Pneumatic tire

Abstract

A pneumatic tire of the present disclosure has one or more sipes on a land portion, and each sipe has a narrow sipe portion extending inward in a tire radial direction from a portion open to a tread, and a widened portion extending to a sipe bottom while communicating to a tire radial inner end of the narrow sipe portion, the cutter groove width is larger than the cutter groove width of the narrow cutter groove part. The tire radial extension length of the widened portion is greater than the tire radial extension length of the narrow sipe portion. The widened portion has, on a side communicating with the narrow sipe portion, a portion defined by two tire radial outer edges that are inclined with respect to the tire radial direction in a cross-sectional view and extend in a straight line. Each tire-radial-direction outer edge extends obliquely at an inclination angle of 30-70 degrees with respect to the width direction in a cross-section orthogonal to the extension direction of the sipe.

Description

Technical Field

[0001] The present disclosure relates to a pneumatic tire. Background Art

[0002] Generally, the tread surface portion of a pneumatic tire has grooves for draining water. However, as wear progresses, the volume of the grooves decreases, which causes a problem of reduced drainage performance as wear progresses.

[0003] In response to this, techniques for improving the drainage performance of a tire during wear progress have been proposed, which involve providing slits in the tread surface portion that increase in width as wear progresses (see, for example, Patent Document 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-540077 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, if the width of the slit increases as wear progresses, the rigidity of the land portion decreases, which may lead to insufficient wet grip performance.

[0009] Therefore, an object of the present disclosure is to provide a pneumatic tire that improves drainage performance during wear progress while minimizing a decrease in the rigidity of the land portion.

[0010] Means for Solving the Problems

[0011] The gist of the present disclosure is as follows.

[0012] (1) A pneumatic tire having a land portion defined by grooves on the tread surface of the tread portion, wherein

[0013] the land portion has one or more slits,

[0014] the slit has a narrow slit portion and a widened portion, the narrow slit portion extending radially inward of the tire from an opening leading to the tread surface, the widened portion being connected to the radially inner end of the narrow slit portion and extending to the bottom of the slit, the slit width of the widened portion being greater than the slit width of the narrow slit portion,

[0015] the radially extending length of the widened portion is greater than the radially extending length of the narrow slit portion,

[0016] the widened portion has a portion defined by two radially outer edges of the tire on the side connected to the narrow slit portion, the radially outer edges extending linearly at an angle with respect to the tire radius in a cross-sectional view, and

[0017] Each radial outer edge of each said tire extends at an inclination angle of 30° to 70° with respect to the width direction in a cross-section perpendicular to the extending direction of the sipes.

[0018] Herein, the term "tread surface of the tread portion" means the entire circumferential outer surface of the tread portion that contacts the road surface when the inflated tire is mounted on the applicable rim, filled with the specified internal pressure, and loaded with the maximum load.

[0019] The term "sipes" means sipes having a width (opening width) narrow enough to close when contacting the ground.

[0020] Unless otherwise specified, terms such as "extension length", "sipe width", "inclination angle", etc., and the following shapes and dimensions are based on the reference conditions where the inflated tire is mounted on the applicable rim, filled with the specified internal pressure, and unloaded.

[0021] As used herein, the term "applicable rim" means the standard rim of applicable dimensions (the measuring rim in the European Standard Handbook and the design rim in the TRA Yearbook) described in the industrial standards effective for the region where the tire is produced and used, such industrial standards being, for example, the JATMA Yearbook of the JATMA (Japan Automobile Tire Manufacturers Association), the standard handbook of the ETRTO (European Tyre and Rim Technical Organization) in Europe, and the yearbook of the TRA (Tire and Rim Association, Inc.) in the United States (that is, the foregoing "rims" include current dimensions and future dimensions to be listed in the above industrial standards. Examples of "future dimensions to be listed" may be the dimensions listed as "FUTURE DEVELOPMENTS" in the 2013 edition of the ETRTO). For dimensions not listed in these industrial standards, the term "applicable rim" means a rim having a width corresponding to the bead width of the inflated tire.

[0022] As used herein, "specified internal pressure" means the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel of the appropriate size and ply rating as described in the foregoing JATMA Yearbook and other industrial standards. In the case where the dimensions are not listed in the foregoing industrial standards, "specified internal pressure" means the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted.

[0023] In addition, the term "maximum load" means the load corresponding to the above maximum load capacity.

[0024] Here, when each tire radially inner edge does not extend linearly in the cross-sectional view, the term "tilt angle of each tire radially inner edge with respect to the width direction in the cross-section perpendicular to the direction of the groove" shall mean the "tilt angle" when approximated by a straight line using the least squares method.

[0025] Here, the term "tread end" refers to the outermost position in the tire width direction on the ground contact surface under the maximum load condition. Further, the term "circumferential main groove" refers to a groove having a groove width (opening width) of 2 mm or more among the grooves extending in the tire circumferential direction.

[0026] Effects of the Invention

[0027] According to the present disclosure, a pneumatic tire can be provided that improves drainage performance during wear progress while minimizing a reduction in land rigidity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the drawings:

[0029] Figure 1 is an expanded view schematically showing a tread pattern of a pneumatic tire according to an embodiment of the present disclosure;

[0030] Figure 2 is a cross-sectional view of a width-direction groove;

[0031] Figure 3 is a cross-sectional view of a width-direction groove in a modified example;

[0032] Figure 4 is a cross-sectional view of the pneumatic tire in the tire width direction according to an embodiment of the present disclosure; and

[0033] Figure 5 is a cross-sectional view of the pneumatic tire in the tire width direction according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Here, the internal structure of the pneumatic tire (hereinafter simply referred to as "tire") may be the same as that of a conventional tire. As an 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. Further, the tire may also have a carcass that annularly straddles the bead portions and a belt portion disposed radially outside the crown portion of the carcass.

[0035] Figure 1 is an expanded view schematically showing a tread pattern of a pneumatic tire according to an embodiment of the present disclosure.

