Pneumatic tires and tire vulcanization molds

Abstract

To provide a pneumatic tire and a tire vulcanization mold that can improve off-road performance in muddy terrain. [Solution] The groove wall surface 72 of the main groove 7 provided on the tread surface 3f includes an uneven region 10 on which a plurality of protrusions 40 are arranged. When viewed from a direction perpendicular to the groove wall surface 72, the shape of the protrusions 40 has a longitudinal direction and a transverse longitudinal direction and tapers toward both sides in the longitudinal direction. The longitudinal direction of the protrusions 40 is oriented toward the tire diameter direction. The protrusions 40 have a ridge line 44 extending in the longitudinal direction in a region on one side in the longitudinal direction, a first slope 41 whose protrusion height decreases toward one side in the transverse direction from the ridge line 44, a second slope 42 whose protrusion height decreases toward the other side in the transverse direction from the ridge line 44, and a third slope 43 located in a region on the other side in the longitudinal direction, whose protrusion height decreases toward the other side in the longitudinal direction.

Description

Technical Field

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

Background Art

[0002] Patent Documents 1 and 2 each describe a pneumatic tire in which the groove wall surface of a groove provided on the tread surface includes an uneven region. The tire described in Patent Document 1 is intended to improve snow traction performance, and the uneven region is constituted by a plurality of recesses that open in a triangular shape on the tread surface and the wall surface of the block. Further, in the tire described in Patent Document 2, although the shapes of the minute protrusions arranged at a density of 1 to 5 per 1 mm include a frustum of a cone shape, a columnar shape, and a pyramid shape, there is room for improvement in the performance of traveling on rough roads in muddy areas. 2 Regarding the performance of traveling on rough roads in muddy areas, there is room for improvement.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire and a tire vulcanizing mold capable of improving the performance of traveling on rough roads in muddy areas.

Means for Solving the Problems

[0005] The pneumatic tire of this disclosure is provided with grooves on the tread surface. The groove wall surface includes an uneven region in which a plurality of protrusions are arranged. Viewed from a direction perpendicular to the groove wall surface, the shape of the protrusions has a longitudinal direction and a transverse longitudinal direction and tapers toward both sides in the longitudinal direction. The longitudinal direction of the protrusions is oriented toward the tire radial direction. The protrusions have a ridge extending longitudinally in a region on one side in the longitudinal direction, a first slope whose protruding height decreases toward one side in the transverse direction from the ridge, a second slope whose protruding height decreases toward the other side in the transverse direction from the ridge, and a third slope located in the region on the other side in the longitudinal direction, whose protruding height decreases toward the other side in the longitudinal direction.

[0006] The tire vulcanizing mold of this disclosure includes a projection for forming grooves provided on the tread surface of a tire. The side wall surface of the projection includes an uneven region in which a plurality of depressions are arranged. Viewed from a direction perpendicular to the side wall surface, the shape of the depressions has a longitudinal direction and a transverse longitudinal direction and tapers toward both sides in the longitudinal direction. The longitudinal direction of the depressions is oriented toward the tire radial direction. The depressions include a mold ridge extending longitudinally in a region on one side in the longitudinal direction, a first mold slope whose depression depth decreases toward one side in the transverse direction from the mold ridge, a second mold slope whose depression depth decreases toward the other side in the transverse direction from the mold ridge, and a third mold slope located in the region on the other side in the longitudinal direction, whose depression depth decreases toward the other side in the longitudinal direction. [Brief explanation of the drawing]

[0007] [Figure 1] A tire meridian cross-section diagram showing an example of a pneumatic tire. [Figure 2] Plan view showing an example of a tread pattern. [Figure 3] Plan view showing another example of a tread pattern [Figure 4] Cross-sectional view of the tire's main groove along the meridian. [Figure 5] View of the main groove wall from the front. [Figure 6] Plan view of the protrusion [Figure 7](A) Side view, (B) Cross-sectional view taken along arrow AA, and (C) Cross-sectional view taken along arrow BB of the projection [Figure 8] Perspective view of the protrusion [Figure 9] (A) Side view and (B) Perspective view of the projection in the modified example [Figure 10] A tire meridian cross-section diagram showing an example of a tire vulcanization mold. [Figure 11] Cross-sectional view of the tire meridian at the protruding section [Figure 12] View of the side wall of the protrusion from the front. [Figure 13] Plan view of the recess [Figure 14] (A) Side view section of the depression, (B) section viewed from arrow CC, and (C) section viewed from arrow DD. [Modes for carrying out the invention]

[0008] Embodiments of this disclosure will be described with reference to the drawings.

