TIRES

Abstract

Task To reduce the occurrence of a crack originating from a depressed section defining a maximum depth of a regenerated groove. Solution A tire includes: a circumferential main groove (21) extending in a tire circumferential direction in a tread surface; a treadwear indicator (2) protrudingly disposed from a groove bottom (21A) of the circumferential main groove (21); and a depressed portion (3) formed in a top portion (2A) of the treadwear indicator (2) and defining a maximum depth of the circumferential main groove (2) after regrooving. The recessed portion (3) is formed with a depth (Hr) from the upper portion (2A) of the treadwear indicator (2) in a range of 2.5 mm or more and 10.0 mm or less, is formed with a radius (Rr1) of a rounded chamfer of an opening portion (3A) in a range of 0.5 mm or more and 8.0 mm or less, and is formed with a radius (Rr2) of a rounded chamfer of a lower portion (3C) in a range of 0.5 mm or more and 4.0 mm or less.

Description

Technical area

[0001] The invention relates to a tire. State of the art

[0002] For example, Patent Document 1 describes an invention of a tire in which a depressed portion defining a maximum depth of a groove after regeneration is arranged at a groove bottom to regenerate the groove of a tread. Literature listPatent literature

[0003] Patent Document 1: WO 2013 / 087473 Brief description of the inventionTechnical problem

[0004] If the depressed portion is located at the groove bottom, cracks may be generated from the depressed portion due to the stress applied to the groove bottom during travel.

[0005] An object of the present invention is to provide a tire that can reduce the occurrence of cracks originating from a depressed portion defining a maximum depth of a regenerated groove. Solution to the problem

[0006] To achieve the above-described object, a tire according to one aspect of the present invention includes: a circumferential main groove extending in a tire circumferential direction in a tread portion; a treadwear indicator protruding from a groove bottom of the circumferential main groove; and a depressed portion formed in an upper portion of the treadwear indicator and defining a maximum depth of the circumferential main groove after regrooving.The recessed portion is formed with a depth from the upper portion of the treadwear indicator in a range of 2.5 mm or more and 10.0 mm or less, is formed with a radius of a rounded chamfer of an opening portion in a range of 0.5 mm or more and 8.0 mm or less, and is formed with a radius of a rounded chamfer of a lower portion in a range of 0.5 mm or more and 4.0 mm or less. Advantageous effects of the invention

[0007] The present invention can reduce the occurrence of a crack originating from a depressed portion defining a maximum depth of a regenerated groove. Brief description of the drawings Fig. 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment. Fig. 2 is an enlarged plan view of a circumferential main groove of the pneumatic tire according to an embodiment. Fig. 3 is a cross-sectional view taken along line AA of Fig. 2. Fig. 4 is a cross-sectional view taken along line BB of Fig. 2. Fig. 5 is a table showing results of performance tests of pneumatic tires according to embodiments. Fig. 6 is a table showing results of performance tests of pneumatic tires according to embodiments. Description of embodiments

[0008] The embodiment according to the present invention will be described in detail below with reference to the drawings. However, the invention is not limited to the embodiments. Components of the embodiments include elements that are interchangeable while maintaining consistency with the invention, as well as obviously interchangeable elements. Also, a plurality of modified examples described in the embodiments can be combined within the scope obvious to a person skilled in the art.

[0009] In the following description, the term "tire radial direction" refers to a direction perpendicular to the tire rotation axis (not illustrated), which is a rotation axis of a pneumatic tire 1. The term "tire radial direction inner side" refers to a side toward the tire rotation axis in the tire radial direction, and the term "tire radial direction outer side" refers to a side away from the tire rotation axis in the tire radial direction of the embodiment. The term "tire circumferential direction" refers to a circumferential direction with the tire rotation axis as the center axis.The term "tire width direction" refers to a direction parallel to the tire rotation axis, the term "tire width direction inner side" refers to a side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the term "tire width direction outer side" refers to an equatorial plane of the tire CL in the tire width direction. The term "tire equatorial plane CL" refers to a plane perpendicular to the tire rotation axis and passing through the tire width center of the pneumatic tire 1. The tire equatorial plane CL is aligned at a position in the tire width direction with the tire width center line, which corresponds to the tire width center position of the pneumatic tire 1. The "tire equator line" refers to a line in the tire circumferential direction of the pneumatic tire 1 that lies on the tire equatorial plane CL.The term “cross-section in the tire meridian direction (meridian cross-sectional view)” refers to a cross-section of the tire taken along a plane that includes the tire’s axis of rotation.