[0036] As Figure 1As shown, the tire in this example has a plurality of (three in the shown example) circumferential main grooves 2 (2a, 2b, 2c) extending in the circumferential direction of the tread on the tread surface 1 of the tread portion, and a plurality of (four in the shown example) land portions 3 (3a, 3b, 3c, 3d) defined between two circumferential main grooves 2 adjacent to each other in the tread width direction among the plurality of circumferential main grooves 2 or between the circumferential main grooves 2 (2a, 2c) and the tread end TE. In this example, one circumferential main groove 2b is located at the tire equatorial plane CL, and the other circumferential main grooves 2a and 2c are located in one tire half portion (on one side) and the other tire half portion (on the other side) in the tread width direction with the tire equatorial plane CL as the boundary, respectively. In this example, two land portions 3 are arranged in each tire half portion in the tread width direction. As shown, the land portions 3b, 3c are the land portions located on the central side in the tread width direction, and the land portions 3a, 3d are the land portions located adjacent to the tread end TE.

[0037] In Figure 1 the shown example, there are three circumferential main grooves, but there may also be two or four or more. Therefore, the number of land portions may also be three or five or more. In addition, in this example, all the land portions are ribbed land portions 3, but at least one land portion may be a non-ribbed land portion, that is, a block-shaped land portion. It should be noted that the term "ribbed land portion" refers to a land portion that is not completely divided by a width direction groove extending in the tread width direction in the tread circumferential direction. Therefore, in the specification, even if a land portion is completely divided by a width direction groove in the tread circumferential direction, the land portion is still a "ribbed land portion".

[0038] The groove width (opening width (the opening width measured perpendicular to the extending direction of the groove in the plan view)) of the circumferential main groove 2 is not particularly limited because the groove width depends on the number of the circumferential main grooves 2, but it can be, for example, 5 mm to 25 mm. Similarly, the groove depth (maximum depth) of the circumferential main groove 2 is not particularly limited, but it can be, for example, 6 mm to 18 mm.

[0039] In the shown example, in the plan view of the tread surface 1, the circumferential main grooves 2 all extend along the tread circumferential direction (without inclination), but at least one circumferential main groove 2 can extend obliquely with respect to the tread circumferential direction, and in this case, it can extend with an inclination angle of, for example, 5° or less with respect to the tread circumferential direction. In addition, in the shown example, the circumferential main grooves 2 all extend linearly along the tread circumferential direction, but at least one circumferential main groove 2 can have a serrated or curved shape.

[0040] In the illustrated example, each land portion 3 has a plurality of widthwise grooves 4 extending in the tread width direction. Specifically, in this example, each of the land portions 3a and 3d (rib-like in the illustrated example) adjacent to the tread end TE has three widthwise grooves 4 within the shown range, and each groove 4 extends from the tread end TE toward the inner side in the tread width direction and terminates within the land portions 3a and 3d (rib-like in the illustrated example). Further, each of the land portions 3b and 3c (rib-like in the illustrated example) on the center side in the tread width direction has three widthwise grooves 4 within the shown range, and each groove 4 extends from the circumferential main groove 2b located on the tire equatorial plane CL toward the outer side in the tread width direction and terminates within the land portions 3b and 3c (rib-like in the illustrated example). The number of the widthwise grooves 4 can be appropriately set. In the illustrated example, all the land portions 3 have the widthwise grooves 4. However, when the tread surface 1 has the widthwise grooves 4, it is sufficient if any one of the land portions 3 has the widthwise grooves 4, and preferably, the land portions 3 (land portions 3a and 3d in the illustrated example) defined by the tread end TE have the widthwise grooves 4.

[0041] Here, the groove width (opening width, the opening width measured perpendicular to the extending direction of the groove in the plan view) of the widthwise groove 4 is not particularly limited because the groove width also depends on the number of the widthwise grooves 4, but for example, it can be 1.0 mm to 1.5 mm. Similarly, the depth (maximum depth) of the widthwise groove 4 is not particularly limited, but for example, it can be 4 mm to 18 mm.

[0042] In the illustrated example, all the widthwise grooves 4 extend along the tread width direction (without inclination), but at least one widthwise groove 4 can extend obliquely with respect to the tread width direction. In this case, preferably, the widthwise groove extends at an inclination angle of 45° or less and more preferably 30° or less with respect to the tread width direction. Further, in the illustrated example, all the widthwise grooves 4 extend linearly along the tread width direction, but at least one widthwise groove 4 can have a bent portion.

[0043] Here, from the viewpoint of improving drainage performance, the widthwise groove 4 preferably opens to the tread end TE or the circumferential main groove 2 as in the illustrated example. On the other hand, in order to increase the rigidity of the land portion 3, the widthwise groove 4 can be configured not to open to the tread end TE or the circumferential main groove 2, and both ends of the widthwise groove 4 can terminate within the land portion 3. In the land portion 3 defined by two circumferential main grooves 2 adjacent to each other in the tread width direction, the widthwise groove 4 can open in either one of the two circumferential main grooves 2.

[0044] Each land portion 3 also has a plurality of widthwise grooves 5 extending in the tread width direction. In the illustrated example, each land portion 3 has a plurality of widthwise grooves 5 extending in the tread width direction. Specifically, in this example, each of the land portions 3a and 3d adjacent to the tread ends TE has three widthwise grooves 5 within the illustrated range, and each widthwise groove 5 extends outward in the tread width direction from the circumferential main grooves 2a and 2c and terminates within the land portions 3a and 3d. Further, each of the land portions 3b and 3c on the center side in the tread width direction has three widthwise grooves 5 within the illustrated range, and each widthwise groove 5 extends inward in the tread width direction from the circumferential main grooves 2a and 2c and terminates within the land portions 3a and 3d. The number of widthwise grooves can be set appropriately. In the illustrated example, all of the land portions 3 have widthwise grooves 5. However, when the tread surface 1 has widthwise grooves 5, if any one of the land portions 3 has widthwise grooves 5, that is sufficient, and preferably, the land portions 3 defined by the tread ends TE (in the illustrated example, the land portions 3a and 3d) have widthwise grooves 5.

