JP2016088338A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compatibly achieve rough road traveling performance, and rolling resistance performance and high-speed durability performance.SOLUTION: In a pneumatic tire, tread rubber 26 extends in a buttress part 16, installed between a tread part 14 and a sidewall part 12, to form an inner rubber layer 30, sidewall rubber 28 overlaps with the outside of the inner rubber layer to form an outer rubber layer 32 serving as a surface of the buttress part, and the tread rubber 26 is made of rubber having a 300% modulus larger than that of the sidewall rubber 28. The surface of the buttress part 16 is provided with a plurality of first projecting parts 36 arranged at intervals in a tire circumferential direction C and extending in a tire meridian direction M, a plurality of recessed parts 38 each formed by recessing the surface of the buttress part 16 between the adjacent first projecting parts 36, and second projecting parts 40 each projecting in the recessed part 38 by a projection amount H2 smaller than a recess amount H4 of the recessed part.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire.

  In the pneumatic tire, not only the running performance on a paved road but also the running performance on an unpaved land, that is, the bad road running performance may be required. Conventionally, a technique for increasing the rubber volume of the buttress portion has been taken in order to ensure rough road running performance. However, when the rubber volume of the buttress portion is increased, the low heat generation performance is impaired, and deterioration of rolling resistance performance and high-speed durability performance becomes a problem.

  Patent Document 1 discloses a so-called TOS type pneumatic tire in which a buttress portion is formed such that a width direction end portion of a tread rubber is overlapped with a radially outer end portion of a sidewall rubber. However, in the case of the TOS method, the sidewall rubber having high cut resistance is not exposed to the surface in the buttress portion. Inferior to

  On the other hand, Patent Document 2 discloses a structure in which a tread rubber is extended to a buttress portion and a surface of the buttress portion is formed by overlapping a sidewall rubber on the outside of the tread rubber in a heavy duty pneumatic tire. Has been. However, the modulus relationship between the tread rubber and the buttress portion is not disclosed, and it is not disclosed to provide unevenness on the surface of the buttress portion.

JP 2002-67619 A JP 2013-173507 A

  An object of the present invention is to provide a pneumatic tire capable of achieving both rough road running performance, rolling resistance performance and high-speed durability performance.

  In the pneumatic tire according to the present embodiment, a tread rubber constituting a tire contact surface extends to a buttress portion provided between a tread portion and a sidewall portion, and an inner rubber layer is formed. Side rubber is overlapped on the outer side of the rubber layer to form an outer rubber layer that forms the surface of the buttress part, and the tread rubber is made of rubber having a higher modulus of 300% than the side wall rubber, and the surface of the buttress part In addition, a plurality of first protrusions extending in the tire meridian direction arranged at intervals in the tire circumferential direction, and a recess formed by denting the surface of the buttress part between the adjacent first protrusions, In the concave portion, a second convex portion that protrudes with a projection amount smaller than the concave amount of the concave portion is provided.

  According to the present embodiment, the tread rubber having a high modulus is extended to the buttress portion to form an inner rubber layer, and the sidewall rubber is covered thereon to form the outer rubber layer that forms the surface of the buttress portion. By adopting the above-mentioned peculiar uneven shape including the first convex part that contributes to rough road running performance and the concave part that contributes to rolling resistance performance and high-speed durability performance while suppressing heat generation, the buttress part has a rough road running performance. And both rolling resistance performance and high-speed durability performance can be achieved.

The half sectional view of the pneumatic tire concerning one embodiment. The principal part expansion perspective view which shows the buttress part of the pneumatic tire. III-III sectional view taken on the line of FIG. FIG. 4 is a sectional view taken along line IV-IV in FIG. 2. VV sectional view taken on the line of FIG. Sectional drawing for demonstrating the dimensional relationship of each site | part in the buttress part.

  FIG. 1 is a right half cross-sectional view of a pneumatic tire according to an embodiment cut along a meridian cross section including a tire rotation axis. Here, since the tire is symmetrical, the left half is not shown. In the figure, CL indicates a tire equator plane, and TE indicates a ground contact end during normal running.

