JP2013060075A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving run flat durability and dry/wet maneuvering stability with a simple constitution.SOLUTION: A sidewall part of this pneumatic tire has a reinforcing rubber layer formed so that one end side extends toward a tread part and the other end side extends toward a bead part, on the inner surface side facing to a tire cavity area, the tread part of the pneumatic tire has a plurality of main grooves extending in the tire circumferential direction at an interval in the tire width direction, and the one end side in the tire radial direction of the reinforcing rubber layer is arranged so as to overlap in the tire width direction with at least a part in the tire circumferential direction of the outermost main groove positioned on the outermost side in the tire width direction among the plurality of main grooves.

Description

  The present invention relates to a pneumatic tire having a bead portion, a sidewall portion, and a tread portion.

  Today, a pneumatic tire called a so-called run-flat tire that can travel a predetermined distance with an internal pressure of zero (atmospheric pressure) or close to zero has been proposed.

  These run-flat tires are mainly mounted on high-performance sports cars and luxury sedan passenger cars, etc., and the driving stability of passenger cars is remarkably improved even when the tires are flat (punk) during high-speed driving on general roads and highways. It is required to be able to travel to a predetermined place safely, for example, about 100 km without losing.

For example, a pneumatic tire with improved run flat durability compared to a conventional run flat tire is known (Patent Document 1).
This pneumatic tire has a tread portion having a cap rubber having a main groove and a base rubber located on the inner peripheral side of the cap rubber, and a pair of sidewall portions having side reinforcing rubber layers located on both sides of the tread portion. And have. Furthermore, the pneumatic tire has a buckling suppressing member that suppresses buckling on the inner peripheral side of the main groove and in the vicinity of the main groove. The hardness of the buckling suppressing member is set higher than the hardness of the cap rubber and the base rubber.

JP 2006-123829 A

  In the pneumatic tire described above, the run-flat durability can be improved by newly providing a high-hardness buckling suppressing member, but the buckling can be suppressed without providing a new member. It is desirable in that it can suppress the increase of.

  Then, an object of this invention is to provide the pneumatic tire which can improve run flat durability and dry / wet steering stability by simple structure.

An aspect of the present invention is a pneumatic tire having a bead portion, a sidewall portion, and a tread portion.
The sidewall portion has a reinforcing rubber layer formed so that one end side extends toward the tread portion and the other end side extends toward the bead portion on the inner surface side facing the tire cavity region,
The tread portion has a plurality of main grooves extending in the tire circumferential direction at intervals in the tire width direction,
One end side of the reinforcing rubber layer in the tire radial direction overlaps at least a part of the outermost main groove located on the outermost side in the tire width direction of the plurality of main grooves in the tire width direction. It is preferable to be provided.

The area of the reinforcing rubber layer that overlaps the outermost main groove in the tire width direction is preferably 20% or more of the area of the outermost main groove.
The thickness of the portion of the reinforcing rubber layer that overlaps the outermost main groove in the tire width direction is preferably 1.0 mm or greater and 6.0 mm or less.

It is preferable that at least one of the plurality of main grooves excluding the outermost main groove is provided so as to extend in a zigzag shape in the tire circumferential direction.
It is preferable that the JISA hardness of the center portion in the tire width direction of the cap tread rubber constituting the tread portion is 3 to 10 degrees smaller than the JISA hardness of both ends of the cap tread rubber in the tire width direction.

  According to the pneumatic tire of the above aspect, run-flat durability and dry / wet handling stability can be improved with a simple configuration.

It is a figure showing the section of the pneumatic tire of this embodiment. It is the elements on larger scale which expanded the outermost main groove periphery of the pneumatic tire shown in FIG. It is a figure explaining the modification of the reinforcement rubber layer of the pneumatic tire shown in FIG. (A), (b) is a figure explaining an example of several main grooves. (A), (b) is a figure explaining the modification of several main grooves.

  Hereinafter, the pneumatic tire of the present invention will be described in detail.

FIG. 1 is a view showing a cross section of a pneumatic tire (hereinafter referred to as a tire) 10 of the present embodiment. Although the tire 10 of the present embodiment will be described as a tire having a tire size of 225 / 65R17, the present invention is not limited to this tire size.
The pneumatic tire 10 is, for example, a passenger car tire. Passenger car tires are tires defined in Chapter A of JATMA YEAR BOOK 2009 (Japan Automobile Tire Association Standard). In addition, the present invention can also be applied to light truck tires defined in Chapter B.

