tire

Abstract

To provide a tire improved in on-ice gripping performance.SOLUTION: A tire 1 has land parts 4 on a tread surface 2. The land part 4 is equipped with a sipe unit 8 composed of a pair of sipes 7. Each of the pair of sipes 7 has both ends in an extending direction of the sipe 7 which terminate in the land part 4. In the pair of sipes 7, only portions in a tire width direction oppose to each other in a tire circumferential direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to tires. [Background technology]

[0002] Traditionally, tires, especially studless tires, have had narrow grooves called sipes on the tread surface to improve the tire's grip performance on ice. These sipes allow water that seeps out as the ice melts at the tire's contact surface to be discharged outside the contact surface, thereby improving the tire's grip performance on ice.

[0003] For example, Patent Document 1 proposes a technology that improves ice grip performance by densely arranging sipes while suppressing a decrease in the rigidity of the land portion. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-186827 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, conventional technology has not adequately achieved a balance between the rigidity of the land portion and water discharge through sipes, and further improvements in the ice grip performance of tires are still needed.

[0006] In view of these circumstances, the object of the present invention is to provide a tire with improved grip performance on ice. [Means for solving the problem]

[0007] The tire according to the present invention is a tire having a land portion on its tread surface, wherein the land portion comprises a sipe unit composed of a pair of sipes, each of the pair of sipes extending such that both ends in the direction of sipe extension terminate within the land portion, and the pair of sipes face each other in the tire circumferential direction only in the tire width direction. According to the present invention, the tire's grip performance on ice can be improved.

[0008] In the tire according to the present invention, it is preferable that each of the pair of sipes extends linearly such that the angle φ it makes with the tire width direction satisfies 0° < φ < 45°. With a tire having such a configuration, the sipes can contribute not only to improving braking force and driving force in the tire circumferential direction, but also to improving lateral grip performance (turning force) in the tire width direction.

[0009] In the tire according to the present invention, it is preferable that a plurality of the sipe units are arranged repeatedly in the circumferential direction of the tire on the land portion to form a row of sipe units, and that the plurality of sipe units constituting the row of sipe units are arranged such that both ends in the tire width direction are aligned on a straight line extending along the circumferential direction of the tire. With a tire having such a configuration, the area of ​​the land portion where the row of sipe units is arranged can be reduced to reduce the amount of blank area where sipes are not provided.

[0010] In the tire according to the present invention, the land portion preferably comprises a plurality of rows of sipe units arranged in the tire width direction, wherein a plurality of sipes included in a first row of sipe units extend inclined toward one side in the tire circumferential direction as it moves toward one side in the tire width direction, and a plurality of sipes included in a second row of sipe units adjacent to the first row of sipe units extend inclined toward one side in the tire circumferential direction as it moves toward the one side in the tire width direction. With a tire having such a configuration, it becomes easier to position the blade for forming the sipes in the mold during tire manufacturing, and the production of the tire mold becomes easier.

[0011] In the tire according to the present invention, it is preferable that each of the plurality of sipes included in the second sipe unit row extends along the extension of any of the sipes included in the first sipe unit row. With a tire having such a configuration, the ice grip performance of the tire can be further improved.

[0012] In the tire according to the present invention, the land portion preferably comprises a plurality of rows of sipe units arranged in the tire width direction, wherein a plurality of sipes included in a first row of sipe units extend inclined toward one side in the tire width direction toward one side in the tire circumferential direction, and a plurality of sipes included in a second row of sipe units adjacent to the first row of sipe units extend inclined toward the other side in the tire circumferential direction, as it moves toward one side in the tire width direction. With a tire having such a configuration, the ice grip performance of the tire can be further improved.

[0013] In the tire according to the present invention, when the length of the sipe in the tire width direction is d (mm) and the depth of the sipe is h (mm), then d × h = 150 (mm) 2 ) or less, where n is the number of sipes within the land area, BW is the maximum width of the land area in the tire width direction, and the outer contour area of ​​the land area is (mm²). 2The equivalent tire circumferential length of the land portion obtained by dividing the above by the maximum width BW is defined as BL (mm). The equivalent number of sipes N is expressed as d × n / BW. The average sipe interval in the tire circumferential direction is expressed as BL / (N + 1). When the sipe density SD in the tire circumferential direction is expressed as the reciprocal of the average sipe interval, i.e., SD = (N + 1) / BL = ((d × n / BW) + 1) / BL, it is preferable that SD is 0.15 (1 / mm) or more. According to the tire having such a configuration, the ice grip performance of the tire can be further improved.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a tire with improved ice grip performance.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a developed view schematically showing a tread pattern of a tire according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic view showing the lifting of the block land portion around the sipe. [Figure 3] FIG. 3 is a schematic view showing the arrangement of sipe units shown in FIG. 1. [Figure 4] FIG. 4 is a cross-sectional view showing the A - A' cross-section shown in FIG. 3. [Figure 5] FIG. 5 is a schematic view showing the arrangement of sipe units different from that shown in FIG. 3. [Figure 6] FIG. 6 is a schematic view showing the arrangement of a plurality of sipe unit rows in the first embodiment. [Figure 7] FIG. 7 is a schematic view showing the arrangement of sipe unit rows when the tire width direction interval v is 0 and the tire circumferential direction offset u is (d + s) × tan φ. [Figure 8] FIG. 8 is a schematic view showing the arrangement of sipe units in which sipes are connected by shallow grooves in the first embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing the B - B' cross-section shown in FIG. 8. [Figure 10] FIG. 10 is a developed view schematically showing a tread pattern of a tire according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a schematic view showing the arrangement of a plurality of sipe unit rows in the second embodiment. [Figure 12] FIG. 12 is a schematic view showing the arrangement of sipe unit rows when the tire width direction interval v is 0 and the tire circumferential direction offset u is (d + s) × tan φ. [Figure 13] FIG. 13 is a schematic view showing the arrangement of sipe units in which sipes are connected by shallow grooves in the second embodiment. [Figure 14] FIG. 14 is a table showing examples and comparative examples. [Figure 15] FIG. 15 is a diagram showing the block rigidity and the contact area in the examples and comparative examples shown in FIG. 14.

MODE FOR CARRYING OUT THE INVENTION

[0016] Hereinafter, embodiments of a tire according to the present invention will be described with reference to the drawings. The same reference numerals are given to common members and parts in each figure. However, note that the drawings are schematic, and the ratios of the respective dimensions may be different from the actual ones.

[0017] In this specification, the “tire width direction” refers to a direction parallel to the rotation axis of the tire. The “tire radial direction” refers to a direction orthogonal to the rotation axis of the tire. The “tire circumferential direction” refers to a direction in which the tire rotates around the rotation axis of the tire.

[0018] Also, in this specification, the side closer to the rotation axis of the tire along the tire radial direction is referred to as the “inner side in the tire radial direction”, and the side farther from the rotation axis of the tire along the tire radial direction is referred to as the “outer side in the tire radial direction”. On the other hand, the side closer to the tire equatorial plane CL along the tire width direction is referred to as the “inner side in the tire width direction”, and the side farther from the tire equatorial plane CL along the tire width direction is referred to as the “outer side in the tire width direction”.

[0019] In this specification, unless otherwise specified, the positional relationships of each element of a tire shall be measured under standard conditions. In this specification, "standard conditions" refers to the state in which the tire is mounted on the rim of the wheel (the applicable rim), filled to the specified internal pressure, and unloaded.