[0009] Figure 1 is a meridian cross-sectional view of a pneumatic tire T according to this embodiment. The pneumatic tire T is an automobile tire comprising 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 connected to the radially outward ends of each of the sidewall portions 2. An annular bead core 1a is embedded in the bead portion 1. The bead core 1a is formed by covering a converging body such as steel wire with rubber. A bead filler 1b is positioned radially outward from the bead core 1a. The bead filler 1b is formed of triangular-shaped rubber extending radially outward from the bead core 1a.

[0010] Here, the tire meridian cross-section is the cross-section obtained when the tire T is cut by a plane containing the central axis (axis of rotation) of the tire T. The tire circumferential direction is the direction around the central axis of the tire T. The tire radial direction is the direction along the diameter of the tire T. The side closer to the central axis is the radially inner side of the tire, and the side further away from the central axis is the radially outer side of the tire. The tire axial direction is the direction parallel to the central axis. The side closer to the tire equator TC, which is located at the center of the tire axial direction of the tire T, is the radially inner side of the tire, and the side further away from the tire equator TC is the radially outer side of the tire.

[0011] Unless otherwise specified, the dimensions and angles of each part of the tire are determined in an unloaded state, mounted on a standard rim and filled with the standard internal pressure. The standard rim is the rim specified for each tire by each standard in the standard system on which the tire is based; for example, it is the standard rim for JATMA, and the "Measuring Rim" for TRA and ETRTO. The standard internal pressure is the air pressure specified for each tire by each standard in the standard system on which the tire is based; for truck and bus tires and light truck tires, it is the maximum air pressure for JATMA, the value corresponding to the Load Index listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO. For passenger car tires, it is usually 180kPa, but for tires marked Extra Load or Reinforced, it is 220kPa.

[0012] The tire T includes a carcass 4 that extends in a toroidal shape across between a pair of bead portions 1. The carcass 4 is wound up from the inner side to the outer side in the tire axial direction so as to sandwich the bead core 1a and the bead filler 1b. The carcass 4 is formed by a carcass ply formed by rubber-coating a carcass cord. The carcass cords are aligned in a direction intersecting with the tire circumferential direction (for example, a direction at an angle of 75 to 90 degrees with respect to the tire circumferential direction). As the material of the carcass cord, a metal such as steel or an organic fiber such as polyester, rayon, nylon, or aramid is preferably used.

[0013] The tire T includes a belt 5 laminated on the outer side in the tire radial direction of the carcass 4. The belt 5 is formed by a plurality (two in this embodiment) of belt plies laminated on each other. Each belt ply is formed by rubber-coating a belt cord. The belt cords are aligned in a direction inclined with respect to the tire circumferential direction (for example, a direction at an angle of 20 to 30 degrees with respect to the tire circumferential direction). As the material of the belt cord, a metal such as steel is preferably used. The plurality of belt plies are laminated such that the belt cords cross each other in opposite directions therebetween.

[0014] In this embodiment, a belt reinforcing material 6 is laminated on the outer side in the tire radial direction of the belt 5. The belt reinforcing material 6 is formed by a belt reinforcing ply formed by rubber-coating a belt reinforcing cord. The belt reinforcing cords are aligned substantially parallel to the tire circumferential direction. The belt reinforcing ply is formed, for example, by spirally winding one or a plurality of rubber-coated belt reinforcing cords along the tire circumferential direction. As the material of the belt reinforcing cord, the above-described organic fiber is preferably used. The belt reinforcing material 6 covers the entire surface of the belt 5, but it may also be in a form that partially covers the belt 5 (for example, only both ends).

[0015] On the tread surface 3f that constitutes the outer peripheral surface of the tread portion 3, a tread pattern corresponding to the required tire performance and usage conditions is formed. FIG. 2 is a plan development view showing an example of the tread pattern provided in the pneumatic tire T. The tread pattern is a block pattern having a shape symmetric with respect to the tire equator TC. However, it is not limited to this, and for example, a rib pattern as shown in FIG. 3 may be used, or a tread pattern having a shape asymmetric with respect to the tire equator TC may also be used.

