JP2011042325A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of maintaining excellent steering stability performance and excellent ride quality performance, and capable of reducing the rolling resistance while preventing degradation of the braking performance. <P>SOLUTION: In the pneumatic tire, a plurality of main grooves 2 extending in the circumferential direction, and a plurality of land parts 3 divided by the main grooves 2 are formed in a tread surface 1, a rubber layer 6 made of low-modulus rubber having the 100% tensile modulus of 0.1-1.0 kgf/mm<SP>2</SP>is arranged on a groove bottom surface including both groove bottom corner parts and a groove wall surface in an area of 35% of the groove depth in at least one main groove 2 out of the plurality of main grooves 2, and the rubber layer 6 is divided by the groove bottom surface of the main groove 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a plurality of main grooves extending in the circumferential direction and a plurality of land portions divided by the main grooves are formed on a tread surface.

  Conventionally, in order to reduce the rolling resistance of pneumatic tires, the tire mass can be reduced by reducing the tread thickness, etc., or the loss tangent (loss tangent = loss elastic modulus) as rubber (tread rubber) placed in the tread part. / Storage rubber (hereinafter simply referred to as “tan δ”) is used. Here, although the rolling resistance can be reduced by using a rubber having a low tan δ, the tread rubber is easily bent, so that the contact area of the tread rubber is reduced, the steering stability performance of the pneumatic tire is deteriorated, and braking is performed. There is a decrease in performance and further deterioration in ride performance. Thus, the reduction in rolling resistance of the pneumatic tire and the steering stability performance and riding comfort performance are in a trade-off relationship. Therefore, it is very difficult to reduce the rolling resistance of a pneumatic tire while maintaining performance such as steering stability performance and riding comfort performance, and there is still much room for improvement.

Here, in the following Patent Document 1, in a heavy-duty pneumatic tire including a tread portion that is formed on the outside and formed with a cap rubber formed with a groove that opens to the outside, and a base rubber disposed on the inside thereof, The groove bottom rubber is disposed at least at the groove bottom edge of the groove, and the dynamic storage elastic modulus E of the cap rubber (C), the base rubber (B), and the groove bottom rubber (G) is E _B > E _C > E A pneumatic tire with _G relation is described. According to such a configuration, although the occurrence of cracks in the groove of the tread portion can be suppressed, it is not possible to reduce the rolling resistance of the pneumatic tire while maintaining performance such as steering stability performance and riding comfort performance.

  Further, in Patent Document 2 below, the groove wall surface located in the lower region of 30 to 50% of the groove depth from the groove bottom of the circumferential groove extending in the tire circumferential direction on the tread surface has a JIS hardness of 40 to 50 and a thickness. A pneumatic tire having a rubber layer of 2 mm or less is described. According to such a configuration, although the steering stability performance on the snowy road surface is improved, the steering stability performance on the dry road surface tends to be deteriorated, and it is possible to achieve both the steering stability performance of the pneumatic tire and the reduction of the rolling resistance. Absent.

Japanese Patent Laid-Open No. 06-191221 JP 2004-123021 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire with reduced rolling resistance while maintaining good steering stability performance and riding comfort performance and preventing deterioration of braking performance. There is to do.

  In order to achieve the above object, the present inventors use a pneumatic tire in which a plurality of main grooves extending in the circumferential direction and a plurality of land portions divided by the main grooves are formed on the tread surface. The degree of distortion in the land area during tire running was measured, and the relationship between the degree of distortion and rolling resistance was studied earnestly. As a result, in such a pneumatic tire, in the tire meridian direction cross section, a deformation in which the vicinity of the center of the land portion wall surface swells toward the main groove side during tire traveling, a so-called saddle-shaped deformation, causes a change in the main groove. It has been found that the distortion increases at the corner of the groove bottom where the radius of curvature is small and the distortion tends to concentrate. As a result of further investigations, the present inventors said that by reducing the distortion at the corner of the bottom of the main groove, heat generation at this portion can be suppressed and the rolling resistance of the pneumatic tire can be reduced. Obtained knowledge. The present invention has been made as a result of the above-described studies, and achieves the above-described object with the following configuration.

