Patent Description:
There has been conventionally known a pneumatic tire provided with a tread including a plurality of circumferential grooves extending in a tire circumferential direction and a plurality of lands partitioned by the plurality of circumferential grooves in a tire width direction, sipes being formed in the plurality of lands (for example, see International Publication No. <CIT>). In the pneumatic tire disclosed in International Publication No. <CIT>, a chamfer is formed between an opening end on one side or each side in the width direction of the sipe, and a ground contact surface.

In the pneumatic tire disclosed in International Publication No. <CIT>, a mold forming a shape of the tread including the chamfer and the sipe includes a projection for forming the sipe and a main body for forming a portion including the chamfer, the projection and the main body being made of different members in some cases. At this time, when, after forming the shape of the tread, blast cleaning involving blowing out high-pressure gas, such as dry-ice cleaning, is applied to the mold, a portion in the main body in which the chamfer is formed may be deformed and turned up from the projection. Depending on the cleaning method for the mold, this may result in a reduction in the durability of the mold. In addition, in the tire, there is room for improvement in terms of improving the drainage efficiency.

The European patent Application <CIT> refers to a tire having a tread portion axially divided into two shoulder land regions, two middle land regions and one crown land region by two shoulder circumferential grooves and two crown circumferential grooves.

The European patent Application <CIT> refers to a tire including a tread portion with a designated install direction to a vehicle to have an inboard tread edge, and an outboard tread edge.

Japanese patent Application <CIT> relates to a tire having shallow grooves with cipes on the grove bottoms, and blocks in the direction of the cipes cross the circumferential direction of the tire.

The European patent Application <CIT>, which is prior art according to Art. <NUM>(<NUM>) EPC, discloses a tire including a tread portion including a first shoulder land portion provided with first shoulder lateral grooves extending from a first tread edge to a first shoulder circumferential groove, a second shoulder land portion provided with second shoulder lateral grooves extending from a second tread edge and terminating within the second shoulder land portion.

It is a purpose of the present invention to provide a pneumatic tire that can provide improved durability of a mold even when blast cleaning involving blowing out high-pressure gas is applied to the mold forming a shape of the tire, and that makes it possible to improve drainage properties during use of the tire.

A pneumatic tire according to the present invention comprises a tread including a plurality of lands and a sipe formed in at least one of the lands, wherein an inclined surface is formed between an opening end on at least one side in a width direction of the sipe and a ground contact surface, the inclined surface having a linear shape in cross section and continuing from the ground contact surface, and an intermediate surface is formed between the inclined surface and the sipe, the intermediate surface having an inclination angle with respect to the ground contact surface of <NUM> degrees or having an inclination angle with respect to the ground contact surface that is smaller than an inclination angle of the inclined surface with respect to the ground contact surface.

According to the above-described pneumatic tire, in a mold for forming a shape of a tire, in a case where a projection for forming a sipe and a main body for forming a portion including an inclined surface are formed of different members, a top surface is provided at a portion in the main body coming in contact with the projection, the top surface corresponding to an intermediate surface and coming in contact with the projection at an angle close to a right angle to the projection. The top surface contacts a side surface of the projection at an angle smaller than that without the intermediate surface on an interior space side of the mold even when blast cleaning involving blowing out high-pressure gas is applied to the mold. Therefore, the main body can be prevented from being deformed turning up from the protrusion. Accordingly, the durability of the mold can be improved. In addition, a water accommodating region in the groove of the tire is increased by the formation of the intermediate surface, whereby the drainage properties during use of the tire can be improved.

According to the pneumatic tire according to the present disclosure, the durability of a mold can be improved even when blast cleaning involving blowing out high-pressure gas is applied to the mold forming a shape of the tire, and the drainage properties during use of the tire can be improved.

Embodiment(s) of the present invention will be described based on the following figures, wherein:.

Hereinafter, a pneumatic tire according to an example of an embodiment of the present invention will be described in detail with reference to the drawings. The embodiment described below is merely exemplary, and the present invention is not limited to the following embodiment.

