tire

Abstract

To provide a tire that improves wet performance while simultaneously suppressing cracking and preventing a decrease in dry performance. [Solution] The tread portion 2 is provided with a plurality of circumferential main grooves 30 that extend in the circumferential direction of the tire, a plurality of land portions 20 partitioned by the circumferential main grooves 30, a chamfered sipe 40 that is provided on the land portion 20 and has at least one end closed within the land portion 20, and has a chamfer 43 on the opening 42 to the tread contact surface 3 which is the surface of the tread portion 2, and a short shallow groove 45 that is provided on the land portion 20 on the extension of the chamfer 43 of the chamfered sipe 40, spaced apart from the chamfer 43, and has a depth from the tread contact surface 3 that is shallower than the chamfer 43.

Description

Technical Field

[0005]

[0001] The present invention relates to a tire.

Background Art

[0002] In conventional tires, in order to improve wet performance, which is the running performance on a wet road surface, a tread pattern in which sipes are arranged in the tread portion is often adopted. Also, among tires having sipes, there are some that aim to improve various performances by devising the arrangement form of the sipes. For example, in the tire described in Patent Document 1, a plurality of lands partitioned by main grooves include sipes and shallow grooves, and the shallow grooves extend so as to surround the sipes in a plan view of the tread.

[0003] Also, in the pneumatic tire described in Patent Document 2, the planar shape at the end portion of the sipes within the land portion is formed in a circular shape. Further, in the pneumatic tire described in Patent Document 3, auxiliary sipes separated from the main sipes are formed on both sides of the closed end of the main sipes that are blocked within the land portion, and the closed end of the main sipes and the auxiliary sipes on both sides thereof have an overlap in a direction orthogonal to the extending direction of the main sipes, and the extending direction of the auxiliary sipes is oblique with respect to the extending direction of the main sipes.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of sipes where the ends are closed within the land area, stress concentration is likely to occur at the closed ends of the sipes, making them prone to cracking. One method to suppress cracks occurring at the ends of sipes is to form the end portion of the sipe in an annular shape, as described in Patent Document 2. However, when the end portion of the sipe is formed in an annular shape, the rigidity of the annular portion formed at the end of the sipe in the land area tends to decrease. In this case, the decrease in the rigidity of the land area may lead to a decrease in dry performance, which is the driving performance on dry road surfaces. For this reason, when improving wet performance by placing sipes in the tread area, it has been extremely difficult to suppress cracks occurring at the ends of the sipes while suppressing a decrease in dry performance.

[0006] The present invention has been made in view of the above, and aims to provide a tire that can improve wet performance while simultaneously suppressing cracking and preventing a decrease in dry performance. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the tire according to the present invention is characterized by comprising: a plurality of circumferential main grooves arranged in the tread portion and extending in the circumferential direction of the tire; a plurality of land portions partitioned by the circumferential main grooves; a chamfered sipe arranged in the land portion, at least one end of which is closed within the land portion, and which has a chamfer at the opening to the surface of the tread portion; and a short shallow groove arranged in the land portion on the extension of the chamfer of the chamfered sipe, spaced apart from the chamfer, and having a depth from the surface of the tread portion that is shallower than the chamfer.

[0008] Furthermore, in the above-mentioned tire, it is preferable that the chamfered sipes and the short, shallow grooves are at least located on the land portion of the tire that is situated on the equatorial plane.

[0009] Furthermore, in the above-mentioned tire, it is preferable that the chamfer has a depth within the range of 0.5 mm to 3.0 mm.

[0010] Furthermore, in the above-mentioned tire, it is preferable that the short, shallow grooves have a depth within the range of 0.1 mm to 1.0 mm.

[0011] Furthermore, in the above-mentioned tire, the distance from the chamfer to the short, shallow groove is preferably within the range of 1.0 mm to 3.0 mm.

[0012] Furthermore, in the above-mentioned tire, it is preferable that the ratio of the width W2 of the short, shallow groove in the tire width direction to the width W1 of the land portion where the short, shallow groove is located in the tire width direction is within the range of 0.05 ≤ W2 / W1 ≤ 0.2.

[0013] Furthermore, in the above-mentioned tire, it is preferable that the ratio of the width W3 of the chamfered sipe in the tire width direction to the width W1 of the land portion on which the chamfered sipe is arranged in the tire width direction is within the range of 0.3 ≤ W3 / W1 ≤ 0.7. [Effects of the Invention]

[0014] The tire according to the present invention has the effect of improving wet performance while simultaneously suppressing cracking and preventing a decrease in dry performance. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a meridional cross-sectional view of a tire showing the main parts of a pneumatic tire according to an embodiment. [Figure 2] Figure 2 is a view taken along arrow AA in Figure 1. [Figure 3] Figure 3 is a detailed view of section B in Figure 2. [Figure 4] Figure 4 is a cross-sectional view of the CC shown in Figure 3. [Figure 5] Figure 5 is a cross-sectional view of EE in Figure 3. [Figure 6] Figure 6 is a detailed view of section B in Figure 2, illustrating the relative arrangement of the chamfered sipes and the short, shallow grooves. [Figure 7]FIG. 7 is a modified example of a pneumatic tire according to an embodiment, and is an explanatory diagram showing a form in which the chamfer of the chamfered groove is formed in an oblique shape. [Figure 8A] FIG. 8A is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 8B] FIG. 8B is a chart showing the results of a performance evaluation test of a pneumatic tire.

MODE FOR CARRYING OUT THE INVENTION

[0016] Hereinafter, embodiments of the tire according to the present invention will be described in detail based on the drawings. Note that the present invention is not limited by this embodiment. In addition, the components in the following embodiments include those that can be replaced by those skilled in the art and can be easily conceived, or those that are substantially the same.

[0017] [Embodiment] In the following description, as an example of the tire according to the present invention, a pneumatic tire 1 will be used for explanation. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, and other gases.