[0045] Here, the width of the widthwise groove 5 (the opening width (the opening width measured perpendicular to the extending direction of the groove in the plan view)) is not particularly limited because it also depends on the number of widthwise grooves 5, but it can be, for example, from 0.2 mm to 1.0 mm. Similarly, the depth (the maximum depth) of the widthwise groove 5 is not particularly limited, but it can be set to, for example, from 4.0 mm to 18.0 mm.

[0046] In the illustrated example, all of the widthwise grooves 5 extend along the tread width direction (without inclination), but at least one widthwise groove 5 can extend obliquely with respect to the tread width direction. In this case, preferably, the widthwise groove 5 extends at an inclination angle of 45° or less and more preferably 30° or less with respect to the tread width direction. Further, in the illustrated example, all of the widthwise grooves 5 extend linearly along the tread width direction, but at least one widthwise groove 5 can have a bent portion.

[0047] Here, from the viewpoint of improving drainage performance, the widthwise groove 5 preferably opens to the tread end TE or the circumferential main groove 2, as in the illustrated example. On the other hand, in order to increase the rigidity of the land portion 3, the widthwise groove 5 can be configured not to open to the tread end TE or the circumferential main groove 2, and both ends of the widthwise groove 5 can terminate within the land portion 3. Further, in the land portion 3 defined by two circumferential main grooves 2 adjacent to each other in the tread width direction, the widthwise groove 5 can open in either one of the two circumferential main grooves 2.

[0048] Here, in the illustrated example, when viewed circumferentially of the tread, the widthwise grooves 4 and the widthwise sipes 5 are alternately arranged. This allows for a more appropriate balance in the rigidity of the land portions 3. On the other hand, when viewed circumferentially of the tread, there may be positions where two or more widthwise grooves 4 are continuously arranged between two adjacent widthwise sipes 5 in the tread circumferential direction, or there may be positions where two or more widthwise sipes 5 are continuously arranged between two adjacent widthwise grooves 4 in the tread circumferential direction.

[0049] In addition, in the illustrated example, both the widthwise grooves 4 and the widthwise sipes 5 terminate at the center in the tread width direction of the land portions 3, but when projected in the tread circumferential direction, the widthwise grooves 4 and the widthwise sipes 5 may have an overlapping portion, or may be arranged not to overlap.

[0050] In this way, the pneumatic tire of the present embodiment has land portions defined by grooves in the tread surface 1 of the tread portion, and the land portions 3 have one or more sipes.

[0051] Figure 2 is a cross-sectional view of the widthwise sipe (in a cross-section perpendicular to its extending direction). As Figure 2 shown, the widthwise sipe 5 has a narrow sipe portion 5a and a widened portion 5b. The narrow sipe portion 5a extends from the opening leading to the tread surface 1 to the radially inner side of the tire, and the widened portion 5b is connected to the radially inner end of the narrow sipe portion 5a and extends to the sipe bottom 5c, having a sipe width larger than that of the narrow sipe portion 5a.

[0052] In this example, the narrow sipe portion 5a is a flat-plate-shaped sipe having a constant (that is, equal to the opening width at the tread surface 1) sipe width (measured parallel to the tread surface 1 in the cross-sectional view). On the other hand, the narrow sipe portion 5a may be a three-dimensional sipe that extends while being bent in the depth direction.

[0053] In this embodiment, the widened portion 5b has: a sipe width gradually increasing portion 51, where the sipe width gradually increases from the radially outer side to the inner side of the tire and is connected to the narrow sipe portion; and a sipe width gradually decreasing portion 53, where the sipe width gradually decreases from the radially outer side to the inner side of the tire and extends to the sipe bottom. In this example, the widened portion 5b has an intermediate portion 52 between the sipe width gradually increasing portion 51 and the sipe width gradually decreasing portion 53, and the sipe width of the intermediate portion 52 has a small variation. In addition, in the illustrated example, the sipe bottom 5c is straight, but it may also be curved, and a curved shape is preferred to prevent cracks from occurring in the sipe bottom 5c.

[0054] In the illustrated example, the widened portion 5b is diamond-shaped in the cross-sectional view. In other words, when the widths of the connecting portions of the narrow groove portion 5a and the connecting portions of the middle portion 52 and the groove bottom 5c are considered as points, the approximate shape of the cross-sectional view of the widened portion 5b is diamond-shaped.

[0055] Here, the widened portion 5b has a portion defined by two radially outer tire edges 5b1, 5b2 on the side connected to the narrow groove portion 5a. The radially outer tire edges 5b1, 5b2 extend linearly at an angle with respect to the tire radial direction in the cross-sectional view, and each of the radially outer tire edges 5b1, 5b2 extends at an inclination angle θ1 of 30° to 70° (more preferably, 40° to 65°) with respect to the width direction in a cross-section perpendicular to the groove extending direction. In the illustrated example, the radially outer tire edge 5b1 and the radially outer tire edge 5b2 are inclined in opposite directions at the same inclination angle with respect to the width direction in a cross-section perpendicular to the groove extending direction (such that the extension lines cross each other). Therefore, in this example, the groove width gradually increasing portion 51 is substantially an isosceles triangle in the cross-sectional view (when the width of the connecting portion of the narrow groove region portion 5a is considered as a point).

