JP7335486B2 - pneumatic tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire that achieves both shock burst resistance and high-speed durability.

Since extra-road tires are used with relatively high air pressure, the tires receive a large shock during running, and there is a risk of damage due to, for example, carcass destruction (shock burst). For this reason, extra road tires are required to ensure shock burst resistance performance.

In order to ensure the shock burst resistance performance, it is conceivable to provide a reinforcing layer in the vicinity area including the tire equatorial plane (tire width direction center area), which is the area where the load is most applied during running. For example, a method is known in which a full cover layer is provided over the entire tire width direction outside the belt layer in the tire radial direction, and then a center cover layer is provided in the tire width direction center region outside the tire radial direction of the full cover layer. (Patent Document 1). By adopting such a configuration, it is possible to locally reinforce the tire width direction center region on the outer side of the belt layer in the tire radial direction, thereby ensuring shock burst resistance performance.

JP 2017-137032 A

However, providing the center cover layer increases the tread gauge in the center area. This is especially noticeable in extra-road tires that are used with relatively high air pressure, and as a result of excessive load being applied to the area where the tread gauge is increased, the tire contact length increases and the contact with other areas increases. Due to the significant difference in ground pressure, there is a risk that excellent high-speed durability performance cannot be exhibited.

In addition, as in the technique disclosed in Patent Document 1, particularly when a strip-shaped sound absorbing material is introduced into the tire inner cavity, the strip-shaped sound absorbing material or the There is a risk that the rubber layer that is arranged close to this will deteriorate, and as a result, excellent high-speed durability performance will not be exhibited.

The present invention has been made in view of the above circumstances, and on the premise of ensuring shock burst resistance performance, excellent high-speed durability performance even when a strip-shaped sound absorbing material is introduced into the tire inner cavity. To provide a pneumatic tire capable of exhibiting

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 band-shaped sound absorbing material is formed inside the inner liner in the tire radial direction,
At least three of the four tire width direction end points of the two circumferential main grooves located on both sides of the center land portion in the tire width direction, including two points that are boundaries with these land portions. When the first contour line of the tread surface is an arc centered radially inward,
A tire profile line of the center land portion protrudes radially inward of the first contour line of the tread surface.

In the pneumatic tire according to the present invention, the tire profile line of the center land portion is improved. As a result, the pneumatic tire according to the present invention exhibits excellent high-speed durability performance even when a band-shaped sound absorbing material is introduced into the tire lumen on the premise of ensuring shock burst resistance performance. can do.

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 tire side sectional view showing the pneumatic tire according to the embodiment of the invention.

EMBODIMENT OF THE INVENTION Below, embodiment (basic form and additional forms 1-5 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 has a groove width (maximum width) of 7.5 mm or more and 8.5 mm or less and a groove depth (maximum groove depth) of 7.0 mm or more and 8.5 mm or less. It means groove.

When there are three circumferential main grooves (not shown), the two land portions located at the center in the width direction of the tire correspond to the center land portion, and the nearest land portion on the outer side in the width direction of the tire is the center land portion. It corresponds to the second land part. In the case where there are four circumferential main grooves (the case shown in FIG. 1), the two land portions 22 located at the center in the tire width direction correspond to the center land portions, and are closest to each other on the outer side in the tire width direction. The land portions 24 and 26 correspond to the second land portion. Furthermore, when there are five circumferential main grooves (not shown), the two land portions located at the center in the width direction of the tire correspond to the center land portion, and the nearest land portion on the outer side in the width direction of the tire corresponds to the center land portion. It corresponds to the second land part. Both the center land portion and the second land portion may be so-called ribs or so-called blocks.

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 strip-shaped sound absorbing material 38 is formed inside the inner liner 28 in the tire radial direction. The strip-shaped 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 strip-like sound absorbing material 38 . The band-like 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, as shown in FIG. A circular arc passing through at least three points including two points E2 and E3 that form boundaries with the center land portion 22 among the end points E1, E2, E3, and E4 in the tire width direction, and having a center on the inner side in the tire radial direction (shown in the figure). If the arc passing through all of the end points E1 to E4 in the case) is the first contour line L1 of the tread surface, the tire profile line of the center land portion 22 is aligned with the first contour line L1 of the tread surface in the tire radial direction. It protrudes inward.

(action, etc.)
In the pneumatic tire according to the present embodiment, as shown in FIG. 1, a center cover layer 34b that locally covers the central region of the belt layer 32 in the tire width direction is provided outside the full cover layer 34a in the tire radial direction. Therefore, it is possible to locally reinforce the center region in the width direction of the tire, which is the region where the load is most applied during running, and to ensure shock burst resistance performance (Action 1).

Further, in the pneumatic tire according to the present embodiment, as shown in FIG. 1, the tire profile line of the center land portion 22 is protruded radially inward with respect to the first contour line L1 of the tread surface. It is possible to suppress protrusion of the center land portion 22 to the outside in the tire radial direction during running, and to suppress an increase in the tire contact length. As a result, the difference in contact pressure between the center land portion 22 and the second land portions 24, 26 can be suppressed, and excellent high-speed durability performance can be exhibited (Action 2).

