Patent ID: 12194783

DETAILED DESCRIPTION

An embodiment of the present invention will be described below with reference to the drawings.

FIG.1is a transverse cross-sectional view of a tread portion2of a tire1of the present embodiment.FIG.1is a meridian cross-sectional view including the tire rotation axis of the tire1in a standardized state. The tire1of the present embodiment is used as, for example, a pneumatic tire for a passenger car. The present invention may be applied to, for example, light truck tires and van tires on which high load acts during running.

In the case of a pneumatic tire for which various standards are defined, the “standardized state” represents a state where a tire is mounted on a standardized rim and is inflated to a standardized internal pressure and no load is applied to the tire. In the case of non-pneumatic tires and tires for which various standards are not defined, the standardized state represents a standard use state which corresponds to a purpose of use of the tire and in which no load is applied to the tire. In the description herein, unless otherwise specified, dimensions and the like of components of the tire are represented as values measured in the standardized state.

In a standard system including a standard on which the tire is based, the “standardized rim” represents a rim that is defined by the standard for each tire, and is, for example, “standard rim” in the JATMA standard, “Design Rim” in the TRA standard, or “Measuring Rim” in the ETRTO standard.

In a standard system including a standard on which the tire is based, the “standardized internal pressure” represents an air pressure that is defined by the standard for each tire, and is “maximum air pressure” in the JATMA standard, the maximum value recited in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, or “INFLATION PRESSURE” in the ETRTO standard.

As shown inFIG.1, the tread portion2includes, for example, a plurality of main grooves3extending continuously in the tire circumferential direction, and a plurality of land portions4demarcated by the plurality of main grooves3.

FIG.2is an enlarged plan view of the land portion4. As shown inFIG.2, in the present embodiment, the land portion4is, for example, formed as a block array including a plurality of blocks6in the tire circumferential direction. The blocks6are demarcated between a plurality of lateral grooves5extending across the land portion4in the tire axial direction. In the present invention, the land portion4is not limited to such a structure, and may be, for example, a rib extending continuously in the tire circumferential direction.

In the description herein, in some of the figures, a first side A1in the tire circumferential direction, a second side A2opposite to the first side A1in the tire circumferential direction, a first side B1in the tire axial direction, and a second side B2opposite to the first side B1in the tire axial direction are indicated by arrows. Unless otherwise specified, in figures illustrating the land portion4in a planar view, the upward direction corresponds to the first side A1in the tire circumferential direction, the downward direction corresponds to the second side A2in the tire circumferential direction, the leftward direction corresponds to the first side B1in the tire axial direction, and the rightward direction corresponds to the second side B2in the tire axial direction.

In the land portion4, a plurality of closed sipes8are aligned in the tire axial direction. In the present embodiment, a plurality of sipe groups7in each of which the closed sipes8are aligned are disposed in one block6. One sipe group7is, for example, formed of three to seven closed sipes8.

In the description herein, the “sipe” represents a cut portion which has a minute width such that a width between two sipe walls opposing each other is not greater than 1.5 mm. In a preferable mode, in the present embodiment, the width of the closed sipe8is not greater than 1.0 mm. In the description herein, the “closed sipe” represents a sipe that has both ends terminating in the land portion4. In the present embodiment, the sipe group7disposed in the block6is merely formed of the closed sipes8. In other words, no sipe is connected to the edge of the block6. However, the present invention is not limited to such a structure. A sipe disposed near the edge of the block6may be a non-closed sipe which has one end opened at the edge.

FIG.3is an enlarged plan view of the closed sipe8of the present embodiment.FIG.4is a transparent perspective view of an example of the inside of the closed sipe8of the present embodiment. In the description herein, in the transparent perspective view likeFIG.4, the edge of the closed sipe8on the tread surface is indicated by a solid line, and the shape of the inside of the closed sipe8is indicated by dashed lines. As shown inFIG.3andFIG.4, each of the closed sipes8includes a sipe bottom8d, a first end8aand a second end8bin the tire axial direction, a first sipe piece11, a second sipe piece12, a third sipe piece13, and at least one tie bar20.