[0056] In addition, the widened portion 5b has a portion defined by two radially inner tire edges 5b3 and 5b4 on the side of the groove bottom 5c. The radially inner tire edges 5b3 and 5b4 are inclined with respect to the tire radial direction, and each of the radially inner tire edges 5b3 and 5b4 extends at an inclination angle θ2 of 30° to 60° (more preferably, 35° to 55°) with respect to the width direction in a cross-section perpendicular to the groove extending direction. In the illustrated example, the radially inner tire edge 5b3 and the radially inner tire edge 5b4 are inclined in opposite directions at the same inclination angle with respect to the width direction in a cross-section perpendicular to the groove extending direction (such that the extension lines cross each other). Therefore, in this example, the groove width gradually decreasing portion 53 is substantially an isosceles triangle in the cross-sectional view (when the width of the groove bottom is considered as a point).

[0057] Here, the groove width w1 of the narrow groove portion 5a is not particularly limited, but can be, for example, 0.2 mm to 1.0 mm. The extension length h1 of the narrow groove portion 5a in the tire radial direction is not particularly limited, but can be, for example, 2.0 mm to 12 mm.

[0058] The maximum width w2 of the widened portion 5b is not particularly limited, but can be, for example, 1.2 mm to 6.0 mm. The extension length h2 of the widened portion 5b in the tire radial direction is longer than the extension length h1 of the narrow groove portion 5a in the tire radial direction, and is not particularly limited, but can be, for example, 2.5 mm to 11.0 mm.

[0059] In Figure 2In the example, the extension length h21 of the gradually increasing part 51 of the groove width in the tire radial direction is not particularly limited, but may be, for example, 1.0 mm to 3.0 mm; the extension length h22 of the middle part 52 in the tire radial direction is not particularly limited, but may be, for example, 0.2 mm to 0.4 mm; the extension length h23 of the gradually decreasing part 53 of the groove width in the tire radial direction is not particularly limited, but may be, for example, 1.5 mm to 8.0 mm. The groove depth (maximum depth) h of the width-direction groove 5 is not particularly limited, but may be, for example, 4.0 mm to 18.0 mm.

[0060] The ratio h21 / h23 is preferably 0.9 to 1.1. In addition, the width of the groove bottom 5c is preferably greater than the groove width of the narrow groove part 5a.

[0061] The effects of the pneumatic tire of the present embodiment will be described below.

[0062] First, since the pneumatic tire of the present embodiment has one or more width-direction grooves 5 and the width-direction grooves 5 have widened parts 5b in the land part 3, the drainage performance during wear progress can be improved. In addition, since the extension length h2 of the widened part 5b in the tire radial direction is longer than the extension length h1 of the narrow groove part 5a in the tire radial direction, the period during which the drainage performance can be improved can be ensured for a long time.

[0063] The present inventor focused on the rigidity caused by the shape of the land part itself defined by the grooves, and when the shape of the widened part in the cross-sectional view is rectangular, various-shaped rubber parts were provided at the corners of the widened part to enhance the rigidity at the corners. Therefore, the present inventor found that, as Figure 2 in the case of the rubber parts 61 to 63 shown, the case where the shape in the cross-sectional view is triangular has a higher burden rate of compressive rigidity per unit volume than the case where the shape in the cross-sectional view is rectangular, and the rigidity can be effectively improved. In addition, the inventor also focused on the inclination angle of the hypotenuse of the triangular rubber part in the cross-sectional view with respect to the width direction in the cross-section perpendicular to the groove extension direction. Therefore, the present inventor found that, as can be seen in the following examples, when the inclination angles of the two radially outer edges 5b1 and 5b2 of the tire with respect to the width direction in the cross-section perpendicular to the groove extension direction are 30° to 70° (more preferably, 40° to 65°), or when the inclination angles of the two radially inner edges 5b3 and 5b4 of the tire with respect to the width direction in the cross-section perpendicular to the groove extension direction are 30° to 60° (more preferably, 35° to 55°), the burden rate of compressive rigidity per unit volume is the highest.

[0064] In the present embodiment, the widened portion 5b has a portion defined by two radially outer tire edges 5b1 and 5b2 on the side connected to the narrow groove portion 5a. The radially outer tire edges 5b1 and 5b2 extend linearly at an angle with respect to the tire radius in a sectional view, and each of the radially outer tire edges 5b1 and 5b2 extends at an inclination angle of 30° to 70° with respect to the width direction in a section perpendicular to the groove extending direction. Therefore, the rigidity of the land portion defined by the groove is relatively high with respect to the groove volume.

[0065] As described above, for the pneumatic tire according to the present embodiment, the drainage performance during wear progress can be improved while minimizing the reduction of land rigidity.

[0066] As in the above embodiment, preferably, the widened portion 5b has a portion defined by two radially inner tire edges 5b3 and 5b4 on the side of the groove bottom 5c. The radially inner tire edges 5b3 and 5b4 are inclined with respect to the tire radius, and each of the radially inner tire edges 5b3 and 5b4 extends at an inclination angle of 30° to 60° (more preferably, 35° to 55°) with respect to the width direction in a section perpendicular to the groove extending direction. This enables a shape with relatively high rigidity with respect to the groove volume to be provided even on the side of the groove bottom 5c, thereby further suppressing the reduction of land rigidity.

[0067] To achieve the above effects, preferably, the widened portion 5b has a groove width gradually increasing portion 51 and a groove width gradually decreasing portion 53. In the groove width gradually increasing portion 51, the groove width gradually increases from the radially outer side to the inner side of the tire and is connected to the narrow groove portion 5a. In the groove width gradually decreasing portion 53, the groove width gradually decreases from the radially outer side to the inner side of the tire and extends to the groove bottom 5c. Similarly, the widened portion 5b is preferably diamond-shaped in a sectional view.

[0068] Figure 3 is a sectional view of the widthwise groove in the modified example. Figure 3 The widthwise groove 5 shown also has: a narrow groove portion 5a that extends from an opening leading to the tread surface 1 toward the radially inner side of the tire; and a widened portion 5b that is connected to the radially inner end of the narrow groove portion 5a and extends to the groove bottom 5c and has a groove width larger than that of the narrow groove portion 5a. Figure 3 The groove shown is Figure 2 different from the widthwise groove shown in that it has a smaller maximum width.

