JP2020100205A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire which prevents ground pressure of a land part from becoming nonuniform, and suppresses reduction of a ground contact area.SOLUTION: A pneumatic tire includes a tread part with a tread surface. The tread part includes: a shoulder main groove that is a main groove disposed on the outermost side in a tire width direction, among plural main grooves extending along a tire circumferential direction; and a shoulder land part partitioned by the shoulder main groove and a ground contact end. The tread surface includes: a first arc, a second arc and a third arc that are continuous outward in the tire width direction from a tire equator surface, on a cross section of a tire meridian surface; a first boundary that is a boundary between the first arc and the second arc; and a second boundary that is a boundary between the second arc and the third arc. The first boundary and the second boundary are arranged on the shoulder land part.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pneumatic tire.

Conventionally, for example, a pneumatic tire includes a plurality of main grooves extending along the tire circumferential direction and a plurality of land portions defined by the plurality of main grooves and the ground contact end. The tread surface of the pneumatic tire includes a first arc, a second arc, and a third arc that are continuous from the tire equatorial plane toward the outer side in the tire width direction in the cross section of the tire meridian surface (for example, patents). Reference 1).

By the way, when the pneumatic tire comes into contact with the road surface, the tread surface becomes flat along the road surface. At this time, the tread surface is deformed with the boundary as a fulcrum. As a result, the ground contact pressure near the boundary becomes high, so that the ground contact pressure is likely to be uneven.

JP, 2013-60129, A

Therefore, an object is to provide a pneumatic tire capable of suppressing non-uniform ground contact pressure in the land portion and suppressing a decrease in ground contact area.

The pneumatic tire includes a tread portion having a tread surface, and the tread portion is a shoulder main groove that is a main groove arranged on the outermost side in the tire width direction among a plurality of main grooves extending along the tire circumferential direction. And a shoulder land portion defined by the shoulder main groove and the ground contact end, the tread surface being continuous from the tire equatorial plane toward the outer side in the tire width direction in the cross section of the tire meridian surface. An arc, a second arc and a third arc, a first boundary that is a boundary between the first arc and the second arc, and a second boundary that is a boundary between the second arc and the third arc, The first boundary and the second boundary are arranged on the shoulder land portion.

Further, in the pneumatic tire, the shoulder land portion includes a closed groove extending so as to intersect the tire circumferential direction and separated from the shoulder main groove and the ground contact end, and the first boundary is the shoulder main groove. May be arranged between the closed groove and the closed groove, and the second boundary may be arranged between the closed groove and the grounded end.

Further, in the pneumatic tire, the shoulder land portion is equally divided into four in the tire width direction so that from the inner side in the tire width direction, the inner region, the first central region, the second central region, and the outer region. And at least one of the first boundary and the second boundary may be arranged in the first central region or the second central region.

Further, in the pneumatic tire, the shoulder land portion includes an open groove that is connected to the shoulder main groove and is separated from the ground contact end, and the open groove is at least one of the first boundary and the second boundary. May intersect with the first central region or the second central region.

Further, in the pneumatic tire, the shoulder land portion is equally divided into two in the tire width direction, from the inner side in the tire width direction, includes an inner land portion and an outer land portion, the first boundary, The second boundary may be disposed on the inner land portion and the second boundary may be disposed on the outer land portion.

FIG. 1 is a cross-sectional view of a main part of a pneumatic tire according to an embodiment in a tire meridian plane. FIG. 2 is a development view of relevant parts on a tread surface of the pneumatic tire according to the same embodiment. FIG. 3 is an enlarged cross-sectional view of a main part of a tire meridian surface of the pneumatic tire according to the same embodiment.

Hereinafter, one embodiment of a pneumatic tire will be described with reference to FIGS. 1 to 3. In each drawing, the dimensional ratios of the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios of the drawings do not necessarily match.

In each drawing, a first direction D1 is a tire width direction D1 that is parallel to a tire rotation axis that is a rotation center of a pneumatic tire (hereinafter, also simply referred to as “tire”) 1, and a second direction D2 is The tire radial direction D2, which is the diameter direction of the tire 1, and the third direction D3 is the tire circumferential direction D3 around the tire rotation axis.