[0018] Furthermore, in the following explanation, the tire radial direction refers to the direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1. The inner side of the tire radial direction refers to the side toward the tire rotation axis in the tire radial direction, and the outer side of the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis. The inner side of the tire width direction refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side of the tire width direction refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane perpendicular to the tire rotation axis and passing through the center of the tire width of the pneumatic tire 1. The position of the tire equatorial plane CL in the tire width direction coincides with the center line in the tire width direction, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the distance in the tire width direction between the outermost parts in that direction, that is, the distance between the parts furthest from the tire equatorial plane CL in that direction. The tire equatorial line is a line on the tire equatorial plane CL that runs along the circumferential direction of the pneumatic tire 1. In the following explanation, the tire meridional section refers to the cross-section obtained when the tire is cut by a plane containing the tire's axis of rotation.

[0019] Figure 1 is a meridional cross-sectional view of a tire showing the main parts of a pneumatic tire 1 according to this embodiment. The pneumatic tire 1 shown in Figure 1 is a radial tire for a passenger car, as an example of a pneumatic tire. In this embodiment, when viewed in the meridional cross-section of the tire, the tread portion 2 is located at the outermost part in the radial direction of the tire, and the tread portion 2 has a tread rubber 4 made of a rubber composition. The surface of the tread portion 2, that is, the part that comes into contact with the road surface when the vehicle (not shown) on which the pneumatic tire 1 is mounted is driven, is formed as a tread contact surface 3, and the tread contact surface 3 constitutes a part of the contour of the pneumatic tire 1.

[0020] Shoulder portions 5 are located at both outer ends of the tread portion 2 in the tire width direction, and sidewall portions 8 are positioned on the inner side of the shoulder portions 5 in the tire diameter direction. In other words, the sidewall portions 8 are located on both sides of the tread portion 2 in the tire width direction. To put it another way, the sidewall portions 8 are located at two locations on both sides of the pneumatic tire 1 in the tire width direction, forming the outermost exposed portion of the pneumatic tire 1 in the tire width direction.

[0021] A bead portion 10 is located on the radially inner side of each sidewall portion 8 located on both sides in the tire width direction. Similar to the sidewall portions 8, the bead portions 10 are arranged in two places on both sides of the tire equatorial plane CL; that is, a pair of bead portions 10 are arranged on both sides in the tire width direction of the tire equatorial plane CL. A bead core 11 is provided in each bead portion 10, and a bead filler 12 is provided on the radially outer side of the bead core 11. The bead core 11 is an annular member formed by bundling bead wires, which are steel wires, into a ring shape, and the bead filler 12 is a rubber member positioned radially outer of the bead core 11.

[0022] Furthermore, a belt layer 14 is arranged in the tread portion 2. The belt layer 14 is composed of a multilayer structure in which multiple belts 141, 142 and a belt cover 143 are laminated, and in this embodiment, two layers of belts 141, 142 are laminated. The belts 141, 142 that make up the belt layer 14 are made by coating multiple belt cords made of steel or organic fiber material such as polyester, rayon, or nylon with coated rubber and rolling them, and the belt angle, which is defined as the inclination angle of the belt cords with respect to the circumferential direction of the tire, is within a predetermined range (for example, 20° or more and 55° or less). Also, the belt angles of the two layers of belts 141, 142 are different from each other. For this reason, the belt layer 14 is configured as a so-called cross-ply structure in which the two layers of belts 141, 142 are laminated with the inclination directions of the belt cords intersecting each other. In other words, the two layers of belts 141, 142 are provided as so-called cross belts, in which the belt cords of each belt 141, 142 are arranged in a direction that intersects each other.

[0023] Furthermore, the belt cover 143 is constructed by covering multiple belt cover cords made of steel or organic fiber materials such as polyester, rayon, or nylon with coated rubber and rolling them, and the belt angle, defined as the inclination angle of the belt cover cords with respect to the tire circumferential direction, is within a predetermined range (for example, 0° or more and 10° or less). Also, the belt cover 143 is a strip material made by covering one or more belt cover cords with coated rubber, and this strip material is constructed by winding it spirally around the tire rotation axis from the outside of the two layers of belts 141 and 142 in the tire radial direction.

[0024] A carcass layer 13 containing the cords of radial ply is continuously provided on the inner side of the belt layer 14 in the tire radial direction and on the tire equatorial plane CL side of the sidewall portion 8. Therefore, the pneumatic tire 1 according to this embodiment is configured as a so-called radial tire. The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass ply stacked together, and is toroidally stretched between a pair of bead portions 10 arranged on both sides in the tire width direction to form the tire's skeleton.

[0025] More specifically, the carcass layer 13 is positioned from one of a pair of bead portions 10 located on both sides in the tire width direction to the other bead portion 10, and is wrapped around the bead core 11 in the tire width direction outward along the bead core 11 so as to enclose the bead core 11 and the bead filler 12. The bead filler 12 is a rubber material that is placed in the space formed on the radially outward side of the bead core 11 when the carcass layer 13 is folded back at the bead portion 10 in this way. The belt layer 14 is positioned on the radially outward side of the portion of the carcass layer 13 located in the tread portion 2 that spans between the pair of bead portions 10 in this way. The carcass ply of the carcass layer 13 is constructed by covering multiple carcass cords made of steel or organic fiber materials such as aramid, nylon, polyester, or rayon with a coating rubber and then rolling them. The carcass cords that make up the carcass ply are arranged in parallel, with an angle in the tire's circumferential direction that aligns with the tire's meridian, while also maintaining an angle in the circumferential direction of the tire.

[0026] In the bead portion 10, rim cushion rubber 17 is arranged on the inner side in the tire radial direction and the outer side in the tire width direction of the bead core 11 and the reversal portion of the carcass layer 13, forming the contact surface of the bead portion 10 with the rim flange. In addition, an inner liner 16 is formed along the carcass layer 13 on the inside of the carcass layer 13, or on the inner side of the carcass layer 13 in the pneumatic tire 1. The inner liner 16 forms the inner surface 18 of the tire, which is the inner surface of the pneumatic tire 1.

[0027] Figure 2 is a view along arrow AA in Figure 1. The tread portion 2 has multiple circumferential main grooves 30 extending in the tire circumferential direction on the tread contact surface 3, and the surface of the tread portion 2 is divided into multiple land areas 20 by the circumferential main grooves 30. In this embodiment, four circumferential main grooves 30 are arranged in the tire width direction. Specifically, the circumferential main grooves 30 consist of two inner circumferential main grooves 31 arranged on both sides of the tire equatorial plane CL in the tire width direction, and two outer circumferential main grooves 35 arranged one on each side of the two inner circumferential main grooves 31 in the tire width direction. All four circumferential main grooves 30 are formed to extend linearly along the tire circumferential direction.

