JP7335485B2 - pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire that achieves both high-speed durability performance and uniformity.

Conventionally, there is known a technique of forming a sound absorbing material made of sponge on the tire inner cavity side of the tread portion in order to reduce road noise by reducing tire cavity resonance (Patent Documents 1 and 2).

In the technologies disclosed in Patent Documents 1 and 2, the tread band deforms depending on the severe use of the tire, such as an increase in the average running speed of the vehicle, and an unexpected external force is applied to the sound absorbing material. , there is a risk that the excellent durability performance of the sound absorbing material cannot be obtained. Therefore, in recent years, a pneumatic tire has been developed in which the durability performance of the sound absorbing material is improved so as to withstand such a situation (Patent Document 3).

Japanese Patent No. 3612059 JP-A-2005-138760 Japanese Patent No. 4960626

However, when the pneumatic tire described in Patent Document 3 is used for a long period of high-speed driving, the sound absorbing material is excessively heat-accumulated and damaged due to the large area where the sound absorbing material is provided. There is a risk that high-speed durability performance cannot be achieved.

Moreover, in recent years, there has been an increasing demand for improvements in tire uniformity in order to improve the steering stability performance and ride comfort of tires.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire that achieves uniformity equal to or greater than that of conventional tires and that has improved high-speed durability performance.

In the pneumatic tire according to the present invention, at least two center land portions are defined by at least three circumferential main grooves provided in the tread portion,
In the tread portion, at least one full-cover layer arranged outside the belt layer in the tire radial direction and covering the entire width of the belt layer, and the belt layer arranged outside the full-cover layer in the tire radial direction. and at least one center cover layer that locally covers the central region in the tire width direction,
A sound absorbing material is formed inside the inner liner in the tire radial direction,
The sound absorbing material has a uniform thickness and width, extends in a meandering direction in the tire circumferential direction, has an equal arrangement area on both sides in the tire width direction of the tire equatorial plane, and has a uniform thickness and width in the tire circumferential direction. The serpentine pitch is constant.

In the pneumatic tire according to the present invention, improvements are added to the shape and extension of the sound absorbing material. As a result, according to the pneumatic tire according to the present invention, both high-speed durability performance and uniformity can be achieved.

FIG. 1 is a tire meridional cross-sectional view showing a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a perspective view of a pneumatic tire according to an embodiment of the invention. FIG. 3 is a schematic diagram showing a part of the arrangement mode of the sound absorbing material with respect to the belt of the pneumatic tire according to the embodiment of the present invention.

EMBODIMENT OF THE INVENTION Below, embodiment (a basic form and additional forms 1 and 2 shown below) of the pneumatic tire which concerns on this invention is described in detail based on drawing. It should be noted that these embodiments do not limit the present invention. In addition, the components of the above embodiments include components that can be easily replaced by those skilled in the art, or components that are substantially the same. Further, the various forms included in the above embodiments can be arbitrarily combined within the scope obvious to those skilled in the art.

[Basic form]
The basic configuration of the pneumatic tire according to the present invention will be described below.

In the following description, the tire radial direction refers to the direction perpendicular to the rotation axis of the pneumatic tire, the tire radial direction inner side refers to the side facing the rotation axis in the tire radial direction, and the tire radial direction outer side refers to the tire radial direction. The side away from the rotation axis. In addition, the tire circumferential direction refers to a circumferential direction around the rotation axis. Furthermore, the tire width direction refers to a direction parallel to the rotation axis, the tire width direction inner side refers to the side facing the tire equatorial plane CL (tire equator line) in the tire width direction, and the tire width direction outer side refers to the tire width direction. , the side away from the tire equatorial plane CL. The tire equatorial plane CL is a plane perpendicular to the rotation axis of the pneumatic tire and passing through the center of the tire width of the pneumatic tire.

FIG. 1 is a tire meridional cross-sectional view showing a tread portion of a pneumatic tire according to an embodiment of the present invention. In addition, the pneumatic tire shown in the figure is mounted on a normal rim, air pressure of 180 kPa to 350 kPa is applied, and a load of 50% to 95% of the normal load is applied. The meridional cross-sectional view of the pneumatic tire is a view showing the cross-sectional shape of the pneumatic tire appearing on a plane perpendicular to the tire equatorial plane.