In the tire width direction D1, the inner side is the side closer to the tire equatorial plane S1, and the outer side is the side farther from the tire equatorial plane S1. Further, in the tire radial direction D2, the inner side is the side closer to the tire rotation axis, and the outer side is the side far from the tire rotation axis.

The tire equatorial plane S1 is a surface that is orthogonal to the tire rotation axis and is located at the center of the tire 1 in the tire width direction D1, and the tire meridian plane is a surface that includes the tire rotation axis and the tire equator. It is a surface orthogonal to the surface S1. The tire equatorial line L1 is a line at which the outer surface (the tread surface 2a, which will be described later) of the tire 1 in the tire radial direction D2 and the tire equatorial surface S1 intersect.

As shown in FIG. 1, the tire 1 according to the present embodiment includes a pair of bead portions 11 each having a bead 11a, a sidewall portion 12 extending from each bead portion 11 to the outside in the tire radial direction D2, and a pair of sidewalls. The tread portion 13 is connected to the outer end portion of the portion 12 in the tire radial direction D2 and has an outer surface in the tire radial direction D2 that comes into contact with the road surface. In the present embodiment, the tire 1 is a pneumatic tire 1 into which air is put and is mounted on the rim 20.

Further, the tire 1 is arranged inside the carcass layer 14 and a carcass layer 14 spanned between a pair of beads 11a and 11a (only one is shown in FIG. 1), and retains air pressure. Therefore, the inner liner layer 15 having an excellent function of preventing gas permeation is provided. The carcass layer 14 and the inner liner layer 15 are arranged along the tire inner circumference over the bead portion 11, the sidewall portion 12, and the tread portion 13.

The bead portion 11 includes a rim strip rubber 11b forming an outer surface, and the sidewall portion 12 includes a sidewall rubber 12a forming an outer surface of the sidewall portion 12. The tread portion 13 includes a tread rubber 2 having a tread surface 2 a that constitutes an outer surface of the tread portion 13, and a belt layer 16 arranged between the tread rubber 2 and the carcass layer 14.

The tread surface 2a has a grounding surface that actually contacts the road surface, and the outer end of the grounding surface in the tire width direction D1 is one of the grounding ends 2b and 2b (in FIG. 1 and FIG. Only shown). Further, the tread surface 2a is formed by assembling the tire 1 on the regular rim 20 and placing the tire 1 vertically on a flat road surface in a state of being filled with the regular internal pressure, and grounding the road surface when a regular load is applied. Refers to.

The regular rim 20 is a rim 20 that is defined for each tire 1 in the standard system including the standard on which the tire 1 is based. For example, the standard rim for JATMA, the “Design Rim” for TRA, and the ETRTO. If so, it becomes “Measuring Rim”.

The regular internal pressure is the air pressure that each standard defines for each tire 1 in the standard system including the standard on which the tire 1 is based. If it is JATMA, the maximum air pressure is used. If it is TRA, the table "TIRE LOAD LIMITS AT VARIOUS COL The maximum value described in “INFLATION PRESSSURES” is “INFLATION PRESSURE” for ETRTO, but 180 kPa for tire 1 for passenger cars.

The regular load is a load that each standard defines for each tire 1 in the standard system including the standard on which the tire 1 is based. If JATMA is the maximum load capacity, if TRA, the maximum load described in the above table If the value is ETRTO, it is "LOAD CAPACITY", but if the tire 1 is for passenger cars, it is 85% of the corresponding load with an internal pressure of 180 kPa.

Further, the tread surface 2a is continuous from the tire equatorial plane S1 toward the outside in the tire width direction D1 in the cross section of the tire meridian surface in the unloaded state in which the tire 1 is mounted on the regular rim 20 and filled with the regular internal pressure. The first circular arc 2c, the second circular arc 2d, the third circular arc 2e, and the fourth circular arc 2f are provided. As shown in FIGS. 1 and 2, the tread surface 2a is a boundary between the first circular arc 2c and the second circular arc 2d, a first boundary 2g, and a boundary between the second circular arc 2d and the third circular arc 2e. It has two boundaries 2h and a third boundary 2i which is a boundary between the third arc 2e and the fourth arc 2f.