[0010] Fig. Figure 1 is a meridian cross section of a pneumatic tire 1 of the present embodiment, illustrating a cross section of a region on one side of the tire rotation axis in the tire radial direction. In the present embodiment, a heavy-duty radial pneumatic tire mounted on a heavy-duty vehicle such as a truck or bus will be described as an example. The pneumatic tire 1 of the present embodiment is particularly suitable for use as a tire mounted on a drive shaft of a heavy-duty vehicle.

[0011] The pneumatic tire 1 of the embodiment has an annular structure with the tire rotation axis as its center and includes, as shown in Fig. 1, a pair of bead cores 11, a pair of bead fillers 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16 and a pair of rim cushion rubbers 17.

[0012] The pair of bead cores 11 include one or more bead wires made of steel and manufactured by being wound multiple times in a ring shape, embedded in bead portions, and constituting cores of the bead portions on both sides in the tire width direction.

[0013] The pairs of bead fillers 12 are each composed of a lower filler 121 and an upper filler 122 and are arranged on outer sides of the pair of bead cores 11 in the tire radial direction and reinforce the bead portions.

[0014] The carcass layer 13 has a single-layer structure including one carcass ply or a multi-layer structure including a plurality of laminated carcass plies. The carcass layer 13 extends in a toroidal shape between the two bead cores 11, thereby forming the frame of the tire. Both end portions of the carcass layer 13 are turned over to the outer sides in the tire width direction and are fixed to wrap the bead cores 11 and the bead fillers 12. The carcass ply of the carcass layer 13 is formed by covering a plurality of carcass cords made of steel with a coating rubber and performing a rolling process thereon.The carcass ply of the carcass layer 13 has a cord angle (defined as the inclination angle in the longitudinal direction of the carcass cords with respect to the tire circumferential direction) of 80 degrees or more and 90 degrees or less for a radial tire and 30 degrees or more and 45 degrees or less for bias tires as absolute values.

[0015] The belt layer 14 is made of a plurality of belt plies 141 to 144 that are laminated and arranged around an outer periphery of the carcass ply 13. The belt plies 141 to 144 include a high-angle belt 141, a pair of cross belts 142, 143, and a belt cover 144. The high-angle belt 141 is constituted by covering a plurality of steel belt cords with coating rubber and performing a rolling process on the belt cords, and has a cord angle (defined as an inclination angle in a longitudinal direction of the belt cord with respect to the tire circumferential direction) of 45 degrees or more and 70 degrees or less as an absolute value.The pair of cross belts 142, 143 are constituted by covering a plurality of belt cords made of steel with coating rubber and subjecting the belt cords to a rolling process, and each has a cord angle of 10 degrees or more and 55 degrees or less as an absolute value. The pair of cross belts 142, 143 have cord angles that each have opposite signs and are layered so that the belt cords intersect in the longitudinal direction of the belt cords (a so-called cross-ply structure is formed). The belt cover 144 is constituted by covering a plurality of belt cover cords made of steel or an organic fiber material with coating rubber and subjecting the belt cover cords to a rolling process, and has a cord angle of 10 degrees or more and 55 degrees or less as an absolute value.

[0016] The tread rubber 15 is arranged on an outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 and constitutes a tread portion of the pneumatic tire 1. In the tread portion, the tread rubber 15 forms a tread surface (tread contact surface) 15A on an outer peripheral surface that comes into contact with a road surface in the course of running.

[0017] The pair of sidewall rubbers 16 are each arranged on an outer side of the carcass layer 13 in the tire width direction and constitute sidewall portions on both sides in the tire width direction.

[0018] The pair of rim cushion rubbers 17 extend from an inner side in the tire radial direction of the respective bead core 11 and the turned-up portions of the carcass layer 13 toward the outer side in the tire width direction and constitute rim fitting surfaces of the bead portions.

[0019] As in Fig. As illustrated in Figure 2, the pneumatic tire 1 of the embodiment includes a tread pattern on a tread surface 15A. Here, the dimensions of the tread pattern are measured when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state.