Here, the regular rim means a "standard rim" defined by JATMA, a "design rim" defined by TRA, or a "measuring rim" defined by ETRTO. In addition, the normal load refers to the "maximum load capacity" defined by JATMA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "LOAD CAPACITY" defined by ETRTO.

A pneumatic tire 1 shown in FIG. 1 has a tread portion 10 . The tread portion 10 is made of a rubber material (tread rubber) or the like, is located on the outermost side of the pneumatic tire 1 in the tire radial direction, and its surface forms the contour of the pneumatic tire 1 . The surface of the tread portion 10 is formed as a tread surface 12 that comes into contact with the road surface when a vehicle (not shown) on which the pneumatic tire 1 is mounted runs.

The tread surface 12, as shown in FIG. 24 and 26 are partitioned.

Here, the circumferential main groove is a groove having a groove width (maximum width) of 7.5 mm or more and 8.5 mm or less and a groove depth (maximum depth) of 7.5 mm or more and 8.5 mm or less. Say.

Further, in the pneumatic tire according to the present embodiment, as shown in FIG. 1, the inner liner 28, the carcass layer 30, the belt layer 32 (belts 32a to 32c), A belt cover layer 34 (a full cover layer 34a and a center cover layer 34b) and a tread rubber layer 36 are provided.

That is, at least one full cover layer 34a, one in FIG. Further, at least one center cover layer 34b, one center cover layer 34b in FIG.

Furthermore, in the pneumatic tire according to the present embodiment, as shown in FIG. 1, a sound absorbing material 38 is formed inside the inner liner 28 in the tire radial direction. The sound absorbing material 38 is made of a porous material having open cells, and has a predetermined sound absorbing characteristic based on its porous structure. For example, foamed urethane can be used as the porous material forming the sound absorbing material 38 . The sound absorbing material 38 is adhered to the inner liner 28 via an adhesive 40, for example, in a region of the inner surface of the tire corresponding to the tread portion 10. As shown in FIG. For example, a double-sided tape can be used as the adhesive 40 .

Under this premise, in the pneumatic tire according to the present embodiment, the sound absorbing material 38 has uniform thickness and width. Here, the thickness means the dimension of the sound absorbing material 38 in the tire radial direction, and the width means the dimension in the direction perpendicular to the extending direction of the sound absorbing material 38 .

Normally, the sound absorbing material 38 exerts its sound absorbing effect, so it is important that the volume of the sound absorbing material 38 is 20% or more of the volume of the inside of the tire filled with air when the vehicle is running (the tire is rotating). In the present embodiment, the thickness and width of the sound absorbing material 38 are uniform as described above. It can be calculated considering the width shown below.

FIG. 2 is a perspective view of the pneumatic tire according to this embodiment. As shown in the figure, in the pneumatic tire according to the present embodiment, the sound absorbing material 38 extends in the tire circumferential direction while meandering, and the arrangement area is equal on both sides of the tire equatorial plane CL in the tire width direction. . Further, in the pneumatic tire according to the present embodiment, the meandering pitches of the sound absorbing material 38 (the wavelengths in the meandering shape of the sound absorbing material) are the same.

2, the pneumatic tire 1 is cut along the line AA′ perpendicular to the tire equatorial plane CL. When the inner cavity surface of the tire is deployed and viewed from above, the area of the sound absorbing material 38 on one side in the tire width direction of the tire equatorial plane CL and the area of the sound absorbing material 38 on the other side in the tire width direction are equal to each other. means equal.

(action, etc.)
In the pneumatic tire according to the present embodiment, the sound absorbing material 38 extends in the tire circumferential direction while meandering. That is, in the pneumatic tire shown in FIG. 2, the sound absorbing material 38 extends in the tire circumferential direction while changing the arrangement area of the sound absorbing material 38 in the tire width direction. According to such an arrangement form of the sound absorbing material, compared with the conventional technology (for example, the invention described in Patent Document 3), the arrangement area of the sound absorbing material can be significantly smaller and dispersed. As a result, it is possible to prevent damage to the sound absorbing material 38 due to excessive heat accumulation (Action 1).

