Pneumatic tire

Abstract

An object of the present invention is to provide a pneumatic tire having a sipe in which the occurrence of a crack is suppressed.SOLUTION: A pneumatic tire of the present invention is a pneumatic tire in which a sipe is formed in a land portion, wherein the sipe has a main portion and an end portion, and the main portion and the end portion are smoothly connected to each other in a plan view.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] BACKGROUND ART Conventionally, pneumatic tires have been proposed that have sipes, each of which has a circular or elliptical hole connected to the end of a linear portion in plan view (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-001614 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the pneumatic tire as described above, angular portions are formed at the connection portions between the linear portions and the holes, and there is a risk of cracks occurring at these portions.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire having sipes that suppress the occurrence of cracks. [Means for solving the problem]

[0006] The gist and configuration of the present invention are as follows. (1) A pneumatic tire with sipes formed in the land portion, The sipe has a main body and an end portion, A pneumatic tire, characterized in that, in a plan view, the main body portion and the end portion are smoothly connected.

[0007] (2) A pneumatic tire according to (1), wherein the main body and the end are connected to form a continuously curved line without any angular portions when viewed in a plane.

[0008] (3) The pneumatic tire according to (1) or (2), wherein the sipe is a closed sipe whose both ends terminate within the land portion.

[0009] (4) The pneumatic tire according to any one of (1) to (3), wherein the main body portion is a linear portion in a plan view.

[0010] (5) The end portion has, from the side closest to the main body portion, a first curved portion, a second curved portion, and a third curved portion, The pneumatic tire according to any one of (1) to (4), wherein, in a plan view, the third curved portion has a semicircular shape, and the radius of curvature of the contour line of the third curved portion is 0.7 mm or more.

[0011] (6) The pneumatic tire according to (5), wherein, in a plan view, the radius of curvature of the contour line of the third curved portion is 1.5 times or less the sipe width of the main body portion. Here, "sipe width" refers to the opening width of the sipe when the pneumatic tire is mounted on an applicable rim, inflated to the specified internal pressure, and no load is applied. If the sipe width varies along the extension direction of the sipe, the term "sipe width" refers to the maximum width. Furthermore, when dimensions and shapes are mentioned in this specification, unless otherwise specified, they refer to the dimensions and shapes when the pneumatic tire is mounted on an applicable rim, inflated to the specified internal pressure, and no load is applied.

[0012] In this specification, the term "applicable rim" refers to the standard rim (Measuring Rim in the ETRTO Standards Manual, Design Rim in the TRA Year Book) for the applicable size that is described or will be described in the future, as an industrial standard in effect in the region where the tire is produced and used, such as the JATMA Year Book of the Japan Automobile Tire Manufacturers Association (JATMA) in Japan, the Standards Manual of the European Tyre and Rim Technical Organization (ETRTO) in Europe, or the Year Book of the Tire and Rim Association, Inc. (TRA) in the United States. (In other words, the "rim" in the above "wheel" includes not only current sizes but also sizes that may be included in the above industrial standards in the future. An example of a "size to be described in the future" is the size listed under "FUTURE DEVELOPMENTS" in the 2013 edition of the ETRTO.) However, in the case of a size not described in the above industrial standards, the term refers to a rim with a width that corresponds to the bead width of the tire. Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) that corresponds to the maximum load capacity of a single wheel for the applicable size and ply rating as specified in the above JATMA etc., and in the case of sizes not specified in the above industry standards, "specified internal pressure" refers to the air pressure (maximum air pressure) that corresponds to the maximum load capacity specified for each vehicle on which the tire is fitted.

[0013] (7) The sipe width of the end portion is larger than the sipe width of the main body portion, In plan view, The first curved portion and the second curved portion are smoothly connected, The first curved portion has a center of curvature on the outer side of the sipe, The second curved portion has a center of curvature on the inside of the sipe, a connection point between the first curved portion and the second curved portion is an inflection point, The pneumatic tire according to (5) above, wherein the second curved portion and the third curved portion are smoothly connected.

[0014] (8) The pneumatic tire according to (5), wherein, in a plan view, the radius of curvature of the contour line of the third curved portion is smaller than the radius of curvature of the contour line of the second curved portion.

[0015] (9) The sipe has a shape that is line-symmetrical with respect to a center line of the sipe width in a plan view, The pneumatic tire according to (7), wherein the first curved portion and the second curved portion are point-symmetric with respect to the connection point on each of the one side and the other side of the center line.