[0020] In this specification, "applicable rim" refers to the standard rim (Measuring Rim in ETRTO's STANDARDS MANUAL, Design Rim in TRA's YEAR BOOK) for applicable sizes, which is an industrial standard valid in the region where the tire is produced and used, and is listed in or will be listed in the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organization) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States, etc. For sizes not listed in the above industrial standards, "applicable rim" refers to a rim with a width corresponding to the tire bead width. "Applicable rim" includes current sizes as well as sizes that may be included in the above industrial standards in the future. An example of "applicable sizes that will be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the 2013 edition of ETRTO's STANDARDS MANUAL.

[0021] In this specification, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel for the applicable size and ply rating as described in the above-mentioned industrial standards such as the JATMA YEAR BOOK. For sizes not listed in the above-mentioned industrial standards, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, in this specification, "specified load" refers to the load corresponding to the maximum load capacity of a single wheel for the applicable size and ply rating as described in the above-mentioned industrial standards. For sizes not listed in the above-mentioned industrial standards, "specified load" refers to the load corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted.

[0022] In this specification, "tread surface" refers to the outer circumference of the tire that comes into contact with the road surface when the tire is mounted on the applicable rim, filled to the specified internal pressure, and rolled under the specified load. "Tread edge" refers to the edge of the tread surface in the tire width direction.

[0023] Furthermore, "sipe" refers to a sipe whose width is 1 mm or less in an area of ​​50% or more of its depth under standard conditions. Here, the depth of the sipe is measured in a direction perpendicular to the tread surface under standard conditions, and the width of the sipe is measured in a direction parallel to the tread surface in a cross section perpendicular to the direction of extension on the tread surface. Furthermore, "length in the direction of extension of the sipe" refers to the length of the center line formed by connecting the center points in the width direction of the sipe on the tread surface under standard conditions. Unless otherwise specified, distances or lengths related to sipes are also measured in a unfolded view of the tread surface under standard conditions, with the above center line as the reference.

[0024] In this embodiment, unless otherwise specified, the internal structure of the tire may be the same as that of a conventional tire. For example, the tire may have a pair of bead portions, a pair of sidewall portions connected to the pair of bead portions, and a tread portion disposed between the pair of sidewall portions. Alternatively, the tire may have a carcass that spans the pair of bead portions in a toroidal manner, and a belt disposed on the radially outer side of the crown portion of the carcass.

[0025] In the following description, tires are assumed to be filled with air and mounted on vehicles such as passenger cars. However, the inner cavity of a tire may be filled with a fluid other than air, and tires may be mounted on vehicles other than passenger cars.

[0026] Hereinafter, a tire 1 according to an embodiment of the present invention will be described with reference to the drawings.

[0027] (First embodiment) Figure 1 is a schematic unfolded view of the tread pattern of a tire 1 (1A) according to a first embodiment of the present invention. In Figure 1, a portion of the tread surface 2 of tire 1A is shown in an unfolded view from the radially outer side of the tire (unfolded view of the tread surface 2).

[0028] As shown in Figure 1, the tire 1A has one or more (four in the illustrated example) circumferential main grooves 3 (3A, 3B, 3C, 3D) extending in the circumferential direction of the tire on the tread surface 2, and a plurality of (five in the illustrated example) land areas 4 (4A, 4B, 4C, 4D, 4E) partitioned between adjacent circumferential main grooves 3 in the tire width direction, or by a circumferential main groove 3 (3A or 3D) and the tread edge TE. In this embodiment, the circumferential main grooves 3A and 3B are located in one half of the tire width direction with the tire equatorial plane CL as the boundary, and the other circumferential main grooves 3C and 3D are located in the other half of the tire width direction with the tire equatorial plane CL as the boundary. In this embodiment, one land area 4 (4C) is arranged on the tire equatorial plane CL, and two land areas 4 (4A and 4B, 4D and 4E) are arranged in each half of the tire width direction.

[0029] The number of circumferential main grooves 3 on tire 1A may be any number other than four. Depending on the number of circumferential main grooves 3, the number of land areas 4 on tire 1A may also be any number other than five. Furthermore, tire 1A may be configured so that the tread surface 2 does not have circumferential main grooves 3. In this case, tire 1A may have one land area 4 on the tread surface 2 that is partitioned between the two tread ends TE in the tire width direction.

[0030] In the illustrated example, all circumferential main grooves 3 extend along the circumferential direction of the tire. In this specification, "straight line X extends along the Y direction" means that straight line X extends parallel to the Y direction, or straight line X extends approximately parallel to the Y direction. "The direction of extension of straight line X is approximately parallel to the Y direction" means, for example, that the angle between the direction of extension of straight line X and the Y direction is in the range of 5 degrees or less. However, at least one circumferential main groove 3 may extend at an angle greater than 5 degrees with respect to the circumferential direction of the tire. In addition, in the illustrated example, all circumferential main grooves 3 extend linearly along the circumferential direction of the tire, but at least one circumferential main groove 3 may have a shape other than a straight line, such as a zigzag or curved shape, either overall or in part.

[0031] The width of the circumferential main groove 3 is not particularly limited as it depends on the number of circumferential main grooves 3, but may be, for example, 4 to 15 mm. The width of the circumferential main groove 3 is measured as the opening width perpendicular to the direction of groove extension when viewed from the outside of the tire radially in a planar view in the standard state. Similarly, the depth (maximum depth) of the circumferential main groove 3 is not particularly limited, but may be, for example, 6 to 20 mm. The width of the circumferential main groove 3 does not have to be constant along the direction of extension of the circumferential main groove 3, and may differ from one another depending on the position of the tread surface 2 on which the circumferential main groove 3 is provided.

[0032] In tire 1A, each land area 4 is divided into multiple block land areas 6 by one or more widthwise grooves 5 that extend in the tire width direction, completely crossing the land area 4.

[0033] In the illustrated example, the widthwise grooves 5 all extend in the tire width direction, completely traversing the land area 4. For example, within the illustrated area, the land area 4C is divided into three adjacent block land areas 6A, 6B, and 6C in the tire circumferential direction by two widthwise grooves 5A and 5B that are adjacent in the tire circumferential direction. In this specification, "a straight line X extends in the Y direction" means that the straight line X has at least a component in the Y direction. That is, "a straight line X extends in the Y direction" means that the straight line X may extend along the Y direction, or the straight line X may extend at a predetermined angle with respect to the Y direction. The widthwise grooves 5 may extend linearly in the tire circumferential direction, or they may extend in a shape other than a straight line, such as a zigzag or curved shape. The widthwise grooves 5 may extend along the tire width direction, or they may extend at an angle greater than 0° and less than 45° with respect to the tire width direction, as in the illustrated example.

[0034] The width (opening width) of the lateral groove 5 is not particularly limited as it depends on the number of lateral grooves 5, but may be, for example, 2 to 10 mm. The width of the lateral groove 5 is measured as the opening width perpendicular to the direction of groove extension when viewed from the outside of the tire radially in a planar view in the standard state. Similarly, the depth (maximum depth) of the lateral groove 5 is not particularly limited, but may be, for example, 5 to 20 mm. However, the width of the lateral groove 5 is not limited in any way as long as it is greater than or equal to the width that prevents adjacent block land portions 6 in the circumferential direction of the tire from contacting each other when in the standard state. Furthermore, the width of the lateral groove 5 does not have to be constant along the direction of extension of the lateral groove 5, and may differ from each other depending on the position of the land portion 4 on which the lateral groove 5 is provided.