In addition, in the pneumatic tire according to the present embodiment, the thickness and width of the sound absorbing material 38 are both uniform, so that the contact area of the sound absorbing material 38 with the inner liner 26 is excessively different in the tire circumferential direction. Furthermore, the volume of the sound absorbing material 38 in contact with the inner liner 26 is not excessively varied in the tire circumferential direction. Therefore, even when the vehicle is driven at high speed for a long time, the separation of the sound absorbing material 38 from the inner liner 28 can be effectively suppressed (operation 2).

Furthermore, in the pneumatic tire according to the present embodiment, the areas where the sound absorbing material 38 is arranged are equal on both sides in the tire width direction of the tire equatorial plane CL, and the meandering pitch of the sound absorbing material 38 is constant in the tire circumferential direction. . Thus, in addition to the effects 1 and 2 described above, it is possible to achieve a uniformity equal to or greater than that of the conventional art (effect 3).

As described above, in the pneumatic tire according to the present embodiment, the damage due to heat accumulation caused by the extension of the sound absorbing material 38 is suppressed (action 1), and the inner liner 28 of the sound absorbing material 38 caused by the shape of the sound absorbing material 38 is reduced. It is possible to achieve excellent high-speed durability performance in combination with the suppression of peeling from the surface (action 2). In addition, in the pneumatic tire according to the present embodiment, due to the arrangement area and the arrangement mode of the sound absorbing material 38, uniformity equal to or higher than that of the conventional one is realized (effect 3), thereby achieving excellent high-speed durability as described above. In addition to achieving performance, it is also possible to achieve a high level of steering stability and ride comfort.

In addition, as shown in FIG. 2, the pneumatic tire of the present embodiment described above has a bead portion B, a sidewall portion S, and a tread portion from the inside to the outside in the tire radial direction in a meridional cross-sectional view of the tire. have T. Then, the pneumatic tire includes, for example, a carcass layer (member 30 in FIG. 1) that extends from the tread portion to the bead portions on both sides and is wound around a pair of bead cores in a tire meridian cross-sectional view. , a belt layer, etc. (member 32 in FIG. 1) sequentially formed on the outer side of the carcass layer in the tire radial direction.

In addition, the pneumatic tire of the present embodiment is produced through the normal manufacturing processes, that is, the tire material mixing process, the tire material processing process, the green tire molding process, the vulcanization process, the inspection process after vulcanization, and the like. It is obtained through When manufacturing the pneumatic tire of the present embodiment, in particular, convex portions corresponding to the desired circumferential main grooves and land portions are formed on the inner wall of the vulcanization mold, and this mold is used. Vulcanize.

[Additional forms]
Next, additional modes 1 and 2 that can optionally be implemented with respect to the basic mode of the pneumatic tire according to the present invention will be described.

(Additional form 1)
FIG. 3 is a schematic diagram showing a part of the arrangement mode of the sound absorbing material with respect to the belt of the pneumatic tire according to the embodiment of the present invention. In the basic form, as shown in FIG. 3, the tire width direction ends E1 to E3 of the sound absorbing material 38 are positioned inside the tire width direction ends e1 and e2 of the belt layers in the tire width direction, and the sound absorbing material The extension dimension D1 in the tire width direction of 38 is preferably 70% or more and 90% or less of the tire width direction dimension (belt width) d of the belt layer (additional mode 1).

The tire width direction ends E1 to E3 of the sound absorbing material 38 are located inside the tire width direction ends e1 and e2 of the belt layers. As a result, even if the vehicle is driven at high speed for a long time and the tire is subjected to a large centrifugal force and rises, the sound absorbing member 38 in FIG. 1 is less likely to be distorted due to the rise. Therefore, the sound absorbing material 38 does not come off from the inner liner 28, which in turn prevents the sound absorbing material 38 from being damaged, thereby realizing even higher high-speed durability.

