Patent Description:
Conventionally, there have been proposed various pneumatic tires in which linear or zigzag sipes are provided in land portions of a tread portion (see, for example, Patent Document <NUM> below). The sipes exert a road surface scratching force (edge effect) by their edges, and consequently enhance performance on ice.

A tire in accordance with claim <NUM> is known from <CIT>. Related tires are described in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

In general, high traction performance and braking performance on ice (Hereinafter, these may be collectively referred to as "braking/driving performance") are required. Therefore, in many cases, the land portions of the tread portion are provided with a plurality of sipes extending in the tire axial direction and arranged in the tire circumferential direction.

In recent years, on the other hand, as the performance of vehicles become improved, there is a demand for improved turning performance on ice. Therefore, in some cases, in order to increase the frictional force in the tire axial direction, sipes including a component extending in the tire circumferential direction are arranged. When a plurality of such sipes are arranged in the tire circumferential direction, the number of the sipes which can be arranged per unit length in the tire circumferential direction of the land portion tends to decrease. Therefore, there is a possibility that the braking/driving performance on ice will be impaired.

In view of the above problems, the present invention has been devised, and
a main problem is to provide a tire improved in braking/driving performance and turning performance on ice.

The problem is solved by a tire having the features of claim <NUM>. Sub-claims are directed at preferable embodiments of the invention.

The present invention is a tire including a tread portion, wherein.

The first sipe piece is connected to the third sipe piece on the first side in the tire circumferential direction. The second sipe piece is connected to the third sipe piece on the second side in the tire circumferential direction. The first end and the second end are positioned on the second side in the tire circumferential direction than the first sipe piece, and on the first side in the tire circumferential direction than the second sipe piece. The closed sipe includes a first outer sipe piece extending from the first end to the first sipe piece, and a second outer sipe piece extending from the second end to the second sipe piece.

According to an embodiment of the invention, the third sipe piece is inclined with respect to the tire axial direction at an angle larger than those of the first sipe piece and the second sipe piece.

According to an embodiment of the invention, the overlapping length in the tire axial direction of two of the closed sipes is <NUM>% to <NUM>% of the maximum axial length of the closed sipes.

According to an embodiment of the invention, an angle between the first sipe piece and the third sipe piece, and an angle between the second sipe piece and the third sipe piece are each not less than <NUM> degrees.

According to an embodiment of the invention,an angle between the first sipe piece and the first outer sipe piece, and an angle between the second sipe piece and the second outer sipe piece are each not less than <NUM> degrees.

According to an embodiment of the invention, with respect to two of the closed sipes which are adjacent to each other in the tire axial direction, the second sipe piece of the closed sipe on one side overlaps in the tire axial direction with the first sipe piece of the closed sipe on the other side, the second outer sipe piece of the closed sipe on one side extends from the second sipe piece toward the first side in the tire circumferential direction, and the first outer sipe piece of the closed sipe on the other side extends from the first sipe piece toward the second side in the tire circumferential direction.

According to an embodiment of the invention, each of the first sipe piece and the second sipe piece extends at an angle of +/-<NUM> degrees with respect to the tire axial direction.

According to an embodiment of the invention, the closed sipe includes a bent portion extending in the tire radial direction in a zigzag manner in a sipe cross section.

According to an embodiment of the invention, the first sipe piece is disposed on the first side in the tire circumferential direction than the second sipe piece, the first sipe piece and the second sipe piece are each configured as a bent portion extending in the tire radial direction in a zigzag manner in the respective sipe cross section, and the bent portion includes an outer inclined portion which continues to an edge of the closed sipe and extends while inclining to one direction with respect to the tire radial direction, wherein the outer inclined portion belonging to the first sipe piece is inclined to the first side in the tire circumferential direction toward an inside in the tire radial direction, and wherein the outer inclined portion belonging to the second sipe piece is inclined to the second side in the tire circumferential direction which is opposite to the first side in the tire circumferential direction, toward an inside in the tire radial direction.

According to an embodiment of the invention, the first sipe piece is disposed on the first side in the tire circumferential direction than the second sipe piece and on the first side in the axial direction than the second sipe piece, the closed sipe comprises a first outer sipe piece extending from the first end to the first sipe piece toward the first side in the tire circumferential direction, and a second outer sipe piece extending from the second end to the second sipe piece toward the second side in the tire circumferential direction which is opposite to the first side, wherein the first sipe piece and the second sipe piece are each configured as a bent portion extending in the tire radial direction in a zigzag manner in the respective sipe cross section, the bent portion includes an outer inclined portion which continues to an edge of the closed sipe and extends while inclining to one direction with respect to the tire radial direction, the outer inclined portion belonging to the first sipe piece is inclined to the first side in the tire circumferential direction toward an inside in the tire radial direction, and wherein the outer inclined portion belonging to the second sipe piece is inclined to the second side in the tire circumferential direction which is opposite to the first side in the tire circumferential direction, toward an inside in the tire radial direction.

According to an embodiment of the invention, the first sipe piece is disposed on the first side in the tire circumferential direction than the second sipe piece, and on the first side in the axial direction than the second sipe piece, the closed sipe comprises a first outer sipe piece extending from the first end to the first sipe piece toward the first side in the tire circumferential direction, and a second outer sipe piece extending from the second end to the second sipe piece toward the second side in the tire circumferential direction which is opposite to the first side, wherein the first sipe piece, the second sipe piece, the third sipe piece, the first outer sipe piece and the second outer sipe piece are each configured as a bent portion extending in the tire radial direction in a zigzag manner in the respective sipe cross section, the bent portion includes an outer inclined portion which continues to an edge of the closed sipe and extends while inclining to one direction with respect to the tire radial direction, the outer inclined portion belonging to the first sipe piece and the outer inclined portion belonging to the second sipe piece each incline to the first side in the tire circumferential direction toward an inside in the tire radial direction, the outer inclined portion belonging to the first outer sipe piece and the outer inclined portion belonging to the second outer sipe piece each incline to the first side in the tire axial direction toward an inside in the tire radial direction, and wherein the outer sloped portion belonging to the third sipe piece inclines to the second side in the tire axial direction which is opposite to the first side in the tire axial direction, toward an inside in the tire radial direction.