As shown inFIG.3, in the present embodiment, the first end8ais an end of the closed sipe8on the first side B1in the tire axial direction. The second end8bis an end of the closed sipe8on the second side B2in the tire axial direction. The first sipe piece11extends in the tire axial direction on the first end8aside relative to the third sipe piece13. The first sipe piece11extends at a first angle θ1relative to the tire axial direction.

The second sipe piece12extends in the tire axial direction on the second end8bside relative to the third sipe piece13. The second sipe piece12extends at a second angle θ2relative to the tire axial direction. The third sipe piece13is continuous with the first sipe piece11and the second sipe piece12at a first intersecting portion18and a second intersecting portion19, respectively, and extends at a third angle θ3different from the first angle θ1and the second angle θ2relative to the tire axial direction.

In such arrangement, in the closed sipe8of the present embodiment, the first sipe piece11is disposed on the first side A1relative to the second sipe piece12in the tire circumferential direction, and on the first side B1relative thereto in the tire axial direction. In the present embodiment, the first sipe piece11is continuous with the first side A1of the third sipe piece13in the tire circumferential direction. The second sipe piece12is continuous with the second side A2of the third sipe piece13in the tire circumferential direction.

In the present embodiment, each of the first sipe piece11, the second sipe piece12, and the third sipe piece13linearly extends. However, the present invention is not limited to such a structure. As long as a region in which the sipe is bent is formed at the first intersecting portion18and the second intersecting portion19, the sipe pieces may be curved or bent with a wavy amplitude. In the description herein, an angle of each portion in the closed sipe8is measured at the center line (line that equally divides the sipe opening width) of the sipe in a planar view (hereinafter, referred to as “tread planar view”) in which the tread portion2is developed into a plane. Each of the first angle θ1and the second angle θ2described above is, for example, not greater than 20° and preferably not greater than 10°. In the present embodiment, the first angle θ1and the second angle θ2are equal to each other, and the first sipe piece11and the second sipe piece12extend parallel to the tire axial direction. The third angle θ3is, for example, greater than each of the first angle θ1and the second angle θ2and is, for example, 60 to 80°. The other sipe pieces included in the closed sipe8of the present embodiment will be described below.

As shown inFIG.4, the tie bar20is a region in which the sipe walls opposing each other are partially connected, and, thus, the sipe bottom8dlocally protrudes outward in the tire radial direction. InFIG.4, the tie bar20is indicated as a void. However, the tie bar20is formed of a rubber member in which the sipe bottom8dprotrudes, in practice. The tie bar20is expected to allow deformation of the closed sipe8to be inhibited, and allow uneven wear around the closed sipe8to be reduced. However, in a conventional embodiment, the tie bar20is disposed at the center portion of the first sipe piece11or the center portion of the second sipe piece12, and deformation of the closed sipes8thus tends to be insufficiently inhibited.

As shown inFIG.2, the closed sipes8aligned in the tire axial direction overlap each other in the tire axial direction and the tire circumferential direction. “The closed sipes8overlap each other in the tire axial direction” means that an imaginary region obtained by extending one closed sipe8in parallel to the tire circumferential direction overlaps the closed sipe8adjacent to the one closed sipe8. “The closed sipes8overlap each other in the tire circumferential direction” means that an imaginary region obtained by extending one closed sipe8in parallel to the tire axial direction overlaps the closed sipe8adjacent to the one closed sipe8. Such arrangement of the sipes can enhance on-ice performance whereas uneven wear tends to be caused around the sipes.

As shown inFIG.4, the tie bar20includes a first tie bar21disposed in the first sipe piece11. As shown inFIG.3, the center21c, in the sipe length direction, of the first tie bar21is disposed closer to the first intersecting portion18than the center11c, in the length direction, of the first sipe piece11is. A distance L2from an end21aof the first tie bar21on the first intersecting portion18side to the first intersecting portion18is not greater than 25% of a length L1(so-called periphery length along the sipe length direction) of the first sipe piece11.