[0016] (10) The land portion is a block, The pneumatic tire according to any one of (1) to (9), wherein only one sipe is arranged in each block. Here, a "block" refers to a land portion that is completely divided in the tire circumferential direction by a widthwise groove. Therefore, when a land portion is not completely divided in the tire circumferential direction because a widthwise groove terminates within the land portion, or when a land portion is completely divided in the tire circumferential direction by a sipe, it is considered to be a rib-like land portion rather than a block.

[0017] (11) The land portion is a block, A plurality of the sipes are arranged in each block in the tire circumferential direction, The pneumatic tire according to any one of (1) to (10), wherein, among the plurality of sipes, the depth of the sipes located on the trailing side of the block is shallower than the depth of the sipes located on the leading side of the block. Here, "sipe depth" refers to the sipe depth (maximum depth) when a pneumatic tire is mounted on an applicable rim, inflated to a specified internal pressure, and no load is applied.

[0018] (12) The land portion is a block, The sipes are widthwise sipes extending in the tire width direction, The pneumatic tire according to any one of (1) to (11), wherein the length of the sipe in the tire width direction is 70% or less of the length of the block in the tire width direction.

[0019] (13) The land portion is a block, The sipes are arranged in a plurality in the tire width direction in each of the blocks, The pneumatic tire according to any one of (1) to (11), wherein the total length of the plurality of sipes in the tire width direction is 70% or less of the length of the block in the tire width direction.

[0020] (14) The land portion is a block, The pneumatic tire according to any one of (1) to (13), wherein the sipe is disposed in a central portion of the block in the tire circumferential direction. Here, the "circumferential center of the block" refers to the central 50% of the circumferential region of the block between both circumferential ends of the block in a plan view. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a pneumatic tire having sipes that suppress the occurrence of cracks. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a diagram schematically showing a tread pattern of a pneumatic tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is a plan view for explaining the shape of a sipe used in the present invention. [Figure 3] FIG. 1 is a diagram illustrating an example of an arrangement of communication devices. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. A typical internal structure of a pneumatic tire (hereinafter also referred to simply as "tire") can be used, and therefore a detailed description will be omitted. As an example, the tire of this embodiment can include a pair of bead portions, a carcass toroidally spanning the pair of bead portions, and a belt disposed radially outward of the carcass. The tire of the present invention is suitable for use as a heavy-duty tire (particularly a tire for trucks and buses).

[0024] Fig. 1 is a diagram showing a schematic diagram of a tread pattern of a pneumatic tire according to one embodiment of the present invention. As shown in Fig. 1, this tire has a plurality of (four in the illustrated example) circumferential main grooves 2 (2a to 2d) on a tread surface 1.

[0025] The number of circumferential main grooves 2 is not particularly limited and may be one to three or five or more. In the illustrated example, the circumferential main grooves 2a to 2d all extend linearly, but they may extend in a zigzag or curved pattern. In the illustrated example, the circumferential main grooves 2a to 2d extend without inclination in the tire circumferential direction, but the circumferential main grooves 2a to 2d may extend at an inclination angle of 5° or less with respect to the tire circumferential direction. In the illustrated example, two circumferential main grooves 2a, 2b are arranged in one half of the tire width direction bounded by the tire equatorial plane CL, and two circumferential main grooves 2c, 2d are arranged in the other half of the tire width direction, but this case is not limited thereto, and for example, any of the circumferential main grooves 2 may extend on the tire equatorial plane CL. The groove width (opening width) of the circumferential main grooves 2a to 2d is not particularly limited, but may be, for example, 6 to 9 mm, and the groove depth (maximum depth) of the circumferential main grooves 2a to 2d is not particularly limited, but may be, for example, 15 to 18 mm.

[0026] One or more land portions 3 are formed on the tread surface 1. In the illustrated example, five land portions 3a to 3e are defined and formed by the tread edge TE and four circumferential main grooves 2a to 2d. In this example, the land portions 3a and 3b are located on one half in the tire width direction, the land portion 3c is located on the tire equatorial plane CL, and the land portions 3d and 3e are located on the other half in the tire width direction. The number of land portions 3 corresponds to the number of circumferential main grooves 2.

