Pneumatic tire and tire vulcanization mold

Abstract

To provide a pneumatic tire and a tire vulcanization mold that can reduce noise caused by grooves on a tread surface and improve rough road performance.SOLUTION: A pneumatic tire has a main groove 7 provided in a tread surface 3f. The main groove 7 includes an uneven region 70 between a groove edge 74 of the main groove 7 and a groove bottom surface 71 of the main groove 7. In the uneven region 70, protrusions 10 are arranged along a groove length direction and groove depth direction. The protrusions 10 have rising surfaces 11 that rise from groove wall surfaces 72 of the main groove 7 and face in the groove length direction, and inclined top surfaces 12 that extend in the groove length direction while gradually decreasing their protruding height from the groove wall surfaces 72.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a pneumatic tire and a tire vulcanization mold used for vulcanizing and molding the pneumatic tire. [Background technology]

[0002] Patent Documents 1 and 2 each describe a pneumatic tire in which a plurality of minute protrusions are formed on the groove wall surfaces of the grooves in order to reduce noise caused by the grooves on the tread surface, such as air column resonance and pumping noise. Furthermore, although the pneumatic tire described in Patent Document 2 claims to have improved mud performance, the shapes of the minute protrusions mentioned are merely truncated cones, cylinders, and pyramids, and it is believed that there is room for improvement in terms of performance on rough roads, such as muddy ground. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-96534 [Patent Document 2] Japanese Patent Publication No. 2022-128121 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure has been made in consideration of the above-described circumstances, and its purpose is to provide a pneumatic tire and a tire vulcanization mold that can reduce noise caused by grooves on the tread surface and improve off-road performance. [Means for solving the problem]

[0005] The pneumatic tire of the present disclosure comprises a groove provided in a tread surface, the groove including an uneven region between the groove edge and the groove bottom surface of the groove, and protrusions arranged in the uneven region along the groove length direction and groove depth direction, the protrusions having a rising surface rising from the groove wall surface of the groove and facing in the groove length direction, and an inclined top surface extending in the groove length direction while gradually decreasing the protruding height relative to the groove wall surface.

[0006] The tire vulcanizing mold disclosed herein includes protrusions for molding grooves formed on the tread surface of a tire, the protrusions including an uneven region between an inside corner edge corresponding to a groove edge of the groove and a top surface corresponding to a groove bottom surface of the groove, the uneven region including depressions arranged along the groove length direction and groove depth direction, the depressions having a recessed surface recessed from a side wall surface of the protrusion and facing the groove length direction, and an inclined bottom surface extending in the groove length direction while gradually decreasing the recess depth relative to the side wall surface. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a tire meridian cross-sectional view showing an example of a pneumatic tire according to an embodiment of the present invention; [Figure 2] Planar development showing an example of a tread pattern [Figure 3] Tire meridian cross section of main groove [Figure 4] Front view of the main groove wall [Figure 5] (A) Three-view of the protrusion and (B) AA cross section [Figure 6] Perspective view of the protrusion [Figure 7] Enlarged view showing three protrusion rows included in the uneven area [Figure 8] FIG. 10 is a front view of a groove wall surface of a main groove in a modified example. [Figure 9] FIG. 10 is a front view of a groove wall surface of a main groove in a modified example. [Figure 10] Planar development showing an example of a tread pattern [Figure 11] 1 is a tire meridian cross-sectional view showing an example of a tire vulcanization mold according to an embodiment of the present invention; [Figure 12]Tire meridian cross section of protrusion [Figure 13] (A) Front view of the side wall of the protrusion and (B) XX cross section DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0009] 1 is a tire meridian cross-sectional view showing an example of a pneumatic tire T according to this embodiment. The pneumatic tire T is a pneumatic tire for automobiles that includes a pair of bead portions 1, a pair of sidewall portions 2 extending radially outward from each of the bead portions 1, and a tread portion 3 that continues to the radially outer ends of each of the sidewall portions 2. A tread surface 3f that forms the outer peripheral surface of the tread portion 3 has a tread pattern formed thereon according to the required tire performance and usage conditions.

