Pneumatic tire and tire vulcanization mold

Abstract

To provide a pneumatic tire and a tire vulcanization mold that can reduce air column resonance noise and improve noise performance.SOLUTION: A pneumatic tire includes main grooves 7 extending in a tire circumferential direction on a tread surface. The main grooves 7 include serration regions 70 between groove edges 74 of the main grooves 7 and groove bottom surfaces 71 of the main grooves 7. In the serration regions 70, ridges 10 extending in the tire radial direction are arranged in the tire circumferential direction. The ridges 10 protrude from groove wall surfaces 72 that extend from the groove bottom surface 71 outward in the tire radial direction.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] Air column resonance is known as a type of noise caused by tires. Air column resonance occurs when an air column is generated in a tubular space formed between the main grooves on the tire's tread surface and the road surface, and the air is repeatedly compressed and released as the tire travels. Patent Document 1 describes a pneumatic tire in which recesses and protrusions are formed on the groove wall surfaces of the main grooves on the tread surface in order to reduce air column resonance without impairing drainage performance. However, the recesses and protrusions are formed by narrow grooves recessed into the groove wall surfaces and arranged at intervals around the tire, leaving room for improvement in terms of reducing air column resonance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-69305 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 air column resonance noise and improve noise performance. [Means for solving the problem]

[0005] The pneumatic tire of the present disclosure has a main groove extending circumferentially on the tread surface of the tire, the main groove including a serration region between the groove edge of the main groove and the groove bottom surface of the main groove, and in the serration region, ridges extending radially along the tire are arranged circumferentially, and the ridges protrude from groove wall surfaces extending radially outward from the groove bottom surface.

[0006] The tire vulcanizing mold disclosed herein includes protrusions for molding main grooves extending circumferentially on the tread surface of the tire, the protrusions including a serration region between an inside corner edge corresponding to a groove edge of the main groove and a top surface corresponding to a groove bottom surface of the main groove, and in the serration region, depressions extending radially along the tire are arranged circumferentially, and the depressions are recessed from a sidewall surface extending radially outward from the top surface. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a tire meridian cross-sectional view showing an example of a pneumatic tire according to a first embodiment; [Figure 2] Planar development showing an example of a tread pattern [Figure 3] Tire meridian cross section of main groove [Figure 4] Cross-sectional perspective view of the main groove [Figure 5] A perspective view of ridges arranged in a serration region. [Figure 6] Front view of the main groove wall [Figure 7] FIG. 10 is a front view of a groove wall surface of a main groove in a modified example. [Figure 8] FIG. 10 is a front view of a groove wall surface of a main groove in a modified example. [Figure 9] FIG. 1 is a tire meridian cross-sectional view showing an example of a tire vulcanization mold according to a first embodiment. [Figure 10] Tire meridian cross section of protrusion [Figure 11] Cross-sectional perspective view of the protrusion [Figure 12] FIG. 10 is a plan development showing an example of a tread pattern according to a second embodiment. [Figure 13] Front view of the main groove wall [Figure 14] 10 is a perspective view of a ridge in the third embodiment; [Figure 15] Close-up of the ridge top DETAILED DESCRIPTION OF THE INVENTION

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

[0009] [First embodiment] First, a first embodiment will be described with reference to Figures 1 to 11. Figure 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] FIG. 2 is a planar development 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. FIG. 3 is a tire meridian cross-sectional view of the main groove 7. FIG. 4 is a cross-sectional perspective view of the main groove 7. FIG. 5 is a perspective view of ridges 10 arranged in a serration region 70, which will be described later. FIG. 6 is a front view of a groove wall surface 72 of the main groove 7. 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.

[0015] As shown in FIG. 2 , this embodiment employs a tread pattern that is asymmetric with respect to the tire equator TC. Such a tire T may be a tire for which the rotation direction is not specified. The tread pattern is a so-called rib pattern, but is not limited to this. The tire T includes main grooves 7 that extend continuously along the tire circumferential direction on the tread surface 3f, and lateral grooves 8 that extend in a direction intersecting with the main grooves 7. The main grooves 7 extend linearly, but are not limited to this. For example, the main grooves 7 may have a shape that includes a portion inclined at an angle of 5 degrees or less with respect to the tire circumferential direction, and therefore may be grooves that extend in a zigzag pattern along the tire circumferential direction. In the case of grooves that extend in a zigzag pattern, it is preferable that the grooves include a see-through region (a region that can be seen through in the tire circumferential direction without being obstructed by the groove wall surfaces 72 of the main grooves 7).