  The tire circumferential direction described below refers to the direction of rotation of the tread surface when the pneumatic tire 10 is rotated about the tire rotation axis, and the tire radial direction is orthogonal to the tire rotation axis. The extending radial direction refers to the tire radial direction outer side, which is the side away from the tire rotation axis in the tire radial direction. The tire width direction refers to a direction parallel to the tire rotation axis direction, and the tire width direction outer side refers to both sides of the pneumatic tire 10 that are separated from the tire center line CL in the tire width direction.

  The pneumatic tire 10 has a carcass ply layer 12, a belt layer 14, and a bead core 16 as a bead portion as a skeleton material. Around these skeleton materials, a tread rubber layer 18 as a tread portion, a side rubber layer 20 as a sidewall portion, a bead filler rubber layer 22, a rim cushion rubber layer 24, an inner liner rubber layer 26, and a reinforcement It mainly has a reinforcing rubber layer 27 as a part, a first main groove 28, and a pair of second main grooves 29.

  The carcass ply layer 12 is a member in which a toroidal shape is formed by winding between a pair of annular bead cores 16 and includes a first ply material 12a and a second ply material 12b. . The end portion of the first ply material 12a is located on the outer side in the tire radial direction compared to the maximum width position R (shown in FIG. 1) of the tire 10, and the end portion of the second ply material 12b is the bead filler rubber layer 22. It is located on the outer side in the tire radial direction at the end and on the inner side in the tire radial direction from the maximum width position R. A belt layer 14 is provided outside the carcass ply layer 12 in the tire radial direction. The belt layer 14 includes steel belt members 14a and 14b obtained by coating rubber on steel cords inclined at a predetermined angle, for example, 20 to 30 degrees with respect to the tire circumferential direction, and parallel to the tire circumferential direction or in the tire circumferential direction. And an organic fiber reinforcing material 14c in which organic fibers inclined at a predetermined angle are covered with rubber. The width of the lower steel belt material 14a in the tire width direction is longer than that of the upper steel belt material 14b. The steel belt materials 14a and 14b are inclined in the opposite directions of the steel cords, and the steel belt materials 14a and 14b form a crossing layer. Furthermore, since the organic fiber reinforcing material 14c is provided on the outer side in the tire radial direction of the crossing layer, the belt layer 14 suppresses the expansion of the carcass ply layer 12 due to the filled air pressure.

A tread rubber layer 18 is provided outside the belt layer 14 in the tire radial direction, and a side rubber layer 20 is connected to an end of the tread rubber layer 18. A rim cushion rubber layer 24 is provided at an end of the side rubber layer 20 on the inner side in the tire radial direction, and the rim cushion rubber layer 24 is in contact with a rim flange _{Rf of} a wheel on which the tire 10 is mounted. The bead core 16 is sandwiched between the portion of the carcass ply layer 12 before being wound around the bead core 16 and the portion of the carcass ply layer 12 wound around the bead core 16 on the outer side in the tire radial direction of the bead core 16. A bead filler rubber layer 22 is provided so as to be in contact with each of the above. Further, on the inner surface side of the side rubber layer 20, that is, the surface side facing the tire cavity region filled with air surrounded by the tire 10 and the wheel, the reinforcing rubber layer 27 and the inner liner rubber layer 26 are arranged in order from the side rubber layer 20. However, the inner liner rubber layer 26 is provided so as to be in contact with the tire cavity region over the entire inner peripheral surface of the tire 10.

  Further, on the outer surface in the tire radial direction of the tread rubber layer 18, a first main groove 28 extending linearly in the tire circumferential direction and a pair of second main grooves 29 extending linearly in the tire circumferential direction are provided on the tire. It is provided at intervals in the width direction. Each of the pair of second main grooves 29 is an outermost main groove provided at the outermost side in the tire width direction among the main grooves provided in the tire 10, that is, at both ends in the tire width direction. The first main groove 28 is a main groove excluding the outermost main groove among the main grooves provided in the tire 10, and is provided at least one between the pair of second main grooves 29 in the tire width direction. .

The reinforcing rubber layer 27 is provided along the carcass ply layer 12 on the inner side in the tire width direction of the carcass ply layer 12 in the two side regions formed between each of the pair of bead cores 16 and the end of the tire tread. A layer with a crescent cross-sectional shape. The reinforcing rubber layer 27 is a member that supports the sidewall portion so that it does not bend due to a load even when it is in a run-flat state.
As shown in FIG. 1, the end of the reinforcing rubber layer 27 on the outer side in the tire radial direction extends along the carcass ply layer 12 toward the tread rubber layer 18. Further, the end portion on the inner side in the tire radial direction of the reinforcing rubber layer 27 extends toward the bead core 16 along the carcass ply layer 12.