[0016] The tire T includes main grooves 7 and lateral grooves 8 as grooves provided in 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 the main grooves 7. The main grooves 7 extend linearly, but are not limited to this, and for example, a shape including a portion inclined at an angle of 5 degrees or less with respect to the tire circumferential direction may be used, and thus, a groove extending in a zigzag shape along the tire circumferential direction may also be used. In the case of a groove extending in a zigzag shape, it is preferable to include a see-through region (a region that can be seen without being blocked by the groove wall surface 72 of the main groove 7 when viewed in the tire circumferential direction).

[0017] FIG. 4 is a tire meridian cross-sectional view of the main groove 7. FIG. 5 is a view of the groove wall surface 72 of the main groove 7 as viewed from the front. FIG. 6 is a plan view of the protrusion 40. Regarding the protrusion 40, the plan view (or plan view) refers to a view (or way of viewing) from a direction perpendicular to the groove wall surface 72. FIG. 7 is a (A) side view, (B) cross-sectional view taken along the A-A arrow, and (C) cross-sectional view taken along the B-B arrow of the protrusion 40. FIG. 8 is a perspective view of the protrusion 40. The configuration of the main groove 7 described below may be applied to any of the plurality of main grooves 7 provided in the tread surface 3f, and it is also possible to apply it to all the main grooves 7.

[0018] As shown in Figure 4, the main groove 7 has a groove bottom surface 71 and a pair of groove wall surfaces 72 extending radially outward from the groove bottom surface 71. The groove wall surfaces 72 are smoothly connected to the groove bottom surface 71 via a connecting surface 73 with a circular arc cross-section. The radius of curvature R of the connecting surface 73 is, for example, 1.5 to 3.5 mm. In this embodiment, the groove wall surface 72 extends linearly between the groove edge 74 formed by the tread surface 3f and the groove wall surface 72, and the radially outer end 75 of the connecting surface 73. The groove width W7 of the main groove 7 in the tire axial direction is, for example, 5.0 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, 5.0 mm or more, preferably 6.0 mm or more.

[0019] As shown in Figures 4 and 5, the groove wall surface 72 includes an uneven region 10 in which a plurality of protrusions 40 are arranged. In Figure 5, the left-right direction corresponds to the groove length direction (tire circumferential direction in the case of the main groove 7), and the up-down direction corresponds to the groove depth direction (tire diameter direction). The uneven region 10 is composed of a plurality of protrusions 40 arranged repeatedly in both the groove length direction and the groove depth direction. Each of the plurality of protrusions 40 protrudes from the groove wall surface 72. The uneven region 10 only needs to be formed on at least one of the groove wall surfaces 72, but it is preferable that it be formed on each of the pair of groove wall surfaces 72, as in this embodiment.

[0020] Viewed from a direction perpendicular to the groove wall surface 72, the shape of the projection 40 has a longitudinal direction LD and a transverse longitudinal direction SD, and tapers toward both sides of the longitudinal direction LD. The longitudinal direction LD of the projection 40 is oriented in the direction of the tire diameter. The projection 40 has a ridge line 44, a first slope 41, a second slope 42, and a third slope 43. The ridge line 44 extends in the longitudinal direction LD in the region of one longitudinal side LD1. The first slope 41 decreases in projection height toward one transverse side SD1 from the ridge line 44. The second slope 42 decreases in projection height toward the other transverse side SD2 from the ridge line 44. The third slope 43 is located in the region of the other longitudinal side LD2 and decreases in projection height toward the other longitudinal side LD2.

[0021] This configuration enhances traction against mud that enters the groove, improving off-road performance in muddy terrain. Since the longitudinal LD ​​of the projection 40 is oriented in the tire diameter direction (groove depth direction), the first slope 41 and the second slope 42 are oriented in the groove length direction, and traction is generated by these shearing the mud. The shape of the projection 40, which tapers towards both sides of the longitudinal LD, is advantageous for separating the mud from the groove wall surface 72 and discharging it out of the groove due to the centrifugal force accompanying tire rotation. In addition, the placement of the third slope 43 in the region of the other longitudinal LD2 of the projection 40 results in a relatively simple plan view shape, making it easier for particles (plastic beads, glass beads, dry ice, etc.) to enter during mold cleaning, thus suppressing mold contamination.