[0016] 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.

[0017] The main groove 7 includes a serration region 70 between the groove edge 74 of the main groove 7 and the groove bottom surface 71 of the main groove 7. In this embodiment, the serration region 70 is formed on each of a pair of groove wall surfaces 72, but it is sufficient that the serration region 70 is formed on at least one of the groove wall surfaces 72. It is preferable that the groove bottom surface 71 does not have the serration region 70. In the serration region 70, ridges 10 extending along the tire radial direction are arranged in the tire circumferential direction. The ridges 10 protrude from the groove wall surfaces 72 that extend from the groove bottom surface 71 outward in the tire radial direction. With this configuration, the micro-vibrations of the ridges 10 protruding from the groove wall surfaces 72 during driving disperse the frequency of air column resonance, thereby reducing air column resonance and improving noise performance.

[0018] As shown in FIG. 5, the ridge 10 has a height H10 based on the groove wall surface 72. In this embodiment, the height H10 is substantially constant along the extension direction of the ridge 10. From the viewpoint of ensuring the above-mentioned effect of reducing air column resonance, the height H10 is preferably 0.1 mm or more. Furthermore, from the viewpoint of reducing air resistance in the main groove 7 during running (i.e., resistance of air flowing inside the main groove 7 in the tire circumferential direction), the height H10 is preferably 0.5 mm or less. The ridge 10 has a width W10 that is larger than the height H10. The width W10 is set to, for example, 1.5 to 3.5 times the height H10. In this embodiment, the width W10 is substantially constant along the extension direction of the ridge 10.

[0019] When the height H10 of the ridges 10 is small, on the order of 0.1 to 0.5 mm, the roughness of the serration region 70 is appropriately small, which is advantageous for reducing air resistance in the main grooves 7 during driving and improving fuel economy. This is because when air flowing inside the main grooves 7 contacts the serration region 70 during driving, relatively small air vortices are generated at the tops of the ridges 10, which can reduce pressure resistance by suppressing air separation or by separating air further rearward. From the perspective of appropriately achieving this effect, the arrangement pitch P10 of the ridges 10 is preferably 2 to 8 times the height H10, and more preferably 2 to 6 times.

[0020] From the viewpoint of reducing air resistance in the main groove 7 during running, it is preferable that the ridge 10 has a shape in which the width gradually increases toward the groove wall surface 72, and in this embodiment, a triangular shape is adopted. Such a triangular shape may have a rounded apex, in which case the radius of curvature of the apex is, for example, 0.3 mm or less. The ridge 10 has a pair of side surfaces 11 rising from the groove wall surface 72, and the opening angle θ11 between the pair of side surfaces 11 is, for example, 90±45 degrees. In this embodiment, adjacent ridges 10 are arranged spaced apart from each other, but this is not limited thereto and they may also be arranged so as to be in contact with each other.

[0021] Within the main groove 7, air also flows in the gaps 14 between adjacent ridges 10 in the tire circumferential direction as the tread surface 3f comes into contact with the ground. Specifically, the air flows in such a manner that it passes through the radially outer ends 12 of the ridges 10 and enters the gaps 14, flows along the ridges 10, and then passes through the radially inner ends 13 of the ridges 10 and exits the gaps 14. In order to reduce the resistance of the air flowing through the main groove 7 and improve fuel economy, it is preferable to suppress the air resistance in these gaps 14 (i.e., the resistance of the air flowing through the gaps 14 in the tire radial direction).