  In the present specification, the tire width direction is a direction parallel to the tire rotation axis and is synonymous with the tire axis direction, and is indicated by a symbol W in the drawing. The tire radial direction (radial direction) is a direction perpendicular to the tire rotation axis, and is indicated by a symbol K in the figure. The tire meridian direction is a direction along the tire cross-sectional profile when cut along a plane including the tire rotation axis, and is indicated by a symbol M in the drawing. The tire circumferential direction is a circumferential direction around the tire rotation axis, and is indicated by a symbol C in the figure. These may be simply referred to as width direction, radial direction, meridian direction, and circumferential direction, respectively.

  The tire includes a pair of left and right bead portions 10, a pair of left and right sidewall portions 12 extending outward in the tire radial direction from the bead portions 10, a tread portion 14 constituting a ground contact surface, and both sides in the width direction of the tread portion 14. A pair of left and right buttress portions 16 that connect the sidewall portions 12 are provided. Here, the buttress portion 16 is a portion provided between the tread portion 14 and the sidewall portion 12 and is not grounded during normal traveling such as a paved road, but is in a road surface state on a bad road such as an unpaved land. This is the part that is grounded. As shown in the figure, in the tire according to the present embodiment, the cross-sectional profile from the tread portion 14 to the buttress portion 16 is not a cliff-like depressed shape with the ground contact end TE as a boundary, but is gently curved from the tread portion 14 The shape reaches the portion 16.

  A carcass 18 extending between the pair of bead portions 10 is embedded in the tire. The carcass 18 extends from the tread portion 14 through the buttress portion 16 and the sidewall portion 12, and is locked by an annular bead core 20 embedded in the bead portion 10. The carcass 18 includes at least one (two in the illustrated example) carcass ply in which carcass cords are arranged at an angle of 70 to 90 degrees with respect to the circumferential direction, and is disposed along the tire inner surface.

  A belt 22 is disposed on the outer peripheral side of the carcass 18 in the tread portion 14. The belt 22 includes a belt ply in which belt cords are inclined with respect to the circumferential direction. In this example, the belt 22 includes two belt plies. A belt reinforcing layer 24 made of an organic fiber cord spirally wound in a circumferential direction called a cap ply is provided on the outer periphery of the belt 22.

  A tread rubber 26 constituting a tire ground contact surface is provided on the outer side in the radial direction of the belt 22. In this example, the tread rubber 26 is composed of two layers of a cap rubber layer 26A that forms a tire ground contact surface and a base rubber layer 26B provided on the inner side. Although not shown, a predetermined tread pattern is formed on the surface of the tread rubber 26 by a longitudinal groove extending in the circumferential direction or a lateral groove extending in a direction intersecting the longitudinal groove.

  A sidewall rubber 28 is provided on the outer surface side of the carcass 18 in the sidewall portion 12. The sidewall rubber 28 is a rubber member that constitutes the surface (outer surface) of the sidewall portion 12 and is formed of a general rubber composition having a high cut resistance.

  In the buttress portion 16, a joint portion between the end portion in the width direction of the tread rubber 26 and the end portion in the radial direction of the sidewall rubber 28 is provided on the outer surface side of the carcass 18. Specifically, the cap rubber layer 26A of the tread rubber 26 constituting the tire contact surface extends beyond the end portion 22E of the belt 22 to the buttress portion 16 on the outer side in the width direction. A rubber layer 30 is formed. Further, the outer end rubber layer 32 forming the surface (outer surface) of the buttress portion 16 is overlapped on the outer side of the extended tread rubber 26 (that is, the inner rubber layer 30). Is formed. That is, the end portion in the tire radial direction of the sidewall rubber 28 is provided so as to overlap the end portion in the tire width direction of the tread rubber 26, and the tread rubber 26 is not exposed to the tire surface in the buttress portion 16. Has been. The boundary surface 34 between the tread rubber 26 and the sidewall rubber 28 is formed in an inclined surface shape in which the thickness of the tread rubber 26 gradually decreases as the side wall portion 12 is approached.