[0035] The number of widthwise grooves 5 crossing each of the land sections 4 may be any number. Depending on the number of widthwise grooves 5, the number of block land sections 6 that the land section 4 has may also be any number. Furthermore, the land section 4 may be configured not to be crossed by widthwise grooves 5, that is, the land section 4 may be configured as a rib-shaped land section that is continuous without interruption in the circumferential direction.

[0036] The land section 4 is equipped with a sipe unit 8 consisting of a pair of sipes 7. More specifically, the block land section 6 included in the land section 4 has a sipe unit 8 consisting of a pair of sipes 7A and 7B. Hereafter, unless otherwise distinguished, sipes 7A and 7B will simply be referred to as sipes 7.

[0037] Each of the pair of sipes 7A and 7B constituting the sipe unit 8 extends such that both ends in the direction of extension of the sipe 7 terminate within the land portion 4. More specifically, each of the pair of sipes 7A and 7B extends such that both ends in the direction of extension of the sipe 7 terminate within the block land portion 6. In other words, the sipe 7 does not have an open end that opens into the circumferential main groove 3 or the widthwise groove 5 that demarcates the land portion 4. In this way, because the sipe 7 does not have an open end and the block land portion 6 around the sipe 7 is connected, the block land portion 6 is less likely to collapse around the sipe 7, and the rigidity of the block land portion 6 is improved.

[0038] Generally, as shown in Figure 2, when an external force such as friction is applied from the road surface to the contact surface of the tread tread 2 that is in contact with the road surface, the block land portion 6 collapses towards the gap of the sipe 7, causing the block land portion 6 around the sipe 7 to lift up from the road surface U. Figure 2 is a schematic diagram showing the lift up U of the block land portion 6 around the sipe 7. Figure 2 is shown as a circumferential cross-sectional view of the tire 1A, cut along the circumferential direction of the tire. When an external force is applied to the tire 1A in the direction indicated by the arrow in Figure 2, the block land portion 6 on the side of the sipe 7 to which the external force is applied will lift up. In contrast, because the block land portions 6 around the sipe 7 are connected, the block land portions 6 around the sipe 7 restrain each other, and the lift up U of the block land portion 6 around the sipe 7 from the road surface can be suppressed by the applied external force, and the contact area of ​​the tire 1A can be increased when an external force is applied. This prevents a decrease in the rigidity of the land portion of tire 1A caused by placing sipes 7 on the block land portion 6, and consequently prevents a decrease in the contact area of ​​tire 1A. As a result, the ice grip performance of tire 1A is improved.

[0039] Referring again to Figure 1, each of the pair of sipes 7A and 7B that make up the sipe unit 8 extends linearly and inclined with respect to the tire width direction, as shown in Figure 1, i.e., in an unfolded view of the tread surface 2.

[0040] The configuration of the sipe unit 8 will be described below with reference to Figures 3 and 4. Figure 3 is a schematic diagram showing the arrangement of the sipe unit 8 shown in Figure 1. Figure 4 is a cross-sectional view showing the A-A' section (a section perpendicular to the extension direction of the sipe 7) shown in Figure 3. In Figure 3, each of the pair of sipes 7A and 7B constituting the sipe unit 8 extends linearly such that the angle φ it makes with the tire width direction satisfies 0° < φ < 45°. In this way, because the sipes 7A and 7B are inclined with respect to the tire width direction, they can contribute not only to improving braking force and driving force in the tire circumferential direction, but also to improving lateral grip performance (turning force) in the tire width direction. In particular, by setting φ < 45°, the tire width direction component of the sipe 7 becomes larger than the tire circumferential component, allowing the sipe 7 to contribute to improving braking force and driving force in the tire circumferential direction, which is the most important aspect for safety. In this embodiment, the sipes 7A and 7B extend parallel to each other. However, sipes 7A and 7B may each extend at different angles relative to the tire width direction.

[0041] In Figure 3, the length of the sipe 7 in the extending direction is indicated by 'a'. The length 'a' of the sipe 7 in the extending direction is, for example, between 3 and 15 mm. Preferably, the length 'a' of the sipe 7 is between 3 and 10 mm, and more preferably between 3 and 5 mm. The length 'a' of the sipe 7 may also be determined according to the depth (maximum depth) h of the sipe 7. Specifically, the length 'a' of the sipe 7 is determined when the length d (d = a × cosφ) of the sipe 7 in the tire width direction and the depth h of the sipe 7 are d × h ≤ 150 mm. 2 The length a of the sipe 7 may be determined according to the depth h, within the range that satisfies the following conditions. Preferably, the length a of the sipe 7 is d × h ≤ 100 mm. 2 It is defined within the range that satisfies ferred × h ≤ 50 mm2 It is determined within the range that satisfies the following conditions. The depth h of sipe 7 is, for example, 3 mm or more. The depth h of sipe 7 may be, for example, 6.7 mm.

[0042] Referring to Figure 4, the cross-sectional shape perpendicular to the extension direction of the sipe 7 on the tread surface 2 will be described. In this embodiment, as shown in Figure 4(a), the cross-section perpendicular to the extension direction of the sipe 7 is approximately rectangular. In the sipe 7 shown in Figure 4(a), the width w of the sipe 7 is 1 mm or less, as described above, and may be, for example, 0.4 mm. However, the cross-section perpendicular to the extension direction of the sipe 7 may be a shape other than rectangular. For example, as shown in Figure 4(b), the sipe 7 may have a shape in which the groove bottom portion is bulging in the cross-section perpendicular to the extension direction of the sipe 7. Alternatively, for example, the sipe 7 may have a shape in which the groove bottom portion is rounded in the cross-section perpendicular to the extension direction of the sipe 7. For example, in the cross-section perpendicular to the extension direction of the sipe 7 shown in Figure 4(a), both ends of the groove bottom portion in the width direction of the sipe 7 may be chamfered, or the groove bottom portion may be semicircular. In the sipe 7 shown in Figure 4(b), the width w of the sipe 7 may be, for example, 0.4 mm in a region of 50% or more of the depth of the sipe 7.

[0043] Referring again to Figure 3, sipe 7B is positioned offset from sipe 7A by an offset s in the tire width direction and an offset q in the tire circumferential direction. The offset s in the tire width direction of sipes 7A and 7B may be determined, for example, within a range that satisfies s ≥ 1.5 mm.

[0044] The pair of sipes 7A and 7B constituting the sipe unit 8 face each other in the tire circumferential direction, but only in the tire width direction. Here, "line segments X and Y face each other in the Z direction" means that line segments X and Y are separated from each other in the Z direction, and that the ends of line segment Y are located on two straight lines extending from both ends of line segment X along the Z direction. However, "sipes 7A and 7B face each other in the tire circumferential direction, but only in the tire width direction" also includes the case where only the endpoints of sipes 7A and 7B are located on a straight line extending along the tire circumferential direction. In this embodiment, sipes 7A and 7B are offset by s in the tire width direction. In Figure 3, a portion 7a of sipe 7A in the tire width direction and a portion 7b of sipe 7B in the tire width direction face each other in the tire circumferential direction. At this time, the length d (d=a×cosφ) of each sipe 7A and 7B in the tire width direction, and the offset s of sipes 7A and 7B in the tire width direction satisfy ds≧0. As a result, as shown by the shaded area in Figure 3, when the pair of sipes 7A and 7B included in the sipe unit 8 are projected along the tire circumferential direction, at least one of sipes 7A and 7B extends seamlessly across the tire width direction of the sipe unit 8. Therefore, by widening the length of the sipe unit 8 in the tire width direction within the range where ds≧0 is satisfied, without changing the length of each sipe 7 constituting the sipe unit 8, it is possible to widen the range in which the sipe unit 8 can exert edge effect and water removal effect while maintaining the sipe density in the block land portion 6. This improves the ice grip performance of tire 1A.