[0069] The narrow groove portion 51 is Figure 2 the same as that shown, and thus will not be described again. Additionally, in Figure 3In this case, the widened portion 5b has a gradually increasing groove width portion 51 and a gradually decreasing groove width portion 53. In the gradually increasing groove width portion 51, the groove width gradually increases from the radially outer side to the inner side of the tire and is connected to the narrow groove portion 5a. In the gradually decreasing groove width portion 53, the groove width gradually decreases from the radially outer side to the inner side of the tire and extends to the bottom of the groove. In this example, the widened portion 5b has an intermediate portion 52 between the gradually increasing groove width portion 51 and the gradually decreasing groove width portion 53, and the intermediate portion 52 has a substantially constant groove width. In the illustrated example, the intermediate portion 52 is defined as straight in the cross-sectional view, but it may also be curved within a range where the groove width is substantially constant. Further, in the illustrated example, the bottom 5c of the groove is straight, but it may also be curved, and a curved shape is preferred to prevent cracks from forming in the bottom 5c of the groove.

[0070] In the illustrated example, the widened portion 5b in the cross-sectional view is substantially hexagonal. In other words, when the widths of the connecting portions of the narrow groove portion 5a and the bottom 5c of the groove are regarded as points, the general shape in the cross-sectional view of the widened portion 5b is hexagonal ( Figure 2 different from the intermediate portion 52 which is not regarded as a point).

[0071] As in Figure 2 the case of, the widened portion 5b has a portion defined by two radially outer tire edges 5b1 and 5b2 on the side connected to the narrow groove portion 5a. The radially outer tire edges 5b1 and 5b2 extend linearly at an angle with respect to the tire radius in the cross-sectional view, and each of the radially outer tire edges 5b1 and 5b2 extends at an inclination angle θ1 of 30° to 70° (more preferably, 40° to 65°) with respect to the width direction in a cross-section perpendicular to the groove extending direction. In the illustrated example, the radially outer tire edge 5b1 and the radially outer tire edge 5b2 are inclined in opposite directions at the same inclination angle with respect to the width direction in a cross-section perpendicular to the groove extending direction (such that the extension lines cross each other). Therefore, in this example, the gradually increasing groove width portion 51 is approximately isosceles triangular in the cross-sectional view.

[0072] Further, as in Figure 2In the case as described above, the widened portion 5b has a part defined by two radially inner edges 5b3 and 5b4 of the tire on one side of the bottom 5c of the groove, the radially inner edges 5b3 and 5b4 of the tire are inclined radially with respect to the tire, and each of the radially inner edges 5b3 and 5b4 of the tire extends at an inclination angle θ2 of 30° to 60° (more preferably, 35° to 55°) with respect to the width direction in a cross-section perpendicular to the extending direction of the groove. In the illustrated example, the radially inner edge 5b3 of the tire and the radially inner edge 5b4 of the tire are inclined in opposite directions at the same inclination angle with respect to the width direction in a cross-section perpendicular to the extending direction of the groove (such that the extension lines cross each other). Therefore, in this example, the groove width gradually decreasing portion 53 is substantially an isosceles triangle in the cross-sectional view.

[0073] Here, the groove width w1 of the narrow groove portion 5a is not particularly limited, but may be, for example, 0.2 mm to 1.0 mm. The extending length h1 of the narrow groove portion 5a in the tire radial direction is not particularly limited, but may be, for example, 2.0 mm to 12 mm.

[0074] The maximum width w2 of the widened portion 5b is not particularly limited, but may be set to, for example, 2.0 mm to 4.0 mm. The extending length h2 of the widened portion 5b in the tire radial direction is longer than the extending length h1 of the narrow groove portion 5a in the tire radial direction, and is not particularly limited, but may be, for example, 2.0 mm to 6.0 mm.

[0075] In Figure 3 the example, the extending length h21 of the groove width gradually increasing portion 51 in the tire radial direction is not particularly limited, but may be, for example, 0.8 mm to 2.5 mm; the extending length h22 of the middle portion 52 in the tire radial direction is not particularly limited, but may be, for example, 0.4 mm to 1.5 mm; the extending length h23 of the groove width gradually decreasing portion 53 in the tire radial direction is not particularly limited, but may be, for example, 0.6 mm to 2.0 mm. The groove depth (maximum depth) h of the groove 5 in the width direction is not particularly limited, but may be, for example, 4.0 mm to 18.0 mm.

[0076] In Figure 3 the case, the ratio h21 / h23 is preferably 0.7 to 1.3. In addition, it is preferable that the width of the bottom 5c of the groove is larger than the groove width of the narrow groove portion 5a.

[0077] Figure 3 The modification in Figure 3 also has the effect of improving the drainage performance during wear progress while minimizing the reduction of the land portion rigidity. In addition, in

[0078] The above example illustrates the case of a groove extending in the tire width direction (without inclination), i.e., a width-direction groove, but the groove can also be a width-direction groove extending at an angle with respect to the tire width direction. In addition, the groove can be a circumferential groove extending along the tire circumference. In this case, the shape and dimensions in a cross-section orthogonal to the tire circumference (the extending direction of the circumferential groove) will be, for example, as Figure 2 and Figure 3 shown. In addition, a pattern combining width-direction grooves and circumferential grooves can also be used.

[0079] The pneumatic tire of the present embodiment is particularly suitable for use as a passenger car tire and a heavy-duty tire (especially truck and bus tires).