The radius of curvature of the first arc 2c is larger than the radius of curvature of the second arc 2d, the radius of curvature of the second arc 2d is larger than the radius of curvature of the third arc 2e, and the curvature of the third arc 2e. The radius is larger than the radius of curvature of the fourth arc 2f. The shape of the tread surface 2a is symmetrical with respect to the tire equatorial plane S1.

The radius of curvature of each of the arcs 2c to 2f is not particularly limited. The radius of curvature of the first arc 2c is preferably, for example, 200% to 1100% of the radius of curvature of the second arc 2d. The radius of curvature of the second arc 2d is preferably, for example, 200% to 400% of the radius of curvature of the third arc 2e.

The first boundary 2g and the second boundary 2h are arranged inside the tire width direction D1 with respect to the ground contact end 2b, and the third boundary 2i is arranged outside the tire width direction D1 with respect to the ground contact end 2b. ing. As a result, when the tire 1 travels on a flat road surface, the first boundary 2g and the second boundary 2h normally contact the road surface, while the third boundary 2i does not contact the road surface. The number of arcs 2c to 2f is not particularly limited.

Further, the tread rubber 2 is provided with a plurality of (only one is shown in FIGS. 1 and 2) main grooves 3 extending in the tire circumferential direction D3. The main groove 3 extends continuously in the tire circumferential direction D3. The main groove 3 is a straight main groove extending parallel to the tire circumferential direction D3. The main groove 3 may be configured to extend in a zigzag shape along the tire circumferential direction D3.

Further, for example, the main groove 3 is provided with a so-called treadwear indicator (not shown) in which the groove is shallow so that the degree of wear can be seen by exposing the main groove 3 as it wears. Further, for example, the main groove 3 has a groove width that is 3% or more of the distance between the ground contact ends 2b and 2b (the dimension in the tire width direction D1). Further, for example, the main groove 3 has a groove width of 5 mm or more.

In the plurality of main grooves 3, the pair of main grooves 3, 3 arranged on the outermost side in the tire width direction D1 are referred to as shoulder main grooves 3, 3. In the present embodiment, two main grooves 3 (only one is shown in FIGS. 1 and 2) are provided, so that each of the main grooves 3 and 3 is a shoulder main groove 3. is there. The number of the main grooves 3 is not particularly limited, and for example, three or more may be provided. In that case, the main groove arranged between the pair of shoulder main grooves 3 and 3 is the center main groove. Say.

The tread rubber 2 also includes a plurality of land portions 4 and 5 defined by the main groove 3 and the ground contact end 2b. In the plurality of land portions 4 and 5, the land portion 4 defined by the shoulder main groove 3 and the ground contact end 2b is referred to as a shoulder land portion 4, and the land portion 5 defined by the main grooves 3 and 3 is It is called Center Rikubu 5.

The shoulder land portion 4 is arranged outside the shoulder main groove 3 in the tire width direction D1, and the center land portion 5 is arranged between the pair of shoulder land portions 4 and 4. In this embodiment, three land portions 4 and 5 are provided (only two are shown in FIGS. 1 and 2), but the number of land portions 4 and 5 is Not limited.

As shown in FIG. 2, the land portions 4 and 5 include a plurality of land grooves 6 to 8. The land grooves 6 to 8 extend so as to intersect the tire circumferential direction D3. The land grooves 6 to 8 are recesses having a groove width of 1.6 mm or more. The land portions 4 and 5 may be provided with sipes having a groove width of less than 1.6 mm and extending so as to intersect the tire circumferential direction D3. Further, the land portions 4 and 5 may be provided with a circumferential groove having a groove width smaller than that of the main groove 3 and extending continuously or intermittently along the tire circumferential direction D3.

Then, the tread rubber 2 has a tread pattern formed by the main groove 3 and the land grooves 6 to 8. In the present embodiment, the tire 1 adopts a symmetrical tread pattern that does not specify the mounting direction in the vehicle. The tread pattern of FIG. 2 is a tread pattern that is point-symmetric with respect to an arbitrary point on the tire equator line L1.

The tire 1 may employ a tread pattern that is axisymmetric with respect to the tire equator line L1 as a symmetrical tread pattern that does not specify the mounting direction in the vehicle. Further, the tire 1 may employ an asymmetric tread pattern that specifies the mounting direction in the vehicle. The tire 1 for designating the mounting direction on the vehicle has a display unit for displaying the mounting direction on the vehicle, for example, in the sidewall portion 12.