[0045] Referring again to Figure 1, in the land portion 4, multiple sipe units 8 are spaced apart from each other and arranged repeatedly in the circumferential direction of the tire to form a sipe unit row 9. In the illustrated example, in one block land portion 6, three sipe units 8 are arranged repeatedly in the circumferential direction of the tire to form a sipe unit row 9. However, the number of sipe units 8 constituting one sipe unit row 9 may be any number of two or more.

[0046] In Figure 3, the multiple sipe units 8 constituting the sipe unit row 9 are arranged repeatedly at a pitch p in the circumferential direction of the tire. In this embodiment, the multiple sipes 7 arranged on the block land portion 6 extend substantially parallel to each other in an unfolded view of the tread surface 2. Here, if the distance in the circumferential direction of the tire between adjacent sipe units 8 in the sipe unit row 9 is denoted as the inter-unit distance r, then the inter-unit distance r is given by r = pq. In particular, when the pitch p of the sipe units 8 constituting the sipe unit row 9 and the circumferential offset q of the sipes constituting the sipe unit 8 are q = p / 2, then r = q, and all the sipes 7 included in the sipe unit row 9 are arranged at equal intervals in the circumferential direction of the tire. For this reason, it is preferable to set q in the range of (p / 2) × 0.8 to (p / 2) × 1.2, and more preferably to set q to p / 2, thereby making the sipe density in the circumferential direction of the tire on the block land portion 6 uniform. This allows the tread surface 2 to contact the road surface more uniformly, equalizing the distribution of contact pressure applied to the contact surface of the tread surface 2, and increasing the contact area of ​​the tire 1A.

[0047] It is preferable that the multiple sipe units 8 constituting the sipe unit row 9 are arranged such that both ends in the tire width direction are aligned in a straight line extending along the tire circumferential direction. Specifically, in Figure 3, both ends E1 and E2 in the tire width direction of the multiple sipe units 8 constituting the sipe unit row 9 are aligned in a straight line extending along the tire circumferential direction. This reduces the amount of blank area (area enclosed by dashed lines in the figure) where sipes 7 are not provided within the area of ​​the block land portion 6 where the sipe unit row 9 is located. For comparison, Figure 5 shows a different arrangement of sipe units 8 than in Figure 3. In Figure 5, the both ends in the tire width direction of each of the multiple sipe units 8 constituting the sipe unit row 9 are not aligned in a straight line extending along the tire circumferential direction. Comparing Figure 3 and Figure 5, the area enclosed by dashed lines in Figure 3 is smaller than the area enclosed by dashed lines in Figure 5. In this way, by arranging the ends of the multiple sipe units 8 constituting the sipe unit row 9 in the tire width direction along a straight line extending in the tire circumferential direction, the amount of blank area where sipes 7 are not provided within the area of ​​the block land portion 6 where the sipe unit row 9 is located can be reduced. However, the arrangement of the sipe units 8 may be as shown in Figure 5.

[0048] Referring again to Figure 1, the land section 4 comprises multiple rows of sipe units 9 arranged in the tire width direction. In the illustrated example, in the land sections 4A and 4E of the block land section 6, two rows of sipe units 9 are arranged in the tire width direction. In addition, in the land sections 4B, 4C, and 4D of the block land section 6, four rows of sipe units 9 are arranged in the tire width direction. However, the number of rows of sipe units 9 arranged in a single block land section 6 may be any number.

[0049] The arrangement of the multiple sipe unit rows 9 in the first embodiment will now be described with reference to Figure 6. Figure 6 is a schematic diagram showing the arrangement of the multiple sipe unit rows 9 in the first embodiment. In Figure 6, two sipe unit rows 9A and 9B are arranged side by side in the tire width direction.

[0050] In the first embodiment shown in Figure 6, the multiple sipes 7 included in two adjacent sipe unit rows 9A and 9B in the tire width direction extend between sipe unit rows 9A and 9B, inclined in the same direction with respect to the tire width direction. Specifically, the multiple sipes 7 included in the first sipe unit row 9A extend inclined so that they move toward one side in the tire width direction (right side in the drawing) toward one side in the tire circumferential direction (upward side in the drawing). Furthermore, the multiple sipes 7 included in the second sipe unit row 9B adjacent to the first sipe unit row 9A extend inclined so that they move toward one side in the tire width direction (right side in the drawing) toward one side in the tire circumferential direction (upward side in the drawing), similar to the multiple sipes 7 included in the first sipe unit row 9A.

[0051] In this way, multiple sipes 7 included in multiple adjacent sipe unit rows 9 in the tire width direction are arranged to extend in the same direction between the sipe unit rows 9, making it easier to position the blades for forming the sipes 7 in the mold during tire manufacturing, and thus simplifying the production of the mold for tire 1A.

[0052] In Figure 6, the distance between adjacent sipe unit rows 9A and 9B in the tire width direction is shown by v. The offset in the tire circumferential direction between adjacent sipe unit rows 9A and 9B in the tire width direction is shown by u. The distance v in the tire width direction and the offset u in the tire circumferential direction may be set to any arbitrary value.

[0053] The tire widthwise spacing v is preferably -s ~ s (s > 0). Here, s is the offset in the tire widthwise direction between a pair of sipes 7 that constitute the sipe unit 8. Note that a positive value for the tire widthwise spacing v means that, as shown in Figure 6, the area between the ends of sipe unit row 9A in the tire widthwise direction and the area between the ends of sipe unit row 9B adjacent to sipe unit row 9A in the tire widthwise direction are separated by a spacing v in the tire widthwise direction. On the other hand, a negative value for the tire widthwise spacing v means that the area between the ends of sipe unit row 9A in the tire widthwise direction and the area between the ends of sipe unit row 9B adjacent to sipe unit row 9A in the tire widthwise direction overlap by the absolute value of the spacing v in the tire widthwise direction. By defining the tire widthwise spacing v in this way, the amount of blank area (the area enclosed by the dashed line in the figure) where sipes 7 are not provided within the range of the block land portion 6 where adjacent sipe unit rows 9A and 9B are located in the tire widthwise direction is reduced.

[0054] More preferably, the spacing v in the tire width direction is set to 0, and the tire circumferential offset u is (d+s)×tanφ. Here, φ is the angle between each of the pair of sipes 7 constituting the sipe unit 8 and the tire width direction, d is the length of the sipe 7 in the tire width direction, and s is the offset in the tire width direction between the pair of sipes 7 constituting the sipe unit 8. Figure 7 shows a schematic diagram of the arrangement of the sipe unit row 9 when the spacing v in the tire width direction is 0 and the tire circumferential offset u is (d+s)×tanφ.

[0055] By setting the tire widthwise spacing v to 0, as shown by the shaded area in Figure 7, when multiple sipes 7 arranged in the tire widthwise direction are projected along the tire circumferential direction, the tire widthwise components of the multiple sipes 7 are arranged continuously without gaps in the tire widthwise direction. This allows the sipes 7 to be evenly distributed without gaps across multiple sipe unit rows 9, improving the edge effect and water removal effect on the block land portion 6. Furthermore, because the sipes 7 are evenly distributed without gaps across multiple sipe unit rows 9, the sipe density on the block land portion 6 can be made uniform. As a result, the tread surface 2 can be made to contact the road surface more uniformly, and the distribution of ground pressure applied to the contact surface of the tread surface 2 can be made uniform, thereby increasing the contact area of ​​the tire 1A.