[0020] “Specified rim” refers to a “standard rim” defined by JATMA, a “design rim” defined by the Tire and Rim Association Inc. (TRA), or a “measurement rim” defined by the European Tire and Rim Technical Organization (ETRTO). “Specified internal pressure” refers to a “maximum inflation pressure” specified by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. A specified load refers to a “maximum load capacity” specified by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or a “LOAD CAPACITY” specified by ETRTO.

[0021] The groove width is measured as the maximum value of the distance between the opposing groove walls of a groove opening portion on the tread contact surface when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. In a configuration where the groove opening portion includes a notch portion or a chamfered portion, the groove width is measured using as endpoints the intersection points of an extension line of a tread contact surface and the extension lines of the groove walls in a cross-sectional view parallel to the tire width direction and the tire radial direction.

[0022] Groove depth is measured as the maximum value of the distance from the tread contact surface to the groove bottom when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded condition. In a configuration where a groove bottom includes partially depressed / protruded portions or a sipe, the groove depth is measured excluding the partially depressed / protruded portions or the sipe.

[0023] The pneumatic tire 1 includes at least two circumferential main grooves 21 in the tread surface 15A. The pneumatic tire 1 of the embodiment also includes circumferential narrow grooves 22 in the tread surface 15A.

[0024] The circumferential main grooves 21 each extend in the tire circumferential direction and include an annular structure extending continuously along the entire circumference of the tire. Two circumferential main grooves 21 are arranged in the tire width direction with the tire equatorial plane CL interposed therebetween. The circumferential main groove 21 is defined as a groove having a treadwear indicator 2 (see Fig. 2 to 4) is mandatorily provided as specified by JATMA. In the embodiment, the circumferential main groove 21 has a groove width W of 10.0 mm or more and 20.0 mm or less as shown in Fig. 2, and a groove depth H of 10.0 mm or more and 25.0 mm or less, as shown in Fig. 4 illustrates.

[0025] In the pneumatic tire 1, three land portions 31, 32 arranged in the tire width direction and extending along the tire circumferential direction are formed by the two circumferential main grooves 21 on the tread surface 15A. Specifically, the pneumatic tire 1 includes a center land portion 31 defined between the two circumferential main grooves 21 and two shoulder land portions 32 respectively defined on the outer sides of the circumferential main grooves 21 in the tire width direction. The center land portion 31 is arranged to enclose the tire equatorial plane CL. The shoulder land portions 32 are respectively arranged on the two outermost sides of the tread surface 15A in the tire width direction.

[0026] The circumferential narrow groove 22 extends along the tire circumferential direction in the center land portion 31 and includes an annular structure arranged continuously over the entire circumference of the tire. In the embodiment, the two circumferential main grooves 21 are adjacent in the tire width direction and arranged side by side with the tire equatorial plane CL interposed therebetween. At least one circumferential narrow groove 22 may be arranged in the center land portion 31. In the embodiment, the circumferential narrow groove 22 has a groove width of 1.0 mm or more and 5.0 mm or less and a groove depth of 5.0 mm or more and 25.0 mm or less. The circumferential narrow groove 22 has a narrower groove width than the circumferential main groove 21.

[0027] When the pneumatic tire 1 has a narrow circumferential groove 22, the center land portion 31 includes two first center land portions 31A, each defined between the main circumferential groove 21 and the narrow circumferential groove 22 and adjacent to each other in the tire width direction. When the pneumatic tire 1 includes two narrow circumferential grooves 22, the center land portion 31 includes two first center land portions 31A, each defined between the main circumferential groove 21 and the narrow circumferential groove 22, adjacent to each other in the tire width direction, and a second center land portion 31B defined between the two narrow circumferential grooves 22. The second center land portion 31B is arranged to enclose the tire equatorial plane CL.

[0028] In the pneumatic tire 1 of the embodiment, when the groove depth of the circumferential main groove 21 becomes shallower and the remaining groove is reduced due to wear of the tread surface 15A, regrooving or deep cutting of the groove bottom 21A can be implemented to have the remaining groove depth of the circumferential main groove 21. The regroovable pneumatic tire 1 is configured before regrooving to allow a volume of the tread rubber 15 to be transferred from the groove bottom 21A of the circumferential main groove 21 to the belt layer 14 (the belt ply 143 in Fig. 1) closest to the main circumferential groove 21 in the tire radial direction, even after regrooving. In the regroovable pneumatic tire 1, a "REGROOVED" marking is applied to the sidewall portion.