Of the land grooves 6 and 7 of the shoulder land portion 4, the land groove 6 separated from the shoulder main groove 3 and the ground contact end 2b is referred to as a closed groove 6, and is connected to the shoulder main groove 3 and separated from the ground contact end 2b. 7 is called an open groove 7. The proportion of the closed grooves 6 (or the open grooves 7) among the land grooves 6 and 7 of the shoulder land portion 4 is not particularly limited.

For example, the ratio of the closed groove 6 (or the open groove 7) among the land grooves 6 and 7 of the shoulder land portion 4 may be 50% or more, may be larger than 50%, or may be 50% or less. , Or less than 50%. In the present embodiment, the proportion of the closed grooves 6 (or the open grooves 7) among the land grooves 6 and 7 of the shoulder land portion 4 is 50%.

Further, the shoulder land portion 4 includes an inner land portion 4a and an outer land portion 4b from the inner side in the tire width direction D1 by equally dividing the shoulder land portion 4 in the tire width direction D1. The inner land portion 4a includes an inner region 4c and a first central region 4d from the inner side in the tire width direction D1 by being equally divided into two in the tire width direction D1. The second center region 4e and the outer region 4f are provided from the inside in the tire width direction D1 by dividing the tire into two equal parts in the width direction D1.

That is, the shoulder land portion 4 is equally divided into four in the tire width direction D1, so that the inner region 4c, the first central region 4d, the second central region 4e, and the outer region 4f are arranged from the inside in the tire width direction D1. Equipped with. Each of the inner region 4c and the outer region 4f is also referred to as an end portion of the shoulder land portion 4, and the combined region of the first and second central regions 4d and 4e is also referred to as a central portion of the shoulder land portion 4.

Here, the tire 1 according to the present embodiment employs a configuration that suppresses uneven ground contact pressures on the land portions 4 and 5, and the configurations will be described below.

First, when one of the boundaries 2g and 2h is arranged on the land portions 4 and 5, the ground contact pressure of the boundaries 2g and 2h of the land portions 4 and 5 becomes high, and the ground pressure of the land portions 4 and 5 increases. Is likely to be uneven. Therefore, both the first boundary 2g and the second boundary 2h are arranged on the shoulder land portion 4. Thereby, since the two boundaries 2g and 2h are arranged in the shoulder land portion 4, the ground contact pressure of the shoulder land portion 4 is dispersed into the first boundary 2g and the second boundary 2h. Therefore, it is possible to prevent the ground contact pressure of the shoulder land portion 4 from becoming uneven.

On the other hand, since the boundaries 2g and 2h are not arranged in the center land portion 5, the ground contact pressure of the center land portion 5 does not become non-uniform due to the boundaries 2g and 2h. As a result, it is possible to prevent the ground pressures of the land portions 4 and 5 from becoming uneven.

Moreover, the first boundary 2g is arranged on the inner side land portion 4a of the shoulder land portion 4, and the second boundary 2h is arranged on the outer side land portion 4b of the shoulder land portion 4. As a result, the ground contact pressure of the shoulder land portion 4 is distributed to the inner land portion 4a and the outer land portion 4b, so that the ground pressure of the inner land portion 4a and the land pressure of the outer land portion 4b become uneven. Can be suppressed. Therefore, it is possible to further suppress the uneven ground contact pressure of the shoulder land portion 4.

By the way, of the land portions 4 and 5, the end portions (the inner region 4c and the outer region 4f) are more likely to be grounded on the road surface than the center portions (the first and second central regions 4d and 4e). As a result, the ground pressure of the end portions (the inner region 4c and the outer region 4f) is likely to be higher than the ground pressure of the central portions (first and second central regions 4d, 4e).

Therefore, the second boundary 2h is arranged in the central portion (second central region 4e) of the shoulder land portion 4. Moreover, when the boundaries 2g and 2h intersect the land grooves 6 and 7, the ground contact pressure at the intersecting position becomes high, whereas the second boundary 2h intersects the open groove 7.

