JP2009279951A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire furnished with a belt reinforcing layer and exerting excellent high-speed durability, capable of reducing the rolling resistance and enhancing the belt durability. <P>SOLUTION: The pneumatic tire is equipped with a tread part 1, sidewall parts 2, a bead part 3, carcass 5, a belt including an inclined belt layer 6 and the belt reinforcing layer 7, and tread rubber 9, characterized by that the cord drive-in density Ds of the belt reinforcing layer 7 in its shoulder side region is made smaller than the drive-in density Dc of the center side region about the boundary positioned at one quarter of the tread surface 8 half width, wherein the ratio Dc/Ds lies within the range of 110-125%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that has improved high-speed durability, reduced rolling resistance, and improved belt durability.

  As a conventional pneumatic tire intended to improve high-speed durability, for example, a belt comprising a plurality of belt cords extending at a relatively small angle (for example, 15 to 35 °) with respect to the tire equatorial plane. Two or more layers are arranged in a direction in which the cords cross each other, and an inclined belt layer and one or more belt cords are spirally wound in an extending posture in the tread circumferential direction. And a belt reinforcing layer.

  In this tire, since the expansion of the tread portion in the circumferential direction is suppressed by the belt reinforcing layer, the tire diameter growth due to the centrifugal force during high-speed running can be suppressed. Because the out-of-plane bending rigidity in the circumferential direction of the tread portion is increased, the vertical rigidity of the tire is increased, the ride comfort performance is reduced, and the contact length is shortened and the contact area is reduced, so that the steering stability is reduced. There was a problem that decreased.

Therefore, for example, Patent Document 1 discloses a belt in which the inclination angle of the belt cord of the two inclined belt layers with respect to the tire equatorial plane extends at a high angle (for example, 45 to 85 °) and intersects with each other. A structure is disclosed, according to which the belt cord extends at a relatively small angle with respect to the tire equatorial plane as in the prior art, compared to a belt structure that intersects each other between layers. By reducing the circumferential out-of-plane bending stiffness inherent to the belt by facilitating elongation and compression deformation due to the tensile force and compressive force of the tread, Thus, the vertical rigidity of the pneumatic tire can be reduced to improve the riding comfort performance, and the contact length can be increased to improve the handling stability accompanying the increase in the contact area.
Moreover, according to the tire of patent document 1, steering stability can be improved also by increasing cornering power based on the increase in a contact area.

However, in this tire described in Patent Document 1, a large interlaminar shear in the circumferential direction is provided between the end of the inclined belt layer that is relatively easy to extend in the circumferential direction and the end of the belt reinforcing layer that is difficult to extend in the circumferential direction. Since distortion will occur, the rolling resistance will also increase due to the occurrence of this distortion, and there is a risk of lowering the durability of the belt where interlayer separation is likely to occur between the inclined belt layer and the belt reinforcing layer. there were.
JP 2006-193032 A

  Therefore, the present invention provides a pneumatic tire having a belt reinforcing layer and capable of exhibiting excellent high-speed durability while reducing rolling resistance and improving belt durability.

  A pneumatic tire according to the present invention includes a tread portion, a pair of sidewall portions, a pair of bead portions, and a carcass made of at least one carcass ply extending in a toroid shape between bead cores in each bead portion, Two or more inclined belts that are arranged on the outer peripheral side of the crown region of the carcass and are each belt layer cord extending in a direction inclined with respect to the tire equatorial plane, and the belt layer cords intersect each other between the layers. A belt including a belt reinforcing layer formed by spirally winding a layer and one or a plurality of cords in an extending posture in the tread circumferential direction, and a tread rubber disposed radially outward of the belt The belt side reinforcement layer cord cord has a driving density Ds of the shoulder side region at the center side region with a quarter of the half width of the tread tread as a boundary. And less than implantation density Dc, the ratio Dc / Ds is characterized in that in the range of 110-125%.

Here, the “extending posture in the tread circumferential direction” means a state in which the cord extends at an angle within a range of 0 to 5 ° with respect to the tire equator plane.
“Cord driving density” refers to the number of cords included per unit width of 50 mm in the tread width direction in the belt reinforcing layer in which the cords are arranged in parallel.