[0022] From the viewpoint of effectively enhancing the traction effect provided by the uneven surface 10, the angle of the longitudinal LD ​​with respect to the tire radial direction is preferably less than 45 degrees, and more preferably less than 30 degrees. In this embodiment, one longitudinal side LD1 of the projection 40 faces the groove bottom side (inward in the tire radial direction). This causes the third slope 43 to face the tread side (outward in the tire radial direction), which is convenient for discharging mud out of the groove. It is preferable that the groove bottom surface 71, including the connecting surface 73, does not have an uneven surface 10. This is because the groove bottom surface 71 contributes less to off-road performance in muddy terrain compared to the groove wall surface 72, and providing an uneven surface 10 on the connecting surface 73 would require complex mold processing.

[0023] Each projection 40 has a length L40 in the longitudinal direction and a width W40 in the short direction SD. The length L40 is set to, for example, 2.0 to 5.0 times the width W40. The width W40 is preferably 0.5 mm or more, and more preferably 1.0 mm or more. The width W40 is, for example, 3.0 mm or less. In this embodiment, a plurality of projections 40 with the same length L40 and width W40 are arranged to form a recessed area 10 (see Figure 5).

[0024] The ridge line 44 has an end 44a on one longitudinal side LD1 and an end 44b on the other longitudinal side LD2. End 44a is substantially located on the groove wall surface 72. End 44b is located away from the groove wall surface 72, and the projection height gradually decreases from end 44b toward end 44a. End 44b is located in the region of the longitudinal side LD1 with respect to the center of the longitudinal LD ​​of the projection 40. In this embodiment, end 44b is set to a position that overlaps with the top portion 40t, which will be described later, in a plan view. The length L44 of the ridge line 44 in a plan view is set to be, for example, 20% or more and less than 45% of the length L40. The cross-sectional shape of the ridge line 44 shown in Figure 7(B) is pointed in a V shape, but it may also be a curved shape via a circular arc with a radius of curvature of 0.5 mm or less, for example.

[0025] The first slope 41 and the second slope 42 may each be formed by planes extending to the groove wall surface 72. In plan view, the first slope 41 has a shape that tapers toward both sides in the longitudinal direction LD. The first slope 41 is formed in a triangular shape in plan view. The second slope 42 is formed to be symmetric to the first slope 41 with respect to the edge line 44. In this embodiment, the opening angle θ between the first slope 41 and the second slope 42 is obtuse (i.e., 90 degrees < θ < 180 degrees). With this configuration, advantageous effects such as reduced snagging when removing tires from the tire vulcanization mold and reduced contamination by promoting the entry of the above-mentioned particles during mold cleaning are achieved.

[0026] The third inclined surface 43 is located on the other longitudinal side LD2 of the first inclined surface 41 and the second inclined surface 42. The third inclined surface 43 may be formed by a plane extending toward the groove wall surface 72. The third inclined surface 43 has a plan view shape that tapers toward both sides in the longitudinal direction LD. The portion of the third inclined surface 43 that tapers toward one longitudinal side LD1 is located between the first inclined surface 41 and the second inclined surface 42 in the short direction SD. The projection 40 has its apex 40t, which is the part furthest from the groove wall surface 72, in the region of one longitudinal side LD1, and the third inclined surface 43 extends from the apex 40t toward the other longitudinal side LD2. With respect to the groove wall surface 72, the apex 40t is at a higher position than the end 44b, but these height positions may be the same.

[0027] The boundary 45 between the first slope 41 and the third slope 43 extends from end 44b inclined toward the other longitudinal side LD2 toward the other short side SD1. The boundary 46 between the second slope 42 and the third slope 43 extends from end 44b inclined toward the other short side SD2 toward the other longitudinal side LD2. The boundaries 45 and 46 extend in a straight line in plan view and, together with the ridge line 44, form a Y shape. The boundaries 45 and 46 may also extend in a curved shape in plan view. In this embodiment, the boundaries 45 and 46 are formed in a stepped shape, but they may also be formed by ridge lines.