[0029] When regrooving, it is necessary to allow the volume of the tread rubber 15 from the groove bottom 21A of the newly cut main circumferential groove 21 to the belt layer 14 (the belt ply 143 in Fig. 1) which is closest to the main circumferential groove 21 in the tire radial direction. Accordingly, as shown in the Fig. As illustrated in Figures 2 to 4, the pneumatic tire 1 is provided with a recessed portion 3 prior to regrooving to define the maximum cutting depth. The recessed portion 3 is referred to as a regrooving depth indicator. The recessed portion 3 is disposed in an upper portion 2A, which is an outer side surface of the treadwear indicator 2, located in the tire radial direction.

[0030] The treadwear indicator 2 provided with the depressed portion 3 is arranged to protrude from the groove bottom 21A of the circumferential main groove 21 toward the tread surface side (the outer side in the tire radial direction) to which the circumferential main groove 21 opens. The treadwear indicator 2 has a height T set to 1.6 mm. As shown in Fig. 2 and Fig. 3, the treadwear indicator 2 is formed with a radius Rt1 of an arcuate rising portion 2B that rises from the groove bottom 21A of the circumferential main groove 21 in the range of 5 mm or more and 25 mm or less. The treadwear indicator 2 is formed with a radius Rt2 of an arcuate shoulder portion 2C that is continuous from the rising portion 2B to the upper portion 2A in the range of 1 mm or more and 15 mm or less. The upper portion 2A is formed as a surface configured such that a portion without a depressed portion 3 extends along the tire circumferential direction. As shown in Fig. 2 and Fig. As illustrated in Fig. 4, the treadwear indicator 2 is formed with a radius Rt3 of an arcuate connecting portion connected to a groove wall 21B of the circumferential main groove 21 in the range of 1 mm or more and 6 mm or less. The treadwear indicator 2 is formed with a tire circumferential direction length (dimension) Lt1 of the treadwear indicator 2 in the range of 30 mm or more and 120 mm or less, where the length Lt1 is a distance between portions where the rising portion 2B connects to the groove bottom 21A of the circumferential main groove 21. The treadwear indicator 2 is formed with a length (dimension) Lt2 in the tire circumferential direction of the upper portion 2A in the range of 15 mm or more and 30 mm or less, the length Lt2 being a distance between intersection portions of the surface of the upper portion 2A and an extension of the rising portion 2B.The treadwear indicator 2 is formed with a length (dimension) Wt in the tire width direction in the range of 5 mm or more and 20 mm or less, where the length Wt is a distance between connecting portions each connecting to the groove wall 21B of the circumferential main groove 21.

[0031] As described above, the recessed portion 3 is disposed in the upper portion 2A of the treadwear indicator 2 and formed to be recessed from the upper portion 2A toward an inner side in the tire radial direction. The recessed portion 3 is formed with a depth Hr from the upper portion 2A of the treadwear indicator 2 in the range of 2.5 mm or more and 10.0 mm or less.

[0032] The recessed part 3 is formed with a radius Rr1 of a rounded chamfer, which forms an edge of an opening portion 3A open at the upper portion 2A of the treadwear indicator 2 in the range of 0.5 mm or more and 8.0 mm or less. The upper portion 2A of the treadwear indicator 2 and an inner wall surface 3B of the recessed portion 3 are seamlessly connected by the rounded chamfer at the opening portion 3A.

[0033] The recessed portion 3 is formed with a length (dimension) Lr in the tire circumferential direction in the range of 2 mm or more and 18 mm or less at the edge where the rounded chamfer of the opening portion 3A connects to the upper portion 2A of the treadwear indicator 2. The recessed portion 3 is formed with a length (dimension) Wr in the tire width direction in the range of 2 mm or more and 10 mm or less at the edge where the rounded chamfer of the opening portion 3A connects to the upper portion 2A of the treadwear indicator 2.

[0034] The recessed portion 3 is formed with an inner diameter Dr that forms the inner wall surface 3B in the range of 1.2 mm or more and 8.0 mm or less. The recessed portion 3 is formed with the inner wall surface 3B having a circular shape in a plan view from the tread surface 15A. Alternatively, the recessed portion 3 is formed with the inner wall surface 3B having an elliptical shape in a plan view from the tread surface 15A.

