Patent Description:
A pneumatic tire includes a tread as a portion to be in contact with a road surface. The tread includes a plurality of blocks. Sipes are formed in each block. The sipe is a narrow groove and has functions of adjusting hardness of the block, increasing a gripping force by increasing the number of edges of the block, and the like. The sipe in the pneumatic tire is molded using sipe blades provided in a mold for molding a tire.

For example, <CIT> discloses a tire in which a plurality of minute protrusions are formed on a wall surface of a sipe, a water repellent effect of the wall surface of the sipe is improved, and water inside the sipe is discharged.

In addition, <CIT> discloses a pneumatic tire in which irregularities are formed on an inner wall surface of a sipe, a friction coefficient between inner wall surfaces is improved, and a block is prevented from being greatly deformed.

Further, <CIT> discloses a pneumatic tire in which a recessed portion (space portion) is formed on an inner wall surface of a sipe, and a water removal property is secured. Also, <CIT> discloses a tire tread which comprises elastomeric material and has a plurality of grooves therein, defining ground engaging elastomeric elements, wherein the elastomeric elements include a sipe which has a first surface area and an opposite facing second surface area, each surface area having a plurality of recesses or protrusions, each recess having a centroid aligned with a centroid of a protrusion, and the combination of recesses and protrusions interlock increasing the rigidity of the elastomeric elements. Also, <CIT> discloses a tire wherein a plurality of sipes are provided in a tread surface of a block and, in the sipes, there are formed protrusions on a first sipe wall surface and recesses on a second sipe wall surface, the recesses engaging with the protrusions. In addition, <CIT> discloses that collapse of portions of the block sandwiched by the sipes is suppressed due to engagement of the protrusions and the recesses. Also, <CIT> discloses a pneumatic tire, and in a tread of the tire there are provided blocks each of which is formed from a plurality of main and auxiliary grooves, wherein at least one notch is furnished, and a projection is formed on one of the mating surfaces of the notch in its inner side, while a dimple to mesh with the projection is formed at the other surface. Also, <CIT> discloses a tire wherein in a tread part a plurality of circumferential grooves and a plurality of lateral grooves are provided so as to demarcate a plurality of blocks, and in each block, a plurality of sipes are provided, wherein in each sipe, a protrusion is formed on one of a pair of wall surfaces, and a recess engaging with the protrusion is formed on the other of the pair of wall surfaces.

However, in the tire disclosed in <CIT>, although the plurality of minute protrusions are formed on the wall surface of the sipe and the water repellent effect of the sipe is improved, the minute protrusions may inhibit drainage from the sipe, and maneuver stability performance on a wet road surface may decrease. Here, the maneuver stability performance on the wet road surface is performance such that a pneumatic tire can travel while gripping a road surface in an environment where the road surface is wet in rainy weather or the like.

In addition, in the pneumatic tire disclosed in <CIT>, although the friction coefficient is improved, an improvement in maneuver stability performance on a wet road surface is not considered.

Further, in the pneumatic tire disclosed in <CIT>, although the space portion is formed on the inner wall surface of the sipe and the water removal property is secured, since the space portion is large, block rigidity may decrease, and maneuver stability performance on a dry road surface may decrease. Here, the maneuver stability performance on the dry road surface is performance such that a pneumatic tire can travel while gripping a road surface in an environment of a dry road surface.

Therefore, an object of the present invention is to provide a pneumatic tire and a mold for molding a tire that are capable of improving maneuver stability performance on wet road surface and maneuver stability performance on dry road surface.

The pneumatic tire according to the present invention is a pneumatic tire including a tread including a block in which at least one sipe is formed. A plurality of recesses are formed in one wall surface of each of the at least one sipe. The recesses change in volume toward at least one of a tire radial direction and a tire axial direction in the block.

According to the pneumatic tire and the mold for molding a tire of the present invention, the maneuver stability performance on the wet road surface and the maneuver stability performance on the dry road surface can be improved.

Hereinafter, an example of an embodiment according to the present invention will be described in detail. In the following description, specific shapes, materials, directions, numerical values, and the like are examples for ease of understanding of the present invention, and can be appropriately changed according to applications, purposes, specifications, and the like.

A pneumatic tire <NUM> according to an example of an embodiment will be described with reference to <FIG> and <FIG>.