<FIG> is a perspective view of a pneumatic tire <NUM> according to an example of an embodiment. As illustrated in <FIG>, the pneumatic tire <NUM> includes a tread <NUM> which is a portion coming in contact with a road surface. Hereinafter, the "pneumatic tire <NUM>" is referred to as the "tire <NUM>". The tread <NUM> has a tread pattern including a plurality of lands, and is formed into an annular shape along a tire circumferential direction.

The tread <NUM> includes lands <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> partitioned by four circumferential primary grooves <NUM>, <NUM>, <NUM>, and <NUM>, for example. The land is a projection projecting outwardly in a tire radial direction from a reference surface of the tread <NUM>. The "reference surface" refers to a virtual surface along a bottom surface of the deepest circumferential primary groove, which means an outer circumferential surface of the tread <NUM> where no land exists. The tread <NUM> has, as the above-described lands, a center land <NUM> including a center CL in a tire width direction, mediate lands <NUM> and <NUM> provided on both sides in the tire width direction of the center land <NUM> across the first circumferential primary grooves <NUM> and <NUM>, respectively, and shoulder lands <NUM> and <NUM> provided on outer sides in the tire width direction of the two mediate lands <NUM> and <NUM> across the second circumferential primary grooves <NUM> and <NUM>, respectively, the center land <NUM>, the mediate lands <NUM> and <NUM>, and the shoulder lands <NUM> and <NUM> being partitioned by the four circumferential primary grooves <NUM>, <NUM>, <NUM>, and <NUM>.

Each of the center land <NUM>, the two mediate lands <NUM>, and <NUM>, and the two shoulder lands <NUM> and <NUM> is continuously formed into a rib shape along the whole circumference in the tire circumferential direction.

The tire <NUM> includes side walls <NUM> provided more toward the outer sides in the tire width direction than the tread <NUM> and bulging most outwardly in the tire width direction, and beads (not illustrated) to be fixed to a rim of a wheel. The side walls <NUM> and the beads are formed into an annular shape along the tire circumferential direction. The side walls <NUM> extend from both ends in the width direction of the tread <NUM> toward an inner side in the tire radial direction.

The tire <NUM> is a pneumatic tire to be filled with air at a predetermined pressure. The tread <NUM> and the side walls <NUM> are made of different kinds of rubber, for example.

Each of the shoulder lands <NUM> and <NUM> arranged at both ends in the width direction of the tread <NUM> includes a ground contact end T which is an end on the outer side in the tire width direction of a ground contact surface. The end in the tire width direction of each of the shoulder lands <NUM> and <NUM> protrudes outwardly in the tire width direction more than the ground contact end T and is gradually curved inwardly in the tire radial direction so that the outer circumferential surface bulges toward the outer side. The portion protruding outwardly in the tire width direction more than the ground contact end T of each of the shoulder lands <NUM> and <NUM> is referred to as a buttress.

The "ground contact ends T" refers to both ends in the tire width direction of a region contacting a flat road surface when a load which is <NUM>% of a regular load at a regular internal pressure is applied in a state in which the tire <NUM> which is yet to be used is mounted on a regular rim and is filled with air to achieve the regular internal pressure.

Here, the "regular rim" is a rim defined by a tire standard, and refers to a "standard rim" in the case of JATMA, refers to a "Design Rim" in the case of TRA, and refers to a "Measuring Rim" in the case of ETRTO. The "regular internal pressure" refers to a "maximum air pressure" in the case of JATMA, refers to a maximum value described in the Table of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and refers to an "INFLATION PRESSURE" in the case of ETRTO. The "regular load" refers to a "maximum load capability" in the case of JATMA, a maximum value described in the Table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and a "LOAD CAPACITY" in the case of ETRTO.

Although not illustrated, the tire <NUM> includes a carcass, a belt, and an inner liner. The carcass is a cord layer coated with rubber, and forms a skeleton of the tire <NUM> which endures a load, a shock, an air pressure, or the like. The belt is a reinforcement band arranged between the rubber constituting the tread <NUM> and the carcass. The belt firmly tightens the carcass to improve the rigidity of the tire <NUM>. The inner liner is a rubber layer provided on the inner circumferential surface of the carcass and maintains the air pressure of the tire <NUM>. The bead has a bead core and a bead filler.

