JP2009040358A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of achieving excellent performance such as high speed durability and stability in steering simultaneously in a well-balanced manner and suitable for being mounted to a vehicle having, in particular, a negative camber angle. <P>SOLUTION: Pieces of edge cushion rubber 6a, 6b are arranged on inner peripheral sides of both ends 5a, 5b of a belt layer 5 in the pneumatic radial tire specified in a direction for being mounted to the vehicle. respectively, a 100% modulus of each edge cushion rubber 6a, 6b at 100°C is set to be equal to a modulus of the coat rubber in the belt layer 5 or smaller, and each of tanδ of the edge cushion rubber 6a at the inner side of the vehicle and the edge cushion rubber 6b at the outer side of the vehicle is set to be smaller than 0.15 and not smaller than 0.15 or more, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire. More specifically, the present invention relates to a pneumatic radial tire that balances high-speed durability and steering stability in a well-balanced manner, and particularly suitable for mounting on a vehicle having a negative camber angle. Regarding tires.

  In the case of a tire that is mounted on a vehicle with a large negative camber angle, such as a recent high-performance vehicle, the contact pressure on the inner side of the vehicle is larger than that on the outer side of the vehicle. However, there is a problem that separation easily occurs.

  On the other hand, in order to suppress separation at the end of the belt layer during high-speed running, there is a proposal to ensure high-speed durability by arranging a low exothermic cushion rubber with a small tan δ on the inner peripheral side at both ends of the belt layer. Yes (see, for example, Patent Document 1). This proposal is considered to be an effective measure for tires for high-speed vehicles with negative camber.

However, in the case of a tire that is attached to a vehicle with a negative camber angle, the load on the tread during straight running and turning travel varies greatly between the inside of the vehicle and the outside of the vehicle. There is a problem that the steering stability performance at the time of high-speed driving, in particular, good steering stability performance at the time of lane change cannot be ensured only by reducing the tan δ.
JP 2003-237313 A

  An object of the present invention is to eliminate such conventional problems, and is suitable for mounting on a pneumatic radial tire that balances high-speed durability performance and steering stability performance in a well-balanced manner, particularly a vehicle having a negative camber angle. Is to provide a simple pneumatic radial tire.

  In order to achieve the above object, the pneumatic radial tire of the present invention winds up an end portion of a carcass layer around a pair of left and right bead cores, and disposes a belt layer on the outer periphery of the carcass layer in a tread portion. In a pneumatic radial tire in which an edge cushion rubber is arranged on the inner peripheral side of each end portion of the tire and a mounting direction is specified for a vehicle equipped with a negative camber, the belt layer has 100% modulus at 100 ° C. of the edge cushion rubber. The tan δ of the edge cushion rubber at 60 ° C. is smaller than that of the outer side of the vehicle and less than 0.15 on the inner side of the vehicle, and less than 0.15 on the outer side of the vehicle. It is characterized by being 15 or more.

Furthermore, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(5).
(1) The 100% modulus at 100 ° C. of the edge cushion rubber is set to the outside of the vehicle, and the 100% modulus at 100 ° C. of the edge cushion rubber is made equal to or less than the 100% modulus of the coat rubber of the belt layer at 100 ° C.
The tan δ at 60 ° C. of the edge cushion rubber is set smaller than the vehicle outer side on the vehicle inner side, less than 0.15 on the vehicle inner side, and larger than the vehicle inner side when set to 0.15 or more on the vehicle outer side.
(2) The cord angle of the carcass layer is set to 90 to 75 ° with respect to the tire circumferential direction, and at least a winding end portion on the vehicle outer side of the carcass layer is extended to the inner peripheral side of the belt layer.
(3) The cap tread rubber in the tread portion is composed of at least two types of rubber compositions having different tan δ adjacent in the tire width direction, and the tan δ at 60 ° C. of the rubber composition is directed from the vehicle inner side to the vehicle outer side. To increase gradually.
(4) At least one main groove extending in the tire circumferential direction is formed on the surface of the tread portion, and the groove area ratio in the ground contact region is made larger on the vehicle inner side centering on the tire equator than on the vehicle outer side.
(5) The flatness is set to 50% or less.

  According to the present invention, since the 100% modulus at 100 ° C. of the belt edge cushion rubber is made equal to or less than the 100% modulus at 100 ° C. of the coat rubber of the belt layer, the stress applied to the end portion of the belt layer as a result of high speed running is reduced to the edge. The cushion rubber can effectively relax, suppress separation, and improve high-speed durability.

  Moreover, since tan δ at 60 ° C. of the belt edge cushion rubber is made smaller on the vehicle inner side than on the vehicle outer side, even when the belt edge cushion rubber is mounted on a vehicle with a negative camber angle, heat generation at the belt layer end on the vehicle inner side is suppressed. While improving the high-speed durability, it is possible to maintain the rigidity at the end of the belt layer on the outside of the vehicle and improve the steering stability during lane change and turning while traveling at high speed.

