the strand S is set to 1.0 to 2.0 mm, most preferably 1.3 to 1.7 mm, and the twist pitch Pc of the strand S in the steel cord 6s is set. The thickness may be set to 2.0 to 5.0 mm, most preferably 3.0 to 4.0 mm. As a result, road noise can be more reliably reduced while maintaining good ride comfort and steering stability.

  Here, if the twist pitch Ps of the steel element wire 7 is less than 1.0 mm, or if the twist pitch Pc of the strand S is less than 2.0 mm, the hook effect of the belt cover layer 6 is insufficient and road noise is reduced. If the reduction effect cannot be obtained sufficiently, and the twist pitch Ps of the steel strand 7 is more than 2.0 mm or the strand pitch Pc of the strand S is more than 5.0 mm, In the lift process, the steel cord 6s easily bites into the belt layer 5 and causes high-speed durability to deteriorate.

  As described above, in the pneumatic radial tire of the present invention, the steel cord constituting the belt cover layer has a damping ratio of 0.008 to 0.017, so that the steel cord is belted in the lift process during vulcanization molding. It is possible to reduce road noise without impairing the ride comfort and handling stability of the tire after vulcanization while efficiently preventing it from getting into the layer. It can be preferably applied to high-performance vehicles.

  Compared with tires of the present invention (Examples 1 to 3) in which the tire size is 205 / 55R16, the tire structure is as shown in FIG. 1, and the steel cord 6s constituting the belt cover layer 6 has a different damping ratio as shown in Table 1. Tires (Comparative Examples 1 and 2) were produced. In each tire, the structure of the steel cord 6s constituting the belt cover layer 6 is 3 × 3, the strand diameter is 0.10 mm, the twist pitch Ps of the steel strand 7 in the strand S is 1.5 mm, and the strands S The twisted pitch Pc of the steel is 3.5 mm, the two belt layers 4 and 5 are made of steel cord, the structure is 1 × 4, the wire diameter is 0.28 mm, the damping ratio is 0.020, the tire The cord angle with respect to the circumferential direction was 30 °.

  For comparison, a composite fiber cord in which a steel monofilament (elementary wire diameter: 0.17 mm) is wound at an angle of 30 ° around a nylon fiber cord (840d / 2) is used as a cord constituting the belt cover layer 6. A comparative tire (Comparative Example 3) was prepared.

  These six types of tires were evaluated for ride comfort, handling stability and road noise characteristics by the following test methods, and the results are also shown in Table 1.

[Ride comfort]
Each tire is assembled in a rim (size: 6.5JJ), filled with air pressure 200kPa and mounted on the front and rear wheels of a 2500cc domestic passenger car, and a test course consisting of asphalt road surface at a speed of 50-80km / h It was run and sensory evaluation was performed by three skilled test drivers. The results were averaged and listed in Table 1 by the 5-point method with Comparative Example 1 taken as 3. The larger the value, the better the ride comfort.

[Maneuvering stability]
Each tire is assembled in a rim (size: 6.5JJ), filled with air pressure 200kPa and mounted on the front and rear wheels of a 2500cc domestic passenger car. It was run and sensory evaluation was performed by three skilled test drivers. The results were averaged and listed in Table 1 by the 5-point method with Comparative Example 1 taken as 3. The larger the value, the better the steering stability.

[Road noise characteristics]
Each tire is installed in the rim (size: 6.5JJ), filled with air pressure 200kPa, and installed on the front and rear wheels of a 2500cc domestic passenger car with a sound collecting microphone installed inside the driver's seat window. A test course consisting of a road surface was run at a speed of 50 km / h, and the sound pressure in the vicinity of a frequency of 315 Hz was measured. The results are shown in Table 1 using an index with Comparative Example 1 as 100. The smaller the value, the better the road noise characteristics.

  From Table 1, it can be seen that the tire of the present invention reduces road noise without impairing ride comfort and steering stability as compared with Comparative Examples 1 and 2. In addition, Comparative Example 3 using a composite fiber cord as a cord constituting the belt cover layer has insufficient effects of improving ride comfort, handling stability and road noise characteristics, respectively, as compared with the tire of the present invention. It was confirmed.

l Pneumatic radial tire 2 Tread part 3 Carcass layer 4, 5 Belt layer 6 Belt cover layer 6s Steel cord 7 Steel strand S Strand ζ Damping ratio

Claims (4)

A plurality of belt layers having cord directions intersecting between the layers are arranged on the outer periphery of the carcass layer in the tread portion, and substantially 0 ° with respect to the tire circumferential direction in the entire outer peripheral side and / or both end regions of the belt layer. In a pneumatic radial tire provided with a belt cover layer made of a steel cord spirally wound at an angle of
A pneumatic radial tire having a damping ratio ζ defined by the following formula of the steel cord of 0.008 to 0.017.
ζ = [1 / {2π (m−1)}] × ln (Hα / Hβ)
(However, Hα is the height of the vibration wave after α seconds have passed since the vibration was input to the steel cord, Hβ is the vibration after β seconds (α <β) has elapsed since the vibration was input to the steel cord. Wave height, m: Number of vibration waves from the time α seconds passed after the vibration was input to the steel cord to the time β seconds passed)   The steel cord has M strands (provided that M = 3 to 5) formed by twisting N strands (where N = 3 to 4) of steel strands having a strand diameter of 0.08 to 0.15 mm. The pneumatic radial tire according to claim 1, comprising an M × N structure formed by twisting and twisting each other.   The pneumatic radial tire according to claim 2, wherein the twist direction of the steel strand in the strand and the twist direction of the strand in the steel cord are the same.   The pneumatic radial according to claim 2 or 3, wherein the strand pitch of the steel strand in the strand is 1.0 to 2.0 mm and the strand pitch of the strand in the steel cord is 2.0 to 5.0 mm. tire.