At a plurality of positions in the tire circumferential direction on each of shoulder lands <NUM> and <NUM>, a plurality of lug grooves <NUM> are formed to extend in a substantially tire width direction. An inner end of each lug groove <NUM> in the tire width direction terminates within the shoulder lands <NUM> and <NUM>, and is not opened to the wall surfaces of the shoulder lands <NUM> and <NUM>. The formation of such lug grooves <NUM> enables improvement in drainage properties toward the outer sides in the tire width direction.

In the ground contact surfaces of the center land <NUM> and the mediate lands <NUM> and <NUM>, a plurality of sipes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are formed to extend in a direction inclined with respect to the tire width direction, or are formed into a V shape. The sipes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> each improve an edge effect to scrape snow and ice, and have an effect to achieve superior braking capability and maneuvering stability on snowy and icy road surfaces.

In the case illustrated in <FIG>, the sipes <NUM> to <NUM>, <NUM>, and <NUM> inclined with respect to the tire width direction are formed in the center land <NUM> and each of the mediate lands <NUM> and <NUM>, and a V-shaped sipe <NUM> is formed in the mediate land <NUM> on one side in the tire width direction.

Note that in the center land <NUM>, a circumferential secondary groove <NUM> extending in the tire circumferential direction is formed, which has a width smaller than that of each of the circumferential primary grooves <NUM>, <NUM>, <NUM>, and <NUM>.

Hereinafter, as examples of the sipes inclined with respect to the tire width direction, the first and second sipes <NUM> and <NUM> in the center land <NUM> will be mainly described, and as an example of the sipe formed into a V shape, a fourth sipe <NUM> will be described, which is formed in the mediate land <NUM> on one side in the tire width direction. <FIG> is a plan view of a portion A of <FIG>. <FIG> is an enlarged perspective view when a portion B of <FIG> is viewed from an end on a circumferential primary groove <NUM> side of a first groove <NUM>. <FIG> is a diagram illustrating a cross section taken along a line C-C of <FIG>.

A plurality of first sipes <NUM> are formed on the first circumferential primary groove <NUM> side which is one side of the center land <NUM>. A plurality of second sipes <NUM> are formed on the first circumferential primary groove <NUM> side which is the other side of the center land <NUM>. The plurality of first sipes <NUM> are formed separately from each other at a plurality of positions in the tire circumferential direction. The plurality of second sipes <NUM> are formed separately from each other at a plurality of positions different from those of the first sipes <NUM> in the tire circumferential direction. In the center land <NUM>, an inner end in the tire width direction of each of the first sipes <NUM> and the second sipes <NUM> is terminated at a position where the inner end does not reach the circumferential secondary groove <NUM>, the inner end being one end in the longitudinal direction of each of the first sipes <NUM> and the second sipes <NUM>. When viewed from an outer side in the tire radial direction, the first sipe <NUM> is longer than the second sipe <NUM>.

The first sipe <NUM> is included in the first groove <NUM> extending in the direction inclined with respect to the tire width direction. In the first groove <NUM>, an opening end when viewed from the outer side in the tire radial direction is tapered in a substantially triangular shape. The first groove <NUM> includes the first sipe <NUM>, two first inclined surfaces <NUM> and <NUM> formed on both sides in the width direction of the first sipe <NUM>, and an intermediate surface <NUM> formed between the first inclined surfaces <NUM> and <NUM> and the first sipe <NUM>. In the center land <NUM>, an inner end in the tire width direction of the first groove <NUM> is also terminated at a position where the inner end does not reach the circumferential secondary groove <NUM>, the inner end being one end in the longitudinal direction, similarly to the first sipe <NUM>.