As shown in <FIG>, the pneumatic tire <NUM> includes a tread <NUM> including blocks <NUM>, in each of which sipes <NUM> are formed. According to the pneumatic tire <NUM>, maneuver stability performance on a wet road surface and maneuver stability performance on a dry road surface can be improved, as will be described in detail later.

Hereinafter, each member will be described with respect to a tire axial direction X, a tire circumferential direction Y, and a tire radial direction Z. In the tire axial direction X, a tire width may be described using an equator side and a shoulder side. Further, in the tire axial direction X, the block <NUM> may be described using a block central portion and two block end sides. Further, in the tire radial direction Z, a description may be given using a block surface side and a bottom side. In the drawings, an equator CL, a shoulder side SH, and a block surface SF are shown in respective directions.

The tread <NUM> is a portion in the pneumatic tire <NUM> to be in contact with a road surface. The tread <NUM> includes a plurality of blocks <NUM> divided by main grooves <NUM> and sub grooves <NUM>. The blocks <NUM> are each formed in the same rectangular shape in a plan view, and are aligned in the tread <NUM>. However, a shape of the blocks <NUM> according to the present embodiment is not limited thereto, the blocks <NUM> may have a rhomboid shape or a parallelogram shape as long as the blocks <NUM> are divided by the main grooves <NUM> and the sub grooves <NUM>, and the shape is not particularly limited.

Each main groove <NUM> is a groove formed linearly to extend along the tire circumferential direction Y. Each sub groove <NUM> is a groove formed linearly to extend along the tire axial direction X. However, a shape of the main groove <NUM> or a shape of the sub groove <NUM> according to the present embodiment is not limited thereto, the main groove <NUM> may be inclined with respect to the tire circumferential direction Y, and the sub groove <NUM> may be inclined with respect to the tire axial direction X.

As shown in <FIG> and <FIG>, three sipes <NUM> are formed in the block <NUM>. The sipe <NUM> is a groove having a width narrower than at least that of the main groove <NUM> and the sub groove <NUM>, and is formed such that a depth of the groove is in the tire radial direction Z. However, the number of sipes <NUM> is not limited to that according to the present embodiment, and three to five sipes <NUM> may be formed in the block <NUM>.

The sipe <NUM> is formed linearly along the tire axial direction X. However, a shape of the sipe <NUM> according to the present embodiment is not limited thereto, and for example, the sipe <NUM> may be inclined with respect to the tire axial direction X, may be formed in a waveform shape, or may be formed in a zigzag shape.

According to the sipes <NUM>, hardness of the block <NUM> in the tread <NUM> can be adjusted by changing the shape or the number of the sipes <NUM>. The number of edges of the block <NUM> is increased by the sipes <NUM>, and a gripping force of the pneumatic tire <NUM> can be improved. Further, a water film on a wet road surface or on an icy and snowy road surface can be absorbed by the sipes <NUM>, the blocks <NUM> can be brought into close contact with the road surface or ice, and the gripping force of the pneumatic tire <NUM> can be improved.

Recesses <NUM> according to a first embodiment will be described with reference to <FIG>.

A plurality of recesses <NUM> are formed in one wall surface 40A of the sipe <NUM>.

According to the recesses <NUM>, water on the block surface SF of the tread <NUM> can be absorbed, and a water absorption effect of the sipe <NUM> can be improved. A portion in the wall surface 40A of the sipe <NUM> other than portions in which the recesses <NUM> are formed is formed as a flat surface. Here, the flat surface is a surface having a maximum height (Rz) of <NUM> to <NUM> and an arithmetic average roughness (Ra) of <NUM> to <NUM>, which are defined in JISB0601:<NUM> (ISO4287:<NUM>, Amd. <NUM>:<NUM>).

Here, both wall surfaces 40A and 40B of the sipe <NUM> are surfaces of the sipe <NUM> facing each other in the tire circumferential direction Y. However, a configuration in which the recesses <NUM> are formed in the one wall surface 40A of the sipe <NUM> is not limited to the recess <NUM> according to the present embodiment, and the recesses <NUM> may be formed in the other wall surface 40B of the sipe <NUM>. According to the invention, a surface facing the recesses <NUM> is a flat surface, and the recesses <NUM> are only formed in the one wall surface 40A of the sipe <NUM>.

The recess <NUM> according to the present invention is formed in a hemispherical shape or the recess <NUM> has a semi-ellipsoid shape. It is preferable that the recess <NUM> according to the present embodiment is formed in a portion from the block surface side to <NUM> or more when a length (sipe depth) of the sipe <NUM> in the tire radial direction Z is set to <NUM>. It is preferable that the recess <NUM> according to the present embodiment is formed at a length of <NUM> or more when a length of the sipe <NUM> in the tire axial direction X is set to <NUM>.