According to an embodiment of the invention, the bent portion includes at least two bent elements which are convex toward the same direction.

According to an embodiment of the invention, the two bent elements have the same length in the tire radial direction.

According to an embodiment of the invention, the closed sipe includes a vertical portion which continues to an inside in the tire radial direction of the bent portion and extends parallel to the tire radial direction.

According to an embodiment of the invention, the entire closed sipe extends linearly in the tire radial direction in a sipe cross section.

According to an embodiment of the invention, the closed sipe includes a connecting portion in which sipe walls facing each other are connected to each other and which protrudes outward in the tire radial direction.

According to an embodiment of the invention, the connecting portion is provided in at least one of the first sipe piece and the second sipe piece.

According to an embodiment of the invention, the connecting portion is provided in each of the first sipe piece and the second sipe piece.

According to an embodiment of the invention, the width of the connecting portion along the length direction of the closed sipe is <NUM>% to <NUM>% of the length of the first sipe piece.

According to an embodiment of the invention, the height in the tire radial direction of the connecting portion is <NUM>% to <NUM>% of the maximum depth of the closed sipe.

According to an embodiment of the invention, the connecting portion is provided in each of the first sipe piece and the second sipe piece, and the height in the tire radial direction of the connecting portion provided in the first sipe piece is the same as the height in the tire radial direction of the connecting portion provided in the second sipe piece.

According to an embodiment of the invention, the tread portion includes a shoulder land portion positioned on the outermost side in the tire axial direction, wherein the shoulder land portion comprises a plurality of shoulder blocks divided by a plurality of lateral grooves extending in a tire axial direction, and the shoulder block is provided with a plurality of the closed sipes.

In the present invention, by adopting the above configurations, it is possible to exhibit excellent braking/driving performance and turning performance on ice.

Hereinafter, an embodiment of the present invention will be described based on the drawings. <FIG> shows a cross-sectional view of a tread portion <NUM> of a tire <NUM> of the present embodiment. <FIG> is a meridian cross sectional view including the tire rotation axis, of the tire <NUM> under a normal state. The tire <NUM> of the present embodiment is suitably used as, for example, a pneumatic tire for passenger cars. However, it is not limited to such an embodiment, and the tire <NUM> of the present invention may be used for heavy loads, for example.

In the case of a pneumatic tire for which various standards have been established, the "normal state" is a state in which the tire mounted on a regular rim is inflated to a regular internal pressure but loaded with no load.

In the case of tires for which various standards have not been established or non-pneumatic tires, the normal state means a standard usage state corresponding to the purpose of use of the tire and a no-load state.

In this specification, unless otherwise specified, dimensions and the like of various parts of the tire are the values measured under the normal state.

Each of the configurations described in this specification shall allow for normal errors involved in rubber molded products.

The "regular rim" is a rim defined for each tire by a standard in a standard system including the standard on which the tire is based, for example, "Standard Rim" in JATMA, "Design Rim" in TRA, and "Measuring Rim" in ETRTO,.

The "regular internal pressure" is air pressure defined for each tire by a standard in a standard system including the standard on which the tire is based, for example, "MAXIMUM AIR PRESSURE" in JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, "INFLATION PRESSURE" in ETRTO.

As shown in <FIG>, the tread portion <NUM> is provided with, for example, a plurality of main grooves <NUM> continuously extending in the tire circumferential direction, and a plurality of land portions <NUM> divided thereby.

<FIG> shows an enlarged plan view of the land portion <NUM>. As shown in <FIG>, the land portion <NUM> of the present embodiment is configured, for example, as a row of blocks including a plurality of blocks <NUM> in the tire circumferential direction. The blocks <NUM> are defined between a plurality of lateral grooves <NUM> crossing the land portion <NUM> in the tire axial direction. The land portion <NUM> of the present invention is not limited to such an example, and may be a rib continuously extending in the tire circumferential direction, for example.

In some of the figures in this specification, there are indicated by arrows,.

Unless otherwise noted, in the figures showing the plan views of the land portions <NUM>,.

In the land portion <NUM>, a plurality of closed sipes <NUM> are arranged in the tire axial direction.

In the present embodiment, a plurality of sipe groups <NUM> each made up of a plurality of closed sipes <NUM> is disposed in one block <NUM>. For example, one sipe group <NUM> is made up of <NUM> to <NUM> closed sipes <NUM>.

In this specification, the "sipe" is a slit having a minute width, and refers to that having a width of <NUM> or less between two sipe walls facing each other.

As a preferable mode, the above-said width of the closed sipe <NUM> of the present embodiment is <NUM> or less.

In addition, in this specification, the term "closed sipe" refers to a sipe whose both ends are terminated within the land portion <NUM>.

The sipe group <NUM> provided in the block <NUM> of the present embodiment consists of the closed sipes <NUM> only. In other words, none of the sipes are connected to the edges of the block <NUM>.

The present invention is however, not limited to such a mode, and the sipe arranged near the edge of the block <NUM> may be a non-closed sipe having one end opened at the edge.

In <FIG>, there is shown an enlarged view of the closed sipe <NUM> of <FIG>.

As shown in <FIG>, each closed sipe <NUM> comprises a first end 8a and a second end 8b, and a first sipe piece <NUM>, a second sipe piece <NUM> and a third sipe piece <NUM>.

