JP7275464B2 - pneumatic tire - Google Patents

Description

Embodiments of the present invention relate to pneumatic tires.

In pneumatic tires mounted on vehicles such as trucks and buses, in order to achieve both wear resistance and low fuel consumption, the tread rubber is divided into a cap rubber layer forming the tread surface and a base arranged radially inward. It is known to form a two-layer structure with a rubber layer. Rubber having excellent abrasion resistance is used for the cap rubber layer, and low heat-generating rubber having a low loss tangent tan δ is used for the base rubber layer.

For example, Patent Document 1 discloses that the ratio of the low heat-generating base rubber layer is increased in the shoulder portion where heat generation is the highest in the tread portion, and the thickness of the cap rubber layer in the tread central region is reduced at the shoulder portion. It is described that the thickness is made larger than the thickness of the cap rubber layer, thereby achieving both wear resistance and fuel efficiency.

In Patent Document 2, in order to prevent rib tearing in the tread shoulder portion, the volume of the base rubber layer covering the outer end of the belt in the axial direction of the tire is reduced, and substantially the entire shoulder rib is composed of the cap rubber layer. is disclosed.

JP 2007-137411 A JP 2017-210077 A

However, if the proportion of the base rubber layer in the shoulder portion is too high as in Patent Document 1, the base rubber layer is likely to be exposed early due to wear in the case of a worn form in which the amount of wear in the shoulder portion is large. Since the base rubber layer generally wears quickly and is vulnerable to external damage, if the base rubber layer is exposed, the tire must be replaced early. In addition, if the lug grooves provided in the shoulder portion are deep, the base rubber layer is exposed to the lug grooves, and cracks tend to occur starting from the exposed portions of the base rubber layer when bumping on uneven road surfaces or stones. .

On the other hand, if the volume of the base rubber layer is small as in Patent Document 2, the effect of low fuel consumption due to the low heat build-up base rubber layer is impaired.

SUMMARY OF THE INVENTION In view of the above points, an object of an embodiment of the present invention is to provide a pneumatic tire capable of preventing premature exposure of a base rubber layer while improving fuel efficiency.

A pneumatic tire according to an embodiment of the present invention includes a tread rubber provided in a tread portion, and a belt layer including a plurality of belts provided inside the tread rubber in the tire radial direction,
The tread rubber is composed of a cap rubber layer having a tread surface that contacts the road surface, and a base rubber layer disposed radially inward of the cap rubber layer,
The belt layer includes a maximum width belt having the maximum width and an outermost belt arranged on the outermost side in the tire radial direction,
The intersection of the interface between the cap rubber layer and the base rubber layer and the outermost belt lateral reference line extending in the tire axial direction from the outer end of the outermost belt in the axial direction of the tire is the outer end of the maximum width belt in the axial direction of the tire. from the intersection of the normal line extending from the tread surface to the outermost belt lateral reference line, in the axial direction of the tire,
The axially outer end of the cap rubber layer covers the axially outer end of the base rubber layer and terminates radially inward of the axially outer end of the base rubber layer, The outer end of the base rubber layer in the tire axial direction is located further outward in the axial direction than the end of the tread surface.

In this specification, unless otherwise specified, the dimensions and the like of each part of the pneumatic tire are values measured with the pneumatic tire mounted on a regular rim and filled with 50 kPa. A regular rim is a rim defined for each tire in a standard system that includes the standard on which the tire is based. Measuring Rim".

According to this embodiment, the volume of the base rubber layer can be ensured by setting the axially outer end of the base rubber layer to the axially outer side of the end of the tread surface. In addition, by setting the interface between the cap rubber layer and the base rubber layer inside the intersection of the normal line extending from the outer end of the maximum width belt to the tread surface and the outermost belt lateral reference line, the base rubber layer You can make it less exposed. Therefore, early exposure of the base rubber layer can be prevented while improving fuel efficiency.

A half cross-sectional view showing a tire width direction cross section of a pneumatic tire according to one embodiment. Enlarged view of main part of Fig. 1

Hereinafter, embodiments will be described with reference to the drawings.