2 and 3 are partially enlarged views in which the periphery of the second main groove 29 is enlarged. As shown in FIGS. 2 and 3, the end of the reinforcing rubber layer 27 on the outer side in the tire radial direction is provided so as to overlap with at least a part of the second main groove 29 in the tire circumferential direction in the tire width direction. ing. Conventionally, since a buckling suppressing member for suppressing buckling has been disposed inside the second main groove 29 in the tire radial direction, the cost has increased. In the present embodiment, with the above configuration, the rigidity of the second main groove 29 can be increased by the reinforcing rubber layer 27, so that the grounding characteristics in the run-flat state can be improved. Therefore, in the present embodiment, buckling during non-run-flat traveling can be suppressed without providing a new member such as a buckling suppressing member, so that buckling durability and dry / wet can be achieved with a simple configuration. Steering stability can be improved.
In addition, as shown in FIG. 2, when the end portion on the outer side in the tire radial direction of the reinforcing rubber layer 27 is located on the outer side in the tire width direction with respect to the end portion on the inner side in the tire width direction of the second main groove 29, When the thickness of the reinforcing rubber layer 27 at the outer end in the tire width direction of the two main grooves 29 is T1, it is preferable that T1 is 1 to 6 mm from the viewpoint of improving the buckling durability. Further, as shown in FIG. 3, when the end portion of the reinforcing rubber layer 27 on the outer side in the tire radial direction is located on the inner side in the tire width direction of the end portion of the second main groove 29 on the inner side in the tire width direction, When the thickness of the reinforcing rubber layer 27 at the inner end in the tire width direction of the two main grooves 29 is T2, T2 is preferably 1 to 6 mm from the viewpoint of improving the buckling durability. Here, the thickness of the reinforcing rubber layer 27 refers to a dimension in the tire radial direction. The thickness value (1 to 6 mm) may be the maximum value of the thickness of the portion of the reinforcing rubber layer 27 that overlaps the second main groove 29 in the tire width direction. The thickness value is preferably an average value in that the buckling durability of the present embodiment is more effectively exhibited.

FIGS. 4A and 4B are diagrams illustrating an example of the first main groove 28 and the second main groove 29. As described above, the end of the reinforcing rubber layer 27 on the outer side in the tire radial direction is provided so as to overlap with at least a part of the second main groove 29 in the tire circumferential direction in the tire width direction. Here, the end of the reinforcing rubber layer 27 on the outer side in the tire radial direction is provided so as to continuously overlap the bottom surface of the second main groove 29 along the tire circumferential direction, as shown in FIG. Alternatively, as shown in FIG. 4B, it may be provided so as to intermittently overlap the bottom surface of the second main groove 29 along the tire circumferential direction. Further, the area of the reinforcing rubber layer 27 that overlaps the bottom surface of the second main groove 29 (shown by hatching in FIGS. 4A and 4B) is 20% or more of the area of the bottom surface of the second main groove 29. It is preferable that the buckling durability is further improved.
When the length in the tire circumferential direction of the portion of the second main groove 29 on the outer side in the tire width direction where the reinforcing rubber layer 27 does not overlap the second main groove 29 in the tire width direction is X. In addition, the total length X of one second main groove 29 is preferably 10% or less of the length of the second main groove 29 in the tire circumferential direction. Further, the maximum value of the length X is 5% or less, more preferably 3% or less, of the length of the second main groove 29 in the tire circumferential direction.

In the tire 10, the JIS hardness of the cap tread rubber constituting the tread rubber layer 18 may be equal or different between the center portion C on the tire width direction center side and the shoulder portions Sh on both ends in the tire width direction. May be.
Here, the boundary A (shown in FIG. 1) between the center portion C and the shoulder portion Sh is, for example, arranged within a range of ± 5 mm in the tire width direction from the outer end of the second main groove 29 in the tire width direction. Alternatively, it may be arbitrarily determined according to the tread pattern of the tire 10, the arrangement of the first main groove 28 and the second main groove 29, or the like.

  When the JISA hardness of the cap tread rubber of the center portion C and the JISA hardness of the cap tread rubber of the shoulder portion Sh are different, for example, the JISA hardness of the cap tread rubber of the center portion C is set to the cap tread rubber of the shoulder portion Sh. It may be larger than the JISA hardness. In this case, it is preferable to set the JISA hardness of the cap tread rubber of the center portion C to, for example, 70 to 75, and to set the JISA hardness of the cap tread rubber of the shoulder portion Sh to, for example, 62 to 67. Furthermore, it is more preferable that the JIS hardness of the cap tread rubber of the center portion C is 3 to 10 degrees larger than the JIS hardness of the cap tread rubber of the shoulder portion Sh.

