Patent Description:
Tires that include tread land portions with sipes are known. Patent Literature (PTL) <NUM> describes a tire of this type.

As in a tire described in PTL <NUM>, the provision of sipes in a tread land portion improves wet gripping performance. However, as wear on a surface of the tread land portion progresses, compressive stiffness of the tread land portion increases. As a result, the contact area between the surface of the tread land portion and a road surface becomes small, the wet gripping performance deteriorates as compared to an initial state before the progress of the wear (hereinafter simply referred to as "initial state"). Namely, there is still room for improvement in the wet gripping performance of the tire described in PTL <NUM> during the progress of the wear on the tread land portion.

It would be helpful to provide a tire having sipes that are capable of improving wet gripping performance during the progress of wear on a tread land portion.

A tire as a first aspect of the present invention is a tire including, in a tread surface, a tread land portion partitioned by a partitioning groove or by the partitioning groove and a tread edge, wherein the tread land portion includes a sipe extending from a surface of the tread land portion inwardly in a tire radial direction,.

According to the present invention, it is possible to provide a tire having sipes that are capable of improving wet gripping performance during the progress of wear on a tread land portion.

Embodiments of a tire will be exemplarily described with reference to the drawings. In each figure, common members and components are indicated with the same reference numerals.

In this specification, "tread surface" means an outer circumferential surface over an entire circumference of the tire that comes into contact with a road surface when the tire mounted on a rim and filled with a specified internal pressure is rolled under a maximum load (hereinafter also referred to as "maximum load condition"). "Tread edges" refer to outer edges of the tread surface in a tire width direction.

In this specification, "rim" means a standard rim (Measuring Rim in ETRTO's STANDARDS MANUAL and Design Rim in TRA's YEAR BOOK) in an applicable size as described in or to be described in an industrial standard valid for regions where tires are produced and used, such as JATMA YEAR BOOK of the JATMA (The Japan Automobile Tyre Manufacturers Association, Inc. ) in Japan, STANDARDS MANUAL of the ETRTO (The European Tyre and Rim Technical Organisation) in Europe, YEAR BOOK of TRA (The Tire and Rim Association, Inc. ) in the United States, and the like, but in the case of a size not listed in these industrial standards, the "applicable rim" refers to a rim with a width corresponding to a bead width of tires. The term "rim" includes current sizes, as well as sizes that may be to be included in the aforementioned industrial standards in the future. Examples of the "sizes to be included in the future" may be sizes listed as "<NPL>.

In this specification, "specified internal pressure" refers to an air pressure (maximum air pressure) corresponding to a maximum load capacity of a single wheel in the applicable size and ply rating described in the aforementioned JATMA YEAR BOOK or other industrial standards. In the case of sizes not listed in the aforementioned industrial standards, the "specified internal pressure" refers to an air pressure (maximum air pressure) corresponding to a maximum load capacity specified for each vehicle on which the tire is mounted. Also, in this specification, "maximum load" means a load corresponding to a maximum load capacity in the applicable sized tire described in the aforementioned industrial standards, or, in the case of a size not listed in the aforementioned industrial standards, a load corresponding to a maximum load capacity specified for each vehicle on which the tire is mounted.

<FIG> is a drawing illustrating a pneumatic tire <NUM> (hereinafter referred to simply as "tire <NUM> ") as a first comparative embodiment of the tire.

<FIG> illustrates a tire widthwise cross section of the tire <NUM> in a plane including a central axis.

As illustrated in <FIG>, the tire <NUM> includes a tread portion 1a, a pair of sidewall portions 1b extending from both ends of the tread portion 1a in a tire width direction B to the inside in a tire radial direction A, and a pair of bead portions 1c provided at inner ends of the sidewall portions 1b in the tire radial direction A. The tire <NUM> is a tubeless type radial tire, but the configuration thereof is not particularly limited. The "tread portion 1a" refers to a portion sandwiched between tread edges TE on both sides in the tire width direction B. Each of the "bead portions 1c" refers to a portion where a bead member <NUM> described later is located in the tire radial direction A. Each of the "sidewall portions 1b" refers to a portion between the tread portion 1a and the bead portion 1c.