[0028] The circumferential main groove 30 referred to here is a longitudinal groove extending in the circumferential direction of the tire, and has a wear indicator (slip sign) inside that indicates the end of wear. The circumferential main groove 30 formed in this manner has a maximum groove width of 3.0 mm or more and a maximum groove depth of 5.0 mm or more.

[0029] The land area 20, which is partitioned by the circumferential main grooves 30, has a center land area 21, a second land area 22, and a shoulder land area 23. Of these, the center land area 21 is the land area 20 located between the inner circumferential main grooves 31, and both sides in the tire width direction are partitioned by the inner circumferential main grooves 31. Since the two inner circumferential main grooves 31 are located on both sides of the tire equatorial plane CL, the center land area 21, which is partitioned on both sides in the tire width direction by the inner circumferential main grooves 31, is located on the tire equatorial plane CL.

[0030] The second land area 22 is a land area 20 located between the inner circumferential main groove 31 and the outer circumferential main groove 35, which are adjacent in the tire width direction, and is a land area 20 that is partitioned on both sides in the tire width direction by the inner circumferential main groove 31 and the outer circumferential main groove 35. That is, the inner part of the second land area 22 in the tire width direction is partitioned by the inner circumferential main groove 31, and the outer part in the tire width direction is partitioned by the outer circumferential main groove 35. The shoulder land area 23 is a land area 20 located outside the outer circumferential main groove 35 in the tire width direction, and is partitioned on the inner side in the tire width direction by the outer circumferential main groove 35. Furthermore, the second land area 22 and the shoulder land area 23 are located on both sides of the tire equatorial plane CL in the tire width direction, respectively.

[0031] Of the land sections 20 partitioned by the circumferential main grooves 30, the center land section 21 and the second land section 22 are each equipped with chamfered sipes 40, short shallow grooves 45, curved shallow grooves 50, and connecting sipes 51, respectively. In other words, the chamfered sipes 40, short shallow grooves 45, curved shallow grooves 50, and connecting sipes 51 are located in the center land section 21, which is a land section 20 located on the tire's equatorial plane CL, and in the second land section 22, which is a land section 20 adjacent to the center land section 21 via the inner circumferential main grooves 31, respectively.

[0032] Of these, the curved shallow groove 50 has one end communicating with the circumferential main groove 30 and the other end terminating within the land portion 20. It extends in the tire width direction, and the direction of the inclination from the tire width direction to the tire circumferential direction changes between the two ends in the longitudinal direction of the curved shallow groove 50, causing it to curve in a convex manner toward the tire circumferential direction. The curved shallow groove 50 has a groove width in the range of 0.5 mm to 1.5 mm and a maximum depth from the tread contact surface 3 in the range of 0.2 mm to 2.0 mm.

[0033] Furthermore, the connecting sipe 51 has one end that communicates with the opposite end of the curved shallow groove 50 from the end that terminates within the land portion 20, and the other end that communicates with a circumferential main groove 30 that is different from the circumferential main groove 30 that the curved shallow groove 50 communicates with, among the two circumferential main grooves 30 that demarcate both sides of the land portion 20 in the tire width direction. In addition, the connecting sipe 51 is positioned on the extension of the portion of the curved shallow groove 50 that the connecting sipe 51 communicates with. In other words, the angle of inclination of the connecting sipe 51 in the tire circumferential direction with respect to the tire width direction is substantially the same as the angle of inclination of the portion of the curved shallow groove 50 that terminates within the land portion 20 rather than the curved portion.

[0034] In this embodiment, the sipes are formed in the shape of narrow grooves on the tread contact surface 3. When a pneumatic tire 1 is mounted on a specified rim and under specified internal pressure conditions, the walls constituting the narrow grooves do not come into contact with each other when unloaded. However, when a vertical load is applied to a flat plate, and the narrow grooves are located on the contact surface formed on the flat plate, or when the land portion 20 on which the narrow grooves are formed collapses, the walls constituting the narrow grooves, or at least a portion of the parts provided on the walls, come into contact with each other due to the deformation of the land portion 20.

[0035] The specified rim referred to here is the "standard rim" as defined by JATMA, the "Design Rim" as defined by TRA, or the "Measuring Rim" as defined by ETRTO. The specified internal pressure is the "maximum air pressure" as defined by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or the "INFLATION PRESSURES" as defined by ETRTO. In this embodiment, the connecting sipe 51 has a groove width in the range of 0.5 mm to 1.5 mm, a maximum depth of 2.0 mm or more from the tread contact surface 3, and a depth less than or equal to the maximum depth of the circumferential main groove 30.

[0036] Figure 3 is a detailed view of section B in Figure 2. Figure 4 is a cross-sectional view of CC in Figure 3. Figure 5 is a cross-sectional view of EE in Figure 3. The following description of the chamfered sipes 40 and short shallow grooves 45 will be representative of the chamfered sipes 40 and short shallow grooves 45 located in the central land section 21 and the chamfered sipes 40 and short shallow grooves 45 located in the second land section 22, but the chamfered sipes 40 and short shallow grooves 45 located in the second land section 22 are formed in a similar manner.

[0037] The chamfered sipe 40 is positioned on the land portion 20, with at least one end closed within the land portion 20, and has a chamfer 43 at the opening 42 to the tread contact surface 3, which is the surface of the tread portion 2. In other words, the chamfered sipe 40 has a sipe body portion 41 which is formed in a narrow groove shape and forms the main body of the chamfered sipe 40, and a chamfer 43 formed at the opening 42 to the tread contact surface 3 in the sipe body portion 41. The sipe body portion 41 of the chamfered sipe 40 has a groove width in the range of 0.5 mm to 1.5 mm, a maximum depth from the tread contact surface 3 of 2.0 mm or more, and a depth that is less than or equal to the maximum depth of the circumferential main groove 30.