[0010] Here, the tire meridian cross section is a cross section obtained by cutting the tire T along a plane including the central axis (tire rotation axis) of the tire. The tire radial direction is the direction along the diameter of the tire. The side closer to the central axis of the tire T is the inner side in the tire radial direction, and the side away from the central axis of the tire T is the outer side in the tire radial direction. The tire width direction is the direction parallel to the central axis of the tire. The side closer to the tire equator TC located at the center of the tire T in the tire width direction is the inner side in the tire width direction, and the side away from the tire equator TC is the outer side in the tire width direction. The tire circumferential direction is the direction around the central axis of the tire T.

[0011] An annular bead core 1a and a bead filler 1b are embedded in the bead portion 1. The bead core 1a is formed of a bundle of rubber-coated steel wires or the like. The bead filler 1b is formed of rubber with a roughly triangular cross section and is located radially outward of the bead core 1a.

[0012] The carcass layer 4 is provided in a toroidal shape between the pair of bead portions 1. The ends of the carcass layer 4 are wound up so as to sandwich the bead core 1a and the bead filler 1b. The carcass layer 4 is composed of a carcass ply formed by rubber-coating carcass cords extending approximately perpendicular to the tire circumferential direction. Organic fiber cords such as polyester, rayon, nylon, and aramid are preferably used as the carcass cords. A belt layer 5 is laminated on the radially outer side of the carcass layer 4, and a belt reinforcing layer 6 is laminated on the radially outer side of the belt layer 5.

[0013] The belt layer 5 is composed of a plurality of belt plies (two in this embodiment). Each belt ply is formed by rubber-coating belt cords that extend obliquely with respect to the tire circumferential direction, and the belt cords are layered so that they cross each other in opposite directions between plies. Steel cords are preferably used for the belt cords. The belt reinforcing layer 6 is composed of reinforcing plies that are formed by rubber-coating reinforcing cords that extend along the tire circumferential direction. Organic fiber cords such as polyester, rayon, nylon, and aramid are preferably used as the reinforcing cords.

[0014] 2 is a plan view showing an example of a tread pattern formed on the tread surface 3f. The tire T has main grooves 7 extending in the tire circumferential direction on the tread surface 3f. The main grooves 7 extend linearly, but are not limited to this. For example, the main grooves 7 may have a shape including a portion inclined at an angle of 5 degrees or less with respect to the tire circumferential direction, and therefore may be grooves extending in a zigzag pattern along the tire circumferential direction. In the case of grooves extending in a zigzag pattern, it is preferable that the grooves include a see-through region (a region that can be seen through when viewed in the tire circumferential direction without being obstructed by the groove wall surfaces 72 of the main grooves 7).

[0015] FIG. 3 is a tire meridian cross-section of the main groove 7. FIG. 4 is a front view of the groove wall surface 72 of the main groove 7. FIG. 5 shows (A) a three-view diagram of a protrusion 10 described later and (B) an AA cross-section. The BB and CC cross-sections have the same shape as the AA cross-section, so they are not shown. FIG. 6 is a perspective view of the protrusion 10. The configuration of the main groove 7 described below may be applied to any of the multiple main grooves 7 provided on the tread surface 3f, or may be applied to all of the main grooves 7.

[0016] As shown in Fig. 2, this embodiment employs a tread pattern that is symmetrical with respect to the tire equator TC. The tread pattern is a so-called block pattern, but is not limited to this. The tire T has main grooves 7 and lateral grooves 8 as grooves provided on the tread surface 3f. The main grooves 7 extend continuously along the tire circumferential direction, and the lateral grooves 8 extend in a direction intersecting with the main grooves 7.

[0017] The pneumatic tire T in this embodiment is a rotational direction specified tire in which the rotational direction is specified. The rotational direction is specified, for example, by a marking on the outer surface of the sidewall portion 2. The arrow RD1 indicates the front side in the rotational direction, which corresponds to the "leading side" that touches the ground first when the vehicle moves forward. The arrow RD2 indicates the rear side in the tire rotational direction, which corresponds to the "kicking side" that touches the ground last when the vehicle moves forward.