The distance L2represents the shortest distance from the end21ato the first intersecting portion18in the tread planer view. In a case where a position of the end21aof the first tie bar21changes in the height direction of the first tie bar21, the position of the end21ais specified at the center position, in the height direction, of the first tie bar21. The first intersecting portion18is the vertex of the bent portion formed by connecting the first sipe piece11and the third sipe piece13to each other, and specified by the center line of the sipe in the tread planar view.

In conventional arrangement of the tie bar20, the closed sipe8is opened and closed according to the tread portion2being brought into contact with the ground and released, and the opening tends to be the largest near the first intersecting portion18at which the first sipe piece11and the third sipe piece13are continuous with each other, and heel-and-toe wear is likely to be generated particularly near the first intersecting portion18. Particularly, high load acts on a tire mounted to a light truck or a van, and this tendency is thus significant.

In the present invention, the first tie bar21is disposed near the first intersecting portion18at which the closed sipe8tends to be greatly opened, so that large opening near the first intersecting portion18and twisting of rubber are inhibited, and uneven wear such as heel-and-toe wear around the sipes can be reduced. The tire1of the present invention has such a mechanism and can thus exhibit excellent uneven wear resistance. The tire of the present invention can also be expected to have improved outer appearance by the above-described effect when the tire is worn.

The structure of the present embodiment will be described below in more detail. The structures described below represent specific modes of the present embodiment. Therefore, needless to say, also when the structures described below are not provided, the present invention can exhibit the above-described effects. Also when any one of the structures described below is applied alone to the tire of the present invention having the above-described features, improvement of performance corresponding to each structure can be expected. Furthermore, in a case where some of the structures described below are applied in combination, complex performance improvement corresponding to the structures can be expected.

The distance L2is preferably not greater than 20% of the length L1of the first sipe piece11and more preferably not greater than 10% of the length L1. In a more preferable mode, the end21aof the first tie bar21may be substantially disposed at the first intersecting portion18(that is, the distance L2is 0). Thus, the above-described effect is more assuredly exhibited. As described below, the first tie bar21may be continuous with a tie bar disposed in the third sipe piece13, and the tie bar20may be disposed over the first sipe piece11and the third sipe piece13.

The first tie bar21extends substantially with a constant width in the tire radial direction. However, the present invention is not limited to such a structure. A width W1(width along the first sipe piece11), in the sipe length direction, of the first tie bar21is preferably not less than 10% of the length L1of the first sipe piece11and more preferably not less than 20% of the length L1, and preferably not greater than 50% of the length L1and more preferably not greater than 30% of the length L1. Thus, uneven wear resistance can be enhanced while frictional force exhibited on ice by the closed sipes8is maintained. In a case where the width W1changes in the height direction of the first tie bar21, the width W1is measured at the center position, in the height direction, of the first tie bar21.

As shown inFIG.4, the maximum height h1of the first tie bar21is 10% to 90% of the maximum depth dl of the closed sipe8. The height h1is preferably determined as appropriate according to the purpose of the tire. From such a viewpoint, in the case of winter tires for which on-snow performance is important, the height h1is preferably 40% to 50% of the maximum depth dl of the closed sipe8. Meanwhile, in the case of tires for all seasons which are considered to be used throughout the year, the height h1is preferably 60% to 70% of the depth dl. Thus, performance according to the purpose of the tire is obtained.

As shown inFIG.4, in the present embodiment, the tie bar20includes a second tie bar22disposed in the second sipe piece12. From the viewpoint of enhancing uneven wear resistance, the second tie bar22has substantially the same structure as the first tie bar21. That is, as shown inFIG.3, the center22c, in the sipe length direction, of the second tie bar22is disposed closer to the second intersecting portion19than the center12c, in the length direction, of the second sipe piece12is. A distance L4from an end22aof the second tie bar22on the second intersecting portion19side to the second intersecting portion19is not greater than 25% of a length L3of the second sipe piece12. The above-described configuration of the first tie bar21can be applied to the second tie bar22, and the description thereof is omitted.