The recesses <NUM> according to the present invention include recesses 41A, 41B, 41C, and 41D having different volumes of recessed portions (hereinafter referred to as a recess volume). The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from the block surface side to the bottom side in the tire radial direction Z in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, a region in which the recesses 41C are formed, and a region in which the recesses 41D are formed. The recesses 41A, 41B, 41C, and 41D are formed to align on one side (the equator side in the example in <FIG>) in the tire axial direction X.

The recesses 41A, 41B, 41C, and 41D increase in recess volume in an order of the recesses 41A, 41B, 41C, and 41D. In other words, the recess volumes of the recesses <NUM> increase from the block surface side to the bottom side in the tire radial direction Z. The numbers of the recesses 41A, 41B, 41C, and 41D according to the present embodiment are the same.

Gaps <NUM> are formed between the regions in which the recesses 41A, 41B, 41C, and 41D are formed. A size of each gap <NUM> is larger than at least an interval between the recesses 41A, 41B, 41C, and 41D in the regions in which the recesses 41A, 41B, 41C, and 41D are formed, respectively.

With the above configuration, the maneuver stability performance on the wet road surface and the maneuver stability performance on the dry road surface can be improved. More specifically, since, among the plurality of recesses <NUM>, the recess volume of the recess <NUM> on the bottom side is larger than the recess volume of the recess <NUM> on the block surface side in the tire radial direction Z, in-plane rigidity can be reduced, a ground contact area can be increased, and the maneuver stability performance on the wet road surface can be improved.

In addition, since, among the plurality of recesses <NUM>, the recess volume of the recess <NUM> on the block surface side is smaller than the recess volume of the recess <NUM> on the bottom side in the tire radial direction Z, surface rigidity can be increased, and a decrease in maneuver stability performance on a dry road surface can be prevented.

A mold <NUM> as an example of an embodiment will be described with reference to <FIG>.

As a mold for molding a tire, the mold <NUM> is a mold for molding the pneumatic tire <NUM> described above. The pneumatic tire <NUM> includes the tread <NUM> including the blocks <NUM> in which the sipes <NUM> are formed as described above, and sidewalls (not shown) forming side surfaces. According to the mold <NUM>, the pneumatic tire <NUM> capable of improving maneuver stability performance on a wet road surface and maneuver stability performance on a dry road surface can be molded.

Hereinafter, each member will be described with respect to the tire axial direction X, the tire circumferential direction Y, and the tire radial direction Z of the above-described pneumatic tire <NUM> molded by using the mold <NUM>.

The mold <NUM> includes a tread mold <NUM> for molding a surface of the tread <NUM> of the pneumatic tire <NUM>, and a pair of side molds <NUM> for molding surfaces of the sidewalls.

The tread mold <NUM> includes a main body <NUM> having a tread molding surface <NUM>, protrusions <NUM> protruding from the tread molding surface <NUM>, and sipe blades <NUM> protruding from the tread molding surface <NUM> and provided between the protrusions <NUM>.

The main body <NUM> is made of a metal material, for example, an aluminum alloy. As the aluminum alloy, for example, an AC4-based alloy or an AC7-based alloy is preferably used. The protrusions <NUM> are portions for molding the main grooves <NUM> in the pneumatic tire <NUM>. The protrusions <NUM> are made of a metal material that is same as that forming the main body <NUM>.

The sipe blades <NUM> according to the example of the embodiment will be described with reference to <FIG>.

The sipe blades <NUM> mold the sipe <NUM> of the pneumatic tire <NUM>. Each sipe blade <NUM> protrudes from the tread molding surface <NUM> between the protrusions <NUM> in the tire radial direction Z. The sipe blade <NUM> has a flat plate shape and may be made of a metal material, for example, stainless steel. Preferable examples of the stainless steel include SUS303, SUS304, SUS630, and SUS631. When a three-dimensional molding machine is used, SUS304L, <NUM>-4PH corresponding to SUS630, or the like, is preferably used.

In a general processing method for the sipe blade <NUM>, a shape thereof is formed using a press molding machine. In the processing method when there is a change in shape in a thickness direction of the sipe blade <NUM> according to the present invention, the shape thereof is formed by cutting using machining. By using the three-dimensional molding machine, a complicated shape that is difficult to attain by machining can be formed.