  More preferably, in such a tire, the belt reinforcing layer is made of a high elongation cord, and the breaking elongation of the high elongation cord is made 10 to 20% larger in the shoulder side region than in the center side region.

Here, the “high elongation cord” generally means that a plurality of strands are loosely twisted together, and the strands are easy to move with each other and greatly stretched with a relatively small load, so that the total amount of elongation until breakage is large. For example, a cord having an elongation at break of 4.5 to 5.5% is meant.
“Elongation at break” means a value calculated from the result of a tensile test according to JIS Z 2241.

Preferably, the tread rubber is composed of at least two layers having different rubber types.
In this case, more preferably, the tread rubber has a cap-and-base structure including a cap rubber positioned on the outer peripheral side and a base rubber positioned on the inner peripheral side.

Preferably, tan δ of the base rubber is made smaller than that of the cap rubber.
Here, tan δ is a loss factor.

  More preferably, the tan δ of the base rubber is in the range of 0.03 to 0.12.

  Incidentally, the thickness of the base rubber is preferably in the range of 0.5 to 5 mm.

It is preferable that the thickness t _{1 of} the base rubber on the tire equatorial plane and the thickness t ₂ at a position 45% of the tread width from the tire equatorial plane satisfy the relationship of t ₁ <t _2. , more preferably, a thickness _{t 2,} and 1.2 to 10 times the thickness _{t 1.}

Further, it is preferable that the base rubber is made of different rubber types in the center portion and the shoulder portion of the tread surface, and more preferably, the base rubber has a 100% modulus at the center portion of the tread surface. Make it smaller.
Here, “100% modulus” is a tensile stress measured by preparing a JIS dumbbell-shaped No. 3 sample and performing a tensile test at a speed of 500 ± 50 mm / min at room temperature in accordance with JIS K6251. .

  By the way, it is also preferable that only the tread rubber portion disposed on the outer side in the tread width direction has a cap-and-base structure, and in this case, more preferably, the width of the tread rubber portion disposed on the inner side in the tread width direction is 30 to 80% of the tread width.

Here, the “tread width” refers to a linear distance between both ends of a tread pattern portion of a tire in which a tire is mounted on an applied rim, filled with a specified internal pressure, and in a no-load state.
In this case, “applied rim” and “specified internal pressure” refer to the rim and internal pressure specified in the industry standard effective in the region where the tire is produced and used, and the industry standard is, for example, JATMA in Japan. (Japan Automobile Tire Association) YEAR BOOK, European ETRTO (European Tire and Rim Technical Organization) STANDARD MANUAL, in the United States TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BO.

  Also preferably, the cord of the belt reinforcing layer is an aromatic polyamide cord or a steel cord.

  In the conventional tire, a large circumferential shear strain is generated between the end portion of the inclined belt layer and the end portion of the belt reinforcing layer, which may cause an increase in rolling resistance and a decrease in belt durability.

  Therefore, in the present invention, particularly, at the quarter of the half width of the tread surface, the driving density Ds of the shoulder side region of the cord of the belt reinforcing layer is made smaller than the driving density Dc of the center region, and the ratio Dc / As Ds is in the range of 110 to 125%, the so-called effect of the belt reinforcement layer is relatively reduced in the shoulder side region, thereby ensuring the radial growth suppression force at the time of high-speed rotation of the tire. It is possible to reduce the circumferential shear strain between the end portion of the inclined belt layer and the end portion of the belt reinforcing layer while reducing the out-of-plane bending rigidity in the direction, and hence the vertical rigidity of the tire. Accordingly, strain energy loss due to large deformation of the tread portion can be reduced, rolling resistance can be reduced, and belt durability can be improved.

  That is, if the ratio of the driving density of the belt reinforcing layer is less than 110%, the elongation of the shoulder side region becomes small, the circumferential shear strain at the end of the inclined belt layer and the end of the belt reinforcing layer increases, and the rolling resistance deteriorates. On the other hand, if it exceeds 120%, the circumferential extension of the shoulder side region becomes large, and the contact length of the shoulder side region where the generation of strain energy loss is large becomes long, so that the rolling resistance is deteriorated.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a meridian cross-sectional view of a half portion of a tire, showing an embodiment of the pneumatic tire of the present invention in a state where the pneumatic tire is assembled to an applied rim and filled with a prescribed internal pressure.