[0080] Figure 4 is a cross-sectional view of the pneumatic tire according to an embodiment of the present disclosure in the tire width direction. As Figure 4 shown, the tire can include an RF tag as a communication device. The RF tag includes an IC chip and an antenna. For example, the RF tag can be arranged, for example, by being sandwiched between a plurality of members of the same type or different types constituting the tire. This makes it easier to attach the RF tag during tire manufacturing and improves the productivity of the tire including the RF tag. In this example, the RF tag can be arranged by being sandwiched between the bead filler and other components adjacent to the bead filler. The RF tag can be embedded in any component constituting the tire. In this way, compared with the case where the RF tag is arranged by being sandwiched between a plurality of components constituting the tire, the load applied to the RF tag can be reduced. This improves the durability of the RF tag. In this example, the RF tag can be embedded in rubber components such as tread rubber and sidewall rubber. Preferably, the RF tag is not arranged at a position at the boundary between components having different rigidity levels in the direction along the peripheral length (the direction along the outer surface of the tire in the tire width-direction cross-sectional view). In this way, the RF tag is not arranged at a position where strain is likely to concentrate due to the difference in rigidity. Therefore, the load applied to the RF tag can be reduced. This improves the durability of the RF tag. In this example, preferably, the RF tag is not arranged at the boundary between the end of the carcass and the component (e.g., sidewall rubber) adjacent to this end of the carcass in the tire width-direction cross-sectional view. The number of RF tags is not particularly limited. The tire can include only one RF tag, or can include two or more RF tags. Here, the RF tag is described as an example of a communication device, but communication devices other than the RF tag can also be used.

[0081] For example, the RF tag can be disposed in the tread face of the tire. In this way, the RF tag will not be damaged by side cuts on the tire. For example, the RF tag can be disposed at the center in the tire width direction of the tread face. The center of the tread is a position where deflection in the tread face is not concentrated. In this way, the load applied to the RF tag can be reduced. This improves the durability of the RF tag. In addition, this also prevents communication performance differences of the tire from the two outer sides in the tire width direction with the RF tag. In this example, the RF tag can be disposed within a range of, for example, 1 / 2 of the tread width in the tire width direction centered on the tire equatorial plane. For example, the RF tag can be disposed at the tread end in the tire width direction. If the position of the reader that communicates with the RF tag is predetermined, the RF tag can be disposed, for example, at the tread end on the side closer to the reader. In this example, the RF tag can be disposed within a range of, for example, 1 / 4 of the tread width in the tire width direction with the tread end as the outer end.

[0082] The RF tag can be disposed, for example, closer to the tire cavity than the carcass including one or more carcass plies that cross the bead portion. In this way, the RF tag becomes less vulnerable to damage from external impacts on the tire (such as side cuts and nail punctures, etc.). As an example, the RF tag can be disposed in close contact with the carcass surface on the tire cavity side. As another example, when there is another component closer to the tire cavity than the carcass, the RF tag can be disposed, for example, between the carcass and this other component located at a position closer to the tire cavity than the carcass. An example of another component located at a position closer to the tire cavity than the carcass is the inner liner that forms the inner surface of the tire. As another example, the RF tag can be attached to the inner surface of the tire facing the tire cavity. By having a structure in which the RF tag is attached to the inner surface of the tire, it is easy to attach the RF tag to the tire, and it is easy to inspect and replace the RF tag. In other words, the ease of attachment and maintenance of the RF tag can be improved. In addition, by attaching the RF tag to the inner surface of the tire, compared with a structure in which the RF tag is buried inside the tire, it can be prevented that the RF tag becomes the core of tire failure. In addition, when the carcass has a plurality of carcass plies and there is a position where the plurality of carcass plies overlap each other, the RF tag can be disposed between the overlapping carcass plies.

[0083] For example, the RF tag may be disposed in the tread surface portion of the tire on the radially outer side of the belt portion including one or more belt plies. As an example, the RF tag may be disposed on the radially outer side of the belt portion of the tire and in close contact with the belt portion. As another example, when a reinforcing belt layer is provided, the RF tag may be disposed on the radially outer side of the reinforcing belt layer of the tire and in close contact with the reinforcing belt layer. As yet another example, the RF tag may be embedded in the tread rubber on the radially outer side of the belt portion of the tire. By disposing the RF tag in the tread surface portion of the tire on the radially outer side of the belt portion, communication with the RF tag from the radially outer side of the tire is less likely to be interfered with by the belt portion. This improves the communication performance with the RF tag from the radially outer side of the tire. Further, the RF tag may be embedded in the tread rubber on the radially inner side of the belt portion of the tire. In this way, the radially outer side of the RF tag is covered by the belt portion, so the RF tag is less likely to be damaged by an impact from the tread surface or a nail piercing the tread surface. As an example thereof, the RF tag may be disposed between the belt portion and the carcass located on the radially inner side of the belt portion. Further, when the belt portion includes a plurality of belt plies, the RF tag in the tread surface portion of the tire may be disposed between any two belt plies. In this way, the radially outer side of the RF tag is covered by one or more belt plies, so the RF tag becomes less likely to be damaged by an impact from the tread surface or a nail piercing the tread surface.

[0084] Figure 5 FIG. 4 is a cross-sectional view in the tire width direction of a pneumatic tire according to another embodiment of the present disclosure. The RF tag may be disposed, for example, between the cushion rubber and the tread rubber, or between the cushion rubber and the sidewall rubber. In this way, the impact on the RF tag can be mitigated by the cushion rubber. This improves the durability of the RF tag. Further, for example, the RF tag may be embedded in the cushion rubber. Further, the cushion rubber may be composed of a plurality of rubber members of the same or different types adjacent to each other. In this case, the RF tag may be disposed by being sandwiched between the plurality of rubber members constituting the cushion rubber.