FIG.5is a cross-sectional view taken along a line A-A inFIG.3. As shown inFIG.5, the closed sipe8preferably includes a bent portion25that zigzags in the tire radial direction on the sipe transverse cross-section. The closed sipe8having such a structure can enhance stiffness of the land portion when the sipe walls opposing each other come into contact with each other, and uneven wear resistance can be further enhanced.

The bent portion25preferably includes two or more first protrusions26that protrude on one side. In the present embodiment, the bent portion25includes two first protrusions26and one second protrusion27that protrude on the other side between the two first protrusions26. A bent width W2of the bent portion25is, for example, 0.1 to 1.0 mm. Thus, molding defect can be inhibited during vulcanization and molding while the above-described effect is exhibited.

In the present embodiment, the closed sipe8preferably includes a perpendicular portion32that extends parallel to the tire radial direction and is continuous with the inner side, in the tire radial direction, of the bent portion25. A length L5, in the tire radial direction, of the perpendicular portion32is, for example, 10% to 30% of the maximum depth dl of the closed sipe8. The length L5, in the tire radial direction, of the perpendicular portion32is preferably less than the height h1(shown inFIG.4) of the first tie bar21. Thus, a knife blade of the vulcanization mold for forming the bent portion25easily sticks in raw rubber of the tire during vulcanization and molding, and deformation of the knife blade or damage to the knife blade is inhibited.

As shown inFIG.2, in the present embodiment, the plurality of the closed sipes8are disposed along the tire axial direction. However, the plurality of the closed sipes8may be inclined relative to the tire axial direction to a certain degree. Specifically, an imaginary straight line28(indicated by alternate long and two short dashes line) connecting between the first end8aof the closed sipe8disposed at the end of the first side B1in the tire axial direction, and the second end8bof the closed sipe8disposed at the end of the second side B2in the tire axial direction is, for example, inclined relative to the tire axial direction at an angle of not greater than 45°, preferably not greater than 15°, and more preferably not greater than 5°. However, arrangement of the closed sipes8is not limited to such arrangement, and can be changed according to the shape of the land portion.

In a more preferable mode, in the present embodiment, the first ends8aof the closed sipes8included in one sipe group7are disposed on the same imaginary belt15(indicated by dots inFIG.2) extending parallel to the tire axial direction at a minute width. The width of the imaginary belt15is, for example, not greater than 3.0 mm. In a more preferable mode, the first ends8aof the closed sipes8are disposed on the same imaginary straight line extending parallel to the tire axial direction. Similarly, the second ends8bof the closed sipes8are disposed on the same imaginary belt (not shown) extending parallel to the tire axial direction at a minute width. The width of the imaginary belt is, for example, not greater than 3.0 mm. In a more preferable mode, the second ends8bof the closed sipes8are disposed on the same imaginary straight line extending parallel to the tire axial direction.

FIG.6is an enlarged plan view of a plurality of the closed sipes8. As shown inFIG.6, an overlap length L7, in the tire axial direction, over which two closed sipes8adjacent to each other overlap each other is preferably 10% to 40% of the maximum length L6, in the tire axial direction, of the closed sipe8. The overlap length L7is preferably 2.0 to 5.0 times the width W1of the first tie bar21. Thus, excellent on-ice performance is exhibited while uneven wear resistance of the land portion4is maintained.

In the present embodiment, the first end8aand the second end8bare each disposed closer to the second side A2in the tire circumferential direction than the first sipe piece11is, and disposed closer to the first side A1in the tire circumferential direction than the second sipe piece12is. In other words, the first end8aand the second end8bare disposed in a region obtained by extending the third sipe piece13toward the both ends in the tire axial direction in parallel to the tire axial direction.

As shown inFIG.3, in the present embodiment, the closed sipe8includes a first outer sipe piece16and a second outer sipe piece17. The first outer sipe piece16extends from the first end8ato the first sipe piece11. The second outer sipe piece17extends from the second end8bto the second sipe piece12. The closed sipe8having such a structure allows high frictional force to be exhibited in the tire axial direction by the first outer sipe piece16and the second outer sipe piece17, and on-ice cornering performance is enhanced.