[0018] As shown in Figures 3 and 4, the main groove 7 has a groove bottom surface 71 and a pair of groove wall surfaces 72 extending from the groove bottom surface 71 outward in the tire radial direction. The groove bottom surface 71 includes a connecting surface 73 having an arc-shaped cross section that smoothly connects to the groove wall surfaces 72. The radius of curvature R of the connecting surface 73 is, for example, 1.5 to 2.75 mm. In this embodiment, the groove wall surfaces 72 extend linearly between a groove edge 74 formed by the tread surface 3f and the groove wall surfaces 72 and an outer end 75 of the connecting surface 73 in the tire radial direction. The groove width W7 of the main groove 7 in the tire width direction is, for example, 4.0 mm or more, preferably 6.0 mm or more. The groove depth D7 of the main groove 7 in the tire radial direction is, for example, 4.0 mm or more, preferably 6.0 mm or more.

[0019] The main groove 7 includes a concave-convex region 70 between a groove edge 74 of the main groove 7 and a groove bottom surface 71 of the main groove 7. The concave-convex region 70 may be formed on at least one groove wall surface 72, but is preferably formed on each of the pair of groove wall surfaces 72 as in this embodiment. It is preferable that the concave-convex region 70 is not formed on the groove bottom surface 71. In the concave-convex region 70, protrusions 10 are arranged along the groove length direction and groove depth direction. The left-right direction and the up-down direction in FIG. 4 correspond to the groove length direction (the tire circumferential direction in the case of the main groove 7) and the groove depth direction (the tire radial direction), respectively.

[0020] The protrusions 10 have rising surfaces 11 that rise from the groove wall surfaces 72 and face in the groove length direction, and inclined top surfaces 12 that extend in the groove length direction while gradually decreasing their protruding height relative to the groove wall surfaces 72. With this configuration, the protrusions 10 arranged in the uneven region 70 diffusely reflect sound generated inside the grooves, thereby reducing noise caused by the grooves on the tread surface 3f, such as air column resonance and pumping noise. Furthermore, because the protrusions 10 have the above-described rising surfaces 11 and inclined top surfaces 12, they are more likely to exert traction on mud that has entered the grooves, thereby improving rough road performance on muddy ground and the like.

[0021] The protrusions 10 protrude inward in the groove width direction (toward the groove center). The protrusion height of the protrusions 10 relative to the groove wall surface 72 is greatest at the upper end of the rising surface 11 and decreases with increasing distance from the rising surface 11. The protrusion height H10 (maximum height) of the protrusions 10 relative to the groove wall surface 72 is preferably 0.5 mm or less in order to reduce the resistance of air and water flowing inside the main groove 7. Furthermore, in order to ensure the above-mentioned noise reduction effect, the protrusion height H10 is preferably 0.1 mm or more.

[0022] When the protrusion height H10 of the protrusions 10 is small, about 0.1 to 0.5 mm, the roughness of the uneven surface in the uneven region 70 is appropriately small, which is advantageous for reducing air resistance in the main groove 7 during driving and improving fuel efficiency. This is because when air flowing inside the main groove 7 contacts the uneven region 70 during driving, relatively small air vortices are generated at the tops of the protrusions 10, which can reduce pressure resistance by suppressing air separation or by separating air further rearward. From the viewpoint of appropriately achieving this effect, the arrangement pitch P10r of the protrusions 10 in the groove length direction (see FIG. 7) is preferably 2 to 8 times, and more preferably 2 to 6 times, the protrusion height H10.

[0023] The length L10 of the protrusions 10 in the groove length direction is preferably greater than the protrusion height H10. The length L10 is set to, for example, 0.8 mm or more. From the viewpoint of ensuring the number of protrusions 10 aligned in the groove length direction, the length L10 is preferably 2.8 mm or less. In the uneven region 70, preferably four or more, more preferably six or more, protrusions 10 are aligned along the groove length direction.

[0024] The length D10 of the protrusions 10 in the groove depth direction is preferably greater than the protrusion height H10. The length D10 is set to, for example, 1.0 mm or more. From the viewpoint of ensuring the number of protrusions 10 aligned in the groove depth direction, the length D10 is preferably 3.0 mm or less. In the uneven region 70, preferably four or more, more preferably six or more, protrusions 10 are aligned along the groove depth direction. In this embodiment, the length D10 is set to the same size as the length E10 and the length F10 shown in FIG. 5, but is not limited to this.