The first end 8a is the end of the closed sipe <NUM> on the first side B1 in the tire axial direction.

The second end 8b is the end of the closed sipe <NUM> on the second side B2 in the tire axial direction.

The first sipe piece <NUM> extends in the tire axial direction on the first end 8a side of the third sipe piece <NUM>.

The second sipe piece <NUM> extends in the tire axial direction on the second end 8b side of the third sipe piece <NUM>.

Between the first sipe piece <NUM> and the second sipe piece <NUM>, the third sipe piece <NUM> is inclined with respect to the tire axial direction.

With this arrangement, in the closed sipe <NUM> of the present embodiment, the first sipe piece <NUM> is positioned on the first side A1 in the tire circumferential direction and on the first side B1 in the tire axial direction of the second sipe piece <NUM>.

Further, in the present embodiment, the first sipe piece <NUM> continues to the third sipe piece <NUM> om the first side A1 in the tire circumferential direction.

The second sipe piece <NUM> continues to the third sipe piece <NUM> on the second side A2 in the tire circumferential direction.

The closed sipes <NUM> arranged in the tire axial direction overlap each other in the tire axial direction and the tire circumferential direction.

The expression "the closed sipes <NUM> overlap each other in the tire axial direction" means such a mode that a virtual region obtained by extending one closed sipe <NUM> parallel to the tire circumferential direction overlaps with the closed sipe <NUM> adjacent thereto.

The expression "the closed sipes <NUM> overlap each other in the tire circumferential direction" means such a mode that a virtual region obtained by extending one closed sipe <NUM> in parallel with the tire axial direction overlaps the closed sipe <NUM> adjacent thereto.

In the present invention, by adopting the above configurations, it is possible to exhibit excellent braking/driving performance and turning performance on ice. The reason for this is presumed to be the following mechanism.

The sipe group <NUM> of the present invention includes a plurality of closed sipes <NUM> arranged in the tire axial direction. Since the closed sipes <NUM> are difficult to open during braking and driving, they are less likely to be clogged with snow or ice inside, and the edge effect can be stably exhibited over a long period of time. Thus, the anti-snow clogging performance when running on snow is improved.

In addition, the closed sipes <NUM> increase the pattern rigidity of the land portion <NUM> and enhance the steering stability on dry road surfaces.

Further, since the third sipe piece <NUM> is inclined with respect to the tire axial direction, it exerts a frictional force in the tire axial direction on ice, thereby capable of improving turning performance on ice.

Furthermore, since the second sipe piece <NUM> of the closed sipe <NUM> overlaps the first sipe piece <NUM> of the closed sipe <NUM> adjacent in the tire axial direction and the tire circumferential direction, it is possible to provide many closed sipes <NUM> in the land portion <NUM>, and excellent braking/driving performance can be exhibited on ice.

In the present embodiment, a virtual region obtained by extending the second sipe piece <NUM> of one closed sipe <NUM> parallel to the tire circumferential direction overlaps with the first sipe piece <NUM> of the closed sipe <NUM> adjacent thereto.

Further, a virtual region obtained by extending the third sipe piece <NUM> of one closed sipe <NUM> parallel to the tire axial direction overlaps with the third sipe piece <NUM> of the closed sipe <NUM> adjacent thereto. The present invention is however, not limited to such a mode.

Hereinafter, a more detailed configuration of the present embodiment will be described.

As shown in <FIG>, the sipe group <NUM> of the present embodiment extends along the tire axial direction, but may extend with a certain degree of inclination with respect to the tire axial direction.

Specifically, an virtual straight line <NUM> (indicated by a two-dot chain line), which connecting between a first end 8a of the closed sipe <NUM> provided at the end on the first side B1 in the tire axial direction, and a first end 8b of the closed sipe <NUM> provided at the end on the second side B2 in the tire axial direction, is, for example, <NUM> degrees or less, preferably <NUM> degrees or less, and more preferably <NUM> degrees or less with respect to the tire axial direction.

The sipe group <NUM> is however, not limited to such a mode, and can be changed according to the shape of the land portion, and as described later, for example, the virtual straight line <NUM> may extend obliquely.

As a further preferable mode, in the present embodiment, the first end 8a of each closed sipe <NUM> is placed in the same imaginary zone <NUM> (colored in <FIG>) extending parallel to the tire axial direction with a minute width.

The width of the imaginary zone <NUM> is, for example, <NUM> or less.

As a further preferable mode, the first ends 8a of the respective closed sipes <NUM> are placed on a same virtual straight line extending parallel to the tire axial direction.

Similarly, the second end 8b of each closed sipe <NUM> is placed in the same imaginary zone (not shown) extending parallel to the tire axial direction with a minute width.

The width of the imaginary zone is, for example, <NUM> or less. As a further preferable mode, the second ends 8b of the respective closed sipes <NUM> are placed on a same virtual straight line extending parallel to the tire axial direction.

It is preferable that, as shown in <FIG>, the overlapping length L2 of two closed sipes <NUM> adjacent to each other in the tire axial direction is <NUM>% to <NUM>% of the maximum length L1 in the tire axial direction of the closed sipe <NUM>.

Thereby, excellent braking/driving performance is exhibited while maintaining the wear resistance of the land portion <NUM>.

If the overlapping length L2 is less than <NUM>% of the length L1, the edge component in the tire axial direction disposed on the land portion <NUM> is reduced, and the braking/driving performance on ice may deteriorate.

If the overlapping length L2 exceeds <NUM>% of the length L1, the clearance between two closed sipes <NUM> adjacent to each other becomes narrow, which may cause uneven wear of the land portion. Each length of the sipe is measured at the widthwise center line of the sipe.