[0027] The land portions 3a and 3e are located at the outermost positions in the tire width direction and are the outermost land portions in the tire width direction. In the illustrated example, the land portions 3a and 3e have multiple widthwise grooves 4 extending in the tire width direction, and multiple blocks 5 are formed by two widthwise grooves 4 adjacent to each other in the tire width direction. The land portions 3a and 3e are therefore block-shaped land portions. In the illustrated example, the widthwise grooves 4 extend without inclination in the tire width direction, but they may extend at an inclination angle of 60° or less with respect to the tire width direction. The groove width (opening width) of the widthwise grooves 4 is not particularly limited, but may be, for example, 30 to 40 mm. The groove depth (maximum depth) of the widthwise grooves 4 is not particularly limited, but may be, for example, 5 to 6 mm. In this example, no sipes are arranged in the land portions 3a and 3e. This increases the rigidity of the outermost land portions in the tire width direction.

[0028] The land portions 3b and 3d are intermediate land portions adjacent to the tire widthwise inner sides of the outermost land portions 3a and 3e, respectively. A plurality of open sipes 6 (sipes whose ends communicate with the circumferential main groove 2 or the tread edge TE) extending in the tire width direction are formed in the land portions 3b and 3d. The land portions 3b and 3d are rib-like land portions. In the illustrated example, the open sipes 6 extend without inclination in the tire width direction, but may extend at an inclination angle of 60° or less with respect to the tire width direction. The sipe width (opening width) of the open sipes 6 is not particularly limited, but may be, for example, 26 to 34 mm. The sipe depth (maximum depth) of the open sipes 6 is not particularly limited, but may be, for example, 18 to 21 mm. In the illustrated example, only one closed sipe 7, both ends of which terminate within the land portions 3b and 3d, is arranged between two circumferentially adjacent open sipes 6. In the illustrated example, the closed sipe 7 extends without inclination in the tire width direction, but it may extend at an inclination angle of 60° or less with respect to the tire width direction.

[0029] The land portion 3c is a central land portion located on the tire equatorial plane CL. The land portion 3c has one narrow groove 8 extending in the tire circumferential direction through the tire widthwise center of the land portion 3c (extending on the tire equatorial plane CL in the illustrated example), and two small land portions 9, 10 are defined and formed by the circumferential main grooves 2b, 2c and the narrow groove 8. In the illustrated example, the small land portion 9 is located in one half in the tire width direction, and the small land portion 10 is located in the other half in the tire width direction. Each small land portion 9, 10 has multiple widthwise grooves 11 extending in the tire width direction, and multiple blocks 12 are formed by two widthwise grooves 4 adjacent in the tire width direction. The small land portions 9, 10 are therefore block-shaped small land portions. In the illustrated example, the widthwise grooves 11 extend without inclination in the tire width direction, but may extend at an inclination angle of 60° or less with respect to the tire width direction. The groove width (opening width) of the widthwise groove 11 is not particularly limited, but can be, for example, 19 to 25 mm, and the groove depth (maximum depth) of the widthwise groove 11 is not particularly limited, but can be, for example, 15 to 18 mm. In each block 12, only one closed sipe 13 is arranged in the tire circumferential direction between two circumferentially adjacent widthwise grooves 11 in the illustrated example, the closed sipe 13 having both ends terminating within the land portions 9, 10. In the illustrated example, the closed sipe 13 extends without inclination in the tire width direction, but it may extend at an inclination angle of 60° or less with respect to the tire width direction.

[0030] As described above, the tire of this embodiment has sipes 6, 7, and 13 formed in the land portion 3. Since the shape of the sipes is shown schematically in Fig. 1, the shape of the closed sipes 7 and 13 will be described in detail below. In this embodiment, the open sipe 6 has a flat plate-like shape.

[0031] Fig. 2 is a plan view illustrating the shape of the sipes used in the present invention. As shown in Fig. 2, the closed sipes 7, 13 (hereinafter simply referred to as sipes 7, 13) have a main body portion 20 and an end portion 24, and the main body portion 20 and the end portion 24 are smoothly connected in a plan view. In other words, the main body portion 20 and the end portion 24 are connected to form a continuously curved line without any angular portions in a plan view. In the illustrated example, the sipes 7, 13 have a shape that is line-symmetrical with respect to the center line of the sipe width in a plan view, but this is not limited to this case. The extension length x1 of the entire sipes 7, 13 is not particularly limited, but can be, for example, 20 to 33 mm.