That is, the pneumatic tire according to the present invention is a pneumatic tire in which a plurality of main grooves extending in the circumferential direction and a plurality of land portions divided by the main grooves are formed on a tread surface. At least one of the main grooves has a groove bottom surface including both corners of the groove and a groove wall surface in a region of 35% of the groove depth from the groove bottom with a 100% tensile modulus of 0.1 to 0.1%. A rubber layer made of a low modulus rubber of 1.0 kgf / mm ² is disposed, and the rubber layer is divided at the groove bottom surface of the main groove.

In the pneumatic tire, a rubber layer made of a low modulus rubber of 0.1 to 1.0 kgf / mm ² at 100% tensile modulus on the groove bottom surface including both corners of the groove and the groove wall surface in the main tire. Is arranged. As a result, the concentration of strain at the groove bottom corner portion caused by the deformation of the land portion at the time of tire contact is alleviated, and heat generation at the groove bottom corner portion is suppressed. As a result, the rolling resistance of the pneumatic tire can be reduced.

  By the way, the rubber disposed in the tread portion of the pneumatic tire contributes to the out-of-plane bending rigidity in the width direction of the tire tread portion together with the belt disposed in the tire radial direction from the tread portion. Among the rubbers arranged in the section, the rubber arranged on the bottom surface of the main groove where the rubber thickness is particularly thin in the tire radial direction serves as a supporting point in the bending direction, so that the out-of-plane bending rigidity in the width direction. Will greatly contribute. In the pneumatic tire, the rubber layer made of low modulus rubber is divided at the groove bottom surface of the main groove. That is, since not all of the groove bottom surface of the main groove is composed of low modulus rubber, it is possible to suppress a decrease in out-of-plane bending rigidity in the width direction. As a result, in the pneumatic tire, steering stability performance and riding comfort performance can be maintained.

  In addition, in the pneumatic tire, the rubber layer made of low modulus rubber is disposed only on the groove wall surface in the region of 35% of the groove depth from the groove bottom. That is, since the rubber layer made of the low modulus rubber is not exposed on the tread surface, the rubber physical properties are uniform over the entire tread surface, and a reduction in braking performance can be prevented.

  In the pneumatic tire, it is preferable that a split width in the width direction of the rubber layer is 20 to 50% with respect to a groove width of the main groove on the tread surface. According to such a configuration, the balance between the relaxation of the strain concentration at the corner of the groove bottom caused by the deformation of the land portion at the time of tire contact and the suppression of the decrease in the out-of-plane bending rigidity in the width direction of the tire tread portion is more balanced. A good balance can be achieved. As a result, it is possible to achieve both a reduction in rolling resistance of a pneumatic tire and maintenance and improvement of steering stability performance and riding comfort performance in a more balanced manner.

  In the pneumatic tire, the rubber layer is preferably formed in a pair of crescent shapes in a meridian cross section. According to such a configuration, by reducing the amount of rubber layer made of low modulus rubber to the minimum necessary, while reducing the concentration of strain at the groove bottom corner caused by deformation of the land portion at the time of tire contact, A decrease in the out-of-plane bending rigidity of the tire tread surface in the width direction can be further suppressed. As a result, the reduction in rolling resistance of the pneumatic tire and the maintenance and improvement of the steering stability performance and the riding comfort performance can be particularly well balanced, and the deterioration of the braking performance can be surely prevented.

An example of a meridional direction sectional view of a tread portion of the pneumatic tire of the present invention An example of a partially enlarged view of the main groove portion of FIG. Another example of a partially enlarged view of the main groove portion of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an example of a meridional direction sectional view of a tread portion of a pneumatic tire of the present invention, and FIG. 2 is a partially enlarged view of a main groove portion of FIG. In FIG. 1, WD indicates the tire width direction.