The distance L3 in the tire circumferential direction between the second end 8b of one closed sipe <NUM> and the first end 8a of the closed sipe <NUM> adjacent thereto is, for example, not more than <NUM>%, preferably not more than <NUM>% of the length L6 in the tire circumferential direction the third sipe piece <NUM>.

In the present embodiment, the second end 8b is positioned on the first side A1 in the tire circumferential direction than the first end 8a.

Thereby, a decrease in rigidity of the land portion <NUM> is suppressed, and wear resistance performance and steering stability on dry road surfaces are ensured.

In the present embodiment, the first end 8a and the second end 8b are located
on the second side A2 in the tire circumferential direction of the first sipe piece <NUM>, and on the first side A1 in the tire circumferential direction of the second sipe piece <NUM>.

In other words, the first end 8a and the second end 8b are located within a region (not shown) formed by extending the third sipe piece <NUM> toward both sides in the tire axial direction in parallel with the tire axial direction.

Moreover, the closed sipe <NUM> of the present embodiment includes a first outer sipe piece <NUM> and a second outer sipe piece <NUM>.

The first outer sipe piece <NUM> extends from the first end 8a to the first sipe piece <NUM>.

The second outer sipe piece <NUM> extends from the second end 8b to the second sipe piece <NUM>.

Such closed sipe <NUM> provides a large frictional force in the tire axial direction by means of the first outer sipe piece <NUM> and the second outer sipe piece <NUM>, thereby enhancing turning performance on ice.

The angle between the first sipe piece <NUM> and the third sipe piece <NUM> and.

In the present embodiment, the above two angles are <NUM> to <NUM> degrees.

Thereby, wear at the bent portions of the closed sipe <NUM> is suppressed, and uneven wear resistance is improved.

From a similar point of view, the angle between the first sipe piece <NUM> and the first outer sipe piece <NUM> and the angle between the second sipe piece <NUM> and the second outer sipe piece are each, for example, not less than <NUM> degrees, preferably not less than <NUM> degrees. In the present embodiment, the above two angles are <NUM> to <NUM> degrees.

In this embodiment, each of the sipe pieces of the closed sipe <NUM> extends linearly.

For example, each of the sipe pieces may extend in a curved manner.

Each of the axial length L4 of the first sipe piece <NUM> and the axial length L5 of the second sipe piece <NUM> is greater than the axial length of the third sipe piece <NUM>.

Each of the length L4 of the first sipe piece <NUM> and the length L5 of the second sipe piece <NUM> is <NUM>% to <NUM>% of the axial length L1 of the closed sipe <NUM>.

The angle of the first sipe piece <NUM> with respect to the tire axial direction and the angle of the second sipe piece <NUM> with respect to the tire axial direction are, for example, in a range of +/-<NUM> degrees, preferably in a range of +/-<NUM> degrees. Each of the first sipe piece <NUM> and the second sipe piece <NUM> of the present embodiment extends parallel to the tire axial direction. Such first sipe piece <NUM> and second sipe piece <NUM> help to effectively enhance the braking/driving performance on ice.

As shown in <FIG>, in a more preferable mode, the first sipe pieces <NUM> of the closed sipes <NUM> are arranged in a same imaginary zone (not shown) extending parallel to the tire axial direction with a minute width. The width of the imaginary zone is, for example, <NUM> or less.

In a more preferable mode, the first sipe pieces <NUM> of the closed sipes <NUM> are arranged on a same virtual straight line extending parallel to the tire axial direction.

Thereby, the braking/driving performance is improved while maintaining the uneven wear resistance performance.

Similarly, the second sipe pieces <NUM> of the closed sipes <NUM> are arranged in a same imaginary zone (not shown) extending parallel to the tire axial direction with a minute width. The width of the imaginary zone is, for example, <NUM> or less. In a more preferable mode, the second sipe pieces <NUM> of the closed sipes <NUM> are arranged on a same virtual straight line extending parallel to the tire axial direction.

As shown in <FIG>, the length L6 in the tire circumferential direction of the third sipe piece <NUM> is, for example, smaller than the length L1 in the tire axial direction of the closed sipe <NUM>.

The length L6 of the third sipe piece <NUM> is smaller than the length L4 in the tire axial direction of the first sipe piece <NUM> and the length L5 in the tire axial direction of the second sipe piece <NUM>.

Specifically, the length L6 of the third sipe piece <NUM> is <NUM>% to <NUM>% of the length L1 of the closed sipe <NUM>.

Such third sipe piece <NUM> enhances turning performance on ice while maintaining uneven wear resistance performance.

The third sipe piece <NUM>, for example, is inclined to the second side A2 in the tire circumferential direction from the first sipe piece <NUM> toward the second side B2 in the tire axial direction.

The third sipe piece <NUM> is arranged at a larger angle with respect to the tire axial direction than the first sipe piece <NUM> and the second sipe piece <NUM>.

However, the third sipe piece <NUM> may, for example, extend parallel to the tire circumferential direction.

The angle of the third sipe piece <NUM> of the present embodiment with respect to the tire axial direction is, for example, not less than <NUM> degrees, preferably <NUM> to <NUM> degrees. Such third sipe piece <NUM> improves turning performance on ice, while providing frictional force in the tire circumferential direction too.

As shown in <FIG>, the closed sipes <NUM> of the present embodiment are arranged so that the third sipe pieces <NUM> become parallel to each other.

Thereby, the uneven wear resistance of the land portion <NUM> and the steering stability on dry road surfaces are improved.