The first sipe <NUM> is a groove which extends in a linear direction inclined with respect to the tire width direction and has a rectangular shape in a cross section taken along a plane perpendicular to the longitudinal direction of the first sipe <NUM>. The first inclined surface <NUM>, which is one of the two first inclined surfaces <NUM> and <NUM>, is a surface provided between an opening end on one side in the width direction of the first sipe <NUM> and a ground contact surface S, the surface having a linear shape in cross section and continuing from the ground contact surface S.

The first inclined surface <NUM>, which is the other of the two first inclined surfaces <NUM> and <NUM>, is a surface provided between an opening end on the other side in the width direction of the first sipe <NUM> and the ground contact surface S, the surface having a linear shape in cross section and continuing from the ground contact surface S. Each of the two first inclined surfaces <NUM> and <NUM> has a plurality of surfaces distorted in such a manner that an inclination angle with respect to the ground contact surface gradually changes along the longitudinal direction of the first groove <NUM>, the plurality of surfaces being connected via ridge lines M1, M2, and M3 each located in the middle in the longitudinal direction of the first groove <NUM>. On the other hand, the first inclined surfaces <NUM> and <NUM> may each have a configuration in which a plurality of planar regions are connected via a ridge line at a middle position in the longitudinal direction of the first groove <NUM>. Alternatively, the first inclined surfaces <NUM> and <NUM> each may be formed of only one plane.

As illustrated in <FIG>, an inclination angle θ1 of the first inclined surface <NUM>, which is one of the first inclined surfaces, with respect to the ground contact surface S is larger than an inclination angle θ2 of the first inclined surface <NUM>, which is the other of the first inclined surfaces, with respect to the ground contact surface S.

The intermediate surface <NUM> is a flat surface which is formed between each of the two first inclined surfaces <NUM> and <NUM> and the first sipe <NUM> and is substantially parallel to the ground contact surface S. Therefore, the inclination angle of the intermediate surface <NUM> with respect to the ground contact surface S is <NUM> degrees. The intermediate surface <NUM> is formed to surround the opening end of the first sipe <NUM> when viewed from the outer side in the tire radial direction. Therefore, the intermediate surface <NUM> includes a rectangular region <NUM> formed between the first inclined surface <NUM>, which is one of the first inclined surfaces, and the opening end of the first sipe <NUM>, and a rectangular region <NUM> formed between the first inclined surface <NUM>, which is the other of the first inclined surfaces, and the opening end of the first sipe <NUM>. A wall surface <NUM> is connected to a portion sandwiched between leading edges of the two first inclined surfaces <NUM> and <NUM> so as to rise from a leading edge of the intermediate surface <NUM> toward the ground contact surface S.

Therefore, one end in the longitudinal direction of the first groove <NUM> is a tapered shape when viewed from the ground contact surface S side. The width of each of the first inclined surfaces <NUM> and <NUM> decreases toward one end in the longitudinal direction of the first groove <NUM>, when the first groove <NUM> is viewed from the ground contact surface S side. In addition, the first sipe <NUM> is positioned offset to one side (left side in <FIG>) in the width direction of the first groove <NUM>, when the first groove <NUM> is viewed from the ground contact surface S side.

The two first inclined surfaces <NUM> and <NUM> are two inclined surfaces formed on both sides in the width direction of the first sipe <NUM>, and the intermediate surface <NUM> is formed on both sides of the first sipe <NUM> in the width direction of the first groove <NUM>. This can improve the durability of a mold even when blast cleaning involving blowing out high-pressure gas is applied to the mold forming a shape of the tire <NUM>, and improve the drainage properties of the tire <NUM>, as described later.

Note that in the first groove <NUM>, the intermediate surface <NUM> is formed on both sides in the width direction of the first sipe <NUM>, but it is only required that the intermediate surface is formed on at least one side in the width direction of the first sipe <NUM> positioned offset in the first groove <NUM>, and therefore, the intermediate surface on the other side in the width direction may be omitted.

<FIG> is an enlarged perspective view when a portion D of <FIG> is viewed from an end on a circumferential primary groove <NUM> side of a second groove <NUM>. <FIG> is a diagram illustrating a cross section taken along a line E-E of <FIG>.