[0056] In Figure 7, each of the multiple sipes 7 included in the second sipe unit row 9B extends along the extension of any of the sipes 7 included in the first sipe unit row 9A. As a result, in the block land portion 6, the multiple sipes 7 are arranged in a straight line in the tire width direction. Therefore, preferably, by setting u in the range of ((d+s)×tanφ)×0.8 to ((d+s)×tanφ)×1.2, and more preferably u to (d+s)×tanφ, water taken into the voids of the sipes 7 is drained in the tire width direction along the multiple sipes 7 arranged in a straight line, thereby improving the ice grip performance in the land portion 4. Furthermore, since the multiple sipes 7 included in adjacent sipe unit rows 9A and 9B are arranged in the same straight line, it becomes easier to manufacture the mold on which the blades for forming the sipes 7 are arranged.

[0057] Referring again to Figure 1, each of the land blocks 6 in land sections 4A and 4E has 12 sipes 7, and each of the land blocks 6 in land sections 4B, 4C, and 4D has 24 sipes 7. However, the number of sipes 7 placed in a single land block 6 may be any number.

[0058] For example, the number of sipes 7 placed on the block land portion 6 may be determined based on the sipe density SD in the tire circumferential direction. The sipe density SD in the tire circumferential direction is an index that represents the density at which transverse sipes, which are provided to completely cross the block land portion 6, are arranged in the tire circumferential direction. Outer contour area of ​​block land portion 6 (mm 2 If we let BL (mm) be the equivalent tire circumferential length of the block land portion 6 obtained by dividing ) by the maximum width BW, and let N' be the number of transverse sipes that completely cross the block land portion 6, then the average sipe spacing in the tire circumferential direction is expressed as BL / (N'+1). The sipe density SD in the tire circumferential direction is expressed by the following equation (1) as the reciprocal of the average sipe spacing. SD = (N'+1) / BL (1)

[0059] The "outer contour area" of the block's land portion 6 refers to the area enclosed by the outer contour of the block's land portion 6 when viewed in an unfolded view of the tread surface 2. Therefore, even if non-contact areas such as sipes, small holes, or narrow grooves are located within the block's land portion 6, this area does not exclude the area of ​​those sipes, small holes, or narrow grooves.

[0060] The following describes how to calculate the sipe density SD in this embodiment. For example, assume that multiple sipes 7 are provided on the rhombus-shaped block land portion 6, as shown in the sipe shape diagram of Figure 14. First, let n be the number of sipes 7 within the block land portion 6, let d (mm) be the length of the sipes 7 in the tire width direction, and let BW (mm) be the maximum width of the block land portion 6 in the tire width direction. Then the equivalent number of sipes N is expressed as d × n / BW. Here, the equivalent number of sipes N is the number obtained when the sipes 7 of this embodiment are converted into transverse sipes (equivalent sipes) that completely cross the block land portion 6. Furthermore, if BL (mm) is the equivalent tire circumferential length of the block land portion 6, then the average sipe spacing in the tire circumferential direction is expressed as BL / (N+1). Here, the average sipe spacing in the tire circumferential direction is the spacing of the equivalent sipes in the tire circumferential direction on the block land portion 6 when the sipes 7 of this embodiment are converted into equivalent sipes. The sipe density SD in the circumferential direction of the tire is expressed by the following equation (2) as the reciprocal of the average sipe spacing. SD=(N+1) / BL=((d×n / BW)+1) / BL (2)

[0061] The number of sipes 7 within the block 6 (n), the length of the sipes 7 in the tire width direction (d), the maximum width of the block 6 in the tire width direction (BW), and the outer contour area of ​​the block 6 are values ​​measured from an unfolded view of the tread surface 2.

[0062] For example, the block's land portion 6 may have multiple sipes 7 arranged such that the sipe density SD is 0.15 (1 / mm) or more. This can improve the ice grip performance of the tire 1A.

[0063] Multiple sipes 7 may be connected by shallow grooves 10 in the block land portion 6. Figure 8 is a schematic diagram showing the arrangement of a sipe unit 8 in which sipes 7 are connected by shallow grooves 10 in the first embodiment. The block land portion 6 shown in Figure 8 corresponds, for example, to the block land portion 6B of tire 1A shown in Figure 1. In Figure 8, four rows of sipe unit 9 are arranged in the tire width direction in the block land portion 6. Three sipe units 8 are repeatedly arranged in the tire circumferential direction in the sipe unit row 9. In Figure 8, sipes 7 arranged in a straight line in the tire width direction are connected by shallow grooves 10 that completely cross the block land portion 6. In Figure 8, a cross-section (B-B' section) of tire 1A cut along the extending direction of the shallow groove 10 is shown in Figure 9. In Figure 9, the depth (maximum depth) H of the shallow groove 10 may be determined according to the depth h of the sipes 7. For example, the depth H of the shallow groove 10 may be set in the range of 5 to 60% of the depth h of the sipe 7, preferably in the range of 5 to 20%. For example, the depth h of the sipe 7 may be 6.7 mm and the depth H of the shallow groove 10 may be 0.7 mm. With this configuration, water taken into the voids of the sipe 7 is drained through the shallow groove 10 in the tire width direction, thereby improving the ice grip performance of the block land portion 6.

[0064] Referring again to Figure 1, the block land portion 6 of tire 1A may be provided with sipes other than the sipe unit 8 described above. For example, in the illustrated example, multiple zigzag sipes 11 are provided on land portions 4A and 4E, extending in the tire width direction toward the tread edge TE. This improves drainage on the tread surface 2 and improves the ice grip performance of tire 1A.

[0065] (Second embodiment) Hereinafter, a second embodiment of the present invention, tire 1(1B), will be described with reference to Figure 10. Figure 10 is a schematic unfolded view showing the tread pattern of tire 1B according to the second embodiment of the present invention. Hereinafter, when tires 1A and 1B are not specifically distinguished, they will simply be referred to as tire 1.

[0066] As shown in Figure 10, the second embodiment differs from the first embodiment in that multiple sipes 7 included in two adjacent sipe unit rows 9 in the tire width direction are arranged to extend in different directions between the sipe unit rows 9. The second embodiment will be described below, focusing on the differences from the first embodiment. Note that parts having the same configuration as in the first embodiment are denoted by the same reference numerals.

[0067] Similar to the first embodiment, the tire 1B has one or more (four in the illustrated example) circumferential main grooves 3 (3A, 3B, 3C, 3D) extending in the circumferential direction of the tire on the tread surface 2, and a plurality of (five in the illustrated example) land areas 4 (4A, 4B, 4C, 4D, 4E) partitioned between adjacent circumferential main grooves 3 in the tire width direction, or by a circumferential main groove 3 (3A or 3D) and the tread edge TE.

[0068] In tire 1B, similar to the first embodiment, each land area 4 is divided into multiple block land areas 6 by one or more widthwise grooves 5 that extend across the entire land area 4 in the tire width direction. For example, within the shown area, land area 4C is divided into three block land areas 6A, 6B, and 6C adjacent in the tire circumferential direction by two widthwise grooves 5A and 5B adjacent in the tire circumferential direction.