[0028] Viewed from a direction perpendicular to the groove wall surface 72, the third inclined surface 43 is larger than the first inclined surface 41 and the second inclined surface 42. That is, in plan view, the third inclined surface 43 has a larger area than the first inclined surface 41 and a larger area than the second inclined surface 42. This allows the plan view shape of the projection 40 to be simpler, which is advantageous in suppressing mold contamination. In plan view, the tip of the other longitudinal side LD2 of the third inclined surface 43 is pointed in a V-shape, but it may also be a rounded shape as shown by the dashed line in Figure 6.

[0029] As shown in Figure 6, the projection 40 is formed in a rhombic shape in plan view. In this embodiment, the plan view shape of the projection 40 is substantially composed of three surfaces (first to third inclined surfaces 41 to 43). Therefore, it is easy to ensure the size of each inclined surface. In addition, because the projection 40 has such a simple shape, it is easier for particles to penetrate during mold cleaning compared to when it has a relatively complex shape, which is advantageous in suppressing mold contamination. The surface roughness of the first to third inclined surfaces 41 to 43 may be substantially the same as each other, or they may differ for each surface.

[0030] The projection 40 has a projection height H40 from the groove wall surface 72 to the top 40t. From the viewpoint of effectively enhancing the traction effect due to the uneven region 10, the projection height H40 is preferably 0.1 mm or more, and more preferably 0.3 mm or more. Furthermore, to avoid excessively reducing drainage performance, the projection height H40 is preferably 0.5 mm or less. The ratio of the width W40 to the projection height H40 (W40 / H40) is, for example, 1.2 to 10.0. The flat shape of the projection 40 is advantageous for separating the mud that has entered between the projections 40 from the groove wall surface 72.

[0031] As shown in Figure 5, gaps 50 may be provided between adjacent protrusions 40. That is, multiple protrusions 40 may be arranged in a manner that they do not come into contact with each other, while maintaining a spacing corresponding to the gaps 50. However, from the viewpoint of ensuring an appropriate density of the protrusions 40, it is preferable that the size of the gaps 50 is 1.0 mm or less. The size of the gaps 50 may be substantially zero, and adjacent protrusions 40 may be arranged in a manner that they come into contact with each other.

[0032] In the example shown in Figure 5, multiple rows of protrusions 40A are formed, with the protrusions 40 arranged in the short direction SD. The phase of each row of protrusions 40A is half a phase shift in the longitudinal direction LD and the short direction SD relative to the phase of other adjacent rows of protrusions 40A. With this configuration, the protrusions 40 that taper toward both sides in the longitudinal direction LD are arranged closely together, thereby enhancing the traction effect of the uneven area 10 and improving the ability to traverse rough terrain in muddy conditions.

[0033] From the viewpoint of improving off-road performance in muddy terrain, the length L10 of the uneven region 10 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 a lateral groove 8 opens into the groove wall surface 72 of the main groove 7, the lengths L10 and L72 are measured within the range between adjacent lateral grooves 8 in the tire circumferential direction. When a lateral groove 8 does not open into the groove wall surface 72 of the main groove 7, the lengths L10 and L72 are measured within the range of one full turn of the tire circumferential direction. The length L72 is determined at the groove edge 74.

[0034] In this embodiment, the outer end 76 of the uneven region 10 in the tire radial direction is located at the groove edge 74, and the inner end 77 of the uneven region 10 in the tire radial direction is located at the outer end 75 of the connecting surface 73 in the tire radial direction. With this configuration, the size of the uneven region 10 in the groove depth direction is ensured, thereby enhancing the effect of improving off-road performance in muddy terrain. The outer end 76 of the uneven region 10 may be located away from the groove edge 74 in the tire radial direction, but it is preferable that it be located further outward in the tire radial direction than the center in the groove depth direction. Also, the inner end 77 of the uneven region 10 may be located away from the outer end 75 of the connecting surface 73 in the tire radial direction, but it is preferable that it be located further inward in the tire radial direction than the center in the groove depth direction.

[0035] When the area ratio of the uneven area 10 to the region between the groove edge 74 and the outer end 75 of the connecting surface 73 (excluding the opening region of the lateral groove 8) is called the arrangement range ratio, the arrangement range ratio in at least one main groove 7 is preferably 50% or more, and more preferably 80% or more, from the viewpoint of enhancing the effect of improving off-road performance in muddy terrain.