A plurality of protrusions <NUM> are formed on one side surface 60A of the sipe blade <NUM>. Each protrusion <NUM> is a portion for forming the recess <NUM> of the sipe <NUM> in the pneumatic tire <NUM> described above. The protrusion <NUM> according to the present invention is formed in a hemispherical or a semi-ellipsoid shape. It is preferable that the protrusion <NUM> according to the present embodiment is formed in a portion from a block surface side to <NUM> or more when a length (sipe depth) of the sipe <NUM> in the tire radial direction Z is set to <NUM>. It is preferable that the protrusion <NUM> according to the present embodiment is formed at a length of <NUM> or more when a length of the sipe <NUM> in the tire axial direction X is set to <NUM>.

The protrusions <NUM> according to the present invention include protrusions 61A, 61B, 61C, and 61D having different volumes of protruding portions (hereinafter referred to as a protrusion volume). The protrusions <NUM> are formed by respectively gathering and aligning protrusions having the same volume. In the sipe blade <NUM>, regions in which the protrusions <NUM> are formed are arranged from the block surface side to a bottom side in the tire radial direction Z in an order of a region in which the protrusions 61A are formed, a region in which the protrusions 61B are formed, a region in which the protrusions 61C are formed, and a region in which the protrusions 61D are formed.

The protrusions 61A, 61B, 61C, and 61D increase in protrusion volume in an order of the protrusions 61A, 61B, 61C, and 61D. In other words, the protrusion volumes of the protrusions <NUM> increase from the block surface side to the bottom side in the tire radial direction Z. The numbers of the protrusions 61A, 61B, 61C, and 61D according to the present embodiment are the same.

The recess <NUM> according to other examples of embodiments will be described with reference to <FIG>.

In the following second to twelfth embodiments, an arrangement pattern of the recesses 41A, 41B, 41C, and 41D according to the first embodiment is changed. In the following embodiments, since the recess <NUM> is the same as that according to the first embodiment described above except for the arrangement pattern of the recesses 41A, 41B, 41C, and 41D, a description thereof will be omitted.

As shown in <FIG>, the recesses <NUM> according to the second embodiment include the recesses 41A, 41B, 41C, and 41D having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from a block surface side to a bottom side in the tire radial direction Z in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, a region in which the recesses 41C are formed, and a region in which the recesses 41D are formed.

The recesses 41A, 41B, 41C, and 41D increase in recess volume in an order of the recesses 41A, 41B, 41C, and 41D. In other words, the recess volumes of the recesses <NUM> increase from the block surface side to the bottom side in the tire radial direction Z. The numbers of the recesses 41A, 41B, 41C, and 41D according to the present embodiment decrease in the order of the recesses 41A, 41B, 41C, and 41D. In other words, areas of the regions in which the recesses 41A, 41B, 41C, and 41D are respectively formed are the same.

With the above configuration, since, among the plurality of recesses <NUM>, the recess volume of the recess <NUM> on the bottom side is larger than the recess volume of the recess <NUM> on the block surface side in the tire radial direction Z, in-plane rigidity can be reduced, a ground contact area can be increased, and maneuver stability performance on a wet road surface can be improved. In addition, since, among the plurality of recesses <NUM>, the recess volume of the recess <NUM> on the block surface side is smaller than the recess volume of the recess <NUM> on the bottom side in the tire radial direction Z, surface rigidity can be increased, and a decrease in maneuver stability performance on a dry road surface can be prevented.

As shown in <FIG>, the recesses <NUM> according to the third embodiment include the recesses 41A, 41B, 41C, and 41D having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from a block surface side to a bottom side in the tire radial direction Z in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, a region in which the recesses 41C are formed, and a region in which the recesses 41D are formed. The recesses 41A, 41B, 41C, 41D are formed to align on one side in the tire axial direction X.

The recesses 41A, 41B, 41C, and 41D decrease in recess volume in an order of the recesses 41A, 41B, 41C, and 41D. In other words, the recess volumes of the recesses <NUM> decrease from the block surface side to the bottom side in the tire radial direction Z. The numbers of the recesses 41A, 41B, 41C, and 41D according to the present embodiment are the same.