[0038] A chamfered sipe 40, having a sipe body 41 and a chamfer 43, extends in the tire width direction and is inclined toward the tire circumferential direction with respect to the tire width direction. The inclination angle θ of the chamfered sipe 40 toward the tire width direction with respect to the tire circumferential direction is within the range of 30° to 80°. In this embodiment, the inclination angles θ of the multiple chamfered sipes 40 arranged on the land portion 20 are substantially all the same.

[0039] The chamfer 43 formed on the opening 42 of the sipe body portion 41 of the chamfered sipe 40 is formed on one of the edges on both sides of the sipe body portion 41 in the groove width direction at the opening 42. In other words, the chamfer 43 of the chamfered sipe 40 is formed on only one of the edges on both sides of the sipe body portion 41 in the groove width direction at the opening 42 of the chamfered sipe 40, and not on the other edge.

[0040] The chamfer 43 of the chamfered sipe 40 is formed over the entire length of the chamfered sipe 40. In this embodiment, the chamfer 43 is a so-called razed chamfer 43, which is formed in a roughly rectangular notch shape when viewed in a cross-sectional view of the chamfered sipe 40 in the direction extending from the sipe body portion 41, as shown in Figure 4. The chamfer 43 formed in the opening 42 of the chamfered sipe 40 has a depth Dc from the tread contact surface 3 in the range of 0.5 mm to 3.0 mm.

[0041] The short, shallow groove 45 is positioned on the extension of the chamfer 43 of the chamfered sipe 40 in the land portion 20, spaced apart from the chamfer 43, and is formed as a shallow groove with a relatively short length, recessed from the tread contact surface 3, with a depth shallower than the chamfer 43 of the chamfered sipe 40. More specifically, the short, shallow groove 45 is positioned near the closed end of the chamfered sipe 40 within the land portion 20, on the extension of the chamfer 43 in the extending direction of the chamfered sipe 40, spaced apart from the chamfer 43.

[0042] The short, shallow grooves 45, located near the chamfer 43 of the chamfered sipe 40 and separated from the chamfer 43, have a distance G from the chamfer 43 of the chamfered sipe 40 in the direction of extension of the chamfered sipe 40 that is within the range of 1.0 mm to 3.0 mm. In addition, the depth Ds of the short, shallow grooves 45 from the tread contact surface 3 is within the range of 0.1 mm to 1.0 mm.

[0043] Thus, the width W2 in the tire width direction of the short shallow groove 45, which is positioned near the chamfer 43 of the chamfered sipe 40 and spaced away from the chamfer 43, is within the range of 0.05 ≤ W2 / W1 ≤ 0.2 when compared to the width W1 of the land portion 20 where the short shallow groove 45 is positioned. Furthermore, the width W3 of the chamfered sipe 40 in the tire width direction is within the range of 0.3 ≤ W3 / W1 ≤ 0.7 when compared to the width W1 of the land portion 20 where the chamfered sipe 40 is positioned.

[0044] Figure 6 is a detailed view of section B in Figure 2, and is an explanatory diagram of the relative arrangement of the chamfered sipe 40 and the short shallow groove 45. In the short shallow groove 45, the width Ws of the sipe body portion 41 in the groove width direction of the chamfered sipe 40 is smaller than the width Wc of the chamfer 43 in the groove width direction of the sipe body portion 41. Specifically, the width Wc of the chamfer 43 in the groove width direction of the sipe body portion 41 is in the range of 1.0 mm to 3.0 mm, and the ratio of the width Ws of the short shallow groove 45 in the groove width direction of the sipe body portion 41 to the width Wc of the chamfer 43 is in the range of 0.5 ≤ Ws / Wc ≤ 1.5.

[0045] The short, shallow grooves 45 formed in this manner are positioned on an extension of the line extending from the center line CC of the chamfer 43 in the groove width direction of the sipe body portion 41 toward the side where the short, shallow grooves 45 are located.

[0046] Furthermore, the short shallow groove 45 is positioned on the side of the groove width direction of the sipe body 41 where the chamfer 43 is located, rather than on the extension line EL which is drawn by extending the edge on the chamfer 43 side of the opening 42 of the sipe body 41 toward the short shallow groove 45. In other words, the short shallow groove 45 is positioned on the side of the groove width direction of the sipe body 41 where the chamfer 43 is located, rather than on the extension line EL which is drawn by extending the wall surface on the side of the sipe body 41 where the chamfer 43 is located toward the short shallow groove 45.

[0047] The chamfered sipes 40 and short shallow grooves 45, which are formed in this manner and arranged in multiples on each land portion 20, and the curved shallow grooves 50 and the communicating sipes 51 that communicate with the curved shallow grooves 50 are arranged alternately in the circumferential direction of the tire.

[0048] Furthermore, the chamfered sipes 40, which are arranged in multiples on each land section 20, have different circumferential main grooves 30 that communicate with adjacent chamfered sipes 40 in the tire circumferential direction via the curved shallow grooves 50 and connecting sipes 51. Also, the curved shallow grooves 50 and connecting sipes 51, which are arranged in multiples on each land section 20, have different circumferential main grooves 30 that communicate with adjacent curved shallow grooves 50 and connecting sipes 51 in the tire circumferential direction via the chamfered sipes 40 and short shallow grooves 45. Moreover, the curved shallow grooves 50 that are adjacent to each other in the tire circumferential direction via the chamfered sipes 40 and short shallow grooves 45 are arranged in opposite directions in the tire circumferential direction. In other words, the chamfered sipes 40 and short shallow grooves 45, and the curved shallow grooves 50 and connecting sipes 51, which are arranged in multiples on a single land section 20, are arranged in a staggered pattern in the tire circumferential direction.

[0049] Furthermore, the curved shallow grooves 50 and connecting sipes 51, which are positioned between adjacent chamfered sipes 40 and short shallow grooves 45 in the circumferential direction of the tire, are positioned such that the distance between one chamfered sipe 40 and short shallow groove 45 located on both sides of the curved shallow groove 50 and connecting sipe 51 in the circumferential direction of the tire is shorter than the distance between the other chamfered sipe 40 and short shallow groove 45. In addition, the curved shallow grooves 50 and connecting sipes 51, which are positioned in multiples on each land section 20, are all oriented in the same direction in the circumferential direction of the chamfered sipe 40 and short shallow groove 45 that are closer in the circumferential direction of the tire.