A pneumatic tire 10 according to one embodiment shown in FIG. 1 includes a tread portion 12 forming a ground contact surface, a pair of left and right bead portions, and a pair of left and right sidewall portions 14 interposed between the tread portion 12 and the bead portions. Consists of A pneumatic tire 10 according to this embodiment is a heavy-duty pneumatic tire that is mounted on a truck, a bus, or the like.

In the figure, the symbol CL indicates the tire equatorial plane corresponding to the axial center of the tire. In this example, the pneumatic tire 10 is symmetrical with respect to the tire equatorial plane CL.

Here, the tire axial direction is a direction parallel to the tire rotation axis, and indicated by WD in the drawings. The inner side in the tire axial direction WD is the direction toward the tire equatorial plane CL, and the outer side in the tire axial direction WD is the direction away from the tire equatorial plane CL. Further, the tire radial direction is a direction perpendicular to the tire rotation axis, and is indicated by symbol RD in the drawings. The inner side in the tire radial direction RD is the direction toward the tire rotation axis, and the outer side in the tire radial direction RD is the direction away from the tire rotation axis. The tire circumferential direction is the direction on the circumference centering on the tire rotation axis.

The pneumatic tire 10 includes a carcass layer 16 extending in a toroidal shape across a pair of bead portions. The carcass layer 16 extends from the tread portion 12 through the side wall portions 14 on both sides to reach the bead portion and is locked at the bead portion. The carcass layer 16 is composed of at least one carcass ply formed by arranging carcass cords such as steel cords substantially perpendicular to the tire circumferential direction and covering the cords with rubber.

In the tread portion 12 , a belt layer 18 is provided on the outer side of the carcass layer 16 in the tire radial direction RD, and a tread rubber 20 is laminated on the outer side of the belt layer 18 in the tire radial direction RD.

The belt layer 18 is composed of a plurality of belts 22, 24, 26 provided inside the tread rubber 20 in the tire radial direction RD. The belts 22, 24, 26 are formed by arranging belt cords such as steel cords at an angle of, for example, 10° to 35° with respect to the circumferential direction of the tire and covering the cords with rubber. In this example, the belt layer 18 has a three-layer structure having three belts of a first belt 22, a second belt 24 and a third belt 26 in order from the inside in the tire radial direction RD.

The first belt 22 is an innermost belt (hereinafter referred to as "innermost belt 22") that is arranged on the innermost side in the tire radial direction RD. The second belt 24 is a maximum width belt (hereinafter referred to as "maximum width belt 24") having the maximum width (belt width, that is, the dimension of the belt in the axial direction WD of the tire) among the three belts. The third belt 26 is the outermost belt (hereinafter referred to as the "outermost belt 26") arranged on the outermost side in the tire radial direction RD.

The width of the maximum width belt 24 is not particularly limited, and may be, for example, 0.80 to 0.95 times the tread width TW. The width of the innermost belt 22 and the outermost belt 26 is also not particularly limited, and may be 0.80 to 0.95 times the width of the maximum width belt 24, for example.

The belt layer 18 is provided with belt cushion rubbers 28 having a triangular cross-section on the inner side in the tire radial direction RD of both ends thereof so that the both ends thereof are gradually separated from the carcass layer 16 . Also, between the maximum width belt 24 and the outermost belt 26, an outermost belt lower rubber 30 having a triangular cross-section is provided so that both end portions thereof are gradually separated from each other as they move outward in the tire axial direction WD. there is

The tread rubber 20 has a two-layer structure consisting of a cap rubber layer 34 having a tread surface 32 that contacts the road surface, and a base rubber layer 36 arranged inside the cap rubber layer 34 in the tire radial direction RD.