With the above configuration, since the recess volume of the recess <NUM> on the block surface side is larger than the recess volume of the recess <NUM> on the bottom side in the tire radial direction Z, water absorption performance can be improved and maneuver stability performance on a wet road surface can be improved. In addition, since the recess volume of the recess <NUM> on the bottom side is smaller than the recess volume of the recess <NUM> on the block surface side in the tire radial direction Z, it is possible to prevent a decrease in in-plane rigidity and prevent a decrease in maneuver stability performance on a dry road surface.

As shown in <FIG>, the recesses <NUM> according to the fourth embodiment include the recesses 41A, 41B, 41C, and 41D having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from a block surface side to a bottom side in the tire radial direction Z in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, a region in which the recesses 41C are formed, and a region in which the recesses 41D are formed.

The recesses 41A, 41B, 41C, and 41D decrease in recess volume in an order of the recesses 41A, 41B, 41C, and 41D. In other words, the recess volumes of the recesses <NUM> decrease from the block surface side to the bottom side in the tire radial direction Z. The numbers of the recesses 41A, 41B, 41C, and 41D according to the present embodiment increase in the order of the recesses 41A, 41B, 41C, and 41D. In other words, areas of the regions in which the recesses 41A, 41B, 41C, and 41D are respectively formed are the same.

As shown in <FIG>, the recesses <NUM> according to the fifth embodiment include the recesses 41A, 41B, 41C, and 41D having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from an equator side to a shoulder side in the tire axial direction X in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, a region in which the recesses 41C are formed, and a region in which the recesses 41D are formed. The recesses 41A, 41B, 41C, and 41D are formed to align on a block surface side in the tire radial direction Z.

The recesses 41A, 41B, 41C, and 41D increase in recess volume in an order of the recesses 41A, 41B, 41C, and 41D. In other words, the recess volumes of the recesses <NUM> increase from the equator side to the shoulder side in the tire axial direction X. The numbers of the recesses 41A, 41B, 41C, and 41D according to the present embodiment are the same.

With the above configuration, since the number of recesses <NUM> on the block surface side is larger than that of recesses <NUM> on a bottom side in the tire radial direction Z, water absorption performance can be improved, and maneuver stability performance on a wet road surface can be improved. In addition, since the number of the recesses <NUM> on the bottom side is smaller than that of the recesses <NUM> on the block surface side in the tire radial direction Z, it is possible to prevent a decrease in in-plane rigidity and prevent a decrease in maneuver stability performance on a dry road surface.

As shown in <FIG>, the recesses <NUM> according to the sixth embodiment include the recesses 41A, 41B, 41C, and 41D having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from an equator side to a shoulder side in the tire axial direction X in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, a region in which the recesses 41C are formed, and a region in which the recesses 41D are formed.

The recesses 41A, 41B, 41C, and 41D increase in recess volume in an order of the recesses 41A, 41B, 41C, and 41D. In other words, the recess volumes of the recesses <NUM> increase from the equator side to the shoulder side in the tire axial direction X. The numbers of the recesses 41A, 41B, 41C, and 41D according to the present embodiment decrease in the order of the recesses 41A, 41B, 41C, and 41D. In other words, areas of the regions in which the recesses 41A, 41B, 41C, and 41D are respectively formed are the same.

With the above configuration, water on the block surface SF of the tread <NUM> can be absorbed, and a water absorption effect of the sipe <NUM> can be improved.

As shown in <FIG>, the recesses <NUM> according to the seventh embodiment include the recesses 41A, 41B, 41C, and 41D having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from an equator side to a shoulder side in the tire axial direction X in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, a region in which the recesses 41C are formed, and a region in which the recesses 41D are formed. The recesses 41A, 41B, 41C, and 41D are formed to align on a block surface side in the tire radial direction Z.

The recesses 41A, 41B, 41C, and 41D decrease in recess volume in an order of the recesses 41A, 41B, 41C, and 41D. In other words, the recess volumes of the recesses <NUM> decrease from the equator side to the shoulder side in the tire axial direction X. The numbers of the recesses 41A, 41B, 41C, and 41D according to the present embodiment are the same.

As shown in <FIG>, the recesses <NUM> according to the eighth embodiment include the recesses 41A, 41B, 41C, and 41D having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from an equator side to a shoulder side in the tire axial direction X in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, a region in which the recesses 41C are formed, and a region in which the recesses 41D are formed.

The recesses 41A, 41B, 41C, and 41D decrease in recess volume in an order of the recesses 41A, 41B, 41C, and 41D. In other words, the recess volumes of the recesses <NUM> decrease from the equator side to the shoulder side in the tire axial direction X. The numbers of the recesses 41A, 41B, 41C, and 41D according to the present embodiment increase in the order of the recesses 41A, 41B, 41C, and 41D. In other words, areas of the regions in which the recesses 41A, 41B, 41C, and 41D are respectively formed are the same.