[0032] As shown in FIG. 2, the main body portion 20 is a linear portion in a plan view. The main body portion 20 may have a flat plate shape. The sipe width w20 (opening width) of the main body portion 20 is not particularly limited, but may be 0.5 to 1.0 mm. The sipe depth (maximum depth) of the main body portion 20 is not particularly limited, but may be 1 to 20 mm. The extension length x20 of the main body portion 20 can be set appropriately depending on the width of the land portion in the tire width direction, and is not particularly limited, but may be 1 to 5 times the extension length x2 of the end portion 24.

[0033] The end portion 24 has, from the side closest to the main body portion 20, a first curved portion 21, a second curved portion 22, and a third curved portion 23. The sipe width w1 of the end portion 24 is larger than the sipe width w20 of the main body portion 20, and is not particularly limited, but can be, for example, 1 to 5 mm.

[0034] The shape of the first curved portion 21 in a plan view will be described below. In the illustrated example, the first curved portion 21 has a center of curvature outside the sipes 7, 13 and has an arcuate contour line. In the first curved portion 21, the sipe width gradually increases with increasing distance from the main body portion 20. The radius of curvature R21 of the contour line of the first curved portion 21 is not particularly limited, but can be, for example, 1 to 5 mm.

[0035] Next, the shape of the second curved portion 22 in a plan view will be described. In the illustrated example, the second curved portion 22 has a center of curvature inside the sipes 7, 13 and has an arc-shaped contour line. In the second curved portion 22, the sipe width gradually increases with increasing distance from the main body portion 20. The radius of curvature R22 of the contour line of the second curved portion 22 is not particularly limited, but can be, for example, 1 to 5 mm.

[0036] Next, the connection between the first curved portion 21 and the second curved portion 22 in a plan view will be described. As shown in the figure, the first curved portion 21 and the second curved portion 22 are smoothly connected. The connection point between the first curved portion 21 and the second curved portion 22 is an inflection point (because the first curved portion 21 has a center of curvature on the outer side of the sipes 7, 13, and the second curved portion 22 has a center of curvature on the inner side of the sipes 7, 13). In the illustrated example, the first curved portion 21 and the second curved portion 22 are point-symmetric with respect to the connection point. The first curved portion 21 and the second curved portion 22 are point-symmetric with respect to the connection point on one side and the other side of the center line of the sipe width as the boundary. In the central region (e.g., the central 50% region) in the sipe extension direction of the region combining the first curved portion 21 and the second curved portion 22, the contour shape of the sipes 7, 13 is approximately linear (a shape in which arcs with a contour curvature radius of 0.5 mm or more are connected point-symmetrically).

[0037] Next, the shape of the third curved portion 23 in a plan view will be described. In the illustrated example, the third curved portion 23 has a center of curvature inside the sipes 7, 13, an arcuate contour line, and a semicircular shape. In the third curved portion 23, the sipe width gradually decreases as it moves away from the main body portion 20. The radius of curvature R23 of the contour line of the third curved portion 23 is preferably 0.7 mm or more, and is preferably 1.5 times or less the sipe width w20 of the main body portion 20.

[0038] Next, the connection between the second curved portion 22 and the third curved portion 23 in a plan view will be described. As shown in the figure, the second curved portion 22 and the third curved portion 23 are smoothly connected. In a plan view, the radius of curvature R23 of the contour line of the third curved portion 23 is smaller than the radius of curvature R22 of the contour line of the second curved portion 22. In the example shown, the second curved portion 22 and the third curved portion 23 form a shape that is a part of a substantial circle in a plan view. The effects of the pneumatic tire of this embodiment will be described below.

[0039] In the tire of this embodiment, sipes 6, 7, and 13 are formed in the land portion 3, and the sipes (closed sipes 7 and 13 in this embodiment) have a main body portion 20 and an end portion 24, and in plan view, the main body portion 20 and the end portion 24 are smoothly connected. More specifically, in plan view, the main body portion 20 and the end portion 24 are connected to form a continuously curved line without any angular portions. Therefore, according to the tire of this embodiment, it is possible to prevent cracks from occurring that originate from angular portions, thereby suppressing the occurrence of cracks.

[0040] The sipes are preferably closed sipes 7, 13, both ends of which terminate within the land portion 3. This is because the rigidity of the land portion 3 can be increased.

[0041] The end portion 24 has, from the side closest to the main body portion 20, a first curved portion 21, a second curved portion 22, and a third curved portion 23, and in plan view, it is preferable that the third curved portion 23 has a semicircular shape and that the radius of curvature R23 of the contour line of the third curved portion 23 is 0.7 mm or more. This is because it is also possible to suppress cracks from occurring at the end of the sipe (the end of the third curved portion 23). On the other hand, from the viewpoint of ensuring the rigidity of the land portion 3 by preventing the sipe from becoming too large, it is preferable that the radius of curvature R23 of the contour line of the third curved portion 23 is 1.5 times or less the sipe width of the main body portion 20 in plan view.