The tire <NUM> includes the bead members <NUM>, a carcass <NUM>, an inclined belt <NUM>, a circumferential belt <NUM>, tread rubber <NUM>, side rubber <NUM>, and an inner liner <NUM>. Each of the bead members <NUM> includes a bead core 3a and a bead filler 3b.

The bead member <NUM> is provided with the bead core 3a and the bead filler 3b that is disposed outside the bead core 3a in the tire radial direction A. The tire <NUM> is provided with the carcass <NUM> that straddles between the pair of bead cores 3a. The carcass <NUM> is composed of a carcass ply in which cords made of steel or the like are arranged. Furthermore, the tire <NUM> is provided with the inclined belt <NUM> that is disposed outside a crown portion of the carcass <NUM> in the tire radial direction A. The inclined belt <NUM> is composed of a belt ply in which cords made of organic fibers, steel, or the like are arranged. In the belt ply constituting the inclined belt <NUM>, the cords extend inclinedly at an angle of <NUM>° or more with respect to a tire circumferential direction C. There may be two or more belt plies constituting the inclined belt <NUM>. The tire <NUM> is also provided with the circumferential belt <NUM> disposed outside the inclined belt <NUM> in the tire radial direction A. The circumferential belt <NUM> is composed of a belt ply in which cords made of organic fibers, steel, or the like are arranged. In the belt ply constituting the circumferential belt <NUM>, the cords extend along the tire circumferential direction C. "The cords extend along the tire circumferential direction" means that the inclination angle of the cords with respect to the tire circumferential direction C is <NUM>° or more and less than <NUM>°. There may be two or more belt plies constituting the circumferential belt <NUM>.

The tire <NUM> is also provided with the tread rubber <NUM> disposed outside the circumferential belt <NUM> in the tire radial direction A, and the side rubber <NUM> disposed outside each side portion of the carcass <NUM> in the tire width direction B. Furthermore, the tire <NUM> is provided with the inner liner <NUM> that is laminated on an inner surface of the carcass <NUM>.

The tire <NUM> has the above-described cross sectional structure in the tire widthwise cross section, but not limited to this cross sectional structure and may be a tire having another cross sectional structure. The tire <NUM> has a symmetrical structure with respect to a tire equatorial plane CL, but is not limited to this structure and may be a tire asymmetrical with respect to the tire equatorial plane CL.

The tire <NUM> includes, in a tread surface T, tread land portions <NUM> that are partitioned by partitioning grooves <NUM>, or by the partitioning grooves <NUM> and the tread edges TE. Each of the "partitioning grooves" refers to a groove the minimum width of which at a groove edge is <NUM> or more when a tire in an unused state is mounted on an applicable rim and filled with a specified internal pressure, and under no load. In the tire <NUM>, each of the tread land portions <NUM> is partitioned by circumferential grooves <NUM> as the partitioning grooves <NUM>, or by the circumferential groove <NUM> and the tread edge TE. Each of the "circumferential grooves" refers to the partitioning groove, and an annular groove extending over the entire circumference of the tire circumferential direction C along the tire circumferential direction C. The circumferential grooves <NUM> extend in parallel to the tire circumferential direction C but may be inclined at an angle of <NUM>° or less with respect to the tire circumferential direction C, as long as the circumferential grooves <NUM> extend along the tire circumferential direction C. The circumferential grooves <NUM> extend in straight lines in developed view of the tread surface T, but are not limited to this configuration and may extend in zigzag or wavy shapes along the tire circumferential direction C. Note that, the tire <NUM> may have one or more widthwise grooves extending in the tire width direction B, as the partitioning grooves <NUM>.

More specifically, the tread surface T is provided with four of the circumferential grooves <NUM> and three rib-shaped land portions, as the tread land portions <NUM>, each partitioned between adjacent two of the four circumferential grooves <NUM>. Each of the "rib-shaped land portions" means an annular land portion that is partitioned between two of the circumferential grooves, that is not divided into separate land portions in the tire circumferential direction C by a partitioning groove extending in the tire width direction B, that is continuous over the entire circumference in the tire circumferential direction C. The three rib-shaped land portions of the present embodiment include a center land portion 32a and two intermediate land portions 32b adjacent to the center land portion 32a on both sides in the tire width direction B. In addition, shoulder land portions 32c are each partitioned between each of two of the circumferential grooves <NUM> on both outer sides in the tire width direction B, of the four circumferential grooves <NUM>, and the tread edge TE. The shoulder land portion 32c may be constituted of, for example, block-shaped land portions, as a plurality of the tread land portions <NUM>, which are partitioned by the tread edges TE and the partitioning grooves.