As a result, the ground contact pressure in the central portion (second central region 4e) of the shoulder land portion 4 can be effectively increased. Therefore, the ground contact pressure at the ends of the shoulder land portion 4 (inner region 4c and outer region 4f) and the ground contact pressure at the central portion of the shoulder land portion 4 (first and second central regions 4d, 4e) become uneven. Can be suppressed.

By the way, when the boundaries 2g and 2h intersect the land grooves 6 and 7, the ground contact pressure at the intersecting position becomes high, whereas the first and second boundaries 2g and 2h are separated from the closed groove 6. There is. Specifically, the first boundary 2g is arranged between the shoulder main groove 3 and the closed groove 6, and the second boundary 2h is arranged between the closed groove 6 and the grounding end 2b. Thereby, it is possible to prevent the ground contact pressure from locally increasing at the position of the closed groove 6 in the shoulder land portion 4.

The first distance W1 between the first boundary 2g and the tire equator line L1 and the second distance W2 between the second boundary 2h and the tire equator line L1 are not particularly limited. The second distance W2 is preferably 110% to 300% of the first distance W1, for example.

Further, the relationship between the distance W3 between the first boundary 2g and the second boundary 2h and the dimension 4 of the shoulder land portion 4 in the tire width direction D1 is not particularly limited. The distance W3 between the first boundary 2g and the second boundary 2h is preferably, for example, 30% to 80% of the dimension 4 of the shoulder land portion 4 in the tire width direction D1.

Further, the tire 1 according to the present embodiment employs a configuration that suppresses a reduction in the ground contact area, and the configuration will be described below with reference to FIG.

First, as shown in FIG. 3, the ground contact area affects a distance (referred to as “camber amount”) W5 in the tire radial direction D2 between the tread surface 2a of the tire equatorial surface S1 and the tread surface 2a of the shoulder land portion 4. .. The camber amount W5 can also be said to be 1/2 of the difference between the tire outer diameter at the position of the tire equatorial plane S1 and the tire outer diameter at the position of the shoulder land portion 4.

Then, for example, as the camber amount W5 increases, the outer region of the tire 1 in the tire width direction D1 floats above the ground, making it more difficult to contact the ground. That is, as the camber amount W5 is larger, the position of the ground contact end 2b is closer to the inner side in the tire width direction D1. This reduces the ground contact area.

Therefore, in the tire 1 according to the present embodiment, both the first boundary 2g and the second boundary 2h are arranged on the shoulder land portion 4. As a result, the camber amount W5 can be reduced as compared with the configuration in which at least one of the boundaries 2g and 2h is arranged on the land portion 5 inside the shoulder land portion 4 in the tire width direction D1. Therefore, it is possible to prevent the ground contact area from decreasing.

As described above, the pneumatic tire 1 according to the present embodiment includes the tread portion 13 having the tread surface 2a, and the tread portion 13 is the tire width direction among the plurality of main grooves 3 extending along the tire circumferential direction D3. A shoulder main groove 3 which is a main groove 3 arranged on the outermost side of D1 and a shoulder land portion 4 defined by the shoulder main groove 3 and the ground contact end 2b are provided, and the tread surface 2a is a tire meridian. In the cross section of the surface, a first arc 2c, a second arc 2d, and a third arc 2e that are continuous from the tire equatorial plane S1 toward the outside in the tire width direction D1, and a boundary between the first arc 2c and the second arc 2d. And a second boundary 2h which is a boundary between the second circular arc 2d and the third circular arc 2e, the first boundary 2g and the second boundary 2h being the shoulder land portion 4 Is located in.

According to such a configuration, since both the first boundary 2g and the second boundary 2h are arranged in the shoulder land portion 4, the ground contact pressure of the shoulder land portion 4 is the first boundary 2g and the second boundary 2h. Dispersed in. As a result, it is possible to prevent the contact pressure of the land portions 4 and 5 from becoming uneven.

Moreover, both the first boundary 2g and the second boundary 2h are arranged in the shoulder land portion 4, which is the outermost land portion in the tire width direction D1. As a result, the distance W5 in the tire radial direction D2 between the tread surface 2a of the tire equatorial plane S1 and the tread surface 2a of the shoulder land portion 4 can be reduced. Therefore, it is possible to suppress a decrease in the ground contact area.