[0050] In each of the chamfered sipes 40 arranged in multiple locations on the land section 20, the chamfer 43 is provided on the edge of the sipe body 41 at the opening 42 that is closer to the curved shallow groove 50 or the connecting sipe 51 in the tire circumferential direction, out of the edges on both sides in the groove width direction of the sipe body 41. In other words, in each of the chamfered sipes 40 arranged in multiple locations on the land section 20, the chamfer 43 is provided on the edge of the sipe body 41 that is on the same side in the tire circumferential direction, out of the edges on both sides in the groove width direction of the sipe body 41.

[0051] For these reasons, the chamfered sipes 40 arranged in multiple locations on the land portion 20 are arranged alternately in the circumferential direction of the tire, with chamfered sipes 40 having a chamfer 43 on the acute angle side and chamfered sipes 40 having a chamfer 43 on the obtuse angle side at the corner formed by the circumferential main groove 30 and the chamfered sipe 40.

[0052] When mounting the pneumatic tire 1 according to this embodiment onto a vehicle, the pneumatic tire 1 is mounted onto a rim wheel, and then inflated by filling it with air before mounting it to the vehicle. When a vehicle equipped with the pneumatic tire 1 is driven, the pneumatic tire 1 rotates while the lower part of the tread contact surface 3 of the tread portion 2 contacts the road surface. When a vehicle equipped with the pneumatic tire 1 is driven on a dry road surface, it is driven mainly by the frictional force between the tread contact surface 3 and the road surface, which transmits driving force and braking force to the road surface and generates turning force.

[0053] Furthermore, when driving on a wet road surface, water between the tread contact surface 3 and the road surface enters the circumferential main grooves 30 and chamfered sipes 40, and the vehicle drives while draining the water between the tread contact surface 3 and the road surface through these grooves. In particular, the chamfered sipes 40 of the pneumatic tire 1 according to this embodiment have chamfers 43 at the openings 42 of the sipe body portion 41, which makes it easier to absorb water between the tread contact surface 3 and the road surface and easier to drain the water between the tread contact surface 3 and the road surface. As a result, the tread contact surface 3 can easily make contact with the road surface even on a wet road surface, and the frictional force between the tread contact surface 3 and the road surface allows the vehicle to drive.

[0054] Furthermore, since one end of the chamfered sipe 40, which is positioned on the tread contact surface 3, is closed within the land portion 20, it is possible to ensure wet performance, which is the driving performance on wet roads, while suppressing a decrease in the rigidity of the land portion 20 on which the chamfered sipe 40 is positioned.

[0055] Generally, when the end of a sipe is closed within the land area 20, when the load from a vehicle is applied to the land area 20, stress concentration is likely to occur near the closed end of the sipe within the land area 20, and cracks are likely to occur due to this stress concentration. As a method to suppress cracks occurring at the end of the sipe in the land area 20, for example, as described in Patent Document 2, a method can be considered in which the end of the sipe is made annular to suppress stress concentration at the end of the sipe and suppress the occurrence of cracks. However, when the end of the sipe is made annular, the rigidity near the end of the sipe in the land area 20 tends to decrease.

[0056] If the rigidity of the land section 20 decreases, it becomes difficult to ensure dry performance, which is the driving performance on dry road surfaces. Therefore, if the ends of the sipes in the land section 20 are made ring-shaped to suppress cracks that occur at the ends of the sipes, although the occurrence of cracks can be suppressed, it becomes difficult to ensure dry performance.

[0057] In contrast, in the pneumatic tire 1 according to this embodiment, a chamfered sipe 40 is arranged on the land portion 20, with one end closed within the land portion 20 and having a chamfer 43 at the opening 42. A short, shallow groove 45 is arranged on the extension of the chamfer 43 at the closed end of the chamfered sipe 40, spaced apart from the chamfer 43, with a depth Ds from the tread contact surface 3 being shallower than the depth Dc of the chamfer 43. Therefore, the chamfered sipe 40 with the chamfer 43 effectively drains water between the tread contact surface 3 and the road surface, ensuring wet performance, while the chamfered sipe 40, with one end closed within the land portion 20, suppresses a decrease in the rigidity of the land portion 20, thus ensuring dry performance.

[0058] Furthermore, since a short, shallow groove 45 is positioned near the closed end of the chamfered sipe 40, on the extension of the chamfer 43 and spaced away from the chamfer 43, the stress concentration acting on the closed end of the chamfered sipe 40 due to the load acting on the land portion 20 when a vehicle is running can be dispersed by the short, shallow groove 45. In other words, the stress concentration acting near the closed end of the chamfered sipe 40 can be dispersed between the end of the chamfered sipe 40 and the short, shallow groove 45, thereby suppressing the occurrence of a large stress concentration at the end of the chamfered sipe 40. Consequently, cracks caused by stress concentration near the closed end of the chamfered sipe 40 within the land portion 20 can be suppressed by the short, shallow groove 45.

[0059] Furthermore, since the short, shallow groove 45 is positioned on the extension of the chamfer 43 of the chamfered sipe 40, it is possible to suppress large stress concentrations at the end of the chamfered sipe 40 while also suppressing the occurrence of areas with low rigidity in the land portion 20. In other words, if the short, shallow groove 45 is positioned on the extension of the sipe body portion 41, the rigidity of the land portion 20 between the sipe body portion 41, which is deeper than the chamfer 43, and the short, shallow groove 45 tends to be low. In contrast, when the short, shallow groove 45 is positioned on the extension of the chamfer 43 of the chamfered sipe 40, it is possible to suppress the occurrence of areas with low rigidity in the land portion 20. This makes it possible to ensure dry performance while suppressing cracks caused by stress concentrations near the closed end of the chamfered sipe 40 within the land portion 20.

[0060] Furthermore, by positioning the short, shallow groove 45 near the closed end of the chamfered sipe 40, even if a crack occurs at the end of the sipe body portion 41 of the chamfered sipe 40, the crack will extend in the direction of the short, shallow groove 45, which is the direction of lower rigidity near the end of the sipe body portion 41. Therefore, the extension of the crack that occurs at the end of the sipe body portion 41 can be stopped by the short, shallow groove 45, thereby suppressing the large growth of the crack. As a result, it is possible to improve wet performance while simultaneously suppressing cracks and preventing a decrease in dry performance.