As shown in <FIG>, the length L7 in the tire circumferential direction of the first outer sipe piece <NUM> and the length L8 in the tire circumferential direction of the second outer sipe piece <NUM> are, for example, smaller than the length in the tire circumferential direction of the third sipe piece <NUM>. The length L7 of the first outer sipe piece <NUM> and the length L8 of the second outer sipe piece <NUM> are preferably not more than <NUM>%, more preferably <NUM>% to <NUM>% of the length L6 of the third sipe piece <NUM>. This ensures a sufficient clearance between two closed sipes <NUM> adjacent to each other. Therefore, uneven wear resistance is maintained, and demoldability during vulcanization molding is ensured.

With respect to the tire circumferential direction, the first outer sipe piece <NUM> and the second outer sipe piece <NUM> are each inclined in a direction opposite to the third sipe piece <NUM>. The angle of the first outer sipe piece <NUM> with respect to the tire circumferential direction and the angle of the second outer sipe piece <NUM> with respect to the tire circumferential direction are each, for example, not more than <NUM> degrees, preferably <NUM> to <NUM> degrees.

In a preferable mode, the angle of the first outer sipe piece <NUM> and the angle of the second outer sipe piece <NUM> are the same as the angle of the third sipe piece <NUM> with respect to the tire circumferential direction.

However, it is not limited to such mode, and the first outer sipe piece <NUM> and the second outer sipe piece <NUM> may extend parallel to the tire circumferential direction, for example.

In the present embodiment, in two closed sipes <NUM> adjacent in the tire axial direction, the second sipe piece <NUM> of the closed sipe <NUM> on one side overlaps in the tire axial direction with the first sipe piece <NUM> of the closed sipe <NUM> on the other side.

The second outer sipe piece <NUM> of the closed sipe <NUM> on one side extends from the second sipe piece <NUM> toward the first side A1 in the tire circumferential direction.

The first outer sipe piece <NUM> of the closed sipe <NUM> on the other side extends from the first sipe piece <NUM> toward the second side A2 in the tire circumferential direction.

Thereby, the above-described effects are exhibited more reliably.

Next, the internal configuration of the closed sipe <NUM> will be described.

<FIG> shows a see-through perspective view showing an example of the interior portion of the closed sipe <NUM>, and
<FIG> shows a cross-sectional view taken along line A-A of <FIG>.

In this specification, in a see-through perspective view such as <FIG>, the edges of the closed sipe <NUM> at the tread surface is indicated by a solid line, and the shape of the interior portion of the closed sipe <NUM> is indicated by a broken line.

As shown in <FIG>, in the present embodiment, the entire closed sipe <NUM> extends linearly in the tire radial direction in its sipe cross-section.

In the present invention, even if the cross-sectional shape of the sipe is linear as described above, the rigidity of the land portion <NUM> is maintained by the closed sipe <NUM> whose both ends are terminated within the land portion <NUM>, therefore, sufficient steering stability and resistance to uneven wear are exhibited.

On the other hand, the closed sipe <NUM> having such sipe cross section helps to improve demoldability during vulcanization molding, reduce the defect rate during tire production, and reduce manufacturing and maintenance costs for the vulcanization mold.

<FIG> shows a see-through perspective view showing another example of the interior portion of the closed sipe <NUM>. <FIG> shows a B-B line cross-sectional view and a C-C line cross-sectional view of <FIG>.

In the present embodiment, as shown in <FIG> and <FIG>, the first sipe piece <NUM> and the second sipe piece <NUM> are each configured as a bent portion <NUM> extending zigzag in the tire radial direction in the sipe cross section.

Such closed sipe <NUM> increases the rigidity of the land portion <NUM> in the tire circumferential direction, and can exhibit excellent braking/driving performance on ice.

The bent portion <NUM> includes an outer inclined portion <NUM> which continues to the edge of the closed sipe <NUM> and extends while inclining to one direction with respect to the tire radial direction.

In the embodiment shown in <FIG>, the outer inclined portion <NUM> belonging to the first sipe piece <NUM> is inclined to the first side A1 in the tire circumferential direction toward the inside in the tire radial direction. Whereas the outer inclined portion <NUM> belonging to the second sipe piece <NUM> is inclined to the second side A2 in the tire circumferential direction toward the inside in the tire radial direction.

Thereby, a rubber portion surrounded by the first sipe piece <NUM>, the third sipe piece <NUM> and the first outer sipe piece <NUM>, and a rubber portion surrounded by the second sipe piece <NUM>, the third sipe piece <NUM> and the second outer sipe piece <NUM>, secure large volumes, and as a result, it is possible to suppress rubber chipping at the time of demolding during vulcanization molding.

<FIG> shows a D-D line cross-sectional view and a E-E line cross-sectional view of <FIG>.

As shown in <FIG> and <FIG>, in the present embodiment, each of the first outer sipe piece <NUM> and the second outer sipe piece <NUM> is configured as a bent portion <NUM> extending zigzag in the tire radial direction in the sipe cross-section.

Such closed sipe <NUM> increases the rigidity of the land portion <NUM> in the tire axial direction, and can exhibit excellent turning performance on ice.

In the embodiment shown in <FIG>, the outer inclined portion <NUM> belonging to the first outer sipe piece <NUM> is inclined to the first side B1 in the tire axial direction toward the inside in the tire radial direction.

The outer inclined portion <NUM> belonging to the second outer sipe piece <NUM> is inclined to the second side B2 in the tire axial direction toward the inside in the tire radial direction.

Thereby, it is possible to suppress rubber chipping at the time of demolding during vulcanization molding by the same mechanism as described above.

The configuration of the bent portion <NUM> can be varied depending on the purpose of the tire.

In another embodiment, it may be possible that the first sipe piece <NUM> and the second sipe piece <NUM> have the cross-sectional shapes shown in <FIG>, and other portions extend parallel to the tire radial direction, for example.