  In the present embodiment, the cap rubber layer 26 </ b> A of the tread rubber 26 is formed of rubber having a 300% modulus higher than that of the sidewall rubber 28. That is, the 300% modulus (M300t) of the cap rubber layer 26A is larger than the 300% modulus (M300s) of the sidewall rubber 28. Preferably, the 300% modulus of the cap rubber layer 26A is 130 to 170% of the 300% modulus of the sidewall rubber 28 (that is, M300t / M300s is in the range of 1.3 to 1.7). Here, the 300% modulus is a tensile stress at 300% elongation measured according to JIS K6251 (dumbbell shape No. 3).

  Thus, according to the present embodiment, the high modulus cap rubber layer 26A is disposed on the buttress portion 16, and the sidewall rubber 28 having high cut resistance is overlapped thereon. Since the high modulus cap rubber layer 26A is disposed inside as the inner rubber layer 30, the rigidity of the buttress portion 16 located on the outer side in the width direction from the end portion 22E of the belt 22 can be increased. It is possible to increase the reaction force (= driving force) by suppressing the deformation when grounded at. Further, by arranging the sidewall rubber 28 having high cut resistance on the inner rubber layer 30 as the outer rubber layer 32, the cut resistance in the buttress portion 16 can be improved. For this reason, it is possible to ensure rough road running performance.

  In the present embodiment, the surface of the buttress portion 16 is provided with a specific uneven shape described in detail below.

  As shown in FIG. 2, a plurality of first convex portions 36 extending in the meridian direction M are provided on the surface of the buttress portion 16 at intervals in the circumferential direction C, and the adjacent first convex portions 36 are arranged. A plurality of concave portions 38 formed by denting the surface of the buttress portion 16 are provided therebetween, and a second convex portion 40 having a small protruding amount is provided in each concave portion 38. As shown in FIG. 3, these are all formed of a sidewall rubber 28. By providing the 1st convex part 36, rough road running property can be improved. Further, by providing the recess 38 between the first recesses 36, it is possible to reduce the rubber volume and suppress the heat generation, and to improve the rolling resistance performance and the high speed durability performance. Further, by providing the second convex portion 40 in the concave portion 38, the out-of-plane bending rigidity of the concave portion 38 can be compensated.

  The first convex portion 36 is a raised portion that is built up with respect to the basic contour line B of the buttress portion 16 as shown in FIG. 6. The first convex portion 36 extends from the position near the radially outer end 34A of the boundary surface 34 between the tread rubber 26 and the sidewall rubber 28 toward the sidewall portion 12 along the meridian direction M, as shown in FIG. As shown, the meridian dimension is larger than the circumferential dimension. The first convex portions 36 are arranged in parallel in the circumferential direction C at a constant interval. In this example, the interval is set larger than the circumferential dimension of the first convex portion 36. The protrusion amount H1 of the first convex portion 36 with respect to the reference contour line B is not particularly limited, and may be, for example, 1.0 to 4.0 mm.

  Here, the basic contour line B of the buttress portion 16 is a curve that smoothly connects the contour lines (cross-sectional profile lines) of the upper and lower portions of the buttress portion 16 excluding the above-described irregular shape in the tire meridian section as shown in FIG. This corresponds to the contour line of the buttress portion when the uneven shape is not provided.

  As shown in FIG. 6, the first convex portion 36 is disposed within the range of the overlapping portion of the tread rubber 26 and the sidewall rubber 28 when viewed from the normal direction N of the buttress portion 16. That is, the first convex portion 36 is formed in a range where the boundary surface 34 exists behind the normal line direction N shown in FIG. The length L1 (that is, the meridian dimension) of the first convex portion 36 along the meridian direction M is along the meridian direction M of the overlapping portion (that is, the boundary surface 34) between the tread rubber 26 and the sidewall rubber 28. It is preferable that it is 50 to 90% of the length L0. Thus, the 1st convex part 36 which contributes to improvement of bad road running property was set in the range where the high modulus tread rubber 26 was arranged inside, and was grounded outside end 22E of belt 22 outside. In this case, the reaction force (= driving force) can be increased by suppressing the deformation.