  As shown in FIG. 1, the pneumatic tire according to the present invention has a tread tread surface 1 formed with a plurality of main grooves 2 extending in the circumferential direction and a plurality of land portions 3 partitioned by the main grooves 2. A belt layer 5 composed of at least one belt is provided on the inner side in the tire radial direction from the tread including the portion 3, and a carcass layer 4 is provided on the inner side in the tire radial direction of the belt layer 5. Furthermore, although not shown, the pneumatic tire according to the present invention includes a pair of left and right annular bead cores, and both ends of the carcass layer 4 are locked between the bead cores.

  In the present invention, the land portion 3 may be composed of ribs separated only by a plurality of main grooves 2 extending in the circumferential direction, or a plurality of main grooves 2 extending in the circumferential direction and in the width direction. It may be composed of blocks divided by extending lateral grooves, and may be composed of ribs and blocks.

As shown in FIGS. 1 and 2, in the pneumatic tire according to the present invention, at least one main groove 2 among the plurality of main grooves 2 includes a groove bottom surface including both groove bottom corners of the main groove 2, and A rubber layer 6 made of low modulus rubber having a tensile modulus of 100% and 0.1 to 1.0 kgf / mm ² is disposed on a groove wall surface in a region 35% of the groove depth from the groove bottom. According to this configuration, since the rubber layer 6 made of low modulus rubber is disposed on the groove bottom surface and the groove wall surface including the corners of the groove bottom where distortion tends to concentrate in the main groove 2, The concentration of strain at the groove bottom corner generated by the deformation of the portion 3 is alleviated, and heat generation at the groove bottom corner is suppressed. As a result, the rolling resistance of the pneumatic tire can be reduced. In the present invention, the “groove bottom corner” is a portion of the main groove 2 having a small radius of curvature (portion R indicated by a dotted line in FIG. 1), and the land portion 3 is deformed when the tire travels. It means the part where distortion is concentrated most.

  In the present embodiment, as shown in FIGS. 1 and 2, an example is shown in which the thickness of the rubber layer 6 is substantially constant on the groove bottom surface and the groove wall surface. When the thickness of the rubber layer 6 is substantially constant, the thickness is preferably 3.0 mm or less (approximately 35% or less of the groove depth H1 of the main groove 2).

  The rubber layer 6 is disposed on the groove bottom surface including the groove bottom corners of all the main grooves 2 among the plurality of main grooves 2 and on the groove wall surface in a region 35% of the groove depth from the groove bottom. Alternatively, the land portion 3 may be disposed only in a portion where the land portion 3 is most deformed when the tire contacts the ground, for example, the main groove 2 located on the outer side in the width direction.

  In the pneumatic tire according to the present invention, the rubber layer 6 made of low modulus rubber is divided at the groove bottom surface of the main groove 2. That is, since not all of the groove bottom surface of the main groove 2 is composed of low modulus rubber, it is possible to suppress a decrease in out-of-plane bending rigidity in the width direction. As a result, in this pneumatic tire, steering stability performance and riding comfort performance can be maintained.

  In the pneumatic tire according to the present embodiment, the split width W2 in the width direction of the rubber layer 6 is 0.2W1 ≦ W2 ≦ 0.5W1 (W2 is greater than the groove width W1 of the main groove 2 on the tread surface 1). 20 to 50% of W1). According to such a configuration, the strain concentration at the corner of the groove generated by the deformation of the land portion 3 at the time of tire contact is alleviated and the decrease in the out-of-plane bending rigidity in the width direction of the tire tread portion is further suppressed. A balance can be achieved. On the other hand, when W2 ≦ 0.2W1, the out-of-plane bending rigidity in the width direction of the tire tread surface portion may be reduced, and the steering stability performance and the riding comfort performance may not be maintained. When 0.5W1 ≦ W2, In some cases, the rubber layer 6 cannot be disposed at the corners of the groove bottom of the groove 2, and the rolling resistance cannot be reduced. In order to achieve both of these characteristics in a particularly well-balanced manner, it is more preferable that W2 is approximately 35% of W1 (specifically, 0.3W1 ≦ W2 ≦ 0.4W1). In the present invention, the groove width W1 of the main groove 2 on the tread surface 1 is exemplified by 6 to 12 mm.