[0069] The land section 4, as in the first embodiment, includes a sipe unit 8 composed of a pair of sipes 7. More specifically, the block land section 6 included in the land section 4 has a sipe unit 8 composed of a pair of sipes 7A and 7B.

[0070] Each of the pair of sipes 7A and 7B constituting the sipe unit 8 extends such that both ends in the direction of extension of the sipe 7 terminate within the land portion 4, similar to the first embodiment. More specifically, each of the pair of sipes 7A and 7B extends such that both ends in the direction of extension of the sipe 7 terminate within the block land portion 6.

[0071] Each of the pair of sipes 7A and 7B constituting the sipe unit 8 extends linearly and inclined with respect to the tire width direction when viewed in an unfolded view of the tread surface 2, similar to the first embodiment. Each of the pair of sipes 7A and 7B constituting the sipe unit 8 extends linearly such that the angle φ it makes with the tire width direction satisfies 0° < φ < 45°.

[0072] Similar to the first embodiment, the pair of sipes 7A and 7B constituting the sipe unit 8 face each other only in the tire width direction in the tire circumferential direction.

[0073] In the land portion 4, multiple sipe units 8 are arranged repeatedly in the tire circumferential direction, similar to the first embodiment, to form a sipe unit row 9. In the illustrated example, in one block land portion 6, three sipe units 8 are arranged repeatedly in the tire circumferential direction to form a sipe unit row 9. Preferably, the multiple sipe units 8 constituting the sipe unit row 9 are arranged such that both ends in the tire width direction are aligned in a straight line extending along the tire circumferential direction.

[0074] In the land section 4, multiple rows of sipe units 9 are arranged in the tire width direction. In the illustrated example, in the land sections 4A and 4E of the block land section 6, two rows of sipe units 9 are arranged in the tire width direction. In addition, in the land sections 4B, 4C, and 4D of the block land section 6, four rows of sipe units 9 are arranged in the tire width direction.

[0075] The arrangement of the multiple sipe unit rows 9 in the second embodiment will now be described with reference to Figure 11. Figure 11 is a schematic diagram showing the arrangement of the multiple sipe unit rows 9 in the second embodiment. In Figure 11, two sipe unit rows 9A and 9B are arranged side by side in the tire width direction.

[0076] In the second embodiment shown in Figure 11, unlike the first embodiment, the multiple sipes 7 included in two adjacent sipe unit rows 9A and 9B in the tire width direction extend between sipe unit rows 9A and 9B at different inclinations with respect to the tire width direction. Specifically, the multiple sipes 7 included in the first sipe unit row 9A of the multiple sipe unit rows 9A and 9B extend at an inclination toward one direction in the tire circumferential direction (upward in the drawing) as you move toward one side in the tire width direction (right side in the drawing). On the other hand, the multiple sipes 7 included in the second sipe unit row 9B adjacent to the first sipe unit row 9A extend at an inclination toward the other side in the tire circumferential direction (downward in the drawing) as you move toward one side in the tire width direction (right side in the drawing).

[0077] The arrangement of the sipe unit rows 9 in this manner makes it less likely for the tire 1B to collapse when an external force is applied to it, as the block land portion 6 in the area where adjacent sipe unit rows 9A and 9B are located support each other. For example, when an external force is applied in the direction indicated by the arrow in Figure 11, the block land portion 6 around the sipe 7 included in sipe unit row 9A collapses downward to the right in the drawing. On the other hand, the block land portion 6 around the sipe 7 included in sipe unit row 9B collapses downward to the left in the drawing. In this way, when an external force is applied to the tire 1B, the block land portion 6 in the area where adjacent sipe unit rows 9A and 9B are located in the tire width direction tilt and collapse in different directions in the tire width direction, but they support each other, making it less likely for the tire to collapse. As a result, the rigidity of the block land portion 6 is increased. Furthermore, when an external force is applied to the tread surface 2 in the circumferential direction of the tire, the components of the external force applied to the block land portion 6 around the sipe unit rows 9A and 9B cancel each other out, thereby suppressing the application of unexpected forces in the tire width direction to the tire 1B and minimizing any impact on the handling stability of the vehicle on which the tire 1B is mounted.

[0078] In Figure 11, the length of the sipe 7 in the extending direction is shown as a, and the angle between the sipe 7 and the tire width direction is shown as φ. In this embodiment, the multiple sipes 7 included in one sipe unit row 9 extend substantially parallel to each other in an unfolded view of the tread surface 2. In the sipe unit 8, a pair of sipes 7A and 7B are positioned offset from each other by an offset s in the tire width direction and an offset q in the tire circumferential direction. Furthermore, the multiple sipe units 8 constituting the sipe unit row 9 are arranged repeatedly at a pitch p in the tire circumferential direction. Here, if the distance between adjacent sipe units 8 in the tire circumferential direction in the sipe unit row 9 is denoted as the inter-unit distance r, then the inter-unit distance r is given by r = pq.

[0079] In particular, when the pitch p of the sipe units 8 constituting the sipe unit row 9 and the offset q of the sipes constituting the sipe unit 8 in the tire circumferential direction are q = p / 2, then r = q, and all the sipes 7 included in the sipe unit row 9 are arranged at equal intervals in the tire circumferential direction. For this reason, it is preferable to set q in the range of (p / 2) × 0.8 to (p / 2) × 1.2, and more preferably to set q to p / 2, which makes it possible to equalize the sipe density in the tire circumferential direction in the block land portion 6. As a result, the tread surface 2 can be made to contact the road surface more uniformly, the distribution of ground pressure applied to the contact surface of the tread surface 2 can be equalized, and the contact area of ​​the tire 1B can be increased.

[0080] In Figure 11, the distance between adjacent sipe unit rows 9A and 9B in the tire width direction is indicated by v. The offset in the tire circumferential direction between adjacent sipe unit rows 9A and 9B in the tire width direction is indicated by u.

[0081] The tire widthwise spacing v is preferably -s ~ s (s > 0). Here, s is the offset in the tire widthwise direction between a pair of sipes 7 of the sipe unit 8 that constitute the sipe unit row 9. Note that a positive value for the tire widthwise spacing v means that, as shown in Figure 11, the area between the ends of sipe unit row 9A in the tire widthwise direction and the area between the ends of sipe unit row 9B adjacent to sipe unit row 9A in the tire widthwise direction are separated by a spacing v in the tire widthwise direction. On the other hand, a negative value for the tire widthwise spacing v means that the area between the ends of sipe unit row 9A in the tire widthwise direction and the area between the ends of sipe unit row 9B adjacent to sipe unit row 9A in the tire widthwise direction overlap by the absolute value of the spacing v in the tire widthwise direction. By defining the tire widthwise spacing v in this way, the amount of blank area (the area enclosed by the dashed line in the figure) where sipes 7 are not provided within the range of the block land portion 6 where adjacent sipe unit rows 9A and 9B are located in the tire widthwise direction is reduced.

[0082] More preferably, the spacing v in the tire width direction is set to 0, and the tire circumferential offset u is (d+s)×tanφ. Here, φ is the angle between each of the pair of sipes 7 constituting the sipe unit 8 and the tire width direction, d is the length of the sipe 7 in the tire width direction, and s is the offset in the tire width direction between the pair of sipes 7 constituting the sipe unit 8. Figure 12 shows a schematic diagram of the arrangement of the sipe unit row 9 when the spacing v in the tire width direction is 0 and the tire circumferential offset u is (d+s)×tanφ.