  The concave portions 38 are provided so as to be recessed with respect to the basic contour line B of the buttress portion 16 as shown in FIG. 6, and one concave portion 38 is provided at each interval of the first convex portions 36 as shown in FIG. Accordingly, the first convex portions 36 and the concave portions 38 are alternately provided in the circumferential direction C. The recess 38 is a recess extending in the meridian direction M, and the meridian dimension is set larger than the circumferential dimension. As shown in FIG. 4, the formation range of the concave portion 38 in the meridian direction M coincides with the first convex portion 36. Therefore, the concave portion 38 is also disposed within the range of the overlapping portion of the tread rubber 26 and the side wall rubber 28 when viewed from the normal direction N of the buttress portion 16, and the length along the meridian direction M of the concave portion 38. L4 is preferably 50 to 90% of the length L0 along the meridian direction M of the overlapping portion between the tread rubber 26 and the sidewall rubber 28. The recess amount H4 with respect to the reference contour line B of the recess 38 is not particularly limited, and may be, for example, 1.0 to 3.0 mm. In addition, you may provide the recessed part 38 connected with the horizontal groove 15 provided in the tread part 14, as shown in FIG.

  As shown in FIGS. 5 and 6, the second convex portion 40 projects from the bottom surface of the concave portion 38 with a projection amount H2 that is smaller than the concave amount H4 of the concave portion 38 (H2 <H4). One is provided in each recess 38. The 2nd convex part 40 is a convex part extended along the meridian direction M from the radial direction outer side end 38A of the recessed part 38, and is formed in the strip shape where the direction of a meridian direction dimension is larger than the circumferential direction dimension. The length L2 along the meridian direction M of the second convex portion 40 is shorter than the length L4 along the meridian direction M of the concave portion 38, and is preferably 50 to 80% of L4. Thus, by not providing the 2nd convex part 40 in the meridian direction whole of the recessed part 38, the soil removal property by the depression at the time of stepping in on rough roads and kicking can be improved. The protrusion amount H2 of the second protrusion 40 is preferably 30 to 60% of the recess amount H4 of the recess 38.

  As shown in FIG. 2, a third convex portion 42 extending in the circumferential direction C is continuously provided on the surface of the buttress portion 16 over the entire circumference of the tire. The third convex part 42 is connected to the radially inner end 36A of the plurality of first convex parts 36. In this example, the first convex part 36 and the third convex part 42 are connected without a step. ing. As shown in FIG. 6, the third convex portion 42 is a raised portion that is built up with respect to the basic contour line B of the buttress portion 16. It has a function to stop moving inward in the radial direction. The protrusion amount H3 of the third convex portion 42 with respect to the reference contour line B is not particularly limited, and may be, for example, 1.0 to 4.0 mm. A plurality of narrow grooves 44 extending in the circumferential direction C are provided on the surface of the third convex portion 42 at regular intervals.

  In the pneumatic tire according to the present embodiment as described above, the tread rubber 26 with a high modulus is extended to the buttress portion 16 to form the inner rubber layer 30, and the sidewall rubber 28 is covered thereon to cover the buttress portion 16. On the outer rubber layer 32 forming the surface, the buttress portion 16 is provided with a first convex portion 36 that contributes to rough road running performance, and a concave portion 38 that contributes to rolling resistance performance and high-speed durability performance while suppressing heat generation. Furthermore, since the 2nd convex part 40 which compensates the out-of-plane bending rigidity of the recessed part 38 was provided, it can make a bad road running property, rolling resistance performance, and high-speed durability performance compatible.

  Each dimension value in the present embodiment is in a normal state with no load in which a tire is mounted on a regular rim and filled with a regular internal pressure. A regular rim is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, a standard rim for JATMA, a “Design Rim” for TRA, or a rim for ETRTO. "Measuring Rim". In addition, the normal internal pressure is the air pressure defined by each standard for each tire in the standard system. If it is JATMA, it is the maximum air pressure, and if it is TRA, it is described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" If the maximum value is ETRTO, "INFLATION PRESSURE" is assumed.

  As mentioned above, although embodiment was described, this embodiment is shown as an example and is not intending limiting the range of invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  In order to show the effect of the above embodiment, pneumatic radial tires (size: 255 / 60R18 108S) of Examples 1 to 3 and Comparative Examples 1 to 3 were prototyped. Each prototype tire was the same except for the configuration of the buttress portion, and the buttress portion was manufactured according to the specifications shown in Table 1.