  In the pneumatic tire according to the present invention, the rubber layer 6 made of low modulus rubber is disposed only on the groove wall surface in the region of 35% of the groove depth from the groove bottom. That is, since the rubber layer 6 made of the low modulus rubber is not exposed on the tread tread 1, the rubber physical properties are uniform throughout the tread tread 1, and the braking performance can be prevented from being lowered. In this embodiment, when the groove depth of the main groove 2 is H1, and the height of the rubber layer 6 measured from the groove bottom toward the outer side in the tire radial direction is H2, 0.15H1 ≦ H2 ≦ 0. .35H1 is set. When H2 ≦ 0.15H1, the effect of reducing rolling resistance may not be sufficiently exhibited. When 0.35H1 ≦ H2, the tread tread surface 1 is low in the middle to final stages of wear associated with tire use. The rubber layer 6 made of modulus rubber may be exposed, resulting in a reduction in braking performance. In order to achieve particularly good balance between reducing rolling resistance and preventing braking performance, H2 should be approximately 25% of H1 (specifically, 0.20H1 ≦ H2 ≦ 0.30H1). Is preferred. In the present invention, the groove depth H1 of the main groove 2 is exemplified by 6 to 10 mm.

In the present invention, the rubber part constituting the tread including the land part 3 other than the rubber layer 6 made of the low modulus rubber is higher in the modulus rubber than the low modulus rubber disposed in the rubber layer 6, specifically, 100 A rubber having a tensile modulus of 0.15 to 2.0 kgf / mm ² and a modulus of 100% in the range of 2.0G to 20G, where G is 100% tensile modulus of the low modulus rubber. It is preferable to configure. Such a low modulus rubber (rubber layer 6) and a high modulus rubber (rubber constituting the tread other than the rubber layer 6) are known to those skilled in the art (for example, polymers, oils and reinforcing agents constituting the main rubber component). Etc.).

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the main groove is configured as described above, and any conventionally known material, shape, structure, manufacturing method, etc. can be adopted in the present invention. it can.

[Other Embodiments]
In the above-described embodiment, as shown in FIGS. 1 and 2, the example in which the thickness of the rubber layer 6 is substantially constant on the groove bottom surface and the groove wall surface is shown. However, as shown in FIG. 3, in the present invention, the rubber layer 6 may be formed in a pair of crescent shapes in a meridian cross section. According to such a configuration, the concentration of strain at the corners of the groove bottom caused by deformation of the land portion 3 at the time of tire contact is alleviated by minimizing the usage amount of the rubber layer 6 made of low modulus rubber. Meanwhile, it is possible to further suppress the decrease in the out-of-plane bending rigidity in the width direction of the tire tread surface. As a result, the reduction in rolling resistance of the pneumatic tire and the maintenance and improvement of the steering stability performance and the riding comfort performance can be particularly well balanced, and the deterioration of the braking performance can be surely prevented.

  Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described. In addition, the evaluation item in an Example etc. measured as follows.

(1) Rolling resistance Using a test tire, the rolling resistance measured in the drum running test was evaluated as an index. The rolling resistance of Comparative Example 1 is indexed as 100, and the smaller the index is, the lower the rolling resistance is. The running conditions were as follows: drum diameter = 1.7 m, camber angle = 0 °, internal pressure = 230 kPa, speed = 80 km / h, load = 6.5 kN.

(2) Steering stability performance A test tire was mounted on an actual vehicle (domestic 3000cc class SUV (sport utility vehicle)), and it was evaluated by sensory evaluation while running on a dry road surface. The result of Comparative Example 1 is shown as an index with 100, and the larger the value, the better the steering stability performance on the dry road surface.

(3) Riding comfort performance The test tire was mounted on a real vehicle (domestic 3000cc class SUV (sport utility vehicle)), and the vehicle was evaluated on the dry road surface by sensory evaluation. The result of Comparative Example 1 is shown as an index with the value 100, and the larger the value, the better the riding comfort performance.