  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.

  In FIG. 1, a pneumatic radial tire 1 has both ends 3 a and 3 a of a carcass layer 3 wound around a pair of left and right bead cores 2 and 2, and belt layers 5 and 5 are disposed on the outer periphery of the carcass layer 3 in a tread portion 4. In addition, edge cushion rubbers 6a and 6b are arranged on the inner peripheral sides of both end portions 5a and 5b of the inner belt layer 5, and the mounting direction with respect to the vehicle is designated.

  In the pneumatic radial tire 1 of the present invention, the edge cushion rubbers 6a and 6b have the 100% modulus at 100 ° C. equal to or less than the 100% modulus at 100 ° C. of the coat rubber (not shown) of the belt layer 5, The tan δ at 60 ° C. of the edge cushion rubber 6a arranged inside the vehicle is less than 0.15, preferably 0.10 or less, and the tan δ at 60 ° C. of the edge cushion rubber 6b arranged outside the vehicle is 0.15 or more, preferably 0.20 or more.

  As described above, the edge cushion rubbers 6a and 6b have the 100% modulus at 100 ° C. equal to or less than the 100% modulus of the coat rubber of the belt layer 5 at 100 ° C. The edge cushion rubbers 6a and 6b can efficiently relieve the stress applied to 5a and 5b, respectively, to suppress separation and improve high-speed durability.

  Furthermore, the tan δ at 60 ° C. of the edge cushion rubbers 6a and 6b was set to be less than 0.15 for the edge cushion rubber 6a on the vehicle inner side and 0.15 or more for the edge cushion rubber 6b on the vehicle outer side, so that the negative camber angle Even when mounted on a given vehicle, while suppressing the heat generation at the belt layer end portion 5a inside the vehicle and improving the high speed durability, the rigidity at the belt layer end portion 5b outside the vehicle is ensured and the vehicle is running at high speed. It is possible to improve the steering stability during lane change and turning.

  The tan δ of the edge cushion rubbers 6a and 6b described above was measured using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho) under the conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ± 2%, and a temperature of 60 ° C. The value of time.

  In the present invention, the 100% modulus at 100 ° C. of the edge cushion rubber 6a disposed on the vehicle outer side is preferably larger than the 100% modulus at 100 ° C. of the edge cushion rubber 6b disposed on the vehicle inner side. As a result, high-speed durability and steering stability can be balanced at a high level in a well-balanced manner.

  In the embodiment of FIG. 1, the carcass layer 3 is composed of one layer and the belt layer 5 is composed of two layers. However, the number of the carcass layer 3 and the belt layer 5 is not limited to this. . However, the carcass layer 3 may be composed of a small number of layers from the viewpoint of weight reduction. When the carcass layer 3 is constituted by a small number of layers as described above, the cord angle of the carcass layer 3 is set to 90 to 75 ° with respect to the tire circumferential direction, and at least the winding end portion 3a of the carcass layer 3 outside the vehicle is provided. As shown in FIG. 1, the belt layer 5 may be extended to the inner peripheral side. Thereby, the casing rigidity of a tire can be improved and the steering stability at the time of high-speed driving | running | working can be improved reliably.

  As described above, the pneumatic tire 1 in which the rolled-up end portion 3a of the carcass layer 3 extends to the inner peripheral side of the belt layer 5 is provided with a large camber angle because the casing rigidity of the tire is improved. When it is mounted on a vehicle, the end portions 5a and 5b of the belt layer 5 are likely to be distorted. In the present invention, since the low modulus rubber is disposed as the edge cushion rubbers 6a and 6b, the rigidity at the end portions 5a and 5b of the belt layer 5 can be ensured and distortion can be efficiently suppressed.

  In the present invention, preferably, as shown in FIG. 2, the cap tread rubber 4G in the tread portion 4 is made of at least two types (three types in the figure) of rubber compositions 4a, 4b having different tan δ adjacent in the tire width direction. 4c, and the tan δ at 60 ° C. of these rubber compositions 4a, 4b, and 4c may be increased stepwise from the vehicle inner side toward the vehicle outer side. Thereby, when it mounts | wears with the vehicle to which the camber angle | corner was provided, heat_generation | fever of the tread part 4 in a vehicle inner side is suppressed efficiently, and high-speed durability can be improved further.

  In the present invention, more preferably, at least one main groove extending in the tire circumferential direction is formed on the surface of the tread portion 4, and the groove area ratio in the ground contact region is defined as the vehicle inner side and the vehicle outer side centering on the tire equator. Therefore, it is preferable to make these groove area ratios larger on the vehicle inner side than on the vehicle outer side. As a result, when mounted on a vehicle with a camber angle, it is possible to achieve both the suppression of heat generation of the tread portion 4 on the inner side of the vehicle and the enhancement of the grip force against the road surface, thereby further improving the handling stability. it can.