[0036] In this embodiment, an example is shown in which the groove wall surface 72 of the main groove 7 includes an uneven region 10. However, instead of this, or in addition, the groove wall surface of the lateral groove 8 may also include an uneven region as described above. In the lateral grooves of winter tires or all-season tires (for example, mud and snow tires marked with "M&S" or "M+S"), if the outer edge of the uneven region in the tire radial direction is located around 50% (for example, 40-60%) of the groove depth of the lateral groove 8, the edge effect of the groove edge of the lateral groove 8 is utilized until the middle of wear, and then, in the stage where it functions as a summer tire thereafter, the uneven region of the groove wall surface can improve off-road performance in muddy terrain.

[0037] In the modified version of the projection 40 shown in Figure 9, the boundaries 45 and 46 have a rounded shape. Boundaries 45 and 46 each have an arc-shaped curved surface that is convex in the direction away from the groove wall surface 72. A curved surface of a similar shape is also provided between the third inclined surface 43 and the groove wall surface 72 in the region of the other longitudinal side LD2 of the projection 40. With this configuration, advantageous effects can be obtained, such as reducing snagging when removing the tire from the tire vulcanization mold and promoting the entry of particles during mold cleaning, thereby suppressing contamination.

[0038] Figure 10 is a meridian cross-sectional view of a tire vulcanization mold M used for vulcanizing a pneumatic tire T. In Figure 10, the tire T is shown by a dashed line, and the tire T is set in the mold M with its axial direction facing up and down. The mold M comprises a pair of bead rings Mb into which the bead portion 1 of the tire T is fitted, a pair of side mold portions Ms that contact the sidewall portion 2 of the tire T, and a tread mold portion Mt that contacts the tread portion 3 of the tire T.

[0039] The mold M includes 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 sections Ms and the inner surface of the tread mold section Mt. The inner surface of the tread mold section Mt is provided with an uneven surface for forming a tread pattern. The tread mold section Mt is composed of a plurality of sectors divided in the circumferential direction of the tire, which are clustered together in an annular shape. The mold M is a segmented mold with such a segmented tread mold section Mt, but is not limited thereto; for example, it may be a two-piece mold divided into upper and lower halves in the center of the tread mold section.

[0040] The mold M is equipped with protrusions for forming grooves to be provided on the tread surface 3f of the tire T. Specifically, the mold M is equipped with a protrusion 9 for forming the main groove 7 and a protrusion 89 (see Figure 12) for forming the lateral groove 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 groove 7 and lateral groove 8.

[0041] Figure 11 is a cross-sectional view of the projection 9 along the tire meridian. Figure 12 is a front view of the side wall surface 92 of the projection 9. Figures 11 and 12 correspond to inverted versions of Figures 4 and 5, respectively. The projection 9 has a top surface 91 and a pair of side wall surfaces 92 extending radially outward from the top surface 91. The side wall surfaces 92 are smoothly connected to the top surface 91 via a connecting surface 93 with a circular arc cross-section. The side wall surfaces 92 extend linearly between an inner corner edge 94 corresponding to the groove edge 74 of the main groove 7 and the radially outer end of the connecting surface 93 corresponding to the connecting surface 73 of the main groove 7. The side wall surface 92 includes an uneven region 90 in which a plurality of depressions 100 are arranged.

[0042] Figure 13 is a plan view of the recess 100. Figure 14 is a (A) side cross-sectional view, (B) cross-sectional view taken along arrow CC, and (C) cross-sectional view taken along arrow DD of the recess 100. Figure 14 corresponds to an inverted version of Figure 7. When viewed from a direction perpendicular to the side wall surface 92, the shape of the recess 100 has a longitudinal direction LD and a transverse longitudinal direction SD, and tapers toward both sides of the longitudinal direction LD. The recess 100 has a mold ridge 104 extending in the longitudinal direction LD in the region of one longitudinal side LD1, a first mold slope 101 whose recess depth decreases toward one transverse side SD1 from the mold ridge 104, a second mold slope 102 whose recess depth decreases toward the other transverse side SD2 from the mold ridge 104, and a third mold slope 103 located in the region of the other longitudinal side LD2, whose recess depth decreases toward the other longitudinal side LD2.