(4) Braking performance Measure the reciprocal of the stopping distance when the test tire is mounted on an actual vehicle (domestic 3000cc class SUV (sports utility vehicle)) and the running speed is reduced from 100 km / h to 0 km / h on a dry road surface. Index evaluation was performed. The result of Comparative Example 1 is shown as an index with the value of 100, and the larger the value, the better the braking performance.

Example 1
A plurality of main grooves 2 extending in the circumferential direction and a plurality of land portions 3 partitioned by the main grooves 2 are formed on the tread surface 1, and all the main grooves 2 are shown in FIGS. 1 and 2. Rubber layer 6 (H1 = 9.0 mm, W1 = 9.8 mm, (100% tensile modulus of rubber layer 6) = 0.2 kgf / mm ² , H2 = 2.25 mm, W2 = 3.4 mm (W2 is W1 35%) and (thickness of rubber layer 6) = 1 mm) were prepared (tire size: 285 / 60R18 116V, rim 18 × 8-JJ). Table 1 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 1
A pneumatic tire having the same configuration as that of Example 1 was manufactured except that the main groove 2 was provided but the rubber layer 6 was not provided. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 2
A pneumatic tire having the same configuration as in Example 1 was manufactured except that the 100% tensile modulus of the rubber layer 6 was changed to 0.1 kgf / mm ² . Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 3
A pneumatic tire having the same configuration as that of Example 1 was manufactured except that W2 = 2.0 mm (W2 was 20% of W1). Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 4
As shown in FIG. 3, the pneumatic tire having the same configuration as that of Example 1 except that the rubber layer 6 is formed in a pair of crescent shapes in a meridian cross-sectional shape ((maximum thickness of the rubber layer 6) = 1 mm). Manufactured. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 5
A pneumatic tire having the same configuration as that of Example 1 was manufactured except that W2 = 1.0 mm (W2 was 10% of W1). Table 1 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 2
A pneumatic tire having the same configuration as that of Example 1 was manufactured except that W2 = 0 mm (the rubber layer 6 was not divided at the groove bottom surface of the main groove 2). Table 1 shows the results of the above evaluation using such a pneumatic tire.

  From the results in Table 1, it can be seen that in the pneumatic tires according to Examples 1 to 4, the steering stability performance and the riding comfort performance are maintained, the deterioration of the braking performance is prevented, and the rolling resistance is reduced. On the other hand, in the pneumatic tire according to Comparative Example 2, since the rubber layer is not divided at the groove bottom surface of the main groove, the out-of-plane bending rigidity in the width direction of the tire tread portion is reduced. For this reason, it turns out that steering stability performance deteriorates especially. In addition, in the pneumatic tire according to Example 5, since the split width in the width direction of the rubber layer is narrow, the out-of-plane bending rigidity in the width direction of the tire tread portion tends to decrease. The reduction in rolling resistance and the maintenance and improvement of steering stability performance and riding comfort performance cannot be achieved in a well-balanced manner. Therefore, comparing the result of Example 5 with the results of Examples 1 to 4, in the present invention, the dividing width in the width direction of the rubber layer is set to the groove width of the main groove on the tread surface. It turns out that it is preferable to set it as 20 to 50%.

1: Tread surface 2: Main groove 3: Land portion 4: Carcass layer 5: Belt layer 6: Rubber layer

Claims (3)

In a pneumatic tire in which a plurality of main grooves extending in the circumferential direction and a plurality of land portions divided by the main grooves are formed on the tread surface,
At least one main groove among the plurality of main grooves has a groove bottom surface including both corners of the groove and a groove wall surface in a region 35% of the groove depth from the groove bottom with a 100% tensile modulus of 0. A rubber layer made of a low modulus rubber of 1 to 1.0 kgf / mm ² is disposed,
The pneumatic tire according to claim 1, wherein the rubber layer is divided at a groove bottom surface of the main groove.   The pneumatic tire according to claim 1, wherein a split width in a width direction of the rubber layer is 20 to 50% with respect to a groove width of the main groove on a tread surface.   The pneumatic tire according to claim 1, wherein the rubber layer is formed in a pair of crescent shapes in a meridian cross section.

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