<FIG> is a developed view illustrating a part of the tread surface T of the tread portion 1a of the tire <NUM>. Specifically, <FIG> is a developed view illustrating the center land portion 32a and a vicinity of the center land portion 32a in the tread surface T. <FIG> is a cross sectional view along the line I-I of <FIG>. <FIG> is a cross sectional view along the lines II-II of <FIG>. <FIG> is a cross sectional view along the line III-III of <FIG>.

As illustrated in <FIG>, the center land portion 32a, being the rib-shaped land portion, includes sipes <NUM> extending from a surface of the center land portion 32a to the inside in the tire radial direction A. Each of the "sipes" means a groove that extends from a tread surface to the inside in a tire radial direction and a groove the maximum width of which at the tread surface is less than <NUM> when a tire in an unused state is mounted on an applicable rim and filled with a specified internal pressure, and under no load. The sipes <NUM> are provided in the center land portion 32a, but where to provide the sipes <NUM> is not particularly limited as long as the sipes <NUM> are provided in the tread land portion <NUM>. Accordingly, the sipes <NUM> may be provided in any tread land portion <NUM>, regardless of whether the tread land portion <NUM> is the center land portion 32a, the intermediate land portion 32b, or the shoulder land portion 32c, and further regardless of the tread land portion <NUM> is the rib-shaped land portion or the block-shaped land portion. Therefore, in the following, when the center land portion 32a, the intermediate land portions 32b, and the shoulder land portions 32c are not distinguished, and when the rib-shaped land portions and the block-shaped land portions are not distinguished, these land portions are simply described as "tread land portions <NUM>".

As illustrated in <FIG>, the sipe <NUM> includes a widened portion <NUM> with a larger sipe width than positions adjacent in a sipe longitudinal direction D. The "sipe longitudinal direction" is a direction in which the sipe <NUM> extends in the tread surface T. The "sipe width" refers to the distance between opposite inner walls constituting the sipe. The sipe width of the sipe <NUM> in the present embodiment is the distance between opposite inner walls in a direction (same direction as the tire circumferential direction C) perpendicular to the tire radial direction A and the sipe longitudinal direction D (same direction as the tire width direction B in the present embodiment).

In addition, the cross-sectional area of the widened portion <NUM> in cross section perpendicular to the tire radial direction A is larger on the inside than on the outside in the tire radial direction A. Thereby, even when wear on a surface of the tread land portion <NUM> progresses, increase in the cross-sectional area of the widened portion <NUM> can prevent increase in the compressive stiffness of the tread land portion <NUM>. In this way, the sipes <NUM> can improve wet grip performance during the progress of the wear on of the tread land portion <NUM>.

As illustrated in <FIG>, the widened portion <NUM> of the comparative embodiment includes three tubular portions <NUM> with different lengths in the tire radial direction A. The three tubular portions <NUM> extend from a bottom of the sipe outwardly in the tire radial direction A at different positions in the sipe longitudinal direction D. The tubular portions <NUM> have larger sipe widths than positions adjacent in the sipe longitudinal direction D. More specifically, each of the tubular portions <NUM> of the present embodiment is constituted of a first recess <NUM> formed in one of the inner walls of the sipe <NUM> and a second recess <NUM> formed in the other inner wall of the sipe <NUM>. The first recess <NUM> and the second recess <NUM> are located opposite each other. The first recess <NUM> is constituted of a curved surface 65a, which is in an arc shape in cross section perpendicular to the tire radial direction A and extends in the tire radial direction A, and flat bottom surfaces 65b, which are located on the inside and outside in the tire radial direction A with respect to the curved surface 65a so as to be opposite each other. The second recess <NUM> is constituted of a curved surface 66a, which is in an arc shape in cross section perpendicular to the tire radial direction A and extends in the tire radial direction A, and flat bottom surfaces 66b, which are located on the inside and outside in the tire radial direction A with respect to the curved surface 66a so as to be opposite each other. Note that, the bottom surface 65b of the first recess <NUM> located on the inside in the tire radial direction A and the bottom surface 66b of the second recess <NUM> located on the inside in the tire radial direction A are continuous to be flush with each other at the bottom of the sipe and constitute the same plane. In contrast, the bottom surface 65b of the first recess <NUM> located on the outside in the tire radial direction A and the bottom surface 66b of the second recess <NUM> located on the outside in the tire radial direction A are separated by a slit <NUM> and not continuous.