[0042] It is preferable that the sipe width of the end portion 24 is larger than the sipe width of the main body portion 20, that the first curved portion 21 and the second curved portion 22 are smoothly connected in a plan view, that the first curved portion 21 has a center of curvature on the outside of the sipe, that the second curved portion 22 has a center of curvature on the inside of the sipe, that the connection point between the first curved portion 21 and the second curved portion 22 is an inflection point, and that the second curved portion 22 and the third curved portion 23 are smoothly connected. This is because the smooth connection of the entire sipe in this form can further suppress the occurrence of cracks.

[0043] In a plan view, the radius of curvature R23 of the contour line of the third curved portion 23 is preferably smaller than the radius of curvature R22 of the contour line of the second curved portion 22. This is because the rigidity of the land portion 3 can be ensured by preventing the sipes 7, 13 from becoming too large.

[0044] The land portions 3 are blocks 12, and it is preferable that only one sipe 13 is disposed in each block 12. This is because it is possible to prevent distortion of the block 12 on the trailing edge from becoming large, in particular.

[0045] The land portions are blocks, and a plurality of sipes are arranged in each block in the circumferential direction of the tire, and it is preferable that the depth of the sipes located on the trailing edge of the block is shallower than the depth of the sipes located on the leading edge of the block. This is because, even when a block has a plurality of sipes, such a configuration can prevent distortion, particularly on the trailing edge of the block, from becoming large.

[0046] The land portions are blocks 12, the sipes 13 are widthwise sipes extending in the tire width direction, and the length of the sipes 13 in the tire width direction is preferably 70% or less of the length of the blocks 12 in the tire width direction. This is because it is possible to suppress a decrease in the rigidity of the blocks 12 while suppressing slippage on the trailing edge of the blocks.

[0047] The land portions are blocks 12, and a plurality of sipes 13 are arranged in each block 12 in the tire width direction, and the total length of the plurality of sipes 13 in the tire width direction is preferably 70% or less of the length of the block 12 in the tire width direction. This is because when a block has a plurality of sipes, it is possible to suppress a decrease in the rigidity of the block 12 while suppressing slippage on the trailing side of the block.

[0048] The land portions are the blocks 12, and the sipes 13 are preferably disposed in the center of the blocks 12 in the tire circumferential direction, because this can suppress slippage on the trailing edge of the blocks.

[0049] An example of the arrangement of the communication device will be described below. FIG. 3 is a diagram showing an example of the arrangement of the communication device. A tire may include an RF tag as the communication device 100. The RF tag includes an IC chip and an antenna. The RF tag may be arranged, for example, by being sandwiched between multiple components of the same or different types that make up the tire. This makes it easier to attach the RF tag during tire production, improving the productivity of tires equipped with RF tags. In this example, the RF tag may be arranged, for example, by being sandwiched between a bead filler and another component adjacent to the bead filler. The RF tag may also be embedded in any of the components that make up the tire. This reduces the load on the RF tag compared to when the RF tag is arranged by being sandwiched between multiple components that make up the tire. This improves the durability of the RF tag. In this example, the RF tag may be embedded in a rubber component such as tread rubber or side rubber. It is preferable that the RF tag is not arranged at a position that is a boundary between components with different rigidities in the periphery length direction, which is the direction along the outer surface of the tire in a cross-sectional view in the tire width direction. By doing so, the RF tag is not placed in a position where distortion is likely to concentrate due to a difference in rigidity. Therefore, the load applied to the RF tag can be reduced. This can improve the durability of the RF tag. In this example, it is preferable that the RF tag is not placed in a position that is, for example, a boundary between the end of the carcass and a member adjacent to the end of the carcass (for example, a side rubber) in a cross-sectional view in the tire width direction. The number of RF tags is not particularly limited. A tire may be equipped with only one RF tag, or may be equipped with two or more RF tags. Here, an RF tag is described as an example of a communication device, but a communication device other than an RF tag may also be used.