With the above configuration, since the recess volume of the recess <NUM> on the shoulder side is smaller than the recess volume of the recess <NUM> on the equator side in the tire axial direction X, maneuver stability performance on a dry road surface can be improved.

As shown in <FIG>, the recesses <NUM> according to the ninth embodiment include the recesses 41A, 41B, and 41C having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from a block central portion to two block end portions in the tire axial direction X in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, and a region in which the recesses 41C are formed. The recesses 41A, 41B, and 41C are formed to align on a block surface side in the tire radial direction Z.

The recesses 41A, 41B, and 41C decrease in recess volume in an order of the recesses 41A, 41B, and 41C. In other words, the recess volumes of the recesses <NUM> decrease from the block central portion to two block end sides in the tire axial direction X. The numbers of the recesses 41A, 41B, and 41C according to the present embodiment are the same.

As shown in <FIG>, the recesses <NUM> according to the tenth embodiment include the recesses 41A, 41B, and 41C having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from a block central portion to two block end portions in the tire axial direction X in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, and a region in which the recesses 41C are formed.

The recesses 41A, 41B, and 41C decrease in recess volume in an order of the recesses 41A, 41B, and 41C. In other words, the recess volumes of the recesses <NUM> decrease from the block central portion to two block end sides in the tire axial direction X. The number of the recesses 41A, 41B, and 41C according to the present embodiment increases in the order of the recesses 41A, 41B, and 41C. In other words, areas of the regions in which the recesses 41A, 41B, and 41C are respectively formed are the same.

With the above configuration, since the recess volume of the recess <NUM> on the two block end sides is smaller than the recess volume of the recess <NUM> in the central portion in the tire axial direction X, maneuver stability performance on a dry road surface can be improved.

As shown in <FIG>, the recesses <NUM> according to the eleventh embodiment include the recesses 41A, 41B, and 41C having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from a block central portion to two block end portions in the tire axial direction X in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, and a region in which the recesses 41C are formed. The recesses 41A, 41B, and 41C are formed to align on a block surface side in the tire radial direction Z.

The recesses 41A, 41B, and 41C increase in recess volume in an order of the recesses 41A, 41B, and 41C. In other words, the recess volumes of the recesses <NUM> increase from the block central portion to two block end sides in the tire axial direction X. The number of the recesses 41A, 41B, and 41C according to the present embodiment are the same.

As shown in <FIG>, the recesses <NUM> according to the twelfth embodiment include the recesses 41A, 41B, and 41C having different recess volumes. The recesses <NUM> are formed by respectively gathering and aligning recesses having the same volume. In the block <NUM>, regions in which the recesses <NUM> are formed are arranged from a block central portion to two block end portions in the tire axial direction X in an order of a region in which the recesses 41A are formed, a region in which the recesses 41B are formed, and a region in which the recesses 41C are formed.

The recesses 41A, 41B, and 41C increase in recess volume in an order of the recesses 41A, 41B, and 41C. In other words, the recess volumes of the recesses <NUM> increase from the block central portion to two block end sides in the tire axial direction X. The numbers of the recesses 41A, 41B, and 41C according to the present embodiment decrease in the order of the recesses 41A, 41B, and 41C. In other words, areas of the regions in which the recesses 41A, 41B, and 41C are respectively formed are the same.

According to the above configuration, since the recess volume of the recess <NUM> on the two block end sides is larger than the recess volume of the recess <NUM> in the central portion in the tire axial direction X, maneuver stability performance on a wet road surface can be improved.

Claim 1:
A pneumatic tire (<NUM>) comprising:
a tread (<NUM>) including a block (<NUM>) in which at least one sipe (<NUM>) is formed, wherein
a plurality of recesses (<NUM>) are formed in one wall surface (40A, 40B) of each of the at least one sipe (<NUM>), and
the recesses (<NUM>) change in volume toward at least one of a tire radial direction (Z) and a tire axial direction (X) in the block (<NUM>),
characterized in that the recesses (<NUM>) are formed in a hemispherical shape or a semi-ellipsoid shape,
the recesses (<NUM>) are formed by gathering and aligning recesses having the same volume, and
a surface facing the recesses (<NUM>) is a flat surface.