Conversely, positions of the sipe <NUM> that are adjacent to the tubular portions <NUM> in the sipe longitudinal direction D do not constitute the widened portion <NUM>. In other words, in one of the inner walls of the sipe <NUM>, a position adjacent to the first recess <NUM> in the sipe longitudinal direction D is composed of a first flat portion <NUM> parallel to the sipe longitudinal direction D. In addition, in the other inner wall of the sipe <NUM> of the present embodiment, a position adjacent to the second recess <NUM> in the sipe longitudinal direction D is composed of a second flat portion <NUM> parallel to the sipe longitudinal direction D. Note that a portion of one of the inner walls of the sipe <NUM> that is outside the first recess <NUM> in the tire radial direction A is composed of a flat portion that is flush with the first flat portion <NUM>. Also, a portion of the other inner wall of the sipe <NUM> that is outside the second recess <NUM> in the tire radial direction A is composed of a flat portion that is flush with the second flat portion <NUM>. Therefore, the sipe <NUM> is constituted of the tubular portions <NUM>, which are each constituted of the first recess <NUM> and the second recess <NUM>, and the slit <NUM>, which is constituted of the flat portion including the first flat portion <NUM> (hereinafter, the entire flat portion including the first flat portion <NUM> is hereinafter simply referred to as "first flat portion <NUM>", for convenience of explanation) and the flat portion including the second flat portion <NUM> (hereinafter, the entire flat portion including the second flat portion <NUM> is hereinafter simply referred to as "second flat portion <NUM>", for convenience of explanation).

The minimum sipe width of the tubular portion <NUM> is equal to or larger than the maximum sipe width of the slit <NUM>. In other words, the minimum sipe width between the first recess <NUM> and the second recess <NUM> is equal to or larger than the maximum sipe width between the first flat portion <NUM> and the second flat portion <NUM>. The sipe width of the slit <NUM> is constant regardless of the position in the tire radial direction A and the position in the sipe longitudinal direction D. The maximum sipe width of the slit <NUM> of the present embodiment is not particularly limited as long as the maximum sipe width of the slit <NUM> is less than <NUM>, but may be set in a range of, for example, <NUM> to <NUM>. In addition, the minimum sipe width of the tubular portion <NUM> of the present embodiment should be equal to or larger than the maximum sipe width of the slit <NUM>, and may be set in a range of, for example, more than <NUM> and less than <NUM>.

As described above, the sipe width of the slit <NUM> is constant regardless of the position in the tire radial direction A and the position in the sipe longitudinal direction D, but is not limited to this configuration. The sipe width of the slit <NUM> may vary depending on the position in the tire radial direction A and the position in the sipe longitudinal direction D. Also, the tubular portion <NUM> has a constant sipe width, in cross-sectional views (refer to <FIG> and <FIG>) perpendicular to the sipe longitudinal direction D, regardless of the position in the tire radial direction A, but is not limited to this configuration. The sipe width of the tubular portion <NUM> may vary in cross sectional views (refer to <FIG> and <FIG>) perpendicular to the sipe longitudinal direction D, depending on the position in the tire radial direction A. Thus, for example, the tubular portion <NUM> may have a portion the sipe width of which gradually increases from the outside to the inside in the tire radial direction A in cross sectional views (refer to <FIG> and <FIG>) perpendicular to the sipe longitudinal direction D. The tubular portion <NUM> may be configured such that the sipe width of the entire tubular portion <NUM> gradually increases from the outside to the inside in the tire radial direction A in cross sectional views (refer to <FIG> and <FIG>) perpendicular to the sipe longitudinal direction D.