[0061] Furthermore, since the chamfered sipes 40 are positioned at least on the land portion 20 located on the tire's equatorial plane CL, the drainage performance near the tire's equatorial plane CL can be improved by the chamfered sipes 40, and the rigidity of the land portion 20 located on the tire's equatorial plane CL, where the ground pressure tends to be high, can be ensured by one end of the chamfered sipes 40 being closed within the land portion 20. In addition, since the short, shallow grooves 45 are also positioned on the land portion 20 located on the tire's equatorial plane CL, the stress concentration near the closed end of the chamfered sipes 40 in the land portion 20 located on the tire's equatorial plane CL, where the ground pressure tends to be high, can be dispersed by the short, shallow grooves 45, thereby suppressing the occurrence of cracks. As a result, wet performance can be improved more reliably, while simultaneously suppressing cracks and preventing a decrease in dry performance.

[0062] Furthermore, since the chamfer 43 of the chamfered sipe 40 has a depth Dc within the range of 0.5 mm to 3.0 mm, it is possible to improve drainage performance with the chamfered sipe 40 while suppressing a decrease in the rigidity of the land area 20 where the chamfered sipe 40 is placed. In other words, if the depth Dc of the chamfer 43 of the chamfered sipe 40 is less than 0.5 mm, the depth Dc of the chamfer 43 is too shallow, which may make it difficult to ensure drainage performance with the chamfered sipe 40. In this case, even if the chamfered sipe 40 is placed on the land area 20, it may be difficult to effectively improve wet performance. Also, if the depth Dc of the chamfer 43 of the chamfered sipe 40 is deeper than 3.0 mm, the depth Dc of the chamfer 43 is too deep, which may easily reduce the rigidity of the land area 20 where the chamfered sipe 40 is placed. In this case, the dry performance may easily decrease due to the reduced rigidity of the land area 20.

[0063] In contrast, if the depth Dc of the chamfer 43 of the chamfered sipe 40 is within the range of 0.5 mm to 3.0 mm, the chamfered sipe 40 can improve drainage while suppressing a decrease in the rigidity of the land area 20 where the chamfered sipe 40 is placed. As a result, it is possible to improve wet performance while more reliably suppressing a decrease in dry performance.

[0064] Furthermore, since the depth Ds of the short shallow groove 45 is within the range of 0.1 mm to 1.0 mm, it is possible to suppress the decrease in rigidity of the land portion 20 on which the short shallow groove 45 is located, while distributing the stress concentration that occurs near the end of the chamfered sipe 40 by the short shallow groove 45. In other words, if the depth Ds of the short shallow groove 45 is less than 0.1 mm, the depth Ds of the short shallow groove 45 is too shallow, and even if the short shallow groove 45 is located near the end of the chamfered sipe 40, it may be difficult to effectively distribute the stress concentration that occurs near the end of the chamfered sipe 40 by the short shallow groove 45. Also, if the depth Ds of the short shallow groove 45 is deeper than 1.0 mm, the depth Ds of the short shallow groove 45 is too deep, and there is a risk that the rigidity of the land portion 20 on which the short shallow groove 45 is located will be easily reduced by the short shallow groove 45.

[0065] In contrast, when the depth Ds of the short shallow groove 45 is within the range of 0.1 mm to 1.0 mm, the reduction in rigidity of the land portion 20 where the short shallow groove 45 is located can be suppressed, while the stress concentration that occurs near the end of the chamfered sipe 40 can be effectively dispersed by the short shallow groove 45. As a result, it is possible to more reliably achieve both crack suppression and suppression of the decrease in dry performance.

[0066] Furthermore, since the distance G from the chamfer 43 of the chamfered sipe 40 to the short shallow groove 45 is within the range of 1.0 mm to 3.0 mm, it is possible to suppress the decrease in rigidity near the portion between the chamfered sipe 40 and the short shallow groove 45 in the land portion 20, while distributing the stress concentration that occurs near the end of the chamfered sipe 40 by the short shallow groove 45. In other words, if the distance G from the chamfer 43 of the chamfered sipe 40 to the short shallow groove 45 is less than 1.0 mm, the distance G from the chamfer 43 to the short shallow groove 45 is too small, which may result in a decrease in rigidity near the portion between the chamfered sipe 40 and the short shallow groove 45 in the land portion 20, making the rigidity of the land portion 20 more susceptible to decrease. Furthermore, if the distance G from the chamfer 43 of the chamfered sipe 40 to the short shallow groove 45 is greater than 3.0 mm, the distance G from the chamfer 43 to the short shallow groove 45 is too large. Therefore, even if the short shallow groove 45 is placed near the end of the chamfered sipe 40, it may be difficult for the short shallow groove 45 to effectively disperse the stress concentration that occurs near the end of the chamfered sipe 40.

[0067] In contrast, if the distance G from the chamfer 43 of the chamfered sipe 40 to the short shallow groove 45 is within the range of 1.0 mm to 3.0 mm, it is possible to suppress the decrease in rigidity near the portion between the chamfered sipe 40 and the short shallow groove 45 in the land portion 20, while effectively dispersing the stress concentration that occurs near the end of the chamfered sipe 40 with the short shallow groove 45. As a result, it is possible to more reliably achieve both crack suppression and suppression of the decrease in dry performance.

[0068] Furthermore, the short shallow groove 45 has a ratio of width W2 of the short shallow groove 45 in the tire width direction to width W1 of the land portion 20 where the short shallow groove 45 is located, which is within the range of 0.05 ≤ W2 / W1 ≤ 0.2. Therefore, it is possible to suppress the decrease in rigidity of the land portion 20 where the short shallow groove 45 is located, while distributing the stress concentration that occurs near the end of the chamfered sipe 40 by the short shallow groove 45. In other words, if the ratio of width W2 of the short shallow groove 45 to width W1 of the land portion 20 is W2 / W1 < 0.05, the width W2 of the short shallow groove 45 in the tire width direction is too small, and even if the short shallow groove 45 is located near the end of the chamfered sipe 40, it may be difficult to effectively distribute the stress concentration that occurs near the end of the chamfered sipe 40 by the short shallow groove 45. Furthermore, if the ratio of the width W2 of the short shallow groove 45 to the width W1 of the land area 20 is W2 / W1 > 0.2, the width W2 of the short shallow groove 45 in the tire width direction is too large, which may cause the rigidity of the land area 20 on which the short shallow groove 45 is located to be easily reduced by the short shallow groove 45.