The tread surface 32 is an outer peripheral surface of the tread portion 12 that forms a contact surface. The tread portion 12 has a tread surface 32 and a pair of left and right side surfaces 38, and thus has an outwardly convex shape in the tire radial direction RD. A radially outer surface of the tread portion 12 (specifically, a cap rubber layer 34) is a tread surface 32, and extends from an end (outer end in the tire axial direction) 32A of the tread surface 32 inward in the tire radial direction RD like a cliff. The existing tire axial outer surface (so-called buttress surface) is a side surface 38 (hereinafter referred to as "tire outer surface 38"). An edge 32A of the tread surface 32 is a tread ground edge. The tread width TW is the dimension of the tread surface 32 in the axial direction of the tire, and is the distance between the ends 32A on both sides.

The cap rubber layer 34 has a tire axially outer end 34A that covers the tire axially outer end 36A of the base rubber layer 36, and is positioned further than the tire axially outer end 36A1 of the base rubber layer 36 in the tire radial direction. It terminates inside the RD. That is, the axially outer end 34A1 of the cap rubber layer 34 is located outside the axially outer end 36A1 of the base rubber layer 36 in the tire axial direction WD and inside the tire radially RD. As a result, the base rubber layer 36 is covered with the cap rubber layer 34 over its entire width and is not exposed on the tire outer surface 38 . The tire axially outer end portion 36A of the base rubber layer 36 covers the tire axially outer end 24A of the maximum width belt 24, and the maximum width belt lateral reference line 56, which will be described later, is located outside the tire axial direction WD of the outer end 24A. (See FIG. 2) and ends inward in the tire radial direction RD.

The sidewall rubber 40 arranged on the outside of the carcass layer 16 and on the sidewall portion 14 has a tire radially outer end portion 40A that corresponds to the tire axially outer end portion 34A of the tread rubber 20 (specifically, the cap rubber layer 34). and extends to the tread portion 12. Therefore, the side surface 38 of the tread portion 12 has a portion adjacent to the end 32A of the tread surface 32 formed of the cap rubber layer 34, and a portion adjacent to the radially inner side thereof formed of the sidewall rubber 40. .

Here, a rubber having a smaller loss tangent tan δ than that of the cap rubber layer 34 is used for the base rubber layer 36 . For example, the base rubber layer 36 may be made of rubber having a tan δ of 0.04 to 0.12, and the cap rubber layer 34 may be made of rubber having a tan δ of 0.10 to 0.22. may

In addition, rubber having a hardness higher than that of the base rubber layer 36 is used for the cap rubber layer 34 . For example, the cap rubber layer 34 may be made of rubber having a hardness within the range of 60-70, and the base rubber layer 36 may be made of rubber having a hardness within the range of 55-62.

By using a low-heat-generating rubber for the base rubber layer 36 in this manner, it is possible to improve fuel efficiency, and to suppress heat generation near the ends of the belt layer 18, thereby improving the durability of the belt layer 18. can be made Further, by using a rubber that is hard to wear and a rubber that is resistant to cut chips for the cap rubber layer 34, wear resistance and damage resistance (crack resistance) can be improved.

As used herein, tan δ of rubber is a value measured using a viscoelastic spectrometer at a temperature of 70° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 1%. In addition, the rubber hardness is JIS K6253-1-2012 3.2 durometer hardness, and is measured under an atmosphere of 23°C using a type A durometer for general rubber (medium hardness). .

The tread surface 32 is provided with a plurality (three in this example) of circumferential main grooves 42 extending in the tire circumferential direction, thereby defining a plurality of land portions. Lug grooves 46 extending in the tire axial direction WD are spaced apart in the tire circumferential direction in tread shoulder portions 44, which are land portions on the outer side in the axial direction WD of the circumferential main grooves 42 arranged on the outermost side in the tire axial direction WD. are set apart. The lug grooves 46 are lateral grooves having one end open at the end 32A of the tread surface 32 and the other end terminating within the tread shoulder portion 44 .

Reference numeral 48 denotes an inner liner, which is an air permeation resistant layer provided on the entire inner surface of the tire.

In the pneumatic tire 10 according to the present embodiment, the arrangement, dimensions, etc. of each part of the tread portion 12 are set as follows in the tire axial cross section in the normal rim assembly state shown in FIGS. 1 and 2 . Here, the tire axial direction section is a section along the tire axial direction WD, and can also be called a tire meridian direction section. As described above, the normal rim assembly state is a state in which the pneumatic tire 10 is mounted on the normal rim and filled with an internal pressure of 50 kPa.