Further, in the pneumatic tire 1 according to the present embodiment, the shoulder land portion 4 includes a closed groove 6 that extends so as to intersect the tire circumferential direction D3 and that is separated from the shoulder main groove 3 and the ground contact end 2b. The first boundary 2g is arranged between the shoulder main groove 3 and the closed groove 6, and the second boundary 2h is arranged between the closed groove 6 and the ground contact end 2b. The composition.

According to such a configuration, when the first and second boundaries 2g and 2h intersect the closed groove 6, the ground contact pressure at the intersecting position becomes high, whereas the first and second boundaries 2g and 2h. Is separated from the closed groove 6. Thereby, it is possible to prevent the ground contact pressure from locally increasing at the position of the closed groove 6 in the shoulder land portion 4.

Further, in the pneumatic tire 1 according to the present embodiment, the shoulder land portion 4 is equally divided into four in the tire width direction D1, so that the inner region 4c and the first center are arranged from the inside in the tire width direction D1. An area 4d, a second central area 4e, and an outer area 4f are provided, and at least one of the first boundary 2g and the second boundary 2h (the second boundary 2h in the present embodiment) is the first central area 4d. Alternatively, it is arranged in the second central region 4e (in the present embodiment, the second central region 4e).

According to such a configuration, in the shoulder land portion 4, the ground pressure of the inner region 4c and the outer region 4f tends to be higher than the ground pressure of the first and second central regions 4d, 4e, At least one of the first boundary 2g and the second boundary 2h is arranged in the first central region 4d or the second central region 4e. As a result, the ground pressure in the central region 4e is increased due to the boundary 2h, so that the ground pressures in the inner region 4c and the outer region 4f and the ground pressures in the first and second central regions 4d, 4e become uneven. Can be suppressed.

Further, in the pneumatic tire 1 according to the present embodiment, the shoulder land portion 4 is provided with an open groove 7 that is connected to the shoulder main groove 3 and is separated from the ground contact end 2b. At least one of the first boundary 2g and the second boundary 2h (the second boundary 2h in the present embodiment), the first central region 4d or the second central region 4e (the second central region in the present embodiment). The structure is such that they intersect in the region 4e).

According to such a configuration, since the open groove 7 intersects at least one of the first boundary 2g and the second boundary 2h in the central regions 4d and 4e, the ground pressure of the central region 4e is caused by the boundary 2h. Can be higher. Thereby, it is possible to further suppress the non-uniformity of the ground pressures of the inner region 4c and the outer region 4f and the ground pressures of the first and second central regions 4d and 4e.

Further, in the pneumatic tire 1 according to the present embodiment, the shoulder land portion 4 is equally divided into two in the tire width direction D1, so that the inner land portion 4a and the outer land portion 4a are arranged from the inner side in the tire width direction D1. A portion 4b is provided, and the first boundary 2g is arranged on the inner land portion 4a, and the second boundary 2h is arranged on the outer land portion 4b.

According to such a configuration, since the first boundary 2g is arranged on the inner land portion 4a and the second boundary 2h is arranged on the outer land portion 4b, the ground contact pressure of the shoulder land portion 4 becomes the boundary 2g, 2h. Due to this, they are dispersed in the inner land portion 4a and the outer land portion 4b. As a result, it is possible to prevent the contact pressure of the inner land portion 4a and the contact pressure of the outer land portion 4b from becoming uneven.

The pneumatic tire 1 is not limited to the configuration of the above-described embodiment, and is not limited to the above-described operational effects. Needless to say, the pneumatic tire 1 can be variously modified without departing from the scope of the present invention. For example, it is needless to say that one or a plurality of configurations and methods according to the various modifications described below may be arbitrarily selected and used for the configurations and methods according to the above-described embodiments.

(1) In the pneumatic tire 1 according to the above embodiment, the first boundary 2g and the second boundary 2h are separated from the closed groove 6. However, the pneumatic tire 1 is not limited to such a configuration. For example, at least one of the first boundary 2g and the second boundary 2h may be configured to intersect the closed groove 6.

(2) Further, in the pneumatic tire 1 according to the above embodiment, the first boundary 2g is arranged in the inner region 4c, and the second boundary 2h is arranged in the second central region 4e. is there. However, the pneumatic tire 1 is not limited to such a configuration. For example, the first boundary 2g may be arranged in the first central region 4d or the second central region 4e. Further, for example, the second central region 4e may be arranged in the inner region 4c, the first central region 4d, or the outer region 4f.