[0085] The RF tag can be disposed at a position, for example, in a sidewall portion or a bead portion of a tire. For example, the RF tag can be disposed on the sidewall portion or the bead portion on a side closer to a reader that can communicate with the RF tag. In this way, the communication performance between the RF tag and the reader can be improved. As an example, the RF tag can be disposed between a carcass and a sidewall rubber, or between a tread rubber and a sidewall rubber. For example, the RF tag can be disposed between a position where the tire has a maximum width and a position in the tire radial direction of the tread surface. In this way, compared with a configuration in which the RF tag is disposed on the inner side in the tire radial direction of the position where the tire has the maximum width, the communication performance with the RF tag from the outer side in the tire radial direction of the tire can be improved. For example, the RF tag can be disposed on the inner side in the tire radial direction of the position where the tire has the maximum width. In this way, the RF tag is disposed near the bead portion having a higher rigidity. Therefore, the load applied to the RF tag is reduced, which in turn improves the durability of the RF tag. As an example, the RF tag can be disposed at a position adjacent to a bead core in the radial direction or the tire width direction. The area around the bead core is less likely to be strained. Therefore, the load applied to the RF tag is reduced, which in turn improves the durability of the RF tag. In particular, it is preferable that the RF tag is disposed on the inner side in the tire radial direction of the position where the tire has the maximum width and on the outer side in the tire radial direction of the bead core in the bead portion. In this way, the durability of the RF tag can be improved, while the communication between the RF tag and the reader is less likely to be interfered with by the bead core, and the communication performance of the RF tag can be improved. Further, when the sidewall rubber is composed of a plurality of rubber members of the same or different types adjacent to each other in the tire radial direction, the RF tag can be disposed by being sandwiched between the plurality of rubber members constituting the sidewall rubber.

[0086] Such as Figure 4As shown, the RF tag can be arranged by being sandwiched between the bead filler and a component adjacent to the bead filler. In this way, the RF tag can be arranged at a position where strain is less likely to concentrate due to the configuration of the bead filler. Therefore, the load applied to the RF tag is reduced, which in turn improves the durability of the RF tag. The RF tag can be arranged, for example, by being sandwiched between the bead filler and the carcass. The portion of the carcass that sandwiches the RF tag together with the bead filler can be located at a position outside the tire width direction with respect to the bead filler, or can be located at a position inside the tire width direction with respect to the bead filler. When the portion of the carcass that sandwiches the RF tag together with the bead filler is located at a position outside the tire width direction of the bead filler, the load applied to the RF tag caused by an impact or damage to the tire from the outside in the tire width direction of the tire can be further reduced. This makes it possible to further improve the durability of the RF tag. In addition, the bead filler can have a portion configured adjacent to the sidewall rubber. In this case, the RF tag can be arranged by being sandwiched between the bead filler and the sidewall rubber. In addition, the bead filler can also have a portion configured adjacent to the rubber chafer. In this case, the RF tag can be arranged by being sandwiched between the bead filler and the rubber chafer.

[0087] As Figure 5As shown, the RF tag can be arranged between the reinforcing member and the member adjacent to the reinforcing member. In this way, the RF tag can be arranged at a position where strain is less likely to concentrate due to the placement of the reinforcing member. Therefore, the load applied to the RF tag is reduced, which in turn improves the durability of the RF tag. For example, the RF tag can be arranged by being sandwiched between the reinforcing member and the sidewall rubber. Alternatively, the RF tag can be arranged by being sandwiched between the reinforcing member and the carcass. The portion of the carcass that sandwiches the RF tag together with the reinforcing member in place can be located on the outer side in the tire width direction with respect to the reinforcing member, or can be located on the inner side in the tire width direction with respect to the reinforcing member. When the portion of the carcass that sandwiches the RF tag together with the reinforcing member in place is located on the outer side in the tire width direction with respect to the reinforcing member, the load applied to the RF tag caused by an impact or damage to the tire from the outer side in the tire width direction of the tire can be further reduced. This makes it possible to further improve the durability of the RF tag. The reinforcing member can also include a portion disposed adjacent to the rubber bead filler. In this case, the RF tag can be arranged by being sandwiched between the reinforcing member and the rubber bead filler. The reinforcing member can include a portion adjacent to the cap rubber on the outer side in the tire width direction. In this case, the RF tag can be arranged by being sandwiched between the reinforcing member and the cap rubber. The reinforcing member can be composed of a plurality of rubber members having different hardnesses. In this case, the RF tag can be arranged by being sandwiched between the plurality of rubber members constituting the reinforcing member. The RF tag can be arranged by being sandwiched between the cap rubber and the member adjacent to the cap rubber. For example, the RF tag can be arranged by being sandwiched between the cap rubber and the carcass ply. In this way, the impact on the RF tag can be mitigated by the cap rubber, and this improves the durability of the RF tag.

[0088] The RF tag can be arranged, for example, between the rubber bead filler and the sidewall rubber. In this way, the RF tag can be arranged at a position where strain is less likely to concentrate due to the arrangement of the rubber bead filler. This reduces the load applied to the RF tag and improves the durability of the RF tag. The RF tag can be arranged, for example, by being sandwiched between the rubber bead filler and the carcass. In this way, the load applied to the RF tag due to an impact or damage from the rim can be reduced. This improves the durability of the RF tag.

[0089] As Figure 5As shown, the RF tag can be arranged by being sandwiched between the steel bead filler and another component adjacent to the outer or inner side of the steel bead filler in the tire width direction. In this way, when the tire deforms, the position of the RF tag is less likely to change. This reduces the load applied to the RF tag when the tire deforms, and this improves the durability of the RF tag. Another component adjacent to the outer or inner side of the steel bead filler in the tire width direction can be a rubber member, such as a rubber bead filler. In addition, another component adjacent to the outer or inner side of the steel bead filler in the tire width direction can be, for example, the carcass.

[0090] As Figure 4 shown, a belt reinforcement layer can be provided on the outer side in the tire radial direction of the belt. For example, the belt reinforcement layer can be made of cords made of polyethylene terephthalate, and the cords are continuously spirally wound in the tire circumferential direction. By applying an adhesive under a tension of 6.9×10 -2 N / tex or greater to make the cords, and the elastic modulus under a load of 29.4 N measured at 160 °C can be 2.5 mN / tex% or greater. In addition, the belt reinforcement layer can be arranged to cover the entire belt, or can be arranged to cover only the two ends of the belt. Additionally, the winding density per unit width of the belt reinforcement layer can vary according to the position in the width direction. In this way, road noise and flat spots can be reduced without reducing high-speed durability.