[0050] The RF tag may be disposed, for example, in the tread portion of the tire. In this manner, the RF tag will not be damaged by a side cut of the tire. The RF tag may be disposed, for example, in the tread center portion in the tire width direction. The tread center portion is a position in the tread portion where flexure is less likely to concentrate. In this manner, the load applied to the RF tag can be reduced. This improves the durability of the RF tag. Also, it is possible to prevent differences in communication with the RF tag from both outer sides of the tire in the tire width direction. In this example, the RF tag may be disposed, for example, within a range of 1 / 2 the tread width centered on the tire equatorial plane in the tire width direction. The RF tag may be disposed, for example, at a tread edge in the tire width direction. If the position of a reader that communicates with the RF tag is predetermined, the RF tag may be disposed, for example, at a tread edge on one side closer to the reader. In this example, the RF tag may be disposed, for example, within a range of 1 / 4 the tread width in the tire width direction, with the tread edge as the outer end.

[0051] The RF tag may be positioned, for example, closer to the tire cavity than a carcass including one or more carcass plies spanning between bead portions. This configuration makes the RF tag less susceptible to damage from external impacts to the tire, side cuts, nail penetration, and other damage. As one example, the RF tag may be positioned in close contact with the surface of the carcass facing the tire cavity. As another example, if there is another component closer to the tire cavity than the carcass, the RF tag may be positioned between the carcass and another component located closer to the tire cavity than the carcass. An example of another component located closer to the tire cavity than the carcass is an inner liner that forms the tire inner surface. As another example, the RF tag may be attached to the inner surface of the tire facing the tire cavity. Configuring the RF tag to be attached to the inner surface of the tire makes it easier to attach the RF tag to the tire and to inspect and replace the RF tag. In other words, the ease of attaching and maintaining the RF tag can be improved. Furthermore, by attaching the RF tag to the inner surface of the tire, it is possible to prevent the RF tag from becoming the core of tire failure, compared to a configuration in which the RF tag is embedded in the tire. Furthermore, when the carcass has multiple carcass plies and there is a position where multiple carcass plies are overlapped, the RF tag may be disposed between the overlapped carcass plies.

[0052] The RF tag may be arranged, for example, in the tread portion of the tire, radially outward of a belt including one or more belt plies. As one example, the RF tag may be arranged radially outward of the belt in the tire radial direction and in close contact with the belt. As another example, if a reinforcing belt layer is provided, the RF tag may be arranged radially outward of the reinforcing belt layer in close contact with the reinforcing belt layer. As another example, the RF tag may be embedded in the tread rubber radially outward of the belt. By arranging the RF tag radially outward of the belt in the tread portion of the tire, communication with the RF tag from outside the tire in the tire radial direction is less likely to be obstructed by the belt. Therefore, communication with the RF tag from outside the tire in the tire radial direction can be improved. As another example, the RF tag may be arranged radially inward of the belt in the tread portion of the tire. In this way, the radially outward side of the RF tag is covered by the belt, making the RF tag less susceptible to damage from impacts from the tread surface or nail penetration. As one example, the RF tag may be placed in the tread portion of the tire, between the belt and the carcass located radially inward of the belt. Also, if the belt has multiple belt plies, the RF tag may be placed in the tread portion of the tire, between any two belt plies. In this way, the outer side of the RF tag in the tire radial direction is covered by one or more belt plies, making the RF tag less susceptible to damage from impacts from the tread surface or nail penetration.

[0053] The RF tag may be disposed, for example, sandwiched between the cushion rubber and the tread rubber or between the cushion rubber and the side rubber. In this way, the cushion rubber can absorb impacts on the RF tag. This improves the durability of the RF tag. The RF tag may also be embedded in the cushion rubber. Furthermore, the cushion rubber may be made up of multiple adjacent rubber members of the same or different types. In such a case, the RF tag may be disposed sandwiched between the multiple rubber members that make up the cushion rubber.

[0054] The RF tag may be disposed, for example, in a sidewall portion or a bead portion of the tire. The RF tag may be disposed, for example, in one sidewall portion or one bead portion that is closer to a reader capable of communicating with the RF tag. This arrangement improves communication between the RF tag and the reader. As an example, the RF tag may be disposed between the carcass and the side rubber or between the tread rubber and the side rubber. The RF tag may be disposed, for example, between the tire's maximum width position and the tread surface position in the tire radial direction. This arrangement improves communication with the RF tag from outside the tire in the tire radial direction, compared to a configuration in which the RF tag is disposed radially inward of the tire's maximum width position. The RF tag may be disposed, for example, radially inward of the tire's maximum width position. This arrangement allows the RF tag to be disposed near the bead portion, which has high rigidity. This reduces the load applied to the RF tag, thereby improving the durability of the RF tag. As an example, the RF tag may be disposed adjacent to the bead core in the tire radial direction or the tire width direction. Distortion is less likely to concentrate near the bead core. This reduces the load on the RF tag, improving its durability. In particular, it is preferable that the RF tag be positioned radially inward of the tire's maximum width and radially outward of the bead core of the bead portion. This improves the durability of the RF tag, and communication between the RF tag and a reader is less likely to be obstructed by the bead core, improving the RF tag's communication performance. Furthermore, when the side rubber is composed of multiple rubber members of the same or different types adjacent to each other in the tire radial direction, the RF tag may be sandwiched between the multiple rubber members that make up the side rubber.