  By configuring the tire 10 in this manner, the rigidity of the center portion C can be increased, and therefore, the buckling in which the center portion C is recessed in the tire radial direction can be suppressed even in the run-flat state. . Moreover, since it is not necessary to newly provide a member for suppressing buckling, an increase in weight of the tire 10 can be suppressed. In particular, when the area ratio of the groove of the center portion C to the area of the center portion C is larger than the area ratio of the groove of the shoulder portion Sh to the area of the shoulder portion Sh, or a tread pattern formed with a large groove width is used. In such a case, the buckling suppressing effect can be further improved.

  On the other hand, the JIS hardness of the cap tread rubber of the center portion C may be smaller than the JIS hardness of the cap tread rubber of the shoulder portion Sh. In this case, it is preferable that the JISA hardness of the cap tread rubber of the center portion C is set to 62 to 67, for example, and the JISA hardness of the cap tread rubber of the shoulder portion Sh is set to 70 to 75, for example. Furthermore, it is more preferable that the JIS hardness of the cap tread rubber of the center portion C is 3 to 10 degrees smaller than the JIS hardness of the cap tread rubber of the shoulder portion Sh.

  By configuring the tire 10 in this way, the rigidity of the shoulder portion Sh can be increased, so that deformation of the shoulder portion Sh can be suppressed even in the run-flat state. Moreover, since it is not necessary to newly provide a member for suppressing buckling, an increase in weight of the tire 10 can be suppressed. In particular, when the area ratio of the groove of the center portion C to the area of the center portion C is smaller than the area ratio of the groove of the shoulder portion Sh to the area of the shoulder portion Sh, or a tread pattern formed with a small groove width is used. In such a case, the buckling suppressing effect can be further improved.

(Modification)
FIGS. 5A and 5B are diagrams showing a modification of the embodiment. In the modification shown in FIG. 5A, each of the plurality of first main grooves 28 is provided to extend in a zigzag shape in the tire circumferential direction. Here, the term “zigzag extending in the tire circumferential direction” means that the portion inclined with respect to the tire circumferential direction extends in the tire circumferential direction while turning back so that the inclination directions are alternate. By adopting such a configuration, the load applied to each of the plurality of first main grooves 28 is distributed, so that buckling that occurs when the plurality of first main grooves 28 are deformed by receiving the load can be suppressed. it can. Further, as shown in FIG. 5B, one of the plurality of first main grooves 28 may be provided so as to extend linearly in the tire circumferential direction. Further, the plurality of first main grooves 28 may be provided so as to be symmetric with respect to the tire center line CL, or may be provided so as to be asymmetric with respect to the tire center line CL.

  The tire 10 of the above embodiment uses the carcass ply material 12 having two layers of the ply material of the first ply material 12a and the second ply material 12b, but the carcass ply layer having one ply material may be used. Good. Moreover, the fiber used for the carcass ply layer 12 is not limited to an organic fiber, and a steel wire can also be used.

[Example]
Hereinafter, in order to investigate the effect of the pneumatic tire of the present invention, various tires (tire size: 245 / 40R199 94V) were produced. The contact area change rate was determined for the manufactured tire. Here, the contact area change rate is obtained as a ratio of the contact area of the tread portion during run-flat traveling to the contact area of the tread portion during normal traveling. The contact area change rate indicates that the higher the value, the better the buckling suppression.
The produced tire is mounted on a rim for measurement specified in ETRTO (European Tire and Rim Technical Organization). The tire hollow area is filled with the maximum air pressure (250 kPa) specified by ETRTO, and when the maximum load (670 kgf) specified by ETRTO is applied to the tire, the contact area of the tread portion is determined as the tread during normal driving. Measured as the contact area of the part. In addition, the air pressure in the tire cavity region is 0 kPa, and the contact area of the tread when the maximum load (670 kgf) specified by ETRTO is applied to the tire is measured as the contact area of the tread during run-flat running. did.