(1) The intersection point P between the interface 50 between the cap rubber layer 34 and the base rubber layer 36 and the outermost belt lateral reference line 52 extending from the tire axially outer end 26A of the outermost belt 26 in the tire axial direction WD is the maximum width. The intersection point Q between the outermost belt lateral reference line 52 and the normal line 54 extending from the tire axially outer end 24A of the belt 24 to the tread surface 32 is located on the inner side in the tire axial direction.

Here, the outermost belt lateral reference line 52 is a straight line extending parallel to the tire axial direction WD from the thickness center of the tire axial direction outer end 26A. A normal line 54 is a normal line at a point on the tread surface 32 that passes through the center of thickness of the axially outer end 24A of the tire. intersect at right angles with The intersection point P is the intersection point between the interface 50 and the outermost belt lateral reference line 52 , and the intersection point Q is the intersection point between the normal line 54 and the outermost belt lateral reference line 52 .

As in (1) above, by setting the intersection point P on the outermost belt lateral reference line 52 to the inner side of the intersection point Q in the tire axial direction WD, the tread shoulder portion 44 (particularly, its portion on the outer side in the tire axial direction WD) is , the interface 50 between the cap rubber layer 34 and the base rubber layer 36 is lowered. Therefore, even if the tread shoulder portion 44 is worn with a large amount of wear, the base rubber layer 36 can be prevented from being exposed at an early stage, and wear resistance can be improved. Further, even when the lug grooves 46 provided in the tire shoulder portion 44 are deep, the base rubber layer 36 is less likely to be exposed to the lug grooves 46, and the occurrence of cracks in the lug grooves 46 can be suppressed.

(2) The axially outer end 36A1 of the base rubber layer 36 is located outside the end 32A of the tread surface 32 in the axial direction WD. That is, the outer end 36A1 of the base rubber layer 36 is located outside the tire axial direction WD position of the tread edge 32A in the tire axial direction.

By setting the outer end 36A1 of the base rubber layer 36 outside the tread edge 32A in the tire axial direction WD in this way, the interface 50 between the cap rubber layer 34 and the base rubber layer 36 is kept low at the tread shoulder portion 44. However, the volume of the base rubber layer 36 can be secured. Therefore, it is possible to improve fuel economy while preventing early exposure of the base rubber layer 36 .

(3) On the maximum width belt lateral reference line 56 extending in the tire axial direction WD from the tire axially outer end 24A of the maximum width belt 24, the thickness La of the base rubber layer 36 and the tire axially outer end of the maximum width belt 24 A ratio La/Lt of the distance Lt from 24A to the tire outer surface 38 is 0.10 to 0.50. Here, the maximum width belt lateral reference line 56 is a straight line extending parallel to the tire axial direction WD from the thickness center of the tire axial direction outer end 24A.

When La/Lt is 0.10 or more, the low heat build-up of the base rubber layer 36 is enhanced, which is advantageous for improving fuel efficiency and durability. Further, when La/Lt is 0.50 or less, the effect of suppressing early exposure of the base rubber layer 36 can be enhanced. More preferably, the lower limit of La/Lt is 0.20 or more, and the upper limit is 0.40 or less, 0.35 or less, or 0.30 or less.

(4) On the outermost belt lateral reference line 52, the ratio Ka/Kt between the thickness Ka of the base rubber layer 36 and the distance Kt from the tire axially outer end 26A of the outermost belt 26 to the tire outer surface 38 is 0. 0.10 to 0.45.

When Ka/Kt is 0.10 or more, the low heat build-up of the base rubber layer 36 is enhanced, which is advantageous for improving fuel efficiency and durability. Further, when Ka/Kt is 0.45 or less, the effect of suppressing early exposure of the base rubber layer 36 can be enhanced. More preferably, the lower limit of Ka/Kt is 0.20 or more, and the upper limit is 0.40 or less, 0.35 or less, or 0.30 or less.