[0055] The RF tag may be disposed sandwiched between the stiffener and a member adjacent to the stiffener. In this way, the RF tag can be disposed in a position where the stiffener prevents strain from concentrating. This reduces the load on the RF tag. This improves the durability of the RF tag. The RF tag may be disposed sandwiched between the stiffener and a side rubber, for example. Furthermore, the RF tag may be disposed, for example, sandwiched between the stiffener and the carcass. The portion of the carcass that sandwiches the RF tag together with the stiffener may be located on the outer side of the stiffener in the tire width direction, or on the inner side of the stiffener in the tire width direction. When the portion of the carcass that sandwiches the RF tag together with the stiffener is located on the outer side of the stiffener in the tire width direction, the load applied to the RF tag due to impact or damage from the outside of the tire in the tire width direction can be further reduced. This can further improve the durability of the RF tag. The stiffener may have a portion disposed adjacent to the rubber chafer. In such a case, the RF tag may be disposed sandwiched between the stiffener and the rubber chafer. The stiffener may have a portion adjacent to the hat rubber on the outer side in the tire width direction. In such a case, the RF tag may be disposed sandwiched between the stiffener and the hat rubber. The stiffener may be composed of a plurality of rubber members with different hardnesses. In such a case, the RF tag may be disposed sandwiched between a plurality of rubber members constituting the stiffener. The RF tag may be disposed sandwiched between a hat rubber and a member adjacent to the hat rubber. The RF tag may be disposed sandwiched, for example, between the hat rubber and the carcass ply. In this way, the impact on the RF tag can be absorbed by the hat rubber. This improves the durability of the RF tag.

[0056] The RF tag may be disposed, for example, sandwiched between the rubber chafer and the side rubber. In this way, the RF tag can be disposed in a position where the placement of the rubber chafer makes it less likely for distortion to concentrate. This reduces the load on the RF tag. This improves the durability of the RF tag. The RF tag may be disposed, for example, sandwiched between the rubber chafer and the carcass. In this way, it reduces the load on the RF tag due to impact or damage from the rim. This improves the durability of the RF tag.

[0057] The RF tag may be sandwiched between the nylon chafer and another member adjacent to the nylon chafer on the outer or inner side in the tire width direction. This makes it difficult for the position of the RF tag to fluctuate when the tire deforms. This reduces the load applied to the RF tag when the tire deforms. This improves the durability of the RF tag. The nylon chafer may, for example, have a portion adjacent to the rubber chafer on the outer side in the tire width direction. In this case, the RF tag may be sandwiched between the nylon chafer and the rubber chafer. The nylon chafer may, for example, have a portion adjacent to the side rubber on the outer side in the tire width direction. In this case, the RF tag may be sandwiched between the nylon chafer and the side rubber. The nylon chafer may, for example, have a portion adjacent to the stiffener on the inner side in the tire width direction. In this case, the RF tag may be sandwiched between the nylon chafer and the stiffener. Furthermore, the nylon chafer may have a portion adjacent to the hat rubber, for example, on the inner side in the tire width direction. In such a case, the RF tag may be disposed by being sandwiched between the nylon chafer and the hat rubber. Furthermore, the nylon chafer may have a portion adjacent to the carcass, for example, on the inner side in the tire width direction. In such a case, the RF tag may be disposed by being sandwiched between the nylon chafer and the carcass. Furthermore, the nylon chafer may have a portion adjacent to the wire chafer, for example, on the inner side in the tire width direction. In such a case, the RF tag may be disposed by being sandwiched between the nylon chafer and the wire chafer. In this way, the RF tag may be disposed by being sandwiched between the nylon chafer and another member adjacent to the nylon chafer on the outer or inner side in the tire width direction. In particular, by covering the outer side of the RF tag in the tire width direction with the nylon chafer, the load applied to the RF tag due to impact or damage from the outside of the tire in the tire width direction can be further reduced. Therefore, the durability of the RF tag can be further improved.