[0069] In contrast, if the ratio of the width W2 of the short, shallow groove 45 to the width W1 of the land section 20 is within the range of 0.05 ≤ W2 / W1 ≤ 0.2, then the reduction in rigidity of the land section 20 on which the short, shallow groove 45 is located can be suppressed, while the stress concentration that occurs near the end of the chamfered sipe 40 can be effectively dispersed by the short, shallow groove 45. As a result, it is possible to more reliably achieve both crack suppression and suppression of the decrease in dry performance.

[0070] Furthermore, the chamfered sipe 40 can improve drainage performance while suppressing a decrease in the rigidity of the land area 20 where the chamfered sipe 40 is located, because the ratio of the width W3 of the chamfered sipe 40 in the tire width direction to the width W1 of the land area 20 where the chamfered sipe 40 is located in the tire width direction is within the range of 0.3 ≤ W3 / W1 ≤ 0.7. In other words, if the ratio of the width W3 of the chamfered sipe 40 to the width W1 of the land area 20 is W3 / W1 < 0.3, the width W3 of the chamfered sipe 40 in the tire width direction is too small, and even if the chamfered sipe 40 is placed on the land area 20, it may be difficult to effectively improve drainage performance with the chamfered sipe 40. Furthermore, if the ratio of the width W3 of the chamfered sipe 40 to the width W1 of the land portion 20 is W3 / W1 > 0.7, the width W3 of the chamfered sipe 40 in the tire width direction is too large, which may cause the rigidity of the land portion 20 on which the chamfered sipe 40 is placed to be easily reduced by the chamfered sipe 40.

[0071] In contrast, if the ratio of the width W3 of the chamfered sipe 40 to the width W1 of the land section 20 is within the range of 0.3 ≤ W3 / W1 ≤ 0.7, then the chamfered sipe 40 can effectively improve drainage while suppressing a decrease in the rigidity of the land section 20 on which the chamfered sipe 40 is placed. As a result, wet performance can be improved while more reliably suppressing a decrease in dry performance.

[0072] [Differentiation] In the embodiment described above, the chamfer 43 of the chamfered sipe 40 is formed in a substantially rectangular notch shape when viewed in a cross-sectional view of the chamfered sipe 40 in the extending direction of the sipe body portion 41, but the chamfer 43 may be formed in a shape other than this.

[0073] Figure 7 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the chamfer 43 of the chamfer sipe 40 is formed in an oblique shape. The chamfer 43 of the chamfer sipe 40 may be formed in an oblique shape such that, when viewed in a cross-sectional view of the chamfer sipe 40 in the extending direction of the sipe body 41, the depth decreases as it moves away from the sipe body 41 in the width direction of the sipe body 41, as shown in Figure 7. In other words, the chamfer 43 of the chamfer sipe 40 may be formed in a general chamfer shape, which is approximately triangular when viewed in a cross-sectional view of the chamfer sipe 40 in the extending direction of the sipe body 41.

[0074] In this case, the depth Dc of the chamfer 43 is determined by the maximum depth, and the short shallow groove 45 is positioned shallower than the maximum depth Dc of the chamfer 43. Regardless of the shape of the chamfer 43, the chamfer sipe 40 can improve drainage and wet performance by providing the chamfer 43 at the opening 42 of the sipe body 41.

[0075] Furthermore, in the embodiment described above, the multiple chamfered sipes 40 arranged on the land portion 20 all have substantially the same inclination angle θ, but the multiple chamfered sipes 40 arranged on the land portion 20 may be arranged with multiple inclination angles θ.

[0076] Furthermore, in the embodiment described above, the chamfered sipes 40 and short shallow grooves 45 are arranged on all land portions 20 located on the inner side in the tire width direction of the outer circumferential main groove 35. However, the chamfered sipes 40 and short shallow grooves 45 do not necessarily have to be arranged on all land portions 20 located on the inner side in the tire width direction of the outer circumferential main groove 35.

[0077] Furthermore, although the above-described embodiment used a pneumatic tire 1 as an example of a tire according to the present invention, the tire according to the present invention may be other than a pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without filling with gas.

[0078] [Examples] Figures 8A and 8B are charts showing the results of performance evaluation tests for pneumatic tires. Below, we will describe the performance evaluation tests conducted on the above-mentioned pneumatic tire 1, comparing it with a conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and a comparative example pneumatic tire used for comparison with the pneumatic tire 1 according to the present invention. The performance evaluation tests included tests for crack resistance, dry handling stability, and wet braking performance.

[0079] The performance evaluation test was conducted by mounting a pneumatic tire (size 245 / 40R18 97Y as defined by JATMA) onto a JATMA standard rim wheel with a rim size of 18×8J, attaching the test tire to a sedan-type front-wheel-drive test vehicle, adjusting the air pressure to 240kPa, and driving the evaluation vehicle.

[0080] The evaluation method for each test item was as follows: For crack resistance, a road test was conducted on a test vehicle equipped with the test tire, and after driving 30,000 km, the number and length of cracks that occurred on the tread contact surface 3 of the land area 20 were investigated. Crack resistance was evaluated by expressing the reciprocal of the crack occurrence rate and growth rate that occurred on the tread contact surface 3 as an index with Conventional Example 1, described later, set to 100. A higher value indicates lower crack occurrence and growth rates, and thus superior crack resistance.

[0081] Furthermore, dry handling stability performance was evaluated by having test vehicles equipped with test tires drive on a dry asphalt test course, and by expressing the feeling evaluation of lane change performance and cornering performance by test drivers as an index with Conventional Example 1 (described later) set to 100. A higher value for dry handling stability performance indicates better lane change performance and cornering performance on dry surfaces, and thus superior dry handling stability performance.