[0025] The angle θ11 of the rising surface 11 relative to the groove wall surface 72 is set to, for example, 80 degrees or more. Considering the ease of demolding when removing the tire T from the mold during vulcanization molding, the angle θ11 is preferably 90 degrees or more, and more preferably exceeds 90 degrees. The angle θ11 is set to, for example, 110 degrees or less. The inclined top surface 12 extends linearly between one end located at the upper end of the rising surface 11 and the other end where the protruding height relative to the groove wall surface 72 is substantially zero. The other end of the inclined top surface 12 may be located away from the groove wall surface 72 at a protruding height lower than that of the rising surface 11.

[0026] In addition to the rising surface 11 and inclined top surface 12 described above, the protrusion 10 further has a pair of side wall surfaces 13 that rise from the groove wall surface 72 and face in the groove depth direction. The side wall surfaces 13 are formed in a triangular shape when viewed in the groove depth direction, and in this embodiment, are arranged at side ends Es of an arrow feather shape described below. The angle θ13 of the side wall surfaces 13 with respect to the groove wall surface 72 is set to, for example, 80 to 110 degrees. From the viewpoint of reducing the interval G10 (the interval between the side wall surfaces 13) between adjacent protrusions 10 in the groove depth direction and increasing the arrangement density of the protrusions 10, it is preferable that the angle θ13 is substantially 90 degrees.

[0027] As shown in Figures 4 and 6, adjacent protrusions 10 in the groove depth direction are arranged with the rising surfaces 11 facing in the same direction. In this example, protrusions 10 each having a rising surface 11 facing one side in the groove length direction and an inclined top surface 12 whose protrusion height gradually decreases toward the other side in the groove length direction are repeatedly arranged in the groove depth direction. This configuration increases traction by the protrusions 10 in a predetermined direction, which is advantageous for improving rough road performance. The spacing G10 between adjacent protrusions 10 in the groove depth direction is, for example, 0.05 to 0.3 mm, and is set to 0.1 mm in this embodiment.

[0028] In this embodiment, the rising surface 11 faces the trailing side (rear side RD2 in the direction of rotation). Therefore, the protruding height of the inclined top surface 12 gradually decreases toward the leading side (front side RD1 in the direction of rotation). With this configuration, when traveling on rough road surfaces such as muddy ground or sand, or wet road surfaces such as puddles, the trailing side has a scraping effect, which tends to improve traction. Furthermore, the gradual decrease in the protruding height of the protrusion 10 toward the leading side is advantageous for reducing the resistance of air and water flowing inside the main groove 7. From this perspective, the angle θ12 of the inclined top surface 12 with respect to the groove wall surface 72 is preferably 120 degrees or more, and more preferably 150 degrees or more.

[0029] When viewing the groove wall surface 72 from the front, the protrusion 10 is formed in a polygonal shape. In this embodiment, the protrusion 10 is formed in an arrow feather shape (an example of a polygonal shape) and has a raised surface 11 on the side of the feather rear end Er. Such an arrow feather-shaped protrusion 10 improves the effect of scraping out mud and the like with the raised surface 11, making it easier to provide traction, while also reducing resistance to air and water flowing within the groove. The arrow feather shape includes a feather rear end Er that is concave in the groove length direction (in this embodiment, the forward side RD1 in the rotational direction), a feather tip Ef that is convex in that direction, and a pair of side ends Es that connect them and extend in the groove length direction.

[0030] As shown in FIG. 4, in this embodiment, a protrusion row C10 is formed, in which protrusions oriented in the same arrow feather shape are aligned in the groove depth direction. The protrusion row C10 extends in a zigzag pattern along the groove depth direction. In the uneven region 70, the protrusion row C10 is repeatedly arranged along the groove length direction. FIG. 7 is an enlarged view showing three protrusion rows C10 included in the uneven region 70. FIG. 7(A) shows the embodiment shown in FIG. 4, and FIGS. 7(B) and (C) show its modified examples. FIGS. 7(A) and (B) show examples in which adjacent protrusions 10 in the groove length direction are aligned with the direction in which their rising surfaces 11 face, while FIG. 7(C) shows an example in which this is not the case.