  Specifically, Examples 1 to 3 are examples having the buttress portion configuration according to the embodiment. Comparative Example 1 is an example in which the end portion in the width direction of the tread rubber is overlapped on the outer end portion in the radial direction of the sidewall rubber in the buttress portion (the sidewall rubber is not exposed in the buttress portion). Also did not form. Comparative Example 2 is an example in which only the concave portion 38 is provided in the buttress portion as compared with Comparative Example 1. Comparative Example 3 is an example in which the uneven shape of the buttress portion is omitted from Example 2. As for the 300% modulus, the 300% modulus (M300t) of the tread rubber (cap rubber layer) is kept constant at 10 MPa, and the 300% modulus (M300s) of the sidewall rubber is changed to change the ratio between the two (M300t / M300s). Was changed as described in the table.

About each pneumatic tire of an example and a comparative example, rolling resistance performance, high-speed endurance performance, trauma resistance on a rough road, and runability were evaluated. The evaluation method is as follows.
(1) Rolling resistance performance: The rolling resistance was measured under ISO conditions, and the results were indexed with Comparative Example 1 as 100. The larger the value, the smaller the rolling resistance and the better.
(2) High-speed durability performance: Evaluation was performed under ECE-R30 conditions, and the results were indexed with Comparative Example 1 as 100. The larger the value, the better.
(3) Trauma resistance on rough roads: Cars were evaluated for rough roads. A 1-ton pickup truck was used as the evaluation vehicle, and the degree of injury (width, depth) was indexed with Comparative Example 1 being 100. The larger the value, the better.
(4) Driving performance on rough roads: Cars were evaluated for rough roads. A 1-ton pickup truck was used as the evaluation vehicle, and the feeling evaluation when traveling on a rough road was indexed with Comparative Example 1 as 100. The larger the value, the better.

  The results are as shown in Table 1, and in Examples 1 to 3 according to the present embodiment, both bad road running performance, rolling resistance performance and high-speed durability performance are compatible with Comparative Examples 1 to 3. Excellent effect.

DESCRIPTION OF SYMBOLS 12 ... Side wall part, 14 ... Tread part, 16 ... Buttress part, 26 ... Tread rubber, 26A ... Cap rubber layer, 28 ... Side wall rubber, 30 ... Inner rubber layer, 32 ... Outer rubber layer, 34 ... Interface 36 ... 1st convex part, 38 ... Concave part, 40 ... 2nd convex part, 42 ... 3rd convex part, C ... Tire circumferential direction, M ... Tire meridian direction

Claims (6)

A tread rubber that constitutes the tire ground contact surface extends to a buttress portion provided between the tread portion and the sidewall portion to form an inner rubber layer, and a sidewall rubber is overlapped on the outer side of the inner rubber layer. An outer rubber layer forming the surface of the buttress portion is formed, and the tread rubber is made of rubber having a modulus 300% higher than that of the sidewall rubber,
A plurality of first convex portions extending in the tire meridian direction arranged at intervals in the tire circumferential direction on the surface of the buttress portion and a surface of the buttress portion being recessed between the adjacent first convex portions A pneumatic tire provided with a recessed portion and a second protruding portion that protrudes with a protruding amount smaller than the recessed amount of the recessed portion in the recessed portion.   The pneumatic tire according to claim 1, wherein a third convex portion extending in a tire circumferential direction is provided on a surface of the buttress portion so as to be connected to an inner end in a tire radial direction of the plurality of first convex portions.   3. The pneumatic tire according to claim 1, wherein the first convex portion is disposed within a range of an overlapping portion between the tread rubber and the sidewall rubber as viewed from a normal direction of the buttress portion.   The air according to claim 3, wherein a length along the tire meridian direction of the first convex portion is 50 to 90% of a length along the tire meridian direction of an overlapping portion between the tread rubber and the sidewall rubber. Enter tire.   The pneumatic tire according to any one of claims 1 to 4, wherein a length along the tire meridian direction of the second convex portion is 50 to 80% of a length along the tire meridian direction of the concave portion. .   The pneumatic tire according to any one of claims 1 to 5, wherein a 300% modulus of the tread rubber is 130 to 170% of a 300% modulus of the sidewall rubber.

Images