[0082] Furthermore, wet braking performance was evaluated by conducting braking tests on a test vehicle equipped with the test tires on an asphalt road test course with a water depth of 1 mm, starting from an initial speed of 40 km / h. The reciprocal of the braking distance was expressed as an index with Conventional Example 1 (described later) set to 100. A higher index indicates a shorter braking distance on a wet road surface and superior wet braking performance.

[0083] Performance evaluation tests were conducted on 20 types of pneumatic tires, including Conventional Examples 1 and 2, which are examples of conventional pneumatic tires; Examples 1 to 17, which are pneumatic tires 1 according to the present invention; and Comparative Examples, which are pneumatic tires compared to pneumatic tires 1 according to the present invention. Of these, Conventional Example 1 does not have chamfered sipes, and the sipes are ordinary sipes without chamfers, and short shallow grooves are not arranged. Conventional Example 2 also does not have chamfered sipes, and the sipes are sipes with annular ends as in Patent Document 2, and short shallow grooves are not arranged. The Comparative Examples have chamfered sipes, but short shallow grooves are not arranged.

[0084] In contrast, Examples 1 to 17, which are examples of the pneumatic tire 1 according to the present invention, all have chamfered sipes 40, and short shallow grooves 45 are arranged on the extension of the chamfer 43 of the chamfered sipes 40. Furthermore, the pneumatic tire 1 according to Examples 1 to 17 differs in the depth Ds (mm) of the short shallow grooves 45, the distance G (mm) between the chamfer 43 of the chamfered sipes 40 and the short shallow grooves 45, the ratio W2 / W1 of the width W1 of the land portion 20 to the width W2 of the short shallow grooves 45, and the ratio W3 / W1 of the width W1 of the land portion 20 to the width W3 of the chamfered sipes 40.

[0085] Performance evaluation tests were conducted using these pneumatic tires 1. As shown in Figures 8A and 8B, the pneumatic tires 1 according to Examples 1 to 17 were found to have improved crack resistance and wet braking performance compared to Conventional Example 1, and to have at least the same level of dry handling stability as Conventional Example 1. In other words, the pneumatic tires 1 according to Examples 1 to 17 can improve wet performance while simultaneously suppressing cracks and preventing a decrease in dry performance.

[0086] This disclosure encompasses the following inventions: Invention [1] Multiple circumferential main grooves are arranged in the tread area and extend in the circumferential direction of the tire, Multiple land areas are demarcated by the aforementioned circumferential main groove, A chamfered sipe is a sipe that is arranged on the land portion and has at least one end closed within the land portion, and has a chamfer at the opening to the surface of the tread portion, A short, shallow groove is provided on the extension of the chamfer of the chamfer sipe in the land portion, spaced apart from the chamfer, and the depth from the surface of the tread portion is shallower than the chamfer. A tire characterized by having the following features. invention[2] The tire according to invention [1], wherein the chamfered sipes and the short, shallow grooves are arranged at least on the land portion of the tire located on the equatorial plane. Invention [3] The tire according to invention [1] or invention [2], wherein the chamfer has a depth in the range of 0.5 mm to 3.0 mm. invention [4] The tire according to any one of inventions [1] to [3], wherein the short, shallow groove has a depth in the range of 0.1 mm or more and 1.0 mm or less. invention [5] The tire according to any one of inventions [1] to [4], wherein the distance from the chamfer to the short shallow groove is in the range of 1.0 mm or more and 3.0 mm or less. invention [6] A tire according to any one of inventions [1] to [5], wherein the width W2 of the short shallow groove in the tire width direction is in ratio to the width W1 of the land portion in the tire width direction where the short shallow groove is arranged, and the ratio is within the range of 0.05 ≤ W2 / W1 ≤ 0.2. invention [7] A tire according to any one of inventions [1] to [6], wherein the width W3 of the chamfered sipe in the tire width direction is in ratio to the width W1 of the land portion on which the chamfered sipe is arranged in the tire width direction, and the ratio is within the range of 0.3 ≤ W3 / W1 ≤ 0.7. [Explanation of Symbols]

[0087] 1. Pneumatic tire 2 Tread section 3. Tread contact surface 4 Tread Rubber 5 Shoulder section 8 Sidewall section 10 Bead section 11 Bead core 12 Bead Fillers 13. Carcass layer 14 Belt Layer 16 Inner liner 17 Rim cushion rubber 18 Tire interior 20 Land 21 Center Track and Field Club 22 Second Track and Field Club 23 Shoulder Track and Field Club 30 Circumferential main groove 31 Inner circumferential main groove 35 Outer circumferential main groove 40 chamfered sipes 41 Sipe main body 42 Opening 43 Chamfering 45 Short shallow groove 50 Curved shallow grooves 51 Connecting sipes

Claims

1. Multiple circumferential main grooves are arranged in the tread area and extend in the circumferential direction of the tire, Multiple land areas are demarcated by the aforementioned circumferential main groove, A chamfered sipe is a sipe that is arranged on the land portion and has at least one end closed within the land portion, and has a chamfer at the opening to the surface of the tread portion, A short, shallow groove is provided on the extension of the chamfer of the chamfer sipe in the land portion, spaced apart from the chamfer, and the depth from the surface of the tread portion is shallower than the chamfer. A tire characterized by having the following features.

2. The tire according to claim 1, wherein the chamfered sipes and the short, shallow grooves are at least arranged on the land portion located on the equatorial plane of the tire.

3. The tire according to claim 1, wherein the chamfer has a depth in the range of 0.5 mm to 3.0 mm.

4. The tire according to claim 1, wherein the short, shallow groove has a depth in the range of 0.1 mm or more and 1.0 mm or less.

5. The tire according to claim 1, wherein the distance from the chamfer to the short shallow groove is within the range of 1.0 mm to 3.0 mm.

6. The tire according to claim 1, wherein the width W2 of the short shallow groove in the tire width direction is in ratio to the width W1 of the land portion in the tire width direction where the short shallow groove is arranged, and the ratio is within the range of 0.05 ≤ W2 / W1 ≤ 0.

2.

7. The tire according to claim 1, wherein the width W3 of the chamfered sipe in the tire width direction is in ratio to the width W1 of the land portion on which the chamfered sipe is arranged in the tire width direction, and the ratio is within the range of 0.3 ≤ W3 / W1 ≤ 0.7.

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