[0083] By setting the tire widthwise spacing v to 0, as shown by the shaded area in Figure 12, when multiple sipes 7 arranged in the tire widthwise direction are projected along the tire circumferential direction, the tire widthwise components of the multiple sipes 7 are arranged continuously without gaps in the tire widthwise direction. This allows the sipes 7 to be evenly distributed without gaps across multiple sipe unit rows 9, improving the edge effect and water removal effect on the block land area 6. Furthermore, because the sipes 7 are evenly distributed without gaps across multiple sipe unit rows 9, the sipe density on the block land area 6 can be made uniform. As a result, the tread surface 2 can be made to contact the road surface more uniformly, and the distribution of ground pressure applied to the contact surface of the tread surface 2 can be made uniform, thereby increasing the contact area of ​​the tire 1B.

[0084] In Figure 12, each of the multiple sipes 7 included in the second sipe unit row 9B extends so as to intersect with the extension line along the direction of extension of any of the sipes 7 included in the first sipe unit row 9A. Therefore, when water taken into the void of one sipe 7 is drained from the sipe 7 along the direction of extension of the sipe 7, it is taken back into the other sipes 7 that extend so as to intersect with the extension line of the sipe 7, thus preventing a decrease in ice grip performance on the land portion 4.

[0085] In tire 1B, the number of sipes 7 arranged on the block land portion 6 may be determined based on the sipe density SD as described above in the first embodiment. For example, multiple sipes 7 may be arranged on the block land portion 6 such that the sipe density SD is 0.15 (1 / mm) or more. This suppresses the reduction in rigidity of the block land portion 6 of tire 1B caused by the arrangement of sipes 7 on the block land portion 6, and consequently suppresses the reduction in the contact area of ​​tire 1B. As a result, the ice grip performance of tire 1B can be improved.

[0086] In tire 1B, as in the first embodiment, multiple sipes 7 on the block land portion 6 may be connected by shallow grooves 10 that cross the block land portion 6 in the tire width direction. Figure 13 is a schematic diagram showing the arrangement of sipe units 8 in which sipes 7 are connected by shallow grooves 10 in the second embodiment. The block land portion 6 shown in Figure 13 corresponds, for example, to the block land portion 6B of tire 1B shown in Figure 10. In Figure 13, four rows of sipe unit rows 9 are arranged in the tire width direction on the block land portion 6. In the sipe unit row 9, three sipe units 8 are repeatedly arranged in the tire circumferential direction. Each of the sipes 7 (for example, 7A in Figure 13) is connected to a sipe 7 (7C in Figure 13) whose one end is located on the extension line along the direction of extension of sipe 7 (7A) by a shallow groove 10 that completely crosses the block land portion 6. In other words, in tire 1B, multiple sipes 7 in the block land portion 6 are connected by zigzag shallow grooves 10 that cross the block land portion 6 in the tire width direction. The depth H of the shallow grooves 10 may be determined according to the depth h of the sipes 7, as in the first embodiment. With this configuration, water taken into the gaps of the sipes 7 is drained in the tire width direction through the shallow grooves 10, thereby improving the ice grip performance of the block land portion 6. [Examples]

[0087] Below, an embodiment of tire 1 according to one embodiment of the present invention will be described with reference to Figures 14 and 15. Figure 14 is a table showing the examples and comparative examples. Figure 15 is a diagram showing the block stiffness and contact area in the examples and comparative examples shown in Figure 14.

[0088] Finite element method (FEM) simulations were performed on the tires of Examples 1-2 and Comparative Examples 1-3 shown in Figure 14. Block stiffness and contact area were evaluated under conditions where a vertical load was applied, calculated by multiplying the outer contour area of ​​the block's land area by the standard contact pressure of a passenger car tire, which is 230 kPa. In Examples 1-2 and Comparative Examples 1-3, the evaluation was performed assuming that the sipes shown in the sipe shape diagram in Figure 14 were placed on a rhomboid block land area with a length of 45.6 mm in the circumferential direction and a length of 27 mm in the tire width direction.

[0089] As a result, as shown in Figure 15, the embodiment showed improved block stiffness Kx (N / mm) and actual contact area Ar (mm) during shear compared to the comparative example with the same sipe density. 2 The results showed improvement in both aspects. For example, in Comparative Example 2, Kx increased by 11% and Kx increased by 23% compared to Example 2. Here, block stiffness Kx (N / mm) is the shear input value in the same direction when the lateral displacement in the circumferential direction of the tire is 1 mm, and the actual contact area Ar (mm) during shear is also shown. 2 ) is the remaining contact area when partial lift occurs, where the shear input in the circumferential direction of the tire is 0.3 times the above-mentioned vertical load. Thus, in the tire 1 according to one embodiment of the present invention, ice grip performance can be improved by achieving both sipe density and land rigidity (in other words, improving land rigidity while maintaining sipe density, or increasing sipe density while maintaining land rigidity).

[0090] From the above, it has become clear that the tire 1 according to one embodiment of the present invention improves the ice grip performance of the tire 1.

[0091] As described above, each embodiment of the present invention provides a tire 1 having a land portion 4 (block land portion 6) on the tread surface 2, wherein the land portion 4 (block land portion 6) is equipped with a sipe unit 8 composed of a pair of sipes 7, each of the pair of sipes 7 extending such that both ends in the direction of extension of the sipe 7 terminate within the land portion 4 (block land portion 6), and only a portion of each pair of sipes 7 in the tire width direction faces each other in the tire circumferential direction. With this configuration, the reduction in rigidity of the land portion 4 (block land portion 6) of the tire 1 due to the arrangement of sipes 7 on the land portion 4 (block land portion 6) can be suppressed, and consequently, the reduction in the contact area of ​​the tire 1 can be suppressed. Furthermore, while maintaining the sipe density in the land portion 4 (block land portion 6), the range in which the sipes 7 can exert edge effect and water removal effect can be widened. As a result, the ice grip performance of the tire 1 can be improved.

[0092] In each embodiment of the present invention, it is preferable that each of the pair of sipes 7 extends linearly such that the angle φ it makes with the tire width direction satisfies 0° < φ < 45°. With this configuration, the sipes 7 can contribute not only to improving braking force and driving force in the tire circumferential direction, but also to improving lateral grip performance (turning force) in the tire width direction.

[0093] In each embodiment of the present invention, in the land portion 4 (block land portion 6), a plurality of sipe units 8 are arranged repeatedly in the circumferential direction of the tire to form a sipe unit row 9, and it is preferable that the plurality of sipe units 8 constituting the sipe unit row 9 are arranged such that both ends in the tire width direction are aligned in a straight line extending along the circumferential direction of the tire. With this configuration, the area of ​​the land portion 4 (block land portion 6) where the sipe unit row 9 is arranged can be reduced to minimize the blank area where sipes 7 are not provided.

[0094] In the tire 1A according to the first embodiment of the present invention, the land portion 4 (block land portion 6) comprises a plurality of rows of sipe units 9 arranged in the tire width direction, and it is preferable that a plurality of sipes 7 included in the first row of sipe units 9A of the plurality of rows of sipe units 9 extend inclined toward one side in the tire circumferential direction as it moves toward one side in the tire width direction, and a plurality of sipes 7 included in the second row of sipe units 9B adjacent to the first row of sipe units 9A extend inclined toward one side in the tire circumferential direction as it moves toward one side in the tire width direction. With this configuration, it becomes easier to position the blade for forming the sipes 7 in the mold during tire manufacturing, and the production of the mold for tire 1A becomes easier.