  In the figure, 1 is a tread portion, 2 is a pair of sidewall portions extending radially inward continuously to the respective side portions of the tread portion 1, and 3 is a radially inward direction of the sidewall portion 2. The continuous bead portions are shown in FIG.

  Here, each side part of the carcass ply embedded in, for example, a pair of bead cores 4 that is embedded in the bead part 3 is wound around the bead core 4 from the inner side to the outer side in the tire width direction. A carcass 5 made of, for example, a single carcass ply and having a radial structure is provided, and a belt layer cord is disposed on the outer peripheral side of the crown region of the carcass 5 with respect to the tire equatorial plane, for example, 45-80. Two or more layers of rubber-coated belt layers, in the figure, two inclined belt layers 6, extending in a direction inclined at an angle of 0 °, and belt layer cords intersecting each other between layers, A radially outer side of the inclined belt layer 6 is provided with, for example, a single belt reinforcing layer 7 made of a rubber-coated cord extending substantially along the tire equatorial plane. Configure belt layer 7, to arrange the tread rubber 9 forming a tread surface 8 radially outward of the belt.

  Furthermore, in this pneumatic tire, with the quarter of the half width W of the tread tread as the boundary, the driving density Ds of the shoulder side region of the cord of the belt reinforcing layer is made smaller than the driving density Dc of the center side region, The ratio Dc / Ds is in the range of 110 to 125%.

  In such a pneumatic tire, the belt reinforcing layer 7 is preferably formed of a high elongation cord, and the breaking elongation of the high elongation cord is increased by 10 to 20% in the shoulder side region than in the center side region.

  By making the belt reinforcement layer 7 a high elongation cord with a high breaking elongation, the elongation at a relatively low load is selected to be large, and the ride comfort is improved by suppressing an increase in out-of-plane bending rigidity. While suppressing the diameter growth during high-speed running under a state of reduced elongation after being greatly stretched by the load, the total elongation until breakage is large, so that the inclined belt layer 6 and the belt reinforcing layer 7 The interlaminar shear strain can be reduced to improve belt durability.

  In addition to making the driving density Ds of the cord of the belt reinforcing layer 7 smaller than the driving density Dc of the shoulder side region, the breaking elongation of the high elongation cord is adjusted to the shoulder of the tread tread surface 8. By making the side region 10-20% larger than the center side region, the circumferential relative strain between the end of the belt reinforcing layer 7 and the end of the inclined belt layer 6 can be further reduced, and this is It is possible to reduce energy loss due to strain generated between them, reduce rolling resistance, and improve belt durability.

FIG. 2 is a meridian cross-sectional view similar to FIG. 1, showing another embodiment of the pneumatic tire of the present invention with respect to a half portion of the tire.
In addition to what is shown in FIG. 1, the tread rubber 9 is composed of at least two layers having different rubber types, more preferably, a cap rubber 10 which is made of different rubber types and located on the outer peripheral side, and an inner peripheral side. The cap and base structure which consists of two types of two-layer rubber | gum with the base rubber 11 located in this.

Thus, even if the tread rubber 9 is greatly bent, the tread rubber 9 can be multi-layered with different types of rubber and the physical properties of each rubber type can be appropriately selected as required. In addition, the degree of freedom in design can be increased so that the rolling resistance does not deteriorate.
On the other hand, since laminating three or more rubber layers makes the tire molding operation difficult, laminating two rubber layers is appropriate.

Here, preferably, the base rubber 11 is formed with a rubber type having a tan δ smaller than that of the cap rubber 10.
According to this configuration, the cap rubber 10 in contact with the road surface has a large tan δ and a sufficient grip force on the road surface as a two-layer structure in which the base rubber 11 has a small tan δ rubber and the cap rubber 10 has a large tan δ rubber. While the base rubber 11 is formed by the rubber type to be exhibited, the energy loss due to the strain can be suppressed to be small by the base rubber 11 that does not come into contact with the road surface, and both the steering stability and the reduction of the rolling resistance can be achieved well.

In this case, the tan δ of the base rubber 11 is set in the range of 0.03 to 0.12, and the energy loss due to strain can be sufficiently reduced.
That is, if the tan δ of the base rubber 11 exceeds 0.12, the strain energy loss cannot be sufficiently reduced, and if it is less than 0.03, the rigidity of the base rubber 11 decreases, and the fracture characteristics deteriorate. , Tend to be unable to ensure sufficient fracture characteristics.