[0091] Example

[0092] (Example 1)

[0093] To verify the effectiveness of the present disclosure, simulations were conducted to evaluate Figure 2 the sipe (Example 1) shown in Figure 3 the sipe (Example 2) shown in, and the shear rigidity of the sipe having a widened portion that is rectangular in cross-section (the construction of the narrow sipe portion is the same as that of Example 1 and 2, and the maximum width of the widened portion is also the same as that of Example 1 and 2) (Comparative Example).

[0094] For Example 1, w1 = 0.2 mm, w2 = 3.0 mm, h1 = 3.2 mm, h21 = 1.75 mm, h22 = 0.10 mm, and h23 = 1.75 mm; each outer edge in the tire radial direction extends at an inclination angle of 52° with respect to the width direction in a cross-section perpendicular to the sipe extension direction; and each inner edge in the tire radial direction extends at an inclination angle of 52° with respect to the width direction in a cross-section perpendicular to the sipe extension direction.

[0095] For Example 2, w1 = 0.2 mm, w2 = 2.6 mm, h1 = 3.2 mm, h21 = 1.22 mm, h22 = 0.88 mm, and h23 = 1.5 mm; each radially outer edge of the tire extends at an inclination angle of 52° with respect to the width direction in a cross-section perpendicular to the extending direction of the knife groove; and each radially inner edge of the tire extends at an inclination angle of 48° with respect to the width direction in a cross-section perpendicular to the extending direction of the knife groove.

[0096] The evaluation of the shear rigidity is carried out by comparing the frictional force in the shear direction that occurs on the tread surface when a tread block (30.0 × 36.0 × 8.0 mm) containing a knife groove is subjected to a shear strain of approximately 6.0%.

[0097] When setting the comparative example as an index of 100 (the higher the number, the higher the shear rigidity), the value of Example 1 is 102.9.

[0098] Next, tests are carried out on Examples 1 and 2 to evaluate the distortion when removed from the mold. In order to calculate the maximum distortion that occurs when the blade is removed from the mold, the test is performed by photographing the blade pulled out from the mold. In the evaluation where the distortion of Example 1 is set as an index of 100 (the larger the number, the greater the distortion), the value of Example 2 is 78.3, and Example 2 can better suppress the distortion than Example 1.

[0099] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)]

[0100] In order to achieve a sustainable society, the SDGs have been proposed. One implementation of the present disclosure is considered to contribute to the technologies of "No. 12 - Ensure sustainable consumption and production patterns" and "No. 13 - Take urgent action to combat climate change and its impacts".

[0101] List of reference numerals

[0102] 1 Tread

[0103] 2 Circumferential main groove

[0104] 3 Tread block

[0105] 4 Width direction groove

[0106] 5 Width direction knife groove

[0107] 5a Narrow knife groove part

[0108] 5b Widening part

[0109] 5c Knife groove bottom

[0110] 51 Knife groove width gradually increasing part

[0111] 52 Middle part

[0112] 53 Groove width gradually decreasing part

[0113] 61 - 64 Rubber parts

[0114] 100, 200 Communication devices

[0115] CL Tire equatorial plane

[0116] TE Tread end

Claims

1. A pneumatic tire having a tread surface on a tread face thereof with land portions defined by grooves, wherein, the land portions have one or more sipes, the sipes have a narrow sipe portion and a widened portion, the narrow sipe portion extending radially inward of the tire from an opening leading to the tread surface, the widened portion being connected to a radially inner end of the narrow sipe portion and extending to the bottom of the sipe, the sipe width of the widened portion being greater than the sipe width of the narrow sipe portion, the radially extending length of the widened portion in the tire is greater than the radially extending length of the narrow sipe portion in the tire, the widened portion has a part defined by two radially outer edges of the tire on a side connected to the narrow sipe portion, the radially outer edges of the tire extending linearly at an angle with respect to the tire radius in a sectional view, and each of the radially outer edges of the tire extends at an inclination angle of 30° to 70° with respect to the width direction in a section perpendicular to the extending direction of the sipe.

2. The pneumatic tire according to claim 1, wherein, each of the radially outer edges of the tire extends at an inclination angle of 40° to 65° with respect to the width direction in a section perpendicular to the extending direction of the sipe.

3. The pneumatic tire according to claim 1 or 2, wherein, the widened portion has a part defined by two radially inner edges of the tire on a side of the bottom of the sipe, the radially inner edges of the tire being inclined with respect to the tire radius, and each of the radially inner edges of the tire extends at an inclination angle of 30° to 60° with respect to the width direction in a section perpendicular to the extending direction of the sipe.

4. The pneumatic tire according to any one of claims 1 to 3, wherein, the widened portion has a sipe width gradually increasing portion and a sipe width gradually decreasing portion, in the sipe width gradually increasing portion, the sipe width gradually increases from the radially outer side to the inner side of the tire and is connected to the narrow sipe portion, in the sipe width gradually decreasing portion, the sipe width gradually decreases from the radially outer side to the inner side of the tire and extends to the bottom of the sipe.

5. The pneumatic tire according to any one of claims 1 to 4, wherein, the widened portion is substantially diamond-shaped in section.

6. The pneumatic tire according to any one of claims 1 to 4, wherein, the widened portion is substantially hexagonal in section.

7. The pneumatic tire according to any one of claims 1 to 6, wherein, the narrow sipe portion is a flat sipe.

8. The pneumatic tire according to any one of claims 1 to 6, wherein, the narrow sipe portion is a three-dimensional sipe that extends while being bent in the depth direction.

9. The pneumatic tire according to any one of claims 1 to 8, having one or more circumferential main grooves extending in the tire circumferential direction, and the sipes are provided at least on the outermost land portions in the tire width direction defined by the tread ends and the circumferential main grooves.

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