[0022] From the viewpoint of reducing air resistance in the gap 14, it is preferable to roughen the side surface 11 appropriately, and for example, the arithmetic mean roughness Ra of the side surface 11 is set to 1.3 to 1.9 μm. The arithmetic mean roughness Ra is measured in accordance with JIS B0601:2013 (ISO 4287:187, Amd.1:2009). Setting the arithmetic mean roughness Ra of the side surface 11 to 1.3 μm or more is advantageous for suppressing poor rubber flow during vulcanization molding and properly forming the ridge 10. Furthermore, by setting the arithmetic mean roughness Ra of the side surface 11 to 1.9 μm or less, the side surface 11 does not become excessively rough, and the shape of the ridge 10 is not affected.

[0023] As shown in Fig. 6, in this embodiment, the extension direction of the ridge 10 coincides with the tire radial direction, and the inclination angle θ10 of the ridge 10 with respect to the tire radial direction is substantially zero. To enhance the effect of reducing air resistance in the main groove 7 during driving, the inclination angle θ10 is preferably 60 degrees or less, and more preferably less than 45 degrees. Furthermore, when intentionally inclining the ridge 10 in consideration of the effect of improving traction, which will be described later, it is possible to set the inclination angle θ10 of the ridge 10 to 15 degrees or more.

[0024] From the viewpoint of ensuring the effect of reducing air column resonance noise, the tire circumferential length L70 of the serration region 70 is preferably 50% or more, and more preferably 80% or more, of the tire circumferential length L72 of the groove wall surface 72. When the lateral grooves 8 open into the groove wall surface 72, the lengths L70 and L72 are each measured in the range between adjacent lateral grooves 8 in the tire circumferential direction. When the lateral grooves 8 do not open into the groove wall surface 72, the lengths L70 and L72 are each measured in the range of one circumference of the tire in the tire circumferential direction. The length L72 is determined at the groove edge 74.

[0025] In this embodiment, the tire radially outer end 12 of the ridge 10 is located at the groove edge 74, and the tire radially inner end 13 of the ridge 10 is located at the tire radially outer end 75 of a connecting surface 73 that has an arc-shaped cross section and connects the groove bottom surface 71 and the groove wall surface 72. With this configuration, it is easy to ensure the length of the ridge 10, thereby enhancing the effect of reducing air column resonance noise and the effect of suppressing air resistance in the main groove 7 during driving. It is preferable that the inner end 13 of the ridge 10 be located at or further outward in the tire radial direction than the outer end 75 of the connecting surface 73 so as not to prevent the air flowing along the ridge 10 from escaping through the gap 14.

[0026] In the modified example shown in Fig. 7, the radially outer end 12 of the ridge 10 is positioned away from the groove edge 74 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 12 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 to this. For example, the separation distance D1 may change so as to become smaller as it approaches the lateral groove 8.

[0027] In the modified example shown in FIG. 8 , the tire radially inner end 13 of the ridge 10 is positioned away from the tire radially outer end 75 of the connecting surface 73 toward the tire radially outer side. By moving the inner end 13 away from the groove bottom surface 71 in this manner, air flowing along the ridge 10 can easily escape through the gap 14. A separation distance D2 between the inner end 13 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 have to be set uniformly, and may vary along the tire circumferential direction. The separation distance D2 can also be set together with the above-mentioned separation distance D1.

[0028] 9 is a tire meridian cross-sectional view of a tire vulcanization mold M used for vulcanizing a pneumatic tire T. In FIG. 9, 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.

[0029] 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.

[0030] The mold M has protrusions 9 for forming main grooves 7 extending in the tire circumferential direction on the tread surface 3f of the tire T. The uneven surface includes not only the protrusions 9 but also protrusions (not shown) for forming lateral grooves 8. During vulcanization molding, the protrusions 9 are pressed against the tread surface of the unvulcanized tire, thereby forming the main grooves 7.

[0031] Fig. 10 is a tire meridian cross-section of the protrusion 9. Fig. 11 is a cross-sectional perspective view of the protrusion 9. The protrusion 9 has a top surface 91 and a pair of sidewall surfaces 92 extending from the top surface 91 outward in the tire radial direction. 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 a serration 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 serration region 90, depressions 20 extending along the tire radial direction are arranged in the tire circumferential direction. The depressions 20 are recessed from the sidewall surfaces 92 that extend from the top surface 91 outward in the tire radial direction.