Such closed sipe <NUM> can exhibit excellent braking/driving performance on ice while improving demoldability during vulcanization molding.

In yet another embodiment, it may be possible that the first outer sipe piece <NUM> and the second outer sipe piece <NUM> have the cross-sectional shapes shown in <FIG>, and other portions extend parallel to the tire radial direction, for example. Such closed sipe <NUM> can exhibit excellent turning performance on ice while improving demoldability during vulcanization molding.

<FIG> shows a see-through perspective view showing the interior portion of yet another closed sipe <NUM>.

As shown in <FIG>, in the present embodiment, each sipe piece of the closed sipe <NUM> is configured as a bent portion <NUM> extending in a zigzag shape in the tire radial direction.

Such closed sipe <NUM> when closed, can further increase the rigidity of the land portion <NUM>, and can exhibit excellent uneven wear resistance performance.

In the embodiment shown in <FIG>, the inclination directions of the outer inclined portions <NUM> of the respective sipe pieces interfere with each other.

Therefore, in the present embodiment, it is preferable that the outer inclined portions <NUM> have the following configuration.

That is, in the present embodiment, the outer inclined portion <NUM> belonging to the first sipe piece <NUM> and the outer inclined portion <NUM> belonging to the second sipe piece <NUM> are each inclined to the first side A1 in the tire circumferential direction toward the inside in the tire radial direction.

In addition, the outer inclined portion <NUM> belonging to the first outer sipe piece <NUM> and the outer inclined portion <NUM> belonging to the second outer sipe piece <NUM> are each inclined to the first side B1 in the tire axial direction toward the inside in the tire radial direction.

Further, the outer inclined portion <NUM> belonging to the third sipe piece <NUM> is inclined to the second side B2 in the tire axial direction toward the inside in the tire radial direction.

With the above configuration, each sipe piece is configured as the bent portion <NUM>, and the above effects can be exhibited.

In the present invention, the closed sipe <NUM> having the planar shape shown in <FIG> and <FIG> may have any of the cross-sectional shapes shown in <FIG>.

In <FIG>, there is shown an enlarged cross-sectional view of the bent portion <NUM>. It is preferable that the bent portion <NUM> includes two or more first convex portions <NUM> which are convex toward one side as shown in <FIG>.

The bent portion <NUM> of the present embodiment is constructed by two first convex portions <NUM>, and one second convex portion <NUM> which is convex toward the other side between the two first convex portions <NUM>.

The center line <NUM> in the width direction of the bent portion <NUM> comprises a first vertex 25a bent at the first convex portion <NUM> and a second vertex 25b bent at the second convex portion <NUM>.

Moreover, it is preferable that a virtual straight line (not shown) connecting between both ends of the center line <NUM> of the bent portion <NUM> is parallel to the tire radial direction. Moreover, it is preferable that the second vertex 25b is positioned on the virtual straight line.

The center line <NUM> of the bent portion <NUM> includes an outer end 25o on the outer side in the tire radial direction, and an inner end 25i on the inner side in the tire radial direction. The bent portion <NUM> comprises two bent elements <NUM>. The bent element <NUM> of the present embodiment is composed of a first bent element <NUM> from the outer end 25o to the second vertex 25b, and a second bent element <NUM> from the second vertex 25b to the inner end 25i.

In the present embodiment, the length L9 in the tire radial direction of the first bent element <NUM> (the distance in the tire radial direction from the outer end 25o to the second vertex 25b) and the length L10 in the tire radial direction of the second bent element <NUM> (the distance in the tire radial direction from the inner end 25i to the second vertex 25b) are the same as each other.

Such bent portion <NUM> can uniformly improve traction performance and braking performance on ice.

The bending width W1 of the bent portion <NUM> (the distance in the width direction of the sipe from the first vertex 25a to the second vertex 25b) is, for example, <NUM> to <NUM>. Thereby, molding defects during vulcanization molding are suppressed while exhibiting the above-described effects.

It is preferable that the closed sipe <NUM> comprises a vertical portion <NUM> which continues to the inner side in the tire radial direction of the bent portion <NUM> and extends parallel to the tire radial direction.

The length L11 in the tire radial direction of the vertical portion <NUM> is, for example, <NUM>% to <NUM>% of the maximum depth d1 of the closed sipe <NUM>.

Thereby, during vulcanization molding, a knife blade of the vulcanization mold for forming the bent portion <NUM> can easily pierce the raw rubber of the tire, thereby, deformation and breakage of the knife blade are suppressed.

<FIG> shows a see-through perspective view showing another example of the interior portion of the closed sipe <NUM>. As shown in <FIG>, the closed sipe <NUM> of the present embodiment includes a connecting portion <NUM> in which sipe walls facing each other are partially connected with each other and which protrudes outward in the tire radial direction.

In general, when a sipe contact with the ground and a load in the tire circumferential direction is applied, shear deformation such that one sipe wall and the other sipe wall of the sipe are displaced in the depth direction of the sipe is likely to occur.

In addition, such deformation may lead to a decrease in the rigidity of the tread portion in the tire circumferential direction, which may lead to a decrease in braking performance on dry road surfaces and on ice, and uneven wear such as heel-and-toe wear around the sipes.

In addition, such uneven wear tends to make deterioration in tire performance due to wear more pronounced.

Since the closed sipe <NUM> shown in <FIG> can suppress the above-described deformation by the connecting portion <NUM>, it is possible to improve steering stability and braking performance even on ice.

In addition, suppressing the deformation described above is highly effective in suppressing uneven wear (heel-and-toe wear). Therefore, the closed sipe <NUM> having the connecting portion <NUM> suppresses uneven wear, thereby reducing changes in tire performance due to wear, and thus it becomes possible to provide a tire capable of maintaining high safety over a long period of time.