Preferably, the thickness of the base rubber 11 is set to 0.5 to 5 mm without changing the total thickness of the cap base structure.
If the thickness is less than 0.5 mm, the rubber thickness is too thin and the effect of suppressing strain energy loss is too small. On the other hand, if it exceeds 5 mm, the volume of the base rubber generally having low rigidity is too large. Steering stability tends to deteriorate.

By the way, tires are generally designed in a curved shape that protrudes radially outward in the meridian cross section.
On the other hand, when the outer contour line of the tread portion in the meridian section is a flat straight line, the ground contact length of the shoulder portion is long and the ground contact length of the center portion is long if there is no roundness in the tire width direction. Short, uneven grounding shape. In such a contact shape, the contact pressure on the shoulder portion of the tire is likely to increase and the contact length becomes longer, so that wear of the shoulder portion is promoted. Therefore, for the reason of suppressing the early wear of the shoulder portion, the shape is rounded in the curve width direction that protrudes outward in the radial direction.

When such a tire surface is pressed against the road surface, the center portion bends a lot to generate a force (wiping force) toward the center in the width direction of the ground surface. The distortion due to the wiping force is larger than that at the center portion, particularly at the shoulder portion, and the rolling resistance at the tread shoulder portion is further increased due to the energy loss due to the strain at this time.
In order to reduce the energy loss caused by such wiping force, it is effective to place a large deformation on the base rubber having a small tan δ.

Therefore, in the other embodiment of the present invention shown in FIG. 3, in particular, the thickness t ₁ of the base rubber 11a on the tire equator plane and the thickness t ₂ at a position of 45% of the tread width TW from the tire equator plane. Satisfy the relationship of t ₁ <t ₂ .
According to this configuration, the deformation due to the large wiping force generated in the shoulder portion is particularly greatly absorbed by the base rubber 11a having a large thickness and a small tan δ, and the center portion having a large belt tension has the required physical properties. Under the action of the cap rubber 10a, the rigidity against the lateral force generated during cornering is increased and the cornering power is increased, so that the rolling resistance can be effectively suppressed and the steering stability can be effectively improved.

Here, more preferably, a thickness _{t 2,} and 1.2 to 10 times the thickness _{t 1.}
That is, when t ₂ is less than 1.2 times t ₁ , the effect of reducing energy loss due to the wiping force of the shoulder portion is reduced, whereas when t ₂ exceeds 10 times t ₁ , the base rubber 11a of the shoulder portion is reduced. There is a tendency that the weight of the tire increases because the thickness of the tire is too thick.

In the embodiment shown in FIG. 4, the base rubber is different from the base rubber 11 b _{1 at} the center portion of the tread tread surface 8 and the base rubber 11 b _{2 at the} shoulder portion. For example, the width of the center portion is 40 to 80% of the tread width TW.

With this configuration, for example, by changing the 100% modulus of the center portion, which has a high contribution to steering stability, to 2.2 MPa and the 100% modulus of the shoulder portion, which has a high contribution to rolling resistance, to 1.7 MPa rubber, respectively. Thus, it is possible to achieve both improvement in handling stability and reduction in rolling resistance. For example, the base rubber 11b ₂ having a small tan δ in the shoulder portion is particularly greatly deformed to suppress an increase in rolling resistance. ₂ can be of a soft rubber type, and the base rubber 11b ₁ at the center can be of a hard rubber type in order to ensure steering stability.

Again, more preferably, 100% modulus of the base rubber, the base rubber 11b ₂ of the shoulder portion of the tread surface, lower than the base rubber 11b ₁ of the center portion.

With this configuration, the base rubber 11b ₂ of the shoulder portion is subjected to a large portion of deformation due to the wiping force, so that even when a large strain occurs, the energy loss can be suppressed low and the rolling resistance can be reduced. .

In the embodiment shown in FIG. 5, only the tread rubber portion arranged on the outer side in the tread width direction is divided into two layers of the cap rubber 10 c located on the outer peripheral side and the base rubber 11 c located on the inner peripheral side. The cap and base structure is as follows.
Here, by disposing the base rubber 11c having a small tan δ on the outer side in the tread width direction, even if the base rubber 11c is deformed by the wiping force, the loss of energy can be suppressed to a small amount. Regardless, the rolling resistance can be kept sufficiently small.