Each of an angle θ4between the first sipe piece11and the third sipe piece13, and an angle θ5between the second sipe piece12and the third sipe piece13is, for example, not less than 80° and preferably not less than 90°. In the present embodiment, the angle θ4and the angle θ5are each 100 to 120°. Thus, wear at a portion at which the closed sipe8is bent is reduced, and uneven wear resistance is enhanced.

From a similar viewpoint, each of an angle θ6between the first sipe piece11and the first outer sipe piece16, and an angle θ7between the second sipe piece12and the second outer sipe piece is, for example, not less than 80° and preferably not less than 90°. In the present embodiment, the above-described two angles are each 100 to 120°.

The length L1of the first sipe piece11and the length L3of the second sipe piece12are each greater than the length of the third sipe piece13. The length L1of the first sipe piece11and the length L3of the second sipe piece12are each 35% to 45% of the largest length L6(shown inFIG.6), in the tire axial direction, of the closed sipe8.

As shown inFIG.6, the length L8, in the tire circumferential direction, of the third sipe piece13is, for example, 3.0 to 5.0 times the width W1of the first tie bar21. The third sipe piece13having such a structure contributes to well-balanced enhancement of uneven wear resistance and on-ice performance.

As shown inFIG.2, in the present embodiment, the closed sipes8are disposed such that the third sipe pieces13are parallel to each other. Thus, uneven wear resistance is further enhanced.

As shown inFIG.3, the first outer sipe piece16and the second outer sipe piece17each have a length less than the third sipe piece13. The length of the first outer sipe piece16is preferably 40% to 60% of the length of the third sipe piece13. The same applies to the second outer sipe piece17. The first outer sipe piece16and the second outer sipe piece17having such structures contribute to well-balanced enhancement of uneven wear resistance and on-ice performance.

As shown inFIG.6, in the present embodiment, in the two closed sipes8adjacent to each other in the tire axial direction, the second sipe piece12of the closed sipe8on one side overlaps the first sipe piece11of the closed sipe8on the other side in the tire axial direction. The second outer sipe piece17of the closed sipe8on the one side extends from the second sipe piece12toward the first side A1in the tire circumferential direction. The first outer sipe piece16of the closed sipe8on the other side extends from the first sipe piece11toward the second side A2in the tire circumferential direction. Thus, the above-described effect is more assuredly exhibited.

FIG.7is a transparent perspective view of an example of the inside of the closed sipe8according to another embodiment of the present invention. In the other embodiment described below, the components common to those of the above-described embodiment are denoted by the same reference numerals, and the above-described structures can be applied to the components.

As shown inFIG.7, the tie bar20of the present embodiment includes at least one third tie bar23disposed in the third sipe piece13. The end of the first tie bar21on the first intersecting portion18side is disposed at the first intersecting portion18. The third tie bar23includes a first reinforcing tie bar23acontinuous with the first tie bar21. Thus, the closed sipe8of the present embodiment includes a tie bar disposed over the first sipe piece11and the third sipe piece13. The tie bar having such a structure can effectively inhibit the first sipe piece11and the third sipe piece13from being opened, and uneven wear can be reduced.

In a more preferable mode, the closed sipe8of the present embodiment includes the second tie bar22, and the end of the second tie bar22on the second intersecting portion19side is disposed at the second intersecting portion19. The third tie bar23includes a second reinforcing tie bar23bcontinuous with the second tie bar22. Thus, the closed sipe8of the present embodiment includes a tie bar disposed over the second sipe piece12and the third sipe piece13. Such arrangement of the tie bar allows enhancement of uneven wear resistance.

The tire1of the present invention can be obtained by a known manufacturing method by using a vulcanization mold having a sipe blade corresponding to the shape of the above-described sipe.

The tire according to the embodiments of the present invention has been described above in detail. However, the present invention is not limited to the above-described specific embodiments, and various modification can be made to implement the present invention.