(5) On the normal line 54, the ratio Ta/Tt between the thickness Ta of the base rubber layer 36 and the distance Tt from the tire axially outer end 24A of the maximum width belt 24 to the tread surface 32 is 0.10 to 0. .30.

When Ta/Tt is 0.10 or more, the low heat build-up of the base rubber layer 36 is enhanced, which is advantageous for improving fuel efficiency and durability. Further, when Ta/Tt is 0.30 or less, the effect of suppressing early exposure of the base rubber layer 36 can be enhanced. More preferably, Ta/Tt has a lower limit of 0.15 or more and an upper limit of 0.25 or less.

(6) The tire axial position F of the changing point R of the interface 50, which is the starting point at which the thickness of the cap rubber layer 34 begins to increase at the tread shoulder portion 44, is located from the axially outer end 26A of the outermost belt 26 to the outermost end 26A of the outermost belt 26. It is within a distance of 2.5% of the outer belt width BW (see FIG. 1).

The thickness of the cap rubber layer 34 here is the thickness of the cap rubber layer 34 in the tire radial direction RD, and the distance between the tread surface 32 and the interface 50 in the tire radial direction RD (except for the groove portion). thickness). The outermost belt width BW is the distance between both ends of the outermost belt 26 in the tire axial direction WD (tire axial distance).

The change point R of the interface 50 is the point where the thickness of the cap rubber layer 34 begins to increase outward in the axial direction WD of the tire. That is, in the tread shoulder portion 44, there is a point where the thickness of the cap rubber layer 34 starts increasing from a constant value outward in the tire axial direction WD due to the change in the curvature of the interface 50. The change point R is the change point. Therefore, the change point R can also be called a curvature change point. Therefore, the thickness of the cap rubber layer 34 is constant on the inner side of the change point R in the tire axial direction WD. The thickness of layer 34 increases.

(6) above means that the axial position F of the change point R substantially coincides with the axially outer end 26A of the outermost belt 26 . That is, the tire axial position F of the change point R is set within a range of ±2.5% of the outermost belt width BW, which is the width of the outermost belt 26, centered on the tire axial position of the outer end 26A. It is By setting in this way, it becomes easier to achieve both suppression of early exposure of the base rubber layer 36 and improvement of fuel efficiency.

(7) The tire axial position F of the change point R of the interface 50 is outside the tire axial direction outer end 22A of the innermost belt 22 in the tire axial direction WD. As a result, the volume of the base rubber layer 36 can be increased to improve low heat build-up.

Tire size: Examples and comparative examples were carried out on heavy-duty pneumatic radial tires of 225/70R19.5. The basic configurations of the tires of Examples and Comparative Examples are the same as those described in the above embodiment, and prototype tires were manufactured with the specifications shown in Table 1 below. In all the examples and comparative examples, a rubber having a tan δ of 0.15 and a rubber hardness of 65 was used for the cap rubber layer 34, and a rubber having a tan δ of 0.08 and a rubber hardness of 59 was used for the base rubber layer 36. I used rubber. Each prototype tire was evaluated for fuel efficiency, crack resistance, durability and wear resistance. The evaluation method is as follows.

・Low fuel consumption: Rolling resistance was measured under the conditions of rim size (6.75 x 19.5), internal pressure (760 kPa), vertical load (15.0 kN), and speed (80 km/h). was evaluated with an index based on the value of Comparative Example 2 being 100. The larger the index, the smaller the rolling resistance and the better the fuel efficiency.

・Crack resistance: Running on the drum under the conditions of rim size (6.75 × 19.5), internal pressure (760 kPa), vertical load (17.7 kN), speed (40 km / h), cracks in the lug grooves. The value of Comparative Example 2 was set to 100, and the running time until the occurrence of was evaluated by an index. The larger the index, the longer the running time and the better the crack resistance.