  In the present invention, the cord materials used for the carcass layer 3 and the belt layer 5 are not limited, but it is preferable to use rayon as the carcass layer 3 and steel as the belt layer 5.

  As described above, in the pneumatic radial tire 1 of the present invention, the edge cushion rubbers 6a and 6b are disposed on the inner peripheral sides of the both end portions 5a and 5b of the belt layer 5, respectively, and the modulus of the edge cushion rubbers 6a and 6b is set. Even if it is mounted on a vehicle with a negative camber angle, the tan δ is made smaller on the inner side of the belt than on the outer side of the vehicle, while being equal to or less than the modulus of the coat rubber of the belt layer. It has a good balance with the property, and exhibits an excellent effect particularly on a flat tire having a flatness ratio of 50% or less.

  The tire size is 235 / 40R18, the tire structure is the same as in FIG. 1, all the specifications except the edge cushion rubbers 6a and 6b are common, and the modulus and tan δ of the edge cushion rubbers 6a and 6b are changed as shown in Table 1, Tires (Conventional Examples 1 and 2), tires of the present invention (Examples 1 and 2) and comparative tires (Comparative Examples 1 and 2) were produced. In each tire, the tread pattern was symmetric, and the 100% modulus of the coated rubber of the belt layer 5 at 100 ° C. was 4.7 Mpa.

  These six types of tires were evaluated for high-speed durability and steering stability by the following test methods, respectively, and the results are also shown in Table 1.

[High-speed durability]
Each tire is filled with an air pressure of 250 kPa, and an indoor drum tester (drum diameter: 1707 mm) is attached to the tester with a camber angle (−2.5 °), and 85% of the maximum load capacity specified by JATMA. The vehicle was run for 10 minutes at an initial speed of 200 km / h, and then the speed was increased stepwise by 10 km / h every 10 minutes, and the travel distance until the failure occurred was measured. The results were evaluated by an index with Conventional Example 1 being 100. The larger the value, the better.

[Maneuvering stability]
Each tire is filled with air pressure of 250 kPa, mounted on the front and rear wheels of a vehicle (four-wheel drive, displacement: 4 liters), and an average speed of 130 km / h while repeating a lane change on a test course of 2 km per lap consisting of an asphalt road surface. The car was run for 4 laps, and sensory evaluation was performed by a skilled test driver. The result was evaluated by a five-point method (1: poor, 2: slightly inferior, 3: reference, 4: slightly superior, 5: excellent) with Conventional Example 1 as 3 (reference).

  From Table 1, it can be seen that the tire of the present invention improves the high-speed durability and the handling stability in a well-balanced manner as compared with the conventional tire and the comparative tire.

It is sectional drawing which shows the pneumatic radial tire which consists of embodiment of this invention. It is sectional drawing which shows the pneumatic radial tire which consists of other embodiment of this invention.

Explanation of symbols

l Pneumatic radial tire 2 Bead core 3 Carcass layer 3a Winding end portion of carcass layer 4 Tread portion 5 Belt layer 5a, 5b End portion of belt layer 6a, 6b Edge cushion rubber

Claims (6)

Winding up the end of the carcass layer around a pair of left and right bead cores, placing a belt layer on the outer periphery of the carcass layer in the tread portion, and arranging edge cushion rubber on the inner peripheral side of both ends of the belt layer, In pneumatic radial tires with a specified mounting direction for vehicles with negative camber,
The edge cushion rubber has a 100% modulus at 100 ° C. equal to or less than the 100% modulus of the belt layer coat rubber at 100 ° C., and
A pneumatic radial tire in which the tan δ at 60 ° C. of the edge cushion rubber is smaller than the vehicle outer side on the vehicle inner side, less than 0.15 on the vehicle inner side, and 0.15 or more on the vehicle outer side.   2. The pneumatic radial tire according to claim 1, wherein the edge cushion rubber has a 100% modulus at 100 ° C. larger on the outside of the vehicle than on the inside of the vehicle.   The cord angle of the carcass layer is set to 90 to 75 ° with respect to the tire circumferential direction, and at least a winding end portion on the vehicle outer side of the carcass layer extends to the inner peripheral side of the belt layer. Or a pneumatic radial tire according to 2;   The cap tread rubber in the tread portion is composed of at least two types of rubber compositions having different tan δ adjacent in the tire width direction, and the tan δ at 60 ° C. of the rubber composition is gradually increased from the vehicle inner side toward the vehicle outer side. The pneumatic radial tire according to claim 1, 2 or 3, wherein the pneumatic radial tire is made larger.   The at least one main groove extending in the tire circumferential direction is formed on the surface of the tread portion, and the groove area ratio in the ground contact region is larger on the vehicle inner side centering on the tire equator than on the vehicle outer side. The pneumatic radial tire according to 3 or 4.   The pneumatic radial tire according to claim 1, wherein the flatness is 50% or less.

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