As described above, the sipe <NUM> has the three tubular portions <NUM> at different positions in the sipe longitudinal direction D. The three tubular portions <NUM> of the present embodiment include a first tubular portion 52a located on the side of one end in the tire width direction B, a second tubular portion 52b located on the side of the other end in the tire width direction B, and a third tubular portion 52c located between the first tubular portion 52a and the second tubular portion 52b in the tire width direction B. As illustrated in <FIG>, in the present embodiment, the first tubular portion 52a and the second tubular portion 52b are approximately equal in length L1 in the tire radial direction A. Also, as illustrated in <FIG>, length L2 of the third tubular portion 52c in the tire radial direction A is shorter than the length L1 of the first tubular portion 52a and the second tubular portion 52b. Therefore, as the surface of the tread land portion <NUM> wears down from the initial state, the first tubular portion 52a and the second tubular portion 52b are exposed to the surface of the tread land portion <NUM> earlier than the third tubular portion 52c. As the wear on the surface of the tread land portion <NUM> further progresses, the third tubular portion 52c is exposed to the surface of the tread land portion <NUM>. Therefore, the first tubular portion 52a, the second tubular portion 52b, and the third tubular portion 52c are all exposed to the surface of the tread land portion <NUM>.

In this way, by varying the lengths of the plurality of tubular portions <NUM> extending from the bottom of the sipe to the outside in the tire radial direction A, the number of the tubular portions <NUM> to be exposed can be increased, as the wear on the surface of the tread land portion <NUM> progresses. This allows the cross-sectional area of the widened portion <NUM> to increase even as the wear on the surface of the tread land portion <NUM> progresses. Therefore, it is possible to achieve the compressive stiffness of the tread land portion <NUM> according to the amount of the wear on the surface of the tread land portion <NUM>, and to improve wet gripping performance with a simple configuration during the progress of the wear on the tread land portion <NUM>. Note that, the cross-sectional area of the tubular portion <NUM> in cross section perpendicular to the tire radial direction A means, in the same cross section, the area of a region sandwiched between opposite portions of the inner walls of the sipe <NUM> that constitute the tubular portion <NUM>. In the comparative embodiment, the cross-sectional area of the tubular portion <NUM> in cross section perpendicular to the tire radial direction A means, in the same cross section, the area of a region sandwiched between the first recess <NUM> and the second recess <NUM>.

Although the sipe longitudinal direction D of the sipe <NUM> coincides with the tire width direction B, the sipe longitudinal direction D is not limited to the tire width direction B. Therefore, the sipe longitudinal direction D of the sipe <NUM> may coincide with, for example, the tire circumferential direction C. Also, the sipe longitudinal direction D of the sipe <NUM> may be, for example, a direction inclined to the tire width direction B and the tire circumferential direction C. Furthermore, the sipes <NUM> each extend in a straight line in the surface of the tread land portion <NUM>, but are not limited to this configuration. The sipes <NUM> may each extend in an arc, zigzag, or wavy shape in the surface of the tread land portion <NUM>.

The sipes <NUM> cross the rib-shaped land portion, as the tread land portion <NUM>, in the tire width direction B and are connected to the circumferential grooves <NUM> on both sides in the tire width direction B, but are not limited to this configuration. For example, the sipes <NUM> may terminate in the tread land portion <NUM>. The sipes <NUM> may be configured such that, for example, one end in the sipe longitudinal direction D is connected to the circumferential groove <NUM> and the other end in the sipe longitudinal direction D terminates in the tread land portion <NUM>.

Furthermore, the sipes <NUM> of extend from the surface of the tread land portion <NUM> along the tire radial direction A inwardly in the tire radial direction A, but are not limited to this configuration. For example, the sipes <NUM> may extend from the surface of the tread land portion <NUM> in a direction inclined to the tire radial direction A inwardly in the tire radial direction A. In addition, the sipes <NUM> extend in straight lines from the surface of the tread land portion <NUM> inwardly in the tire radial direction A in a cross-sectional view (refer to <FIG> and <FIG>) perpendicular to the tire width direction B, but are not limited to this configuration. For example, the sipes <NUM> may extend, in the same cross-sectional view, in an arc, zigzag, or wavy shape from the surface of the tread land portion <NUM> inwardly in the tire radial direction A.