・Durability: Running on a drum under conditions of rim size (6.75 x 19.5), internal pressure (760 kPa), vertical load (26.5 kN), and speed (40 km/h), no damage to the tread. The running time until occurrence was evaluated as an index with the value of Comparative Example 2 being 100. The larger the index, the longer the running time and the better the durability.

・Abrasion resistance: 200,000 when mounted on a truck loaded with a load of 17.7 kN per tire under the conditions of rim size (6.75 x 19.5) and internal pressure (760 kPa). km. Then, the groove depth was measured to obtain the amount of wear, and the reciprocal of the average value was evaluated as an index with the value of Comparative Example 2 being 100. The larger the index, the smaller the amount of wear and the better the wear resistance.

The results are shown in Table 1. In Comparative Example 2, the axially outer end 36A1 of the base rubber layer 36 is on the inner side in the axial direction WD of the tread edge 32A. Therefore, in Comparative Example 2, the volume of the base rubber layer 36 with low heat build-up was small, and the low heat build-up was poor, resulting in poor fuel efficiency and durability. In Comparative Example 1, the intersection point P between the outermost belt lateral reference line 52 and the interface 50 is located outside the intersection point Q between the outermost belt lateral reference line 52 and the normal line 54 in the tire axial direction WD. Therefore, in Comparative Example 1, although excellent in fuel efficiency and durability, the base rubber layer 36 was exposed early due to wear of the tread rubber 20, resulting in poor crack resistance and wear resistance.

In contrast, in Examples 1 to 9, the axially outer end 36A1 of the base rubber layer 36 is located outside the tread edge 32A in the axial direction WD, and the outermost belt lateral reference line 52 and the interface 50 is located inside the axial direction WD of the intersection Q between the outermost belt lateral reference line 52 and the normal line 54 . Therefore, in Examples 1 to 9, compared to Comparative Example 2, by increasing the volume of the base rubber layer 36, it was possible to improve fuel efficiency and durability. Further, early wear of the base rubber layer 36 can be suppressed, and deterioration of crack resistance and wear resistance can be suppressed as compared with Comparative Example 1. Therefore, fuel efficiency, crack resistance, durability and wear resistance could be improved in a well-balanced manner.

Although several embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10... Pneumatic tire 12... Tread part 18... Belt layer 20... Tread rubber 22... Innermost belt 22A... Tire axial direction outer end 24... Maximum width belt 24A... Tire axial direction outer end 26 Outermost belt 26A Outer end in axial direction of tire 32 Outer end of tread surface 32A End of tread surface 34 Cap rubber layer 34A Outer end of cap rubber layer in axial direction 36 Base rubber layer 36A... Tire axial direction outer end of base rubber layer 36A1... Tire axial direction outer end of base rubber layer 38... Tire outer surface 44... Tread shield portion 50... Interface 52... Outermost belt lateral reference line , 54 Normal line 56 Maximum width belt lateral reference line WD Tire axial direction RD Tire radial direction BW Outermost belt width P Intersection point between interface and outermost belt lateral reference line Q Intersection point between the normal line and the outermost belt lateral reference line, R: change point of the interface

Claims (4)