EXAMPLES

Pneumatic tires each having the plurality of closed sipes described above and having a size of 195/65R15 were produced as test tires according to the specifications indicated in Table 1. As a test tire for comparative example 1, a tire in which the closed sipes did not include tie bars was produced. As test tires for comparative examples 2 and 3, tires in each of which a distance from the end of the first tie bar to the first intersecting portion was greater than 25% of the length of the first sipe piece were produced. The test tires had substantially the same structure except for the above-described matters. Each test tire was tested for uneven wear resistance. The specifications common to the test tires and a test method were as follows.Rim on which the tire was mounted: 15×6.0 JTire internal pressure: front wheel 230 kPa, rear wheel 230 kPaTest vehicle: front-wheel-drive car having an engine displacement of 1500 ccPositions at which the tires were mounted: all wheels
<Uneven Wear Resistance>

The above-described test vehicle was caused to run on an ordinary road over a certain distance. Thereafter, a state where uneven wear such as heel-and-toe wear was generated around the closed sipe was visually confirmed and evaluated. The results are indicated as scores with the uneven wear generating state of comparative example 1 being 100. The greater the value is, the less uneven wear is and the more excellent uneven wear resistance is.

Table 1 indicates the test results.

TABLE 1Comp.Comp.Ex. 1Ex. 2Ex. 1Ex. 2Ex. 3Ex. 4Presence or absence of tieAbsentPresentPresentPresentPresentPresentbarDistance L2 from end of first—35251550tie bar to first intersectingportion/length L1 of first sipepiece (%)Uneven wear resistance100102105109114117(Score)

According to the test results, it was confirmed that the tires of the examples exhibited excellent uneven wear resistance as compared with the tires of the comparative examples.

APPENDIX

The present invention includes the following aspects.

Invention 1

A tire including a tread portion, in whichthe tread portion includes a land portion,a plurality of closed sipes each having a width of not greater than 1.5 mm are aligned in a tire axial direction in the land portion,each of the closed sipes includesa sipe bottom,a first end and a second end in the tire axial direction,a first sipe piece extending on the first end side at a first angle relative to the tire axial direction,a second sipe piece extending on the second end side at a second angle relative to the tire axial direction,a third sipe piece continuous with the first sipe piece and the second sipe piece at a first intersecting portion and a second intersecting portion, respectively, the third sipe piece extending at a third angle different from the first angle and the second angle relative to the tire axial direction, andat least one tie bar formed by the sipe bottom locally protruding outward in a tire radial direction,the closed sipes aligned in the tire axial direction overlap each other in the tire axial direction and a tire circumferential direction,the tie bar includes a first tie bar disposed in the first sipe piece,a center, in a sipe length direction, of the first tie bar is disposed closer to the first intersecting portion than a center, in a length direction, of the first sipe piece is, anda distance from an end of the first tie bar on the first intersecting portion side to the first intersecting portion is not greater than 25% of a length of the first sipe piece.

Invention 2

The tire according to invention 1, in whichthe tie bar includes a second tie bar disposed in the second sipe piece,a center, in the sipe length direction, of the second tie bar is disposed closer to the second intersecting portion than a center, in a length direction, of the second sipe piece is, anda distance from an end of the second tie bar on the second intersecting portion side to the second intersecting portion is not greater than 25% of a length of the second sipe piece.

Invention 3

The tire according to invention 1 or 2, in which a width, in the sipe length direction, of the first tie bar is 10% to 50% of the length of the first sipe piece.

Invention 4

The tire according to any one of inventions 1 to 3, in which a maximum height of the first tie bar is 10% to 90% of a maximum depth of the closed sipe.

Invention 5

The tire according to any one of inventions 1 to 4, in whichthe tie bar includes at least one third tie bar disposed in the third sipe piece,the end of the first tie bar is disposed at the first intersecting portion, andthe third tie bar includes a first reinforcing tie bar continuous with the first tie bar.

Invention 6

The tire according to any one of inventions 1 to 5, in which each closed sipe includes a bent portion that zigzags in the tire radial direction, on a transverse cross-section of the sipe.