  Here, when the width of the tread rubber portion arranged on the inner side in the tread width direction is 30 to 80% of the tread width, from the center of the tread to the outer side in the width direction from the position of 15% of the tread width TW. The base rubber 11c having a small tan δ is disposed in the region for the wiping force that starts to increase and reaches the maximum at a position of 40 to 50% of the tread width TW, thereby effectively reducing the loss in the region with a large amount of deformation. Thus, the rolling resistance of the tire can be efficiently reduced.

Incidentally, the cord of the belt reinforcing layer 7 is preferably an aromatic polyamide cord or a steel cord.
That is, by making the cord of the belt reinforcing layer 7 an aromatic polyamide cord, the compression rigidity of the belt reinforcing layer 7 can be relatively reduced, the out-of-plane bending rigidity is reduced, and steering stability and ride comfort are reduced. Can be improved. For example, the cord of the belt reinforcing layer 7 can be a Kevlar cord.
In addition, since the cord of the belt reinforcement layer 7 is made of steel cord, the tensile strength in the belt circumferential direction can be ensured, so that the tensile strength in the belt circumferential direction is reduced and the tire diameter grows at high speeds. Can be suppressed, and a reduction in high-speed durability can be suppressed.

  Next, a tire having a structure as shown in FIGS. 1 to 5 and having a size of 195 / 65R15 was manufactured as a prototype, and the carcass is a carcass ply made of a polyethylene cord extending at an angle of 90 ° with respect to the tire equatorial plane. The inclined belt layer is made of two layers in which steel cords arranged at an inclination angle of 70 ° with respect to the tire equatorial plane are crossed between the layers, and are arranged in parallel on the outer peripheral side thereof. An embodiment in which a belt reinforcing layer formed by spirally winding a ribbon-shaped strip formed by coating a plurality of steel cords with rubber is provided, and other specifications are changed as shown in Tables 1 and 2. Belt durability, steering stability, riding comfort and rolling resistance were measured for each of Example Tires 1 to 7 and Comparative Example Tires 1 to 3.

The thickness of the base rubber at the center was measured at the position of the tire equator, and the thickness of the base rubber at the shoulder was measured at a position 60 mm from the tire equator in the tire width direction.
Tan δ was measured by performing a tensile test on a sample having a width of 4.7 mm, a length of 20 mm, and a thickness of 2 mm under the conditions of a strain amplitude of 2%, a frequency of 52 Hz, and a measurement temperature of 25 ± 3 ° C.

ＨＣ：ハイエロンゲーションコード

HC: High elongation code

(Belt durability)
For each of the example tires 1 to 7 and the comparative example tires 1 to 3, the tire is assembled to a 6.0 J × 15 rim, the internal pressure is 180 kPa, the camber angle is −1 °, the slip angle is 0 °, and the load is 8 kN. , Using a steel drum tester with a diameter of 3 m, continuously running at a speed of 150 km / h for 100 hours, then dismantling over the entire circumference of the tire, and the length of the crack between the steel belt and the spiral belt, The longest position was evaluated. The results are shown in Table 3.

(Maneuvering stability)
For each of Example tires 1 to 7 and Comparative tires 1 to 3, the tires were assembled on a 6.0 J × 15 rim and the filling internal pressure was set to 210 kPa and 2500 cc of a domestic FR vehicle. A running test including a lane change of 150 km / h, a limit turning of 80 km / h, and an acceleration from 50 km / h was carried out on the test course, and the feeling was evaluated as a perfect score of 10 points. The results are shown in Table 3.

(Ride comfort)
For each of Example tires 1 to 7 and Comparative tires 1 to 3, the tires were assembled on a 6.0 J × 15 rim and the filling internal pressure was set to 210 kPa and 2500 cc of a domestic FR vehicle. The test result was evaluated by running at a speed of 60 km / h by running a test course that reproduced the crossing of a highway joint, a cobblestone road, and a railroad crossing, with a full score of 10 points. The results are shown in Table 3.