[0031] In the example of FIG. 7(A), adjacent protrusion rows C10 in the groove length direction are arranged with a phase (zigzag phase) offset in the groove depth direction. Therefore, a void 14 surrounded by the rising surface 11 and the inclined top surface 12 is provided between adjacent protrusion rows C10 in the groove length direction. With this configuration, traction is enhanced by the shearing effect of mud and other debris that has entered the void 14, thereby improving rough-road performance. Furthermore, the fact that the void 14 faces the inclined top surface 12 is advantageous in preventing mud from clogging in the void 14. In this embodiment, diamond-shaped voids 14 are provided by offsetting the phase by half the arrangement pitch P10c of the protrusions 10 in the groove depth direction.

[0032] In the example of Figure 7(B), adjacent protrusion rows C10 in the groove length direction are arranged with the same phase (zigzag phase) in the groove depth direction. Therefore, although the arrangement pitch P10r of the protrusions 10 in the groove length direction is the same as in the example of Figure 7(A), there is no void 14 surrounded by the rising surface 11 and the inclined top surface 12, and therefore it is difficult to achieve the above-mentioned effect of increasing traction. Although such a configuration can be applied, from the perspective of improving rough road performance, it is preferable to arrange adjacent protrusion rows C10 with the phase in the groove depth direction shifted, as shown in Figure 7(A).

[0033] In the example of Figure 7(C), adjacent protrusion rows C10 in the groove length direction are arranged with the arrow feather shapes facing in opposite directions and the phase (zigzag phase) in the groove depth direction aligned. Therefore, between adjacent protrusion rows C10 in the groove length direction, a void 15 surrounded by the rising surface 11 and a void 16 surrounded by the inclined top surface 12 are provided. With this configuration, traction is improved by the shearing effect of mud and other particles that have entered the void 15, thereby effectively improving rough-road driving performance. Moreover, because the void 15 faces the rising surface 11 in both directions in the groove length direction, traction can be improved in both directions in the groove length direction.

[0034] From the viewpoint of ensuring the effect of reducing noise such as air column resonance, the length L70 of the uneven region 70 in the groove length direction is preferably 50% or more, and more preferably 80% or more, of the length L72 of the groove wall surface 72 in the groove length direction. When the lateral grooves 8 open into the groove wall surface 72 of the main groove 7, the lengths L70 and L72 are each measured in the range between the lateral grooves 8 adjacent in the tire circumferential direction. When the lateral grooves 8 do not open into the groove wall surface 72 of the main groove 7, the lengths L70 and L72 are each measured in the range of one circumference around the tire in the tire circumferential direction. The length L72 is determined at the groove edge 74.

[0035] In this embodiment, a radially outer end 76 of the uneven region 70 is located at a groove edge 74, and a radially inner end 77 of the uneven region 70 is located at a radially outer end 75 of a connecting surface 73 having an arc-shaped cross section that connects a groove bottom surface 71 and a groove wall surface 72. This configuration makes it easy to ensure the size of the uneven region 70 in the groove depth direction, thereby enhancing the effects of reducing noise such as air column resonance and improving rough road driving performance. The inner end 77 of the uneven region 70 is preferably located at or radially outward of the outer end 75 of the connecting surface 73.

[0036] In the modified example shown in FIG. 8, the radially outer end 76 of the uneven region 70 is positioned away from the groove edge 74 of the main groove 7 toward the radially inner side of the tire. With this configuration, an edge component extending linearly along the tire circumferential direction appears at the groove edge 74, thereby enhancing the edge effect of the main groove 7 in the lateral direction. The separation distance D1 of the outer end 76 from the groove edge 74 is set to, for example, 1.0 to 2.0 mm. In the example of FIG. 7, the separation distance D1 is constant along the tire circumferential direction, but is not limited thereto. For example, the separation distance D1 may change so as to become smaller as it approaches the lateral groove 8.