[0035] The recessed portion 3 is formed with an inner wall surface 3B having a shape that can taper from the rounded slope of the opening portion 3A to a rounded slope of a lower portion 3C, and is formed at an angle of 0 degrees or more and 45 degrees or less with respect to the tire radial direction. In other words, the recessed portion 3 may be a hole in the shape of a column or an elliptical column, or a conical hole that tapers from the opening portion 3A to the lower portion 3C.

[0036] The recessed portion 3 is formed with a radius Rr2 in the range of 0.5 mm or more and 4.0 mm or less of the rounded chamfer forming the periphery of the lower portion 3C. The recessed portion 3 encloses the lower portion 3C, and the lower portion 3C and the inner wall surface 3B are seamlessly connected by the rounded chamfer.

[0037] In the pneumatic tire 1 according to the present embodiment described above, the depressed portion 3 is formed with the depth Hr from the upper portion 2A of the treadwear indicator 2 in the range of 2.5 mm to 10.0 mm or less, is formed with the radius Rr1 of the rounded chamfer of the opening portion 3A in the range of 0.5 mm or more and 8.0 mm or less, and is formed with the radius Rr2 of the rounded chamfer of the lower portion 3C in the range of 0.5 mm or more and 4.0 mm or less.

[0038] The pneumatic tire 1 can reduce the occurrence of a crack originating from the opening portion 3A of the depressed portion 3 even in the final stage of wear (for example, immediately before the upper portion 2A of the treadwear indicator 2 appears on the tread surface 15A). To achieve this effect, in the pneumatic tire 1, the depressed portion 3 is preferably formed with the depth Hr in the range of 3.0 mm or more and 5.0 mm or less, is formed with the radius Rr1 of the rounded chamfer of the opening portion 3A in the range of 2.0 mm or more and 5.0 mm or less, and is formed with the radius Rr2 of the rounded chamfer of the lower portion 3C in the range of 1.0 mm or more and 3.0 mm or less.

[0039] In the pneumatic tire 1 according to the embodiment, the depressed portion 3 is formed with the inner diameter Dr in the range of 1.2 mm or more and 8.0 mm or less, and is formed with the angle with respect to the tire radial direction of the inner wall surface 3B, which can be tapered from the rounded chamfer of the opening portion 3A to the rounded chamfer of the bottom portion 3C of 0 degrees or more and 45 degrees or less.

[0040] The pneumatic tire 1 can significantly achieve the effect of reducing the occurrence of a crack originating from the opening portion 3A of the depressed portion 3. To achieve this effect, in the pneumatic tire 1, the depressed portion 3 is preferably formed with the inner diameter Dr in the range of 2.0 mm or more and 6.0 mm or less, and is formed with the angle of the inner wall surface 3B with respect to the tire radial direction of 0 degrees or more and 15 degrees or less.

[0041] In the pneumatic tire 1 according to the embodiment, the depressed portion 3 is formed with a ratio of the length (dimension) Lr of the opening portion 3A in the tire circumferential direction to the length (dimension) Lt2 of the upper portion 2A of the treadwear indicator 2r in the tire circumferential direction in the range of 20% or more and 70% or less. Furthermore, in the pneumatic tire 1 according to the embodiment, the depressed portion 3 is formed with a ratio of the length (dimension) Wr of the opening portion in the tire width direction to the length (dimension) Wt of the treadwear indicator 2 in the tire width direction in the range of 20% or more and 95% or less.

[0042] The pneumatic tire 1 can significantly achieve the effect of reducing the occurrence of a crack originating from the opening portion 3A of the recessed portion 3. To achieve this effect, in the pneumatic tire 1, for example, in the case of a tire size of 315 / 70R22.5, the ratio Lr / Lt2 is preferably 40% and the ratio Wr / Wt is preferably 90%.

[0043] In the pneumatic tire 1 according to the embodiment, the depressed portion 3 is formed with the edge where the rounded bevel of the opening portion 3A connects with the upper portion 2A of the treadwear indicator 2, the edge having a circular shape when viewed in plan from the tread surface 15A. Alternatively, the depressed portion 3 is formed with the edge where the rounded bevel of the opening portion 3A connects with the upper portion 2A of the treadwear indicator 2, the edge having an elliptical shape when viewed in plan from the tread surface 15A. In other words, the depressed portion 3 is formed with the opening portion 3A having a circular shape or an elliptical shape when viewed from the tread surface 15A.