The second sipe <NUM> is included in the second groove <NUM> extending in the direction inclined with respect to the tire width direction. The second groove <NUM> extends substantially parallel to the first groove <NUM>. In the second groove <NUM>, an opening end when viewed from the outer side in the tire radial direction is tapered in a substantially triangular shape. The second groove <NUM> includes the second sipe <NUM>, a second inclined surface <NUM> formed on one side in the width direction of the second sipe <NUM>, and an intermediate surface <NUM> formed between the second inclined surface <NUM> and the second sipe <NUM>. In the center land <NUM>, an inner end in the tire width direction of the second groove <NUM> is also terminated at a position where the inner end does not reach the circumferential secondary groove, the inner end being one end in the longitudinal direction, similarly to the second sipe <NUM>.

As illustrated in <FIG>, the second sipe <NUM> extends in the linear direction inclined with respect to the tire width direction. The second inclined surface <NUM> is a surface provided between an opening end on one side in the width direction of the second sipe <NUM> and the ground contact surface S, the surface having a linear shape in cross section and continuing from the ground contact surface S. The second inclined surface <NUM> is a surface distorted in such a manner that an inclination angle with respect to the ground contact surface S gradually changes along the longitudinal direction of the second groove <NUM>. The second inclined surface <NUM> may have a configuration in which a plurality of planes are connected via ridge lines at a plurality of positions in the longitudinal direction of the second groove <NUM>, similarly to the first inclined surfaces <NUM> and <NUM>. Alternatively, the second inclined surface <NUM> may be formed of only one plane.

The intermediate surface <NUM> is a flat surface substantially parallel to the ground contact surface S, which is formed between the second inclined surface <NUM> and the second sipe <NUM> and whose inclination angle with respect to the ground contact surface S is <NUM> degrees. The intermediate surface <NUM> is a rectangular region connecting an opening end on one side in the width direction of the second sipe <NUM> and the second inclined surface <NUM> when viewed from the outer side in the tire radial direction. A wall surface <NUM> rising along the tire radial direction toward the ground contact surface S is connected to a leading edge of the second sipe <NUM> via a planar region <NUM> which is substantially parallel to the ground contact surface S.

Therefore, one end in the longitudinal direction of the second groove <NUM> is formed into a tapered shape when viewed from the ground contact surface S side. The width of the second inclined surface <NUM> decreases toward one end in the longitudinal direction of the second groove <NUM>, when the second groove <NUM> is viewed from the ground contact surface S side. This also improves the durability of a mold even when blast cleaning involving blowing out high-pressure gas is applied to the mold forming a shape of the tire <NUM>, and improves the drainage properties of the tire <NUM>, as in the case of the first groove <NUM>.

A third groove <NUM> formed on one side in the tire width direction of the mediate land <NUM>, which is one of the mediate lands, includes a third sipe <NUM>, an inclined surface formed on only one side in the width direction of the third sipe <NUM>, and an intermediate surface between the third sipe <NUM> and the inclined surface, similarly to the second groove <NUM> illustrated in <FIG> and <FIG>.

A fifth groove <NUM> formed on one side in the tire width direction of the mediate land <NUM>, which is the other of the mediate lands, includes a fifth sipe <NUM>, two inclined surfaces formed on both sides in the width direction of the fifth sipe <NUM>, and an intermediate surface between the fifth sipe and each inclined surface, similarly to the first groove <NUM> illustrated in <FIG> and <FIG>.

A sixth groove <NUM> formed on the other side in the tire width direction of the mediate land <NUM>, which is the other of the mediate lands, includes a sixth sipe <NUM>, an inclined surface formed on only one side in the width direction of the sixth sipe <NUM>, and an intermediate surface between the sixth sipe <NUM> and the inclined surface.