In the comparative embodiment, the length L1 (refer to <FIG> and <FIG>) of the first and second tubular portions 52a and 52b in the tire radial direction A is longer than the length L2 (refer to <FIG> and <FIG>) of the third tubular portion 52c in the tire radial direction A, but is not limited to this configuration. For example, the length of the first and second tubular portions 52a and 52b in the tire radial direction A may be shorter than the length of the third tubular portion 52c in the tire radial direction A. In addition, the first tubular portion 52a and the second tubular portion 52b have approximately equal length L1 in the tire radial direction A, but may have different lengths. None of the plurality of tubular portions <NUM> is exposed to the surface of the tread land portion <NUM> in the initial state. However, the plurality of tubular portions <NUM> may include one that is exposed to the surface of the tread land portion <NUM> in the initial state, in other words, that extends from the bottom of the sipe to the tread surface T in the initial state.

Furthermore, the sipe <NUM> has the three tubular portions <NUM>, but is not limited to this configuration. In a case in which the widened portion <NUM> of the sipe <NUM> is constituted of only a plurality of tubular portions <NUM>, the sipe <NUM> should be provided with at least two tubular portions <NUM> having different lengths in the tire radial direction A. Thus, the sipe <NUM> may have, for example, only two tubular portions <NUM>. Alternatively, the sipe <NUM> may have, for example, four or more tubular portions <NUM>.

The tubular portion <NUM> is in an approximately circular shape in cross section perpendicular to the tire radial direction A, but is not limited to this cross-sectional shape. The tubular portion <NUM> may be in, for example, an oval shape or a polygonal shape such as a quadrangular shape, in the above cross section. That is, the first recess <NUM> and the second recess <NUM> are in the arc shape in cross section perpendicular to the tire radial direction A, but are not limited to this configuration and may be various cross-sectional shapes such as, for example, a U-shape, V-shape, or rectangular shape. Furthermore, the tubular portion <NUM> is constituted of the first recess <NUM> and the second recess <NUM>, but is not limited to this configuration. The first recess <NUM> may be formed only in one of the inner walls of the sipe <NUM>, and the other inner wall of the sipe <NUM> may be a flat portion that is flush with the second flat portion <NUM>. Also, one of the inner walls of the sipe <NUM> may be a flat portion that is flush with the first flat portion <NUM>, and the second recess <NUM> may be formed only in the other inner wall of the sipe <NUM>.

The cross-sectional area of the tubular portion <NUM> in cross section perpendicular to the tire radial direction A is constant regardless of the position in the tire radial direction A, but is not limited to this configuration. The cross-sectional area of the tubular portion <NUM> in cross section perpendicular to the tire radial direction A may vary depending on the position in the tire radial direction A. In particular, it is preferable that the cross-sectional area of the tubular portion <NUM> in cross section perpendicular to the tire radial direction A is larger on the inside than on the outside in the tire radial direction A. Thereby, even in a case in which the wear on the surface of the tread land portion <NUM> progresses from the initial state and all of the plurality of tubular portions <NUM> are exposed to the surface of the tread land portion <NUM>, and thereafter the wear further progresses, increase in compressive stiffness can be prevented. Such tubular portions <NUM> have a configuration, for example, in which the sipe widths gradually increase inwardly in the tire radial direction A. With such tubular portions <NUM>, it is possible to realize a configuration in which the cross-sectional areas of the tubular portions <NUM> perpendicular to the tire radial direction A gradually increase.

The plurality (three in the comparative embodiment) of tubular portions <NUM> have an approximately equal cross-sectional area in the same cross section perpendicular to the tire radial direction A, but are not limited to this configuration. The plurality of tubular portions <NUM> may have different cross-sectional areas in the above cross section.

Next, a tire <NUM> as a second comparative embodiment not forming part of the present invention will be exemplarily described. <FIG> and <FIG> illustrate a sipe <NUM> of the tire <NUM>. <FIG> is a cross-sectional view in the same position as <FIG>. <FIG> is a drawing illustrating a widened portion <NUM> of the sipe <NUM> in cross section that is perpendicular to the cross section illustrated in <FIG> and parallel to the tire radial direction A. Compared with the tire <NUM> of the first embodiment, the tire <NUM> differs in the configuration of the widened portion and shares other configurations. Therefore, here, the difference from the tire <NUM> of the first embodiment is mainly explained, and the common points are omitted.