[0044] The pneumatic tire 1 can significantly obtain the effect of reducing the occurrence of a crack originating from the opening portion 3A of the depressed portion 3.

[0045] In the pneumatic tire 1 according to the embodiment, the opening portion 3A is formed in a circular shape or an elliptical shape when viewed from the tread surface 15A, and the opening portion 3A is formed with an aspect ratio of the edge where the rounded chamfer of the opening portion 3A connects to the upper portion 2A of the treadwear indicator 2, which is in the range of 1.0 or more and 5.0 or less in a plan view viewed from the tread surface 15A.

[0046] The pneumatic tire 1 can significantly obtain the effect of reducing the occurrence of a crack originating from the opening portion 3A of the depressed portion 3.

[0047] In the pneumatic tire 1 according to the embodiment, the connecting portion between the rounded chamfer of the opening portion 3A of the depressed portion 3 and the groove wall 21B of the circumferential main groove 21 is connected by the rounded chamfer, and the depressed portion 3 is formed with the radius Rr3 of the rounded chamfer of the connecting portion in the range of 1.0 mm or more and 5.0 mm or less.

[0048] The pneumatic tire 1 can reduce the occurrence of a crack by seamlessly connecting the groove wall 21B of the circumferential main groove 21 and the opening portion 3A of the recessed portion 3 through the rounded chamfer. To achieve this effect, the pneumatic tire 1 is preferably formed with the radius Rr3 of the rounded chamfer of the connecting portion of 2.0 mm.

[0049] The pneumatic tire 1 according to the embodiment includes two or more of the circumferential main grooves 21. In addition, the depressed portion 3 is arranged in the circumferential main groove 21 on the outermost side in the tire width direction.

[0050] According to the pneumatic tire 1, the circumferential main groove 21 on the outermost side in the tire width direction has a higher stress on the groove bottom 21A than the other circumferential main grooves 21 during running, whereby the effect of reducing cracking is significantly obtained by the depressed portion 3 having the configuration described above.

[0051] In the present embodiment, as described above, the pneumatic tire 1 was described as an example of a tire. The pneumatic tire 1 can be inflated with any gas, including air and inert gas such as nitrogen. However, the configuration of the tread pattern of the pneumatic tire 1 described in the present embodiment can be applied to other tires as desired within the scope apparent to one skilled in the art. Examples of other tires include an airless tire and a solid tire. Examples

[0052] Fig. 5 and Fig.6 are tables showing the results of performance tests of pneumatic tires according to the embodiment. The following describes the performance evaluation tests conducted on pneumatic tires of a prior art example, pneumatic tires of a comparative example, and pneumatic tires of examples according to the embodiment. For performance evaluation tests, crack resistance performance tests were conducted.

[0053] In the crack resistance performance evaluation test, a pneumatic tire (test tire) with a size of 315 / 70R22.5 is mounted on a specified rim, filled with air at a specified internal pressure of 78%, and run on a drum test bench under an atmosphere with an ambient temperature of 30°C and an ozone concentration of 150 pphm, at a specified load, and a speed of 50 km / h. In this case, a travel distance is measured when a crack (a crack originating from a depressed portion when the depressed portion is arranged) generated at the groove bottom of the circumferential main groove occurs. Based on the measurement results, the evaluation is expressed as index values, with the value of the prior art example assigned the reference (100). In this evaluation, higher values ​​are preferable.

[0054] The pneumatic tire of the prior art example includes a depressed portion, but the shape is not within the specified range. The pneumatic tire of the comparative example does not include a depressed portion.

[0055] The pneumatic tires of the examples each include a depressed portion and the shape is within the specified range.

[0056] As can be seen from the test results, the pneumatic tires of the examples are improved in wear resistance performance with respect to the prior art example.

[0057] The present disclosure includes the following inventions. Invention 1

[0058] One tire, including: a main circumferential groove extending in a tire circumferential direction in a tread surface; a tread wear indicator protruding from a groove bottom of the main circumferential groove; and a depressed portion formed in an upper portion of the treadwear indicator and defining a maximum depth of the main circumferential groove after regrooving; of the in-depth section, which is formed with a depth from the upper portion of the tread wear indicator in a range of 2.5 mm or more and 10.0 mm or less, which is formed with a radius of a rounded chamfer of an opening portion in a range of 0.5 mm or more and 8.0 mm or less, and which is formed with a radius of a rounded chamfer of a lower portion in a range of 0.5 mm or more to 4.0 mm or less. Invention 2