[0037] In the modified example shown in FIG. 9 , an inner end 77 in the tire radial direction of the uneven region 70 is positioned away from an outer end 75 in the tire radial direction of the connecting surface 73 toward the tire radial direction. The groove bottom 71, which is unlikely to come into contact with mud, contributes little to traction, and there is a risk of mud clogging if mud comes into contact with the protrusion 10 near the groove bottom 71. Therefore, it is preferable to position the inner end 77 away from the groove bottom 71 in this manner. A separation distance D2 between the inner end 77 and the outer end 75 of the connecting surface 73 is set to, for example, 1.0 to 2.0 mm. The separation distance D2 does not need to be set uniformly, but may vary along the tire circumferential direction. The separation distance D2 can also be set together with the separation distance D1 described above.

[0038] In this embodiment, an example has been shown in which the pneumatic tire T is a rotational direction specified tire, but the present invention is not limited to this and may be a tire in which the rotational direction is not specified. In such a case, it is also possible to adopt a tread pattern asymmetric with respect to the tire equator TC as shown in FIG. 10. This tread pattern is a so-called rib pattern, but is not limited to this. In a tire in which the rotational direction is not specified, when applying an uneven region 70 formed by arranging arrow feather-shaped protrusions 10, it is possible to adopt the form shown in FIG. 7(C).

[0039] In this embodiment, an example has been shown in which the main groove 7 includes the above-described uneven region 70, but alternatively or in addition, the lateral grooves 8 provided in the tread surface 3f may also include the above-described uneven region. In the lateral grooves of a winter tire or all-season tire (for example, a mud & snow tire designated "M&S" or "M+S"), if the above-described separation distance D1 (see FIG. 8) is set to about 50% (for example, 40 to 60%) of the groove depth of the lateral groove 8, the groove edges of the lateral grooves 8 will provide an edge effect until the middle of wear, and after that, when the tire begins to function as a summer tire, the uneven regions on the groove walls can improve the rough road performance.

[0040] 11 is a tire meridian cross-sectional view of a tire vulcanization mold M used for vulcanizing a pneumatic tire T. In FIG. 11, the tire T is shown by a broken line, and the tire T is set in the mold M with the tire width direction facing up and down. The mold M includes a pair of bead rings Mb into which the bead portions 1 of the tire T are fitted, a pair of side mold portions Ms for molding the sidewall portions 2 of the tire T, and a tread mold portion Mt for molding the tread portion 3 of the tire T.

[0041] The mold M has a tire molding surface Mf that contacts the outer surface of the tire T set in the mold M. The tire molding surface Mf includes the inner surfaces of a pair of side mold portions Ms and the inner surface of the tread mold portion Mt. The inner surface of the tread mold portion Mt is provided with an uneven surface for forming a tread pattern. The tread mold portion Mt is composed of multiple sectors that are divided in the tire circumferential direction and are gathered together to form a ring. The mold M is a segmented mold that has a tread mold portion Mt with such a divided structure, but is not limited to this and may be, for example, a two-piece mold that is divided into upper and lower halves at the center of the tread mold portion.

[0042] The mold M has protrusions for molding grooves to be provided in the tread surface 3f of the tire T. Specifically, the mold M has protrusions 9 for molding the main grooves 7 and protrusions 89 (see FIG. 13(A)) for molding the lateral grooves 8. During vulcanization molding, the tire molding surface Mf including the protrusions 9 and 89 is pressed against the tread surface of the unvulcanized tire, thereby forming a tread pattern including the main grooves 7 and lateral grooves 8.

[0043] FIG. 12 is a tire meridian cross-section of the protrusion 9. FIG. 13 shows (A) a front view of the sidewall surface 92 of the protrusion 9 and (B) an XX cross-section. The YY and ZZ cross-sections are omitted from the illustration because they have the same shape as the XX cross-section. The protrusion 9 has a top surface 91 and a pair of sidewall surfaces 92 extending radially outward from the top surface 91. The top surface 91 includes a connecting surface 93 having an arc-shaped cross section that smoothly connects to the sidewall surfaces 92. The protrusion 9 includes an uneven region 90 between an inside corner edge 94 corresponding to the groove edge 74 of the main groove 7 and the top surface 91 corresponding to the groove bottom surface 71 of the main groove 7. In the uneven region 90, depressions 20 are arranged side by side along the groove length direction (the length direction of the protrusion) and the groove depth direction (the protrusion protruding direction).