Further, by setting the extension dimension D1 of the sound absorbing material 38 in the tire width direction to be 70% or more of the tire width direction dimension (belt width) d of the belt layer, the sound absorbing material 38 is dispersed over a wide range in the tire width direction. can do For this reason, it is possible to more efficiently prevent damage to the sound absorbing material 38 due to excessive heat accumulation, and furthermore excellent high-speed durability performance can be achieved.

On the other hand, by setting the extension dimension D1 in the tire width direction of the sound absorbing material 38 to be 90% or less of the tire width direction dimension (belt width) d of the belt layer, if the vehicle runs at high speed for a long time, Even if the tire receives a large centrifugal force and rises, the sound absorbing material 38 in FIG. 1 is less likely to be distorted due to the rise. Therefore, it is possible to more effectively suppress breakage due to peeling of the sound absorbing material 38 from the inner liner 28, thereby achieving even better high-speed durability.

Note that when the extension dimension D1 of the sound absorbing material 38 in the tire width direction is 73% or more and 87% or less of the tire width direction dimension (belt width) d of the belt layer, the above effects are achieved at a higher level. In the case of 75% or more and 85% or less, each of the above effects is exhibited at a higher level, which is more preferable.

(Additional form 2)
In the basic form or the form obtained by adding the additional form 1 to the basic form, the width D2 of the sound absorbing material 38 in FIG. , the meandering pitch number is preferably 25 or more and 35 or less (additional mode 2). Here, the number of meandering pitches is the number of meandering pitches present in the tire circumferential direction of one meandering pitch length P shown in FIG.

By setting the width D2 of the sound absorbing material 38 to be 15% or more of the tire width direction dimension d of the belt layer, the sound absorbing material 38 can be sufficiently formed with respect to the inner liner 28, and the cavity resonance noise of the tire can be As a result, road noise can be reduced. In addition, by making the belt layer 15% or more of the tire width direction dimension d, it is possible to suppress heat accumulation in the vicinity of the tire equatorial plane CL, so that the sound absorbing material 38 is further suppressed from being peeled off from the inner liner 28. Damage to the sound absorbing material 38 can be prevented more efficiently, and even higher high-speed durability can be achieved.

On the other hand, by setting the width D2 of the sound absorbing material 38 to 25% or less of the tire width direction dimension d of the belt layer, a sufficient number of meandering pitches is ensured and heat storage of the sound absorbing material 38 near the tire equatorial plane CL is achieved. can be further suppressed. As a result, damage to the sound absorbing material 38 due to excessive heat accumulation can be more efficiently suppressed, and further excellent high-speed durability performance can be achieved.

By setting the width D2 of the sound absorbing material 38 to 18% or more and 22% or less of the tire width direction dimension d of the belt layer, each of the above effects can be exhibited at a higher level, which is preferable.

Next, by setting the number of meandering pitches to 25 or more, the sound absorbing material 38 formed on the inner liner 28 can be further dispersed in the tire width direction, and a sufficient area for disposing the sound absorbing material 38 can be secured. can. As a result, it is possible to further reduce road noise by reducing tire cavity resonance.

On the other hand, by setting the number of meandering pitches to 35 or less, the heat accumulation of the sound absorbing material 38 near the tire equatorial plane CL is further suppressed without excessively increasing the arrangement area of the sound absorbing material 38 with respect to the inner liner 28. be able to. As a result, damage to the sound absorbing material 38 due to excessive heat accumulation can be more efficiently suppressed, and further excellent high-speed durability performance can be achieved.

When the number of meandering pitches is 27 or more and 33 or less, it is preferable because the above effects are exhibited at a higher level. It is more preferable than being played.

(Production of test tire)
The tire size is 275/40R21 107Y, and each component shown in FIG. 34b), a tread rubber layer 36 and a sound absorbing material 38), a pneumatic tire having land portions 22, 24 and 26 shown in FIG. Pneumatic tires of Examples and Examples 1 to 7 were produced. The width of the sound absorbing material 38 was made uniform in both the conventional example and Examples 1 to 7. Further, the thickness of the sound absorbing material 38 in the conventional example (corresponding to the technology disclosed in Patent Document 3) is set to the maximum thickness. Furthermore, in both the conventional example and Examples 1 to 7, the sound absorbing material 38 is set to have the same area on both sides of the tire equatorial plane CL in the tire width direction.