A pneumatic tire comprising a tread rubber provided in a tread portion and a belt layer consisting of a plurality of belts provided inside the tread rubber in the tire radial direction,
The tread rubber is composed of a cap rubber layer having a tread surface that contacts the road surface, and a base rubber layer disposed radially inward of the cap rubber layer,
The belt layer includes a maximum width belt having the maximum width and an outermost belt arranged on the outermost side in the tire radial direction,
The intersection of the interface between the cap rubber layer and the base rubber layer and the outermost belt lateral reference line extending in the tire axial direction from the outer end of the outermost belt in the axial direction of the tire is the outer end of the maximum width belt in the axial direction of the tire. from the intersection of the normal line extending from the tread surface to the outermost belt lateral reference line, in the axial direction of the tire,
The axially outer end of the cap rubber layer covers the axially outer end of the base rubber layer and terminates radially inward of the axially outer end of the base rubber layer, The axially outer end of the base rubber layer is located axially outwardly of the end of the tread surface,
The thickness La of the base rubber layer and the distance from the axially outer end of the maximum width belt to the tire outer surface on the maximum width belt lateral reference line extending in the tire axial direction from the tire axially outer end of the maximum width belt The ratio La / Lt to Lt is 0.10 to 0.50,
A pneumatic tire characterized by: A pneumatic tire comprising a tread rubber provided in a tread portion and a belt layer consisting of a plurality of belts provided inside the tread rubber in the tire radial direction,
The tread rubber is composed of a cap rubber layer having a tread surface that contacts the road surface, and a base rubber layer disposed radially inward of the cap rubber layer,
The belt layer includes a maximum width belt having the maximum width and an outermost belt arranged on the outermost side in the tire radial direction,
The intersection of the interface between the cap rubber layer and the base rubber layer and the outermost belt lateral reference line extending in the tire axial direction from the outer end of the outermost belt in the axial direction of the tire is the outer end of the maximum width belt in the axial direction of the tire. from the intersection of the normal line extending from the tread surface to the outermost belt lateral reference line, in the axial direction of the tire,
The axially outer end of the cap rubber layer covers the axially outer end of the base rubber layer and terminates radially inward of the axially outer end of the base rubber layer, The axially outer end of the base rubber layer is located axially outwardly of the end of the tread surface,
On the outermost belt lateral reference line, the ratio Ka/Kt between the thickness Ka of the base rubber layer and the distance Kt from the outer end of the outermost belt in the axial direction of the tire to the outer surface of the tire is 0.10 to 0.45. is
A pneumatic tire characterized by: A pneumatic tire comprising a tread rubber provided in a tread portion and a belt layer consisting of a plurality of belts provided inside the tread rubber in the tire radial direction,
The tread rubber is composed of a cap rubber layer having a tread surface that contacts the road surface, and a base rubber layer disposed radially inward of the cap rubber layer,
The belt layer includes a maximum width belt having the maximum width and an outermost belt arranged on the outermost side in the tire radial direction,
The intersection of the interface between the cap rubber layer and the base rubber layer and the outermost belt lateral reference line extending in the tire axial direction from the outer end of the outermost belt in the axial direction of the tire is the outer end of the maximum width belt in the axial direction of the tire. from the intersection of the normal line extending from the tread surface to the outermost belt lateral reference line, in the axial direction of the tire,
The axially outer end of the cap rubber layer covers the axially outer end of the base rubber layer and terminates radially inward of the axially outer end of the base rubber layer, The axially outer end of the base rubber layer is located axially outwardly of the end of the tread surface,
On the normal line, the ratio Ta/Tt between the thickness Ta of the base rubber layer and the distance Tt from the outer end of the maximum width belt in the tire axial direction to the tread surface is 0.10 to 0.30.
A pneumatic tire characterized by: A pneumatic tire comprising a tread rubber provided in a tread portion and a belt layer consisting of a plurality of belts provided inside the tread rubber in the tire radial direction,
The tread rubber is composed of a cap rubber layer having a tread surface that contacts the road surface, and a base rubber layer disposed radially inward of the cap rubber layer,
The belt layer includes a maximum width belt having the maximum width and an outermost belt arranged on the outermost side in the tire radial direction,
The intersection of the interface between the cap rubber layer and the base rubber layer and the outermost belt lateral reference line extending in the tire axial direction from the outer end of the outermost belt in the axial direction of the tire is the outer end of the maximum width belt in the axial direction of the tire. from the intersection of the normal line extending from the tread surface to the outermost belt lateral reference line, in the axial direction of the tire,
The axially outer end of the cap rubber layer covers the axially outer end of the base rubber layer and terminates radially inward of the axially outer end of the base rubber layer, The axially outer end of the base rubber layer is located axially outwardly of the end of the tread surface,
The axial position of the change point of the interface at which the thickness of the cap rubber layer begins to increase at the tread shoulder portion is 2.5 times the width of the outermost belt from the axially outer end of the outermost belt in the tire axial direction. within % distance,
A pneumatic tire characterized by:

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