In addition, since the above-described closed sipe <NUM> is difficult to open, the inside of the sipe is less likely to be clogged with snow during running.

Such action suppresses the swelling of the side wall of the block <NUM> provided with the closed sipes <NUM>, so the volume of the groove separating the block <NUM> can be secured, thereby it becomes possible to suppress the deterioration of the performance on snow and ice.

The above-described deformation of the sipe tends to occur first in a portion of the sipe having a large component in the tire axial direction, and propagates to a portion of the sipe having a large component in the tire circumferential direction. Therefore, it is preferable to suppress the deformation in the portion of the sipe where the component in the tire axial direction is large.

From this point of view, it is preferable that the connecting portion <NUM> is provided on at least one of the first sipe piece <NUM> and the second sipe piece <NUM>, for example.

In the present embodiment, as a more preferable mode, the connecting portion <NUM> is provided on each of the first sipe piece <NUM> and the second sipe piece <NUM>. Thereby, the above-described effects can be surely obtained.

The height in the tire radial direction of the connecting portion <NUM> provided in the first sipe piece <NUM> is, for example, <NUM>% to <NUM>% of the height in the tire radial direction of the connecting portion <NUM> provided in the second sipe piece <NUM>. Preferably, they are the same. Thereby, the rigidity around the closed sipe <NUM> is uniformly increased by the two connecting portions <NUM>, and the above-described effects can be further improved.

The connecting portion <NUM> extends in the tire radial direction with a constant width, for example.

The width W2 of the connecting portion <NUM> provided in the first sipe piece <NUM> (the width along the length of the closed sipe <NUM>) is preferably <NUM>% to <NUM>%, more preferably <NUM>% to <NUM>% of the length L4 (shown in <FIG>) of the first sipe piece <NUM>.

The width of the connecting portion <NUM> provided on the second sipe piece <NUM> is set in the same range in relation to the length L5 (shown in <FIG>) of the second sipe piece <NUM>.

Thereby, the above effects can be sufficiently exhibited while maintaining the frictional force provided by the edges of the closed sipe <NUM>.

When the width of the connecting portion <NUM> changes in the tire radial direction, the width is measured at the center position in the tire radial direction of the connecting portion <NUM>.

The height h1 in the tire radial direction of the connecting portion <NUM> is, for example, <NUM>% to <NUM>% of the maximum depth d1 (shown in <FIG>) of the closed sipe <NUM>. On the other hand, it is preferable that the height h1 is appropriately determined according to the purpose of the tire. This is because, as shown in <FIG>, when the land portion <NUM> provided with the closed sipe <NUM> having the connecting portion <NUM> is worn, the connecting portion <NUM> is exposed and the edge component of the closed sipe <NUM> is reduced.

From this point of view, as shown in <FIG>, in the case of a winter tire emphasizing on-snow performance, it is preferable that the height h1 is <NUM>% to <NUM>% of the maximum depth d1 of the closed sipe <NUM>. On the other hand, in the case of an all-season tire for year-round use, it is preferable that the height h1 is <NUM>% to <NUM>% of the depth d1. Thereby, performance appropriate to the purpose of the tire can be obtained.

In <FIG>, there is shown a see-through perspective view showing still another example of the interior portion of the closed sipe <NUM>.

In the present embodiment, the closed sipe <NUM> is provided with connecting portions <NUM> in the first sipe piece <NUM> and the second sipe piece <NUM> as in the embodiment shown in <FIG>, and further, the third sipe piece <NUM> is also provided with a connecting portion <NUM>.

In the embodiment of <FIG>, as the third sipe piece <NUM> is also provided with the connecting portion <NUM>, deformation of the closed sipe <NUM> in the tire axial direction is further suppressed. Therefore, further improvements in steering stability and turning performance on ice can be expected.

Hereinafter, in the embodiment shown in <FIG>, the connecting portion <NUM> provided in the first sipe piece <NUM> may be referred to as a first connecting portion 26a, the connecting portion <NUM> provided in the second sipe piece <NUM> as a second connecting portion 26b, and the connecting portion <NUM> provided in the third sipe piece <NUM> as a third connecting portion 26c.

To the first connecting portion 26a and the second connecting portion 26b shown in <FIG>, the configurations of the connecting portions <NUM> shown in <FIG> can be applied, and the descriptions thereof will be omitted here.

Further, in a preferred mode, the first connecting portion 26a and the second connecting portion 26b have substantially the same configuration. Thereby, progress of wear becomes uniform around the first sipe piece <NUM> and around the second sipe piece <NUM>, and uneven wear is suppressed.

The height h2 of the third connecting portion 26c is, for example, <NUM>% to <NUM>% of the maximum depth d1 (shown in <FIG>) of the closed sipe <NUM>.

On the other hand, it is preferable that the height h2 is appropriately determined according to the purpose of the tire. This is because, as shown in <FIG>, when the land portion <NUM> provided with the closed sipe <NUM> having the connecting portion <NUM> is worn, the first connecting portion 26a, the second connecting portion 26b, and the third connecting portion 26c are exposed, and the edge component of the closed sipe <NUM> is reduced.

From this point of view, as shown in <FIG>, in the case of a winter tire emphasizing on-snow performance, it is preferable that the height h2 is <NUM>% to <NUM>% of the maximum depth d1 of the closed sipe <NUM>.

On the other hand, in the case of an all-season tire for year-round use, it is preferable that the height h2 is <NUM>% to <NUM>% of the depth d1. Thereby, performance appropriate to the purpose of the tire can be obtained.

Further, the height h2 of the third connecting portion 26c is, for example, <NUM>% to <NUM>% of the height h1 of the first connecting portion 26a or the second connecting portion 26b. In a more desirable mode, the height h1 is the same as the height h2. Thereby, uneven wear is further suppressed.