[0058] The RF tag may be sandwiched between the wire chafer and another adjacent member on the inner or outer side of the wire chafer in the tire width direction. This makes it difficult for the position of the RF tag to fluctuate when the tire deforms. This reduces the load applied to the RF tag when the tire deforms. This improves the durability of the RF tag. The other adjacent member on the inner or outer side of the wire chafer in the tire width direction may be, for example, a rubber member such as a rubber chafer. Furthermore, the other adjacent member on the inner or outer side of the wire chafer in the tire width direction may be, for example, a carcass.

[0059] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. For example, the present invention can be applied to any tire in which sipes are formed in the land portions, and the tread pattern can be various in which sipes are formed in the land portions. Furthermore, the open sipe can have a main body portion and an end portion, and the main body portion and the end portion can be smoothly connected in a plan view. Various other modifications and variations are possible. [Explanation of symbols]

[0060] 1: tread surface, 2: Circumferential main groove, 3: Rikube, 4: Width direction groove, 5: Block, 6: Open sipe, 7: Closed sipes, 8: Narrow groove, 9: Small land area, 10: Small land area, 11: Width direction groove, 12: Block, 13: Closed sipe, 20: Main body, 21: 1st curved part, 22: Second curved part, 23: Third curve part, 24: end, 100: Communication equipment

Claims

1. A pneumatic tire having sipes formed in land portions, The sipe has a main body and an end portion, A pneumatic tire, characterized in that, in a plan view, the main body portion and the end portion are smoothly connected.

2. The pneumatic tire according to claim 1 , wherein the main body portion and the end portion are connected to form a continuously curved line without any angular portions in a plan view.

3. The pneumatic tire according to claim 1 or 2, wherein the sipe is a closed sipe, both ends of which terminate within the land portion.

4. The pneumatic tire according to claim 1 or 2, wherein the main body portion is a linear portion in a plan view.

5. The end portion has, from a side closer to the main body portion, a first curved portion, a second curved portion, and a third curved portion, The pneumatic tire according to claim 1 or 2, wherein the third curved portion has a semicircular shape in a plan view, and a curvature radius of a contour line of the third curved portion is 0.7 mm or more.

6. The pneumatic tire according to claim 5 , wherein, in a plan view, a radius of curvature of the contour line of the third curved portion is 1.5 times or less the sipe width of the main body portion.

7. The sipe width of the end portion is larger than the sipe width of the main body portion, In plan view, the first curved portion and the second curved portion are smoothly connected, The first curved portion has a center of curvature on the outer side of the sipe, the second curved portion has a center of curvature on the inner side of the sipe, a connection point between the first curved portion and the second curved portion is an inflection point, The pneumatic tire according to claim 5 , wherein the second curved portion and the third curved portion are smoothly connected.

8. The pneumatic tire according to claim 5 , wherein, in a plan view, a radius of curvature of the contour line of the third curved portion is smaller than a radius of curvature of the contour line of the second curved portion.

9. The sipe has a shape that is line-symmetrical with respect to a center line of the sipe width in a plan view, The pneumatic tire according to claim 7 , wherein the first curved portion and the second curved portion are point-symmetric with respect to the connection point on each of one side and the other side of the center line.

10. The land portion is a block, The pneumatic tire according to claim 1 or 2, wherein only one sipe is arranged in each of the blocks.

11. The land portion is a block, A plurality of the sipes are arranged in each block in the tire circumferential direction, The pneumatic tire according to claim 1 or 2, wherein the depth of the sipes located on the trailing side of the block is shallower than the depth of the sipes located on the leading side of the block.

12. The land portion is a block, The sipes are widthwise sipes extending in the tire width direction, The pneumatic tire according to claim 1 or 2, wherein a length of the sipe in the tire width direction is 70% or less of a length of the block in the tire width direction.

13. The land portion is a block, The sipes are arranged in a plurality in the tire width direction in each of the blocks, The pneumatic tire according to claim 1 or 2, wherein a total length of the plurality of sipes in the tire width direction is 70% or less of a length of the block in the tire width direction.

14. The land portion is a block, The pneumatic tire according to claim 1 or 2, wherein the sipe is disposed at a center portion of the block in the tire circumferential direction.

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