[0044] The depressions 20 have depression surfaces 21 that are depressed from the side wall surfaces 92 of the protrusions 9 and face the groove length direction, and an inclined bottom surface 22 that extends in the groove length direction while gradually decreasing in depression depth relative to the side wall surfaces 92. The main grooves 7 of the pneumatic tire T obtained by vulcanization molding using such a mold M include an uneven region 70 that corresponds to the uneven region 90 of the protrusions 9. Furthermore, the protrusions 10 arranged in the uneven region 70 have rising surfaces 11 that correspond to the depression surfaces 21 and inclined top surfaces 12 that correspond to the inclined bottom surfaces 22. For details of the preferred dimensions, shapes, arrangements, etc. of the protrusions 9 and the depressions 20, the above-mentioned descriptions of the main grooves 7 and the protrusions 10 can be referred to.

[0045] It will be understood by those skilled in the art that the above-described embodiments are examples of the following aspects.

[0046] [1] The pneumatic tire of the present disclosure comprises a groove provided in a tread surface, the groove including an uneven region between the groove edge and the groove bottom surface of the groove, and protrusions arranged in the uneven region along the groove length direction and groove depth direction, the protrusions having a rising surface rising from the groove wall surface of the groove and facing in the groove length direction, and an inclined top surface extending in the groove length direction while gradually decreasing the protruding height relative to the groove wall surface.

[0047] With this configuration, the protrusions arranged in the uneven area diffusely reflect the sound generated inside the grooves, thereby reducing noise caused by the grooves on the tread surface, such as air column resonance and pumping noise. Furthermore, because the protrusions have the above-mentioned raised surfaces and inclined top surfaces, they are more likely to exert traction on mud that has entered the grooves, improving the vehicle's ability to travel on rough roads, such as muddy ground.

[0048] [2] In the pneumatic tire of the above [1], the protrusions adjacent in the groove depth direction may be arranged with the raised surfaces facing in the same direction. This configuration increases the traction of the protrusions 10 in the predetermined direction, which is advantageous for improving rough road performance.

[0049] [3] In the pneumatic tire of [1] or [2] above, the rotation direction may be specified, and the raised surface may face the trailing edge. With this configuration, when traveling on rough road surfaces such as muddy ground or sandy areas, or wet road surfaces such as puddles, the trailing edge has a scraping effect, which tends to improve traction.

[0050] [4] In the pneumatic tire of any one of the above [1] to [3], the protrusion may be configured to be formed in an arrow feather shape, with the raised surface located at the rear end of the arrow feather. With this configuration, the raised surface is more effective in scraping out mud and the like, making it easier to exert traction, while at the same time reducing resistance to air and water flowing through the grooves.

[0051] [5] The pneumatic tire of [4] above may have a configuration in which a projection row is formed by arranging the projections, each having the same arrow feather-shaped orientation, in the groove depth direction, and adjacent projection rows in the groove length direction are arranged with a phase shift in the groove depth direction. With this configuration, a void space is provided surrounded by the raised surface and the inclined crest surface, which increases traction by shearing mud and other debris that has entered the void space, thereby improving rough-road performance. Furthermore, since the void space faces the inclined crest surface, it is advantageous in preventing mud from clogging the void space.

[0052] [6] In the pneumatic tire of [4] above, a protrusion row may be formed by arranging the protrusions, each having the same arrow feather-shaped direction, in the groove depth direction, and adjacent protrusion rows in the groove length direction are arranged with the arrow feather-shaped directions opposite to each other but aligned in phase in the groove depth direction. With this configuration, a void surrounded by raised surfaces is provided, which enhances traction by the shearing effect of mud and other materials that have entered the void, thereby improving rough-road performance. Moreover, since the void faces the raised surfaces on both sides of the groove length direction, traction can be enhanced in either direction of the groove length.

[0053] [7] In the pneumatic tire of any one of the above [1] to [6], the protrusions may have a protruding height of 0.5 mm or less from the groove wall surface. Protrusions having such a height are preferable in terms of reducing resistance to air and water flowing in the groove.