(Rolling resistance)
For each of Example tires 1 to 7 and Comparative example tires 1 to 3, the tire was assembled to a 6.0 J × 15 rim in accordance with SAE J1269, the filling internal pressure was 210 kPa, the load mass was 450 kg, and the speed The tire was rolled at 80 km / h, and the rolling resistance of the axle was measured and evaluated using a drum testing machine having a steel plate surface having a diameter of 1.7 m. The results are shown in Table 3 as an index.
In addition, the index value in a table | surface is what controlled the value of the comparative example tire 1, and rolling resistance is so small that an index value is small, and it shows that tire performance is favorable.

  From the results of Table 3, Example tires 1-7 can improve belt durability and reduce rolling resistance without significantly changing steering stability and riding comfort as compared with Comparative Examples Tires 1-3. did it.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a meridian cross-sectional view of a half portion of a tire, showing an embodiment of a pneumatic tire of the present invention in a state where the pneumatic tire is assembled to an application rim and filled with a specified internal pressure. It is meridian sectional drawing which shows other embodiment of the pneumatic tire of this invention about the half part of a tire. It is meridian sectional drawing which shows other embodiment of the pneumatic tire of this invention about the half part of a tire. It is meridian sectional drawing which shows other embodiment of the pneumatic tire of this invention about the half part of a tire. It is meridian sectional drawing which shows other embodiment of the pneumatic tire of this invention about the half part of a tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass 6 Inclined belt layer 7 Belt reinforcement layer 8 Tread tread 9 Tread rubber 10 Cap rubber 11 Base rubber

Claims (14)

A tread portion, a pair of sidewall portions, a pair of bead portions, a carcass made of at least one carcass ply extending in a toroid shape between bead cores in each bead portion, and an outer peripheral side of the crown region of the carcass Each of the belt layer cords arranged and extending in a direction inclined with respect to the tire equatorial plane, and two or more inclined belt layers in which the belt layer cords cross each other and one or a plurality of belt layers cords In a pneumatic tire comprising a belt including a belt reinforcing layer formed by spirally winding a cord in a tread circumferential direction and a tread rubber disposed radially outward of the belt,
With the quarter of the width of the tread tread as a boundary, the driving density Ds of the shoulder side region of the cord of the belt reinforcing layer is made smaller than the driving density Dc of the center region, and the ratio Dc / Ds is 110 to 125%. A pneumatic tire characterized by being in the range.   The pneumatic tire according to claim 1, wherein the belt reinforcing layer is made of a high elongation cord, and the elongation at break of the high elongation cord is 10 to 20% larger in the shoulder side region than in the center side region.   The pneumatic tire according to claim 1 or 2, wherein the tread rubber is composed of at least two layers having different rubber types.   The pneumatic tire according to claim 3, wherein the tread rubber has a cap-and-base structure including a cap rubber positioned on the outer peripheral side and a base rubber positioned on the inner peripheral side.   The pneumatic tire according to claim 4, wherein the base rubber has a tan δ smaller than that of the cap rubber.   The pneumatic tire according to claim 5, wherein tan δ of the base rubber is in a range of 0.03 to 0.12.   The pneumatic tire according to any one of claims 4 to 6, wherein the base rubber has a thickness of 0.5 to 5 mm. The thickness t ₁ of the base rubber on the tire equatorial plane and the thickness t ₂ at a position of 45% of the tread width from the tire equatorial plane satisfy the relationship of t ₁ <t ₂ . Pneumatic tire described in 2. The thickness _{t 2} is the pneumatic tire according to claim 8 which is 1.2 to 10 times the thickness _{t 1.}   The pneumatic tire according to any one of claims 5 to 7, wherein the base rubber is made of different rubber types at the center portion and the shoulder portion of the tread surface.   The pneumatic tire according to claim 10, wherein a 100% modulus of the base rubber is made smaller than a center portion at a shoulder portion of a tread surface.   The pneumatic tire according to any one of claims 5 to 7, wherein only a tread rubber portion disposed on the outer side in the tread width direction has a cap-and-base structure.     The pneumatic tire according to claim 12, wherein the tread rubber portion disposed inside in the tread width direction has a width of 30 to 80% of the tread width.   The pneumatic tire according to any one of claims 1 to 12, wherein the cord of the belt reinforcing layer is made of an aromatic polyamide cord or a steel cord.

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