<FIG> is an enlarged perspective view of a portion F of <FIG>. A fourth groove <NUM> is formed on the other side in the tire width direction of the mediate land <NUM>, which is one of the mediate lands. In the fourth groove <NUM>, an opening end is formed into a substantial V shape with a tapered end when viewed from the outer side in the tire radial direction. The fourth sipe <NUM> is formed along the longitudinal direction of the fourth groove <NUM>. Thus, the fourth sipe <NUM> is formed into a substantial V shape when viewed from the outer side in the tire radial direction. In addition, the fourth groove <NUM> includes the fourth sipe <NUM>, two fourth inclined surfaces 91a and 91b formed on both sides in the width direction of the fourth sipe <NUM>, and an intermediate surface 91c formed between each of the fourth inclined surfaces 91a and 91b and the fourth sipe <NUM>. The fourth groove <NUM> has the same configuration as the first groove <NUM> illustrated in <FIG> and <FIG> except that the overall shape is a substantial V shape.

In a method of manufacturing the tire <NUM> including the above-described tread <NUM>, intermediary bodies of the tread <NUM>, the carcass, and the beads are formed of tire raw materials, and then a green tire which is an unvulcanized tire is molded by using the formed intermediary bodies in combination. The tire <NUM> having a predetermined shape is vulcanization-molded by heating and pressing the green tire using a tire vulcanization mold. At this time, in the tire vulcanization mold, a projection having a shape conforming to a groove shape is previously formed in a portion where a groove having a sipe is formed.

<FIG> is a schematic sectional view of a portion forming the first groove <NUM> of <FIG> in a tire vulcanization mold <NUM> for forming the tread <NUM> of the tire <NUM>. In the case where the first groove <NUM> having the intermediate surface <NUM> on both sides in the width direction of the first sipe <NUM> is formed as illustrated in <FIG>, the tire vulcanization mold <NUM> partially illustrated in <FIG> is used. In the mold <NUM>, a plate <NUM> forming a projection <NUM> is embedded and fixed to a crest of a ridge <NUM> formed in a main body <NUM> of the mold <NUM>, and in the crest of the ridge <NUM>, a top surface <NUM> is provided between inclined surfaces <NUM> and <NUM> and the plate <NUM>, the top surface <NUM> corresponding to the intermediate surface <NUM> (<FIG>) and being substantially perpendicular to side surfaces of the plate <NUM>. For example, the plate <NUM> made of a stainless alloy is partially embedded and fixed to the main body <NUM> of the mold made of an aluminum alloy so as to project from an inner surface of the main body <NUM>.

In the tire vulcanization mold <NUM>, the ridge including the top surface, and the plate are also formed in a portion corresponding to each of the second to sixth grooves <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In the tire vulcanization mold <NUM>, a cross-sectional shape corresponding to each of the fourth groove <NUM> and the fifth groove <NUM> has the same shape as that illustrated in <FIG>. In the tire vulcanization mold <NUM>, a shape corresponding to each of the second groove <NUM>, the third groove <NUM>, and the sixth groove <NUM> has the same shape as a shape where one of the two inclined surfaces <NUM> and <NUM> of the ridge <NUM> and the top surface between the one inclined surface and the plate <NUM> are omitted from the shape illustrated in <FIG>.

By manufacturing the tire <NUM> using such a tire vulcanization mold <NUM>, it is possible to form, in the tread <NUM> of the tire <NUM>, a groove having an intermediate surface between a sipe and an inclined surface, the groove corresponding to the plate <NUM> and the ridge <NUM>.

According to the above-described tire <NUM>, in the tire vulcanization mold <NUM> for forming the shape of the tire <NUM>, in the case where the projection <NUM> for forming a sipe and the main body <NUM> for forming a portion including an inclined surface of a groove are formed of different members, the top surface <NUM> is provided at a portion in the main body <NUM> coming in contact with the projection <NUM>, the top surface <NUM> corresponding to an intermediate surface and coming in contact with the projection <NUM> at an angle close to a right angle to the projection <NUM>. Therefore, when blast cleaning involving blowing out high-pressure gas is applied to the tire vulcanization mold <NUM>, the main body <NUM> can be prevented from being deformed and turned up from the projection <NUM> even when high-pressure air which is gas is blown to the main body <NUM> in the vicinity of the projection <NUM>.