[0043] The side wall surface 92 and the recess 100 have configurations corresponding to the groove wall surface 72 and the projection 40, respectively. Furthermore, the mold ridge line 104, the first mold slope 101, the second mold slope 102, and the third mold slope 103 of the recess 100 have configurations corresponding to the ridge line 44, the first slope 41, the second slope 42, and the third slope 43 of the projection 40, respectively. With this mold M, a pneumatic tire T is obtained in which the groove wall surface 72 of the main groove 7 includes an uneven region 10 formed by arranging multiple projections 40. The configuration of the tire T has already been explained with reference to Figures 1 to 9, and an effect of improving off-road performance in muddy terrain can be obtained. For details on other configurations, preferred dimensions, shape, arrangement, and modifications of the recess 100, refer to the previously described explanation of the projection 40.

[0044] Those skilled in the art will understand that the embodiments described above are specific examples of the following embodiments.

[0045] [1] The pneumatic tire of this disclosure is provided with grooves on the tread surface. The groove walls include an uneven region with a plurality of protrusions arranged thereon. Viewed from a direction perpendicular to the groove wall, the shape of the protrusions has a longitudinal direction and a transverse longitudinal direction and tapers toward both sides in the longitudinal direction. The longitudinal direction of the protrusions is oriented toward the tire diameter direction. The protrusions have a ridge extending longitudinally in a region on one side in the longitudinal direction, a first slope whose protrusion height decreases toward one side in the transverse direction from the ridge, a second slope whose protrusion height decreases toward the other side in the transverse direction from the ridge, and a third slope located in the region on the other side in the longitudinal direction, whose protrusion height decreases toward the other side in the longitudinal direction. With this configuration, the off-road performance in muddy terrain can be improved.

[0046] [2] In the pneumatic tire described in [1] above, one longitudinal side of the projection may face the bottom of the groove. This causes the third slope to face the tread side (outward in the radial direction of the tire), which is convenient for discharging mud and soil out of the groove.

[0047] [3] In the pneumatic tire described in [1] or [2] above, the first and second slopes may each be formed by planes extending to the groove wall surface. This ensures the size of the first and second slopes and, consequently, enhances the traction effect due to the uneven surface.

[0048] [4] In any one of the above [1] to [3] pneumatic tires, the opening angle between the first and second inclined surfaces may be obtuse. Such a configuration is useful for reducing snagging during tire demolding and for suppressing mold contamination.

[0049] [5] In any one of the pneumatic tires described in [1] to [4] above, the third slope may be larger than the first and second slopes when viewed from a direction perpendicular to the first reference plane. This can result in a simpler planar shape of the protrusion, which is advantageous in reducing mold contamination.

[0050] [6] In any one of the above [1] to [5] pneumatic tires, the groove wall surface may be smoothly connected to the groove bottom surface via a connecting surface with a circular arc cross-section, and the groove bottom surface including the connecting surface may not have the aforementioned uneven region. This is because the groove bottom surface contributes less to off-road performance in muddy terrain compared to the groove wall surface, and creating an uneven region on the connecting surface would require highly difficult mold processing.

[0051] [7] In any one of the above [1] to [6] pneumatic tires, the protruding height of the projection may be 0.5 mm or less. With this configuration, an excessive decrease in drainage performance can be prevented.

[0052] [8] In any one of the pneumatic tires described in [1] to [7] above, multiple rows of protrusions are formed with the protrusions arranged in the short direction, and the phase of the row of protrusions is offset by half a phase in the longitudinal and short directions relative to the phase of other adjacent rows of protrusions. This arrangement allows the protrusions to be closely spaced, thereby enhancing the traction effect due to the uneven surface and improving off-road performance in muddy terrain.

[0053] [9] The tire vulcanizing mold of this disclosure includes a projection for forming grooves provided on the tread surface of a tire. The side wall surface of the projection includes an uneven region in which a plurality of depressions are arranged. Viewed from a direction perpendicular to the side wall surface, the shape of the depressions has a longitudinal direction and a transverse longitudinal direction and tapers toward both sides in the longitudinal direction. The longitudinal direction of the depressions is oriented toward the tire radial direction. The depressions have a mold ridge extending longitudinally in a region on one side in the longitudinal direction, a first mold slope whose depression depth decreases toward one side in the transverse direction from the mold ridge, a second mold slope whose depression depth decreases toward the other side in the transverse direction from the mold ridge, and a third mold slope located in the region on the other side in the longitudinal direction, whose depression depth decreases toward the other side in the longitudinal direction. With this configuration, since the groove wall surface of the grooves provided on the tread surface of the vulcanized tire includes the uneven region described above, the off-road performance in muddy terrain can be improved.