In Table 1, the widthwise end position of the sound absorbing material means the tire widthwise position of points E1 to E3 shown in FIG. Further, regarding the extension dimension D1, width D2, belt layer width d, and meandering pitch number in Table 1, the extension dimension in the tire width direction of the sound absorbing material 38 shown in FIG. It is an index defined based on the tire width direction dimension (belt width) and the meandering pitch length P, respectively.

(Evaluation of high-speed durability performance)
Next, each of the above test tires was set in an indoor drum tester (drum radius 854 mm), and preliminarily run for 30 minutes at a speed of 50 km / hour with an air pressure of 360 kPa and a load of 7.26 kN. Then, the speed was gradually increased from 260 km/h to 10 km/h every 10 minutes with a load of 7.26 kN, and the speed at the time of tire destruction was measured. Here, the term "at the time of tire destruction" refers to the time at which it is confirmed that damage has occurred due to peeling between the rubber and the cords constituting the tire, or between the rubber and the rubber. Then, based on the measured speed, an index evaluation was performed with the conventional example as a standard (100). In this evaluation, the larger the index, the higher the speed at which the tire breaks, indicating that the high-speed durability performance is excellent.

(Evaluation of uniformity)
Each test tire (20 tires each) was mounted on a rim wheel having a JATMA standard rim (rim size: 21×9.5J) and filled with a normal internal pressure (200 kPa). Specifically, the radial force variation (RFV) was measured according to the method specified in Tire Uniformity JASO C607 "Testing Method for Uniformity of Automobile Tires", and the yield was evaluated from the results. Then, based on this evaluation result, an index evaluation was performed with the conventional example set to 100. The results are also shown in Table 1. In this index evaluation, the higher the numerical value, the better the uniformity and the better the uniformity.

According to Table 1, all of the pneumatic tires of Examples 1 to 7 belonging to the technical scope of the present invention (predetermined improvements were made to the shape and extension of the sound absorbing material) It can be seen that both high-speed durability performance and uniformity are achieved at a higher level than the conventional pneumatic tire, which is not within the technical scope.

1 pneumatic tire 10 tread portion 12 tread surface 14, 16, 18, 20 circumferential main groove 22, 24, 26 land portion 28 inner liner 30 carcass layer 32 belt layer 32a, 32b, 32c belt 34 belt cover layer 34a full cover Layer 34b Center cover layer 36 Tread rubber layer 38 Sound absorbing material 40 Adhesive B Bead CL Tire equatorial plane D1 Extension dimension of sound absorbing material 38 in the tire width direction D2 Width D2 of sound absorbing material 38
d Dimension of belt layer in tire width direction (belt width)
E1, E2, E3 Ends of the sound absorbing material 38 in the tire width direction e1, e2 Ends of the belt layer in the tire width direction P1 meandering pitch length S Side wall portion T Tread portion

Claims (2)

At least two land portions are defined by at least three circumferential main grooves provided in the tread portion,
In the tread portion, at least one full cover layer that is arranged outside the belt layer in the tire radial direction and covers the entire width of the belt layer; and at least one center cover layer that locally covers the central region in the tire width direction,
A pneumatic tire in which a sound absorbing material is formed radially inward of an inner liner,
The sound absorbing material has a uniform thickness and width, extends in a meandering direction in the tire circumferential direction, has an equal arrangement area on both sides in the tire width direction of the tire equatorial plane, and has a uniform thickness and width in the tire circumferential direction. The serpentine pitch is constant,
The tire width direction end of the sound absorbing material is located inside the tire width direction end of the belt layer in the tire width direction, and the extension dimension of the sound absorbing material in the tire width direction is the tire width of the belt layer. A pneumatic tire characterized by being 70% or more and 90% or less of a directional dimension. The pneumatic tire according to claim 1, wherein the width of the sound absorbing material is 15% or more and 25% or less of the tire width direction dimension of the belt layer, and the meandering pitch number is 25 or more and 35 or less.

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