For example, the tire vulcanization mold <NUM> may be cleaned by dry-ice cleaning, which is one kind of blast cleaning. In the dry-ice cleaning, the tire vulcanization mold <NUM> is cleaned by blasting, with high-pressure air, dry-ice particles having relatively low hardness to an inner surface of the tire vulcanization mold <NUM>. In this case, the high-pressure air and the dry-ice particles are blown between the main body <NUM> and the plate <NUM> of the mold <NUM> in directions of arrows α in <FIG>. At this time, the top surface <NUM> of the ridge <NUM> contacts the side surfaces of the plate <NUM> forming the projection <NUM> at an angle smaller than that without the top surface <NUM>, e.g., at substantially a right angle. Therefore, a force is likely to act on the top surface <NUM> in the outward direction (downward side in <FIG>) perpendicular to the top surface <NUM>, and the high-pressure air is unlikely to enter a gap between the top surface <NUM> and the plate <NUM>. Accordingly, the main body <NUM> can be prevented from being deformed and turned up from the projection <NUM>. As a result, the durability of the tire vulcanization mold <NUM> can be improved. In addition, a water accommodating region in the groove of the tire <NUM> is increased by the formation of the intermediate surface, whereby the drainage properties during use of the tire can be improved.

<FIG> is a schematic sectional view of a portion forming a groove in a tire vulcanization mold 100a for forming a tread of a tire according to a comparative example. In the tire according to the comparative example, in the groove having a sipe, an intermediate surface is not formed between a sipe opening end and an inclined surface continuing from the ground contact surface. Therefore, in the tire vulcanization mold 100a, a top surface substantially perpendicular to side surfaces of a plate <NUM> is not formed between a ridge <NUM> of a main body 101a and the plate <NUM> fixed to a crest of the ridge <NUM>. Accordingly, inclined surfaces <NUM> and <NUM> of the ridge <NUM> and the side surfaces of a projection <NUM> formed by the plate <NUM> contact each other at an angle significantly greater than <NUM> degrees on the interior space side of the mold 100a. Therefore, in the case where the high-pressure air and the dry-ice particles are blown in directions of arrows β in <FIG>, the high-pressure air is likely to enter a gap between the inclined surfaces <NUM> and <NUM> of the ridge <NUM> and the plate <NUM>. Accordingly, when the blowing time of high-pressure air is increased due to the increase of the cleaning time for the mold 100a, the main body 101a of the mold 100a may be deformed and turned up from the projection <NUM>. This may reduce the durability of the tire vulcanization mold 100a. According to the embodiment, this disadvantage can be eliminated.

In the embodiment, for example, one end in the longitudinal direction of the first groove <NUM> including the first sipe <NUM> terminates within the corresponding land <NUM>, and one end in the longitudinal direction of the first groove <NUM> is formed into a tapered shape when viewed from the ground contact surface S side. The width of each of the inclined surfaces <NUM> and <NUM> decreases toward one end in the longitudinal direction of the first groove <NUM>, when the first groove <NUM> is viewed from the ground contact surface S side. In the configuration, in the mold for forming the first groove <NUM>, the inclination angle with respect to the tire radial direction of the inclined surfaces <NUM> and <NUM> of the ridge <NUM> is reduced at a portion corresponding to one end in the longitudinal direction of the first groove <NUM>. In this case, when there is no intermediate surface between the inclined surfaces <NUM> and <NUM> and the first sipe <NUM>, the corresponding ridge <NUM> of the mold <NUM> is likely to be deformed and turned up from the projection <NUM>. Therefore, the formation of the intermediate surface <NUM> in the embodiment can provide a significant effect of improving the durability of the mold <NUM>.