[0095] In the tire 1A according to the first embodiment of the present invention, it is preferable that each of the plurality of sipes 7 included in the second sipe unit row 9B extends along the extension of any of the sipes 7 included in the first sipe unit row 9A. With this configuration, water taken into the gaps of the sipes 7 is drained in the tire width direction along the plurality of sipes 7 arranged in a straight line, thereby further improving the ice grip performance of the tire 1A.

[0096] In the tire 1B according to the second embodiment of the present invention, the land portion 4 (block land portion 6) includes a plurality of sipe unit rows 9 arranged side by side in the tire width direction. Among the plurality of sipe unit rows 9, the plurality of sip es 7 included in the first sipe unit row 9A extend inclined so as to face one side in the tire circumferential direction as they face one side in the tire width direction. It is preferable that the plurality of sip es 7 included in the second sipe unit row 9B adjacent to the first sipe unit row 9A extend inclined so as to face the other side in the tire circumferential direction as they face one side in the tire width direction. According to such a configuration, when an external force is input to the tire 1B, the land portions 4 (block land portions 6) in the range where the adjacent sipe unit rows 9 are arranged support each other, making it difficult to collapse. For this reason, the rigidity of the land portion 4 (block land portion 6) increases, and as a result, the ground contact area of the tire 1B can be increased. Thereby, the ice grip performance of the tire 1B can be further improved.

[0097] In the tire 1 according to each embodiment of the present invention, when the length of the sipe 7 in the tire width direction is d (mm) and the depth of the sipe 7 is h (mm), d×h is 150 (mm 2 ) or less. Let the number of sip es 7 in the land portion 4 (block land portion 6) be n, the maximum width of the land portion 4 (block land portion 6) in the tire width direction be BW (mm), and the outer contour area of the land portion 4 (block land portion 6) (mm 2 ) divided by the maximum width BW, the equivalent tire circumferential length of the land portion 4 (block land portion 6) be BL (mm). Let the equivalent sipe number N be expressed as d×n / BW, the average sipe interval in the tire circumferential direction be expressed as BL / (N + 1), and when the sipe density SD in the tire circumferential direction is expressed as the reciprocal of the average sipe interval, SD=(N + 1) / BL = ((d×n / BW)+1) / BL, it is preferable that SD is 0.15 (1 / mm) or more. According to such a configuration, it is possible to increase the sipe density while suppressing a decrease in the rigidity of the land portion 4 (block land portion 6) of the tire 1 due to the arrangement of the sip es 7 in the land portion 4 (block land portion 6). Thereby, the ice grip performance of the tire 1 can be improved.

[0098] The present invention has been described based on the drawings and embodiments, but it should be noted that those skilled in the art can make various modifications and alterations based on the present invention. Therefore, it should be noted that these modifications and alterations are within the scope of the present invention. For example, the configurations or functions included in each embodiment can be rearranged in a way that is not logically contradictory. Furthermore, the configurations or functions included in each embodiment can be used in combination with other embodiments, and multiple configurations or functions can be combined into one, divided, or partially omitted. [Explanation of Symbols]

[0099] 1(1A, 1B): Tire, 2: Tread surface, 3(3A, 3B, 3C, 3D): Circumferential main groove, 4(4A, 4B, 4C, 4D, 4E): Land area, 5(5A, 5B): Width direction groove, 6(6A, 6B, 6C): Block land area, 7(7A, 7B, 7C): Sipe, 7a, 7b: Part of sipe, 8: Sipe unit, 9(9A, 9B): Row of sipe unit, 10: Shallow groove, a: Sipe length, h: Sipe depth, w: Sipe width, d: Sipe length in the tire width direction, s: Offset in the tire width direction, q: Offset in the tire circumferential direction, φ: Angle between sipe and tire width direction, p: Unit pitch in the tire circumferential direction, r: Distance between units in the tire circumferential direction, v: Spacing in the tire width direction between adjacent rows of sipe units u: Offset in the tire circumferential direction between adjacent sipe unit rows in the tire width direction, SD: Sipe density, N: Equivalent number of sipes, BW: Maximum width in the tire width direction of the block's land portion, BL: Equivalent circumferential length of the block's land portion, A-A', B-B': Cross-section, E1, E2: Ends of sipe units in the tire width direction, TE: Tread edge, CL: Tire equatorial plane, Ar: Actual contact area under shear, Kx: Block stiffness, H: Depth of shallow groove, U: Lift

Claims

1. A pneumatic tire having a tread surface with one or more circumferential main grooves formed along the circumferential direction of the tire, where the space between adjacent circumferential main grooves, or the space between the tread edge and the adjacent circumferential main groove, functions as a land area. The aforementioned land portion has a block land portion located between two widthwise grooves that completely traverse the land portion in the tire width direction, The aforementioned block land portion has a sipe unit composed of a pair of sipes, Both of the pair of sipes are formed in a straight line, and both are positioned so that both ends terminate within the block land portion. The pair of sipes are such that only a portion of each other in the tire width direction faces the other in the tire circumferential direction. The aforementioned block land portion comprises a plurality of rows of sipe units arranged in the tire width direction, Each of the plurality of sipe unit rows includes a plurality of sipe units arranged repeatedly in the circumferential direction of the tire, A tire in which the spacing between adjacent rows of sipe units in the tire width direction is 0 or greater than 0.

2. The tire according to claim 1, wherein each of the pair of sipes is arranged linearly such that the angle φ it makes with the tire width direction satisfies 0° < φ < 45°.

3. The tire according to claim 1 or 2, wherein each of the plurality of sipe units included in each of the plurality of rows of sipe units is arranged such that both ends in the tire width direction are aligned in a straight line along the tire circumferential direction.

4. Among the multiple rows of sipe units, the multiple sipes included in the first row of sipe units are arranged in a way that they are inclined so that they move toward one side in the tire width direction toward one side in the tire circumferential direction. The tire according to claim 3, wherein a plurality of sipes included in a second sipe unit row adjacent to the first sipe unit row are arranged inclined so as they move toward one side in the tire width direction toward the one side in the tire circumferential direction.

5. The tire according to claim 4, wherein each of the plurality of sipes included in the second row of sipe units is positioned on an extension of any of the sipes included in the first row of sipe units.

6. Among the multiple rows of sipe units, the multiple sipes included in the first row of sipe units are arranged in a way that they are inclined so that they move toward one side in the tire width direction toward one side in the tire circumferential direction. The tire according to claim 3, wherein a plurality of sipes included in a second sipe unit row adjacent to the first sipe unit row are arranged inclined so as they move toward one side in the tire width direction toward the other side in the tire circumferential direction.

7. When the length of the sipe in the tire width direction is d (mm) and the depth of the sipe is h (mm), then d × h = 150 (mm) ２ ) and below, Let n be the number of sipes within the block's land portion, let BW (mm) be the maximum width of the block's land portion in the tire width direction, and let (mm) be the outer contour area of ​​the block's land portion. ２ The tire according to any one of claims 1 to 6, wherein the equivalent tire circumferential length of the block land portion obtained by dividing ) by the maximum width BW is denoted as BL (mm), the equivalent number of sipes N is expressed as d × n / BW, the average sipe spacing in the tire circumferential direction is expressed as BL / (N + 1), and the sipe density SD in the tire circumferential direction is expressed as the reciprocal of the average sipe spacing, so SD = (N + 1) / BL = ((d × n / BW) + 1) / BL, and SD is 0.15 (1 / mm) or more.

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