[0054] [8] The tire vulcanization mold of the present disclosure includes protrusions for molding grooves provided in the tread surface of a tire, the protrusions including a concave-convex region between an inside corner edge corresponding to the groove edge of the groove and a top surface corresponding to the groove bottom surface of the groove, the concave-convex region including depressions arranged along the groove length direction and the groove depth direction, the depressions having a depressed surface depressed from a sidewall surface of the protrusion and facing the groove length direction, and a sloping bottom surface extending in the groove length direction while gradually decreasing in depression depth relative to the sidewall surface. This configuration provides a pneumatic tire that can reduce noise caused by the grooves in the tread surface and improve rough-road performance.

[0055] The pneumatic tire of the present disclosure can be configured in the same manner as a normal pneumatic tire, except that the grooves on the tread surface are configured as described above, and any of the conventionally known materials, shapes, structures, manufacturing methods, etc. can be adopted.

[0056] The tire vulcanizing mold of the present disclosure can be configured in the same manner as a normal tire vulcanizing mold, except that the protrusions for forming grooves on the tread surface are configured as described above, and any of the conventionally known materials, shapes, structures, mechanisms, etc. can be adopted.

[0057] Although the embodiments of the present disclosure have been described based on the drawings, it should be understood that the specific configuration is not limited to this embodiment. The scope of the present disclosure is indicated not only by the description of the above embodiments but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0058] The pneumatic tire and tire vulcanization mold of the present disclosure are not limited to the above-described embodiments, and are not limited to the above-described effects. The pneumatic tire and tire vulcanization mold of the present disclosure can be improved or modified in various ways without departing from the spirit and scope of the present disclosure. Furthermore, the configurations employed in the above-described embodiments can be combined in any desired manner. [Explanation of symbols]

[0059] 1 bead portion, 2 sidewall portion, 3 tread portion, 3f tread surface, 7 main groove, 8 lateral groove, 9 protrusion, 10 protrusion, 11 rising surface, 12 inclined top surface, 21 depressed surface, 22 inclined bottom surface, 70 uneven region, 71 groove bottom surface, 72 groove wall surface, 73 connecting surface, 74 groove edge, 90 uneven region, 91 top surface, 92 side wall surface, 94 inside corner edge, C10 protrusion row, Ef arrow feather tip, Er arrow feather rear end

Claims

1. The tire has grooves on the tread surface, the groove includes a concave-convex region between a groove edge of the groove and a groove bottom surface of the groove; In the uneven region, protrusions are arranged along the groove length direction and the groove depth direction, The protrusion has a rising surface that rises from the groove wall surface of the groove and faces in the groove length direction, and an inclined top surface that extends in the groove length direction while gradually decreasing its protruding height from the groove wall surface.

2. The pneumatic tire according to claim 1 , wherein the protrusions adjacent to each other in the groove depth direction are arranged so that the raised surfaces face in the same direction.

3. The direction of rotation is specified, The pneumatic tire according to claim 1 , wherein the raised surface faces the trailing edge.

4. The pneumatic tire according to claim 1 , wherein the protrusion is formed in an arrow feather shape, and the raised surface is located on a rear end side of the arrow feather.

5. A row of protrusions is formed by arranging the protrusions, each having the same arrow feather shape, in the groove depth direction, 5. The pneumatic tire according to claim 4, wherein the projection rows adjacent in the groove length direction are arranged with a phase difference in the groove depth direction.

6. A row of protrusions is formed by arranging the protrusions, each having the same arrow feather shape, in the groove depth direction, 5. The pneumatic tire according to claim 4, wherein the projection rows adjacent in the groove length direction are arranged with the arrow feather shapes oriented in opposite directions to each other and aligned in phase in the groove depth direction.

7. The pneumatic tire according to any one of claims 1 to 6, wherein the protrusions have a protruding height of 0.5 mm or less from the groove wall surface.

8. The tire has a protrusion for forming a groove on a tread surface, the protrusion includes an uneven region between an inside corner edge corresponding to a groove edge of the groove and a top surface corresponding to a groove bottom surface of the groove, In the uneven region, depressions are arranged along the groove length direction and the groove depth direction, The tire vulcanizing mold has a recessed surface that is recessed from the side wall surface of the protrusion and faces in the groove length direction, and a sloping bottom surface that extends in the groove length direction while gradually decreasing its recessed depth relative to the side wall surface.

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