[0032] The pneumatic tire T obtained by vulcanization molding using such a mold M has a main groove 7 including a serration region 70 formed by an arrangement of the ridges 10 as described above. The groove bottom surface 71, groove wall surface 72, and connecting surface 73 of the main groove 7 are formed by the top surface 91, side wall surface 92, and connecting surface 93, respectively. The serration region 70 and the ridge 10 are formed by the serration region 90 and the depressions 20, respectively. Therefore, for details of the preferred dimensions, shapes, and arrangements of the protrusions 9 and the depressions 20, the above-mentioned explanations regarding the main groove 7 and the ridges 10 can be referred to.

[0033] [Second embodiment] Next, a second embodiment will be described with reference to Figures 12 and 13. The second embodiment can be configured similarly to the first embodiment except for the configuration described below, so a description of the commonalities will be omitted and differences will be mainly described. The same reference numerals will be used to designate components already described in the first embodiment, and duplicated descriptions will be omitted.

[0034] The pneumatic tire T in the second embodiment is a rotation direction specified tire in which the rotation direction is specified. The rotation direction is specified, for example, by a marking on the outer surface of the sidewall portion 2. As shown in FIG. 12, 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. Arrow RD1 indicates the front side in the rotation direction, which corresponds to the "leading side" that hits the ground first as the vehicle moves forward. Arrow RD2 indicates the rear side in the tire rotation direction, which corresponds to the "kicking side" that hits the ground last as the vehicle moves forward.

[0035] As shown in FIG. 13 , in this embodiment, the ridge 10 is inclined radially outward toward the leading edge (the forward side RD1 in the direction of rotation). This configuration improves traction when traveling on rough road surfaces such as muddy or sandy areas, or wet road surfaces such as puddles, because it provides a scraping effect on the trailing edge. To achieve this effect, the inclination angle θ10 of the ridge 10 is preferably 15 degrees or greater. Furthermore, to enhance the effect of reducing air resistance in the main groove 7 during traveling, the inclination angle θ10 is preferably 60 degrees or less.

[0036] Although not shown, in the tire vulcanization mold M for vulcanizing and molding the pneumatic tire T of the second embodiment, the serration area 90 included in the protrusion 9 has an arrangement of depressions 20 that are inclined toward the leading edge toward the outside in the tire radial direction.

[0037] [Third embodiment] Next, a third embodiment will be described with reference to Figures 14 and 15. The third embodiment can be configured similarly to the first and second embodiments except for the configuration described below, so a description of the commonalities will be omitted and differences will be mainly described. The same reference numerals will be used to designate components already described in the first embodiment, and duplicated descriptions will be omitted.

[0038] FIG. 14 is a perspective view of ridges 10 arranged in the serration region 70. In the third embodiment, the ridge 10 has a pair of side surfaces 11 rising from the groove wall surface 72 and a tip surface 15 located between them. The ridge 10 has a shape whose width gradually increases toward the groove wall surface 72, and in this embodiment, a trapezoidal shape is adopted. Because the tip surface 15 of the ridge 10 is formed flat, it is easier to form than a triangular ridge with a sharp apex (see the first embodiment). The width W15 of the tip surface 15 is not particularly limited, but is set to, for example, 0.25 to 0.7 times the width W10 of the ridge 10.

[0039] The tip end surface 15 is provided with a plurality of minute protrusions 16 that are smaller in height than the ridges 10 (i.e., H10 > H16). This configuration is advantageous for reducing air resistance in the main grooves 7 during driving and enhancing the effect of improving fuel efficiency. This is because when air flowing inside the main grooves 7 comes into contact with the serration region 70 during driving, the plurality of minute protrusions 16 frequently generate relatively small air vortices, which suppress air separation or cause air separation further rearward, thereby effectively reducing pressure resistance.

[0040] The height H16 of the microprotrusions 16 is, for example, 0.5 to 5 μm. The width W16 of the microprotrusions 16 is set to, for example, 2 to 4 times the height H16 of the microprotrusions 16. In this embodiment, an example is shown in which the microprotrusions 16 are provided in a dome shape or a hemisphere shape, but the shape of the microprotrusions 16 is not limited to this.