In addition, in the embodiment, the first sipe <NUM> is positioned offset to one side (left side in <FIG>) in the width direction of the first groove <NUM>, when the first groove <NUM> is viewed from the ground contact surface S side, and the intermediate surface <NUM> is formed on at least one side of the first sipe <NUM> in the width direction of the first groove <NUM>. In this case, in the inclination angles θ1 and θ2 of the inclined surfaces <NUM> and <NUM> of the first groove <NUM> with respect to the ground contact surface S, the angle θ1 of the inclined surface <NUM> on one side in the width direction of the first groove <NUM> is larger than the angle θ2 of the inclined surface <NUM> on the other side in the width direction of the first groove <NUM>. In this case, when there is no intermediate surface between the inclined surface <NUM> on one side in the width direction of the first groove <NUM> and the first sipe <NUM>, the corresponding main body <NUM> of the mold <NUM> is likely to be deformed and turned up from the projection <NUM>. Therefore, the formation of the intermediate surface in the embodiment can provide a significant effect of improving the durability of the mold <NUM>.

When the inclination angle of the inclined surface of each of the grooves <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> with respect to the ground contact surface is equal to or larger than <NUM> degrees and below <NUM> degrees, the main body of the mold is likely to be deformed and turned up from the projection by the blast cleaning. In this way, in the case where the inclination angle of the inclined surface with respect to the ground contact surface is equal to or larger than <NUM> degrees and below <NUM> degrees, the formation of the intermediate surface between the inclined surface and the sipe can provide a more significant effect of improving the durability of the mold.

In the above-described embodiment, the case has been described where the intermediate surface of the groove is a surface which is provided between the inclined surface and the sipe of the groove, and whose inclination angle with respect to the ground contact surface S is <NUM> degrees. On the other hand, the intermediate surface is not limited thereto, and the inclination angle of the intermediate surface with respect to the ground contact surface S may be larger than <NUM> degrees, and smaller than the inclination angle of the inclined surface with respect to the ground contact surface.

<FIG> is a diagram corresponding to <FIG> according to another example of an embodiment. As illustrated in <FIG>, in a first groove 70a, intermediate surfaces 73a, 73b are formed between each of two first inclined surfaces <NUM>, <NUM> and the first sipe <NUM>. The inclination angles θ3 and θ4 of each of the intermediate surfaces 73a, 73b with respect to the ground contact surface S are larger than <NUM> degrees, and smaller than the inclination angles θ1 and θ2 of the first inclined surfaces <NUM>, <NUM>, to which the intermediate surfaces 73a, 73b are connected, with respect to the ground contact surface S (θ3<θ1, θ4<θ2).

In the above-described embodiment, the case has been described where the intermediate surface is formed in each groove including a sipe formed in each of the center land <NUM> and the mediate lands <NUM> and <NUM>, but the grooves each including the intermediate surface may be formed in only some of the plurality of lands.

Claim 1:
A pneumatic tire (<NUM>), comprising:
a plurality of lands (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>); and
a tread (<NUM>) including a sipe (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) formed in at least part of the lands (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>),
wherein an inclined surface (<NUM>, <NUM>, <NUM>, 91a, 91b) is formed between an opening end on at least one side in a width direction of the sipe (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and a ground contact surface (S), the inclined surface (<NUM>, <NUM>, <NUM>, 91a, 91b) having a linear shape in a cross section taken along a plane perpendicular to the longitudinal direction of the sipe (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), and continuing from the ground contact surface (S), and
an intermediate surface (<NUM>, 73a, 73b, <NUM>, 91c) is formed between the inclined surface (<NUM>, <NUM>, <NUM>, 91a, 91b) and the sipe (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), the intermediate surface (<NUM>, 73a, 73b, <NUM>, 91c) having an inclination angle with respect to the ground contact surface (S) of <NUM> degrees or having an inclination angle with respect to the ground contact surface (S) that is smaller than an inclination angle of the inclined surface (<NUM>, <NUM>, <NUM>, 91a, 91b) with respect to the ground contact surface (S) and characterised in that
the one end in the longitudinal direction of a groove (<NUM>, 70a, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) including the sipe (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is formed into a tapered shape when viewed from the ground contact surface (S) side, and a width of the inclined surface (<NUM>, <NUM>, <NUM>, 91a, 91b) is reduced toward the one end in the longitudinal direction of the groove (<NUM>, 70a, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) when the groove (<NUM>, 70a, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is viewed from the ground contact surface (S) side.