The width W3 of the third connecting portion 26c (the width along the length direction of the closed sipe <NUM>) is, for example, <NUM>% to <NUM>%, preferably <NUM>% to <NUM>% of the length L12 of the third sipe piece <NUM> (the length along the length direction of the closed sipe <NUM>). In a more preferable mode, the widths W2 of the first connecting portion 26a and the second connecting portion 26b and the width W3 of the third connecting portion 26c are the same. Thereby, it is possible to further suppress uneven wear around the closed sipe <NUM>.

In <FIG> and <FIG>, there are shown enlarged plan views of land portions of other embodiments of the present invention. In <FIG> and <FIG>, the same reference numerals are assigned to the configurations described above, and descriptions thereof are omitted here.

In the embodiment shown in <FIG>, a sipe, which is adjacent to a longitudinal edge 6e extending in the tire circumferential direction of the block <NUM>, is configured as a non-closed sipe <NUM> communicating with the longitudinal edge 6e. The non-closed sipe <NUM> of the present embodiment has, for example, such a shape that the closed sipe <NUM> communicates with the longitudinal edge 6e at the first sipe piece <NUM> or the second sipe piece <NUM>.

Such sipe configuration helps to further improve the braking/driving performance on ice.

The block <NUM> of the embodiment shown in <FIG> is provided with a sipe group <NUM> of closed sipes <NUM> arranged obliquely with respect to the tire axial direction.

Specifically, a virtual straight line <NUM> (indicated by a two-dot chain line), which connects between a first end 8a of the closed sipe <NUM> provided at the end on the first side B1 in the tire axial direction and a second end 8b of the closed sipe <NUM> provided at the end on the second side B2 in the tire axial direction, is, for example, <NUM> to <NUM> degrees with respect to the tire axial direction. In this embodiment, especially, turning performance on ice is improved.

It is preferable that the closed sipes <NUM> of the present invention are provided in at least shoulder blocks. The shoulder block is a block included in a shoulder land portion located on the outermost side in the tire axial direction of the tread portion <NUM>.

In general, when braking on a dry road surface, a large load tends to act on the shoulder blocks, and the rigidity of the shoulder blocks in the tire circumferential direction tends to be insufficient.

In other words, in order to improve braking performance on dry road surfaces, it is important to improve the rigidity in the tire circumferential direction of the shoulder blocks.

On the other hand, the closed sipes <NUM> of the present invention can be expected to increase block stiffness compared to conventional sipes.

Therefore, by providing the closed sipes <NUM> in the shoulder blocks, the braking performance on dry road surfaces can be effectively improved.

In particular, the closed sipe <NUM> including the connecting portions <NUM> shown in <FIG> or <FIG> can reliably increase the rigidity of the block and further improve the braking performance on dry road surfaces.

While the tire of one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above and may be practiced with various modifications within the scope of the appended claims.

Pneumatic tires of size <NUM>/65R15 having the above-described sipe group were experimentally manufactured based on the specifications in Table <NUM>.

As a comparative example, a tire in which a block a was provided with a plurality of sipes b extending in a zigzag pattern as shown in <FIG>, was experimentally manufactured. The sipe b of the comparative example extends linearly in the tire radial direction as a whole.

Each test tire had substantially the same configuration, except for the shape of the sipe.

Each test tire was tested for traction performance on ice, braking performance on ice, and turning performance on ice.

Common specifications to the test tires and test methods are as follows.

When the test vehicle on which each test tire was mounted was run on an ice road, the traction performance was evaluated by the driver's senses.

The results are grades based on the traction performance of the comparative example being <NUM>, and a higher value indicates better traction performance on ice.

When the test vehicle on which each test tire was mounted was run on the ice road, the braking performance was evaluated by the driver's senses.

The results are grades based on the braking performance of the comparative example being <NUM>, and a higher value indicates better braking performance on ice.

When the test vehicle on which each test tire was mounted was run on the ice road, the turning performance was evaluated by the driver's senses.

The results are grades based on the turning performance of the comparative example being <NUM>, and a higher value indicates better turning performance on ice.

The results of the tests are shown in Table <NUM>.

Claim 1:
A tire (<NUM>) including a tread portion (<NUM>), wherein the tread portion (<NUM>) includes a land portion (<NUM>),
in the land portion (<NUM>), a plurality of closed sipes (<NUM>) having a width of not more than <NUM> are arranged in a tire axial direction,
each of the closed sipes (<NUM>) includes a first end (8a), a second end (8b), a first sipe piece (<NUM>) extending in the tire axial direction on the first end (8a) side, a second sipe piece (<NUM>) extending in the tire axial direction on the second end side (8b), and a third sipe piece (<NUM>) inclined with respect to the tire axial direction between the first sipe piece (<NUM>) and the second sipe piece (<NUM>), and
the closed sipes (<NUM>) are arranged in the tire axial direction overlapping with each other in the tire axial direction and the tire circumferential direction,
characterized in that
the first sipe piece (<NUM>) is connected to the third sipe piece (<NUM>) on the first side (A1) in the tire circumferential direction,
the second sipe piece (<NUM>) is connected to the third sipe piece (<NUM>) on the second side (A2) in the tire circumferential direction,
the first end (8a) and the second end (8b) are positioned on the second side (A2) in the tire circumferential direction than the first sipe piece (<NUM>), and on the first side (A1) in the tire circumferential direction than the second sipe piece (<NUM>), and
the closed sipe (<NUM>) includes a first outer sipe piece (<NUM>) extending from the first end (8a) to the first sipe piece (<NUM>), and a second outer sipe piece (<NUM>) extending from the second end (8b) to the second sipe piece (<NUM>).