[0041] 15(A) and 15(B) are enlarged views of the tip surface 15 of the ridge 10. In Fig. 15, the vertical direction corresponds to the extension direction of the ridge 10, and the horizontal direction corresponds to the width direction of the ridge 10. In Fig. 15, the positional relationship of the minute protrusions 16 is depicted schematically, and the size of the minute protrusions 16 relative to the tip surface 15 may be smaller (or larger) than that seen in Fig. 15.

[0042] In the example of Figure 15(A), the multiple microprotrusions 16 do not overlap one another in the extension direction of the ridge 10 when viewed in the width direction of the ridge 10. In contrast, in the example of Figure 15(B), the multiple microprotrusions 16 overlap one another in the extension direction of the ridge 10 when viewed in the width direction of the ridge 10. In Figure 15(B), an imaginary line VL extending parallel to the width direction of the ridge 10 on the tip surface 15 passes through the microprotrusions 16 wherever it is set. With this configuration, the multiple microprotrusions 16 can efficiently generate multiple small air vortices, making it possible to more effectively suppress pressure resistance.

[0043] Although not shown, in a tire vulcanization mold M for vulcanizing and molding a pneumatic tire T of the third embodiment, the serration region 90 included in the protrusion 9 is an arrangement of trapezoidal depressions 20 corresponding to the ridges 10. Furthermore, a plurality of minute recesses for molding minute protrusions 16 are provided on the bottom surface of the depression 20 corresponding to the tip surface 15 of the ridge 10. For details of the preferable dimensions, shape, arrangement, etc. of such depressions 20 and minute recesses, the above-mentioned explanations regarding the ridges 10 and minute protrusions 16 can be referred to.

[0044] It will be understood by those skilled in the art that the above-described embodiments are examples of the following aspects.

[0045] [1] A pneumatic tire according to the present disclosure includes a tread surface having main grooves extending circumferentially along the tire circumferential direction, the main grooves including serration regions between the groove edges and the groove bottom surfaces of the main grooves, and the serration regions have ridges arranged in the tire radial direction and protruding from groove walls extending radially outward from the groove bottom surfaces. With this configuration, the micro-vibrations of the ridges protruding from the groove walls disperse the frequency of air column resonance during running, thereby reducing air column resonance and improving noise performance.

[0046] [2] In the pneumatic tire of the above item [1], the ridges may be inclined relative to the tire radial direction. With this configuration, when the tire is mounted so that the ridges are inclined radially outward toward the leading edge, it is possible to improve traction when traveling on rough road surfaces such as muddy ground or sandy areas, or wet road surfaces such as puddles.

[0047] [3] In the pneumatic tire of [1] or [2] above, the rotation direction may be specified, and the ridges may be inclined radially outward toward the leading edge of the tire. This configuration improves traction when traveling on rough road surfaces such as muddy ground or sandy areas, or wet road surfaces such as puddles.

[0048] [4] In the pneumatic tire of any one of the above [1] to [3], a configuration may be adopted in which the tire radially outer end of the ridge is disposed on the groove edge, and the tire radially inner end of the ridge is disposed on the tire radially outer end of a connecting surface that has an arc-shaped cross section and connects the groove bottom surface and the groove wall surface. This configuration makes it easy to ensure the length of the ridge, which is advantageous in terms of reducing air column resonance noise and suppressing air resistance in the main groove during driving.

[0049] [5] In the pneumatic tire of any one of the above [1] to [3], the radially outer end of the ridge may be disposed away from the groove edge 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, thereby enhancing the edge effect of the main groove in the lateral direction.

[0050] [6] In the pneumatic tire of any one of the above [1] to [3] and [5], the tire radially inner end of the ridge may be disposed away radially outward from the tire radially outer end of the connecting surface, which has an arc-shaped cross section and connects the groove bottom surface and the groove wall surface. With this configuration, air flowing along the ridge can easily escape through gaps between adjacent ridges in the tire circumferential direction, thereby reducing resistance to air flowing through the gaps.

[0051] [7] In any one of the pneumatic tires [1] to [6] above, the ridge may have a pair of side surfaces rising from the groove wall surface and a tip surface located between them, and the tip surface may be provided with a plurality of minute protrusions that are shorter in height than the ridge. With this configuration, the plurality of minute protrusions generates multiple small air vortices, thereby suppressing pressure resistance. This effectively reduces air resistance in the main groove during driving.