As described above, in the pneumatic tire according to the present embodiment, on the premise that the shock burst resistance performance is ensured by improving the tire profile line of the center land portion (action 1 above), even if the tire inner cavity is Even when the strip-shaped sound absorbing material is introduced, excellent high-speed durability performance can be exhibited (operation 2 above), and both shock burst resistance performance and high-speed durability performance can be achieved at a high level.

Although not shown, the pneumatic tire of the present embodiment described above has a bead portion and a sidewall portion from the inside to the outside in the tire radial direction in a meridional cross-sectional view, similarly to a conventional pneumatic tire. and a tread portion. 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 to 5 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)
In the basic configuration, when the center cover layer 34b has a thickness of 0.10 mm or more and 0.40 mm or less in FIG. When the thickness of the layer 34b is 0.40 mm or more and 1.00 mm or less, the protrusion amount of the center land portion 22 is 0.25 mm or more and 0.5 mm or less, and the thickness of the center cover layer 34b is 1.00 mm or more. When the length is 0.50 mm or less, the amount of protrusion of the center land portion 22 is preferably 0.50 mm or more and 0.75 mm or less (additional mode 1).

In the present embodiment, the thickness of the center cover layer 34b and the amount of protrusion of the center land portion 22 inward in the tire radial direction are linked. The thickness of the tread rubber directly above the tire radial direction is reduced. As a result, the sum of the thickness of the center cover layer 34b and the thickness of the tread rubber directly above the center cover layer 34b in the tire radial direction is always kept substantially constant, and by efficiently obtaining a local reinforcing effect in the vicinity of the tire equatorial plane CL, Shock burst performance can be secured at a higher level.

On the other hand, without excessively increasing the amount of protrusion of the center land portion 22 with respect to the thickness of the center cover layer 34b, the thickness of the tread rubber is sufficiently secured directly above the center cover layer 34b in the tire radial direction. It is possible to increase the shear rigidity and further improve the shock burst resistance performance.

(Additional form 2)
In the basic form or the form obtained by adding the additional form 1 to the basic form, in FIG. Of the four tire width direction end points E5, E6, E1, E2 (E3, E4, E7, E8) of the two circumferential main grooves 14, 18 (16, 20) located on both sides in the tire width direction, these A circular arc passing through at least three points including two points E6 and E1 (E4 and E7) that form a boundary with the land portion 24 (26) of the tire and having a center on the inner side in the tire radial direction (in the case of the figure, all points E5 , E6, E1, E2 (arcs passing through E3, E4, E7, E8)) of the tread surface, the tire profile line of the second land portions 24, 26 is defined as the second contour line L2 (L2) of the tread surface. second contour lines L2, L2 (additional form 2).

By projecting the tire profile line of the second land portion 24 (26) outward in the tire radial direction with respect to the second contour line L2 (L2) of the tread surface, the center land portion 22 is projected outward in the tire radial direction during running. In addition, it is possible to further suppress an increase in the tire contact length. Moreover, with such a configuration, the difference in contact pressure between the center land portion 22 and the second land portion 24 (26) can be further suppressed. As a result, according to such a configuration, excellent high-speed durability performance can be exhibited at a high level.

(Additional form 3)
In the basic configuration or a configuration in which at least one of the additional configuration 1 and the additional configuration 2 is added to the basic configuration, as shown in FIG. A ratio P1/P2 between the amount of protrusion P1 and the amount of protrusion P2 of the second land portion 24 (26) to the outside in the tire radial direction with respect to the second contour line L2 (L2) is 0.50 or more and 0.70 or less. (Additional configuration 3) is preferred.

By setting the ratio P1/P2 to 0.50 or more, it is possible to further suppress protrusion of the center land portion 22 to the outside in the tire radial direction during running, thereby further suppressing an increase in the tire contact length. Moreover, with such a configuration, the difference in contact pressure between the center land portion 22 and the second land portion 24 (26) can be further suppressed. As a result, according to such a configuration, excellent high-speed durability performance can be exhibited at a higher level.

On the other hand, by setting the ratio P1/P2 of both protrusion amounts to 0.70 or less, the thickness of the tread rubber directly above the center cover layer 34b in the tire radial direction is sufficiently secured, and the local By efficiently obtaining a strong reinforcing effect, it is possible to ensure a higher level of shock burst resistance performance.

Further, when the ratio P1/P2 is 0.55 or more and 0.65 or less, the above effects are exhibited at a higher level, which is more preferable.

(Additional form 4)
In the basic mode or in the mode in which at least one of the additional modes 1 to 3 is added to the basic mode, the center cover layer 34b shown in FIG. 4) is preferred. Since the center cover layer 34b includes organic fiber cords obtained by twisting nylon having relatively high elongation and aramid having relatively high strength, the contact length is prevented from becoming excessively large compared to the case of using steel cords. In addition, it is possible to reduce heat generation by suppressing deflection of the tread portion, thereby efficiently improving high-speed durability performance.

(Additional form 5)
In the basic form or in the form obtained by adding at least one of the additional forms 1 to 4 to the basic form, the strip-shaped sound absorbing material 38 shown in FIG. 5) is preferred.