That is, for example, both the first boundary 2g and the second boundary 2h may be arranged in the central portions (central regions 4d and 4e) of the shoulder land portion 4. Further, for example, both the first boundary 2g and the second boundary 2h are not the center parts (the central regions 4d and 4e) of the shoulder land part 4 but the end parts (the inner region 4c or the outer region 4f) of the shoulder land part 4. It may be configured to be arranged in.

(3) Further, in the pneumatic tire 1 according to the above embodiment, the open groove 7 is configured to intersect the first boundary 2g and the second boundary 2h. However, the pneumatic tire 1 is not limited to such a configuration. For example, the open groove 7 may be configured to intersect with the first boundary 2g and be separated from the second boundary 2h. Further, for example, the open groove 7 may be separated from the first boundary 2g and the second boundary 2h.

(4) Further, in the pneumatic tire 1 according to the above embodiment, the first boundary 2g is arranged in the inner land portion 4a, and the second boundary 2h is arranged in the outer land portion 4b. The composition. However, the pneumatic tire 1 is not limited to such a configuration. For example, both the first boundary 2g and the second boundary 2h may be arranged in the inner land portion 4a. Further, for example, both the first boundary 2g and the second boundary 2h may be arranged in the outer land portion 4b.

DESCRIPTION OF SYMBOLS 1... Pneumatic tire, 2... Tread rubber, 2a... Tread surface, 2b... Ground contact end, 2c... 1st circular arc, 2d... 2nd circular arc, 2e... 3rd circular arc, 2f... 4th circular arc, 2g... 1st boundary 2h... 2nd boundary, 2i... 3rd boundary, 3... Shoulder main groove, 4... Shoulder land part, 4a... Inner land part, 4b... Outer land part, 4c... Inner area, 4d... 1st center area, 4e ...Second central region, 4f...outside region, 5...center land portion, 6...land groove (closed groove), 7...land groove (open groove), 8...land groove, 11...bead portion, 11a...bead, 11b ... rim strip rubber, 12... sidewall portion, 12a... sidewall rubber, 13... tread portion, 14... carcass layer, 15... inner liner layer, 16... belt layer, 20... rim, D1... tire width direction, D2... Tire radial direction, D3... tire circumferential direction, L1... tire equatorial line, S1... tire equatorial plane

Claims (5)

With a tread portion having a tread surface,
The tread portion is partitioned by a shoulder main groove, which is a main groove arranged on the outermost side in the tire width direction among a plurality of main grooves extending along the tire circumferential direction, and the shoulder main groove and the ground contact end. With a shoulder land part,
The tread surface is a boundary between the first circular arc, the second circular arc, and the third circular arc that are continuous from the tire equatorial plane toward the outer side in the tire width direction in the cross section of the tire meridian surface, and the boundary between the first circular arc and the second circular arc. And a second boundary which is a boundary between the second circular arc and the third circular arc,
The said 1st boundary and the said 2nd boundary are pneumatic tires arrange|positioned at the said shoulder land part. The shoulder land portion includes a closed groove extending so as to intersect the tire circumferential direction and separated from the shoulder main groove and the ground contact end,
The first boundary is arranged between the shoulder main groove and the closed groove,
The pneumatic tire according to claim 1, wherein the second boundary is arranged between the closed groove and the ground contact end. The shoulder land portion is provided with an inner region, a first central region, a second central region, and an outer region from the inner side in the tire width direction by equally dividing into four in the tire width direction,
The pneumatic tire according to claim 1, wherein at least one of the first boundary and the second boundary is arranged in the first central region or the second central region. The shoulder land portion includes an open groove that is connected to the shoulder main groove and is separated from the ground contact end,
The pneumatic tire according to claim 3, wherein the open groove intersects at least one of the first boundary and the second boundary in the first central region or the second central region. The shoulder land portion is equally divided into two in the tire width direction, from the inner side in the tire width direction, an inner land portion and an outer land portion,
The first boundary is disposed on the inner land portion,
The pneumatic tire according to any one of claims 1 to 4, wherein the second boundary is arranged in the outer land portion.

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