[0052] [8] In the pneumatic tire of [7] above, the small protrusions may overlap each other in the extension direction of the ridge as viewed in the width direction of the ridge. With this configuration, the small protrusions can efficiently generate multiple small air vortices to suppress pressure resistance, thereby more effectively suppressing air resistance in the main groove during driving.

[0053] [9] In the pneumatic tire of any one of the above items [1] to [8], the ridge may have a height of 0.5 mm or less. A ridge having such a height is preferable for reducing resistance to air flowing inside the main groove along the tire circumferential direction.

[0054]

[10] The tire vulcanization mold of the present disclosure includes protrusions for molding main grooves extending circumferentially on the tread surface of a tire, the protrusions including serration regions between inside corner edges corresponding to groove edges of the main grooves and top surfaces corresponding to groove bottom surfaces of the main grooves, the serration regions including recesses extending radially of the tire arranged circumferentially of the tire, the recesses being recessed from sidewall surfaces extending radially outward from the top surfaces. With this configuration, a pneumatic tire can be obtained that can reduce air column resonance noise by the main grooves as described above.

[0055] The pneumatic tire of the present disclosure can be configured in the same manner as a normal pneumatic tire, except that the main 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 way as a normal tire vulcanizing mold, except that the protrusions for molding the main grooves 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, 9 protrusion, 10 ridge, 11 side surface, 12 tire radially outer edge, 13 tire radially inner edge, 15 tip surface, 16 minute protrusion, 70 serration area, 71 groove bottom surface, 72 groove wall surface, 73 connecting surface, 74 groove edge, 75 tire radially outer edge, 90 serration area, 91 top surface, 92 side wall surface, 94 inside corner edge

Claims

1. A main groove extending along the tire circumferential direction on the tread surface is provided, the main groove includes a serration region between a groove edge of the main groove and a groove bottom surface of the main groove, In the serration region, ridges extending along the tire radial direction are arranged in the tire circumferential direction, The ridge protrudes from a groove wall surface that extends from the groove bottom surface outward in the tire radial direction.

2. The pneumatic tire according to claim 1 , wherein the ridge is inclined relative to the tire radial direction.

3. The direction of rotation is specified, The pneumatic tire according to claim 1 , wherein the ridge is inclined toward the leading edge toward the outside in the tire radial direction.

4. an outer end of the ridge in the tire radial direction is disposed on the groove edge; The pneumatic tire according to claim 1 , wherein an inner end in the tire radial direction of the ridge is disposed at an outer end in the tire radial direction of a connecting surface that has an arc-shaped cross section and connects the groove bottom surface and the groove wall surface.

5. The pneumatic tire according to claim 1 , wherein an outer end of the ridge in the tire radial direction is disposed away from the groove edge toward the inner side in the tire radial direction.

6. 2. The pneumatic tire according to claim 1, wherein an inner end of the ridge in the tire radial direction is disposed away from an outer end of a connecting surface having an arc-shaped cross section connecting the groove bottom surface and the groove wall surface toward the tire radial direction.

7. the ridge has a pair of side surfaces rising from the groove wall surface and a tip surface located therebetween, The pneumatic tire according to claim 1 , wherein the tip end surface is provided with a plurality of small protrusions each having a height smaller than that of the ridge.

8. The pneumatic tire according to claim 7 , wherein the plurality of minute protrusions overlap each other in the extending direction of the ridge when viewed in the width direction of the ridge.

9. The pneumatic tire according to any one of claims 1 to 8, wherein the ridge has a height of 0.5 mm or less.

10. The tire has a protrusion for forming a main groove extending along the tire circumferential direction on a tread surface of the tire, the protrusion includes a serration region between an inside corner edge corresponding to a groove edge of the main groove and a top surface corresponding to a groove bottom surface of the main groove, In the serration region, recesses extending along the tire radial direction are arranged in the tire circumferential direction, The depression is recessed from a sidewall surface extending from the top surface outward in the tire radial direction.

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