Tables 1 and 2 below show the specifications of Comparative Examples and Examples 1 to 11 and the contact area change rate at that time.
The comparative example is a tire in which the second main groove 29 (outermost main groove) and the reinforcing rubber layer 27 do not overlap in the tire width direction. In Example 1, a part of the reinforcing rubber layer 27 was provided so as to overlap the bottom surface of the second main groove 29 (outermost main groove) in the tire width direction. Moreover, in Examples 1-4, the 2nd main groove 29 (outermost main groove) of the area of the part which overlaps with the bottom face of the 2nd main groove 29 (outermost main groove) among the reinforcement rubber layers 27 in a tire width direction. The ratio with respect to the area of the bottom surface was changed.
In Examples 5 to 7, the maximum value of the thickness of the portion of the reinforcing rubber layer 27 that overlaps the second main groove 29 (outermost main groove) in the tire width direction was changed.
Furthermore, in Example 8, the first main groove 28 was provided so as to extend in a zigzag shape in the tire circumferential direction.
Further, in Examples 9 to 11, the difference between the JIS hardness of the cap tread rubber of the shoulder portion Sh and the JIS hardness of the cap tread rubber of the center portion C was changed. In addition, in the column of “JISA hardness of rubber of shoulder portion−JISA hardness of rubber of center portion” in the table below, when the value is a positive value, the JISA hardness of the cap tread rubber of the shoulder portion Sh is It represents that it is larger than the JIS hardness of the cap tread rubber.

From the comparison between the comparative example and Example 1, by providing a part of the reinforcing rubber layer 27 so as to overlap the second main groove 29 (outermost main groove) in the tire width direction, the contact area change rate can be improved. I understand.
Further, from comparison between Examples 1 to 4, the area of the reinforcing rubber layer 27 overlapping the second main groove 29 (outermost main groove) in the tire width direction is the second main groove 29 (outermost main groove). It has been found that the contact area change rate is improved when the area of the groove is 20% or more.
Furthermore, from the comparison with Examples 5-7, when the thickness of the part which overlaps with the 2nd main groove 29 (outermost main groove) and the tire width direction among the reinforcement rubber layers 27 is 1.0 mm or more and 6.0 mm or less In addition, it was found that the rate of change in contact area is improved.
Further, from comparison between Examples 5 and 8, it was found that the contact area change rate is improved by providing the first main groove 28 so as to extend in a zigzag shape in the tire circumferential direction.
Further, from comparison of Examples 9 to 11, when the JIS hardness of the cap tread rubber of the shoulder portion Sh is 3 to 10 degrees larger than the JIS hardness of the cap tread rubber of the center portion C, that is, the cap tread rubber of the center portion C. It has been found that when the JISA hardness is 3 to 10 degrees smaller than the JISA hardness of the cap tread rubber of the shoulder portion Sh, the contact area change rate is improved.
As mentioned above, the effect of the tire of this embodiment is clear.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, this invention is not limited to the said embodiment, Of course, in the range which does not deviate from the main point of this invention, you may make a various improvement and change. is there.

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Carcass ply layer 12a 1st ply material 12b 2nd ply material 14 Belt layers 14a and 14b Steel belt material 14c Organic fiber reinforcement 16 Bead core 18 Tread rubber layer 20 Side rubber layer 22 Bead filler rubber layer 24 Rim cushion rubber Layer 26 Inner liner rubber layer 27 Reinforcing rubber layer 28 First main groove 29 Second main groove

Claims (5)

A pneumatic tire having a bead portion, a sidewall portion, and a tread portion,
The sidewall portion has a reinforcing rubber layer formed so that one end side extends toward the tread portion and the other end side extends toward the bead portion on the inner surface side facing the tire cavity region,
The tread portion has a plurality of main grooves extending in the tire circumferential direction at intervals in the tire width direction,
One end side of the reinforcing rubber layer on the outer side in the tire radial direction overlaps at least a part of the outermost main groove located on the outermost side in the tire width direction among the plurality of main grooves in the tire width direction. Provided as
A pneumatic tire characterized by that.   2. The pneumatic tire according to claim 1, wherein an area of a portion of the reinforcing rubber layer that overlaps with an outermost main groove in a tire width direction is 20% or more of an area of the outermost main groove.   The pneumatic tire according to claim 1 or 2, wherein a thickness of a portion of the reinforcing rubber layer that overlaps with the outermost main groove in the tire width direction is 1.0 mm or greater and 6.0 mm or less.   The pneumatic tire according to any one of claims 1 to 3, wherein at least one main groove excluding the outermost main groove among the plurality of main grooves is provided so as to extend in a zigzag shape in a tire circumferential direction. . 5. The JIS hardness at the center portion in the tire width direction of the cap tread rubber constituting the tread portion is 3 to 10 degrees smaller than the JIS hardness at both ends in the tire width direction of the cap tread rubber. The pneumatic tire according to item.