FIG. 3 is a tire side sectional view showing a pneumatic tire according to an embodiment of the invention. This figure shows only a portion radially inward of the inner liner 28 of the pneumatic tire 1 shown in FIG. there is As shown in the figure, the belt-like sound absorbing material 38 has one discontinuity in the tire circumferential direction, and this portion serves as an intermittent portion 42 .

By making the band-like sound absorbing material 38 discontinuous in at least one place in the tire circumferential direction to form an intermittent portion 42, the band-like sound absorbing material 38 can be applied to the inner liner in a rolling state in which the tire is filled with air and a load is applied. Shear strain on the bonding surface can be relaxed. As a result, heat generation between the strip-shaped sound absorbing material 38 and the inner liner 28 can be suppressed, and further excellent high-speed durability performance can be exhibited.

(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 strip-shaped sound absorbing material 38), and having a center land portion 22 and a second land portion 24 (26) shown in the figure, and further shown in Tables 1 and 2 below. Pneumatic tires of Conventional Example, Comparative Examples 1 and 2, and Examples 1 to 7, which satisfy various conditions shown, were manufactured.

Here, in Tables 1 and 2 below, P1 refers to the tire diameter from the contour line of the tread surface (dotted line in FIG. 2) to the tire profile line (solid line in FIG. 2) with respect to the center land portion 22 in FIG. P2 is the maximum amount of protrusion inward in the direction, and P2 refers to the second land portion 24 (26) in FIG. is the maximum amount of protrusion to the outside in the tire radial direction.

(Evaluation of shock burst resistance performance)
Each test tire thus prepared was assembled to a wheel (ETRTO standard rim) with a rim size of 21 x 9.5J, the air pressure was set to 220kPa (Reinforced/Extra Load Tires), and a plunger with a plunger diameter of 19 ± 1.6mm was installed. Tire strength (tire breaking energy) was measured by performing a tire breaking test (JIS K 6302) in which a tire is pressed against the center of the tread at a load speed (push speed of plunger) of 50.0±1.5 m/min. . Then, the measured real value (unit: J) of the fracture energy was converted into an index based on the conventional example (100) and evaluated. This evaluation means that the larger the numerical value, the larger the fracture energy and the better the shock burst resistance (Tables 3 and 4).

(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 under a load of 4 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 (Tables 3 and 4).

According to Tables 1 to 4, from Example 1 belonging to the technical scope of the present invention (the tire profile line of the center land portion protrudes inward in the tire radial direction with respect to the first contour line of the tread surface) The pneumatic tire of Example 7 achieves a higher level of both shock burst resistance and high-speed durability than the pneumatic tire of the conventional example, which does not belong to the technical scope of the present invention. It turns out.

Reference Signs List 1 pneumatic tire 10 tread portion 12 tread surface 14, 16, 18, 20 circumferential main groove 22 center land portion 24, 26 second 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 belt-shaped sound absorbing material 40 adhesive 42 intermittent portion CL tire equatorial plane E1, E2, E3, E4, E5, E6, E7, E8 tire width direction end point L1 first contour line L2 Second contour line X, Y, Z Tire width direction area

Claims (5)

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 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 band-shaped sound absorbing material is formed radially inward of an inner liner,
At least one of the center land portions is a specific center land portion, and of the four tire width direction end points of the two circumferential main grooves located on both sides of the specific center land portion in the tire width direction, these land portions When the first contour line of the tread surface is an arc that passes through at least three points including two points that are the boundary between the
The tire profile line of the specific center land portion protrudes inward in the tire radial direction with respect to the first contour line of the tread surface,
Four of the two circumferential main grooves located on both sides in the tire width direction of a second land portion adjacent to the specific center land portion and positioned outside the specific center land portion in the tire width direction. When the second contour line of the tread surface is an arc that passes through at least three of the end points, including two points that are boundaries with these land portions, and has a center radially inward of the tire,
A pneumatic tire, wherein a tire profile line of the second land portion protrudes outward in the tire radial direction with respect to the second contour line of the tread surface. When the thickness of the center cover layer is 0.10 mm or more and less than 0.40 mm, the amount of protrusion of the center land portion is 0.05 mm or more and 0.20 mm or less, and the thickness of the center cover layer is 0.40 mm. When the thickness is more than 1.00 mm, the amount of protrusion of the center land portion is 0.25 mm or more and 0.50 mm or less, and when the thickness of the center cover layer is 1.00 mm or more and 1.50 mm or less, the specific The pneumatic tire according to claim 1, wherein the protrusion amount of the center land portion is 0.50 mm or more and 0.75 mm or less. 3. The ratio of the amount of protrusion of the specific center land portion with respect to the first contour line and the amount of protrusion of the second land portion with respect to the second contour line is 0.50 or more and 0.70 or less according to claim 1 or 2. pneumatic tires. The pneumatic tire according to any one of claims 1 to 3, wherein the center cover layer includes organic fiber cords made by twisting nylon and aramid. The pneumatic tire according to any one of claims 1 to 4, wherein the strip-shaped sound absorbing material is discontinuous in at least one location in the tire circumferential direction.

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