[0059] The tire according to invention 1, wherein the in-depth section is formed in a range of 1.2 mm or more and 8.0 mm or less of an inner diameter and formed at an angle with respect to a tire radial direction of an inner wall surface, which may be tapered from the rounded bevel of the opening portion to the rounded bevel of the lower portion of 0 degrees or more and 45 degrees or less. Invention 3

[0060] The tire according to invention 1 or 2, wherein the in-depth section with a ratio of a dimension in the tire circumferential direction of the opening portion to a dimension in the tire circumferential direction of the upper portion of the treadwear indicator in a range of 20% or more and 70% or less, and with a ratio of a dimension of the opening portion in the tire width direction to a dimension of the Treadwear indicator in the tire width direction is formed in a range of 20% or more and 95% or less. Invention 4

[0061] The tire according to any one of inventions 1 to 3, wherein the recessed portion is formed with an opening portion having a circular shape or an elliptical shape as viewed from the tread surface. Invention 5

[0062] The tire according to any one of inventions 1 to 3, wherein the recessed portion formed with the opening portion having a circular shape or an elliptical shape as viewed from the tread surface and formed with an aspect ratio of the opening portion in a range of 1.0 or more and 5.0 or less. Invention 6

[0063] The tire according to any one of inventions 1 to 5, wherein the recessed portion formed with a connecting portion between the rounded bevel of the opening portion and a groove wall of the main circumferential groove, which are connected by a rounded bevel, and with a radius of the rounded chamfer of the connecting portion in a range of 1.0 mm or more and 5.0 mm or less. Invention 7

[0064] The tire according to any one of inventions 1 to 6, wherein two or more of the circumferential main grooves are arranged and the depressed portion is arranged in the circumferential main groove on an outermost side in the tire width direction. List of reference symbols 1 pneumatic tire (tire) 2 Tread wear indicator 2A Upper Section 3 In-depth section 3A Opening section 3B interior wall surface 3C Lower Section 21 Main circumferential groove 21A grooved bottom 21B groove wall QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2013 / 087473

[0003]

Claims

[1] Tires, comprising: a main circumferential groove extending in a tire circumferential direction in a tread surface; a tread wear indicator protruding from a groove bottom of the main circumferential groove; and a depressed portion formed in an upper portion of the treadwear indicator and defining a maximum depth of the main circumferential groove after regrooving; the in-depth section, which is formed with a depth from the upper portion of the tread wear indicator in a range of 2.5 mm or more and 10.0 mm or less, which is formed with a radius of a rounded chamfer of an opening portion in a range of 0.5 mm or more and 8.0 mm or less, and which is formed with a radius of a rounded chamfer of a lower portion in a range of 0.5 mm or more to 4.0 mm or less. [2] Tire according to claim 1, wherein the in-depth section is formed in a range of 1.2 mm or more and 8.0 mm or less of an inner diameter and formed at an angle with respect to a tire radial direction of an inner wall surface, which may be tapered from the rounded bevel of the opening portion to the rounded bevel of the lower portion of 0 degrees or more and 45 degrees or less. [3] Tire according to claim 1, wherein the in-depth section formed with a ratio of a tire circumferential dimension of the opening portion to a tire circumferential dimension of the upper portion of the treadwear indicator in a range of 20% or more and 70% or less, and formed with a ratio of a tire widthwise dimension of the opening portion to a tire widthwise dimension of the treadwear indicator in a range of 20% or more and 95% or less. [4] The tire according to claim 1, wherein the recessed portion is formed with the opening portion having a circular shape or an elliptical shape as viewed from the tread surface. [5] Tire according to claim 1, wherein the in-depth section is formed with the opening portion having a circular shape or an elliptical shape as viewed from the tread surface and with an aspect ratio of the opening portion in a range of 1.0 or more and 5.0 or less. [6] Tire according to claim 1, wherein the in-depth section formed with a connecting portion between the rounded bevel of the opening portion and a groove wall of the main circumferential groove, which are connected by a rounded bevel, and with a radius of the rounded chamfer of the connecting portion in a range of 1.0 mm or more and 5.0 mm or less. [7] Tire according to claim 1, wherein two or more of the main circumferential grooves are arranged and the depressed portion is arranged in the circumferential main groove on an outermost side in the tire width direction.

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