The sipe <NUM> is provided with the widened portion <NUM> the sipe width of which is larger than positions adjacent in the sipe longitudinal direction D. The cross-sectional area of the widened portion <NUM> in cross section perpendicular to the tire radial direction A is larger on the inside than on the outside in the tire radial direction A. This point is the same as that of the widened portion <NUM> of the first embodiment.

As illustrated in <FIG> and <FIG>, the widened portion <NUM> has tubular portions <NUM> extending from a bottom of the sipe outwardly in the tire radial direction A. This point is also similar to the tubular portions <NUM> of the first embodiment.

As illustrated in <FIG> and <FIG>, the cross-sectional area of each of the tubular portions <NUM> in cross section perpendicular to the tire radial direction A is larger on the inside than on the outside in the tire radial direction A. The tubular portion <NUM> differs from the tubular portion <NUM> of the above-described first embodiment in that this configuration is essential.

As illustrated in <FIG> and <FIG>, the sipe <NUM> has the two tubular portions <NUM>, but is not limited to this configuration. The sipe <NUM> should be provided with at least one tubular portion <NUM> the cross-sectional area of which in cross section perpendicular to the tire radial direction A is larger on the inside than on the outside in the tire radial direction A. By configuring such a tubular portion <NUM>, wet gripping performance during the progress of wear on the tread land portion <NUM> can be enhanced with a simple configuration. Note that, the number of the tubular portions <NUM> to be provided in the single sipe <NUM> may be determined as appropriate according to the length of the sipe <NUM> in the sipe longitudinal direction D and other factors.

As illustrated in <FIG> and <FIG>, the tubular portions <NUM> are each constituted of a first recess <NUM> formed in one of inner walls of the sipe <NUM> and a second recess <NUM> formed in the other inner wall of the sipe <NUM> at an opposite position to the first recess <NUM>. The tubular portion <NUM>, which is constituted of the first recess <NUM> and the second recess <NUM>, has a conical trapezoidal shape the diameter of which expands toward the inside in the tire radial direction A, but is not limited to this configuration, as long as the tubular portion <NUM> is configured such that the cross-sectional area in cross section perpendicular to the tire radial direction A is larger on the inside than on the outside in the tire radial direction A.

Next, a tire <NUM> as a third embodiment illustrating ef the present invention will be exemplarily described. <FIG> and <FIG> illustrate a sipe <NUM> of the tire <NUM>. <FIG> is a cross-sectional view in the same position as <FIG>. <FIG> is a drawing illustrating a widened portion <NUM> of the sipe <NUM> in cross section that is perpendicular to the cross section illustrated in <FIG> and parallel to the tire radial direction A. Compared with the tire <NUM> of the first embodiment, the tire <NUM> of the present embodiment of the invention differs in the configuration of the widened portion and shares other configurations. Therefore, here, the difference from the tire <NUM> of the first embodiment is mainly explained, and the common points are omitted.

As illustrated in <FIG> and <FIG>, the sipe <NUM> is provided with the widened portion <NUM> the sipe width of which is larger than positions adjacent in the sipe longitudinal direction D. The cross-sectional area of the widened portion <NUM> in cross section perpendicular to the tire radial direction A is larger on the inside than on the outside in the tire radial direction A. This point is the same as that of the widened portion <NUM> of the first embodiment.

As illustrated in <FIG> and <FIG>, the widened portion <NUM> of the present invention has a branch tubular portion <NUM> that branches into a plurality of portions in the sipe longitudinal direction D from the outside to the inside in the tire radial direction A. In the branch tubular portion <NUM>, tubular pieces 271a are branched and increased from the outside to the inside in the tire radial direction A, so that the cross-sectional area of the branch tubular portion <NUM> in cross section perpendicular to the tire radial direction A increases. Each of the tubular pieces 271a, which constitute the branch tubular portion <NUM>, has a larger sipe width than positions adjacent in the sipe longitudinal direction D, as in the tubular portion <NUM> of the first embodiment. By configuring such a branch tubular portion <NUM>, wet gripping performance during the progress of wear on the tread land portion can be enhanced with a simple configuration. The number of branches from each tubular piece 271a of the branch tubular portion <NUM>, the shape and cross-sectional area of each tubular piece 271a in cross section perpendicular to the tire radial direction A, and the like are not particularly limited. That is, the configuration of each tubular piece 271a is not particularly limited as long as the cross-sectional area of the branch tubular portion <NUM> in cross section perpendicular to the tire radial direction A is larger on the inside than on the outside in the tire radial direction A. Note that, in the sipe <NUM> of the present invention, parts where the branch tubular portion <NUM> is not provided and parts between the six tubular pieces 271a are composed of slits <NUM>.