[0054] The pneumatic tire of this disclosure can be constructed in the same way as a normal pneumatic tire, except that the grooves on the tread surface are configured as described above, and any conventionally known materials, shapes, structures, and manufacturing methods can be used.

[0055] The tire vulcanizing mold of this disclosure can be constructed in the same way as a conventional tire vulcanizing mold, except that the protrusions for forming the grooves on the tread surface are configured as described above, and any conventionally known materials, shapes, structures, and mechanisms can be used.

[0056] This disclosure is not limited in any way to the embodiments described above, and various improvements and modifications are possible without departing from its essence. Furthermore, the configurations adopted in the embodiments described above can be adopted in any combination. [Explanation of Symbols]

[0057] Tread surface 3f, 7 Main groove (example of groove), 8 Lateral groove (example of groove), 9 Protrusion, 10 Uneven area, 40 Projection, 40A Row of projections, 40t Top, 41 First slope, 42 Second slope, 43 Third slope, 44 Ridge, 71 Groove bottom, 72 Groove wall, 73 Connecting surface, 90 Uneven area, 92 Side wall, 100 Recess, 101 First mold slope, 102 Second mold slope, 103 Third mold slope, 104 Mold ridge, LD Longitudinal direction, LD1 One side of longitudinal direction, LD2 Other side of longitudinal direction, SD Short direction, SD1 One side of short direction, SD2 Other side of short direction, T Pneumatic tire

Claims

1. The tread surface is equipped with grooves, The groove wall surface of the groove includes an uneven region in which multiple protrusions are arranged, When viewed from a direction perpendicular to the groove wall surface, the shape of the projection has a longitudinal direction and a transversely longitudinal direction, and tapers toward both sides in the longitudinal direction. The longitudinal direction of the aforementioned projection is oriented in the direction of the tire diameter, The aforementioned protrusion is A ridge extending in the longitudinal direction in a region on one side in the longitudinal direction, A first slope whose protruding height decreases toward one side in the shorter direction from the aforementioned ridge, A second slope whose protruding height decreases toward the other side in the shorter direction from the aforementioned ridge, A pneumatic tire having a third slope positioned in the region on the other side in the longitudinal direction, with its protruding height decreasing toward the other side in the longitudinal direction.

2. The pneumatic tire according to claim 1, wherein one longitudinal side of the projection faces the bottom of the groove.

3. The pneumatic tire according to claim 1, wherein the first slope and the second slope are each formed by planes extending to the groove wall surface.

4. The pneumatic tire according to claim 1, wherein the angle of opening between the first slope and the second slope is obtuse.

5. The pneumatic tire according to claim 1, wherein, when viewed from a direction perpendicular to the groove wall surface, the third slope is larger than the first and second slopes.

6. The groove wall surface is smoothly connected to the groove bottom surface via a connecting surface with a circular arc cross-section. The pneumatic tire according to claim 1, wherein the groove bottom surface including the connecting surface is not provided with the uneven region.

7. The pneumatic tire according to claim 1, wherein the protruding height of the projection is 0.5 mm or less.

8. Multiple rows of protrusions are formed, with the aforementioned protrusions arranged in the short direction. The pneumatic tire according to any one of claims 1 to 8, wherein the phase of the row of protrusions is shifted by half a phase in the longitudinal and transverse directions of the protrusions with respect to the phase of other rows of protrusions adjacent to it.

9. It is equipped with protrusions for forming grooves on the tread surface of the tire, The side wall surface of the projection includes an uneven region in which multiple indentations are arranged, When viewed from a direction perpendicular to the side wall surface, the shape of the recess has a longitudinal direction and a transversely longitudinal direction, and tapers toward both sides in the longitudinal direction. The longitudinal direction of the aforementioned depression is oriented in the direction of the tire diameter, The aforementioned depression is, In the region on one side in the longitudinal direction, the mold ridge extends in the longitudinal direction, A first mold slope, in which the depth of depression is reduced toward one side in the shorter direction from the mold ridge, A second mold slope, in which the depth of depression is reduced toward the other side in the shorter direction from the mold ridge, A tire vulcanizing mold having a third mold inclined surface located in the region on the other side in the longitudinal direction, with the depth of depression decreasing toward the other side in the longitudinal direction.

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