As illustrated in <FIG>, the branch tubular portion <NUM> of the present invention extends from a bottom of the sipe to the surface of the tread land portion <NUM>. More specifically, in the branch tubular portion <NUM> of the present invention, one first tubular piece 271a1 extends from the surface of the tread land portion <NUM> inwardly in the tire radial direction A. An inner end of the one first tubular piece 271a1 in the tire radial direction A is branched in two into a second tubular piece 271a2 and a third tubular piece 271a3. An inner end of the second tubular piece 271a2 in the tire radial direction A is branched in two into a fourth tubular piece 271a4 and a fifth tubular piece 271a5. An inner end of the third tubular piece 271a3 in the tire radial direction A is branched in two into the fifth tubular piece 271a5 and a sixth tubular piece 271a6. Note that, the fifth tubular piece 271a5 is a tubular piece that is branched from each of the second tubular pieces 271a2 and the third tubular piece 271a3 and merged into one. In the present invention, inner ends of the first to sixth tube pieces 271a1 to 271a6 in the tire radial direction A have an approximately equal shape and cross-sectional area in cross section perpendicular to the tire radial direction A. Therefore, the cross-sectional area of the branch tubular portion <NUM> in cross section perpendicular to the tire radial direction A is larger on the inside than on the outside in the tire radial direction A.

As illustrated in <FIG>, the sipe <NUM> of the present invention is provided with only one of the branch tubular portion <NUM>, but is not limited to this configuration. A plurality of the branch tubular portions <NUM> may be provided at different positions in the sipe longitudinal direction D. That is, the sipe <NUM> should have at least one of the branch tubular portion <NUM>. The number of the branch tubular portions <NUM> provided in the single sipe <NUM> may be determined as appropriate according to the length of the sipe <NUM> in the sipe longitudinal direction D and other factors.

The tire of the present invention is not limited to the specific configurations illustrated in the embodiments described above, but can be transformed and modified in various ways as long as it does not depart from the scope of the claims. In the first to third embodiments described above, the sipes <NUM>, <NUM>, and <NUM> are formed in the center land portion 32a as the tread land portion, but may be formed in the intermediate land portions 32b or the shoulder land portions 32c. In addition, the sipes <NUM>, <NUM>, and <NUM> of the first to third embodiments described above are formed in the rib-shaped land portion, but may be formed in a block-shaped land portion.

Claim 1:
A tire (<NUM>, <NUM>) comprising, in a tread surface (T), a tread land portion (<NUM>) partitioned by a partitioning groove (<NUM>) or by the partitioning groove (<NUM>) and a tread edge (TE), wherein
the tread land portion (<NUM>) includes a sipe (<NUM>, <NUM>) extending from a surface of the tread land portion (<NUM>) inwardly in a tire radial direction (A),
the sipe (<NUM>, <NUM>) includes a widened portion (<NUM>, <NUM>) with a larger sipe width than a position adjacent in a sipe longitudinal direction (D), and
a cross-sectional area of the widened portion (<NUM>, <NUM>) in cross section perpendicular to the tire radial direction (A) is larger on inside than on outside in the tire radial direction (A),
wherein the widened portion (<NUM>, <NUM>) includes at least two tubular portions (<NUM>, <NUM>) extending from a bottom of the sipe (<NUM>, <NUM>) outwardly in the tire radial direction (A) at different positions in the sipe longitudinal direction (D), and
wherein a cross-sectional area of at least one of the tubular portions (<NUM>, <NUM>) in cross section perpendicular to the tire radial direction (A) is larger on inside than on outside in the tire radial direction (A) in such a manner that the sipe width of the entire tubular portion (<NUM>, <NUM>) gradually increases from the outside to the inside in the tire radial direction (A).